Silver sintering has been the de facto standard for attaching wide band gap (WBG) dies -- GaN and SiC -- to their packages for good reason: 430 W/m-K thermal conductivity, proven performance in high-temperature automotive and industrial environments. But silver is expensive and subject to electromigration, and a new generation of pressure-assisted copper sintering materials is making a serious case for displacing it. Copper delivers around 400 W/m-K thermal conductivity -- close enough -- with lower cost and stronger resistance to electromigration-driven degradation over time.
The reliability argument for copper is actually stronger than the cost argument. WBG devices in EV powertrains and grid infrastructure spend their lives in high-temperature, high-humidity, mechanically stressed environments. Copper sintered joints have shown better mechanical strength through thermal cycling, and copper's higher tensile strength and lower CTE give it a structural advantage in those conditions. Silver's electromigration risk -- gradual performance degradation in the joint layer -- is a known long-term concern that copper largely avoids.
The catch is process complexity. Pressure-assisted sintering adds tooling requirements and tighter process controls compared to silver, which can be applied with lower pressure or even pressureless in some formulations. For high-volume manufacturing of commodity power modules this is a real barrier; for demanding automotive or aerospace applications where the reliability case is strongest, it is an acceptable trade.
The broader context: WBG semiconductors are projected to grow at over 13% CAGR and are on track to displace silicon across EV, telecom, and grid applications. Die attach materials are not a glamorous part of that story, but they are a real constraint -- thermal management at the package level determines whether the GaN or SiC device can actually run at its rated performance. Copper sintering maturing to production readiness matters.