CN110732806A - Soldering flux and solder paste - Google Patents

Abstract

An object of the present invention is to provide a flux and a solder paste that can improve the effect of suppressing the increase in adhesion. The flux of the present invention is a flux containing a metal passivating agent, and the metal passivating agent contains a hydrazide-based nitrogen compound.

Description

Flux and Solder Paste

technical field

The present invention relates to fluxes and solder pastes.

Background technique

From the viewpoints of cost and reliability, bonding and assembly of electronic components to substrates of electronic devices is often performed by soldering using solder paste.

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

Patent Document 1 discloses a solder paste composition comprising a flux composition and solder alloy powder, the flux composition comprising a rosin resin, an acrylic resin, an activator, a thixotropic agent, an antioxidant, and a solvent, and as an antioxidant, a phenol At least one of a triazole-based antioxidant, a triazole-based antioxidant, and a phosphorus-based antioxidant. This document discloses that the above-mentioned solder paste composition can suppress the occurrence of cracks by suppressing the thermal degradation of the flux residue even when the above-mentioned solder paste composition is used for an electronic circuit board placed in an environment with a large temperature difference and a large thermal shock. And the effect of its development, further exerts good meltability, wettability and other properties.

Patent Document 2 discloses a solder paste obtained by mixing a tin-based lead-free solder powder with a rosin-based flux containing 0.01 to 10% by mass of at least one salicyl selected from salicylamide and its derivatives amide compound. This document discloses that the salicylic amide compound is preferentially adsorbed on the surface of the solder powder to prevent the solder powder from reacting with the components of the flux, especially with an activator called an organic amine hydrohalide or an organic acid, thereby preventing the The viscosity change of the solder paste caused by this reaction.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2017-100181

Patent Document 2: WO2002/043916

However, Patent Document 1 is not aware of the so-called problem of suppressing the increase in viscosity over time. On the other hand, with respect to Patent Document 2, further suppression of the viscosity change of the solder paste described in Patent Document 2 is sought.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a flux and a solder paste which can improve the effect of suppressing the thickening.

As a result of earnest studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by using a flux containing a metal passivator as a flux containing a hydrazide-based nitrogen compound, leading to the completion of the present invention.

That is, the flux of the present invention is a flux containing a metal passivating agent, and the metal passivating agent contains a hydrazide-based nitrogen compound.

The solder paste of the present invention is composed of a solder material and the flux of the present invention.

Invention effect

ADVANTAGE OF THE INVENTION According to this invention, the flux and solder paste which can improve the tackifying suppressing effect can be provided.

Detailed ways

Hereinafter, the form for implementing this invention (henceforth "this embodiment") is demonstrated. However, the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.

In the present specification, the "thickening inhibitory effect" refers to the effect of suppressing the increase in viscosity of the prepared solder paste over time when the solder paste is prepared.

It should be noted that in this specification, the content of each element can be measured by, for example, ICP-AES analysis based on JIS Z3910.

[Flux]

The flux of this embodiment contains a metal passivating agent. Metal passivators contain hydrazide nitrogen compounds. When the metal passivator contains a hydrazide-based nitrogen compound, the flux can improve the effect of suppressing the increase in viscosity. Therefore, the flux is suitable as, for example, a flux for soldering.

(metal passivator)

Metal passivators contain hydrazide nitrogen compounds. The hydrazide-based nitrogen compound may be a nitrogen compound having a hydrazide skeleton, and examples thereof include dodecanedioic acid bis[2-(2-hydroxybenzoyl)hydrazide], N,N'-bis[3-( 3,5-Di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, sebacic acid disalicylhydrazide, N-salicylidene-N'-salicylic hydrazide, m-nitrophenylhydrazide, 3-amino Phthalic acid hydrazide, phthalic acid dihydrazide, adipic acid hydrazide, oxalylbis(2-hydroxy-5-octylbenzylidene hydrazide), N'-benzoylpyrrolidone carboxylic acid hydrazide , N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hydrazine, etc. These hydrazide-based nitrogen compounds may be used alone or in combination of two or more. Among these, dodecanedioic acid bis[2-(2-hydroxybenzoyl)hydrazide] is preferable from the viewpoint of being excellent in the thickening inhibitory effect.

