Nanowire Impregnated Poly-dimethyl Siloxane for Flexible, Thermally Conductive Fan-Out Wafer-Level Packaging

Abstract

FlexTrate TM , a flexible hybrid electronics (FHE) platform based on fan-out wafer level packaging (FOWLP) has demonstrated low die shift by using room temperature cured poly-dimethyl siloxane (PDMS) as a molding compound. In this paper, we investigate the enhancement of the thermal conductivity in PDMS used in the FlexTrate TM process to allow for better thermal management via microwave welding of commercially available copper nanowires dispersed in an uncured PDMS matrix, followed by a standard curing process. We also evaluate the thermal stability of PDMS, necessary if FlexTrate TM assemblies are to be used in conjunction with commonly used solder reflow processes, and show that PDMS is stable at standard reflow temperatures. Thermal conductivity enhancement using the microwave welding process is shown to be minimal, with a peak enhancement of ~40%.