Determination of thermally induced deformations in electronic packages by Moire interferometry

An accurate and highly sensitive experimental procedure for measuring deformation in a device is discussed. Specimens obtained by slicing 1-Mb DRAM (dynamic random-access-memory) devices were heated uniformly from room temperature to 90°C. The resulting Moire fringe patterns were recorded and analyzed using digital image processing, and axial displacements in the device were computed. It was observed that severe displacement gradients occurred at the silicon chip corners, whereas minimal gradient was seen at and above the chip. A relatively high gradient occurred at and beneath the copper lead frame. The technique proved to be extremely successful in detecting full field displacement patterns necessary for reliable stress analysis of devices