JP4784293B2 - Reflow furnace - Google Patents

Description

The present invention relates to a reflow furnace to full volume removal device you remove the flux fumes generated in the furnace is installed when soldered to the printed circuit board coated with the solder paste.

  Generally, solder paste is used when soldering a printed circuit board in a reflow furnace. In soldering using a solder paste, first, the solder paste is applied to a soldering portion of a printed circuit board with a printing device or a dispenser, and an electronic component is mounted on the applying portion. Then, the printed circuit board on which the electronic component is mounted is heated in a reflow furnace to melt the solder paste and solder the printed circuit board and the electronic component.

  A reflow furnace for soldering printed circuit boards is composed of a preheating zone, a main heating zone, and a cooling zone. The printed circuit board coated with solder paste is preheated by a heater in the preheating zone. Soldering is performed by the main heating with the heater of No. 1 and cooling with the cooler in the cooling zone.

  The solder paste is obtained by kneading solder powder and flux into a viscous paste. The flux used for this solder paste is obtained by dissolving solid components such as pine resin, activator and thixotropic agent in a high boiling point solvent. Therefore, when the printed circuit board coated with the solder paste is heated in a reflow furnace, it is first heated to 100 to 150 ° C. with a heater in the preheating zone, and the solvent in the solder paste is volatilized and the solid component is melted. The melted solid component reduces and removes the oxide adhering to the printed circuit board, and cleans the soldered portion. Next, the printed circuit board is heated to 200 ° C. or higher by the heater in the main heating zone, and the solder powder is melted and spreads on the cleaned soldered portion. Then, after the melted solder is sufficiently wetted and spread on the soldering portion, it is cooled by the cooler in the cooling zone and the molten solder is solidified to complete the soldering.

  By the way, the solder paste applied to the printed circuit board is fumed as the solvent is volatilized in the preheating zone, and when the solid component melted in the preheating zone is exposed to a high temperature in the heating zone, the solder paste also becomes fumes. Float inside. These solvent and solid component fumes are used in labyrinths installed at relatively low temperatures in the furnace, such as conveyors that transport printed boards in the furnace, fans that circulate hot air, frames that constitute the furnace, and furnace entrances and exits. When it comes into contact, etc., it is cooled and dewed, and when the temperature is lowered, it becomes a sticky solid.

  A problem arises when a large amount of these fumes (hereinafter referred to as fume solids) adheres to the members constituting the reflow furnace. In other words, if a large amount of solid fume adheres to the conveyor for transporting the printed circuit board, the printed circuit board adheres to the conveyor, and the printed circuit board does not leave the conveyor when it is unloaded and is wound on the sprocket of the conveyor to break the printed circuit board and blow hot air. If a large amount adheres to the fan, the rotation of the fan slows down and the blowing of hot air weakens, and if a large amount adheres to the frame that is the structure of the reflow furnace, the accumulated solid fumes fall on the printed circuit board being transported and printed. If the substrate is soiled and adhered to the labyrinth for preventing the inflow of outside air at the entrance / exit, the solid fume comes into contact with the printed circuit board and causes the electronic component to fall off from a predetermined position.

In view of the problem due to the adhesion of these solid fumes, many methods and apparatuses for removing fumes in the furnace have been proposed. (Patent Documents 1 to 8)
JP-A-4-13475 JP-A-4-46667 JP-A-4-251661 JP 7-77346 A Japanese Patent Laid-Open No. 7-212028 JP 10-335807 A Japanese Utility Model Publication No. 54-41411 Japanese Utility Model Publication No. 64-20964

  In a conventional reflow furnace with a fume removal device, the removal of the fume is not sufficient, and when the gas from which the fume has been removed by the removal device returns to the furnace, the fume is condensed in the low temperature portion of the furnace, as described above. There was a problem. In addition, in a removal device using a filter for filtering a fume-containing gas as in Patent Document 4, if even a small amount of fume solid matter adheres to the filter, the passage of the fume-containing gas is prevented, and the reflow furnace and the removal device are circulated. Will get worse. The present invention is capable of removing most of the fumes generated in the furnace, and has no effect on the circulation between the reflow furnace and the fume removing apparatus even if some solid fume adheres to the dew condensation means. The object is to provide a reflow furnace with a device.

