Lid Integral Cold Plate Topology: Integration, Performance, and Reliability

Abstract

We demonstrate the lidintegral silicon coldplate topology as a way to bring liquid cooling closer to the heat source integrated circuit (IC). It allows us to eliminate one thermal interface material (TIM2), to establish and improve TIM1 during packaging, to use waferlevel processes, and to ease integration in firstlevel packaging. We describe the integration and analyze the reliability aspects of this package using modeling and test vehicles. To compare the impact of geometry, materials, and mechanical coupling on warpage, strains, and stresses, we simulate finite element models of five different topologies on an organic landgrid array (LGA) carrier. We measure the thermal performance in terms of thermal resistance from coldplate base to inlet liquid and obtain 15 mm2 K/W at 30 kPa pressure drop across the package. We build two different topologies using silicon coldplates and injectionmolded lids. Gasketattached coldplates pass an 800 kPa pressure test, and directattached coldplates fracture in the coldplate. The results advise to use a compliant layer between coldplate and manifold lid and promise a uniformly thick TIM1 layer in the Si–Si matched topology. The work shows the feasibility of composite lids with integrated silicon coldplates in high heat flux applications.