電子構裝之力學分析與量化可靠度評估
Date Issued
2005
Date
2005
Author(s)
林有玉
DOI
zh-TW
Abstract
In study the reliability of electronic packages from mechanics point of view, the analytical result of stress and strain obtained from finite element analysis and fatigue life prediction based on a certain rule are all constant values. However, the real outcomes of package life obtained in laboratories appear to have probability distributions and are frequently plotted in Weibull probability papers. To investigate possible causes of this contradiction, analytical work is performed in the present study. The work includes, first, a finite element analysis based on the assumption that certain geometric parameters are random variables. The maximum strain of a certain type of flip-chip package subjected to thermal-cyclic loading is found, and the fatigue life of the package is determined base on a modified Coffin-Manson equation. Both quantities are random variables owing to the randomness of the geometric parameters. It is found that, among different geometric parameters, the size of the solder bump affects the fatigue life of the package the most. It may cause the fatigue life to have a coefficient of variation (c.o.v.) of 10.65% under the assumption that the solder diameter is a random variable between 0.27 mm and 0.33 mm. In the second phase of the present study, the modified Coffin-Manson equation is considered to have a certain random nature. This can be achieved by assuming certain parameters in the equation are random variables. Through mathematical derivation, it is shown that the predicted fatigue lives may have different mean values and different variations, and the difference may be tremendous under certain assumptions. It is concluded that both random geometric configuration and random life prediction rule may cause the fatigue life of the package to have distribution following certain probability density functions as those obtained from experiments.
Subjects
覆晶構裝體
可靠度
隨機疲勞壽命分配
flip-chip package
reliability
probability distribution
Type
thesis
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