Re: [EE] Carbon Ink PCB Insulation Issues?

It could be because the insulating material is carried in a solvent that is dissolving some of the conductive material.

If the two materials are from the same manufacturer and designed to work together, it should not happen when the materials are used strictly according to directions.

So I would think there are a couple of likely possibilities- the two materials are incompatible or the directions are not being followed. Maybe there is a bake cycle that is not being followed or maybe the materials *are* supposed to be compatible but they have added an unauthorized thinner that is incompatible. 

Just an educated guess..

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> On Nov 1, 2025, at 6:20 AM, Jason White <[email protected]> wrote:
> 
> I've got a commercial application where an overseas "PCB" manufacturer is
> attempting to manufacture low cost carbon ink membranes (very similar to
> snap dome switch membranes but repurposed for a niche application that uses
> its flexibility) with 2 layers of carbon ink separated by an insulating
> layer PCB photo resist.
> 
> A curious problem that they keep running into is that their insulating
> layers are conductive, but only overtop of the carbon traces! Even after
> moving from one layer of photoresist/ink to two layers the test coupons
> they produce often measure 1-10kohms between overlapping traces
> separated by two layers of insulating ink.
> 
> They appear to use standard silkscreen printing methods and standard UV
> cure PCB photoresist.
> 
> I was wondering if any of the veterans on here (those that are left) might
> have any insight.
> 
> The only thing I can think of is that carbon dust might be
> contaminating/transferring/sticking through the thin layers of insulating
> ink/photoresist they deposit on the PCBs.
> 
> --
> Jason White
> --
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