JP5242542B2 - Metal concentration measuring method and metal concentration automatic management device - Google Patents

Description

  The present invention relates to a method for measuring a metal concentration of a plating solution using an absorptiometric method and an automatic metal concentration management apparatus.

  A metal layer forming technique such as a printed circuit board or a semiconductor wafer using an electrolytic plating method or an electroless plating method has been used for a long time. The absorptiometry is used as a method for measuring the metal concentration in the plating solution in each of the methods described above, and automatic management is performed from the measurement results so as to keep the metal concentration (component concentration) in the plating solution constant. Yes.

  In recent years, electrolytic plating and electroless plating have been used in a wider range of applications. However, as semiconductor wafers become smaller and semiconductor packages become smaller and denser, metal layer films In order to reduce the thickness variation, it is necessary to perform the plating process with higher accuracy. In order to perform high-precision plating, it is very important to control the component concentration, pH, and solution temperature in the plating solution.

  Many methods for measuring the metal concentration in the plating solution using the absorptiometry have been proposed. As an example, Patent Document 1 discloses a method for measuring the nickel concentration of an electroless nickel plating solution that accurately measures the nickel concentration by absorptiometry even when the number of turns proceeds.

  Moreover, in patent document 2, in the technique which analyzes Ni density | concentration in an electroless composite nickel plating solution, it solves the problem that analysis accuracy falls due to the presence of suspended particles, and it is inexpensive to ensure practically sufficient analysis accuracy. An automatic analysis / management apparatus for an electroless composite plating solution is disclosed.

  Furthermore, Patent Document 3 discloses a method for measuring the sulfuric acid concentration in a plating solution, which can be measured with a simple operation.

Japanese Patent Laid-Open No. 10-142143 (published May 29, 1998) JP 2002-47575 A (February 15, 2002) JP 2003-4726 A (January 8, 2003)

  However, the nickel concentration measurement method disclosed in Patent Document 1 does not consider the influence of the component concentration change of the plating solution. For this reason, when a change in the additive concentration occurs, the absorbance value used when calculating the metal concentration is affected, and the error in the measured value of the metal concentration increases. Therefore, the variation in the metal concentration in the plating solution is increased, and as a result, the variation in the metal layer thickness is increased.

  FIG. 7 is a graph summarizing absorbance data obtained with a plating solution in which the nickel concentration is changed in a commercially available electroless nickel plating solution. FIG. 8 is a graph summarizing the absorbance data obtained with a plating solution with a different additive concentration in a commercially available electroless nickel plating solution.

  In Patent Document 1, a continuous spectrum light source having a wavelength in the range of 600 nm to 800 nm is used. However, as shown in FIGS. 7 and 8, it can be seen that the absorbance within the above range is greatly influenced by the nickel concentration and the additive concentration. Therefore, in the plating process, if the processing area or processing amount of the object to be plated changes, or if the additive concentration changes due to removal of the plating solution or changes over time, it becomes a cause of variation in nickel concentration measurement. .

  The invention of Patent Document 2 is an invention limited to automatic analysis and management of electroless composite nickel plating solution, and selects a wavelength range of 250 to 350 nm or 450 to 550 nm as one measurement wavelength. In this invention, 350 to 450 nm or 550 to 800 nm are selected as other measurement wavelengths that do not overlap with each other.

  Furthermore, what is measured in Patent Document 3 is not the metal concentration but the sulfuric acid concentration.

  The present invention has been made in view of the above-mentioned conventional problems, and the object thereof is to obtain a metal concentration measuring method capable of obtaining an accurate metal concentration and improving the uniformity of the height of the plating film. And providing a metal concentration automatic management device.

  The metal concentration measuring method of the present invention is a metal concentration measuring method for measuring a metal concentration in a plating solution immediately and continuously using an absorptiometric method in order to solve the above-mentioned problem. Filling the cell, irradiating the cell with light of the first wavelength from the light source, receiving the light transmitted through the cell with a light receiver to obtain a first absorbance, and second light from the light source. The step of irradiating the cell with light having a wavelength and receiving the light transmitted through the cell with the light receiver to obtain the second absorbance, and the first absorbance and the second absorbance, A step of obtaining a ratio, a step of obtaining an additive concentration associated with the obtained absorbance ratio, using a first correlation in which the absorbance ratio and the additive concentration are associated; The first absorbance and the metal concentration determined for each additive concentration Obtaining the metal concentration associated with the first absorbance using the second correlation determined by the obtained additive concentration among the correlated second correlations; It is characterized by including.

  According to the invention, the absorbance ratio does not depend on the change in the metal concentration, and is correlated with the additive concentration.

