TWI793780B - Solder paste - Google Patents

Abstract

Provided is a solder paste containing a solder powder and a flux, the solder powder containing U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the balance Sn, and having an α dose of 0.02 cph/ cm² or less; the flux containing a halogen-based activator, a rosin, a thixotropic agent and a solvent, and not containing 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.

Description

solder paste

This invention relates to solder paste.

The solder material is solder paste containing solder powder and flux.

In electronic components mounted on printed circuit boards, miniaturization and high performance are increasingly required. As this electronic component, a semiconductor package is mentioned, for example. In semiconductor packaging, semiconductor elements with electrodes are sealed with resin components. A solder bump made of solder material is formed on the electrode. With this solder material, the semiconductor element and the printed circuit board are soldered and connected.

In welding materials, the influence of α -rays on soft errors becomes a problem. In order to reduce the adverse effect on the operation of such semiconductor elements, the development of low- α radiation-dosage materials including solder materials has been actively carried out.

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

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

Generally, Sn contains lead (Pb) and bismuth (Bi) as impurities. ²¹⁰ Pb and ²¹⁰ Bi, which are radioactive isotopes among Pb and Bi, undergo β decay to become ²¹⁰ Po, and ²¹⁰ Po undergoes α decay to generate α rays when ²⁰⁶ Pb is produced. A cascade of decays in this uranium series can be considered the main cause of alpha radiation from welding materials.

In the evaluation of the amount of α -rays generated from materials, the unit is often "cph/cm ² ". "cph/cm ² " is an abbreviation of "counts per hour/cm ² ", which means the count of α -rays per 1 cm ² and per hour.

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

Regarding Bi, the half-life of ²¹⁰ Bi is about 5 days. Regarding Pb, the half-life of ²¹⁰ Pb is about 22.3 years. Then, these degrees of influence (existence ratio) can be set to be represented by the following formula (see Non-Patent Document 1). That is, the influence of Bi on the generation of α- rays is extremely 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 mentioned above, conventionally, in the design of materials with low α radiation dose, U and Th are generally removed, and Pb is more thoroughly removed.

In addition, it is known that the amount of α- rays generated from welding materials basically increases due to changes over time (hereinafter also referred to as time-dependent changes). This reason can be considered that β-decay of radiative Pb and radiative Bi in the solder alloy increases the amount of Po, and then α- decay of Po produces α- rays. Materials with an extremely low amount of α -rays hardly contain such radioactive elements, but the amount of α -rays may increase with time due to segregation of ²¹⁰ Po. ²¹⁰ Po originally radiates α- rays, but because it segregates in the center of the solder alloy when the solder alloy solidifies, the radiated α- rays are shielded by the solder alloy. Then, as time passes, ²¹⁰ Po is uniformly dispersed in the alloy, so that α -rays also exist on the surface to be inspected, so the amount of α -rays increases due to time-lapse (see Non-Patent Document 2).

As mentioned above, due to the influence of the very small amount of impurities contained in the solder alloy, the amount of α- rays generated increases. Therefore, in the design of materials with low α- ray dose, it is difficult to deal with it by only adding various elements as in the conventional manufacturing method of solder alloys.

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

On the other hand, the flux used in soldering has the function of chemically removing the metal oxide existing on the metal surface of the solder and the object to be joined as the soldering object, and maintaining the metal element on the boundary between the two. Efficiency of movement. Therefore, by performing soldering using flux, an intermetallic compound can be formed between the solder and the metal surface of the object to be bonded, thereby obtaining a strong bond.

[Prior Art Literature]

[Patent Document]

[Patent Document 1] Japanese Unexamined Patent Publication No. 2010-156052

[Patent Document 2] Japanese Unexamined Patent Publication No. 2015-98052

[Non-patent literature]

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

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

For example, in the method described in Patent Document 2, in the method of adding As to the solder alloy in order to suppress the thickening of the solder paste over time, the addition of As also includes the radiation contained in As in the alloy. Sex isotopic impurities. In this case, due to the presence of radioactive elements in the impurities, the amount of α- rays generated from the welding material increases.

In addition, among the fluxes used in solder paste, it is required that the solder has a high wetting speed on the metal surface of the object to be joined and that the solder wettability is good.

When soldering is performed using solder balls, if the wettability of the solder to the metal surface of the object to be joined cannot be ensured, it becomes difficult for the solder to wet and spread uniformly on the electrodes. When the wettability of the solder is poor, the position of the solder ball relative to the electrode will deviate, and the solder ball will be in a state where the solder ball is deviated from the electrode pad (dropped ball), which may easily lead to poor bonding or poor electrical conduction.

The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to provide a solder paste capable of improving the wettability of solder, suppressing the increase in viscosity of the solder paste over time, and suppressing the occurrence of soft errors.

The inventors of the present invention have studied for the purpose of designing a solder alloy with a low α- ray dose that can suppress the increase in viscosity of solder paste over time without adding As accompanied by impurities containing radioactive elements. Through related studies, it has been found that by setting the composition of an alloy containing Sn as a main component and a low α- ray dose, and making the flux used in the solder paste free of organic acids with a carbon number of 5 or less, it is possible to suppress the solder paste from drifting. Viscosity over time.

In addition, they discovered that the wettability of solder is sufficient by making the flux used for a solder paste contain a halogen-type activator, and came to complete this invention.

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

One aspect of the present invention is a solder paste consisting of solder powder and flux. The solder powder is composed of a solder alloy having 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 rest of the alloy composition of Sn, and the amount of α rays is 0.02cph/cm ² or less; the aforementioned flux contains: halogen-based activator, rosin , a thixotropic agent, and a solvent; the aforementioned flux does not contain an organic acid with a carbon number of 5 or less, and the content of the aforementioned halogen-based activating agent is not less than 0.1% by mass and not more than 4% by mass relative to the total amount of the aforementioned flux.

In the solder paste of the above-mentioned one state, it is preferable that the above-mentioned alloy composition is further such that Pb is less than 2 mass ppm.

In the solder paste of the above-mentioned one state, it is preferable that the above-mentioned alloy composition is further such that As is less than 2 mass ppm.

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

In the solder paste of the above-mentioned one state, the alloy composition preferably further includes at least one of Bi: 0% by mass to 0.3% by mass, and Sb: 0% by mass to 0.9% by mass.

In the above-mentioned solder paste in one state, the above-mentioned alloy composition preferably 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 aforementioned alloy composition.

In the solder paste of the above-mentioned state, after heat-treating at 100°C for 1 hour to a flaky solder alloy sheet with an area of 900 cm ² on one side, the α- ray dose of the above-mentioned solder alloy is preferably 0.02 Below cph/ ^cm2 .

In the solder paste of the above-mentioned one state, the α- ray dose of the above-mentioned solder alloy is preferably 0.002 cph/cm ² or less.

In the solder paste of the above-mentioned one state, the α- ray dose of the above-mentioned solder alloy is preferably 0.001 cph/cm ² or less.

In the aforementioned solder paste, the aforementioned solder powder is preferably composed of solder alloy particle groups with an average particle size of 0.1 to 15 μm .

In the solder paste of the above-mentioned one aspect, it is preferable that the above-mentioned solder powder has two or more types of solder alloy particle groups with different average particle diameters.

In the solder paste of the aforementioned aspect, the aforementioned halogen-based activator preferably contains amine hydrohalide.

In the solder paste related to the above-mentioned one state, the aforementioned amine hydrohalide preferably contains a salt selected from cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrahydrobromide At least one selected from the group consisting of fluoroborate, ethylamine hydrobromide, diphenylguanidine hydrobromide and ethylamine hydrochloride.

In the solder paste of the aforementioned aspect, the aforementioned halogen-based activator preferably further contains an organic halogen compound other than the aforementioned amine hydrohalide.

In the solder paste related to the above-mentioned one aspect, the above-mentioned rosin preferably contains at least A sort of.

In the above-mentioned solder paste of one aspect, the rosin preferably further contains rosin ester, and the rosin ester preferably contains hydrogenated rosin methyl ester.

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

In the above-mentioned solder paste, the above-mentioned organic acid with carbon number of 6 or more is preferably selected from the group consisting of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimer acid, carotene At least one selected from the group consisting of myristic acid, palmitic acid and 12-hydroxystearic acid.

In the aforementioned solder paste, the thixotropic agent preferably contains at least one selected from the group consisting of ester-based thixotropes, amide-based thixotropes and sorbitol-based thixotropes.

In the above-mentioned solder paste of one aspect, it is preferable that the above-mentioned ester-based thixotropic agent contains at least one selected from the group consisting of hydrogenated castor oil and ethyl myristate.

In the aforementioned solder paste, the amide-based thixotropic agent preferably contains at least one selected from the group consisting of 4-methylbenzamide and ethylidene bishydroxystearamide.

In the above-mentioned solder paste, the sorbitol-based thixotropic agent preferably contains a compound selected from the group consisting of bis(4-methylbenzylidene)sorbitol and dibenzylidene sorbitol. at least one.

In the above-mentioned solder paste of one aspect, the above-mentioned soldering flux preferably further contains an amine-based activator.

In the above-mentioned solder paste, it is preferable that the above-mentioned flux further contains an organophosphorus compound.

