[Diy_efi] info

Mike niche
Mon Oct 31 14:51:52 UTC 2005 

At 10:24 PM 10/31/05, you wrote:
>But...but...but...  We're not talking about any of that.  We're talking
>about a conformally coated PCB that got washed in antifreeze.  Convincing
>people to do unnecessary stuff through 'scientific dissertation' isn't
>necessarily a helpful thing. The simplest solution is frequently the better,
>again MHO.

Bill, please understand, we didnt know *at the time* it was conformally coated.

Water may be simple but it *does* cause problems - especially where
there are any number of analog circuits. Incidentally, Isopropanol is
also a pretty simple molecule IMHO  ;)

The simplest solution is to use the one which is the recommended
solvent - not  the cheapest and easily accessible if you want the best
professional outcome longterm.

>Moot point now since John merely blew it off and it is running again. :-)

Well, with respect, we dont really know its moot because anyone with
even minor experience of electronics *knows* the first impression doesnt
mean lasting reliability and freedom from long term corrosion. 

ie. A board can look as nice cleaned with water as any other solvent.

Eg.
We had a local PCB supplier some 12 years back, now bankrupt. He
produced process control alarm boards. Yes, he washed em in water
and I might add in an ultrasonic tank so he was sure water would get into
the nooks and cranies and not fully dry out before he coated them in
plain old varnish. The boards lasted 2 to 3 years before random failures.

Suffice it to say, the varnish cracked in some places, the mineralisation
from the first lot of water left hygroscopic areas which conducted
along the varnish cracks, the boards failed. The company demanded the
replacement of all the varnished boards, through legal mechanisms they
drove the company bankrupt, the guy who bought the rights is an ex plumber,
thought he knew it all, didnt read any tech specs on electrolytic caps,
boards or even had trouble with the term 'hygroscopic"...

Had they used the recommended solvent at the time - guess the outcome ?

Bill, with electronics - it is necessary to use the recommended solvent.

There is a responsibility in ensuring we are properly informed where others
rely on our expertise and not blind faith or hope that water is simple.

It is fully appropriate to offer a dissertation based upon experience and
knowledge of chemical compatibility issues as there are others reading this.

If your business is dependent on supplying boards in commercial
quantity and you expect to stay in business on that basis in the long
term using water from whatever source then I advise caution. If you
are not doing it as your primary income source, as perhaps a hobby where
you are still learning of long term effects, then you take your
risks and I hope you can connect the cause with the effect and are open
to learn from the experience of others to save you uncertainty,

