A Cu-Plate-Bonded System-in-Package (SiP) With Low Spreading Resistance of Topside Electrodes for Voltage Regulators

This paper presents a system-in-package (SiP) with Cu-plate bonding for voltage regulators. The SiP reduces the power loss by 23% and the thermal resistance by 44% compared to those of a SiP with wire bonding. Copper plates reduce the spreading resistance of the topside electrodes in the MOSFETs, leading to lower power loss. They also act as heat spreaders, leading to lower thermal resistance. The lower power loss and lower thermal resistance contribute toward decreasing a topside temperature that is 18.5°C less than that of a wire-bonded SiP. The Cu plate in the low-side MOSFET has a slit at the center that reduces solder strain between the die and lead frame by 12%. The Cu plates in the high-side and low-side MOSFETs have bumps projecting into the solder layer, resulting in a solder layer that is uniform and thick enough to relax the solder strain.