When the fume-containing gas is passed between a large number of pipes having a low temperature, the fume is condensed on the pipe surface, and when the fume-containing gas is passed through a thin long hole, the fume is condensed in the long hole. Condensation in the form of a plate material when the contained gas is passed between plate members standing up and down from the top and bottom, and when these are combined, condensation is promoted, especially after passing between cold pipes to other condensation means When the combination is allowed to pass, the condensation effect is further promoted.Fume solid matter adheres to the pipes installed at intervals, and the solid fume adheres to the elongated holes. The present invention has been completed by paying attention to the fact that even if fumes adhere to the plate material, the flow of gas is not hindered .

  The present invention relates to a method for removing fumes from a fumes-containing gas generated in a reflow furnace, wherein the fumes-containing gas generated in the furnace is discharged from the outlet of the reflow furnace to the outside of the furnace, and the fumes-containing gas is discharged to the outside of the furnace. A fume removal method in a reflow furnace characterized in that a fume is condensed by each dew condensing means and passed through a plurality of dew condensing means in an installed fume removal apparatus to remove the fume from the fumes-containing gas.

In the present invention, a discharge port is provided at an appropriate location of the reflow furnace, and the discharge port and the inlet of the box-shaped fume removing device are connected by a pipe, and a plurality of fume removing devices are provided in the fume removing device. In the reflow furnace, the dew condensation means is installed, and the outlet of the fume removing device is connected to an appropriate part of the reflow furnace by a pipe.

  In the present invention, since the fume-containing gas discharged from the reflow furnace is passed through the plurality of dew condensation means, the fume is always condensed by any of the dew condensation means, and most of the fumes can be removed. In particular, in the present invention, even if a large amount of fume solid matter adheres to the dew condensation means, it does not hinder the flow of gas, so it is excellent in maintainability that it is not necessary to wash the fume solid matter for a long period of time. Yes. Therefore, according to the present invention, in the gas that has passed through the fume removal device and returned to the furnace, there is almost no fumes, and no fume solid matter adheres to low temperature components in the furnace. This produces an excellent effect that the conventional reflow furnace does not cause.

  In the present invention, the fume is condensed in any of the dew condensation means by passing the fume-containing gas through the plurality of dew condensation means. Examples of the dew condensation means used in the present invention include a multi-tube dew condensation means, a labyrinth type dew condensation means, and a long hole side-by-side dew condensation means.

  Multi-tube dew condensation means is a box-type removal device installed with a large number of pipes penetrating through it, and the fumes that are in contact with the pipe surface by cooling the pipe by flowing outside air into the pipe. Allow the fume to condense on the pipe surface. When a large amount of fume solid matter adheres to the pipe surface, the fume solid matter is in a liquid state at the initial stage of attachment, and therefore flows down along the pipe. However, in a long period of time, solid fume accumulates on the pipe, and heat conduction with the pipe deteriorates, so that condensation may be difficult. In that case, the multi-tube type dew condensation means is removed from the fume removing device and washed with a solvent. For this purpose, the multi-tube type dew condensation means should be removable.

  The labyrinth type dew condensation means is a structure in which a plurality of plate members are erected alternately from above and below in the fume removal apparatus. When a plurality of plate members are erected alternately in this manner, the distance passing through these plate members becomes long, and the fume-containing gas is cooled, so that condensation occurs on the plate members. The high-viscosity liquid fume solid that is condensed in the form of a plate material flows down along the plate material. If the solid fume accumulates over a long period of time and the heat conduction with the plate deteriorates, the plate is removed and washed with a solvent. Therefore, it is preferable that the plate material, particularly the plate material erected from below, be removable.

  As shown in FIG. 10, the long hole side-by-side dew condensation means is a structure in which a number of plates are combined in a lattice shape in the vertical and horizontal directions to form a rectangular long hole, and a hexagonal long hole is a gap as shown in FIG. For example, a honeycomb structure in which the holes are lined up, a structure in which a number of corrugated plates are stacked and the holes are corrugated as shown in FIG. As the fume-containing gas passes through the elongated hole, it is cooled and condensed in the elongated hole. The material of the condensing means for juxtaposed long holes used in the present invention may be any material such as metal, resin, paper, etc., but metal aluminum is particularly suitable.

