JPH0633249A - System for automatically controlling copper electroless-plating bath - Google Patents

Abstract

PURPOSE:To provide a system capable of automatically controlling a copper plating soln., especially its pH, with precision in the copper electroless-plating bath. CONSTITUTION:The copper concn., HCHO (reducing agent) concn. and pH of a copper plating soln. are controlled by adding solns. of CuSO4, HCHO and sodium hydroxide. In this case, since the pH of the soln. is lowered by addition of HCHO soln., the amt. of NaOH soln. to be added is determined in consideration of the amt. of the NaOH soln. necessary to adjust the pH, and the NaOH soln. is added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for automatically controlling an electroless copper plating bath, which can control each component of a copper plating solution during a copper plating operation, and particularly can accurately control the pH of the copper plating solution. The present invention relates to an electroless copper plating bath automatic management system.

[0002]

2. Description of the Related Art Compared with the electroplating method, the electroless plating method can obtain a coating of uniform thickness on all parts only by contacting the object to be plated with the plating solution, and the hardness of the deposits. There are features such as high price. For that purpose, it is necessary to appropriately manage the copper plating solution.

Conventionally, control of an electroless copper plating bath is an item necessary for control of a copper plating solution. For example, copper concentration, reducing agent concentration, and pH value are measured over time, and a preset control value is used. If it is low, the copper plating operation is continued while adding the replenisher to adjust the concentration of each component to the control value. At this time, since each component is controlled independently and independently, in many cases, each component influences each other, and even if the theoretical addition amount is added, the control value is not adjusted in many cases.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a method for replenishing and adding each component during the electroless plating operation in order to adjust the component composition of the copper plating solution to a preset control value. An object of the present invention is to provide an electroless copper plating bath automatic control system capable of accurately adjusting pH to a control value.

[0005]

The electroless copper plating bath automatic management system according to the present invention is an electroless copper plating solution comprising a copper salt, a reducing agent and a pH adjusting agent, and each component added during the copper plating operation. It is characterized in that the addition amount of the pH adjusting agent required for adjusting the change in the pH of the copper plating solution due to the above is calculated by complex calculation.

Preferably, the copper salt is a copper sulphate solution, the reducing agent is a formaldehyde solution and the pH adjusting agent is a sodium hydroxide solution.

[0007]

The control items of the copper plating solution are copper concentration, formaldehyde concentration and pH value, and each component in the copper plating solution is measured over time during the copper plating operation. Based on the measured values, the addition amount of each component required to adjust the concentration of each component to a control value is determined, and the copper plating liquid is adjusted by supplementing and adding to the copper plating liquid.

When formaldehyde is added to the copper plating solution for adjusting the formaldehyde concentration, the pH of the copper plating solution is lowered. In this case, the composition of the copper plating solution is not accurately adjusted to the control value. When such a copper plating solution is used, it may cause poor quality of the product to be plated.

On the other hand, if the amount of sodium hydroxide added to adjust the pH drop of the copper plating solution due to the addition of formaldehyde is added to determine the amount of sodium hydroxide added and the copper plating solution is replenished and added, copper is added. The plating solution composition can be adjusted to a control value with high accuracy. By using the copper plating solution properly managed in this way, it is possible to obtain a product to be plated of good quality.

[0010]

EXAMPLES The present invention will be described in detail below with reference to examples.

Example 100 g of copper sulfate (pentahydrate), formaldehyde (37
% Water solution) in 10 liters of water and pH 12.4 with 1 mol / l sodium hydroxide solution.
Then, 10 liters of the copper plating solution was prepared and used. The concentration of each component in this copper plating solution is 2.5 g / l of copper,
Formaldehyde was 2.5 ml / l.

The copper plating reaction was carried out at 70 ° C., and an epoxy copper clad laminate was used as a sample to be plated. Two hours after the copper plating treatment, the concentration of each component of the copper plating solution was 2.2 g of copper /
1 and formaldehyde changed to 0.8 ml / l, and the pH dropped to 12.2. The composition of the copper plating solution was adjusted using 63 g / l copper sulfate solution (solution A), 37% formaldehyde solution (solution B), and 1 mol / l sodium hydroxide solution (solution C).

