Try using nitrogen in the reflow oven.

For a short term fix, try screening a little paste on the hole prior to
reflow (make sure you can still insert components).

You may also have a problem with spray fluxer setup. Are your getting flux
all the way up the barrel. Place a paper towel or glass over a bare board and
run it over the fluxer. If there is very little flux over some holes, you
need to adjust the fluxer setup.

My other question is why do you need full hole fill? I have shipped heavy
components in high vibration/shock environments on single sided panels with
no reliability issues from several employers. Test your products with your
worst case hole fill. They will probably pass vibration and shock testing in
most class II and III applications for many components.

Aric Parr
Sr. Process Engineer
Eaton Corporation
1400 S. Livernois
PO Box 5020
Rochester Hills, MI 48308-5020
248 608 7780
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---------- Original Text ----------

From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 12/16/99 7:53 AM:

I am having problems with wave soldering OSP boards.  After the boards have
seen
a heat cycle (reflow), they are impossible to get hole fill on topside without
first cleaning the boards to remove either oxidation or hardened OSP.  I don't
know which one I have because I haven't had them analyzed yet.  The flux used
to
wave solder the boards is a very weak customer dictated rosin no clean flux.
The OSP is Cu106A.  I am not familiar with OSPs.  They won't do HASL either.
Any insight?  Suggestions?  Assistance?

As it stands now, the process is to flux with high solids water soluble/heat to
clean the board-->wash off flux-->immediately wave solder with rosin containing
no clean.  This is not a production process........

Jason Smith
Process Materials Engineer
Lexmark Electronics

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