JPH0718473A - Method for restoring and maintaining liquid etchant capacity - Google Patents

Abstract

PURPOSE:To accelerate the electrolytic oxidation reaction of an anode and to continuously restore and maintain the capacity of a liq. etchant by linking an electrolytic cell with an etching device in operation. CONSTITUTION:An electrolyte-permeable anode 8 consisting of a porous material is provided in an anode compartment 5, an electrolytic cell is divided by a proton permselective cation-exchange membrane 7 into the anode compartment 5 and cathode compartment 6, and a liq. etchant contg. ferrous ion or ferric ion or cuprous ion and cupric ion is continuously supplied from the inlet of the anode compartment 5, permeated through the anode 8 and oxidized. Consequently, the area of the electrode plate is reduced, and the capacity of the etchant is continously restored and maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to ferric ions or
The present invention relates to a method of recovering and maintaining the ability of an etching solution containing copper ions as a main component and etching a metal to be etched with the ferric ions or the cupric ions.

[0002]

2. Description of the Related Art In recent years, electronic products have been widely used, and the production amount thereof has been increasing more and more. As a result, the use amount of etched parts has been increasing. In particular, the amount of printed wiring parts used is increasing.

By the way, in order to manufacture a printed wiring, a circuit is drawn by drawing a circuit with a masking agent on a copper foil substrate in which a copper foil is stuck on an insulating plate, and then dissolving the unmasked portion with an etching solution. Widely used is to melt the non-masking part by forming the electric circuit by drawing the necessary parts to make an electric circuit or drawing a wiring diagram on a stainless steel thin plate and then melting the non-masking part to make a lead frame. Various aqueous solutions containing an oxidizing agent having the action of dissolving copper and the like are used as the etching solution for the purpose, but from the viewpoint of dissolution rate and quality, an aqueous solution of ferric chloride or cupric chloride is used. Widely used.

Further, as described above, when the metal is continuously etched by using the etching solution containing the ferric ion or the cupric ion as the main component, the ferric ion in the etching solution becomes ferrous iron. Since the copper ion and the cupric ion are reduced to the cuprous ion and the etching ability is gradually lowered, the etching solution having the lowered etching ability has been conventionally used, for example, sodium hypochlorite (NaClO) or excess. An oxidizing agent such as hydrogen oxide is added to oxidize ferrous ions or cuprous ions to form ferric ions or cupric ions to chemically recover the etching ability of the solution. There are also things. However, in this method, every time the oxidation treatment with the oxidizing agent is performed, NaCl
Such by-products will be accumulated, and the accumulation of these by-products will limit the number of times that the solution can be regenerated, and a large amount of water will enter with the oxidizer and the concentration of the solution will decrease. was there.

Therefore, as a regenerating method for electrochemically recovering the etching ability of an etching solution containing ferric ion or cupric ion as a main component without producing a by-product such as NaCl, for example, Japanese Patent Laid-Open Publication No. Hei 2 -310382
The one described in Japanese Patent Publication is known.

[0006]

However, this regenerating method uses an electrolytic cell having an anode chamber and a cathode chamber to fill the entire amount of the etching solution in the anode chamber and adjust the iron ion concentration of the etching solution. Then, the direct current is used to oxidize the ferrous ions of the etching solution to ferric ions to restore the etching ability. That is, since the etching solution is regenerated by a so-called batch process in which the entire amount of the etching solution is taken out and regenerated while the etching apparatus using the etching solution is stopped, the etching solution cannot be regenerated in conjunction with the operation of the etching apparatus. There was no problem. Further, since the anion exchange membrane is used while accommodating the aqueous solution containing hydrochloric acid in the cathode chamber, chlorine ions will move from the cathode chamber to the anode chamber by energization,
There is also a problem that the balance of chlorine ion concentration in the etching solution and in the electrolytic solution in the cathode chamber must always be controlled.

An object of the present invention is to provide a method for recovering and maintaining the capacity of an etching solution by increasing the rate of electrolytic oxidation reaction at the anode and continuously recovering and maintaining the etching capacity of the etching solution while interlocking with the operating etching solution apparatus. It is in.

