Patent Publication Number: US-6710614-B1

Title: Methods for using an interposer/converter to allow single-sided contact to circuit modules

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of application Ser. No. 09/414,203, filed Oct. 7, 1999, now U.S. Pat. No. 6,200,144, which is a divisional of application Ser. No. 08/810,048, filed Mar. 4, 1997, now U.S. Pat. No. 6,004,142, issued Dec. 21, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an interface adapter for providing single-sided electrical contact to a circuit card bearing contact elements on two sides. 
     2. State of the Art 
     Modern personal computers are designed to be easily upgraded by swapping out old components and replacing them with newer, faster, and higher capacity parts. For example, computer memory such as dynamic random access memory (DRAM) is upgraded by inserting single in-line memory modules (SIMMs) into preexisting sockets on a motherboard. SIMMs are small circuit cards with memory chips attached and a single-sided edge connector having a data width of 32-bits. Dual in-line memory modules (DIMMs) provide greater data widths (64- and 72-bits) and higher memory density, particularly useful for size-limited applications such as notebook computers. Microprocessors are also trending toward greater data (word) widths. DIMMs have dual-sided edge connectors to maintain a small form factor with wider data widths. The trend in state-of-the-art microprocessors is also toward wider word widths. This trend is generating demand for higher performance memory components such as DIMMs. 
     SIMMs and DIMMS are tested for bum-in (infant mortality) and functionality. For purposes of bum-in testing, standard SIMM and DIMM sockets can be used to test for infant mortality. Functional testing is performed on automatic test equipment, typically with a “bed of nails” type interface which was originally designed to simultaneously test a plurality of individually packaged dice. However, in the case of a SIMM card, with its single line of edge contacts on one side of the card, such test equipment may be easily adapted to electrically connect to the contacts of SIMM cards placed flat in a carrier tray such as a JEDEC (Joint Electronic Device Engineering Council)-configured tray. In such a case, eight to ten of the SIMM cards may be tested per tray on a tester of the aforementioned configuration at one time. 
     The current generation of circuit card test trays for SIMMs are not, however, adaptable to handle the dual-sided connectors of DIMMs because one-half of the edge connectors or contacts of the DIMM cards face opposite the test side of the tray by which contact is made. One possible solution is to design the DIMMs with through-hole or via-connected test pads extending from one side of the card to the other side, thus providing all edge connector contacts on one side of the card for test purposes. However, this potential solution requires greater use of limited circuit board real estate, as well as greater cost because of the additional traces and through-holes required. Moreover, the added conductive trace complexity may introduce more defects into the cards themselves, lowering yield for other than die-related failures. 
     Other circuit boards and cards employing dual-sided connectors and presenting similar test and contact problems include (by way of example only) other multichip modules (MCMs) including other dice in addition to or in lieu of memory dice, as well as triple in-line memory modules (TRIMMs). 
     Electrical sockets for connecting SIMMs are taught by Lwee et al. (U.S. Pat. No. 5,256,078, Oct. 26, 1993, hereinafter the “&#39;078” patent). Electrical sockets for connecting DIMMs are taught by Noschese et al. (U.S. Pat. No. 5,511,985, Apr. 30, 1996, hereinafter the “&#39;985” patent). While suitable for burn-in testing, neither the &#39;078 patent nor the &#39;985 patent teach a circuit card receptacle for routing edge connector traces from one side of the circuit card to the other side to facilitate testing of the card from a single side. Thus, there is a need in the art for a circuit card receptacle which allows single-sided testing of circuit cards or boards having dual-sided edge connectors to avoid the necessity for investing in new and different test equipment to accommodate such dual-sided connector configurations. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention comprises, in several embodiments, a circuit card receptacle for routing dual-sided edge connectors from any kind of multichip module (MCM) for effecting electrical contact from a single side of the receptacle. The invention may be combined with a test tray suitable for automatic testing of MCMs with automatic test equipment utilizing a bed of nails or other probe-type load board interface. 
