KR830002335B1 - PH measurement electrode in aqueous solution - Google Patents

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Description

PH measurement electrode in aqueous solution

1 to 4 are diagrams showing an automatic management system of a chemical plating liquid using an electrode for pH measurement according to the present invention.

The present invention relates to an electrode for measuring pH of an aqueous solution, and more particularly to a pH measuring main electrode that can be accurately measured for a long time continuously by converting the pH and reducing agent concentration of the chemical copper plating solution to a pH value.

In the case of gloss plating for decoration on ABS resin, copper base plating was performed by chemical copper plating to give electrical conductivity to the resin surface.

In this case, the mechanical strength of the base plating film is not a problem. Therefore, the composition management of plating liquids such as chemicals affecting the plating film was intermittently performed.

These days, the formation of a conductor by chemical copper plating directly on an insulating substrate is performed. In this case, the plated coating is important for mechanical properties in addition to conductivity. The mechanical properties of the chemical copper plating film are influenced by the concentration of the main component of the plating liquid. For this reason, the plating liquid composition needs to be managed continuously.

Until now, continuous management of the chemical copper plating solution composition has not been carried out as follows (a) to (c) regarding pH, reducing agent concentration, copper ions and complexing agent.

(a) pH: A certain amount of acid solution is added to a certain amount of chemical copper plating solution (e.g. pH = 12.3) to adjust the pH to 4-9, and the pH of the solution is adjusted by a glass electrode-caromel electrode. Measure as potential.

If the measured potential is different from the potential indicated by the new plating solution, this becomes a signal and the control device is driven to supply the replenishment solution to the plating solution so that the pH value is the same as that of the new plating solution. 83635).

(b) Reducing agent concentration: To a certain amount of chemical copper plating solution, add excess sodium sulfite and sodium sulfite anti-crushing agent to react with formaldehyde and sulfite ions more than the amount necessary for the reaction with the total amount of formaldehyde as reducing agent. By reacting with unreacted sulfite ions and excess oxo, the parallel potential between the remaining oxo and oxo ions is measured by a gold electrode-induction electrode.

When the measurement potential is different from the potential indicated by the new plating solution, the control device is driven to supply the supply liquid so that the amount of formaldehyde is the same amount as that of the new plating solution (Japanese Patent Laid-Open No. 54-1093).

(c) Cu ⁺² ion and the complexing agent concentration in the chemical copper plating liquid complexing agent is added to metal ions such as Fe ⁺³ in the chemical copper plating solution of the certain amount is present to excess than the Cu ⁺² ions are metal ions and Complexes are formed between the complexing agent liberated from Cu ⁺² ions consumed by plating and the complexing agent which was present in the free state.

By measuring the potential change before and after the addition of Fe ⁺³ using a gold electrode-a red electrode, the concentration of the released complexing agent can be known.

The free complexing agent concentration obtained by measurement is subtracted from the concentration values of all known complexing agents in the new chemical copper plating solution, and the complexing agent forming a complex with Cu ⁺² ions. The amount of positive and negative Cu ⁺² ions is indirectly obtained. When the transfer is different from the amount of the new chemical copper plating solution, the control device is driven to supply the replenishment liquid so that the amount of Cu ⁺² ions is the same as that of the new plating liquid (Japanese Patent Application No. 53-149389).

All complexing agent concentrations are obtained by measuring the potential with a gold electrode-magnetism electrode by adding a sufficient Fe ^{+ 3} ion to react with all complexing agents. When the measured amount of all the complexing agents differs from the amount of the new plating solution, the control unit is driven to supply the supply liquid so that the amount of all the complexing agents is the same as that of the new plating solution (Japanese Patent Application No. 53-149389).

However, in the method of (a), the chemical copper plating solution penetrates into the glass of the glass electrode, so that continuous measurement can be performed for only a few hours, and furthermore, a measurement error increases after about 3 hours.

