Radiant curtain heating assembly for crest welder

Abstract

A crest welder includes a housing, a conveyor movable relative to the housing, a preheating module positioned along the conveyor, and a curtain module positioned at an inlet of the housing, the curtain module including at least one curtain and a heating element. A curtain module for a crest welder or reflow oven includes at least one curtain and a heating element. A method of containing inert gas around a conveyor in a channel of a crest welder or reflow oven. In some embodiments, the method includes: providing a curtain module at an end of the channel, the curtain module including at least one curtain and at least one heating element; and controlling the temperature of the heating element.

Description

BACKGROUND 1. TECHNICAL FIELD The present application relates generally to surface mounting of electronic components onto printed circuit boards by employing a wave soldering process, and more particularly to a radiant curtain heating assembly configured to ensure an oxygen-free environment during the wave soldering process. 2. BACKGROUND In the manufacture of printed circuit boards, electronic components can be mounted to the printed circuit board through a process known as "wave soldering." In a typical wave soldering machine, the printed circuit board is moved on an inclined path by a conveyor, through a fluxing station, a pre-heating station, and finally through a wave soldering station. At the wave soldering station, a wave of solder is caused to surge upward through a wave solder nozzle and contact the portions of the printed circuit board to be soldered (by a pump). As used herein, the term "circuit board" or "printed circuit board" as used herein includes any type of substrate assembly having electronic components, including, for example, wafer substrates.

[0002] The wave soldering process has made progress by transitioning from traditional tin-lead solder to lead-free materials. These new solder materials have reduced the process window to the point that some processes now require pre-heating in an oxygen-free environment prior to the soldering process to prevent the formation of oxides on the solder joints. SUMMARY

[0003] One aspect of the present disclosure relates to a wave soldering machine of the type used to join electronic components to a substrate. In one embodiment, the wave soldering machine includes a housing including a passageway, a conveyor extending through the passageway, the conveyor configured to move a workpiece through the passageway, a pre-heating module positioned along the passageway, and a curtain module positioned at an entrance to the passageway, the curtain module including at least one curtain and a heating element.

[0004] In some embodiments, the curtain module further includes a mounting plate, each of the at least one curtains is secured to the mounting plate, and the heating element is secured to the mounting plate.

[0005] In some embodiments, the heating element is a radiant heating element.

[0006] In some embodiments, the curtain module further includes an insulating layer, wherein the heating element is positioned between the insulating layer and the mounting plate.

[0007] In some embodiments, the curtain module further includes an insulating cover, wherein the insulating layer is positioned between the insulating cover and the heating element.

[0008] In some embodiments, the mounting plate has a first side and a second side opposite the first side, and each curtain is secured to the first side of the mounting plate and the heating element is secured to the second side of the mounting plate.

[0009] In some embodiments, the heating element is a radiant heating element.

[0010] In some embodiments, the at least one curtain includes a plurality of curtains.

[0011] In some embodiments, each curtain is secured to the mounting plate by at least one curtain retainer extending along a length of the respective curtain.

[0012] In some embodiments, the curtain module includes an upper curtain module subassembly positioned above the conveyor and a lower curtain module subassembly positioned below the conveyor.

[0013] In some embodiments, a curtain of the at least one curtain of the upper curtain module subassembly overlaps a curtain of the at least one curtain of the lower curtain module subassembly.

[0014] In some embodiments, each curtain of the at least one curtain is made of a material that includes fiberglass.

[0015] Another aspect of the present disclosure relates to a curtain module for a wave solder machine or reflow oven. In one embodiment of a curtain module for a wave solder machine or reflow oven, the curtain module includes at least one curtain; and a heating element.

[0016] In some embodiments, the curtain module further includes a mounting plate, each curtain of the at least one curtain is secured to the mounting plate, and the heating element is secured to the mounting plate.

[0017] In some embodiments, the heating element is a radiant heating element.

[0018] In some embodiments, the curtain module further includes an insulation layer, wherein the heating element is positioned between the insulation layer and the mounting plate.

[0019] In some embodiments, the curtain module further includes an insulation cover, wherein the insulation layer is positioned between the insulation cover and the heating element.

