Copper etching solution

Abstract

The invention provides a copper etching solution which can reliably inhibit electrochemical corrosion, is easy in bath management, and is excellent in etching speed. The copper etching solution of the present invention comprises an alkaline aqueous solution, and is characterized by containing 1-70 g / L of copper, 10-500 g / L of ammonia water in terms of 25% ammonia water, and 5-500 g / L of an ammonium salt, the ammonium salt is one or more ammonium salts selected from the group consisting of an ammonium salt of an inorganic acid, an ammonium salt of a sulfonic acid, an ammonium salt of a saturated fatty acid, an ammonium salt of an aromatic carboxylic acid, an ammonium salt of a hydroxy acid, and an ammonium salt of a dicarboxylic acid.

Description

[0001] This application is a divisional application of the international application PCT / JP2018 / 025863 filed on July 9, 2018, which entered the national phase on January 8, 2020, and has the Chinese national phase application number 201880045782.7, entitled "Copper Etching Solution". Technical Field

[0002] This invention relates to a copper etching solution. Background Technology

[0003] Conventionally, methods for forming circuit patterns include a subtraction process where a resist is formed on a substrate with a copper foil of approximately 20 μm covering the entire surface, followed by etching to remove the exposed copper foil. Furthermore, methods for forming finer circuit patterns include a semi-additive process (SAP) where a seed layer is formed on the surface of a resin substrate using electroless copper plating, a resist is applied to this seed layer, and a circuit is formed using electrolytic copper plating, followed by etching to remove the seed layer remaining on the substrate between the circuits.

[0004] In the semi-additive process, copper etching solutions used for etching away the seed layer, i.e., for electroless copper plating, include, for example, sulfuric acid / hydrogen peroxide type (Patent Documents 1-3), hydrochloric acid / divalent copper type (Patent Document 4), and hydrochloric acid / ferrous type (Patent Document 5).

[0005] On the other hand, in order to reduce electrical contact resistance or improve solder wettability, there are known techniques for electroplating the surface of copper that constitutes the circuit with metals that are more expensive than copper (metals with a low tendency to ionize), such as gold, silver, or palladium.

[0006] However, when using the copper etching solution described in Patent Documents 1-5 to etch copper that is conductive to a metal more expensive than copper, the etching of copper that is conductive to a metal more expensive than copper is accelerated (electrochemical corrosion) compared to copper that is not conductive to the expensive metal. As a result, problems arise such as increased circuit resistance or circuit breaks as the circuit becomes finer, or even accelerated dissolution and disappearance of the circuit, leading to the peeling (disappearance) of the plating of the expensive metal on the circuit surface.

[0007] To address the aforementioned problems, etching solutions containing hydrogen peroxide, inorganic acids, chloride ions, and cyclohexylamine or piperidine are known as suitable for use with copper that is more expensive than copper (Patent Document 6). With this copper etching solution, the inhibition effect on electrochemical corrosion decreases when the chloride ion concentration is 1 ppm, and the etching rate decreases when it exceeds 20 ppm; therefore, a chloride ion concentration of 1 to 20 ppm is preferred. When etching copper that is conductive to gold and copper that is not conductive to gold (copper alone) with this copper etching solution, the diameter of the copper conductive to gold after etching exceeds 90% of the diameter of the copper alone. Therefore, this copper etching solution is considered to have excellent performance in inhibiting electrochemical corrosion.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent No. 4430990

[0011] Patent Document 2: Japanese Patent No. 4434632

[0012] Patent Document 3: Japanese Patent Application Publication No. 2009-149971

[0013] Patent Document 4: Japanese Patent Application Publication No. 2006-111953

[0014] Patent Document 5: Japanese Patent No. 3962239

[0015] Patent Document 6: Japanese Patent Application Publication No. 2013-245401 Summary of the Invention

[0016] The problem the invention aims to solve

[0017] However, regarding the copper etching solution described in Patent Document 6, when the diameter of the copper before etching is 0.45 mm, the maximum difference in diameter between the copper connected to gold and the individual copper pieces after etching is 0.045 mm (45 μm). Therefore, this copper etching solution requires further suppression of electrochemical corrosion. Furthermore, the suitable chlorine concentration range for this copper etching solution is 1–20 ppm, necessitating strict bath management, which is difficult. Consequently, the etching rate of this copper etching solution is slow, thus requiring a higher etching rate.

[0018] The purpose of this invention is to provide a copper etching solution that can effectively suppress electrochemical corrosion, is easy to manage, and has an excellent etching rate.

[0019] Problem Solving Methods

[0020] The copper etching solution of the present invention is an alkaline copper etching solution, characterized in that it contains 1 to 70 g / L of copper, 10 to 500 g / L of ammonia when converted to 25% ammonia water, and 5 to 500 g / L of ammonium salt. The ammonium salt is selected from one or more ammonium salts selected from the group consisting of ammonium salts of inorganic acids, namely ammonium sulfate, ammonium bicarbonate, ammonium nitrate, ammonium salts of sulfonic acids, namely ammonium methanesulfonate, ammonium salts of saturated fatty acids, namely ammonium acetate, ammonium salts of aromatic carboxylic acids, namely ammonium benzoate, ammonium salts of hydroxy acids, namely ammonium lactate, and ammonium salts of dicarboxylic acids, namely ammonium oxalate.

