JP2021003730A - Flux and solder paste - Google Patents

Abstract

To provide a flux where solder wettability is improved and low residue after reflowing can be realized and to provide a solder paste containing the flux.SOLUTION: A flux contains a fatty acid and an imidazole compound. The total content of the fatty acid and the imidazole compound is 40-95% to the total amount of the flux. The fatty acid is at least one of a saturated fatty acid having a number of carbon atoms of a main chin of 10 or less and an unsaturated fatty acid having a number of carbon atoms of a main chin of 18 or less.SELECTED DRAWING: None

Description

The present invention relates to a flux used for soldering and a solder paste containing the flux.

When mounting a bonded component on an electronic circuit board such as a printed wiring board, a solder paste in which a solder alloy and a flux are mixed is used. The solder paste is applied to the electrode portion on the surface of the electronic circuit board, and is heated (reflowed) in a state where the electrode portion of the joint component is in contact with the electrode portion. As a result, the solder alloy is melted to form a solder joint, and the substrate and the joint component are joined via the solder joint.

The flux contained in the solder paste is generally composed of a rosin, an activator, a solvent, a thixotropy and the like. Among these, rosin is the main component that occupies about half of the total flux, and since it has high activity, it improves the wettability of the solder. On the other hand, since rosin is non-volatile, it remains around the solder joint as a residue after reflow. The residue in the flux containing rosin reduces the adhesion between the resin and the substrate in the post-mounting process, for example, when sealing the resin, or hinders the bonding between the electrode and the substrate when performing wire bonding. There was a risk of it.

Conventionally, after removing the residue by performing a cleaning process using a cleaning agent, post-processes such as resin sealing and wire bonding have been performed. However, due to problems such as air pollution by the cleaning agent and cost increase in the cleaning process, No cleaning is required. In order to carry out the post-process without washing, it is desirable to reduce the residue after reflow as much as possible. Therefore, in recent years, the development of a flux capable of achieving a low residue without containing rosin has been promoted. For example, Patent Document 1 discloses a flux in which an organic acid mixture composed of an organic acid having 10 or more carbon atoms is used as an activator to reduce the residue after reflow without washing.

Japanese Patent No. 6399242

However, for example, in the flux containing no rosin as in Patent Document 1, in order to improve the wettability of the solder instead of the rosin, a non-volatile activator (for example, having 10 or more carbon atoms) is part of the activator. It was necessary to contain the organic acid). Therefore, it is difficult to sufficiently volatilize the flux component at the reflow temperature, and as a result, the residue after reflow cannot be sufficiently reduced.

The present invention has been made in view of the above circumstances, and provides a flux capable of improving the wettability of solder and reducing the residue after reflow, and a solder paste containing the flux. Make it an issue.

The flux according to the present invention contains a fatty acid and an imidazole compound.

Since both the fatty acid and the imidazole compound have high activity, the flux improves the wettability of the solder without using a non-volatile activator. Furthermore, since both the fatty acid and the imidazole compound are volatile components, the residue after reflow can be reduced.

The flux according to the present invention preferably has a total content of the fatty acid and the imidazole compound of 40% by weight or more and 95% by weight or less with respect to the entire flux.

With such a configuration, the flux can further improve the wettability of the solder.

In the flux according to the present invention, the fatty acid is preferably at least one of a saturated fatty acid having 10 or less carbon atoms in the main chain and an unsaturated fatty acid having 18 or less carbon atoms in the main chain.

With such a configuration, the flux can have a high viscosity and the viscosity can be adjusted in an appropriate range.

The flux according to the present invention preferably has at least one unsaturated fatty acid selected from the group consisting of oleic acid, linoleic acid, and linolenic acid.

With such a configuration, the flux can be adjusted in viscosity to a more appropriate range.

The flux according to the present invention is that the imidazole compound is at least one selected from the group consisting of 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole. preferable.

These imidazole compounds volatilize below 260 ° C. Generally, the reflow temperature is 260 ° C. or lower from the viewpoint of suppressing damage to parts. Therefore, when the imidazole compound volatilizes at 260 ° C. or lower, the flux can further reduce the residue after reflow.