[0020] In some embodiments, the mounting plate has a first side and a second side opposite the first side, and each curtain is secured to the first side of the mounting plate and the heating element is secured to the second side of the mounting plate.

[0021] In some embodiments, the heating element is a radiant heating element.

[0022] In some embodiments, the at least one curtain includes a plurality of curtains.

[0023] In some embodiments, each curtain of the at least one curtain is secured to the mounting plate by at least one curtain retainer extending along a length of the respective curtain.

[0024] In some embodiments, the curtain module includes an upper curtain module subassembly and a lower curtain module subassembly positioned below the upper curtain module subassembly.

[0025] In some embodiments, a curtain of the at least one curtain of the upper curtain module subassembly overlaps a curtain of the at least one curtain of the lower curtain module subassembly.

[0026] In some embodiments, each curtain is made of a material that includes glass fibers.

[0027] Another aspect of the present disclosure relates to a method of containing an inert gas around a conveyor in a tunnel of a wave solder machine or reflow oven. In one embodiment of the method of containing an inert gas around a conveyor in a tunnel of a wave solder machine or reflow oven, the method includes: providing a curtain module at an end of the tunnel, the curtain module including at least one curtain and at least one heating element; and controlling a temperature of the at least one heating element.

[0028] In some embodiments, the at least one heating element is a radiant heating element.

[0029] In some embodiments, the curtain module includes: an upper curtain module subassembly positioned in the tunnel above the conveyor and including a first heating element of the at least one heating element; and a lower curtain module subassembly positioned in the tunnel below the conveyor and including a second heating element of the at least one heating element, and the method, and controlling the temperature of the heating element includes controlling a first temperature of the first heating element and controlling a second temperature of the second heating element.

[0030] In some embodiments, the first temperature and the second temperature are not equal. BRIEF DESCRIPTION OF DRAWINGS

[0031] The drawings are not intended to be to scale. In the drawings, like or similarly designated components have the same reference numbers. For purposes of clarity, not every component can be called out in every drawing. In the drawings: Figure 1 is an isometric view of a wave solder machine; Figure 2 is a side view of a wave solder machine with an outer packaging removed to reveal internal components of the wave solder machine, the wave solder machine including a plurality of preheater assemblies and a solder station; Figure 3is a perspective view of a curtain module of the present disclosure in a tunnel of a wave solder machine; Figure 4 is Figure 3 is an exploded view of the curtain module of Figure 5 is Figure 3 is an exploded view of a subassembly of the curtain module of Figure 6 is a schematic side view of a workpiece passing through Figure 3 the curtain module of Figure 7 is a flowchart of an embodiment of a method of controlling temperature in a tunnel, such as a tunnel of a wave solder machine or a reflow oven. DETAILED DESCRIPTION

[0032] The present disclosure will now be described in detail for purposes of illustration only and not limitation, by reference to the drawings. The present disclosure does not limit its application to the details of construction and arrangement of the components set forth in the following description or illustrated in the drawings. The principles expressed in the present disclosure are applicable to other embodiments and can be practiced or carried out in various ways. Also, the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "containing," "involving," and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as other items.

[0033] Wave solder machines are typically designed to include a series of preheaters for the purpose of heating printed circuit boards ("PCBs") prior to contact with a bath of molten solder. Some processes require that this heating be performed in an oxygen-free environment. For these processes, the preheaters must be sealed relative to the conveyor tunnel through which the printed circuit boards travel so as to not allow external air to penetrate. The preheater assembly of embodiments of the present disclosure includes a radiant curtain heating assembly configured to maintain an inert environment through the conveyor tunnel during preheating and soldering.

[0034] For purposes of illustration, and with reference to Figure 1Embodiments of the present disclosure will now be described with reference to a wave solder machine, generally designated 10, for performing solder coating on printed circuit boards 12, which can be referred to herein as electronic substrates. Wave solder machine 10 is one of several machines in a printed circuit board production / assembly line. As shown, wave solder machine 10 includes a housing 14 that accommodates the components of the machine. This arrangement is such that a conveyor 16 transports printed circuit boards to be processed by wave solder machine 10. As each printed circuit board 12 enters wave solder machine 10, it travels along conveyor 16, along an inclined path through a tunnel 18, a fluxing station, generally designated 20, and a pre-heating station, generally designated 22, to condition the printed circuit board for wave soldering. Once conditioned (i.e., heated), printed circuit board 12 travels to a wave soldering station, generally designated 24, to apply solder to the printed circuit board. A controller 27 is provided to automate the operation of the several stations of wave solder machine 10, including but not limited to fluxing station 20, pre-heating station 22, and wave soldering station 24, in a well-known manner.

