JP6880438B2 - Solder paste - Google Patents

Description

The present invention relates to solder paste.

Joining and assembling electronic components to the substrate of an electronic device is often performed by soldering with solder paste from the viewpoint of cost and reliability.

As a method of applying the solder paste to the substrate of an electronic device, for example, there is a method of using screen printing using a metal mask. In this case, it is necessary to appropriately adjust the viscosity of the solder paste in order to ensure the printability of the solder paste. However, the solder paste is inferior in storage stability, and as a result, the viscosity of the solder paste may increase over time.

Further, in the solder material forming the solder paste, the difference between the liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T S) increases, for example, the electronic device substrate When the solder paste is applied to the solder and solidified, the structure of the solder material tends to be non-uniform, and as a result, the reliability in the future may decrease.

Patent Document 1 discloses a solder paste containing a lead-free solder powder, a rosin-based resin, an activator, a solvent, and a hindered phenol-based compound. This document discloses that when a hindered phenol-based compound is combined with a lead-free solder powder, deterioration of the lead-free solder powder and the solder paste film during reflow can be prevented. This document discloses only an example using a lead-free solder powder having a composition of Sn: 96.5% by mass, Ag: 3.0% by mass, and Cu: 0.5% by mass.

JP-A-2002-283097

However, Patent Document 1 is not intended to suppress an increase in viscosity with time or to have excellent reliability. Therefore, a solder paste having both a thickening suppressing effect and reliability in a well-balanced manner is desired.

Therefore, an object of the present invention is to provide a solder paste that can achieve both a thickening suppressing effect and reliability in a well-balanced manner.

As a result of diligent research to solve the above problems, the present inventors have found that the solder paste is a solder paste composed of a solder material and a flux, and the solder material contains Sn or Sn-based alloy and Bi in a specific ratio. We have found that the above problems can be solved by containing a hindered phenolic compound in the flux, and have completed the present invention.

That is, the solder paste of the present invention is a solder paste composed of a solder material and a flux, and the solder material is a Sn or Sn-based alloy, As of 20 to 300 mass ppm, and 50 mass ppm to 3.0 mass. % Bi, and the flux contains a hindered phenolic compound.

According to the present invention, it is possible to provide a solder paste having both a thickening suppressing effect and reliability in a well-balanced manner.

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described. However, the present invention is not limited to this, and various modifications can be made without departing from the gist thereof.

As used herein, the term "thickness suppressing effect" refers to an effect of suppressing an increase in viscosity of the prepared solder paste over time when the solder paste is prepared.

In this specification, the content of each element can be measured by, for example, analyzing by ICP-AES in accordance with JIS Z 3910.

[Solder paste]
The solder paste of this embodiment is a solder paste composed of a solder material and a flux. The solder material contains Sn or Sn-based alloy, As of 20 to 300 mass ppm, and Bi of 50 mass ppm to 3.0 mass%. The flux contains a hindered phenolic compound. By providing the solder paste of the present embodiment with the above-mentioned structure, the thickening suppressing effect can be improved. Further, the solder material forming the solder paste of the present embodiment is provided with the configuration described above, the difference between the liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T _S ) can be reduced. Therefore, for example, even if the solder paste containing the solder material is applied to the substrate of an electronic device and solidified, the solder paste can maintain the uniformity of the structure of the solder material. As a result, the solder paste is excellent in reliability such as cycle characteristics. As described above, by providing the solder paste with the above structure, it is possible to achieve both the thickening suppressing effect and the reliability in a well-balanced manner.

(Solder material)
The solder material contains Sn or Sn-based alloys. Sn or Sn-based alloys may contain unavoidable impurities.

Sn may be, for example, Sn (3N material) having a purity of 99.9% or more, Sn (4N material) having a purity of 99.99% or more, and 99.999%. It may be Sn (5N material) having purity.

The Sn content may be, for example, 40% by mass or more, 50% by mass or more, 70% by mass or more, or 90% by mass or more with respect to the entire solder material. There may be.

