Richard,
Can you weight it or do we just guess and make assumptions?
Got Scale?
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Monday, January 09, 2012 9:45 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble flux
Hi, Bob
I can assure you that the amount of water retained on a CCA after blow-off is very significant.
Water is trapped inside of connector bodies, underneath all flat components, and many other places that cannot be blown dry. Blowing boards with air may get most of the visible moisture off of the board, but leaves a lot of water behind. In addition, even a grounded blower unit can build up a charge of over 250 volts, enough to damage many ESD components. Blow-off is also somewhat expensive because it is time consuming and you need a pretty good compressor running almost at a 100% duty cycle. Also, almost all compressed air has some oil or other contaminants in the line.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Monday, January 09, 2012 7:35 AM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble flux
Terry,
You pooh-pooh tap water but failed to state two important parameters:
1. Dissolved content in tap water. Let's assume it is all ionic in nature. (500mg / L Seems like worst case)
2. Amount of water that remains on a board (average per sq. inch) after blow off.
I would love to see the results of a test as you propose. Let us not argue like CAD Monkeys, let us do an experiment.
I would ask that you weight the PCB after the final blow off of tap water and then after a hot air dry, the difference being retained tap water residue. I am very curious as to the weight of tap water contained on a board after blow off. That should directly relate to final ionic residue and water ionic content.
I do not have a scale here that is sensitive to where I can measure the difference. I hope you do.
Does ANYONE on this list have a PCB, water, air gun, oven and sensitive scale?
Can anyone suggest a sensitive scale I can buy for not too much money? Is so I will buy one and test.
Thanks,
Bob Kondner
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry Munso
Sent: Sunday, January 08, 2012 10:51 PM
To: [log in to unmask]
Subject: Re: [TN] Cleaning water soluble flux
I find it interesting that the use of tap water is still being proposed. Let's look at the residues in tap water in industrial regions. High levels of chloride, sulfate and and sodium and processing through sand filtration creating soluble silica globules that hold concentrated pockets of contaminants. This approached worked with rosin based fluxes in the 90s. But lets look at the level of circuit sensitivity of today's hardware (where a half meg ohm drift will shut down a critical circuit and maybe the entire system) and the effect of residues that are moisture absorbing and conductive are creating performance problems. I propose that we run a series of evaluations comparing tap water, to RO water to DI water. Then i propose that we evaluate the results by ion chromatography using both the C3 localized extractions and bag extractions of our Umpire 2 SIR test board. Using the IPC SIR conditions of 40C/93% with continuous monitoring to assess the residue effects. Oh yes it's true that the resistivity drops to nothing but not due ionic contamination that is found in tap water but the absorption of CO2 that has no residual effect on the active circuitry. Oh and if you paid attention I suggested the the board be rinsed with DI water steam and not tested in my lab so how much simpler can that be.
Terry Munson
Foresite Inc
765-457-8095
On Jan 8, 2012, at 8:11 PM, "Robert Kondner" <[log in to unmask]> wrote:
> Before you go through the expense and effort of doing DI to clean and
> rinse try doing a tap clean and rinse WITH a blow off cycle. Have some
> ionic contamination tests run afterwards, they will be very clean if
> you have a good blow off.
>
> Washing with Di water is kind of silly, how long does Di water remain
> DI after a wash of dirty boards start? Maybe 100 ms? Wash with tap.
>
> Rinse in DI might help but a blow off of tap water leaves only tiny
> amounts of material even with very hard tap water. It really depends
> on water entrapment issues and then even a rinse is questionable.
>
> Try something simple and measure.
>
> Bob K.
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Terry Munson
> Sent: Saturday, January 07, 2012 7:44 PM
> To: [log in to unmask]
> Subject: Re: [TN] Cleaning water soluble flux
>
> They should look at DI water steam to clean and rinse. We have
> effectively cleaned 2331-ZX flux. With stop steam cleaning. Call me at 765-457-8095.
>
> Terry Munson
> Foresite
> 765-457-8095
>
>
> On Jan 7, 2012, at 6:36 PM, Gary Bremer <[log in to unmask]> wrote:
>
>> I am presently working as an contractor for the next few months then
>> back
> to unemployment, last place I worked was Jet Propulsion Laboratory on
> the Mars Science Laboratory. These are lighted panels for various
> aircraft and the company policy is for J-STD-001/IPC-A-610 Class 3 The
> failure is with miniature T-1 lamps that stop working after going through an baking process.
> Other boards that use these lamps but use RMA flux do not have this
> problem, I suspect the cleaning process and the flux. They do not
> check ionic contamination and handle the boards with bare hands and
> the operators even know when components are ESD sensitive or not. I
> have recommended they change the cleaning process to an Aqueous type
> batch cleaner but this cost money which they do not wish to spend.
> Their process person believes that their process is fine and something
> else is causing the problem (bad lamps, forming lamp leads, etc.). This goes against all my knowledge and training.
>>
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