Abstract:
An electronic module test assembly comprising a frame, an array of contact pins, and at least one latch. The frame has a recess formed therein for receiving an electronic module. The array of contact pins is anchored to the frame. The contact pins have resiliently depressible terminals forming a resiliently depressible contact array in the recess. The latch is movably mounted to the frame for latching the electronic module to the frame. The latch is movable relative to the frame and engages an outer edge of the electronic module when the electronic module is disposed against the resiliently depressible contact array. The resiliently depressible contact array biases the electronic module against the latch.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to test sockets for electronic modules and, more particularly, to a test socket for a ball grid array electronic module.  
           [0003]    2. Brief Description of Earlier Developments  
           [0004]    The continued desire of consumers for ever smaller electronic device has spurred increased miniaturization of electronic components. In response, manufacturers have been driven to add more and more components into smaller integrated electronic packages or modules. One such module is the “Bluetooth” architecture, system-on-a-chip or “super component” module developed by Lucent Technologies and Ericsson. The “Bluetooth” super component module incorporates an entire RF/baseband radio subsystem into a single component. The electronic modules must be tested for purposes of quality assurance (QA) after manufacture, as well as for R&amp;D purposes. QA testing is basic, checking the general operation of the manufactured module such as the existence of open connection or shorts in the module. One example of a conventional test socket for reliability or “burn-in” testing of IC chips is disclosed in U.S. Pat. No. 5,807,104. This test socket has a base with a positioning plate with contacts slidingly contained therein. An IC chip is placed on the positioning plate, and the socket has a hinged cover which is closed over the chip bringing the chip into contact with the contacts in the positioning plate. Another example of a conventional apparatus for testing ball grid array packaged integrated circuits is disclosed in U.S. Pat. 5,955,888. The apparatus here has a nesting member to hold the integrated circuit (IC). The nesting member is resiliently supported on a printed circuit board. A device handler is placed over the IC, and presses the IC and nesting member down to contact spring loaded pins in the printed circuit board. As can be realized from the above examples, conventional testing sockets have a substantially closed architecture which interferes with an operator&#39;s ability to access components mounted on the tested module. This arrangement is generally suitable for some general reliability testing but does not lend itself to specific fault investigation or R&amp;D testing of the electronic modules. R&amp;D testing is performed on the modules as part of design development and integration of a given module type within the system of a given electronic device. Accordingly, in order to perform R&amp;D testing of a module, operators may have to access individual miniature components on the electronic module. Unimpeded access to the miniature components on electronic modules such as the “Bluetooth” super component modules is generally not available with conventional test sockets. The present invention overcomes the problems of the prior art as will be described in greater detail below.  
         SUMMARY OF THE INVENTION  
         [0005]    In accordance with a first embodiment of the present invention, an electronic module test assembly is provided. The test assembly comprises a frame, an array of contact pins, and at least one latch. The frame has a recess formed therein for receiving an electronic module. The array of contact pins is anchored to the frame. The contact pins have resiliently depressible terminals forming a resiliently depressible contact array in the recess. The latch is movably mounted to the frame for latching the electronic module to the frame. The latch is movable relative to the frame and engages an outer edge of the electronic module when the electronic module is disposed against the resiliently depressible contact array. The resiliently depressible contact array biases the electronic module against the latch.  
           [0006]    In accordance with a second embodiment of the present invention, an electronic module test socket is provided. The test socket comprises an insulating frame, at least one contact pin, and at least one latch. The insulating frame has an electronic module receiving recess formed therein. The contact pin is secured to the frame. The contact pin has a resiliently movable contact terminal disposed in the recess. The latch is connected to the frame. The latch is movable relative to the frame for locking an electronic module received in the recess to the frame. When the electronic module is received in the recess, the electronic module resiliently moves the contact terminal effecting contact between the module and contact terminal and allowing the latch to move and engage a top side of the module. This maintains the module in contact with the contact terminal and leaves an access area over the module substantially open for a user to access module components on the top side of the module.  
