Hi, Guy
Why do you see an increase in solder defects from the wash, which is usually done after double-sided reflow is completed through both sides? Are you cleaning between side one and side two?
If so, there are solder pastes available that do not require washing until reflow is complete; they can go through side one reflow and then through side two, and then wash. I have qualified two of these solder pastes for different clients. At each location, their DPU and DPMO was benchmarked along with their cleanliness data. After the pastes themselves were evaluated and qualified, we went back to verify the performance of the paste by measuring the effect on the DPU for the primary product and the overall DPMO. They showed very significant improvements. Because these two customers particularly wanted to be able to skip the wash between side one and side two, we paid careful attention to the effect on cleanliness.
The Ionograph results (customer #2) and the Omegameter (customer #1) both improved. I encourage you to check to see if your solder paste is of this type, and if not you may wish to evaluate a new paste that is. Not having to go through the wash between side one and side two is definitely a timesaver and a cost reduction. Especially if you are noting a decrease in solderability due to the wash.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
Sent: Thursday, March 06, 2008 8:30 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning No-clean
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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