Abstract:
A plunger for holding and moving electronic components in particular for introduction and removal of IC&#39;s to and from a contacting device connected to a test bed comprises a plunger head with at least one suction head for sectional contact with a component. A heat-conducting body, temperature-controlled by means of a fluid, is arranged such that the suction-contacted component is in contact with the heat-conducting body. The suction head passes through the heat-conducting body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the U.S. national phase of International Application No. 
     PCT/EP2008/008390 filed 2 Oct. 2008, which designated the U.S. and claims priority to German Application No. DE 10 2007 047 679.7 filed 5 Oct. 2007, the entire contents of each of which are hereby incorporated by reference. 
     FIELD 
     The invention relates to a plunger for holding and moving electronic components, in particular for moving ICs to and from a contacting device, which is connected to a test device, having a plunger head which comprises at least one suction head for sucking in a component and a heat conducting body according to the preamble of claim  1 . 
     BACKGROUND AND SUMMARY 
     Electronic components such as ICs (semiconductor components with integrated circuits) are usually tested for their functionality before they are mounted on printed circuit boards, for example, or used otherwise. The components to be tested are contacted by an automatic handling machine, usually called a “handler”, with contacting devices which in particular are in the form of contact bases, and are in electrical contact with a test head of a test device. After the end of the test process, the components are removed from the contacting devices by means of the handler, and sorted depending on the test result. 
     To hold and contact the components, handlers usually have plungers, i.e. longitudinally movable piston-like holding units, which can move back and forth and which can hold the components by means of a vacuum, in particular by applying a suction force. After the components have been placed, the plungers are brought within the handler into a position in which they can be moved forward on a straight path towards contacting devices, until the components come into contact with the contacting devices. After the test processes are carried out, the components are removed from the test head by means of the plunger, and positioned so that they can be removed from the handler via a discharge station and sorted depending on the test result. 
     To be able to carry out the tests under predetermined temperature conditions, it is also known to bring the components to predetermined temperatures before the test process. These temperatures can be, for example, in a range from −60° C. to +200° C. 
     The temperature of the components is usually controlled in a convective and/or conductive manner in a heat-insulated temperature control chamber, which can be arranged inside or outside the handler. In this case, multiple components are brought to the desired temperature simultaneously inside the temperature control chamber, before they are put onto the plungers and moved forward by them to the contacting devices. A disadvantage here is that in the time between the heating and the contacting of the components, or during the contacting of the components, heat losses occur, with the result that at the time of the test, the components are no longer at the precise setpoint temperature. The individual components which have been temperature controlled together in the temperature control chamber can also have different temperatures. The components may also lose electrical power during the electrical test. 
     From U.S. Pat. No. 5,977,785 A, a plunger according to the preamble of claim  1  is known. The plunger there has a head piece with a plurality of suction heads and a heat conducting body in the form of a contact plate which is arranged separately from the suction heads, and which can be heated or cooled by means of a hot or cold fluid. The sucked-in components rest against the contact plate and can be temperature controlled thereby. The temperature-controlled fluid is fed to the contact plate and taken away from it in closed circuits. However, a disadvantage is that the head piece is of complex construction and therefore must be relatively large, since the feed and take-off lines for the temperature-controlled fluid take up a relatively large amount of space and the contact plate must also be correspondingly large. For very small electronic components or for arrangements in which a plurality of plunger heads must be arranged closely next to one another, this known plunger head is unsuitable. 
     The invention is based on the object of creating a plunger of the above-mentioned kind, with which tests of electronic components can be carried out under predetermined temperature conditions as precisely as possible. The plunger should also be simply constructed and have a small overall size in the head region, so that it is suitable even for small components. 
     According to the invention, the suction head is fed through the heat conducting body. By way of the heat conducting body according to the invention, there is a very quick and intense transfer of heat from the heat conducting body to the component via heat conduction. Owing to its large surface area and the material it is made of, the temperature of the heat conducting body itself can be controlled extremely quickly using a fluid, which preferably consists of a gas, in particular clean air or nitrogen. The fluid can thus be conveyed from the interior of the handler or via fluid lines of the plunger to the heat conducting body. Depending on whether the components are to be tested at low temperature, ambient temperature or high temperature, the heat conducting body, and thus the component, is either cooled, kept at ambient temperature or heated. Because the temperature of the components is controlled directly at the plunger head, the temperature of the component which is held on the plunger can be controlled while it is being delivered to the assigned contacting device, and even during the test process, so that heat losses during the delivery movement and during the test process do not occur, or at least can be minimised. It is thus possible to control the temperature of the component in a very precise manner. The head piece can also be simply constructed and have a small overall size, so that the plunger can not only be used for large components, but also for very small ones. 
