EP3178562A1

EP3178562A1 - Object disassembly method and disassembly device

Info

Publication number: EP3178562A1
Application number: EP16196409.3A
Authority: EP
Inventors: Yuichi Hata; Syougo Utumi; Genichiro Matsuda; Takao Namihira
Original assignee: Panasonic Corp
Current assignee: Panasonic Corp
Priority date: 2015-12-08
Filing date: 2016-10-28
Publication date: 2017-06-14
Anticipated expiration: 2036-10-28
Also published as: CN106853411A; EP3178562B1; JP2017104796A; CN106853411B; JP6404808B2

Abstract

The present disclosure provides an object disassembly method and an object disassembly device that can disassemble an object through a prescribed number of times of discharging in accordance with change in an electric conductivity of liquid in disassembly processing and change in a shape of a processed object. At least one of a distance and a discharge voltage between a positive electrode and a ground electrode can be changed. A peak value of discharge current is maintained constant through continuous discharging by changing at least one of the distance and the discharge voltage between the electrodes during monitoring of the peak value of the discharge current.

Description

BACKGROUND

1. Technical Field

The present disclosure relates to an object disassembly method and an object disassembly device which disassemble a substrate or an object including the substrate by causing pulse power discharging in liquid.

2. Description of the Related Art

Various kinds of work are required for recycling used home appliances and the like. In dismantling, it is required to individually disassemble various forms of screw fastening parts and soldering parts, which makes it difficult to achieve automation, and thus manual dismantling by a worker is mainly employed. The manual dismantling provides the flexibility of work but has low operation efficiency, and thus it has been desired to develop a method of automatically and efficiently dismantling various kinds of used home appliances.
PTL 1 discloses a method in which objects to be recycled, including ceramic components such as a battery and a fuse, computer components, and capacitors are placed still in a reaction container filled with liquid, and pulse discharge is generated between a plurality of electrode rods and a container substrate provided in the liquid so as to destroy plastic exteriors and the like.
FIG. 9 is a diagram illustrating the configuration of the conventional object disassembly device disclosed in PTL 1. Device 101 includes container 102 filled with liquid for housing a recycle material. Container 102 includes, for example, container body 103 made of stainless steel in a particularly simple exemplary embodiment. Container body 103 includes a cover side (upper) flange, a bottom side (lower) flange, container cover 104a, and container substrate 104b. Three electrodes 105 are preferably inserted into or integrated with container cover 104a at positions equally spaced from each other. Electrodes 105 each include a part extending in the vertical direction, in other words, a part extending substantially parallel to a cylindrical wall of container body 103. Container cover 104a and container substrate 104b are connected with the corresponding flanges of container body 103 through a large number of connecting parts uniformly distributed on their peripheral parts. Capacitor 107 is charged by charger 108 through resistor 109. Electrodes 105 are connected with capacitor 107 through high-voltage switchgear 106a and safety switchgear breaker 106b connected with earth or ground potential. The connection between capacitor 107 and electrodes 105 generates pulse discharge, which disassembles an object to be recycled that is introduced to a liquid medium. The disassembly proceeds as a high voltage pulse is applied a plurality of times within a predetermined number of repetitions at a predetermined time interval (hereinafter referred to as "continuous discharging" in short).

Citation List

Patent Literature

PTL 1: Japanese Translation of PCT Publication No. 2014-532548
However, the processing of disassembling by continuous discharging is performed under a fixed discharge condition, and thus energy applied to an object to be recycled during continuous discharging differs from that before the continuous discharging because of change in the electric conductivity of surrounding liquid and change in the shape of a processed object through the processing. This causes insufficient disassembly and excessive disassembly of the processed object after the processing.

