HK40081502A - Solder alloy, solder powder, solder paste, solder ball, solder preform, and solder joint - Google Patents

Description

Solder alloy, solder powder, solder paste, solder ball, solder preform and solder joint

Technical Field

The invention relates to solder alloys, solder powders, solder pastes, solder balls, pre-formed solder and soldered joints.

This application is based on the priority claim on Japanese application No. 2020-071024, filed on Japanese application at 4/10/2020, and the contents thereof are incorporated herein.

Background

Electronic components mounted on printed circuit boards are increasingly required to be smaller and have higher performance. Examples of the electronic component include a semiconductor package. In the semiconductor package, a semiconductor element having an electrode is sealed with a resin composition. A solder bump made of a solder material is formed on the electrode. In addition, a solder material connects the semiconductor element and the printed circuit board.

In the solder material, the influence of the alpha ray on the soft error becomes a problem. In order to reduce such adverse effects on the operation of semiconductor elements, development of low α -ray materials including solder materials has been carried out.

The main cause of the α -ray source is, for example, a trace amount of radioactive element contained in a solder alloy in a solder material, particularly, a base tin (Sn) base metal. The solder alloy can be produced by melt-mixing the raw material metals. In the solder alloy, in order to design a low α -ray amount material, it is important to remove radioactive elements such as uranium (U), thorium (Th), polonium (Po) which become upstream from the alloy composition.

In contrast, it is technically not difficult to remove U, th, and Po in refining Sn base metals (see, for example, patent document 1).

In general, sn contains lead (Pb) and bismuth (Bi) as impurities. Radioactivity in Pb and BiIsotope of carbon monoxide ²¹⁰ Pb and ²¹⁰ bi undergoes beta decay to ²¹⁰ Po， ²¹⁰ Alpha decay of Po to generate ²⁰⁶ Pb generates α rays. This series of decays (uranium series) is believed to be the main cause of alpha ray generation from the solder material.

In the evaluation of the amount of alpha rays generated from a material, the unit "cph/cm" is often used ² ”。“cph/cm ² "is" counts per hours/cm ² "short for" means every 1cm ² Middle, count of alpha rays every 1 hour.

Regarding the half-life of Pb and Bi, the following is described.

With respect to the Bi, the metal oxide, ²¹⁰ the half-life of Bi is about 5 days. With respect to Pb, ²¹⁰ the half-life of Pb is about 22.3 years. Further, it is said that the degree of influence (presence ratio) thereof can be expressed by the following formula (see non-patent document 1). That is, the influence of Bi on α -ray generation is very low compared to Pb.

[ ²¹⁰ Bi]≒[ ²¹⁰ Pb]/1.6×10 ³

In the formula (2) ²¹⁰ Bi]To represent ²¹⁰ Molar concentration of Bi. [ ²¹⁰ Pb]To represent ²¹⁰ Molar concentration of Pb.

As described above, conventionally, in the design of a low α dose material, U, th has been generally removed to further completely remove Pb.

In addition, it is known that the amount of α rays generated from the solder material substantially increases due to a change with time. This is said to be caused by beta decay of radioactive Pb and radioactive Bi in the solder alloy, increase of Po amount, and then alpha decay of Po to generate alpha rays.

These radioactive elements are hardly contained in a material having an extremely low alpha ray content, but because of the very low alpha ray content ²¹⁰ The segregation of Po may increase the amount of α rays with time. ²¹⁰ Po originally radiates α rays, but segregates in the central portion of the solder alloy when the solder alloy solidifies, and thus the radiated α rays are shielded by the solder alloy. Furthermore, as time passes, the temperature of the molten steel, ²¹⁰ po is uniformly dispersed in the alloy, andsince the α -ray exists on the surface on which the α -ray is detected, the amount of the α -ray increases with time (see non-patent document 2).

As described above, the amount of α rays generated is increased by the influence of a very small amount of impurities contained in the solder alloy. Therefore, in designing a material with a low α -ray dose, it is difficult to add only various elements as in the conventional method for producing a solder alloy.

For example, a method of adding arsenic (As) to a solder alloy is known for suppressing thickening of a solder paste to suppress an increase in viscosity with time (see, for example, patent document 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2010-156052

Patent document 2: japanese laid-open patent publication No. 2015-98052

Non-patent document

Non-patent document 1: radio active nucleic Induced Soft Errors at group Level; IEEE TRANSACTIONS NUCLEAR SCIENCE, DECEMBER 2009, VOL.56, NO.6, p.3437-3441

Non-patent document 2: energy Dependent Efficiency in Low Back ground Alpha Measurements and Impacts on Accurate Alpha Characterization; IEEE TRANSACTIONS NUCLEAR SCIENCE, DECEMBER 2015, VOL.62, NO.6, p.3034-3039

Disclosure of Invention

Problems to be solved by the invention

In order to suppress the thickening of the solder paste with time, for example, in a method of adding As to a solder alloy As described in patent document 2, the alloy also contains impurities by adding As. In this case, the amount of α rays generated from the solder material increases due to the presence of the radioactive element in the impurity.

In recent years, electronic devices having solder joints such as CPUs (Central Processing units) are required to be downsized and have high performance. Along with this, miniaturization of electrodes of printed circuit boards and electronic devices is required. Since the electronic component is connected to the printed circuit board via the electrodes, the solder joints connecting the electrodes are also reduced as the electrodes are miniaturized.

Furthermore, in order to bond fine electrodes, it is necessary to improve mechanical properties of a solder joint. However, depending on the element, when the content thereof is increased, the liquidus temperature rises, the temperature difference (Δ T) between the liquidus temperature and the solidus temperature becomes large, and segregation occurs at the time of solidification to form an uneven alloy structure. If the solder alloy has such an alloy structure, the mechanical properties such as tensile strength of the soldered joint are poor, and the solder alloy is likely to break due to external stress. This problem has become more pronounced with the recent miniaturization of electrodes.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a solder alloy that can suppress an increase in viscosity with time of a solder paste, a small temperature difference (Δ T) between a liquidus temperature and a solidus temperature, improve mechanical strength, and suppress the occurrence of a soft error, a solder powder composed of the solder alloy, a solder paste containing the solder powder and a flux, and a solder ball, a preformed solder and a solder joint composed of the solder alloy.

Means for solving the problems

The present inventors have studied for the purpose of designing a solder alloy with a low α -ray dose that can suppress the thickening of a solder paste with time without adding As accompanied by impurities including radioactive elements. According to the research, the following findings are found: the above object can be achieved by providing an alloy composition containing Sn as a main component and predetermined amounts of Bi and Sb which are metals that are more noble than Sn in terms of ionization tendency, and the present invention has been completed.