  Therefore, using the first correlation, the additive concentration associated with the obtained absorbance ratio is obtained, and the second correlation determined by the obtained additive concentration is used. And obtaining the metal concentration associated with the first absorbance. Thereby, an accurate metal concentration can be obtained, and the height uniformity of the plating film can be improved. As a result, it is possible to stabilize the mounting quality.

  In the metal concentration measuring method, the plating solution may be an electroless nickel plating solution. Thereby, the nickel concentration can be accurately obtained as the metal concentration.

In the metal concentration measurement method, the first wavelength is in a range of 390 nanometers to 420 nanometers, or 660 nanometers to 690 nanometers,
The second wavelength may be in a range of 700 nm to 760 nm. Thereby, an accurate metal concentration in the plating solution can be measured.

  In the metal concentration measuring method, the light having the first wavelength and the light having the second wavelength may be light that is spectrally separated so that the half-value width is 1 nanometer or more and 50 nanometers or less. .

  As a result, two different absorbances (the first absorbance and the second absorbance) can be obtained, so that an accurate metal concentration in the plating solution can be measured.

  The metal concentration measuring method may include a step of obtaining the first correlation and the second correlation before the step of filling the cell with the plating solution.

  Thus, using the first correlation in which the absorbance ratio and the additive concentration are associated with each other, the step of obtaining the additive concentration associated with the obtained absorbance ratio, and the addition Among the second correlations determined for each agent concentration, in which the first absorbance and the metal concentration are associated with each other, using the second correlation determined by the obtained additive concentration, The step of obtaining the metal concentration associated with the first absorbance can be performed.

  In order to solve the above problems, the metal concentration automatic management device of the present invention is a metal concentration automatic management device that measures the metal concentration of a plating solution in a plating tank and keeps the metal concentration constant. A cell filled with the plating solution sucked from, a light source that emits light having a first wavelength and light having a second wavelength to the cell, and a light receiver that receives light transmitted through the cell. An absorbance measurement unit for obtaining a first absorbance and a second absorbance, and an absorbance ratio for obtaining a ratio of absorbances obtained from the first absorbance and the second absorbance obtained by the absorbance measurement unit. Using the first correlation in which the acquisition unit is associated with the absorbance ratio and the additive concentration, the additive concentration acquisition unit obtains the additive concentration associated with the obtained absorbance ratio. And the upper limit defined for each additive concentration. Of the second correlations in which the first absorbance and the metal concentration are associated with each other, the second correlation determined by the obtained additive concentration is used to associate with the first absorbance. A metal concentration acquisition unit for obtaining the metal concentration, a first chemical solution replenishment unit for replenishing a pH adjusting agent for adjusting the pH of the plating solution in the plating tank, and the composition of the plating solution in the plating tank A second chemical solution replenisher for replenishing the first replenisher for stabilizing the solution, and a third chemical solution replenisher for replenishing the second replenisher for stabilizing the composition of the plating solution in the plating tank. And a section.

  According to the invention, the absorbance ratio does not depend on the change in the metal concentration, and is correlated with the additive concentration.

  Therefore, the additive concentration acquisition unit obtains the additive concentration associated with the obtained absorbance ratio using the first correlation in which the absorbance ratio and the additive concentration are associated with each other. . At the same time, the metal concentration acquisition unit uses the second correlation determined by the obtained additive concentration among the second correlations in which the first absorbance and the metal concentration are associated with each other. And obtaining the metal concentration associated with the first absorbance. Accordingly, it is possible to obtain an accurate metal concentration and to improve the height uniformity of the plating film. As a result, it is possible to stabilize the mounting quality.

  Moreover, the said metal concentration automatic management apparatus is equipped with the said 1st-3rd chemical | medical solution replenishment part. Thereby, about the plating solution in the said plating tank, pH can be adjusted and a composition can be stabilized. Therefore, after measuring the metal concentration of the plating solution in the plating tank, the metal concentration can be kept constant. As a result, the film thickness of the plating is stabilized, so that variations in the product on which the plating is formed can be eliminated. .

  Furthermore, the first correlation and the second correlation can be created in advance based on an experiment using the metal concentration automatic management device. Therefore, an accurate metal concentration can be obtained.

  In the metal concentration automatic management apparatus, the plating solution may be an electroless nickel plating solution. Thereby, the nickel concentration can be accurately obtained as the metal concentration.

  In the metal concentration automatic management device, the first wavelength is in a range of 390 nm to 420 nm, or 660 nm to 690 nm, and the second wavelength is 700 nm. It may be in the range of 760 nanometers or less. Thereby, an accurate metal concentration in the plating solution can be measured.