In the above-mentioned solder paste, it is preferable that the above-mentioned flux further contains an antioxidant.

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

The following describes the present invention in more detail.

In this specification, "ppb" related to the solder alloy composition is "ppb by mass" unless otherwise specified. "ppm" is "ppm by mass" unless otherwise specified. "%" means "mass%" unless otherwise specified.

(solder paste)

The solder paste of this embodiment is composed of specific solder powder and specific flux.

The aforementioned solder powder is composed of a solder alloy having U: less than 5 mass ppb, Th: less than 5 mass ppm, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the remainder of Sn The composition of the alloy, and the amount of α- rays is 0.02cph/cm ² or less.

The aforementioned flux contains: a halogen-based activator, rosin, a thixotropic agent, and a solvent.

The aforementioned flux does not contain organic acids with carbon numbers below 5.

Content of the said halogen-type activator is 0.1 mass % or more and 4 mass % or less with respect to the total amount of the said flux.

〈Solder powder〉

The solder powder used in the solder paste of this embodiment is composed of a solder alloy having U: less than 5 mass ppb, Th: less than 5 mass ppb, Pb: less than 5 mass ppm, As: less than An alloy composition consisting of up to 5 mass ppm and the remainder of Sn, and an α- ray dose of 0.02 cph/cm ² or less.

The solder alloy of this embodiment has an alloy composed of U: less than 5 mass ppm, Th: less than 5 mass ppm, Pb: less than 5 mass ppm, As: less than 5 mass ppm, and the rest of Sn composition.

"U: less than 5 mass ppb, Th: less than 5 mass ppb"

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

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

《Pb: less than 5 mass ppm》

Generally, Sn contains Pb as an impurity. This radioactive isotope in Pb undergoes β decay to ²¹⁰ Po, and ²¹⁰ Po undergoes α decay to generate α rays when ²⁰⁶ Pb is produced. Therefore, the content of Pb as an impurity in the solder alloy is preferably extremely small.

In this embodiment, the content of Pb in the solder alloy is less than 5 ppm, preferably less than 2 ppm, and most preferably less than 1 ppm relative 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 increase in viscosity of the solder paste over time, but with the addition of As, the alloy also contains radioactive elements derived from As impurities, resulting in α produced from the solder material. Increased radiation dose.

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

In this embodiment, the As content in the solder alloy is less than 5 ppm, preferably less than 2 ppm, and most preferably less than 1 ppm relative 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.

"Any Element"

Regarding the solder alloy of this embodiment, the alloy composition may contain elements other than the above-mentioned elements as needed.

By soldering, a Sn-containing intermetallic compound (Sn-containing intermetallic compound) is formed near the joint interface in the solder alloy, and when the Sn-containing intermetallic compound is precipitated, the mechanical strength of the solder joint deteriorates.

On the other hand, for example, regarding the solder alloy of this embodiment, the alloy composition preferably further contains Ni: 0 mass ppm to 600 mass ppm and Fe: 0 mass ppm to 100 mass ppm, in addition to the above elements.

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 joint interface.

When the solder alloy contains Ni, the formation of the aforementioned Sn-containing intermetallic compound is suppressed and the mechanical strength of the solder joint is maintained. On the other hand, when the Ni content in the solder alloy exceeds 600 ppm, the SnNi compound is precipitated near the joint interface in the solder alloy, and the mechanical strength of the solder joint may deteriorate.

In this embodiment, the content of Ni in the solder alloy is preferably not less than 0 ppm and not more than 600 ppm, more preferably not less than 20 ppm and not more than 600 ppm, more preferably not less than 40 ppm and not more than 600 ppm, relative to the total mass (100% by mass) of the solder alloy. .

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

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

The term "needle crystal" here refers to a crystal in which the ratio of the long axis to the short axis, that is, the aspect ratio, is 2 or more in one crystal derived from the SnFe compound.

In this embodiment, the content of Fe in the solder alloy is preferably not less than 0 ppm and not more than 100 ppm, more preferably not less than 20 ppm and not more than 100 ppm, more preferably not less than 40 ppm and not more than 80 ppm, relative to the total mass (100% by mass) of the solder alloy. .

Regarding the solder alloy of this embodiment, the alloy composition preferably satisfies the following formula (1).

20≦Ni+Fe≦700 (1)

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

Both Ni and Fe in the formula (1) are elements that inhibit the formation of Sn-containing intermetallic compounds at the joint interface. In addition, in this embodiment, both Ni and Fe are beneficial to suppress the viscosity increase of the solder paste over time.

In order to enhance the above-mentioned effect of suppressing the formation of Sn-containing intermetallic compounds 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 relative to the total mass of the solder alloy (100% by mass). ), preferably more than 20ppm and less than 700ppm. The total content of Ni and Fe is especially It is preferably from 40 ppm to 700 ppm, more preferably from 40 ppm to 600 ppm, most preferably from 40 ppm to 200 ppm.

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

In addition, in the case where Ni and Fe are present at the same time in the present embodiment, the ratio of Ni and Fe in the solder alloy is calculated as the mass ratio represented by Ni/Fe, preferably 0.4 to 30, and more preferably 0.4 or more. 10 or less, more preferably 0.4 to 5, most preferably 0.4 to 2.

If the mass ratio of Ni/Fe is in the aforementioned preferred range, the effect of the present invention can be more easily obtained.

For example, regarding the solder alloy of this embodiment, the alloy composition may further contain at least one of Ag: 0% by mass to 4% by mass and Cu: 0% by mass to 0.9% by mass, in addition to the above elements.

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

Ag is any element that can form Ag ₃ Sn on the crystal interface to improve the reliability of the solder alloy. In addition, Ag is an element whose ionization tendency is higher than that of Sn, and by coexisting with Ni and Fe, the effect of suppressing the viscosity increase of solder paste over time can be enhanced. Furthermore, if the content of Ag in the solder alloy is within the above-mentioned range, the rise of the melting point of the alloy can be suppressed, so it is not necessary to increase the reflow temperature excessively.

In this embodiment, the content of Ag in the solder alloy is preferably not less than 0% and not more than 4%, particularly preferably not less than 0.5% and not more than 3.5%, with respect to the total mass (100% by mass) of the solder alloy, and more preferably More than 1.0% and less than 3.0%, especially good is more than 2.0% and less than 3.0%.

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

Cu is used in general solder alloys and is an arbitrary element that can improve the joint strength of solder joints. In addition, Cu-based elements that tend to ionize at a higher potential than Sn can enhance the effect of suppressing the viscosity increase of solder paste over time by coexisting with Ni and Fe.

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

In this embodiment, when there are Cu and Ni at the same time, the ratio of Cu and Ni in the solder alloy is calculated as the mass ratio represented by Cu/Ni, preferably 8 or more and 175 or less, and especially preferably 10 or more and 150 or less .

If Cu/Ni of this mass ratio exists in the said range, the effect of this invention will be acquired more easily.

In this embodiment, when there are Cu and Fe at the same time, the ratio of Cu and Fe in the solder alloy is calculated as the mass ratio represented by Cu/Fe, preferably 50 to 350, especially preferably 70 to 250 .

If the mass ratio of Cu/Fe is in the aforementioned preferable range, it is easier to obtain the effect of the present invention.

In this embodiment, when there are Cu, Ni, and Fe at the same time, the ratio of Cu, Ni, and Fe in the solder alloy is preferably 7 or more and 350 or less in terms of mass ratio represented by Cu/(Ni+Fe). , preferably not less than 10 and not more than 250.

If the mass ratio of Cu/(Ni+Fe) is in the aforementioned preferable range, it is easier to obtain the effect of the present invention.

For example, regarding the solder alloy of this embodiment, the alloy composition may further contain at least one of Bi: 0% by mass to 0.3% by mass and Sb: 0% by mass to 0.9% by mass, in addition to the above elements.

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

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

In this embodiment, the content of Bi in the solder alloy is preferably from 0% to 0.3%, particularly preferably from 0.0020% to 0.3%, with respect to the total mass (100% by mass) of the solder alloy, more preferably 0.01% to 0.1%, most preferably 0.01% to 0.05%.

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

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

In this embodiment, the content of Sb in the solder alloy is preferably not less than 0% and not more than 0.9%, particularly preferably not less than 0.0020% and not more than 0.9%, and more preferably 0.01% to 0.1%, most preferably 0.01% to 0.05%.

Regarding the solder alloy of this embodiment, when the alloy composition further contains at least one of Bi: 0 mass % to 0.3 mass % and Sb: 0 mass % to 0.9 mass %, the aforementioned alloy composition preferably satisfies the following State (2) formula.

0.03≦Bi+Sb≦1.2 (2)

In the formula (2), Bi and Sb each represent the content (mass %) in the aforementioned 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. Besides, in this embodiment, both Bi and Sb are beneficial to the wettability of the solder alloy.

The total content of Bi and Sb in the solder alloy is preferably from 0.03% to 1.2%, particularly preferably from 0.03% to 0.9%, and more preferably from 0.3% to the total mass (100% by mass) of the solder alloy. Below 0.9%.

