JP2007281394A - Flux gas removal method for reflow soldering apparatus and reflow soldering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflow soldering unit and a method for removing flux gas in the reflow soldering unit by efficiently cooling and liquidizing flux gas in a furnace ambient gas via a cooling module in a chiller and easily removing flux adhered on the surface of the cooling module. <P>SOLUTION: A chiller 15 with a cooling machine 14 produces frost on a surface of a cooling module 26. In this way, it cools an ambient gas fed to the cooling module 26 and retained in a furnace 1 and liquidizes flux gas in such a way that flux collects on the surface of steam, resulting in flux gas removal. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and an apparatus for removing a flux gas contained in an atmospheric gas in a furnace in a reflow soldering process.

  In general, a reflow soldering apparatus has a preheating chamber, a reflow chamber, and a cooling chamber in order in a furnace along a conveyor conveyance line, and a substrate on which electronic components are mounted is conveyed in the furnace by the conveyor. The board on which the electronic components are mounted is coated with paste-like cream solder at the soldering location, heated to a predetermined high temperature in the preheating chamber, and heated to a high soldering temperature in the reflow chamber. Cream solder is melted. Then, the molten solder is cooled and solidified while passing through the cooling chamber following the reflow chamber, and the soldering is completed.

  In the reflow soldering process, when the cream solder applied to the substrate is heated, flux, alcohol, and the like contained in the cream solder are evaporated as gas (hereinafter referred to as flux gas). When the flux gas is cooled, it liquefies and solidifies (hereinafter simply referred to as liquefaction), and there is a problem of adhering to the wall surface of the cooling chamber in the furnace, the substrate being transported, and the like.

  In the case of a reflow soldering apparatus in which the atmosphere gas is an inert gas such as nitrogen gas, the furnace is maintained at a predetermined oxygen concentration in order to keep the soldering quality constant. An oxygen concentration meter is provided to detect the oxygen concentration of the gas.

  Commonly used oxygen concentration meters are equipped with electrodes of zirconia and platinum. These electrodes are broken by impure gas such as isopropyl alcohol, and if impure gas is mixed, it burns and consumes oxygen, which affects the oxygen concentration. There is a problem such as giving.

  In order to solve the above problems, the high-temperature atmosphere gas in the furnace is taken into the cooling device, brought into contact with the surface of the cooling part of the cooling device and cooled, and the flux gas contained in the atmosphere gas is liquefied. Collecting is generally performed (see Patent Document 1 and Patent Document 2).

The cooling device is generally configured so that the cooling unit can be detached. When cleaning and removing the flux adhering to the cooling unit, the cooling unit is removed from the cooling device, and the flux adhering to the surface of the cooling unit is removed from the alcohol. It is cleaned and removed using chemicals such as
JP-A-5-50218 JP 2005-191177 A

  The problem to be solved by the present invention is that the flux gas contained in the atmospheric gas in the furnace is efficiently cooled and liquefied in the cooling part of the cooling device, and the flux adhering to the surface of the cooling part is easily removed. It is an object of the present invention to provide a flux gas removing method and apparatus for a reflow soldering apparatus.

In order to solve the above problems, the present invention employs the following means. That is,
The present invention is directed to a flux gas removal method for a reflow soldering apparatus in which the atmosphere gas in the furnace is guided to a cooling device and cooled by a cooling unit of the cooling device to remove the flux gas contained in the atmosphere gas. Frost is made to adhere to the surface of the cooling part of the apparatus, and atmospheric gas is brought into contact with the surface of the frost to cool and remove the flux gas contained in the atmospheric gas.

  Although the atmospheric gas may be directly guided to the cooling unit of the cooling device, it is preferable to cool by air or water before the atmospheric gas is brought into contact with the frost surface of the cooling unit.

  The atmospheric gas from which the flux gas has been removed by the cooling device is returned to the furnace or supplied to an oxygen concentration meter that detects the oxygen concentration in the furnace.

  The reflow soldering apparatus of the present invention is a reflow soldering apparatus that guides atmospheric gas in a furnace to a cooling device and cools it by a cooling unit of the cooling device, wherein the cooling unit surface of the cooling device is set to a temperature below the frost point. It is characterized by being.

