JP6824082B2 - Flux recovery device - Google Patents

Description

The present invention relates to, for example, a flux recovery device used in a reflow device.

A reflow device is used in which a solder composition is supplied in advance to an electronic component or a printed wiring board, and the substrate is conveyed into a reflow furnace by a conveyor. In the heating zone of the reflow device, hot air is blown against the substrate to melt the solder in the solder composition and solder the electrodes of the substrate and the electronic components. The solder composition comprises powder solder, solvent and flux. Flux contains rosin as a component, removes the oxide film on the surface of the metal to be soldered, prevents reoxidation due to heating during soldering, reduces the surface tension of the solder and improves wetting. It acts as a coating agent. This flux is vaporized by heating and fills the reflow furnace as a fume. Fume (vaporized flux) easily adheres to low-temperature parts, liquefies when cooled, and drops from the adhered parts, so it may adhere to the upper surface of the substrate, and the performance of the substrate. Will be damaged. In addition, it may have a great influence on the reflow process due to accumulation in a portion where the temperature drops in the furnace body. Therefore, the flux in the reflow furnace is removed or recovered.

In recent years, lead-free solder reflow is generally inferior in wettability to Sn-Pb cream solder, and therefore the reflow temperature also changes. Therefore, the flux is made heat resistant to reduce the wettability. It is made to suppress. That is, the amount of the rosin component contained in the solder paste is increased, and a component that is not easily thermally decomposed is used. This results in an increase in the fume released into the furnace body.

For example, in Patent Document 1 below, an in-pipe fin, for example, a spiral fin, in which the outer peripheral surface is freely inserted / detached in a cooled pipe to substantially lengthen the length when the atmospheric gas passes through the pipe. A flux recovery device that efficiently recovers the flux using the above is described.

Japanese Patent No. 5366395

In the flux recovery device described in Patent Document 1, the flux gradually adheres to the inner surface of the pipe during use, the passage of the atmospheric gas taken out from the furnace body becomes narrow, and the flux recovery performance may deteriorate. , It has been desired to further lengthen the maintenance cycle.

Therefore, an object of the present invention is to provide a flux recovery device capable of preventing a deterioration in flux recovery performance by removing the flux adhering to the inner surface of the pipe.

The present invention includes a tubular cooling unit that cools by passing a refrigerant through a gap provided on the outer circumference.
A recovery container that collects the liquefied flux that collects in the cooling unit,
In-pipe fins that are freely inserted / detached in the cooling unit and form a passage path through which the atmospheric gas derived from the soldering device passes.
A circulation means that returns the atmospheric gas that has passed through the cooling unit to the soldering equipment,
It is a flux recovery device in which a plurality of plate-shaped fins of inner pipe fins are attached, and a shaft portion having a hole for blowing an inert gas toward the inner wall surface of the cooling unit is formed on the peripheral surface.

According to at least one embodiment, the flux adhering to the inner wall can be blown off by the inert gas, and deterioration of the flux recovery performance can be prevented. In addition, maintenance work can be performed automatically. The effects described here are not necessarily limited, and may be any of the effects described in the present specification. In addition, the contents of the present invention are not limitedly interpreted by the effects exemplified in the following description.

FIG. 1 is a schematic diagram showing an outline of a conventional 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 cross-sectional view showing an example of the configuration of one heating zone of the reflow device. FIG. 4 is a cross-sectional view of the first embodiment of the present invention. FIG. 5 is a perspective view of an example of an in-pipe fin according to the first embodiment of the present invention. FIG. 6 is a schematic diagram of a part of the fins in the pipe. FIG. 7 is a cross-sectional view showing a modified example of the first embodiment of the present invention. It is sectional drawing used for the explanation of the 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described. The description will be given in the following order.
<1. Example of reflow device>
<2. First Embodiment>
<3. Second Embodiment>
<4. Modification example>
It should be noted that one embodiment described below is a preferred specific example of the present invention and is provided with various technically preferable limitations, but the scope of the present invention is particularly limited to the present invention in the following description. Unless otherwise stated to limit, the present invention shall not be limited to these embodiments.