However, the aforementioned "total content of Bi and Sb" refers to the content of Sb when the content of Bi in the solder alloy is 0%, and refers to the content of Bi when the content of Sb in the solder alloy is 0%. When Bi and Sb are present at the same time, it refers to the total content of these.

In this embodiment, when Bi and Sb are present at the same time, the ratio of Bi and Sb in the solder alloy is based on the mass ratio represented by Sb/Bi, preferably from 0.01 to 10, and especially preferably from 0.1 to 5. .

If the mass ratio of Sb/Bi is in the aforementioned preferable range, it is easier to obtain the effects of the present invention.

"The Remainder: Sn"

Regarding the solder alloy of this embodiment, the remainder of the alloy composition is composed of Sn. In addition to the above elements, unavoidable impurities may also be contained. Even if it contains unavoidable impurities, it will not affect the above effects.

"Amount of Alpha Rays"

The α- ray dose of the solder alloy of this embodiment is 0.02 cph/cm ² or less.

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

From the viewpoint of suppressing soft errors under higher-density packaging, the amount of α -rays generated from the solder alloy of this embodiment is preferably less than 0.01cph/cm ² , more preferably less than 0.002cph/cm ² , More preferably, it is 0.001 cph/cm ² or less.

The amount of α- rays generated from the solder alloy can be measured in the following manner. The measurement method of this α- ray dose is based on JEDEC STANDARD which is an international standard.

Step (i):

A gas flow type α- ray dose measuring device is used.

As a measurement sample, a thin piece of solder alloy formed by melting a solder alloy into a thin sheet with an area of 900 cm ² on one side was used.

The aforementioned solder alloy flakes were set in the aforementioned α- ray dosimetry device as a measurement sample, and the place was flushed with PR gas.

The PR gas system uses the JEDEC STANDARD that follows the international standard. That is to say, the PR gas system used in the measurement is set as follows: After filling the gas high-pressure tank with a mixed gas of 90% argon and 10% methane, it takes more than 3 weeks to decay the impurity radon (Rn) in the gas.

Step (ii):

The α- ray dose measurement was performed for 72 hours after the PR gas was passed through the α- ray dose measuring device provided with the solder alloy sheet for 12 hours and left to stand.

Step (iii):

The average α -ray dose was calculated as "cph/cm ² ". Regarding abnormal points (counts obtained by vibration of the device, etc.), the counts for the 1-hour portion were removed.

The α- ray dose of the solder alloy of the present embodiment is preferably 0.02 cph/cm ^{2 or} less after heat treatment at 100° C. , preferably less than 0.01cph/cm ² , more preferably less than 0.002cph/cm ² , especially preferably less than 0.001cph/cm ² .

It shows that the solder alloy with this amount of α- rays is less likely to cause segregation of ²¹⁰ Po in the alloy, and it is useful because the influence caused by the change of the amount of α- rays over time is small. By applying a solder alloy that exhibits this α- ray dose, the occurrence of soft errors is further suppressed, and it becomes easier to further ensure stable operation of semiconductor devices.

[Manufacturing method of solder alloy]

The solder alloy of this embodiment can be produced by using a production method having steps of, for example, melting and mixing raw material metals containing at least one of Ni and Fe and Sn.

Since the aim is to design a solder alloy with low α- ray dose, it is preferable to use a material with low α- ray dose as the raw material metal. , Th and Pb were removed. Sn as a raw material metal can be manufactured using the manufacturing method described in Unexamined-Japanese-Patent No. 2010-156052 (patent document 1), for example.

Ni and Fe which are raw material metals can be respectively used, for example, according to Japanese Patent No. 5692467.

For the operation of melting and mixing the raw material metals, conventionally known methods can be used.

The solder powder of this embodiment can be produced by: dropping molten solder alloy to obtain particles, or spraying method of centrifugal spraying, atomization method, liquid granulation method, lump solder A generally known method such as a method of alloy pulverization. In order to form particles, the dropping or spraying in the dropping method or spraying method is preferably performed in an inert environment or in a solvent.

The solder powder in this embodiment is preferably spherical powder. By being a spherical powder, the fluidity of the solder alloy is improved.

In the case where the solder powder of this embodiment is a spherical powder, in the powder size classification (Table 2) in JIS Z 3284-1:2014, it is preferable to satisfy symbols 1 to 8, especially to satisfy the sub-number 4 to 8. When the particle size of the solder powder satisfies this condition, the surface area of the powder will not be too large, the increase in the viscosity of the solder paste over time will be suppressed, and the aggregation of fine powder will be suppressed, thereby suppressing the increase in the viscosity of the solder paste. Therefore, finer parts can be welded.

In addition, the solder powder of this embodiment is preferably composed of solder alloy particles with an average particle size of 0.1 to 50 μm , and more preferably solder alloy particles with an average particle size of 1 to 25 μm . As for the group, it is more preferable to use a group of solder alloy particles having an average particle size of 1 to 15 μm .

When the particle size of the solder powder is in the aforementioned preferable range, it becomes easy to suppress the increase in the viscosity of the solder paste over time.

Here, the average particle diameter of the solder powder means the particle diameter at 50% of the integrated value in the particle size distribution measured by a laser diffraction scattering particle size distribution measuring device.

In addition, it is preferable that the solder powder of this embodiment has two or more kinds of solder alloy particle groups with different particle size distributions at the same time. This improves the smoothness of the solder paste and improves workability such as ease of printing.

Examples of the solder powder include, for example, solder alloy particle groups having two or more different average particle diameters. As an example, a solder alloy particle group (S1) having an average particle diameter of 5 μm or more and less than 10 μm and a solder having an average particle diameter of 1 μm or more and less than 5 μm can be suitably mentioned. Solder powder of alloy particle group (S2).

The mixing ratio of the solder alloy particle group (S1) and the solder alloy particle group (S2) is calculated by the mass ratio represented by (S1)/(S2), preferably (S1)/(S2)=9/1 to 1/ 9, preferably 9/1 to 3/7, more preferably 9/1 to 5/5.

Regarding the solder powder of this embodiment, the true sphericity of the spherical powder is preferably at least 0.8, more preferably at least 0.9, more preferably at least 0.95, and most preferably at least 0.99.

The so-called "sphericity of spherical powder" here can be measured by using a CNC image measurement system (Ultra Quick Vision ULTRA QV350-PRO manufactured by Mitutoyo Co., Ltd.) using the minimum zone center method (MZC (Minimum Zone Circle) method). Measuring device) to measure.

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

〈Soldering flux〉

The flux used in the solder paste of this embodiment contains: a halogen-based activator, rosin, a thixotropic agent, and a solvent. In addition, the aforementioned flux does not contain organic acids with a carbon number of 5 or less. Content of the said halogen type activator is 0.1 mass % or more and 4.0 mass % or less with respect to the total amount of the said flux.

The flux used in the solder paste of this embodiment can improve the wettability of solder by containing a halogen-based activator. The solder paste of this embodiment can suppress the viscosity increase of the solder paste over time by not containing an organic acid with a carbon number of 5 or less.

《Halogen active agent》

Examples of the halogen-based activator include amine hydrohalides, organic halogen compounds other than amine hydrohalides, and the like.

Amine hydrohalides are compounds obtained by reacting amines with hydrogen halides. The amines here include, for example: ethylamine, diethylamine, triethylamine, ethylenediamine, diphenylguanidine, xylylguanidine, methyl imidazole (Methyl Imidazole), 2-ethyl-4-methyl Examples of the imidazole and the like, and examples of the hydrogen halide include hydrides of chlorine, bromine, and iodine.

More specifically, the amine hydrohalides include, for example: cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, ethylamine hydrobromide, diphenylguanidine hydrobromide Bromate, ethylamine hydrochloride, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, isopropylamine Hydrobromide, Diethylamine Hydrobromide, Dimethylamine Hydrobromide, Dimethylamine Hydrochloride, Rosinamine Hydrobromide, 2-Ethylhexylamine Hydrochloride, Isopropylamine Hydrochloride , cyclohexylamine hydrochloride, 2-piperidine hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethyl Cyclohexylamine Hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, di Allylamine hydrochloride, diallylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrochloride Hydrobromide, hydrazine dihydrobromide, pyridine hydrobromide, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, di Methylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, D-bran Amino acid hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2-piperidine hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoric acid Salt, Diethylamine Hydrofluoride, 2-Ethylhexylamine Hydrofluoride, Cyclohexylamine Hydrofluoride, Ethylamine Hydrofluoride, Rosinamine Hydrofluoride, Cyclohexylamine Tetrafluoroborate And dicyclohexylamine tetrafluoroborate, etc.

In addition, as the halogen-based activating agent, for example, salts obtained by reacting amines with tetrafluoroboric acid (HBF ₄ ), and complexes obtained by reacting amines with boron trifluoride (BF ₃ ) can also be used.

The aforementioned complexes include, for example, boron trifluoride piperidine (Boron Trifluoride Piperidine) and the like.

Examples of organic halogen compounds other than amine hydrohalides include trans-2,3-dibromo-2-butene-1,4-diol, triallyl hexabromoisocyanurate, isocyanurate Tris-(2,3-dibromopropyl) cyanurate, 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, etc.