Cheers

Mike






>Bill
>
>> From: "Mike" <niche at iinet.net.au>
>> 
>> At 09:49 PM 10/31/05, you wrote:
>>> I've 25 years in electronics myself, Mike.  Washed many circuit boards in
>>> water with no issues.  Add on that the fact that this particular board is
>>> conformally coated and a rinse in water becomes a non-issue as long as it is
>>> dried promptly.
>> 
>> Sure no problem - that is *your* experience within your expectations
>> and based upon your acceptable level of delivery. I am only prepared to
>> wait 5mins before packing pallets of boards in antistatic, dry and clean with
>> no
>> chance of deposits, perhaps you are prepared to wait rather longer or
>> mess about loading and unloading an oven instead of basic overhead
>> infra red lamps, time is money - even in pilot production of a few hundred
>> boards at a time.
>> 
>> Incidentally the price of true distilled water is comparable to the price
>> of Isopropanol and some component manufacturers recommend the
>> latter explicitly.
>> 
>> My experience is that water causes problems in fine level analog
>> circuitry and that Isopropanol is the solvent designed to be used on the vast
>> majority of components and circuit boards, hybrids, integrated circuits etc.
>> 
>> Eg. If you have designed a fuel cell amplifier with a 40nA per ppm resolution
>> then you might change your mind or rather be happy to subsidise several
>> pilot production runs and alter your design layout so designs are not so
>> critical to board clearances where mineralisation might be an issue...
>> 
>> It would also be clear that one type of design is more or less
>> susceptible than another, digital designs are rather more robust to
>> mineralisation deposits, analog rather less so. Many boards are not
>> conformally coated and we didnt know in advance if the posters was.
>> 
>> General rule I consider is rationalise behind industry leaders at
>> the point in the market that has the greater return index for the
>> complexity of the product. ie. Understand their reasons and their
>> expectations in context with that which the client expects.
>> 
>> If you are into pilot production with the lowest rate of return on
>> analog circuitry then Isopropanol is the recommended solvent
>> by the component manufacturers, dries the fastest, leaves no
>> mineralisation deposits and is comparable to cost of true distilled water.
>> 
>> .
>> 
>> I'm going back to finding a way to pump oil into my pump backwards
>> so the darn thing can get primed without taking the thing apart <sigh>
>> 
>> Rgds
>> 
>> Mike
>> 
>> 
>> 
>> 
>> 
>>> Bill  
>>> 
>>>> From: "Mike" <niche at iinet.net.au>
>>>> 
>>>> At 08:33 PM 10/31/05, you wrote:
>>>>> We're talking about rinsing the board in water,  not putting it in a bath
>>>>> for a month.  Sheesh,  it's a shame how this list has deveolved into
>>>>> endless
>>>>> pissing contests and hair splitting. Back in the old days before the DIY-WB
>>>>> fiasco made the list implode there was real, serious efi content here.  Now
>>>>> it's just mostly this kind of junk.
>>>> 
>>>> I'm sorry Bill,
>>>> 
>>>> I was only intending to bring factual content and made no personal
>>>> references - unlike others on this group, hope you were not sensitised by
>>>> earlier emails, read on.
>>>> 
>>>> Water can get into all sorts of tiny places and cause electrolytic
>>>> conduction,
>>>> such as analog circuits where even a slight change in resistance from
>>>> built up deposits from even a few minutes of electrolysis can affect long
>>>> term stability. Bill,  I was uncritically warning against using water, and
>>>> didnt intend to offend you... I'm not A.W  <chuckle>
>>>> 
>>>> Case in point, the analog parts of EFI inputs such as log to linear dont
>>>> need much change in resistance to cause drift or offset errors - even a
>>>> little bit of water in the wrong places even for a few minutes can cause
>>>> offset errors which are enough to make a board unusable for hours or
>>>> until its properly flushed with Isopropanol. Fortunately the board the
>>>> poster was referring to is nicely coated, some arent...
>>>> 
>>>> Please accept Bill, that other posters have specific experience of
