CN111337455A - Concentration detection system for electroplating solution - Google Patents
Concentration detection system for electroplating solution Download PDFInfo
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- CN111337455A CN111337455A CN202010307292.9A CN202010307292A CN111337455A CN 111337455 A CN111337455 A CN 111337455A CN 202010307292 A CN202010307292 A CN 202010307292A CN 111337455 A CN111337455 A CN 111337455A
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Abstract
The invention discloses a concentration detection system for an electroplating solution, which comprises: a DFB laser; 50/50 a coupler; a reflector with a second preset distance is arranged between the first collimating mirror arranged in one of the light paths and the 50/50 coupler; a second collimating mirror arranged in the other light path and a cuvette for containing an electroplating solution; the balance detector is used for forming optical interference between the reference optical signal and the detection optical signal to generate an interference laser signal and converting the interference laser signal into a target voltage signal; the oscilloscope is used for acquiring parameters of the target voltage signal and displaying the waveform of the target voltage signal; data processing means for determining the maximum voltage amplitude U of the target voltage signalmTo calculate the refractive index n of the electroplating solution30And calculating the concentration of the electroplating solution according to a refractive index-concentration conversion expression which is established in advance and corresponds to the electroplating solution. The invention can automatically and rapidly detect the concentration of the solution, has accurate detection result, and has the advantages of simple and convenient operation, accurate measurement and the like.
Description
Technical Field
The invention relates to the technical field of detection, in particular to a concentration detection system for an electroplating solution.
Background
This section merely provides background information related to the present application so as to enable those skilled in the art to more fully and accurately understand the present application, which is not necessarily prior art.
Taking the production of punched nickel-plated steel strip by electroplating process using electroplating solution as an example: the punched nickel-plated steel strip is formed by plating nickel on the punched steel strip by using the electroplating solution through an electroplating process, has wide application and is widely used as an electrode substrate material of a nickel-hydrogen-nickel separator chargeable battery pole at present. The process parameters of the electroplating process include the concentration of the plating solution, pH, temperature, current density, etc., wherein the concentration of the plating solution is a very important process parameter. When the concentration is lower, the phenomenon of water electrolysis can occur, so that a coating cannot be obtained and energy waste is caused; when the concentration is higher, the internal stress of the coating is increased, and the coating has the phenomena of peeling, cracking, poor ductility and the like, so that the service performance of the product is poor. Therefore, the concentration of the plating solution needs to be detected at any time during the process of passing the punched steel strip through the plating process to ensure that the concentration of the plating solution meets the process standard. Generally, the electroplating solution required for nickel plating of punched steel strip is made of HBO3、NiCl2And NiSO4Composition, wherein the reference standard for each solution is HBO3The concentration is 30 +/-5 g/L, NiSO4The concentration is 300 +/-10 g/L, NiCl2The concentration of (b) is 30. + -.5 g/L.
However, the traditional chemical titration method is still adopted for detecting the concentration of the electroplating solution in the existing nickel plating process of the punched steel strip, 8-hour off-line testing time is needed, the detection time is long, the real-time detection requirement of the concentration of the electroplating solution is difficult to meet, and the defect that detection errors are large due to the fact that detection personnel think to participate is also existed.
Therefore, in the prior art, on the premise of determining or knowing the solute components of the electroplating solution, the concentration of the electroplating solution is usually determined by a chemical titration method in the production practice process, the detection time is long, the efficiency is low, the accuracy is low, the real-time knowledge of the concentration of the electroplating solution in the production practice is not facilitated, and the electroplating parameters are timely and correspondingly adjusted according to the concentration change of the electroplating solution, so that the production efficiency and the electroplating production quality are difficult to ensure.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a concentration detection system for an electroplating solution, which can realize non-contact rapid real-time detection on the electroplating solution and has higher detection precision.
The invention discloses a concentration detection system for an electroplating solution, which comprises:
DFB laser for generating a known light intensity I0The measuring laser of (1);
50/50 coupler for dividing the measuring laser into two paths of measuring laser to emit outwards to form light paths respectively;
a reflector with a second preset distance is arranged between the first collimating lens in one of the light paths and the 50/50 coupler, wherein one path of measuring laser is reflected by the reflector to generate a reference light signal, and the reference light signal is returned to the 50/50 coupler through the first collimating lens;
the second collimating mirror and the cuvette used for containing the electroplating solution are arranged in the other light path, and the other path of sub-measurement laser generates a detection light signal after being refracted and reflected by the cuvette and the electroplating solution in the cuvette, so that the detection light signal returns to the 50/50 coupler through the second collimating mirror, wherein a second preset distance is reserved between the cuvette and the 50/50 coupler, so that the detection light signal can form light interference with the reference light signal;
the balance detector is used for forming optical interference between the reference optical signal and the detection optical signal to generate an interference laser signal and converting the interference laser signal into a target voltage signal;
the oscilloscope is used for acquiring parameters of the target voltage signal and displaying the waveform of the target voltage signal;
data processing means for determining the maximum voltage amplitude U of the target voltage signalmTo calculate the refractive index n of the electroplating solution30Calculating the concentration of the electroplating solution according to a refractive index-concentration conversion expression which is pre-established and corresponds to the electroplating solution;
wherein the data processing device utilizes the maximum voltage amplitude U of the target voltage signalmThe refractive index n of the plating solution is calculated according to the following formula30：
K is a predetermined coefficient for converting current to voltage by the balance detector, K1For balancing the predetermined coefficient of conversion of the light intensity of the detector 32 into optical power, I1Representing the light intensity of the reference light signal, I1＝I0/2，K2Representing the attenuation constant of the intensity of one of the sub-beams of measuring laser, n10Is the refractive index of air, n20Is the refractive index of the cuvette and r is the responsivity of the equilibrium detector.
