In recent years, silver sinter materials have grown in popularity in power module assembly, especially for die attach. When compared to traditional solders, silver sinter offers numerous benefits including higher thermal and electrical conductivity, which allows higher operating temperatures with increased reliability and without the concern of melting. A major application where sintered die attach has become mainstream is in power modules for EV inverters.
As EV production matures and continues its rapid growth, areas for potential cost reduction become the focus. One possible avenue for cost reduction would be to implement copper sinter material instead of silver. With properties similarly superior to solder, copper can potentially result in a lower cost bonding solution compared to silver.
Now, it is easy to quickly conclude that copper is significantly cheaper than silver (close to 100X), so the material cost saving must be huge. However, it is not that simple. Unlike silver sinter, copper sinter materials are not yet mature or scaled up to the volumes that offer significant price breaks (economies of scale). A further consideration is that due to copper’s tendency to readily oxidize, it is necessary to utilize protective environments such as N2, for certain process steps including; pre-dry, die-bond and sintering. This, along with potentially longer process times, adds to the overall cost.
There are clear benefits, however, in switching to copper sinter for the bonding. It will be possible to remove costly silver plating from substrates/lead-frames, and sinter directly to bare copper or nickel surfaces. An ongoing trend is to evaluate silver sinter for bonding direct to bare copper, which offers the savings from removing silver plating from the surfaces. Protection against oxidation will be required so this becomes a logical application for evaluating copper sinter paste also.
To conclude, the potential for copper sinter is huge and the applications are present today. As the material and processes mature and economies of scale are realized, along with the ability to remove silver plating from bonding surfaces, the full cost saving of switching from silver to copper can be attained. Silver is expected to remain the dominant sinter material in the short term, but copper is coming quick and fast!
Check out Indium’s range of copper and silver sinter paste products at www.indium.com or reach out to me at dpayne@indium.com with any questions related to sintering or sinter materials.