JPH0633251A - System for automatically controlling copper electroless-plating bath - Google Patents

Abstract

PURPOSE:To control the components of a copper plating soln. to the control limit with precision by setting the total amt. of the plating soln., detecting a decrease in the water content in the soln. due to vaporization and supplying water to make the total amt. of the soln. constant. CONSTITUTION:A specified amt. of the copper electroless-plating soln. consisting of the copper salt, reducing agent and pH regulator is filled in a plating tank, and the concns. of the components of the soln. are measured with time during operation. A requisite component is replenished, when the component is decreased below the preset control value. In this system for automatically controlling a plating bath, the decrease in water content of the plating soln. due to vaporization is detected by the level sensor provided in the plating tank. When the liq. level is lowered below a specified value, water is supplied, and the supply of water is stopped when the liq. level is raised to the specified level.

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 precisely manages each component of a copper plating solution during a copper plating operation. The present invention relates to an electroless copper plating bath automatic management system which detects a decrease in water content from a copper plating solution and supplies water as needed so that the total amount of the copper plating solution is always constant.

[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, a copper concentration, a reducing agent concentration, and a pH value are measured with time, and a preset control limit value is set. If it is lower, the copper plating operation is continued while adding the replenisher to adjust the concentration of each component to the control limit value.

[0004]

However, in the control of this type of electroless copper plating bath, when the necessary component concentrations of the copper plating solution are analyzed and these concentrations fall below a preset control value. In addition, the state of the copper plating solution must be kept constant by adding a replenishing solution. Therefore, in this case, the addition amount of the replenishing liquid is determined based on the control value and the total amount of the liquid set in advance in the plating liquid management device. However, in the electroless copper plating operation, high temperature (about 70
Since it is carried out for a long time at (° C.), water is evaporated from the copper plating solution, and the total amount of the solution in the plating solution tank is reduced. Therefore, in this case, there is a difference between the total amount of the actual liquid in the plating bath and the total amount of the preset liquid, and the actual component concentration when the replenisher is added is the preset control value. It may slip off.

Therefore, an object of the present invention is to detect a change in water content from the copper plating solution due to evaporation during the electroless plating operation so that the total amount of the copper plating solution in the plating solution tank is always constant. An object of the present invention is to provide an automatic electroless copper plating bath management system capable of supplying water as needed and adjusting the components of a copper plating solution to control limits with high accuracy.

[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 electroless copper plating bath configured to analyze the component concentrations of the copper plating solution in the plating solution tank and supplement the necessary components when each component falls below a preset control value. In the automatic management system, the total amount of the copper plating solution in the plating solution tank is set, and a decrease change in water content from the copper plating solution due to evaporation is detected, and the total amount of the copper plating solution in the plating solution tank is always constant. It is characterized by supplying water as needed.

In the above electroless copper plating bath automatic management system, when the change in water content from the copper plating solution due to evaporation in the plating solution tank changes, a level sensor for detecting the liquid level is provided in the plating solution tank, It can be set so that water is supplied when the surface reaches a certain level or lower, and water supply is stopped when the liquid level reaches a certain level.

Further, the decrease in water content from the copper plating solution due to evaporation in the plating solution tank is provided with a temperature sensor for detecting the solution temperature in the plating solution tank. It is possible to calculate the amount of evaporation of water and set the supply of water in proportion to the amount of evaporation of water.

Further, due to the decrease in water content from the copper plating solution due to evaporation in the plating solution tank, a vapor pressure sensor for detecting the water vapor pressure is provided above the copper plating solution surface of the plating solution tank to allow natural evaporation of water. The amount can be calculated and the water can be set to be supplied in proportion to the natural evaporation amount of the water.

[0010]

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 necessary for adjusting the concentration of each component to the control limit value is determined, and the copper plating liquid is replenished and added to adjust the copper plating liquid.

Therefore, during the copper plating operation, a decrease in water content from the copper plating solution due to evaporation in the plating solution tank is detected, and an amount of water corresponding to this decrease is supplied at any time so that the amount of water in the plating solution tank is increased. By keeping the total amount of the copper plating solution constant, the components of the copper plating solution can be adjusted to the control limit values 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.

[0012]

EXAMPLE Next, an example of the electroless copper plating bath automatic control system according to the present invention will be described.

