Minh-Nhat Nguyen

Calculation limits of the homogeneous effective thermal conductivity approach in modeling of printed circuit board

Electronic components are continuously getting smaller. They embed more and more powered functions which exacerbate the temperature rise in component/board interconnect areas. Their design optimization is henceforth mandatory to control the temperature excess and to preserve component reliability. To allow the electronic designer to early analyze the limits of their power dissipation, an analytical model of a multi-layered electronic board was established with the purpose to assess the validity of conventional board modeling approaches. For decades, a vast majority of authors have been promoting a homogenous single layer model that lumped the layers of the board using effective orthotropic thermal properties. The work presents the thermal behavior comparison between a detailed multi-layer representation and its deducted equivalent lumped model for an extensive set of variable parameters, such as effective thermal conductivities calculation models or source size. The results highlight the fact that the conventional practices for Printed Circuit Board modeling can dramatically underestimate source temperatures when their size is very small.

Practical analytical steady-state temperature solution for annealed pyrolytic graphite spreader: Partial results

The capability to efficiently transfer the heat away from high powered electronic devices is a ceaseless challenge. More than ever, the aluminium or copper heat spreaders seem less suitable for maintaining the component sensitive temperature below manufacturer operating limits. Emerging materials, such as Annealed Pyrolytic Graphite (APG), propose a new alternative to conventional solid conduction without the gravity dependence of a heat-pipe solution. Unfortunately, the ultrahigh performance rising of APG core is restricted to in-plane thermal conductivities which can be 200 times higher than its through-the-thickness conductivity. So a lower-than-anticipated cross-plane thermal conductivity or a higher-than-anticipated interlayer thermal resistance would compromise APG-based material as efficient heat spreaders. In order to analyse the sensitivity of these parameters on the effective thermal performances, an analytical model for predicting the temperature distribution over an APG flat-plate was developed. To demonstrate its relevance, it was compared to numerical simulations for a set of boundary conditions. The comparison shows a high agreement between both calculations to predict the centroid and average temperatures of heating sources. The pertinence of the practical expression used for modelling APG flat-plates thermal behaviour appears quite relevant for early stage design, our concern.

Steady-state temperature solution for early design of Annealed Pyrolytic Graphite heat spreader: Full results

The capability to efficiently transfer the heat away from high-powered electronic devices is a ceaseless challenge. More than ever, the aluminum or copper heat spreaders seem less suitable for maintaining the component sensitive temperature below manufacturer operating limits. Some emerging materials, such as Annealed Pyrolytic Graphite, are a new alternative to conventional solid conduction without the gravity dependence of a heat-pipe solution. Unfortunately, the ultrahigh performance rising of APG core is restricted to in-plane thermal conductivities which can be 200 times higher than its through-the-thickness conductivity. So a lower cross-plane thermal conductivity or a higher than anticipated interlayer thermal resistance would compromise APG-based materials as efficient heat spreaders. In order to analyze the sensitivity of these parameters on the effective thermal performances, an analytical model for predicting the temperature distribution over an APG flat-plate was developed. Its relevance was compared to numerical simulations and experiments for a set of boundary conditions.