Heating device and heating method

Abstract

To provide a heating device and a heating method which can heat an object to be heated utilizing vaporization of inert liquid and a wavelength-control infrared heater that radiates an infrared ray in a specific wavelength range, and then can collect the inert liquid from a surface of the object to be heated in the device, which can suppress consumption caused by taking-out the inert liquid from the device.SOLUTION: Inert liquid 5 is supplied to a surface of an object 4 to be heated, and then heating of the object to be heated and collection of the inert liquid on the surface of the object to be heated are executed with a wavelength control infrared heater 6 which radiates an infrared ray in a wavelength range in which functional groups which are different from functional groups included in the object to be heated and are contained in molecules constituting the inert liquid can absorb.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heating device and a heating method for heating an object by utilizing vaporization of an inert liquid and an infrared heater that radiates infrared rays of only a specific wavelength. [Background technology]

[0002] 2. Description of the Related Art A heating device that uses an inert liquid and an infrared heater for heating is known as a reflow furnace used for soldering in processes such as mounting electronic components (see, for example, Patent Document 1).

[0003] 4 is a schematic configuration diagram of Patent Document 1. The configuration disclosed in Patent Document 1 is as follows.

[0004] The heating device 101 has an inlet section 102, an inert liquid spray tank 103, a preheat section 104, a steam tank 105, and an outlet section 106, which are arranged in series along the conveyor 107. In the inert liquid spray tank 103, a spray nozzle 108 for spraying the inert liquid is provided toward the conveyor 107, and a duct for collecting the excess of the inert mist is arranged on the opposite side. This collection duct 109 is connected to a mist collection tank 110 equipped with a suction blower, and further connected to a liquid reservoir section 112 of the steam tank 105 via a pump 111a. In the preheat section 104, an infrared preheater 115 is arranged along the conveyor 107. The liquid reservoir section 112 is connected to a temperature regulator 113 via a pipe 116a, and to the spray nozzle 108 via a pump 111b and a pipe 116b. The spray nozzle 108 applies an inert mist to the workpiece 114 before it is preheated.

[0005] The workpiece 114, which is put onto the transport conveyor 107 from the carry-in section 102, is sprayed with an inert mist by a spray nozzle 108 in an inert liquid spray tank 103. Thereafter, the workpiece 114 is preheated by an infrared preheater 115 in a preheat section 104, and is transported to a vapor tank 105 in which a vapor phase of the inert liquid is formed. In the vapor tank 105, the workpiece 114 is reflow-heated by the latent heat of condensation of the vaporized inert liquid, and after the mounted components on the workpiece 114 are soldered, the workpiece 114 is transported from an unloading section 106. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-47466 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the configuration of Patent Document 1, after the workpiece 114 is heated by the steam tank 105, the inert liquid condensed on the surface of the workpiece remains on the workpiece 114 and is carried out of the furnace, resulting in a loss of the inert liquid and an increase in running costs.

[0008] In consideration of these points, the present invention aims to provide a heating device and a heating method that make it possible to recover an inert liquid from the surface of a heated object within the device after the heated object has been heated. [Means for solving the problem]

[0009] In order to achieve the above object, a heating device according to one aspect of the present invention comprises: A heating device that heats an object to be heated by utilizing vaporization of an inert liquid and heating by an infrared heater, A heating chamber for heating the object to be heated; A conveying unit that conveys the object to be heated into and out of the heating chamber; an inert liquid supply unit that supplies the inert liquid to a surface of the object to be heated in the heating chamber; an inert liquid recovery unit disposed at a lower portion of the heating chamber and configured to recover the inert liquid from the heating chamber; an infrared heater that radiates infrared rays in a wavelength range that is different from the functional groups contained in the object to be heated and that is absorbed by the functional groups contained in the molecules that constitute the inert liquid in the heating chamber; A heater control unit that controls heater power of the infrared heater; The heating chamber is provided with an exhaust section that exhausts the vaporized inert liquid from the heating chamber and recovers the vaporized inert liquid in the inert liquid recovery section.

