SBIR Phase I: A Novel Electroless Nickel/Immersion Gold (ENIG) Surface Finish for Better Reliability of Electronic Assemblies

这个小企业创新研究第一阶段项目将开发一种具有成本效益的新型化学镍浸金（ENIG）表面处理，以实现坚固的焊点，提高电子组件的可靠性。目前可用的ENIG表面处理容易出现所谓的“黑垫”，这是电偶超腐蚀的地方，导致焊料脱湿、焊点脆性、组件断开和电子组件整体故障。现有的替代表面处理要么非常昂贵，要么不能完全解决黑垫缺陷，而且它们会损害其他关键性能。即将开发的具有成本效益的新型ENIG将消除黑焊盘和与腐蚀相关的问题，实现坚固的焊点，并为最终消费者提供更高质量和可靠性的电子组装产品。这将使制造商避免重大的产品现场故障和由此产生的后果。这项新技术将成为现有ENIG（市场价值超过4亿美元）和其他表面处理（市场价值超过10亿美元）的潜在替代品。该项目的智力优势包括开发一种具有成本效益的新型ENIG，以消除黑焊盘并实现坚固的焊点。黑垫缺陷的根本原因是浸金过程的超腐蚀活性，其产生于镍磷表面的晶间边界和裂纹。在金和镍原子之间发生电偶超腐蚀，导致镍的耗竭和局部区域磷原子的富集。拟议的研究将在金和镍磷界面上使用界面工程方法来防止黑色焊盘，并消除电子组件中的脆性焊料故障。拟议的第一阶段研究的主要目标是实现耐腐蚀性的显着改善（消除黑垫）和获得坚固的焊点（消除脆性焊点失效）。这将包括确定正确的界面化学和工艺参数。将采用电化学腐蚀试验和酸性试验对新工艺的耐腐蚀性进行评价。此外，焊点强度和性能（脆性/延展性）将使用球剪切试验和冷球拉伸试验进行研究。

This Small Business Innovation Research Phase I project will develop a cost-effective novel Electroless Nickel Immersion Gold (ENIG) surface finish to achieve robust solder joints for better reliability of electronic assemblies. Currently available ENIG surface finishes are prone to so-called "black pads", which are sites of galvanic hyper corrosion that lead to failures associated with de-wetting of solder, brittle solder joints, component disconnection, and overall malfunction of electronic assemblies. Existing substitute surface finishes are either very expensive or do not resolve the black pad defects fully, and they can compromise other key properties. The cost-effective novel ENIG to be developed will eliminate black pads, corrosion related issues, achieve robust solder joints and provide improved quality & reliability of electronic assembly products to end consumers. This will allow manufacturers to avoid major product field failures and the resulting consequences. This new technology would be a potential replacement for existing ENIG (with a market value in excess of $400 million) and other surface finishes (representing a market exceeding $1 billion).The intellectual merit of this project includes development of a cost-effective novel ENIG to eliminate black pads and achieve robust solder joints. The root cause of black pad defects has been identified as hyper corrosion activity of the immersion gold process which originates at intergranular boundaries and crevices of the nickel-phosphorous surface. Galvanic hyper-corrosion occurs between gold and nickel atoms, resulting in nickel depletion and an enrichment of phosphorous atoms in the localized area. The proposed research would use an interfacial engineering approach at the gold and nickel-phosphorous interfaces to prevent black pads and eliminate brittle solder failures in the electronic assemblies. The main objective of the proposed Phase I research is to achieve marked improvement in corrosion resistance (eliminate black pads) and attain robust solder joints (eliminate brittle solder joint failures). This will involve identifying right interfacial chemistry and process parameters. Corrosion resistance of this new process will be evaluated using electrochemical corrosion tests and acid tests. In addition, solder joint strength and properties (brittle/ductile) will be investigated using ball shear tests and cold ball pull tests.