JP4944507B2 - Etching solution - Google Patents

Description

  The present invention is an etching solution for etching nickel, chromium, nickel chromium alloy and iron nickel chromium alloy, and the nickel, chromium, nickel chromium alloy and iron nickel chromium alloy while minimizing the dissolution of copper. The present invention relates to an etchant that can be etched.

  At present, electronic devices are becoming lighter, thinner and smaller as represented by mobile phones, and the wiring boards used for them are based on polyimide films with light, thin, and bendable characteristics. In recent years, flexible wiring boards have been widely used.

  As such a flexible wiring board, a flexible wiring board in which a copper foil is laminated on a polyimide film is used. As a method for producing the base material of the flexible wiring board, a method has been proposed in which the copper foil surface is made uneven and the polyimide and the copper foil are bonded together by an anchor effect.

  However, in this method, when the copper circuit is formed by etching, the copper unevenness at the joint portion between the resin and copper, that is, the copper thickness is different, so the circuit made by etching unnecessary portion of copper. There is a problem that the side surface becomes jagged and the electrical characteristics deteriorate.

  Therefore, a method has been proposed in which a nickel chrome alloy layer is extremely thinly formed on a polyimide film by sputtering as a plating base, and copper is plated thereon.

  However, this method has a problem that, even after forming a circuit by etching unnecessary portions of copper, the underlying nickel chrome layer formed by sputtering remains undissolved, resulting in a decrease in electrical insulation. Therefore, an etching solution that can remove only the underlying nickel chromium layer formed by sputtering without etching the copper in the circuit portion has been proposed.

  As such an etchant, an aqueous solution containing ferric chloride as a main component is generally used.

  However, since ferric chloride is a component of a copper etching solution used to form a copper circuit, there is a problem that the solubility of copper is high and the resulting copper circuit is corroded.

  Therefore, as an alternative to an aqueous solution containing ferric chloride as a main component, an etching solution containing a permanganate with low solubility of copper, or electrolytic reduction followed by sulfuric acid, hydrochloric acid, hydrofluoric acid, carboxylic acid, phosphoric acid A method of acid treatment is proposed.

  However, the above-mentioned permanganate is a hazardous substance designated as a PRTR-designated substance, and permanganate has been designated as a substance to be reduced by many companies as a central nervous system poisoning substance. It is difficult to adopt. In addition, in the technique of performing acid treatment after electrolytic reduction, it is necessary to prepare an electrolyzer, and since the treatment process is two-stage, the operation management is cumbersome and the industrial process is difficult to employ. There is.

Therefore, a method of using hydrogen peroxide in the copper etching step and then performing an acid treatment is also employed. However, when sulfuric acid is used in the acid treatment step, the nickel chrome alloy layer is not sufficiently etched, and the nickel chrome layer There is a problem that remains. Further, when hydrochloric acid is used in the acid treatment process, there is a problem that hydrochloric acid is mixed into the copper etching process and the copper circuit is excessively dissolved, and it is difficult to control the mixing of the hydrochloric acid.
Japanese Unexamined Patent Publication No. 7-228984

  The object of the present invention is to solve the above-mentioned conventional problems, and can etch nickel, chromium, nickel-chromium alloy and iron-nickel-chromium alloy while minimizing the dissolution of copper, which is environmentally friendly and harmful. It is to provide a low etching solution.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an etching solution comprising a combination of sulfuric acid and a specific carboxylic acid can achieve the above object, and has completed the present invention.

  That is, the present invention is an etching solution for etching nickel, chromium, nickel-chromium alloy and iron-nickel-chromium alloy, and comprises an aqueous solution containing sulfuric acid and hydroxycarboxylic acid and / or aminocarboxylic acid. An etching solution is provided.

  Examples of the hydroxycarboxylic acid used in the etching solution of the present invention include malic acid, tartaric acid, and lactic acid.

  The aminocarboxylic acid used in the etching solution of the present invention is preferably a basic aminocarboxylic acid or a neutral aminocarboxylic acid, and particularly includes glycine (aminoacetic acid), alanine, histidine, tryptophan and the like.

  The sulfuric acid concentration is preferably 3.6 g / L or more, more preferably 100 to 1100 g / L, from the viewpoint of adjusting the etching rate to an appropriate range. Most preferably, it is 200-600 g / L. If it is less than 3.6 g / L, the etching is poor, and if it is less than 100 g / L, the etching rate is slow. From the viewpoint of etching performance, the higher the concentration of sulfuric acid, the better. However, if it exceeds 600 g / L, the calorific value due to the heat of hydration of sulfuric acid increases, which may be dangerous in adjustment work. Is most preferred.

