Abstract:
A method and apparatus for constructing a probe card assembly is provided. A probe pin is inserted into an aperture of an inverted socket enclosure to cause a probe pin shoulder of the probe pin to make contact with an aperture shoulder of the aperture. An upper end of the probe pin protrudes from the aperture after the probe pin shoulder makes contact with the aperture shoulder. A compressible member is inserted into the aperture to position an upper end of the compressible member to make contact with a lower portion of the probe pin. A substrate is aligned over the inverted socket enclosure so that the lower end of the compressible member is in contact with a substrate contact located on the substrate. The substrate is affixed in a non-permanent manner to the inverted socket enclosure.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an approach for creating a spring-loaded probe pin assembly. 
     BACKGROUND 
     The approaches described in this section are approaches that could be pursued, but not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated, it should not be assumed that any of the approaches described in this section qualify as prior art merely by virtue of their inclusion in this section. 
     In the manufacture of certain probe cards and the like, each probe of the probe card is electroformed (e.g., as part of a group of probes), singulated, and then mechanically bonded (e.g., one at a time) onto the probe card. This process is time and resource intensive. Further, often it is necessary to perform additional work to realign any misaligned probes on the probe card before the probe card may be satisfactorily used in testing. Such rework may interfere with the bonds holding the probes to the probe card. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is a side, sectional view of an assembly according to an embodiment of the invention; 
         FIG. 2  is an overhead plan view of  FIG. 1  according to an embodiment of the invention; 
         FIG. 3  is an enlarged view of the circled area of  FIG. 2  according to an embodiment of the invention; 
         FIG. 4  is an enlarged side, sectional view of line A-A of  FIG. 3  according to an embodiment of the invention; 
         FIG. 5  is a further enlarged view of  FIG. 4  further illustrating initial contact of a tip portion of a probe pin with a wafer according to an embodiment of the invention; 
         FIG. 6  is the structure of  FIG. 5  in contact with the wafer at overdrive according to an embodiment of the invention; and 
         FIG. 7  is a flowchart illustrating a process of assembling a probe card assembly in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention. 
     Functional Overview 
     In an exemplary embodiment of the present invention, a socket with precisely formed apertures  400  is adapted to retain respective probe pin  102 /compressible member  402  assemblies in precise alignment at desired lean angle(s)  120 . The guidance provided to the probe pin  102 /compressible member  402  assemblies by respective apertures  400  substantially reduces or eliminates the alignment problems associated with the convention probe cards regarding reworking. Assembly of exemplary probe card assembly  500  is also simplified as, in essence, probe pins  102  and compressible members  402  may just be dropped into respective apertures  400  of socket enclosure  100  and then space transformer/structure/substrate  110  may be attached to socket enclosure  100  to retain them therein. Further, in an exemplary embodiment, the space transformer/structure/substrate  110  is removably attached to socket enclosure  100  so that individual probe pins  102  and/or compressible members  402  may be replaced as needed to permit repair of the probe card assembly  500  while keeping the same multi-layer ceramic (MLC) structure. In an embodiment, compressible member  402  may be a resiliently compressible member (such as a spring or the like) that compresses in response to a force asserted against a probe pin in contact the resiliently compressible member. 
     Spring-Loaded Probe Pin Assembly 
       FIG. 1  is a side, sectional view of an assembly in accordance with an embodiment of the invention. As illustrated in  FIG. 1 , socket enclosure  100  may have a plurality of conductors  114  slidingly within respective apertures  400  (as shown in  FIG. 4 ) and may be affixed to structure  110  mechanically and/or by using attachment compound  112  (as depicted in  FIG. 1 ). Non-limiting, illustrative approaches for mechanically affixing conductors  114  to structure  110  include the use of pins, bolts, screws, or the like. Structure  110  may be any type of structure, such as a space transformer (as depicted) or any type of substrate such as a printed circuit board (PCB), a multi-layered organic (MLO) substrate, or a multi-layered ceramic (MLC) substrate (see, for example,  FIGS. 5 and 6 ). 
     In one embodiment, structure  110  may be removably attached to socket enclosure  100 . In another exemplary embodiment, structure  110  may be permanently attached to socket enclosure  100 . It is noted that if structure  110  is not permanently attached to socket enclosure  100 , structure  110  and socket enclosure  100  may be separated so that individual conductors  114  (or individual pins  102  or compressible members  402 ) may be relatively easily be replaced or repaired to repair probe card assembly  500 . 
