TW202138577A - 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 paste, solder balls, solder preforms and solder joints

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

This application claims priority based on Japanese Application No. 2020-070927 filed in Japan on April 10, 2020, and its content is cited here.

Among electronic components mounted on printed circuit boards, miniaturization and high performance are gradually required. Examples of such electronic components include semiconductor packages. In the semiconductor package, a semiconductor element with electrodes is encapsulated with a resin component. Solder bumps made of solder materials are formed on the electrode system. In addition, the solder material connects the semiconductor element and the printed circuit board.

In solder materials, the influence of alpha rays on soft errors is a problem. In order to alleviate such adverse effects on the operation of semiconductor devices, the development of low alpha radiation materials containing solder materials was carried out.

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

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

Generally speaking, Sn contains lead (Pb) and bismuth (Bi) as impurities. ²¹⁰ Pb and ²¹⁰ Bi, which are radioactive isotopes of Pb and Bi, undergo β decay to become ²¹⁰ Po, and ²¹⁰ Po undergoes α decay to produce ²⁰⁶ Pb, which produces α rays. The series of decays (uranium series) are said to be the main cause of the generation of alpha rays from solder materials.

In addition, in the evaluation of the amount of alpha rays generated from materials, the unit often uses "cph/cm ² ". "Cph/cm ² "is the abbreviation of "counts per hours/cm ² ", which means the count 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 approximately 22.3 years. In addition, the degree of influence (existence ratio) can be expressed by the following formula (refer to Non-Patent Document 1). That is, compared with Pb, the influence of Bi on the generation of alpha rays is very low.

[ 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 mentioned above, in the past, in the design of low-α-dose materials, U and Th were generally removed, and Pb was further removed completely.

In addition, the amount of alpha rays generated from solder materials is known to change with the passage of time, which basically increases the amount of alpha rays. It is said that the cause of this is that the radioactive Pb and radioactive Bi in the solder alloy undergo β decay to increase the amount of Po. Then, Po undergoes α decay to produce α rays.

In materials with very low alpha radiation, although these radioactive elements are hardly contained, sometimes due to ^{the segregation of 210} Po, the alpha radiation dose increases with the passage of time. ²¹⁰ Po originally emits α rays, but when the solder alloy solidifies, it segregates in the center of the solder alloy, so the emitted α rays will be shielded by the solder alloy. Then, as time elapses, ²¹⁰ Po will be uniformly dispersed in the alloy and will also be present on the surface where α rays are detected, so the dose of α rays will increase with time (refer to Non-Patent Document 2).

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

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

For the above-mentioned printed circuit board packaging, from the viewpoint of connection strength, etc., when packaging electronic parts of a certain size, a method of inserting terminals into through holes of the substrate and packaging is adopted. The packaging operation of such electronic parts usually uses flow soldering. Flow soldering is a method of soldering by contacting the solder jet surface of the solder bath with the connection surface of the printed circuit board.

There must be a solder bath in flow soldering. In the solder bath, high-temperature molten solder will flow for a long time. Therefore, from the viewpoint of corrosion resistance, the material of the solder bath is stainless steel whose main component is iron (Fe). However, due to long-term use, sometimes the inner surface of the solder bath will be eroded by Fe.

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

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2010-156052 A

[Patent Document 2] JP 2015-98052 A

[Patent Document 3] JP 2008-168322 A

[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 increase in the viscosity 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 so that the alloy also contains impurities. At this time, due to the presence of radioactive elements in its impurities, the amount of alpha rays generated from the solder material will increase.

In addition, as in the solder alloy described in Patent Document 3, when a solder alloy containing Sn as a main component contains a large amount of Fe, needle-like crystals derived from the SnFe compound may precipitate, which may cause a short circuit in the circuit.

In addition, a solder alloy containing Sn as a main component may contain a large amount of nickel (Ni) in order to improve wettability. If the Ni content is high, SnCuNi compounds will precipitate near the joint interface of the solder alloy, which may reduce the mechanical strength of the solder joint.

The present invention was developed in view of the above 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 flux, and a solder ball composed of the solder alloy , Solder preforms and solder joints, in which the solder alloy can suppress the increase in the viscosity of the solder paste over time, is not prone to short circuit of the circuit, improves the mechanical strength of the solder joint, and suppresses the occurrence of soft errors.

The inventors of the present invention conducted research for the purpose of designing a solder alloy with a low alpha dose that can suppress the increase in viscosity of the solder paste over time without adding As that is accompanied by an impurity containing a radioactive element. Through such research, it is found that it contains Sn as the main component and a predetermined amount such as the base metal, which is a melting point of 1455 that is heated at high temperature during refining or processing. The alloy composition of Ni with a temperature of ℃ and Fe with a melting point of 1538 ℃ can achieve the aforementioned purpose, and the present invention is finally completed.

That is, in order to solve the above-mentioned problems, the present invention adopts the following means.

