JPH0487686A - Method for controlling amount of ozone injected into etching solution - Google Patents

Abstract

PURPOSE:To continuously and properly control the amt. of ozone injected into an etching soln, at the time of regeneration by continuously measuring the oxidation-reduction potential of the etching soln. contg. ferric salt as a principal component. CONSTITUTION:A deteriorated etching soln. in an etching vessel 1 is continuously introduced into a sampling vessel 12 by a pump 11 and the oxidation- reduction potential of the etching soln. is continuously measured with an ORP electrode 13. The oxidation-reduction potential is about 560mV in the case of about >=5g/l concn. of ferrous ions (Fe<2+>) and about 1,100mV in the case of about <=5g/l concn. When the oxidation-reduction potential measured with the electrode 13 rises suddenly, an ozonizer 8 is switched off. When the oxidation--reduction potential lowers, the ozonizer 8 is switched on.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is used for etching electronic components made of iron-based materials, and involves injection of ozone to regenerate an etching solution mainly composed of ferric salts. Concerning how to control the amount.

[Conventional technology]

For example, electronic parts made of iron-based alloys such as stainless steel,
In the molding process of IC lead frames, vapor deposition masks, etc., these are processed in advance through a process of photoresist coating → exposure stage development, and the areas from which the resist has been removed are treated with ferric chloride (FeC1s) and nitric acid Etching is carried out using an etching solution containing a ferric salt such as iron (Fe(NOx)) as a main component.

The ferric salt etching solution has as its main component any one of ferric hydrochloride, sulfate, and nitrate, or a mixture thereof, and has an anion common to that of the ferric salt. It is an aqueous solution to which an acid is added to adjust the pH. For example, in the case of hydrochloride, hydrochloric acid is added. When a member to be etched is treated with this ferric salt etching solution, etching is carried out by the following reaction.

2Fe"10Fe' -+ 3Fe" When used repeatedly, the ferric salt in the etching solution changes to ferrous salt, so the oxidizing power is lost and the etching speed decreases, making it difficult to use as an etching solution. Its performance deteriorates and it becomes unusable. Therefore, it is necessary to oxidize and regenerate this ferrous salt to increase the concentration of ferric salt and to adjust the specific gravity to keep the iron concentration constant.For example, to regenerate ferric chloride (FeC1t), Oxidative regeneration methods using hydrogen peroxide and chlorine gas and electrolytic oxidation methods are known, but
All of these require complicated and expensive equipment and are therefore not suitable.

In response, a method has been proposed that utilizes the strong oxidizing power of ozone to oxidize and regenerate the ferrous salt in the deteriorated etching solution into ferric salt, and is published in Japanese Patent Application Laid-open No. 62230991 and Japanese Patent Application Laid-Open No. It is described in 62-230992.

Regeneration of the etching solution by ozone is carried out by the following reaction.

2FeC1t +Os + 2HCI→2FeC1s
+ 100 g of HtO This method has the advantage that it has excellent regeneration efficiency and can be carried out in a volume of 5 with simple equipment.

FIG. 4 is a schematic diagram showing an outline of an etching apparatus capable of regenerating a deteriorated etching solution using ozone. In FIG. 4, the member to be etched, whose surface is covered with resist and only the etched portion is exposed, moves on a roller conveyor above the etching bath l. Here, the direction of movement of the member to be etched is shown by a dotted line arrow, and the direction of gas or liquid flow is shown by a solid line arrow.The ferric chloride etching solution contained in the etching tank 1 is sucked up by the pump 2, and then sent to the spray nozzle. Etching is carried out continuously by spraying the member to be etched while it is traveling through the etching tube 3.

The deteriorated etching solution is sent to the reaction tower 5 by a pump 4, and is sprayed from a spray nozzle 6 installed in the upper part of the reaction tower 5 to prevent the generation of bubbles. On the other hand, after the air compressed by the compressor 7 is sent to the ozone generator 8 and ozonized, this ozonized air is diffused into the deteriorated enching liquid through the aeration pipe 9 installed at the lower part of the reaction tower 5. Ru. Unreacted ozone passes through the exhaust ozone decomposition tower 10 and is converted into harmless oxygen and released into the atmosphere. The etching solution that has been regenerated after staying in the reaction tower 5 for a certain period of time is returned to the etching tank 1, and by repeating the above process, the degraded etching solution in the etching tank 1 is gradually regenerated.

By the way, in the above etching process, the concentration of ferrous ions was about 5g#! When the temperature is below, unreacted ozone is discharged from the reaction tower 5, and the oxidation reaction no longer progresses. Therefore, in order to determine the amount of ozone to be injected, the concentration of ferrous ions (Fe2'') in the etching solution is measured. The red color produced by the reaction is measured by spectrophotometry using the following procedure.

