Programmable devices to route signals on probe cards

Abstract: A probe card of a wafer test system includes one or more programmable ICs, such as FPGAs, to provide routing from individual test signal channels to one of multiple probes. The programmable ICs can be placed on a base PCB of the probe card, or on a daughtercard attached to the probe card. With programmability, the PCB can be used to switch limited test system channels away from unused probes. Programmability further enables a single probe card to more effectively test devices having the same pad array, but having different pin-outs for different device options. Reprogrammability also allows test engineers to re-program as they are debugging a test program. Because the programmable IC typically includes buffers that introduce an unknown delay, in one embodiment measurement of the delay is accomplished by first programming the programmable IC to provide a loop back path to the test system so that buffer delay can be measured, and then reprogramming the programmable IC now with a known delay to connect to a device being tested. (end of abstract)