In a preferred embodiment, the data processing apparatus specifically includes:
the interface unit is connected with the oscilloscope to acquire a target voltage signal from the oscilloscope;
the curve fitting module is used for carrying out nonlinear curve fitting on the target voltage signal superposition of at least 5 continuous periods to obtain a curve equation;
the extreme value calculation module is used for solving the maximum values of the curve equation in each period and determining the average value of the maximum values of at least 5 periods as the maximum voltage amplitude of the interference voltage signal;
the database is used for prestoring a refractive index-concentration conversion expression of the electroplating solution;
and the concentration calculation module is used for calculating the concentration of the electroplating solution according to a refractive index-concentration conversion expression which is predetermined and corresponds to the electroplating solution in the database.
In a preferred embodiment, the data processing apparatus further comprises:
and the noise reduction processing module is arranged between the interface unit and the curve fitting module and is used for carrying out noise reduction processing on the interference voltage signal by adopting mean value filtering.
In a preferred embodiment, the curve fitting module performs nonlinear curve fitting on the parameters of the target voltage signal by using a sine curve superposition approximation method to obtain a curve equation.
In a preferred embodiment, the pre-establishing in the database a refractive index-concentration conversion expression corresponding to the plating solution specifically includes:
taking solute same as the electroplating solution to respectively prepare a plurality of known solutions with given concentration;
and respectively detecting each known solution, calculating the corresponding refractive index of each known solution by a data processing device according to the target electrical signal corresponding to the interference laser signal of each known solution, and performing linear fitting according to the given concentration of each known solution and the refractive index obtained by corresponding calculation to generate a refractive index-concentration conversion expression.
In a preferred embodiment, the measurement laser is a macroscopic laser with a central wavelength of 1310 nm.
In a preferred embodiment, the concentration detection system for the electroplating solution further comprises a red laser for generating a macroscopic red laser to the 50/50 coupler using the red laser to assist in determining the second predetermined distance between the cuvette and the 50/50 coupler while using the DFB laser, provided that the first predetermined distance between the mirror and the 50/50 coupler is determined.
In a preferred embodiment, the DFB laser is connected to the 50/50 coupler by an optical fiber, the 50/50 coupler is connected to the first collimating mirror and the second collimating mirror by optical fibers, respectively, and the 50/50 coupler is connected to the balanced detector by an optical fiber.
Compared with the prior art, the invention has the following beneficial effects:
the invention adopts the interference laser signal formed by the laser after being refracted and reflected by the electroplating solution and the reference light signal, determines the maximum voltage amplitude of the interference voltage signal after converting the interference laser signal into the corresponding interference voltage signal, and utilizes the concentration of the electroplating solution with the maximum voltage amplitude, thereby automatically and rapidly detecting the concentration of the solution, having accurate detection result, and having the advantages of simple and convenient operation, accurate measurement and the like. Therefore, the invention carries out non-contact rapid real-time detection on the electroplating solution based on the laser interferometry, has short detection time and higher detection precision, provides a basis for adjusting the parameters of the electroplating production process in time, and is beneficial to improving the electroplating production efficiency and optimizing the electroplating production process.
Drawings
Fig. 1 is a block diagram of a solution concentration detection system disclosed in the present invention.
Fig. 2 is a schematic diagram of a circuit configuration of a balanced detector.
FIG. 3 is a waveform diagram of a target voltage signal corresponding to a laser interference signal when detecting 5g/L of NiSO4 solution.
Fig. 4 is a schematic diagram of a refractive index-concentration conversion expression generated by fitting the relationship between the concentration and the refractive index of a plurality of solutions of NiSO4 of known concentration.
FIG. 5 is a graph showing the distribution of a plurality of known concentrations of NiCl2And (3) fitting the relationship between the concentration of the solution and the refractive index to generate a schematic diagram of a refractive index-concentration conversion expression.
