Operation Manual

4. As the solder flows, you’ll see it drawn down into the hole in the board. This is an indication that the area is hot enough for
a good solder join. If the solder floats, it indicates that the area is not yet hot enough.
5. Remove the solder from the join first, followed by the iron. (If you remove the iron first, the solder will harden and leave
your spool of solder stuck to the contact!)
If all went well, you’ll be left with a solid solder join that will last for many years. If not, don’t be disheartened—just press the
iron against the join to reflow the solder, and use the desoldering wick if you need to clean up a spill or any excess. A perfect
solder joint should have a shape somewhat like a volcano, rising up from the surface of the board to meet the leg of the
component.
Never leave the iron in contact with the parts for more than a few seconds. This is especially important when soldering heat-
sensitive components like integrated circuits, which can be damaged by prolonged contact with a hot soldering iron. If you’re
using a temperature-controlled solder station, make sure the temperature is set to an appropriate level for the solder being used
(check the solder’s packaging or data sheet for details).
When you’ve finished, remember to re-tin the tip of the iron. If you don’t, the tip may corrode in storage and need to be
replaced significantly sooner than would otherwise be the case.
Remember to heat both surfaces with the iron. Heating only one surface results in what is known as a dry joint or cold joint, where the solder is not
properly mated to one surface. Over time, these joints will fail and need to be re-soldered.
As with any skill, soldering takes practice. Many electronics shops sell kits that include a printed circuit board and a selection of
components, which you can use to practice soldering through-hole components. Some add-on boards for the Raspberry Pi are
also provided in kit form and require soldering, including the Slice of Pi from Ciseco. You’ll learn about these in Chapter 13,
“Add-on Boards”.