JP2023016070A - Transportation heating device - Google Patents

Abstract

To provide a transportation heating device capable of preventing generation of scrap metal and suppressing a variation in the in-plane temperature distribution of a substrate.SOLUTION: A transportation heating device comprises: a heating device which is constituted so that one or more heating furnaces are arranged and a hot blast is blown to an object to be heated by the heating furnace; and a transport conveyor for transporting a substrate to the heating device. The transport conveyor comprises: transporting chains comprising facing link plates, shafts or rollers provided between the link plates, and attachments for mounting the substrate; metal rails each of which has a U-shaped cross section in which an upper surface part, a lower surface part and a side surface part are continuously formed, and in each of which the transporting chain is arranged in a space between the upper surface part and the lower surface part; and a plurality of rod-like lower side resin guides which are made of heat-resistant and non-conductive resin, are inserted in grooves formed in the lower surface parts of the metal rails so as to extend in a transporting direction, and are brought into contact with lower surfaces of the shafts or the rollers.SELECTED DRAWING: Figure 4

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conveying/heating apparatus applied to a reflow apparatus that conveys an object to be heated by a chain.

The transport chain is regulated in its running state by rails. For example, transport chains are used to transport electronic components or printed circuit boards in reflow machines. A reflow apparatus includes a reflow oven to which an object to be heated, such as a printed circuit board, is supplied by a conveying chain. A reflow furnace is configured, for example, in which a plurality of heating furnaces (furnace bodies) corresponding to a plurality of zones are arranged in order along a transport path from an inlet to an outlet. The multiple zones have roles such as heating zones and cooling zones depending on their functions.

In the heating zone, hot air is blown against the board to melt the solder and solder the electrical wiring circuit of the printed board and the electrodes of the electronic parts. In a reflow device, desired soldering is achieved by controlling the temperature during heating according to a desired temperature profile. In such a reflow machine, it is necessary to take into account the fact that fine metal scraps are generated due to the friction between the conveying chain and the guide rails, and prevent metal scraps from adhering to the printed circuit board and causing short circuits on the circuit board. must be prevented.

Patent Literature 1 describes that a chain rail made of polyamide-imide resin is arranged below the chain to support the chain. It is described that this configuration can improve wear resistance, heat resistance, and durability.

JP-A-11-79349

In the device described in Patent Document 1, the entire chain rail is made of polyamide-imide resin. However, in the case of a reflow device, since a plurality of furnace bodies are arranged in order, the chain rail has a length of several meters or more, and the chain rail made of resin lacks the strength and the chain rail does not have sufficient strength. There is a problem of warping.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a conveying and heating apparatus in which such problems do not occur.

The present invention comprises a heating device in which a single or a plurality of heating furnaces are arranged and configured to blow hot air onto an object to be heated by the heating furnaces, and a conveyer for carrying substrates into the heating device. ,
The transport conveyor is
a conveying chain comprising shafts or rollers provided between opposing link plates and attachments for mounting substrates;
a metal rail having a U-shaped cross section in which an upper surface portion, a lower surface portion, and a side surface portion are continuously formed, and a conveying chain is arranged between the upper surface portion and the lower surface portion;
A plurality of rod-shaped lower resin guides made of resin having heat resistance and non-conductivity, which are inserted into grooves formed on the lower surface of the metal rail to extend in the conveying direction and are in contact with the lower surface of the shaft or roller. It is a conveying heating device provided.

According to at least one embodiment, it is possible to prevent the substrate from being defective due to the generation of metal scraps, and it is possible to suppress variations in the temperature distribution in the surface of the substrate and perform good soldering. Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure. Also, the effects illustrated in the following description should not be construed as limiting the content of the present invention.