[0010] In addition, a heating method according to another aspect of the present invention includes the steps of: A heating method for heating an object to be heated by vaporizing an inert liquid and using an infrared heater, comprising: The object to be heated is carried into a heating chamber, The inert liquid is supplied to a surface of the object to be heated, The object to be heated is heated by irradiating the object with infrared rays from the infrared heater in a wavelength range that is different from the functional group contained in the object to be heated and that is absorbed by the functional group contained in the molecule constituting the inert liquid, thereby heating the inert liquid, and The inert liquid vaporized from the surface of the object to be heated is exhausted from the heating chamber and collected. Effect of the Invention

[0011] As described above, according to the heating device and heating method of the above aspects of the present invention, it is possible to recover the inert liquid remaining on the surface of the object to be heated within the device after the object to be heated, thereby reducing running costs. [Brief description of the drawings]

[0012] [Figure 1] 1 is a schematic diagram of a heating device according to a first embodiment of the present invention; [Diagram 2] A diagram showing temperature data when an object to be heated that has been supplied with an inert liquid is heated using a general infrared heater. [Diagram 3] Schematic diagram of a heating device according to a second embodiment of the present invention. [Figure 4] Schematic diagram of a conventional heating device DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] FIG. 1 is a schematic configuration diagram of a heating device 1 according to a first embodiment of the present invention.

[0015] The heating device 1 includes a heating chamber 2, a conveying section 3, an inert liquid supply section 8, an inert liquid recovery section 23, a wavelength-controlled infrared heater 6, a heater control section 7, and an exhaust section 24, and heats the object to be heated 4 by vaporizing the inert liquid 5 and utilizing the wavelength-controlled infrared heater 6.

[0016] The heating chamber 2 is an internal space of a heating section 22 that heats an object 4 to be heated.

[0017] The transport section 3 transports the object 4 to and from the heating position 20 located at the middle in the vertical direction within the heating chamber 2, and is composed of, for example, a belt conveyor.

[0018] The inert liquid supplying unit 8 supplies the inert liquid 5 to the surface of the object 4 in the heating chamber 2, for example, to the side and upper surfaces excluding the lower surface placed on the conveying unit 3. Specifically, a plurality of nozzles as an example of the inert liquid supplying unit 8 are arranged on the side wall surface side above the heating position 20 of the object 4 on the conveying unit 3 in the heating chamber 2, facing the object 4, and supply the inert liquid 5 to the surface of the object 4 by spraying the liquid. In the inert liquid supplying unit 8, the inert liquid 5 stored in the inert liquid tank 11 arranged below the heating chamber 2 is pumped out by the pump 12, and the inert liquid 5 is supplied from the inert liquid supplying unit 8 to the surface of the object 4 through the piping 13a while the liquid amount is adjusted by the valve 9a that opens and closes the piping 13a and the liquid amount control unit 9c that controls the opening and closing of the valve 9a based on the measured liquid amount.

[0019] The inactive liquid recovery unit 23 has an inactive liquid recovery port 10 for recovering the inactive liquid 5, which is disposed at the bottom of the heating chamber 2, and an inactive liquid tank 11. Specifically, the inactive liquid recovery port 10 for recovering the inactive liquid 5 accumulated on the bottom surface of the heating chamber 2 is provided below the heating chamber 2. The inactive liquid 5 discharged from the inactive liquid recovery port 10 is recovered in the inactive liquid tank 11 disposed below the inactive liquid recovery port 10. In FIG. 1, as an example, the inactive liquid recovery port 10 is disposed below the heating position 20 on the transport unit 3 and at the center of the bottom surface of the heating chamber 2, and the bottom surface of the heating chamber 2 is inclined in a cone shape toward the inactive liquid recovery port 10, so that the inactive liquid 5 can be efficiently recovered.

[0020] The wavelength-controlled infrared heater 6 radiates infrared rays in the heating chamber 2 in a wavelength region that is different from the functional groups contained in the object to be heated 4 and that is absorbed by the functional groups contained in the molecules that constitute the inert liquid 5. Specifically, the wavelength-controlled infrared heater 6 that radiates infrared rays of a specific wavelength is installed above the heating position 20 in the center of the heating chamber 2, as will be described in detail later.

[0021] The heater control unit 7 controls the heater power of the wavelength control infrared heater 6 to control heating.

[0022] The exhaust unit 24 exhausts the vaporized inert liquid 5 from the heating chamber 2 through the exhaust port 14 using an exhaust device such as a suction fan or a pump for reducing pressure, and recovers it in the inert liquid tank 11. Specifically, the exhaust port 14 for exhausting the vaporized inert liquid 5 from the heating chamber 2 is provided on the ceiling of the heating chamber 2. The vaporized inert liquid 5 exhausted through an exhaust duct 15 connected to the exhaust port 14 is sent to a condenser 16 that cools the gas and condenses it into a liquid, where it is liquefied. The liquefied inert liquid 5 is recovered in the inert liquid tank 11 via a pipe 13b.

[0023] The heating device control unit 30 controls the operations of the transport unit 3, the heater control unit 7, the pump 12, the liquid amount control unit 9c, and the exhaust unit .

