JPH06121978A - Method for removing impurity in waste water for washing printed circuit board - Google Patents

Abstract

PURPOSE:To surely remove impurities such as microbe, metal ions and org. matter in waste water for washing printed circuit boards at low cost, and thereby, to supply the treated water reuseable for the washing of printed circuit boards. CONSTITUTION:The waste water for washing printed circuit boards is treated in adsorbing and removing processes 14, 15 using activated carbon and/or ion- exchange resin, and electrochemical removing process 2 using a fixed floor type three dimensional electrode 5 to remove impurities. In the electrochemical removing process, sterilization efficiency for microbe is high as compared to conventional UV irradiation, etc., and at least a part of metallic ion and org. matter can be removed by adsorption or decomposition in this process. By combining the adsorbing and removing processes, impurities in the waste washing water can almost completely be removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for removing impurities in printed circuit board cleaning wastewater, and more specifically, a cleaning wastewater containing flux residues for cleaning printed circuit boards is combined with a physicochemical adsorption treatment and an electrochemical treatment. Then, the present invention relates to a method for removing microorganisms, metals and organic compounds contained in the waste water and reusing them for cleaning printed circuit boards.

[0002]

2. Description of the Related Art Conventionally, a CFC solvent has been widely used as a cleaning agent for cleaning and removing a flux residue used in a soldering process of a printed circuit board in the electronic industry. However, the solvent not only has an adverse effect on the human body,
For example, it is causing great damage to the natural environment by destroying the ozone layer in the atmosphere. Therefore, restrictions on the use of the solvent are a global requirement. In order to avoid the solvent, it is necessary to develop a water-soluble flux that does not require cleaning with the solvent, or to use an alkaline saponifying agent, which is a substitute cleaning agent for the fluorocarbon solvent. However, even if these alternative technologies are developed, the use of flux is indispensable, and when cleaning the printed circuit board, various metals and organic substances contained in the flux are mixed in the cleaning wastewater, and the wastewater is directly cleaned from the cleaning board. When reused, it causes contamination of the printed circuit board.

Therefore, it is necessary to treat the waste water to remove impurities and to reuse it as clear cleaning water for cleaning the printed circuit board. The usual wastewater treatment is a fine particle removal process,
It includes an organic substance removing step, an ionic substance removing step, and the like. The printed circuit board is usually washed at a relatively high temperature of about 40 to 70 ° C, and microorganisms such as fungi and fungi easily grow in the treated water (substantially pure water) clarified through the above steps. When such treated water is used for cleaning the printed circuit board, troubles such as clogging of the cleaning nozzle, contamination of the printed circuit board, etc., and a decrease in the pass rate of the printed circuit board occur.

Ion exchange resin, activated carbon, etc. are used for removing the ionic substances, and the metals and organic compounds contained in the cleaning waste water are adsorbed and removed by the activated carbon, ion exchange resin, etc. However, if the cleaning wastewater is treated for a long time, the load of activated carbon or ion exchange resin may increase, and the cleaning efficiency may decrease. Further, a technique of irradiating with ultraviolet rays to sterilize and remove impurities, especially microorganisms, in the cleaning wastewater of the printed circuit board has been developed, but sufficient ultraviolet light irradiation cannot achieve sufficient sterilization efficiency and contains microorganisms. There is a drawback that the cleaning drainage water is likely to be reused and the printed circuit board is easily contaminated.

[0005]

Problems to be Solved by the Invention Printed circuit boards must be prevented from being contaminated by trace amounts of impurities as much as possible, and by removing impurities in cleaning waste water including microorganisms and organic substances as much as possible, they can be reused. It is necessary to clean the printed circuit board. Since a large amount of cleaning wastewater is generated, it is particularly desirable that the large-scale treatment can be carried out at a low cost by means of a labor-free method.

SUMMARY OF THE INVENTION Therefore, the present invention provides a method for treating printed circuit board cleaning wastewater to remove impurities such as microorganisms and organic substances in the cleaning wastewater to the maximum extent, and then reusing it for cleaning the printed circuit board, particularly in a large amount. It is an object of the present invention to provide a method capable of treating the cleaning wastewater of (1) at low cost by using a relatively simple device.

