JP7569348B2 - Transport heating device - Google Patents

Description

The present invention relates to a transport and heating device that is applied to, for example, a reflow device.

The reflow device is equipped with a reflow furnace to which a workpiece to be heated, such as a printed circuit board, is supplied by a conveyor chain. The reflow furnace is configured, for example, with multiple heating furnaces corresponding to multiple zones arranged in sequence along a conveyor path from an entrance to an exit. The multiple zones serve as heating zones, cooling zones, etc.

In the heating zone, hot air is blown onto the workpiece, melting the solder in the solder composition and soldering the electrodes of the printed circuit board to the electronic components. In the reflow device, the temperature during heating is controlled according to the desired temperature profile to achieve the desired soldering. That is, the first section is a temperature rise section where the temperature rises due to heating, the next section is a preheat section where the temperature is almost constant, the next section is a reflow section, and the final section is a cooling section.

For example, Patent Document 1 describes a reflow apparatus that maintains a high temperature difference between adjacent zones. The reflow apparatus in Patent Document 1 is provided with an external circulation duct that forms an external circulation path that draws the atmosphere in multiple chambers out of the chambers and introduces it back into each of the multiple chambers, a cooling means that cools the atmosphere passing through the external circulation path, a flow control valve that can control the flow rate of the atmosphere introduced into each chamber, and a control means that controls the opening of the flow control valve. Then, control is performed to selectively introduce the atmosphere into the chamber where it is desired to lower the temperature.

JP 2008-279502 A

In a configuration such as that described in Patent Document 1, in which the atmosphere in the chamber is removed and cooled, and the temperature of the cooled atmosphere is lowered and then introduced back into the chamber, there is a risk that the cooling means will become large in order to lower the temperature of the atmosphere.

The object of the present invention is therefore to provide a transport and heating device that can quickly lower the temperature of the furnace body using a configuration that differs from the configuration that cools and returns the atmosphere in the chamber.

The present invention has a heating device in which a plurality of heating furnaces are arranged and configured to blow hot air onto a workpiece by the heating furnaces, and a transport conveyor that carries the workpiece into the heating device,
Each of the heating furnaces is composed of an upper furnace body and a lower furnace body,
A box-shaped upper temperature adjustment unit is arranged in front of or behind the upper furnace body of at least some of the heating furnaces in the conveying direction, and a box-shaped lower temperature adjustment unit is arranged in front of or behind the lower furnace body of at least some of the heating furnaces in the conveying direction,
The upper temperature adjustment unit is located in close proximity to or in contact with the wall surface of the upper furnace body, and the lower temperature adjustment unit is located in close proximity to or in contact with the wall surface of the lower furnace body;
This is a conveying and heating device in which the upper temperature adjustment section and the lower temperature adjustment section each have a medium inlet and a medium outlet , and multiple interference plates with a height smaller than the inner diameter are arranged alternately inside .

According to at least one embodiment, the temperature inside the furnace body in which the upper temperature adjustment unit and the lower temperature adjustment unit are provided can be reduced by supplying a medium to the upper temperature adjustment unit and the lower temperature adjustment unit. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present invention. Furthermore, the contents of the present invention should not be interpreted as being limited by the effects exemplified in the following description.

FIG. 1 is a schematic diagram showing an outline of a conventional reflow apparatus to which the present invention can be applied. FIG. 2 is a graph showing an example of a temperature profile during reflow. FIG. 3 is a cross-sectional view of a reflow apparatus used to explain one embodiment of the present invention. FIG. 4 is a cross-sectional view taken along line AA of FIG. FIG. 5 is a cross-sectional view taken along line BB of FIG. FIG. 6 is a cross-sectional view used to explain the operation during production of one embodiment of the present invention. FIG. 7 is a cross-sectional view used to explain the operation during production of an embodiment of the present invention. FIG. 8 is a cross-sectional view used to explain another operation during production of an embodiment of the present invention. FIG. 9 is a cross-sectional view used to explain another operation during production of an embodiment of the present invention. FIG. 10 is a cross-sectional view used to explain the operation at the time of switching the product type in one embodiment of the present invention. FIG. 11 is a cross-sectional view used to explain the operation at the time of switching the product type in one embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the embodiments in the following order.
<1. Example of a reflow device>
2. One embodiment
3. Modifications
It should be noted that the embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are applied thereto. However, the scope of the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited thereto.

<1. Example of a reflow device>
Fig. 1 shows a schematic configuration of a conventional reflow apparatus to which the present invention can be applied. A workpiece having surface mount electronic components mounted on both sides of a printed wiring board is placed on a transport conveyor and is carried into the heating device of the reflow apparatus from a carry-in entrance 11. The transport conveyor transports the workpiece in the direction of the arrow (from left to right in Fig. 1) at a predetermined speed, and the workpiece is removed from a carry-out exit 12. The transport direction of the transport conveyor is horizontal.