The content of the hydrazide-based nitrogen compound is preferably more than 0 and 10% by mass or less with respect to the entire flux. The content is more preferably 0.01% by mass or more, still more preferably 0.05% by mass or more, particularly preferably 0.10% by mass or more, more preferably 7.5% by mass or less, still more preferably 5.0% by mass or less, and particularly preferably 1.0% by mass or less. By making the said content into 0.01 mass % or more, a flux is excellent in the effect of suppressing thickening and the effect of suppressing fluctuation of the thixotropy ratio. Therefore, when printing using a flux-containing solder paste, the filling properties of the openings of the screen or the film are excellent, and the openings can be filled even if the openings are minute openings. On the other hand, by making the said content into 10 mass % or less, a flux is excellent in the thickening inhibitory effect and the reaction inhibitory effect with Cu at the time of the temperature cycle test in soldering.

The metal deactivator may contain other compounds than hydrazide nitrogen compounds. Examples of other compounds include amide-based nitrogen compounds, triazole-based nitrogen compounds, melamine-based nitrogen compounds, hindered phenol-based compounds, and the like.

The amide-based nitrogen compound may be a nitrogen compound having an amide skeleton, and examples include N,N'-bis{2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy] Ethyl} oxamide and so on.

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

As a melamine type nitrogen compound, the nitrogen compound which has a melamine skeleton may be sufficient, and melamine, a melamine derivative, etc. are mentioned.

The hindered phenolic compound may be a compound having a hindered phenol skeleton, and examples include triethylene glycol ether-bis(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, N,N'- Hexamethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide], 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) base)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazine, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxybenzene ( 3,5-Di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide), 3,5 -Di-tert-butyl-4-hydroxybenzylphosphonate diethyl ester, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl) Benzene etc.

The content of the hydrazide-based nitrogen compound in the metal deactivator may be, for example, 80% by mass or more, preferably 85% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, and particularly preferably 100% by mass .

The flux may contain resin. Examples of resins include rosin-based resins, (meth)acrylic resins, urethane-based resins, polyester-based resins, phenoxy resins, vinyl ether-based resins, terpene resins, and modified terpene resins (eg, aromatic modified terpene resins). terpene resin, hydrogenated terpene resin, hydrogenated aromatic modified terpene resin, etc.), terpene phenol resin, modified terpene phenol resin (such as hydrogenated terpene phenol resin, etc.), styrene resin, modified styrene Resins (such as styrene acrylic resins, styrene maleic resins, etc.), xylene resins, modified xylene resins (such as phenol-modified xylene resins, alkylphenol-modified xylene resins, phenol-modified resols) Toluene resin, polyol modified xylene resin, polyoxyethylene addition xylene resin, etc.) and so on. These resins are used alone or in combination of two or more. Among these, it is preferable that the resin is at least one selected from the group consisting of rosin-based resins and (meth)acrylic-based resins. It is worth noting that "(meth)acrylic resin" here refers to a concept including methacrylic resin and acrylic resin.

Examples of the rosin-based resin include raw material rosin such as gum rosin, wood rosin, and tall oil rosin, and derivatives obtained from the raw material rosin. Derivatives include, for example, purified rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, modified α,β-unsaturated carboxylic acid (acrylated rosin, maleated rosin, fumaric rosin, etc.), and purified polymerized rosin. Compounds, hydrides and disproportionates, as well as refined products, hydrides and disproportionates of α,β-unsaturated carboxylic acid modified products, etc. These rosin-based resins are used alone or in combination of two or more.

