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I teach Electronics and design electronic toys and gadgets.

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  • GWSC commented on synthdood's instructable DIY PCB using Liquid Photoresist 4 months ago
    DIY PCB using Liquid Photoresist

    I used a similar product in the 70's. It was a Kodak red coloured positive resist. We had a dipping system to make sure the coating was of a consistent thickness. It used a small motor gearbox to lower and then raise the PCB in to and then out of a tank filled with resist liquid. The tank was about 300hx300wx25d and was filled with the resist. We made a lid that fitted snugly when it was not in use to prevent evaporation and keep it sealed from UV light. The motor was designed so when you pressed the start button the PCB was lowered into the resist. Once it reached the bottom it began to raise the PCB. The motor had a speed control to adjust its operating speed, so you could control the speed that it entered and more importantly the speed that it was raised from the resist. By control...

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    I used a similar product in the 70's. It was a Kodak red coloured positive resist. We had a dipping system to make sure the coating was of a consistent thickness. It used a small motor gearbox to lower and then raise the PCB in to and then out of a tank filled with resist liquid. The tank was about 300hx300wx25d and was filled with the resist. We made a lid that fitted snugly when it was not in use to prevent evaporation and keep it sealed from UV light. The motor was designed so when you pressed the start button the PCB was lowered into the resist. Once it reached the bottom it began to raise the PCB. The motor had a speed control to adjust its operating speed, so you could control the speed that it entered and more importantly the speed that it was raised from the resist. By controlling the speed it was raised out of the liquid resist you were able to control the thickness of the resist. At a slower speed the resist coating was thinner, because the resist had more time to drain off the surface of the PCB. Raising the PCB more quickly would give less time for the resist to slide off the surface of the PCB and so the resist would be thicker.It gave very consistent results when adjusted correctly. After coating the PCB it was baked in an oven at 80 deg C, for 10 min. The oven was actually an incubator used for chemical cultures and incubating eggs. If you didn't have an oven you could leave the coated PCB overnight in a box or cupboard for the resist to dry (maybe your resist is similar).The downside is that both sides of the PCB were coated, so more resist was used and the PCB had to be made slightly larger, to enable 2 holes to be drilled along one edge so it could be attached by a couple of hooks to to the motor system.Before we designed the dipping tanks we simply used a soft brush to coat the PCB as evenly as possible before putting it in the oven. after doing this for awhile you got pretty good at it.Nowadays I use Kinsten pre coated positive resist PCB, which gives the most consistent results you could wish for..

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  • GWSC enrolled in CNC Class8 months ago