JP2023066568A - Valuable metal recovery method and valuable metal recovery device - Google Patents

Abstract

To recover with efficiency a valuable metal from a substrate using a metal forming an alloy with the valuable metal.SOLUTION: A valuable metal recovery device 10 includes a pretreatment device 12 having a pretreatment chamber 20, a microwave irradiation device 14 having microwave irradiation chamber 70, a posttreatment device 16 having a posttreatment chamber 90, and conveying member 18. In the pretreatment chamber 20, a valuable metal recovery agent containing an additive metal that forms an alloy with the valuable metal and a flux that promotes alloying of the additive metal that forms an alloy with the valuable metal is placed on the valuable metal of the composite to obtain a body to be heated P1. The microwave irradiation chamber 70 irradiates the object to be heated P1 with a magnetic field based on microwaves to heat the object to be heated P1 to form an alloy containing the valuable metal and the additive metal to obtain an alloyed object to be heated P2. The post-treatment chamber 90 strips part or larger of the alloy from the alloyed body to be heated P2. The transport member 18 transports the object P to be processed between the pretreatment chamber 20, the microwave irradiation chamber 70 and the posttreatment chamber 90.SELECTED DRAWING: Figure 7

Description

The present application relates to a method and apparatus for recovering valuable metals bonded onto substrates using microwaves.

Conventionally, a metal roller brush is used to scrape off and recover metal components on a substrate (Patent Document 1). However, in the metal component recovery method of Patent Document 1, the metal component is peeled off from the base material with a strong physical force, so the base material is also scraped off. As a result, the recovery rate of the metal is lowered, and there is a possibility that impurities such as metal semiconductors and metal oxides such as alumina, which are contained in the base material and are difficult to separate from the metal, may be mixed. Valuable metals such as gold, silver, or copper have high melting temperatures and are strongly bonded onto the substrate. Therefore, in the metal recovery method of Patent Document 1, the valuable metal is less likely to peel off from the substrate.

JP 2014-54593 A

The present application has been made in view of such circumstances, and an object thereof is to recover a valuable metal bonded to a substrate by using an additive metal that forms an alloy with the valuable metal.

The valuable metal recovery method of the present application forms an alloy with the valuable metal bonded on the base material, and alloys the additive metal with the valuable metal with the additive metal having a lower melting point than the melting point of the valuable metal. It has a microwave irradiation step of forming an alloy containing a valuable metal and an additive metal by irradiating and heating a magnetic field based on microwaves while being in contact with a flux that promotes, and a peeling step of peeling the alloy from the base material. .

The valuable metal recovery device of the present application is an additive metal that forms an alloy with the valuable metal on the valuable metal of the composite having the base material and the valuable metal joined on the base material, and the alloying of the additive metal with the valuable metal. A pretreatment device equipped with a pretreatment chamber for obtaining a heated body by installing a valuable metal recovery agent containing a flux that promotes , a microwave irradiation device having a microwave irradiation chamber for forming an alloy containing a valuable metal and an additive metal to obtain an alloyed heated body, and a post-treatment chamber for peeling off a part or more of the alloy from the alloyed heated body and a transfer member for transferring the object to be processed in this order between the pretreatment chamber, the microwave irradiation chamber, and the posttreatment chamber.

In the valuable metal recovery method of the present application, heating by a microwave-based magnetic field forms an alloy containing a valuable metal and an additive metal having a melting point lower than the melting point of the valuable metal. The formation of an alloy reduces the bonding strength between the valuable metal and the base material. Therefore, compared to the method of heating and melting the valuable metal bonded to the base material by heat transfer, convection, or radiation, it is possible to lower the bonding strength between the base material and the valuable metal in a short period of time while reducing the amount of energy used. . This alloy containing a valuable metal with reduced bonding strength to the substrate can be easily peeled off from the substrate using a metal blade or the like.

The valuable metal recovery apparatus of the present application comprises a pretreatment chamber in which an alloy is formed with the valuable metal joined on the base material, and a valuable metal recovery agent containing additive metals is placed on the valuable metal, and a magnetic field based on microwaves is used. A microwave irradiation chamber for heating an object to be heated to form an alloy containing a valuable metal and an additive metal, a post-treatment chamber for stripping the alloy from a substrate, and transporting the object to be treated between these chambers A carrier member is provided. Therefore, the valuable metal bonded to the substrate can be efficiently recovered.

