JP2022060054A - Solder paste - Google Patents

Abstract

To provide a solder paste which can improve wettability of solder, suppress increase in viscosity of solder paste over time, and suppress occurrence of soft error.SOLUTION: A solder paste comprises: solder powder comprising U of less than 5 mass ppb, Th of less than 5 mass ppb, Pb of less than 5 mass ppb, As of less than 5 mass ppb, and the remainder comprising Sn, and has α-dose of 0.02cph/cm2 or less; and a flux which contains halogen-based activator, rosin, thixotropic agent and solvent, and does not contain an organic acid with a carbon number of 5 or less. A content of the halogen-based activator is 0.1% by mass or more and 4% by mass or less.SELECTED DRAWING: None

Description

The present invention relates to solder paste.

As the solder material, a solder paste containing solder powder and flux is used.
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 an electrode is sealed with a resin component. Solder bumps made of a solder material are formed on this electrode. With this solder material, the semiconductor element and the printed circuit board are soldered, and both are connected.

In solder materials, the influence 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 metal. 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. Radioactive isotopes 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 decays in the 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 hour / 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 the generation of α rays 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 further 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 the radioactive Pb and the radioactive Bi in the solder alloy are β-decayed to increase the amount of Po, and the 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. The ²¹⁰ Po originally emits α rays, but since it segregates at the center of the solder alloy during solidification of the solder alloy, 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).

On the other hand, the flux used for soldering has the effect of chemically removing metal oxides present on the metal surface of the solder and the object to be soldered, and enabling the movement of metal elements at the boundary between the two. have. Therefore, by soldering using a flux, an intermetallic compound can be formed between the solder and the metal surface of the object to be joined, and a strong bond can be obtained.

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

Radioactive Nuclear Integrated Soft Errors at Ground Level; IEEE TRANSACTIONS ON NUCLEAR SCIEENCE, DECEMBER 2009, VOL. 56, NO. 6, p. 3437-3441 Energy December Efficiency in Low Blankround Alpha Mechanisms and Impacts on Accurate Alpha characterization; IEEE TRANSACTIONS ON MENU. 62, NO. 6, p. 3034-3039

For example, in the method of adding As to the solder alloy in order to suppress the thickening of the solder paste over time as in the method described in Patent Document 2, the addition of As is contained in the alloy. Impurities with radioactive isotopes will also be included. In this case, the presence of radioactive elements in the impurities increases the α-dose generated from the solder material.

Further, in the flux used for the solder paste, it is required that the solder wetting speed is high and the solder wetting property is good with respect to the metal surface of the object to be joined.
When soldering using a solder ball, if the wettability of the solder cannot be ensured on the metal surface of the object to be joined, it becomes difficult for the solder to evenly wet and spread on the electrodes. When the wettability and spreadability of the solder deteriorates, the position of the solder ball is displaced with respect to the electrode, and the solder ball is in a state of being detached from the electrode pad (ball missing), which causes a problem that poor bonding or poor conductivity is likely to occur.

The present invention has been made in view of the above circumstances, and is a solder capable of enhancing the wettability of the solder, suppressing an increase in the viscosity of the solder paste over time, and suppressing the occurrence of soft errors. The purpose is to provide a paste.

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.
Based on this study, the alloy composition has a low α dose containing Sn as the main component, and the flux used for the solder paste does not contain an organic acid having 5 or less carbon atoms. It was found that it is possible to suppress the thickening of the paste.
In addition, it has been found that the flux used in the solder paste contains a halogen-based activator, so that the wettability of the solder becomes sufficient, and 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 a solder paste composed of a solder powder and a flux, wherein the solder powder has U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: 5 mass. It is made of a solder alloy having an alloy composition of less than ppm and the balance of Sn, and having an α dose of 0.02 cf / cm ² or less. The flux does not contain an organic acid having 5 or less carbon atoms, and the content of the halogen-based activator is 0.1% by mass or more and 4% by mass or less with respect to the total amount of the flux. There is a solder paste.

In the solder paste according to the above aspect, the alloy composition preferably has Pb of less than 2 parts by mass.

In the solder paste according to the above aspect, the alloy composition preferably has As of less than 2 parts by mass.

In the solder paste according to the above aspect, it is preferable that the alloy composition further contains at least one of Ag: 0% by mass or more and 4% by mass or less, and Cu: 0% by mass or more and 0.7% by mass or less.

In the solder paste according to the above aspect, the alloy composition may further contain at least one of Bi: 0% by mass or more and 0.3% by mass or less, and Sb: 0% by mass or more and 0.9% by mass or less. preferable.

In the solder paste according to the above aspect, it is preferable that the alloy composition further satisfies the following formula (2).
0.03 ≤ Bi + Sb ≤ 1.2 (2)
In the formula (2), Bi and Sb each represent the content (mass%) in the alloy composition.

In the solder paste according to the above aspect, the solder alloy has an α dose after being heat-treated at 100 ° C. for 1 hour on a sheet-shaped solder alloy sheet having an area of 900 cm ² on one surface. , 0.02 cph / cm ² or less is preferable.

In the solder paste according to the above aspect, it is preferable that the α dose of the solder alloy is 0.002 cf / cm ² or less.

In the solder paste according to the above aspect, it is preferable that the α dose of the solder alloy is 0.001 cf / cm ² or less.

In the solder paste according to the above aspect, it is preferable that the solder powder is composed of a group of solder alloy particles having an average particle diameter of 0.1 to 15 μm.

In the solder paste according to the above aspect, it is preferable that the solder powder has two or more kinds of solder alloy particle groups having different average particle diameters.

In the solder paste according to the above aspect, the halogen-based activator preferably contains an amine hydrohalide hydrochloride.

In the solder paste according to the above aspect, the amine halide hydrobromide is cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrafluoroborate. , Ethylamine hydrobromide, diphenylguanidine hydrobromide and ethylamine hydrochloride preferably contain at least one selected from the group.

In the solder paste according to the above aspect, it is preferable that the halogen-based activator further contains an organic halogen compound other than the amine hydrohalide.

In the solder paste according to the above aspect, it is preferable that the rosin contains at least one selected from the group consisting of a polymerized rosin, an acrylic acid-modified hydrogenated rosin, an acrylic acid-modified rosin, a disproportionated rosin and a hydrogenated rosin. ..

In the solder paste according to the above aspect, it is preferable that the rosin further contains a rosin ester, and the rosin ester contains hydrogenated rosin methyl.

In the solder paste according to the above aspect, it is preferable that the flux further contains an organic acid having 6 or more carbon atoms.

The solder paste according to the above aspect may contain at least one selected from the group consisting of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimeric acid, myristic acid, palmitic acid and 12-hydroxystearic acid. preferable.

In the solder paste according to the above aspect, the thixotropy preferably contains at least one selected from the group consisting of ester-based thixotropy, amide-based thixotropy and sorbitol-based thixotropy.

In the solder paste according to the above aspect, the ester thixotropy preferably contains at least one selected from the group consisting of castor oil and ethyl myristate.

In the solder paste according to the above aspect, the amido thixotropic agent preferably contains at least one selected from the group consisting of 4-methylbenzamide and ethylenebishydroxystearic acid amide.

In the solder paste according to the above aspect, the sorbitol-based thixotropy preferably contains at least one selected from the group consisting of bis (4-methylbenzylidene) sorbitol and dibenzylidene sorbitol.

In the solder paste according to the above aspect, it is preferable that the activator further contains an amine-based activator.

