Method for regenerating removal solution and method for producing regenerated removal solution

Abstract

This method for regenerating a remover liquid comprises: a step wherein a nickel / chromium-containing layer is removed from a substrate, which is provided with the nickel / chromium-containing layer and a copper-containing layer, with use of a remover liquid during the production of a printed wiring board by means of a semi-additive method; a step wherein the remover liquid after use is recovered; and a step wherein the remover liquid, which has been recovered in the recovery step, is brought into contact with a chelating resin. With respect to this method for regenerating a remover liquid, the chelating resin has a functional group represented by formula (1). In formula (1), a plurality of R moieties represent a same divalent hydrocarbon group having from 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted by halogen atoms.

Description

[Technical Field]

[0001] The present disclosure relates to a method for regenerating a removal solution and a regenerated removal solution.

[0002] This application claims priority to Japanese Application No. 2020-194326, filed on November 24, 2020, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0003] As electronic devices become smaller and lighter, efforts are being made to miniaturize the wiring portions of printed wiring boards. One method for miniaturizing the wiring portions of printed wiring boards involves, for example, forming a seed layer on the surface of an insulating resin layer, covering the area other than the circuit area with a plating resist, and then selectively forming a metal layer only on the circuit area by electroplating. Furthermore, after removing the plating resist, the seed layer other than the circuit area is removed using a seed layer remover to form a printed wiring board (see JP 2004-6773 A). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2004-6773 Summary of the Invention

[0005] The method for regenerating a remover according to the present disclosure includes, during the production of a printed wiring board by a semi-additive process, a step of removing a nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer using a remover; a step of recovering the used remover; and a step of contacting the remover recovered in the recovering step with a chelating resin, wherein the chelating resin has a functional group represented by the following formula (1):

[0006] [ka] (In formula (1), multiple R's are the same divalent hydrocarbon group having 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted with halogen atoms.) DETAILED DESCRIPTION OF THE INVENTION

[0007] [Problem to be solved by the invention] For example, in the manufacture of printed wiring boards, a seed layer is formed on a substrate, and a copper plating layer or the like is laminated thereon. Examples of seed layers include layers containing nickel and chromium. Part of such seed layers is removed during the manufacturing process, and a nickel-chromium-containing layer remover is generally used for this removal. A nickel-chromium-containing layer remover is a solution for removing the nickel-chromium-containing layer. Hereinafter, this may be simply referred to as the remover. Such removers cannot be reused. This is because, when the seed layer is immersed in the remover, metal components from other layers of the printed wiring board dissolve in the remover, increasing the metal concentration in the remover and resulting in reduced etching performance.

[0008] In particular, in fine printed wiring boards, a decrease in etching performance can cause peeling of wiring portions, which ultimately affects the performance of the circuit board.

[0009] The present disclosure has been made based on these circumstances, and aims to provide a method for regenerating a remover that can extend the life of the remover and obtain a regenerated remover that can suppress peeling of wiring portions when used in the manufacture of printed wiring boards.

[0010] [Effects of this disclosure] According to the present disclosure, it is possible to produce a regenerated remover that can extend the life of the remover and suppress peeling of wiring portions when used in the manufacture of printed wiring boards.

[0011] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] The method for regenerating a remover according to the present disclosure includes, during the production of a printed wiring board by a semi-additive process, a step of removing a nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer using a remover; a step of recovering the used remover; and a step of contacting the remover recovered in the recovering step with a chelating resin, wherein the chelating resin has a functional group represented by the following formula (1):

[0013] [ka] (In formula (1), multiple R's are the same divalent hydrocarbon group having 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted with halogen atoms.)

