JP7052320B2 - Flux for soldering - Google Patents

Description

The present invention relates to a flux for soldering. More specifically, the present invention relates to a water-based soldering flux.

For mounting electronic components on electronic devices, soldering using solder is advantageous in terms of cost and reliability, and is generally performed. Soldering methods include soldering solder containing solder with a soldering iron, reflow soldering method in which solder paste, solder preform, solder balls, etc. are redissolved in a reflow furnace and soldered. There is a flow soldering method in which a printed board and electronic parts are brought into contact with solder to perform soldering.

Generally, a liquid flux (post-flux) is used in the flow soldering method. The liquid flux has a role of removing the surface oxide film on the soldered surface of the electronic circuit board and ensuring the wettability of the molten solder on the soldered surface. The liquid flux is obtained by dissolving a solid component such as rosin or an activator in a solvent, and is applied to the soldered surface of an electronic circuit board with a foam fluxer or a spray fluxer before soldering. After that, the electronic circuit board is put into a preheater and heated at 100 to 150 ° C. to remove the solvent.

Alcohols such as isopropyl alcohol, in which rosin and an activator are well dissolved, have been used as the solvent for the liquid flux. However, the use of volatile organic compounds (VOCs) such as alcohol has been restricted in recent years because they cause air pollution when released into the atmosphere. For these reasons, a liquid flux with a reduced VOC amount is desired even in the flow soldering method, and water-based fluxes mainly using water as a solvent have been developed so far (see, for example, Patent Documents 1 and 2). ).

Patent Document 1 describes a flux that uses only water as a solvent as the water-based flux, but due to the high latent heat of evaporation of water and high surface tension, water is completely water even after being heat-treated by the preheater. Was not removed, and there was a problem that many solder balls were generated in the soldering. Further, due to the high surface tension of water as a solvent, the water-based flux has a problem that it does not spread well on the soldered surface. Further, since the aqueous flux has low solubility of the activator and rosin in water, it is a non-uniform solution and has a problem in workability.

Patent Document 1 also describes an aqueous flux using a mixed solvent of water and isopropanol in order to improve workability. However, since the mixed solvent contains highly flammable isopropanol, the aqueous flux is flammable. Since it has a point and is classified as a dangerous substance by the Fire Service Act, there was a problem in handleability.

Patent Document 2 describes an aqueous flux containing a surfactant in order to dissolve an activator or rosin in water. However, when the water-based flux is applied to the soldered surface and soldered, there is a problem that the surfactant remains in the flux residue, the insulation resistance is lowered, and the electrical reliability after soldering is deteriorated. there were.

Japanese Unexamined Patent Publication No. 8-1322282 Japanese Unexamined Patent Publication No. 2002-120089

According to the present invention, even when water is contained, the dryness in the heat treatment is high, the solderability is good, the wettability to the soldered surface is good, there is no ignition point, and the properties are uniform. Another object of the present invention is to provide a soldering flux having high electrical reliability.

As a result of diligent studies, the present inventors have found that the above-mentioned problems can be solved by a soldering flux containing a predetermined azeotropic compound having a specific azeotropic point and a predetermined activator, and have completed the present invention. That is, the present invention relates to the following soldering flux.

1. 1. General formula (1): R ¹ -O- [-CH ₂ -CH ₂ -O] n-R ²
(In the formula (1), n represents an integer of 1 or 2. When n is 1, R ¹ represents a hydrogen atom, R ² represents an alkyl group having 1 to 4 carbon atoms, and when n is 2. R ¹ and R ² independently represent an alkyl group having 1 to 3 carbon atoms), and include a glycol-based compound (a1) and water (a2) having a boiling point of 120 to 200 ° C. under normal pressure. Contains the co-boiling mixture (A), as well as the activator (B).
(A) A flux for soldering, in which the co-boiling point of the component under normal pressure is 90 to 100 ° C.

2. 2. Item 2. The soldering flux according to Item 1, wherein the weight ratios of the component (a1) and the component (a2) in the component (A) are 10 to 45% by weight and 55 to 90% by weight.

3. 3. Item 2. The soldering flux according to Item 1 or 2, wherein the component (B) is an aliphatic dicarboxylic acid having an alkylene group having 2 to 6 carbon atoms or an alkenylene group having 2 to 6 carbon atoms in the molecule.

4. The soldering flux according to any one of Items 1 to 3, further comprising a rosin-based resin (C) and a tertiary amine (D).

