Surface mount soldering

Surface mount components can be tiny. And consequently, soldering them (or soldering anything to a PCB) can be a bit intimidating. But the truth is that it's not as hard as you might expect.

First, some basic pointers. Half the battle is in the preparation. You're going to need several things at your disposal. A decent soldering iron, for starters. You want to use the largest tip that will work, but no larger. The story's the same with solder; you'll want something reasonable thin but not too tiny. Specifics will depend on your situation. So those are the obvious things. But you also need non-obvious things. You're going to want a stand for the iron, and a sponge to clean the tip. You're going to need plenty of light, preferably on adjustable worklights. If they're the sort with magnifying glasses on them, so much the better. You're also going to want a good, comfortable chair. It seems trivial, but it most certainly is not.

So after taking a moment to make sure you've got everything together, you can get to work.

These instructions as written are directed at soldering SMD components such as resistors and whatnot. But they can be reinterpreted to apply to just about anything you have to deal with. In all cases it's in your best interest to read all the way through and make sure you understand everything before you ever plug in your iron.

Place the iron on one of the solder pads and heat it up. You should see the pad melt. Flow a little bit of solder onto that pad and remove the iron.

Pick up the component with tweezers, or failing that small pliers. For larger integrated circuits, you may be able to get away with using your fingers. Get it mostly into position, then heat up the solder you just put down. It will tend to pull the component toward it a bit, so be careful. Keep the solder molten until you get the components into position (so it's mostly straight, and the contacts are above their solder pads). You don't need to add any more solder at this stage; you're just tacking the component down. Then take away the iron.

Place the iron on the other (or just another, if you have more than 2 contacts) solder pad (rule of thumb: when you can avoid directly touching the component, do- you may need a fairly small tip), heat it up, and flow solder onto it. You may choose to use a bit of flux first; if so, don't forget that most kinds of flux leave potentially problematic residue. Remember to sweat this joint a bit, especially if you use flux; just keeping the iron on it a moment after pulling away the solder can make all the difference. There's no hard rule about how long to sweat a joint, as there are so many variables, so it's a judgment call. As a vague general estimate, a bit under a second is usually fine. If you have a particularly heat-vulnerable component, be especially careful.

Go back to the first side. Heat it up again, and if needed add more solder. Again, sweat the joint.

If you have 2 contacts, you're done. If not, here's some extra advice. Above, we tacked down one side of the component and then secured the other side. But if you have more contacts, that may not be quite enough. What you want to do instead is tack down one of the corner contacts, and then the one at the far corner from it. Make darn sure the pins on the device line up with the solder pads- don't be afraid to redo a joint to ensure this. Then start by soldering the contact at another, not-yet-soldered corner. Continue on in a line until you hit one of your tack joints; just as above, give it a good inspection and flow on more solder if needed. Then just continue on down the other side.

The main thing, of course, is to relax.

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