Photopatternable silicone compositions for electronic packaging applications

A growing need for low stress high temperature thick film materials has prompted the development of new spin-coatable photopatternable silicones (Dow Corning(R) WL-5000 series) to assist manufactures in building the next generation of electronic devices. These new negative-tone materials can be easily coated onto electronic substrates and patterned using standard i-line and broadband lithographic processes. Films ranging from 6 to 50 mum have been demonstrated with patterned features resolved to an aspect ratio of less than 1.3. The etched regions provide a sloped sidewall and curved surfaces to facilitate metallization processes. The films are cured at low temperatures (150 to 250degreesC) to provide low modulus values in the range of 150 to 500 MPa, are inherently hydrophobic, and are based on cure chemistry that is acid free and delivers thermally stable cross-links. As a result, the films show very little shrinkage during thermal cure (similar to2%), do not require extended high temperature processing, and provide a very low residual stress (<8 MPa). They also show excellent thermal stability and mechanical integrity when exposed to high temperatures. A simple wet process has been developed to facilitate film rework and allow for sacrificial layer applications.