WO2021205760A1 - Solder alloy, solder powder, solder paste, solder ball, solder preform, and solder joint - Google Patents

Abstract

The present invention uses a solder alloy that has an alloy composition containing less than 5 mass ppb of U, less than 5 mass ppb of Th, less than 5 mass ppm of Pb, less than 5 mass ppm of As, 0-0.9 mass% of Bi, and 0-0.3 mass% of Sb, the remaining portion being Sn, that satisfies formula (1), and that has an alpha ray amount of 0.02 cph/cm² or less.　(1): 0.005≤Bi+Sb≤1.2. In formula (1), Bi and Sb each represent the contained amount (mass%) thereof in the alloy composition.　By using the solder alloy according to the present invention, it is possible to suppress an increase in viscosity of a solder paste over the course of time, increase mechanical properties by having little difference in temperature (ΔT) between a liquidus line temperature and a solidus line temperature, and suppress occurrence of soft errors.

Description

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

The present invention relates to solder alloys, solder powders, solder pastes, solder balls, solder preforms and solder joints.
The present application claims priority based on Japanese Patent Application No. 2020-071024 filed in Japan on April 10, 2020, the contents of which are incorporated herein by reference.

Electronic components mounted on printed circuit boards are increasingly required to be smaller and have higher performance. Examples of such electronic components include semiconductor packages. In a semiconductor package, a semiconductor element having electrodes is sealed with a resin component. Solder bumps made of a solder material are formed on this electrode. Further, the solder material connects the semiconductor element and the printed circuit board.

In solder materials, the effect of α rays on soft errors becomes a problem. In order to reduce such adverse effects on the operation of semiconductor devices, low α-dose materials including solder materials are being developed.

The factor that becomes the α-ray source is, for example, a trace amount of radioactive elements contained in the solder alloy in the solder material, particularly the base tin (Sn) bullion. The solder alloy can be produced by melting and mixing the raw material metals. In such a solder alloy, it is important to remove upstream radioactive elements such as uranium (U), thorium (Th), and polonium (Po) from the alloy composition in order to design a low α-dose material.
On the other hand, it is not technically difficult to remove U, Th, and Po in the refining of Sn bullion (see, for example, Patent Document 1).
Generally, Sn contains lead (Pb) and bismuth (Bi) as impurities. Radioisotopes ²¹⁰ Pb and ²¹⁰ Bi in Pb and Bi are β-decayed to ²¹⁰ Po, ²¹⁰ Po is α-decayed, and α rays are generated when ^{206 Pb is generated.} This series of decay (uranium series) is said to be the main cause of α-ray generation from solder materials.

In the evaluation of the α dose generated from the material, "cph / cm ² " is often used as the unit. “Cph / cm ² ” is an abbreviation for “counts per hours / cm ² ” and means the number of alpha rays counted per 1 ^{cm 2 per hour.}

The half-lives of Pb and Bi are as follows.
For Bi, the half-life of ^{210 Bi is about 5 days.} For Pb, the half-life of ^{210 Pb is about 22.3 years.} The degree of influence (abundance ratio) can be expressed by the following equation (see Non-Patent Document 1). That is, the influence of Bi on α-ray generation is much lower than that of Pb.
[ ²¹⁰ Bi] ≒ [ ²¹⁰ Pb] /1.6 × 10 ³
In the formula, [ ²¹⁰ Bi] represents the molar concentration of ^{210 Bi.} [ ²¹⁰ Pb] represents the molar concentration of ^{210 Pb.}

As described above, conventionally, in the design of low α-dose materials, it is common to remove U and Th, and then thoroughly remove Pb.

Further, it is known that the α dose generated from the solder material basically increases with the passage of time. It is said that this is because radioactive Pb and radioactive Bi in the solder alloy are β-decayed, the amount of Po is increased, and Po is α-decayed to generate α rays.
Although the material having an extremely low α-dose contains almost no of these radioactive elements, the α-dose may increase with time due to the segregation of ^{210 Po. 210} Po originally emits α rays, but when the solder alloy is solidified, it segregates at the center of the solder alloy, so that the emitted α rays are shielded by the solder alloy. Then, with the passage of time, ²¹⁰ Po is uniformly dispersed in the alloy and is also present on the surface where α rays are detected, so that the α dose increases with time (see Non-Patent Document 2).

As described above, the generated α-dose increases due to the influence of a very small amount of impurities contained in the solder alloy. For this reason, in the design of low α-dose materials, it becomes difficult to simply add various elements as in the conventional manufacturing method of solder alloys.
For example, a method of adding arsenic (As) to a solder alloy is known in order to suppress the increase in viscosity of the solder paste over time (see, for example, Patent Document 2).

Japanese Unexamined Patent Publication No. 2010-156052 Japanese Unexamined Patent Publication No. 2015-98052

In order to suppress the thickening of the solder paste over time, in the method of adding As to the solder alloy, for example, as in the method described in Patent Document 2, impurities are also contained in the alloy due to the addition of As. become. In this case, the presence of radioactive elements in the impurities increases the α dose generated from the solder material.

Further, in recent years, electronic devices having a solder joint such as a CPU (Central Processing Unit) are required to be miniaturized and have high performance. Along with this, it is necessary to reduce the size of the electrodes of the printed circuit board and the electronic device. Since the electronic device is connected to the printed circuit board via the electrode, the solder joint connecting the two becomes smaller as the electrode becomes smaller.
Further, in order to join fine electrodes, it is necessary to improve the mechanical properties of the solder joint. However, depending on the element, as its content increases, the liquidus temperature rises, the temperature difference (ΔT) between the liquidus temperature and the solidus temperature increases, and segregation occurs during solidification, resulting in non-uniformity. Alloy structure is formed. When the solder alloy has such an alloy structure, the solder joint is inferior in mechanical properties such as tensile strength and easily breaks due to external stress. This problem has become remarkable with the recent miniaturization of electrodes.

The present invention has been made in view of the above circumstances, suppresses an increase in the viscosity of the solder paste over time, has a small temperature difference (ΔT) between the liquidus line temperature and the solidus line temperature, and has mechanical properties. Solder alloy that can enhance and suppress the occurrence of soft errors, solder powder made of this solder alloy, solder paste containing this solder powder and flux, solder balls made of this solder alloy, solderp It is an object of the present invention to provide a remodeling and a solder joint.