The flux according to the present invention preferably has a ratio of the content of the imidazole compound to the content of the fatty acid of 0.2 or more and 4.9 or less.

With such a configuration, the flux can have a high viscosity and the viscosity can be adjusted in an appropriate range.

The solder paste according to the present invention contains the above-mentioned flux and a solder alloy powder having a melting point of 260 ° C. or lower.

By containing the above-mentioned flux, the solder paste can improve the wettability of the solder and reduce the residue after reflow.

The solder paste according to the present invention preferably has a flux content of 8% by weight or more and 12% by weight or less with respect to the entire solder paste.

With such a configuration, the solder paste can further improve the wettability of the solder and further reduce the residue after reflow.

According to the present invention, it is possible to provide a flux capable of excellent wettability of solder and reducing the residue after reflow, and a solder paste containing the flux.

Hereinafter, the flux according to the embodiment of the present invention and the solder paste containing the flux will be described.

<Flux>
(fatty acid)
The flux according to this embodiment contains fatty acids. The fatty acid is preferably at least one of a saturated fatty acid having 10 or less carbon atoms in the main chain and an unsaturated fatty acid having 18 or less carbon atoms. Examples of the saturated fatty acid include nonanoic acid, octanoic acid, decanoic acid, heptanic acid, 2-ethylhexanoic acid, 2-hexyldecanoic acid, 4-methylnonanoic acid and the like. Among these, the saturated fatty acid is preferably a saturated fatty acid having 9 or less carbon atoms in the main chain. The unsaturated fatty acid having 18 or less carbon atoms is preferably at least one selected from the group consisting of oleic acid, linoleic acid, and linolenic acid. As the fatty acid, one type may be used alone, or two or more types may be used in combination.

The fatty acid content is preferably 11% by weight or more, more preferably 15% by weight or more, based on the total flux. The fatty acid content is preferably 60% by weight or less, more preferably 51% by weight or less, based on the total flux. When two or more kinds of fatty acids are contained, the content is the total content of fatty acids.

(Imidazole compound)
The flux according to this embodiment contains an imidazole compound. Here, the imidazole compound means a compound having an imidazole group. The imidazole compound is preferably an imidazole compound that volatilizes at 260 ° C. or lower. Examples of such an imidazole compound include 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole and the like. The imidazole compound may be used alone or in combination of two or more.

The content of the imidazole compound is preferably 11% by weight or more, more preferably 15% by weight or more, based on the total flux. The content of the imidazole compound is preferably 54% by weight or less, more preferably 50% by weight or less, based on the total flux. When two or more kinds of imidazole compounds are contained, the content is the total content of the imidazole compounds.

The flux according to the present embodiment preferably has a total content of the fatty acid and the imidazole compound in an amount of 40% by weight or more, more preferably 60% by weight or more, based on the total content of the flux. Further, the total content is preferably 95% by weight or less, more preferably 90% by weight or less, based on the entire flux.

The flux according to the present embodiment has a ratio of the content of the imidazole compound to the content of the fatty acid preferably 0.2 or more, more preferably 0.5 or more, and more preferably 0.8 or more. Is particularly preferable. The ratio is preferably 4.9 or less, more preferably 2.1 or less, and particularly preferably 1.0 or less.

The flux according to the present embodiment contains a fatty acid and an imidazole compound. Since all the fluxes containing the fatty acid and the imidazole compound have high activity, the wettability of the solder is improved. Furthermore, since both the fatty acid and the imidazole compound are volatile components, the residue after reflow can be reduced.

The flux according to the present embodiment can further improve the wettability of the solder when the total content of the fatty acid and the imidazole compound is 40% by weight or more and 95% by weight or less with respect to the entire flux.

The flux according to the present embodiment has high viscosity and viscosity because the fatty acid is at least one of a saturated fatty acid having 10 or less carbon atoms in the main chain and an unsaturated fatty acid having 18 or less carbon atoms in the main chain. It can be adjusted to an appropriate range.

