Abstract:
The invention relates to an assembly device for microcomponents that are disposed in a magazine. The inventive assembly device does not require any optical systems and allows for an exact positioning of the microcomponents. The assembly will also be unaffected by any position changes of the microcomponents caused by wastage. The assembly device is provided with mechanical alignment devices that engage with or act upon adjustment structures of the magazine. The assembly device further comprises clamping devices for fixing the magazine and at least one plunger for ejecting at least one microcomponent from the magazine. An assembly platform is provided in the upper tool or in the lower tool of the assembly device and receives the microcomponents in a defined position. The invention further relates to a method for assembling microcomponents and to a corresponding magazine.

Description:
FIELD OF THE INVENTION 
   The invention relates to a magazine and an assembly device for microcomponents that are arranged in the magazine. The invention further relates to a method for assembling microcomponents that are arranged in a magazine. 
   BACKGROUND OF THE INVENTION 
   Microcomponents are delivered to the processor in a magazine, where they must be removed from the magazine for assembly. In a magazine such as the one described, for instance, in German Laid Open Publication DE 197 09 136 A1, the microcomponents are integrated in the wafer-type magazine, so that they are protected from damage during transport. The microcomponents must be ejected from this magazine by means of a plunger. 
   For this purpose, the entire magazine wafer must first be positioned in such a way that each component that is to be removed from the magazine is exactly at the location where it is to be installed in an already existing structure of microcomponents. If, for instance, a gear unit is to be assembled from microcomponents, the corresponding gears must be positioned exactly above the shafts that are to receive them and must then be ejected from the magazine. Currently, the magazine wafers are grasped and positioned either by hand or by means of an automatically operated gripper system. 
   Positioning by hand decisively depends on the skill and concentration of the person involved. Positioning aids that may be arranged in the magazine can be used only to a limited extent or not at all. 
   In automatic gripper systems, limit stops are used, for instance, against which the edge of the magazine wafer is placed. However, due to the shrinkage of the magazine and microcomponent material that occurs during the manufacturing process, the position of the microcomponents changes. The molding tool is therefore made larger, so that this systematic shrinkage during production of the microcomponents is taken into account. Shrinkage tolerances, however, result in positional tolerances of the microcomponents within the magazine. Consequently, even those microcomponents that are arranged adjacent to the guide edge may have shifted, such that they are not arranged at the intended position within the magazine. To be able to remove a plurality of components from the wafer magazine, the magazine must be pushed back and forth by means of a displacement device, so that incorrect positions of microcomponents can add up. This has the result that the ejection tools, such as plungers or the like, are not arranged at the position where the components to be removed are actually located, or the components to be removed are not located exactly above the position where the structure receiving them is arranged. This causes damage to either the components or the magazine, or damage to the larger microstructures on which the microcomponents are to be mounted, or even damage to the ejection tools. 
   Optical methods, i.e. image analysis processes, are therefore already being used for the positioning of microcomponents, as described, for instance, in G. Reinhart et al., “Flexible Montage von Miniaturbauteilen” [Flexible Assembly of Miniature Components], F+M 105 (1997) 1-2, pp. 43–45. This presents the problem of insufficient contrast, however, because both the magazine and the microcomponents are made of similar materials or, if a separator is produced, even of identical materials. As a result, the position of the corresponding microcomponents cannot be determined exactly. Consequently, the required accuracy of 5 μm and better, which is often required for the precise positioning of the microcomponents, cannot be met. 
   A further drawback is that image recognition and analysis systems are costly and require a relatively long time for positioning because the wafer magazine or the tools must be moved in several spatial directions. 
   Furthermore, the wafer magazine can bend as the microcomponents are ejected, which also causes malpositioning. 
   SUMMARY OF THE INVENTION 
   Thus, it is the object of the invention to provide an assembly device that does not require the use of optical systems and that ensures precise positioning of the microcomponents arranged in a magazine. Any positional changes of the microcomponents that occur due to shrinkage should not affect the assembly process. A further object of the invention is to provide a magazine that enables a simple positioning of microcomponents and a method for assembling microcomponents arranged in the magazine, in which damage to the microcomponents or the magazine or the ejection tools is prevented. 
