TWI832936B - Flux - Google Patents

Abstract

The present invention provides a flux for welding soldering alloy, comprising at least one selected from the group consisting of chlorendic acid amides and chlorendates.

Description

flux

This invention relates to fluxes for soldering solder alloys.

The fixation and electrical connection of electronic components in electronic equipment such as the assembly of electronic components on printed circuit boards is generally performed by soldering, which is the most advantageous in terms of cost and reliability. The commonly used methods for this kind of soldering are the flow soldering method in which printed circuit boards and electronic components are brought into contact with molten solder for soldering, and the solder in the form of solder paste, solder preform or solder ball is re-soldered in a reflow oven. Reflow soldering method that melts and performs soldering.

In this soldering, a flux is used as an auxiliary agent that allows solder to easily adhere to printed circuit boards and electronic components. Flux plays a role in (1) metal surface cleaning (chemically removing the oxide film on the metal surface of printed circuit boards and electronic parts and cleaning the surface to enable soldering), (2) reoxidation prevention ( Covers the clean metal surface during welding to block contact with oxygen and prevent re-oxidation of the metal surface due to heating), (3) interfacial tension reduction (reduces the surface tension of the molten solder and improves the metal surface The wettability effect caused by the solder) and many other useful effects.

In the soldering of printed circuit boards using the flow soldering method, flux (post-flux) is applied to the soldering area before or after electronic components are mounted. Thereafter, the printed circuit board coated with flux is passed over the solder sprayed by the flow soldering device to perform flow soldering.

As a flux used in conventional flow soldering methods, Patent Document 1 proposes a flux containing at least 0.2 to 4% by mass selected from the group consisting of a main resin, an activator, an acidic phosphate ester and its derivatives. A compound, no-clean resin-based flux for lead-free soldering. Patent Document 2 describes that the generation of solder bridges and balls during soldering can be suppressed by using a flux containing both an activator containing chlorine atoms and an organic phosphorus compound in a specific ratio. Patent Document 3 describes that a flux containing a rosin-based resin and a specific activator can fully suppress solder rejection or solder bridges during soldering even when lead-free soldering is used. [Prior technical literature] [Patent Document]

[Patent Document 1] International Publication No. 2008/072654 [Patent Document 2] Japanese Patent No. 6322881 [Patent Document 3] Japanese Patent Application Publication No. 2013-126671

[Problem to be solved by the invention]

However, the fluxes described in Patent Documents 1 to 3 are not yet sufficient to improve solder wettability when used in solder alloys, and there are also issues to be solved regarding stability during long-term storage.

In view of the above circumstances, an object of the present invention is to provide a flux for welding solder alloys that fully improves solder wettability and has excellent stability during long-term storage. [Means used to solve problems]

As a result of intensive research in order to solve the above-mentioned problems, the present inventors found that the above-mentioned problems can be solved by using a flux containing at least one selected from the group consisting of chloro-acid amide and chloro-acid ester. Complete the present invention. That is, the present invention is as follows.

[1] A flux used for welding solder alloys, containing at least one selected from the group consisting of chloride amide and chloride ester. [2] The flux of [1] above, wherein the total content of the aforementioned chloride amide and chloride ester is more than 0% by mass and less than 5% by mass relative to the entire flux. [3] The flux of [1] or [2] above, wherein the aforementioned chloride amide is at least one selected from the group consisting of compounds represented by the following formulas (1) to (6);

[4] The flux according to any one of the above [1] to [3], wherein the aforementioned chlorobridge acid ester is selected from the group consisting of chlorobridge acid monomethyl ester, chlorobridge acid monoethyl, chlorobridge acid monoisopropyl, and chlorobridge acid ester. One or more species from the group consisting of monoethylene glycol ester and dimethyl chloride. [5] The flux according to any one of the above [1] to [4] further contains a solvent. [6] The flux of [5] above, wherein the aforementioned solvent is 2-propanol. [7] The flux according to any one of the above [1] to [6], wherein the aforementioned welding is flow welding. [8] A method of manufacturing a joint body, which includes the step of welding a solder alloy to the surface of a substrate treated with the flux according to any one of [1] to [7] above to form a joint body. [9] The manufacturing method of [8] above, wherein the aforementioned welding is flow welding. [10] A joined body obtained by the manufacturing method of [8] or [9] above. [11] A flux activator containing at least one selected from the group consisting of chloride amide and chloride ester. [Effects of the invention]

According to the present invention, it is possible to provide a flux for welding solder alloys that fully improves solder wettability and has excellent stability during long-term storage.

Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail. However, the present invention is not limited thereto, and various changes can be made within the scope that does not deviate from the gist of the invention.