5. Item 2. The soldering flux according to any one of Items 1 to 4, wherein the flux does not contain a surfactant.

Since the soldering flux of the present invention (hereinafter, also referred to as "flux") contains a co-boiling mixture (A) containing water and a glycol-based compound as a solvent, the solvent is more volatile than the water-based flux containing only water. It is fast and has excellent drying properties. Since the azeotropic mixture (A) does not remain on the soldered surface after the heat treatment, the solder balls are suppressed and the solderability is improved. Further, the flux of the present invention has good wettability to the soldered surface, and the coating on the surface becomes easy. Further, the flux of the present invention can also suppress the solder bridge in the soldering process.

The flux of the present invention has no flash point, is easy to handle, and is excellent in workability. Further, in the flux of the present invention, the activator and rosin are well dissolved in the azeotropic mixture to form a uniform solution, and it is easy to apply the flux to the soldered surface. Further, since the flux of the present invention does not require a surfactant, the insulation resistance of the flux residue is high, and the electrical reliability after soldering is high.

The flux of the present invention is a predetermined azeotropic mixture containing a predetermined glycol-based compound (a1) having a specific boiling point (hereinafter referred to as (a1) component) and water (a2) (hereinafter referred to as (a2) component). A) (hereinafter referred to as the component (A)) and a predetermined activator (B) (hereinafter referred to as the component (B)). The "azeotropic mixture" described in the present specification is a mixture having the same composition of the gas phase and the liquid phase.

The component (A) is an azeotropic mixture containing the components (a1) and (a2). The component (A) has a co-boiling point under normal pressure (hereinafter, simply referred to as “co-boiling point”) at about 90 to 100 ° C, preferably about 95 to 100 ° C, and more preferably about 97 to 99 ° C. be. In addition, "normal pressure" means standard atmospheric pressure. Further, the surface tension of the component (A) is lower than that of water, and the value thereof is not particularly limited, but is preferably less than 45 dyn / cm, and more preferably less than 35 dyn / cm. Since the component (A) has a co-boiling point lower than the boiling point of water and a surface tension lower than that of water, the volatilization rate is higher than that of water, and the drying property is improved in the heat treatment (100 to 150 ° C.) with the preheater. It gets higher. Further, since the component (A) mainly contains the component (a1) having a high boiling point and the component (a2) which is water, it does not have a flash point.

The component (a1) is a general formula (1): R ¹ -O- [-CH ₂ -CH ₂ -O] n-R ² (in formula (1), n represents an integer of 1 or 2. When 1, R ¹ indicates a hydrogen atom, R ² indicates an alkyl group having 1 to 4 carbon atoms, and when n is 2, R ¹ and R ² independently indicate an alkyl group having 1 to 3 carbon atoms. It is a glycol-based compound represented by.). In the general formula (1), when n is 1 and R ² is an alkyl group having 5 or more carbon atoms, or when n is 2 and at least one of R ¹ and R ² is an alkyl group having 4 or more carbon atoms. If neither R ¹ nor R ² is a hydrogen atom, the water solubility of the component (a1) becomes low, and the component (A) does not become a uniform solution. Further, when n is 2 and either R ¹ or R ² is a hydrogen atom, or when n is 3 or more, the drying property of the component (A) becomes low.

The component (a1) has a boiling point of about 120 to 200 ° C., preferably about 130 to 190 ° C., more preferably 140 to It is about 180 ° C.

As a specific example of the component (a1), when n in the general formula (1) is 1, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-iso -Propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-sec-butyl ether, ethylene glycol mono-tert-butyl ether and the like can be mentioned. When n is 2, diethylene glycol ethyl is used. Examples thereof include methyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl-iso-propyl ether, diethylene glycol methyl-n-propyl ether, diethylene glycol ethyl-iso-propyl ether, and diethylene glycol ethyl-n-propyl ether. These can be used alone or in combination of two or more. Among them, at least one selected from the group consisting of ethylene glycol mono-iso-propyl ether, ethylene glycol mono-tert-butyl ether, and diethylene glycol ethylmethyl ether is preferable from the viewpoint of high drying property.

Examples of the component (a2) include pure water, ultrapure water, purified water, distilled water, ion-exchanged water, tap water and the like. The component (a2) may be soft water or hard water.

For the component (A), if necessary, the general formula (2): R ³ -O- [-CH ₂ -CH (CH ₃ ) -O] n-R ⁴ (in the formula (2), n is 1 Or 2. When n is 1, R ³ indicates an alkyl group having 1 to 4 carbon atoms, R ⁴ indicates a hydrogen atom, and when n is 2, R ³ and R ⁴ independently have 1 carbon atoms. It may contain a glycol-based compound (a3) (hereinafter, component (a3)) represented by (indicating an alkyl group of 3). In the general formula (2), when n is 1 and R ³ is an alkyl group having 5 or more carbon atoms, or when n is 2 and at least one of R ³ and R ⁴ is an alkyl group having 4 or more carbon atoms. If neither R ³ nor R ⁴ is a hydrogen atom, the water solubility of the component (a1) becomes low, and the component (A) does not become a uniform solution. Further, when n is 2 and any one of R ³ and R ⁴ is a hydrogen atom, or when n is 3 or more, the drying property of the component (A) becomes low.

