JPS6032820B2 - Method and device for controlling reducing agent concentration in chemical copper plating solution - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method and device for controlling the concentration of a reducing agent in a chemical copper plating solution, and particularly to a method and a control device for controlling the concentration of formaldehyde in a chemical steel plating solution. Regarding a control device.

[Background of the invention]

Recently, chemical steel plating has been applied directly to desired parts of insulating substrates.
Printed wiring boards are manufactured by forming wiring patterns for three hours.

The wiring pattern needs to have excellent mechanical properties as well as electrical properties as a conductor.
However, the characteristics of the above wiring pattern depend on the composition of the chemical steel plating solution, especially the concentration of formaldehyde, which is a reducing agent. That is, formaldehyde is rapidly consumed by reactions during plating, self-decomposition, evaporation, etc. When the formaldehyde concentration is lower than a desired value, the plating speed becomes slow, and when the formaldehyde concentration is higher than the desired value, the plating film becomes brittle and the plating solution decomposes. Therefore, it is necessary to maintain the formaldehyde concentration in the chemical steel plating solution at a desired value for a long time.

For this purpose, it is required to accurately measure formaldehyde concentration over a long period of time. Conventionally, the formaldehyde concentration in chemical steel plating solutions was determined by neutralizing a certain amount of the plating solution with acid, then mixing it with sodium sulfite,
Formaldehyde and sodium sulfite are reacted as shown in formula 1 below, and the amount of caustic soda produced at this time is measured as a multiplication value using a glass electrode and a reference electrode, and the formaldehyde concentration is adjusted so that this pH value becomes a constant value. Was.

HCHO+Na2S03 10 days 20 days NaOH+C ratio (N
aS03) OH ...... [1' However, in the above method, since the fence of the liquid to be measured is 13 to 14, the glass electrode is attacked by alkali and deteriorates, and salt errors and differences also occur. Therefore, it became impossible to accurately measure the M value over time, and accurate formaldehyde concentration control could not be performed over a long period of time.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art and provide a method and apparatus for controlling the reducing agent concentration in a chemical steel plating solution with high accuracy over a long period of time.

[Summary of the invention]

And, the above purpose is to use steel ions, a mirroring agent for steel ions,
Add sodium sulfite in excess of the amount of formaldehyde to a certain volume of a chemical steel plating solution consisting of formaldehyde, alkali metal hydroxide, and water, and add p.p.
A certain amount of a pH buffering agent exhibiting H buffering effect is added, and sodium sulfite and formaldehyde in a chemical steel plating solution are reacted quickly and without the influence of impurities as in the formula '1' above. p which shows pH buffering effect between 2 and 9
By adding a certain amount of H buffer, the sodium sulfite and iodine remaining in the chemical steel plating solution are allowed to react as shown in equation (2).

Na2S03 1120&0koNa2S0412HI
...■ At this time, if formaldehyde is in excess of a predetermined value and iodine remains, iodine will be in an equilibrium state as shown in equation {3' below.

120 ko21-...
...{3} On the other hand, when formaldehyde is insufficient than the predetermined value and sodium sulfite remains, it indicates the natural potential of the chemical steel plating solution.

That is, the formaldehyde concentration in the chemical steel plating solution is measured by detecting the natural potential of the equilibrium potential of the plating solution generated by this '31 equation equilibrium reaction.

That is, the formaldehyde concentration is controlled by comparing the detected potential and a set potential. Note that if the pH is less than 2, iodine will be decomposed, so the equilibrium reaction of '3' above will not occur.

Also, if the shoes are larger than 9, iodine reacts with caustic soda as shown in formula {41, becomes Nal○, and becomes 12+2N
aOH 10 Nalo 20...'41
Sulfite is oxidized by Nal0, and the change in potential from the natural level of the plating solution to the equilibrium level of formula 31 cannot be detected. Note that the potential is detected by using gold or platinum as a main electrode in combination with a reference electrode.

The pH buffering agent having a buffering effect in the fences 6 to 12 is preferably potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium carbonate, borax, sodium citrate, ammonium chloride or sodium dimethylglycine.

