Measurement of microbump thermal resistance in 3D chip stacks

  title={Measurement of microbump thermal resistance in 3D chip stacks},
  author={E. G. Colgan and Paul S. Andry and Bing Dang and J. H. Magerlein and Joana Maria and R. J. Polastre and J. Wakil},
  journal={2012 28th Annual IEEE Semiconductor Thermal Measurement and Management Symposium (SEMI-THERM)},
The thermal resistance of Pb-free ~25 μm diameter microbumps with pitches of 50, 71, and 100 μm has been measured with and without underfill in four high chip stacks. With underfill, the unit thermal resistance values were 8.0, 15.5, and 19.0 C-mm2/W for 50, 71, and 100 μm pitch microbumps, respectively. The average microbump height was 16.1 microns. For the 50 μm pitch case, the thermal conduction through the underfill is roughly equal to that of the microbumps alone.