JP2023144356A - Carrying heating apparatus - Google Patents

Abstract

To prevent unevenness in temperature from occurring in an object to be heated.SOLUTION: A carrying heating apparatus includes: a heating apparatus in which a plurality of heating furnaces are aligned and which is configured to blow hot air to an object to be heated by using the heating furnaces; and a carrying conveyor for carrying the object to be heated into the heating apparatus. Each of the heating furnaces comprises an upper furnace body and a lower furnace body. The carrying heating apparatus further includes: fans provided in the upper furnace body and the lower furnace body, respectively; pressurization chambers provided in the upper furnace body and the lower furnace body, respectively; and straightening plates which are provided in the pressurization chambers and to which hot air is blown from the fans. The straightening plate is provided only on the outer side of the outer periphery of the fan.SELECTED DRAWING: Figure 5

Description

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

The reflow apparatus includes a reflow oven to which a workpiece to be heated, such as a printed circuit board, is supplied by a conveyor chain. The reflow oven has a configuration in which, for example, a plurality of heating furnaces corresponding to a plurality of zones are sequentially arranged along a conveyance path from an inlet to an outlet. The plurality of zones have roles such as heating zones and cooling zones.

In the heating zone, hot air is blown against the workpiece to melt the solder in the solder composition and solder the electrodes of the printed circuit board and the electronic components. In a reflow apparatus, desired soldering is achieved by controlling the temperature during heating according to a desired temperature profile. In other words, the first section is a temperature rising section where the temperature rises due to heating, the next section is a preheating section where the temperature is almost constant, the next section is a reflow (main heating) section, and the last section is a heating section where the temperature rises due to heating. is considered to be the cooling part.

For example, Patent Document 1 states that the convection for gas discharge and recovery is more active as it approaches the recovery port, and stagnates as it moves away from the recovery port. It is described that a problem in which a region appears and uneven soldering accuracy occurs on a heated object is solved. In Patent Document 1, a cross-shaped collection port is opened at approximately the center of the discharge surface in the feeding direction of the object to be heated and at approximately the center in the width direction of the object to be heated. In addition, a conical shroud that expands toward the blower is provided between the recovery port and the blower that discharges heated gas, so that the gas recovered from the recovery port is guided to swirl around the conical shroud. The structure is such that the air is sucked into the blower. A spiral heater is built inside the shroud. In Patent Document 1, the gas collected from the recovery port is guided to a conical shroud in a swirling manner, is sucked into the blower, and is heated by a heater during the long swirling process as it passes through the interior of the shroud. The configuration is as follows.

Japanese Patent Application Publication No. 2005-72423

However, the configuration described in Patent Document 1 improves the configuration in which the collection port is provided close to the discharge port on the discharge surface, and is different from the configuration in which the collection port is provided around the discharge surface (blowout panel). was not applicable.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conveyance heating device that can be applied to a structure having a recovery port around a blow-off panel and that can prevent unevenness in the temperature of an object to be heated.

The present invention includes a heating device in which a plurality of heating furnaces are arranged and configured to blow hot air onto an object to be heated by the heating furnace, and a conveyor for carrying the object to be heated into the heating device. ,
Each of the heating furnaces is composed of an upper furnace body and a lower furnace body,
A fan provided in each of the upper furnace body and the lower furnace body,
A pressurized chamber provided in each of the upper furnace body and the lower furnace body,
It is equipped with a rectifying plate installed in the pressurized chamber and blows hot air from a fan.
This is a conveyance heating device in which a current plate is provided only outside the outer periphery of the fan.

According to at least one embodiment, since the current plate is provided only outside the outer periphery of the fan, it is possible to reduce variations in the wind pressure on the object to be heated and to reduce unevenness in the temperature of the object to be heated. Note that the effects described here are not necessarily limited, and may be any effect described in the present invention. Furthermore, the contents of the present invention are not to be interpreted as being limited by the effects illustrated 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 sectional view of a reflow apparatus used to explain one embodiment of the present invention. FIG. 4 is a sectional view taken along line AA in FIG. FIG. 5 is a sectional view taken along line BB in FIG. FIG. 6 is a sectional view used to explain the operation during production of an embodiment of the present invention. FIG. 7 is a cross-sectional view used to explain the operation during product type switching according to an embodiment of the present invention. 8A, FIG. 8B, and FIG. 8C are plan views showing a plurality of examples of current plates. FIGS. 9A and 9B are plan views showing further examples of current plates.

