JPH04300090A - Water-soluble cream solder - Google Patents

Abstract

PURPOSE:To obtain the water-soluble cream solder which is improved in solderability, printability and change with lapse of time which are problems with the conventional water-soluble cream solder. CONSTITUTION:This water-soluble cream solder is formed by adding 1 to 80wt.% reaction product of at least >=1 kinds of the isopropanol amines selected from monopropanol amine, diisopropanol amine and triisopropanol amine and tartaric acid into the flux of the water-soluble cream solder.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-soluble cream solder whose flux residue after soldering can be easily washed away with water or hot water.

0002

[Prior Art] Cream solder containing flux as a main component is often used for soldering electronic components and printed circuit boards. The flux residue of cream solder, which is mainly composed of pine resin, has relatively high insulating properties and is less corrosive, so it did not pose much of a problem if the flux residue was left as is after soldering. However, in recent years, as electronic parts have become more delicate and electronic equipment has become more precise, there is a growing demand for the complete removal of flux residue, which has not been a problem in the past. It has become. Problems caused by not removing flux residue in recent soldering of electronic components are enumerated below. ■If used in an environment above the softening temperature of flux residue (approximately 80°C), insulation resistance will decrease. (2) When molding the soldered portion with resin after soldering the lead portion of an electronic component, flux residue impairs adhesion to the resin. ■If tiny solder balls adhere to flux residue, insulation resistance may drop or short circuits may occur. ■Flux residue covers the surface of the soldered part, causing poor contact with the checker pin during in-circuit testing. Therefore, in modern electronic devices that require high reliability, it has become necessary to remove flux residue after soldering, even with cream solder containing pine resin as a main component. The flux residue of the cream solder can only be cleaned with fluorocarbon or chlorine-based organic solvents such as Freon or Trichloride, but these organic solvents pose problems in terms of the global environment and occupational health, so they should not be used. It has become regulated. Due to the problem of organic solvent regulations, cream solder using water-soluble flux, whose flux residue can be washed away with water or hot water, has recently been attracting attention. In conventional water-soluble cream solder, the flux is mainly composed of glycerin, polyethylene glycol, or water-soluble resin, and a water-soluble activator is added to the flux.

[Problems to be Solved by the Invention] Incidentally, in order to solder electronic components to a printed circuit board, the cream solder must satisfy the following conditions. ■Good solderability. ■Good printability. ■It has appropriate viscosity and can hold electronic parts adhesively. ■Flux and solder powder should not separate during storage. ■It is unlikely to cause changes over time such as changes in viscosity or deterioration of solderability even after a long period of time. Conventional water-soluble cream solders cannot satisfy all of the above conditions, and have particular problems with soldering properties, printability, and aging. An object of the present invention is to provide a water-soluble cream solder that fully satisfies the above conditions.

0004

[Means for Solving the Problems] As a result of various studies to achieve the above object, the present inventor learned that the reaction product of isopropanolamine and tartaric acid has such characteristics, and has developed the present invention. Completed.

The gist of the present invention is to provide a water-soluble cream solder in which the flux residue can be removed by washing with water or hot water after soldering, in which monoisopropanolamine, diisopropanolamine, This is a water-soluble cream solder characterized by containing 1 to 80% by weight of a reaction product of at least one kind of isopropanolamine selected from triisopropanolamine and tartaric acid.

In the present invention, if less than 1% by weight of the above-mentioned reaction product is added, the problems of water-soluble cream solder cannot be solved, but if it exceeds 80% by weight, it will actually impair printability and adhesion. It becomes like this.

As mentioned above, there are three types of isopropanolamine: monoisopropanolamine, diisopropanolamine, and triisopropanolamine, and they have properties as shown in Table 1.

[0008]

[Table 1]

The reaction product of at least one kind of isopropanolamine selected from Table 1 and tartaric acid is, for example, a resinous product obtained by adding 1 mole of tartaric acid to 2 moles of triisopropanolamine and gradually heating the mixture. . The mixing ratio of triisopropanolamine and tartaric acid is not limited to the above mixing ratio; triisopropanolamine:tartaric acid may be 1 mol:1 mol, or triisopropanolamine:tartaric acid may be 1 mol:2 mol. That is, any temperature may be used as long as the bond between the NH2 group and the COOH group can be formed, but it is usually preferably about 120 DEG to 180 DEG C. Alternatively, the reaction rate may be adjusted by adding a solvent such as butyl carbitol or hexylene glycol during the reaction.

0010

[Action] The reaction product of isopropanolamine and tartaric acid has good soldering properties by itself and has a resinous appearance similar to pine resin, making it extremely suitable as a base material for flux. The product has amphiphilic properties, meaning that it is soluble in water as well as in organic solvents such as butyl carbitol and hexylene glycol, so it can be used as a flux component for thixotropic agents and active ingredients. Another advantage is that there is a wider range of materials to choose from. By using the reaction product of isopropanolamine and tartaric acid, which has such excellent properties, as a flux component of water-soluble cream solder, we can provide cream solder with excellent printability, solderability, and stability over time. It becomes possible to do so.

[0011]

EXAMPLES AND COMPARATIVE EXAMPLES A reaction product of 2 moles of triisopropanolamine and 1 mole of tartaric acid was used in the examples of the present invention. The synthesis method will be described below. Two moles of triisopropanolamine were added to a four-necked flask equipped with a stirrer, a thermometer, and a condenser, and the mixture was stirred at 80°C. While adding 1 mol of tartaric acid little by little, the mixture was reacted at 130° C. for 10 minutes, and then slowly cooled to obtain a resinous product (hereinafter referred to as TIPA).

(Example 1)

(Example 2)

(Example 3)

(Example 4)

(Comparative example 1)

(Comparative example 2)

(Comparative Example 3) Table 2 shows the performance test results of Examples and Comparative Examples.

[0019]

[Table 2]

*1; Printability was evaluated using a pattern for 48 pins with a lead pitch of 0.5 mm *2; Evaluation was performed using fillet shape of solder on QFP leads *3; Evaluation was performed based on viscosity change during storage at room temperature *4; I.P.C.
-SP-819 Evaluated on 4, 6, 4 *5; Evaluated on the state of separation of solder powder and flux after being left at room temperature for one week

[0021]

[Effects of the Invention] As described in detail above, the cream solder according to the present invention can solve the problems of conventional water-soluble cream solder such as solderability, printability, and deterioration over time. Since it can be easily cleaned with cold or hot water, it has excellent effects in that it does not cause any problems in terms of environmental destruction or occupational health.

Claims (1)

[Claims] Claim 1: A water-soluble cream solder whose flux residue can be removed by washing with water or hot water after soldering, wherein the flux of the cream solder contains at least one member selected from monoisopropanolamine, diisopropanolamine, and triisopropanolamine. The reaction product of the above isopropanolamine and tartaric acid is 1 to 80%
A water-soluble cream solder characterized by containing % by weight.