21

Poor Wetting
The example clearly shows poor wetting on the surface of the component leads with satisfactory pad wetting on the PCB. The component should be tested for solderability using a wetting balance or the dip and inspect test. Either the components have been stored for too long a period of time or the tin/lead coating on the leads was too thin. As an example a tin/lead coating of 5um should provide a solderable life in excess of one year.