Chemotransfer for DIY PCBs

Making PCBs with the toner transfer method has been around since you could buy your traces at Radio Shack. There are a million techniques for removing copper from sheets of fiberglass, from milling to using resist pens, to the ubiquitous laser printer toner transfer. Here’s a technique we haven’t seen before. [Darko Volk] is calling this ‘chemotransfer’. It’s mostly a laser printer toner transfer process, but the toner is transferred from paper to copper with the help of a special mix of solvents.

This chemotransfer process is almost identical to the usual process of making a toner transfer PCB. First, the design is printed in reverse on dextrin-coated paper, the paper is placed down on polished copper, the entire assembly is sent through a laminator, and finally the board is etched with the chemical of your choice. The key difference here is a solvent applied to the copper just before the design is laid down. [Darko Volk] made a mixture of 25% “cleaning petrol” (benzene, naphtha, or gasoline, or some sort of light hydrocarbon, apparently), 5% linseed oil, and 70% isopropanol. This apparently aids in releasing the toner from the paper and sticking it down to the copper.

From there, the process is effectively a standard toner transfer process. [Darko Volk] is using a solution of sodium persulphate for the etch, and rigged a camera up to a CNC machine for the drilling.

This process can be expanded to two-layer boards very easily using a light table to align the layers of paper before placing them down on the copper. You can check out a video of the fabrication of a single side and double sided board below.

Thanks [Andrej] for the tip.

Filed under: chemistry hacks

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