   This object is attained by an assembly device having an upper tool and a lower tool. These tools are provided with mechanical alignment means, clamping means, plungers and an assembly platform. 
   Mechanical alignment means are provided, which engage with adjustment structures of the magazine. 
   For this purpose, the magazine according to the invention is provided with adjustment structures for engagement with mechanical alignment means during the assembly of the microcomponents. Possible adjustment structures are projections, indentations or openings in the magazine material with which the alignment means interact to bring about the alignment of the microcomponents located in the magazine. 
   The adjustment structures are preferably circular, cylindrical, triangular, square or polygonal structures formed in the magazine material. The adjustment structures are preferably openings with a diameter of 100 μm to 3 mm. 
   In the simplest case, the adjustment structures are circular holes or openings in the magazine material. 
   These adjustment structures can essentially be divided into three groups. The adjustment structures can be provided on the magazine level, the cluster level or the microcomponent level, which depends on the tolerances of the components to be assembled, their arrangement and the shrinkage of the magazine and microcomponent material. The best positioning accuracy is achieved if adjustment structures for positioning the magazine and the microcomponents are used on the component level. The adjustment structures on the component level are arranged adjacent to the microcomponent to be removed, so that material shrinkage is negligible because the distances between the component to be assembled and the associated adjustment structure are small. 
   The adjustment structures on the magazine level, cluster level or component level can have the same size. It is advantageous, however, if the adjustment structures decrease in size from the magazine level to the microcomponent level because they would otherwise require too much space due to the clearly greater number of structures. 
   Preferred therefore are diameters ranging from 1 mm to 3 mm are used for the adjustment structures on the magazine level, from 500 μm to 1 mm on the cluster level and 100 μm to 500 μm on the component level. 
   The adjustment structures of all the levels are preferably provided in a regular arrangement. Since the assembly device and the device for displacing the magazine are computer-controlled, the arrangement of the adjustment structures is preferably selected in such a way that programming of the control units is made as simple as possible. 
   The assembly device is further provided with clamping means for fixing the magazine. These clamping means are arranged in such a way that they engage with the magazine in the area of the components to be assembled, so that when the microcomponents are ejected from the magazine, bending and thus positional shifting of the microcomponents is nearly prevented. 
   The clamping means are preferably integrated in the alignment means. This means that the magazine, during adjustment, is also clamped or fixed, either at the same time or offset in time. 
   Furthermore, at least one plunger is provided for ejecting at least one microcomponent. This plunger is preferably arranged between the alignment and/or clamping means. It is advantageous if the upper and lower tools each have at least two alignment structures between which the microcomponent or components to be assembled are arranged. 
   Finally, the assembly device is also provided with an assembly platform, which can be arranged in the lower or in the upper tool. The microcomponents or other larger component structures that are to be equipped with additional microcomponents are placed on this assembly platform. The assembly platform thus serves to receive the positioned microcomponents. The assembly platform and the plunger can preferably be moved independently from one another perpendicularly to the surface of the magazine. It is also possible to provide a coupled movement of the assembly platform and the plunger. 
   The mechanical alignment means preferably comprise an upper and a lower alignment device, which are arranged opposite one another. At least one of the alignment devices is movable in vertical direction. Since the magazine is placed horizontally into the assembly device, the vertical direction is identical with the direction normal to the plane of the magazine. 
   At least one of the alignment devices is provided with at least one pin, which is preferably a pilot pin that engages with the corresponding adjustment structure of the magazine. The diameter of the pilot pins preferably ranges from 100 μm to 3 mm and is adapted to the adjustment structures. 
   The pin preferably has a center point, so that when the pin engages with the adjustment structure, the magazine can be laterally shifted into the intended position. If the magazine has first been roughly adjusted, the engagement of the pins with the adjustment structure of the magazine causes a fine adjustment of the magazine and thus the components to be removed from the magazine. 
   The center point preferably has a truncated cone shaped or a conical surface. The associated cone angle is preferably 50° to 90°. 