_{^{[I -] / [I 2}} ] is different, (c) In the above (b), (c), method if you do not measure to purify the pH, (b) how the formaldehyde used in the quantification (定量) of In the method, the reaction error between Fe ⁺³ ions and the complexing agent was increased, and there was a drawback that the management of the correct reducing agent concentration, Cu ⁺² ion concentration, and all complexing agent concentrations became inaccurate after 3 hours.

It is an object of the present invention to remove the above-mentioned drawbacks of the prior art, to provide a pH electrode for measuring the pH of the aqueous solution, in particular, the pH of the chemical copper plating solution and the reducing agent concentration to a pH value suitable for continuous long-term accurate measurement .

As a main electrode for pH measurement capable of meeting the above object, a copper oxide (Cu ₂ O) electrode obtained by etching a metal or the like with an inorganic acid of 0.1 to 14 N and then treating with an alkali metal hydroxide is provided according to the present invention. .

The copper oxide electrode is etched with pure copper having a purity of 99.9% or more with 0.1 to 14 N of nitric acid, hydrochloric acid, and sulfuric acid as an inorganic acid at a liquid temperature of 18 ° C. to 50 ° C. for 1 second to 10 seconds, and then 0.1 to 1 N. It is preferable that the liquid is oxidized at 18 ° C. to 50 ° C. for 5 to 30 minutes in an aqueous solution of an alkali metal hydroxide, and the treatment under other conditions is not preferable because the electrode surface does not become a stable copper oxide.

The following describes the principle and advantages of pH measurement by the copper oxide station obtained by the present invention.

The reaction of Formula (1) occurs between this electrode and the chemical copper plating solution (using a red electrode as a reference nation), and the potential is measured in the relation of Formula (2).

_{Cu 2 O + H 2 O →} CuO + 2H + + 2e - ············ (1)

E = 0.669 + 0.0591 pH (...) (2)

E in the sheet 2 is represented by the potential V based on the hydrogen electrode.

Equation (1) is related to pH only, so it is not affected by the copper ion concentration in the liquid even in the chemical copper plating solution, and the electrode deterioration by the so-called electrochemical substitution reaction which may be caused by reduction precipitation of copper ions does not occur. . Therefore, no penetration of the chemical copper plating solution occurs in the oxide electrode as in the glass electrode.

Therefore, the pH of the chemical copper plating liquid can be detected as an accurate and stable potential change.

In the reaction of formula (1), even though the cupric oxide on the polar surface is dissolved by the chelating agent of divalent copper ions present in the chemical copper plating solution, the first oxidation of the electrode surface is carried out by oxygen dissolved in the plating solution. Since copper is oxidized to cupric oxide and cuprous oxide is supplied by oxidation of metal of the electrode, it is stable. Therefore, the pH of the plating liquid can be measured by detecting the potential using the reference electrode. The relationship between the plating liquid pH and the potential by the copper oxide electrode is particularly stable when the plating liquid has a pH of 11 or more.

That is, at 25 degreeC, the relationship of Formula (3) is obtained.

^{E = - 0.0019 × pH 4 ·} 74 (Vvs · SCE) ············ (3)

Formaldehyde concentration, a representative reducing agent in the chemical copper plating solution, changes the pH of the plating solution by changing the pH of the plating solution by mixing a predetermined concentration and a sodium sulfite solution sufficient to complete the reaction of the following formula (4) with the predetermined concentration and the plating solution. The copper oxide electrode and the reference electrode can be detected as an electric potential and measured indirectly.

HCHO + Na ₂ SO ₃ + H ₂ O → NaOH + HCH (NaSO ₃ ) OH (4)

As the reference electrode used in combination with the copper oxide electrode, a conventional electrode such as a magenta electrode and a silver-silver softening electrode is used.

The acid used in the production of the copper oxide electrode is preferably an inorganic acid such as hydrochloric acid, sulfuric acid or nitric acid, preferably nitric acid, and the alkali metal hydroxides are practically NaOH and KOH.

As metal copper, purity of 99.9% or more is preferable, and the shape may be a plate or a wire.

And since the reducing agent concentration can be measured accurately, it is similarly measured exactly with the concentration of the reducing agent.

