JP2005023340A - Etching method for printed circuit board and etching liquid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etching method and an etching liquid by which a high insulation resistance value can be obtained without causing a short-circuit even in fine wiring in an etching treatment of a two-layer plated board using a polyimide film. <P>SOLUTION: In the two-layer plated board, a thin sputtering film 2 of an Ni-Cr alloy is applied for improving the adhesion between a polyimide film 1 and copper layers 3 and 4 and preventing migration. In the etching method for the two-layer plated board, after etching treatment with a ferric chloride solution or hydrochloric acid-containing cupric chloride solution, treatment is performed by using one or more kinds selected from a hydrochloric acid-containing acidic etching liquid and potassium ferricyanide or permanganate-containing etching liquid, so that the remaining 2' of the etching of the Ni-Cr alloy is dissolved without the side etching and damage to the copper layers. Thus, the fine wiring having the high insulation resistance without causing the short-circuit can be obtained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method and etching solution for a two-layer plating substrate in which a Ni—Cr alloy layer is provided between a polyimide film as a base material used for a printed wiring board, a flexible wiring board, a TAB tape, and the copper layer.
[0002]
[Prior art]
In recent years, with the miniaturization of equipment, a substrate having a thinner copper layer than the conventional three-layer type using a copper foil and an adhesive is required in order to cope with the higher density of wiring patterns. In order to satisfy this requirement, a two-layer type substrate in which a copper layer is formed on a polyimide film as a base material by combining a sputtering method and a plating method capable of reducing the thickness in place of a conventional bonded copper foil. Is now becoming mainstream.
Under these circumstances, the adhesion between the polyimide film of the base material and the copper layer is due to CuO or Cu at the interface. ₂ In order to maintain the adhesive strength of 1000 g / cm with the copper layer required for the printed wiring board, Cr is formed as an intermediate layer between the base material and the copper layer. It has been proposed to provide a Ni—Cr alloy layer (see Patent Document 1).
[0003]
In this case, as shown in FIG. 1, for the purpose of improving adhesion, a two-layer plated substrate using a polyimide film has a thin film 2 such as a Ni—Cr alloy as a seed layer on a polyimide surface 1 of a base material by sputtering or the like ( By forming a copper layer 3 (0.1 to 1.5 μm) by a sputtering method or the like and then forming a copper layer 4 (1 to 8 μm) by an electroplating method. Manufactured. In order to form a wiring pattern by etching the two-layer plating substrate thus manufactured, for example, ferric chloride (FeCl2) is used as an etching solution. ₃ ) Dissolved in water and ferric chloride solution and cupric chloride (CuCl) ₂ ・ 2H ₂ O) is dissolved in water and etched using a cupric chloride solution with an appropriate amount of hydrochloric acid added.
[0004]
Patent Document 1 discloses an example in which a ferric chloride solution is used as an etching solution. That is, as shown in FIG. 1, when using a Ni—Cr alloy for the seed layer 2, the copper layer 3 and the copper plating with a ferric chloride etchant in the range of Ni content of 5 at% to 80 at%. It has been shown that layer 4 and Ni-Cr alloy layer 2 can be etched simultaneously.
On the other hand, Patent Document 2 discloses a method for etching a Cr metal layer, a Cr alloy layer, and a Cr compound layer, which are used for a rust-proofing process such as a copper plate, in a printed wiring board or an IC metal package substrate with a non-alkali aqueous solution. Yes.
However, in the etching method using these etching solutions, the etching residue of the Ni—Cr alloy layer is generated, and a sufficient etching result cannot be obtained.
[0005]
[Patent Document 1]
JP-A-6-120630
[Patent Document 2]
Japanese Patent Application Laid-Open No. 10-126039
[0006]
[Problems to be solved by the invention]
However, in the conventional two-layer substrate etching method, as shown in FIG. 2, when the unnecessary portion of the Ni—Cr alloy layer 2 is removed by the etching process, sufficient etching cannot be performed, and the region outside the copper wiring is removed. There was a problem that the etching residue 2 ′ of the Ni—Cr alloy layer 2 was likely to occur. The etching residue 2 ′ of the Ni—Cr alloy layer 2 is likely to occur in a portion where the copper wiring is dense, that is, the number of copper wirings formed on the polyimide film [1] is large and dense. Therefore, for example, in a tape carrier having a very narrow conductor gap [Pa] such as a tape carrier used for a driver for driving a liquid crystal panel, removal of unnecessary portions of the Ni—Cr alloy layer 2 is likely to be insufficient. The adjacent copper wiring is short-circuited by the etching residue 2 ′ of the Ni—Cr alloy layer 2 and there is a problem that a high insulation resistance cannot be obtained and a defective product is obtained.
