Jason:
We have tried some OSP boards using what is suppose to be the "good stuff"
OSP Cu106A. What we found was each heat cycle, i.e., reflow bottom, reflow
top???, and/or glue operation for bottom side requiring a bake cycle, etc.,
etc. . . . Every heat cycle the OSP is exposed to reduces your odds of
getting the quality you or the customer would like at post wavesolder.
As far as help or a solution, I am not sure what to say except maybe some
things to consider. First, check the date code of the OSP boards. OSP
boards normally have a shelf life. Second, reduce the amount of heat cycles
the OSP is exposed to as much as possible. Third, go out of the box and
eliminate the OSP and if possible do a paste-in-hole rather than wavesolder.
So as not to mislead you into thinking paste-in-hole is a panacea,
paste-in-hole presents another volume of opportunities for hole fill and
potential wetting issues. Paste-In-Hole can be done, but will require some
experimentation on your part with paste application/stencils/lead to hole
ratios/etc . . . Fourth, the comment on HASL process. Your comment on
"They won't do HASL either.", is/are "They" the customer or your PWB
supplier? Do you have other options? Finally, what are your requirements
for hole fill and does your inspection and customer know and understand
these requirements?
Hopefully this can help a little. There are a lot of TechNetters out there
that are a lot more apt at giving you some great direction and ideas. If
they haven't left for Christmas break.
Ron Hollandsworth
-----Original Message-----
From: Jason Smith [mailto:[log in to unmask]]
Sent: Thursday, December 16, 1999 7:50 AM
To: [log in to unmask]
Subject: Re: [TN] OSP and wave soldering
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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