[0035] Reference is made to Figure 2 Fluxing station 20 is configured to apply flux to the printed circuit board as it travels on conveyor 16 through wave solder machine 10. Pre-heating station 22 includes several pre-heaters designed to incrementally increase the temperature of the printed circuit board as it travels along conveyor 16 through tunnel 18 to prepare the printed circuit board for the wave soldering process. As shown, wave soldering station 24 includes a wave solder nozzle in fluid communication with a reservoir of solder 24a. A pump is provided within the reservoir to deliver molten solder from the reservoir to the wave solder nozzle. Once soldered, the printed circuit board exits wave solder machine 10 via conveyor 16 to another station provided in the production line. In some embodiments, wave solder machine 10 can be further configured to include a flux management system to remove volatile contaminants from tunnel 18 of the wave solder machine.

[0036] To provide the desired gaseous environment in tunnel 18, a curtain module (generally designated 26 in Figure 2 ) is arranged at the entrance of tunnel 18. In some embodiments, a curtain module similar to curtain module 26 can be arranged at the exit of tunnel 18.

[0037] Reference is now made to Figure 3 and Figure 4Embodiments of the curtain module 26 include an upper curtain subassembly 28A and a lower curtain subassembly 28B. The upper curtain subassembly 28A is mounted above the conveyor 16, which includes two spaced apart tracks 17. The lower curtain subassembly 28B is mounted below the conveyor 16. The upper curtain subassembly 28A and the lower curtain subassembly 28B are configured to contain a desired gaseous environment along the conveyor within the tunnel 18. In some embodiments, the desired gaseous environment is an inert gaseous environment. In some embodiments, the inert gas is nitrogen.

[0038] As shown in the exploded view of FIG. 1, the upper curtain subassembly 28A includes a plurality of curtains 30 that depend downward from a mounting plate 32 toward the conveyor 16, and the lower curtain subassembly 28B includes a plurality of curtains 30 that extend upward from the mounting plate 32 toward the conveyor 16. The structure of each curtain module subassembly 28A, 28B is described in further detail below. Figure 4

[0039] The mounting plate 32 of each curtain module subassembly 28A, 28B is secured to the structure forming the tunnel 18 of the wave soldering machine 10 in a spaced facing relationship with the conveyor 16.

[0040] Figure 5 An exploded view of the upper curtain subassembly 28A is shown. A heating element 34 is secured to the mounting plate 32 on a side of the mounting plate opposite the conveyor 16. A thermal barrier 36 is secured to the heating element 34, and a cover 38 is secured over the thermal barrier 36.

[0041] The structure of the lower curtain subassembly 28B is the same as the structure of the upper curtain subassembly 28A, but inverted.

[0042] The mounting plate 32 is secured to the structure forming the tunnel 18. The mounting plate 32 has a lower surface 40 and an upper surface 42. The mounting plate 32 is configured to support a plurality of curtains 30 that depend from the lower surface 40 of the mounting plate 32. In addition, the mounting plate 32 is configured to support a heating element 34 supported on the upper surface 42 of the mounting plate 32, and a thermal barrier 36 and a thermal cover 38 positioned over the heating element 34.

[0043] The mounting plate 32 is configured to conduct heat from the heating element 34 to the curtains 30. The mounting plate 32 is made of at least one thermally conductive material. For example, the mounting plate 32 can be made of a material that includes a metal.

[0044] ​The heating elements 34 of the curtain module subassembly are configured to heat workpieces (e.g., printed circuit boards 12) on the conveyor 16 as they pass through the curtain module 26 before the workpieces reach the preheat module 22. The heating elements 34 of the curtain module subassembly help preheat the workpieces before they enter the preheat module 22, thereby alleviating the burden on the preheat module 22 to heat the workpieces to a desired temperature. As a result, the curtain module 26 allows the workpieces to spend less time in the preheat module 22 and travel at a faster speed on the conveyor through the wave soldering machine 10.