As the Sn-based alloy, for example, it has a composition of Sn-Ag alloy, Sn-Cu alloy, Sn-Ag-Cu alloy, Sn-Ag-Cu-Ni-Co alloy, Sn-In alloy, Sn-Sb alloy and the like. Examples thereof include alloys and alloys having the above composition to which As, Ag, Cu, In, Ni, Co, Sb, Ge, P, Fe, Zn, Al, Ga and the like are added. The Sn content in the Sn-based alloy is not particularly limited, and can be, for example, more than 40% by mass.

The Sn and Sn-based alloys are preferably Sn, Sn—Cu alloys, or Sn—Ag—Cu alloys from the viewpoint of excellent reliability by reducing ΔT. From the same viewpoint, the Sn—Cu alloy preferably contains Cu in an amount of more than 0 and 1.0% by mass or less (preferably 0.5 to 1.0% by mass), and the balance is Sn. From the same point of view, the Sn-Ag-Cu alloy contains Ag of more than 0 and 3.5% by mass or less (preferably 1.0 to 3.5% by mass), more than 0 and 1.0% by mass. It is preferable that Cu is contained in an amount of% or less (preferably 0.1 to 1.0% by mass) and the balance is Sn.

The Ag content is preferably 0.05 to 3.5% by mass, preferably 0.1 to 3.0% by mass, based on the entire solder material, from the viewpoint of excellent reliability by reducing ΔT. Is more preferable, and 0.5 to 3.0% by mass is further preferable. Further, the Cu content is preferably 0.01 to 0.9% by mass, and 0.05 to 0.75% by mass, based on the entire solder material, from the viewpoint of excellent reliability by reducing ΔT. It is more preferably 0.1% by mass, and even more preferably 0.1 to 0.7% by mass. The preferable numerical ranges of the Ag and Cu contents are independent of each other, and the Ag and Cu contents can be determined independently.

The solder material contains 20 to 300 mass ppm of As. When the content of As is 20 mass ppm or more, the increase in viscosity is suppressed, and the effect of suppressing thickening is excellent. When the content of As is not more than 300 mass ppm, it can reduce the difference (ΔT = T _L -T _S) and the liquidus temperature (T _L) and the solidus temperature (T _S), the cycle characteristics, etc. Excellent in reliability. Therefore, when the As content is 20 to 300 mass ppm, the solder paste of the present embodiment can achieve both the thickening suppressing effect and the reliability in a well-balanced manner. From the same viewpoint, the content of As is preferably 30 to 250 mass ppm, more preferably 50 to 200 mass ppm, based on the entire solder material. As may be formed together with Sn or a Sn-based alloy (for example, an intermetallic compound or a solid solution), or may exist as a simple substance of As or an oxide separately from the Sn-based alloy.

The solder material contains 50% by mass (0.0050% by mass) to 3.0% by mass of Bi. When the Bi content is 50 mass ppm or more, the increase in viscosity is suppressed, and the effect of suppressing thickening is excellent. When the content of Bi is less than 3.0 wt%, can reduce the difference (ΔT = T _L -T _S) and the liquidus temperature (T _L) and the solidus temperature (T _S), Cycle Excellent reliability such as characteristics. Therefore, when the Bi content is 50% by mass to 3.0% by mass, the solder paste of the present embodiment can achieve both the thickening suppressing effect and the reliability in a well-balanced manner. From the same viewpoint, the Bi content is preferably 50% by mass (0.0050% by mass) to 1.0% by mass, and 100% by mass (0.010% by mass) with respect to the entire solder material. More preferably, it is ~ 1.0% by mass.

Bi may exist in the form of an alloy (for example, an intermetallic compound, a solid solution, etc.) together with Sn or a Sn-based alloy, or may exist separately from Sn and a Sn-based alloy.

The method for producing the solder material of the present embodiment is not particularly limited, and examples thereof include a method for producing the solder material by melting and mixing the raw material metal.