[0014] The remover used to remove the nickel-chromium-containing layer generally contains hydrochloric acid, sulfuric acid, etc. In addition to nickel and chromium, such removers also dissolve a small amount of copper contained in the wiring. The copper dissolution rate increases as the copper ion concentration in the remover increases. Therefore, the life of the remover is determined by the copper ion concentration in the remover. The inventors believed that maintaining a low copper ion concentration in the remover is necessary to extend the life of the remover and prevent peeling of the manufactured circuit, and conducted extensive research. As a result, they discovered that copper ions in the remover can be adsorbed onto a chelating resin having a functional group represented by the above formula (1) by contacting the remover with a chelating resin. The method for regenerating the remover involves recovering the used remover after the semi-additive process for removing the nickel-chromium-containing layer and contacting it with a chelating resin having a functional group represented by the above formula (1). This reduces the copper ion concentration in the regenerated remover. The regenerated remover has a reduced copper ion concentration, which makes it possible to suppress the progress of dissolution of copper contained in the wiring portion during the process of removing the nickel-chromium-containing layer while improving the removal effect of the nickel-chromium-containing layer, thereby suppressing peeling of the wiring portion.

[0015] The functional group is preferably a bis(2-pyridylmethyl)amino group. When the chelating resin has the functional group represented by the formula (1), the effect of removing the nickel-chromium-containing layer can be further improved.

[0016] In addition, a regenerated removal solution according to another embodiment of the present disclosure is a regenerated removal solution for a semi-additive process obtained by the regeneration method, and contains a pyridine-based compound, and the concentration of the pyridine-based compound is preferably more than 0 ppm and not more than 5000 ppm. Such a regenerated removal solution has a good effect of removing a nickel-chromium-containing layer.

[0017] Preferably, the regenerating and removing solution further contains chloride ions and copper ions, has a pH of 1 or less, and has a copper ion concentration of 1 ppm or more and 2000 ppm or less, which can further improve the removal effect of the nickel-chromium-containing layer.

[0018] [Details of the embodiments of the present disclosure] Hereinafter, a method for regenerating a remover solution and a regenerated remover solution according to an embodiment of the present disclosure will be described in detail.

[0019] <How to regenerate the removal solution> The method for regenerating a removing solution according to the present disclosure is a method for producing a printed wiring board by a semi-additive process, comprising the steps of: removing a nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer using a removing solution; recovering the used removing solution; and contacting the removing solution recovered in the recovering step with a chelating resin, wherein the chelating resin has a functional group represented by the following formula (1). The "step of removing the nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer using a removing solution" is sometimes referred to as the "step of removing a nickel-chromium-containing layer." The "step of recovering the used removing solution" is sometimes referred to as the "step of recovering the used removing solution." The "step of contacting the removing solution recovered in the recovering step with a chelating resin" is sometimes referred to as the "step of contacting the recovered removing solution with a chelating resin."

[0020] [ka] (In formula (1), multiple R's are the same divalent hydrocarbon group having 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted with halogen atoms.)

[0021] (Step of removing the nickel-chromium-containing layer) This process is carried out in the manufacturing process of a printed wiring board using a semi-additive process. The substrate having the nickel-chromium-containing layer and the copper-containing layer is not particularly limited as long as it includes at least a nickel-chromium-containing layer and a copper-containing layer. The substrate is a substrate in the middle of manufacturing a printed wiring board using a semi-additive process. Such a substrate is manufactured, for example, by the following method.

[0022] First, a base film is prepared. The base film may be made of, for example, polyimide, polyethylene terephthalate, liquid crystal polymer, or fluororesin. A nickel-chromium-containing layer is laminated thereon. Examples of lamination methods include electroless plating, sputtering, vapor deposition, and coupling agent application. A copper-containing conductive layer is laminated on the nickel-chromium-containing layer. Examples of methods for laminating the conductive layer include electroless plating, coating a metal microparticle dispersion containing dispersed metal microparticles, drying and sintering, sputtering, and vapor deposition. Next, a resist film having openings corresponding to the wiring pattern is laminated on the conductive layer. Examples of methods for laminating the resist film include coating and drying a liquid resist composition, and thermocompression bonding a sheet-shaped resist composition. The sheet-shaped resist composition may be, for example, a dry film. Next, a copper plating layer is formed on the conductive layer exposed through the openings in the resist film. The resist film is then removed. The resist film can be removed using a known remover, primarily composed of, for example, 2-amineethanol, tetramethylammonium hydroxide, or an organic acid. The conductive layer exposed by removing the resist film is then removed. The conductive layer can be removed using, for example, a sulfuric acid-hydrogen peroxide solution, sometimes called piranha solution.

