Flux and method for producing joined body

Abstract

Disclosed are a flux containing rosin, an active agent, and a solvent, the active agent containing an imidazole compound and two dicarboxylic acids, the two dicarboxylic acids being combined with malonic acid using one selected from succinic acid, adipic acid, and sebacic acid, and a method for preparing a joined body using the flux. Or the soldering flux contains rosin, an active agent and a solvent, the active agent contains an imidazole compound and two dicarboxylic acids, and the two dicarboxylic acids are combined with succinic acid and one selected from suberic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid. According to the present invention, it is possible to provide a flux capable of increasing the leg size and suppressing the occurrence of bridging during soldering.

Description

(19) State Intellectual Property Office (12) Invention Patent Application (10) Application Publication Number (43) Application Publication Date (21) Application Number 202510931261.3 (22) Application Date 2025.07.07 (30) Priority Data 2024-111652 2024.07.11 JP (71) Applicant Senju Metal Industries, Ltd. Address Tokyo, Japan (72) Inventors Hirano Satsuki Yamazaki Hiroyuki Shinohara Takema (74) Patent Agency Beijing Runping Intellectual Property Agency Co., Ltd. 11283 Patent Attorney Liu Bing (51) Int.Cl. B23K 35 / 363 (2006.01) B23K 35 / 40 (2006.01) B23K 35 / 362 (2006.01) (54) Invention Title: Flux and Joint (57) Abstract: This invention discloses a flux and a method for preparing a joint using the flux. The flux contains rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are selected from succinic acid, adipic acid, and sebacic acid, and malonic acid. Alternatively, the flux contains rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are selected from octanoic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid, and succinic acid. According to this invention, a flux that can increase the solder leg size and suppress bridging during soldering can be provided. Claims 1 page, Description 18 pages, CN 121315519 A 2026.01.13 CN 1 21 31 55 19 A 1. A flux, which is a soldering flux for using Sn-Bi-based solder, comprising rosin, an activator and a solvent, wherein the activator comprises an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are composed of a combination of dicarboxylic acid (Ic) and malonic acid, wherein the dicarboxylic acid (Ic) is selected from succinic acid, adipic acid and sebacic acid, wherein the content of rosin relative to the total mass (100% by mass) of the flux is 3% by mass or more and 25% by mass or less, the content of the imidazole compound relative to the total mass (100% by mass) of the flux is 0.1% by mass or more and 1.5% by mass or less, and the total content of the two dicarboxylic acids relative to the total mass (100% by mass) of the flux is 0.5% by mass or more and 6% by mass or less. The mass ratio of the dicarboxylic acid (IC) to malonic acid, expressed as a dicarboxylic acid (IC) / malonic acid mass ratio, is 10 / 90 or more and 90 / 10 or less, and the flux excludes fluxes containing three or more dicarboxylic acids. 2. The flux according to claim 1, wherein the mass ratio of the dicarboxylic acid (IC) / malonic acid mass ratio is 40 / 60 or more and 75 / 25 or less.3. A flux for soldering Sn-Bi based solder, comprising rosin, an activator, and a solvent, wherein the activator comprises an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are composed of a combination of dicarboxylic acid (2c) and succinic acid, wherein the dicarboxylic acid (2c) is selected from octanoic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid; wherein, relative to the total mass (100% by mass) of the flux, the content of the rosin is 3% by mass or more and 25% by mass or less; wherein, relative to the total mass (100% by mass) of the flux, the content of the imidazole compound is 0.1% by mass or more and 1.5% by mass or less; wherein, relative to the total mass (100% by mass) of the flux, the total content of the two dicarboxylic acids is 0.5% by mass or more and 6% by mass or less; and wherein the mass ratio of the dicarboxylic acid (2c) to succinic acid, expressed as a dicarboxylic acid (2c) / succinic acid mass ratio, is 10 / 90 or more and 90 / 10 or less. Furthermore, the flux excludes fluxes containing three or more dicarboxylic acids. 4. The flux according to claim 3, wherein the mass ratio of the dicarboxylic acid (2c) / succinic acid is 10 / 90 or more and 60 / 40 or less. 5. The flux according to any one of claims 1 to 4, wherein the mass ratio of the two dicarboxylic acids to the imidazole compound is 0.30 or more and 50 or less, expressed as a mass ratio of the two dicarboxylic acids / imidazole compound. 6. A method for preparing a bond, comprising the step of obtaining a bond by welding a solder alloy onto the surface of a substrate treated with the flux according to any one of claims 1 to 4, wherein the solder alloy is composed of an alloy containing Sn and Bi. Claims 1 / 1 page 2 CN 121315519 A Flux and Bond Technical Field

[0001] The present invention relates to flux and a method for preparing a bond. Background Art

[0002] Generally, components are fixed to a substrate and components are electrically connected to a substrate by welding. In welding, methods such as flow welding and reflow welding are used depending on the size of the objects to be joined.

[0003] For example, in flow welding, flux is first applied to a substrate on which the component is mounted. Then, while conveying the substrate on which the component is mounted, molten flux sprayed from below the substrate is brought into contact with the welding surface, thereby performing welding.

[0004] The flux used in welding usually contains resin components, solvents, activators, etc. For example, Patent Document 1 discloses a flux containing rosin as a resin component, a solvent, and specific hydroxybenzoic acid and monocarboxylic acid as activators. The flux disclosed in Patent Document 1 is considered to be a flux suitable for flow welding.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2024-34098 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] However, in recent years, from the viewpoint of energy saving, Sn-Bi-based solders containing Sn and Bi, which can be soldered at lower temperatures, have been used. When using Sn-Bi-based solders containing more Bi, their hard and brittle properties become a disadvantage, and the bonding strength of the joined objects becomes a problem.

[0010] To address this problem, a method to improve the bonding strength by increasing the solder leg size (the size of the molten and solidified solder) has been considered. However, when soldering with existing fluxes, the solder leg shape is poor, or even if the solder leg size can be increased, bridging occurs, making it difficult to balance both aspects.

[0011] The present invention has been made in view of the above circumstances, and provides a flux that can increase the solder leg size and suppress the generation of bridging during soldering, and a method for preparing a joint using the flux.

[0012] Means for Solving the Problem

[0013] In order to solve the above-mentioned problem, the present invention adopts the following structure.

[0014] [1] A flux containing rosin, an activator and a solvent, wherein the activator contains an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are composed of a combination of dicarboxylic acid (1c) and malonic acid, wherein the dicarboxylic acid (1c) is selected from succinic acid, adipic acid and sebacic acid.

[0015] [2] A flux containing rosin, an activator and a solvent, wherein the activator contains an imidazole compound and two dicarboxylic acids, wherein the two dicarboxylic acids are composed of a combination of dicarboxylic acid (2c) and succinic acid, wherein the dicarboxylic acid (2c) is selected from octanoic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid.

[0016] [3] The flux according to [1] or [2], wherein the mass ratio of the two dicarboxylic acids to the imidazole compound, expressed as a mass ratio of the two dicarboxylic acids / imidazole compound, is 0.30 or more and 50 or less.

