Material For Wide Area Resistive Layers

No. Thick film inks are finely ground metal oxides mixed with finely ground low-melting glass - heat the ink enough to melt the glass and you've got your resistive thick film.

In principle you could replace the glass with epoxy resin or some low- melting thermo-plastic (like wax), but I don't know of anybody who has done it.

-- Bill Sloman, Nijmegen

Antistatic foam, or antistatic plastic bags, or, if you can still get them, the antistatic chip carriers which single DIL ICs would often be supplied in.

Worth a try, but only because it's easy.

Cheers

As a start, you could calculate the needed resistivity then search for materials.

For A=3D30mm^2, l=3D3mm, and R=3D1K, /p/=3D100 ohm-meters.

Maybe carbon-load some wax, or silicone? Or clay? Or plaster?

-- Cheers, James Arthur

carbon Graphite, Charcoal ?

Jamie

Can't you read? He's tried carbon fibre and the resistance was still far too low. Even a one atom thick layer of carbon is too conductive for a lot of purposes.

-- Bill Sloman, Nijmegen

e_

But carbon composition does go high in the resistance range. So I guess the approach is to use a lot less C, and try to ensure the current takes a very wiggly path. Perhaps produce a solid block with a low carbon content, grind that up and use it instead of pure C powder in your inky layer.

NT

Use 0402 resistors, I guess around a hundred in parallel. Conductive epoxy them to one electrode end-on, then glue on the other electrode.

No, that's just silly. Can you give more detail?

Cheers

I spoke with a guy whose parents used to bake composition resistors in their kitchen. I didn't get the recipe.

There is that carbon foam-like material that Jameco sells but that may be too low in resistance - but if it is skived (cut is parallel to surface to make thinner) that might get in your ballpark. There are conductive plastics of all kinds of resistivities available as well.

ire_

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e.

The problem is that as you raise the target resistance it gets progressively more difficult to hit the progressively narrower gap between mix giving you a sufficiently wiggly path to give you the resistance you want and a mix where the paths never actually connect.

When we ran into trouble with using a single atom layer of carbon, it wasn't because we couldn't get the resistance we wanted, but rather that the people laying down the carbon got peeved about frequently making the layer too thick and having to strip it off and start over.

-- Bill Sloman, Nijmegen

I suspect a salty bread recipe with glue and a pinch of carbon would work :)

NT