Detailed Description
To further clarify the technical solutions and effects adopted by the present application to achieve the intended purpose, the following detailed description is given with reference to the accompanying drawings and preferred embodiments according to the present application. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
The invention discloses a concentration detection system for an electroplating solution, which is used for carrying out non-contact rapid real-time detection on the electroplating solution based on a laser interferometry technology, has short detection time and higher detection precision, provides a basis for adjusting electroplating production process parameters in time, and is beneficial to improving the electroplating production efficiency and optimizing the electroplating production process.
As shown in fig. 1, the solution concentration detection system according to the present invention includes: the DFB laser 2, 50/50 coupler 31, first collimator 41, second collimator 42, mirror 5, cuvette 6, balanced detector 32, oscilloscope 7 and data processing device 8.
The DFB laser 2 is used to generate a known light intensity I0The measuring laser of (1). For example, with a laser of type LP1310-SAD2 manufactured by Thorlab, usa, current and temperature control is performed by a constant current temperature control source (for example, with a module of type ITC4001 manufactured by Thorlab, usa) to generate a measuring laser invisible to the naked eye (for example, the measuring laser generated by the DFB laser 2 is a non-visible to the naked eye laser with a central wavelength of 1310 nm), and the detection accuracy is improved by generating the measuring laser invisible to reduce the interference of visible light in the detection environment.
The DFB laser 2 is connected to the input of the 50/50 coupler 31 by an optical fibre, and the two outputs of the 50/50 coupler 31 are connected to the first collimator 41 and the second collimator 42 respectively by optical fibres. The measuring laser emitted by the DFB laser 2 is uniformly divided into two paths of light intensity I through the 50/50 coupler 310And the sub-measurement lasers of/2 (one path is reference light and the other path is object light) are respectively output from the two output ends. The reference light is emitted to the reflective mirror 5 through the first collimator 41, and a first reflected light is generated after passing through the reflective mirror 5, and the first reflected light returns to the 50/50 coupler 31 through the first collimator 41 to form a reference light signal; meanwhile, the object light is emitted to the cuvette 6 through the second collimator 42, the object light is refracted in the cuvette 6 and the plating solution in the cuvette 6 to generate a second reflected light, and the second reflected light returns to the 50/50 coupler 31 through the second collimator 42 to form a detection light signal. Because the reference light signal and the detection light signal respectively originate from the reflected laser of the two paths of sub-measuring lasers, the light intensity of the reference light signal and the light intensity of the detection light signal are both I0/2。
When the DFB laser 2 emits one measuring laser beam, the 50/50 coupler 31 divides the measuring laser beam emitted from the DFB laser 2 into two sub-measuring laser beams uniformly. One of the sub-measurement lasers reaches the reflective mirror 5 through the first collimator 41 at normal incidence, and after being reflected by the reflective mirror 5, a reference light signal is generated, and the reference light signal returns to the 50/50 coupler 31 through the first collimator 41. And the other sub-measurement laser reaches the cuvette 6 through the second collimator 42, and after the other sub-measurement laser is transmitted in the air through the second collimator 42 and is emitted to the cuvette 6 made of glass at a normal incidence angle, because the refractive indexes of the light in the air, the glass and the electroplating solution are different, the sub-measurement laser is firstly refracted at an air-glass interface when entering the cuvette 6 from the air at the normal incidence, is secondly refracted at a glass-electroplating solution interface when exiting the cuvette 6 to the electroplating solution, is then reflected and is refracted again to return to the air from the solution interface in the cuvette 6 to form a detection optical signal, and the detection optical signal can return to the 50/50 coupler 31 through the second collimator 42 when the second collimator 52 is in a perpendicular relationship with the cuvette 6.
In addition, a second preset distance is set between the cuvette 6 and the coupler 31 of 50/50, a first preset distance is set between the reflector 5 and the coupler 31 of 50/50, and when the distance between one of the cuvette 6 or the reflector 5 and the coupler 31 of 50/50 is adjusted, the optical path difference between the detection optical signal and the reference optical signal is smaller than the coherence length of the measurement laser, so that the detection optical signal and the reference optical signal can generate an interference laser signal after interference. Therefore, by adjusting the distance between one of the cuvette 6 or the mirror 5 and the 50/50 coupler 31, the optical path difference between the detection optical signal and the reference optical signal is smaller than the coherence length of the measurement laser, and the detection optical signal and the reference optical signal interfere with each other to generate an interference laser signal.
Furthermore, since the DFB laser 2 emits the measuring laser invisible to the naked eye, in order to facilitate the rapid determination of the distance between one of the cuvette 6 or the reflector 5 and the 50/50 coupler 31 during the detection process and to rapidly adjust the distance to allow the detection optical signal to interfere with the reference optical signal, the rapid automatic detection system of the present invention further includes a tuning laser emitting visible light, for example, the tuning laser is a red laser capable of generating red laser with a center wavelength of 658 nm. When the red laser and the DFB laser 2 are simultaneously accessed, the red laser generates macroscopic red laser, the first preset distance between the reflector 5 and the coupler 50/50 can be adjusted under the condition that the second preset distance between the cuvette 6 and the coupler 50/50 is determined, the oscilloscope 7 is used for observing and ensuring that the detection light signal and the reference light signal can form interference, the reflector 5 is stopped moving, the specific position of the reflector 5 is determined at the moment, the red laser is closed, and the detection light signal and the reference light signal can form interference certainly.
