JPH0158270B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method for controlling and managing a copper chloride etching solution, and a method for effectively controlling and managing an etching solution so that copper-clad laminates and the like can be etched efficiently and with high precision. Pertains to.

It is well known that a cupric chloride solution is used as an etching solution when etching copper and copper alloys. When performing etching with the etching solution, it is important to keep the composition and concentration of the etching solution constant without causing sudden changes in the etching rate, so as to prevent sudden changes in the etching rate. . Factors that rapidly change the etching rate are the cuprous chloride concentration, cupric chloride concentration, hydrochloric acid concentration, and hydrogen peroxide concentration in the solution.

Conventionally, as a method to control these concentrations, the concentration of cuprous chloride was detected using an ORP meter, potentiostatic electrometer, or colorimeter, and the hydrogen peroxide and the regenerated theoretical amount of hydrochloric acid were mixed with the hydrogen peroxide replenishment amount. It was proportionally replenished directly into the etching bath or regeneration bath etching solution, and the concentration of cupric chloride was detected with a hydrometer and generally controlled by replenishing water or hydrochloric acid. In this way, conventionally, the concentration of cuprous chloride and cupric chloride in the liquid has been controlled and managed by a method that detects only the concentration.

However, with such control and management methods, the concentration of hydrochloric acid in the etching solution cannot be directly detected, and the balance between the hydrogen peroxide and hydrochloric acid that is replenished is likely to be lost, making it difficult to obtain a constant concentration of hydrochloric acid. It had the disadvantage that it was difficult to maintain and etch it. Particularly in recent years, a high concentration of free hydrochloric acid of about 2 to 6 moles/h is often used because of the need to increase the etching rate and productivity. For example, if the amount of processed printed circuit boards or the density of circuit patterns changes, the rate of consumption of hydrochloric acid due to air oxidation as a side reaction changes, and the concentration of hydrochloric acid in the bath changes.For example, in a high concentration hydrochloric acid bath, hydrochloric acid Varying from 2.5 mol/min to 4.5 mol/min, the etching rate varies from 28 μm/min to 50 μm/min. As described above, the etching rate varies greatly due to changes in the hydrochloric acid concentration, and this is becoming a major problem.

In order to eliminate the above-mentioned variations in etching speed and perform etching with high precision, the present inventors have conducted various studies on methods of controlling the composition and concentration of the etching solution, and directly detected the concentration of hydrochloric acid in the etching solution. Through this, we discovered a method to manage and control the concentration of the liquid composition.

That is, in the present invention, when regenerating a copper chloride etching solution by adding hydrochloric acid and hydrogen peroxide, a part of the etching solution is extracted outside the system from an etching apparatus equipped with an etching tank, a detection tank, a regeneration tank, etc. The solution is diluted with water or alkaline water, the hydrochloric acid concentration of the solution is detected continuously or intermittently, and a part of the etching device is replenished with water or hydrochloric acid according to the preset hydrochloric acid concentration range, and etching is performed. This is a method for controlling and managing an etching solution, which is characterized by controlling the concentration of hydrochloric acid in the solution.

According to the method of the present invention, variations in the concentration of hydrochloric acid in the etching solution are reduced, the balance between hydrogen peroxide and hydrochloric acid can be maintained constant, and stable etching can be performed over a long period of time.

In the method of the present invention, when responding and controlling based on the instructions of a PH meter, the dilution ratio is preferably 2 to 200 times, taking into account that the HCl concentration in the etching solution is usually 1 to 6 mol/cm and the characteristics of the PH meter. is 5 to 100 times larger. This makes it possible to keep the pH in the measurement solution within ±0.03, and the sampling error within ±5%, making it possible to control the HCl concentration in the etching solution within ±5% of the set value. It is.

