Patent Publication Number: US-2023147071-A1

Title: Soldering apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application relates and claims priority to German Patent Application No. 10 2021 129 129.1, filed Nov. 9, 2021, the entirety of which is hereby incorporated by reference. 
     BACKGROUND 
     The invention relates to a soldering apparatus, in particular a reflow soldering apparatus, for the continuous soldering of printed circuit boards along a transport direction, comprising a process channel comprising a preheating zone, a soldering zone and/or a cooling zone, having a base body and a cover hood, wherein the cover hood is displaceable between a closed position and an open position, wherein nozzle plates, fan units, air ducts conducting the process gas, filter elements and/or cooling elements are provided in the base body. 
     By means of reflow soldering apparatus, so-called SMD components (surface-mounted devices) are soldered onto the surface of printed circuit boards by means of solder paste. The solder paste, which is in particular a mixture of solder metal granules, flux and pasty components, is applied to or printed onto the surface of the printed circuit boards for reflow soldering. The components to be soldered are then planted into the solder paste. In the reflow soldering process, the material for soldering, i.e. the assembly consisting of printed circuit board, solder paste and the components to be soldered, are preheated in a preheating zone along the process channel and in a soldering zone heated to a temperature above the melting point of the solder paste. As a result, the solder paste melts and the solder joints are formed. In a cooling zone, if one is present, the material for soldering is cooled until the melted solder solidifies before said material is removed from the reflow soldering apparatus. 
     Soldering apparatus for the continuous soldering of printed circuit boards are known from DE 10 2019 128 780 A1, DE 10 2019 125 981 A1 and DE 10 2005 055 283 A1. 
     In the case of reflow soldering apparatus, the process channel is generally formed by two channel halves, an upper and a lower channel half. The lower channel half is provided in or on the base body and the upper channel half is provided in or on the cover hood. Further components, such as, for example, nozzle plates, fan units, air ducts conducting the process gas, filter elements and/or cooling elements, are generally provided in or on the process channel or in or on the base body and in or on the cover hood. Overall, a desired temperature profile is thus provided in the process channel along the transport direction, wherein the process gas is blown into the process channel, sucked out of said channel, in particular cooled in the cooling zone, cleaned and fed back to the process channel. 
     In particular in the cooling zone, condensate forms during the cooling of the process gas, which can lead to contamination of the machine. 
     SUMMARY OF THE INVENTION 
     The object of the invention is to provide a soldering apparatus with which, in particular, the cooling zone is advantageously designed such that impurities are prevented and/or individual components are easily accessible in particular in the base body. 
     This object is achieved by means of a soldering apparatus. Consequently, in particular in the cooling zone, it is provided that a drawer that can be pulled out along a pull-out direction running transversely to the transport direction is provided in the base body, said drawer having a bottom, a front wall and a rear side, which can in particular be formed by a rear wall or comprise a rear wall, wherein air ducts for conducting the process gas, at least one replaceable filter element and/or at least one cooling device are provided in the drawer. 
     By providing the drawer that can be pulled out transversely to the transport direction and in particular in the vertical direction, the at least one replaceable filter element and/or the cooling device that is provided in the drawer are consequently easily accessible. Since moisture or vapors contained on the cooling device in the process gas condense, by providing the drawer, it is particularly advantageous to collect the condensate in the drawer and, if necessary, to ultimately remove it by opening the drawer. Furthermore, the provision of the drawer is advantageous in order to visually check and/or replace the filter element. An exchange of the filter element when the drawer is open is comparatively easy to accomplish. 
     Furthermore, it is advantageous if air ducts are formed and arranged in the base body in such a way that the process gas is conducted out of the process channel vertically downwards into an entry channel provided on the front wall of the drawer, wherein the entry channel is deflected in the region of the bottom of the drawer towards a cooling device comprising a cooling plate. The cooling plate preferably extends at least in sections along the bottom of the drawer. The described manner of conducting the process gas makes it possible to ensure that the moisture and vapors present in the process gas condense on the cooling plate on the bottom of the drawer. This has the advantage that the condensate collects at the bottom of the drawer. The cooling plate has dimensions that are suitable for adequately condensing vapors present in the process gas. The cooling plate can be actively cooled, for example by means of energizable cooling elements. The cooling plate can also be arranged such that it is cooled by the ambient atmosphere. 
