JP2011143435A - Reflowing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflowing apparatus in which mist concentration of gas in a reflowing furnace is measured, and if the concentration becomes higher than a preset value, an alarm is generated and flux removal capability is enhanced. <P>SOLUTION: Gas in the furnace is inhaled through a zone Z6 acting as a main heating part, and the inhaled gas is discharged in the furnace from a discharge part of a zone Z7 through a flux recovery unit 31 and a blower 32. A measured value of a dustmeter 23 by light scattering method is supplied to a controller 33. The controller 33 compares the measured value to a preset threshold value, and if the measured value becomes higher than the threshold value, generates an alarm using an alarm unit 35 and increases the number of revolution of a fan of the flux recovery unit 31 and/or the blower 32. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a reflow apparatus, and more particularly to measurement of gas generated inside the reflow apparatus and control based on the measurement result.

  A reflow apparatus is used in which a solder composition is supplied in advance to an electronic component or a printed wiring board, and the board is conveyed in a reflow furnace by a conveyor. The reflow apparatus includes a transport conveyor for transporting a substrate, and a reflow furnace main body to which a substrate as an object to be heated is supplied by the transport conveyor. For example, the reflow furnace is divided into a plurality of zones along a transfer path from a carry-in port to a carry-out port, and the plurality of zones are arranged in-line. The plurality of zones have roles such as a heating zone and a cooling zone depending on their functions.

Each of the heating zones has an upper furnace body and a lower furnace body. For example, hot air is blown against the substrate from the upper furnace body of the zone, and hot air is blown against the substrate from the lower furnace body, thereby melting the solder in the solder composition and Is soldered. In the reflow apparatus, desired soldering can be performed by controlling the surface temperature of an object to be heated, for example, a substrate, according to a desired temperature profile. Such a reflow apparatus can perform soldering in a non-contact manner, and can prevent oxidation because it performs soldering in an atmosphere of an inert gas such as nitrogen gas (N ₂ ).

  The solder composition contains powder solder, a solvent, and a flux. Flux contains rosin as a component, removes the oxide film on the metal surface to be soldered, prevents reoxidation by heating during soldering, reduces the surface tension of the solder and wets it. It acts as a coating agent that improves

  This flux is vaporized by heating and fills the reflow furnace. The vaporized flux is called solvent gas, mist, fume and the like. In this specification, the term mist is used to mean liquid fine particles dispersed in a gas. Mist easily adheres to a low temperature part, and when mist adheres, it drops from the adhering part and may adhere to the upper surface of the substrate, impairing the performance of the substrate. In addition, there is a case where the reflow process is greatly affected by depositing on a portion where the temperature decreases in the furnace. Therefore, it is necessary to remove or recover the flux component contained in the atmospheric gas in the reflow furnace.

  In the following Patent Document 1, the internal gas is derived from the cooling zone next to the solder melting zone, the mist and flux vapors are removed by the mist removing device, and the nitrogen gas is mixed and returned to the cooling zone. Is described.

  Furthermore, in the reflow apparatus proposed in Patent Document 2, the atmospheric gas taken out from the reflow furnace is taken out of the furnace, and the taken atmospheric gas is heated to a high temperature at which the catalyst acts, and then passes through the oxidation catalyst. Thus, there has been proposed a method in which the flux component contained in the atmospheric gas is oxidized and decomposed into water (steam) and carbon dioxide gas.

Japanese Utility Model Publication No. 05-087987 JP 2006-160591 A

  The device described in Patent Literature 1 or Patent Literature 2 does not monitor the mist removal effect of the flux recovery device or the catalyst, and there is a risk that a gas having a high mist concentration is released outside the furnace of the reflow device. Furthermore, since these devices are always operated so that the flux recovery device and the catalyst device exhibit a certain capacity, there is a possibility that wasteful power consumption may occur.

  Therefore, an object of the present invention is to provide a reflow device capable of saving labor by detecting that there is a high possibility that a gas having a high mist concentration is released to the outside and further controlling the operation of the mist removing device. There is to do.

In order to solve the above-described problem, the present invention provides a reflow apparatus for reflowing an object to be transported by controlling the temperature of a reflow furnace.
The amount of mist contained in the gas inside the reflow furnace or the amount of mist contained in the gas flowing out to the outside is led to a light scattering type dust measuring device,
Compare the measurement result of the dust measuring device with the threshold value,
When the measurement result is larger than the threshold value, the reflow device generates a detection signal indicating that the measurement result is larger than the threshold value.
An alarm is generated by the detection signal.

