Corrosion Resistance of Different PCB Surface Finishes in Harsh Environments

davef

August 14, 2012

Thanks for your paper. It was fascinating to learn that the corrosion resistance of immersion tin is the reason that it’s preferred in the automotive sector. the corrosion resistance properties of Hi-P ENIG surprised me. I always associated Hi-P ENIG with ‘black pad.’ Please help me understand more about Hi-P ENIG and black pad.

Mustafa Özkök

August 15, 2012

Dear Dave, adding phosphor into the nickel layer increases the hardness and improves the corrosion resistance and makes it other side also more resistant for the Gold deposition (Au-thickness is lower), therefore the solder wetting is slightly less compared to Med. Phos ENIG but still much better than OSP, immersion Tin or Immersion Silver. The Phoshorus enrichment in case of Black Pad is something totally diffrent and is not related to the High Phosphor ENIG Process. In case you drop me an e-mail I can forward you more details. vbr Mustafa

Zana

September 6, 2012

Interesting and enlightening, we will be doing a job with enig bords soon, I would like to have this information if possible. I am new to ENIG finish and will appreciate any info. Thank you and best regards Mustafa. Aybars Ocal

davef

January 17, 2013

Following-up on the above thread, Mustafa emailed me the following papers on black pad: * Identification and Prevention of “Black Pad” [http://www.smtnet.com/library/index.cfm?fuseaction=view_article&article_id=1859 ] * Solving the ENIG Black Pad Problem: An ITRI Report on Round 2, F.D.Bruce Houghton, Celestica, Inc., North York, Ontario, Canada [http://www.smtnet.com/library/index.cfm?fuseaction=view_article&article_id=1860 ]

Mustafa Özkök

August 13, 2012

Dear Selha, thank you for your comment. Of corse this paper is only some little picture, more percisely a part of the "corrosion resistance" picture of the surface finish world. The aim of this paper was too look only from the corrosion resistance point of view on the surface finishes. HASL was not avalible for us at the time when we run these tests. I agree that it would made the data more complete. Adding Phosphor into the ENIG maybe was not the right for your application but High Phosphor ENIG is well used since more than 10 years in the Mobile phone area successfully. Therefore it depends on the application and the requirements which surface finish may fit to which application. There are pros and cons for each surface finish.

selha

August 14, 2012

Dear MOEZKOEK, Thank's a lot for those more informations. I agree it's very difficult to have the best finition for all the products, especialy in our case: we are sub contractor for PCBA! Best regards.