In the present embodiment, the form of the solder material is not particularly limited, and may be, for example, a particulate form such as a powder form (solder powder). From the viewpoint of excellent fluidity, the solder material is preferably in the form of particles, more preferably in the form of powder.

Examples of the method for producing the particulate solder material include a dropping method for obtaining particles by dropping a molten solder material, a spraying method for centrifugal spraying, and a method for crushing a bulk solder material. In the dropping method and the spraying method, the dropping and spraying are preferably carried out in an inert atmosphere or a solvent in order to form particles.

When the solder material is in the form of particles, the solder material has a size (particle size distribution) corresponding to symbols 1 to 8 in the powder size classification (Table 2) in JIS Z 3284-1: 20 14. It is more preferable to have a size (particle size distribution) corresponding to symbols 4 to 8, and it is further preferable to have a size (particle size distribution) corresponding to symbols 5 to 8. This enables soldering to fine parts.

[flux]
As used herein, the term "flux" refers to the entire components of the solder paste other than the solder material.

The flux contains a hindered phenolic compound as a metal inactivating agent. Since the flux contains a hindered phenolic compound, the solder material can improve the thickening suppressing effect.

The hindered phenolic compound refers to a phenolic compound having a bulky substituent (for example, a branched or cyclic alkyl group such as a t-butyl group) at at least one of the ortho positions of the phenol. The hindered phenolic compound is not particularly limited, and is, for example, bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [ethylenebis (oxyethylene)], N, N. '-Hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], 1,6-hexanediolbis [3- (3,5-di-tert-butyl-4) -Hydroxyphenyl) propionate], 2,2'-methylenebis [6- (1-methylcyclohexyl) -p-cresol], 2,2'-methylenebis (6-tert-butyl-p-cresol), 2,2' -Methylenebis (6-tert-butyl-4-ethylphenol), triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate], 1,6-hexanediol-bis -[3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6- (4-hydroxy-3,5-di-t-) Butylanilino) -1,3,5-triazine, pentaerythrityl-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,2-thio-diethylenebis [3-( 3,5-Di-tert-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N'-hexamethylenebis (3) , 5-Di-t-butyl-4-hydroxy-hydrocinnamamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate-diethyl ester, 1,3,5-trimethyl-2, Examples thereof include 4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene. These hindered phenolic compounds may be used alone or in combination of two or more.

The content of the hindered phenolic compound is preferably 0.5 to 10% by mass with respect to the total flux. When the content is 0.5% by mass or more, the solder paste can further improve the thickening suppressing effect. When the content is 10% by mass or less, the solder paste can further improve the solder wettability. From the same viewpoint, the content is more preferably 1.0 to 5.0% by mass, and further preferably 2.0 to 4.0% by mass.

The flux preferably contains a resin. The content of the resin may be, for example, 30 to 60% by mass with respect to the entire flux.

The resin is not particularly limited, and is, for example, a rosin-based resin, a (meth) acrylic-based resin, a urethane-based resin, a polyester-based resin, a phenoxy resin, a vinyl ether-based resin, a terpene resin, or a modified terpene resin (for example, an aromatic-modified terpene). Resin, hydrogenated terpene resin, hydrogenated aromatic modified terpene resin, etc.), terpene phenol resin, modified terpene phenol resin (for example, hydrogenated terpene phenol resin, etc.), styrene resin, modified styrene resin (for example, styrene acrylic resin, styrene). Maleine resin, etc.), xylene resin, modified xylene resin (for example, phenol-modified xylene resin, alkylphenol-modified xylene resin, phenol-modified resole-type xylene resin, polyol-modified xylene resin, polyoxyethylene-added xylene resin, etc.) and the like. These resins may be used alone or in combination of two or more. Among these, the resin is preferably one or more selected from the group consisting of rosin-based resins and (meth) acrylic-based resins. The term "(meth) acrylic resin" as used herein refers to a concept that includes a methacrylic resin and an acrylic resin.

