TWI540015B - Lead free solder ball - Google Patents

Description

Lead-free solder balls

The present invention relates to a lead-free solder ball for use in an electrode of an electronic component such as a semiconductor. In particular, in the Ni electrode portion such as Au plating and Cu, a Cu electrode portion coated with a water-soluble preflux can be used at the same time, and a lead-free solder ball having a low failure mode when the electronic component on which the electrode is mounted can be used.

Recently, electronic devices used in electronic devices have been miniaturized and multi-functionalized due to miniaturization of electronic devices and speeding up of electronic signals. The electronic components that are miniaturized and multi-functional are BGA (Ball Grid Array), CSP (Chip Size Package), and MCM (Multi Chip Module) (hereinafter referred to as BGA). The BGA is on the back surface of the BGA substrate, and a plurality of electrodes are provided on the substrate in a lattice position. When the BGA is mounted on a printed circuit board, it is performed by soldering a BGA electrode and a solder pad of the printed circuit board. When the printed circuit board of the BGA is mounted, not only the solder is supplied to each electrode but also the welding is laborious, and the solder is not supplied from the outside to the electrode in the middle of the substrate. Here, in order to mount the BGA on the printed circuit board, a method of placing the solder on the BGA electrode in advance is performed. This is referred to as solder bump formation.

Solder balls, solder paste, etc. are used for the solder bump formation of the BGA. When a solder bump is formed by solder balls, an adhesive flux is applied to the BGA electrode, and the solder ball is placed on the electrode coated with the flux. Thereafter, the BGA substrate is heated by a heating device such as a reflow furnace, and solder bumps are formed on the electrodes by melting the solder balls. A semiconductor substrate such as a BGA substrate or a CSP substrate is collectively referred to as a module substrate. Further, when solder bumps are formed on the wafer pads by solder paste, a metal mask having holes of about the same size as the pads is placed at a position corresponding to the wafer pads, and the metal mask is soldered. The paste is flattened with a squeegee and the solder paste is applied to the wafer pads. Thereafter, the wafer is heated in a reflow furnace to melt the solder paste to form solder bumps.

In other words, in the conventional BGA system, a tin ball of a Sn-Pb alloy is used as a solder bump. The Sn-Pb solder ball not only has good solderability to the BGA electrode, but particularly, the eutectic composition of the Sn-Pb has a melting point which does not cause thermal influence on the BGA element or the substrate during soldering, and has a soft Pb. Therefore, even if an electronic component or an electronic device is used, the impact can be absorbed, and the life of the electronic component or the electronic device can be greatly contributed. At present, the use of Pb is regulated on a global scale. Of course, the Sn-Pb eutectic composition used is also regulated by conventional soldering.

Conventionally, a Sn-Ag-Cu-based solder alloy such as Sn-3.0Ag-0.5Cu or Sn-4.0Ag-0.5Cu has been used as a composition of lead-free solder balls for BGA. Although the lead-free solder alloys have good temperature cycling characteristics, when the portable electronic device using the solder balls composed of the solder alloys is dropped, the interface peeling off from the solder ball connection interface is liable to occur, and thus it is considered to be inferior. Falling impact.

The composition of the solder alloy for lead-free solder balls for preventing the impact of portable electronic devices is characterized by mass% from (1) Ag: 0.8 to 2.0%, (2) Cu: 0.05 to 0.3%, and 3) In: 0.01% or more, not more than 0.1%, Ni: 0.01 to 0.04%, Co: 0.01 to 0.05%, and Pt: 0.01 to 0.1%, one or more selected from the group, and the remaining part of Sn. The lead-free solder alloy (WO2006/129713A, Patent Document 1) is a lead-free solder alloy comprising Ag: 1.0 to 2.0% by mass, Cu: 0.3 to 1.5% by mass, and the remaining portion of Sn and incidental impurities. Further, it includes one or two or more kinds of Sb: 0.005 to 1.5% by mass, Zn: 0.05 to 1.5% by mass, Ni: 0.05 to 1.5% by mass, and Fe: 0.005 to 0.5% by mass, and Sb, Zn, Ni, and Fe. A lead-free solder alloy having a total content of 1.5% by mass or less (JP-A-2002-239780, Patent Document 2), which satisfies 0.1 to 1.5% of Ag, 0.5 to 0.75% of Cu, and 12.5 ≦Cu/Ni by mass%. A lead-free solder alloy composed of Ni, a remaining portion of Sn, and an incidental impurity of ≦100 (WO2007/081006A, Patent Document 3), containing Ag: 1.0 to 2.0% by mass, Cu: 0.3 to 1.0% by mass, and Ni: 0.005 ~0.10% by mass, a remaining portion of Sn, and a lead-free solder alloy composed of incidental impurities (WO2007/102588A, Patent Document 4). In addition, a method of applying a flux to an electrode portion of a module substrate as a method of unbonding when a module such as a BGA substrate is bonded to a printed circuit board is disclosed (WO2006-134891A, Patent Document 5).