     According to an advantageous embodiment, the heat conducting body comprises a central axial through-opening, through which the suction head is guided. The contact surface between the heat conducting body and the component is thus kept extremely large so the temperature of the component can be controlled particularly effectively. A plurality of decentralised through-openings may also be provided in the heat conducting body, through each of which a suction head penetrates. 
     According to an advantageous embodiment, the plunger head comprises a retaining base which supports the sucked-in component and has an axial passage, in which the heat conducting body is arranged around the suction head or heads. In this embodiment the retaining body and heat conducting body are thus different parts, which simplifies production. Furthermore, it is therefore also possible for the heat conducting body and the retaining base to be made of different materials and to thus match these materials in an optimal manner to their respective applications. For example, the retaining base may be made of an electrically non-conductive material, in particular a plastics material, whilst the heat conducting body may be made of a particularly effective heat conducting metal. Alternatively however, it is also possible for the retaining base itself to be configured as a heat conducting body, i.e. for the retaining base to be configured in such a way that some regions of the retaining base, which contact the component, conduct heat particularly well in particular, a retaining base of this type may have fins or pins on its rear side which enlarge its surface and over which fluid flows. 
     According to an advantageous embodiment, the heat conducting body is held resiliently relative to the retaining base, in particular so as to be resiliently displaceable in the axial direction relative to the retaining base. Even if the size or shape of the components differs, it is thus ensured that they rest as flat as possible against the heat conducting body in order to ensure a good level of heat conduction. 
     It is particularly advantageous for the heat conducting body to be tiltably arranged relative to the longitudinal axis of the plunger. Even if the connecting legs (pins) of the component are not completely uniformly curved owing to tolerances, and the body of the component is tilted slightly out of its intended position or if the legs rest on supporting strips (lead backers) of the retaining base, complete surface contact of the body of the component against the heat conducting body is thus also ensured. 
     According to an advantageous embodiment, the heat conducting body consists of a disc-shaped body with fins projecting therebeyond, the disc-shaped body comprising a flat front face which can be contacted with the component, and the fins projecting rearwards beyond the disc-shaped body. The heat conducting body can thus be configured in a particularly compact manner, it also being possible to use extremely long fins which project rearwards into a fluid guide channel and which enable a particularly good transfer of heat from the fluid to the heat conducting body. 
     According to an advantageous embodiment, the retaining base comprises fluid guide recesses in its rear side, which open into the axial passage in the retaining base so at the rear side of the retaining base conveyed fluid can be guided towards the heat conducting body arranged in the axial passage in a targeted manner. It can thus be easily ensured that the greatest possible amount of fed, possibly temperature-controlled fluid flows directly over the heat conducting body, controlling the temperature of said body in a particularly effective manner. 
     According to an advantageous embodiment, the heat conducting body is displaceably guided by bolts extending in an axial direction and having a bolt head with a front face at their front end, which front face forms an axial stop for the component, and having a rear face which forms an axial stop for the heat conducting body. The heat conducting body is thus expediently pushed forward by springs which are arranged around the bolts. The heat conducting body is thus held resiliently and flexibly in the retaining base in a relatively simple and compact manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is explained in more detail below by way of example with reference to the drawings, in which: 
         FIG. 1  is a perspective view of a plunger, a plunger head being shown separately from the other parts of the plunger; 
         FIG. 2  is a longitudinal section through a plunger head together with a schematic view of the heat conducting body, albeit without the suction head; 
         FIG. 3  is a plan view of the heat conducting body from  FIG. 2 ; 
         FIG. 3   a  is a plan view of an alternative heat conducting body. 