The component (a3) has a boiling point of about 120 to 200 ° C., preferably about 130 to 190 ° C., more preferably 140 to, because the component (A) has a co-boiling point and its flammability is low. It is about 180 ° C.

Even when the component (A) is contained, the surface tension is lower than that of water, and the drying property is high as described above. Further, since the component (a3) has a high boiling point, the component (A) does not have a flash point as described above.

As a specific example of the component (a3), when n in the general formula (2) is 1, for example, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso -Propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-iso-butyl ether, propylene glycol mono-sec-butyl ether, propylene glycol mono-tert-butyl ether and the like can be mentioned. When n is 2, dipropylene Glycolethylmethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol methyl-iso-propyl ether, dipropylene glycol methyl-n-propyl ether, dipropylene glycol ethyl-iso-propyl ether, dipropylene glycol ethyl -N-propyl ether and the like can be mentioned. These can be used alone or in combination of two or more. Among them, at least one selected from the group consisting of propylene glycol mono-iso-propyl ether, propylene glycol mono-tert-butyl ether, and dipropylene glycol ethylmethyl ether is preferable from the viewpoint of high drying property.

The component (A) is prepared by mixing the component (a1), the component (a2) and the component (a3) used as necessary by various known means. The weight ratio of the component (a1), the component (a2), and the component (a3) is not particularly limited, but can be appropriately set in consideration of having a co-boiling point and high drying property. Specifically, when the component (A) does not contain the component (a3), the weight ratios of the components (a1) and (a2) in the component (A) are about 10 to 45% by weight and 55 to 90% by weight. The degree is preferable, about 20 to 40% by weight, and more preferably about 60 to 80% by weight. When the component (A) contains the component (a3), the weight ratios of the component (a1), the component (a2) and the component (a3) in the component (A) are about 5 to 35% by weight and 30 to 30 in order. It is preferably about 90% by weight, preferably about 5 to 35% by weight, more preferably about 10 to 30% by weight, more preferably about 40 to 80% by weight, and more preferably about 10 to 30% by weight.

The content of the component (A) is not particularly limited, but from the viewpoint of good wettability of the flux, the weight ratio of the flux is preferably about 75 to 99.9% by weight, more preferably about 84 to 99.5% by weight. preferable.

As the component (B), any known activator can be used without limitation as long as it is an activator that can be used as a flux for soldering. The component (B) is not particularly limited, but is preferably an aliphatic dicarboxylic acid having an alkylene group having 2 to 6 carbon atoms or an alkenylene group having 2 to 6 carbon atoms in the molecule from the viewpoint of suppressing solder bridging. , An aliphatic dicarboxylic acid having an alkylene group having 4 to 6 carbon atoms in the molecule is more preferable. Further, the aliphatic dicarboxylic acid may be either a non-halogen aliphatic dicarboxylic acid or a halogen-based aliphatic dicarboxylic acid, or may contain both. The component (B) is different from the component (C) described later.

Specific examples of the component (B) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid and the like. These can be used alone or in combination of two or more. Among them, one or more selected from the group consisting of succinic acid, glutaric acid, and adipic acid is preferable from the viewpoint of suppressing the solder bridge.

The component (B) does not affect the co-boiling point of the component (A). Although the details are unknown, it is presumed that the component (B) is in a solid state under the co-boiling point and has almost no vapor pressure and does not affect the co-boiling point. Further, since the component (B) has low flammability, the flux containing the components (A) and (B) usually does not have a flash point. Further, since the component (B) is highly soluble in the component (A), the flux containing the components (A) and (B) is usually a uniform solution.

The content of the component (B) is not particularly limited, but the weight ratio in the flux is preferably about 0.1 to 5% by weight, more preferably about 0.5 to 3% by weight, from the viewpoint of suppressing the solder bridge.

The flux of the present invention may further contain a rosin-based resin (C) (hereinafter referred to as a component (C)) and a tertiary amine (D) (hereinafter referred to as a component (D)), or salts thereof. ..

The component (C) is not particularly limited as long as it is a rosin-based resin. Specific examples of the component (C) include purified natural rosin (gum rosin, tall oil rosin, wood rosin) derived from Mao pine, slush pine, Merckshi pine, Shikaya pine, Theda pine, Daio pine and the like. Purified rosin obtained from the above, hydrogenated rosin obtained by hydrogenating natural rosin, disproportionated rosin obtained by disproportionating natural rosin, α, β unsaturated carboxylic acid-modified rosin, polymerized rosin, etc. Can be mentioned. These can be used alone or in combination of two or more. The component (C) is preferably an α or β unsaturated carboxylic acid-modified rosin because it easily interacts with the component (D) described later. Note that the component (C) does not affect the co-boiling point of the component (A), similarly to the component (B). Further, since the component (C) also has low flammability, the flux containing the component (C) does not have a flash point.