           [0007]    In accordance with a method of the present invention, a method for testing an electronic module is provided. The method comprises the steps of providing a test socket, and inserting an electronic module in the test socket. The test socket is provided with an electronic module receiving recess therein, and an array of spring loaded contact pins having resiliently depressible contact terminals projecting into the recess. The test socket is provided with a movable latch for latching the electronic module in the receiving recess. The electronic module is inserted into the socket through a top opening of the receiving recess. The electronic module is inserted into the receiving recess to resiliently depress the contact terminals so that the latch is allowed to move over the module and engage an outer edge of the module. The latch holds the module against the resiliently depressed contact terminals. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:  
         [0009]    [0009]FIG. 1 is a perspective view of an electronic module test assembly, incorporating features of the present invention in accordance with a first preferred embodiment, an electronic module and a printed circuit board;  
         [0010]    [0010]FIG. 2 is a cross-sectional view of the test assembly shown in FIG. 1 with the electronic module installed in the test assembly;  
         [0011]    [0011]FIG. 3 is a perspective view of a spring loaded ball plunger of the test assembly shown in FIG. 1;  
         [0012]    [0012]FIG. 4 is a top plan view of the test assembly shown in FIG. 1;  
         [0013]    [0013]FIG. 5 is a partial cross-sectional view of an electronic module test assembly in accordance with a second preferred embodiment of the present invention; and  
         [0014]    [0014]FIG. 6 is a magnified partial cross-sectional view of the electronic module test assembly in FIG. 5 showing features of a latch assembly in the test assembly. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0015]    Referring to FIG. 1, there is shown an perspective view of a test assembly  10  incorporating features of the present invention in accordance with a first preferred embodiment of the present invention, an electronic module M and a printed circuit board B. Although the present invention will be described with reference to the single embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms of embodiments. In addition, any suitable size, shape or type of elements or materials could be used.  
         [0016]    In general, test assembly  10  comprises a socket frame  12 , latches  16  and an array  18  of spring loaded contact pins  20 . The socket frame  12  has a module receiving recess  14 . Latches  16  are mounted to the frame  12  to latch a module in the recess. The array of spring loaded contact pins  20  projects into the recess  14 . Test assembly  10  is mounted on test board B with terminal ends of the contact pins  20  connected to contact pads on the test board. Test assembly  10  interfaces the module M with test board B. The module M is inserted into the receiving recess  14  of the socket frame  12  until latches  16  engage the module. Contact pins  20  in the recess make contact with contacts on the module thereby effecting a connection between the module and contacts on the PCB. The open architecture of the test assembly  10  allows a user substantially unimpaired access to the top of the module M located in the receiving recess  14  of the test assembly  10 .  
         [0017]    In greater detail, and referring still to FIG. 1, the electronic module M is a surface mounted electronic module, such as for example a “Bluetooth” architecture module. The present invention however is applicable equally to any other suitable surface mounted electronic module or package. The module M generally comprises a printed circuit board  100 . The module M has a number of components  102  located on the top surface  101  of the circuit board. The components  102  may be integrally formed in the PCB  100  or may be otherwise mounted to the top of the PCB. The components  102  may be of any suitable type. In the case of a “Bluetooth” module, for example, the components may incorporate an entire RF base band radio subsystem onto the module. Referring also to FIG. 2, the module M also has an array of contacts  108  on the bottom surface  103  of the PCB  100 . In the preferred embodiment the contact array on the PCB  100  is a ball grid array (BGA). In alternate embodiments, the contact array on the PCB of the electronic module may have any other suitable type of surface mounting contacts. Test board B is shown in FIG. 1 as a representative test board. The test board B thus generally comprises a PCB  200  with suitable integrated circuits (not shown) for performing desired testing on the module M. The PCB  200  also has an array  202  of contacts located on the upper surface of the board.  
