We still see a few orders for such a beast...we have been pretty successful however in getting customers to see the benefits of SMOBC.

Adhesion over tin/lead reflow is difficult considering how smooth such a surface is. On those jobs we do see it we run the panels through a pumice scrubber before solder mask coating, this does a pretty good job in creating a rough surface for the mask to adhere to. Of course once they run the boards down their assembly line, and the tin/lead flows again, under the mask, well all bets are off...

All I can suggest is to present your case to customers as strong as possible, even offer them samples of SMOBC-HASL for them to evaluate, etc etc...we did that long ago...costs a few bucks but it worked out for the best...good luck

Franklin

  ----- Original Message ----- 
  From: Steve Gregory 
  To: [log in to unmask] 
  Sent: Wednesday, March 31, 2004 3:41 PM
  Subject: [TN] Solder mask over Tin/Lead...


  Hi All!

  I'm just wondering if I'm missing something. Is there any performance reason
  whatsoever, that requires solder mask over Tin/Lead instead of using SMOBC
  (Solder Mask Over Bare Copper)?

  Got a board in receiving inspection that I got called back to look at because
  the mask was failing tape test. When I saw the board, it was solder mask over
  Tin/Lead, just like it was called out on the drawing. The mask had already
  lost adhesion in a few places, but we hadn't done anything to it yet
  assembly-wise...

  I see didn't see this particular boards drawing before we went out and bought
  it, otherwise I would have thrown-up a red flag then. What suprised me
  though, is that our fab vendor didn't say anything before they built it. Is anything
  other than SMOBC being used regularly. I thought solder mask over Tin/Lead
  was ancient stuff, and that everybody learned not to do that anymore...

  -Steve Gregory-

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