The heating device is configured such that multiple heating furnaces are arranged along the transport path from the entrance 101 to the exit 102, and the heating furnaces blow hot air (heated atmospheric gas) onto the workpieces. Multiple heating furnaces (called zones) are arranged in-line. The seven zones Z1 to Z7 from the entrance side are heating zones, and the two zones Z8 and Z9 on the exit side are cooling zones. Forced cooling units 103 are provided in association with the cooling zones Z8 and Z9. Each of the heating zones Z1 to Z7 has an upper furnace body and a lower furnace body, each of which includes a blower, heater, blowing panel, etc. Note that this number of zones is just an example, and a configuration having a different number of zones may also be used.

The multiple zones Z1 to Z9 described above control the temperature of the workpiece according to a temperature profile during reflow. Figure 2 shows an example of a temperature profile. The horizontal axis is time, and the vertical axis is the surface temperature of the workpiece, such as a printed wiring board on which electronic components are mounted. The first section is the temperature rise section R1 where the temperature rises due to heating, the next section is the preheat section R2 where the temperature is almost constant, the next section is the reflow (main heating) section R3, and the final section is the cooling section R4.

The temperature rise section R1 is a period during which the board is heated from room temperature to the preheat section R2 (e.g., 150°C to 170°C). The preheat section R2 is a period during which, for example, isothermal heating is performed to activate the flux, remove the oxide film on the surface of the electrodes and solder powder, and eliminate uneven heating of the printed wiring board. The reflow section R3 (e.g., peak temperature of 220°C to 240°C) is a period during which the solder melts and the joint is completed. In the reflow section R3, the temperature needs to be raised to a temperature that exceeds the melting temperature of the solder. Even after the preheat section R2, there is unevenness in the temperature rise, so in the reflow section R3, heating to a temperature that exceeds the melting temperature of the solder is required. The final cooling section R4 is a period during which the printed wiring board is rapidly cooled and the solder composition is formed. In the case of lead-free solder, the temperature in the reflow section R3 is higher (e.g., 240°C to 260°C).

In FIG. 2, curve 201 shows an example of a temperature profile for lead-free solder. An example of a temperature profile for Sn-Pb eutectic solder is shown by curve 202. Since the melting point of lead-free solder is higher than that of eutectic solder, the set temperatures in preheat section R2 and reflow section R3 are higher than those for eutectic solder.

In the reflow device shown in FIG. 1, the temperature control of the heating section R1 in FIG. 2 is mainly handled by zones Z1 and Z2. The temperature control of the preheating section R2 is mainly handled by zones Z3, Z4, and Z5. The temperature control of the reflow section R3 is handled by zones Z6 and Z7. The temperature control of the cooling section R4 is handled by zones Z8 and Z9. There are gaps between the multiple furnace bodies (zones) mentioned above.

2. One embodiment
Fig. 3 is a cross-sectional view of a portion of a heating device consisting of multiple zones, Fig. 4 is a cross-sectional view taken along line A-A in Fig. 3, and Fig. 5 is a cross-sectional view taken along line B-B in Fig. 3. Zones Z(n-1), Zn, and Z(n+1) included in the heating zones are shown along the conveying direction of the workpiece W. The upper furnace body and the lower furnace body of the heating zones Z1 to Z7 of the reflow device have the same configuration as that shown in Figs. 3, 4, and 5.

In each zone, an upper furnace body and a lower furnace body are provided facing each other, and in the gap between the upper furnace body and the lower furnace body, a workpiece W having surface-mount electronic components mounted on one or both sides of a printed circuit board is transported by the transport conveyors 1a, 1b. The upper furnace body and the lower furnace body are filled with atmospheric gas, for example nitrogen (N2) gas. The upper furnace body blows hot air (heated atmospheric gas) downward onto the workpiece W to heat it, and the lower furnace body blows hot air upward onto the workpiece W to heat it. Infrared rays may be irradiated along with the hot air.

In the upper furnace body, a fan 3 (rotating blades) rotated by a motor 2 is placed in a pressure chamber 4, and hot air is blown downward from the pressure chamber 4 through holes formed in a blow-out panel 5. A baffle plate may be placed between the fan 3 and the blow-out panel 5 to disperse the air from the fan 3 and prevent uneven temperature on the surface of the workpiece W. The fan 3 is an axial fan or a centrifugal fan. A heater 6 is provided on the negative pressure side of the fan 3. The fan 3, blow-out panel 5, and heater 6 are placed in a furnace body surrounded by a furnace wall 7.

