As Earl says this is most likely to be PCB related from your description. I still see this when doing failure investigations and can be a real show stopper.

Bob Willis
Electronic Presentation Services
2 Fourth Avenue
Chelmsford Essex CM1 4HA
England
www.bobwillis.co.uk
Tel: (44) 01245 351502 Fax: (44) 01245 496123

Single solution to your seminar, conference or roadshow www.seminar-registrations.com
  ----- Original Message ----- 
  From: Earl Moon 
  To: [log in to unmask] 
  Sent: Thursday, November 15, 2001 6:28 AM
  Subject: Re: [TN] ENIG-Black Pad


  Get back to your board supplier as soon as possible and discuss. I haven't
  seen, or even heard of this problem in over six months now. I am in touch
  with many ENIG users - as designers, assemblers, and test folks using mostly
  the big board fab houses though some protos are made in smaller shops.

  I hope the problems is lessening because board shops are doing a better job
  with better plating/coating chemistries and processes. Much has been written
  on this problem on this forum, so look in the archives.

  Black pad is exactly as you describe and opens are easily found during test
  but that's very unfortunate as then it's way too late. As received, you
  cannot tell the problem exists.

  Visually, upon device removal, non-wetted pads appear black where
  non-wetting is observed often with solder "bumps or ridges" where wetting
  did occur.
  There is no possibility of rendering the black surfaces solderable. You
  can't scrape it off and no matter how many times you try, you cannot solder
  to it though I did once have success taking the boards back to the supplier
  and have them HASL coated after stripping off the surface coating.

  Wish you the very best in your unfortunate situation,

  MoonMan

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