[1] 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: 0 mass ppm or more and 100 mass ppm or less, and the remainder being Sn alloy composition; the solder alloy satisfies the following formula (1), and the alpha dose is 0.02 cph/ cm ² or less.

20≦Ni+Fe≦700 (1)

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

[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 alpha dose is 0.02 cph/cm ² or less ；

20≦Ni+Fe≦700 (1)

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

[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 series respectively represent the content (mass ppm) in the aforementioned alloy composition.

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

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

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

[7] 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: 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 One type; the remainder is Sn; the solder alloy satisfies the following formula (1), and the alpha dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

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

[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 as the mass ratio shown by Cu/Ni, and the α-ray dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

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

[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 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 the remainder is an alloy composition of Sn, and satisfies the following formula (1), Cu, Ni, and Fe The ratio is 7 or more and 350 or less in terms of the mass ratio shown by Cu/(Ni+Fe), and the alpha dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

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

[10] 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; 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 shown by Cu/Fe, and the α-ray dose is 0.02 cph/cm ² or less.

20≦Ni+Fe≦700 (1)

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

[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 in terms of a mass ratio shown 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% by mass and 4% by mass or less.

[13] The solder alloy according to any one of [1] to [12], wherein the alloy composition further contains Bi: 0% by mass or more and 0.3% by mass or less, and Sb: 0% by mass or more and 0.9% by 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 respectively represent the content (mass%) in the aforementioned alloy composition.

[15] The solder alloy according to any one of [1] to [14], wherein the solder alloy ^{sheet formed into a sheet with an area of 900 cm 2} on one side is heated at 100°C for 1 hour The subsequent alpha dose is 0.02 cph/cm ² or less.

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

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

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

[19] The solder powder described in [18] simultaneously has two or more types of solder alloy particles with different particle size distributions.

[20] A solder paste containing the solder powder described in [18] or [19] and flux.

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

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

[23] A solder joint comprising the solder alloy described in 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 flux, a solder ball composed of the solder alloy, a solder preform, and a solder joint can be provided, Among them, the solder alloy system can suppress the increase in the viscosity of the solder paste over time, is not prone to short circuit of the circuit, improves the mechanical strength of the solder joint, and suppresses the occurrence of soft errors.

The present invention will be explained in detail below.

In this manual, the "ppb" of the solder alloy composition is "quality ppb" unless otherwise specified. "Ppm" means "mass ppm" unless otherwise specified. "%" means "mass%" as long as there is no special designation.

(Solder alloy)

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

20≦Ni+Fe≦700 (1)

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

<Alloy composition>

The solder alloy system of this 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 or less, and Fe: 0 mass ppm or more and 100 mass ppm or less, and an alloy composition in which the balance is Sn, and satisfies the aforementioned 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 this embodiment, from the viewpoint of setting the amount of α rays generated from the solder alloy to 0.02cph/cm ² or less, relative to the total mass (100% by mass) of the solder alloy, U and Th in the solder alloy The content 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 speaking, Sn contains Pb as an impurity. The radioisotope in Pb undergoes β decay to become ²¹⁰ Po, and when ²¹⁰ Po undergoes α decay to produce ²⁰⁶ Pb, α rays are generated. 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, relative to the total mass (100% by mass) of the solder alloy, the content of Pb in the solder alloy is less than 5 ppm, preferably less than 2 ppm, and more preferably less than 1 ppm. In addition, the lower limit of the Pb content 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 in suppressing the viscosity increase of the solder paste over time, but 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 this embodiment, the purpose is to try to suppress the increase in viscosity of the solder paste over time without adding As accompanied by impurities containing radioactive elements.

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

By soldering, Sn-containing intermetallic compounds (including Sn-containing intermetallic compounds) are formed in the vicinity of the joint interface in the solder alloy. If the Sn-containing intermetallic compounds are precipitated, the mechanical strength of the solder joint will deteriorate.

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

Ni is an element that inhibits the formation of Sn-containing intermetallic compounds at the joint 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, if the Ni content in the solder alloy exceeds 600 ppm, SnNi compounds will be precipitated in the vicinity of the joint interface in the solder alloy, and the mechanical strength of the solder joint may deteriorate.

In this embodiment, relative to the total mass (100% by mass) of the solder alloy, the Ni content 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, 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 joint interface. Moreover, within the predetermined content range, the precipitation of needle crystals generated by the SnFe compound can be suppressed, and the short circuit of the circuit can be prevented.

The “needle crystals” referred to herein refer to crystals in which the ratio of the long axis to the short axis, that is, the aspect ratio, is 2 or more in one crystal derived from a SnFe compound.

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

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

20≦Ni+Fe≦700 (1)

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

Both Ni and Fe in the formula (1) are elements that inhibit the formation of Sn-containing intermetallic compounds at the joint interface. Moreover, 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 viscosity increase of the solder paste with time, the total mass of the solder alloy (100% by mass) is the sum of Ni and Fe in the solder alloy 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 "the total content of Ni and Fe" 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. It has both Ni and In the case of Fe, it is the total content of these.

