JP2003290765A - Wastewater treatment method for cleaning printed wiring boards - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating printed circuit board washing wastewater, which can reduce the flux reduction due to the fall of the filtration membrane and can obtain the water quality of low FI value. SOLUTION: In a method for treating washing wastewater discharged from a printed wiring board manufacturing process, the pH of the wastewater is adjusted to 6 to 10 in a pH adjusting tank, and the pH-adjusted wastewater is treated by a membrane filtration device. Characterized method of treating printed wiring board cleaning wastewater.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating printed wiring board cleaning wastewater. Specifically, it relates to a method for treating cleaning wastewater discharged from a resist process, a plating process, an etching process, a soldering process, a surface treatment process and the like in a printed wiring board manufacturing process.

[0002]

2. Description of the Related Art In the manufacture of printed wiring boards, there are resist processes, plating processes, etching processes, soldering processes, surface treatment processes, etc. Various chemicals are used in various processes, and various cleaning agents are used. To wash. Therefore, copper, iron, tin, and
Nonionic components such as inorganic acids, organic acids, amides and imides include rosin, polyglycol, surfactants and the like, which are treated by a coagulation method or a sand filtration method. In recent years, attempts have been made to highly treat such wastewater, recover water, and reuse it. One of the ways
First, there is a method of filtering waste water with an ultrafiltration membrane or a microfiltration membrane and treating the filtered water with a reverse osmosis membrane separation. However, when the cleaning wastewater discharged from the process of manufacturing a printed wiring board is treated with a filtration membrane (which is referred to as an ultrafiltration membrane or a microfiltration membrane), the filtration capacity of the filtration membrane is reduced (hereinafter referred to as Flux reduction). There was a problem that it would happen.

[0003]

An object of the present invention is to solve the above problems. That is, it is an object of the present invention to provide a method for treating waste water of a printed wiring board, which can reduce the decrease in Flux due to the outer ring of the filtration membrane and can also obtain water quality with a low FI value.

[0004]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems, and as a result, the problems can be solved by a method of adjusting the pH of wastewater for washing a printed wiring board and separating it with a filtration membrane. And completed the present invention. That is, the present invention is as follows. (1) In the method of treating cleaning wastewater discharged from the printed wiring board manufacturing process, the pH of the wastewater is adjusted to 6 in a pH adjusting tank.
A method for treating printed wiring board cleaning wastewater, wherein the wastewater adjusted to pH -10 and treated with pH is treated with a membrane filtration device. (2) The filtration membrane used in the membrane filtration device is an ultrafiltration membrane having a molecular weight cutoff of 3,000 to 1,000,000 or a pore diameter of 0.01.
The method for treating printed wiring board cleaning wastewater according to (1), which is a microfiltration membrane of ˜1 micron.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below, focusing on particularly preferable embodiments thereof. The term “printed wiring board cleaning drainage” as used in the present invention refers to drainage from the printed wiring board manufacturing process. Specifically, a resist process, a plating process, an etching process, a resist stripping process, a soldering process,
It is the wastewater from the surface treatment process. Collected wastewater obtained by collecting these wastewater is also the wastewater to be treated in the present invention.

In the drainage, ferric chloride used for etching, hydrochloric acid, copper dissolved from a copper plate, tin as a plating component, flux of rosin as a main component used for soldering, other inorganic acids, organic acids, and peroxides. It contains hydrogen oxide, amides and imides derived from resists, sodium silicate derived from cleaning agents, sodium carbonate, polyglycols, surfactants, etc. Usually, the pH is often drained on the acidic side. This waste water is sent to a pH adjusting tank to adjust the pH. The pH adjusting tank used in the present invention includes an adjusting tank, a caustic soda tank, a caustic soda injection pump, a drainage supply pump,
It is preferably composed of a water feed pump, a pH meter, a pH controller, a liquid level meter and a stirrer.

