Soldering flux composition

Abstract

To provide a soldering flux composition that can sufficiently inhibit adhesion of dross to a substrate.SOLUTION: A soldering flux composition contains (A) an activator, (B) a resin, and (C) a solvent. The component (A) contains (A1) a C2-3 dicarboxylic acid. The content of the component (A1) is from 0.1 mass% to 10 mass% inclusive relative to 100 mass% of the flux composition. The content of the component (B) is from 1 mass% to 25 mass% inclusive relative to the 100 mass% of the flux composition.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a soldering flux composition. [Background technology]

[0002] In addition to the so-called reflow soldering method, a method of soldering an electronic substrate and an electronic component by bringing an electronic component temporarily attached to an electronic substrate into contact with a jet of molten solder, also known as a flow soldering method, is used. In this flow soldering method, a flux composition such as that described in Patent Document 1 is used before the component is brought into contact with the jet of molten solder.

[0003] Furthermore, there is a trend toward the use of lead-free solder alloys in flow soldering. The most commonly used lead-free solder alloy is a tin (Sn)-silver (Ag)-copper (Cu) solder alloy, known as an SAC solder alloy. However, in recent years, with the promotion of carbon neutrality, soldering using low-melting-point solders (such as Sn-Bi solder alloys) has been attracting attention. While the soldering temperature for SAC solder alloys is 255°C to 265°C, Sn-Bi solder alloys can be soldered at around 190°C to 200°C. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-243787 Summary of the Invention [Problem to be solved by the invention]

[0005] In the case of flow soldering, Sn-Bi solder alloys can be soldered at much lower temperatures than SAC solder alloys. However, Sn-Bi solder alloys are more susceptible to oxidation than SAC solder alloys, and may generate oxides (hereinafter also referred to as "dross") in the molten state. Furthermore, this dross may adhere to the substrate and cause short circuits and reduced insulation.

[0006] An object of the present invention is to provide a soldering flux composition that can sufficiently suppress the adhesion of dross to a substrate. [Means for solving the problem]

[0007] According to the present invention, there is provided the following soldering flux composition. [1] A soldering flux composition comprising (A) an activator, (B) a resin, and (C) a solvent, The component (A) contains (A1) a dicarboxylic acid having 2 to 3 carbon atoms, the blending amount of the (A1) component is 0.1% by mass or more and 10% by mass or less with respect to 100% by mass of the flux composition, The blending amount of the (B) component is 1% by mass or more and 25% by mass or less with respect to 100% by mass of the flux composition. A soldering flux composition. [2] The soldering flux composition according to [1], The component (A1) contains malonic acid. A soldering flux composition. [3] The soldering flux composition according to [1] or [2], The solidus temperature of the lead-free solder alloy used for soldering is 140°C or less. A soldering flux composition. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide a soldering flux composition that can sufficiently suppress the adhesion of dross to a substrate. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Soldering flux composition] The soldering flux composition of this embodiment (hereinafter simply referred to as "flux composition") contains (A) an activator, (B) a resin, and (C) a solvent, as explained below, and contains (A1) a dicarboxylic acid having 2 to 3 carbon atoms as the (A) activator. The blending amount of component (A1) is required to be 0.1% by mass or more and 10% by mass or less, relative to 100% by mass of the flux composition, and the blending amount of component (B) is required to be 1% by mass or more and 25% by mass or less, relative to 100% by mass of the flux composition.

[0010] The flux composition according to this embodiment can sufficiently suppress the adhesion of dross to a board even when soldering is performed using lead-free solder with a relatively low melting point. In this specification, lead-free solder refers to a solder metal or alloy to which no lead is added. However, the presence of lead as an unavoidable impurity in lead-free solder is permitted, but in this case, the amount of lead is preferably 300 ppm by mass or less.