Examples of the rosin-based resin include raw material rosins such as gum rosin, wood rosin, and tall oil rosin, and derivatives obtained from raw material rosins. Derivatives include, for example, purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin and α, β unsaturated carboxylic acid modified products (acrylic acid rosin), maleated rosin, fumarized rosin, etc.), and polymerized rosin Examples thereof include purified products, hydrogenated products and disproportionated products, and purified products, hydrogenated products and disproportionated products of α and β unsaturated carboxylic acid modified products. These rosin-based resins may be used alone or in combination of two or more.

The content of the rosin-based resin may be, for example, 30 to 60% by mass with respect to the entire flux.

Examples of the (meth) acrylic resin include homopolymers of (meth) acrylic monomers and copolymers of two or more types of (meth) acrylic monomers. Examples of the (meth) acrylic monomer include (meth) acrylic acid, itaconic acid, maleic acid, crotonic acid, methyl (meth) acrylic acid, ethyl (meth) acrylic acid, butyl (meth) acrylic acid, and (meth) acrylic acid. Hexil, propyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate , (Meta) tetradecyl acrylate, (meth) lauryl acrylate, stearyl (meth) acrylate and the like. These (meth) acrylic resins may be used alone or in combination of two or more.

By containing the (meth) acrylic resin in the resin, the temperature cycle reliability can be improved. When a repeated thermal stress of high temperature and low temperature is applied to the mounting portion or the joint portion, a highly crystalline material such as rosin may crack and absorb moisture from the crack. On the other hand, by including a soft (meth) acrylic resin in the resin, the above-mentioned cracks can be suppressed, and as a result, the temperature cycle reliability can be improved. The content of the (meth) acrylic resin is, for example, 0 to 40% by mass with respect to the entire flux, and is preferably 20 to 30% by mass from the viewpoint of excellent temperature cycle reliability. The content of the (meth) acrylic resin is, for example, 0 to 80% by mass with respect to the entire resin, and is preferably 30 to 80% by mass from the viewpoint of excellent temperature cycle reliability.

The flux may contain an organic acid-based activator (organic acid) in order to improve solderability. Organic acids include adipic acid, azelaic acid, eicosanic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, dibutylaniline diglycolic acid, suberic acid, sebacic acid, thioglycolic acid, terephthal Acid, dodecanedioic acid, parahydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris isocyanurate (2-carboxyethyl), glycine, 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- Kinolincarboxylic acid, 3-hydroxybenzoic acid, malic acid, p-anisic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, dimer acid, hydrogenated dimer acid, trimeric acid, hydrogenated trimmer Acids and the like can be mentioned.

The content of the organic acid may be, for example, 0 to 10% by mass with respect to the entire flux.

