LED PCB and preparation method thereof

Abstract

The invention relates to the technical field of PCBs, and particularly discloses an LED PCB and a preparation method thereof, and the method comprises the steps: providing a PCB substrate; a via hole is formed in the PCB substrate, and a narrowing part is formed in the via hole; filling ink into the via hole; and curing the printing ink to enable the printing ink to be tightly combined with the interior of the via hole. The device can be stably and reliably applied to a high-temperature and high-pressure mold pressing process.

Description

Technical Field

[0001] This invention belongs to the field of PCB electroplating technology, and particularly relates to an LED PCB board and its preparation method. Background Technology

[0002] PCB, short for Printed Circuit Board, is the provider of electrical connections for electronic components. Its main function is to provide support, fixation, and connection for electronic components, and to interconnect them through various forms of circuitry. The PCB for Mini LED is the circuit board used to carry and drive the Mini LED chips (typically 50-200 micrometers in size). It is not only a simple circuit carrier, but also a key component for achieving high brightness, high contrast, and high dynamic range (HDR) display effects, and is widely used in high-end televisions, professional monitors, automotive screens, and more.

[0003] In the manufacturing process of Mini LED PCBs, via plugging is a crucial step. The main purpose of this step is to fill the holes and achieve surface smoothing, meeting the requirements for fine circuit fabrication and improving the electrical reliability of the circuit board. The via plugging process also has additional requirements in the Mini LED manufacturing process. The Mini LED manufacturing process mainly includes material receiving, sorting, printing, SPI, die bonding, high-pressure nitrogen furnace soldering, SMT, electrical testing, molding, cutting, and calibration / warehousing. Among these, a key step in the Mini LED manufacturing process is molding: the board covered with LED chips is placed in a mold, molding compound (AB glue) is injected, and encapsulation is performed at high temperature (typically 175-185 ℃) and high pressure (typically 1.0-1.5 tons) to protect the chip and achieve optical effects.

[0004] Existing hole-filling technology uses resin hole-filling process. The traditional resin hole-filling process includes the following steps: resin hole filling, that is, filling the hole with special resin filler through screen printing or vacuum injection → high temperature curing of resin → grinding to remove excess resin from the surface to achieve a smooth surface.

[0005] However, resin plugging technology has inherent drawbacks such as high cost and complex process: 1. Long process flow: Resin plugging requires multiple independent processes such as filling, curing, and grinding, resulting in a long production process. 2. High cost: Specialized pore-filling resins are expensive, and the grinding process generates dust, requiring additional cleaning and dust removal equipment.

[0006] 3. Expensive raw materials: The price of the required special resin is also more expensive than that of solder resist ink materials.

[0007] 4. Low production efficiency and prominent bottlenecks: The curing of resin takes a long time and the grinding process is inefficient, making the entire via-filling process a bottleneck in PCB production and restricting the improvement of overall production capacity.

[0008] 5. Product quality issues: The resin plugging and grinding process can easily cause board deformation. In addition to grinding away excess resin, it can also grind away the copper on the board surface, resulting in a waste of copper resources.

[0009] Furthermore, when ink-filled vias are applied to boards that require molding processes, a technical obstacle arises: the ink shrinks after curing, and its viscosity and cohesive strength are typically lower than those of specialized resin materials. If a traditional vertical hole wall structure is used, the ink adheres only physically to the hole wall, lacking effective stress points. Therefore, under the high temperature and pressure of the molding process, the ink filler is easily extruded entirely or voids are created at the interface. This causes the molding adhesive to leak from the component mounting surface (e.g., the LED bead surface) through these voids to the other side of the board (e.g., the IC surface), contaminating the product. The leaked adhesive contaminates precision circuitry, leading to product malfunction and scrapping. It also contaminates the molding die of the molding machine. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a highly reliable and low-cost LED PCB board and its preparation method, which can be stably and reliably applied to high-temperature and high-pressure molding processes.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a method for manufacturing an LED PCB board, comprising: Provide PCB substrates; A via is formed on the PCB substrate, and a narrowing portion is formed inside the via; The ink is filled into the through hole; The ink is cured to ensure that it is tightly bonded to the interior of the through hole.

