Current control method for direct-current copper electroplating and application

Abstract

The invention relates to the technical field of copper electroplating, in particular to a current control method for direct-current copper electroplating and application. Comprising the following steps that S1, a plating piece is placed in copper plating liquid, a PLC program controls current to be started, and when set production current is reached, a flash plating layer is electroplated on the surface of the plating piece; s2, the PLC program controls current interruption, and the plating piece is kept to be soaked in the copper plating liquid; and S3, the PLC program controls the current to be started again for copper plating. According to the current control method, by accurately controlling the power-off time and the flash plating time in the electroplating process, it is ensured that copper ions are evenly distributed on the cathode, and copper wires and copper particles are prevented from being generated due to local oxidation and additive enrichment.

Description

Technical Field

[0001] This invention relates to the field of copper electroplating technology, specifically to a current control method and application for DC copper electroplating. Background Technology

[0002] Printed circuit boards (PCBs) are the core carriers of electronic components. Their hole metallization thickening technology relies on DC electroplating, which forms a dense copper layer on the hole walls through an electrolytic reaction. This layer must ensure conductivity while maintaining insulation between patterns to prevent short circuits. However, PCB manufacturing processes are lengthy and have complex control factors. Defects in copper wires and copper particles are frequent. Traditional process improvements that rely on manual intervention are costly and have limited effectiveness, easily leading to mass production interruptions and delivery losses.

[0003] Chinese invention patent application CN115835530A discloses a method for processing a circuit board and the circuit board itself. The method includes: performing preliminary processing on the circuit board to be processed; electroplating the pre-processed circuit board; wherein the electroplating time is divided into at least two time periods, and different waveforms of current are used for electroplating in different time periods. Through this method, the application effectively improves the electroplating production efficiency of circuit boards and shortens the product manufacturing cycle while ensuring good deep plating capability and high reliability for circuit boards with high aspect ratios. However, it does not address the issue of defective copper wires and copper particles. Summary of the Invention

[0004] The first aspect of the present invention provides a current control method for DC copper electroplating, comprising the following steps: S1, placing the workpiece in a copper plating solution, and using a PLC (Programmable Logic Controller) program to control the current to turn on, and when the set production current is reached, electroplating a flash plating layer on the surface of the workpiece; S2, using the PLC program to control the current to interrupt, keeping the workpiece immersed in the copper plating solution; S3, using the PLC program to control the current to turn on again to perform copper plating.

[0005] Optionally, the plated part includes a pretreatment before step S1, which includes surface grinding, chemical copper plating, oxidation, cleaning, lamination, exposure, and development.

[0006] The thickness of the flash coating is no greater than 8 μm.

[0007] The electroplating time in S1 is 10-600s; the current interruption time is 1-300s.

[0008] Optionally, the electroplating time in S1 is 100-400s; the current interruption time is 10-50s.

[0009] Optionally, the electroplating time in S1 is 200-400s; the current interruption time is 20-50s.

[0010] This study found that first electroplating a flash plating layer on the surface of the workpiece, followed by a controlled current interruption for a period of time before electroplating, can improve the defective phenomenon of copper wires or copper particles during electroplating. By first covering the workpiece with a thin electroplating layer, the difference in copper surface in contact with the copper plating solution is reduced, and the abnormal reaction is effectively stopped at the moment of violent reaction. This allows for a secondary distribution of the plating solution components, which may be because the workpiece is relatively flat at this time, and the chemical potential can be kept consistent.

[0011] The time to reach the set production current in S1 is 15-30 seconds.

[0012] Before step S3 begins, steps S1 and S2 are repeated sequentially, with the number of repetitions ranging from 1 to 10 rounds, where each repetition of steps S1 and S2 constitutes one round.

[0013] During the repeated S1, the time to reach the set production current does not exceed 1 second.

[0014] The copper plating solution comprises copper sulfate, sulfuric acid, and water.

[0015] The temperature of the copper plating solution is 20-30℃.