         [0018]    As noted before, the test assembly  10  has a socket frame  12 , latches  16  and a contact array  18 . Socket frame  12  is made of insulating material as will be described in greater detail below. In the preferred embodiment, shown in FIGS. 1 and 2, the socket frame  12  comprises layers  22 - 30 , and fasteners  36 . Two board layers  24 ,  28  are substantially similar to each other. Each board layer  24 ,  28  may be made from hard plastic or any other suitable insulating material. The boards  24 ,  28  are preferably cut from plastic sheets, though the boards may be formed in any other suitable manner. Accordingly, boards  24 ,  28  are substantially flat and as seen in FIG. 2, the boards  24 ,  28  are of similar thickness in this embodiment. In alternate embodiments the thickness of the boards may vary as desired. Each board  24 ,  28  is formed in a general rectangular shape. Each board  24 ,  28  also has a pair of scallops  38 ,  40  which are preferably cut into the opposite longitudinal sides  24 S,  28 S of the boards (see FIG. 1). The scallops  38 ,  40  are located in the sides of the boards  24 ,  28  so that when the boards are stacked the scallops  38 ,  40  are generally aligned with each other. Each board  24 ,  28  has an array of contact holes  46 ,  48 . The contact holes  46 ,  48  extend through the respective board. Holes  46 ,  48  may be formed into the boards  24 ,  28  by drilling or any other suitable boring means. Each board  24 ,  28  also has four through holes (not shown) for fasteners  36 .  
         [0019]    As seen best in FIG. 2, in the preferred embodiment, the socket frame  12  has a thin intermediate layer  26 . Layer  26  is cut or formed otherwise from high strength, elastic polyimide sheet such as Kapton® sheet available from DuPont®. The polyimide sheet from which frame layer  26  is cut may have a thickness of about 30 or 50 mils though in alternate embodiments the thickness of layer  26  may vary as desired. In other alternate embodiments, this layer of the frame may be made from any other suitable material. As can be realized from FIG. 1, layer  26  has a shape which conforms substantially to the shape of board layers  24 ,  28  described before. Thus, layer  26  also has a general rectangular shape, with scallops  41  formed in the longitudinal sides to line up with the scallops  38 ,  40  in board layers  24 ,  28 . As shown in FIG. 2, layer  26  is also provided with an array of holes  52  for holding contacts  20 . The holes may be punched or cut into layer  26 . The holes  52  in layer  26 , are located to line up with the contact holes  46 ,  48  in board layers  24 ,  28 . Holes  52 , however, are smaller than the matching holes  46 ,  48  in board layers  24 ,  28  as will be described further below. Layer  26  also has four fastener through holes (not shown) for fasteners  36 .  
         [0020]    Board layer  30  is the bottom layer of the socket frame  12 . Except as otherwise noted below, board layer  30  is generally similar to layers  24 ,  28  described previously. Thus, like layers  24 ,  28 , board layer  30  is also cut or formed from hard plastic to have a general rectangular shape with scallops  42  formed into longitudinal sides  30 S. Contact holes  50  are drilled through the board layer to align with matching holes  46 ,  48  in layers  24 ,  26 . Layer  30  also has four fastener holes (not shown) for fasteners  36 . However, unlike layers  24 ,  28 , in the preferred embodiment, the fastener holes in layer  30  are threaded to engage mating threads on fasteners  36 . The fastener through holes in layers  24 ,  26 ,  28  are unthreaded. In addition, board layer  30  may be provided with receiving holes for mounting guide pins  60  into the board layer. The holes in layer  30  for guide pins  60  are blind holes made in the lower surface  32  of the board. In the preferred embodiment, board layer  30  has four guide holes for four guide pins  60 , though in alternate embodiments the board may have any suitable number of holes therein for mounting guide pins. For example, the board may have several alternate patterns of guide holes to allow installation of the guide pins in one of the several patterns to suit a given configuration of holes in the test board. The bottom surface  32  of board layer  30  may also have standoff legs or chocks (not shown)located in any suitable pattern to support the test socket  10  off the test board B. The standoff legs may be formed integral with the board layer  30  or may otherwise attach to the bottom surface by any suitable means such as adhesive.  
