Radio-Electronics imageTitle: "Printed Circuit Update"
Published: Aug 1992
Author: Don Lancaster

Toner is the magic powder used to create the final hard copy images in today's copiers and PostScript laser printers. Until recently, it was absurd to even suggest that toner could ever be "as good as" real printer's ink. Or as cheap, versatile, durable, or colorful.

From time to time in the past, we have looked at the new direct-toner method for making printed circuit boards. The new direct-toner method promises to revolutionize hacker PC boards, doing the job in minutes for pennies with zero darkroom work or other special techniques.

The two key secrets to the direct-toner method are that laser-printer toner does make an outstanding etch resist, and that the great PostScript computer language makes printed circuit layout exceptionally fast, fun and easy to do. From any computer, using nothing but your favorite word processor.

One early transfer film sheet was TEC-200 film from Meadow Lake. Sadly, many hackers swore at this new product, rather than by it. Even though many of the partial-transfer problems were caused by improperly cleaned boards, no doing a pre-etch or pre-heat, by using an old copier (instead of an SX laser printer), and trying to use an iron (instead of a Kroy Kolor machine or suitable heat press of some sort). As we saw last month, a very much improved transfer film is now offered by Technics, Inc as PCBF-1000, Both of these products suffer a common flaw; They both expect a "differential transfer" to take place reliably in the real world. You first ask all of your toner to stick loosely to the transfer film. Later you expect all of the toner to adhere strongly to the board, leaving zero residue on the film.

The differential transfer problem has been solved in spades by a brand new "Toner Transfer System" offered by Pulsar. The system is basically a polyester film coated with some high-tech sugar water. There are two different ways to use the film, called "cold method" and the "hot method". Both methods open all sorts of new hacker opportunities.

The hot method is best for hacker circuit boards. With the hot method, you will laser print a backwards but positive image. As with the previous films, you then iron the toner onto a super-clean bare printed circuit board. You now have toner that is very tightly stuck to both the PC board and the paper.

Soak the board in warm water for a few minutes, and all the -tech sugar water dissolves, floating away the backing sheet and leaving pretty near all of the toner on circuit board nearly all of the time. [This reference to "nearly" has been improved to "all" of the time with our improvements to our techniques over the years]. Gently wash the board in warm water to remove any residue. Then etch as usual.

The cold method is best for circuit-board component-callout overlays, dial plates, and ordinary decals. Print the normal and positive image to the paper. Then spray the image using several light coats of a clear lacquer, urethane, or epoxy. Cut out all your images slightly oversized and soak them in warm water. Then transfer the images just as you would any model-railroad decal. You can either remove the lacquer with alcohol to get at the bare toner, or add additional and more protecting clear sprays for extra durability.

Those cold method results look especially impressive when you use a color copier. Note that you can now transfer toner onto anything. For the first of our two contests this month, just show me something new, different, or off-the-wall that you can do using either the not or cold method of this transfer system. As this month's resource sidebar, I have gathered together a few of the better known direct-toner resources.

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