[0006]

The present invention relates to a method for removing impurities in a printed circuit board cleaning wastewater, in which the impurities are removed by activated carbon and / or ion-exchange resin adsorption and a fixed bed type three-dimensional electrode is used. The present invention can also be used as a method for collecting and reusing the cleaning water for cleaning a printed board containing impurities. The present invention will be described in detail below. In the method of the present invention, the removal of impurities is carried out in combination with the physicochemical adsorption step and the electrochemical removal step, whereby the microorganisms which are impurities are almost completely sterilized in the electrochemical step and the metal which is another impurity is used. Ozone, hydrogen peroxide, hypochlorite, which may remove organic substances and organic substances by adsorption or electrochemical oxidative decomposition to reduce the load on the adsorbent in the adsorption process and cause corrosion of the metal part of the printed circuit board. This makes it possible to supply the cleaning wastewater as substantially completely clarified treated water for cleaning a printed circuit board and reuse it without using an oxidizing agent such as an acid ion.
The microorganisms of the present invention include bacteria (bacteria), filamentous fungi (molds), yeasts, transformants, unicellular algae, protozoa, viruses and the like.

The order of the treatment of the cleaning wastewater by the physicochemical adsorption removal step and the electrochemical removal step in the present invention is not limited, and any step may be performed first, and each step need not be a single step. A plurality of adsorption removal steps and electrochemical removal steps may be provided. The adsorption removal step in the present invention preferably includes at least two steps of an activated carbon adsorption removal step and an ion exchange resin adsorption removal step, and the order of both adsorption removal steps is not limited. Organic matter (mainly nonionic organic matter) in the cleaning wastewater in the activated carbon adsorption removal process
Is adsorbed on activated carbon and removed.

In the ion exchange resin adsorption removal step, metal ions such as lead, copper, zinc, tin and aluminum, which are impurities in the cleaning waste water, in which the metal portion of the printed circuit board is dissolved, and organic acids derived from the flux are removed. . As the ion exchange resin to be used, those conventionally used in the production of deionized water may be used without limitation, and granular, powdery, etc. weakly acidic cation exchange resins (having, for example, a carboxylic acid group as an exchange group) or Strongly acidic cation exchange resin (having a sulfonic acid group as an exchange group) or weakly basic anion exchange resin (having a tertiary amine group as an exchange group)
Alternatively, a strongly basic anion exchange resin (having, for example, a quaternary ammonium salt group as an exchange group) is used alone or in combination. Among the positive and negative anion exchange resins, the hydrogen type strongly acidic cation exchange resin is particularly effective in removing metal ions, while the hydroxyl type strongly basic anion exchange resin is effective in removing organic substances.

The electrochemical removal step in the present invention is a step of removing impurities in the cleaning wastewater by bringing the cleaning wastewater into contact with the fixed bed type three-dimensional electrode. The fixed bed type three-dimensional electrode is housed in the electrolytic cell body to form a fixed bed type three-dimensional electrode electrolytic cell. The fixed bed type three-dimensional electrode electrolytic cell having the following constitution can be used. The electrolytic cells are a fixed bed type three-dimensional electrode electrolytic cell, that is, a fixed bed type single electrode type electrolytic cell and a fixed bed type bipolar electrode type electrolytic cell. In these electrolytic cells, the three-dimensional electrode of the electrolytic cell has a huge surface area. This is advantageous in that the contact area between the electrode surface and the cleaning drainage can be increased, which allows the device size to be reduced and the electrochemical removal efficiency to be increased.

When the cleaning wastewater is supplied to the fixed bed type three-dimensional electrode electrolytic cell, the microorganisms in the cleaning wastewater contact the anode or cathode of the electrolytic cell or the dielectric or particles for fixed bed formation described later due to liquid flow. However, it is considered that sterilization is performed by subjecting these surfaces to a strong redox reaction or contact with a high-potential electric current, which weakens their activity or kills themselves. Therefore, in the electrochemical removal step of the present invention, it is sufficient that the microorganisms in the cleaning wastewater come into contact with the electrodes to which a voltage is applied, the dielectric, the particles for forming a fixed bed, etc. It is not essential to cause a substantial electrolytic reaction accompanied by the generation of gas such as oxygen, but rather it is preferable to apply a low electric potential to the electrode surface so that a substantial electrolytic reaction does not occur. This is uneconomical because wasteful power is used for gas generation reactions other than sterilizing microorganisms, and the generated gas covers the electrode surface, reducing the efficiency with which microorganisms contact the electrode surface, resulting in sterilization efficiency. Because it can make things worse.

