JPH0673563A - Etching method - Google Patents

Abstract

PURPOSE:To continuously etch a material in the best condition at all times by supplying the aq. solns. contg. chlorates, hydrogen chloride, ferric chloride and hydrogen chloride based on the detection results of the oxidation-reduction potential and hydrogen chloride concn. of an etchant. CONSTITUTION:Aq. solns. are supplied to an etchant in a tank 1 by 5-6.5mols of HCl and 2. 5-30mols of FeCl3 per mol of the chlorate. In this case, the etchant is sent to a part 2 for detecting the oxidation-reduction potential, HCl concn. and sp.gr., and an aq. FeCl3 soln. is supplied to the tank 1 from a storage tank 3 by using a control signal wiring A when the detection result of the oxidation- reduction potential decreases below the set value. Similarly, the aq. solns. of HCl and chlorates are supplied to the tank 1 from storage tanks 4 and 5, and the supply of the solns. is topped when the oxidation-reduction potential increases above the set value. The aq. FeCl3 soln. is supplied to the tank 1 from the storage tank 3 by using a wiring B when the HCl concn. decreases below the set value, and aq. HCl is supplied from the storage tank 4 to the tank 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method, and more particularly to copper, iron, and iron using an aqueous solution of ferric chloride.
It relates to a method for continuous etching of metals such as nickel and their alloys.

[0002]

2. Description of the Related Art In the etching of copper with an aqueous solution of ferric chloride, copper ions and ferrous ions in the etching solution increase due to the reaction of the following equation as the etching progresses, and the etching rate decreases accordingly. Fe ⁺⁺⁺ + Cu ⁰ → Fe ⁺⁺ + Cu ⁺ Fe ⁺⁺⁺ + Cu ⁺ → Fe ⁺⁺ + Cu ⁺⁺

In order to solve this problem, in the conventional continuous etching of copper with an aqueous solution of ferric chloride, a method has been adopted in which the effective etching distance is lengthened to secure a practical line speed. However, this method has drawbacks such as high equipment cost and a large amount of chemical solution. Further, these drawbacks are the same as in the etching of metals other than copper.

[0004]

As a method for solving such a drawback, a chlorate and hydrogen chloride are supplied to an etching solution and ferrous chloride produced by the etching is returned to ferric chloride to remove the etching solution. Japanese Patent Laid-Open No. 64-87788 and Japanese Patent Laid-Open No. 2-14968 disclose a method for recovering the performance of the above-mentioned method. However, the etching method is insufficient to cope with the recent miniaturization and high density of electronic parts. Is.

The above-mentioned etching method uses a chlorate as an oxidant and simultaneously supplies hydrogen chloride consumed in this reaction. However, during the etching, air oxidation of ferrous ions also occurs. However, this also consumes hydrogen chloride, and hydrogen chloride is also lost by evaporation. For this reason, in this method, this is dealt with by increasing the amount of hydrogen chloride to be supplied in advance in excess of the reaction equivalent of the chlorate.

That is, in this method, the concentration of hydrogen chloride decreases when a material having a small etching area is sprayed or the material has a large etching amount, and the concentration of hydrogen chloride increases when a material having a large etching amount is etched, which causes variations in etching performance. It becomes a factor.

Further, in order to cope with the miniaturization of the printed wiring board circuit and the increase in the number of lead frames, it is necessary to suppress the concentration of hydrogen chloride which damages the etching resist and roughens the etching surface. However, the conventional methods are difficult to perform because hydrogen hydroxide is consumed by air oxidation or the like to form metal hydroxides, which drastically reduces etching performance.

Therefore, it is an object of the present invention to provide a method capable of continuously performing etching under the best conditions.

[0009]

The present invention detects the amount of ferrous chloride produced by etching a metal by measuring the redox potential, and based on this result, an aqueous chlorate solution, an aqueous hydrogen chloride solution, It is a continuous etching method of supplying ferric chloride, further detecting the hydrogen chloride concentration, and supplying an aqueous solution containing hydrogen chloride. According to the present invention, it is possible to solve all the problems related to the etching so far. .

