TW202006145A - Cu core ball, soldering head, soldering paste and foaming solder capable of realizing high sphere degree, low hardness and suppressing discoloration - Google Patents

Abstract

An object of the present invention is to provide a Cu core ball formed by covering a Cu ball with a metal layer, which is capable of realizing high sphere degree and low hardness as well as suppressing discoloration. To achieve the object, there is provided a Cu core ball 11A, which includes a Cu ball 1 and a solder layer 3 covering the surface of the Cu ball 1. The Cu ball 1 has at least one selecting from Fe, Ag or Ni with a total content of 5.0 mass ppm or more and 50.0 mass ppm or less, S with a content of 0 mass ppm or more and 1.0 mass ppm or less, P with a content of 0 mass ppm or more and 3.0 mass ppm or less, and the balance being Cu and other impurity elements. The purity of the Cu ball 1 is 99.995% by mass or more and 99.9995% by mass or less. The sphere degree is 0.95 or more. The solder layer is made of (Sn-Cu)-based solder alloy containing Sn and Cu.

Description

Cu core ball, solder joint, solder paste and foam solder

The invention relates to a Cu core ball formed by coating a Cu ball with a metal layer, and a soldering joint, a solder paste and a foam solder using the Cu core ball.

In recent years, due to the development of small-sized information equipment, the electronic components mounted have been rapidly reduced in size. Due to the requirement of miniaturization, electronic components are applied to the ball grid array (hereinafter referred to as "BGA") with electrodes on the back side in order to cope with the narrowing of connection terminals and the reduction of package area.

Electronic parts using BGA are, for example, semiconductor components. In the semiconductor module, a semiconductor wafer having electrodes is sealed with resin. Solder bumps are formed on the electrode system of the semiconductor wafer. The solder bumps are formed by bonding solder balls to the electrodes of the semiconductor wafer. The semiconductor device using the BGA is mounted on the printed circuit board by bonding the solder bumps melted by heating to the conductive land of the printed circuit board. In addition, in order to meet the requirements of further high-density packaging, three-dimensional high-density packaging in which semiconductor devices are stacked in the height direction is being studied.

The high-density packaging of electronic parts is caused by the alpha line entering the memory cell of a semiconductor integrated circuit (IC) and causing a soft error to rewrite the memory content. Therefore, in recent years, the development of welding materials and Cu balls with a low alpha line to reduce the content of radioactive isotope elements has been developed. Patent Document 1 discloses a Cu ball containing Pb and Bi and having a purity of 99.9% or more and 99.995% or less with a low amount of α-line. Patent Document 2 discloses a Cu ball capable of achieving a purity of 99.9% or more and 99.995% or less, a true sphericity of 0.95 or more, and a Vickers hardness of 20 HV or more and 60 HV or less.

However, when the crystal grains of the Cu balls are finer, the Vickers hardness becomes larger, so the durability against external stress becomes lower and the drop impact resistance becomes worse. Therefore, Cu balls used for packaging electronic components are required to have a predetermined flexibility, that is, a Vickers hardness of a predetermined value or less.

In order to make soft Cu balls, the custom is to increase the purity of Cu. This is because the impurity element functions as a crystal nucleus in the Cu ball. Therefore, when there are few impurity elements, the crystal grains grow larger, and as a result, the Vickers hardness of the Cu ball becomes smaller. However, when the purity of the Cu ball is increased, the true sphericity of the Cu ball becomes lower.

When the true sphericity of the Cu ball is low, there is a possibility that the self-alignment cannot be ensured when the Cu ball is packaged on the electrode, and at the same time, the height of the Cu ball becomes uneven during the packaging of the semiconductor chip and may cause joint failure Situation.

Patent Document 3 discloses a Cu ball having a mass ratio of Cu of more than 99.995%, and a total mass ratio of P and S of 3 ppm or more and 30 ppm or less, and having appropriate true sphericity and Vickers hardness.

In addition, when the three-dimensional high-density packaged semiconductor component is BGA, when the solder ball is placed on the electrode of the semiconductor wafer and reflowed, the solder ball may collapse due to the weight of the semiconductor component. When this happens, the solder is extruded from the electrodes, and there is a possibility that the electrodes will contact each other and a short circuit may occur between the electrodes.

In order to prevent such short-circuit accidents, there is a proposal to disclose a solder bump that does not collapse due to its own weight or deform when the solder melts. Specifically, a ball formed of metal or the like is used as a core, and a core material obtained by coating the core with solder is used as a solder bump. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 5435182 [Patent Document 2] Japanese Patent No. 5585571 [Patent Document 3] Japanese Patent No. 6256616

[Problems to be Solved by the Invention]

However, it is newly understood that Cu balls containing more than a predetermined amount of S have a problem that sulfides and sulfur oxides are formed during heating and they are easily discolored. The discoloration system of the Cu ball becomes the cause of the deterioration of the wettability, and the deterioration of the wettability system causes the non-wetting and the deterioration of the self-alignment. In this way, it is not suitable to use the coating of the metal layer because of the low adhesion between the surface of the Cu ball and the metal layer, which is easy to discolor, and the oxidation and reactivity of the surface of the metal layer. On the other hand, when the true sphericity of the Cu ball is low, the true sphericity of the Cu core ball formed by coating the Cu ball with the metal layer also becomes low.

Therefore, an object of the present invention is to provide a Cu core ball that realizes high sphericity and low hardness and uses a Cu ball capable of suppressing discoloration, and a solder joint, solder paste, and foam solder using the Cu core ball. [Means to solve the problem]

The present invention is as follows. (1) A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, the total content of at least one of the Cu ball system Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, S content is 0 mass ppm or more and 1.0 mass ppm or less, P content is 0 mass ppm or more and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, and the purity of Cu balls is 99.995 mass% or more and 99.9995% by mass or less, the true sphericity is 0.95 or more, and the solder layer system (Sn-Cu) solder alloy containing Sn and Cu. (2) The Cu core ball as described in (1) above, wherein the content of the solder layer system Cu is greater than 0% by mass and 3.0% by mass or less, and Sn is the remainder. (3) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of a (Sn-Cu)-based solder alloy containing Sn and 0.1 to 3.0% by mass of Cu, and will be in the solder layer The concentration ratio (%) of Cu contained in it is set as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or the concentration ratio (%) = (average value of the measured value (Mass %)/target content (mass %)) × 100, the concentration ratio is in the range of 70.0 to 130.0%. (4) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of a (Sn-Cu)-based solder alloy containing Sn and 0.1 to 3.0% by mass of Cu, and will be in the solder layer The concentration ratio (%) of Cu contained in it is set as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or the concentration ratio (%) = (average value of the measured value (Mass %)/target content (mass %)) × 100, the concentration ratio is in the range of 90.0 to 110.0%. (5) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of (Sn-0.7Cu)-based solder alloy containing Sn and Cu, and the Cu contained in the solder layer The concentration ratio (%) is set as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or the concentration ratio (%) = (average value of the measured value (mass %)/ Target content (mass %)) × 100, the concentration ratio is in the range of 72.9 to 97.1%. (6) The Cu core ball as described in (1) or (2) above, wherein the solder layer is composed of (Sn-3.0Cu)-based solder alloy containing Sn and Cu, and the Cu contained in the solder layer The concentration ratio (%) is set as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or the concentration ratio (%) = (average value of the measured value (mass %)/ Target content (mass %)) × 100, the concentration ratio is in the range of 81.7 to 108.7%. (7) The Cu core ball according to any one of the above (1) to (6), wherein the true sphericity is 0.98 or more. (8) The Cu core ball according to any one of the above (1) to (6), wherein the true sphericity is 0.99 or more. (9) The Cu core ball according to any one of the above items (1) to (8), wherein the amount of α line is 0.0200 cph/cm ² or less. (10) The Cu core ball according to any one of the above items (1) to (8), wherein the amount of α line is 0.0010 cph/cm ² or less. (11) The Cu core ball according to any one of the above items (1) to (10), which includes a metal layer covering the surface of the Cu ball, and the surface of the metal layer is covered with a solder layer, and the true sphericity is 0.95 or more . (12) The Cu core ball as described in (11) above, wherein the true sphericity is 0.98 or more. (13) The Cu core ball as described in (11) above, wherein the true sphericity is 0.99 or more. (14) The Cu core ball according to any one of the above items (11) to (13), wherein the amount of α line is 0.0200 cph/cm ² or less. (15) The Cu core ball according to any one of the above items (11) to (13), wherein the amount of α line is 0.0010 cph/cm ² or less. (16) The Cu core ball according to any one of the above items (1) to (15), wherein the diameter of the Cu core ball is 1 μm or more and 1000 μm or less. (17) A welding head using the Cu core ball as described in any one of (1) to (16) above. (18) A solder paste using the Cu core ball as described in any one of (1) to (16) above. (19) A foam solder using the Cu core ball as described in any one of (1) to (16) above. [Effect of the invention]

According to the present invention, it is realized that the Cu balls have high true sphericity and low hardness, and the discoloration of the Cu balls can be suppressed. By realizing high sphericity of Cu balls, it is possible to achieve high sphericity of Cu core balls formed by coating Cu balls with metal layers, and while ensuring self-alignment when encapsulating Cu ball cores on electrodes, It is possible to suppress the deviation of the height of the Cu core ball. In addition, by realizing the low hardness of the Cu ball, the Cu core ball formed by coating the Cu ball with the metal layer can also improve the drop impact resistance. In addition, since the discoloration of the Cu ball can be suppressed, it is possible to suppress the sulfide and sulfur oxide from adversely affecting the Cu ball, and it is suitable for using the coating of the metal layer and the wettability becomes good.

Forms for carrying out the invention

The present invention will be described in more detail below. In this specification, the units (ppm, ppb, and %) of the composition of the metal layer of the Cu core ball represent the ratio to the mass of the metal layer (mass ppm) unless otherwise specified. , Quality ppb, and quality %). In addition, the units (ppm, ppb, and %) of the composition of the Cu balls represent the ratio to the mass of the Cu balls (mass ppm, mass ppb, and mass %) unless otherwise specified.

FIG. 1 shows an example of the configuration of the Cu core ball 11A according to the first embodiment of the present invention. As shown in FIG. 1, the Cu core ball 11A according to the first embodiment of the present invention includes the Cu ball 1 and the solder layer 3 covering the surface of the Cu ball 1.

