Circulating system and regeneration process for chlorine-free electrolysis of PCB (printed circuit board) acidic etching solution

Abstract

The invention relates to the technical field of etching liquid treatment, in particular to a circulating system and regeneration process for chlorine-free electrolysis of PCB acid etching liquid, and the circulating system comprises an etching spraying unit, an etching liquid collecting unit, an additive adding unit, an electrolysis unit and a regenerated liquid collecting unit, the output end of the etching spraying unit is sequentially connected with the etching liquid collecting unit, the electrolysis unit and the regenerated liquid collecting unit; the output end of the regenerated liquid collecting unit is communicated with the input end of the etching spraying unit; the inherent circulation mode of the etching unit is changed, the anode chlorine evolution risk is reduced, meanwhile, the circulation flow between the etching system and the electrolysis system is reduced, and the electrolytic regeneration process stability and the electrolytic regeneration efficiency of the etching waste liquid are improved.

Description

Technical Field

[0001] The invention relates to the technical field of etching liquid treatment, and in particular to a circulation system and a regeneration process for chlorine-free electrolysis of PCB acid etching liquid. Background Art

[0002] The main components of the acidic etching solution are hydrochloric acid, sodium chloride, cupric chloride and hypochlorous acid, of which the recyclable components are sodium chloride and cupric chloride. Through regeneration treatment, the emission of harmful substances can be effectively reduced, the negative impact on the environment can be reduced, the ecological environment can be protected, and it is in line with the concept of sustainable development. Moreover, the acidic etching solution is regenerated so that the originally discarded etching solution can be reused, saving the cost required for preparing new liquid. Therefore, it is very necessary to regenerate the acidic etching solution. At present, the acidic etching solution regeneration treatment technology such as: Patent CN102127765B discloses an acidic etching waste liquid recycling system, and its main process is: a part of the etching waste liquid enters the anode chamber, and the other part enters the cathode liquid buffer tank. The cathode electrolyte circulates in the cathode chamber and the cathode liquid buffer tank. The anode chamber electrolyte is electrolytically oxidized and mixed with a part of the electrolyte flowing out of the cathode liquid buffer tank as a regenerated etching solution.

[0003] Patent CN217378033U discloses a chlorine-free electrically regenerated PCB acidic circulating etching system, which includes an acidic etching module, an electrochemical module and a regeneration module. The copper-containing acidic etching liquid produced by the acidic etching module enters the electrochemical module and the regeneration module in sequence through a liquid pipeline, and is finally recycled to the acidic etching module.

[0004] Patent CN117385359A discloses a method for regenerating an acidic etching solution by chlorine-free electrolysis. The acidic etching solution is used for etching to obtain etching waste liquid. The obtained etching waste liquid enters the anode chamber and cathode chamber of the electrolytic cell for electrolytic treatment respectively. The anode liquid obtained in the anode chamber overflows into the transfer tank and is then reused in the etching operation. The cathode chamber obtains copper and cathode liquid, and the cathode liquid enters the circulation tank and is then reused in the electrolytic treatment of the cathode chamber. The generation of chlorine is suppressed, and no oxidant needs to be added to the etching line after reuse, and the incremental wastewater is also reduced.

[0005] At present, the chlorine-free electrolytic regeneration technology used for PCB acid etching liquid in the existing technology is to innovate and improve the "electrolytic system", and is designed to passively cooperate with the etching system as much as possible. The etching waste liquid and the etching working liquid in the etching system are mixed in the collection tank. The concentration of monovalent copper is low, and the corresponding ORP value is high, which is easy to cause chlorine evolution reaction, which is not conducive to electrolytic regeneration; because the higher the ORP value, the more sensitive the ORP value is to the change of monovalent copper concentration, and a small change in the concentration of monovalent copper will cause the ORP value to fluctuate greatly. In addition, since there is a certain delay in ORP value monitoring, when the ORP value signal is fed back to the rectifier, it is easy to cause the current output of the rectifier to be disordered. The disordered current output of the rectifier will cause the electrolytic system to frequently precipitate chlorine. At the same time, the etching liquid needs to circulate at a large flow rate between the etching production line and the electrolytic production line to meet the demand. Taking the etching production line of the three-stage etcher as an example, if the electrolysis efficiency is to be guaranteed and the etching production line does not add oxidants, the circulation flow of the etching production line and the electrolytic production line cannot be less than 40m 3 / H, especially when etching production lines are used for thick plates and concentrated production, the required circulation volume may even need to reach 60m 3 / H. Summary of the invention

[0006] In order to solve the problems in the prior art that the rectifier current output is easily disordered, chlorine evolution is prone to occur, and the etching solution is difficult to circulate at a large flow rate between etching and electrolysis, the present invention provides a circulation system and regeneration process for chlorine-free electrolysis of PCB acid etching solution, which greatly improves the overall performance of the etching waste liquid electrolysis regeneration process.

