Clemens J. M. Lasance

Creation and evaluation of compact models for thermal characterisation using dedicated optimisation software

The collaborative European project DELPHI, completed in November 1996, was concerned with the creation and experimental validation of thermal models for a range of electronic parts. Many DELPHI principles and results have been extensively discussed in open literature over the last five years (e.g. Rosten et al. 1997; Lasance et al. 1997); however, one of the topics that has not been treated in sufficient detail is the creation and evaluation or the compact models themselves. This paper tries to fill this gap. We have shown that a dedicated optimisation tool can have the potential to create models and to investigate the consequences of changing the model or the set of boundary conditions. It paves the way to thermal data-on-demand, a procedure by which a supplier provides the end-user with a model that is either suitable for all applications or tuned to a specific application, in almost real time.

The world of thermal characterization according to DELPHI-Part I: Background to DELPHI

The accurate prediction of the temperatures of critical electronic parts at the package, board and system level is seriously hampered by the lack of reliable, standardized input data that characterize the thermal behaviour of these parts. The recently completed collaborative European project DELPHI has been concerned with the creation and experimental validation of thermal models (both detailed and compact) of a range of electronic parts, including mono-chip packages, heat sinks, electrolytic capacitors, transformers, and interfacing materials. The ultimate goal of the DELPHI project was to get component manufacturers to supply validated thermal models of their parts to end users by adopting the experimental techniques used to validate the detailed thermal conduction models of the parts, and the methods to generate compact models. Part II of this paper contains technical information on both experimental and numerical methods. In order to reduce design-cycle time and physical prototyping, equipment manufacturers need to ascertain the thermal performance of new systems at the earliest possible stage of the design process. Accurate, validated thermal models of the critical parts used in the design are needed to provide the thermal precision necessary to design out the functional and reliability failures that result from component overheating.

The world of thermal characterization according to DELPHI-Part II: Experimental and numerical methods

For pt.I see ibid., vol.20, no.4, pp.384-91 (1997). The purpose of the second part of the DELPHI survey paper is twofold. First, to describe the experimental methods that have been developed to validate the numerical models generated to characterize a certain electronic part in full detail and second, to highlight the various approaches that were studied to generate compact models from the detailed models. It can be concluded that the results of the experimental as well as the numerical methods which are highlighted in this part are characterized by a high accuracy, typically of the order of 95% or better.

Ten Years of Boundary-Condition- Independent Compact Thermal Modeling of Electronic Parts: A Review

In order to reduce design-cycle time and physical prototyping, equipment manufacturers need to ascertain the thermal performance of new systems at the earliest possible stage of the design process. In the early 1990s, some European industries began to realize that the accurate prediction of the temperatures of critical electronic parts at the package, board, and system levels was seriously hampered by a lack of reliable, standardized input data that characterize the thermal behavior of these parts. It was the start of a number of European projects concerned with the creation and experimental calibration of thermal models for a range of electronic parts. The ultimate goal of these projects was to get component manufacturers to supply calibrated compact thermal models (CTMs) of their parts to end users by adopting the experimental techniques used to calibrate the detailed thermal conduction models of the parts and the methods to generate compact models. This review paper is written with the purpose of presenting a condensed overview of the history, background, philosophy, methodology, and standardization aspects of compact thermal modeling to non-experts. Some space is devoted to the basic concepts of thermal resistance and thermal characterization because many designers have an incorrect perception of the physics underlying these concepts.

Two benchmarks to facilitate the study of compact thermal modeling phenomena

The paper discusses two benchmark cases to facilitate the study of compact thermal models for the purpose of component thermal characterization. The benchmarks represent idealised concepts of respectively a leaded package (PFQP-style) and an area-array package (BGA-style). Two different boundary conditions sets are included because both package types require such. The objective of the paper is to formulate a framework that can be used by everyone working in the field. In this way, comparison of results emerging from alternative approaches in defining compact models becomes much easier. The benchmarks are also prepared for the study of time-dependent compact models, but in this paper only steady state models are discussed. The paper also proposes a definition of Boundary-Condition-Independence and discusses a possible division of thermal characterization responsibilities between component manufacturers and their customers.

Thermal management for LED applications

In this chapter, after a generic discussion of thermal testing techniques used to characterize packaged semiconductor devices; the latest practical test methods widespread in thermal testing of LED components and SSL luminaires are discussed. Thus, the focus is on the latest, power semiconductor and LED-specific test procedures, environments and thermal metrics—all derived from the classical JEDEC JESD51 family of testing standards. Detailed discussion is devoted to the transient extension of the so-called static test method and the differential measurement principle in its practical realization. Different representations of the thermal impedance are presented starting from the classical Zth(t) functions ending with the so-called structure functions. These are discussed in depth because they became the de facto standard in laboratory testing of thermal properties of LED components, in reliability analysis and in quality assurance at leading LED manufacturers. The basic concepts are introduced through practical examples.

On the standardization of thermal characterization of LEDs

Nowadays the demand for thermal standards for power LEDs is increasing. On the one hand metrics for fair comparison of competing products are needed; on the other hand, designers of power LED-based applications demand reliable and meaningful data for their daily work. Todays data sheet information does hardly meet any of these requirements. In earlier papers [1] [2] we compared the current situation in the LED world with the situation in the IC world over twenty years ago, observed that much can be learned from the progress achieved, and concluded with a proposal for action. This paper addresses thermal issues that are specific to light emitting diodes (in fact, also semiconductor devices), the drawbacks of the current situation with respect to the information in the data sheets, and emphasizes the need for electro-thermal models. It also includes a new version of the proposal for action. Note: This paper is an update of a paper presented at THERMINIC 2008[3].

Thermally driven reliability issues in microelectronic systems: status-quo and challenges

Abstract To meet the needs of future microelectronics and microsystems, we need a paradigm shift in the approach to system reliability. It is emphasized that the scientific success of many nano/micro-related projects will never lead to a business success without breakthroughs in the way industry is handling quality and reliability through the whole value chain. The paper discusses several reasons for these facts and offers a perspective for future improvements. The paper is essentially a mix between an overview paper and some personal observations in an editorial style.

Challenges in thermal interface material testing

Characterization of thermal properties of thermal interface materials (TIMs) has gained increasing importance as the relative percentage of overall semiconductor package material thermal resistance attributable to the TIMs has increased. The development of new TIM materials has increasingly focused on materials with very high performance and, in certain instances, with very thin in-situ application thickness. These trends have placed increasing focus on the characterization methods, characterization equipment, and accuracy and repeatability of results. This discussion focuses mainly on standardization aspects, standardized laboratory measurement methodology, and application-specific measurements

Enhanced electronic system reliability - challenges for temperature prediction

Using telecommunication as an example, it is argued that the electronics industry badly needs a change in attitude toward reliability thinking. The role of thermal design and reliability qualification is discussed in context of current industrial needs for short design cycles and rapid implementation of new technologies. Current and future practices are discussed in the context of newly-emerging reliability standards. Finally, two multi-company projects targeting the improvement of reliability through better temperature-related information are described.