Patent Publication Number: US-2023141430-A1

Title: Soldering apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application relates and claims priority to German Patent Application No. 10 2021 129 131.3, 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 continuous soldering of printed circuit boards along a transport direction, having a process channel that comprises a preheating zone, a soldering zone and a cooling zone, having a base body and a cover hood, which can be displaced between a closed position and an open position, wherein nozzle plates, fan units, air channels carrying the process gas, filter elements and/or cooling elements are provided in the base body. 
     Reflow soldering apparatuses are used to solder so-called SMD (surface-mounted devices) components onto the surface of printed circuit boards using solder paste. The solder paste, which is in particular a mixture of solder metal granules, soldering flux and pasty constituents, is applied or printed onto the surface of the printed circuit boards for reflow soldering. The components to be soldered are then placed in the solder paste. In the reflow soldering process, the soldering material, i.e. the assembly consisting of printed circuit board, solder paste and components to be soldered, is, along the process channel, preheated in a preheating zone and heated in a soldering zone to a temperature that is above the melting point of the solder paste. This causes the solder paste to melt and the solder joints to form. In a cooling zone—if one is available—the soldering material is cooled until the molten solder solidifies, before it is removed from the reflow soldering apparatus. 
     Soldering apparatuses for 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 reflow soldering apparatuses, the process channel is usually 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. In or on the process channel or in or on the base body and in or on the cover hood, further structural elements, such as nozzle plates, fan units, air channels carrying the process gas, filter elements and/or cooling elements, are usually provided. Overall, a desired temperature profile is thus provided along the transport direction in the process channel, wherein the process gas is blown into the process channel, extracted from it, cooled in the cooling zone in particular, cleaned and fed back into the process channel. 
     From machines of the applicant with the designation HotFlow 3 or Hotflow 4, it is known to provide fan units on the base body vertically below the process channel and to blow process gas from the fan units vertically upwards through a nozzle plate into the process channel. In this case, it has been found that condensate forming in the cooling zone collects on the fan units and contaminates them, resulting in an amount of maintenance that is not inconsiderable. 
     SUMMARY OF THE INVENTION 
     The invention is based on the object of providing a soldering apparatus with which, in particular, the cooling zone is advantageously designed in such a manner that contamination is avoided. 
     This object is achieved by a soldering apparatus. Consequently, it is provided in particular that at least one fan unit is arranged in or on the base body laterally next to the process channel in the transport direction, and that air channels are arranged and provided in such a manner that process gas is blown into the process channel during operation of the at least one fan unit, that the process gas is directed through a filter element after passing through the process channel, and that the filtered process gas is drawn in by the at least one fan unit. 
     The provision of the at least one fan unit laterally next to the process channel in the transport direction, and not vertically below the process channel, has the advantage that the overall height of the soldering apparatus is reduced, the process channel can be arranged correspondingly lower, and the fan units are easily accessible for repair and maintenance. In addition, better heat dissipation of the heat generated by the fan units is possible, since the heat generated by the fan units can be dissipated laterally next to the process channel. This improves the cooling of the fan motors and increases their service life. Nevertheless, a closed air circuit that is substantially transverse to the transport direction can be provided. 
     It is advantageous if the at least one fan unit is not only arranged laterally next to the process channel, but also in a plane below the process channel, and that air channels are arranged and provided in such a manner that, during operation of the at least one fan unit, process gas is blown by the at least one fan unit laterally below the process channel and is deflected there vertically upwards into the process channel. Precisely because the preferably multiple fan units are provided on the one hand laterally next to the process channel and on the other hand below the process channel, air can be guided substantially in a straight line along a plane into the region below the process channel. 
     In addition, it is advantageous if the at least one fan unit comprises a fan motor, a rotor shaft and a fan wheel provided on the rotor shaft, wherein the rotor shaft is arranged transversely to the transport direction and in a manner running in the vertical direction, spaced laterally from the process channel, wherein the fan motor is arranged vertically above the fan wheel. Such a design has the advantage that contaminants do not collect in the fan motor. Even if contaminants or condensate should accumulate or collect on the fan wheel or rotor shaft, they will not enter the fan motor. Since the fan motor is arranged vertically above the fan wheel, contaminants and condensate are deposited underneath the fan wheel as a result of gravity, in particular when the fan units are switched off. This saves maintenance expense, reduces wear on the fan motors and extends the service life of the fan units. 