Preferably, an internal gas is led from the reflow furnace to an external flux recovery device, and a gas circulation path is configured in which the gas passing through the flux recovery device is returned to the reflow furnace,
The number of rotations of the cooling fan of the flux recovery device is controlled to be higher by the detection signal.
The detection signal is controlled so that the flow rate of the gas flowing through the gas circulation path is increased.
A dust measuring device to which a part of the gas flowing through the gas circulation path is supplied is provided.

  According to the present invention, it is possible to detect that the concentration of mist in the gas flowing out from the reflow device has increased, and to generate an alarm based on the detection. Furthermore, when the gas in the furnace is led out, the mist is removed by the flux recovery device or the catalyst device, and the gas from which the mist has been removed is returned to the furnace, the fan of the flux recovery device is changed according to the concentration of the mist. By controlling the operation, the gas flow rate, or the degree of opening and closing of the ventilation duct, power saving can be achieved.

It is a basic diagram which shows the outline of the reflow apparatus which can apply this invention. It is a graph which shows an example of the temperature profile at the time of reflow. It is a basic diagram for demonstrating 1st Embodiment of this invention. It is a flowchart for demonstrating an example of the control action in 1st Embodiment of this invention. It is a flowchart for demonstrating the other example of the control action in 1st Embodiment of this invention. It is an approximate line figure for explaining a 2nd embodiment of this invention.

The best mode for carrying out the invention (hereinafter referred to as an embodiment) will be described below. The description will be given in the following order.
<1. First Embodiment>
<2. Second Embodiment>
<3. Modification>
The embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are given. However, the scope of the present invention is particularly limited to the present invention in the following description. Unless otherwise stated, the present invention is not limited to these embodiments.

<1. First Embodiment>
"Example of reflow equipment"
FIG. 1 shows a schematic configuration of a reflow apparatus to which the present invention can be applied. A plurality of embodiments described below are preferable specific examples of the present invention, and various technically preferable limitations are given. However, the scope of the present invention will be particularly described in the following description. Unless stated to limit the invention, it is not limited to these embodiments.

  An object to be heated, on which electronic components for surface mounting are mounted on both sides of the printed wiring board, is placed on a conveyor, and is carried into the furnace body of the reflow apparatus from the carry-in entrance 11. For example, a conveyor having a configuration of a roller chain for conveyance conveys the object to be heated in a direction indicated by an arrow (left to right as viewed in FIG. 1), and the object to be heated is taken out from the carry-out port 12. Each of the carry-in ports 11 and 12 is provided with gas seal portions 21 and 22 as gas outflow restriction portions that prevent the atmospheric gas in the furnace from flowing out to the outside. As the gas seal portions 21 and 22, for example, a labyrinth seal mechanism can be used. In the gas seal portions 21 and 22, when the pressure in the furnace becomes high, the gas in the furnace flows out to the outside. Further, as indicated by a two-dot chain line, the entire reflow device is surrounded by an outer plate (housing), and exhaust ducts 23a and 23b are provided on the outer plate. Conventionally, the exhaust duct is always fully opened, and the gas flowing out from the reflow device is discharged outside the factory. In the first embodiment of the present invention, the opening amount of the exhaust ducts 23a and 23b is controllable from a completely closed state to a fully opened state.

  A reflow furnace is sequentially divided into, for example, nine zones Z1 to Z9 along the conveyance path from the carry-in port 11 to the carry-out port 12, and these zones Z1 to Z9 are arranged in-line. Seven zones Z1 to Z7 from the inlet side are heating zones, and two zones Z8 and Z9 on the outlet side are cooling zones. A forced cooling unit 14 is provided in relation to the cooling zones Z8 and Z9. Furthermore, flux recovery units 17 and 18 are provided in relation to the cooling zones Z8 and Z9.

