A method for characterizing the relative content level of additive byproducts in copper electroplating solution and its application

Abstract

This invention discloses a method for characterizing the relative content level of additive by-products in copper electroplating solutions and its application. The copper electroplating solution includes copper sulfate and additives. The characterization method includes the following steps: i. By testing the ultraviolet absorption spectrum curves of copper sulfate solutions of different concentrations at wavelengths of 320-400 nm, the functional relationship W between the copper sulfate concentration and the area of ​​the absorption spectrum curve is obtained; ii. Based on the copper sulfate concentration in the copper electroplating solution to be tested, the area S1 of the theoretical absorption spectrum curve of the copper electroplating solution to be tested is calculated using the functional relationship W, and then the area S2 of the actual absorption spectrum curve of the copper electroplating solution to be tested is measured. The difference between S1 and S2 is calculated as ΔS, and the relative content level of additive by-products in the copper electroplating solution is determined based on ΔS. This testing method is easy to operate, simple, and efficient, and can provide effective guidance for the normal production and maintenance of pulse electroplating lines, especially suitable for the printed circuit board industry.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology, specifically relating to a method for characterizing the relative content level of additive by-products in copper electroplating solutions and its application. Background Technology

[0002] During pulse electroplating, organic additives in the copper plating solution are prone to decomposition reactions under energized conditions, generating byproducts. As plating time increases, these byproducts accumulate, and when their content reaches a certain level, they adversely affect the deep plating capability of high aspect ratio holes on printed circuit boards, even directly impacting product reliability. The industry commonly uses carbon core filtration and carbon treatment methods to periodically purify the plating solution and reduce the content of byproducts.

[0003] Currently, monitoring the content of additive by-products in copper electroplating solutions is a challenge for the industry. Studies have shown that combining solid-phase extraction and high-performance liquid chromatography can effectively determine the content of additive by-products in copper electroplating solutions, but these methods are complex to operate and costly, making them unsuitable for the printed circuit board industry. Summary of the Invention

[0004] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for characterizing the relative content level of additive by-products in copper electroplating solutions, which is characterized by its simple operation.

[0005] The present invention also proposes the application of the above characterization method.

[0006] In a first aspect, the present invention provides a method for characterizing the relative content level of additive by-products in a copper electroplating solution, wherein the copper electroplating solution comprises copper sulfate and additives, and the characterization method comprises the following steps:

[0007] i. By testing the ultraviolet absorption spectrum curves of copper sulfate solutions of different concentrations at wavelengths of 320-400 nm, the functional relationship W between the copper sulfate concentration and the area of ​​the absorption spectrum curve was obtained.

[0008] ii. Based on the concentration of copper sulfate in the copper plating solution to be tested, the area S1 of the theoretical absorption spectrum curve of the copper plating solution to be tested is calculated through the functional relationship W. Then, the area S2 of the actual absorption spectrum curve of the copper plating solution to be tested is measured, and the difference between S1 and S2 is calculated as ΔS. Based on ΔS, the relative content level of additive by-products in the copper plating solution is determined.

[0009] The method for characterizing the relative content level of additive by-products in copper electroplating solution according to embodiments of the present invention has at least the following beneficial effects: The present invention characterizes the relative content level of additive by-products in copper electroplating solution by the difference in the area of ​​ultraviolet absorption spectrum curves. It is easy to operate, simple and efficient, and can provide effective guidance for the normal production and maintenance of pulse electroplating lines, especially suitable for the printed circuit board industry.

[0010] At wavelengths of 320-400 nm, changes in the concentrations of inorganic components and organic additives (if the organic additives contain copper sulfate, then the components other than copper sulfate) in the electroplating solution do not cause changes in the spectral curves within this wavelength range. Therefore, the characterization method of this invention is accurate and reliable.

[0011] This invention uses the functional relationship W and the difference between the area S1 of the theoretical absorption spectrum curve and the area S2 of the actual absorption spectrum curve of the copper electroplating solution to characterize the relative content level of additive by-products in the copper electroplating solution. This can effectively characterize the content of the by-products in the copper electroplating solution, thereby purifying the copper electroplating solution in a timely manner, reducing the content of the by-products, and improving the reliability of the product.