   Furthermore, the pilot pin is advantageously arranged on a base part with a shoulder. The foil magazine rests against this shoulder during the alignment process. A clamping device engaging on the opposite side of the magazine is used to press the magazine against this shoulder and thus to clamp it. 
   The pilot pin preferably merges into the shoulder via a truncated cone shaped collar. During the clamping process, the truncated cone shaped collar is pressed into the magazine material, which further enhances the clamping action and improves the positioning tolerance. 
   The length of the pilot pin is preferably larger than the thickness of the magazine, such that the pilot pin reaches through the magazine and protrudes on the opposite side of the magazine. The opposite alignment device is preferably provided with a pin socket with which the pilot pin engages. This can simultaneously ensure a mutual fine adjustment of the upper and the lower tool, so that assembly accuracy is further improved. 
   The pin socket preferably has a flat end face that presses against the outside of the magazine and thus, in cooperation with the pilot pin or its shoulder, clamps the magazine. 
   Irrespective of the mutual adjustment of the upper and lower tool by means of the pilot pins, the upper and lower tool can be arranged so as to be adjustable in relation to the respectively other tool, which is made possible by corresponding control devices. 
   The plunger is preferably arranged in the upper tool, so that the microcomponents can be ejected from the magazine in downward direction. 
   The assembly device has the advantage that material shrinkage does not negatively affect the assembly of the microcomponents. The alignment of the magazine by means of adjustment structures, which are added to the magazine when the microcomponents are produced, makes it possible in the assembly process to use the existing positional accuracy of the microcomponents, which is already realized in the magazine. The simultaneous clamping fixation of the magazine in the area of the adjustment structures nearly prevents the magazine from bending in the area of the microcomponents to be assembled. Optical systems do not have to be used for adjustment. Optical systems may possibly be used to check whether a magazine is present in the device. 
   The adjustment of the magazine and the microcomponents can be combined with an additional adjustment of the upper and lower tool of the assembly device. At the same time, the plunger is aligned relative to the previously positioned microcomponents in the opposite tool of the assembly device. In this manner, the microcomponents are adjusted relative to the tools of the assembly device and relative to the existing microcomponents that are to receive the components to be assembled. Damage to the microcomponents is thus prevented. 
   Preferably, the plunger or plungers, the assembly platform and the pins can be exchanged. This exchange can take place automatically, so that the assembly device becomes an assembly robot or stepper. This makes it possible to adapt the device to different microcomponents and magazines, so that even complex structures can be assembled in a simple manner. 
   The method for assembling the microcomponents arranged in a magazine provides that the magazine is grasped and positioned together with the microcomponent to be assembled and is first roughly adjusted. Subsequently, the magazine is fine adjusted by means of adjustment structures disposed in the magazine and the microcomponent to be assembled is then ejected from the magazine. 
   The fine adjustment is preferably done by means of adjustment structures on the magazine level, the cluster level or the microcomponent level. 
   The fine adjustment is effected by the engagement of mechanical alignment means with the adjustment structures. This causes the magazine to be adjusted or shifted on the magazine level. 
   The magazine, during adjustment, is preferably clamped either at the same time or offset in time. During the adjustment process, the magazine is displaceably supported in the horizontal plane so that the positional change that occurred due to shrinkage can be compensated. 
   The magazine is preferably arranged above the assembly position of the microcomponents and is ejected onto an assembly platform. 
   The component or components located on the assembly platform, e.g. microcomponents or larger component structures, are fixed by applying a vacuum. 
   The finished microsystem, e.g. a gear unit, is removed, for instance, by a gripper. 