  Since the present invention causes frost to adhere to the cooling section and liquefies the flux gas, the following effects are achieved. Since the frost temperature is low and the surface of the frost is uneven and has a large surface area, the flux gas can be efficiently cooled and liquefied. In addition, since the flux adheres to the surface of the frost, when removing the flux adhering to the cooling unit, the frost melts by stopping the cooling of the cooling unit of the cooling device, and the flux is also removed together with the melted frost. Therefore, it is possible to easily remove the flux adhering to the cooling unit. Incidentally, conventionally, the flux adhering to the cooling unit is cleaned and removed using a chemical such as alcohol, which takes time, cost and cost.

  If the atmosphere gas is cooled by air or water before contacting the frost surface of the cooling unit, the flux gas can be cooled and liquefied by air cooling or water cooling and removed. Furthermore, since the temperature of the atmospheric gas sent to the cooling part to which the frost is attached can be lowered, the cooling liquefaction of the flux gas in the cooling part to which the frost is attached can be performed more effectively.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the reflow soldering apparatus includes three preheating chambers 2, one reflow chamber 3, and one cooling chamber 4 in a furnace 1. It has in order along. In each chamber 2, 3, 4, an inert gas, in this embodiment nitrogen gas, is supplied to prevent solder oxidation, and the printed circuit board 6 on which electronic components are mounted is placed in the furnace 1 by the conveyor 5. Be transported. The printed circuit board 6 on which electronic components are mounted has paste-like cream solder applied to the soldering locations.

  As shown in FIGS. 1 and 3, 7 is a blower, 8 is a motor that drives the blower 7, 9 is a heater, and 10 is a wind guide device. Thus, the hot air circulation device 11 is configured, and the hot air circulation device 11 is provided above and below the preheating chamber 2 and the reflow chamber 3 with the conveyor 5 interposed therebetween. In the cooling chamber 4, cooling air circulation devices 12 are provided above and below the conveyor 5. The cooling air circulation device 12 is different from the hot air circulation device 11 only in that it does not include a heater, and the other configurations are the same.

Therefore, in the preheating chamber 2 and the reflow chamber 3, the atmospheric gas in the furnace 1 heated by the heater 9 is sucked into the blower 7 from the suction port facing the rotation axis direction of the blower 7 and provided in the radial direction of the blower 7. The air is discharged from the discharge port to the air guide device 10, guided by the air guide device 10, and sprayed onto the printed circuit board 6 on the conveyor 5 from a plurality of gas outlets. Thereafter, as described above, the atmospheric gas is sucked from the suction port of the blower 7 and discharged from the discharge port. In this manner, the atmospheric gas is circulated through the chambers 2 and 3 by the hot air circulation device 11 and the printed circuit board 6 is heated. In the cooling chamber 4, atmospheric gas as cooling air circulates in the cooling chamber 4 to cool the printed circuit board 6 on the conveyor.

  Therefore, the printed circuit board 6 on which electronic components are mounted is heated to a predetermined temperature in the preheating chamber 2 while being conveyed by the conveyor 5, and then the cream solder is heated and melted in the reflow chamber 3, and the molten solder is cooled in the cooling chamber 4. Once solidified, the electronic component is soldered onto the substrate.

  In the above reflow soldering process, when the cream solder applied to the substrate is heated, the flux or alcohol contained in the cream solder evaporates as a gas, and the flux gas is cooled in the cooling chamber 4 or the like. Then, it liquefies and adheres to the wall surface of the cooling chamber 4 or the like, the printed board 6 to be conveyed, or the like. Therefore, in this embodiment, as shown in FIG. 2 and the like, a part of the atmospheric gas in the cooling chamber 4 is air-cooled by the air-cooling radiator 13 and further cooled by the cooling device 15 by the refrigerator 14. By doing so, the flux gas contained in the atmospheric gas is liquefied and removed, and the atmospheric gas from which the flux gas has been removed is returned to the cooling chamber 4.

  The air-cooled radiator 13 will be described with reference to FIGS.