That is, the etching method according to the present invention is a continuous metal etching method using a ferric chloride aqueous solution, wherein 1 mol of a chlorate selected from the group consisting of sodium chlorate, potassium chlorate and calcium chlorate is used. To hydrogen chloride 5 to 6.5 mol and ferric chloride 2.5 to 3
When the chlorate aqueous solution, the hydrogen chloride aqueous solution and the ferric chloride aqueous solution are supplied to the etching solution at a ratio of 0 mol, the oxidation-reduction potential of the etching solution is detected, and the above solutions are separately used or hydrogen chloride based on the detection result. A mixed solution of an aqueous solution and ferric chloride and an aqueous chlorate solution are supplied to the etching solution to continuously maintain a preset redox potential,
In addition, the hydrogen chloride concentration of the etching solution is detected, and based on this detection result, the hydrogen chloride aqueous solution or the hydrogen chloride aqueous solution and the ferric chloride aqueous solution are supplied to the etching solution separately or as a mixed solution to obtain the preset hydrogen chloride concentration. It is characterized by being maintained continuously.

In the etching method according to the present invention,
Chloric acid, which is detected by detecting the oxidation-reduction potential, can be appropriately supplied by the air oxidation of ferrous iron that changes depending on the operating conditions of the etching apparatus and the replenishment of hydrogen chloride lost due to evaporation. The supply ratio of salt and hydrogen chloride can be set to the reaction equivalent or a value close thereto.

As a result, the hydrogen chloride content in the etching solution can be suppressed to an extremely low level, the etching resist is not damaged, the amount of underetching is minimized, and the etched metal surface is smoothed. Etching becomes possible.

The detection of the redox potential in the present invention may be carried out using a normal ORP electrode. The detection of the hydrogen chloride concentration may be performed with a pH electrode, and other means such as an automatic titrator may be selected.

The supply ratio of the chlorate and hydrogen chloride supplied based on the detection result of the redox potential is preferably 5 to 6.5 mol of hydrogen chloride per mol of chlorate, more preferably the reaction equivalent. It is better to use 6 mol. Although the aqueous solution containing hydrogen chloride to be supplied for hydrogen chloride detection is appropriately supplied, it is preferable to set the hydrogen chloride concentration in the etching solution to 0 to 3% by selecting the control set value.

The lower the concentration of hydrogen chloride in the etching solution, the more accurate the etching becomes possible, but the etching rate decreases. Resist used, target metal,
It may be appropriately determined depending on the fine density.

Usually, when a dry film is used as a resist and a copper foil of a printed wiring board is etched,
When the concentration of hydrogen chloride in the etching solution is around 1% and nickel alloys, nickel and chromium alloys are the target,
Good results are obtained when the content is 2% or less.

The supply of ferric chloride is carried out in order to adjust the concentration of metals such as copper and nickel in the etching solution, which increases with the progress of etching, to a constant level, and depending on the target metal and the required etching performance. The supply amount may be appropriately changed. For example, iron or an iron-based alloy having a high iron content may be reduced, and if the Cr content is high, the etching performance may be deteriorated. Practically, it is preferably 2.5 to 30 mol per mol of chlorate.

Taking these factors into consideration, the redox potential and the hydrogen chloride concentration in the etching solution are set in advance, and the chlorate aqueous solution, the hydrogen chloride aqueous solution and the chloride chloride solution are set in accordance with the changes in the redox potential in the etching solution. The ferric iron solution may be added separately or a mixed solution of a hydrogen chloride aqueous solution and a ferric chloride aqueous solution and a chlorate aqueous solution may be added to the etching solution.
The hydrogen chloride aqueous solution or the hydrogen chloride aqueous solution and the ferric chloride aqueous solution may be added to the etching solution separately or as a mixed solution according to the change in the hydrogen chloride concentration.

The chlorate used in the present invention is selected from, for example, sodium chlorate, potassium chlorate, calcium chlorate, etc., and is supplied in the form of an aqueous solution, and the concentration thereof is 35-40 in the case of sodium chlorate. It is good to set it as%.

Hydrogen chloride is preferably supplied as an aqueous solution of 30 to 35%, and ferric chloride is preferably supplied as an aqueous solution of 40 to 50 ° Be.

It should be noted that it is necessary to mix the aqueous solutions of hydrogen chloride and ferric chloride in advance in the above-mentioned proportions before supplying the equipment,
It is preferable from the viewpoint of safety in handling.

The supply of the aqueous solution of hydrogen chloride corresponding to the detection of the concentration of hydrogen chloride is preferably carried out simultaneously with the aqueous solution of ferric chloride in order to keep the amount of dissolved metal constant. More preferably, it is supplied as an aqueous solution of a mixture with ferric iron.