FIG. 2 shows an example of the configuration of the Cu core ball 11B according to the second embodiment of the present invention. As shown in FIG. 2, the Cu core ball 11B according to the second embodiment of the present invention includes a Cu ball 1 and a surface of the Cu ball 1 selected from the group consisting of one or more elements selected from Ni, Co, Fe, and Pd. The metal layer 2 above the layer and the solder layer 3 covering the surface of the metal layer 2.

FIG. 3 shows an example of the configuration of an electronic component 60 in which a semiconductor semiconductor wafer 10 is mounted on a printed board 40 using Cu core balls 11A or Cu core balls 11B according to an embodiment of the present invention. As shown in FIG. 3, the Cu core ball 11A or the Cu core ball 11B is encapsulated on the electrode 100 of the semiconductor wafer 10 by applying flux to the electrode 100 of the semiconductor wafer 10 and the molten solder layer 3 is wet and expanded . In this example, the structure in which the Cu core ball 11A or the Cu core ball 11B is encapsulated in the electrode 100 of the semiconductor wafer 10 is referred to as a solder bump 30. The solder bump 30 of the semiconductor wafer 10 is bonded to the electrode 41 of the printed circuit board 40 through the molten solder layer 3 or the solder after the solder paste applied to the electrode 41 is melted. In this example, the structure in which the solder bump 30 is packaged on the electrode 41 of the printed board 40 is referred to as a solder joint 50.

In the Cu core balls 11A and 11B of each embodiment, the total content of at least one of the Cu balls 1 series Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, and the S content is 0 mass ppm or more and 1.0 Mass ppm or less, P content is 0 mass ppm or more and less than 3.0 mass ppm, the remainder is Cu and other impurity elements, the purity of Cu ball 1 is 4N5 (99.995 mass%) or more and 5N5 (99.9995 mass%) or less, true The sphericity is above 0.95.

The Cu core sphere 11A according to the first embodiment of the present invention can improve the sphericity of the Cu core sphere 11A by increasing the sphericity of the Cu sphere 1 coated with the solder layer 3. In addition, the Cu core ball 11B according to the second embodiment of the present invention can improve the spherical degree of the Cu core ball 11B by increasing the spherical degree of the Cu ball 1 coated with the metal layer 2 and the solder layer 3. Hereinafter, a preferred aspect of the Cu ball 1 constituting the Cu core balls 11A and 11B will be described.

･Sphericality of Cu balls: 0.95 or more In the present invention, the true sphericity refers to the deviation from the true sphere. The degree of true sphericity means the arithmetic average calculated when the diameters of 500 Cu balls are divided by the long diameter. The value means that the closer to the upper limit of 1.00, the closer to the true sphere. The true sphericity system is obtained using various methods such as the least square center method (LSC method), the smallest zone center method (MZC method), the largest inscribed center method (MIC method), and the smallest circumscribed center method (MCC method). In the present invention, the length of the major axis and the length of the diameter refer to the length measured using an Ultra Quick Vision, ULTRA QV350-PRO measuring device manufactured by Mitutoyo Corporation.

From the viewpoint of maintaining an appropriate space between the substrates, the Cu ball 1 is preferably a sphericity of 0.95 or more, a sphericity of 0.98 or more, more preferably 0.99 or more, and a Cu ball 1 When the degree is less than 0.95, since the Cu ball 1 has an indefinite shape, a highly uneven bump is formed at the time of bump formation, and the possibility of joint failure is increased. When the sphericity is 0.95 or more, since the Cu ball 1 system does not melt at the welding temperature, it is possible to suppress variations in the height of the welding head 50. With this, it is possible to surely prevent poor bonding between the semiconductor wafer 10 and the printed board 40.

･Cu ball purity: 99.995 mass% or more and 99.9995 mass% or less Generally, compared with higher purity Cu, since the lower purity Cu can ensure the impurity element that becomes the crystalline nucleus of the Cu ball 1 in Cu, the true sphericity is higher. On the other hand, the electrical conductivity and thermal conductivity of the Cu ball 1 with lower purity deteriorate.

Therefore, when the purity of the Cu ball 1 series is 99.995 mass% (4N5) or more and 99.9995 mass% (5N5) or less, a sufficient sphericity can be ensured. In addition, when the purity of the Cu ball 1 is 4N5 or more and 5N5 or less, not only can the amount of α-line be sufficiently reduced, but also the deterioration of the conductivity and thermal conductivity of the Cu ball 1 due to the decrease in purity can be suppressed.

When manufacturing the Cu ball 1, the Cu material, which is an example of the metal material formed into a small piece of a predetermined shape, is melted by heating and the molten Cu becomes spherical by surface tension, and is solidified by quenching to become a Cu ball 1. During the process of solidification of molten Cu from the liquid state, crystal grains grow in spherical molten Cu. At this time, when there are many impurity elements, the impurity element system becomes a crystal nucleus and crystal grain growth is suppressed. Therefore, the spherical molten Cu is a Cu ball 1 with a high degree of sphericity due to the growth of fine crystal grains. On the other hand, when there are few impurities, there are relatively few crystal nuclei, so grain growth is not suppressed and grows with a certain direction. As a result, a part of the spherical molten Cu-based surface protruded and solidified, and the true sphericity became low. As the impurity element, Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, U, Th, etc. can be considered.

The purity of the Cu ball 1 and the content of impurities in the sphericity will be described below.

･Total content of at least one of Fe, Ag and Ni: 5.0 mass ppm or more and 50.0 mass ppm or less Among the impurity elements contained in the Cu ball 1, the total content of at least one of Fe, Ag, and Ni is particularly preferably 5.0 mass ppm or more and 50.0 mass ppm or less. That is, when any one of Fe, Ag, and Ni is contained, the content of one kind is preferably 5.0 mass ppm or more and 50.0 mass ppm or less, and when Fe, Ag, and Ni contains two or more kinds, two or more kinds The total content of is preferably 5.0 mass ppm or more and 50.0 mass ppm or less. Since Fe, Ag, and Ni become crystalline nuclei during the melting of the Cu ball 1 manufacturing step, when Cu contains a certain amount of Fe, Ag, or Ni, Cu balls 1 with a high degree of sphericity can be manufactured. Therefore, at least one of Fe, Ag, and Ni becomes an important element in order to estimate the content of the impurity element. Furthermore, when the total content of at least one of Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, not only can the discoloration of the Cu ball 1 be suppressed, but also after the Cu ball 1 is slowly heated, the Slow cooling can achieve the required Vickers hardness without performing the annealing step to slowly recrystallize the Cu balls 1.

･S content is 0 mass ppm or more and 1.0 mass ppm or less The Cu balls 1 containing a predetermined amount or more of S form sulfides and sulfur oxides upon heating, which easily discolor and have low wettability. Therefore, the content of S must be 0 mass ppm or more and 1.0 mass ppm or less. The Cu sphere 1 formed with more sulfide and sulfur oxides becomes darker on the surface of the Cu sphere. Therefore, as described in detail later, when the result of measuring the brightness of the surface of the Cu ball is equal to or less than a predetermined value, the formation of sulfide and sulfur oxide can be suppressed and the wettability can be determined to be good.

･P content is 0 mass ppm or more and less than 3.0 mass ppm The P system changes to phosphoric acid or Cu complex, which may adversely affect the Cu ball 1. In addition, since the hardness of the Cu ball 1 containing P in a predetermined amount increases, the content of P is preferably 0 mass ppm or more and less than 3.0 mass ppm, preferably less than 1.0 mass ppm.

･Other impurities The content of impurity elements such as Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au, etc. (hereinafter referred to as "other impurity elements") contained in the Cu ball 1 other than the above impurity elements is It is preferably 0 mass ppm or more and less than 50.0 mass ppm.

In addition, as described above, the Cu ball 1 system contains at least one of Fe, Ag, and Ni as an essential element. However, since the Cu ball 1 system cannot prevent elements other than Fe, Ag, and Ni from being mixed in accordance with the current technology, it substantially contains other impurity elements other than Fe, Ag, and Ni. However, when the content of other impurity elements is less than 1 mass ppm, the effect of adding each element and the influence are not easily manifested. In addition, when analyzing the elements contained in the Cu ball, when the content of the impurity element is less than 1 mass ppm, the value is below the detection limit of the analysis device. Therefore, when the content of at least one of Fe, Ag, and Ni is 50 mass ppm in total, and the content of other impurity elements is less than 1 mass ppm, the purity of the Cu ball 1 is substantially 4N5 (99.995 mass %). When the total content of at least one of Fe, Ag, and Ni is 5 mass ppm, and the content of other impurity elements is less than 1 mass ppm, the purity of the Cu ball 1 is substantially 5N5 (99.9995 mass %).

･Vickers hardness of Cu ball: 55.5HV or less The Vickers hardness of the Cu ball 1 is preferably 55.5 HV or less. When the Vickers hardness is large, the durability against external stress is reduced and the drop impact resistance is deteriorated, and cracks are easily generated. In addition, when an auxiliary force such as pressurization is applied during the formation of the bumps and the joints of the three-dimensional package, the electrode may collapse due to the use of hard Cu balls. Furthermore, when the Vickers hardness of the Cu ball 1 is large, the crystal grain system becomes smaller than a certain value or more, which may cause deterioration in conductivity. When the Vickers hardness of the Cu ball 1 is 55.5 HV or less, the drop impact resistance is also good, cracking can be suppressed, electrode collapse, etc. can also be suppressed, and deterioration in conductivity can also be suppressed. In this embodiment, the lower limit of the Vickers hardness may be greater than 0HV, preferably 20HV or more.

･Cu ball alpha line amount: 0.0200cph/cm ² or less In high-density packaging of electronic parts, in order to make the alpha line amount to the extent that soft errors do not cause problems, the alpha line amount of Cu ball 1 is 0.0200cph/cm ² or less good. From the viewpoint of suppressing soft errors in further high-density packaging, the amount of α line is preferably 0.0100 cph/cm ² or less, preferably 0.0050 cph/cm ² or less, more preferably 0.0020 cph/cm ² or less, and most preferably 0.0010cph/cm ² or less. In order to suppress soft errors caused by the amount of α-line, the radioisotope content of U, Th, etc. is preferably less than 5 mass ppb.