  Aluminum dew condensation means has good heat conduction, so when high temperature gas comes into contact with it, it absorbs the temperature and propagates it to the pedestal for installing the dew condensation means installed in the long holes and the surroundings. Reduce the temperature. Therefore, the long hole side-by-side dew condensation means made of aluminum tends to dew fume. The long hole side-by-side dew condensation means made of aluminum can wash the solidified fume by simply removing the long hole side-by-side dew condensation means and immersing it in a cleaning liquid if a large amount of solid fume adheres. Later, it can be used again as a long hole side-by-side dew condensation means. Therefore, the long hole side-by-side dew condensation means should be removable.

  The resin long hole side-by-side dew condensation means is inferior in heat conductivity to aluminum. However, when a large amount of fume solid matter adheres, it can be removed by simply immersing it in a cleaning solution and can be reused. And the paper long hole side-by-side dew condensation means is inferior in heat conduction to aluminum, but it is cheaper.If a large amount of fume solids adheres, it is not washed and only replaced with a new one. There is the convenience of being able to finish.

  In addition, if the bottom plate of the removal device is inclined so as to be lowered along the flow direction of the fume-containing gas, the dew condensation is caused by the multi-tube type dew condensation means, the labyrinth type dew condensation means, or the long hole side-by-side dew condensation means. The liquid fume dripping down flows downward along the bottom plate. Therefore, if a drain is connected to the lowermost part of the bottom plate, the liquid fume can be extracted from the drain.

  In the removal apparatus of the present invention, a plurality of dew condensation means are installed in the box-shaped body, but the multi-tube type dew condensation means is installed in the direction of flow of the fumes-containing gas, that is, near the inlet of the fumes-containing gas, Next, when other dew condensation means is installed, the dew condensation effect in each dew condensation means is promoted. That is, the dew condensation means used in the present invention condenses by lowering the temperature of the gas containing fumes, but among the dew condensation means, the multi-tube type dew condensation means has a significant cooling effect and is discharged from the reflow furnace. If the temperature of the high-temperature fume-containing gas is lowered by the multi-tube type dew condensation means, the dew condensation effect in the subsequent dew condensation means is improved.

  Therefore, in the fume removing apparatus of the present invention, the multi-tube type dew condensation means is first installed in the flow direction of the gas containing fumes, and then the long hole side-by-side dew condensation means is installed, or the labyrinth type next to the multi-tube type dew condensation means. Install dew condensation means, install multi-tube dew condensation means next to long hole type dew condensation means, install labyrinth type dew condensation means, or install multi-tube type dew condensation means next to labyrinth type dew condensation means, elongate hole parallel arrangement A mold dew condensation means may be installed.

  In the present invention, the fumes-containing gas generated in the reflow furnace is sucked in an appropriate place in the reflow furnace, discharged outside the furnace with a pipe, and connected to a removing device. The gas from which the fumes have been removed is reintroduced into the reflow furnace, but the location where the fumes removed gas is introduced into the furnace varies depending on the structure of the reflow furnace and the structure of the heater. For example, in a reflow furnace in which a stirrer is installed in the furnace and the heater simply convects hot air, a hole is drilled at an appropriate location in the muffle, and an introduction pipe is connected to the hole to remove the fumes removed. May be introduced into the furnace. In addition, a heater with a structure in which a plurality of hot air circulation heaters are installed and hot air blown from the heater outlet is sucked in from the same heater inlet is introduced into an appropriate hot air circulation heater or cold air circulation cooler. You may make it connect the pipe and introduce | transduce the gas after a fume removal directly to a heater or a cooler.

  Furthermore, as a part where the gas after the removal of fumes is introduced into the furnace, a part where the reflux pipe is close to the entrance and exit is preferable. That is, if atmospheric gas without fumes flows out from a location close to the entrance / exit, it is difficult for outside air to enter the furnace due to the curtain action.