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

As a (meth)acrylic-type resin, the homopolymer of a (meth)acrylic-type monomer, and the copolymer of two or more types of (meth)acrylic-type monomers are mentioned, for example. Examples of the (meth)acrylic monomer include (meth)acrylic acid, itaconic acid, maleic acid, crotonic acid, methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acrylic acid. Butyl (meth)acrylate, hexyl (meth)acrylate, propyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate ester, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, lauryl (meth)acrylate, octadecyl (meth)acrylate, and the like. These (meth)acrylic resins are used alone or in combination of two or more.

When the resin contains a (meth)acrylic resin, the temperature cycle reliability can be improved. When repeated thermal stress of high temperature and low temperature is applied to the mounted part or the joint part, there is a possibility that a material with high crystallinity such as rosin is cracked and moisture is absorbed from the crack. On the other hand, by including a flexible (meth)acrylic resin in the resin, the above-mentioned cracks are 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 relative to the entire flux, and 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 relative to the entire resin, and preferably 30 to 80% by mass from the viewpoint of excellent temperature cycle reliability.

30-60 mass % is preferable with respect to the whole flux of resin, 35-55 mass % is more preferable, and 40-50 mass % is more preferable.

In order to improve solderability, the flux may contain an organic acid activator (organic acid). Examples of the organic acid include adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, dipicolinic acid, and dibutylaniline diethylene glycol. acid, suberic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanedioic acid, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, maleic acid acid, malonic acid, lauric acid, benzoic acid, tartaric acid, tris(2-carboxyethyl)isocyanurate, glycine, 1,3-cyclohexanedicarboxylic acid, 2,2-bis(hydroxymethyl) ) propionic acid, 2,2-bis(hydroxymethyl)butyric acid, 2,3-dihydroxybenzoic acid, 2,4-diethylglutaric acid, 2-quinolinecarboxylic 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, trimer acid, hydrogenated trimer acid, etc.

Content of an organic acid can be 0-10 mass % with respect to the whole flux, for example.

In order to improve solderability, the flux may contain an amine activator (amine). Examples of the amine include aliphatic amines, aromatic amines, amino alcohols, imidazoles, benzotriazoles, amino acids, guanidines, hydrazides, and the like. Examples of aliphatic amines include dimethylamine, ethylamine, n-propylamine, isopropylamine, trimethylamine, allylamine, n-butylamine, diethylamine, sec-butylamine, tert-butylamine, N,N-dimethylethylamine , isobutylamine, cyclohexylamine, etc. As an aromatic amine, aniline, N-methylaniline, diphenylamine, N-isopropylaniline, p-isopropylaniline, etc. are mentioned, for example. 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'-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N',N",N"- Penta(2-hydroxypropyl)diethylenetriamine and the like. Examples of imidazoles include 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-cyano Ethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methane Imidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine oxazine, 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-phenylimidazolyl isocyanuric acid adduct, 2-phenyl-4,5 -Dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole, 1-dodeca Alkyl-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 Product, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2 -(4-thiazolyl) benzimidazole, benzimidazole and the like. Examples of the benzotriazole include 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-methyl) Phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3',5'-di-tert-amylphenyl)benzotriazole, 2-(2'-hydroxy-5'-tertiary Octylphenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tert-octylphenol], 6-(2-benzoxy Triazolyl)-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 azole, 2,2'-[[(methyl-1H-benzotriazol-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 azole, 2,6-bis[(1H-benzotriazol-1-yl)methyl]-4-methylphenol, 5-methylbenzotriazole, and the like. Examples of amino acids include alanine, arginine, asparagine, aspartic acid, cysteine hydrochloride, glutamine, glutamic acid, glycine, histidine, isoleucine, leucine Amino acid, lysine hydrochloride, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, beta-alanine, gamma-aminobutyric acid acid, δ-aminovaleric acid, ε-aminocaproic acid, ε-caprolactam, 7-aminoheptanoic acid, etc. As a guanidine, dicyandiamide, 1, 3- diphenylguanidine, 1, 3- di-o-toluidine etc. are mentioned, for example.

