Precious Metals in Power Modules
Precious metal materials used in power devices require three main functions to support highly reliable and high-performance operation.
【Three functional classifications of precious metal materials in power devices】
| # | Classification | Function Name | Description | Typical Precious Metals |
|---|---|---|---|---|
| 1 | Electrical function | Improvement of conductivity and contactability | Flow a stable current with low resistance Ensuring electrical connectivity such as wire bonding |
Au, Ag, Pd |
| 2 | Thermal function | Heat dissipation and junction heat conduction | Efficiently dissipate heat from the device Thermal resistance reduction by backside junction (sintering) |
Ag, Au |
| 3 | Chemical and interfacial stabilization | Antioxidation, diffusion, and interface stabilization | Antioxidation at high temperatures Prevents metal diffusion with Cu and Al Ensuring interface reliability |
Pt, Pd, Au |
Role images for each function
✅ Electrical functions (electrodes and wiring)
- Au and Ag: Very high conductivity and low contact resistance
- Pd: Difficult to oxidize and high contact stability with Ni and Cu
✅ Thermal functions (heat dissipation and bonding)
- Ag: One of the highest thermal conductivity among metals (≈ 400 W/mK)
- Sintered Ag: Mainstream as a backside bonding material for SiC and IGBT
- AuSn solder: Eutectic bonding material with excellent high-temperature reliability
✅ Chemical and interfacial stability (barrier and stability)
- Pt/Pd: Hardly oxidizable at high temperatures, ideal for diffusion barriers with other metals
- Au: Hardly oxidizable, high chemical stability at metal interfaces