[0012] In some embodiments, the via includes a through hole penetrating the PCB substrate and a metal layer formed on the inner wall of the through hole; Along the thickness direction of the PCB substrate, the thickness of the metal layer is not equal or the inner diameter of the via is not equal, so that the via forms a narrowing portion.

[0013] In some embodiments, along the thickness direction of the PCB substrate, the thickness of the metal layer increases from both ends of the via towards the middle, so that the via forms a waist-shaped narrowing portion.

[0014] In some embodiments, along the thickness direction of the PCB substrate, the inner diameter of the through hole decreases from both ends toward the middle, or the inner diameter of the through hole decreases from top to bottom, so that the through hole forms a narrowing portion.

[0015] In some embodiments, along the thickness direction of the PCB substrate, the height of the via is H, and the height of the narrowing portion is h, where h = (1 / 5~1 / 2) * H; The maximum inner diameter of the through hole is R, and the minimum inner diameter of the narrowing part is r. r and R satisfy: r = (40% - 90%) * R.

[0016] In some embodiments, the inner diameter of the through hole is 0.1~0.5mm, and the inner diameter of the narrowed portion is 0.04~0.45mm. The height H of the through hole is 0.2-3.0mm, and the height h of the narrowed portion is 0.04-1.5mm.

[0017] In some embodiments, the inner wall of the through hole protrudes in the axial direction to form a protrusion; The protrusion includes at least one inclined or curved surface, which provides a force point for the cured ink filling the via to be mounted toward the mounting surface of the PCB substrate.

[0018] In some embodiments, forming a via on the PCB substrate, wherein forming a narrowing portion within the via includes: Through holes are formed on the PCB substrate by mechanical drilling or laser drilling; The PCB substrate is placed in a pulse electroplating bath for electroplating. By controlling the ratio of positive and negative currents, the duration of positive and negative currents, and the electroplating temperature, the surface of the PCB substrate and the vias are electroplated to form a narrowing portion in the vias.

[0019] In some embodiments, the forward current density of the electroplating is 1~10 A / dm². 2 ; The reverse current density of the electroplating is 25~35A / dm. 2 ; The positive pulse width of the electroplating is 200~400ms; The reverse pulse width of the electroplating is 1~10ms; The positive current time for the electroplating is 50-88 minutes; The reverse current time for the electroplating is 0.3~1.8 minutes; The electroplating temperature is 35~50℃; The ink is a solder resist ink with a surface tension of 10~50mN / m.

[0020] In some embodiments, the electroplating solution used for electroplating comprises the following components, based on mass concentration: Copper sulfate 180~300g / L, sulfuric acid 40~100g / L, chloride ion 0.03~0.12g / L, iron source 5~10g / L, accelerator 0.0005~0.02g / L, carrier 0.05~1.5g / L, brightener 0.0001~0.01g / L, and leveling agent 0.0005~0.015g / L; The accelerator includes any one or a combination of at least two of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, or sodium N,N-dimethyldithiopropane sulfonate. The carrier includes any one or a combination of at least two of polyethylene glycol and EO / PO polyether; The leveling agent includes any one or a combination of at least two of the following: a phenyltetrazopentane group compound, a thiazole derivative, or a compound containing a phenyltetrazopentane group.

[0021] In another aspect of the present invention, an LED PCB board includes a PCB substrate: A via is formed on the PCB substrate, and a narrowing portion is formed inside the via; The through hole is filled with ink, and after the ink is cured, it is tightly bonded to the interior of the through hole.

[0022] In some embodiments, the via includes a through hole penetrating the PCB substrate and a metal layer formed on the inner wall of the through hole; Along the thickness direction of the PCB substrate, the thickness of the metal layer is not equal or the inner diameter of the via is not equal, so that the via forms a narrowing portion.

[0023] In some embodiments, along the thickness direction of the PCB substrate, the height of the via is H, and the height of the narrowing portion is h, where h = (1 / 5~1 / 2) * H; The maximum inner diameter of the through hole is R, and the minimum inner diameter of the narrowing part is r. r and R satisfy: r = (40% - 90%) * R.

[0024] In some embodiments, the inner wall of the through hole protrudes in the axial direction to form a protrusion; The protrusion includes at least one inclined or curved surface, which provides a force point for the cured ink filling the via to be mounted toward the mounting surface of the PCB substrate.

