Patent Document

TECHNICAL FIELD 
   The present invention relates to devices for testing integrated circuits. 
   BACKGROUND OF THE INVENTION 
   Integrated circuits are commonly tested before installation. Test sockets are used to determine whether the integrated circuit can make the required electrical connections to pads or leads on the integrated circuit package. This requires an integrated circuit to be placed in the test device under test conditions to allow for both thermal testing of the package and checking terminal connections. Given the high volume of integrated circuits to be tested, it is preferable if the device is adaptable to automation. 
   U.S. Pat. No. 6,353,329 “Integrated Circuit Test Socket Lid Assembly” to Kiffe discloses a test socket for integrated circuits (ICs). The test socket includes a socket body, allowing electrical connections to be made between the terminals of an integrated circuit and a test board. The socket is mounted in a base that is attached to a lid by a removable hinge. The removable hinge is noted within this reference as the means allowing this device to be adapted to automation. A pressure plate and an actuator for the pressure plate are retained within a frame of the lid by a cover plate. A latch secures the lid to the base. Activation of the actuator exerts force on the pressure plate. An integrated circuit held within the test device is moved to the socket by the pressure plate. The bottom surface of the pressure plate includes a plurality of channels extending from an open central area of the pressure place to the peripheral edges of the pressure plate. This provides some ability to allow air to circulate, although no flow through circulation is possible. 
   U.S. Pat. No. 5,646,447 “Top Loading Cam Activated Test Socket for Ball Grid Arrays” to Ramsey et al. discloses a socket where an IC package may be inserted and removed. An IC is placed into a hinged lever arm forming a frame around a socket. The base of the socket has a slidable plate having holes with elongated contacts extending into each hole. The socket also has a cam axle and cam handle located opposite the hinged lever arm. When the frame is pressed down, the frame contacts the cam handle, which causes the slidable plate to move, driving the IC contacts into contact with the socket contacts. 
   U.S. Pat. No. 5,545,050 “IC Socket” to Sato et al. discloses an electrical IC socket which has Y-shaped contact pieces which are more flexible in accommodating a lead from an IC chip, thereby ensuring good contact. The socket has a lid which is spring-biased and, when lowered, pushes the leads against the heads of the contact pieces. 
   It is an object of the invention to provide a test device for integrated circuits. Ideally, such a test device is adaptable to automation and allows for the thermal testing of integrated circuits. This test device preferably would allow integrated circuit packages of varying height into the test device, allow viewing of the integrated circuit during the test process, provide a means to align the terminals of the integrated circuit, and provide a means to hold the integrated circuit during the test process. 
   SUMMARY OF THE INVENTION 
   The above objects have been achieved with a device for testing integrated circuits (ICs). The device includes a base holding a test socket (socket body). The test socket has a means for receiving the terminals (e.g. pad, pins, or other terminals) of an integrated circuit. The lid is joined to the base by a hinge. The lid assembly may be secured by a locking mechanism, that securely holds the lid assembly and base together. A test device, such as an integrated circuit, is held between the lid assembly and base. A pressure plate is retained within the lid assembly. The lid assembly may include a handle, which is fixed to the cam plate. The handle can be rotated a certain distance in either direction, as the handle turns the cam plate also rotates in unison. The lid assembly includes a plurality of fixed bearing assemblies and a cam plate having a circumferential circuit of inclined surfaces, which ride upon the bearing assemblies. As the cam plate moves over the bearing assemblies, the incline along the cam plate forces the cam plate in a downward position. This cam plate subsequently forces the pressure plate in a downward direction. A thrust bearing assembly may or may not be used between the pressure plate and the cam plate to eliminate rotational forces from the cam plate to the pressure plate. Stop points along the incline of the cam plate may consist of notches or grooves which may arrest the bearing assemblies at different points along the incline of the cam plate. The inclined surfaces that make up the cam may or may not terminate in grooves which may or may not be evenly displaced around the cam plate within the lid assembly such that said grooves and inclined surfaces may or may not form a continuous circuit, each groove sized in a method to arrest the bearings assemblies in place. Pressure exerted by the pressure plate on the IC brings the terminals of the integrated circuit into contact with the test socket. Rotating the handle in the opposite direction can subsequently reverse the movement of the cam plate and bring it in an upward direction. The cam plate may or may not be biased against the bearings assemblies by the use of some load, such as spring loading. The cam plate mechanism may also be a cam groove with an incline within a cylindrical, square, or otherwise shaped pressure plate assembly. The pressure plate assembly would be retained in the lid and be the embodiment of the handle, cam plate and pressure plate. As the pressure plate assembly moves over the bearing assemblies, the incline of the cam inside the pressure plate assembly forces the pressure plate assembly in a downward or upward direction, depending on which direction the pressure plate assembly is rotated. A thrust bearing assembly may or may not be used in the pressure plate assembly and may be between the pressure plate assembly and the cam assembly to eliminate rotational forces from the cam assembly to the pressure plate assembly. Stop points along the incline of the cam groove in the assembly may consist of notches or grooves which may arrest the bearing assemblies at different points along the incline of the cam groove within the pressure plate assembly. The inclined surfaces that make up the cam may or may not terminate in grooves which may or may not be evenly displaced around the cam groove within the pressure plate assembly such that said grooves and inclined surfaces may or may not form a continuous circuit, each groove sized in a method to arrest the bearings assemblies in place. 
