JPS63132795A - Solder flux - Google Patents

Abstract

PURPOSE:To provide high flux activity to a solder flux and to permit easy cleaning with freon 113 alone by consisting said flux of monoester of diphenic acid. CONSTITUTION:This flux for soldering is the flux consisting of the monoester of diphenic acid which consists of monoalkyl ester of 3-18C. The flux is usually obtd. by dissolving the monoester of diphenic acid in a general org. solvent such as isopropanol and and the control of the flux activity is also possible by adding various amines, hydrochloride, hydrobromade, etc., thereof and other known materials thereto. The solder flux having the excellent solderability and cleanability by the freon 113 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flux used in soldering.

(Conventional technology) Fluxes conventionally used to remove oxide films on metal surfaces and improve solder adhesion during soldering can be roughly divided into inorganic and organic compounds. .

Inorganic acids include inorganic acids such as hydrochloric acid and phosphoric acid, and inorganic salts such as zinc chloride and ammonium chloride, but these are highly corrosive and require washing with water after soldering. therefore,
There are many problems with printed circuit boards equipped with electronic components that are difficult to wash with water.

Organic acids include organic acids such as lactic acid and stearic acid, halogenated salts of various amines such as diethylamine and propylamine,
There are resins such as rosin. Halogenated salts of organic acids and amines are highly corrosive, even if to a lesser extent than inorganic types, and generally require cleaning after soldering, except when used in small quantities as an auxiliary component of flux. . In addition, the cleaning agent in this case has many restrictions, such as the requirement that it be highly polar. Rosin system has the ability to dissolve metal oxides (hereinafter referred to as
Although it has the disadvantage of low flux activity (referred to as flux activity), it is often used especially for soldering to printed circuit boards because of its low corrosivity and good electrical insulation properties. In the case of rosin-based flux, cleaning is often omitted after soldering due to its characteristics. However, in fields where high reliability is required for industrial equipment such as computers and communication equipment,
The 7 lux component must be washed away after applying the shiva/da.

(Problem to be Solved by the Invention) In addition to water, cleaning agents for 7 Lacs include alcohols such as ethanol and Impropatol, chlorinated hydrocarbons such as methylene chloride and methyl chloroform, 1,1
．． 2-) Refer a Fluorine-based hydrocarbons such as -1,2,2-trifluoroethane (hereinafter referred to as Freon 1ts-i) are used.

In recent years, when cleaning printed circuit boards with various parts mounted on them, Freon 113 has been used because it has little effect on the mounted parts, is flame retardant, has low toxicity, and is easy to dispose of waste liquid. There is a strong desire to use it as a cleaning agent. However, the conventional 7lux has 1 fluorocarbon.
13, which has the disadvantage of being difficult to clean. Among them, rosin-based flux belongs to the category that is easy to clean with Freon 113, but it still does not have sufficient cleaning properties and
It is necessary to wash with a mixture of 15 and alcohol 69, and there are many restrictions on its use.

(Means for solving the problem) In view of the above situation, the present inventors conducted various studies with the aim of obtaining a soldering flux that has high flux activity and can be easily cleaned using 70-113 alone. As a result, we found a flux composition suitable for the purpose and arrived at the present invention.

That is, the present invention is a soldering flux characterized by being made of diphenic acid monoester. Preferably, the diphenic acid monoester is a 7-lactide monoester consisting of a monoalkyl ester of an alkyl group having 5 to 18 carbon atoms. More preferred is a 7-lux consisting of a monoalkyl ester of an alkyl group having 6 to 12 carbon atoms.

When the number of carbon atoms in the alkyl group of the monoester moiety is smaller than 5 or larger than 18, the detergency against Freon 113 decreases. Furthermore, dialkyl esters of diphenic acid have low flux activity.