That is, the present invention adopts the following means to solve the above problems.

One embodiment of the present invention is a solder alloy having an alloy composition of: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to 0.3 mass% inclusive, and the balance being Sn, satisfying the following formula (1), and alpha-rayThe amount was 0.02cph/cm ² The following.

0.005≤Bi+Sb≤1.2 (1)

(1) In the formula, bi and Sb represent the contents (mass%) thereof in the foregoing alloy composition.

One embodiment of the present invention is a solder alloy having an alloy composition of: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi: more than 0 mass% and 0.9 mass% or less, and Sb:0 to 0.3 mass% and the balance of Sn, and satisfies the following formula (1), and the alpha-ray amount is 0.02cph/cm ² The following.

0.005≤Bi+Sb≤1.2 (1)

(1) In the formula, bi and Sb represent the content (mass%) of each in the foregoing alloy composition.

One embodiment of the present invention is a solder alloy having an alloy composition of: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to less than 0.1% by mass, and the balance being Sn, the alpha ray amount satisfying the following formula (1) being 0.02cph/cm ² The following.

0.005≤Bi+Sb≤1.2 (1)

(1) In the formula, bi and Sb represent the content (mass%) of each in the foregoing alloy composition.

In addition, one embodiment of the present invention is a solder powder composed of the solder alloy according to the above-described one embodiment of the present invention.

Another aspect of the present invention is a solder paste including the solder powder according to the first aspect of the present invention and a flux.

In addition, one embodiment of the present invention is a solder ball comprising the solder alloy according to the above-described one embodiment of the present invention.

In addition, one embodiment of the present invention is a preform solder composed of the solder alloy according to the above-described one embodiment of the present invention.

In addition, one embodiment of the present invention is a solder joint made of the solder alloy according to the above-described one embodiment of the present invention.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided a solder alloy capable of suppressing an increase in viscosity of a solder paste with time, reducing a temperature difference (Δ T) between a liquidus temperature and a solidus temperature, improving mechanical characteristics, and suppressing occurrence of a soft error, 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 preform solder, and a solder joint.

Detailed Description

The present invention will be described in more detail below.

In the present specification, the "ppb" relating to the composition of the solder alloy is "mass ppb" unless otherwise specified. The "ppm" is "mass ppm" unless otherwise specified. "%" is "% by mass" unless otherwise specified.

(solder alloy)

A solder alloy according to one embodiment of the present invention has the following alloy composition: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to 0.3 mass% and the balance of Sn, and satisfies the following formula (1), and the alpha-ray amount is 0.02cph/cm ² The following.

0.005≤Bi+Sb≤1.2 (1)

(1) In the formula, bi and Sb represent the contents (mass%) thereof in the foregoing alloy composition.

< composition of alloy >

The solder alloy of the present embodiment has the following alloy composition: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to 0.3 mass% inclusive, and the balance being Sn, and satisfies the above formula (1).

U: less than 5 mass ppb, th: less than 5ppb by mass

U and Th are radioactive elements. In order to suppress the occurrence of soft errors, it is necessary to suppress their content in the solder alloy.

In the present embodiment, the amounts of U and Th in the solder alloy are adjusted so that the amount of alpha rays generated from the solder alloy is 0.02cph/cm ² From the viewpoints below, the amounts of the components were less than 5ppb each based on the total mass (100 mass%) of the solder alloy. From the viewpoint of suppressing the occurrence of soft errors in high-density mounting, the contents of U and Th are preferably 2ppb or less, respectively, with lower contents being better.

Pb: less than 5 mass ppm

Generally, pb is contained in Sn as an impurity. The radioactive isotope in Pb undergoes beta decay to become ²¹⁰ Po， ²¹⁰ Alpha decay of Po to generate ²⁰⁶ Pb generates alpha rays. Therefore, it is preferable that the content of Pb as an impurity in the solder alloy is as small as possible.

In the present embodiment, the content of Pb in the solder alloy is less than 5ppm, preferably less than 2ppm, and more preferably less than 1ppm, based on the total mass (100 mass%) of the solder alloy. The lower limit of the Pb content in the solder alloy may be 0ppm or more.

As: less than 5 mass ppm

When As is added to the solder alloy, it is effective for suppressing the thickening of the solder paste with time, but As is added, the alloy also contains radioactive elements, and the amount of α rays generated from the solder material increases.

The present embodiment aims to suppress thickening of a solder paste with time without adding As accompanied by impurities including radioactive elements.

In the present embodiment, the content of As in the solder alloy is less than 5ppm, preferably less than 2ppm, and more preferably less than 1ppm, with respect to the total mass (100 mass%) of the solder alloy. The lower limit of the As content in the solder alloy may be 0ppm or more.

Bi:0 to 0.9 mass% and Sb:0 to 0.3 mass%, and (1) formula

The reason why the viscosity of the solder paste increases with time is considered to be that the solder powder reacts with the flux.

The effect of suppressing the thickening of the solder paste with time is exerted by suppressing the reaction with the flux. Thus, the element having low reactivity with the flux includes an element having a low ionization tendency. Generally, ionization of an alloy is considered as a standard electrode potential which is an ionization tendency of an alloy composition. For example, snAg alloys containing Ag, which is expensive relative to Sn, are less susceptible to ionization than Sn. Therefore, it is presumed that an alloy containing an element more noble than Sn is hard to be ionized, and the effect of suppressing the thickening of the solder paste with time can be improved.

Bi:0 to 0.9 mass%

Bi is an element whose ionization tendency is more expensive than Sn, and is an element which exhibits a low reactivity with a flux and exhibits an effect of suppressing thickening of a solder paste with time. Further, bi is an element that can suppress the deterioration of wettability because Bi lowers the liquidus temperature of the solder alloy and reduces the viscosity of the molten solder. However, according to the content thereof, the solidus temperature is significantly lowered, and the temperature difference (Δ T) between the liquidus temperature and the solidus temperature becomes wide.

In the present embodiment, the content of Bi in the solder alloy is 0% to 0.9%, preferably 0.030% to 0.9%, based on the total mass (100% by mass) of the solder alloy.

Alternatively, the lower limit of the Bi content in the solder alloy is 0% or more, preferably 0.0025% or more, more preferably 0.0050% or more, further preferably 0.010% or more, and particularly preferably 0.030% or more, with respect to the total mass (100% by mass) of the solder alloy. On the other hand, the upper limit of the Bi content in the solder alloy is 0.9% or less, preferably 0.7% or less, more preferably 0.5% or less, further preferably 0.3% or less, and particularly preferably 0.1% or less, with respect to the total mass (100% by mass) of the solder alloy.

