Today's commercial PCBs employ sophisticated design tools and manufacturing techniques, but some hobbyists still delight in making DIY boards.
In 1958, my parents emigrated from London to the then Rhodesia (now Zimbabwe). I was two years old. Rhodesia was a lovely country to grow up in, but later I got interested in electronics, and it has to be said that Rhodesia was not the center of the electronics universe.
When I was around 14 years old, my dad used to buy me Practical Electronics magazine every month. Therein I found an advert for a Do-it-Yourself (DIY) kit for printed circuit boards (PCBs), so I got one of my doting relatives in the UK to buy me one for Christmas. The kit consisted of a few bits of single-sided PCB that were about the same size as those oversized postage stamps from tiny island nations; a "Decon-Dalo" pen, which was a bit like a felt tip pen, whose function was to dispense etch-resistant ink onto the PCBs; a miniscule packet of Ferric Chloride etchant crystals; and a few pages of "projects" with accompanying PCB layout diagrams.
The entire kit came in such a small box that I felt a little cheated, but I got to work and started to produce some PCBs. The Decon-Dalo pen produced tracks with a minimum width of around 1.5mm (a bit bigger than 1/32 inch) and if you tried to draw a pad with a hole in the middle, it would end up about 4mm in diameter. Any smaller, and you had to scratch a hole in the middle with a pin. If you used transistors, you had to leave the leads long! Nevertheless I did make a few PCBs with the kit and I was hooked.
Later, while I was still at school, I discovered Positiv20 -- a German-produced aerosol for coating a PCB with a photosensitive layer. I had to dry my PCBs in mum's oven set very low. Using a positive transparency, you could then expose your PCB.
The Positiv20 literature recommended various ultraviolet (UV) lamps, but -- following the advice of a friend -- I found that five minutes in sunlight worked just fine. You then "developed" your board in a 7-grams-per-litre solution of Caustic Soda (a.k.a. Sodium Hydroxide, a.k.a. "Mum's drain cleaner"). You then had a board with a light green pattern of tracks on it ready to etch. But therein came my next problem -- I could not find a source for the ferric chloride I needed for etching.
Fortunately, my physics teacher was "into" electronics and was my "goto guy" for all problems electronic. He told me how to make my own etchant. You started off with yellow hydrochloric acid (HCl), which was easily available as swimming pool acid (we all had swimming pools). You dissolved some old nails in this, resulting in a light green liquid that was ferrous chloride (FeCl3). You then added some hydrogen peroxide (H2O2), which was readily available from chemists (girls used it to lighten their hair). This, by a mystical bubbly reaction that I've forgotten, produces ferric chloride (FeCl2), which -- at least in my case -- was dark brown, smelled vile, and -- probably due to residual hydrochloric acid -- ate holes in my clothes. This lasted forever and never seemed to lose its potency. My mother set aside my oldest clothes as the only ones I was allowed to wear for my PCB production exploits. I had, by then, acquired a couple of fine-tipped drawing pens and could produce my own transparencies, which meant I got far better results than from the Decon-Dalo pen.
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