Further, ammonium salts, amines, amine salts such as ammonium chloride, ammonium bromide, ethylenediamine, which are described in JP-A-2-149684,
Monoethanolamine can also be added to the etching solution. The amount of these used is such that the amount in terms of nitrogen is 0.02 to 3% by weight with respect to the total amount of the etching solution, and preferably 0.05 to 2% by weight.

Further, in order to maintain the etching performance, it is preferable to install a specific gravity meter and supply water to keep the specific gravity of the etching solution constant based on the detection result. The specific gravity of the etching solution is 1.1 to 1.6, preferably 1.3 to
Better keep it at 1.5.

Further, the etching temperature is preferably 30 to 70 ° C. as is usually done, and is preferably 30 to 50 ° C. when an etching tank made of hard vinyl chloride is used.

The etching method of the present invention can be carried out by either a dipping method or a spray method. In the case of the spray method,
The pressure is preferably 0.5 to 5.0 kg / cm ² .

Next, one embodiment of an apparatus suitable for carrying out the etching method of the present invention will be described with reference to FIG. In FIG. 1, the etching solution in the etching tank (1) is passed through the etching solution feed pipe (11), and is fed to the redox potential, hydrogen chloride concentration and specific gravity detection section by the etching solution feed pump (6). Further, the overflowed etching solution is returned to the etching tank (1) through the etching solution return pipe to circulate the etching solution. This etching solution circulation is always performed.

When the measurement result of the oxidation-reduction potential becomes less than the set value, the control signal wiring (A) relating to the oxidation-reduction potential is used, the ferric chloride aqueous solution feed pump (7) is operated, and the ferric chloride is fed. The ferric chloride aqueous solution is supplied from the aqueous solution storage tank (3) to the etching tank (1) through the ferric chloride aqueous solution supply pipe (14). Similarly, the hydrogen chloride aqueous solution feed pump (8) is operated to supply the hydrogen chloride aqueous solution from the hydrogen chloride aqueous solution storage tank (4) to the etching tank (1) through the hydrogen chloride aqueous solution supply pipe (15). Similarly, the chlorate solution feed pump (9) is operated to supply the chlorate solution from the chlorate solution storage tank (5) to the etching tank (1) through the chlorate solution supply pipe (16). When the measured value of the oxidation-reduction potential exceeds the set value, the control signal wiring (A) relating to the oxidation-reduction potential is used to stop each pump and stop the supply of each aqueous solution.

When the measurement result of the hydrogen chloride concentration becomes less than the set value, the control signal wiring (B) relating to the hydrogen chloride concentration is used, the ferric chloride aqueous solution feed pump (7) is operated, and the ferric chloride is The ferric chloride aqueous solution is supplied from the aqueous solution storage tank (3) to the etching tank (1) through the ferric chloride supply pipe (14).
Similarly, the hydrogen chloride aqueous solution feed pump (8) is operated to supply the hydrogen chloride aqueous solution from the hydrogen chloride aqueous solution storage tank (4) to the etching tank (1) through the hydrogen chloride aqueous solution supply pipe (15).
When the measured hydrogen chloride concentration exceeds the set value, the signal control wiring (B) relating to the hydrogen chloride concentration is used to stop each pump and stop the supply of each aqueous solution.

When the measurement result of the specific gravity exceeds the set value,
Using the control signal wiring (C) that is concerned with specific gravity, open the water supply pipe solenoid valve (10), and through the water supply pipe, etch tank (1)
Supply water to. When the measurement result of the specific gravity becomes less than the set value, the control signal wiring (C) relating to the specific gravity is used to close the water supply pipe solenoid valve (10) to stop the water supply.

The etching solution in the etching tank (1) increased by the supply of each aqueous solution and water is discharged from the etching tank (1) due to overflow.