In the solder paste according to the above aspect, it is preferable that the flux further contains an organic phosphorus compound.

In the solder paste according to the one aspect, it is preferable that the flux further contains an antioxidant.

According to the present invention, it is possible to provide a solder paste capable of improving the wettability of the solder, suppressing an increase in the viscosity of the solder paste over time, and suppressing the occurrence of soft errors.

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 paste)
The solder paste of the present embodiment is composed of a specific solder powder and a specific flux.
The solder powder has an alloy composition consisting of U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the balance of Sn, and has an α dose. It is made of a solder alloy having a capacity of 0.02 cph / cm ² or less.
The flux contains a halogen-based activator, a rosin, a thixotropic agent, and a solvent.
The flux does not contain an organic acid having 5 or less carbon atoms.
The content of the halogen-based activator is 0.1% by mass or more and 4% by mass or less with respect to the total amount of the flux.

<Solder powder>
The solder powder used in the solder paste of the present embodiment has an alloy composition consisting of U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, and the balance of Sn, and has an α dose. It is made of a solder alloy having a mass of 0.02 cph / cm ² or less.

The solder alloy in the present embodiment has an alloy composition consisting of U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the balance of Sn.

≪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, respectively, 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 from impurities derived from As, and the solder material The α-dose generated from the solder increases.
In the present embodiment, it is an object to suppress the 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 content of As in the solder alloy may be 0 ppm or more.

≪Arbitrary element≫
Regarding the solder alloy in the present embodiment, the alloy composition may contain an element other than the above-mentioned elements, if necessary.
By soldering, the formation of Sn-containing intermetallic compounds (intermetallic compounds containing Sn) progresses in the vicinity of the bonding interface in the solder alloy, and when the Sn-containing intermetallic compounds precipitate, the mechanical strength of the solder joint deteriorates. ..
On the other hand, for example, regarding the solder alloy in the present embodiment, in addition to the above-mentioned elements, the alloy composition further includes 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. Is preferably contained.

Ni: 0 mass ppm or more and 600 mass ppm or less Ni is an element that suppresses the formation of Sn-containing intermetallic compounds at the bonding interface.
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 Ni content in the solder alloy exceeds 600 ppm, the SnNi compound 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, still more preferably 40 ppm, based on the total mass (100% by mass) of the solder alloy. It is 600 ppm or less.

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 needle-like crystals due to the SnFe compound is suppressed, and 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, still more preferably 40 ppm, based on the total mass (100% by mass) of the solder alloy. More than 80 ppm and less.

Regarding the solder alloy in the present embodiment, it is preferable that the alloy composition satisfies the following formula (1).
20 ≦ Ni + Fe ≦ 700 (1)
In the formula (1), Ni and Fe each represent the content (mass ppm) in the alloy composition.

Both Ni and Fe in the formula (1) 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.
In order to enhance the effect of suppressing the formation of the Sn-containing intermetallic compound and the effect of suppressing the thickening of the solder paste over time, the total content of Ni and Fe in the solder alloy is the total mass of the solder alloy. It is preferably 20 ppm or more and 700 ppm or less with respect to (100% by mass). The total content of Ni and Fe is more preferably 40 ppm or more and 700 ppm or less, further preferably 40 ppm or more and 600 ppm or less, and most preferably 40 ppm or more and 200 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 ppm, and the content of Fe in the solder alloy is 0 ppm. Is the content of Ni, and when both Ni and Fe are present, the total content of these is obtained.

Further, 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. It is preferably 0.4 or more and 10 or less, more preferably 0.4 or more and 5 or less, and particularly preferably 0.4 or more and 2 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.

For example, with respect to the solder alloy in the present embodiment, the alloy composition is, 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. May be contained.

Ag: 0% by mass or more and 4% by mass or less Ag is an optional element capable of forming Ag ₃ Sn at the crystal interface to improve the reliability of the solder alloy. Further, Ag is an element whose ionization tendency is noble with respect to Sn, and when it coexists with Ni and Fe, it enhances the effect of suppressing the thickening of the solder paste over time. Further, when the Ag content in the solder alloy is within the above range, it is possible to suppress an increase in the melting point of the alloy, so that it is not necessary to raise the reflow temperature excessively.
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 used in general solder alloys and capable of improving the bonding strength of solder joints. Further, Cu is an element whose ionization tendency is noble with respect to Sn, and when it coexists with Ni and Fe, it enhances the effect of suppressing the thickening of the solder paste over time.
In the present embodiment, the Cu content 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 Ni are used together in this embodiment, the ratio of Cu and Ni in the solder alloy is preferably 8 or more and 175 or less, and more preferably 10 or more as the mass ratio represented by Cu / Ni. It is 150 or less.
If Cu / Ni 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 and Fe are used together in the present embodiment, the ratio of Cu and Fe in the solder alloy is preferably 50 or more and 350 or less, more preferably 70 or more, as the mass ratio expressed by Cu / Fe. It is 250 or less.
If Cu / Fe 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, Ni, and Fe are used together in this embodiment, the ratio of Cu, Ni, and Fe in the solder alloy is preferably 7 or more and 350 or less as the mass ratio expressed by Cu / (Ni + Fe). , More preferably 10 or more and 250 or less.
If the mass ratio of Cu / (Ni + Fe) is in the above-mentioned preferable range, the effect of the present invention can be more easily obtained.

For example, with respect to the solder alloy in the present embodiment, the alloy composition is, in addition to the above-mentioned elements, Bi: 0% by mass or more and 0.3% by mass or less, and Sb: 0% by mass or more and 0.9% by mass or less. It may contain at least one kind.

Bi: 0% by mass or more and 0.3% by mass or less Bi is an element that has low reactivity with flux and exhibits an effect of suppressing thickening of solder paste over time. Further, 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.
In the present embodiment, the Bi content in the solder alloy is preferably 0% or more and 0.3% or less, more preferably 0.0020% or more and 0.% with respect to the total mass (100% by mass) of the solder alloy. It is 3% or less, more preferably 0.01% or more and 0.1% or less, and most preferably 0.01% or more and 0.05% or less.

Sb: 0% by mass or more and 0.9% by mass or less Sb is an element that has low reactivity with flux and exhibits an effect of suppressing thickening of solder paste over time, like Bi. If the content of Sb in the solder alloy is too large, the wettability deteriorates. Therefore, when adding Sb, it is necessary to make the content appropriate.
In the present embodiment, the content of Sb in the solder alloy is preferably 0% or more and 0.9% or less, more preferably 0.0020% or more and 0. It is 9% or less, more preferably 0.01% or more and 0.1% or less, and most preferably 0.01% or more and 0.05% or less.

Regarding the solder alloy in the present embodiment, when the alloy composition further contains at least one of Bi: 0% by mass or more and 0.3% by mass or less and Sb: 0% by mass or more and 0.9% by mass or less, the alloy. The composition preferably satisfies the following formula (2).
0.03 ≤ Bi + Sb ≤ 1.2 (2)
In the formula (2), Bi and Sb each represent the content (mass%) in the alloy composition.

Both Bi and Sb in the formula (2) are elements showing 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 is preferably 0.03% or more and 1.2% or less, more preferably 0.03% or more, based on the total mass (100% by mass) of the solder alloy. It is 0.9% or less, more preferably 0.3% or more and 0.9% or less.

However, the above-mentioned "total content of Bi and Sb" is the content of Sb when the content of Bi in the solder alloy is 0%, and the content of Sb in the solder alloy is 0%. In some cases, it is the content of Bi, and in the case of having both Bi and Sb, it is the total content of these.