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

In order to improve solderability, the flux may contain a covalently bonded halogen activator (covalently bonded halogen). Examples of covalently bonded halogens include trans-2,3-dibromo-2-butene-1,4-diol, 2,3-dibromo-1,4-butanediol, 2,3- Dibromo-1-propanol, 2,3-dichloro-1-propanol, 1,1,2,2-tetrabromoethane, 2,2,2-tribromoethanol, pentabromoethane, tetrabromoethane Carbon, 2,2-bis(bromomethyl)-1,3-propanediol, meso-2,3-dibromosuccinic acid, chloroalkane, chlorinated fatty acid ester, n-hexadecyl tribromide Methylammonium, Tris(2,3-dibromopropyl)isocyanurate, 2,2-bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl] Propane, bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]sulfone, ethylenebispentabromobenzene, 2-chloromethyloxirane, chloro bridge acid , chloro bridge acid anhydride, brominated bisphenol A epoxy resin, etc.

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

To improve solderability, the flux may contain an amine hydrohalide activator (amine hydrohalide). As the amine hydrohalide salt, the hydrohalide salt of an amine exemplified as the amine is exemplified. Examples of the amine hydrohalide include stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, pyridine hydrobromide, and isopropylamine hydrochloride. Bromate, cyclohexylamine hydrobromide, diethylamine hydrobromide, monoethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide, dimethylamine hydrobromide, dimethylamine Amine hydrochloride, rosinamine hydrobromide, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride, 2-pipercoline hydrobromide, 1,3-di Benzidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride, trinonylamine hydrobromide, diethylaniline hydrobromide, 2- Diethylaminoethanol hydrobromide, 2-diethylaminoethanol hydrochloride, ammonium chloride, diallylamine hydrochloride, diallylamine hydrobromide, monoethylamine hydrochloride, monoethylamine hydrobromide acid salt, diethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide , pyridine hydrochloride, aniline hydrobromide, butylamine hydrochloride, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine hydrobromide, ethyl Diamine dihydrobromide, rosinamine hydrobromide, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L-glutamic acid hydrochloride, N-methylmorpholine Hydrochloride, betaine hydrochloride, 2-pipercoline hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluorate, 2- Ethylhexylamine hydrofluoride, cyclohexylamine hydrofluoride, ethylamine hydrofluorate, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, dicyclohexylamine tetrafluoroborate, etc. .

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

The flux may contain solvents. Examples of the solvent include water, alcohol-based solvents, glycol ether-based solvents, terpene alcohols, and the like. Examples of the alcohol-based solvent include isopropanol, 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-hexyn-2,5-diol, 2,3-dimethyl- 2,3-Butanediol, 1,1,1-Tris(hydroxymethyl)ethane, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 2,2′-oxobis(oxymethylene) Methyl)bis(2-ethyl-1,3-propanediol), 2,2-bis(hydroxymethyl)-1,3-propanediol, 1,2,6-trihydroxyhexane, bis[2,2 ,2-Tris(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, erythritol, threo Sugar alcohol, guaiacol glyceryl ether, 3,6-dimethyl-4-octyne-3,6-diol, 2,4,7,9-tetramethyl-5-decyne-4,7 -Diols, etc. Examples of glycol ether-based solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, and diethylene glycol monohexyl ether. ether, diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, diethylene glycol monohexyl ether, tetraethylene glycol dimethyl ether, etc.

Content of a solvent can be 0-80 mass % with respect to the whole flux, for example, Preferably it is 20-60 mass %.

