Maintenance method of pyrophosphate copper plating solution

Abstract

The invention discloses a maintenance method of a pyrophosphate copper plating solution, which comprises the following steps: S1, measuring the concentration of copper ions in the pyrophosphate copper plating solution, and supplementing copper pyrophosphate according to the concentration of copper pyrophosphate required in a standard formula of the pyrophosphate copper plating solution; s2, measuring the concentration of pyrophosphate radicals in the pyrophosphate copper plating solution treated in the step S1, supplementing potassium pyrophosphate according to the mass ratio (P ratio) of the pyrophosphate radicals to copper ions required in the standard formula of the pyrophosphate copper plating solution, and adjusting the pH value of the system to 8.60-8.77 by supplementing the potassium pyrophosphate; and S3, adding ammonia water into the pyrophosphate copper plating solution treated in the step S2 according to the pH value required in the standard formula of the pyrophosphate copper plating solution to adjust the pH value. According to the maintenance method disclosed by the invention, the used pyrophosphate copper plating solution can still obtain a qualified copper plating layer through maintenance.

Description

Technical Field

[0001] The invention relates to the technical field of electroplating, and more specifically to a maintenance method for a pyrophosphate copper plating solution. Background Art

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

[0003] In addition to the module integration method, SIP technology also has different requirements for components. The process of component mounting is one of the typical differences. The promotion of embedded chip multilayer ceramic capacitors is a better solution. Chip multilayer ceramic capacitors (MLCC) are one of the most common components in various electronic products. Generally, since they are mainly used for PCB surface mounting, the electrodes at the ends of MLCC are generally tin-plated copper layers. The difference between embedded MLCC (copper terminal MLCC) and conventional MLCC is that its end welding layer is a smooth, dense and non-oxidized copper-plated copper layer, which requires the copper electroplating process to be stable and efficient during the copper electroplating process.

[0004] Copper plating technology occupies an important position in surface electroplating technology. For a long time, copper plating has been dominated by cyanide copper plating. Because cyanide is highly toxic and pollutes the environment, people gradually replaced cyanide copper plating with a variety of copper plating processes such as pyrophosphate copper plating, copper sulfate copper plating, and HEDP copper plating. Among them, the pyrophosphate copper plating solution has a simple composition, is non-toxic, 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 has been used for a period of time, the content of each component has decreased, resulting in the quality of the obtained copper plating layer being unqualified, the copper plating layer is no longer bright and smooth, pinholes and burning phenomena appear, and the color is no longer uniformly reddish and 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 of the invention

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

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] The present invention provides a maintenance method for a pyrophosphate copper plating solution, comprising the following steps:

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

[0010] S2. First, measure the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1, and then supplement potassium pyrophosphate according to the mass ratio of pyrophosphate and copper ions (P ratio) required 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;

[0011] S3. According to the required pH value in the standard formula of the pyrophosphate copper plating solution, ammonia water is added to the pyrophosphate copper plating solution treated in step S2 to adjust the pH.

[0012] The reason why the pH value of the pyrophosphate copper plating solution maintenance method of the present invention is adjusted to 8.60-8.77 by potassium pyrophosphate supplementation is that if the pH value of the potassium pyrophosphate supplementation system is less than 8.60, the subsequent addition of ammonia water will be excessive, so that the pyrophosphate in the system is hydrolyzed to become orthophosphate, resulting in the final copper plating layer being reddish, dark and uneven, reducing the brightness of the copper plating layer and increasing the hole diameter on the copper plating layer; if the pH value of the potassium pyrophosphate supplementation system is greater than 8.77, the subsequent addition of ammonia water will be too small, causing the copper plating layer to be atomized, and the copper plating layer is no longer smooth and flat, reducing the brightness of the copper plating layer and increasing the hole diameter on the copper plating layer.

[0013] In the present invention, the quality standard of the copper-plated layer obtained by using the pyrophosphate copper plating solution is: "the copper-plated layer is bright and flat, without pinholes and burnt phenomena, and the color is uniformly reddish and dark", or "the brightness of the copper-plated layer is ≥85%, holes appear on the copper-plated layer, and the diameter of the holes is ≤0.01mm", or "the brightness is ≥80% and <85%, holes appear on the copper-plated layer, and the diameter of the holes is ≤0.01mm", that is, when the copper-plated layer meets any one of the three requirements, the quality of the copper-plated layer is considered to be qualified.