[0016] The second aspect of the present invention provides an application of the DC copper plating current control method, which is applied to the production of copper plating.

[0017] Optionally, copper electroplating production can still guarantee excellent electroplating quality when applied to at least one of the following conditions: the ambient temperature of electroplating is ≥25℃ and the conductivity of the water used for electroplating is ≥50μs / cm.

[0018] Beneficial effects 1. Electroplating a flash plating layer on the surface of the workpiece, then interrupting the current for a period of time before electroplating again, can improve the defective copper wires or copper particles in the electroplating process.

[0019] 2. By controlling the electroplating time in S1 to be 10-600s and the current interruption time to be 1-300s, the copper wire defect rate can be less than 5%.

[0020] 3. By controlling the electroplating time in S1 to be 100-400s and the current interruption time to be 10-50s, the copper wire defect rate can be less than 0.5%.

[0021] 4. The product appearance obtained by the present invention is completely consistent with that of conventional electroplating, without affecting the continued processing of subsequent processes, and meets the standard requirements of customers and industry general specifications.

[0022] 5. The present invention has no special requirements for process flow and equipment model, and has universal applicability in the PCB industry.

[0023] 6. The electroplating process of the present invention can ensure excellent electroplating quality even in environments with an ambient temperature ≥25℃ or a water conductivity ≥50μs / cm. Attached Figure Description

[0024] Figure 1 The image shows the surface morphology of the plated part after treatment by the method in Example 2.

[0025] Figure 2 The surface morphology of the plated part after being treated by the method in Comparative Example 1 is shown.

[0026] Figure 3 The image shows the surface morphology of the plated part after treatment by the method in Example 4.

[0027] Figure 4 The surface morphology of the plated parts after treatment by method 2 is shown in Comparative Example 2. Detailed Implementation

[0028] Example 1 A current control method for DC copper plating, implemented using gantry DC electroplating, comprises the following steps: S1, placing the pre-treated workpiece in the copper plating solution, and controlling the current to turn on using a PLC program. When the set production current is reached, a flash plating layer is electroplated on the surface of the workpiece; S2, the PLC program controls the current to be interrupted, keeping the workpiece immersed in the copper plating solution; S3, the PLC program controls the current to turn on again for copper plating, wherein the thickness of the copper plating layer is 40 μm.

[0029] The pretreatment steps are as follows: (1) Grind the part to be plated through a 300-mesh sandbag to obtain a rough copper surface, and then proceed to the next process; (2) Pass the part to be plated through the chemical copper plating process normally. After passing through this process, the copper surface is covered with a thin layer of chemical copper that is very easy to oxidize, and then proceed to the next process; (3) Place the part to be plated in a weak acid solution with a pH of 0.7 and a mass percentage of 1% for 10 minutes, and then wash and dry it in the post-drying line. After drying, it is directly exposed to the electroplating workshop, which is a humid space filled with acid mist. After the product is placed for 4 hours for deep oxidation, it proceeds to the next process; (4) Pass the part to be plated through the pretreatment (brushing, 500 mesh + 1200 mesh) and water washing (spray pressure 1.5 ± 0.5 kg / m) normally. 2 Pickling (concentration 2±1wt%), water washing (spray pressure 1.5±0.5kg / m³) 2(5) The workpiece to be plated is normally pressed (pressing temperature 110±5℃) and exposed (exposure energy 18±2mj) to realize the image transfer on the board surface, and then proceed to the next process; (6) The workpiece to be plated is processed through the developing process (developer concentration 1±0.2wt%) to create the circuit pattern on the board surface, and then proceed to the next process; (7) The workpiece to be plated is directly exposed in the electroplating workshop, which is a humid space (50±10%RH), and the product is placed for 4 hours for deep oxidation.

[0030] The undisclosed pretreatment parameters are common industry practices and do not affect subsequent DC electroplating of copper; therefore, they are not limited.

