Abstract:
A programmable connector for use with a burn-in tester for manufactured integrated circuits is provided with an array of programming regions which can be selectively activated and deactivated to accommodate a specific testing configuration depending on the type of IC being tested and on the type of test being performed. The activation process is achieved using a conductive solution, applied selectively to the programming regions from a hand-held pen-type implement. The solution dries following application and serves to close a circuit between two electrically isolated conductive portions of the programming region. The solution is removable, using a solvent or other material, deactivation of the programming region for re-configuring the programmable connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     (Not applicable) 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to electrical devices, and more particularly, to programmable connectors for selectively connecting multiple circuits. 
     2. Description of Related Art 
     Following manufacture, integrated circuits are typically powered up and run for a test period prior to shipping to customers in order to weed out those devices which fail prematurely. This process is called burn-in and is typically performed at elevated temperatures to help accelerate early failures, or “infant mortalities.” The burn-in system typically consists of a burn-in tester which provides the electrical test signals to the packaged integrated circuit, referred to as the device under test (“DUT”), and an oven which provides the temperature acceleration. The DUT is loaded into a load board and placed in the oven. The load board is constructed using conventional printed circuit board techniques and materials. Electrical test signals are routed from the burn-in tester through the load board to the appropriate terminals or pins of the DUT package. 
     Conventionally, there is a wide variety of types of integrated circuit packages and number of pins on each package. In addition, for a given package type and pin count there is an infinite number of products which can be housed inside it. This means the routing of the electrical test signals to the pins of the package presents an extremely large number of combinations. Historically, a separate load board has been made for each product, wherein the traces on the load board which carry the electrical test signals are routed to the specific pins, or leads, of the product. This is a “hard wired” design which does not allow for changes in the routing of the electrical test signals either to accommodate different devices to be tested or to perform different tests on a device. If the product pinout changes, a new load board must be manufactured to be able to burn it in. Likewise, a new load board needs to be manufactured for every new product. 
     Load boards are expensive and their wiring to the burn-in tester is labor intensive and time-consuming. Part of the expense is due to a robustness requirement, whereby the load boards need to be able to operate at elevated temperatures (up to 350° C. or more), provide little if any signal degradation and remain reliable for one to two years of continuous operation at the elevated temperatures. It therefore becomes important to minimize the need to replace load boards, to thereby reduce the production costs of integrated circuits. One way to minimize the need to replace load boards is to make them more versatile in their applicability. 
     Versatility can be achieved using a programmable connector which operates as a selectively configurable wiring interface between the load board on which the DUT is mounted and the burn-in tester. The programmable connector is thus designed to accommodate the electrical configuration of a variety of DUTs. Typically, the programmable connector employs a mechanical jumpering system, wherein transversely extending conductors are selectively connected to each other by placement of pins or other conducting bridges between them, as illustrated in FIG.  1 . Conductors  12 A and  12 B are normally spaced apart and isolated from each other, for instance by an intervening insulating substrate  11  on which they are mounted in the programmable connector. One set of these conductors,  12 A, is in electrical connection with the burn-in tester (not shown). The other set,  12 B, is in electrical connection with the DUT (not shown). Programming the connector is effected using conducting pins  10  inserted in holes  16 A formed on one side of the connector and holes  16 B formed on the other side. The holes  16 A and  16 B are surrounded by conducting lands  18 A and  18 B, respectively, which are electrically contiguous with conductors  12 A and  12 B. When inserted in holes  16 A and  16 B, pins  10  make contact with the associated lands  18 A and  18 B and in this manner connect the corresponding connectors  12 A and  12 B. A plurality of pins  10  are used to make the connections required by the particular DUT and the test to be performed. 
     Other methods of selectively connecting a DUT to a burn-in testor are known. One known method uses an operationally similar scheme to that described above. Instead of holes, the connector is provided with arrays of header pins protruding outwardly from the programmable connector, each header pin being associated with a connector which is either in connection with the DUT or the burn-in testor. The header pins can be selectively shunted together to bridge the connection between the DUT and the burn-in tester in a selectively configurable manner. 
     The above prior art schemes suffer from several disadvantages, including those associated with size, cost, reliability and complexity. Because in both prior art systems discussed pins are used which protrude perpendicularly from the connector, the profile of the connector is increased in the pin direction, detracting from the stackability of the connectors when employed in sets of more than one. Additionally, especially with respect to the header pin system, the cost per device is high because of the increased complexity of the device. The use of pins to effect an essentially mechanical connection also introduces reliability concerns. Good electrical contact must be insured with the manual insertion of each pin or with the shunting of each pair of pins for proper operation. Finally, the complexity of the devices, especially the header type connector, increases the probability of failure of the device. 