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

  The temperature raising portion R1 is a period in which the substrate is heated from room temperature to a preheating portion R2 (for example, 150 ° C. to 170 ° C.). The preheating portion R2 is a period for performing isothermal heating, activating the flux, removing the oxide film on the surface of the electrodes and solder powder, and eliminating the heating unevenness of the printed wiring board. The main heating portion R3 (for example, 220 ° C. to 240 ° C. at the peak temperature) is a period in which the solder is melted and the joining is completed. In the main heating part R3, the temperature needs to be raised to a temperature exceeding the melting temperature of the solder. Even when the preheating portion R2 has passed, the main heating portion R3 needs to be heated to a temperature exceeding the melting temperature of the solder because there is uneven temperature rise. The last cooling part R4 is a period in which the printed wiring board is rapidly cooled to form a solder composition.

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

  In the reflow apparatus, the zones Z1 and Z2 are mainly responsible for the temperature control of the temperature raising portion R1 in FIG. The zones Z3, Z4 and Z5 are mainly responsible for the temperature control of the preheating part R2. The zones Z6 and Z7 are responsible for temperature control of the main heating unit R3. The zone Z8 and the zone Z9 are responsible for temperature control of the cooling unit R4.

Each of the heating zones Z1 to Z7 has an upper furnace body 15 and a lower furnace body 16 each including a blower. For example, hot air (heated atmospheric gas) is blown against an object to be heated conveyed from the upper furnace body 15 and the lower furnace body 16 in the zone Z1. The object to be heated is one in which electronic components for surface mounting are mounted on both sides of a printed wiring board. Further, the upper furnace body 15 and the lower furnace body 16 are filled with an inert gas such as nitrogen gas (N ₂ ). In addition, you may irradiate infrared rays with a hot air.

  The upper furnace body 15 in the heating zones Z1 to Z7 includes, for example, a blower configured as a turbo fan, a heater configured by bending a plurality of heater wires, and a panel (heat storage member) having a large number of small holes through which hot air passes. The hot air that has passed through the small holes of the panel is blown against the object to be heated from above. The lower furnace body 16 has the same configuration as the upper furnace body 15.

  At the time of reflow, the object to be heated is conveyed at a predetermined speed by the conveying means such as a conveying chain through the gap between the upper furnace body and the lower furnace body, and the temperatures of the upper furnace body and the lower furnace body are preset. The temperature is controlled so that Furthermore, the air flow rate of the blower is also set to a predetermined value.

  As shown in FIG. 3, the gas sucked from the furnace in the zone Z <b> 6 of the main heating unit is supplied to the flux recovery unit 31. In FIG. 3 and other figures, the gas flow path is indicated by a bold line, and the electrical signal path is indicated by a solid line. The flux recovery unit 31 cools the atmospheric gas taken out from the furnace, aggregates the flux components in the atmospheric gas, and recovers the liquid flux. For cooling, a fan is provided to cool the gas by air cooling.

  The gas after flux recovery from the flux recovery unit 31 is supplied to the blower 32. The blower 32 creates a gas flow, and the gas flows in the pipe at a desired speed. The output gas of the blower 32 is discharged into the furnace of the zone Z7 of the main heating unit adjacent to the zone Z6. The zone for returning the gas may be any zone.

In FIG. 3, a catalyst device 34 may be provided as indicated by a broken line. The catalyst device 34 has a configuration in which the atmospheric gas taken out from the reflow furnace is heated to a high temperature (300 ° C. to 400 ° C.) at which the catalyst acts by the heating unit and then passed through the oxidation catalyst. The catalyst is made of, for example, platinum, lanthanum, palladium or rhodium. When the atmospheric gas passes through the catalyst, oxygen is added and the catalyst decomposes the organic component of the flux in the atmospheric gas into carbon dioxide (CO ₂ ), water (H ₂ O), and the like. A catalyst device 34 is provided instead of the flux recovery unit 31. Or you may provide both the catalyst apparatus 34 and a flux collection | recovery unit.

"Dust measuring device"
In the first embodiment of the present invention, a dust measuring device 23 for measuring the concentration of mist in the gas flowing out of the reflow furnace is provided. The dust measuring device 23 is based on a light scattering method. As shown in FIG. 3, the dust measuring device 23 is provided outside the inlet side and the outlet side where the gas seal portions 21 and 22 are provided. Gas extracted from the vicinity of the inlet and the vicinity of the outlet is supplied to the dust measuring device 23. The dust measuring device 23 may be arranged on one of the inlet side and the outlet side. Further, the dust measuring device 23 may be provided inside the gas seal portions 21 and 22. From the viewpoint of the performance of the dust measuring device 23, it is preferable that the dust measuring device 23 performs the measurement in a state where the mist is reduced to some extent. For example, gas is taken out from the gas seal portions 21 and 22. It is also effective to lengthen the pipe to the dust measuring device 23.