After the detection light signal and the reference light signal are transmitted to the balance detector 32, the balance detector 32 converts the interference light signal into a target voltage signal, and the target voltage signal is transmitted to the oscilloscope 7 for display. The oscilloscope 7 is used for acquiring parameters of a target voltage signal and displaying the waveform of the target voltage signal to intuitively reflect the waveform of the target voltage signal, namely, intuitively reflect the waveform of an interference laser signal, so that an operator can judge whether the interference signal is formed or not by the waveform of the interference laser signal displayed on the oscilloscope 7, and an intuitive auxiliary reference is provided for the operator to adjust the distance between the reflector 5 or the cuvette 6 and the 50/50 coupler 31; meanwhile, the oscilloscope 7 is a medium through which the target voltage signal is transmitted from the balance detector 32 to the data processing device 8.
A data processing device 8 (e.g., a high-performance computer) acquires a target voltage signal from the oscilloscope 7 and processes the data. The data processing device 8 specifically includes an interface unit 81, a noise reduction processing module 82, a curve fitting module 83, an extremum calculation module 84, a database 85, and a concentration calculation module 86.
The interface unit 81 is used for connecting with the oscilloscope 7 to acquire a target voltage signal from the oscilloscope 7. For example, MATLAB software is installed in the data processing device 8, and parameters of the target voltage signal are acquired from the oscilloscope 7 through the MATLAB software.
The noise reduction module 82 is configured to perform noise reduction on the interference voltage signal by using mean filtering, for example, performing noise reduction by using a 20 × 20 filtering template.
The curve fitting module 83 is configured to apply a sinusoidal superposition approximation method to the parameters of the target voltage signal subjected to the noise reduction processing by the noise reduction processing module 82, and perform nonlinear curve fitting on the target voltage signal superposition of at least 5 continuous periods to obtain a curve equation. Wherein the curve equation is generally fitted by superposing target voltage signals of 5-10 periods.
The extreme value calculating module 84 is configured to solve the maximum values of the curve equation in each period, and determine the maximum voltage amplitude of the interference voltage signal as an average value of the maximum values of at least 5 periods.
The database 85 is used for pre-storing a refractive index-concentration conversion expression of the electroplating solution. Therefore, for electroplating solutions with different solutes, the corresponding refractive index-concentration conversion expression (the specific determination process is described below) needs to be predetermined and stored in the database 85
The concentration calculating module 86 is used for calculating the concentration of the electroplating solution according to a predetermined refractive index-concentration conversion expression corresponding to the electroplating solution in the database 85.
The invention utilizes the principle of optical interference, two beams of light, namely a detection light signal and a reference light signal, have time and space coherence, and form an interference laser signal when the detection light signal and the reference light signal both tend to coincide infinitely in time and space, and the refractive index of the electroplating solution is correspondingly determined by utilizing the characteristics of the interference laser signal. Specifically, the invention utilizes the maximum voltage amplitude of a target voltage signal obtained by converting an interference laser signal to calculate and determine the refractive index of the electroplating solution. The theoretical basis or the working principle of calculating the refractive index of the electroplating solution by utilizing the maximum voltage amplitude of the target voltage signal is explained as follows:
the equation for monochromatic two-beam interference is:
i in the formula (1)gRepresents the intensity of interference light, I1And I2Respectively representing the light intensity, phi, of the reference light signal and the detected light signal1-φ2Is the phase of the interfering light. In addition, since the measurement laser light emitted from the DFB laser 2 is approximately monochromatic, the spectral bandwidth λmVery small, the phase of the interfering light varies between (-pi, pi), and thus, as can be seen from formula (1)Maximum value of interference light intensity IgmComprises the following steps:
in combination with the fresnel formula, when a single color plane light is incident on the interface of two media, it is generally divided into a reflected wave and a refracted wave. Wherein the Fresnel formula is
Wherein the amplitudes of the incident light, reflected light and refracted light are respectively represented by E1、E′1And E2It is shown that the incident light and the reflected light of the corresponding parallel and perpendicular incident surfaces and reflecting surfaces are respectively ES1、EP1、E′S1And E'P1The incident angle, the reflection angle and the refraction angle are respectively theta1、θ2And theta3The refractive indexes of the pre-refraction medium and the post-refraction medium are n respectively1And n2。
In the invention, two paths of measuring laser are approximately normal incidence and respectively irradiate to the reflector 5 and the cuvette 6, namely theta1＝θ2＝θ3＝00Therefore, the difference between the S and P components disappears, so that the reflectance satisfies the following formula (5):
wherein I and I' are the incident light intensity and the reflected light intensity, respectively.