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

[0015] Preferably, in step S1, the temperature during the supplementation of copper pyrophosphate is ≤55°C.

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

[0017] Preferably, in step S2, the temperature during the supplementation of potassium pyrophosphate is ≤55°C.

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

[0019] The maintenance method of the pyrophosphate copper plating solution of the present invention controls the concentration to be ≤55°C when replenishing copper pyrophosphate and potassium pyrophosphate, so as to prevent the pyrophosphate (copper pyrophosphate and potassium pyrophosphate) from being hydrolyzed into orthophosphate at a temperature greater than 55°C, thereby ultimately affecting 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 copper plating brightener.

[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 copper plating brightener concentration is 4-5 mg / L.

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

[0029] Preferably, in step S2, the mass ratio of pyrophosphate to copper ions (P ratio) required 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 pyrophosphate to copper ions (P ratio) required in the standard formula of the pyrophosphate copper plating solution is 7.75-7.90.

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

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

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

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

[0035] The copper ion concentration in the pyrophosphate copper plating solution was measured by titration analysis using PAN [1-(2-pyridyl azo)-2-naphthol] indicator and EDTA as a standard solution added into the pyrophosphate copper plating solution.

[0036] More preferably, the titration endpoint of the titration analysis is when the solution changes from purple-red to green.

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

[0038] Using PAN [1-(2-pyridyl azo) -2-naphthol] indicator, zinc acetate is added as a standard solution to the pyrophosphate copper plating solution treated in step S1 to change the color of the PAN indicator, and then an EDTA standard solution is added for back titration to measure the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1.

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

[0040] More preferably, the titration endpoint of the back titration is a change from purple to orange-green.

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

[0042] The maintenance method of the pyrophosphate copper plating solution of the present invention realizes the maintenance of the pyrophosphate copper plating solution by first replenishing copper pyrophosphate, then replenishing pyrophosphoric acid, and finally replenishing ammonia water, so that the used pyrophosphate copper plating solution can still prepare a qualified copper plating layer through maintenance. The maintenance method can make the pyrophosphate copper plating solution recyclable for a long time, which is beneficial to reducing production costs and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0044] Figure 2 This is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Example 1.

[0045] Figure 3 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Example 2.

[0046] Figure 4 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Comparative Example 2.

[0047] Figure 5 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Comparative Example 3. DETAILED DESCRIPTION

[0048] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0049] In the maintenance method of the pyrophosphate copper plating solution of each embodiment of the present invention and the comparative example, 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 with ammonia water in step S3, the dosage relationship between the increased concentration of ammonia water in the pyrophosphate copper plating solution and the pH value is Y=8.58+0.05X, wherein X is the increased concentration of ammonia water in the pyrophosphate copper plating solution, in units of mmol / L, Y is the pH value of the pyrophosphate copper plating solution after adding ammonia water (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 water;

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

[0051] According to the standard formula of pyrophosphate copper plating solution in Example 1, 1L 97g / L copper pyrophosphate solution was prepared, and then 2.8g pyrophosphate and 5mg copper plating brightener imidazole were added, and then the pH was adjusted to 8.58 with potassium pyrophosphate. Then, while adding ammonia water and calculating the increased concentration of ammonia water in the system, the pH value was measured to obtain Figure 1 The XY relationship diagram shown in the figure, and then the dosage relationship between X and Y is obtained by linear fitting: Y=8.58+0.05X.

[0052] Example 1

[0053] This embodiment provides a maintenance method for a pyrophosphate copper plating solution, comprising the following steps:

[0054] S1. First measure the copper ion concentration in the pyrophosphate copper plating solution, and then add copper pyrophosphate according to the copper pyrophosphate concentration required in the standard formula of the pyrophosphate copper plating solution, as follows:

[0055] (1) preparing 100 L of pyrophosphate copper plating standard solution according to the standard formula of the pyrophosphate copper plating solution and using it to plate a copper layer on an embedded MLCC for 12 hours to obtain a pyrophosphate copper plating solution;

[0056] (2) adding water to the pyrophosphate copper plating solution to make up to 100 L, mixing evenly, to obtain a pyrophosphate copper plating solution after adding water;

