Brian,

 Thank You.  I was considering the IPA to reduce the surface tension with the thought it would help remove/dilute wash water under parts. (I got this idea from your book!)

 My blow off air source is probably dirty (Oil free diaphragm pump with  a 5 micron filter) and blow off is a slight pain. Eliminating the blow off would be eliminate a minor hassle. (I do wash with tap so I wanted something to remove tap water.)

 I lack the ability to measure final contamination levels in house so I am just trying to find the easiest procedure that makes sense. I only do this hand process for proto and small runs but even for these small quantities I don't want to be doing anything stupid. The rinse with distilled / IPA solution sounds like a simple "No Brainer" with the elimination of blow off a plus. I have an oven for a dry.  

Bob K.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Sunday, February 05, 2012 2:55 AM
To: [log in to unmask]
Subject: Re: [TN] Is 99% USP IPA what most folks use?

In the cleaning machines I used to make, we had a dosing pump that permitted 0-10% IPA added to the open circuit DI rinse water. We recommended commercial 99.5% grade, easily and cheaply obtainable in Europe. Excellent results.

However, I feel you may be barking up the wrong tree. This does not significantly aid drying because the alcohol azeotrope evaporates first, leaving just the water. Don't forget that the residual water will be in the places where you least want contamination, so you will have the most contamination round the solder joints where the capillaries are smallest.

It doesn't matter two hoots what the impurity levels in water or IPA are. What counts are the contamination levels on your assembly at the end of the day and the nature of these contaminants. It is up to you to qualify the reliability of the final product under the conditions of use, not to worry about whether Lake Michigan is polluted and with what.

Brian

On 05/02/2012 02:24, Robert Kondner wrote:
> Hi,
>
>
>
> I was reading through the Ellis book on cleaning and I noticed adding 
> IPA to water reduces surface tension.
>
>
>
> Neat, I figure that is a simple way to improve a rinse. I was planning 
> on final rinse with distilled water so I don't need to bother with 
> blow off as much.
>
>
>
> Just for fun I looked into various grades and it looks like dissolved 
> materials is about .005% or 39mg / Liter. (1 L = 780gram)
>
>
>
> Hmmmm, That sounds rather high compared to distilled water. I mean 
> Lake Michigan is 170 mg/L I think.
>
>      (See:
> http://www.aquapurefilters.com/contaminants/163/total-dissolved-solids
> .html)
>
>
>
> No one would think twice about dipping a cleaning swap into IPA to 
> clean a board. But Lake Michigan water? Holy Cow!
>
>
>
> Did I find the wrong specs on the IPA?
>
>
>
> Bob K.
>
>
>
>
>
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