Abstract:
Disclosed is a device for releasable connecting an interface with a load board for providing a mechanically pressing of the components against each other. The device comprises a toroidal lock, which is operated by at least one lever to transmit the lock from a releasing position to a locking position. This device enables a quick change of Load boards to the interface with a reproducible positioning.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a device for releasable connecting an interface with test equipments.  
         [0002]     Testers such as IC testers are provided for generating dedicated analog and/or digital signals to a device under test (DUT) and analyzing the response thereof. Such testers are described in detail e.g. in the co-pending European patent application No. 99105625.0 by the same applicant, EP-A-88299, U.S. Pat. No. 5,499,248 or U.S. Pat. No. 5,453,995.  
         [0003]     In most cases, the provision of signals from the tester to a specific application site of the DUT has to be matched with the specific mechanical and electrical properties of the tester as well as of an application equipment handling the DUT.  
         [0004]      FIG. 1  shows an example of a typical DUT application equipment such as a wafer prober  10  for transporting and positioning highly sensitive silicon wafers as DUTs. The wafers (not visible inside the wafer prober  10 ) are internally connected to a probe card  20  as interface of the wafer prober  10  towards a tester  25  (in  FIG. 1  only symbolized as a general block). Wafer probers are generally applied for testing integrated circuit in the earliest possible production phase.  
         [0005]     The probe card  20  is typically a device-specific printed circuit board (PCB), e.g. with high-density contact needles on the wafer side and gold-plated contact pads on the tester side (as the side visible in  FIG. 1 ). The probe card  20  normally straddles the dense (needle) pattern from the wafer side to a wider pad pattern for contacting the tester  25 . The size of the probe card  20  is generally limited by the hardware of the wafer prober  10 . The wafer prober  10  has to ensure a reliable electrical contact between the contact pads of the wafer and the probe card  20 .  
         [0006]     A load board  30  represents the electrical and mechanical interface of the tester  25  towards the DUT. The Load board  30  normally is a device specific printed circuit board (PCB) custom-built for the specific requirements of the DUT application equipment and can be exchanged dependent on the respective application. More details about the load boards  30  are described in particular in the aforementioned copending European patent application No. 99105625.0. In case that the load board  30  is provided as a custom-built exchangeable part, the load board  30  is often contacted within the tester  25  by means of spring-loaded contact pins (also called “Pogo™”).  
         [0007]     While the load board  30  and the probe card  20  are electrically optimized (e.g. with respect to signal speed, signal purity, impedance, and transmission rate) regarding either the tester  25  or the DUT of the wafer prober  10 , a good electrical and mechanical matching between the load board  30  and the probe card  20  has to be achieved. This becomes in particular important with increasing signal transmission rates going up to two Gigabit per second.  
         [0008]     In the example of  FIG. 1 , an interface tower  50  (also called “Pogo™ tower”) is used as interface between the load board  30  and the probe card  20 . The interface tower  50  converts the pin pattern (normally rectangular arrangement) of the load board  30  of the tester to the pattern (normally round and more dense) of the probe card  20 . In the example of  FIG. 1 , the interface tower  50  further has to bring signals from the tester  25  through a round-shaped hole in a head plate of the wafer prober  10  and bridge the spatial distance between the load board  30  and the probe card  20 .  
         [0009]     All the interfacing provided by the interface tower  50  has to be done with a minimum loss in performance for the entire test system provided by the tester  25  and the application equipment of the wafer prober  10 . That means, that all parts in the electrical path of the interface tower  50  have to maintain a controlled impedance (normally  50  D) and a high contact quality for each provided tester channel (e.g. more than 1.000 channels).  
         [0010]     The interface tower  50  comprises rods for adjusting and fixing the interface tower  50  to different load boards  30 . The load boards  30  are fixed by screw connections.  
         [0011]     To ensure the high contact quality it is requested, that the mechanical and electrical contact between the interface tower and the load board is after each change of load board of the same condition. Therefore all screw connections have to be tighten up properly to achieve the required mechanical and electrical contact between the interface tower and the Load board. A visual control is not possible given. The screw connections are furthermore very time consuming for changing load boards.  
       SUMMARY OF THE INVENTION  
       [0012]     It is therefore an object of the present invention to provide a device for easily and reproducible connecting an interface with a test equipment. The object is solved by the independent claim. Preferred embodiments are shown by the dependent claims.  
         [0013]     According to the invention, a device for releasable connecting is provided with a ring-shaped or toroidal lock. After the load board is positioned to the interface they will be fixed against one another by a movement of the lock and the electrical contact between the interface and the load board is achieved.  