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

If the Ni/Fe mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

≪Any element≫

The alloy composition of the solder alloy of this embodiment can contain elements other than the above-mentioned elements as required.

For example, in addition to the above-mentioned elements, the alloy composition of the solder alloy of this 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.

Ag: 0% by mass or more and 4% by 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, Ag-based ionization tends to be a noble metal element compared to Sn, and the coexistence of Ni and Fe improves the effect of suppressing the viscosity increase of the solder paste over time. Furthermore, if the Ag content in the solder alloy is within the above range, the increase in the melting point of the alloy can be suppressed, so it is not necessary to excessively increase the reflow temperature.

In this embodiment, relative to the total mass (100% by mass) of the solder alloy, the Ag content in the solder alloy is preferably 0% or more and 4% or less, more preferably more than 0% and 4% or less, 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% by mass or more and 0.9% by 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 with respect to Sn, and the coexistence of Ni and Fe improves the effect of suppressing the viscosity increase of the solder paste over time.

In this embodiment, relative to the total mass (100% by mass) of the solder alloy, 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, 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 Cu and Ni are present at the same time, the ratio of Cu to Ni in the solder alloy is based on the mass ratio shown by Cu/Ni, preferably 8 or more and 175 or less, more preferably 10 or more and 150 or less .

If the Cu/Ni of such a mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

When both Cu and Fe are present in this embodiment, the ratio of Cu to Fe in the solder alloy is based on the mass ratio shown by Cu/Fe, preferably 50 or more and 350 or less, more preferably 70 or more and 250 or less.

If the Cu/Fe mass ratio is in the above-mentioned preferred range, the effect of the present invention can be obtained more easily.

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 calculated by the mass ratio shown by Cu/(Ni+Fe), which is preferably 7 or more and 350 or less, more Preferably, it is 10 or more and 250 or less.

If the Cu/(Ni+Fe) of such a mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

As an implementation form of the solder alloy, it can include U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and Ni: 0 mass ppm or more 600 mass ppm or less, and Fe: alloy composition that exceeds 0 mass ppm and 100 mass ppm or less, and the remainder is Sn, satisfies the above formula (1), and has an alpha dose of 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 of the implementation forms of the solder alloy, it may include U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and Ni: more than 0 At least one of 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: more than 0 mass% and 0.9 mass% or less, and The remainder is the alloy composition of Sn, which satisfies the above formula (1), and has an alpha dose of 0.02 cph/cm ² or less. In the alloy composition of the solder alloy, the ratio of Ni to Fe can be more than 0.4 to 30 in terms of the mass ratio shown by Ni/Fe.

In addition, as one of the implementation forms of the solder alloy, it may include U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and 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 the remainder is an alloy composition of 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 shown by Cu/Ni, and the α-ray dose is 0.02 cph/cm ² or less. In the alloy composition of the solder alloy, the ratio of Ni to Fe can be more than 0.4 to 30 in terms of the mass ratio shown by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0% by mass and 4% by mass or less.

In addition, as one of the implementation forms of the solder alloy, it may include U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and 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 the remainder is an alloy composition of Sn, and satisfies the above formula (1), Cu The ratio of Ni to Fe is 7 or more and 350 or less in terms of the mass ratio shown by Cu/(Ni+Fe), and the α-ray dose is 0.02cph/cm ² or less. In the alloy composition of the solder alloy, the ratio of Ni to Fe can be more than 0.4 to 30 in terms of the mass ratio shown by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0% by mass and 4% by mass or less.

In addition, as one of the solder alloys, the form of implementation may include U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and Ni: 0 mass ppm or more and 600 mass ppm or less, and Fe: more than 0 mass ppm and less than 100 mass ppm, Cu: more than 0 mass% and 0.9 mass% or less, and the remainder is an alloy composition of Sn, and satisfies the above formula (1), Cu and The ratio of Fe is 50 or more and 350 or less in terms of the mass ratio shown by Cu/Fe, and the alpha dose is 0.02 cph/cm ² or less. In the alloy composition of the solder alloy, the ratio of Ni to Fe can be 0.4 or more and 30 or less in terms of the mass ratio shown by Ni/Fe. Furthermore, the aforementioned alloy composition may further contain Ag: more than 0% by mass and 4% by mass or less.

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

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

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

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

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

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

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

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

0.03≦Bi+Sb≦1.2 (2)

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

In the formula (2), Bi and Sb are elements that show the effect of suppressing the viscosity increase of the solder paste over time. Moreover, in this embodiment, both Bi and Sb contribute to the wettability of the solder alloy.

Relative to the total mass of the solder alloy (100% by mass), 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 0.9%.

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

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

If the Sb/Bi of such a mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

≪Remaining part: Sn≫

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

<α dose>

The alpha radiation dose of the solder alloy system of this 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 parts.