SUMMARY

The present disclosure is intended to solve the above-described conventional problem and an object thereof is to provide an object disassembly method and an object disassembly device which enable disassembly of an object through a prescribed number of times of discharging in accordance with change in the electric conductivity of liquid and change in the shape of the processed object during disassembly processing.
To solve the above-described problem, an object disassembly method according to an aspect of the present disclosure disassembles a substrate or an object including the substrate by performing discharging in liquid a plurality of times, and is characterized as follows.
Specifically, the method includes, when a positive electrode and a ground electrode are provided in liquid held in a container and a substrate or an object including the substrate is placed on a discharge path between the positive electrode and the ground electrode in the liquid or in a region to which shock wave generated by discharging travels in the liquid, measuring a peak value of discharge current flowing through the discharge path during discharging, and controlling a discharge condition so that the measured peak value of the discharge current is maintained constant.
An object disassembly device according to another aspect of the present disclosure is configured to disassemble a substrate or an object including the substrate by performing discharging in liquid a plurality of times, and is characterized as follows.
Specifically, the object disassembly device includes a container holding the liquid, a positive electrode and a ground electrode disposed in the liquid in the container, a pulse power source configured to apply a high voltage pulse between the positive electrode and the ground electrode, and an electric current meter configured to measure discharge current flowing between the positive electrode and the ground electrode during discharging. The object disassembly device further includes a discharge condition adjustment device configured to adjust a discharge condition between the positive electrode and the ground electrode, and a controller. The object disassembly device further includes at least one of an inter-electrode distance adjustment mechanism configured to change a distance (inter-electrode distance) between the positive electrode and the ground electrode and a discharge voltage adjustment mechanism configured to adjust a discharge voltage. The controller performs such control that a peak value of the discharge current is maintained constant by adjusting at least one of the inter-electrode distance and the discharge voltage through a corresponding one of the inter-electrode distance adjustment mechanism and the discharge voltage adjustment mechanism while measuring the peak value of the discharge current through the electric current meter.
The above-described aspects of the present disclosure enable disassembly of an object through a prescribed number of times of discharging in accordance with change in the electric conductivity of liquid and change in the shape of the processed object during disassembly processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an object disassembly device utilizing pulse power discharging according to an exemplary embodiment of the present disclosure;
FIG. 2 is a process chart of maintaining a discharge current peak value constant by changing a distance between discharging electrodes in object disassembly utilizing pulse power discharging;
FIG. 3 is a process chart of maintaining the peak value of the discharge current constant by changing a discharge voltage in the object disassembly utilizing pulse power discharging;
FIG. 4 is a diagram illustrating evaluation results of separation of a component from a substrate and disassembly of the substrate for different peak values of the discharge current;
FIG. 5 is a diagram illustrating evaluation results of disassembly of a resin case, separation of a component from a substrate, and disassembly of the substrate for different peak values of the discharge current and different numbers of times of discharging;
FIG. 6 is a diagram illustrating influence of a voltage and a distance between electrodes on the peak value of the discharge current in pulse power discharging;
FIG. 7 is a diagram illustrating evaluation results of separation of the component from the substrate, disassembly of the resin case, and excessive disassembly of the resin case for different widths of the discharge current;
FIG. 8 is a schematic diagram of an object disassembly device which utilizes pulse power discharging and includes an object moving and holding mechanism; and
FIG. 9 is a schematic diagram of a conventional object disassembly device utilizing pulse power discharging.

DETAILED DESCRIPTION

An object disassembly device and an object disassembly method according to an exemplary embodiment of the present disclosure generate pulse discharging between electrodes placed still in liquid and perform object disassembly utilizing discharging or shock wave induced by the discharging.
Exemplary embodiments of the present disclosure will be described below with reference to the accompanying drawings.

