TWI762200B - Solder alloy, solder powder, solder paste, solder ball, solder preform and solder joint - Google Patents

Abstract

The present invention uses a solder alloy which has an alloy composition including U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm or more and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less and the balance of Sn, satisfies the formula (1), and has an α ray dose of 0.02 cph/ cm² or less.

20 ≦ Ni + Fe ≦ 700 (1)

In the formula (1), Ni and Fe each represents the content (mass ppm) in the alloy composition.

According to the solder alloy of the present invention, the increase in viscosity of solder paste over time can be suppressed, the short circuit in circuits can be less likely to cause, the mechanical strength of solder joint can be increased, and the occurrence of soft errors can be suppressed.

Description

Solder alloys, solder powders, solder pastes, solder balls, solder preforms and solder joints

The present invention relates to solder alloys, solder powders, solder pastes, solder balls, solder preforms and solder joints.

This application claims priority based on Japanese Patent Application No. 2020-070927 for which it applied to Japan on April 10, 2020, the content of which is incorporated herein by reference.

In electronic components mounted on printed circuit boards, miniaturization and high performance are increasingly required. As such an electronic component, a semiconductor package is mentioned, for example. In the semiconductor package, a semiconductor element having electrodes is packaged with a resin composition. Solder bumps made of solder material are formed on the electrode system. In addition, the solder material connects the semiconductor element and the printed circuit board.

In solder materials, the effect of alpha rays on soft errors becomes problematic. In order to alleviate such adverse effects on the operation of semiconductor devices, development of low alpha radiation dose materials containing solder materials has been carried out.

The main cause of the α-ray source is, for example, the solder alloy in the solder material, especially the trace amount of radioactive elements contained in the tin (Sn) base metal that becomes the base material. Solder alloys can be produced by melting and mixing raw material metals. In such solder alloys, in order to design low alpha dose materials, it is important to remove upstream radioactive elements such as uranium (U), thorium (Th), and polonium (Po) from the alloy composition.

On the other hand, it is not technically difficult to remove U, Th, and Po in the refining of Sn base metal (for example, refer to Patent Document 1).

Generally, lead (Pb) and bismuth (Bi) are contained in Sn as impurities. Among Pb and Bi, ²¹⁰ Pb and ²¹⁰ Bi, which are radioactive isotopes, undergo beta decay to become ²¹⁰ Po, while ²¹⁰ Po undergoes alpha decay to generate ²⁰⁶ Pb, which generates alpha rays. This series of decays (uranium series) is said to be the main cause of the generation of alpha rays from the solder material.

In addition, in the evaluation of the amount of alpha radiation generated from the material, the unit "cph/cm ² " is often used. “cph/cm ² ” is the abbreviation of “counts per hours/cm ² ”, which means the number of alpha rays per 1 cm ² per hour.

The half-lives of Pb and Bi are as follows.

Regarding Bi, the half-life of ²¹⁰ Bi is about 5 days. Regarding Pb, the half-life of ²¹⁰ Pb is about 22.3 years. In addition, these influence degrees (existence ratio) can be represented by the following formula (refer nonpatent literature 1). That is, the influence of Bi on the generation of alpha rays is very low compared to that of Pb.

[ ²¹⁰ Bi]≒[ ²¹⁰ Pb]/1.6×10 ³

In the formula, [ ²¹⁰ Bi] represents the molar concentration of ²¹⁰ Bi. [ ²¹⁰ Pb] represents the molar concentration of ²¹⁰ Pb.

As described above, conventionally, in the design of low α radiation dose materials, U and Th are generally removed, and Pb is further removed completely.

In addition, the amount of alpha radiation generated from the solder material is known to vary with time, substantially increasing the amount of alpha radiation. It is said that the reason for this is that radioactive Pb and radioactive Bi in the solder alloy undergo beta decay to increase the amount of Po, and then Po undergoes alpha decay to generate alpha rays.

In materials with extremely low alpha radiation doses, although these radioactive elements are hardly contained, the alpha radiation dose may increase over time due to the segregation of ²¹⁰ Po. ²¹⁰ Po originally emits alpha rays, but when the solder alloy solidifies, segregation occurs at the center of the solder alloy, so the alpha rays emitted are shielded by the solder alloy. Then, as time elapses, ²¹⁰ Po is uniformly dispersed in the alloy and also exists on the surface where the α-rays are detected, so the amount of α-rays increases with time (see Non-Patent Document 2).

As described above, due to the influence of the extremely small amount of impurities contained in the solder alloy, the amount of α rays generated increases. Therefore, it is difficult to add only various elements in the design of low alpha radiation dose materials, such as the conventional manufacturing methods of solder alloys.

For example, a method of adding arsenic (As) to a solder alloy is known in order to suppress the viscosity increase of the solder paste over time (for example, refer to Patent Document 2).

In the packaging of the printed circuit board as described above, from the viewpoint of connection strength, etc., when packaging electronic components having a certain size, a method of inserting terminals into through holes of the substrate and packaging is adopted. The packaging operation of such electronic components is usually performed using flow soldering. Flow soldering is a method of soldering by bringing the solder jet surface of the solder bath into contact with the connection surface of the printed circuit board.

There must be a solder bath in flow soldering. In a solder bath, hot molten solder flows for a long time. Therefore, from the viewpoint of corrosion resistance, stainless steel or the like whose main component is iron (Fe) is used for the material of the solder bath. However, due to prolonged use, the inner surface of the solder bath may be corroded by Fe corrosion.

Patent Document 3 discloses a solder alloy containing predetermined amounts of Fe and Ge in order to suppress Fe corrosion in a solder bath for flow soldering.

[Prior Art Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2010-156052

[Patent Document 2] Japanese Patent Laid-Open No. 2015-98052

[Patent Document 3] Japanese Patent Laid-Open No. 2008-168322

[Non-patent literature]

[Non-Patent Document 1] Radioactive Nuclei Induced Soft Errors at Ground Level; IEEE TRANSACTIONS ON NUCLEAR SCIENCE, DECEMBER 2009, VOL.56, NO.6, p.3437-3441

[Non-Patent Document 2] Energy Dependent Efficiency in Low Background Alpha Measurements and Impacts on Accurate Alpha Characterization; IEEE TRANSACTIONS ON NUCLEAR SCIENCE, DECEMBER 2015, VOL.62, NO.6, p.3034-3039

In order to suppress the thickening of the solder paste over time, for example, as described in Patent Document 2, the method of adding As to the solder alloy is to add As to make the alloy also contain impurities. At this time, the amount of alpha rays generated from the solder material increases due to the presence of radioactive elements in impurities.

Further, as in the solder alloy described in Patent Document 3, when a large amount of Fe is contained in the solder alloy containing Sn as a main component, needle-like crystals derived from the SnFe compound are precipitated, and there is a possibility of short circuit.

Moreover, in the solder alloy containing Sn as a main component, in order to improve wettability, a large amount of nickel (Ni) may be contained. If the Ni content is large, the SnCuNi compound will precipitate in the vicinity of the bonding interface of the solder alloy, and there is a possibility that the mechanical strength of the solder joint may be lowered.