     As shown in  FIG. 1 , the upper end  104  of probe pins  102  ends in tip portion  106 . The upper end  104  of probe pins  102  may extend from apertures  400  (depicted in  FIG.4 ) at a specified lean angle  120  (as shown in  FIG. 5 ) relative to socket enclosure  100  and substrate  110 . In an embodiment, lean angle  120  may be from about between 0° to 45°. According to certain embodiments of the invention, lean angle  120  may be between about 5° to 30°, and in other embodiments, lean angle  120  is between about 10° to 15°. Lean angle  120  may be selected in consideration of ensuring a sufficient or desired scrubbing action of tip portions  106  of probe pins  102  against upper circuit member contacts  504  (see  FIG. 5 ). 
     The pattern of apertures and conductors  114  may be designed to mirror or match the pattern of upper circuit member contacts  504  with which probe card assembly  500  may be employed. 
     Socket enclosure  100  may be comprised of a non-conductive material such as a ceramic, e.g., zirconia alumina. For example, socket enclosure  100  may be comprised of a material so as to permit at least as little as a 150 micron spacing between adjacent apertures  400 . It is noted that socket enclosure  100  may permit a pitch, i.e., socket enclosure  100  may allow adjacent apertures as close as, for example, of about 100 microns or closer. 
     Probe pins  102  may be comprised of an electrically conductive material such as nickel, stainless steel, copper manganese (CuMn), palladium (Pd) or alloys thereof and may further be coated with a conductive material, such as gold (Au). 
     In an embodiment of the invention that employs attachment compound  112 , attachment compound  112  may be comprised of an adhesive compound such as, a glue-type material or epoxy. Whether attachment compound  112  (as illustrated in  FIG. 1 ) is used and/or mechanical attachments are used to attach socket enclosure  100  to structure  110 , such compounds or attachments may also be employed proximate the center of socket enclosure  100 , which may account for the tendency of the socket enclosure  100  to separate from structure  110 , especially at the center, due to the cumulative action and force of the compressible members  402  against structure  110  and contacts  432  (see  FIG. 4 ). 
       FIG. 2  depicts an overhead plan view of  FIG. 1  according to an embodiment of the invention. As shown in  FIG. 2 , probe pins  102  may be disposed in an array within socket enclosure  100 . While one hundred twenty (120) probe pins  102  are illustrated in  FIG. 2 , fewer or more probe pins  102  may be so disposed within socket enclosure  100  as desired. For example, in one exemplary embodiment of the present invention up to three thousand plus (3000+) compressible member (spring) loaded probe pins  102  may be employed in an array. 
       FIG. 3  depicts an enlarged view of  FIG. 2  at circle “3” according to an embodiment of the invention. As shown in  FIG. 3 , each and every upper portion  104  of respective probe pins  102  may be disposed in an essentially identical fashion within apertures  400  and have essentially identical lean angles  120  (see  FIG. 5  for example). Alternatively, certain probe pins  102  may be disposed in different orientations from one another. 
       FIG. 4  depicts a sectional view of  FIG. 3  along line A-A according to an embodiment of the invention. As shown in  FIG. 4 , each conductor  114  may be slidingly received within aperture  400 . Each conductor  114  may comprise an upper electrically conductive probe pin  102  and a lower electrically conductive compressible member  402 . Probe pin  102  may include upper portion  104 , and lower portion  408  having a greater diameter to define a shoulder  410 . Probe pin  102  may be a unitary structure. Upper end  430  of compressible member  402  may contact lower portion  408  of probe pin  102 . Lower portion  408  of probe pin  102  may simply rest on top of upper end  430  of compressive member  402  so that compressive member  402  may bias probe pin shoulder  410  against aperture shoulder  420  and maintain contact between probe pin  102  and compressive member  402 . Alternatively, lower portion  408  of probe pin  102  may be affixed to upper end  430  of compressive member  402  using, for example, an electrically conductive glue or adhesive. Also, in addition to, or instead of, the use of an electrically conductive glue or adhesive, lower portion  408  of probe pin  102  may include a narrowed portion (not shown), at least a portion of which is adapted for receipt within upper end  430  of compressive member  402 . In yet another exemplary embodiment, probe pin  102  and compressible member  402  may be a single, unitary structure. 
     As illustrated in  FIGS. 2 ,  3  and  4 , upper portions  104  of probe pins  102  may include shaped upper portion  105  terminating in tip portion  106 . Tip portion  106  may be designed so as to facilitate electrical contact with upper circuit member contacts  504  (see  FIG. 5  for example) and may facilitate a scrubbing motion against such upper circuit member contacts  504  (see  FIGS. 5 and 6  for example) to remove or penetrate any layer overlying contacts  504  such as an oxide coating, for example. Shaped upper portion  105  may comprise a pyramidal shape as shown in  FIG. 3  or  FIG. 4  with a flat tip portion  106  designed to maximize scrubbing. Such a pyramidal shape has been discovered by the inventors to achieve a sharp enough tip portion  106  to maximize scrubbing while at the same time minimizing wear of probe pin  102 . In another exemplary embodiment, tip portion  106  may be rounded. It is noted that probe pins  102  may be provided as a pre-existing item (for example from third parties) and may then be further processed to form pyramidal-shaped upper portion  105 . 