The present inventors have studied for the purpose of designing a low α-dose solder alloy capable of suppressing thickening of solder paste over time without adding As with impurities containing radioactive elements. Through such studies, it was found that the above object can be achieved by adjusting the alloy composition to contain Sn as a main component and a predetermined amount of Bi and Sb, which are noble metals as compared with Sn in ionization tendency. , The present invention has been completed.
That is, the present invention employs the following means in order to solve the above problems.

One aspect of the present invention is 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: 0% by mass or more and 0.9% by mass or less, and Sb. : It has an alloy composition of 0% by mass or more and 0.3% by mass or less, and the balance is Sn, satisfies the following formula (1), and has an α dose of 0.02 cph / cm ² or less. It is a solder alloy.
0.005 ≤ Bi + Sb ≤ 1.2 (1)
In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.

One aspect of the present invention is 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. : It has an alloy composition of 0% by mass or more and 0.3% by mass or less, and the balance is Sn, satisfies the following formula (1), and has an α dose of 0.02 cph / cm ² or less. It is a solder alloy.
0.005 ≤ Bi + Sb ≤ 1.2 (1)
In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.

One aspect of the present invention is 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: 0% by mass or more and 0.9% by mass or less, and Sb. : It has an alloy composition of 0% by mass or more and less than 0.1% by mass, and the balance is Sn, satisfies the following formula (1), and has an α dose of 0.02 cph / cm ² or less. It is a solder alloy.
0.005 ≤ Bi + Sb ≤ 1.2 (1)
In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.

Further, one aspect of the present invention is a solder powder characterized by being composed of a solder alloy according to the one aspect of the present invention.

Further, one aspect of the present invention is a solder paste characterized by containing the solder powder and the flux according to the one aspect of the present invention.

Further, one aspect of the present invention is a solder ball characterized by being made of a solder alloy according to the one aspect of the present invention.

Further, one aspect of the present invention is a solder preform characterized by being made of a solder alloy according to the one aspect of the present invention.

Further, one aspect of the present invention is a solder joint characterized by being made of a solder alloy according to the one aspect of the present invention.

According to the present invention, the increase in the viscosity of the solder paste over time is suppressed, the temperature difference (ΔT) between the liquidus line temperature and the solidus line temperature is small, the mechanical properties can be improved, and soft errors occur. It is possible to provide a solder alloy capable of suppressing the above, a solder powder made of this solder alloy, a solder paste containing the solder powder and a flux, a solder ball made of this solder alloy, a solder preform and a solder joint. ..

The present invention will be described in more detail below.
In the present specification, "ppb" relating to the solder alloy composition is "mass ppb" unless otherwise specified. “Ppm” is “mass ppm” unless otherwise specified. “%” Is “mass%” unless otherwise specified.

(Solder alloy)
The solder alloy according to one aspect of the present invention has U: less than 5% by mass, Th: less than 5% by mass, Pb: less than 5% by mass, As: less than 5% by mass, Bi: 0% by mass or more and 0.9% by mass. The following, and Sb: 0% by mass or more and 0.3% by mass or less, and having an alloy composition in which the balance is Sn, satisfying the following formula (1), and having an α dose of 0.02 cph / cm ² or less. Is.
0.005 ≤ Bi + Sb ≤ 1.2 (1)
In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.

<Alloy composition>
The solder alloy 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, Bi: 0 mass% or more and 0.9 mass% or less, and Sb: It has an alloy composition of 0% by mass or more and 0.3% by mass or less, and the balance is Sn, and satisfies the above formula (1).

<< U: less than 5 mass ppb, Th: less than 5 mass ppb >>
U and Th are radioactive elements. In order to suppress the occurrence of soft errors, it is necessary to suppress these contents in the solder alloy.
In the present embodiment, the contents of U and Th in the solder alloy are based on the total mass (100% by mass) of the solder alloy from the viewpoint that the α dose generated from the solder alloy is 0.02 cf / cm ^{2 or less.} , Each less than 5 ppb. From the viewpoint of suppressing the occurrence of soft errors in high-density mounting, the contents of U and Th are preferably 2 ppb or less, and the lower the better.

<< Pb: less than 5 mass ppm >>
Generally, Sn contains Pb as an impurity. The radioactive isotope in this Pb undergoes β-decay to become ²¹⁰ Po, and ²¹⁰ Po undergoes α-decay to generate α-rays when ^{206 Pb is generated.} For this reason, it is preferable that the content of Pb, which is 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 5 ppm, preferably less than 2 ppm, and more preferably less than 1 ppm with respect to the total mass (100% by mass) of the solder alloy. The lower limit of the Pb content in the solder alloy may be 0 ppm or more.

≪As: less than 5 mass ppm≫
Adding As to the solder alloy is effective in suppressing the thickening of the solder paste over time, but with the addition of As, the alloy also contains radioactive elements, and the α dose generated from the solder material increases. It will increase.
An object of the present embodiment is to suppress thickening of the solder paste over time without adding As with impurities containing radioactive elements.
In the present embodiment, the content of As in the solder alloy is less than 5 ppm, preferably less than 2 ppm, and more preferably less than 1 ppm with respect to the total mass (100% by mass) of the solder alloy. The lower limit of the As content in the solder alloy may be 0 ppm or more.

<< Bi: 0% by mass or more and 0.9% by mass or less, Sb: 0% by mass or more and 0.3% by mass or less, equation (1) >>
It is considered that the reason why the viscosity of the solder paste increases with time is that the solder powder reacts with the flux.
The effect of suppressing the thickening of the solder paste over time is exhibited by suppressing the reaction with the flux. From this, an element having a low ionization tendency can be mentioned as an element having a low reactivity with the flux. Generally, the ionization of an alloy is considered in terms of the ionization tendency as the alloy composition, that is, the standard electrode potential. For example, a SnAg alloy containing Ag, which is noble to Sn, is less likely to be ionized than Sn. Therefore, it is presumed that the alloy containing an element nobler than Sn is difficult to ionize, and the effect of suppressing the thickening of the solder paste over time can be enhanced.

