| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that the solderability is poor when a heat sink is formed of a steel sheet, a solder ball is formed at a part of the heat sink at the time of flow soldering, and possibly falls off after a circuit ball is assembled, and the unit price of the heat sink becomes higher when eliminating these problems by performing silver plating on the heat sink.SOLUTION: A land is formed around a through hole where a part of a heat sink faces the back surface of a substrate, and the through hole is closed by piling a solder on the land, so that a part of the heat sink is not exposed to the back surface of the substrate.SELECTED DRAWING: Figure 3 |