Therefore, in the present invention, the anode potential and the cathode potential are set to a base potential lower than +2.0 V (vs.SHE) and a potential lower than -2.0 V (vs.SHE), respectively, and gas generation is accompanied. While electrochemical treatment may be performed, the applied potential is +0.2 to +1.2 when the anodic potential does not substantially generate oxygen.
V (vs.SCE), the cathode potential is virtually zero with hydrogen generation
It is desirable to set the voltage to -1.0 V (vs. SCE).
That is, since a large amount of cleaning wastewater is generated, the amount of electric power required for cleaning wastewater treatment by the method of the present invention often occupies most of the processing cost. The amount of electric power is [electric power] = [voltage] ×
It is expressed as [current], and the amount of power is zero when no current flows and no gas is generated, but the amount of water to be treated is enormous when the current to the extent that gas is generated flows, and therefore the amount of power consumption is enormous. become. When the amount of water to be treated is small and the current flowing is also small, the increase or decrease in the voltage value does not affect the power consumption so much, but in the case of a large amount of treatment as in the present invention, a slight voltage drop causes a large power consumption. Reduce. Therefore, in the electrochemical removal step of the present invention, it is desirable to apply a potential at which substantially no gas is generated, and when it is necessary to confirm that the treatment is actually carried out efficiently. It is desirable to carry out the electrochemical treatment while applying the minimum potential necessary to generate a small amount of gas.

However, the organic matter in the cleaning wastewater can be decomposed by anodic oxidation depending on the value of the applied anode potential.
Therefore, if the removal of organic substances in the adsorption removal process is not sufficient or if the load on the ion exchange resin is to be reduced, +0.5 to +1.5 V (vs.
It is possible to apply anodic potential of (SHE) and simultaneously perform sterilization and organic matter decomposition in the electrochemical removal step. The electrodes in the fixed-bed type three-dimensional electrode electrolytic cell generally include a three-dimensional electrode and a feeding electrode, and the three-dimensional electrode has a shape according to the electrolytic cell used above, and the fixed-bed type bipolar electrode electrolytic cell. When using, a porous material permeable to the cleaning wastewater,
For example, carbonaceous materials such as granular, spherical, felt-like, woven cloth-like, porous block-like, etc., carbonaceous materials such as graphite, carbon fiber, etc., or nickel, copper, stainless steel, iron, titanium, etc. having the same shape. An electric field is applied to a plurality of preferably granular, spherical, fibrous, felt-like, woven cloth-like, porous block-like, sponge-like dielectrics formed of a metal material or a material obtained by coating a noble metal on the metal material. The dielectric is polarized by applying a DC voltage or an AC voltage between the power-supplying electrodes which are placed inside and are installed at both ends of a plate-shaped or expanded mesh-shaped or perforated plate-shaped porous plate. It is possible to provide a fixed-bed type bipolar electrode electrolytic cell containing a three-dimensional electrode formed by forming an anode and a cathode at one end and the other end, respectively. A three-dimensional material which functions as or cathode as the anode is placed so as not to short-circuit alternately and electrically connected may be a fixed bed multi-pole type electrolytic cell in Germany.