[0008]

In order to achieve the above object, the ability recovery maintaining method according to claim 1 is, for example, as shown in FIG.
The electrolysis cell shown in Fig. 2 is used, and the electrolysis cell sandwiches an anode 8 made of a porous material permeable to an electrolytic solution, an anode chamber 5 having an inlet 11 and an outlet 12 on both sides, a cathode 13 and an inorganic material. A cathode chamber 6 having an inlet 32 and an outlet 33 for a cathode electrolyte of an acid aqueous solution or an aqueous salt solution is provided, and the anode chamber 5 and the cathode chamber 6 are partitioned by a proton selective permeable ion exchange membrane 7. An etching solution containing ferrous and ferric ions or cuprous and cupric ions in the etching solution storage tank 1 is supplied from an inlet 11 of the anode chamber 5 to obtain a liquid-permeable porous anode 8 Of the cathode 13 and the anode 8 while the cathode electrolyte is supplied from the cathode electrolyte storage tank 30 by the circulation pump 31 from the inlet 32 of the cathode chamber 6 and flows out to the outlet 33. Apply a direct current to the Iron ions or cuprous ions continuously oxidized to ferric ions or cupric ions,
The etching ability of the etching solution is recovered and maintained.

The porous material forming the anode 8 is a liquid-permeable porous plate made of a material having a corrosion resistance that is not etched by an etching solution, for example, carbon, titanium, zirconium, tartan and their alloys, preferably carbon. As the anode 8, for example, an electrode of a porous graphite plate, an electrode obtained by coating a porous plate obtained by processing powdery or fibrous titanium into a plate with a catalyst layer, and the like are used. Further, the cathode may be made of any material that is resistant to corrosion and is not corroded by the cathode electrolyte. For example, a stainless plate is used in a dilute sulfuric acid aqueous solution or a salt aqueous solution.

That is, the use of the above-mentioned porous plate for the anode 8 is one of the features of the method of the present invention, in which the electrode plate area increases and the reaction proceeds rapidly, which enables continuous treatment, and Since the reaction can be performed until the concentration of the ferrous ion or the cuprous ion becomes extremely thin, the electrolytic oxidation treatment can be performed until the etching ability is sufficiently restored. A catalyst may be attached to the anode to further accelerate the reaction.

Noble metal oxides, preferably platinum group metals such as iridium, ruthenium, palladium and platinum, or oxides thereof are effective as the catalyst.

Further, in the present invention, a cation exchange membrane having proton selective permeability is used as an ion exchange membrane for partitioning the anode chamber and the cathode chamber to prevent metal ions in the anode chamber from flowing out to the cathode chamber. That is also one of the features of the present invention. Therefore, it is possible to use an aqueous solution of an inorganic acid or an aqueous solution of a salt as the electrolytic solution in the cathode chamber.

Some of the cation exchange membranes having a proton selective permeability permeate protons 5 to 10 times faster than iron and copper ions. If such a cation exchange membrane is used, the cathode chamber is Almost no metal ions move. Even if some mixed metal ions are deposited as metal on the cathode, the concentration is extremely thin, so it does not adhere firmly to the electrode and is discharged to the outside by the circulating electrolyte solution. It can be filtered off.

The acidic electrolyte is an aqueous solution of a mineral acid such as sulfuric acid, hydrochloric acid or nitric acid, and the aqueous salt solution is NaCl or K.
Cl, CaCl ₂ , Na ₂ SO ₄ , K ₂ SO ₄ , NaN
Common salt aqueous solutions such as O ₃ and KNO ₃ can be used. The concentration is not particularly limited, but an aqueous solution of about 0.1 to 5 mol is preferable.

The completed equipment may have a large number of electrolysis units so as to have a capacity suitable for the throughput. Each electrolysis unit can be connected either in series or in parallel.

The embodiment shown in FIG. 1 shows a two-tank type partitioned by an insulating partition plate 4, and the etching apparatus 1 is installed at the inlet 11 and the outlet 12 of each anode chamber 5 in each of these tanks.
The etching liquid supply pipe 2 and the regenerated etching liquid return pipe 3 extending from the etching liquid storage tank 1 of 0 are connected,
A circulation pump 14 provided in the supply pipe 2 forms a circulation path between the liquid storage tank 1 and the circulation pump 14.