[0021] The preferred pH value for the copper etching solution of this invention is 7.8 to 11.

[0022] As the copper etching solution of the present invention, the ammonium salt preferably contains ammonium sulfate and the content of the ammonium sulfate is 5 to 300 g / L.

[0023] As the copper etching solution of the present invention, the ammonium salt preferably contains ammonium sulfate and ammonium bicarbonate, wherein the content of ammonium sulfate is 5 to 80 g / L and the content of ammonium bicarbonate is 0.5 to 200 g / L.

[0024] As the copper etching solution of the present invention, the ammonium salt preferably contains ammonium sulfate and ammonium acetate, wherein the content of ammonium sulfate is 5-80 g / L and the content of ammonium acetate is 5-100 g / L.

[0025] The effects of the invention

[0026] The copper etching solution of the present invention is an alkaline copper etching solution containing 10 to 500 g / L of the aforementioned ammonium salt, which can suppress electrochemical corrosion. Furthermore, while the copper etching solution contains copper, ammonia, and the aforementioned ammonium salt, the concentrations of each component are not as low as ppm and have a wide concentration range, thus allowing for easy bath management. Attached Figure Description

[0027] Figure 1 This is a schematic cross-sectional view showing the shape of the circuit before etching with the copper etching solution of this embodiment.

[0028] Figure 2 A schematic cross-sectional view showing the shape of a circuit after etching with a copper etching solution of the prior art.

[0029] Figure 3 This is a schematic cross-sectional view showing the shape of the circuit etched using the copper etching solution of this embodiment.

[0030] Figure 4 This is an explanatory diagram illustrating the etching test method.

[0031] Explanation of symbols

[0032] 1. Resin substrate; 2. Two crystal layers; 2a and 2b, portions of crystal layer 2 to be etched away; 3a and 3b circuits; 4. Electrode; 5. Gold film on the circuit; 6. Nickel film on the circuit; 7. Nickel film on the electrode; 8. Gold film on the electrode; 9. Inner layer circuit; 11. Copper etching solution; 15. Copper plate; 16. Gold plate; L. Retraction amount; W. Circuit substrate. Detailed Implementation

[0033] The following describes embodiments of the copper etching solution of the present invention.

[0034] 1. Copper etching solution

[0035] The copper etching solution of this embodiment is based on an alkaline copper etching solution, characterized by containing 1-70 g / L of copper, 10-500 g / L of ammonia (equivalent to 25% ammonia solution), and 5-500 g / L of ammonium salt. The alkaline nature of the copper etching solution in this embodiment inhibits electrochemical corrosion.

[0036] Copper: Copper is a component of the copper-ammonia complex ([Cu)). II (NH3)4] 2+ The copper ions supplied by the copper-ammonia complex act as an oxidant in the copper etching solution. Examples of copper used in the copper etching solution include metallic copper, copper oxides, and copper salts. From the viewpoint of water solubility, water-soluble copper salts such as copper sulfate pentahydrate (CuSO4·5H2O) and copper carbonate are preferred; copper sulfate pentahydrate is particularly suitable from the viewpoint of ease of preparation.

[0037] The copper content in the copper etching solution ranges from 1 to 70 g / L. Within this range, a good etching rate and good bath stability are ensured. When the copper content is below 1 g / L, the insufficient copper relative to ammonia leads to a reduction in the formation of copper-ammonia complexes, resulting in a decreased etching rate, which is undesirable. A decrease in etching rate leads to a decline in production performance. On the other hand, when the copper content exceeds 70 g / L, the excess copper relative to ammonia leads to the precipitation of copper (copper hydroxide), which is also undesirable.

[0038] Ammonia: Ammonia is the source of ammonia that forms the copper-ammonia complex and can also be used as a pH adjuster. The ammonia content in the copper etching solution, when converted to 25% ammonia, is in the range of 10–500 g / L. Within this range, a good etching rate can be ensured while maintaining the pH within a range that inhibits electrochemical corrosion. When the ammonia content is below 10 g / L, insufficient ammonia relative to copper leads to copper precipitation, which is therefore undesirable. On the other hand, when the ammonia content exceeds 500 g / L, the pH becomes too high, or it becomes difficult to maintain the pH within the range of 7.8–10 during continuous use, which is also undesirable.

[0039] Ammonium salts: Ammonium salts are components that provide counterions for copper-ammonia complexes and have the function of inhibiting electrochemical corrosion. As ammonium salts, one or more ammonium salts selected from the group consisting of ammonium salts of inorganic acids such as ammonium sulfate, ammonium bicarbonate, and ammonium nitrate; ammonium salts of sulfonic acids such as ammonium methanesulfonate; ammonium salts of saturated fatty acids such as ammonium acetate; ammonium salts of aromatic carboxylic acids such as ammonium benzoate; ammonium salts of hydroxy acids such as ammonium lactate; and ammonium salts of dicarboxylic acids such as ammonium oxalate can be used.

