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How to Make a Mylar Circuit Board

Mylar is a thin plastic polyurethane plastic film, similar to cellophane. Mylar is just one of several brands of a similar product. The film is frequently used to coat and preserve identification cards, in food packaging, as a laminate over paper or to insulate electrical components. Because it doesn't conduct electricity well, it is frequently used to coat circuit boards. The board itself isn't made of Mylar, but Mylar serves as a protectant and insulant.

Things You'll Need

Mylar adhesive sheet or laminate
polymide sheet, copper coated, less than 2 mm thick
acid resistant container, large enough to hold circuit board
muriatic acid or ferric chloride
schematic drawing
blank circuit board
solid-ink printer or ink pen, thick

Instructions

- 1
  Obtain the schematic for the electric circuit or device you are trying to make. The schematic will detail every electrical component in the device, along with how they are interconnected. However, instead of using wires, you will connect them through conductive metal strips fastened to the circuit board.
- 2
  Select a circuit board. This is the stiff mounting base, usually green or gray in color, that you fasten the electrical components to. It should be large enough to house all the components in the circuit without them touching one another, which could cause a short circuit, malfunction and possibly even fire. The schematic may include a suggested dimension for the circuit board.
- 3
  Cut a sheet of conductive foil, such as polymide, the size and shape of the circuit board.
- 4
  Mark out the connections on the polymide sheet by covering the copper or other conductive material with solid ink. You can do this manually, using a sharp-tip marker or similar ink pen, or you can use a graphics program to design the connections and use a solid ink printer to print them directly on the polymide.
- 5
  Douse the polymide in a corrosive solution such as muriatic acid or ferric chloride for five minutes. This will eat away the exposed copper, but leave the copper under the ink in place. The wiring, then, is automatically etched in the surface of the polymide.
- 6
  Fasten the etched sheet of polymide directly to the top of the circuit board. However, for some applications, you don't need the circuit board.
- 7
  Spread an adhesive Mylar coating over the circuit board. Alternatively, you can slip the unmounted sheets of polymide through a laminator and coat them in Mylar. If you don't have a laminator, you can apply the Mylar by covering both the Mylar and the board with a towel and pressing down with a hot iron. That will add a layer of Mylar protection to the entire surface of the circuit board.
- 8
  Solder the electrical components in place according to the schematic. Ensure there is a good mechanical connection between the leads of the components and the conductive strips on the polymide.

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