One of the sub-measurement lasers is transmitted through the air and enters the cuvette 6 at a normal incidence angle, and therefore, the first refraction occurs between the air and the glass wall of the cuvette 6, so that the measurement laser can be obtained by combining the formula (3):
in the formula (6) I11And l'12Respectively representing the incident light intensity and the reflected light intensity of the measuring laser entering the glass interface, n20The refractive index of the cuvette (glass) (1.5090 as known from the prior art), n10Is the refractive index of air (air is known from the prior art to have a refractive index of 1.0003).
Assuming a refractive intensity I entering the glass wall of the cuvette 6 from air12According to the law of conservation of energy in combination with equation (6)
The combination formula (7) can convert the formula (3) into
In the formula I12And l'22Respectively representing the incident light intensity and the reflected light intensity of the laser entering the liquid interface of the electroplating solution in the cuvette 6, n30Expressed as the refractive index of the plating solution in the cuvette 6.
Further assume that the intensity of refraction I from the glass wall of the cuvette 6 back into the air32Combining the formula (3) and the formula (7) can be seen
From this, the refracted light intensity I32I.e., the intensity of the detected optical signal that is refracted back 50/50 to coupler 31 against the plating solution in cuvette 6.
In addition, since two sub-measuring lasers are formed by the 50/50 coupler 31, the two sub-measuring lasers are not required to be coupled to each other
I1＝I11(10)
Adjusting the mirror 5 to I32Is object light of interferenceDue to n10And n20Is a known constant, so
The maximum interference light intensity obtained by substituting (7) to (12) into the formula (5) is
Igm＝C2KI1(13)
Further referring to fig. 2, the balanced detector 32 is composed of two parallel reverse-biased photodiodes D1 and D2 and an operational amplifier U, and has a structure as shown in fig. 2. The voltage signal corresponding to the reference optical signal is input to the cathode of the photodiode D1, the voltage signal corresponding to the detection optical signal is input to the cathode of the photodiode D2, and the operational amplifier U performs superposition processing of summing the voltage signals corresponding to the reference optical signal and the detection optical signal, so that the output end of the operational amplifier U outputs an interference voltage signal corresponding to the interference laser signal.
Suppose that: the power and phase of the reference light signal passing through the photodiode D1 are PS(t) and phi3The power and phase of the detected optical signal passing through the photodiode D2 are PL(t) and phi4The frequency difference between the reference optical signal and the detected optical signal is ωIF(ii) a The photodiode D1 and the photodiode D2 are devices of the same type, and the responsivity is r, then the output current signal of the balance detector 32 is
The two beams of measuring laser of this system are split by the 50/50 coupler 31, so ωIFWhen the voltage signal is equal to 0, the output voltage signal is
Where k is a predetermined coefficient for converting the current to a voltage by the balanced detector 32 (specifically, the operational amplifier U).
Since the light intensity is equal to the light power per unit area and the areas of the photodiodes D1 and D2 are fixed during the study of the present application, the light intensity is equal to the light power per unit area
P＝K1I3(16)
In the formula K1Is a constant number, K1For balancing the predetermined coefficient (in practice K) of conversion of the light intensity of the detector 32 into optical power1Determined by the actual photosensitive area of photodiodes D1 and D2, which is equal to one square meter divided by the actual photosensitive area of the photodiodes), I3In order to obtain the light intensity of the light beam passing through the photodiode, in the system developed in the present application, the two light beams passing through the balanced detector 32 are derived from the 50/50 coupler 31 to split the interference light into two sub-measuring lasers, and one of the sub-measuring lasers is subjected to a certain intensity attenuation, so that the intensity of the light beam passing through the balanced detector is reduced
In the formula K2Represents the attenuation constant (K) of one of the sub-measuring lasers2Predetermined constant, which can be determined by measurement in advance), the maximum voltage amplitude U of the target voltage signal corresponding to the interference light signal can be obtained by substituting the equations (13) and (17) into the equation (15)mIs composed of
In the formula of UmAnd K is a variable, therefore
Equation (18) is reduced to
Therefore, the maximum voltage amplitude U of the target voltage signal corresponding to the interference light signal can be obtainedmDetermining K, and obtaining the refractive index n of the plating solution in the cuvette 6 using the formula (12) when K is determined30。
Therefore, the data processing device 8 obtains the parameters of the target voltage signal from the oscilloscope 7, and can quickly calculate the refractive index n of the electroplating solution by determining the maximum voltage amplitude of the target voltage signal and substituting the maximum voltage amplitude into the formula (20)30。
To verify the refractive index n of the solution determined by the calculation of equation (20)30The experiments were designed as follows: the test was performed by using 0.9% NaCl solution, 5% glucose solution, 70% alcohol and rapeseed oil, and comparing with the standard refractive index. Firstly, carrying out noise reduction treatment on interference signals obtained by adopting the system on 0.9% NaCl solution, 5% glucose solution, 70% alcohol and rapeseed oil, and then carrying out nonlinear curve fitting on the interference signals subjected to noise reduction. Finally, the maximum voltage amplitude of the interference voltage signal is obtained by deriving the fitted equation, and the refractive index is obtained by substituting the maximum voltage amplitude of the interference voltage signal into equation (20) as shown in table 1.