[0017] [4] The flux according to any one of [1] to [3], wherein, relative to the total mass of the flux expressed in 100% by mass, the content of the imidazole compound is 0.1% by mass or more and 1.5% by mass or less.

[0018] [5] The flux according to any one of [1] to [4], wherein, relative to the total mass of the flux expressed in 100% by mass, the total content of the two dicarboxylic acids is 0.5% by mass or more and 6% by mass or less.

[0019] [6] The flux according to any one of [1] to [5], wherein the rosin content is 3% by mass or more and 25% by mass or less relative to the total mass of the flux expressed in 100% by mass.

[0020] [7] The flux according to any one of [1] to [6], wherein the flux is a welding flux using Sn-Bi-based solder.

[0021] [8] The flux according to any one of [1] to [7], wherein the flux does not contain three or more dicarboxylic acids.

[0022] [9] The flux according to any one of [1], [3] to [8], wherein the mass ratio of the dicarboxylic acid (1c) to malonic acid, expressed as a mass ratio of dicarboxylic acid (1c) / malonic acid, is 10 / 90 or more and 90 / 10 or less.

[0023]

[10] The flux according to any one of [2] to [8], wherein the mass ratio of the dicarboxylic acid (2c) to succinic acid, expressed as a mass ratio of dicarboxylic acid (2c) / succinic acid, is 10 / 90 or more and 90 / 10 or less.

[0024]

[11] The flux according to any one of [1], [3] to [9], wherein the mass ratio expressed as dicarboxylic acid (1c) / malonic acid is 40 / 60 or more and 75 / 25 or less.

[0025]

[12] The flux according to any one of [2] to [8],

[10] , wherein the mass ratio expressed as dicarboxylic acid (2c) / succinic acid is 10 / 90 or more and 60 / 40 or less.

[0026]

[13] A method for preparing a joint comprising a step of obtaining a joint by soldering a solder alloy onto the surface of a substrate treated with the flux according to any one of [1] to

[12] , wherein the solder alloy is composed of an alloy containing Sn and Bi.

[0027] Effects of the Invention

[0028] According to the present invention, it is possible to provide a flux that can increase the solder leg size and suppress the generation of bridging during soldering, and a method for preparing a joint using the flux.

[0029] This flux is suitable for use as a Sn-Bi based flux. Detailed Embodiments

[0030] Hereinafter, preferred examples of the flux and the preparation method of the joint of the present invention will be described. The following examples are examples described for better understanding of the gist of the invention, and the present invention is not limited unless specifically specified. Changes, additions, omissions, etc., in quantity, material, amount, value, ratio, etc. can be made without departing from the gist of the present invention.

[0031] (Fluoride)

[0032] The flux of the first aspect of the present invention contains rosin, an activator and a solvent, wherein the activator contains an imidazole compound and two dicarboxylic acids.

[0033] The two dicarboxylic acids contained in the flux are specifically a combination (1) or a combination (2) as described below.

[0034] Combination of two dicarboxylic acids (1): a combination of one of succinic acid, adipic acid and sebacic acid (hereinafter, sometimes referred to as dicarboxylic acid (1c)) and malonic acid

[0035] Combination of two dicarboxylic acids (2): a combination of one of octanoic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid (hereinafter, sometimes referred to as dicarboxylic acid (2c)) and succinic acid

[0036] That is, even if it is a flux containing dicarboxylic acids, a flux containing only one dicarboxylic acid, a flux containing two dicarboxylic acids that are different from the combination (1) or combination (2), or a flux containing three or more dicarboxylic acids, is outside the scope of fluxes of this manner.

[0037] Therefore, for example, fluxes containing a combination (1) of the two dicarboxylic acids and two or more other dicarboxylic acids of the combination (1) are outside the scope of fluxes of this type because they also contain three or more dicarboxylic acids. Additionally, fluxes containing two or three selected from succinic acid, adipic acid, and sebacic acid, and malonic acid, also contain three or more dicarboxylic acids and are therefore outside the scope of fluxes of this type.

[0038] Similarly, fluxes containing a combination (2) of the two dicarboxylic acids and two or more other dicarboxylic acids of the combination (2) also contain three or more dicarboxylic acids and are therefore outside the scope of fluxes of this type. Fluxes containing two or more selected from octanoic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid, and succinic acid, also contain three or more dicarboxylic acids and are therefore outside the scope of fluxes of this type.

[0039] As one embodiment of the flux of this method, a flux containing rosin, an activator, a solvent, and other ingredients as needed, wherein the activator contains an imidazole compound and a combination of the two dicarboxylic acids (1) (first embodiment).

[0040] As another embodiment of the flux of this method, a flux containing rosin, an activator, a solvent, and other ingredients as needed, wherein the activator contains an imidazole compound and a combination of the two dicarboxylic acids (2) (second embodiment).

[0041] <First Embodiment>

[0042] The flux of the first embodiment contains rosin, an activator, a solvent, and other ingredients as needed. The activator in the first embodiment contains an imidazole compound and a combination of the two dicarboxylic acids (1).

[0043] Rosin

[0044] In this embodiment, "rosin" includes natural resin containing a mixture of rosin acid and its isomers, with rosin acid as the main component, and substances obtained by chemically modifying natural resins (sometimes called rosin derivatives).

[0045] The term “main component” as used herein refers to a component that constitutes a compound and has a content of 40% or more by mass in that compound.

[0046] The content of rosin acid in the natural resin is 40% by mass or more, and as an example, it is 40% by mass or more and 80% by mass or less relative to the natural resin.

[0047] Representative examples of isomers of rosin acid include neorosin acid, longleaf rosin acid, and L-piperidine.

[0048] Examples of the above-mentioned "natural resin" include, for example, rosin resin, wood rosin, and oil rosin.

[0049] In the present invention, "substances obtained by chemically modifying natural resins (rosin derivatives)" include substances obtained by subjecting the "natural resin" to one or more treatments selected from hydrogenation, dehydrogenation, neutralization, epoxide addition, amidation, dimerization and polymerization, esterification, and Diels-Alder cyclization addition.

[0050] Examples of rosin derivatives include, for example, purified rosin and modified rosin.

[0051] Examples of modified rosin include, for example, hydrogenated rosin, polymerized rosin, polymerized hydrogenated rosin, disproportionated rosin, acid-modified rosin, rosin ester, acid-modified hydrogenated rosin, acid anhydride-modified hydrogenated rosin, acid-modified disproportionated rosin, acid anhydride-modified disproportionated rosin, phenol-modified rosin, and α,β-unsaturated carboxylic acid modified products (acrylated rosin, maleated rosin, fumaric acid-modified rosin, etc.), as well as purified products, hydrides and disproportions of the polymerized rosin, and purified products, hydrides and disproportions of the α,β-unsaturated carboxylic acid modified products, rosin alcohol, rosin amine, hydrogenated rosin alcohol, rosin ester, hydrogenated rosin ester, rosin soap, hydrogenated rosin soap, acid-modified rosin soap, etc.