[0025] The beneficial effects of this invention are: (1) This invention forms a via with a narrowed portion on a PCB substrate, fills the via with ink, and then cures the ink to ensure a tight bond between the ink and the interior of the via. This prevents the ink filler from being squeezed out entirely or creating voids at the interface under the high temperature and pressure of the molding process, which would otherwise cause the molding adhesive to leak from the component mounting surface (e.g., the LED bead surface) to the other side of the board (e.g., the IC surface) through the voids. This invention replaces the existing through-hole with a via with a narrowed portion. The convex surface at the narrowed portion provides a strong stress point for the cured ink, solving the problems of ink being squeezed out under high pressure or creating voids at the interface, thus improving the reliability of the PCB.

[0026] (2) The present invention can directly use solder resist ink to replace expensive hole-filling special resin, which can reduce material costs by more than 30%; at the same time, it eliminates the need for independent grinding process and related equipment investment, resulting in a significant reduction in overall production costs. (3) The hole-plugging process of the present invention can be integrated into the existing solder resist process, which shortens the production cycle, improves production efficiency, and avoids the quality risks that grinding may bring. (4) This invention can be applied to various PCB products that require high voltage packaging. It is highly feasible and has broad application prospects. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for preparing an LED PCB board provided by the present invention; Figure 2 This is a structural schematic diagram of an embodiment of an LED PCB board provided by the present invention; Figure 3 This is the present invention. Figure 2 Metallographic cross-section of the LED PCB board shown; Figure 4 This is a schematic diagram of another embodiment of an LED PCB board provided by the present invention; Figure 5 These are the process flow diagrams for Examples 1 and 2; Figure 6 This is the process flow diagram of Example 3; Figure 7 This is the process flow diagram of Example 4. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below. This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Raw materials whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0029] like Figure 1 As shown, the present invention provides a method for preparing an LED PCB board, comprising: S101, Provide PCB substrate.

[0030] The PCB substrate can be selected from existing rigid substrates, flexible substrates or rigid-flexible combined substrates. The rigid substrate can be selected from FR-4, CEM-1 / CEM-3, etc., and the flexible substrate is made of flexible insulating materials such as polyimide or polyester film, which can be bent and folded.

[0031] S102. A through hole is formed on the PCB substrate, and a narrowing portion is formed inside the through hole.

[0032] Specifically, in combination Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, the via 2 includes a through hole 21 penetrating the PCB substrate 1 and a metal layer 22 formed on the inner wall of the through hole. Along the thickness direction of the PCB substrate 1, the thickness of the metal layer 22 is not equal or the inner diameter of the through hole 21 is not equal, so that the via forms a narrowing portion 3.

[0033] This invention forms a via 2 with a narrowed portion 3 on a PCB substrate 1, and fills the via 2 with ink. The cured ink bonds tightly to the interior of the via, preventing the ink filler from being squeezed out entirely or creating voids at the interface under the high temperature and pressure of the molding process. This prevents the molding adhesive from leaking from the component mounting surface (e.g., the LED bead surface) to the other side of the board (e.g., the IC surface) through these voids. By replacing the existing through-hole with a via 2 having a narrowed portion, this invention provides a strong stress point for the cured ink, solving the problems of ink being squeezed out under high pressure or creating voids at the interface, thus improving the reliability of the PCB.

[0034] The through-hole 2 has a narrowing portion 3 inside, meaning the inner wall of the through-hole protrudes axially to form a protrusion 20. The surface of the protrusion provides a stress point for the curing ink filling the through-hole. Preferably, the protrusion 20 includes at least one inclined or curved surface, which provides a stress point for the curing ink filling the through-hole towards the mounting surface of the PCB substrate, preventing the ink from being squeezed out under high pressure and leaking from the component mounting surface to the other side of the board through the resulting gaps. More preferably, the protrusion includes at least two inclined or curved surfaces, which are symmetrically arranged.

[0035] In some preferred embodiments, such as Figure 2 and Figure 3 As shown, the protrusion 20 includes a curved surface, which is an arc-shaped surface that protrudes towards the mounting surface of the PCB substrate. The arc-shaped surface can provide a force-bearing point towards the mounting surface of the PCB substrate for the cured ink filling the vias. The force-bearing surface is large and uniform, preventing the ink from being squeezed out under high pressure.

