Abstract:
A high power Cobra interposer with an integrated guard plate, which is utilized for the testing of electrical products. The guard plate and the upper die of the interposer assembly are integrated into a single unit, thereby eliminating a portion of the structure. The Cobra structure utilizes a novel hole configuration in the upper die portion of the interposer structure, whereby only a small portion of the Cobra tip protrudes, rendering it less susceptible to being damaged in comparison with current designs.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the provision of a high power Cobra interposer with an integrated guard plate, which is utilized for the testing of electrical products. 
         [0003]    In the electronics technology, numerous semiconductor products are tested at the module level in a so-called “burn-in” test whereby a significant proportion thereof are contacted by means of a specialized socket which utilizes so-called Cobra or snake-like wire contacts. These Cobra contacts are housed in an assembly, which is referred to as an interposer and protrude from the top thereof, so as to align with holes that are formed in a movable guard plate. Upon depression of the guard plate, the electrical contacts at the protruding ends of the Cobra pass through the holes in the movable guard plate and are pressed against the product module mounting the semiconductor product so as to produce a temporary electrical connection providing information as to the integrity of the semiconductor products. 
         [0004]    2. Discussion of the Prior Art 
         [0005]    Presently, Cobra interposer and guard plate designs, which are utilized in the burn-in testing of semiconductor products, are subject to various problems, which at times may lead to incorrect readings and resultingly potential failures of the testing equipment. 
         [0006]    In essence, among the drawbacks, which are currently encountered may be that the guard plate, which generally constituted of a coated metal part, occasionally electrically shorts to the module. Furthermore, the interposer dies, which mount the Cobra contacts, are normally produced from a ceramic base material and have a tendency to break during repeated use, whereas in addition thereto, the Cobra contacts are easily bent during use and sometimes tend to stick in the holes, which are formed in the guard plate. Moreover, the electrical current and carrying capacity of the Cobra contacts may not be sufficient for newer up-to-date semiconductor products, which frequently require higher current levels, whereby the foregoing problems may result in increased maintenance costs and in reduced hardware utilization. 
         [0007]    The above problems are currently being addressed in the technology by either providing a more robust coating of the metallic guard plate, which may provide some significant alleviation of the problems, however inasmuch as the base metal structure thereof is still employed, there may also be a potential residual problem of electrical short-circuiting. 
         [0008]    A new Cobra hole-drilling design may be utilized, which may render the dies more robust, but the material may always still be brittle, inasmuch as it is based on a ceramic-based structure. Furthermore, the unacceptable bending of the pins of the Cobra contacts can only be addressed through a training of skilled operators, and may represent a problem in current designs, whereas the sticking contacts of the Cobras may also present a cleanliness issue and must be constantly monitored. As an alternative, so-called pogo contacts have been utilized for the highest-current or power semiconductor products but are extremely expensive, and a vendor socket solution has been qualified, but the current capacity thereof is only half of that of the pogo. 
         [0009]    Concerning the foregoing, although numerous publications are in evidence which address the probing of electrical equipment through, for example, burn-in testing, these have not fully solved the difficulties, as described hereinabove. In particular, Satou, et al., U.S. Patent Publication No. 2004/0257098 A1 discloses a probe card, which provides for the ready assembly and testing of various electrical products. 
         [0010]    Similarly, Okubo, et al., U.S. Pat. No. 6,300,783 B1 describes equipment and methods for testing electrical semiconductor products. Also similarly, Vinh, U.S. Pat. No. 5,952,843 discloses a plurality of wire type contacts, which pass through the interposer plate and guard plate in order to be able to have the protruding ends provide electrical connections of a temporary nature with semiconductor products. 
         [0011]    The foregoing is also applicable to Nam, U.S. Pat. No. 5,850,148, which discloses a vertical probe card apparatus having needles for contacting semiconductor products; and finally, the publication by Kulicke &amp; Soffa, entitled “Cobra FP Probe Card for Multi-Dut Logic &amp; Memory Applications” provides for a Cobra probe card which, however, requires the utilization of interposer structures that are subject to the disadvantages or drawbacks described hereinabove. 
       SUMMARY OF THE INVENTION 
       [0012]    Accordingly, in order to obviate or ameliorate the drawbacks and disadvantages encountered in the prior art with regard to the burn-in testing of semiconductor products, the present invention relates to a novel redesign configuration in the testing of equipment, wherein the guard plate and the upper die of the interposer assembly are integrated into a single unit thereby eliminating a portion of the structure which heretofore has exhibited a tendency to generate the difficulties encountered in the prior art aspects of semiconductor testing utilizing the Cobra contact design, wherein the present invention relates to the utilization of a non-ceramic die material and a new and novel Cobra contact. 
