JPS6131959A - Method for measuring ph of electroplating liquid - Google Patents

Abstract

PURPOSE:To eliminate the error by temp. and to measure exactly the pH of a plating liquid by drawing the sample in a plating cell into an electrode chamber provided to the outside of the plating cell and operating the signal outputs from an electrode for pH measurement and temp. detector of the electrode chamber and the temp. sensor of the plating cell. CONSTITUTION:The sample in the plating cell 1 is drawn into the electrode chamber 2 by a pump 4 and the signal outputs from the electrode 15 for pH measurement and temp. detector 6 provided to the chamber 2 and the signal output from the temp. sensor 18 of the cell 1 are inputted to an operating element 19. The error owing to the difference between the temp. in the plating cell and the temp. in the chamber 2 is corrected by the specific operation equation, by which the pH of the plating liquid in the cell is measured with good accuracy. The automatic control is executed by a program control 20 to feed respective liquids from a washing liquid tank 6, the 1st calibrating liquid tank 7 and the 2nd calibrating liquid tank to the chamber 2 and to execute washing and automatic calibration of the electrode 15 as well. The measurement of the pH of the plating liquid with high accuracy is thus made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applicability] The present invention relates to a method for measuring electroplating liquid, and an object of the present invention is to enable easy maintenance and highly accurate automatic measurement.

[Prior art]

The electroplating solution level affects the current efficiency, the properties of the plating film, the deterioration of the plating solution, etc., so it must be controlled within an appropriate range. For this reason, highly accurate field measurements are desired, but since the characteristics of the electrodes change, it is difficult to maintain accuracy unless calibrated frequently.

Therefore, in order to maintain measurement accuracy, it is necessary to be able to automatically clean and calibrate the electrodes.

By the way, conventional field measurements are performed by inserting electrodes directly into the plating tank, which makes it difficult to automate calibration and other tasks.
The measurement accuracy was also too high to be expected.

On the other hand, in the past, a measurement chamber for sampling the sample in the plating tank was installed separately from the plating tank to facilitate automatic cleaning and automatic calibration, but this method Since changes were not taken into consideration, measurement errors could not be ignored, making it difficult to accurately measure the output value in the plating tank.

[Purpose of the invention]

Therefore, the present invention provides a new measuring method that is easy to perform automatic cleaning and automatic calibration, and can measure the field inside the plating tank with high precision.

[Structure of the invention]

In order to achieve the above object, the present invention provides an electrode chamber for sampling a sample in the plating tank separately from the plating tank, periodically introduces a cleaning solution and a calibration solution into the electrode chamber, and performs automatic cleaning and automatic calibration. At the same time, the electrode chamber is provided with a temperature measurement electrode and a temperature sensor, and a detection signal of the temperature measurement electrode, a detection signal of the temperature detector, and a temperature signal indicating the temperature of the sample in the plating tank are provided. The gist is that the output value of the sample in the plating tank can be requested by calculation from three parties.

〔Example〕

FIG. 1 shows an apparatus for realizing the measuring method of the present invention, in which 1 is a plating bath, and 2 is a nine-electrode chamber installed separately from the plating bath 1. A sample (plating solution) in the plating tank 1 is introduced into the electrode chamber 2 by the sampling pump 4 when the plating solution introduction valve 3 is in the open state p, and is subjected to measurement. On the other hand, the sample after the measurement is returned to the plating bath 1 through the return tube 5.

6 is a cleaning liquid tank, 7 is a first calibration liquid tank, and 8 is a second calibration liquid tank. By operating the introduction pump 12, the electrode can be introduced into the electrode chamber 2. Reference numeral 13 denotes a pressure air introduction valve, and when introducing the canned liquid into the electrode chamber 2, this valve is also opened for a certain period of time. Bubbling is performed using pressurized air.

14 is a discharge valve, 15 is an electrode for measuring mortality disposed in the electrode chamber 2, and 16 is a temperature detector. If the temperature measurement electrode itself has a built-in temperature sensor, that can be used, and there is no need to provide a separate temperature sensor. Reference numeral 17 indicates a detection signal from the temperature sensor 16 and the temperature measurement electrode 15 which stores KCl to be introduced into the reference electrode in the temperature measurement electrode 15.
This is a calculation unit that calculates the state of the sample in the plating tank l by calculation from the operator. Note that if the plating bath 1 is kept at a constant temperature, the temperature sensor 18 is not necessary. In that case, a signal indicating a constant temperature may be generated by a resistor or the like and input to the calculation section 19. Add is the above 6 valves,
The pumps operate in a certain order, automatically cleaning,
This is a program controller that performs calibration solution introduction and sampling operations.

