Increased Operating Temperature and Power Cycling Capability
The solder layer between the chip and DBC substrate is the next largest in size in a power module after the baseplate-to-DBC substrate solder layer. Substituting these solder layers with a sintered joint can increase the operating temperature and power cycling capability and the heat dissipation from the chips can be further improved.
The SiNTER Technology for power modules launched by Semikron Danfoss in 2007 utilizes a fine silver powder and innovative production process. At a temperature of around 250°C and under high pressure, the silver powder becomes a sintered layer of very low porosity, connecting chip and DBC substrate in an extremely stable configuration up to the melting point of silver at 962°C.
This high melting temperature, four times higher compared to a SnAg solder layer, is the key for the two to three times better power cycling capability and long-term reliability at high operating temperatures. Today’s standard SnAg solder already exhibits aging at 125°C.
The images below illustrate the achievable improvements with an example: in a soldered module aging of the solder leads to increased chip temperatures much earlier than in the sintered modules due to deterioration of thermal paths. The module with the sintered joint between the chip and the DBC substrate has a longer service life.
Due to a layer thickness of at least 70% thinner than a solder layer and about three times better thermal conductivity, an approximately fifteen times lower thermal resistance results for the sintered layer. Further advantages over a solder connection are, for example, a lower coefficient of thermal expansion and higher tensile strength.