[Previous Technical Literature]

[Patent Document]

[Patent Document 1] WO2006/129713A

[Patent Document 2] JP-A-2002-239780

[Patent Document 3] WO2007/081006A Bulletin

[Patent Document 4] WO2007/102588A Bulletin

[Patent Document 5] WO2006/134891A

In order to improve the drop impact resistance of the Sn-Ag-Cu type solder ball, the patent documents 1 to 4 reduce the content of Ag and lower the hardness of the solder, thereby increasing the amount of impact absorption and reducing the content of Cu. The intermetallic compound layer such as Cu6Sn5 on the joint surface of the solder pad and the solder is thinned to prevent the loss of the content of Ag and Cu by adding the iron group element such as Ni, Fe, Co, etc. The strength of the solder itself is improved.

However, even if a solder ball which is resistant to falling impact measures of Patent Documents 1 to 4 is used, there is a problem that the malfunction caused by the falling of the electronic device cannot be reduced. When this point is analyzed, it is understood that the failure caused by the falling of the electronic device in the increase is not only caused by the bonding interface between the solder ball and the substrate as disclosed in Patent Documents 1 to 5, as compared with the conventional Sn-Pb solder. When bonding to a module substrate such as a BGA substrate or a printed circuit board, the solder component called the solder ball for the BGA electrode is not mixed with the solder component of the solder paste for soldering the printed circuit board (Fig. 1). Defects are new defects due to the transfer of conventional Sn-Pb solder to lead-free solder.

However, it can be understood that the unfused generation system mostly occurs in a tin ball composed of Sn-Ag-Cu-Ni which is developed as a countermeasure against drop impact by the solder ball composed of Sn-3.0Ag-0.5Cu. problem. Most of the reasons for the unfusion are to improve the impact of the solder ball. Therefore, the added Ni forms Sn and the intermetallic compound, and the precipitation of the solder ball surface interferes with the solder composition of the solder ball and the solder paste and solder composition.

Also, the following may also be the cause of unfusion. When the printed substrate is heated and the bending is severe, the solder balls are separated from the solder paste. When the separation solder ball and the solder paste are maintained for heating, the solder ball will be oxidized due to high temperature. When the flux exuded by the solder paste covers the surface of the solder ball and the flux loses its active force, the oxide film on the surface of the solder ball cannot be removed even when the solder paste is in contact with the solder ball during the cooling process during the cooling process, so Fusion. As this countermeasure, the method of Patent Document 5 is effective.

Next, it is clarified from the examples that the unfused system is composed of a composition of a solder ball, resulting from a compound formed inside the solder ball, Cu6Sn5 or (Cu, Ni)6Sn5. When the component to which the solder ball is bonded is mounted on the mounting substrate, the mounting substrate on which the solder paste is applied is printed, and the electrode side to which the solder ball is bonded is placed downward. After that, heating is performed, and the solder ball is melted while the solder ball is melted until it is fused. However, when a large amount of the compound Cu6Sn5 or (Cu, Ni)6Sn5 formed inside the solder ball is generated, the inside of the compound sinks the ball when the solder ball is melted, and precipitation occurs in the vicinity of the outermost surface of the bump. By this phenomenon, it was confirmed that the fusion of the solder paste was hindered and the cause of the fusion failure was caused (Fig. 2, Fig. 3).