         [0021]    Referring now also to FIG. 4, which shows a plan view of the top of the socket frame  12 , the upper layer  22  of the socket frame preferably comprises two independent end blocks  62 R,  62 L. End block  62 R is similar, but opposite hand to end block  62 L and similar features are similarly numbered. The end blocks  62 R,  62 L will be described below with specific reference to block  62 L unless otherwise noted. End block  62 L generally comprises a raised inner section  64 L with an outer mounting flange  66 L depending therefrom. The block  62 L is a one piece member which may be molded or otherwise formed from plastic. As seen in FIGS. 1 and 4, the inner section has a general channel configuration with a center wall  68 L extending laterally across the block and two side wall  70 L,  72 L projecting inwards from the center wall  68 L (see FIG. 4). The lateral wall  68 L and two side walls  70 L,  72 L define a channel  74 L which extends from the top  34  to the bottom surface  76 L of the block  62 L (see FIG. 1). As shown in FIG. 4, the channel  74 L has a pair of inner locating steps  78 L formed in the inside corners of the channel (FIG. 1 shows the inner step  68 R for the channel  74 R in block  62 R which is representative of the inner steps  68 R,  68 L in both blocks  62 R,  62 L). The inner steps  78 L are sized so that the locating or guide chamber  80 L in between the steps conforms closely to the shape of the ends  104  of the electronic module M. In the preferred embodiment, a stop or snubber flange  82 L is located in the locating channel  80 L (the stop  82 R located in the locating channel  80 R of block  62 R is shown in FIG. 1). The center wall  68 L has a bore  84 L formed therethrough which opens into the locating channel  80 L. As shown in FIGS.  2 , mounting flange  66 L is stepped from the top  34  of the block  62 L. The upper surface  86 C of the mounting flange is substantially flat. The mounting flange has a pair of fastener holes  88 L for fasteners  36 .  
         [0022]    Referring now to FIGS. 2 and 3, in the preferred embodiment, each block section  62 R,  62 L has a spring loaded ball plunger  300 . A perspective view of the ball plunger is shown in FIG. 3. The ball plunger  300  shown in FIG. 3 is an example of a suitable ball plunger which may be used with this preferred embodiment of the present invention. As such, the ball plunger  300  comprises a cylindrical casing  302 , a spring (not shown) and a ball  306 . The ball  306  and spring are housed in the casing  302 . The spring biases the ball  306  so that a portion of the base protrudes through an opening  304  at one end of the plunger. The outer surface of the casing may be threaded to allow the plunger to be mounted into a suitable threaded bore. The plunger may also be provided with features or facets (e.g. hexagonal socket for Allen wrenches) at one end to allow engagement to a suitable torque tool. As is shown in FIGS. 1 and 2, the ball plungers  300  are threaded into the bores  84 L,  84 R of the end blocks  62 L,  62 R. The ball plungers  300  are threaded into the blocks until the protruding portions of the spring loaded balls  306  project into the locating channels  80 L,  80 R of the end blocks  62 L,  62 R.  
         [0023]    As noted before, the test assembly  10  includes an array  18  of contact pins  20 . The details of the contact pins  20  are shown in FIG. 2. In the preferred embodiment, the contact pins  20  are spring loaded pins or pogo-pins. The contact pins  20  are substantially the same. Each pin  20  generally comprises a hollow cylindrical casing  90 , a spring loaded terminal pin  92  and a spring  94 . Casing  90  is made out of any suitable metal such as for example cartridge brass, or aluminum alloy. The casing  90  has a closed terminal end  96  and an open end  98 . The casing  90  has a lower section  98 , an intermediate mounting section  120  and an upper section  122 . The length of the lower section  98  may be established as desired. For example, in FIG. 2, the contact pin  20  is configured for surface mounting the terminal end  96  to a contact on the test board B. Thus, the lower section  98  is such that the terminal end  96  of the pin is located with a small standoff from the lower surface  32  of the test socket frame  12 . In alternate embodiments, the lower section of the pin may be lower to allow insertion of the pin into a hole of the test board. The mounting section  120  of contact pin  20  is located on top of the lower section. In the mounting section  120 , the outer casing has an annular indentation  124  forming a wasp waist shape. The upper section  122  extends from the mounting section upwards. The upper section  15  is shown in FIG. 2 as having a length sufficient to extend through board layer  24 , though in alternate embodiments the upper section may be provided with any length sufficient to stably hold the casing in the hole  46  of board layer  24 . The outer casing  90  has a diameter which allows the casing to pass freely through contact holes  46 ,  48   50  in the board layers  24 ,  28 ,  30  of the socket frame.  
