Method of manufacturing power supply circuit board with blind via

Abstract

The application provides a manufacturing method of a power supply circuit board containing blind holes, which optimizes the conductive butt joint mode of inner layers and outer layers, directly uses the residual copper layer on the bottom of the deep drilling blind hole of an L3-L4 super-thick copper core plate to replace a cover copper layer, then metallizes the deep drilling blind hole through copper sinking and VCP electroplating, laser drills after lamination, and electroplating fills holes on the residual copper layer of the laser blind drilling, so that the inner layers and the outer layers are conductive; meanwhile, the deep drilling blind hole pressing and glue filling do not need a resin plug hole, effectively shorten the manufacturing process, improve the efficiency, and save the cost.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing, and in particular to a method for manufacturing a power circuit board containing blind and buried vias. Background Technology

[0002] The power supply boards are mainly used in products involving photovoltaic inverters, rail power supplies, industrial power supplies, medical power supplies, automotive power management systems, power distribution systems, energy storage, and charging pile power control motherboards, among other fields.

[0003] Currently, the mainstream copper thickness design for power supply boards is 2oz to 4oz. In the future, the demand for high-power, high-current server power supplies, requiring high heat resistance and heat dissipation, will favor thicker copper PCBs. With a fixed line width, increasing copper thickness is equivalent to increasing the circuit cross-sectional area, providing characteristics such as high current carrying capacity, reduced thermal strain, good heat dissipation, and resistance to voltage breakdown. Some high-heat-resistant, high-heat-dissipation power supply PCBs will use an ultra-thick inner copper layer and a 2oz outer layer, connecting the inner and outer layers through blind vias to achieve network conductivity while simultaneously meeting the requirements of high heat resistance and high heat dissipation for the PCB.

[0004] The current industry standard method is to first fabricate buried vias on an ultra-thick copper core board, plug the vias with resin, and then perform electroplating to fill the gaps (POFV process) to create a capping copper layer. Next, the inner layer circuitry is fabricated and laminated, followed by laser drilling of blind vias, filling, and electroplating to make the outer and inner layers conductive. However, this process has the following drawbacks:

[0005] (1) The process is long. The buried hole needs to be filled with resin and then electroplated to fill it (POFV process), which increases the production time.

[0006] (2) Increased manufacturing costs: Since the laser blind vias in the outermost layer need to be connected to the inner layer, the buried vias require resin plugging and electroplating filling processes (POFV process) to create a copper overlay. The resin plugging process requires resin plugging, resin curing, and resin polishing, while the electroplating filling process requires copper plating and VCP electroplating, both of which require manpower and material resources, greatly increasing manufacturing costs. Summary of the Invention

[0007] The present invention provides a method for manufacturing a power circuit board with blind vias to solve at least one of the above-mentioned technical problems.

[0008] To address the aforementioned problems, as one aspect of the present invention, a method for manufacturing a power circuit board containing blind and buried vias is provided, comprising:

[0009] Step 1, Cutting materials:

[0010] The copper-clad laminate is cut to the design size using a cutting machine to produce L3-L4 ultra-thick copper core boards with a thickness of 0.1mm and a diameter of 8 / 8OZ (excluding copper).

[0011] Step 2, Drill blind holes with controlled depth:

[0012] A depth-controlled blind hole with a diameter of 0.45 mm, a depth of 0.45 mm, and a residual copper layer thickness of 0.15 ± 0.05 mm at the bottom is machined on the two middle layers of the laminated board (the depth-controlled blind hole depth to diameter ratio ≤ 1:1).

[0013] Step 3, hole metallization;

[0014] Step 4, internal light imaging;

[0015] Step 5, inner layer etching;

[0016] Step 6: Layers L1 and L4 are laminated on the outside of the two middle layers.

[0017] Step 7, Browning and Copper Reduction:

[0018] The copper thickness on the surface is reduced to 7-9 μm by uniform chemical etching.

[0019] Step 8, Laser drilling:

[0020] Laser blind holes are machined on the board after the copper reduction process is performed using a laser drilling machine.

[0021] Step 9, Plating Copper 2:

[0022] After laser drilling, the plate is subjected to hole metallization treatment to form a conductive layer in the substrate area in the middle of the plate.

[0023] Step 10, Electroplating to fill holes:

[0024] After copper plating 2, the copper plating layer of the board is thickened by electroplating to fill the laser blind holes, so that the L1, L2, L3 three-layer network and the L2, L3, L4 three-layer network are conductive.