Hereinafter, the present invention will be described with reference to embodiments. Note that the explanation will be given in the following order.
<1. An example of reflow equipment>
<2. One embodiment>
<3. Modified example>
The embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are attached thereto. Unless otherwise stated, the invention is not limited to these embodiments.

<1. An example of reflow equipment>
FIG. 1 shows a schematic configuration of a conventional reflow apparatus to which the present invention can be applied. A workpiece having electronic components for surface mounting mounted on both sides of a printed wiring board is placed on a conveyor and carried into a heating device of a reflow apparatus through a carry-in port 11. The conveyor conveys the work in the direction of the arrow (from left to right in FIG. 1) at a predetermined speed, and the work is taken out from the exit 12. The transport direction of the transport conveyor is the horizontal direction.

The heating device is configured such that a plurality of heating furnaces are arranged along a conveyance path from an inlet 101 to an outlet 102, and the heating furnaces blow hot air (heated atmospheric gas) onto the workpiece. There is. A plurality of heating furnaces (referred to as zones) are arranged in-line. Seven zones Z1 to Z7 from the inlet side are heating zones, and two zones Z8 and Z9 from the outlet side are cooling zones. A forced cooling unit 103 is provided in connection with cooling zones Z8 and Z9. Each of the heating zones Z1 to Z7 has an upper furnace body and a lower furnace body each including a blower, a heater, a blowout panel, and the like. Note that this number of zones is just an example, and a configuration having a different number of zones may be used.

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

The temperature increasing portion R1 is a period in which the substrate is heated from room temperature to the preheating portion R2 (eg, 150° C. to 170° C.). The preheating section R2 is a period for performing isothermal heating, for example, to activate the flux, remove oxide films on the surfaces of the electrodes and solder powder, and eliminate uneven heating of the printed wiring board. The reflow section R3 (for example, peak temperature of 220° C. to 240° C.) is a period in which the solder melts and the bond is completed. In the reflow section R3, it is necessary to raise the temperature to a temperature exceeding the melting temperature of the solder. In the reflow section R3, even after passing through the preheat section R2, there is uneven temperature rise, so heating to a temperature exceeding the melting temperature of the solder is required. The final cooling section R4 is a period in which the printed wiring board is rapidly cooled and the solder composition is formed. Note that in the case of lead-free solder, the temperature in the reflow section R3 is higher (for example, 240° C. to 260° C.).

In FIG. 2, curve 1 shows an example of the temperature profile of lead-free solder. An example of the temperature profile in the case of Sn--Pb eutectic solder is shown by curve 2. 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 of eutectic solder.

In the reflow apparatus shown in FIG. 1, zones Z1 and Z2 are mainly responsible for controlling the temperature of the temperature rising section R1 in FIG. Zones Z3, Z4, and Z5 are mainly responsible for controlling the temperature of preheat section R2. Zones Z6 and Z7 are responsible for temperature control of the reflow section R3. Zone Z8 and zone Z9 are in charge of temperature control of cooling section R4. A gap exists between the plurality of furnace bodies (between zones) described above.

<2. One embodiment>
3 is a cross-sectional view of a part of the heating device consisting of a plurality of zones, FIG. 4 is a cross-sectional view taken along line AA in FIG. 3, and FIG. 5 is a cross-sectional view taken along line BB in FIG. be. A zone Zn included in the heating zone is shown along the transport direction of the workpiece W (arrow direction in FIG. 3). The upper and lower furnace bodies of the heating zones Z1 to Z7 of the reflow apparatus have the same configuration as shown in FIGS. 3, 4, and 5.

Each zone is provided with an upper furnace body and a lower furnace body facing each other, and electronic components for surface mounting are mounted on one or both sides of a printed circuit board within the opposing gap between the upper furnace body and the lower furnace body. Workpiece W is transported by transport conveyors 1a and 1b. The upper furnace body and the lower furnace body are filled with atmospheric gas, such as nitrogen (N2) gas. The upper furnace body blows hot air (heated atmospheric gas) downward to the workpiece W to heat the workpiece W, and the lower furnace body blows hot air upward to the workpiece W to heat the workpiece W. Heat. Note that infrared rays may be irradiated together with hot air.

