JP7550253B2 - 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.

In a conveying and heating device, such as a reflow device, a conveying chain is used to convey an object to be heated, such as a printed circuit board on which electronic components are mounted. The reflow device is equipped with a reflow furnace to which the object to be heated, such as a printed circuit board, is supplied by the conveying chain. The reflow furnace is configured, for example, with multiple heating furnaces corresponding to multiple zones arranged in sequence along a conveying path from an entrance to an exit. Depending on their function, the multiple zones serve as heating zones, cooling zones, etc.

In the heating zone, hot air is blown onto the board, 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 heating temperature is controlled according to the desired temperature profile to achieve the desired soldering.

The conveyor chain is endless and is attached between the sprockets, so it runs not only inside the furnace (inside the heating device) but also outside the furnace (outside the heating device). Conventionally, the conveyor chain was run directly below the lower furnace body without being restricted in position, and a metal guide mechanism with a U-shaped cross section, for example, was provided below the lower furnace body, and the conveyor chain was stored inside the guide mechanism.

Patent Document 1 describes a configuration in which a conveyor rail is provided to stabilize the movement of the conveyor chain inside the furnace, and upper and lower metal key members are attached to the grooves of the conveyor rail, and the conveyor chain is supported by these key members.

JP 2012-106273 A

In the configuration described in Patent Document 1, if the conveyor chain vibrates while running inside the furnace, the upper key material absorbs the vertical vibrations of the chain, ensuring stable running of the chain. However, there is no disclosure or suggestion that the running of the conveyor chain outside the furnace is regulated by a conveyor rail, and vibrations of the conveyor chain outside the furnace may affect soldering. Also, in a configuration in which the conveyor chain slides inside a metal guide mechanism outside the furnace, metal pieces (contamination) are generated during continuous operation due to vibrations of the conveyor chain, etc. If metal pieces are brought into the furnace, there is a possibility that they will adhere between the electrodes of the workpiece (printed wiring board), and in the worst case, this could cause a short circuit in the workpiece.

Therefore, the object of the present invention is to provide a conveying and heating device that can stably perform heating treatment of objects to be heated inside the furnace by stabilizing the running of the conveying chain outside the furnace.

The present invention provides a heating device in which a plurality of heating furnaces are arranged and hot air is blown onto an object to be heated by the heating furnaces;
In a conveying and heating device having a conveying chain for conveying a workpiece to a heating device and conveying the workpiece from the heating device,
The conveyor chain is endless and communicates between the inside and outside of the heating device.
A guide unit is provided outside the heating device to regulate the trajectory of the conveyor chain,
This conveying and heating device is characterized in that the guide section is made up of a plurality of divided guide sections connected to each other, and only the ends of the divided guide sections near the front in the traveling direction of the conveying chain are fixed .

According to at least one embodiment, the guide portion can flexibly follow the conveyor chain, stabilizing the running of the conveyor chain outside the furnace. In addition, the generation of metal pieces (contamination) can be suppressed. Note that the effects described here are not necessarily limited, and any of the effects described in the present invention may be used. In addition, 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 example of a reflow apparatus to which the present invention can be applied. FIG. 2 is a plan view for explaining the rail guide according to one embodiment of the present invention. FIG. 3 is a cross-sectional view used to explain a rail guide and a return rail according to one embodiment of the present invention. 4A, 4B, and 4C are partial plan views showing several examples of shapes of joints of a rail guide. FIG. 5 is a partial plan view used to explain the shape of a joint of the rail guide.

The following describes an embodiment of the present invention. Note that the embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are included, but 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.

Figure 1 shows a schematic configuration of a reflow device 1 to which the present invention can be applied. The reflow device 1 includes a reflow furnace 2 as a heating device, a conveyor chain 3a for conveying a heated object, such as a printed circuit board with surface-mount electronic components mounted on both sides (hereinafter referred to as a workpiece) W, into and out of the reflow furnace 2, a rotating body, such as sprockets 5a, 5b, 5c, and 5d, that defines the movement path of the conveyor chain 3a, and an outer plate 6. The conveyor chain 3 is endless and communicates with the inside and outside of the reflow furnace, and is hung over the sprockets 5a, 5b, 5c, and 5d. A conveyor chain 3b is provided parallel to the conveyor chain 3a, and the workpiece W is conveyed by the conveyor chains 3a and 3b (referred to as conveyor chain 3 when there is no need to distinguish between the two conveyor chains).