[0040] The ammonium salt content in the copper etching solution is 5–500 g / L, which is the total amount of all ammonium salts. An ammonium salt content within this range can suppress electrochemical corrosion. An ammonium salt content below 5 g / L cannot suppress electrochemical corrosion and is therefore undesirable. On the other hand, when the ammonium salt content exceeds 500 g / L, the etching rate becomes too fast, which is also undesirable. When the etching rate becomes too fast, it becomes difficult to control the etching time after shortening it. Furthermore, it may fail to suppress electrochemical corrosion or lead to increased costs, which is also undesirable. The ammonium salt content is preferably 20–300 g / L, more preferably 50–200 g / L.

[0041] In the case of copper etching solutions containing ammonium sulfate as an ammonium salt, the ammonium sulfate content is preferably 5 to 300 g / L. When the ammonium sulfate content is below 5 g / L, the etching rate decreases, which is therefore not preferred. On the other hand, when the ammonium sulfate content exceeds 300 g / L, the etching rate becomes too fast or the bath stability decreases, making precipitation more likely, which is also not preferred.

[0042] In the case of copper etching solutions containing ammonium sulfate and ammonium bicarbonate as ammonium salts, the ammonium sulfate content is preferably 5–80 g / L, and the ammonium bicarbonate content is preferably 0.5–200 g / L. Ammonium bicarbonate can also be used as a pH buffer. When the ammonium sulfate content is below 5 g / L, the etching rate decreases, which is not preferred. On the other hand, when the ammonium sulfate content exceeds 80 g / L, the etching rate becomes too fast or the bath stability decreases, making precipitation more likely, which is also not preferred. Furthermore, when the ammonium bicarbonate content is below 0.5 g / L, the etching rate decreases, which is also not preferred. On the other hand, when the ammonium bicarbonate content exceeds 200 g / L, the etching rate becomes too fast or the bath stability decreases, making precipitation more likely, which is also not preferred.

[0043] Furthermore, in the case of copper etching solutions containing ammonium sulfate and ammonium acetate as ammonium salts, the content of ammonium sulfate is preferably 5 to 80 g / L, and the content of ammonium acetate is preferably 5 to 100 g / L. Ammonium acetate can also be used as a pH buffer. When the content of ammonium sulfate is less than 5 g / L, the etching rate decreases, which is not preferred. On the other hand, when the content of ammonium sulfate exceeds 80 g / L, the etching rate becomes too fast or cannot suppress electrochemical corrosion, which is also not preferred. Similarly, when the content of ammonium acetate is less than 5 g / L, the etching rate decreases, which is also not preferred. On the other hand, when the content of ammonium acetate exceeds 100 g / L, the etching rate becomes too fast or cannot suppress electrochemical corrosion, which is also not preferred.

[0044] In addition to the above-mentioned components, the copper etching solution of this embodiment may also contain inhibitors that inhibit copper etching or surfactants that reduce surface tension.

[0045] The copper etching solution of this embodiment contains copper, ammonia and the aforementioned ammonium salts, but the concentrations are not as low as ppm and the concentration range is wide, thus allowing for easy bath management.

[0046] pH: The preferred pH of the copper etching solution is 7.8 to 11. The pH of the copper etching solution can be adjusted, for example, by adding ammonia. When the pH of the copper etching solution is within this range, electrochemical corrosion can be effectively suppressed, resulting in excellent bath stability. A pH less than 7.8 leads to copper precipitation, which is therefore undesirable. On the other hand, it is difficult to raise the pH above 11 when only ammonia is added. Furthermore, when the pH exceeds 10, it is difficult to maintain the pH within the specified range, which is also undesirable.

[0047] Bath temperature: The bath temperature of the copper etching solution is preferably adjusted to 10–60°C. When the bath temperature is below 10°C, the etching rate slows down, which is not preferred. On the other hand, when the bath temperature exceeds 60°C, the etching rate becomes too fast and the bath stability decreases, which is also not preferred.

[0048] Etching rate: When the copper etching solution contains 1-70 g / L of copper, which is equivalent to 10-500 g / L of ammonia water when converted to 25% ammonia water, and 5-500 g / L of the above-mentioned ammonium salts, and the pH is 7.8-11 and the bath temperature is 10-60℃, it can etch copper at a rate of 0.2-40 μm / min (chemical copper plating).

[0049] Therefore, the copper etching solution according to this embodiment can achieve a higher etching rate compared to copper etching solutions composed of acidic aqueous solutions. The etching rate can be easily controlled by adjusting the concentration of the components in the copper etching solution.

[0050] 2. Etching method using copper etching solution

[0051] Next, the etching method using the copper etching solution of this embodiment will be explained. The copper etching solution of this embodiment is, for example, suitable for use in etching away seed layers remaining on the substrate between circuits after a printed circuit board has been manufactured using a semi-additive process.

