Silicon carbide climbs the mountain of manufacturability
Power strategist Kevin Speer of Littelfuse talks to Nick Flaherty about pricing, specification and the prospects for the latest wide bandgap power technologies, silicon carbide (SiC) and gallium nitride (GaN).

Wide bandgap technologies in power designs are starting to mature and gain industry acceptance. The Electronica exhibition this year saw both technologies gaining ground.

“The inflexion point is customers understanding the system benefits rather than just the Transistor price, and that’s happening now,” said Kevin Speer, global manager of technology strategy for power semiconductors at Littelfuse. “What has changed is people are starting to realise the expense of passives and cooling – copper and aluminium are expensive.”

In December, Littelfuse invested in US SiC startup Monolith semiconductor, although it is looking at both technologies.

“We are looking at everything,” said Speer. “GaN will carve out a niche – there’s a place for it, and that will depend on the voltage, probably in the 30 to 40V range. The problem at 650V is you are also competing with silicon and silicon carbide and its going to be a bloodbath. For low voltage motor drives the IGBT will remain dominant but for some of the higher power supplies for data centres GaN is a good fit.”

“I think we are reaching a critical point with SiC now. We are getting close to the ideal switch but that’s not enough and we have to overcome a range of other challenges,” he said.

LIttelfuse is planning to launch a 1200V SiC transistor in a TO247 three lead package in Q1 17, manufactured at the Lubbock, Texas fab run by German foundry X-fab.  

“We specify the maximum leakage at 100µA up to 170°C. In the community there has been the tendency to specify a 1200V 80mΩ device where that is the typical rating rather than the max rating and this is not very useful for engineers, so if we say its 80mΩ it’s the maximum rating. At 25°C it is typically 65mΩ.”