         FIG. 4  is a plan view of an electronic component; 
         FIG. 5  is a perspective view of an alternative embodiment of a plunger head, tilting forwards; 
         FIG. 6  is a perspective view of the plunger head from  FIG. 5 , tilting rearwards; 
         FIG. 7  is an exploded view of the plunger head from  FIGS. 5 and 6 ; 
         FIG. 8  is a front view of the plunger head from  FIG. 5 ; 
         FIG. 9  is a sectional view along line IX-IX from  FIG. 8 ; and 
         FIG. 10  is a sectional view along line X-X from  FIG. 8 , the component being shown above. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a partly exploded view of a plunger  1 . The plunger  1  comprises a plunger head  2  which can hold an electronic component  3  at its front end by way of a suction force. In the embodiment shown, the component  3  is a component comprising integrated circuits, IC for short, which comprises a component body  4  and connecting legs  5  projecting laterally therefrom, as can be seen in  FIG. 4 . The plunger  1  may, however, also be used to hold and move other components, such as BGA or QFN components. 
     The plunger head  2  may be arranged on a cuboidal base body  6  and is held thereon in a lateral direction by spring tongues  7  which are fixed to the base body  6  via screws  8  and project forwards in an axial direction beyond the base body  6 . The plunger head  2  can thus be slightly displaced together with the component  3  in the lateral direction when the plunger head  2  is retracted into a centring device (not shown) by pushing the plunger  1 , which device is arranged in the vicinity of a contact base (not shown). 
     The base body  6  is connected to a rear end piece  10  via two guide rods  9  which are arranged parallel to the longitudinal axis of the plunger  1 . Screws  11  can be seen in  FIG. 1 , with which the guide rods  9  are screwed at the front end thereof to the base body  6 . 
     The plunger  1  is longitudinally movably held on a guiding device  12  via the two guide rods  9 , which guiding device comprises guide sleeves (not shown in greater detail), in which the guide rods  9  are displaceably guided. The guiding device  12  can, for example, be fixed (in a way not shown in greater detail) to a rotating carriage or swivelling device, with which the plunger  1 , together with the component  3  arranged thereupon, can be brought into a position in which the plunger  1  can be pushed forward in a straight line (to the left in  FIG. 1 ) into a contact position, in which the connecting legs  5  of the component  3  ( FIG. 4 ) are arranged on corresponding connecting contacts (not shown) of a contact base. The forward movement is effected by means of a feed device (not shown) which presses on a rear end face  13  of the rear end portion  10 . The plunger  1  is moved back into its initial position by a restoring spring (not shown), the rear end of which is fixed to the plunger guiding device  12  and the front end of which is fixed to the base body  6 . 
     As can be seen in  FIGS. 1 and 2 , the plunger head  2  comprises a retaining base  14  which consists of a cuboidal base portion  15  and a front base portion  16  of reduced diameter which projects in an axial direction beyond the base portion  15 . The front base portion  16  comprises four leg supporting webs  17  (lead backers) which, on four sides, delimit a central axial passage  18  in the retaining base  14 . The connecting legs  5  of the components  3  rest on the front end faces of the leg supporting webs  17  when the components  3  are held on the plunger head  2 . 
     As shown schematically in  FIG. 2 , a heat conducting body  19  is arranged in the central passage  18 , the front end face  20  of which heat conducting body is arranged in the vicinity of the front end of the front base portion  16 . The heat conducting body  19  consists of a disc-shaped body with a plurality of fins  21  which extend radially outwardly and rearwardly, i.e. against the direction in which the fluid flows. The heat conducting body  19  is also made of an effective heat conducting material. The front end face  20  of the heat conducting body  19  is flat and arranged in such a way that the body  4  of the component can completely contact the front end face  20  when the component  3  is arranged on the plunger head  2 . 
     The outer diameter of the heat conducting body  19  is only slightly smaller than the diameter of the passage  18 . If fluid having a specific temperature is introduced into the passage  18  from the rear, i.e. from the right-hand side in  FIG. 2 , only a very small amount of fluid can then flow past the heat conducting body  19  without contacting it and instead the fluid is forced to flow past through the gaps and slits between the fins  21 , a large amount of fluid thus contacting the heat conducting body  19 . 