         [0024]    The casing  90  however, results in an interference with holes  52  in the Kapton® layer  26  of the frame as will be explained further below. The spring loaded terminal pin  92  has a lower contact bushing  130 , an upper contact end  132 , and a connecting rod  134  extending therebetween. The bushing  130  is sized to form a close sliding fit in the bore of the lower section  98 . The bushing  130  however is prevented by the annular groove  124  from moving past the mounting section  120 . Bushing  130  may be made from brass or any other suitable metal with good sliding properties. The outer surface of the bushing contacts the inner surface of the casing  90  to effect electrical contact therebetween. The upper contact end  132  of the spring terminal pin  92  is located outside the outer casing  90 . The contact end  132  may include blades or any other suitable feature terminating in a sharp upper edge  134  or one or more piercing tips. Spring  94  may be a helically wound metal wire spring or any other suitable axial spring. Spring  94  is held in the lower section  98  of the pin casing  90 . The spring rests against the bottom of the lower section  98  and the bushing  130  of the terminal pin  92  rests on the spring. Thus, inward axial movement of the pin (in the direction indicated by arrow R) causes the bushing  130  to compress the spring  94 .  
         [0025]    Testing assembly  10  may be assembled in any desirable manner. By way of example, test frame  12  is formed by stacking layers  22 ,  24 ,  26 ,  28 ,  30 . Ball plungers  300  shown in FIG. 2 may be installed in the respective end blocks  62 L,  62 R before or after assembly of the test frame. Fitted guide pins (not shown) may be inserted in the contact holes to help align the contact holes in the board layers. Otherwise, the fasteners  36  may have shanks with diameters fitted to the fastener holes such that insertion of the fasteners through the holes in the boards  24 ,  26 ,  28 ,  30  results in alignment of the corresponding contact holes in the boards. After the layers  22 ,  24 ,  26 ,  28 ,  30  are stacked together, the fasteners  36  are threaded into the bottom layer  30  to secure the layers together and form the socket frame  12 . As seen in FIG. 1, the channels  74 L,  74 R in the end blocks  62 L,  62 R define the module receiving recess  14  in the socket frame  12 . The gaps between opposing side walls  72 L,  72 R,  70 L,  70 R define side openings  15  into the recess  14 . The scallops  38 ,  41 ,  40 ,  42  in the longitudinal sides of layers  24 ,  26 ,  28 ,  30  are generally aligned to form finger recesses  136  on opposite sides of the socket frame. Guide pins (see FIG. 2) for guiding installation of the socket frame  12  on the test board B are preferably inserted into appropriate holes in the bottom  32  of the socket frame after the frame is assembled. Otherwise, the guide pin  60  may be installed into board layer  30  at any other suitable time. The contact pins  20  of the array  18  are also inserted into the socket frame  12  after assembly. The contact pins  20  may be held on a common carrier frame (not shown) and inserted into the contact holes through receiving recess bottom surface  54 . As noted before, the outer casing  90  slides freely through the holes  46 ,  48 ,  50  in board layers  24 ,  28 ,  30  but has an interference fit in hole  52  of the Kapton® layer  26 . Kapton® layer  26  is however sufficiently elastic so that under sufficient down force, the rounded end  96  of casing  90  will elastically expand hole  52  to allow the lower section  98  of the casing to pass through the hole. Insertion of the pin  20  into the socket is stopped when the mounting section  120  reaches the Kapton® layer  26 . The elastically expanded hole  52  returns to its original size and enters into the annular groove  124  of the mounting section. This locks the contact pin  20  into the socket frame  12 . As seen in FIG. 2, in this position the bottom ends  96  of the contact pins extend out of the bottom  32  of the frame. The resilient upper contact ends  132  of the contacts project from the bottom surface  54  into the receiving recess  14  of the socket frame. It can be realized from FIG. 2, that in alternate embodiments the Kapton® layer may be located in any desired location in the layer stack in conjunction with the mounting section on the contact pin casing being positioned to coincide with the Kapton® layer. In other alternate embodiments, the socket frame may be made from any desired number of layers, or may be a molded one-piece member. The complete testing assembly  10  may be mounted to the test board B by placing the guide pins  60  into receiving holes (not shown) in the PCB  200  (see FIG. 1). In the case of surface mounted arrangement such as shown in FIG. 2, the bottom contact ends  96  of pins  20  rest against contact pads on PCB  200  and are soldered to the contacts using wave flux soldering for example. In alternate embodiments, the pin contact ends may extend sufficiently for through mounting the pins to the test board PCB.  