     Furthermore, it is advantageous if the at least one fan unit is arranged and the fan wheel is formed in such a manner that process gas is drawn in axially on the intake region facing away from the fan motor and is blown in the radial direction. Consequently, process gas is drawn in from vertically below and discharged laterally in a horizontal direction. 
     A plurality of fan units is preferably provided for the targeted movement of the process gas in the base body, wherein at least one shielding plate is provided axially below the intake region, which shielding plate shields the intake region of the at least one fan unit from the filter region. This ensures that process gas does not flow directly from the filter element to the fan unit but is deflected via the respective shielding plate. 
     Furthermore, it is advantageous if a guide channel is provided laterally next to the at least one fan unit in the transport direction at the level of the fan wheel and below the process channel, such that the process gas coming from the at least one fan unit is initially blown laterally below the process channel and is then guided vertically upwards into the process channel. During operation of the at least one fan unit, process gas is thus blown into the process channel in the cooling zone in such a manner that the soldering material is blown on from below. 
     It is also advantageous if a plurality of fan units is provided one behind the other along a line parallel to the transport direction, the rotor shafts of which are formed to run parallel to one another. Such an arrangement can be used to create an air circuit that extends in the transport direction, wherein the main directions of air flow are transverse to the transport direction. 
     Furthermore, it is conceivable that the cover hood can be pivoted about a hood axis between the closed position and the open position and that the at least one fan unit is provided in a transverse direction running transversely to the transport direction between the hood axis and the process channel, such that the at least one fan unit is provided on the side of the process channel located close to the hood axis. This has the advantage that the at least one fan unit is not in the way of operating personnel when opening the hood and working in the process channel. Consequently, access to the process channel when the cover hood is opened is not disturbed by the provision of the at least one and preferably more fan units. 
     Furthermore, it is advantageous if air channels and a cooling element, in particular in the form of a heat exchanger, are provided in such a manner that process gas, before being blown into the process channel, passes through the cooling element and then enters the process channel through a nozzle plate. When passing through the cooling element, the process gas can be cooled down further. By providing the nozzle plate, a comparatively uniform and ideally laminar flow can be provided within the process channel. 
     Furthermore, it is advantageous if, in particular, air channels and a cooling device are provided in the cooling zone in such a manner that the process gas is guided along the cooling device comprising a cooling plate after passing through the process channel and before passing through the filter element. This ensures that moisture and vapors absorbed by the process gas when passing through the cooling plate can condense on the cooling plate before the process gas is directed through the filter element. 
     It is also advantageous if the cooling plate runs along a cooling plane that runs obliquely to the horizontal line and has a drip tray in its vertically lower region. This allows liquid condensing on the cooling plate to be collected in the drip tray following the slope of the cooling plate. Furthermore, the drip tray is transparent, in particular, such that it is possible to visually check whether and how much condensate is present in the drip tray. The drip tray is further preferably detachably arranged such that the emptying of the drip tray is possible in a simple manner. 
     Furthermore, it is advantageous if the filter element in the cooling zone runs along a filter plane that runs obliquely to the horizontal line. The oblique arrangement of the filter plane allows its surface area to be increased compared to a horizontal arrangement, thus increasing the filter capacity. In addition, moisture collecting in the filter element can drip off better. The filter element can comprise a filter grid and a filter fleece provided in or on the filter grid. 
     It is particularly advantageous if the cooling plane and the filter plane enclose an acute angle. This results in optimized air guidance and an overall optimized cooling result and filtering result of the process gas. 
     Furthermore, it can be provided that air channels are formed and arranged in such a manner that the process gas is discharged vertically downwards from the process channel on the side facing away from the at least one fan unit via an insertion channel and is deflected toward the cooling plate. 
     Furthermore, it is advantageous if a drawer, which can be pulled out along a pull-out direction running transversely to the transport direction and has a bottom, a front wall and a rear side, which in particular can be formed by a rear wall or can comprise a rear wall, is provided in the base body in the cooling zone, wherein air channels for guiding the process gas, at least one filter element and 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 the cooling device provided in the drawer are consequently easily accessible. Since vapors contained in the process gas condense at the cooling device, it is particularly advantageous by providing the drawer to collect the condensate in the drawer and, if necessary, to ultimately remove it by opening the drawer. Further, the provision of the drawer is advantageous for visually inspecting and/or replacing the filter element. Replacing the filter element when the drawer is opened is comparatively easy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further details and advantageous embodiments of the invention can be found in the following description, by means of which an exemplary embodiment of the invention is described and explained. 