Next will be described with reference to the accompanying drawings an embodiment of an automatic management system for chemical plating solution using the electrode according to the present invention.

Example 1

The following chemical copper plating solution (a) was put in the plating bath (a) (1) of FIG. 1, and chemical copper plating was performed on the plating conditions of the following (b).

銅線)을 0.1N 질산으로 액은 50℃에서 10초간 에칭처리하고, 이어서 0.1N 수산화나트륨의 수용액중에서 액은 50℃로 30분간 산화처리 한것)과 참조전극으로서의 은-염화은 전극(8)사이에서의 전위차가 제어장치(10)에 의해 검출된다.The plating liquid is circulated and stirred through the circulation pump 2 and the mixer 3. The plating liquid to be analyzed is sampled by the sampling pump 4 through the cooler 5 and the solenoid valve 6 opened in three directions to the plating liquid pH detection chamber 7 (main electrode chamber 7 and reference electrode chamber 7 '). Configured), the copper oxide electrode 9 according to the present invention (diameter 1 mm, purity 99.9% bare copper wire (

The solution was etched with 0.1 N nitric acid for 10 seconds at 50 ° C., and then the solution was oxidized at 50 ° C. for 30 minutes in an aqueous solution of 0.1 N sodium hydroxide) and the silver-silver chloride electrode as a reference electrode (8) The potential difference between them is detected by the controller 10.

And 11 membranes.

When the detection potential is smaller than the potential set in the control device 10, a signal is output from the control device 10 to the supply pump 12, and the supply pump 12 supplies the plating liquid pH until the detection potential exceeds the set potential. The replenishment liquid (e) in the replenishment liquid tank 13 for adjustment is supplied to the plating tank 1 through the vane 14 and the mixer 3.

The sampling liquid better to the pH detection chamber 7 is discarded.

On the other hand, the saturated Kcl aqueous solution of the standard liquid bath 15, which is given as the standard liquid for the reference electrode 15 as the reference liquid (c), is obtained by the sampling pump 4 so that the potential of the silver-silver chloride electrode in the reference electrode chamber 7 'can be stably obtained. It continues to be supplied.

The saturated Kcl solution exiting the reference electrode chamber 7 'is discarded.

The 7N nitrate aqueous solution of the cleaning liquid tank 16, which is given as the cleaning liquid of the copper oxide electrode 16 as the cleaning liquid of the copper oxide electrode by switching the electron vanes 6 opened in three directions under the automatic management of the plating liquid, has a sampling pump 4 ) To be supplied to the main electrode chamber 7 '' for about 10 seconds.

In this way, the plating liquid could be automatically managed for 168 hours continuously. In this case, the sampling rate of the sampling pump 4 was 50 ml / l, the temperature at the time of detecting the plating liquid by the cooler 5 was about 25 ° C., and the set potential with respect to the plating liquid pH was -0.260V.

Example 2

When the chemical treatment liquid of the following (a) is used for acid pickling of the metal, the copper oxide electrode, the titration liquid, the replenishment liquid, and the standard liquid whose pH should always be 4.7 are the following (b)-(c) PH was controlled using the device of FIG. 1 as shown in FIG. As a result, the same result as in Example 1 was obtained.

(a) Chemical treatment solution: 12N hydrochloric acid

(b) Copper oxide electrode: copper wire with a diameter of 1mm (purity 99.99%)

Was etched at 30 ° C. for 5 seconds using 0.5 N hydrochloric acid, and then oxidized at 0.5 ° C. for 15 minutes with 0.5 N potassium hydroxide.

(c) titrant (d) supplement: 12N hydrochloric acid

HCOONa: 136g (e) Standard solution: 0.1N hydrochloric acid

Water: Volume 1L

Example 3

When the chemical treatment solution of (a) is used for alkali cleaning of metals, the same electrode electrode titrant, replenishment solution, and standard solution which should always have a pH of 12.0 are used as given in (b)-(e) below. PH was controlled using the apparatus of FIG. As a result, the same result as in Example 1 was obtained.