[0023] The substrate thus obtained is a substrate having at least a nickel-chromium-containing layer and a copper-containing layer on a base material.

[0024] Next, the nickel-chromium-containing layer is removed from the substrate having the nickel-chromium-containing layer and the copper-containing layer using a remover. Here, the nickel-chromium-containing layer is dissolved and removed using a remover that corrodes nickel and chromium. The dissolution is performed, for example, by placing the remover in a liquid tank and immersing the substrate in the remover.

[0025] The unused remover preferably contains chloride ions and has a pH of 1 or less. By removing the nickel-chromium-containing layer under strongly acidic conditions with a pH of 1 or less, the effect of removing the nickel-chromium-containing layer can be further improved. The strong acid component is preferably hydrochloric acid, and specifically, an aqueous hydrochloric acid solution with a concentration of 5% by mass or more and 20% by mass or less is preferred.

[0026] The remover used may be an unused remover, a regenerated remover (described later), or any combination of unused remover, regenerated remover, and used remover.

[0027] In the nickel-chromium containing layer removing step, the nickel-chromium containing layer is removed by dissolving it.

[0028] (Process for collecting used removal solution) In this step, the used remover (hereinafter also referred to as used remover) is recovered. The used remover has a higher copper ion concentration than an unused remover because copper from the copper-containing layer is dissolved therein. As the copper ion concentration in the remover increases, the copper dissolution rate increases. Therefore, the lifetime of the remover is determined by the copper ion concentration in the remover. Therefore, after the step of obtaining the used remover according to the present disclosure, a step of measuring the copper ion concentration of the used remover may be optionally provided. If the measurement result shows that the copper ion concentration is lower than a predetermined concentration, the used remover can be reused as is. On the other hand, if the copper ion concentration is higher than the predetermined concentration, the remover can be regenerated in the next step. The remover is recovered in the step of recovering the remover from the nickel-chromium-containing layer.

[0029] (Step of contacting the recovered removal solution with a chelating resin) In this step, the used removing liquid recovered in the recovering step is brought into contact with a chelating resin to regenerate the used removing liquid.

[0030] The chelating resin has a functional group represented by the following formula (1). By contacting the removing solution with this chelating resin, copper ions in the removing solution can be adsorbed, and the resulting regenerated removing solution can maintain a low copper ion concentration. This extends the life of the removing solution and improves the nickel-chromium-containing layer removal effect, while suppressing the progress of dissolution of copper contained in the wiring portion during the nickel-chromium-containing layer removal process. Furthermore, peeling of the wiring portion can be suppressed even when manufacturing fine printed wiring boards.

[0031] [ka]

[0032] In the above formula (1), multiple Rs are the same divalent hydrocarbon group having 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted with halogen atoms.

[0033] Examples of the divalent hydrocarbon group having 1 to 5 carbon atoms represented by R include a divalent chain hydrocarbon group having 1 to 5 carbon atoms and a divalent alicyclic hydrocarbon group having 3 to 5 carbon atoms. The chain hydrocarbon group may be either linear or branched.

[0034] Examples of the divalent chain hydrocarbon group include a divalent chain saturated hydrocarbon group and a divalent chain unsaturated hydrocarbon group.

[0035] Examples of the divalent chain saturated hydrocarbon group include a methanediyl group (-CH2-), an ethanediyl group (-C2H4-), a propanediyl group (-C3H6-), a butanediyl group (-C4H8-), a dimethylethanediyl group (-C4H8-), a dimethylmethanediyl group (-C3H6-), a methylethanediyl group (-C5H 10 -) etc.

