Patent Abstract:
A handling tool for electronic components includes a holding opening, to which a vacuum pressure may be applied and at which components to be handled are able to be held via vacuum pressure. At least one counter support, which outwardly projects beyond the opening plane in an operating position, is situated inside the holding opening. The component held by vacuum pressure is supported in the region of its surface acted upon by vacuum pressure, in such a way that this same surface bends concavely when viewed from the side of the vacuum pressure.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a handling tool for components, e.g., electronic components. 
     2. Description of Related Art 
     Handling tools for components, in particular electronic components, are already known. They are used in assembly devices and die-bonding devices, for instance, and utilized to produce electronic circuits; the components are picked up by the handling tools, i.e., the pick-up and bonding devices, using vacuum pressure, in particular, placed on a circuit board by the handling tool and fixed in place there. The handling tools known from the related art are constructed such that they have a holding opening, to which vacuum pressure is applied so that the components when touched by the holding opening are retained in the holding opening by the vacuum pressure prevailing inside the handling tool in conjunction with the ambient air pressure. Depending on their thickness, i.e., especially their material strength and flexibility, the components are bent into the holding opening at the holding opening, so that a deformation/bending of the component into the holding opening occurs. On the side of the component to be fixed in place on the circuit board or the substrate, this deformation causes a cavity (concave shape) to form, which leads to shrink holes and gas inclusions in the placement. Especially when the component is placed on epoxide, solder or seal glass, irreversible errors arise in the process, which result in a high rejection rate or which, as a minimum, have an adverse effect on the quality of the bonding. Furthermore, if the component has only low material strength, the vacuum pressure can bend the component at the holding opening to such an extent that damage occurs. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a handling tool for components, in particular electronic components, which avoids the mentioned disadvantages. 
     To this end, a handling tool for components, in particular electronic components, is provided, which has a holding opening to which vacuum pressure may be applied and at which the component to be handled is able to be held via vacuum pressure. It is provided that at least one counter support is situated inside the vacuum pressure opening, which outwardly projects beyond the opening plane in an operating position (an operating position is understood as a position of the handling tool in which the component to be handled is retained at the holding opening by vacuum pressure). In contrast to the related art, the holding opening is thus not completely open but has at least one counter support, which counteracts the deformation of the component in the direction of the vacuum pressure acting on it (i.e., into the holding opening) in an operating position. Moreover, it permits the (slight) deformation of the component in exactly the reverse direction, so that—when viewed from the placement level—it is not a concave but a convex form that comes about, i.e., the component thus is placed on the substrate not via its edge sides first, but via its midsection (which is pressed outwardly by the counter support, that is to say, toward the substrate). If the placement side is a planar bonding surface as is normally the case in the related art, a centrical surface mounting of the component takes place in the beginning, so that possible gases are pushed in an outward direction, toward the edges, once the handling tool sets down the component, instead of being retained in the center of the component by the edges that made contact first. The development of shrink holes because of surface inclusions in the placement on top of the bonding medium is avoided in this case. In addition, canting due to a non-parallel placement of the component is able to be prevented because the concave form compensates for an offset with respect to the substrate upon placement of the component. 
     In one further development, a sleeve having the holding opening is supported on the counter support in a manner allowing axial displacement. Depending on the material strength of the component to be picked up and its deformation by the application of vacuum pressure, the sleeve, which is axially displaceable counter to its weight force, is shifted axially toward the rear, so that the counter support projects a little further from the holding opening than in the idle state. The deformation of the component is solely dependent upon the material strength of the component and the magnitude of the vacuum pressure that is applied to the component at the holding opening. This produces sufficient deformation as well as a convex form with respect to the side of the component to be placed on the substrate. When the vacuum pressure is switched off in order to detach the component, the sleeve slides and projects beyond the counter support due to its weight, so that the component is removed from the counter support. 
     In one additional preferred development, the sleeve is supported in a manner allowing axial displacement counter to the spring force. Instead of its own weight, in this instance a defined spring force causes the resetting of the axial displacement, which spring force may also be designed to be adjustable via additional external means as known from the related art, such as via a thread by which the spring excursion is able to be regulated, thereby allowing the spring force action to be set in a highly precise manner. 
     In one additional, especially preferred development, the magnitude of the vacuum pressure is individually controllable by a control device, in particular as a function of the component. The vacuum pressure applied to the component at the vacuum pressure opening is able to be controlled/regulated in order to produce an advantageous desired deformation of the component at all times and, of course, to generate the holding force required for reliable and fault-free handling of the component. Especially components having low material strength, such as thin chips, for instance, require more of a slight vacuum pressure application since they weigh only very little on the one hand, i.e., the holding force is therefore achieved very quickly but, on the other hand, there is a not inconsiderable risk of breakage if they are deformed to an excessive extent. Components having high material strength require a higher application of vacuum pressure since they are not easily deformed as desired at the holding opening by the counter support and by the axially displaceable sleeve, so that the desired convex form is obtained. This specific development makes it possible to regulate the vacuum pressure depending on the component strength and nature in such a way that all components undergo substantially the same convex development on the side facing the substrate, and very reliable processing is possible in this regard, so that cavities in the placement and the shrink holes produced thereby are avoided. 