The flux may contain an amine-based activator (amine) in order to improve solderability. Examples of amines include amine aliphatic amines, aromatic amines, amino alcohols, imidazoles, benzotriazoles, amino acids, guanidines, hydrazides and the like. Examples of the aliphatic amine include dimethylamine, ethylamine, 1-aminopropane, isopropylamine, trimethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N, N-dimethylethylamine, isobutylamine and cyclohexyl. Amine and the like can be mentioned. Examples of the aromatic amine include aniline, N-methylaniline, diphenylamine, N-isopropylaniline, p-isopropylaniline and the like. Examples of amino alcohols include 2-aminoethanol, 2- (ethylamino) ethanol, diethanolamine, diisopropanolamine, triethanolamine, N-butyldiethanolamine, triisopropanolamine, N, N-bis (2-hydroxyethyl). -N-cyclohexylamine, N, N, N', N'-tetrax (2-hydroxypropyl) ethylenediamine, N, N, N', N'', N''-pentakis (2-hydroxypropyl) diethylenetriamine, etc. Can be mentioned. Examples of the imidazole include 2-methylimidazole, 2-undecyl imidazole, 2-heptadecyl imidazole, 1,2-dimethyl imidazole, 2-ethyl-4-methyl imidazole, 2-phenyl imidazole and 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-undecyl imidazolium trimerite, 1-cyanoethyl-2-phenylimidazolium trimerite, 2,4-diamino-6- [2' -Methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6- [2'-undecylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino- 6- [2'-ethyl-4'-methylimidazolyl- (1')]-ethyl-s-triazine, 2,4-diamino-6- [2'-methylimidazolyl- (1')]-ethyl-s -Triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H- Pyrrolo [1,2-a] benzimidazole, 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 2-methylimidazoline, 2-phenylimidazoline, 2,4-diamino-6-vinyl-s-triazine, 2,4-Diamino-6-vinyl-s-triazine isocyanuric acid adduct, 2,4-diamino-6-methacryloyloxyethyl-s-triazine, epoxy-imidazole adduct, 2-methylbenzoimidazole, 2-octylbenzoimidazole , 2-Pentylbenzoimidazole, 2- (1-ethylpentyl) benzoimidazole, 2-nonylbenzoimidazole, 2- (4-thiazolyl) benzoimidazole, benzoimidazole and the like. Examples of the benzotriazole include 2- (2'-hydroxy-5'-methylphenyl) benzotriazole and 2- (2'-hydroxy-3'-tert-butyl-5'-methylphenyl) -5-chlorobenzo. Triazole, 2- (2'-hydroxy-3', 5'-di-tert-amylphenyl) benzotriazole, 2- (2'-hydroxy-5'-tert-octylphenyl) benzotriazole, 2,2'- Methylenebis [6- (2H-benzotriazole-2-yl) -4-tert-octylphenol], 6- (2-benzotriazolyl) -4-tert-octyl-6'-tert-butyl-4'-methyl -2,2'-Methylenebisphenol, 1,2,3-benzotriazole, 1- [N, N-bis (2-ethylhexyl) aminomethyl] benzotriazole, carboxybenzotriazole, 1- [N, N-bis ( 2-Ethylhexyl) aminomethyl] methylbenzotriazole, 2,2'-[[(methyl-1H-benzotriazole-1-yl) methyl] imino] bisethanol, 1,2,3-benzotriazole sodium salt aqueous solution, 1 -(1', 2'-dicarboxyethyl) benzotriazole, 1- (2,3-dicarboxypropyl) benzotriazole, 1-[(2-ethylhexylamino) methyl] benzotriazole, 2,6-bis [( 1H-benzotriazole-1-yl) methyl] -4-methylphenol, 5-methylbenzotriazole and the like can be mentioned. Amino acids include alanine, arginine, aspartic acid, aspartic acid, cysteine hydrochloride, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine, lysine monohydrochloride, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, Examples thereof include β-alanine, γ-aminobutyric acid, δ-aminovaleric acid, ε-aminohexanoic acid, ε-caprolactam and 7-aminoheptanoic acid. Examples of guanidine include carbodihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, 1,3-bis (hydrazinocarbonoethyl) -5-isopropylhydrandine, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, 7, Examples thereof include 11-octadecaziene-1,18-dicarbohydrazide and isophthalic acid dihydrazide. Examples of the hydrazide include dicyandiamide, 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine and the like.

The amine content may be, for example, 0 to 20% by mass with respect to the total flux.

The flux may contain a covalent halogen activator (covalent halogen) in order to improve solderability. Examples of the covalent halogen include trans-2,3-dibromo-2-butene-1,4-diol, 2,3-dibromo-1,4-butanediol, 2,3-dibromo-1-propanol, and the like. 2,3-Dichloro-1-propanol, 1,1,2,2-tetrabromoethane, 2,2,2-tribromoethanol, pentabromoethane, carbon tetrabromide, 2,2-bis (bromomethyl)- 1,3-Propanediol, meso-2,3-dibromoethane, chloroalkane, chlorinated fatty acid ester, n-hexadecyltrimethylammonium bromide, triallyl isocyanurate 6 bromide, 2,2-bis [3,5 −Dibromo-4- (2,3-dibromopropoxy) phenyl] propane, bis [3,5-dibromo-4- (2,3-dibromopropoxy) phenyl] sulfone, ethylenebispentabromobenzene, 2-chloromethyloxylane , Hetic acid, hetic acid anhydride, bromide bisphenol A type epoxy resin and the like.