When Bi and Sb are used together in the present embodiment, the ratio of Bi and Sb in the solder alloy is preferably 0.01 or more and 10 or less, more preferably 10 or less, as the mass ratio expressed by Sb / Bi. It is 0.1 or more and 5 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.

≪Remaining part: Sn≫
Regarding the solder alloy in the present embodiment, the alloy composition is composed of Sn as the balance. 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 in this embodiment has an α dose of 0.02 cph / 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 generated from the solder alloy in 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. It is 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 formed by melting a solder alloy into a sheet having an area of 900 cm ² on one side is used.
The solder alloy sheet is installed as a measurement sample in the α-dose measuring device, and PR gas is purged therein.

As the PR gas, a gas that complies with the international standard JEDEC STANDARD is used. That is, the PR gas used for the measurement is assumed to be the disintegration of the impurity radon (Rn) in the gas 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.

In the solder alloy of the present embodiment, the α dose of the solder alloy sheet formed into a sheet having an area of 900 cm ² on one surface after being heat-treated at 100 ° C. for 1 hour is 0.02 cf. It is preferably / 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 0.001 cf / cm. It is ² or less.
Solder alloys exhibiting such an α dose are useful because they are less likely to segregate ²¹⁰ Po in the alloy and are less affected by changes in the α dose over time. By applying a solder alloy exhibiting such an α dose, the occurrence of soft errors is further suppressed, and it becomes easier to secure stable operation of the semiconductor element.

[Manufacturing method of solder alloy]
The solder alloy in the present embodiment can be produced, for example, by using a production method having a step of melt-mixing at least one of Ni and Fe and a raw material metal containing Sn.
Since the purpose is to design a solder alloy with a low α-dose, it is preferable to use a low-α-dose material as the raw material metal. Further, it is preferable to use one from which U, Th and Pb have been removed.
As the Sn as the raw material metal, for example, one manufactured according to the manufacturing method described in Japanese Patent Application Laid-Open No. 2010-156052 (Patent Document 1) can be used.
As the raw material metals Ni and Fe, for example, those manufactured according to Japanese Patent No. 5692467 can be used.
A conventionally known method can be used for the operation of melting and mixing the raw metal.

The solder powder in the present embodiment is produced by a dropping method of dropping a molten solder alloy to obtain particles, a spraying method of centrifugal spraying, an atomizing method, an in-liquid granulation method, a method of crushing a bulk solder alloy, and the like. , A known method can be adopted. The dropping or spraying in the dropping method or the spraying method is preferably carried out in an inert atmosphere or a solvent in order to form particles.

The solder powder in this embodiment is preferably a spherical powder. The spherical powder improves the fluidity of the solder alloy.
When the solder powder in 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 be there. 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 is increased. May be suppressed. Therefore, it is possible to solder to finer parts.

Further, as the solder powder in the present embodiment, it is preferable to use a solder alloy particle group having an average particle diameter of 0.1 to 50 μm, and a solder alloy particle group having an average particle diameter of 1 to 25 μm is used. It is more preferable to use a solder alloy particle group having an average particle diameter of 1 to 15 μm.
When the particle size of the solder powder is in the above-mentioned preferable range, the increase in viscosity of the solder paste with time is likely to be suppressed.
The average particle size of the solder powder referred to here means the particle size at an integrated value of 50% in the particle size distribution measured by the laser diffraction / scattering type particle size distribution measuring device.

Further, it is preferable that the solder powder in 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.
For example, the solder powder may have two or more kinds of solder alloy particles having different average particle diameters. As an example, a solder powder having both a solder alloy particle group (S1) having an average particle diameter of 5 μm or more and less than 10 μm and a solder alloy particle group (S2) having an average particle diameter of 1 μm or more and less than 5 μm can be preferably mentioned.
The mixing ratio of the solder alloy particle group (S1) and the solder alloy particle group (S2) is (S1) / (S2) = 9/1 to 1 / as the mass ratio represented by (S1) / (S2). 9 is preferable, 9/1 to 3/7 is more preferable, and 9/1 to 5/5 is even more preferable.

Regarding the solder powder in the present embodiment, the sphericity of the spherical powder is preferably 0.8 or more, more preferably 0.9 or more, further preferably 0.95 or more, and particularly 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 an arithmetic mean value calculated when, for example, 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.

<Flux>
The flux used in the solder paste of the present embodiment includes a halogen-based activator, a rosin, a thixotropic agent, and a solvent. In addition, the flux does not contain an organic acid having 5 or less carbon atoms. The content of the halogen-based activator is 0.1% by mass or more and 4.0% by mass or less with respect to the total amount of the flux.

The flux used in the solder paste of the present embodiment can enhance the wettability of the solder by containing a halogen-based activator. Since the solder paste of the present embodiment does not contain an organic acid having 5 or less carbon atoms, it is possible to suppress an increase in viscosity of the solder paste over time.

<< Halogen-based activator >>
Examples of the halogen-based activator include an amine hydrohalide, an organic halogen compound other than an amine halide hydride, and the like.

Amine hydrohalide is a compound obtained by reacting an amine with hydrogen halide. Examples of the amine here include ethylamine, diethylamine, triethylamine, ethylenediamine, diphenylguanidine, ditrilguanidine, methylimidazole, 2-ethyl-4-methylimidazole and the like, and examples of the hydrogen halide include chlorine and the like. Examples include bromine and hydrides of iodine.
More specifically, examples of the amine halide hydride include cyclohexylamine hydrobromite, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, and diphenyl. Guanidin Hydrobromide, Ethylamine Hydrochloride, Stearylamine Hydrochloride, diethylaniline Hydrochloride, Diethanolamine Hydrochloride, 2-Ethylhexylamine Hydrobromide, pyridine Hydrochloride, Isopropylamine Hydrochloride, Diethylamine Hydrobromide, Dimethylamine Hydrobromide, Dimethylamine Hydrochloride, Rodinamine Hydrobromide, 2-Ethylhexylamine Hydrochloride, Isopropylamine Hydrochloride, Cyclohexylamine Hydrochloride, 2-Pipecholine Hydrogen Bromide Hydroate, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazinehydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride, diallylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride , Hydrazin dihydrochloride, Hydrazin monobromide, Hydrazin dibromide, Ppyridine hydrochloride, Aniline hydrobromide, Butylamine hydrochloride, Hexylamine hydrochloride, n-octylamine hydrochloride, Dodecyl Amine hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L- Glutamine hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-pipecholine hydride, cyclohexylamine hydride, 1,3-diphenylguanidine fluoride, diethylamine fluorinated, 2-Ethylhexylamine Hydrochloride, Cyclohexylamine Hydrochloride, Ethylamine Hydrochloride, Rosinamine Hydrochloride, Cyclohexylamine Tetrafluoroborate, Dicyclohexylamine Tetrafluoroborate, etc. Can be mentioned.

Further, as the halogen-based activator, for example, a salt obtained by reacting an amine with tetrafluoroboric acid (HBF ₄ ) and a complex obtained by reacting an amine with boron trifluoride (BF ₃ ) can also be used.
Examples of the complex include boron trifluoride piperidine and the like.