     In the first embodiment of the invention, a U-shaped receptacle for circuit cards bearing dual-sided edge connectors or contacts is provided. The U-shaped receptacle allows direct connection of a “bed of nails” type load board to edge connectors on one side of a circuit card, termed for convenience the “test” side, and additionally provides test pads on the test side of the receptacle electrically connected to the nontest side edge connectors of the circuit card. The U-shaped receptacle is preferably pivotally mounted on a test tray for easy insertion and removal of the circuit cards and correct placement of the test pads to face the bottom of the tray. 
     A second embodiment of the invention also provides a circuit card receptacle pivotally mounted on a test tray. When viewed from a side elevation, the circuit card receptacle routes edge connector traces from both sides of the card to test pads on one surface of the receptacle located between the pivot point and the edge connector receptacle. 
     A third embodiment of the invention also provides a circuit card receptacle pivotally mounted on a test tray and, as illustrated, routes dual-sided edge connector traces to test pads on one surface of the receptacle. In this embodiment, a side elevation view reveals that the receptacle contains a pivot point located between test pads routed from edge connector traces and the edge connector receptacle. 
     It should be noted that the first embodiment may employ a pivot point located between the test points and the bottom or base of the “U,” or a pivot point may be on the legs of the “U.” 
     In the fourth embodiment, fixed circuit card receptacles are mounted on a test tray such that circuit cards inserted in the receptacles are perpendicular to the test tray. In this embodiment, both sets of edge connector traces of the card are routed to test pads located on the underside of the tray. This embodiment provides greater card density for testing in comparison to the others if suitable test equipment is available. Hereinafter, this embodiment is referred to as the fixed perpendicular embodiment. 
     An alternative means, and a fifth embodiment, for mounting the card receptacles on the test tray is the use of a quick-release mechanism for securing and removing each card receptacle from the tray. This method of mounting provides the advantages of the pivot mounting arrangements, first, by facilitating insertion and removal of circuit cards from the receptacle and, second, by allowing the receptacle with card inserted to be held coplanar with the test tray. Thus, a quick-release mechanism could be substituted for the pivot mounting mechanisms described in the first three embodiments above. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     FIG. 1 is a perspective, generic view of the invention as used with a test tray and a multichip module to be tested. 
     FIGS. 2A and 2B are side elevation and top views of a first embodiment of the invention employing a U-shaped, pivoting receptacle. 
     FIG. 3 is a side elevation of a second embodiment of the invention where the test pads are located between the pivot point of a pivotable circuit card receptacle and the edge connector receptacle. 
     FIG. 4 is a side elevation of a third embodiment of the invention where the pivot point of a pivoting circuit card receptacle is located between the test pads and the edge connector receptacle. 
     FIG. 5 is a side elevation of a fourth embodiment of the invention, also referred to as the fixed perpendicular embodiment, where the circuit card receptacles are rigidly fixed to the test tray which holds circuit cards under test perpendicular to the test tray. 
     FIG. 6 is a side elevation of a fifth embodiment of the invention, wherein a quick-release mechanism employing a snap-in type receptacle is used in lieu of a pivoting receptacle. 
     FIG. 7 is a perspective view of stackable test trays suitable for use with the receptacle embodiments illustrated in FIGS. 1,  2 A,  2 B,  3 ,  4  and  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An understanding of the detailed description of the invention is facilitated by drawing FIGS. 1 through 7. The embodiments of the invention each solve the problem of interfacing a dual-sided circuit card to a single-sided load board used in functional testing without resorting to expensive retooling of the tester interface or purchase of different test equipment. 