The present invention has been made in view of the above-mentioned matters, and its object is to provide a solder alloy, a solder powder composed of the solder alloy, a solder paste containing the solder powder and a flux, and a solder ball composed of the solder alloy , Solder preforms and solder joints, wherein the solder alloy can inhibit the viscosity increase of the solder paste over time, it is difficult to cause short circuits in the circuit, the mechanical strength of the solder joints is improved, and the occurrence of soft errors is suppressed.

The inventors of the present invention have conducted studies with the aim of designing a solder alloy with a low alpha radiation dose that can suppress the temporal thickening of the solder paste without adding As accompanying an impurity containing a radioactive element. Through such research, it was found that the melting point of 1455, which is a high-melting-point metal, is made to contain Sn as the main component and a predetermined amount such as that of the base metal, which is heated at high temperature during refining or processing. The alloy composition of Ni with a melting point of 1538°C and Fe with a melting point of 1538°C can achieve the aforementioned objects, and finally the present invention is completed.

That is, in order to solve the above-mentioned subject, this invention employs the following means.

[1] A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni : 0 mass ppm or more and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, and the remainder is Sn; the solder alloy satisfies the following formula (1), and the α radiation dose is 0.02cph/ cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[2] A solder alloy having an alloy composition including U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni : 0 mass ppm or more and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less, and the remainder is Sn; the solder alloy satisfies the following formula (1), and the α radiation dose is 0.02 cph/cm ² or less ;

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[3] The solder alloy according to [1] or [2], wherein the alloy composition further satisfies the following formula (1');

40≦Ni+Fe≦200 (1’)

In the formula (1'), Ni and Fe represent the contents (mass ppm) in the aforementioned alloy composition, respectively.

[4] The solder alloy according to any one of [1] to [3], wherein Pb is less than 2 mass ppm.

[5] The solder alloy according to any one of [1] to [4], wherein As is less than 2 mass ppm.

[6] The solder alloy according to any one of [1] to [5], wherein the alloy composition further contains Ag: 0 mass % or more and 4 mass % or less, and Cu: 0 mass % or more and 0.9 mass % or less at least one of them.

[7] A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni : more than 0 mass ppm and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less; Ag: more than 0 mass % and 4 mass % or less, and Cu: more than 0 mass % and 0.9 mass % or less at least One; the remainder is Sn; the solder alloy satisfies the following formula (1), and the α radiation dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[8] A solder alloy having an alloy composition including U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni : more than 0 mass ppm and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less; Cu: 0 mass % or more and 0.9 mass % or less; the remainder is Sn; the solder alloy satisfies the following formula (1), The ratio of Cu to Ni is 8 or more and 175 or less in terms of the mass ratio represented by Cu/Ni, and the α radiation dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[9] A solder alloy containing U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm or more 600 mass ppm ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, Cu: more than 0 mass % and 0.9 mass % or less, and the remainder is Sn in an alloy composition that satisfies the following formula (1), and the ratio of Cu, Ni and Fe is The ratio is 7 or more and 350 or less as a mass ratio represented by Cu/(Ni+Fe), and the α radiation dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[10] A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni : 0 mass ppm or more and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less; Cu: more than 0 mass % and 0.9 mass % or less; the remainder is Sn; the solder alloy satisfies the following formula (1) , the ratio of Cu to Fe is 50 or more and 350 or less in terms of the mass ratio represented by Cu/Fe, and the α radiation dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

[11] The solder alloy according to any one of [7] to [10], wherein the ratio of Ni to Fe is 0.4 or more and 30 or less as a mass ratio represented by Ni/Fe.

[12] The solder alloy according to any one of [8] to [11], wherein the alloy composition further contains Ag: more than 0 mass % and 4 mass % or less.

[13] The solder alloy according to any one of [1] to [12], wherein the alloy composition further contains Bi: 0 mass % or more and 0.3 mass % or less, and Sb: 0 mass % or more and 0.9 mass % or less at least one of them.

[14] The solder alloy according to [13], wherein the alloy composition further satisfies the following formula (2),

0.03≦Bi+Sb≦1.2 (2)

(2) In the formula, Bi and Sb represent the contents (mass %) in the aforementioned alloy composition, respectively.

[15] The solder alloy according to any one of [1] to [14], wherein the solder alloy sheet formed into a sheet having an area of 900 cm ² on one side is subjected to a heat treatment at 100° C. for 1 hour The latter alpha radiation dose is 0.02 cph/cm ² or less.

[16] The solder alloy according to any one of [1] to [15], wherein the α radiation dose is 0.002 cph/cm ² or less.

[17] The solder alloy according to any one of [16], wherein the α radiation dose is 0.001 cph/cm ² or less.

[18] A solder powder comprising the solder alloy according to any one of [1] to [17].

[19] The solder powder according to [18], comprising two or more types of solder alloy particle groups having different particle size distributions at the same time.

[20] A solder paste containing the solder powder according to [18] or [19] and a flux.

[21] A solder ball comprising the solder alloy according to any one of [1] to [17].

[22] A solder preform comprising the solder alloy according to any one of [1] to [17].

[23] A solder joint comprising the solder alloy according to any one of [1] to [17].

According to the present invention, a solder alloy, a solder powder composed of the solder alloy, a solder paste containing the solder powder and a flux, a solder ball composed of the solder alloy, a solder preform and a solder joint can be provided, The solder alloy system can inhibit the viscosity increase of the solder paste over time, is not easy to cause short circuit in the circuit, improves the mechanical strength of the solder joint, and inhibits the occurrence of soft errors.

The present invention will be explained in detail below.

In this specification, the "ppb" concerning the composition of the solder alloy is "mass ppb" unless otherwise specified. "ppm" means "mass ppm" unless otherwise specified. "%" means "mass %" unless otherwise specified.

(solder alloy)

The solder alloy system according to one aspect of the present invention has U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm An alloy composition of 600 mass ppm or more and Fe: 0 mass ppm or more and 100 mass ppm or less, and the remainder being Sn, which satisfies the following formula (1), and the α radiation dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

<Alloy composition>

The solder alloy of the present embodiment has U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm or more and 600 mass ppm ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, and an alloy composition in which the remainder is Sn, and satisfies the above-mentioned formula (1).

≪U: Less than 5 quality ppb, Th: less than 5 quality ppb≫

U and Th are radioactive elements. In order to suppress the occurrence of soft errors, the content of these in the solder alloy must be suppressed.

In the present embodiment, from the viewpoint of setting the amount of α radiation generated from the solder alloy to 0.02 cph/cm ² or less, U and Th in the solder alloy relative to the total mass of the solder alloy (100% by mass) The content of each is less than 5ppb. From the viewpoint of suppressing the occurrence of soft errors in high-density packaging, the contents of U and Th are preferably 2 ppb or less, respectively, and the lower the better.

≪Pb: Less than 5 mass ppm≫

Generally, Sn contains Pb as an impurity. The radioisotope in the Pb undergoes beta decay to become ²¹⁰ Po, and ²¹⁰ Po undergoes alpha decay to generate ²⁰⁶ Pb, which produces alpha rays. In this case, it is preferable that the content of Pb which is an impurity in the solder alloy is also extremely small.

In this embodiment, the content of Pb in the solder alloy is less than 5 ppm, preferably less than 2 ppm, more preferably less than 1 ppm, relative to the total mass (100% by mass) of the solder alloy. In addition, the lower limit of the content of Pb in the solder alloy may be 0 ppm or more.