For solder balls for BGA or CSP, drop resistance is necessary of. One of the effective means for resisting the impact of falling, the modification of the interface compound, as disclosed in Patent Documents 1 to 4, the addition of Ni is a means of improvement. However, in the unfused viewpoint, Ni also becomes an element which produces a compound, and thus the amount which can be added is limited. When it is considered that it is not fused and inhibits the addition of Cu or Ni, it is not suitable for the solder ball which is mounted on a portable device such as a BGA or a CSP because it loses the drop impact resistance.

The problem to be solved by the present invention is to develop a solder ball of a Sn-Ag-Cu-Ni composition which is improved in solder strength such as drop impact resistance, and to develop a solder alloy for solder balls which does not undergo unfusion, and to suppress the solder ball. The interface in the bonding interface is peeled off, and by suppressing the unfusion caused between the solder ball and the solder paste, the failure mode when the electronic component is dropped is low, and the bonded printed substrate is even in the implementation of the Cu electrode and the Ni underlayer. On the Au plating or Au/Pd plating surface treatment of electrolytic Ni/Au and electroless Ni/Pd/Au electrolysis, it is also possible to obtain a solder ball for BGA or CSP having an effect.

The present inventors have found that the drop impact resistance and the unintegrated incidence rate are low iron ball solder alloys caused by the fall of the portable electronic device, and the iron alloy gold containing the Ni in the impact solder alloy is dropped. When the surface of the solder ball is deposited, the incidence of unfusion will become high and the failure caused by the falling of the portable electronic device will often occur, so as to specify the amount of Ni added to the solder alloy, so that the unfused, portable The problem caused by the fall of the electronic device is reduced, and the present invention is completed.

In the present invention, Ag is set to 0.5 to 1.1% by mass, and Cu is set to 0.7 to 0.8% by mass, and the remainder is Sn as a Sn-Ag-Cu base solder. For this reason, the tin ball of the present invention is reduced in the amount of Cu in the solder alloy composed of the Sn-Ag-Cu3 element, and in the patent documents 1 to 4 in which the intermetallic compound of Cu6Sn5 formed at the interface of the Cu electrode is suppressed. The difference in the technique is that the Cu content in the Sn-Ag-Cu3 element solder alloy is in the vicinity of the eutectic point of 0.75 mass%, and the addition of Ni does not reduce the Cu content in the solder, thereby inhibiting the formation of Intermetallic compound of Cu6Sn5 at the interface of Cu electrode.

This is because the Cu content in the solder alloy composed of the Sn-Ag-Cu3 element of the present invention is limited to the vicinity of the eutectic point of 0.75 mass%, and the Cu is in the solder alloy of the Sn-Ag-Cu3 element in a saturated state. Cu diffusion is suppressed by the Cu electrode.

Another feature of the tin ball of the present invention is that the Cu content in the solder alloy composed of the Sn-Ag-Cu3 element is set to be about 0.75 mass% in the vicinity of the eutectic point, not only suppressing Cu diffusion from the Cu electrode, but also The same effect can be obtained also for Ni in the relationship between Cu and a completely solid solution, and therefore has an effect of suppressing Ni diffusion even at the Ni electrode. Further, by adding Ni in advance to the solder, the effect of suppressing the diffusion of Ni and Cu from the component electrode and the substrate electrode is improved, and the formation of the joint interface by the fine intermetallic compound is resistant to the Ni electrode. The impact of falling is also improved.

The Ag of the present invention is 0.5 to 1.1% by mass, Cu is 0.7 to 0.8% by mass, and the amount of Ni added to the tin solder for the remaining portion of Sn is 0.05 to 0.08% by mass. In the present invention, it will be added to Sn-Ag-Cu The amount of Ni in the solder alloy is 0.05 to 0.08 mass%, and Ni is not concentrated on the surface of the Sn-Ag-Cu solder ball, and the solder ball for the BGA electrode having better temperature cycle characteristics and drop impact resistance can be obtained. .

