# How to remove Kapton polyimide film from Pyralux cupper sheet?

I want to etch Pyralux sheet and will follow this tutorial. The sheet I want to try is LF9120R and it is 1 oz of copper per square ft (or 305g/m^2). They describe the sheet as:

copper-clad laminated composites are constructed of DuPont Kapton polyimide film with copper foil on one or both sides, bonded together with a proprietary C-staged modified acrylic adhesive. All copper clad laminates are available with rolled, annealed copper or electro-deposited copper. In addition, both types are available with double-treated copper (nodules of electro-deposited copper on both sides of the copper foil). Double-treated copper, if used, eliminates surface preparation steps prior to resist or coverlay lamination.

After etching out the copper off, removing the vinyl from the sheet, I want to remove the Kapton polymide film as well. Any suggestions what I can use to remove it?

UPDATE Yes, it is exactly what I want. I know it is going to be fragile, and will have no support.

• so that you just have unetched copper foil? That's going to be super fragile – W5VO Mar 9 '16 at 18:33
• that is exactly what I want and need – KingsInnerSoul Mar 9 '16 at 18:38
• Copper foil and a laser cutter. Or normal resist, no art, on the backside of plain foil - simple solvent removal of resist on both sides, at least for the process I used to use. – Ecnerwal Mar 9 '16 at 18:39
• I think @Ecnerwal has it right. Start with just the foil; that way you won't have any substrate to remove. You'll need to add resist (or matching art) to the back of the foil. – bitsmack Mar 9 '16 at 19:37
• As others have correctly read, I am proposing not using the kapton film product at all. If the end product you want is 1 ounce copper foil, start with that, and either directly cut it, or directly etch it, requiring respectively removing nothing, or removing resist only. Practically speaking, you might want something a bit heaver than 1 ounce copper, though. – Ecnerwal Mar 9 '16 at 21:16

A Dupont rep replied back with:

Attached a method to etch the Kapton but the problem will be to remove the Pyralux LF adhesive which holds the copper onto the Kapton. There isn't a good way to remove this adhesive.

Also, as I cannot attach PDF documents here - I am adding a screenshot of "Faster Caustic Eteching of Kapton H, E, and KN Types":

In addition, I found a thesis written by `Gordon Michael Coutts" where he modifies the above formula as follows:

bulk material is etched from the Kapton substrate using 9 wt. % KOH in a solution of 80 wt. % ethanol and 20 wt. % water. The static etch time is 15 minutes to remove 3.5mil of Kapton as shown in Figure 4.18e. Upon completion of etching, the substrate must be rinsed under flowing DI water for at least 5 minutes to remove insoluble reacted material [85]. The substrates must then be baked for 30 minutes at 100ºC to remove moisture absorbed during the etch process [page 102 or 120/203]

to sum things up, DuPont's paper states that 0.4mil (6mils over 15 minutes) of Kapton is etched per minute when using 6% KOH with 80/20 ethanol/water ratios @ 70C. While David's formula etches 3.5mils of Kapton in 15 minutes when using 9% KOH instead of 6%.

• Thanks for letting us know what you found! I'll remember this in case I ever need to dissolve Kapton :) – bitsmack Mar 10 '16 at 17:31

As I read that description, thte Kapton polyimide film is the body or substrate of the board (what would be fiberglass in "normal" boards). If you remove that, you will just have your copper tracks and pads, with nothing to support them.

• that is exactly what I want – KingsInnerSoul Mar 9 '16 at 18:38