A method for maintaining a pyrophosphate copper plating solution

Abstract

The application discloses a kind of pyrophosphate copper plating solution maintenance method, comprising the following steps: S1 first measure the copper ion concentration in pyrophosphate copper plating solution, then according to the required copper pyrophosphate concentration in pyrophosphate copper plating solution standard formula to supplement copper pyrophosphate;S2 first measure the pyrophosphate concentration in pyrophosphate copper plating solution treated in step S1, then according to the required mass ratio (P ratio) of pyrophosphate and copper ion in pyrophosphate copper plating solution standard formula to supplement potassium pyrophosphate, and by the supplement of potassium pyrophosphate, the pH of system is adjusted to 8.60-8.77;S3 according to the required pH value in pyrophosphate copper plating solution standard formula to add ammonia water in pyrophosphate copper plating solution treated in step S2 to carry out pH adjustment.The maintenance method of the application can make used pyrophosphate copper plating solution still be able to obtain qualified copper plating layer by maintenance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electroplating, more particularly to a maintenance method of a pyrophosphate copper plating solution. BACKGROUND

[0002] With the in-depth development of intelligent and interconnected technology, the selection and layout of low-loss and high-density electronic components become important technical issues. The creation of system-in-package (SIP) containing multiple ICs and passive components integrated into a package by using semiconductors has become a key innovation in the modern electronics field. SIP technology has been widely used in various industries, including consumer electronics, automobiles, aerospace and medical devices.

[0003] In addition to the integration mode of the module, the requirements for components in SIP technology are also different, and the process of component mounting is one of the typical differences. The implementation of the embedded type chip multilayer ceramic capacitor is a good solution. Chip multilayer ceramic capacitors (MLCC) are one of the most common components in various electronic products. Generally, since they are mainly used for surface mounting on PCBs, the electrodes of MLCC terminals are usually tin-plated copper layers. The embedded MLCC (copper terminal MLCC) is different from the conventional MLCC in that the terminal solder layer is a smooth, dense and non-oxidized copper-plated copper layer, which requires that the electroplating copper process be stable and efficient during electroplating copper.

[0004] Copper plating technology occupies an important position in surface plating technology. For a long time, cyanide copper plating has been the dominant method. However, due to its high toxicity and environmental pollution, people have gradually replaced cyanide copper plating with pyrophosphate copper plating, copper sulfate copper plating, HEDP copper plating and other copper plating processes. Among them, the pyrophosphate copper plating solution has simple composition and no toxicity, and does not require ventilation equipment. The main salt part is composed of copper pyrophosphate and potassium pyrophosphate, the solution is stable, the electroplating efficiency is high, and a relatively thick copper plating layer can be obtained. However, after the pyrophosphate copper plating solution is used for a period of time, the content of each component decreases, resulting in a non-compliant copper plating layer quality, a non-bright and smooth copper plating layer, pinholes and burning phenomenon, and a non-uniform color ranging from red to dark.

[0005] Therefore, it is of great significance to develop a maintenance method for pyrophosphate copper plating solution to maintain the quality of the copper plating layer. SUMMARY

[0006] The purpose of the present application is to solve the problems of the prior art and provide a maintenance method for a pyrophosphate copper plating solution.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:

[0008] The application provides a pyrophosphate copper plating solution maintenance method, which comprises the following steps:

[0009] S1. First, the copper ion concentration in the pyrophosphate copper plating solution is measured, and then the copper pyrophosphate is supplemented according to the required copper pyrophosphate concentration in the standard formula of the pyrophosphate copper plating solution;

[0010] S2. First, the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1 is measured, and then the potassium pyrophosphate is supplemented according to the required mass ratio (P ratio) of pyrophosphate and copper ions in the standard formula of the pyrophosphate copper plating solution, and the pH of the system is adjusted to 8.60-8.77 through the supplementation of potassium pyrophosphate;

[0011] S3. Ammonia is added in the pyrophosphate copper plating solution treated in step S2 for pH adjustment according to the required pH value in the standard formula of the pyrophosphate copper plating solution.

[0012] In the pyrophosphate copper plating solution maintenance method, the pH of the system is adjusted to 8.60-8.77 through the supplementation of potassium pyrophosphate, because if the pH of the system is less than 8.60, the subsequent ammonia addition amount will be too much, the pyrophosphate in the system will be hydrolyzed into orthophosphate, the finally obtained copper plating layer will be non-uniformly reddish and dark, the brightness of the copper plating layer is reduced, and the hole diameter on the copper plating layer is increased; if the pH of the system is greater than 8.77, the subsequent ammonia addition amount will be too little, the copper plating layer will be fogged, the copper plating layer will not be smooth and flat, the brightness of the copper plating layer is reduced, and the hole diameter on the copper plating layer is increased.