The pH buffer having a buffering effect at pH 2 to 9 is preferably potassium hydrogen citrate, potassium dihydrogen phosphate, sodium citrate, glycine, or potassium hydrogen phthalate.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 1 Chemical steel plating liquid composition CuS04・QLO...12taE
DTA-2Na...40TaNaOH...11Yuhi CHO...3Yu Additive
・・・・・・A small amount of water ・・・・・・
・・・Amount to make the whole 1〆 0 Sodium sulfite solution composition Na2S03 ・・・・・・1
8.9 Ta Na2B40?・10th 20th ・
・・・・・・20 t water ・・・・Amount m to make the whole thing overnight Iodine solution composition K1
・・・・・・40 pm 12
...12-692ta KH2P04
・・・・・・100 tons of water ・・・Total amount for one night A chemical steel plating solution having the composition shown in 1 above is pumped from the plating tank 1 shown in the figure at a rate of 20 discharges per hour using the multiple tube pump 2. At the same time, a sodium sulfite solution having a composition of 0 was sampled from the sodium sulfite solution tank shown in the figure at a flow rate of 20' per hour using a multiple tube pump 2 and mixed in a T-tube 5.

Furthermore, the iodine solution having the composition m is sampled from the iodine solution tank 4 using a polyurethane tube pump at a flow rate of 20 minutes per hour, and is added to the chemical steel plating solution to which sodium sulfite has been added using the T-tube 6. Mixed.

The addition conditions for sodium sulfite solution and iodine solution are as follows.

First, it can be seen from the previous equation 11 that the reaction molar ratio between sodium sulfite and formaldehyde is 1:1. In addition, the reaction molar ratio between sodium sulfite and iodine is also the same as [2] above.
It can be seen from the formula that the ratio is 1:1. Next, the formaldehyde concentration in the chemical shrinkage solution 1 in the plating pot 1 is determined as Hmo
l/k Sodium sulfite concentration in sodium sulfite solution 0 in sodium sulfite solution tank 3 is Smol/so, iodine concentration in iodine solution m in iodine solution tank 4 is Ymol
/ Sotoshi, chemical steel plating solution 1, sodium sulfite solution 0
, the sampling rate of the iodine solution m in the multiple tube pump 2 is V/h, then YXV=SXV/day XV...[51 Therefore, the relationship of equation (2) holds true.

Y=S-day...{6' Therefore, H=0.1 mol/so(3 evening/Z), S=0.
If 19 hol/end (18.9 evening/so), then Y=0.
08 hol/so (12.692 evening/so).

This mixed solution enters the potential detection cell 7 in the figure, and the platinum electrode 8
The detected potential is inputted to the digital voltmeter of the control device consisting of a digital voltmeter and a digital comparator, and the detected potential is displayed. .1 V (formaldehyde concentration, equivalent to 3.0 m/s), and the formaldehyde concentration began to be adjusted. The formaldehyde concentration in the chemical steel plating solution is 3.
When the detection potential is less than 0/g, the detection potential is M. in the table. 1
~M. 5 shows the natural potential of the chemical steel plating solution which is smaller than the set potential of -0.1V, and in these cases, the difference between the detected potential and the set potential serves as a signal to open the solenoid valve 11 and release formaldehyde. Formaldehyde solution was replenished from the supply tank 12 to the Metsusa tank 1, and when the detection potential reached -0.1V, the supply was stopped. ±Relationship between formaldehyde concentration and detection potential Also, when the formaldehyde concentration in the chemical steel plating solution is 3.0 μm or more, the detection potential is as shown in the table M. 6~M. -0.1V of the set potential as shown in 10.
In these cases, the difference between the detected potential and the detected potential becomes a signal, and formaldehyde is added to the chemical steel plating solution until the two values become equal. Solution was not replenished.

