Hi‐rel Multilayer Plated‐through Hole Utilising the EE‐1™ Process

This paper describes the use of the EE‐1 process for making high‐reliability multilayer boards. The EE‐1 process eliminates the need for flash electroless copper for plated‐through holes. With this process, copper is directly electrodeposited onto an activated through‐hole. In addition to eliminating electroless deposition, the EE‐1 process claims to simplify process control, provide excellent copper‐to‐copper adhesion, and total backlight PTH coverage. Production experience with the process is extensive as it has been used at Photocircuits, Atlanta, since January 1986 in the fabrication of double‐sided boards. Test data of joint reliability and physical properties of copper in PTHs of multilayer boards obtained through this unique approach are presented. A special test, which directly measures the bond strength between through‐hole deposited copper and inner foil of multilayers, is also discussed.