[Flux] The flux used for soldering the solder alloy according to this embodiment contains at least one selected from the group consisting of chloride amide and chloride ester. Chlorobridge acid amide and chlorobridge acid ester function as flux activators. By using the flux of this embodiment, the wettability of the solder alloy can be fully improved. Welding can be performed by either flow welding or reflow welding. Since the effect of the present invention is more significant, flow welding is preferably performed.

The total content of the chloride amide and the chloride ester is preferably more than 0 mass % and less than 5 mass %, more preferably more than 0 mass % and less than 1 mass %, relative to the entire flux, and more preferably Preferably, it is 0.2 mass % or more and 0.7 mass % or less, and especially preferably, it is 0.3 mass % or more and 0.6 mass % or less. When the total content of chloride amide and chloride ester exceeds 0% by mass, solder wettability and storage stability tend to improve. On the other hand, the upper limit of the total content of chloroamide and chloroamide is not particularly limited. If it exceeds 5% by mass, the active ingredients in the residue will increase, so there is a tendency for hygroscopicity to occur. As a result, the insulation resistance value decreases and the reliability decreases. In addition, hygroscopicity may cause stickiness of residues, etc., so it is preferably 5% by mass or less.

The chlorobridge acid amide is not particularly limited, and examples thereof include the dehydration condensate of chlorobridge acid and cyclohexylamine, or the cyclohexylamine salt of the dehydration condensate of chlorobridge acid and cyclohexylamine. Specific examples include compounds represented by the above formulas (1) to (6). Among these, from the viewpoint of flux activity or compatibility, the dehydration condensation product of cyclohexylamine or its cyclohexylamine salt is particularly preferred.

Moreover, the chloroamide acid amide also includes the chloroamide acid amide dimer represented by the following formula (7) or the chloroamide acid amide multimer, etc., and the condensation or permeation amine of two or more types of chloroamide acid amide, etc. And bonded compounds.

(In the formula, R represents an optionally substituted linear or branched alkylene group, an alkylene glycol group, or an oxyalkylene group).

The carbon number of the alkylene group, alkylene glycol group, and oxyalkylene group represented by R is not particularly limited, but is preferably 1 to 54, and more preferably 2 to 36.

Furthermore, the chlorobridge acid amide also includes a compound in which a chlorobridge acid amide represented by the following formula (8) and a chlorobridge acid ester are bonded directly or via an amine, alcohol, or the like.

(In the formula, R is synonymous with the above).

In addition, the chloroamide amide also includes various isomers (structural isomers, optical isomers, etc.) of the above compounds, or salts (amine salts, etc.) of the above compounds.

Chloramides may be used singly or in combination of two or more types.

In addition, the above-mentioned various chloroamide amide can be produced using known methods.

The chlorobridge acid ester is not particularly limited, and examples include chlorobridge acid monomethyl ester, chlorobridge acid monoethyl, chlorobridge acid monoisopropyl, chlorobridge acid monoethylene glycol, and the like; Dimethyl chloroacid, diester of chloroacid, etc. Among these, from the viewpoint of flux activity or compatibility, monoesters of residual carboxylic acids are particularly preferred, and isopropyl ester is particularly preferred.

In addition, the chlorobridge acid ester also includes two or more kinds of chlorobridge acid esters such as a chlorobridge acid ester dimer or a chlorobridge acid ester multimer represented by the following formula (9), which are condensed or bonded through alcohol or the like. compound.

(In the formula, R represents an optionally substituted linear or branched alkylene group, an alkylene glycol group, or an oxyalkylene group).

The carbon number of the alkylene group, alkylene glycol group, and oxyalkylene group represented by R is not particularly limited, but is preferably 1 to 54, and more preferably 2 to 36.

In addition, the chloroacid ester also includes various isomers (structural isomers, optical isomers, etc.) of the above-mentioned compounds, or salts (amine salts, etc.) of the above-mentioned compounds.

Chlorobridge acid ester can be used individually by 1 type, and can also use 2 or more types together.

In addition, the above-mentioned various chlorobridge acid esters can be produced using known methods.

The flux in this embodiment may contain chlorobridge acid and/or chlorobridge acid anhydride in addition to at least one selected from the group consisting of chlorobridge acid amide and chlorobridge acid ester. The total content of chlorobridged acid and chlorobridged acid anhydride is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0% by mass, relative to the entire flux. . When the content of chloro-bridged acid and chloro-bridged acid anhydride is too high, the stability of the flux during long-term storage tends to decrease.

The flux according to this embodiment may further contain optional components in addition to at least one selected from the group consisting of chloride amide and chloride ester. Examples of optional components include solvents, rosin, active agents, and matting agents.

