Polymer thick film (PTF) and flex technologies for low cost power electronics packaging

Abstract

Electronic power converters have been designed, produced, and disseminated in mass quantities using a number of fabrication techniques, from standard PCB technologies for low cost applications, to thick film on ceramic, to direct bond copper (DBC) for high power, higher cost applications. Each approach holds a share of the power packaging market, but they all restrict, for the most part, circuit and package designs to 2D boards. One potential pathway into the third dimension is by the use of multilayers, an approach which becomes increasingly difficult with each additional layer added beyond the first, and with the exception of high performance solutions is typically cost prohibitive for the majority of applications. This paper demonstrates the feasibility and viability of an alternative low cost power packaging option which uses familiar industry technologies in a unique manner: flexible polymer substrates. Flex technology uses industry standard PCB and/or thick film processes, offers the lower cost, higher performance solutions inherent with the majority of polymer plastics, and as a final bonus, frees the designer to more efficiently use all three dimensions. The researchers have shown the feasibility of this low cost alternative solution through the fabrication and testing of integrated power modules (IPMs) which use flex polymer substrates in conjunction with both surface mount and bare dice. These DC/DC power converters transform 120 V/240 V inputs to 9V, 7 W outputs, and illustrate the miniaturization advantages of fully utilizing the 3D space offered by flex circuitry.