As the dielectric, activated carbon, graphite,
When a carbon-based material such as carbon fiber is used and the cleaning wastewater is treated while generating oxygen gas from the anode, the dielectric is easily oxidized by oxygen gas and easily dissolved as carbon dioxide gas. In order to prevent this, a porous material which is usually used as an insoluble metal electrode is formed by coating a platinum group metal oxide such as iridium oxide or ruthenium oxide on a base material such as titanium on the side of the dielectric which is positively polarized. It may be installed in contact with each other so that oxygen generation mainly occurs on the porous material. Further, as another type of fixed bed type bipolar electrode electrolytic cell, for example, an anode and a cathode for power feeding are installed in a cylindrical electrolytic cell body, and a large number of conductive materials functioning as a three-dimensional electrode are provided between both electrodes for power feeding. There is an electrolytic cell in which fixed bed forming particles and a smaller number of insulating particles made of a synthetic resin or the like having an electrically insulating property than the fixed bed forming particles are mixed almost uniformly. When a potential is applied by energizing between both electrodes for supplying electricity in the electrolytic cell, the fixed bed forming particles are polarized in the same manner as the dielectric material, and one end thereof is positively charged and the other end is negatively charged to form each fixed bed. An electric potential is generated in the particles for use, and each particle is given a function of sterilizing microorganisms in the cleaning wastewater. The insulating particles have a function of preventing both of the power feeding electrodes from being electrically connected by the electrically conductive particles for forming the fixed bed to cause a short circuit.

When a monopolar fixed bed type electrolytic cell is used, the electrolytic cell described above or one of each of the three-dimensional materials each of which functions as an anode or a cathode by itself, with or without a diaphragm, is used. It should be installed inside. This electrochemical removal step kills microorganisms that are likely to cause contamination of the ion exchange resin and are more likely to remain in the cleaning wastewater. Therefore, even if the washing wastewater that has undergone the electrochemical removal process is supplied to the ion exchange resin tower in the adsorption removal process, the load on the ion exchange resin does not increase, and the ion exchange capacity of the ion exchange resin is always maximized. It becomes possible to do.

Further, in the cleaning drainage, the above-mentioned lead, copper, zinc,
Although metal ions such as tin and aluminum remain, tin and copper in the metal ions are electrolytically deposited on the cathode surface of the fixed bed type three-dimensional electrode in the electrolytic cell and removed from the cleaning drainage. Therefore, it is convenient to install the adsorption-removal step using the ion-exchange resin on the downstream side of the electrochemical removal step because the load on the ion-exchange resin is reduced. Regardless of which type of electrode is used, if there is a void that allows the liquid to flow without contacting the electrodes, dielectrics, and particles in the electrolytic tank through which the cleaning wastewater to be treated flows, the processing efficiency of the cleaning wastewater decreases. It is desirable that the electrodes, etc. be arranged so that the flow of the cleaning waste water in the electrolytic cell does not short pass.

Even if the inside of the electrolytic cell is divided by a diaphragm to form an anode chamber and a cathode chamber, it is possible to carry on electricity as it is without using the diaphragm, but without using the diaphragm and the distance between the electrodes. Alternatively, when the distance between the dielectric and the electrode or between the dielectrics is narrowed, an electrically insulating spacer such as a mesh spacer made of an organic polymer material is inserted between both electrodes or between the dielectrics to prevent short circuit. can do. Further, when a diaphragm is used, it is desirable to use a porous material such as having an opening ratio of 10% or more and 95% or less, preferably 20% or more and 80% or less so as not to interfere with the movement of circulating cleaning wastewater. The diaphragm must have micropores having a pore size that allows at least the cleaning waste water to permeate. The flow rate of the cleaning wastewater supplied to the electrolytic cell may be defined so that the cleaning wastewater can efficiently contact the surface of the electrode or the like, and if it is a complete laminar flow, the lateral movement is small and the electrode, the dielectric Since contact with the body and the surface of the fine particles is reduced, it is preferable to form a turbulent state, and it is particularly preferable to use a turbulent flow having a Reynolds number of 500 or more.

In the present invention, the printed board cleaning wastewater is processed through a circulation system including an electrochemical removal step and an adsorption removal step and supplied again to the printed board cleaning step. It is desirable to install a filter to remove the microbial carcasses that have been sterilized in the removal process. In the method of the present invention, in addition to the electrochemical removal step and the adsorption removal step, other steps such as an ultraviolet irradiation step may be installed together.

