Interesting. If I do go ahead with this method it looks like the safest way would be to select a particular pen from a particular manufacturer, then carry out the conductivity testing suggested by Brian Ellis and hope that the manufacturer doesn't subsequently change the formulation. I doubt that for this sort of product they would inform their customers about a change. Could this be a potential product for a supplier of PCB assembly and rework accessories? 

Jenny

-----Original Message-----
From: Kevin Glidden [mailto:[log in to unmask]] 
Sent: 02 November 2006 13:22
Subject: Re: UV flourescent pens for rework identification.

I was very curious on this one, so I contacted the supplier of the UV pens I found from an internet search, and asked them if the pens were non-conductive.
This is their response:

----------------------------------------------------------------------------
----------
From: BLACK LIGHT WORLD [mailto:[log in to unmask]]
Sent: Wednesday, November 01, 2006 5:41 PM
To: [log in to unmask]
Subject: Re: Invisible Pens

Buy a one oz bottle and see if you can electricute yourself : )  I have no idea. 
This is the winner of the oddest questions we have received year to date.
Where do we
send the prize? I will say that we sell thousands of gallons a year for circuit board marking projects. Also for info our MSDS is on all products same page. Gook luck.

Thank You
Anthony
www.blacklightworld.com
www.germjuice.com
www.germaglow.com
[log in to unmask]
Fax 270 721-0073
Sales @ Service 270 524-5746

----------------------------------------------------------------------------
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Looks like the testing proposed by Brian is the only option to truly get the
answer!   Good luck!

Kevin


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Thursday, November 02, 2006 4:01 AM
To: [log in to unmask]
Subject: Re: [TN] UV flourescent pens for rework identification.

Why halides? All ionic contamination is bad, not just halides. If the UV ink is water soluble, there is an easy test: Take a small PP beaker, rinse it out several times with DI water, along with the probe of a conductivity meter, then fill with the best DI water you can lay your hands on (pref <0.2 µS-cm). Dip the felt of the marker in it and gently stir the surface with it (do not cause turbulence). If the conductivity remains ± stable, then have no fear, it's OK.

If the ink is alcohol based, you can do the same but use a ~50% solution of IPA/water and start with a conductivity of <0.05 µS-cm.

If the solvent is non-polar, you will have to scribble on a demonstrably clean PP substrate, allow to dry completely, and repeat the second test above, but immersing the sample in the IPA/water mix for, say, 5 minutes.

Remember to run a control sample without ink for all the tests to establish a baseline for comparison, as there will be a rise in conductivity from CO2 absorption.

Brian

Jenny Drake wrote:
> Thanks for the quick replies. From what you are saying it looks like I 
> will need to do some testing on a particular pen and ink to see if it 
> is suitable for PCB's. If I buy just a general UV marker pen it could 
> be chock full of halide ionics for example. Unfortunately I can't use 
> a washable flux, or ink as the assemblies can't be cleaned. The PCB is 
> part of a larger ceramic and stamped metal component, which has 
> several cavities that would be nearly impossible to get water, or 
> solvent out of.
> 
> Regards,  Jenny
> 
> -----Original Message-----
> From: Kevin Glidden [mailto:[log in to unmask]]
> Sent: 01 November 2006 21:04
> Subject: Re: UV flourescent pens for rework identification.
> 
>  http://www.blacklightworld.com/non%20porous%20pen.htm\
> 
> ???
> 
> Don't think this is made expressly for PCBs....not sure if it is 
> conductive or not...
> 
> Kevin Glidden
> Manufacturing Engineer
> Astronics Luminescent Systems Inc.
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
> Sent: Wednesday, November 01, 2006 3:22 PM
> To: [log in to unmask]
> Subject: Re: [TN] UV flourescent pens for rework identification.
> 
>         Hi Jen:
>                Use FluxMarker, P/N FM5WSO, a water soluble marker that 
> comes in different colors. It works well and comes off easily. I am 
> sure that you can find vendors through Google.
> 
>         Good Luck
>         Ramon
> 
> 
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Jenny Drake
> Sent: Wednesday, November 01, 2006 8:37 AM
> To: [log in to unmask]
> Subject: [TN] UV flourescent pens for rework identification.
> 
> Has anyone any experience using pens with ink that is invisible under 
> normal light, but shows up under UV for identifying areas of PCB's 
> needing rework?
> This would remove the need to place and remove stickers on the 
> components and PCB and be invisible to the end customer.
> 
> Various pens are on the market for to let you mark your property, but 
> there is no information that I've been able to find for their use on 
> PCB's.
> Ideally I would want one that has been shown to be safe for use on 
> electronics and have low ionic contamination.
> 
> Regards,  Jen
> 
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