[0036] Examples of the divalent linear unsaturated hydrocarbon group include an ethenediyl group (-C2H2-), a propenediyl group (-C3H4-), a butenediyl group (-C4H6-), a methylenemethanediyl group (-C2H4-), a methyleneethanediyl group (-C3H4-), a methylenepropanediyl group (-C4H6-), an ethylideneethanediyl group (-C4H6-), an ethynediyl group (-C2H2-), a propynediyl group (-C3H2-), a butynediyl group (-C4H4-), a vinylethynyl group (-C4H2-), an ethynylpropenediyl group (-C5H4-), and a pentadiynediyl group (-C5H2-).

[0037] Examples of the divalent alicyclic hydrocarbon group include a divalent alicyclic saturated hydrocarbon group and a divalent alicyclic unsaturated hydrocarbon group.

[0038] Examples of the divalent alicyclic saturated hydrocarbon group include a cyclopropanediyl group (-C3H4-), a cyclobutanediyl group (-C4H6-), and a cyclopentanediyl group (-C5H8-).

[0039] Examples of the divalent alicyclic unsaturated hydrocarbon group include a cyclopentenediyl group (-C5H6-).

[0040] Examples of halogen atoms with which some of the hydrogen atoms in the hydrocarbon group may be substituted include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms.

[0041] The functional group is preferably a bis(2-pyridylmethyl)amino group. When the chelating resin has the functional group represented by the formula (1), the effect of removing the nickel-chromium-containing layer can be further improved.

[0042] The base material of the chelating resin can be, for example, polystyrene, styrene-divinylbenzene copolymer, etc. By using such a chelating resin, the copper ions in the used removal solution can be effectively reduced.

[0043] The method for contacting the chelating resin with the used removal solution can be, for example, a method using a known chelating resin tower, in which the chelating resin is filled in the chelating resin tower, and the used removal solution is passed through the chelating resin tower to remove copper ions from the used copper-containing layer removal solution.

[0044] As another method for contacting the chelating resin with the used removing solution, the chelating resin can be directly added to the used removing solution without using a chelating resin tower, and the chelating resin can be removed by filtration after a predetermined time has elapsed.

[0045] The amount of chelating resin used is preferably 50 L or more and 200 L or less per 200 L of used removal solution.

[0046] The regenerated removal solution obtained after this step may be returned to the step of removing the nickel-chromium-containing layer. In this case, the removal step, recovery step, and contacting step may be repeated for the same substrate, and the regenerated removal solution may be circulated. Alternatively, the regenerated removal solution may be used in a subsequent step of removing the nickel-chromium-containing layer of another substrate.

[0047] <Regeneration removal liquid> The regenerated removal solution of the present disclosure is obtained by a method for regenerating the removal solution. The regenerated removal solution preferably contains a pyridine-based compound, and the concentration of the pyridine-based compound is preferably greater than 0 ppm and less than or equal to 5000 ppm. When the concentration of the pyridine-based compound is in the above range, the nickel-chromium-containing layer can be effectively removed.

[0048] When the chelating resin has a functional group represented by the above formula (1), a small amount of pyridine-based compounds derived from the functional group may be generated in the regenerating and removing solution. These pyridine-based compounds are compounds resulting from the decomposition of the chelating resin having the above functional group. The concentration of the pyridine-based compounds in the regenerating and removing solution is preferably 0 ppm or greater than 0 ppm and not greater than 5000 ppm. The presence of pyridine-based compounds in the regenerating and removing solution inhibits the removal of nickel and chromium. Therefore, by setting the concentration of the pyridine-based compounds within the above range, the inhibitory effect of the pyridine-based compounds on the removal of nickel and chromium can be reduced.

[0049] Preferably, the regenerating and removing solution further contains chloride ions and copper ions, has a pH of 1 or less, and has a copper ion concentration of 1 ppm or more and 2000 ppm or less. When the regenerating and removing solution is strongly acidic with a pH of 1 or less, the effect of removing the nickel-chromium-containing layer containing nickel and chromium can be further improved. When the copper ion concentration of the regenerating and removing solution is within the above range, the effect of removing the nickel-chromium-containing layer can be improved.

