JPH0347694A - Preflux for soldering - Google Patents

Abstract

PURPOSE:To obtain good solderability even after exposure to a high temp. after application of the preflux obtd. by consisting the preflux of an aq. soln. contg. one or >=2 kinds of acrylic acid copolymers as coating film components or a suspension contg. these components. CONSTITUTION:This preflux consists of one or >=2 kinds of the acrylic acid copolymer, methacrylic acid copolymer or maleic acid copolymer and is applied on the surface of copper and copper alloys. The essential components of the coating film components are representatively the copolymers consisting of 2 or >=3 kinds of acrylic acid, methacrylic acid, maleic acid, alkyl ester acrylate, alkyl ester methacrylate, alkyl ester maleate, styrene or alpha-methylene styrene. The film formed on the surface of the copper metals is highly resistant to heat and is capable of exhibiting an effect in the process of displaying and packaging electronic parts on a printed wiring board in either of the above- mentioned cases.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a preflux for soldering, and is particularly suitable as a surface treatment agent for printed wiring boards.

Conventional technology Conventional soldering prefluxes used to protect circuits made of copper or copper alloys on printed wiring boards, etc., include rosin-based prefluxes that coat the entire printed wiring board, and rosin-based prefluxes that coat the entire printed wiring board, and chemical prefluxes that selectively coat the circuit parts of the printed wiring board. An imidazole-based material that reacts is used.

Rosin-based preflux is made by dissolving natural rosin, rosin ester, rosin modified maleic acid resin, etc. in an organic solvent, and preflux is applied to the entire printed wiring board by coating with a roll coater, spraying, or dipping. Since this method involves spreading and drying to form a film, it has the disadvantage that the working environment and safety are significantly impaired due to volatilization of the organic solvent.

Although imidazole-based preflux has excellent workability, this flux tends to deteriorate and stick when exposed to high temperatures1, and there is a fear that it may sometimes inhibit the action of bost flux.

Problems to be Solved by the Invention In recent years, as a method for bonding electronic components to printed wiring boards,
Surface mounting methods are often used.

According to this method, electronic components are temporarily attached to the board, and there are many opportunities for the printed wiring board to be exposed to high temperatures such as cream solder paste flow. It has become highly desirable to have excellent solderability in the cold state.

Means for Solving the Problems In view of the above circumstances, the inventors of the present invention repeated numerous tests in order to derive a soldering preflux with excellent workability and heat resistance, and surprisingly found that copper and On the surface of the copper alloy, one or more of acrylic acid copolymers, methacrylic acid copolymers, or maleic acid copolymers, especially acrylic acid, methacrylic acid, maleic acid, acrylic acid alkyl esters, and methacrylic acid alkyl esters. When applying an aqueous solution containing as a coating component a copolymer consisting of two or more of maleic acid alkyl ester, styrene, or α-methylstyrene, or a suspension containing these, the intended purpose is achieved. He recognized the scales and was able to complete the present invention.

The coating film components of the preflux of the present invention include two or more of acrylic acid, methacrylic acid, maleic acid, acrylic acid alkyl ester, methacrylic acid alkyl ester, maleic acid alkyl ester, styrene, or α-methylstyrene. Typical copolymers include styrene/α-methylstyrene/acrylic acid copolymer, alkyl acrylate/alkyl methacrylate copolymer, styrene/alkyl acrylate copolymer, styrene/methacrylic acid copolymer, and styrene/α- A methylstyrene/acrylic acid/maleic acid half ester copolymer is preferred.

These coating film components are usually neutralized with ammonia or an organic amine to give a pi (7.5 to 9.0, preferably 8.0
~8.5 used as an aqueous solution or suspension.

The preflux of the present invention is applied to printed wiring boards, etc.
When dried by heating to a temperature of 100° C. or higher, water and ammonia or organic amines are volatilized, and the coating applied to the metal surface becomes insolubilized.

Since it is difficult to make acrylic acid copolymers, methacrylic acid copolymers, or maleic acid copolymers with large molecular weights water-soluble, they should be used as oil-in-water emulsions by emulsion polymerization or the like.

In carrying out the present invention, acrylic acid copolymers,
A water-soluble and low boiling point solvent such as methanol, ethanol, isopropyl alcohol, butanol, acetone, etc. is appropriately blended into an aqueous solution or suspension containing one or more methacrylic acid copolymers or maleic acid copolymers. For example, the drying time can be shortened and the thickness of the coating film can be made uniform.

The preflux for soldering of the present invention is generally applied to the surface of copper or copper alloy by using a roll coater, but it may also be applied by brushing, spraying, or dipping.

Example 1 A styrene/α-methylstyrene/acrylic acid copolymer (trade name: “Joncryl Aqueous Solution J-62J, manufactured by Johnson Polymer ■) having an acid value of 200, a pH of 8.4, and a viscosity of 2000 cps was mixed with water and isopropyl alcohol at a ratio of 95:5. The solid content was adjusted to 10% using a diluted solution, and this aqueous solution was applied to multiple copper plates with a brush, pre-dried using a dryer, and then placed in a hot air drying oven for 10 minutes.
0'C for 5 minutes, 180'C for 10 minutes, 200''C for 10 minutes, 220°C for 10 minutes and 240°C for 10 minutes.
After heating each copper plate for 1 minute, a solder spread test was conducted on each copper plate using a rosin-based post flux (trade name: rJS-64J, manufactured by Hiroki Co., Ltd.) according to the regulations of JIS-Z-3197.

