JPH0633250A - System for automatically controlling copper electroless-plating bath - Google Patents

Abstract

PURPOSE:To form a high-quality copper plating film and to prolong the service life of a plating soln. by increasing the plating soln. component concn. at the start of plating in the Cu electroless plating and then controlling the component concn. to a preset value. CONSTITUTION:CuSO4 is used as a Cu salt, formaldehyde as the reducing agent for Cu ion and NaOH as the pH regulator in the Cu electroless-plating solution to plate a material with copper. In this case, the concns. of the Cu salt, reducing agent, pH regulator, etc., are increased at the start of plating, and then gradually decreased to the preset values according to the decrease of each component concentration. Consequently, a defective Cu plating film due to the abnormal deposition of Cu is not formed, and the service life of the plating soln. is prolonged since the plating soln. is not decomposed.

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, and in particular, to obtain a product of good quality by changing the concentration of each component in a copper plating solution during a copper plating reaction. The present invention relates to an electroless copper plating bath automatic management system capable of performing.

[0002]

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

Conventionally, the control of the electroless copper plating solution is an item necessary for the control of the copper plating solution. For example, the copper concentration, the reducing agent concentration, and the pH value are measured with time, and the control values are set in advance. When the temperature becomes low, the copper plating reaction is continued while adding the replenishing solution and adjusting the concentration of each component to the control value. Normal,
The preset control value of each component concentration is not changed from the start to the end of the copper plating reaction.

[0004]

Generally, in order to start the copper plating reaction, a highly reactive copper plating solution having a high concentration of each component is required. On the other hand, the concentration of the copper plating solution required to constantly maintain the copper plating reaction is usually lower than the concentration at the start of the copper plating reaction. If the copper plating reaction is continued while the concentration of each component in the copper plating solution remains high at the start of the reaction, decomposition and abnormal deposition of the copper plating solution will occur.

It is an object of the present invention to provide an automatic management system that promptly starts a copper plating reaction and does not cause decomposition or abnormal deposition of a copper plating solution during the copper plating reaction.

[0006]

The electroless copper plating bath automatic management system according to the present invention is a plating solution tank filled with a predetermined amount of an electroless copper plating solution consisting of a copper salt, a reducing agent and a pH adjusting agent, An automatic electroless copper plating bath configured to analyze the component concentrations of the copper plating solution in the plating solution tank and replenish the necessary components when each component falls below a preset control value. In the control system, the control value of each component concentration is set high at the start of the copper plating reaction,
After the copper plating reaction is started, the control value of each component concentration is changed to a preset value.

In the above electroless copper plating bath automatic control system, preferably, the copper salt is a copper sulfate solution, the reducing agent is a formaldehyde solution, and the pH adjusting agent is a sodium hydroxide solution.

[0008]

[Function] The control items of the copper plating solution are copper concentration, formaldehyde concentration, and pH value. Liquid management of the copper plating solution is to measure each component concentration over time during the copper plating reaction, and when the concentration becomes lower than the preset control value, add a replenishing solution to keep the copper plating solution in a constant state. To hold in.

With respect to the control value of each component concentration, a copper plating solution having a high concentration of each component is used to start the copper plating reaction. This promptly starts the copper plating reaction. After the copper plating reaction starts,
The copper plating reaction is continued by switching to the preset control value of each component concentration to obtain a copper plated product. This method can prevent the occurrence of abnormal deposition and decomposition during the copper plating reaction. As a result, the copper-plated product has good quality, and the copper-plating solution can be used with a long life.

[0010]

EXAMPLES Examples of the electroless copper plating bath automatic control system according to the present invention will be described below in detail with reference to the accompanying drawings.

Example 100 g of copper sulfate (pentahydrate), formaldehyde (37
% Water solution) in 10 liters of water and pH 12.6 with 1 mol / l sodium hydroxide solution.
Then, 10 liters of the copper plating solution was prepared and used. The concentration of each component of this copper plating solution was as follows: copper: 2.6 g / liter, formaldehyde: 0.04 mol / liter,
The pH was 12.6.

The copper plating reaction was carried out at 70 ° C., and an epoxy copper clad laminate was used as a sample to be plated.

As the copper plating reaction proceeded, the copper concentration decreased and approached the lower limit of the control value as shown in FIG. 63 g
/ L copper sulphate solution was replenished and added to raise the copper concentration to the upper limit of the control value. The copper plating reaction starts quickly,
After that, the control value was changed to a lower value as shown in Fig. 1, and copper:
The amount was 2.4 g / liter, formaldehyde was 0.027 mol / liter, and pH was 12.4. Then, the above copper sulfate solution was replenished repeatedly to continue the copper plating reaction while keeping the copper concentration within the control limit range.

During this time, copper deposition proceeded normally, and no abnormal decomposition of the copper plating solution was observed. As a result, the obtained copper plated body had a good copper plating film. Also,
The copper plating solution could be used for a relatively long period of time.

Comparative Example 100 g of copper sulfate (pentahydrate), formaldehyde (37
% Water solution) in 10 liters of water and pH 12.6 with 1 mol / l sodium hydroxide solution.
Then, 10 liters of the copper plating solution was prepared and used. The concentration of each component of this copper plating solution was as follows: copper: 2.6 g / liter, formaldehyde: 0.04 mol / liter,
The pH was 12.6.

The copper plating reaction was carried out at 70 ° C., and an epoxy copper clad laminate was used as a sample to be plated.

As the copper plating reaction progressed, the copper concentration decreased as shown in FIG. 2 and approached the lower limit of the control value. 63 g
/ L copper sulphate solution was replenished and added to raise the copper concentration to the upper limit of the control value. The copper plating reaction started quickly. After that, replenishment of the copper sulfate solution was repeated without changing the control value, and the copper plating reaction was continued while keeping the copper concentration within the control limit range.

During this time, abnormal precipitation of copper occurred and decomposition of the copper plating solution was also observed. As a result, the obtained copper-plated body had a poor copper-plated coating. In addition, the life of the copper plating solution was short.

[0019]

As described above, according to the present invention, the control value of each component concentration is set to a high value at the start of the copper plating reaction, and the control value is changed to a low value after the copper plating reaction starts. Therefore, the decomposition and abnormal deposition of the copper plating solution could be prevented. As a result, the quality of the copper-plated product was ensured and the life of the copper-plating solution was extended.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a copper concentration control state of a copper plating solution by an electroless copper plating bath automatic control system according to the present invention.

FIG. 2 is an explanatory view showing a comparative example of a copper concentration control state of a copper plating solution by a conventional electroless copper plating bath automatic control system.

Claims (2)

[Claims] 1. A plating solution tank is filled with a predetermined amount of an electroless copper plating solution comprising a copper salt, a reducing agent, and a pH adjusting agent, and the component concentrations of the copper plating solution in the plating solution tank are analyzed. However, in the automatic electroless copper plating bath management system configured to replenish necessary components when each component falls below the preset control value, the control value of each component concentration is set at the start of the copper plating reaction. After the copper plating reaction is set to a high value, the automatic control system for electroless copper plating bath is characterized in that the control value of each component concentration is changed to a preset value. 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 adjuster is sodium hydroxide.