电子封装陶瓷基板表面镀金修饰与腐蚀机理

Surface modification of ceramic substrate for electronic packaging by gold plating and related corrosion mechanism

高可靠电子封装基板多通过镀Au进行表面修饰,形成保护层,从而避免表面导体的氧化和腐蚀。介绍了化学镀镍/浸金(ENIG)和化学镀镍/钯/浸金(ENEPIG)这两个主流镀金工艺,探讨了相应镀Au基板变色、氧化、腐蚀等问题的特征、过程和机理。Ni/Au镀层腐蚀主要与Ni–Au扩散、Ni–P腐蚀、杂质腐蚀等因素有关;Ni/Pd/Au镀层的腐蚀主要由Au层缺陷、镀层剥离、有机污染等原因导致。归纳了镀Au基板的两类腐蚀模型:一类是干热条件下即可完成的氧化腐蚀,另一类是电解质溶液环境中发生的原电池腐蚀。

The surface of highly reliable ceramic substrate for electronic packaging is usually modified by gold plating to form a protective coating which can prevent the surface conductors from oxidation and corrosion.Two common Au plating processes i.e.electroless nickel plating/immersion gold(ENIG)and electroless nickel plating/electroless palladium plating/immersion gold(ENEPIG)were introduced.The characteristics,formation processes,and mechanisms of the problems occurring on Au-coated ceramic substrate such as discoloration,oxidation,and corrosion were discussed.The corrosion of Ni/Au coating is primarily caused by diffusion between Ni coating and Au coating,corrosion of Ni-P coating,and impurity-initiated corrosion.While the causes for the corrosion of Ni/Pd/Au coating are the existence of defects in Au coating,peeling,and contamination by organic compounds.Two types of corrosion models for Au-coated ceramic substrates were summarized:(1)oxidative corrosion that can occur under dry and heat conditions;and(2)galvanic corrosion that can occur in electrolyte environment.