  In the metal concentration automatic management device, the light having the first wavelength and the light having the second wavelength may be light that has been split so that the half-value width is not less than 1 nanometer and not more than 50 nanometers. Good.

  As a result, two different absorbances (the first absorbance and the second absorbance) can be obtained, so that an accurate metal concentration in the plating solution can be measured.

  In the metal concentration automatic management device, the first chemical solution replenishing unit may replenish the pH adjusting agent to the plating solution in the plating tank.

  In the metal concentration automatic management device, the second chemical solution replenishing unit replenishes the plating solution in the plating tank with the first replenishing solution, and the first replenishing solution contains a metal component and a stabilizer. May be included.

  Further, in the metal concentration automatic management device, the third chemical solution replenishing unit replenishes the plating solution in the plating tank with the second replenishing solution, and the second replenishing solution includes a reducing agent and an organic acid. It may contain salt.

  With the first to third chemical solution replenishers, the pH of the plating solution in the plating tank can be adjusted and the composition can be stabilized.

  As described above, the metal concentration measuring method of the present invention includes a step of filling a cell with a plating solution, irradiating the cell with light of a first wavelength from a light source, and using the light receiver to transmit the light transmitted through the cell. Receiving light and obtaining a first absorbance; and irradiating the cell with light having a second wavelength from the light source, and receiving the light transmitted through the cell with the light receiver to obtain a second absorbance. And obtaining the ratio of absorbance from the first absorbance and the second absorbance, and using the first correlation in which the absorbance ratio and the additive concentration are associated with each other. Of the second correlation in which the step of obtaining the additive concentration associated with the absorbance ratio and the first absorbance and the metal concentration defined for each additive concentration are associated with each other, Using the second correlation determined by the obtained additive concentration, the first And obtaining the metal concentration associated with the light intensity, the method comprising.

  In addition, as described above, the metal concentration automatic management device according to the present invention includes the cell filled with the plating solution sucked from the plating tank, the light having the first wavelength, and the light having the second wavelength. A light source that emits light to the cell; a light receiver that receives light transmitted through the cell; and an absorbance measurement unit that obtains a first absorbance and a second absorbance, and the first absorbance obtained by the absorbance measurement unit. The absorbance obtained above using an absorbance ratio acquisition unit that obtains an absorbance ratio from the absorbance of 1 and the second absorbance, and a first correlation in which the absorbance ratio and additive concentration are associated with each other. An additive concentration acquisition unit that obtains an additive concentration that is associated with the ratio of the second correlation, and a second correlation that is defined for each additive concentration and that associates the first absorbance with the metal concentration. Of these, the second determined by the additive concentration obtained above Using a correlation, a metal concentration acquisition unit that obtains the metal concentration associated with the first absorbance and a pH adjusting agent for adjusting the pH of the plating solution in the plating tank are replenished. The chemical solution replenishing portion, the second chemical solution replenishing portion for replenishing the first replenisher solution for stabilizing the composition of the plating solution in the plating tank, and the composition of the plating solution in the plating tank are stabilized. And a third chemical solution replenishment unit for replenishing the second replenisher solution.

  Therefore, it is possible to obtain an accurate metal concentration and to provide a metal concentration measuring method and a metal concentration automatic management device capable of improving the height uniformity of the plating film.

(A) is a front view which shows the structure of the metal concentration automatic management apparatus used in order to implement the metal concentration measuring method of the plating solution which concerns on embodiment of this invention, (b) is the metal concentration of (a). It is an enlarged view of the light absorbency measurement part in an automatic management apparatus, (c) is a perspective view which shows the cell holding member in the metal concentration automatic management apparatus of (a). It is the graph which put together the data of the light absorbency acquired with the plating solution which changed nickel concentration in the electroless nickel plating solution marketed. It is the graph which put together the data of the light absorbency acquired with the plating solution which changed the additive density | concentration in the electroless nickel plating solution marketed. It is a graph which shows the result of having plotted the ratio of the light absorbency in each condition which changed nickel concentration and additive concentration. It is a graph which shows the calibration curve of nickel concentration according to additive concentration. It is a graph which shows the spectrum of incident light. It is the graph which put together the data of the light absorbency acquired with the plating solution which changed nickel concentration in the electroless nickel plating solution marketed. It is the graph which put together the data of the light absorbency acquired with the plating solution which changed the additive density | concentration in the electroless nickel plating solution marketed.

  One embodiment of the present invention will be described below with reference to FIGS.

