Hirel Multilayer Platedthrough Hole Utilising the EE1 Process

This paper describes the use of the EE1 process for making highreliability multilayer boards. The EE1 process eliminates the need for flash electroless copper for platedthrough holes. With this process, copper is directly electrodeposited onto an activated throughhole. In addition to eliminating electroless deposition, the EE1 process claims to simplify process control, provide excellent coppertocopper 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 doublesided 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 throughhole deposited copper and inner foil of multilayers, is also discussed.