DBC substrates as a base for power MCM's

Abstract

Multichip modules (MCM) for high current applications are needed for applications such as power amplifiers, inverters and DC-DC converters. The use of traditional thin and thick film hybrid substrates for high current applications is limited due to thin metallization layers and relatively high electric resistance of the conductors. Using DBC (direct bond copper) technology, thick copper foils (0.125-0.7 mm) are clad to alumina or aluminum nitride. Cu patterning is done by technology similar to that for PCB processing. The thick Cu conductors provide excellent current carrying capability and heat spreading of attached power dice. The strong adhesion of the Cu-to-ceramic bond reduces the thermal expansion coefficient in the plane to values only slightly higher than those of the ceramic itself (7.2-7.6/spl times/10/sup -6/). This allows direct die attach of large dice without TEC control layers. As DBC technology uses Cu foils, integrated lead-offs can be realized. This technology was developed by Curamik/sup (R)/ Electronics and is now in volume production. A new via technology combined with integrated leads allow the design of low weight hermetic packages with improved thermal performance. As the via resistance is <10/sup -4/ /spl Omega/, there is practically no current limitation in comparison to glass sealed feedthroughs of conventional hermetic metal packages. High end MCMs with extremely low thermal resistance (<0.03 K/W) can be achieved by integration of 3D micro channels for liquid cooling beneath the power circuit area. This is also a potential future solution for high speed microprocessor systems.