Bi: 0% by mass or more and 0.9% by mass or less Bi is an element whose ionization tendency is noble with respect to Sn, has low reactivity with flux, and exhibits an effect of suppressing thickening of solder paste over time. be. In addition, Bi is an element capable of suppressing deterioration of wettability because it lowers the liquidus temperature of the solder alloy and reduces the viscosity of the molten solder. However, depending on the content, the solidus temperature is remarkably lowered, and the temperature difference (ΔT) between the liquidus temperature and the solidus temperature becomes wide.
In the present embodiment, the content of Bi in the solder alloy is 0% or more and 0.9% or less, preferably 0.030% or more and 0.9, based on the total mass (100% by mass) of the solder alloy. % Or less.
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, based on the total mass (100% by mass) of the solder alloy. , 0.010% or more is more preferable, and 0.030% or more is particularly preferable. 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, and 0.5% or less with respect to the total mass (100% by mass) of the solder alloy. More preferably, 0.3% or less is further preferable, and 0.1% or less is particularly preferable.
For example, as 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, with respect to the total mass (100% by mass) of the solder alloy. % 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. It is 0.1% or less.

Sb: 0% by mass or more and 0.3% by mass or less Sb is an element having an ionization tendency noble to Sn, has low reactivity with flux, and suppresses thickening of solder paste over time, like Bi. It is an element that shows an effect. If the content of Sb in the solder alloy is too large, the wettability deteriorates. Therefore, when Sb is added, it is necessary to set the content to an appropriate level.
In the present embodiment, the content of Sb in the solder alloy is 0% or more and 0.3% or less, preferably 0.0040% or more and 0.3, based on the total mass (100% by mass) of the solder alloy. % Or less, more preferably 0.010% or more and 0.3% or less.
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, based on the total mass (100% by mass) of the solder alloy. , 0.0050% or more is more preferable, and 0.010% or more is particularly preferable. 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, and less than 0.1% with respect to the total mass (100% by mass) of the solder alloy. More preferably, 0.090% or less is further preferable.
For example, as one embodiment of the solder alloy, the content of Sb in the solder alloy is 0% or more and 0.3% or less, preferably 0.0025, with respect to the total mass (100% by mass) of the solder alloy. % Or more and 0.1% or less, more preferably 0.0040% or more and less than 0.1%, further preferably 0.0050% or more and 0.090% or less, and particularly preferably 0.010% or more. It is 0.090% or less.

The alloy composition of the solder alloy of the present embodiment satisfies the following equation (1).
0.005 ≤ Bi + Sb ≤ 1.2 (1)
In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.

Both Bi and Sb in the formula (1) are elements that show the effect of suppressing the thickening of the solder paste over time. In addition, in this embodiment, both Bi and Sb also contribute to the wettability of the solder alloy.
The total content of Bi and Sb in the solder alloy needs to be 0.005% or more and 1.2% or less with respect to the total mass (100% by mass) of the solder alloy, preferably 0.03. Must be greater than or equal to% and less than or equal to 1.2%. 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, based on the total mass (100% by mass) of the solder alloy. Yes, 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.
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, and 0, based on the total mass (100% by mass) of the solder alloy. .02% or more is more preferable, and 0.03% or more is further preferable. 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, and 0, based on the total mass (100% by mass) of the solder alloy. 9.9% or less is more preferable, 0.5% or less is further preferable, and 0.1% or less is particularly preferable.
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, with respect to the total mass (100% by mass) of the solder alloy. It is 0.02% or more and 0.9% or less, more preferably 0.03% or more and 0.5% or less, and particularly preferably 0.03% or more and 0.1% or less.

However, the "total content of Bi and Sb" is the content of Sb when the content of Bi in the solder alloy is 0% by mass, and the content of Sb in the solder alloy is 0% by mass. When it is%, it is the content of Bi, and when it has both Bi and Sb, it is the total content of these.

Further, when Bi and Sb are used together in the present embodiment, the ratio of Bi and Sb in the solder alloy is preferably 0.008 or more and 10 or less as the mass ratio represented by Sb / Bi, and more. It is preferably 0.01 or more and 10 or less, more 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.
If the mass ratio of Sb / Bi is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

≪Arbitrary element≫
The alloy composition of the solder alloy of the present embodiment may contain elements other than the above-mentioned elements, if necessary.
For example, in the alloy composition of the solder alloy of the present embodiment, in addition to the above-mentioned elements, 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 is further added. It may be contained.

Ag: 0% by mass or more and 4% by mass or less Ag is an _{arbitrary element capable of forming Ag 3} Sn at the crystal interface to improve the reliability of the solder alloy. In addition, Ag is an element whose ionization tendency is noble with respect to Sn, and when it coexists with Bi and Sb, the effect of suppressing thickening of the solder paste over time is enhanced.
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%, based on the total mass (100% by mass) of the solder alloy. It is less than or equal to, more preferably 1.0% or more and 3.0% or less, and particularly 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 optional element that is used in general solder alloys and can improve the joint strength of solder joints. Further, Cu is an element whose ionization tendency is noble with respect to Sn, and when it coexists with Bi and Sb, the effect of suppressing thickening of the solder paste over time is enhanced.
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 0.1% or more, based on the total mass (100% by mass) of the solder alloy. It is 8% or less, more preferably 0.2% or more and 0.7% or less.

When Cu and Bi are used together in the present embodiment, the ratio of Cu and Bi in the solder alloy is preferably 0.5 or more and 280 or less as the mass ratio represented by Cu / Bi, and more preferably. It is 0.5 or more and 150 or less, more preferably 0.5 or more and 20 or less, and particularly preferably 1 or more and 15 or less.
If the Cu / Bi of such a mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

When Cu and Sb are used together in the present embodiment, the ratio of Cu and Sb in the solder alloy is preferably 1 or more and 280 or less, and more preferably 1 or more as the mass ratio represented by Cu / Sb. It is 150 or less, more preferably 5 or more and 125 or less.
If the Cu / Sb having such a mass ratio is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

When Cu, Bi and Sb are used together in this embodiment, the ratio of Cu, Bi and Sb in the solder alloy is preferably 0.4 or more and 150 or less as the mass ratio represented by Cu / (Bi + Sb). It is more preferably 5 or more and 100 or less.
If the mass ratio of Cu / (Bi + Sb) is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

For example, the alloy composition of the solder alloy of the present embodiment further contains at least one of 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, in addition to the above-mentioned elements. You may.

