Platform for Automotive Traction Inverters can use Si or SiC Devices

July 20, 2018 by Paul Shepard

Developments within automotive technology are ever more centered around the electrification of the drivetrain and demand for high quality IGBT and silicon carbide power modules is increasing rapidly. A key approach to meeting the stringent automotive requirements and speeding up the time-to-market is the development of a new power module technology platform.

That is why Danfoss has introduced the new DCM™ technology platform which is especially suited to match the technical design challenges of automotive traction inverters for HEV/EVs. The DCM™ technology platform comprise of Danfoss' market leading technologies: Danfoss Bond Buffer® that combines sintered die attach and copper wire bonding, transfer molding processes for robust packages, to liquid cooling technologies namely ShowerPower® and SP3D®.

The DCM™ is a robust, chip independent technology platform and designed for Si and SiC semiconductors. The technology platform is well-defined, based on proven technologies, and yet scalable and customized to meet specific requirements.

The DCM™1000 power module covers 750V semiconductors in silicon, and the DCM™1000X covers 1200V semiconductors, either in silicon or silicon carbide. Both are designed to operate under harshest conditions and includes Danfoss Bond Buffer®, Shower Power 3D® and transfer molding.

Danfoss Bond Bu­ffer® technology (DBB®)

Standard aluminum wire bonding technology is limited by the current carrying capability of the wire. Several manufacturers developed alternatives ranging from the .XT process from Infineon, the SKiN technology from Semikron to the DBB® technology from Danfoss, all of which are copper based.

The DBB® technology enables copper wire bonding on standard semiconductor chips. Thin copper foil (the bond buffer) is sintered on the topside semiconductor metallization upon which copper wire bonding can be attached. Sintering of both bond buffer and chip to substrate are done in the same process step.

DBB enables power cycling capabilities that are 15-times higher than seen in Al wire bonded power modules. This lifetime benefit can be used to operate at higher junction temperatures without need for current derating. Increased power cycling capability also reduces the semiconductor area inside a power module leading to reduced cost.

Key is the robust top-side copper to copper contact with lower thermo-mechanical stress as well as lower steady state and transient thermal resistances because of the increased contacting surface. The electrical characteristics are improved as well as the copper foil on top of the die reduces voltage drop and adds thermal buffer and heat spreader. Therefore, conduction losses are reduced and short circuit properties are improved.

Simulations and measurements have proven that the limits for the "lifetime - output current tradeoff" have been pushed. This means that the lifetime improvement for DBB® over standard wire bonding combined with the improved thermal performance of SP3D® over e.g. pin fin coolers, give an increase of output current of 20-30% over the state-of-the-art automotive traction modules using comparable semiconductor areas.