For example, in one embodiment of the solder alloy, the content of Bi in the solder alloy is 0% or more and 0.9% or less, preferably 0.0025% or more and 0.7% or less, more preferably 0.0050% or more and 0.5% or less, further preferably 0.010% or more and 0.3% or less, and particularly preferably 0.030% or more and 0.1% or less, based on the total mass (100% by mass) of the solder alloy.

Sb:0 to 0.3 mass% inclusive

Sb is an element whose ionization tendency is more expensive than Sn, and is an element which has low reactivity with a flux and exhibits an effect of suppressing the thickening of a solder paste with time, similarly to Bi. Since the wettability deteriorates if the Sb content in the solder alloy is too large, it is necessary to set the Sb content to an appropriate level when the Sb is added.

In the present embodiment, the content of Sb in the solder alloy is 0% to 0.3%, preferably 0.0040% to 0.3%, and more preferably 0.010% to 0.3% with respect to the total mass (100% by mass) of the solder alloy.

Alternatively, the lower limit of the Sb content in the solder alloy is 0% or more, preferably 0.0025% or more, more preferably 0.0040% or more, further preferably 0.0050% or more, and particularly preferably 0.010% or more, based on the total mass (100% by mass) of the solder alloy. On the other hand, the upper limit of the Sb content in the solder alloy is 0.3% or less, preferably 0.1% or less, more preferably less than 0.1%, and further preferably 0.090% or less, based on the total mass (100% by mass) of the solder alloy.

For example, in one embodiment of the solder alloy, the content of Sb in the solder alloy is 0% to 0.3%, preferably 0.0025% to 0.1%, more preferably 0.0040% to less than 0.1%, further preferably 0.0050% to 0.090%, and particularly preferably 0.010% to 0.090%, based on the total mass (100% by mass) of the solder alloy.

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

0.005≤Bi+Sb≤1.2 (1)

(1) In the formula, bi and Sb represent the contents (mass%) thereof in the foregoing alloy composition.

(1) In the formula, bi and Sb are both elements exhibiting an effect of suppressing the thickening of the solder paste with time. In addition, in the present embodiment, both Bi and Sb contribute to the wettability of the solder alloy.

The total content of Bi and Sb in the solder alloy must be 0.005% to 1.2%, preferably 0.03% to 1.2%, based on the total mass (100% by mass) of the solder alloy. The total content of Bi and Sb in the solder alloy is 0.005% or more, preferably 0.03% or more and 1.0% or less, more preferably 0.03% or more and 0.9% or less, further preferably 0.03% or more and 0.5% or less, and particularly preferably 0.03% or more and 0.1% or less, based on the total mass (100% by mass) of the solder alloy.

Alternatively, the lower limit of the total content of Bi and Sb in the solder alloy is 0.005% or more, preferably 0.01% or more, more preferably 0.02% or more, and further preferably 0.03% or more, based on the total mass (100% by mass) of the solder alloy. On the other hand, the upper limit of the total content of Bi and Sb in the solder alloy is 1.2% or less, preferably 1.0% or less, more preferably 0.9% or less, further preferably 0.5% or less, and particularly preferably 0.1% or less, based on the total mass (100% by mass) of the solder alloy.

For example, the total content of Bi and Sb in the solder alloy is preferably 0.01% or more and 1.0% or less, more preferably 0.02% or more and 0.9% or less, further preferably 0.03% or more and 0.5% or less, and particularly preferably 0.03% or more and 0.1% or less, based on the total mass (100% by mass) of the solder alloy.

The "total content of Bi and Sb" is the content of Sb when the content of Bi in the solder alloy is 0 mass%, the content of Bi when the content of Sb in the solder alloy is 0 mass%, and the total content of Bi and Sb when Bi and Sb are present at the same time.

In the case where Bi and Sb are simultaneously contained in the present embodiment, the ratio of Bi to Sb in the solder alloy is preferably 0.008 or more and 10 or less, more preferably 0.01 or more and 10 or less, further preferably 0.1 or more and 5 or less, particularly preferably 0.1 or more and 2 or less, and most preferably 0.1 or more and 1 or less in terms of the mass ratio Sb/Bi.

When the Sb/Bi ratio is in the above-described preferable range, the effect of the present invention can be more easily obtained.

(random elements)

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

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

Ag:0 to 4 mass% inclusive

Ag can be formed in grain boundary ₃ Sn is an arbitrary element that improves the reliability of the solder alloy. In addition, ag is an element whose ionization tendency is more expensive than Sn, and is present together with Bi and Sb, thereby improving the effect of suppressing the thickening of the solder paste with time.

In the present embodiment, the content of Ag in the solder alloy is preferably 0% or more and 4% or less, more preferably 0.5% or more and 3.5% or less, further preferably 1.0% or more and 3.0% or less, and particularly preferably 2.0% or more and 3.0% or less, with respect to the total mass (100% by mass) of the solder alloy.

Cu:0 to 0.9 mass%

Cu is an arbitrary element used in a general solder alloy and can improve the bonding strength of a solder joint. Cu is an element whose ionization tendency is more expensive than Sn, and is present together with Bi and Sb, thereby improving the effect of suppressing the thickening of the solder paste with time.

In the present embodiment, the content of Cu in the solder alloy is preferably 0% or more and 0.9% or less, more preferably 0.1% or more and 0.8% or less, and further preferably 0.2% or more and 0.7% or less, with respect to the total mass (100% by mass) of the solder alloy.

In the case where Cu and Bi are present together in the present embodiment, the ratio of Cu to Bi in the solder alloy is preferably 0.5 or more and 280 or less, more preferably 0.5 or more and 150 or less, further preferably 0.5 or more and 20 or less, and particularly preferably 1 or more and 15 or less in terms of the mass ratio represented by Cu/Bi.

If the mass ratio of Cu/Bi is in the above-described preferred range, the effects of the present invention can be more easily obtained.

In the case where Cu and Sb are present at the same time in the present embodiment, the ratio of Cu to Sb in the solder alloy is preferably 1 or more and 280 or less, more preferably 1 or more and 150 or less, and further preferably 5 or more and 125 or less in terms of the mass ratio represented by Cu/Sb.

If the mass ratio of Cu/Sb is in the above-described preferred range, the effects of the present invention can be more easily obtained.

In the case where Cu, bi, and Sb are simultaneously contained in the present embodiment, the ratio of Cu to Bi to Sb in the solder alloy is preferably 0.4 or more and 150 or less, more preferably 5 or more and 100 or less in terms of the mass ratio represented by Cu/(Bi + Sb).

