This joint often looks non shiney and grainy, especially at the interface. This joint may adhere for a while, but can be expected to fail in time. This joint likely does not have feathered edges where it interfaces with the pad and with the lead. It is generally has a solder globule appearance rather than with feathered edges. It may be shiney.
Pads can even unadhere to the circuit board if too much heat is applied.
Soldering a contaminated board or one with excessive oxide will produce a non-functioning joint . The solder will tend to roll off the joint rather than bond. Soldering with no flux or too little flux will produce a non acceptable solder joint Solder will often ball up and be globular in appearance. Soldering electronic parts with acid core solder, corrosive flux, or conductive flux. Many times, soldered components or wires must be removed.