JP4368672B2 - Circuit board heating apparatus and method, and reflow furnace equipped with the heating apparatus - Google Patents

Description

  The present invention relates to a heating apparatus and a heating method for heating a circuit board on which an electronic component is mounted by blowing hot air in an atmosphere gas, and a reflow furnace for soldering a circuit board using the heating apparatus.

  Currently, SMD (Surface Mounted Device) in which various electronic components are mounted on the surface of a circuit board and soldered is widely used in electronic devices. In order to manufacture this SMD, in many cases, an electronic component is mounted on a circuit board on which cream solder is printed, and soldering is performed by heating in a reflow furnace. This reflow furnace heats the circuit board while the circuit board on which the electronic components are mounted is transported horizontally by the transport device in the furnace, thereby melting the solder and soldering the circuit board and the electronic parts. It is a heating furnace that performs. This reflow furnace is usually an atmosphere furnace, and the circuit board is heated in an atmosphere gas such as nitrogen to prevent oxidation or the like that occurs during soldering.

  As a circuit board heating apparatus, a heating apparatus that blows hot air on the circuit board to melt the solder is widely used. This heating device includes a circulation fan that circulates the atmospheric gas in the reflow furnace, a heater that heats the circulated atmospheric gas, and a spray nozzle that blows the heated atmospheric gas onto the circuit board. This heating device is installed above and below the circuit board and heats the upper and lower surfaces of the circuit board.

The heating method using this heating apparatus is as follows.
Atmospheric gas is circulated in the furnace by a circulation fan. And after circulating atmospheric gas is heated with a heater, it blows off from a blowing nozzle, is sprayed on a circuit board, and heats a circuit board. After that, while being sucked by the circulation fan and circulating in the furnace, it is again heated by the heater and the same cycle is repeated. By the above, the circuit board conveyed one after another can be heated.

  In this heating apparatus, in order to effectively heat the circuit board, a method of blowing hot air onto the circuit board is important. For this reason, various proposals have been made for a blowout nozzle for blowing out hot air.

As an example, as shown in FIG. 7A, a hot air blowing unit 106 that blows the heated atmospheric gas onto the circuit board 102 that is carried in the direction of arrow A by the carrying device, and hot air suction that draws in the blown hot air A heating device provided with the section 107 has been proposed. Further, the hot air blowing portion 106 and the hot air suction portion 107 are installed at an interval shorter than the length of the circuit board 102. (See Patent Document 1.)
In FIG. 7A, the flow of hot air is indicated by arrows, but in this heating apparatus, the atmospheric gas heated by a hot air generator (not shown) is blown out from the hot air blowing unit 106 and the circuit board 102. Heat up. Then, the bounced atmospheric gas is sucked by the hot air suction unit 107 and returned to the hot air generation unit again, and the same cycle is repeated.
Japanese Patent No. 2682138

In the above-described heating device, the heat transfer rate between the atmospheric gas to be sprayed and the circuit board 102 can be increased by shortening the installation interval between the hot air blowing unit 106 and the hot air suction unit 107. However, in the structure of the hot air blowing part 106 and the hot air suction part 107 shown in Patent Document 1, there is a limit in reducing the installation interval.
In addition, the circuit board 102 that is transported horizontally has a strong heating area in which the upper and lower sides are sandwiched between hot air blowing parts 106 and is heated strongly, and the upper and lower parts are sandwiched in a hot air suction part 107 and is weakly heated. The area will be heated while passing alternately. Therefore, since it is not heated uniformly, it does not affect the quality of soldering. In addition, the temperature of the circuit board that has risen in the strong heating region may decrease in the weak heating region, resulting in a problem that the heating efficiency is lowered as compared with the case where uniform heating is possible.

  Furthermore, in this heating apparatus, the atmospheric gas that bounces off the circuit board 102 is sucked into the hot air suction portion 107 (see FIG. 7A), but the circuit board as shown in FIG. 7B. In the state where 102 does not exist, the atmospheric gas is not rebounded, so it is considered that not only the hot air suction part 107 on the blowing side but also the hot air suction part 107 on the opposite side is reached and sucked.

