VitroCoat GI - Ultra-thin adhesive layer for metallization of glass interposer

In this paper a glass-copper interface adhesion promoting thin film is described that forms chemical bonds with glass, and mechanically and possibly chemically anchors to copper to create strong, reliable adhesion between the glass substrate and the deposited metal. Wet chemical deposition of a low volatile organic content (VOC), emissions free, cost-effective, water based coating solution was used to create a thin, transparent metal oxide film that then enables electroless, and electrolytic copper plating directly onto glass. With this approach, a copper film thickness of 30µm can be applied without delamination from the smooth glass. Adhesion at 15µm Cu thickness as measured by 90° peel strength tests can achieve values of ≥4 N/cm. Thermal and stress tests using lead free reflow conditions and Highly Accelerated Stress Testing (HAST) were carried out with manageable to minimal adhesion loss. Through hole plating of aspect ratios up to 5:1 are also demonstrated. Photolithography of fine-lines as small as 5/5 µm was feasible, with very small undercut observed.