Examples of the solvent include water, alcohol solvents, glycol ether solvents, and terpineols. Examples of alcohol-based solvents include 2-propanol, ethanol, 1,2-butanediol, isobornylcyclohexanol, 2,4-diethyl-1,5-pentanediol, and 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, 1,1,1-hydroxymethylethane, 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-Shen(hydroxymethyl)ethyl]ether, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, butanetetraol, Thritol, guaiacol glyceryl ether, 3,6-dimethyl-4-octyne-3,6-diol, and 2,4,7,9-tetramethyl-5-decyne-4 ,7-diol. Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, 2-methylpentane-2,4-diol, and diethylene glycol monohexyl ether. , diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, hexyl diglycol, and tetraethylene glycol dimethyl ether. Among the above, alcohol-based solvents are particularly preferred from the viewpoint of volatility. In addition, from the viewpoint of suppressing esterification of rosin, organic acids as active agents, etc., and solvents, 2-propanol is preferred. A solvent can be used individually or in combination of 2 or more types.

In the case of flux for flow soldering, the content of the solvent is preferably 75 to 94 mass %, more preferably 80 to 92 mass %, and still more preferably 85 to 90 mass % relative to the entire flux. In the case of flux used for reflow soldering, the solvent content is preferably 20 to 75 mass %, more preferably 25 to 55 mass %, and still more preferably 30 to 50 mass % relative to the entire flux. .

Examples of rosin include acid-modified rosin, refined rosin, hydrogenated rosin, non-homogenized rosin, rosin ester, and polymerized rosin. Rosin is a non-volatile component contained in rosin from Pinaceae plants. Examples of rosin include tall rosin, gum rosin, and wood rosin. Acid-modified rosin refers to rosin that has been treated with acid. Acid modified rosin can also be hydrogenated. Examples of acid-modified rosin include acrylic acid-modified rosin, acrylic acid-modified hydrogenated rosin, maleic acid-modified rosin, and maleic acid-modified hydrogenated rosin. Rosin can be used alone or in combination of two or more kinds. By containing rosin, flux tends to improve the wettability of the solder alloy.

In the case of flux for flow soldering, the content of rosin relative to the entire flux is preferably 3 to 18 mass %, more preferably 6 to 15 mass %, and still more preferably 9 to 12 mass %. In the case of flux used for reflow soldering, the content of rosin relative to the entire flux is preferably 0 to 65 mass %, more preferably 5 to 60 mass %, and still more preferably 20 to 50 mass %. . By setting the rosin content within the above range, the wettability of the solder alloy tends to be further improved.

Examples of the active agent include organic acids, halogen-based active agents (such as organic halogen compounds and amine hydrohalides), amines, and organic phosphorus-based compounds (such as phosphonate esters and phenyl-substituted hypophosphorous acid). The active agent may be used alone or in combination of two or more types. By containing activators, flux can further improve the wettability of the solder alloy.

Examples of organic acids include adipic acid, azelaic acid, eicosanedioic acid, citric acid, glycolic acid, succinic acid, salicylic acid, diglycolic acid, pyridinedicarboxylic acid, and dibutylaniline diglycolic acid. , suberic acid, sebacic acid, thioglycolic acid, terephthalic acid, dodecanedioic acid, p-hydroxyphenylacetic acid, picolinic acid, phenylsuccinic acid, phthalic acid, fumaric acid, horse Lenic acid, malonic acid, lauric acid, benzoic acid, tartaric acid, glutaric acid, palmitic acid, ginseng isocyanate (2-carboxyethyl ester), 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, tris Polymer acids, and hydrogenated trimer acids.

Examples of the organic halogen compound include 1,2,4,5-tetrabromobenzene, trans-2,3-dibromo-2-butene-1,4-diol, and 2,3-dibromo-1,4-diol. Butanediol, 2,3-dibromo-1-propanol, 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-dibromosuccinic acid, chloroalkane, chlorinated fatty acid ester, bromination n-Hexadecyltrimethylammonium, triallylisocyanurate 6 bromide, 2,2-bis[3,5-dibromo-4-(2,3-dibromopropoxy )phenyl]propane, bis[3,5-dibromo-4-(2,3-dibromopropoxy)phenyl]propane, ethylidenebispentabromobenzene, 2-chloromethyloxirane , and brominated bisphenol A epoxy resin.