     There therefore exists a long felt need to provide a simple programmable connector which is inexpensive to produce, has minimal profile and is readily stackable, and which is reliable and easy to operate. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the present invention, a programmable connector is provided with programming regions which can be selectively activated using a conductive solution applied to the programming regions. The regions can be deactivated using a solvent or other material to remove the conductive solution. 
     Preferably, an array of programming regions is provided on a surface of the programmable connector, Each programming region is associated with a first conductor in connection with the burn-in tester and a second conductor in connection with the device under test. The first and second conductors have conductive portions which are electrically isolated from each other. A support region is disposed between the two portions, which support region serves to support the solution such that when the solution is applied to the programming region, it completes an electrical path between the conductive portions of the first and second conductors. 
     More preferably, the array of programming regions is in the form of an ordered matrix, with the pair of conductive portions of each programming portion being in the shape of two bars of an equal sign, making for easy visual recognition by the operator. Similarly, it is preferred that the conductive solution be visible, and be dispensed from a hand-held pen-type implement. Similarly, it is preferred that the solvent for removing the solution be dispensed from a hand-held pen-type “erasing” implement. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     Many advantages of the present invention will be apparent to those skilled in the art with a reading of this specification in conjunction with the attached drawings, wherein like reference numerals are applied to like elements and wherein: 
     FIG. 1 is a schematic drawing showing a prior art programmable connector; 
     FIG. 2 is a schematic drawing showing a testing system in accordance with the invention; 
     FIG. 3 is an isometric, partial cut-away view of a programmable connector in accordance with the invention; 
     FIG. 4A is a top plan view of a pair of programming regions in accordance with the invention; 
     FIG. 4B is a cross-sectional view taken along line  4 B— 4 B of  4 A; 
     FIG. 5 is a top plan view of a pair of programming regions in which an one programming region is activated in accordance with the invention; 
     FIG. 6 is a schematic view showing a shared pad arrangement in accordance with the invention; and 
     FIG. 7 is a schematic view showing a dedicated pad arrangement in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 2-7 schematically show exemplary testing system and programmable connector in accordance with the present invention. The connector  20  operates as an interface between a device under test (DUT) such as packaged integrated circuit  32  which is mounted on a load board  36 , and a burn-in tester  28  which issues test signals to and receives and monitors response signals from the DUT during the testing process. Two-way arrows  22  and  24  represent signal traffic between the devices. 
     As can be seen from FIGS. 2 and 3, connector  20  comprises generally an insulating substrate  26 . On one surface of connector  20  is provided an array of programming regions  30 . FIG. 3 details the layout of the programming regions  30  of FIG.  2 . Each programming region  30  comprises a conductive portion  34  of a conductive trace  38  in confronting relationship with a conductive portion  42  of a pad  40 , best seen in FIGS. 4A and 4B. Additionally, each programming region  30  comprises a support region  62 , whose function is described below. 
     Traces  38  and pads  40 , along with conductive portions  34  and  42 , are all made of suitable metallic or other conductive materials readily formed on or embedded in substrate  26  in accordance with known circuit board fabrication techniques. Also provided on connector  20 , on an opposite surface thereof or at least in substantial electrical isolation from conductive trace  38  is a conductive trace  44 , also comprising suitable metallic or other conductive materials. Trace  38  is one of an array of such traces provided on or in connector  20 , while trace  44  is also one of an array of similar traces provided in substantial isolation from traces  38 . Although exemplarily these traces are shown to extend in substantially straight lines along opposite surfaces of connector  20  and orthogonally to each other, it is to be understood that other shapes and relative directions of the traces are contemplated. At least one of traces  38  is in electrical communication with burn-in tester  28 , while at least one of traces  44  is in electrical communication with the DUT such as packaged integrated circuit  32 , via load board  36 . It is also contemplated that connector  20  and load board  36  may be integrally formed as one contiguous structure, rather than as discrete devices as exemplarily shown. 
     Preferably, but not necessarily, traces  38  are buried beneath the surface of the connector  20 , with only the portions  34  thereof being exposed outside an insulating material, such as substrate  26  or other suitable non-conductive laminate or other layer (not shown), which forms the surface of the connector  20 . In a similar manner, pads  40  are buried beneath the surface of substrate  26 , with only portions  42  thereof being exposed. Portions  34  and  42  can be raised so as to protrude outwardly through the surface of connector  20 . Alternatively, the material forming the surface, such as the laminate or other layer, can be etched away to define portions  34  and  42 . 