The content of the covalent halogen may be, for example, 0 to 5% by mass with respect to the entire flux.

The flux may contain an amine hydrohalide activator (aminehal hydrohalide) in order to improve solderability. Examples of the amine hydrohalide include amine halide hydrolates exemplified as amines. Examples of the amine halogenated hydroxide include stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, and isopropylamine hydrofluorate. Cyclohexylamine hydrofluoric acid salt, diethylamine hydrofluoric acid salt, monoethylamine hydrofluoric acid salt, 1,3-diphenylguanidine hydrofluoric acid salt, dimethylamine hydrofluoric acid salt, dimethylamine hydrochloride, rosinamine odor Hydrofluoric acid salt, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipecholine hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazinehydrate odor Hydrofluoric acid salt, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrofluorate, 2-diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride Salt, diallylamine hydrofluoric acid salt, monoethylamine hydrochloride, monoethylamine hydrofluorate, diethylamine hydrochloride, triethylamine hydrofluorate, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monoodor Hydrofluoric acid, hydrazine dibromide, pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine bromide Hydrofluorate, ethylenediamine hydrofluorate, rosinamine hydrofluorate, 2-phenylimidazole hydrofluorate, 4-benzylpyridine hydrofluorate, L-glutamate, N-methylmorpholine hydrochloride Salt, betaine hydrochloride, 2-pipecholine hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluorate, diethylamine hydrofluorate, 2-ethylhexylamine hydrofluorate , Cyclohexylamine hydrofluorate, ethylamine hydrofluorate, rosinamine hydrofluorate, cyclohexylaminetetrafluoroborate, dicyclohexylaminetetrafluoroborate and the like.

The content of the amine hydrohalide may be, for example, 0 to 2% by mass with respect to the entire flux.

The flux may contain a solvent. Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, terpineols and the like. Examples of the alcohol-based solvent include 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-hexine-2,5-diol, 2,3-dimethyl-2,3-butanediol, 1,1,1-tris (hydroxymethyl) ) Ethan, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2'-oxybis (methylene) bis (2-ethyl-1,3-propanediol), 2,2-bis (hydroxymethyl) ) -1,3-Propanediol, 1,2,6-trihydroxyhexane, bis [2,2,2-tris (hydroxymethyl) ethyl] ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexane Diol, 1,4-cyclohexanedimethanol, erythritol, tretol, guayacol glycerol ether, 3,6-dimethyl-4-octin-3,6-diol, 2,4,7,9-tetramethyl-5-decine- Examples thereof include 4,7-diol. Examples of glycol ether-based solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, and hexyl diglycol. , Tetraethylene glycol dimethyl ether and the like.

The content of the solvent may be, for example, 0 to 80% by mass with respect to the entire flux.

The flux may contain a thixotropic agent. Examples of the thixotropy include wax-based thixotropy, amide-based thixotropy, and the like. Examples of the wax-based thixotropy include castor oil and the like. Examples of amido-based thixo agents include laurate amide, palmitate amide, stearic acid amide, bechenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucate amide, unsaturated fatty acid amide, and p-toluene. Methane amide, aromatic amide, methylene bisstearic acid amide, ethylene bislauric acid amide, ethylene bishydroxystearic acid amide, saturated fatty acid bis amide, methylene bisoleic acid amide, unsaturated fatty acid bis amide, m-xylylene bisstearate amide, Examples thereof include aromatic bisamide, saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, substituted amide, methylol stearate amide, methylol amide, and fatty acid ester amide.

The content of the thixotropic agent may be, for example, 0 to 15% by mass with respect to the entire flux.

In the present embodiment, the mass ratio of the content of the solder material to the content of the flux (solder material: flux) is, for example, 95% by mass of the solder material: 5% by mass of the flux to 5% by mass of the solder material: 95% by mass of the flux. It may be%, preferably 95% by mass of the solder material: 5% by mass of the flux to 85% by mass of the solder material: 15% by mass of the flux.