Examples of amine hydrohalides include boron trifluoride piperidine, stearylamine hydrochloride, diethylaniline hydrochloride, diethanolamine hydrochloride, 2-ethylhexylamine hydrobromide, and pyridine hydrochloride. Bromate, isopropylamine hydrobromide, cyclohexylamine hydrobromide, diethylamine hydrobromide, monoethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide Salt, dimethylamine hydrobromide, dimethylamine hydrochloride, rosin amine hydrochloride, 2-ethylhexylamine hydrochloride, isopropylamine hydrochloride, cyclohexylamine hydrochloride , 2-methylpiperidine hydrobromide, 1,3-diphenylguanidine hydrochloride, dimethylbenzylamine hydrochloride, hydrazine hydrate hydrobromide, dimethylcyclohexylamine hydrochloride , trinonylamine hydrobromide, diethylaniline hydrobromide, 2-diethylaminoethanol hydrochloride, 2-diethylaminoethanol hydrochloride, ammonium chloride, diene Propylamine hydrochloride, diallylamine hydrobromide, monoethylamine hydrochloride, monoethylamine hydrobromide, diethylamine hydrochloride, triethylamine hydrobromide , triethylamine hydrochloride, hydrazine monohydrochloride, hydrazine dihydrochloride, hydrazine monohydrobromide, hydrazine dihydrobromide, pyridine hydrochloride, aniline hydrobromide, butylamine salt acid salt, hexylamine hydrochloride, n-octylamine hydrochloride, dodecylamine hydrochloride, dimethylcyclohexylamine hydrobromide, ethylenediamine dihydrobromide, rosin amine hydrogen Bromate, 2-phenylimidazole hydrobromide, 4-benzylpyridine hydrobromide, L-glutamine hydrochloride, N-methylmorpholine hydrochloride, betaine hydrochloride, 2 -Meperidine hydroiodide, cyclohexylamine hydroiodide, 1,3-diphenylguanidine hydrofluoride, diethylamine hydrofluoride, 2-ethylhexylamine hydrofluoride, Cyclohexylamine hydrofluoride, ethylamine hydrofluoride, rosinamine hydrofluoride, cyclohexylamine tetrafluoroborate, and dicyclohexylamine tetrafluoroborate.

Examples of amines include aliphatic amines, aromatic amines, amine alcohols, azoles, amino acids, guanidines, and hydrazides. Examples of aliphatic amines include dimethylamine, ethylamine, 1-aminopropane, isopropylamine, trimethylamine, allylamine, n-butylamine, diethylamine, and sec-butylamine. amine, tert-butylamine, N,N-dimethylethylamine, isobutylamine, and cyclohexylamine. Examples of aromatic amines include aniline, N-methylaniline, diphenylamine, N-isopropylaniline, and p-isopropylaniline. Examples of aminoalcohols include 2-aminoethanol, 2-(ethylamino)ethanol, diethanolamine, diisopropanolamine, triethanolamine, N-butyldiethanolamine, triisopropanolamine, N,N- Bis(2-hydroxyethyl)-N-cyclohexylamine, N,N,N',N'-bis(2-hydroxypropyl)ethylenediamine, and N,N,N',N",N" - Wu(2-hydroxypropyl)diethylenetriamine. Examples of azoles include imidazole, 3,5-dimethylpyrazole, benzotriazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 1,2-dimethylimidazole. 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-benzene imidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1 -Cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate Salt, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-deca Monoalkyl imidazolyl-(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-phenyl Imidazole, epoxy-imidazole adduct, 2-methylbenzimidazole, 2-octylbenzimidazole, 2-pentylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-nonylbenzimidazole, 2-(4-thiazolyl)benzimidazole, and benzimidazole. Examples of amino acids include alanine, arginine, asparagine, aspartic acid, cysteine hydrochloride, glutamine, glutamic acid, glycine, histidine, and isoleucine. Acid, leucine, lysine monohydrochloride, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, beta-alanine , γ-aminobutyric acid, δ-aminovaleric acid, ε-aminocaproic acid, ε-caprolactam, and 7-aminoheptanoic acid.

Examples of phosphonate include 2-ethylhexyl (2-ethylhexyl) phosphonate, n-octyl (n-octyl) phosphonate, and n-decyl (n-decyl) phosphonate. and n-butyl (n-butyl)phosphonate.

Examples of phenyl-substituted hypophosphorous acid include phenyl hypophosphorous acid and diphenyl hypophosphorous acid.

The content of the activator is preferably 0.1 to 12.0 mass%, more preferably 0.3 to 8.0 mass%, and still more preferably 0.5 to 4.0 mass% relative to the entire flux. By setting the content of the activator within the above range, the wettability of the solder alloy tends to be further improved.

Examples of matting agents include palmitic acid. One type of matting agent can be used alone or two or more types can be used in combination. By containing a matting agent, the flux can eliminate the luster of the joint part of the joint body, making it easier to inspect the appearance of this part.