The flux according to the present embodiment can adjust the viscosity to a more appropriate range when the unsaturated fatty acid is at least one selected from the group consisting of oleic acid, linoleic acid, and linolenic acid. ..

The flux according to the present embodiment is at least one in which the imidazole compound is selected from the group consisting of 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole. These imidazole compounds volatilize below 260 ° C. Generally, the reflow temperature is 260 ° C. or lower from the viewpoint of suppressing damage to parts. Therefore, when the imidazole compound volatilizes at 260 ° C. or lower, the flux can further reduce the residue after reflow.

The flux according to the present embodiment has a high viscosity and the viscosity can be adjusted within an appropriate range by having the ratio of the content of the imidazole compound to the content of the fatty acid being 0.2 or more and 4.9 or less. it can.

(Activator)
The flux according to the present embodiment may further contain an activator from the viewpoint of further improving the wettability of the solder. The activator is preferably a volatile activator from the viewpoint of reducing the residue after reflow. Examples of the volatile activator include an organic acid-based activator, an amine compound-based activator, and a halogen compound-based activator. Among these, the activator is preferably an organic acid-based activator from the viewpoint of reducing the environmental load. The activator may be used alone or in combination of two or more.

The organic acid-based activator is not particularly limited, and is not particularly limited, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, capric acid, lauric acid, myristic acid, pentadecylic acid and palmitic acid. , Margaric acid, stearic acid, tubercrostearic acid, arachidic acid, behenic acid, lignoseric acid, glycolic acid and other monocarboxylic acids; oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelli acid, suberic acid, Dicarboxylic acids such as azelaic acid, sebacic acid, fumaric acid, maleic acid, tartaric acid, diglycolic acid, methylsuccinic acid, phenylsuccinic acid; dimer acid, levulinic acid, lactic acid, acrylic acid, benzoic acid, salicylic acid, anisic acid, citric acid , Tris (2-carboxyethyl) isocyanurate and other organic acids.

The amine compound-based activator is not particularly limited, and examples thereof include trimethylamine, triethylamine, tetramethylethylenediamine, ethylenediamine, triethylenediamine, triethanolamine, aniline, pyridine, and piperidine.

The halogen compound-based activator is not particularly limited, and for example, trans-2,3-dibromo-2-butene-1,4-diol, dibromosalicylic acid, tris (2,3-dibromopropyl) isocyanurate. And so on.

The content of the activator is preferably 1% by weight or more, more preferably 5% by weight or more, based on the total amount of the flux. The content of the activator is preferably 10% by weight or less, more preferably 8% by weight or less, based on the total amount of the flux. When two or more kinds of activators are contained, the content is the total content of the activators.

The activator may contain a non-volatile activator. The content of the non-volatile activator is preferably 20% by weight or less with respect to the entire flux. Even if the content of the non-volatile activator is 20% by weight or less, good wettability is exhibited due to the high activity of the fatty acid and the imidazole compound.

(Thixotropic agent)
The flux according to the present embodiment may further contain a thixotropic agent from the viewpoint of further enhancing the thixotropic property of the flux. Examples of the thixotropy include castor oil, fatty acid amide, kaolin, colloidal silica, organic bentonite, glass frit and the like. Among these, the thixotropy is preferably a fatty acid amide from the viewpoint of increasing volatility. Examples of the fatty acid amide that enhances volatility include stearic acid amide, lauric acid amide, palmitic acid amide, oleic acid amide, erucic acid amide, bechenic acid amide, and myristic acid amide. The thixotropy may be used alone or in combination of two or more.

The content of the thixotropy is preferably 1% by weight or more, more preferably 8% by weight or more, based on the total flux. The thixotropy content is preferably 20% by weight or less, more preferably 12% by weight or less, based on the total flux. When two or more kinds of thixotropic agents are contained, the content is the total content of thixotropic agents.