TABLE 1 Standard comparison of the detected refractive index and the standard refractive index of each experimental solution
As can be seen from the above table 1, the refractive index error determined by calculation according to the present invention is within 0.0003, which falls within the allowable range of the refractive index detection error of the solution by other technical means, indicating that the refractive index detection result of the electroplating solution based on optical interference according to the present invention is more accurate.
The refractive index-concentration conversion expression is preset in the database 85, and the method for the refractive index-concentration conversion expression pre-established for the electroplating solution is as follows: (1) because the solute of the electroplating solution is determined but the concentration is unknown, a plurality of known solutions with given concentrations can be respectively prepared by taking the solute with different qualities of the electroplating solution; (2) detecting the refractive index corresponding to each known solution with different concentration by the steps S1-S4; (3) and performing linear fitting according to the given concentration of each known solution and the refractive index obtained by corresponding calculation to generate a refractive index-concentration conversion expression. Therefore, since the solute contained in the solution is determined in practice, the refractive index-concentration conversion expressions may be determined in advance for different solutes.
Therefore, the step of detecting the concentration of the plating solution using the concentration detection system of the present invention specifically includes the following steps S1-S5.
And S1, connecting the measuring laser into a 50/50 coupler, dividing the measuring laser into two paths of sub-measuring lasers, emitting the sub-measuring lasers outwards to form light paths respectively, arranging a reflector in one light path, and arranging a cuvette in the other light path.
Step S2, the electroplating solution with known solute but unknown concentration is sampled and placed into the cuvette 6, one path of measuring laser is reflected by the reflector 5 to generate a reference light signal, the other path of measuring laser is refracted by the cuvette 6 and the electroplating solution in the cuvette 6 to generate a detection light signal, and the reference light signal and the detection light signal form light interference by adjusting the position of the cuvette 6 or the reflector 5 to generate an interference laser signal.
Step S3, the interference laser signal is converted into a corresponding target voltage signal by the balance detector 32.
As shown in fig. 2, the balanced detector 32 converts the detection light signal and the reference light signal into corresponding voltage signals through a photodiode, and then performs summation operation on the two voltage signals by using an operational amplifier, so as to output a target voltage signal corresponding to the interference laser signal at an output end of the operational amplifier.
And step S4, determining the maximum voltage amplitude of the target voltage signal, and calculating the refractive index of the electroplating solution by using the maximum voltage amplitude of the target voltage signal.
And step S5, according to the solute of the electroplating solution, a refractive index-concentration conversion expression corresponding to the electroplating solution is established in advance, and the concentration of the electroplating solution is calculated according to the refractive index of the electroplating solution by using the refractive index-concentration conversion expression.
The process of determining the expression for the refractive index-concentration conversion is further described by taking as an example the plating solution required for nickel plating of the punched steel strip. Wherein the electroplating solution required by the nickel plating of the punched steel strip is HBO3、NiCl2And NiSO4Composition, wherein the reference standard for each solution is HBO3The concentration is 30 +/-5 g/L, NiSO4The concentration is 300 +/-10 g/L, NiCl2The concentration of (b) is 30. + -.5 g/L. The following description is made fully in terms of single solution concentration and mixed solution, respectively.
(1) For single solute NiSO4The electroplating solution is detected, and a corresponding refractive index-concentration conversion expression is determined, wherein the steps are as follows:
step 1.1, first use NiSO4And distilled water were added to prepare a plurality of plating solutions of known concentrations at 5g/L, 10g/L, 15g/L, 20g/L, 25g/L and 30g/L, respectively.
Step 1.2, respectively detecting a plurality of electroplating solutions with known concentrations by using a rapid concentration detection system to obtain a target voltage signal which is generated when each electrolytic solution is detected and is converted correspondingly to an interference laser signal, then, under the premise of carrying out noise reduction processing on the interference voltage signal, for example, taking 5g/L electrolytic solution as an example, a data processing device 8 obtains the target voltage signal corresponding to the laser interference signal when 5g/L electrolytic solution is detected from an oscilloscope 7, and carries out mean value filtering and noise reduction processing on the target voltage signal to obtain a waveform (the abscissa represents time, the unit ms, the ordinate represents voltage, and the unit V) with at least 5 periods as shown in FIG. 3; then, a maximum value is obtained after further curve fitting, and the maximum value is determined as the maximum voltage amplitude of the target voltage signal, for example, in the case of 5g/L of the electrolytic solution, the average value of the maximum values is determined as the maximum voltage amplitude of the electrolytic solution of 5g/L for each of the waveforms of at least 5 cycles shown in fig. 3.