The matting agent is preferably 0.01 to 4.0 mass %, more preferably 0.05 to 3.0 mass %, and still more preferably 0.1 to 2.0 mass % relative to the entire flux. By setting the content of the matting agent within the above range, visual inspection of the joint portion of the joined body tends to be easier.

[Solder alloy] The flux of this embodiment can be used for either flow soldering or reflow soldering. From the viewpoint of solder wettability, it is preferably used for flow soldering. The solder alloy used for flow welding can be a solder alloy with a known composition. Specifically, Sn-Ag alloy, Sn-Cu alloy, Sn-Ag-Cu alloy, Sn-In alloy, Sn-Pb alloy, Sn-Bi alloy, Sn-Ag-Cu-Bi alloy, or any of the above Ag, Cu, In, Ni, Co, Sb, Ge, P, Fe, Zn, Ga, etc. are further added to the alloy composition.

As is an element that can inhibit the yellow change caused by oxidation of the solder surface after soldering. As has low reactivity with flux and is a noble element compared to Sn, so it is thought to have a viscosity-increasing inhibitory effect. When As is less than 25 ppm by mass, the viscosity-increasing inhibitory effect cannot be fully exerted. The lower limit of the As content is 25 mass ppm or more, preferably 50 mass ppm or more, more preferably 100 mass ppm or more. On the other hand, when there is too much As, the wettability of the solder alloy deteriorates. The upper limit of the As content is 300 mass ppm or less, preferably 250 mass ppm or less, more preferably 200 mass ppm or less.

Bi and Pb have low reactivity with flux and can inhibit the viscosity of solder paste used in reflow soldering. In addition, these elements will lower the liquidus temperature of the solder alloy and reduce the viscosity of the molten solder, so they are elements that can suppress the deterioration of wettability caused by As.

If at least one element of Bi and Pb is present, deterioration of wettability due to As can be suppressed. When the solder alloy of this embodiment contains Bi, the lower limit of the Bi content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, still more preferably 75 mass ppm or more, and particularly preferably 100 mass ppm. ppm or more, preferably 250 mass ppm or more. When the solder alloy of this embodiment contains Pb, the lower limit of the Pb content is more than 0 mass ppm, preferably 25 mass ppm or more, more preferably 50 mass ppm or more, still more preferably 75 mass ppm or more, and particularly preferably 100 mass ppm. ppm or more, preferably 250 mass ppm or more.

On the other hand, when the content of these elements is too high, the solidus temperature significantly decreases, so the temperature difference ΔT between the liquidus temperature and the solidus temperature becomes too wide. When ΔT is too wide, during the solidification process of the molten solder, a high-melting crystalline phase with a small content of Bi or Pb precipitates, so the Bi or Pb in the liquid phase is concentrated. After that, when the temperature of the molten solder further decreases, a low-melting crystalline phase with a high concentration of Bi or Pb segregates. Therefore, the mechanical strength, etc. of the solder alloy may be deteriorated. In particular, the crystalline phase with a high Bi concentration is hard and brittle, so when it segregates in the solder alloy, the mechanical strength, etc. will be significantly reduced.

From this point of view, when the solder alloy of the present embodiment contains Bi, the upper limit of the Bi content is 25,000 mass ppm or less, preferably 10,000 mass ppm or less, more preferably 1,000 mass ppm or less, and still more preferably 600 mass ppm or less. The best value is less than 500 ppm by mass. When the solder alloy of this embodiment contains Pb, the upper limit of the Pb content is 8000 mass ppm or less, preferably 5100 mass ppm or less, more preferably 5000 mass ppm or less, still more preferably 1000 mass ppm or less, particularly preferably 850 mass ppm or less, optimally 500 mass ppm or less.

The solder alloy of this embodiment preferably satisfies the following formula (1).

275≦2As+Bi+Pb (1) In the above formula (1), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition.

As, Bi, and Pb are all elements that exhibit viscosity-increasing inhibitory effects. The total amount of viscosity increase and suppression is preferably 230 ppm by mass or more. In the formula (1), the As content is twice as high because As has a higher viscosity-increasing inhibitory effect than Bi or Pb.

(1) When the formula does not reach 275, the viscosity-increasing inhibitory effect tends to be insufficient. The lower limit of the formula (1) is 275 or more, preferably 300 or more, more preferably 700 or more, and still more preferably 900 or more. On the other hand, the upper limit of (1) is not particularly limited in terms of the viscosity-increasing inhibitory effect. From the perspective of making ΔT an appropriate range, it is preferably 25,200 or less, more preferably 15,200 or less, and still more preferably 10,200 or less. , the best is below 8200, the best is below 5300.

The upper limit and the lower limit appropriately selected from the above preferred embodiments are the following formulas (1a) and (1b).