[0012] In some embodiments of the present invention, step i includes the following steps:

[0013] S1-1, Prepare copper sulfate standard solutions of different concentrations;

[0014] S1-2, using deionized water as a reference solution, the ultraviolet absorption spectra of copper sulfate standard solutions of different concentrations prepared in step S1-1 in the 320-400 nm wavelength range were measured using an ultraviolet spectrophotometer.

[0015] S1-3: Calculate the area of ​​the ultraviolet absorption spectrum curve corresponding to each concentration in step S1-2 using integration, and obtain the functional relationship W between the copper sulfate concentration and the area of ​​the ultraviolet absorption spectrum curve.

[0016] In some preferred embodiments of the present invention, the copper sulfate concentration is expressed as copper sulfate pentahydrate concentration, and the copper sulfate standard solution includes copper sulfate standard solutions with copper sulfate pentahydrate concentrations of 20 g / L, 40 g / L, 60 g / L, and 80 g / L.

[0017] In some embodiments of the present invention, in the characterization method, the copper sulfate concentration is expressed as copper sulfate pentahydrate concentration, and the copper sulfate pentahydrate concentration has a linear relationship with the area of ​​the absorption spectrum curve in the range of 20-80 g / L.

[0018] In some embodiments of the present invention, the copper sulfate concentration is expressed as the concentration of copper sulfate pentahydrate, and the functional relationship W is y = ax + b, where y is the area of ​​the absorption spectrum curve and x is the concentration of copper sulfate pentahydrate.

[0019] In some preferred embodiments of the present invention, the functional relationship W is y = 0.0214x + 0.3848, where the unit of x is g / L.

[0020] In some preferred embodiments of the present invention, in the functional relationship W, the coefficient of determination R 2 It is approximately 0.9921.

[0021] In some embodiments of the present invention, in step ii, the method for testing the concentration of copper sulfate in the copper plating solution to be tested includes at least one of ultraviolet spectrophotometry or titration.

[0022] In some embodiments of the present invention, the copper plating solution is a pulsed copper plating solution.

[0023] In some embodiments of the present invention, the additive is at least one of a brightener or a wetting agent.

[0024] When the copper plating solution is a pulsed copper plating solution, the additives mainly include two categories: brighteners (also known as accelerators) and wetting agents (also known as carriers or inhibitors), and also contain halide ions (such as chloride ions).

[0025] Among them, brighteners, wetting agents and Cl - It also promotes copper electrodeposition, and within a certain range, the promoting effect is enhanced as the concentration of brightener increases.

[0026] Wetting agents are usually large molecular weight polyol compounds (such as polyethylene glycol, PEG), which decompose into smaller molecular weight polyol compounds during electroplating.

[0027] Brighteners are typically organic compounds containing disulfide bonds (such as sodium polydisulfide dipropane sulfonate, SPS). Their decomposition byproducts are oxides of disulfide bonds. The decomposition of brighteners produces various, sometimes unstable, byproducts with different oxidation states, including sulfoxides (monoxides), sulfinates (dioxides), or sulfonates (trioxides). Although these byproducts lose their accelerating effect, they still have adsorption properties, competing with the brightener for adsorption in the pores, leading to reduced brightener adsorption and decreased deep plating capability. (See reference...) Figure 1-3 :in Figure 1 It contains no byproducts, including brighteners, wetting agents, and Cl. - Adsorption diagram, Figure 2 This diagram illustrates the competitive adsorption of brighteners and byproducts. Figure 3A schematic diagram showing how byproducts of brightener decomposition hinder the accelerating effect of the brightener.

[0028] In some embodiments of the present invention, the additive content in the copper electroplating solution is 0.5-31.5 mL / L.

[0029] In some preferred embodiments of the present invention, the additive includes a wetting agent, which is a solution containing polyethylene glycol, and the content of the wetting agent in the copper electroplating solution is 10-30 mL / L.