[0007]
The cause of the poor insulation resistance is that when etching is performed using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, the etching rate of the Ni—Cr alloy layer 2 is higher than the etching rate of the copper layers 3 and 4. This is because an etching residue 2 ′ of the Ni—Cr alloy layer 2 is generated because it is slow.
That is, in the normal cupric chloride solution containing hydrochloric acid (general composition: cupric chloride 200 g / L, hydrochloric acid 150 mL / L), an etching residue of the Ni—Cr alloy layer is generated. Therefore, if the hydrochloric acid concentration is increased, sufficient etching of the Ni—Cr alloy layer may be possible, but problems such as side etching and damage of the copper layer occur. The present invention is characterized in that the etching residue of the Ni—Cr alloy layer after the etching treatment with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid is removed. Of course, side etching or damage of the copper layer does not occur. In addition, since the copper layer is etched with hydrochloric acid alone, and the copper ions are further accumulated in the solution, the etching of the copper layer is accelerated and damaged. It is made not to etch.
[0008]
Further, as means for preventing the etching residue 2 'of the Ni-Cr alloy layer 2, there is a method of increasing the time taken for the etching process of the Ni-Cr alloy layer 2, but if the processing time is lengthened, the copper layers 3 and 4 As a result, the copper wiring is thinned and disconnected.
[0009]
A first object of the present invention is to etch a ferric chloride solution or hydrochloric acid in a two-layer plating substrate etching method in which a Ni—Cr alloy layer 2 is provided between a polyimide film 1 as a base material and copper layers 3 and 4. An object of the present invention is to provide a technique capable of eliminating a short circuit defect and obtaining a high insulation resistance by removing the Ni—Cr remaining 2 ′ after the etching treatment using the cupric chloride solution that is contained.
[0010]
The second object of the present invention is to reduce the dissolution of the copper wiring by reducing the dissolution of the copper wiring in the method for removing the Ni—Cr remaining 2 ′ after the etching process using the ferric chloride solution or the cupric chloride solution containing hydrochloric acid. The object is to provide a technique with less side etching of wiring.
A third object of the present invention is to provide an etching solution having a specific composition suitable for achieving the object of the present invention.
The above object can be achieved by the following present invention or embodiments.
[0011]
[Means for Solving the Problems]
(1) Regarding a two-layer plating substrate using a polyimide film, in the etching method of a two-layer plating substrate in which a Ni—Cr alloy layer is provided between a base polyimide film and a copper layer, (A) a ferric chloride solution Alternatively, after etching with a cupric chloride solution containing hydrochloric acid, (B) one or more of an acidic etching solution containing hydrochloric acid, an alkaline etching solution containing potassium ferricyanide or permanganate is used in combination. An etching method characterized by the above.
(2) The copper layer is etched with an etchant that selectively etches only the copper layer without dissolving the Ni-Cr alloy layer, instead of the etchant of the ferric chloride solution or the cupric chloride solution containing hydrochloric acid. The Ni-Cr alloy layer is etched by using one or more of an acidic etching solution containing hydrochloric acid and an alkaline etching solution containing potassium ferricyanide or permanganate later (1) The etching method as described in 4. above.
[0012]
(3) The acidic etching solution containing hydrochloric acid contains 1 to 12N hydrochloric acid, and further contains at least one of an oxidizing agent, a surfactant, a complexing agent, an accelerator, a copper corrosion inhibitor, and a reducing agent. The etching method according to (1) or (2), wherein the etching method is performed with a solution.
(4) An alkaline etching solution containing potassium ferricyanide or permanganate contains 0.1 to 30% by weight of potassium ferricyanide or permanganate and 0.01 to 30% by weight of sodium hydroxide or potassium hydroxide, Further, the etching method according to any one of (1) to (3), wherein the treatment is performed with a solution containing at least one of an oxidizing agent, a complexing agent, a pH buffering agent, and an accelerator.
