AES Semigas


30 October 2020

Transphorm releases latest high-voltage GaN reliability data

Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-Q101-qualified gallium nitride (GaN) field-effect transistors (FETs) for high-voltage power conversion applications — has released updated information regarding its GaN technology’s quality and reliability (Q+R). Currently, the firm’s GaN platform offers a FIT rate of <1 failure per billion hours in real-world applications, indicating very high reliability. The FIT calculation is based on more than 10 billion (10bn) field hours of operation accumulated from an installed base of about 250MW.

Transphorm’s devices are in use across a wide range of applications spanning 65W to 3kW. Examples include universal, fast-charging adapters for smartphones and laptops; rugged, broad industrial power modules; and 1.5-3.0kW Titanium-class data-center power supplies, which meet the high-power-efficiency ecodesign requirements mandated by the European Parliament and the Council (ErP: Directive 2009/125/EC).

Transphorm’s GaN versus SiC reliability

Silicon carbide (SiC) power devices are an alternative power conversion solution and in a later stage of maturation than power GaN solutions. Although SiC offers more than a trillion hours of field operation compared to Transphorm GaN’s 10bn hours due to being commercially available longer, recent reports indicate that SiC’s field failure FIT rate is 4.1, illustrating what is claimed to be excellent field reliability achieved to date by Transphorm’s GaN with a FIT of <1.

In-house reliability = In-field reliability = Accuracy

Extrinsic reliability, also referred to as early life failure (ELF) or infant mortality, is determined via in-house manufacturer analysis — identifying material, design and process control defects that may cause parts to fail. Alternatively, field failure measures the number of devices that fail in customer systems in production in relation to the total number of parts sold.

When assessing FIT rate, the above two metrics — ELF and field failure — are studied. The convergence of these two rates means that a semiconductor manufacturer’s internal reliability assessments are accurate; a customer can have confidence in that reported level of device performance.

Transphorm announced a field failure FIT of 3.1 in January 2019, then 2.2 later in 2019. Now, the firm’s field failure FIT of <1 aligns more closely with its current ELF FIT rate of 0.61, measured at 520V (80% V(BL)DSS, which is the JEDEC standard).

For customers, knowing the ELF statistics of a technology is essential to controlling warranty claims, says Transphorm. The firm follows the standard industry practice as defined in JEDEC’s JESD74A standard for measuring its ELF rate. Ensuring conservative results, Transphorm tests its devices to their maximum spike rating and an appropriate use temperature of 85°C. Despite JEDEC qualification requiring ELF rate testing, only silicon device manufacturers commonly report it — most GaN and SiC power electronics manufacturers do not.
“To the best of our knowledge, Transphorm is currently the only high-voltage GaN semiconductor company to report ELF,” says Ron Barr, VP of quality & reliability. “Customers require certain information when comparing wide-bandgap technologies. So, we aim for transparency here. And accuracy, as we frequently see reliability data being calculated differently or manipulated in uncommon ways yet being reported as the same metric type,” he adds. “Given this trend, our education efforts are focused heavily on explaining the proper methods that must be used to prove business-critical metrics and why.”

Transphorm says that it educates the industry on the most effective Q+R testing methods as well as how to interpret the results to ensure customers have accurate reliability data for business-critical decision making. For more information, watch Transphorm’s latest video on reliability testing:

Transphorm’s reliability reports available on its website will be updated by the end of 2020 to include ELF FIT rates of all Gen II and Gen III GaN FETs.

Tags: Transphorm GaN-on-Si GaN HEMT



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