  Hereinafter, the reflow furnace of the present invention will be described with reference to the drawings. FIG. 1 is a front sectional view of a first embodiment of the reflow furnace of the present invention, FIG. 2 is a partially enlarged sectional view of the fume removing device, FIG. 3 is a perspective view with the front plate and the top plate of FIG. 2 removed, and FIG. 5 is a front sectional view of a second embodiment of the reflow furnace of the present invention, FIG. 5 is a partially enlarged sectional view of the fume removing device, FIG. 6 is a perspective view of the front plate and the top plate of FIG. 5 removed, and FIG. 8 is a front sectional view of a third embodiment of the furnace, FIG. 8 is a partially enlarged sectional view of the fume removing apparatus, and FIG. 9 is a perspective view in which the front plate and the top plate of FIG. 8 are removed.

  First, a first embodiment of the reflow furnace of the present invention will be described with reference to FIGS. The reflow furnace 1 is covered with a muffle 2, and a tunnel-like furnace 3 is formed inside. In the furnace 3, a conveyor 4 is placed that carries a printed circuit board P and travels in the direction of arrow A. In the furnace 3, preheating heaters 5u, 5d, 6u, 6d, main heating heaters 7u, 7d, and coolers 8u, 8d are installed on the upper and lower portions with the conveyor 4 interposed therebetween. There are gaps 9 and 9 between the preheating heaters 5u and 6u installed in the upper part of the furnace 3 and between the main heating heater 7u and the cooler 8u, and the upper muffle 2 in the gap has an outlet. 10 and 10 are formed.

  Discharge pipes 11 and 11 are connected to the discharge port 10, and two fume removal devices 12 and 12 are integrally installed on the upper outside of the reflow furnace. The inlets 13 and 13 of the fume removing devices 12 and 12 are connected. The fume removing device 12 has a box shape, and a front plate (not shown) can be removed so that internal cleaning and maintenance can be easily performed. The top plate 14 of the fume removing device 12 is horizontal, but the bottom plate 15 is inclined so as to descend from the inlet 13 along the flow direction of the fume-containing gas. An outlet 16 is formed at the center of the top plate 14, and a drain pipe 18 having a cock 17 is connected to the center of the bottom plate 15.

  A reflux pipe 19 is connected to the outlet 16 of the fume removing device 12. The reflux pipe is lowered downward, and a blower 20 is installed in the middle, and is further routed laterally below the muffle 2. The recirculating pipe 19 laid sideways is inserted into the furnace from the lower muffle 2 and is inserted into an appropriate place, for example, between the preheated lower heaters 5d and 6d or between the lower heater 7d and the lower cooler 8d. Inserted into the furnace. .

  In the fume removing device 12, a multi-tube type dew condensation means 21 and a long hole side-by-side dew condensation means 22 are installed in order from the flow direction of the fume-containing gas, that is, the direction of the inflow port 13.

  The multi-tube type dew condensation means 21 has a large number of pipes 22 installed vertically. The upper part of the pipes 22... Is fixed in the collection box 23, and the lower part is fixed to the fixed plate 24. A flexible exhaust duct 26 having a suction pump 25 and communicating with the outside of the reflow furnace is connected to the upper portion of the collection box 23. Openings 27 and 28 are respectively formed in the top plate 14 and the bottom plate 15 where the multi-tube type dew condensation means 21 is installed. The opening 27 of the top plate 14 is smaller than the collection box 23, but from the fixed plate 24. And the opening 28 of the bottom plate 15 is smaller than the fixed plate 24. A frame 29 that is horizontal to the bottom plate 15 is fixed to the upper portion of the opening 28 of the bottom plate 15. That is, in order to install the multi-tube dew condensation means 21 in the fume removing device 12, the lower part of the multi-pipe dew condensation means 21 is inserted from the opening 27 of the top plate 15 and the mounting plate 24 is placed on the frame 29. The collection box 23 is placed on the periphery of the opening 27 of the top plate 15. And the flange formed in the circumference | surroundings of the collection box 23 is fixed with the clamp which is not shown in figure, and an upper and lower mounting part will be in a sealing state with a removal apparatus. If a large amount of fumes adhere to the surface of the pipes 22 and the effect of dew condensation becomes poor, the clamp is removed, and then the multi-tube dew condensation means 20 is pulled up and washed with a solvent.

  The long hole side-by-side dew condensation means 30 has a large number of rectangular long holes 31... Arranged in the flow direction. The long hole side-by-side dew condensation means 30 has a block shape and is easily installed on the pedestal 32. The long hole side-by-side dew condensation means is removed from the pedestal 32 when a large amount of fumes adheres in the long holes 31.

