Brian

Thank-you for that information, it is most helpful albeit a little late for
the customer in question - 1998!

...but let me get this straight - the residues of an OA flux (some or all?)
will serve to lower the ST sufficiently to assure good cleaning performance,
yes?

Graham Naisbitt

> Sorry, Graham, but I insist. The residues of the flux itself contains a
> large excess of surfactants which lower the surface tension of the wash
> water to ~25-30 dyne-cm. Most saponifier solutions have an ST of 30-35
> dyne-cm. The only effect that saponifiers would have is to replace the
> acid residues with equally corrosive alkaline ones. It's a waste of time
> and money adding saponifiers. Furthermore, if your wash cycle contains
> saponifier, you must have a second water-only wash cycle before the
> rinse starts, to wash off the saponifier residues. Not all machines
> permit this. What I said in my previous message still stands.
>
> A pre-rinse in a chelating neutraliser (which is NOT a saponifier),
> BEFORE washing is beneficial. This can be in a static hold tank. This is
> a time proven method. This is demonstrated in the streaming video at
> http://www.protonique.com/video/ (this is quite old and the components
> are BIG, but the principle is still valid).
>
> Brian
>
> Graham Naisbitt wrote:
>
>> Hello Mike
>>
>> I knew I shouldn't have.....but can't help myself......
>>
>> I agree with you, but what I am referring to is the use of a closed-loop
>> pure water 'OA' type process where no chemistry is used only pure water.
>>
>> Surfactants to my knowledge are not used in isolation, saponifiers (soaps)
>> will be needed as well, and make sure the surfactant has excellent
>> rinseability (silicone base is not a good thing in this instance). Whatever,
>> it is wash chemistry and there will be an effect on the life of the filter
>> beds and the transfer of wash 'chemistry' getting into the rinse zone(s).
>> Clearly the use of saponifiers that generally have to include surfactants
>> for that very reason, require a somewhat more complex cleaning system.
>>
>>> From my perspective, the pure OA approach, as Brian alluded to in his reply,
>> isn't adequate to ensure thorough cleansing on high density low stand-off
>> devices.
>>
>> ...ah! That perennial question: How clean is clean?
>>
>> Graham Naisbitt
>>
>>
>>> Hello Graham: I have to disagree with your statement regarding the need for
>>> saponification to get under low standoff components. The need was to reduce
>>> surface tension which can be achieved with a surfactant. With a surfactant
>>> the surface tension of the wash water is lowered allowing it under low
>>> standoff components to flush out OA flux residues. It also does not leave
>>> behind the saponifier chemistry.
>>> Saponification is quite a different animal than a surfactant. The saponifier
>>> converts non water soluble residues to hydrophilic or water soluble ones.
>>> The saponifier typically has a surfactant as part of it's make up to allow
>>> better wetting or penetration but contains other components if not rinsed
>>> that can be detrimental to the electrical performance of the assembly. The
>>> obvious advantage of the saponifier is that it will remove other
>>> contaminates on the PCA besides the flux that are not water soluble.
>>>
>>> With that said we do use a saponifier but have very good process control on
>>> the types and angles of our spray nozzles in wash and rinse. Along with
>>> increasing temperature through the various rinse stages to facilitate the
>>> complete flushing and removal of the saponifier.
>>>
>>> Just a clarification as sometimes these two terms saponifier and surfactant
>>> are used interchangeably.
>>>
>>>
>>> Regards
>>>
>>> Michael Barmuta
>>>
>>> Staff Engineer
>>>
>>> Fluke Corp.
>>>
>>> Everett WA
>>>
>>> 425-446-6076
>>>
>>> -----Original Message-----
>>> From: Graham Naisbitt [mailto:[log in to unmask]]
>>> Sent: Tuesday, May 04, 2004 5:41 AM
>>> To: [log in to unmask]
>>> Subject: Re: [TN] OA / RMA
>>>
>>>
>>> I must be mad sending this to challenge The Oracle himself but....
>>>
>>> The real beauty of the OA process is that it required only water - as
>>> distinct from Aqueous Process where Water Soluble, or some would say Water
>>> Washable fluxes were used that required some cleaning chemistry.
>>>
>>> Aqueous processes I always thought of as a misnomer and that it should be
>>> called Semi-Aqueous - ergo water only v water plus chemistry.
>>>
>>> However, the drawback with the Water Only approach is that it proved to be
>>> inadequate for some of the newer low stand-off devices such as micro-BGA,
>>> flip-chip and some of the smaller discreets <0604. Saponification had to
>>> added in order, not only to get under such devices but, more importantly, to
>>> get the darned stuff out from underneath including the "dissolved"
>>> contaminants.
>>>
>>> IMHO - Graham Naisbitt
>>>
>>>
>>>> I installed the first OA (misnomer, WS is better) full scale
>>>> wave-soldering production line in Switzerland (if not in Europe) as long
>>>> ago as 1965. The company in question is still using it,four soldering
>>>> machines later. I have since aided in many others, throughout the world.
>>>> Advantages of WS:
>>>> - better quality soldering with fewer rejects
>>>> - more tolerant of poorly solderable components
>>>> - widest operating window
>>>> - no expensive cleaning products
>>>> - minimal pollution from overall process
>>>> - lowest production costs
>>>> Disadvantages:
>>>> - requires good process control
>>>> - unforgiving of errors
>>>> - good quality cleaning equipment rarer than you think
>>>> - flux itself is fairly corrosive
>>>> Summary:
>>>> - requires a serious approach and qualification
>>>> - with this proviso, this is the way to go.
>>>>
>>>> Brian
>>>>
>>>> Dehoyos, Ramon wrote:
>>>>
>>>>>                Hi Technetters:
>>>>>                Has anybody done a comparison study of RMA/OA fluxes for
>>>>> wavesolder?  Or any personal experiences in this regard will be
>>>
>>> appreciated.
>>>
>>>>>                Thanks in Advance
>>>>>                Ramon
>>>>>
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>>
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>

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