>>>> troublesome issues. In my particular experience as an engineer
>>>> of some 23 years experience, water is the worst thing to use in or near
>>>> any analog circuits for even a few minutes. In one example a CO sensor
>>>> board that had a high gain stage and 40nA sensr current was affected
>>>> by the moisture from a finger smear and a wipe with a damp towel
>>>> only made matters worse and even after drying it didnt improve.
>>>> 
>>>> The other assumption is that water is clean, sorry it aint. Tap water
>>>> is full of minerals, they get deposited when they dry and can leave
>>>> traces to affect analog circuits, that only takes a few minutes not months !
>>>> And if you are prompted to get distilled then why not get Isopropanol
>>>> and do the job properly, it is electronics.
>>>> 
>>>> Isopropanol has no minerals and is the solvent of choice for cleaning
>>>> boards, follow the industry lead and avoid water - well <cough> unless its
>>>> really distilled (not demineralised), used for as short a period as possible
>>>> and board dried in an oven immediately thereafter...
>>>> 
>>>> Its a cute way too look at solvents by distinghuishing them as
>>>> aggressive or otherwise, again I'm trying to be factual without making
>>>> any criticism - I never made any personal indictment, I wanted
>>>> to be clear its really an interpretation of a chemical compatibility issue
>>>> and sure you are welcome to interpret your view of a solvent as
>>>> aggressive or passive - frankly, I am incapable of seeing it that way.
>>>> 
>>>> No pissing contest Bill, facts presented without personal
>>>> criticism and from a wealth of industrial experience in recognition
>>>> of chemical compatibility issues...
>>>> 
>>>> Rgds
>>>> 
>>>> Mike
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> Bill
>>>>> 
>>>>>> From: "Mike" <niche at iinet.net.au>
>>>>>> Reply-To: diy_efi at diy-efi.org
>>>>>> Date: Mon, 31 Oct 2005 12:02:03 +0800
>>>>>> To: diy_efi at diy-efi.org
>>>>>> Subject: Re: [Diy_efi] info
>>>>>> 
>>>>>> At 05:13 AM 10/31/05, you wrote:
>>>>>>> Actually,  they call water the 'universal solvent' for a reason.  I'd
>>>>>>> start
>>>>>>> there,  and if it appears there is some residue the water can't get I
>>>>>>> might
>>>>>>> try more agressive solvents.
>>>>>> 
>>>>>> mmmm, not really - Water is a fairly good ionic solvent but suffers
>>>>>> from the H to OH equilibria, in that its neutrality is probabilisitc,
>>>>>> when it gets to actually dissolve anything and is either acidic or caustic
>>>>>> as a consequence and has repercussions on that basis. Vis a vis
>>>>>> using water as engine coolant where electrolytic damage is so prevalent,
>>>>>> the H to OH equilibrium seems to win out regardless of what chemicals
>>>>>> are added. That green inhibitor needs frequent changing, what I've
>>>>>> settled on is a tannin type pill which coats the alloy with a protective
>>>>>> layer and seems to work effectively for long periods. The only downside
>>>>>> is a little brown sludge if instructions/amounts not precisely adhered to.
>>>>>> 
>>>>>> Electronic components are not generally designed for immersion
>>>>>> in water, sure some can tolerate water for cleaning - but for electronics
>>>>>> Isopropanol is more generally accepted as the universal cleaner
>>>>>> and might be interpreted as the universal solvent for pollutants
>>>>>> affecting electronic repair and service. Its also ionic and boards
>>>>>> shouldnt be left in it for long otherwise there electrolytic effects.
>>>>>> The good thing about it is - its so volatile and drys off in a few
>>>>>> mere seconds on some occasions, plenty of ventilation is essential
>>>>>> as it is combustible and although it smells (ok) I wouldnt breath
>>>>>> the stuff at all if I could help it.
>>>>>> 
>>>>>> Interesting your comment re "aggressive" bringing a human emotive
>>>>>> issue to one of chemical compatibility. What I mean to say is there
>>>>>> are so many products and processes that have only a compatibility
>>>>>> issue not one which is either passive or aggressive
>>>>>> and to use those terms seems discontinuous with solvents. Sure,