     FIG. 1 shows an exemplary, pictorial view of the invention comprising a circuit card receptacle  2  mounted on a test tray  3 . The test tray  3  could be fabricated with any number of receptacles  2 , limited only by tray size and the number of circuit card test pins  11  (also termed “pogo pins,” “nails” or “probes”) available on the load board  13 . Load board  13  is connected to a test interface adapter  200 , which in turn is connected to a functional test system  202  comprising a computer controlled by a software test program. FIG. 1 shows a representative circuit card  19  which is to be inserted  41  into the receptacle  2 . The circuit card  19  has a dual-sided edge connector  15  with two rows of edge connector traces  6  and  8 , one on the nontest side  43  and another (not visible in FIG. 1) on the test side  45 . Mounted on the circuit card  19  are integrated circuit dice  17 . The circuit card  19  engages the receptacle  2  at a socket or slot  10 , which may be formed with either closed or open lateral ends but, if with open ends, also providing tabs or stops proximate each end for proper lateral card location. The edge connector traces  6  of nontest side  43  of the circuit card edge connector  15  connect with mating edge contacts  27  (one shown in broken lines in FIG. 1) within the slot  10  connected to circuit traces  7  extending from within the socket or slot  10  to a first row of test pads  9  located on the test side of the receptacle  2 . Similarly, the edge connector traces  8  of test side  45  of the circuit card edge connector  15  connect with mating edge contacts  31  within the socket or slot  10  connected to circuit traces  7   a  extending from within the socket or slot  10  to an additional, second row of test pads  9  also located on the test side of receptacle  2 . Mating edge contacts may comprise any suitable structures, such as leaf spring contacts or zero-insertion-force (ZIF) contacts. Further, circuit traces  7  and  7   a  are desirably routed and configured for minimal length and matched impedance. The receptacle  2  is rotatable as shown at  23  about an axis  24  extending between pivot or hinge points  5  to facilitate insertion and removal  41  of the circuit card  19  under test. The test pins or probes  11  of the load board  13  mechanically contact and electrically communicate with the test pads  9  arrayed in a mating configuration when the test tray  3  is aligned and engaged with the load board  13 . The five embodiments of the invention are described in further detail in FIGS. 2 through 7. 
     FIG. 2A shows a side cross-sectional elevation of the first embodiment of the invention. A U-shaped half-socket receptacle  1  is provided to route the edge connector traces  6  on nontest side  43  of circuit card  19  to test pads  9  by circuit traces  7 , using mating edge contacts  27 . This embodiment further allows direct connection  29  to test side edge connector traces  8  on the circuit card  19 . It should be noted that, in this embodiment, test pads  9  and test side edge connector traces  8  lie in a substantially coplanar relationship parallel to the plane of test tray  3  for coequal contact with load board  13 . Since only one side of circuit card  19  is connected by circuit traces  7  to test pads  9 , while connector traces  8  make direct contact with test pins  11 , it may be desirable to include components in circuit traces  7  so that impedance matching may be achieved. The half-socket receptacle  1  is pivotally mounted  5  on a test tray  3  to allow: (1) linear insertion and removal  41  of a circuit card  19  to be tested, and (2) rotation  23  of the circuit card  19  until it is coplanar with the test tray  3  and ready to interface with the “pogo” pins or nails  11  on the load board  13 . FIG. 2B shows the circuit card  19  held in the half-socket receptacle  1  by slots  22  in legs  21  of the “U” engaging the lateral marginal extremities of the circuit card  19 . The circuit card  19 , inserted in the half-socket receptacle  1 , is held coplanar within the test tray  3  by a retaining clip  25  extending or protruding from test tray  3  to engage the top of the circuit card opposite the edge connector  15 . The retaining clip  25  could be of any conventional design such as a leaf or bow spring, a spring-loaded ball detent, or a pivoting post, and so will not be further described herein. This embodiment may be modified to provide test pads electrically connected to edge connector traces  6 ,  8  on both sides of a circuit card  19  by configuring receptacle  1  as shown in FIGS. 3 and 4 and subsequently described herein. 