From the viewpoint of suppressing soft errors in higher-density packaging, the α-ray dose in the solder alloy of this embodiment is preferably 0.01 cph/cm ² or less, more preferably 0.002 cph/cm ² or less, and even more preferably It is less than 0.001cph/cm ^2.

The alpha dose generated from the solder alloy can be measured as follows. The method for determining the alpha dose is based on the international standard JEDEC STANDARD.

Sequence (i):

Use the airflow type α-ray dosing device.

As for the measurement sample, a solder alloy sheet was used. The solder alloy sheet was a molten solder alloy and was shaped into a sheet with an area of 900 cm ^{2 on} one side.

The solder alloy piece is set as a measurement sample in the α dose measuring device, and PR gas is discharged here.

In addition, the use of the PR gas system is based on the international standard JEDEC STANDARD. That is, the PR gas system used for the measurement is set to fill a gas cylinder with a mixed gas of 90% argon and 10% methane, and then decay of radon (Rn) for more than 3 weeks.

Sequence (ii):

In the α dose measuring device provided with the solder alloy flakes, the PR gas was allowed to flow for 12 hours and left to stand, and then the α dose measurement was performed for 72 hours.

Sequence (iii):

Calculate the average alpha dose as "cph/cm ² ". The abnormal point (measurement measured by device vibration, etc.) is the one-hour measurement that is removed.

[Method of manufacturing solder alloy]

The solder alloy system of this embodiment can be manufactured, for example, by using a manufacturing method having a step of melting and mixing a raw material metal containing at least one of Ni and Fe and Sn.

For the purpose of designing a solder alloy with low alpha dose, it is preferable to use low alpha dose materials as its raw materials. For example, as raw materials, Sn, Ni, and Fe are preferably high-purity ones, and Remove U, Th and Pb.

The Sn system as a raw material metal can be manufactured using, for example, the manufacturing method described in JP 2010-156052 A (Patent Document 1).

Ni and Fe as the raw material metals can be manufactured in accordance with Japanese Patent No. 5692467, for example.

The operation of melting and mixing the raw material metals can use conventionally known methods.

Generally speaking, in solder alloys, the constituent elements constituting the solder alloy do not function independently, but when the content of each constituent element is all within a predetermined range, various effects can be exerted. If the solder alloy according to the implementation type described above, the content of each constituent element is within the above range, the increase in the viscosity of the solder paste over time can be suppressed, the short circuit of the circuit is not easy to occur, and the mechanical strength of the solder joint is improved, while suppressing The occurrence of a soft error. That is, the solder alloy of this embodiment can be used as a target low-α radiation material, and can be applied to the formation of solder bumps around the memory to suppress the occurrence of soft errors.

In the case of this embodiment, the content of each constituent element is outside the above-mentioned range, and it is related to the suppression of Fe corrosion, the suppression of the viscosity increase of the solder paste over time, the improvement of the mechanical strength of the solder joint, and the suppression of the short circuit of the circuit. The Fe and Ni satisfy the predetermined relationship, which can fully exert the effect of the present invention.

In addition, in this embodiment mode, the purpose is to design a low-α radiation solder alloy that can suppress the increase in viscosity of the solder paste over time without actively adding As. In contrast, a solder alloy containing Ni and Fe, which are high-melting-point metals heated at a high temperature during refining or processing of the base metal, in a specific ratio is used to achieve the goal.

The reason for obtaining such an effect is not certain, but it is estimated as follows.

Sn used for solder alloys with low alpha dose is very high purity, and when the molten alloy is solidified, the crystal size of Sn becomes larger. In addition, the oxide film in the Sn also forms a compliant loose oxide film. Therefore, by adding Ni and Fe, which are high melting point metals, the crystal size is reduced and a dense oxide film is formed. As the reactivity of the alloy and the flux is suppressed, the viscosity increase of the solder paste over time can be suppressed.

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

The solder alloy showing such an alpha dose is not easy to cause ^{segregation of 210} Po in the alloy, and it is useful because the effect of the change in the alpha dose over time is small. By using a solder alloy that exhibits such an alpha dose, the occurrence of soft errors can be suppressed, and the stable operation of the semiconductor device can be more easily ensured.

(Solder powder)

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

The solder powder of this embodiment is suitable for the solder paste described later.

Solder powder can be produced by: the dropping method of dropping molten solder alloy to obtain particles, the spraying method of centrifugal spraying, the atomization method, the granulation method in liquid, the method of crushing the bulk solder alloy, etc. . In the dripping method or spraying method, the dripping or spraying is preferably performed in an inactive environment or in a solvent in order to form particles.

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

When the solder powder of this embodiment is spherical powder, in the classification of powder size in JIS Z 3284-1:2014 (Table 2), it is better to satisfy the marks 1 to 8, and to satisfy the marks 4 to 8. 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 will be suppressed, and the aggregation of fine powder will be suppressed, and the increase in the viscosity of the solder paste will be suppressed. Therefore, it is possible to weld finer parts.

