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4 February 2019

Transphorm releases quality and reliability data behind device shipment numbers

Transphorm Inc of Goleta, near Santa Barbara, CA, USA — which designs and manufactures JEDEC- and AEC-Q101-qualified high-voltage (HV) gallium nitride (GaN) field-effect transistors (FETs) for high-voltage (HV) power conversion applications — has announced the first complete validation data set for GaN power FETs in the range 600V and higher. This information expands on Transphorm’s announcement in December indicating that it has shipped over 250,000 GaN FETs to date.

“In the power conversion market, quality, reliability and performance are the three main factors used when vetting transistors,” says Philip Zuk, VP of technical marketing worldwide. “We’ve always operated with the mindset that prioritizing quality and reliability will result in high-voltage GaN’s success,” he adds. “We’re proud to see that strategy deliver positive results and felt it important to release the validation data so that potential and existing customers can understand GaN’s true capabilities.”

Availability of the two new data types, Early Life Failure (ELF) and Field Failure, that round out the validation data set marks another milestone for high-voltage GaN technology, says the firm, further positioning its GaN reliability as competitive to and poised to likely surpass that of alternative solutions — silicon and silicon carbide (SiC) — given that Transphorm’s power conversion technology is in its first maturation stage whereas silicon transistors have long-since matured and SiC is a decade into its development.

High-voltage GaN reliability: a complete view

Transphorm’s complete data set includes five components of product reliability:

  • Product Qualification: defined by JEDEC and AEC-Q101 standards.
  • Testing beyond standard requirements: includes high-voltage switching, single-event burnout (SEB), high-temperature operation lifetime (HTOL) and high-temperature gate bias (HTGB) testing at elevated temperatures and voltages.
  • Intrinsic Lifetime: measures device’s ‘wear-out’ lifetime; also defines failure modes and acceleration factors.
  • Extrinsic Lifetime or ELF: forecasts field failure rates in failure in time (FIT) or parts per million (ppm) per year rates; used for warranty calculations.
  • Field Failure: measures a device’s actual field performance in customer applications.

“Intrinsic data alone is not enough,” states Ron Barr, VP of quality and reliability. “Intrinsic testing gives us the acceleration factors that we use in conjunction with Early Life Failure testing to determine the product’s infant mortality rate. This makes it easy for customers to accurately vet GaN devices. Pairing intrinsic data with extrinsic data and Field Failure rates provides a complete baseline for how GaN FETs will perform.”

Extrinsic Early Lifetime Failure

Intrinsic failure rates give unrealistically optimistic views of product reliability, says Transphorm. ELF (Infant Mortality) provides the most realistic view via FIT and ppm rates. Early Lifetime Failure assesses potential defects in materials, design and process control that may cause parts to fail. Notably, ELF causes most customer warranty claims and typically occurs sooner and at higher rates than wear-out failures. Given this, customers use ELF data to determine warranty risks and costs. Transphorm’s ELF is: 0.45 FIT; 4ppm.

Field Failure

Field Failure measures the number of devices that fail in customer systems in production in relation to the total number of parts sold. Transphorm has shipped over 250,000 FETs and accumulated over 1.3 billion field hours of operation, resulting in the following Field Failure rates: 3.1 FIT; 27.4 ppm (conservative estimate)

Transphorm says that its Field Failures align with that of SiC, which is reported to be less than 5 FIT. Further, the firm’s ppm rate continues to decrease over time regardless of application, suggesting that reliability is better than currently reported.

Intrinsic Lifetime is essentially a device’s theoretical lifetime, assuming that material wear-out is the only contributor to the part’s longevity. The data is created using the ‘Physics of Failure’ methodology, which involves measuring time to failure when stressing parts with voltage and temperature, and building related models used to predict ultimate lifetime.

Transphorm’s Intrinsic GaN wear-out:

  • mean time before failure [MTBF] = 1e11 hours [11m+ years];
  • lifetime [100ppm] = 100m hours [11,415 years].

Tags:  E-mode GaN FETs Power electronics

Visit:  www.transphormusa.com/en/document/high-voltage-gan-switch-reliability

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