[0013] In the application, the quality qualification standard of the copper plating layer obtained by the pyrophosphate copper plating solution is that the copper plating layer is bright and flat, has no pinholes and scorching phenomenon, and is uniformly reddish and dark in color, or the brightness of the copper plating layer is greater than or equal to 85%, holes appear on the copper plating layer, and the diameter of the holes is less than or equal to 0.01 mm, or the brightness is greater than 80% but less than 85%, holes appear on the copper plating layer, and the diameter of the holes is less than or equal to 0.01 mm, that is, when the copper plating layer meets any one of the three requirements, the quality of the copper plating layer is considered to be qualified.

[0014] In the application, the P ratio refers to the mass ratio of pyrophosphate and copper ions.

[0015] Preferably, in step S1, the temperature when the copper pyrophosphate is supplemented is less than or equal to 55°C.

[0016] More preferably, in step S1, the temperature when the copper pyrophosphate is supplemented is 50-55°C.

[0017] Preferably, in step S2, the temperature when the potassium pyrophosphate is supplemented is less than or equal to 55°C.

[0018] More preferably, in step S2, the temperature when the potassium pyrophosphate is supplemented is 50-55°C.

[0019] The maintenance method of the pyrophosphate copper plating solution of the present application controls the concentration ≤55°C when the copper pyrophosphate and potassium pyrophosphate are supplemented, in order to prevent the pyrophosphate (copper pyrophosphate and potassium pyrophosphate) from hydrolyzing into orthophosphate at >55°C, which ultimately affects the quality of the copper plating layer.

[0020] Preferably, in step S3, the mass concentration of the ammonia water is 25-28%.

[0021] Preferably, the standard formula of the pyrophosphate copper plating solution contains copper pyrophosphate, potassium pyrophosphate, pyrophosphoric acid, and ammonia water (NH3·H2O).

[0022] More preferably, the standard formula of the pyrophosphate copper plating solution also contains at least one of the copper plating brighteners.

[0023] More preferably, the copper plating brightener is at least one of imidazole, thiazole, thiadiazole, and selenium dioxide.

[0024] Preferably, the pyrophosphate copper plating solution contains copper pyrophosphate, potassium pyrophosphate, pyrophosphoric acid, and ammonia water (NH3·H2O).

[0025] More preferably, the pyrophosphate copper plating solution also contains a copper plating brightener.

[0026] More preferably, the copper plating brightener is at least one of imidazole, thiazole, thiadiazole, and selenium dioxide.

[0027] More preferably, the concentration of the copper plating brightener is 4-5 mg / L.

[0028] Preferably, in step S1, the required concentration of copper pyrophosphate (Cu2P2O7) in the standard formula of the pyrophosphate copper plating solution is 85-100 g / L.

[0029] Preferably, in step S2, the mass ratio of the required pyrophosphate and copper ions (P ratio) in the standard formula of the pyrophosphate copper plating solution is 7.5-8.0.

[0030] More preferably, in step S2, the mass ratio of the required pyrophosphate and copper ions (P ratio) in the standard formula of the pyrophosphate copper plating solution is 7.75-7.90.

[0031] Preferably, the required concentration of potassium pyrophosphate (K4P2O7) in the standard formula of the pyrophosphate copper plating solution is 420-520 g / L.

[0032] Preferably, the required ammonia water concentration in the pyrophosphate copper plating solution standard formula is 50-80 mmol / L.

[0033] Preferably, the required pH in the pyrophosphate copper plating solution standard formula is 8.90.

[0034] Preferably, in step S1, the measurement method of the copper ion concentration in the pyrophosphate copper plating solution is:

[0035] The copper ion concentration in the pyrophosphate copper plating solution is measured by adding EDTA as a standard solution to the pyrophosphate copper plating solution for titration analysis using PAN [1-(2-pyridylazo)-2-naphthol] indicator.

[0036] More preferably, the titration end point of the titration analysis is the change of the solution from purple red to green.

[0037] Preferably, in step S2, the measurement method of the pyrophosphate concentration in the pyrophosphate copper plating solution is:

[0038] The pyrophosphate concentration in the pyrophosphate copper plating solution after step S1 is measured by adding zinc acetate as a standard solution to the pyrophosphate copper plating solution after step S1 to change the color of the PAN indicator, and then adding EDTA standard solution for back titration.

[0039] More preferably, the color change of the PAN indicator is from green to purple.