[0032]

EXAMPLES Examples and comparative examples of the present invention will be described below. In addition, the raw material compounding amounts in the following examples are weight ratios, and the percentages are weight percentages. Example 1 Spray type etching bath (effective etching distance of 4 m,
The printed wiring board copper foil was etched using the equipment of FIG. 1 in which a liquid management amount of 900 liters) was combined with a liquid management device for detecting and controlling the oxidation-reduction potential, hydrogen chloride concentration, and specific gravity. The control set values were as follows. Redox potential: 530 mV, hydrogen chloride concentration: 275 mV
(Measurement and control of potential generated from pH electrode with voltmeter), specific gravity 1.360. As the medicine, a mixed solution of 100 parts of ferric chloride aqueous solution of 40 ° Be and 3 parts of ammonium chloride (this is referred to as solution A), 35% hydrochloric acid aqueous solution (this is referred to as solution B),
A mixed solution of 100 parts of 38% sodium chlorate aqueous solution and 0.1 part of diethylenetriamine (this is referred to as solution C) was used, and according to the detection result of the redox potential of the etching solution, A
Liquid, liquid B, and liquid C are supplied so that the molar ratio of ferric chloride: hydrogen chloride: sodium chlorate is 4.7: 6.0: 1,
Liquids A and B were supplied at the same ratio as above according to the detection result of hydrogen chloride concentration, and water was supplied according to the detection result of specific gravity. Etching solution temperature is 45 ° C, spray pressure is 2.0 kg / c
m ^2, conveyor speed 4.2m / min and, copper foil thickness 45μ
m, copper foil removal rate 60% double-sided plate (this is D plate), copper foil thickness 45 μm, copper foil removal rate 18% double-sided plate (this is E
Respectively multiplied by a plate) 8 hours was 50 m ^2, 60 m ² process. During this time, according to each control set value, each chemical solution,
Water is automatically supplied and ferrous chloride concentration is 0.42 to 0.44
Mol / liter, hydrogen chloride concentration 0.52 to 0.55%,
The specific gravity was controlled to 1.358 to 1.360, and no defective products related to etching were generated. Also, the line width is 100μ
m, the etch factor (copper foil thickness / side etch) of a 100 μm circuit between lines was 3.8. The amounts of the A liquid and the B liquid supplied based on the detection of the hydrogen chloride concentration were larger in the E plate treatment than in the D plate treatment. I continued to operate under the same conditions for 3 months, but there was no trouble such as sludge generation,
No etching bath cleaning or liquid exchange was required.

Example 2 The same etching equipment as in Example 1 was used. The liquids A and B of Example 1 were mixed so that the molar ratio of ferric chloride: hydrogen chloride was 5: 6 (this is referred to as liquid F). The supply ratio of the F liquid and the C liquid was set such that the molar ratio of ferric chloride: hydrogen chloride: chlorate was 5: 6: 1, the control set value of the hydrogen chloride concentration was 260 mV, and the conveyor speed was 5. 2 m / min, and other conditions were the same as in Example 1. Copper foil thickness 35
The μm double-sided plate was treated for 5000 m ² over 10 days. When the redox potential of the etching solution becomes less than the set value, the F solution,
The liquid C was supplied, and the liquid F was supplied when the potential related to the hydrogen chloride concentration fell below the set value. Of the composition of the etching solution, the hydrogen chloride concentration was 0.38 to 0.40%, and the others were the same as in Example 1. Further, the copper concentration is 75 to 78 g /
It was liter. There was no trouble such as sludge generation, and the etching state was a uniform finish from the beginning to the end of etching. The etch factor of the circuit having a line width of 70 μm was 3.7.

Example 3 The same etching equipment as in Example 1 was used to etch the lead frame and the like. The control set values are as follows. Redox potential: 600 mV, potential related to hydrogen chloride concentration: 245 mV, specific gravity 1.490. 48 ° as a drug
Mixed solution of Be ferric chloride aqueous solution and 35% hydrochloric acid aqueous solution so that the molar ratio of ferric chloride: hydrogen chloride is 16: 6.2 (this is referred to as liquid G), 38% sodium chlorate Using a mixed solution of 100 parts of aqueous solution and 0.1 part of triethylenetetramine (referred to as H solution), according to the detection result of redox potential, G solution and H solution were treated with ferric chloride: hydrogen chloride: chloric acid. The sodium was supplied at a molar ratio of 16: 6.2: 1, and the liquid G was supplied according to the detection result of the hydrogen chloride concentration. Etching temperature 50 ℃, spray pressure 1.8kg /
and cm ^2, 42- alloy material, lead frame having a thickness of 0.2 mm, and camera parts of SUS-304 material was etched. The conveyor speed was appropriately changed depending on the object to be etched. Although the SUS material having a slow etching rate and a small etching area was used, the hydrogen chloride concentration detector worked during the processing, and only the G solution was frequently supplied. The analysis results of the etching solution during the operation for 10 days showed that the concentration of ferrous chloride was 0.23 to 0.25 mol / liter and the concentration of hydrogen chloride was 0.2.
09-0.12%, and the specific gravity changed from 1.488 to 1.490. The finished dimensions of each product, the linearity of etching, and the smoothness of the metal surface were all good, and no defects related to etching occurred.

