A method for full-amount recycling and reusing of waste liquid of circuit board acidic etching

Abstract

The application discloses a method for full-amount recycling and utilization of circuit board acidic etching waste liquid, and belongs to the technical field of acidic etching waste liquid treatment. The application controls the high synergy of the acidic etching production line and the diaphragm electrolysis regeneration of the etching waste liquid through proper technical means. Chlorine generated by diaphragm electrolysis and low-copper regenerated etching liquid are returned to the etching production line. The surplus chlorine in the anode area is temporarily stored in the form of bleaching water by absorbing the liquid alkali. When the oxidant amount of the etching production line is insufficient, chlorine is prepared by bleaching water and hydrochloric acid to make up for it. The technical problem of the increment of the acidic etching waste liquid recycling and regeneration waste liquid is solved. The method for full-amount recycling and utilization of the acidic etching waste liquid can not only improve the added value of the etching waste liquid copper product of a PCB manufacturing enterprise and the market competitiveness of the enterprise, but also avoids the secondary pollution of the environment in the outsourcing treatment process of the etching waste liquid, and has good economic and environmental benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of acid etching waste liquid treatment, in particular to a method for full-amount recycling of circuit board acid etching waste liquid. BACKGROUND

[0002] PCB (printed circuit board) is the support body of electronic product components and is the most basic hardware carrier in today's information society. The PCB industry is the pillar industry of China's electronic information industry, and its growth rate is the same as that of the electronic information industry. After decades of PCB production practice, the production process has been greatly improved, but the method for making circuit patterns on circuit boards still uses the subtractive process. That is, a copper-clad plate is made into a circuit pattern through processes such as cutting, film pasting, pattern transfer, development, etching, and film stripping. Then, the production of the circuit board is completed through processes such as pressing, drilling, copper electroplating, and outer layer manufacturing. The inner layer etching adopts an acid etching method, and the oxidation-reduction potential and copper ion concentration in the etching solution are maintained within a certain range to maintain the etching rate. Oxidizing agent and hydrochloric acid need to be continuously added during the etching process, and the overflow etching solution becomes etching waste liquid. The main components of the acid etching waste liquid are copper chloride and hydrochloric acid (containing about 10% copper). The annual production of PCB copper-containing waste liquid in China exceeds one million tons. The traditional treatment method for acid etching waste liquid is that PCB enterprises entrust third-party qualified enterprises for centralized treatment. However, due to the low fee that the third-party enterprises can feedback to the PCB enterprises, the large loss of copper value for the circuit board enterprises, and the green manufacturing requirements of the PCB enterprises, the on-line recycling method for PCB acid etching waste liquid has gradually been accepted by various PCB enterprises since 2018. According to statistics, by the end of 2022, more than 40% of the acid etching waste liquid of PCB enterprises has been treated through on-line recycling. The related patents for on-line recycling of acid etching waste liquid include CN201810753588.6, CN201920899749.2, and CN202020657282.3. However, due to the switching of different material numbers in the circuit etching production process, the etching copper thickness, and the different etching copper areas, the requirements for etching rate are different, and the demand for oxidizing agent is large or small. The current density of the regenerated acid etching waste liquid by diaphragm electrolysis is relatively balanced, and the amount of chlorine gas produced is constant, which cannot meet the demand of the etching production line. A large amount of oxidizing agent (sodium chlorate solution) and hydrochloric acid still needs to be supplemented, causing the expansion of the acid etching waste liquid. Only 70-80% of the acid etching waste liquid can be recycled on-line, and the remaining 20-30% still needs to be treated by entrusting third-party qualified enterprises. For PCB enterprises that pursue green manufacturing and cost reduction and efficiency improvement, there is an urgent need for a process for full-amount on-line recycling of acid etching waste liquid. SUMMARY