In FIG. 1, only one of the two conveyor chains 3a and 3b arranged parallel to the conveying direction, namely, conveyor chain 3a, is shown. For example, a roller chain is used as conveyor chain 3. The outer plate 6 is a case that covers the whole structure.

After the workpiece W is carried into the reflow furnace 2 through the carry-in entrance 7, it is transported by the transport chain 3 in the direction of the arrow (from left to right in FIG. 1) at a predetermined speed, and is finally carried out through the carry-out exit 8. Although not shown, a workpiece carrying-in device for carrying the workpiece W is provided in front of the carry-in entrance 7, and a workpiece carrying-out device for sending the workpiece W to the outside is located behind the carry-out exit 8. Within the range in which the transport chain 3 runs outside the reflow furnace 2, a guide section as described below is provided in the substantially flat outside-furnace running range 9 (the range of sprockets 5c and 5d), and the trajectory of the transport chain 3 is regulated by the guide section.

Along the transport path from the entrance 7 to the exit 8, the reflow furnace 2 as a heating device is divided into, for example, nine zones Z1 to Z9, and these zones Z1 to Z9 are arranged in-line. The seven zones Z1 to Z7 from the entrance 7 side are heating zones, and the two zones Z8 and Z9 on the exit 8 side are cooling zones. Forced cooling units (not shown) are provided in association with the cooling zones Z8 and Z9. Note that the number of zones is an example, and other numbers of zones may be provided. The multiple zones Z1 to Z9 control the temperature of the workpiece W according to the temperature profile during reflow. Each of the heating zones Z1 to Z7 has an upper heating furnace and a lower heating furnace, each of which includes a blower.

The first section is the heating section R1, where the temperature rises due to heating, the next section is the preheating section R2, where the temperature is almost constant, the next section is the reflow section R3, and the last section is the cooling section R4. The heating section R1 is the period during which the board is heated from room temperature to the preheating section R2 (e.g., 150°C to 170°C). The preheating section R2 is the period during which 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 workpiece. The reflow section R3 (e.g., 220°C to 240°C at peak temperature) is the period during which the solder melts and the joint is completed. In the reflow section R3, it is necessary to raise the temperature to a temperature that exceeds the melting temperature of the solder. The last cooling section R4 is the period during which the printed circuit board is rapidly cooled and the solder composition is formed. In addition, in the case of a lead-free solder alloy composition such as Sn-3.0Ag-0.5Cu, the temperature in the reflow section will be higher (e.g., 240°C to 260°C).

In the reflow device 1, the temperature control of the heating section R1 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.

As shown in FIG. 2, the outside furnace travel area 9 is provided with two parallel rail guides 11a and 11b (when there is no need to distinguish between the two rail guides, they are referred to as rail guide 11) as guide sections. The rail guide 11a is, for example, a combination of four divided guide parts Ga1, Ga2, Ga3, and Ga4, and the rail guide 11b is, for example, a combination of four divided guide parts Gb1, Gb2, Gb3, and Gb4.

The conveyor chains 3a and 3b travel in the direction indicated by the arrows, and the trajectories of the conveyor chains 3a and 3b are regulated by rail guides 11a and 11b. In FIG. 2, the leading position 12 and the terminal position 13 in the traveling direction of the conveyor chains 3a and 3b are respectively indicated by dashed lines. In the rail guide 11a, only the front end of the guide part Ga1 near the leading position 12 is fixed to a fixed part such as a frame, and in the rail guide 11b, only the front end of the guide part Gb1 near the leading position 12 is fixed to a fixed part such as a frame. As a fixing method, a normal method such as screw fastening can be used.

