Integrated Monolithic Probe Card

During the production of integrated circuits it is necessary to perform electrical testing at the wafer level. This requires the formation of temporary electrical connections between bond pads on the wafer’s surface and testing equipment. The interface that provides these connections is called a probe card. Each probe usually consists of bent, chemically sharpened fine tungsten needle. The PCB provides electrical connections between the probes and ports to which test equipment is connected.

Traditionally, individual probes are arranged by hand into arrays and then fixed into position by gluing them to a ridged ring using an epoxy. This ring is then attached to the PCB and individual electrical contacts are made between each probe and the PCB. As integrated circuit dimensions shrink, the number and density of probes required is increasing. The production of probe cards by traditional processes is becoming increasingly expensive and time consuming and so an alternative manufacturing method is necessary.

To this end, we have designed, fabricated and tested a number of suitable probe structures using lithographically defined micro-machining techniques. The use of such manufacturing processes breaks the relationship between time/cost and probe pitch/count since all probes are formed simultaneously. Our most recent structures consist of three dimensional nickel cantilevers formed over a shaped elastomer layer. The probes provide robust and stable electrically connections whist permitting probe pitches as small as 23 µm. The flexibility of the manufacturing process allows probes to be fabricated on a wide variety of substrates affording the direct integration of probes with testing circuitry.

For further information contact: David Wood