ITO (Indium Tin Oxide) Coated PET Plastic

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chi86
 
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ITO (Indium Tin Oxide) Coated PET Plastic

Post by chi86 »

Hello,
I wanted to ask if there is any kind of data sheet for the ITO coated sheet. I would be interested in the max. temperature this foil can stand. Is there any knowledge about the deterioration when it is in contact with a fluid?

Thanks!

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adafruit_support_mike
 
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Re: ITO (Indium Tin Oxide) Coated PET Plastic

Post by adafruit_support_mike »

I'm afraid we don't have any datasheet for it.

The temperature limits of the plastic will be significantly lower than the limits of the ITO. The film is Polyethylene Tetraphthalate (PET), which is the same stuff used in soda bottles. Its actual melting point is about 250C, but it gets pretty floppy above 150F.

The strength of the ITO coating will also depend mostly on the strength of the plastic. The conductive layer is only a few microns thick, so it doesn't provide any mechanical protection.

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chi86
 
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Re: ITO (Indium Tin Oxide) Coated PET Plastic

Post by chi86 »

Thanks for the information!

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chi86
 
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Re: ITO (Indium Tin Oxide) Coated PET Plastic

Post by chi86 »

I would have an additional question: Is there any current limit which i can apply to the foil? Or anything else I should keep in mind?

Any help is greatly appreciated! Thanks!

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adafruit_support_mike
 
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Re: ITO (Indium Tin Oxide) Coated PET Plastic

Post by adafruit_support_mike »

The sheet resistance of the ITO is about 50 ohms.

The physics of resistance depends on the length and width of the current path. If you make the path twice as long, the resistance doubles. If you make the path twice as wide, the resistance falls to half. If you make the path twice as long *and* twice as wide, the changes cancel and the overall resistance stays the same. That makes resistance a 'size invariant' property of matter.

So once you've scraped away (or cut) the plastic to make separate conductive paths, you can estimate the resistance of each path by laying the sheet over a piece of graph paper and finding the largest squares that will cover each part of the path. Each square will be equivalent to a 50 ohm resistor.

In most cases, the total path resistance will be high enough to keep the current at manageable levels. You can get short circuits by putting two large conductors close together and laying the ITO sheet across them though. That happens when people forget to use a current limiting resistor for one of the circular soft pots: viewtopic.php?f=1&t=57762

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chi86
 
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Re: ITO (Indium Tin Oxide) Coated PET Plastic

Post by chi86 »

Thanks! Now it is clear!

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