The adjustment of the copper concentration is performed according to FIG.
The addition amount of the solution (copper sulfate solution) of 31.7 ml was determined and added to the copper plating solution. The formaldehyde concentration was adjusted by obtaining 25 ml of the solution B (formaldehyde solution) required for the adjustment from FIG. 3 and adding it to the copper plating solution. To adjust the pH, first, from FIG. 1, an addition amount of 50 ml (T) of the solution C (sodium hydroxide solution) necessary for adjusting the pH of the copper plating solution was obtained. Next, the pH drop of the copper plating solution due to the addition of solution B (formaldehyde solution) to the copper plating solution was obtained from FIG. 4, and the addition amount of the sodium hydroxide solution necessary to adjust this pH drop was calculated from FIG.
ml (S) was determined. A total of 75 ml of the sodium hydroxide solution added with T and S was added to the copper plating solution to adjust the pH of the copper plating solution.

As a result, the pH of the obtained copper plating solution is 1
In 2.4, the copper plating solution could be adjusted properly. By using such a copper plating solution,
A good copper-plated product could be obtained.

Comparative Example 100 g of copper sulfate (pentahydrate), formaldehyde (37
% Water solution) in 10 liters of water and pH 12.4 with 1 mol / l sodium hydroxide solution.
Then, 10 liters of the copper plating solution was prepared and used. The concentration of each component in this copper plating solution is 2.5 g / l of copper,
Formaldehyde was 2.5 ml / l.

The copper plating reaction was carried out at 70 ° C., and an epoxy copper clad laminate was used as a sample to be plated. Two hours after the copper plating treatment, the concentration of each component of the copper plating solution was 2.2 g of copper /
1 and formaldehyde changed to 0.8 ml / l, and the pH dropped to 12.2. The composition of the copper plating solution was adjusted using 63 g / l copper sulfate solution (solution A), 37% formaldehyde solution (solution B), and 1 mol / l sodium hydroxide solution (solution C).

The copper concentration was adjusted by determining the required addition amount of solution A (copper sulfate solution) of 31.7 ml from FIG. 2 and adding it to the copper plating solution. Figure 3 shows the adjustment of formaldehyde concentration.
Amount of liquid B (formaldehyde solution) required from 25
ml was determined and added to the copper plating solution. To adjust the pH, add the required amount of solution B (copper sulfate solution) of 50 m from Fig. 1.
1 was determined and added to the copper plating solution.

As a result, the pH of the obtained copper plating solution was 1
Only 2.3, and the copper plating solution could not be properly adjusted. It was not possible to obtain a good plated product by using such a copper plating solution.

[0019]

During the electroless copper plating operation, a copper sulfate solution, a formaldehyde solution, and a sodium hydroxide solution are added in order to adjust the copper concentration, formaldehyde concentration, and pH, which are control items of the copper plating solution. In this case, addition of the formaldehyde solution lowers the pH of the copper plating solution.
The pH of the copper plating solution is accurately adjusted to a control value by adding the sodium hydroxide solution required for adjusting this pH decrease, determining the addition amount of the sodium hydroxide solution, and adding it to the copper plating solution. By using the copper plating solution properly managed in this way, it is possible to obtain a product to be plated of good quality.

[Brief description of drawings]

FIG. 1 is a graph showing a change in pH of a copper plating solution due to addition of a sodium hydroxide solution.

FIG. 2 is a graph showing changes in copper concentration in a copper plating solution due to addition of a copper sulfate solution.

FIG. 3 is a graph showing changes in formaldehyde concentration in a copper plating solution due to addition of a formaldehyde solution.

FIG. 4 is a graph showing a pH change of a copper plating solution due to addition of a formaldehyde solution.

Claims (2)

[Claims] 1. An electroless copper plating solution comprising a copper salt, a reducing agent and a pH adjusting agent, which is a pH adjusting agent necessary for adjusting the change in pH of the copper plating solution due to each component replenished and added during the copper plating operation. An electroless copper plating bath automatic management system characterized in that the additive amount is compositely calculated and determined. 2. The electroless copper plating bath automatic management system according to claim 1, wherein the copper salt is copper sulfate, the reducing agent is formaldehyde, and the pH adjusting agent is sodium hydroxide.