MEMS probe card assembly having decoupled electrical and mechanical probe connections
Probes are connected to the space transformer via multiple carrier plates. Electrical contacts from the probes to the space transformer are by way of spring tail features on the probes that connect to the space transformer and not to the carrier plates. In other words, the carrier plates are purely mechanical in function. This configuration can significantly reduce probe array fabrication time relative to sequential placement of individual probes on the space transformer. Multiple probe carrier plates can be populated with probes in parallel, and the final sequential assembly of carrier plates onto the space transformer has a greatly reduced operation count. Deviations of the space transformer from flatness can be compensated for.
1. A probe array comprising:
a space transformer;
two or more probe carrier plates mechanically affixed to a surface of the space transformer, wherein each of the probe carrier plates has two or more probes mechanically affixed to it such that tips of the probes face away from the space transformer;
wherein the probe carrier plates are laterally separated from each other with respect to the surface of the space transformer;
wherein electrical connections between the probes and the space transformer are made by spring features of the probes that contact the space transformer without contacting the probe carrier plates;
wherein the probes of the probe carrier plates are configured to make electrical contact to a device under test.
2. The probe array of claim 1 , wherein the probes include one or more posts configured to provide mechanical attachment points to the probe carrier plates.
3. The probe array of claim 2 , wherein adjacent probes in the probe array have their respective posts staggered with respect to each other, whereby a spacing between the adjacent probes can be reduced.
4. The probe array of claim 1 , wherein the space transformer has a locally adjustable vertical displacement configured to make the tips of the probes coplanar for all probes of the probe array.
5. The probe array of claim 4 , wherein the locally adjustable vertical displacement is provided by bonds between the carrier plates and the space transformer having a fabrication-adjustable bond thickness for each of the carrier plates.
6. A method of making a probe array, the method comprising:
providing two or more probe carrier plates;
mechanically affixing two or more probes to each of the probe carrier plates to provide a probe carrier assembly corresponding to each of the probe carrier plates;
providing a space transformer;
after all of the probe carrier plates are fully populated with their corresponding probes, mechanically affixing the probe carrier assemblies to the space transformer;
wherein electrical connections between the probes and the space transformer are made by spring features of the probes that contact the space transformer without contacting the probe carrier plates.
7. The method of claim 6 , wherein the space transformer has a locally adjustable vertical displacement configured to make the tips of the probes coplanar for all probes of the probe array.
8. The method of claim 7 , wherein the locally adjustable vertical displacement is provided by bonds between the carrier plates and the space transformer having a fabrication-adjustable bond thickness for each of the carrier plates, and further comprising adjusting bond thicknesses to provide planarity of the probe tips.