         FIG.  1    shows a side view of a reflow soldering apparatus from an angle at the front with the cover hood closed; 
         FIG.  2    shows a front view of the reflow soldering apparatus according to  FIG.  1    with the cover hood open and the hood flaps open; 
         FIG.  3    shows the reflow soldering apparatus according to  FIG.  1    from an angle at the front with the cover hood open and the hood flaps open; 
         FIG.  4    shows the reflow soldering apparatus according to  FIG.  1    from an angle at the rear with the cover hood open and the hood flaps open; 
         FIG.  5    shows a cross-section through the cooling zone of the reflow soldering apparatus according to  FIG.  1    without cladding with the drawer closed; 
         FIG.  6    shows a cross-section through the reflow soldering apparatus according to  FIG.  1    with the drawer open; 
         FIG.  7    shows a section of the base body of the reflow soldering apparatus with a drawer according to  FIGS.  6  and  7    in an illustration of a single part; 
         FIG.  8    shows a drawer of the reflow soldering apparatus according to  FIGS.  6  and  7   ; and 
         FIG.  9    shows 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 soldering material. The reflow soldering apparatus  10  has an inlet  12  and an outlet  14 , wherein the soldering material to be soldered enters the reflow soldering apparatus  10  via the inlet  12  and is discharged from the reflow soldering apparatus  10  via the outlet  14 . The soldering material 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 can be seen from  FIGS.  1  and  2   , a communication unit  36  with a display screen and an input device is provided, by means of which communication can be established with a machine control system of the reflow soldering apparatus  10 . 
     The soldering material, i.e., the printed circuit board provided with solder paste and fitted with electronic components, is initially heated in the preheating zone  20 , to a temperature below the melting temperature of the solder paste. In the soldering zone  22 , the printed circuit board is heated to a process temperature above the melting point of the solder paste for a specified period of time, such that the paste melts in the soldering zone in order to solder the electronic components to the printed circuit board. In the cooling zone  24 , the soldering material is cooled such that the liquid solder solidifies before the soldering material is removed at the outlet  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 can be seen 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 swung open about a hood axis  32  extending parallel to the transport direction  18 . Swinging open the cover hood  25  provides access to the interior of the process channel  16  and the transport system  34  for visual inspection, maintenance, cleaning, setup, replacement and repair as necessary. 
     As can be seen further from  FIG.  2   , the hood flaps  26 ,  28  can be swung open about a flap axis  38  running parallel to the hood axis  32 . By swinging open the hood flaps  26 ,  28 , the hood space  30  located above the process channel and thus above the upper channel half becomes accessible by providing fan modules, heating elements and air channels. The flap axis  38  is arranged above the hood axis  32 , not only when the cover hood  25  is opened, 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 readily seen in  FIG.  2   , the hood axis  32  is located in the region of 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 upper nozzle plates  40  and other components located in the hood space  30  are arranged on the cover hood  25  in such a manner that they are also swung open when 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   , the process channel  16  is accessible from the front longitudinal side  42  when the cover hood  25  is opened and that the upper hood space  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 opened, and thus when the process channel  16  is exposed, gas flowing out of the process channel  16  does not flow into the upper hood space  30  covered by the cover flaps  26 ,  28 . Further, a plurality of operators can simultaneously inspect or maintain, on the one hand, the process channel  16  and, independently, the hood space  30  covered by the cover flaps  26 ,  28 . 
     As can be seen from  FIGS.  4  and  5   , a plurality of fan units  50  with fan motors  51  are located above the upper channel half in the hood space  30  covered by the hood flaps  26 ,  28  and are provided to generate a provided air flow in the process channel  16 . The fan units  50  in the preheating zone  20  and the process zone  22  may additionally have heating elements in order to provide a predetermined temperature. By means of the fan units  50  or their fan motors  51 , suitably heated or also cooled process gas is introduced from above through the nozzle plates  40  into the process channel  16  and then drawn in again via the longitudinal sides of the process channel  16 . 
     Consequently, if the cover hood  25  is opened, the process channel  16  in particular and the transport system provided therein are accessible. If the hood flaps  26 ,  28  are opened, in particular the fan units  50  provided therein with their heating elements, if any, and air channels likewise provided therein are accessible. 