[0013]
(5) An acidic etching solution containing hydrochloric acid, containing 1 to 12N hydrochloric acid, and at least one selected from an oxidizing agent, a surfactant, a complexing agent, an accelerator, a copper corrosion inhibitor, and a reducing agent. Etching liquid characterized by containing.
(6) It consists of an alkaline etching solution containing potassium ferricyanide or permanganate, 0.1-30 wt% potassium ferricyanide or permanganate, 0.1-30 wt% sodium hydroxide or potassium hydroxide. And an etching solution containing at least one selected from an oxidizing agent, a complexing agent, a pH buffering agent and an accelerator.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
As described above, the present invention is a two-layer plating in which a Ni—Cr alloy layer 2 is provided between a polyimide film 1 as a base material used for a printed wiring board, a flexible wiring board, a TAB tape, and the copper layers 3 and 4. The present invention relates to a substrate etching method and an etching solution.
[0015]
Hereinafter, the present invention will be described with reference to the accompanying drawings.
As shown in FIG. 1, the substrate according to the present invention is a thin Ni—Cr alloy sputtering layer for the purpose of improving adhesion between the base polyimide film 1 and the copper layers 3 and 4 and preventing migration. 2 is given. In order to obtain a copper wiring using this substrate, the present invention is based on the etching residue of a Ni—Cr alloy layer generated in a conventionally used ferric chloride solution or a cupric chloride solution containing hydrochloric acid. An etching solution having a new specific composition that can be etched without side etching or damage.
As shown in FIG. 2, a resist 5 is applied to the copper layer 4 of the substrate by an ordinary method, and then dried, exposed and developed by an ordinary method, and then a ferric chloride solution or a cupric chloride solution containing hydrochloric acid. After the etching treatment, by processing with an acidic etching solution or an alkaline etching solution containing hydrochloric acid of the present invention, a fine pitch copper wiring having a high insulation resistance with little side etching and damage of the copper layer, that is, shown in FIG. Comb patterns 6a and 6b having a pattern pitch of 40 μm were formed (corresponding to 4 in FIG. 2). If the pattern pitch is 50 μm or more, it can be handled only by the conventional etching process using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid. The insulation resistance between the comb electrodes is generally 10 ¹² Ω or more, especially 10 ¹² -10 ¹³ A high value of Ω is obtained.
[0016]
That is, in the present invention, after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, an acidic etching solution containing hydrochloric acid, an alkaline etching solution containing potassium ferricyanide or permanganic acid is used alone or in combination. 2 layer plating characterized in that the Ni—Cr remaining 2 ′ as shown in FIG. 2 is dissolved without side etching or damage of the copper layer to obtain a fine wiring having no short circuit and high insulation resistance. This is a method for etching a substrate.
[0017]
The insulation resistance between the wirings after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid is usually 10 ⁸ -10 ¹⁰ Ω, but after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, the remaining 2 ′ of Ni—Cr is removed by treating with an acidic etching solution containing hydrochloric acid of the present invention. ¹² High insulation resistance of Ω or more can be obtained. The hydrochloric acid concentration of the acidic etching solution containing hydrochloric acid is preferably 1-12 N. However, if the hydrochloric acid concentration is low, the etching rate of the Ni—Cr alloy layer decreases and the processing time becomes long. On the other hand, if it is 6N or more, the etching rate of the Ni—Cr alloy layer is increased, but adverse effects such as the generation of hydrochloric acid mist occur. Therefore, the hydrochloric acid concentration is preferably 2 to 6N.
[0018]
The acidic etching solution containing hydrochloric acid may appropriately contain additives such as an oxidizing agent, a surfactant, a complexing agent such as an organic acid, a Ni-Cr dissolution accelerator, a copper dissolution inhibitor, and a reducing agent. it can. In general, the amount of these additives is preferably 0.01 to 20%. The treatment method of the acidic etching solution containing hydrochloric acid can be either a spray method or an immersion method.