[0030] In some preferred embodiments of the present invention, the mass fraction of polyethylene glycol in the wetting agent is 8-12%.

[0031] In some preferred embodiments of the present invention, the additive includes a brightener, which is a solution containing sodium polydithiopropane sulfonate, and the brightener content in the copper electroplating solution is 0.5-1.5 mL / L.

[0032] In some more preferred embodiments of the present invention, the sodium polydithiopropane sulfonate has a mass fraction of 6-8% in the brightener.

[0033] In a second aspect, the present invention proposes the application of the above-described characterization method in determining the hole depth plating capability or the purification effect of copper plating solution.

[0034] In some embodiments of the present invention, the application is in the determination of hole depth plating capability, including the following steps: determining the hole depth plating capability of the copper electroplating solution based on ΔS combined with the plate thickness and thickness-to-diameter ratio of the plated part.

[0035] Based on the relative content level of the additive byproducts, the hole depth plating capability of the copper plating solution for parts with different thickness-to-diameter ratios can be determined. The relative content level of byproducts can be determined based on ΔS, thus determining the degree of side reactions in the copper plating solution, and consequently, the hole depth plating capability of the copper plating solution for parts with different thickness-to-diameter ratios.

[0036] In some embodiments of the present invention, the application is in the determination of the purification effect of copper electroplating solution, including the following steps: determining the purification effect of the copper electroplating solution based on the relative content level of the additive by-products.

[0037] In some preferred embodiments of the present invention, the purification effect is the effect of purifying the copper electroplating solution by means of carbon core filtration or carbon treatment.

[0038] In some more preferred embodiments of the present invention, the application includes the following step: determining the purification capacity of different types of carbon cores for copper electroplating solutions based on the relative content level of the additive by-products.

[0039] In some embodiments of the present invention, the application is in the determination of hole depth plating capability. The determination criteria for hole depth plating capability include: when the plate thickness is 3.5 mm, the thickness-to-diameter ratio is 18:1 and ΔS≥16, the hole depth plating capability of the copper electroplating solution is determined to be reduced.

[0040] In some embodiments of the present invention, the judgment criteria further include determining that the hole depth plating capability of the copper electroplating solution decreases when the plate thickness is 3.5 mm, the thickness-to-diameter ratio is 12:1 and ΔS≥19.

[0041] In a third aspect, the present invention proposes the application of the above-described characterization method in the preparation of printed circuit boards or in evaluating the production capacity of electroplating production lines.

[0042] In the printed circuit board industry, Total Organic Carbon (TOC) is commonly used to measure the content of byproducts from additives in electroplating solutions. Industry experience suggests that higher TOC indicates more byproducts. However, in reality, in a steady-state plating solution, the TOC content remains constant unless new organic matter is added or removed. Although the composition of the plating solution may change drastically due to various chemical reactions, the TOC measurement remains constant. Furthermore, fluctuations in the concentration of additives in the plating solution can also cause changes in TOC. The accumulation of decomposition products from brighteners and wetting agents leads to an increase in TOC. However, byproducts from brightener decomposition alone typically reduce the ability to achieve deep plating. Therefore, the TOC value cannot accurately reflect the actual situation of byproduct formation from additive decomposition. There is no clear intrinsic relationship between TOC growth and byproduct content; its correlation with electroplating performance is highly empirical.

[0043] This invention uses the functional relationship W to characterize the relative content level of additive byproducts in the copper plating solution by utilizing the difference between the area of ​​the theoretical absorption spectrum curve corresponding to the concentration of copper sulfate in the copper plating solution and the area of ​​the actual measured absorption spectrum curve of the copper plating solution. This can effectively characterize the content of the byproducts in the copper plating solution, thereby more accurately reflecting the actual production capacity of the production line.

