ENEPIG finish: An alternative solution for space printed circuit boards (PCB)

ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) is emerging as a process offering technical benefits for users and assemblers. The ENEPIG finish is an interesting alternative to ENIG (Electroless Nickel Immersion Gold) since ENEPIG is not concerned with “black pad” or nickel corrosion risk. Electroless palladium is deposited onto the nickel phosphorous layer and finished with immersion gold. Analyses were firstly performed on ENEPIG PCB before assembly to raise any risk linked with this finish. Full destructive physical analyses (optical inspections, microsections, wettability tests with/without accelerated ageing tests, SIR, etc.) were completed with an industrial survey and physical analysis (chemical etching, ionic polishing, X-Ray fluorescence, etc.). They revealed positive results in terms of cosmetic, wettability and reliability. Lessons learned during these first analyses shall be used for the second phase of this project: a full reliability evaluation on ENEPIG assembly test boards and its comparison with fused tin/lead finish (considering tin/lead process and tin/lead packages).