Incidentally, the chemical steel plating solution containing sodium sulfite and iodine that came out of the potential detection cell 7 was discharged to a discharge tank 13. [Effects of the Invention] That is, a certain amount of the sodium sulfite solution and iodine solution of B and M are mixed with the chemical steel plating solution of 1 above, the potential of this mixed solution is detected, and this detected potential is - of the set potential. 0.1
If it was smaller than V, formaldehyde was replenished, and if it was larger, formaldehyde was stopped. When the formaldehyde concentration was controlled for 5 consecutive feeding periods, the formaldehyde concentration was controlled with an accuracy of -5%.

Furthermore, since the electrodes are not degraded by alkali and salt errors do not occur, the formaldehyde concentration can be controlled with high precision for a longer period of time.

Furthermore, the control method and control device of the present invention can also be applied to control of reducing agent concentration in chemical silver plating using formaldehyde as a reducing agent.

[Brief explanation of the drawing]

The figure is a block diagram of an automatic concentration control device for formaldehyde in a steel plating solution. 1...Metting pot, 2...Multiple tube pump, 3...Sodium sulfite solution tank, 4...
...Iodine solution tank, 7...Potential detection cell, 8...
...Platinum electrode, 9...Reference electrode, 12...
...Replenishment tank.

Claims (1)

[Claims] 1. A chemical copper plating solution consisting of copper ions, a complexing agent for copper ions, formaldehyde, an alkali metal hydroxide, and water is added to a certain volume of a chemical copper plating solution containing more than the amount of formaldehyde. The formaldehyde and the sodium sulfite are reacted by adding excess sodium sulfite and a pH buffering agent having a pH buffering effect at pH 6 to 12, and then iodine is added to this and a pH buffering agent having a pH buffering effect at pH 2 to 9. If the formaldehyde content is less than the desired value and sodium sulfite remains, use the natural chemical copper plating solution with a value lower than the set potential of the control device. The potential is detected by a gold or platinum main electrode and a reference electrode, and the difference between the detected potential and the set potential becomes a signal.Formaldehyde is replenished into the chemical plating solution until the detected potential becomes equal to the set potential. If the blended amount is larger than the desired value and iodine remains, the iodine molecule I with a value larger than the set potential of the control device is
The equilibrium potential of __2 and iodine ion I^- is detected using a gold or platinum electrode and a reference electrode, and the difference between this detected potential and the set potential becomes a signal, and formaldehyde is heated to the chemical copper plate until the detected potential becomes equal to the set potential. A method for controlling the concentration of a reducing agent in a chemical copper plating solution, characterized in that the plating solution is not replenished. 2 A pH buffering agent that exhibits a pH buffering effect at pH 6 to 12 is
The chemical copper plating solution according to claim 1, characterized in that it is potassium dihydrogen phosphate, disodium hydrogen phosphate, sodium carbonate, borax, sodium citrate, ammonium chloride, or sodium dimethylglycine. How to control the concentration of reducing agent inside. 3 A pH buffering agent that has a pH buffering effect at pH 2 to 9 is
A method for controlling the concentration of a reducing agent in a chemical copper plating solution according to claim 1, characterized in that potassium hydrogen citrate, potassium dihydrogen phosphate, sodium citrate, glycine, or potassium hydrogen phthalate is used. . 4 A device that mixes a certain volume of a chemical copper plating solution with a solution containing sulfite ions and a pH buffering agent that has a pH buffering effect in the pH range of 6 to 12, and a device that mixes a certain volume of a solution that contains sulfite ions and a pH buffering agent that has a pH buffering effect in the pH range of 6 to 12, and a device that mixes a certain volume of a solution that contains sulfite ions and a pH buffering agent that has a pH buffering effect in the pH range of 2 to 9.
A device that mixes a fixed volume of an aqueous solution containing a buffer, a device that detects the potential of this mixed solution, and if the detected potential is smaller than a preset potential, the potential difference becomes a signal and becomes the detected potential. The controller replenishes formaldehyde until the set potentials are equal, and if the detected potential is greater than the preset potential, the difference becomes a signal and stops formaldehyde replenishment until the detected potential becomes equal to the set potential. A device for controlling the concentration of a reducing agent in a chemical copper plating solution.