[0019]
The treatment temperature of the acidic etching solution containing hydrochloric acid is preferably 20 ° C. to 90 ° C. If the temperature is low, the dissolution rate of Ni—Cr is slowed down and the etching time is lengthened. Further, when the temperature is high, the etching rate of Ni—Cr is fast, but the generation of hydrochloric acid mist increases and the amount of copper dissolved increases, so that the temperature is more preferably 40 ° C. to 70 ° C. The treatment time of the acidic etching solution containing hydrochloric acid is preferably 30 seconds to 10 minutes. Further, since the etching solution containing hydrochloric acid is of an acidic type, there is an advantage that an inexpensive alkali dissolution type resist can be used.
[0020]
The insulation resistance between the wirings after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid is usually 10 ⁸ -10 ¹⁰ Ω, but after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, the Ni—Cr remaining 2 ′ is obtained by treating with an alkaline etchant containing potassium ferricyanide or permanganate of the present invention. Is removed and another 10 ¹² High insulation resistance of Ω or more can be obtained.
When the resist is an alkali-soluble type, the treatment is performed after the resist is removed in advance. Since the alkaline etching solution of the present invention does not dissolve copper, there is a feature that no copper damage occurs even without a resist. In the case of an alkali-resistant resist, it is preferable in the process that the resist is removed after the treatment with an alkaline etching solution.
[0021]
The alkaline etching solution contains at least one oxidizing agent selected from potassium ferricyanide or permanganate, and is made alkaline by adding an alkali such as sodium hydroxide or potassium hydroxide. The alkaline etching solution may contain a complexing agent, a pH buffer, a reaction accelerator, and the like.
The concentration of the oxidizing agent in the alkaline etching solution is preferably 0.1 to 30%, but a high concentration solution may cause crystal precipitation, and at a low concentration, the etching rate is low and the etching time is increased. Therefore, 1 to 20% is more preferable.
[0022]
The alkali concentration in the alkaline etching solution is preferably 0.01 to 30%. However, when the concentration is high, the polyimide film of the base material is damaged, and at a low concentration, the etching rate is low and the etching time is increased. 1 to 20% is more preferable. The pH range due to the addition of alkalis is preferably 10 to 14, but if the pH is high, the etching rate is high, but the polyimide is damaged. If the pH is low, there is no damage to the material, but the etching rate is slow, so a more preferable pH range is 11-13.
The treatment temperature of the alkaline etching solution is preferably 10 to 90 ° C., but damage to the polyimide film of the base material occurs at high temperatures, and 20 to 50 ° C. is more preferable because the etching rate is low and the etching time increases at low temperatures. . The treatment time of the alkaline etching solution is preferably 15 seconds to 5 minutes. Since there is no dissolution of copper, the treatment time may be long, but 30 seconds to 2 minutes is more preferable in the process.
[0023]
The treatment method of the alkaline etching solution can be either a spray method or an immersion method. In the case where an acidic etching solution containing hydrochloric acid or an alkaline etching solution containing potassium ferricyanide or permanganate according to the present invention is individually treated after etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid. High insulation resistance can be obtained, but there may be a slight Ni—Cr remaining 2 ′ partially depending on processing conditions. Since the partially remaining Ni—Cr remaining 2 ′ is not a continuous film, it is not plated due to a decrease in insulation resistance or electroless tin plating in the next process.
[0024]
After etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, the solution is treated with an acidic etchant containing hydrochloric acid of the present invention, and further treated with an alkaline etchant containing potassium ferricyanide or permanganate of the present invention. By doing so, the Ni—Cr remaining 2 ′ is completely removed, and it becomes possible to manufacture fine wiring with high reliability without side etching or damage of the copper layer.
[0025]
According to the above means, the following operation can be obtained.
After etching with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, an acidic etching solution containing hydrochloric acid or an alkaline etching solution containing potassium ferricyanide or permanganate according to the present invention is used in combination of one or more. Thus, the Ni—Cr remaining 2 ′ of the seed layer can be removed, and a highly reliable fine wiring can be manufactured without side etching or damage of the copper layer.
