Abstract:

The research object is a substrate which includes a plastic ball grid array package structure and single power level conversion chips. In order to calculate its fatigue life under thermal vibration coupling loading conditions, an approach to calculating fatigue lifetime under coupled loads is developed based on the incremental damage superposition theory. This approach adopts the Anand unified viscoplasticity theory to describe the mechanical behavior of the solder material under the thermal cycle load condition, and adopts the Coffin-Manson equation adjusted by the thermal cycle load frequency to calculate the fatigue lifetime. The random vibration damage in different temperature environments is calculated. Taking the time fraction of each temperature in the thermal cycle load as the weight, the random vibration damage is averaged. The total damage is obtained by superposing the average damage of random vibration and thermal cycle damage, and then the fatigue life is obtained. The result shows that the fatigue lifetime of the research object meets the use requirements under the specific combined thermal stress and vibration loading conditions.

Key words: combined thermal stress and vibration loading conditions, electronic packaging structures, incremental damage superposition approach, fatigue lifetime analysis