Ni: 0% by mass or more and 600% by mass or less When soldering promotes the formation of Sn-containing intermetallic compounds (Sn-containing intermetallic compounds) in the vicinity of the bonding interface in the solder alloy, and this Sn-containing intermetallic compound is precipitated. , The mechanical strength of the solder joint deteriorates.
Ni is an element that suppresses the formation of the Sn-containing intermetallic compound at the bonding interface.
When the solder alloy contains Ni, the formation of the Sn-containing intermetallic compound is suppressed, and the mechanical strength of the solder joint is maintained. On the other hand, if the content of Ni in the solder alloy exceeds 600 mass ppm, SnNi compounds may precipitate in the vicinity of the bonding interface in the solder alloy, and the mechanical strength of the solder joint may deteriorate.
In the present embodiment, the content of Ni in the solder alloy is preferably 0 ppm or more and 600 ppm or less, more preferably 20 ppm or more and 600 ppm or less, based on the total mass (100% by mass) of the solder alloy.

Fe: 0 mass ppm or more and 100 mass ppm or less Fe is an element that suppresses the formation of Sn-containing intermetallic compounds at the bonding interface, similar to Ni. In addition, within a predetermined content range, precipitation of acicular crystals due to the SnFe compound is suppressed, and a short circuit of the circuit can be prevented.
The term "acicular crystal" as used herein refers to a crystal derived from one SnFe compound having an aspect ratio of 2 or more, which is the ratio of the major axis to the minor axis.
In the present embodiment, the content of Fe in the solder alloy is preferably 0 ppm or more and 100 ppm or less, more preferably 20 ppm or more and 100 ppm or less, based on the total mass (100% by mass) of the solder alloy.

When the alloy composition of the solder alloy of the present embodiment further contains at least one of 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, the alloy composition is as follows ( It is preferable to satisfy the formula 2).
20 ≦ Ni + Fe ≦ 700 (2)
In the formula (2), Ni and Fe each represent the content (mass ppm) in the alloy composition.

Both Ni and Fe in the formula (2) are elements that suppress the formation of Sn-containing intermetallic compounds at the bonding interface. In addition, in the present embodiment, both Ni and Fe also contribute to the effect of suppressing the thickening of the solder paste over time.
The total content of Ni and Fe in the solder alloy is preferably 20 ppm or more and 700 ppm or less, more preferably 40 ppm or more and 700 ppm or less, still more preferably 40 ppm, based on the total mass (100% by mass) of the solder alloy. More than 600 ppm or less.

However, the above-mentioned "total content of Ni and Fe" is the content of Fe when the content of Ni in the solder alloy is 0 mass ppm, and the content of Fe in the solder alloy is 0 mass ppm. When it is ppm, it is the content of Ni, and when it has both Ni and Fe, it is the total content of these.

When Ni and Fe are used together in the present embodiment, the ratio of Ni and Fe in the solder alloy is preferably 0.4 or more and 30 or less as the mass ratio represented by Ni / Fe, and more preferably. It is 0.4 or more and 10 or less, and more preferably 0.4 or more and 5 or less.
If the mass ratio of Ni / Fe is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

≪Remaining part: Sn≫
The balance of the alloy composition of the solder alloy of the present embodiment is Sn. In addition to the above-mentioned elements, unavoidable impurities may be contained. Even if it contains unavoidable impurities, it does not affect the above-mentioned effects.

<Α dose>
The solder alloy of this embodiment has an α dose of 0.02 cf / cm ² or less.
This is an α-dose that does not cause soft errors in high-density mounting of electronic components.
The α dose in the solder alloy of the present embodiment is preferably 0.01 cf / cm ² or less, more preferably 0.002 cf / cm ² or less, from the viewpoint of suppressing soft errors in further high-density mounting. , More preferably 0.001 cf / cm ² or less.

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

Procedure (i):
A gas flow type α dosimetry device is used.
As a measurement sample, a solder alloy sheet obtained by melting a solder alloy and forming a sheet having an area of 900 cm ^{2 on one surface is used.}
The solder alloy sheet is installed as a measurement sample in the α-dosimetry device, and PR gas is purged therein.

For PR gas, use one that complies with the international standard JEDEC STANDARD. That is, it is assumed that the PR gas used for the measurement is the decay of radon (Rn) after 3 weeks or more have passed since the gas cylinder was filled with the mixed gas of 90% argon and 10% methane.

Procedure (ii):
The PR gas is allowed to flow in the α-dose measuring device on which the solder alloy sheet is installed for 12 hours, and then the α-dose is measured for 72 hours.

Procedure (iii):
The average α-dose is calculated as ^{“cph / cm 2”.} Abnormal points (counts due to device vibration, etc.) are removed from the count for one hour.

[Manufacturing method of solder alloy]
The solder alloy of the present embodiment can be produced, for example, by using a production method having a step of melting and mixing at least one of Bi and Sb and a raw material metal containing Sn.
Since the purpose is to design a low α-dose solder alloy, it is preferable to use a low-α-dose material as the raw material metal. In addition, it is preferable to use the one from which U, Th and Pb have been removed.
As the raw material metal, for example, a Sn produced according to the production method described in JP-A-2010-156502 (Patent Document 1) can be used.
As the Bi as the raw material metal, for example, one manufactured according to Japanese Patent Application Laid-Open No. 2013-185214 can be used.
As the raw material metal, for example, one manufactured in accordance with Japanese Patent No. 5692467 can be used.
A conventionally known method can be used for the operation of melting and mixing the raw metal.

Generally, in a solder alloy, each constituent element constituting the solder alloy does not function independently, and various effects can be exhibited only when the contents of each constituent element are all within a predetermined range. .. According to the solder alloy of the embodiment described above, when the content of each constituent element is within the above range, the increase in viscosity of the solder paste over time can be suppressed, the mechanical strength of the solder joint can be increased, and the mechanical strength of the solder joint can be increased. , The occurrence of soft errors can be suppressed. That is, the solder alloy of the present embodiment is useful as a target low α-dose material, and by applying it to the formation of solder bumps around the memory, it is possible to suppress the occurrence of soft errors.