[0024] The heating method using the heating device 1 having the above-described configuration is as follows.

[0025] The object to be heated 4 is, for example, a circuit board, and is carried from outside the heating chamber 2 into the heating chamber 2 by the carrying section 3, and is carried to a heating position 20 in the center of the heating chamber 2.

[0026] Thereafter, a constant amount of inert liquid 5 is supplied to the surface of the object 4 by the inert liquid supply unit 8. Then, the inert liquid 5 on the surface of the object 4 is heated by infrared rays radiated from the wavelength-controlled infrared heater 6, the heater power of which is controlled by the heater control unit 7, and heat is transferred from the inert liquid 5 to the object 4. This transfer of heat heats the object 4 to a predetermined temperature, and the object 4 is preheated.

[0027] After the preheating, the heater power of the wavelength-controlled infrared heater 6 is increased to heat the inactive liquid 5 and the object 4 to a temperature equal to or higher than the melting point of the solder, thereby performing reflow soldering.

[0028] Furthermore, even after soldering, heating is continued with the wavelength-controlled infrared heater 6 to vaporize all of the inert liquid 5 remaining on the surface of the heated object 4, and the vaporized inert liquid 5 is exhausted from the exhaust port 14, liquefied in the condenser 16, and then collected in the inert liquid tank 11.

[0029] Here, the wavelength-controlled infrared heater 6 will be described in detail. The wavelength distribution of infrared rays emitted from a general infrared heater is determined according to Planck's law by the product of the thermal radiation spectrum of a perfect black body, which is uniquely determined by absolute temperature, and the inherent emissivity spectrum of the material of the heating part of the infrared heater, which is made of metal or dielectric. The thermal radiation spectrum of a perfect black body shows a broad wavelength distribution, and the emissivity spectrum of a material also shows a distribution biased to a specific wavelength depending on the material, but it was difficult to emit infrared rays with a wavelength distribution having a narrow band peak similar to the absorption wavelength of the functional group of the molecule that constitutes a specific material. However, in recent years, research has been actively conducted on microfabricating the surface structure of the heating part to control the emissivity spectrum. Structures used for emissivity control include a structure in which metal holes or protrusions are periodically arranged in a two-dimensional plane on two thin layers of metal and dielectric, or a layered structure in which two types of dielectrics with different refractive indices are alternately layered on a metal layer. In this way, by designing the fine structure of the surface of the heat generating portion of the infrared heater, it is possible to radiate infrared rays with a wavelength distribution having a narrow band peak at any wavelength.

[0030] Here, a process of heating the object 4 using the inert liquid 5 and the wavelength-controlled infrared heater 6 having the above-mentioned structure that radiates infrared rays in a specific wavelength range will be described.

[0031] First, we will explain the case where a general infrared heater is used. Figure 2 shows data obtained by measuring the temperature of two points on the surface of the object 4 to be heated when the object 4 to be heated, on whose surface an inert liquid 5 is supplied, is heated using a general infrared heater.

[0032] In the first half of the heating process, the heater power of the infrared heater is set to a value (W1) at which the temperature of the heated object 4 becomes the first stage temperature of the temperature profile, and the surface temperature of the heated object 4 stabilizes at the first stage temperature after a certain time has elapsed immediately after the start of heating. This is because the infrared radiant heat supplied from the infrared heater to the inert liquid 5 on the surface of the heated object 4 and the heat of vaporization taken from the heated object 4 when the inert liquid 5 on the surface of the heated object 4 vaporizes balance each other, resulting in an equilibrium state.

[0033] In the latter half of the heating process, the heater power of the infrared heater was set to a value (W2) that brings the temperature of the heated object 4 to the second stage temperature of the temperature profile, so the surface temperature of the heated object 4 reaches the second stage temperature, which is higher than in the first half of the heating process. This is because the heat equilibrium state on the surface of the heated object 4 shifts to the higher temperature side due to an increase in the radiated heat from the infrared heater. In this way, the temperature of the heated object 4 can be controlled by adjusting the energy of the irradiated infrared rays.

[0034] At the end of the heating process, the measurement data shown by the solid line in Figure 2 shows that all of the inert liquid 5 remaining on the surface of the heated object 4 at the measurement point has evaporated, so the heated object 4 is only supplied with radiant heat from the infrared heater, and the surface temperature of the heated object 4 shown by the solid line in Figure 2 rises sharply. On the other hand, the measurement data shown by the dotted line in Figure 2 shows that there is still inert liquid 5 remaining on the surface of the heated object 4 at the measurement point, so there is no sharp rise in surface temperature like the solid line temperature data.

