ELECTROPOLISHING METHOD OF COPPER AND COPPER ALLOY MADE LEAD FRAME

摘要

PURPOSE: To provide an electropolishing method for electropolishing a copper or a copper alloy made lead frame so as to directly silver its surface. ;CONSTITUTION: A copper or copper alloy made lead frame is electropolished by using a noncontact type electropolishing device, electropolishing liquid which contains 20-40g/l sulfuric acid, 40-80g/l NH₄Cl and 0.08-0.25g/l nonionic surface active agent at temp. of 40-50°C and DC current having a ripple frequency of 40-120Hz. At this time, the lead frame is electropolished such that alternately at a positive electrode side and a negative electrode side, time that the lead frame acts as the positive electrode is 3.3 times or more than time that the lead frame acts as the negative electrode and current density is 1.0-3.0A/dm².;COPYRIGHT: (C)1996,JPO