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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