Copper descaling capability and material decision

Copper descaling is an acidic process to remove heat scale and oxide formation on leadframe materials of copper and its alloys prior to tin electroplating ^{[1, 2]}. This process needed for excellent solderability result. In this study, three types of copper descaler chemistry which is sodium persulfate base, with anti smut element, from three different chemical suppliers were chosen and the performance of etching capability against five types of copper alloys that were C19400 (K65), C18090 (K62), C70250 (K55), C19210 (K80) and C50710 (MF202) was studied. Design Expert software was used to assist in this selection. The objective is to select one copper descaling chemistry and it is capable to etch minimum one micron of the copper alloy leadframe surface. It was found that copper descaler chemistry from supplier A has the advantages compared to the other two suppliers, B and C, and it capable to etch one micron for all the five copper alloys with very minimum etch variation. For suppliers B and C the etch capability varies for each five copper alloy. Thus, based on the data from this study, chemistry from supplier A has been selected as the chemical descaling chemistry to be used in Infineon.