Further, the supply pipe 2 and the return pipe 3 are provided with ORP measuring devices 15 and 16 for measuring the oxidation-reduction potential ORP of the etching liquid, and the liquid storage tank 1 is provided with a PH.
A measuring device 17, a pycnometer 18 and an ion concentration meter 19 for ferric ion or cupric ion 19 are provided, and a chlorine gas detector 20 is provided at the gas phase portion on the outlet side of the anode chamber 5 to provide an etching solution. Capacity, that is, whether or not the etching solution can be determined, and the Baume value of the etching solution can be controlled to a predetermined value, and the desired hydrochloric acid content necessary for the reproduction of the etching solution can be supplied, With this etching solution, the ability recovery and maintenance of the etching solution according to the object to be etched and the purpose can be automatically controlled. That is, based on the measurement result of the PH measuring device 17, by driving the hydrochloric acid injection pump 21, a desired hydrochloric acid solution can be replenished from the hydrochloric acid tank 22, and water injection is performed based on the measurement result of the hydrometer 18. By driving the pump 23, it is possible to replenish a desired amount of water from the water tank 24 and control the Baume value of the etching liquid to a predetermined value.

Therefore, when the capacity recovery process of the etching liquid is performed, the ORP value is measured by the ORP measuring devices 15 and 16, and the ORP value is measured by the PH measuring device 17 and the hydrometer 18.
The H value and the Baume value can be controlled by controlling the electrolytic current while measuring the chlorine gas concentration by the chlorine gas detector 20 and controlling the replenishment of the hydrochloric acid solution and water. Can be maintained at a predetermined value according to the type and purpose of etching, and its performance can be recovered and maintained. Also, by controlling the electrolysis current, operation without chlorine gas generation can be performed. Electrolyte temperature is 40 ~
The temperature is preferably 60 ° C., and the current density is 5 to 10
0 mA / cm ² is preferred.

[0019]

According to the method of the present invention, an etching solution containing a little more aged ferrous ions or cuprous ions is supplied from the inlet of the anode chamber and continuously oxidized (Fe ²⁺
→ Fe ³⁺ + e or Cu ⁺ → Cu ²⁺ + e), and the ability of the etching solution is recovered, and the ability can be continuously maintained without producing a by-product.

Moreover, since the cation exchange membrane is used as the ion exchange membrane for partitioning the two electrode chambers, there is no next problem of the prior art (JP-A-2-310382) using the anion exchange membrane. That is, in the anion exchange membrane, it is necessary to correct that the electrolyte composition of the cathode chamber is constantly changing in order to move the anions in the electrolyte of the cathode chamber to the anode chamber during operation. Since anions move from the cathode chamber to the anode chamber during operation, it is not possible to use a cathode electrolyte solution containing an acid or salt of anions other than the anions contained in the etching solution. There is no problem.

Further, if an ordinary cation exchange membrane is used, during operation, metal cations in the anode chamber move to the cathode chamber, the concentration of metal ions in the cathode electrolyte increases, and these metals are deposited on the cathode surface. Because of the precipitation, the electrodes must be replaced frequently, which makes handling difficult. In addition, when the current density is increased, the deposited metal becomes dendritic, falls off from the electrode, and accumulates or floats in the electrolyte in the form of sludge, causing a short circuit.
Therefore, due to such problems, it has been considered that ordinary cation exchange membranes cannot be used, but due to recent advances in ion exchange membranes, metal ions hardly permeate, but protons selectively permeate. Membranes have been developed, and the above-mentioned problems can be solved by using this proton-selective cation exchange membrane in this method. Therefore, in the method of the present invention, the electrolytic solution in the cathode chamber does not change during operation, so that the etching solution in the anode chamber may always be controlled so as to have optimum conditions for etching.
In addition, since the cation exchange membrane has a larger ionic conductivity than the anion exchange membrane and has good durability in an acidic solution,
Suitable for this purpose.