Examples of the organic halogen compound other than the amine hydrohalide include trans-2,3-dibromo-2-butene-1,4-diol, triallyl isocyanurate 6 bromide, and tris isocyanurate- (2,3-). Dibromopropyl), 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. Be done.
Examples of the organic halogen compound other than the hydrogen halide hydride include a halide carboxyl compound, for example, 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5 -Carboxyl iodide compounds such as iodoanthranyl acid; carboxyl compounds chloride such as 2-chlorobenzoic acid and 3-chloropropionic acid; 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, 2-bromobenzoic acid and the like. Examples include the brominated carboxyl compound of.

In the flux used for the solder paste of the present embodiment, one or more halogen-based activators can be used.
The halogen-based activator preferably contains an amine hydrohalide hydrochloride.
Amine halides are cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylaminetetrafluoroborate, ethylamine hydrobromide, diphenylguanidine. It preferably contains at least one selected from the group consisting of hydrobromide and ethylamine hydrochloride, and comprises cyclohexylamine hydrobromide, hexadecylamine hydrobromide and stearylamine hydrobromide. It is more preferable to include one or more selected from the group.
Organic halogen compounds other than amine hydrogen halides are selected from the group consisting of trans-2,3-dibromo-2-butene-1,4-diol and tris-isocyanurate- (2,3-dibromopropyl). It is preferable to include one or more.

The total content of the halogen-based activator in the flux is 0.1% by mass or more and 4.0% by mass or less with respect to the total amount (100% by mass) of the flux, and is 0.5% by mass or more. More preferably, it is 4.0% by mass or less.
The content of the organic halogen compound in the flux is preferably 0% by mass or more and 4.0% by mass or less, and 0.9% by mass or more 2 with respect to the total amount (100% by mass) of the flux. More preferably, it is 0.0% by mass or less.
The content of the amine halide hydride in the flux is preferably 0% by mass or more and 4.0% by mass or less, preferably 0.1% by mass, based on the total amount (100% by mass) of the flux. It is more preferably% or more and 4.0% by mass or less, and further preferably 0.5% by mass or more and 2.0% by mass or less.

《Rosin》
Examples of the rosin 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, acid-modified rosin, phenol-modified rosin and α, β-unsaturated carboxylic acid-modified products (acrylicized rosin, maleated rosin, fumarization). (Rodin, etc.), and purified products, hydrides, and disproportionated products of the polymerized rosin, and purified products, hydrides, and disproportionated products of the α, β unsaturated carboxylic acid modified products.
In the flux used for the solder paste of the present embodiment, rosin can be used alone or in combination of two or more.
The rosin may further contain a rosin ester.
The rosin ester preferably contains hydrogenated rosin methyl.
This methyl hydrogenated rosinate is an ester obtained from a hydrogenated cyclic fatty acid obtained from rosin and a methyl alcohol, also known as methyl hydrogenated abietic acid, and has a CAS number: 8050-15-5. be.
The rosin preferably contains at least one selected from the group consisting of polymerized rosin, acrylic acid-modified hydrogenated rosin, acrylic acid-modified rosin, disproportionated rosin and hydrogenated rosin, preferably from polymerized rosin and methyl hydrogenated rosin. It is more preferable to include at least one selected from the group.

The total content of the rosin in the flux is preferably 30.0% by mass or more and 60.0% by mass or less with respect to the total amount (100% by mass) of the flux. It is more preferably 50.0% by mass or less, and further preferably 40.0% by mass or more and 50.0% by mass or less.
The content of the rosin ester in the flux is preferably 0% by mass or more and 30.0% by mass or less, and 5.0% by mass or more and 20.0% by mass with respect to the total amount (100% by mass) of the flux. % Or less, more preferably 5.0% by mass or more and 10.0% by mass or less.
When the flux contains a rosin ester, the content of the rosin ester is preferably 0% by mass or more and 60.0% by mass or less with respect to the total amount of the rosin, and 10.0% by mass or more and 50.0. It is more preferably 10.0% by mass or less, and further preferably 10.0% by mass or more and 20.0% by mass or less.

《Thixotropic agent》
Examples of the thixotropic agent include an ester-based thixotropy, an amide-based thixotropy, and a sorbitol-based thixotropy.

Examples of the ester-based thixotropy include ester compounds, and specific examples thereof include castor oil, ethyl myristate, and the like.

Examples of the amide-based thixo agent include monoamide, bisamide, and polyamide, and specific examples thereof include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, and oleic acid. Amides, erucic acid amides, unsaturated fatty acid amides, 4-methylbenzamides (p-toluamides), p-toluenemethaneamides, aromatic amides, hexamethylenehydroxystearic acid amides, substituted amides, methylolstearate amides, methylolamides, fatty acids. Monoamides such as ester amides; methylene bisstearic acid amides, ethylene bislauric acid amides, ethylene bishydroxy fatty acid (c6 to 24 carbon atoms of fatty acids) amides, ethylene bishydroxystearic acid amides, saturated fatty acid bisamides, methylene bisoleic acid amides, Bisamides such as unsaturated fatty acid bisamides, m-xylylene bisstearic acid amides, and aromatic bisamides; saturated fatty acid polyamides, unsaturated fatty acid polyamides, aromatic polyamides, tris 1,2,3-propanetricarboxylic acids (2-methylcyclohexylamides). ), Cyclic amide oligomers, non-cyclic amide oligomers and other polyamides.

The cyclic amide oligomer includes an amide oligomer in which dicarboxylic acid and diamine are cyclically polycondensed, an amide oligomer in which tricarboxylic acid and diamine are cyclically polycondensed, an amide oligomer in which dicarboxylic acid and triamine are cyclically polycondensed, and tricarboxylic acid. Amido oligomer in which triamine is cyclically polycondensed, dicarboxylic acid and amide oligomer in which tricarboxylic acid and diamine are cyclically polycondensed, amide oligomer in which dicarboxylic acid and tricarboxylic acid and triamine are cyclically polycondensed, dicarboxylic acid and diamine Examples thereof include an amide oligomer in which triamine is cyclically polycondensed, an amide oligomer in which tricarboxylic acid and diamine and triamine are cyclically polycondensed, and an amide oligomer in which dicarboxylic acid and tricarboxylic acid and diamine and triamine are cyclically polycondensed. ..

When the acyclic amide oligomer is an amide oligomer in which a monocarboxylic acid and diamine and / or triamine are polycondensed in an acyclic manner, the amide in which the dicarboxylic acid and / or the tricarboxylic acid and the monoamine are polycondensed in an acyclic manner. Examples thereof include the case of an oligomer. When it is an amide oligomer containing a monocarboxylic acid or a monoamine, the monocarboxylic acid and the monoamine function as terminal molecules (terminal molecules), and become an acyclic amide oligomer having a reduced molecular weight. When the acyclic amide oligomer is an amide compound in which a dicarboxylic acid and / or a tricarboxylic acid and a diamine and / or a triamine are cyclically polycondensed, the acyclic amide oligomer is an acyclic polymer amide polymer. Further, the acyclic amide oligomer also includes an amide oligomer in which a monocarboxylic acid and a monoamine are cyclically condensed.

Examples of the sorbitol-based thixo agent include dibenzylidene-D-sorbitol, bis (4-methylbenzylidene) -D-sorbitol, (D-) sorbitol, monobenzylidene (-D-) sorbitol, and mono (4-methylbenzylidene). -(D-) Sorbitol and the like can be mentioned.