On the other hand, when using the titration method, the sum of the alkali sampling error and titration error due to batch operation is ±
By suppressing the concentration to 5%, the HCl concentration in the etching solution can be controlled within ±5% of the set value. Also PH
Due to the characteristics of the meter, titration device, etc., the measurement temperature is 5 to 60.
It can be applied at any temperature within the temperature range of °C, but in order to reduce errors due to temperature changes in the detection liquid, use a temperature compensation electrode or a constant temperature bath to maintain a constant temperature. It is preferable to measure as a condition. Titration methods include, for example, PH
Potentiometric titration using a meter or temperature titration using a thermistor can be applied.

Water or alkaline water is used as the diluent. As the alkaline water, an aqueous solution of 0.01 to 100 g of caustic soda, caustic potash, soda carbonate, etc. at a constant concentration is used.

By using an alkaline aqueous solution, devices such as a dilution measuring tank and a pump can be downsized, and the dilution ratio can be as low as 2 to 50 times, making it possible to reduce sampling errors and measurement errors.

The alkali used in the titration is a fixed concentration aqueous solution of 10 to 200 g/ml of caustic soda, caustic potash, soda carbonate, etc.

The hydrochloric acid concentration of the etching solution may be detected at any point from the time it is discharged from the etching tank until it enters the regeneration tank, or from the regeneration tank until it enters the etching tank. In order to accurately detect the aging state of the etching solution, it is preferable to detect the solution discharged from the etching tank, and when finely adjusting the hydrochloric acid concentration suitable for etching, the process from the regeneration tank to the etching tank is detected. It is preferable to detect at When detecting the concentration of the liquid discharged from the etching tank until it enters the regeneration tank, it can be carried out continuously, but when detecting it during the process from the regeneration tank to the etching tank, there is hydrogen peroxide in the liquid to be detected. Since a considerable amount of hydrogen peroxide is contained, bubbles are generated and sampling errors are likely to occur. Therefore, for example, if hydrogen peroxide exceeding 30 ppm is present, it is preferable to detect it intermittently.

When temperature titration is performed, the liquid discharged from the etching tank located between the etching tank and the regeneration tank is detected. Hydrochloric acid for replenishment may be added to any part of the etching apparatus, but it is generally added to the regeneration tank or the etching tank.

When carrying out the method of the present invention, specifically, PH
Automatic control such as operating a solenoid valve, metering pump, timer, etc. so that a predetermined amount of hydrochloric acid is automatically added from the hydrochloric acid tank to the etching solution in response to an indication of a value or potential value or a titration value. can do.

The method of the present invention detects the cuprous chloride concentration using a conventional ORP meter, potentiostatic electrometer, or colorimeter.
When replenishing hydrogen peroxide, in addition to the method of replenishing a fixed amount of hydrochloric acid in proportion to the amount of hydrogen peroxide replenishment, the method of the present invention allows replenishment of finely adjusted amounts of hydrochloric acid and water. Also, replenish hydrogen peroxide.
It is also possible to carry out using an ORP meter, potentiostatic electrolyzer, or colorimeter, and to supplement hydrochloric acid separately by the method of the present invention.

As described above, according to the method of the present invention, only the concentration of hydrochloric acid can be accurately detected and controlled directly without being affected by the concentrations of cupric chloride, cuprous chloride, and hydrogen peroxide in the copper chloride etching solution. Etching can be carried out.

Next, the method of the present invention will be explained using examples.

Example 1 A spray-type etching machine equipped with a regeneration tank that circulates an etching solution with a composition of CuCl ₂ 2 mol/, CuCl 0.01 mol/, and HCl 3 mol/min (equipment of etching solution 360, circulation rate 400/min). )
A 100 ml PH measurement tank equipped with a PH electrode (including control and compensation), a stirrer, and a diluent and stock solution inlet was heated at a flow rate of 2 ml/min from a bypass installed in a part of the etching solution circulation path. The etching solution is continuously extracted, and tap water for dilution is simultaneously continuously supplied to the PH measurement tank at a flow rate of 130 ml/min. (Before operation, the electrodes were calibrated and the PH meter was calibrated by flowing an etching solution with a known concentration.) One-sided phenolic resin copper-clad laminate (Cu foil 35 μm) (total 800 m ² ) Etching
The spraying was carried out for 8 hours at 50°C±1°C, a spray pressure of 1.3 kg, and a conveyor speed of 4 m/min. As a result, a uniform etching rate was obtained with little pH variation, and no etching defects occurred at all. Figure 1 shows the changes over time in the hydrochloric acid concentration and pH in the solution in this case.

