Embedded Fluid Cooling of Close-Packed Via Arrays in Glass

Data from single-phase water microgap cooling experiments conducted on via-enhanced low-conductivity interposers are presented and discussed. The interposers, fabricated with copper thermal via arrays in 400 μm thick glass, are intended to provide a high degree of thermal isolation between adjacent components hosted in a 2.5D package architecture. The interposer surface temperature rise in response to a central heated chiplet is measured as array parameters are varied. This rise is contrasted with results for comparable bulk Si interposers. Conjugate heat transfer modeling is performed in order to explain the results of the experiments, and suggests conditions under which via-enhanced low-k interposer performance can be improved. A new microgap test is undertaken and the via array sample is shown to outperform Si at upstream distances equal or greater than 1.38 mm. At this breakeven distance, the local surface thermal coupling coefficient is 0.24 K/W.