Reflow equipment

Abstract

The purpose is to reduce the power consumption of the reflow equipment, reduce the amount of inert gas used, and stabilize the temperature and atmosphere inside the furnace. [Solution] This reflow apparatus comprises a heating zone made up of multiple zones, a cooling zone for cooling soldered objects to be heated, and a transport section for transporting the objects to be heated, and has at least two flux recovery devices, each of which is configured to take in gas in the heating zone and cool it to reduce the flux components in the gas and emit gas with reduced flux components, and inert gas for creating a low-oxygen atmosphere in the heating zone is supplied to a first cooling tubular section of the first flux recovery device, the inert gas emitted from the first cooling tubular section is supplied to a second cooling tubular section of the second flux recovery device through a piping section with a heat dissipation function, and the inert gas emitted from the second cooling tubular section is supplied to the heating zone.

Description

[Technical Field]

[0001] The present invention relates to a reflow apparatus having a plurality of flux collection devices. [Background technology]

[0002] The reflow device is equipped with a reflow furnace to which a workpiece to be heated, such as a printed circuit board with surface-mounted components mounted on both sides, is supplied by a conveyor chain. The reflow furnace is configured, for example, with multiple heating zones each having a heating furnace and one or more cooling zones arranged in sequence along a conveyance path from an inlet to an outlet.

[0003] Each heating zone has an upper furnace body and a lower furnace body, and for example, hot air is blown onto the substrate from the upper furnace body of the zone, and hot air is blown onto the substrate from the lower furnace body of the zone, melting the solder in the solder composition and soldering the electrodes of the substrate to the electronic components.

[0004] The solder composition includes powder solder and flux. The flux contains rosin and other ingredients and acts as a coating agent to remove oxide films from the metal surface to be soldered, prevent reoxidation due to heating during soldering, and reduce the surface tension of the solder to improve wetting.

[0005] This flux vaporizes when heated, filling the reflow furnace. Vaporized flux tends to adhere to areas with low temperatures, and when vaporized flux adheres, it can drip from the area where it adheres and adhere to the top surface of the board, impairing the performance of the board. It can also accumulate in areas of the furnace where the temperature is low, significantly affecting the reflow process. Therefore, a flux recovery device is installed outside the furnace to remove or recover the flux inside the reflow furnace.

[0006] A known method is to introduce high-temperature gas from the furnace into a flux collection device, where the gas is cooled to condense the flux components. After flux collection, the gas is returned to the furnace. Cooling methods include water cooling and air cooling. In the case of the water cooling method, a separate chilled water circulation device (chiller) is required, which increases the size of the device and power consumption.

[0007] Another advantage is that soldering in a reflow soldering device in a low-oxygen atmosphere, such as a nitrogen atmosphere, can prevent oxidation of the electrodes on the substrate. For example, Patent Document 1 listed below describes a configuration in which the atmospheric gas in the heating chamber is led to a separation means outside the furnace body to remove the solvent gas, and then returned to the furnace body, and nitrogen gas is supplied to the separation means from a nitrogen gas generator to cool the separation means. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 04-258368 Summary of the Invention [Problem to be solved by the invention]

[0009] The flux collection device described in Patent Document 1 is air-cooled, which is advantageous in terms of power consumption. However, the flux collection device is installed in common for the entire heating chamber. Therefore, in order to remove the solvent gas from the entire heating chamber, the separation means becomes large, which poses a problem of difficulty in accommodating it within the housing of the reflow soldering device. Furthermore, maintaining flux collection performance in a large device poses a problem of increasing the amount of inert gas used for heat exchange by increasing the flow rate of high-temperature gas from the furnace.

[0010] Therefore, an object of the present invention is to provide a reflow soldering apparatus having a plurality of flux collection devices, which can simplify the configuration for supplying cooling inert gas to each flux collection device, and can maintain flux collection performance with a smaller amount of inert gas used, and which can heat the inert gas to a certain extent before returning it to the furnace. [Means for solving the problem]

[0011] The present invention relates to a reflow soldering apparatus comprising a heating zone consisting of multiple zones including a zone for soldering an object to be heated, a cooling zone disposed after the heating zone for cooling the object to be soldered, and a transport unit for transporting the object to be heated within the heating zone and the cooling zone. at least two first and second flux collection devices; each of the first and second flux recovery devices is configured to take in gas in a heating zone and cool it to reduce flux components in the gas, and to discharge the gas with reduced flux components; an inert gas for creating a low-oxygen atmosphere in the heating zone is supplied to a first cooling tubular part of the first flux collection device, and the inert gas discharged from the first cooling tubular part is supplied to a second cooling tubular part of the second flux collection device through a piping part having a heat dissipation function; The reflow apparatus is configured such that the inert gas exiting the second cooling tubular portion is supplied to the heating zone. [Effects of the Invention]