The front ends of guide parts Ga2 and Gb2 abut against the rear ends of the leading guide parts Ga1 and Gb1. Furthermore, the front ends of guide parts Ga3 and Gb3 abut against the rear ends of guide parts Ga2 and Gb2, and the front ends of guide parts Ga4 and Gb4 abut against the rear ends of guide parts Ga3 and Gb3. A stopper such as a protrusion that regulates the position of the front ends of guide parts Ga1 and Gb1 is provided at the leading position 12. In this case, a gap is provided between the front ends of guide parts Ga1 and Gb1 and the stopper, with a length that takes into account thermal expansion, deformation, etc. of rail guides 11a and 11b.

In this way, rail guide 11a consisting of guide parts Ga1 to Ga4 and rail guide 11b consisting of guide parts Gb1 to Gb4 are formed. Note that the number of guide parts for each rail guide is just an example, and the rail guide may be formed with any number of guide parts. Since rail guide 11 is configured by connecting multiple guide parts that are not fixed except for the top, each guide part is aligned by driving the conveyor chain, and a seamless chain path can be formed. In other words, since there are no steps or joints, the occurrence of problems such as vibration can be suppressed. In addition, the temperature of rail guide 11 rises when it comes into contact with conveyor chain 3, causing the rail guide 11 to stretch, but this stretch can be absorbed.

The material of the guide parts Ga1 to Ga4 of the rail guide 11a and the guide parts Gb1 to Gb4 of the rail guide 11b is, for example, a non-conductive resin, and among them, a non-conductive heat-resistant resin is preferable. Non-conductivity is a necessary characteristic to prevent short circuits on the workpiece, and heat resistance is a necessary characteristic for the conveyor chain 3 to be heated to high temperatures. For example, Delrin (registered trademark) is used. Other resins such as MC nylon and PEEK may also be used. By using these resins, it is possible to prevent short circuits on the workpiece due to the influence of metal pieces (contamination) that may occur when the conveyor chain 3 slides on the rail guide 11. In addition, metals such as stainless steel that have been subjected to surface treatment such as nitriding treatment may be used as the rail guide 11. The surface treatment suppresses the generation of metal pieces, and the size of the generated metal pieces can be made small enough to not cause a short circuit on the workpiece.

Figure 3 is a cross-sectional view in a direction perpendicular to the traveling direction of the conveyor chain (properly referred to as the width direction). The rail guide 11 has a groove 14 formed in the center, and the conveyor chain 3 runs inside the groove 14. The wall surfaces on both sides of the groove 14 of the rail guide 11 can regulate the displacement of the conveyor chain 3 in the width direction. Furthermore, the rail guide 11 is stored in the return rail 21. Note that the return rail 21 is omitted in Figure 2. The return rail 21 is made of a metal such as stainless steel, and has a bottom surface 22a and side surfaces 22b and 22c that are raised from both sides of the bottom surface 22a. The tips of the side surfaces 22a and 22b are bent parallel to the bottom surface 22a. The rail guide 11 is inserted from an opening at the top of the return rail 21.

The conveyor chain 3 has a pinned link plate 32 with a pin 31 on which the workpiece is placed, a link plate 33, and a roller (or bush) 34 located between the pinned link plate 32 and the link plate 33 and in contact with the sprocket. The width of the groove 14 of the rail guide 11 is made larger than the length between the pinned link plate 32 and the link plate 33, and a gap exists between the conveyor chain 3 and the wall surface of the groove 14.

The gap allows the conveyor chain 3 to be displaced slightly in the width direction. Inside the furnace, the distance between the two conveyor chains is prevented from fluctuating because there is a risk of the workpiece W falling off, but outside the furnace, there is no need for this, so the conveyor chain 3 is allowed to be displaced in the width direction. As a result, wear due to contact between the conveyor chain 3 and the rail guide 11 can be avoided. Furthermore, because some variation is allowed not only in the distance between the conveyor chains but also in the distance between the two rail guides, a simple installation method can be adopted in which the rail guides are fixed only at their tips.

