2D Grating Pitch Mapping of a through Silicon Via (TSV) and Solder Ball Interconnect Region Using Laser Diffraction: IEEE Electronic Components and Technology Conference, 2016

Planar Strain mapping of interconnects, such as Ball Grid Arrays (BGA) and Through-Silicon Vias (TSVs), is an important step in the development and testing of electronics packages, as excessive strain can lead to device failure. Today, the two most widely adopted methods of experimental strain field measurement, Digital Image Correlation and Moiré Interferometry, encounter limitations when the average strain magnitude drops below 1μm on thermally loaded samples. DIC provides only limited fields of view and increases measurement complexity, while Moiré Interferometry suffers from resolution near material interfaces. If well bonded to a surface, changes in periodicity of a thin diffraction grating can be strongly dependent on the strain field. The local grating periodicity, can then be measured using laser diffraction. We present a means of mapping the pitch of a grating bonded to the surface of a through-silicon via interconnect in two dimensions over a wide field of view, with a high degree of repeatability at room and elevated temperature.