基于析因实验设计的QFN热可靠性分析

Thermal Reliability Analysis for QFN based on Factorial Experimental Design

在微电子封装器件的生产或使用过程中,由于封装材料热膨胀系数不匹配,不同材料的交界处会产生热应力,热应力是导致微电子封装器件失效的主要原因之一。文章采用MSC.Marc有限元软件,分析了QFN器件在回流焊过程中的热应力、翘曲变形、主应力及剪应力,并由析因实验设计得到影响热应力的关键因素。研究表明:在回流焊过程中,QFN器件的最大热应力出现在芯片与粘结剂接触面的边角处;主应力和剪切应力的最大值也出现在芯片与粘结剂连接的角点处,其值分别为21.42MPa和-28.47MPa;由析因实验设计可知粘结剂厚度对QFN热应力的影响最大。

In the processes of production and use, the thermal stress will be produced at the interface between different materials due to the mismatch of thermal expansion coefficient. And the thermal stress is one of main reasons that cause microelectronic packaging devices failure. In this paper, the finite element software MSC. Marc was employed to analyze the thermal stress, warpage, principal stress and shear stress of QFN during reflow process. The factorial experimental design was conducted to obtain the main effective factors of thermal stress. The results show that the maximum thermal stress of QFN during reflow process occurs at the comer point of chip and chip adhesive; The maximum principal stress and shear stress also appears in the comer point of chip and chip adhesive, and the values were 21.42MPa and -28.47MPa respectively; The thermal stress was influenced mainly by the thickness of chip adhesive through factorial experimental design.