Kevin,
OSP is a good surface finish. Most are a LOT better than when they were
first introduced in the 1990s.  Shelf life will depend in large part on how
you store them and the particular OSP you pick.  You can get selective ENIG
for test points, but then you have to consider where you put them!  I have
not seen undue damage caused by the use of OSP over say ENIG because of
environmental considerations - Coca Cola will do in a PCBA no matter what
the finish.  :(  Yeah, I know you are really talking about atmospheric
environments - overall I would say the finish is "average".

Bev
Blackberry

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Glidden, Kevin
Sent: Tuesday, May 21, 2013 12:39 PM
To: [log in to unmask]
Subject: [TN] OSP processing inputs?

Hi all,

It looks like I will be getting some PCBs with OSP finish on them to process
thru SMT.  I've not yet used this surface finish, so for me there are a lot
of unknowns.
Some background info:
1 The PCBs will be single sided SMT, so I will not have to worry about
solderability of second side reflow.
2 We are using Sn63Pb37, not lead-free.
3 We are using water soluble ORM0 paste and DI water wash only (no chemical)
4 We typically process with ImAg.
5 MIL/AERO target service environment

I have read some that shelf life is reduced to around 6 months and that OSP
covered pads cannot be used as test points and therefore test pads need to
be solder coated.  I've also read some of the conference papers which seem
to indicate corrosion/environmental performance is at least as good as what
we would get with ImAg.

Any other suggestions / caveats ?

Is there an IPC spec for this finish?

Thanks in advance!

Kevin


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