Power tester solution for electric and hybrids

Thermal reliability issues can result in EV/HEV automotive recalls, and the ever wider adoption of electric and hybrid cars has created a specific need for this solution. The Mentor Graphics MicReD Power Tester 600A product also meets the industry’s need for power electronics thermal simulation and test.

Delta Electronics develops high efficiency and high density power module products. “We apply the Power Tester 1,500A to gain insight into the lifetime performance and assure the reliability of the IGBT module,” said Andy Liao, Section Manager, Delta Electronics. “The Power Tester 600A could provide a scalable solution that would allow us to measure many discrete power devices or modules concurrently. This increased testing throughput would give us statistical failure data that we need in order to accurately predict the field lifetime of the products.”

Reliability, Accuracy and Scalability Solves EV/HEV Power Electronics

Thermal Issues: Designers of today’s EV/HEVs are faced with significant mission critical challenges - foremost among these is ensuring the thermal reliability of power electronics modules; detecting potential degradation of IGBTs caused by a range of standard drive cycles; and identifying the underlying damage root causes. There has been a record level of US auto-maker recalls and these include thermal reliability of EVs/HEVs - last year in the US there were 51.26 million recalled vehicles. Back in 2014 Ford recalled around 74,000 older model Ford Escape and Mercury Mariner crossover vehicles due to concerns that the electronic hybrid system may overheat. Lazlo Tolnay – Product Line Director commented: “This underlines the importance of reliability predictions and proper simulation and testing of power electronics in electric vehicles and hybrids. It is a concern for the industry and this is where we’re trying to help.”

Degradation

Tolnay continued: “What happens in an electric vehicle is the components repeatedly go on and off in their lifetime, and because of that it creates thermal stress which leads to degradation of the device. The big question then is of course, is what is the implication for the lifetime of the device and what is the underlying root cause of the degradation. So, there can be different reasons such as wire bond degradation, metalisation layer mismatch, solder fatigue, die and substrate cracks. What we do in our simulation and testing is create this failure but also capture the change in the thermal structure, which will show how we arrived at this failure.”

Mentor’s MicReD Power Tester 600A solution provides test results that scale to real world requirements:

• Comprehensive diagnostics for thermal reliability: The MicReD Power Tester 600A product provides a simple reliability testing process for lifecycle estimation. Device set-up is easy and power cycles are fully automated. The T3Ster ‘structure function’ feature inside the Power Tester yields non-destructive ‘failure-in-progress’ data for each IGBT. All diagnostic information is recorded during testing, from current, voltage and die temperature sensing, to ‘structure function’ changes that point to reasons for failures in the package structure. Package development, reliability and batch checking of incoming parts can now be tested before production.
• Simulation accuracy: The MicReD Power Tester 600A product can power IGBT modules through tens of thousands of cycles. This provides ‘real time’ failure-in-progress data for diagnostics, significantly reducing test time and eliminating the need for post-mortem or destructive failure analysis. Associated 3D CFD (computational fluid dynamics) simulation errors can be reduced from typically up to 20% to 0.5% for accurate thermal characterisation of IGBTs and components due to Mentor’s calibration technology solely found in the MicReD T3Ster product.
• Scalability - tests up to 128 IGBTs in Series: Up to eight MicReD 600A Power Testers can be chained together to allow users to power cycle up to 128 IGBTs simultaneously in a system test. The MicReD Power Tester 600A product delivers 48V under load, and users can deal with components mounted externally on cooling systems for maximum flexibility. The MicReD Power Tester 600A also meets the needs of emerging de facto EV/HEV power electronics testing best practices such as those currently being developed for the German automotive industry.

MicReD Power Tester 600A - part of a comprehensive solution

The MicReD Power Tester 600A product can be coupled with Mentor’s leading CFD simulation technologies. Mentor’s FloTHERM and FloEFD 3D CFD software provide front loading thermal simulation of power modules. When coupled with the Flowmaster full vehicle thermo-fluid system-of-system 1D CFD modelling tool, this yields unparallelled levels of accuracy. This is done via MicReD’s T3Ster technology providing CFD input material properties for automated model calibration functionality to accurately simulate the real temperature response of an EV/HEV’s dynamic power input. This combination of technologies allows users to generate IGBT thermal lifetime failure estimations with the greatest accuracy possible.

“The MicReD Power Tester 600A is an extension of our total solution in automotive thermal engineering, and there is no other product like this for the EV/HEV market today,” stated Roland Feldhinkel, General Manager of Mentor Graphics Mechanical Analysis Division. “We have leveraged our best in class products to deliver a comprehensive thermal simulation and hardware test solution that meets auto-maker EV/HEV industry needs while supporting the rapid growth forecast for the market in the next few years.

“Combining simulation and test makes sense. Sometimes you get better simulations if you have measured test data. Very often simulations will lack accuracy because the boundary conditions, material properties etc, are not understood. So this combination is very beneficial for customers and Mentor is the only company that is doing it.

“The automotive industry requires a high volume of testing because they are not allowed to make lifetime predictions based on measuring one device, they need to measure multiple devices or they can’t make predictions on reliability. So to address these standards you need a high throughput and this is what this power tester is for and it is exactly what is needed for the automotive industry. It was not developed in a remote think-tank somewhere; it was developed in close collaboration with our customers.”