Furthermore, an air layer wall 8 is provided facing the furnace wall 7 at a specified distance, and an upper air layer 9 is formed between the furnace wall 7 and the air layer wall 8 as an upper insulating air layer. As shown in FIG. 4, an inlet 10 and an outlet 11 are attached to the upper air layer 9. Although not shown, air is supplied to the inlet 10 through piping from fans provided for each zone, and air is discharged from the outlet 11 through piping to the fan. A control means such as a valve is provided in the air path, and air is supplied/stopped from being supplied to the upper air layer 9. Note that a fan and piping common to multiple zones may be provided.

The lower furnace body, like the upper furnace body, is surrounded by furnace walls 17 and has a fan (rotating blades) 13 rotated by a motor 12, a blowing panel 15, and a heater 16 arranged inside. The fan 13 is arranged inside the pressurized chamber 14. Hot air is blown upward through holes formed in the blowing panel 15. A baffle plate may be arranged between the fan 13 and the blowing panel 15 to disperse the air from the fan 3 and prevent uneven temperatures on the surface of the workpiece W.

Furthermore, an air layer wall 18 is provided facing the furnace wall 17 at a predetermined distance, and a lower air layer 19 is formed between the furnace wall 17 and the air layer wall 18 as a lower insulating air layer. As shown in FIG. 4, an inlet 20 and an outlet 21 are attached to the lower air layer 19. Although not shown, air is supplied to the inlet 20 through piping from fans provided for each zone, and air is discharged from the outlet 21 through piping to the fan. A control means such as a valve is provided in the air path, and air is supplied/stopped from being supplied to the lower air layer 19. Note that a fan and piping common to multiple zones may be provided.

The upper air layer 9 and the lower air layer 19 are configured to be isolated from the internal space of the furnace in which reflow is performed. Therefore, air can be used as the medium to be introduced into the upper air layer 9 and the lower air layer 19. Note that the type of medium to be introduced may be a gas other than air (e.g., nitrogen gas) or a liquid (e.g., water).

The shaded components in FIG. 3 are the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41. In one embodiment, the upper temperature adjustment unit 31 is disposed in the gap between the upper furnace bodies located in front of the workpiece transport direction of zones Z(n-1), Zn, and Z(n+1), and the lower temperature adjustment unit 41 is disposed in the gap between the lower furnace bodies located in front of the workpiece transport direction of zones Z(n-1), Zn, and Z(n+1). The upper temperature adjustment unit 31 is located in close proximity to or in contact with the air layer wall 8, which is the wall surface of the upper furnace body, and the lower temperature adjustment unit 41 is located in close proximity to or in contact with the air layer wall 18, which is the wall surface of the lower furnace body.

The upper temperature adjustment unit 31 has a sealed structure as shown in FIG. 5. For example, it is a metal box-shaped object that is welded all around, and a medium inlet 32 and a medium outlet 33 are attached to one side of the box by welding all around. In addition, interference plates 34 protrude inward from the opposing sides of the box alternately. The height of the interference plates 34 is slightly smaller than the inner diameter (height) of the box. Therefore, the medium, such as air, supplied from the medium inlet 32 passes through the gap between the tip and the inner surface of the interference plate 34 and is discharged from the medium outlet 33. By providing the interference plate 34, the length of the path through which the air flows inside the upper temperature adjustment unit 31 becomes longer than when the interference plate 34 is not provided, and the cooling effect of the upper temperature adjustment unit 31 can be increased.

The lower temperature adjustment unit 41 has a similar configuration to the upper temperature adjustment unit 31 described above. A medium inlet and a medium outlet are provided below the lower temperature adjustment unit 41. The medium inlets 32 of the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 are connected to a common pipe, and the medium outlets 33 are connected to a common pipe (not shown). Air is supplied/stopped to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 through the common pipe.

The upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 are sealed structures, and are therefore isolated from the internal space of the furnace in which reflow is performed. Therefore, air can be used as the medium introduced to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41. The type of medium introduced may be a gas other than air (e.g., nitrogen gas) or a liquid (e.g., water). In addition, the supply and stop of the medium to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 are independent of the supply and stop of the medium to the upper air layer 9 and the lower air layer 19, and the supply and stop of the medium are controlled separately.

The upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 do not need to be provided in all heating zones, but may be provided in some of the zones. In particular, the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 are provided in the reflow section (main heating) where the temperature becomes high.

The operation of one embodiment of the present invention will be described. Figures 6 and 7 show the operation during production in which the workpiece W is fed and reflowed. Figures 6, 8, and 10 are drawings corresponding to Figure 3. However, zone Z (n-1) is omitted. Figures 7, 9, and 11 are drawings corresponding to Figure 4, and show a cross section of zone Zn. During production, the atmosphere heated by the heaters 6, 16 is blown onto the workpiece W by the fans 3, 13 through the blowing panels 5, 15. In addition, the atmosphere is sucked into the fans 3, 13 through the space between the pressurized chambers 4, 14 and the furnace walls 7, 17 and blown out. During production, the supply and discharge of air to the upper air layer 9 and the lower air layer 19, as well as the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41, are stopped.