[0057] (3) taking 1 mL of the pyrophosphate copper plating solution after adding water, adding 100 mL of deionized water and 7 drops of PAN [1-(2-pyridyl azo) -2-naphthol] indicator with a concentration of 0.02 g / L, at which time the solution turns purple-red, and titration analysis is performed using 0.1 mol / L EDTA as a standard solution. The titration endpoint is when the solution changes from purple-red to green. The amount of EDTA used is recorded and the copper ion concentration in the pyrophosphate copper plating solution after adding water in step (2) is calculated to be 36 g / L;

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

[0059] S2. First measure the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1, then supplement potassium pyrophosphate according to the mass ratio of pyrophosphate and copper ions (P ratio) required 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 1mL of the pyrophosphate copper plating solution treated in step (4) of step S1, add 100mL of deionized water, 7 drops of PAN [1-(2-pyridyl azo) -2-naphthol] indicator at a concentration of 0.02g / L, and 10mL1mol / L zinc acetate standard solution, mix, at this time PAN indicator changes from green to purple, boil and cool, then transfer to a 200mL volumetric flask to volume, then take 100mL, add 10mLpH = 10 ammonia-ammonium chloride buffer solution, back titrate with 0.1mol / L EDTA standard solution, the titration end point is from purple to orange-green, record the amount of EDTA and calculate that the potassium pyrophosphate concentration in the pyrophosphate copper plating solution treated in step (4) of step S1 is 425g / L;

[0061] b. At 55 ° C., 3500 g of potassium pyrophosphate was added to the pyrophosphate copper plating solution treated in step (4) of step S1, and the solution was dissolved by stirring to make the P ratio in the system reach the required 7.75 in the standard formula of the pyrophosphate copper plating solution, and 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. According to the pH value required in the standard formula of the pyrophosphate copper plating solution, ammonia water is added to the pyrophosphate copper plating solution treated in step S2 to adjust the pH, as follows:

[0063] The pH value of the pyrophosphate copper plating solution treated in step b in step S2 is 8.60. According to the formula Y=8.58+0.05X, it is calculated that (8.90-8.60) / (0.05)mmol / L×100L=0.6mol ammonia water needs to be added to adjust the pH value of 100L of the pyrophosphate copper plating solution to 8.90. The pH value in the system is measured with a pH meter, and it is found that the pH value reaches the pH value of 8.90 required in the standard formula of the pyrophosphate copper plating solution;

[0064] in:

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

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

[0067] Embodiment 2-3 and comparative example 1-2 provide different maintenance methods for pyrophosphate copper plating solutions, which differ from embodiment 1 in that the amount of potassium pyrophosphate supplemented in step S2 and the pH value of the system after the potassium pyrophosphate supplementation are different from the P ratio required in the standard formula of the pyrophosphate copper plating solution, the amount of ammonia water supplemented in step S3 and the pH value of the system after the ammonia water supplementation are different, and the rest are referred to embodiment 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 pyrophosphate copper plating solutions, which differ from Example 1 in that the temperature when copper pyrophosphate is supplemented in step S1 and the temperature when potassium pyrophosphate is supplemented in step S2 are different, and the rest are referenced 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 Testing

[0077] Take 15L of the pyrophosphate copper plating solution treated by the maintenance method of each embodiment or comparative example, add 520g of steel balls and 520g of zirconium oxide balls under the conditions of current 25A and rotation speed 15 rpm, and then copper-plate the copper layers of 1000 embedded MLCCs respectively, and use the VR-6000 3D microscope of Keyence to check the quality of the copper plating layers, and rate the quality of the copper plating layers;

[0078] Among them, the classification of copper plating quality levels is as follows:

[0079] "Grade 0" means that the copper plating layer is bright and smooth, without pinholes and burnt phenomena, and the color is uniformly reddish and dark;

[0080] "Level 1" means that the brightness of the copper plating layer is ≥85%, holes appear on the copper plating layer, and the diameter of the holes is ≤0.01mm;

[0081] "Level 2" means that the brightness is ≥80% and <85%, holes appear on the copper plating layer, and the diameter of the holes is ≤0.01mm;

[0082] "Level 3" means that the brightness is ≥75% and <80%, holes appear on the copper plating layer, and the diameter of the holes is ≤0.02mm;

[0083] "Level 4" means that the brightness is ≥70% and <75%, holes appear on the copper plating layer, and the diameter of the holes is ≤0.03mm;

[0084] "Level 5" means that the brightness is ≥65% and <70%, holes appear on the copper plating layer, and the diameter of the holes is ≤0.04mm;