Another object of the present embodiment is to design a low α-dose solder alloy capable of suppressing thickening of solder paste over time without actively adding As. On the other hand, the purpose is achieved by adopting a solder alloy containing Bi and Sb, which are metals having an ionization tendency higher than Sn, in a specific ratio in addition to Sn as a main component.
The reason why such an effect is obtained is not clear, but it is presumed as follows.
Sn for low α-dose solder alloys has a very high purity, and when the molten alloy is solidified, the crystal size of Sn becomes large. Further, the oxide film in Sn also forms a sparse oxide film corresponding to the oxide film. Therefore, by adding Bi and Sb, which are metals that have a higher ionization tendency than Sn and are difficult to ionize, the crystal size is reduced and a dense oxide film is formed, so that the reactivity between the alloy and the flux Therefore, it is possible to suppress the thickening of the solder paste over time.

In addition, in the solder alloy of the present embodiment, the α dose after heat treatment at 100 ° C. for 1 hour is applied to the solder alloy sheet formed into a sheet ^{having an area of 900 cm 2 on one surface.} It is preferably 0.02 cf / cm ² or less, more preferably 0.01 cf / cm ² or less, still more preferably 0.002 cf / cm ² or less, and particularly preferably 0. It is 001 cph / cm ² or less.
A solder alloy exhibiting such an α dose is ^{useful because segregation of 210} Po is unlikely to occur in the alloy and the influence of changes in the α dose over time is small. By applying a solder alloy exhibiting such an α dose, the occurrence of soft errors is further suppressed, and stable operation of the semiconductor element can be more easily ensured.

(Solder powder)
The solder powder according to one aspect of the present invention is made of the above-mentioned solder alloy according to one aspect of the present invention.
The solder powder of this embodiment is suitable for the solder paste described later.
Solder powder is produced by known methods such as a dropping method of dropping a molten solder alloy to obtain particles, a spraying method of centrifugal spraying, an atomizing method, a submerged granulation method, and a method of crushing a bulk solder alloy. Can be adopted. In the dropping method or the spraying method, the dropping or spraying is preferably carried out in an inert atmosphere or a solvent in order to form particles.

The solder powder of this 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, it is preferable that the symbols 1 to 8 are satisfied, and the symbols 4 to 8 are satisfied in the powder size classification (Table 2) in JIS Z 3284-1: 2014. It is more preferable to have. When the particle size of the solder powder satisfies this condition, the surface area of the powder is not too large, the increase in the viscosity of the solder paste over time is suppressed, and the aggregation of the fine powder is suppressed, so that the viscosity of the solder paste increases. May be suppressed. Therefore, it is possible to solder to finer parts.

Further, it is preferable that the solder powder of the present embodiment also has two or more kinds of solder alloy particle groups having different particle size distributions. As a result, the slipperiness of the solder paste is enhanced, and workability such as easy printing is improved.

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, still more preferably 0.99 or more.

The "spherical degree of spherical powder" referred to here shall be measured using a CNC image measurement system (Ultra Quick Vision ULT RA QV350-PRO measuring device manufactured by Mitutoyo Co., Ltd.) that uses the minimum region center method (MZC method). Can be done.
The sphericity represents the deviation from the sphere, and is, for example, an arithmetic mean value calculated when the diameter of each of 500 solder alloy particles is divided by the major axis, and the value is 1.00, which is the upper limit. The closer it is, the closer it is to a true sphere.

(Solder paste)
The solder paste according to one aspect of the present invention contains the solder powder according to one aspect of the present invention and a flux.

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

Examples of the resin component include rosin-based 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 α, β unsaturated carboxylic acid modified products (acrylicated rosin, maleated rosin, fumarized rosin, etc.), and the polymerized rosin. Examples thereof include purified products, hydrogenated products and disproportionate products of the above, and purified products, hydrogenated products and disproportionate products of the α, β unsaturated carboxylic acid modified products, and two or more of them can be used.
In addition to rosin-based resins, the resin components include terpene resin, modified terpene resin, terpenephenol resin, modified terpenephenol resin, styrene resin, modified styrene resin, xylene resin, modified xylene resin, acrylic resin, polyethylene resin, and acrylic. -Polyethylene copolymer resin, epoxy resin and the like can be mentioned.
Examples of the modified terpene resin include aromatic modified terpene resin, hydrogenated terpene resin, hydrogenated aromatic modified terpene resin and the like. Examples of the modified terpene phenol resin include hydrogenated terpene phenol resin and the like. Examples of the modified styrene resin include styrene acrylic resin and styrene maleic acid resin. Examples of the modified xylene resin include a phenol-modified xylene resin, an alkylphenol-modified xylene resin, a phenol-modified resol-type xylene resin, a polyol-modified xylene resin, and a polyoxyethylene-added xylene resin.

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

Examples of organic acids include succinic acid, glutaric acid, adipic acid, pimelli acid, suberic acid, azelaic acid, sebacic acid, dimer acid, propionic acid, 2,2-bishydroxymethylpropionic acid, tartrate acid, malic acid and glycol. Examples thereof include acids, diglycolic acid, thioglycolic acid, dithioglycolic acid, stearic acid, 12-hydroxystearic acid, palmitic acid, oleic acid and the like.

Examples of amines 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-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 trimerite, 1-cyanoethyl-2-phenylimidazolium trimerite, 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-hydroxymethyl Imidazole, 2,3-dihydro-1H-pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazolin, 2,4- Diamino-6-vinyl-s-triazine, 2,4-diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2 -Methylbenzoimidazole, 2-octylbenzoimidazole, 2-pentylbenzoimidazole, 2- (1-ethylpentyl) benzoimidazole, 2-nonylbenzoimidazole, 2- (4-thiazolyl) benzoimidazole, 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-benzotriazole-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-benzotriazole-1-yl) methyl] imino] bisethanol, 1- (1', 2'-di Carboxyethyl) benzotriazole, 1- (2,3-dicarboxypropyl) benzotriazole, 1-[(2-ethylhexylamino) methyl] benzotriazole, 2,6-bis [(1H-benzotriazole-1-yl)) Methyl] -4-methylphenol, 5-methylbenzotriazole, 5-phenyltetrazole and the like can be mentioned.

