Effect of Ag Sintered Bondline Thickness on High-Temperature Reliability of SiC Power Devices

Nano-Ag sintering is a promising die-attach technology for the wide bandgap semiconductive power devices, while the high cost of nanosilver limits industrial application. Reducing bondline thickness (BLT) is effective for cost-saving but its effects on reliability have been rarely studied, especially at high-temperature operation. In this work, an organic-free nanostructured silver film was prepared by pulsed laser deposition (PLD) for various BLT joints. The effect of BLT (3.5– $60~\mu \text{m}$ ) on the high-temperature reliability of die-attached modules was systematically investigated. The results indicated that with the increase of BLT, the shear strength and power cycling number of joints both increased. The optimal BLT ranged in 25– $50~\mu \text{m}$ considering both reliability and cost. It was very interesting to find that the connection ratio along the BLT direction existed two valleys at the die- and DBC-bondline interfaces, which clearly corresponded to the crack propagating in the power cycling test.