Thermal Management in Direct Chip Attach Assemblies

Abstract

Direct chip attach (DCA) packaging technologies are finding increasing application in electronics manufacturing particularly in telecommunications and consumer electronics. In these systems, bare die are interconnected directly to a printed circuit board. The two primary forms of DCA included chip on board (COB) where the die are attached face up and wirebonded to the substrate and flip chip on board (FCOB) where bumped die are interconnected active face down directly to low-cost organic substrates. In the current work, thermal management of four direct chip attach technologies is investigated. Experimental measurements are conducted exploring the junction-to-ambient thermal resistance and thermal dissipation paths for COB interconnection and three FCOB interconnect technologies including solder attach, anisotropic adhesive attach, and isotropic adhesive attach. A first-order chip-scale thermal design model is developed for flip chip assemblies exhibiting good agreement with the experimental measurements.