[0044] In a fourth aspect, the present invention proposes the application of the above-described characterization method or the above-described application in electroplating. Attached Figure Description

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0046] Figure 1 It contains no byproducts, including brighteners, wetting agents, and Cl. - Adsorption diagram;

[0047] Figure 2 Schematic diagram showing the competitive adsorption of brightener and byproducts;

[0048] Figure 3 A schematic diagram showing how byproducts of brightener decomposition hinder the accelerating effect of brightener.

[0049] Figure 4 This is an absorption spectrum curve of copper sulfate pentahydrate standard solutions of different concentrations in Example 1 of the present invention;

[0050] Figure 5 This is a graph showing the functional relationship between the concentration of copper sulfate pentahydrate and the area of ​​the absorption spectrum curve in Example 1 of the present invention.

[0051] Figure 6 This is a characterization diagram of the relative content level of additive by-products in the copper electroplating solution in Example 1 of the present invention;

[0052] Figure 7 This is a graph showing the change in the content of additive by-products in the copper plating solution during a usage cycle in Example 2 of the present invention (the horizontal axis represents the cumulative relative usage time of the copper plating solution).

[0053] Figure 8 This is a graph showing the absorption spectrum of the copper electroplating solution at different times in the experimental examples of this invention.

[0054] Figure 9 The absorption spectrum curves of solutions 1-3 prepared in the experimental examples of this invention are shown below;

[0055] Figure 10 This is an absorption spectrum curve of additive A solutions at different concentrations in the experimental examples of this invention;

[0056] Figure 11 This is an absorption spectrum curve of additive B solutions at different concentrations in the experimental examples of this invention;

[0057] Figure 12 This is an absorption spectrum curve of sulfuric acid solutions with different volume fractions in the experimental examples of this invention;

[0058] Figure 13 This is an absorption spectrum curve of hydrochloric acid at different concentrations in the experimental examples of this invention. Detailed Implementation

[0059] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0060] In the examples and comparative examples, the copper electroplating solution refers to an electroplating solution in which additives were added before and during the electroplating process. The copper electroplating solution obtained through the electroplating production process includes brighteners and wetting agents, both of which are commercially available. The brightener is a solution containing sodium polydisulfide dipropane sulfonate, with a mass fraction of 6-8% and a mass fraction of copper sulfate of 0.3-0.5%. The wetting agent is a solution containing polyethylene glycol, with a mass fraction of 8-12% and a mass fraction of copper sulfate of 0.3-0.5%. Through dynamic replenishment of additives in the copper electroplating solution, the content of additives in the copper electroplating solution is achieved as follows: brightener content is 0.5-1.5 mL / L, and wetting agent content is 10-30 mL / L.

[0061] Example 1

[0062] This embodiment provides a method for characterizing the relative content level of additive by-products in copper electroplating solutions, including the following steps:

[0063] (I) Different masses of copper sulfate pentahydrate were dissolved in water to prepare standard solutions of copper sulfate pentahydrate with different concentrations. The concentrations of copper sulfate pentahydrate in the standard solutions were 20 g / L, 40 g / L, 60 g / L and 80 g / L, respectively.

[0064] (II) Using deionized water as a reference solution, determine the ultraviolet absorption spectra of copper sulfate pentahydrate standard solutions of different concentrations obtained in step (I) in the 320-400 nm wavelength range (e.g., ...). Figure 4 As shown), the area under the absorption spectra of copper sulfate pentahydrate standard solutions at 320-400 nm for different concentrations was calculated using integration. An x-y curve was then plotted between the area under the absorption spectra of different concentrations of copper sulfate pentahydrate standard solutions at 320-400 nm and their concentrations (e.g., ...). Figure 5 As shown in the figure, the corresponding relationship was established, and the standard equation for the area of ​​the absorption spectrum curves of different copper sulfate pentahydrate aqueous solutions was obtained: y = 0.0214x + 0.3848. Where y is the area of ​​the absorption spectrum curve of the measured copper sulfate pentahydrate standard solution in the 320-400 nm range, x is the concentration of copper sulfate pentahydrate in the sample (unit: g / L), and the coefficient of determination R0 is... 2 The value of 0.9921 indicates that copper sulfate pentahydrate exhibits good linearity within the range of 20-80 g / L, allowing for accurate calculation of its area under the curve. (Note: Values ​​measured by different types of quartz cuvettes and UV spectrophotometers may vary slightly.)