In addition, the solder powder of this embodiment preferably 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 spherical powder has a sphericity of 0.8 or more, more preferably 0.9 or more, even 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 measurement system (ULTRA QUICK VISION ULT RA QV350-PRO measurement device manufactured by MITSUTOYO) using the minimum zone center method (MZC method) .

The so-called true sphericity means the deviation from the true sphere. For example, the arithmetic average calculated by dividing the diameter of 500 solder alloy particles by the major diameter indicates that the closer the value is to the upper limit of 1.00, the closer to the true sphere.

(Solder paste)

The solder paste related to one aspect of the present invention contains the solder powder related to one aspect of the present invention and flux.

<Flux>

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

Examples of the resin component system include rosin resins.

Examples of the rosin resin system include rosin, a raw material rosin such as rosin gum, wood rosin, and pine pine rosin, and derivatives derived from the raw material rosin.

The derivatives are, for example, refined rosin, hydrogenated rosin, heterogeneous rosin, polymerized rosin, and α, β unsaturated carboxylic acid modified products (acrylated rosin, maleated rosin, fumarated rosin, etc.), and the polymerized rosin The purified product, hydride, and heterogeneous product, and the purified product, hydride, and heterogeneous product of the α,β unsaturated carboxylic acid modified product, etc., can be used in two or more types.

In addition, resin components include rosin resins, 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.

Examples of the modified terpene resin include aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, and the like. Examples of the modified terpene phenol resin include hydrogenated terpene phenol resin. Modified styrene Examples of the olefin resin include styrene acrylic resin and styrene maleic acid resin. Modified xylene resins include phenol-modified xylene resin, alkylphenol-modified xylene resin, phenol-modified resorcinol-type xylene resin, polyol-modified xylene resin, polyoxyethylene adduct two Toluene resin, etc.

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

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

The amine system includes, for example, ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethyl 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-cyanoethyl 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- Pyrrole [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-methylpropanoxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzene Bisimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, benzimidazole, 2 -(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tertiary butyl-5'-methylphenyl)-5-cyclobenzo Triazole, 2-(2'-hydroxy-3',5'-di-tertiary pentylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tertiary octylphenyl)benzene O-triazole, 2,2'-methylene bis[6-(2H-benzotriazole-2-yl)-4-third octylphenol], 6-(2-benzotriazole)- 4-third octyl-6'-tertiary butyl-4'-methyl-2,2'-methylene bisphenol, 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]diethanol, 1-(1',2'-dicarboxyethyl)benzotris Azole, 1-(2,3-dicarboxypropyl)benzotriazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzo Triazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole and the like.

Examples of the halogen-based active agent system include amine hydrohalides and organic halogen compounds.

Amine hydrohalides are compounds that react amines with hydrogen halides. The amine system here includes, for example, ethylamine, ethylenediamine, triethylamine, diphenylguanidine, xylylguanidine, methylimidazole, 2-ethyl-4-methylimidazole, etc., and examples of hydrogen halides include The hydride of chlorine, bromine and iodine.

Examples of the organic halogen compound system include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isotrihydroate 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. .

Examples of the thixotropic agent include wax-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.

Examples of the wax-based thixotropic agent include castor oil.

Examples of the amide-based thixotropic agent include monoamide-based thixotropic agents, bis-amide-based thixotropic agents, and polyamide-based thixotropic agents. Specifically, laurylamide, palmitamide, and stearylamine can be cited. , Behenylamide, hydroxystearylamide, saturated fatty amide, oleamide, mustard amide, unsaturated fatty acid amide, p-toluamide, aromatic amide, methylene distearyl Amide, ethylene bislauric amide, ethylene bishydroxystearyl amide, saturated fatty bis amide, methylene bis oleamide, unsaturated fatty bis amide, meta-xylene bis stearyl amide Amine, aromatic diamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, methylol stearyl amide, methylol amide, fatty acid ester amide Wait.

Examples of the sorbitol-based thixotropic agent include benzhydryl-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, and the like.

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

Examples of alcohol solvents include isopropanol, 1,2-butanediol, isobornylcyclohexanol, 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-ginseng (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 -Ginseng (hydroxymethyl) ethyl) ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, butanetetraol, threitol, Guaiacol glycerol ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol Wait.

The glycol ether solvent system includes, for example, diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, and diethylene glycol monohexyl Ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, etc.

Examples of the metal inactivating agent system include hindered phenol-based compounds and nitrogen compounds. By making the soldering flux contain either a phenol-based compound or a nitrogen compound, it is easy to increase the viscosity-inhibiting effect of the solder paste.

The "metal inactivating agent" referred to here refers to a compound that has the property of preventing metal deterioration by contact with a certain compound.

The so-called hindered phenol-based compound refers to a phenol-based 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 a tertiary butyl group).