Fig. 2 is a top view image of the heated sample of Example 1, (a) before heating, (b) during heating, and (c) after heating. 1 is an electron microscope image of the alloy of Example 1. FIG. X-ray diffraction patterns of the alloy of Example 1, Sn, and Ag ₃ Sn, respectively. FIG. 10 is an image of the top surface of the sample to be heated in Example 3, (a) before heating, (b) during heating, and (c) after heating. Fig. 2 is a top view image of the sample composite of Comparative Example 1, (a) before heating, (b) during heating, and (c) after heating. Electron micrograph of the alloy of Example 2 and elemental mapping of tin and silver. 1 is a schematic side view of a valuable metal recovery device according to an embodiment; FIG. BRIEF DESCRIPTION OF THE DRAWINGS The cross-sectional schematic diagram of the pretreatment apparatus of embodiment. The cross-sectional schematic diagram of the pretreatment apparatus of other embodiment. The cross-sectional schematic diagram of the pretreatment apparatus of other embodiment. The cross-sectional schematic diagram of the pretreatment apparatus of other embodiment. BRIEF DESCRIPTION OF THE DRAWINGS The cross-sectional schematic diagram of the microwave irradiation apparatus of embodiment. FIG. 2 is a schematic cross-sectional view of the post-processing device of the embodiment; FIG. 2 is a schematic cross-sectional view of a post-processing device of another embodiment; FIG. 2 is a schematic top view of a valuable metal recovery device of another embodiment.

Hereinafter, a valuable metal recovery apparatus and a valuable metal recovery method of the present application will be described based on embodiments and examples. Redundant description will be omitted as appropriate. FIG. 7 schematically shows a side view of the valuable metal recovery device 10 of the embodiment of the present application. The valuable metal recovery apparatus 10 is an apparatus for treating the object P to be treated in order of pretreatment, microwave irradiation treatment, and posttreatment. Note that the object to be processed P may be referred to as a composite C, an object to be heated P1, an alloyed object to be heated P2, or an object to be processed P3 after peeling, depending on the stage of treatment.

The valuable metal recovery device 10 includes a pretreatment device 12 , a microwave irradiation device 14 , a posttreatment device 16 and a conveying member 18 . The conveying member 18 is transported between the pretreatment chamber 20 constituting the pretreatment device 12, the microwave irradiation chamber 70 constituting the microwave irradiation device 14, and the posttreatment chamber 90 constituting the posttreatment device 16 in this order. The object P to be processed is transported. The valuable metal recovery method of the present application includes a microwave irradiation step and a stripping step, and is carried out using, for example, the valuable metal recovery device 10 .

FIG. 8 schematically shows a cross section of the pretreatment device 12 having a basic configuration. The pretreatment device 12 includes a pretreatment chamber 20 , an application section 22 , a tank 24 and a pipe 26 . In the pretreatment chamber 20, the valuable metal recovery agent M is placed on the valuable metal V of the composite C to obtain the object to be heated P1. The composite C and the object to be heated P1 are conveyed in the direction of the arrow in FIG. 8 (the same applies hereinafter). The pretreatment chamber 20 is a hollow structure partitioned so that the object P to be treated can be carried in and out by the conveying member 18 and the valuable metal recovery agent M is not diffused around. It should be noted that the pretreatment chamber, or the microwave irradiation chamber or posttreatment chamber, which will be described later, does not necessarily have to be partitioned by a structure, and the object to be heated P1, the alloyed object to be heated P2, and the object to be processed after peeling P3 can be a region of space.

Composite C comprises a substrate S and a valuable metal V bonded onto the substrate S. "Bonded on a substrate" means the state of being bonded or fused onto the substrate via an adhesive or fusion agent, the state of being fused onto the substrate, and the state of being physically bonded to the substrate. It shows the state of being deposited on a base material by bonding or chemical bonding. Examples of the substrate S include a solar cell substrate, a substrate portion of a printed circuit board, a ceramics substrate, and an insulating substrate for heat dissipation. Metal wiring formed in solar cells, printed circuit boards, and the like is often composed of valuable metals such as gold, silver, or copper. Since these valuable metals have a low weight ratio to the base material and are chemically adhered to the base material and are difficult to peel off, active recovery and recycling have not been attempted.