<1. Example of reflow device>
FIG. 1 shows a schematic configuration of a conventional reflow device 101 to which the present invention can be applied. In FIG. 1, for convenience of explanation, the illustration of the flux recovery device arranged outside the reflow furnace is omitted. An object to be heated on which surface mount electronic components are mounted on both sides of the printed circuit board is placed on a conveyor and is carried into the furnace body of the reflow device from the carry-in port 11. The conveyor conveyor conveys the object to be heated in the direction of the arrow (from left to right toward FIG. 1) at a predetermined speed, and the object to be heated is taken out from the carry-out port 12. The transport direction of the conveyor is horizontal.

The reflow furnace is sequentially divided into, for example, nine zones Z1 to Z9 along the transfer path from the carry-in inlet 11 to the carry-out port 12, and these zones Z1 to Z9 are arranged in-line. The seven zones Z1 to Z7 from the inlet side are heating zones, and the two zones Z8 and Z9 on the outlet side are cooling zones. A forced cooling unit 14 is provided in connection with the cooling zones Z8 and Z9.

The plurality of zones Z1 to Z9 described above control the temperature of the object to be heated according to the temperature profile at the time of reflow. FIG. 2 outlines an example of a temperature profile. The horizontal axis is time, and the vertical axis is the surface temperature of a printed circuit board on which an object to be heated, for example, an electronic component, is mounted. The first section is the heating section R1 where the temperature rises due to heating, the next section is the preheating section R2 whose temperature is almost constant, the next section is the main heating section R3, and the last section is the main heating section R3. It is a cooling unit R4.

The temperature raising section R1 is a period for heating the substrate from room temperature to the preheating section R2 (for example, 150 ° C to 170 ° C). The preheat portion R2 is a period for performing isothermal heating, activating the flux, removing the oxide film on the surface of the electrode and the solder powder, and eliminating uneven heating of the printed circuit board. The main heating portion R3 (for example, 220 ° C to 240 ° C at the peak temperature) is a period during which the solder is melted and the bonding is completed. In the main heating unit R3, it is necessary to raise the temperature to a temperature exceeding the melting temperature of the solder. Even if the heating portion R3 has passed through the preheating portion R2, the temperature rise is uneven, so that the heating to a temperature exceeding the melting temperature of the solder is required. The final cooling unit R4 is a period in which the printed circuit board is rapidly cooled to form a solder composition.

In FIG. 2, curve 1 shows the temperature profile of the lead-free solder. The temperature profile in the case of Sn—Pb eutectic solder is shown by curve 2. Since the melting point of the lead-free solder is higher than the melting point of the Sn—Pb eutectic solder, the set temperature in the preheat portion R2 is higher than that of the Sn—Pb eutectic solder.

In the reflow device, the zones Z1 and Z2 are mainly in charge of temperature control of the temperature raising unit R1 in FIG. Zones Z3, Z4 and Z5 are mainly in charge of temperature control of the preheat unit R2. Zones Z6 and Z7 are in charge of temperature control of the heating unit R3. Zone Z8 and Zone Z9 are in charge of temperature control of the cooling unit R4.

Each of the heating zones Z1 to Z7 has an upper furnace body 15 including a blower and a lower furnace body 35, respectively. For example, hot air is blown to the objects to be heated transported from the upper furnace body 15 and the lower furnace body 35 of the zone Z1.

An example of the heating device will be described with reference to FIG. For example, FIG. 3 shows a cross section when the zone Z6 is cut at a plane orthogonal to the transport direction. In the facing gap between the upper furnace body 15 and the lower furnace body 35, an object to be heated (hereinafter referred to as a work) W on which electronic components for surface mounting are mounted on both sides of the printed circuit board is placed on the conveyor 31. Be transported. The inside of the upper furnace body 15 and the inside of the lower furnace body 35 are filled with an atmospheric gas such as nitrogen (N2) gas. The upper furnace body 15 and the lower furnace body 35 blow hot air (heated atmospheric gas) to the work W to heat the work W. Infrared rays may be irradiated together with hot air.

