Grant:
Sorry for not picking up on all the comments on the flux/ICT issues and this
may be a repeat. There are many capable TechNetters to answer these
questions. Anyhow, here goes . . . You may want to access the cost of
cleaning RMA flux residues with an expensive inline cleaner or cleaners
(plural), versus getting rid of most all cleaners in lieu of using a
low-residue flux. Second, using a low-residue VOC free also has some
advantages such as no emissions, cleaner operating machine, and no fire
suppression system required. Plus the advantage of not cleaning at all, if,
you don't have to clean. Too make a already long reply a little shorter see
what it takes to maintain the RMA system versus replacing incircuit probes
or cleaning the probes. The right combo of SMT paste and low-residue flux
can minimize the affect on ICT. Oh by the way, solder ball issue, I have
some solder ball issues I have been called in to investigate at the present
time. Areas I will look at are Mask, pin protrusion, conveyor speed at
wavesolder, conveyor finger cleanliness, and along with conveyor speed it's
relationship to top side board temperature and flux condition at contact
with the solder chip wave or main wave. Two other possibles are hot air
knife process and humidity inside the machine around the pot.
Hope I didn't miss the barn too far.
Ron Hollandsworth
-----Original Message-----
From: Grant Emandien [mailto:[log in to unmask]]
Sent: Friday, August 20, 1999 6:51 AM
To: [log in to unmask]
Subject: [TN] Solder/Flux/ICT Issue
Hi again,
Thanks for all the input as it has now directed me towards fluxes (and
control thereof) and ICT.
Leading from one of the members advice of low residue flux I stumbled across
this Kester comment:
'Flux selection does have some play as to the occurrence of solder balls. A
rule of thumb is that the lower the solids content of the flux is the more
solder balls will be noted when all other parameters are held constant. This
is sort of a dilemma for us as a flux manufacturer in that if we increase
the solids content, we will more than likely have an adverse impact on probe
testing of final soldered assemblies. The aesthetics of the final soldered
assembly will also be affected as you can imagine.' This was posted in 1993
so any idea on what has since transpired and is this statement still valid
wrt the solids content?
Geez, my research thusfar has brought an array of variables to this party
such as test pin profiles and type, gold plating vs gold alloy, pin base
material hardness, spring force etc. on the ICT aside. Nevertheless it is
now beginning to get interesting.
As a comment, I hope my research drives me away from introducing another
process i.e. cleaning of assemblies hence and control of flux effluent (we
are coincidentally reviewing ISO14000) etc. and rather focus on improving
the existing process i.e. flux residue reduction (without cleaning) and ICT
issues.
Thanks again to all,
Grant
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