VCP copper plating equipment and copper plating method

Abstract

The invention relates to the technical field of electrocoppering, in particular to VCP copper plating equipment and a copper plating method. Comprising a copper plating pretreatment tank (1), an electroplating tank (2) and a copper plating aftertreatment tank (3) which are sequentially connected, and a direct current rectifier (4) and a pulse rectifier (6) are connected in the electroplating bath (2). The direct-current rectifier and the pulse rectifier are connected in the electroplating bath, and direct-current copper plating and pulse copper plating are sequentially carried out, so that copper wire badness and copper particle badness can be effectively reduced; the electroplating time in the steps S2, S3 and S5 is limited, and the copper wire reject ratio and the copper particle reject ratio of the plated part can be reduced to be smaller than 1%; meanwhile, the scheme of the invention has no special requirements on the brand and model of liquid medicine, has universality in the PCB industry, and effectively reduces the production cost.

Description

Technical Field

[0001] This invention relates to the field of copper electroplating technology, specifically to a VCP copper plating equipment and copper plating method. Background Technology

[0002] Printed circuit boards (PCBs), as the core carriers of electronic components, rely on copper plating technology for their hole metallization thickening process. A dense copper layer needs to be formed on the hole walls to ensure conductivity and insulation. Currently, the industry mainly uses two types of processes: First, DC electroplating: using a DC rectifier with DC copper plating solution, this is low-cost but cannot solve copper wire / particle defects. Copper wires easily cause short circuits, and copper particles cause surface unevenness. Traditional manual intervention methods have limited improvement effects and often cause mass production interruptions. Second, pulse electroplating: using a pulse rectifier with a dedicated pulse copper plating solution. While this can suppress copper wire / particle defects, the solution is expensive, and the equipment has poor compatibility, making widespread mass production difficult. Especially in high-density PCB manufacturing, uneven copper ion distribution leads to local deposition rate differences, exacerbating the copper wire / particle problem. Therefore, there is an urgent need for a device solution that can directly apply pulse technology in a DC plating bath environment to achieve defect control at low cost.

[0003] Chinese invention patent application CN106676591A discloses a method for processing a circuit board and a circuit board. The method for processing the circuit board includes: performing preliminary processing on the circuit board to be processed; electroplating the pre-processed circuit board to be processed; wherein the electroplating time is divided into at least two time periods, and different waveform currents are used for electroplating in different time periods. However, the separation between the two types of processes has not been overcome: DC and pulse processes require independent chemical systems, which cannot balance cost and yield. Summary of the Invention

[0004] The first aspect of the present invention provides a VCP copper plating equipment, comprising a copper plating pretreatment tank, an electroplating tank and a copper plating posttreatment tank connected in sequence; the electroplating tank is equipped with a DC rectifier and a pulse rectifier.

[0005] A second aspect of the present invention provides a copper plating method using a VCP copper plating apparatus, comprising the following steps:

[0006] S1: Pre-treat the plated parts in the copper plating pretreatment tank, add electroplating solution to the electroplating tank, and transfer the pre-treated plated parts to the electroplating tank.

[0007] S2: Turn on the DC rectifier to perform DC copper plating, and turn off the DC rectifier after the copper plating is completed;

[0008] S3: Turn on the pulse rectifier to perform pulse copper plating, and turn off the pulse rectifier after the copper plating is completed;

[0009] S4: Repeat steps S2-S3 0-10 times;

[0010] S5: Turn on the DC rectifier to perform DC copper plating, and turn off the DC rectifier after the copper plating is completed;

[0011] S6: Transfer the copper-plated parts to the copper post-plating treatment tank for post-processing.

[0012] The pulse rectifier has three current modes: forward current, reverse current, and instantaneous interruption current.