In the flux used for the solder paste of the present embodiment, the thixotropic agent can be used alone or in combination of two or more.
Among the above, the thixotropic agent preferably contains at least one selected from the group consisting of ester-based thixotropic agents, amide-based thixotropic agents, and sorbitol-based thixotropic agents.
The ester thixotropic agent preferably contains at least one selected from the group consisting of castor oil and ethyl myristate.
The thixotropic agent preferably contains at least one selected from the group consisting of bisamide and monoamide.
The amide-based thixo agent preferably contains at least one selected from the group consisting of 4-methylbenzamide and ethylenebishydroxystearate amide, and more preferably contains ethylenebishydroxystearic acid amide.
The sorbitol-based thixo agent preferably contains at least one selected from the group consisting of bis (4-methylbenzylidene) sorbitol and dibenzylidene sorbitol, and more preferably contains bis (4-methylbenzylidene) sorbitol.

The total content of the thixo agent in the flux is preferably 4.0% by mass or more and 20.0% by mass or less, preferably 6.0% by mass, based on the total amount (100% by mass) of the flux. It is more preferably% or more and 13.0% by mass or less, and further preferably 6.0% by mass or more and 10.0% by mass or less.
The content of the ester-based thixo agent in the flux is preferably 1.0% by mass or more and 15.0% by mass or less, preferably 2.0% by mass, based on the total amount (100% by mass) of the flux. It is more preferably% or more and 10.0% by mass or less, and further preferably 3.0% by mass or more and 7.0% by mass or less.
The content of the amido-based thixotropic agent in the flux is preferably 0% by mass or more and 5.0% by mass or less, preferably 2.0% by mass or more, with respect to the total amount (100% by mass) of the flux. It is more preferably 3.0% by mass or less.
The content of the sorbitol-based thixotropic agent in the flux is preferably 0% by mass or more and 5% by mass or less, and 1.0% by mass or more, with respect to the total amount (100% by mass) of the flux. It is more preferably 0% by mass or less.

"solvent"
As the solvent, one type may be used alone, or two or more types may be mixed and used.
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, 2-methylpentane-2,4 -Diol, 1,1,1-tris (hydroxymethyl) propane, 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, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1, Examples thereof include 4-cyclohexanedimethanol, 2,4,7,9-tetramethyl-5-decine-4,7-diol and the like.
Examples of the glycol ether-based solvent include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methylpropylene triglucol, and butyl. Examples thereof include propylene triglucol, triethylene glycol butyl methyl ether, and tetraethylene glycol dimethyl ether.

The solvent preferably contains one or more selected from the group consisting of glycol ether solvents and terpineols.
The glycol ether solvent preferably contains hexyl diglycol.

The total content of the solvent in the flux is preferably 30% by mass or more and 60% by mass or less, and 33% by mass or more and 50% by mass or less with respect to the total amount (100% by mass) of the flux. It is more preferable to have.

<< Organic acid with 5 or less carbon atoms >>
The flux used in the solder paste of the present embodiment does not contain an organic acid having 5 or less carbon atoms.
Examples of the organic acid having 5 or less carbon atoms include monocarboxylic acids having 5 or less carbon atoms, oxalic acid, malonic acid, succinic acid, glutaric acid, diglycolic acid and the like.

<< Other ingredients >>
The flux in the present embodiment may contain other components, if necessary, in addition to the halogen-based activator, rosin, thixotropic agent and solvent.
Examples of other components include activators other than halogen-based activators, resin components other than rosin-based resins, metal deactivating agents, surfactants, silane coupling agents, antioxidants, colorants and the like.

Examples of the activator other than the halogen-based activator include an organic acid-based activator, an amine-based activator, and an organic phosphorus compound.

Organic acid activator:
The organic acid-based activator may contain an organic acid having 6 or more carbon atoms. Examples of organic acids having 6 or more carbon atoms include adipic acid, azelaic acid, eicosanic acid, salicylic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, terephthalic acid, dodecanedic acid, and parahydroxyphenyl. Acetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, lauric acid, benzoic acid, tartaric acid, tris isocyanurate (2-carboxyethyl), 1,3-cyclohexanedicarboxylic acid, 2,2-bis (hydroxymethyl) propionic acid, 2,2-bis (hydroxymethyl) butanoic acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, p-anisic acid, stearic acid, 12- Hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, palmitic acid, pimelic acid, caproic acid, enanthic acid, capric acid, pelargonic acid, isoperalgonic acid, capric acid, caproleic acid, undecanoic acid, lauric acid, Lindel acid, tridecanoic acid, myristoleic acid, pentadecanoic acid, isopalmitic acid, palmitreic acid, hiragon acid, hydrnocarpine acid, margaric acid, isostearic acid, ellagic acid, petroseric acid, morotinic acid, eleostearic acid, tariphosphate, bacsen Acid, liminoreic acid, vernophosphate, sterclinic acid, nonadecanic acid, eikosanoic acid, dimer acid, trimer acid, hydrogenated dimer acid, which is a hydrogenated dimer acid, hydrogenated dimer acid, hydrogenated trimer acid Examples thereof include hydrogenated trimeric acid.

Examples of dimer acid and trimer acid include dimer acid which is a reaction product of oleic acid and linoleic acid, trimer acid which is a reaction product of oleic acid and linoleic acid, and dimer acid and acrylic acid which are reaction products of acrylic acid. Trimmer acid which is a reaction product of, dimer acid which is a reaction product of methacrylic acid, trimer acid which is a reaction product of methacrylic acid, dimer acid which is a reaction product of acrylic acid and methacrylic acid, reaction of acrylic acid and methacrylic acid. Reaction of trimeric acid, which is a reaction product of oleic acid, dimer acid, which is a reaction product of oleic acid, trimeric acid, which is a reaction product of oleic acid, dimer acid, which is a reaction product of linoleic acid, and trimeric acid, which is a reaction product of linoleic acid. Dimer acid, which is a reaction product of linolenic acid, trimer acid, which is a reaction product of acrylic acid and oleic acid, dimer acid, which is a reaction product of acrylic acid and oleic acid, trimer acid, which is a reaction product of acrylic acid and oleic acid, acrylic acid and linoleic acid. Dimeric acid, which is a reaction product of acrylate, trimer acid, which is a reaction product of acrylic acid and linoleic acid, dimer acid, which is a reaction product of acrylic acid and linolenic acid, and trimer acid, which is a reaction product of acrylic acid and linolenic acid. Dimeric acid, which is a reaction product of methacrylic acid and oleic acid, trimeric acid, which is a reaction product of methacrylic acid and oleic acid, dimer acid, which is a reaction product of methacrylic acid and linoleic acid, and reaction of methacrylic acid and linoleic acid. Trimmer acid, which is a reaction product of methacrylic acid and linolenic acid, trimeric acid, which is a reaction product of methacrylic acid and linolenic acid, dimer acid, which is a reaction product of oleic acid and linolenic acid, oleic acid. Trimmer acid, which is a reaction product of linolenic acid, dimer acid, which is a reaction product of linoleic acid and linolenic acid, trimer acid, which is a reaction product of linoleic acid and linolenic acid, and the above-mentioned hydrogenated products of each dimer acid. Examples thereof include a certain hydrogenated dimer acid, a hydrogenated trimer acid which is an adjunct of each of the above-mentioned trimer acids, and the like.
For example, dimer acid, which is a reaction product of oleic acid and linoleic acid, is a dimer having 36 carbon atoms. Further, trimeric acid, which is a reaction product of oleic acid and linoleic acid, is a trimer having 54 carbon atoms.