[0003] In view of the above deficiencies of the off-line intermittent recycling of the PCB (PCB) desmear waste liquid, the application provides a method for full-amount recycling of the PCB acidic etching waste liquid, and the acidic etching production line and the diaphragm electrolysis of the etching waste liquid are highly coordinated through appropriate technical means, the chlorine gas generated by the diaphragm electrolysis is returned to the etching production line with the low-copper regenerated etching liquid, the excess chlorine gas in the anode region is absorbed by the liquid alkali to be temporarily stored in the form of bleaching water, and when the oxidant amount of the etching production line is insufficient, the chlorine gas is prepared by the bleaching water and hydrochloric acid to be supplemented, so that the technical problem of the increment of the etching waste liquid recycling is solved, and the method for full-amount recycling of the etching waste liquid is realized, and the content of the application is as follows:

[0004] The application aims to provide a method for full-amount recycling of the PCB acidic etching waste liquid, and the technical point is that the method comprises the following steps:

[0005] Step one: the etching waste liquid overflowed from the PCB etching production line is pretreated to make the copper content be 110-140 g / L, and is collected to a transfer tank to be added to a diaphragm electrolysis tank in a continuous additive manner to generate chlorine gas, metal copper and regenerated etching liquid by electrolysis regeneration, the regenerated etching liquid is returned to the PCB etching production line, and the chlorine gas is partly transported to the PCB etching production line by negative pressure and partly absorbed by the liquid alkali to be temporarily stored in the form of bleaching water and hydrochloric acid, the current density is precisely controlled, and the concentration of copper ions in the diaphragm electrolysis tank is kept to be 40-60 g / L;

[0006] Step two: the bleaching water and the hydrochloric acid obtained in step one are respectively stored in a turnover tank, are connected with a chlorine gas generator to generate chlorine gas and sodium chloride solution, the start of the chlorine gas preparation and the chlorine gas generation amount are controlled by the oxidation-reduction potential of the acidic etching liquid in the PCB etching production line, and the generated chlorine gas and the chlorine gas in step one are transported to the PCB etching production line by negative pressure;

[0007] Step three: the chlorine gas generated in steps one and two is transported to the etching tank by the negative pressure generated by the etching production line circulating pump and the Venturi flowmeter and is fully mixed with the etching liquid, the transport amount of the chlorine gas is controlled by the oxidation-reduction potential of the acidic etching liquid in the PCB etching production line, when the oxidation-reduction potential is high, the chlorine gas generated by the electrolysis tank is stopped to be transported to the PCB etching production line, the chlorine gas generated by the electrolysis tank is switched to the bleaching water preparation system, when the oxidation-reduction potential is low, the chlorine gas is started to be transported to the etching line system, when all the chlorine gas generated by the electrolysis tank is transported to the PCB etching production line and still cannot meet the requirement of the oxidation-reduction potential of the acidic etching liquid, the chlorine gas preparation system in step two is started, the speed of the chlorine gas generated in step two is controlled according to the oxidation-reduction potential value of the acidic etching liquid in the PCB etching production line and the amount of the chlorine gas generated by the diaphragm electrolysis of the etching waste liquid in step one, and the concentration of the hydrochloric acid in the PCB etching production line is maintained at 2.0-2.5 mol / L by the regenerated etching liquid generated in step two;

[0008] Step four, the sodium chloride solution generated in step two is concentrated by evaporation under reduced pressure, centrifuged, dried, and then high-purity sodium chloride crystals are obtained.

[0009] In order to better achieve the above technical solutions, the waste liquid pretreatment in step one of the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application includes filtering impurities in the etching waste liquid.

[0010] In order to better achieve the above technical solutions, the redox potential of the acidic etching liquid in steps two and three of the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application is 520-580 mv.

