On pads with OSP, the solder paste will stay where it is placed and will 
     not reflow to cover additional pad area. This is perfectly acceptable as 
     long as solder joint quality is good. 
     
     While the boards look strange, tests I have conducted show that there are 
     no reliability issues with what appears to be exposed copper around the 
     solder fillets. I believe there is residual OSP coating left on the pad.
     
     Denis Mori
     Hewlett-Packard
     Roseville, CA

______________________________ Forward Header __________________________________
Subject: RE: OSP pads not fully covered with solder
Author:  Non-HP-Nicholas.wander ([log in to unmask]) at 
HP-Roseville,mimegw3
Date:    3/11/97 10:36 AM


I noticed the same thing on one of our prototype boards that had Entek 
106A on it. There was very little solder on some of the .020 pitch 
surface mount pads. In many cases, most of the pad was not covered with 
solder and the pad surface was copper colored and probably still had the 
Entek coating on it. There was a small amount of solder around the leads 
and in some cases only part of the lead had a solder fillet. The solder 
that was there was wetted to the leads and the pads, and the solder 
joint looked good except that there was not enough solder volume. I 
asked our assembly vendor to investigate this and am still waiting for 
an answer.
     
Nick Wander
Unisys, Roseville, MN. 
     
>----------
>From:  Michael Forrester[SMTP:[log in to unmask]] 
>Sent:  Tuesday, March 11, 1997 7:14 AM
>To:    [log in to unmask]
>Subject:       Unidentified subject! 
>
>We recently tried an OSP (Entek Plus CU106A) on one of our new designs. 
>The board contains fine pitch
>surface mount and thru-hole.  Both our PCB manufacturer and assembly house 
>have dealt with OSP's in the past.
>When we received the assembled boards back from our assembly house we 
>noticed that the solder did not fully
>cover various pads.  The assembly house said that they opened up the 
>aperture on the stencil to allow sufficient
>solder paste to be deposited to cover the entire pad. 
>
>The solder joints look excellent.  Our assembly house says that there must 
>have been contaminants in the processing
>of the OSP coating at the PCB manufacturing house.  As of yet I have not 
>received a response from our PCB board house.
>Has anyone heard of this situation?  If the PCB vendor comes back and says 
>the problem is not on their end who should
>I believe?  Thank you in advance.
>
>Mike Forrester
>LeCroy Corp.
>[log in to unmask]
>
>
>
     
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