≪As: Less than 5 mass ppm≫

The addition of As to the solder alloy is effective for suppressing the thickening of the solder paste over time, but along with the addition of As, radioactive elements are also included in the alloy, which increases the amount of alpha rays generated from the solder material.

In the present embodiment, the purpose is to suppress the increase in viscosity of the solder paste over time without adding As accompanying impurities containing radioactive elements.

In this embodiment, the content of As in the solder alloy is less than 5 ppm, preferably less than 2 ppm, more preferably less than 1 ppm, relative to the total mass (100% by mass) of the solder alloy. In addition, the lower limit of the content of As in the solder alloy may be 0 ppm or more.

≪Ni: 0 mass ppm or more and 600 mass ppm or less, Fe: 0 mass ppm or more and 100 mass ppm or less, formula (1)≫

By soldering, a Sn-containing intermetallic compound (Sn-containing intermetallic compound) is formed in the vicinity of the bonding interface in the solder alloy. When the Sn-containing intermetallic compound is precipitated, the mechanical strength of the solder joint is deteriorated.

Ni: 0 mass ppm or more and 600 mass ppm or less

Ni is an element that suppresses the formation of Sn-containing intermetallic compounds at the bonding interface.

By containing Ni in the solder alloy, the formation of the aforementioned Sn-containing intermetallic compound can be suppressed, and the mechanical strength of the solder joint can be maintained. On the other hand, when the content of Ni in the solder alloy exceeds 600 ppm, SnNi compounds are precipitated in the vicinity of the bonding interface in the solder alloy, and the mechanical strength of the solder joint may be deteriorated.

In this embodiment, the content of Ni in the solder alloy is 0 ppm or more and 600 ppm or less, preferably more than 0 ppb and 600 ppm or less, more preferably 20 ppm or more and 600 ppm or less, relative to the total mass (100 mass %) of the solder alloy, More preferably, it is 40 ppm or more and 600 ppm or less.

Fe: 0 mass ppm or more and 100 mass ppm or less

Like Ni, Fe is an element that suppresses the formation of Sn-containing intermetallic compounds at the bonding interface. In addition, within a predetermined content range, precipitation of needle-like crystals generated by the SnFe compound can be suppressed, thereby preventing short circuit of the circuit.

The "needle crystal" as used herein refers to a crystal in which the ratio of the major axis to the minor axis, that is, the aspect ratio is 2 or more in one crystal derived from the SnFe compound.

In this embodiment, the content of Fe in the solder alloy is 0 ppm or more and 100 ppm or less, preferably more than 0 ppb and 100 ppm or less, more preferably 20 ppm or more and 100 ppm or less, relative to the total mass (100 mass %) of the solder alloy, More preferably, it is 40 ppm or more and 80 ppm or less.

The alloy composition in the solder alloy of the present embodiment satisfies the following formula (1).

20≦Ni+Fe≦700 (1)

In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively.

Both Ni and Fe in the formula (1) are elements that suppress the formation of Sn-containing intermetallic compounds at the bonding interface. Furthermore, in this embodiment, both Ni and Fe contribute to the effect of suppressing the viscosity increase of the solder paste over time.

In order to obtain the aforementioned effect of suppressing the formation of intermetallic compounds containing Sn and the effect of suppressing the thickening of solder paste over time, the sum of Ni and Fe in the solder alloy relative to the total mass of the solder alloy (100% by mass) The content must be 20 ppm or more and 700 ppm or less. The total content of Ni and Fe is preferably 40 ppm or more and 700 ppm or less, more preferably 40 ppm or more and 600 ppm or less, and most preferably 40 ppm or more and 200 ppm or less.

However, the aforementioned "content of Ni and Fe in total" refers to the content of Fe when the content of Ni in the solder alloy is 0 ppm, and the content of Ni when the content of Fe in the solder alloy is 0 ppm. In the case of Fe, it is the total content of these.

Further, in the present embodiment, when both Ni and Fe are present, the ratio of Ni to Fe in the solder alloy is preferably 0.4 or more and 30 or less, more preferably 0.4 or more and 10, in terms of the mass ratio represented by Ni/Fe. Hereinafter, it is more preferably 0.4 or more and 5 or less, particularly preferably 0.4 or more and 2 or less.

If such a mass ratio of Ni/Fe is within the aforementioned preferable range, the effect of the present invention can be more easily obtained.

≪Any element≫

The alloy composition in the solder alloy of the present embodiment may contain elements other than the above-mentioned elements as required.

For example, the alloy composition system in the solder alloy of the present embodiment may further contain at least one of Ag: 0 mass % or more and 4 mass % or less, and Cu: 0 mass % or more and 0.9 mass % or less, in addition to the above elements.

Ag: 0 mass % or more and 4 mass % or less

Ag is an arbitrary element that can form Ag ₃ Sn at the crystal interface to improve the reliability of the solder alloy. In addition, the Ag-based ionization tendency is a noble metal element compared to Sn, and the coexistence of Ni and Fe improves the effect of suppressing the thickening of the solder paste over time. Furthermore, if the content of Ag in the solder alloy is within the above-mentioned range, the rise of the melting point of the alloy can be suppressed, so it is not necessary to increase the reflow temperature excessively.

In this embodiment, the content of Ag in the solder alloy is preferably 0% or more and 4% or less, more preferably more than 0% and 4% or less, relative to the total mass (100% by mass) of the solder alloy. Again More preferably, it is 0.5% or more and 3.5% or less, particularly preferably 1.0% or more and 3.0% or less, and most preferably 2.0% or more and 3.0% or less.

Cu: 0 mass % or more and 0.9 mass % or less

Cu is an arbitrary element that is used in general solder alloys and can improve the bonding strength of solder joints. In addition, Cu-based ionization tends to be a noble metal element relative to Sn, and the coexistence of Ni and Fe improves the effect of suppressing the thickening of the solder paste over time.

In this embodiment, the content of Cu in the solder alloy is preferably 0% or more and 0.9% or less, more preferably more than 0% and 0.9% or less, relative to the total mass (100% by mass) of the solder alloy. More preferably, it is 0.1% or more and 0.8% or less, and particularly preferably 0.2% or more and 0.7% or less.

In this embodiment, when both Cu and Ni are present, the ratio of Cu to Ni in the solder alloy is based on the mass ratio represented by Cu/Ni, preferably 8 or more and 175 or less, more preferably 10 or more and 150 or less. .

If the mass ratio of Cu/Ni is within the aforementioned preferable range, the effect of the present invention can be more easily obtained.

In the present embodiment, when both Cu and Fe are present, the ratio of Cu to Fe in the solder alloy is preferably 50 or more and 350 or less, more preferably 70 or more and 250 or less, in terms of the mass ratio represented by Cu/Fe.

If the mass ratio of Cu/Fe is within the aforementioned preferable range, the effect of the present invention can be more easily obtained.

In this embodiment, when Cu, Ni and Fe are present at the same time, the ratio of Cu, Ni and Fe in the solder alloy is preferably 7 or more and 350 or less in terms of the mass ratio represented by Cu/(Ni+Fe), and more Preferably it is 10 or more and 250 or less.

If the mass ratio of Cu/(Ni+Fe) is within the aforementioned preferable range, the effect of the present invention can be more easily obtained.

As one embodiment of the solder alloy, U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm or more 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less, and the remainder is Sn alloy composition, which satisfies the above formula (1), and the α radiation dose is 0.02 cph/cm ² or less.