In the present invention, the Cu content in the Sn-Ag-Cu3 element solder alloy is in the vicinity of the eutectic point of 0.75 mass%, and the formation of Cu is suppressed even if the Cu content in the solder is not reduced by adding Ni. Intermetallic compound of Cu6Sn5 at the electrode interface. Further, by adding a small amount of Ni of the present invention to the Sn-Ag-Cu3 element solder alloy, the SnCu compound: Cu6Sn5 in the solder is fine, and the particles of the intermetallic compound formed at the interface between the part and the substrate electrode are also changed. It is small and forms a joint interface that is not easily damaged.

When the amount of Ni added is less than 0.05% by mass and is too small, the above-described effects are not easily obtained, and the drop impact resistance cannot be improved. In addition, when the amount of addition exceeds 0.08 mass% and is excessive, the concentration of Ni in the joint interface compound increases, and a weak and fragile joint interface is formed, so that the drop impact resistance is reduced. Moreover, excessive addition of Ni cannot avoid an increase in solder hardness and is not suitable for impact resistance. Thus, when the amount of Ni added is insufficient, the drop impact resistance tends to decrease.

By using the tin ball of the present invention, the Cu electrode and the Ni electrode have the drop impact resistance, and the effect of the non-fusion suppression can be used to reduce the failure mode when the electronic component on which the electrode is mounted is lowered. The ball system has the advantage of being able to flexibly respond to frequently changing electrodes.

According to the solder ball of the present invention, even if a water-soluble preflux (also referred to as OSP or Organic Solderbility Preservatives) is applied to the Cu electrode of the Cu pad, Ni plating such as Au plating or Pd/Au plating is used. In the Ni electrode of the electrode of the substrate, it is also possible to obtain the bonding of the electrode of the BGA or CSP in the low failure mode when the electronic component is dropped to the printed substrate.

1‧‧‧BGA parts

2‧‧‧Installation substrate

3‧‧‧ solder bump fusion

4‧‧‧ solder bumps are not fused

5‧‧‧Installing heated solder balls

6‧‧‧Installing heated solder paste

7‧‧‧Unfused

8‧‧‧ Compounds that are hindered by fusion

9‧‧‧BGA side electrode

10‧‧‧ joint interface compound with drop resistance

11‧‧‧ solder bumps

12‧‧‧ Joint interface compounds that do not have drop-resistant properties due to insufficient Cu content

13‧‧‧ Does not have the resistance to falling due to insufficient Ni content Interface compound

14‧‧‧ solder pads

[Fig. 1] An example of unfused phenomenon

[Fig. 2] Example of fusion of solder paste caused by compounds inside the solder ball

[Fig. 3] An enlarged view of the fusion of the solder paste caused by the compound inside the solder ball

[Fig. 4] The joint interface compound layer in Example 2

[Fig. 5] The bonding interface compound layer in Comparative Example 9

[Fig. 6] The bonding interface compound layer in Comparative Example 10

[Fig. 7] Mode diagram of interface peeling

[Fig. 8] Unfused mode diagram

[Embodiment]

The Cu layer electrode of the present invention has a drop ball impact resistance similar to that of the Ni electrode, and is preferably used for forming a bump of a PKG member such as a BGA or a CSP having a lower electrode.

The Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention, in Ag When the content is less than 0.5% by mass, the solder strength is lowered, and when the impact stress due to dropping or the like is taken, there is a problem that the solder is easily broken. When the content of Ag exceeds 1.1% by mass, the hardness of the solder becomes high, and the impact absorption is lowered, so that the interface is peeled off. Therefore, in the alloy for a solder ball of the present invention, the content of Ag must be 0.5 to 1.1% by mass, and 0.9 to 1.1% by mass is preferable.

Further, the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention has a Cu content of less than 0.7% by mass and is separated by a eutectic point of Sn-Ag-Cu, so that it is used for a Cu electrode. When the Cu electrode Cu is diffused into the solder, the intermetallic compound of Cu6Sn5 at the interface of the Cu electrode becomes thick, and the drop impact resistance is deteriorated. When the content of Cu in the Sn-Ag-Cu-Ni solder alloy exceeds 0.8% by mass, since it is separated from the eutectic point of Sn-Ag-Cu, it becomes in the reaction layer between the solder alloy and the Cu electrode. As a result, the intermetallic compound of Cu6Sn5 is likely to be generated, and as a result, the intermetallic compound of Cu6Sn5 formed at the interface between the Cu electrode and the solder joint interface portion becomes thick. Therefore, the content of Cu contained in the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention must be 0.7 to 0.8% by mass.