     In their closed position, shown in  FIG.  1   , the two hood flaps  26 ,  28  have a horizontal section  52  located close to the flap axis  38  and extending in a substantially horizontal direction. This horizontal section  52  is adjoined by an oblique section  56  that is remote from the flap axis  38  and forms an obtuse angle  54  with the horizontal section  52 . Handles  58  for opening the two hood flaps  26 ,  28  are provided on the oblique section, as is particularly clear from  FIG.  4   . The obtuse angle  54  can be seen clearly, in particular in  FIG.  2   . 
     The base body  60  stands on a floor by means of feet  62 . The feet  62  are provided on a lower frame  64 . Furthermore, drive units  66  for motorized opening and closing of the cover hood  25  are provided, which are supported on the lower frame  64  at one end and on the cover hood  25  at the other end. As is also clear from  FIG.  5   , which shows the cover hood  25  without cladding, the cover hood  25  comprises gantry-like frame legs  68 , each of which has a first support section  70  directed toward the hood axis  32  and a second support section  72  directed toward the respective drive unit  66 . A center section  74  is provided between each of the two support sections  72 . 
     As can be seen from the sectional view through the cooling zone  24  according to  FIG.  5   , a plurality of fan units  100  arranged behind one another in the transport direction  18  is provided in the base body  60  laterally next to the process channel  16  in the transport direction  18  and in a plane below the transport channel  18 , wherein only one fan unit  100  can be seen in each case in the sectional view according to  FIGS.  5  and  6   . The fan units  100  correspond in structure to the fan units  50  and, as can be seen from  FIGS.  5  and  6   , are located 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 wheel  106  provided on the rotor shaft  104 . The respective fan wheel  106  is a radial fan wheel that, in  FIG.  5   , draws in process gas  108  axially from below from an intake region  109  and that blows away process gas  110  in the radial direction. The respective rotor shaft  104  is laterally spaced from the process channel  16  in the horizontal direction by the dimension  112 , as is clear from  FIG.  5   . The respective rotor shaft  104  runs in a vertical direction. The arrangement is such that the respective fan motor  102  sits vertically above the respective fan wheel  106 . 
     During operation of the fan units  100 , process gas  110  is blown into a substantially horizontally running guide channel  114 , which runs adjacent to the fan wheel  106  in a transverse direction running transversely to the transport direction  18 , initially laterally next to and then vertically below the process channel  16 . The process gas is then blown in vertically upwards through the guide channel  114 , through a cooling element in the form of a heat exchanger  116 , in which the process gas is further cooled, and through a lower nozzle plate  118  from below into the process channel  16 . Consequently, the soldering material to be cooled is blown on from below within the cooling zone  24 . 
     At the solder material provided in the process channel  14 , the process gas  120  blown in is directed toward the front longitudinal side  42 . There, the process gas  124  enters an insertion channel  122  and is directed vertically downwards. In the region  123 , the insertion channel  122  provided on the base body  60  merges into an input channel  125  that is provided in a drawer  126 . The drawer  126  is shown closed in  FIG.  5    and open in  FIG.  6   . Moreover, the drawer  126  is shown as a single part in  FIGS.  8  and  9   . The drawer  126  is accessible from the front side  42  of the base body  60 . Openable doors are provided on the front side of the base body  60  shown in  FIG.  3   , behind which doors the drawer  126  is provided. 
     The drawer  126  looks on a bottom  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  that is formed to run horizontally. The inlet channel  125  directs process gas in the region of the bottom  128  toward a cooling device  136  formed as a cooling plate  134 . 
     As can be seen in particular from  FIGS.  5  and  6   , the cooling plate  134  runs obliquely to the upper edge  133  or to the horizontal line  137  and slopes down forward, i.e. toward the front longitudinal side  42  or toward the front wall  130  of the drawer  126 . A removable drip tray  138  is provided on the bottom  128  of the drawer  126  in the region of the front wall  130 . Condensate that condenses on the cooling plate  134  collects in the drip tray  138 . In the present embodiment, the cooling plate  134  is cooled by ambient air. However, it is conceivable that active cooling elements, for example a heat exchanger or a cooling element that can be supplied with power, are provided in the region of the cooling plate  134 , in order to achieve a higher cooling capacity. 
     In particular, the removable and emptiable drip tray  138  is formed to be translucent, such that the fill level of the drip tray  138  can be visually inspected. 