[0052] The etching reaction of copper caused by copper etching solution is represented by the following formula (1). Formula (1) represents the reaction in which copper ammonia complex (2 valence) contained in copper etching solution acts as an oxidant to dissolve metallic copper, i.e., the seed crystal layer, and then generates copper ammonia complex (1 valence).

[0053] …(1)

[0054] The copper-ammonia complex (monovalent) is regenerated into a copper-ammonia complex (divalent) by the ammonia and dissolved oxygen in the copper etching solution. This regeneration reaction is represented by the following formula (2). The regenerated copper-ammonia complex (divalent) is then used again in the etching reaction of formula (1).

[0055] …(2)

[0056] Figure 1 The seed layer removed using the copper etching solution of this embodiment is shown. A seed layer 2 is formed on the surface of a resin substrate 1 by chemical copper plating. Circuits 3a and 3b and an electrode 4 are formed on this seed layer 2 by electrolytic copper plating. Subsequently, the portion 2a between circuits 3a and 3b and the portion 2b between circuit 3a and electrode 4 in the seed layer 2 are removed using the copper etching solution of this embodiment. Hereinafter, 2a and 2b will be referred to as the portions of the seed layer 2 to be etched away.

[0057] To reduce electrical contact resistance or improve solder wettability, a gold film 5 is deposited on the surfaces of circuits 3a and 3b by electroplating or electroless plating. Furthermore, to prevent copper from diffusing from circuits 3a and 3b to the gold film 5, a nickel film 6 is deposited between circuits 3a and 3b and the gold film 5 by electroplating or electroless plating. That is, a nickel film 6 is deposited on the surfaces of circuits 3a and 3b, and a gold film 5 is deposited on top of it.

[0058] Similar to circuits 3a and 3b, a nickel film 7 and a gold film 8 are deposited on the surface of electrode 4 by electroplating or chemical plating.

[0059] Circuit 3a is electrically connected to the gold film 5 disposed on its own surface, and also electrically connected to a gold film disposed on the surface of an object other than itself. In this embodiment, circuit 3a is electrically connected to the gold film 8 disposed on the surface of the electrode 4 via an inner layer circuit 9 embedded in the resin substrate 1. The inner layer circuit 9 is made of a metal with excellent conductivity, and in this embodiment, it is made of copper. Hereinafter, circuit 3a will be referred to as "a circuit that conducts with a metal more expensive than copper". The expensive metal mentioned here refers to "gold".

[0060] On the other hand, circuit 3b is only electrically connected to the gold film 5 disposed on its own surface, and not electrically connected to the gold films 5 and 8 disposed on the surfaces of objects other than itself. Among these, in Figure 1 As shown in the state before etching, circuit 3b is electrically connected to the gold film 5 disposed on the surface of circuit 3a via the seed layer 2. However, after the seed layer 2 is removed by etching, it becomes not electrically connected to circuit 3a. Therefore, it can be considered that circuit 3b is not electrically connected to any other gold films 5, 8 other than the gold film 5 disposed on the surface of circuit 3b itself. Hereinafter, circuit 3b will be referred to as "a circuit that is not conductive with a metal more expensive than copper".

[0061] Will Figure 1 When the resin substrate 1 shown is immersed in copper etching solution, ideally only the portions 2a and 2b of the seed layer 2 that need to be etched are etched. However, in reality, not only these portions 2a and 2b, but also the portions directly below the circuits 3a and 3b and the electrode 4 in the seed layer 2, and the sides of the circuits 3a and 3b themselves and the electrode 4 themselves, will undergo dissolution (undercutting). Hereinafter, the amount of undercutting of the circuits 3a and 3b will be referred to as the "retraction amount L". Furthermore, it is preferable to end the etching at the point when the portions 2a and 2b of the seed layer 2 that need to be etched are removed and the surface of the resin substrate 1 underneath is exposed. Hereinafter, the point at which the surface of the resin substrate 1 underneath is exposed after etching will be referred to as "appropriate etching". Furthermore, the thickness of the seed layer 2 is not completely uniform throughout its surface. Therefore, in order to completely and reliably remove the portions 2a and 2b of the seed layer 2 that need to be etched, etching beyond the appropriate amount is required.

[0062] As for the amount of backtracking L, for example, it can be calculated using the following formula (3).

[0063] The backoff amount L = [(diameter of circuits 3a and 3b before etching) - (diameter of circuits 3a and 3b after etching)] / 2 … (3)

[0064] Alternatively, the nickel film 6 and gold film 5 on circuits 3a and 3b may not be etched by the copper etching solution of this embodiment, so the distance from the end face of the nickel film 6 or the gold film 5 to the side face of circuits 3a and 3b may be set as the back distance L.