[0035] In this way, the temperature change on the surface of the object 4 varies depending on the uneven wetting of the inert liquid 5 on the surface of the object 4, so it is very difficult to use a general infrared heater to completely evaporate the inert liquid 5 on the surface of the object 4 without excessively raising the temperature of the object 4. In general heat treatment, the temperature of the object 4 is controlled within a certain range, and a sudden temperature rise like the final part of the temperature data indicated by the solid line in Figure 2 must be avoided because it leads to quality defects.

[0036] Next, in the first embodiment, a case where the heated object 4 is heated using a wavelength-controlled infrared heater 6 that has a fine structure on its surface and emits only infrared rays of a specific wavelength, and an inert liquid 5 will be described. The wavelength-controlled infrared heater 6 is structured to emit infrared rays in a wavelength range that is different from the functional groups contained in the heated object 4 and that is absorbed by the functional groups contained in the molecules that constitute the inert liquid 5, that is, to emit infrared rays in a wavelength range that is absorbed by the functional groups of the molecules that constitute the inert liquid 5 and not absorbed by the functional groups of the molecules that constitute the heated object 4. After the inert liquid 5 is supplied to the heated object 4 that has been transported to the heating position 20 in the heating chamber 2, the inert liquid 5 is heated by the infrared rays emitted from the wavelength-controlled infrared heater 6 described above, and heat is transferred from the inert liquid 5 to the heated object 4, thereby heating the heated object 4 to the same temperature as the inert liquid 5. As in the case of using a general infrared heater, the temperature of the heated object 4 changes depending on the heater power of the wavelength-controlled infrared heater 6. The heater power of the wavelength-controlled infrared heater 6 is controlled to heat the object 4 to a temperature required for preheating, and preheating is performed. After preheating, the heater power of the wavelength-controlled infrared heater 6 is increased to a value at which the temperature of the object 4 rises to the solder melting point temperature, and reflow soldering is performed. Even after soldering is completed, the inert liquid 5 and the object 4 continue to be heated by the wavelength-controlled infrared heater 6, so that the inert liquid 5 on the surface of the object 4 further vaporizes and the drying progresses. With a conventional infrared heater, the object 4 absorbs infrared rays from the part where the inert liquid 5 has disappeared from the surface, and the temperature of the object 4 rises excessively. In contrast, in the first embodiment, by irradiating infrared rays of a wavelength that is absorbed by functional groups contained in the molecules constituting the inert liquid 5 that are different from the functional groups contained in the object 4, it is possible to suppress the temperature of the object 4 from rising excessively even if infrared rays are irradiated to the part where the inert liquid 5 of the object 4 has evaporated. Therefore, even if there is uneven wetting of the inert liquid 5, the inert liquid 5 on the surface of the object 4 can be easily vaporized and exhausted from the exhaust port 14. Therefore, it becomes possible to recover the inert liquid 5 remaining on the surface of the object 4 by the inert liquid recovery unit 23 in the heating device 1, and the running cost can be reduced.

[0037] In addition, it is necessary to supply the inert liquid 5 to the surface of the object 4 so that the inert liquid 5 on the surface of the object 4 is not completely vaporized while the object 4 is heated at the required temperature for the required time. On the other hand, if the inert liquid 5 is supplied so much that it washes off the surface immediately after printing the cream solder, the cream solder may also flow out together. Therefore, the amount of the inert liquid 5 supplied at one time must be kept below the amount at which the cream solder is not washed away. Therefore, by distributing the supply opportunity of the inert liquid 5 to the object 4 to not only before preheating but also during preheating, after preheating, or during reflow heating, and appropriately supplying additional inert liquid 5 to the object 4, it is possible to perform any heating profile without washing off the cream solder. The upper limit of the amount of the inert liquid 5 supplied at one time is determined in consideration of the viscosity of the cream solder or the affinity with the inert liquid 5.

[0038] An example of the inert liquid 5 is a fluorine-based inert liquid having a perfluoroalkyl group, and its absorption wavelengths are 7.4 to 7.8 μm and 8.6 to 9.0 μm. An example of the heated object 4 is an epoxy resin used in mounting boards, and its absorption wavelengths are 6.5 to 6.8 μm and 7.9 to 8.4 μm. In other words, if the wavelength-controlled infrared heater 6 emits infrared rays in the wavelength range of 7.4 to 7.8 μm or 8.6 to 9.0 μm, the heated object 4 can be heated using the inert liquid 5 as described above.

