Bill
For some peculiar reason, the message posted by Joseph Kane has been
re-routed as though it is from me!? Jack - have you got your Technet ears
on?
My question is actually shown at the bottom of this lot.....and I agree with
you, but that was going to be my next question!
BTW, I am aware of a couple of IPA cleaners, but only 1 of the batch type
described - that blew its door across the factory one day, long ago!
> Graham,
>
> I am familiar with the "dishwasher" machine that you have described. My
> curiosity is about the dishwasher machine where you use 75% isopropyl
> alcohol and 25% water. Was this dishwasher specially made for this solution?
> The reason I ask is due to the explosive nature of IPA. Normally anything to
> do with IPA requires explosion proof motors and accessories.
>
> Could you please comment? (cud u pls com?, I couldn't resist)
>
> Thanks,
>
> Bill Kasprzak
> Moog Inc. Manufacturing Engineering, Electronics
>
>
>> -----Original Message-----
>> From: Graham Naisbitt [SMTP:[log in to unmask]]
>> Sent: Tuesday, April 22, 2003 6:47 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] Cleaning Question - Rinse water resistivity?
>>
>>> We have set up our Emulsonators with wash time of 30 minutes and
>>> rinse time of 15, but the rinse cycle will continue for up to 30
>>> minutes if wash sump resistivity does not reach at least 1
>>> megohm-centimeter. If this level is not met within 30 minutes, the
>>> cycle will abort.
>>>
>>> FYI to the group, this is a batch "dishwasher" style machine, with
>>> counter-rotating spray arms at top and bottom, and separate wash
>>> and rinse tanks. The wash tank contains water with 5 or 10% of wash
>>> chemistry, in our case Bioact EC-7R. Bioact is not miscible, and
>>> separates, but pumping action creates an emulsion that is pretty
>>> effective at removing RMA flux.
>>>
>>> After the wash cycle, the emulsion drains back into the wash tank,
>>> the valves close, and DI water is pumped into the cleaning chamber
>>> from a separate tank and recirculating loop. In this loop, rinse
>>> water drains from the wash chamber into a decanter, where Bioact
>>> floats to the top, and the water returns to the rinse tank. Rinse
>>> tank water is pumped through a particle filter, carbon, and
>>> mixed-bed before it flows into the wash chamber.
>>>
>>> Since water does not mix with Bioact, the rinse operation uses
>>> water to mechanically remove the solvent, basically "pushing"
>>> the Bioact residue off of the board surfaces. Any solvent left
>>> on the board will include flux and ionic residues dissolved within.
>>> In our process, boards come out with no visible flux residue, but
>>> we use these systems for gross flux removal, not final ionic
>>> cleanliness. Before conformal coat, we clean with a separate
>>> dishwasher containing 75% IPA and 25% DI water.
>>>
>>
>> Joseph
>>
>> So before you coat - and seal in anything nasty - how do you determine if
>> the end product will be reliable?
>>
>> Do you do any ROSE / SEC testing? If so, what level do work to?
>>
>> --
>> Regards Graham Naisbitt
>>
>> [log in to unmask]
>>
>> Cell: +44 79 6858 2121
>>
>> Concoat Limited - Engineering Reliability in Electronics
>>
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>
--
Regards Graham Naisbitt
[log in to unmask]
Cell: +44 79 6858 2121
Concoat Limited - Engineering Reliability in Electronics
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