Transport unit for transporting printed circuit boards and soldering equipment

Abstract

Transport unit (50) for transporting printed circuit boards along a transport direction (18) within at least one zone of a soldering system (10), in particular a reflow soldering system, wherein a base part (68) with a driveable output shaft (72) is provided, characterized in that at least two output gears (94) rotatably coupled to the output shaft (72) are provided, that at least two detachably attachable and removable drive parts (86 to 91) with each a drive gear (92) are provided such that the drive parts (86 to 91) have drive rollers (96) rotatably coupled to the drive gear (92), which act against the printed circuit board to transport the printed circuit board through the zone, that when the drive parts (86 to 91) are attached to the base part (68), the respective output gear (94) is in engagement with the associated drive gear (92).and that receiving parts (76 to 81) extending in the transport direction (18) are provided on the base part (68) for receiving and detachably fastening the drive parts (86 to 91), wherein the receiving parts (76 to 81) each have the output gear (94) which can be engaged with the drive gear (92) and driven by the output shaft (72).

Description

The invention relates to a transport unit for conveying printed circuit boards along a transport direction within at least one zone of a soldering system, such as a reflow soldering system. The invention also relates to soldering systems, in particular reflow soldering systems, for continuous soldering of printed circuit boards in a process channel along a transport direction, wherein the process channel includes at least one preheating zone, at least one soldering zone, and at least one cooling zone, and wherein the soldering zone includes a pressure chamber comprising a base part and a cover part that can be raised relative to the base part during operation of the reflow soldering system. The pressure chamber is in particular a negative pressure chamber; however, it is also conceivable that the pressure chamber is designed as a positive pressure chamber. Reflow soldering systems are used to solder surface-mount devices (SMDs) onto printed circuit boards (PCBs) using solder paste. The solder paste, which is a mixture of solder metal granules, flux, and paste-like components, is applied or printed onto the PCB surface. The components to be soldered are then placed into the solder paste. During the reflow soldering process, the assembly—consisting of the PCB, solder paste, and components—is preheated along the process channel in the preheating zone and then heated in the soldering zone to a temperature above the melting point of the solder paste. This melts the solder paste, forming the solder joints. The assembly is then cooled in the cooling zone until the molten solder solidifies before being removed from the reflow soldering system. In reflow soldering systems, the process channel is covered by a protective hood to ensure the desired temperature profile and a defined atmosphere within the channel. Furthermore, process gases form in the channel, which can be extracted and purified. To achieve improved process results, it is known to provide a negative pressure or vacuum chamber in the soldering zone and to configure it such that the soldering process takes place in the vacuum chamber at a negative pressure significantly below atmospheric pressure. This ensures that gas and air bubbles, flux residues, and other contaminants are drawn out by the negative pressure during the soldering process, thereby increasing the quality of the soldered joints. Similarly, the quality of the soldered joints can be improved by using a positive pressure chamber within which the soldering process takes place. Reflow soldering systems with vacuum chambers are known from DE 10 2009 028 865 B4 and US 2009 / 0 014 503 A1. Reflow soldering systems are also known from DE 201 02 064 U1 and DE 199 11 887 C1, which provide a vacuum chamber comprising a base and a lid in the form of a vacuum bell that can be lifted relative to the base. The lid can be lifted from the base to allow the workpiece to be inserted into and removed from the vacuum chamber. Furthermore, a two-part conveyor system is known from US patent 4,844,231 A, wherein a drive unit for driving production parts is connected to conveyor rollers via belts. DE 199 00 461 A1 discloses a transport device for transport containers, wherein the power transmission can be effected by gears. The invention is based on the objective of providing an input transport unit that can be used in particular in a pressure chamber of the soldering system and that has advantageous properties. This problem is solved by a transport unit with the features of claim 1. In particular, it is provided that a base part is provided with an output shaft, which can be driven by a rotary drive, and at least two output gears rotatably coupled to the output shaft; that at least two detachably and removable drive parts, each with a drive