Thermal and Mechanical Considerations for Silicon-Resin High-Density Substrate

We examine the thermomechanical tradeoffs in a novel technology for high-density interconnect substrates. Fabricated from silicon (Si) wafers with planar cavities of highly filled composite encapsulant, the technology leverages established Si photolithography but offers improved mechanical properties. Modules are subject to thermomechanical stress during encapsulant cure, assembly reflow, module fabrication, and operation. We show that improvements in junction-to-ambient sinking offset the heat density increase in such systems and low expansion encapsulants prevent failure during cure and subsequent processing. We employ finite element modeling and materials testing to show the effect of wafer design and material selection on the in-plane and through-plane stresses in the module.