[0011] The flux composition according to this embodiment is particularly effective when the solidus temperature of the lead-free solder alloy is 140°C or lower. Examples of such lead-free solder alloys include solder alloys containing Bi. Specific solder alloy systems include Sn-Bi, Sn-Ag-Bi, Sn-Ag-Sb-Bi, Sn-Bi-Sb-In, Sn-Bi-Sb-In-Ni-Co, and Sn-Bi-Sb-Cu-In-Ni-Co systems. Among these alloy systems, the Sn-Bi, Sn-Ag-Bi, and Sn-Ag-Sb-Bi systems are preferred. Specific solder alloy compositions include Sn-57Bi-1Ag, Sn-58Bi, Sn-35Bi-1Ag, Sn-45Bi-1.5Sb-0.5Ag, Sn-50Bi-1Sb-0.5In, Sn-50Bi-1Sb-0.5In-0.05Ni-0.1Co, and Sn-50Bi-1Sb-2Cu-0.5In-0.05Ni-0.1Co. Of these alloy compositions, Sn-58Bi is preferred.

[0012] [Component (A)] The (A) activator used in this embodiment contains (A1) a dicarboxylic acid having 2 to 3 carbon atoms. The synergistic effect of combining this (A1) component with the (B) resin described below can suppress adhesion of dross to the substrate. Examples of the component (B1) include oxalic acid and malonic acid. Of these, malonic acid is preferred from the viewpoint of solderability. These may be used alone or in combination of two or more.

[0013] The blending amount of component (A1) must be 0.1% by mass or more and 10% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (A1) is less than 0.1% by mass, adhesion of dross to the substrate cannot be sufficiently suppressed. On the other hand, if the blending amount of component (A1) is more than 10% by mass, precipitates tend to form in the flux composition. From the same viewpoint, the blending amount of component (A1) is preferably 0.2% by mass or more and 8% by mass or less, more preferably 0.5% by mass or more and 5% by mass or less, and particularly preferably 0.5% by mass or more and 3% by mass or less, based on 100% by mass of the flux composition.

[0014] The component (A) may further contain (A2) a dicarboxylic acid having 4 to 8 carbon atoms. This component (A2) can further improve the effect of inhibiting the adhesion of dross. Examples of the (B2) component include succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid. Among these, succinic acid is preferred from the viewpoint of its effect of suppressing the adhesion of dross. These may be used alone or in combination of two or more.

[0015] The blending amount of component (A2) is preferably 0.1 to 5% by mass, more preferably 0.5 to 4% by mass, and particularly preferably 1 to 3% by mass, based on 100% by mass of the flux composition. When the blending amount of component (A2) is within this range, the effect of suppressing dross adhesion can be further improved.

[0016] Component (A) may further contain a known activator (component (A3)) other than components (A1) and (A2). Component (A3) may include organic acids other than components (A1) and (A2), non-dissociative activators consisting of non-dissociative halogenated compounds, and amine-based activators. These may be used alone or in combination of two or more. Examples of organic acids other than the components (A1) and (A2) include monocarboxylic acids, dicarboxylic acids other than the components (A1) and (A2), and other organic acids. Monocarboxylic acids include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, These include caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, tuberculostearic acid, arachidic acid, behenic acid, lignoceric acid, and glycolic acid. Dicarboxylic acids include azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, and diglycolic acid. Other organic acids include dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid, and picolinic acid.

[0017] Non-dissociative activators made of non-dissociative halogenated compounds include non-salt organic compounds in which halogen atoms are covalently bonded.These halogenated compounds may be compounds formed by covalent bonds of chlorine, bromine, or fluorine, such as chlorides, bromides, and fluorides, or may be compounds having covalent bonds of any two or all of chlorine, bromine, and fluorine.These compounds preferably have polar groups such as hydroxyl groups or carboxyl groups, such as halogenated alcohols or halogenated carboxyls, in order to improve their solubility in aqueous solvents. Halogenated alcohols include, for example, brominated alcohols (such as 2,3-dibromopropanol, 2,3-dibromobutanediol, trans-2,3-dibromo-2-butene-1,4-diol (TDBD), 1,4-dibromo-2-butanol, and tribromoneopentyl alcohol), chlorinated alcohols (such as 1,3-dichloro-2-propanol and 1,4-dichloro-2-butanol), fluorinated alcohols (such as 3-fluorocatechol), and other similar compounds. Carboxyl halides include iodinated carboxyls (such as 2-iodobenzoic acid, 3-iodobenzoic acid, 2-iodopropionic acid, 5-iodosalicylic acid, and 5-iodoanthranilic acid), chlorinated carboxyls (such as 2-chlorobenzoic acid and 3-chloropropionic acid), brominated carboxyls (such as 2,3-dibromopropionic acid, 2,3-dibromosuccinic acid, and 2-bromobenzoic acid), and other similar compounds.

