Interesting, we have observed changes in soldering performance on immersion silver boards when we first change our DI beds.
Our DPMO count goes up until the resistivity level of the water settles down to less than 10 Meg. Our perception, though not measured, was that this was also true for immersion tin. We don't often solder to immersion tin.
We observe no measurable change in performance of Gold Flash protected patterns.
We change our beds when they are unable to return the tank to something higher than 1 Meg.
We have seen a measureable change in performance of very sensitive RF circuits if we allow cleaning water to drop below 500K.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry L. Munson
Sent: Thursday, March 06, 2008 8:31 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning No-clean
Well it seems that the questions of water quality for cleaning are far
reaching. But to address the question of will 18 meg ohm DI water cause the
soldering issues. We have cleaned thousands of assemblies after part removal
(water intolerant parts cleaned with saponifier) using DI water STEAM (from 18
meg ohm source) and rinsed with final rinse at 16-18 meg ohm. with no
solderability problems. We have recovered thousands of connectors with a tin plating
and an oxide film causing them to be unsolderable. By running them through
the inline Aquastorm 200 with the EnviroGold 816 saponifier at 10% (not any of
the other saponifiers) we were able to remove the oxide film that was causing
the solder wetting problem and all of the connectors were 100% solderable
after rinsing with 18 meg ohm final rinse water. We then baked the connectors
in a cross flow oven at 85 C and the connectors were still 100% solderable.
If DI water is so aggressive that in a normal inline cleaning process where
it is not sitting in pools of DI water for 10-15 minutes, then it should not
have allowed these connectors or boards to meet solderability issues for both
SMT and through hole. Everyone seems to have their opinion about water
quality and for those of you that are effectively cleaning with tap water and no
saponifier, more power to you. I have not been able to achieve the needed
level of quality without using the above cleaning parameters.
Terry Munson
Foresite
765-457-8095
In a message dated 3/6/2008 7:31:27 A.M. Eastern Standard Time,
[log in to unmask] writes:
I agree with Brian on this aspect of water purity for cleaning and would
add: Very pure water can actually cause soldering problems when used in cleaning
sequences between the secondary and primary or hand soldering steps.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Thursday, March 06, 2008 7:21 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning No-clean
I have had customers clean very successfully assemblies with ordinary
tap water, although I don't recommend it. If the bulk (>95%) of the
water is removed mechanically (efficient air knives or centifuges), then
you can get away with quite impure water. If you just allow the water to
evaporate on the surface, then the cleaner the water the better. I wrote
a number of pages on this subject in my book (pp 204 ff). I suggested 1
µS-cm was OK for most applications. Then it also depends on the application.
Another "how long is a piece of string" question.
Brian
Schaefer, Chris wrote:
> Terry,
>
> A little off the subject. How important do you think it is to use high
quality DI water as opposed to using 200K DI water in an Inline Aqueous System?
I typically use something in the range of 12-18Mohm DI water at a minimum at
the final rinse whether its a chemistry inline wash or purely a water wash.
We produce Class 3 product that requires zero residuals at 10-40X, with less
than 10.06NaCl/ sq.in. ionics. The company I am currently working for does not
believe 10-18Mohm water is necessary, but we continue to have cleaning
issues that are caused by poor process, old chemistry, and likely the water.
>
> Any thoughts?
>
> Thank You,
>
> Chris - AKA Booker
>
>
>
> Chris Schaefer
> Suntron Corporation
> Process Engineer
>
> 800 N. Brutscher Street
> Newberg, OR 97132
> Work Phone: 503.554.6270
> Cell Phone: 785.248.9016
> Email: [log in to unmask]
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry L. Munson
> Sent: Wednesday, March 05, 2008 8:22 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning No-clean
>
> Dan and Brian
> We have qualified clients who clean a no clean and have since the mid 90's
(Les Hymes was one of the first). But we have found that with a rescue
cleaning and only if you have water tolerant parts (if not those need to be
removed) that you can effectively clean a residue that was not designed to be
cleaned.
> These residues do need a good saponifier, low pressure inline (not able
to do in a standard batch system), heated to 140-150 F wash and rinse with
DI water at 10 meg ohm or better, but this is not enough by itself but we
found that if we use DI steam after wash and before rinse then we are able to
clean under low standoff components, BGA's, and with a little help QFN and
PQFN
> packages. We presented this information at the IPC Midwest Expo 2007,
authored
> by Eric Camden. We have successfully been rescue cleaning for the last
7 years no clean assemblies that were 6-12 months old. So it is very doable
but standard batch cleaning with a saponifier has not proven to us or our
customers who we have help implement this type of cleaning that batch or
standard inline cleaning is able to do the job.
>
> Terry Munson
> Foresite
> 765-457-8095
>
>
>
>
> In a message dated 3/5/2008 10:53:25 A.M. Eastern Standard Time,
[log in to unmask] writes:
>
> "Generally speaking I have not seen good results in trying to clean off
no-clean flux. They call it "no-clean" for a reason."
>
> Agreed!!! Even if you succeed to do the job well - it can be done with
some fluxes - it will not be very easy and may be quite costly. I have always
said, if you clean, use a flux which was designed from the start for easy
cleaning.
>
> €0.02 worth
>
> Brian
>
> Dan Mauro wrote:
>> Folks,
>>
>>
>>
>> I have a need to clean No-clean residue from PCBA's. Can this be
>> achieved with water washer and some type of saponifier ? Can anybody
>> suggest a batch process?
>>
>>
>>
>> Thanks,
>>
>> Dan
>>
>>
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