[0065] Figure 1 The resin substrate 1 shown includes a circuit 3a that is conductive to a metal more expensive than copper and a circuit 3b that is not conductive to the same metal. When the portions 2a and 2b of the seed layer 2 to be etched are etched using the copper etching solution described in Patent Documents 1-5, such as... Figure 2As shown, the retreat amount L of circuit 3a is significantly larger than that of circuit 3b. At this time, the increased thinning (undercutting) of circuit 3a leads to an increase in resistance or a break in the wire. Consequently, as circuit 3a disappears, the nickel film 6 and gold film 5 on the surface of circuit 3a will peel off (disappear).

[0066] In contrast, when etching the seed layer 2 using the copper etching solution of this embodiment, such as Figure 3 As shown, the retreat amount L of circuit 3a can be controlled to the same extent as in the case of circuit 3b. Furthermore, even when etching exceeds a suitable amount, the difference between the retreat amount L of circuit 3a and circuit 3b can be suppressed from increasing.

[0067] Therefore, the copper etching solution according to this embodiment can suppress electrochemical corrosion, making the etching amount of copper (circuit 3a) that is conductive to a metal more expensive than copper and copper (circuit 3b) that is not conductive to the expensive metal equal. This prevents the copper conductive to the more expensive metal from being etched excessively compared to the copper that is not conductive to the expensive metal, thus avoiding problems such as increased resistance or broken wires. Furthermore, by preventing the disappearance of the copper conductive to the more expensive metal (circuit 3a), the problem of peeling off the nickel film 6 and gold film 5 deposited on the surface of the copper can be prevented.

[0068] In this embodiment, copper is used as the conductor in circuit 3a, which is a metal more expensive than copper. Gold is used as the expensive metal. However, in addition to gold, silver, palladium, iridium, platinum, or alloys thereof can also be listed as metals more expensive than copper.

[0069] In this embodiment, for the copper circuit 3b, which is not conductive to a metal more expensive than copper, an example is given where a gold film 5 is provided on the surface of the circuit 3b itself via a nickel film 6. However, examples can also be given where no film is provided on the surface (top) of the circuit and there is no conductive connection between the circuit and the gold film provided on the surface of an object other than itself (copper that is not in contact with or conductive to a metal more expensive than copper). For such a circuit that is not in contact with or conductive to a metal more expensive than copper, the copper etching solution of this embodiment can control the retreat amount L of the circuit and the retreat amount L of the circuit 3a that is conductive to a metal more expensive than copper to be at the same level. Furthermore, in the case where no film is provided on the surface of the circuit and the surface is exposed, both the side and top of the circuit are etched. Therefore, for such a circuit, it is preferable to use the above formula (3) to calculate the retreat amount L.

[0070] The present invention will now be described in detail based on embodiments and other specific examples.

[0071] Example

[0072] 1. Etching test using circuit board

[0073] 1-1. Preparation of Copper Etching Solution

[0074] Here, etching tests were conducted using a circuit board. First, the copper etching solutions for Examples 1 to 3 shown in Table 1 were prepared. In Table 1, "-" indicates that the component was not added. In Table 1, the values ​​shown in parentheses in the column for copper sulfate decahydrate are converted to copper values. In Comparative Example 1, a commercially available copper etching solution (sulfuric acid-hydrogen peroxide, pH below 1) was used. In Comparative Example 2, a commercially available copper etching solution (acidic bath containing chlorine, pH below 1) was used. In Comparative Example 3, an acidic copper etching solution containing ferric sulfate (pH below 1) was prepared, and the bath temperature was set to 35°C.

[0075] Table 1

[0076]

[0077] 1-2. Etching Test

[0078] Secondly, as described below, etching tests were conducted using circuit boards. As test pieces, circuit boards were used that had circuits conductive to a metal more expensive than copper and circuits not conductive to the same metal on a resin substrate. For example... Figure 1 As shown, the test piece has a seed layer 2 formed on the surface of a resin substrate 1 by chemical copper plating. On this seed layer 2, circuits 3a and 3b and electrodes 4 are formed by electrolytic copper plating. Circuits 3a and 3b each have a diameter of 40 μm, and their surfaces are coated with a nickel film 6 and a gold film 5. Electrode 4 has a diameter of 100 μm, larger than that of circuits 3a and 3b, and its surface is coated with a nickel film 7 and a gold film 8. Furthermore, circuit 3a is electrically connected to the gold film 8 of electrode 4 via an inner layer circuit 9 embedded in the resin substrate 1. On the other hand, circuit 3b is electrically connected to the gold film 5 on its own surface, but not to any other gold films 5 or 8. In this test piece, 10 circuits 3a, 50 circuits 3b, and 10 electrodes 4 are mixed and disposed on the resin substrate 1, with each circuit 3a connected to one electrode 4.

[0079] The test piece was immersed in the copper etching solution of this embodiment. The time point at which the portions 2a and 2b of the seed layer 2 to be etched away disappeared and the surface of the resin substrate 1 below was exposed was defined as the appropriate etching time. The time from the start of immersion to the appropriate etching time was defined as "T". JE The test pieces were immersed in copper etching solution until T was reached. JE 3 times the time (T) JE ×3) up to. In addition, the time T from the start of impregnation to the appropriate amount of etching. JE The process varies depending on the composition, pH, and bath temperature of the copper etching solution.