(a) chemical treatment liquid

NaOH: 20g

Water: Amount to make 1L whole

(b) Copper oxide electrode: A copper wire (purity: 9.9%) having a diameter of 1 mm is etched for 5 seconds at 30 ° C. with 0.5 N sulfuric acid and then oxidized for 15 minutes at 30 ° C. with 0.5 N sodium hydroxide.

(c) titrant (d) feed

12N hydrochloric acid:: 37.5ml NaOH: 400g

KH ₂ PO ₄ : 6.8g Water: Volume of 1l

Water: Amount of 1 l of the whole (e) Standard solution: 0.1 N hydrochloric acid

Example 4

PH and formaldehyde concentration management were performed by chemical copper plating in the same manner as in Example 1 with the same chemical copper plating solution as in Example 1.

The pH control was the same as in Example 1 except that the following (b) was used as the copper oxide electrode, and the control of formaldehyde concentration was performed in the automatic analysis solution, copper oxide electrode, and copper oxide corresponding to (a)-(b) below. The cleaning liquid of the electrode and the replenishment liquid for adjusting the formaldehyde concentration were used.

(a) Formaldehyde autoanalyte

Na ₂ SO ₃ : 100 g

Water: Quantity to make 1l whole quantity

(b) Copper oxide electrode: Copper wire (purity 99, 99%) having a diameter of 1 mm is etched with 14 N sulfuric acid at 18 ° C. for 1 second and then oxidized with 1 N sodium hydroxide at 18 ° C. for 5 minutes.

The management system is as shown in FIG.

The sampling liquid exiting the pH detection chamber 7 of FIG. 2 is formed with the automatic formaldehyde analysis liquid of (a) sampled by the sampling pump 4 through the solenoid valve 18 in the titration tank 17. After entering the mixer 19 and being sufficiently stirred, it enters the main electrode chamber 20 'of the formaldehyde concentration detection chamber 20. Thus, the potential difference between the copper oxide electrode 9 'and the silver-silver chloride electrode 9 is detected in the control device 10. 11 'is a membrane. When the detection potential is less than the electric potential set in the control device, a signal is output from the supply pump control device 10 to the supply pump 21, and the valve 23 and the mixer 3 are removed from the supply liquid tank 22 for formaldehyde concentration adjustment. The saturated KCl aqueous solution of the standard liquid tank 15 is always supplied by the sampling pump 4 as the standard liquid for the electrode until the detection potential exceeds the set potential in the plating tank 1 through. The sampling liquid of the plating liquid leaving the formaldehyde copper detection chamber 20 and the saturated KCl solution leaving the reference electrode chamber 7 'are discarded. By switching the solenoid valves 6 and 18 opened in three directions before automatically managing the plating liquid, the 7N nitrate aqueous solution of the cleaning liquid tank 16 given as (c) above as the copper oxide electrode cleaning liquid was sampled. By (4), it is comprised so that it may be supplied to the detection chambers 7 and 20 for about 10 second.

By the automatic management device of pH and formaldehyde concentration of the plating liquid, the plating liquid could be continuously managed for 168 hours continuously.

In this case, the sampling rate of the sampling pump 4 was 50 ml / l, the temperature at the time of detecting the plating liquid by the cooler 5 was about 25 ° C., the setting potential of the plating liquid pH was -0.260V, and the setting potential of the formalin concentration was 0.053V. .

Under these conditions, the plating solution pH was automatically managed between 12.3 ± 0.07 and formalin concentration between 3 ± 0.14 ml / l. During 30 hours of automatic management, the detection electrode did not deteriorate at all.

Example 5

The chemical copper plating was carried out in the same manner as in Example 1 with the same chemical copper plating solution as in Example 1, and / pH, the second copper ionic copper, and the complexing agent concentration were managed.

pH control is the same as in Example 1, and when the ion concentration and the complexing agent concentration in FIG. 2 are used, the automatic analysis solution, the electrode, the copper concentration control liquid, and the complexing agent concentration adjustment given as follows (a)-(e) A supplement was used.