[0011] In order to better achieve the above technical solutions, the concentration of monovalent copper ions in the acidic etching liquid in the PCB etching production line in the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application is 0.3 g / L or less. Different PCB board numbers require different etching copper areas and thicknesses in the etching production line, and the speed of monovalent copper ions generated in the etching bath liquid is large or small. In order to maintain the total monovalent copper ions in the etching bath liquid at 0.3 g / L or less, the etching bath liquid needs to be continuously supplemented with oxidizing agents to oxidize the monovalent copper ions to maintain the ORP (oxidation-reduction potential) at 520-560 mv. When the chlorine gas produced by the diaphragm electrolysis of the etching waste liquid is not fully used in the etching production line, the chlorine gas is recycled to the bleaching water production system. When the ORP of the etching bath liquid in the etching production line is still lower than the set range when the chlorine gas produced by the diaphragm electrolysis of the etching waste liquid is fully recycled to the etching bath liquid in the etching production line, the step two chlorine gas preparation system is started, and the amount of chlorine gas generated is adjusted according to the size change of the ORP in the etching production line.

[0012] In order to better achieve the above technical solutions, the titanium material resistant to chlorine ion corrosion is used for the evaporation under reduced pressure of the sodium chloride in step four of the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application.

[0013] In order to better achieve the above technical solutions, the encapsulated stainless steel centrifuge is used for the centrifugal separation in step four of the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application.

[0014] In order to better achieve the above technical solutions, the enamel rotary dryer is used for the drying in step four of the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application.

[0015] Compared with the prior art, the method for full-circulation recycling of printed circuit board (PCB) acidic etching waste liquid of the application can achieve the following beneficial effects:

[0016] The method for full-amount recycling of circuit board acid etching waste liquid provided by the application controls the acid etching production line and the diaphragm electrolysis regeneration of etching waste liquid in high coordination through appropriate technical means, the chlorine gas generated by diaphragm electrolysis is returned to the etching production line with low copper regenerated etching liquid, the excess chlorine gas in the anode area is absorbed by liquid alkali in the form of bleaching water, and when the oxidizing agent amount of the etching production line is insufficient, chlorine gas is prepared from bleaching water and hydrochloric acid to supplement, which solves the technical problem of waste liquid increment in acid etching waste liquid recycling and regeneration, realizes the method for full-amount recycling of acid etching waste liquid, can not only improve the added value of copper products of etching waste liquid of PCB manufacturing enterprises and enhance the market competitiveness of enterprises, but also avoids the secondary pollution of environment in the outsourcing treatment process of etching waste liquid, and has good economic and environmental benefits. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The process flowchart of the application is shown in the figure. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be described clearly and completely in combination with specific embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the application.

[0019] The method for full-amount recycling of circuit board acid etching waste liquid provided by the application uses hydrochloric acid with a mass concentration of 31% as chemical pure hydrochloric acid, uses polydimethylammonium chloride as an electrolytic additive, uses 30% mass concentration sodium hydroxide solution as liquid alkali, uses acid etching waste liquid as production waste liquid for PCB etching process of PCB circuit board production enterprises, the copper content of the acid etching waste liquid is 110-140 g / L, the hydrochloric acid content is 2.0-2.5 mol / L, the diaphragm electrolytic cell, the bleaching water preparation system, the chlorine gas generator and the acid etching waste liquid regeneration liquid recycling system are all prior art, and will not be described in detail.

[0020] Example 1

[0021] The method for full-amount recycling of circuit board acid etching waste liquid comprises the following steps:

[0022] Step one, the etching waste liquid overflowed from the PCB etching production line is pretreated (the waste liquid pretreatment includes filtering the impurities in the etching waste liquid) to make the copper content 125 g / L, collected to the transfer tank to add to the diaphragm electrolytic cell in a continuous additive manner to carry out electrolysis regeneration to generate chlorine gas, metal copper and regenerated etching liquid, the regenerated etching liquid returns to the PCB etching production line, part of the chlorine gas is transported to the PCB etching production line by negative pressure, part of the chlorine gas is absorbed by liquid alkali to prepare bleaching water and hydrochloric acid, and the current density is set to 200 A / m 2 so that the concentration of copper ions in the diaphragm electrolytic cell is 60 g / L;

[0023] Step two, the bleaching water and hydrochloric acid obtained in step one are respectively stored in the turnover tank, connected with the chlorine gas generator to generate chlorine gas and sodium chloride solution, the start of chlorine gas preparation and the amount of chlorine gas generated are controlled by the redox potential of the acidic etching liquid in the PCB etching production line, and the generated chlorine gas and the chlorine gas in step one are transported to the PCB etching production line by negative pressure.