     FIG. 3 is a side elevation of the second embodiment of the invention. A receptacle  2  including a slot or socket  10  is provided to route connector traces or contacts  6 ,  8  from both sides of the dual-sided edge connector  15  to test pads  9  on receptacle  2 . The receptacle  2  is pivotally mounted at  5  to the test tray  3  and locates test pads  9  between the pivot point  5  and the circuit card socket or slot  10 . Like the first embodiment, the receptacle  2  is pivotally mounted on a test tray  3  to facilitate insertion and removal  41  of the circuit card  19  and rotation  23  of the circuit card  19  until it is coplanar with the test tray  3  and ready to interface with the pogo pins  11  of the load board  13 . The circuit card  19  is held in the receptacle  2  by socket or slot  10 . The edge contacts  27  and  31  of socket  10  mechanically and electrically engage the connector traces  6 ,  8  of dual-sided edge connector  15  of the circuit card  19  and are respectively routed to test pads  9  by circuit traces  7  and  7   a  of receptacle  2 . The circuit card  19  is held coplanar within the test tray  3  by a retaining clip  25  of any suitable configuration, as previously discussed, at the edge of the circuit card opposite that occupied by the edge connector  15 . 
     FIG. 4 shows a side elevation of the third embodiment of the invention. A receptacle  4  is provided to route connector traces or contacts  6 ,  8  from opposing sides of the dual-sided edge connector  15  to test pads  9  on receptacle  4 . The socket  4  is pivotally mounted at  5  to the test tray  3 . The pivot point  5  is located between the test pads  9  and the circuit card slot  10  of receptacle  4 . Like prior disclosed embodiments, the receptacle  4  is pivotally mounted on a test tray  3  to allow insertion and removal  41  of the circuit card  19  under test and rotation  23  of the circuit card until it is coplanar with the test tray  3  and ready to interface with the pogo pins  11  on the load board  13 . The circuit card  19  is held in the receptacle by a socket or slot  10 , which mechanically and electrically engages the dual-sided edge connector  15  of the circuit card  19 . The circuit card  19  is held coplanar within the test tray by a retaining clip  25  of suitable design at the end opposite the edge connector. The advantage of this embodiment over the second embodiment is that the direct connection  29  of the pogo pins  11  against the test pads  9  tends to hold the circuit card coplanar within the test tray  3 , permitting use of a much less robust retaining clip  25 , or eliminating the need for same altogether. The first embodiment may be modified in a similar manner by movement of pivot or hinge points accordingly. 
     A fourth embodiment of the invention, shown in FIG. 5, provides a plug-in receptacle  40  removably mounted on a test tray  3  such that each circuit card  19  under test is mounted perpendicular to the test tray  3 . In this embodiment, the circuit card  19  is received in a socket or slot  10  and the receptacle  40  routes connector traces  6  and  8  by circuit traces  7  and  7   a  to test pads  9  on the bottom of the receptacle  40 . While receptacle  40  is preferably formed separately from test tray  3  and is plugged thereinto in a snap-in fashion as depicted in FIG. 5, a tray with a plurality of integrally-molded receptacles  40  may be fabricated. The advantage of this embodiment is that potentially more circuit cards could be mounted on a tray. However, this embodiment does not facilitate stacking of trays with mounted circuit cards  19  ready to test because the circuit cards  19  project from the plane of the tray. In comparison, test trays incorporating the first three embodiments can be stacked easily to facilitate movement and storage of the loaded test trays in an automated production test environment. Further, the circuit density in the fixed perpendicular embodiment may require upgraded test equipment. 
     The various pivot mounting mechanisms described above may be replaced by a quick-release mechanism, such as depicted in FIG.  6 . Such a quick-release mechanism allows rapid fixing and removal of the receptacle to, in turn, facilitate insertion and removal of the circuit card to be tested. The quick-release mechanism also allows the card and receptacle combination to lie coplanar with the test tray, as with the pivoting embodiments. Once the cards and receptacles are secured, the entire tray can be interfaced with a bed of nails-type load board on a functional tester. Thus, a quick-release mechanism substitutes for the pivot mount. The pivot mounting scheme is preferable only because it is integrated, whereas the quick-release scheme permits preloading of circuit cards in receptacles for subsequent insertion in trays. Trays using both pivoting and quick-release receptacles may be easily stacked. 