[0065] (III) Take a certain amount of the copper plating solution to be tested (the sample should be taken from the plating solution in the continuous production process to ensure the stability of its composition), and measure and analyze the concentration of copper sulfate pentahydrate in it. The measurement and analysis includes the following steps:

[0066] 1) Pipette 2.0 mL of the copper plating solution to be tested into a 250 mL Erlenmeyer flask;

[0067] 2) Add 50 mL of DI water;

[0068] 3) Add 20 mL of ammonia-ammonium chloride buffer solution with pH = 10;

[0069] 4) Add 3-5 drops of PAN indicator;

[0070] 5) Titrate the solution obtained in step 4) with 0.1 mol / L EDTA until the solution turns grass green;

[0071] 6) Calculated using the formula: CuSO4·5H2O (g / L) = 12.5 × V EDTA The concentration of copper sulfate pentahydrate was calculated to be 70.8 g / L.

[0072] By substituting the calculated concentration of copper sulfate pentahydrate into the standard equation obtained in step (II), the area of ​​the absorption spectrum curve of copper sulfate pentahydrate in the copper plating solution to be tested in the 320-400nm range can be determined.

[0073] (IV) Take a certain amount of the electroplating solution to be tested in a quartz cuvette, using deionized water as a reference solution. Scan the electroplating solution at a wavelength of 320-400 nm using a UV spectrophotometer to obtain the absorption spectrum curve. Integrate the curve area and use the difference ΔS between the area of ​​this curve and the area of ​​the copper sulfate pentahydrate curve in step (III) to characterize the relative content level of by-products of electroplating chemical additives (e.g., Figure 6 As shown): The area of ​​the actual absorption spectrum curve (the area of ​​the upper curve) is 14.2, the area of ​​the theoretical absorption spectrum curve (the area of ​​the lower curve) is y = 0.0214x + 0.3848 = 0.0214 × 70.8 + 0.3848 = 1.9, and the shaded area ΔS is 14.2 - 1.9 = 12.3.

[0074] Example 2

[0075] This embodiment provides the application of a method for characterizing the relative content level of additive by-products in copper electroplating solutions in electroplating, including:

[0076] By monitoring the area change of the absorption spectrum curve of the copper plating solution in the 320-400nm wavelength range within a usage cycle (30 days, or 14-30 days depending on production conditions), the following methods can be used to analyze the changes in the area of ​​the absorption spectrum curve of the copper plating solution within a usage cycle (e.g., ...). Figure 7As shown in the figure, its deep plating capability under different thickness-to-diameter ratios was found to be decreasing when ΔS (area) reaches 16, indicating that its deep plating capability for holes with a thickness of 3.5 mm and a thickness-to-diameter ratio of 18:1 begins to decline; when ΔS reaches 19, it indicates that its deep plating capability for holes with a thickness of 3.5 mm and a thickness-to-diameter ratio of 12:1 begins to decline.

[0077] After purifying the plating solution through a certain degree of carbon core filtration (or carbon treatment), the relative content of by-products will decrease to some extent. When the measured ΔS drops below 19, it indicates that the content of by-products is relatively low, and its ability to deep-plate holes with a thickness of 3.5mm and an aspect ratio of 12:1 returns to normal. When the measured ΔS drops below 16, it indicates that the content of by-products is further reduced, and its ability to deep-plate holes with a thickness of 3.5mm and an aspect ratio of 18:1 also returns to normal.

[0078] Take a sample of the copper electroplating solution to be tested from the production line, and determine the relative content level of its additive byproducts according to the characterization method in Example 1. If the calculated ΔS is 14 (<16), according to the results above in this example, the electroplating production line can normally produce printed circuit boards with a thickness of 3.5mm and an aspect ratio of 18:1 or less. If the calculated ΔS is 17 (<19), the electroplating production line can normally produce printed circuit boards with a thickness of 3.5mm and an aspect ratio of 12:1 or less. If it is necessary to normally produce printed circuit boards with a thickness of 3.5mm and an aspect ratio of 18:1, the copper electroplating solution still needs to be further purified so that ΔS is reduced to below 16 before normal production can begin.