The organic acid-based activator may be used alone or in combination of two or more.
The organic acid-based activator preferably contains at least one selected from the group consisting of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimeric acid, myristic acid, palmitic acid and 12-hydroxystearic acid. It is more preferable to contain at least one selected from the group consisting of sebacic acid and myristic acid.
The content of the organic acid-based activator in the flux is preferably 0% by mass or more and 10% by mass or less, and 0% by mass or more and 5% by mass or less, based on the total amount (100% by mass) of the flux. It is more preferable that it is 0.5% by mass or more and 2.0% by mass or less.

Amine-based activator:
Examples of the amine-based activator include alkylamine compounds such as ethylamine, triethylamine, ethylenediamine, triethylenetetramine, cyclohexylamine, hexadecylamine and stearylamine;
Amino alcohol compounds such as N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine;
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 trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6- [2'-methylimidazolyl- (1) ')]-Ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6- [2'- Ethyl-4'-methylimidazolyl- (1')] -ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s-triazine isocyanuric acid adduct , 2-Phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-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 admazole, 2-methylbenzoimidazole, 2-octylbenzoimidazole, 2-pentylbenzoimidazole , 2- (1-ethylpentyl) benzoimidazole, 2-nonylbenzoimidazole, 2- (4-thiazolyl) benzoimidazole, benzoimidazole, 1,2,4-triazole, 2- (2'-hydroxy-5'- Methylphenyl) benzotriazole, 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'-hydroxy-3', 5'-di- ter t-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'-dicarboxyethyl) 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 other azoles. System compounds;
Guanidine compounds such as diphenylguanidine and ditrilguanidine;
And so on.
As the amine-based activator, one type may be used alone, or two or more types may be mixed and used.

Amine-based activators include cyclohexylamine, hexadecylamine, stearylamine, N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine, 2-phenylimidazole, 1,2,4-triazole and ditril. It preferably contains at least one selected from the group consisting of guanidine.
The content of the amine-based activator in the flux is preferably 0% by mass or more and 30% by mass or less, and 0.5% by mass or more and 20% by mass, based on the total amount (100% by mass) of the flux. The following is more preferable.

Organophosphorus compounds:
Examples of the organic phosphorus compound include an acidic phosphoric acid ester, an acidic phosphonic acid ester, and an acidic phosphinic acid ester.
Examples of the acidic phosphate ester include methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, monobutyl acid phosphate, butyl acid phosphate, dibutyl acid phosphate, butoxyethyl acid phosphate and 2-ethyl. Kisyl Acid Phosphate, Bis (2-ethylhexyl) Phosphate, Monoisodecyl Acid Phosphate, Diisodecyl Acid Phosphate, Lauryl Acid Phosphate, Isotridecyl Acid Phosphate, Stearyl Acid Phosphate, Oleyl Acid Phosphate, Beef Fat Phosphates, palm oil phosphates, isostearly acid phosphates, alkyl acid phosphates, tetracosyl acid phosphates, ethylene glycol acid phosphates, 2-hydroxyethyl methacrylate acid phosphates, dibutylpyrophosphates acid phosphates and the like can be mentioned. ..
Examples of the acidic phosphonic acid ester include 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, n-butyl (n-butyl) phosphonate, and isodecyl. Examples thereof include alkyl (alkyl) phosphonates such as (isodecyl) phosphonates and diethyl (p-methylbenzyl) phosphonates.
Examples of the acidic phosphinic acid ester include phenyl-substituted phosphinic acid and the like. Examples of the phenyl-substituted phosphinic acid include phenylphosphinic acid and diphenylphosphinic acid.

As the organic phosphorus compound, one kind may be used alone, or two or more kinds may be mixed and used.
It is more preferable that the organic phosphorus compound contains at least one selected from the group consisting of monoisodecyl acid phosphate, diisodecyl acid phosphate, 2-ethylhexyl (2-ethylhexyl) phosphonate and phenylphosphinic acid.
The total content of the organic phosphorus compound in the flux is preferably 0% by mass or more and 5.0% by mass or less, preferably 0.3% by mass or more, with respect to the total amount (100% by mass) of the flux. It is more preferably 0.5% by mass or less.

Resin components other than rosin-based resin:
Resin components other than the rosin-based resin include, for example, terpene resin, modified terpene resin, terpenephenol resin, modified terpenephenol resin, styrene resin, modified styrene resin, xylene resin, modified xylene resin, acrylic resin, polyethylene resin, acrylic-. Examples thereof include polyethylene copolymer resin and epoxy resin.
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.

Metal inactivating agent:
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 phenol-based compound refers to a phenol-based 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] oxamid, compounds represented by the following chemical formulas and the like.

（式中、Ｚは、置換されてもよいアルキレン基である。Ｒ^１及びＲ^２は、それぞれ独立して、置換されてもよい、アルキル基、アラルキル基、アリール基、ヘテロアリール基、シクロアルキル基又はヘテロシクロアルキル基である。Ｒ^３及びＲ^４は、それぞれ独立して、置換されてもよいアルキル基である。）

(In the formula, Z is an alkylene group which may be substituted. R ¹ and R ² are an alkyl group, an aralkyl group, an aryl group, a heteroaryl group and a cycloalkyl which may be substituted independently, respectively. 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 deactivating agent include hydrazide-based nitrogen compounds, amide-based nitrogen compounds, triazole-based nitrogen compounds, and melamine-based 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 a nitrogen compound having a triazole skeleton, and may be 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''-hexax (methoxymethyl) melamine and the like.

The metal inactivating agent preferably contains bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylenebis (oxyethylene)].
The content of the metal deactivating agent is preferably 0% by mass or more and 10.0% by mass or less, and 0.6% by mass or more and 3.0% by mass or less, based on the total amount (100% by mass) of the flux. The following is more preferable.

Surfactant:
Examples of the surfactant include nonionic surfactants, weak cationic surfactants and the like.
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. Be done.
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 the surfactant other than the above include polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ether, polyoxyalkylene alkyl ether, polyoxyalkylene ester, polyoxyalkylene alkyl amine, polyoxyalkylene alkyl amide and the like. ..

Flux content in solder paste:
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 content of the flux in the solder paste is in this range, the effect of suppressing thickening due to the solder powder is sufficiently exhibited. In addition, the effect of the components blended in the flux, that is, soldering with less generation of voids can be easily realized.

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.

As described above, in the solder paste of the present embodiment, a solder powder having an alloy composition containing Sn as a main component and being made of a low α-dose solder alloy is adopted. In the solder paste in which such a solder powder and a specific flux are combined, changes with time such as an increase in viscosity are unlikely to occur, and it is possible to suppress the occurrence of soft errors. In addition, according to the solder paste of the present embodiment, the wettability of the solder can be further enhanced by selecting the component to be blended in the flux.

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 content of each constituent element is all within a predetermined range. .. According to the solder alloy in the above-described embodiment, the occurrence of soft errors can be suppressed when the content of each constituent element is within the above range. That is, the solder alloy in 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.

Further, in the present embodiment, a solder alloy containing Ni and Fe, which are refractory metals that are heated at a high temperature during refining or processing of the bare metal, in a specific ratio without actively adding As. By adopting the above, the effect of suppressing the thickening of the solder paste over time can be made more excellent.
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 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 the refractory metals Ni and Fe, the crystal size is reduced and a dense oxide film is formed, so that the reactivity between the alloy and the flux is suppressed, so that the solder paste can be used over time. It is possible to suppress thickening.

Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the following Examples.