When the mass ratio of Cu/(Bi + Sb) is in the above-described preferred range, the effects of the present invention can be more easily obtained.

For example, the alloy composition in the solder alloy of the present embodiment may contain, in addition to the above elements, ni:0 mass ppm or more and 600 mass ppm or less, and Fe: at least one kind of the metal oxide particles is 0 mass ppm or more and 100 mass ppm or less.

Ni:0 to 600 mass ppm inclusive

By soldering, the formation of an Sn-containing intermetallic compound (an intermetallic compound containing Sn) advances in the vicinity of a joining interface in a solder alloy, and if the Sn-containing intermetallic compound precipitates, the mechanical strength of a soldered joint deteriorates.

Ni is an element that suppresses the formation of the aforementioned Sn-containing intermetallic compound at the joint interface.

By containing Ni in the solder alloy, the formation of the Sn-containing intermetallic compound is suppressed, and the mechanical strength of the soldered joint can be maintained. On the other hand, if the Ni content in the solder alloy exceeds 600 mass ppm, snNi compounds are precipitated in the vicinity of the joining interface in the solder alloy, and there is a concern that the mechanical strength of the soldered joint is deteriorated.

In the present embodiment, the Ni content in the solder alloy is preferably 0ppm or more and 600ppm or less, more preferably 20ppm or more and 600ppm or less, with respect to the total mass (100 mass%) of the solder alloy.

Fe:0 to 100 mass ppm inclusive

Like Ni, fe is an element that suppresses the formation of Sn-containing intermetallic compounds at the bonding interface. In addition, within the predetermined content range, precipitation of needle-like crystals due to the SnFe compound can be suppressed, and short-circuiting of the circuit can be prevented.

Here, "needle-like crystals" mean crystals having an aspect ratio of 2 or more, which is the ratio of the major axis to the minor axis, among crystals derived from 1 kind of SnFe compound.

In the present embodiment, the content of Fe in the solder alloy is preferably 0ppm or more and 100ppm or less, more preferably 20ppm or more and 100ppm or less, with respect to the total mass (100 mass%) of the solder alloy.

The alloy composition in the solder alloy of the present embodiment further contains Ni:0 mass ppm or more and 600 mass ppm or less, and Fe: in the case of at least one of 0 mass ppm or more and 100 mass ppm or less, the alloy composition preferably satisfies the following formula (2).

20≤Ni+Fe≤700 (2)

(2) In the formula, ni and Fe represent the respective contents thereof (mass ppm) in the foregoing alloy composition.

(2) In the formula, ni and Fe are both elements for suppressing the formation of Sn-containing intermetallic compounds at the bonding interface. In addition, in the present embodiment, both Ni and Fe are also advantageous in the effect of suppressing the thickening of the solder paste with time.

The total content of Ni and Fe in the solder alloy is preferably 20ppm or more and 700ppm or less, more preferably 40ppm or more and 700ppm or less, and further preferably 40ppm or more and 600ppm or less, with respect to the total mass (100 mass%) of the solder alloy.

The "total content of Ni and Fe" is the content of Fe when the content of Ni in the solder alloy is 0 mass ppm, the content of Ni when the content of Fe in the solder alloy is 0 mass ppm, and the total content of Ni and Fe when both Ni and Fe are present.

In the case where Ni and Fe are both contained in the present embodiment, the ratio of Ni and Fe in the solder alloy is preferably 0.4 or more and 30 or less, more preferably 0.4 or more and 10 or less, and further preferably 0.4 or more and 5 or less in terms of the mass ratio represented by Ni/Fe.

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

The balance: sn

The balance of the alloy composition in the solder alloy of the present embodiment is Sn. In addition to the above elements, inevitable impurities may be contained. Even when unavoidable impurities are contained, the above effects are not affected.

< alpha ray dose >

The amount of alpha rays of the solder alloy of the present embodiment was 0.02cph/cm ² The following.

This is an α -ray amount to the extent that soft errors do not become a problem in high-density mounting of electronic components.

From the viewpoint of suppressing soft errors in further high-density mounting, the α -ray amount in the solder alloy of the present embodiment is preferably 0.01cph/cm ² Less, more preferably 0.002cph/cm ² The lower, more preferably 0.001cph/cm ² The following.

The amount of α -rays generated from the solder alloy can be measured as follows. The above-mentioned method for measuring the amount of alpha rays is based on JEDEC STANDARD which is an international STANDARD.

Step (i):

a gas flow type α -ray amount measuring device was used.

As a sample for measurement, a solder alloy was melted and molded to have an area of 900cm on one surface ² The sheet-like solder alloy sheet of (1).

The α -ray measuring apparatus was provided with the solder alloy sheet as a measurement sample, and the PR gas was purged therefrom.

Note that, as the PR gas, a gas according to JEDEC STANDARD, which is an international STANDARD, is used. That is, the PR gas used for the measurement is a gas obtained by decay of radon (Rn) over 3 weeks from filling a gas bomb with a mixed gas of argon gas 90% to methane 10%.

Step (ii):

in the α -ray measurement apparatus provided with the solder alloy sheet, the PR gas was allowed to flow for 12 hours and left standing, and then α -ray measurement was performed for 72 hours.

Step (iii):

the average alpha ray dose was taken as "cph/cm ² "calculate. Outliers (counting based on device vibration, etc.) remove their 1 hour count.

[ method for producing solder alloy ]

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

For the purpose of designing a solder alloy with a low α -ray dose, it is preferable to use a low α -ray dose material as the raw material metal, and for example, it is preferable to use a high-purity material and a material from which U, th and Pb are removed, respectively, among Sn, bi and Sb which are the raw material metals.

Sn as a raw material metal can be produced by a production method described in, for example, jp 2010-156052 a (patent document 1).

Bi as a raw material metal can be produced, for example, according to Japanese patent laid-open publication No. 2013-185214.

Sb as a raw material metal can be produced, for example, according to japanese patent No. 5692467.

The raw material metals may be melt-mixed by a conventionally known method.

In general, in a solder alloy, when each constituent element constituting the solder alloy does not function alone, and the content of each constituent element is within a predetermined range, various effects can be exhibited for the first time. According to the solder alloy of the above-described embodiment, the content of each constituent element is in the above-described range, so that the viscosity of the solder paste is suppressed from increasing with time, the mechanical strength of the soldered joint is improved, and the occurrence of a soft error can be suppressed. That is, the solder alloy of the present embodiment is useful as a target low α -ray amount material, and can suppress the occurrence of soft errors by being applied to the formation of solder bumps around a memory.