275≦2As+Bi+Pb≦25200 (1a) 275≦2As+Bi+Pb≦5300 (1b) In the above formulas (1a) and (1b), As, Bi, and Pb each represent the content (mass ppm) in the alloy composition.

The solder alloy of this embodiment preferably satisfies the following formula (2).

0<2.3×10 ^-4 ×Bi+8.2×10 ^-4 ×Pb≦7 (2) In the above formula (2), Bi and Pb each represent the content (mass ppm) in the alloy composition.

Bi and Pb suppress the deterioration of wettability caused by the inclusion of As, but if the content is too high, ΔT will increase, so strict management is required. Especially in alloy compositions containing both Bi and Pb, ΔT is likely to increase. In this embodiment, the increase in ΔT can be suppressed by specifying the total value of the Bi and Pb contents multiplied by a specific coefficient. In the formula (2), the coefficient of Pb is greater than the coefficient of Bi. This is because Pb contributes more to ΔT than Bi, and only a small increase in content can significantly increase ΔT.

(2) The solder alloy of formula 0 does not contain the two elements Bi and Pb, and cannot suppress the deterioration of wettability caused by the inclusion of As. (2) The lower limit of the formula exceeds 0, preferably 0.02 or more, more preferably 0.03 or more, still more preferably 0.05 or more, particularly preferably 0.06 or more, and most preferably 0.11 or more. On the other hand, when the formula (2) exceeds 7, the temperature range of ΔT becomes too wide, so when the molten solder solidifies, a crystal phase with a high concentration of Bi or Pb segregates, and the mechanical strength, etc. deteriorates. The upper limit of (2) is 7 or less, preferably 6.56 or less, more preferably 6.40 or less, still more preferably 5.75 or less, still more preferably 4.18 or less, particularly preferably 2.30 or less, and most preferably 0.90 or less.

The upper limit and the lower limit are appropriately selected from the above preferred embodiments, and the formula (2a) below is obtained.

0.02≦2.3×10 ^-4 ×Bi+8.2×10 ^-4 ×Pb≦0.9 (2a) In the above formula (2a), Bi and Pb each represent the content (mass ppm) in the alloy composition.

Ag is any element that can form Ag ₃ Sn at the crystal interface and improve the mechanical strength of the solder alloy. In addition, Ag is a noble element that has an ionization tendency compared to Sn, and by coexisting with As, Pb, and Bi, it contributes to the viscosity-increasing inhibitory effect of these elements. The Ag content is preferably 0 to 4%, more preferably 0.5 to 3.5%, and still more preferably 1.0 to 3.0%.

Cu is any element that can improve the joint strength of solder joints. In addition, Cu is a noble element that has an ionization tendency compared to Sn, and coexists with As, Pb, and Bi, thereby promoting the viscosity-increasing inhibitory effect of these elements. The Cu content is preferably 0 to 0.9%, more preferably 0.1 to 0.8%, and still more preferably 0.2 to 0.7%.

The remainder of the solder alloy of this embodiment is Sn. In addition to the aforementioned elements, unavoidable impurities may also be included. Even if it contains unavoidable impurities, it will not affect the aforementioned effects. In addition, as will be described later, even if elements not contained in this embodiment are contained as unavoidable impurities, the aforementioned effects will not be affected. When the In content is too high, ΔT becomes wider, so if it is 1000 mass ppm or less, the above-mentioned effects will not be affected.

[solder paste] The content of solder alloy and flux in the solder paste is not limited. For example, the solder alloy can be 5 to 95 mass %, and the flux can be 5 to 95 mass %.

The solder paste of this embodiment preferably contains zirconia powder. Zirconia suppresses the increase in paste viscosity that occurs with time. This is presumably because the oxide film thickness on the surface of the solder powder remains the same as before being put into the flux due to the inclusion of zirconium oxide. Although the details are not clear, it is presumed as follows. Generally, the active ingredients of the flux are slightly active even at room temperature, so the surface oxide film of the solder powder becomes thinner through reduction, which causes the powders to agglomerate with each other. Therefore, it is presumed that by adding zirconium oxide powder to the solder paste, the active ingredient of the flux reacts preferentially with the zirconium oxide powder, thereby maintaining a level where the oxide film on the surface of the solder powder does not agglomerate.

In order to give full play to such an effect, the content of zirconia powder in the solder paste is preferably 0.05~20.0% relative to the total mass of the solder paste. If it is 0.05% or more, the above-mentioned effects can be exerted. If it is 20.0% or less, the content of metal powder can be ensured and the viscosity prevention effect can be exerted. The content of zirconium oxide is preferably 0.05~10.0%, and more preferably 0.1~3%.