[0080] Subsequently, after TJE T JE ×2、T JE At a time point of immersion time of ×3, the test piece was removed from the copper etching solution and cut parallel to its thickness direction. Subsequently, using a digital microscope, the retraction amount L of five circuits 3a and 3b on the cut surface of the test piece was measured, and their average value was calculated. The results are shown in Table 2.

[0081] In Table 2, the symbols in the "Etching Speed" column have the following meanings.

[0082] ○: Etching rate is between 1μm / min and 3μm / min.

[0083] △: Etching speed exceeds 3μm / min and is below 7μm / min.

[0084] ×: Etching rate is between 0 μm / min and 1 μm / min, or exceeds 7 μm / min.

[0085] Furthermore, in Table 2, the symbols in the "Retreat Amount" column have the following meanings. Here, ΔL is the absolute value of the difference between the retreat amount of circuit 3a and the retreat amount of circuit 3b. When this ΔL is large, it can be considered that electrochemical corrosion has occurred at least in circuit 3a.

[0086] ○: ΔL is between 0 μm and 0.3 μm.

[0087] △: ΔL exceeds 0.3μm and is less than 1μm.

[0088] ×: ΔL exceeds 1μm, or at least one of circuits 3a and 3b disappears, or the nickel film 6 and gold film 5 on their surfaces are peeled off.

[0089] Table 2

[0090]

[0091] evaluate

[0092] As shown in Table 2, for the copper etching solutions of Examples 1-3, the time T until the appropriate amount of etching is achieved... JE 3 times the time (T) JE At the time point (×3), the evaluation of the amount of retreat was also "○". Therefore, it can be seen that, for the copper etching solutions of Examples 1-3, even after the time T until adequate etching is achieved... JE 3 times the time (T) JE At time point ×3), no electrochemical corrosion occurred in circuit 3a.

[0093] Furthermore, regarding the copper etching solutions of Examples 1-3, the etching rate was evaluated as "○" or "△". This indicates that the copper etching solutions of Examples 1-3 exhibit excellent etching rates.

[0094] On the other hand, regarding the copper etching solutions of Comparative Examples 1-3, both the retreat amount and etching rate were worse than those of the copper etching solutions of Examples 1-3. Even the copper etching solution of Comparative Example 2, which had the highest retreat amount among Comparative Examples 1-3, still showed poor performance after a certain time T until adequate etching was achieved. JE 3 times the time (T) JE At time point ×3), the evaluation of the retreat amount is only "△". Therefore, it can be concluded that, for the copper etching solution in Comparative Example 2, after time T until the appropriate amount of etching is achieved... JE 3 times the time (T) JE At time point ×3), electrochemical corrosion occurred in circuit 3a.

[0095] Regarding the copper etching solution of Comparative Example 1, which had the second highest evaluation of retreat amount among Comparative Examples 1-3, the time T until adequate etching was achieved was [missing information]. JE Twice the time (T) JE At time point ×2), the evaluation of the amount of retreat is “× (※1)”. Therefore, regarding the copper etching solution of Comparative Example 1, after time T until adequate etching is achieved... JE Twice the time (T) JE At time point ×2), electrochemical corrosion occurred in circuit 3a.

[0096] Furthermore, regarding the copper etching solution of Comparative Example 3, which had the lowest evaluation of retreat amount among Comparative Examples 1-3, the time T until adequate etching was achieved... JE At the specified time point, the amount of retreat was evaluated as "× (※2)". Therefore, regarding the copper etching solution of Comparative Example 3, after the time T until adequate etching was achieved... JE At the specified time point, electrochemical corrosion occurred in circuit 3a. Furthermore, it is known that electrochemical corrosion occurred in both circuit 3a and circuit 3b. After circuits 3a and 3b disappeared, the nickel film 6 and gold film 5 on the surface of circuits 3a and 3b were peeled off.

[0097] These results show that, compared with the copper etching solutions of Comparative Examples 1-3, the copper etching solutions of Examples 1-3 have a superior inhibitory effect on electrochemical corrosion.

[0098] Furthermore, for the copper etching solutions of Comparative Examples 1 to 3, the etching rate was rated as "×". This indicates that the copper etching solutions of Comparative Examples 1 to 3 had low etching rates.

[0099] The copper etching solutions of Examples 1-3 are discussed in detail with reference to Table 1. In the copper etching solution of Example 2, the content of copper sulfate 5-hydrate is low, approximately 1 / 6 of that in Example 1. Therefore, the content of ammonia water needs to be controlled to approximately 1 / 3 of that in Example 1 to prevent excessive ammonia. Thus, regarding the copper etching solution of Example 2, it can be considered that the amount of copper-ammonia complex formed is less than that in Example 1, resulting in a lower etching rate than in Example 1, specifically between 1 μm / min and 3 μm / min.