(a) cupric ions automatic liquid analysis _{Fe 2 (SO 4) 3 (} NH 4) 2 SO 4 · 24H 2 O: 25.130g

CuSO ₄ 5H ₂ O: 14.107 g Water; Quantity to make whole quantity 1l

HCOONa: 64g (c) electrode (concentration of second copper ion, complexing agent concentration

12N hydrochloric acid: 30ml main electrode: platinum

Water: Positive auxiliary electrode with total quantity of 1 l: Negative-silver chloride electrode

(b) Autoanalyte of complexing agent (d) Replenishment solution for copper concentration adjustment

(b-1) Triethylene retramine solution CuSO ₄ · 5H ₂ O: 250 g

Triethylene Retramine: 100ml Water: Amount of 1l in total quantity

12N hydrochloric acid: 164ml (e) Supplement for adjusting the concentration of complexing agent

Water: Amount of total amount 1 l EDTA, 2Na: 100 g

(b-2) Iron ions-containing liquid water: Amount of total quantity to 1 l

The management system was as shown in FIG. 3, and the pH management was carried out at 1-14 in the figure first, and the result similar to Example 1 was obtained. Subsequently, the sampling liquid exiting the pH detection chamber 7 of FIG. 3 is fed to the mixer 25 together with the second copper ion automatic analysis liquid of (a) sampled by the sampling pump 4 in the titration tank 24. After the mixture is sufficiently stirred, it enters the main electrode chamber 26 ′ of the second copper ion concentration detection chamber 26. Thus, the potential difference between the platinum electrode 27 and the silver-silver chloride electrode 9 'is detected by the controller 10. 11 '' is a membrane.

When the detection potential is smaller than the potential set in the control device, a signal is output to the supply pump 28, whereby the supply pump 28 causes the valve 30 and the mixer 3 to be supplied from the second liquid concentration adjusting supply tank 29. The liquid of (d) is supplied into the plating bath 1 until the detection potential exceeds the set potential. On the other hand, in order to ensure that the potential of the silver-silver chloride electrode 9 'in the reference electrode chamber 26' 'is obtained stably, the reference electrode chamber 26 from the reference electrode chamber 7' 'of the pH detection chamber 7 is obtained. '') Is continuously supplied with saturated KCl solution. The saturated aqueous solution exiting the reference electrode chamber 26 '' of the second copper ion concentration detection chamber 26 enters the reference electrode chamber 35 '' of the complexing agent concentration detection chamber 35 and is then discarded.

The sampling liquid exiting the second copper ion concentration detection chamber 26 is mixed with the triethylene retamine solution (b-1) sampled by the sampling pump 4 in the titration tank 31 to the mixer 32. After the mixture is sufficiently stirred, it is put into the mixer 34 together with the iron ion-containing liquid of (b-2) sampled by the sampling pump 4 in the titration tank 33, and sufficiently stirred and reacted. .

Thereafter, this liquid is placed in the main electrode chamber 35 'of the complexing agent concentration detection chamber 35. Thus, the potential difference between the platinum electrode 27 'and the silver-silver chloride electrode 9' 'is detected in the controller 10.

The 11 '' is Vibrain. When the detection potential is lower than the potential set in the control device 10, a signal is output from the control device 10 to the supply pump 36, whereby the supply pump 36 is a valve in the supply liquid tank 37 for adjusting the complexing agent concentration. (38) and the mixer 3 are opened, and when the detection potential exceeds the setting in the plating bath 1, the liquid of (e) is supplied.

The sampling liquid exiting the main electrode chamber 27 'is discarded. In this way, the second copper ion concentration complexing agent concentration was automatically managed for 168 hours continuously.

In this case, the sampling rate of the sampling pump 4 is 50 ml / l, the temperature at the time of detecting the plating liquid by the cooler 5 is about 25 ° C, the setting potential of the plating liquid pH is -0.260V, and the setting potential of the second copper ion concentration is The set potential of 0.168V and the complexing agent was 0.261V.

