镍层耐硝酸腐蚀性测试——一种简单的预先探测ENIG镍层“黑盘”现象的测试方法

随着更加精细的SMT、BGA等表面贴装技术的运用,化学沉镍金(ENIG)作为线路板最终表面处理得到了越来越广泛的应用,同时可怕的“黑盘”现象也随之更广泛地“流行”起来,直接导致贴装后元器件焊接点不规则接触不良。为了贯彻执行最好的流程控制和采取有效的预防措施,了解这种焊接失败的产生机理是非常重要的,及早的观测到可能发生“黑盘”现象的迹象变得同样关键。本文介绍了一种简单的预先探测ENIG镍层“黑盘”现象的测试方法-镍层耐硝酸腐蚀性测试,这种测试可以用于作为一种常规的测试方法监测一般化学沉镍溶液在有效使用寿命范围内新鲜沉积的镍层的质量。利用Weibull概率统计分析在不同的金属置换周期(MTO)下镍层的可靠性能表现。结合试验结果得出了一个镍层耐硝酸腐蚀性的判定标准。

Implementing a Simple Corrosion Test Methodology for Early Detection of Black Pad Phenomenon in Electroless Nickel/Immersion Gold Plating

With the widespread application of electroless nickel / immersion gold (ENIG) plating as the final PCB surface finish for fine pitch SMT and BGA packaged devices during assembly, the much dreaded black pad phenomenon has correspondingly been more prevalent, incurring sporadic solder joint failures. While understanding the failure mode mechanism is important in implementing the best process control and preventive measures, an early detection of the tell-tale signs of possible black pad occurring is equally critical. This paper describes a simple nitric acid corrosion resistance test methodology that can be practically incorporated as one of the routine process control tools for monitoring the as-plated electroless nickel deposits over the useful bath life of the conventional electroless nickel solution. A Weibull distribution is employed to predict the reliability performance over different electroless nickel bath metal turnovers (MTOs), and based on experimental results, an acceptance criterion is drawn out for this test.