     In one preferred development, the counter support is traversed by at least one vacuum pressure supply channel. The application of vacuum pressure to the vacuum pressure opening thus is implemented via the counter support and not by other constructive measures. This offers the advantage that especially when an axially displaceable sleeve is provided, a largely sealed constructive development is possible, which is very easy to produce, in which the sleeve is simply placed on the counter support so as to be axially displaceable, and a spring force is applied to the sleeve at its end (not facing the opening plane) by a helical compression spring, for example. A very effective handling tool is therefore able to be produced using only a few components. 
     In another, especially preferred development, the counter support is centrically situated in the vacuum pressure opening. This development readily permits a precisely centered development of the convex deformation on the component. In the same way, the constructive implementation of the handling tool, e.g., in the form of an essentially cylindrical or rod-shaped counter support and a cylindrical sleeve, is very easy. 
     In one further especially preferred development, the counter support has a rounded tip, in particular a conical tip. The development with a rounded tip prevents damage or injuries to the surface of the component and allows for an even force application to the component by the counter support at the time of the vacuum pressure application and deformation. 
     In one especially preferred development, the rounded tip is designed as exchangeable counter-pressure tip. This makes it easy to adapt the geometry and material characteristics of the counter-pressure tip to the particular application fields and the requirements of the components to be processed. This is especially advantageous in cases where sensitive electronic components are processed and/or the handling tool processes frequently changing types of components having different compositions and sensitivities. The exchange of the counter-pressure tip can be undertaken manually by an operator or else automatically, preferably while providing a plurality of counter-pressure tips in a storage rack or a similar device. 
     Furthermore, a method for handling components is provided, in particular electronic components, which includes the following steps:
         aspirating a component by vacuum pressure and holding the component via the vacuum pressure;   supporting the component held by vacuum pressure in the region of its surface acted upon by vacuum pressure, in such a way that this same surface, in particular the component, bends concavely when viewed from the side of the vacuum pressure.       

     In contrast to the related art, the component according to the invention is therefore essentially not held in a flat position by vacuum pressure, but in a concave position (viewed from the side of the vacuum pressure). As a consequence, the component is deformed in a manner that produces a convex form on the side opposite the substrate on which the component is mounted, in particular in the center of the surface of the component. To this extent the component is supported on the handling tool in several places, i.e., in particular in the center of the component from the side of the vacuum pressure, and toward the edge of the component, the support points lying at the edge of the component being located downstream from the suction direction, so that the mentioned bending of the component comes about. This ensures that the component first sets down on the substrate with the convex center area lying opposite the substrate, so that no shrink holes and/or extended shrink hole regions distributed across the entire surface of the component are able to form. 
     In one additional method variant, the placement of the component takes place at the edges of a holding opening to which a vacuum pressure is applied, the support being rendered upstream from the placement when viewed in the suction direction. The component thus is placed at a holding opening that may have a tubular, in particular cylindrical design, for example. Since vacuum pressure is applied to this holding opening, the component is retained at the holding opening with the aid of the vacuum pressure, support being provided upstream from the placement (viewed in the suction direction). This is accomplished in that the holding opening shifts in the suction direction (i.e., downstream), especially via a longitudinally variable support of the holding opening relative to a support point that retains the component in the center of the surface, as described in connection with the above described handling tool. 
     In a further, preferred development of the method, the magnitude of the vacuum pressure may be selected to be variable. This makes it possible to regulate the vacuum pressure that causes the component to be retained at the holding opening, and to adjust it to the nature and structure of the component, in particular. Furthermore, given a longitudinally displaceable placement of the holding points, especially the holding opening, it is also possible in this way to adjust the magnitude of the bending relative to the point of support within certain limits. In particular damage to the component by the bending is also able to be prevented in this manner. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  shows a handling tool according to the present invention, in longitudinal section. 
         FIG. 2  shows an embodiment of the counter support having an exchangeable counter-pressure tip. 