The hindered phenolic compound is not particularly limited. For example, bis[3-(3-tertiarybutyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], N, N '-Hexamethylene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propane amide], 1,6-hexanediol bis[3-(3,5-di -Tert-butyl-4-hydroxyphenyl)propionate], 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-methylene Base bis(6-tertiary butyl-p-cresol), 2,2'-methylene bis(6-tertiary 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-hydroxyl (Phenyl) propionate), 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine , Octylerythritol group-tetra[3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2-sulfur-diethylene bis[3-(3,5 -Di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N, N'-hexamethylene bis(3,5-di-tert-butyl-4-hydroxy-hydrocinnamidine), 3,5-di-tert-butyl-4-hydroxybenzyl phosphate group- Diethyl, 1,3,5-trimethyl-2,4,6-ginseng (3,5-di-tert-butyl-4-hydroxybenzene Methyl)benzene, N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]glaxamide, the following chemical formula The compounds shown etc.

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

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

The hydrazine-based nitrogen compound may be a nitrogen compound having a hydrazine skeleton, and examples thereof include dodecanedioic acid bis[N2-(dihydroxybenzyl)hydrazine], N,N'-bis[3-( 3,5-Di-tert-butyl-4-hydroxyphenyl)propanyl]hydrazine, sebacic acid bis-salicylic hydrazine, N-salicylic acid-N'-salicylic hydrazine, m-nitro Benzohydrazine, 3-aminophthalic hydrazine, dihydrazine phthalate, hydrazine adipic acid, oxalyl bis(2-hydroxy-5-octylbenzylidene hydrazine) , N'-benzylpyrrolidone hydrazine formate, N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanyl)hydrazine, etc.

The amide-based nitrogen compound may be a nitrogen compound having an amide skeleton, including N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane Glycyloxy]ethyl}glaxamide and the like.

The triazole-based nitrogen compound may be a nitrogen compound having a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salanamide, 3-amino-1,2, 4-triazole, 3-(N-salaniline)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 and melamine derivatives. More specifically, for example, amine triazine, alkylated amine triazine, alkoxy alkylated amine triazine, melamine, alkylated melamine, alkoxy alkylated melamine, N2-butyl melamine, N2,N2-diethyl melamine, N,N,N',N',N",N"-land (methoxymethyl) melamine, etc.

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

Examples of the surfactant include nonionic surfactants and weak cationic surfactants.

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

The weak cationic surfactant system includes, for example, 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 acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, and polyoxyalkylene alkylenes. Base amines, polyoxyalkylene alkyl amides and the like.

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

If 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 exhibited.

The solder paste of this embodiment can be manufactured by a general manufacturing method in the technical field to which the invention belongs.

The blending components constituting the flux are heated and mixed to prepare a flux, and in the flux, the solder powder is stirred and mixed to obtain a solder paste. In addition, the effect of suppressing the increase in viscosity over time is expected, and unlike the above-mentioned solder powder, zirconia powder can be further formulated.

(Solder ball)

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

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

The solder ball of this embodiment can be manufactured by a dropping method using a general method in the technical field to which the invention belongs.

The particle size of the solder balls is preferably 1 μm or more, more preferably 10 μm or more, even 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, even more preferably 600 μm or less, and particularly preferably 300 μm or less.

In addition, the particle size of the solder balls is 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 one aspect of the present invention is composed of the solder alloy according to one 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 can include gaskets, rings, pellets, discs, ribbons, threads, etc.

(Solder joint)

The solder joint according to one aspect of the present invention is composed of the solder alloy according to one 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 part mainly formed of a solder alloy.

The solder joint of this embodiment is formed, for example, by joining the solder alloy of the above embodiment to electrodes of PKG (Package) such as IC chips and electrodes of substrates such as PCB (printed circuit board).

In addition, the solder joint of this embodiment can be manufactured by a method generally used in the technical field of the invention, such as mounting one solder ball of the above embodiment on an electrode coated with flux. .

(Example)

Hereinafter, the present invention will be explained in more detail with examples, but the present invention is not limited by these examples.

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

<Solder Alloy>

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

The raw material metals were melted and stirred to prepare the solder alloys of the respective examples having the alloy compositions shown in Table 1A to Table 16B.

<Solder Powder>

The solder alloy of each example was melted, and the solder powder was produced by the atomization method. The solder powder is composed of the solder alloy of each example having the alloy composition shown in Table 1A to Table 16B, and is in accordance with JIS Z 3284. -1: The powder size classification in 2014 (Table 2) meets the size (particle size distribution) of mark 4.

<Preparation of Flux (F0)>

Use rosin resin as the resin component.

Use thixotropic agents, organic acids, amines and halogen-based active agents as active ingredients.

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

42 parts by mass of rosin, 35 parts by mass of glycol ether 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 were mixed to prepare flux (F0).

<Manufacture of Solder Paste>

The aforementioned flux (F0) and solder powder composed of the solder alloys of the respective examples having the alloy compositions shown in Table 1A to Table 16B were mixed to produce solder paste.