The alloy composition in the solder alloy may further contain at least one of Ag: 0 mass % or more and 4 mass % or less, and Cu: 0 mass % or more and 0.9 mass % or less.

In addition, as one embodiment of the solder alloy, U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: more than 0 mass ppm and 600 mass ppm or less, Fe: more than 0 mass ppm and 100 mass ppm or less, Ag: more than 0 mass % and 4 mass % or less, and Cu: at least one of more than 0 mass % and 0.9 mass % or less, and The remainder is an alloy composition of Sn, which satisfies the above-mentioned formula (1), and has an α radiation dose of 0.02 cph/cm ² or less. In the alloy composition in the solder alloy, the ratio of Ni to Fe may be more than 0.4 to 30 in terms of mass ratio represented by Ni/Fe.

In addition, as one embodiment of the solder alloy, U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: more than 0 Mass ppm or more and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, Cu: more than 0 mass % and 0.9 mass % or less, and an alloy composition in which the remainder is Sn, and satisfies the above formula (1), Cu The ratio to Ni is 8 or more and 175 or less in terms of the mass ratio represented by Cu/Ni, and the α radiation dose is 0.02 cph/cm ² or less. In the alloy composition in the solder alloy, the ratio of Ni to Fe may be more than 0.4 to 30 in terms of mass ratio represented by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0 mass % and 4 mass % or less.

In addition, as one embodiment of the solder alloy, U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: more than 0 Mass ppm and 600 mass ppm or less, Fe: 0 mass ppm or more and 100 mass ppm or less, Cu: more than 0 mass % and 0.9 mass % or less, and an alloy composition with the remainder being Sn, and satisfying the above formula (1), Cu The ratio of Ni to Fe is 7 or more and 350 or less in terms of mass ratio represented by Cu/(Ni+Fe), and the α radiation dose is 0.02 cph/cm ² or less. In the alloy composition in the solder alloy, the ratio of Ni to Fe may be more than 0.4 to 30 in terms of mass ratio represented by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0 mass % and 4 mass % or less.

Moreover, as one embodiment of the solder alloy, U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm ppm or more and 600 mass ppm or less, Fe: more than 0 mass ppm and 100 mass ppm or less, Cu: more than 0 mass % and 0.9 mass % or less, and an alloy composition with the remainder being Sn, and satisfying the above formula (1), Cu and The ratio of Fe is 50 or more and 350 or less as a mass ratio represented by Cu/Fe, and the α radiation dose is 0.02 cph/cm ² or less. In the alloy composition in the solder alloy, the ratio of Ni to Fe may be 0.4 or more and 30 or less as a mass ratio represented by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0 mass % and 4 mass % or less.

For example, the alloy composition in the solder alloy of the present embodiment may further contain at least Bi: 0 mass % or more and 0.3 mass % or less, and Sb: 0 mass % or more and 0.9 mass % or less in addition to the above-mentioned elements. A sort of.

Bi: 0 mass % or more and 0.3 mass % or less

Bi is an element that has low reactivity with flux and exhibits the effect of inhibiting viscosity increase of solder paste over time. In addition, Bi is an element which reduces the liquidus temperature of the solder alloy and reduces the viscosity of the molten solder, so that it is an element that can suppress the deterioration of the wettability.

In this embodiment, the content of Bi in the solder alloy is preferably 0% or more and 0.3% or less, more preferably 0.0020% or more and 0.3% or less, relative to the total mass (100% by mass) of the solder alloy. More preferably, it is 0.010% or more and 0.3% or less.

Sb: 0 mass % or more and 0.9 mass % or less

Like Bi, Sb is an element that has low reactivity with the flux and exhibits the effect of suppressing the thickening of the solder paste over time. If the content of Sb in the solder alloy is too large, the wettability will be deteriorated, so when Sb is added, it must be set to an appropriate content.

In this embodiment, the content of Sb in the solder alloy is preferably 0% or more and 0.9% or less, more preferably 0.0020% or more and 0.9% or less, relative to the total mass (100% by mass) of the solder alloy. More preferably, it is 0.010% or more and 0.9% or less.

When the alloy composition in the solder alloy of the present embodiment further contains at least one of Bi: 0 mass % or more and 0.3 mass % or less, and Sb: 0 mass % or more and 0.9 mass % or less, the alloy composition system satisfies the following ( 2) formula is better.

0.03≦Bi+Sb≦1.2 (2)

(2) In the formula, Bi and Sb represent the contents (mass %) in the aforementioned alloy composition, respectively.

Both Bi and Sb in the formula (2) are elements that exhibit the effect of inhibiting the viscosity increase of the solder paste over time. Furthermore, in this embodiment, both Bi and Sb contribute to the wettability of the solder alloy.

With respect to the total mass (100 mass %) of the solder alloy, the total content of Bi and Sb in the solder alloy is preferably 0.03% or more and 1.2% or less, more preferably 0.03% or more and 0.9% or less, and still more preferably 0.3% % above and 0.9% below.

However, the aforementioned "content of Bi and Sb in total" refers to the content of Sb when the content of Bi in the solder alloy is 0%, and is the content of Bi when the content of Sb in the solder alloy is 0%. Bi and Sb are the total content of these.

When both Bi and Sb are present in the present embodiment, the ratio of Bi to Sb in the solder alloy is preferably 0.01 or more and 10 or less, more preferably 0.1 or more and 5 or less, in terms of the mass ratio represented by Sb/Bi.

If the mass ratio of Sb/Bi is within the aforementioned preferable range, the effect of the present invention can be more easily obtained.

≪Remainder: Sn≫

The remainder of the alloy composition in the solder alloy of the present embodiment is composed of Sn. In addition to the above-mentioned elements, unavoidable impurities may be contained. When unavoidable impurities are contained, the above-mentioned effects are not affected.

<alpha radiation dose>

The alpha radiation dose of the solder alloy of the present embodiment is 0.02 cph/cm ² or less.

This is the amount of alpha radiation that does not cause soft errors to be a problem in high-density packaging of electronic components.

From the viewpoint of suppressing soft errors in higher-density packaging, the alpha radiation dose in the solder alloy of the present embodiment is preferably 0.01 cph/cm ² or less, more preferably 0.002 cph/cm ² or less, and still more preferably 0.001cph/cm ² or less.

The amount of alpha radiation generated from the solder alloy can be determined in the following manner. The measurement method of such a radiation dose is based on JEDEC STANDARD of international standards.

Sequence (i):

An air-flow type alpha dose measuring device was used.

For the measurement sample, a solder alloy sheet is used, which is a sheet of molten solder alloy formed into a sheet having an area of 900 cm ² on one side.

The above-mentioned solder alloy sheet was set as a measurement sample in the above-mentioned α-ray dose measuring apparatus, and PR gas was exhausted there.

In addition, the PR gas system is used in accordance with the JEDEC STANDARD which is an international standard. That is, the PR gas system used for the measurement is set to decay of radon (Rn) after 3 weeks or more after the gas cylinder is filled with a mixed gas of 90% argon-10% methane.

Sequence (ii):

In the alpha dose measuring apparatus provided with the solder alloy sheet, the PR gas was allowed to flow for 12 hours, and then the alpha dose was measured for 72 hours.