gear, are provided such that the drive parts have drive rollers rotatably coupled to the respective drive gear, which act against the circuit board to transport the circuit board through the zone; and that when the drive part is attached to the base part, the respective output gear is in engagement with the corresponding drive gear. When the drive part is removed from the base part, the drive gear is consequently no longer in engagement with the output gear. The drive gear and the output gear are designed as gears. Furthermore, the base part includes receiving parts extending in the transport direction for receiving and detachably attaching the drive components. Each receiving part has a driven gear that can be engaged with the drive gear and driven by the output shaft. The respective drive component can therefore be placed onto or removed from its corresponding receiving part. Preferably, a fastening device is provided by means of which the drive components can be attached to the respective receiving parts. It is conceivable that a screw connection, particularly one that can be manually operated, is provided. This type of transport unit has the advantage that the drive components can be easily replaced. To release the rotary coupling between the driven and driven gears, the drive component simply needs to be removed from the base, which lifts the drive gear away from the driven gear. When the drive component is mounted on the base, the driven gear and driven gear are in direct engagement. Removing the drive components is necessary because they require regular inspection, cleaning, maintenance, and, if necessary, repair. This is especially important when the transport unit is used in a pressure chamber of the reflow soldering system, where it is exposed to high temperatures and high mechanical stresses. The ease of removing and replacing the drive components reduces downtime for the reflow soldering system and thus increases its productivity. Advantageously, the drive components feature a multitude of drive rollers arranged in series in the transport direction, with adjacent drive rollers being rotaryally coupled to each other via gears, and with at least one of the gears being rotaryally coupled to the drive wheel. By providing several drive rollers arranged in series, reliable transport of the printed circuit boards through the respective zone can be ensured. Because the individual drive rollers are rotaryally coupled to each other via gears, no sliding movement occurs between the components, making the transport unit comparatively low-maintenance and requiring relatively little lubricant. Furthermore, the drive components are highly robust; in particular, they can be easily removed, replaced, and / or cleaned. The base is advantageously designed as a frame with two side panels extending in the transport direction and two crossbeams extending transversely to the transport direction. Such a base can preferably be easily removed from the respective zone of the soldering system in order to replace, clean, or maintain the entire transport unit as needed. This has proven particularly advantageous when the transport unit is used within a pressure chamber of the soldering system. The drive shaft preferably extends in a transverse direction and is rotatably mounted on the two side panels. This makes it possible for the drive shaft to drive several drive components, or their drive wheels and drive rollers, located between the side panels. Furthermore, it is advantageous if at least one, and preferably several, receiving parts are arranged to be movably adjustable in the transverse direction on the stiles. Such transverse adjustment allows for adaptation to the width of the printed circuit boards. Depending on the width of the printed circuit board to be soldered, a corresponding adjustment of the receiving parts, and thus also of the drive components, can be achieved. For this purpose, a suitable bearing arrangement can be provided between the receiving parts and the stiles, for example, a sliding bearing or a bearing arrangement using rolling bearings. Furthermore, it is advantageous if the receiving parts each provide a coupling gear that is rotaryally coupled to both the drive gear and the output shaft. The coupling gear is preferably arranged to be axially displaceable on the output shaft, thus allowing the receiving part to be moved and adjusted laterally, while simultaneously ensuring a rotary coupling between the output shaft and the coupling gear. It is conceivable that the output shaft has a non-circular cross-section and is designed, for example, as a square shaft, and in particular as a square or hexagonal shaft. The coupling gear then has a receiving contour complementary to the outer contour of the drive shaft, so that the coupling gear is slidably arranged on the output shaft but is nevertheless rotaryally coupled to it. Furthermore, it has proven advantageous to provide at least one adjusting shaft extending in the transverse direction, coupled to at least one receiving part in such a way that the