FIRST EXEMPLARY EMBODIMENT

FIG. 1 illustrates an aspect of an object disassembly device according to a first exemplary embodiment of the present disclosure.
Object disassembly device 1 includes container 3 holding liquid 2 (for example, filled with water), positive electrode 4 and ground electrode 5 disposed facing each other at an interval therebetween in liquid 2, pulse power source 6 configured to apply high voltage pulse to positive electrode 4, electric current meter 7 configured to measure discharge current, and inter-electrode distance adjustment mechanism 8 configured to move at least positive electrode 4 in a vertical direction. Ground electrode 5 is grounded. Inter-electrode distance adjustment mechanism 8 serves as an exemplary discharge condition adjustment device.
Object 9 is a target to be disassembled, and is held in liquid 2 between positive electrode 4 and ground electrode 5. In FIG. 1, object 9 is placed on ground electrode 5 but may be supported so as not to make contact with positive electrode 4 or ground electrode 5 by a supporting member.
Controller 10 is connected with pulse power source 6, electric current meter 7, and inter-electrode distance adjustment mechanism 8. Controller 10 controls inter-electrode distance adjustment mechanism 8 so as to adjust a distance (inter-electrode distance) between positive electrode 4 and ground electrode 5.
Pulse power source 6 is capable of applying an optional voltage. For example, pulse power source 6 may be a Marx generator. Discharging occurs between positive electrode 4 and ground electrode 5. Object 9 held between positive electrode 4 and ground electrode 5 is disassembled through discharging or shock wave induced by the discharging.
As for a shape of positive electrode 4 and a shape of ground electrode 5, FIG. 1 illustrates an example in which a leading end of positive electrode 4 has a circular cone shape, and ground electrode 5 has a flat plate shape. Since the disassembly proceeds through discharging, these electrodes may have various shapes in accordance with a shape or a material of object 9 or a shape to be achieved after disassembly. Ground electrode 5 may have, for example, a reticular shape, a lattice shape, or a spiral shape instead of the flat plate shape.
In FIG. 1, positive electrode 4 and ground electrode 5 are disposed facing each other with object 9 interposed therebetween, but positions of the electrodes are not particularly limited because discharging occurs in the liquid as long as at least one positive electrode 4 and one ground electrode 5 are provided and a nearest distance between positive electrode 4 and ground electrode 5 is smaller than 100 mm. For example, positive electrode 4 and ground electrode 5 may be placed above object 9. For example, a plurality of positive electrodes 4 or a plurality of ground electrodes 5 may be provided, or a plurality of positive electrodes 4 and a plurality of ground electrodes 5 may be provided. Directions to which the leading ends of positive electrode 4 and ground electrode 5 point are not limited because generation of discharging is hardly affected by these directions.
As for a position of object 9 with respect to positive electrode 4 and ground electrode 5, since disassembly proceeds when object 9 is on a discharge path between positive electrode 4 and ground electrode 5 in the liquid or in a region to which shock wave generated by discharging travels. Object 9 does not necessarily need to be in contact with positive electrode 4 or ground electrode 5 nor placed between positive electrode 4 and ground electrode 5.
Inter-electrode distance adjustment mechanism 8 is capable of changing the distance between positive electrode 4 and ground electrode 5 by moving the electrodes. Although inter-electrode distance adjustment mechanism 8 is a mechanism capable of changing a height of positive electrode 4 in FIG. 1, a mechanism capable of changing a height of ground electrode 5 is applicable. A movement distance depends on a size of object 9 to be processed or a discharge condition and thus cannot be particularly specified, but an exemplary movement stroke is 100 mm, which is an upper limit allowing generation of pulse discharging in the liquid with the present configuration, so as to deal with a large change in an electric conductivity of liquid 2. Exemplary movement accuracy is set to be not larger than 1 mm, which is a thickness of an electric component, so as to follow change in a distance between an electrode and a processed object, which occurs when the electric component is separated from a substrate.
Object 9 to be disassembled is not particularly limited but is preferably a thin object so that the entire object is equally provided with an effect of the shock wave due to discharge. Examples of the object include an electrical product such as a cellular phone, a game machine, or a flat-panel television, an electronic substrate, and a solar battery. The configuration of the disassembly device for object 9 enables such adjustment that the discharge current measured by electric current meter 7 is maintained constant in accordance with change in the electric conductivity of liquid 2 and change in the shape of object 9 along disassembly.