Furthermore, since the melting points of these valuable metals are as high as about 1000°C, conventional heating methods using heat transfer, convection, or radiation, such as electric furnaces or hot air, require a large amount of energy to heat and melt the valuable metals. Met. According to the valuable metal recovery apparatus or the valuable metal recovery method of the present application, since the valuable metal can be recovered using microwave irradiation, the amount of energy used can be reduced compared to these conventional heating methods. Valuable metals are elements of period 4 or higher and groups 3 to 16 of the periodic table, and refer to metals composed of a single element or alloys composed of two or more elements. Examples of the composite C include a solar cell, a printed circuit board, a ceramic substrate having a valuable metal on its surface, and a heat dissipation insulating substrate having a valuable metal on its surface.

The applicator 22 has a plurality of holes on its lower surface, and discharges the valuable metal recovery agent M from these holes toward the valuable metal V of the composite C. As shown in FIG. The valuable metal recovery agent M contains an additive metal D that forms an alloy with the valuable metal V, and a flux F that promotes the alloying of the additive metal D with the valuable metal. The additive metal D is a metal that forms an alloy with the valuable metal V and has a melting point lower than that of the valuable metal V.

Additive metal D includes tin, indium, bismuth, or aluminum when the valuable metal is gold, silver, or copper. The flux F promotes the alloying of the additive metal D and the valuable metal V. Examples of the flux F include a liquid containing an acid component, an organic component such as alcohol, and an alloying-promoting component such as rosin. A valuable metal recovery agent M is stored in a tank 24 and supplied to the application section 22 through a pipe 26 .

FIG. 9 schematically shows a cross section of a pretreatment device 30 according to another embodiment of the present application. In the pretreatment device 30, the flux F and the additive metal D are sequentially applied to the composite C, so that the valuable metal recovery agent M having the additive metal D and the flux F is deposited on the valuable metal (not shown) of the composite C. It installs and obtains the to-be-heated body P1. The pretreatment device 30 includes coating units 32 and 33 , receiving members 34 and 35 , transfer belts 36 , 37 , 38 and 39 as transfer members, and a pretreatment chamber 40 . The application unit 32 stores the flux F and discharges the flux F toward the valuable metal of the composite C. As shown in FIG. In the sieve-like coating part 33, powder of the additive metal D is stored and the additive metal D is sprinkled toward the flux F on the composite body C. As shown in FIG.

The receiving member 34 collects the excess flux F. The receiving member 35 recovers the excess additive metal D. The transport belt 36 transports the composite C. As shown in FIG. The conveying belt 37 conveys the object to be processed P including the composite C and the flux F coated on the upper surface of the composite C. As shown in FIG. In the conveying belt 38, the additive metal D is sprinkled on the flux F while the object P to be processed is conveyed, and the object to be heated P1 is produced. The conveyor belt 39 vibrates the object to be heated P<b>1 while conveying it, and causes the excessive additive metal D to drop onto the receiving member 35 . The pretreatment chamber 40 is a region where the valuable metal recovery agent M is placed on the valuable metal of the composite C to obtain the object to be heated P1.

In the pretreatment device 30, conveying belts 36 and 37 are provided so as to form a gap, through which excess flux F can be recovered and reused. Therefore, the flux F can be continuously discharged from the application part 32, and the flux F can be uniformly and efficiently placed on the valuable metal of the composite C. Further, in the pretreatment device 30, the conveyor belts 38 and 39 are provided so as to form a gap, through which the excessive additive metal D can be recovered and reused. Therefore, the additive metal D can be continuously lowered from the application portion 33, and the additive metal D can be uniformly and efficiently placed on the flux F on the composite C.

FIG. 10 schematically shows a cross section of a pretreatment device 50 according to another embodiment of the present application. The pretreatment device 50 includes an application section 52 , conveyance belts 36 and 37 as conveyance members, and a pretreatment chamber 54 . The spray-type applicator 52 sprays and applies the valuable metal recovery agent M toward the valuable metal (not shown) of the composite C. The pretreatment chamber 54 is a region where the valuable metal recovery agent M is placed on the valuable metal of the composite C to obtain the object to be heated P1. In the pretreatment device 50 , the valuable metal recovery agent M is applied in the form of fine particles onto the valuable metal of the composite C by the spray-type applicator 52 . Therefore, the valuable metal recovery agent M easily adheres to the valuable metal. In addition, since the valuable metal recovery agent M is applied only on the upstream conveyor belt 36, the valuable metal recovery agent M can be easily dried on the downstream conveyor belt 37.

