基于电阻应变的无铅焊点损伤临界点在线检测

Damage Critical Point of Lead-free Solder Joint Detected On-line base on Resistance Strain

蠕变损伤是引起焊点失效的重要因素,实验表明在蠕变过程中存在一个临界点,在临界点之前蠕变呈现一种缓慢的增长趋势,而在临界点之后蠕变加速进行,导致焊点很快失效。找出此临界点对了解焊点的性能及寿命预测有重要意义,但传统的蠕变测试方法不能实时测得焊点的蠕变损伤临界点。研究表明焊点的蠕变损伤与其电阻变化存在着线性关系,因此可以通过测量焊点的电阻变化来监测其蠕变情况。文章以单个无铅焊点为研究对象,利用特制的无铅焊点微电阻在线测量系统,实时监测焊点在蠕变过程中的电阻变化,并利用二次移动平均法建立焊点电阻的预测模型,通过对比预测电阻值与实测值的差异实时找出焊点的损伤临界点,为蠕变测试研究提供了一种新的方法。

Damage caused by creep is an important factor in the failure of solder joints. Experimental results indicate that during the creep there is a critical point time, before which the performance of solder joint shows a smooth linear change, while after which the performance dramatically degrades and fails before long. Therefore, it is of great significance for us to identify this point to judge the solder joint failure and predict the life of it. It is difficult to detect the damage critical point by traditional methods in real-time test. Studies show that there is linear relationship between the solder joint creep damage and its resistance changes, so the critical point can be detected by measuring the solder joint resistance. In this paper, an electronic testing system was developed by which the resistance of the solder joint under load can be measured and stored automatically. Then a forecasting model of the resistance was established by using double moving average method, the predicted value generated from which were compared with the measured value by which the damage critical point can be identified in realtime tests. This provides a new approach for the creep study of solder joint.