A substrate or object 9 including the substrate is placed on the discharge path between positive electrode 4 and ground electrode 5 in the liquid or in the region to which shock wave generated by discharging travels in the liquid, and object 9 is disassembled through a plurality of times of discharging from positive electrode 4. FIG. 2 illustrates a process of changing the distance between positive electrode 4 and ground electrode 5 so that a peak value of the discharge current is maintained constant in a predetermined range allowing disassembly of a component on the substrate, from the substrate or object 9 including the substrate, without destroying the component. The peak value of the discharge current is a maximum value of current flowing at discharging operation. The maximum value of the current may be set upon removal of a noise component depending on a condition. The peak value of the discharge current allowing disassembly of a component on the substrate without destroying the component from the substrate or object 9 including the substrate will be described in detail later.
The above-described process includes step S001 in which positive electrode 4 or ground electrode 5 is moved to an initial position, an optional discharge voltage, and step S002 in which discharging is performed at a width of the discharge current (hereinafter referred to as a pulse width) that is a time from rise of the discharge current until its return to zero voltage. The process further includes step S003 in which controller 10 determines whether a total number of times of discharging after step S002 has reached a predetermined target number of times of discharging, step S004 in which controller 10 determines whether the peak value of the discharge current at the discharging in step S002 is in a predetermined range, and step S005 in which controller 10 determines whether the peak value of the discharge current at the discharging in step S002 is smaller than a predetermined value. The process further includes step S006 in which inter-electrode distance adjustment mechanism 8 reduces the inter-electrode distance under control of controller 10 if it is determined in step S005 that the peak value of the discharge current is smaller than the predetermined value, and step S007 in which inter-electrode distance adjustment mechanism 8 increases the inter-electrode distance under control of controller 10 if it is determined in step S005 that the peak value of the discharge current is not smaller than the predetermined value. The process includes the above-described seven steps.
First, in step S001, positive electrode 4 or ground electrode 5 is moved to an initial position. The initial position to which the electrode is moved needs to be in such a range that the peak value of the discharge current does not exceed the predetermined value but discharging occurs.
Subsequently, in step S002, discharging is performed at an optional discharge voltage and the width of the discharge current (hereinafter referred to as the pulse width) that is a time from rise of the discharge current until its return to zero voltage. The discharge voltage and the pulse width are preferably set in advance based on a material or hardness of a processed object, or a target disassembly state and a target number of times of discharging. In particular, a preferable pulse width will be described in detail later.
Subsequently, in step S003, controller 10 determines whether the total number of times of discharging after step S002 has reached the predetermined target number of times of discharging. If controller 10 determines that the total number of times of discharging has reached the predetermined target number of times of discharging, the process is ended. If controller 10 determines that the total number of times of discharging has not reached the predetermined target number of times of discharging, the process proceeds to step S004. The target number of times of discharging is optionally determined but preferably determined in advance as appropriate because an insufficient number of times of discharging results in insufficient disassembly of the substrate or object 9 including the substrate, and an excessive number of times of discharging generates minute dust or the like of the substrate or object 9 including the substrate, which requires, for example, cleaning of the liquid.
In step S004, controller 10 determines whether the peak value of the discharge current at the discharging in step S002 is smaller than the predetermined value, in other words, whether the peak value of the discharge current is in the predetermined range. If controller 10 determines that the peak value of the discharge current is not in the predetermined range, the process proceeds to step S005. If controller 10 determines that the peak value of the discharge current is in the predetermined range, the process returns to step S002.
In step S005, controller 10 determines whether the peak value of the discharge current is smaller than the predetermined value, in other words, whether the peak value of the discharge current is in the predetermined range. If controller 10 determines that the peak value of the discharge current is in the predetermined range, the process proceeds to step S006. If controller 10 determines that the peak value of the discharge current is not in the predetermined range, the process proceeds to step S007.
In step S006, inter-electrode distance adjustment mechanism 8 reduces the distance between positive electrode 4 and ground electrode 5 under control of controller 10. When positive electrode 4 and ground electrode 5 are brought closer to each other, a resistance along the discharge current is reduced and the peak value of the discharge current increases accordingly, so that the peak value of the discharge current is more likely to be in the predetermined range at subsequent discharging.
After step S006, the process returns to step S002 again, in which discharging is performed. Measurement of the peak value of the discharge current may be performed by measuring current flowing through part of a circuit, instead of current between the discharging electrodes, such as current flowing through a wire between the ground electrode and GND.