[0052] Examples of rosin amines include, for example, dehydrorosin amine, dihydrorosin amine, etc. Rosin amine refers to so-called disproportionated rosin amine. Instruction manual 3 / 18 pages 5 CN 121315519 A

[0053] In the flux of the first embodiment, rosin may be used alone or in combination with two or more.

[0054] The rosin preferably contains rosin derivatives, more preferably contains at least one selected from acid-modified rosin, hydrogenated rosin, polymerized rosin and acid-modified hydrogenated rosin, and even more preferably contains at least one selected from acid-modified hydrogenated rosin, hydrogenated rosin and polymerized rosin.

[0055] As acid-modified hydrogenated rosin, from the viewpoint of solderability, acrylic acid-modified hydrogenated rosin is preferred. That is, the rosin preferably contains at least one selected from acrylic acid-modified hydrogenated rosin, hydrogenated rosin and polymerized rosin.

[0056] The rosin used in the flux of this embodiment may, for example, be a combination of acid-modified hydrogenated rosin and hydrogenated rosin, a combination of acid-modified hydrogenated rosin and partially hydrogenated rosin, or polymerized rosin.

[0057] The rosin content in the flux of the first embodiment can be arbitrarily selected, and is preferably 3% or more and 25% or less relative to the total mass (100% by mass) of the flux, more preferably 4% or more and 20% or less by mass.It can also be 5% or more by mass and less than 17% by mass, 8% or more by mass and less than 15% by mass, etc.

[0058] Surfactant

[0059] The surfactant in the first embodiment contains an imidazole compound and the following combination (1).

[0060] The imidazole compound can refer to imidazoles, preferably compounds containing an imidazole ring. It also includes compounds in which the nitrogen or carbon on the imidazole ring is substituted by a substituent.

[0061] Combination of two dicarboxylic acids (1): a combination of one of succinic acid, adipic acid, and sebacic acid with malonic acid

[0062] · Imidazole compound

[0063] Examples of imidazole compounds include, for example, 2-methylimidazolium, 2-ethylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium; 2-phenylimidazolium, 2-phenylimidazolium isocyanuric acid adduct, 2- Phenyl-4-methylimidazolium, 2-phenyl-4,5-dihydroxymethylimidazolium, 2-phenyl-4-methyl-5-hydroxymethylimidazolium, 1-cyanoethyl-2-phenylimidazolium, 1-benzyl-2-phenylimidazolium, 1-benzyl-2-methylimidazolium; epoxy-imidazolium adducts; benzimidazole, 2-methylbenzimidazole, 2-pentylbenzimidazole, 2-octylbenzimidazole, 2-nonylbenzimidazole, 2-(1-ethylpentyl)benzimidazole, 2-(4-thiazolyl)benzimidazole; 2,3-dihydro-1H-pyrrolo[1,2-a]benzimidazole; 1-dodecyl-2-methyl-3-benzylimidazolium chloride, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate; etc.

[0064] In the flux of the first embodiment, the imidazole compound may be used alone or in combination with two or more.

[0065] As described above, alkyl-substituted imidazole compounds are preferred, more preferably imidazole compounds selected from 2-methylimidazolium, 2-ethylimidazolium, 2-undecylimidazolium, 2-heptadecanylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium and 1-cyanoethyl-2-ethyl-4-methylimidazolium, further preferably imidazole compounds selected from 2-methylimidazolium, 2-ethylimidazolium, 2-undecylimidazolium, 2-heptadecanylimidazolium, 1,2-dimethylimidazolium and 2-ethyl-4-methylimidazolium, and most preferably 2-undecylimidazolium.

[0066] · Combination of two dicarboxylic acids (1)

[0067] The combination of two dicarboxylic acids (1) is any one of the following: succinic acid and malonic acid, adipic acid and malonic acid, or sebacic acid and malonic acid.

[0068] In the combination (1), from the viewpoint of solder lead size, a combination of succinic acid and malonic acid, a combination of sebacic acid and malonic acid are more preferred, and a combination of succinic acid and malonic acid is even more preferred.

[0069] The mass ratio of one of succinic acid, adipic acid and sebacic acid (as described above, also referred to as “dicarboxylic acid (1c)” on page 4 / 18 of the specification, 6 CN 121315519 A) to malonic acid in the combination (1), expressed as a mass ratio of dicarboxylic acid (1c) / malonic acid, is preferably 10 / 90 or more and 90 / 10 or less, more preferably 25 / 75 or more and 75 / 25 or less, and even more preferably 40 / 60 or more and 60 / 40 or less.

[0070] The content of the imidazole compound in the flux of the first embodiment can be arbitrarily selected, and is preferably 0.1% by mass or more and 2.0% by mass or less relative to the total mass (100% by mass) of the flux, more preferably 0.3% by mass or more and 1.8% by mass or less, further preferably 0.5% by mass or more and 1.5% by mass or less, and even more preferably 0.7% by mass or more and 1.5% by mass or less.

[0071] The total content of the two dicarboxylic acids in the flux of the first embodiment can be arbitrarily selected, and is preferably 0.5% by mass or more and 6% by mass or less relative to the total mass (100% by mass) of the flux, more preferably 1% by mass or more and 4% by mass or less. For example, it can be 0.7% by mass or more and 5% by mass or less, 2.0% by mass or more and 3.0% by mass or less, etc.

[0072] The mass ratio of the combination of two dicarboxylic acids (1) to the imidazole compound in the flux of the first embodiment, expressed as a mass ratio of two dicarboxylic acids / imidazole compound, is preferably 0.30 or more and 50 or less, more preferably 0.50 or more and 45 or less, and even more preferably 1 or more and 40 or less. For example, it may also be 1 or more and 20 or less, 1 or more and 5 or less, 1 or more and 3 or less, etc.

[0073] When the mass ratio of two dicarboxylic acids / imidazole compound is within the above-mentioned preferred range, the solder joint size can be easily controlled.

[0074] Other activators

[0075] In addition to the imidazole compound and the combination of two dicarboxylic acids (1), the activator in the first embodiment may also contain other activators as needed.

[0076] Examples of other activators include halogen compounds, organic acids other than dicarboxylic acids, organophosphorus compounds, etc.

[0077] Examples of halogen compounds include, for example, amine hydrohalates, organic halogen compounds other than amine hydrohalates, etc.

[0078] Aminohydrohalides are compounds formed by reacting amines with hydrogen halides. Examples of amines include aliphatic amines, guanidines, and azoles. Examples of hydrogen halides include, for example, hydrides of chlorine, bromine, and iodine.

[0079] Examples of aliphatic amines include ethylamine, dimethylamine, diethylamine, triethylamine, 2-ethylhexylamine, cyclohexylamine, and ethylenediamine. Examples of guanidines include 1,3-diphenylguanidine, 1,3-di-o-tolylguanidine, 1-o-tolylguanidine, 1,3-di-o-isopropylphenylguanidine, and 1,3-di-o-isopropylphenyl-2-propionylguanidine.