[0026]
After the etching treatment with the ferric chloride solution or the cupric chloride solution containing hydrochloric acid, the acidic etching solution containing hydrochloric acid of the present invention, the alkaline etching solution containing potassium ferricyanide or permanganate, or one or more of them are used. By processing in combination, Ni—Cr remaining 2 ′ of the seed layer can be removed, and an etching solution of a ferric chloride solution or a cupric chloride solution containing hydrochloric acid that has been proven for a long time and has established technology can be used as it is. There is a merit.
Further, the etching solution of the ferric chloride solution or the cupric chloride solution containing hydrochloric acid by the etching method of the present invention is used to form the Ni—Cr alloy layer 2 such as hydrogen peroxide / sulfuric acid or hydrogen peroxide / nitric acid. By changing to an etching solution that selectively dissolves only the copper layers 3 and 4 without dissolving, the copper layers 3 and 4 and the Ni—Cr alloy layer 2 can be selectively etched. It can be applied as an etching method for manufacturing a resistance-embedded wiring board using the layer 2 as a resistor.
[0027]
The composition of the etching liquid used for the etching method of the two-layer plating substrate which provided the Ni-Cr alloy layer between the polyimide film of the base material and the copper layer regarding the two-layer plating substrate using the polyimide film of the present invention, (I) In the case of an acidic etching solution containing hydrochloric acid, it contains 1 to 12 N hydrochloric acid, and at least one of an oxidizing agent, a surfactant, a complexing agent, an accelerator, a copper corrosion inhibitor, and a reducing agent. It contains more than seeds. (II) In the case of an alkaline etching solution containing potassium ferricyanide or permanganate, 0.1 to 30% by weight of potassium ferricyanide or permanganate, and 0.1 to 30% by weight of sodium hydroxide or hydroxide It contains potassium, and further contains at least one of an oxidizing agent, a complexing agent, a pH buffering agent and an accelerator.
[0028]
The acidic etching solution (I) can contain the following additives.
(Oxidant)
Hydrogen peroxide, perchloric acid, sodium metanitrobenzenesulfonate, potassium permanganate, ceric ammonium nitrate, ammonium persulfate, sodium perborate, etc.
(Inorganic acid)
Inorganic acids such as sulfuric acid, nitric acid, hydrofluoric acid, hydrobromic acid, phosphoric acid, polyphosphoric acid, boric acid and their salts.
[0029]
(Surfactant)
Anionic surfactants such as sodium lauryl sulfate, nonionic surfactants such as polyoxyethylene lauryl alcohol, cationic surfactants such as alkyl ammonium, and amphoteric surfactants such as lauryl betaine.
(Complexing agent)
Acetic acid, formic acid, propionic acid, butyric acid, glycolic acid, lactic acid, chloroacetic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid, picrine Acid, itaconic acid, crotonic acid, styrene sulfonic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid, glycine, alanine, sodium glutamate, etc.
[0030]
(Accelerator)
Thiourea, sodium thiocyanate, thiosulfate, mercaptobenzimidazole, mercaptobenzothiazole, sodium benzenesulfonate, propylsulfonic acid, sodium allylsulfonate, thiomalic acid, sodium phenolsulfonate, thiosalicylic acid, toluenesulfonic acid, xanthogenic acid Compounds containing sulfur, such as potassium and mercaptopropane sulfonic acid.
[0031]
(Copper corrosion inhibitor)
Benzotriazole, dimercaptothiodiazole, sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, etc.
(Reducing agent)
Sodium sulfite, sodium thiosulfate, formalin, hydrazine, hydroxylamine compound, hypophosphorous acid, DMAB, ascorbic acid, sodium erythorbate, tocopherol, glycerin, maltose, lactose, hydroquinone, phenol, catechol, sorbitol, pyrogallol, titanium trichloride , Zinc powder and so on.
[0032]
The alkaline etching solution (II) can contain the following additives.
(Oxidant)
Hydrogen peroxide, perchloric acid, sodium metanitrobenzenesulfonate, sodium metanitrobenzoate, ammonium persulfate, etc.
(Complexing agent)
Acetic acid, formic acid, propionic acid, butyric acid, glycolic acid, lactic acid, chloroacetic acid, acrylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalate Acid, salicylic acid, picric acid, itaconic acid, crotonic acid, styrene sulfonic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, cyclohexanediaminetetraacetic acid, pyrophosphoric acid, polyphosphoric acid, metaphosphoric acid, tripolyphosphoric acid, glycine, alanine, sodium glutamate, ethylenediamine , Triethanolamine, tetramethylenehexamine, dimethylamine and the like.