Further, in the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention, the content of Ni is less than 0.05% by mass, and the effect of adding Ni does not occur, and the Ni electrode Ni is easily diffused at the interface. Since the intermetallic compound is easily formed, the Ni content in the Sn-Ag-Cu-Ni solder alloy must be 0.05% by mass or more. In the same manner, when the content of Ni exceeds 0.08 mass%, the hardness of the solder increases as the concentration of Ni in the intermetallic compound formed at the joint interface increases and the joint strength decreases. In the case of an impact, the interface peeling will become easy to occur. Further, when the content of Ni exceeds 0.08% by mass, the rate of non-fusion is increased. Therefore, the Ni content of the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention must be 0.05 to 0.08% by mass.

In the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention, one or more elements selected from the group consisting of Fe, Co, and Pt may be further added in a total amount of 0.003 to 0.1% by mass. The addition of an alloy for solder balls of Fe, Co, and Pt elements has an effect of improving the drop because the intermetallic compound formed at the joint interface is made finer and the thickness is suppressed. The element selected from Fe, Co, and Pt is less than 0.003 mass%, and it is extremely difficult to obtain the above effect. When the addition is more than 0.1 mass%, the solder bump hardness increases and the interface peeling adversely affects the impact.

In the Sn-Ag-Cu-Ni solder alloy of the solder ball of the present invention, one or more elements selected from the group consisting of Bi, In, Sb, P, and Ge may be further added in a total amount of 0.003 to 0.1% by mass.

After the solder ball is mounted on the module substrate, the determination of whether or not to solder is performed by image recognition. If the tin ball is discolored to yellow or the like, it is determined to be a malfunction in the image recognition. Therefore, it is preferred that the solder balls are not discolored by reflow.

The effect caused by the addition of Bi, In, Sb, P, and Ge is such that it is possible to avoid errors in the bump quality inspection by preventing discoloration due to heat or the like. The element selected from Bi, In, Sb, P, and Ge is less than 0.003 mass%, and it is extremely difficult to obtain the above effect. When the addition is more than 0.1 mass%, the solder bump hardness increases and the effect of the drop improvement may be lost.

The tin ball of the present invention is used as an electrode. The diameter of the solder ball is 0.1 mm or more and 0.3 mm or more are preferable, and 0.5 mm or more is preferable. In recent years, the miniaturization of electronic devices has progressed, and the solder balls mounted on electronic components have continued to be miniaturized. For the bonding of the flip chip, a solder ball of 0.1 mm or less is widely used, and the solder ball for the electrode containing the CSP or the BGA of the solder ball of the present invention is 0.1 mm or more in the mainstream.

[Examples]

A solder alloy composed of the following table was produced, and a solder ball having a diameter of 0.3 mm was produced by a gas ball formation method (gas phase method). Using this solder ball, a CSP substrate was manufactured by the following procedure.

1. In the CSP module substrate, reflow soldering is performed using flux WF-6400 manufactured by Senju Metal Industry Co., Ltd., and each component of the solder is used as an electrode to manufacture a CSP, wherein the CSP module substrate has a size. Electrolytic Ni/Au, electrolyzed Ni/Pd/Au, Cu pads of 12×12 mm, electrodes treated with OSP for solder balls of various compositions.

2. A glass epoxy substrate (FR-4) having a size of 30 × 120 mm and a thickness of 0.8 mm was printed in accordance with an electrode pattern and solder paste. The CSP manufactured in 1 was mounted at 220 ° C for 40 seconds and the peak temperature was 245 ° C. The conditions are to be refluxed.

3. The drop impact test was carried out by the following conditions. In the test method, a glass epoxy substrate was mounted on a CSP manufactured in 2, and the both ends of the substrate were fixed at a position of 10 mm from the pedestal using a special jig. According to the JEDEC standard, an impact of an acceleration of 1500 G was repeatedly applied, and a period in which the initial resistance value was increased by 1.5 times was regarded as a fracture, and the number of drops was recorded.