>>>>>> the appearance is either one is more or less aggressive than another
>>>>>> but it comes down to a sheer compatibility only in the long run.
>>>>>> 
>>>>>> Also water is (AFAIK) only ionic whereas Isopropanol is ionic and
>>>>>> covalent in terms of its capacity to dissolve most pollutants which
>>>>>> can affect electronics, the Isopropanol is designed around for that
>>>>>> purpose.
>>>>>> 
>>>>>> Rgds
>>>>>> 
>>>>>> Mike
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>> 
>>>>>>> Again,  just mho.
>>>>>>> 
>>>>>>> Bill
>>>>>>> 
>>>>>>>> From: "Mike" <niche at iinet.net.au>
>>>>>>>> 
>>>>>>>> At 08:31 AM 10/29/05, you wrote:
>>>>>>>>> I'd remove it from the case,  wash down the PCB and case good with
>>>>>>>>> clear
>>>>>>>>> clean water,  then blow it with compressed air and let it dry for a few
>>>>>>>>> days.
>>>>>>>>> Once I was sure it was complete dry I'd reassemble it and try running
>>>>>>>>> it.
>>>>>>>>> What id there to loose?
>>>>>>>> 
>>>>>>>> Best solvent to remove other things is Isopropyl alcohol (Isopropanol),
>>>>>>>> let dry normally - dont use compressed air, there is potential for
>>>>>>>> localised
>>>>>>>> static damage,
>>>>>>>> 
>>>>>>>> Rgds
>>>>>>>> 
>>>>>>>> Mike
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>>> Just MHO :-)
>>>>>>>>> 
>>>>>>>>> Bill
>>>>>>>>> 
>>>>>>>>> From: "Lee M. Lemoine" <llemoine at gmail.com>
>>>>>>>>> 
>>>>>>>>>> John, if antifreeze can damage paint, think about
>>>>>>>>>> what it may do
>>>>>>>>>> to a PCB.
>>>>>>>>>> You could spend a lot of time replacing parts, and
>>>>>>>>>> still have an
>>>>>>>>>> unreliable
>>>>>>>>>> ECU. Wrecking yard option sounds good. Make sure it
>>>>>>>>>> comes from a
>>>>>>>>>> car
>>>>>>>>>> without a leaky heater core.
>>>>>>>>>> 
>>>>>>>>>> Geoff H
>>>>>>>>> 
>>>>>>>>>> 
>>>>>>>>> _______________________________________________
>>>>>>>>> Diy_efi mailing list
>>>>>>>>> Diy_efi at diy-efi.org
>>>>>>>>> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>>>>>>> 
>>>>>>>> 
>>>>>>>> Regards from
>>>>>>>> 
>>>>>>>> 
>>>>>>>> Mike
>>>>>>>> Perth, Western Australia
>>>>>>>> VL Commodore Fuse Rail that wont warp or melt !
>>>>>>>> Twin tyres for most sedans, trikes and motorcycle sidecars
>>>>>>>> http://niche.iinet.net.au
>>>>>>>> _______________________________________________
>>>>>>>> Diy_efi mailing list
>>>>>>>> Diy_efi at diy-efi.org
>>>>>>>> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>>>>>> 
>>>>>>> _______________________________________________
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>>>>>> 
>>>>>> 
>>>>>> Regards from
>>>>>> 
>>>>>> 
>>>>>> Mike
>>>>>> Perth, Western Australia
>>>>>> VL Commodore Fuse Rail that wont warp or melt !
>>>>>> Twin tyres for most sedans, trikes and motorcycle sidecars
>>>>>> http://niche.iinet.net.au
>>>>>> _______________________________________________
>>>>>> Diy_efi mailing list
>>>>>> Diy_efi at diy-efi.org
>>>>>> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>>>>> 
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>>>> 
>>>> 
>>>> Regards from
>>>> 
>>>> 
>>>> Mike
>>>> Perth, Western Australia
>>>> VL Commodore Fuse Rail that wont warp or melt !
>>>> Twin tyres for most sedans, trikes and motorcycle sidecars
>>>> http://niche.iinet.net.au
>>>> _______________________________________________
>>>> Diy_efi mailing list
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>>> 
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>> 
>> 
>> Regards from
>> 
>> 
>> Mike
>> Perth, Western Australia
>> VL Commodore Fuse Rail that wont warp or melt !
>> Twin tyres for most sedans, trikes and motorcycle sidecars
>> http://niche.iinet.net.au
>> _______________________________________________
>> Diy_efi mailing list
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>> http://lists.diy-efi.org/mailman/listinfo/diy_efi
>
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Regards from


Mike
Perth, Western Australia
VL Commodore Fuse Rail that wont warp or melt !
Twin tyres for most sedans, trikes and motorcycle sidecars
http://niche.iinet.net.au

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