[0045] The heating element 34 is positioned on the upper surface 42 of the mounting plate 32. In some embodiments, the heating element 34 is secured to the mounting plate 32. For example, in some embodiments, the heating element 34 can be secured to the mounting plate 32 by a suitable fastener system, such as an adhesive or a clamp.

[0046] The heating element 34 can be made of a variety of materials. Figure 5 In the embodiment of the present invention, the heating element 34 includes a sheet 44 made of silicone. In other embodiments, the sheet of the heating element can be made of silicone and / or one or more other materials.

[0047] exist Figure 5 In the embodiment of FIG. 4 , the heating element 34 is electrically powered. The heating element includes an electrical coil 46 extending through the sheet 44 . The electrical coil 46 includes a first electrical lead and a second electrical lead, each indicated at 48 , extending from the coil and from the sheet. The first and second electrical leads 48 , 48 can be connected to a voltage source (not shown) to generate an electrical current through the coil 46 in the sheet. Applying the current to the electrical coil 46 causes heat from the coil 46 to be released into the sheet 44 .

[0048] Insulator 36 and insulating cover 38 provide thermal insulation for heating element 34 so that heat from heating element 34 is at least substantially or completely conducted through mounting plate 32. Insulator 36 is positioned on a surface of heating element 34 opposite mounting plate 32 so that insulator 36 is sandwiched between heating element 34 and insulating cover 38.

[0049] The insulation layer 36 has a thermal conductivity that achieves the desired heating of the curtain 30. The lower thermal conductivity of the insulation layer 36 results in less heat being transferred from the heating element 34 to the insulation cover 38, and more heat being transferred from the heating element 34 to the mounting plate 32, the curtain 30, and the workpiece (printed circuit board 12) beneath the curtain 30 of the upper subassembly 28A.

[0050] Similarly, the lower thermal conductivity of the thermal barrier 36 allows less heat to be transferred from the heating element 34 to the thermal cover 38 and more heat to be transferred from the heating element 34 to the mounting plate 32, the curtain 30, and the workpiece 12 above the curtain 30 of the lower subassembly 28B.

[0051] The thermal barrier can be made of one or more materials that produce the desired thermal conduction properties.

[0052] Turning now to the opposite side of the mounting plate 32, the curtains 30 are secured to the mounting plate by curtain retainers. Specifically, in embodiments, two curtain retainers 50A, 50B secure each curtain 30 to the mounting plate. Each curtain retainer 50A, 50B is in the form of a longitudinally extending C-shaped channel. The first curtain retainer 50A is secured to the lower surface 40 of the mounting plate 32, for example, by threaded fasteners or welding. To secure the curtain 30 to the mounting plate 32, the curtain 30 is bent into a U-shape over the second curtain retainer 50B. The curtain 30 and the second curtain retainer 50B are received in the C-shaped channel of the first curtain retainer 50A. Fasteners, such as threaded fasteners, extend through the second retainer 50B, through the curtain 30, through the first curtain retainer 50A, and into the mounting plate 32. When the mounting plate 32 is positioned with its lower surface 40 extending horizontally, the free end of each curtain extends downward from the lower surface of the mounting plate.

[0053] As described above, each curtain 30 is bent over the curtain retainers 50A, 50B with a middle portion 52 of each curtain 30 being received between the two curtain retainers 50A, 50B to secure the curtain 30 to the mounting plate 32. Each curtain 30 extends from the secured middle portion 52 to a first free end 54 of the curtain 30 and to a second free end 56 of the curtain 30. In alternative embodiments, each curtain 30 includes a single free end and a secured end that is secured to the first side of the mounting plate.

[0054] The first free end 54 and the second free end 56 are independently movable and independently bendable. Thus, as electrical components travel through the tunnel 18 in a direction from the first free end 54 toward the second free end 56, the electrical components first contact and bend the first free end 54 and next contact and bend the second free end 56. In some embodiments, the ends 54, 56 of the curtain 30 are bent just enough to accommodate the electrical components passing through the tunnel, thereby maintaining the desired gas environment in the tunnel 18. Due to the resilient nature of the curtain 30, each of the free ends 54, 56 returns to their original shape when no longer in contact with the electrical components passing through the tunnel.

