A Study of Measurement Methods for Detecting Voiding and Delamination of Die Attach Materials in Power Semiconductor Devices Available to Purchase

There are three basic methods used to detect voiding and delamination of die attach materials in semiconductor devices. (1)Electrical measurement of a temperature sensitive parameter (e.g. V_be, V_gs) under pulsed power conditions is preferred by manufacturers because the data is easily and quickly obtainable during final electrical test; but electrical measurements are only sensitive to gross voiding or delamination. (2)X-ray analysis produces images which are generally accepted as proof of voiding; but X-ray is completely insensitive to delamination or degradation from thermal stress. (3)Use of Scanning Acoustic Microscopy (SAM) as a non-intrusive analysis tool is increasing in the semiconductor industry and provides accurate evidence of delamination in cases where the other two methods fail. The use of all three methods is recommended to maintain a reliable power product fabrication line at its peak of quality with respect to die attach coverage. This paper will compare and contrast the three methods during thermal shock stress in two manufacturer's power Insulated Gate Bipolar Transistor (IGBT) using a lead-tin solder die attach material.