The α, β-unsaturated carboxylic acid-modified rosin is a compound obtained by adding α, β-unsaturated carboxylic acids to the natural rosin and / or purified rosin (hereinafter, also referred to as raw material rosin) by deal with alder. Examples of the α and β unsaturated carboxylic acids include (meth) acrylic acid, fumaric acid, and (maleic anhydride) maleic acid. The Diels-Alder reaction may be carried out according to various known methods. Specifically, for example, a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube, etc. is charged with raw material rosin and α, β unsaturated carboxylic acids, in the presence or absence of a solvent, and as a catalyst. In the presence or absence of the above, the two may be reacted at a temperature of about 180 to 240 ° C. for usually about 1 to 9 hours. The reaction vessel should have a closed structure, and preferably further purged with an inert gas stream such as nitrogen.

The α, β unsaturated carboxylic acid-modified rosin may be hydrogenated by various known methods after the reaction. Hydrogenation is not particularly limited, and a known method can be adopted. Specifically, for example, heating in the presence of a hydrogenation catalyst, usually under hydrogen pressurization of 1 to 25 MPa, preferably 5 to 20 MPa, for about 0.5 to 7 hours, preferably 1 to 5 hours can be mentioned. .. As the hydrogenation catalyst, various known catalysts such as a carrying catalyst such as palladium carbon, rhodium carbon, ruthenium carbon, and platinum carbon, and metal powders such as palladium, nickel, and platinum can be used. The amount of the catalyst used is usually about 0.01 to 5 parts by weight, preferably 0.01 to 3.0 parts by weight, based on 100 parts by weight of the α and β unsaturated carboxylic acid-modified rosin. The hydrogenation temperature is about 100 to 300 ° C, preferably 150 to 290 ° C.

The acid value of the component (C) (JIS K 0070; hereinafter, the same applies when the acid value is referred to) is not particularly limited, but is preferably 160 mgKOH / g or more in that it easily interacts with the component (D) described later. About 180 to 310 mgKOH / g is more preferable.

The content of the component (C) is not particularly limited, but the weight ratio in the flux is preferably about 0.5 to 15% by weight, more preferably about 1 to 10% by weight, in terms of increasing the insulation resistance of the flux residue. It is preferable, and about 1 to 5% by weight is particularly preferable.

A non-rosin-based resin can also be used in combination with the component (C) as long as the desired properties are not impaired. Specific examples of the non-rosin resin include synthetic resins such as epoxy resin, acrylic resin, polyimide resin, nylon resin, polyacrylonitrile resin, vinyl chloride resin, vinyl acetate resin, polyolephine resin, fluororesin, ABS resin, and isoprene. Examples thereof include rubber, styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), nylon rubber, nylon-based elastomers, and elastomers such as polyester-based elastomers. These can be used alone or in combination of two or more.

The component (D) is not particularly limited as long as it is a tertiary amine. The component (D) is indispensably used when the component (C) is used for the flux, and the carboxyl group of the component (C) and the amino group of the component (D) interact with each other to form (C) and (D). The component has high solubility in the component (A). The component (D) is preferably a hydrophilic amine having a solubility in water at 20 ° C. of at least 10% by weight because of its high solubility in the component (A), and from the same point of view, the following general formula ( The monoamine (D1) represented by 3) (hereinafter, also referred to as (D1) component) and the polyamine (D2) represented by the following general formula (4) (hereinafter, also referred to as (D2) component) are more preferable. .. The component (D) may be either one component of the component (D1) or the component (D2), or may contain both components.

General formula (3): (R ⁵ ) (3-m) N- [ _CH2 -CH (Y) -OH] m
(In formula (3), Y represents a hydrogen atom or a methyl group, m represents an integer of 1 to 3. When m is 1, R ³ represents an alkyl group having 1 to 3 carbon atoms, and m is 2. At this time, R ⁵ indicates an alkyl group having 1 to 4 carbon atoms.)

General formula (4): (R ⁶ ) R ⁷ N- (CH ₂ ) l-NR ⁸ (R ⁹ )
(In the formula (4), l represents an integer of 1 to 6, and R ⁶ , R ⁷ , R ⁸ and R ⁹ independently represent an alkyl group having 1 to 3 carbon atoms.)

