PRECISION-MEASUREMENT AND MAPPING OF DIE-ATTACH THERMAL-RESISTANCE

The thermal resistance of the attachment between a die and its carrier contributes strongly to the total temperature rise In an electronic s ystem. The die attach resistance often differs substantially from the value predicted using the bulk thermal conductivity of the attachment material because of partial voiding and delamination. These defects ca n be introduced during the attachment process or during subsequent exp osure to humidity or temperature fluctuations. This manuscript develop s a technique for precisely measuring the spatially-averaged die-attac h thermal resistance and for mapping spatial variations of the resista nce in the plane of the die. The spatially-averaged resistance measure ments use transient electrical heating and thermometry at frequencies up to 1 kHz to achieve a value of the uncertainty near 10(-6) m(2) K/W , which is a substantial improvement over existing steady-state method s. Spatial variations are captured using scanning laser-reflectance th ermometry and a deconvolution method detailed here. The data in this m anuscript show the impact of the adhesive material, the adhesive thick ness, and the attachment pressure on the thermal resistance, as well a s the spatial variation of the resistance resulting from incomplete co ntact.