金在电子产品和装饰性产品中的应用十分广泛，其稳定的化学性质不仅能够对基底起到良好的保护作用，金黄的色泽还具有装饰效果。虽然电镀金和置换镀金均能够沉积金层，但是金层的质量还存在不可控的难题，诸如基底形状会影响镀层的均匀性、“黑盘”现象的产生以及镀层厚度有限等。近年来，随着电子产品的快速发展，许多行业对电路板的整体质量提出了越来越高的要求，金层对保证电子器件的可靠性起着非常重要的作用。还原镀金是克服上述缺陷的一个重要研究领域，特别是环境友好的无氰镀金技术已成为研究热点。对氰化物体系和无氰体系镀金液常用还原剂(包括亚硫酸盐、二甲基胺硼烷、次磷酸盐、联氨、抗坏血酸、硼氢化钠、硫脲和其他还原剂)及促进剂的研究和作用基本原理进行了总结，重点阐述了镍和金对这些还原剂的催化活性。大部分还原剂仅受镍和金其中一种金属的催化，在沉积初始阶段和后期阶段，两种或多种还原剂的复配是实现反应速率保持较高的一种可行方案。沉积厚金依赖于可被金催化氧化的还原剂。最后展望了无氰还原镀金的发展方向。

Gold is widely used in electronic products and decorative products. Its stable chemical properties can not only play an important role in the protection of the substrate, golden color also has a decorative function. Although electroplating gold and immersion gold can deposit gold coatings, the qualities of the gold coatings remain some problems. The basic premise of electroplating successfully is that the workpiece is connected with the power source. In addition, the quality of the gold coating by electroplating is also greatly affected by the shape of the workpiece, so that the circuit board with complex lines is difficult to deposit great quality coating efficiently through electroplating. Immersion gold is through the corrosion of the substrate to achieve gold deposition. Once the corrosion is excessive, the “black pad” phenomenon will happen, which is adverse to the corrosion resistance of the coating. In recent years, with the rapid development of electronic products, higher requirements have been put forward for the quality of circuit boards. The gold layer plays a very important role in ensuring the reliability of electronic devices. Chemical reduction gold plating is an important research field to overcome the above defects, especially the eco-friendly cyanide-free gold plating that has become a research hotspot. This paper summarizes the research and basic principles of common reducing agents including sulfite, dimethylamine borane, hypophosphite, hydrazine, ascorbic acid, sodium borohydride, thiourea, and other reducing agents as well as promoters in cyanide and cyanide-free gold plating solutions, especially the catalytic activity of nickel and gold on these reducing agents. Most reductants are catalyzed by only one of these two metals, so the combination of two or more reductants is a feasible scheme to keep the reaction rate high in both the initial stage and the later stage of deposition. The deposition of thick gold depends on reductants which can oxidize rapidly with the catalysis of gold. Also, the future development in cyanide-free reduction gold plating has been prospected.