In the light scattering method, the concentration of dust is measured by utilizing the fact that when light is radiated to dust suspended in the air, the light hits the dust and is scattered. That is, the amount of scattered light is proportional to the concentration of dust. The mass concentration (unit: mg / m ³ ) is determined by multiplying the measured value of the dust measuring device by the mass concentration conversion coefficient. However, in this invention, you may use the measurement result which shows the quantity of the relative dust before converting into mass concentration. The dust measuring device by the light scattering method has an advantage of following and reacting with high sensitivity to changes in the concentration of dust.

  The dust measuring device forms a gas flow with a suction port that sucks the gas to be measured, a light emitting unit and a light receiving unit that have an optical path that crosses the passage of the gas from the suction port, an exhaust port that discharges the gas to the outside And a controller (microcomputer) that controls the entire apparatus, an operation switch, a display unit, and a USB (Universal Serial Bus) interface. Normally, the dust measuring device has a filter through which the gas after measurement passes, but in the present invention, the filter may not be provided. The measurement result of the dust measuring device 23 is supplied to the controller 33 via, for example, a USB cable.

"Example of control using measured values of dust measuring device"
The rotational speed of the fan of the flux recovery unit 31 and the rotational speed of the blower 32, or one of the rotational speeds, are controlled by a detection signal (control signal) from the controller 33. Further, a detection signal from the controller 33 is supplied to the alarm device 35, and the generation of the alarm is controlled. The alarm is generated by sound generation, lamp lighting, or the like. When the catalyst device 34 is equipped, the detection signal is used for ON / OFF control of the heating unit of the catalyst device. Furthermore, an alarm may be used to detect that the performance of the catalyst is deteriorated (deterioration) and notify that the catalyst needs to be cleaned. Furthermore, the opening / closing amounts of the exhaust ducts 23a and 23b may be controlled by a control signal formed from the measurement result of the dust measuring device. That is, when it is detected that the amount of mist is small, the exhaust ducts 23a and 23b are closed or the exhaust amount is reduced, and when it is detected that the amount of mist is large, the exhaust duct 23a and The opening amount of 23b is increased or it is made full open.

  FIG. 4 is a flowchart showing a control operation by the controller 33. In step S1, the mist is measured by the dust measuring device 23. The measured value is supplied to the controller 33. In step S2, the measured value is compared with a threshold value. The threshold value is a preset value. If the measured value is smaller than the threshold value, the process returns to step S1 and the measurement is continued.

  If it is determined in step S2 that the measured value is greater than the threshold value, a detection signal indicating that the measured value is greater than the threshold value is generated. In step S3, the fan of the flux recovery device 31 is detected by the detected signal. The rotational speed and / or the rotational speed of the blower 32 is increased. At the same time, the alarm device 35 is driven to generate an alarm. Note that the threshold value for controlling the occurrence of an alarm and the threshold value for controlling the rotational speed may be different. When the amount of mist measured by the dust measuring device 23 exceeds the threshold value, the number of rotations of the fan of the flux recovery device 31 is increased and cooling is performed, and the number of blowers 32 is increased. The amount of gas passing through the flux recovery device 31 is increased. As a result, the ability to remove mist is increased and mist is reduced.

  In step S4, it is determined whether or not the main switch that controls the operation of the reflow device is OFF. If the main switch is ON, the process returns to step S1 (mist measurement). If the main switch is OFF, the process ends.

  In step S3, when the rotational speed of the fan of the flux recovery device 31 and / or the rotational speed of the blower 32 is increased, a high rotational speed is maintained for a predetermined time, and when the predetermined time has elapsed, the rotational speed is normally set. Automatically return to the value of. However, when it is detected that the measured value is less than or equal to the threshold value, the rotational speed may be returned to the normal value. By such control, it is possible to reduce power consumption as compared with the case where the fan / blower is always operated at a relatively high rotational speed. Further, maintenance work such as cleaning of the filter of the flux recovery device 31 can be performed in response to an alarm.

"Other examples of control using measured values of dust measuring device"
Another example of the control method will be described with reference to the flowchart of FIG. In another example, it is determined whether or not an object to be heated has entered the reflow furnace, and ON / OFF of the rotation of the fan / blower is controlled according to the determination result.