   An alternative provides that the magazine be used to remove the finished microsystem. The last microcomponent to be mounted is preferably ejected only partially from the magazine, such that on the one hand it is still anchored in the magazine and on the other hand it is also already pressed onto the component structure to be equipped, which holds it. As the magazine is removed from the assembly device, the finished microsystem can also be removed from the assembly device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention will now be described in greater detail with reference to the drawings in which: 
       FIG. 1  is a top view of a wafer-type magazine, 
       FIG. 2  is a top view of a cluster of the magazine wafer shown in  FIG. 1 , 
       FIG. 3  is a schematic sketch of an assembly device, 
       FIGS. 4   a, b  are vertical sections through an assembly device according to a first embodiment, 
       FIG. 5  is a vertical section through an assembly device according to another embodiment, and 
       FIG. 6  is a detail section of an alignment device according to a further embodiment. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a top view of a wafer-type magazine  4 , which is divided into square clusters  41  in which microcomponents  3  are arranged. This is a so-called foil magazine in which the microcomponents are integrated. In the embodiment shown, the microcomponents  3  are gears, which as planetary gears are to be built into a gear unit. For this reason, the gears are arranged in groups of three  31   a–d  according to their subsequent position in the gear unit. 
   The wafer-type magazine  4  has a round outer contour with a straight stop face  43 . Along the outer circumference, four equidistant adjustment structures  42   a–d  in the form of circular holes are provided. These are adjustment structures on the wafer level. 
   Each cluster  41  also has adjustment structures  44   a–d  in the four corner points, as may be seen in detail in  FIG. 2 . The four microcomponent groups also have associated adjustment structures  45   a–d  which are arranged around the corresponding microcomponent group  31   a–d . Both the adjustment structures  44   a–d  and the adjustment structures  45   a–d  are holes with which the alignment means can engage. Depending on whether the positional tolerances of the microcomponents due to the shrinkage of the magazine and component material are large or small compared to the assembly tolerances of the microcomponents, the adjustment structures  42   a–d , the adjustment structures  44   a–d  or the adjustment structures  45   a–d  can be used for aligning the magazine  4  or the microcomponents  3   a–c.    
     FIG. 3  shows a schematic outline of an inventive assembly device. The foil magazine  4  is located on a foil magazine carrier  11  arranged on a table, which enables displacement in XY direction as well as a pivoting motion about the normal to the magazine surface (Z axis). This so-called XY and theta table  15  is located on an assembly table  100 . The upper tool comprises an upper main translator  12 , which is movable in Z direction. On or in this main translator  12  an upper differential translator  9  is arranged, which can be moved in Z direction relative to the upper main translator  12 . The upper differential translator  9  carries a plunger holder  1 , which is also movable in Z direction relative to the upper differential translator  9 . The plunger holder  1  carries a plunger  2  by means of which the microcomponents  3  that are arranged in the foil magazine are ejected from the magazine. 
   The lower tool is also provided with a lower main translator  13 , which is movable in Z direction. On or in the lower main translator  13 , a lower differential translator  10  is arranged, which is also movable in Z direction. The lower differential translator  10  carries a platform holder  14  on which an assembly platform  8  is mounted, which may possibly carry previously assembled microcomponents  7 . Both the upper main translator  12  and the lower main translator  13  are arranged on an assembly base  16 . Either the lower or the upper main translator is pivotable about the Z axis relative to the assembly base  16 . The adjustment means of the upper and the lower tool or their components make it possible to adjust the device components relative to one another. This adjustment is done before the microcomponents are assembled. Thereafter, the mutual assignment of the components does not have to be changed again. 
     FIG. 4   a, b  shows a vertical section through an assembly device, which comprises an upper tool  101  and a lower tool  102 , between which the magazine with microcomponents  3   a  and  3   b  is horizontally arranged. 
   The magazine  4  is held by a magazine carrier  11  and is roughly positioned by shifting the magazine carrier  11 . Magazine carrier  11  comprises a lower part  11   a  and an upper part  11   b . The lower part  11   a  is provided with pins  11   c , which engage with the adjustment structures  42   a–d  or  44   a–d  of the magazine  4 . The individual components of the upper tool  101  or the lower tool  102  have already been described with reference to  FIG. 3 , so that only details of the alignment device will now be explained. 
