Effects of Copper Foil Type and Surface Preparation on Fine Line Image Transfer in Primary Imaging of Printed Wiring Boards

Abstract

SummaryA laboratory study compares fine line print & etch (P/E) and pattern plate performance on base materials with a variety of copper foils and surface preparations. Foil types include fine grain copper, double treat copper, reverse treated foil, vendor copper, and electroless copper surfaces. Surface preparation methods include alumina jet cleaning, pumice scrubbing, brush cleaning, and chemical cleaning. Surfaces are characterized by contact profilometry, offcontact optical profilometry, Optically Stimulated Electron Emission (OSEE), and water break test. Evaluation criteria are instant adhesion (tape test), P/E minimum line and space resolution, minimum isolated line held, and (AOI) yields on a 75 micron test pattern. Furthermore, pattern plate performance is judged by degree of underplating, minimum developed space, and resolution. Limitations of such a laboratory study are pointed out and results are compared to production experience.