[0007] A circulation system for chlorine-free electrolysis of PCB acid etching liquid comprises an etching spray unit, an etching liquid collecting unit, an auxiliary agent adding unit and an electrolysis unit, and also comprises a regeneration liquid collecting unit. The output end of the etching spray unit is connected to the etching liquid collecting unit, the electrolysis unit and the regeneration liquid collecting unit in sequence; the output end of the regeneration liquid collecting unit is cyclically connected to the input end of the etching spray unit.

[0008] Furthermore, the regeneration liquid collecting unit is connected to an auxiliary agent adding unit, and the auxiliary agent adding unit is opened when the electrolysis unit operates abnormally.

[0009] Further, the electrolysis unit includes an anode chamber, a cathode chamber, and a cation exchange membrane located between the anode chamber and the cathode chamber;

[0010] The output end of the etching waste liquid collection unit is connected to the input end of the anode chamber and the input end of the cathode chamber respectively, and the output end of the anode chamber is connected to the input end of the regeneration liquid collection unit.

[0011] Furthermore, the anode chamber is provided with an ORP monitor, and the cathode chamber is provided with a specific gravity monitor.

[0012] Furthermore, an etching waste liquid pump is provided between the output end of the etching liquid collection unit and the input end of the electrolysis unit;

[0013] An electrolysis recycling pump is provided between the output end of the electrolysis unit and the input end of the regeneration liquid collection unit;

[0014] A spray pump is provided between the output end of the regeneration liquid collecting unit and the input end of the etching spray unit.

[0015] Based on the above-mentioned chlorine-free electrolysis circulation system of PCB acid etching solution, the present invention also provides a regeneration process, including a process of electrolyzing the etching waste liquid to obtain an anolyte and a process of regenerating and reusing the obtained anolyte, wherein the ORP value of the electrolytically treated etching waste liquid is less than 490mV, and the concentration of monovalent copper ions is ≥4g / L, and the process of regenerating and reusing the anolyte is that the anolyte flows to a regeneration liquid collection unit and then is reused in the etching operation.

[0016] The material flow is as follows:

[0017] The acidic etching liquid is passed through the etching spray unit to obtain etching waste liquid, which is collected in the etching liquid collection unit and then sent to the electrolysis unit for electrolysis treatment through the etching waste liquid pump. The obtained cathode liquid is sent to the anode chamber through the pump, and is electrolyzed together with the etching waste liquid in the anode chamber to obtain the anode liquid. The obtained anode liquid is sent to the regeneration liquid collection unit through the electrolysis return pump, and then flows out of the regeneration liquid collection unit as the regenerated etching liquid and is sent back to the etching spray unit through the spray pump;

[0018] Among them, when the copper ion concentration is lower than 40g / L, it is necessary to replenish the etching waste liquid into the cathode chamber.

[0019] Furthermore, the ORP value in the anode chamber is controlled to be 550-600mV, and the ORP value is controlled by adjusting the electrolysis equipment. When the ORP value is greater than 600mV, the power supply is disconnected, and when the ORP value is less than 550mV, the current density is adjusted to 300-500A / m 2 .

[0020] Furthermore, the main component of the acidic etching solution is CuCl 2 , HCl, NaCl, among which the divalent copper ion concentration is 120-140g / L, the chloride ion concentration is 260-300g / L, and the acidity is 1.5-3.0mol / L.

[0021] Furthermore, the electrochemical reaction in the anode chamber of the electrolysis unit is as follows: Cu + -e - =Cu 2+ ;

[0022] Furthermore, the electrochemical reaction in the cathode chamber of the electrolysis unit is as follows: Cu 2+ +e - =Cu + , Cu + +e - =Cu.