Examples of the halogen-based activator include amine hydrogen halides and organic halogen compounds.
Amine halide hydrohydrate is a compound obtained by reacting an amine with hydrogen halide. Examples of the amine here include ethylamine, ethylenediamine, triethylamine, diphenylguanidine, ditrilguanidine, methylimidazole, 2-ethyl-4-methylimidazole and the like, and examples of the hydrogen halide include chlorine, bromine and the like. Examples include hydrides of iodine.
Examples of the organic halogen compound include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate 6 bromide, 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, Examples thereof include 3-dibromo-1,4-butanediol and 2,3-dibromo-2-butene-1,4-diol.

Examples of the thixotropy include wax-based thixotropy, amide-based thixotropy, sorbitol-based thixotropy, and the like.
Examples of the wax-based thixotropy include castor oil and the like.
Examples of amido-based fatty acid agents include monoamide-based fatty acid agents, bis-amide-based fatty acid agents, and polyamide-based fatty acid agents. , Saturated fatty acid amide, oleic acid amide, erucic acid amide, unsaturated fatty acid amide, p-toluenemethane amide, aromatic amide, methylene bisstearate amide, ethylene bislauric acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bis amide , Methylenebisoleic 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, methylolstearic acid amide, methylolamide, fatty acid Examples include ester amide.
Examples of the sorbitol-based thixotropy include dibenzylidene-D-sorbitol, bis (4-methylbenzylidene) -D-sorbitol and the like.

Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, terpineols and the like.
Examples of the alcohol solvent include isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, and the like. 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexine-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris ( Hydroxymethyl) ether, 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-tris (hydroxymethyl) ethyl] ether, 1-ethynyl-1-cyclohexanol, 1,4 -Cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, treitol, guayacol glycerol ether, 3,6-dimethyl-4-octine-3,6-diol, 2,4,7,9-tetramethyl-5- Descin-4,7-diol and the like can be mentioned.
Examples of the glycol ether-based 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. Can be mentioned.

Examples of the metal inactivating agent include hindered phenolic compounds and nitrogen compounds. When the flux contains either a hindered phenolic compound or a nitrogen compound, the effect of suppressing the thickening of the solder paste can be easily enhanced.
The term "metal inactivating agent" as used herein refers to a compound having the ability to prevent the metal from deteriorating due to contact with a certain compound.

The hindered phenolic compound refers to a phenolic compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at at least one of the ortho positions of the phenol.
The hindered phenolic compound is not particularly limited, and is, for example, bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylenebis (oxyethylene)], N, N. '-Hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], 1,6-hexanediolbis [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-3,5-di-t-) Butylanilino) -1,3,5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3-( 3,5-Di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3) , 5-Di-t-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, N'-bis [2- [2- (3,5-di-tert-butyl-4-hydroxyphenyl) ) Ethylcarbonyloxy] ethyl] oxamide, compounds represented by the following chemical formulas and the like.

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

Examples of the nitrogen compound in the metal inactivating agent include hydrazide nitrogen compounds, amide nitrogen compounds, triazole nitrogen compounds, and melamine nitrogen compounds.

The hydrazide-based nitrogen compound may be any nitrogen compound having a hydrazide skeleton, and is bis dodecanoate [N2- (2-hydroxybenzoyl) hydrazide], N, N'-bis [3- (3,5-di-tert). -Butyl-4-hydroxyphenyl) propionyl] hydrazine, decandicarboxylic acid disalicyloyl hydrazide, N-salicylidene-N'-salityl hydrazide, m-nitrobenzhydrazide, 3-aminophthalhydrazide, phthalic acid dihydrazide, adipate hydrazide , Oxalobis (2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidone carboxylic acid hydrazide, N, N'-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) Hydrazide and the like can be mentioned.

The amide-based nitrogen compound may be any nitrogen compound having an amide skeleton, and N, N'-bis {2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxyl] ethyl. } Oxamide and the like can be mentioned.

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

The melamine-based nitrogen compound may be any nitrogen compound having a melamine skeleton, and examples thereof include melamine and melamine derivatives. More specifically, for example, trisaminotriazine, alkylated trisaminotriazine, alkoxyalkylated trisaminotriazine, melamine, alkylated melamine, alkoxyalkylated melamine, N2-butyl melamine, N2, N2-diethyl melamine, N, Examples thereof include N, N', N', N'', N''-hexakis (methoxymethyl) melamine and the like.

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

Examples of the surfactant include nonionic surfactants and weak cationic surfactants.
Examples of the nonionic surfactant include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymer, aliphatic alcohol polyoxyethylene adduct, aromatic alcohol polyoxyethylene adduct, polyhydric alcohol polyoxyethylene adduct and the like. Can be mentioned.
Examples of the weak cationic surfactant include terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adduct, aromatic amine polyoxyethylene adduct, and polyvalent amine polyoxy. Examples include polyethylene adducts.

Examples of surfactants other than the above include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkyl amines, polyoxyalkylene alkyl amides and the like. ..

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, based on the total mass (100% by mass) of the solder paste. It is more preferably 5 to 15% by mass.
When the flux content is in this range, the thickening suppressing effect caused by the solder powder is sufficiently exhibited.

The solder paste of the present embodiment can be produced by a production method common in the art.
A solder paste can be obtained by heating and mixing the compounding components constituting the flux to prepare a flux, and stirring and mixing the solder powder in the flux. Further, in anticipation of the effect of suppressing thickening over time, zirconium oxide powder may be further blended in addition to the solder powder.

(Solder ball)
The solder ball according to one aspect of the present invention is made of the above-mentioned solder alloy according to one aspect of the present invention.
The solder alloy of the above-described embodiment can be used as a solder ball.
The solder ball of the present embodiment can be manufactured by using a dropping method which is a common method in the art.
The particle size of the solder balls 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 size of the solder balls 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 size of the solder balls 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.

(Solder preform)
The solder preform according to one aspect of the present invention is made of the above-mentioned solder alloy according to one aspect of the present invention.
The solder alloy of the above-described embodiment can be used as a preform.
Examples of the shape of the preform of the present embodiment include washers, rings, pellets, discs, ribbons, wires, and the like.

