How To Solder Wires To Pins. 32 wires need to be soldered on this connector. A small hacksaw is handy for cutting through all the tracks.
Add a little bit of solder, if needed, just to fill any empty space inside of the pin. After twisting you have to solder on the twist of the terminals.
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Also if you make the board several holes wider than the arduino and then drill the holes out a bit, you can thread the wires up and down and then solder which give a bit of strain relief and is really secure And allow the solder to melt.