The upper furnace body 15 includes, for example, a blower 16 having a turbofan configuration and baffles 17a and 17b arranged to face each other in order to disperse the air from the blower 16 and make the temperature distribution in the furnace uniform. The work W has a heater 18 formed by folding back a plurality of heater wires and a heating panel (heat storage member) 19 having a large number of small holes through which hot air passes, and hot air passing through the small holes of the heating panel 19 becomes a work W. On the other hand, it is sprayed from above. The heating panel 19 is, for example, an aluminum metal plate in which a large number of small holes are formed.

The lower furnace body 35 also has the same configuration as the upper furnace body 15 described above. That is, for example, the blower 26 having a turbofan configuration, the baffle plates 27a and 27b arranged opposite to each other in order to disperse the air from the blower 26 and make the temperature distribution in the furnace uniform, and the heater wire. It has a heater 28 configured by folding back a plurality of times, and a heating panel (heat storage member) 29 having a large number of small holes through which hot air passes. Hot air that has passed through the small holes of the heating panel 29 is blown from below to the work W.

A flux recovery device 41 is provided for the upper furnace body 15. The flux recovery device 41 is installed on the back side of the upper furnace body 15 in a space surrounded by an outer plate, for example. A flux recovery device 61 is provided for the lower furnace body 35. The flux recovery device 61 is installed on the back side of the lower furnace body 35, for example, in a space surrounded by an outer plate. The flux recovery device 41 includes a cooling unit 42 for cooling the atmospheric gas led out from the upper furnace body 15, and a recovery container 43 for recovering the flux liquefied by cooling. Similarly, the flux recovery device 61 includes a cooling unit 62 for cooling the atmospheric gas led out from the lower furnace body 35, and a recovery container 63 for recovering the flux liquefied by cooling.

A hole 52 is provided as an outlet for leading the atmospheric gas to the flux recovery device 41 in the path through which the hot air is circulated by the blower 16. The hole 52 is provided in a place where the pressure is high in the furnace. At a place where the pressure is low, a hole 53 is provided as an introduction port for introducing the gas from the flux recovery device 41 into the upper furnace body 15. These holes 52 and 53 actually correspond to the openings on one end side of the connecting pipes 54 and 55, respectively. Each of the connecting pipes 54 and 55 and the connecting pipe of the flux recovery device 41 are connected by a hose (not shown). Also in the lower furnace body 35, the atmospheric gas is led out to the flux recovery device 61 from the holes provided at the places where the pressure is high in the furnace, and the gas from which the flux component is reduced from the flux recovery device 61 has a low pressure in the furnace. It is introduced from the hole provided in the place. As described above, the circulation means including the flux recovery devices 41 and 61 is provided.

The flux recovery devices 41 and 61 are provided in the zones where the atmospheric gas is heavily polluted in each zone of the reflow device. However, flux recovery devices 41 and 61 may be arranged in all zones of the reflow device.

Unlike the heating zones, the cooling zones Z8 and Z9 do not have heaters 18 and 28, and the cooling gas (inert gas such as N2 gas or air) is passed through the cooling panel by the blowers provided above and below. It is configured to be sprayed on the work W. The cooling panel is a metal plate made of aluminum or the like in which a large number of small holes are formed.

<2. First Embodiment>
The present invention is applied to the flux recovery device 41 or 61 of the reflow device described above. In the following description, an embodiment in which the present invention is applied to the flux recovery device 41 will be described, but the present invention can be similarly applied to the flux recovery device 61.

The cooling unit 42 of the flux recovery device 41 is a structure in which a cylindrical upper unit 71, a cooling unit 72, and a lower unit 73 having substantially the same diameter are separably connected. The upper unit 71 is provided with a connecting pipe 74, and the lower unit 73 is provided with a connecting pipe 75. Although not shown, the connecting pipe 75 is provided with a gas circulation device, and the gas from which the flux component has been removed by the gas circulation device is returned to the upper furnace body 15 of the reflow device.

