Abstract:
A burn-in oven is provided with a wall that has a number of vertically stacked, laterally extending slots aligned with each of the burn-in-board supports in the oven. When a burn-in-board is placed in the oven on the supports, an edge portion of the burn-in-board extends through a slot into a connector area. Each of the slots has a shutter associated therewith that will move from an open position to permit the burn-in-board connector portion to extend through the slot, to a closed position wherein the shutter covers the slot. A cam operator moves the shutters to a closed position, except when a burn-in-board is extending through a particular slot, it will support the shutter in its open position and the shutter will not be moved by the cam. All the shutters associated with openings through which no burn-in-board connector portion extends will be closed to prevent air flow from the burn-in oven.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to use of shutters or doors on the side rear of a burn-in oven that will cover the slots through connector portions of burn-in-boards for coupling to test circuits. All end connector portion of the board protrudes out of the oven, for connection of the test circuits to power and to carry signals indicating the temperature and other characteristics of the integrated circuits on such boards. The shutters or doors cover burn-in-board slots that are not being used so heat from the oven does not escape, and air flow is also controlled.  
         [0002]     The use of burn-in-boards for testing integrated circuits and circuit packages has advanced over the years. The burn-in ovens that are in use will support a number of individual boards, with each board having a substantial number of individual integrated circuits for testing. These boards usually have one end or edge that is provided with connector portions that are electrically connected to mating connector portions leading to driver/receiver board that will control the power to the individual circuits, as well as receiving test information from the circuits and temperature signals for controlling the environment in which the circuits are tested.  
         [0003]     U.S. Pat. No. 4,900,948 shows an environmental system for testing individual burn-in-boards. At the present time, more forced air cooling has become desirable because of the increased power requirements of the circuits and the consequent heat that is evolved. Higher operating temperatures also are accommodated by the more recent ovens.  
         [0004]     Generally speaking, the burn-in-boards are oriented horizontally, but have edges that extend through slots to the exterior to connect to suitable connectors for voltage regulator, driver/receiver boards or circuits.  
         [0005]     One aspect of use in a multiple board oven is that the slots that provide openings for the contact ends of individual burn-in-boards may not all be used during a test sequence, and its desirable to close off air flow and reduce heat transfer from the heated enclosure into the connector area or portions of the burn-in oven.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention relates to a burn-in oven that has a wall provided with slots that open between the interior of the oven, and a connector region. The connectors at the edge of the burn-in-boards can be passed to the exterior of the oven, and connected to driver/receiver boards or directly to other controls in a cool environment. The burn-in-boards are provided with sealing or blocks that have surfaces to seal around the slots. Gaskets are used for insuring that air flow does not pass from the interior of the oven out through the slots when there is a burn-in-board installed.  
         [0007]     In an oven with a large number of vertically stacked guides for burn-in-boards and slots, not all of the slots of the oven will be occupied for each test. Many times the circuits being tested will be fewer than the capacity of the oven, and the driver/receiver boards for such slots are desirably left unconnected.  
         [0008]     The present invention provides shutters or doors, one for each burn-in-board slot, that will close all of the burn-in-board connector slots that are not in use. As shown, there are air control trays with air slots or valves above each burn-in-board. All of such trays that can be installed in an oven are installed, to close the oven wall slots for the trays with seal bars. The tray slots or valves regulate air flow to the burn-in-boards in use.  
         [0009]     The closing of the burn-in-board connector slots insures that hot air from the interior of the oven will not be exhausted into the connector region, and the temperature in the connector region can be maintained substantially lower than that of the oven.  
         [0010]     An actuator system will open all of the shutters or doors simultaneously and it includes sliding actuators that have cams that are engaged by cam followers on the shutters to operate the hinged shutters or doors. After the shutters have been opened, the burn-in-boards are inserted into the oven, with the connector section on the burn-in-board extending out through a slot. The shutter for the occupied slot will be held open by a portion of the connector section. After all of the burn-in-boards that are being tested have been inserted, the actuator system and sliding actuator members will be reversed and the cams will close the shutters or doors for slots through which there are no burn-in-board connectors. The cams are designed so the cam followers on the shutters being held open by inserted burn-in-boards will not engage the respective cam during the reverse movement of the sliding actuator members.  
