JPH09127052A - Quantitative determination method for secondary brightener in plating liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a quantitative determination method in which the concentration of a secondary brightener in plating liquid can be determined easily and precisely by applying a constant voltage in a state that a rotating electrode is at a standstill and in a state that the electrode is turned, measuring the precipitation speeds, and finding the ratio of the precipitation speeds in both states. SOLUTION: An Ni plating liquid which contains a secondary brightener as a test liquid 2 is put into a testing tank 1, and the ratio of a precipitation speed in a state that a rotating electrode 3 is at a standstill to a precipitation speed in a state that the electrode 3 is turned is found. The contact frequency of the secondary brightener with the electrode 3 is higher during its rotation than at its standstill, the precipitation obstruction action of the secondary brightener acts on the turning electrode 3 more according to its concentration, and the precipitation speed is lowered. Since the ratio of its reduction is proportional to the concentration of the secondary brightener, the concentration of the secondary brightener can be found on the basis of the ratio of the precipitation speed at the standstill of the electrode to that in its rotation. When the secondary brightener in a proper quantity is replenished on the basis of a concentration value determined in this manner, a good plating treatment can be executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for quantifying a secondary brightening agent in a plating solution, and more particularly to a simple tester for the concentration of the secondary brightening agent in a metal plating solution, which has hitherto been impossible to carry out a quantitative analysis. The method of easily and accurately quantifying by an electrochemical measuring means.

[0002]

2. Description of the Related Art Generally, metal plating liquids such as nickel are
The following main components and additives are contained, and each plays the following role.

[0003]

[Table 1]

By the way, in the plating process, the plating bath composition in the plating bath is appropriately supplemented with a component corresponding to the component lost in the plating process so that the plating bath composition is always kept uniform. Is done.

Therefore, it is necessary to accurately determine the concentrations of the constituent components in the plating bath in order to appropriately replenish the deficiency component to the plating bath.

[0006]

However, among the above components of the plating solution, the main component and the primary brightening agent can be obtained by chemical analysis or instrumental analysis of their concentrations in the plating solution. No suitable analysis method has been proposed for the component (1), and in general, the appearance of the plating surface obtained by the plating treatment is visually judged.

[0007] In particular, the secondary brightener is an important component responsible for the leveling function of forming a uniform plating surface according to the unevenness of the surface to be plated, but conventionally, it has to be accurately quantified by chemical analysis or instrumental analysis. However, the plating is performed using a Hull cell plate, and the concentration is estimated from the glossiness of the formed plating film and the leveling effect.

It is an object of the present invention to solve the above conventional problems and provide a method for easily and accurately quantifying the concentration of the secondary brightening agent in the metal plating solution.

[0009]

2 in the plating solution of the present invention
The method for quantifying the secondary brightener is to quantify the secondary brightener in the plating solution using a test device in which a fixed electrode and a rotating electrode are arranged in a test tank and a power source for applying a voltage between both electrodes is used. In the method, a plating solution is placed in the test tank, a predetermined voltage is applied to the rotary electrode in a stationary state to measure a deposition rate, and a predetermined voltage is applied to the rotary electrode in a rotated state. The deposition rate was measured, and the ratio of the deposition rate when the rotating electrode was stationary and when it was rotating was calculated.
It is characterized in that the next brightener concentration is obtained.

The action mechanism of the leveling effect of the secondary brightening agent is microscopically based on the fact that the metal deposition rate at the concave portion of the surface to be plated is increased and, conversely, the metal deposition rate at the convex portion is decreased. As a result, the plating film thickness of the concave portion is increased and the plating film thickness of the convex portion is decreased to form a smooth plating film surface having no irregularities.

That is, the secondary brightening agent adjusts the above-mentioned deposition rate because the secondary brightening agent has a high contact frequency with the projecting protrusions on the plated surface and a low contact frequency with the recessed portions. Its direct function is to prevent deposition on the contact surface.

In the present invention, the ratio of the deposition rate when the rotary electrode is stationary and the deposition rate when the rotary electrode is rotated is determined by utilizing the characteristics of the secondary brightener. That is, the contact frequency of the secondary brightener with the rotating electrode is higher during rotation than during rest. Therefore, the rotating electrode in rotation is more effective in inhibiting the deposition of the secondary brightening agent than the stationary rotating electrode, depending on its concentration, and the deposition rate is low.