(Solder joint)
The solder joint according to one aspect of the present invention is made of the above-mentioned solder alloy according to one aspect of the present invention.
The solder joint of the present embodiment is composed of an electrode and a solder joint. The solder joint portion refers to a portion mainly formed of a solder alloy.
The solder joint of the present embodiment is formed by, for example, joining an electrode of a PKG (Package) such as an IC chip and an electrode of a substrate such as a PCB (printed circuit board) with the solder alloy of the above-described embodiment. be able to.
Further, the solder joint of the present embodiment is manufactured by processing by a method common in the art, such as mounting one solder ball of the above-described embodiment on one electrode coated with flux and joining the solder joint. can do.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples.
In this embodiment, unless otherwise specified, "ppb" for the solder alloy composition is "mass ppb", "ppm" is "mass ppm", and "%" is "mass%".

<Solder alloy>
(Examples 1 to 414, comparative examples 1 to 8)
The raw metal was melted and stirred to prepare solder alloys of each example having the alloy compositions shown in Tables 1A to 25B.

<Solder powder>
The solder alloys of each example are melted and composed of the solder alloys of each example having the alloy compositions shown in Tables 1A to 25B by the atomization method. A solder powder having a size (particle size distribution) satisfying the symbol 4 was prepared.

<Preparation of flux (F0)>
A rosin-based resin was used as the resin component.
A thixotropic agent, an organic acid, an amine and a halogen-based activator were used as the active ingredient.
A glycol ether solvent was used as the solvent.
42 parts by mass of rosin, 35 parts by mass of glycol ether solvent, 8 parts by mass of thixo agent, 10 parts by mass of organic acid, 2 parts by mass of amine, and 3 parts by mass of halogen-based activator are mixed and flux ( F0) was prepared.

<Manufacturing of solder paste>
The flux (F0) and a solder powder made of the solder alloys of each example having the alloy compositions shown in Tables 1A to 25B were mixed to produce a solder paste.
The mass ratio of the flux (F0) to the solder powder was set to flux (F0): solder powder = 11:89.

<Evaluation>
Using the solder paste described above, the suppression of thickening was evaluated.
Further, using the above-mentioned solder alloy, the temperature difference (ΔT) between the liquidus temperature and the solidus temperature of the solder powder was evaluated, and the α dose was evaluated, respectively. Furthermore, a comprehensive evaluation was conducted.
The details are as follows. The evaluation results are shown in Tables 1A to 25B.

[Suppression of thickening]
(1) Verification method The viscosity of the solder paste immediately after preparation was measured using PCU-205 manufactured by Malcolm Co., Ltd. at a rotation speed of 10 rpm, 25 ° C., and in the air for 12 hours.

(2) Judgment criteria 〇: The viscosity after 12 hours is 1.2 times or less as compared with the viscosity when 30 minutes have passed immediately after the preparation of the solder paste.
X: The viscosity after 12 hours exceeds 1.2 times the viscosity when 30 minutes have passed immediately after the preparation of the solder paste.
If this determination is "◯", it can be said that a sufficient thickening suppressing effect has been obtained. That is, it is possible to suppress an increase in the viscosity of the solder paste over time.

[Temperature difference between liquidus temperature and solidus temperature (ΔT)]
(1) Verification method For the solder powder before mixing with the flux (F0), SII Nanotechnology Co., Ltd., model number: EXSTAR DSC7020 was used, the sample amount was about 30 mg, and the temperature rise rate was 15 ° C./min. DSC measurement was performed to obtain the solidus temperature and the liquidus temperature. ΔT (° C.) was determined by subtracting the solidus temperature from the obtained liquidus temperature.

(2) Judgment criteria 〇: ΔT is 10 ° C. or lower.
X: ΔT exceeds 10 ° C.
If this determination is "◯", it can be said that segregation is less likely to occur during solidification and a non-uniform alloy structure is less likely to be formed because the temperature difference between the liquidus temperature and the solidus temperature is small. That is, the mechanical strength of the solder joint can be increased.

[Α dose]
(1) Verification method 1
The α-dose was measured by using an α-dose measuring device of a gas flow proportional counter and following the above-mentioned procedures (i), (ii) and (iii).
As a measurement sample, a solder alloy sheet immediately after production was used.
This solder alloy sheet was obtained by melting the solder alloy immediately after production and forming it into a sheet ^{having an area of 900 cm 2 on one surface.}
This measurement sample was placed in an α-dose measuring device, and PR-10 gas was allowed to flow for 12 hours and allowed to stand, and then the α-dose was measured for 72 hours.

(2) Judgment criteria 1
〇 〇: The α dose generated from the measurement sample was 0.002 cf / cm ² or less.
〇: α dose generated from the measurement sample is 0.002cph / cm ² than was 0.02cph / cm ² or less.
X: The α dose generated from the measurement sample was more than ^{0.02 cf / cm 2.}
If this judgment is "○○" or "○", it can be said that the solder material has a low α dose.

(3) Verification method 2
The α dose was measured in the same manner as in (1) Verification method 1 above, except that the measurement sample was changed.
As a measurement sample, a solder alloy sheet formed by melting a solder alloy immediately after production ^{and forming a sheet having an area of 900 cm 2} on one surface is heat-treated at 100 ° C. for 1 hour and allowed to cool. board.

(4) Judgment criteria 2
〇 〇: The α dose generated from the measurement sample was 0.002 cf / cm ² or less.
〇: α dose generated from the measurement sample is 0.002cph / cm ² than was 0.02cph / cm ² or less.
X: The α dose generated from the measurement sample was more than ^{0.02 cf / cm 2.}
If this judgment is "○○" or "○", it can be said that the solder material has a low α dose.

(5) Verification method 3
After storing the solder alloy sheet of the measurement sample whose α-dose was measured in the above (1) verification method 1 for one year, the α-dose is again followed by the above-mentioned procedures (i), (ii) and (iii). Was measured to evaluate the change in α dose over time.

(6) Judgment criteria 3
〇 〇: The α dose generated from the measurement sample was 0.002 cf / cm ² or less.
〇: α dose generated from the measurement sample is 0.002cph / cm ² than was 0.02cph / cm ² or less.
X: The α dose generated from the measurement sample was more than ^{0.02 cf / cm 2.}
If this determination is "○○" or "○", it can be said that the generated α-dose does not change with time and is stable. That is, it is possible to suppress the occurrence of soft errors in electronic devices.