(Metal concentration automatic management device 1)
Fig.1 (a) is a front view which shows the structure of the metal concentration automatic management apparatus 1 used in order to implement the metal concentration measuring method of the plating solution which concerns on embodiment of this invention. FIG.1 (b) is an enlarged view of the light absorbency measurement part 2 in the metal concentration automatic management apparatus 1 of Fig.1 (a).

  The metal concentration automatic management device 1 is a metal concentration automatic management device that measures the metal concentration of the plating solution in the plating tank 3 and keeps the metal concentration constant. The absorbance measuring unit 2, the plating tank 3, and the tubes 4a to 4a. 4e, a control unit 8, metering pumps 9a to 9c, a pH adjuster storage tank 10, and replenisher storage tanks 11 and 12. The absorbance measurement unit 2 includes a light source 5, a cell 6, a light receiver 7, a plating solution suction pump 13 a, and a pH meter 24.

  In the metal concentration automatic management device 1, the plating solution is sucked from the plating tank 3 by the plating solution suction pump 13 a and the plating solution sampling tube 4 a and is introduced into the cell 6 of the absorbance measuring unit 2.

For example, the cell 6 is held by a cell holding member 14 shown in the perspective view of FIG. Incident light L <b> 1 (incident light amount I ₀ ) emitted from the light source 5 is applied to the plating solution filled in the cell 6 through the cell window 14 a provided in the cell holding member 14. The light receiver 7 receives the light L2 (transmitted light amount I) that has been transmitted through the cell 6 and emitted from the other cell window 14b. As described above, the metal concentration automatic management device 1 measures the absorbance or transmittance of the plating solution filled in the cell 6 based on the incident light amount I ₀ and the transmitted light amount I.

  The plating solution filled in the cell 6 is discharged to the plating tank 3 through the plating solution discharge tube 4b after measuring the absorbance.

As described above, the incident light amount L1 applied to the plating solution filled in the cell 6 from the light source 5 is I ₀ , and the transmitted light amount of the light L2 that passes through the cell 6 and is received by the light receiver 7 Assuming I, the absorbance A is defined by the following equation (1).
A = log ₁₀ (I ₀ / I) (1)
The relationship between the absorbance A and the component concentration Cn (that is, the metal concentration (nickel concentration in the present embodiment)) is expressed by the following equation (2) from Lambert-Beer's law.
A = εCnl (2)
In the above equation (2), ε is the molar extinction coefficient, and l is the optical path length. The optical path length l is a distance through which light passes through the liquid. In the metal concentration automatic management apparatus 1, the optical path length l is a distance between the inner walls of the cell 6 shown in FIG.

  Therefore, the metal concentration automatic management apparatus 1 can immediately and continuously measure the component concentration Cn in the plating solution based on the Lambert-Beer law by obtaining the absorbance A using the absorptiometry. Is possible.

  In addition, absorptiometry (absorptiometry or absorptiometry) is to measure the degree of light absorption by a target substance when the sample solution is irradiated with light and the light passes through the sample, that is, the absorbance. Thus, the concentration of the target substance is quantitatively analyzed.

  In the present embodiment, a known electroless nickel plating solution is filled in the plating tank 3. The main components of the electroless nickel plating solution are nickel sulfate as a metal source, hypophosphite as a reducing agent, and organic acid salt as an additive.

  Further, the incident light L1 irradiated from the light source 5 and used for measuring the absorbance has at least two wavelengths. The at least two wavelengths may be obtained by spectrally separating light with an optical filter or a monochromator, for example.

  In the metal concentration automatic management device 1, the pH adjusting agent 10 a is replenished (supplied) to the plating tank 3 by the first chemical solution replenishing unit having the pH adjusting agent storage tank 10, the metering pump 9 a and the tube 4 c. The pH of the plating solution filled in the plating tank 3 is controlled by a pH meter 24 that measures and monitors the pH of the plating solution. When the plating solution filled in the plating tank 3 is an electroless nickel plating solution, for example, the pH adjusting agent 10a is replenished to the plating tank 3 so that the pH falls within the range of 4.6 ± 0.1. .

  When the plating solution filled in the plating tank 3 is an electroless nickel plating solution, the pH is shifted to the acidic side by performing the plating treatment. Therefore, a predetermined amount is replenished to the replenishing liquids 11a and 12a in accordance with the replenishment timing of the replenishing liquids 11a and 12a described later. For example, when one replenisher 11a, 12a is replenished, two pH adjusters 10a are replenished.

  When the plating solution filled in the plating tank 3 is an electroless nickel plating solution, the pH is shifted to the acidic side by performing the plating treatment. In this case, as the pH adjuster 10a, alkaline aqueous ammonia is used.