[0024] Step three, the chlorine gas generated in steps one and two is transported to the etching tank by the negative pressure generated by the etching production line circulating pump and the Venturi flow meter and fully mixed with the etching liquid, the amount of chlorine gas transported is controlled by the redox potential of the acidic etching liquid in the PCB etching production line, the redox potential of the acidic etching liquid is 550 mv, when the redox potential is higher than 550 mv, the chlorine gas generated by the electrolytic cell is stopped to be transported to the PCB etching production line, the chlorine gas generated by the electrolytic cell is switched to the bleaching water preparation system, when the redox potential is lower than 550 mv, the chlorine gas transportation etching line system is started, when the chlorine gas generated by the electrolytic cell is all transported to the PCB etching production line and still cannot meet the requirement of the redox potential of the acidic etching liquid, the chlorine gas preparation system in step two is started, the speed of the chlorine gas generated in step two is controlled according to the redox potential value of the acidic etching liquid in the PCB etching production line and the amount of the chlorine gas generated by the diaphragm electrolysis regenerated etching waste liquid in step one; the concentration of hydrochloric acid in the PCB etching production line is maintained at 2.0-2.5 mol / L by the regenerated etching liquid generated in step two; the concentration of monovalent copper ions in the acidic etching liquid in the PCB etching production line is 0.3 g / L or lower. The speed of chlorine gas generation in the anode area of the diaphragm electrolytic cell is 3.6 kg / h, the demand for chlorine gas in the etching production line is 2.5 kg / h, and the surplus 1.1 kg of chlorine gas is prepared into sodium hypochlorite solution by liquid alkali absorption.

[0025] Step four, the sodium chloride solution generated in step two is concentrated by vacuum evaporation, centrifuged and dried to obtain high-purity sodium chloride crystals. The titanium material resistant to chlorine ion corrosion, enamel vacuum evaporator is used for vacuum evaporation and concentration of sodium chloride. The encapsulated stainless steel centrifuge is used for centrifugal separation. The enamel rotary dryer is used for drying.

[0026] Example 2

[0027] A method for full-amount recycling and regeneration of a circuit board acidic etching waste liquid includes the following steps:

[0028] Step one, the etching waste liquid overflowed from a PCB etching production line is pretreated (the waste liquid pretreatment includes filtering impurities in the etching waste liquid) to make the copper content 140 g / L, collected to a transfer tank, and added to a diaphragm electrolytic cell in a continuous additive manner for electrolytic regeneration to generate chlorine gas, metallic copper, and regenerated etching liquid, the regenerated etching liquid is returned to the PCB etching production line, and the chlorine gas is partly transported to the PCB etching production line by negative pressure and partly prepared into bleaching water and hydrochloric acid by absorption of liquid alkali, and the current density is set to 240 A / m 2 so that the concentration of copper ions in the diaphragm electrolytic cell is 50 g / L;

[0029] Step two, the bleaching water and the hydrochloric acid obtained in step one are respectively stored in a turnover tank and connected with a chlorine gas generator to generate chlorine gas and sodium chloride solution, the start of chlorine gas preparation and the chlorine gas generation amount are controlled by the oxidation-reduction potential of the acidic etching liquid in the PCB etching production line, and the generated chlorine gas and the chlorine gas in step one are transported to the PCB etching production line by negative pressure.

