薄型QFP封装热传仿真分析

文章采用有限元数值模拟方法，对薄型引脚式表面贴装QFP封装元件的详细模型进行数值模拟，分析了各种因素对封装体热阻的影响。结果表明：采用高导热印刷电路板，封装体热性能得到较大提高，θJA为35．74℃／W，但是不同类型的电路板对θJC，的影响不大。随着气流流速增大，高导热印刷电路板上封装体的θJA。由35．74℃／W降低至24．06℃／W，显示出极好的热传特性，并且当气流流速增大到一定程度时，θJA值趋于稳定。真实功率载荷条件下，该封装元件中芯片的最大等效应力为70．2MPa，低于芯片的最大断裂强度，并且其水平面的最大剪应力仅为25MPa，不会造成芯片和粘结层以及塑封层之间的分层破坏。

Numerical Thermal Analysis for Low-profile QFP

In this paper,a detailed low-profile QFP model was analyzed by the numerical simulation method, involved with different influencing factors of thermal properties.The simulating results show that using multi-layer Test Board is a perfect way to improve package's thermal performance,its theta JA is 35.74℃/ W,but different test board has little effect on theta JC;as forced air velocity increased,theta JA reduces from 35.74℃/W to 24.06℃/W,and when the velocity is increased to some extent,theta JA would not change anymore;applying the real power to the package,the maximum von mises stress and shear stress of the die is 70.2 MPa and 25 MPa,which is allowed,and would not cause the package and its die to be destroyed.