[0013] This research found that by first electroplating a copper layer onto the surface of the workpiece using direct current, followed by pulsed copper plating, the rectifier in the pulsed copper plating stage can alternate between three current modes: forward and reverse current, and instantaneous interruption current. This improves the problem of poor copper wire or copper particle quality during electroplating. The first stage of direct current electroplating thickens the copper on the hole walls and surface, ensuring conductivity. In the second stage, under the action of the pulsed reverse current, the copper wire and copper particles are decomposed, solving the problem of excessively rapid copper growth at individual points and replenishing copper ions in the solution during reverse electrolysis (cathode forward plating: Cu). 2+ +2e → Cu↓, reverse cathode plating: Cu - 2e → Cu 2+ This is beneficial for positive copper plating.

[0014] Optionally, the pretreatment includes the following steps: sandbag grinding, chemical copper plating, deep oxidation, brushing, water washing, acid washing, drying, lamination, exposure, development, and deep oxidation.

[0015] Optionally, the pretreatment includes the following steps in sequence: sanding, chemical copper plating, deep oxidation, brushing, water washing, acid washing, water washing, drying, lamination, exposure, development, and deep oxidation.

[0016] S4: Repeat steps 0-5 of S2-S3.

[0017] The ratio of the reverse current setting value to the forward current setting value output by the pulse rectifier is -1.5 to 0.

[0018] Optionally, the reverse current output of the pulse rectifier is set to -800 to -50A.

[0019] The copper plating time in S2 is 10-600s.

[0020] The copper plating time in S3 is 100-600s.

[0021] The copper plating time in S5 is 100-600s.

[0022] The thickness of the copper plating in S2 is 1-5 μm.

[0023] The ratio of the copper plating thickness in S2 to the copper plating thickness in S3 is 1:(0.5-2).

[0024] Optionally, the ratio of the copper plating thickness in S2 to the copper plating thickness in S3 is 1:(0.5-2).

[0025] The thickness of the copper plating in S5 is 3-30 μm.

[0026] Optionally, the thickness of the copper plating in S5 is 5-30 μm.

[0027] The copper plating solution comprises copper sulfate and sulfuric acid.

[0028] The temperature of the copper plating solution is 20-30℃.

[0029] Beneficial effects

[0030] 1. The present invention has a DC rectifier and a pulse rectifier connected in the electroplating tank. By performing DC copper plating and pulse copper plating in sequence, the defects of copper wires and copper particles can be effectively reduced.

[0031] 2. By limiting the electroplating time in S2, S3 and S5, the present invention can reduce the copper wire defect rate and copper particle defect rate of the plated parts to <1%.

[0032] 3. The present invention performs a specific pretreatment on the plated parts before electroplating, which further improves the surface characteristics of the copper wires and copper particles in the plated parts, and can completely avoid defects in the copper wires and copper particles.

[0033] 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.

[0034] 5. The present invention does not have any special requirements for the brand and model of the solution, and has universal applicability in the PCB industry. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the VCP copper plating equipment in Example 1.

[0036] Figure 2 The surface morphology of the plated parts after treatment by the method in Comparative Example 1 is shown (red circles indicate copper wire defects).

[0037] Figure 3 The surface morphology of the plated parts after treatment by the method in Comparative Example 1 is shown (red circles indicate copper particle defects).

[0038] Figure 4 The image shows the surface morphology of the plated part after treatment by the method in Example 3 (red circles indicate copper wire defects).

[0039] Figure 5The image shows the surface morphology of the plated part after treatment by the method in Example 3 (red circles indicate copper particle defects).

[0040] in, Figure 1 1. Pretreatment tank; 2. Electroplating tank; 3. Copper plating posttreatment tank; 4. DC rectifier; 5. Pulse rectifier. Detailed Implementation

[0041] Example 1

[0042] A VCP copper plating equipment, such as Figure 1 As shown, it includes a copper plating pretreatment tank 1, an electroplating tank 2, and a copper plating posttreatment tank 3 connected in sequence; the electroplating tank 2 is equipped with a DC rectifier 4 and a pulse rectifier 5.

[0043] A copper plating method using VCP copper plating equipment comprises the following steps:

[0044] S1: The workpiece is pretreated in copper plating pretreatment tank 1. Electroplating solution (formula: sulfuric acid: 230g / L, copper sulfate: 65g / L, Cl ions 50ppm, brightener 0.3ml / L, leveling agent 2.5ml / L, wetting agent 12ml / L, solvent is water; Guangdong Shuocheng Technology Co., Ltd., model: SCC-200T) is added to electroplating tank 2. The pretreated workpiece is then transferred to electroplating tank 2.