[0030] Step three, the chlorine gas generated in steps one and two is transported to the etching tank by the negative pressure generated by the etching production line circulating pump and the Venturi flowmeter and fully mixed with the etching liquid, the transport amount of the chlorine gas is controlled by the oxidation-reduction potential of the acidic etching liquid in the PCB etching production line, the oxidation-reduction potential of the acidic etching liquid is 540 mv, when the oxidation-reduction potential is higher than 540 mv, the chlorine gas generated by the electrolytic cell is stopped from being transported to the PCB etching production line, the chlorine gas generated by the electrolytic cell is switched to the bleaching water preparation system, when the oxidation-reduction potential is lower than 540 mv, the chlorine gas transport etching line system is started, when the chlorine gas generated by the electrolytic cell is all transported to the PCB etching production line and still cannot meet the requirement of the oxidation-reduction potential of the acidic etching liquid, the chlorine gas preparation system in step two is started, the speed of the chlorine gas generated in step two is controlled according to the oxidation-reduction potential value of the acidic etching liquid in the PCB etching production line and the amount of the chlorine gas generated by the diaphragm electrolytic regenerated etching waste liquid in step one; the concentration of the hydrochloric acid in the PCB etching production line is maintained at 2.25 mol / L by the regenerated etching liquid generated in step two; the concentration of the monovalent copper ions in the acidic etching liquid in the PCB etching production line is 0.3 g / L or lower. The speed of the chlorine gas generated in the anode region of the diaphragm electrolytic cell is 4.3 kg / h, the demand of the etching production line for chlorine gas is 4.8 kg / h, and the insufficient chlorine gas is provided by the sodium hypochlorite solution and the hydrochloric acid prepared in example 1.

[0031] Step four, the sodium chloride solution generated in step two is evaporated back to concentration under reduced pressure, centrifuged, dried to obtain high-purity sodium chloride crystals. The sodium chloride is evaporated back to concentration under reduced pressure using titanium material resistant to chlorine ion corrosion, enamel vacuum evaporator. The centrifugation uses a coated stainless steel centrifuge. Drying is done using an enamel rotary dryer.

[0032] Example 3

[0033] A method for full-amount recycling and regeneration of a circuit board acidic etching waste liquid includes the following steps:

[0034] Step one, the etching waste liquid overflowed from the PCB etching production line is pretreated (the waste liquid pretreatment includes filtering impurities in the etching waste liquid) to make the copper content 110 g / L, collected into a transfer tank to continuously add a diaphragm electrolytic cell for electrolytic regeneration to generate chlorine gas, metal copper and regenerated etching liquid, the regenerated etching liquid is returned to the PCB etching production line, part of the chlorine gas is transported to the PCB etching production line by negative pressure, part of the chlorine gas is prepared into bleaching water and hydrochloric acid by absorbing liquid alkali, and the current density is set to 150 A / m 2 so that the concentration of copper ions in the diaphragm electrolytic cell is 40 g / L;

[0035] Step two, the bleaching water and hydrochloric acid obtained in step one are respectively stored in a turnover tank, connected with a chlorine gas generator to generate chlorine gas and a sodium chloride solution, the start of chlorine gas preparation and the amount of chlorine gas generated are controlled by the redox potential of the acidic etching liquid in the PCB etching production line, and the generated chlorine gas and the chlorine gas in step one are transported to the PCB etching production line by negative pressure;

[0036] Step three, the chlorine gas produced by step one and step two is transported to the etching tank and the etching solution by the negative pressure generated by the etching production line circulating pump and the venturi flow meter, the amount of chlorine gas transported is controlled by the redox potential of the acid etching solution in the PCB etching production line, when the redox potential is higher than 520mv, the chlorine gas produced by the electrolytic tank is stopped to be transported to the PCB etching production line, the chlorine gas produced by the electrolytic tank is switched to the bleaching water production system, when the redox potential is lower than 520mv, the chlorine gas transportation system is started, when the chlorine gas produced by the electrolytic tank is all transported to the PCB etching production line and still cannot meet the requirement of the redox potential of the acid etching solution, the step two chlorine gas preparation system is started, the speed of the chlorine gas produced by step two is controlled according to the redox potential value of the acid etching solution in the PCB etching production line and the amount of chlorine gas produced by the diaphragm electrolysis of the etching waste liquid; the concentration of hydrochloric acid in the PCB etching production line is maintained at 2.0-2.5mol / L by the regenerated etching solution produced by step two; the concentration of monovalent copper ions in the acid etching solution in the PCB etching production line is 0.3g / L or less. The speed of chlorine gas production in the anode area of the diaphragm electrolytic tank is 2.2kg / h, the demand for chlorine gas in the etching production line is 2.2kg / h, and the chlorine gas produced by the diaphragm electrolysis of the acid etching waste liquid is balanced with the demand for chlorine gas in the etching production line.

