ESD to the display inducing currents measured using a substitution PC board

ESD to a display may upset or damage the display or the touch circuit. The ESD may have a visible spark carrying current to the frame of the mobile device, to the connecting flex cable, or into the display by penetrating the glue between the glass layers. It may also be a sparkless ESD that causes corona charging on the surface of the glass having currents as high as 10 A. A measurement technique is presented that allows measurement of the currents on all traces, including ground of flex cables that connect from the display to the main board of a mobile device. The main board is substituted by a PCB that has the same connections to the body of the mobile device and the same shape, i.e., the same electromagnetic affects. However, all connections to the display are terminated in resistive structures that allow measuring the currents in the flex cable individually. Besides measuring ESD currents, the substitution board offers various other applications with respect to the coupling and propagation of self-interference causing signals or EMI problems.