Therefore, it is considered that the flow of the atmospheric gas circulating in the reflow furnace varies greatly depending on the presence or absence of the circuit board 102 accompanying the conveyance, and the furnace pressure in the reflow furnace varies greatly accordingly.
In a reflow furnace, an atmosphere gas such as nitrogen gas is filled in the furnace, and the furnace pressure is set slightly higher than the outside air to prevent the outside air from flowing into the furnace. If the furnace pressure fluctuates, it is necessary to supply a larger amount of atmospheric gas into the furnace in order to prevent outside air from flowing even when the furnace pressure is lowered. In this case, since the average furnace pressure rises, the flow rate of the non-atmospheric gas flowing out of the furnace also increases, and the consumption of the atmospheric gas further increases.
These atmospheric gases such as nitrogen are expensive and cause a problem that the running cost for operating the reflow furnace increases.

  Accordingly, the object of the present invention is to solve the above-mentioned problems, to increase the heating efficiency by uniformly heating the circuit board, and to reduce the fluctuation of the furnace pressure accompanying the conveyance of the circuit board, thereby reducing the atmospheric gas. An object of the present invention is to provide a circuit board heating apparatus and method, and a reflow furnace equipped with this heating apparatus.

In order to achieve the above object, a first embodiment of a circuit board heating apparatus according to the present invention is configured so that a circuit board transported by a transport apparatus in a shell filled with an atmospheric gas is heated for each heating zone. A heating device for setting and heating, wherein a circulation fan that circulates the atmospheric gas in the shell, a discharge passage on the discharge side of the circulation fan, and a suction passage on the suction side of the circulation fan are provided independently. The heating device chamber, the heater that heats the atmospheric gas circulated by the circulation fan, the atmospheric gas heated by the heater is blown out, the blowing nozzle that blows on the circuit board, and the atmospheric gas in the shell is sucked into the circulation fan The suction panel is provided with a suction-only area where only the suction port is arranged, and a mixed area where the blow- out nozzle and the suction port are arranged close to each other. It is characterized by that.

  In another embodiment of the circuit board heating apparatus of the present invention, the suction-only area is composed of a row of suction ports arranged perpendicular to the conveyance direction of the circuit board, and the pitch between the rows is one of the zone length. / 4 or more and 1 or less.

  In another embodiment of the circuit board heating device of the present invention, the suction-only area is composed of a row of suction ports arranged in parallel with the conveyance direction of the circuit board, and this row is more than the conveyance rail of the conveyance device. It is installed outside.

  Another embodiment of the circuit board heating device of the present invention is characterized in that the blowout nozzles and the suction ports are arranged alternately in the mixed region.

  Another embodiment of the circuit board heating device of the present invention is characterized in that the nozzle port and the suction port of the blowout nozzle are arranged in the same plane in the mixed region.

  Another embodiment of the apparatus for heating a circuit board according to the present invention is characterized in that, in the mixed region, the blowing nozzles are arranged so as to form vertices of squares, rhombuses, or equilateral triangles.

  Another embodiment of the circuit board heating device of the present invention has a relationship of 2 <P / D <6 when the nozzle opening has a circular shape with a diameter D and the blowout nozzles are arranged at a pitch P. It is characterized by that.

  Another embodiment of the circuit board heating device of the present invention is characterized in that the suction pressure from the suction port is a suction pressure of 150 Pa or less.

  Another embodiment of the circuit board heating device of the present invention is characterized in that the blow-out flow path is disposed outside the suction flow path.

  A first embodiment of the reflow furnace of the present invention is a reflow furnace for soldering a circuit board using the above-described circuit board heating apparatus.