The flux may contain a thixotropic agent. As a thixotropic agent, a wax type thixotropic agent, an amide type thixotropic agent, etc. are mentioned, for example. As a wax type thixotropic agent, hydrogenated castor oil etc. are mentioned, for example. Examples of amide-based thixotropic agents include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, hydroxystearic acid amide, saturated fatty acid amide, oleic acid amide, erucic acid amide, and unsaturated fatty acid amide. , p-toluamide, aromatic amide, substituted amide, hydroxymethyl stearic acid amide, methylol amide, fatty acid ester amide, etc. As the amide-based thixotropic agent, a bis-amide-based thixotropic agent and/or a polyamide-based thixotropic agent may be used, and as the bis-amide-based thixotropic agent, methylenebisstearic acid amide, ethylenebislauric acid are exemplified Amide, ethylene bishydroxystearic acid amide, saturated fatty acid bisamide, methylene bisoleic acid amide, unsaturated fatty acid bisamide, metaxylylene bis stearic acid amide, aromatic bisamide, etc., as polyamides. The amide-based thixotropic agent includes saturated fatty acid polyamide, unsaturated fatty acid polyamide, aromatic polyamide, and the like.

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

[Solder Paste]

The solder paste of this embodiment consists of a solder material and the flux of this embodiment. When the solder paste contains the flux of the present embodiment, the effect of suppressing thickening can be enhanced. It is worth noting that the "flux" mentioned here refers to all components other than the solder material in the solder paste.

(solder material)

The solder material preferably contains Sn or Sn-based alloy. Sn or Sn-based alloys may contain unavoidable impurities.

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

Examples of Sn-based alloys include Sn-Ag alloys, Sn-Cu alloys, Sn-Ag-Cu alloys, Sn-Ag-Cu-Ni-Co alloys, Sn-In alloys, Sn-Bi alloys, and Sn-Sb alloys. Alloys, Sn-Pb alloys, etc. alloys with As, Bi, Sb, Pb, Ag, Cu, In, Ni, Co, Ge, P, Fe, Zn, Al, Ga, etc. added to the alloys with the above-mentioned compositions alloy. The Sn content in the Sn-based alloy is not particularly limited, but can be, for example, more than 40% by mass.

Sn and Sn-based alloys are preferably Sn and Sn—Cu from the viewpoint of being able to reduce the difference between the liquidus temperature ( _{T L} ) and the solidus temperature ( _TS ) (ΔT= _TL −TS ) Alloy or Sn-Ag-Cu alloy. When ΔT is reduced, for example, even when a solder paste containing the above-mentioned solder material is applied to a 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. From the same viewpoint, the Sn—Cu alloy preferably contains more than 0 and 1.0 mass % or less (preferably 0.5 to 1.0 mass %) of Cu, and the remainder is Sn. From the same viewpoint, the Sn-Ag-Cu alloy preferably contains more than 0 and 3.5 mass % or less (preferably 1.0 to 3.5 mass %) of Ag, and preferably contains more than 0 and 1.0 mass % or less (preferably 0.1 to 1.0 mass %) of Ag Cu, the remainder is Sn.

From the viewpoint of excellent reliability by reducing ΔT, the content of Ag is preferably 0.05 to 3.5% by mass, more preferably 0.1 to 3% by mass, and even more preferably 0.5 to 3% by mass relative to the entire solder material. In addition, from the viewpoint of excellent reliability by reducing ΔT, the content of Cu is preferably 0.01 to 0.9 mass %, more preferably 0.05 to 0.75 mass %, and further preferably 0.1 to 0.7 mass % with respect to the entire solder material. . It is worth noting that the preferred numerical ranges of the above-mentioned Ag and Cu contents are independent of each other, and the contents of Ag and Cu can be determined independently.

The content of Sn may be, for example, 40 mass % or more, 50 mass % or more, 70 mass % or more, or 90 mass % or more with respect to the whole solder material. On the other hand, when the solder material contains Pb, the content of Pb with respect to the whole solder material may be 90 mass % or more, and the content of Sn with respect to the whole solder material may be 5 mass % or more, and 10 mass % or more.