FIG. 1 is a schematic diagram showing an outline of an example of a reflow device 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 front view used for explaining the conveying chain. FIG. 4 is a cross-sectional view for explaining the chain guide portion in one embodiment of the present invention. 5A, 5B and 5C are a plan view, side view and cross-sectional view of an upper resin guide and a lower resin guide in one embodiment of the present invention. 6A and 6B are a plan view and a cross-sectional view when the test substrate is transported by the transport chain. FIG. 7 is a graph showing temperature changes measured using a conventional chain guide and temperature changes measured using a chain guide according to one embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described. The embodiment described below is a preferred specific example of the present invention, and is subject to various technically preferable limitations. It shall not be limited to these embodiments unless there is a description to the effect that the

FIG. 1 shows a schematic configuration of a conventional reflow device 101 to which the present invention can be applied. The reflow apparatus 101 includes a reflow furnace 102, a carrier chain 103 for passing an object to be heated, for example, a substrate W having surface-mounted electronic components mounted on both sides thereof, through the reflow furnace 102, and a rotating chain that defines the movement path of the carrier chain 103. It comprises bodies (idlers, sprockets, etc.) 105 a, 105 b, 105 c, 105 d and a skin 106 . Note that FIG. 1 shows only one conveying chain 103 of the two parallel conveying chains.

The reflow furnace 102 is for heating the substrate W from above and below and cooling it after heating. The conveying chain 103 is one of two conveying chains arranged in parallel with the conveying direction. For example, a roller chain is used as the transport chain 103 . The outer plate 106 is a case for covering the whole.

The substrate W is carried into the reflow furnace 102 from the carry-in port 107, then transported at a predetermined speed in the direction of the arrow (from left to right in FIG. 1) by the transport chain 103, and finally taken out from the carry-out port 108. be Although not shown, a substrate loading device for loading the substrate W is provided in front of the loading port 107, and a substrate unloading device for delivering the substrate W to the outside is arranged in the rear stage of the loading port 108. .

The reflow furnace 102 is sequentially divided into nine zones Z1 to Z9, for example, along the transfer path from the carry-in port 107 to the carry-out port 108, and these zones Z1 to Z9 are arranged inline. Seven zones Z1 to Z7 from the inlet 107 side are heating zones, and two zones Z8 and Z9 on the outlet 108 side are cooling zones. Forced cooling units (not shown) are provided in connection with cooling zones Z8 and Z9. Note that the number of zones is an example, and other numbers of zones may be provided. A plurality of zones Z1 to Z9 control the temperature of the substrate W according to the temperature profile during reflow. Each of the heating zones Z1-Z7 has an upper heating unit and a lower heating unit each including a blower.

The plurality of zones Z1 to Z9 described above control the temperature of the object to be heated according to the temperature profile during reflow. FIG. 2 shows an outline of an example of the temperature profile. The horizontal axis represents time, and the vertical axis represents the surface temperature of an object to be heated, such as a printed wiring board on which electronic components are mounted. The first section is a temperature raising section R1 where the temperature rises by heating, the next section is a preheating (preheating) section R2 with a substantially constant temperature, the next section is a reflow (main heating) section R3, and the last section The section is the cooling section R4.

The temperature rising section R1 is a period during which the substrate is heated from room temperature to the preheating section R2 (for example, 150.degree. C. to 170.degree. C.). The preheating part R2 is a period for 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 portion R3 (eg, 220° C. to 240° C. at peak temperature) is the period during which the solder melts and the joint is completed. In the reflow portion R3, it is necessary to raise the temperature to a temperature exceeding the melting temperature of the solder. Even after passing through the preheating portion R2, the reflow portion R3 has an 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 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 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 temperature profile for 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 the preheating section R2 and the reflow section R3 are higher than those of eutectic solder.

In the reflow apparatus shown in FIG. 1, the zones Z1 and Z2 mainly take charge of the temperature control of the temperature raising section R1 in FIG. Zones Z3, Z4 and Z5 are mainly responsible for temperature control of the preheating section R2. Zones Z6 and Z7 take charge of temperature control of the reflow section R3. Zones Z8 and Z9 take charge of temperature control of the cooling section R4.

An example of the carrier chain 103 in one embodiment will be described. FIG. 3 shows units that constitute the conveying chain 103 . In FIG. 3, 31 is a pin, 32a and 32b are inner link plates, 33a and 33b are outer link plates, 34 are rollers, and 35 is a link plate with pins. A pinned link plate 35 has substrate holding pins 37 . A roller 34 is attached to the pin 31 . The pin 31 is supported by two inner link plates 32a and 32b facing in parallel with the roller 34 and two outer link plates 33a and 33b facing in parallel. A conveying chain having shafts such as bushes or sleeves between the inner link plates 32a and 32b may be used without providing rollers.