In the upper furnace body, a fan (rotating blade) 3 rotated by a motor 2 is arranged in a pressurizing chamber 4, and hot air is blown downward from the pressurizing chamber 4 through a rectifying plate 12 and a blowing panel 5. The blowout panel 5 is a rectangular metal plate in which a large number of holes are formed so as to cover the opening of the pressurizing chamber 4 . The rectifier plate 12 is arranged between the fan 3 and the blow-off panel 5 in the pressurizing chamber 4, and prevents unevenness in the wind pressure on the workpiece W on the workpiece W surface, and prevents unevenness in temperature on the workpiece W surface. Fan 3 is a centrifugal fan (for example, a turbo fan). A heater 6 is arranged on the negative pressure side of the fan 3. These fan 3, blowout panel 5, and heater 6 are arranged in a furnace body surrounded by a furnace wall 7.

Further, an air layer wall 8 is provided opposite the furnace wall 7 at a predetermined interval, and an upper air layer 9 as an upper insulating air layer is formed between the furnace wall 7 and the air layer wall 8. 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 a fan provided for each zone, and air is led out from the outlet 11 to the fan through piping. A control means such as a valve is provided in the air path to supply/stop the supply of air to the upper air layer 9. Note that a common fan and piping may be provided for multiple zones.

Like the upper furnace body, the lower furnace body includes a fan (rotary blade) 13 rotated by a motor 12, a rectifier plate 22, a blowout panel 15, and a heater 16 arranged inside the furnace body surrounded by a furnace wall 17. There is. A heater 16 is arranged on the negative pressure side of the fan 13. The fan 13 and the rectifying plate 22 are arranged within the pressurizing chamber 14 . Hot air is blown upward through the current plate 22 and the blowout panel 15. The blowout panel 15 is a metal plate in which a large number of holes are formed so as to cover the opening of the pressurizing chamber 14 . The current plate 22 is disposed between the fan 13 and the blowout panel 15, and prevents unevenness in the wind pressure on the workpiece W on the surface of the workpiece W, and prevents unevenness in temperature on the surface of the workpiece W. Fan 13 is a centrifugal fan (for example, a turbo fan).

The current plate 12 and the current plate 22 have similar shapes. FIG. 5 shows an example of the current plate 22 (shown with diagonal lines; the same applies hereinafter). The upper furnace body and the lower furnace body are provided so that a rectangular blow-out panel 5 and a rectangular blow-out panel 15 face each other. The rectifying plate 22 is a metal plate in which a large number of holes are formed, and a rectangular, eg, square, opening is formed in the center of the metal plate. The length of one side of this opening is slightly larger than the diameter of the fan 13. That is, the current plate 22 is provided only outside the outer periphery of the fan 13. The current plate 12 also has the same shape as the current plate 22. Note that the current plate 12 and the current plate 22 may also be provided in the cooling zone. Note that the current plate 12 and the current plate 22 are not limited to a configuration in which openings are formed in one plate, but may be configured in such a manner that two or more parts are bonded together.

Further, an air layer wall 18 is provided opposite the furnace wall 17 at a predetermined interval, and a lower air layer 19 as a lower insulating air layer is formed between the furnace wall 17 and the air layer wall 18. 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 a fan provided for each zone, and air is led out from the outlet 21 to the fan through piping. A control means such as a valve is provided in the air path to supply/stop the supply of air to the lower air layer 19. Note that a common fan and piping may be provided for multiple zones.

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

The operation of one embodiment of the present invention will be described. FIG. 6 shows an operation during production in which the workpiece W is flowed and reflowed. FIG. 6 is a drawing corresponding to FIG. 4. During production, the atmosphere heated by the heaters 6 and 16 is blown onto the workpiece W by the fans 3 and 13 through the rectifier plates 12 and 22 and the blow-off panels 5 and 15. The atmosphere passes through the openings of the rectifier plates 12 and 22 and the holes in the panel portion around the openings. Then, the hot air blown onto the work passes through the space between the pressurized chambers 4, 14 formed around the blow-off panels 5, 15 and the furnace walls 7, 17, and returns to the negative pressure side of the fans 3, 13. The atmosphere is sucked into fans 3 and 13 and blown out. During production, the supply and discharge of air to and from the upper air layer 9 and the lower air layer 19 are stopped.