(solvent)
The flux according to the present embodiment may contain a solvent from the viewpoint of adjusting the viscosity of the flux within an appropriate range. Examples of the solvent include glycol ethers such as diethylene glycol monohexyl ether (hexyl diglycol), diethylene glycol dibutyl ether (dibutyl diglycol), diethylene glycol mono2-ethylhexyl ether (2 ethyl hexyl diglycol), and diethylene glycol monobutyl ether (butyl diglycol). Classes; aliphatic compounds such as n-hexane, isohexane, n-heptane; esters such as isopropyl acetate, methyl propionate, ethyl propionate, Cosmol 43N (trade name); methyl ethyl ketone, methyl-n-propyl ketone, diethyl. Ketones such as ketones; ethanol, n-propanol, isopropanol, isobutanol, octanediol, trimethylpropane, neopentyl glycol, 2,5-dimethyl-2,5-hexanediol, 3-methyl-1,5-pentane Examples thereof include alcohols such as diol and fine oxocol (trade name, registered trademark). As the solvent, one type may be used alone, or two or more types may be used in combination.

The content of the solvent is preferably 1% by weight or more, more preferably 8% by weight or more, based on the entire flux. The content of the solvent is preferably 38% by weight or less, more preferably 20% by weight or less, based on the entire flux. When two or more kinds of solvents are contained, the content is the total content of the solvents.

The flux according to the present embodiment may contain at least one selected from, for example, a stabilizer, a surfactant, an antifoaming agent, and a corrosion inhibitor as other additives. The total content of the other additives is not particularly limited, and can be, for example, 5% by weight or less based on the total flux.

The flux according to the present embodiment preferably does not contain a resin from the viewpoint of reducing the residue after reflow. When the flux contains a resin, the content thereof is preferably 5% by weight or less with respect to the entire flux from the viewpoint of reducing the residue after reflow.

Examples of the resin include rosin-based resins such as gum rosin, tall oil rosin, wood rosin, polymerized rosin, hydrogenated rosin, disproportionated rosin, acrylicized rosin, rosin ester, acid-modified rosin, and ultralight rosin; known synthetic resins. And so on.

The method for producing the flux according to the present embodiment is not particularly limited. For example, a fatty acid, an imidazole compound, and if necessary, an activator, a thixotropic agent, a solvent, and other additives are put into a heating container, and then heated to 100 to 120 ° C. to dissolve all the raw materials. Then, by cooling to room temperature, the flux according to this embodiment can be obtained.

The flux according to the present embodiment includes, but is not limited to, a fatty acid, an imidazole compound, an activator, a thixotropy, a solvent, and other additives. The flux according to the other embodiment comprises a fatty acid, an imidazole compound, an activator, a thixo agent, a solvent and other additives, preferably a fatty acid, an imidazole compound and an activator. ..

<Solder paste>
The solder paste according to the present embodiment contains the above-mentioned flux and a solder alloy powder having a melting point of 260 ° C. or lower. The solder paste according to the present embodiment preferably has a flux content of 8% by weight or more and 12% by weight or less with respect to the entire solder paste.

Generally, the reflow temperature is 260 ° C. or lower from the viewpoint of suppressing damage to parts. Therefore, a solder alloy powder having a melting point of 260 ° C. or lower is usually used. Examples of such solder alloy powders include Sn—Pb-based eutectic solder alloys and lead-free solder alloys. Examples of the lead-free solder alloy include alloys containing tin, silver, copper, indium, zinc, bismuth, antimony and the like. More specifically, Sn / Ag, Sn / Ag / Cu, Sn / Cu, Sn / Ag / Bi, Sn / Bi, Sn / Ag / Cu / Bi, Sn / Sb, Sn / Zn / Bi, Sn / Alloys such as Zn, Sn / Zn / Al, Sn / Ag / Bi / In, Sn / Ag / Cu / Bi / In / Sb, and In / Ag can be mentioned.

The solder paste according to the present embodiment contains the above-mentioned flux and a solder alloy powder having a melting point of 260 ° C. or lower. By containing the above-mentioned flux, the solder paste can improve the wettability of the solder and reduce the residue after reflow.

