Advanced adhesion enhancement system for high frequency PCB manufacturing

This work demonstrates the development of surface treatment systems of copper which can meet all of the challenges of mobile electronic devices manufacturing for high frequency function. These challenges are low signal loss and enhanced functional performances. The developed surface treatment systems adopted subsequent treatment of organic coating and organosilane coating so called “adhesion promotor” on top of copper surface to provide the strongest possible bond strength. Firstly, this work has been focused upon the relationship between Signal Integrity (SI) data and Surface Roughness Data. The investigation at high frequency region shows the greatest correlation between relative surface area increase (RSAI) and measured signal loss. The loss of measured signal integrity is linearly increased as a function of RSAI increase, due to more augmented effect of the skin effect at high frequency. As the basis for low roughness oxide replacement process (OR HF#1, OR HF1 VS and OR HF#2), modification was done by adjusting different components in the etching solution. Significantly improved signal integrity are shown for all processes. At the same time, adhesion promotor (organic or oganosilane coating) is successfully enhanced adhesion performance and thermal reliability. Adhesion promotor compensating the loss of adhesion performance due to reduced mechanical anchoring of low roughness surface. Further move to the future high frequency electronics manufacturing, advanced adhesion promotor process is developed as alternative. Contrary to oxide replacement, this process is based on ferric sulfate chemistry in etching solution. Combination of low roughness and chemical bond from organosilane coating implies the process as the best fit to high frequency electronics manufacturing, where low insertion loss is required.