In step S005, if controller 10 determines that the peak value of the discharge current is not smaller than the predetermined value (is not within the predetermined range), it is determined, based on the determination in step S004 performed before step S005, that the peak value of the discharge current is larger than the predetermined value. In order to reduce the peak value of the discharge current, in step S007, inter-electrode distance adjustment mechanism 8 increases the inter-electrode distance under control of controller 10. When the inter-electrode distance is increased, a resistance between the electrodes is increased accordingly, thereby reducing the peak value of the discharge current. After step S007, the process returns to step S002 again to perform discharging.
Through the process illustrated in FIG. 2, the peak value of the discharge current can be maintained constant in the predetermined range.
When at least positive electrode 4 and ground electrode 5 are provided in the liquid, and a substrate or an object including the substrate is placed on the discharge path between the electrodes in the liquid or in the region to which shock wave generated by discharging travels in the liquid, object 9 is disassembled through a plurality of times of discharging from the electrodes. FIG. 3 illustrates a process of changing the discharge voltage through pulse power source 6 so that the peak value of the discharge current is maintained constant in the predetermined range. Pulse power source 6 serves as an exemplary discharge condition adjustment device such as a discharge voltage adjustment mechanism.
Processing content in steps S001 to S005 is the same as that in FIG. 2, and thus a detailed description thereof will be omitted. If controller 10 determines that the peak value of the discharge current is smaller than the predetermined value (within the predetermined range) in step S005, step S008 is performed in which pulse power source 6 increases its voltage under control of controller 10. When the voltage is increased, the discharge current is increased at the same inter-electrode distance, thereby increasing the peak value of the discharge current. After step S008, the process returns to step S002 again, in which discharging is performed.
If controller 10 determines that the peak value of the discharge current is not smaller than the predetermined value (not within the predetermined range) in step S005, pulse power source 6 reduces its voltage under control of controller 10 in step S009 so as to reduce the peak value of the discharge current. Thereafter, the process returns to step S002 again, in which discharging is performed.
Through the process illustrated in FIG. 3, the peak value of the discharge current can be maintained constant in the predetermined range.
The following describes the peak value of the discharge current allowing separation of a component from a substrate without destroying the substrate.
A disassembly processing test using the object disassembly device illustrated in FIG. 1 was performed on a substrate on which a component is mounted by soldering.
A producing condition of object 9 is as follows.
Such a substrate was used on which a 16-pin IC element as a component was mounted by soldering all 16 pins of the element so as to have a soldering intensity of 1 kgf per substrate. The mounted element had a height of 5 mm. With this condition, five IC elements were mounted on one substrate.
For example, object 9 was disassembled by the device illustrated in FIG. 1 through discharging at a discharge voltage of 250 kV, a pulse frequency of 1 Hz, and 10 times of pulsing. The peak value of the discharge current was maintained constant at an arbitrary value between 7 kA and 34 kA inclusive by changing the distance between positive electrode 4 and ground electrode 5. Object 9 was processed while being placed on ground electrode 5.
The disassembly processing test was evaluated for each object after the test, in terms of separation of the IC element from the substrate and disassembly of the substrate. FIG. 4 illustrates evaluation results of separation of the IC element from the substrate and disassembly of the substrate at different peak values of the discharge current in this test. In FIG. 4, as for the separation of the IC element from the substrate, "satisfactory" indicates that five IC elements were all separated from the substrate after discharging, and "unsatisfactory" indicates that not all of the five IC elements were separated. As for the disassembly of the substrate, "satisfactory" indicates that the substrate was not disassembled into two pieces or more, and "unsatisfactory" indicates that the substrate was disassembled into two pieces or more. Since object 9 was disassembled through the disassembly processing test, object 9 produced under an identical condition was used for each of test conditions 1 to 9, and a total of nine objects were used in the disassembly processing test.
FIG. 4 indicates that the component can be separated from the substrate without disassembly of the substrate when the peak value of the discharge current is in a range from 10 kA to 30 kA inclusive.
The following describes the peak value of the discharge current allowing separation of a component from a substrate without disassembly of the substrate in an object including the substrate, for example, an object in which the substrate, on which the component is mounted by soldering, is fixed in a resin case.
A disassembly processing test using the object disassembly device illustrated in FIG. 1 was performed on an object including a substrate.
