KR100297955B1 - Apparatus and Process for Regeneration a Used Acid Cupric Chloride Etchant - Google Patents

Abstract

The present invention relates to an apparatus and a method for regenerating a waste caustic solution which is a solution containing a metal in a bivalent form. The apparatus comprises a tank in which a caustic solution is originally supplied; A first electrolysis cell for converting the solution from the tank into a solution containing a metal in the monovalent form of the high fraction; And a second electrolytic tank for plating the metal from the solution containing the monohydric metal of the high fraction.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and a method for regenerating waste copper oxychloride caustic,

The present invention relates to a method and apparatus for regenerating copper scouring aid by electrolysis.

Copper oxychloride caustic (CuCl ₂ / HCl) is widely used in the production of printed wiring boards, especially in the production of inner layers of double-layered boards. These caustics generally account for more than 50% of printed circuit board manufacturing and are increasingly in use.

The overall reaction during copper corroding with cupric chloride / hydrochloric acid is as in Scheme 1:

Cu + CuCl ₂ = ₂ CuCl

As shown in this equation, the active caustic compound CuCl ₂ is consumed and the total solution copper is increased. Currently, most PWB machines chemically regenerate the caustic solution using oxidizing agents such as chlorine dioxide or hydrogen peroxide to revert to CuCl ₂ . In addition to risk, discomfort and chemical treatment costs, significant costs and environmental liability associated with the regular treatment of excess caustic generated are imposed. In terms of safety, chlorine-related risks can be managed. In terms of cost, chlorine is the preferred oxidizing agent. However, many PWB plants prefer to use safer, more mild hydrogen peroxide / HCl systems, despite higher prices.

The printed wiring board industry has recognized the existence of significant incentives for the environment as well as the cost of developing efficient electrolytic regeneration methods that replace chemical regeneration. One such effort to meet the requirements of the printed wiring board industry is described in U.S. Patent No. 5,421,966 to Oxley (hereinafter referred to as the '966 patent).

The '966 patent relates to an on-line regenerative electrolysis apparatus and method of a copper oxychloride corrosion bath. The apparatus uses a regeneration method that is the opposite of the reaction of Scheme (1) to simultaneously maintain the concentration of copper chloride and copper chloride within a desired range while allowing the copper metal that has been corroded into the system to be completely removed. The preferred system described in the '966 patent employs flow-through graphites or carbon anodes and flow-by cathodes that allow control of current / potential parameters. Cells including anodes and cathodes have the advantage of using low operating voltages that result in low waste heat generation and lower electrical costs. The design is simple, the control of the on-line process is improved, and work efficiency and reliability are improved even in unexpected repair and power failure.

Oxley (Oxley) device although the less, CuCl there is still more efficient and productive apparatus and methods need to regenerate the _second caustic solution.

It is therefore an object of the present invention to provide an improved apparatus and method for regenerating a caustic solution.

It is another object of the present invention to provide such an apparatus and method which have a particular utility in regenerating copper caustic corrosives.

It is a further object of the present invention to provide such an apparatus and method for producing high quality copper in the form of slabs currently being traded.

It is yet another object of the present invention to provide such an apparatus and method that operate efficiently over a wide range of current densities for ease of use at various printed circuit board processing rates.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic diagram of an apparatus of the present invention.

Figure 2 is an isometric view of a first electrolysis cell that converts a solution comprising a bivalent metal into a monovalent form.

3 is an isometric view of a second electrolytic cell plating a metal from a cathodic electrolytic solution containing predominantly the monolithic metal.

Description of the Related Art

12: waste caustic collecting barrel 14: first electrolysis cell

16: Second electrolysis cell 18: Electrolyte control tank

25: pump 42: cathode chamber

44: anode chamber 66: separating wall

The above objects are achieved by the apparatus and method of the present invention.

According to one embodiment of the present invention, the apparatus for regenerating the caustic is extensively operated in a waste fluid collection cylinder containing a supply portion of the waste caustic solution to be regenerated. This caustic agent mainly includes metals such as copper (japonica) in a bivalent form. The apparatus consists of one regulating tank which receives the caustic solution from the waste collection tank and holds a solution containing a high proportion of the metal, for example, cuprous, in a monovalent form. A first electrolytic means, such as a first electrochemical cell, acts on the solution from the conditioning tank. The first electrolysis means converts the bivalent metal in the solution supplied from the waste solution collecting bar into a solution containing a higher proportion of the metal in the monovalent form. After passing through the first electrolytic means, a solution containing a high proportion of metal in the monovalent form is returned to the regulating tank. The apparatus includes a second electrolytic means, such as a second electrochemical cell, supplied with a solution containing a high proportion of metal in monovalent form. In the second electrochemical means, the monovalent metal is converted to a metal, preferably a metal in slab form.

