Extension of high density interconnect multichip module technology for MEMS packaging

In this paper, we describe research into extending the General Electric (GE) Chip-on-Flex (COF) process for packaging microelectromechanical systems (MEMS). COF is a derivative of the high density interconnect (HDI) used for multichip module packaging of microelectronics. COF is a high performance, low cost multichip packaging technology in which die are encased in a molded plastic substrate and interconnects are made via a thin-film structure formed over the components. For MEMS packaging, the standard COF process has been modified to Include laser ablating windows in the interconnect overlay to allow access to MEMS. Special purpose surface and bulk micromachining test die were developed and packaged with CMOS electronics using the COF process. The COF/MEMS packaging technology is well-suited for applications in which monolithic integration of MEMS and electronics is not optimal.