The particle size of the zirconia powder in the solder paste is preferably 5 μm or less. When the particle size is 5 μm or less, the paste printability can be maintained. There is no particular lower limit, as long as it is 0.5 μm or more. The above particle diameter is based on the SEM photograph of the zirconia powder. For each powder with 0.1 μm or more, the projected equivalent circle diameter was obtained through image analysis and used as the average value.

The shape of the zirconium oxide is not particularly limited. If it is an irregular shape, the contact area with the flux will be large, thereby inhibiting the viscosity increase. If it is spherical, good fluidity can be obtained, and therefore excellent printability as a paste can be obtained. Just choose the shape appropriately according to the desired characteristics.

The manufacturing method of the soldering flux and solder paste of this embodiment is not limited, and they can be manufactured by mixing raw materials simultaneously or sequentially by any method.

[Joint body and manufacturing method thereof] The method of manufacturing a joint body according to this embodiment includes soldering a solder alloy to the surface of a substrate treated with a flux containing at least one selected from the group consisting of chloride amide and chloride ester to form a joint. body steps (hereinafter referred to as "joining steps").

Details of the flux and solder alloy used in the manufacturing method of this embodiment are as described in the above items of [Flux] and [Solder Alloy].

The manufacturing method of this embodiment may further include, before the joining step, a step of treating the surface of the substrate with a flux containing at least one selected from the group consisting of chloride amide and chloride ester (hereinafter Called "pre-processing step").

The treatment method in the pretreatment step and the joining method in the joining step are not particularly limited, and methods generally implemented in this technical field can be used. Welding is preferably performed by flow welding.

The joint body includes a substrate, a solder alloy soldered to the surface of the substrate, and flux residue. An example of the substrate is a printed wiring board. Examples of the bonded body include a printed circuit board on which electronic components are mounted on a printed wiring board. [Example]

The present invention will be described in more detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto.

(evaluate) (1) Evaluation of solder wettability For the fluxes prepared in Examples and Comparative Examples, the wetting speed was evaluated based on the soldering zero-cross time measured by dipping solder (menisco) in a arcuate shape. The conditions for arc-shaped solder dipping are as follows. ･Solid sample: Copper plate (width 5mm × length 25mm × thickness 0.5mm; no oxidation treatment, etc.) ･Soldering bath temperature: 280℃ (Solder alloy: Sn-3Ag-0.5Cu) ･Immersion speed: 20mm/sec ･Immersion depth: 5mm ･Measurement time: 10sec ･Flux treatment: Dip the copper plate into flux (immersion depth is about 10mm) The evaluation criteria for wetting speed are as follows. 〇〇: Welding zero cross time is less than 3 seconds 〇: Welding zero-cross time is less than 6 seconds ×: Welding zero-cross time exceeds 6 seconds

(2) Storage stability The storage stability of the fluxes prepared in Examples and Comparative Examples was evaluated. Storage stability is evaluated by the reduction rate of acid value after humidified storage. Humidification conditions are as follows. ･Initial acid value: Calculate the initial acid value by the sum of the acid value of each material × blending ratio ･Humidification conditions: 50℃, 5 hours The evaluation criteria for storage stability are as follows. 〇: The acid value is within 30% of the initial acid value. ×: The acid value decreased by more than 30% compared with the initial acid value.

The fluxes of Examples A1~57, B1~56 and Comparative Examples A1~3, B1~3 were prepared with the composition shown in the table below. Furthermore, the numerical values of each component in the table below represent the mass % of each component relative to the total mass of the flux. The "remainder" in the "solvent" column represents the amount of the total components other than the solvent by adding the solvent. Make the entire flux 100% by mass.

In addition, the chlorobridged acid amide (1) to (6) in the table are chlorobridged acid amide having the structures represented by the above-mentioned formulas (1) to (6) respectively. In the table, chlorobridge acid monomethyl ester represents a compound represented by the following formula (10), chlorobridge acid monoethyl ester represents a compound represented by the following formula (11), and chlorobridge acid monoisopropyl ester represents a compound represented by the following formula (12). The compound, chlorobridge acid monoethylene glycol ester, represents a compound represented by the following formula (13), and chlorobridge acid dimethyl ester represents a compound represented by the following formula (14). Each compound includes its isomers (structural isomers, stereoisomers).

