# Ampacity of Conductive Tape

How do I measure ampacity of conductive tape? I want to replace a wired battery to equipment connection with copper adhesive tape because I need a very low profile on the connection.

The maximum current will be 200mA, max voltage 14V. Would standard copper adhesive tape be capable of carrying this current? Length of connection will be 4cm, width of copper tape track will be 1cm.

Like this one for example: https://ie.farnell.com/3m/1181-12mm/foil-shielding-tape-adhesive/dp/1653450?st=copper%20foil%20tape

• Note that the linked tape has electrically conductive adhesive - whatever you stick it to will be electrically connected to it. – rdtsc Aug 8 '19 at 19:28
• Are you intending for the adhesive to carry 200mA? – Spehro Pefhany Aug 8 '19 at 20:00

Your tape's datasheet mentions a resistance of 5 mOhms per square. This means a square of any dimension will have a resistance of 5 mOhms between its opposite sides.

The way to use this specification is to count how many squares are in the length of your tape. Since it is 12.7mm (half inch) wide, a length of 50mm (2 inches) is 4 squares, each a half inch. Thus the resistance of 50mm of tape is 20 mOhms.

This will be fine for 200mA, the tape will dissipate less than 1mW).

Note you can get this tape for much much cheaper on ebay. Try "slug tape" or "guitar pickup shield tape" or just "adhesive copper tape".

• Is the adhesive similar to the 3M tape for the cheap stuff? – Voltage Spike Aug 8 '19 at 19:05
• The rolls I got do stick very well, even when soldering on it. Likewise, I got some cheapo kaptan tape (Chinese ripoff of Kapton), pretty good. But as always with cheap stuff... YMMV, no guarantee! – peufeu Aug 8 '19 at 19:11
• I'm not thrilled with the breakabilty of the cheap kapton. It doesn't come off the rolls well. – Voltage Spike Aug 8 '19 at 19:13

The thickness is 0.0026in and 0.5in wide. This means it has a cross sectional area of 0.00115in^2 which corresponds to AWG18 or AWG19 wire. So if the resistance is the same (which it should be pretty close if both are made from copper) then it would be acceptable to compare the cross sectional area.

Powerstream says 14A is the max, but it really depends on how high temp is acceptable for your application. I'm willing to bet copper tape will dissipate heat to air (or metal) more readily than a wire, and could possibly tolerate more current than 14A

A 12.7x0.04mm, 0.508mm2 copper section, should be similar to a 20 AWG cable, 0.033 $$\\Omega\$$/m, with a 5.0 A Ampacity (NFPA tables, 90 deg., Single Conductor, Insulated Ref.3).

Assuming the 12.7x0.026mm, 0.3302mm2 acrylic conductive section have less than 50% conductivity of copper, we could safely assume the tape is similar to a 19 AWG cable, with a 6.0A Ampacity (Interpolated, NFPA tables).

As reference, the NFPA ampacities are more conservative than the NEC ampacities, i.e. a 12 AWG cable has 20 A Ampacity (NFPA) vs 30 A (NEC) for 90 deg.

Remember those ampacities are for single conductor, insulated. In this case the conductor is "half insulated", which should give an additional margin.

• Where are you getting your ampacities from? 22AWG is often rated as being able to carry up to 8A in the materials I have seen. so 1.8A for 19AWG seems very very low. – DKNguyen Aug 8 '19 at 19:20
• Edited. I would better stick to NFPA, which states 3A for a single insulated 22AWG conductor. 8A for a 22 AWG cable could not be a safe estimate. Remember NEC ampacity for 12 AWG is only 30A for 90 deg, which is 10 times the section of a 22 AWG cable. – Brethlosze Aug 9 '19 at 4:04

200mA is nothing. Should be fine. But if you really want to measure ampacity then run enough current through it until it the adhesive gives out, something melts or burns, or is too hot for your liking. Whichever happens first. That's really all ampacity comes down to. It's dependent on a lot on operating conditions and what you are willing to put up with.

Or if voltage drop is your limiting factor then run enough current through it that your voltage drop is more than you can tolerate it.