QFP组件的优化模拟及焊点热疲劳寿命的预测

Optimum simulation and prediction on thermal fatigue life of soldered joints of QFP devices

采用有限元方法研究了方形扁平式封装QFP(quadflatpackage)组件的优化模拟及引线宽度与间距对焊点疲劳寿命的影响规律。结果表明,在QFP64组件的所有焊点中,最外侧焊点的正前面存在最大应变值,易产生裂纹,发生疲劳破坏,为组件的最脆弱部位。QFP引线间距固定时,随着引线宽度的增加,焊点等效应变值逐渐增加,焊点可靠性降低,热疲劳寿命降低;QFP引线宽度固定时,随着引线间距的增加,存在一个焊点热疲劳寿命最大值;所选取的计算模型中,当引线宽度为0.15mm,引线间距为0.45mm时,焊点可靠性最高,组件具有最长的疲劳寿命。

Optimum simulation for QFP devices and effects of lead widths and lead pitches of QFP on the thermal fatigue life of soldered joints of QFP devices were studied by means of FEM method. Results indicate that the maximum strain value exists at the front of the outside soldered joint in all the soldered joints of QFP64, where is the weakest position at which cracks initiation take place easily and lead to failure owing to thermal fatigue finally. When the lead pitches are constant, the equivalent strain existing in soldered joints increases with the increasing of lead widths, the reliability of the soldered joints declines and the thermal fatigue life decreases. When the lead widths are unvaried, the equivalent strain existing in soldered joints doesn't decrease at all times in which there exists a maximum value of the thermal fatigue life with the increase of lead pitches. While lead width is 0.15mm and lead pitch is 0.45mm of QFP64, the reliability of the soldered joint is highest and the device can be served for longest time.