Analysis and enhancement of bond strength of acrylic sheets to metallic substrates for use in LIGA-type processing

In thick photoresist applications (in LIGA-like processes), commercially available acrylic sheets are bonded to a substrate as an alternative to the casting and in-situ polymerization of PMMA. The factors affecting the adhesion of a thick acrylic sheet to different substrates have been studied. In case of copper and titanium substrates the bond-strength can be improved by roughening the surface through chemical oxidation which then provides a mechanical interlocking between the resist and substrate surfaces. Annealing of PMMA sheet before gluing and use of adhesion promoter such as organosilane further improves the bond strength at the resist-substrate interface. The resist adhesion to various substrates (Ti, TiOx, Cu, CuOx, Au, Ni, Cr, Si) is evaluated by measuring the debonded length of the acrylic sheet during a mechanical cleaving test.