无铅波峰焊不同板厚通孔焊点的填充性研究

The Study of Hole Filling Performance of PCB with Different Thickness by Wave Soldering

分析了影响通孔填充性的因素,包括PCB的设计因素和波峰焊接工艺因素。其次运用试验设计方法研究了通孔填充性与众多因素的关系,对试验结果的方差分析表明影响通孔填充性的显著因子有PCB的板厚、锡炉温度和浸锡时间等,通过回归分析得出预测填充不足缺陷的数学模型,该模型是以缺陷为应变量,各影响因子为自变量的统计学关系方程。同时还对不同板厚的通孔焊点可靠性进行了分析,仅考虑焊点满足相同的机械抗拉力条件,焊点其他参数一致而板厚增加时,对通孔填充率的要求可有所降低;但通过热循环试验得出随着板厚的增加,焊点更易较早的出现裂纹,焊点填充不足时有进一步加快生成表面裂纹的趋势。

Taguchi DOE is used to study the impacts of lead-free process parameters and PCB design factors on vertical hole filling of PTH in wave soldering. The experiment data received are analyzed by applying method of analysis of variance （ANOVA） and regression analysis. The results show that the most significant factors that influence hole filling are board thickness, solder temperature and contact time with solder wave. A statistical equation is received which describes the relationship of defects and influence factors, and it can be used to forecast defects number when the processing parameters are determinate. Thermal shock test is carried out to investigate the reliability of THT joint with different board thickness. The results show that solder joints with thick board tend to initiate crack earlier and make crack expand faster compared with that with thin board. And partial filling of PTH will accelerate the trend in solder joint with thick board.