Step 1.3, the refractive index corresponding to each electrolytic solution was calculated according to the above description, as shown in table 2 below.
TABLE 2 refractive index measurement data for NiSO4 solution
Step 1.4, performing linear fitting on the given concentration of each electrolytic solution in table 2 and the refractive index obtained by experimental calculation by adopting a sinusoidal curve superposition approximation method, as shown in fig. 4 (the abscissa represents the mass of sugar in each liter of solution, the unit is g/L, and the ordinate represents the refractive index), and finally obtaining a refractive index-concentration conversion expression of the sugar solution, wherein the refractive index-concentration conversion expression is as follows:
n3＝0.0019c1+1.3281 (21)
in the formula n3Denotes NiSO4Refractive index of solution, c1Denotes NiSO4The concentration of the solution.
Wherein, NiSO4The solution concentration vs. refractive index is a straight line with a slope of 0.0019 and a longitudinal intercept of 1.3284, so when NiSO4When the solution concentration was 0, the refractive index was 1.3284, which was consistent with the refractive index 1.3280 of distilled water, indicating that the accuracy of the fitted formula (21) was high.
The refractive index measured in table 2 is taken as an example. The relationship between the maximum value of the interference signal voltage and the refractive index obtained by combining the equations (20) and (21) is as follows
Can utilize NiSO4Solving NiSO by maximum value of solution interference signal4The concentration of the solution, so the maximum value of the interference signal in Table 2 is substituted into the formula (22) to calculate the NiSO4The detected concentration of the solution is shown in the third column of table 3.
TABLE 3 comparison of the given concentration to the measured concentration of the NiSO4 solution
As can be seen from Table 3, for NiSO4The detection of the concentration of the solution is realized, and when the concentration is within the range of 0-30g/L, the detection error isWithin 1.32%, the error is less than 3% of the detection error of the chemical titration method adopted in the industrial field, and the industrial requirement is met.
(2) And detecting the electroplating solution mixed with the solute, and determining a corresponding refractive index-concentration conversion expression, wherein the steps are as the steps 1.1 to 1.4. Only differences or points of emphasis are described:
first, HBO is preset3And NiSO4The concentration of (a) is 31g/L and 300g/L respectively, and NiCl is recycled2Preparing NiCl with distilled water2The solubility of the electrolyte is respectively 30g/L, 40g/L, 50g/L, 60g/L and 70g/L, and the electrolytic solutions with known concentrations are measured to finally obtain NiCl in each part of the electrolytic solution2The refractive index of the solution is shown in table 4.
TABLE 4 NiCl in each plating bath2Refractive index detection data of
NiCl in Table 42Carrying out linear fitting on the solution concentration and the detected refractive index to obtain NiCl2The relationship between the solution concentration and the refractive index, as shown in fig. 5 (abscissa represents mass of sugar per liter of solution, unit g/L, and ordinate represents refractive index), the refractive index-concentration conversion expression of the finally obtained sugar solution is:
n4＝0.0005c2+1.5974 (23)
in the formula n4Represents NiCl2Refractive index of solution, c2Represents NiCl2The concentration of the solution.
From the formula (23), NiCl in the fitted mixed plating solution2The solution concentration versus refractive index is a straight line with a slope of 0.0005 and a vertical intercept of 1.594.
Further combining the formulas (2) and (23) can obtain
Thus, according to equation (24), NiCl may be utilized2Solution NiCl is solved according to maximum voltage amplitude value of target voltage signal corresponding to interference laser signal of solution2The concentration of the solution, so the maximum value of the interference signal in Table 4 is substituted into the formula (24) to obtain NiCl2The concentration of the solution is shown in the second column (column) of Table 5.
TABLE 6 test data for NiCl2 concentration in the plating bath at points
As can be seen from Table 5, NiCl in a mixed plating bath is provided by the method of the present invention2In concentration detection, when the concentration range is 30-70g/L, the detection error is within 2.03 percent, and the error is less than 3 percent of the detection error of a chemical titration method adopted in an industrial field, thereby meeting the industrial requirement.
Therefore, for a scene requiring real-time detection of the solution concentration in actual production, it is often necessary to quickly and accurately detect the concentration of the solution when the composition of the solution is known (i.e., the solute of the solution is determined) but the solution concentration is unknown (e.g., the solution concentration is continuously consumed in the actual production process, so that the concentration of the solution is continuously changed), and therefore, the refractive index-concentration conversion expression only needs to be pre-established in the data processing device 8 according to the solute composition of the electroplating solution. In the actual test, the corresponding refractive index-concentration conversion expression may be selected in step S5 according to the solute composition of the plating solution.