The air-cooling radiator 13 has a plurality of cooling cylinders 16 that are vertically arranged at intervals. The cooling cylinder 16 has a gas passage in the vertical direction, cooling fins 17 are fixed between adjacent cooling cylinders 16, and an air guide case 18 and a blower 19 are provided adjacent to the plurality of cooling cylinders 16. ing. Accordingly, the external air is sent into the air guide case 18 by the blower 19, flows into the cooling cylinder 16 through the air guide case 18, passes through the gap between the adjacent cooling cylinders 16, and goes to the opposite side. Go through.

  Air guide cases 20 and 21 are provided in communication with the upper and lower ends of the plurality of cooling cylinders 16, respectively. An air guide duct 22 is connected to the upper air guide case 20, and the tip of the air guide duct 22 extends to the side wall of the cooling chamber 4 of the furnace 1. On the other hand, a wind guide duct 23 is connected to the side wall portion of the casing 10a of the wind guide device 10 in the cooling air circulation device 12 below the cooling chamber 4, and the tip of the wind guide duct 23 is connected to the air cooling radiator 13 side. The air guide duct 22 and the side wall of the cooling chamber 4 are connected in an airtight manner.

  Therefore, a part of the atmospheric gas discharged to the air guide device 10 by the blower 7 of the cooling air circulation device 12 flows into the air guide duct 23, passes through the air guide duct 22 and the air guide case 20, and the air cooling radiator 13. It flows into the cooling cylinder 16. The atmospheric gas flowing in the cooling cylinder 16 is cooled by the external air flowing in the gap between the adjacent cooling cylinders 16, and the flux gas contained in the atmospheric gas is cooled and liquefied and adheres to the inner surface of the cooling cylinder 16. To be removed.

  Next, the cooling device 15 by the refrigerator 14 will be described with reference to FIGS.

  The cooling casing 24 is a square box surrounded by six surfaces, and has a first gas passage space 25 at the upper end for allowing the atmospheric gas after air cooling to flow into the furnace 1 as it is, and the atmosphere after air cooling. A second gas passage space 27 is provided below the first gas passage space 25 for allowing gas to flow in and cooling in the cooling unit 26 and then returning to the furnace 1.

  The first gas passage space 25 is partitioned and formed at the upper end portion in the cooling casing 24 by a horizontal partition wall 28 and a vertical partition wall 29 provided in the cooling casing 24. The end of the horizontal partition wall 28 in the gas flow direction extends to the front of the side wall of the cooling casing 24, and the first gas passage space 25 is formed at the opening 30 between the end and the side wall of the cooling casing 24. Communicates with the second gas passage space 27. The opening 30 is a shutter member 31 which is provided on the horizontal partition wall 28 so as to be movable back and forth and can be fixed at a predetermined position so that the opening area can be adjusted. In the present embodiment, the atmospheric gas flowing in from the air-cooled radiator 13 side is configured to flow 75% to the first gas passage space 25 side and 25% to the second gas passage space 27 side.

The other end of the horizontal partition wall 28 extends to the front of the side wall of the cooling casing 24, and a vertical partition wall 29 is connected to the end thereof. 32 is an air duct that is connected to the upper wall portion of the cooling casing 24 and communicates with the first gas passage space 25 of the cooling casing 24, and the front end of the duct 32 is connected to the cooling chamber 4 of the furnace 1.

  In the second gas passage space 27, a pair of cooling units 26 of the refrigerator 14 are provided vertically. The cooling unit 26 has a large number of cooling fins 34 (see FIGS. 4 and 6) on the upper surface of the refrigerant passage forming plate 33. The refrigerant passage forming plate 33 has a refrigerant passage 35 (see FIG. 7) inside, and a channel-shaped cover plate member 36 (see FIGS. 4 and 6) having an open front and rear is disposed on the upper surface. The cover plate member 36 has vertical plates standing on the left and right ends of the horizontal cover plate, and a plurality of cooling fins 34 are arranged on the lower surface inside the cover plate member 36 and spaced from each other. It is disposed on the refrigerant passage forming plate 33. Each cooling fin 34 is a single vertical plate, and the upper end surface is formed on an inclined surface that inclines upward from the inlet toward the outlet. The refrigerant of the refrigerator 14 is configured to flow into the refrigerant passage 35 from the inlet of the refrigerant passage 35 of the refrigerant passage forming plate 33, flow through the refrigerant passage 35, and return from the outlet.