[0023] The advantages of the present invention are:

[0024] The present invention changes the inherent circulation mode of the etching machine, adds an etching working liquid collection cylinder, and independently stores the regenerated etching working liquid and the etching waste liquid, so that the concentration of monovalent copper in the etching waste liquid entering the electrolytic cell is increased from 0.4g / L to more than 4g / L, thereby reducing the risk of chlorine precipitation at the anode and reducing the circulation flow between the etching system and the electrolysis system. Compared with the prior art, the 40m 3 The circulation rate above 20m / h can be reduced to 20m 3 / h, which improves the stability of the electrolytic regeneration process of etching waste liquid and increases the electrolytic regeneration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a schematic diagram of a chlorine-free electrolysis process according to Embodiment 1 of the present invention;

[0026] Figure 2 It is a schematic diagram of the chlorine-free electrolysis process of the comparative example of the present invention;

[0027] Figure 3 This is a graph showing the relationship between the concentration of monovalent copper ions in the etching solution and the ORP value. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the invention to clearly and completely describe the technical solutions in the embodiments of the invention. Obviously, the described embodiments are only part of the embodiments of the invention, not all of them. Based on the embodiments in the invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the invention.

[0029] It should be noted that the various installation methods and technical terms mentioned in the invention are technical terms that have long been clearly known in the relevant technical field, so no further explanation is given. In addition, the same reference numerals are used for the same components, but this does not affect and should not constitute an accurate understanding of the technical solution by those skilled in the art.

[0030] Example 1

[0031] A PCB acid etching solution circulation system without chlorine gas electrolysis, such as Figure 1As shown, it includes an etching spray unit, an etching liquid collecting unit, an auxiliary agent adding unit and an electrolysis unit, and also includes a regeneration liquid collecting unit, the output end of the etching spray unit is connected with the etching liquid collecting unit, the electrolysis unit, and the regeneration liquid collecting unit in sequence; the regeneration liquid collecting unit includes a first input end, a second input end and an output end, the first input end of the regeneration liquid collecting unit is connected with the output end of the electrolysis unit, the second input end of the regeneration liquid collecting unit is connected with the auxiliary agent adding unit, and the output end of the regeneration liquid collecting unit is cyclically connected with the input end of the etching spray unit;

[0032] Among them, an etching waste liquid pump is provided between the output end of the etching liquid collection unit and the input end of the electrolysis unit; an electrolysis reuse pump is provided between the output end of the electrolysis unit and the input end of the regeneration liquid collection unit; and a spray pump is provided between the output end of the regeneration liquid collection unit and the input end of the etching spray unit.

[0033] The electrolysis unit includes an anode chamber, a cathode chamber and a cation exchange membrane located between the anode chamber and the cathode chamber; the output end of the etching waste liquid collection unit is respectively connected to the input end of the anode chamber and the input end of the cathode chamber, and the output end of the anode chamber is connected to the input end of the regeneration liquid collection unit.

[0034] The anode chamber is provided with an ORP monitor, and the cathode chamber is provided with a specific gravity monitor.

[0035] A regeneration process of a PCB acid etching solution circulation system without chlorine gas electrolysis, the specific process is as follows:

[0036] The acidic etching liquid is etched by the etching spray unit, and the metal copper on the surface of the PCB board is etched and dissolved to obtain etching waste liquid and flow into the etching liquid collection unit; the etching waste liquid overflows from the etching liquid collection unit and is respectively sent to the anode chamber and cathode chamber of the electrolysis unit through the etching waste liquid pump for electrolysis treatment, the copper obtained by electrolyzing the etching waste liquid in the cathode chamber is deposited on the cathode, and the copper ion concentration in the cathode liquid is 40g / L. When the copper ion concentration in the cathode liquid is lower than 40g / L, the etching waste liquid is supplemented to enter the cathode chamber, and the specific gravity of the cathode liquid finally obtained is 1.16; the obtained cathode liquid is pumped to the anode chamber by a pump, and the etching waste liquid and the cathode liquid are electrolyzed in the anode chamber to obtain an anode liquid, and the monovalent copper ions in the obtained anode liquid are oxidized into divalent copper ions, and finally overflows from the anode chamber, and is pumped to the regeneration liquid collection unit by the electrolysis reuse pump, and flows out from the regeneration liquid collection unit as a reusable regeneration etching liquid and is returned to the etching spray unit by the spray pump.

[0037] The main component of the acidic etching solution is CuCl 2 , HCl, NaCl, among which the divalent copper ion concentration is 120g / L, the chloride ion concentration is 300g / L, and the acidity is 3.0mol / L.

[0038] The electrochemical reaction in the anode chamber of the electrolysis unit is as follows: Cu + -e - =Cu 2+ ;

[0039] The electrochemical reaction in the cathode chamber of the electrolysis unit is as follows: Cu 2+ +e - =Cu + , Cu + +e - =Cu.