     Traces  44  are preferably, but not necessarily, buried beneath the opposite surface of connector  20 , which opposite surface is formed by substrate  26  itself or by a suitable non-conductive laminate or other layer (not shown). Traces  44  are in electrical communication with corresponding pads  40  (and conductive potions  42  thereof) through vias  46  extending through substrate  26  of connector  20 . Vias  46  are formed through conventional printed circuit board fabrication methods, comprising a conductor-lined hole passing from the pad  40  to the trace  44 , and providing a conductive path between a column of pads  40  and an associated trace  44 . Other methods of connecting the pads  40  and traces  44 , such as a transverse wire or trace, fall within the purview of the invention, although the use of vias may be economically more efficient. 
     To program connector  20 , an operator activates a programming region  30  by using a pliant conductive material, such as a solution dispensed in the form of an “ink” from a “pen,” or pen-type device, to “write” a layer of material, shown in the form of a circle, or dot  50 , over support region  62  of programming region  30  in FIG.  5 . The written dot  50  of conductive ink bridges the gap  48  separating portions  34  and  42 , closing a circuit path between the trace  38  of the portion  34  and the trace  44  corresponding to the portion  44 . Support region  62  is made from non-conductive material extending from the portion  34  to portion  42 . This non-conductive material may be the substrate  26  itself, or it may be a laminate or suitable layer which maintains electrical isolation between portions  34  and  42  preceding application of the pliant conductive material dot  50 . It will be appreciated that although depicted as occupying a gap  48 , support region  62  can take any desired shape as long as it functions to support the conductive solution in such a way as to permit the solution to close a circuit path between the portions  34  and  42 . 
     By selectively writing in dots of conductive ink on connector  20 , the operator achieves a specific routing configuration for the connector  20 . This operation, it will be appreciated, is simple and can be performed accurately, with the operator being guided by the “equal sign” appearance of the pair of conductive portions  30 . Of course, it will be appreciated that other shapes can be selected for the conductive portions  34  and  42 , and the choice of the depicted rectangular bars forming the “equal sign” shape is merely one of aesthetics, facilitating easy identification and guidance for the operator during the programming operation. Depending on the particular DUT being tested, an appropriate conductive ink dot pattern can be formed on the connector  20  by writing in one or more dots in appropriate locations on the connector  20 , thus achieving different routing configurations and customizing the DUT-burn-in tester  28  connection in accordance with the particular DUT configuration and the test to be performed thereon. 
     Pens for dispensing conductive solution, or ink, are known in the art and are available from for example Chemtronics™. These pens are self-contained, disposable, handheld tubular devices very much resembling a conventional ink pen writing instrument and containing a limited amount of conductive material dispensed through one end upon that end&#39;s contact with a surface, in this case the support region  62 . The conductive ink comprises a suitable electrically conductive material which dries in place following application. Preferably, the ink is visible, providing the operator with visual feedback indicative of the propriety of the connection written and the configuration of the programmed connector. Additionally, the programming regions  30  can be deactivated if a mistake is made, or for purposes of reconfiguring the connector  20  for use with a different DUT or for performing a different test on the same DUT, as is contemplated. To deactivate a programming region  30 , the conductive ink is removed, or “erased” from support region  62  of the programming region, using appropriate chemical solvents or similar materials. Known solvents or other materials, also dispensed from a pen-type device or sponged on or otherwise applied over the dots targeted for removal readily accomplish this. 
     For purposes of economy, in the above-described exemplary arrangement two conductive portions  42  share a single pad  40 . Thus, as can be seen from FIG. 6, each pair of programming regions  30 A and  30 B involve three traces— 38 A,  38 B and  44 A, such that one or both traces  38 A and  38 B can be connected to trace  44 A by application of conductive ink across gaps  48 A and  48 B. It is also possible that a dedicated system can be provided, as seen in FIG. 7, wherein each programming region  30 C involves only two traces— 38 C and  44 B, and only one connection, between traces  38 C and  44 B, can be made with the conductive ink bridging gap  48 C between conductive portions  42 A on pads  40 A. 
     It will be appreciated that while the invention is described exemplarily in the context of a burn-in tester, limitation to this context is not intended. Rather, the teachings of the invention can be applied for any general electrical routing use, especially applications in which frequent or repeated reprogramming is required. The simplicity of programming and reprogramming the system of the invention readily lend to such applications. 
     The above are exemplary modes of carrying out the invention and are not intended to be limiting. It will be apparent to one of ordinary skill in the art that modifications thereto can be made without inventive departure from the spirit and scope of the invention as set forth in the claims below.