[0045] S2: Turn on DC rectifier 4 to perform DC copper plating for 3 minutes (current is 500A in the positive direction), and turn off DC rectifier 4 after the copper plating is completed;

[0046] S3: Turn on pulse rectifier 5 to perform pulse copper plating for 3 minutes (40ms forward, 2ms reverse, alternating until 3 minutes are accumulated, current is 500A forward, 750A reverse), and turn off pulse rectifier 5 after copper plating is completed;

[0047] S4: Repeat steps S2-S3 for 4 rounds;

[0048] S5: Turn on DC rectifier 4 to perform DC copper plating, and turn off DC rectifier 4 after copper plating is completed;

[0049] S6: Transfer the copper-plated parts to the copper post-plating treatment tank 3 for board surface cleaning.

[0050] The copper plating thickness in S2 is 2.5 μm; the copper plating thickness in S3 is 2 μm; and the copper plating thickness in S5 is 5 μm.

[0051] The pretreatment consists of the following steps: (1) Grinding the part to be plated through a 320-mesh sandbag to obtain a rough copper surface, which is then ready for the next step; (2) Passing the part to be plated through a normal chemical copper plating process. After this process, the copper surface is covered with a thin layer of chemical copper that is easily oxidized, which is then ready for the next step; (3) Immersing 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 washing and drying 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 is ready for the next step; (4) Passing the part to be plated through a normal pretreatment process (brushing, 500 mesh + 1200 mesh) and washing (spraying pressure 1.5 ± 0.5 Kg / m) 2 Acid washing (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.

[0052] Example 2

[0053] The specific implementation method is the same as in Example 1; the difference is that in Example 2: steps S2-S3 are repeated for 3 rounds; the thickness of copper plating in S5 is 15μm.

[0054] Example 3

[0055] The specific implementation method is the same as in Example 1; the difference is that in Example 3: the S2-S3 steps are repeated once; the thickness of the copper plating in S5 is 25μm.

[0056] Example 4

[0057] The specific implementation method is the same as in Example 3; the difference is that no pretreatment is performed on the plated parts in Example 4.

[0058] Comparative Example 1

[0059] A VCP copper plating equipment includes a copper pretreatment tank 1, an electroplating tank 2, and a copper posttreatment tank 3 connected in sequence; a DC rectifier 4 is connected inside the electroplating tank 2.

[0060] A copper plating method using VCP copper plating equipment comprises the following steps:

[0061] S1: The workpiece is pretreated in copper plating pretreatment tank 1. Electroplating solution (formula: sulfuric acid: 230g / L, copper sulfate: 65g / L, Cl ions 50ppm, brightener 0.3ml / L, leveling agent 2.5ml / L, wetting agent 12ml / L, solvent is water; Guangdong Shuocheng Technology Co., Ltd., model: SCC-200T) is added to electroplating tank 2. The pretreated workpiece is then transferred to electroplating tank 2.

[0062] S2: Turn on DC rectifier 4 to perform DC copper plating, and turn off DC rectifier 4 after the copper plating is completed;

[0063] S3: Transfer the copper-plated parts (plating thickness of 30μm) to the copper post-plating treatment tank 3 for post-processing.

[0064] The pretreatment is the same as in Example 1.

[0065] Comparative Example 2

[0066] A VCP copper plating equipment includes a copper pretreatment tank 1, an electroplating tank 2, and a copper posttreatment tank 3 connected in sequence; a pulse rectifier 5 is connected inside the electroplating tank 2.

[0067] A copper plating method using VCP copper plating equipment comprises the following steps:

[0068] S1: The plated parts are pretreated in copper pretreatment tank 1. Electroplating solution (Guangdong Shuocheng Technology Co., Ltd., model: SCC-PA300) is added to electroplating tank 2. The pretreated plated parts are then transferred to electroplating tank 2.

