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LED Thermal Characterization Made Easy

On-demand Web Seminar The webinar will introduce the principles of thermal transient testing – as a general method of semiconductor package characterization by means of physical measurement.

Engineering Edge

Andras Poppe Interview

The prestigious Harvey Rosten Award For Excellence was won by Andras Poppe, Mentor Graphics' Product Marketing Manager for MicReD® (Microelectronics Research and Development) group and faculty member at the Budapest University of Technology, Department of Electronic Devices

What does this award mean to you?
Obtaining this award is a great honor. Especially as the decision is made by a group of highly acknowledged international thermal experts who have deep knowledge, wide overview of electronics cooling and thermal management, and they have a good overview of novelties published in the technical literature. Having been considered for this award by these experts is in itself already an honor.

Which of the previous winners do you most admire and why?
Marta Rencz and Vladimir Szekely won the award in 2001, they were my professors when I began my career. Since then I have worked closely with Marta and Vladimir and have learnt a lot from both of them. In particular, they have taught me the importance of being precise, diligent, finding and emphasizing the essential parts of problems, and considering issues from different angles. Dirk Schweitzer is another Harvey Rosten Award winner whom I also admire.

“Lighting represent about 25% of energy consumption; if this energy usage could be reduced, it will be a significant contribution towards a sustainable economy.”

How did you become an electrical engineer?
Originally I thought I should become a physicist as my mother is a physicist; she was the head of the optical testing laboratory of TUNGSRAM (today: GE Lighting Europe). I spent a lot of time during my summer holidays among the integrating spheres in the dark room of her lab. I always liked physics. As every boy, I loved model railways, even today model railways, especially vehicles running on Hungarian rails are my favourite collector's items. Before finishing secondary school, where I was already specializing in physics, engineering became very attractive, especially as programmable calculators had just come out.

First I started with Sinclair's 4 digit calculator (not yet programmable) using Polish arithmetics. Then a TI-57 calculator which could memorize 44 numbers or program steps. I remember two of my school friends and I, together with our maths teacher, started a competition to see who could write the shortest code that could determine if an integer was a prime. It became clear that programming was something which excited me a lot and at that time the best way to learn computing was to become an electrical engineer.

How did you become interested in LED lighting?
In 2003 colleagues from Lumileds asked us to measure some of their Luceon Emitter samples –one of the first power LEDs. With Gabor Farkas we did thermal transient measurements of these Luexeons at different ambient temperatures and at different forward current levels. We discovered something we found odd: the obtained structure functions were all different, though nothing in the measured physical structure had changed. We began looking for explanation. We deduced that one possible reason for the observed change was the current and temperature dependent energy conversion efficiency of LEDs. We decided that the emitted optical power of LEDs had to be measured and had to be considered in the calculation of the thermal impedances. My mother put us in touch with some former colleagues that were active in photometry. That's how we established our relationship with professor Schanda's team of the University of Pannonia and Lighting Metrics both in Hungary, and Kathleen Murray at Inphora in the US. Within a few months with MicReD, Budapest University of Technology and Economics, University of Pannonia, Lighting Metrics and Inphora, we established the 'TERALED' consortium and obtained a research and development grant from the Hungarian National Committee for Technology Development. The development was also officially called 'TERALED' which we started using as a trade name in marketing, back in 2004. In two years we developed the test setup which is known today as TeraLED® and in December 2005 we shipped the first unit to a major European LED manufacturer.

You've contributed massively to the JEDEC standards, what importance do you believe they play in the future of electronics?
Standards help the industry and end-users of products. They define commonly understood specifications which can be implemented by anybody. With regards to the thermal testing standards that I have been involved with, this is the definition of test procedures, environments and definitions of thermal metrics which correctly define the thermal characterization of an electronic component. Having the test conditions, procedures and metrics standardized, ensures that product data sheets are widely recognized and understood. This results in a fair comparison of products.

Why has the LED become so important?
Today energy conservation has become a major issue – all wasted energy is a contributor to global warming. So saving energy by any means possible is very important, especialy if that saving results in less direct heating of the environment reduced CO2 emission or the reduction of the number of uranium nuclei which need to be subject of fission in nuclear power plants. Lighting represent about 25% of energy consumption; if this energy usage could be reduced, it will be a significant contribution towards a sustainable economy. In the last decade LEDs have evolved a lot and now they are by far the most energy efficient light sources. Compared to the 5% energy conversion efficiency of conventional incandescent bulbs the best white LEDs are approaching an efficiency of 50% - these are figures which speak for themselves.

What are the challenges for the future of Power LEDs?
The challenges are: even higher power, even higher power density, even bigger lighting models and better models to be able to simulate them without having to build a LED luminaire prototype. What we do at Mentor Graphics in this domain helps the solid state lighting industry. And I also do hope that the academic research regarding LEDs that I am involved in at the Budapest University of Technology and Economics also will have a positive impact both on the work of MAD, especially the MicReD team and on the global technical community of the SSL industry.

Harvey Rosten Award

The prestigious Harvey Rosten Award For Excellence was established by the family and friends of Harvey Rosten.

The Award commemorates Harvey's achievements in the field of thermal analysis of elec- tronics equipment, and the thermal modeling of electronics parts and packages. Its aims are to encourage innovation and excellence in these fields.

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