         [0011]     This insures that the control of the environment in the oven for the circuits being tested will be easier, and that the connector region or chamber will not be subjected to the high internal temperatures of the burn-in oven. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a schematic side view of a burn-in oven and a connector housing of typical design with which the present invention will work;  
         [0013]      FIG. 2  is an end view taken on line  2 - 2  in  FIG. 1  to illustrate an exhaust fan, air cooler and chamber for supplying cooling air to the interior of the burn-in oven;  
         [0014]      FIG. 3  is a schematic side view of a burn-in oven with the outer walls removed and showing the shutters for burn-in-board connector slots all in an open position;  
         [0015]      FIG. 4  is an enlarged sectional view taken from an opposite side of the oven from  FIG. 3  showing the shutters in an open position, and the shutter actuators raised, with a pair of burn-in-boards in position;  
         [0016]      FIG. 5  is a side view with the actuators for the shutters moved to close the shutter for burn-in-board connector slots where no burn-in-board is in place; and  
         [0017]      FIG. 6  is an enlarged, fragmentary perspective view of a portion of a burn-in oven showing the shutter in the position shown in  FIG. 5  and with only one valve tray shown. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     In  FIG. 1 , a burn-in oven indicated generally at  10  is an enclosure  11  that has insulated side walls, and a front wall  12  having a door through which burn-in-boards, and also air flow control fan trays or boards can be inserted and held in place with suitable latch handles  14 . Rear wall  16  of the burn-in-board oven has a schematically shown connector housing  18  for driver/receiver boards and connectors between the burn-in-boards and the driver/receiver boards, for housing connectors from the burn-in-boards to signal carrying leads leading to remote locations. Also, connections for air flow valve controls are made in this connector housing  18 .  
         [0019]     The housing  18  is supported at the rear wall  16 , and access to the interior of the housing  18  is provided for connecting the connectors used on the burn-in-boards and fan boards. A controller  20 , such as a PC or other form of computer or processor, is connected into the system.  
         [0020]      FIG. 2 , schematically shows the burn-in oven enclosure  11  with details removed, with the oven access door closed, and illustrating that a cooling air supply plenum  22  can be mounted on one side wall of the burn-in oven  10 , and can provide air flow to the interior of the burn-in oven. An exhaust fan or fans  24  in a plenum  25  on an opposite side of the burn-in oven will draw air through the burn-in oven, as shown, for example, in U.S. patent application Ser. No. 10/020,348, filed Dec. 12, 2001, which is incorporated by reference. The cooling air flow onto circuits comprising devices under test (DUTS) in the present application is controlled by providing boards with valves that will direct air onto circuits on burn-in-boards located below the valves, and then exhausted out through the exhaust plenum  25  using fan  24  for air circulation. The temperature can be controlled in response to measured temperatures at each of the circuits or DUTS.  
         [0021]     In the present invention it is desirable to retain the connector housing  18 , and the connectors that are mounted therein at a much lower temperature than that which is needed in the burn-in oven.  
         [0022]     Referring to  FIG. 3 , it can be seen that the burn-in oven interior comprises a rack or frame  27  that has a series of tracks or supports  26  thereon, which will support burn-in-boards  30 . Interspersed between the tracks  26  are tracks  28  that are used for supporting, as shown, control valve trays  32 . Air flow down onto the circuits being tested (DUTS) on the burn-in-board below each valve tray is controlled, and air flow is exhausted to the exhaust plenum. The cool incoming air flow is through the slots  29  shown in  FIG. 3  that align with chambers above each valve board. Thus, the air flow normally would be perpendicular to the plane of the paper on which  FIG. 3  is drawn.  