Next, the outline of the method of the present invention and a preferred example of the electrolytic cell which can be used in the present invention will be described with reference to the accompanying drawings, but the method of the present invention is not limited thereto. FIG. 1 is a schematic vertical cross-sectional view showing an example of a fixed-bed type bipolar electrode electrolytic cell that can be used as an electrolytic cell of the method of the present invention, and FIG. 2 is a book showing the electrolytic cell of FIG. 1 used in an electrochemical removal step. It is a flow sheet of an invention method.

A mesh-shaped power feeding anode 3 and power feeding cathode 4 are provided in the vicinity of the upper end and the lower end of a cylindrical electrolytic cell body 2 having a flange 1 on the upper and lower sides, respectively.
The electrolytic cell body 2 is preferably formed of an electrically insulating material that can withstand long-term use or re-use, and in particular, synthetic resins such as polyepichlorohydrin, polyvinyl methacrylate, polyethylene, polypropylene, polyvinyl chloride, and polychloroethylene. , Phenol-formaldehyde resin and the like can be preferably used. The power supply anode 3 that gives a positive DC voltage is, for example, a carbon material (for example, activated carbon,
Charcoal, coke, coal, etc., graphite material (for example, carbon fiber, carbon cloth, graphite, etc.), carbon composite material (for example, carbon in which metal is mixed in powder form and sintered), activated carbon fiber nonwoven fabric (for example KE- 1000 felt, Toyobo Co., Ltd.), or a material in which platinum, a platinum group metal, palladium or nickel is supported, and a dimensionally stable electrode (platinum group oxide coated titanium material), platinum coated titanium material, nickel material, stainless steel Made of wood, iron, etc. In addition, the power feeding cathode 4 facing the power feeding anode 3 and applying a negative DC voltage is
For example, it is formed from platinum, stainless steel, titanium, nickel, copper, hastelloy, graphite, carbon material, mild steel or a metal material coated with a platinum group metal.

A plurality of sponge-like fixed bed electrodes 5 in the illustrated example are laminated between the power feeding electrodes 3 and 4, and between the fixed bed electrodes 5 and between the fixed bed electrodes 5 and the above. Four porous diaphragms or spacers 6 are sandwiched between the power feeding electrodes 3 and 4. Each fixed bed electrode 5 is in close contact with the inner wall of the electrolytic cell body 2 and does not pass through the inside of the fixed bed electrode 5, and the leakage flow of the treatment liquid flowing between the fixed bed electrode 5 and the side wall of the electrolytic cell body 2 is minimized. It is arranged to be.
When a diaphragm is used, a woven cloth, a biscuit plate, a particle-sintered plastic, a porous plate, an ion exchange membrane, etc. are used as the diaphragm, and a woven cloth, a porous plate, a net made of an electrically insulating material is used as a spacer. , Rod-shaped materials are used. As shown by reference numeral 2 in FIG. 2, the two electrolytic cell bodies having such a configuration are installed in the cycle of removing impurities of the cleaning waste water as an electrochemical removing step.

In FIG. 2, reference numeral 11 denotes a printed circuit board cleaning system. The cleaning wastewater discharged from the system 11 contains metal ions and organic substances, and the cleaning wastewater is temporarily stored in a waste water storage tank 12. The inside of the system including the storage tank 12 is maintained at about 45 ° C., which is an environment in which microorganisms such as fungi easily grow. The cleaning waste water in the storage tank 12 is supplied from below by the pump to the electrolytic cell main body 2 having the above-described structure as shown by the arrow in FIG. As shown in FIG. 1, the lower surface of the fixed bed electrode 5 is positively polarized and the upper surface thereof is negatively polarized, so that a potential is generated in the fixed bed electrode 5 and between the fixed bed electrodes 5, and the cleaning wastewater flowing in the electrolytic cell has this potential. On the anodic polarization side, sterilization of microorganisms such as mold and bacteria contained in the fixed-bed electrode 5 and decomposition and removal of organic matter are carried out on the anodic polarization side.
Further, reduction deposition of metal ions such as tin and lead is carried out on the negative polarization side, almost no microorganisms are contained, and cleaning drainage from which at least a part of metal ions and organic substances is removed is discharged from above the electrolytic cell main body 2. Taken out.