The solder paste according to the present embodiment has a flux content of 8% by weight or more and 12% by weight or less with respect to the entire solder paste, thereby further improving the wettability of the solder and removing the residue after reflow. It can be further reduced.

The method for producing the solder paste according to the present embodiment is not particularly limited. For example, by mixing the flux and the solder alloy powder, the solder paste according to the present embodiment can be obtained.

Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples.

[Making solder paste]
Each of the raw materials in the blending amounts shown in Tables 1 to 3 was put into a heating container and heated to 120 ° C. to dissolve all the raw materials. Then, by cooling to room temperature, uniformly dispersed flux of each Example and Comparative Example was obtained. The blending amount shown in Table 1 is equal to the content of each component contained in the flux. Next, each flux was mixed so as to be 10% by mass, and solder powder (Sn-3.0 wt% Ag-0.5 wt% Cu) was mixed so as to be 90% by mass to obtain solder pastes of each Example and Comparative Example. It was.

Details of each raw material shown in Tables 1 to 3 are shown below.
(fatty acid)
Pelargonic acid: Made by Tokyo Chemical Industry Co., Ltd., product name "Pelargonic acid"
Octanoic acid: Made by Tokyo Chemical Industry Co., Ltd., product name "n-octanoic acid"
Enanthic acid: Made by Tokyo Chemical Industry Co., Ltd., product name "Enanthic acid"
2-Ethylhexanoic acid: manufactured by Tokyo Chemical Industry Co., Ltd., product name "2-ethylhexanoic acid"
2-Hexyldecanoic acid: Made by Tokyo Chemical Industry Co., Ltd., Product name "2-Hexyldecanoic acid"
Linolenic acid: Made by Tokyo Chemical Industry Co., Ltd., product name "linolenic acid"
Oleic acid: Made by Tokyo Chemical Industry Co., Ltd., product name "oleic acid"
(Imidazole compound)
2PZ-PW: 2-Phenylimidazole, manufactured by Shikoku Chemicals Corporation, product name "2PZ-PW"
2P4MZ: 2-Phenyl-4-methylimidazole, manufactured by Shikoku Chemicals Corporation, product name "2P4MZ"
2E4MZ: 2-Ethyl-4-methylimidazole, manufactured by Shikoku Chemicals Corporation, product name "2E4MZ"
(resin)
KE-604: Acid-modified rosin, manufactured by Arakawa Chemical Industry Co., Ltd., product name "KE-604"
KR-612: Ultra-light color rosin, manufactured by Arakawa Chemical Industry Co., Ltd., product name "KR-612"
Rondis R: Disproportionated rosin, manufactured by Arakawa Chemical Industry Co., Ltd., product name "Londis R"
(solvent)
ODA: KH Neochem Co., Ltd., product name "Octandiol"
Trimethylolpropane: Made by Mitsubishi Gas Chemical Company, Inc., product name "trimethylolpropane"
NPG: Mitsubishi Gas Chemical Company, Inc., product name "Neopentyl Glycol"
DMHD: LUZHOU FUBANG CHEMICAL Co., Ltd., product name "2,5-dimethyl-2,5-hexanediol"
C-43N: Made by Nisshin Oillio Group Co., Ltd., product name "Cosmall 43N"
Fine OxoCol 180A: Made by Nissan Chemical Industries, Ltd., product name "Fine Oxyacid 180A"
MPD: 3-Methyl-1,5-pentanediol, manufactured by Kuraray Co., Ltd., product name "MPD"
HeDG: Hexyldiglycol, manufactured by Nippon Emulsifier Co., Ltd., product name "HeDG"
(Activator)
MeSA: Komatsugawa Chemical Co., Ltd., product name "Methylsuccinic acid"
PhSA: Manufactured by Beijing Hercules Chemicals Co., Ltd., product name "Phenylsucnic Acid"
Adipic acid: Made by Sumitomo Chemical Co., Ltd., product name "Adipic acid"
Glutaric acid: Made by Tokyo Chemical Industry Co., Ltd., product name "glutaric acid"
AZA: Emery Oreo Chemicals Japan Co., Ltd., product name "Emerox 1144"
Maleic acid: Made by Fuso Chemical Industry Co., Ltd., product name "hydrogenic anhydride"
Diglycolic acid: Made by Midori Chemical Co., Ltd., product name "diglycolic acid"
DBBD: Trans-2,3-dibromo-2-butene-1,4-diol, manufactured by Tokyo Chemical Industry Co., Ltd., product name "DBBD"
(Thixotropic agent)
lauramide: Made by Nihon Kasei Co., Ltd., product name "Diamid Y"
stearamide: Made by Kao Corporation, product name "Fatty Acid Amide S"
J-630: N, N'-hexamethylene-bis-12-hydroxystearylamide, manufactured by Ito Oil Co., Ltd., product name "J-630"
Castor oil: Made by Ito Oil Co., Ltd., product name "Castor oil"
(Other additives)
2,2'-Methylenebis (6-tert-butyl-4-methylphenol): Stabilizer, manufactured by Tokyo Chemical Industry Co., Ltd.

