Recent developments of direct bonded copper (DBC) substrates for power modules

DBC substrates are the standard circuit boards for power modules. Using DBC technology, thick copper foils (0.125 mm-0.7 mm) are cladded to alumina or aluminum nitride. The strong adhesion of the copper to ceramic bond reduces the thermal expansion coefficient (TEC) in the horizontal direction only slightly above the TEC of the ceramic itself. This allows direct silicon attach of large dies without using TEC controlling layers. As DBC technology is using copper foils, integral leads overhanging the ceramic can be realized. A new via technology, combined with integrated leads, allows the design of low weight hermetic packages with improved thermal performance. High end multichip modules with extremely low thermal resistance (<0.03 K/W) can be achieved by the integration of 3D micro channels for liquid cooling underneath the power circuit area. A new type of alumina DBC with a flexural strength of >1000 MPa and excellent temperature cycling resistance has been developed.