[0012] According to at least one embodiment, the medium (inert gas) used to cool the flux collection device is also used to cool the first and second flux collection devices, and the inert gas heated therein can be supplied into the furnace. This makes it possible to stabilize the atmosphere in the furnace, suppress temperature drops, reduce the amount of inert gas used, and reduce power consumption by eliminating the need for a chiller. Note that the effects described here are not necessarily limited, and any of the effects described in the present invention may be used. Furthermore, the content of the present invention should not be interpreted as being limited by the effects exemplified in the following description. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an outline of a conventional reflow device to which the present invention can be applied. [Figure 2] FIG. 2 is a graph showing an example of a temperature profile during reflow. [Figure 3] FIG. 3 is a schematic diagram showing a schematic configuration of one embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a more specific configuration of one embodiment of the present invention. [Figure 5] FIG. 5 is a schematic diagram used to explain a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described below with reference to exemplary embodiments in the following order. <1. Example of a reflow device> <2. One embodiment> <3. Modifications> The embodiment described below is a preferred specific example of the present invention, and various technically preferable limitations are attached, 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.

[0015] <1. Example of a reflow device> Figure 1 shows a schematic configuration of a conventional reflow soldering device to which the present invention can be applied. A workpiece, which is a printed wiring board with surface-mount electronic components mounted on both sides, is placed on a transfer conveyor and is carried into the heating device of the reflow soldering device through a carry-in entrance 101. The transfer conveyor carries the workpiece at a predetermined speed in the direction of the arrow (from left to right in Figure 1), and the workpiece is removed from an exit 102. The transfer direction of the transfer conveyor is horizontal.

[0016] The heating device is configured such that multiple heating furnaces are arranged along the transport path from the inlet 101 to the outlet 102, and the heating furnaces blow hot air (heated atmospheric gas) onto the workpieces. Multiple heating furnaces (called zones) are arranged in-line. Eight zones Z1 to Z8 from the inlet side are heating zones, and zone Z9 on the outlet side is a cooling zone. A forced cooling unit 103 is provided in association with cooling zone Z9. Each of heating zones Z1 to Z8 has an upper furnace body and a lower furnace body, each including a blower, heater, blowing panel, etc. Note that this number of zones is just an example, and a configuration with a different number of zones may also be used.

[0017] Furthermore, soldering in a low-oxygen atmosphere has the advantage of suppressing oxidation of the electrode surface. In the reflow soldering apparatus shown in Figure 1, an inert gas, such as nitrogen gas, is supplied to the heating zones, such as zones Z1 and Z8. However, the nitrogen gas supply point may be elsewhere, such as the buffer zone on the entrance side or the buffer zone between the heating zone and the cooling zone.

[0018] Furthermore, a flux collection device 104 is provided in association with zone Z1, and a flux collection device 105 is provided in association with zone Z8. The flux collection devices 104 and 105 are configured to cool the high-temperature gas extracted from the zones to liquefy the flux components and collect the liquid flux components.

[0019] As a cooling method, for example, a water cooling method is used, and cold water from a cold water circulation device (chiller) (not shown) is supplied to the flux collection devices 104, 105. However, as will be described later, in one embodiment of the present invention, nitrogen gas is used to cool the flux collection devices, and the resulting heated nitrogen gas is returned to the furnace. Note that the number and installation locations of the flux collection devices are just an example, and three or more flux collection devices may be provided.

[0020] The above-mentioned multiple zones Z1 to Z9 control the temperature of the workpiece according to a temperature profile during reflow. Figure 2 shows an example of a temperature profile. The horizontal axis represents time, and the vertical axis represents the surface temperature of the workpiece, such as a printed wiring board with electronic components mounted on it. The first section is the temperature rise 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 main heating section R3, and the last section is the cooling section R4. The temperature rise section R1 and preheating section R2 are the preheating sections.

[0021] 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 a period during which isothermal heating is performed, for example, to activate the flux, remove oxide films from the electrodes and solder powder surfaces, and eliminate uneven heating of the printed wiring board. The main heating section R3 (e.g., peak temperature of 220°C to 240°C) is the period during which the solder melts and the bond is completed. In the main heating section R3, the temperature must be raised to a temperature exceeding the solder melting temperature. Since uneven temperature rise still exists even after the preheating section R2, the main heating section R3 must be heated to a temperature exceeding the solder melting temperature. The final cooling section R4 is the period during which the printed wiring board is rapidly cooled and the solder composition is formed. Note that in the case of lead-free solder, the temperature in the main heating section R3 is higher (e.g., 240°C to 260°C).