     The entry channel extending over the bottom of the drawer is advantageously designed such that it opens into a filter region on the side facing the rear side, in which filter region the at least one filter element is provided. This causes process gas, which has cooled sufficiently, to flow out into the filter region and to be able to flow through the filter element there. Since vapors in the process gas have already condensed out on the cooling element, process gas that is at least somewhat dehumidified flows through the filter element. 
     For the targeted movement of the process gas in the base body, a plurality of fan units is preferably provided, wherein at least one shielding plate is provided in the upper region of the drawer that shields an intake region of at least one fan unit towards the filter region. This ensures that process gas does not flow directly from the filter element to the fan unit via the fan units, but is deflected via the shielding plates. 
     Furthermore, it is advantageous if the cooling plate extends along a cooling plane running obliquely to the horizontal and having a drip pan in its region located vertically below. It is advantageous if the drip pan is provided in or on the bottom of the drawer in the region of the front wall. As a result, liquid condensing on the cooling plate and following the slope of the cooling plate can be collected in the drip pan. Furthermore, the drip pan is in particular transparent, so that whether and how much condensate is present in the drip pan can be checked visually. Furthermore, the drip pan is preferably detachably arranged on the drawer, so that emptying the drip pan is possible without opening the drawer. 
     Furthermore, it is advantageous if the filter element in the drawer runs obliquely to the horizontal and in particular in the region of a diagonal of the drawer and thus along a filter plane running obliquely to the horizontal. Due to the oblique arrangement of the filter plane, its surface can be enlarged as compared with a horizontal arrangement, thereby increasing the filter capacity. The filter element can comprise a filter grate and a filter fleece provided in or on the filter grate. 
     Such an arrangement is then particularly advantageous in that the shielding plate covers that part of the filter element that is close to the bottom of the drawer or in which the filter element is located in the lower region of the drawer. Seen from above, the shielding plate, which in particular extends in the horizontal direction, then covers in particular approximately half of the filter element. The arrangement is preferably such that the cover plate is provided in the rear region of the drawer, i.e. in particular adjoining the rear side. 
     It is particularly advantageous if the cooling plane and the filter plane enclose an acute angle. This results in optimized air guidance and overall an optimized cooling result and filtration result of the process gas. The shielding plate then preferably lies above the region where the acute angle between the filter element and the cooling plate is located. 
     It is also conceivable for the drawer to have two, three or more compartments lying next to one another in the pull-out direction, wherein a filter element is provided in each of the compartments. Furthermore, each compartment can be provided with its own entry channel and own shielding plate. As a result, the one drawer turn out very wide, wherein a plurality of air circuits running substantially parallel and transverse to the transport direction can be provided within the drawer by the individual compartments and thus a uniform distribution of the air flow be provided. 
     Furthermore, it is advantageous if a collecting tray is provided beneath the drawer on the base body, which collecting tray serves to collect condensate dripping down or contaminants dropping down when the drawer is open. This ensures that the substrate beneath the soldering apparatus does not get dirtied even when the drawer is open. 
     Furthermore, it is advantageous if a lowering mechanism is provided for lowering the drawer before the drawer is pulled out or as the drawer is being pulled out. Such a lowering mechanism can provide, for example, a lever mechanism by means of which the drawer is lowered as the drawer is being pulled out. This has the advantage that a comparatively snug abutment can be achieved between the drawer and the process channel. This prevents process gas from flowing out between the drawer and the base body when the drawer is closed and lifted. 
     Furthermore, an advantageous embodiment of the invention provides that, in or on the base body, at least one fan unit located on the face of the rear side facing away from the front wall, i.e. in the pull-out direction behind the rear side—and in the transport direction laterally next to the process channel—is provided. The provision of the at least one fan unit in the transport direction laterally next to the process channel, and not in the vertical direction below the process channel, has the advantage that the soldering apparatus has a lower overall height, the process channel can be arranged correspondingly lower and the fan units are easily accessible for repair and maintenance. In addition, a better heat dissipation of the heat generated by the fan units is possible, since the heat generated by the fan units can be discharged laterally next to the process channel. The cooling of the fan motors is thereby improved and the service life of the fan motors is increased. Nevertheless, a closed air circuit that runs substantially transversely to the transport direction can be provided. 