     The inlet channel  125  opens into a filter region  140  on the side facing away from the front wall  130  and facing the rear wall  132 . A filter element  142  is provided in the filter region  140 . As can also be seen in particular from  FIGS.  5  and  6   , the filter element  142 , which can for example provide a filter grid with a filter fleece, runs obliquely to the horizontal line  137  and is formed to slope down toward the rear wall  132 . The filter element  142  then lies in a diagonal line of the drawer  126 . Overall, the plane in which the cooling plate  134  lies and the plane formed by the filter element  142  enclose an acute angle  144 . 
     The drawer  126  has a shielding plate  146  in the rear region above the filter element  142 . As can be seen from  FIG.  5   , the shielding plate  146  is provided between the intake region  109  of the fan wheel  106  and the filter element  142  and consequently shields the intake region  109  of the fan wheel  106 . In particular, the shielding plate  146  shields the region of the filter element  142  that is close to the bottom  128  of the drawer  126 . The provision of the shielding plate  146  consequently means that not the entire upper side of the drawer  126  is open, but rather only the region that is not covered by the shielding plate  146  is open. This results in a favorable air deflection and also a more uniform passage of the process gas through the filter element  142 . 
     To cause the process gas passing through the filter element  142  to be directed toward the intake region of the respective fan unit  100 , a guide plate  148  is provided on the base body  60 . 
     In  FIG.  5    and  FIG.  6   , the drawer  126  is shown in a slightly vertically lowered condition. To raise the drawer  126 , a lowering mechanism  150  with a lever gear is used, which can be operated via a manually operated rod  152 , with which the drawer  126  can be adjusted between a lowering position and a lifting position. In particular, it is conceivable that the lowering mechanism  150  and the drawer  126  are provided behind a door provided at the front side of the base body  60 , such that the lowering mechanism  150  and the drawer  126  are accessible after opening the door. After the drawer  126  has been lowered, it can be pulled out transversely to the transport direction  18 , in a horizontally running pull-out direction  154 , as shown in  FIG.  6   . For this purpose, a horizontal guide  156  in the form of a guide rail for the drawer  126  is shown in  FIG.  6   . 
     Of course, it is also conceivable that the lowering mechanism  150  is operated automatically, for example electrically or pneumatically. 
     A collection tray  155  is provided in the base body  60  below the drawer  126 , which collection tray serves to collect dripping condensate or falling contaminants when the drawer  126  is opened. 
       FIG.  7    shows three fan receptacles  158  for receiving fan units  100 , which are not shown there. The fan receptacles  158  are provided laterally next to the process channel  16  and spaced horizontally with respect to the process channel  16 , such that fan units  100  inserted into the fan receptacles  158  are arranged along a line that runs parallel to the transport direction  18 . The rotor shafts  104  of these fan units  100  are then arranged to run parallel to one another. 
     The fan units  100  to be provided in the three fan receptacles  158  provide a total of three air circuits running transversely to the process direction  118 , wherein the drawer  126 , as shown in  FIGS.  8  and  9   , has for this purpose three compartments  160  lying next to one another in the pull-out direction  154 . The adjacent compartments  160  are separated by compartment walls  162 . Each of the compartments  160  in the drawer  126  has its own inlet channel  125 , its own filter element  142  and its own shielding plate  146 . Consequently, a total of three separate air circuits are provided in the drawer  126 , wherein each air circuit is provided by means of a fan unit  100  provided in the respective fan receptacle  158 . 
     The illustration in  FIG.  7    once again clearly shows the respective circuit of the process gas. A total of 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 process gas  110  is initially blown laterally into the guide channel  114  below the process channel via the respective fan unit  100  and is deflected upwards. The process gas then passes through the heat exchanger  116  before entering the process channel  16  through the nozzle plate  118 . The soldering material is then preferably flowed against and cooled from below over the entire length of the cooling zone  24 . The process gas is extracted from the process channel, via the insertion channel  122  provided at the front side, which insertion channel opens into the respective inlet 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 tray  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 lower side of the respective shielding plate  146 , and is further directed over the upper side of the respective shielding plate  146  toward the respective fan unit  100 . Overall, this ensures that all process gas that flows back into the process channel passes through the filter element  142  and is thus cleaned. 
     As can be seen from  FIGS.  8  and  9   , the respective shielding plates  146  extend from the rear wall  132  toward the front wall  130  such that they cover approximately half of 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 further shown), which can be replaced in a simple manner, is placed.