Next, each operation of automatic cleaning, introduction of calibration solution, and sampling performed by the program controller will be explained.

■ Automatic cleaning and introduction of calibration liquid 1) After opening the discharge valve 14 and discharging the liquid in the electrode channel 2, open the introduction valve 9 and operate the introduction pump 12. As a result, the cleaning liquid is introduced into the electrode chamber 2. At the same time, the pressure air introduction valve 13 is also opened, causing the cleaning liquid to be pulled inside the electrode chamber 2 to enhance the cleaning effect.

1i-) When cleaning is completed, open the discharge valve 14 to drain the cleaning liquid, and then open the introduction valve 10. As a result, the first calibration liquid is introduced into the electrode chamber 2 .

In this case as well, the pressure air introduction valve 13 is opened and the first calibration liquid is bubbled. After bubbling for a sufficient time to remove the influence of the preliquid, the discharge valve 14 is opened and discharged. After the discharge is completed, the introduction valve 10 is opened again and the first calibration liquid is introduced into the electrode chamber 2. Then, the liquid temperature TA in the electrode chamber and the electrode potential 5A at this time are detected, and the detection signals TA and EA are input to the calculation section.

1ii) When the detection is finished, the discharge valve 14 is opened to discharge the first calibration liquid, and then the introduction valve 11 is opened to introduce the second calibration liquid into the electrode chamber 2. In this case, as in the case of the first calibration solution →, the solution is introduced twice.

The first time is to remove the influence of the previous liquid, and the second time is to detect the temperature TB and the electrode potential EB. The detection signals TB and EB detected by the second introduction are input to the calculation unit 19.

■ Sampling operation When the above operation is completed, the discharge valve 14 is opened and the second calibration solution is discharged, and then the sampling pump 4 is activated, the plating solution introduction valve 3 is opened, and a sample is collected into the electrode chamber 2. Ru. Electrode potential EX at this time.

The liquid temperature TXl)i in the electrode chamber is detected and input to the calculation unit together with a temperature signal indicating the temperature n in the plating tank.

(2) Processing in the arithmetic unit When the above-mentioned detection signals and temperature signal Tt are input, the arithmetic unit performs the following processing.

1) Calculating the value of the calibration solution 1st. The value of the calibration liquid is determined from the detected temperature values 'l'A and 'l'B of the second calibration liquid based on the following equation.

Ta=Chi+11+OT+dT"...(1)
However, T is the absolute temperature of the calibration solution. In the above formula a.

b, c, and d are liquid-specific constants; the values of a, b, c, and d for oxalate and 7-talate are shown in the following table as an example.

ii) Calculation of electrode sensitivity A and asymmetric potential B Electrode sensitivity A is calculated based on the following equation.

In addition, when calculating the asymmetric potential B based on the following formula, I
IIA is the output value of the first calibration solution, and raB is the output value of the second calibration solution, which are determined according to equation (1).

α is the temperature correction coefficient of the glass electrode (1/273.15)
It is. Automatic calibration is completed by calculating these A and B.

m) Calculation of the output value in the electrode chamber The output value (Fl(X)) in the electrode chamber is calculated by the following formula.

However, Ex: Electrode potential of the sample in the electrode chamber Tx: Temperature of the sample in the electrode chamber (K) iv) Calculation of the temperature value of the sample in the plating tank When PHX is determined from i) to turtle) above, the temperature in the plating tank Tt The output value of the sample in the plating tank can be determined by calculating according to the following equation together with the temperature signal indicating .

11 [t = F4'Ix -k (Tt -TX)
-(5) where k is the temperature correction coefficient of the plating solution. This k varies depending on the type of plating solution.

The value of k can be determined by analyzing the plating solution. For example, in the case of Zn-pe based plating solution, k = 0.013-0.67Wpe3+
−(61) However, W p e K+ is the Fe3+ concentration (W/V%) of the plating solution. (6) above
If the value of k changes depending on the ion concentration as shown in the formula, it is recommended to store the formula (6) in the calculation section and calculate k by inputting the ion concentration each time a measurement is made. , even if k of the plating solution changes moment by moment, the PHt can be determined without error, which is convenient.

The mt obtained as described above is outputted from the calculation section 19 as a transmission output and displayed on a display section not shown. During calibration, when switching from the first calibration solution to the second calibration solution, the electrode potential changes from EA to EB. If the response speed of the electrode is calculated by measuring the amount of change in the potential of the electrode, the life of the electrode can be objectively determined.

