Patent ID: 7401976

Claim:
A method for detecting a defect in a populated circuit board, said populated circuit board having a first side and an opposite second side, at least said first side being populated with one or more surface mounted components: said method comprising: 1) directing a thermal wave at the second side of said populated circuit board 2) recording a thermographic image of the first side of said populated circuit board once a surface thereof reaches a predetermined transit temperature or a predetermined transit time period has elapsed; and 3) analyzing the obtained thermographic image by comparing the so obtained thermographic image with a standard thermographic image wherein a) the thermal wave is developed by a thermal heater array comprising a plurality of discrete individually controllable heat source elements, said elements each delivering a respective individual energy intensity reflecting the respective energy parameter information therefor comprised in a first block of energy parameter information; b) said first block of energy parameter information comprising, for each of said heat source elements, individual energy parameter information whereby the thermal heater-array may be induced to provide a thermal wave giving rise to a thermographic image indicative of uniform temperature of the surface of the first side of an predetermined unpopulated circuit board; and c) said standard thermographic image having been obtained by i) subjecting the second side of a predetermined populated circuit board to a thermal wave developed by said thermal heater array, said thermal field being applied until a surface of the first side of the predetermined populated circuit board reaches said predetermined transit temperature or said predetermined transit time period has elapsed, said elements of said thermal heater array each being set to deliver a respective individual energy intensity reflecting the energy parameter information of said first block of energy parameter information, and ii) taking said standard thermographic image from the first side of said predetermined populated circuit board once said predetermined transit temperature is reached or said predetermined transit time period has elapsed.