Even during production, as shown in Figs. 8 and 9, air can be supplied and discharged to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 of a specified zone in order to increase the temperature difference between the zones, and the supply and discharge of air to the upper air layer 9 and the lower air layer 19 can be stopped. In the example of Figs. 8 and 9, air is supplied and discharged to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 arranged before and after the workpiece conveying direction of zone Zn. Therefore, it is possible to significantly lower the furnace temperature of zone Zn without temperature interference with the furnace temperatures of the adjacent zones Z(n-1) and Z(n+1). Note that, even during production, not only the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 but also the supply and discharge of air to the upper air layer 9 and the lower air layer 19 may be controlled. Furthermore, the supply and discharge of air to the upper air layer 9 and the lower air layer 19, and the supply and discharge of air to the upper temperature adjustment unit 31 and the lower temperature adjustment unit 41 may be controlled separately. The furnace temperature can be controlled to a desired value by combining these controls.

Figures 10 and 11 show the operation when changing the type of workpiece, changing the profile, or other product type changes. The x symbols in Figure 10 represent the air flow, which is perpendicular to the paper surface, from the front to the back. When changing the setup, air is supplied to and exhausted from all of the upper air layer 9 and lower air layer 19. Air is also supplied to and exhausted from all of the upper temperature adjustment unit 31 and lower temperature adjustment unit 41. This process can shorten the time required for the setup change, improving production efficiency.

As an example, in one embodiment of the present invention, when the temperature in the reflow zone was lowered from 240°C to 210°C, it was confirmed that the time was reduced to half compared to the conventional technology. In addition, when a difference was set between the temperature setting values of adjacent zones and the present invention was compared to the conventional technology, it was confirmed that by applying the technology of the present invention, the deviation from the temperature setting value of the low-temperature zone could be reduced to 1/10 compared to the conventional technology.

3. Modifications
Although the embodiments of the present invention have been specifically described above, they are not limited to the above-mentioned embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the fan is not limited to a configuration in which the fan sucks in the atmosphere from the back, but may be configured to suck in the atmosphere from the front. The present invention is not limited to a printed circuit board, but can also be applied to the reflow of a flexible board, a board in which a rigid board and a flexible board are bonded together, and a rigid-flex board that combines these. Furthermore, the present invention is not limited to a reflow device, but can also be applied to a heating device for curing resin. The configurations, methods, processes, shapes, materials, and values given in the above-mentioned embodiments are merely examples, and different configurations, methods, processes, shapes, materials, and values may be used as necessary. The configurations, methods, processes, shapes, materials, and values of the above-mentioned embodiments can be combined with each other as long as they do not deviate from the gist of the present invention.

Z(n-1), Zn, Z(n+1)...Zone,
101: Carry-in entrance; 102: Carry-out exit; 103: Forced cooling unit;
1a, 1b...conveyor; 3, 13...fan; 6, 16...heater;
7, 17 ... furnace wall, 8, 18 ... air layer wall, 9 ... upper air layer,
19: Lower air layer, 31: Upper temperature adjustment section, 41: Lower temperature adjustment section

Claims (3)

A heating device in which a plurality of heating furnaces are arranged and hot air is blown onto the workpiece by the heating furnaces, and a transport conveyor is provided for transporting the workpiece to the heating device,
Each of the heating furnaces is composed of an upper furnace body and a lower furnace body,
A box-shaped upper temperature adjustment unit is arranged in front of or behind the upper furnace body of at least some of the heating furnaces in the conveying direction, and a box - shaped lower temperature adjustment unit is arranged in front of or behind the lower furnace body of at least some of the heating furnaces in the conveying direction,
The upper temperature adjustment unit is located in close proximity to or in contact with the wall surface of the upper furnace body, and the lower temperature adjustment unit is located in close proximity to or in contact with the wall surface of the lower furnace body,
A conveying and heating device in which the upper temperature adjustment unit and the lower temperature adjustment unit each have a medium inlet and a medium outlet , and a plurality of interference plates having a height smaller than the inner diameter are arranged alternately inside . 2. The conveying and heating device according to claim 1 , wherein air layer walls are provided facing the furnace walls of the upper furnace body and the lower furnace body, and an upper air layer and a lower air layer are formed between the furnace walls and the air layer walls. 3. The transporting and heating device according to claim 2, wherein supply and stop of the medium to the upper temperature adjustment unit and the lower temperature adjustment unit are independent of supply and stop of the medium to the upper air layer and the lower air layer.

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