The outer diameter of the roller 34 is made smaller than the width of the inner link plates 32a, 32b and the outer link plates 33a, 33b. In the example of FIG. 3, the widths of the inner link plates 32a, 32b and the outer link plates 33a, 33b are the same, and the width of the pin-equipped link plate 35 is slightly larger than the widths of the inner link plates and the outer link plates. It is The inner link plate 32a, the outer link plate 33a, and the pin-equipped link plate 35 are arbitrarily referred to as an attachment-equipped link plate portion 36a, and the inner link plate 32b and the outer link plate 33b are arbitrarily referred to simply as the link plate portion 36b. In addition, you may make it have attachments other than a pin.

In the reflow apparatus 101 shown in FIG. 1, a chain guide portion 14 is provided along the transport path from the carry-in port 107 to the carry-out port 108 . FIG. 4 shows a cross section of the chain guide portion 14 . For example, a metal rail 41 made of aluminum extrusion has a U-shaped cross section in which an upper surface portion 41a, a lower surface portion 41b, and a side surface portion 41c are continuously formed. A conveying chain 103 is arranged in the space between the upper surface portion 41a and the lower surface portion 41c.

A groove 42a extending in the conveying direction is formed in the inner surface of the upper surface portion 41a of the metal rail 41. As shown in FIG. The width of the opening extending in the longitudinal direction of the groove 42a is made smaller than the width of the groove. A groove 42b extending in the conveying direction is formed in the inner surface of the lower surface portion 41b facing the upper surface portion 41a. The width of the opening extending in the longitudinal direction of the groove 42b is made smaller than the width of the groove. An upper resin guide 43a made of heat-resistant and non-conductive resin is inserted into the groove 42a. A lower resin guide 43b made of heat-resistant and non-conductive resin is inserted into the groove 42b.

5A, 5B and 5C are a plan view, a side view and a sectional view of the upper resin guide 43a. The upper resin guide 43a is rod-shaped with a predetermined length, for example, 250 (mm). The upper resin guide 43a is, for example, a molded product made of polyamide-imide resin. Polyamideimide resins have properties such as abrasion resistance, heat resistance, and durability. Moreover, it does not contain carbon and does not have conductivity. Therefore, there is no risk of short-circuiting on the substrate due to resin waste generated by friction with the conveying chain 103 . In addition, you may use a polyimide resin as a material.

The upper resin guide 43a has a plate-shaped base portion 44a and ribs 45a projecting from the base portion 44a. The width and thickness of the base portion 44a are set to a value that allows it to be inserted into the groove 42a of the upper surface portion 41a of the metal rail 41, and the height of the rib 45a is set to a value that allows it to protrude outward from the opening of the groove 42a. ing. The width of the rib 45a is slightly smaller than the distance between the link plate portion 36a and the link plate portion 36b of the transport chain 103 facing each other.

Furthermore, both ends of the upper resin guide 43a are chamfered to facilitate insertion into the groove 43a. The width of the base portion 44a is, for example, 7 (mm), the width of the rib 45a is 4 (mm), and the height of the rib 45a is 5.25 (mm). Note that the length of the upper resin guide 43a and the dimensions of the base portion 44a and ribs 45a are examples of values that take into account the required strength and workability. The lower resin guide 43b is also made of the same material as the upper resin guide 43a, and has a shape having a base portion 44b and ribs 45b. For the lengths described above, dozens of upper resin guides 43a and lower resin guides 43b are used. By dividing the upper resin guide 43a and the lower resin guide 43b in this way, the insertion work into the groove can be facilitated, and the influence of expansion and contraction due to temperature change can be reduced.