[0085] Brightness is measured by Keyence VR-6000 3D microscope, Brightness = (1-roughness)%;

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

[0087] It is worth noting that the larger the number of the copper plating quality level, the worse the quality of the copper plating, and when the copper plating quality level is 0-2, it means that the plating quality is qualified;

[0088] The specific experimental results are as follows:

[0089] Table 3 Performance test results of various embodiments and comparative examples

[0090] Copper plating quality level / grade Is the quality of copper plating 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 This is a microscope image of the copper plating layer of the outer electrode of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Example 1. Figure 3 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Example 2. Figure 4 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Comparative Example 2. Figure 5 This is a microscope image of the outer electrode copper plating layer of the copper terminal MLCC product after copper plating treatment with the pyrophosphate copper plating solution of Comparative Example 3.

[0092] from Figure 2-5 As can be seen from Table 3, the reason why the pH of the pyrophosphate copper plating solution maintenance method of the present invention is adjusted to 8.60-8.77 by potassium pyrophosphate supplementation is because if the pH of the potassium pyrophosphate supplementation system is less than 8.60, the subsequent addition of ammonia water will lead to excessive addition, so that the pyrophosphate in the system is hydrolyzed into orthophosphate, resulting in the final copper plating layer being reddish, dark and uneven, reducing the brightness of the copper plating layer, and increasing the diameter of the holes on the copper plating layer; if the pH of the potassium pyrophosphate supplementation system is greater than 8.77, the subsequent addition of ammonia water will lead to too little, causing the copper plating layer to be atomized, and the copper plating layer is no longer smooth and flat, which reduces the brightness of the copper plating layer and increases the diameter of the holes on the copper plating layer.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A maintenance method for a pyrophosphate copper plating solution, characterized in that: The steps include: S1. First measure the copper ion concentration in the pyrophosphate copper plating solution, and then supplement the copper pyrophosphate according to the copper pyrophosphate concentration required in the standard formula of the pyrophosphate copper plating solution; S2. First, measure the pyrophosphate concentration in the pyrophosphate copper plating solution treated in step S1, and then supplement potassium pyrophosphate according to the mass ratio of pyrophosphate and copper ions required 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. According to the required pH value in the standard formula of the pyrophosphate copper plating solution, ammonia water is added to the pyrophosphate copper plating solution treated in step S2 to adjust the pH.

2. The maintenance method of pyrophosphate copper plating solution as claimed in claim 1, characterized in that: In step S1, the temperature during the copper pyrophosphate supplementation is ≤55°C.

3. The maintenance method of pyrophosphate copper plating solution as claimed in claim 2, characterized in that: In step S1, the temperature when supplementing copper pyrophosphate is 50-55°C.

4. The maintenance method of pyrophosphate copper plating solution as claimed in claim 1, characterized in that: In step S2, the temperature during the supplementation of potassium pyrophosphate is ≤55°C.

5. The maintenance method of pyrophosphate copper plating solution as claimed in claim 1, characterized in that: The standard formula of the pyrophosphate copper plating solution contains copper pyrophosphate, potassium pyrophosphate, pyrophosphoric acid and ammonia water.

6. The maintenance method of the pyrophosphate copper plating solution as claimed in claim 5, characterized in that: The standard formula of the pyrophosphate copper plating solution also contains at least one copper plating brightener.

7. The maintenance method of pyrophosphate copper plating solution as claimed in claim 1, characterized in that: Include at least one of the following (1)-(2): (1) In step S1, the copper pyrophosphate concentration required in the standard formula of the pyrophosphate copper plating solution is 85-100 g / L; (2) In step S2, the mass ratio of pyrophosphate to copper ion required in the standard formula of the pyrophosphate copper plating solution is 7.5-8.

0.

8. The maintenance method of the pyrophosphate copper plating solution as claimed in claim 7, characterized in that: In step S2, the mass ratio of pyrophosphate to copper ion required in the standard formula of the pyrophosphate copper plating solution is 7.75-7.

90.

9. The maintenance method of the pyrophosphate copper plating solution as claimed in claim 1, characterized in that: The potassium pyrophosphate concentration required in the standard formula of the pyrophosphate copper plating solution is 420-520 g / L.

10. The maintenance method of the pyrophosphate copper plating solution as claimed in claim 1, characterized in that: The pH required in the standard formula of the pyrophosphate copper plating solution is 8.90.

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