In this embodiment, the solder paste can further contain zirconium oxide powder. The content of the zirconium oxide powder with respect to the total mass of the solder paste is preferably 0.05 to 20.0% by mass, more preferably 0.05 to 10.0% by mass, and most preferably 0.1 to 3% by mass. When the content of the zirconium oxide powder is within the above range, the activator contained in the flux reacts preferentially with the zirconium oxide powder, and the reaction with Sn or Sn oxide on the surface of the solder powder is less likely to occur. The effect of further suppressing the increase in viscosity due to the change is exhibited.

The upper limit of the particle size of the zirconium oxide powder added to the solder paste is not limited, but is preferably 5 μm or less. When the particle size is 5 μm or less, the printability of the paste can be maintained. The lower limit is not particularly limited, but is preferably 0.5 μm or more. The above particle size is the projected circle of the zirconium oxide powder, although the projected circle equivalent diameter is 0.1 μm or more when the SEM photograph of the zirconium oxide powder is taken and the projected circle equivalent diameter is obtained by image analysis for each particle existing in the visual field. The average value of the equivalent diameter. The shape of the zirconium oxide particles is not particularly limited, but if the particles have a different shape, the contact area with the flux is large and the thickening suppressing effect is obtained. When it is spherical, good fluidity can be obtained, so that excellent printability as a paste can be obtained. The shape may be appropriately selected according to the desired characteristics.

In the present embodiment, the solder paste can be produced by kneading the solder material (solder powder) of the present embodiment and the flux by a known method.

The solder paste of the present embodiment is used, for example, for a circuit board having a fine structure in an electronic device, and specifically, by a printing method using a metal mask, a discharge method using a dispenser, a transfer method using a transfer pin, or the like. , Can be applied to the soldered part and reflowed.

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

(Adjustment of solder powder)
Each metal shown in Tables 1 to 10 was melt-mixed so as to have the composition shown in Tables 1 to 10, and powder was prepared by centrifugal spraying in an Ar atmosphere. The numerical values in each table represent the content (mass%) of each metal when the total of the solder powder is 100% by mass, and "Bal" represents the balance. Further, the average particle size of the solder powder JIS Z3284-1: 20 according to the 1 4 measured, JIS Z3284-1 from measurements: were classified according to Table 2 of 20 1 4 powder sizing. The numerical values shown in each table indicate the powder size symbols in Table 2 of JIS Z3284-1: 20 14.

(Preparation of flux)
Each material shown in Tables 1 to 10 was heated and stirred so as to have the composition shown in Tables 1 to 10, and then cooled to prepare a flux. The numerical values in each table represent the content (mass%) of each material when the total flux is 100% by mass. The reagent names and CAS numbers of each material shown in the table are shown below.

-"Metal inactivating agent A"
Reagent name: Bis [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionic acid] [Ethylene bis (oxyethylene)]
CAS No. 36443-68-2
・ "Metal inactivating agent B"
Reagent name: N, N'-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide]
CAS No. 23128-74-7
-"Metal inactivating agent C"
Reagent name: 1,6-Hexanediol bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]
CAS No. 35074-77-2
-"Metal inactivating agent D"
Reagent name: 2,2'-methylenebis [6- (1-methylcyclohexyl) -p-cresol]
CAS No. 77-62-3
・ "Metal inactivating agent E"
Reagent name: 2,2'-methylenebis (6-tert-butyl-p-cresol)
CAS No. 119-47-1
・ "Metal inactivating agent F"
Reagent name: 2,2'-methylenebis (6-tert-butyl-4-ethylphenol)
CAS No. 88-24-4
-"Metal inactivating agent G"
Reagent name: N- (2H-1,2,4-triazole-5-yl) salicylamide CAS No. 36411-52-6
-Reagent name: 2-Ethyl-4-methylimidazole CAS No. 931-36-2
-Reagent name: 2-Undecylimidazole CAS No. 16731-68-3
-Reagent name: Trans-2,3-dibromo-2-butene-1,4-diol CAS No. 3234-02-4
-Reagent name: Triallyl isocyanurate 6 bromide CAS No. 52434-90-9
-Reagent name: Hexyldiglycol CAS No. 112-59-4
-Reagent name: Tetraethylene glycol dimethyl ether CAS No. 143-24-8
-Reagent name: Castor oil CAS No. 8001-78-3