  In the above, when the height of the cooling fins 34 is made constant, the flux is concentrated on the inlet portion and the passage between the cooling fins 34 is easily clogged. For this reason, in the present embodiment, the height of the cooling fin 34 is increased from the inlet toward the outlet. Further, in this case, even if the flux is concentrated on the inlet portion, the space of the inlet portion is wide, so that the passage can be prevented from being clogged with the flux.

  An air guide case 21 on the air-cooling radiator 13 side is connected to the upper surface on the inlet side of the first gas passage space 25 in the cooling casing 24. 37 is an air duct that is connected to the upper wall portion of the cooling casing 24 and communicates with the second gas passage space 27 of the cooling casing 24, and the tip of the duct 37 is connected to the cooling chamber 4 of the furnace 1.

  In the present invention, the surface temperature of the cooling fin 34 of the cooling unit 26 is set to a temperature equal to or lower than the frost point by the cooling device 15 using the refrigerator 14, and cooling is performed by attaching frost to the surface of the cooling fin 34. The atmosphere gas flowing between the fins 34 is cooled to liquefy the flux gas, and the flux is attached to the surface of the frost.

  Hereinafter, the operation of the reflow soldering apparatus will be described.

  While the printed circuit board 6 on which electronic components are mounted is conveyed in the furnace 1 by the conveyor 5, the cream solder on the printed circuit board 6 is brought to a predetermined temperature by the heated atmospheric gas (hot air) circulating in the preheating chamber 2. The molten solder is heated and melted by the heated atmospheric gas (hot air) circulating in the reflow chamber 3, and the molten solder is cooled and solidified by the atmospheric gas (cooling air) circulating in the cooling chamber 4 in the cooling chamber 4, Electronic components are soldered onto the substrate.

  When the cream solder applied to the printed circuit board 6 is heated in the preheating chamber 2 and the reflow chamber 3, the flux or alcohol contained in the cream solder evaporates as a gas, and the flux gas is mixed into the atmosphere gas. Is done.

  When this atmospheric gas is discharged to the wind guide device 10 by the blower 7 in the cooling chamber 4, a part thereof flows into the wind guide duct 23 connected to the wind guide device 10, and enters this duct 23. The air flows into the cooling cylinder 16 of the air-cooled radiator 13 through the air guide duct 22 and the air guide case 20 that are connected in communication. The atmospheric gas flowing in the cooling cylinder 16 is cooled by the external air flowing in the gap between the adjacent cooling cylinders 16, and the flux gas contained in the atmospheric gas is cooled and liquefied and adheres to the inner surface of the cooling cylinder 16. To be removed.

  Since the air cooling radiator 13 is configured to be removable, when removing the flux adhering to the cooling cylinder 16, the air cooling radiator 13 is removed and the flux adhering to the inner surface of the cooling cylinder 16 is washed with a chemical such as alcohol. Removed.

  The atmospheric gas cooled by the air-cooling radiator 13 flows from the air guide case 21 into the cooling casing 24 of the cooling device 15. The atmospheric gas flowing into the cooling casing 24 flows 75% into the first gas passage space 25 and 25% flows into the second gas passage space 27.

  The atmospheric gas flowing through the first gas passage space 25 returns to the cooling chamber 4 of the furnace 1 through the air duct 32.

  The atmospheric gas that has flowed into the second gas passage space 27 flows through the gas passage between the cooling fins 34 of the cooling unit 26, is cooled by the cooling fins 34 with frost, and is contained in the atmospheric gas. Is cooled and liquefied, and the flux adheres to the surface of the frost and is removed.

  The atmospheric gas from which the flux gas has been removed returns to the cooling chamber 4 of the furnace 1 through the air guide duct 37.

  Since the cover plate member 36 and the cooling fin 34 of the cooling unit 26 are configured to be detachable from the cooling casing 24, when removing the flux adhering to the cooling fin 34, the cover plate member 36 and the cooling fin 34 of the cooling unit 26 are cooled. If the fins 34 are taken out from the cooling casing 24, the frost adhering to the cooling fins 34 melts, and the flux is removed together with the melted frosts. Therefore, it is possible to easily remove the flux adhering to the cooling fins 34. .