[0037] Step four, the sodium chloride solution produced by step two is concentrated by vacuum evaporation, centrifuged and dried to obtain high-purity sodium chloride crystals. The titanium material resistant to chlorine ion corrosion and the enamel vacuum evaporator are used for vacuum evaporation and concentration of sodium chloride. The encapsulated stainless steel centrifuge is used for centrifugation. The enamel rotary dryer is used for drying.

[0038] The above examples of the acid etching waste liquid full-amount recycling method have been regenerated by diaphragm electrolysis during production operation, and there is no outsourcing treatment of waste liquid.

[0039] The above only describes the embodiments of the present application and is not used to limit the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the scope of claims of the present application.

Claims

1. A method for the complete recycling and regeneration of acidic etching waste liquid from circuit boards, characterized in that, Includes the following steps: Step 1: The overflow etching waste liquid from the PCB etching production line is pretreated to reduce the copper content to 110-140 g / L. The waste liquid is collected in a transfer tank and added to a diaphragm electrolytic cell as a continuous additive for electrolytic regeneration to generate chlorine gas, metallic copper, and regenerated etching solution. The regenerated etching solution is returned to the PCB etching production line. Part of the chlorine gas is transported to the PCB etching production line under negative pressure, and part of it is absorbed by liquid alkali to prepare bleach and hydrochloric acid for temporary storage. The concentration of copper ions in the diaphragm electrolytic cell is 40-60 g / L. Step 2: The bleach and hydrochloric acid obtained in Step 1 are stored in a transfer tank and connected to a chlorine generator to generate chlorine and sodium chloride solution. The start-up of chlorine preparation and the amount of chlorine generated are controlled by the oxidation-reduction potential of the acidic etching solution in the PCB etching production line. The generated chlorine and the chlorine from Step 1 are transported to the PCB etching production line under negative pressure. Step 3: The chlorine gas generated in Step 1 and Step 2 is transported to the etching tank by the negative pressure generated by the circulating pump and Venturi flow meter of the etching production line and thoroughly mixed with the etching solution. The amount of chlorine gas transported is controlled by the oxidation-reduction potential of the acidic etching solution in the PCB etching production line. When the oxidation-reduction potential is high, the chlorine gas generated in the electrolytic cell is stopped from being transported to the PCB etching production line, and the chlorine gas generated in the electrolytic cell is switched to the bleaching water production system. When the oxidation-reduction potential is low, the chlorine gas transport etching line system is started. When all the chlorine gas generated in the electrolytic cell is transported to the PCB etching production line but still does not meet the oxidation-reduction potential requirements of the acidic etching solution, the chlorine gas preparation system of Step 2 is started. The rate of chlorine gas generated in Step 2 is controlled according to the oxidation-reduction potential value of the acidic etching solution in the PCB etching production line and the amount of chlorine gas generated by the diaphragm electrolysis regeneration etching waste liquid in Step 1. The hydrochloric acid concentration in the PCB etching production line is maintained at 2.0-2.5 mol / L by replenishing the regenerated etching solution produced in step two; Step four: The sodium chloride solution generated in step two is concentrated by vacuum evaporation, centrifugation, and drying to obtain high-purity sodium chloride crystals; The waste liquid pretreatment in step one includes filtering impurities from the etching waste liquid; The oxidation-reduction potential of the acidic etching solution in steps two and three is 520-580 mV; The concentration of monovalent copper ions in the acidic etching solution of the PCB etching production line is below 0.3 g / L; In step four, the sodium chloride vacuum evaporation and concentration process uses a titanium-material, enamel-lined vacuum evaporator resistant to chloride ion corrosion. In step four, the centrifugal separation is performed using a rubber-coated stainless steel centrifuge. In step four, the drying process uses an enamel rotary dryer.

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