My conductive pen is non-conductive.

[Topher925]

I recently purchased a conductive trace pen to make guard rings on a circuit board. The problem is that the conductive pen isn't conductive at all. It has higher resistance than the PCB itself. I've never used one of these things before. Is there something you have to due to make these things conductive or something? Does anyone know of a conductive pen that actually works?

Here's the pen I bought. http://www.newark.com/techspray/2505-n/chemicals-coatings-conductive-pen/dp/69K4414

 

[turbo]

Here's what you should try. Get a conductive-ink pen out of your kit and draw a line on an open space on a piece of circuit-board. Let the ink dry and check the resistance of the "trace" with your DMM. It should be very low, since the silver content of the ink (per manufacturer) is 85%.

The kits often contain "overcoat" pens that contain non-conductive coatings, though I'm sure that you are aware of that. Still if you grabbed an "overcoat" pen instead of a pen containing conductive ink, you would not be able to repair a break in a PCB trace with that.

 

[Topher925]

I already tried writing large traces on a PCB and measuring it with my DMM. I even put a 30 volts across a trace and no current was conducted. I then took a MegaOhm meter to another sample I tried and it was reading the same value as the resistance of the PCB.

The pen says "Conductive Pen" right on it I know its the right one. The ink looks like its just the polymer and Acetone with no silver in it. Its a dull light gray instead of a shiny silver. There is definitely something defective about the pen I think.

 

[turbo]

Anything in the instructions about agitating the pen before using so you have something more than just solvent coming out of the tip?

 

[berkeman]

Anything in the instructions about agitating the pen before using so you have something more than just solvent coming out of the tip?

That's what I was going to suggest. It should probably say something like "shake well before using". The silver may have all precipitated out at the end opposite of the applicator...

 

[Topher925]

I think I found the problem. Like both of you said, the mixture needs to be properly agitated. I originally took the cap off and stuck a paper clip in it to mix it up but this didn't work. So I stuck a paint brush handle all the way to the bottom and found solid silver. I'm going to try mixing it up some more but the silver seems to be in one big solid chunk. I guess the had been sitting on the shelf for quite some time. Maybe a little bit of heat will help things along.

 

[berkeman]

Uh, watch the heat stuff there, cowboy! The liquid is probably flammable...

So this is a can of the stuff? I thought it was a pen like in the picture you linked to. If it's a can, you can get a propeller mixer attachment for your drill at the hardware store -- they work the best for re-mixing paints and such.

 

[Topher925]

Its an actual pen and its made from plastic so I won't be putting a flame to it. I'll just through it in a shallow water bath and heat it up to about 50C or so. I'm mixing it using some thin metal rod. I put a blob of the stuff from the bottom on a PCB board and it is conductive and has a very low resistance. I just have to mix the stuff more evenly now and hopefully I will be able to start drawing traces.

 

[Granta1969]

These silver based pens contain mostly acrylic as the base and so you have to shake them really hard to mix-in that tiny trace of silver. I noticed the package your purchased contained something like 6 pens for around $29.99? Kinda fishy, considering that most of these silver pens run around $20 each for the same size pen. How much silver could they give you in six pens for that low cost? Not much.

Why not use a much cheaper product that will work just as good? Try something like The CircuitWorks CW2000 which is a Nickel Conductive Pen? Nickel is a pretty good conductor. I've seen them for $6 each. Since Nickel is much much cheaper than silver, they put a lot more into it so it should be a tad bit easier to mix.. These are also in an acrylic base.

And also, as another poster mentioned, try some experiments first to figure out the characteristics of the pen. Once you get a feel for it, it should come naturally.