If you’re familiar with electronic assembly, soldering bare copper wire to a printed circuit board (PCB) is straightforward. Wire will solder readily to PCB pads and jumpers. Avoid soldering directly to component leads, as heat may damage them. Take care that your soldering iron doesn’t burn the board by overheating it. Have a schematic handy to double-check your work. Whether you’re building kits or developing projects from scratch, soldering circuit boards can be a satisfying experience.
Jig
You can make any soldering work on printed circuits easier with a jig. The jig holds the card steady for you, at a comfortable angle, freeing your hands for the soldering work. If you do soldering regularly, consider investing in a jig.
Tinning
To prepare bare copper wires, especially stranded wires, it helps to tin them first. First, twist the stranded wire in your fingers so that they’re bundled neatly and tightly in one direction. Touch the soldering iron to the wire and run enough solder to it to coat the wire. Coating the wire makes soldering to the PCB easier, and prevents strands from working loose.
Hole
If you’re soldering wire through a printed circuit board hole, check that your wire will fit through the hole. If it fits, slip the wire from the component side through the hole until a quarter to a half inch protrudes through the bottom. Solder the wire to the pad on the bottom side, then clip off excess wire. If the wire has no insulation, make sure it’s not touching any bare component wires on the top side.
Pad
If no hole is available, you can solder to a pad on the bottom or top side of the board. A pad is a larger area of copper foil, as opposed to the traces, which are thinner. Bend the end of the wire so a sixteenth to an eighth of an inch of the tip is at 90 degrees. It can then lay flat against the pad. Solder the wire directly to the pad. Trim off any excess wire with a wire cutter.
Jumper
You can solder to a bare jumper on the circuit board. A jumper is a stiff, sometimes bare wire that bridges across some traces on the top or bottom of the board. Slip the copper wire under the jumper and bend the wire over the jumper so the connection iss snug. Solder the wire to the jumper using a moderate amount of solder.
ROHS Solder
Tin-lead electronic solder is still widely available. Lead-free solders have been coming into the market also. These are called ROHS, for Reduction of Hazardous Substances, an effort to eliminate toxic metals from electronics. ROHS solder melts at 227 degrees Celsius, compared with tin/lead at 180 degrees Celsius.
Multi-Side Boards
You can see all the connections on a single- or double-sided PCB, so you can be sure of what you’re soldering. You cannot, on the other hand, see inner layers of a multi-layer board, so this is more risky. Unless you have a schematic of the circuit handy, you can’t be sure you’re creating a connection at the right place.
