I'll try to get something posted to the Forum next week. Have a Great Weekend!
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Graham Naisbitt
Sent: Thursday, September 08, 2005 6:35 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning rosin flux residues
Chris
Might you be able to share with us what tests you employed to validate /
qualify the process?
Graham Naisbitt
On 7/9/05 18:46, "Schaefer, Chris" <[log in to unmask]> wrote:
> I agree with Edwin if you are using an inline process or possibly a batch type
> cleaner. We are converting to a rosin base flux with a solids of 15% and plan
> to use the Kyzen A4520 product (surfactant base) soap for the flow solder
> process to enable us to more effectively solder Pb Free components. We have
> performed extensive and very expensive tests to validate/ qualify this
> chemistry and found the following:
>
> - Lower temperatures in the wash bath (thus reducing evaporative
> losses and other advantages)
> - Longer bath life than the previous version of soap by 1.5X depending
> on pcb cleaning volumes and added soils from wave/ smt
> - Greatly improved cleaning underneath fine pitch components
> - Increased cleaning speeds (single pass vs. dual in some cases)
> - "Capable" of cleaning lead free soldering processes
> - Shinier joints if aesthetics are important to you or your customers
> - Reduced Surface Organics
> - Lower ionics
> - any other positive items
>
> ***Note: This is not a commercial for their chemistries, just personnel
> experience with them.***
>
> We are using an AS200 inline water wash with a level 4 chemical isolation to
> aide in the reduction of chemical loss due to dragout/ bath to bath migration
> and Hurricanes to improve cleaning as well. Once we have completely converted
> over to Pb free soldering in all aspects, we will change the A4520 to the
> A4630, which is to be their cleaning chemistry for Pb Free soldering
> processes. We are to begin trials of this material by the end of the year.
>
> ***
> To answer another question concerning Tin/ Lead soldering profiles vs. ENIG
> profiles - we have processed both of these plating types in both the smt and
> flow solder processes without deviating from the original profiles depending
> on the flux type used. The results between the 2 plating types was little
> difference (if any) using a higher solids content flux 15% RMA, but when using
> a lower solids content NC flux (2%) we have had to reduce heat (if possible)
> and/ or increase conveyor speed to allow the flux to last longer. This of
> course would allow reduced surface tension of the flow solder wave enough once
> the PCB contacted the surface to allow for best possible soldering.
>
> ***
>
> Chris Schaefer
> Suntron Corporation
> Process Engineer
> 540 N. Rogers Road
> Olathe, Kansas 66062
> 913.393.5878
> [log in to unmask]
>
> NOTICE:
>
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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Edwin Louis
> Sent: Wednesday, September 07, 2005 6:57 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning rosin flux residues
>
>
> KYZEN makes cleaners that can remove the rosin residues. Ides a cleaning
> chemical, you need agitation. Are these PWAs going through an in-line
> cleaner? Call Mike Bixenman at 615-584-9089.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Paul Klasek
> Sent: Wednesday, September 07, 2005 6:40 AM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning rosin flux residues
>
> On the root cause Juan,
> the 'white stuff' (be flux) should not have creep that far normally
> (granted nothing is normal) : traced this occurrence in same incidence
> (test) to flux overspray (& bake); perhaps check if wave pass applies.
>
> -----Original Message-----
> From: Brian Ellis [mailto:[log in to unmask]]
> Sent: Wednesday, September 07, 2005 6:24 PM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning rosin flux residues
>
>
> IPA is one of the worst cleaning solvents: its only merit is that it is
> polar. If, as you surmise, the residues come from your flux, then they
> are probably a nasty mixture of thermally polymerised and probably
> hydrolysed rosin, along with some residual activators. I am making a
> guess that your flux is "halogen-free", because this kind of flux can be
> the very devil, whether rosin based or not, because the activator
> content is essentially some form of carboxylic acid in much higher
> proportions than you get in organic chloride/bromide type fluxes and
> some of them can polymerise at the drop of a hat.
>
> Isn't the use of HCFC-141b as a solvent forbidden in the EU, anyway?
>
> Now you have a double-whammy of a problem: not just nasty residues, but
> deep in the contacts of a female connector. In this case, my first
> reaction is that an ounce of prevention is worth a kg of cure: change
> your connector to one whose design prevents any chance of the flux
> wicking into the contacts (turned contacts, instead of pressed). If this
> is not possible, then pre-tin them using minimal quantitites of flux,
> such as a good W/S flux, and thoroughly clean, then use little or no
> flux for the assembly. Another tip is to fill the contacts with a tight
> PTFE plug during the tinning/soldering process, to physically prevent
> flux from entering where it didn't ought to.
>
> Now, how to clean inside, where you already have contamination. Bearing
> in mind the blind nature of the parts, you need both chemical and
> mechanical help. You need an expensive solvent and HCFC-225ca/cb with an
> azeotropic blend of methanol will probably be your best bet (much less
> aggressive than HCFC-141b). For the mechanical side, think in terms of
> an interdental toothbrush from your local pharmacy modified to fit in
> one of those small, high-speed, hand-held drills. Soak the parts in the
> solvent for a minute or two and insert the brush at, say, 10,000 rpm in
> each contact, while flooding it with the solvent from a wash bottle.
> Rinse in clean solvent.
>
> There are two problems with this: the solvent is toxic and it is
> environmentally harmful, so you need very good ventilation drawing air
> away from the operator and you need a carbon filter in the ventilation duct.
>
> If you can't get HCFC-225 (made only by Asahi Glass in Japan under the
> trade name AsahiKleen), then try HFC-4310 (DuPont) or HFE (3M), also
> blended azeotropically with methanol. They are less aggressive than the
> HCFC-225 blend, but equally expensive (or more so). Many blends of HFCs
> and HFE contain trans-dichloroethylene and should be avoided if you have
> compatibility problems with HCFC-141b as this solvent (t-DCE) is even
> more aggressive.
>
> Brian
>
> Juan T. Marugán wrote:
>> Hello teachers,
>>
>> we have the following problem in some class 3 units: we have detected a
>> white stuff inside the contacts of female connectors. It could be the main
>> cause of the failures found during testing. Our thought is this substance
>> could be due to a reaction between the rosin flux used when soldered the
>> connectors whit the cleaning solvent (IPA)
>>
>> Two questions:
>>
>> 1) Could you recommend a solvent to remove these residues. We have tried
>> with 141-b, but it could damage some parts of the unit.
>>
>> 2) We would like to send a contaminated connector to a lab for analisys.
>> Could you recommend a technique to determine these substances?
>>
>> Thank you for your help.
>>
>> Juan T. Marugán
>> Indra Sistemas SA
>> Espańa
>>
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