Electrochemical Migration Behavior on FR-4 Printed Circuit Board with Different Surface Finishes

• Published in: Journal of electronic materials 2023-09, Vol.52 (9), p.6121-6132
• Main Authors: Song, Xiaoxiao, Wang, Keyu, Chen, Zhuo, Ren, Kaixu, Liu, Peng
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Circuit boards; Copper; Drop tests; Electronics and Microelectronics; Finishes; Gold; Instrumentation; Lead free; Low conductivity; Materials Science; Nickel; Optical and Electronic Materials; Original Research Article; Precipitates; Printed circuit boards; Printed circuits; Solid State Physics; Solubility; Surface finish; Water drops
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-023-10557-w

The impact of four typical surface finishes on electrochemical migration in printed circuit board production was studied using a modified water drop test, and the electrochemical migration phenomena of each surface finish at different bias voltages were analyzed. Based on the analysis of the experimental results, the four surface finishes were ranked in terms of their ability to resist electrochemical migration, as follows: electroless nickel/immersion gold (ENIG) > lead-free hot air solder leveling (HASL) > HASL > Cu. For the lead-free HASL, HASL, and Cu surface finishes, the growth of dendrites was mainly related to the hydroxide solubility product of metal ions, with a smaller solubility product leading to a larger area of precipitates, which further hindered the emergence and growth of dendrites. The electrochemical migration process of ENIG differed from other surface finishes. Gold was not involved in the electrochemical migration process, and no typical cathodic dendrite growth phenomenon was observed. Only nickel hydroxide and oxide formed from the anode edge and migrated toward the cathode with low conductivity, resulting in high electrochemical migration resistance for the ENIG surface finish.