SnAgCu无铅焊膏用活性物质研究

Study of active substance for SnAgCu lead-free solder paste

以SnAgCu无铅焊膏铺展性能为主要指标,通过回流焊接实验,对用于助焊剂的17种有机酸活性物质进行了筛选。选取两种性能较好的有机酸配成复合活性物质,并对该活性物质的组成进行优化。用湿热试验测试焊后残留物的腐蚀性。结果表明:以羧基官能团比例为3:7的丁二酸和一元酸A混合物作为活性物质,并添加质量约0.66%的乙醇胺调整酸度,得到了pH值约为3的助焊剂;此助焊剂性能优良,可使焊点铺展率达到84%。使用含有此助焊剂的焊膏,采用回流焊接工艺在PCB板上贴装片式元件,所得焊点光亮饱满,且焊后残留物无腐蚀性,可以实现免清洗。

In this study, the effects of 17 kinds of organic acid active substance on the spreadability of SnAgCu soldering paste were studied first through performing reflow soldering. And then, two kinds of organic acid with better performance were selected to form a composite active substance, and the composition of this active substance was optimized. The corrosiveness of welding residue was elevated under a condition of high temperature and high humidity. With the addition of 0.66% （mass fraction） ethanolamine as acidity adaptor and with the mixture of succinic acid and monacid A as active substance in which the ratio of carboxyl group between succinic acid and monacid A is 3：7, soldering flux with a pH value of 3 is obtained. This flux exhibits high performance and makes the spreading rate of solder joint reach 84%. After attaching electronic chip components to PCB with the solder paste containing this flux through reflow soldering, the obtained welding spots are found to be plump and bright. And the welding residue formed is non-corrosive, making the cleanine of welding, residue unnecessary.