The first embodiment of the method for heating a circuit board according to the present invention is a method in which an atmosphere gas is filled in a shell, the temperature is set for each heating zone, and the circuit board is heated while being conveyed by a conveying device. A step of circulating the atmospheric gas in the shell with a circulation fan, a step of heating the atmospheric gas circulated by the circulation fan with a heater, and blowing out the atmospheric gas heated by the heater using the blow nozzle of the blow panel , A step of spraying the circuit board and a step of sucking the atmospheric gas in the shell into the circulation fan using the suction port of the blow-out panel, and sucking in the atmospheric gas in a suction-only area where only the suction port is arranged. performed, the nozzle port of the blowing nozzle has a circular diameter D, and when the blowing nozzle is arranged at a pitch P, having a 2 <relationship P / D <6 In a mixed region blowing nozzle and the suction port is arranged close, and performs suction and blow-out of the atmosphere gas.

  In another embodiment of the method for heating a circuit board according to the present invention, the suction-only region is composed of a row of suction ports arranged perpendicular to the conveyance direction of the circuit board, and the pitch between the rows is one of the zone length. / 4 or more and 1 or less.

  In another embodiment of the method for heating a circuit board according to the present invention, the suction-only area is composed of a row of suction ports arranged in parallel with the transport direction of the circuit board, and this row is more than the transport rail of the transport device. It is installed outside.

  Another embodiment of the method for heating a circuit board according to the present invention is characterized in that atmospheric gas is sucked from the suction port at a suction pressure of 150 Pa or less.

In the circuit board heating device and heating method of the present invention, and in a reflow furnace equipped with this heating device, a mixed region in which the blowout nozzle and the suction port are arranged close to each other, and a suction dedicated in which only the suction port is arranged By providing the region, it is possible to uniformly heat the circuit board, and high heating efficiency can be obtained.
In addition, since the fluctuation of the flow of the atmospheric gas accompanying the conveyance of the circuit board is smaller than that of the conventional heating device, the fluctuation of the furnace pressure can be suppressed, and the consumption of the atmospheric gas can be reduced. .
In addition, by appropriately arranging the blowing nozzles, it is possible to obtain excellent heating performance and to appropriately balance the blowing and sucking of the atmospheric gas.
Furthermore, by arranging the outlet side flow path outside the suction side flow path, the sealing performance and the maintenance performance can be improved, and the running cost and the like can be reduced.

Embodiments of the present invention will be described in detail with reference to the drawings.
(Description of the entire reflow furnace)
FIG. 1 shows an embodiment of a reflow furnace equipped with the heating device of the present invention. The circuit board on which the electronic component is mounted is transported horizontally in the direction of arrow A inside the reflow furnace by a transport device (not shown). The reflow furnace is composed of a 9 zone heating zone and a 2 zone cooling zone. The furnace body has a seal structure and is filled with an atmospheric gas such as nitrogen. In order to maintain sealing performance, the entry side (left side in FIG. 1) and the exit side (right side in FIG. 1) of the reflow furnace have a labyrinth structure.

  The circuit board is printed with normal solder or lead-free solder on the upper surface, and electronic components are mounted thereon, and in this embodiment, the circuit board is transported by a chain conveyor type transport device. The circuit board on which the electronic components are placed enters the furnace from the entry side of the reflow furnace, is preheated while being conveyed in the 1-6 zone of the heating zone, and is conveyed in the 7-9 zone of the heating zone. In addition, the solder is melted and soldered. Furthermore, it is cooled while being transported through the first and second zones of the cooling zone, and then transported from the reflow furnace exit side.

  Zones 1 to 9 of the heating zone of the reflow furnace are equipped with a heating device that blows and heats hot air on the upper surface side and the lower surface side of the circuit board to be conveyed. Moreover, in 1-6 zone which performs preheating, temperature control is performed so that the temperature of the atmospheric gas which sprays gradually from 1 zone may become high. The circuit board heated gradually in the 1st to 6th zones reaches the maximum temperature in the 7th to 9th zones, and the solder is melted and soldered. The structure of the heating device in each zone is substantially the same.