receiving part can be displaced in the transverse direction by rotating the adjusting shaft. The adjusting shaft can, in particular, be designed as a spindle shaft, in which case the respective receiving part has a spindle nut that interacts with the spindle shaft. By rotating the spindle shaft, the respective receiving part can thus be adjusted in the transverse direction. Advantageously, the adjusting shaft, like the output shaft, is rotatably mounted on the side parts of the base part. Furthermore, the spindle nut is rotatable within itself in order to adjust the bearing clearance between the width-adjusting shaft and the spindle nut, or to compensate for play caused by wear during operation. A preferred embodiment provides two edge receiving parts for each receiving an edge drive part, wherein the drive rollers of one edge drive part face the drive rollers of the other edge drive part and are arranged such that, during operation of the transport unit, the printed circuit board rests on the respective drive rollers in the region of its free longitudinal edges. In the region of the free longitudinal edges, the printed circuit boards generally do not have any electronic components, so that the drive rollers can advantageously engage the printed circuit board in this area for transport purposes. Furthermore, it is advantageous if the edge drive components provide longitudinal guides for guiding the printed circuit boards in the transport direction. During operation, these longitudinal guides act against the free edges of the printed circuit boards, ensuring that they can be reliably guided through the soldering system in the transport direction. Furthermore, it is advantageous if at least one central mounting part is provided between the two edge mounting parts to accommodate a central drive element. Such a central drive element then forms a central support, which is particularly necessary when comparatively large printed circuit boards are to be soldered. The central drive element prevents the printed circuit board from bending or sagging in its central area and also ensures reliable transport. Furthermore, it is advantageous if the transport unit has two transport tracks running in the direction of transport, with two edge receiving parts for each transport track and, if necessary, an additional center receiving part between each of the edge receiving parts. This increases the overall capacity of the transport unit and thus also of the entire soldering system. It is advantageous to have several adjusting shafts, one for adjusting the edge mounting parts and another for adjusting the center mounting parts. This allows for easy overall width adjustment of the respective transport track. The aforementioned problem is also solved by a soldering system mentioned above, in particular a reflow soldering system, which is characterized in that a transport unit according to the invention is provided in at least one of the zones and / or in the pressure chamber. As already mentioned, it is preferable to provide such a transport unit in the pressure chamber, since, firstly, the drive components of the transport unit are easily replaceable and, secondly, the transport unit itself is also easily replaceable. Further details and advantageous embodiments of the invention can be found in the following description, which provides a more detailed description and explanation of an exemplary embodiment of the invention. Figure 1 shows a reflow soldering system in side view; Figure 2 shows the reflow soldering system according to Figure 1 in front view; Figure 3 shows a top view of the soldering zone of the reflow soldering system without a cover; Figure 4 shows a perspective view of a two-track transport unit; Figure 5 shows the transport unit according to Figure 4 without a side cover and without a side panel; Figure 6 shows individual parts of the transport unit according to Figure 4 with a removed drive unit; Figure 7 shows a view of a drive unit attached to a receiving part. Figure 1 shows a reflow soldering system 10 for continuous soldering of components. The reflow soldering system 10 has an inlet 12 and an outlet 14, whereby the component to be soldered enters the reflow soldering system 10 via the inlet 12 and is discharged from the reflow soldering system 10 via the outlet 14. The component is transported through the reflow soldering system 10 along a transport direction 18 of a process channel 16 indicated in Figure 1. The process channel 16 includes a preheating zone 20, a soldering zone 22, and a cooling zone 24. The reflow soldering system 10 shown in Fig. 1 has a machine enclosure 25 with three sections 26, 28, and 30 to cover the process channel 16. As can be clearly seen from Fig. 1 and Fig. 2, a communication unit 36 ​​with a screen and an input device is provided, by means of which communication with a machine control of the reflow soldering system 10 is possible. The component to be soldered, i.e., the printed circuit board (PCB) coated with solder paste and populated with electronic components, is