The ideal solder joint for through-hole components should have a wetting angle between 40 and 70 degrees from horizontal, and a smooth, shiny and concave surface. However, it’s really not easy to do. And we always face the following soldering problems.
Stray solder spatters: These bits of solder are held to the board only by sticky flux residue. If they work loose, they can easily cause a short circuit on the board. Fortunately, these are easy to remove with the tip of a knife or tweezers.
Lifted pad: Sometimes you can see a solder pad detached from its circuit board’s surface. This most often occurs when try to de-solder components from the board. The simplest way to repair is to fold the lead over to a still-attached copper trace and solder. Other alternatives are to follow the trace to the next via and run a jumper to there.