[0080] Examples of organohalogen compounds other than amine hydrohalides include, for example, halogenated aliphatic compounds. Halogenated aliphatic compounds are compounds in which some or all of the hydrogen atoms constituting the aliphatic hydrocarbon group are replaced by halogen atoms.

[0081] Examples of halogenated aliphatic compounds include halogenated aliphatic alcohols and halogenated heterocyclic compounds. Examples of halogenated aliphatic alcohols include 1-bromo-2-propanol, 3-bromo-1-propanol, 3-bromo-1,2-propanediol, 1-bromo-2-butanol, 1,3-dibromo-2-propanol, 2,3-dibromo-1-propanol, 2,3-dibromo-1,4-butanediol, 1,4-dibromo-2-butanol, and trans-2,3-dibromo-2-buten-1,4-diol.

[0082] Furthermore, halogen compounds may also be salts formed by reacting an amine with tetrafluoroboric acid (HBF4) or complexes formed by reacting an amine with boron trifluoride (BF3).

[0083] In addition, when using a halogen compound as an activator, one or more compounds may be used alone or in combination.

[0084] As the halogen compound, it is preferably selected from at least one of amine hydrohalates and halogenated aliphatic alcohols, more preferably amine hydrohalates and halogenated aliphatic alcohols (see page 5 / 18 of the specification, CN 121315519 A).

[0085] The content of the halogen compound in the flux of the first embodiment can be arbitrarily selected, and is preferably 0.1% by mass or more and 2% by mass or less, more preferably 0.5% by mass or more and 1.5% by mass or less, relative to the total mass (100% by mass) of the flux. For example, it can be 0.3% by mass or more and 1.2% by mass or less, 0.7% by mass or more and 1.5% by mass or less, etc.

[0086] As an organic acid other than dicarboxylic acid, examples include carboxylic acids and organic sulfonic acids. As the carboxylic acid, examples include aliphatic monocarboxylic acids and aromatic carboxylic acids.

[0087] Examples of aliphatic monocarboxylic acids include, for example, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, isononanoic acid, decanoic acid, decenoic acid, lauric acid (dodecanoic acid), undecanoic acid, 5-dodecenoic acid, tridecanoic acid, myristone acid, pentadecanoic acid, isopalmitic acid, palmitoleic acid, hexadecanoic acid, cyclopentene undecanoic acid, heptadecanic acid, isostearic acid, transoleic acid, parsleyic acid, stearatetraenoic acid, tung acid, tarric acid, isoleic acid, ricinoleic acid, piperidinic acid, styracidin, tarric acid, isoleic acid, ricinoleic acid, piperidinic acid, styracidin, nonadecanic acid, eicosanoic acid, stearic acid, 12-hydroxystearic acid, oleic acid, linoleic acid, linolenic acid, myristic acid, 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butyric acid, etc.

[0088] Examples of aromatic monocarboxylic acids include, for example, salicylic acid, p-hydroxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid, benzoic acid, 2,3-dihydroxybenzoic acid, 2-quinolinecarboxylic acid, 3-hydroxybenzoic acid, 3,4,5-trihydroxybenzoic acid, p-anisic acid; pyridinecarboxylic acid, 3-hydroxypyridinecarboxylic acid, etc.

[0089] Examples of organic sulfonic acids include, for example, aliphatic sulfonic acids, aromatic sulfonic acids, etc. Examples of aliphatic sulfonic acids include, for example, alkyl sulfonic acids, alkanol sulfonic acids, etc. Examples of aromatic sulfonic acids include, for example, 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, p-toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid, etc.

[0090] When using organic acids other than dicarboxylic acids as other active agents, one or more can be used alone or in combination.

[0091] The content of organic acids other than dicarboxylic acids in the flux of the first embodiment can be arbitrarily selected, and is preferably 0.1% by mass or more and 2% by mass or less, more preferably 0.5% by mass or more and 1.5% by mass or less, relative to the total mass (100% by mass) of the flux. For example, it can be 0.3% by mass or more and 1.2% by mass or less, 0.7% by mass or more and 1.0% by mass or less, etc. In addition, organic acids other than dicarboxylic acids may not be included in the flux. For example, the flux may not contain organic acids different from dicarboxylic acids.

[0092] Examples of organophosphorus compounds include acidic phosphate esters, acidic phosphonates, and acidic hypophosphonates.

[0093] The total content of the activator in the flux of the first embodiment can be arbitrarily selected, and is, for example, 2% by mass or more and 10% by mass or less, relative to the total mass (100% by mass) of the flux, or 2% by mass or more and 9% by mass or less. It can also be 3% or more by mass and 8% or less by mass, or 4% or more by mass and 6% or less by mass.

[0094] Solvents

[0095] Examples of solvents in the first embodiment include water, alcohol solvents, glycol ether solvents, terpineols, etc.

[0096] Examples of alcohol-based solvents include ethanol, 1-propanol, 2-propanol (isopropanol), 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-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, 2-methylpentane-2,4-diol, 1,1,1-tris(hydroxymethyl)propane, 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, 1-ethynyl-1-cyclohexanol, 1,4-cyclohexanediol, 1,4-cyclohexanediol, 2,4,7,9-tetramethyl-5-decyn-4,7-diol, 2-hexyl-1-decanol, 2-methyl-2,4-pentanediol (hexanediol), octanediol, etc.

[0097] Examples of glycol ether solvents include diethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether (ethylene glycol butyl ether), ethylene glycol monohexyl ether (ethylene glycol hexyl ether), diethylene glycol monohexyl ether (hexyl diethylene glycol), diethylene glycol dibutyl ether, triethylene glycol monobutyl ether, methyl glycerol, triethylene glycol butyl methyl ether, tetraethylene glycol, tetraethylene glycol dimethyl ether, tripropylene glycol n-butyl ether, etc.

[0098] Examples of terpineols include α-terpineol, β-terpineol, γ-terpineol, and mixtures of terpineols (i.e., mixtures whose main component is α-terpineol and which contain β-terpineol or γ-terpineol), etc.

[0099] Examples of other solvents include, for example, di(2-ethylhexyl) sebacate, liquid paraffin, etc.

[0100] In the flux of the first embodiment, the solvent may be used alone or in combination with two or more solvents.

[0101] As a solvent, it is preferable to contain a solvent with a boiling point of 100°C or less, more preferably an alcohol solvent, and even more preferably at least one selected from ethanol and 2-propanol, particularly preferably 2-propanol.

[0102] The content of solvent in the flux of the first embodiment can be arbitrarily selected, and relative to the total mass (100% by mass) of the flux, for example, it may be 60% by mass or more, 70% by mass or more and 95% by mass or less, 75% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.

[0103] Other Ingredients

[0104] In addition to rosin, activator and solvent, the flux of the first embodiment may contain other ingredients as needed.

[0105] Other components include, for example, resin components other than rosin, thixotropic agents, surfactants, metal passivators, antioxidants, silane coupling agents, colorants, etc. The flux of the first embodiment may also be a composition containing rosin, an imidazole compound, a combination of the two dicarboxylic acids (1), and a solvent, but without a thixotropic agent.

