Title: "Better Iron-On PCB Patterns"
Published: Sep 1993
Author: Alan Nishioka

Make single or double-sided PC boards in your own home with this modern method that takes advantage of computer-aided design and the laser printer to form a resist pattern that is transferred directly to the copper-clad circuit board blank. It is an alternative to other methods that have been used by hobbyists who want to make a few prototype boards for their own use.

The alternatives include the time-honored method of applying adhesive pads and fine-line tape masks directly to the circuit board as the etch resist or the use of ultraviolet-sensitive liquid or film resists and photographic methods for transferring the pattern.

The method described here is based on the use of copying machine/laser printer toner powder to form the resist areas to define the circuit board conductive pattern. The pattern is first drawn on the screen of a personal computer with the aid of easy-to-use circuit board design software. The pattern is then printed out on special film in a laser printer. The toner that defines the pattern on the film is then transferred directly to the copper-clad blank by the application of heat from a house-hold laundry iron.

That toner pattern that adheres to the copper becomes the resist pattern. The adhered toner is able to resist the action of the etchant that removes all of the copper cladding from the blank except that which is under the deposited toner.

The process is effective in making simple, single-sided boards, but it's merits really show up in the preparation of double-sided boards whose patterns must be accurately registered on both sides. The problem of registering both layers is simple compared with the task of trying to achieve the same results with adhesive tape resist masking or even photographic methods. This article assumes that you will be making double-sided PC boards.