Specific examples of the component (D1) include 2- (dimethylamino) ethanol, 2- (diethylamino) ethanol, 2- (di-n-propylamino) ethanol, and 2- (di-iso-propylamino) ethanol. , 1-Dimethylamino-2-propanol, 1-diethylamino-2-propanol, 1-di-n-propylamino-2-propanol, 1-di-iso-propylamino-2-propanol, N-methyldiethanolamine, N -Ethyldiethanolamine, Nn-propyldiethanolamine, N-iso-propyldiethanolamine, Nn-butyldiethanolamine, N-iso-butyldiethanolamine, N-sec-butyldiethanolamine, N-tert-butyldiethanolamine, and triethanolamine. And so on. These can be used alone or in combination of two or more. Among them, one or more selected from the group consisting of 2- (di-iso-propylamino) ethanol, 1-diethylamino-2-propanol, and Nn-butyldiethanolamine is preferable from the viewpoint of solubility.

Specific examples of the component (D2) include, for example, N, N, N', N'-tetramethyldiaminomethane, N, N, N', N'-tetramethylethylenediamine, N, N, N', N'. -Tetramethyl-1,3-diaminopropane, N, N, N', N'-Tetramethyl-1,4-diaminobutane, N, N, N', N'-Tetramethyl-1,5-diaminopentane , N, N, N', N'-tetramethylhexamethylenediamine, N, N, N', N'-tetraethylhexamethylenediamine, N, N, N', N'-tetra-n-propylhexamethylenediamine , And N, N, N', N'-tetra-iso-propylhexamethylenediamine and the like. These can be used alone or in combination of two or more. Among them, from the viewpoint of solubility, N, N, N', N'-tetramethylethylenediamine, N, N, N', N'-tetramethyl-1,3-diaminopropane, and N, N, N' , N'-Tetramethylhexamethylenediamine is preferably one or more selected from the group.

The content of the component (D) is not particularly limited, but the weight ratio in the flux is preferably about 0.1 to 5% by weight, preferably 0.5 to 5%, in terms of suppressing the solder bridge and increasing the insulation resistance. About 3% by weight is more preferable. If the content of the component (D) is less than 0.1% by weight, the solubility of the component (C) in the component (A) is poor, and if it exceeds 5% by weight, the insulation resistance is lowered. When the components (D1) and (D2) are used in combination, the component (D1) is about 10 to 50 parts by weight and the component (D2) is 50 parts by weight with respect to 100 parts by weight of the total amount of (D1) + (D2). It is preferably about 90 parts by weight.

The content ratio of the component (C) and the component (D) in the flux is not particularly limited, but the normal weight ratio [(C) / (D) is high in terms of solubility in the component (A) and the insulation resistance. )] Is about 70/30 to 95/5, preferably about 80/20 to 90/10.

The flux of the present invention may contain a salt formed from the component (C) and the component (D) instead of the components (C) and (D). The salt can be obtained by neutralizing a component (C) and a component (D) with the above-mentioned contents by various known means. The flux of the present invention does not impair the desired properties even when the salt is used instead of the components (C) and (D).

The production method of the flux of the present invention is not particularly limited, but the flux is prepared by mixing the components (A) and (B) and, if necessary, the components (C) and (D) by various known means. .. A salt may be formed in advance from the component (C) and the component (D), and the salt may be mixed in place of the components (C) and (D). The content of each component in the flux is not particularly limited, but when the components (C) and (D) are not contained, the weight ratio of the components (A) and (B) in the flux is about 95 to 99.9% by weight. , About 0.1 to 5% by weight, more preferably about 97 to 99.5% by weight, and more preferably about 0.5 to 3% by weight. When the flux contains the components (C) and (D), the weight ratios of the components (A) to (D) are, in order, about 75 to 99.3% by weight, about 0.1 to 5% by weight, and so on. About 0.5 to 15% by weight, preferably about 0.1 to 5% by weight, preferably about 84 to 98% by weight, about 0.5 to 3% by weight, about 1 to 10% by weight, 0.5 to 3% by weight. The degree is more preferable.

Further, the flux of the present invention may be used in combination with other activators (E) (hereinafter referred to as (E) component) other than the component (B) as long as the desired characteristics are not impaired. Examples of the component (E) include dibasic acids such as azelaic acid, sebacic acid, dodecane diic acid, chlorendic acid, and dimer acid; picolin acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Monobasic acids such as 1,2,3,4-tetrabromobutane, 1,2-dibromo-1-phenylethane, 1-bromo-2-butanol, 1-bromo-2-propanol, 1,4-dibromo -2,3-butanediol, trans / cis-2,3-dibromo-2-butene-1,4-diol, 2,2-bis (bromomethyl) -1,3-propanediol, 3-bromopropionic acid, Examples thereof include halogen-containing compounds such as 2-bromopentanoic acid, ethylamine bromate and diethylamine bromine. Among them, from the viewpoint of suppressing solder bridges, trans / cis-2,3-dibromo-2-butene-1,4-diol, 1-bromo-2-propanol, and 2,2-bis (bromomethyl) -1 , 3-Propanediol, one or more selected from the group consisting of diols is preferable. The content of the component (E) is not particularly limited, but the weight ratio in the flux is preferably about 0.01 to 5% by weight, preferably 0.03, from the viewpoint of suppressing the solder bridge and increasing the insulation resistance. It is more preferably about 3% by weight.