The solder material may contain, for example, 20 to 300 mass ppm of As. By making the content of As 20 mass ppm or more, the increase in viscosity is suppressed, and the effect of suppressing thickening is excellent. By making the content of As 300 mass ppm or less, the wettability deterioration can be further suppressed. Therefore, by making the As content to be 20 to 300 mass ppm, the solder paste of the present embodiment can achieve both the effect of suppressing thickening and reliability in a well-balanced manner. From the same viewpoint, the content of As is preferably 30 to 250 mass ppm with respect to the entire solder material, and more preferably 50 to 200 mass ppm. As can form an alloy together with Sn or Sn-based alloys (eg, intermetallic compounds, solid solutions, etc.), or can exist independently of Sn-based alloys, such as As element or oxides.

The solder material preferably contains Bi in an amount of 50 mass ppm (0.0050 mass %) to 3.0 mass %. When the content of Bi is 50 mass ppm or more, the increase in viscosity is suppressed and the effect of suppressing thickening is excellent. By setting the content of Bi to 3.0 mass % or less, the difference between the liquidus temperature (T _L ) and the solidus temperature (T _S ) (ΔT= _TL -T _S ) can be reduced, and the reliability of cycle characteristics and the like can be reduced. Excellent. Therefore, when the content of Bi is 50 mass ppm to 3.0 mass %, the solder paste of the present embodiment can achieve both the effect of suppressing thickening and reliability in a well-balanced manner. From the same viewpoint, the content of Bi is preferably 50 mass ppm (0.0050 mass %) to 1.0 mass %, more preferably 100 mass ppm (0.010 mass %) to 1.0 mass % with respect to the entire solder material.

The solder material preferably contains Sb in an amount of 20 mass ppm (0.0020 mass %) to 0.5 mass %. By making content of Sb 20 mass ppm or more, a viscosity increase is suppressed and it is excellent in the effect of suppressing thickening. By setting the content of Sb to be 0.5 mass % or less, it is excellent in reliability such as wettability and cycle characteristics. Therefore, by setting the content of Sb to be 20 mass ppm to 0.5 mass %, the solder paste of the present embodiment can achieve both the effect of suppressing thickening and reliability in a well-balanced manner. From the same viewpoint, the content of Sb is preferably 50 mass ppm (0.0050 mass %) to 0.3 mass % with respect to the entire solder material, and more preferably 100 mass ppm (0.010 mass %) to 0.1 mass %.

The solder material preferably contains 20 mass ppm (0.0020 mass %) to 0.7 mass % of Pb. When the content of Pb is 20 mass ppm or more, the increase in viscosity is suppressed and the effect of suppressing thickening is excellent. By setting the content of Pb to 0.7 mass % or less, the difference (ΔT= _{TL −TS} ) between the _liquidus temperature ( _TL ) and the solidus temperature (TS ) can be reduced, and the reliability of cycle characteristics and the like can be reduced. Excellent. Therefore, by setting the content of Pb to be 20 mass ppm to 0.7 mass %, the solder paste of the present embodiment can achieve both the effect of suppressing thickening and reliability in a well-balanced manner. From the same viewpoint, the content of Pb is preferably 50 mass ppm (0.0050 mass %) to 0.5 mass % with respect to the entire solder material, and more preferably 100 mass ppm (0.010 mass %) to 0.3 mass %.

Bi may exist in the form of alloys (eg, intermetallic compounds, solid solutions, etc.) together with Sn or Sn-based alloys, or may exist independently of Sn and Sn-based alloys.

The manufacturing method of the solder material of this embodiment is not specifically limited, For example, the method of manufacturing by melt-mixing a raw material metal is mentioned.

In the present embodiment, the form of the solder material is not particularly limited, and may be, for example, a linear form, a spherical form (solder ball), or a granular form such as a powder form (solder powder). From the viewpoint of excellent fluidity, the form of the solder material is preferably a granular form, and more preferably a powder form.

As a manufacturing method of a granular solder material, the dripping method of dripping a molten solder material to obtain particles, the spray method of centrifugal spraying, the method of pulverizing a lump solder material, etc. are mentioned, for example. In the dropping method or the spraying method, in order to form particles, the dropping or spraying is preferably performed in an inert atmosphere or a solvent.