first heated in preheating zone 20 to a temperature below the melting point of the solder paste. In soldering zone 22, the PCB is heated for a specific duration to a process temperature above the melting point of the solder paste, causing it to melt and solder the electronic components to the PCB. In cooling zone 24, the component is cooled so that the liquid solder solidifies before it is removed from the output 14 of the reflow soldering system 10. A transport system 34 is provided within the reflow soldering system 10 for transporting the printed circuit boards along the transport direction 18. As can be clearly seen from the front view in Fig. 2, the cover 25 can be pivoted open about a pivot axis 32 extending parallel to the transport direction 18. By pivoting open the cover 25, the transport system 34 is accessible for visual inspection, maintenance, cleaning, adjustment, replacement, and, if necessary, repair. In the soldering zone 22 there is a pressure chamber in the form of a vacuum chamber 40, which is formed by a base part 42 shown in the top view according to Fig. 3 and a cover part not shown in the figures, with which the base part 42 can be closed. During operation of the reflow soldering system 10, the cover can be lifted from the base 42 by means of a lifting mechanism. Lifting the cover is necessary to allow the printed circuit boards (PCBs) to be inserted into the vacuum chamber 40. Once the PCBs are in the vacuum chamber 40, the cover is lowered so that it rests on the base 42. In the next step, the vacuum chamber 40 is evacuated using a vacuum pump (not shown), creating a suitable vacuum within the chamber. This vacuum forces out any air inclusions in the liquid solder. After a brief period of vacuum in the vacuum chamber 40, the cover is lifted by means of a corresponding control signal for the lifting mechanism, allowing the PCBs to be removed from the vacuum chamber 40.Advantageously, the circuit boards move through the vacuum chamber 40 at a constant or variable speed within the described process. In the top view shown in Fig. 3, the base part 42 of the pressure chamber 40 and the transport unit 50 provided in the base part 42 are schematically depicted. A total of two parallel transport tracks 60 are provided, along which printed circuit boards can be transported side by side along the transport direction 18 through the process chamber 16 and the vacuum chamber 40. The vacuum chamber 40 has a chamber inlet 62, in which printed circuit boards coming from the transport system 34 are transferred to the transport unit 50, and a chamber outlet 64, in which the printed circuit boards are transferred back to the transport system 34. Figure 4 shows the transport unit 50, which can be inserted into the pressure chamber 40 or into the base part 42 of the pressure chamber 40. The transport systems 34 indicated in Figure 3 could be transport systems corresponding to the transport unit 50. However, it is also conceivable that differently designed transport systems are used there, since these transport systems 34 are subject to less stress than the transport unit 50, which is used inside the pressure chamber 40. The transport unit 50 comprises a base part 66, which is frame-like and has two side parts 68 extending in the transport direction 18 and two crossbeams 70 extending in the transverse direction. A drive shaft 72, rotatably mounted on the side parts 68, is also provided on the base part 66 and can be driven at its free end 74 by a rotary drive (not shown in detail). On the base part 66, a total of six receiving parts 76 to 81 are provided between the side parts 68, on which detachably mounted and removable drive parts 86 to 91 are provided. In Fig. 5, the transport system 50 is shown with only one side part 68 and only with the three receiving parts 76 to 78 and the three drive parts 86 to 88. The drive components 86 to 91 each have a drive wheel 92 which, in the assembled state, as can be clearly seen in Figs. 5 and 7, is engaged with a driven wheel 94 provided on the base component 68 or on the respective receiving components 76 to 81. The drive wheels 92 and the driven wheels 94 are arranged coaxially with each other and coaxially with the output shaft 72 and the frame members 70. The arrangement is such that when the drive components 86 to 91 are removed, as shown in Fig. 6, the respective drive wheel 92 is lifted off the respective driven wheel 94 and is therefore no longer engaged with the respective driven wheel 94. The respective drive components 86 to 91 also have drive rollers 96 rotatably coupled to the respective drive wheel 92. During operation, the printed circuit boards rest on these rollers, which transport the boards through the respective zones 18, 20, 22 or through the pressure chamber 40. As is further evident from Figures 4, 5, and 6, a plurality of drive rollers 96 arranged one behind the other in the transport direction 18 are provided on the drive components 86 to 91. Adjacent drive rollers 96 are rotatably coupled to each other via gears 98. One of these gears