[0022] 2, curve 201 shows an example of a temperature profile for lead-free solder. An example of a temperature profile for Sn-Pb eutectic solder is shown by curve 202. Because the melting point of lead-free solder is higher than that of eutectic solder, the set temperatures in preheating section R2 and main heating section R3 are set higher than those for eutectic solder.

[0023] In the reflow soldering equipment shown in FIG. 1, the temperature control of the heating section R1 in FIG. 2 is mainly handled by zones Z1, Z2, and Z3. The temperature control of the preheating section R2 is mainly handled by zones Z4 and Z5. The temperature control of the main heating section R3 is handled by zones Z6, Z7, and Z8. The temperature control of the cooling section R4 is handled by zone Z9. There are gaps between the multiple furnace bodies (zones) mentioned above. The entire heating furnace that handles the heating section R1 and preheating section R2 is called the preheat zone, the entire heating furnace that handles the main heating section R3 is called the reflow zone, and the entire preheat zone and reflow zone are called the heating zone.

[0024] <2. One embodiment> A first embodiment of the present invention will be described with reference to Fig. 3. Reference numeral 10 generally indicates a reflow soldering apparatus having a configuration similar to that described with reference to Fig. 1. A first flux collection device 11 and a second flux collection device 12 are provided. These flux collection devices 11 and 12 have the same configuration and are installed in the internal space of the reflow soldering apparatus, which is surrounded by an outer plate together with a heating furnace.

[0025] 4 is a diagram showing the configuration of the first embodiment in more detail. The flux collection devices 11 and 12 have the same configuration. They are provided with box-shaped cases 21 and 22, fans 31 and 32, cooling tubular sections 41 and 42 (not shown in FIG. 3), and collection sections 51 and 52 (not shown in FIG. 3) for storing liquefied flux.

[0026] The cases 21 and 22 each have an inlet and an outlet, and a gas flow is formed from the inlet to the outlet. Gas (atmospheric gas) from a predetermined zone in the heating zone of the reflow apparatus 10 where the pressure is relatively high is introduced into the cases 21 and 22, and the gas with reduced flux components is discharged from the cases 21 and 22 and returned to the predetermined zone where the pressure is relatively low.

[0027] The cooling tubular sections 41, 42 are configured, for example, by connecting multiple U-shaped metal tubes, and an inert gas, such as nitrogen gas, is introduced into one end of the metal tubes to create a low-oxygen atmosphere inside the metal tubes. Nitrogen gas is supplied to the cooling tubular section 41 of the flux recovery device 11 from a nitrogen gas generator in the factory. This nitrogen gas is a relatively low-temperature gas, for example, below room temperature, and can be used as a cooling medium. The cooling tubular sections 41, 42 may have other configurations, such as a configuration in which straight metal tubes are arranged in parallel and chambers are provided at both ends, in addition to a configuration in which U-shaped metal tubes are connected.

[0028] Air from the fans 31 and 32 is blown against the cooling tubular portions 41 and 42 to generate cold air, which hits the outer surfaces of the cases 21 and 22 to cool the cases 21 and 22. The gas inside the cases 21 and 22 is cooled, and the flux components are liquefied and collected in the recovery portions 51 and 52.

[0029] In the flux collection device 11, gas in, for example, zone Z8 in the heating zone is introduced into the case 21, and the gas with reduced flux components is discharged from the case 21 and returned to a predetermined zone (zone Z8 or another zone) in the heating zone. Note that the flux collection devices 11 and 12 may have configurations other than those described above, as long as they are configured to reduce the flux components by condensing them through cooling.

[0030] The nitrogen gas coming out from the other end of the cooling tubular section 41 of the flux collection device 11 is supplied to the second cooling tubular section 42 of the flux collection device 12 through the piping section 60 having a heat dissipation function. As a result of being used for cooling in the flux collection device 11, the temperature of the nitrogen gas rises. The piping section 60 having a heat dissipation function has a function of lowering the temperature of the nitrogen gas to a temperature that can be used for cooling in the flux collection device 12.

[0031] For example, in the case where the flux collection device 12 takes in gas from zone Z1 in the heating zone and returns the gas with reduced flux components to a predetermined zone (zone Z1 or another zone) in the heating zone, the distance between zones Z1 and Z8 is relatively long. That is, the piping section 60 becomes relatively long, and the temperature of the nitrogen gas in the piping section 60 can be lowered to a level that can be used for cooling in the flux collection device 12.