Sequence (iii):

The average alpha radiation dose was calculated as "cph/cm ² ". The abnormal point (measurement by vibration of the device, etc.) is excluding the measurement of 1 hour.

[Manufacturing method of solder alloy]

The solder alloy of the present embodiment can be produced, for example, by using a production method having a step of melt-mixing at least one of Ni and Fe and a raw material metal containing Sn.

For the purpose of designing a solder alloy with a low alpha radiation dose, it is preferable to use a low alpha radiation dose material as its raw metal. Remove U, Th and Pb.

The Sn-based metal as the raw material can be produced, for example, by using the production method described in Japanese Patent Laid-Open No. 2010-156052 (Patent Document 1).

Ni and Fe-based raw materials can be used, for example, respectively, according to Japanese Patent No. 5692467 .

For the operation of melt-mixing the raw materials, a conventionally known method can be used.

In general, in a solder alloy, each constituent element constituting the solder alloy does not function independently, and various effects can be exhibited only when the content of each constituent element is all within a predetermined range. According to the solder alloy of the embodiment described above, the content of each constituent element is in the above-mentioned range, the viscosity of the solder paste can be suppressed from increasing with time, the short circuit of the circuit is less likely to occur, the mechanical strength of the solder joint can be improved, and the The occurrence of soft errors. That is, the solder alloy of the present embodiment can be used as a target low alpha radiation dose material, and can be applied to the formation of solder bumps around the memory to suppress the occurrence of soft errors.

In the present embodiment, the content of each constituent element is outside the above-mentioned ranges, and is related to the inhibition of Fe corrosion, the inhibition of the thickening of the solder paste over time, the improvement of the mechanical strength of the solder joint, and the inhibition of the short circuit of the circuit. The Fe and Ni satisfy the predetermined relationship, and the effect of the present invention can be more fully exerted.

In addition, the present embodiment aims to design a low α radiation dose solder alloy which can suppress the viscosity increase of the solder paste over time without actively adding As. In contrast to this, a solder alloy containing Ni and Fe, which are refractory metals, which are heated at high temperatures during refining or processing of the base metal at a specific ratio, is used to achieve the purpose.

There is no certain reason why such an effect can be obtained, but it is presumed as follows.

Sn for a solder alloy with a low alpha radiation dose is of very high purity, and when the molten alloy is solidified, the crystal size of Sn becomes large. In addition, the oxide film in the Sn also forms a loose oxide film that complies with it. Therefore, by adding Ni and Fe, which are high melting point metals, to reduce the crystal size and form a dense oxide film, the reactivity of the alloy and the flux can be suppressed, so the viscosity increase of the solder paste over time can be suppressed.

In addition, it is preferable that the solder alloy of the present embodiment has an α radiation dose of 0.02 cph/cm after heat treatment at 100° C. for 1 hour when the solder alloy sheet is formed into a sheet with an area of 900 cm ² on one side. ² or less, more preferably 0.01 cph/cm ² or less, still more preferably 0.002 cph/cm ² or less, and particularly preferably 0.001 cph/cm ² or less.

Solder alloys exhibiting such a dose of α radiation are less likely to cause segregation of ²¹⁰ Po in the alloy, and are useful because the influence of time-dependent changes in the dose of α radiation is small. By using a solder alloy exhibiting such a dose of α radiation, the occurrence of soft errors is further suppressed, and the stable operation of the semiconductor device can be more easily ensured.

(solder powder)

The solder powder according to one aspect of the present invention is composed of the above-described solder alloy according to one aspect of the present invention.

The solder powder of this embodiment is suitable for use as a solder paste to be described later.

The solder powder can be produced by known methods such as the dropping method of dropping molten solder alloy to obtain particles, the spray method of centrifugal spraying, the atomization method, the granulation method in liquid, the method of pulverizing the bulk solder alloy, and the like. . In the dropping method or the spraying method, the dropping or spraying is preferably carried out in an inert environment or a solvent in order to form particles.

The solder powder of this embodiment is preferably spherical powder. The fluidity of the solder alloy is improved by the spherical powder.

When the solder powder of the present embodiment is spherical powder, in the classification of powder size in JIS Z 3284-1:2014 (Table 2), it is preferable to satisfy symbols 1 to 8, and to satisfy symbols 4 to 8 as better. If the particle size of the solder powder satisfies this condition, the surface area of the powder will not be too large, and the increase in the viscosity of the solder paste over time is suppressed, and the agglomeration of the fine powder is suppressed, and the increase in the viscosity of the solder paste is suppressed. Therefore, finer parts can be welded.

Moreover, it is preferable that the solder powder of this embodiment has two or more types of solder alloy particle groups with different particle size distributions at the same time. Thereby, the smoothness of the solder paste is improved, and the workability such as easy printing is improved.

In the solder powder of this embodiment, the sphericity of the spherical powder is preferably 0.8 or more, more preferably 0.9 or more, still more preferably 0.95 or more, and particularly preferably 0.99 or more.

The so-called "sphericity of spherical powder" can be measured using a CNC image measuring system (ULTRA QUICK VISION ULT RA QV350-PRO measuring device manufactured by MITSUTOYO) using the minimum zone center method (MZC method). .

The so-called sphericity refers to the deviation from the true sphere. For example, the arithmetic mean calculated by dividing the diameter of each solder alloy particle of 500 by the major axis indicates that the value is closer to the upper limit of 1.00 and closer to the true sphere.

(Solder Paste)

The solder paste according to an aspect of the present invention contains the solder powder and flux according to the above-described aspect of the present invention.

<Flux>

The flux used in the solder paste of the present embodiment is composed of, for example, any one of a resin component, an active component, a solvent, and other components, or a combination of two or more of these preparation components.

As a resin component system, rosin-type resin is mentioned, for example.

Examples of the rosin-based resin include raw material rosin, such as rosin gum, wood rosin, and pine oil rosin, and derivatives obtained from the raw material rosin.

The derivatives are, for example, purified rosin, hydrogenated rosin, non-homogenized rosin, polymerized rosin, and α,β unsaturated carboxylic acid modified products (acrylated rosin, maleated rosin, fumaricated rosin, etc.), and the polymerized rosin Two or more kinds of purified products, hydrides, and inhomogeneous products, and purified products, hydrides, and heterogeneous products of the α,β-unsaturated carboxylic acid modified products can be used.

In addition to rosin-based resins, the resin component system includes terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, and modified terpene resins. Xylene resin, acrylic resin, polyethylene resin, acrylic-polyethylene copolymer resin, epoxy resin, etc.

The modified terpene resins include aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, and the like. Hydrogenated terpene phenol resin etc. are mentioned as a modified terpene phenol resin. Modified styrene The vinyl resin includes styrene acrylic resin, styrene maleic acid resin, and the like. Modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resorcinol-type xylene resins, polyol-modified xylene resins, and polyoxyethylene adducts. Toluene resin, etc.

Examples of the active ingredient system include organic acids, amines, halogen-based activators, thixotropic agents, solvents, metal inactivating agents, and the like.

Examples of organic acids include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, and 2,2-bishydroxymethylpropane. acid, tartaric acid, malic acid, glycolic acid, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, oleic acid, etc.

