JPS60104248A - Method for measuring concentration of chelate agent in chemical copper plating liquid - Google Patents

Abstract

PURPOSE:To measure the concn. of a chelate agent in a chemical copper plating liquid and to enable continuous and automatic control of concn. by adding Fe<3+> exceeding slightly the molar concn. of the entire chelate agent contained in the chemical copper plating liquid to said liquid and measuring the oxidation reduction potential thereof. CONSTITUTION:A specified amt. of a copper plating liquid consisting of Cu ion, chelate agent, reducing agent and alkali metal hydroxide is collected from a plating cell 1 by means of a multiplextube pump 2 and a titrating liquid 3 consisting of an aq. soln. of FeCl3 and HCl is drawn from the 1st titrating liquid tank in measuring the chelate agent such as ethylenediamine tetraacetic acid as the chelate agent in said copper plating liquid. Both liquid are mixed and the electrode potential thereof is measured with a Cu ion detecting cell 7 and is inputted to a device 8 for controlling the concn. of the Cu ion. The liquid emitted from the cell 7 is mixed with a specified amt. of the 2nd titrating liquid 11 by a pump 2 in a Tee pipe 4-2 and the concn. is measured with a chelate agent detecting cell 12 and the measured valve is inputted to a control device 13. If the concn. is lower than the respective set values of the devices 8, 13, solenoid valves 9-1, 9-2 are opened and the Cu ion and chelate agent are respectively replenished to the cell 1 from a Cu ion replenishing tank 10 and a chelate agent replenishing tank 14.

Description

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

[Background of the invention]

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

In this case, the plating film that is 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 object to be plated and is carried out of the tank to a non-negligible extent, reducing its concentration.

Note that the mechanical properties of chemical steel 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 concentrations of these components.

Conventionally, the concentration of copper ion chelating agents has not been measured because they are 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 conventional techniques described above and to provide a method for accurately measuring the concentration of a chelating agent in a chemical copper plating solution.

[Summary of the invention]

The above purpose is to increase the molar concentration of all the chelating agents present in a chemical copper plating solution consisting of copper ions, a copper ion chelating agent, a copper ion reducing agent, and an alkali metal hydroxide. A chelate in a chemical copper plating solution characterized by adding trivalent iron ions at a molar concentration slightly higher than that and measuring the redox potential of this solution using an insoluble electrode and a reference electrode to determine the total chelating agent concentration. The present invention provides a method for measuring drug concentration.

The measurement principle of the present invention will be explained below. Chelating agents ethylenediaminetetraacetic acid (hereinafter abbreviated as EDTAJ) and ethylenediaminepentaacetic acid (hereinafter abbreviated as 11i!DPAj) and divalent copper ions react 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 copper merging solution is C moles, and the molar concentration of the chelating agent is TLC moles, then
When the chelating agent is added at a concentration of 1.5 to 5 times the copper ion concentration), divalent copper ions are completely chelated. And platinum,
Using an insoluble main electrode such as gold and a reference electrode, the potential between monovalent copper ions (hereinafter abbreviated as CJ) and divalent copper ion chelate compounds (abbreviated as CM) present in trace amounts in the plating solution is determined. When measured, it will be as shown in formula 1j.

E(s=o, 1ss-o, osq2tottiK(n-
1nr, c=n ---... (1) (However, in formula (1), (stability constant CC &) between 2T4 and EDTA is the molar concentration of Cλ in the plating solution) Above Consider the case where trivalent iron ions (hereinafter abbreviated as FW) are added to a chemical copper plating solution having the concentration relationship expressed by equation (1).

Trivalent iron ions form extremely stable chelate compounds with chelating agents. This is more stable than poly(divalent metal ions). Therefore, if the amount of FW added exceeds (3-1) C mole, which is the difference in concentration between the chelating agent and the chelating agent, the chelated G becomes more stable. Dissociates from the agent and releases free cW
Then, when the potential between CM and CI is measured with the same electrode as above, it becomes as shown in equation (2).