This cleaning wastewater is then supplied to the first filter 13 from below, and while the cleaning wastewater is passing through the filter 13, fine particles, dead bodies of microorganisms, etc. originally contained therein are removed, and the cleaning wastewater (treated water is treated). ) Is taken out from above. This treated water is then supplied into the activated carbon packed tower (adsorption removal step) 14 from below to adsorb and remove the organic matter and the like remaining in contact with the activated carbon in the packed tower 14, and the treated water is the packed tower. Taken out from above 14. This treated water is then supplied into the ion exchange resin packed tower (adsorption removal step) 15 from below, and metal ions and organic acids remaining in contact with the ion exchange resin in the packed tower 15 are adsorbed and removed.
The treated water is taken out from above the packed tower 15. It is desirable to fill the packed column 15 with a mixed resin of both an anion exchange resin and a cation exchange resin. The treated water taken out is then supplied from below to the same electrolytic cell body 2 as the electrolytic cell body installed between the cleaning waste water storage tank 12 and the first filter 13, and the adsorption removal step (activated carbon packed tower 14 and ion exchange resin) is carried out. Metal ions and organic substances that could not be removed in the packed column 15) are removed by adsorption or decomposition and taken out from above the electrolytic cell body 2 as treated water of higher purity. This treated water is circulated to the printed circuit board cleaning system 11 through the second filter 16 and the flow meter 17, and is reused.
Although two electrolytic cell bodies are shown in FIG. 2, the number of electrolytic cell bodies may be one or three or more, and the installation location is not limited to the illustrated position.

FIG. 3 shows another example of a bipolar electrode fixed bed type electrolytic cell which can be used in the method of the present invention. A mesh-shaped power feeding anode 23 and power feeding cathode 24 are provided in the vicinity of the upper end and the lower end inside a cylindrical electrolytic cell body 22 having upper and lower flanges 21, respectively. The electrolytic cell body 22 is preferably made of an electrically insulating material, especially a synthetic resin, which can withstand long-term use or reuse.

A large number of fixed bed forming particles 25 made of a conductive material such as a carbonaceous material and a smaller number of fixed resin forming particles 25, for example, made of a synthetic resin, are provided between the two feeding electrodes 23, 24. The insulating particles 26 are mixed almost uniformly. The insulating particles 26 have a function of preventing the power supply anode 23 and the power supply cathode 24 from being completely short-circuited. When electricity is supplied to the electrolytic cell main body having such a configuration from the bottom while supplying cleaning wastewater as indicated by an arrow, the fixed bed forming particles 25 have a negative power supply anode 23 side and a negative power supply cathode 24 side. It functions as a three-dimensional electrode that is polarized positively and has a huge surface area.
The washing drainage is sterilized in the same manner as in the electrolytic bath.

FIG. 4 exemplifies a single electrode type fixed bed type electrolytic cell which can be used in the present invention. A cylindrical electrolytic cell body 32 having upper and lower flanges 31 has a mesh-shaped power supply anode 33 and power supply cathode 34 near the upper end and the lower end, respectively.
Is provided. The electrolytic cell body 32 is preferably formed of an electrically insulating material, especially a synthetic resin, which can withstand long-term use or reuse. A pair of fixed beds 35 formed of a conductive material such as carbon fiber in a felt shape with a diaphragm 36 sandwiched between the power feeding electrodes 33 and 34 are filled in the anode chamber and the cathode chamber, respectively. The felt-like carbon fibers in the chamber are electrically connected to the power feeding anode 33 and the power feeding cathode 34, respectively, and the fixed bed in the anode chamber is positively charged and the fixed bed in the cathode chamber is negatively charged. When electricity is supplied to this electrolytic cell while supplying raw water from below as indicated by the arrow, the fixed bed 35 functions as a three-dimensional electrode having a huge surface area as in the case of FIGS. Sterilization of microorganisms such as mold and bacteria is performed.

[0026]

EXAMPLES Examples of removing impurities from printed circuit board cleaning waste water by the method of the present invention will be described below, but the examples do not limit the method of the present invention.