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

<Manufacturing of solder alloy>
(Manufacturing Examples 1 to 312)
The raw metal was melted and stirred to prepare solder alloys having the respective alloy compositions shown in Tables 1 to 14.
Sn-3.0Ag-0.5Cu alloy: Production Examples 1 to 4
Sn alloy: Production Examples 5 to 8
Sn-0.7Cu alloy: Production Examples 9-12
Sn-4.0 Ag alloy: Production Examples 13 to 16
Sn—Ni—Fe alloy: Production Examples 17 to 90
Sn-3.5Ag-Ni-Fe alloy: Production Examples 91 to 164
Sn-0.7Cu-Ni-Fe alloy: Production Examples 165 to 238
Sn-3.0Ag-0.5Cu-Ni-Fe alloy: Production Examples 239 to 312
As: 5 mass ppm or more or Pb: 5 mass ppm or more alloy: Production Examples 313 to 320

For the solder alloys of each production example, the α dose was evaluated as follows. The evaluation results are shown in Tables 1 to 14.

[Α dose]
(1) Verification method 1
The α-dose was measured by using the α-dose measuring device of the 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 manufactured 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, PR-10 gas was allowed to flow for 12 hours, and the mixture was 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 cph / cm ² or less.
◯: The α dose generated from the measurement sample was more than 0.002 cf / cm ² and 0.02 cf / cm ² or less.
X: The α dose generated from the measurement sample was more than 0.02 cph / cm ² .
If this determination 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 side is heat-treated at 100 ° C. for 1 hour and then allowed to cool. board.

(4) Judgment criteria 2
〇 〇: The α dose generated from the measurement sample was 0.002 cph / cm ² or less.
◯: The α dose generated from the measurement sample was more than 0.002 cf / cm ² and 0.02 cf / cm ² or less.
X: The α dose generated from the measurement sample was more than 0.02 cph / cm ² .
If this determination 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 in the above-mentioned procedures (i), (ii) and (iii). Was measured to evaluate the change over time in the α dose.

(6) Judgment criteria 3
〇 〇: The α dose generated from the measurement sample was 0.002 cph / cm ² or less.
◯: The α dose generated from the measurement sample was more than 0.002 cf / cm ² and 0.02 cf / cm ² or less.
X: The α dose generated from the measurement sample was more than 0.02 cph / 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.

As shown in Tables 1 to 13, as a result of evaluating the α dose for each of the solder alloys of Production Examples 1 to 312, the solder alloys of Production Examples 1 to 312 were obtained by heating the solder alloy sheet immediately after production at 100 ° C. for 1 hour. It was confirmed that the judgment was "○○" for the treated solder alloy sheet and the solder alloy sheet after being stored for one year.
On the other hand, as a result of evaluating the α dose for each of the solder alloys of Production Examples 313 to 320, the solder alloys of Production Examples 313 to 320 were the solder alloy sheet immediately after production and the solder alloy after heat treatment at 100 ° C. for 1 hour. It was confirmed that the judgment was "x" for all the sheets and the solder alloy sheets after being stored for one year.

<Manufacturing of solder powder>
The solder alloys of each production example were melted, and a solder powder composed of solder alloy particles having the alloy compositions shown in Tables 1 to 13 and having an average particle diameter of 6 μm was produced by an atomizing method.

For the solder alloys of Production Examples 1 to 4 and Production Examples 239 to 312, the solder alloys of each production example are melted, and the solder alloys having the alloy compositions shown in Tables 1 and 11 to 13 are selected by the atomizing method. Therefore, a solder powder composed of a group of solder alloy particles having an average particle diameter of 4 μm was produced.

<Preparation of flux>
(Preparation Examples 1 to 55)
As the resin component, polymerized rosin, acrylic acid-modified hydrogenated rosin, acrylic acid-modified rosin, disproportionated rosin, hydrogenated rosin, and hydrogenated rosin methyl ester were used.
Tarpineol and hexyldiglycol were used as the solvent.
As organic acid-based activators, adipic acid, sebacic acid, dimer acid (36 carbon atoms), hydrogenated dimer acid (36 carbon atoms), trimer acid (54 carbon atoms), myristic acid, palmitic acid, 12-hydroxystearic acid. , Diglycolic acid, succinic acid and glutaric acid were used.
As halogen-based activators, trans-2,3-dibromo-2-butene-1,4-diol, tris isocyanurate (2,3-dibromopropyl), cyclohexylamine hydrobromide, hexadecylamine hydrobromide. Hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrafluoroborate, ethylamine hydrobromide, diphenylguanidine hydrobromide, and ethylamine hydrochloride were used.
As amine-based activators, cyclohexylamine, hexadecylamine, stearylamine, N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine, 2-phenylimidazole, 1,2,4-triazole, ditril Guanidin was used.
As the organic phosphorus compound, 2-ethylhexyl (2-ethylhexyl) phosphonate, phenylphosphinic acid, and (mono- / di-) isodecyl acid phosphate were used.
As the metal inactivating agent, bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylenebis (oxyethylene)] was used.
As the thixo agent, hydrogenated castor oil, ethyl myristate, 4-methylbenzamide, ethylenebishydroxystearic acid amide, bis (4-methylbenzylidene) sorbitol, and dibenzylidene sorbitol were used.

<Manufacturing of solder paste>
(Examples 1 to 45)
The fluxes of Preparation Examples 1 to 3 and Preparation Examples 14 to 55 and the solder powder consisting of the solder alloys of Production Examples 1 to 4 and the solder alloy particle group having an average particle diameter of 6 μm were mixed and described in Examples. 1-46 solder pastes were produced.
The mixing ratio of the flux and the solder powder was set to flux: solder powder = 11:89 as a mass ratio.

(Example 46)
The fluxes of Preparation Examples 1 to 3 and Preparation Examples 14 to 55 and the solder powder composed of the solder alloys of Production Examples 1 to 4 and having an average particle diameter of 6 μm were mixed and carried out. The solder paste of Example 46 was produced.
The mixing ratio of the flux and the solder powder was set to flux: solder powder = 35:65 as a mass ratio.

(Example 47)
The fluxes of Preparation Examples 1 to 3 and Preparation Examples 14 to 55 and the solder powder consisting of the solder alloys of Production Examples 5 to 8 and the solder alloy particle group having an average particle diameter of 6 μm were mixed and carried out. Example 47 solder paste was produced.
The mixing ratio of the flux and the solder powder was set to flux: solder powder = 11:89 as a mass ratio.

(Example 48)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 9 to 12.

(Example 49)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 13 to 16.

(Example 50)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 17 to 90.

(Example 51)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 91 to 164.

(Example 52)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 165 to 238.

(Example 53)
Each solder paste was produced in the same manner as in Example 47, except that the solder alloy in Example 47 was changed to each of the solder alloys of Production Examples 239 to 312.

(Example 54)
In each case, each mixed solder powder having two kinds of solder alloy particle groups having different average particle diameters, which were made of the solder alloys of Production Examples 1 to 4, was produced.
Specifically, each solder alloy particle group (S1a) composed of the solder alloys of Production Examples 1 to 4 and having an average particle diameter of 6 μm and each solder alloy composed of the solder alloys of Production Examples 1 to 4 and having an average particle diameter of 4 μm. The particle group (S2a) was mixed at a mass ratio (S1a) / (S2a) = 50/50 to obtain each mixed solder powder.
Next, each flux of Preparation Examples 1 to 55 and each mixed solder powder were mixed to produce each solder paste.
The mixing ratio of the flux and the total amount of the mixed solder powder was set to flux: mixed solder powder = 11:89 as a mass ratio.

(Example 55)
Each solder paste was produced in the same manner as in Example 54, except that each solder alloy, which is the material of each mixed solder powder in Example 54, was changed to each solder alloy of Production Examples 239 to 312.