[0050] The regenerated removal solution of the present disclosure can be used as a removal solution for removing a nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer in a semi-additive process. The removal method can be, for example, the same method as described above (Step of Removing the Nickel-Chromium-Containing Layer). The regenerated removal solution may be mixed with an unused or used removal solution.

[0051] [Other embodiments] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is not limited to the configurations of the above-described embodiments, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. [Example]

[0052] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0053] [No.1~No.10] The following removers No. 1 to No. 10 were manufactured and their performance in removing nickel-chromium-containing layers from printed wiring boards was evaluated.

[0054] First, a base film made of polyimide film with an average thickness of 25 μm was prepared. In this disclosure, "average thickness" refers to the average thickness measured at five arbitrary points. A conductive pattern including 500 parallel wiring portions was formed on both sides of this base film using a semi-additive process. Specifically, a nickel-chromium-containing layer with an average thickness of 4 nm and made of nickel and chromium was first laminated. Next, a conductive layer with an average thickness of 0.2 μm and made of copper was laminated. Next, a photoresist film was laminated on almost the entire surface of the conductive layer by thermocompression bonding of an acrylic dry film resist. Next, the photoresist film was selectively exposed using a photomask to form developer-soluble and developer-insoluble portions in the photoresist film. Next, the soluble portions were washed away using a developer to form a resist pattern with openings corresponding to the formation areas of multiple wiring portions.

[0055] Next, electrolytic copper plating was carried out on the surface of the conductive layer on which the resist pattern was laminated using a copper sulfate plating bath containing 90 g / L of copper sulfate pentahydrate at 25°C, thereby laminating a metal layer with an average thickness of 10 μm.

[0056] Next, after laminating the metal layer, the resist pattern was removed using a resist remover, and then the conductive layer in the region where the metal layer was not laminated was removed using a conductive layer remover.

[0057] Next, the exposed nickel-chromium-containing layer was removed. The composition of the unused removal solution was 15% hydrochloric acid, 10% sulfuric acid, a copper ion concentration of 50 ppm, and a pH of 1 or less. To remove the nickel-chromium-containing layer, the substrate was immersed in the unused removal solution at a liquid temperature of 45°C. The nickel-chromium-containing layer removal treatment time was 30 seconds.

[0058] Next, to bring the used removal solution into contact with the chelating resin, 50 L of resin was packed into a chelating resin tower, and the used removal solution was passed through at 10 L / min. Three types of chelating resins were used: one with a bis(2-pyridylmethyl)amino group, one with an imidodiacetic acid group, and one with an aminophosphate group. The pH of the resulting regenerated removal solution was all below 1.

[0059] The copper ion concentration in the regenerated removal solution was determined by quantifying the copper ion concentration in the sample solution using an inductively coupled plasma (ICP) emission spectrophotometer.

[0060] The concentration of pyridine-based compounds in the regenerated removal solution was quantified as follows: The sample solution was diluted with water and the absorbance at 263 nm was measured using a UV-1800 ultraviolet-visible spectrophotometer manufactured by Shimadzu Corporation. The concentration of pyridine-based compounds in the regenerated removal solution was calculated and quantified using a calibration curve for bis(2-pyridylmethyl)amine prepared in advance.

[0061] The copper ion concentration and pyridine compound concentration of the regenerated removal solution were changed by adjusting the copper ion concentration of the used removal solution and the number of times the solution was passed through the chelating resin tower. The copper ion concentrations and pyridine compound concentrations of the obtained regenerated removal solution are shown in Table 1 (No. 2 to No. 10). Note that the unused No. product used was an unused removal solution containing 15% hydrochloric acid, 10% sulfuric acid, a copper ion concentration of 50 ppm, and a pH of 1 or less.

[0062] Next, a printed wiring board was obtained by carrying out the process up to the step of removing the conductive layer among the manufacturing processes for the printed wiring boards produced to obtain the above-mentioned regenerated removal solutions No. 2 to No. 10. The line and space of the printed wiring board was 10 μm / 10 μm. For the obtained printed wiring board, the nickel-chromium-containing layer in the region where no metal layer was laminated was removed using only the removal solution having the composition shown in Table 1. In the step of removing the nickel-chromium-containing layer, the substrate was immersed in the regenerated removal solution at a liquid temperature of 45°C. The nickel-chromium-containing layer removal treatment time was 30 seconds.