  In the metal concentration automatic management device 1, the replenisher 11 a is replenished to the plating tank 3 by the second chemical replenisher having the replenisher reservoir 11, the metering pump 9 b and the tube 4 d. Further, in the metal concentration automatic management apparatus 1, the replenisher 12a is replenished to the plating tank 3 by the third chemical replenisher having the replenisher reservoir 12, the metering pump 9c, and the tube 4e.

  The replenishing liquids 11 a and 12 a are liquids for stabilizing the composition of the plating liquid filled in the plating tank 3.

  The composition of the replenisher 11a and the replenisher 12a is different. When the plating solution filled in the plating tank 3 is an electroless nickel plating solution, the replenisher 11a contains a metal component (nickel sulfate) and a stabilizer, and the replenisher 12a contains a reducing agent (hypophosphite). ) And organic acid salts.

  As described above, in the metal concentration automatic management device 1, the pH of the plating solution in the plating tank 3 can be adjusted and the composition can be stabilized by replenishing the pH adjusting agent 10a and the replenishing solutions 11a and 12a. . Therefore, after measuring the metal concentration of the plating solution in the plating tank 3, the metal concentration can be kept constant. As a result, the plating process can be performed uniformly and with good reproducibility, and the plating film thickness is stabilized ( That is, the uniformity of the height of the plating film can be improved). Therefore, it is possible to eliminate variations in products on which plating is formed.

  The metal concentration automatic management device 1 includes a control unit 8. The control unit 8 transmits a control signal to each unit of the metal concentration automatic management device 1.

  Examples of the control signal transmitted from the control unit 8 to the absorbance measurement unit 2 include a signal for controlling driving of the light source 5 and a signal for controlling driving of the plating solution suction pump 13a.

  Further, a signal for controlling the driving of the metering pump 9a is transmitted from the control unit 8 to the metering pump 9a, and a signal for controlling the driving of the metering pump 9b is transmitted from the control unit 8 to the metering pump 9b. A signal for controlling the driving of the metering pump 9c is transmitted to the metering pump 9c.

  The control unit 8 receives a pH signal indicating a pH value from the pH meter 24. Thereby, the signal which controls the drive of the metering pump 9a is transmitted to the metering pump 9a, and the replenishment amount of the pH adjusting agent 10a is controlled.

(Measurement method of nickel concentration)
FIG. 2 is a graph summarizing the absorbance data obtained with a plating solution in which the nickel concentration (Ni concentration) is changed in a commercially available electroless nickel plating solution. FIG. 3 is a graph summarizing the absorbance data obtained with a plating solution with a different additive concentration in a commercially available electroless nickel plating solution.

  From the graph of FIG. 2, the wavelength range near the peaks of the absorbance waveforms 15 to 17 (that is, the wavelength range from 390 nm (nanometer) to 420 nm (the wavelength range from 390 nm to 420 nm)), and the wavelength range from 660 nm to 760 nm. In the region (region where the wavelength is 660 nm or more and 760 nm or less), it can be seen that the increase in absorbance with respect to the increase in nickel concentration is greater than in other wavelength regions.

  A nickel concentration measuring instrument that is commercially available and uses the spectrophotometric method selects the wavelength range near the peak described above, and calculates the nickel concentration from the relationship between the nickel concentration in the wavelength range and the absorbance in the wavelength range. What you are doing is common.

  Further, as shown in the absorbance waveforms 18 to 20 in the graph of FIG. 3, it can be seen that the absorbance value increases as the additive concentration increases under the condition that the nickel concentration is constant.

  From the graph of FIG. 2 and the graph of FIG. 3, when the additive concentration is constant, the absorbance in the wavelength region (wavelength band) near the above-mentioned peak is in a proportional relationship, so the nickel concentration can be calculated. is there. However, it can be seen that when the additive concentration changes, the absorbance in the wavelength region near the peak described above is affected, and the nickel concentration cannot be measured accurately.

  In electroless nickel plating treatment, when replenishment with a replenisher is performed according to nickel consumed, a method of replenishing the additive at the same time is common. Therefore, since the additive concentration is not measured and managed every time it is replenished, the change in the additive concentration due to changes in the processing area and amount of the object to be plated in the plating process, removal of the plating solution, and changes over time If this occurs, it will cause variation in the nickel concentration measurement.