FIG. 11 schematically shows a cross section of a pretreatment device 60 according to another embodiment of the present application. The pretreatment device 60 includes an application section 62 , a tank 63 , transfer belts 36 and 37 as transfer members, and a pretreatment chamber 64 . In the roller transfer type application unit 62, the valuable metal recovery agent M stored in the tank 63 is applied onto the valuable metal (not shown) of the composite C via the surfaces of a plurality of rollers. The pretreatment chamber 64 is a region where the valuable metal recovery agent M is placed on the valuable metal of the composite C to obtain the object to be heated P1. In the pretreatment device 60, the required amount of the valuable metal recovery agent M is applied onto the valuable metal of the composite C by the roller transfer type coating unit 62 without waste. In addition, since the valuable metal recovery agent M is applied only on the upstream conveyor belt 36, the valuable metal recovery agent M can be easily dried on the downstream conveyor belt 37.

FIG. 12 schematically shows a cross section of the microwave irradiation device 14 of the embodiment of the present application. As the microwave irradiation device 14, for example, a microwave heating device described in Japanese Patent Application Laid-Open No. 2019-140103 can be employed. The microwave irradiation device 14 includes a microwave irradiation chamber 70 , a microwave supply device 72 , a control section 73 , a radiation thermometer 74 , an electromagnetic field sensor 75 and a conveying member 76 . In the microwave irradiation chamber 70, the object to be heated P1 is irradiated with a magnetic field based on microwaves, and the object to be heated P1 is heated to form an alloy A containing the valuable metal V and the additive metal D to form an alloyed object to be heated. Get P2.

That is, in the microwave irradiation device 14, a certain aspect of the microwave irradiation process is performed. In this microwave irradiation step, the valuable metal V bonded on the base material S, that is, the valuable metal V on the surface of the composite C, the flux F and the additive metal D having a lower melting point than the melting point of the valuable metal V are in contact with each other, a magnetic field based on microwaves is irradiated and heated to form an alloy A containing a valuable metal V and an additive metal D. Alloy A collects on the substrate S in a spherical shape. Therefore, the valuable metal V is easily peeled off and recovered from the substrate S in the form of the alloy A.

The valuable metal V such as gold or silver has a high melting temperature and is fixed on the substrate S. Therefore, even if the composite C is heated as it is, the valuable metal V is not separated from the base material S. Therefore, by coexisting the additive metal D and the flux F on the valuable metal V and irradiating microwaves, the melting point of the valuable metal V and the adhesion strength to the base material S are lowered, and the valuable metal V is removed in the peeling process described later. V can be recovered.

The microwave irradiation chamber 70 is a cavity resonator having a cylindrical shape, and a microwave irradiation space is formed inside. In the microwave irradiation chamber 70, a standing wave is formed with a minimum electric field strength and a maximum magnetic field strength at the center axis 71 of the cylinder. That is, the valuable metal V can be irradiated with a magnetic field based on microwaves so that the electric field strength is minimal and the magnetic field strength is maximal. This is because if the electric field intensity is minimal, undesirable discharge of the object to be heated P1 can be suppressed, and if the magnetic field intensity is maximal, the heating rate of the object to be heated P1 can be increased.

In addition, "the magnetic field strength is maximum" means that the magnetic field strength of not only the maximum value, but also the magnetic field strength of the surrounding region including the maximum value is greater than the magnetic field strength of the other regions. The magnetic field strength in its surroundings, including the local maximum, is, for example, 3/4 or more of the local maximum. The term "minimum electric field strength" means that the electric field strength not only in the minimum value but also in the surrounding region including the minimum value is smaller than the electric field strength in the other regions. The surrounding electric field intensity including the minimum value is, for example, 1/4 or less of the maximum electric field intensity in the microwave irradiation chamber 70 .