[0055] Heat radiates from the mounting plate 32 toward the center of the tunnel 18. The aforementioned insulation layer 36 improves the efficiency of the curtain module 26. Efficiency can be measured as a comparison of the amount of heat radiated to the center of the tunnel 18 to the amount of energy applied to the lead 48 of the heating element 34 of the curtain module 26.

[0056] Referring now to Figure 6 Each curtain 30 is made of a material flexible enough to allow the curtain 30 to accommodate the electrical components of a workpiece passing through the tunnel 18 on the conveyor 16. The curtains 30 of the upper subassembly 28a and the curtains 30 of the lower subassembly 28B engage the rails 17 and overlap each other in the vertical direction between the rails 17 to build a gas barrier within the tunnel 18. As Figure 6 shown, the free ends 54, 56 of the respective curtains overlap each other in the vertical direction to build a gas barrier along the tunnel 18 before the electrical components pass through one of the curtains 30. The free ends 54, 56 of one of the curtains 30 of the upper subassembly 28A bend to accommodate the electrical components as the workpiece passes between the upper curtain subassembly 28A and the lower curtain subassembly 28B in the direction of arrow A. The free ends 54, 56 of the respective curtain 30 return to their original shape after the electrical components pass through the free ends 54, 56 of the respective curtain 30, thereby maintaining the desired inert gas environment in the tunnel.

[0057] In some embodiments, each curtain is made of a material that includes fiberglass. In some embodiments, each curtain is made of a material that includes fiberglass coated with polytetrafluoroethylene (PTFE).

[0058] In some embodiments of the present disclosure, the curtain module can be provided separately from a wave solder machine or a reflow oven.

[0059] Another aspect of the present disclosure relates to a method of containing an inert gas around a conveyor in a tunnel, such as a tunnel of a wave solder machine or a reflow oven.

[0060] Figure 7 An embodiment of a method 100 of containing an inert gas around a conveyor in a tunnel is shown. At block 110, the method includes providing a curtain module of the present disclosure at an end of the tunnel. The curtain module includes at least one curtain and at least one heating element.

[0061] The method further includes controlling the temperature of the heating element. For example, in some embodiments, the method includes causing the controller 27 to send a signal to the heating element to cause the heating element to generate heat to heat the tunnel to a desired temperature. In some embodiments, the signal sent from the controller 27 to the heating element can be responsive to a signal received by the controller 27 from one or more temperature sensors in the tunnel.

[0062] At block 120, the method includes sensing a temperature in the tunnel. At block 130, the method includes causing the heating elements in the curtain module to heat the tunnel.

[0063] In some embodiments of the method, the heating elements are radiant heating elements.

[0064] In some embodiments of the method, the at least one curtain module includes an upper curtain module subassembly positioned above the conveyor and a lower curtain module subassembly positioned below the conveyor. The upper curtain module subassembly includes a first heating element of the at least one heating element, and the lower curtain module subassembly includes a second heating element of the at least one heating element. The method includes controlling a first temperature of the first heating element and controlling a second temperature of the second heating element. The first temperature and the second temperature can be selectively equal or unequal.

[0065] Although some portions of the above description relate to a wave solder machine, embodiments of the curtain module of the present disclosure and embodiments of the method of the present disclosure can be used with other devices, such as a reflow oven. For example, a radiant curtain module can be arranged at the entrance and exit of a tunnel of a reflow oven in a manner similar to arranging a radiant curtain module at the entrance and exit of a tunnel of a wave solder machine.

[0066] Thus, having described several aspects of at least one embodiment of the present disclosure, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be part of this disclosure, and are intended to be within the spirit and scope of the present disclosure. Accordingly, the preceding description and drawings are by way of example only.

[0067] CLAIMED.

Claims

1. A wave soldering machine, comprising: a housing, the housing including a channel; a conveyor extending through the passage, the conveyor configured to move a workpiece through the passage; a preheating module, the preheating module being positioned along the channel; as well as A curtain module is positioned at the entrance of the channel, the curtain module comprising at least one curtain and a heating element.