[0079] Example 3

[0080] This embodiment provides the application of a method for characterizing the relative content level of additive by-products in copper electroplating solutions in electroplating, including: evaluating the effect of different brands of carbon cores on purifying copper electroplating solutions, wherein the relative content level of additive by-products in the copper electroplating solution is determined according to the characterization method in Example 1, and the copper electroplating solutions treated with carbon cores of brands A and B are the same. Specifically, it includes:

[0081] Using brand A carbon cores to treat copper electroplating solution: the measured ΔS before treatment was 19.2, and after treatment was 13.2. Using brand B carbon cores to treat the electroplating solution: the measured ΔS before treatment was 19.2, and after treatment was 15.3. This indicates that brand A carbon cores are more effective at purifying the electroplating solution and have better adsorption performance for byproducts.

[0082] Practical verification has shown that the performance of copper electroplating solution purified by using brand A carbon core is superior to that purified by using brand B carbon core.

[0083] Therefore, by using the characterization method of the relative content level of additive by-products in the copper electroplating solution of the present invention, the purification effect of the copper electroplating solution can be determined, and further, the purification capacity of different types of carbon cores for the copper electroplating solution can be determined.

[0084] Example 4

[0085] This embodiment provides the application of a method for characterizing the relative content level of additive by-products in copper electroplating solutions in electroplating. The characterization method for the copper electroplating solution is the same as in Embodiment 1, specifically including:

[0086] During continuous production, after a period of use (T1), the copper plating solution's ability to deeply plate printed circuit boards with a thickness of 3.5mm and a thickness-to-diameter ratio of 18:1 decreased. The copper plating solution was tested for the first time: the copper plating solution at this time was taken as sample 1, and the measured ΔS (area) of sample 1 was 17.1.

[0087] After the first carbon core filtration maintenance, the copper plating solution was tested for the second time: the copper plating solution at this time was taken as sample 2, and the measured △S (area) of sample 2 was 11.2, indicating that the deep plating ability was restored.

[0088] After continuing production for a period of time (T2), the deep plating capacity decreased again. A third test was conducted on the copper plating solution: the copper plating solution at this time was taken as sample 3, and the measured ΔS (area) of sample 3 was 17.4.

[0089] After the second carbon core filtration maintenance, the copper plating solution was tested for the fourth time: the copper plating solution at this time was taken as sample 4, and the measured △S (area) of sample 4 was 11.4, indicating that the deep plating ability was restored.

[0090] Both T1 and T2 are 30 days. In addition, depending on the production situation, both T1 and T2 can be 14-30 days.

[0091] Comparative Example 1

[0092] This comparative example discloses the application of a characterization method for the relative content level of additive by-products in copper electroplating solutions in electroplating. To compare the accuracy of traditional characterization methods reflecting changes in the content of additive by-products in copper electroplating solutions with the characterization method of this invention, this comparative example uses a traditional characterization method to test and characterize samples 1-4 in Example 4. The traditional characterization method used is to reflect the change in the content of additive by-products in the copper electroplating solution by testing the TOC (Total Organic Carbon) of the copper electroplating solution. The test results are as follows:

[0093] First test: The TOC in sample 1 was measured to be 3212 ppm;

[0094] Second test: The TOC in sample 2 was measured to be 2932 ppm;

[0095] Third test: The TOC in sample 3 was measured to be 4025 ppm;

[0096] Fourth test: The TOC in sample 4 was measured to be 3743 ppm.