Examples of amines include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 1,2-dimethylimidazole. Imidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2- Phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyano Ethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4 -Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl -(1')]-Ethyl-s-triazine, 2,4-Diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s -Triazine, 2,4-Diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole Isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H- Pyrro[1,2-a]benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2, 4-Diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid Adduct, 2,4-diamino-6-methylpropionyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzene Zimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2 -(2'-Hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-cyclobenzo Triazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzene Triazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzotriazolyl)- 4-Third-octyl-6'-tert-butyl-4'-methyl-2,2'-methylenebisphenol, 1,2,3-benzotriazole, 1-[N,N- Bis(2-ethylhexyl)aminomethyl]benzotriazole, carboxybenzotriazole, 1-[N,N-bis(2-ethylhexyl)aminomethyl]methylbenzotriazole , 2,2'-[[(methyl-1H-benzotriazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole azole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazole Triazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole and the like.

Examples of halogen-based activators include amine hydrogen halide salts, organic halogen compounds, and the like.

Amine hydrogen halide salts are compounds that react amines with hydrogen halides. Examples of the amines here include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, xylylguanidine, methylimidazole, 2-ethyl-4-methylimidazole, and the like, and examples of hydrogen halide include Chlorine, bromine and iodine hydrides.

Examples of organohalogen compounds include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isotrihydroester hexabromide, and 1-bromo-2-butanol , 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanediol, 1,3-dibromo-2 -Propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol, etc. .

The thixotropic agent includes, for example, a wax-based thixotropic agent, an amide-based thixotropic agent, and a sorbitol-based thixotropic agent.

As a wax-type thixotropic agent, castor oil etc. are mentioned, for example.

Examples of the amide-based thixotropic agent include monoamide-based thixotropic agents, diamide-based thixotropic agents, and polyamide-based thixotropic agents, and specifically, laurylamide, palmitamide, and stearylamide , behenic acid amide, hydroxystearyl amide, saturated fatty acid amide, oleic acid amide, mustard amide, unsaturated fatty acid amide, p-toluamide, aromatic amide, methylene bis-stearyl Amide, diethyl dilauroamide, diethyl dihydroxystearyl amide, saturated aliphatic diamide, methylene dioleamide, unsaturated aliphatic diamide, m-xylene distearyl amide Amines, aromatic diamides, saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, substituted amides, hydroxymethyl stearyl amides, hydroxymethyl amides, fatty acid ester amides Wait.

The sorbitol-based thixotropic agent includes, for example, dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, and the like.

Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, terpene alcohols, and the like.

Examples of the alcohol-based solvent include isopropanol, 1,2-butanediol, isocamphenylcyclohexanol, 2,4-diethyl-1,5-pentanediol, and 2,2-dimethyl-1 ,3-Propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl-2 , 3-butanediol, 1,1,1-para(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis(methylene) ) bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2,2 -Sham (hydroxymethyl) ethyl] ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, butane erythritol, threitol, Guaifenesin, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol Wait.

Examples of glycol ether-based solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, and diethylene glycol monohexyl ether. ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, etc.

As a metal inactivating agent system, a hindered phenol type compound, a nitrogen compound, etc. are mentioned, for example. By making the flux contain either a phenolic compound or a nitrogen compound, it is easy to improve the effect of suppressing the increase in viscosity of the solder paste.

The term "metal deactivator" as used herein refers to a compound having a property of preventing metal deterioration by contact with a certain compound.

The hindered phenolic compound refers to a phenolic compound in which at least one of the ortho-positions of the phenol has a bulky substituent (for example, a branched or cyclic alkyl group such as tert-butyl group).

The hindered phenol compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N,N '-Hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propaneamide], 1,6-hexanediol bis[3-(3,5-di - tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-methylene bis(6-tert-butyl-p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3 - tert-butyl-5-methyl-4-hydroxyphenyl)propionate], 1,6-hexanediol-bis-[3-(3,5-di-tert-butyl-4-hydroxy phenyl)propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine , captaerythritol-4[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,2-thio-divinylbis[3-(3,5 -Di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N, N'-Hexamethylenebis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzyl phosphate- Diethyl ester, 1,3,5-trimethyl-2,4,6-para(3,5-di-tert-butyl-4-hydroxybenzene) Methyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, the following chemical formula compounds shown, etc.

(In the formula, Z is a substituted alkylene group. R ¹ and R ² are each independently a substituted alkyl group, aralkyl group, aryl group, heteroaryl group, cycloalkyl group or heterocycloalkyl group. R ³ and R ⁴ are each independently a substituted alkyl group.))

Examples of the nitrogen compound of the metal inactivator include hydrazine-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, melamine-based nitrogen compounds, and the like.

As long as the hydrazine-based nitrogen compound is a nitrogen compound having a hydrazine skeleton, dodecanedioic acid bis[N2-(dihydroxybenzyl)hydrazine], N,N'-bis[3-( 3,5-Di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, sebacic acid dissalylhydrazine, N-salylidene-N'-salylhydrazine, m-nitro Benzohydrazine, 3-aminophthalic acid hydrazine, phthalic acid dihydrazine, adipic acid hydrazine, oxalylbis(2-hydroxy-5-octylbenzylidene hydrazine) , N'-benzylpyrrolidone formate hydrazine, N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine, etc.

The amide-based nitrogen compound may be a nitrogen compound having an amide skeleton, and examples thereof include N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane] Acyloxy] ethyl} oxalamide and so on.

As long as the triazole-based nitrogen compound is a nitrogen compound having a triazole skeleton, N-(2H-1,2,4-triazol-5-yl)salamide, 3-amino-1,2, 4-triazole, 3-(N-salamidyl)amino-1,2,4-triazole, etc.

The melamine-based nitrogen compound may be a nitrogen compound having a melamine skeleton, and examples thereof include melamine, melamine derivatives, and the like. More specifically, for example, saminotriazine, alkylated saminotriazine, alkoxyalkylated saminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butyl melamine, N2,N2-diethylmelamine, N,N,N',N',N",N"-lu (methoxymethyl)melamine, etc.

Examples of other components include surfactants, silane coupling agents, antioxidants, colorants, and the like.

As a surfactant, a nonionic surfactant, a weak cationic surfactant, etc. are mentioned.

Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, aliphatic alcohol polyoxyethylene adduct, aromatic alcohol polyoxyethylene adduct, polyol polyoxyethylene Additives.

Examples of weak cationic surfactants include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, and aromatic amine polyoxyethylene adduct , Polyvalent amine polyoxyethylene adduct.

Surfactants other than the above include, for example, polyoxyalkylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, and polyoxyalkylene alkanes. base amine, polyoxyalkylene alkyl amide, etc.

Relative to the total mass of the solder paste (100% by mass), the content of the flux in the solder paste of this embodiment is preferably 5 to 95% by mass, more preferably 5 to 50% by mass, and preferably 5 to 50% by mass. 15 mass % is still more preferable.

When the content of the flux is within this range, the effect of suppressing the increase in viscosity due to the solder powder can be fully exerted.

The solder paste of this embodiment can be produced by a general production method in the technical field to which the invention pertains.

A flux is prepared by heating and mixing the preparation components constituting the above-mentioned flux, and by stirring and mixing the above-mentioned solder powder in this flux, a solder paste can be obtained. In addition, the effect of suppressing viscosity increase over time is expected, and zirconia powder can be further prepared, unlike the above-mentioned solder powder.