Since the reduction rate of the deposition rate of the rotating rotary electrode relative to the deposition rate of the stationary rotating electrode is proportional to the concentration of the secondary brightener, the deposition rate of the rotating electrode at rest and during rotation is The secondary brightener concentration can be determined from the ratio.

In the method of the present invention, specifically, first, a voltage is applied at a constant speed so that the metal is deposited on the rotary electrode, and then the voltage is reversed to deposit the metal deposited on the rotary electrode in the liquid. A voltage is applied at a constant speed so as to dissolve, and the amount of electricity A after this voltage reversal is obtained.
₀ and calculates the ratio A _n / A ₀ of the electric quantity A _n when rotating at a rotation speed n, a secondary brightening agent concentration in the plating solution on the basis of the ratio A _n / A ₀ It is preferable to ask.

The term "constant speed" means a change in voltage per unit time, and in the present invention, about 20 mV / sec is suitable.

Further, a calibration curve showing the correspondence relationship between the secondary brightener concentration and the ratio A _n / A ₀ is obtained in advance by conducting a test using a plating solution having a known secondary brightener concentration.
Next the ratio A _n measured for plating solutions of unknown brightener concentration
By applying / A ₀ to the calibration curve to obtain the secondary brightener concentration, efficient quantification can be performed.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing a test apparatus suitable for carrying out the present invention, FIG. 2 shows a rotary electrode used in the test apparatus of FIG. 1, and FIG. 2 (b) is a bottom view.

In the test apparatus of this embodiment, the rotary electrode 3 is suspended from above so that the tip is immersed in the test solution 2 in the test tank 1, while the fixed electrode 4 made of a platinum electrode wire is It is inserted from the side part of the test tank 1 and arranged on the bottom surface portion of the test tank 1. A power source 5 applies a voltage between both electrodes, and is connected to the rotating electrode 3 and the fixed electrode 4. Reference numeral 6 is a reference electrode (SCE), and 7 is a recorder.

As shown in FIG. 2, the rotary electrode 3 has a structure in which a platinum electrode 3B is attached to the tip of a stainless rod 3A and is covered with an acrylic resin 3C. As the platinum electrode 3B, a disk-shaped electrode having a diameter of 5 mm and a height of 2 mm was used.

The platinum electrode wire used as the fixed electrode 4 had a diameter of 2 mm and a length of 100 cm.

A Ni plating solution containing a secondary brightening agent was charged as a test solution 2 into the test tank 1 of this test apparatus, and the rotating electrode 3
In a stationary state (0 rpm) or a rotating state (3000 rpm in this embodiment), first, -0.1 V (vs. SC) is applied.
20) mV / sec from E) to -1.3V (vs. SCE)
When polarized to the cathode side at a constant velocity, Ni is deposited on the surface of the rotating electrode 3. Next, 20 mV / se to the anode side
When polarized at a constant speed of c, -0.3 to + 1.2V
During (to SCE), the Ni deposited on the rotating electrode 3 is dissolved. At this time, -0.8 to -1.3V (vs. SC
In the range of E), precipitation of Ni and generation of hydrogen occur in the rotating electrode 3, and conversely, -0.3 to +1.2 V (vs. SC).
In E), since dissolution of Ni occurs, −0.8 to −
The amount of Ni deposited in the range of 1.3 V (vs. SCE) is the amount of N dissolved in the range of -0.3 to +1.2 V (vs. SCE).
i equals the amount.

When the rotating electrode 3 is polarized on the cathode side to −0.1 to −1.3 V (against SCE), the voltage is inverted and then polarized on the anode side. As shown in FIG. In FIG. 3, the solid line indicates when the rotating electrode is stationary, and the broken line indicates when the rotating electrode is rotating.

-0.3 to +1.2 V in FIG. 3 (vs. SCE)
The change in the current density in the range of 1 indicates the state of dissolution of Ni deposited on the rotating electrode 3, which is proportional to the amount of deposition on the rotating electrode 3, that is, the deposition rate. Rotating electrode 3
When the is rotating, the peak of the current density curve is small because the deposition rate is low due to the deposition inhibition by the secondary brightening agent as described above. On the other hand, when the rotating electrode 3 is stationary, the effect of inhibiting the deposition of the secondary brightening agent is small, so that the deposition rate is relatively high and the peak of the current density curve is large.