[0036] In some preferred embodiments, such as Figure 4 As shown, the protrusion 20 includes a slope along the thickness direction of the PCB substrate. The angle between the slope and the axial direction of the through hole is 50~85°. The slope can provide a force point for the cured ink filled in the through hole towards the mounting surface of the PCB substrate. The force surface is large and uniform, which avoids the ink being squeezed out under high pressure.

[0037] The through hole 2 forming the narrowed portion 3 has multiple implementations, including: (1) Along the thickness direction of the PCB substrate 1, the thickness of the metal layer 22 is not equal, so that the via forms a narrowing portion.

[0038] The thickness of the metal layer 22 can vary in various ways, such as increasing from both ends to the middle, increasing from top to bottom, decreasing from top to bottom, or decreasing from top to bottom and then increasing again. As long as it forms a narrow section within the via, the implementation method is not limited to the above embodiment.

[0039] (2) Along the thickness direction of the PCB substrate 1, the inner diameters of the through holes 21 are not equal, so that the through holes form a narrowing portion.

[0040] The inner diameter of the through hole 21 can change in various ways. It can decrease from both ends to the middle, decrease from top to bottom, increase from top to bottom and then decrease, or decrease from top to bottom and then increase. As long as it forms a narrow section within the through hole, the implementation method is not limited to the above embodiments.

[0041] Preferably, the maximum inner diameter of the through hole 2 is R, and the minimum inner diameter of the narrowing portion 3 is r, where r and R satisfy: r = (40% - 90%) * R. When the minimum inner diameter of the narrowing portion 3 is within (40% - 90%) * R, it can provide a strong stress point for the cured ink, solving the problems of ink being squeezed out under high pressure or voids being generated at the interface. When the minimum inner diameter r of the narrowing portion 3 is less than 40% * R, it has the disadvantage of excessive narrowing, which leads to a sharp increase in the difficulty of ink filling and affects the uniformity of the metal layer on the hole wall, resulting in electroplating reliability problems. When the minimum inner diameter r of the narrowing portion 3 is greater than 90% * R, the narrowing effect is not obvious, and it is not much different from the through hole, so it cannot provide enough stress points for the ink and it is difficult to prevent the ink from being squeezed out.

[0042] Preferably, the inner diameter of the through hole 2 is 0.1~0.5mm, and the inner diameter of the narrowing portion 3 is 0.04~0.45mm. More preferably, the inner diameter of the through hole 2 is 0.2~0.5mm, and the inner diameter of the narrowing portion 3 is 0.10~0.35mm.

[0043] Preferably, the narrowing portion 3 is located in the middle or lower part of the through hole. By placing the narrowing portion in the middle or lower part, the present invention ensures that the pressure point of the ink is located in the middle or lower part, thus preventing the ink from being squeezed out under high pressure or creating voids at the interface.

[0044] More preferably, along the thickness direction of the PCB substrate, the height of the via 2 is H, and the height of the narrowing portion 3 is h, where h = (1 / 5~1 / 2)*H. Here, the height of the via 2 is the distance between the upper and lower surfaces of the PCB substrate, and the height of the narrowing portion 3 is the distance between the minimum inner diameter of the narrowing portion and the lower surface of the PCB substrate. When h < H / 5, the narrowing portion is too short, providing insufficient stress points and failing to effectively resist the high-pressure impact during molding, posing a risk of ink extrusion. Disadvantage: When h > H / 2, the narrowing portion is too long, leading to difficulties in ink filling and a tendency to generate air bubbles or incomplete filling.

[0045] Preferably, the height H of the through hole is 0.2-3.0 mm, and the height h of the narrowed portion is 0.04-1.5 mm. More preferably, the height H of the through hole is 1.6-2.4 mm, and the height h of the narrowed portion is 0.32-1.2 mm.

[0046] In some embodiments, forming a via 2 on the PCB substrate 1, and forming a narrowing portion within the via includes the following steps: A through hole 2 is formed on the PCB substrate 1 by mechanical drilling or laser drilling; The PCB substrate 1 is placed in a pulse electroplating bath for electroplating. By controlling the ratio of positive and negative currents, the time of positive and negative currents, and the electroplating temperature, the surface of the PCB substrate and the through holes are electroplated to form a narrowing portion in the through holes.

