Gerald:
I respond partly because your message is confusing, but then I am easily confused these days.
SMOBC means Solder mask over bare Copper, so there should be nothing under the solder mask but Copper, no solder, ENIG, etc.  Your message implies that the solder under the mask causes problems.
My naive mind suspects that if you are getting mask lift, it may be due to moisture turning to steam, and the HASL treatment serves to minimize the contained moisture.

My 2.5 cents.
Rudy Sedlak
RD Chemical Company

--- On Thu, 8/9/12, Gerald Bogert <[log in to unmask]> wrote:

From: Gerald Bogert <[log in to unmask]>
Subject: [TN] SMOBC process
To: [log in to unmask]
Date: Thursday, August 9, 2012, 6:57 AM

August 9, 2012

 

Some of our OEMs manufacture PWBs using the HASL process and they use
solder mask over bare copper (SMOBC) to prevent re-melting of the
tin/lead from the traces during subsequent assembly level soldering
operations.  If SMOBC is not used, the re-melting of the solder causes
blisters under the solder mask coating which can result in peeling or
flaking of some of the solder mask from the traces.

 

We have one OEM who will be manufacturing an ENIG board with solder
mask.  My question is with this finish, will the gold melt during
assembly soldering to cause the same issue as when using HASL?  Also,
does anybody use SMOBC over ENIG?  My understanding that it can be done
but the results are not cosmetically appealing. 


______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________

______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask] 
______________________________________________________________________