   Whichever cam method is used, either a load biased cam plate with inclines, or a cam groove within an assembly, or an embodiment shaped with one or more cam groove cutouts, all of these methods translate rotational movement of the assembly to vertical movement of the assembly. 
   Numerous shim plates may or may not be used between the pressure plate and cam plate, to offset the pressure plate by a certain distance. 
   The device may also include stop and start pins, which limits the rotational travel of the handle with respect to the test device. The handle may contain slots or the pressure plate assembly may contain slots, in which the start pins and stop pins attached to the lid of the test socket ride inside of said slots. The start and stop pins may be placed in different areas on the lid to control, arrest, and limit the travel of the handle rotation, such areas were the start and stop pins are on the lid would follow the path of the slot in the handle. 
   The test device may also include a channel on the pressure plate and/or a channel on the base for viewing of the test device and internal socket parts. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an embodiment of the test device with an integrated circuit to be tested. 
       FIG. 2  shows the test socket of  FIG. 1  in a closed position. 
       FIG. 3  is an exploded view of one embodiment of the test socket of  FIG. 1 . 
       FIG. 4  is a cutaway view showing the operation of the test socket of  FIG. 1 . 
       FIG. 5  is a cutaway view showing the operation of the test socket of  FIG. 1 . 
       FIG. 6  is a cutaway view showing the operation of the test socket of  FIG. 1 . 
       FIG. 7  is a cutaway view showing the operation of the test socket of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The test device of the present invention allows for the testing of integrated circuits. The integrated circuits illustrated in the embodiments have an array of pins (leads) extending from the bottom of the device. However the present test device may accommodate pins, pads or any other terminals on an integrated circuit. If pins are part of the test device (i.e. the device having terminals, the integrated circuit), the socket into which the terminals of the integrated circuit are received may or may not have an array of openings to accommodate the terminals of the integrated circuit device. The socket has some form of conductors that contact the terminals of the integrated circuit. For example a pogo pin socket could be used for such a tester. It is also possible to employ spring contacts, conductive elastomers, stamped metal contacts, or metal foils in the socket to test the integrated circuits. 
   The test device (integrated circuit) may alternatively include leadless pads. The test socket could use a biased ball array to engage the pads, allowing for the testing of the integrated circuit. The socket would then be designed to accommodate these pads. Either pins, pads, a combination of pins and pads, or any other terminal type could be tested using a designed socket. Both standardized and custom designed sockets for use in the present testers are commercially available from Gold Technologies (San Jose, Calif.) as well as other sources. 
   In  FIG. 1 , the test socket  10  features a lid assembly  16  and a base  14 . The device under test  12 , for instance an integrated circuit, fits into a socket body  40  in the base  14 . As will be explained in more detail below, a pressure plate  44  in the lid assembly  16  forces the pins or pads of the device  12  into contact with the socket body  40  when the lid assembly  16  is closed and the pressure plate  44  is activated. 
   With respect to  FIG. 2 , the top of the lid assembly  16  features a rotatable handle  18 . The test socket  10  also has a locking mechanism  42 , which secures the base  14  and lid assembly  16  in a closed position. 
   In  FIG. 3 , one embodiment of the test socket  10  features a base  14  with a socket body  40  for receiving the device  12  under test. The base hinge assembly  38  for connecting the lid assembly  16  and socket body  40  is attached to the base  14 . The locking mechanism  42  is secured to the lid  22 , for securing the base  14  to the lid assembly  16 . 
   The lid assembly  16  has several components. The rotatable handle  18  forms the top of the lid assembly  16 . The handle  18  is above lid  22 , which features four fixed bearing assemblies  24  which are spaced apart from each other. (Although this embodiment features four bearing assemblies  24 , other embodiments may have a different number of bearings.) The lid hinge mechanism  26  forms part of lid  22  as well. 
   A cam plate  28  sits below the lid  22 . This cam plate  28  features a number of inclined surfaces  52  around the circumference of the cam plate  28 . These inclined surfaces  52  are interrupted by grooves  30 , which stall the bearing assemblies  24  travel at regular intervals. 