[0106] As explained above, in the flux of the first embodiment, a specific organic acid is combined in a specific amine. That is, an imidazole compound is selected as the specific amine, and one selected from succinic acid, adipic acid, and sebacic acid and malonic acid are used as the specific organic acid. Although the reason is not yet clear, a unique interaction resulting from the combination of such a specific amine and a specific organic acid is obtained in the flux of the first embodiment. Therefore, it is believed that the solder leg size can be increased and the generation of bridging can be suppressed during soldering.

[0107] The effect of the flux of the first embodiment is particularly significant when using an alloy containing Sn and Bi. That is, the flux of the first embodiment is suitable for use as a Sn-Bi based flux. Sn-Bi based solder, for example, may contain only Sn and Bi, or may be an alloy composed only of Sn and Bi, or may be an alloy containing Sn and Bi. The amount of Sn may be, for example, 30-80%, 40-70%, etc., and the amount of Bi may be, for example, 20-70%, 30-60%, etc.

[0108] <Second Embodiment>

[0109] The flux of the second embodiment contains rosin, an activator, a solvent, and other components as needed. The activator in the second embodiment contains an imidazole compound and a combination of the two dicarboxylic acids (2).

[0110] Rosin

[0111] The description of the rosin in the second embodiment is the same as the description of the rosin in the first embodiment described above.

[0112] In the flux of the second embodiment, rosin may be used alone or in combination with two or more types.

[0113] The rosin preferably contains a rosin derivative, more preferably contains at least one selected from acid-modified rosin, hydrogenated rosin, polymerized rosin, and acid-modified hydrogenated rosin, and even more preferably contains at least one selected from acid-modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin. Specification 7 / 18 pages 9 CN 121315519 A

[0114] As an acid-modified hydrogenated rosin, from the viewpoint of solderability, acrylic acid-modified hydrogenated rosin is preferred. That is, the rosin preferably contains at least one selected from acrylic acid-modified hydrogenated rosin, hydrogenated rosin, and polymerized rosin.

[0115] The rosin used in the flux of this embodiment may, for example, be a combination of acid-modified hydrogenated rosin and hydrogenated rosin, or a combination of acid-modified hydrogenated rosin and partially hydrogenated rosin.

[0116] Relative to the total mass (100% by mass) of the flux, the rosin content in the flux of the second embodiment is preferably 3% by mass or more and 25% by mass or less, more preferably 4% by mass or more and 20% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less.

[0117] Surfactant

[0118] The surfactant in the second embodiment contains an imidazole compound and the following combination (2). Combination (2) of two dicarboxylic acids: a combination of one selected from succinic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid with succinic acid

[0119] Imidazole compound

[0120] As an imidazole compound, the same substance as the substance exemplified in the description of the imidazole compound in the first embodiment can be cited.

[0121] In the flux of the second embodiment, an imidazole compound may be used alone or in combination of two or more.

[0122] Among them, as an imidazole compound, an alkyl-substituted imidazole compound is preferred, more preferably an imidazole compound selected from 2-methylimidazolium, 2-ethylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium, 2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-methylimidazolium, 1-cyanoethyl-2-undecylimidazolium and 1-cyanoethyl-2-ethyl-4-methylimidazolium, even more preferably an imidazole compound selected from 2-methylimidazolium, 2-ethylimidazolium, 2-undecylimidazolium, 2-heptadecylimidazolium, 1,2-dimethylimidazolium and 2-ethyl-4-methylimidazolium, and most preferably 2-undecylimidazolium.

[0123] • Combination of two dicarboxylic acids (2)

[0124] The combination of two dicarboxylic acids (2) is a combination of octanoic acid and succinic acid, a combination of sebacic acid and succinic acid, a combination of methylsuccinic acid and succinic acid, a combination of malic acid and succinic acid, or a combination of malonic acid and succinic acid.

[0125] In the combination (2), from the viewpoint of solder lead size, the combination of malonic acid and succinic acid, the combination of octanoic acid and succinic acid, the combination of sebacic acid and succinic acid, and the combination of methylsuccinic acid and succinic acid are more preferred, and the combination of malonic acid and succinic acid and the combination of sebacic acid and succinic acid are even more preferred.

[0126] The mass ratio of one of the following in combination (2): octanoic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid (also referred to as "dicarboxylic acid (2c)" as described above) to succinic acid, expressed as a mass ratio of dicarboxylic acid (2c) / succinic acid, is preferably 10 / 90 or more and 90 / 10 or less, more preferably 25 / 75 or more and 75 / 25 or less, and even more preferably 40 / 60 or more and 60 / 40 or less.

[0127] The content of the imidazole compound in the flux of the second embodiment can be arbitrarily selected, and is preferably 0.1% by mass or more and 2.0% by mass or less relative to the total mass (100% by mass) of the flux, more preferably 0.3% by mass or more and 1.8% by mass or less, further preferably 0.5% by mass or more and 1.5% by mass or less, and even more preferably 0.7% by mass or more and 1.5% by mass or less.

[0128] The total content of the two dicarboxylic acids in the flux of the second embodiment can be arbitrarily selected, and is preferably 0.5% by mass or more and 6% by mass or less relative to the total mass (100% by mass) of the flux, more preferably 1% by mass or more and 4% by mass or less. For example, it can be 0.7% by mass or more and 5% by mass or less, 2.0% by mass or more and 3.0% by mass or less, etc.

[0129] The mass ratio of the combination of two dicarboxylic acids (2) to the imidazole compound in the flux of the second embodiment, expressed as the mass ratio of two dicarboxylic acids / imidazole compounds as described on page 8 / 18 of the specification 10 CN 121315519 A, is preferably 0.30 or more and 50 or less, more preferably 0.50 or more and 45 or less, and even more preferably 1 or more and 40 or less. It may also be 1 or more and 20 or less, 1 or more and 5 or less, 1 or more and 3 or less, etc.

[0130] When the mass ratio of the two dicarboxylic acids / imidazole compounds is within the above-mentioned preferred range, the solder joint size can be easily controlled.

[0131] · Other activators

[0132] In addition to the imidazole compound and the combination of two dicarboxylic acids (2), the activator in the second embodiment may also contain other activators as needed.

[0133] Examples of other activators include halogen compounds, organic acids other than dicarboxylic acids, organophosphorus compounds, etc. The description of other activators in the second embodiment can be the same as that of the substances exemplified in the description of other activators in the first embodiment.

[0134] When using a halogen compound as an activator, one can be used alone, or two or more can be used in combination.

[0135] As a halogen compound, it is preferable to select at least one of amine hydrohalates and halogenated aliphatic alcohols, and more preferably, amine hydrohalates and halogenated aliphatic alcohols can be used in combination.

[0136] The content of the halogen compound in the flux of the second embodiment can be arbitrarily selected, and is preferably 0.1% or more and 2% or less relative to the total mass (100% by mass) of the flux, more preferably 0.5% or more and 1.5% or less by mass. For example, it can be 0.3% or more and 1.2% or less by mass, 0.7% or more and 1.5% or less by mass, etc.