         FIG. 3  shows a characteristic improved array of residual shrink holes when using the handling tool according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a handling tool  1  for an electronic component  2 , i.e., a chip  3 . Handling tool  1  is made up of a vacuum pressure body  4 , which has a cylindrical bore  5  that is connected to a vacuum pressure system (not shown). In its end region  6 , vacuum pressure body  4  has a conical design  7  and thereby forms a counter support  8  for holding component  2 . Conical design  7  has a rounded tip  37  in the region of the tip. Counter support  8  has two vacuum pressure supply channels  9 , which go out from bore  5  of vacuum pressure body  4  and terminate at conical flanks  10  of counter support  8  on the outside, thereby connecting bore  5  to an aspiration region  11  surrounding the counter support. Counter support  8  is enclosed by an essentially cylindrical sleeve  12 , which is disposed on counter support  8  in axially displaceable manner. At its front end region  13 , the sleeve has tapered walls  14 , so that its sleeve wall  15  has an increasingly weaker design in its end region  13  than in its rear region  16 . End region  13  is the region that is spatially assigned to conical design  7  of counter support  8 . In conjunction with conical design  7  (delimited by conical flank  10  of counter support  8 ), sleeve  12  via its end region  13 , especially its inner walls  17 , forms aspiration region  11  which, facing component  2 , forms a holding opening  18  of handling tool  1 . Holding opening  18  is circular in this instance because of the cylindrical development of sleeve  12 . Counter support  8  is centrically positioned in holding opening  18  with its conical form  7 , a conical tip  19  of counter support  8  projecting slightly toward the outside, i.e., projecting beyond an opening plane  20  formed by holding opening  18  toward the outside. The axial displaceability of sleeve  12  on counter support  8  is delimited by a travel-limiting sleeve  23 , which is adjustable via a screw thread  21 , in particular a fine thread  22 . This travel-limiting sleeve  23  sits on fine thread  22  mounted on rear region  16  of sleeve  12  and is axially adjustable with respect to it, via fine thread  22 . Travel-limiting sleeve  23  overlaps counter support  8  essentially in the form of a ring, and a regulation space  25  is formed between counter support  8  (i.e., its counter support outer wall  24 ) and travel-limiting sleeve  23 . On one side, regulation space  25  is delimited by fine thread  22  adjacent to sleeve  12 , and on the other side, in the region lying opposite of fine thread  22 , by a guide ring  26  resting against counter support  8  or vacuum pressure body  4  in a manner permitting displacement by sliding. On the outside, i.e., on its top surface  27 , guide ring  26  is supported on a spiral compression spring  28 , which in turn is supported on a pressure retainer  29  of vacuum pressure body  4 , which may be formed as circumferential enlargement  30  of cylindrical vacuum pressure body  4 , for example. From here, the spring force is applied to sleeve  12  via travel-limiting sleeve  23  with the aid of spiral compression spring  28 , so that in the rest state (i.e., when no component  2  is grabbed via vacuum pressure), sleeve  12  tends to maintain as much distance as possible from pressure retainer  29 , the largest possible distance being specified by a limiting collar  31  in this case. The degree to which counter support  8  projects beyond holding opening  18  is able to be precisely adjusted via fine thread  22 . 
     When a vacuum pressure P u  is then applied to aspiration region  11  via bore  5  and vacuum supply channels  9 , and when holding tool  1  is lowered onto component  2 , holding opening  18  is sealed by component  2  as soon as contact is established. Vacuum pressure P u  in aspiration region  11  builds up to the extent specified by the vacuum pressure application via bore  5 , which causes sleeve  12  to slide axially in the direction of pressure retainer  29 , counter to the spring force of spiral compression spring  28 , and component  2  to be retained at holding opening  18  by ambient air pressure P E , which exceeds vacuum pressure P u  prevailing in bore  5  and thus in aspiration region  11 . Ambient air pressure P E  acting on component  2  causes it to deform while sleeve  12  experiences a slight further axial displacement such that, on its underside  32  facing the substrate (not shown here), component  2  undergoes a slight convex deformation, which is produced by conical tip  19  of counter support  8 , which now projects slightly beyond opening plane  20  formed in holding opening  18 , due to the now prevailing pressure ratios between ambient air pressure P E  and vacuum pressure P U . Because of the convex deformation of component  2 , its edge regions  33  are raised from an original underside plane  34  of component  2 , so that underside  32  of component  2  is no longer planar. This raising of edge regions  33  out of underside plane  34  occurs on all sides on component  2  as a result of the centrical placement of conical tip  19  of counter support  8  within holding opening  18 ; when component  2  is then placed on the substrate (not shown) via its underside  32 , underside  32  first is lowered onto a protrusion  35  formed essentially centrically on component  2 , so that possibly present gas inclusions are pushed away in the direction of edge regions  33 . Therefore, when handling tool  1  releases component  2 , i.e., when vacuum pressure P U  is canceled, which is accompanied by a corresponding forward sliding of sleeve  12  due to the spring loading by spiral compression spring  28 , and the repelling of component  2  from holding opening  18 , component  2  is placed on the substrate from the inside (starting at protrusion  35 ) toward the outside (in the direction of edge regions  33 ). This makes it virtually completely impossible for air inclusions or shrink holes to occur. 
