JPS58191493A - Method of washing soldered printed board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] (1) Technical Field The present invention relates to soldering (
This invention relates to a method for washing printed circuit boards with water.

(2) Background of the technology Generally, rosin-based flux is used when soldering printed circuit boards for electronic devices onto electronic component printed circuit boards, but since this flux has poor water solubility, corrosive substances can be sufficiently removed by washing with water. Can not. For this reason, attention has been focused on the use of water-bathable organic fluxes in which all components are water-soluble.

(3) Prior art and problems Water-soluble organic flux contains an activator to completely remove the oxide film and alcohols to adjust the viscosity. Monohydric, dihydric and/or trihydric aliphatic alcohols are used in combination as salts and alcohols.

Since the activator is acidic, it will leach salts from the parts after soldering. Because cleaning water or hot water has a high surface tension, salts often remain in the crevices of parts, corroding metal parts and degrading insulation.

(4) Purpose of the Invention The purpose of the present invention is to provide a method for washing printed circuit boards for electronic devices with water, which performs soldering with sufficient strength and does not leave corrosive harmful substances after soldering. .

(5) Structure of the Invention The above object of the present invention is achieved by using water-soluble organic flux.
A method for washing a soldered printed circuit board with water, the method comprising:
This can be achieved by a patented method for washing printed circuit boards with water, which is characterized by using washing water containing 0001 to 1% of a fluorine thread surfactant.

The fluorine thread surfactant may be anionic, nonionic or cationic. In other words, the fluorine thread surfactant, like other surfactants, completely reduces the surface tension of water, penetrates into the narrow gaps between electronic components, and removes any remaining salt residue after soldering. In addition, it does not leave hygroscopic properties after cleaning, so it has the advantage of not degrading electrical insulation.

The content of fluorine thread surfactant in the washing water is 0.001%
When the amount is less than 1 qb, no surfactant effect is observed.
If the amount is larger than that, foaming may occur, which is not advantageous.

(6) Examples and Comparative Examples As shown in Figure 1, a pattern width of 1
．． A comb-shaped copper foil electrode pattern with an on+m pitch and a spacing of 0.4 square meters was made, and a test printed circuit board on which electronic components such as two ICs and a xa7 xenon could be mounted was fabricated. Are there electronic parts on this printed circuit board? It was mounted, a water-soluble organic flux (Fulfametal Kemasu LJ50-33) was applied to the cap, and after preheating, the electronic components were soldered using an automatic soldering machine.

A shower was performed in the following order: pure water, 01% fluorine thread surfactant water bath solution (manufactured by Asahi Glass, Surflon 1: 1-113 or 8-141), and pure water at 60° C. for 1 minute each.

Surflon S-113 is anionic and $-141 is nonionic. B and C in FIG. 2 show the results of measuring the ion residue of the printed board that had been washed and dried with hot air using an ion graph (manufactured by Alpha Metal).

First, the insulation resistance of the comb-shaped electrodes of the hot-air-dried printed board was measured, and the insulation resistance was measured at 90% relative humidity and 40° C. at 0.20 volts and 120° C. ,, insulation resistance was measured. As a result, as shown by B and C in FIG. 3, insulation deterioration was extremely small.

Also, when a cationic fluorine surfactant was included, similar results to those of the anionic and nonionic surfactants were obtained.

Next, as a comparative example, the cleaning process was carried out in the same manner as in the above example except that all three showers were performed with pure water. The amount of ion residue is shown in A1 in FIG. 2. The results of insulation deterioration are shown in A in FIG. Compared to this, the results of B and C obtained by the method of the present invention both had less ion residue and were excellent in terms of insulation deterioration.

(7) Effects of the Invention The method of the present invention sufficiently removes the water-soluble organic flux remaining on the printed circuit board after soldering, and produces highly reliable mounting prints for electronic devices without insulation deterioration or corrosion after washing with water. A substrate can be provided.

[Brief explanation of the drawing]

Figure 1 is a plan view of the comb-shaped electrode pattern, Figure 2 is a graph showing the amount of ions remaining in a cleaning test, and Figure 3 is a graph showing the amount of ions remaining in the cleaning test.
The figure is a graph showing the relationship between electrolytic corrosion time and insulation resistance. A... Comparative example, B, C,... Example Figure 1 Figure 2 Sample ABC

Claims (1)

[Claims] 1. A method for cleaning printed circuit boards soldered using water-soluble organic flux, characterized in that cleaning water containing 0.001 to 1% of fluorine thread surfactant is used. water cleaning method.