12 Mohm rings a bell.... Can't remember anymore... You should contact
the vendor....
Washing just smear things around, soluability of water goes down when
you have impure (lower resistivity) water = already got some stuff in
it...can't dissolve more ....
jk
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
>Sent: Wednesday, April 16, 2003 6:53 AM
>To: [log in to unmask]
>Subject: Re: [TN] Cleaning Question - Rinse water resistivity?
>
>
>Jason
>
>The problems may be more complex. I don't know the machine in
>question, but I gather it is a closed circuit type with an
>in-line DI Column and possibly carbon filter. This is a very
>dangerous combination a) because most machines of this type
>regenerate the water slower than the water is recontaminated
>b) the carbon filter (if fitted) saturates with the non-ionics
>from the solvent very rapidly, so these are recirculated
>straight through the system and back onto your board. These
>will mostly be terpenes but there are also surfactants which
>are hygroscopic. c) the drying system may evaporate the water
>off, leaving the non-volatile contaminants neatly in place.
>
>My advice with HCS products, such as EC-7R, is to a) ensure
>minimum drag-out from the solvent to the first water wash, by
>a long hold period and preferably an air-knife (preferably
>with collected and filtered exhaust to prevent operator
>exposure to d-limonene). The first wash should be lengthy (say
>10 min) with a very powerful pump at a temperature a few
>degrees under the flash point of the solvent, for safety. The
>first rinse should be open-circuit with water taken from the
>final rinse sump. The final rinse should be with freshly
>deionised water at 1 uS-cm or better, without recirculation.
>Drying should start with mechanical removal, such as powerful
>air knives, to blow out contaminated water from under the
>components. Only then should you allow evaporation.
>
>Brian
>
>Jason Wilson wrote:
>> Hi Everyone,
>>
>> I am a new member to the list and I have a question on cleaning.
>> Thanks in advance for any help you can provide. It is much
>> appreciated.
>>
>> What should the value be for rinse water resistivity? The cleaner we
>> have is a AAT Corp Emulsonator 9700.
>>
>> We use an RMA flux (both in wave solder, and in solder paste). The
>> solvent we use is EC7R.
>>
>> Also, we currently rinse for 10 min (+ time to reach resistivity).
>> Does this seem low? We are having trouble with board cleanliness.
>>
>> Once again, thanks for any help provided.
>>
>> Jason
>>
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>>
>>
>>
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