[0097] The test results for Example 4 and Comparative Example 1 are detailed in Table 1:

[0098] Table 1. Comparison of test results between Example 4 and Comparative Example 1

[0099]

[0100]

[0101] A comparison of the test data from Example 4 and Comparative Example 1 shows that the characterization method for the relative content level of additive by-products in the copper electroplating solution used in this invention can more accurately reflect the content of additive by-products in the copper electroplating solution and more accurately reflect the actual production capacity of the production line. Specifically, compared with the first test, TOC increased in Comparative Example 1 in the fourth test, but the deep plating capacity was normal, and ΔS (area) can accurately represent the state of deep plating capacity.

[0102] In addition, to further verify the reliability of the characterization method for testing the relative content level of additive by-products in the copper electroplating solution of the present invention, the following experiments were conducted:

[0103] (I) Using an ultraviolet spectrophotometer, the spectral curves of the pulsed copper plating solution in the wavelength range of 320-400 nm were measured to show different characteristics at different usage times. The spectral curves of the pulsed copper plating solution at the beginning, middle, and end of a maintenance cycle were tested. Detailed test results can be found in [link to test results]. Figure 8 ,in, Figure 8 The display shows the spectral curve of the electroplating solution's entire cycle life, which is 6 months. The early, middle, and late stages represent the 1st, 3rd, and 5th months, respectively.

[0104] (II) The study investigated the differences in the spectral curves of organic and inorganic components in the copper electroplating solution. Additive A was a wetting agent, specifically a solution containing polyethylene glycol, with a mass fraction of 8-12% for polyethylene glycol and 0.3-0.5% for copper sulfate. Additive B was a brightener, specifically a solution containing sodium didithiopropane sulfonate, with a mass fraction of 6-8% for sodium didithiopropane sulfonate and 0.3-0.5% for copper sulfate.

[0105] 1) Based on the composition of the copper electroplating solution, solutions 1-3 were prepared:

[0106] Solution 1: Inorganic components of copper electroplating solution + organic additives A and B;

[0107] Preparation of Solution 2: Inorganic components in copper electroplating solution;

[0108] Preparation of solution 3: Inorganic components of copper electroplating solution excluding copper sulfate;

[0109] In solution 1, organic additive A is added to the copper plating solution at a rate of 15 mL / L, and organic additive B is added to the copper plating solution at a rate of 1.0 mL / L.

[0110] The spectral curves of solutions 1-3 in the wavelength range of 320-400 nm were obtained using a UV spectrophotometer. Figure 9 .Depend on Figure 9 It can be seen that, in copper electroplating solutions, the inorganic components other than copper sulfate exhibit extremely weak ultraviolet absorption. It should be noted that organic additives A and B are commercially available and contain small amounts of copper sulfate; therefore, Figure 9 The absorbance of "inorganic components of copper electroplating solution + organic additives A and B" is slightly greater than that of "inorganic components of copper electroplating solution". The difference in absorbance is caused by the small amount of copper sulfate contained in organic additives A and B.

[0111] 2) Using water as a solvent, solutions of additives A and B at different concentrations, as well as sulfuric acid with different volume fractions and hydrochloric acid of different concentrations, were prepared. Their spectral curves in the wavelength range of 320-400 nm were then measured. Detailed test results can be found in [link to test results]. Figure 10-13 Specifically, this includes:

[0112] Prepare additive A solutions with concentrations of 10 mL / L, 20 mL / L, and 30 mL / L;

[0113] Prepare additive B solutions with concentrations of 0.5 mL / L, 1.5 mL / L, and 2.5 mL / L;

[0114] Prepare sulfuric acid solutions with volume fractions of 10%, 15%, and 20% respectively;

[0115] Prepare hydrochloric acid solutions with concentrations of 40 ppm, 60 ppm, and 80 ppm.

[0116] Depend on Figure 9-13 It can be seen that, apart from copper sulfate, changes in the concentration of other inorganic components and organic additives A and B in the copper electroplating solution do not cause changes in the spectral curve within this wavelength range. The present invention is ingeniously conceived and the data is reliable.