[0040] More preferably, the titration end point of the back titration is the change from purple to orange green.

[0041] Compared with the prior art, the present application has the following beneficial effects:

[0042] The maintenance method of the pyrophosphate copper plating solution of the present application realizes the maintenance of the pyrophosphate copper plating solution by first supplementing copper pyrophosphate, then supplementing pyrophosphate, and finally supplementing ammonia water, so that the used pyrophosphate copper plating solution can still produce qualified copper plating layer after maintenance. The maintenance method can make the pyrophosphate copper plating solution be used for a long time, which is beneficial to reduce production cost and improve production efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The figure is the relationship between the increased concentration (X) of ammonia water in the pyrophosphate copper plating solution and the pH value (Y) of the pyrophosphate copper plating solution after adding ammonia water.

[0044] Figure 2 The figure is the microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the pyrophosphate copper plating solution in Example 1 is subjected to copper plating treatment.

[0045] Figure 3 The microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution in Example 2.

[0046] Figure 4 The microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution in Comparative Example 2.

[0047] Figure 5 The microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution in Comparative Example 3. DETAILED DESCRIPTION

[0048] In order to better illustrate the purposes, technical solutions and advantages of the present application, the present application will be further described below in combination with specific examples.

[0049] In the maintenance method of the pyrophosphate copper plating solution in each embodiment and comparative example of the present application, when the pH of the pyrophosphate copper plating solution is adjusted to the required pH value in the standard formula of the pyrophosphate copper plating solution in step S3, the use relationship between the increased concentration of ammonia in the pyrophosphate copper plating solution and the pH value is Y = 8.58 + 0.05X, wherein X is the increased concentration of ammonia in the pyrophosphate copper plating solution, the unit is mmol / L, Y is the pH value of the pyrophosphate copper plating solution after adding ammonia (or the required pH value in the standard formula of the pyrophosphate copper plating solution), and 8.58 is the pH value of the pyrophosphate copper plating solution before adding ammonia.

[0050] The formula Y = 8.58 + 0.05X is obtained through the following experiment:

[0051] According to the standard formula of the pyrophosphate copper plating solution in Example 1, 1L of 97g / L copper pyrophosphate solution is first configured, then 2.8g of pyrophosphoric acid and 5mg of copper plating brightener imidazole are added, and then the pH is adjusted to 8.58 with potassium pyrophosphate. Then, while adding ammonia and calculating the increased concentration of ammonia in the system, the pH value is measured to obtain the X-Y relationship shown in the following figure: Figure 1 Then, through linear fitting, the use relationship between X and Y is Y = 8.58 + 0.05X.

[0052] Example 1

[0053] The present embodiment provides a maintenance method of a pyrophosphate copper plating solution, which comprises the following steps:

[0054] S1. The concentration of copper ions in the pyrophosphate copper plating solution is first measured, and then copper pyrophosphate is supplemented according to the required copper pyrophosphate concentration in the standard formula of the pyrophosphate copper plating solution, which is specifically as follows:

[0055] (1) Prepare 100 L of pyrophosphate copper plating solution according to the standard formula of the pyrophosphate copper plating solution and use it to plate copper on the inner-embedded MLCC for 12 h to obtain the pyrophosphate copper plating solution;

[0056] (2) Add water to the pyrophosphate copper plating solution to 100 L and mix uniformly to obtain the water-added pyrophosphate copper plating solution;

[0057] (3) Take 1 mL of the water-added pyrophosphate copper plating solution, add 100 mL of deionized water and 7 drops of PAN [1-(2-pyridylazo)-2-naphthol] indicator with a concentration of 0.02 g / L, at this time, the solution turns purple red. Titrate with 0.1 mol / L EDTA as the standard solution, the titration end point is that the solution changes from purple red to green, record the amount of EDTA used and calculate the copper ion concentration in the water-added pyrophosphate copper plating solution in step (2) to be 36 g / L;

[0058] (4) At 55°C, supplement 500 g of copper pyrophosphate to the water-added pyrophosphate copper plating solution in step (2) and stir to dissolve, so that the concentration of copper pyrophosphate in the system reaches the required copper pyrophosphate concentration in the standard formula of the pyrophosphate copper plating solution, at this time the copper ion concentration is 41 g / L, note that the concentration of copper pyrophosphate is not equal to the concentration of copper ion;

[0059] S2. First, measure the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1, then supplement potassium pyrophosphate according to the required mass ratio (P ratio) of pyrophosphate and copper ion in the standard formula of the pyrophosphate copper plating solution, and adjust the pH of the system to 8.60 by supplementing potassium pyrophosphate, as follows:

[0060] a. Take 1 mL of the pyrophosphate copper plating solution treated in step (4) in step S1, add 100 mL of deionized water, 7 drops of PAN [1-(2-pyridylazo)-2-naphthol] indicator with a concentration of 0.02 g / L, and 10 mL of 1 mol / L zinc acetate standard solution, mix well, at this time the PAN indicator changes from green to purple, boil and cool, then transfer into a 200 mL volumetric flask, dilute to volume, then take 100 mL, add 10 mL of ammonia-ammonium chloride buffer solution with pH = 10, titrate with 0.1 mol / L EDTA standard solution, the titration end point is that the solution changes from purple to orange green, record the amount of EDTA used and calculate the potassium pyrophosphate concentration in the pyrophosphate copper plating solution treated in step (4) in step S1 to be 425 g / L;

[0061] b. To the pyrophosphate copper plating solution treated by step (4) in step S1, 3500 g of potassium pyrophosphate was supplemented at 55°C, and the solution was stirred and dissolved until the P ratio in the system reached 7.75 required by the standard formula of the pyrophosphate copper plating solution, and at this time the pH of the system was 8.60, the concentration of copper pyrophosphate was 97 g / L, and the concentration of potassium pyrophosphate was 460 g / L;

[0062] S3. The pH of the pyrophosphate copper plating solution treated by step S2 was adjusted by adding ammonia water according to the pH required by the standard formula of the pyrophosphate copper plating solution, as follows:

[0063] The pH of the pyrophosphate copper plating solution treated by step b in step S2 was 8.60, and according to the formula Y = 8.58 + 0.05X, it was calculated that 100 L of pyrophosphate copper plating solution required 0.6 mol of ammonia water to adjust the pH to 8.90, i.e. (8.90-8.60) / (0.05) mmol / L x 100 L = 0.6 mol. Then the pH of the system was measured by a pH meter, and it was found that the pH reached 8.90 required by the standard formula of the pyrophosphate copper plating solution.

[0064] Wherein:

[0065] The standard formula of the pyrophosphate copper plating solution includes: 97 g / L of copper pyrophosphate, 460 g / L of potassium pyrophosphate, 2.80 g / L of pyrophosphoric acid, 67 mmol / L of ammonia water (NH3·H2O) (the concentration of solute ammonia water in the standard formula of the pyrophosphate copper plating solution is 67 mmol / L by adding 25% ammonia water), and 5 mg / L of copper plating brightener imidazole; the mass ratio of pyrophosphate to copper ions (P ratio) is 7.75, and the pH is 8.90.

[0066] Examples 2-3 and Comparative Examples 1-2

[0067] Examples 2-3 and Comparative Examples 1-2 provide different maintenance methods for pyrophosphate copper plating solutions, which differ from Example 1 in that the amount of potassium pyrophosphate supplemented in step S2 and the pH of the system after the addition of potassium pyrophosphate are different from the P ratio required by the standard formula of the pyrophosphate copper plating solution, the amount of ammonia water supplemented in step S3 and the pH of the system after the addition of ammonia water, and the rest is referred to Example 1, as shown in the following table:

[0068] Table 1 Experimental parameters of Examples 1-3 and Comparative Examples 1-2

[0069]

[0070]

[0071] Note: In the above table, the amount of ammonia water added in step S3 is achieved by adding ammonia water with a mass concentration of 25%.

[0072] Examples 4-6 and Comparative Example 3

[0073] Examples 4-6 and Comparative Example 3 provide different maintenance methods for the pyrophosphate copper plating solution, which differ from Example 1 in that the temperature at which the copper pyrophosphate is supplemented in step S1 and the temperature at which the potassium pyrophosphate is supplemented in step S2 are different, and the rest is referred to Example 1, as shown in the following table:

[0074] Table 2 Experimental parameters of Examples 1, 4-6 and Comparative Example 3

[0075]

[0076] Performance test

[0077] Take 15L of pyrophosphate copper plating solution treated by the maintenance method of each example or comparative example, add 520g steel balls and 520g zirconium oxide balls under the conditions of current 25A and speed 15r / min, then respectively plate 1000 pieces of internal embedded type MLCC, and use the 3D microscope of VR-6000 model of Gains to check the quality of the copper plated layer, and grade the quality of the copper plated layer;

[0078] Among them, the grading of the quality level of the copper plated layer is as follows:

[0079] “0 level” means that the copper plated layer is bright and smooth, without pinholes and burning phenomenon, and the color is uniformly reddish and dark;