[0047] In some embodiments, the thickness of the metal layer 22 is not equal along the thickness direction of the PCB substrate 1, so that the via forms a narrowing portion. In this embodiment, electroplating can be performed using pulsed waveform current. By controlling the ratio of positive and negative currents and the duration of the positive and negative currents, as well as controlling the electroplating temperature, copper is electroplated on the surface of the copper-clad laminate and the vias to form metal layers 22 of different thicknesses, thereby forming a narrowing portion within the via.

[0048] Since the current density is different on both sides and in the middle of the hole, and the magnitude of the current density decreases gradually from the hole opening to the middle of the hole, the formation of metal layers 22 of different thicknesses can be achieved by controlling the magnitude and time of the forward and reverse current densities.

[0049] Preferably, along the thickness direction of the PCB substrate 1, the thickness of the metal layer 22 increases from both ends of the via towards the middle, so that the via forms a waist-shaped narrowing portion.

[0050] The metal layer 22 at both ends of the via dissolves quickly due to the higher current density, while the current density in the middle of the via is lower and it hardly dissolves. Thus, by adjusting the parameters of the positive and negative pulse currents, a thicker metal layer can be plated in the middle of the via wall, forming a tapered structure. This localized reduction in the inner diameter of the via wall creates a "waisted" or "dumbbell" shaped structure that is narrow in the middle and wide at both ends. This narrowed section serves as a support point for subsequent ink filling.

[0051] In some embodiments, the forward current density of the electroplating is 1~10 A / dm². 2 Specifically, it can be 1A / dm 2 2A / dm 2 3A / dm 2 4A / dm 2 5A / dm 2 6A / dm 2 7A / dm 2 8A / dm 2 9A / dm 2 10A / dm 2 However, this is not the only one; The reverse current density of the electroplating is 25~35A / dm. 2 Specifically, it can be 25A / dm 2 26A / dm 2 28A / dm 2 30A / dm 231A / dm 2 32A / dm 2 33A / dm 2 34A / dm 2 35A / dm 2 However, this is not the only one; The positive pulse width of the electroplating is 200~400ms, specifically 200ms, 220ms, 250ms, 270ms, 300ms, 320ms, 330ms, 350ms, 370ms, 390ms, 400ms, but is not limited to these. The reverse pulse width of the electroplating is 1~10ms, specifically 1ms, 2ms, 3ms, 4ms, 5ms, 6ms, 7ms, 8ms, 9ms, 10ms, but is not limited to these. The positive current time for electroplating is 50 to 88 minutes, specifically 50 minutes, 55 minutes, 60 minutes, 65 minutes, 70 minutes, 75 minutes, 80 minutes, 85 minutes, and 88 minutes, but is not limited to these. The reverse current time for electroplating is 0.3 to 1.8 minutes, specifically 0.3 minutes, 0.5 minutes, 0.8 minutes, 1.0 minute, 1.2 minutes, 1.5 minutes, and 1.8 minutes, but is not limited to these. The electroplating temperature is 35~50℃, specifically 35℃, 38℃, 40℃, 42℃, 43℃, 45℃, 48℃, 50℃, but is not limited to this.

[0052] In some embodiments, the electroplating solution used for electroplating comprises the following components, based on mass concentration: Copper sulfate 180~300g / L, sulfuric acid 40~100g / L, chloride ion 0.03~0.12g / L, iron source 5~10g / L, accelerator 0.0005~0.02g / L, carrier 0.05~1.5g / L, brightener 0.0001~0.01g / L, and leveling agent 0.0005~0.015g / L; The accelerator includes any one or a combination of at least two of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, or sodium N,N-dimethyldithiopropane sulfonate. The carrier includes any one or a combination of at least two of polyethylene glycol and EO / PO polyether; The leveling agent includes any one or a combination of at least two of the following: a phenyltetrazopentane group compound, a thiazole derivative, or a compound containing a phenyltetrazopentane group.

[0053] In other embodiments, the inner diameters of the through holes 21 are not equal along the thickness direction of the PCB substrate 1, so that the through holes form a narrowing portion 3. In this embodiment, holes of different sizes or flared holes can be prepared by mechanical drilling or laser drilling, thereby forming the narrowing portion 3 within the through hole 21.

[0054] Preferably, along the thickness direction of the PCB substrate 1, the inner diameter of the through hole 21 decreases from both ends to the middle, so that the through hole forms a narrowing portion 3.