     In order to ensure that the component  3  also lies flat against the heat conducting body  19  even if some of the connecting legs  5  of the component  3  are not optimally aligned, the heat conducting body  19  is resiliently supported in the passage  18  by a spring device  22 , as shown schematically in  FIG. 2 . This spring device  22  is configured in such a way that the heat conducting body  19  may be slightly tilted inside the passage  18 , i.e. can be brought into a diagonal position, so as to match a possible diagonal position of the body  4  of the component and thus maintain close contact with the body  4  of the component. 
     In order to tightly suck the component  3  against the retaining base  14 , the plunger head  2  comprises a flexible suction head which may be configured similarly to a suction head  23  which can be seen in  FIG. 7 . This suction head  23  consists of a front corrugated hose  24  and a hose socket  25  connected thereto. In the embodiment shown in  FIG. 1 , the suction head  23  is connected to a central suction channel  26  which is guided through the base body  6  and connected to a suction line  27  which is in turn guided parallel to and between the guide rods  9  to the rear end piece  10  and is connected there to a vacuum line  10   a  which leads to a vacuum generation device. 
     Although not shown in  FIG. 2 , the suction head  23  is arranged centrally inside the passage  18 , the corrugated hose  24  extending through a central through-opening  28  in the heat conducting body  19  ( FIG. 3 ). The front end of the corrugated hose  24  projects slightly forwards in an axial direction beyond the front end face  20  of the heat conducting body  19 . The body  4  of the sucked-in component  3  can thus be contacted with the suction head  23  and pulled thereby against the heat conducting body  19 , by contraction of the corrugated hose  24 . Owing to the suction force, the component  3  is subsequently pulled further rearwards together with the heat conducting body  19  which, owing to the spring device  22 , is flexibly and resiliently mounted in the axial direction, until the connecting legs  5  of the component  3  rest on the leg supporting webs  17 . 
     In order to bring the component  3  to a specific temperature, which may lie between −60° C. and +200° C. for example, the plunger  1  shown in  FIG. 1  also comprises a fluid feed line  29  which is supplied with fluid via a rear-side connection socket  30 . A heating or cooling device for the supplied fluid may be found inside the fluid feed line  29 . If a heating device is used, it is preferably a heating spiral, by which means the fluid flowing past is heated to the desired temperature. Alternatively however, it is possible that a fluid, in particular clean and temperature-controlled air, which is already at the desired temperature or the temperature of which has already been controlled in a specific manner may have already been fed via the connection socket  30  and introduced into the fluid feed line  29 . 
     The fluid feed line  29  is connected to a fluid feed channel  31  at its front end, which channel penetrates through the base body  6 . The fluid feed channel  31  is connected to a fluid distribution chamber  32  ( FIG. 2 ) which is arranged in the plunger head  2 . Said fluid distribution chamber  32  consists of a conical space which widens towards the rear, into which space the fluid feed channel  31  of the base body  6  opens. The fluid distribution chamber  32  forms the rear portion of the central passage  18 . 
     If the temperature of the component  3  is to be controlled, a correspondingly temperature-controlled fluid is guided via the fluid feed line  29  to the central passage  18 , the heat conducting body  19  being flowed over intensely and its temperature being controlled correspondingly. Some of the fluid also travels through the slits and gaps between the fins  21  of the heat conducting body  19  and directly contacts the component  3 . The component  3  is thus quickly and intensely brought to the temperature of the fluid by way of the fluid and heat conduction between the heat conducting body  21  and the body  4  of the component. 
     A second embodiment of a plunger head  2 ′will now be described with reference to  FIGS. 5 to 10 . 
     The plunger head  2 ′ comprises a retaining base  14 ′ which is configured similarly to the retaining base  14  of the first embodiment, but which can be fixed to a retaining device (not shown) via four fixing holes  33 , which are arranged in the corner regions of the cuboidal base portion  15 ′, which retaining device is in turn fixed to guide rods which are similar to the guide rods  9  of  FIG. 1  or is formed integrally with the guide rods  9 . 
     A heat conducting body  19 ′ is inserted into the central passage  18  of the retaining base  14 ′, which heat conducting body is substantially cuboidal but may be shaped differently, in particular it may be cylindrical. As can be seen in  FIG. 7 , the heat conducting element  19 ′ comprises a flat front end face  20  and rear-side fins  21 . The suction head  23  already described with reference to the first embodiment penetrates through a central, axial through-opening  28  in the heat conducting body  19 ′. 