･Discoloration resistance: brightness above 55 The brightness of the Cu ball 1 is preferably 55 or more. The L* value of the so-called brightness system L*a*b* color system. Since the brightness of the Cu ball 1 in which sulfides and sulfur oxides derived from S are formed on the surface becomes low, when the brightness is 55 or more, it can be said that the sulfides and sulfur oxides can be suppressed. In addition, the Cu balls 1 having a brightness of 55 or more have good wettability during packaging. On the other hand, when the brightness of the Cu balls 1 is less than 55, it can be said that the Cu balls 1 that form sulfides and sulfur oxides cannot be sufficiently suppressed. Sulfide and sulfur oxide not only adversely affect the Cu ball 1 but also deteriorate the wettability when the Cu ball 1 is directly bonded to the electrode. The deterioration of wettability causes the generation of non-wetting and the deterioration of self-alignment.

･Cu ball diameter: 1μm or more and 1000μm or less The diameter of the Cu ball 1 is preferably 1 μm or more and 1000 μm or less, preferably 50 μm or more and 300 μm. In this range, the spherical Cu balls 1 can be stably manufactured, and the connection short circuit when the terminals are at a narrow pitch can be suppressed. Here, for example, when the Cu ball 1 is used as a paste, the "Cu ball" may also be referred to as "Cu powder". When the "Cu ball" system is used for "Cu powder", the diameter of the Cu ball is usually 1 to 300 μm.

Next, the Cu core ball 11A of the first embodiment of the present invention covering the solder layer 3 of the Cu ball 1 and the Cu core ball 11B of the second embodiment covering the solder layer 3 of the metal layer 2 will be described.

･Solder layer The Cu core balls 11A and 11B of the embodiments of the present invention are formed by coating the Cu balls 1 with a solder layer 3 using a solder alloy containing Sn and Cu as essential elements. In particular, the Cu core balls 11A and 11B of the embodiments of the present invention are Cu core balls in which the Cu distribution in the solder layer 3 is uniform, and a solder joint, solder paste, and foam solder using the core balls are provided.

The composition of the solder layer 3 in the embodiment of the present invention is composed of (Sn-Cu) alloy containing Sn and Cu. The content of Sn is preferably 40.0% by mass or more relative to the entire alloy. With respect to the Cu content, the amount of Cu is greater than 0% by mass and less than 3.0% by mass relative to the entire alloy. When the amount of Cu is greater than 0% by mass and less than 3.0% by mass, the concentration ratio of Cu can be controlled Within the predetermined range. Furthermore, when the amount of Cu is in the range of 0.1 to 3.0% by mass relative to the entire alloy, the Cu concentration ratio can be controlled within a predetermined range of 70.0 to 130.0%, and the Cu distribution in the solder layer 3 can be made uniform.

For example, when the target value of the content of Cu is 0.7% by mass, the allowable range of the content and concentration ratio of Cu is 0.51% by mass (concentration ratio 72.9%) to 0.68% by mass (concentration ratio 97.1%), and the concentration ratio of Cu can be controlled Within a predetermined range of 70.0 to 130.0%, the Cu distribution in the solder layer 3 can be made homogeneous. The solder alloy whose target value of Cu content is 0.7% by mass is called (Sn-0.7Cu) solder alloy.

In addition, when the target value of the Cu content is 3.0% by mass, the allowable range of the Cu content and the concentration ratio is 2.45 mass (concentration ratio 81.7%) to 3.26 mass% (concentration ratio 108.7%), and the Cu concentration ratio can be controlled Within a predetermined range of 70.0 to 130.0%, the Cu distribution in the solder layer 3 can be made homogeneous. The solder alloy whose target value of Cu content is 3.0% by mass is called (Sn-3Cu) solder alloy.

In addition, the allowable range is a range in which welding such as bump formation can be performed without problems when it is within this range. The concentration ratio (%) is the ratio (%) of the measured value (mass %) relative to the target content (mass %) or the average value (mass %) of the target content (mass %). . That is, the concentration ratio (%) can be Concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100 or, Concentration ratio (%) = (mean value of measurement value (mass %)/target content (mass %)) × 100.

The concentration ratio of Cu is preferably in the range of 90.0 to 110.0%. Furthermore, even if additional elements are added to the binary solder layer 3 composed of Sn and Cu, the concentration ratio of Cu can be controlled within a predetermined range of 70.0 to 130.0%, preferably 90.0 to 110.0%.

As the additional element, one or more of Ag, Ni, Ge, Ga, In, Zn, Fe, Pb, Bi, Sb, Au, Pd, Co, etc. can be considered.

As described above, the Cu content in the solder layer 3 is 0.7% by mass relative to the target value, and the allowable range is preferably about 0.51% by mass (concentration ratio 72.9%) to 0.68% by mass (concentration ratio 97.1%). The Cu content in the solder layer 3 is 3.0% by mass relative to the target value, and the allowable range is preferably about 2.45% by mass (concentration ratio 81.7%) to 3.26% by mass (concentration ratio 108.7%).

The thickness of the solder layer 3 also differs according to the particle diameter of the Cu ball 1, and in order to ensure a sufficient amount of soldering, the one side in the radial direction is preferably 100 μm or less. The solder layer 3 can be formed by conventional electroplating or electroless plating. However, when the solder layer is formed by melt plating, the particle size of the Cu ball becomes smaller and the film thickness of the solder layer is not uniform. The eccentricity of the Cu ball and the unevenness of the surface of the solder layer become larger, and the true sphericity of the Cu core ball decreases. Therefore, the solder layer 3 is formed by electroplating.

As the electroplating solution, the medium containing water as the main component contains organic acids and Sn and Cu as metal components as essential components. The metal components exist in the form of Sn ions (Sn ²⁺ and/or Sn ⁴⁺ ) and Cu ions (Cu ⁺ /Cu ²⁺ ) in the plating solution. The plating solution system is mainly obtained by mixing a plating mother solution composed of water and organic acids and a metal compound. For the stability of metal ions, it is preferable to contain an organic complexing agent.

As the metal compound in the plating solution, for example, the following can be exemplified. Specific examples of the Sn compound include tin salts of organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, and p-phenolsulfonic acid, tin sulfate, tin oxide, tin nitrate, and tin chloride , Tin bromide, tin iodide, tin phosphate, tin pyrophosphate, tin acetate, tin formate, tin citrate, tin gluconate, tin tartrate, tin lactate, tin succinate, tin sulfonate, tin fluoroborate , Tin fluorosilicate and other sub-Sn compounds. These Sn compound systems can be used alone or in combination of two or more.

Examples of the Cu compound include copper salts of the above-mentioned organic sulfonic acids, copper sulfate, copper oxide, copper nitrate, copper chloride, copper bromide, copper iodide, copper phosphate, copper pyrophosphate, copper acetate, copper formate, and lemon Copper acid, copper gluconate, copper tartrate, copper lactate, copper succinate, copper sulfamate, copper fluoroborate, copper fluorosilicate, etc. These Cu compounds can be used alone or in combination of two or more.

When forming a solder layer composed of Sn-Cu based solder alloy composed of Sn and Cu by electroplating, because Cu is preferentially contained in the solder layer than Sn, there are Cu concentration in the plating solution and Cu in the solder layer The amount is inconsistent, and the concentration distribution of Cu cannot form a uniform solder layer. Therefore, while applying a predetermined DC voltage between the anode electrode and the cathode electrode, the plating process can be performed by adjusting the Cu concentration in the solution while shaking the Cu ball, and the concentration of the plating solution is applied to the solder plating layer Become a certain way to control in the formation.

In the process of generating the solder layer 3 by the electroplating process which controls the concentration of the plating solution in the formation of the solder plating layer, the thickness of the solder layer 3 is carefully monitored. In this example, the thickness of the solder layer 3 Each time the predetermined value increases sequentially, the Cu core ball is collected as a sample each time. After the collected sample was washed and dried, the particle size was measured.

It is known that the Cu content in the solder layer is measured sequentially when the particle size of the Cu core balls in the measurement sequence becomes the target value, and even if the solder layer is sequentially increased by a predetermined thickness, the Cu content at this time is approximately the same as the previous content. Therefore, it can be understood that the Cu concentration distribution is uniform (equal) with respect to the plating thickness and has no concentration gradient. As described above, the film thickness can be uniformly controlled on the reverse side, and the problem of plating with uneven concentration can be achieved by controlling the Cu concentration in the solder layer so that the Cu concentration ratio falls within a predetermined range to obtain a uniform distribution of Cu Cu core ball of the solder layer.

Figure 4 is an enlarged cross-sectional view of a Cu core ball. FIG. 4 shows a Cu core ball 11B formed by coating the Cu ball 1 with the metal layer 2 and coating the metal layer 2 with the solder layer 3. It can be clearly seen from FIG. 4 that the Sn and Cu-based solder layer 3 is uniformly doped while growing.

In addition, as the outermost surface of the solder layer 3 covering the Cu core balls 11A and 11B is closer to the state of a single metal, the crystal grains are larger, so the true sphericity of the Cu core balls tends to decrease. On the other hand, since Cu in the solder layer is approximately homogeneously distributed, the outermost surface of the solder layer is not a single metal, but is in an alloy state and the crystal grains are reduced. As a result, the true sphericity of the Cu core ball is higher than 0.99. When the true sphericity of the Cu core ball is 0.95 or more, when the Cu core ball is mounted on the electrode and reflowed, the position deviation of the Cu core ball can be suppressed and the self-alignment can be improved.

Since the Cu concentration in the solder layer maintains approximately the same state even if the thickness of the solder layer grows, it is clear that the Cu system in the solder layer grows in a state where it is approximately homogeneously distributed. It is possible to perform the plating process in such a manner that the Cu concentration falls within the expected value and the Cu concentration in the plating solution is made homogeneous. In this example, since the Cu content in the solder layer is 0.7 mass% or 3.0 mass% as the target value, the Cu concentration in the plating solution can be controlled so as to reach the target value.

In order to make the Cu concentration distribution in the solder layer fall to the expected value, the system conducts voltage and current control while electroplating. With this plating process, the Cu distribution in the solder layer can be maintained at the expected value.

For the Cu core balls 11A and 11B, the low-α-line Cu core balls 11A and 11B may be configured by using a solder alloy with a low α-line amount in the solder layer 3.