In many solder balls using a Sn-Ag-Cu-Ni-based solder alloy containing Ni as in Patent Document 2, it is understood that the drop impact resistance cannot be obtained even when the Ni electrode is welded.

The same solder balls were used even if the fusion rate was not used, and the CSP substrate was fabricated by the following procedure.

1. The solder balls of each composition were subjected to a treatment at a temperature of 110 ° C and a humidity of 85% for 24 hours.

2. A glass epoxy substrate (FR-4) having a size of 36 × 50 mm and a thickness of 1.2 mm was printed with a solder paste according to an electrode pattern, and a solder ball manufactured by 1 was mounted, and the solder ball was made at a temperature of 220 ° C or more and 40 seconds. °C conditions to enter Line backflow.

3. Using a stereomicroscope, record the unfused number of solder balls and solder paste, and calculate the incidence of unfusion.

Next, using the manufactured solder balls, the wet expansion test was carried out in the following procedure. The substrate material used was the same as the substrate on which the incidence of fusion was investigated.

1. Using a 1.2 mm thick glass epoxy substrate (FR-4) forming a 0.24 mm × 16 mm slit electrode, printing 0.24 mm The flux WF-6400 manufactured by Senju Metal Industry Co., Ltd. with a thickness of 0.1 mm was placed on a solder ball and refluxed at 220 ° C for 40 seconds and a peak temperature of 245 ° C.

2. Using a stereomicroscope, measure the area of the wet enlargement.

In Comparative Examples 7, 9, 10, 11, and 13, the content of the Cu layer is more than 0.8% by mass or the content of the Ni layer is more than 0.07% by mass, which is a composition of the tin-ball alloy contained therein. Therefore, the rate of non-fusion is more than 8%, and the suppression cannot be suppressed. effect.

In particular, the incidence of unfusion of the solder composition Sn-1.5Ag0.5Cu-0.5Ni described in Patent Document 2 of Comparative Example 13 was remarkably increased. This is because the amount of Ni contained in the solder is excessive, and when the generated compound becomes excessive, the fusion property of the solder paste is hindered, and as a result, the rate of unfusion is increased.

In the same Comparative Examples 10 and 11, the Cu content was too large, so that the generated compound became excessively large, and the induced fusion did not occur.

Further, in Comparative Examples 1 and 2, since the amount of Ag was small, it was found that the wet expansion was remarkably lowered. When actually compared with Example 1, the area of wet expansion decreased by about 20% or more. When there is insufficient expansion of moisture, is there any The method is well joined and does not fully maintain the strength of the joint.

In Comparative Examples 3 to 6, 8, 12, 14, and 15, the non-fusion occurrence rate was less than 5%, and the moisture content of the sufficient portion was ensured to be enlarged, but the contents of Ag, Cu, and Ni were not optimized, and thus the ratio was changed. Can't get the drop improvement effect.

Here, the Cu content in the Sn1Ag is fixed to 0.7% by mass, and the Ni content is focused on. When the Ni content is more than 0.08% by mass and 0.1% by mass is selected, the rate of non-fusion is remarkably increased. On the other hand, when it is less than 0.05% by mass and 0.02% by mass is selected, the effect of suppressing unfusion is obtained, but the resistance to fall characteristics cannot be obtained. In general, by selecting the Ni content in an amount of 0.05 to 0.08% by mass, it is possible to obtain a solder alloy having both unmated suppression and drop resistance.

Next, the content of the Cu layer in which the Ni content in Sn1Ag was fixed to 0.05% by mass was confirmed, and the range of improvement with no fusion inhibition and drop resistance was confirmed. When the Cu content exceeds 0.8% by mass and 1% by mass is selected, the rate of unfusion is remarkably increased. In addition, when it is less than 0.7% by mass and 0.5% by mass is selected, the effect of improving the drop is not accompanied, and it is preferable to determine the Cu content of 0.7 to 0.8% by mass as the solder alloy having both of them.