Next, FIG. 2 shows a circuit for determining abnormality of the measuring instrument using the output signal from the calculation section, and is composed of a storage section 21, a comparison section 22, a management accuracy setting section, and a determination section. The storage unit 21 stores the measured values from the previous calibration.

The comparison unit n compares the measurement value output from the storage unit 21 during the previous calibration with the measurement value output from the calculation unit 19 during the current calibration.

Normally, this comparison value should be within a certain small range, but between the previous calibration and the current calibration, for example, there may be damage, dirt, or deterioration in the response membrane of the glass electrode, dirt on the reference electrode, or inner electrode. If an abnormality such as a chemical change occurs, the value will exceed the above range. The management accuracy setting unit is set to the maximum allowable value as the comparison value. This value is determined from the measurement accuracy required for the instrument. The judgment unit U determines whether the comparison value exceeds the setting value of the management accuracy setting department.
111, and if it exceeds it, it will issue an abnormal signal. By detecting abnormal operation in this way, it is possible to manage the accuracy of the instrument during measurements between calibrations, and to make the calibration cycle as long as possible within the required measurement accuracy range. This has the advantage that expensive calibration solutions can be used effectively.

Furthermore, FIG. 3 shows a circuit that automatically adjusts the calibration period using the output signal of the calculation section 19, and the first comparison section 25
, a management accuracy setting section, a second comparing section, and a period determining section. The first comparator 25 calculates the difference between the measured values of the calibration solution before and after calibration. Here, the measurement value of the calibration solution before calibration refers to the measurement value of the calibration solution measured before adjusting the asymmetric potential or electrode sensitivity, and the measurement value of the calibration solution after calibration refers to the measurement value of the calibration solution measured before adjusting the asymmetric potential or electrode sensitivity. This refers to the measured value of the calibration solution after performing The management accuracy setting department sets an allowable limit value in terms of measurement accuracy as the difference between the measured values of the calibration solution before and after calibration. The second comparison unit 27 compares the comparison value with the setting value of the management accuracy setting department. The cycle determination unit determines the calibration cycle from the comparison result of the second comparison unit 27. In other words, if the comparison value of the first comparison section exceeds the setting value of the management accuracy setting department, the calibration cycle is shortened, and conversely, if the comparison value does not exceed the setting value, the calibration cycle is lengthened. do. As a method of lengthening or shortening the calibration cycle, for example, a method of lengthening or shortening the calibration cycle by a unit time interval may be used. The calibration cycle determined by the cycle/period determination section is input to the program controller, and the length of the calibration cycle set in the controller 20 is controlled. In the figure, 29 is a first alarm, which is activated when the comparison value of the first comparison section 6 exceeds the setting value of the management accuracy setting section. (Main) is a second alarm, which is activated when the calibration cycle becomes shorter than the minimum calibration cycle set in the minimum cycle setting section 31.

32 is a comparator.

〔Effect of the invention〕

As explained above, the method for measuring the state of an electroplating solution according to the present invention has the following effects. That is, since the electrode chamber is provided separately from the plating bath, automatic cleaning and automatic calibration are easy to perform, and measurement errors due to temperature drop of the sample during sampling can be determined by determining the temperature of the plating bath and the temperature inside the electrode chamber. In particular, this problem can be solved, and as a result, the output value of the plating solution in the plating tank can be measured with high precision.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an apparatus for realizing the measurement method of the present invention, Fig. 2 is a circuit diagram for determining abnormality in the apparatus shown in Fig. 1, and Fig. 3 shows the calibration cycle of the apparatus shown in Fig. 1. It is a circuit diagram for adjustment. l... plating tank, 2... electrode chamber. Figure 1 Voluntary procedure amendment May 21, 1985 Patent No. 154929 2 Title of invention Method for measuring electroplating liquid 4, Agent 5, Date of amendment order 6, Increased due to amendment The number of inventions to be amended, number 7, is corrected to 4 strokes from the bottom of page 8 of the specification of the present application.

Claims (1)

[Claims] An electrode chamber for sampling the sample in the plating tank is provided separately from the plating tank, and a cleaning solution and a calibration solution are periodically introduced into the electrode chamber to perform automatic cleaning and automatic calibration. A pH measuring electrode and a temperature detector are provided, and the temperature of the sample in the plating tank is detected from three sources: a detection signal of the pH measuring electrode, a detection signal of the temperature detector, and a temperature signal indicating the temperature of the sample in the plating tank. A method for measuring the pH of an electroplating solution, characterized in that the pH value is determined by calculation.