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

<evaluation>

Use the aforementioned solder paste to evaluate the suppression of viscosity increase.

In addition, using the aforementioned solder alloy, the evaluation of the inhibition of precipitation of needle-like crystals, the evaluation of the inhibition of the formation of Sn-containing intermetallic compounds, and the evaluation of the α-ray dose were respectively performed. Furthermore, conduct a comprehensive assessment.

The details are as follows. The evaluated results are shown in Table 1A to Table 16B.

[Thickening inhibition]

(1) Verification method

Regarding the solder paste immediately after preparation, PCU-205 manufactured by Malcohm Co., Ltd. was used, and the viscosity was measured for 12 hours in the atmosphere at a rotation speed of 10 rpm and 25°C.

(2) Judgment criteria

○: Compared with the viscosity of 30 minutes after the solder paste is just prepared, the viscosity after 12 hours is 1.2 times or less.

×: Compared with the viscosity of the solder paste after 30 minutes, the viscosity after 12 hours is more than 1.2 times.

If this judgment is "○", it can be said that a sufficient viscosity increase suppression effect is obtained. That is, the increase in viscosity of the solder paste over time can be suppressed.

[Precipitation inhibition of needle crystals]

(1) Verification method

The solder alloy of each example was melted at 250°C, and cooled to 100°C below the solidus temperature of the entire alloy composition in 10 minutes. For the solder alloy after cooling, a scanning electron microscope (SEM) was used to observe the cross-section at any 5 locations in the range of 300 μm×300 μm. In the cross-sectional SEM photograph, it was confirmed whether there were needle crystals derived from the SnFe compound.

The acicular crystal in this embodiment refers to a crystal whose length-to-width ratio, which is the ratio of the major axis to the minor axis, is 2 or more in one SnFe compound-derived crystal.

(2) Judgment criteria

○: Needle-shaped crystals were not observed in all the SEM observation images at 5 locations.

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

If the judgment is "○", it can be said to have the effect of inhibiting the precipitation of needle-like crystals. That is, it is not easy to short-circuit the circuit.

[Inhibition of formation of Sn-containing intermetallic compounds]

(1) Verification method

The solder alloy of each example was melted at 250°C, and cooled to 100°C below the solidus temperature of the entire alloy composition in 10 minutes. For the solder alloy after cooling, use SEM to observe the cross-section at any 5 locations in the range of 300 μm×300 μm to confirm the presence or absence of Sn(Cu)Ni compounds.

(2) Judgment criteria

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

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

If this judgment is "○", it can be said to have the effect of inhibiting the formation of Sn-containing intermetallic compounds. That is, the mechanical strength of the solder joint can be improved.

[α dose]

(1) Verification method 1

The α dose is measured by an α dose measuring device using a gas flow proportional counter, by following the above-mentioned sequence (i), (ii) and (iii).

Use the solder alloy sheet immediately after manufacture as the measurement sample.

The solder alloy sheet is obtained by melting the manufactured solder alloy and forming it into a sheet with an area of 900 cm ^{2 on} one side.

This measurement sample was placed in an α dose measuring device, and PR-10 gas was allowed to flow for 12 hours, and after it was allowed to stand still, the α dose was measured for 72 hours.

(2) Judgment criteria 1

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

○: The amount of α rays generated from the measurement sample exceeds 0.002 cph/cm ² or more and 0.02 cph/cm ² or less.

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

If the judgment is "○○" or "○", it can be described as a solder material with a low alpha dose.

(3) Verification method 2

Except for changing the measurement sample, the measurement of the alpha dose is performed in the same manner as in (1) Verification Method 1 above.

For the measurement sample, a solder alloy sheet was used to melt the solder alloy just after production, and the solder alloy ^{sheet formed into a flake with a surface area of 900 cm 2} was heated at 100°C for 1 hour and left to cool.

(4) Judgment criteria 2

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

○: The amount of α rays generated from the measurement sample is more than 0.002 cph/cm ² and less than 0.02 cph/cm ² .

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

If the judgment is "○○" or "○", it can be described as a solder material with a low alpha dose.

(5) Verification method 3

After storing for 1 year the solder alloy pieces of the measurement sample of the α-ray dose measured by the above-mentioned (1) Verification Method 1, and again by measuring the α-ray dose according to the above procedures (i), (ii) and (iii), Evaluate the time-dependent changes in alpha radiation.

(6) Judgment criteria 3

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

○: The amount of α rays generated from the measurement sample is more than 0.002 cph/cm ² and less than 0.02 cph/cm ² .

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

If the judgment is "○○" or "○", the amount of alpha radiation produced will not change over time, and it can be said to be stable. That is, it is possible to suppress the occurrence of soft errors in electronic equipment.

[Comprehensive Evaluation]

○: In Table 1A to Table 16B, the inhibition of viscosity increase, the inhibition of precipitation of needle-like crystals, the inhibition of the formation of Sn-containing intermetallic compounds, the α dose immediately after manufacture, the α dose after heat treatment, and the α dose All assessments of changes over time are "○○" or "○".