In the microwave irradiation step, it is preferable to irradiate a magnetic field based on microwaves so that a standing wave of TM ₁₁₀ mode is formed at the contact portion between the valuable metal V and the additive metal D and the flux F. This is because the magnetic field intensity becomes maximum at the central axis 71 of the microwave irradiation chamber 70, and the magnetic field intensity becomes uniform along the central axis 71, so that the object to be heated P1 can be uniformly heated. Further, in the microwave irradiation step, heating is performed at a temperature equal to or higher than the melting point of the additive metal D and lower than the melting point of the valuable metal V, for example, at a temperature equal to or higher than the melting point of the additive metal and 500 ° C. or lower, and the valuable metal V and the additive metal D are heated. It is preferred to form an alloy A containing This is because the valuable metal V can be recovered in the form of the alloy A from the composite C while suppressing the energy used.

The microwave supply device 72 includes a microwave oscillator 77 , a microwave amplifier 78 , an isolator 79 , an impedance matcher 80 and an antenna 82 . Examples of the microwave oscillator 77 include a magnetron microwave oscillator and a microwave oscillator using a semiconductor solid state device. A microwave amplifier 78 amplifies the output of the microwave generated by the microwave oscillator 77 . The isolator 79 protects the microwave oscillator 77 by suppressing reflected waves generated in the microwave irradiation chamber 70 .

Isolator 79 provides microwaves in one direction from microwave oscillator 77 to antenna 82 . Impedance matching device 80 matches the impedance of microwave oscillator 77 , microwave amplifier 78 and isolator 79 with antenna 82 . The antenna 82 generates a magnetic field by microwaves applied from the microwave oscillator 77, introduces the magnetic field into the microwave irradiation chamber 70, and forms a standing wave.

A radiation thermometer 74 measures the temperature of the object P in the microwave irradiation chamber 70 . Temperature information of the object P measured by the radiation thermometer 74 is transmitted to the control unit 73 . The electromagnetic field sensor 75 detects signals corresponding to electromagnetic field energy within the microwave irradiation chamber 70 . An electromagnetic field energy signal detected by the electromagnetic field sensor 75 is transmitted to the controller 73 . The control unit 73 adjusts the microwave frequency in the microwave oscillator 77 and the microwave output in the microwave amplifier 78 based on the temperature information of the object P to be processed and the electromagnetic field energy signal in the microwave irradiation chamber 70. .

The conveying member 76 includes a conveying roller 76r and a conveying sheet 76s. The conveying sheet 76s is sandwiched from above and below by a pair of conveying rollers 76r, 76r. The object to be processed P on the conveying sheet 76s is conveyed in a predetermined direction by the rotation of the conveying rollers 76r, 76r. The transport rollers 76r, 76r do not exist over the entire width of the transport sheet 76s, but are arranged so that the object P on the transport sheet 76s can pass sideways of the transport rollers 76r, 76r.

FIG. 13 schematically shows a cross section of the post-processing device 16 of the embodiment of the present application. The post-treatment device 16 has a post-treatment chamber 90 . In the post-treatment chamber 90, part or more of the alloy A is stripped from the alloyed body to be heated P2. That is, in the post-treatment device 16, a peeling step of peeling the alloy A from the base material S is performed. The post-treatment device 16 includes transfer belts 36 and 37 as transfer members, a post-treatment chamber 90, a brush roll 92 as a stripping member, and an alloy receiver 94 as a recovery member. The brush roll 92 comes into contact with the surface of the alloyed body to be heated P2 and strips the alloy A from the alloyed body to be heated P2. The alloy receiver 94 collects the alloy A separated by the brush roll 92 . That is, when the alloyed object to be heated P2 passes through the brush roll 92, it becomes the object to be treated P3 after peeling, and the alloy A is recovered in the alloy receiver 94. Alloy A is separated into valuable metal V and additive metal D by a known technique.

