Adding own insulation to copper foil?

Thread Starter

SiCEngineer

Joined May 22, 2019
390
Hello all,

First of all, does anybody know of any UK manufacturers of copper foil with included insulation? I have contacted a few companies and none seem to have any stock, and otherwise custom products require large lead times, some even 52 weeks which is not practical for my project.

Alternatively, I was considering buying some standard copper foil of 7mil thickness, and applying my own insulation to each side, something like https://www.digikey.co.uk/en/products/detail/3m-tc/1-5-1218/2649773. Is there anything wrong with this method? I'm fairly new to designing with foils and finding it really difficult to source the right stuff.

Cheers,
SIC
 

Ya’akov

Joined Jan 27, 2019
5,663
Polyamide tape has very good electrical properties for your application and can withstand much higher heat then you’d ever subject it to.

The only thing is you will be making a capacitor. It might be worthwhile to test a sample to see just how high the capacitance gets.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
390
Polyamide tape has very good electrical properties for your application and can withstand much higher heat then you’d ever subject it to.

The only thing is you will be making a capacitor. It might be worthwhile to test a sample to see just how high the capacitance gets.
Very good point. I did consider polyimide I just wasn't sure whether the adhesion process is something that is specialized or if I can just stick it on both sides and call it a day.

Regarding the capacitance - isn't this the case with every transformer coil, especially if it has insulation wrapped around it? I will definitely test the coil, but the insulation is so thin I hope I can get away with it. Furthermore the transformer is LCC topology so a higher capacitance is not the end of the world.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
390
How much voltage does the film need to withstand?
The primary is 20 turns or so and total voltage of 150V or so; it's not particularly to withstand voltage but to stop the turns from shorting against each other when the coil is wound since bare copper touching bare copper will short out the winding.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
390

Ya’akov

Joined Jan 27, 2019
5,663
Very good point. I did consider polyimide I just wasn't sure whether the adhesion process is something that is specialized or if I can just stick it on both sides and call it a day.

Regarding the capacitance - isn't this the case with every transformer coil, especially if it has insulation wrapped around it? I will definitely test the coil, but the insulation is so thin I hope I can get away with it. Furthermore the transformer is LCC topology so a higher capacitance is not the end of the world.
The tape you linked to is 3M polyimide tape.

Yes windings will have capacitance, but since you don't know the dielectric properties of whatever insulation you use, testing to be sure it isn't significant would be prudent For what it's worth I just made a capacitor with layers of copper tape 120mm long and 25mm wide with polyimide dielectric. It reads 494pF and its very stable.

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Thread Starter

SiCEngineer

Joined May 22, 2019
390
The tape you linked to is 3M polyimide tape.

Yes windings will have capacitance, but since you don't know the dielectric properties of whatever insulation you use, testing to be sure it isn't significant would be prudent For what it's worth I just made a capacitor with layers of copper tape 120mm long and 25mm wide with polyimide dielectric. It reads 494pF and its very stable.

Thank you for this. I think this is probably the best way to go, as Shortbus mentioned a conformal coat may not guarantee edges are not going to short, but a polyimide tape some width wider than the copper foil should be good enough for the job. 494pF, especially on the primary side, does not seem like a lot. If this was secondary high voltage winding I think the capacitance would be much more troublesome.
 
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