Example 1 The two electrolytic cell main bodies shown in FIG. 1 are shown together with a filter, an activated carbon packed tower, and an ion exchange resin packed tower.
A cycle for removing impurities in the cleaning wastewater was constructed by connecting as shown in FIG.

The main body of the electrolytic cell is a vinyl chloride resin-made cylinder with a height of 100 mm and an inner diameter of 50 mm, and has a diameter of 50 m, which is made of carbon fiber having an opening ratio of 60%.
m, 3 fixed beds with a thickness of 10 mm, diameter 50 m with an opening ratio of 85%
m and 1.5 mm thick polyethylene resin diaphragms sandwiched between the upper and lower diaphragms made of titanium with platinum plated on the surface, and a mesh-shaped power supply anode and power supply cathode with a diameter of 48 mm and a thickness of 1.0 mm. It was placed in contact. The voltage per fixed bed electrode is 6.5 V, effective current density (calculated from the surface area of the true fixed bed current) 0.5 A / dm
^The electricity was applied so that it would be ² . As the two filters, ordinary commercially available 10-inch cartridge filters were used, and the filter element had an opening diameter of 10 μm. The activated carbon packed tower has a height of 1200 mm and an inner diameter of 100 mm.
The cylindrical container was filled with activated carbon manufactured by Takeda Pharmaceutical Co., Ltd.

The ion exchange tower is made of vinyl chloride and has a height of 50.
Approximately 400 g of hydrogen-type cation exchange resin Amberlite IR-120 B (trade name) having a particle size of 0.45 to 0.60 mm and a hydroxyl group-type anion exchange was used as a cylindrical body having a diameter of 0 mm and an inner diameter of 50 mm. About 400 g of resin Amberlite IRA-410 (trade name) was contained as a mixed bed. The impurities content in the cleaning waste water in the storage tank storing the cleaning waste water from the printed circuit board cleaning system was 20,000 microorganisms / ml, total metal ion concentration 2.3 ppm and TOC (total organic carbon) 24 mg / l. . The cleaning waste water in the storage tank was circulated through the electrolytic cell body, the filter and the packed tower at a rate of 1.2 liters / minute. Amount of impurities in cleaning wastewater in the storage tank, amounts of impurities in cleaning wastewater (treated water) after passing the electrolytic cell body (first electrolytic cell) downstream of the storage tank, and electrolytic cell body downstream of the ion-exchange resin packed tower The amounts of impurities after passing through the (second electrolysis tank) are summarized in Table 1.

[0029]

[Table 1]

It can be seen from Table 1 that the microorganisms become almost zero after passing through the first electrolytic cell, the metal ions are considerably reduced, and the TOC is slightly reduced. It can be seen that the content of impurities in the cleaning wastewater (treated water) after passing through the second electrolytic cell is substantially zero.

[0031]

Comparative Example 1 An ultraviolet irradiation device was installed at the position of the second electrolytic cell instead of the first electrolytic cell and the second electrolytic cell of Example 1, and
Ultraviolet rays with a main wavelength of 250 to 260 nm are 25000 μW
Impurities were removed from the cleaning drainage under the same conditions as in Example 1 except that the cleaning drainage (treated water) was irradiated with an intensity of S / cm ² . Table 2 shows the amount of impurities in the cleaning wastewater in the storage tank and the amount of impurities in the cleaning wastewater (treated water) after passing through the ultraviolet irradiation device.
Summarized in.

[0032]

[Table 2]

It can be seen from Table 2 that the combination of the ultraviolet irradiation step and the adsorption removal step was not able to remove much except microorganisms, and the metal ion concentration and TOC were also higher than in the case of Example 1, and the electrochemical removal step was performed. It can be seen that various impurities in the cleaning wastewater can be removed more efficiently by combining the ultraviolet irradiation and the adsorption removal step when used together with the adsorption removal step.

[0034]

According to the method of the present invention, in the method for removing impurities in the printed board cleaning wastewater, the steps of removing the impurities by adsorption of activated carbon and / or ion exchange resin and the electrochemical removal step using a fixed bed type three-dimensional electrode are performed. A method for removing impurities, which comprises: (claim 1). The printed circuit board cleaning waste water contains metal ions, organic substances, etc., and microorganisms such as fungi and mold propagate. If the cleaning waste water containing these impurities is reused as it is for cleaning the printed circuit board, the impurities may adhere to the printed circuit board. The conventional method of using a chemical addition method or an ultraviolet irradiation method in combination with an adsorption removal step has problems such as residual chemicals and incomplete removal of impurities.

