Thermal Design in a Hybrid System with High Packing Density

The need for higher speed digital systems is likely to lead to power dissipation per unit volume of up to 106 W/m3. One approach is to use a thick film hybrid assembly technology, and various cooling techniques for such a system are examined. Theoretical results for alternative heat transfer mechanisms are presented, and the effects of chip density and size and system thermal resistances are illustrated. The major part of the temperature rise is found to be in the interface between the thick-film substrate and the heat sink. Conduction, forced air, and liquid cooling of the heat sink are compared. Experimental results for a high packing density system show good agreement with the computed results.