     In an embodiment, compressible member  402  may comprise a spring, such as a torsion spring as illustrated in  FIG. 4  or a number of other springs or the like. In another embodiment, compressible member  402  may comprise a series of interlaced conductive wires forming a lattice-like compressible member such as that disclosed in U.S. patent application Ser. No. 10/736,280, filed Dec. 15, 2003, which claims priority of U.S. provisional applications No. 60/457,076, filed Mar. 24, 2003, No. 60/457,258, filed Mar. 25, 2003, and No. 60/462,143, filed Apr. 8, 2003, each incorporated by reference in its entirety herein. As noted, the present invention is not limited, however, to depicted compressible member  402 . Alternative self-supporting configurations may be employed, by other embodiments of the invention, such as a substantially cylindrical tube formed from a conductive mesh. 
     Compressible member  402  may be comprised of an electrically conductive material such as nickel, stainless steel, copper manganese (CuMn), palladium (Pd), or alloys thereof, and may further be coated with a conductive material, such as gold (Au). 
     As illustrated in  FIG. 4 , aperture  400  may be cylindrical with a lower portion  403  having a first diameter and an upper cylindrical portion  401  having a second diameter less than the lower portion&#39;s first diameter so as to define shoulder  420  and to receive upper portions  104  of respective probe pins  102 . It is noted that aperture  400  may be sized to slidingly receive probe pin  102  and specifically, for example, first and second diameters of the aperture may be sized so as to slidingly receive respective lower portion  408  and upper portion  104  of probe pin  102  such that a gap may be maintained between aperture  400  and probe pin  102  except when probe pin shoulder  410  contacts aperture shoulder  420 . 
     Lower end  432  of compressible member  402  may engage contact  404  on substrate  110  so as to bias probe pin  102  upwardly and specifically so as to maintain contact between probe pin shoulder  410  and aperture shoulder  420  absent a downward force against probe pin  102  sufficient to compress compressible member  402 , and hence probe pin  102 , downwardly. While the sizing of aperture  400  may be designed to maintain coaxial alignment of probe pin  102  and/or compressible member  402  within aperture  400 , the spring tension also may also assist in maintaining such coaxial alignment. 
       FIG. 7  is a flowchart illustrating a process of assembling a probe card assembly in accordance with an embodiment of the invention.  FIG. 7  depicts an exemplary process. For example, certain of the steps in  FIG. 7  may be eliminated or replaced by alternative steps. Likewise, the order of the steps may be rearranged in certain configurations of the invention. 
     In step  700 , socket enclosure  100  may be inverted as compared to  FIG. 1 . Thereafter, probe pins  102  may be inserted into the respective socket enclosure apertures  400  so that probe pin shoulder  410  may contact aperture shoulder  420  and upper ends  104  of probe pins  102  may protrude from apertures  400 . 
     In step  702 , single compressible members  402  may then be inserted into respective apertures  400  so that upper ends  430  of compressible members  402  may contact lower portions  408  of respective probe pins  102 . 
     In step  704 , structure  110  may be aligned over inverted socket enclosure  100  so that complimentary substrate contacts  404  may be aligned with respective apertures  400  and/or compressible members  402 . Structure  110  may be mounted to the socket enclosure so that lower ends  432  of compressible members  402  may contact the respective substrate contacts  404 . 
     As discussed above, it is noted that the spring tension caused by the engagement between compressible member  402  and probe pin  102  and substrate contact  404 : (1) may be used to assist in maintaining coaxial alignment of probe pin  102  and/or compressible member  402  with aperture  400 ; and (2) may be used to bias probe pin  102  against shoulder  420  of aperture  400 . 
     In step  706 , structure  110  may be affixed to inverted socket enclosure  100  such as by attachment compound  112 , fasteners, etc. In an embodiment, structure  110  may not be permanently attached to socket enclosure  100  to facilitate repair of individual conductors  114  and/or individual probe pins  102  and /or individual compressible members  402 . In another embodiment, structure  110  may be permanently attached to socket enclosure  100 . 
       FIGS. 5 and 6  illustrate the scrubbing motion achieved by conductor  114  when conductors  114  engage contacts  504  of upper circuit member  502  according to an embodiment. Upper circuit member  502  may be wafer  502  under test or a device under test (DUT). 
     As illustrated in  FIG. 5 , at Initial Contact, probe card assembly  500  may be positioned proximate upper circuit member  502  so that tip ends  106  of conductors  114  may just touch or contact respective upper circuit member contacts  504 . Shoulder  410  of probe pin  102  may remain in contact with shoulder  420  of aperture  400 . 
