Packaging
IR's patent-pending die-on-leadframe (DOL) technology for power inverter packaging delivers lower package inductance and resistance by minimising the number of material layers to improve thermal performance while reducing the number of interconnections. Lower thermal resistance allows use of smaller silicon devices, since generated heat can be dissipated more efficiently.
The significantly lower inverter electrical resistance allows for higher current capabilities with smaller die sizes and lower torque ripple.
A DOL power module includes silicon devices directly soldered to a copper leadframe within an injection-moulded shell. The internal components are connected directly to outside terminals, eliminating intermediate insulation and conductive layers.
For medium to high power applications, DOL packaging offers better electrical conductivity and increased thermal performance than alternative packaging methods using insulated metal substrate (IMS), direct-bonded copper (DBC) to a ceramic substrate, thick film substrates or PCB-based modules.
The first IR devices to use DOL technology are IR's automotive power modules for EPS and EHPS applications. The IR11867-E02 is a 120A module while the IR11867-E01 is a 160A module. The current ratings are continuous capability at maximum junction temperature of 175degreesC and include built-in temperature-sense feedback and bus-current sensing.
Other features include high frequency, low inductance package for electromagnetic compatibility (EMC) and an integrated de-coupling capacitor across the negative and positive buses for electromagnetic interference (EMI) suppression at high frequencies. The DOL modules are housed in a compact 60x36x8mm plastic package.
Limitations in electrical efficiency, the availability of current on the vehicle bus, and torque ripple which adversely affects "steering feel", have delayed the proliferation of EPS into higher curb-weight vehicles beyond four-wheel steering systems.
