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Subject:	Re: **** PCB's - HASL -v- OSP
From:	[log in to unmask]
Reply To:	TechNet E-Mail Forum.
Date:	Thu, 28 Jun 2001 15:12:03 -0500
Content-Type:	text/plain
Parts/Attachments:	text/plain (44 lines)

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?

**Cormac, one responder said co-planarity is one factor to consider in a
comparison, which is true, but not the ONLY reason. If you believe the
marketing literature for OSPs (and if you do, you deserve all the agony you
are about to experience), then the OSP is sacrificial and only survives 1
pass in reflow. Sometimes this is true, other times not true. I have seen
OSP survive 5-6 exposures to reflow conditions without burning off. Lots
of solderability issues if you have multiple passes through reflow. A
significant factor is also the aggressiveness of the flux you will be
using. I have seen a number of manufacturers go to no clean, for the
benefits afforded by a low solids flux, only to find that it was not
aggressive enough to overcome the OSP. If you are using a water soluble
flux, you should not have this problem. If you are going no-clean, then
you have some homework to do.

In addition, we all know that HASL is a nasty, dirty, filthy, rotton (fill
in the descriptor of your choice) process and often leaves nasty, dirty
filthy rotton residues behind. It does nasty things to insulation
resistance. If you are going the no-clean route, HASL residues can kill
your product and sometimes, users of your product. By comparison, OSP is a
much cleaner process and does not impact insulation resistance.

Doug Pauls
Rockwell Collins

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