Water-soluble flux and solder paste

Abstract

To provide a water-soluble flux that enables formation of a solder paste exhibiting superior continuous printability, and a solder paste comprising the water-soluble flux.SOLUTION: A water-soluble flux according to the present invention comprises a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator, wherein the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5 mass% or more and 25.0 mass% or less based on the total water-soluble flux. A solder paste according to the present invention comprises the water-soluble flux and a solder alloy powder.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a water-soluble flux and a solder paste. [Background technology]

[0002] A solder paste containing a mixture of solder alloy powder and flux is used to bond electronic circuit boards, such as printed wiring boards, to bonding components. The solder paste is applied to the electrode portions on the surface of the board, and is heated (reflowed) while the electrode portions of the bonding components are in contact with the electrode portions. This melts the solder alloy powder to form a solder joint, resulting in a bonded structure in which the board and bonding components are bonded via the solder joint.

[0003] The flux contained in solder paste is blended to improve solderability and contains, for example, resin, activator, solvent, antioxidant, thixotropic agent, etc. However, when soldering is performed using a solder paste containing such flux, flux residue remains around the solder joint after reflow. Because such flux residue can cause various problems, efforts are made to reduce the flux residue by cleaning with a cleaning solution to remove it.

[0004] In recent years, from the viewpoint of reducing the environmental impact, there has been a demand for removing flux residues using semi-aqueous or aqueous cleaning solutions without using organic solvents. However, when semi-aqueous or aqueous cleaning solutions are used, there is a problem that the flux residues cannot be sufficiently removed by cleaning.

[0005] To solve these problems, for example, Patent Document 1 discloses a water-soluble flux for solder paste that contains an organic acid polyglycerol ester as a surfactant, benzylidene sorbitol or a benzylidene sorbitol derivative as a thixotropic agent, and a solvent, and that can be washed off with water alone. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-148868 Summary of the Invention [Problem to be solved by the invention]

[0007] However, solder pastes containing such water-soluble fluxes do not have sufficient continuous printability on printed circuit boards and the like, and there is room for improvement.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a water-soluble flux that can produce a solder paste with excellent continuous printability, and a solder paste containing the water-soluble flux. [Means for solving the problem]

[0009] The water-soluble flux according to the present invention contains a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator, and the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5 mass % or more and 25.0 mass % or less with respect to the total mass of the water-soluble flux.

[0010] The solder paste according to the present invention contains the water-soluble flux and a solder alloy powder. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a water-soluble flux that can produce a solder paste with excellent continuous printability, and a solder paste that contains the water-soluble flux. DETAILED DESCRIPTION OF THE INVENTION

[0012] The water-soluble flux and solder paste according to the embodiments of the present invention will be described below.

[0013] <Water-soluble flux> The water-soluble flux according to this embodiment contains a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator.

[0014] (fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct) Examples of fatty acid ethylene oxide adducts or fatty acid polyethylene oxide adducts include compounds in which ethylene oxide or polyethylene oxide is added to a fatty acid such as oleic acid, lauric acid, palmitic acid, stearic acid, behenic acid, or montanic acid. The fatty acid ethylene oxide adduct is preferably at least one selected from the group consisting of stearic acid ethylene oxide adducts and montanic acid ethylene oxide adducts. The fatty acid polyethylene oxide adduct is preferably at least one selected from the group consisting of stearic acid polyethylene oxide adducts and montanic acid polyethylene oxide adducts. The fatty acid ethylene oxide adducts or fatty acid polyethylene oxide adducts may be used alone or in combination of two or more.

[0015] From the viewpoint of obtaining a solder paste with excellent continuous printability, the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5% by mass or more and 25.0% by mass or less, and preferably 10.0% by mass or more and 20.0% by mass or less, based on the total mass of the water-soluble flux. When two or more types of fatty acid ethylene oxide adducts or fatty acid polyethylene oxide adducts are contained, the content is the total content of the fatty acid ethylene oxide adducts or fatty acid polyethylene oxide adducts.