  After the soldering is performed in the 7 to 9 zones of the heating zone, the temperature of the circuit board is gradually lowered in the 1 to 2 zones of the cooling zone, and is carried out from the exit side of the reflow furnace. One zone of the cooling zone is provided with a heating device that heats the upper and lower surfaces of the circuit board to be conveyed, and the structure is substantially the same as the heating device of the 1 to 9 zones of the heating zone. The reflow device in the cooling zone 2 zone is provided with a heating device only on the upper side.

(Description of heating device)
Next, an embodiment of the heating apparatus of the present invention will be described with reference to FIG. FIG. 2 is a view showing a cross section of the heating zone 7 zone indicated by the arrow B in FIG. 1. However, the other heating zone zones have the same structure.

First, the structure of the heating device of this embodiment will be described.
The reflow furnace is covered with a shell 1 having a seal structure and filled with an atmospheric gas such as nitrogen. The circuit board 2 on which the electronic component is placed is transported to the front side of the paper by the transport device 3 installed substantially at the center of the shell 1. Heating devices having the same structure are respectively attached to the upper surface side and the lower surface side of the circuit board 2 to heat the upper surface and the lower surface of the circuit board 2 to be conveyed. Here, the upper heating device will be described as an example.

On the upper side of the circuit board 2, a blowing panel 11 having a hot air blowing nozzle 6 and a cylindrical suction port 7 is provided. A box-shaped heating device chamber 4 is formed by the blowing panel 11 and the shell 1. Yes.
Above the blowout panel 11, a suction chamber 5 connected to the blowout panel 11 via a cylindrical suction port 7 is installed. Further, a circulating fan 8 that is driven by a fan motor 9 to circulate the atmospheric gas in the shell 1 and an electric heater 10 that heats the circulating atmospheric gas are installed above the fan. The fan motor 9 is attached to the outside of the shell 1, but has a structure in which outside air does not flow in by the sealing device 12. A heating device is constituted by the above members.

Next, a method for heating the upper surface of the circuit board using this heating apparatus will be described.
The atmospheric gas in the shell 1 and below the blow-out panel 11 is sucked into the suction chamber 5 from the suction port 7 as indicated by an arrow C by the suction force of the circulation fan 8. Then, the sucked atmospheric gas flows left and right along the upper inner surface of the shell 1 by the circulation fan 8 and is blown out to both sides of the suction chamber 5 as indicated by an arrow D. At this time, the atmospheric gas is heated to a predetermined gas temperature by the electric heater 10.

  Then, the heated atmospheric gas is blown from the blowing nozzle 6 and blown to the upper surface of the circuit board 2 as indicated by an arrow E. Since the heating device chamber 4 is sealed except for the blowing nozzle 6 and the suction port 7, the atmosphere gas blown to the left and right by the circulation fan 8 has no flow path other than the blowing nozzle 6, and the blowing nozzle 6. Can be strongly sprayed onto the upper surface of the circuit board 2. Thereafter, the atmospheric gas is again sucked into the suction chamber 5 from the suction port 7 and repeats the same circulation cycle.

As is clear from FIG. 2, in this embodiment, the flow path on the outlet side (positive pressure side) is disposed outside the flow path on the suction side (negative pressure side), thereby realizing an efficient flow of atmospheric gas. ing. With this arrangement, it is possible to provide a heating device with good sealing properties and maintainability, and it is possible to reduce running costs and the like.
In addition, the suction pressure of the circulation fan 8 can be adjusted to control the atmospheric gas blowing speed at the position of the circuit board 2 to a predetermined value. Usually, a desired spraying speed can be obtained by setting the suction pressure to 150 Pa or lower.
The heating device on the lower surface side of the circuit board 2 has the same structure as the heating device on the upper surface side, and the heating method is the same.