         [0023]      FIGS. 3-6  show a lower burn-in-board  30  that is supported on a set of rails or supports  26 , and above this burn-in-board is a valve tray  32  that is supported on rails or supports  28 . The valve tray or board  32  has valves  34  that control the air flow from a chamber above the burn-in-board onto circuit assemblies or DUTS  36  positioned below the valves.  
         [0024]     Each of the DUTS  36  has a number of individual leads or connectors that are provided along the burn-in-board and which exit at a connector block end  40  that protrudes outside the burn-in oven frame, and which has pin connectors  42  (see  FIGS. 4, 5 , and  6 ) that are connected to suitable connectors  43  for driver/receiver boards or to other controls or devices.  
         [0025]      FIG. 4  is a fragmentary enlarged sectional view of the lower portions of  FIG. 3  illustrates the frame  24  on the interior of the burn-in oven, with the rails or supports  26  and  28  shown. The integrated circuits shown at  36  are positioned on the burn-in-boards, and the flow control valves  36  are on the valve tray or boards  32 . The valves  34  are on valve trays or boards above the respective burn-in-board  30 .  
         [0026]     As perhaps can be best seen in  FIGS. 4, 5 , and  6 , the rear wall of the burn-in oven is provided with a series of cross members  44  and cross support bars  46  that are spaced apart to form burn-in-board connector end openings  48  between each cross member  44  and the higher cross support bar  46 . An opening  49  is formed between each cross member  44  and the next lower cross support bar  46 . The openings  48  are stacked one above another, and each opening  48  receives a connector end  40  of a burn-in-board that passes into the connector housing  18 . End portions  47  of valve trays or boards also pass through the openings  49  into the connector chamber. The burn-in-boards and valve boards carry blocks to close the respective openings when the boards are installed.  
         [0027]     There are shutters or doors  50  that are hinged on the cross support bars  46  and extend all the way across the end wall of the burn-in-oven. The shutters  50  are of size so that when they are closed, as shown in  FIGS. 5 and 6 , the shutters  50  cover the opening  48  between the respective cross support bar  46  and the next lower cross member  44  that define the connector opening  48  for the burn-in-boards. The openings  48  extend laterally across the side of the frame  24 . As can be seen in  FIG. 6 , each of the shutters  50  has a hinge  52  that attaches the door to the cross support bar  46  above each of the respective openings  48  that is covered by the shutter  50  hinged to that rail.  
         [0028]     Pivoting of the shutters  50  to the open position shown in  FIG. 4 , and to a closed position for the shutters  50  above the openings  48  in which no burn-in-board is placed, is controlled by a pair of sliding actuator or cam plates  56 , one positioned on each of the opposite sides of the burn-in-oven frame.  
         [0029]     As shown in  FIG. 5 , where the cam plate  56  is shown in a shutter closing position, sliding movement of the actuator or cam plates  56  is controlled by a pair of actuators  58 , one on each side of the frame  24 , and each of which is fastened with a suitable bracket  60  to an upright post  62  forming the frame  24 . The actuators  58  are identical, and each has an extendable and retractable rod  64  connected through a bracket  66  to the respective actuator or cam plate on opposite sides of the frame  24 .  FIG. 3  shows one actuator  58  retracted in position to lift the actuator or cam plates  56  upwardly, and cause the shutters  50  to be moved to the open position. The actuator or cam plates are provided with one or more guide slots  59  in which a headed retainer pin  59 A will slide.  
         [0030]     The actuator or cam plates  56  are provided with cam tracks  68 , one associated with each of the shutters  50 , and thus each set of cam tracks  68  controls the opening and closing of one of the shutters  50 . Each cam track  68  is formed with a lower curved cam track surface  70  that extends out along a finger  72 , and a shorter, upper cam track surface  74  that terminates at a corner  76  that is spaced inwardly (see  FIG. 5 ) toward the frame from the end of the finger  72  as shown by spacing  75 . Each of the shutters in turn has a control or cam follower rod shown at  78  that has cam follower ends which are positioned in the cam tracks  68  for that shutter. When the actuators  58  are retracted, as shown in  FIG. 3 , the shutters  50  will be lifted or opened, and the followers  78  will be guided along the cam surface  70  all the way out to the end of the finger  72 . This is shown in dotted lines in two places in  FIG. 5 .  
