Water-soluble flux and solder paste

Abstract

To provide a water-soluble flux that enables formation of a solder paste exhibiting relatively superior cleanability, and a solder paste comprising the water-soluble flux.SOLUTION: A water-soluble flux according to the present invention comprises polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an activator, and a thixotropic agent, wherein the content of the polyoxyethylene sorbitan monopalmitate is 4.0 mass% or more and 62.5 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 such problems, for example, Patent Document 1 discloses a water-soluble flux for cored solder that contains vegetable oil, an emulsifier, and an organic acid such as citric acid and can be washed with water alone. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 4-274896 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the solder paste containing the water-soluble flux described in Patent Document 1 does not have sufficient water cleanability, and there is room for improvement in terms of the water-soluble flux.

[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 relatively excellent cleanability, and a solder paste containing the water-soluble flux. [Means for solving the problem]

[0009] The water-soluble flux according to the present invention comprises polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an activator, and a thixotropic agent, and the content of the polyoxyethylene sorbitan monopalmitate is 4.0 mass % or more and 62.5 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 that is relatively easy to clean, 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 polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an activator, and a thixotropic agent.

[0014] (Polyoxyethylene sorbitan monopalmitate) Polyoxyethylene sorbitan monopalmitate is a hydrophilic nonionic surfactant, and commercially available products such as Rheodol (registered trademark) TW-P120 (manufactured by Kao Corporation) can be used.

[0015] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, the content of polyoxyethylene sorbitan monopalmitate is 4.0 mass % or more and 62.5 mass % or less, preferably 10.0 mass % or more and 62.5 mass % or less, and more preferably 10.0 mass % or more and 50.0 mass % or less, based on the total mass of the water-soluble flux.

[0016] (Water-soluble base agent) Examples of water-soluble base agents include fatty acid ethylene oxide adducts, fatty acid polyethylene oxide adducts, polyethylene glycol, ethylene oxide-resorcinol copolymers, polyoxyalkylene acetylene glycols, polyoxyalkylene glyceryl ethers, polyoxyalkylene alkyl ethers, polyoxyalkylene esters, polyoxyalkylene alkylamines, polyoxyalkylene alkylamides, aliphatic alcohol polyoxyethylene adducts, aromatic alcohol polyoxyethylene adducts, polyhydric alcohol polyoxyethylene adducts, polyoxyalkylene adducts of various amines, etc. The water-soluble base agents may be used alone or in combination of two or more.

[0017] 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.

[0018] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, the content of the water-soluble base agent is preferably 5.0 mass % or more and 40.0 mass % or less, and more preferably 7.5 mass % or more and 20.0 mass % or less, based on the total mass of the water-soluble flux.

[0019] (activator) Examples of the activator include organic acid activators, amine compounds, amino acid compounds, amine halogen salts, halogen compounds, and other halogen activators. The activators may be used alone or in combination of two or more.

[0020] 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, picolinic acid, and N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid.

[0021] 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.

[0022] Examples of amino acid compounds 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).

[0023] 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.

[0024] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, 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.

[0025] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, the activator may preferably contain N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid.

[0026] When the activator contains N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, the content of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid is preferably 0.1 mass % or more and 4.0 mass % or less, and more preferably 0.3 mass % or more and 3.0 mass % or less, based on the total mass of the water-soluble flux, from the viewpoint of obtaining a solder paste with relatively excellent cleanability.

[0027] (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-(benzylidene)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.

[0028] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, the content of the thixotropic agent is preferably 0.1 mass % to 5.0 mass % and more preferably 0.5 mass % to 2.0 mass % relative to 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.

[0029] (solvent) The water-soluble flux according to this embodiment may contain a solvent. Examples of the solvent include 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.

[0030] From the viewpoint of obtaining a solder paste with relatively excellent cleanability, the content of the solvent is preferably 1.0 mass % or more and 60.0 mass % or less, more preferably 20.0 mass % or more and 50.0 mass % or less, based on the total mass of the water-soluble flux. When two or more kinds of solvents are contained, the content is the total content of the solvents.

[0031] The water-soluble flux according to this embodiment may contain other additives. Examples of the other additives include stabilizers, surfactants other than polyoxyethylene sorbitan monopalmitate, resins, and antifoaming agents. The additives may be used alone or in combination of two or more.

[0032] The water-soluble flux according to this embodiment contains polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an activator, and a thixotropic agent, and the content of the polyoxyethylene sorbitan monopalmitate is 4.0% by mass or more and 62.5% by mass or less based on the total mass of the water-soluble flux, thereby making it possible to obtain a solder paste with relatively excellent cleanability.