The flux of the present invention may contain additives such as antioxidants, fungicides, and matting agents in addition to the components (A) to (E) as long as the desired properties are not impaired. The content of the additive in the flux is not particularly limited, but is usually about 0.1 to 5% by weight.

Since the flux of the present invention has high drying property of the component (A) which is a solvent, the drying property of the flux itself is also high. Since the component (A) does not remain on the soldered surface after the heat treatment, the solder balls are suppressed in the soldering step, and the solderability is improved. Further, since the flux of the present invention has a low surface tension of the component (A), it has good wettability to the soldered surface, and it is easy to apply the flux to the surface. Further, the flux of the present invention can also suppress the solder bridge in the soldering process.

The flux of the present invention is a non-dangerous substance because it does not have a flash point, is easy to handle, and is excellent in workability. Further, since the flux of the present invention has other components well dissolved in the component (A), it is a uniform solution and can be easily applied to the soldered surface. Further, since the flux of the present invention does not require a surfactant, the insulation resistance of the flux residue is high, and the electrical reliability after soldering is high.

The method of applying the flux of the present invention to the soldered surface is not particularly limited, and examples thereof include a method of immersing terminal parts as they are and a method of applying various fluxers (spray or the like) to the soldered surface. Further, although the flux of the present invention can be used in various known soldering methods, it is preferably used in the flow soldering method.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the technical scope of the present invention is not limited to these examples. Further, in the examples, "parts" and "%" mean "parts by weight" and "% by weight" unless otherwise specified.

(Preparation of azeotropic mixture (A))
Production Example 1
In a 200 ml eggplant-shaped flask, 20 g of (a1) component: ethylene glycol mono-tert-butyl ether (ETB) as a glycol-based compound, and 80 g of (a2) component: ion-exchanged water (hereinafter, simply referred to as water) as water. The solution was prepared by adding and mixing well.

Next, a distillation column, a distilling head, a thermometer, and a Liebig condenser corresponding to the theoretical plate number N = 10 were connected to the eggplant-shaped flask. Next, the eggplant-shaped flask was heated in an oil bath under normal pressure, the solution was boiled, and only a fraction having a boiling point of 100 ° C. or lower was collected to obtain an azeotropic mixture (A).

Next, the composition ratio (% by weight) of each component of the azeotropic mixture (A) was measured using a digital densitometer PR-201α (manufactured by Atago Co., Ltd.). The composition ratio is shown in Table 1.

Production Examples 2 to 6, Comparative Production Examples 1 to 5
In Production Example 1, various azeotropic mixtures (A) were prepared in the same manner as in Production Example 1 except that the component (a1) was changed to that shown in Table 1, and the composition ratio of each component was measured.

<Flash point>
The flash point of the azeotropic mixture (A) obtained in each production example and the comparative production example was measured according to the Cleveland opening method (JIS K2265-4). The evaluation results are shown in Table 1.
(Evaluation criteria)
○: Does not ignite by the Cleveland method.
×: Ignite by the Cleveland method.

<Co-boiling point>
The azeotropic point of the azeotropic mixture (A) obtained in each production example and the comparative production example is determined by measuring the temperature of the steam generated when each solution is boiled in each production example and the comparative production example. rice field. The evaluation results are shown in Table 1.

表１の組成比の単位は重量％である。表１の略語は、以下の通りである。

（化合物の略語及び詳細）
ＥＭ：エチレングリコールモノメチルエーテル（東京化成工業（株）製）
ＥＩＰ：エチレングリコールモノ－ｉｓｏ－プロピルエーテル（東京化成工業（株）製）
ＥＴＢ：エチレングリコールモノ－ｔｅｒｔ－ブチルエーテル（東京化成工業（株）製）
ＤＥＭＥ：ジエチレングリコールエチルメチルエーテル（東京化成工業（株）製）
ＤＥＤＥ：ジエチレングリコールジエチルエーテル（東京化成工業（株）製）
ＤＥＭＩＰ：ジエチレングリコールメチル－ｉｓｏ－プロピルエーテル（東京化成工業（株）製）
ＥＮＨ：エチレングリコールモノ－ｎ－ヘキシルエーテル（東京化成工業（株）製）
ＤＥＮＢ：ジエチレングリコールモノ－ｎ－ブチルエーテル（東京化成工業（株）製）
ＤＥＭＮＢ：ジエチレングリコールメチル－ｎ－ブチルエーテル（東京化成工業（株）製）
ＩＰＡ：イソプロパノール（東京化成工業（株）製）

The unit of the composition ratio in Table 1 is% by weight. The abbreviations in Table 1 are as follows.