         [0026]    Referring still to FIGS. 1 and 2, the module M is inserted into the receiving recess  14  of testing assembly through the opening in the top  34  of the socket frame. As can be realized from FIG. 1, an operator may hold the module, for example, between thumb and forefinger while inserting the module M into recess  14 . Openings  15  in the sides of the recess, and finger recess  136  allow the user to maintain a sure grip on the module M even when the module is fully inserted into the recess. Before the module M is placed into the recess, the upper contact ends  132  of the contact pins  20  are in an extended position. In this position, the tips  134  (see FIG. 2) of the contact ends  132  may be generally aligned with or higher than the spring loaded ball  306  of latches  16 . When the module is inserted into the recess  14 , the module M is moved past the spring loaded balls  306  (which are resiliently deflected aside to allow passage of the module M) to press against the resilient contact ends  132  of the contact pins. The contacts are depressed by the module until the upper surface  101 , of PCB  100  is located below the spring loaded balls  306  which spring back to engage the edges  106  at the end  104  of the module PCB. This position is shown in FIG. 2. The contact ends  132  are resiliently depressed from their extended position and in response urge the module PCB upwards. The spring loaded latches  16  engages outer end edges  106  of the PCB  100  to restrain the module M in the recess. The ends  104  of the module are guidingly held in locating channels  80 L,  8 OR during insertion of the module M, and help align the module M in the recess such that ball contacts  108  on the bottom of the module are aligned with corresponding contact ends  132  of the socket. The tips  134  of the contact ends  132  are sufficiently sharp to pierce the ball contacts of module M and thus effect electrical contact therebetween. As can be realized from FIG. 1 and  2 , the contact array conforms to the ball grid array on the module M. Also, when mounted in the recess  14  of the testing assembly  10 , the upper surface  101  of the module M and the components  102  thereon are exposed and readily accessible to the operator through the opening in the top  34  of the frame as well as the side openings  15 .  
         [0027]    Referring now to FIG. 5, there is shown a partial cross-sectional view of a test assembly  310  in accordance with a second preferred embodiment of the present invention, and module M mounted in the test assembly. Except as otherwise noted below, test assembly  310  is substantially similar to test assembly  10  described previously and shown in FIGS. 1, 2 and  4 . Similar features of the test assemblies in the two preferred embodiments are similarly numbered. The test assembly  310  in the second preferred embodiment also comprises a socket frame  312  with spring contact pins  320  mounted therein. The socket frame  312  has a top layer  322  mounted on a stack  324  of plastic board layers (similar to layers  24 ,  26 ,  28   30  of the frame  12  shown in FIG. 1). The top layer  322  has two end blocks  362 L,  362 R (similar to blocks  62 L,  62 R in FIG. 1) which define the module receiving recess  314  of the socket frame  310  (in a similar manner to that described before for frame  12 ). The spring contacts  320  are similar to the contacts  20  in test assembly  10  shown in FIG. 2. Spring contacts  320  are located in holes in the socket frame to form a contact array  318  matching the ball grid array on the module M. The contact ends  432  of the spring loaded pins  392  of the contact pins  320  project from the bottom  354  into the recess  314  of the socket. The contact ends  432  are disposed initially at an extended height, and upon insertion of the module M into the recess  314  are resiliently depressed to a depressed position as will be described in greater detail below.  