  Next, the operation state in the reflow furnace of the said Example 1 is demonstrated. A solder paste is applied, and a printed circuit board P on which electronic components are mounted on the application part is placed on the conveyor 4 and conveyed in the direction of arrow A. First, the printed circuit board is heated to 100 to 150 ° C. by preheating heaters 5u, 5d, 6u, and 6d installed at the upper and lower portions in the furnace 3. At this time, the solvent in the solder paste is volatilized to form a fume, and the solid component in the solder paste is melted. The printed circuit board is further transferred to the main heaters 7u and 7d, where it is heated to 220 to 250 ° C. Here, the solder powder in the solder paste is melted and spreads wet in the soldered portion, and at the same time, the solid component in the molten state is exposed to a high temperature and becomes a fume. The solvent fume and the solid component fume float in the furnace 3.

  At this time, the blower 20 already installed in the reflux pipe 19 is operated. The gas in the removing device 12 is sucked in the direction of the reflux pipe 19 by the operation of the blower 20. Therefore, the pressure in the fume removing device 12 becomes negative, the gas in the discharge pipe 11 connected to the inlet 13 of the removing device 12 is drawn to the removing device 12, and the fume in the furnace 3 connected to the discharge pipe 11. The contained gas is drawn into the discharge pipe 11. In other words, the fumes-containing gas floating in the furnace 3 flows into the removing device 12 from the outlet 10 of the reflow furnace 1 through the outlet pipe 11 as indicated by the solid line arrow. Since the gas flows directly from the furnace, the temperature is high.

  The fume-containing gas that has flowed into the removal device 12 first passes through the multi-tube dew condensation means 21. At this time, since the suction fan 25 of the exhaust duct 26 connected to the collection box 23 at the upper part of the multi-tube type dew condensation means 21 sucks outside air from below the pipes 22.・ ・ Is cooled by outside air. Therefore, the high-temperature fume-containing gas passing through the multi-tube dew condensation means 21 is cooled by the pipes 22.

  The fume-containing gas from which the temperature has dropped and a certain amount of fumes has been removed then passes through the long holes 31... Of the long hole side-by-side dew condensation means 30 as indicated by arrows. At this time, the fume-containing gas is cooled while passing through the long passage and is condensed on the wall surface of the elongated hole 31. However, since the temperature of the fume-containing gas is lowered by the multi-tube type condensation means 21, the fume-containing gas is also here. Condensation is likely. Also, if the long hole side-by-side dew condensation means is made of aluminum with good heat conduction, the fume-containing gas will be deprived of heat by the long hole side-by-side dew condensation means and the temperature will decrease, making it easier to condense. is there.

  The gas from which the fumes have been removed is drawn by the blower 20 and enters the upper reflux pipe 19 from the outlet 16 of the fume removing device 12, and is introduced into the furnace 3 from a plurality of locations by the lower reflux pipe 19. A part of the reflux pipe is introduced into the furnace 3 from between the lower heaters 5d and 6d and from between the lower heater 7d and the lower cooler 8d.

  Next, a second embodiment of the reflow furnace according to the present invention will be described with reference to FIGS. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  In the fume removing device 12, a multi-tube type dew condensation means 21 and a labyrinth type dew condensation means 33 are installed in order from the flow direction of the fume containing gas, that is, the direction of the inflow port 13. In the labyrinth type dew condensation means, a large number of plate members 34... Are suspended from the upper part, and a large number of plate members 35. The labyrinth structure is separated from the bottom plate 15 and the upper ends of the lower plate members 34 are separated from the top plate 14. The lower plate member 35 is erected on a standing plate 36, and the erected plate is detachably placed on the bottom plate 15 of the box-shaped fume removing device 12. Therefore, when a large amount of solid fume adheres to the lower plate member 35, the standing plate 36 is taken out and washed with a solvent.

  Here, the operation state in the reflow furnace of the said Example 2 is demonstrated. Description of the same contents as those in the first embodiment is omitted.