         [0031]     The operations of the oven requires that all of the valve boards that can be held in the tracks  28  are installed. Thus, a connector end  47  extend through every slot or opening  49  at all times of testing. The burn-in-boards  30  are always associated with a valve board  32  to control cooling flow through the openings controlled by the valves  34  on the valve board down to the circuit components  36  below them. When a burn-in-board  32  is inserted into the frame  24 , the connector end  40  extends through the aligning opening  48  for that burn-in-board to the exterior of the frame  24 , as shown in  FIGS. 3, 4  and  5 , as well as in the lower portion of  FIG. 6 . When the burn-in-board is properly seated so that the latches  14  can be closed, a seal plate  80  engages the cross members above and below the respective opening  48  to seal the opening. The seal plate  80  is carried by the burn-in-board and is perpendicular to the plane of the burn-in-board. The seal plate  80  extends both above and below the burn-in-board as shown in  FIG. 4 . The seal plate  80  has an upper portion  80 A that rests and seals against the cross member  46  defining that particular opening  48 , as shown in  FIG. 4 , and the seal plate  80  has a lower portion  80 B that seals against the lower cross bar  44  defining that opening  48 . The openings  49 , which are formed below the cross members  44 , but above the next lower cross support bar  46 , and in which a valve board  32  is always placed are sealed or closed with a seal block or rail  82  carried on each valve board that will close off the respective opening  49 . The connector  47  portion of the valve board extends out of the slot formed by opening  49 .  
         [0032]     As can be seen in  FIG. 4  where there are two burn-in-boards and four valve boards shown installed, the slots in openings at the connector ends of the two burn-in-boards are blocked. Also, the shutter  50  for the opening through which the burn-in-board extends is held open on the upper surface of the connector block  40  for that burn-in-board. A spring clip  84  is provided at the lower edge of each of the shutters  50 , and the spring clip will rest on the top surface of the connector block  40  of an installed burn-in-board so that the shutter  50  is propped open.  
         [0033]     Assuming that the desired number of burn-in-boards have been put into position in the burn-in oven frame, and that testing is to occur, the actuators  58  are extended, and the shutters or doors  50  that are supported on the valve block  40  of an inserted burn-in-board are held in their open position. The cam follower end of the rods  78  for each shutter held open will clear the corner  76  and the outer edge  77  of a portion of the actuator or cam plates  56  defining the cam track  74  for that shutter or door (see  FIG. 5 ). When the cam plate  57  is moved down, each shutter or door  50  that is supported on the connectors of a burn-in-board will remain in its raised position. The openings  48 , through which a connector end  40  of a burn-in-board extends, will be sealed by the seal block  80  on the burn-in-board. The openings  49  are all closed by the seal plate  82  that are carried by the valve boards.  
         [0034]     The rest of the shutters  50  for openings where no burn-in-board is installed will be cammed shut by the cam tracks  68 , as the cam plates  56  are lowered. The cam actuator ends of the rods  78  will be moved along the cam tracks  68  to the positions shown in  FIG. 5  when the rods  64  of the actuators  58  are extended.  
         [0035]     This will lock the shutters  50  for unused connection slots or openings  48  in their closed positions as shown in  FIG. 6 .  
         [0036]     The connectors for the burn-in-boards can be maintained at a temperature that is substantially lower than that in the burn-in oven because of the blocking of air flow out into the connector housing. The air flow path will be controlled by the valves on the valve boards because the air flow out through the connector openings is blocked by the shutters  50  where there are no burn-in-boards, and by the burn-in-board seal blocks where there are burn-in-boards installed. The openings  49  are closed by valve board seal plates.  
         [0037]     The input side of the oven is closed with an oven door after the latches  14  have been put into position for holding the burn-in-boards and valve boards securely.  
         [0038]     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.