×: In Table 1A to Table 16B, suppression of viscosity increase, suppression of precipitation of needle crystals, suppression of formation of Sn-containing intermetallic compounds, α dose immediately after manufacture, α dose and α dose after heat treatment Among the assessments of changes over time, at least one item 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 Tables 1A to 16B, when the solder alloys of Examples 1 to 370 of the present invention are used, it is confirmed that the viscosity of the solder paste can be inhibited from increasing over time, the short circuit of the circuit is not easily generated, and the mechanical strength of the solder joint is improved. , And suppress the occurrence of soft errors.

On the other hand, when the solder alloys of Comparative Examples 1 to 8 outside the scope of the present invention were used, they all showed suppression of thickening, suppression of precipitation of needle-like crystals, suppression of formation of Sn-containing intermetallic compounds, and α-ray dose The result of at least one variation in the evaluation.

Claims (23)

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, and 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 Alpha radiation is below 0.02cph/cm ² ; 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe systems respectively represent the content (mass ppm) in the aforementioned alloy composition. 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, and 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 Alpha radiation is below 0.02cph/cm ² ; 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe systems respectively represent the content (mass ppm) in the aforementioned alloy composition. The solder alloy according to claim 1, wherein the aforementioned alloy composition further satisfies the following formula (1'); 40≦Ni+Fe≦200 (1’) In the formula (1'), Ni and Fe series respectively represent the content (mass ppm) in the aforementioned alloy composition. The solder alloy according to claim 1, wherein Pb is less than 2 ppm by mass. The solder alloy according to claim 1, wherein As is less than 2 ppm by mass. The solder alloy according to claim 1, wherein the alloy composition further contains at least one of Ag: 0% by mass or more and 4% by mass or less, and Cu: 0% by mass or more and 0.9% by mass or less. 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: more than 0 mass ppm and 100 mass ppm or less; Ag: more than 0% by mass and 4% by mass or less, and Cu: at least one of more than 0% by mass and 0.9% by mass or less; The remaining part is Sn; The solder alloy satisfies the following formula (1), and The alpha dose is 0.02cph/cm ² or less, 20≦Ni+Fe≦700 (1) In the formula (1), Ni and Fe systems respectively represent the content (mass ppm) in the aforementioned alloy composition. 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% by mass or more and 0.9% by mass or less; The remaining part 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 shown by Cu/Ni, and The alpha dose is 0.02cph/cm ² or less, 20≦Ni+Fe≦700 (1) (1) In the formula, Ni and Fe respectively represent the content (mass ppm) in the aforementioned alloy composition. 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, and 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; Cu: more than 0% by mass and 0.9% by mass or less; The remaining part 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 shown by Cu/(Ni+Fe), and The alpha dose is 0.02cph/cm ² or less, 20≦Ni+Fe≦700 (1) (1) In the formula, Ni and Fe respectively represent the content (mass ppm) in the aforementioned alloy composition. 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, and 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% by mass and 0.9% by mass or less; The remaining part 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 shown by Cu/Fe, and The alpha dose is 0.02cph/cm ² or less, 20≦Ni+Fe≦700 (1) (1) In the formula, Ni and Fe respectively represent the content (mass ppm) in the aforementioned alloy composition. The solder alloy according to claim 7, wherein the ratio of Ni to Fe is 0.4 or more and 30 or less in terms of the mass ratio shown by Ni/Fe. The solder alloy according to claim 8, wherein the alloy composition further contains Ag: more than 0% by mass and 4% by mass or less. The solder alloy according to claim 1, wherein the alloy composition further contains at least one of Bi: 0% by mass or more and 0.3% by mass or less, and Sb: 0% by mass or more and 0.9% by mass or less. The solder alloy according to claim 13, wherein the aforementioned alloy composition further satisfies the following formula (2), 0.03≦Bi+Sb≦1.2 (2) In the formula (2), Bi and Sb respectively represent the content (mass%) in the aforementioned alloy composition. The solder alloy of one of said request, wherein the forming of an area of one side of the sheet-like piece of the solder alloy 900cm ^2, α-ray dose administered after a heat treatment of 1 hour at 0.02cph 100 ℃ / cm ² the following. The solder alloy according to any one of claims 1 to 15, wherein the alpha dose is 0.002 cph/cm ² or less. The solder alloy according to claim 16, wherein the alpha dose is 0.001 cph/cm ² or less. A solder powder comprising the solder alloy described in any one of claims 1 to 17. The solder powder described in claim 18 simultaneously has two or more types of solder alloy particle groups with different particle size distributions. A solder paste containing the solder powder described in claim 18 or 19 and flux. A solder ball comprising the solder alloy described in any one of claims 1-17. A solder preform comprising the solder alloy described in any one of claims 1-17. A solder joint comprising the solder alloy described in any one of claims 1-17.