The investigation of the correlation between electroless nickel immersion gold and high-speed signal transmission (IMPACT 2020)

In PCB manufacturing, electroless nickel immersion gold (ENIG) is considered as one of the mature final finishing processes. However, compared to other type of the final finishing, ENIG's higher resistance could result in the gaining of signal loss by skin effect especially for high-speed circuit. The present study was focused on the effect of phosphorus content in electroless nickel on signal integrity of single stripline. According to the literatures, the resistance of electroless nickel deposit is down with decreasing phosphorus content, thus the lower insertion loss was performed on the through hole VIA. Nevertheless, our work indicated that the phosphorus dopant is not a dominant factor in insertion loss, the structure and the surface smoothness affect the attenuation on through hole VIA instead. This investigation presents that the excellent structure and smoothness of electroless nickel layer in ENIG is one of the most economical solution to PCB final finishing for high-speed signal transmission.