<Evaluation>
The wettability (wetting speed of solder) was evaluated for the above flux.
In addition, the solder paste was evaluated for suppressing thickening.
In addition, a comprehensive evaluation was performed based on these evaluation results.
The details are as follows. The evaluation results are shown in Tables 15 to 30.

[Wetability (wetting speed of solder)]
(1) Verification method An evaluation test of wettability (wetting speed of solder) was conducted as follows.
Based on the method of the meniscograph test, a copper plate having a width of 5 mm, a length of 25 mm and a thickness of 0.5 mm, which is a test plate, and a Solder Checker SAT-5200 (manufactured by RHESCA), which is a test device, are used, and the alloy composition Sn- Using a solder alloy having 3Ag-0.5Cu (each numerical value is mass%; balance Sn), the evaluation was performed as follows.
First, the test plate was immersed in the flux of each example measured in a beaker so that the immersion depth was about 10 mm, and the flux was applied to the test plate. Subsequently, after the flux was applied, the test plate to which the flux was applied was immediately immersed in a solder bath of a solder alloy having the alloy composition to obtain a zero cross time (sec).
Subsequently, the flux of each example was measured 5 times, and the average value of the obtained 5 zero cross times (sec) was calculated. The test conditions were set as follows.
Immersion speed in solder bath: 20 mm / sec (JIS Z 3198-4: 2014)
Immersion depth in solder bath: 5 mm (JIS Z 3198-4: 2014)
Immersion time in solder bath: 10 sec (JIS Z 3198-4: 2014)
Solder tank temperature: 280 ° C (JIS C 60068-2-69: 2019 Annex B)
The shorter the average value of the zero cross time (sec), the higher the wetting speed and the better the solder wetting property.

(2) Judgment criteria 〇: The average value of zero cross time (sec) is 2 seconds or less.
X: The average value of zero cross time (sec) exceeds 2 seconds.

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

(2) Judgment criteria 〇: The viscosity after 12 hours is 1.2 times or less 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 preparing the solder paste.
If this determination is "〇", 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.

[Comprehensive evaluation]
◯: In Tables 15 to 30, each evaluation of wettability and suppression of thickening was 〇.
X: In Tables 15 to 30, at least one of the evaluations of wettability and suppression of thickening was x.

In each of the solder pastes of Examples 1 to 55, the wetting rate of the flux was sufficient, and the effect of suppressing thickening was sufficient.
On the other hand, since the solder pastes of Comparative Examples 1 to 4 contained an organic acid having 5 or less carbon atoms, the effect of suppressing thickening was insufficient.
Further, the solder pastes of Comparative Examples 5 to 8 contained an organic acid having 6 or more carbon atoms, but contained an organic acid having 5 or less carbon atoms, so that the effect of suppressing thickening was insufficient.
Further, in the solder pastes of Comparative Examples 9 and 10, since the content of the halogen-based activator was less than 0.1% by mass with respect to the total amount of the flux, the wetting rate of the flux was not sufficient.

The solder pastes of Examples 50 to 53 and 55 were compared with the solder pastes of Examples 1 to 49, and 12 hours after the start of viscosity measurement with respect to the viscosity when 30 minutes had passed immediately after each solder paste was prepared. The viscosity ratio of each solder paste was low.
That is, the solder pastes of Examples 50 to 53 and 55 were superior in the thickening suppressing effect as compared with the solder pastes of Examples 1 to 49.

According to the present invention, it is possible to provide a solder paste capable of improving the wettability of the solder, suppressing an increase in the viscosity of the solder paste over time, and suppressing the occurrence of soft errors. Such solder paste can be used to solder electronic components to a substrate.

Claims (25)

A solder paste consisting of solder powder and flux,
The solder powder has an alloy composition consisting of U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the balance of Sn, and has an α dose. It consists of a solder alloy with a capacity of 0.02 cph / cm ² or less.
The flux contains a halogen-based activator, a rosin, a thixotropic agent, and a solvent.
The flux does not contain an organic acid having 5 or less carbon atoms.
The content of the halogen-based activator is 0.1% by mass or more and 4% by mass or less with respect to the total amount of the flux. Further, the solder paste according to claim 1, wherein the alloy composition has Pb of less than 2 parts by mass. Further, the solder paste according to claim 1 or 2, wherein the alloy composition has As of less than 2 parts by mass ppm. Further, according to any one of claims 1 to 3, 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 paste. Further, any one of claims 1 to 4, wherein the alloy composition contains at least one of Bi: 0% by mass or more and 0.3% by mass or less, and Sb: 0% by mass or more and 0.9% by mass or less. Solder paste described in. Further, the solder paste according to claim 5, wherein the alloy composition satisfies the following formula (2).
0.03 ≤ Bi + Sb ≤ 1.2 (2)
In the formula (2), Bi and Sb each represent the content (mass%) in the alloy composition. The solder alloy has an α-dose of 0.02 cph / cm ² or less after being heat-treated 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. The solder paste according to any one of claims 1 to 6. The solder paste according to any one of claims 1 to 7, wherein the solder alloy has an α dose of 0.002 cf / cm ² or less. The solder paste according to claim 8, wherein the solder alloy has an α dose of 0.001 cf / cm ² or less. The solder paste according to any one of claims 1 to 9, wherein the solder powder is composed of a group of solder alloy particles having an average particle diameter of 0.1 to 15 μm. The solder paste according to any one of claims 1 to 10, wherein the solder powder has two or more kinds of solder alloy particles having different average particle diameters. The solder paste according to any one of claims 1 to 11, wherein the halogen-based activator contains an amine hydrohalide hydrochloride. The amine halide hydrobromide includes cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrafluoroborate, ethylamine hydrobromide, and diphenyl. The solder paste according to claim 12, which comprises at least one selected from the group consisting of guanidine hydrobromide and ethylamine hydrochloride. The solder paste according to claim 12 or 13, wherein the halogen-based activator further contains an organic halogen compound other than the amine hydrohalide hydrochloride. 13. The solder paste described. The rosin further comprises a rosin ester
The solder paste according to claim 15, wherein the rosin ester contains hydrogenated rosin methyl. The solder paste according to any one of claims 1 to 16, wherein the flux further contains an organic acid having 6 or more carbon atoms. The organic acid having 6 or more carbon atoms contains at least one selected from the group consisting of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimeric acid, myristic acid, palmitic acid and 12-hydroxystearic acid. , The solder paste according to claim 17. The solder paste according to any one of claims 1 to 18, wherein the thixotropy comprises at least one selected from the group consisting of an ester-based thixotropy, an amide-based thixotropy, and a sorbitol-based thixotropy. The solder paste according to claim 19, wherein the ester-based thixotropy comprises at least one selected from the group consisting of castor oil and ethyl myristate. The solder paste according to claim 19 or 20, wherein the amido-based thixotropy comprises at least one selected from the group consisting of 4-methylbenzamide and ethylenebishydroxystearic acid amide. The solder paste according to any one of claims 19 to 21, wherein the sorbitol-based thixotropy comprises at least one selected from the group consisting of bis (4-methylbenzylidene) sorbitol and dibenzylidene sorbitol. The solder paste according to any one of claims 1 to 22, wherein the flux further contains an amine-based activator. The solder paste according to any one of claims 1 to 23, wherein the flux further contains an organic phosphorus compound. The solder paste according to any one of claims 1 to 24, wherein the flux further contains an antioxidant.