In addition, organic halogen compounds other than amine hydrohalides also include halogenated carboxyl compounds, such as: 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, 5-iodo Iodinated carboxyl compounds such as anthranilic acid; Chlorinated carboxyl compounds such as 2-chlorobenzoic acid and 3-chloropropionic acid; 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, 2-bromobenzoic acid and other brominated carboxyl compounds, etc.

In the flux used in the solder paste of this embodiment, one or more than two kinds of halogen-based activators can be used.

The halogen-based active agent preferably contains amine hydrohalide.

The amine hydrohalide is preferably selected from the group consisting of cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrafluoroborate, ethylamine hydrobromide, At least one of the group consisting of diphenylguanidine hydrobromide and ethylamine hydrobromide, preferably containing cyclohexylamine hydrobromide, hexadecylamine hydrobromide and stearylamine hydrobromide More than one of the group consisting of acid salts.

Organic halogen compounds other than amine hydrohalides preferably contain trans-2,3-dibromo-2-butene-1,4-diol and isocyanuric acid tri-(2,3- One or more of the group consisting of dibromopropyl) ester.

The total content of the halogen-based activators in the flux is 0.1% by mass to 4.0% by mass, more preferably 0.5% by mass to 4.0% by mass relative to the total amount of the flux (100% by mass).

The content of the organohalogen compound in the flux is preferably from 0% by mass to 4.0% by mass, particularly preferably from 0.9% by mass to 2.0% by mass, relative to the total amount of the flux (100% by mass).

The content of the amine hydrohalide in the flux is preferably from 0% by mass to 4.0% by mass, more preferably from 0.1% by mass to 4.0% by mass, relative to the total amount of the flux (100% by mass). , more preferably not less than 0.5% by mass and not more than 2.0% by mass.

"rosin"

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

Examples of such derivatives include refined rosin, hydrogenated rosin, heterogeneous rosin, polymerized rosin, acid-modified rosin, phenol-modified rosin, and α , β-unsaturated carboxylic acid-modified products (acrylated Rosin, maleated rosin, fumarated rosin, etc.); and the refined product, hydrogenated product and heterogeneous product of the polymerized rosin; and the refined product, hydrogenated product modified by α , β unsaturated carboxylic acid substances and inhomogeneities, etc.

In the flux used in the solder paste of this embodiment, one or more than two types of rosin can be used.

The rosin may further contain rosin esters.

Rosin ester preferably contains hydrogenated rosin methyl ester.

This hydrogenated rosinic acid methyl ester is an ester obtained from hydrogenated cyclic fatty acid obtained from rosin and methanol. It is also called hydrogenated rosinic acid methyl ester and has a CAS number of 8050-15-5.

The rosin preferably contains at least one selected from the group consisting of polymerized rosin, acrylic-modified hydrogenated rosin, acrylic-modified rosin, heterogeneous rosin, and hydrogenated rosin, and more preferably contains polymerized rosin and At least one of the group consisting of methyl hydrogenated abietate.

The total content of the rosin in the flux is preferably from 30.0% by mass to 60.0% by mass, more preferably from 35.0% by mass to 50.0% by mass, with respect to the total amount of the flux (100% by mass) It is 40.0 mass % or more and 50.0 mass % or less.

The content of the rosin ester in the flux is preferably from 0 mass % to 30.0 mass %, more preferably from 5.0 mass % to 20.0 mass %, more preferably 5.0 mass % or more and 10.0 mass % or less.

When the aforementioned flux contains rosin ester, the content of the aforementioned rosin ester is preferably from 0% by mass to 60.0% by mass, particularly preferably from 10.0% by mass to 50.0% by mass, with respect to the total amount of the aforementioned rosin. It is 10.0 mass % or more and 20.0 mass % or less.

"Thrust-changer"

Examples of the thixotropic agent include ester-based thixotropes, amide-based thixotropes, and sorbitol-based thixotropes.

Examples of ester-based thixotropic agents include ester compounds, and specific examples include hydrogenated castor oil, ethyl myristate, and the like.

Amide-based thixotropic agents include, for example, monoamides, bisamides, and polyamides. Specifically, laurylamide, palmitamide, stearamide, diamide, hydroxystearamide, Saturated fatty amide, oleamide, erucamide, unsaturated fatty amide, 4-methylbenzamide (p-toluamide), p-toluamide, aromatic amide, hexamethylene hydroxyl Stearyl amide, substituted amide, hydroxymethyl stearyl amide, hydroxymethyl amide, fatty acid ester amide and other monoamides; methylene bis stearamide, ethyl bis lauramide, stretch Ethyl dihydroxy fatty acid (carbon number C6 to 24 in fatty acid) amide, ethylenyl dihydroxy stearamide, saturated fatty bisamide, methylenebisoleamide, unsaturated fatty bisamide, m-xylene Bisamides such as bis-stearamide and aromatic bisamide; saturated fatty polyamide, unsaturated fatty polyamide, aromatic polyamide, 1,2,3-propanetricarboxylic acid tris(2-methyl) Cyclohexylamide), cyclic amide oligomers, acyclic amide oligomers and other polyamides.

The aforementioned cyclic amide oligomers can be exemplified: dicarboxylic acid and diamine are condensed into cyclic amide oligomers, tricarboxylic acid and diamine are condensed into cyclic amide oligomers, dicarboxylic acid Polycondensation with triamine to form cyclic amide oligomers, polycondensation of tricarboxylic acid and triamine to form cyclic amide oligomers, polycondensation of dicarboxylic acid and tricarboxylic acid with diamine to form cyclic amide Amine oligomers, polycondensation of dicarboxylic acids and tricarboxylic acids and triamines into cyclic amide oligomers, polycondensation of dicarboxylic acids with diamines and triamines into cyclic amide oligomers, tricarboxylic Acids and diamines and triamines are polycondensed into cyclic amide oligomers, dicarboxylic acids and tricarboxylic acids are polycondensed with diamines and triamines into cyclic amide oligomers, etc.

In addition, the above-mentioned acyclic amide oligomers include polycondensation of monocarboxylic acid and diamine and/or triamine into acyclic amide oligomer, dicarboxylic acid and/or tricarboxylic acid and monocarboxylic acid Polycondensation of amines to acyclic amides Amine oligomers, etc. In the case of an amide oligomer containing monocarboxylic acid or monoamine, the monocarboxylic acid and monoamine function as terminal molecules and become an acyclic amide oligomer with reduced molecular weight. In addition, when the acyclic amide oligomer is polycondensed with dicarboxylic acid and/or tricarboxylic acid and diamine and/or triamine to form an acyclic amide compound, it becomes an acyclic polymer A amide polymer. Furthermore, the acyclic amide oligomer also includes the condensed monocarboxylic acid and monoamine to form an acyclic amide oligomer.

Sorbitol-based thixotropic agents include, for example, dibenzylidene-D-sorbitol, bis(4-methylbenzylidene)-D-sorbitol, (D-)sorbitol, monobenzylidene (-D-)sorbitol, mono(4-methylbenzylidene)-(D-)sorbitol, etc.

In the flux used in the solder paste of this embodiment, one or more than two thixotropic agents can be used.

Among the above, the thixotropic agent preferably contains at least one selected from the group consisting of ester-based thixotropes, amide-based thixotropes, and sorbitol-based thixotropes. The ester-based thixotropic agent preferably contains at least one selected from the group consisting of hydrogenated castor oil and ethyl myristate.

The amide-based thixotropic agent preferably contains at least one selected from the group consisting of bisamide and monoamide.

The amide-based thixotropic agent preferably contains at least one selected from the group consisting of 4-methylbenzamide and ethylenyl bishydroxystearyl amide, and is particularly preferably containing ethylenyl bishydroxystearyl Amide.

The sorbitol-based thixotropic agent preferably contains at least one selected from the group consisting of bis(4-methylbenzylidene) sorbitol and dibenzylidene sorbitol, and is especially preferred to contain bis(4-methylbenzylidene) sorbitol. methylbenzylidene) sorbitol.

The total content of the thixotropic agents in the flux is preferably from 4.0% by mass to 20.0% by mass, more preferably from 6.0% by mass to 13.0% by mass, relative to the total amount of the flux (100% by mass). More preferably, it is 6.0 mass % or more and 10.0 mass % or less.

The content of the ester-based thixotropic agent in the flux is preferably from 1.0% by mass to 15.0% by mass, more preferably from 2.0% by mass to 10.0% by mass, relative to the total amount of the flux (100% by mass). , more preferably not less than 3.0% by mass and not more than 7.0% by mass.

The content of the amide-based thixotropic agent in the flux is preferably from 0% by mass to 5.0% by mass, more preferably from 2.0% by mass to 3.0% by mass relative to the total amount of the flux (100% by mass). the following.

The content of the sorbitol-based thixotropic agent in the flux is preferably from 0% by mass to 5% by mass, particularly preferably from 1.0% by mass to 3.0% by mass, relative to the total amount of the flux (100% by mass). the following.

"Solvent"

A solvent can be used individually by 1 type or in mixture of 2 or more types.

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

Alcohol-based solvents include, for example, isopropyl alcohol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, 2,2-dimethyl -1,3-propanediol, 2,5-dimethyl-2,5-hexanediol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,3-dimethyl -2,3-butanediol, 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, 1,4-cyclohexanedimethanol, 2,4,7,9-tetramethyl- 5-decyne-4,7-diol, etc.

