Impact of Copper Through-Package Vias on Thermal Performance of Glass Interposers

In this paper, the thermal performance of glass interposer substrate with copper through-package vias (TPVs) is investigated both experimentally and numerically. Copper via arrays with different via pitches and diameters were fabricated in 114.3 mm × 114.3 mm × 100 μm glass panels using low-cost laser drilling, electroless plating, and electroplating for copper deposition. The thermal performance of such a structure was quantified by measuring an effective thermal conductivity which combines the effect of copper and glass. The effective thermal conductivity of fabricated samples was determined with infrared microscopy and compared with finite-element analysis on unit TPV cell. Using the effective thermal conductivity, further numerical analyses were performed on a 2.5-D interposer, which has two chips mounted side by side with a total heat generation of 3 W. Interconnects and TPV layers in the interposer were modeled as homogeneous layers with an effective thermal conductivity. Using the developed model, the effect of copper TPVs on the thermal performance of silicon and glass interposers was compared. To further characterize the thermal performance of the 2.5-D glass interposer structure, the effects of pitch of interconnects and TPVs and the TPV diameter are presented.