Hand soldering Surface Mount Devices (SMD) scares a lot of DIYers and Makers, but it is easier than what it looks like. Even sometimes, it’s easier than soldering Through Hole Components. Really!
TH Components are naturally held in place by their legs, while SMD are just sitting flat on the PCB, only waiting for the smallest PCB move, to fly away. And, as small and lightweight they are, they fly pretty well and pretty far away!
My first tryouts were disastrous, usually ending by a poor resistor, fried on my iron tip…
So, we need to keep the small component stuck in place, without the need of a third or fourth hand.
The method I use with great success is to first put a small amount of solder on the PCB.
Then, with precision tweezers in one hand and your soldering iron in the other, place the component on the footprint.
When you’re ready, while maintaining the component with the tweezers, put the iron against the solder blob. The heat will melt the solder and, when cooling, the solder joint will keep the component in place. You have one pad done.
If needed, you can move the component again by melting the solder while dragging the component with the tweezers.
The component must be pushed against the PCB. If there’s an angle, you need to correct the position.
When the position is correct, it’s time to solder the second pad.
This time, the technique is more traditional: the solder wire in one hand and the iron in the other, first apply the heat to the pad (PCB pad and component pad) and apply the smallest amount of solder.
Surface mount components are tiny and require less heat than their bigger through hole cousins. You can damage them badly if you let the iron tip in contact too long with pads.
Be extremely careful with the PCB pads themselves. You can damage the copper pad if you apply too much heat.
SMD Pads are small and require less solder tin than for TH pads. The solder joint should be concave (not bulging) and shiny.
In case you put too much solder, use a tin plated de-soldering braid.
Any iron tip can do the job. No need for an expensive tiny one. Mine is a commonn 1 or 2mm wide. However, the tip must be clean.
If you have a regulated iron, set it on the lowest heat.
Finally, if you have to solder components with more than two pads or legs, this technique also works well, as long as you have access to the component pads. You can’t solder BGA or QFN for example. SO, SOIC, SSOP, TSOP, TQFP and so on are ok.
I just use some extra “no clean” flux. It makes things a lot easier.