(solder ball)

The solder ball according to an aspect of the present invention is composed of the solder alloy according to the above-described aspect of the present invention.

The solder alloys of the above-described embodiments can be used as solder balls.

The solder balls of the present embodiment can be produced by a dropping method using a general method in the technical field to which the invention pertains.

The particle size of the solder ball is preferably 1 μm or more, more preferably 10 μm or more, still more preferably 20 μm or more, and particularly preferably 30 μm or more. On the other hand, the particle size of the solder balls is preferably 3000 μm or less, more preferably 1000 μm or less, still more preferably 600 μm or less, and particularly preferably 300 μm or less.

The particle size of the solder ball is, for example, preferably 1 μm or more and 3000 μm or less, more preferably 10 μm or more and 1000 μm or less, still more preferably 20 μm or more and 600 μm or less, and particularly preferably 30 μm or more and 300 μm or less.

(solder preform)

The solder preform according to an aspect of the present invention is composed of the solder alloy according to the above-described aspect of the present invention.

The solder alloy of the above-mentioned embodiment can be used as a preform.

The shape of the preform of this embodiment includes gaskets, rings, pellets, discs, ribbons, threads, and the like.

(solder joint)

The solder joint according to one aspect of the present invention is composed of the solder alloy according to the above-described aspect of the present invention.

The solder joint of this embodiment is composed of electrodes and solder joints. The so-called solder joint means a portion mainly formed of a solder alloy.

The solder joint of this embodiment is formed by, for example, bonding the solder alloy of the above-described embodiment to electrodes of a PKG (Package) such as an IC chip, and electrodes of a substrate such as a PCB (printed circuit board).

In addition, the solder joint of the present embodiment can be manufactured by performing processing by a general method in the technical field to which the invention pertains, such as mounting one of the solder balls of the above-described embodiment on one electrode coated with flux and bonding it. .

(Example)

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

In this embodiment, unless otherwise specified, "ppb" regarding the composition of the solder alloy is "mass ppb", "ppm" is "mass ppm", and "%" is "mass %".

<Solder alloy>

(Examples 1 to 370, Comparative Examples 1 to 8)

The raw material metal was melted and stirred to prepare solder alloys of each example having the alloy compositions shown in Table 1A to Table 16B.

<Solder powder>

The solder alloy of each example was melted, and by atomization, a solder powder was prepared, which was composed of the solder alloy of each example having the alloy composition shown in Table 1A to Table 16B, and was specified in JIS Z 3284 -1: Those satisfying the size (particle size distribution) of symbol 4 in the classification of powder size in 2014 (Table 2).

<Preparation of Flux (F0)>

Rosin-based resin was used as the resin component.

Thixotropic agents, organic acids, amines and halogen-based active agents are used as active ingredients.

A glycol ether-based solvent is used as the solvent.

Flux (F0) was prepared by mixing 42 parts by mass of rosin, 35 parts by mass of glycol ether-based solvent, 8 parts by mass of thixotropic agent, 10 parts by mass of organic acid, 2 parts by mass of amine, and 3 parts by mass of halogen-based activator.

<Manufacture of solder paste>

The above-mentioned flux (F0) and the solder powders composed of the solder alloys of the respective examples having the alloy compositions shown in Table 1A to Table 16B were mixed to manufacture a solder paste.

The mass ratio of flux (F0) to solder powder was set to flux (F0):solder powder=11:89.

<Assessment>

Using the aforementioned solder pastes, evaluations of tackifying inhibition were performed.

In addition, using the above-mentioned solder alloys, the evaluation of inhibition of precipitation of needle crystals, the evaluation of inhibition of formation of Sn-containing intermetallic compounds, and the evaluation of α radiation dose were performed, respectively. Furthermore, a comprehensive evaluation is carried out.

Details are as follows. The results of the evaluation are shown in Tables 1A to 16B.

[Viscosity Inhibition]

(1) Verification method

The viscosity of the solder paste immediately after preparation was measured in the air at 10 rpm and 25° C. for 12 hours using PCU-205 manufactured by Malcohm Co., Ltd.

(2) Judgment criteria

○: The viscosity after 12 hours was 1.2 times or less compared to the viscosity immediately after the preparation of the solder paste for 30 minutes.

×: The viscosity after 12 hours was more than 1.2 times the viscosity at 30 minutes after the preparation of the solder paste.

When this determination is "○", it can be said that a sufficient effect of suppressing thickening is obtained. That is, the viscosity increase of the solder paste over time can be suppressed.

[Precipitation inhibition of needle crystals]

(1) Verification method

The solder alloys of each example were melted at 250°C, and cooled to 100°C below the solidus temperature of the entire alloy composition over 10 minutes. The solder alloy after cooling was cross-sectionally observed at any 5 places in the range of 300 μm×300 μm using a scanning electron microscope (SEM).

The acicular crystal in this example refers to a crystal whose aspect ratio, which is the ratio of the major axis to the minor axis, is 2 or more in one crystal derived from the SnFe compound.

(2) Judgment criteria

○: No needle-like crystals were observed in all the SEM observation images at five places.

×: Needle-shaped crystals were observed in at least one SEM observation image.

When this judgment is "○", it can be said that it has the effect of suppressing the precipitation of needle-like crystals. That is, the short circuit of the circuit can not be easily generated.

[Inhibition of formation of intermetallic compounds containing Sn]

(1) Verification method

The solder alloys of each example were melted at 250°C, and cooled to 100°C below the solidus temperature of the entire alloy composition over 10 minutes. About the solder alloy after cooling, the cross section was observed at any five places in the range of 300 μm×300 μm using SEM, and the presence or absence of the Sn(Cu)Ni compound was confirmed.

(2) Judgment criteria

○: No Sn(Cu)Ni compound was observed in all the SEM observation images at 5 places.

×: Sn(Cu)Ni compound was observed in at least one SEM observation image.

When this determination is "○", it can be said that it has the effect of suppressing the formation of the intermetallic compound containing Sn. That is, the mechanical strength of the solder joint can be improved.

[alpha radiation dose]

(1) Verification method 1

The measurement of the α-ray dose is performed by using the α-ray dose measuring apparatus of the gas flow proportional counter, and according to the above-mentioned procedures (i), (ii) and (iii).

The solder alloy sheet immediately after production was used as a measurement sample.

The solder alloy sheet was obtained by melting the produced solder alloy and molding it into a sheet shape having an area of 900 cm ² on one side.

The measurement sample was placed in an α-ray dose measuring apparatus, and the PR-10 gas was allowed to flow for 12 hours, and then the α-ray dose was measured for 72 hours.

(2) Judgment Criteria 1

○○: The amount of α radiation generated from the measurement sample is 0.002 cph/cm ² or less.

○: The amount of alpha radiation generated from the measurement sample is more than 0.002 cph/cm ² or more and less than or equal to 0.02 cph/cm ² .

×: The amount of α radiation generated from the measurement sample exceeded 0.02 cph/cm ² .

If the judgment is "○○" or "○", it can be said to be a solder material with a low alpha radiation dose.

(3) Verification method 2

The α radiation dose was measured in the same manner as in the above-mentioned (1) Verification method 1, except that the measurement sample was changed.

For the measurement sample, a solder alloy sheet formed by melting the solder alloy immediately after fabrication and formed into a sheet with an area of 900 cm ² on one side was heat-treated at 100° C. for 1 hour and left to cool.