In a preferred embodiment of the present invention, the first electrolysis means comprises an electrolysis cell having a cathode chamber having a flow-through anode therein and a cathode chamber having a flow-through cathode therein, On the other hand, the second electrolysis means includes an electrolytic plating cell having a cathode chamber with a flow-through anode inside and a cathode chamber with a flow-by cathode inside.

A major advantage to the design of the device of the present invention is its modularity.

The cell anode and cathode chambers may be alternately arranged in a stacking order to provide a sufficient area for specific production requirements. This makes it easy to custom design the design for different corrosion capacity requirements. Moreover, the apparatus of the present invention operates at less than 2 volts compared to other caustic regeneration systems operating at 6 to 9 volts. The ability to operate at these low voltages is particularly advantageous because it lowers the cost of electricity. In addition, this eliminates the need to remove heat generated by excess power.

The method of the present invention comprises the steps of: providing a waste fluid collection container comprising a supply of a waste caustic solution to be regenerated, wherein the scouring agent comprises a metal in a predominantly bivalent form; Supplying a waste caustic solution to the regulating tank; Transporting a regulating tank solution containing spent caustic to a first electrolytic cell and converting a large number of bivalent metals in the solution into a solution containing a high proportion of said metal in monovalent form; Returning a solution containing a high proportion of metal in monosaccharide form to the conditioning tank; And simultaneously supplying the solution to the second electrolysis cell to electrolytically convert the monovalent metal in the solution from the second electrolysis cell to the metal itself. The method of the present invention also includes a step of supplying the waste caustic solution to the first and second electrolysis cells as a cathode electrolyte.

Other objects and advantages of the apparatus and method of the present invention, as well as other objects and advantages, will be described in the following detailed description and the accompanying drawings, wherein like numerals designate like elements.

To explain the drawings by reference, Figure 1 while maintaining the corrosion force of CuCl ₂ etchant containing, by reproducing with CuCl ₂ Electrolysis pirate describe online apparatus for creating a metal to sell collected from the apparatus. All of these are carried out while maintaining the corrosion agent Cu ⁺ ion concentration at a low level necessary to achieve an adequate and consistent printed wiring board corrosion rate.

Less gritty and more particularly described, the reduction of the reducing metal and the copper of Cu ⁺ to the Cu ²⁺ Cu ⁺ is a common prismatic electrolytic or electrochemical cell of Cu ⁺ Cu ²⁺ is oxidized to the anode side of each cell Respectively. The design of the prism can be used in the apparatus of the present invention using a high-efficiency porous flow-through electrode, which is a graphite or carbon electrode, which is favorable both for the oxidation of cuprous copper to copper and for the reduction of cupric copper to cuprous. By using this type of electrode, it is possible to avoid the occurrence of an incidental electrode reaction (in particular, chlorine formation at the anode which hinders access). The present inventors have found that plating copper from a solution of copper ions containing a high percentage of cuprous ions is essentially a clue to produce uniform copper electrodeposition free of resin assumptions. Copper can be easily removed from the negative electrode substrate as a single sheet, and has high purity. In addition, the higher the percentage of cuprous relative to cupric copper in solution, the higher the electrical efficiency with which copper is plated. However, if the proportion of copper in the plating solution is too low, Cu ^{+ 2} will cause copper electrodeposition in the flow-through cathode of the cell that is reduced to Cu ⁺ , which should be avoided.

Referring to FIG. 1, the apparatus 10 of the present invention operates on a pulp etchant collecting vessel 12 containing CuCl ₂ lung caustic. Typically, the caustic agent in the waste solution collecting container 12 contains 75 to 200 g / l of high concentration of Cu ²⁺ , for example, Cu ²⁺ . The apparatus includes a first electrolytic or electrochemical cell 14 known as a "knockdown" cell, and a second electrolytic or electrochemical cell 16 serving as a plating cell. In the knockdown cell, the cathodic reaction is the reduction of cupric copper to cuprous. In the plating cell, cuprous copper is reduced by the cathode to copper metal.