[0018] Examples of amine surfactants include amines (polyamines such as ethylenediamine), amine salts (organic acid salts or inorganic acid salts (hydrochloric acid, sulfuric acid, hydrobromic acid, etc.) of amines and amino alcohols such as trimethylolamine, cyclohexylamine, and diethylamine), amino acids (glycine, alanine, aspartic acid, glutamic acid, and valine), and amide compounds. Specific examples include diphenylguanidine hydrobromide, cyclohexylamine hydrobromide, diethylamine salts (hydrochloride, succinate, adipate, sebacate, etc.), triethanolamine, monoethanolamine, and the hydrobromides of these amines.

[0019] The blending amount of component (A) is preferably 0.5% by mass to 10% by mass, more preferably 1% by mass to 8% by mass, even more preferably 1.5% by mass to 6% by mass, and particularly preferably 2% by mass to 4% by mass, based on 100% by mass of the flux composition. If the blending amount is equal to or greater than the lower limit, the solderability can be improved, while if the blending amount is equal to or less than the upper limit, various properties of the flux composition, such as the cleanability, can be ensured.

[0020] [(B) Component] Examples of the resin (B) used in this embodiment include rosin resins, acrylic resins, epoxy resins, and phenolic resins. These may be used alone or in combination of two or more. Among these, rosin resins and acrylic resins are preferred. Examples of rosin-based resins include rosins and rosin-modified resins. Examples of rosins include gum rosin, wood rosin, and tall oil rosin. Examples of rosin-modified resins include disproportionated rosin, polymerized rosin, hydrogenated rosin, and derivatives thereof. Examples of hydrogenated rosins include fully hydrogenated rosin, partially hydrogenated rosin, and hydrogenated products of unsaturated organic acid-modified rosins (also referred to as "hydrogenated acid-modified rosin"), which are rosins modified with unsaturated organic acids (e.g., aliphatic unsaturated monobasic acids such as (meth)acrylic acid, aliphatic unsaturated dibasic acids such as α,β-unsaturated carboxylic acids such as fumaric acid and maleic acid, and unsaturated carboxylic acids having an aromatic ring such as cinnamic acid). These rosin-based resins may be used alone or in combination of two or more. Among these rosin-based resins, hydrogenated acid-modified rosin is preferred from the viewpoint of solderability. The acrylic resin is obtained by polymerizing at least one monomer such as acrylic acid, methacrylic acid, various esters of acrylic acid, various esters of methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, esters of maleic acid, esters of maleic anhydride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, vinyl chloride, and vinyl acetate.

[0021] The blending amount of component (B) must be 1% by mass or more and 25% by mass or less, based on 100% by mass of the flux composition. If the blending amount of component (B) is less than 1% by mass, adhesion of dross to the substrate cannot be sufficiently suppressed. On the other hand, if the blending amount of component (B) is more than 25% by mass, the amount of flux residue becomes too large. From the same viewpoint, the blending amount of component (B) is preferably 5% by mass or more and 18% by mass or less, more preferably 7% by mass or more and 15% by mass or less, and particularly preferably 10% by mass or more and 12% by mass or less, based on 100% by mass of the flux composition.

[0022] [(C) component] The solvent (C) used in this embodiment preferably contains a water-soluble solvent having a boiling point of not more than 100° C. This component (C) allows the flux composition to be adjusted to an appropriate range. Examples of the component (C) include ethyl alcohol, isopropyl alcohol, etc. These may be used alone or in combination of two or more.