         [0013]    In essence, the present invention is directed to a Cobra structure utilizing a novel hole configuration in the upper die portion of the interposer structure, whereby only a small portion of the Cobra tip protrudes, rendering it less susceptible to being damaged in comparison with current designs. Moreover, the present structure eliminates the sticking features and is plug compatible with existing design structure making qualification implementation a simple task to one of skill in this particular testing technology. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Reference may now be made to the following detailed description of a preferred embodiment of the invention, taken in conjunction with the accompanying drawings; in which: 
           [0015]      FIG. 1  illustrates a perspective presentation of a part of a Cobra socket structure with a corner of a guard plate cut away pursuant to the prior art; 
           [0016]      FIG. 2  illustrates a perspective plan representation of a structure for a contact housing and a die pursuant to the present invention; and 
           [0017]      FIGS. 3A through 3C  illustrate the operation of a single Cobra contact in respectively open, initial contact with a module and closed positions. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Reverting to the drawings in specific detail,  FIG. 1  perspectively illustrates a portion of a structure of a prior art socket arrangement  10  with a corner of a guard plate  12  cut away, wherein the guard plate is essentially constituted of a coated metal having a plurality of apertures or holes  14  through which the tips of a Cobra contact  16 , which is mounted on an interposer die or plate  18 , may pass through upon depression of the guard plate  12 . In particular, the Cobra contacts  16  are mounted on the interposer plate  18 , which is normally of a ceramic or plastic material. In particular, as indicated previously, the guard plate  12 , which is a coated metal component, sometimes electronically shorts to the testing module (not shown), thereby providing potentially erroneous electrical output data. 
         [0019]    The interposer die  18 , which is formed of a plate comprised of a ceramic based material and which mounts the Cobra contacts  16  adapted to project upwardly therefrom into and through the holes  14  of the guard plate  12 , may, upon occasion, break by being of a relatively fragile nature, and moreover, the Cobra contacts are easily bent and possibly stick in the holes of the guard plate. Moreover, as indicated, the Cobra contact electrical current capacity may not be sufficient for new and contemplated future semiconductor products which require higher electrical power. 
         [0020]    Reverting to the present invention, there is eliminated the intermediate interposer plate and in that there is shown in  FIG. 2 , for example, only a single cut away die hole  20  and contact  22  in a cut-away portion of the interposer  24 . An upper die  26  is shown in this extended position and the gap between it and a lower die  28  can be clearly ascertained ( FIGS. 3A-3C ). The dies  26 ,  28  are interconnected by means of springs  30 , which can force the upper die into its extended position, and a pair of shoulder screw stops can also be provided herein. 
         [0021]    As indicated, in the open or extended view of the dies  26 ,  28 , as shown in  FIG. 3A , the Cobra contact  22  is protected within the through hole  32  of the upper die, the latter of which may have a funnel shape configuration and which will prevent sticking of the cobra contact in the hole or aperture formed therein. Moreover, only a short distance of the Cobra tip  34 , for example, 0.010″, protrudes from the upper die  26 , rendering it much less susceptible to being damaged in comparison with the extensive projection of the Cobra contact  16  from the interposer plate through the guard plate, as shown in the prior art pursuant to  FIG. 1  of the drawings. As indicated in  FIG. 3B  of the drawings, in the initial contact with the module, the upper die  26  is partly deflected downwardly to a point where the Cobra tip  34  would be just contacting the module (not shown) which mounts the semiconductor product, whereas in the fully closed view of  FIG. 3C , the upper die  26  is fully deflected and the Cobra  22  is in full compression against the module (not shown). Concerning the foregoing, the various structures of the Cobra and its functioning provides an important feature, not at all disclosed in the prior art, as follows: 
         [0022]    One very key feature to making this concept work is the locking of the swaged end  36  of the Cobra  22  into the lower die  28 . Without this feature, when the upper die  26  is returned to the extended position ( FIG. 3A ), many of the Cobra contacts would be lifted upwardly off of the PCB. This would cause unstable contacting with the PCB and would allow the Cobra to protrude further then 0.010″ from the upper die  26  making it more vulnerable to damage. This feature is accomplished through a unique hole profile through which the swaged end  36  of the Cobra  22  is pressed. When the swage passes through the press fit zone, it is free to operate as usual. This feature also drives a new loading technique that requires the contacts be pressed into the lower die first, then the upper die is slid over the Cobra shanks. 
         [0023]    The key feature that enables the guard plate to properly function and eliminates sticking pins, is the design of Cobra shank support hole  40  in the upper die  26 . The narrow portion  42  of the hole  40  has an unconventional minimal length giving the Cobra  22  an extra degree of freedom designed to eliminate sticking pins. Beyond this hole is a larger hole  44  designed to give the Cobra  22  limited freedom to “wipe” and at the same time protect/support the shank. 
         [0024]    The Cobra contact itself can be re-engineered to handle more current. A larger diameter wire made from a lower resistance material with modifications to the formed geometry is necessary to achieve a 4-amp cluster specification. 
         [0025]    From the foregoing, it becomes readily apparent that the present structure in the provision of the Cobra interposer for testing semiconductor products provides important distinctions over the prior art and advantages in the function and reliability thereof. 
         [0026]    Although the foregoing concept is adapted for the contacting of land grid arrays (LGAs) products, a variation of the concept may enable ball grid arrays (BGAs) to be contacted. Moreover, although the concept is designed for burn-in testing of semiconductor products, it may also be applied potentially in test socket areas of the technology. 
         [0027]    While the present invention has been particularly shown and described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms and details may be made without departing from the spirit and scope of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but to fall within the spirit and scope of the appended claims.