     FIG. 7 illustrates stackable test trays  700  according to the invention. Stackable test trays  700  may include pivoting or quick-release receptacles as described above and illustrated in FIGS. 1,  2 A,  2 B,  3 ,  4  and  6 . 
     The quick-release mechanism  100  as shown in FIG. 6 comprises a rectangular, window frame-type receptacle  102  into which a circuit card  19  may be inserted. Receptacle  102  includes an upper window  104  in its upper surface (as depicted in FIG. 6) through which circuit card  19  may be inserted with its dual-sided edge connector  15  extending into shallow slot  110  in receptacle base  112  wherein edge contacts  27  and  31  respectively mechanically and electrically engage connector traces  6 ,  8  of dual-sided edge connector  15 . Edge contacts  27  electrically communicate through circuit traces  7  with a first set of test pads  9  on the bottom of receptacle  102 , while edge contacts  31  communicate through circuit traces  7   a  with a second set of test pads  9  coplanar with the first set. Circuit card  19  is maintained in slot  110  by an elastomeric biasing pad  114  carried by receptacle header  116 . Base  112  and header  116  are joined by side columns  118  extending transversely therebetween. Biasing pad  114  needs to provide only a nominal bias to retain circuit card  19  in receptacle  102  during handling and testing, as receptacle  102 , and not circuit card  19 , sustains the transverse mechanical loading imposed by contact of test pins  11  with test tray  3 . Receptacle  102 , in turn, is secured within receptacle bay  120  of test tray  3  by engagement of linear protrusion  122  (which extends across the top of header  116 ) with slot  124  on one end of bay  120 , while a detent  126  (shown here by way of example as a coil-spring-biased, bullet-shaped element with a hemispherical head) engages dimple or cavity  128  in receptacle base  112 . Test pads  9  are exposed to test pins  11  through test aperture  130  in the bottom of receptacle bay  120  in test tray  3 . 
     In operation, circuit card  19  is loaded into a receptacle  102  as previously discussed. Receptacle  102  is then snapped into a bay  120  in a test tray  3  (each test tray preferably having a number of such bays formed therein), each bay  120  receiving a receptacle  102  carrying a circuit card  19 . A tray of circuit cards  19  is then tested on load board  13 , pogo pins  11  contacting test pads  9  associated with each circuit card  19 . After load testing, receptacles  102  are unloaded by pulling them out of bays  120  transverse to the plane of test tray  3 , overcoming the spring bias of detent  126 . The insertion and removal operation may be manual, and fingerholds (not shown) may be provided on receptacle  102 . Further, an access window  132  may be provided in the bottom of each bay  120  so that a pin-type removal mechanism  134  may engage the headers  116  of receptacles  102  and “pop” them out of test tray  3 , as shown. Receptacles  102  may also be employed for storage, handling and testing of circuit cards  19  before and after load testing for protection of circuit cards  19 . 
     It will be understood that all of the embodiments herein should be formed of a low-static plastic or other polymers, or include an antistatic coating thereon. It will be further understood that each receptacle embodiment may be tailored for a specific card configuration (size and shape, number of contacts, contact pitch, etc.), and that such receptacles will preferably be configured on their exteriors to be interchangeable on carrier trays, in terms of interchangeability of receptacles for others of the same embodiment. 
     Although the present invention has been described with reference to particular embodiments, the invention is not limited to these described embodiments and additions, deletions and modifications to the disclosed embodiments, including without limitation the combination of features of different embodiments, will be apparent to those of ordinary skill in the art and lie within the scope of the claims following this specification.