         [0028]    Referring now also to FIG. 6, the test assembly  310  includes a latch  316  mounted to end block  362 R. The opposite end block  362  is provided with an inwardly extending flange or tab  371  as shown in FIG. 1. The tab  371  on block  362 L and latch  316  on block  362 R cooperate as will be described further below to lock the module M in the recess  314 . Tab  371  is cantilevered into recess  314  from the central wall  368 L of the block. The tab  321  may be integrally molded on the block. The tab  371  is located above the stop  382 L (which is similar but opposite to stop  82 R in FIG. 1) and forms recess  373  for end edge  106  of the module M. The vertical height of tab  371  above the bottom  354  of recess  314  may be set so that the tab  371  is generally level with the tips of the contact ends  432  when the spring loaded pins  392  are in the extended position.  
         [0029]    [0029]FIG. 6 is a magnified partial cross-sectional view of block  362 R showing features of latch  316 . Latch  316  is movably mounted to the center wall  368 R of the block  362 R generally opposite tab  371  (in a relationship similar to that shown for opposing ball plungers  300  in FIG. 4). As seen in FIG. 6, latch  316  generally comprises a latch arm  402 , mount spindle  408 , and spring  412 . Latch arms  402  may be a one piece member made of suitable metal or plastic. The arm  402  generally comprises a mid-section or hub  405 , a catch member  404  and a lever section  406 . Hub  405  has a bore therethrough for spindle  408 . The catch member  404  preferably has an upper cam surface  407 . Spindle  408  is a rod made from any suitable metal or plastic. Spring  412  is a torsion spring made from suitable spring wire which is helically wound. The spring  412  has two engagement ends  412 A,  412 B as shown in FIG. 6. The latch  316  is located within a recess or pocket  410  in wall  368 R of block  362 R. The arm  402  is placed into the pocket  410  with the catch  404  extending into recess  314  and the lever section  406  extending out above the upper surface  334  of the block. The spring  412  is placed in the pocket  410  and the spindle  408  is inserted through the spring and the bore in the arm  402  as seen in FIG. 6. One end  412 B of the spring is interlocked with the lever section  406 , and the other end is locked against the block  362 R. In this position, the spring biases the latch in clockwise direction (indicated by arrow P) against the wall  368 R of the block section. The latch  404  extends into the recess  314  substantially level with the tab  371  of block  362 L (see also FIG. 5).  
         [0030]    In this embodiment the module M may be inserted into the test assembly  10  by placing on end  104  of the module M in recess  373 . The contact ends  432  of spring pins  392  bias portion  106  of the module against tab  371 . The module M may then be pivoted in the direction indicated by arrow I in FIG. 5 into the recess  314 . During rotation into the recess, the module comes into contact with the cam surface  407  of the catch  404  and cams the catch  404  down. This allows the module end  104  to move into the recess  314  to position I 1 , shown in FIG. 6. When the module M is in position I 1 , the cammed catch  404  (shown in phantom in FIG. 6) is released and springs back under bias from spring  412  to its initial position. During the insertion of the module M into recess  314 , the module M resiliently depresses the contact ends  432  of spring pin  392 . After the catch  404  on catch  316  returns to its initial position, the depressed spring pins  392  urge the module M upwards against the catch  404 . The module M is now in position I 2  shown in FIG. 6. The catch  404  of latch  316  engages the edge  106  of the module M and holds module in the test assembly  310 . As in the first preferred embodiment, the module M is held in the socket in such a way that access to the components on the module is substantially unobstructed.  
         [0031]    It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.