FIG. 7 shows the operation when switching types, such as changing the type of workpiece or changing the profile. At the time of product type switching, air is supplied to and discharged from both the upper air layer 9 and the lower air layer 19. This process can shorten the time required to change product types and improve production efficiency.

Modified examples of the shape of the current plate will be described with reference to FIGS. 8A, 8B, 8C, 9A, and 9B. For simplicity, the baffle plate of the lower furnace body will be described, but the baffle plate of the upper furnace body also has a similar shape. However, the current plate of the upper furnace body and the current plate of the lower furnace body may have different shapes.

The rectifier plate 22A shown in FIG. 8A has an opening concentric with the fan 13 formed in the center. The current plate 22A is provided only outside the outer periphery of the fan 13. The rectifier plate 22B shown in FIG. 8B is located outside the outer periphery of the fan 13 and has a band shape extending in the conveyance direction. Two rectifier plates 22B are provided in parallel. The current plate 22C shown in FIG. 8C is a band-shaped member that extends outside the outer periphery of the fan 13 in a direction perpendicular to the conveying direction. Two rectifying plates 22C are provided in parallel.

Like the current plate 22B, the current plate 22D shown in FIG. 9A is a band-shaped member located outside the outer periphery of the fan 13 and extends in the conveyance direction. The difference from the current plate 22B is that a gap is provided between the inner sides of the two surfaces parallel to the conveyance direction of the pressurizing chamber 14. Furthermore, the width may be narrower than that of the current plate 22D, such as a current plate 22E shown in FIG. 9B. Note that a current plate having a shape other than that shown in the drawings may be used.

In one embodiment of the present invention described above, for example, a structure in which the upper furnace body and the lower furnace body are provided with the baffle plate 22B having the same structure, and a structure in which the baffle plate is provided on the entire surface, are applied to a workpiece such as stainless steel of a predetermined thickness. As a result of measuring the temperature on the plate, it was confirmed that temperature unevenness could be reduced. When the peak temperature of reflow is set to 240°C, the variation in the air pressure of the atmosphere passing through the rectifier plate 22B is reduced, and the difference between the highest and lowest temperatures on the workpiece was 5.9°C with the conventional technology. However, in one embodiment of the present invention, the temperature could be improved to 2.5°C.

<3. Modified example>
Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible. For example, the configuration is not limited to a configuration where the fan sucks the atmosphere from the back side, but a configuration where the fan sucks the atmosphere from the front side may be used. Furthermore, the present invention is applicable not only to printed circuit boards but also to reflow of flexible boards, boards made by bonding rigid boards and flexible boards together, and rigid flexible boards that are a combination of these. Furthermore, the present invention is applicable not only to reflow devices but also to heating devices for curing resin. Furthermore, the configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above-mentioned embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. Good too. Further, the configurations, methods, processes, shapes, materials, numerical values, etc. of the above-described embodiments can be combined with each other without departing from the gist of the present invention.

Zn... Zone, 101... Carrying in port, 102... Carrying out port, 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, 12, 22... Straightening plate, 19... Lower air layer

Claims (5)

A heating device in which a plurality of heating furnaces are arranged and configured to blow hot air onto an object to be heated by the heating furnace, and a conveyor for carrying the object to be heated into the heating device,
Each of the heating furnaces is composed of an upper furnace body and a lower furnace body,
a fan provided in each of the upper furnace body and the lower furnace body;
a pressurized chamber provided in each of the upper furnace body and the lower furnace body;
A rectifier plate is provided in the pressurized chamber and blows hot air from the fan,
A conveyance heating device in which the baffle plate is provided only outside the outer periphery of the fan. 2. The conveying heating device according to claim 1, wherein the hot air blown onto the object to be heated passes through a space between the pressurizing chamber and the furnace wall and returns to the negative pressure side of the fan. The conveyance heating device according to claim 1 or 2, wherein a heater is arranged on the negative pressure side of the fan. The conveyance heating device according to any one of claims 1 to 3, wherein the fan is a centrifugal fan. Claims 1 to 4, wherein an air layer wall is provided opposite 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 wall and the air layer wall. The conveyance heating device according to any one of the above.

Images