Atmospheric gas containing fume is introduced into the cooling unit 72 from the connecting pipe 74 through the upper unit 71, and the flux component in the atmospheric gas is liquefied and accumulated at the bottom of the lower unit 73. A drain 76 is provided on the bottom plate of the lower unit 73 via a controllable valve such as a solenoid valve. Further, a collection container 43 (not shown) is arranged in the drain 76, and when the valve is opened, the flux component is collected in the container through the discharge port 76.

The cooling unit 72 cools the atmospheric gas by, for example, a water cooling method. The cooling unit 42 is configured as a two-layer pipe composed of an inner pipe and an outer pipe provided concentrically, and cooling water as a refrigerant is injected into the gap between the pipes from the injection port 77 and discharged from the discharge port 78. .. Although not shown, a cooling water circulation motor is provided for the discharge port 78. The atmosphere gas may be cooled by an air cooling method.

In-pipe fins 81 are used that are freely insertable / detachable in the pipe of the cooling unit 72 to substantially increase the length of atmospheric gas as it passes through the pipe. As shown in FIG. 5, the in-pipe fin 81 has a configuration in which plate-shaped fins 83 are attached to the central pipe 82 as a shaft portion extending in the extension direction of the cooling unit 72 at predetermined intervals. The plate-shaped fin 83 is composed of a slit formed in the radial direction and a disk having a hole into which the central pipe 82 is inserted on the closing side of the slit, and the two semicircles are twisted in opposite directions with the slit in between. Has a shape.

Since the plate-shaped fins 83 form a spiral passage path for the atmospheric gas, the length of this passage path can be made longer than the length in the longitudinal direction of the cooling unit 72. As a result, the effect of removing dirt such as fume in the atmospheric gas can be enhanced. However, with the passage of time for flux recovery, liquefied flux adheres to the inner pipe surface of the cooling unit 72 and a part of the plate-shaped fins 83, and the flux recovery effect is reduced.

Therefore, in the first embodiment of the present invention, in order to automate the maintenance work, an inert gas such as nitrogen gas is periodically blown out from the central pipe 82 to blow off the adhering dirt. As an example, nitrogen gas is supplied from a nitrogen gas supply source (not shown) through a connecting pipe 84 that connects the lower end of the central pipe 82 and the gas introduction port of the bottom plate of the lower unit 73. In addition, during the flux recovery operation, the nitrogen gas blowing operation may be performed in parallel.

A large number of gas ejection holes 85 are formed on the peripheral surface of the central pipe 82. Nitrogen gas ejected from the gas ejection hole 85 is sprayed onto the inner wall surface of the cooling unit 71 and the plate-shaped fins 83, and the dirt adhering to these portions is blown off and dropped downward. The gas ejection hole 85 may be formed on the entire peripheral surface, or may be formed so as to preferentially blow nitrogen gas to a portion where flux is likely to adhere. For example, as shown in FIGS. 5 and 6, the gas ejection hole 85 is formed so as to blow the inert gas toward the connecting portion 86 of the semicircular portion of the plate-shaped fin 83. As described above, in the first embodiment of the present invention, the inert gas can blow off the flux adhering to the inner wall of the cooling unit 72 and the fins 81 in the pipe, so that the atmospheric gas of the cooling unit 72 can be blown away. It is possible to prevent the passage path from being narrowed or the passage path from being blocked, to prevent a decrease in the efficiency of flux recovery, and to reduce the burden of cleaning the inner fin 81.

As shown in FIG. 7, the flux recovery device according to the first embodiment of the present invention may be connected in series. Reference numeral 42A is attached to the cooling part of the first-stage flux recovery device, and reference numeral 42B is attached to the cooling part of the second-stage flux recovery device. The same reference numerals as those in FIG. 4 are attached to each part of each flux recovery device. A recovery container is provided to recover the flux component taken out from the drain 76 of each cooling unit.