Glycol ether solvents include, for example: diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, diethylene glycol monohexyl ether (hexyl diglycol) (Hexyl Diglycol (Diethylene Glycol Monohexyl Ether) )), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl tripropylene glycol, butyl tripropylene glycol, triethylene glycol butyl methyl ether, tetraethylene glycol dimethyl ether, etc.

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

The aforementioned glycol ether solvent preferably contains hexyldiglycol.

The total content of the solvents in the flux is preferably from 30% by mass to 60% by mass, particularly preferably from 33% by mass to 50% by mass, relative to the total amount of the flux (100% by mass).

"Organic Acids with a Carbon Number of 5 or Less"

The flux used in the solder paste of this embodiment does not contain organic acids with a carbon number of 5 or less.

Examples of organic acids having 5 or less carbon atoms include monocarboxylic acids having 5 or less carbon atoms; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, and diglycolic acid; and the like.

"Other Ingredients"

The soldering flux of this embodiment may contain other components as required, 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 inactivators, surfactants, silane coupling agents, antioxidants, colorants, and the like.

Examples of activators other than halogen-based activators include organic acid-based activators, amine-based activators, organophosphorus compounds, and the like.

Organic acid active agent:

The organic acid-based active agent may contain an organic acid having 6 or more carbon atoms. Organic acids having 6 or more carbon atoms include, for example, adipic acid, azelaic acid, eicosanoic diacid, salicylic acid, dipicolinic acid, dibutylaniline diglycolic acid, Suberic acid, sebacic acid, terephthalic acid, dodecanedioic acid, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, lauric acid, Benzoic acid, tartaric acid, tris(2-carboxyethyl) isocyanurate, 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-Quinoline Carboxylic Acid (2-Quinoline Carboxylic Acid), 3-hydroxybenzoic acid, p-anisic acid (p-Anisic Acid), Stearic Acid, 12-Hydroxystearic Acid, Oleic Acid, Linoleic Acid, Linolenic Acid, Myristic Acid, Palmitic Acid, Pimelic Acid Acid), Caproic Acid, Enanthic Acid, Caprylic Acid, Pelargonic Acid, Isononanoic Acid, Capric Acid, Caproleic Acid, Decenoic Acid Monoacid, Lauric Acid, Linderic Acid, Tridecanoic Acid, Myristoleic Acid, Pentadecanoic Acid, Isopalmitic Acid, Palmitoleic Acid, 6,10,14-Deca Hiragoic Acid, Hydnocarpic Acid, Margarine, Isostearic Acid, Elaidic Acid, Petroselinic Acid, 4,8,12, 15-Octadecatetraenoic Acid (Moroctic Acid), Oleostearic Acid (Eleostearic Acid), Tariric Acid (Tariric Acid), Tauric Acid (Vaccenic Acid), Ricinoleic Acid (Ricinoleic Acid), Vernochric Acid ( Vernolic Acid), Sterculic Acid, Nonadecanoic Acid, Eicosic Acid, Dimer Acid, Trimer Acid, Hydrogenated Dimer Acid, which is hydrogenated dimer acid, Hydrogen is added to the hydride of trimer acid, that is, hydrogenated trimer acid and the like.

Dimer acid and trimer acid include, for example, dimer acid which is a reactant of oleic acid and linolenic acid, trimer acid which is a reactant of oleic acid and linolenic acid, and acrylic acid which are reactants dimer acid of acrylic acid, trimer acid of acrylic acid reactant, dimer acid of methacrylic acid reactant, trimer acid of methacrylic acid reactant, acrylic acid and methacrylic acid Dimer acid of reactant, trimer acid of reactant of acrylic acid and methacrylic acid, dimer acid of reactant of oleic acid, trimer acid of reactant of oleic acid, linseed oil Dimer acids which are reactants of linoleic acid, trimer acids which are reactants of linolenic acid, dimer acids which are reactants of linolenic acid, which are Trimer acid of reactant of linolenic acid, dimer acid of reactant of acrylic acid and oleic acid, trimer acid of reactant of acrylic acid and oleic acid, reactant of acrylic acid and linoleic acid dimer acid of acrylic acid and linolenic acid, trimer acid of acrylic acid and linolenic acid, dimer acid of acrylic acid and linolenic acid, trimer of acrylic acid and linolenic acid Dimer acid, a dimer acid that is a reactant of methacrylic acid and oleic acid, a trimer acid that is a reactant of methacrylic acid and oleic acid, a dimer that is a reactant of methacrylic acid and linolenic acid acid, trimer acid which is the reactant of methacrylic acid and linolenic acid, dimer acid which is the reactant of methacrylic acid and linolenic acid, and which is the reactant of methacrylic acid and linolenic acid Trimer acid, dimer acid which is the reactant of oleic acid and linolenic acid, trimer acid which is the reactant of oleic acid and linolenic acid, which belongs to the reaction of linoleic acid and linolenic acid The dimer acid of the substance, the trimer acid belonging to the reactant of linoleic acid and linoleic acid, the hydrogenated dimer acid belonging to the hydrogenated product of the above-mentioned dimer acids, and the trimer acid belonging to the above-mentioned trimer acids Hydrogenated trimer acids of hydrides, etc.

For example, the dimer which is the reactant of oleic acid and linolenic acid is a dimer with 36 carbon atoms. In addition, the trimer, which is a reactant of oleic acid and linolenic acid, is a trimer with 54 carbon atoms.

The organic acid-based activating agent can be used alone or in combination of two or more. The organic acid active agent is preferably composed of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimer acid, myristic acid, palmitic acid and 12-hydroxystearic acid At least one of the group, especially 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 from 0% by mass to 10% by mass, more preferably from 0% by mass to 5% by mass, relative to the total amount of the flux (100% by mass), More preferably, it is 0.5 mass % or more and 2.0 mass % or less.

Amine active agent:

Amine-based activators include, for example, 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-undeca imidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1' )]-ethyl-symmetric triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-symmetric triazine, 2,4-diamino -6-[2'-Ethyl-4'-methylimidazolyl-(1')]-ethyl-symmetric triazine, 2,4-diamino-6-[2'-methylimidazolyl- (1')]-Ethyl-symmetric 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 chloride -3-Benzyl imidazolium, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-symmetric triazine, 2,4-diamino-6- Vinyl-symmetric triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloxyethyl-symmetric triazine, epoxy imidazole adduct, 2-methyl Benzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl) Benzimidazole, benzimidazole, 1,2,4-triazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-th Tributyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-pentylphenyl)benzotriazole, 2 -(2'-Hydroxy-5'-tertoctylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tertiary octylphenol], 6-(2-benzotriazolyl)-4-tertoctyl-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-benzo Triazol-1-yl)methyl]imino]bisethanol, 1-(1',2'-dicarboxyethyl)benzotriazole, 1-(2,3-dicarboxypropyl)benzo Triazole, 1-[(2-ethylhexylamino)methyl]benzotriazole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol , 5-methylbenzotriazole, 5-phenyltetrazole and other azole compounds;

Guanidine compounds such as diphenylguanidine and xylylguanidine, etc.

The amine-based activating agent may be used alone or in combination of two or more.

The amine active agent preferably contains cyclohexylamine, hexadecylamine, stearylamine, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, 2-phenylimidazole, At least one selected from the group consisting of 1,2,4-triazole and xylylguanidine.

The content of the amine-based activator in the flux is preferably from 0% by mass to 30% by mass, particularly preferably from 0.5% by mass to 20% by mass, relative to the total amount of the flux (100% by mass).

Organophosphorus compounds:

As an organic phosphorus compound, an acidic phosphoric acid ester, an acidic phosphonic acid ester, an acidic phosphinate, etc. are mentioned, for example.

Examples of acidic phosphates include: methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, monobutyl acid phosphate, butyl acid phosphate, dibutyl acid phosphate, butyl acid phosphate Oxyethyl ester, 2-ethylhexyl acid phosphate, bis(2-ethylhexyl) phosphate, monoisodecyl acid phosphate, diisodecyl acid phosphate, lauryl acid phosphate, acid Isotridecyl Phosphate, Stearyl Acid Phosphate, Oleyl Acid Phosphate, Tallow Phosphate, Coconut Oil Phosphate, Isostearyl Acid Phosphate, Alkyl Acid Phosphate, Tetradecyl Acid Phosphate Ester, Glycol Acid Phosphate, 2-Hydroxyethyl Methacrylate Acid Phosphate, Dibutyl Pyrophosphate Acid Phosphate, etc.

Examples of acidic phosphonates include: 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, n-decyl (n-decyl) phosphonate, n-butyl Alkyl (n-butyl) phosphonate, isodecyl (isodecyl) phosphonate and other alkyl (alkyl) phosphonate; diethyl (p-methylbenzyl) phosphonate, etc.

As acidic phosphinate, a phenyl-substituted phosphinic acid etc. are mentioned, for example. Examples of the phenyl substituted phosphinic acid include phenylphosphinic acid and diphenylphosphinic acid.