[Discussion on solder alloys] The flux prepared in Example A40 was mixed with the size (particle size distribution) that satisfies mark 4 in the powder size classification (Table 2) of JIS Z 3284-1:2004 and contained the alloy composition shown in Table 15 and Table 16. The solder alloys are mixed to make solder paste. The mass ratio of flux to solder alloy is flux:solder alloy=11:89. Determine the liquidus temperature and solidus temperature of solder alloys. Furthermore, the wettability was evaluated using the solder paste just after production. Similarly, the flux prepared in Example B40 was mixed with a size (particle size) that satisfies mark 4 in the powder size classification (Table 2) of JIS Z 3284-1:2004 containing the alloy composition shown in Table 17 and Table 18. Distribution) solder alloys are mixed to produce solder paste. The mass ratio of flux to solder alloy is flux:solder alloy=11:89. Determine the liquidus temperature and solidus temperature of solder alloys. Furthermore, the wettability was evaluated using the solder paste just after production. Details are as follows.

(3) Evaluation of wettability (paste) The newly produced solder pastes were printed on the Cu board, heated from 25°C to 260°C at a temperature rise rate of 1°C/s in a N2 environment in a reflow furnace, and then cooled to room temperature. Wettability was evaluated by observing the appearance of the cooled solder bumps with an optical microscope. When incompletely melted solder powder is not observed, it is evaluated as "○", and when incompletely melted solder powder is observed, it is evaluated as "×".

(4)ΔT For the solder alloy before being mixed with flux, DSC measurement was performed using SII NanoTechnology Co., Ltd. Model: EXSTAR DSC7020 with a sample amount of about 30 mg and a heating rate of 15°C/min to obtain the solidus temperature and liquid phase. line temperature. ΔT is obtained by subtracting the solidus temperature from the obtained liquidus temperature. When ΔT is 10°C or lower, it is evaluated as "○", and when it exceeds 10°C, it is evaluated as "×".

In Tables 15 to 18, Ag and Cu represent mass %; Ni, Ge, As, Bi, and Pb represent mass ppm.

As shown in Tables 15 to 18, all Examples C and D show narrowing of ΔT. In addition, it was found that all of Examples C and D showed excellent wettability.

[Combination of flux and solder alloy] As a result of the evaluation of the solder paste containing the flux of Example A40 and the solder alloy of Example C1, good results were obtained in terms of ΔT and wettability. As a result of the evaluation of the solder paste containing the flux of Example B40 and the solder alloy of Example D1, good results were obtained in terms of ΔT and wettability.

When various fluxes of Examples A41 to A57 were used respectively to replace the flux of Example A40, good results were obtained in terms of ΔT and wettability. When using various fluxes of Examples B41 to B56 respectively to replace the flux of Example B40, good results were obtained in terms of ΔT and wettability.

Similarly, when the various fluxes of Examples A40 to A57 were combined with the various solder alloys of Example C, good results were obtained in terms of ΔT and wettability. Furthermore, when the various fluxes of Examples B40 to B56 were combined with the various solder alloys of Example D, good results were obtained in terms of ΔT and wettability.

In addition, especially when welded joints using alloys containing more than 25 ppm As are subjected to aging treatment at 100 to 200°C in an atmospheric environment, the yellowing change is suppressed compared to those without As.

This application is based on Japanese patent applications (Special Application No. 2019-098526 and Special Application No. 2019-098522) filed with the Japan Patent Office on May 27, 2019, the contents of which are incorporated herein by reference.

Claims (8)

A flux for welding a solder alloy, which contains at least one selected from the group consisting of a chloride amide and a chloride ester. The total content of bridge acid esters is more than 0 mass % and less than 5 mass %. The aforementioned chloro bridge acid amide is selected from the compounds represented by the following formulas (1) to (4) and (6) to (8). The aforementioned chlorobridge acid ester is selected from the group consisting of chlorobridge acid monomethyl ester, chlorobridge acid monoethyl ester, chlorobridge acid monoisopropyl ester, chlorobridge acid monoethylene glycol ester, chlorobridge acid monoethyl ester, and chlorobridge acid monoethyl ester. One or more species of the group consisting of acid dimethyl ester and chlorobridge acid ester dimer represented by the following formula (9);

(In the formula, R represents a linear or branched alkylene group, an alkylene glycol group, or an oxyalkylene group that may be substituted and has 1 to 54 carbon atoms.) The flux of claim 1 further contains a solvent. The flux of claim 2, wherein the aforementioned solvent is 2-propanol. The flux of claim 1 or 2, wherein the aforementioned welding is flow welding. A method of manufacturing a joint body, which includes the step of welding a solder alloy on the surface of a substrate treated with the flux according to any one of claims 1 to 4 to form a joint body. The manufacturing method of claim 5, wherein the aforementioned welding is flow welding. A joint body obtained by the manufacturing method of claim 5 or 6. A flux activator consisting of one or more chloroamide amide selected from the group of compounds represented by the following formulas (1) to (4) and (6) to (8);

(In the formula, R represents a linear or branched alkylene group, an alkylene glycol group, or an oxyalkylene group that may be substituted and has 1 to 54 carbon atoms.)