The role of the pH adjusting tank is to control the pH of the waste water supplied to the filtration membrane uniformly and with high precision, and
It is to suppress the decrease. Furthermore, the pH of the drainage is set to 6
By controlling to 10 to 10, ions of iron, copper, tin, etc. are converted to ferric hydroxide, copper hydroxide, tin hydroxide, etc. so that they can be separated by an ultrafiltration membrane or a microfiltration membrane. . In addition, organic substances and suspended substances are also taken in by the inorganic hydroxide and are easily separated by the filtration membrane. Specifically, the pH is adjusted to 6 to 10, preferably 7 to 9.

The inorganic hydroxide produced in the pH adjusting tank and the organic matter and suspended matter contained in the waste water are separated by the membrane filtration device used in the present invention to obtain filtered water having a low FI value. The membrane filtration device used in the present invention includes a filtration membrane, a raw water circulation tank, a backwash tank (filtered water tank), a liquid level meter, a pressure gauge, a thermometer, a flow meter, a circulation pump, a backwash pump, and a filtered water feed pump. , A chemical tank, a compressor for supplying air, a chemical injection pump, an automatic valve and the like.

When an ultrafiltration membrane is used in the membrane filtration device used in the present invention, water quality with low turbidity can be obtained. However, an ultrafiltration membrane having a small cutoff molecular weight has a low flux, and therefore, an ultrafiltration membrane having a cutoff molecular weight of 3,000 to 1,000,000, and more preferably 6,000 to 1,000,000 is used. High-flux is obtained when a microfiltration membrane is used in the membrane filtration device used in the present invention.
Is obtained. However, if the pore size is large, the flux tends to be low due to clogging, and the FI value also tends to be high. Therefore, the pore size is preferably 0.01 to 1 μm.
More preferably, a 0.01-0.2 micron microfiltration membrane is used. The module type may be any of spiral type, hollow fiber type, tubular type and plate type, but the membrane area per module is large,
A structure having a structure that easily removes contaminants attached to the membrane, for example, a hollow fiber type external pressure filtration module as used in this embodiment is preferable.

The material of the film may be any of organic films such as polyacrylonitrile, polysulfone, polyether sulfone, polyolefin, cellulose acetate, polyamide, polyvinyl alcohol and polyvinylidene fluoride, and inorganic films such as alumina and zirconia. A membrane made of a material resistant to chemicals such as hydrogen peroxide in the chemical cleaning and drainage when the capacity is lowered, for example, a polyvinylidene fluoride (PVdF) membrane is preferable.

The treatment method by the membrane filtration device may be either external pressure filtration or internal pressure filtration of the cross flow system, pressure filtration for pressurizing the raw water side, or suction filtration for sucking the filtered water side, and a fixed amount of filtered water is required. Either constant flow filtration for filtration or constant pressure filtration for filtration at a constant pressure may be used. Transmembrane pressure difference between the raw water side and the filtered water side (hereinafter referred to as TMP) is 10
KPa to 300 KPa is preferable. Backwash and / or air
It is preferable to periodically discharge the organic substances, inorganic hydroxides and fine particles attached to the film to the outside of the system by physical cleaning such as bubbling. A method of performing backwashing and air bubbling at the same time to remove contaminants and then flushing with water and discharging out of the system, which is used in the examples, is effective.

The discharge frequency depends on the concentrations of organic substances, inorganic hydroxides and fine particles, but it is preferable to discharge 5 to 10% of the treatment amount every 30 minutes to 1 or 2 hours. The Flux-reduced filtration membrane is preferably washed with an alkaline chemical such as caustic soda and sodium hypochlorite, and an acidic chemical such as nitric acid, oxalic acid, hydrochloric acid and sulfuric acid. Since the filtered water obtained by the above method has a low FI value, the treatment stability of the reverse osmosis membrane in the latter stage is also good. Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples.