         [0014]     At least one lever is provided for locking and releasing the toroidal lock. The lever is rotatable about an axis, which is perpendicular to the rotation axis of the lock. This allows to turn the lever towards the load board.  
         [0015]     Preferably, the turning direction of the lever is in the endphase nearly identical to the movement direction of the load board for positioning them to the interface. The axis of the lever is directed parallel to a frame of the load board when situated a locking position to the interface or is positioned perpendicular to the axis of the lock.  
         [0016]     In a preferred embodiment the toroidal lock is located in a support of the interface. This allows to reduce the weight of the load board which will be changed to the interface and the cost for this system. This embodiment further comprises that several bearing rollers are provided for positioning the lock rotatable to the support and for an exact axial guidance to the interface. This enables an exact positioning of the contacts located at the load board to those of the interface.  
         [0017]     Preferably two levers are located preferably stationary with their rotation axis to the interface opposite to one another for an easy handling and to reduce the handling force for locking the toroidal lock. During the locking procedure the mechanically pressing will be increased to ensure finally in the locking position the electrical contact between the components.  
         [0018]     In a further preferred embodiment the lock comprises at least one first guide for receiving at least one bearing attached to the load board and further comprises at least one second guide for securing the lock by at least one bearing to the interface. After positioning the test equipment to the interface the lock engages at the same time with the at least one bearing of the interface and with the at least one bearing of the load board. Therefore, only one rotatable movement of the lock with a preferably small amount of a traverse path enables the locking and releasing.  
         [0019]     In a preferred embodiment the at least one bearing of the interface and the at least one bearing of the load board are located in the same plane crossing the longitudinal axis of the toroidal lock. Therefore, the forces for the mechanically pressing of the interface and the load board against each other will be initiated without producing any additional rotatable forces or shear stresses.  
         [0020]     In a further preferred embodiment the first guide for receiving the bearing of the load board provided in the lock has a first section with a pitch directed to ensure an easily engagement of the load board bearing into the first guide. Further it is provided upstream to the first pitch at least one second section of the guide to rest the bearing in a locking position and to ensure the electromagnetic link between the interface and the load board.  
         [0021]     In a preferred embodiment, the rotatable movement of the lock for locking is limited by the length of second section or an abutment and therefore after changing the load board always the same conditions of the mechanically pressing of the components against each other will be achieved. The bearing of the load board rest in a locking position of the second section of the guide. Therefore, a reliable electrical contact is ensured.  
         [0022]     For transmitting the radial movement of the lock initiated by the lever there is according to a further preferred embodiment provided a hinge bearing. This hinge bearing is positioned in a radial formed slot of the lock. This hinge bearing comprises a shaft for receiving a bearing roller. On a spherical surface of the bearing roller is free rotatable and also free in his angular position to the shaft located in a ring to compensate the transversal movement of the lever, which is tangential to the lock  111 , with respect to the radial movement of the bearing roller carried on the shaft.  
         [0023]     In a further preferred embodiment the lever comprising a mouth for receiving the hinge bearing is provided with a U-shaped guide for securely engaging with the ring of the hinge bearing. This allows an easy and secure handling for locking and releasing the device.  
         [0024]     The above mentioned bearings are for example slide bearings or bearing rollers.  
         [0025]     The assembly according to the invention is formed as a quick-release fastener and enable a quick change and a reproducible positioning of the load boards to the interface. Alternatively it is also in the scope of the invention, that the lock is provided in a support of the Load board and the further components are arranged correspondingly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0026]     The object and many of the attendant advantages of the present invention will be readily appreciated and become better understood by reference to the following detailed description when considering in connection with the accompanied drawings.  
         [0027]     Features that are substantially or functionally equal or similar will be referred to with the same reference sign(s).  
         [0028]      FIG. 1  shows an example of an typical DUT application equipment,  
         [0029]      FIG. 2  shows a perspective view of an interface and a Load board,  
         [0030]      FIG. 3   a/b  show a cross sectional view of the interface and the load board in a releasing and locking position,  
         [0031]      FIG. 4  shows a perspective view on a toroidal lock,  
         [0032]      FIG. 5  shows a cross sectional view of a hinge bearing and  
         [0033]      FIG. 6  shows a perspective view of a lever. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]      FIG. 2  shows a perspective view in detail of the interface  50  and a test equipment  30  such as a load board or a DUT board, which will be lowered to the interface  50  for connecting each other. The load board  30  comprises a frame  60  with a central opening  65 . Apart to the central opening  65  are provided several openings  66  for receiving the contact pads. Next to the central opening  65  are provided bearing rollers  70  on the underside of the frame  60 .  