       FIG. 2  shows a detail view of an example embodiment of counter support  8  from  FIG. 1  having an exchangeable counter-pressure tip  36 . The other components of handling tool  1  have not been illustrated for reasons of clarity. In this instance, rounded tip  37  is designed as exchangeable counter-pressure tip  36 , which is introduced in bore  5  of counter support  8  or vacuum pressure body  4  with the aid of a suitable receptacle  38 . Receptacle  38  is designed as plug-in receptacle  39  for this purpose, but a design in the form of a screw joint or a similar suitable affixation is conceivable as well. Counter-pressure tip  36  has vacuum pressure supply channels  9 , which like in the previously described  FIG. 1 , are developed as regional penetrations of the body of counter-pressure tip  36  and permit a pressure communication between bore  5  of counter support  8  and aspiration region  11  surrounding the counter-pressure tip. Exchangeable counter-pressure tip  36  may have different geometries or material characteristics in order to satisfy the special requirements of even highly sensitive components of all kinds. Furthermore, an uncomplicated and inexpensive exchange of exchangeable counter-pressure tip  36  is possible when wear or damage has occurred, without the need to exchange entire handling tool  1  or at least vacuum pressure body  4 . As a result, it is able to be used for a wide variety of applications and for a multitude of even the most sensitive components; furthermore, handling tool  1  is very easy to service and thus provides considerable cost savings. 
       FIG. 3  shows an enlarged, simplified view of a section  40  of a surface  41  of a substrate  42 , on which component  2  (not shown here), in particular a chip  3  (also not shown), has been mounted. On surface  41  of substrate  42 , in the center of an area  43  that corresponds to the dimensions of component  2  (not shown here), there are individual residual shrink holes  44  (illustrated in highly exaggerated form), which jointly form an extended shrink hole region  45 . When using handling tool  1  (not shown here) according to the present invention, shrink hole region  45  invariably forms in this or in a similar way in the center of area  43 , which is due to the use of counter support  8  (not shown here), in particular conical tip  19  (likewise not shown) and/or exchangeable counter-pressure tip  36  (also not shown here, cf.  FIG. 1  and  FIG. 2  in this context). The shrink hole development in the center of area  43  occurs because component  2  (not shown) first makes contact with substrate  42  in this location. Gas, which could cause additional shrink holes and/or additional inclusions in substrate  42  as soon as component  2  is placed thereon, is able to escape toward the outer edge regions  46  of the surface when using handling tool  1  according to the present invention, so that an inclusion and thus a development of residual shrink holes  44  in regions close to outer edge regions  46  or in large areas on surface  43  does not occur. A few additional small residual shrink holes  44  may develop despite the use of handling tool  1  according to the present invention, whose geometry reflects the geometry of end region  13  of sleeve  12  (not shown here). In the process, a ring of shrink holes  47  develops (shown here for a circular geometry of sleeve  12  in heavily exaggerated form), in which a few shrink holes are produced in a pattern that corresponds to the sleeve geometry. The term ring of shrink holes  47  denotes any geometric design of individual residual shrink holes  44  that corresponds to the geometry of the used sleeve  12  (not shown here) of handling tool  1  (not shown here). As a consequence, there always results a pattern of residual shrink holes  44  that is characteristic for handling tool  1  (not shown here) or for the use of the method according to the present invention. The pattern of the individual residual shrink holes  44  invariably corresponds to the geometries that are found in handling tool  1  (not shown), i.e., especially sleeve  12 , for a possible ring of shrink holes  47 , or counter support  8  (in particular exchangeable counter-pressure tip  36  or conical tip  19 ; cf.  FIG. 1  and  FIG. 2 ). When such a characteristic development of residual shrink holes  44  shows up, it always points to the use of handling tool  1  according to the present invention or the method for handling components according to the present invention. For in contrast to the shrink hole development found in the related art, the shrink hole developments encountered here (to a very slight extent) have a specific geometry. They do not follow a random distribution pattern and are especially not distributed across area  43  in essentially uniform manner. Instead, an accumulation of residual shrink holes  44  in area  43  is found only in places where pressure is exerted by handling tool  1  according to the present invention, i.e., in the region of sleeve  12  (forming a ring of shrink holes  47 ), or counter support  8  and/or conical tip  19  or exchangeable counter-pressure tip  36 , by the development of a shrink hole region  45  on surface  43  in essentially centrical form.

Technology Classification (CPC): 8