Thermal study of additive multilayer circuitry on polymer and metal substrates

A thermal study of an additive technology which is capable of depositing circuit traces directly on a variety of materials, including insulated metal substrates, was performed. These metal printed circuit boards are capable of high thermal dissipation of heat originating from high power components as well as from dense circuitry. The circuit traces are fabricated using electrically conductive composites based on a transient liquid phase sintering (TLPS) technology. The low processing temperature of these composites allows their use with aluminum substrates and with polymer dielectric materials, resulting in multilayer substrate capabilities. An initial investigation of the thermal advantages of this novel technology over conventional copper traces on FR-4 was performed. Finite element analysis was used to compare the two structures. Along with the computer simulation, thermal dissipation was measured using assembled components as well as temperature mapping using emissivity compensated IR imaging. A serpentine pattern was fabricated using a photoimaging technology which is capable of fine lines and spaces. Test structures were made on a variety of substrates including FR-4, Cu-clad FR-4, and Al. Different power levels were applied in the serpentine pattern and thermal imaging showed the heat generated on each of these substrates. The benefit of using an insulated metal substrate with no thermally resistive interfaces is readily apparent from the images. A finite element analysis was also performed and compared with experimental results.