As shown in FIG. 4, the upper resin guide 43a is inserted into the groove 42a of the upper surface portion 41a of the metal rail 41, and the lower resin guide 43b is inserted into the groove 42b of the lower surface portion 41b of the metal rail 41. As shown in FIG. A rib 45b of the lower resin guide 43b protrudes upward from the opening of the groove 42b. It mainly has a function of supporting the conveying chain 103 from below by contacting the upper surface of the rib 45b and the roller 34 of the conveying chain 103 . The rib 45a of the upper resin guide 43a protrudes downward, and the upper surface of the rib 45a is located within the space between the link plate portion 36a with attachment and the link plate portion 36b of the transport chain 103 facing each other. The rib 45a of the upper resin guide 43a may come into contact with the roller 34, but mainly has the function of regulating the position of the transport chain 103 in the width direction.

The thermal conductivity of polyamide-imide resin, which is the material of the upper resin guide 43a and the lower resin guide 43b, is, for example, 0.26 (W/mK), and the thermal conductivity of stainless steel (15 (W/mK)) and aluminum It is a very small value compared to the thermal conductivity (225 (W/mK)) of By providing such an upper resin guide 43a and a lower resin guide 43b, it is possible to suppress the heat dissipation of the substrate edge surface.

As shown in the plan view of FIG. 6A and the cross-sectional view of FIG. 6B, the substrate W is transported with the vicinity of the end surface placed on each of the substrate holding pins 37 of the transport chains 103 arranged in parallel. When the substrate W is heated according to a predetermined profile, it is desirable that the in-plane temperature distribution within the substrate W does not vary.

The heat of the substrate W is radiated to the transport chain 103 through the substrate holding pins 37 and furthermore, the heat is radiated through the chain guide portion 14 . Conventionally, when the transport chain 103 is in contact with the metal rail, the heat of the substrate W is easily dissipated due to the high thermal conductivity of the metal. decreases compared to If the temperature difference is large, there is a possibility that good soldering cannot be performed in the vicinity of the end face. In one embodiment of the present invention, since the conveying chain 103 is in contact with the lower resin guide 43b having extremely low thermal conductivity, it is possible to suppress the temperature drop in the vicinity of the edge surface of the substrate.

6A, 6B and 7, test results regarding heat dissipation of the substrate W will be described. The substrate W in FIGS. 6A and 6B is a substrate for testing, and metal plates 47a and 47b made of, for example, stainless steel are mounted at positions directly above the substrate holding pins 37 in the vicinity of the end surface of the substrate W, and near the center of the substrate W. A stainless metal plate 48 is mounted. The metal plates 47a, 47b and 48 are imitations of electronic components to be mounted. Examples of materials and dimensions of the substrate W and the metal plates 47a, 47b, and 48 are shown below.

Substrate W: SUS304, thickness 1.5 (mm), width x length = 250 x 180 (mm)
Metal plates 47a, 47b: SUS304, diameter 35 (mm), thickness 2.0 (mm)
Metal plate 48: SUS304, diameter 30 (mm), thickness 1.5 (mm)

The reason why the metal plates 47a and 47b and the metal plate 48 have different volumes is to clarify the difference between the heat dissipation in the vicinity of the end faces and the heat dissipation in the region near the center. The graph of FIG. 7 shows the result of measuring the temperature change of each metal plate by putting such a test substrate into a reflow apparatus and measuring it with a temperature detector such as a thermocouple. The horizontal axis of FIG. 7 is time, and the vertical axis is the measured temperature.

In FIG. 7, curve 51 shows the measurement results of metal plate 48 in the case of the conventional reflow device, and curves 52a and 52b show the measurement results of metal plates 47a and 47b in the case of the conventional reflow device. The conventional reflow device has a structure in which the conveying chain 103 is supported and guided by metal rails. In FIG. 7, curve 53 shows the measurement results of metal plate 48 in the case of the reflow apparatus according to one embodiment of the present invention, and curves 54a and 54b show the measurement results of metal plates 47a and 47b in the case of the reflow apparatus according to one embodiment of the present invention. shows the measurement results of As described above, the reflow device according to one embodiment of the present invention has a structure in which the conveying chain 103 is supported and guided by the upper resin guide 43a and the lower resin guide 43b. It should be noted that the time axis is intentionally shifted between the conventional temperature change graph and the temperature change graph of the embodiment of the present invention in order to make the measurement results easier to see.