[0025] This invention optimizes the connection method between the inner and outer layers. It directly uses the residual copper layer (0.15±0.05mm thick) at the bottom of the controlled-depth drilling blind hole on the L3-L4 ultra-thick copper core board to replace the cover copper layer. Then, the controlled-depth drilling blind hole is metallized by copper plating 1 and VCP electroplating 1. After lamination, laser drilling is performed, and the laser blind hole is drilled on the residual copper layer left during the controlled-depth drilling. Then, electroplating is performed to fill the hole, which can achieve the connection between the inner and outer layers. At the same time, the controlled-depth blind hole lamination and filling does not require resin plugging, which effectively shortens the manufacturing process, improves efficiency, and saves costs. Attached Figure Description

[0026] Figure 1 A schematic diagram of the structure of the two middle layers is shown.

[0027] Figure 2 A schematic diagram of the structure following a depth-controlled blind hole is shown.

[0028] Figure 3 A schematic diagram of the structure after hole metallization is shown;

[0029] Figure 4 A schematic diagram of the structure after internal light imaging is shown;

[0030] Figure 5 A schematic diagram of the structure after inner layer etching is shown.

[0031] Figure 6 A schematic diagram of the laminated structure is shown.

[0032] Figure 7 A schematic diagram of the structure after laser drilling is shown.

[0033] Figure 8 A schematic diagram of the structure after electroplating and filling is shown. Detailed Implementation

[0034] The embodiments of the present invention will be described in detail below, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0035] This invention provides a method for manufacturing a high-heat-resistant and high-heat-dissipation power PCB board with blind vias. By optimizing the connection method between the inner and outer layers, the residual copper layer (thickness 0.15±0.05mm) at the bottom of the controlled-depth drilling blind via on an L3-L4 ultra-thick copper core board is used to replace the cover copper layer. Then, the controlled-depth drilling blind via is metallized by copper plating 1 and VCP electroplating 1. After lamination, laser drilling is performed, and the laser blind via is drilled on the residual copper layer left during the controlled-depth drilling. Then, electroplating is performed to fill the hole, which can achieve the connection between the inner and outer layers. At the same time, the controlled-depth blind via lamination and filling does not require resin plugging, which effectively shortens the manufacturing process, improves efficiency, and saves costs.

[0036] Please refer to Figure 8 , Figure 8 The images show the effect after electroplating and filling of holes on a 4-layer substrate. 1 is a controlled-depth blind via (diameter 0.45mm, depth 0.45mm, depth-to-diameter ratio ≤ 1:1); 2 is the copper layer after metallization of the controlled-depth blind via, with a thickness of 20–25μm; 3 is the laser-filled blind via after electroplating; 4 is the L1-L2 layer of flowable prepreg; 5 is the L3-L4 layer of flowable prepreg; 6 is the VCP-plated copper layer, with a thickness of 25–35μm; 7 is the residual copper layer at the bottom of the controlled-depth drilled blind via on the L3-L4 ultra-thick copper core board (residual copper layer thickness 0.15mm, tolerance ±0.05mm); 8 is the base copper thickness of the L3-L4 ultra-thick copper core board, with a copper thickness ≥ 8OZ.

[0037] The method for manufacturing a power circuit board containing blind and buried vias according to the present invention includes the following steps:

[0038] 1. Cutting materials

[0039] The copper-clad laminate is cut to the design size using a cutting machine, producing 0.1mm 8 / 8OZ (excluding copper) L3-L4 ultra-thick copper core boards.

[0040] 2. Controlled depth drilling of blind holes

[0041] After lamination, use a high-speed drilling machine to machine controlled-depth blind holes with a diameter of 0.45mm, a depth of 0.45mm, and a residual copper layer thickness of 0.15±0.05mm at the bottom (the depth-to-diameter ratio of the controlled-depth blind hole is ≤1:1).

[0042] 3. Hole metallization (plated copper 1, VCP plating 1):

[0043] Plating copper 1: The hole metallization treatment is performed on the board after drilling. The main purpose of the treatment is to form a conductive layer in the substrate area in the middle of the board. The resulting copper layer is about 0.02um.

[0044] VCP plating 1: After copper plating, the copper layer of the board is thickened by electroplating. The surface copper is thickened by about 25-35um, and the copper in the blind holes is thickened by about 20-25um, so that the L2 layer and L3 layer are connected.

[0045] 4. Internal light imaging

[0046] Under certain temperature and pressure conditions, a dry film is applied to the board surface, and then a film is used for alignment. Finally, ultraviolet light is used in an exposure machine to cause the unmasked dry film on the film to react and form the desired circuit pattern on the board surface. Then, in the developing section, the film that has not been exposed to light is dissolved by the developing solution. In the etching section, the exposed copper is etched away by the acidic etching solution. Finally, in the stripping section, the film is removed by the stripping solution, exposing the inner layer circuit pattern.