   The upper alignment device  5  is fixed in the upper differential translator  9  and is lifted or lowered by the vertical movement of the upper differential translator. In the view shown in  FIG. 4   a, b , the upper alignment device  5  has already been lowered onto the topside of foil magazine  4 . The upper alignment device  5  has two pins  52   a  and  52   b  between which the two plungers  2   a  and  2   b  and the plunger holder  1  are arranged. The plunger holder  1  is vertically movable relative to the upper differential translator  9 . Each pin  52   a  and  52   b  at its free end is provided with an axial bore that serves as a pin socket  53   a, b  for the pilot pins  60   a, b , which will be described in greater detail below. Pins  52   a, b  have a flat end face  54 , which acts as a clamping means pushing against the topside of magazine  4 . 
   Opposite pins  52   a, b , two pilot pins  60   a  and  60   b  of the lower alignment device  6  are arranged in the lower tool  102 . These pilot pins  60   a, b  have a center point  61  with a truncated cone shaped surface  63  and are arranged on a base part  62   a, b , which is provided with a shoulder  65   a, b . The length of the pilot pins  60   a, b  is larger than the thickness of the magazine  4 , so that pilot pins  60   a, b  reach through the adjustment structures  45   a, b  and engage with the pin socket  53   a, b . With this, not only a positioning in terms of a fine adjustment of magazine  4  is performed, but at the same time possibly also a mutual alignment of the upper tool and the lower tool. Magazine  4  is clamped between the end faces  54  of pins  52   a, b  and shoulder  65   a, b  of the pilot pins  60   a, b.    
   After adjustment and clamping of magazine  4 , the plunger holder  1  with plungers  2   a, b  is lowered and the microcomponents  3   a ,  3   b  are ejected downwardly from magazine  4 . Assembly platform  8 , which is provided with suction ducts  81  and  82 , is arranged on platform holder  14 . By applying a vacuum, microcomponents  7   a, b  are fixed on the assembly platform  8 . 
   Through the mutual alignment of the upper and lower tool and the adjustment of magazine  4 , the bores of gears  3   a, b  are aligned with the pins of microcomponents  7   a, b . By lowering plungers  2   a, b , the microcomponents  3   a, b  are ejected downwardly from magazine  4  and placed onto the existing microcomponents  7   a, b.    
     FIG. 5  shows a further embodiment, which is distinguished from the embodiment depicted in  FIG. 4  by a modified configuration of the upper and lower alignment device. Both pins  52   a, b  and pins  60   a, b  of the alignment devices have truncated cone shaped center points  61 , which engage with bores  45   a, b . In this embodiment, pins  52   a, b  and pins  60   a, b  can interact in such a way that the upper tool and the lower tool are also aligned. The diameter of pins  52   a, b  or  60   a, b  is larger than the diameter of the adjustment structures  45   a, b  of magazine  4 , so that when center points  51  and  61  engage, a shift and thus an adjustment of magazine  4  occurs. 
     FIG. 6  depicts a further embodiment of a pilot pin  60   a . Pin  52   a  has a pin socket  53  with which the pilot pin  60   a  engages. Pilot pin  60   a  has a truncated cone shaped collar  64  that merges into shoulder  65   a  and is pressed into the bottom side of magazine  4  during the clamping and adjustment process. This improves the clamping action and achieves a precise positioning of the magazine.
       1  plunger holder     2   a, b  plunger     3   a–c  microcomponents     4  magazine     5  upper alignment device     6  lower alignment device     7   a, b  microcomponent     8  assembly platform     9  upper differential translator     10  lower differential translator     11  foil magazine carrier     11   a  lower part of magazine carrier     11   b  upper part of magazine carrier     11   c  pin     12  upper main translator     13  lower main translator     14  platform holder     15  XY and theta table     16  assembly base     31   a–d  component group     41  cluster     42   a–d  adjustment structure/wafer level     43  stop edge     44   a–d  adjustment structure/cluster level     45   a–d  adjustment structure/group level     51  center point     52   a, b  pin     53   a, b  pin socket     54  end face     60   a, b  pilot pin     61  center point     62   a, b  base part     63  truncated cone shaped surface     64  collar     65   a, b  shoulder     81  suction duct     82  suction duct     100  assembly table     101  upper tool     102  lower tool