(Explanation of blowout panel)
Next, an embodiment of the blowout panel 11 of the present invention having a blowout nozzle and a suction port will be described. Fig.3 (a) is the figure seen from the arrow F of FIG. 2, and is the top view which looked at the blowing panel above the heating zone 7 zone from the lower side. The circuit board 2 is conveyed in the direction of arrow A in FIG.
FIG. 3B is a side view seen from the arrow G in FIG. 3A, and shows the circuit board 2, the rail 3a of the transfer device, the blowing panel 11, and the blowing nozzle 6 in the width direction of the reflow furnace. The positional relationship of the suction inlet 7 is shown.

In this embodiment, as shown in FIG. 3 (a), a suction-only area in which only the suction ports 7b and 7c are arranged is provided around the blow-out panel 11, and the blow-out nozzles 6 are arranged vertically and horizontally inside thereof. And a mixed area in which the suction ports 7a are alternately arranged.
In this suction-only area, the first suction-only line composed of rows in which the suction ports 7b are arranged perpendicular to the transport direction of the circuit board 2 (the direction of the arrow A), and the suction port 7c transport the circuit board 2 There is a second suction-only line arranged in parallel and arranged in a direction.

  In FIG. 4, two rows provided at the inlet side end and the outlet side end of the 7 zone in the conveyance direction indicated by X are first suction lines, and the conveyance rail 3a of the conveyance device in the width direction indicated by Y is illustrated. Two rows provided outside are the second suction-only lines, and a region indicated by Z surrounded by the lines indicated by X and Y is a mixed region.

Detailed dimensions of the blowout panel 11 are as follows.
Diameter of mixed region blowing nozzle 6: 4 mm
Diameter of suction port 7a: 9mm
Interval (pitch) between adjacent blowing nozzle 6 and suction port 7a: 10 mm
Diameter of first suction line suction port 7b: 12mm
Interval (pitch) between adjacent suction ports 7b: 16 mm
Diameter of second suction line suction port 7c: 12mm
Interval (pitch) between adjacent suction ports 7c: 16mm

In the present embodiment, the circuit board 2 is heated by the heated atmospheric gas blown from the blowing nozzle 6 installed in the mixed region. In this case, the place where the atmospheric gas is blown out and the place where it is sucked in are arranged alternately in close proximity, and are arranged uniformly over the entire zone, so that uniform heating is possible, enabling high-quality soldering, Moreover, high heating efficiency can be obtained.
Furthermore, since a large number of blowout nozzles 6 and suction ports 7a are alternately arranged, fluctuations in the flow of the atmospheric gas due to the presence or absence of a circuit board accompanying conveyance are reduced as compared with the conventional heating device. Variations can also be kept small.

In addition, since the second suction-only line installed in parallel with the transport direction of the circuit board 2 is installed outside the transport rail 3a, the flow of sucking the atmospheric gas is disturbed depending on the presence or absence of the circuit board 2 by the transport. There is little to do. Therefore, it can be said that there is little fluctuation in the furnace pressure due to the conveyance of the circuit board 2.
In addition, since the first suction-only lines installed perpendicular to the transport direction of the circuit board 2 are provided at the entrance end and the exit end of the zone, the atmosphere gas is changed depending on whether the circuit board 2 is transported or not. Even if the flow of suction changes, the influence on the mixed region where the circuit board 2 is actually heated can be minimized. Therefore, the fluctuation of the furnace pressure due to the conveyance of the circuit board 2 can be reduced.

In this embodiment, the installation interval (pitch) of the first suction line is exactly the same as the length of the heating zone 7, but from the simulation results and experimental results with various conditions changed, the pitch is the zone length. If it is 1/4 or more, that is, up to five lines in one zone, it is considered that the furnace pressure fluctuation is not greatly affected. In other words, if the pitch is ¼ or more of the zone length, it is possible to suppress the fluctuation of the furnace pressure due to the presence or absence of the circuit board 2 accompanying the conveyance, and to suppress the consumption of the atmospheric gas less than before. Is possible.
Here, the length of one zone is set to be equal to or longer than the length of the longest circuit board among the circuit boards to be transported. Alternatively, the zone length may be set to 250 mm or more.

