Days before the last issue of Electronics Cooling Magazine was published, we heard news that a significant contributor to our industry, Clemens Lasance, had passed away. Clemens was a long-time editor of this magazine, as well as contributing to the success of multiple conferences and technology developments while at Philips. Besides, Clemens served as a mentor to many of us and played a key role in nurturing multiple generations of experts in cooling for electronics. He was a true source of inspiration.
To recognize Clemens, we reached out to a few people for their thoughts on Clemens; these are shown in alphabetical order of the writer:
“The requirement to provide Boundary Condition Independent (BCI) thermal models of IC packages is today very well appreciated. Independent in terms of their predictive accuracy being independent of the thermal environment that they are simulated in. This is classically defined by the setting of peripheral heat transfer coefficients. In the late 1980s / early 1990s, highly simplistic 1 or 2 thermal resistor ‘equivalent thermal circuit’ models were the state of the art. But those models were only valid, only accurate, when considered in the same thermal environment used to extract them and so certainly not BCI.
Clemens identified the need to augment the equivalent thermal circuit topology to allow for so called ‘shunt resistances’. Thermal heat flow links in the thermal circuit that accommodated lateral spreading of heat within a package that itself was a function of the boundary conditions the package might be subjected to. Both this topology, as well as a standardised way to extract the circuit thermal resistances, were elaborated by the DELPHI program where both Flomerics and Philips were partners. Working with Harvey Rosten, co-founder of Flomerics, Clemens published this seminal paper that is as valid and relevant today as it was in 1995: Lasance et al, “A Novel Approach for the Thermal Characterization of Electronic Parts,” 11th IEEE SEMI-THERM Symposium, Feb 1995.” —Robin Bornoff, Siemens
“I met Clemens at Philips on April 1, 1985 as a fresh graduate on my first day on my first real job, at Philips Applied Technology where we both worked in the department of ‘Heat and Fluid Flow’. The data that got him started on his famous BCI journey was a result of a project I did with Philips Semiconductors, the present NXP, proving that the Rthja could not be used to predict temperatures in operation because the characterization measurements were heavily influenced by the measurement set up. Clemens’ greatness showed when he not only realized that the entire industry was wrong, but set out to rectify the situation, and fearlessly confronted the thermal establishment of the time. To me, this characterized the essential Clemens: a passion for physics, and a passion to defend what he saw as the truth. My longest collaboration with Clemens is as a trainer: Since around 2005 we co-created and co-delivered the ‘Electronics Cooling and Thermal Design’ training, first at Philips and later at the High-Tech Institute in Eindhoven, the Netherlands. Our last project was to grow the training course book into a book on thermal design of electronics from an industrial point of view – to be finished by the remaining co-authors. I worked with Clemens for over 40 years. It is strange that he is not around anymore. He was a mentor and an inspirator and I will miss him.” —Wendy Luiten, WLC (formerly with Philips)
“Clemens was a highly respected colleague. But he was also a true role model to many of us. His technical leadership, integrity, and generous spirit, as well as his unique typically “Dutch” style, left a lasting impression on everyone who had the privilege to work with him. He set a standard for excellence and inspired me to think differently. For example, both of the European projects that I led, Delphi4LED and AI-TWILIGHT, would not have emerged without the inspiration of his previous work on compact models.” —Genevieve Martin, ASML (formerly with Philips)
“Clemens was, first and foremost, a physicist. In the late 1980s and early 1990s, electronics thermal design as an engineering discipline was not as well understood from a scientific perspective as it is today, and for that we owe a great deal to Clemens, for, as Harvey Rosten once put it, “bringing good science to engineers”. He was passionate about improving thermal design to improve product reliability, working with Prof. Michael Pecht at CALCE, helping debunk the use of the Arrhenius model, statistics, and MIL-217 as predictive approaches.
Rja, as a metric was an early casualty, shown to be more a measure of the thermal performance of the test coupon on which it was mounted than the package itself, and as such unusable for design. Clemens efforts in creating package thermal models, and importantly the division of responsibility – that vendors must provide a model that can be used in any environment, so that systems integrators can use that in their specific application environment, led to the development of what we now call DELPHI compact models, which capture enough of the internal heat flow paths to provide useful accuracy. Later he worked with Lorenzo Codecasa which has now led to BCI-ROMs.