A producing condition of object 9 is as follows.
Object 9 was produced with two kinds of samples of sample 1 and sample 2 described below. In sample 1, a substrate was fastened by a screw in an ABS resin case having a dimension of 50 mm x 100 mm x t30 mm, and a lid of the ABS case in which the substrate is placed was fastened by screws at four positions. Such a substrate was used on which a 16-pin IC element as a component was mounted by soldering all 16 pins of the element so as to have a soldering intensity of 1 kgf per substrate. The mounted element had a height of 5 mm. With this condition, five IC elements were mounted on one substrate.
In sample 2, a substrate same as that used in sample 1 was fastened by a screw in an ABS resin case having a dimension of 50 mm x 100 mm x t30 mm, and a lid of the ABS case in which the substrate is placed was fixed by engagement.
This object to be processed was disassembled by the device illustrated in FIG. 1 through discharging at a discharge voltage of 250 kV and a pulse frequency of 1 Hz. The peak value of the discharge current was maintained constant at an arbitrary value in a range from 8 kA to 34 kA inclusive by changing the distance between positive electrode 4 and ground electrode 5. Object 9 was processed while being placed on ground electrode 5.
Disassembly processing was performed at 30 times of pulsing and at 50 times of pulsing. The number of times of pulsing was 30 for test conditions 1 to 7 and 50 for test conditions 8 to 14. The test was performed under a total of 14 conditions.
Under each of the conditions, as the disassembly processing of object 9 proceeds, disassembly of the resin case, separation of the component from the substrate, and disassembly of the substrate occur sequentially or simultaneously depending on the condition.
The disassembly processing test was evaluated for each object after the test, in terms of disassembly of the resin case, separation of the IC element from the substrate, and disassembly of the substrate. FIG. 5 illustrates evaluation results of disassembly of the resin case, separation of the IC element from the substrate, and disassembly of the substrate at different peak values of the discharge current and different numbers of times of discharging.
As for the disassembly of the resin case, "satisfactory" indicates that the lid of the resin case was separated from the case, and "unsatisfactory" indicates that the lid was not separated from the case. As for the separation of the IC element from the substrate, "satisfactory" indicates that the five IC elements were all separated from the substrate after discharging, and "unsatisfactory" indicates that not all of the five IC elements were separated. In a case where the resin case was not disassembled, the lid of the ABS case was removed to check a state of the substrate inside for the evaluation.
As for the disassembly of the substrate, "satisfactory" indicates that the substrate was not disassembled into two pieces or more, and "unsatisfactory" indicates that the substrate was disassembled into two pieces or more. In a case where the resin case was not disassembled, the lid of the ABS case was removed to check the state of the substrate inside for the evaluation.
Since object 9 was disassembled through the disassembly processing test, one sample 1 and one sample 2 produced under an identical condition were used for each of test conditions 1 to 14, and thus a total of 28 objects were used in the disassembly processing test.
FIG. 5 indicates that destruction of the resin case was not affected by the peak value of the discharge current, and when not disassembled, the resin case can be disassembled at a larger number of times of pulsing. FIG. 5 also indicates that, when the peak value of the discharge current is in a range from 10 kA to 30 kA inclusive, the IC element can be separated from the substrate without disassembly of the substrate.
The following describes influence of the inter-electrode distance and the discharge voltage on the peak value of the discharge current.
The influence was examined by using the object disassembly device illustrated in FIG. 1. However, the examination was performed without object 9.
Tap water was used for liquid 2, and the peak value of the discharge current during discharging was measured.
The distance between positive electrode 4 and ground electrode 5 was 10 mm, 20 mm, or 30 mm.
The discharge voltage was 100 kV, 230 kV, or 350 kV.
FIG. 6 illustrates a result. FIG. 6 is a graph illustrating the influence of the voltage and the inter-electrode distance on the peak value of the discharge current in pulse power discharging. The peak value of the discharge current can be controlled based on FIG. 6 through the distance between positive electrode 4 and ground electrode 5 and the discharge voltage. The peak value of the discharge current can be reduced by increasing the inter-electrode distance, or can be increased by reducing the inter-electrode distance. The peak value of the discharge current can be increased by increasing the discharge voltage, or can be reduced by reducing the discharge voltage.
Expressions for controlling a maximum value of the discharge current can be obtained through a procedure as follows.
First, three line segments in FIG. 6 are each approximated by a straight line passing through an origin so as to obtain a relational expression of peak value (Imax) of the discharge current and discharge voltage (E), which is Expression (1) below. $Imax = a \times E$
In the above expression, a represents a gradient of an approximated straight line obtained for each inter-electrode distance, and varies depending on presence and kind of object 9.