[0047] 5. Inner layer etching

[0048] First, the copper layer is etched using a chemical solution, which does not corrode the dry film. After etching, the dry film is removed to expose the desired circuit pattern.

[0049] 6. Lamination

[0050] By stacking prepregs, under certain temperature and pressure, the resin in the prepregs flows and fills the circuitry, substrate, and depth-controlled blind holes. When the temperature reaches a certain level, curing occurs, bonding the layers together.

[0051] 7. Copper reduction by browning

[0052] The surface copper thickness is reduced to 7-9μm by uniform chemical etching.

[0053] 8. Laser drilling

[0054] Laser-drilled blind holes are then machined on the board after copper reduction and brown plating using a laser drilling machine. The depth of the laser drilling extends to the intermediate layers L2 and L3.

[0055] 9. Plating Copper 2: The plate after laser drilling is subjected to hole metallization treatment. The main purpose of the treatment is to form a conductive layer in the substrate area in the middle of the plate. The resulting copper layer is about 0.02um.

[0056] 10. Electroplating for hole filling

[0057] After copper plating 2, the copper plating layer of the board is thickened by electroplating to fill the laser blind holes, so that the L1, L2, L3 three-layer network and the L2, L3, L4 three-layer network are conductive.

[0058] In the above technical solution, the conduction method between the inner and outer layers of the present invention is changed from the connection between buried hole and laser blind hole to the connection between depth-controlled blind hole and laser blind hole, which greatly improves cost saving and production efficiency, and lays a technical foundation for mass production.

[0059] This invention optimizes the connection method between the inner and outer layers. It directly uses the residual copper layer (0.15±0.05mm thick) at the bottom of the controlled-depth drilling blind hole on the L3-L4 ultra-thick copper core board to replace the cover copper layer. Then, the controlled-depth drilling blind hole is metallized by copper plating 1 and VCP electroplating 1. After lamination, laser drilling is performed, and the laser blind hole is drilled on the residual copper layer left during the controlled-depth drilling. Then, electroplating is performed to fill the hole, which can achieve the connection between the inner and outer layers. At the same time, the controlled-depth blind hole lamination and filling does not require resin plugging, which effectively shortens the manufacturing process, improves efficiency, and saves costs.

[0060] The present invention has the following advantages:

[0061] (1) The inner and outer layers are connected without the need to make a copper cover layer (made by resin plugging of buried holes in L2-L3 layers followed by copper plating 2 and VCP electroplating 2) to make laser blind holes connected. The residual copper layer at the bottom after drilling blind holes at controlled depth on L3-L4 ultra-thick copper core board is used to replace the copper cover layer, which shortens the manufacturing process and improves efficiency while saving costs.

[0062] (2) Controlled depth blind hole pressing and filling does not require resin plugging, which shortens the manufacturing process and improves efficiency while saving costs.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a power circuit board containing blind and buried vias, characterized in that, include: Step 1, Cutting materials: The copper-clad laminate is cut into the design size using a cutting machine, producing L3-L4 ultra-thick copper core boards with a substrate thickness of 0.1mm and a copper thickness of 8OZ. Step 2, Drill blind holes with controlled depth: A depth-controlled blind hole with a diameter of 0.45 mm, a depth of 0.45 mm, and a residual copper layer thickness of 0.15 ± 0.05 mm is machined on the middle two layers of laminated board. The depth-to-diameter ratio of the depth-controlled blind hole is ≤ 1:

1. Step 3, Hole metallization; Hole metallization includes copper plating 1 and electroplating 1. Copper plating 1 is to perform hole metallization treatment on the board after drilling, and electroplating 1 is to thicken the copper plating layer on the board after copper plating so that the L2 layer and the L3 layer are connected. Step 4, internal light imaging; Step 5, inner layer etching; Step 6: Layers L1 and L4 are laminated on the outer side of the two middle layers. During lamination, prepregs are stacked, and the resin of the prepregs flows to fill the circuits, substrate, and depth-controlled blind holes. Step 7, Browning and Copper Reduction: The copper thickness on the surface is reduced to 7-9 μm by uniform chemical etching. Step 8, Laser drilling: Laser blind holes are machined on the board after the copper reduction process is performed using a laser drilling machine. Step 9, Plating Copper 2: After laser drilling, the plate is subjected to hole metallization treatment to form a conductive layer in the substrate area in the middle of the plate. Step 10, Electroplating to fill holes: After copper plating 2, the copper plating layer of the board is thickened by electroplating to fill the laser blind holes, so that the L1, L2, L3 three-layer network and the L2, L3, L4 three-layer network are conductive.

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