[0023] The blending amount of component (C) is preferably 70% by mass or more and 98% by mass or less, more preferably 75% by mass or more and 95% by mass or less, and particularly preferably 80% by mass or more and 92% by mass or less, based on 100% by mass of the flux composition. If the blending amount is within this range, the application properties of the flux composition can be adjusted to an appropriate range.

[0024] [Antioxidants] The flux composition according to the present embodiment may contain an antioxidant as needed. Known antioxidants can be used as appropriate. Examples of antioxidants include sulfur compounds, hindered phenol compounds, and phosphite compounds. Among these, hindered phenol compounds are preferred.

[0025] Examples of hindered phenol compounds include N,N'-bis3-(3'5'di-t-butyl-4'-hydroxyphenyl)propionylhexamethylenediamine, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionic acid][ethylene bis(oxyethylene)], N,N'-bis[2-[2-(3,5-di-tert-butyl-4-hydroxyphenyl)ethylcarbonyloxy]ethyl]oxamide, N,N'-bis{3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl}hydrazine, and 2-[1-(2-hydroxy-3,5-di-tert-pentylphenyl)ethyl]-4,6-di-tert-pentylphenyl acrylate.

[0026] When an antioxidant is used, from the viewpoint of the effect of the antioxidant, the blending amount thereof is preferably 0.1 mass % or more and 5 mass % or less, and more preferably 0.5 mass % or more and 3 mass % or less, relative to 100 mass % of the flux composition.

[0027] In addition to the components (A) to (C) and the antioxidant, the flux composition according to this embodiment may contain additives such as a thixotropic agent, an antifoaming agent, a rust inhibitor, a surfactant, etc. The amount of these additives added is preferably 0.01% by mass or more and 5% by mass or less relative to 100% by mass of the flux composition.

[0028] [Soldering method] Next, a soldering method using the flux composition according to this embodiment will be described. The soldering method according to this embodiment includes a component mounting step, a flux application step, and a soldering step, which will be described below.

[0029] In the component mounting process, first, the electronic components are inserted into the electronic board and mounted. Examples of electronic substrates include printed wiring boards. Electronic components can be inserted into through-holes in electronic boards and then soldered to the board (a process known as through-hole mounting). Examples of electronic components include integrated circuits, transistors, diodes, resistors, and capacitors.

[0030] In the flux application step, the above-described flux composition is applied to the soldering surface of the electronic substrate. As the flux composition application device, a spray fluxer or the like can be used from the viewpoint of stability of the amount of application. The amount of flux composition applied is 30 mL / m from the viewpoint of solderability. 2 More than 180mL / m 2 Preferably, it is 40 mL / m or less. 2 More than 150mL / m 2More preferably, it is 50 mL / m or less. 2 More than 120mL / m 2 It is particularly preferred that:

[0031] In the soldering process, the soldering surface of the electronic substrate is brought into contact with molten solder to perform the soldering. The method of contacting the molten solder is not particularly limited as long as it can contact the molten solder with the electronic substrate. For example, a method of contacting the electronic substrate with a jet of molten solder (flow soldering method) may be used. Alternatively, a method of contacting the electronic substrate with a solder bath containing molten solder may be used. The soldering conditions can be set appropriately depending on the melting point of the solder. For example, when using a Sn-Bi solder alloy, the molten solder temperature can be set to 160°C or higher and 210°C or lower (preferably 180°C or higher and 200°C or lower). The preheating temperature can be set to 80°C or higher and 130°C or lower (preferably 90°C or higher and 120°C or lower). [Example]

[0032] The present invention will now be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The materials used in the examples and comparative examples are listed below. (Component (A1)) Activator A: Malonic acid Activator B: Oxalic acid ((A2) component) Activator C: Succinic acid Activator D: Glutaric acid Activator E: Adipic acid ((B) component) Rosin resin: Hydrogenated acid-modified rosin, product name "Pine Crystal KE-604", manufactured by Arakawa Chemical Industries, Ltd. ((C) component) Solvent: Isopropyl alcohol (Other ingredients) Antioxidant: N,N'-bis 3-(3'5'di-t-butyl-4'-hydroxyphenyl)propionylhexamethylenediamine, trade name "Irganox 1098", manufactured by BASF Japan Ltd.

