JPS60104247A - Device for measuring concentration of copper ion and chelate agent in chemical copper plating liquid - Google Patents

Abstract

PURPOSE:To supply a titrating liquid to the 2nd cell if potential is above a specified value by collecting and mixing a chemical copper plating liquid and a titrating liquid, providing a conductive insoluble electrode coupled thereto and a reference electrode and measuring cell potential. CONSTITUTION:A chemical copper plating liquid and the 1st titrating liquid are collected from a plating cell 1 and the 1st titrating liquid 3 at the rate of 20ml/ h. Potentional is measured and the measured value is inputted to a device 8 for controlling concn. of copper ion. When the measured potential is lower than the set potential 0.2V, a solenoid valve 9-1 is opened and the copper ion is replenished into the plating liquid from a copper ion replenishing vessel 10. When the potential exceeds 0.2V, the valve 9-1 is closed and the replenishment is stopped. When the measured potential is higher then 0.43V, a solenoid valve 9-2 is opened and a chelate agent soln. is replenished to the plating cell from a chelate replenishing tank 14 and when the potential falls down to 0.43V or below, the valve 9-2 is closed and the mixed soln. emitted from a chelate agent 12 is discharged into a waste liquid tank 15. The concn. of the copper ion and chelate agent in the chemical copper plating liquid is thus adjusted with good accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for measuring copper ion concentration and chelating agent concentration in a chemical steel plating solution.

[Background of the invention]

Recently, printed wiring boards have been manufactured by providing circuit conductors on an insulating substrate by chemical copper plating.

In this case, the plating film serving as the circuit conductor is required to have good electrical and mechanical properties.

Generally, a chemical steel plating solution consists of copper ions, a chelating agent or complexing agent for copper ions, a reducing agent, and an alkali metal hydroxide.

Then, the copper ions in the chemical steel plating solution are consumed by the plating reaction, and the chelating agent adheres to the plated object and is carried out of the tank to a non-negligible extent, reducing its concentration.

Note that the mechanical properties of chemical copper plating films are significantly affected by the concentration of copper ions and the concentration of chelating agents or complexing agents in the plating solution. Therefore, it is necessary to control the concentration of these components. Conventionally, the concentration of copper ions in chemical steel plating solutions was measured using a colorimetric method. However, with the colorimetric method, the measured value is the PH value,
It was inaccurate because it was strongly influenced by the concentration of ions and compounds other than copper ions, and hydrogen gas in the plating solution. Moreover, the measuring equipment was expensive.

The concentration of the copper ion chelating agent had not yet been measured as it was not consumed in the plating reaction.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide an apparatus for accurately measuring copper ion concentration and chelating agent concentration in a chemical copper plating solution.

[Summary of the invention]

A means for collecting a chemical steel plating solution from a plating tank, a means for collecting a titrant solution, a means for mixing said sampled plating solution and a titrant solution, and a platinum electrode and a reference electrode coupled to a mixing means. a first cell, a second cell comprising a platinum electrode and a reference electrode coupled to said first cell, means for measuring the potential measured in said cell; said first cell and said second cell; This is achieved by an apparatus for measuring the concentration of copper ions and chelating agent in a chemical copper plating solution, which comprises means for supplying a titrant to the second cell provided between the two cells.

The measurement principle of the present invention will be explained below. Chelating agents ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTA) and ethylenediaminepentaacetic acid (hereinafter abbreviated as gDPA) react with divalent copper ions at a molar concentration ratio of 1:1. This reaction is a chelate-forming reaction, and the reaction product is a copper chelate compound.

Now, if the copper ion concentration in the chemical steel plating solution is 0 mol and the chelating agent's molar concentration is n0 mol (generally, 1), then the chelating agent is added 1.5 to 5 times the steel ion concentration. ), the divalent steel ions are completely chelated. And platinum,
Using an insoluble main electrode such as gold and a reference electrode, monovalent steel ions (hereinafter abbreviated as Ou') present in trace amounts in the plating solution are detected.
, and a chelate compound of divalent steel ions (hereinafter abbreviated as CU■), the potential is expressed as in equation (1).0......(1) (However, (1 ) In the formula, the stability constant between Cu■ and BDTA, [:OuI] is the molar concentration of Oul in the plating solution. Consider the case where ions (hereinafter abbreviated as Fem) are added.

Trivalent iron ions form extremely stable chelate compounds with chelating agents, which are more stable than many divalent metal ions. Therefore, when the amount of Fem added slightly exceeds 0 mol (FL-1), which is the difference in hardness between 0uII and the chelating agent, the chelated 0uII dissociates from the chelating agent and becomes free Cu generate. Then, when the potential between □uTI and 011 is measured using the same electrode as above, the equation (2) is obtained. ), free Fe1II is present,
When the potential with the divalent iron ion (hereinafter abbreviated as F-) present in a trace amount in the plating solution is measured using the same electrode as above, (3
) is as follows.

......3 That is, the total Fe weight when the potential changes from E(1) to E(2) is the amount of total free chelating agent (rL-1)0
Equal to moles.