[0032] The piping section 60 may be made of, for example, a pipe made of synthetic resin or metal. To enhance the heat dissipation function, any of a spiral pipe configuration, a pipe configuration with many blades on the surface, a plurality of parallel pipes, or a combination of these may be used. Three or more flux collection devices may be provided, and may be provided in association with any zone.

[0033] In the flux recovery device 12, gas from zone Z1 is introduced into the case 22, and the gas is cooled in the case 22 by the blower 32 and the cooling tubular portion 42, resulting in liquefaction of the flux components. The gas with reduced flux components is returned to a predetermined zone (zone Z1 or another zone) within the heating zone.

[0034] Furthermore, the nitrogen gas, which has been used for cooling in the flux recovery device 12 and has a raised temperature, is returned to a predetermined zone (zone Z1 or another zone) within the heating zone. Therefore, in this case, the gas output from the case 22 and the nitrogen gas may be mixed and returned to a predetermined zone within the heating zone of the reflow device.

[0035] For example, the temperature measurement results for each part when Teflon (registered trademark) is used for the piping part 60 are shown below. The temperatures are measured on the outer surface. Temperature of the gas supplied from zone Z8 to flux recovery device 11: 195°C Temperature of the gas returned from the flux recovery device 11 to a predetermined zone in the heating zone: 100°C Temperature of nitrogen gas extracted from flux recovery device 11: 100°C Temperature of the nitrogen gas supplied from the piping section 60 to the flux recovery device 12: 65° Temperature of the gas supplied from zone Z1 to the flux recovery device 12: 100°C Temperature of the gas returned from the flux recovery device 12 to a predetermined zone in the heating zone: 65°C Temperature of nitrogen gas returned from the flux recovery device 12 to a predetermined zone in the heating zone: 70°C

[0036] <3. Modifications> In one embodiment, the gas in which the flux has been reduced by the first flux collection device 11 is returned to a predetermined zone within the heating zone of the reflow device 10. As shown in Fig. 5, the gas in which the flux components have been reduced by the flux collection device 11 may be supplied to the flux collection device 12 (case 22). That is, the flux collection devices 11 and 12 are connected in series.

[0037] The gas in which the flux components have been reduced by the flux collection device 12 is returned to a predetermined zone within the heating zone of the reflow device 10. In addition, the nitrogen gas used for cooling in the flux collection device 12 is returned to a predetermined zone within the heating zone of the reflow device 10. The configuration shown in Fig. 5 is suitable for use when relatively small flux collection devices 11 and 12 are used.

[0038] 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 concept of the present invention are possible. Note that the configurations, methods, processes, shapes, materials, and numerical values ​​described in the above-described embodiments are merely examples, and different configurations, methods, processes, shapes, materials, and numerical values ​​may be used as necessary. Furthermore, the configurations, methods, processes, shapes, materials, and numerical values ​​of the above-described embodiments may be combined with each other as long as they do not deviate from the spirit of the present invention. [Explanation of symbols]

[0039] 10 reflow device, 11, 12 flux recovery device, 21, 22 case, 31, 32 blower, 41, 42 cooling tubular section, 60 piping section

Claims

1. A reflow soldering apparatus comprising a heating zone consisting of a plurality of zones including a zone for soldering an object to be heated, a cooling zone disposed after the heating zone for cooling the object to be heated after soldering, and a transport unit for transporting the object to be heated within the heating zone and the cooling zone, at least two first and second flux collection devices; each of the first and second flux recovery devices is configured to take in gas in the heating zone and cool it to reduce flux components in the gas, and to discharge the gas with the reduced flux components; an inert gas for creating a low-oxygen atmosphere in the heating zone is supplied to a first cooling tubular part of the first flux collection device, and the inert gas discharged from the first cooling tubular part is supplied to a second cooling tubular part of the second flux collection device through a piping part having a heat dissipation function; The reflow apparatus is configured so that the inert gas exiting the second cooling tubular portion is supplied to the heating zone.

2. 2. The reflow apparatus according to claim 1, wherein the gas in which the flux components have been reduced by each of the first flux collection device and the second flux collection device is returned to a zone within the heating zone.

3. 2. The reflow apparatus according to claim 1, wherein the gas in which the flux components have been reduced by the first flux collection device is supplied to the second flux collection device, and the gas in which the flux components have been reduced by the second flux collection device is returned to a zone within the heating zone.

4. 4. The reflow soldering apparatus according to claim 1, wherein the piping section is formed of a spiral pipe.

5. 4. The reflow soldering apparatus according to claim 1, wherein the piping section is formed of a pipe having a number of blades formed on the surface thereof.

6. 4. The reflow soldering apparatus according to claim 1, wherein the piping section is made up of a plurality of pipes.

Images