[0016] (thixotropic agent) Examples of thixotropic agents include benzylidene sorbitol, benzylidene sorbitol derivatives, hydrogenated castor oil, amides, kaolin, colloidal silica, organic bentonite, and glass frit. Among these, benzylidene sorbitol or a benzylidene sorbitol derivative is preferred from the viewpoint of cleaning properties for flux residue. Examples of benzylidene sorbitol or a benzylidene sorbitol derivative include 1,3:2,4-bis-O-(4-methylbenzylidene)-D-sorbitol and 1,3:2,4-bis-O-benzylidene-D-sorbitol. The thixotropic agents may be used alone or in combination of two or more.

[0017] From the viewpoint of obtaining a solder paste with excellent continuous printability, the content of the thixotropic agent is preferably 0.3 mass % or more and 5.0 mass % or less, more preferably 0.5 mass % or more and 1.5 mass % or less, based on the total mass of the water-soluble flux. When two or more types of thixotropic agents are contained, the content is the total content of the thixotropic agents.

[0018] (solvent) Examples of solvents include known solvents such as glycol ethers such as diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether (dibutyl diglycol), diethylene glycol mono 2-ethylhexyl ether (2-ethylhexyl diglycol), diethylene glycol monobutyl ether (butyl diglycol), triethylene glycol monomethyl ether (methyl triglycol), triethylene glycol monobutyl ether (butyl triglycol), polyethylene glycol dimethyl ether, and tripropylene glycol n-butyl ether; aliphatic compounds such as n-hexane, isohexane, and n-heptane; esters such as isopropyl acetate, methyl propionate, and ethyl propionate; ketones such as methyl ethyl ketone, methyl-n-propyl ketone, and diethyl ketone; and alcohols such as ethanol, n-propanol, isopropanol, and isobutanol. These solvents may be used alone or in combination.

[0019] From the viewpoint of obtaining a solder paste with excellent continuous printability, the content of the solvent is preferably 20.0 mass % or more and 60.0 mass % or less, more preferably 30.0 mass % or more and 55.0 mass % or less, based on the total amount of the water-soluble flux. When two or more kinds of solvents are contained, the content is the total amount of the solvents.

[0020] (activator) The activator is not particularly limited, and examples thereof include organic acid activators, amine compounds, amino acid compounds, amine halogen salts, halogen activators such as halogen compounds, etc. The activators may be used alone or in combination of two or more.

[0021] Examples of organic acid surfactants include monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, pentadecylic acid, myristic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, and glycolic acid; dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, methylsuccinic acid, phenylsuccinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid; and other organic acids such as dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

[0022] The amine compound is not particularly limited, and examples thereof include imidazole compounds and triazole compounds. Examples of the imidazole compounds include benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole (2E4MZ), 2-heptadecylimidazole, 2-undecylimidazole, 1-(4,6-diamino-s-triazin-2-yl)ethyl-2-undecylimidazole, 1-butylimidazole, 2-phenylimidazole, and 4-methyl-2-phenylimidazole. Examples of the triazole compounds include benzotriazole, 1H-benzotriazole-1-methanol, and 1-methyl-1H-benzotriazole. Examples of amine compounds other than the imidazole compounds and triazole compounds include cetylamine, erucic acid amide, 3-(dimethylamino)-1,2-propanediol, 3,5-dimethylpyrazole, dimethylurea, hexahydro-1,3,5-triphenyl-1,3,5-triazine, pyrazinamide, N-phenylglycine, 3-methyl-5-pyrazolone, N-lauroylsarcosine, and 1,3-diphenylguanidine.

[0023] Examples of amino acids include N-acetylphenylalanine (N-acetyl-L-phenylalanine, N-acetyl-DL-phenylalanine, N-acetyl-D-phenylalanine), N-acetylglutamic acid (N-acetyl-L-glutamic acid), N-acetylglycine, N-acetylleucine (N-acetyl-L-leucine, N-acetyl-DL-leucine, N-acetyl-D-leucine), and N-acetylphenylglycine (N-acetyl-N-phenylglycine, N-acetyl-L-phenylglycine, N-acetyl-DL-phenylglycine).