forms the drive wheel 92, which, as is evident from Figure 7, engages with the output wheel 94 in the assembled state. As explained in Fig. 3, the transport unit 50 can transport printed circuit boards along the two transport tracks 60. The receiving parts 76, 77 and 78 with the drive parts 86, 87 and 88 are assigned to one transport track 60. The receiving parts 79, 80, 81 with the drive parts 89, 90, 91 are assigned to the second transport track 60. Figure 5 shows the receiving parts 76, 77, 78 and the drive parts 86, 87, 88 of a single transport track 60. The receiving parts 76, 78 are designed as edge receiving parts, and the middle receiving part 77 as a center receiving part. The drive parts 86, 88 are designed as edge drive parts, and the middle drive part 87 as a center drive part. The edge receiving parts 76, 78 serve to receive the edge drive parts 86, 88, and the center receiving part 77 serves to receive the center drive part 87. The arrangement is such that the drive rollers 96 of the edge drive parts 86, 88 face each other, so that during operation of the transport unit 50, the respective circuit board rests on the respective drive rollers 96 in the area of ​​its free longitudinal edges. The edge drive parts 86, 88 and 89, 91 have longitudinal guides 116, which serve to guide the circuit boards in the transport direction 18 during operation of the system.The center drive part 87 is provided to support the circuit boards in the central area, which additionally drives the circuit board central areas. The receiving parts 79, 80 and 81 and the associated drive parts 89, 90 and 91, which form the second transport track 60, correspond in structure to the receiving parts 76, 77, 78 and drive parts 86, 87, 88 of the first transport track 60. To adjust the width of the respective transport track 60, or the position of the drive components 86 to 91 in the transverse direction, the receiving components 78 to 81 are movably arranged on the beams 70 by means of guide rollers 100. For adjusting the receiving components 76 to 81, two spindle shafts 102 and 104 are provided, rotatably mounted on the side parts 68, which can be driven by rotary drives (not shown in the figures). The spindle shaft 102 is coupled to the edge receiving components 78 and 81 via spindle nuts 106, so that when the spindle shaft 102 is rotated, the two receiving components 78 and 81, and thus the drive components 88 and 91, can be adjusted. The spindle shaft 104 is coupled to the center mounting parts 77 and 80 via spindle nuts, so that when the spindle shaft 104 is rotated the mounting parts 77 and 80, and thus the drive parts 87 and 90, can be adjusted in the transverse direction. To enable rotary coupling of the output gears 94 with the output shaft 72 even when the receiving parts 76 to 81 are adjusted laterally, the receiving parts 76 to 81 have rotaryally coupled connecting gears 108 with the output gears 94, as is particularly evident from Fig. 7. The connecting gears 108 each have a receiving contour 110 that is complementary to the cross-section of the output shaft 72, so that the connecting gears 108, and thus the associated receiving parts 76 to 81 with the drive parts 89 to 91, are laterally displaceable on the output shaft 72 and yet are rotaryally coupled to the output shaft 72. In the embodiment shown in the figures, the output shaft 72 has a hexagonal cross-section, wherein the receiving contour 110 provided on the respective coupling wheels 108 is designed as a hexagonal exception. As can be clearly seen in Fig. 6, the drive components 86 to 91 can be easily removed vertically upwards from their corresponding mounting components 76 to 81. This requires only loosening the fasteners, which in Fig. 6 are designed as hand-operated fastening screws 112. After loosening the fastening screws 112 and removing the respective drive component 86 to 91, the respective drive wheel 92 also lifts off towards the corresponding output wheel 94. When the respective drive component 86 to 91 is placed back onto its corresponding mounting component 76 to 81, the respective drive wheel 92 engages again with the corresponding output wheel 94. As can be clearly seen in Fig. 4, retaining lugs 114 are provided on the frame, via which the entire transport unit 50 can be easily removed from the soldering system 10, or from the corresponding zone 20, 22, 24 or the pressure chamber 40. The described reflow soldering system 10, or rather the described drive unit 50, has the advantage that the individual drive components 86 to 91 can be easily replaced, inspected, maintained, and cleaned. Furthermore, the entire transport unit 50 can also be replaced. The described drive components 86 to 91 are comparatively robust, as only gears and no chains or belts are used. Furthermore, intensive and / or automatic lubrication is unnecessary. The gear-driven design is also significantly less susceptible to contamination in the form of condensate or solder residue. Moreover, compared to conventional chain drives, no chain tensioning device is required.