A plating solution tank is filled with a predetermined amount of copper plating solution set in advance. In this case, as the copper plating solution, a solution obtained by dissolving copper sulfate (pentahydrate) and formaldehyde (as a 37% aqueous solution) in water and adjusting this to a predetermined pH with a sodium hydroxide solution is used. Therefore, when electroless copper plating is performed in this plating solution tank, the temperature of the copper plating solution during the plating reaction becomes about 70 ° C. Therefore, water is evaporated from the copper plating solution, and the total amount of copper plating solution in the plating solution tank is reduced.

Therefore, as a first embodiment of the present invention,
A level sensor for detecting the liquid surface level is provided in the plating solution tank, and water is supplied to the plating solution tank when the liquid level falls below a certain level. Then, when the liquid level reaches a certain level, the supply of water is immediately stopped. In this way, the total amount of the copper plating solution in the plating solution tank is set in advance, the decrease change of the water content from the copper plating solution due to evaporation is properly detected, and the total amount of the copper plating solution in the plating solution tank is always Water can be supplied at any time so as to be constant, and the components of the copper plating solution can be accurately adjusted to control limits.

In a second embodiment of the present invention, a temperature sensor is provided in the plating solution tank to detect the change in water content from the copper plating solution due to evaporation in the plating solution tank. The evaporation amount of water is calculated from the relationship between the temperature and the evaporation rate of water, and the water is supplied in proportion to the evaporation amount of water. Even by configuring as described above, the decrease change of water content from the copper plating solution due to evaporation is properly detected, and water is supplied at any time so that the total amount of the copper plating solution in the plating solution tank is always constant, It is possible to accurately adjust the components of the copper plating solution to control limits.

Furthermore, as a third embodiment of the present invention,
The decrease change of water content from the copper plating solution due to evaporation in the plating solution tank is provided with a vapor pressure sensor that detects the water vapor pressure above the copper plating solution surface of the plating solution tank to calculate the natural evaporation amount of water, The water is supplied in proportion to the natural evaporation amount of the water. Even by configuring as described above, the decrease change of water content from the copper plating solution due to evaporation is properly detected, and water is supplied at any time so that the total amount of the copper plating solution in the plating solution tank is always constant, It is possible to accurately adjust the components of the copper plating solution to control limits.

[0017]

As described above, according to the present invention, a decrease in water content from the copper plating solution due to evaporation in the plating solution tank is detected, and an amount of water corresponding to this decrease is supplied at any time, By keeping the total amount of the copper plating solution in the plating solution tank always constant, the components of the copper plating solution can be accurately adjusted to the control limit values. By using the copper plating solution properly managed in this way, it is possible to obtain a product to be plated of good quality.

Claims (4)

[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 adjuster, and the component concentrations of the copper plating solution in the plating solution tank are analyzed. However, in the electroless copper plating bath automatic management system configured to replenish necessary components when each component falls below the preset control value, set the total amount of copper plating liquid in the plating bath. However, the change in water content from the copper plating solution due to evaporation is detected, and the electroless copper plating bath automatic is characterized by supplying water as needed so that the total amount of the copper plating solution in the plating solution tank is always constant. Management system. 2. The decrease in water content from the copper plating solution due to evaporation in the plating solution tank is provided when a level sensor for detecting the liquid level is provided in the plating solution tank and the liquid level is below a certain level. The electroless copper plating bath automatic management system according to claim 1, wherein water is supplied, and when the liquid level reaches a certain level, the supply of water is stopped. 3. A decrease in water content from the copper plating solution due to evaporation in the plating solution tank is provided with a temperature sensor for detecting the solution temperature in the plating solution tank. 2. The automatic management system for electroless copper plating bath according to claim 1, wherein the amount of evaporation of the water is calculated and the water is supplied in proportion to the amount of evaporation of the water. 4. A vapor pressure sensor for detecting the water vapor pressure is provided above the copper plating liquid surface of the plating liquid tank for the change in the decrease of water content from the copper plating liquid due to evaporation in the plating liquid tank.
The automatic management system for electroless copper plating bath according to claim 1, wherein the natural evaporation amount of water is calculated and the water is supplied in proportion to the natural evaporation amount of water.