Patent Publication Number: US-2023139895-A1

Title: Press-in machine for pressing components into a substrate, in particular into a printed circuit board or carrier plate, with substrate positioning

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application relates and claims priority to German Patent Application No. 10 2021 128 724.3 filed with the German Patent Office on Nov. 4, 2021, the entirety of which is hereby incorporated by reference. 
     BACKGROUND 
     The invention relates to a press-in machine for pressing electrical, electronic, mechanical and/or electromechanical components into a substrate, in particular into a printed circuit board or carrier plate. 
     Such press-in machines are regularly used in the production of a large number of identical printed circuit boards or carrier plates equipped with electrical, electronic, mechanical and/or electromechanical components. The pressing of the components into printed circuit boards or carrier plates represents in particular an alternative to soldering the components. In particular, it has the advantage that no melting of soldering tin is required, that no resulting process gas has to be discharged and that overall the joining process is subject to a comparatively lower energy consumption. 
     The pins provided on the electrical, electronic, mechanical and/or electromechanical components are pressed into metalized holes or bores provided on the substrate when pressed in. An overpressing occurring during the press-in can either be absorbed by the deformation in the metalized hole or by the deformation of the pin. Overall, a quite reliable and also stable connection results. The press-in can be carried out in particular such that the metal partners are joined by cold welding. 
     It has been found that the requirements for pressing components into a substrate such as printed circuit boards or carrier plates are increasing. In particular, the positioning of the substrates with the components in the press-in position, in which the components are then pressed into the substrates, must be done relatively precisely in order to ensure a functionally reliable pressing-in of the joining partners. In this context, it must be taken into account that the pins of the components can pass through the substrates when pressed in and that the free ends of the pins are normally protruding on the side of the substrates facing away from the components during or after the press-in. 
     It has also been found that it is desirable to use press-in machines flexibly, in particular for pressing in different components on one and the same substrates or also on different substrates. 
     In particular when different substrates are to be joined with different components in a press-in machine, it is necessary for the individual substrates to be positioned in a press-in position to be defined in each case before the respective press-in operation in the machine. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to enable the positioning of the substrates in the press-in machine in a simple manner. 
     The object is achieved by a press-in machine for pressing in electrical, electronic, mechanical and/or electromechanical components. 
     Such a press-in machine comprises in particular a moving unit that comprises a receptacle for a substrate and with which the substrate can be moved in a substrate plane that is spanned by an x-axis and a y-axis, and can be placed in a press-in position, in which one or more components are pressed into the substrate. The x-axis and the y-axis are arranged orthogonally to one another and lie in particular in a horizontal plane. 
     Furthermore, a lower tool is provided, which can be moved along a z-axis against the underside of the substrate during or before the press-in. The z-axis is in particular arranged orthogonally to the plane of the substrate, i.e., to the x-axis and to the y-axis. The lower tool can also be rigid, and the substrate with the components to be pressed in can be deposited on the lower tool. With the lower tool, forces that arise during the press-in can be absorbed. 
     Furthermore, an upper tool is provided, which can be moved against the component for pressing the component along the z-axis toward the substrates. Press-in is ultimately effected by means of the upper tool, which presses the component into the substrate, against the underside of which the lower tool is resting for deflecting the press-in forces. 
     Furthermore, a control unit for controlling the moving unit is provided. The control unit can in particular be designed such that it also controls the movement of the upper tool and the lower tool along the z-axis. Furthermore, a sensor is provided for detecting at least one reference mark provided on the substrate. 
     The control unit is configured and designed such that it controls the moving unit depending on the detected reference mark in such a way that the substrate is placed between the lower tool and the upper tool in the press-in position. By detecting the reference mark, a defined reference position of the substrate can be determined. The press-in position can be indicated relative to the reference position or reference mark. Then, when the reference position or the reference mark is known, the substrate can be moved in a positionally accurate manner into the press-in position, i.e., into the target position. 
     Such positioning or placing of the substrate in the press-in position can be done for each of the substrates newly received by the press-in machine. This ensures that the substrate always assumes its press-in position in a positionally precise manner before the press-in process. Overall, this can optimize the press-in and joining processes. 
     After the press-in, the control unit can then continue to control the moving unit in such a way that the moving unit is moved further into a second or further press-in position, in which a second component or further components placed on the substrate are pressed in. Because the second or further press-in position relative to the first or previous press-in position is known, the control unit can precisely control the moving unit. 
     Furthermore, it is advantageous if the lower tool has recesses on its upper side facing the upper tool for receiving free ends of the pins of the component that pass through the soldering plate during the press-in. By providing the recesses on the lower tool, the free ends of the pins can dip into the recesses of the lower tool during the press-in process. This has the advantage that the press-in process is not hindered by the free ends hitting against the lower tool. The quality of the press-in and the joining connection can also be increased as a result. 