[0013]

[Example 1] Washing wastewater discharged from various steps of printed wiring board production was collected, and a part of the wastewater was sent to the pH adjusting tank of the present invention at 500 liters / hr and stirred with a stirrer while stirring with 1N sodium hydroxide. Was injected with a caustic soda injection pump to adjust the pH. Set the pH of the pH controller so that the caustic soda injection pump operates when the pH becomes 7.2 or less and stops when the pH becomes 7.8.
Was adjusted to a range of 7.0 to 8.0. The pH-adjusted wastewater is sent to the circulation tank of the filtration device of the present invention by a water supply pump,
It was filtered with a microfiltration membrane (trade name: "USV-3003"; external pressure filtration module, hollow fiber membrane with an inner diameter of 0.8 mm, material PVdF) having a pore size of 0.1 micron manufactured by Asahi Kasei Corporation. The operating conditions at that time were a constant flow filtration operation, filtered water 450 liters / hr, filtration / backwashing + air bubbling / flushing = 30 minutes / 60 seconds / 30 seconds, discharge 50
It was performed at liter / Hr (recovery rate 90%).

Under the above conditions, the TMP at the start of filtration is 40
KPa, which is converted to a value filtered at a pressure of 100 KPa (hereinafter referred to as 100 KPa-converted Flux)
Was 1125 liters / hr. T after 1 week filtration
MP was 50 KPa and 100 KPa conversion Flux was 900 liter / Hr. At that time, the turbidity of the microfiltration membrane filtered water and the FI value were measured and the ion analysis was performed.
Described in. In addition, the turbidity is "210" manufactured by HAC.
0PTURBIDIMETER ", and the amount of ions was analyzed by an atomic absorption method using a trade name" SOLAAR "manufactured by TJA. The FI value was measured by the method described in JISK3802 4005.

[0015]

Example 2 A part of the same printed wiring board cleaning wastewater as in Example 1 was sent to the pH adjusting tank of the present invention at 500 liters / hr to adjust the pH to a range of 7.0 to 8.0. Asahi Kasei Corp. 0.45 micron pore size microfiltration membrane (trade name: "ULW-348"; internal pressure filtration module, inner diameter 1.1 mm hollow fiber membrane, material PVdF) using internal pressure cross flow method Filtered through. Under the above conditions, the TMP at the start of filtration is 20 KPa and 100 K
The Pa-converted Flux was 2250 liter / Hr.
TMP after filtration for 1 week is 30 KPa, 100 KP
The a-converted Flux was 1500 liters / Hr. The turbidity and FI value of the microfiltration membrane filtered water and the ion analysis at that time were carried out by the same method as in Example 1, and the results are shown in Table 1.

[0016]

[Comparative Example 1] The same procedure as in Example 1 was carried out except that a part of the printed wiring board cleaning drainage was sent to the pH adjusting tank of the present invention at 500 liters / hr to adjust the pH to a range of 4.6 to 5.4. Filtration was carried out under the same conditions as in Example 1. Under the above conditions, TMP at the start of filtration is 40 KPa, and 100 KPa conversion Flu
x was 1125 liters / hr. TMP after filtration for 1 week is 200 KPa, and 100 KPa conversion Flu
x was 225 liters / Hr. The turbidity and FI value of the microfiltration membrane filtered water at that time and the ion analysis were carried out in the same manner as in Example 1, and the results are shown in Table 1.

[0017]

[Table 1]

[0018]

As described in detail above, according to the method for treating a wiring board cleaning wastewater of the present invention, the flux is less likely to be reduced due to fouling of the filtration membrane, and the ion amount in the filtered water and the turbidity component are removed. It is possible to obtain water quality with an FI value of 4 or less.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4D006 GA06 GA07 HA01 HA21 HA41                       HA61 KA02 KA12 KC03 KD11                       KD12 KD16 KD24 MA01 MA02                       MA03 MA22 MB05 MC03 MC18                       MC22 MC29 MC33 MC39 MC54                       MC62 PA01 PB08 PB70 PC22

Claims (2)

[Claims] 1. A method for treating cleaning wastewater discharged from a printed wiring board manufacturing process, wherein the pH of the wastewater is adjusted to 6 to 10 with a pH adjusting tank, and the pH adjusted wastewater is treated with a membrane filtration device. A method for treating printed wiring board cleaning wastewater, characterized by: 2. The filtration membrane used in the membrane filtration device is an ultrafiltration membrane having a molecular weight cutoff of 3,000 to 1,000,000 or a microfiltration membrane having a pore size of 0.01 to 1 micron. Item 2. A method of treating printed wiring board cleaning wastewater according to Item 1.