Abstract
Quad Flat No-leads (QFN) packaging is one of the most commonly used packaging types for microelectronic devices due to its outstanding thermal performance. However, it is difficult to analyze the thermal performance of QFN packaging because numerical simulations and experiments often require a large amount of time and resources. In this work, an analytical thermal resistance network model for calculating the mean die temperature of eccentric QFN packaging on the printed circuit board (PCB) is presented. Based on the heat dissipation path from the die to ambient, the thermal resistance network is established. The analytical solution of the mean die temperature of QFN packaging is obtained by the analytical expressions of each thermal resistance in the thermal resistance network. Simulations by commercial software ANSYS provide a reference for verification of the present model. The comparison of the results between simulation and analytical solution shows that the network model can calculate the mean die temperature of QFN packaging accurately over wide ranges of PCB’s thermal conductivity and heat transfer coefficient, and the maximum relative error is only 4.73%. The present model is fast and resource-saving to predict the mean die temperature of QFN packaging; moreover, it provides an optimization method for QFN packaging design to achieve good reliability.
Highlights
With the increasing integration of electronic products, Quad Flat No-leads (QFN) packaging has become one of the most popular packaging types due to its small size, light weight, and outstanding thermal performance
The analytical solution of the mean die temperature of QFN packaging is obtained by the analytical expressions of each thermal resistance in the thermal resistance network
The comparison of the results between simulation and analytical solution shows that the network model can calculate the mean die temperature of QFN packaging accurately over wide ranges of printed circuit board (PCB)’s thermal conductivity and heat transfer coefficient, and the maximum relative error is only 4.73%
Summary
With the increasing integration of electronic products, Quad Flat No-leads (QFN) packaging has become one of the most popular packaging types due to its small size, light weight, and outstanding thermal performance. Since the multi-thermal resistance network models were complicated and the end-users cannot obtain the information of the packaging internal structure and material, Tal and Nabi put forward an analytic method called PERIMA, which converted the standard IC packaging thermal resistance, junction to case resistance (Rjc), and junction to ambient resistance (Rja) into the junction to top resistance (Rjt) and junction to board resistance (Rjb). This method evaluated thermal resistance in a reasonable range in the absence of packaging information using an analytical algorithm, and it had been successfully applied to some representative IC package types. This model can provide an optimization method for QFN packaging design to achieve good reliability
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