[0137] The total content of the activator in the flux of the second embodiment can be arbitrarily selected. Relative to the total mass (100% by mass) of the flux, it can be, for example, 2% by mass or more and 10% by mass or less, or 2% by mass or more and 9% by mass or less. It can also be 3% by mass or more and 8% by mass or 4% by mass or more and 6% by mass or less.

[0138] Solvent

[0139] Examples of solvents in the second embodiment include water, alcohol solvents, glycol ether solvents, and terpineols. Regarding the description of the solvent in the second embodiment, the same solvents exemplified in the description of the solvent in the first embodiment described above can be used.

[0140] In the flux of the second embodiment, a single solvent can be used, or two or more solvents can be used in combination.

[0141] As a solvent, it is preferable to contain a solvent with a boiling point of 100°C or less, more preferably an alcohol solvent, and even more preferably containing at least one selected from ethanol and 2-propanol, particularly preferably containing 2-propanol.

[0142] The solvent content in the flux of the second embodiment can be arbitrarily selected. Relative to the total mass (100% by mass) of the flux, it can be, for example, 60% by mass or more, 70% by mass or more and 95% by mass or less, 75% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.

[0143] Other components

[0144] In addition to rosin, activator and solvent, the flux of the second embodiment may contain other components as needed.

[0145] Other components include, for example, resin components other than rosin, thixotropic agents, surfactants, metal passivators, antioxidants, silane coupling agents, colorants, etc. The flux of the second embodiment may also be a composition containing rosin, imidazole compounds, a combination (2) of the two dicarboxylic acids mentioned above and a solvent, and without thixotropic agents.

[0146] As explained above, in the flux of the second embodiment, a specific organic acid is combined in a specific amine. That is, an imidazole compound selected from page 9 / 18 of the specification, CN 121315519 A, is used as the specific amine, and succinic acid and one selected from succinic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid are used as the specific organic acids. Although the reason is not yet clear, a unique interaction resulting from the combination of such a specific amine and a specific organic acid is obtained in the flux of the second embodiment. Therefore, it is believed that the solder leg size can be increased and the generation of bridging can be suppressed during soldering.

[0147] The effect of the flux of the second embodiment is particularly significant when using an alloy containing Sn and Bi. That is, the flux of the second embodiment is suitable for use as a Sn-Bi based flux.

[0148] (Method for preparing the bonding body)

[0149] The method for preparing the bonding body according to the second aspect of the present invention is a method comprising the following steps: obtaining a bonding body by soldering a solder alloy onto the surface of a substrate treated with the flux of the first aspect described above. The flux alloy is composed of an alloy containing Sn and Bi.

[0150] As an embodiment of the method for preparing the bonding body of this aspect, a method comprising a component mounting step, a flux coating step, a preheating step, and a soldering step can be cited. The flux used is the flux of the first embodiment described above or the flux of the second embodiment.

[0151] In the component mounting step, the component is mounted on the substrate.

[0152] As an example of the component mounting step, an automatic insertion machine can be used to insert the lead or terminal of the component into a through hole provided in the substrate, and the protruding lead or terminal is nailed to fix the component on the substrate.

[0153] The substrate can be arbitrarily selected, for example, a printed wiring substrate, etc.

[0154] The components can be arbitrarily selected; for example, integrated circuits, transistors, diodes, resistors, capacitors, etc. can be included.

[0155] In the flux coating process, the flux of the above embodiment is applied to the soldering surface of the substrate on which the components are mounted.

[0156] As the flux coating apparatus, spray flux applicators, foam flux applicators, etc. can be included. Among them, from the viewpoint of the stability of the coating amount, spray flux applicators are preferred.

[0157] From the viewpoint of solderability, the flux coating amount is preferably 30 to 180 mL / m2, and can be 40 to 150 mL / m2, or 50 to 120 mL / m2.

[0158] In the preheating process, the substrate on which the components are mounted is preheated. In the preheating process, the temperature of the heated substrate is preferably 80 to 130°C, and more preferably 90 to 120°C.

[0159] In the welding process, the welding surface of the substrate on which the component is mounted is brought into contact with molten solder formed by melting the solder alloy.

[0160] As for the method of bringing the molten solder into contact with the welding surface, any method that can bring the molten solder into contact with the substrate is acceptable and is not particularly limited. Examples of such methods include jetting and immersion.

[0161] The jetting method is a method in which the welding surface of the substrate on which the component is mounted is brought into contact with jetted molten solder. The immersion method is a method in which the welding surface of the substrate on which the component is mounted is brought into contact with the liquid surface of stationary molten solder.

[0162] The method for preparing the bond in this embodiment is useful when using a solder alloy composed of an alloy containing Sn and Bi, and is particularly useful when using an alloy of Sn and Bi (Sn-Bi based solder).

[0163] The welding conditions in the welding process can be appropriately set according to the melting point of the solder alloy.For example, when using Sn-Bi based solder, the temperature of the molten solder is preferably 170 to 220°C, more preferably 180 to 200°C.

[0164] As explained above, in the preparation method of the joint in this embodiment, the flux of the first embodiment or the flux of the second embodiment described above is applied to the welding surface. Therefore, when welding with an alloy containing Sn and Bi, the solder leg size can be increased and the bridging is suppressed. As a result, a joint with improved joint strength can be prepared. In addition, a highly reliable joint that is less likely to cause short circuits and reduced insulation can be prepared.

[0165] Examples

[0166] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

[0167] <Preparation of Flux>

[0168] (Examples 1-16, Comparative Examples 1-12)

[0169] Fluxes of the Examples and Comparative Examples were prepared with the compositions shown in Tables 1-5.

[0170] In the tables, the content of each component represents the proportion (mass%) relative to the total mass (100% by mass) of the flux. The raw materials used are shown below.

[0171] · Rosin

[0172] Polymerized rosin, acrylic acid-modified hydrogenated rosin, partially hydrogenated rosin

[0173] · Surfactants

[0174] Imidazole compounds: 2-undecylimidazole

[0175] Dicarboxylic acids: succinic acid, adipic acid, glutaric acid, octanoic acid, sebacic acid, malonic acid, maleic acid, methylsuccinic acid, malic acid

[0176] Other surfactants: 1,3-diphenylguanidine, monoisopropanolamine, ethylamine hydrobromide, 1,3-diphenylguanidine hydrobromide, trans-2,3-dibromo-2-buten-1,4-diol, palmitic acid

[0177] · Solvent

[0178] 2-Propanol (isopropanol)

[0179] <Preparation of test solder>

[0180] · Sn-Bi solder

[0181] As the master alloy, an ingot composed of an alloy with 58% by mass of Bi and the balance of Sn (Sn-58Bi) was prepared. The ingot was melted to prepare molten solder.

[0182] Sn-Ag-Cu solder

[0183] As the master alloy, an ingot composed of an alloy with 3% by mass of Ag, 0.5% by mass of Cu and the balance of Sn (Sn-3Ag-0.5Cu) was prepared. The ingot was melted to prepare molten solder.

