Fluid handling – Processes – With control of flow by a condition or characteristic of a...
Patent
1993-12-16
1995-09-19
Hepperle, Stephen M.
Fluid handling
Processes
With control of flow by a condition or characteristic of a...
137 93, G05D 1108
Patent
active
054508703
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for detecting concentration of a chemical treating solution used for chemical treatment such as plating and etching, by which concentration of the predetermined component contained in the chemical treating solution can be detected, and to an automatic control apparatus of the chemical treating solution, by which concentration of the predetermined component in the chemical treating solution can be controlled to the command concentration according to the detected result by the concentration detecting apparatus.
BACKGROUND OF THE INVENTION
As the apparatus for automatic control of the concentration of a chemical treating solution, there has been known an apparatus which analyzes the concentration of the predetermined component consumable by the chemical treatment in a chemical treating solution and, when the concentration is detected to be lower than the command concentration based on the analyzed result, automatically supplies a replenisher in a required amount in order to restore the concentration to the predetermined concentration. Another apparatus has also been known which not only computes or calculates the consumed amount per unit time of a component in a chemical treating solution on the basis of the surface area of material to be chemically treated to supply the loss of the component, but also analyzes the component in the chemical treating solution continuously to control the supply amount of the component based on the degree of the concentration (Japanese Patent Application Laid-open No. 199069/1986).
In the former apparatus described above, however, the replenisher to be supplied is added in a required amount after sampling the chemical treating solution, analyzing the concentration of the predetermined component in the chemical treating solution, and further detecting that the concentration has become lower than the predetermined concentration from the analyzed result. Therefore, a time lag from sampling of the chemical treating solution to addition of the replenisher occurs, which is a problem of the apparatus.
That is, for example, in case where electroless copper plating is carried out as a chemical treatment, sodium hydroxide and formalin as a reducing agent in a plating solution as a chemical treating solution reduce copper ion into metal copper to deposit copper plating. As a result, the concentrations of the three components decrease gradually while progressing with the plating reaction. Accordingly, in the above former apparatus, each concentration of the three components is analyzed independently and then loss of each component is supplied based on the analyzed result in electroless copper plating. In this case, if the concentration analysis of each component is carried out by a conventional analytical method in which the concentration of sodium hydroxide is firstly determined by titration, next the copper concentration is determined by absorption spectroscopy, and finally the formalin concentration is determined by titration, it would take as much as 15 to 30 minutes for the analysis. Therefore, the time lag over 15 to 30 minutes would occur in the period from sampling of a plating solution as a chemical treating solution to addition of the replenisher.
Therefore, in the above former apparatus, the analyzed result and the actual concentration at the replenisher-adding point of time are sometimes different largely from each other, which results in a problem that the concentration of the predetermined component in the chemical treating solution can not be accurately controlled to the command concentration by addition of replenisher. Such a problem might cause a serious disturbance on the precise control of concentration of the chemical treating solution to within a narrow range as possible and on the uniformity of physical properties of a plated film formed on material to be treated by the chemical treatment and treating rate. On the other hand, the above latter apparatus is one which calculates the cons
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Ishida Nobumasa
Kojima Fumio
Kondo Koji
Niwa Masashi
Suga Makoto
Hepperle Stephen M.
Nippondenso Co. Ltd.
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