Next, a relation between gradient a and inter-electrode distance (x) is approximated by a quadratic function to obtain constants b, c, and d in Expression (2) below. The approximation with a quadratic function is more accurate than the approximation with a straight line, and is simpler than other functions. $a = b x^{2} + cx + d$
Expression (3) shown below can be obtained from Expressions (1) and (2) so as to obtain the peak value (Imax) of the discharge current. $Imax = (b x^{2} + cx + d) \times E$
With data illustrated in FIG. 7, constants b, c, and d have the following values. $b = - 1.64 \times 10^{- 5}$
$c = 2.90 \times 10^{- 4}$
$d = 4.75 \times 10^{- 2}$
where a unit of Imax is kA, a unit of the voltage is kV, and a unit of the inter-electrode distance is mm.
When the disassembly processing of an object is performed by continuous discharging, the peak value of the discharge current can be maintained constant by obtaining constants b, c, and d in Expression (3) through the above procedure and performing feedback to at least one of the inter-electrode distance and the discharge voltage.
Constants b, c, and d vary with change in the shape of object 9 or change in the electric conductivity of the liquid along the disassembly processing. Thus, it is desirable to maintain the peak value of the discharge current constant by performing the feedback to at least one of the inter-electrode distance and the discharge voltage through derivation of the expressions in a plurality of times of discharging, preferably in each discharging.
The following describes a pulse width preferable for disassembling an object including a substrate, for example, an object in which a substrate on which a component is mounted by soldering is fixed in a resin case.
A disassembly processing test using the object disassembly device illustrated in FIG. 1 was performed on an object including a substrate. The disassembly processing test was evaluated for each object after the test, in terms of disassembly of the resin case, separation of the component from the substrate, and excessive disassembly of the resin case for different widths of the discharge current.
Sample 2 used in the disassembly processing test illustrated in FIG. 5 was used as object 9. Detailed description of the producing condition is already provided above and thus is omitted here. Sample 2 was disassembled through discharging at 30 times of pulsing in the device illustrated in FIG. 1. The distance between positive electrode 4 and ground electrode 5 was 25 mm. The object was processed while being placed on ground electrode 5. The disassembly processing was performed while the maximum value of the discharge current was maintained constant at 23 kA but the pulse width was changed by changing the discharge voltage in a range from 150 kV to 350 kV, a number of capacitors in a circuit of the device illustrated in FIG. 1 and capacitances thereof, and an impedance of an entire discharging circuit.
The disassembly processing test was evaluated for each object after the test, in terms of disassembly of the resin case, separation of the IC element from the substrate, and excessive disassembly of the resin case. FIG. 7 is a diagram illustrating evaluation results of separation of the component from the substrate, disassembly of the resin case, and excessive disassembly of the resin case for different widths of the discharge current.
It is preferable that the excessive disassembly of the resin case does not occur in view of a need to segregate of the resin material after disassembly.
As for the disassembly of the resin case, "satisfactory" indicates that the lid of the resin case was separated from the resin case, and "unsatisfactory" indicates that the lid was not separated from the resin case. As for the separation of the IC element from the substrate, "satisfactory" indicates that the five IC elements were all separated from the substrate after discharging, and "unsatisfactory" indicates that not all of the five IC elements were separated. As for the excessive disassembly of the resin case, "satisfactory" indicates that the resin case was not disassembled in two pieces or more, and "unsatisfactory" indicates that the resin case was disassembled in two pieces or more. The excessive disassembly of the resin case does not include separation of the lid from the resin case.
Since object 9 was disassembled through the test, a total of six objects 9 were used under test conditions 1 to 6.
FIG. 7 indicates that the disassembly of the resin case hardly proceeded when the peak value of the discharge current was constant but a waveform of the discharge current had a width of 0.8 µs or smaller. FIG. 7 also indicates that the excessive disassembly of the resin case occurred when the waveform of the discharge current had a width of 12 µs or larger. FIG. 7 also indicates that the resin case was disassembled while the excessive disassembly of the resin case was prevented when the waveform of the discharge current has a width of 1 µs to 9 µs inclusive.
As described above, according to the first exemplary embodiment, a substrate or object 9 including the substrate can be disassembled through a prescribed number of times of discharging in liquid 2 in accordance with change in the electric conductivity of liquid 2 and change in the shape of a processed object during disassembly processing. Even when the substrate or object 9 including the substrate has various shapes or is made of various materials, the disassembly can be performed under a condition appropriate for a shape and a material of a processed object, thereby achieving disassembly of object 9 through a prescribed number of times of discharging.

