| 摘要 |
PURPOSE:To prevent the separation of molding resin from a lead frame, prevent cracks in the molding resin, and improve the humidity resistance of a device by applying a multiple-layer coating to the reverse surface of a lead frame. CONSTITUTION:The reverse surface of a lead frame is plated with a metal coating 5, such as silver, which offers good adhesion to the lead frame. A second metal coating 6 such as copper, different in the coefficient of thermal expansion from the first metal coating, is applied to the first metal coating. Another metal coating, such as copper or zinc, is applied to the second metal coating. In this manner, metal coatings are sequentially applied using metals that are little different in the coefficient of thermal expansion. The first coating 5 should have a coefficient of thermal expansion close to that of the lead frame 4, while the last coating 7 has a coefficient of thermal expansion close to that of the molding material 2. |