An organophosphorus compound can be used individually by 1 type or in mixture of 2 or more types. The organophosphorus compound is preferably selected from the group consisting of monoisodecyl acid phosphate, diisodecyl acid phosphate, 2-ethylhexyl (2-ethylhexyl) phosphonate and phenylphosphinic acid At least one of the groups.

The total content of the organophosphorus compounds in the flux is preferably from 0% by mass to 5.0% by mass, particularly preferably from 0.3% by mass to 0.5% by mass, relative to the total amount of the flux (100% by mass).

Resin components other than rosin-based resins:

Examples of resin components other than rosin-based resins include terpene resins, modified terpene resins, terpene phenol resins, modified terpene phenol resins, styrene resins, modified styrene resins, xylene resins, and modified xylene resins. resin, acrylic resin, polyethylene resin, acrylic-polyethylene copolymer resin, epoxy resin, etc.

Modified terpene resins include, for example, aromatic modified terpene resins, hydrogenated terpene resins, hydrogenated aromatic modified terpene resins, and the like. As modified terpene phenol resin, hydrogenated terpene phenol resin etc. are mentioned, for example. Modified styrene resins include, for example, styrene acrylic resins, styrene maleic acid resins, and the like. Examples of modified xylene resins include phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified phenolic novolak-type xylene resins, and polyol-modified xylene resins. , Polyoxyethylene plus xylene resin, etc.

Metal Inactivator:

As a metal inactivator, a hindered phenol compound, a nitrogen compound, etc. are mentioned, for example. When the flux contains any one of the hindered phenolic compound and the nitrogen compound, it is easy to increase the thickening suppression effect of the solder paste.

The term "metal deactivator" here refers to a compound that has the ability to prevent metal from deteriorating due to contact with a certain compound.

The hindered phenolic compound refers to a phenolic compound having an expanded substituent (such as a branched or cyclic alkyl group such as tertiary butyl group) on at least one of the ortho positions of the phenol.

The hindered phenolic compound is not particularly limited, and examples thereof include bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenebis(oxyethylene)], N ,N'-hexamethylenebis[3-(3,5-di(tert-butyl)-4-hydroxyphenyl)propanamide], 1,6-hexanediol bis[3-(3,5 -di(tert-butyl)-4-hydroxyphenyl)propionate], 2,2'-methylenebis[6-(1-methylcyclohexyl)-p-cresol], 2,2'-methylene Methylene bis(6-tert-butyl p-cresol), 2,2'-methylenebis(6-tert-butyl-4-ethylphenol), triethylene glycol-bis[3-(3-th Tributyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis-[3-(3,5-di(tert-butyl)-4-hydroxybenzene base) propionate], 2,4-bis-(n-octylthio)-6-(4-hydroxy-3,5-di(tert-butyl)anilino)-1,3,5-triazine , Neopentylthritol-tetrakis[3-(3,5-di(tert-butyl)-4-hydroxyphenyl)propionate], 2,2-thio-diethylenebis[3-(3 ,5-bis(tert-butyl)-4-hydroxyphenyl)propionate], octadecyl-3-(3,5-di(tert-butyl)-4-hydroxyphenyl)propionate , N,N'-hexamethylenebis(3,5-bis(tert-butyl)-4-hydroxy-hydrocinnamic amide), 3,5-bis(tert-butyl)-4-hydroxybenzyl Phosphonate-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]oxamidide, compounds represented by the following chemical formula, etc. .

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

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

The hydrazine-based nitrogen compound may be any nitrogen compound having a hydrazine skeleton, such as dodecanedioic acid bis[N2-(2-hydroxybenzoyl)hydrazine], N,N'-bis[3- (3,5-bis(tertiary butyl)-4-hydroxyphenyl)propionyl]hydrazine, decane dicarboxylic acid disulfisylhydrazine, N-salicylidene-N'-salidylhydrazine, m-nitrogen Diphenylhydrazine, 3-aminophthalhydrazine, dihydrazine phthalate, hydrazine adipate, oxalylbis(2-hydroxy-5-octylbenzylidenehydrazine) , N'-benzoylpyrrolidone carboxylic acid hydrazine, N,N'-bis(3-(3,5-bis(tertiary butyl)-4-hydroxyphenyl)propionyl)hydrazine, etc. .

As long as the amide-based nitrogen compound is a nitrogen compound having an amide skeleton, examples include: N,N'-bis{2-[3-(3,5-bis(tert-butyl)-4-hydroxyphenyl ) propionyloxy] ethyl} oxalamide, etc.

The triazole nitrogen compound may be any nitrogen compound as long as it has a triazole skeleton, and examples thereof include N-(2H-1,2,4-triazol-5-yl)salimidamide, 3-amino-1,2 , 4-triazole, 3-(N-salicyloyl)amino-1,2,4-triazole, etc.

The melamine-based nitrogen compound should just be a nitrogen compound having a melamine skeleton, and examples thereof include melamine, melamine derivatives, and the like. More specifically, for example, triaminotriazine, alkylated triaminotriazine, alkoxyalkylated triaminetriazine, melamine, alkylated melamine, alkoxyalkylated melamine , N2-butyl melamine, N2, N2-diethyl melamine, N, N, N', N', N", N"-hexa(methoxymethyl) melamine, etc.

The metal inactivator preferably contains bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoic acid][ethylenylbis(oxyethylene)]. The content of the metal inactivator is preferably from 0% by mass to 10.0% by mass relative to the total amount of the flux (100% by mass), particularly preferably from 0.6% by mass to 3.0% by mass.

Surfactant:

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

Examples of nonionic surfactants include polyethylene glycol, polyethylene glycol-polypropylene glycol copolymers, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyol polyoxyethylene adducts.

Weak cationic surfactants include, for example: terminal diamine polyethylene glycol, terminal diamine polyethylene glycol-polypropylene glycol copolymer, aliphatic amine polyoxyethylene adducts, aromatic amine polyoxyethylene adducts , Polyamine polyoxyethylene adduct.

Surfactants other than those mentioned above include, for example, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkyl Amines, polyoxyalkylene alkylamides, etc.

Flux content in solder paste:

The content of the flux in the solder paste of this embodiment is preferably 5 to 95% by mass, more preferably 5 to 50% by mass, more preferably 5 to 15% by mass relative to the total mass (100% by mass) of the solder paste. quality%.

When the content of the flux in the solder paste is within this range, the effect of suppressing the increase in viscosity due to the solder powder is fully exhibited. In addition, it is easy to achieve the effect of the composition of the flux, that is, soldering with less generation of voids.

The solder paste of this embodiment can be manufactured by the general manufacturing method in this industry.

A solder paste can be obtained by heating and mixing the prepared components constituting the above-mentioned flux to prepare a flux, and then stirring and mixing the above-mentioned solder powder into the flux. In addition, in anticipation of the effect of suppressing thickening over time, zirconia powder other than the above-mentioned solder powder may be further formulated.

As explained above, in the solder paste of this embodiment, solder powder composed of a solder alloy is used. The solder powder has an alloy composition mainly composed of Sn and has a low dose of α radiation. In a solder paste that combines this solder powder and a specific flux, it is less likely to cause changes over time such as an increase in viscosity, and the occurrence of soft errors can be suppressed. In addition, according to the solder paste of this embodiment, the wettability of the solder can be further improved by selecting the ingredients formulated in the flux.

In general, in a solder alloy, each constituent element constituting the solder alloy does not function independently, and various effects can be exhibited only when the content of each constituent element is within a predetermined range. According to the solder alloy of the embodiment described above, the occurrence of soft errors can be suppressed by setting the content of each constituent element within the above-mentioned range. That is, the solder alloy of this embodiment can be used as a target low- α- ray dose material, and by being suitable for the formation of solder bumps around the memory, the generation of soft errors can be suppressed.

In addition, in the present embodiment, the effect of suppressing the thickening of the solder paste over time can be further improved by using a solder alloy in which As is not actively added but A solder alloy containing Ni and Fe, a refractory metal that is heated at a high temperature during refining or processing of base metals, in a specific ratio.

The reason why this effect is obtained is not yet clear, but it is presumed as follows.

The Sn used for solder alloys with low α- ray dose is of extremely high purity, and when the molten alloy is solidified, the crystal size of Sn will increase. In addition, the oxide film in the Sn also forms a sparse oxide film corresponding to this situation. Therefore, by adding high-melting-point metals Ni and Fe to reduce the crystal size and form a compact oxide film, the reactivity between the alloy and the flux is suppressed, and thus the viscosity of the solder paste over time can be suppressed.

[Example]

The following examples illustrate the present invention, but the present invention is not limited to the following examples.

In this example, unless otherwise specified, "ppb" in relation to the composition of the solder alloy is "ppb by mass", "ppm" is "ppm by mass", and "%" is "% by mass".

<Production of Solder Alloy>

(Manufacturing examples 1 to 312)

The raw material metals were melted and stirred to prepare solder alloys having the alloy compositions shown in Tables 1 to 14, respectively.

Sn-3.0Ag-0.5Cu Alloy: Manufacturing Examples 1 to 4

Sn Alloy: Manufacturing Examples 5 to 8

Sn-0.7Cu alloy: Manufacturing Examples 9 to 12

Sn-4.0Ag 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: Manufacturing 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 evaluation of the α-ray dose was performed in the following manner. The evaluation results are shown in Tables 1 to 14.