In addition, when the solder material is granular, the solder material preferably has a size (particle size distribution) belonging to symbols 1 to 8 in the powder size classification (Table 2) of JIS Z3284-1:2014, and more preferably has a size (particle size distribution) belonging to symbols 4 to 8 The size (particle size distribution) of , more preferably has a size (particle size distribution) belonging to symbols 5 to 8. Thereby, it is possible to solder to delicate parts.

In the present embodiment, the size (particle size distribution) of the granular solder material can be performed according to the laser diffraction particle size distribution measurement test described in 4.2.3 of JIS Z 3284-2:2014.

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

In this embodiment, the solder paste can further contain zirconia powder. The content of the zirconia powder with respect to the entire mass of the solder paste is preferably 0.05 to 20.0 mass %, more preferably 0.05 to 10.0 mass %, and most preferably 0.1 to 3 mass %. When the content of the zirconia powder is within the above range, the activator contained in the flux preferentially reacts with the zirconia powder and hardly reacts with Sn or Sn oxides on the surface of the solder powder, thereby further suppressing the increase in viscosity over time. Effect.

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

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

The solder paste of the present embodiment is used for, for example, a fine-structured circuit board in an electronic device, and specifically, it is possible to use a printing method using a metal mask, a discharging method using a dispenser, a transfer method using a transfer needle, or the like. Reflow welding is performed by applying it to the welded part.

Hereinafter, the present invention will be specifically described using examples, but the present invention is not limited to the contents described in the examples.

Example

(Preparation of flux)

After heating and stirring each material shown in Table 1 and Table 2 to the composition shown in Table 1 and Table 2, the flux was prepared by cooling. The numerical value in each table represents the content (mass %) of each material when the total flux is 100 mass %, and "Bal" represents the remainder. The reagent name and CAS number of each material shown in the table are shown below.

· "Metal deactivator" reagent name: dodecanedioic acid bis[2-(2-hydroxybenzoyl)hydrazide]

CAS number: 63245-38-5

·Reagent name: 2-ethyl-4-methylimidazole

CAS Number: 931-36-2

·Reagent name: 2-Undecylimidazole

CAS number: 16731-68-3

·Reagent name: trans-2,3-dibromo-2-butene-1,4-diol

CAS number: 3234-02-4

·Reagent name: Tris(2,3-dibromopropyl)isocyanurate

CAS number: 52434-90-9

·Reagent name: diethylene glycol monohexyl ether

CAS Number: 112-59-4

·Reagent name: Tetraethylene glycol dimethyl ether

CAS Number: 143-24-8

·Reagent name: Hydrogenated castor oil

CAS number: 8001-78-3

(Preparation of solder paste)

Solder powder ("SAC305") having a composition of Sn-3Ag-0.5Cu (each value is mass %) and the flux of each example and comparative example were kneaded so that the mass ratio (solder powder: flux) was 89: 11, modulated into solder paste. The average particle diameter of the solder powder was measured in accordance with JISZ 3284-1:2014, and based on the measured value, it was classified according to Table 2 of the powder size classification of JISZ 3284-1:2014. The reference number of the powder size in Table 2 of JIS Z 3284-1:2014 is 5.

The solder pastes of the respective Examples and Comparative Examples were subjected to (1) evaluation of inhibition of thickening, (2) evaluation of thixotropic ratio variation, and (3) evaluation of inhibition of reaction with Cu during a temperature cycle test. Each evaluation method is shown below, and Table 1 and Table 2 show the evaluation results.

(1) Evaluation of thickening inhibition

After storing the obtained solder paste at 40° C. for two weeks, the viscosity increase rate represented by the following formula was calculated.

Viscosity increase rate = paste viscosity after storage for two weeks / initial paste viscosity × 100

The viscosity of each paste was measured at a rotational speed of 10 rpm and a measurement temperature of 25°C using a rotational viscometer (PCU-205, manufactured by Markon Co., Ltd.) according to the method described in "4.2 Viscosity characteristic test" of JIS Z 3284-3. . The thickening inhibitory effect was evaluated based on the following criteria.

