A Study Of Die Attach Solder Void’s Impact On Power MOSFET Device Characteristics

During semiconductor assembly process, many assembly materials such as lead frame, die attach solder layer, wires and mold compound will impact the performance of power MOSFET device. In terms of heat dissipation, the quality of die attach solder layer such as solder void size is the main factor which impact the heat dissipation, and that will impact the characteristics of power MOSFET device. The goal of this thesis is to study how the electrical characteristics and thermal performance of power MOSFET device changes with the increment of center solder void.A product with die size92mil*104mil and package TO220is chose to do the study. By testing and analyzing DC parameters, AC parameters, thermal resistance and Safe Operation Area for plenty of samples, get conclusions below:(1) In the results presented, when the center single solder void ratio increase to20%, the temperature sensitive parameters such as BVDSS, Vth, RDS(ON) and VSD are not sensitive to the increment of center single solder void. Meanwhile, AC parameters are not sensitive to the center single solder void too.(2) Rthjc is strongly correlated with center single solder void size. With the center single solder void ratio increases1%, the reading of Rthjc increases0.0384℃/W. While Safe Operation Area is shrinking with the increment of center single solder void. When pulse time is100ms, compare to the unit without void, the SOA of unit with20%void decreasing11%.(3) Considering the electrical characteristics and thermal performance, suggest control the center single solder void size within5%.Based on the quantitative analysis in this thesis, the characteristics of power MOSFET device can be predicted once get center solder void size. Meanwhile, this thesis suggested and verified reasonable center single solder void size. The experimental results can be used to better control solder void in die attach process and improve product quality.