  Therefore, as a method of calculating an accurate nickel concentration by using the graph of FIG. 2 and the graph of FIG. 3 and eliminating the influence due to the change in additive concentration, one measurement wavelength (first wavelength) is 390 nm to A wavelength within a range of 420 nm (390 nm to 420 nm) or 660 nm to 690 nm (660 nm to 690 nm) is selected, and another one measurement wavelength (second wavelength) is a range of 700 nm to 760 nm (700 nm to 760 nm or less). It was found that an accurate metal concentration in the plating solution can be measured by selecting a wavelength within the range and using a correlation between one measurement wavelength and another measurement wavelength.

  FIG. 4 is a graph showing the results of plotting the absorbance ratio α in each condition with the nickel concentration and additive concentration changed. The graph of FIG. 4 is obtained by measuring the absorbance ratio α described later by changing the additive concentration in a plating solution having a constant nickel concentration (for example, 4 g / l, 6 g / l, 8 g / l).

  The absorbance ratio α is a ratio between the absorbance A1 at a wavelength of 400 nm and the absorbance A2 at a wavelength of 720 nm, and is obtained by α = A1 / A2. The absorbance ratio acquisition unit 31 acquires the absorbance ratio α in the metal concentration automatic management apparatus 1 of FIG. 1. The absorbance ratio acquisition unit 31 obtains the absorbances A1 and A2 obtained from the absorbance measurement unit 2 and obtains the absorbance ratio α.

From the graph of FIG. 4, it can be seen that the absorbance ratio α does not depend on the change in the nickel concentration and has a correlation with the additive concentration. In the graph of FIG. 4, the correlation is represented by a linear function, and the correlation equation (approximate equation) shown in the following equation (3) was obtained by an experiment using the metal concentration automatic management device 1 (β is the additive concentration). Is).
α = 0.0151β + 2.0469 (3)
Therefore, the additive concentration acquisition unit 32 uses the first correlation (FIG. 4) in which the absorbance ratio α and the additive concentration β are associated with each other, and associates them with the obtained absorbance ratio α. The additive concentration β is obtained (the additive concentration is calculated using the absorbance ratio α and the correlation equation (3)), and the metal concentration acquisition unit 33 determines the absorbance A1 determined for each additive concentration β. Of the second correlation (calibration curves 21 to 23 in FIG. 5) associated with the nickel concentration, it corresponds to the absorbance A1 using the second correlation determined by the obtained additive concentration β. By obtaining the attached nickel concentration, it is possible to accurately calculate the nickel concentration (metal concentration).

  More specifically, in a nickel plating solution whose nickel concentration is unknown, the absorbance A1 at a wavelength of 400 nm and the absorbance A2 at a wavelength of 720 nm are measured, and the absorbance ratio α = A1 / A2 is calculated.

  Next, the additive concentration β is calculated using the absorbance ratio α obtained as described above and the correlation equation (for example, the correlation equation (3) obtained from the graph of FIG. 4).

  Furthermore, as shown in the graph of FIG. 5, by preparing calibration curves 21 to 23 of nickel concentration for each additive concentration and using the calibration curve corresponding to the additive concentration β obtained above, nickel A concentration is obtained. The calibration curve 21 of FIG. 5 is obtained by measuring the absorbance A1 by changing the nickel concentration in a plating solution having a constant additive concentration (for example, 10 g / l). The calibration curves 22 and 23 are created in the same manner as the calibration curve 21 except that the additive concentrations are different (for example, 15 g / l and 20 g / l).

  The calibration curve 21 is created by fixing the wavelength of the incident light L1 and the additive concentration, and measuring the absorbance by changing the nickel concentration. In preparing the calibration curves 22 and 23, only the additive concentration fixed before changing the nickel concentration differs from the calibration curve 21.

  In addition, the absorbance on the vertical axis in the graph of FIG. 5 is the absorbance at a wavelength of 400 nm. This is because the wavelength when measuring the absorbance A1 was 400 nm. Therefore, the wavelength at the time of absorbance measurement on the vertical axis in the graph of FIG. 5 may be changed according to the wavelength at the time of absorbance A1 measurement.

  Further, the absorbance ratio, additive concentration, and metal concentration may be acquired by the control unit 8 performing calculations based on the signal received from the absorbance measurement unit 2.

(Measurement result of nickel concentration)
Calculation results obtained by actually applying the nickel concentration measuring method for the plating solution according to the embodiment of the present invention are shown below. In the nickel concentration measurement of the electroless nickel plating solution used for a certain period, the nickel concentration of 6.43 g / l obtained by the conventional measuring method and the nickel concentration of 5.81 g / l obtained by chemical analysis are 10. An error of 7% occurred.

  On the other hand, the nickel concentration obtained by the plating solution concentration measuring method according to the embodiment of the present invention is 5.89 g / l, and between the nickel concentration obtained by chemical analysis is 5.81 g / l. The error was 1.4%.

