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Printed circuit board manufacture

Printed circuit board manufacture

Robotics requires lots of control units for different peripherals. Man can buy them (mostly as shields) or create his own ones. The price depends on peripheral. Some of them are order of magnitude lower, some of them are on the same price level. Nevertheless, home-made peripherals provide much more fun and further improve abilities.

It is necessary to devote some time to study the peripheral before the design. I create the circuits in Eagle software. All the boards are designed from the TOP view. This is much more comfortable for me since I can design the board the way it will be mounted.

I print the design to the adhesive part of the adhesive paper using a laser printer. It is necessary to set black print and increase contrast if needed. You need a laser printer since it bonds the toner (powder) from the cylinder to the paper. The circuit must be printed as a mirror image to the BOTTOM view. Since I design the circuit from TOP view, I do not have to make this step. The circuit is transferred to the copper using the following steps:

  • Put a 1/4 cm of cloth to a solid surface. I personally use a towel.
  • Clean and degrease board thoroughly.
  • Snap the printed circuit to the copper using a 1mm stripe of tape.
  • Place the circuit on the cloth copper and circuit downwards.
  • Put clean folded paper on the top.
  • Heat up an iron to middle temperature. I use 2/3 (wool).
  • Put the iron on the paper and leave for 1 minute.
  • Weight the iron (4-6 kg) for another minute.
  • Let cool down to the room temperature.
  • Place inside a bowl with water until the paper starts to peel of itself.
  • Dry and fix potential mistakes using a permanent marker.

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Design in Eagle software
Printed circuit on an adhesive paper
Snaping to the PCB
Ironing the circuit on the PCB
Removing the paper
Ironed circuit

Prepare a container with ferric chloride. Put the board inside carefully with the circuit downwards and let I swim on the fluid surface. Thanks to the high tension of the fluid it stays there without any problems. I personally heat up the fluid using a classical bulb to fasten the process. The required time depends on the fluid quality and temperature as well. Nevertheless, you can see the circuit after a while.

Then, I clean the board using an absorbent paper and remove the toner using nitride based thinner. Clean the board thoroughly and sand it a little. I always put tin layer on the entire board to prevent any malfunction.

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Eatching
Eatching done
Cleaned PCB after eatching
Tinning the PCB
Tinned PCB

Then follows a noisy part – drilling the holes for all the parts. I use 1mm drill bit, 1.2mm for thicker diodes and the rest as it is deeded. Clean the drilled board again. The next step is the mounting of all the parts. I start with passive parts: connectors, sockets, wires. Then I solder resistors and capacitors. As last, I add integrated circuits. The last step is to add label and description for each input / output.

See the samples and video.

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Drilling the holes
Drilled PCBs
Final PCB I
Final PCB II

Video

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