Performance evaluation of acid copper plating films for via filling

Abstract

The acid copper plating process has been extensively applied in the formation of high density interconnections in build-up printed circuit boards (PCBs). However, deposited films obtained by acid copper plating are greatly affected by additives, and sometimes physical properties are weakened in codeposition with additives present in the deposited films. In order to avoid such a breakdown, the authors evaluated the physical properties of the copper films plated in two types of conformal acid copper plating baths that have been in use for general application and two types of acid copper plating baths for via filling. Proper selection of additives was considered to be of great importance for the acid copper plating baths for via filling. The use of additives that easily codeposit with copper was likely to cause the reduction in physical properties of the film. On the other hand, it was confirmed that a copper film with excellent physical properties can be obtained from the conformal type acid copper plating baths by selection of a suitable additive.