SECOND EXEMPLARY EMBODIMENT

Object disassembly device 11 according to a second exemplary embodiment in FIG. 8 is obtained by adding object moving and holding mechanism 12 to the device illustrated in FIG. 1.
Object moving and holding mechanism 12 has a transfer function for moving unprocessed object 9 to a place where disassembly through discharging is performed. With this function, in addition to the above-described effect, such an effect is achieved that object 9 is continuously transferred to a place where disassembly through discharging is performed, which allows continuous disassembly processing. Object moving and holding mechanism 12 can hold object 9 at a particular position with respect to positive electrode 4 and ground electrode 5. In this case, object moving and holding mechanism 12 may directly hold object 9 or may hold a holder or a container holding object 9. Controller 10 is connected with pulse power source 6, electric current meter 7, inter-electrode distance adjustment mechanism 8, and object moving and holding mechanism 12. Controller 10 controls inter-electrode distance adjustment mechanism 8 to adjust the distance between positive electrode 4 and ground electrode 5 based on data of the distance between positive electrode 4 and ground electrode 5.
An effect provided by each exemplary embodiment or modification can be achieved by combining optional exemplary embodiments or modifications among the above-described various exemplary embodiments or modifications as appropriate. A combination of exemplary embodiments, a combination of examples, or a combination of an exemplary embodiment and an example is possible, and also a combination of features in different exemplary embodiments or examples is possible.
A disassembling method and a disassembly device according to an aspect of the present disclosure which disassemble a substrate or an object including the substrate allow a disassembled state and a destroyed state after processing to be maintained constant irrespective of change in an electric conductivity of liquid and change in a shape of a processed object during processing, and are applicable to an object disassembly method and an object disassembly device for small information appliances for recycling, such as a cellular phone and a game machine, and an electronic substrate.

Claims

An object disassembly method of disassembling a substrate or an object including the substrate by performing discharging in liquid a plurality of times, the method comprising:
when a positive electrode and a ground electrode are provided in liquid held in a container, and the substrate or the object including the substrate is placed on a discharge path between the positive electrode and the ground electrode in the liquid or in a region to which shock wave generated by discharging travels in the liquid,

measuring a peak value of discharge current flowing through the discharge path during discharging; and

controlling a discharge condition so that the measured peak value of the discharge current is maintained constant.
The object disassembly method according to claim 1, wherein at least one of a distance and a discharge voltage between the positive electrode and the ground electrode is changed as the discharge condition when the discharge condition is controlled so that the peak value of the discharge current is maintained constant.
The object disassembly method according to claim 1 or 2, wherein the discharge condition is controlled so that the peak value of the discharge current is maintained constant in a range from 10 kA to 30 kA inclusive.
The object disassembly method according to any one of claims 1 to 3, wherein a width of a waveform of the discharge current is set to 1 µs to 9 µs inclusive when the discharge condition is controlled so that the peak value of the discharge current is maintained constant.
An object disassembly device configured to disassemble a substrate or an object including the substrate by performing discharging in liquid a plurality of times, the device comprising:
a container holding the liquid;

a positive electrode and a ground electrode disposed in the liquid in the container;

a pulse power source configured to apply a high voltage pulse between the positive electrode and the ground electrode;

an electric current meter configured to measure discharge current flowing between the positive electrode and the ground electrode during discharging;

at least one of an inter-electrode distance adjustment mechanism configured to change an inter-electrode distance between the positive electrode and the ground electrode and a discharge voltage adjustment mechanism configured to adjust a discharge voltage; and

a controller configured to perform such control that a peak value of the discharge current is maintained constant by adjusting at least one of the inter-electrode distance and the discharge voltage through a corresponding one of the inter-electrode distance adjustment mechanism and the discharge voltage adjustment mechanism while measuring the peak value of the discharge current through the electric current meter.