[0100] Regarding the copper etching solution of Example 3, the content of copper sulfate decahydrate is the same as in Example 1, while the ammonia content is approximately twice that of Example 1. Therefore, it can be considered that the amount of copper-ammonia complex formed is greater than in Example 1. Furthermore, compared to Example 1, which contains a total of 81.2 g / L of ammonium sulfate and ammonium bicarbonate, Example 3 contains a total of 49.5 g / L of ammonium sulfate and ammonium acetate. The amount of ammonium sulfate is the same as in Example 1, but the amount of ammonium acetate is approximately 1 / 2.7 of that of ammonium bicarbonate. Thus, it can be considered that by using ammonium acetate, the etching rate in Example 3 was suppressed compared to Example 1, becoming between 1 μm / min and 3 μm / min.

[0101] 2. Etching test using metal plates

[0102] 2-1. Preparation of Copper Etching Solution

[0103] Here, etching tests were conducted using metal plates. First, copper etching solutions for Examples 4-25 and Comparative Examples 4-9, as shown in Tables 3-7, were prepared. As shown in Table 3, in the copper etching solutions of Examples 4-8 and Comparative Example 4, the amount of ammonium sulfate added was fixed at 50 g / L, the amount of copper sulfate decahydrate added varied from 0.4 to 200 g / L (equivalent to 0.1 to 50 g / L for copper), and the amount of 25% ammonia added varied from 6 to 500 g / L. Furthermore, in the copper etching solutions of Example 9 and Comparative Example 5, the amount of ammonium sulfate added was fixed at 250 g / L, the amount of 25% ammonia added was fixed at 500 g / L, and the amount of copper sulfate decahydrate added varied from 250 to 300 g / L (equivalent to 62.5 to 75 g / L for copper). As shown in Table 4, in the copper etching solutions of Examples 6, 10-15 and Comparative Examples 6-7, the amount of copper sulfate decahydrate added was fixed at 120 g / L (equivalent to 30 g / L of copper), the amount of 25% ammonia added was fixed at 150 g / L, and the amount of ammonium sulfate added varied from 2.5 to 400 g / L. As shown in Table 5, in the copper etching solutions of Examples 16-17 and Comparative Example 8, ammonium bicarbonate was added based on the composition of the copper etching solution of Example 6, and its amount varied from 0.5 to 250 g / L. As shown in Table 6, in the copper etching solutions of Examples 18-20 and Comparative Example 9, ammonium acetate was added based on the composition of the copper etching solution of Example 6, and its amount varied from 5 to 120 g / L. As shown in Table 7, in the copper etching solutions of Examples 21-25, 20 g / L of different types of ammonium salts were added based on the composition of the copper etching solution of Example 6.

[0104] 2-2. Etching Test

[0105] Secondly, as described below, etching tests were conducted using metal plates. Figure 4As shown, firstly, the copper etching solution (copper etching solutions of Examples 4-25 and Comparative Examples 4-9) 11 was placed in beaker 12, heated in a constant temperature water bath 13, and stirred with stirrer 14. Then, copper plate 15 and gold plate 16, serving as test pieces, were immersed in the copper etching solution 11 for 3 minutes. For copper plate 15, an electrolytic copper foil with a thickness of 18 μm was used. For gold plate 16, a metal plate (not shown) with a 1 μm thick gold film formed on the copper plate by electroplating was used, and its surface area was approximately 15 times that of copper plate 15. The immersion of copper plate 15 and gold plate 16 was performed in two cases: a non-conductive state between copper plate 15 and gold plate 16, and a conductive state via lead 17. Furthermore, for both non-conductive and conductive states, the etching rate of copper plate 15 was calculated based on the weight difference before and after immersion. The results are shown in Tables 3-7. In Tables 3-7, the symbols in the "Bath Stability" column have the following meanings. Additionally, in Tables 3-7, "-" indicates that the component was not added, or that the pH or etching rate was not measured after the bath could not be constructed.

[0106] ○: No self-decomposition of the bath occurred, and the bath was stable.

[0107] ×: The bath decomposed itself and could not be reconstructed.

[0108] like Figure 4 As shown, electrochemical corrosion occurs when the copper plate 15 and gold plate 16 are conductive. Conversely, electrochemical corrosion does not occur when the copper plate 15 and gold plate 16 are not conductive. Therefore, in this etching test, the conductive state of the copper plate 15 and gold plate 16 corresponds to circuit 3a, which is conductive with a metal more expensive than copper, in the etching test using the aforementioned circuit board W; the non-conductive state of the copper plate 15 and gold plate 16 corresponds to circuit 3b, which is not conductive with a metal more expensive than copper, in the etching test using the aforementioned circuit board W. Therefore, this etching test can be considered a simplified version of the etching test using the aforementioned circuit board W. Furthermore, the judgment of whether the etching speed is good or bad depends on how the metal being etched is manufactured, whether it is film-formed, and the required etching amount. Therefore, in this etching test, the numerical value of the etching speed itself is not evaluated.