Comparative Example 1 The D plate of Example 1 was etched using the etching equipment of Example 1 with the same control set values and etching conditions except that the hydrogen chloride concentration control mechanism was stopped. 10m
At the time of ² treatments, liquid turbidity occurred, and at 13m ² treatment, short circuit occurred due to insufficient etching, and etching was stopped. After making the composition of the etching solution the same as that of Example 1, solutions A, B, and C were adjusted so that the supply molar ratio of ferric chloride: hydrogen chloride: sodium chlorate was 4.7: 6.5: 1. The flow rate of the liquid supply pump was changed. When the D plate was treated with 100 m ² , the hydrogen chloride concentration gradually decreased to 0.3%. Next, when the F plate of Example 1 was treated with 30 m ^2, liquid turbidity occurred, so the etching treatment was stopped. The etch factor of this product with a line width of 100 μm and a line spacing of 100 μm was 2.2.

Comparative Example 2 When the lead frame was etched using the equipment of Example 3 in which the hydrogen chloride concentration control mechanism was stopped, the etching solution became turbid in 2 hours. So that the supply molar ratio of hydrogen chloride and sodium chlorate is 7: 1,
When the lead frame etching treatment was continued by adjusting the pump flow rates of G liquid and H liquid, the hydrogen chloride concentration in the etching liquid became 0.3% in 3 hours, and the etching linearity deteriorated, so the etching was stopped. . Then SU
The processing of the camera material of S material was carried out for 5 hours, but the processing was stopped due to the generation of sludge. The etching surface of this product at the start of the treatment was a rough surface and was a defective product.

[0037]

The method for etching various metals with ferric chloride of the present invention detects the oxidation-reduction potential, and based on this result, the aqueous chlorate solution and the aqueous hydrogen chloride solution are automatically supplied, and the hydrogen chloride concentration is detected. As a result, by automatically supplying the aqueous solution containing hydrogen chloride, the etching process can be continuously performed under the best conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus for carrying out the present invention.

[Explanation of symbols]

 1 etching tank 2 redox potential, hydrogen chloride concentration, specific gravity detection unit 3 ferric chloride aqueous solution storage tank 4 hydrogen chloride aqueous solution storage tank 5 chlorate aqueous solution storage tank 6 etching liquid feed pump 7 ferric chloride aqueous solution feed pump 8 hydrogen chloride aqueous solution Feed pump 9 Chlorate aqueous solution feed pump 10 Water supply pipe Solenoid valve 11 Etching liquid feed pipe 12 Etching liquid return pipe 13 Water supply pipe 14 Ferric chloride aqueous solution supply pipe 15 Hydrogen chloride aqueous solution supply pipe 16 Chlorate aqueous solution supply pipe 17 Control parts for supplying solutions and water A Control signal wiring related to redox potential B B Control signal wiring related to hydrogen chloride concentration C Control signal wiring related to specific gravity

Front page continued (72) Inventor Yoshitsugu Ishizuka 7-35 Higashiohisa, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A method for continuously etching a metal with an aqueous solution of ferric chloride, wherein 5 to 6 hydrogen chloride is added to 1 mol of a chlorate selected from the group consisting of sodium chlorate, potassium chlorate and calcium chlorate. When the chlorate aqueous solution, the hydrogen chloride aqueous solution and the ferric chloride aqueous solution were supplied to the etching solution at a ratio of 0.5 mol and 2.5 to 30 mol of ferric chloride, the redox potential of the etching solution was detected. Based on the detection result, the solution is separately supplied or a mixed solution of a hydrogen chloride aqueous solution and a ferric chloride aqueous solution and a chlorate aqueous solution are continuously supplied to the etching solution to maintain a preset redox potential, Moreover, the hydrogen chloride concentration of the etching solution is detected, and based on this detection result, the hydrogen chloride aqueous solution or the hydrogen chloride aqueous solution and the ferric chloride aqueous solution are etched separately or as a mixed solution. Etching method characterized by continuously maintaining a preset hydrogen chloride concentration is supplied to the grayed solution.