     Especially if the pins penetrating the substrate project on the underside of the substrate after the press-in operation, precise positioning and placement of the substrate in the press-in position is required before the press-in. Only in this way can it be ensured that the free ends of the pins can actually dip into the recesses on the upper side of the lower tool. 
     The upper tool can be adapted to the geometry of the component to be pressed in on its underside facing the lower tool. However, it is also conceivable for the design of the underside of the upper tool to be flat and recess-free. 
     It has been found to be advantageous if the reference mark is a substrate edge. The substrate can consequently be fed to the press-in machine, and the substrate edge can be detected by the sensor. Based on the detected reference mark, the substrate can then be moved into the press-in position. 
     It is also conceivable that the reference mark is a fiducial mark that is present on the substrate. Such fiducial marks are known on printed circuit boards in order to serve as optical reference points for the automated machining of the printed circuit board, in particular for the introduction of bores or vias. 
     A further, particularly preferred embodiment of the invention provides that the reference mark detected by the sensor is a reference bore present on the substrate. The sensor is then designed such that it can detect the reference points, and in particular the center axis or center point thereof. The reference bore can have, for example, a predefined diameter that can be detected by the sensor, whereby the sensor can then deduce the center axis or the center point. After the detection of the reference bore, the substrate is preferably moved further such that the reference bore is located centrally below the sensor, i.e., the sensor center axis and the central axis of the reference bore correspond or are aligned along a common straight line. The substrate then assumes its reference position. After that, the substrate, starting from the reference position of the substrate, can be moved relative to the reference position into the press-in position. 
     Furthermore, it is advantageous if the control unit is further configured and designed in such a way that during the movement of the receptacle along the x-axis in the direction of travel the sensor detects, for example, a substrate edge of a substrate present in the receptacle that is in the front with respect to the direction of travel, and that, depending on the detected substrate edge, the moving unit is further controlled in such a way that the receptacle is moved in the substrate plane along the x-axis and/or the y-axis such that the reference mark is located within the detection region of the sensor. It is advantageous if the position and the distance of the reference mark from the substrate edge are known. After the substrate edge has been acquired, the reference mark can be “searched” in a predetermined region by corresponding exiting of the region. 
     Accordingly, various steps are therefore conceivable: In a first step, the substrate edge is detected. In particular, it can thus be detected that a substrate has been fed to the press-in machine and is present. Especially when the location of the reference mark on the substrate with respect to the substrate edge is stored, the substrate can be moved in a second step such that the reference mark is located in the detection region of the sensor. There, the reference mark can then be detected in a third step and, starting from the reference mark, the substrate can be moved in a fourth step into the target or press-in position by means of the moving unit. In a subsequent step, the press-in can then take place. 
     Furthermore, it is advantageous if the substrates have metalized through-holes, wherein the reference bore in the substrate is such that it has been produced in the machining operation for the substrate in which through-holes for receiving pins of the components are introduced into the substrate. This has the advantage that both the through-holes and the reference bore have been produced in the same machining operation, and in particular in the same clamping of the substrate. This ensures that the positions of the reference bore relative to the through-holes are comparatively accurate. The position of the through-holes can consequently be reliably deduced from the position of the reference bore. Thus, if the substrate is moved into the press-in position, it is thus ensured that the through-holes assume an exact position relative to the reference bore and that ultimately the press-in process can be carried out with a precisely positioned substrate. 
     The sensor as such can be designed in particular as an optoelectronic sensor or as a camera. In particular, a light barrier sensor can be used as optoelectronic sensor. A CCD camera in which the reference position can be deduced by means of pattern recognition methods can in particular be used as the camera. 
     Furthermore, it is advantageous if the moving unit and/or the control unit are configured such that an acceleration and/or braking of the receptacle along the x-axis and/or y-axis takes place in such a way that components present on the substrate do not change their position on the substrate before they are pressed in during the acceleration and/or braking of the receptacle. The acceleration and braking thus take place in particular such that the components do not tilt over on the substrate before they are pressed during the braking or acceleration process. A secure positioning of the components on the substrate and a secure press-in of the components into the substrate can also take place as a result. 
     The aforementioned object is also achieved by a method for operating a press-in machine for pressing components into a substrate, in particular for operating a press-in machine according to the invention that has the features of claim  10 . 
     The method is characterized in that at least one reference mark present on the substrate is detected by the sensor and in that the moving unit is placed in the press-in position between the lower tool and the upper tool depending on the detected reference mark. 