The connection pipe 75 of the cooling unit 42A of the first-stage flux recovery device and the connection pipe 75 of the cooling unit 42B of the second-stage flux recovery device are connected. That is, the atmospheric gas from which the fume has been removed to some extent by passing through the cooling unit 42A downward is taken in from the lower side of the cooling unit 42B and flows upward.

In the cooling unit 42B, the gas from which the fume has been further removed is sent from the connecting pipe 74 to the gas introduction port 92 of the gas circulation motor 91. The gas sent out from the gas outlet 93 by the gas circulation motor 91 is returned to the upper furnace body of the soldering apparatus through a pipe (not shown).

Tables 1 and 2 show the results of measuring the temperature of the atmospheric gas at a plurality of measurement points of the flux recovery device having the configuration shown in FIG. 7, respectively. In Tables 1 and 2, M1 to M6 represent measurement points, as shown in FIG. The measurement point M1 represents a measurement point in the upper unit 71 of the cooling unit 42A. The measurement point M2 represents a measurement point in the cooling unit 72 of the cooling unit 42A. The measurement point M3 represents a measurement point in the connecting pipe 75 of the cooling unit 42A. The measurement point M4 represents a measurement point in the cooling unit 72 of the cooling unit 42B. The measurement point M5 represents a measurement point in the connecting pipe 74 of the cooling unit 42B. The measurement point M6 represents a measurement point in the gas outlet 93 of the gas circulation motor 91.

Table 1 showing the measurement results shows the measurement results when the gas circulation motor 91 has a frequency of 50 Hz and the circulating air volume is 612 liters / minute, and Table 2 shows the measurement results when the gas circulation motor 91 has a frequency of 35 Hz and the circulating air volume is 420 liters. The measurement result in the case of / minute is shown. The cooling capacity is indicated by how much the temperature of the atmospheric gas at the measurement point M1 drops at the final measurement point M6.

The measurement results in Table 1 show that the atmospheric gas at 211.2 ° C. can be finally cooled to 56.7 ° C. The measurement results in Table 2 show that the atmospheric gas at 203.7 ° C can be finally cooled to 46.9 ° C. In the case of the configuration in which the gas is not blown out from the central pipe 82, since the temperature of 213 ° C can be lowered only to 75 ° C, it can be seen that the cooling performance is improved and the flux recovery capacity is improved. Further, by blowing out the gas from the central pipe 82, not only the cooling performance is improved, but also the passage path of the atmospheric gas of the cooling unit 72 can be prevented from being narrowed or the passage path is blocked, and the flux can be prevented. It is possible to prevent a decrease in collection efficiency.

<3. Second Embodiment>
A second embodiment of the present invention will be described with reference to FIG. The same reference numerals are given to the parts corresponding to the first embodiment. Further, as in the first embodiment, the second embodiment can similarly apply the present invention to the flux recovery device 61.

The cooling unit 42'of the flux recovery device according to the second embodiment is a structure in which a cylindrical upper unit 71, a cooling unit 72, and a lower unit 73 having substantially the same diameter are separably connected. The upper unit 71 is provided with a connecting pipe 74, and the lower unit 73 is provided with a connecting pipe 75. Although not shown, the connecting pipe 75 is provided with a gas circulation device, and the gas from which the flux component has been removed by the gas circulation device is returned to the upper furnace body 15 of the reflow device.

Atmospheric gas containing fume is introduced into the cooling unit 72 from the connecting pipe 74 through the upper unit 71, and the flux component in the atmospheric gas is liquefied and accumulated on the partition plate 87 of the lower unit 73. A connecting pipe 88 connects the partition plate 87 and the drain 76 attached to the bottom plate of the lower unit 71. Further, a collection container 43 (not shown) is arranged in the drain 76, and when the valve is opened, the flux component is collected in the container through the discharge port 76.

The cooling unit 72 cools the atmospheric gas by a water cooling method as in the first embodiment. The cooling unit 42 is configured as a two-layer pipe composed of an inner pipe and an outer pipe provided concentrically, and cooling water as a refrigerant is injected into the gap between the pipes from the injection port 77 and discharged from the discharge port 78. ..