(Preparation of solder paste)
The solder powder and the flux were kneaded so that the mass ratio (solder powder: flux) was 89:11 to prepare a solder paste.

The solder pastes of each Example and Comparative Example were evaluated for (1) thickening suppression, and the solder powder used in each Example and Comparative Example was evaluated for reliability (2). Each evaluation method is shown below, and the evaluation results are shown in Tables 1 to 10.

(1) Evaluation for suppression of thickening of the obtained solder paste, using a rotational viscometer (PCU-205, manufactured by Malcolm Co., Ltd.) according to the method described in "4.2 Viscosity Characteristic Test" of JIS Z 3284-3. The viscosity was continuously measured for 12 hours at a rotation speed of 10 rpm and a measurement temperature of 25 ° C. Then, the initial viscosity (viscosity after 30 minutes of stirring) and the viscosity after 12 hours were compared, and the thickening suppressing effect was evaluated based on the following criteria.
Viscosity after 13 hours ≤ Initial viscosity x 1.2: Viscosity increase over time is small and good (○)
Viscosity after 13 hours> Initial viscosity x 1.2: Viscosity increase over time is large and defective (x)

(2) Evaluation of reliability The obtained solder powder was heated at a temperature of 5 ° C./min (180 ° C. to 250 ° C.) using a differential scanning calorimeter (EXSTAR DSC7020, manufactured by SII Nanotechnology Co., Ltd.). cooling rate: -3 ° C. / min (250 ℃ ~150 ℃), carrier gas: perform DSC measurement under the measurement conditions of the N _2, measured liquidus temperature (T _L) and the solidus temperature (T _S) did. Then, calculate the difference between the liquidus temperature (T _L) and the solidus temperature (T _S) and _{(ΔT = T L -T S)} , were evaluated based on the following criteria.
ΔT within 10 ° C: Excellent reliability (○)
ΔT exceeds 10 ° C: Inferior in reliability (×)
If the difference between the solder powder liquidus temperature (T _L) and the solidus temperature _{(T S) (ΔT = T} L -T S) is large, applying a solder paste containing the solder powder to the substrate of the electronic device However, when solidifying, a structure having a high melting point tends to precipitate on the surface of the solder powder. When a structure having a high melting point is deposited on the surface of the solder powder, then a structure having a low melting point is sequentially deposited toward the inside of the solder powder, and the structure of the solder powder tends to be non-uniform, which lowers reliability such as cycleability. It causes.

The solder material of the present invention can be used for various purposes because it is excellent in reliability such as thickening suppressing effect and cycle characteristics.

Claims (3)

It is a solder paste consisting of solder material and flux.
The solder material is Sn, 20 to 300% by mass of As, 50% by mass to 3.0% by mass of Bi, 0.0% by mass or more and 3.5% by mass or less of Ag, and 0.0% by mass or more 1 .0% by mass or less of Cu (where Sn, 170 to 220% by mass of As, 0.55 to 1.15% by mass of Bi, 0% by mass or more and 2.05% by mass or less of Ag, and 0.0% by mass. (Excluding lead-free solder alloys consisting of Cu of% or more and 0.66% by mass or less)
The flux contains a hindered phenolic compound and
A solder paste in which the content of the hindered phenolic compound is 0.5 to 10% by mass with respect to the entire flux. The solder paste according to claim 1, wherein the Bi content is 50% by mass to 1.0% by mass with respect to the entire solder material. The solder paste according to claim 1 or 2 , wherein the solder material has a particulate form.