[0031] The thickness of the flash plating layer is 0.01 μm; the electroplating time in S1 is 10 s; the current interruption time is 1 s.

[0032] The time to reach the set production current in S1 is 25 seconds.

[0033] The copper plating solution (Shuocheng SCC200T) consists of the following components: sulfuric acid: 210 g / L, copper sulfate: 75 g / L, Cl ions: 50 ppm, brightener: 0.2 mL / L, leveling agent: 0.3 mL / L, wetting agent: 15 mL / L, and water as the solvent.

[0034] Example 2 The specific implementation method is the same as in Example 1; the difference is that the thickness of the flash plating layer in Example 2 is 2.5 μm; the electroplating time in S1 is 300 s; and the current interruption time is 30 s.

[0035] Example 3 The specific implementation method is the same as in Example 1; the difference is that the thickness of the flash plating layer in Example 3 is 5μm; the electroplating time in S1 is 600s; and the current interruption time is 300s.

[0036] Example 4 A current control method for DC copper plating, implemented using VCP (Vertical Continuous Plating), comprises the following steps: The workpiece to be plated is passed through a VCP DC plating line. A PLC program is used to shut off the current in the second copper tank of the VCP DC plating line and remove the titanium mesh connection point, ensuring that the closed loop of the second copper tank is broken, achieving no current in the second copper tank and ensuring that the workpiece is in a power-off mode during the plating process; (the first copper plating tank plating for 180 seconds yields a copper thickness of 2.7 μm, and the second copper tank has no current for 180 seconds). During the plating process, the measured product shows no current in the second copper tank. The workpiece is then passed through the VCP DC plating line again, with a cumulative copper plating thickness of 45 μm.

[0037] The pretreatment of the parts to be plated is as follows: the parts to be plated are ground through a 300-mesh sandbag to obtain a rough copper surface, and then proceed to the next process; the parts to be plated are normally passed through the chemical copper gantry electroless copper plating process. After passing through this process, the copper surface is covered with a thin layer of chemical copper that is very easy to oxidize. After electroless copper plating, the parts are dried and then proceed to the next process; the parts to be plated are normally passed through the VCP DC electroplating line. After electroplating, product marking and copper particle inspection on the board surface are performed.

[0038] The undisclosed pretreatment parameters are common industry practices and do not affect subsequent DC electroplating of copper; therefore, they are not limited.

[0039] Comparative Example 1 The pretreated workpiece is placed in the copper plating solution, and the PLC program controls the current to turn on. When the set production current is reached, copper plating is performed. The pretreatment is the same as in Example 1.

[0040] Comparative Example 2 The pretreated parts are then passed through a VCP DC electroplating line; the pretreatment is the same as in Example 7.

[0041] Comparative Example 3 The copper plating bath solution was treated with 1wt% H2O2 and high-efficiency carbon core filtration for 4 hours. The pretreated parts were placed in the copper plating solution, and the PLC program controlled the current to turn on. When the set production current was reached, copper plating was performed. The pretreatment was the same as in Example 1.

[0042] Comparative Example 4 Add 5 mL / L of formaldehyde to the copper plating bath solution for sterilization. Place the pretreated workpiece in the copper plating solution. The PLC program controls the current to turn on. When the set production current is reached, copper plating is performed. The pretreatment is the same as in Example 1.

[0043] Comparative Example 5 After draining the copper plating tank, a new tank is prepared. The pre-treated parts are placed in the copper plating solution, and the PLC program controls the current to turn on. When the set production current is reached, copper plating is performed. The pre-treatment is the same as in Example 1.

[0044] Performance testing methods and data 1. The plated parts obtained according to the methods of Examples 1-3, Comparative Examples 1, and Comparative Examples 3-5 were first passed through the same alkaline etching line and then through the same automatic optical inspection instrument. The number of defective copper wires was counted, and the data is shown in Table 1.

