化镍电锡技术在PCB表面装饰中的应用

Electroless nickel and electroplated tin for PCB final finishing

表面终饰能防止PCB表面铜线路及焊盘的氧化和腐蚀,并保障基板上焊盘与贴装(SMT)器件等的可焊性。常用表面终饰中,化学镀镍浸金具有良好的抗氧化、可焊性高和润湿能力好、适用于打线等性能优势,但价格高昂。为平衡PCB表面终饰的性能和成本,本文在铜表面化学镀镍,沉积2μm的Ni层后,再电镀锡层形成Cu/Ni/Sn三层结构,以Ni层阻挡Cu-Sn之间的合金化,提高界面的抗电迁移性能,抑制锡须生长,并保留锡层良好的润湿和焊接特性。所获镀层进行了可靠性测试,抗氧化测试,电气测试等,并与沉锡技术进行了对比,本方法性能优越,价格适中,且适合水平线生产。

The surface final finishing process plays a crucial role in preventing oxidation and corrosion of copper traces and pads on PCBs,while ensuring the solderability of pads for components such as Surface Mount Technology(SMT)devices.Among the commonly used surface finishing techniques,electroless nickel immersion gold(ENIG)offers excellent advantages such as high oxidation resistance,superior solderability,and good wetting properties,making it suitable for wire bonding applications.However,the high cost of ENIG poses a challenge.To balance the performance and cost of PCB surface finishing,this study explores a method that involves chemically depositing a 2μm nickel layer on the copper surface,followed by electroplating a tin layer to form a Cu/Ni/Sn three-layer structure.The nickel layer serves as a barrier to prevent alloying between copper and tin,thus improving the resistance to electromigration at the interface and suppressing tin whisker growth,while retaining the desirable wetting and soldering characteristics of the tin layer.The obtained coatings underwent reliability testing,oxidation testing,electrical testing,and were compared with the Immersion tin technique.The proposed method demonstrates superior performance,moderate cost,and suitability for horizontal production.