JPS629263A - Method and instrument for measuring metal corrosion speed - Google Patents

Abstract

PURPOSE:To make measurement with a specified liquid compsn. by connecting a metal to be inspected and reference material to a voltmeter in common use as an ammeter in specific corrosive fluid, measuring the current and voltage and measuring the corrosion speed of the metal to be inspected. CONSTITUTION:The metal 2 to be inspected such as copper and the reference material 3 such as carbon rod are immersed into an etching liquid 1. The metal 2 and the material 3 are connected to the voltmeter 4 in common use as the ammeter by a conductor wire 5 and the current and voltage are measured. The dissolution rate of copper by the etching liquid can be thereby directly measured. Since the metal corrosion speed is measured and the compsn. of the etching liquid is controlled by the measured value thereof, the etching stage is stabilized.

Description

Detailed Description of the Invention (a) Industrial Application Field This invention is a method for measuring the metal corrosion rate due to changes in the composition of an etching solution in a specific fluid (corrosive fluid). The current and voltage generated during melting are converted into the dissolution rate of the metal to be tested using a device with a specific structure of an ammeter and voltmeter consisting of the metal to be tested (sample electrode) and the comparative substance (counter electrode). The purpose is to constantly control the liquid composition by measuring the metal corrosion rate.

(b) Conventional technology Conventionally, the metal corrosion rate in a specific liquid has been measured using a measurement method based on changes in the weight of the metal to be inspected (test metal) and observation of its appearance, or a It was determined by an electrochemical measurement method that measures the oxidation and reduction changes in a specific fluid as the dissolution rate of the metal to be tested based on the generated potential difference (ORP). Similarly, for etching, devices having specific structures based on these measurement methods have been used.

The etching process uses a liquid (etching solution) that corrodes the copper.
This process involves removing copper from areas other than those protected by the etching resist. Only after this process is the printed wiring board completed, and the etching process is complete. Printed circuit boards have become indispensable in the current social movement that demands electronics, and the role of the etching process in manufacturing printed circuit boards is extremely important as electronics progress. becomes.

As demand demands, etching methods will shift from patch methods to automatically controlled methods that allow for continuous operation. In such a background, the etching solution itself also transitions to an etching solution that can be used continuously.

In order to continuously use an etching solution, it is necessary to keep the solution composition constant.

(As an example) In the case of cupric chloride etching solution, Cu+Cul2→Cu2l2... (1) Cu2l
2+2Hl+H2O2→2Cul2+2H2O・・・
・(2) In the case of alkaline etchant etching solution, Cu
+Cu(NH3)4l2→2Cu(NH3)2l...
...(1)2Cu(NH3)2l+2NH4l+2NH
4oH+1/2O2→2Cu(NH3)4l2+3H2
O...(2) Equation (1) indicates an etching process. Copper corrodes into divalent copper and changes to monovalent copper. Equation (2) shows the regeneration process. Each regeneration aid is added to the liquid that has changed to monovalent copper to promote it to divalent copper.

If the etching process and regeneration process are always constant, the etching solution can be used continuously. By measuring the corrosion rate of copper, etc. as the composition of the etching solution changes, it is possible to keep the composition of the etching solution constant.

The conventional method of controlling the composition of the etching solution is to judge it visually based on the corrosion state of the product and the chromaticity of the etching solution. A method of controlling liquid composition changes due to pH using a pH meter. A method of controlling liquid composition changes due to specific gravity using a hydrometer. A method of controlling liquid composition changes due to chromaticity using an optical meter. A method in which changes in liquid composition due to neutralization etc. are controlled by a suitability test, and a method in which changes in liquid composition due to oxidation and reduction potentials are controlled using an ORP meter, etc. have been used.

(c) Problems to be Solved by the Invention The immersion measurement method for measuring the metal corrosion rate in a specific fluid requires time to judge the results and is not suitable for continuous measurement. Measuring the oxidation/reduction potential in a liquid, which is an electrochemical measurement method, is affected by pH and temperature changes in the liquid. If the range becomes narrower and continuous measurements are taken, the error range will become larger. Since the ORP electrode is not a dissolvable metal, it is difficult to directly sense the potential difference that occurs in the fluid.

In addition, the method of determining the liquid composition control of the etching solution by human vision causes errors depending on the physical condition at the time, and cannot always achieve a constant value. In control using a PH meter, control within the measurement range is possible, but in the actual device, it indicates outside the measurement range of the PH meter. Although it can be measured by operations such as dilution, it takes time and is not suitable for continuous measurement.

Control using a hydrometer is possible if the etching solution composition is a single type, but errors occur if the etching solution composition is complex. In control using an optical meter, the concentration is judged by the shade of color, so colored substances (
Colorless and transparent substances (solutions, etc.) are fine.
If so, an error will occur.

Control by suitability tests provides the best judgment for knowing the liquid composition, but is not suitable for continuous measurement because it takes time to make judgments.

Since control by an ORP meter measures the ratio of oxides and reduced substances, the measurement range is narrow and is affected by pH and temperature changes, resulting in errors during continuous measurements. Due to the nature of ORP, chloride etching is measurable, but with strong oxidizing power, no potential difference is observed and correlation is difficult to appear, which puts restrictions on its use. This is because current ORP electrodes are not soluble metals, so it is difficult to directly sense the potential difference that occurs in the etching solution. If the control system is used, the control accuracy will improve, but the scale and cost of the control system will increase, and the system will become quite complex, requiring careful attention and skill each time it is used. The above control method is
Because it is fundamentally not directly measured or difficult to measure continuously, it is difficult to use as a control value for control in corrosive fluids such as etching solutions, and is only a standard or guideline.

