QFP器件微焊点可靠性分析

Mechanical properties of soldered joints of QFP devices

通过数值模拟对QFP焊点力学性能的影响规律进行了研究,高密度化引线以及使用无铅钎料时焊点的等效应力较小.结果表明,引线数的增加以及钎料的无铅化显著提高了焊点抗拉强度,激光再流焊比红外再流焊的抗拉强度的提高了25%左右.锡铅钎料QFP断口表面晶粒较粗大,而无铅钎料的QFP断口处晶粒较细,红外再流焊加热方式下形成的焊点断口有大小不等的韧窝存在,断裂方式兼有脆性断裂和韧性断裂的特征,而激光加热方式下焊点的断口呈现均匀的韧窝形貌,断裂方式属于韧性断裂.实际焊接试验结果与理论模拟结果相吻合.

Mechanical properties of soldered joints of quad flat packge(QFP) devices are investigated by numerical simulation,and the results of simulation indicate that soldered joints of high density in leads and the lead-free exhibit lower equivalent stress.The results of experiment indicate that the tensile strength of SnAgCu soldered joints is significantly greater than that of SnPb soldered joints,and the tensile strength of devices soldered by laser reflow increases by 25% than that by infrared reflow.The fracture microstructure of QFP for SnPb solder is coarse, but for SnAgCu solder is fine.The dimples in the fracture of joints formed by infrared reflow welding are not uniform,which the fracture includes brittle fracture and toughness fracture;but those by laser soldering are uniform,which fracture is toughness fracture.The experiment results are close to the simulated result.