Next, the metal layer 2 covering the Cu ball 1 of the Cu core ball 11B according to the second embodiment of the present invention will be described.

･Metal layer The metal layer 2 is composed of, for example, two or more layers of Ni plating, Co plating, Fe plating, Pd plating, or an electroplated layer (single layer or multiple layers) of elements of Ni, Co, Fe, and Pd. The metal layer 2 is used when the Cu core ball 11B is used for solder bumps. The soldering temperature is not melted but remains and contributes to the height of the solder joint. Therefore, the sphericity is higher and the diameter deviation is less. And constitute. In addition, from the viewpoint of suppressing soft errors, it can be configured such that the amount of α line becomes lower.

･Composition and film of metal layer When the composition of the metal layer 2 is composed of a single Ni, Co, Fe, or Pd, and the metal layer 2 is constituted, in addition to unavoidable impurities, Ni, Co, Fe, and Pd are 100%. In addition, the metal system used in the metal layer 2 is not limited to a single metal, and an alloy obtained by combining two or more elements from Ni, Co, Fe, or Pd may also be used. Moreover, the metal layer 2 may be a layer composed of a single Ni, Co, Fe, or Pd, or may be an appropriate combination of layers of alloys obtained by combining two or more elements from Ni, Co, Fe, or Pd. Composed of multiple layers. The thickness T2 of the metal layer 2 is, for example, 1 μm to 20 μm.

･Cu core ball alpha line amount: 0.0200 cph/cm ² or less The alpha line amount of the Cu core ball 11A in the first embodiment of the present invention and the Cu core ball 11B in the second embodiment is preferably 0.0200 cph/cm ² or less . This is the amount of alpha line to the extent that soft errors in high-density packaging of electronic parts are not a problem. The amount of α line of the Cu core ball 11A according to the first embodiment of the present invention can be achieved by the amount of α line of the solder layer 3 constituting the Cu core ball 11A being 0.0200 cph/cm ² or less. Therefore, since the Cu core ball 11A of the first embodiment of the present invention is coated with such a solder layer 3, it shows a low amount of α-line. The amount of α-line of the Cu core ball 11B according to the second embodiment of the present invention can be achieved by the amount of α-line of the metal layer 2 and the solder layer 3 constituting the Cu core ball 11B being 0.0200 cph/cm ² or less. Therefore, the Cu core ball 11B according to the second embodiment of the present invention is coated with such a metal layer 2 and a solder layer 3, so it shows a low amount of α-line. From the viewpoint of suppressing soft errors in further high-density packaging, the amount of α line is preferably 0.0100 cph/cm ² or less, preferably 0.0050 cph/cm ² or less, more preferably 0.0020 cph/cm ² or less, and most preferably 0.0010cph/cm ² or less. In order to set the amount of α-line of the Cu ball 1 to 0.0200 cph/cm ² or less, the contents of U and Th of the metal layer 2 and the solder layer 3 are each 5 ppb or less. In addition, from the viewpoint of suppressing soft errors in current or future high-density packaging, the contents of U and Th are preferably 2 ppb or less each.

･Sphericality of Cu nucleus: above 0.95 The Cu core ball 11A of the first embodiment of the present invention covering the Cu ball 1 with the solder layer 3 and the Cu core ball 11B of the second embodiment of the present invention covering the Cu ball 1 with the metal layer 2 and the solder layer 3 The sphericity is preferably 0.95 or more, the true sphericity is preferably 0.98 or more, and more preferably 0.99 or more. When the true sphericity of the Cu core balls 11A and 11B is less than 0.95, the Cu core balls 11A and 11B have an indefinite shape, so when the Cu core balls 11A and 11B are mounted on the electrodes and reflowed, the Cu core balls 11A and 11B are misaligned. Shift and self-alignment also deteriorates. When the true sphericity of the Cu core balls 11A and 11B is 0.95 or more, the self-alignment when the Cu core balls 11A and 11B are packaged in the electrode 100 of the semiconductor wafer 10 and the like can be ensured. Moreover, the true sphericity of the Cu ball 1 is also 0.95 or more. Since the Cu core balls 11A and 11B do not melt at the temperature at which the Cu ball 1 and the metal layer 2 are welded, variations in the height of the welding head 50 can be suppressed. With this, it is possible to surely prevent poor bonding between the semiconductor wafer 10 and the printed board 40.

･The barrier function of the metal layer during reflow, in the solder (paste) used for bonding between the Cu core ball and the electrode, when the Cu of the Cu ball diffuses, a large amount is formed in the solder layer and the connection interface When the hard and brittle Cu ₆ Sn ₅ and Cu ₃ Sn intermetallic compounds are subjected to impact, cracks may progress and the connection may be destroyed. Therefore, in order to obtain sufficient connection strength, it is only necessary to suppress (barrier) the diffusion of Cu from the Cu ball to the solder. Therefore, in the Cu core ball 11B of the second embodiment, since the metal layer 2 functioning as a barrier layer is formed on the surface of the Cu ball 1, the diffusion of Cu of the Cu ball 1 into the solder of the paste can be suppressed.

･Solder paste, foam solder, solder joint Moreover, the solder paste can also be constituted by including Cu core balls 11A or Cu core balls 11B in the solder. By dispersing the Cu core ball 11A or the Cu core ball 11B in the solder, a foam solder can be constituted. The Cu core ball 11A or the Cu core ball 11B can also be used to form a welded joint joining electrodes.

･Cu ball manufacturing method Next, an example of the manufacturing method of the Cu ball 1 will be described. As an example of the metal material, Cu material is placed on a heat-resistant plate such as ceramic (hereinafter referred to as "heat-resistant plate") and heated together with the heat-resistant plate in a furnace. The bottom of the heat-resistant plate is provided with many hemispherical circular grooves. The diameter and depth of the groove can be appropriately set according to the particle diameter of the Cu ball 1, and for example, the diameter is 0.8 mm and the depth is 0.88 mm. In addition, the wafer-shaped Cu material obtained by cutting the Cu thin wire is thrown into the groove of the heat-resistant plate one at a time. A heat-resistant plate with a Cu material put in the trench is heated to 1100 to 1300°C in a furnace filled with ammonia decomposition gas and heat-treated for 30 to 60 minutes. At this time, when the temperature in the furnace becomes equal to or higher than the melting point of Cu, the Cu material system melts and becomes spherical. Subsequently, the inside of the furnace is cooled and shaped by quenching the Cu balls 1 in the grooves of the heat-resistant plate.

In addition, as another method, there is an atomization method in which molten Cu is dropped from an orifice provided at the bottom of the crucible, and the droplet is cooled to room temperature (for example, 25° C.) to form a ball into Cu ball 1; and thermoelectric A method for making balls by heating Cu cutting metal to above 1000°C by slurry.

In the manufacturing method of the Cu ball 1, before forming the Cu ball 1, the Cu material of the raw material of the Cu ball 1 may be heat-treated at 800 to 1000°C.

As the Cu material of the raw material of the Cu ball 1, for example, a nugget material, a metal wire material, a plate material, or the like can be used. From the viewpoint of not excessively reducing the purity of the Cu ball 1, the purity of the Cu material may be greater than 4N5 and 6N or less.

In this way, when a high-purity Cu material is used, the above-mentioned heat treatment may not be performed, and the retention temperature of molten Cu may be reduced to about 1000° C. as before. In this way, the aforementioned heat treatment system can be appropriately omitted and changed according to the purity of the Cu material and the amount of α-line. In addition, when Cu balls 1 with a high α-line amount and shaped Cu balls 1 are produced, the Cu balls 1 can be reused as a raw material and the α-line amount can be reduced.

As a method of forming the solder layer 3 on the produced Cu ball 1, the above-mentioned plating method or electroless plating method can be used.

As a method of forming the metal layer 2 on the produced Cu ball 1, a method such as a conventional electrolytic plating method can be used. For example, when forming a Ni-plated layer, a Ni plating solution is prepared by using a Ni metal block (bullion) or a Ni metal salt to immerse and deposit Cu balls 1 to form a Ni-plated layer The surface of the Cu ball 1. In addition, as another method of forming the metal layer 2 such as a Ni plating layer, a conventional electroless plating method or the like can also be used. When the solder layer 3 is formed on the surface of the metal layer 2 using Sn alloy, the above-mentioned plating method or electroless plating method can be used. [Example]

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these. The Cu balls of Examples 1 to 19 and Comparative Examples 1 to 12 were manufactured using the compositions shown in Tables 1 and 2 below, and the sphericity, Vickers hardness, amount of α-line, and discoloration resistance of the Cu balls were measured.

In addition, the Cu balls of the above Examples 1 to 19 were coated with the solder layer of the solder alloy of Composition Examples 1 to 2 shown in Table 3 to produce the Cu core balls of Examples 1A to 19A and measure the Cu core balls. True sphericity. Furthermore, the Cu spheres of the above Examples 1 to 19 were coated with a metal layer and a solder layer using the solder alloy of Composition Examples 1 to 2 shown in Table 4 to produce Cu core balls of Examples 1B to 19B and measure the Cu The true sphericity of the nuclear ball.

Further, by using the solder layers of the solder alloys of Composition Examples 1 to 2 shown in Table 5 to coat the Cu balls of the above Comparative Examples 1 to 12, Cu core balls of Comparative Examples 1A to 12A were manufactured and the trueness of the Cu core balls was measured Sphericity. Furthermore, by using the metal layer and the solder layers of the solder alloys of Composition Examples 1 to 2 shown in Table 6 to coat the Cu balls of the above Comparative Examples 1 to 12, Cu core balls of Comparative Examples 1B to 12B were manufactured and the Cu cores were measured The true degree of the ball.

In the following table, the unitless numbers indicate mass ppm or mass ppb. In detail, the table shows the values of the content ratios of Fe, Ag, Ni, P, S, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, and Au, which represent mass ppm. ">1" means that the content ratio of the impurity element to the Cu ball is less than 1 mass ppm. In addition, the numerical values showing the content ratio of U and Th in the table represent mass ppb. ">5" means that the content ratio of the impurity element to the Cu ball is less than 5 mass ppb. "Total amount of impurities" means the total ratio of impurities contained in Cu balls.