[0033]
(PH buffer)
Sodium tetraborate, sodium hydrogen phosphate, sodium phosphite, boric acid, sodium metasilicate, ammonium sulfate, ammonium chloride, phthalic acid, etc.
(Accelerator)
Thiourea, sodium thiocyanate, sodium naphthalenesulfonate, saccharin, thiosulfate, mercaptobenzimidazole, mercaptobenzothiazole, sodium benzenesulfonate, thioglycolic acid, thiodiglycol, propylsulfonic acid, sodium dimethyldithiocarbamate, diethyldithiocarbamine Sodium acid, sodium allyl sulfonate, thiomalic acid, sodium phenol sulfonate, thiosalicylic acid, toluene sulfonic acid, potassium xanthate, mercaptopropane sulfonic acid and the like.
[0034]
Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. The Ni—Cr sputtered layer in each example had a thickness in the range of 3 to 10 nm.
(Comparative Example 1)
A photoresist is applied on the copper plating layer 4 side of a two-layer substrate using a Ni—Cr alloy as a seed layer shown in FIG. 1 by an ordinary method, dried, exposed and developed, and then a normal ferric chloride solution is used. Etching was performed to form comb patterns 6a and 6b with a pitch of 40 μm shown in FIG. After the resist is stripped, the insulation resistance between the electrodes is 10 ⁹ It became Ω.
[0035]
(Comparative Example 2)
The ferric chloride solution of Comparative Example 1 was replaced with a normal cupric chloride solution containing hydrochloric acid, and a comb pattern having a pitch of 40 μm was formed in the same process. After the resist is stripped, the insulation resistance between the electrodes is 10 ⁹ It became Ω.
[0036]
(Comparative Example 3)
In Comparative Example 1, after etching with a ferric chloride solution, immersed in a cerium ammonium nitrate solution containing nitric acid, which is an etching solution of Cr, for 3 minutes at room temperature. After removing the resist, the insulation resistance between the electrodes of the comb pattern was measured. Then 10 ¹² A high insulation resistance of Ω was obtained. However, the copper wiring was also side-etched to make it extremely thin, and the copper surface was roughened and damaged.
[0037]
(Example 1)
In Comparative Example 1, after etching with a ferric chloride solution, it was immersed in an acidic etching solution containing hydrochloric acid of the present invention at 50 ° C. for 5 minutes. After resist removal, the insulation resistance between the electrodes of the comb pattern was measured. ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0038]
(Example 2)
In Comparative Example 1, an etching process was performed with a ferric chloride solution to form a comb pattern with a pitch of 40 μm, and after removing the resist, it was immersed in an alkaline etching solution containing potassium ferricyanide of the present invention at 30 ° C. for 2 minutes. After washing and drying, the insulation resistance between the electrodes is 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0039]
Example 3
After removing the resist in Example 1, it was further immersed in an alkaline etching solution containing potassium ferricyanide of the present invention at 30 ° C. for 2 minutes. After washing and drying, the insulation resistance between the electrodes is 10 ¹³ A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0040]
(Example 4)
A comb-shaped electrode was prepared in the same manner by replacing the ferric chloride solution of Example 2 with a cupric chloride solution containing hydrochloric acid. The insulation resistance between the electrodes is 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0041]
(Example 5)
The ferric chloride solution of Example 3 was replaced with a cupric chloride solution containing hydrochloric acid to produce a comb-shaped electrode by the same operation. The insulation resistance between the electrodes is 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0042]
(Example 6)
A comb-shaped electrode was prepared in the same manner by replacing the ferric chloride solution of Example 4 with a cupric chloride solution containing hydrochloric acid. The insulation resistance between the electrodes is 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0043]
(Example 7)
A comb-shaped electrode was prepared in the same manner by replacing the alkaline etching solution containing potassium ferricyanide of Example 3 with an alkaline etching solution containing potassium permanganate. The insulation resistance between the electrodes is 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
[0044]
(Example 8)
The copper layer was etched by changing the ferric chloride solution of Example 1 to a hydrogen peroxide solution / nitric acid-based etching solution that selectively etches only the copper layer, thereby forming a comb-shaped electrode. Then, after dipping in an acidic etching solution containing hydrochloric acid of the present invention at 50 ° C. for 5 minutes, etching the Ni—Cr alloy layer, stripping the resist, and measuring the insulation resistance between the electrodes, 10 ¹² A high insulation resistance of Ω was obtained. No side etching or damage of the copper layer was observed.