FIG. 14 schematically shows a cross section of a post-processing device 96 according to another embodiment of the present application. The post-treatment device 96 includes transfer belts 36 and 37 as transfer members, a post-treatment chamber 97 , a squeegee 98 as a stripping member, and an alloy receiver 94 . When the alloyed object to be heated P2 passes through the squeegee 98, it becomes the object to be treated P3 after peeling, and the alloy A is recovered in the alloy receiver 94. By analyzing the composition of the valuable metals and additive metals of the alloy A, the recovery rate (%) of the valuable metals can be calculated from the following formula.
(mass of exfoliated alloy - mass of additive metal in exfoliated alloy)/mass of valuable metal on substrate x 100

FIG. 15 schematically shows the upper surface of a valuable metal recovery device 100 according to another embodiment of the present application. The valuable metal recovery device 10 was a continuous device, but the valuable metal recovery device 100 of this embodiment is a disc type device. That is, the valuable metal recovery apparatus 100 includes a pretreatment device 12 having a pretreatment chamber 20, a microwave irradiation device 14 having a microwave irradiation chamber 70, a posttreatment device 16 having a posttreatment chamber 90, and a conveying member. It has certain transport belts 102 , 104 , 106 and a buffer 108 .

The object P to be processed is transported from the buffer 108 to the pretreatment chamber 20 by the transport belt 102, becomes the object to be heated P1 in the pretreatment chamber 20, is returned to the buffer 108, and is transported from the buffer 108 by the transport belt 104 to the microwave irradiation chamber. 70, the material to be alloyed P2 is returned to the buffer 108 in the microwave irradiation chamber 70, and is transported from the buffer 108 to the post-treatment chamber 90 by the transfer belt 106, where the alloy A is recovered in the post-treatment chamber 90. After being peeled off, it is returned to the buffer 108 as the object to be processed P3. That is, the object to be processed P is transported in this order between the pretreatment chamber 20, the microwave irradiation chamber 70, and the posttreatment chamber 90 by the transfer belts 102, 104, and 106. FIG.

Example 1
Unless otherwise specified, the same raw materials, various equipments, various devices, calculation formulas, etc. were used in each example. First, a 10 mm×10 mm square sample substrate was cut out from a silicon substrate (high-purity silicon wafer, AS ONE) as a base material. A silver paste (REXALPHA RAFS074, Toyo Ink) was applied to the entire surface of the sample substrate by casting to a thickness of 60 μm. Using an electric oven, heat at 100°C for 0.5 hours, then heat at 400°C for 3 hours, and bond a silver thin film, which is a valuable metal, to the center of the sample substrate in a rectangular shape of about 5 mm x about 10 mm. A sample composite was obtained. In addition, tin powder (Wako Pure Chemical), which is an additive metal, and flux 1 (TEL30, Trusco) are mixed so that the mass ratio is 5: 2, and a rotation and revolution stirrer (Awatori Mixer, Thinky) is used. and kneaded at 2000 rpm for 1 minute to obtain a tin paste. The tin paste was applied to the entire silver thin film surface of the sample composite to obtain a heated sample.

As a microwave irradiation device, a microwave heating device described in JP-A-2019-140103 was used. This microwave heating device consists of a microwave oscillator (maximum output 200 W, Ryowa Denshi), a TM ₁₁₀ cavity resonator (Ryowa Denshi) in which a glass cloth is arranged as a sample mounting table, and a USB camera (L- 851, Hozan) and a lens (L-870, Hozan), and a thermo camera for temperature measurement (PI400i, Optris).

The heated sample was placed on the glass cloth inside the TM ₁₁₀ cavity. A microwave of 2.45 GHz was irradiated into the TM ₁₁₀ cavity at 100 W, and it was confirmed that the surface temperature of the heated sample reached 364° C. after 17 seconds. At this time, tin melted and formed an alloy with the silver thin film. The surface temperature of the sample to be heated was calculated from a thermal image using temperature analysis software (PIX-Connect, Optris) based on the emissivity of the silicon substrate of 0.73. Top images of the heated sample before heating, during heating (10 seconds after the start of microwave magnetic field irradiation), and after heating are shown in FIGS. 1(a) to 1(c).

After that, the heated sample was removed from the TM ₁₁₀ cavity resonator, allowed to cool, and then the alloy was peeled off from the sample substrate using tweezers. An electron microscope image of this alloy is shown in FIG. No metal interface was observed in the structure within the alloy, and it was confirmed that a uniform alloy phase was formed. Further, as a result of analysis with an X-ray diffractometer (SmartLab, Rigaku), it was confirmed that this alloy was a composite of Sn and Ag ₃ Sn. The respective X-ray diffraction patterns of this alloy, Sn (PDF No. 00-004-0673), and Ag ₃ Sn (PDF No. 01-084-8210) are shown in FIG. Further, composition analysis of this alloy was carried out using SEM-EDS (S-4800, Hitachi), and as a result, tin:silver was 91.34:8.66 in terms of the substance amount ratio (so-called molar ratio). Based on this numerical value, the recovery rate of silver was calculated. The recovery of silver in Example 1 was 96%.