The blowout panel of the present invention is not limited to the above-mentioned dimensions, but can take various other dimensions as required.
In the above-described embodiment, the heating 7 zone has been described as an example, but the heating devices in other zones also have the same structure.

(Placement of blowout nozzle)
Next, the arrangement of the blowing nozzles provided in the mixed area will be described in detail.
In the embodiment shown in FIG. 3, the blowing nozzles are arranged so as to form a square apex, but even if other arrangements are adopted, the circuit board can be similarly heated uniformly. FIG. 5A shows a form that forms a square similar to the above-described embodiment, and FIG. 5B shows an embodiment that forms a rhombus. Further, as shown in FIG. 5C, it is also possible to arrange them so as to form a triangle.

Here, FIG. 6 shows the result of measuring the heat transfer coefficient between the atmospheric gas to be blown and the circuit board by changing the combination of the size of the blow nozzle and the pitch between the blow nozzles. In the graph of FIG. 6, when the nozzle opening of the blowout nozzle is circular and its diameter is D, and the pitch between the blowout nozzles is P, the ratio P / D is taken on the horizontal axis, and relative heat transfer is performed. The rate is taken on the vertical axis. This relative heat transfer coefficient is set to 1 as a reference heat transfer coefficient at which practically sufficient heating can be performed. As is apparent from this graph, when P / D is 6 or more, the heat transfer coefficient becomes too small to perform sufficient heating. On the other hand, when P / D is 2 or less, there are too many blowing parts, and balance with suction cannot be taken, and uniform blowing cannot be obtained.
From the above, it is considered appropriate to set P / D, which is the ratio of the nozzle pitch to the hole diameter, within a range satisfying 2 <P / D <6. By setting to this range, uniform heating is possible, and excellent heating performance can be obtained, and the balance between blowing and sucking of atmospheric gas can be appropriately taken.

  Further, as described above, in the arrangement of the blowing nozzles, by setting the suction pressure from the suction port to a suction pressure of 150 Pa or lower, a desired blowing speed can be obtained, and uniform and sufficient heating is possible. It can be performed.

(Other embodiments)
Next, other embodiments will be described.
In the above-described embodiment, the first suction-only line and the second suction-only line are provided as the suction-only area, but a mode in which only one of the lines is provided according to the required gas suction amount is also considered. It is done. Further, the suction-only area is not limited to a line-shaped area, and an area having a plurality of rows is also conceivable.

  In addition, regarding the positional relationship between the blowout nozzle and the suction port, in the above-described embodiment, the arrangement is on the same plane, but the present invention is not limited to this arrangement, and any other arrangement Can be considered.

Moreover, in the above-mentioned embodiment, although the heating apparatus of this invention is installed in both surfaces of a circuit board, it is also possible to combine this heating apparatus and other heating apparatuses, such as an electric heater.
Furthermore, the present invention is not limited to the above-described embodiment, and various other embodiments are conceivable.

It is a schematic diagram showing the whole reflow furnace provided with the heating device of the present invention. It is sectional drawing which shows the structure of the heating apparatus of this invention. It is (a) top view and (b) side view which show one embodiment of the blowing panel of this invention. It is a figure which shows the 1st suction exclusive line of the blowing panel of this invention, the 2nd suction exclusive line, and a mixing | blending area | region. It is a figure which shows various embodiment of arrangement | positioning of the blowing nozzle of the blowing panel of this invention. It is a graph which shows the relationship between nozzle pitch / hole diameter and a heat transfer coefficient. It is the figure which showed the flow of the atmospheric gas blown from the conventional blowing nozzle, (a) shows the case where a circuit board exists, (b) shows the case where a circuit board does not exist.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shell 2 Circuit board 3 Conveying device 3a Conveying rail 4 Heating device chamber 5 Chamber 6 Blowing nozzle 7 Suction port 7a Suction port 7b Suction port 7c Suction port 8 Circulating fan 9 Fan motor 10 Electric heater 11 Blowing panel 12 Sealing device 102 Circuit board 106 Outlet nozzle 107 Suction port