In addition, the apparatus 10 includes a cathode electrolyte regulating tank 18. The solution in this tank contains a high proportion of cuprous copper and the cupric concentration in the solution is preferably maintained in the range of about 0.3 to about 2.5 g / l by the knockdown cell 14. If desired, the solution may include a plating additive, such as from about 10 to about 25 ppm of a surfactant, to improve the quality of the copper precipitate by keeping the copper deposition better in terms of surface area and increasing the stiffness. The copper content of the solution remains substantially constant since copper in the solution is replenished with a corrosion solution replenishment via line 20. [ Pump 21 may be incorporated into line 20 to generate a desired flow rate. The discharge line 34 is provided to send the excess solution back from the tank 18 to the waste solution collecting container 12. The current in the knockdown cell 14 is set at a value somewhat higher than the current in the plating cell 16 to supply the plating solution from the waste solution collecting tank 12 to the cathode electrolyte tank 18 to replace the copper deposited in the plating cell (B) from the negative electrode electrolyte tank 18 to overflow from the negative electrode electrolyte to the waste solution collecting tank to provide an amount of space for the flow of the collecting tube solution into the negative electrode electrolyte tank, Thereby reducing the cupric ions in the solution supplied from the collection cylinder 12 to the cathode electrolyte tank 18. The exact knockdown cell current is determined from the anode electrolyte tank copper ion concentration and the plating cell current.

As can be seen in Figure 1, the solution of the tank 18 is supplied to the cathodes of the cells 14 and 16 by flow loops 22 and 24. Each of the loops preferably has a pump 25 or other flow control means incorporated therein to produce a desired catholyte solution flow rate. Typically, the cathode electrolyte flow rate ranges from about 8.0 cm / sec to about 50.0 cm / sec in cell 16 and from about 2.0 cm / sec to 10.0 cm / sec in cell 14.

Is supplied from the spent causticizer collecting tube 12 via the lines 28 and 29 to the positive electrode of each of the cells 14 and 16. Line 26 supplying lines 28 and 29 has a pump 27 integrated in the line to provide a desired etchant / anodic electrolyte flow rate, preferably about 1.0 cm / sec to about 6.0 cm / sec. The return lines 30 and 32 are provided to return the caustic / anodic electrolytic solution to the waste solution collecting container 12. On the anode side, the reaction taking place in each of the cells 14 and 16 is the oxidation reaction of cuprous copper to cupric copper.

Referring to FIG. 2, the knockdown cell 14 is formed by a tank 40 having a cathode chamber 42 and an anode chamber 44, which are preferably separated by a separation wall 46. Preferably, the tank is made from polyvinyl chloride (PVC), although other plastics are also acceptable. The separating wall 46 is preferably made of a porous plate, preferably a hydrophilic membrane on which hydrophilic membranes of similar size are placed, a porous ceramic plate made of sulphided glass or porous plastic, And a plate of solid PVC having a hole in it. A gasket (not shown) is provided on both sides of the separating wall 46 to seal the cell. Each of the chambers 42 and 44 provides the inlets 43 and 45 and the outlets 47 and 49 for the cathode electrolyte and the anode electrolyte, respectively.

The anode chamber 44 includes an anode 48 and the cathode chamber includes a cathode 50. [ These two large surface areas are formed from flow-through porous electrodes, preferably graphite or carbon felt. This type of electrode is used for both positive and negative electrodes due to the low ionic concentration of the reaction promoted in each electrode.

3, the plating cell 16 also comprises a cathode 60 having a cathode chamber 62 separated by a separation wall 66 and a tank 60 having an anode chamber 64. The tank 60 is also made from a chemically resistant plastic, preferably PVC. Further, the separation wall 66 is also preferably formed by a plate of solid PVC with a porous window (as described above). A gasket (not shown) is also provided on both sides of the separation wall 66 to provide cell seal. Inlets 61 and 63 and outlets 65 and 67 are provided in each of the chambers 62 and 64 so that each cathode electrolyte / anode electrolyte can flow through it.

The cathode chamber 62 preferably has one or more cathodes 68, each of which is a flow-by-graphite plate cathode. The cathode (s) 68 are arranged so that the cathode (s) can be periodically removed to recover the plated copper metal thereon. The anode chamber 64 preferably has a cathode 70, which is preferably a flow-through porous electrode, preferably a graphite or carbon felt.

The anode and cathode (s) of each of cells 14 and 16 are connected to a suitable power supply (not shown) to provide the desired current level. Suitable electrical connections known in the art may be used to connect the positive and negative electrodes to the power supply. In a 100 g / hr system, a current of about 65.8 amperes is provided across the anode and cathode in the kneaded cell 14, and a current of 46.9 amperes is provided across the anode and cathode in the plating cell 16 Oxidation and reduction reactions may occur.

The inventors have found that using the apparatus 10 of the present invention, the copper plating rate can be performed at 0.18 grams / hour per square centimeter. Moreover, acceptable quality deposits can occur at current densities up to about 120 mA / cm < ² >.

One of the advantages of plating copper from a solution having a high copper ion concentration is that intermittent operation is possible. The already plated copper remains unmelted even when the plating current is interrupted and the negative electrode is still immersed in the negative electrode electrolyte. This is a great advantage for a small printed circuit board factory to choose non-continuous operation while still maintaining constant operating conditions.

