High-Sensitivity Measurement of Thermal Deformation in a Stacked Multichip Package

The thermal deformation of a stacked multichip package, which is a newly developed electronic package, was measured by phase-shifting moireacute interferometry. We developed this method using a wedged glass plate as a phase shifter to obtain displacement fields having a sensitivity of 30nm/line. This method also enabled the quantitative determination of the strain distributions in all observation areas. Thermal loading was applied from room temperature (25degC) to elevated temperatures of 75degC and 100degC where the thermal strains were examined and compared. The results showed that the longitudinal strain epsiv
_xx
was concentrated at the ends of two silicon chips, and the longitudinal strain epsiv
_yy
increased between the two silicon chips. The shear strain gamma
_xy
increased at the end of the lower silicon chip from 0.17% to 0.30% when the temperature increased by 25degC