Patent ID: 9697380
Date: 2017-07-04
CPC Classifications: G01N,G01R,G06F,H05K

Claim:
1. A method, implemented on at least one processor circuit, of operating, for an integrated circuit (IC) chip mounted on a surface of a printed circuit board (PCB) of a computer system, a security apparatus including a Wheatstone bridge circuit that includes four regions of an X-ray opaque, optically opaque and electrically resistive conformal coating layer, each region of the four regions configured as a corresponding resistor in the Wheatstone bridge circuit, the method comprising: measuring, with a monitoring device in electrical communication with the at least one processor circuit and with a voltage source, a first resistance value of the Wheatstone bridge circuit; storing, using the at least one processor circuit, the first resistance value; measuring, with the monitoring device and a voltage source, a second resistance value of the Wheatstone bridge circuit; determining, by comparing with the at least one processor circuit, the second resistance value to the first resistance value, a difference between the second resistance value and the first resistance value, the difference corresponding to the removal of a portion of the electrically resistive conformal coating layer included in at least one resistor of the Wheatstone bridge circuit; and executing, with the at least one processor circuit, in response to a difference between the second resistance value of the Wheatstone bridge circuit and the first resistance value of the Wheatstone bridge, a protective action on the IC chip.