In operation, a constant concentration of Cu²⁺Ions containing CuCl₂ The waste caustic is placed in the waste solution collecting container 12, which can be collected in the corrosion system. The pulverulent caustic is supplied to the cathode electrolyte control tank 18, which is a tank that overflows the same amount of low copper content solution into the pulp caustic pool. The solution from the cathode electrolyte control tank is supplied to the cathode of the knockdown cell 14. The corrosive agent from the waste solution collecting container 12 is supplied to the anode of the cell 14. On the negative electrode side, Cu²⁺The ion is a constant concentration of Cu⁺Ions. The reduced cathode electrolyte solution is returned to the tank 18. On the positive electrode side of the cell 14, a low-concentration Cu⁺≪ / RTI >²⁺. At the same time, the negative electrode electrolyte containing a high proportion of cuprous ion is supplied from the tank 18 to the negative electrode of the plating cell 16 and the corrosive agent from the waste solution collecting tank 12 is supplied to the positive electrode of the plating cell 16. The current is applied across the cell 16. On the cathode surface, the copper metal is plated from the cathode electrolyte to the cathode surface. On the anode electrolyte surface of the cell 16, Cu⁺Cu²⁺.

If desired, the N ₂ batch padding on the cathode electrolyte solution to the Cu ⁺ can substantially prevent or minimize the oxidation chemically by Cu ^2+.

While the present invention has been described in terms of regenerating a CuCl ₂ caustic solution, it should be appreciated that the apparatus and method of the present invention can be used to regenerate other types of solutions.

Apparatus and methods for regenerating a CuCl ₂ caustic solution, which satisfies the objects, methods and advantages previously described in accordance with the present invention, are clearly provided. It will be apparent to those skilled in the art that other variations, changes and alternatives may be made to the invention. These variations, variations and alternatives are intended to be included in the disclosure of the present invention.

A major advantage to the design of the device of the present invention is its modularity. The cell anode and cathode chambers may be alternately arranged in a stacking order to provide a sufficient area for specific production requirements. This will facilitate custom production of the design for different corrosion capacity requirements. Moreover, the apparatus of the present invention operates at less than 2 volts, as compared to other caustic regeneration systems operating at 6 to 9 volts. The ability to operate at these low voltages is particularly advantageous because it lowers the cost of electricity. In addition, this eliminates the need to remove heat generated by excess power.

Claims (5)

Means for supplying a solution of a scavenging agent containing copper (III) chloride in hydrochloric acid to the conditioning tank (18); (18) connected to said regulating tank (18), said solution containing said copper containing bivalent copper from said regulating tank (18) and converting said solution with said bivalent copper to a solution comprising monovalent copper, A first electrochemical cell comprising an anode chamber (44) having an anode (48) therein and a cathode chamber (42) having a flow-through cathode (50) therein; Means for sending said solution comprising said monovalent copper back to said conditioning tank (18); Means (34) for returning the overflowing solution from the regulating tank (18) back to the waste solution collecting tank (12); (68) is connected to the cathode chamber (62) and the flow chamber (62) in which the flow-through cathode (68) is located, - a second electrochemical cell (16) consisting of a plating cell comprising an anode chamber (64) with a through anode (70) inside; And Means for supplying the waste caustic solution to the anode chamber of the first and second electrochemical cells as a cathode electrolyte, Waste liquid gathering tub 12. Device for recovering the waste caustic solution of CuCl _2, including. The apparatus of claim 1, wherein the flow-through anode (48) and the flow-through cathode (50) are each formed by flow-through electrodes formed from graphite or carbon felt. 3. The apparatus according to claim 2, wherein the corrosive solution is supplied to the anode chamber (44) and the solution containing monovalent copper is supplied to the cathode chamber (42). The apparatus of claim 1, wherein the anode (70) comprises a flow-through graphite or carbon felt anode, and the cathode (68) comprises a flow-bygraphite plate cathode. Feeding a large amount of spent caustic solution containing divalent copper to the conditioning tank 18 at a concentration ranging from about 0.3 g / l to about 2.5 g / l; Sending a solution overflowing from the regulating tank (18) to the waste solution collecting container (12); Supplying a solution from said conditioning tank (18) to a first electrochemical cell (14); Converting the solution having the bivalent copper in the first electrochemical cell (14) to a solution containing monovalent copper by electrolysis; Returning said solution containing said monovalent copper to said regulating tank (18); Supplying a solution containing said monovalent copper from said conditioning tank (18) to a second electrochemical cell (16); Converting said monovalent copper in said solution into a metal by electrolysis in said second electrochemical cell (16); And And supplying the spent caustic solution to the anodic chambers of the first and second electrolytic cells as a positive electrode electrolytic solution in order to regenerate the spent CuCl ₂ caustic solution in the waste solution collecting basin.

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