Cormac,
The OSP process can be a very good process if it fits your particular
application. It provides nice contrast to the solder paste for post screen
print visual, however you can loose contrast from between your masking and
the copper colored fiducials, so you might have occasional lighting issues
with your placement equipment fiducial cameras since the fiducials may have
a range of copper coloring over time.
If you are using a bed-o-nails tester, understand that contact will differ,
and you may need to look at new probe pins. If this is a mixed technology
board, you should investigate the wave solder process quite well. OSP
typically does not wet (accept solder) as well as some of the other
finishes, and many folks have a tough transition over to no clean wave
solder process with OSP products. Top side solder is a bit more difficult
to achieve, and you may need to invest in a nice spray fluxer if you don't
already have one.
Going to OSP also should include some company wide handling procedures.
Gloves are recommended, or at least make sure boards are only handled by the
edges.
If you have a batch process, beware. Once the OSP boards go through the
first reflow process, you don't want them sitting around too long. You
might have problems if you run side A on Monday, side B on Tuesday, and Wave
them on Wednesday. Especially if you have additional processes like a few
water cleanings. If you use alcohol to clean misprints from screen print or
the SMT adhesive process, your WIP shelf life is reduced, and you might run
into problems.
Each reflow might remove 20%, each wash might remove 25%, and alcohol could
remove 75% of the OSP.
If you run clean parts, a fairly steady process, and get your handling
process down, OSP can be a very good thing. We have ran nearly 1 million
OSP boards a month over the last 6 years with great success. Good luck.
Steve Abrahamson
> -----Original Message-----
> From: Cormac MacMahon [SMTP:[log in to unmask]]
> Sent: Thursday,June 28,2001 10:57 AM
> To: [log in to unmask]
> Subject: [TN] **** PCB's - HASL -v- OSP
>
> Folks,
>
> I am an NPI Engineer at Artesyn technologies and I am new to the Surface
> Mount
> Technology. Can anyone shed some light on the differences between HASL and
> OSP.
> We are currently using HASL but are looking at migrating to OSP. What are
> the
> pros and cons of one over the other? What sort of processing issues do we
> see
> with OSP on SMT lines?
>
> Any help appreciated
> Cormac MacMahon
>
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