Under these conditions, pH was 12.3 ± 0.07, secondary copper ion concentration was 14.1 ± 0.65g / l, and complexing agent concentration was 40 ± 2g / l.

The detection electrode did not deteriorate at all for 30 hours of automatic management.

Example 6

After the pH and the second copper ions were measured in the same manner as in Example 5 in the automatic management of the same chemical plating solution as in Example 1 with the system shown in FIG. 4, the same copper oxide electrode as in Example 1 was used. A reducing agent concentration was measured in the same manner as in Example 4, and then a complexing agent concentration was measured in the same manner as in Example 5. The same results as in Examples 4 and 5 were obtained with respect to each other and the respective measured components.

The pH control was the same as in Example 1, and when the second copper ion concentration, the reducing agent concentration and the complexing agent concentration were administered, an automatic assay solution, an electrode, and a replenishment solution for concentration adjustment were used as shown in (a)-(b) below. .

As shown in FIG.

First, pH control and second copper ion concentration complexing agent concentration management were performed in the same manner as in Example 1 and Example 5 in 1-14 of FIG. In this embodiment, the sampling solution exiting the second copper ion concentration detection chamber 26 flows into two branches, one flow being introduced into the main electrode chamber 7 'of the complexing agent detection chamber 20, The other flow is mixed with the sulfite ion-containing liquid of (b-1) described above sampled in the titration tank 31 by the sampling pump 4 after the flow rate is adjusted by the sampling pump 4 32) and mixed with the iodine-containing liquid of (b-2) described above, which is sampled in the titration tank 33 by the sampling pump 4, and then sufficiently mixed. Stir and react. This flow is then put into the main electrode chamber 35 'of the reducing agent detection formula 35, and the potential difference between the platinum electrode 27' and the on-silver chloride electrode 9 '' is controlled by the control device 10. Is detected.

11 '' is a heavy brain. When the detection potential is lower than the electric potential set in the control device, a signal is applied from the control device 10 to the supply pump 36, whereby the supply pump 36 is connected to the valve 38 and the supply liquid tank 37 for reducing agent adjustment. The feed liquid of (f) is supplied through the mixer 3 into the plating bath 1 until the detection potential exceeds the set potential. The sampling solution exiting the main electrode chamber 35 'is discarded.

On the other hand, the standard solution of (h) above the reference electrode chamber 20 'of the complexing agent concentration detection chamber 20 is a silver-silver chloride electrode 9 in the reference electrode chamber 35' 'of the reducing agent concentration detection chamber 35. In order to obtain a stable potential at ''), it is supplied to the reference electrode chamber 35 '' of the reducing agent concentration detection chamber 35 and then discarded through it.

In this way, the pH, the second copper ion concentration, the reducing agent concentration, and the complexing agent concentration of the chemical copper plating solution were continuously managed for 100 hours continuously.

In this case, the sampling rate of the sampling pump 4 is 50 ml / l, the temperature at the time of detecting the plating liquid by the cooler 5 is about 25 ° C., the set potential of the pH of the plating liquid is -0.260V, and the second copper ion concentration is used. The set potential of the setting potential was 0.100 V, the set potential of the reducing agent concentration was 0.050 V, and the set potential of the complexing agent concentration was 0.150 V.

Under these conditions, the pH is 12.3 ± 0.04, the second copper ion concentration is 13 ± 0.52g / l, the reducing agent concentration is 3 ± 0.15ml / l, and the ring agent concentration is 40 ± 0.8g / l. Could. As described above, since the pH of the amount of money can be accurately measured for a long time even by using the copper acid exchange electrode according to the present invention, it becomes possible to accurately manage the pH of the plating liquid.

Claims (1)

The metal copper is etched for 1 second to 10 seconds at a liquid temperature of 18 ° C.-50 ° C. using 0.1 N-1 N inorganic acid, followed by a solution temperature of 18 ° C. using a solution of 0.1 N-1 N alkali metal hydroxide. An electrode for pH measurement of an aqueous solution, characterized in that the surface is made of copper oxide by oxidation treatment at −50 ° C. for 5 minutes to 30 minutes.

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