[Noisebridge-discuss] flexible circuit board material works in wax-deposition printers!

Jake jake at spaz.org
Fri Oct 25 22:58:20 UTC 2013


Get some thin sheets of polyimide which have copper on one or both sides. 
Polyimide is a yellow polymer with a high melting temperature and is 
sometimes called Kapton. A common type of copper-coated polyimide is 
DuPont "Pyralux" material.

Pyralux sheets come in many different varieties of polyimide thickness, 
copper thickness and adhesive thickness (the "adhesive" is between the 
copper and polyimide holding everything together.) Copper thickness is 
given in oz per square foot, while adhesive and Kapton thickness is given 
in mil (1 mil =0.001 inch).

Pyralux LF7062 (pictured) has 1/2 oz Cu, 1/2 mil adhesive and 1 mil 
Kapton. This works OK but is a bit thin and crinkly for the printer to 
LF9120 has 1 oz Cu, 1 mil adhesive and 2 mil Kapton - seems to work best 
in the printer
LF9210 has 2 oz Cu, 1 mil adhesive and 1 mil Kapton - stiffer, but works 

Other options are double sided copper ( a sandwich of Cu/Kapton/Cu held 
together with adhesive) and a roughened surface, denoted by R at the end 
of the part number.

The roughened sheets and double sided sheet work OK. However, Pyralux with 
2 oz or thicker copper can be difficult to feed to the printer, especially 
if there is copper on both sides.

See if you can get a free sample from DuPont. Occasionally, Pyralux sheets 
turn up on eBay.

Cut the Pyralux sheets to 8.5x11 or 8.5x14 inches with scissors or a 
knife. Avoid smudging the copper with fingerprints or oil, which can block 
the etch solution later. To protect the printer, try to keep the edges 
relatively flat and free of burrs.

For direct printing on the copper film, locate a solid-ink printer. These 
are commonly confused with laser printers, but instead print melted wax. 
Unlike most inkjets, the wax makes a good protective layer for copper 
etching, and unlike laser printers, solid ink printers don't rely on 
locally charging the paper surface, which could be troublesome when the 
paper is replaced by a copper sheet.

Some models are Tektronix Phaser 840, 850, 860, and Xerox Phaser 8200, 
8400, 8500, 8560, and 8860. You might find one in an office. Most Phaser 
models are regular laser printers, so check under the hood for the solid 
ink blocks (pictured) if you're not sure.

If you don't have access to a solid ink printer, the "toner transfer" iron 
on method, using a laser-printed design, could replace this step.

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