  The concentration of hydroxycarboxylic acid and / or aminocarboxylic acid is preferably 0.005 mol / L or more, more preferably 0.03 mol / L or more, from the viewpoint of setting the etching rate to an appropriate range. Preferably it is 0.05 mol / L or more. The upper limit is not particularly limited and can be used up to an amount that can be dissolved in sulfuric acid. However, even if the concentration is high, the etching effect is not significantly affected, so that it is preferably 1.70 mol / L from the viewpoint of economy.

  In the etching solution of the present invention, it is particularly preferable that the sulfuric acid concentration is 360 g / L to 1100 g / L and the hydroxycarboxylic acid and / or aminocarboxylic acid concentration is 0.005 mol / L to 1.70 mol / L.

  As the water in which the sulfuric acid and the hydroxycarboxylic acid and / or aminocarboxylic acid are dissolved in the etching solution of the present invention, it is preferable to use pure water, distilled water, or ion-exchanged water that does not contain impurities.

  Next, an etching method using the etching solution of the present invention will be described.

  The etching solution of the present invention can be used by a method such as an immersion method or a spray method. In the case of processing a wiring plate having a thin line pattern, it is preferable to use a spray method in order to bring the etching solution into sufficient contact between the wirings and shorten the etching time.

  More specifically, the etching process using the etching solution of the present invention includes an alloy layer forming process for forming an alloy layer such as Ni—Cr on a substrate, and a copper layer for further forming a copper plating layer on the alloy layer. A plating layer forming process, an exposure process in which a photosensitive resin is coated on the copper plating layer and then exposed by masking in a predetermined pattern, and a first etching process process in which the copper plating layer is removed together with unnecessary resin after the exposure. It can be performed after each step. That is, the etching process using the etching solution of the present invention is a second etching process step of removing the alloy layer exposed in the first etching process using the etching solution of the present invention.

  A polyimide resin substrate is preferably used as the substrate. Further, as the material for forming the alloy layer, nickel, chromium, nickel chromium alloy and iron nickel chromium alloy are used, and at least one of these is used in use, but nickel chromium alloy and iron nickel chromium alloy are preferably used. It is done. Each process of the alloy layer forming process, the copper plating layer forming process, the exposure process, and the first etching process can be performed without particular limitation using a method usually used in manufacturing this type of wiring board.

  In the second etching treatment step, the temperature at which the etching solution of the present invention is used is usually preferably from room temperature to 90 ° C., but the higher the temperature, the better the etching rate, so 40 ° C. to 80 ° C. It is preferable to set it as ° C. The etching time is preferably 30 seconds to 2 minutes.

  The etching solution of the present invention can satisfactorily etch the underlying nickel, chromium, nickel-chromium alloy and iron-nickel-chromium alloy without over-dissolving the copper circuit, and is environmentally friendly and less harmful. is there.

  The etching solution of the present invention is useful for the production of a printed wiring board, for example.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited to these.
[Example 1]
As shown in Table 1, the sulfuric acid concentration is changed in the range of 0 to 1800 g / L, and the aminocarboxylic acid (glycine) is changed in the range of 0.005 mol / L to 1.70 mol / L. The etching solution was prepared, and the etching solution was put in a 1 L beaker up to a mark of 500 mL and maintained at 65 ° C. in a high-temperature bath. A sample piece (20 mm × 50 mm) in which a nickel chromium layer was formed on a polyimide film base material was prepared. The sample piece was immersed in an etching solution and oscillated at 60 reciprocations per minute for 1 minute, and then the etching state was visually observed. The results are shown in Table 1. In Table 1, the shaded portion indicates a range where good removal of the nickel chromium layer was confirmed.

From Table 1, it can be seen that a good etching effect was confirmed when the sulfuric acid concentration was 370 g / L and the glycine concentration was 0.005 mol / L or more and 0.70 mol / L or less.
[Example 2]
As shown in Table 2, various aminocarboxylic acids were added at a concentration of 0.05 mol / L to 360 g / L of sulfuric acid to prepare an etching solution, and sample pieces were prepared in the same manner as in Example 1. Etching was performed, and the etching state was visually observed. The results are shown in Table 2. As aminocarboxylic acids, basic aminocarboxylic acids and neutral aminocarboxylic acids alanine, histidine and tryptophan were used, and acidic aminocarboxylic acids aspartic acid, glutamic acid and arginine were used.