[0055] Preferably, along the thickness direction of the PCB substrate 1, the inner diameter of the through hole 21 decreases from top to bottom, so that the through hole forms a narrowing portion 3.

[0056] In this embodiment, the inner diameter of the through hole 21 is changed to form a narrowed portion 3. The thickness of the metal layer 22 can be the same or different.

[0057] S103. Fill the through hole with ink.

[0058] The ink 4 is solder resist ink, which is a protective coating on a printed circuit board (PCB) that covers the copper lines. It is used to prevent soldering and form a protective layer to prevent short circuits, oxidation, and damage.

[0059] Preferably, the surface tension of the solder resist ink is 10~50 mN / m, which allows it to wet the inner wall of the via 2 and form a tight bond with the interior of the via. If the surface tension of the solder resist ink is too low, it will form an excessively thin covering layer on the via, failing to fill the via and form a tight bond. If the surface tension of the solder resist ink is too high, it will not effectively wet the inner wall of the via 2, easily forming spherical or concave shapes, resulting in gaps between the solder resist ink and the interior of the via.

[0060] This invention allows solder resist ink to be directly filled into the vias, replacing expensive hole-filling resin, reducing material costs by more than 30%; at the same time, it eliminates the need for independent grinding processes and related equipment investment, resulting in a significant reduction in overall production costs.

[0061] S104. The ink is cured to ensure that the ink is tightly bonded to the interior of the through hole.

[0062] After the ink of the present invention is cured, it forms a tight bond with the inside of the through hole under the action of the narrowing part, so as to avoid the ink filler being pressed out as a whole or voids being generated at the interface under the high temperature and high pressure of the molding process, which would cause the molding adhesive to leak from the mounting surface of the component (such as the LED bead surface) to the other side of the board (such as the IC surface) through the generated voids.

[0063] In another aspect of the present invention, an LED PCB board includes a PCB substrate 1: A via 2 is formed on the PCB substrate 1, and a narrowing portion 3 is formed inside the via 2. The through hole is filled with ink 4, and after the ink is cured, it is tightly bonded to the interior of the through hole 2.

[0064] In some embodiments, the via 2 includes a through hole 21 penetrating the PCB substrate 1 and a metal layer 22 formed on the inner wall of the through hole. Along the thickness direction of the PCB substrate 1, the thickness of the metal layer 22 is not equal or the inner diameter of the through hole 21 is not equal, so that the via forms a narrowing portion 3.

[0065] This invention forms a via 2 with a narrowed portion 3 on a PCB substrate 1, and fills the via 2 with ink. The cured ink bonds tightly to the interior of the via, preventing the ink filler from being squeezed out entirely or creating voids at the interface under the high temperature and pressure of the molding process. This prevents the molding adhesive from leaking from the component mounting surface (e.g., the LED bead surface) to the other side of the board (e.g., the IC surface) through these voids. By replacing the existing through-hole with a via 2 having a narrowed portion, this invention provides a strong stress point for the cured ink, solving the problems of ink being squeezed out under high pressure or creating voids at the interface, thus improving the reliability of the PCB.

[0066] The through-hole 2 has a narrowing portion 3 inside, meaning the inner wall of the through-hole protrudes axially to form a protrusion 20. The surface of the protrusion provides a stress point for the curing ink filling the through-hole. Preferably, the protrusion 20 includes at least one inclined or curved surface, which provides a stress point for the curing ink filling the through-hole towards the mounting surface of the PCB substrate, preventing the ink from being squeezed out under high pressure and leaking from the component mounting surface to the other side of the board through the resulting gaps. More preferably, the protrusion includes at least two inclined or curved surfaces, which are symmetrically arranged.

[0067] In some preferred embodiments, the curved surface is an arc-shaped surface that protrudes towards the mounting surface of the PCB substrate. The arc-shaped surface provides a force-bearing point towards the mounting surface of the PCB substrate for the cured ink filling the vias. This force-bearing surface is large and uniform, preventing the ink from being squeezed out under high pressure.

[0068] In some preferred embodiments, the angle between the inclined surface and the axial direction of the via is 50-85° along the thickness direction of the PCB substrate. The inclined surface can provide a force point for the cured ink filled in the via towards the mounting surface of the PCB substrate. The force-bearing surface is large and uniform, which avoids the ink being squeezed out under high pressure.