Take an appropriate amount of sample into a 100 m volumetric flask.

↓ 1. Add 5 m of 10-phenanthroline solution (0, IN/VX). ↓ Add 10m of ammonium acetate solution (50m/νχ).

↓ Add water to make 1001.

↓ Leave for 20 minutes.

↓ Transfer a part of this to a 10mm absorption cell and set the wavelength to 510ns.
Measure the absorbance in the vicinity and determine the concentration from a calibration curve prepared in advance.

Based on the results thus obtained, the ozone injection amount is controlled by turning on and off the power to the ozone generator 11B.

[Third Problem to be Solved by the Invention] However, there are the following problems in controlling the amount of ozone injection in the above-mentioned apparatus. In other words, since the amount of ozone to be injected is determined by measuring the ferrous ion (Fe''') concentration in the etching solution and using the reaction equation described above, it is easy to inject too much ozone. The reactivity of ferrous ions in the etching solution with ozone decreases, and unreacted ozone is released into the atmosphere, which is not only uneconomical but also causes environmental problems because ozone is harmful. On the other hand, if the amount of ozone injected is too small, the degraded etching solution will not be regenerated sufficiently, resulting in problems such as the etching time taking longer than necessary or the desired etching being impossible.

Furthermore, the measurement of ferrous ion concentration is as follows: 1. Since the red color produced by the reaction between the lO-fluorinated nandroline solution and ferrous ions is measured using spectrophotometry, continuous measurements cannot be performed, and therefore the etching solution cannot be continuously regenerated. It is difficult to control the amount of ozone injection, and there are many aspects that are extremely inefficient, such as manually turning on and off the power of the ozone generator 1i8 to measure the ferrous ion concentration.

The present invention has been made in view of the above points, and its purpose is to continuously control the amount of ozone injected for regenerating an etching solution containing ferric salt as a main component to an appropriate amount. The aim is to provide a means of

[Means to solve the problem]

In order to solve the above problems, the method of the present invention collects the degraded etching solution in a sampling tank, then continuously measures the redox potential with an electrode installed in the sampling tank, and then injects the ozone based on the measurement results. It determines the amount.

[Function] As described above, the present invention continuously measures the oxidation-reduction potential with the ORP electrode and controls the ozone injection amount to determine the appropriate amount, so it is possible to perform accurate etching and automate etching solution regeneration. This improves yield and efficiency, and at the same time, when the etching solution is regenerated, almost no unreacted ozone is released into the atmosphere.

〔Example〕

FIG. 1 is a schematic diagram showing an outline of an etching apparatus to which the present invention is applied, and parts common to those in FIG. 4 are represented by the same reference numerals. In Figure 1, there is a deteriorated work.

The process of supplying ozone to the tinda liquid to regenerate it is the same as in the case of Fig. 4, so its explanation will be omitted, but the difference between Fig. 1 and Fig. 4 is that the amount of ozone injected is changed. It is important to have a device that can automatically control the amount to be appropriate. ! l] FIG. 1 shows a pump 11 that samples the degraded etching solution in the etching tank 1, and a sampling tank 1 that stores the sampled degraded etching solution.
2, and the ORP installed in the sampling tank 12.
(Oxidation-Reduction Pote
ntial) electrode 13. With this ozone injection amount control device, the deteriorated etching solution in the etching tank 1 is constantly sampled by the pump 11 and guided to the sampling tank 12, and the etching solution is heated to 0 RPi [
13, the oxidation-reduction potential of the constantly deteriorated etching solution is measured.

When the ferrous ion (Fe”) concentration exceeds 5 g/f, the redox potential shows a value around 5601, and conversely, the ferrous ion is oxidized by ozone, and the ferrous ion (F
e”) and its concentration exceeds a certain level, the oxidation-reduction potential becomes a value around 1100 sV. Therefore, by continuously measuring this oxidation-reduction potential using the ORP electrode 13, the first Iron ion concentration is 5g
/j! You can tell whether or not the oxidation by ozone is nearing completion.

That is, according to the present invention, the point at which the redox potential measured by the ORP electrode 13 suddenly changes (approximately 560 mV→
The dotted line in Figure 1 connects the operations of turning off the power to the ozone generator 81B by capturing the point at which the voltage changes to approximately 1100 mV, and turning on the power to the ozone generator 8 when the measured redox potential becomes low. This can be done automatically using signals from an electric circuit.

In the present invention, by appropriately controlling the amount of ozone injection in this way, excessive ozone is not injected, and the amount of unreacted ozone entering the exhaust ozone decomposition tower 10 is reduced, making it more economical. It also has the advantage of reducing the frequency of replacing the ozone decomposition material and making maintenance easier.