Claims

Transport unit (50) for transporting printed circuit boards along a transport direction (18) within at least one zone of a soldering system (10), in particular a reflow soldering system, wherein a base part (68) is provided with a driveable output shaft (72), characterized in that at least two output gears (94) rotatably coupled to the output shaft (72) are provided, that at least two drive parts (86 to 91) detachably and removable from the base part (68) are provided, each with a drive gear (92) such that the drive parts (86 to 91) have drive rollers (96) rotatably coupled to the drive gear (92), which act against the printed circuit board to transport the printed circuit board through the zone, and that, in the case of drive parts (86 to 91) attached to the base part (68), the respective output gear (94) is in engagement with the associated drive gear (92).and that receiving parts (76 to 81) extending in the transport direction (18) are provided on the base part (68) for receiving and detachably fastening the drive parts (86 to 91), wherein the receiving parts (76 to 81) each have the output gear (94) which can be engaged with the drive gear (92) and driven by the output shaft (72). Transport unit (50) according to claim 1, characterized in that the drive parts (86 to 91) have a plurality of drive rollers (96) arranged one behind the other in the transport direction (18), wherein adjacent drive rollers (96) are rotaryally coupled to each other via gears (98) and wherein at least one gear (98) is rotaryally coupled to the drive gear (92). Transport unit (50) according to claim 1 or 2, characterized in that the base part (68) is designed in a frame-like manner with two side parts (68) extending in the transport direction (18) and with two crossbeams (70) extending in a transverse direction to the transport direction (18). Transport unit (50) according to claim 3, characterized in that the arrangement is such that the frame can be detachably and removablely arranged in the soldering system (10). Transport unit (50) according to claim 3 or 4, characterized in that the output shaft (72) extends in the transverse direction and is rotatably mounted on the two side parts. Transport unit (50) according to claim 3, characterized in that at least one receiving part (76 to 81) is movably and adjustably arranged in the transverse direction on the stiles (70). Transport unit (50) according to claim 6, characterized in that the receiving parts (76 to 81) each provide a coupling gear (108) which is rotatably coupled to the output gear (94) and to the output shaft (72) and is arranged to be axially displaceable on the output shaft (72). Transport unit (50) according to claim 6 or 7, characterized in that at least one adjusting shaft (102, 104) extending in the transverse direction is provided which is coupled to at least one receiving part (76 to 81) in such a way that the receiving part (76 to 81) can be displaced in the transverse direction by rotating the adjusting shaft (102, 104). Transport unit (50) according to one of the preceding claims, characterized in that two edge receiving parts (76, 78 and 79, 81) are provided for receiving one edge drive part (86, 88 and 89, 91) each, wherein the drive rollers (96) of one edge drive part (86, 88 and 89, 91) face the drive rollers (96) of the other edge drive part (86, 88 and 89, 91) and are arranged such that, during operation of the transport unit (50), the circuit board rests on the respective drive rollers (96) in the area of ​​its free longitudinal edges. Transport unit (50) according to claim 9, characterized in that longitudinal guides (116) for guiding the circuit boards in the transport direction (18) are provided on the edge drive parts (86, 88 and 89, 91). Transport unit (50) according to claim 9 or 10, characterized in that at least one central receiving part (77, 80) for receiving a central drive part (87, 90) is provided between the edge receiving parts (76, 78 and 79, 81). Transport unit (50) according to claim 11, characterized in that the transport unit (50) has two transport tracks (60) extending in the transport direction, wherein for each transport track (60) two edge receiving parts (76, 78 and 79, 81) and / or one center receiving part (77, 80) is provided. Soldering system (10), in particular reflow soldering system, for continuous soldering of printed circuit boards in a process channel (16) along a transport direction (18), wherein at least one preheating zone (20), at least one soldering zone (22) and at least one cooling zone (24) are provided in the process channel (16), wherein a pressure chamber (40) is provided in the soldering zone, which has a base part (42) and a cover part which can be raised relative to the base part (42) during operation of the reflow soldering system (10), characterized in that at least in one of the zones (20, 22, 24) and / or in the pressure chamber (40) a transport unit (50) according to one of the preceding claims is provided.

Images