Further, in the present invention, since the porous material is used for the anode, the following effects can be obtained. That is, the concentration of ferrous ions or cuprous ions in the etching solution supplied from the solution inlet to the anode chamber is often low, and particularly when the electrolytic solution in use is continuously treated. In such a case, if the reaction on the anode does not proceed quickly, it cannot be continuously processed by being attached to the etching equipment, and there is no choice but to perform batch processing. If the concentration of ferrous ions or cuprous ions is low, chlorine ions are easily oxidized and chlorine gas is likely to be generated.
However, in the method of the present invention, the anode electrode is formed of a porous material, and since the electrolytic solution is devised so as to undergo electrolytic oxidation while passing through the porous anode, the electrode area is usually smaller than that of the impermeable electrode. The reaction rate is increased by several tens of times, the chlorine gas is not generated, and the electrolytic oxidation can be continuously performed at a high current density even when the concentration of ferrous iron or cuprous ion in the etching solution is extremely low. Therefore, the total electrode area can be kept to a minimum and the equipment can be downsized, and the equipment cost can be reduced and the economic effect can be great. Further, a noble metal oxide, mainly ruthenium oxide, on the anode made of the porous material,
It is possible to promote the oxidation reaction by supporting a catalyst composed of iridium oxide, and by using carbon for the anode, it is possible to obtain corrosion resistance to an etching solution, and in comparison with a corrosion resistant material such as titanium. This is advantageous in terms of workability and cost.
Further, according to the invention of claim 5, it is possible to control the PH value and the Baume value according to the type of etching and the purpose.

[0023]

【Example】

[0024]

[First embodiment] 4 kg on average 32 kg / day in one day (10 hours)
A storage tank 1 containing 3200 liters of the etching solution in the process of etching a lead frame for etching two alloys was directly connected to an electrolytic solution-maintaining electrolytic cell having the same structure as the electrolytic cell shown in FIG. The specifications of this capacity maintaining electrolytic cell were as follows. Arrangement of unit electrolytic cells 20 cells in series Anode 500 × 1000 mm Liquid permeability of 5 mm thickness Porous carbon plate Anode chamber 500 × 1000 × 70 mm Cathode 500 × 1000 mm 1.2 mm thick Impermeable hard graphite plate Cathode chamber 500 × 1000 × 70mm Ion exchange membrane Asahi Kasei Proton Selective Permeability Cation Exchange Membrane ORP measurement device Installed at each one inlet and outlet of treated etching solution Specific gravity meter Installed in etching solution storage tank PH Measuring instrument Same as above Fe ³⁺ concentration meter Same as above Chlorine gas detector Installed on top of electrolysis tank Etching solution temperature 45 ± 2 ℃ Etching solution is etching solution storage tank 1 in etching line
It is supplied by the circulation pump 14 at a rate of 150 liters / minute and is evenly distributed to the anode chamber 5 of each unit tank.

The etching liquid enters a portion of the portion partitioned by each porous anode 8 on the side opposite to the ion exchange membrane 7, passes through the porous anode 8 and enters the ion exchange membrane 7 side, and then the etching liquid storage tank. Return to 1. 5% in the cathode electrolyte storage tank 30
Of the hydrochloric acid solution, and the circulation pump 31
It is supplied from the inlet 32 of the above, is made to flow out to the outlet 33, and is returned to the cathode electrolytic solution tank 30.

The composition of the etching solution before use is as follows: iron ion content 15.5% (ferric chloride content 95% or more), hydrochloric acid content 0.2.
%, The nickel concentration increases as the etching progresses. Normally 42 alloy, stainless steel and other metals to be etched have a Baume value of 4 for uniform etching.
It is necessary to control the Fe ³⁺ ion concentration to be 11% or more while controlling at 6 ± 0.5. In this example, the maximum voltage was set to 150 V, and the control was performed so that the operation could be performed at the maximum voltage in which the chlorine gas was not generated. Further, hydrochloric acid was automatically supplied so that the PH value could be maintained at -0.8 ± 0.2, and water was automatically supplied so that the Baume value could be maintained at 46 ± 0.5.