(Abbreviations and details of compounds)
EM: Ethylene glycol monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
EIP: Ethylene glycol mono-iso-propyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
ETB: Ethylene glycol mono-tert-butyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
DEME: Diethylene glycol ethylmethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
DEDE: Diethylene glycol diethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
DEMIP: Diethylene glycol methyl-iso-propyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
ENH: Ethylene glycol mono-n-hexyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
DENB: Diethylene glycol mono-n-butyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
DENNB: Diethylene glycol methyl-n-butyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.)
IPA: Isopropanol (manufactured by Tokyo Chemical Industry Co., Ltd.)

(Preparation of flux)
Example 1
A flux was prepared by dissolving 0.72 parts of succinic acid (manufactured by Tokyo Chemical Industry Co., Ltd., the same applies hereinafter) in 99.28 parts of the azeotropic mixture (A) obtained in Production Example 1. The composition is shown in Table 2.

Examples 2 to 14, Comparative Examples 1 to 6
Various fluxes were prepared in the same manner as in Example 1 except that the raw material compositions shown in Tables 2 to 4 were changed. The azeotropic mixture (A)'obtained in Comparative Production Example 4 has a flash point and is classified as a dangerous substance under the Fire Service Act, and therefore was not used in flux preparation.

<Appearance of flux>
The fluxes obtained in each Example and Comparative Example were allowed to stand at 25 ° C. for 1 hour, and then the appearance of the flux was visually judged and evaluated according to the following criteria. The evaluation results are shown in Tables 2-4.
(Evaluation criteria)
◯: The appearance of the flux is uniform.
X: The appearance of the flux is cloudy or separated.

<Flux wettability>
For the co-boiling mixture (A) used in each Example and Comparative Example, an automatic surface tension meter CBVP-A3 (manufactured by Kyowa Surface Science Co., Ltd.) was used, and the surface tension at 25 ° C. was measured by the Wethelmy method (plate method). The measurement was performed, and the wettability of the flux was evaluated from the surface tension according to the following evaluation criteria. The evaluation results are shown in Tables 2-4. The lower the surface tension of the azeotropic mixture (A), the higher the wettability of the flux of the present invention.
(Evaluation criteria)
⊚: Surface tension is less than 35 dyn / cm.
◯: Surface tension is 35 dyn / cm or more and less than 45 dyn / cm.
Δ: Surface tension is 45 dyn / cm or more and less than 55 dyn / cm.
X: Surface tension is 55 dyn / cm or more.

<Flux dryness>
Weigh 1.00 g of the azeotropic mixture (A) used in each Example and Comparative Example into an ointment can and let it stand in a precision thermostat DF-62 (manufactured by Yamato Scientific Co., Ltd.) set at 80 ° C. The time until the azeotropic mixture (A) was completely volatilized (drying time) was measured, and the drying property of the flux was evaluated from the drying time according to the following evaluation criteria. The evaluation results are shown in Tables 2-4. If the azeotropic mixture (A), which is a solvent, has a high drying property, the flux of the present invention also has a high drying property.
(Evaluation criteria)
⊚: Drying time is less than 25 minutes.
◯: Drying time is 25 minutes or more and less than 35 minutes.
Δ: Drying time is 35 minutes or more and less than 45 minutes.
X: Drying time is 45 minutes or more.

<Soldering performance (solder bridge)>
The flux obtained in each Example and Comparative Example was sprayed at 0.6 g / cm ² on a printed circuit board on which a QFP (Quad Flat Package) component having a lead pitch of 0.5 mm and 0.65 mm was mounted. The printed circuit board after flux application was preheated and flow-soldered with a jet soldering device, and the soldering performance was evaluated based on the presence or absence of a QFP bridge (solder bridge). The evaluation criteria are as follows. The evaluation results are shown in Tables 2-4.
(Flow soldering conditions)
Printed circuit board size: 10 cm x 15 cm
Flux coating device: SPT-300XL (manufactured by Institute of Industrial Science, Labor and Welfare)
Jet soldering equipment: Cell Solder C250 (manufactured by Victory)
Solder composition: Sn-0.7Cu-0.05Ni-Ge (LLS227N manufactured by Solder Coat Co., Ltd.)
Flux coating amount: 0.6 g / cm ²
Preheat temperature: 110 ° C
Soldering temperature: 255 ° C
Soldering time: 3 seconds (evaluation standard)
⊚: No bridge occurs in any QFP component having a lead pitch of 0.5 mm and 0.65 mm.
◯: No bridge is generated in the QFP component having a lead pitch of 0.65 mm, and a bridge is generated in the QFP component having a lead pitch of 0.5 mm.
X: Bridges occur in both QFP components having lead pitches of 0.5 mm and 0.65 mm.