     As illustrated in  FIG. 6 , for example, probe card assembly  500  and upper circuit member  502  may be urged together so that upper circuit member contact  504  forces probe pin  102  downwardly (towards or to a maximum designed limit at the overdrive (“O.D.”) position), compressing compressible member  402  to cause retraction of probe pin  102  within aperture  400 . This angled “Z Travel” (over travel or overdrive)  606  of probe pin  102  may cause tip end  106  to horizontally scrub (leftwards as illustrated in  FIGS. 5 and 6 , for example) against upper circuit member contact  504  by “Scrubbing Motion”  608  to remove or penetrate any contaminate layer over contact  504 , such as an oxide layer (not shown), to facilitate electrical contact between conductor  114  and contact  504 . It is noted that in the exemplary embodiment illustrated in  FIGS. 5-6 , lean angle  120  remains substantially constant during Z Travel  606 . 
     In an embodiment, the angle of Z Travel  606  may be from about greater than 0.0 (zero) to upwards of 10.0/1000 inches. A large maximum Z Travel or overdrive  606  may help to ensure contact between probe pins  102  and respective contacts  504 , but may also lead to a more rapid wear out of probe card assembly  500 . In certain embodiments of the invention, a maximum Z Travel  606  may be from about 3.5/1000 to 5.0/1000 inches. Further, in certain embodiments of the invention, Z Travel  606  may be from about 0.0 (zero) to 2.0/1000 inches. It is noted that with the improved planarity/co-planarity of probe pin tip ends  106  that is accomplished with the teachings of the present invention, smaller and smaller (maximum) Z Travel and/or overdrive  606  may be achieved while still permitting contact between probe pins  102  and respective contacts  504 . While embodiments of the invention have been described with reference to a single touchdown, or contact, between conductors  114  and upper circuit member contacts  504 , in practice multiple touchdowns may be employed during the testing of a single upper circuit member  504 , such as a memory wafer. 
     By employing the present invention, a considerable amount of manufacturing process steps currently used to build a probe card assembly may be eliminated. Assembly in accordance with an exemplary embodiment of the present invention reduces to a few relatively simple process steps using well-know technologies, such as (1) EDM (electrical discharge machining) and the use of a shaped electrode with a high voltage discharge to remove material and achieve a desired shape without any mechanical touching and/or forming of the material to form probe pins  102 , or (2) Auto-CNC (housing machining process, or an automated, sophisticated machining process) where a two-dimensional (2D) electronic drawing is inputted into a precise multi-axis grinding machine which converts the 2D drawing into a three-dimensional shaped structure from a template material, for example, metal or ceramic) to form socket enclosure  100  with spaced apertures  400  and/or probe pins  102 , for example, with a high rate of accuracy and repeatability as compared to certain current assembly processes to form probes/probe card assemblies for wafer testing which are more involved, complex and time consuming. Thus, compared to certain conventional processes, cost, development time, and production cycle times may be reduced. Of course, these processes are exemplary in nature, and the present invention is not limited thereto. 
     In an embodiment of the invention, a socket enclosure may be employed which would enable not only exceptional probe tip alignment, with exceptional coplanarity of the respective probe tips throughout the entire array by providing directional guidance to the probe pin itself, but also substantially uniform scrubbing motion at most every touchdown, or contact, between the probe pin tip and the respective contact on the device under test (DUT). As noted above, this may also permit a lower maximum Z Travel and/or overdrive  606 . 
     The exemplary embodiments of the present invention may enable a new generation of flip-chip wafer probe cards to support pad pitches, or space between adjacent pads, as low as at least, for example, about 150 microns. 
     While the present invention is described primarily with respect to spring-loaded probe pins configured at a lean angle, it is not limited thereto. For example, according to certain exemplary embodiments of the present invention, the spring-loaded probe pins may be provided orthogonal (or substantially orthogonal) to the surface of the underlying substrate (i.e., the substrate through which the spring-loaded probe pins are supported). 
     While the present invention has been described primarily with respect to probe cards for wafer testing of semiconductor devices, it is not limited thereto. Certain of the teachings may be applied to other technologies, for example, package testing of semiconductor devices. 
     In the foregoing specification, embodiments of the invention have been described with reference to numerous specific details that may vary from implementation to implementation. Thus, the sole and exclusive indicator of what is the invention, and is intended by the applicants to be the invention, is the set of claims that issue from this application, in the specific form in which such claims issue, including any subsequent correction. Any definitions expressly set forth herein for terms contained in such claims shall govern the meaning of such terms as used in the claims. Hence, no limitation, element, property, feature, advantage or attribute that is not expressly recited in a claim should limit the scope of such claim in any way. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.