Nickel-Free Surface Finish Solution FOR 5G, RF, Microwave, High-Frequency-HDI PCB Applications-Relibility in Focus

ABSTRACT Tremendous growth and evolution of high-speed internet-enabled devices has driven the innovations in high frequency/high-density electronic assemblies. The need for fast data transmission and small geometric form-factors can be difficult to attain without compromising the performance due to signal loss. Among the primary factors affecting the integrity of high frequency signals is the surface finish applied on PCB copper pads – a need commonly met by technology manufacturers through the electroless nickel immersion gold process, ENIG. However, a well-documented limitation of ENIG is its insertion loss due to the inferior conductivity of nickel over copper, leading to higher conductor losses. Additionally, nickel’s ferromagnetic properties adversely affect circuit performance. The result is an overall reduced performance in high-frequency data transfer rate for ENIG-applied electronics, compared to bare copper. The selection criteria of surface finish for 5G, high frequency, high density application involves minimal insertion loss, long shelf life, cost-effective and high reliability. There are few options (EPIG, EPAG, DIG, etc.) available in the market and their pros and cons will be discussed. Moreover, two innovative nickel-less approaches involving a proprietary nano-engineered barrier layer have shown superior benefits over contemporaries in terms of lower insertion loss and better reliability. The reliability testing involving these two novel approaches compared with the currently available options will be highlighted. Reliability testing includes solderability evaluation & contact resistance evaluation following up to 6 reflow cycles, solder joint reliability evaluation, etc.