In the present embodiment, the purpose is to design a low α -ray amount solder alloy that can suppress the thickening of a solder paste with time without adding As actively. In contrast, the object is achieved by using a solder alloy containing Bi and Sb, which are metals having a higher ionization tendency than Sn, in a specific ratio in addition to Sn as a main component.

The reason why the above-described effect is obtained is not clear, but is presumed as follows.

The purity of Sn for a solder alloy with a low α -ray dose is very high, and when the alloy after melting is solidified, the crystal size of Sn increases. In addition, the oxide film of Sn also forms a corresponding sparse oxide film. Therefore, by adding Bi and Sb, which are metals that tend to be more noble than Sn and are less likely to be ionized, the crystal size can be reduced, a dense oxide film is formed, and the reactivity of the alloy with the flux is suppressed, so that the thickening of the solder paste with time can be suppressed.

In addition, the solder alloy of the present embodiment has an area of 900cm on one surface formed by molding ² The amount of alpha rays after the heat treatment at 100 ℃ for 1 hour is preferably 0.02cph/cm ² The concentration is preferably 0.01cph/cm or less ² The concentration is preferably 0.002cph/cm ² The concentration is preferably 0.001cph/cm ² The following.

The solder alloy exhibiting such an alpha ray amount is less likely to be caused in the alloy ²¹⁰ Po segregation, influence of change with time of alpha ray amountSmall, useful. By applying a solder alloy exhibiting such an α -ray amount, the occurrence of soft errors is further suppressed, and it becomes easier to ensure stable operation of the semiconductor element.

(solder powder)

The solder powder according to one embodiment of the present invention includes the solder alloy according to one embodiment of the present invention.

The solder powder of the present embodiment is suitably used as a solder paste described later.

The solder powder can be produced by a known method such as a dropping method of dropping a molten solder alloy to obtain particles, a spraying method of centrifugal spraying, an atomizing method, a granulating method in a liquid, or a method of pulverizing a bulk solder alloy. The dropping or spraying in the dropping method or the spraying method is preferably carried out in an inert atmosphere or a solvent for forming the granular form.

The solder powder of the present embodiment is preferably a spherical powder. The spherical powder improves the fluidity of the solder alloy.

When the solder powder of the present embodiment is a spherical powder, the solder powder is produced in accordance with JIS Z3284-1: 2014 (table 2), the reference symbols 1 to 8 are preferably satisfied, and the reference symbols 4 to 8 are more preferably satisfied. If the particle size of the solder powder satisfies this condition, the surface area of the powder is not excessively large, and the increase in viscosity of the solder paste with time is suppressed, and the aggregation of fine powder is suppressed, and the increase in viscosity of the solder paste is sometimes suppressed. Therefore, it becomes possible to solder to a finer component.

The solder powder of the present embodiment preferably has at least 2 solder alloy particle groups having different particle size distributions at the same time. This improves the workability, such as improving the sliding property of the solder paste and facilitating printing.

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

The "sphericity of spherical powder" can be measured by using a CNC image measuring system (ULTRA QUICK VISION ULT RA QV350-PRO measuring apparatus manufactured by Mitutoyo Corporation) using the minimum region center method (MZC method).

The sphericity is a deviation from the sphere, and is an arithmetic average value calculated by dividing the diameter of each solder alloy particle by the major axis, for example, 500 pieces, and indicates that the value is closer to the sphere as the upper limit is 1.00.

(solder paste)

A solder paste according to an embodiment of the present invention contains the solder powder according to the above-described embodiment of the present invention and a flux.

< soldering flux >

The flux used in the solder paste of the present embodiment is composed of, for example, any of a resin component, an active component, a solvent, and other components, or a combination of 2 or more kinds of blending components thereof.

Examples of the resin component include rosin resins.

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

Examples of the derivative include purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, and modified products of α, β unsaturated carboxylic acid (acrylated rosin, maleylated rosin, fumarylated rosin, etc.), purified products, hydrogenated products, disproportionated products of the polymerized rosin, purified products, hydrogenated products, disproportionated products of the modified products of the α, β unsaturated carboxylic acid, etc., and 2 or more kinds thereof can be used.

In addition, examples of the resin component include, in addition to the rosin-based resin, terpene resins, modified terpene resins, terpene-phenolic resins, modified terpene-phenolic resins, styrene resins, modified styrene resins, xylene resins, modified xylene resins, acrylic resins, polyethylene resins, acrylic-polyethylene copolymer resins, epoxy resins, and the like.

Examples of the modified terpene resin include an aromatic modified terpene resin, a hydrogenated terpene resin, and a hydrogenated aromatic modified terpene resin. Examples of the modified terpene phenol resin include hydrogenated terpene phenol resins and the like. Examples of the modified styrene resin include styrene acrylic resins and styrene maleic acid resins. Examples of the modified xylene resin include phenol-modified xylene resin, alkylphenol-modified xylene resin, phenol-modified methyl xylene resin, polyol-modified xylene resin, and polyoxyethylene-added xylene resin.

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

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

Examples of the amine include ethylamine, triethylamine, ethylenediamine, triethylenetetramine, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2' -methylimidazolyl- (1 ') ] -ethyl-sym-triazine, 4324 zxf 4324-diamino-6- [2' -undecylimidazolyl- (1 ') ] -ethyl-sym-32triazine, 3245-diamino-6- [2' -methylimidazolyl- (1 ') ] -ethyl-4 ' -isocyanato-triazine, and 376 ' -iminomethyl-2 ' -isocyanato-32, and a adduct of [ 1' -methylethyl-32-iminomethyl-2 ' -isocyanato-triazine, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo [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, and mixtures thereof 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adducts, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2- (1-ethylpentyl) benzimidazole, 2-nonylbenzimidazole, 2- (4-thiazolyl) benzimidazole, 2- (2 ' -hydroxy-5 ' -methylphenyl) benzotriazole, 2- (2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylphenyl) -5-chlorobenzotriazole, 2- (2 ' -hydroxy-3 ',5' -di-tert-amylphenyl) benzotriazole, 2- (2 ' -hydroxy-5 ' -tert-octylphenyl) benzotriazole, 2,2' -methylenebis [6- (2H-benzotriazol-2-yl) -4-tert-octylphenol ], 6- (2-benzotriazolyl) -4-tert-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 ] diethanol, 1- (1 ',2' -dicarboxyethyl) benzotriazole, 1- (2,3-dicarboxypropyl) benzotriazole, 1- [ (2-ethylhexylamino) methyl ] benzotriazole, 2,6-bis [ (1H-benzotriazol-1-yl) methyl ] -4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole, and the like.

Examples of the halogen-based active agent include amine hydrohalide salts and organic halogen compounds.

Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. Examples of the amine include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, ditolylbutylguanidine, methylimidazole, and 2-ethyl-4-methylimidazole, and examples of the hydrogen halide include hydrides of chlorine, bromine, and iodine.

Examples of the organic halogen compound include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate hexabromide, 1-bromo-2-butanol, 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1,4-dibromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-2-butene-1,4-diol and the like.

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

Examples of the wax thixotropic agent include hydrogenated castor oil and the like.

Examples of the amide-based thixotropic agent include monoamide-based thixotropic agents, bisamide-based thixotropic agents, and polyamide-based thixotropic agents, and specific examples thereof include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluamide, aromatic amide, methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamide, methylene bisoleic acid amide, unsaturated fatty acid bisamide, m-xylylene bisstearic acid amide, aromatic bisamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, methylol stearic acid amide, methylolamide, and fatty acid ester amide.

Examples of the sorbitol thixotropic agent include dibenzylidene-D-sorbitol and bis (4-methylbenzylidene) -D-sorbitol.

Examples of the solvent include water, alcohol solvents, glycol ether solvents, terpineol, and the like.

Examples of the alcohol solvents include isopropanol, 1,2-butanediol, isobornyl cyclohexanol, 2,4-diethyl-1,5-pentanediol, 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-tris (hydroxymethyl) ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2 '-oxybis (methylene) bis (2-ethyl-1,3-propanediol), 2,2-bis (hydroxymethyl) -3426-propanediol, guaiacyl 6296' -oxybis (methylene) bis (2-ethyl-1,3-propanediol, 3292-bis (hydroxymethyl) -35zxft 3527-ethylene glycol, 3258-trihydroxy-3552-ethylene-3552-propylene glycol, glycerol-4235-ethylene glycol, and triethoxy-3558 zxft-ethylene-3527-ethylene glycol.

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

Examples of the metal deactivator include hindered phenol compounds and nitrogen compounds. The flux contains either a hindered phenol compound or a nitrogen compound, and thus the thickening suppression effect of the solder paste is easily improved.

The "metal deactivator" refers to a compound having the property of preventing the metal from being deteriorated by contact with a certain compound.

The hindered phenol compound is a phenol compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at least in the ortho position to the phenol.

The hindered phenol compound is not particularly limited, and examples thereof include triethylene glycol ether-bis (3-t-butyl-4-hydroxy-5-methylphenyl) propionate, N, N '-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionamide ], 1,6-hexanediol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate ], 2,2' -methylenebis [6- (1-methylcyclohexyl) -p-cresol ], 2,2 '-methylenebis (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-hydroxyphenyl) propionate ], 2,4-bis- (N-octylthio) -6- (4-hydroxy-4924 zxft-butylamino) -496242-tetra-tert-butyl-4-hydroxyphenyl) propionate ], 3543-di-tert-butyl-4-ethylphenol, 3- (3-tert-butyl-4-hydroxy-9843), and pentaerythrityl-bis [3- (3-tert-butyl-4-hydroxyphenyl) propionate ], and further, octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N '-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, N' -bis [2- [2- (3,5-di-tert-butyl-4-hydroxyphenyl) ethylcarbonyloxy ] ethyl ] oxamide, a compound represented by the following formula, and the like.

(wherein Z is an optionally substituted alkylene group. R ¹ And R ² Each independently is an optionally substituted alkyl, aralkyl, aryl, heteroaryl, cycloalkyl or heterocycloalkyl group. R is ³ And R ⁴ Each independently is an optionally substituted alkyl group. )

Examples of the nitrogen compound in the metal deactivator include a hydrazide nitrogen compound, an amide nitrogen compound, a triazole nitrogen compound, and a melamine nitrogen compound.

The hydrazide-based nitrogen compound may be any nitrogen compound having a hydrazide skeleton, and examples thereof include dodecanedioic acid bis [ N2- (2-hydroxybenzoyl) hydrazide ], N '-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl ] hydrazine, sebacic acid bis-salicyloyl hydrazide, N-salicylidene-N' -salicyloyl hydrazide, m-nitrobenzoyl hydrazide, 3-aminophthalic acid hydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxabis (2-hydroxy-5-octylbenzylidene hydrazide), N '-benzoylpyrrolidone carboxylic acid hydrazide, N' -bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) hydrazine, and the like.

The amide 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) propionyloxy ] ethyl } oxamide and the like.

The triazole nitrogen compound may be any nitrogen compound having a triazole skeleton, and examples thereof include N- (2H-1,2,4-triazol-5-yl) salicylamide, 3-amino-1,2,4-triazole, and 3- (N-salicyloyl) amino-1,2,4-triazole.

The melamine nitrogen compound may be any nitrogen compound having a melamine skeleton, and examples thereof include melamine and melamine derivatives. More specifically, for example, triaminotriazine, alkylated triaminotriazine, alkoxyalkylated triaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butylmelamine, N2-diethylmelamine, N', N ", N ″ -hexa (methoxymethyl) melamine, and the like can be given.

Examples of the other components include a surfactant, a silane coupling agent, an antioxidant, and a colorant.

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

Examples of the nonionic surfactant include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, aliphatic alcohol polyoxyethylene adduct, aromatic alcohol polyoxyethylene adduct, and polyhydric alcohol polyoxyethylene adduct.

Examples of the weakly cationic surfactant include a terminal diamine polyethylene glycol, a terminal diamine polyethylene glycol-polypropylene glycol copolymer, an aliphatic amine polyoxyethylene adduct, an aromatic amine polyoxyethylene adduct, and a polyamine polyoxyethylene adduct.

Examples of the surfactant other than those mentioned above include polyoxyalkylene acetylene glycols, polyoxyalkylene glycerin ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, and polyoxyalkylene alkylamides.

The content of the flux in the solder paste of the present embodiment is preferably 5 to 95% by mass, more preferably 5 to 50% by mass, and still more preferably 5 to 15% by mass, based on the total mass (100% by mass) of the solder paste.

When the content of the flux is within this range, the effect of suppressing the thickening by the solder powder can be sufficiently exhibited.

The solder paste of the present embodiment can be manufactured by a manufacturing method that is common in the art.

The solder paste can be obtained by heating and mixing the components constituting the flux to prepare the flux, and stirring and mixing the solder powder in the flux. Further, the effect of suppressing the thickening with time is expected, and a zirconia powder may be further added in addition to the solder powder.

(solder ball)

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

The solder alloy of the above embodiment may be used in the form of a solder ball.

The solder ball of the present embodiment can be manufactured by using a method common in the art, i.e., a dropping method.

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

The particle diameter 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, further preferably 20 μm or more and 600 μm or less, and particularly preferably 30 μm or more and 300 μm or less.