  The fume-containing gas from which the temperature has been lowered by the passage of the multi-tube dew condensation means 21 and from which a certain amount of fumes has been removed then passes between the many plate members 34 and 35 of the labyrinth type dew condensation means 33 as indicated by arrows. To do. At this time, the fume-containing gas is cooled while passing through the long passage and is condensed on the surfaces of the plate members 34 and 35. However, the temperature of the fume-containing gas is lowered by the previous multi-tube type condensation means 21, so that But it is easy to condense.

  A third embodiment of the reflow furnace according to the present invention will be described with reference to FIGS. The same parts as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted.

  The fume-containing gas from which the temperature has been lowered by the passage of the previous multi-tube dew condensation means 21 and from which a certain amount of fume has been removed is dispersed in a wide range while the fume is removed by the elongated hole-type dew condensation means 30. . Thereafter, the fume-containing gas dispersed over a wide range passes through a large number of plate members 34 and 35 of the labyrinth type dew condensation means 33. At this time, the fume-containing gas is cooled while passing through the passage between the long plate materials and is condensed on the surface of the plate material, but the fume-containing gas is condensed because the temperature is lowered by the multi-tube type condensation means 21 described above. Cheap.

  Since the dew condensation means used in the present invention can be removed, when a large amount of solid fume adheres to these dew condensation means, remove the front plate (not shown), take out each dew condensation means and wash it with a solvent. Then, after cleaning, it is installed again at a predetermined position to remove the fumes from the fumes-containing gas. Further, the liquid fume adhering to each dew condensation means drips downward and reaches the bottom plate 15. At this time, since the bottom plate 15 is inclined, the liquid fume flows along the inclined bottom plate 15 to the inclined lower portion. A drain 18 is installed at the lower part of the slope, and if liquid fumes accumulate in the lower part of the slope, the drain cock 17 is opened to allow the liquid fumes to flow out and be recovered.

  In the embodiment of the present invention, the discharge ports formed in the muffle of the furnace have been described as being formed in two places between the preheating heater and between the main heating heater and the cooler. You may form in a location. Further, when the gas from which the fumes have been removed is returned to the furnace, it may be returned to an appropriate position of the muffle, not only between the lower heaters or between the lower heater and the cooler as in the embodiment.

  The present invention is suitable for a reflow furnace using a solder paste, but can also be used when using fumes that are generated during heating, such as an adhesive or a conductive paste, in addition to the solder paste.

Is a front sectional view of the first embodiment of the reflow furnace of the present invention. Partial enlarged sectional view of the fume removing device The perspective view which removed the front board and top plate of FIG. Front sectional view of a second embodiment of the reflow furnace of the present invention Partial enlarged sectional view of the fume removing device The perspective view which removed the front board and top plate of FIG. Front sectional view of a third embodiment of the reflow furnace of the present invention Partial enlarged sectional view of the fume removing device The perspective view which removed the front board and top plate of FIG. Rectangular shaped long hole side-by-side dew condensation means Honeycomb long hole side-by-side dew condensation means Corrugated long hole side-by-side dew condensation means

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflow furnace 2 Muffle 3 Furnace 4 Conveyor 12 Fume removal apparatus 21 Fume removal apparatus 30 Elongated hole type dew condensation means 33 Labyrinth type dew condensation means

Claims (3)

Appropriate positions in the outlet of the reflow furnace is provided with, together with and the inlet of the fumes removal apparatus of the exhaust outlet and the box-shaped body are connected by a pipe, the inside the fume removal device has multiple condensation means are installed, also the outlet of the fumes removal apparatus is connected to the appropriate position of the reflow furnace in the pipe, a reflow furnace, characterized in that the removal of fumes from the fume-containing gas by condensation of the fumes each condensation section In
In the fume removing device, a multi-tube dew condensation unit, a long-hole dew condensation unit, a labyrinth dew condensation unit, a multi-pipe dew condensation unit, a labyrinth dew condensation unit, and a long-hole dew condensation unit are sequentially arranged in the flow direction of the fume-containing gas. A reflow furnace characterized by being installed . The fume removal device are denoted by the declination downward the bottom plate of the box-like body along the fume flow direction, a reflow furnace according to claim 1, characterized in that the drain is attached to the bottom. The fume removal device inlet on each side are formed, have an outlet flow at the center is formed, a reflow furnace according to claim 1, wherein a plurality of condensing means symmetrically are installed

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