[Diy_efi] info
Bill Shaw
b.shaw
Mon Oct 31 15:34:13 UTC 2005
Oh brother. Ok, I'll agree that some other people using some other
materials and some other circuits have had problems with water. This
particular conformally coated PCB , however, should have no problems with a
water rinse and dry.
Bill
> From: "Mike" <niche at iinet.net.au>
> Reply-To: diy_efi at diy-efi.org
> Date: Mon, 31 Oct 2005 22:51:52 +0800
> To: diy_efi at diy-efi.org
> Subject: Re: [Diy_efi] info
>
> 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
>>>>>>>>
>>>>>>>> _______________________________________________
>>>>>>>> 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
>>>>>>
>>>>>> _______________________________________________
>>>>>> 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
>>>>
>>>> _______________________________________________
>>>> 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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>> 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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