[0040] The ORP value in the etching solution collection unit is less than 490mV, and the concentration of monovalent copper ions flowing into the anode chamber is greater than 4g / L;

[0041] The ORP value in the anode chamber is controlled by adjusting the electrolysis equipment: when the ORP monitor in the anode chamber detects that the ORP value is lower than 550mV, the current density is adjusted to 400A / m 2 .

[0042] The concentration of monovalent copper ions in the anode chamber is controlled by the ORP value: the ORP value in the anode chamber is controlled to be 550 mV.

[0043] In this embodiment, the circulation volume of the three-stage etching machine production line is 20m 3 / H, the amount of oxidant used for etching one ton of copper is 20kg.

[0044] In this embodiment, the etching liquid collecting unit collects waste liquid with an ORP value of less than 490 mV, which does not meet the etching requirements.

[0045] Example 2

[0046] This embodiment is the same as embodiment 1, except that the divalent copper ion concentration of this embodiment is 140 g / L, the chloride ion concentration is 260 g / L, and the acidity is 1.5 mol / L;

[0047] The specific gravity of the cathode liquid obtained in the cathode chamber of this embodiment is 1.18;

[0048] The ORP value in the anode chamber of the present embodiment is controlled by adjusting the electrolysis equipment: when the ORP monitor in the anode chamber detects that the ORP value is higher than 600mV, the power supply is disconnected.

[0049] In this embodiment, the concentration of monovalent copper ions in the anode chamber is controlled by the ORP value: the ORP value in the anode chamber is controlled to be 600 mV.

[0050] Comparative Example

[0051] A PCB acid etching solution circulation system without chlorine gas electrolysis, such as Figure 2 As shown, it includes an etching spray unit, an etching liquid collecting unit, an auxiliary agent adding unit and an electrolysis unit, wherein the etching spray unit is interconnected with the etching liquid collecting unit, the etching liquid collecting unit is interconnected with the electrolysis unit, the etching liquid collecting unit includes a first input end, a second input end, a third input end, a first output end and a second output end, wherein the output end of the etching spray unit is connected to the first input end of the etching liquid collecting unit, the first output end of the etching liquid collecting unit is connected to the input end of the electrolysis unit, the output end of the electrolysis unit is connected to the second input end of the etching liquid collecting unit, and the second output end of the etching liquid collecting unit is connected to the input end of the etching spray unit; the third input unit of the etching liquid collecting unit is connected to the auxiliary agent adding unit.

[0052] The process is as follows:

[0053] The etching waste liquid obtained by etching with acidic etching liquid flows to the etching liquid collection unit; the etching waste liquid pump enters the anode chamber and cathode chamber of the electrolytic cell for electrolytic treatment respectively, and the anode liquid obtained in the anode chamber flows back to the etching liquid collection unit, and then is reused in the etching operation through the spray pump; the cathode liquid obtained in the cathode chamber enters the circulation tank, and then is reused in the electrolytic treatment of the cathode chamber; the ORP value of the etching liquid collection unit is 500-550mV. The concentration of monovalent copper ions in the anode chamber of the electrolytic unit is 0.4g / L.

[0054] The main component of the acidic etching solution is CuCl 2 , HCl, NaCl, among which the divalent copper ion concentration is 120g / L, the chloride ion concentration is 300g / L, and the acidity is 3.0mol / L.

[0055] The circulation volume of the production line of the three-stage etching machine in this comparative example is 40m 3 / H, the amount of oxidant used for etching one ton of copper is 60kg.

[0056] In this comparative example, the etching liquid collecting unit collects waste liquid and regenerated etching liquid after adding sub-liquid, oxidant and hydrochloric acid, and its chemical composition and concentration are exactly the same as those of the etching working liquid.

[0057] analyze:

[0058] The electrochemical reaction at the anode of the electrolytic cell is as follows:

[0059] Monovalent copper preferentially reacts: Cu + -e=Cu 2+ ;

[0060] In the case of insufficient monovalent copper, chloride ions participate in the reaction: 2Cl - -e=Cl 2

[0061] Principle: The electrolytic cell and the etching machine are connected and circulated, and the monovalent copper ions in the etching solution continuously enter the anode chamber of the electrolytic cell. Since the redox potential of the monovalent copper ions is much lower than that of the chloride ions, the monovalent copper ions will be oxidized at the anode before the chloride ions. Figure 3 It can be seen that the concentration of monovalent copper ions is related to the ORP value of the etching solution. Usually, the ORP setting value of the etching solution in the etching production line is a value between 500-550mV. The concentration of monovalent copper in the etching solution is approximately 0.4-2.6g / L (0.006-0.04mol / L). The lower the concentration of monovalent copper ions, the higher the ORP value of the etching solution. The ORP value of the anode liquid can be controlled by adjusting the current output by the rectifier of the electrolysis system during the electrolysis process. Only when the anode liquid is always maintained at a certain ORP value can the anode not produce chlorine during the electrolysis process.