Next, when the deteriorated ferric chloride etching solution was regenerated with ozone, the results of measuring the exhaust ozone concentration, the ferrous ion concentration in the etching solution, and the oxidation reduction potential with respect to the treatment time are shown in Figure 2 (a). , (b) and (C), in which the deteriorated etching solution 100- is put into the reaction tower 5 and the liquid temperature is brought to 55°C, and then an ozone concentration of 23 mg / j! ozonated air is blown into the etching solution to regenerate the deteriorated etching solution.
Composition analysis results of deteriorated etching solution, oxidation-reduction potential,
The specific gravity is as shown in Table 1.

Table 1 As a result, as shown in FIG. 2(a), the concentration of exhausted ozone is 0 until 31 minutes after ozone injection, and it can be seen that the exhausted ozone starts to be emitted. At that time, the ferrous iron concentration becomes <5 g/f or less as shown in Figure 2 (b), and the oxidation-reduction potential becomes
As shown in figure (C), the voltage suddenly increases from around 560mV to 1100m.
It rises to around V. Therefore, by monitoring the oxidation-reduction potential in the etching solution with an ORP electrode and stopping ozone injection when this potential rises rapidly, waste ozone can be prevented from being released into the atmosphere (and the ferrous iron concentration Mo5
g/j! Can be kept below.

Similarly, using the same deteriorated etching liquid as shown in Table 1, 100 m of the deteriorated etching liquid was put into the reaction tower 5 and the liquid temperature was brought to 60°C. Ozone concentration from 9 to 25mg/j! The deteriorated etching solution was regenerated by blowing ozonized air into it, and the results obtained are shown in Figures 3 (a) to (C). In this case, most of the results were similar to those in Figures 2 (a) to (C). The same is true in Figure 3 (a
), the exhaust ozone concentration is 0 until 34 minutes after ozone injection, after which exhaust ozone starts to come out, and the ferrous iron concentration at that time is <5g#! as shown in Figure 3(b). The following becomes
As shown in FIG. 3(C), the oxidation-reduction potential rapidly increases from around 560μ to around 1100−ν. therefore,
The oxidation-reduction potential in the etching solution is monitored with an ORP electrode,
By stopping ozone injection when this potential rapidly increases, it is possible to reduce the ferrous iron concentration to 5871 or less without releasing waste ozone into the atmosphere, which is exactly the same as above. .

〔Effect of the invention〕

Ferric salt etching solution is used for etching electronic components made of iron-based materials. In order to regenerate the etching solution that has deteriorated due to repeated etching, it is effective to inject ozone. The etching process was completed by measuring the ferrous ion concentration, but this method is difficult to automate and is inefficient. I wasn't getting it. Solve this problem
The present invention has the following advantages as described in the embodiments.

In the method of the present invention, the oxidation-reduction potential is continuously measured using an ORP electrode at the end of regeneration of the ferric salt etching solution, and the results are fed to an ozone ordering machine.

The appropriate amount of ozone to be injected can be automatically determined and supplied, and almost no unreacted ozone is released into the atmosphere, resulting in an efficient, economical and stable etching process that does not pollute the environment. Realized.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an outline of an etching apparatus to which the present invention is applied, and FIGS. 2 and 3 are diagrams showing the following relationships depending on processing conditions, respectively. , Figure 3 (a
1 is a diagram showing the relationship between processing time and exhaust ozone concentration when a deteriorated ferric chloride etching solution is regenerated with ozone; Figures 2 (C) and 3 (C) are diagrams showing the relationship between the ferrous ion concentration in the liquid, and Figure 4 is a diagram showing the relationship between treatment time and redox potential. 1 is a schematic diagram showing an outline of a conventional etching apparatus. 1: Enching tank, 2, 4, 11: Pump 36: Spray nozzle, 5: Reaction tower, 7: Comprenosa, 8 Niosin generator, 9: Diffuser pipe, 1o: Exhaust ozone decomposition tower, 12: Sampling tank, 13: 0RPii pole. L Rimachi Tomo (mil) Ren a kinema (kuru + h) Processing yo U sub (mi 几) Fig. 3 Processing time + n) 2DPIQM (WL + n) Immediately at the time of karashiku (rtu1 le) Fig. 2

Claims (1)

[Claims] 1) Etching iron-based members using an etching solution consisting of an aqueous solution containing at least one of ferric hydrochloride, sulfate, and nitrate as a main component and added with an acid having the same anion as the ferric salt. When injecting ozone into the etching solution that has deteriorated due to processing to regenerate the deteriorated etching solution, the deteriorated etching solution is collected in a sampling tank, and then the oxidation-reduction potential is continuously increased by an electrode installed in the sampling tank. A method for controlling the amount of ozone injected into an etching solution, the method comprising: measuring the amount of ozone injected into an etching solution, and determining the amount of ozone injected based on the measurement result.