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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