Nondestructive testing of electric contacts by time-resolved infrared radiometry

The bonding of small electric contacts consisting of small platelets of silver alloys welded to thin copper sheets has been tested by time-resolved photothermal radiometry with step-function surface heating. The contact platelet can be regarded as a heat sink coupled to the substrate by the thermal resistance of the welding joint. Identification of good and poor bonding is possible within 50 ms by analysing the normalized signal of the temperature response.