[0039] As described above, according to the first embodiment, after the inert liquid 5 is supplied to the surface of the object to be heated 4, infrared rays in a wavelength range that is different from the functional groups contained in the object to be heated 4 and that is absorbed by the functional groups contained in the molecules that constitute the inert liquid 5 are irradiated, that is, the object to be heated 4 is heated by irradiating infrared rays in a wavelength range that is absorbed by functional groups that are contained in the molecules that constitute the inert liquid 5 and not contained in the molecules that constitute the object to be heated 4, and then the inert liquid 5 remaining on the surface of the object to be heated 4 can be recovered by the inert liquid recovery section 23 within the heating device 1, thereby reducing running costs.

[0040] FIG. 3 is a configuration diagram of the heating device 1 in the second embodiment of the present invention. In the second embodiment, a pipe 13c for sending compressed air to the inert liquid supply unit 8 is connected to the heating device 1 of the first embodiment, and compressed air is supplied from the inert liquid supply unit 8 to the heating chamber 2 by the compressor 17 under the control of the heating device control unit 30. When air is supplied, the valve 9a of the pipe 13a for sending the inert liquid 5 to the inert liquid supply unit 8 is closed by the heating device control unit 30, and the valve 9b of the pipe 13c for sending compressed air is opened by the heating device control unit 30, so that air can be supplied from the compressor 17 to the heating chamber 2. When air supply is stopped, the valve 9a of the pipe 13a is opened by the heating device control unit 30, and the valve 9b of the pipe 13c for sending compressed air is closed by the heating device control unit 30, so that the air supply from the compressor 17 is stopped. In this way, it is possible to cool the heated object 4 with air after heating by infrared rays.

[0041] In this way, by using the heating device 1 utilizing the wavelength-controlled infrared heater 6 and the inert liquid 5, a steam tank is not required to evaporate the inert liquid 5 by heating with the heater 6 and fill the space with steam, and the energy input can be reduced, leading to energy savings in the process.

[0042] In addition, by appropriately combining any of the various embodiments or modifications described above, it is possible to achieve the effects of each of them. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features of different embodiments or examples are also possible. [Industrial Applicability]

[0043] The heating device and the heating method according to the above aspects of the present invention can perform a desired heat treatment with low running costs, high efficiency, and space saving by vaporizing an inert liquid and heating with infrared rays. Therefore, the above aspects of the present invention can be applied as a highly efficient heating device to heat treatment devices that perform various heat treatments such as drying furnaces, baking furnaces, curing furnaces, and reflow furnaces in the manufacturing process of industrial products or home appliances or the manufacturing process of various electronic components. [Explanation of symbols]

[0044] 1 Heating device 2 Heating chamber 3. Conveyor 4 Object to be heated 5 Inert liquid 6 Wavelength Control Infrared Heater 7 Heater control section 8 Inert liquid supply section 9a Valve 9b Valve 9c Liquid volume control section 10 Inactive liquid collection port 11 Inert liquid tank 12 Pump 13a Piping 13b Piping 13c Piping 14 Exhaust port 15 Exhaust duct 16 Condenser 17 Compressor 20 heating positions 22 Heating section 23 Inactive liquid recovery section 24 Exhaust section 30 Heating device control section 101 Heating device 102 Loading section 103 Inert liquid spray tank 104 Preheat section 105 Steam Tank 106 Unloading section 107 Transport Conveyor 108 Spray Nozzle 109 Recovery Duct 110 Mist collection tank 111a Pump 111b Pump 112 Liquid reservoir 113 Temperature controller 114 Work 115 Infrared Preheater 116a Pipeline 116b Pipeline

Claims

1. A heating device that heats an object to be heated by using vaporization of an inert liquid and an infrared heater, A heating chamber for heating the object to be heated; an inert liquid supply unit that supplies the inert liquid to a surface of the object to be heated in the heating chamber; an infrared heater that radiates infrared rays in a wavelength range that is different from the functional groups contained in the object to be heated and that is absorbed by the functional groups contained in the molecules that constitute the inert liquid, within the heating chamber; A heating device comprising:

2. 2. The heating device according to claim 1, further comprising a compressor connected to the inert liquid supply unit and configured to send compressed air into the heating chamber to cool the object to be heated.

3. A heating method for heating an object to be heated in a heating chamber by vaporizing an inert liquid and using an infrared heater, comprising: The inert liquid is supplied to a surface of the object to be heated, The object to be heated is heated by irradiating the object with infrared rays from the infrared heater in a wavelength range that is different from the functional group contained in the object to be heated and that is absorbed by the functional group contained in the molecule constituting the inert liquid, thereby heating the inert liquid. Heating method.

4. The heating method according to claim 3 , further comprising the step of: sending compressed air into the heating chamber to cool the object to be heated.

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