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I never did the sticky-tape and photoresist circuit cards. But Radio Shack sold some circuit transfer-decals that you pressed onto your cleaned copper board, pr

by chiph 6y ago

I never did the sticky-tape and photoresist circuit cards. But Radio Shack sold some circuit transfer-decals that you pressed onto your cleaned copper board, prior to dunking it in the etchant solution. The trick was to remember that the order of the pins was reversed, since you were laying out the underside.

squarefoot 6y ago
I used the transfer decal method extensively for ICs/pads along with fine tip water resistant markers for traces. The trick that helped me a lot in avoiding errors was to redraw the circuit mirrored before writing it on the pcb, that is, with ICs having pin 1 on the upper right instead on the upper left. With time I learned to think the circuit mirrored and routed, so all my diagrams were drawn on paper very close to how they would appear on the pcb. Of course I mean a bunch of TTL/CMOS ICs, or one-two LSI max, and some transistors. Anything more complex would have been a nightmare to make this way, at least for me. Edit: The transparent sheets with pcb traces transfered on them are called "acetate sheets", made of the same material used in transparency projectors slides. They're used to transfer the drawing onto copper boards previously treated with photosensitive material via exposition to UV light, then the boards can be etched by the usual FeCl solution.
HeyLaughingBoy 6y ago
I actually started one level lower than that: in high school, those cost too much, but I discovered that a Sharpie made good, cheap etch resist :-) Later at my first job, we made our own prototypes in the basement. We had a giant Agfa stat camera that would take the 2x artwork and reduce it 50% onto clear film that we would use to expose photosensitive resist coated PCB and then etch. I really, really don't miss those days :-)
- Gibbon1 6y ago
  First job the draftsman would layout PCB's with tape and pads on mylar sheets And then we'd send those out to be reduced. Then to the FAB house who'd run some prototypes. All told the whole process seemed to take about 3 months from scratch. The couple of times I delt with homemade PCB's... janky. If I had to prototype something I'd buy vector board with plated through holes and then solder wire wrap wire to sockets. Quicker and almost as reliable as a professional PCB.
- p_l 6y ago
  Using sharpies for etch resistant drawing was common method described to me in electronics books from 1970s or so (German series by Dieter Nuhrman, unfortunately I don't know the original title, was sold in Poland as "Elektronika łatwiejsza niż przypuszczasz", literally "Electronics (is) easier than you thought")

by chiph 6y ago

squarefoot 6y ago

I used the transfer decal method extensively for ICs/pads along with fine tip water resistant markers for traces. The trick that helped me a lot in avoiding errors was to redraw the circuit mirrored before writing it on the pcb, that is, with ICs having pin 1 on the upper right instead on the upper left. With time I learned to think the circuit mirrored and routed, so all my diagrams were drawn on paper very close to how they would appear on the pcb. Of course I mean a bunch of TTL/CMOS ICs, or one-two LSI max, and some transistors. Anything more complex would have been a nightmare to make this way, at least for me. Edit: The transparent sheets with pcb traces transfered on them are called "acetate sheets", made of the same material used in transparency projectors slides. They're used to transfer the drawing onto copper boards previously treated with photosensitive material via exposition to UV light, then the boards can be etched by the usual FeCl solution.

HeyLaughingBoy 6y ago

I actually started one level lower than that: in high school, those cost too much, but I discovered that a Sharpie made good, cheap etch resist :-) Later at my first job, we made our own prototypes in the basement. We had a giant Agfa stat camera that would take the 2x artwork and reduce it 50% onto clear film that we would use to expose photosensitive resist coated PCB and then etch. I really, really don't miss those days :-)

Gibbon1 6y ago
First job the draftsman would layout PCB's with tape and pads on mylar sheets And then we'd send those out to be reduced. Then to the FAB house who'd run some prototypes. All told the whole process seemed to take about 3 months from scratch. The couple of times I delt with homemade PCB's... janky. If I had to prototype something I'd buy vector board with plated through holes and then solder wire wrap wire to sockets. Quicker and almost as reliable as a professional PCB.
p_l 6y ago
Using sharpies for etch resistant drawing was common method described to me in electronics books from 1970s or so (German series by Dieter Nuhrman, unfortunately I don't know the original title, was sold in Poland as "Elektronika łatwiejsza niż przypuszczasz", literally "Electronics (is) easier than you thought")