A high performance polymer thin film Power electronics packaging technology

GE Global Research Center has developed a new packaging technology targeted at high performance, high power applications. The technology is called Power Overlay (POL) and involves the use of flex based interconnect structures to package and interconnect power electronic devices. The basic structure has multiple bare chip power transistors and/or diodes solder attached directly down to a thick copper metallization on a high thermal conductivity substrate. The topside of the power devices are bonded to the bottom of a thin polyimide film coated with a polymeric adhesive. The film contains large via openings (250 microns or larger) and with thick copper (100 microns or more) filling the via holes, making a metallurgical contact to the chip pads and forming a topside interconnect structure. A standard electronics grade encapsulatesis used to fill the gaps between chips, providing electrical breakdown protection, moisture protection, mechanical structure and stress relief. This structure has exceptional thermal and electrical performance, a small footprint, a thin profile, and high reliability. The top surface, which is planar, can also be used for heat removal either as an alternative to the backside cooling or as a second thermal path with double sided cooling. POL test results have shown 2x to 3x thermal improvement. The excellent electrical performance is derived from the replacement of wirebonds, with their high electrical parasitics, with a planar interconnect structure with low electrical parasitics. POL modules have demonstrated >80% reductions in overshoot, 3:1 improvements in thermal performance, and 10:1 reduction in inductive and resistive parasitics. POL power modules are capable of hundreds of watts dissipation per square inch, and are designed to handle more than 2000 V and more than 1000 A. The POL process was developed with low cost in mind, with no need for fine line photo-patterning, micro-vias, laser ablation nor precision Pick & Place equipment. This paper provides details of the POL process and structures, shows working modules and presents performance and reliability data.