<Soldering performance (solder ball)>
In the printed circuit board after the flow soldering, the number of scattered solder balls was visually counted to evaluate the soldering performance. The evaluation criteria are as follows. The evaluation results are shown in Tables 2-4.
(Evaluation criteria)
⊚: 3 or less solder balls.
◯: 4 to 7 solder balls.
×: 8 or more solder balls.

<Insulation resistance>
The flux obtained in each Example and Comparative Example was applied to the comb-shaped substrate 2 type specified in JISZ3197. The substrate coated with the flux was dried in a dryer at 110 ° C. for 5 minutes, and then immersed in a solder bath (metal type: Sn-37Pb) at 235 ° C. for 3 seconds for soldering. Then, the substrate was pulled up and cooled to room temperature. Further, the substrate was left in a constant temperature and humidity chamber having a temperature of 85 ° C. and a humidity of 85%, and the resistance value (Ω) of the flux residue after 168 hours was measured to evaluate the insulation resistance. The evaluation criteria are as follows. The evaluation results are shown in Tables 2-4.
(Evaluation criteria)
◯: The resistance value is 1.0 × ¹⁰⁸ Ω or more.
X: The resistance value is less than 1.0 × ¹⁰⁸ Ω.

The unit of the blending amount in Tables 2 to 4 is the part by weight, and the abbreviations and annotations are as follows.
(1) Surfactant.
(2) Since the flux was separated into two layers, no other evaluation was performed.

(Abbreviations and details of compounds)
Succinic acid: Tokyo Chemical Industry Co., Ltd. Glutaric acid: Tokyo Chemical Industry Co., Ltd. Adipic acid: Tokyo Chemical Industry Co., Ltd. KE-604: Acrylicized rosin (acid value 236 mgKOH / g, Arakawa Chemical Industry Co., Ltd.) Made)
Marquid No. 31: Rosin fumarated (acid value 186 mgKOH / g, manufactured by Arakawa Chemical Industry Co., Ltd.)
Marquid No. 33: Rosin maleated (acid value 303 mgKOH / g, manufactured by Arakawa Chemical Industry Co., Ltd.)
TMHMDA: N, N, N', N'-tetramethylhexamethylenediamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
BIDE: N-butyldiethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.)
DBD: trans-2,3-dibromo-2-butene-1,4-diol (manufactured by HighChem Co., Ltd.)
LDA: Betaine lauryldimethylaminoacetic acid (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)

Claims (4)

General formula (1): R ¹ -O- [-CH ₂ -CH ₂ -O] n-R ²
(In the formula (1), n represents an integer of 1 or 2. When n is 1, R ¹ represents a hydrogen atom, R ² represents an alkyl group having 1 to 4 carbon atoms, and when n is 2. R ¹ and R ² independently represent an alkyl group having 1 to 3 carbon atoms), a glycol-based compound (a1) having a boiling point of 120 to 200 ° C. under normal pressure, water (a2), and necessary. General formula (2): R ³ -O- [-CH ₂ -CH (CH ₃ ) -O] n-R ⁴ according to
(In the formula (2), n represents 1 or 2. When n is 1, R ³ represents an alkyl group having 1 to 4 carbon atoms, R ⁴ represents a hydrogen atom, and when n is 2, R ³ And ^R4 independently represent an alkyl group having 1 to 3 carbon atoms), and a co-boiling mixture (A) consisting only of a glycol-based compound (a3) having a boiling point of 120 to 200 ° C. under normal pressure. , As well as the activator (B),
(A) The co-boiling point of the component under normal pressure is 90 to 100 ° C.
The content of the component (B) has a weight ratio of 0.1 to 5% by weight in the flux.
The component (B) is an aliphatic dicarboxylic acid having an alkylene group having 2 to 6 carbon atoms or an alkenylene group having 2 to 6 carbon atoms in the molecule.
Flux for soldering (however, surfactant is not included). The component (A) is composed of the component (a1) and the component (a2), and the weight ratios of the component (a1) and the component (a2) in the component (A) are 10 to 45% by weight and 55 to 90% by weight. , The soldering flux according to claim 1. The first aspect of the present invention, wherein the weight ratios of the component (a1), the component (a2) and the component (a3) in the component (A) are 5 to 35% by weight, 30 to 90% by weight, and 5 to 35% by weight. Flux for soldering. The soldering flux according to any one of claims 1 to 3, further comprising a rosin-based resin (C) and a tertiary amine (D).