     Consequently, the reference position of the substrate is known by detecting the reference mark. From the reference position or the actual position of the substrate, the substrate can then be moved into the target position, i.e., into the press-in position, and placed there for the press-in. 
     The reference mark can be a substrate edge, a fiducial mark and/or a reference bore. 
     Furthermore, it is advantageous if, in a first step, when the substrate is moved along the x-axis in the direction of travel, for example, the front substrate edge in the direction of travel is detected, when in a second step, depending on the detected substrate, the substrate is moved in the substrate plane along the x-axis and/or the y-axis in such a way that the reference mark is located in the detection region of the sensor. In a third step, the reference mark can be detected and, in a fourth step, the substrate can be moved into the press-in position. In a fifth step, the press-in can take place. Overall, the substrate can thereby be positioned reliably in the press-in machine for the press-in. 
     Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which an exemplary embodiment of the invention is described and explained in more detail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings show: 
         FIG.  1    a press-in machine; 
         FIG.  2    the moving unit of the press-in machine according to  FIG.  1   ; and 
         FIGS.  3   a  and  3   b    are side elevation and plan views, respectively, of a lower tool of the press-in machine according to  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a press-in machine  10  that has a base body  12  and a gantry  14 . A lower tool  16  is provided on the base body  12 , which is movably arranged with a lower pressing unit  17  along a vertical z-axis  18 . An upper tool  20  that interacts with the lower tool  16  during the press-in process is shown on the gantry  14 , said upper tool  20  being displaceable along the z axis  18  toward a substrate  31  in the form of a carrier plate or printed circuit board  32  with an upper pressing unit  22  that engages on the gantry  14 . 
     The press-in machine  10  comprises a moving unit  24 , which provides a receptacle  26  for the substrate  31  or the printed circuit board  32 . 
     The moving unit  24 , which is shown in  FIG.  2   , has an inlet  28  and an outlet  30 , wherein the printed circuit board  32  shown in  FIG.  2    can be moved between the inlet  28  and the outlet  30  along an x-axis  34  by means of a transport drive  37  having two motors. The transport drive  37  drives conveyor belts  40  on which the printed circuit board  32  comes to rest. The belts  40  are guided in transport rails  42 . 
     When the circuit boards  32  are moved into the inlet  28 , electrical or electronic components are present on the printed circuit board  32 , which are pressed into the printed circuit board  32  with the press-in machine  10 . Such components are not shown in  FIG.  2   ; the pins of the components can be placed onto metalized through-holes, which are provided in the printed circuit board  32 , or can be inserted somewhat. 
     For the supply of printed circuit boards  32 , it is conceivable that upstream of the inlet  28  a feed device is provided with which the printed circuit boards  32  are supplied. To discharge the printed circuit boards  32  after the pressing operation, it is conceivable that a discharge unit is connected downstream of the outlet  30 . 
     With the moving unit  24 , the printed circuit board  32  can be moved along the x-axis  34  and along a y-axis  36 , which is arranged perpendicular to the x-axis  34  and perpendicular to the z-axis  18 . The printed circuit board  32  can consequently be moved with the moving unit  24  in a plane, which is spanned by the x-axis  34  and the y-axis  36 . 
     An x-axis drive  38  is provided for moving the printed circuit board in the receptacle  26  in the x-direction  34 . By appropriately controlling the x-axis drive  38 , the receptacle  26  together with the printed circuit board can consequently be moved in the x direction  34 . 
     The moving unit  24  also provides a y-axis drive  44 , with which the transport rails  42 , and thus the printed circuit board  32 , can be moved in the y-direction  36 . Depending on the control of the x-drive  38  and the y-drive  44 , the printed circuit board  32  can consequently be moved freely in the plane defined by the x-axis  34  and the y-axis  36 . 
     Furthermore, a control unit  45 , for example a PLC control, is provided, which is schematically indicated in  FIG.  2    and serves to control the x-axis drive  38  and the y-axis drive  44 . With the control unit  45 , the upper tool  20  and the lower tool  16  can also be moved along the z axis  18  independently of one another and away from one another. 
     In  FIG.  2   , a stop sensor  46  is provided in the region of one of the transport rails  42 . The stop sensor  46 , which can be designed, for example, as a light barrier, detects the entry of a front edge  47  of the printed circuit board  32  during the movement of the printed circuit board from the inlet  28  to the outlet  30 . 
       FIG.  2    shows a further sensor  48 , a position sensor, with which a reference mark  50  that is present on the printed circuit board  32  can be detected. The reference mark  50  can be, for example, the front edge  47  or a reference bore  52  in the printed circuit board  32  or a fiducial mark on the printed circuit board  32 . 
     Both the stop sensor  46  and the position sensor  48  are connected to the control unit  45  and supply generated sensor signals to the control unit  45 . 
     For transporting a printed circuit board  32  from the inlet  28  to the outlet  30 , the transport drive  37  is controlled by the control unit  45  such that the printed circuit board  32  is moved toward the outlet  30 . As soon as the stop sensor  46  detects the front edge  47  of the printed circuit board  32 , the transport drive  37  is stopped. Because the stopping does not take place abruptly so as to prevent the components from falling over, the printed circuit board is moved somewhat beyond the stop sensor  46  until it ultimately comes to a standstill. 
     The printed circuit board  32  is then fixed in the moving unit  24  by means of fixing means  54 , so that it cannot escape upward or downward in the z-direction  18 . The fixing means  54  can be clamping elements or clamping springs, which act against the printed circuit board  32 . 
     In a next step, the printed circuit board  32  is moved in the x-direction  34  and y-direction  36  until the sensor  48  detects the reference mark  50 . Because the distance from the front edge  47  to the reference mark  50  is known, the printed circuit board  32  can be moved with the moving unit  24  in a targeted manner into the region where the reference mark  50  is present. 
     The sensor  48  can be, for example, an optoelectronic sensor, such as a light barrier or a camera, which detects the reference mark  50 . If the sensor  48  has detected the reference mark  50 , a defined reference position or actual position of the printed circuit board  32  is known. Starting from this reference position, the printed circuit board  32  can be moved in a next step in the x-direction  34  and y-direction  36  into a desired position, namely into the press-in position, in which components present on the printed circuit board  32  are pressed in by means of the tools  16  and  20 . This is possible because the press-in position relative to the reference position or reference mark is known and is stored accordingly. The control unit  45  is thus configured such that it controls the x-drive  38  and the y-drive  44  in such a way that the printed circuit board  32  is placed starting from the reference position between the lower tool  16  and the upper tool  20  in the press-in position that is known relative to the reference position. 
     After reaching the press-in position, the lower tool  16  is moved along the z-axis against the underside of the printed circuit board  32 , so that the tool  16  comes to rest against the printed circuit board  32 . The press-in is ultimately carried out by the upper tool  20  by the component being pressed into the printed circuit board  32 , while the lower tool  16  deflects press-in forces into the base body  12  on the underside of the circuit board  32 . Consequently, one or more components placed on the printed circuit board  32  can be pressed into the printed circuit board  32  by means of the tools  16  and  20  simultaneously or sequentially by moving the printed circuit board  32  into different press-in positions. 
     Even if two different sensors  46  and  48  are shown in  FIG.  2   , it is conceivable for the sensor  48  also to assume the task of the stopper sensor  46 , namely to determine whether the front edge  47  has traveled over the sensor  48 , so that the transport drive  37  is then stopped. 
     As already mentioned, the reference mark  50  can be the front edge  47  of the printed circuit board. However, it has been shown that printed circuit boards  32  can have production-related size deviations of a few tenths of a millimeter, and that this is too imprecise for precise positioning of the press-in position. Therefore, it is advantageous to provide a reference bore  52  as a reference mark, the position of which bore with respect to the metalized through-holes present in the printed circuit board  32 , in which the pins of the electronic components are inserted is comparatively accurate. In particular, the position of the reference bore  52  with respect to the through-holes of the printed circuit board  32  is very accurate when the reference bore  52  is created in the same machining operation as the through-holes of the printed circuit board  32 . 
       FIG.  3    shows the lower tool  16  as a single part in a side view ( FIG.  3     a ) and in plan view ( FIG.  3   b   ). On its upper side  55  facing the upper tool  20 , the lower tool  16  provides recesses  56  in the form of blind holes that have a diameter of 1/10 to 1.5 millimeters. The recesses  56  serve to receive free ends of the pins of the electronic components passing through the printed circuit board  32  during the press-in. By providing the recesses  56 , it is ensured that the free ends do not impede the press-in operation when the components are pressed into the printed circuit board  32 , but can dip into the recess  56 . Therefore, because it is also ensured that during the press-in process the free ends of the pins can dip into the recesses  56 , it is necessary to move the printed circuit board  32  relatively precisely into the press-in position before the press-in and to place it there. 
     The moving unit  24  or the drives  38  and  44  thereof is/are controlled by the control unit  45  in such a way that an acceleration and braking of the receptacle  24  takes place in such a way that components present on the printed circuit board  32  do not change their position on the printed circuit board before being pressed in during acceleration and/or during braking of the receptacle  24 , and in particular do not tip over.