Preliminary failure-mode characterization of emerging direct-lead-bonding power module. Comparison with standard wire-bonding interconnection

Abstract

Direct-lead-bonding (DLB) and wire-bonding, in epoxy-moulded package, are compared in terms of functional characteristics, failure-mode and post-fault high-current capability of a dual-chip power module (PM), with respect to I2T and critical energy. Wire-bonding power modules have shown poor thermal behaviour, a high and unstable RCE (the chip fault residual resistance), and sometimes a fuse-effect when used in gel-filled power modules. However, DLB power modules demonstrated a very good thermal and electrical behaviour, a very low and stable RCE under high energy failure. After non-destructive defect localization thanks to Lock-In Thermography coupled to RX tomography, the authors were able to confirm the formation of a metallic bridge under wire-bondings and through the chips and solder in DLB, which explains low RCE values for this technology. The DLB interconnection appears to be a promising technology for power module. Nevertheless, the absence of wire-fuse-effect in case of extreme failure, compared to classical wire-bonding, leads the authors to rethink fail-safe and fault-tolerant strategies for critical converter.