○: The viscosity increase rate is 120% or less

×: The viscosity increase rate is more than 120%

(2) Evaluation of thixotropic ratio variability

After storing the obtained solder paste at 40° C. for two weeks, the thixotropic ratio variation rate represented by the following formula was calculated.

Change rate of thixotropic ratio = thixotropic ratio of solder paste after storage for two weeks / thixotropic ratio of initial paste × 100

Each thixotropic ratio was calculated according to the following formula using a rotational viscometer (PCU-205, manufactured by Markon Co., Ltd.) at a measurement temperature of 25°C.

Thixotropic ratio = LOG (viscosity at 3 rpm/viscosity at 30 rpm)

Based on the obtained thixotropy ratio fluctuation rate, evaluation of thixotropy ratio fluctuation was performed according to the following criteria.

○: The thixotropic ratio change rate is 120% or less

×: Thixotropic ratio change rate is more than 120%

(3) Evaluation of reaction inhibition with Cu during temperature cycle test

The resulting solder paste was printed onto a Cu-OSP substrate using a metal mask with an opening diameter of 5.0 mm and a thickness t of 0.15 mm. Next, a reflow soldering process was performed while raising the temperature from 25°C to 250°C at a temperature increase rate of 1.2°C/sec in a nitrogen atmosphere. Next, the Cu-OSP substrate was observed at 125°C for 30 minutes, 25°C for 5 minutes, 40°C for 30 minutes, and 25°C for 5 minutes. The reactivity (greening) of Cu was evaluated for inhibition of reaction with Cu based on the following criteria.

○○: In all the raised portions with N=10, no residues were found to turn green

○: Greening was observed in all the raised portions with N=10, but it was not considered that the entire residue portion turned green

×: In any of the raised portions with N=10, the entire portion with residues turned green

In addition, by adding As, Bi, Sb, and Pb in predetermined amounts to the solder materials used in the respective examples, while maintaining excellent thixotropy ratio variability, a more excellent effect of suppressing thickening was obtained.

Industrial Applicability

The flux and solder paste of the present invention can be used in various applications for which the effect of suppressing thickening is excellent.

Claims (11)

1 . A flux, which is a flux containing a metal passivating agent, wherein the metal passivating agent contains a hydrazide-based nitrogen compound. 2 . The flux according to claim 1 , wherein the content of the hydrazide-based nitrogen compound is more than 0 and 10 mass % or less with respect to the entire flux. 3 . 3 . The flux according to claim 1 , wherein the content of the hydrazide-based nitrogen compound is 0.01 to 1.00 mass % with respect to the entire flux. 4 . 4 . The flux according to claim 1 , wherein the hydrazide-based nitrogen compound is dodecanedioic acid bis[2-(2-hydroxybenzoyl)hydrazide]. 5 . 5 . The flux according to claim 1 , wherein the flux contains a resin, and the resin is one or more selected from the group consisting of a rosin-based resin and an acrylic resin. 6 . 6 . The flux according to claim 5 , wherein the content of the resin is 30 to 60 mass % with respect to the entire flux. 7 . 7 . A solder paste, characterized in that, the solder paste is composed of a solder material and the flux according to any one of claims 1 to 6 . 8. The solder paste according to claim 7, wherein the solder material contains Sn or a Sn-based alloy. 9 . The solder paste according to claim 8 , wherein the Sn-based alloy is a Sn-based alloy containing more than 0 and 3.5 mass % or less of Ag and/or more than 0 and 1.0 mass % or less of Cu. 10 . 10. The solder paste of any one of claims 7 to 9, wherein the solder paste further comprises zirconia powder. 11 . The solder paste according to claim 10 , wherein the content of the zirconia powder with respect to the entire mass of the solder paste is 0.05 to 20.0 mass %. 12 .