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 system. 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 can be introduced during the attachment process or during subsequent exposure to humidity or temperature fluctuations. This manuscript develops a technique for precisely measuring the spatially averaged die-attach thermal resistance and for mapping spatial variations of the resistance in the plane of the die. The spatially-averaged resistance measurements use transient electrical heating and thermometry at frequencies up to 1 kHz to achieve a value of the uncertainty near 10-6 m2K/W, which is a substantial improvement over existing steady-state methods. Spatial variations are captured using scanning laser-reflectance thermometry and a deconvolution method detailed here. The data in this manuscript show the impact of the adhesive material, the adhesive thickness, and the attachment pressure on the thermal resistance, as well as the spatial variation of the resistance resulting from incomplete contact.