･Manufacture of Cu balls Study the manufacturing conditions of Cu balls. As an example of a metal material, Cu material is prepared as a bulk metal material. As the Cu materials of Examples 1 to 13, 19 and Comparative Examples 1 to 12, a material with a purity of 6N was used, and as the Cu materials of Examples 14 to 18, a material with a purity of 5N was used. After each Cu material was put into the crucible, the temperature of the crucible was raised to 1200°C and heated for 45 minutes to melt the Cu material, and the molten Cu was dropped from the orifice provided at the bottom of the crucible and the generated droplets were rapidly cooled to At room temperature (18°C), the pellets are made into Cu pellets. With this, Cu spheres having an average particle diameter of the values shown in the following tables were produced. The elemental analysis system can analyze with high accuracy using inductively coupled plasma mass analysis (ICP-MS analysis) and glow discharge mass analysis (GD-MS analysis). In this example, the sphere diameter of the Cu spheres analyzed by ICP-MS was 250 μm for Examples 1 to 19 and Comparative Examples 1 to 12.

･Manufacture of Cu nuclear ball Using the Cu balls of Examples 1 to 19 described above, for Examples 1A to 19A, a thickness of 23 μm on one side and a solder alloy of Composition Examples 1 to 2 were used to form a solder layer by electroplating to produce Example 1A to 19A Cu core ball.

Furthermore, using the Cu balls of Examples 1 to 19 described above, for Examples 1B to 19B, a Ni plating layer was formed as a metal layer with a thickness of 2 μm on one side, and a composition example 1 to 2 was used with a thickness of 23 μm on one side The solder alloy of Example 1B to 19B was produced by forming a solder layer by an electroplating method.

In addition, the Cu balls of Comparative Examples 1 to 12 were used to form a solder layer with a thickness of 23 μm on one side and the solder alloy of Composition Examples 1 to 2 to produce Cu core balls of Comparative Examples 1A to 12A. In addition, the Cu balls of the above Comparative Examples 1 to 12 were used to form a Ni-plated layer as a metal layer with a thickness of 2 μm on one side, and a solder layer was formed with a thickness of 23 μm on one side and using the solder alloy of Composition Examples 1 to 2 for comparison. Example 1B ~ 12B Cu core ball.

Hereinafter, each evaluation method of the true sphericity of Cu balls and Cu core balls, the amount of α-line of Cu balls, Vickers hardness, and discoloration resistance will be described in detail.

･Sphericality The sphericity of Cu spheres and Cu core spheres is measured using a CNC image measuring system. The device is Ultra Quick Vision and ULTRA QV350-PRO manufactured by Mitutoyo.

[Evaluation Criteria of Sphericality] In the following tables, the evaluation criteria for the sphericity of Cu balls and Cu core balls are as follows. ○○○: Sphericality is 0.99 or more ○○: The true sphericity is 0.98 or more and less than 0.99 ○: The true sphericity is 0.95 or more and less than 0.98 ×: The true sphericity is less than 0.95

·Vickers hardness The Vickers hardness of the Cu ball is measured in accordance with "Vickers hardness test-test method JIS Z2244". As the apparatus, a miniature Vickers hardness tester made by Akashi, and an Akashi micro hardness tester MVK-F 12001-Q were used.

[Vickers hardness evaluation criteria] In the following tables, the evaluation criteria for the Vickers hardness of Cu balls are as follows. ○: Greater than 0HV and less than 55.5HV ×: greater than 55.5HV

. alpha line The method for measuring the α-ray amount of Cu balls is as follows. The measurement of the amount of α-line is an α-line measuring device using an airflow ratio counter. The measurement sample is in a flat shallow-bottomed container of 300 mm×300 mm, and the Cu balls are covered until the bottom of the container cannot be seen. After putting this measurement sample into an α-ray measuring device and leaving the PR-10 airflow for 24 hours, the amount of α-ray was measured.

[Evaluation Criteria for α Line Amount] In the following tables, the evaluation criteria for the α line amount of Cu balls are as follows. ○: The amount of α line is 0.0200cph/cm ² or less ×: The amount of α line is more than 0.0200cph/cm ²

In addition, the PR-10 gas (90% of argon-10% of methane) used for the measurement was filled with PR-10 gas in a gas high-pressure tank for more than 3 weeks. Use the high-pressure tank that has been used for more than 3 weeks in accordance with JEDEC STANDARD-Alpha Radiation Measurement in Electronic Materials JESD221 (JEDEC Standard-Alpha Radiation Measurement JESD221) specified by JEDEC (Joint Electron Device Engineering Council; The radon that enters the atmosphere of the gas high-pressure tank does not produce an alpha line.

･Discoloration resistance In order to measure the discoloration resistance of the Cu ball, the Cu ball was heated at 200°C for 420 seconds using a thermostat in an atmospheric environment and the change in brightness was measured, and whether the Cu ball was sufficiently able to withstand the change with time was evaluated . Luminance is measured using a CM-3500d spectrophotometer made by Konica Minolta, at a D65 light source, a 10-degree field of view, and the spectral transmittance is measured according to JIS Z 8722 "Color Measurement Method-Color of Reflecting and Transmitting Objects". L*a*b*). In addition, (L*a*b*) is a substance specified in JIS Z 8729 "Color representation method-L*a*b* color system and L*u*v* color system". L* is brightness, a* is redness, and b* is yellowness.

[Evaluation criteria for discoloration resistance] In the following tables, the evaluation criteria for the discoloration resistance of Cu balls are as follows. ○: The brightness after 420 seconds is 55 or more ×: The brightness after 420 seconds is less than 55.

·Overview Cu balls having ○, ○○, or ○○○ in which any of the above-mentioned evaluation methods and evaluation criteria of true sphericity, Vickers hardness, α-line amount, and discoloration resistance were evaluated as ○ in the comprehensive evaluation. On the other hand, Cu balls with any one of X, sphericity, Vickers hardness, α-line amount, and discoloration resistance were evaluated as X in the comprehensive evaluation.

In addition, the Cu core ball having a true sphericity of ○ or ○○ or ○○○ in the above evaluation method and evaluation standard was evaluated as ○ in the comprehensive evaluation together with the evaluation of the Cu ball. On the other hand, Cu core balls with a true sphericity of × were evaluated as × in the comprehensive evaluation. In addition, even in the evaluation of the Cu core ball, the true sphericity is ○ or ○○ or ○○○. For the evaluation of the Cu ball, any one of the true sphericity, Vickers hardness, the amount of α line, and the discoloration resistance is The Cu core ball of × is evaluated as × by comprehensive evaluation.

In addition, since the Vickers hardness of the Cu core ball depends on the Ni plating layer which is an example of the solder layer and the metal layer, the Vickers hardness of the Cu core ball is not evaluated. However, when the Cu core ball and the Vickers hardness of the Cu ball are within the range specified in the present invention, the Cu core ball has good drop impact resistance and can suppress cracking and electrode collapse, and can also suppress electrical conductivity. Deterioration.

On the other hand, when the V core hardness of the Cu core ball is large and exceeds the range specified by the present invention, the durability against external stress becomes lower and the drop impact resistance becomes worse. The subject is prone to cracking.

Therefore, the Cu core balls using the Cu balls of Comparative Examples 8 to 11 having a Vickers hardness greater than 55.5 HV are not suitable for the evaluation of the Vickers hardness, so the comprehensive evaluation is evaluated as ×.

In addition, since the discoloration resistance of the Cu core ball depends on the Ni plating layer which is an example of the solder layer and the metal layer, the discoloration resistance of the Cu core ball is not evaluated. However, when the brightness of the Cu ball is within the range specified by the present invention, it is possible to suppress the sulfide and sulfur oxide on the surface of the Cu ball, and it is suitable to use a coating of a metal layer such as a solder layer or a Ni-plated layer.

On the other hand, when the brightness of the Cu ball is lower than the range specified by the present invention, the Cu ball cannot suppress the sulfide and sulfur oxide on the surface, and it is not suitable for coating with a metal layer such as a solder layer or a Ni plating layer.

Therefore, the Cu core balls of the Cu balls of Comparative Examples 1 to 6 having a brightness of less than 55 after 420 seconds were not suitable for evaluation of discoloration resistance, so the comprehensive evaluation was evaluated as ×.

In addition, the amount of α line of the Cu core ball depends on the composition of the plating solution raw material constituting the solder layer covering the Cu ball and each element in the composition. When the Ni plating layer as an example of the metal layer covering the Cu ball is provided, it also depends on the raw material of the plating solution constituting the Ni layer.

When the Cu ball is a low α-line amount specified by the present invention, and the raw material of the plating solution constituting the solder layer and the Ni plating layer is the low α-line amount specified by the present invention, the Cu core ball also becomes the low α-line amount specified by the present invention. On the other hand, when the raw material of the plating solution constituting the solder layer and the Ni-plated layer is a high α-line amount larger than the α-line amount specified by the present invention, even if the Cu ball is the above-mentioned low α-line amount, the Cu core ball becomes larger than that specified by the present invention The amount of alpha is high.

In addition, when the amount of α-line of the electroplating solution raw material constituting the solder layer and the Ni-plated layer shows a somewhat higher amount of α-line than the low amount of α-line specified by the present invention, it is possible to remove impurities by the above-mentioned plating process. It is reduced until the amount of α line is within the range of low α line prescribed by the present invention.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

As shown in Table 1, the Cu balls of each example with a purity of 4N5 or more and 5N5 or less can achieve good results in any comprehensive evaluation. Therefore, it can be said that the purity of the Cu ball is preferably 4N5 or more and 5N5 or less.

The details of the evaluation will be described below. As in Examples 1 to 12, 18, Cu balls with a purity of 4N5 or more and 5N5 or less, and containing Fe, Ag, or Ni of 5.0 mass ppm or more and 50.0 mass ppm or less are in the true sphericity , Comprehensive evaluation of Vickers hardness, the amount of α-line and discoloration resistance can obtain good results. As shown in Examples 13 to 17, 19, Cu balls with a purity of 4N5 or more and 5N5 or less and containing a total of 5.0 mass ppm or more and 50.0 mass ppm or less of Fe, Ag, and Ni, in terms of true sphericity, Vickers hardness, α-line amount and The comprehensive evaluation of discoloration resistance can also yield good results. In addition, it is not shown in the table that, from each of Examples 1, 18, and 19, the Fe content was changed to 0 mass ppm or more and less than 5.0 mass ppm, the Ag content was changed to 0 ppm or more and less than 5.0 mass ppm, and Ni was changed. Cu balls with a content of 0 mass ppm or more and less than 5.0 mass ppm and the total of Fe, Ag, and Ni set to 5.0 mass ppm or more are also comprehensively evaluated in terms of true sphericity, Vickers hardness, α-line amount, and discoloration resistance. Can get good results.