[Evaluation of residue]
Using a TG / TDA device (TG 8120, manufactured by Rigaku Co., Ltd.), each flux of 5 mg was weighed in an aluminum pan, and heated to 573 K at a heating rate of 10 K / min under a nitrogen stream. At that time, the weight change rate due to TG at 533K was measured. The results are shown in Tables 1-3. Those having a weight change rate of 95% or more were judged to be good.

[Wetability evaluation]
Each solder paste was printed on an FR-4 resin substrate (OSP-treated) so as to have a thickness of 120 μm and a mask aperture ratio of 100%. Then, using a solder reflow device (NIS-20-82-C manufactured by Atec), heat treatment was performed in a nitrogen atmosphere having an oxygen concentration of 1000 ppm. In the heat treatment, first, the heat treatment was started (normal temperature) to 180 ° C. at 1.5 ° C./sec, and then maintained at 180 ° C. for 100 seconds. Then, the temperature was raised from 180 ° C. to 250 ° C. at 2.0 ° C./sec, maintained at 250 ° C. for 15 seconds, and then cooled from 250 ° C. to room temperature at 3.0 ° C./sec. The wettability evaluation was visually performed based on the following criteria.
⊚: Solder is wet and spread over the entire land.
◯: There is no unmelted solder.

As can be seen from the results in Table 1, the solder paste of each example satisfying all the requirements of the present invention had a weight change rate of 95% or more due to TG, and was able to reduce the residue after reflow. In addition, the solder paste of each example had good solder wettability.

On the other hand, the solder paste of Comparative Example 1 containing no fatty acid and imidazole compound has good solder wettability, but has a weight change rate of 68% due to TG, and the residue after reflow can be sufficiently reduced. There wasn't.

Claims (8)

A flux containing a fatty acid and an imidazole compound. The flux according to claim 1, wherein the total content of the fatty acid and the imidazole compound is 40% by weight or more and 95% by weight or less with respect to the entire flux. The flux according to claim 1 or 2, wherein the fatty acid is at least one of a saturated fatty acid having 10 or less carbon atoms in the main chain and an unsaturated fatty acid having 18 or less carbon atoms. The flux according to claim 3, wherein the unsaturated fatty acid is at least one selected from the group consisting of oleic acid, linoleic acid, and linolenic acid. Any one of claims 1 to 4, wherein the imidazole compound is at least one selected from the group consisting of 2-phenylimidazole, 2-ethyl-4-methylimidazole, and 2-phenyl-4-methylimidazole. The flux described in one. The flux according to any one of claims 1 to 5, wherein the ratio of the content of the imidazole compound to the content of the fatty acid is 0.2 or more and 4.9 or less. A solder paste containing the flux according to any one of claims 1 to 6 and a solder alloy powder having a melting point of 260 ° C. or lower. The solder paste according to claim 7, wherein the content of the flux is 8% by weight or more and 12% by weight or less with respect to the entire solder paste.