He approached everything with passion and enjoyed a lively discussion on topics ranging from American coffee to world politics. Only the brave would engage him in a conversation about Nusselt number correlations, which he regarded as “correligeon”, for scientifically grounded reasons, backed by a full journal paper. Like the double Espressos he loved, Clemens energized those around him. A unique individual who shaped our industry, its hardware and software, and those of us who were lucky enough to have known him.” — John Parry, Siemens
“Clemens was a champion for thermal standards, both in terms of compact modelling and characterization. His name is closely connected to numerous European research projects in the thermal field (DELPHI, SEED, PROFIT). He was the first to raise the flag for LEDs where existing thermal testing standards were not sufficient and initiated a series of actions that resulted in a book on “Thermal Management for LED Applications” published by Springer and in kicking off actions in the JEDEC JC15 committee for the development of LED specific thermal testing standards. It was a great honour for me to co-edit the Springer book with him.” — Andras Poppe, Budapest University of Technology and Economics
“Clemens was among the first to recognize the importance of thermal transient testing in package characterization. He encouraged the development of T3ster, the thermal transient tester, although he could never accept its name. It was a real pleasure to work with him. Not only because he was full of original, new ideas, but also for his personality, humor, and kindness, which always supported new paths. And for the reassuring smile that has never left the corner of his mouth.” — Marta Rencz, BME, co-founder of THERMINIC
“Bonnie Mack, now at Ciena, would be program chair and Clemens Lasance would be general chair for SEMI-THERM Symposium in March 2005; Bonnie called out of the blue to invite me to take on the role of vice program chair for 2005. I was deeply honored. In those days, the program committee abstract review meeting was held in person, a day or more of discussion and voting. I recall Clemens as general chair in a session held in Boston; I was astounded at how perceptive Clemens’ comments were and his ability to review so many abstracts. I came to see in subsequent years how deeply immersed in the review process Clemens was, along with others, which is the basis for the very high quality of the Symposium.
Clemens had just a few quirks. In thermal interface materials, vendors in the late 1990s generally included data sheet values for thermal resistance (°C/W); I was working for the first company to manufacture phase-change TIMs, and the ASTM D 5470 test standard was still relatively new. I had been trying to convince other TIM vendor companies to give values per unit area (°C-in2/W), along with input power applied, test method, and other useful test descriptions. Clemens of course used every discussion as an opportunity to rail against any company and country that refused to use metric values – along with his commentary about the hopelessly weak US concept of what a good cup of coffee is. (Clemens also strongly disliked use of the term “thermal impedance” as he viewed this as misappropriation of an electrical term.) Clemens, Cameron Murray (3M), Marta Rencz (Micred and TU Budapest), and I got together to iron out SEMI-THERM manuscript and presentation for 2006, illustrating the purposes of three major TIM test methodologies and the challenges faced for TIM characterization and development.
Geneviève Martin (then with Philips in Eindhoven), Clemens, and I had a very pleasant dinner one night in the center of Eindhoven. These are the friendships that have meaning for a lifetime in one’s career. Clemens was a remarkable, dedicated individual who has contributed greatly to SEMI-THERM and to characterization and understanding in the entire community.” — Dave Saums, DS&A LLC
“I looked forward at SEMI-THERM each year to seeing Clemens Lasance. He was easy to talk to (at least for me) and we could talk about almost anything. “Almost anything” is the key phrase in the prior sentence! There were a few topics we approached very gingerly so as not to get too excited by either of us. One was politics in general – left or right, that kind of thing. He preferred the order and protocols of the left to the chaos that the right always seemed to bring about in his view. Another had to do with the disparity in thinking about time between Europeans and Americans. He repeated to me more than once that Americans thought a “long time” was 50 years, whereas Europeans thought 500 years was on the short side of the time spectrum. He was all for change as long as it took many years.
In the area of electronics thermal management, I thought Clemens could match up to anyone. I often had discussions that resulted in my edification on thermal topics that I had no knowledge of – he would carefully explain things to make sure I understood his lesson. I was able to somewhat return the favor by discussing certain thermal measurement techniques and equipment that I had developed. It pleased me that he seemed to enjoy these discussions as much as I did.
I have missed Clemens over the last several years – for our discussions, “arguments”, and his contributions to the electronics thermal measurement field that have helped us all.” — Bernie Siegel, TEA (retired) & SEMI-THERM co-founder
“I was sad to hear about the passing of my friend and excellent thermal management colleague Clemens. He was a mentor, advocate, always responsive to requests, and one of the fastest technical paper reviewers one would ever meet. He certainly had his opinions and was quick to defend them but would also find the time to discuss. Working with him on technical conferences and this magazine was insightful, and he left a legacy of improving the way we manage cooling electronics. After Clemens left his editor position at Electronics Cooling I had asked him to write an additional Thermal Facts and Fairy Tales column with the suggestion that “correligion” was a possible topic and the reprinted article in this issue was the result. Reviewing the email exchanges related to revising this article was fun and reminded me that this was the only time I ever used the term ‘polemical’. Clemens was a passionate individual but was also willing to at least listen to other points of view. We all learned from him about challenging basic assumptions and are grateful for his influence in this area. He will be missed, and we wish his wife and daughter comfort.” — Jim Wilson, Raytheon (retired) and former editor of Electronics Cooling
