The conceivable accuracy of experimental and numerical thermal analyses of electronic systems

In the past decade, we have observed a significant worldwide increase in the use of computational codes to calculate the thermal behavior of electronic systems. The benefits of these ´virtual prototyping tools´ are undisputed when it comes to performing parametric studies in early design phases. However, when the objective of the calculation is accuracy, as required for subsequent reliability and performance assessments, the discussion about the level of accuracy that we can expect in practice becomes far from trivial, as will be shown in this paper. A natural question is how accurate numerical simulations are when compared to well-designed experiments in prototypes or final products. Many studies demonstrate amazing agreement, the conclusion often being that ´validation of the numerical model´ has been proven. It will be demonstrated that these conclusions are subject to serious doubts. This paper discusses ´every´ topic associated with a comparison between numerical and experimental results that is based on first principles, not on fitting parameters until the two results match. The final conclusion is inevitable: the situation when all computations at the system level can be used for accurate temperature prediction is still a long way off.