Furthermore, as shown in Example 18, Sb, Bi, Zn, Al, As, Cd, Pb, In, Sn, Au each containing Fe, Ag, or Ni of 5.0 mass ppm or more and 50.0 mass ppm or less and other impurity elements The Cu ball of Example 18 with 50.0 mass ppm or less can also obtain good results in the comprehensive evaluation of true sphericity, Vickers hardness, α-line amount, and discoloration resistance.

For the Cu core balls, as shown in Tables 3 and 4, by using the solder layer of the solder alloy of Composition Example 1 containing 0.7 mass% of Cu and the remainder being Sn, the Cu balls of Examples 1 to 19 were coated The formed Cu core balls of Examples 1A to 19A; and the Cu balls of Example 1 to Example 19 were coated with a Ni-plated layer, and then Example 1B formed by coating the solder layer using the solder alloy of Composition Example 1 The ~19B Cu core ball can also obtain good results in the comprehensive evaluation of the true sphericity.

Cu core balls of Examples 1A to 19A formed by covering the Cu balls of Example 1 to Example 19 by using the solder layer of the solder alloy of Composition Example 2 containing 3.0% by mass of Cu and the remainder of Sn; and The Cu balls of Examples 1 to 19 are coated with a Ni-plated layer, and then the Cu core balls of Examples 1B to 19B formed by coating the solder layer of the solder alloy of Composition Example 2 for comprehensive evaluation of the sphericity Good results can also be obtained.

In addition, it is not shown in the table. From Examples 1, 18, and 19, the Fe content was changed to 0 mass ppm or more and less than 5.0 mass ppm, and the Ag content was changed to 0 mass ppm or more and less than 5.0 mass ppm. The content of Ni is changed to a Cu ball of 0 mass ppm or more and less than 5.0 mass ppm, and the total of Fe, Ag, and Ni is set to 5.0 mass ppm or more, by using any of the solder alloys of Composition Example 1 to Composition Example 2 Cu core ball coated with a solder layer, and the Cu ball is coated with a Ni-plated layer, and then a Cu core ball coated with a solder layer using a solder alloy of any of Composition Example 1 to Composition Example 2, The comprehensive evaluation of the true sphericity can also get good results.

On the other hand, in the Cu ball of Comparative Example 7, not only the total content of Fe, Ag, and Ni was less than 5.0 mass ppm, but U, Tu was less than 5 mass ppb, and other impurity elements were less than 1 mass ppm. Comparative Example 7 Cu balls of Comparative Example 7, Cu balls of Comparative Example 7, Cu core balls of Comparative Example 7A covered with the solder layer of the solder alloy of each composition example, and Cu balls of Comparative Example 7 covered with Ni-plated layer, and further each composition The Cu core ball of Comparative Example 7B covered with the solder layer of the example solder alloy did not reach a sphericity of 0.95. In addition, even if an impurity element is contained, the Cu ball of Comparative Example 12 in which the total content of at least one of Fe, Ag, and Ni does not reach 5.0 mass ppm, and the Cu ball of Comparative Example 12 is obtained by using the solder alloy of each composition example The Cu core ball of Comparative Example 12A covered with a solder layer, and the Cu ball of Comparative Example 12 covered with a Ni-plated layer, and the Cu core of Comparative Example 12B formed by coating a solder layer using a solder alloy of each composition example Ball, the true sphericity has not reached 0.95 From these results, Cu balls with a total content of at least one of Fe, Ag, and Ni that did not reach 5.0 mass ppm, and Cu core balls formed by coating the Cu balls with the solder layer using the solder alloy of each composition example It can be said that the Cu core ball covered with the Ni plating layer and the Cu core ball formed by using the solder layer of the solder alloy of each composition example cannot achieve high sphericity.

In addition, in Comparative Example 10, the total content of Cu spherical Fe, Ag, and Ni was 153.6 mass ppm and the content of other impurity elements was each 50 mass ppm or less, but the Vickers hardness was more than 55.5 HV, and good results could not be obtained. Moreover, in the Cu ball of Comparative Example 8, not only the total content of Fe, Ag, and Ni is 150.0 mass ppm, but also the content of other impurity elements, especially Sn is 151.0 mass ppm, which is significantly greater than 50.0 mass ppm and the Vickers hardness is Above 55.5HV, good results cannot be obtained. Therefore, even if the Cu balls have a purity of 4 N5 or more and 5 N5 or less, the V-Vickers hardness of the Cu balls whose total content of at least one of Fe, Ag, and Ni exceeds 50.0 mass ppm becomes large, and it can be said that low hardness cannot be achieved. In this way, when the Vickers hardness of the Cu ball is larger than the range specified by the present invention, the durability against external stress becomes low and the drop impact resistance is deteriorated. At the same time, the problem that cracks easily occur cannot be solved. In addition, it can be said that each of them contains other impurities in the range not exceeding 50.0 mass ppm.

From these results, Cu balls with a purity of 4N5 or more and 5N5 or less and containing at least one of Fe, Ag, and Ni in a total content of 5.0 mass ppm or more and 50.0 mass ppm or less can be said to achieve high sphericity And low hardness and inhibit discoloration. A Cu core ball formed by coating the Cu ball with the solder layer of the solder alloy of each composition example, a Cu layer ball coated with the Ni-plated layer, and then a solder layer using the solder alloy of each composition example The Cu core ball realizes a high degree of sphericity, and by achieving a low hardness of the Cu ball, as a Cu core ball, it has good drop impact resistance and can suppress cracking and also suppress electrode collapse, etc., and can also suppress conduction Sexual deterioration. Furthermore, it is suitable for coating using a metal layer such as a solder layer, a Ni plating layer, and the like, by suppressing discoloration of Cu balls. The content of other impurities is preferably 50.0 ppm by mass or less.

Not shown in the table, Cu balls with the same composition and spherical diameters of 1 μm or more and 1000 μm or less are capable of comprehensive evaluation of true sphericity, Vickers hardness, amount of α line, and discoloration resistance. Get good results. Therefore, it can be said that the ball diameter of the Cu ball is preferably 1 μm or more and 1000 μm or less, and preferably 50 μm or more and 300 μm or less.

The Cu ball of Example 19 has a total content of Fe, Ag, and Ni of 5.0 mass ppm or more and 50.0 mass ppm or less and contains 2.9 mass ppm of P. In terms of true sphericity, Vickers hardness, amount of α line, and discoloration resistance Comprehensive evaluation can get good results. The Cu ball of Example 19 was coated with a solder layer using the solder alloy of each composition example, and the Cu ball of Example 19 was coated with a Ni plating layer, and then by using the solder alloy of each composition example The Cu core balls formed by the solder layer obtained good results in the comprehensive evaluation of the sphericity. The total content of Fe, Ag, and Ni in the Cu ball system of Comparative Example 11 is 50.0 mass ppm or less as in the Cu ball of Example 19, but the Vickers hardness is greater than 5.5 HV, which is different from the Cu ball of Example 19 result. In addition, the Vickers hardness of Comparative Example 9 was also greater than 5.5HV. This is considered to be because the P content of Comparative Examples 9 and 11 is significantly large. From this result, it is understood that when the P content increases, the Vickers hardness increases. Therefore, it can be said that the content of P is preferably less than 3 ppm by mass, and preferably less than 1 ppm by mass.

In the Cu balls of each example, the amount of α line is 0.0200 cph/cm ² or less. Therefore, in the solder alloy covering the composition examples 1 and 2 of the Cu balls of each of Examples 1 to 19, each element is a low α-line amount prescribed by the present invention, and the Cu core balls of each of the examples 1A to 19A also become the current The amount of low alpha line prescribed by the invention. In addition, when an Ni plating layer provided as an example of a metal layer coated with Cu balls is used, in addition to the solder alloy, each element constituting the Ni plating layer is a low α-line amount prescribed by the present invention, and each of Examples 1B to 19B The Cu core ball also becomes a low α-line amount prescribed by the present invention.

Furthermore, through the process of electroplating in the formation of the solder layer and the Ni-plating layer, the impurities of the radiated alpha rays contained in the alloy are removed, even if the alpha amount of the alloy before electroplating is lower than the low alpha amount prescribed by the present invention When showing a somewhat higher amount of α-line, the amount of α-line after electroplating can also be reduced to the range of low α-line amount specified by the present invention.

Accordingly, when the Cu core balls of the embodiments are used in high-density packaging of electronic parts, the material of the plating solution constituting the solder layer and the Ni-plated layer is a low α-line amount prescribed by the present invention, and soft errors can be suppressed.

In the Cu ball of Comparative Example 7, good results were obtained in the discoloration resistance, while on the other hand, in the Comparative Examples 1 to 6, the good results were not obtained in the discoloration resistance system. When comparing the Cu balls of Comparative Examples 1 to 6 with the Cu balls of Comparative Example 7, the difference in these compositions is only the content of S. Therefore, in order to obtain good results in discoloration resistance, it can be said that the S content must be less than 1 mass ppm. The content of S in any of the Cu spheres of each example is less than 1 mass ppm, and it can be said that the content of S is preferably less than 1 mass ppm.

Next, in order to confirm the relationship between the S content and the discoloration resistance, the Cu balls of Example 14, Comparative Example 1 and Comparative Example 5 were heated at 200° C., and before shooting heating, after heating for 60 seconds, after 180 seconds, 420 Photographs after seconds and the brightness is measured. Tables 7 and 5 are graphs showing the relationship between the time to heat each Cu ball and the brightness.