When operating under the above conditions, the ORP value set before entering the anode chamber 5 of each unit electrolytic cell through the supply pipe 2 connected to the etching solution storage tank 1 is 600 on average.
In mV, electrolysis current averaged 215 A, outlet ORP measurements averaged 618 mV, and voltage averaged 100 V. The PH value is -0.8 and is kept almost constant, and the Baume value is 4
It was kept at 6.0. Thus, the total net operating time is 18
After 2 hours, the ferric ion concentration in the etching solution was kept at 11.0% or more during this period, and the etching proceeded favorably at the same rate. The components of the etching solution after use were as follows. Ferric content 11.0% Ferrous content 0.1% Hydrochloric acid 0.2% Nickel content 4.4%

[0028]

[Second Embodiment] FIG. 1 shows an etching liquid storage tank 1 containing 3200 liters of etching liquid in the process of an etching line for producing a printed circuit for etching an average copper amount of 50 kg / day for one day (10 hours). The electrolytic bath having the same structure as the electrolytic bath for maintaining the ability of the etching solution was directly connected. PH measuring device 17
The operation was carried out under exactly the same conditions as in the first embodiment except that a hydrochloric acid concentration meter was set instead of No. 2 and a ferric ion concentration meter 19 was replaced with a second copper ion concentration meter. The composition of the etching solution before use contains 15.2% of iron ions (95% or more of ferric chloride) and 3% of hydrochloric acid, and the copper concentration increases as etching proceeds. Normally, in order to perform copper etching evenly, it is necessary to maintain the Fe ³⁺ ion concentration at 7% or higher while maintaining the Baume value of 46 ± 0.5 and keep the hydrochloric acid content within the range of 1 to 5%. is there. In this example, the maximum voltage was set to 150 V, and the control was performed so that the maximum voltage in which the chlorine gas was not generated could be operated. Also,
The hydrochloric acid content was automatically supplied so as to be maintained at 3 ± 1%, and the water was automatically supplied so that the Baume value was maintained at 46 ± 0.5. The average electrolysis current when operating under the above conditions is 2
At 40 A, the voltage averaged 90V. The average hydrochloric acid content was kept at 3.0%, and the Baume value was kept at 46.0. The operation was stopped when the net operating time reached 95 hours. During this time, the ferric ion concentration in the etching solution was maintained at 7.0% or more, and the etching proceeded favorably at the same rate. The components of the etching solution after use were as follows. Ferric content 7.1% Ferrous content 0.2% Hydrochloric acid 3.2% Cupric acid content 8.8%

[0029]

[Third Embodiment] The operation was carried out under exactly the same conditions as in the first embodiment except that the number of unit electrolytic cells arranged in series was 24 and a 5% sulfuric acid aqueous solution was used as the cathode chamber electrolytic solution. The electrolysis current was 185 A on average and the voltage was 117 V on average. The etching proceeded well at a constant rate for about 178 hours. The components of the etching liquid after use were almost the same as in the first embodiment.

[0030]

[Fourth Embodiment] The operation was carried out under exactly the same conditions as in the first embodiment except that the number of unit electrolytic cells arranged in series was 26 and a 5% NaCl aqueous solution was used as the cathode electrolyte. Electrolytic current 0 average 170
A, and the voltage was 128 V on average. The etching proceeded well at a constant rate for about 186 hours. The components of the etching liquid after use were almost the same as in the first embodiment.

[0031]

First Comparative Example In the first comparative example, instead of the liquid permeable porous carbon plate of the first example, a liquid impermeable hard graphite plate having a thickness of 1.2 mm is provided at the bottom with an interval of 50 mm. The operation was performed under the same conditions as in Example 1 except that the battery was opened and set in the anode chamber.

The current is 140 A on average and the voltage is 135 V on average.
Met. When the operation was continued for about 53 hours, the Fe ³⁺ concentration meter fell ^below 11%, and the operation was stopped because it continued to decrease. In this comparative example, since the current does not flow sufficiently, the Fe ³⁺ ion concentration cannot be maintained, and the maintenance capacity of the etching solution is reduced by about 35% as compared with the first example, and sufficient performance is exhibited. The result was impossible. The components of the etching solution after use were as follows. Ferric content 10.5% Ferrous content 3.5% Hydrochloric acid 0.1% Nickel content 1.5%

[0033]

Second Comparative Example The operation was carried out under exactly the same conditions as in the first example except that a normal cation exchange membrane having no proton selectivity was used as the ion exchange membrane. The current was 225 A on average and the voltage was 100 V on average. At the beginning of the operation, the reaction proceeded in the same manner as in the first embodiment, but after the reaction started, about 5
Black brown precipitates began to appear on the cathode when time passed,
After about 10 hours, the entire surface of the cathode was covered, and eventually it became a sponge and floated on the electrolytic solution, making it impossible to continue electrolysis. Collect the precipitates generated in this way,
After washing and drying, it was found that the main component was iron, which was small in weight but large in volume.