The solder wetting time was determined using a test piece (5 mm x 5 mm
After degreasing and soft etching, the treated aqueous solution was applied with a brush, pre-dried using a dryer, and then placed in a hot air drying oven for 3 minutes at 100°C and 10 minutes at 200°C. Each was heated and immersed in a post Franks before measurement, using a solder wettability tester (
Product name 5AT-2000 (manufactured by Resca), solder temperature 240°C, immersion depth 2mm, immersion speed 16mm/
The measurement was performed under the conditions of sec.

The test results were as shown in Table 1.

Example 2 An alkyl acrylate/alkyl methacrylate copolymer (trade name: Joncryl Emulsion J-, 741J, manufactured by Johnson Polymer ■) having an acid value of 54, a pH of 8.4, and a viscosity of 151 cps was mixed with water and isopropyl alcohol at a ratio of 95:5. The solid content was adjusted to 10% using a diluted solution, and this emulsion was applied to a copper plate in the same manner as in Example 1, and a solder spreading test and solder wetting time were measured. The test results are shown in Table 1. It was as shown in 1.

Example 3 A styrene/alkyl acrylate copolymer (trade name: Joncryl Emulsion J-450J, manufactured by Johnson Polymer ■) having an acid value of 100, a pH of 8.4, and a viscosity of 500 cps was mixed with water and isopropyl alcohol at 95:5.
The solid content was adjusted to 10% using a diluted solution, and this emulsion was applied to a copper plate in the same manner as in Example 1, and a solder spreading test and solder wetting time were measured. The test results are shown in Table 1. It was as shown in 1.

Example 4 Alkyl acrylate/alkyl methacrylate copolymer with acid value 87, PH 8.3, and viscosity 500 cps (trade name: "Joncryl Emulsion J-632J, Johnson Holimer I!") Water and isopropyl alcohol at 95: The emulsion was adjusted to have a solid content of 10% using a diluted solution prepared as No. It was as shown in Table 1.

Example 5 Styrene with acid value 28, pH 8.4, and viscosity 500 cps.
Methacrylic acid copolymer (trade name: Johncryl Emulsion J-790J, manufactured by Johnson Polymer ■)
was adjusted to a solid content of 10% with a diluted solution of water and isopropyl alcohol in a ratio of 95:5, and this emulsion was applied to a copper plate in the same manner as in Example 1, and the solder spreading test and solder wetting time were conducted. When measured,
The test results were as shown in Table 1.

Example 6 Styrene/α-methylstyrene/acrylic acid/maleic acid half ester copolymer with acid value 205, pH 8.3, and viscosity 4000 cps (trade name: “Joncryl Aqueous Solution J
-501J, manufactured by Johnson Polymer ■) The solid content was adjusted to 10% with a diluted solution of water and isopropyl alcohol in a ratio of 95:5, and this emulsion was applied to a copper plate in the same manner as in Example 1. When the solder spreading test and solder wetting time were measured, the test results were as shown in Table 1.

Comparative Example 1 10 g of 2-undecyl-4-methylimidazole and 4.5 ml of acetic acid were added to 1 liter of water and stirred well to adjust the pH to 4.7.
A treatment aqueous solution was prepared, and a surface-polished copper plate was immersed in this treatment solution at a temperature of 30°C for 15 seconds, taken out, washed with water and dried to prepare a test piece, which was treated in the same manner as in the previous example. However, when a solder spreading test and a solder wetting time were measured, the test results were as shown in Table 1.

Comparative Example 2 A copper plate was added to a commercially available oleic acid-based prefluris (trade name [Kannogu Guard # 118J, Tamura Kaken ■) for 30 minutes.
After soaking for 1 minute at a temperature of °C, taking it out and drying it,
The surface is coated with rosin ester preflaris (product name:
Solderite C-161RJ, Tamura Kaken ■) was applied with a brush and dried using a hair dryer to make a test piece.
This was treated in the same manner as in the previous example, and the solder spreading test and solder wetting time were measured, and the test results were as shown in Table 1.

Table 1 Test Results - Table of Effects of the Invention According to the preflux of the present invention, the film formed on the surface of copper-based metal has excellent heat resistance and has good solderability even after being exposed to high temperatures. Therefore, it can exhibit particularly remarkable effects in the process of surface mounting electronic components on printed wiring boards.

Claims (2)

[Claims] (1) Preflux for soldering consisting of an aqueous solution containing one or more types of acrylic acid copolymer, methacrylic acid copolymer, or maleic acid copolymer as a coating component, or a suspension containing these. (2) The main component of the coating film component is two or more of acrylic acid, methacrylic acid, maleic acid, acrylic acid alkyl ester, methacrylic acid alkyl ester, maleic acid alkyl ester, styrene, or α-methylstyrene. Preflux for soldering consisting of an aqueous solution containing a copolymer or a suspension containing these.