In reply to Thomas Lepsche
Thank-you for your explanation - that makes sense.
I would however, like to point out that the solution (if you will forgive the
pun), may harbour issues that fundamentally affect your bottom line.
Think of it this way:
A good old fashioned rosin flux used a solids content at around 15%. A modern
no-clean or no-solids, may have NO solids or at least less than 2%. So how do
you get it to wet the board without dripping everywhere? By adding wetting
agents - that's how.
BUT - during the pre-heat to soldering, like everything that gets hot, the
surface of the board expands and it becomes hydroscopic - it becomes absorbant
to these lower solids products. Furthermore, the epoxy mask is generically
more hydroscopic and no-cleans typically require a higher pre-heat. Thus these
extra liquids are better able to be absorbed into the board through the mask
and once in, and the surfaces cooled down, will be almost impossible to
extract by whatever means. This may also be why some suggest hot ionic extract
testing. (If you do that, watch out carefully for bromine flame retarder
leaching thru to the surface).
AND this is not going to be cleaned?? Check out Professor Laura Turbini's
papers on CAF - glycol wetting agents initiating Cathodic Anodic
Filamentation?
All fluxes leave residues - there is fluxless soldering but not zero residue
fluxing. Are these residues benign? You are running no-clean therefore ionic
extract testing/cleaning should not be used? How will you test?
Check out IPC-TM-650 and the newish IPC-9201 for SIR testing. There are many
new developments in this area alone as a direct result of the above.
NOW - I am not going to suggest that no-clean must not be cleaned but I am
strongly commending that more thorough process validation be done to better
determine the reliability potential of the product and thus - reduce field
failure and reduce corporate risk. Either clean "cleanables" or don't clean
no-cleans.
By the way, we do have some belt and suspender personnel - and they are hotly
pursued! In merry olde England, in the county of Yorkshire, the expression is
"belt, braces and a piece of string" but I know what you mean.
Graham Naisbitt
Concoat Ltd Email: [log in to unmask]
Alasan House, Albany Park Tel: +44 (0)1276 691100
Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227
-----Original Message-----
From: TechNet Mail Forum On Behalf Of Lepsche, Thomas G (NM75)
Sent: Monday, August 04, 1997 2:46 PM
To: [log in to unmask]
Subject: Re: [TECHNET] No-clean flux query
Graham,
You, obviously do not have any belt and suspender personnel at your
facility. At my facility we do have such persons and the theory goes
something like this " We really don't trust the performance of no-clean
fluxes on our CCA's. We really want clean boards for maximum
performance, but if we err in cleaning, we want to leave a residue that
really didn't need to be cleaned off anyway." We are therefore covered
with an explanation for the customer no matter what happens and have the
best of all worlds. Quality and acceptability of the product and CYA is
of most importance, cost and process difficulty is of minor importance.
Semper Fi
Tom
>----------
>From: Graham Naisbitt[SMTP:[log in to unmask]]
>Sent: Sunday, August 03, 1997 5:21 PM
>To: [log in to unmask]
>Subject: Re: [TECHNET] No-clean flux query
>
>In reply to Yuan's message on Friday, I am baffled.
>
>Why do you want a "No-Clean" flux that you can clean? Do you mean a low or no
>solids product instead?
>
>From our experience, trying to clean no-clean is not good news. Finding the
>right chemistry to work for you can be a time consuming and difficult
>project.
>I therefore strongly suggest that whatever trials you conduct, make sure they
>are as close as possible to production conditions. I.e. run minimum 4 hour
>tests with largest possible number of assemblies not just 10 or 12.
>
>Yuan correctly indicates that there will be residues. The issue is not so
>much
>visual appearance but whether any remaining residues could impair circuit
>reliability.
>
>So when you do get to your trials, try producing through J-STD-001, and
>testing to IPC-TM-650 (and IPC9201) with inspection to IPC-610
>
>I would love to hear from others, their views on this topic.
>
>Graham Naisbitt
>
>
>Concoat Ltd Email: [log in to unmask]
>Alasan House, Albany Park Tel: +44 (0)1276 691100
>Camberley, Surrey GU15 2PL UK Fax: +44 (0)1276 691227
>
>
>-----Original Message-----
>From: TechNet Mail Forum On Behalf Of [log in to unmask]
>Sent: Friday, August 01, 1997 5:31 PM
>To: [log in to unmask]
>Subject: [TECHNET] No-clean flux query
>
> Hello,
>
> My company would like to move to No Clean flux for rework of PCBA's.
>
> The main criteria we are looking for is the following:
>
> 1. High Quality Solder Joint
> 2. Easy to work with
> 3. Low residue
> 4. Capability to be water washed
> 5. Capability to be not cleaned
> 6. The residue be contained at the location of the solder joint.
> 7. The residue be formulated in such a way that it will not collect
> dust and debris.
>
> Any information about such fluxes are appreciated.
>
> Thanks,
>
> Yuan
> (303)417-5655
>
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