How to Solder a Solid Joint on Your Electronics Project
The most common form of soldering when creating electronic projects is soldering component leads to copper pads on the back of a printed circuit board. If you can do that, you'll have no trouble with other types of soldering, such as soldering two wires together or soldering a wire to a switch terminal.
The following steps outline the procedure for soldering a component lead to a printed circuit board:
Pass the component leads through the correct holes.
Check the circuit diagram carefully to be sure you have installed the component in the correct location. If the component is polarized (such as a diode or an integrated circuit) verify that the component is oriented correctly. You don't want to solder it in backward.
Secure the component to the circuit board.
If the component is near the edge of the board, the easiest way to secure it is with an alligator clip. You can also secure the component with a bit of tape.
Clamp the circuit board in place with your third-hand tool or vise.
Orient the board so that the copper-plated side is up. If you're using a magnifying glass, position the board under the glass.
Make sure you have adequate light.
If you have a desktop lamp, adjust it now so that it shines directly on the connection to be soldered.
Touch the tip of the soldering iron to both the pad and the lead at the same time.
It's important that you touch the tip of the soldering iron to both the copper pad and the wire lead. The idea is to heat them both so that solder will flow and adhere to both.
The easiest way to achieve the correct contact is to use the tip of the soldering iron to press the lead against the edge of the hole.
Let the lead and the pad heat up for a moment.
It should take only a few seconds for the lead and the pad to heat up sufficiently.
Apply the solder.
Apply the solder to the lead on the opposite side of the tip of the soldering iron, just above the copper pad. The solder should begin to melt almost immediately.
Do not touch the solder directly to the soldering iron. If you do, the solder will melt immediately, and you may end up with an unstable connection, often called a cold joint, where the solder doesn't properly fuse itself to the copper pad or the wire lead.
When the solder begins to melt, feed just enough solder to cover the pad.
As the solder melts, it will flow down the lead and then spread out onto the pad. You want to feed just enough solder to completely cover the pad, but not enough to create a big glob on top of the pad.
Be stingy when applying solder. It's more common to have too much solder than too little, and it's a lot easier to add a little solder later if you didn't get quite enough coverage than it is to remove solder if you applied too much.
Remove the solder and soldering iron and let the solder cool.
Be patient — it will take a few seconds for the solder to cool. Don't move anything while the joint is cooling. If you inadvertently move the lead, you'll create an unstable cold joint that will have to be resoldered.
Trim the excess lead by snipping it with wire cutters right just above the top of the solder joint.
Use a small pair of wire cutters so you can trim it close to the joint.