[0033] [Example 1] 12% by mass of rosin resin, 1% by mass of activator A, 1% by mass of activator C, and 86% by mass of solvent were placed in a container and mixed to obtain a flux composition.

[0034] [Examples 2 to 11 and Comparative Examples 1 to 5] A flux composition was obtained in the same manner as in Example 1, except that the materials were mixed according to the composition shown in Table 1.

[0035] [Evaluation of flux composition] The properties of the flux composition (dross adhesion, redness, reliability) were evaluated by the following methods, and the results are shown in Table 1. (1) Dross adhesion 0.15 mL of the flux composition was applied to a glass substrate (size: 50 mm × 50 mm, thickness: 0.7 mm), and the applied substrate was heated and dried at 100°C for 5 minutes to obtain a pretreated substrate. Next, the pretreated substrate was immersed in molten solder in a small jet soldering bath in an air atmosphere for 5 seconds. The presence or absence of dross on the substrate was visually confirmed, and the adhesion of dross was evaluated according to the following criteria. ◎: No dross adheres. ○: There is some dross attached. △: A small amount of dross is attached. ×: A large amount of dross is attached. (2) Red Eyes The flux composition was uniformly applied to a printed circuit board using a brush, and the applied board was heated and dried at 100°C for 5 minutes to obtain a pretreated board. The pretreated board was then immersed in molten solder in a small jet soldering bath in an air atmosphere for 5 seconds. The board was visually inspected for red spots (areas where the copper foil was visible due to non-wetting of the solder), and the red spots were evaluated according to the following criteria. ○: No red eye occurs. △: There is some red eye. ×: Red eyes are present. (3) Reliability Reliability was evaluated using a method conforming to the insulation resistance test of JIS Z3197 (2021). Specifically, a comb-shaped substrate (conductor width: 0.318 mm, conductor spacing: 0.318 mm) was coated with the flux composition, and then dipped into a solder bath for soldering to obtain a test substrate. The test substrate was placed in a constant temperature and humidity chamber set to 85°C and 85% RH, and DC 45V to 50V was applied between the electrodes. Then, the insulation resistance value was measured at DC 100V every hour. The insulation resistance value was measured up to 168 hours, and reliability was evaluated according to the following criteria. ○: Within 168 hours, the insulation resistance value was 1.0×10 9 It never went below Ω. ×: Within 168 hours, the insulation resistance value is 1.0×10 9 It was below Ω.

[0036] [Table 1]

[0037] As is clear from the results shown in Table 1, when the flux composition of the present invention was used (Examples 1 to 11), all of the dross adhesion, redness, and reliability were good. Therefore, it was confirmed that the present invention can sufficiently suppress the adhesion of dross to the substrate. [Industrial Applicability]

[0038] The soldering flux composition of the present invention can be particularly suitably used as a technique for mounting electronic components on electronic substrates such as printed wiring boards of electronic devices.

Claims

1. A soldering flux composition comprising (A) an activator, (B) a rosin-based resin, and (C) a solvent, the component (A) contains (A1) malonic acid and (A2) a dicarboxylic acid having 4 to 8 carbon atoms, the blending amount of the component (A1) is 0.6% by mass or more and 3% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the (A2) component is 1% by mass or more and 3% by mass or less with respect to 100% by mass of the flux composition, the blending amount of the component (A) is 1% by mass or more and 6% by mass or less with respect to 100% by mass of the flux composition, The blending amount of the (B) component is 5% by mass or more and 18% by mass or less with respect to 100% by mass of the flux composition. A soldering flux composition.

2. The soldering flux composition according to claim 1, The solidus temperature of the lead-free solder alloy used for soldering is 140°C or less. A soldering flux composition.

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