  In the above embodiment, a part of the air-cooled atmospheric gas is led to the cooling unit 26 of the cooling device 15 according to the capacity of the refrigerator 14. However, the total amount of the air-cooled atmospheric gas is increased by increasing the capacity of the refrigerator. Of course, it may be configured to guide the air to the cooling unit 26 of the cooling device 15.

  In the present embodiment, the ambient gas is air-cooled before being cooled by the cooling unit 26 of the cooling device 15, but is configured to be directly cooled by the cooling unit 26 of the cooling device 15 without being cooled by air or water. You can also.

  Moreover, in this embodiment, although the flux gas contained in the atmospheric gas in the cooling chamber 4 of the furnace 1 was removed and returned to the cooling chamber 4 again, the present invention is not limited to this. Needless to say.

  Moreover, although what used nitrogen gas as an atmospheric gas in the furnace 1 was shown in this embodiment, atmospheric gas is not restricted to nitrogen gas. For example, air may be used.

  Moreover, in this embodiment, although the structure which removes the flux gas contained in the atmospheric gas in the furnace 1 and returns in the furnace 1 was shown, this invention is not restricted to this, The inside of the furnace 1 is shown. Needless to say, the present invention may be applied to a line for supplying atmospheric gas in the furnace 1 to an oxygen concentration meter for detecting the oxygen concentration.

It is a front view which shows the furnace of a reflow soldering apparatus. It is explanatory drawing which shows the structure of one Embodiment of this invention. It is a longitudinal cross-sectional view which shows the reflow soldering apparatus in one Embodiment of this invention. It is a longitudinal section showing an air cooling radiator and a cooling device. It is a front view which shows an air-cooling radiator (a fan and a wind guide case are abbreviate | omitted). It is a longitudinal cross-sectional view which shows a cover board member and a cooling fin. It is a top view of a refrigerant passage formation board.

Explanation of symbols

  1 .... Furnace, 2 .... Preheating chamber, 3 .... Reflow chamber, 4 .... Cooling chamber, 5 .... Conveyor, 6 .... Printed circuit board with electronic parts, 7 .... Blower, 8 .... Motor, 9 ..Heater, 10 .. Air guide device, 10 a... Air guide casing, 11 ..Hot air circulation device, 12 ..Cooling air circulation device, 13 ..Air cooling radiator, 14 .. Refrigerating machine, 15. , 16 ··· Cooling tube, 17 ··· Cooling fins, 18 · · Air guide case, 19 · · Blower, 20, 21 · · Air guide case, 22, 23 · · Air guide duct, 24 · · Cooling casing, 25 ..First gas passage space, 26 ..Cooling section, 27 ..Second gas passage space, 28 ..Horizontal partition wall, 29 ..Vertical partition wall, 30 ..Opening portion, 31 ..Shutter member, 32 ..Air guide ducts, 33 .. Refrigerant passage forming plates, 34 .. Cooling fins, 35 .. Medium passage, 36 ... cover plate member, 37 ... air guide duct.

Claims (5)

  In the flux gas removal method of the reflow soldering apparatus, wherein the atmosphere gas in the furnace is guided to the cooling device and cooled by the cooling unit of the cooling device to remove the flux gas contained in the atmosphere gas, the cooling unit of the cooling device A flux gas removing method for a reflow soldering apparatus, wherein frost is attached to the surface of the frost, and an atmosphere gas is brought into contact with the surface of the frost to cool the flux to remove the flux gas contained in the atmosphere gas.   2. The flux gas removing method for a reflow soldering apparatus according to claim 1, wherein the ambient gas is cooled by air or water before it is brought into contact with the frost surface of the cooling section.   3. The method for removing a flux gas from a reflow soldering apparatus according to claim 1, wherein the atmospheric gas from which the flux gas has been removed by a cooling device is returned to the furnace.   3. The flux gas removal method for a reflow soldering apparatus according to claim 1, wherein the atmospheric gas from which the flux gas has been removed by a cooling device is supplied to an oxygen concentration meter that detects the oxygen concentration in the furnace.   In the reflow soldering apparatus for introducing the atmospheric gas in the furnace to the cooling device and cooling it by the cooling unit of the cooling device, the surface of the cooling unit of the cooling device is set to a temperature below the frost point. apparatus.

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