  Thus, it was confirmed that the nickel concentration measurement accuracy by the plating solution concentration measurement method according to the embodiment of the present invention is much higher than the nickel concentration measurement accuracy by the conventional measurement method.

  As described above, the metal concentration measurement method according to the present embodiment is a metal concentration measurement method in which the metal concentration in the plating solution is measured immediately and continuously using the absorptiometry. Filling the cell, irradiating the cell with light having a first wavelength (for example, 400 nm) from the light source 5, receiving the light transmitted through the cell 6 with the light receiver 7, and obtaining the absorbance A1, and the light source 5 To the second wavelength (for example, 720 nm) to the cell 6, the light transmitted through the cell 6 is received by the light receiver 7, and the absorbance A2 is obtained, and the absorbance A1 and the absorbance A2 are used. Using the first correlation (for example, FIG. 4) in which the ratio α is obtained and the absorbance ratio α and the additive concentration β are associated with each other, the absorbance α is associated with the obtained ratio α. The step of obtaining the additive concentration β and the absorption defined for each additive concentration β Of the second correlation (for example, FIG. 5) in which the degree A1 and the metal concentration are associated with each other, the second correlation that is determined by the obtained additive concentration β is associated with the absorbance A1. Obtaining the metal concentration.

  Thereby, the metal concentration (nickel concentration) in the nickel plating solution can be measured more accurately than in the conventional measurement. Therefore, the nickel concentration of the nickel plating solution can be stabilized, and the uniformity of the height of the plating film can be improved.

  The metal concentration measurement method may include a step of obtaining the first correlation and the second correlation before the step of filling the cell 6 with the plating solution.

  Thus, using the first correlation in which the absorbance ratio α and the additive concentration β are correlated, obtaining the additive concentration β correlated with the obtained absorbance ratio α, and Among the second correlations determined for each additive concentration β, in which the absorbance A1 is associated with the metal concentration, the second correlation determined by the obtained additive concentration β is used. The step of obtaining the metal concentration associated with the absorbance A1 can be executed.

  The first correlation and the second correlation can be created in advance based on an experiment using the metal concentration automatic management apparatus 1. Thereby, the exact said metal concentration can be obtained.

(Incident light L1)
FIG. 6 is a graph showing the spectrum of the incident light L1 according to this embodiment. In the graph of FIG. 6, the horizontal axis indicates the wavelength x (unit: nm (nanometer), for example), and the vertical axis indicates the light intensity y.

  In the case where the intensity of the incident light L1 is expressed by a function y = f (x), when ymax is ymax and x = y1, y2 (x2> x1) The full width at half maximum W is obtained by W = x2-x1.

  As the incident light L1, it is necessary to use a split light, and it is preferable to use a split light so that the half width W is 1 nm or more and 50 nm or less.

  As the above reason, when the continuous spectrum shown in Patent Document 1 is used, two different absorbances (for example, absorbances A1 and A2) cannot be obtained. As a result, the absorbance ratio α cannot be calculated, and as a result, the nickel concentration cannot be measured.

  On the other hand, since the absorbances A1 and A2 can be obtained by using the light as described above as the incident light L1, the accurate nickel concentration in the plating solution can be measured.

  In the present embodiment, the measurement of the nickel concentration in the plating solution has been described. However, the present invention is not limited to this, and it goes without saying that the concentration of a metal other than nickel can be measured in the same manner.

  Further, regarding the graph of FIG. 4, the wavelength 400 nm when determining the absorbance A1 and the wavelength 720 nm when determining the absorbance A2 are merely examples. The wavelength for obtaining the absorbance A1 may be selected from the wavelengths within the range of the one measurement wavelength, and the wavelength for obtaining the absorbance A2 may be selected from the wavelengths within the range of the other one measurement wavelength.

  Further, the wavelength for obtaining the absorbance A1 is selected from the wavelengths within the range of the one other measurement wavelength, and the wavelength for obtaining the absorbance A2 is selected from the wavelengths within the range of the one measurement wavelength. Also good. In this case, the proportionality constant in the correlation equation is negative.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  Since the metal concentration measuring method and the metal concentration automatic management apparatus of the present invention can obtain an accurate metal concentration and can improve the uniformity of the height of the plating film, the printed circuit board, the semiconductor device, and the chip component. It can be suitably used for electronic parts such as connectors.

