So far as flux is concerned modern low solids no-cleans [are available that]
don't have sufficient resin to block pins so this needn't be an issue.
The max temp of a Pb- wave is not necessarily that much higher than Pb+, but
is worth checking: in this respect I would also be looking to make sure that
the resist/soldermask is Pb- capable. If the resist is not Pb-capable, or
under cured, it can make a deposit on pads which is very difficult to get
through, This can happen with just heat or combination of some flux solvents
with extra heat on mask can lead to this problem. Have you tried probing an
unfluxed board?
Regards
Mike Fenner
Indium Corporation
T: + 44 1908 580 400
M: + 44 7810 526 317
F: + 44 1908 580 411
E: [log in to unmask]
W: www.indium.com
Pb-free: www.Pb-Free.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Thursday, October 05, 2006 7:51 PM
To: [log in to unmask]
Subject: Re: [TN] Lead free ICT testing problems
Are you talking only the ICT bottomside bed of nails fixtures? Then look
at the wave solder flux.
Are you talking about flying probe? Then look at the paste flux.
Are you talking false fails from physically smaller solder joints?
The lead-free solder joints should not be causing any difference in the
probe-ability, unless you are really seeing open solder joints that are
being closed by the probing action.
However, the no-clean flux residues from your Pb-free wave solder
process and reflow process are now probably being "baked on" a little
harder than they were with the no-clean fluxes from your 63/37 process,
as the process temperatures are higher. Thus you get more false fails
because the test pins have a tougher time breaking through the flux
coating.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Joel Alexander
Sent: Thursday, October 05, 2006 1:15 PM
To: [log in to unmask]
Subject: [TN] Lead free ICT testing problems
We are seeing intermittent false failures on lead free assemblies. We
would have these occasionally with leaded solder but it has
significantly increased with lead free. We are using SN100C in our wave
solder and Superior 420-S no clean flux. Are there any types of probe
pins that can produce better yields with lead free solder.
Joel Alexander
APSCO Quality Assurance Manager
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