[Table 7]

From the table, when the brightness before heating and the brightness after 420 seconds of heating are compared, the brightness of Example 14, Comparative Examples 1, and 5 before heating is near the values of 64 and 65. After heating for 420 seconds, the brightness of Comparative Example 5 containing 30.0 ppm by mass of S became the lowest, followed by Comparative Example 1 containing 10.0 ppm by mass of S, and the order of Example 14 with an S content of less than 1 ppm by mass . Therefore, it can be said that the greater the content of S, the lower the brightness after heating. Since the Cu balls of Comparative Examples 1 and 5 have a brightness of less than 55, Cu balls containing S of 10.0 mass ppm or more form sulfides and sulfur oxides when heated, which can be said to be easily discolored. In addition, when the content of S is 0 mass ppm or more and 1.0 mass ppm or less, the formation of sulfides and sulfur oxides can be suppressed and it can be said that the wettability is good. In addition, when the Cu balls of Example 14 were packaged on the electrode, they exhibited good wettability.

As described above, the purity is 4N5 or more and 5N5 or less, the total content of at least one of Fe, Ag, and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, and the S content is 0 mass ppm or more and 1.0 mass ppm or less, P The Cu balls of the present embodiment having a content of 0 mass ppm or more and less than 3.0 mass ppm have a true sphericity of 0.95 or more, so that a high true sphericity can be achieved. By realizing high sphericity, it is possible to ensure self-alignment when encapsulating Cu balls in electrodes and the like, and suppress variations in the height of Cu balls. The Cu core balls formed by coating the Cu balls of this example with a solder layer; and the Cu core balls formed by coating the Cu balls of this example with a metal layer and further coating the metal layer with a solder layer can obtain the same effect.

In addition, since the Vickers hardness of any of the Cu ball systems of this embodiment is 55 HV or less, low hardness can be achieved. By realizing low hardness, the drop resistance of Cu balls can be improved. The Cu core ball formed by coating the Cu ball of this embodiment with a solder layer by achieving a low hardness of the Cu ball; and the Cu core formed of a metal layer by coating the Cu ball of this embodiment by using a metal layer The ball has good drop impact resistance and can suppress cracking, and can also suppress electrode collapse and the like and can also suppress deterioration of conductivity.

Furthermore, any of the Cu ball systems of this embodiment can suppress discoloration. By suppressing the discoloration of the Cu balls, and suppressing the adverse effects of sulfides and sulfur oxides on the Cu balls, the wettability when the Cu balls are packaged on the electrode is improved. The coating of a metal layer such as a solder layer or a Ni-plated layer is suitable for suppressing discoloration of Cu balls.

In addition, the Cu material system of this embodiment uses Cu bulk metal materials with a purity of more than 4N5 and 6N or less, and produces Cu balls with a purity of 4N5 or more and 5N5 or less, but even if a metal wire or plate material of more than 4N5 and 6N or less is used In addition, both the Cu ball and the Cu core ball can obtain good results in the comprehensive evaluation.

On the surface of the Cu ball 1, a Cu alloy ball 11A formed by forming a solder layer 3 using a solder alloy having a Cu content of more than 0% by mass and 3.0% by mass or less, the remainder being Sn and not containing Ag, 11B, even if the object to be joined is a Cu-OSP substrate obtained by applying a pre-flux treatment to the surface of the Cu layer, even if it is an electrolytic Ni/Au electroplated substrate obtained by performing electrolytic Ni/Au plating on the surface of the Cu layer, The strength of impacts such as falling and the strength of stretching caused by temperature changes called thermal cycles can obtain predetermined strengths deemed necessary.

Solder balls made using solder alloys that do not contain Ag have a lower thermal cycle strength than solder balls made using solder alloys that contain Ag. In the Cu core balls 11A and 11B of the respective examples, although the solder layer 3 is formed using a solder alloy not containing Ag, compared with the Cu core ball manufactured using a solder alloy containing Ag, in addition to being able to obtain the drop strength considered necessary In addition, the strength of the thermal cycle is increased.

Next, the distribution of elements other than Sn in the Cu layer in the Cu core ball formed by coating the surface of the Cu ball with the solder layer using the Sn-based solder alloy will be described. As a solder layer covering Cu balls, as shown in Japanese Patent Laid-Open No. 2007-44718 (referred to as Patent Document 4) and Japanese Patent No. 5367924 (referred to as Patent Document 5), it is possible to use a solder containing Sn as a main component alloy.

In Patent Document 4, the surface of the Cu ball is coated with a Sn-based solder alloy composed of Sn and Bi to form a solder layer. The Sn-based solder alloy containing Bi has a melting temperature of 130 to 140°C and is called low temperature solder.

In Patent Document 4, a concentration gradient in which the content of Bi contained in the solder layer is lighter on the inner side (inner peripheral side) and becomes thicker toward the outer side (outer peripheral side) is electroplated.

Patent Literature 5 also discloses a solder bump formed by plating a Sn-based solder alloy composed of Sn and Bi on Cu balls. In Patent Document 5, a concentration gradient in which the content of Bi contained in the solder layer is thicker on the inner side (inner peripheral side) and lighter toward the outer side (outer peripheral side) is electroplated.

The technical system of Patent Document 5 and Patent Document 4 have completely opposite concentration gradients. This is considered to be because the concentration control according to Patent Document 5 is simpler and easier to manufacture than when it is according to Patent Document 4.

As mentioned above, the elements added when the Sn-based solder alloy with Sn added to the binary element or more is plated on the surface of the Cu ball of the coating Cu ball and placed on the electrode of the semiconductor wafer for reflow treatment Patent Documents 4 and 5 having a concentration gradient in the solder layer cause the following problems.

The technique disclosed in Patent Document 4 has a solder layer having a Bi concentration that is lighter on the inner peripheral side and thicker on the outer peripheral side. When such a concentration gradient (the inner side is lighter and the outer side is thicker), the Bi melts. The timing may be slightly shifted between the inner peripheral side and the outer peripheral side.

When the melting timing shifts, the outer surface of the Cu core ball begins to melt, and the area on the inner peripheral surface side is a part of the molten and doped part that has not been melted. As a result, a slight position deviation occurs on the side where the core material melts shift. In a high-density package with a narrow pitch, this position shift may cause a fatal defect in the soldering process.

The concentration gradient of Bi in Patent Document 5 is opposite to that in Patent Document 1. At this time, in order to connect the semiconductor device, heat treatment by reflow is performed. As in Patent Document 5, when the Bi concentration in the solder layer is thicker on the inner peripheral side and lighter on the outer peripheral side, the Bi density on the inner peripheral side is higher, so the solder has a higher Bi density from the inner peripheral side. The area began to melt. Since the Bi region on the inner peripheral side melts, and the Bi region on the outer peripheral side has not yet begun to melt, volume expansion occurs relatively quickly on the Bi region side on the inner peripheral side.

Due to the speed of this volume expansion on the inner and outer peripheral sides, there is a pressure difference between the inner and outer peripheral sides of Bi (outside air), and when the outer peripheral side of Bi begins to melt, the pressure difference caused by the volume expansion on the inner and peripheral sides becomes the core The Cu ball produced a flying state. Such occurrences must be avoided.

In this manner, when the Cu core ball having the solder layer composed of the Sn-based solder alloy composed of Sn and Bi has a concentration gradient of Bi in the solder layer, defects occur.

Generally, a core material in which a binary or more solder alloy in which Cu is added to Sn is coated and nucleated. When Cu has a predetermined concentration gradient in the solder layer, it is considered to cause the same problem as Bi described above.

Therefore, the effect of the uniform distribution of Cu in the solder layer 3 will be described. In order to confirm that the Cu concentration distribution in the solder layer 3 is a value commensurate with the target value, the following experiment was performed. (1) A Cu core ball 11B having a composition (Sn-0.7Cu) of the solder layer 3 is manufactured under the following conditions. In the following examples, Cu balls having the composition of Example 17 shown in Table 1 were used. ･Cu ball 1 diameter: 250μm ･Thickness of metal layer (Ni-plated layer) 2: 2μm ･Film thickness of solder layer 3: 23μm ･Cu core ball 11B diameter: 300μm

In order to facilitate the measurement using the experimental results, as the Cu core ball 11B, a Cu core ball having a thin solder layer is manufactured.

The electroplating method is manufactured by electroplating technology. (2) Ten Cu core balls 11B formed with a solder layer of (Sn-0.7Cu) based solder alloy of the same composition are prepared as samples. Use these as Sample A. (3) Ten samples A were sealed with resin. (4) The sealed samples A and the resin were ground together and the cross-section of each sample A was observed. The observation device is FE-EPMAJXA-8530F manufactured by JEOL.

FIG. 6 is an explanatory diagram showing an example of a method of measuring the Cu concentration distribution of Cu core balls. The solder layer 3 is divided into an inner layer 16a, an intermediate layer 16b, and an outer layer 16c from the surface side of the Cu ball 1 for convenience. The inner layer 16a is from the surface of the Cu ball 1 to 9 μm, the intermediate layer 16b is from 9 to 17 μm, and the outer layer 16c is set to 17 to 23 μm. From the inner layer 16a, the intermediate layer 16b and the outer layer 16c, as in In this example, an inner layer region 17a, an intermediate layer region 17b, and an outer layer region 17c each having a thickness of 5 μm and a width of 40 μm are cut out in this example, and each region is used as a measurement region, and the concentration of Cu is measured by qualitative analysis. This operation is performed for each of the inner layer 16a, the intermediate layer 16, and the outer layer 16c for a total of 10 fields of view.

The concentration ratio of each layer obtained by measuring the Cu concentration of the inner layer, the intermediate layer, and the outer layer of the solder layer is shown in Table 8 below.

Table 8 shows the average value of the Cu concentration of each of the solder layers measured in each of the 10 Cu core balls in Sample A, and the Cu concentration ratio when the target Cu content (target value) is 0.7% by mass .

The sample A system measures the Cu concentration of the inner layer, the intermediate layer, and the outer layer for each of the 10 Cu core balls as described above. For sample A, the measured values of the Cu concentration of the inner layer, middle layer, and outer layer of each of the 10 Cu core balls are not shown in Table 8.