Example 2
A heated sample was obtained in the same manner as in Example 1, except that Flux 1 was changed to Flux 2 (BS-850, Taiyo Denki Sangyo). Thereafter, in the same manner as in Example 1, the sample to be heated was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample to be heated reached 402° C. 28 seconds after the start of microwave magnetic field irradiation, and that the melted tin and silver thin films formed an alloy. In the same manner as in Example 1, exfoliation of the alloy, analysis of the composition of the alloy, and calculation of the silver recovery rate were performed. Elemental mapping of this alloy using SEM-EDS is shown in FIG. In addition, the recovery rate of silver in Example 2 was 86%.

Example 3
A sample composite was obtained in the same manner as in Example 1. Further, a tin foil having a thickness of 300 μm was obtained by spreading the tin powder with a hammer. Flux 1 was applied to one side of this tin foil. A heated sample was obtained by placing this tin foil over the entire surface of the silver thin film of this sample composite through the applied Flux 1. Thereafter, in the same manner as in Example 1, the sample to be heated was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample to be heated reached 500° C. 15 seconds after the start of microwave magnetic field irradiation, and that the melted tin and silver thin films formed an alloy. FIGS. 4(a) to 4(c) show top images of the heated sample before heating, during heating (7 seconds after the start of microwave magnetic field irradiation), and after heating. In addition, in the same manner as in Example 1, the exfoliation of the alloy, the composition analysis of the alloy, and the calculation of the silver recovery rate were performed. The recovery of silver in Example 3 was 89%.

Example 4
The sample to be heated was heated in the same manner as in Example 1, except that the microwave was irradiated at 150 W. It was confirmed that the surface temperature of the sample to be heated reached 375° C. 13 seconds after the start of the microwave magnetic field irradiation, and that the melted tin and silver thin films formed an alloy. In the same manner as in Example 1, exfoliation of the alloy, analysis of the composition of the alloy, and calculation of the silver recovery rate were performed. The recovery of silver in Example 4 was 85%.

Example 5
A sample composite was obtained in the same manner as in Example 1. Further, the indium powder (Kennis) was spread with a hammer to obtain an indium foil having a thickness of 400 μm. Flux 1 was applied to one side of this indium foil. A heated sample was obtained by placing this indium foil over the entire surface of the silver thin film of this sample composite through the applied Flux 1. Thereafter, in the same manner as in Example 4, the sample to be heated was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample to be heated reached 458° C. 14 seconds after the start of microwave magnetic field irradiation, and that the melted indium and silver thin film formed an alloy. In the same manner as in Example 1, exfoliation of the alloy, analysis of the composition of the alloy, and calculation of the silver recovery rate were performed. The recovery of silver in Example 5 was 74%.

Example 6
A sample composite was obtained in the same manner as in Example 1. Further, bismuth (Kennis) was pulverized with a hammer to obtain bismuth powder. Flux 1 was applied to the entire surface of the silver thin film of this sample composite, and this bismuth powder was dispersed to obtain a heated sample. Thereafter, in the same manner as in Example 4, the sample to be heated was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample to be heated reached 461° C. 13 seconds after the start of the microwave magnetic field irradiation, and that the melted bismuth and the silver thin film formed an alloy. In the same manner as in Example 1, exfoliation of the alloy, analysis of the composition of the alloy, and calculation of the silver recovery rate were performed. The recovery of silver in Example 6 was 74%.

Comparative example 1
A sample composite was obtained in the same manner as in Example 1. As in Example 1, this sample composite was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample composite reached 791° C. 79 seconds after the start of microwave magnetic field irradiation. However, the thin silver film did not melt and could not be peeled off from the silicon substrate. Top surface images of the heated sample before heating, during heating (90 seconds after the start of microwave magnetic field irradiation), and after heating are shown in FIGS. 5(a) to 5(c). Melting of the silver thin film could not be confirmed. Also, the silver thin film could not be peeled off from the silicon substrate. In other words, the silver on the sample composite could not be recovered in the absence of the additive metal that forms an alloy with silver.

