Thermal management with additive multilayer circuitry on metal substrates

Abstract

High density microelectronic circuit substrates have been fabricated by additive processing on metal substrates. The circuit traces and vias are fabricated using an electrically conductive paste and permanent photoimageable dielectric materials developed for microvia technologies. The conductive material is a metal-polymer composite based on transient liquid phase sintering (TLPS) technology. Bulk thermal conductivity measurements of the TLPS conductive composites show that they have similar thermal conductivity to solder. The low processing temperature (<250/spl deg/C) allows their use on Al substrates. The key attribute of the technology is its fine line multilayer circuit capability on metal substrates. To show the advantages of the additive metal substrate technology over conventional approaches, thermal dissipation has been measured by temperature mapping using emissivity compensated IR imaging. A serpentine pattern was fabricated on a variety of substrates, including Cu-clad FR-4 and Al. Thermal imaging shows the much higher power dissipating capabilities of the Al substrate. A prototype thermal test board was also fabricated and assembled with power components. The thermal dissipation of the power components was measured to be up to 75% more efficient than the baseline, a printed circuit board with thermal vias and a heat sink. The multilayer circuit technology described here was also used to fabricate a large area heat sensor which has 1600 thermocouples per square centimeter and a sensitivity of 40 mV/(W/cm/sup 2/).