(Pre-formed solder)

The preform solder according to one embodiment of the present invention is composed of the solder alloy according to one embodiment of the present invention.

The solder alloy according to the above embodiment can be used as a preform.

Examples of the shape of the preform according to the present embodiment include a gasket, a ring, a pellet, a disk, a tape, and a string.

(solder joint)

A solder joint according to an embodiment of the present invention is composed of the solder alloy according to the above-described embodiment of the present invention.

The solder joint of the present embodiment is composed of an electrode and a solder joint. The solder joint refers to a portion mainly formed of a solder alloy.

The solder joints of the present embodiment can be formed by bonding electrodes of PKGs (packages) such as IC chips and electrodes of substrates such as PCBs (printed circuit boards) with the solder alloys of the above embodiments, for example.

The solder joint of the present embodiment can be manufactured by a method that is usual in the art, such as mounting 1 solder ball of the above-described embodiment on 1 electrode coated with flux and bonding the same.

Examples

The present invention will be described in further detail with reference to examples below, but the present invention is not limited to these examples.

In the present example, "ppb" and "ppm" and "%" in the solder alloy composition are "mass ppb", "mass ppm" and "% by mass", respectively, unless otherwise specified.

< solder alloy >

(examples 1 to 414 and comparative examples 1 to 8)

The raw material metals were melted and stirred to prepare solder alloys of respective examples having alloy compositions shown in tables 1A to 25B.

< solder powder >

The solder alloys of the examples were melted, and the solder alloy compositions of the examples, each having an alloy composition shown in tables 1A to 25B, were prepared by an atomization method, and the alloy compositions were measured in accordance with JIS Z3284-1: 2014 (table 2) which satisfies the size (particle size distribution) of symbol 4.

< preparation of soldering flux (F0) >

A rosin resin is used as the resin component.

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

A glycol ether solvent is used as the solvent.

42 parts by mass of rosin, 35 parts by mass of a glycol ether solvent, 8 parts by mass of a thixotropic agent, 10 parts by mass of an organic acid, 2 parts by mass of an amine, and 3 parts by mass of a halogen-based active agent were mixed to prepare a flux (F0).

< manufacture of solder paste >

Solder pastes were produced by mixing the flux (F0) with solder powders composed of solder alloys of examples having the alloy compositions shown in tables 1A to 25B, respectively.

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

< evaluation >

The paste was used to evaluate the suppression of thickening.

Further, using the solder alloy, the temperature difference (Δ T) between the liquidus temperature and the solidus temperature of the solder powder and the α -ray amount were evaluated. Further, comprehensive evaluation was performed.

The details are as follows. The evaluation results are shown in tables 1A to 25B.

[ inhibition of thickening ]

(1) Verification method

For the solder paste just after the preparation, malcolm co., ltd: PCU-205, at rotational speed: the viscosity was measured at 10rpm at 25 ℃ for 12 hours in the air.

(2) Criterion for determination

Good: the viscosity after 12 hours is 1.2 times or less as high as the viscosity immediately after the preparation of the solder paste after 30 minutes.

X: the viscosity after 12 hours is more than 1.2 times as high as the viscosity at the time of 30 minutes from immediately after the preparation of the solder paste.

If the judgment is "good", it can be said that a sufficient thickening suppressing effect is obtained. That is, an increase in viscosity of the solder paste with time can be suppressed.

[ temperature difference (Delta T) between liquidus temperature and solidus temperature ]

(1) Verification method

For the solder powder before mixing with the flux (F0), a solder powder manufactured by SII NanoTechnology inc, model: EXSTAR DSC7020, sample size: about 30mg, rate of temperature rise: DSC measurement was carried out at 15 ℃ per minute to obtain the solidus temperature and the liquidus temperature. The solidus temperature was subtracted from the obtained liquidus temperature to determine Δ T (c).

(2) Criterion for determination

Good: delta T is 10 ℃ or lower.

X: Δ T exceeds 10 ℃.

If the evaluation is "good", the temperature difference between the liquidus temperature and the solidus temperature is small, and therefore it can be said that segregation is not easily caused at the time of solidification and an uneven alloy structure is not easily formed. That is, the mechanical strength of the soldered joint can be improved.

[ alpha ray dose ]

(1) One of the verification methods

The measurement of the α -ray amount was performed according to the above steps (i), (ii), and (iii) using an α -ray amount measuring device of a gas flow rate ratio counter.

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

The solder alloy sheet was molded by melting the solder alloy just after the production into a sheet having a surface area of 900cm ² The sheet-like product of (1).

The measurement sample was placed in an α -ray measuring apparatus, and after flowing and standing a PR-10 gas for 12 hours, the α -ray amount was measured for 72 hours.

(2) One of the criteria for determination

Good component: the amount of alpha rays generated from the measurement sample was 0.002cph/cm ² The following.

Good: the alpha ray generated by the self-determination sample exceeds 0.002cph/cm ² And is 0.02cph/cm ² The following.

X: the alpha ray generated by the self-determination sample exceeds 0.02cph/cm ² 。

If the judgment is "good quality" or "good quality", it can be said to be a solder material with a low alpha-ray dose.

(3) Second verification method

The measurement of the α -ray dose was performed in the same manner as in the verification method (1) except that the measurement sample was changed.

As a sample for measurement, a solder alloy immediately after production was melted and formed to have an area of 900cm on one surface ² The sheet-like solder alloy sheet of (2) was subjected to heat treatment at 100 ℃ for 1 hour and then naturally cooled for use.

(4) Second criterion of determination

Good for good: the amount of alpha rays generated from the measurement sample was 0.002cph/cm ² The following.

Good component: the alpha ray generated by the self-determination sample exceeds 0.002cph/cm ² And is 0.02cph/cm ² The following.

X: the alpha ray generated by the self-determination sample exceeds 0.02cph/cm ² 。

If the judgment is "good quality" or "good quality", it can be said to be a solder material with a low alpha-ray dose.

(5) Third verification method

After a solder alloy sheet of a measurement sample in which the α -ray amount was measured by one of the above-described (1) verification methods was stored for 1 year, the α -ray amount was measured again in accordance with the above-described steps (i), (ii), and (iii), and the change with time in the α -ray amount was evaluated.

(6) Third judgment reference

Good for good: the amount of alpha rays generated from the measurement sample was 0.002cph/cm ² The following.

Good component: the alpha ray generated by the self-determination sample exceeds 0.002cph/cm ² And is 0.02cph/cm ² The following.

X: the alpha ray generated by the self-determination sample exceeds 0.02cph/cm ² 。

If the evaluation is "good quality" or "good quality", it can be said that the generated α -ray amount is not changed with time and is stable. That is, occurrence of soft errors in the electronic device class can be suppressed.

[ comprehensive evaluation ]

Good: in tables 1A to 25B, each evaluation of the thickening suppression, the temperature difference (Δ T) between the liquidus temperature and the solidus temperature, the α -ray amount immediately after production, the α -ray amount after heat treatment, and the temporal change in the α -ray amount is "good" or "good".

X: in tables 1A to 25B, at least 1 of the respective evaluations of the inhibition of thickening, the temperature difference (Δ T) between the liquidus temperature and the solidus temperature, the α ray dose immediately after production, the α ray dose after heat treatment, and the change with time in the α ray dose was x.

[ 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 ]

[ Table 17A ]

[ Table 17B ]

[ Table 18A ]

[ Table 18B ]

[ Table 19A ]

[ Table 19B ]

[ Table 20A ]

[ Table 20B ]

[ Table 21A ]

[ Table 21B ]

[ Table 22A ]

[ Table 22B ]

[ Table 23A ]

[ Table 23B ]

[ Table 24A ]

[ Table 24B ]

[ Table 25A ]

[ Table 25B ]

As shown in tables 1A to 25B, it was confirmed that, in the case of using the solder alloys to which examples 1 to 414 of the present invention were applied, the solder paste could be inhibited from increasing in viscosity with time, the mechanical strength of the soldered joint could be improved, and the occurrence of soft errors could be inhibited.

On the other hand, the results of at least 1 difference in the thickening suppression, the temperature difference (Δ T) between the liquidus temperature and the solidus temperature, and the evaluation of the α -ray amount were shown in all the cases where the solder alloys of comparative examples 1 to 8 outside the range of the present invention were used.

Claims (24)

1. A solder alloy having the following alloy composition: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to 0.3 mass% inclusive, with the balance being Sn,

satisfies the following formula (1), and

alpha rayThe linear quantity is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

2. A solder alloy having the following alloy composition: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi: more than 0 mass% and 0.9 mass% or less, and Sb:0 to 0.3 mass% inclusive, and the balance being Sn,

satisfies the following formula (1), and

alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

3. A solder alloy having the following alloy composition: u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb:0 to less than 0.1 mass% and the balance of Sn,

satisfies the following formula (1), and

alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

4. Solder alloy according to any of claims 1 to 3, wherein the alloy composition further satisfies the following formula (1'),

0.03≤Bi+Sb≤0.1(1’)

(1') in the formula, bi and Sb represent the contents (% by mass) of each in the alloy composition.

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

6. Solder alloy according to any of claims 1 to 5, wherein As is below 2 mass ppm.

7. Solder alloy according to any of claims 1 to 6, wherein the alloy composition further contains Ag: 0% by mass or more and 4% by mass or less and Cu: at least one of 0 mass% or more and 0.9 mass% or less.

8. A solder alloy having the following alloy composition:

u: less than 5 mass ppb, th: less than 5 mass ppb, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi: more than 0 mass% and 0.9 mass% or less, and Sb: more than 0 mass% and 0.3 mass% 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 is

The balance of Sn, and the balance of Sn,

satisfies the following formula (1), and

alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

9. A solder alloy having the following alloy composition:

u: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi: more than 0 mass% and 0.9 mass% or less, and Sb: 0% by mass or more and 0.3% by mass or less;

cu: more than 0 mass% and 0.9 mass% or less; and is

The balance of Sn, and the balance of Sn,

satisfies the following formula (1),

the ratio of Cu to Bi is 0.5 to 280 in terms of a mass ratio of Cu/Bi, and

the alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

10. A solder alloy having the following alloy composition:

u: less than 5 mass ppb, th: less than 5 mass ppb, pb: less than 5 mass ppm, and As: less than 5 mass ppm;

bi:0 mass% or more and 0.9 mass% or less and Sb: at least one kind of 0 mass% to 0.3 mass%;

cu: more than 0 mass% and 0.9 mass% or less; and is

The balance of Sn, and the balance of Sn,

satisfies the following formula (1),

the ratio of Cu to Bi to Sb is 0.4 to 150 by mass ratio Cu/(Bi + Sb), and

alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

11. A solder alloy having the following alloy composition: by

U: less than 5 mass ppb, th: less than 5ppb by mass, pb: less than 5 mass ppm, as: less than 5 mass ppm, bi:0 mass% or more and 0.9 mass% or less, and Sb: more than 0 mass% and 0.3 mass% or less;

cu: more than 0 mass% and 0.9 mass% or less; and is

The balance of Sn, and the balance of Sn,

satisfies the following formula (1),

the ratio of Cu to Sb is 1 to 280 inclusive in terms of a mass ratio Cu/Sb, and

alpha ray dose is 0.02cph/cm ² In the following, the following description is given,

0.005≤Bi+Sb≤1.2 (1)

(1) Wherein Bi and Sb represent the content (mass%) of each in the alloy composition.

12. Solder alloy according to any of claims 9 to 11, wherein the alloy composition also contains Ag: more than 0 mass% and not more than 4 mass%.

13. The solder alloy according to any one of claims 1 to 12, wherein a ratio of Bi to Sb is 0.008 or more and 10 or less in a mass ratio Sb/Bi.

14. Solder alloy according to any of claims 1 to 13, wherein the alloy composition also contains Ni:0 mass ppm or more and 600 mass ppm or less and Fe: at least one kind of the metal oxide particles is 0 mass ppm or more and 100 mass ppm or less.

15. The solder alloy according to claim 14, wherein the alloy composition further satisfies the following formula (2),

20≤Ni+Fe≤700 (2)

(2) In the formula, ni and Fe represent their respective contents (mass ppm) in the alloy composition.

16. Solder alloy according to any of claims 1 to 15, wherein the area for molding into one side is 900cm ² The amount of alpha rays after the heat treatment at 100 ℃ for 1 hour was 0.02cph/cm ² The following.

17. Solder alloy according to any one of claims 1 to 16, having an alpha dose of 0.002cph/cm ² The following.

18. Solder alloy according to claim 17, having an alpha dose of 0.001cph/cm ² The following.

19. Solder powder consisting of the solder alloy according to any one of claims 1 to 18.

20. Solder powder according to claim 19 simultaneously having groups of 2 or more solder alloy particles with different particle size distributions.

21. A solder paste comprising the solder powder of claim 19 or 20 and a flux.

22. A solder ball consisting of the solder alloy of any one of claims 1 to 18.

23. A preformed solder consisting of the solder alloy of any one of claims 1 to 18.

24. A solder joint made of the solder alloy according to any one of claims 1 to 18.