Comparative example 2
A sample composite and a tin foil were obtained in the same manner as in Example 3. A heated sample was obtained by placing this tin foil over the entire surface of the silver thin film of this sample composite. In the same manner as in Example 1, this sample to be heated was heated by microwave magnetic field irradiation. It was confirmed that the surface temperature of the sample to be heated reached 755° C. 70 seconds after the start of microwave magnetic field irradiation. However, tin did not melt, and alloying of tin and silver thin film could not be confirmed. Also, the silver thin film could not be peeled off from the silicon substrate. In other words, the silver on the sample composite could not be recovered in the absence of the flux that promotes the alloying of silver, which is a valuable metal, and tin, which is an additive metal.

REFERENCE SIGNS LIST 10, 100 Valuable metal recovery device 12, 30, 50, 60 Pretreatment device 14 Microwave irradiation device 16, 96 Post-treatment device 18 Conveying member 20, 40, 54, 64 Pretreatment chamber 22, 32, 33, 52, 62 Applicator 24, 63 Tank 26 Piping 34, 35 Receiving member 36, 37, 38, 39, 102, 104, 106 Conveyor belt 70 Microwave irradiation chamber 71 Central shaft 72 Microwave supply device 73 Control unit 74 Radiation thermometer 75 Electromagnetic field Sensor 76 Conveying member 76s Conveying sheet 76r Conveying roller 77 Microwave oscillator 78 Microwave amplifier 79 Isolator 80 Impedance matching device 82 Antenna 90, 97 Post-processing chamber 92 Brush roll 94 Alloy receiver 98 Squeegee 108 Buffer P Object to be processed S Base material V Valuable metal C Composite D Added metal F Flux M Valuable metal recovery agent P1 Object to be heated A Alloy P2 Alloyed object to be heated P3 Object to be treated after peeling

Claims (8)

A flux that forms an alloy with the valuable metal bonded on the substrate and promotes the alloying of the additive metal with the valuable metal and the additive metal that has a melting point lower than the melting point of the valuable metal. A microwave irradiation step of irradiating and heating a magnetic field based on microwaves while contacting with to form an alloy containing the valuable metal and the additive metal;
a peeling step of peeling the alloy from the substrate;
Valuable metal recovery method having. In claim 1,
In the microwave irradiation step, the valuable metal recovery method includes irradiating the valuable metal with a magnetic field based on the microwave so that the electric field intensity is minimal and the magnetic field intensity is maximal. In claim 1 or 2,
In the microwave irradiation step, a magnetic field based on the microwave is applied to the contact portion between the valuable metal and the additive metal so that a standing wave of TM ₁₁₀ mode is formed. In any one of claims 1 to 3,
In the microwave irradiation step, the valuable metal recovery method includes heating at a temperature equal to or higher than the melting point of the additive metal and lower than the melting point of the valuable metal to form an alloy containing the valuable metal and the additive metal. In claim 4,
In the microwave irradiation step, the valuable metal recovery method includes heating the additive metal at a melting point or higher and 500° C. or lower to form an alloy containing the valuable metal and the additive metal. In any one of claims 1 to 5,
A valuable metal recovery method, wherein the valuable metal is silver and the additive metal is at least one of tin, indium and bismuth. facilitating the alloying of an additive metal that forms an alloy with said valuable metal and said additive metal with said valuable metal on said valuable metal of a composite having a substrate and said valuable metal bonded onto said substrate; a pretreatment device having a pretreatment chamber in which a valuable metal recovery agent containing flux is installed to obtain an object to be heated;
A microwave irradiation chamber for irradiating the object to be heated with a magnetic field based on microwaves to heat the object to form an alloy containing the valuable metal and the additive metal to obtain an alloyed object to be heated. a microwave irradiation device;
a post-treatment device comprising a post-treatment chamber for stripping part or more of the alloy from the alloyed body to be heated;
a conveying member that conveys an object to be processed in this order between the pretreatment chamber, the microwave irradiation chamber, and the posttreatment chamber;
Valuable metal recovery equipment with. In claim 7,
A valuable metal recovery device, wherein the post-treatment device includes a stripping member that contacts the surface of the alloyed body to be heated and strips the alloy from the alloyed body to be heated, and a recovery member that recovers the stripped alloy. .

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