Therefore, the amount of electricity flowing through this portion A (rotational speed n
The amount of electricity when the rotating electrode is rotated at (= 3000) rpm is A _n (= A ₃₀₀₀ ), and the amount of electricity when the rotating electrode is stationary is A _0.
And ) And calculating A _n / A ₀ ,
The ratio of the deposition rate when the rotating electrode is stationary and when it is rotating can be obtained.

In the following, A _n / A ₀ is referred to as a relative precipitation rate ratio.

The relationship between the secondary brightener concentration and the relative deposition rate ratio A _n / A ₀ was determined by the above test method.
As shown in FIG. 4, there was a linear proportional relationship.

Therefore, a calibration curve showing the correspondence relationship between the secondary brightener concentration and the relative deposition rate ratio A _n / A ₀ is obtained in advance by conducting a test using a plating solution having a known secondary brightener concentration. By applying the relative deposition rate ratio A _n / A ₀ measured for the plating solution of which the secondary brightener concentration is unknown to the calibration curve, the secondary brightener concentration can be easily obtained.

In the present invention, if the rotation speed of the rotary electrode is too small, the relative deposition rate ratio with respect to the secondary brightener concentration does not significantly change. Therefore, the rotation speed of the rotary electrode is 2000 to 4000 rpm, particularly 2800-3200
It is preferably set to rpm. In addition, this rotation speed is 400
If it exceeds 0 rpm, a turbulent flow will occur around the electrodes, and the measurement accuracy may decline.

Further, although the Ni plating solution has been described in the above embodiment, the present invention is not limited to the Ni plating solution, and Pb,
It is also effective for quantifying the secondary brightening agent in other metal plating solutions such as Sn.

[0031]

As described above in detail, according to the method of quantifying the secondary brightening agent in the plating solution of the present invention, the concentration of the secondary brightening agent in the metal plating solution, which has been conventionally impossible to quantitatively analyze. Can be quantified easily and accurately. Therefore, by supplying an appropriate amount of secondary brightening agent based on the quantified value of the secondary brightening agent, the plating bath composition can be easily maintained as one unit, and a good plating treatment can be performed with a uniform plating bath. It can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of a test apparatus suitable for implementing the present invention.

2 (a) is a front view of a rotary electrode of the test apparatus of FIG. 1, and FIG. 2 (b) is a bottom view of the same.

FIG. 3 is a graph showing the relationship between potential and current density.

FIG. 4 is a graph showing the relationship between the secondary brightener concentration and the relative deposition rate ratio.

[Explanation of symbols]

 1 test tank 2 test solution 3 rotating electrode 4 fixed electrode 5 power supply 6 reference electrode

Claims (3)

[Claims] 1. A method of quantifying a secondary brightening agent in a plating solution using a test device having a fixed electrode and a rotating electrode arranged in a test tank and having a power source for applying a voltage between both electrodes. Then, the plating solution is put into the test tank, a predetermined voltage is applied with the rotary electrode stationary, and the deposition rate is measured, and a predetermined voltage is applied with the rotary electrode rotated to measure the deposition rate. A method for quantifying the secondary brightening agent in the plating solution, which comprises measuring and determining the ratio of the deposition rate when the rotating electrode is stationary and when the rotating electrode is rotating, and then determining the concentration of the secondary brightening agent in the plating solution from this ratio. . 2. The method according to claim 1, wherein when a voltage is applied to the electrode in order to obtain a deposition rate, the voltage is first applied at a constant speed so that metal is deposited on the rotating electrode, and then the voltage is reversed to rotate. applying a deposited metal on the electrode voltage so as to dissolve in the liquid at a constant speed, it obtains the current air amount a after the voltage reversal, the electric quantity a ₀ during rotary electrode stationary, at a rotation speed n A plating solution characterized by calculating a ratio A _n / A ₀ with respect to the electricity amount A _n when rotated, and determining a secondary brightening agent concentration in the plating solution based on the ratio A _n / A _0. Method for quantifying secondary brighteners in products. 3. The calibration curve according to claim 1, which shows a correspondence relationship between the secondary brightener concentration and the ratio A _n / A ₀ by performing a test using a plating solution having a known secondary brightener concentration in advance. The secondary gloss in the plating solution is obtained by applying the ratio A _n / A ₀ measured for a plating solution having an unknown secondary brightener concentration to the calibration curve to obtain the secondary brightener concentration. Method for quantifying agents.