The distance between the side portions 22b and 22c of the return rail 21 is greater than the width of the rail guide 11, and there are gaps 23a and 23b between the side surfaces on both sides of the rail guide 11 and the inner surfaces of the side portions 22b and 22c of the return rail 21. The rail guide 11 is not fixed to the bottom surface portion 22a of the return rail 21 except for the leading portion, so the rail guide 11 moves in the width direction. In this case, the side portions 22b and 22c of the return rail 21 restrict large displacement of the rail guide 11 in the width direction, preventing the rail guide 11 from bending so much that the conveyor chain 3 cannot run smoothly. However, if the possible displacement of the conveyor chain 3 in the width direction is small, the return rail 21 may not be provided.

The structure of the joints between the guide parts will be described with reference to Figures 4A, 4B, and 4C. While these figures show the joints between guide parts Ga1 and Ga2 of the rail guide 11a, the joints of the other guide parts can have a similar configuration. In one embodiment of the present invention, one end of the guide part protrudes relative to the other end in the width direction of the rail guide, and the ends abut or engage with each other.

In the example shown in FIG. 4A, the front end of the guide part Ga2 protrudes from the rear end of the guide part Ga1, and when the joint of the guide parts is viewed from above, the line L1 formed by the joint does not have a sharp part and is curved. In the example shown in FIG. 4B, the line L2 formed by the joint is wedge-shaped. FIGS. 4A and 4B are examples of abutment. Furthermore, FIG. 4C is an example in which a rectangular protrusion is formed at approximately the center position of the front end of the guide part Ga2, and this protrusion engages with a notch formed in the rear end of the guide part Ga1. The line L3 formed by the joint is bent at a right angle. Due to the configuration of these abutting or engaging end faces, even if the rail guide 11 is slightly tilted, it is aligned (followed) by the drive of the conveyor chain 3, so that the conveyor chain 3 can run stably.

The shapes shown in Figures 4A, 4B, and 4C are just examples, and various other shapes are possible. However, as shown in Figure 5, a shape in which the line L4 formed by the joint between guide parts Ga1 and Ga2 is a straight line coinciding with the width direction is not appropriate. As shown in Figure 5, such a joint is more likely to cause misalignment in the width direction of the two guide parts when a force in the width direction is applied to the rail guide 11a, as compared to the joints shown in Figures 4A, 4B, and 4C. As a result, a step is created in the running path of the rail guide 11, causing a problem in which the smooth running of the conveyor chain 3 is lost.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-mentioned embodiments, and various modifications based on the technical concept of the present invention are possible. For example, the present invention is not limited to printed circuit boards, but can also be applied to the reflow of flexible boards, boards in which rigid boards and flexible boards are bonded together, and rigid-flex boards that combine these. The present invention can also be applied to a reflow device with a single heating furnace (one zone). Furthermore, the present invention can be applied not only to reflow devices, but also to heating devices for curing resins. 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 spirit of the present invention.

1 ... reflow device, 3, 3a, 3b ... conveyor chain, W ... work,
9: Outside furnace travel range; 11, 11a, 11b: Rail guides; Ga1 to Ga4, Gb1 to Gb4: Guide parts; 14: Groove; 21: Return rail

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 furnaces;
A conveying and heating device having a conveying chain that conveys a workpiece to the heating device and conveys the workpiece out of the heating device,
the conveyor chain is endless and communicates with the inside of the heating device and the outside of the heating device,
a guide portion for regulating a trajectory of the conveyor chain is provided outside the heating device;
A conveying and heating device characterized in that the guide portion is made up of a plurality of divided guide portions connected to each other, and only the ends of the divided guide portions near the front of the conveying chain in the traveling direction are fixed . The conveying and heating device according to claim 1 , wherein the joints of the divided guide portions are of an abutting or interlocking structure. The conveying and heating device according to claim 1 or 2, wherein the dividing guide section has a longitudinal groove in which the conveying chain is arranged, and a gap is provided between the conveying chain and a wall of the groove. The conveying and heating device according to claim 1 or 2, which is provided with a regulating section that regulates the widthwise position of the guide section. The conveying and heating device according to claim 1 or 2, wherein the guide portion is made of a non-conductive resin.

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