EMI shielding tape - embossed or conductive adhesive? - Page 1
Forum section: electronics / general

author: e100
author_rank: Frequent Contributor
timestamp: August 29, 2018, 07:57:14 am
content: I'm trying to ground the chrome plated pole pieces in a guitar pickup and not having much luck with copper tape that has conductive adhesive. My suspicion is that the conductive spheres embedded in the adhesive are too widely spaced so the narrow 2mm x 60mm contact area is missing all of them. The adhesive is definitely conductive to some degree as I can drag a smooth piece of wire across the adhesive side and hear my continuity tester make a sound.Does anyone know if the embossed type of shielding tape like this 3M typehttps://multimedia.3m.com/mws/media/37376O/tape-1245.pdfis likely to work better with thin contact areas. My limited understanding is that the copper has been punched through from the cooper side so that you effectively get a 'through hole' like on a through hole plated PCB, except there's no plating. Unfortunately the datasheet doesn't tell you the pitch between the holes.

author: Munsterfield
author_rank: Newbie
timestamp: August 29, 2018, 06:56:46 pm
content: What makes you say that you are not having much luck with grounding the pickups? Are you measuring the resistance, and it isn't what you expect, or are you trying to solve some sort of EMC problem and the copper tape isn't resolving it?

author: Ian.M
author_rank: Super Contributor
timestamp: August 29, 2018, 08:23:31 pm
content: A picture against a graduated background like graph paper would be worth a thousand words.

author: e100
author_rank: Frequent Contributor
timestamp: August 30, 2018, 03:22:58 am
content: Quote from: Munsterfield on August 29, 2018, 06:56:46 pmThere's no electrical continuity (> 20 Meg) between the copper tape and the pole piece. The purpose of grounding is to reduce the level of mains related capacitively coupled interference.

author: e100
author_rank: Frequent Contributor
timestamp: August 30, 2018, 03:39:52 am
content: Quote from: Ian.M on August 29, 2018, 08:23:31 pmIt's a ceramic bar magnet sandwiched between two chromed steel plates surrounded by a plastic housing.In this picture one of the two poles is partly covered by copper tape.The wires at the ends are connected to the two coils in the pickup.

author: Ian.M
author_rank: Super Contributor
timestamp: August 30, 2018, 05:00:34 am
content: I'm assuming there isn't any (or not enough) core surface exposed underneath.I think a little fillet of conductive silver paint between copper tape flat on the face of the coil former butting up to the chromed core, and the chromed core itself would do wonders. Key the surfaces first with a fibreglass pencil and locally degrease with a Q-tip loaded with solvent.

author: MudAndSnow
author_rank: Contributor
timestamp: August 30, 2018, 03:12:59 pm
content: Wasn't able to view your pictures so not sure if these would be a good fit but these shield clips might be worth a look.https://www.digikey.com/catalog/en/partgroup/ez-shield-clips/36327Solder those on then push on a shield. If dk doesnt have a suitable shield, try your local hobby / model / hvac / hardware store for thin sheet metal and cut and bend shields to fit. You could do that without the clips by soldering your shield but then its harder to remove the shield.I havent tried the clips yet but I recently tried foil tape and bent and soldered sheet metal on a 4GHz project. The tape worked ok when wrapped all the way around and pushed tight but the sheet metal worked great.