A new evaluation method of thermal transient measurement results

In this paper, a careful theoretical analysis of the thermal dynamics of an electronic device and its package was carried out in order to study the problem of the equivalent thermal circuit implementation. It was found that the device temperature evolution in time is ruled by an infinite and convergent series of time constants. The knowledge of the first n terms of the time-constant spectrum obtained from the temperature transient measurements allows the complete characterization of a suitable and reliable equivalent thermal circuit structured as a Cauer low-pass network with n cells. The total thermal resistance is therefore evaluated as a sum of several contributions due to given parts of the whole system. The techniques allowing the physical identifications of these contributions are also discussed. Furthermore, the influence of plastic coverage on the device thermal behavior is taken into account. The proposed characterization method is also applied to one-dimensional (1-D) multilayered simulated structures in order to study the influence of the number of time constants used for the analysis and effects of local defects or modifications of the material thermal properties.

Thermal resistance analysis by induced transient (TRAIT) method for power electronic devices thermal characterization. I. Fundamentals and theory

For pt.I see ibid., vol.13, no.6, p.1208-19 (1998). The TRAIT method for thermal characterization of electronic devices, whose theory was exposed in part I for one-dimensional (1-D) structures, was here applied to systems having heat fluxes with three-dimensional (3-D) dependence in order to demonstrate that the spatial resolution of the thermal resistance analysis is still qualitatively maintained in this type of structure too. The analytical procedure was first applied to simulated structures whose temperature transients and steady-state fields were obtained by means of a finite-element thermal simulation program. In these cases, the knowledge of the steady-state temperature distribution allowed identifying the thermal physical domains which correspond to the cells of the calculated equivalent thermal circuit composed by resistances and capacitances. Furthermore, some experiments on real electronic devices with purposely designed assembling structures were exposed and discussed. The samples were power-integrated circuits with plastic packages mounted on various substrates and Schottky diodes in TO-3 packages. The experiments on both simulated and real devices demonstrated that TRAIT analysis, being able to recognize the localization of some induced defects, maintains its spatial resolution character, despite the large distortion of the thermal domains occurring when the defects are close to the heat source.

Thermal resistance analysis by induced transient (TRAIT) method for power electronic devices thermal characterization. II. Practice and experiments

A comparison of methods for estimating hourly diffuse solar radiation from global solar radiation

A solar radiation algorithm for ecosystem dynamic models

In this paper the thermal behavior of the semiconductor device is referred to the junction. Devices consisting of multiple parts which are non homogeneous and with varying outlines are subdivided into homogeneous elements with simple outlines which are successively related to the junction. Thermal impedance calculations of cylindrical and spherical sectors are given numerically. Stationary thermal impedances provide the framework to assemble a valid succession of transient thermal impedances. The analysis is expanded for long heating cycles by a simple lumped-component approach with limits of validity.

Transient thermal impedance of semiconductor devices

Optical characteristics of silicon solar cells and of coatings for temperature control

Stationary silicon solar cell converter calculations

Cooling fins of equal thickness and known heat transfer have a definite thermal impedance which is hard to determine analytically. Computing generally valid curves of normalized variables eliminates most of this analysis and establishes simple relations for design parameters and impedance. Optimum design proportions appear in the analysis, eliminating the trial-and-error approach to find them. Comparative analysis of cooling systems is facilitated.

Thermal impedance of cooling fins

The instantaneous forward voltage drop of silicon diodes of different sizes and processes is investigated over four magnitudes of current density. The temperature influence is determined. An equation relating the instantaneous forward voltage drop to current density and junction temperature is given. An expression of the average forward voltage drop and power loss as function of current density and conduction angle is developed.

Werner Luft

Papers

Transient thermal impedance of semiconductor devices

Optical characteristics of silicon solar cells and of coatings for temperature control

Stationary silicon solar cell converter calculations

Thermal impedance of cooling fins

Forward voltage drop and power loss in silicon rectifiers