The 7Lux of the present invention is usually obtained by dissolving 1 to 40 fi of diphenic acid monoester in a general organic solvent such as Impropatool, depending on the purpose, and ethylamine, diethylamine, triethylamine,
Other known amines such as isopropylamine, cyclohexylamine, aniline, toluidine, morpholine, jetanolamine, and their hydrochlorides and hydrobromides may be added to adjust the 7-lux activity. can. Further, as the solvent, methanol, ethanol, acetone, ethyl acetate, toluene, etc., or a mixture thereof can also be used.

When applying the 7lux of the present invention to printed circuit boards, common methods such as brush, spray, and dip coating methods are possible.

(Example) Below, the effects of the present invention will be illustrated by examples.

Note that the tests shown in Examples are conducted by the following method.

Test A (solder expansion rate) ゛ After polishing and cleaning the surface of the phosphorus-deoxidized copper plate,
The size after 1 hour oxidation treatment in QC electric furnace is so×5
Prepare the oxo and 5 dragon copper plates. On top of this KJI8 Z
Wrap the H3OA1.6 (7) wire solder specified in -5282 around a rod with a diameter of 5 um, and place the solder ring (0,249) made by cutting the ring.

Place approximately o, o s t of flux sample in the center of the solder and heat to 260 CK. The solder spreading area S<dl) is measured using a granimeter. The expansion rate P (→ is determined by the following formula.

tnP-4,605+ tn(1-0,07528-'
) Test B (cleanability test) A copper-clad printed circuit board with many through-holes was used as a test piece, a solder flux sample was applied to it at approximately 259/mR, and 25% of eutectic solder was applied using a jet method.
Attach it to the copper circuit surface with 00. Next, this is washed with a two-tank washing machine using Freon 113 as a washing agent. 25 in the first tank
In the second tank, 15c of immersion cleaning was performed, and in the third tank, steam cleaning was performed for 20 seconds each. After observing the cleaned test piece with the naked eye for the presence or absence of 7lux residue, etc., a mixture of isopropanol and distilled water having a resistivity value of 80810'Ω or more and distilled water (mixed volume ratio is 7
5 to 25) as an ionic residue extraction solution, add 16 wIt to 10 (to) 2 surface areas of the test piece, and extract 16 wIt at room temperature.
Sonicate for 5 minutes. Take out the test piece from the liquid and measure the specific resistance value (Ω·l) of the extracted liquid.

Example 1 Each diphenic acid monoester and polymerized rosin shown in Table 1 were dissolved in isopropanol to form a solution with a concentration of 50% by weight. These were used as solder 7 lux samples and evaluated by Test A and Test B. The results are shown in Table 1.

Table 1 Example 2 A mixture of diphenic acid mono-2-ethylhexyl ester, diphenic acid monolauryl ester, diphenic acid mono-n-hexyl ester, and polymerized rosin with each of the adjuvants shown in Table 2 was prepared by improvisation. It was dissolved in a tool to form a solution with a concentration of 30% by weight. These were evaluated as 7 lux samples by Test A and Test B. The results are shown in Table 2JC.

Table 2 (Effects of the invention) Among the test results of the examples, the higher the specific resistance value of the extract obtained by treating the printed circuit board after cleaning with a mixture of ingropanol and water, the more the printed circuit board becomes This indicates that the amount of ionic residue remaining is small. therefore,
This means that the flux can be easily cleaned by Freon 115. Further, the larger the value of the solder spread rate, the higher the flux activity and the better the solderability.

As is clear from the results of the Examples, the flux of the present invention has excellent solderability and cleanability with Freon 113, and is extremely useful industrially. In particular, it is highly useful when soldering electronic components to copper-clad printed circuit boards.

(References) JP-A-47-79175, JP-A-49-97750, JP-A-9
-z26545, 50-20957, 5G-209
58, 5G-80985, 51-44575, 5
2-152) 1146, 56. -54798, 56
-54799, 56-109298, 56-109
299, 59-Procedure Ne City Official Book (Voluntary) January 29, 1988

Claims (2)

[Claims] (1) A soldering flux characterized by comprising diphenic acid monoester. (2) The soldering flux according to claim 1, wherein the diphenic acid monoester is a monoalkyl ester of an alkyl group having 3 to 18 carbon atoms.