Copper foil is used for EMI shielding because it does two jobs at once: it reflects and absorbs radiated fields, and being conductive it can tie a shield to ground. The question that decides the price is almost never "copper or not" — it is whether the foil needs a plating, and which one.
Why plain copper foil is usually enough
Bare copper has the highest conductivity of the foils used in shielding work, and a pressure-sensitive copper foil tape is the cheapest way to line a cavity, wrap a cable or make a ground strap. The two things it does not do well are surviving humidity without oxidising, and surviving repeated rubbing. Oxide on the surface raises contact resistance exactly where a shield needs it lowest.
What each plating changes
Plating is a trade: you give up some conductivity to gain corrosion resistance, abrasion resistance or solderability. That is the whole decision.
| Foil | What the plating adds | What it costs you | Typical reason to specify it |
|---|---|---|---|
| Plain copper (rolled or electrodeposited) | Highest conductivity of the options here; solders directly | Oxidises in humid air; surface wears under rubbing | Cavity lining, cable wrap, ground straps, prototypes |
| Nickel-plated copper | Corrosion and abrasion resistance; stable contact resistance over time | Lower conductivity than bare copper; harder to solder | Foil that is exposed, handled or rubbed — battery tabs, shielding cans, gaskets |
| Tin-plated copper | Solderability plus corrosion resistance | Lower conductivity than bare copper; tin whisker risk on some finishes | Joints that are soldered and also see humidity |
| Gold-plated copper | No oxide growth, stable low contact resistance | Highest cost by a wide margin | Test fixtures, RF gaskets, small contact pads where resistance must not drift |
If the part is inside an enclosure and never touched, plain copper is the sensible choice. If it is a contact surface that gets mated, unmated and handled, the plating is buying you stability, not conductivity.
What we stock
We supply the plain-copper end of this list, as tape rather than as sheet:
- No.8323 — rolled copper foil, 0.07 mm, with a conductive acrylic adhesive, 25 mm × 20 m. Conductive through the thickness and along the surface, UL510 flame retardant. This is the tape for cavity lining, grounding runs and cable wrapping.
- No.833 — aluminium foil, 0.08 mm, 25 mm × 20 m. Shielding and heat reflection rather than current carrying.
We do not stock nickel-plated, tin-plated or gold-plated foil, and we do not list vacuum-deposited nano-carbon foil. If your drawing specifies one of those finishes, the tape above is not a drop-in substitute — the plating is usually there for a reason that plain copper will not meet.
Width, adhesive and the details that actually go wrong
- Conductive adhesive matters. A copper foil with a plain acrylic adhesive conducts along the foil but not through the adhesive layer. If the shield has to bond through the tape to the surface underneath, the adhesive must be conductive — No.8323 uses a conductive acrylic.
- Width is a wrap decision, not a shielding decision. A 25 mm roll wrapped at 50% overlap covers about 12 mm of run per pass. Narrower strips follow tight radii better; wider strips cover panels faster.
- Oxide is the failure mode. On bare copper, clean the surface before applying, and re-terminate ground points that have been open to humid air for a long time.
Questions
Is copper foil tape the same as EMI shielding tape?
In practice yes — "EMI shielding tape" in a parts list almost always means a copper or aluminium foil tape with a conductive adhesive. What separates products is the foil thickness, the adhesive's conductivity and the plating.
Can I use plain copper tape instead of nickel-plated?
Only if the foil is protected and not rubbed. Nickel plating is specified for corrosion and wear resistance on exposed or handled surfaces; plain copper will shield just as well on day one, but the contact resistance drifts as the surface oxidises.
Do you cut custom widths or die-cut shapes?
We stock 25 mm × 20 m rolls. For other widths or die-cut parts, send the drawing through the contact form and we will tell you what is possible — we will not quote a size we cannot supply.
Which side of the tape is conductive?
On No.8323 both the foil and the adhesive are conductive, which is what allows a wrap to ground through to the surface underneath. On a foil tape with a non-conductive adhesive, only the exposed foil face conducts.
See the copper and aluminium foil tapes we stock — or read the No.8323 copper foil tape specification.