What does a shiny area on the inside of a soldered joint indicate?

A shiny area on the inside of a soldered joint typically indicates that the joint was properly heated and that the solder has flowed correctly into the joint. This is primarily due to the melting of the solder, which creates a shiny, smooth finish. When solder is adequately heated, it is drawn into the joint by capillary action and forms a strong bond.

With that understanding, a shiny area does not suggest an inadequate amount of solder was used, as this would more likely result in a lack of fill and potentially a dull or rough surface. Instead, if there is sufficient solder present and the joint has been properly heated, you would see a shiny, smooth appearance, signifying a well-executed solder joint. Therefore, the presence of shine indicates proper soldering practice rather than a deficiency.