[ Alpha ray dose]

(1) Verification method 1

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

As the measurement sample, solder alloy flakes immediately after manufacture were used.

This solder alloy sheet was produced by melting the solder alloy immediately after production and forming it into a sheet with an area of 900 cm ² on one side.

The measurement sample was placed in an α- ray dosimeter, and PR-10 gas was allowed to flow for 12 hours, and the α- ray dose was measured for 72 hours after standing still.

(2) Judgment criteria 1

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

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

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

If this judgment is "○○" or "○", it can be called a welding material with low α radiation dose.

(3) Verification method 2

Except for changing the measurement sample, the measurement of the α -ray dose is carried out in the same manner as in the verification method 1 of (1) above.

The measurement sample is used: For the solder alloy sheet which is melted and formed into a thin sheet with an area of 900cm ² on one side, it is heated at 100°C for 1 hour and left to cool.

(4) Judgment criteria 2

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

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

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

If this judgment is "○○" or "○", it can be called a welding material with low α radiation dose.

(5) Verification method 3

Store the solder alloy sheet of the measurement sample after measuring the α -ray dose in the verification method 1 of the above (1) for one year, then follow the above-mentioned steps (i), (ii) and (iii) to measure the α -ray dose again, and evaluate Time-dependent changes in the dose of α- rays.

(6) Criterion 3

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

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

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

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

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

[Table 10]

[Table 11]

[Table 12]

[Table 13]

[Table 14]

As shown in Tables 1 to 13, the evaluation of the α- ray dose was carried out for each of the solder alloys of Production Examples 1 to 312. As a result, it was confirmed that in the solder alloys of Production Examples 1 to 312, the solder alloy sheet immediately after production, and The judgment results of the solder alloy flakes after heat treatment at 100°C for 1 hour and the solder alloy flakes after one year of storage were both "○○".

On the other hand, as a result of evaluating the α- ray dose for each of the solder alloys of Production Examples 313 to 320, it was confirmed that in the solder alloys of Production Examples 313 to 320, 100°C was performed on the solder alloy sheet immediately after production. The results of the judgment of the solder alloy flake after heat treatment for 1 hour and the solder alloy flake after one year of storage were both "×".

<Manufacturing of solder powder>

The solder alloys of each production example were melted, and solder powders containing solder alloys having the alloy compositions shown in Table 1 to Table 13 and having an average particle diameter of 6 μm were produced by an atomization method. particle swarmers.

In addition, for the solder alloys of Production Examples 1 to 4 and Production Examples 239 to 312, the solder alloys of each Production Example were melted, and solder powder was produced by an atomization method. Solder alloys having the alloy compositions shown in 11 to 13, and containing solder alloy particle groups with an average particle diameter of 4 μm.

<Preparation of Flux>

(Modulation examples 1 to 55)

Resin components are used: polymerized rosin, acrylic-modified hydrogenated rosin, acrylic-modified rosin, heterogeneous rosin, hydrogenated rosin, hydrogenated rosin methyl ester.

The solvent system uses terpineol and hexyl diglycol.

Organic acid-based active agents used: adipic acid, sebacic acid, dimer acid (36 carbons), hydrogenated dimer acid (36 carbons), trimer acid (54 carbons), myristic acid , palmitic acid, 12-hydroxystearic acid, diglycolic acid, succinic acid, glutaric acid.

Halogen-based activators are used: trans-2,3-dibromo-2-butene-1,4-diol, tris(2,3-dibromopropyl) isocyanurate, cyclohexylamine hydrogen Bromate, Cetylamine Hydrobromide, Stearylamine Hydrobromide, Cyclohexylamine Tetrafluoroborate, Ethylamine Hydrobromide, Diphenylguanidine Hydrobromide, Ethylamine Hydrochloride.

Amine-based active agents are used: cyclohexylamine, hexadecylamine, stearylamine, N,N,N',N'-tetra(2-hydroxypropyl)ethylenediamine, 2-phenylimidazole, 1,2 , 4-triazole, xylylguanidine. Organophosphorus compounds are used: 2-ethylhexyl (2-ethylhexyl) phosphonate, phenylphosphinic acid, (mono/di) isodecyl acid phosphate.

The metal inactivating agent is used: bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylenylbis(oxyethylene)].

The thixotropic agent is used: hydrogenated castor oil, ethyl myristate, 4-methylbenzamide, ethylenyl bishydroxystearamide, bis(4-methylbenzylidene) sorbitol, di benzylidene sorbitol.

〈Manufacturing of solder paste〉

(Example 1 to 45)

The fluxes of Preparation Examples 1 to 3, Preparation Examples 14 to 55, and solder powders containing the solder alloys of Preparation Examples 1 to 4 and containing solder alloy particle groups with an average particle diameter of 6 μm were mixed to manufacture Solder Pastes of Examples 1 to 45.

The mixing ratio of flux and solder powder is set as flux:solder powder=11:89 in terms of mass ratio.

(Example 46)

Each of the fluxes of Preparation Examples 1 to 3 and Preparation Examples 14 to 55, and the solder powder containing each of the solder alloys of Preparation Examples 1 to 4 and containing a solder alloy particle group with an average particle diameter of 6 μm were mixed to manufacture Solder paste of Example 46.

The mixing ratio of flux and solder powder is set as flux:solder powder=35:65 in terms of mass ratio.

(Example 47)

The fluxes of Preparation Examples 1 to 3 and Preparation Examples 14 to 55, and the solder powders containing the solder alloys of Preparation Examples 5 to 8 and containing solder alloy particle groups with an average particle diameter of 6 μm were mixed to obtain The solder paste of Example 47 was produced.

The mixing ratio of flux and solder powder is set as flux:solder powder=11:89 in terms of 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 in 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 in 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 in 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 in 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 in 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 in Production Examples 239 to 312.

(Example 54)

Manufacture: each mixed solder powder containing each of the solder alloys of Manufacture Examples 1 to 4, and simultaneously having two types of solder alloy particle groups with different average particle diameters.

Specifically, each solder alloy particle group (S1a) including the solder alloys of Production Examples 1 to 4 and having an average particle diameter of 6 μm , and the solder alloys of Production Examples 1 to 4 and having an average particle diameter of 4 μm Each solder alloy particle group (S2a) of m was mixed at a mass ratio (S1a)/(S2a)=50/50 to obtain each mixed solder powder.

Next, each flux and each mixed solder powder of Preparation Examples 1 to 55 were mixed to manufacture each solder paste.

The mixing ratio of flux and the total amount of mixed solder powder is set as flux:mixed solder powder=11:89 in terms of mass ratio.

(Example 55)

Each solder paste was produced in the same manner as in Example 54, except that the respective solder alloys used as the material of the respective mixed solder powders in Example 54 were changed to the respective solder alloys of Production Examples 239 to 312.

<Evaluate>

Evaluation of wettability (wetting speed of solder) was performed for the aforementioned flux.

In addition, each evaluation of viscosity increase inhibition was performed for the aforementioned solder pastes.

In addition, aggregate evaluations are made from the results of these evaluations.

The details are as follows. The evaluation results are shown in Tables 15 to 30.

[Wettability (wetting speed of solder)]

(1) Verification method

The evaluation test of wettability (wetting speed of solder) was performed in the following manner.

According to the method of Meniscograph Test, a copper plate with a width of 5 mm x a length of 25 mm x a thickness of 0.5 mm is used as a test plate and a Solder Checker SAT-5200 (manufactured by RHESCA) as a test device, and an alloy with A solder alloy composed of Sn-3Ag-0.5Cu (each numerical value is mass %; the remainder is Sn) was evaluated in the following manner.

First, the test board was immersed in the flux of each example measured in the beaker so that the depth of immersion would be about 10 mm, and the flux was applied to the test board. Next, after coating the flux, the test board coated with the flux was quickly dipped in a solder bath having the solder alloy of the aforementioned alloy composition to obtain the zero crossing time (sec).

Next, the flux of each example was measured 5 times, and the average value of the zero-cross time (sec) of 5 obtained was calculated. The test conditions were set as follows.

Dipping speed into the solder tank: 20mm/sec (JIS Z 3198-4: 2014)

Immersion depth into the solder tank: 5mm (JIS Z 3198-4: 2014)

Dipping time into the solder tank: 10sec (JIS Z 3198-4: 2014)

Solder bath temperature: 280°C (JIS C 60068-2-69: 2019 Appendix B)

The shorter the average value of zero crossing time (sec), the faster the wetting speed, which means better solder wettability.

(2) Judgment criteria

◯: The average value of the zero cross time (sec) is 2 seconds or less.

×: The average value of the zero cross time (sec) exceeds 2 seconds.

[Viscosity inhibition]

(1) Verification method

For the solder paste immediately after production, the viscosity was measured for 12 hours at a rotation speed of 10 rpm, 25° C., and in air using PCU-205 manufactured by Malcom Co., Ltd.

(2) Judgment criteria

◯: The viscosity after 12 hours is 1.2 times or less than the viscosity at 30 minutes immediately after preparation of the solder paste.

