Rubbery conductive 'ink'

Try asking these people:

Most of their products last much longer if kept in a fridge or ideally a freezer.

There are pre-formed EMI gaskets available for this. Google "conductive elastomer"

Thanks, it's going to be a complex structure so if I used a preformed conductive elastomer gasket I'd have to get it CNC cut and it would be kind of a spider web .. not sure that would work unless it could be CNC knife cut onto a substrate that remains intact until it's applied. I've gotten non-conductive gaskets cut other ways (including water jet) but that won't work.

--sp

do a search on "conductive caulk"

Tradename BARE conductive ink, used for laying conductive tracks on textiles etc, so presumably somewhat flexible, but conductive enough, bulkable enough?

On Sun, 29 May 2016 09:15:13 +0100, N_Cook Gave us:

It is so that it will not crack when flexed and become discontinuous.

Yes, but they'll be narrow walls between so I don't think handling it would work.

This sort of thing with the board sandwiched between two machined pieces:

Couldn't you separate sections into regular shapes?

Internal requirements differ from those exposed to the external environment, so it might be possible to split that function, as well.

RL

So the gasket has to allow for the entire board's thickness? I don't think that is normally expected of an EM gasket. Normally the case will mate with an added provision for gasket placement within the wall edge.

You should decouple board mounting function and case seam function.

RL

No, it's to fill a gap (which I will specify) between the board and the sealing wall (on each side of the board).

I'm lost.

It's the wall or it's the seal. The board can't provide a seal, though it might be wedged into it, in non-critical locations.

You can gasket the board-edge to the wall (why?) or gasket the seal to itself.

Either could use leaf-spings, which would do a better job for EMC than an elastomer.

RL

I'm not explaining this very well, obviously.

Suppose you invert an ice-cube tray on a PCB. The same on the bottom of the PCB. The board is the size of the whole tray. Wherever the wall is (each compartment), you have a bare gold ground ring with stitched vias through. The board and walls won't be perfectly flat so there needs to be some compliance to get complete contact.

So imagine maybe a nominal 0.01" of gap filled with 0.015" of conductive rubbery gasket stuff down the middle that squeezes a bit to reduce the gap to the mechanically imposed 0.01". Result is many EMI-sealed compartments. In my case, the compartments will be irregular shapes.

It's the flat surface of the board on both sides, not the edge.

How about a dispensed conductive gasket

It adds another process step but has the advantage that it is guaranteed to stay in place during assembly.

Perfect! That's the stuff - and Laird is the source for the material.

Thanks, Reinhardt.

--sp