Ef2 offing 0.153 + 0.0592 no 0 pa (Cri/ (
(2) When the amount of FJ added slightly exceeds the chelating agent concentration (30 mol), free FJ will exist, and a trace amount of FJ will be present in the plating solution. When the potential between valent iron ions (hereinafter abbreviated as F and II) is measured using the same electrode as the previous one, K is obtained as shown in equation (3).

Ef31 = [ ], 771 + 0.0592 no Opa (FI
F)/(Pg) =-·f31n.

That is, when the potential changes from E(1) to E(3), the total amount of F and N is equal to the total amount of chelating agent rLC moles. This will be explained in detail.

Example 1 t Composition of plating liquid and plating conditions c, sat 580...14.9BDTA
-2Na・-------...-4t3j'NaOH・・
−・−・−・−・−・−・・12157% Formalin・・−・−・・・・10ml Addition amount・・・・・・
・ ・ ・ Small amount of water ・ ・ ・ ・ ・ ・ ・ １ ノ ノ ノ 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全 全F4Cj, 18. IJiHCj 10m
j Water・・・・・・・・・Amount with total as 1j First titration condition setting Potential, 28V Main electrode 0.3φ platinum wire reference electrode Saturation Amagi electrode Titration rate 20rnl/2nd titration Condition setting potential: +054v Main electrode: 03ψ platinum wire reference electrode Saturated Amagi electrode Titration rate: 20 milL The plating solution and the titrant solution were sampled from the plating tank 1 and the first titration tank 6 at a rate of 20ml and 1μ using the multiple tube pump 2, respectively. did. Both liquids were mixed in a T-tube 4-1. Next, this mixed solution was placed in a copper ion detection cell equipped with a platinum electrode 6-1 and a saturated f< electrode 5-1, and the electrode potential was measured.

This measured potential was input to the copper ion concentration control device 8.

If this input is lower than the set potential 028V, the solenoid valve 9-1
[A replenishment pump may be used instead of the solenoid valve] was opened, and the copper ion solution was replenished from the copper ion replenishment tank 10 to the plating oak. When the input was higher than 0.28V, the solenoid valve 6 was closed and replenishment was stopped.

The mixed liquid coming 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 ml/JL using the multiple tube pump 2 in 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 measurement potential was manually input to the chelating agent control device 16. When this input is higher than the set potential of the chelating agent control device, 054V, the solenoid valve 9-2 opens, and the chelating agent solution is replenished from the chelating agent supply tank 14 to the plating tank 1, and the voltage is 054V.
When the temperature became lower than that, the electromagnetic valve 9-2 was closed and replenishment was stopped.

Concentration control was carried out continuously for 100 hours.

During this time, the copper ion concentration and the chelating agent concentration were separately subjected to chemical analysis intermittently to check the accuracy of the illegal analysis, and the analysis accuracy was ±5%.

〔Effect of the invention〕

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

[Brief explanation of drawings]

The figure is a configuration diagram of an automatic concentration control device for a chelating agent in a chemical copper plating solution. 1...Plating tank 3...First drop of foot liquid 5-1, 5-2...Saturated Amagi Seipoku 6-1.
6-2・・・・・・－・－・・Platinum electrode 7・・・・・・・・・・
- Steel ion detection cell 8... Copper ion concentration control device 10...
--- Copper ion supply tank 11 --- Second titrant 12 --- Chelating agent detection cell 16 ---
...Chelating agent control device 14...Chelating agent supply tank Representative patent attorney Akio Takahashi

Claims (1)

[Claims] A chemical steel plating solution consisting of copper ions, a copper ion chelating agent, a copper ion reducing agent, and an alkali metal hydroxide has a molar concentration that slightly exceeds the molar concentration of all the chelating agents present in this plating solution. A method for measuring the concentration of a chelating agent in a chemical copper plating solution, which comprises adding trivalent iron ions of .