Then, the total chelating agent concentration is determined from the amount (m 0 mol) required for Fem to form a chelate compound with all the chelating agents, and the value obtained by subtracting the above (rL-1) 0 mol from this is the total CuII # [Examples of the Invention] The present invention will be explained in detail below using Examples.Example 1 1. Composition of plating solution and plating conditions CuSO4.5H20... ...14f
EDTA-2Nα ・・・・・・・・・41.5
fNαOH・・・・・・・・・12237% formalin ・・・・・・・・・10rnt addition amount ・・・・・・・・・Small amount of water ・・・・・・・・・・Plating temperature 70°C Plating area 1 drr? /l Plating speed 2.5 μ/h Sampling speed 20 doors t/h ■ Titrant composition and titration conditions Titrant composition Fe013 18.1 ? HO110mt Water...Amount to make the whole 1L First titration condition setting potential +028 ■ Main electrode 0.5 @ platinum wire reference electrode Saturation Amagi electrode titration rate 20 doors t/h Second titration Condition setting゛Potential +〇, 54V Main electrode 0.37 platinum wire reference electrode Saturated Chigi electrode Titration rate 20rnt/h The above plating solution and the above titration solution were each pumped into a multiple tube pump 2 at a rate of 20 doors t/h. Samples were taken from the plated tank 1 and the first titration tank 3. Both liquids were mixed in a T-tube 4-1. Next, apply this m mixture to Platinum &6-1 and saturated Amagi electrode 5.
-1, and the electrode potential was measured. This measured potential was input to the copper ion 7vIk degree control device 8. When this input is lower than the set potential of 0.28V, the solenoid valve 9-1 (a replenishment pump may be used to replace the 1iL solenoid valve) opens, and the copper ion solution from the copper ion replenishment tank 10 is deposited. The tank was replenished. input is 0.28
When it became higher than V, the solenoid valve 6 was closed and replenishment was stopped.

The m mixture that came out of the copper ion detection self was mixed with the titrant liquid collected from the second titration tank 11 at a rate of 20 mA/A using the multiple tube pump 2 through the T-tube 4-2. This mixed solution was placed in a chelating agent detection cell 12 equipped with a platinum electrode 6-2 and a saturated Amagi electrode 5-2, and the electrode potential was measured.The measured potential was input to the chelating agent control device 13. If this person's electric potential is higher than the set potential of the chelating agent control device by 0.54V, the solenoid valve 9-2 opens and the chelating agent supply tank 1
From 0.4, the chelating agent solution is replenished into the plating tank 1.
When the voltage dropped to 54V, solenoid valve 9-2 closed and replenishment was stopped. The m mixture that came out of the chelating agent detection cell 12 was discharged into a waste liquid tank 15.

Concentration control was carried out continuously for 100 hours. During that time, the copper ion concentration and chelating agent concentration were separately chemically analyzed intermittently to check the accuracy of the illegal analysis, and it was found that there was one body of analytical particles with ±5 cm.Example 2 ■ Determination of the composition of the plating solution Conditions Same as ■ in Example 1 ■ First titrant composition and titration conditions Titrant composition 011804 ・5HzU 14.0f)
12804 5.0m4 Water... Volume to make the whole 1L Titration condition setting potential +○, 2■ Main electrode 05z platinum wire reference electrode Saturated Amagi electrode titration rate 207/A ■ Second titrant composition and titration conditions Titrant composition: Fe0t318.3 y HCL 10ml Water: 1 ton as a whole Titration conditions: Set potential: +〇, 43V Main electrode: 0.3Z white rice reference electrode: Saturated Amagi electrode Titration rate: 20d/A The above plating solution and the first titrant were collected from the plating tank 1 and the first titration tank 3 at a rate of 20 ml/liter using the multiple tube pump 2, respectively. Thereafter, the potential was measured in the same manner as in Example 1. This measured potential was input to the copper ion concentration control device 8.

If this input is lower than the set potential of 020V, the solenoid valve 9-1
opens, and when the power of copper ions supplied to the plating solution from the copper ion supply 4W10 becomes higher than 0.20V, the electromagnetic valve 6 closes and the supply is stopped.The mixed solution exiting the copper ion detection self is The second titrant liquid collected from the second titration tank 11 at a rate of 20 mj/A with the multiple tube pump 2 and the T-tube 4
Mixing was started at -2 and then the potential was measured in the same manner as in Example 1. The measured potential was input to the chelating agent control device. This input is 0.45 of the set potential of the chelating agent control device.
When the voltage is higher than V, the solenoid valve 9-2 opens and the chelating agent solution is replenished from the chelating agent replenishing tank 14 to the plating tank.
When the voltage became as low as 4 sV, the solenoid valve 9-2 was closed and replenishment was performed.

The α mixture liquid that came out of the chelating agent detection cell 12 was discharged into a waste liquid tank 15.

Note that if the second titrant solution is added intermittently every 10 hours, the plating solution when this solution is not added can be reused.

An example in which the concentration was controlled for 50 hours.

The analysis accuracy was the same as that of 1.

〔Effect of the invention〕

As described above, according to the present invention, the copper ion concentration and the chelating agent concentration in the chemical steel plating solution can be adjusted with high precision. It can also be continuously and automatically controlled.

[Brief explanation of the drawing]

The figure is a configuration diagram of an automatic concentration control device for copper ions and chelating agents in a chemical copper plating solution. 1...Metalized tank 3...First titrant 5-1.5-2...Saturated Amagi electrode 6-1.6-
2...Platinum electrode 7...Copper ion detection cell 8...Copper ion concentration control device 10...Copper ion supply tank 11... Second titrant 12...Chelating agent detection cell 13...Chelating agent control device 14...Chelating agent supply tank

Claims (1)

[Claims] A means for collecting a chemical steel plating solution from a plating tank, a means for collecting a titrant solution, a means for combining the sampled plating solution and a titrant solution, a conductive insoluble electrode coupled to the combining means; a first cell comprising a reference electrode, means for measuring the potential measured in the cell, a second cell comprising an electrically conductive insoluble electrode coupled to said first cell and a reference electrode; 1. An apparatus for measuring copper ion and chelating agent concentration in a chemical copper plating solution, comprising means for supplying a titrant to the second cell, which is provided between the first cell and the second cell.