     It is advantageous if the at least one fan unit is arranged not only laterally next to the process channel, but also in a plane below the process channel and that air ducts are arranged and provided such that, during operation of the at least one fan unit, process gas is blown by the at least one fan unit to laterally below the process channel and is deflected there vertically upwards into the process channel. Precisely by the preferably several fan units being provided on the one hand next to the process channel and in addition below the process channel as well, air can be guided substantially in a straight line along a plane up to and into the region below the process channel. 
     Furthermore, it is advantageous if air ducts are provided in such a way that, during operation of the at least one fan unit, process gas is blown into the process channel, that the process gas after passage through the process channel is passed through the filter element and that the filtered process gas is sucked in by the at least one fan unit. This results in a closed circuit that runs substantially transversely to the transport direction. Here, the process gas runs through regions provided on the base body and also regions inside the drawer. 
     Thereby, it is further advantageous if, during operation of the at least one fan unit, process gas in the cooling zone is blown into the process channel such that the material for soldering is blown at from below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
       The drawings show: 
         FIG.  1    a reflow soldering apparatus in a side view obliquely from the front with closed cover hood; 
         FIG.  2    the reflow soldering apparatus according to  FIG.  1    in front view with an open covering hood and opened hood flaps; 
         FIG.  3    the reflow soldering apparatus according to  FIG.  1    from obliquely to the front with an open cover hood and opened hood flaps; 
         FIG.  4    the reflow soldering apparatus according to  FIG.  1    from obliquely to the rear with an open cover hood and opened hood flaps; 
         FIG.  5    a cross-section through the cooling zone of the reflow soldering apparatus according to  FIG.  1    without machine panels with drawer closed; 
         FIG.  6    a cross-section through the reflow soldering apparatus according to  FIG.  1    with drawer open; 
         FIG.  7    a detail of the base body of the reflow soldering apparatus with drawer according to  FIGS.  6  and  7    in an exploded representation; 
         FIG.  8    a drawer of the reflow soldering apparatus according to  FIGS.  6  and  7   ; and 
         FIG.  9    a longitudinal section through the drawer according to  FIG.  8   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    shows a reflow soldering apparatus  10  for the continuous soldering of material for soldering. The reflow soldering apparatus  10  has an entry  12  and an exit  14 , wherein the material for soldering reaches the reflow soldering apparatus  12  via the entry  10  and is discharged from the reflow soldering apparatus  14  via the exit  10 . The material to be soldered is transported along a transport direction  18  through a process channel  16  indicated in  FIG.  1   . A preheating zone  20 , a soldering zone  22  and a cooling zone  24  are provided in the process channel  16 . 
     As is clear from  FIGS.  1  and  2   , a communications unit  36  is provided with a display screen and an input device, by means of which it is possible to communicate with a machine controller of the reflow soldering apparatus  10 . 
     The material to be soldered, that is to say the printed circuit board provided with solder paste and populated with electronic components, is first heated in the preheating zone  20  to a temperature that is below the melting temperature of the solder paste. In the soldering zone  22 , the printed circuit board is heated for a certain time to a process temperature that lies above the melting point of the solder paste, so that this melts in the soldering zone in order to solder the electronic components to the printed circuit board. In the cooling zone  24 , the material to be soldered is cooled so that the liquid solder solidifies before the material to be soldered is removed at the exit  14  of the reflow soldering apparatus  10 . 
     A transport system  34  is provided within the reflow soldering apparatus  10  for transporting the printed circuit boards along the transport direction  18 . 
     As is clear from  FIG.  2   , the reflow soldering apparatus  10  has a cover hood  25  with two hood flaps  26 ,  28 . The cover hood  25  can be pivoted open about a hood axis  32  extending parallel to the transport direction  18 . By the cover hood  25  pivoting, the interior of the process channel  16  and the transport system  34  become accessible so that they can be checked visually, maintained, cleaned, set up, replaced and, if necessary, repaired. 
     As is further apparent from  FIG.  2   , the hood flaps  26 ,  28  can be pivoted open about a flap axis  38  running parallel to the hood axis  32 . By the hood flaps  26 ,  28  pivoting upward, the hood compartment  30  above the process channel and thus lying above the upper channel half, in which compartment fan modules, heating elements and air ducts are provided, becomes accessible. The flap axis  38  is arranged above the hood axis  32 , namely not only when the cover hood  25  is open, but also when the cover hood  25  is closed. 
     The soldering apparatus  10  has two longitudinal sides  42  and  44  and two narrow sides  46  and  48 . As can be clearly seen in  FIG.  2   , the hood axis  32  is located in the region of the one rear longitudinal side  44 . In contrast, the flap axis  38  is located in the region of the front longitudinal side  42 , or is closer to the front longitudinal side  42  than to the rear longitudinal side  44 . 
     In  FIG.  3   , in which on the one hand the cover hood  25  and on the other hand the hood flaps  26 ,  28  are open, the open process channel  16  can be seen in particular. The process channel  16  is formed by two channel halves, an upper channel half and a lower channel half. The lower channel half with the lower nozzle plates  118  is provided in or on a base body  60  and the upper channel half with the upper nozzle plates  40  is provided in or on the cover hood  25 . The upper channel half and the upper nozzle plates  40  and further components located in the hood chamber  30  are arranged on the cover hood  25  such that they are pivoted open as the cover hood  25  is opened and the process channel  16  is released. 
     Such an arrangement ensures that, as is clear from  FIGS.  2  to  4   , when the cover hood  25  is open, the process channel  16  is accessible from the front longitudinal side  42 , and that the upper hood compartment  30  covered by the hood flaps  26 ,  28  is accessible from the other rear longitudinal side  44 . Among other things, this has the advantage that, when the cover hood  25  is being opened, and thus when the process channel  16  is being uncovered, gas flowing out of the process channel  16  does not flow into the upper hood compartment  30  covered by the cover flaps  26 ,  28 . Furthermore, a plurality of operators can monitor or maintain the process channel  16  at the same time and independently thereof the hood compartment  30  covered by the cover flaps  26 ,  28 . 
     As is clear from  FIGS.  4  and  5   , a plurality of fan units  50  with fan motors  51  is located above the upper channel half in the hood chamber  30  covered by the hood flaps  26 ,  28 , said fan motors being provided for generating an intended air flow in the process channel  16 . The fan units  50  in the preheating zone  20  and in the process zone  22  can additionally have heating elements in order to provide a prespecified temperature. By means of the fan units  50  or the fan motors  51  thereof, correspondingly heated or cooled process gas as well is introduced from above through the nozzle plates  40  into the process channel  16  and then sucked in again via the longitudinal sides of the process channel  16 . 
     If the cover hood  25  is opened, the process channel  16  and the transport system provided therein will therefore in particular be accessible. If the hood flaps  26 ,  28  are opened up, in particular the fan units  50  provided therein will be accessible together their possibly provided heating elements and likewise the air ducts provided there. 
     In their closed position, which is shown in  FIG.  1   , the two hood flaps  26 ,  28  have a horizontal section  52 , which is located close to the flap axis  38  and extends substantially in the horizontal direction. This horizontal section  52  is adjoined by a sloping section  56 , which is remote from the flap axis  38  and which with the horizontal section  52  encloses an obtuse angle  54 . As is clear in particular from  FIG.  4   , handles  58  for opening the two hood flaps  26 ,  28  are provided on the sloping section. The obtuse angle  54  can in particular be clearly seen in  FIG.  2   . 
     The base body  60  stands on a substrate by means of feet  62 . The feet  62  are provided on a lower frame  64 . Furthermore, drive units  66  are provided for the motorized opening and closing of the cover hood  25 , which are braced at one end on the lower frame  64  and at the other end on the cover hood  25 . As is also clear from  FIG.  5   , which shows the cover hood  25  without its panels, the cover hood  25  comprises portal-like frame arms  68 , each of which has a first support section  70  directed towards the hood axis  32  and a second support section  72  directed toward the respective drive unit  66 . A central section  74  is provided between the two support sections  72 . 
     As is clear from the section according to  FIG.  5    through the cooling zone  24 , a plurality of fan units  100  arranged one after the other in the transport direction  18  is provided in the base body  60  in the transport direction  18  laterally next to the process channel  16  and in a plane below the transport channel  18 , wherein in each case only one fan unit  100  can be seen in the section according to  FIGS.  5  and  6   . The fan units  100  correspond in structure to the fan units  50  and, as is clear from  FIGS.  5  and  6   , lie in the transverse direction between the hood axis  32  and the process channel  16 . 
     The fan units  100  each have a fan motor  102 , a rotor shaft  104  driven by the fan motor  102  and a fan impeller  106  provided on the rotor shaft  104 . The respective fan impeller  106  is a radial fan impeller that in  FIG.  5    from a intake region  109  sucks in process gas  108  axially from below and blows the process gas  110  away in the radial direction. Thereby, as is clear from  FIG.  5   , the respective rotor shaft  104  is laterally spaced apart from the process channel  16  in the horizontal direction by the dimension  112 . The respective rotor shaft  104  runs in the vertical direction. Thereby, the arrangement is such that the respective fan motor  102  sits vertically above the respective fan impeller  106 . 
     During operation of the fan units  100 , process gas  110  is blown into a guide channel  114  that extends substantially horizontally and at the fan impeller  106  then runs in transverse direction extending transversely to the transport direction  18  initially laterally next to and subsequently perpendicular to the process channel  16 . Via the guide channel  114 , the process gas is then blown vertically upwards through a cooling element in the form of a heat exchanger  116 , in which the process gas is cooled further, and is blown into the process channel  16  from below through a lower nozzle plate  118 . Consequently, the material for soldering that is to be cooled is blown onto from below within the cooling zone  24 . 
     The process gas  120  being blown in is conducted towards the front longitudinal side  42  onto the material for soldering provided in the process channel  14 . The process gas  124  there enters a feed duct  122  and is guided vertically downwards. In the region  123 , the feed duct  122 , which is provided on the base body  60 , merges into an entry channel  125 , which is provided in a drawer  126 . The drawer  126  is shown in the closed state in  FIG.  5    and in the open state in  FIG.  6   . The drawer  126  is also shown as an individual part in  FIGS.  8  and  9   . The drawer  126  is accessible from the front side  42  of the base body  60 . On the front side of the base body  60  shown in  FIG.  3   , openable doors are provided, behind which the drawer  126  is provided. 
     The drawer  126  provides a base  128 , a front wall  130  and a rear side in the form of a rear wall  132 . The drawer  126  also has an upper edge  133 , which is designed running horizontally. In the region of the bottom  128 , the entry channel  125  deflects process gas towards a cooling device  136  formed as a cooling plate  134 . 
     As is clear in particular from  FIGS.  5  and  6   , the cooling plate  134  runs obliquely to the upper edge  133  or to the horizontal  137  and declines to the front, that is to say towards the front longitudinal side  42  or to the front wall  130  of the drawer  126 . In the region of the front wall  130 , a removable drip pan  138  is provided on the bottom  128  of the drawer  126 . Condensate, which condenses on the cooling plate  134 , collects in the drip pan  138 . In the present embodiment, the cooling plate  134  is cooled by ambient air. However, it is conceivable for active cooling elements, for example a heat exchanger or an energizable cooling element, to be provided in the region of the cooling plate  134  in order to achieve a greater cooling performance. 
     The removable and emptyable drip pan  138  is in particular designed to be transparent to light, so that the fill level of the drip pan  138  can be checked visually. 
     On the side facing away from the front wall  130  and facing the rear wall  132 , the entry channel  125  opens into a filter region  140 . A filter element  142  is provided in the filter region  140 . As is also clear in particular from  FIGS.  5  and  6   , the filter element  142 , which can for example be provided with a filter grate with a filter fleece, runs obliquely to the horizontal  137  and is formed declining towards the rear wall  132 . Thereby, the filter element  142  is located on a diagonal of the drawer  126 . Overall, the plane in which the cooling plate  134  is located and the plane formed by the filter element  142  encloses an acute angle  144 . 
