Seven leads for seven new SiC FETs

  • Jul 25, 2022
  • UnitedSiC

Seven is an auspicious number, from days of the week to wonders of the ancient world, continents, brides, brothers and Snow White’s little friends. Many people choose it as their ‘lucky’ number, and it certainly is a handy number of leads to fit on a D2PAK semiconductor package. The extra four leads over the standard D2PAK-3L version make all the difference when you want to maximize the practical performance of a SiC FET with more flexibility and design choice. One lead is used for a Kelvin connection to the source, to avoid interaction between load current and gate drive, one is for the gate and the other five are parallel connections to the source, minimizing resistance and lead inductance.

Of course, the ‘prime’ attribute of the D2PAK-7L is that it is low profile and surface-mount, suiting modern automated assembly techniques in power-dense AC/DC, DC/DC and inverter products. Older end-product designs often needed to use leaded devices in packages such as TO-247, for their ability to conduct heat out to a substantial external heatsink, while providing appropriate lead separation for use at high voltages. This has the disadvantage however of requiring the manual operation of nut and screw fixing and of through-hole soldering. Now, with silver-sintering die-attach and advanced wafer-thinning technology, thermal performance of UnitedSiC’s new D2PAK-7L package is excellent when mounted on a PCB or insulated metal substrate with liquid cooling. In fact, because of the extremely low losses of the Gen 4 750V-rated SiC FETs  used in these packages, PCB pads alone can often provide sufficient heatsinking up to significant power levels in applications such as battery chargers and motor drives. UnitedSiC are making parts available with seven on-resistance options from 60 milliohms down to 9 milliohms, to suit a wide range of applications and budgets. No competitive parts come close, with the nearest only achieving 11 milliohms, Figure 1.

Figure 1: UnitedSiC D2PAK-7L SiC FET RDS(on) versus competition

The D2PAK-7L package provides performance advantages over TO-247 types, with inherently better external spacing between source and drain connections for easier PCB layout and compliance with safety agency creepage and clearance requirements. The smaller package dimensions also reduce bond-wire lengths – an important advantage as die RDS(ON) and die sizes continue to shrink.Inductance is reduced because of shorter wire-bonds and smaller loops of the gull-wing lead lengths, with consequently lower voltage spikes generated from the rapid di/dt rates possible with silicon carbide switch technology.

The introduction of the D2PAK-7L package to the UnitedSiC 750V SiC FET series opens up new cost/performance sensitive applications with its smaller form-factor, improved cost effectiveness, and lower losses. Ruggedness is also enhanced with its low inductance, its Kelvin gate connection and extra voltage headroom afforded by their 750V rating.

The UnitedSiC online FET-Jet CalculatorTM includes the D2PAK-7L parts in its library, so optimum versions can be chosen for your application, with an instant read-out of efficiency, component losses and junction temperature rise for a chosen conversion topology and cooling arrangement.

So, whether seven is your lucky number or not, it still signifies a major step forward in SiC FET packaging. Give it a try for your next power product design.