Cold Joints

Cold Joints

A joint in which the solder does not make good contact with the component lead or printed circuit board pad is called a cold joint. It's a soldered joint that was made incorrectly as the solder was melted on to the metal, but the metal was not hot enough to melt the solder, meaning that the solder didn't really flow and is not bonded to the metal. A cold joint is a mechanical joint at best: it may hold together for a while, but it will eventually break loose, and it will never conduct electricity very well. Cold joints occur when the component lead or solder pad moves before the solder is completely cooled. Cold joints make a really bad electrical connection and can prevent your circuit from working, and should be removed.

Cold joints are easily fixed, and can be recognized by a characteristic grainy, dull gray color. First, remove the old solder with a desoldering tool or simply by heating it up and flicking it off with the iron. Once the old solder is off, you can resolder the joint, making sure to do it right by keeping still as it cools.