化镍浸金焊盘的金/镍互溶失效分析

Analysis of Gold/Nickel Miscible Failure of ENIG Welding Pad

化镍浸金(ENIG)工艺由于其良好的平整性、焊接性、导电性、键合性,以及金(Au)本身稳定性好、不易被氧化的特点而被广泛地应用于PCB表面处理中。但由于ENIG工艺复杂,对PCB板厂的要求高,管控不当就会出现各种质量问题,其中金层不溶、缩锡就是常见的问题之一。某PCB中ENIG焊盘金/镍互溶导致焊接过程中上锡不良,具体表现为金不溶、缩锡问题,利用光学显微镜、场发射电子扫描显微镜分析、X射线能谱分析、微切片技术、离子研磨技术和俄歇电子能谱等分析技术手段来进行分析论证,结合化镍浸金机理分析PCB中ENIG焊盘金/镍互溶的失效机理,并给出了预防控制建议,对于提高焊盘质量与可靠性具有重要的意义。

Electroless Nikel/Immersion Gold(ENIG)process is widely used in PCB surface treatment due to its excellent flatness,weldability,conductivity,bonding properties,as well as the stability and resistance to oxidation of gold itself.However,due to the complex ENIG process and high requirements for PCB manufacturers,improper control can lead to various quality problems,among which gold layer insolubility and tin shrinkage are common issues.The gold/nickel interpenetration of ENIG solder pads in a PCB leads to poor soldering during the soldering process,which is manifested as gold insolubility and tin shrinkage.The failure mechanism of ENIG pad gold/nickel miscible in PCB is analyzed and demonstrated by means of optical microscope,field emission electron scanning microscope analysis,X-ray energy spectrum analysis,microslice technology,ion grinding technology and Auger electron spectrum analysis combined with nickel leaching mechanism.The prevention and control suggestions are given,which is of great significance to improve the quality and reliability of the pad.