The target Cu content (target value) of sample A was 0.7% by mass. At this time, the Cu concentration ratio (%) of each of the 10 Cu core balls in the sample A was calculated from the Cu concentration measurement value and obtained by the following formula (1). Concentration ratio (%)=(measured value/0.7)×100･･･(1)

In addition, when the average value of the Cu concentration is 10 as the number of Cu core balls as a sample, it can be obtained by the following formula (2). The average value of the concentration of Cu = the total value of 10 measurement values/10･･･(2)

Furthermore, when the target Cu content (target value) is 0.7% by mass, the concentration ratio (%) of the sample A can be obtained from the average value of the measured values of the Cu concentration and by the following formula (3) . Concentration ratio (%) = (average of measured values/0.7) × 100･･･(3)

[Table 8]

As shown in Table 8, for Sample A, the average value of the Cu concentration in the inner layer region 17a is 0.58% by mass, the concentration ratio is 82.9%, and the average value of the Cu concentration in the intermediate layer region 17b is 0.68% by mass. The concentration ratio was 97.1%, the average value of the Cu concentration in the outer layer region 17c was 0.51% by mass, and the concentration ratio was 72.9%.

In this way, the inner layer region 17a, the middle layer region 17b, and the outer layer region 17c are each, because the Sb concentration in the solder layer is within the allowable range of 0.51% by mass to 0.68% by mass, and the concentration ratio is 72.9 to 97.1%, approximately The Cu concentration ratio falling within the target value is 70 to 130%.

Then, for example, 10 Cu core balls manufactured in the same batch as these Samples A are each extracted, and each is bonded to the substrate by a normal reflow process. The joint results are also shown in Table 8.

Regarding the results of the joining, those in which no defective joints were measured in all samples were judged as "good".

Either of the following situations does not occur: the inner peripheral side melts faster than the outer peripheral side and the volume expansion difference between the inner peripheral side and the outer peripheral side causes the Cu core ball 11B to fly out, and because the entire solder layer 3 is substantially uniform Ground melting and there is no possibility that the position of the core material is shifted due to the shift of the melting time sequence, so there is no possibility of short circuit between the electrodes due to the shift of the position or the like. Therefore, it is judged as "good" because no joint failure has occurred at all and a good result can be obtained.

As described above, in the case of the (Sn-0.7Cu) solder alloy, the results in Table 8 show that the range of 0.51% by mass (concentration ratio 72.9%) to 0.68% by mass (concentration ratio 97.1%) is an allowable range.

Next, the same measurement is performed when the solder layer 3 of the Sn-based solder alloy composed of (Sn-3Cu) is formed. At this time, the distribution of Cu is 3% by mass as a target value, and the allowable range is 2.45% by mass (concentration ratio 81.7%) to 3.26% by mass (concentration ratio 108.7%). The manufacturing method of the Cu core ball is the same as in the example using the Cu core ball using the solder alloy (Sn-0.7Cu) as the sample A described above.

The specifications of the diameters of the Cu balls and Cu core balls used, the thickness of the metal layer (Ni-plated layer) and the solder layer, and the experimental conditions are the same as those of the sample A except for the composition of the solder layer.

The results are shown as Sample B in Table 8. At this time, because the target value of Cu is 3% by mass, as shown in the sample B, it is 2.45~3.26% by mass (any one is the average of 10 measurements for the same sample), although there is some deviation (the minimum of the average 2.45 mass% (concentration ratio 81.7%) to a maximum of 3.26 mass% (concentration ratio 108.7%), but within the allowable range. Therefore, it is known that it falls between 2.45 mass% (concentration ratio 81.7%) to 3.26 mass% (concentration ratio 108.7%%). The joining determination system is the same as the example of Sample A, and since it is possible to obtain a good result that does not cause joint failure at all, it is determined as “good”.

The content (target value) of Cu targeted by sample B is 3 (mass %). Therefore, the concentration ratio (%) of the sample B in Table 8 can be obtained by the following formula (4).

Concentration ratio (%)=(average value of measurement value/3)×100･･･(4) Table 9 summarizes the results of Examples A and B. The concentration ratio of Cu is 72.9% to 108.7% by mass. Here, when measuring the true sphericity of the Cu core spheres prepared in the examples of sample A and the examples of sample B, either is 0.99 or more and satisfies 0.95 or more.

[Table 9]

The concentration ratio (%) in Table 9 can be obtained by the following formula (5). Concentration ratio (%)=(measured value/target value)×100･･･(5)

In addition, when the Cu concentration in the solder layer 3 changes, there is a phenomenon that a position shift occurs, the Cu core ball 11B is blown away, and the like.

As described above, in each of Examples A and B, since the Cu in the solder layer is homogeneous, the Cu concentration ratio of Cu in the entire region including the inner and outer peripheral sides is within a predetermined range with respect to the film thickness of the solder layer Inside. Therefore, the Cu core ball system of the present invention in which the Cu in the solder layer is homogeneous does not produce the following situation: the inner circumferential side melts faster than the outer circumferential side and the volume expansion difference between the inner circumferential side and the outer circumferential side causes the Cu core ball to burst. Flying matters.

In addition, since the Cu in the solder layer is homogeneous and the entire range of the Cu core ball melts substantially uniformly, there is almost no time difference in the melting timing in the solder layer. As a result, there is no possibility that the position of the Cu core ball will be shifted due to the shift of the melting time sequence, so there is no possibility that a short circuit or the like will occur between the electrodes due to the shift or the like. Therefore, by using the Cu core ball, a high-quality welding head can be provided.

1‧‧‧Cu ball 11A, 11B‧‧‧Cu core ball 2‧‧‧Metal layer 3‧‧‧ solder layer 10‧‧‧Semiconductor chip 16a‧‧‧Inner area 16b‧‧‧ Middle area 16c‧‧‧Outer area 17a‧‧‧Inner area 17b‧‧‧Middle level area 17c‧‧‧Outer area 100、41‧‧‧electrode 30‧‧‧Solder bump 40‧‧‧ printed circuit board 50‧‧‧welding head 60‧‧‧Electronic parts

Fig. 1 is a diagram showing a Cu core ball according to the first embodiment of the present invention. Fig. 2 is a diagram showing a Cu core ball according to the second embodiment of the present invention. FIG. 3 is a diagram showing a configuration example of an electronic component using Cu core balls according to each embodiment of the present invention. Figure 4 is an enlarged cross-sectional view of a Cu core ball. Fig. 5 is a graph showing the relationship between the heating time and the brightness of the Cu balls of Examples and Comparative Examples after heating at 200°C. FIG. 6 is an explanatory diagram showing an example of a method of measuring the Cu concentration distribution of Cu core balls.

1‧‧‧Cu ball

3‧‧‧ solder layer

11A‧‧‧Cu nuclear ball

Claims (19)

A Cu core ball comprising a Cu ball and a solder layer covering the surface of the Cu ball, Cu ball system The total content of at least one of Fe, Ag and Ni is 5.0 mass ppm or more and 50.0 mass ppm or less, The content of S is 0 mass ppm or more and 1.0 mass ppm or less, The content of P is 0 mass ppm or more and less than 3.0 mass ppm, The remaining part is Cu and other impurities. The purity of the aforementioned Cu balls is 99.995% by mass or more and 99.9995% by mass or less. The true sphericity is above 0.95, The aforementioned solder layer is a Sn-Cu solder alloy containing Sn and Cu. The Cu core ball as described in item 1 of the patent application scope, wherein the content of the aforementioned solder layer system Cu is greater than 0% by mass and 3.0% by mass or less, and Sn is the remainder. The Cu core ball as described in item 1 or 2 of the patent application scope, in which the solder layer is composed of (Sn-Cu) solder alloy containing Sn and 0.1 to 3.0% by mass of Cu, which will be contained in the solder layer The concentration ratio (%) of Cu is set as the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or When the concentration ratio (%) = (average of measured values (mass %)/target content (mass %)) × 100, the concentration ratio is in the range of 70.0 to 130.0%. The Cu core ball as described in item 1 or 2 of the patent application, wherein the solder layer is composed of a (Sn-Cu) solder alloy containing Sn and 0.1 to 3.0% by mass of Cu, Set the concentration ratio (%) of Cu contained in the solder layer to the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or When the concentration ratio (%) = (average measurement value (mass %)/target content (mass %)) × 100, the concentration ratio is in the range of 90.0 to 110.0%. The Cu core ball as described in item 1 or 2 of the patent application scope, wherein the solder layer is composed of (Sn-0.7Cu) solder alloy containing Sn and Cu, Set the concentration ratio (%) of Cu contained in the solder layer to the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or When the concentration ratio (%) = (average measurement value (mass %)/target content (mass %)) × 100, the concentration ratio is in the range of 72.9 to 97.1%. The Cu core ball as described in item 1 or 2 of the patent application range, wherein the solder layer is composed of (Sn-3.0Cu) solder alloy containing Sn and Cu, Set the concentration ratio (%) of Cu contained in the solder layer to the concentration ratio (%) = (measured value (mass %)/target content (mass %)) × 100, or When the concentration ratio (%) = (average of measured values (mass %)/target content (mass %)) × 100, The aforementioned concentration ratio is in the range of 81.7 to 108.7%. The Cu core ball according to any one of the items 1 to 6 of the patent application scope, wherein the true sphericity is 0.98 or more. The Cu core ball according to any one of the items 1 to 6 of the patent application range, wherein the true sphericity is 0.99 or more. The Cu core ball according to any one of items 1 to 8 of the patent application range, in which the amount of α line is 0.0200 cph/cm ² or less. The Cu core ball according to any one of items 1 to 8 of the patent application range, in which the amount of α line is 0.0010 cph/cm ² or less. The Cu core ball according to any one of claims 1 to 10, which includes a metal layer covering the surface of the Cu ball, and covers the surface of the metal layer with the solder layer and has a true sphericity of 0.95 or more. The Cu core ball as described in item 11 of the patent application scope, wherein the true sphericity is above 0.98. The Cu core ball as described in item 11 of the patent application scope, wherein the true sphericity is above 0.99. The Cu core ball according to any one of items 11 to 13 of the patent application range, in which the amount of α line is 0.0200 cph/cm ² or less. The Cu core ball according to any one of items 11 to 13 of the patent application range, in which the amount of α line is 0.0010 cph/cm ² or less. The Cu core ball according to any one of the items 1 to 15 of the patent application range, wherein the diameter of the Cu core ball is 1 μm or more and 1000 μm or less. A welding head uses the Cu core ball as described in any one of the patent application items 1 to 16. A solder paste using the Cu core ball as described in any one of patent application items 1 to 16. A foam solder uses the Cu core ball as described in any one of the patent application items 1 to 16.

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