In the method of the present invention, the electrochemical removal process is combined with the conventional adsorption removal process so that the impurities in the cleaning waste water can be removed almost completely. In the electrochemical removal step of the present invention, a fixed-bed type three-dimensional electrode is used, and the fixed-bed type three-dimensional electrode is brought into contact with microorganisms in the washing wastewater over a large surface area to sterilize them by applying an electric potential to the microorganisms. Ions can be removed by reductively adsorbing them on the surface, and by oxidizing or reductively decomposing certain organic substances. Therefore, the electrochemical removal step acts on all of the main impurities such as microorganisms, metal ions and organic substances in the cleaning wastewater, and by combining with the adsorption removal step, the content of the impurities is reduced to almost zero, and a clear treatment is performed. It is possible to collect it as water and circulate it in the printed board cleaning process to reuse it (claim 3).

Furthermore, the present invention is economical because it does not use chemicals, does not require post-treatment of chemicals, and has a much higher microbial sterilization efficiency than ultraviolet irradiation, and is a very effective method for removing impurities in cleaning wastewater. Is. When an electrochemical removal step is installed on the upstream side of the adsorption removal step (claim 2), at least a part of metal ions, organic substances, etc. in the cleaning wastewater are removed in the electrochemical removal step, and thus the adsorption is performed. The load of ion exchange resin and activated carbon in the removal process is reduced,
These contaminations can be minimized.

[Brief description of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing an example of a fixed-bed type bipolar electrode electrolytic cell that can be used as an electrolytic cell in the method of the present invention.

FIG. 2 is a flow chart of an impurity removal cycle in which the electrolytic cell of FIG. 1 is combined with a filter, an activated carbon packed column and an ion exchange resin packed column.

FIG. 3 is a schematic vertical cross-sectional view showing another example of a bipolar electrode fixed bed type electrolytic cell that can be used in the method of the present invention.

FIG. 4 is a schematic vertical cross-sectional view illustrating a single electrode fixed bed type electrolytic cell that can be used in the present invention.

[Explanation of symbols]

1 ... Flange 2 ... Electrolyzer body 3, 4 ...
Power supply electrode terminal 5 ・ ・ ・ Fixed bed 6 ・ ・ ・ Spacer 11 ・ ・ ・ Printed board cleaning system 12 ・ ・ ・ Storage tank 13 ・ ・ ・ First filter 14 ・ ・ ・ Activated carbon packing tower 15 ・ ・ ・ Ion exchange resin packing Tower 16 ・ ・ ・ Second filter 17 ・ ・ ・ Flowmeter

[Procedure amendment]

[Submission date] October 7, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

[Figure 4]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C02F 9/00 Z 7446-4D H05K 3/26 7511-4E (72) Inventor Hiroyuki Hashimoto Tokyo Hino Konica Stock Company, 1st Sakura-cho, Yokohama (72) Inventor Go Takahashi Konica Stock Company, 1st Sakura-cho, Hino-shi, Tokyo In-house

Claims (3)

[Claims] 1. A method for removing impurities in a printed circuit board cleaning wastewater, which comprises a step of removing the impurities by adsorption of activated carbon and / or an ion exchange resin and an electrochemical removal step using a fixed bed type three-dimensional electrode. Characteristic impurity removal method. 2. The method according to claim 1, wherein an electrochemical removal step is installed upstream of the adsorption removal step. 3. The printed circuit board cleaning drainage is activated carbon and / or
Alternatively, the ion-exchange resin adsorption removal process and the electrochemical removal process using a fixed bed type three-dimensional electrode are performed to remove impurities in the printed circuit board cleaning wastewater and collect them, and the recovered water is used as printed circuit board cleaning water. A method for collecting wastewater for cleaning printed circuit boards, which is characterized by being recycled.