[0062] In the comparative example, the etching waste liquid and the etching regeneration liquid are mixed in the etching liquid collection unit, resulting in a high ORP value (550mV) and a low concentration of monovalent copper entering the electrolysis unit (0.4g / L), resulting in a high risk of chlorine evolution, which is not conducive to electrolytic regeneration. In the production line of the three-stage etching machine, a large circulation volume (40m 3 / H).

[0063] In Example 1 and Example 2, the etching regeneration liquid and the etching waste liquid are stored separately, and the ORP value of the obtained etching waste liquid is lower than 490mV, and the monovalent copper concentration is greater than 4g / L, so that the concentration of monovalent copper ions entering the anode chamber is maintained at a certain value, and its ORP value is increased by electrolysis. Compared with the comparative example, since the monovalent copper concentration in the etching waste liquid entering the electrolysis unit is greatly increased (from 0.4g / L to 4g / L), the risk of anode chlorine precipitation is reduced, the generation of chlorine gas is suppressed, and the consumption of oxidant is significantly reduced (from 60kg per ton of copper in the comparative example to 20kg per ton of copper), and the circulation volume required between the etching production line and the electrolysis production line is also significantly reduced. The circulation volume of the production line of the three-stage etching machine is 40m 3 / H reduced to 20m 3 / H.

[0064] For those skilled in the art, the invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the invention; therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the invention is defined by the appended claims rather than the above description, so it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any minor modifications, equivalent substitutions and improvements made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the technical solution of the present invention.

Claims

1. A chlorine-free electrolysis circulation system for PCB acid etching solution, comprising an etching spray unit, an etching solution collection unit, an additive adding unit and an electrolysis unit, characterized in that: It also includes a regeneration liquid collecting unit. The output end of the etching spray unit is connected to the etching liquid collecting unit, the electrolysis unit, and the regeneration liquid collecting unit in sequence; the output end of the regeneration liquid collecting unit is connected to the input end of the etching spray unit.

2. A PCB acid etching solution chlorine-free electrolysis circulation system according to claim 1, characterized in that: The regeneration liquid collecting unit is communicated with the auxiliary agent adding unit.

3. A PCB acid etching solution chlorine-free electrolysis circulation system according to claim 1, characterized in that: The electrolysis unit comprises an anode chamber, a cathode chamber and a cation exchange membrane located between the anode chamber and the cathode chamber; The output end of the etching waste liquid collection unit is connected to the input end of the anode chamber and the input end of the cathode chamber respectively, and the output end of the anode chamber is connected to the input end of the regeneration liquid collection unit.

4. A PCB acid etching solution chlorine-free electrolysis circulation system according to claim 3, characterized in that: The anode chamber is provided with an ORP monitor, and the cathode chamber is provided with a specific gravity monitor.

5. A PCB acid etching solution chlorine-free electrolysis circulation system according to claim 1, characterized in that: An etching waste liquid pump is provided between the output end of the etching liquid collecting unit and the input end of the electrolysis unit; An electrolysis recycling pump is provided between the output end of the electrolysis unit and the input end of the regeneration liquid collection unit; A spray pump is provided between the output end of the regeneration liquid collecting unit and the input end of the etching spray unit.

6. A regeneration process of the chlorine-free electrolytic circulation system for PCB acid etching solution based on any one of claims 1 to 5, comprising a process of electrolyzing the etching waste liquid to obtain an anolyte and a process of regenerating and reusing the obtained anolyte, characterized in that: The ORP value of the electrolytically treated etching waste liquid is less than 490mV, and the concentration of monovalent copper ions is greater than or equal to 4g / L. The process of regenerating and reusing the anolyte is that the anolyte flows to the regeneration liquid collection unit and is then reused in the etching operation.

7. The regeneration process of CB acid etching solution without chlorine electrolysis according to claim 6, characterized in that: The main components of the acidic etching solution are CuCl2, HCl, and NaCl, wherein the concentration of divalent copper ions is 120-140 g / L, the concentration of chloride ions is 260-300 g / L, and the acidity is 1.5-3.0 mol / L.

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