DESCRIPTION OF SYMBOLS 1 Metal concentration automatic management apparatus 2 Absorbance measuring part 3 Plating tank 4a-4e Tube 5 Light source 6 Cell 7 Light receiver 8 Control part 9a-9c Metering pump 10 pH adjuster storage tank 10a pH adjuster 11,12 Replenisher storage tank 11a , 12a Replenisher 13a Plating solution suction pump 14 Cell holding member 14a, 14b Cell window 15-17, 18-20 Absorbance waveform 21-23 Calibration curve 24 pH meter 31 Absorbance ratio acquisition unit 32 Additive concentration acquisition unit 33 Metal concentration Acquisition part A Absorbance A1 Absorbance (first absorbance)
A2 absorbance (second absorbance)
Cn component concentration I transmitted light quantity I ₀ incident light quantity L1 incident light L2 light W half width l optical path length x wavelength y light intensity α ratio of absorbance β additive concentration

Claims (12)

A metal concentration measurement method for measuring a metal concentration in a plating solution immediately and continuously using an absorptiometry,
Filling the cell with the plating solution;
Irradiating the cell with light of a first wavelength from a light source, receiving the light transmitted through the cell with a light receiver, and obtaining a first absorbance;
Irradiating the cell with light of a second wavelength from the light source, receiving the light transmitted through the cell with the light receiver, and obtaining a second absorbance;
Obtaining a ratio of absorbance from the first absorbance and the second absorbance;
Using the first correlation in which the absorbance ratio and the additive concentration are associated with each other, obtaining the additive concentration associated with the obtained absorbance ratio;
Of the second correlations determined for each additive concentration, in which the first absorbance is associated with the metal concentration, the second correlation determined by the obtained additive concentration is used. Obtaining the metal concentration associated with the first absorbance;
A metal concentration measuring method comprising:   The metal concentration measuring method according to claim 1, wherein the plating solution is an electroless nickel plating solution. The first wavelength is in a range of 390 nm to 420 nm, or 660 nm to 690 nm,
The metal concentration measuring method according to claim 1, wherein the second wavelength is in a range of 700 nm to 760 nm.   2. The light according to claim 1, wherein the light having the first wavelength and the light having the second wavelength are light that has been split so that a half-value width is not less than 1 nanometer and not more than 50 nanometers. Metal concentration measurement method.   The metal concentration measuring method according to claim 1, further comprising a step of obtaining the first correlation and the second correlation before the step of filling the plating solution into the cell. A metal concentration automatic management device that measures the metal concentration of the plating solution in the plating tank and keeps the metal concentration constant,
A cell filled with the plating solution sucked from the plating tank; a light source that emits light having a first wavelength and light having a second wavelength to the cell; and light received by the cell is received. An absorbance measuring unit for obtaining the first absorbance and the second absorbance,
An absorbance ratio acquisition unit for obtaining a ratio of absorbance from the first absorbance and the second absorbance obtained by the absorbance measurement unit;
Using the first correlation in which the absorbance ratio and the additive concentration are associated, an additive concentration acquisition unit that obtains the additive concentration associated with the obtained absorbance ratio;
Of the second correlations determined for each additive concentration, in which the first absorbance is associated with the metal concentration, the second correlation determined by the obtained additive concentration is used. A metal concentration obtaining unit for obtaining the metal concentration associated with the first absorbance,
A first chemical solution replenisher for replenishing a pH adjuster for adjusting the pH of the plating solution in the plating tank;
A second chemical solution replenisher for replenishing the first replenisher for stabilizing the composition of the plating solution in the plating tank;
A third chemical replenisher for replenishing a second replenisher for stabilizing the composition of the plating solution in the plating tank;
A metal concentration automatic management device comprising:   7. The metal concentration automatic management device according to claim 6, wherein the plating solution is an electroless nickel plating solution. The first wavelength is in a range of 390 nm to 420 nm, or 660 nm to 690 nm,
The metal concentration automatic management apparatus according to claim 6, wherein the second wavelength is in a range of 700 nanometers or more and 760 nanometers or less.   The light having the first wavelength and the light having the second wavelength are light that is spectrally divided so that a half-value width is not less than 1 nanometer and not more than 50 nanometers. Automatic metal concentration management device.   The metal concentration automatic management device according to claim 6, wherein the first chemical solution replenishing unit replenishes the plating solution in the plating tank with the pH adjuster. The second chemical liquid replenishing unit replenishes the plating liquid in the plating tank with the first replenishing liquid,
11. The automatic metal concentration management apparatus according to claim 10, wherein the first replenisher includes a metal component and a stabilizer. The third chemical solution replenishing unit replenishes the plating solution in the plating tank with the second replenishing solution,
12. The metal concentration automatic management device according to claim 11, wherein the second replenisher includes a reducing agent and an organic acid salt.

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