[0034]

According to the present invention, the etching solution supplied from the inlet of the anode chamber is oxidized by the anodic reaction while passing through the anode made of the porous material, so that the etching solution can be formed without producing by-products. Ability can be continuously restored. Moreover, since the anode is made of a porous material to allow the etching liquid to permeate therethrough, the area of contact of the etching liquid with the anode can be increased, the reaction rate by the anode can be increased, and chlorine gas is also generated. Since the electrolytic oxidation can be performed without using the electrode, the capacity recovery and maintenance capacity can be increased while the electrode plate area is kept small.

In addition, since the cation exchange membrane having a proton selective permeability is used as the ion exchange membrane, there is almost no permeation of metal ions and only the protons can be selectively permeated. It does not change during the operation, and therefore, the etching solution in the anode chamber can be maintained at the ferric ion or cupric ion concentration which is the optimum condition for etching, and the regenerating ability can be improved. Further, by supporting the catalyst on the anode, the anode reaction can be promoted, the activity of the anode can be increased, the recovery of the performance of the etching solution can be promoted, and the reaction rate can be improved, which enables energy saving. Furthermore, by using carbon as the porous material forming the anode, it is chemically stable and corrosion-resistant, and more easily processed than the chemically stable materials such as titanium and platinum. It is also advantageous in terms of aspects.

Further, the hydrochloric acid content necessary for recovering the etching ability of the etching solution is replenished based on the measurement result of the PH measuring device or the hydrochloric acid concentration meter, and the Baume value of the etching solution is controlled based on the measurement result of the hydrometer. By doing so, it is possible to control the PH value and the Baume value according to the type of etching and the purpose, and it is possible to optimally perform etching with an etching solution.

As described above, the service life of the etching solution can be extended, which contributes to cost reduction, pollution prevention, and resource saving. Also, the line speed of the etching line can be stabilized,
In addition, the quality of the product after etching is stable, and thus the defect rate can be significantly reduced, which can greatly contribute to the improvement in productivity of printed circuit boards and the like by the etching process.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of an electrolytic cell used in the method of the present invention.

[Explanation of symbols]

5 Anode chamber 6
Cathode chamber 7 Proton selective permeation ion exchange membrane 8 Anode 11
Entrance 12 exit 13
Cathode 17 PH measuring instrument 18
Hydrometer

Claims (5)

[Claims] 1. A method of maintaining and recovering the ability of an etching solution, which comprises ferric ion or cupric ion as a main component and etches a metal to be etched with the ferric ion or cupric ion, wherein the electrolytic solution is permeated. With an inlet and an outlet on both sides of an anode made of a porous material having a porous property, a cathode and a cathode chamber having an electrolytic solution of an inorganic acid aqueous solution or a salt aqueous solution, and the anode chamber and the cathode chamber are defined. And an etching solution containing ferrous ions and ferric ions or cuprous ions and cupric ions from the inlet side of the anode chamber. While supplying, passing through the anode and flowing to the outlet side, a direct current is caused to flow between the cathode and the anode, and ferrous ions
A method for recovering and maintaining the capacity of an etching solution, which comprises continuously oxidizing iron ions or cuprous ions to cupric ions to recover and maintain the etching capacity of the etching solution. 2. The method for recovering and maintaining the ability of an etching solution according to claim 1, wherein a catalyst made of a noble metal oxide is supported on the anode. 3. The method for recovering and maintaining the ability of an etching solution according to claim 2, wherein a catalyst made of ruthenium oxide or iridium oxide is used as the catalyst made of a noble metal oxide. 4. The method for recovering and maintaining the ability of an etching solution according to claim 1, wherein the anode made of a porous material is made of carbon. 5. The hydrochloric acid content necessary for recovering the etching ability of the etching solution is replenished based on the measurement result of the PH measuring device or the hydrochloric acid concentration meter, and the specific gravity of the etching solution is kept constant based on the measurement result of the hydrometer. The method for recovering and maintaining the ability of an etching solution according to claim 1, which is controlled.