[0080] “1 level” means that the brightness of the copper plated layer is ≥85%, and holes appear on the copper plated layer, and the diameter of the holes is ≤0.01mm;

[0081] “2 level” means that the brightness is ≥80% and <85%, and holes appear on the copper plated layer, and the diameter of the holes is ≤0.01mm;

[0082] “3 level” means that the brightness is ≥75% and <80%, and holes appear on the copper plated layer, and the diameter of the holes is ≤0.02mm;

[0083] “4 level” means that the brightness is ≥70% and <75%, and holes appear on the copper plated layer, and the diameter of the holes is ≤0.03mm;

[0084] “5 level” means that the brightness is ≥65% and <70%, and holes appear on the copper plated layer, and the diameter of the holes is ≤0.04mm;

[0085] The brightness is measured by the 3D microscope of VR-6000 model of Gains, and the brightness=(1-roughness)%;

[0086] The diameter of the hole was also directly measured by the 3D microscope of the model VR-6000 of Keyence;

[0087] It is worth noting that the greater the number of the quality grade of the copper plating layer is, the worse the quality of the copper plating layer is, and the quality grade of the copper plating layer is 0-2, which means that the quality of the copper plating layer is qualified;

[0088] The specific experimental results are shown as follows:

[0089] Table 3: Performance test results of each example and comparative example

[0090] Quality level of copper plating layer Whether the quality of copper plating layer is qualified Example 1 0 Yes Example 2 1 Yes Example 3 1 Yes Comparative Example 1 3 No Comparative Example 2 3 No Example 4 2 Yes Example 5 2 Yes Example 6 2 Yes Comparative Example 3 5 No

[0091] Figure 2 Figure 2 is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution of Example 1. Figure 3 Figure 3 is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution of Example 2. Figure 4 Figure 4 is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution of Comparative Example 2. Figure 5 Figure 5 is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after the copper plating treatment by the pyrophosphate copper plating solution of Comparative Example 3.

[0092] From Figures 2-5 As can be seen from Table 3, the maintenance method of the pyrophosphate copper plating solution of the present application adjusts the pH of the system to be 8.60-8.77 by the supplement of potassium pyrophosphate, because if the pH of the system is less than 8.60, the subsequent ammonia water will be added in too much amount, the pyrophosphate in the system will be hydrolyzed into orthophosphate, the red and dark uneven copper plating layer will be obtained, the brightness of the copper plating layer is reduced, and the diameter of the hole on the copper plating layer is increased; if the pH of the system is greater than 8.77, the subsequent ammonia water will be added in too little amount, the copper plating layer will be fogged, the copper plating layer is no longer smooth and flat, the brightness of the copper plating layer is reduced, and the diameter of the hole on the copper plating layer is increased.

[0093] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, but not to limit the protection scope of the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the essence and scope of the technical solutions of the present application.

Claims

1. A method for maintaining a pyrophosphate copper plating bath, characterized in that, It comprises the following steps: S1. First measure the concentration of copper ions in the pyrophosphate copper plating solution, then supplement the copper pyrophosphate according to the required concentration of copper pyrophosphate in the standard formula of the pyrophosphate copper plating solution; S2. First measure the concentration of pyrophosphate in the pyrophosphate copper plating solution treated in step S1, then supplement potassium pyrophosphate according to the required mass ratio of pyrophosphate to copper ions in the standard formula of the pyrophosphate copper plating solution, and adjust the pH of the system to 8.60-8.77 by supplementing potassium pyrophosphate; S3. Add ammonia water to the pyrophosphate copper plating solution treated in step S2 to adjust the pH according to the required pH value in the standard formula of the pyrophosphate copper plating solution; In step S1, the temperature during the supplement of copper pyrophosphate is 50-55℃, and the required concentration of copper pyrophosphate in the standard formula of the pyrophosphate copper plating solution is 85-100g / L; In step S2, the temperature during the supplement of potassium pyrophosphate is ≤55℃, and the required mass ratio of pyrophosphate to copper ions in the standard formula of the pyrophosphate copper plating solution is 7.75-7.90; The standard formula of the pyrophosphate copper plating solution contains copper pyrophosphate, potassium pyrophosphate, pyrophosphoric acid, and ammonia water; The required concentration of potassium pyrophosphate in the standard formula of the pyrophosphate copper plating solution is 420-520g / L; The required pH in the standard formula of the pyrophosphate copper plating solution is 8.

90.

2. The method of maintaining a pyrophosphate copper plating solution according to claim 1, wherein The standard formula of the pyrophosphate copper plating solution also contains a copper plating brightener.

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