JPH10142144A - Metal ion concentration measuring method of nonelectrolytic plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable with high accuracy even in the case that the concentration of a plating solution is increased and that a transmittance is reduced by increasing the output of a light source and increasing the amount of projection light at the time when the transmittance is reduced in absorptiometry. SOLUTION: Light emitted from a light source 2 is transmitted through a flow cell 1 into which a nonelectrolytic plating solution is introduced. Transmitted light is received at a photosensor 3. The output of the phtosensor 3 is amplified at a preamplifier 6 and is inputted to a CPU 7. The output of a phtosensor 4 is also amplified at a preamplifier 8 and is inputted to the CPU 7. The CPU 7 operates a transmittance from the amount of projection light and the amount of transmitted light. When the concentration of the plating solution becomes high and the transmittance operated by the CPU 7 is reduced, a signal is sent from the CPU 7 to a light source electric power controller 5 to increase the electric power supplied to the light source 2 and to increase the amount of projection light. By this, as the absolute value of amount of transmitted light is increased, errors in absorbance are not increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a metal ion concentration of an electroless plating solution by an absorption photometry.

[0002]

2. Description of the Related Art In electroless plating such as electroless nickel plating, metal ions in a plating solution are precipitated as metal on a work surface by a catalytic reduction reaction of the work metal. Goes down gradually. Therefore, the plating solution is sampled and the metal ion concentration is measured by the absorption spectrophotometry, and the plating solution management is performed so that the amount of metal ions in the plating solution is always kept at a predetermined value.

[0003] The measurement of the metal ion concentration by the absorptiometry is such that the electroless plating solution is introduced into the inside of the flow cell 1 as shown in FIG. It is done in. The projection amount from the light source 2 and L _0, when the quantity of transmitted light measured by the photosensor 3 and the L _1, refers to t = L ₁ / L ₀ and transmittance, E = log (1 / t ) and the absorbance That. In this case, since the absorbance E is generally directly proportional to the metal ion concentration, the metal ion concentration in the electroless plating solution can be determined from the absorbance E.

Conventionally, as shown in FIG. 3, the light source power controller 5 as a photosensor 4 placed in the vicinity of the light source 2 by detecting the projection amount L ₀ at all times the projection amount L ₀ is constant
Control the electric power applied to the light source 2. Therefore that controls the projection amount L ₀ constant as, CPU 7 may be calculated transmittance t based on only the output of the photo sensor 3 is amplified by the preamplifier 6. However, since the absolute value of the amount of transmitted light L ₁ and the plating solution concentration is high becomes transmittance decreases decreases, the output of the photo sensor 3 becomes small. Therefore, there is a problem that the error in the value of the absorbance E calculated as E = log (1 / t) becomes larger than when the plating solution concentration is low.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned conventional problems. Even when the plating solution concentration is increased and the transmittance is lowered, the metal ions are as accurately as when the plating solution concentration is low. The purpose of the present invention is to provide a method for measuring the metal ion concentration of an electroless plating solution capable of measuring the concentration.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. In measuring the metal ion concentration of an electroless plating solution by an absorption spectrophotometry, the output of a light source when the transmittance is reduced is measured. , And the measurement is performed by increasing the amount of projected light. Hereinafter, preferred embodiments of the present invention will be described.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 is a view showing a first embodiment of the present invention. Similar to the conventional example, 1 is a flow cell into which an electroless plating solution is led, 2 is a light source such as an LED, and 3 is a transparent cell. A photosensor 4 for receiving light is a photosensor arranged near the light source 2, and 5 is a light source power controller. The output of the photo sensor 3 is amplified by a preamplifier 6 and then CP
The output of the photosensor 4 is also input to the CPU 7 after being amplified by the preamplifier 8. CP
U7 calculates the transmittance t and projection amount L ₀ from the amount of transmitted light L ₁ by the formula t = L ₁ / L _0.

[0008] When the plating solution concentration and increases the transmittance decreases the amount of transmitted light L ₁ as described is but decreases, the transmittance t of CPU7 is calculated in the present invention is decreased, CP
It sends a signal to the light source power controller 5 from U7, increasing the projection amount L ₀ increases the power supplied to the light source 2. Therefore, the absolute value of the amount of transmitted light L ₁ even when the transmittance is decreased to increase, not an error of the conventional way absorbance E is increased as compared to the case of a low plating solution concentration.

[Second Embodiment] FIG. 2 is a view showing a second embodiment of the present invention. In this embodiment, the output A of the photosensor 3 for receiving the transmitted light of the flow cell 1, the electroless plating solution is introduced, the output B and the comparator 9 of the photosensor 4 for detecting a projection amount L ₀ from the light source 2 And the high-order selection switch 10 selects the larger signal. Then, a control signal is sent to the light source power controller 5 so that the selected signal is kept constant, and the output of the light source 2 is controlled.

In this embodiment, the output A of the photo sensor 3 is less than the steady maximum metal ion concentration in actual use.
Is designed to be larger than the output B of the photosensor 4 and close to the maximum output. In the case where it is equal to or less than the highest metal ion at the time of actual use, as in the first embodiment,
Since the light source power controller 5 controls the amount of light emitted from the light source 2 so that the output A of the photosensor 3 that receives the transmitted light is constant, the measurement error of the absorbance can be reduced. The metal ion concentration becomes more than the highest concentration of normal, select the high-level selection switch 10 is output B if the output A of the photosensor 3 and the output B of the photo sensor 4 increases, and detects the projection amount L ₀ from the light source 2 The output of the light source 2 is controlled so that the output B of the photo sensor 4 becomes constant. As a result, the output B of the photo sensor 4 does not saturate, so that the dynamic range of the measurement circuit can be effectively used, and the measurement accuracy in actual use can be improved.

[0011]

As described above, according to the present invention, when the transmittance of the electroless plating solution is reduced, the output of the light source is increased, and the measurement is performed by increasing the amount of projected light.
There is an advantage that the measurement accuracy can be prevented from lowering due to a decrease in the amount of transmitted light, and the metal ion concentration can be measured with stable accuracy regardless of a change in the concentration of the electroless plating solution.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment.

FIG. 2 is a block diagram showing a second embodiment.

FIG. 3 is a block diagram showing a conventional method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Flow cell to which electroless plating solution is led 2 Light source 3 Photosensor which receives transmitted light 4 Photosensor which detects emitted light amount L ₀ 5 Light source power controller 6 Preamplifier 7 CPU 8 Preamplifier 9 Comparator 10 High-order selection switch

Claims (1)

[Claims] 1. A method of measuring a metal ion concentration of an electroless plating solution by an absorptiometric method, wherein the output of a light source is increased when the transmittance is reduced and the amount of projected light is increased to perform the measurement. Method for measuring metal ion concentration of electrolytic plating solution.