[0024] Examples of halogen-based activators include amine halogen salts and halogen compounds. Examples of amines in amine halogen salts include diethylamine, dibutylamine, tributylamine, diphenylguanidine, and cyclohexylamine. Examples of halogens in amine halogen salts include fluorine, chlorine, bromine, and iodine. Examples of halogen compounds include tris(2,3-dibromopropyl)isocyanurate, 2,3-dibromo-2-butene-1,4-diol, 2-bromo-3-iodo-2-butene-1,4-diol, TBA-bis(2,3-dibromopropyl ether), and 4,4'-diiodobiphenyl.

[0025] From the viewpoint of obtaining a solder paste with excellent continuous printability, the content of the activator is preferably 0.5% by mass or more and 40.0% by mass or less, more preferably 2.0% by mass or more and 20.0% by mass or less, based on the total mass of the water-soluble flux. When two or more types of activators are contained, the content is the total content of the activators.

[0026] The water-soluble flux according to this embodiment may contain other additives. Examples of the other additives include stabilizers, surfactants, resins, and antifoaming agents. The additives may be used alone or in combination of two or more.

[0027] The water-soluble flux according to this embodiment contains a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator, and the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5% by mass or more and 25.0% by mass or less based on the total mass of the water-soluble flux, thereby providing a solder paste with excellent continuous printability.

[0028] In the water-soluble flux according to this embodiment, the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct may be 10.0% by mass or more and 20.0% by mass or less based on the total mass of the water-soluble flux, thereby obtaining a solder paste with even better continuous printability.

[0029] In the water-soluble flux according to this embodiment, the fatty acid ethylene oxide adduct may be at least one selected from the group consisting of stearic acid ethylene oxide adduct and montanic acid ethylene oxide adduct, thereby providing a solder paste with even better continuous printability.

[0030] In the water-soluble flux according to this embodiment, the fatty acid polyethylene oxide adduct may be at least one selected from the group consisting of a stearic acid polyethylene oxide adduct and a montanic acid polyethylene oxide adduct, thereby providing a solder paste with even better continuous printability.

[0031] <Solder paste> The solder paste according to this embodiment contains the above-mentioned water-soluble flux and solder alloy powder.

[0032] The alloy of the solder alloy powder is not particularly limited, and examples thereof include lead-free solder alloys and eutectic solder alloys containing lead. From the viewpoint of reducing environmental impact, the alloy of the solder alloy powder is preferably a lead-free solder alloy. Examples of such alloys include alloys containing tin, silver, copper, indium, zinc, bismuth, antimony, etc. More specifically, examples of alloy compositions include Sn / Ag, Sn / Ag / Cu, Sn / Cu, Sn / Ag / Bi, Sn / Bi, Sn / Ag / Cu / Bi, Sn / Sb, Sn / Zn / Bi, Sn / Zn, Sn / Zn / Al, Sn / Ag / Bi / In, Sn / Ag / Cu / Bi / In / Sb, and In / Ag. Among these, the alloy composition is preferably Sn / Ag / Cu. Furthermore, Sn / Ag / Cu preferably further contains at least one element selected from the group consisting of In, Bi, Sb, and Ni. Such alloys contain unavoidable impurities. "Avoidable impurities" refer to components that are inevitably mixed in during the manufacturing process and are acceptable within a range that does not affect the effects of the present invention.

[0033] The solder paste according to this embodiment is obtained by mixing the water-soluble flux and the solder alloy powder. The content of the water-soluble flux is preferably 5% by mass or more and 20% by mass or less based on the total solder paste. The content of the solder alloy powder is preferably 80% by mass or more and 95% by mass or less based on the total solder paste.

[0034] The solder paste according to this embodiment contains the water-soluble flux and the solder alloy powder, and has excellent continuous printability.

