Hi OSP'ers

We've been using CU106A ever since it came out (actually before it came
out). We design many boards with OSP (and HASL) surface finishes. The
effects in the attached are normal AND desirable (obviously, as long as
joint parameters are met). 

The exposed copper, although unsightly, is not  a reliability issue as
stated below. We went a little further in our work here which strongly
suggested that electrically balanced comb patterns with OSP coated
finely spaced etch lines lasted longer in the test environment(s) than
the same combs with solder coated etch lines. In this case, visual
appearance was NOT a good predictor of reliability !

Gerry
=============================================================
>----------
>From:
>	[log in to unmask][SMTP:[log in to unmask]
>.com]
>Sent: 	Tuesday, March 11, 1997 5:56 PM
>To: 	[log in to unmask]
>Subject: 	RE: OSP pads not fully covered with solder
>
>     
>     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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