Transient thermal strain measurements in electronic packages

The development of thermal strains in a memory device as it undergoes heating changes from room temperature to 80°C is investigated. The strains were monitored using an ultrasensitive displacement measuring technique called fractional fringe Moire interferometry (FFM) which provided an enormous amount of displacement data in two orthogonal directions, from which all in-plane strain components in the package were determined. As the package was heated, displacement data were continuously recorded and digitally stored for strain computations. The technique is described and the extraction of strains is presented. A sample strain distribution is given for a corner of the silicon chip, which is though to be a high strain concentration zone