[0063] [evaluation] (Rate of peeling of wiring) For the printed wiring boards from which the nickel-chromium-containing layer had been removed using the removers No. 1 to No. 10, the number of peeled lines was detected by visual inspection to determine the incidence rate [%] of short circuits caused by residues of the nickel-chromium-containing layer.

[0064] (Rate of occurrence of short circuits due to nickel-chromium containing layer residue) For the printed wiring boards from which the nickel-chromium-containing layer had been removed using the removers No. 1 to No. 10, the incidence of short circuits due to the residue of the nickel-chromium-containing layer was determined by detecting the number of short circuits through an electrical inspection.

[0065] The evaluation results of the incidence of peeling of wiring portions and the incidence of short circuits due to residues of the nickel-chromium-containing layer are shown in Table 1. Note that "<10" for the pyridine compound concentration indicates that it is below the detection limit (10 ppm).

[0066] [Table 1]

[0067] As shown in Table 1, when the nickel-chromium-containing layer was removed using the regenerated removal solution (Nos. 2 to 8) regenerated with a chelating resin having a bis(2-pyridylmethyl)amino group, the occurrence of peeling of the wiring portion was low, and the results were good. In particular, Nos. 2, 4, and 5, like the unused product No. 1, did not show peeling of the wiring portion or short circuits due to nickel-chromium-containing layer residue. In Nos. 2, 4, and 5, the copper ion concentration in the regenerated removal solution was 50 ppm or more and 2000 ppm or less, and the pyridine compound concentration was 5000 ppm or less.

[0068] On the other hand, when the regenerated remover solutions (Nos. 9 and 10) regenerated with a chelating resin having an imidodiacetic acid group or an aminophosphate group were used, the occurrence rate of peeling of the wiring was high.

[0069] As described above, according to the method for regenerating a remover solution of the present disclosure, the concentration of copper ions in the regenerated remover solution can be maintained low, thereby improving the removal effect of the nickel-chromium-containing layer and suppressing the progress of dissolution of copper contained in the wiring portion during the process of removing the nickel-chromium-containing layer. Therefore, it is understood that the life of the remover solution can be extended and printed wiring boards can be obtained that can suppress peeling of the wiring portion even when manufacturing fine printed wiring boards.

Claims

1. In the manufacture of a printed wiring board by a semi-additive process, a step of removing a nickel-chromium-containing layer from a substrate having a nickel-chromium-containing layer and a copper-containing layer using a nickel-chromium-containing layer remover; a step of recovering the used nickel-chromium-containing layer removing solution; a step of contacting the nickel-chromium-containing layer removal solution recovered in the recovering step with a chelating resin, The method for regenerating a nickel-chromium-containing layer removal solution, wherein the chelating resin has a functional group represented by the following formula (1): 【Chemistry 1】 (In formula (1), multiple R's are the same divalent hydrocarbon group having 1 to 5 carbon atoms. Some of the hydrogen atoms in the hydrocarbon group may be substituted with halogen atoms.)

2. 2. The method for regenerating a nickel-chromium-containing layer removal solution according to claim 1, wherein the functional group is a bis(2-pyridylmethyl)amino group.

3. A method for producing a regenerated removal solution for a semi-additive process, comprising: A method for producing a regenerated remover solution, comprising a step of using the method for regenerating a remover solution according to claim 1 or 2.

4. The regenerated removal solution contains a pyridine compound, The method for producing a regenerated removal solution according to claim 3, wherein the concentration of the pyridine-based compound is more than 0 ppm and not more than 5000 ppm.

5. The regenerated removal solution further contains chloride ions and copper ions, 5. The method for producing a regenerated removal solution according to claim 4, wherein the regenerated removal solution has a pH of 1 or less and a copper ion concentration of 1 ppm or more and 2000 ppm or less.

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