无铅焊点蠕变电阻测试系统的研制

Development of creep resistance test system for lead-free solder joints

以Sn-3．SAg焊料制作的截面积1mm。的单个焊点试样为测试对象，基于电阻应变与裂纹生长等效模型，利用在线四探针法电阻测量技术，研制了焊点蠕变电阻测试系统。系统由测试仪、测试装置和上位机软件creep组成，实现微电阻、拉力、温度测量和测试数据的实时存储、实时应变曲线的绘制。测试结果表明：系统具有较高的稳定性，电阻测量最大相对误差为0．27％。在20-29MPa应力范围下，Sn-3．5Ag焊点试样的电阻应变一时间测试曲线清晰地展示了剪切蠕变行为的第Ⅱ，Ⅲ阶段，为观测无铅焊点剪切蠕变特性提供了一种高效、简捷的可选手段。

Using single creep specimens with a 1 mm2 cross sectional area, which are developed and fabricated with lead-free solder （Sn-3.5Ag）, as the test objects, a creep resistance test system based on the equivalent mode of resistance strain and crack developing is designed to test the resistance strain and observe the shear creep quality of solder joints, with in-situ micro electronic-resistance measurement using four-probe techniques. This test system is composed of test instrument, test device and software-creep, and it is able to measure small resistance, load, temperature and store experiment data and depict strain curve in real time. The experimental results show that this system has comparatively high stability and the largest measuring error of resistance is 0.27 %. Under a shear stress of 20 ~29 MPa, the resistance strain-time test curve for Sn-3.5Ag solder joints shows the Ⅱand theⅢ stage of shear creep clearly, and the result supplies an efficient, convenient way for observing the shear creep quality of lead-free solder joints.