[0109] Table 3

[0110]

[0111] Table 4

[0112]

[0113] Table 5

[0114]

[0115] Table 6

[0116]

[0117] Table 7

[0118]

[0119] evaluate

[0120] As shown in Table 3, for the copper etching solutions of Examples 4-9, there was almost no difference in etching speed between copper plate 15 and gold plate 16 when they were not conductive and when they were conductive. This indicates that the copper etching solutions of Examples 4-9 have excellent inhibitory effects on electrochemical corrosion. On the other hand, for the copper etching solution of Comparative Example 4, the etching speed when conductive was three times faster than when not conductive, indicating that electrochemical corrosion occurred. Furthermore, the copper etching solution of Comparative Example 5 had low bath stability and could not be used for etching tests. From the above, it can be seen that copper etching solutions with a copper content of 1-62.5 g / L and a 25% ammonia water content of 10-500 g / L have excellent inhibitory effects on electrochemical corrosion.

[0121] As shown in Table 4, for the copper etching solutions of Examples 6, 10-15, there was almost no difference in etching rate between the copper plate 15 and the gold plate 16 when they were not conductive and when they were conductive. This indicates that the copper etching solutions of Examples 6, 10-15 have excellent inhibitory effects on electrochemical corrosion. On the other hand, for the copper etching solutions of Comparative Examples 6-7, the etching rate was 1.12 to 2.1 times faster when conductive compared to when it was not conductive, indicating that electrochemical corrosion occurred. From the above, it can be concluded that copper etching solutions with an ammonium sulfate content of 5-300 g / L have excellent inhibitory effects on electrochemical corrosion.

[0122] As shown in Table 5, for the copper etching solutions of Examples 16-17, there was almost no difference in etching rate between copper plate 15 and gold plate 16 when they were not conductive and when they were conductive. This indicates that the copper etching solutions of Examples 16-17 have excellent inhibitory effects on electrochemical corrosion. On the other hand, the copper etching solution of Comparative Example 8 had low bath stability and could not be used for etching tests. From the above, it can be seen that copper etching solutions containing ammonium sulfate and ammonium bicarbonate as ammonium salts, with an ammonium bicarbonate content of 0.5-200 g / L, have excellent inhibitory effects on electrochemical corrosion.

[0123] As shown in Table 6, for the copper etching solutions of Examples 18-20, there was almost no difference in etching speed between the copper plate 15 and the gold plate 16 when they were not conductive and when they were conductive. This indicates that the copper etching solutions of Examples 18-20 have excellent inhibitory effects on electrochemical corrosion. On the other hand, for the copper etching solution of Comparative Example 9, the etching speed when conductive was 23.5 times faster than when it was not conductive, indicating that electrochemical corrosion occurred. From the above, it can be seen that copper etching solutions containing ammonium sulfate and ammonium acetate as ammonium salts, with an ammonium acetate content of 5-100 g / L, have excellent inhibitory effects on electrochemical corrosion.

[0124] As shown in Table 7, for the copper etching solutions of Examples 21-25, there was almost no difference in etching speed between the copper plate 15 and the gold plate 16 when they were not conductive and when they were conductive. This indicates that the copper etching solutions of Examples 21-25 have excellent inhibitory effects on electrochemical corrosion. It can also be seen from the above that when ammonium sulfate is combined with one ammonium salt selected from the group consisting of ammonium nitrate, ammonium methanesulfonate, ammonium benzoate, ammonium lactate, and ammonium oxalate, an etching solution with excellent inhibitory effects on electrochemical corrosion can also be obtained.

[0125] The results above show that using the copper etching solutions from Examples 4 to 25, and with... Figure 1 When the circuit board W shown is etched, the same results as those obtained with the copper etching solutions in Examples 1 to 3 can be obtained.

[0126] Industrial practicality

[0127] The copper etching solution of the present invention can suppress electrochemical corrosion and achieve a high etching rate. Because it suppresses electrochemical corrosion, it is suitable for etching substrates where copper is conductive to a metal more expensive than copper, or where copper is not conductive to that expensive metal. Furthermore, the copper etching solution of the present invention is applicable to various fields of electronic circuit boards, semiconductors, etc.

Claims

1. A copper etching solution which is an alkaline copper etching solution for removing a seed layer remaining on a substrate between copper circuits when a printed wiring board is manufactured by a semi-additive process, characterized by comprising 1 to 70 g / L of copper, 10 to 500 g / L of ammonia water when converted to 25% ammonia water, and an ammonium salt, the ammonium salt being 5 to 80 g / L of ammonium sulfate and 0.5 to 200 g / L of ammonium hydrogen carbonate, or 5 to 80 g / L of ammonium sulfate and 5 to 100 g / L of ammonium acetate, the pH of the copper etching solution being 7.8 to 11, and the absolute value of the difference in undercut amount between a circuit through which gold, a metal more expensive than copper, is conducted and a circuit through which gold, a metal more expensive than copper, is not conducted being 0.3 μm or less at a bath temperature of 10 to 60°C during removal of the seed layer. ​ ​ ​ ​

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