[0045] 2. Following the current control method of Example 2, a batch verification of the number of defective copper wires was conducted (compared to Example 1). The results are shown in Table 2. Figures 1-2 As shown in Table 2, the surface characteristics of the electroplated copper wire obtained by the method in Example 2 (fewer copper wire dots) are better than those of the traditional method (Comparative Example 1).

[0046] 3. The copper particle count of the plated parts obtained according to the methods of Example 4 and Comparative Example 2 was statistically analyzed, and the results are shown in Table 3. Figures 3-4 As shown in Table 3, the surface properties (fewer copper particles) of the plated parts obtained by the method in Example 4 are better than those of the traditional method (Comparative Example 2).

[0047] In Table 3, " / " indicates that there are too many copper particles to be counted accurately.

[0048] Table 1 Item Number of tests Number of copper wire points Copper wire failure rate Example 1 900 37 4.11% Example 2 900 4 0.44% Example 3 900 15 1.67% Comparative Example 1 900 453 50.33% Comparative Example 3 900 415 46.11% Comparative Example 4 900 389 43.22% Comparative Example 5 900 476 52.89% Table 2 Batch No. Current control method Number of tests Number of copper wire points Copper wire failure rate PC1003005 Comparative Example 1 2647 358 13.5% PC1005001 Comparative Example 1 3361 872 25.9% PC1003012 Comparative Example 1 1879 376 20.0% PC1005003 Comparative Example 1 2427 483 19.9% PC1004004 Comparative Example 1 1636 362 22.1% PC1003009 Comparative Example 1 2963 329 11.1% PC1003004 Example 2 2884 8 0.3% PC1006001 Example 2 2668 6 0.2% PC1003007 Example 2 1683 2 0.1% PC1004003 Example 2 1946 4 0.2% PC1004008 Example 2 3425 7 0.2% PC1003003 Example 2 2774 5 0.2% PC1006003 Example 2 2964 3 0.1% PC1005004 Example 2 1995 4 0.2% Table 3 Item Current control method Number of tests Number of copper wire points Copper wire failure rate Group A Example 4 10 0 0% Group B Comparative Example 2 Comparative Example 2 10 / 100% As shown in Table 1-3, electroplating a flash plating layer on the surface of the workpiece, followed by a period of current interruption, and then electroplating again can improve the defective copper wires or copper particles in the electroplating process.

Claims

1. A method for controlling the current in DC copper electroplating, characterized in that, Includes the following steps: S1, The workpiece is placed in the copper plating solution, and the PLC program controls the current to turn on. When the set production current is reached, a flash plating layer is electroplated on the surface of the workpiece; S2, The PLC program controls the current to turn off, keeping the workpiece immersed in the copper plating solution; S3, The PLC program controls the current to turn on again to perform copper plating on the workpiece.

2. The current control method for DC copper electroplating according to claim 1, characterized in that, The electroplating time in S1 is 10-600s; the current interruption time is 1-300s.

3. The current control method for DC copper electroplating according to claim 1, characterized in that, The electroplating time in S1 is 100-400s; the current interruption time is 10-50s.

4. The current control method for DC copper electroplating according to claim 1, characterized in that, The thickness of the flash coating is no greater than 8 μm.

5. The current control method for DC copper electroplating according to claim 1, characterized in that, The time to reach the set production current in S1 is 15-30 seconds.

6. The current control method for DC copper electroplating according to claim 1, characterized in that, Before step S3 begins, steps S1 and S2 are repeated sequentially, with the number of repetitions ranging from 1 to 10.

7. The current control method for DC copper electroplating according to claim 6, characterized in that, During the repeated S1, the time to reach the set production current does not exceed 1 second.

8. The current control method for DC copper electroplating according to claim 1 or 7, characterized in that, The copper plating solution comprises copper sulfate, sulfuric acid, and water.

9. The current control method for DC copper electroplating according to claim 1, characterized in that, The temperature of the copper plating solution is 20-30℃.

10. An application of the DC copper plating current control method according to any one of claims 1-9, characterized in that, It is used in the production of electroplated copper.

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