1. Technical Field
The present invention relates to probe assemblies in general, and in particular to a probe card that electrically connects a semiconductor wafer to a tester for testing the semiconductor wafer.
2. Description of Related Art
When performing a wafer level test, a probe card containing multiple conductive probes is brought into contact with a chip located on a semiconductor wafer. The probes then transfer various test signals generated by a tester to each integrated circuit within the chip.
During the testing process, the tips of the probes need to be abrasively cleaned on a regular basis in order to provide good electrical contacts. After each cleaning cycle, however, the lengths of the probes are slightly shortened. Once the probes become too short to be useful for testing purposes, the probe card also becomes useless and should be discarded. Since the cost of a new probe card is relatively high, it would be desirable to extend the useful life of a probe card as much as possible.
In accordance with a preferred embodiment of the present invention, a probe card includes a top plate, a disc, a removable plate and multiple micro probes. One of the micro probes includes a curved segment and a linear segment connected to each other at an angle stop. The linear segment is shorter than the curved segment. The top plate includes a set of holes formed therein, and one of the holes is configured to receive the curved segment of the micro probe. The disc includes a set of holes formed therein, and one of the holes is configured to receive the linear segment of the micro probe at the angle stop. The removable plate is removably connected to the disc, and the removable plate includes a set of holes formed therein, wherein one of the holes is configured to receive the linear segment of the micro probe.
All features and advantages of the present invention will become apparent in the following detailed written description.
The invention itself, as well as a preferred mode of use, further objects, and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:
a-4b are close-up views of the relevant part of
a-5c show the progression of the usage of the probe card from
Referring now to the drawings and in particular to
With reference now to
Alignment plate 14 lies within recessed area 12a and butting against solid area 12b. Top plate 11 lies across recessed area 12a and extends over solid area 12b. Top plate 11 is removably fixed to an upper surface of solid area 12b via screws 25 and 26. Similarly, removable plate 19 is removably fixed to a lower surface of solid area 12b via screws 27 and 28.
Top plate 11 includes a first planar surface 21, a second planar surface 22 and multiple holes 16 to receive the curved segment of micro probes 15 for providing electrical contacts to a tester (not shown). Alignment plate 14 also has a set of holes matching the set of holes 16 in top plate 11. Alignment plate 14 allows micro probes 15 to be temporarily aligned to top plate 11.
Referring now to
Preferably, first contact tip 31 is configured to provide electrical contact to electronic test circuitry of a tester, and second contact tip 34 is configured to provide electrical contact to a contact pad located on an integrated circuit. First and second contact tips 31, 34 can be any shape, such as flat, cone shaped, or rounded.
With reference now to
Recessed area 12a of disc 12 has a thickness t1, and removable plate 19 has a thickness t2. Along with the length of linear segment 33 of micro probe 15, thickness t1 and thickness t2 define the vertical distance micro probes 15 may be compressed (or travel). In
During the process of wafer level testing, second contact tips 34 of micro probes 15 need to be abrasively cleaned on a regular basis in order to maintain good electrical contacts with bumps 41 on integrated circuit 40. After each cleaning cycle, the lengths of linear segments 33 become slightly shortened (i.e., less than the optimal distance c). Eventually, the lengths of linear segments 33 below removable plate 19 become too short to be useful.
In order correct the above-mentioned problem, removable plate 19 can be removed by loosening screws 27 and 28 (from
As has been described, the present invention provides an improved probe card for testing integrated circuits on a semiconductor wafer. The progression of the usage of the improved probe card is illustrated in
While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.