Claims (13)

A heating device that heats a circuit board transported by a transport device by setting a temperature for each heating zone in a shell filled with atmospheric gas,
A circulation fan for circulating the atmospheric gas in the shell;
A heating device chamber in which a discharge passage on the discharge side of the circulation fan and a suction passage on the suction side of the circulation fan are provided independently;
A heater for heating atmospheric gas circulated by the circulation fan;
A blowout nozzle that blows off the atmospheric gas heated by the heater and blows it onto the circuit board;
A suction port for sucking the atmospheric gas in the shell into the circulation fan,
A suction-only area in which only the suction port is arranged, and a mixed area in which the blowing nozzle and the suction port are arranged close to each other are provided in the blowing panel, and the nozzle port of the blowing nozzle has a circular shape with a diameter D. And when the blowing nozzles are arranged at a pitch P,
2 <P / D <6
A circuit board heating apparatus having the following relationship:   The suction exclusive area is composed of a row of the suction ports arranged perpendicular to the transport direction of the circuit board, and the pitch between the rows is not less than ¼ of the zone length and not more than 1. The apparatus for heating a circuit board according to claim 1.   The suction-only area is constituted by a row of the suction ports arranged in parallel with the conveyance direction of the circuit board, and the row is installed outside a conveyance rail of the conveyance device. The circuit board heating apparatus according to 1 or 2.   4. The circuit board heating apparatus according to claim 1, wherein in the mixed region, the blow-out nozzles and the suction ports are alternately arranged. 5.   5. The circuit board heating apparatus according to claim 1, wherein in the mixed region, the nozzle port of the blowout nozzle and the suction port are arranged so as to be aligned in the same plane. 6.   6. The circuit board heating according to claim 1, wherein in the mixed region, the blowing nozzle is arranged to form a vertex of a square, a rhombus, or an equilateral triangle. 7. apparatus. Heating device of the circuit board according to any one of claims 1 to 6, the suction pressure from the suction port is characterized in that it is a less suction pressure 150 Pa. The blowout flow path, the heating device of the circuit board according to any one of claims 1 to 7, characterized in that than the suction passage is disposed outside. Using a heating device of the circuit board according to any one of claims 1 to 8, a reflow furnace to perform soldering of the circuit board. Filling the shell with atmospheric gas, setting the temperature for each heating zone, and heating while transporting the circuit board by the transport device,
Circulating the atmospheric gas in the shell with a circulation fan;
Heating the atmospheric gas circulated by the circulation fan with a heater;
Blowing out the atmospheric gas heated by the heater using a blowing nozzle of a blowing panel, and blowing it onto the circuit board;
Sucking atmospheric gas in the shell to the circulation fan using a suction port of the blow-out panel ,
In the suction-only area where only the suction port is arranged, the atmosphere gas is sucked, the nozzle port of the blowing nozzle has a circular shape with a diameter D, and when the blowing nozzle is arranged at a pitch P,
2 <P / D <6
A method for heating a circuit board, comprising: blowing out and sucking in atmospheric gas in a mixed region in which the blowout nozzle and the suction port having the relationship are arranged close to each other. The suction exclusive area is composed of a row of the suction ports arranged perpendicular to the transport direction of the circuit board, and the pitch between the rows is not less than ¼ of the zone length and not more than 1. The method for heating a circuit board according to claim 10 . The suction-only area is constituted by a row of the suction ports arranged in parallel with the conveyance direction of the circuit board, and the row is installed outside a conveyance rail of the conveyance device. The method for heating a circuit board according to 10 or 11 . The method for heating a circuit board according to any one of claims 10 to 12 , wherein the atmospheric gas is sucked from the suction port at a suction pressure of 150 Pa or less.

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