To prevent the generation of a soldering defect of a QFP due to the formation of a bridge between electrode lands by a method wherein two sheets of dry film-shaped solder resists are exposed and developed to form solder dams of a specified thickness or thicker in desired positions on the desired surface out of the surfaces of the solder resists.
Two sheets of photosensitive solder resists 6a and 6b consisting of the same material are superposed on a printed circuit board 7 to paste the resists to the board 7 and an exposure and a developing are perfomed on the resists. Thereby, solder dams of a thickness of 100 to 200μm are made to complete. At this time, a creamy solder is made a hole-filling printing in recessed parts 9, which are generated due to a difference between the thicknesses of the dams 8 and electrode lands 2, for obtaining a good soldered bonding. Then, after the hole-filling printing is made, terminals of a terminal pitch of 0.5mm of a QFP are mounted on the prescribed electrode lands 2. After the terminals are mounted, a creamy solder is preheated and thereafter, the creamy solder is heated. As the flow of the creamy solder to the adjacent electrode lands 2 is blocked by the solder dams 8, such trouble that a bridge is formed between the lands is not generated.
KUBO MINORU
MORITA KOJI
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