Therefore, the concentration of the obtained electroplating solution can be automatically and quickly detected, the detection is quick and accurate, the method has the advantages of simplicity and convenience in operation, accurate measurement and the like, is quick and non-contact real-time detection, provides accurate reference basis for timely adjusting and optimizing the electroplating solution or electroplating process parameters, and is favorable for improving the electroplating process efficiency.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims (8)
1. A concentration detection system for an electroplating solution, comprising:
DFB laser for generating a known light intensity I0The measuring laser of (1);
50/50 coupler for dividing the measuring laser into two paths of measuring laser to emit outwards to form light paths respectively;
a reflector with a second preset distance is arranged between the first collimating lens in one of the light paths and the 50/50 coupler, wherein one path of measuring laser is reflected by the reflector to generate a reference light signal, and the reference light signal is returned to the 50/50 coupler through the first collimating lens;
the second collimating mirror and the cuvette used for containing the electroplating solution are arranged in the other light path, and the other path of sub-measurement laser generates a detection light signal after being refracted and reflected by the cuvette and the electroplating solution in the cuvette, so that the detection light signal returns to the 50/50 coupler through the second collimating mirror, wherein a second preset distance is reserved between the cuvette and the 50/50 coupler, so that the detection light signal can form light interference with the reference light signal;
the balance detector is used for forming optical interference between the reference optical signal and the detection optical signal to generate an interference laser signal and converting the interference laser signal into a target voltage signal;
the oscilloscope is used for acquiring parameters of the target voltage signal and displaying the waveform of the target voltage signal;
data processing means for determining the maximum voltage amplitude U of the target voltage signalmTo calculate the refractive index n of the electroplating solution30Calculating the concentration of the electroplating solution according to a refractive index-concentration conversion expression which is pre-established and corresponds to the electroplating solution;
wherein the data processing device utilizes the maximum voltage amplitude U of the target voltage signalmThe refractive index n of the plating solution is calculated according to the following formula30：
K is a predetermined coefficient for converting current to voltage by the balance detector, K1For balancing the predetermined coefficient of conversion of the light intensity of the detector 32 into optical power, I1Representing the light intensity of the reference light signal, I1＝I0/2，K2Representing the attenuation constant of the intensity of one of the sub-beams, n10Is the refractive index of air, n20Is the refractive index of the cuvette and r is the responsivity of the equilibrium detector.
2. The system for detecting the concentration of an electroplating solution according to claim 1, wherein the data processing device specifically comprises:
the interface unit is connected with the oscilloscope to acquire a target voltage signal from the oscilloscope;
the curve fitting module is used for carrying out nonlinear curve fitting on the target voltage signal superposition of at least 5 continuous periods to obtain a curve equation;
the extreme value calculation module is used for solving the maximum values of the curve equation in each period and determining the average value of the maximum values of at least 5 periods as the maximum voltage amplitude of the interference voltage signal;
the database is used for prestoring a refractive index-concentration conversion expression of the electroplating solution;
and the concentration calculation module is used for calculating the concentration of the electroplating solution according to a refractive index-concentration conversion expression which is predetermined and corresponds to the electroplating solution in the database.
3. The concentration detection system for electroplating solution according to claim 2, wherein the data processing apparatus further comprises:
and the noise reduction processing module is arranged between the interface unit and the curve fitting module and is used for carrying out noise reduction processing on the interference voltage signal by adopting mean value filtering.
4. The concentration detection system for electroplating solution according to claim 2, wherein the curve fitting module is configured to perform nonlinear curve fitting on the parameters of the target voltage signal by using a sine curve superposition approximation method to obtain a curve equation.
5. The system of claim 3, wherein the pre-establishing of the refractive index-concentration conversion expression corresponding to the plating solution in the database comprises:
taking solute same as the electroplating solution to respectively prepare a plurality of known solutions with given concentration;
and respectively detecting each known solution, calculating the corresponding refractive index of each known solution by a data processing device according to the target electrical signal corresponding to the interference laser signal of each known solution, and performing linear fitting according to the given concentration of each known solution and the refractive index obtained by corresponding calculation to generate a refractive index-concentration conversion expression.
6. The concentration detection system for an electroplating solution according to claim 1, wherein the measurement laser is a non-visible laser having a central wavelength of 1310 nm.
7. The concentration detection system for an electroplating solution according to claim 6, further comprising a red laser configured to generate a macroscopic red laser to the 50/50 coupler using the red laser to assist in determining the second predetermined distance between the cuvette and the 50/50 coupler while using the DFB laser, provided that the first predetermined distance between the mirror and the 50/50 coupler is determined.
8. The concentration detection system for electroplating solution according to claim 1, wherein the DFB laser is connected to the 50/50 coupler via an optical fiber, the 50/50 coupler is connected to the first collimating mirror and the second collimating mirror via optical fibers, and the 50/50 coupler is connected to the balanced detector via optical fibers.
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Application publication date: 20200626 Assignee: CHANGDE JINGWEI CRADLE TECHNOLOGY CO.,LTD. Assignor: HUNAN University OF ARTS AND SCIENCE Contract record no.: X2023980036949 Denomination of invention: Concentration detection system for electroplating solutions Granted publication date: 20220923 License type: Common License Record date: 20230625 |