What is the characteristic appearance of a cold tin-lead solder joint?

A good tin-lead solder joint should look smooth and shiny. If the joint is not heated sufficiently during the soldering process, the solder will not melt completely or flow properly into the connection. This lack of heat results in a "cold" solder joint. The characteristic appearance of a cold tin-lead solder joint is a dull, grainy, rough, or lumpy surface, which creates a poor electrical and mechanical connection. The incorrect options represent either a perfect joint (bright and shiny) or unrelated issues (dark black spots or excessive solder).