It is concluded that in the composition consisting of Ag 0.5 to 1.1% by mass, Cu 0.7 to 0.8% by mass, Ni 0.05 to 0.08% by mass, and the remaining portion of Sn, the Ni electrode portion such as Au plating and Cu, The Cu electrode portion coated with the water-soluble preflux can be used in combination, and both the interface peeling suppressing effect and the non-fusion suppressing effect can be obtained, so that a solder alloy having a low failure mode when the electronic component of the electrode is dropped can be obtained.

[Industrial Applicability]

According to the present invention, there is provided a solder ball for an electrode which is resistant to drop impact regardless of a Cu electrode or a Ni electrode. When the amount of Ni added to the solder alloy of the ternary composition of the Sn-Ag-Cu is more than 0.1% by mass and is too large, the compound containing Ni on the surface of the solder ball is likely to be precipitated and the fusion of the solder paste is likely to occur. In the tin ball system of the present invention, the amount of Ni is suppressed to 0.05 to 0.08% by mass. Therefore, the phenomenon that the compound precipitates on the surface of the solder ball is less likely to occur, and the effect of suppressing the unfusion phenomenon is also exhibited.

Claims (13)

A lead-free solder solder ball characterized in that it is mounted on a module substrate for BGA and CSP, and is used as a solder ball for an electrode, and is composed of Ag 0.5 to 1.1% by mass, Cu 0.7 to 0.8% by mass, and Ni0.05. ~0.08 mass%, and the remaining part of Sn constitutes a solder composition. The lead-free solder ball of claim 1, wherein the solder composition is composed of a solder composed of Ag 0.9 to 1.1% by mass, Cu 0.7 to 0.8% by mass, Ni 0.05 to 0.08% by mass, and a remaining portion of Sn. The lead-free solder solder ball of claim 1, wherein the solder composition is composed of a solder composed of Ag 1.0% by mass, Cu 0.75% by mass, Ni 0.07% by mass, and the remaining portion Sn. The lead-free solder ball of claim 1, wherein one or more elements selected from the group consisting of Fe, Co, and Pt are added to the solder composition in a total amount of 0.003 to 0.1% by mass. The lead-free solder ball of claim 1, wherein one or more elements selected from the group consisting of Bi, In, Sb, P, and Ge are added to the solder composition in a total amount of 0.003 to 0.1% by mass. The lead-free solder solder ball of claim 1, wherein the solder composition is composed of Ag 0.9 to 1.1% by mass, Cu 0.7 to 0.8% by mass, Ni 0.05 to 0.08% by mass, and remaining portion Sn, further in the foregoing One or more elements selected from Fe, Co, and Pt are added to the solder composition, and the total amount is 0.003 to 0.1% by mass. A lead-free solder solder ball of claim 1, wherein The solder composition is composed of Ag 1.0% by mass, Cu 0.75% by mass, Ni 0.07% by mass, and remaining portion Sn, and further adds one or more elements selected from Fe, Co, and Pt to the solder composition, for a total of 0.003. ~0.1% by mass. The lead-free solder solder ball of claim 1, wherein the solder composition is composed of Ag 0.9 to 1.1% by mass, Cu 0.7 to 0.8% by mass, Ni 0.05 to 0.08% by mass, and remaining portion Sn, further in the foregoing One or more elements selected from Bi, In, Sb, P, and Ge are added to the solder composition, and the total amount is 0.003 to 0.1% by mass. The lead-free solder solder ball of claim 1, wherein the solder composition is composed of Ag 1.0% by mass, Cu 0.75% by mass, Ni 0.07% by mass, and a remaining portion of Sn, and further added to the solder composition by Bi, One or more elements selected from In, Sb, P, and Ge are 0.003 to 0.1% by mass in total. The lead-free solder ball of any one of claims 1 to 9, wherein the solder ball has a diameter of 0.1 mm or more. The lead-free solder ball of any one of claims 1 to 9, wherein the solder ball has a diameter of 0.3 mm or more. The lead-free solder ball of any one of claims 1 to 9, wherein the solder ball has a diameter of 0.5 or more. Method for forming solder bumps of module substrate, which is a method for forming solder bumps on a module substrate having electrodes selected by electrolyzing Ni/Au electrodes, electroless Ni/Pd/Au electrodes, and Cu-OSP electrodes Use solder balls of any of claims 1 to 9 for soldering.