(4) Judgment Criteria 2

○○: The amount of α radiation generated from the measurement sample is 0.002 cph/cm ² or less.

○: The amount of α radiation generated from the measurement sample was more than 0.002 cph/cm ² and not more than 0.02 cph/cm ² .

×: The amount of α radiation generated from the measurement sample exceeded 0.02 cph/cm ² .

If the judgment is "○○" or "○", it can be said to be a solder material with a low alpha radiation dose.

(5) Verification method 3

After storing the solder alloy sheet of the measurement sample of the α radiation dose measured by the above (1) Verification method 1 for 1 year, by measuring the α radiation dose again according to the above procedures (i), (ii) and (iii), and Time-dependent changes in alpha radiation dose were evaluated.

(6) Judgment Criteria 3

○○: The amount of α radiation generated from the measurement sample is 0.002 cph/cm ² or less.

○: The amount of α radiation generated from the measurement sample was more than 0.002 cph/cm ² and not more than 0.02 cph/cm ² .

×: The amount of α radiation generated from the measurement sample exceeded 0.02 cph/cm ² .

If the judgment is "○○" or "○", the amount of α rays generated does not change over time, and it can be said to be stable. That is, the occurrence of soft errors in electronic devices can be suppressed.

[Comprehensive Evaluation]

○: In Table 1A to Table 16B, inhibition of thickening, inhibition of precipitation of needle-like crystals, inhibition of formation of intermetallic compounds containing Sn, α radiation dose immediately after production, α radiation dose after heat treatment, and α radiation dose Each evaluation of changes over time is "○○" or "○".

×: In Table 1A to Table 16B, inhibition of thickening, inhibition of precipitation of needle-like crystals, inhibition of formation of intermetallic compounds containing Sn, α radiation dose immediately after production, α radiation dose after heat treatment, α radiation dose At least one of the evaluations of changes over time is ×.

[Table 1A]

[Table 1B]

[Table 2A]

[Table 2B]

[Table 3A]

[Table 3B]

[Table 4A]

[Table 4B]

[Table 5A]

[Table 5B]

[Table 6A]

[Table 6B]

[Table 7A]

[Table 7B]

[Table 8A]

[Table 8B]

[Table 9A]

[Table 9B]

[Table 10A]

[Table 10B]

[Table 11A]

[Table 11B]

[Table 12A]

[Table 12B]

[Table 13A]

[Table 13B]

[Table 14A]

[Table 14B]

[Table 15A]

[Table 15B]

[Table 16A]

[Table 16B]

As shown in Table 1A to Table 16B, when using the solder alloys of Examples 1 to 370 to which the present invention is applied, it was confirmed that the viscosity increase of the solder paste over time can be suppressed, the short circuit of the circuit is less likely to occur, and the mechanical strength of the solder joint can be improved. , and suppress the occurrence of soft errors.

On the other hand, when the solder alloys of Comparative Examples 1 to 8, which fall outside the scope of the present invention, were used, all showed inhibition of thickening, inhibition of precipitation of needle-like crystals, inhibition of formation of intermetallic compounds containing Sn, and α radiation dose. Variation in at least one of the assessments.

Claims (23)

A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm ppm or more and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, and the remainder is Sn; The solder alloy satisfies the following formula (1), and Alpha radiation dose is below 0.02cph/cm ² ; 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm ppm or more and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less, and the remainder is Sn; The solder alloy satisfies the following formula (1), and Alpha radiation dose is below 0.02cph/cm ² ; 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. The solder alloy according to claim 1, wherein the alloy composition further satisfies the following formula (1'); 40≦Ni+Fe≦200 (1’) In the formula (1'), Ni and Fe represent the contents (mass ppm) in the aforementioned alloy composition, respectively. The solder alloy according to claim 1, wherein Pb is less than 2 mass ppm. The solder alloy according to claim 1, wherein As is less than 2 mass ppm. The solder alloy according to claim 1, wherein the alloy composition further contains at least one of Ag: 0 mass % or more and 4 mass % or less, and Cu: 0 mass % or more and 0.9 mass % or less. A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: more than 0 Mass ppm and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less; Ag: more than 0 mass % and 4 mass % or less, and Cu: at least one of more than 0 mass % and 0.9 mass % or less; The remainder is Sn; The solder alloy satisfies the following formula (1), and The alpha radiation dose is below 0.02cph/ ^cm2 , 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: more than 0 Mass ppm and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less; Cu: 0 mass % or more and 0.9 mass % or less; The remainder is Sn; The solder alloy satisfies the following formula (1), The ratio of Cu to Ni is 8 or more and 175 or less in terms of the mass ratio represented by Cu/Ni, and The alpha radiation dose is below 0.02cph/ ^cm2 , 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm ppm or more and 600 mass ppm or less, and Fe: 0 mass ppm or more and 100 mass ppm or less; Cu: more than 0 mass % and 0.9 mass % or less; The remainder is Sn; The solder alloy satisfies the following formula (1), The ratio of Cu, Ni and Fe is 7 or more and 350 or less in terms of the mass ratio represented by Cu/(Ni+Fe), and The alpha radiation dose is below 0.02cph/ ^cm2 , 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. A solder alloy having an alloy composition comprising U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, Ni: 0 mass ppm ppm or more and 600 mass ppm or less, and Fe: more than 0 mass ppm and 100 mass ppm or less; Cu: more than 0 mass % and 0.9 mass % or less; The remainder is Sn; The solder alloy satisfies the following formula (1), The ratio of Cu to Fe is 50 or more and 350 or less in terms of the mass ratio represented by Cu/Fe, and The alpha radiation dose is below 0.02cph/ ^cm2 , 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe represent the content (mass ppm) in the aforementioned alloy composition, respectively. The solder alloy according to claim 7, wherein the ratio of Ni to Fe is 0.4 or more and 30 or less as a mass ratio represented by Ni/Fe. The solder alloy according to claim 8, wherein the alloy composition further contains Ag: more than 0 mass % and 4 mass % or less. The solder alloy according to claim 1, wherein the alloy composition further contains at least one of Bi: 0 mass % or more and 0.3 mass % or less, and Sb: 0 mass % or more and 0.9 mass % or less. The solder alloy according to claim 13, wherein the alloy composition further satisfies the following formula (2), 0.03≦Bi+Sb≦1.2 (2) In the formula (2), Bi and Sb represent contents (mass %) in the aforementioned alloy composition, respectively. The solder alloy according to claim 1, wherein the alpha radiation dose after heat treatment at 100° C. for 1 hour is 0.02 cph/cm ² for the solder alloy sheet formed into a sheet with an area of 900 cm ² on one side. the following. The solder alloy according to any one of claims 1 to 15, wherein the alpha radiation dose is 0.002 cph/cm ² or less. The solder alloy according to claim 16, wherein the alpha radiation dose is 0.001 cph/cm ² or less. A solder powder comprising the solder alloy according to any one of claims 1 to 17. The solder powder according to claim 18 has two or more types of solder alloy particle groups having different particle size distributions at the same time. A solder paste containing the solder powder described in claim 18 or 19 and a flux. A solder ball comprising the solder alloy described in any one of claims 1 to 17. A solder preform comprising the solder alloy of any one of claims 1 to 17. A solder joint comprising the solder alloy described in any one of claims 1 to 17.