In the graph of FIG. 7, the central metal plate 48 has a smaller heat capacity than the other metal plates 47a and 47b, so the temperature is the highest as indicated by curves 51 and 53. FIG. The metal plates 47a and 47b have the same heat capacity, but in order to adjust the width of the substrate, one of the conveyor rails (the outer side in the conveying width direction of the furnace body) is fixed, and the other (the center side in the conveying width direction of the furnace body) is fixed. Since the metal plate 47b is movable, the metal plate 47b closer to the conveyor rail side on the center side of the furnace body in the conveying path is given more heat than the metal plate 47a. 54b) has a higher temperature than the temperature change of the metal plate 47a (curves 52a and 54a).

In the conventional reflow apparatus, the peak temperature of the temperature change (curve 51) of the metal plate 48 near the center, the peak temperature of the temperature change (curve 52a) of the metal plate 47a near the end face, and the temperature change of the metal plate 47b ( The temperature difference ΔT1 of the peak temperature of curve 52b) was 16.5°C. On the other hand, in the reflow apparatus of one embodiment of the present invention, the peak temperature of the temperature change (curve 53) of the metal plate 48 in the region near the center, the peak temperature of the temperature change (curve 54a) of the metal plate 47a near the end surface, and The temperature difference ΔT2 of the peak temperature of the temperature change (curve 54b) of the metal plate 47b was 11.4°C.

Since the peak value of the temperature change of the metal plate 48 in the region near the center is the same between the conventional reflow apparatus and the reflow apparatus according to one embodiment of the present invention, the reflow apparatus according to one embodiment of the present invention can The temperature drop in the area can be made smaller than in the conventional reflow equipment. Therefore, the in-plane temperature variation of the substrate can be reduced, and the risk of defective soldering by the reflow device can be reduced.

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 are possible based on the technical idea of the present invention. For example, the material of the metal rail is not limited to aluminum and may be stainless steel. In addition, the present invention is applicable not only to printed circuit boards, but also to flexible substrates, substrates in which a rigid substrate and a flexible substrate are bonded together, and rigid-flex substrates in which these are combined. Further, the present invention can be applied to a reflow apparatus having a one-stage (one-zone) heating furnace. Furthermore, the present invention can be applied not only to a reflow device but also to a heating device or the like for curing resin. In addition, the configurations, methods, steps, shapes, materials, numerical values, etc. given in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. may Also, the configurations, methods, steps, 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.

DESCRIPTION OF SYMBOLS 101... Reflow apparatus, 103... Conveyance chain, W... Substrate,
14... Chain guide portion, 36a... Link plate portion with attachment,
36b... link plate portion, 37... substrate holding pin, 41... metal rail,
41a ... upper surface portion, 41b ... lower surface portion, 41c ... side surface portion,
42a, 42b... groove, 43a... upper resin guide, 43b... lower resin guide, 44a... base, 45a... rib

Claims (4)

A heating device in which a single or a plurality of heating furnaces are arranged, and is configured to blow hot air onto an object to be heated by the heating furnace, and a conveyor for carrying the substrate to the heating device,
The transport conveyor is
a conveying chain comprising link plates facing each other, shafts or rollers provided between the link plates, and attachments for mounting substrates;
a metal rail having a U-shaped cross section in which an upper surface portion, a lower surface portion, and a side surface portion are continuously formed, and a conveying chain is arranged between the upper surface portion and the lower surface portion;
A plurality of rod-shaped lower resin guides made of heat-resistant and non-conductive resin, inserted into grooves formed in the lower surface of the metal rail to extend in the conveying direction, and in contact with the lower surface of the shaft or roller. and a conveying heating device. A plurality of rod-shaped upper resins made of resin having heat resistance and non-conductivity, which are inserted into grooves formed in the upper surface of the metal rail so as to extend in the conveying direction and face the upper surface of the shaft or roller. The conveying and heating device according to claim 1, comprising a guide. 3. The conveying and heating device according to claim 2, wherein each of said lower resin guide and said upper resin guide has a base inserted into said groove, and a rib projecting from said base and having a width smaller than the interval between said link plates. . 4. The conveying and heating device according to claim 2, wherein the material of each of said lower resin guide and said upper resin guide is polyamide-imide resin.

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