Ron,
1) Low solids no clean does not require nitrogen. I've used it for years on
SMD in a previous life. Please note that the process window for solderability
and design is narrowed with low solids in air relative to nitrogen.
2) Nitrogen only benefits yield if you use no clean. But costs can be
justified on dross elimination alone. Yield improvement is a secondary cost
savings on many panels.
3) Tighten supplier cleanliness specs before conversion, and verify
capability. Do what's necessary if a supplier cannot provide clean parts prior
to your process.
4) The right no clean causes no problems at in-circuit if a spray fluxer is
used. Foaming or waving a no clean will substantially increase residues.
Call or e-mail me (local call for ITT Fort Wayne)if you want to discuss any fine
details.
Aric
Please note that my opinions are not necessarily those of my current employer
______________________________ Reply Separator _________________________________
Subject: No-clean/Test Probes/Cleaning
Author: "Ron Hollandsworth"<[log in to unmask]> at INTERNET
Date: 6/27/97 8:21 AM
Hello Technet!
We are in the process of implementing a no-clean/low-residue process
in a Class 3, High Reliabiity, manufacturing process. Obviously I
have some soul searching questions.
First, I see the need to clean. Hopefully with a low cost cleaning
process. Why? If all the no-clean process is in place, general
statement, and parts come in that cause failure after cleanliness
testing, then, "how do the boards get cleaned?" Yes, one should have
their suppliers online, but, this can be a cruel world sometimes and
scrapping them isn't an option.
Second, test probes at Incircuit test. Is there a no-clean flux that
can be probed without having to replace test probes? Many suppliers
claim their no-clean is probeable, but, there is a significant cost
because of the residues left on the probes. This can get very
expensive. Our existing Incircuit test process with cleaned boards is
very inexpensive. If there is a no-clean flux out there, would the
users be willing to share the brand name, or even entertain a
benchmarking visit? Low-residue fluxes/pastes could be used, but, I
have heard this makes a nitrogen process necessary. Nitrogen
processes can also be very expensive. Can a low-residue process be
used without nitrogen if the components/boards are solderable
(solderability good)?
Third, how many have "skunk works"? By this I mean, "how many have
cleaners in the back room for those problem child
boards/processes/products? We have some special products that must be
cleaned...i.e...space, high voltabe power supplies, etc. Need some
help/suggestions/advice (please keep it clean so to speak). Thanks.
I see the need to have a cleaning operation somewhere inhouse and
possibly in the production process. Looking at costs: First, it
would seem that costs at Incircuit would get pretty salty if you had
to continually change/clean test probes. Second, to use a low-residue
flux/paste nitrogen requirements can off set savings by going to a
low-residue technology. Third, I can't scrap boards if they fail
cleanliness because a supplier forgot to clean them.
We would like very much to transition to a no-clean/low-residue
technology (no-clean or low-residue). I am not a against this
technology, so please don't misunderstand this e:mail. I feel that
no-clean may not really mean "no-clean". I know these subjects have
been on the TechNet before, but could we resurrect them once again?
Thanks for listening, need some feedback.
RON
[log in to unmask]
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