[0184] <Evaluation of flux>

[0185] As shown below, the evaluation of solder lead size and bridging caused by each flux was performed. The results of these evaluations are shown in Tables 1 to 5.

[0186] [Evaluation of solder pad size and bridging]

[0187] 900 μL of flux for each embodiment and comparative example was prepared and applied by spraying to a substrate having the following through-hole pads (holes penetrating the substrate and the copper foil around them) to obtain a pretreated substrate.

[0188] Through-hole pads

[0189] Outline shape: circular

[0190] Inner diameter (hole diameter): 0.5mm

[0191] Width of through-hole pad (half the difference between the inner and outer diameters of the through-hole pad): 0.25mm

[0192] Spacing of through holes: 2.5mm

[0193] Number of through-hole pads (n): 48

[0194] Surface treatment: Cu-OSP Specification 11 / 18 pages 13 CN 121315519 A

[0195] Next, flow soldering is performed by contacting molten solder with the pretreated substrate under a nitrogen atmosphere.

[0196] Then, for the substrate that has undergone flow soldering, the volume of the solder feet is measured using a laser microscope (VK-X1050) manufactured by Keyence Corporation, and the average value of the solder foot volume is calculated.

[0197] In addition, for the substrates that underwent flow soldering, bridging (solder bridging) was counted visually. Bridging, for example, can refer to molten solder flowing into areas where it should not be present and solidifying, resulting in an undesirable connection.

[0198] The following shows the evaluation criteria for solder lead size and bridging occurrence.

[0199] Evaluation criteria for evaluating solder leg size

[0200] Pass: Solder leg size is 1.400 mm3 or more

[0201] Fail: Solder leg size is less than 1.400 mm3

[0202] Evaluation criteria for evaluating bridging

[0203] Pass: Number of bridging is zero

[0204] Fail: Number of bridging is 1 or more

[0205] [Table 1]

[0206]

[0207] (Quantity of dicarboxylic acid and evaluation results based on solder differences)

[0208] Comparison of Example 1 and Comparative Example 7 and Reference Examples 1 and 2

[0209] The flux of Example 1 contains rosin, activator and solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and succinic acid and malonic acid are used as the two dicarboxylic acids.

[0210] The flux of Comparative Example 7 contained rosin, an activator, and a solvent. The activator contained an imidazole compound and a dicarboxylic acid. 2-Undecylimidazole was used as the imidazole compound, and only malonic acid was used as the dicarboxylic acid.

[0211] The flux of Reference Example 1 had the same composition as the flux of Example 1.

[0212] The flux of Reference Example 2 had the same composition as the flux of Comparative Example 7.

[0213] Comparison of Example 1 and Comparative Example 7: (Using Sn-Bi-based solder in the evaluation)

[0214] During flow soldering with Sn-Bi-based solder in contact with the pretreated substrate, it was confirmed that the solder pad size was larger when using the flux of Example 1 compared to the case where the flux of Comparative Example 7 was used (pages 12 / 18, CN 121315519 A 7).

[0215] Furthermore, it was confirmed that bridging was suppressed when using the flux of Example 1. Bridging occurred when the flux of Comparative Example 7 was used.

[0216] Reference Example 1 and Reference Example 2: (Using Sn-Ag-Cu-based solder in the evaluation)

[0217] During flow soldering with Sn-Ag-Cu-based solder in contact with the pretreated substrate, the solder pad size was increased when using the flux of Example 1 and when using the flux of Comparative Example 7. However, bridging occurred in both cases.

[0218] The results shown in Table 1 confirm that during flow soldering, when Sn-Bi flux is brought into contact with the pretreated substrate, the solder joint size can be increased and bridging can be suppressed only when the flux of Example 1 is used.

[0219] [Table 2]

[0220] Specification 13 / 18 pages 15 CN 121315519 A

[0221] (Evaluation results based on solder differences)

[0222] Comparison of Example 2 and Reference Example 3

[0223] As shown in Table 2, the fluxes of Example 2 and Reference Example 3 both contain rosin, activator, and solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and adipic acid and malonic acid are used as the two dicarboxylic acids. That is, the flux of Example 2 and the flux of Reference Example 3 have the same composition.

[0224] During flow soldering, the solder lead size can be increased when Sn-Ag-Cu solder is brought into contact with the pretreated substrate. However, bridging occurs (Reference Example 3).

[0225] In contrast, during flow soldering, the solder lead size can be increased and bridging is suppressed when Sn-Bi solder is brought into contact with the pretreated substrate (Example 2).

[0226] Comparison of Example 3 and Reference Example 4

[0227] As shown in Table 2, the fluxes of Example 3 and Reference Example 4 both contain rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and sebacic acid and malonic acid are used as the two dicarboxylic acids. That is, the flux of Example 3 and the flux of Reference Example 4 have the same composition.

[0228] During flow soldering, the solder lead size can be increased when Sn-Ag-Cu solder is brought into contact with the pretreated substrate, but bridging occurs (Reference Example 4).In contrast, during flow soldering with Sn-Bi solder in contact with the pretreated substrate, it was confirmed that the solder lead size could be increased and bridging was suppressed (Example 3).

[0229] Comparison of Example 13 and Reference Example 5

[0230] As shown in Table 2, the fluxes of Example 13 and Reference Example 5 both contain rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and succinic acid and octanoic acid are used as the two dicarboxylic acids. That is, the flux of Example 13 and the flux of Reference Example 5 have the same composition.

[0231] During flow soldering with Sn-Ag-Cu solder in contact with the pretreated substrate, although the solder lead size could be increased, bridging occurred (Reference Example 5). In contrast, during flow soldering with Sn-Bi solder in contact with the pretreated substrate, it was confirmed that the solder lead size could be increased and bridging was suppressed (Example 13).

[0232] Comparison of Example 14 and Reference Example 6

[0233] As shown in Table 2, the fluxes of Example 14 and Reference Example 6 both contain rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and succinic acid and methylsuccinic acid are used as the two dicarboxylic acids. That is, the flux of Example 14 and the flux of Reference Example 6 have the same composition.

[0234] During flow soldering, when Sn-Ag-Cu solder is brought into contact with the pretreated substrate, although the solder lead size can be increased, bridging occurs (Reference Example 6). In contrast, during flow soldering, when Sn-Bi solder is brought into contact with the pretreated substrate, it was found that the solder lead size can be increased and the generation of bridging is suppressed (Example 14).

[0235] Comparison of Example 15 and Reference Example 7

[0236] As shown in Table 2, the fluxes of Example 15 and Reference Example 7 both contain rosin, an activator, and a solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and succinic acid and malic acid are used as the two dicarboxylic acids. That is, the flux of Example 15 and the flux of Reference Example 7 have the same composition.

[0237] During flow soldering with Sn-Ag-Cu solder in contact with the pretreated substrate, although the solder lead size can be increased, bridging occurs (Reference Example 7). In contrast, during flow soldering with Sn-Bi solder in contact with the pretreated substrate, it was confirmed that the solder lead size can be increased and the bridging is suppressed (Example 15).