[Examples 3 to 5, Comparative Examples 1 to 3]
A nickel chromium alloy layer having a thickness of 10 mm was formed on a polyimide film substrate by sputtering. Next, a copper plating layer having a thickness of 8 μm is formed on the nickel chrome layer by copper plating, a photosensitive resin is applied on the copper plating layer by 4 μm, and then exposure is performed by masking in a predetermined pattern and irradiating with ultraviolet rays. went. After the exposure, using a hydrogen peroxide / sulfuric acid-based etching solution described in JP 2006-013307 A (Example 1), etching was performed at 45 ° C. for 3 minutes to etch the copper plating layer together with unnecessary portions of the resin. (First etching step).

  Next, each etching solution shown in Table 3 is prepared, and the exposed nickel chrome alloy layer in the wiring board in which the copper circuit is formed on the nickel chrome alloy layer manufactured by the first etching process is etched. Was carried out as follows. The results are shown in Table 3.

・ Creation of evaluation board Cut the wiring board on which the copper circuit is formed to 25mm width x 50mm length, and make both ends in the length direction with chemical-resistant tape with chemical-resistant epoxy resin of width 30mm x length 100mm An evaluation substrate was prepared by pasting on a support plate.

Etching solution Each etching solution having the composition shown in Table 1 was poured into a 1-L glass tall beaker up to a mark of 500 ml, and the temperature was kept at 65 ° C in a thermostatic bath to prepare a processing etching solution.

-Second etching step The above-described evaluation substrate was immersed in the above-described etching solution, rocked at 60 reciprocations / minute left and right, and the etching state of the nickel chromium alloy layer was visually observed.

  In Examples 3 to 5 using the etching solution of the present invention, the nickel chromium alloy layer was well removed in a short time (60 seconds to 180 seconds), but in Comparative Examples 1 to 3, it was not sufficiently removed even in 180 seconds. . The state of the copper circuit was also confirmed visually. The results are shown in Table 3.

  For reference, FIG. 1 (electron micrograph) shows the state of the nickel chromium alloy layer and the copper plating layer etched with the etching solution of Example 5.

  Here, the upper part of FIG. 1 is an electron micrograph showing the state of the untreated copper plating layer and nickel chrome alloy layer before the second etching process, and the middle part of FIG. 1 is for the untreated evaluation. It is an electron micrograph which shows the state after performing the etching process for 60 second with the etching liquid of Example 5 about a board | substrate, The lower stage of FIG. 1 is the conventional potassium permanganate and sodium hydroxide about the board | substrate for an unprocessed evaluation. It is an electron micrograph which shows the state after performing etching processing for 60 seconds using.

  As is clear from the results shown in FIG. 1, it can be seen that when the etching solution of the present invention is used, only the nickel chromium alloy layer can be sufficiently removed without eroding the copper circuit layer.

  As is clear from the results shown in Table 3, the etching solution of the present invention can remove the nickel chromium alloy layer in a short time without damaging the copper circuit.

The upper part of FIG. 1 is an electron micrograph showing the state of the untreated copper plating layer and nickel chrome alloy layer before performing the second etching process, and the middle part of FIG. 1 is an example of an untreated evaluation substrate. 5 is an electron micrograph showing a state after etching for 60 seconds with an etching solution of No. 5, and the lower part of FIG. 1 shows an untreated substrate for evaluation that was etched for 60 seconds using a conventional permanganate. It is an electron micrograph which shows the state after a long time.

Claims (5)

An etching solution for a nickel chromium alloy comprising an aqueous solution containing only sulfuric acid and hydroxycarboxylic acid and / or aminocarboxylic acid.   2. The etching solution for a nickel chromium alloy according to claim 1, wherein the aminocarboxylic acid is a basic aminocarboxylic acid or a neutral aminocarboxylic acid.   The nickel chrome alloy etching solution according to claim 1, wherein the hydroxycarboxylic acid is tartaric acid or malic acid.   The sulfuric acid concentration is 100 g / L or more and 1100 g / L or less, and the hydroxycarboxylic acid and / or aminocarboxylic acid concentration is 0.005 mol / L or more and 1.70 mol / L or less. The etching solution for nickel chromium alloys as described in the item. The flexible wiring board which formed the circuit by removing copper of the unnecessary part by etching after copper plating on the nickel chromium alloy layer, for the nickel chromium alloy according to any one of claims 1 to 4 An etching method in which only the nickel-chromium alloy is removed without immersing the copper in the circuit portion by dipping in an etching solution.

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