[0033] In the water-soluble flux according to this embodiment, the polyoxyethylene sorbitan monopalmitate may be contained in an amount of 10.0% by mass or more and 62.5% by mass or less based on the total mass of the water-soluble flux, thereby making it possible to obtain a solder paste with even better cleanability.

[0034] In the water-soluble flux according to this embodiment, the activator may contain N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid, which allows for the production of a solder paste with even better cleanability.

[0035] <Solder paste> The solder paste according to this embodiment contains the above-mentioned water-soluble flux and solder alloy powder.

[0036] 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.

[0037] 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.

[0038] The solder paste according to this embodiment contains the water-soluble flux and the solder alloy powder, and has relatively excellent cleanability.

[0039] The present invention includes the following aspects. [1] A water-soluble flux comprising polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an activator, and a thixotropic agent, wherein the content of the polyoxyethylene sorbitan monopalmitate is 4.0 mass% or more and 62.5 mass% or less with respect to the entire water-soluble flux. [2] The water-soluble flux according to [1], wherein the polyoxyethylene sorbitan monopalmitate is contained in an amount of 10.0% by mass or more and 62.5% by mass or less based on the total mass of the water-soluble flux. [3] The water-soluble flux according to [1] or [2], wherein the activator contains N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid. [4] A solder paste comprising the water-soluble flux according to any one of [1] to [3] and a solder alloy powder. [Example]

[0040] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0041] <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.

[0042] Next, each water-soluble flux and solder alloy powder (SAC305: Sn 96.5%, Ag 3.0%, Cu 0.5%) were mixed in the amounts shown in Tables 2 to 4 to obtain solder pastes for each example and comparative example.

[0043] [Table 1]

[0044] [Table 2]

[0045] [Table 3]

[0046] [Table 4]

[0047] <Preparation of test substrate> Using a printer (YSP, manufactured by Yamaha Motor Co., Ltd.), the solder paste of each example and comparative example was printed on an evaluation board under the following printing conditions: The evaluation board had 20 linear pads arranged in a row (either a horizontal row or a vertical row) with a line and space (L / S) ratio of 0.20 / 0.20.

[0048] (Printing conditions) Printing environment: Temperature 25±1℃, humidity 50±10%RH Printing squeegee: Metal squeegee Squeegee angle: 60° Mask thickness: 120 μm Printing speed: 40mm / sec Printing pressure: 50N Pad size: Line width: 0.2mm, Line length: 1.50mm Pad material: OSP treated copper

[0049] Next, the substrate on which the solder paste was printed was heated under the following temperature conditions to melt the solder alloy powder and form a soldered portion (i.e., a portion where the solder alloy powder was melted and integrated).The substrate was preheated under the following temperature condition (i) and then heated under the following temperature condition (ii).

[0050] (Temperature conditions) (i) During preheating Heating rate: 1.0 to 3.0°C / sec Preheat temperature: 150-190℃ / 60-100 seconds Heating environment: Air (ii) When solder melts Heating rate: 1.0 to 2.0°C / sec Melting temperature: 219°C or higher / 30 seconds or more Peak temperature: 230-250℃

[0051] Finally, the substrate with the soldered portions formed thereon was placed in pure water at 40°C and washed for 5 minutes in an ultrasonic cleaner, after which the substrate was dried to prepare a test substrate for each example and comparative example.

[0052] <Evaluation of cleaning ability> The condition of the spaces between adjacent soldered joints (19 locations) in the soldered joints with a line and space (L / S) of 0.20 / 0.20 on two test boards of the example and each comparative example was visually inspected and evaluated based on the following criteria. The evaluation results are shown in Tables 2 to 4. ◎: No residue was found between the soldered joints in any of the 19 locations on either of the two boards. ○: No residue was found between the soldered joints at any of the 19 locations on one board. ×: Residue was observed on both sheets.

[0053] As can be seen from the results in Tables 2 to 4, the solder pastes containing the water-soluble fluxes of the examples that meet all the requirements of the present invention are relatively excellent in cleanability.

Claims

1. The composition comprises polyoxyethylene sorbitan monopalmitate, a water-soluble base agent, an active agent, and a thixotropic agent, A water-soluble flux, wherein the content of the polyoxyethylene sorbitan monopalmitate is 4.0 mass % or more and 62.5 mass % or less based on the total mass of the water-soluble flux.

2. 2. The water-soluble flux according to claim 1, wherein the polyoxyethylene sorbitan monopalmitate is contained in an amount of 10.0 mass % or more and 62.5 mass % or less based on the total mass of the water-soluble flux.

3. The water soluble flux of claim 1, wherein the activator comprises N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid.

4. A solder paste comprising the water-soluble flux according to any one of claims 1 to 3 and a solder alloy powder.

Images