Classification:
Prologue:
Epilogue:

On the attached note:

 OSP coatings are fragile, and require careful handling.  Fingerprints will
sometimes affect solderability, with mild fluxes.  More likely though, the
preheat in the assembly process could be too high, causing oxidation of the Cu
surface just prior to assembly reflow.  Quality of the preclean prior to the
application of the 106A is also critical.  Also possible, is mechanical damage
to the Cu surface prior to paste apply; this mechanical damage to the pads
could also expose virgin Cu to the atmosphere.    If you don't need two or
three pass solder processing, standard Entek rather than the
Entek + may  be better.  If the problem is repetitive, analyze the pads prior
to paste apply with IR Spectra or other surface analysis techniques to look for
organics and oxides .  After reflow, you still may be able to detect organics
if they are thick and have not burned away on areas that did not solder.

Also, you may want to investigate solder paste stencil height, which will
affect solder volume, and the wetting angle at the base of the solder joint.  A
highly solderable component lead will attract the solder so that full wetting
of the pad may not occur if solder volume is low and pad is overly large.
Wetting angle will help tell you if you have a solderability problem.

Jim Herard
<a href="/scripts/wa.exe?LOGON=A3%3Dind9703%26L%3DTECHNET%26E%3D0%26P%3D702444%26B%3D--%26T%3Dtext%252Fplain%3B%2520name%3D%2522MEMO%252003%2F11%2F97%252011%3A33%3A36%2522%26N%3DMEMO%252003%2F11%2F97%252011%3A33%3A36" target="_parent" >[log in to unmask]</a>

---------------------- Forwarded by Jim Herard/Endicott/IBM on 03-11-97 11:22 AM
 ---------------------------

        TechNet-request @ ipc.ipc.org
        03-11-97 11:05 AM


To: TechNet @ ipc.org@internet
cc:
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.
<a href="/scripts/wa.exe?LOGON=A3%3Dind9703%26L%3DTECHNET%26E%3D0%26P%3D702444%26B%3D--%26T%3Dtext%252Fplain%3B%2520name%3D%2522MEMO%252003%2F11%2F97%252011%3A33%3A36%2522%26N%3DMEMO%252003%2F11%2F97%252011%3A33%3A36" target="_parent" >[log in to unmask]</a>


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