     The heat conducting body  19 ′ is inserted into the central passage  18  of the retaining base  14 ′ with a small lateral gap. 
     A retaining element  34  is screwed onto the rear side of the retaining base  14 ′ via screws  35  which penetrate holes  36  in the retaining base  14 ′ and can be screwed into screw holes  37  in the retaining element  34 . The retaining element  34  spans the central passage  18  of the retaining base  14 ′. 
     On the one hand, the retaining element  34  acts as a connecting element for the suction head  23 , and on the other hand it resiliently holds the heat conducting body  19 ′. The retaining element  34  comprises a front suction line socket  38 , to which the hose socket  25  of the suction head  23  can be attached. One or more suction lines  39  ( FIG. 7 ) extend from the suction line socket  38  to a rear suction line socket  40 . This suction line socket  40  is connected to a vacuum generation device via a suction line (not shown). 
     In order to resiliently hold the heat conducting body  19 ′, the retaining element  34  comprises four screw holes  41 , into which the rear threaded portions of four elongate bolts  42  can be screwed. The bolts  42  extend parallel to one another and in the axial direction of the plunger  1 . The bolts  42  also penetrate through axial though openings  43  which are formed in the corner regions of the heat conducting body  19 ′ and have a substantially greater diameter than the bolts  42 . The bolts  42  comprise a bolt head  44  at their front end, which bolt heads are arranged in recesses  45  in the front end region of the heat conducting body  19 ′. The height of the bolt heads  44  is thus somewhat smaller than the depth of the recesses  45 . 
     As can be seen, in particular from  FIG. 10 , the heat conducting body  19 ′ is pushed forwards by springs  46  in the form of compression springs which are arranged around the bolts  42  and are guided thereby. At their rear ends the springs  46  are supported on the retaining element  34  whilst at their front ends they are supported in a front region of the heat conducting body  19 ′. The displacement of the heat conducting body  19 ′ in a forwards direction is delimited by the bolt heads  44  which thus act as an axial stop. Provided no component  3  is arranged on the plunger head  2 ′, the front end face of the bolt heads  44  is set back slightly relative to the front end face  20  of the heat conducting body  19 ′, as can be seen in  FIG. 10 . On the other hand, if a component  3  is indeed arranged on the suction head  23  and sucked-in thereby, the body  4  of the component pushes the heat conducting body  19 ′ back until the body  4  of the component abuts the front end faces of the bolt heads  44 . The bolts  22  thus act as axial stops for the component  3 , it being possible to adjust the position of these stops by screwing the bolts  42  more tightly into the screw holes  41  or by unscrewing them slightly. 
     As can be seen, in particular from  FIG. 9 , the plunger head  2 ′ also comprises an axially extending ejector pin  47  which extends centrally through the suction head  23  and is supported at the rear end on an ejector spring  48 . If no component  3  is arranged on the plunger head  2 ′, the ejector pin  47  projects slightly forwards, beyond the suction head  23 , as can be seen in  FIG. 10 . If a component  3  is indeed arranged on the suction head, the body  4  of the component pushes the ejector pin  47  back against the bias of the spring  48 , as shown in  FIG. 9 . When the component  3  is to be removed from the plunger head  2 ′ after testing and no more suction force is applied by the suction head  23 , the ejector pin  47  supports the removal of the component  3  from the plunger head  2 ′ by way of the bias of the ejector spring  48 . 
     In the embodiment shown in  FIGS. 5 to 10 , the heat conducting body  19 ′ does not project rearwards beyond the retaining base  14 ′ or only projects therebeyond slightly, the retaining base being covered in part on the rear side by the retaining element  34 . In order to still ensure that the heat conducting body  19 ′ can be flowed over effectively by a temperature-controlled fluid, the retaining base  14 ′ comprises fluid guide recesses  49  ( FIG. 6 ) on its rear side which extend laterally outwards from the central passage  18  until they reach the vicinity of two opposite edge regions of the retaining base  14 ′. Some of the fins  21  are exposed by these fluid guide recesses  49  in such a way that they can be flowed over more effectively by the fluid, which is guided against the rear side of the retaining base  14 ′ and led to the heat conducting body  19 ′ via the fluid guide recesses  49 , and their temperature can be correspondingly controlled.