     The drawer  126  has a shielding plate  146  in the rear region above the filter element  142 . As is clear from  FIG.  5   , the shielding plate  146  is provided between the intake region  109  of the fan impeller  106  and the filter element  142  and consequently shields the intake region  109  of the fan impeller  106 . The shielding plate  146  shields in particular the region of the filter element  142  that is located close to the bottom  128  of the drawer  126 . By providing the shielding plate  146 , the entire upper side of the drawer  126  is consequently not opened; rather, only the region that is not covered by the shielding plate  146  is opened. As a result, a favorable air deflection is brought about and moreover a more uniform conduction of the process gas through the filter element  142 . 
     In order to cause the process gas that is passing through the filter element  142  to be guided towards the intake region of the respective fan unit  100 , a guide plate  148  is provided on the base body  60 . 
       FIG.  5    and  FIG.  6    show the drawer  126  in a slightly vertically lowered state. To raise the drawer  126 , a lowering mechanism  150  with a lever mechanism, which can be operated by means of a manually operable rod  152  with which the drawer  126  can be adjusted between a lowering position and a raising position, is used. In particular, it is conceivable for the lowering mechanism  150  and the drawer  126  to be provided behind a door provided on the front side of the base body  60 , so that the lowering mechanism  150  and the drawer  126  are accessible after the door is opened. After the drawer  126  has been lowered, it can, as shown in  FIG.  6   , be pulled out transversely to the transport direction  18 , in a horizontally extending direction  154 . For this purpose,  FIG.  6    shows a horizontal guide  156  in the form of a guide rail for the drawer  126 . 
     Of course, it is also conceivable for the lowering mechanism  150  to be operated in an automated manner, for example electrically or pneumatically. 
     In the base body  60 , a collecting tray  155  is provided underneath the drawer  126 , the collecting tray being used to collect condensate dripping down when the drawer  126  is open or contaminants dropping down. 
       FIG.  7    shows three fan receptacles  158  for receiving fan units  100 , which are not shown here. The fan receptacles  158  are provided laterally adjacent to the process channel  16  and spaced apart in the horizontal direction to the process channel  16 , namely in such a way that fan units  100  that are inserted into the fan receptacles  158  are arranged along a line running parallel to the transport direction  18 . The rotor shafts  104  of these fan units  100  are then arranged running parallel to one another. 
     With the fan units  100  to be provided in the three fan receptacles  158 , a total of three air circuits running transversely to the process direction  118  are provided, wherein the drawer  126 , as shown in  FIGS.  8  and  9   , has three compartments  160  that lie next to one another in the pull-out direction  154 . The adjacent compartments  160  are separated by component walls  162 . Each of the compartments  160  in the drawer  126  has its own entry channel  125 , its own filter element  142  and its own shielding plate  146 . Consequently, a total of three air circuits separated from one another are provided in the drawer  126 , wherein each air circuit is provided by means of a fan unit  100 , which is provided in the respective fan receptacle  158 . 
     The respective circuit of the process gas is again clearly apparent from the representation according to  FIG.  7   . In total, 3 air circuits are provided, which run substantially transversely to the transport direction  18 . The air circuit provided by the respective fan unit  100  is such that, via the respective fan unit  100 , process gas  110  is first blown laterally into the guide channel  114  below the process channel and then deflected upwards. The process gas then passes through the heat exchanger  116  before it reaches the process channel  16  through the nozzle plate  118 . The material for soldering is then preferably flowed onto from below over the entire length of the cooling zone  24  and cooled. The process gas is extracted from the process channel, specifically via the feed duct  122  provided on the front side, which opens into the respective entry channel  125  of the drawer  126 . The process gas then flows along the bottom  128  or the cooling plate  134  into the respective filter region  140 . Condensate contained in the process gas condenses on the cooling plate  134  and collects in the drip pan  138 , which can preferably be emptied without opening the drawer  126 . The process gas then flows through the respective filter element  142 , is deflected at the underside of the respective shielding plate  146  and is guided further over the upper side of the respective shielding plate  146  towards the respective fan unit  100 . Overall, it is thereby achieved that all process gas that flows back into the process channel passes the filter element  142  and is thus cleaned. 
     As is clear from  FIGS.  8  and  9   , the respective shielding plates  146  extend from the rear wall  132  towards the front wall  130  such that they cover approximately half the filter element  142 . In  FIGS.  8  and  9   , the filter element  142  is formed by a wire mesh shown in  FIG.  8   , in which a filter fleece (not shown), which can be replaced in a simple manner, is formed.