[0238] As can be seen from the results shown in Tables 1 and 2, the effect of using the flux of the embodiments of the present invention is significant when using Sn-Bi solder.Specification 14 / 18 pages 16 CN 121315519 A

[0239] [Table 3]

[0240]

[0241] (Evaluation results of flux of the first embodiment: Examples 1 to 12)

[0242] As shown in Table 3, the fluxes of Examples 1 to 12 all contain rosin, activator and solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound. The two dicarboxylic acids are selected from succinic acid, adipic acid and sebacic acid and malonic acid (equivalent to the flux of the first embodiment). Specification 15 / 18 pages 17 CN 121315519 A

[0243] It can be confirmed from the results shown in Table 3 that when the Sn-Bi-based flux is brought into contact with the pretreated substrate for flow soldering, the fluxes of Examples 1 to 12 can be used to increase the solder leg size and suppress the generation of bridging.

[0244] [Table 4]

[0245]

[0246] (Evaluation results of flux of the second embodiment: Examples 1, 4 to 6, 12 to 16)

[0247] As shown in Table 4, the fluxes of Examples 1, 13, 4, 5, 14, 15, 16, 6, and 12 all contain rosin, activator, and solvent. The activator contains an imidazole compound and two dicarboxylic acids. 2-Undecylimidazolium is used as the imidazole compound, and the two dicarboxylic acids are selected from one of octanoic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid, and succinic acid (equivalent to the flux of the second embodiment).

[0248] The results shown in Table 4 confirm that, during flow soldering where Sn-Bi-based flux contacts the pretreated substrate, the fluxes of Examples 1, 13, 4, 5, 14, 15, 16, 6, and 12 can increase the solder leg size and suppress bridging.

[0249] [Table 5]

[0250] Specification 17 / 18 pages 19 CN 121315519 A

[0251] (Evaluation results of fluxes of comparative examples)

[0252] As shown in Table 5, the fluxes of Comparative Examples 1 to 3 and 8 all contain two dicarboxylic acids in combinations different from the combination (1) or combination (2) of the two dicarboxylic acids, and are fluxes outside the scope of the present invention.

[0253] The flux of Comparative Example 4 contains three dicarboxylic acids, and is a flux outside the scope of the present invention.

[0254] The flux of Comparative Example 5 does not contain dicarboxylic acids, and is a flux outside the scope of the present invention.

[0255] The fluxes of Comparative Examples 6, 7, and 12 all contain only one dicarboxylic acid, which is outside the scope of the present invention.

[0256] The flux of Comparative Example 9 does not contain an imidazole compound, which is outside the scope of the present invention.

[0257] The fluxes of Comparative Examples 10 and 11 both contain amine compounds different from imidazole compounds, and are fluxes outside the scope of the present invention.

[0258] As can be seen from the results shown in Table 5, when using Sn-Bi-based flux to contact the pretreated substrate during flow soldering, when using the fluxes of Comparative Examples 1 to 12, either or both of the evaluation of solder lead size and the evaluation of bridging were poor results.

[0259] Preferred embodiments of the present invention have been described above, but the present invention is not limited to these embodiments. Additions, omissions, substitutions, and other modifications to the structure can be made without departing from the spirit of the present invention. The present invention is not limited by the above description, but only by the scope of the appended claims.Specification Page 18 / 18 20 CN 121315519 A Abstract The present invention discloses a flux and a preparation method of a bonded body using the flux, the flux comprises rosin, an active agent and a solvent, wherein the active agent comprises an imidazole compound and two dicarboxylic acids, and the dicarboxylic acids are used in combination with malonic acid and one selected from the group consisting of succinic acid, adipic acid and sebacic acid; or the flux comprises rosin, an active agent and a solvent, wherein the active agent comprises an imidazole compound and two dicarboxylic acids, and the two dicarboxylic acids are used in combination with succinic acid and one selected from the group consisting of suberic acid, sebacic acid, methylsuccinic acid, malic acid and malonic acid. According to the present invention, it is possible to provide a flux capable of increasing the weld leg size and suppressing the occurrence of bridging during soldering.。

Claims

1. A flux for soldering Sn-Bi based solder, comprising rosin, an activator, and a solvent. The active agent contains an imidazole compound and two dicarboxylic acids. The two dicarboxylic acids are composed of a combination of dicarboxylic acid (1c) and malonic acid. The dicarboxylic acid (1c) is selected from succinic acid, adipic acid, and sebacic acid. The rosin content, relative to the total mass of flux (100% by mass), is 3% by mass or more and 25% by mass or less. The content of the imidazole compound relative to the total mass of the flux (100% by mass) is 0.1% by mass or more and 1.5% by mass or less. The total content of the two dicarboxylic acids relative to the total mass of the flux (100% by mass) is 0.5% by mass or more and 6% by mass or less. The mass ratio of the dicarboxylic acid (IC) to malonic acid, expressed as a dicarboxylic acid (IC) / malonic acid mass ratio, is 10 / 90 or more and 90 / 10 or less. Furthermore, the flux excludes fluxes containing three or more dicarboxylic acids.

2. The flux according to claim 1, wherein, The mass ratio expressed as dicarboxylic acid (1c) / malonic acid is 40 / 60 or more and 75 / 25 or less.

3. A flux for soldering Sn-Bi based solder, comprising rosin, an activator, and a solvent. The active agent contains an imidazole compound and two dicarboxylic acids. The two dicarboxylic acids are composed of a combination of dicarboxylic acid (2c) and succinic acid. The dicarboxylic acid (2c) is selected from one of octanoic acid, sebacic acid, methylsuccinic acid, malic acid, and malonic acid. The rosin content, relative to the total mass of flux (100% by mass), is 3% by mass or more and 25% by mass or less. The content of the imidazole compound relative to the total mass of the flux (100% by mass) is 0.1% by mass or more and 1.5% by mass or less. The total content of the two dicarboxylic acids relative to the total mass of the flux (100% by mass) is 0.5% by mass or more and 6% by mass or less. The mass ratio of the dicarboxylic acid (2c) to succinic acid, expressed as a dicarboxylic acid (2c) / succinic acid mass ratio, is 10 / 90 or more and 90 / 10 or less. Furthermore, the flux excludes fluxes containing three or more dicarboxylic acids.

4. The flux according to claim 3, wherein, The mass ratio expressed as dicarboxylic acid (2c) / succinic acid is 10 / 90 or more and 60 / 40 or less.

5. The flux according to any one of claims 1 to 4, wherein, The mass ratio of the two dicarboxylic acids to the imidazole compound, expressed as a mass ratio of two dicarboxylic acids / imidazole compound, is 0.30 or more and 50 or less.

6. A method for preparing a bonding body, comprising the step of obtaining the bonding body by welding a solder alloy onto the surface of a substrate treated with the flux according to any one of claims 1 to 4, wherein the solder alloy is composed of an alloy containing Sn and Bi.