In-pipe fins 81 are used that are freely insertable / detachable in the pipe of the cooling unit 72 to substantially increase the length of atmospheric gas as it passes through the pipe. The in-pipe fin 81 is the same as that in the first embodiment described above (see FIG. 5). However, in the second embodiment, the shaft to which the plate-shaped fin 83 is attached is the rotating shaft 94.

The rotating shaft 94 is rotated by a motor 95 as a driving unit provided under the partition plate 87 of the lower unit 73. A reduction mechanism such as a gear mechanism may be provided between the rotation shaft of the motor 95 and the rotation shaft 94, if necessary.

In the second embodiment of the present invention, in order to automate the maintenance work, the inner fin 81 is rotated by rotating the motor 95 periodically, and the dirt adhering to the inner wall of the cooling unit 72 is scraped off. Be done. The rotation operation of the in-pipe fin 81 may be performed in parallel during the flux recovery operation. As described above, in the second embodiment of the present invention, the flux adhering to the inner wall of the cooling unit 72 can be scraped off, so that the passage path of the atmospheric gas of the cooling unit 72 is narrowed or the passage path is narrowed. Can be prevented from being blocked, and the efficiency of flux recovery can be prevented from being lowered.

<4. Modification 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 may be a combination of the above-described first embodiment and the second embodiment. In addition, the configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. You may. In addition, the configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments can be combined with each other without departing from the gist of the present invention.

11 ... Carry-in inlet, 12 ... Carry-out outlet, 15 ... Upper furnace body, 31 ... Conveyor conveyor, 35 ... Lower furnace body, 41, 61 ... Flux recovery device, 42, 62・ ・ ・ Cooling part, 43, 63 ・ ・ ・ Flux recovery container, 71 ・ ・ ・ Upper unit,
72 ... Cooling unit, 73 ... Lower unit, 81 ... Pipe fins,
82 ... Central pipe, 83 ... Plate fin, 85 ... Gas ejection hole,
89 ... motor, 91 ... gas circulation motor, 94 ... rotary shaft, 95 ... motor

Claims (5)

A tubular cooling unit that cools by passing refrigerant through the gaps provided on the outer circumference,
A recovery container that collects the liquefied flux that collects in the cooling unit, and
In-pipe fins that are freely inserted / detached into the cooling unit and form a passage path through which the atmospheric gas derived from the soldering apparatus passes.
A circulation means for returning the atmospheric gas that has passed through the cooling unit to the soldering apparatus, and
A flux recovery device in which a plurality of plate-shaped fins of the inner pipe fins are attached, and a shaft portion having holes formed on the peripheral surface for blowing an inert gas toward the inner wall surface of the cooling unit is provided. A tubular cooling unit that cools by passing refrigerant through the gaps provided on the outer circumference,
A recovery container that collects the liquefied flux that collects in the cooling unit, and
In-pipe fins that are freely inserted / detached into the cooling unit and form a passage path through which the atmospheric gas derived from the soldering apparatus passes.
A circulation means for returning the atmospheric gas that has passed through the cooling unit to the soldering apparatus, and
A flux recovery device including a drive unit for rotating a shaft portion to which a plurality of plate-shaped fins included in the pipe fins are attached. The cooling unit is arranged substantially vertically, the atmospheric gas is introduced into the upper unit communicating with one opening of the cooling unit, and the liquefied flux is taken out from the lower unit of the cooling unit into the recovery container. The flux recovery device according to claim 1 or 2. The plate-shaped fin is composed of a slit formed in the radial direction and a disk having a hole into which the shaft portion is inserted on the closing side of the slit, and the two semicircular portions are opposite to each other with the slit in between. The flux recovery device according to any one of claims 1 to 3, which has a twisted shape. The flux recovery device according to claim 4, wherein the hole formed on the peripheral surface of the shaft portion blows an inert gas toward the connecting portion of the semicircular portion of the plate-shaped fin.

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