×: The viscosity after 12 hours is more than 1.2 times the viscosity when 30 minutes have elapsed immediately after preparation of the solder paste.

When this judgment is "◯", it can be said that a sufficient thickening inhibitory effect was obtained. That is, the increase in viscosity of the solder paste over time can be suppressed.

[Total evaluation]

○: In Tables 15 to 30, each evaluation of wettability and thickening inhibition is ○.

×: In Tables 15 to 30, at least one of the evaluations of wettability and inhibition of thickening was ×.

[Table 15]

[Table 16]

[Table 17]

[Table 18]

[Table 19]

[Table 20]

[Table 21]

[Table 22]

[Table 23]

[Table 24]

[Table 25]

[Table 26]

[Table 27]

[Table 28]

[Table 29]

[Table 30]

The wetting speed of the flux of the solder pastes of Examples 1 to 55 is sufficient, and the effect of suppressing thickening is 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.

In addition, although the solder pastes of Comparative Examples 5 to 8 contained an organic acid having 6 or more carbon atoms, they contained an organic acid having 5 or less carbon atoms, so the effect of suppressing thickening was insufficient.

In addition, since the content of the halogen-based activator in the solder pastes of Comparative Examples 9 and 10 was less than 0.1% by mass relative to the total amount of the flux, the wetting speed of the flux was insufficient.

Compared the solder pastes of Examples 50 to 53 and 55 with the solder pastes of Examples 1 to 49, the viscosity of each solder paste 12 hours after the start of viscosity measurement was compared with the viscosity of each solder paste 30 minutes after preparation. ratio is lower. That is, the solder pastes of Examples 50 to 53 and 55 are superior in the thickening suppression effect compared to the solder pastes of Examples 1 to 49.

[Industrial Applicability]

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

Claims (24)

A solder paste consisting of solder powder and flux. The solder powder is composed of a solder alloy. The solder alloy has an alloy composition composed of the following: 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 at least one of Ni: 0 mass ppm to 600 mass ppm and Fe: 0 mass ppm to 100 mass ppm, and Sn in the remainder; In addition, the solder alloy has an α-ray dose of 0.02 cph/cm ² or less; the aforementioned solder powder is composed of solder alloy particles with an average particle size of 0.1 to 15 μm, and the aforementioned flux contains: a halogen-based activator, rosin, shaker Modifiers and solvents; the aforementioned flux does not contain organic acids with carbon numbers of 5 or less, the content of the aforementioned flux is 5 to 95% by mass relative to 100% by mass of the total mass of the aforementioned solder paste, and the content of the aforementioned halogen-based active agent is relatively When the total amount of the aforementioned flux is 0.1 mass % to 4 mass %, the aforementioned alloy composition satisfies the following (1) formula; The unit of content in the aforementioned alloy composition is ppm by mass. A solder paste consisting of solder powder and flux. The solder powder is composed of a solder alloy. The solder alloy has an alloy composition composed of the following: 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 at least one of Ag: 0 mass % to 4 mass %, Cu: 0 mass % to 0.9 mass %, and Ni: 0 mass ppm 600 mass ppm or less and Fe: at least one of 0 mass ppm to 100 mass ppm, and Sn in the rest; and the solder alloy is α-ray dose of 0.02cph/cm ² or less; the aforementioned solder powder is composed of an average grain The flux is composed of solder alloy particles with a diameter of 0.1 to 15 μm. The aforementioned flux contains: a halogen-based activator, rosin, a thixotropic agent, and a solvent; the aforementioned flux does not contain organic acids with a carbon number of 5 or less. The content of the aforementioned flux 5 to 95% by mass relative to 100% by mass of the total mass of the solder paste, the content of the halogen-based activator relative to the total amount of the flux is 0.1% by mass to 4% by mass, and the alloy composition satisfies the following: 1) Formula; 20≦Ni+Fe≦700 (1) (1) In the formula, Ni and Fe respectively represent the content in the aforementioned alloy composition, and the unit is ppm by mass. A solder paste consisting of solder powder and flux. The solder powder is composed of a solder alloy. The solder alloy has an alloy composition composed of the following: 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 at least one of Bi: 0 mass % to 0.3 mass % and Sb: 0 mass % to 0.9 mass %, and Sn in the remainder; In addition, the solder alloy has an α-ray dose of 0.02 cph/cm ² or less; the solder powder is composed of solder alloy particles with an average particle size of 0.1 to 15 μm, and the solder flux contains: a halogen-based activator, rosin, shaker Modifiers and solvents; the aforementioned flux does not contain organic acids with a carbon number of 5 or less, the content of the aforementioned flux is 5 to 95% by mass relative to 100% by mass of the total mass of the aforementioned solder paste, and the content of the aforementioned halogen-based activator is relatively When the total amount of the aforementioned flux is 0.1 mass % to 4 mass %, the aforementioned alloy composition satisfies the following (2) formula; The unit of content in the aforementioned alloy composition is % by mass. A solder paste consisting of solder powder and flux. The solder powder is composed of a solder alloy. The solder alloy has an alloy composition composed of the following: 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 at least one of Ag: 0 mass % to 4 mass %, Cu: 0 mass % to 0.9 mass %, and Bi: 0 mass % % to 0.3 mass % and Sb: at least one of 0 mass % to 0.9 mass %, and the remaining part of Sn; and the solder alloy is the one whose α-ray dose is 0.02 cph/cm ² or less; the aforementioned solder powder is obtained by the average Composed of solder alloy particles with a particle size of 0.1 to 15 μm, the aforementioned flux contains: a halogen-based activator, rosin, a thixotropic agent, and a solvent; the aforementioned flux does not contain organic acids with a carbon number of 5 or less, and the aforementioned flux The content is 5 to 95% by mass relative to 100% by mass of the total mass of the solder paste, the content of the halogen-based activator is 0.1% by mass to 4% by mass relative to the total amount of the flux, and the alloy composition satisfies the following (2) formula; 0.03≦Bi+Sb≦1.2 (2) (2) In formula, Bi and Sb respectively represent the content in the said alloy composition, and the unit is mass %. The solder paste according to any one of claims 1 to 4, wherein the alloy composition is further such that Pb is less than 2 mass ppm. The solder paste according to any one of claims 1 to 4, wherein the alloy composition is further such that As is less than 2 mass ppm. The solder paste according to any one of Claims 1 to 4, wherein after heat-treating a sheet-shaped solder alloy sheet with a surface area of 900 cm ² at 100°C for 1 hour, the solder alloy The amount of α rays is 0.02cph/cm ² or less. The solder paste according to any one of claims 1 to 4, wherein the α-ray dose of the solder alloy is 0.002 cph/cm ² or less. The solder paste according to claim 8, wherein the amount of α rays of the aforementioned solder alloy is 0.001 cph/cm ² or less. The solder paste according to any one of claims 1 to 4, wherein the solder powder has at least two types of solder alloy particle groups with different average particle diameters. The solder paste according to any one of claims 1 to 4, wherein the halogen-based activator contains amine hydrohalide. The solder paste as described in claim item 11, wherein the aforementioned amine hydrohalides contain cyclohexylamine hydrobromide, hexadecylamine hydrobromide, stearylamine hydrobromide, cyclohexylamine tetrafluoro At least one selected from the group consisting of borate, ethylamine hydrobromide, diphenylguanidine hydrobromide and ethylamine hydrochloride. The solder paste according to claim 11, wherein the halogen-based activator further contains an organic halogen compound other than the amine hydrohalide. The solder paste according to any one of claims 1 to 4, wherein the rosin is selected from the group consisting of polymerized rosin, acrylic-modified hydrogenated rosin, acrylic-modified rosin, heterogeneous rosin and hydrogenated rosin At least one of the groups. The solder paste according to claim 14, wherein the aforementioned rosin further contains rosin ester, The aforementioned rosin ester contains hydrogenated rosin methyl ester. The solder paste according to any one of claims 1 to 4, wherein the flux further contains an organic acid having 6 or more carbon atoms. The solder paste according to claim 16, wherein the organic acid having 6 or more carbon atoms is selected from the group consisting of adipic acid, sebacic acid, dimer acid, hydrogenated dimer acid, trimer acid, myristic acid At least one selected from the group consisting of palmitic acid, palmitic acid and 12-hydroxystearic acid. The solder paste according to any one of Claims 1 to 4, wherein the thixotropic agent is selected from the group consisting of an ester-based thixotropic agent, an amide-based thixotropic agent, and a sorbitol-based thixotropic agent. at least one. The solder paste according to claim 18, wherein the ester-based thixotropic agent contains at least one selected from the group consisting of hydrogenated castor oil and ethyl myristate. The solder paste according to claim 18, wherein the amide-based thixotropic agent contains at least one selected from the group consisting of 4-methylbenzamide and ethylenyl bishydroxystearamide. The solder paste according to claim 18, wherein the sorbitol-based thixotropic agent contains at least A sort of. The solder paste according to any one of claims 1 to 4, wherein the soldering flux further contains an amine-based activator. The solder paste according to any one of claims 1 to 4, wherein the flux further contains an organic phosphorus compound. The solder paste according to any one of claims 1 to 4, wherein the flux further contains an antioxidant.