[0035] The present invention includes the following aspects. [1] A composition comprising a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator; A water-soluble flux, wherein the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5 mass % or more and 25.0 mass % or less with respect to the entire water-soluble flux. [2] The water-soluble flux according to [1], wherein the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 10.0 mass % or more and 20.0 mass % or less with respect to the total amount of the water-soluble flux. [3] The water-soluble flux according to [1] or [2], wherein the fatty acid ethylene oxide adduct is at least one selected from the group consisting of stearic acid ethylene oxide adduct and montanic acid ethylene oxide adduct. [4] The water-soluble flux according to any one of [1] to [3], wherein the fatty acid polyethylene oxide adduct is at least one selected from the group consisting of a stearic acid polyethylene oxide adduct and a montanic acid polyethylene oxide adduct. [5] A solder paste comprising the water-soluble flux according to any one of [1] to [4] and a solder alloy powder. [Example]

[0036] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0037] <Preparing solder paste> The materials shown in Table 1 were placed in a heating vessel in the amounts shown in Tables 2 to 4, and all materials were dissolved by heating to 180°C. The materials were then cooled to room temperature, yielding uniformly dispersed water-soluble fluxes for each Example and Comparative Example. The amounts shown in Table 1 are equal to the contents of the components contained in the water-soluble flux.

[0038] Next, 11 mass % of each water-soluble flux and 89 mass % of solder alloy powder (SAC305: Sn 96.5%, Ag 3.0%, Cu 0.5%) were mixed to obtain solder pastes for each example and comparative example.

[0039] [Table 1]

[0040] [Table 2]

[0041] [Table 3]

[0042] [Table 4]

[0043] <Evaluation of continuous printing> The continuous printability of the solder paste of each example and comparative example was evaluated using a printing machine (YSP, manufactured by Yamaha Motor Co., Ltd.). More specifically, a metal mask was placed on the evaluation board, and 200 g of the solder paste of each example and comparative example was placed on the metal mask. Rolling was performed four times to ensure that the solder paste was applied to the metal mask. The back of the metal mask was then dry-cleaned, and printing was performed 10 times under the printing conditions described below. The continuous printability was evaluated based on the following index. Printing was performed continuously on 10 boards, and the land pattern locations of the QFP with a 0.4 mm pitch were visually observed and evaluated based on the following index. The evaluation results are shown in Tables 2 to 4. ○: No bridging occurred. ×: A bridge occurred or printing was not possible.

[0044] (Printing conditions) Printing environment: Temperature 24-26°C, humidity 50-60%RH Printing squeegee: Metal squeegee Squeegee angle: 60° Metal mask thickness: 120 μm Printing speed: 40mm / sec Printing pressure: 50N Pad shape and size: Linear (line width: 0.20 mm, line length: 1.50 mm) Number of pads: 20 Pad material: OSP treated copper

[0045] As can be seen from the results in Tables 2 to 4, the solder pastes containing the water-soluble fluxes of the examples that satisfy all the requirements of the present invention are excellent in continuous printing properties.

Claims

1. The composition comprises a fatty acid ethylene oxide adduct or a fatty acid polyethylene oxide adduct, a thixotropic agent, a solvent, and an activator; A water-soluble flux, wherein the content of the fatty acid ethylene oxide adduct or fatty acid polyethylene oxide adduct is 7.5 mass % or more and 25.0 mass % or less with respect to the entire water-soluble flux.

2. 2. The water-soluble flux according to claim 1, wherein the content of the fatty acid ethylene oxide adduct or the fatty acid polyethylene oxide adduct is 10.0 mass % or more and 20.0 mass % or less with respect to the entire water-soluble flux.

3. 2. The water-soluble flux according to claim 1, wherein the fatty acid ethylene oxide adduct is at least one selected from the group consisting of a stearic acid ethylene oxide adduct and a montanic acid ethylene oxide adduct.

4. 2. The water-soluble flux according to claim 1, wherein the fatty acid polyethylene oxide adduct is at least one selected from the group consisting of a stearic acid polyethylene oxide adduct and a montanic acid polyethylene oxide adduct.

5. A solder paste comprising the water-soluble flux according to any one of claims 1 to 4 and a solder alloy powder.

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