Challenges in the Manufacture of Glass Substrates for Electrical and Optical Interconnect

For high density electrical interconnect, the production of fine feature, fine pitch substrates is difficult, due to limitations in manufacturing processes and the dimensional stability of conventional laminate materials. In order to enable the further uptake of flip-chip technology, new materials and methods for substrate manufacture are required. Glass as a substrate material offers a number of potential advantages including dimensional stability and close coefficient of thermal expansion match to Si. Furthermore, its optical clarity makes it suitable as a conduit for the transmission of light signals for applications in the growing area of optical interconnect. This paper describes preliminary work to investigate the key challenges of laser machining, metallization and lamination that are involved in the manufacture of multilayer substrates from thin glass sheets. Laser machining has been used to create microvias and other features in the glass and work is underway to determine appropriate process windows. The metallization of glass using electroless copper has been investigated and found to be very dependent on the surface pre-treatments. Finally, pressure assisted-low temperature bonding has been considered as a method for the lamination of the glass sheets to create a multilayer structure