The pattern pitch of the comb-shaped electrode as shown in FIG. 3 obtained in each of the above examples was 40 μm (pattern 20 μm / space 20 μm), and the etching residue was several nm or less to measurement impossible.
[0045]
【The invention's effect】
As described above, according to the etching method of the present invention, Ni—Cr after etching treatment with a ferric chloride solution or a cupric chloride solution containing hydrochloric acid, which has been conventionally difficult at a low cost and with a simple process. The remaining 2 'can be removed without side etching or damage to the copper layers 3 and 4, and an excellent effect is obtained that a fine wiring having high insulation resistance can be easily obtained. The present invention is particularly useful for printed wiring boards, flexible wiring boards, TAB tapes, etc., but can also be used for etching methods for manufacturing resistance-incorporating wiring boards using Ni-Cr alloy layers as resistors.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a two-layer polyimide substrate to which an etching method of the present invention is applied.
FIG. 2 is a schematic cross-sectional view after etching the two-layer substrate of FIG. 1 according to the present invention with an etching solution using a ferric chloride solution or a cupric chloride solution containing hydrochloric acid.
FIG. 3 is a schematic plan view of a comb-shaped electrode formed on a polyimide film substrate using the two-layer substrate of FIG. 1 according to the present invention.
[Explanation of symbols]
1 Polyimide film 2 Ni-Cr alloy layer
Ni-Cr remaining after 2 'etching 3 Copper layer 4 Copper plating layer
5 Resist film 6a Comb electrode 6b Comb electrode
Pa Space between conductors Pb Pattern pitch

Claims (6)

Regarding the two-layer plating substrate using the polyimide film, in the etching method of the two-layer plating substrate in which the Ni—Cr alloy layer is provided between the base polyimide film and the copper layer, (A) a ferric chloride solution or hydrochloric acid is used. After the etching treatment with the cupric chloride solution containing, (B) one or more of an acidic etching solution containing hydrochloric acid, an alkaline etching solution containing potassium ferricyanide or permanganate is used in combination. Etching method to do. Instead of the ferric chloride solution or the etching solution of the cupric chloride solution containing hydrochloric acid, the Ni—Cr alloy layer is not dissolved but the copper layer is etched with the etching solution that selectively etches only the copper layer, and then the hydrochloric acid is added. The etching according to claim 1, wherein the Ni—Cr alloy layer is etched by using one or more of an acidic etching solution containing hydrogen, potassium ferricyanide, or an alkaline etching solution containing permanganate in combination. Method. An acidic etching solution containing hydrochloric acid contains 1 to 12N hydrochloric acid, and further contains at least one of an oxidizing agent, a surfactant, a complexing agent, an accelerator, a copper corrosion inhibitor, and a reducing agent. The etching method according to claim 1, wherein the etching method is performed. An alkaline etching solution containing potassium ferricyanide or permanganate contains 0.1 to 30% by weight potassium ferricyanide or permanganate and 0.01 to 30% by weight sodium hydroxide or potassium hydroxide, and further an oxidizing agent. The etching method according to claim 1, wherein the etching method comprises treating with a solution containing at least one of a complexing agent, a pH buffering agent, and an accelerator. It consists of an acidic etching solution containing hydrochloric acid, contains 1 to 12N of hydrochloric acid, and further contains at least one selected from oxidizing agents, surfactants, complexing agents, accelerators, copper corrosion inhibitors and reducing agents. Etching liquid characterized by the above. It consists of an alkaline etching solution containing potassium ferricyanide or permanganate, containing 0.1 to 30 wt% potassium ferricyanide or permanganate, 0.1 to 30 wt% sodium hydroxide or potassium hydroxide, An etching solution comprising at least one selected from an oxidizing agent, a complexing agent, a pH buffer, and an accelerator.

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