[0117] In summary, this invention employs a simple ultraviolet spectrophotometric test, characterizing the relative content of additive byproducts in copper electroplating solutions by the difference in the area of ​​the absorption spectral curves. This method is easy to operate, simple, and efficient. Furthermore, by using the difference in the area of ​​the absorption spectral curves, it enables the determination of the hole depth plating capability for workpieces with different aspect ratios, as well as the assessment of the purification effect of the copper electroplating solution, thereby determining the purification capability of different types of carbon cores for copper electroplating solutions. The characterization method described in this invention can be applied to printed circuit board manufacturing and electroplating production line capacity assessment, providing effective guidance for the normal production and maintenance of pulse electroplating lines, and is particularly suitable for the printed circuit board industry.

[0118] It should be noted that the term "approximately" in the numerical values ​​used in this article means an error of ±2%.

[0119] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for characterizing the relative content level of additive by-products in copper electroplating solution, characterized in that, The copper electroplating solution comprises copper sulfate and additives, wherein the additives are at least one of brighteners or wetting agents; the characterization method comprises the following steps: i. By testing the ultraviolet absorption spectrum curves of copper sulfate solutions of different concentrations at wavelengths of 320-400 nm, the functional relationship W between the copper sulfate concentration and the area of ​​the absorption spectrum curve was obtained. ii. Based on the concentration of copper sulfate in the copper plating solution to be tested, the area S1 of the theoretical absorption spectrum curve of the copper plating solution to be tested is calculated through the functional relationship W. Then, the area S2 of the actual absorption spectrum curve of the copper plating solution to be tested is measured, and the difference between S1 and S2 is calculated as ΔS. Based on ΔS, the relative content level of additive by-products in the copper plating solution is determined. In the characterization method, the copper sulfate concentration is expressed as copper sulfate pentahydrate concentration, which is in the range of 20-80 g / L. The functional relationship W is y=0.0214x+0.3848, where y is the area of ​​the absorption spectrum curve, x is the copper sulfate pentahydrate concentration, and the unit of x is g / L.

2. The method for characterizing the relative content level of additive by-products in copper electroplating solution according to claim 1, characterized in that, In step ii, the method for testing the concentration of copper sulfate in the copper plating solution to be tested includes titration.

3. The method for characterizing the relative content level of additive by-products in copper electroplating solution according to claim 1, characterized in that, The copper plating solution is a pulsed copper plating solution.

4. The method for characterizing the relative content level of additive by-products in copper electroplating solution as described in claim 1 is applied to the determination of hole depth plating capacity or purification effect of copper electroplating solution.

5. The application according to claim 4, characterized in that, The application is in the determination of hole depth plating capability, and includes the following steps: The hole depth plating capability of the copper electroplating solution is determined based on ΔS combined with the plate thickness and thickness-to-diameter ratio of the plated part.

6. The application according to claim 4, characterized in that, The application is in the determination of the purification effect of copper electroplating solution, and includes the following steps: The purification effect of the copper electroplating solution is determined based on the relative content level of the additive by-products.

7. The application according to claim 4, characterized in that, The purification effect refers to the effect of purifying the copper electroplating solution using carbon core filtration or carbon treatment methods.

8. The application according to claim 4, characterized in that, The application includes the following steps: determining the purification capacity of different types of carbon cores for copper electroplating solutions based on the relative content level of the additive by-products.

9. The application according to claim 4, characterized in that, The application is in the determination of hole depth plating capability. The determination criteria for hole depth plating capability include: when the plate thickness is 3.5mm, the thickness-to-diameter ratio is 18:1 and ΔS≥16, the hole depth plating capability of the copper electroplating solution is determined to be reduced.

10. The application according to claim 9, characterized in that, The judgment criteria also include determining that the hole depth plating capability of the copper electroplating solution decreases when the plate thickness is 3.5 mm, the thickness-to-diameter ratio is 12:1 and ΔS≥19.

11. The method for characterizing the relative content level of additive by-products in the copper electroplating solution as described in claim 1 is used in the preparation of printed circuit boards or in evaluating the production capacity of electroplating production lines.

12. The characterization method according to any one of claims 1-3 or the application according to any one of claims 4-10 in electroplating.

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