   The cam plate  28  sits on a thrust bearing assembly  34 , which allows the cam plate to rotate freely and independent of the pressure plate housing  36 . The handle  18  and cam plate  28  are attached by fasteners such as screws  97 . Four threaded fasteners  20  (Although this embodiment features four fasteners  20 , other embodiments may have a different number of threaded fasteners) is attached to pressure plate housing  36  and passes through the lid  22 . Springs  21  can be placed between the head of the threaded fastener  20  and the lid  22 . Lid  22  may have some means of a lid lip to retain the springs  21 . The force of the springs  21  between the lid  22  and the head of the threaded fastener  20 , pulls the pressure plate  44 , thrust bearing assembly  34 , and cam plate  28  against the bearing assemblies  24  in the lid  22 . In this way, the bearing assemblies  24  are always contacting the cam plate  28  because of the bias of the springs  21 . As previously discussed, another way to achieve this means is to use a cam assembly with both top and bottom cam plates to create a cam groove in the cam assembly. 
   A pin  9  may be inserted through groove  7  on handle  18  and secured into lid  22 . If this feature is included the pin acts as a stop pin to limit rotation to the length of groove  7 . 
   The thrust bearing assembly  34  fits in an indentation  54  in pressure plate housing  36 . The thrust bearing assembly consists of the thrust bearing  32  and two shims  33 . Shims  33  may be placed between the thrust bearing  32  and the pressure plate housing  36 , and between the cam plate  28  and thrust bearing  32 , to increase the distance of the pressure plate housing  36  with respect to the cam plate  28 . The pressure plate  44  is attached, or is part of pressure plate housing  36  and is situated below the pressure plate housing  36 . As shown in  FIG. 1 , the portion of the pressure plate  44  is shaped such that when it comes into contact with the device  12 , it will push the pins of the device into the socket body  40 . Referring again to  FIG. 3 , the handle  18  and cam plate  28  are attached by screws  97 , which fit in holes  51 . Referring again to  FIG. 3 , threaded fasteners  20  are attached to the pressure plate housing  36 , the threaded fasteners pass through lid  22  and springs  21  are between the lid lip  50  and the head of the fastener  20 . This means retains the handle  18 , cam plate  28  thrust bearing assembly  34 , and pressure plate housing  36 , in the lid  22 , forming the embodiment of the lid assembly  16 . 
   The operation of the embodiment of the test socket shown in  FIG. 3  is illustrated in  FIGS. 4 ,  5 ,  6 , and  7 . With respect to  FIG. 4 , when the handle  18  has not been turned, i.e., before the pressure plate  44  has been “activated,” the bearing assembly  24  rests in or near a groove  30 . In  FIG. 5 , the handle  18  is rotated slightly. This causes the bearing assembly  24  to leave the groove  30  and begin (relatively) moving up the inclined surface of the cam plate  28  (as shown in  FIG. 3 , in this embodiment the cam plate  28  is actually rotated when the handle  18  is rotated, because they are attached to each other). Referring again to  FIG. 5 , as the inclined surface  52  moves relative to the bearing assembly  24 , the rotational force of this movement is converted to vertical force and the pressure plate  44  is pushed down. The downward movement of the pressure plate  44  places pressure on the device  12 , pushing the device  12  down and into contact with the socket body. In  FIGS. 6 and 7 , the rotation of the cap handle  18  continues, causing greater displacement of the pressure plate  44 . As the pressure plate  44  is pushed downward, the device  12  is brought into closer contact with the socket body until the pins of the device  12  lock into the holes of the socket body. 
   Another method of achieving the translation of rotational movement to vertical movement is by bringing the pressure plate into contact with the device by rotating the pressure plate housing containing the bearings assemblies within the surface housing. The inclined surfaces are situated in the ceiling of the surface housing. Unlike the embodiment shown in  FIG. 3 , the bearings assemblies are actually rotated. The embodiments of  FIGS. 1–7  may be either manually or robotically activated. 
   As shown in  FIG. 1 , both pressure plate  44  and base  14  may or may not include openings or grooves to allow one to access or view the device under test. The opening on pressure plate  44  is at the center of the pressure plate. In addition, sight grooves on the base extend from the sides of the test socket  40  to the exterior of the test device. This channel serves a number of functions. This channel may provide a location for gripping the side of the IC during manual or mechanical insertion or removal of the IC into the test device. This channel also provides a means to access or view the device while the test socket is in the closed position. 
   A feature of the test socket is incremental mechanical lowering of the pressure plate. An IC may either have pins or pads, and the height of the IC could vary considerably. If the test device has a pressure plate which is lowered a known amount, determined by the mechanical size of the device, the user has a better tool for testing different ICs having differing heights. Shims between the thrust bearing and pressure plate housing can further accommodate the varying height changes of the IC&#39;s. In the present device, a cam plate on the lid assembly has an inclined surface extending about the interior circumference of the cam plate. A plurality of grooves along this circumference receives bearing assemblies, which are attached to the lid. A rotating handle engages the cam plate and allows rotation of the bearings assemblies from one groove to the next. This lowers the cam plate a discrete, mechanically defined, incremental distance. The cam plate engages the pressure plate, lowering the pressure plate the same distance. 
   The present invention may be manufactured out of a durable material, such as metal or thermoplastic.

Technology Category: 3