2. The wave soldering machine according to claim 1, wherein: The curtain module further includes a mounting plate to which each of the at least one curtain is secured and to which the heating element is secured.

3. The wave soldering machine according to claim 2, wherein: The heating element is a radiant heating element.

4. The wave soldering machine according to claim 2, wherein: The curtain module further includes an insulating layer, wherein the heating element is positioned between the insulating layer and the mounting plate.

5. The wave soldering machine according to claim 4, wherein: The curtain module further includes an insulating cover, wherein the insulating layer is positioned between the insulating cover and the heating element.

6. The wave soldering machine according to claim 2, wherein: The mounting plate has a first side and a second side opposite the first side, and each curtain is secured to the first side of the mounting plate and the heating element is secured to the second side of the mounting plate.

7. The wave soldering machine according to claim 6, wherein: The heating element is a radiant heating element.

8. The wave soldering machine according to claim 6, wherein: The at least one curtain comprises a plurality of curtains.

9. The wave soldering machine according to claim 6, wherein: Each curtain is secured to the mounting plate by at least one curtain retainer extending along the length of the respective curtain.

10. The wave soldering machine according to claim 1, wherein: The curtain module includes an upper curtain module subassembly positioned above the conveyor and a lower curtain module subassembly positioned below the conveyor.

11. The wave soldering machine according to claim 10, wherein: A curtain in at least one curtain of the upper curtain module subassembly overlaps a curtain in at least one curtain of the lower curtain module subassembly.

12. The wave soldering machine according to claim 1, wherein: Each of the at least one curtain is made of a material comprising glass fibers.

13. A curtain module for a wave soldering machine or a reflow oven, the curtain module comprising: at least one curtain; as well as Heating element.

14. The curtain module of claim 13, further comprising a mounting plate, each of the at least one curtain being secured to the mounting plate, and the heating element being secured to the mounting plate.

15. The curtain module according to claim 14, wherein: The heating element is a radiant heating element.

16. The curtain module according to claim 14, further comprising a heat insulation layer, wherein: The heating element is positioned between the insulation layer and the mounting plate.

17. The curtain module of claim 16, further comprising a thermal insulation cover, wherein: The insulation layer is positioned between the insulation cover and the heating element.

18. The curtain module according to claim 14, wherein: The mounting plate has a first side and a second side opposite the first side, and each curtain is secured to the first side of the mounting plate and the heating element is secured to the second side of the mounting plate.

19. The curtain module according to claim 18, wherein: The heating element is a radiant heating element.

20. The curtain module according to claim 18, wherein The at least one curtain comprises a plurality of curtains.

21. The curtain module according to claim 18, wherein: Each curtain of the at least one curtain is secured to the mounting plate by at least one curtain retainer extending along the length of the respective curtain.

22. The curtain module according to claim 13, wherein: The curtain module includes an upper curtain module subassembly and a lower curtain module subassembly positioned below the upper curtain module subassembly.

23. The curtain module according to claim 22, wherein: A curtain in at least one curtain of the upper curtain module subassembly overlaps a curtain in at least one curtain of the lower curtain module subassembly.

24. The curtain module according to claim 13, wherein: Each curtain is made of a material comprising glass fibers.

25. A method of containing an inert gas around a conveyor in a tunnel of a wave soldering machine or a reflow oven, the method comprising: providing a curtain module at the end of the channel, the curtain module comprising at least one curtain and at least one heating element; as well as The temperature of the at least one heating element is controlled.

26. The method of claim 25, wherein: The at least one heating element is a radiant heating element.

27. The method of claim 25, wherein: The curtain module comprises: an upper curtain module subassembly positioned in the channel above the conveyor and comprising a first heating element of the at least one heating element; and a lower curtain module subassembly positioned in the channel below the conveyor and including a second heating element of the at least one heating element, and the method, and Wherein, controlling the temperature of the heating element includes controlling a first temperature of the first heating element and controlling a second temperature of the second heating element.

28. The method of claim 27, wherein: The first temperature and the second temperature are not equal.

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