When the liquid composition is controlled using various measuring instruments in the actual equipment, the measurement state due to changes in the concentration of the etching liquid appears to be based on the set value (value when etching is good), and the stable liquid composition of the etching liquid is determined. Although it looks similar, the conductor width is 0.1
In the etching process of precision substrates arranged in large numbers on the order of mm, slight errors due to direct measurement or difficulty in continuous measurement lead to excessive addition of regeneration aids, worsening the etch factor, and reducing the conductor width. Corrosion conditions such as thinning tended to occur, and over-etching and etching defects tended to occur. Therefore, it was difficult to maintain a constant composition of the etching solution.

This invention is a method for measuring the metal corrosion rate due to a change in the liquid composition in a specific fluid (corrosive fluid). ) and a comparative substance (counter electrode), it is converted and displayed as the dissolution rate of the metal being tested, and by measuring the metal corrosion rate, it is always constant. The purpose of this is to control the liquid composition.

(d) Means to solve the problem As a method of measuring the metal corrosion rate in a specific fluid, the metal to be inspected is immersed in each fluid, and when the metal to be inspected itself dissolves, it is proportional to the concentration of the fluid. Since the metal itself generates current and voltage, the current and voltage generated by the metal to be inspected are measured, converted and displayed as the corrosion rate. As mentioned above, the current and voltage generated by the metal to be inspected itself is used as a device with a specific structure of ammeter and voltmeter consisting of the metal to be inspected and a comparative substance, and directly measures the dissolution rate of the metal to be inspected. It is. Regarding the apparatus for measuring the metal corrosion rate due to changes in the composition of the etching solution, referring to FIG. Use copper. A carbon rod is used as comparative material 3. Inspected metal 2
One end and one end of the comparison substance 3 are connected to an ammeter/voltmeter 4 using a conductive wire to measure the current and voltage. In this method, a metal to be inspected 2 is used as a sample electrode for an etching solution 1 that dissolves copper, and a carbon rod that becomes passive in the etching solution 1 is used as a counter electrode as a comparison substance 3. Since the apparatus is configured as described above, it is possible to directly measure the corrosion rate of copper in the etching solution. What can be directly measured is that an etching solution that dissolves copper is adaptable to minute changes, and the composition of the etching solution exhibits redox changes, pH fluctuations, and other properties. However, if it does not have the property of dissolving copper, it will show a constant value. In this manner, the present invention can be used as a sample electrode for all metals to be inspected for which corrosion rates are to be measured, allowing direct measurement.

(F) Example The present invention has a specific structure in which one end of the metal to be inspected using the target metal as an electrode for measuring the dissolution rate and one end of the comparison material using a carbon rod as the counter electrode is connected to an ammeter and voltmeter using a conductive wire. It is a device with

As an embodiment, liquid composition control in an actual apparatus will be explained based on FIG. 2 of the drawing. A in the drawing shows an etching machine. The substrate runs on the conveyor C, and the etching liquid 1 is applied by the pressure pump 5 to corrode the substrate. After passing through the conveyor C, the etching solution 1 changes from divalent copper to monovalent copper. As this cycle progresses, the etching solution 1 in the liquid bath B gradually changes from divalent to monovalent copper. As the metal to be inspected 2 in the etching solution 1 corrodes, the ammeter and voltmeter 4 comprising the comparison substance 3 shows respective measured values, and as the etching power of the etching solution 1 decreases,
Measured values also change. The regeneration aid 6 is added to the liquid tank B by the regeneration aid injection pump 7 at a current and voltage value that best dissolves the metal 2 to be inspected using the ammeter and voltmeter 4.

In addition, although copper was used as the metal to be tested in the etching that corrodes copper, the metal to be tested, that is, the sample electrode, can be used for all metals for which the metal corrosion rate is to be measured. Although a carbon rod was used, it can be used as a comparison material for any current-carrying material that can serve as a counter electrode. In Figure 1, the metal to be inspected and the comparative substance were individually immersed in the etching solution and measured, but the metal to be inspected and the comparative substance can also be integrated into one electrode, and the calculation display section is performed by a computer and displayed. It is also possible to increase the speed and set each condition by program.

(E) Effects of the Invention As explained above, the present invention is a method for measuring metal corrosion rate due to changes in liquid composition in a specific fluid (corrosive liquid).
This is a device that measures the metal corrosion rate due to changes in the composition of the etching solution.By using the present invention, even when etching precision substrates with a large number of conductors with a width of about 0.1 mm, etching with a stable solution composition can be achieved. This has the effect of keeping the amount of addition of regeneration aid due to etching and overetching constant.

In addition, based on the measurement results using actual equipment, we can manage the composition of the etching solution, stabilize the etching process, improve product quality,
It has the effect of reducing the defective rate, increasing production volume, preventing excessive addition of recycling aids, and reducing production costs. Because of this structure, there is no need for a new measurement space, and it can be used with existing equipment. It can be installed to any device without damaging conventional equipment, and
By adding a certain amount of regeneration aid, hydrogen peroxide is reduced from one-fifth to eight liters per liter of regeneration aid in conventional cupric chloride etching solution.
Etching can be performed with one-times the amount used, which has the effect of reducing the amount of regeneration aid.

[Brief explanation of drawings]

The figures show an embodiment of the measuring device of the present invention. The first figure shows a method and apparatus for measuring metal corrosion rate, and the second figure shows an embodiment of etching control in the actual device. . A...Etching machine B...Liquid tank C...Conveyor 1...Etching solution 2...Metal to be inspected 3...Comparison material 4. ... Ammeter and voltmeter 5 ... Pressure pump 6 ... Regeneration aid

Claims (2)

[Claims] (1) Method for measuring metal corrosion rate in a specific fluid. (2) A device in which one end of the metal to be inspected and one end of the reference material are connected with a conductive wire and connected to an ammeter and voltmeter.