[comprehensive evaluation]
〇: In Tables 1A to 25B, thickening suppression, temperature difference between liquidus temperature and solidus temperature (ΔT), α dose immediately after production, α dose after heat treatment, and change over time of α dose Each evaluation was "○○" or "○".
X: In Tables 1A to 25B, thickening suppression, temperature difference between liquidus temperature and solidus temperature (ΔT), α dose immediately after production, α dose after heat treatment, and change over time of α dose Of each evaluation, at least one was x.

As shown in Tables 1A to 25B, in all cases where the solder alloys of Examples 1 to 414 to which the present invention was applied were used, the increase in viscosity of the solder paste over time was suppressed, and the solder joint was mechanically It was confirmed that the strength can be increased and the occurrence of soft errors can be suppressed.

On the other hand, when the solder alloys of Comparative Examples 1 to 8 which are outside the scope of the present invention are used, the thickening is suppressed, the temperature difference between the liquidus temperature and the solidus temperature (ΔT), and At least one of the α-dose assessments showed inferior results.

Claims (24)

1. 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: 0 mass% or more and 0.9 mass% or less, and Sb: 0 mass% or more and 0. It has an alloy composition of 3% by mass or less and the balance is Sn.
   Satisfy the following formula (1) and
   A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
   0.005 ≤ Bi + Sb ≤ 1.2 (1)
   In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
2. 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: 0 mass% or more and 0. It has an alloy composition of 3% by mass or less and the balance is Sn.
   Satisfy the following formula (1) and
   A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
   0.005 ≤ Bi + Sb ≤ 1.2 (1)
   In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
3. 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: 0 mass% or more and 0.9 mass% or less, and Sb: 0 mass% or more and 0. It has an alloy composition of less than 1% by mass and the balance is Sn.
   Satisfy the following formula (1) and
   A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
   0.005 ≤ Bi + Sb ≤ 1.2 (1)
   In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
4. The solder alloy according to any one of claims 1 to 3, wherein the alloy composition satisfies the following formula (1').
   0.03 ≤ Bi + Sb ≤ 0.1 (1')
   In the formula (1'), Bi and Sb each represent the content (mass%) in the alloy composition.
5. The solder alloy according to any one of claims 1 to 4, wherein Pb is less than 2 parts by mass ppm.
6. The solder alloy according to any one of claims 1 to 5, wherein As is less than 2 parts by mass ppm.
7. Further, according to any one of claims 1 to 6, the alloy composition 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. Solder alloy.
8. 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 less than 0.9 mass%, and Sb: more than 0 mass% 0. 3% by mass or less,
   Ag: more than 0% by mass and 4% by mass or less, and Cu: more than 0% by mass and 0.9% by mass or less, and at least one of them.
   The rest is Sn,
   Has an alloy composition consisting of
   Satisfy the following formula (1) and
   A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
   0.005 ≤ Bi + Sb ≤ 1.2 (1)
   In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
9. 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: 0 mass% or more and 0. 3% by mass or less,
   Cu: More than 0% by mass and 0.9% by mass or less
   The rest is Sn,
   Has an alloy composition consisting of
   Satisfy the following formula (1)
   The ratio of Cu and Bi is 0.5 or more and 280 or less as a mass ratio represented by Cu / Bi, and
   A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
   0.005 ≤ Bi + Sb ≤ 1.2 (1)
   In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
10. 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% by mass or more and 0.9% by mass or less, and Sb: 0% by mass or more and 0.3% by mass or less.
    Cu: More than 0% by mass and 0.9% by mass or less
    The rest is Sn,
    Has an alloy composition consisting of
    Satisfy the following formula (1)
    The ratio of Cu, Bi and Sb is 0.4 or more and 150 or less as a mass ratio represented by Cu / (Bi + Sb), and
    A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
    0.005 ≤ Bi + Sb ≤ 1.2 (1)
    In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
11. 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: 0 mass% or more and 0.9 mass% or less, and Sb: more than 0 mass% 0. 3% by mass or less,
    Cu: More than 0% by mass and 0.9% by mass or less
    The rest is Sn,
    Has an alloy composition consisting of
    Satisfy the following formula (1)
    The ratio of Cu and Sb is 1 or more and 280 or less as a mass ratio represented by Cu / Sb, and
    A solder alloy having an α dose of 0.02 cf / cm ^{2 or less.}
    0.005 ≤ Bi + Sb ≤ 1.2 (1)
    In the formula (1), Bi and Sb each represent the content (mass%) in the alloy composition.
12. Further, the solder alloy according to any one of claims 9 to 11, wherein the alloy composition contains Ag: more than 0% by mass and 4% by mass or less.
13. The solder alloy according to any one of claims 1 to 12, wherein the ratio of Bi and Sb is 0.008 or more and 10 or less as a mass ratio represented by Sb / Bi.
14. The solder according to any one of claims 1 to 13, wherein the alloy composition contains at least one of 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. alloy.
15. The solder alloy according to claim 14, wherein the alloy composition satisfies the following formula (2).
    20 ≦ Ni + Fe ≦ 700 (2)
    In the formula (2), Ni and Fe each represent the content (mass ppm) in the alloy composition.
16. Claim 1 that the α dose after heat treatment at 100 ° C. for 1 hour on a solder alloy sheet formed into a sheet having an area of 900 cm ^{2 on one surface is 0.02 cf / cm 2} or less. The solder alloy according to any one of 15 to 15.
17. The solder alloy according to any one of claims 1 to 16, wherein the α dose is 0.002 cf / cm ^{2 or less.}
18. The solder alloy according to claim 17, wherein the α dose is 0.001 cf / cm ^{2 or less.}
19. A solder powder made of the solder alloy according to any one of claims 1 to 18.
20. The solder powder according to claim 19, which also has two or more types of solder alloy particle groups having different particle size distributions.
21. A solder paste containing the solder powder according to claim 19 or 20 and a flux.
22. A solder ball made of the solder alloy according to any one of claims 1 to 18.
23. Solder preform made of the solder alloy according to 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.