[0069] S2: Turn on pulse rectifier 5 to perform DC copper plating, and turn off pulse rectifier 5 after copper plating is completed;

[0070] S3: Transfer the copper-plated parts (plating thickness of 30μm) to the copper post-plating treatment tank 3 for post-processing.

[0071] The pretreatment is the same as in Example 1.

[0072] Performance testing methods and data

[0073] The plated parts obtained by the methods in the examples and comparative examples were first patterned using the same alkaline etching line, and then the copper surface was scanned using the same automatic optical inspection instrument to identify copper wires and copper particles. The number of defective copper wires and copper particles was counted to obtain the copper wire defect rate and copper particle defect rate. The data are shown in Table 1. Figure 2-3 and Figure 4-5 The comparison shows that the surface characteristics (fewer spots) of the electroplated copper wires and copper particles obtained by the processing scheme of Example 3 are better than those of the traditional method (Comparative Example 1), and the shape of the copper wires and copper particles is also significantly smaller.

[0074] Table 1

[0075]

[0076]

[0077] As shown in Table 1, the surface characteristics of the electroplated copper wires and copper particles obtained by the processing schemes of Examples 1-4 are better than those of the traditional method (Comparative Example 1). The shape of the copper wires and copper particles is also significantly smaller. In particular, the electroplated parts of Examples 1-2 and 4 that have undergone specific pretreatment have further improved the surface characteristics of the electroplated copper wires and copper particles, which can completely avoid defects in copper wires and copper particles. The effect is comparable to that of Comparative Example 2, which only uses pulse electroplating. However, Examples 1-3 can use general electroplating solutions, which effectively reduces production costs (Comparative Example 2's pulse rectifier requires a specific pulse copper plating solution, which is expensive).

Claims

1. A VCP copper plating equipment, characterized in that, It includes a copper plating pretreatment tank (1), an electroplating tank (2) and a copper plating posttreatment tank (3) connected in sequence; the electroplating tank (2) is equipped with a DC rectifier (4) and a pulse rectifier (5).

2. A copper plating method using a VCP copper plating apparatus according to claim 1, characterized in that, Includes the following steps: S1: The plated parts are pretreated in the copper plating pretreatment tank (1), and the electroplating solution is added to the electroplating tank (2). The pretreated plated parts are then transferred to the electroplating tank (2). S2: Turn on the DC rectifier (4) to perform DC copper plating, and turn off the DC rectifier (4) after the copper plating is completed; S3: Turn on the pulse rectifier (5) to perform pulse copper plating, and turn off the pulse rectifier (5) after the copper plating is completed; S4: Repeat steps S2-S3 0-10 times; S5: Turn on the DC rectifier (4) to perform DC copper plating, and turn off the DC rectifier (4) after the copper plating is completed; S6: Transfer the copper-plated parts to the copper post-plating tank (3) for post-processing.

3. The copper plating method using VCP copper plating equipment according to claim 2, characterized in that, S4: Repeat steps 0-5 of S2-S3.

4. The copper plating method using VCP copper plating equipment according to claim 3, characterized in that, The ratio of the reverse current setting value to the forward current setting value output by the pulse rectifier (5) is -1.5 to 0.

5. The copper plating method using VCP copper plating equipment according to claim 3, characterized in that, The copper plating time in S2 is 10-600s.

6. The copper plating method using VCP copper plating equipment according to claim 5, characterized in that, The copper plating time in S3 is 100-600s.

7. The copper plating method using VCP copper plating equipment according to claim 6, characterized in that, The copper plating time in S5 is 100-600s.

8. The copper plating method using VCP copper plating equipment according to claim 7, characterized in that, The thickness of the copper plating in S2 is 1-5 μm.

9. The copper plating method using VCP copper plating equipment according to claim 8, characterized in that, The ratio of the copper plating thickness in S2 to the copper plating thickness in S3 is 1:(0.5-2).

10. The copper plating method using a VCP copper plating apparatus according to any one of claims 2-9, characterized in that, The pretreatment process includes the following steps in sequence: sandbag grinding, chemical copper plating, deep oxidation, brushing, water washing, acid washing, water washing, drying, lamination, exposure, development, and deep oxidation.

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