For comparison, changes in the concentration of hydrochloric acid in the conventional detection method are also shown.

Example 2 A portion of the etching solution circulating in an etching machine using an etching solution having the same composition as in Example 1 was intermittently drawn out 4 ml/time,
The mixture was mixed and diluted with 1 ml of water, the pH was measured, and the electromagnetic valve for supplying hydrochloric acid or water was operated based on the detected PH value in the same manner as in Example 1 to replenish the solution with hydrochloric acid or water.
Intermittent withdrawals were performed for 5 minutes per cycle.
Using this control method, a copper-clad laminate (802 m ² in total) was etched for 8 hours under the same conditions as in Example 1, but the variation in hydrochloric acid concentration was ±4% of the set value, and a consistent etching finish could not be achieved. Ta.

Example 3 Using an etching solution with the same composition as in Example 1, an etching machine equipped with an etching tank and a regeneration tank and in which the etching solution circulates, the circulating etching solution was intermittently drawn out 4 ml/time, and 150 ml of the etching solution was intermittently drawn out.
NaOH water was added, mixed and diluted, and the pH was measured. PH
The set value is set to 4.0 (HCl neutralization point), and if the value is higher than that, the solenoid valve installed in the replenishment water tank is opened and reversed.
The solenoid valve of the replenishment hydrochloric acid tank is opened when the value is below 4.0. This control method makes it possible to
Etching of 801 m ² ) was carried out for 8 hours, and the variation in hydrochloric acid concentration was within ±3% of the set value, making it possible to perform consistent etching.

Example 4 Consisting of an etching solution with the same composition as Example 1,
Using the same etching machine as in Example 1, 5 ml of etching solution was intermittently drawn out, and 1/2
Titration was carried out using a temperature titration device using a thermistor using a specified KOH aqueous solution. So that the solenoid valve of the water tank to be refilled will open when the measured value exceeds the set value.
Conversely, the solenoid valve for the hydrochloric acid tank that is refilled is opened when the level falls below the set value. Using this control method,
Etching of a copper-clad laminate (802 m ² in total) was carried out for 8 hours, and the variation in hydrochloric acid concentration was within ±5% of the set value, and consistent etching was achieved.

Comparative Example 1 A copper-clad laminate (795 m ² in total) was etched under the same conditions as in Example 1 using a conventional etching machine (ORP meter and hydrometer control system) that circulated an etching solution with the same composition as in Example 1. 8 hours
I did it.

After 3 hours, the hydrochloric acid concentration reached 2.6 mol/min, and etching began to become insufficient. The ratio of hydrogen peroxide and hydrochloric acid in the replenishment solution is set to 1:1 by H ₂ O ₂ concentration detection.
When etching was performed by changing the ratio from 2.4 to 1:2.8, over-etching began to occur after 7 hours. After 8 hours of operation, the concentration of hydrochloric acid was 4.1 mol/.

[Brief explanation of drawings]

FIG. 1 shows changes over time in the hydrochloric acid concentration and pH in the etching solution. 1 shows the change in the concentration of hydrochloric acid when controlled by the method of the present invention, and 2 shows the change in the concentration of hydrochloric acid when controlled by the conventional method.

Claims (1)

[Claims] 1. When regenerating copper chloride etching solution by adding hydrochloric acid and hydrogen peroxide, a part of the etching solution is extracted from the etching device equipped with an etching tank, a detection tank, a regeneration tank, etc., and the solution is replaced with water or an alkali. The etching solution is diluted with water, the hydrochloric acid concentration in the etching solution is detected continuously or intermittently, water or hydrochloric acid is replenished into a part of the etching device according to the preset hydrochloric acid concentration range, and the hydrochloric acid concentration in the etching solution is measured. A method for controlling and managing an etching solution, characterized by controlling: