Thermal Modeling and Design Optimization of PCB Vias and Pads

Abstract

Miniature power semiconductor devices mounted on printed circuit boards (PCBs) are normally cooled by means of PCB vias, copper pads, and/or heatsinks. Various reference PCB thermal designs have been provided by semiconductor manufacturers and researchers. However, the recommendations are not optimal, and there are some discrepancies among them, which may confuse electrical engineers. This paper aims to develop analytical thermal resistance models for PCB vias and pads, and further to obtain the optimal design for thermal resistance minimization. Firstly, the PCB via array is thermally modeled in terms of multiple design parameters. A systematic parametric analysis leads to an optimal trajectory for the via diameter at different PCB specifications. Then an axisymmetric thermal resistance model is developed for PCB thermal pads where the heat conduction, convection and radiation all exist; due to the interdependence between the conductive/radiative heat transfer coefficients and the board temperatures, an algorithm is proposed to fast obtain the board-ambient thermal resistance and to predict the semiconductor junction temperature. Finally, the proposed thermal models and design optimization algorithms are verified by computational fluid dynamics (CFD) simulations and experimental measurements. Index terms-thermal resistance model, thermal management, printed circuit board (PCB), PCB via, thermal pad. NOMENCLATURE Bi Biot number h Heat transfer coefficient (W/(m 2 •K)) hconv Convective heat transfer coefficient (W/(m 2 •K)) hradi Radiative heat transfer coefficient (W/(m 2 •K)) k Thermal conductivity of a material (W/(m•K)) k1 Lateral thermal conductivity of the copper zone (W/(m 2 •K)) k2 Lateral thermal conductivity of the FR4 zone (W/(m 2 •K))

Power Electronics Reliability: State of the Art and Outlook

“…12(b). With the application of SiC and GaN devices, new challenges come from the nonlinearity of thermal impedance in a wide range of temperature stresses [96,97], as well as PCB board-level thermal modeling and optimization [98].…”

Electrothermal Design of a Discrete GaN-Based Converter for Integrated Modular Motor Drives

“…8. The copper layers serve as a heat spreader for better heat transfer [23] and they are also used in effective magnetic field cancellation routing to reduce the parasitics of the converter.…”

“…The instantaneous conduction losses in the reverse conduction path is calculated from the reverse output charactereistcs by multiplying the reverse current by the corresponding voltage drop to get a curve for the instantaneous loss P cond (t) versus the reverse current i d (t) and then a fitting is done. P cond (t) is fitted by the polynomial in (23). The instantaneous reverse conduction loss of the selected switch doesn't show a significant dependence on the temperature.…”

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“…No que se refere às técnicas de medição recomenda-se a utilização de uma ponteira de tensão com baixa capacitância e um pequeno comprimento do conector do ground. Quanto maior o comprimento do condutor de ground maior será a indutância associada e maior será a interação com a capacitância da ponteira, alterando os valores da frequência de ressonância dos elementos parasitas do sistema, definida em (9).…”