  In step S5, it is determined whether an object to be heated has entered the reflow furnace. For example, the presence or absence of an object to be heated can be determined by a sensor that detects the object to be heated provided on the inlet side of the reflow furnace. If it is determined that the object to be heated is in the reflow furnace, the process proceeds to step S1. If it is determined that the object to be heated is not in the reflow furnace, the rotation of the fan / blower is turned off in step S7. Then, the process returns to step S5.

  In step S <b> 1, the mist is measured and the measured value is supplied to the controller 33. Since the process after step S1 is the same as the example of control mentioned above, it abbreviate | omits about the description. Thus, since the rotation of the fan / blower is stopped when the object to be heated is not in the reflow furnace, the power consumption can be suppressed.

  Other examples of the control method described above can be similarly applied to ON / OFF control of the heater of the heating unit of the catalyst device 34.

<Second Embodiment>
As shown in FIG. 6, the second embodiment of the present invention is an example in which a dust measuring device 37 is arranged outside the furnace of the reflow device. As in the first embodiment, the mist is removed by the internal gas sucked from the zone Z6 of the reflow device passing through the flux recovery device 31 and the blower 32. The gas output from the blower 32 is supplied to the branching device 35.

  The gas path is branched into two by the branching device 35. The gas passing through one branch is supplied to the dust measuring device 37. The measured value of the dust measuring device 37 is supplied to the controller 33. The controller 33 controls the fan and / or the blower 32 of the flux recovery apparatus 31 by the control method shown in the flowchart of FIG. 4 described above or another control method shown in the flowchart of FIG. When the catalyst device 34 is provided, the heater of the catalyst device 34 is controlled by a detection signal from the controller 33.

  In the second embodiment, since the mist can be measured outside the furnace of the reflow apparatus, it is not necessary to take out the measurement value from the reflow apparatus. In addition, you may measure the mist of the gas before flux removal with the dust measuring apparatus 37. FIG.

"Modification"
Although the embodiment of the present invention has been specifically described above, the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible. For example, instead of comparing the measured value (instantaneous value) measured in real time by the dust measuring device with the threshold value, the averaged value of the measured value or the integrated value of the measured value is compared with the threshold value. Also good. Furthermore, a plurality of values can be set as threshold values to be compared with the measurement values of the dust measuring device, and the threshold values may be set in accordance with the reflow set temperature or accuracy. That is, the threshold value is stored in the storage unit at intervals of the reflow heating temperature, for example, every 10 ° C. When the heating temperature is changed by changing the object to be heated, a threshold value corresponding to the heating temperature may be set automatically or by measuring the temperature, and the measurement may be performed.

DESCRIPTION OF SYMBOLS 11 ... Carry-in port 12 ... Carry-out port 14 ... Forced cooling unit 15 ... Upper furnace body 16 ... Lower furnace body 18, 19, 31 ... Flux collection unit 23a, 23b ... Exhaust ducts Z1 to Z10 Zones 21, 22 Gas seals 23 Dust measuring device 32 Blower 33 Controller 34 Catalyst device 35 Alarm device

Claims (6)

In the reflow apparatus for reflowing the heated object to be conveyed by controlling the temperature of the reflow furnace,
The amount of mist contained in the gas inside the reflow furnace or the amount of mist contained in the gas flowing out to the outside is led to a light scattering type dust measuring device,
A reflow device for generating a detection signal according to the measurement result of the dust measuring device.   The reflow apparatus according to claim 1, wherein an alarm is generated by the detection signal.   The reflow device according to claim 1 or 2, wherein an opening amount of the exhaust duct is controlled by the detection signal. From the reflow furnace, the internal gas is guided to an external flux recovery device, and a gas circulation path is configured in which the gas that has passed through the flux recovery device is returned to the reflow furnace,
The reflow device according to claim 1, 2 or 3, wherein the detection signal is controlled so that the number of rotations of the cooling fan of the flux recovery device becomes higher. From the reflow furnace, the internal gas is guided to an external flux recovery device, and a gas circulation path is configured in which the gas that has passed through the flux recovery device is returned to the reflow furnace,
4. The reflow apparatus according to claim 1, wherein the flow rate of the gas flowing through the gas circulation path is controlled by the detection signal.   The reflow apparatus according to claim 4 or 5, further comprising a dust measuring device to which a part of the gas flowing through the gas circulation path is supplied.

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