         [0035]     The interface  50  comprises a frame  51  with a plurality of recesses  52  for receiving the segment  53 . Those segments are adapted to receive double-sighted spring-loaded contacts  55  (“Pogo™”) to provide an transmission of an electrical signal between the load board  30  and the probe card  20 . The interface  50  also comprises a central opening  56  which corresponds to the opening  66  of the load board  30 . Adjacent to the central opening  56  a device  110  according to the invention for releasable connecting the load board  30  to the interface  50  is provided. This device  110  comprises at least a toroidal lock  111 , which is positioned in a support  112  surrounding the central opening  56 . The lock  111  comprises first guides  114  for receiving the bearing  70  of the load board  30 , when the load board  30  is positioned to the interface  50  according the cross sectional view in  FIG. 3   a . The lock  111  is provided according to  FIG. 2  in a receiving position  116 . This receiving  116  position is given, if levers  117  of the lock  111  are in an upright position. This means, that entrances  118  of the first guides  114  are exactly in the angular position, in which the bearing  70  are attached to the load board  30 . For an easily positioning of the load board  30  to the interface  50  there are provided at least one guide rod  67  on the interface  50  and at least one inlet-funnel  68  which engage to one another before the bearing  70  are located to the first guide  114 .  
         [0036]      FIG. 3   a  shows an intermediate or a receiving position  116  of the load board  30  to the interface  50  in a cross sectioned view. In this position the locking procedure can be started. The lever  117  will be operated by turning about an axis  119  which is perpendicular to the rotation axis of the lock  111 . The handle of the lever  117  will be parallel located to the surface of the load board  30  in a locking position  120  according to  FIG. 3   b . During the locking procedure the load board  30  will be pressed against the double-sighted spring-loaded contacts  55  to eliminate the distance A. A press load for example of at least 3.000 Newton has to be introduced by the lever  117  to move the load board  30  against the spring loaded contacts  55  for the electrical contact.  
         [0037]     In  FIG. 4  is shown a perspective view of the lock  111 . For the radial guidance of the lock  111  are provided bearings  121 , which are supported on the circumferential wall of the support  112 . Very close to the bearings  121  are positioned first guides  114  and also second guides  131  which have preferable the same length as the first one. The second guide  131  is provided to secure the lock  111  to the interface  50  with a bearing  132 . The entrance  118  of the first guide  114  is positioned for receiving the load board  30  in the same plane as the bearing  132  is positioned. This has the advantage, that by introducing the radial movement of the lock  111  by the lever  117  the tension force onto the bearings  70  of the load board  30  and those of the bearings  132  are in the same plane and do not cause share stresses or any torque.  
         [0038]     The bearings  132  are preferably positioned in equal distance to each other around the lock  111 . Preferably they are attached to wall sections  134  between the recesses  52  of the frame  51 . Therefore the transmission of force can be uniform over the diameter of the lock  111 .  
         [0039]     The first guide  114  comprises a first section  136  with a pitch which can be followed by an at least second section with a higher pitch than the first. At least one further section  137  is provided, which pitch is opposite to the pitch of the first section  136  to ensure a save positioning of the lever  117  in a locking position. Due to the different pitches of the sections  136 ,  137  an easy handling and a reproducible position, pressure and a self holding locking is achieved. This allows an ergonomic handling.  
         [0040]     For transmitting the movement of the lever  117 , which is tangential with respect to the lock, to the radial movement of the lock  111  there is provided an hinge bearing  160 , which is shown in detail in  FIG. 5 . The hinge bearing  160  comprises a shaft  161  carrying a bearing roller  162 , which is free rotatable and moveable along the axis of the shaft  61 . On a spherical surface of the roller  162  is positioned an outer ring  170 . This ring  170  is also rotatable on the roller  162  and angular moveable according the arrow  171 . This allows the transmission of a transversal movement especially for the movement tangential to the lock  111  into a radial movement of the lock  111 .  
         [0041]     The lever  117  shown in more detail according to  FIG. 6  comprises a mouth  180  with a recess  181  for receiving and guiding the ring  170 . Therefore securely the initiated force on the handle of the lever  117  is secure transmitted into a rotatable movement of the lock  111  for transferring the lock  111  from a receiving position  116  into a locking position.