[0069] The through hole 2 forming the narrowed portion 3 has multiple implementations, including: (3) Along the thickness direction of the PCB substrate 1, the thickness of the metal layer 22 is not equal, so that the via forms a narrowing portion.

[0070] The thickness of the metal layer 22 can vary in various ways, such as increasing from both ends to the middle, increasing from top to bottom, decreasing from top to bottom, or decreasing from top to bottom and then increasing again. As long as it forms a narrow section within the via, the implementation method is not limited to the above embodiment.

[0071] (4) Along the thickness direction of the PCB substrate 1, the inner diameters of the through holes 21 are not equal, so that the through holes form a narrowing portion.

[0072] The inner diameter of the through hole 21 can change in various ways. It can decrease from both ends to the middle, decrease from top to bottom, increase from top to bottom and then decrease, or decrease from top to bottom and then increase. As long as it forms a narrow section within the through hole, the implementation method is not limited to the above embodiments.

[0073] Preferably, the maximum inner diameter of the through hole 2 is R, and the minimum inner diameter of the narrowing portion 3 is r, where r and R satisfy: r = (40% - 90%) * R. When the minimum inner diameter of the narrowing portion 3 is within (40% - 90%) * R, it can provide a strong stress point for the cured ink, solving the problems of ink being squeezed out under high pressure or voids being generated at the interface. When the minimum inner diameter r of the narrowing portion 3 is less than 40% * R, it is excessively narrowed, which also leads to a sharp increase in the difficulty of ink filling and affects the uniformity of the metal layer on the hole wall, resulting in electroplating reliability issues. When the minimum inner diameter r of the narrowing portion 3 is greater than 90% * R, the narrowing effect is not obvious, and it is not much different from the through hole, so it cannot provide enough stress points for the ink and it is difficult to achieve the effect of preventing the ink from being squeezed out.

[0074] Preferably, the inner diameter of the through hole 2 is 0.1~0.5mm, and the inner diameter of the narrowing portion 3 is 0.04~0.45mm. More preferably, the inner diameter of the through hole 2 is 0.2~0.5mm, and the inner diameter of the narrowing portion 3 is 0.10~0.35mm.

[0075] Preferably, the narrowing portion 3 is located in the middle or lower part of the through hole. By placing the narrowing portion in the middle or lower part, the present invention ensures that the pressure point of the ink is located in the middle or lower part, thus preventing the ink from being squeezed out under high pressure or creating voids at the interface.

[0076] More preferably, along the thickness direction of the PCB substrate, the height of the via 2 is H, and the height of the narrowing portion 3 is h, where h = (1 / 5~1 / 2)*H. Here, the height of the via 2 is the distance between the upper and lower surfaces of the PCB substrate, and the height of the narrowing portion 3 is the distance between the minimum inner diameter of the narrowing portion and the lower surface of the PCB substrate. When h < H / 5, the narrowing portion is too short, providing insufficient stress points and failing to effectively resist the high-pressure impact during molding, with the risk of ink being squeezed out. When h > H / 2, the narrowing portion is too long, leading to difficulties in ink filling and the potential for internal air bubbles or incomplete filling.

[0077] Preferably, the height H of the through hole is 0.2-3.0 mm, and the height h of the narrowed portion is 0.04-1.5 mm. More preferably, the height H of the through hole is 1.6-2.4 mm, and the height h of the narrowed portion is 0.32-1.2 mm.

[0078] The present invention will be further illustrated below with specific embodiments. Example 1 like Figure 5 As shown, a method for manufacturing an LED PCB board includes: (1) Provide copper-clad laminates (as shown in process I in the figure); (2) A through hole with a diameter of 0.2 mm is formed on the PCB substrate using a drilling machine (as shown in process II in the figure); (3) First, copper is deposited on the surface of the copper-clad laminate to achieve interlayer electrical connection; then, a pulse electroplating equipment is used to add a mixed copper plating solution containing a special copper plating brightener, a copper plating carrier, and a copper solution, and electroplating is performed using a pulse waveform current. By controlling the ratio of positive and negative currents, the duration of positive and negative currents, and the electroplating temperature, the pulse electroplating is a repeated sequence of positive and negative pulses. The anode is a non-oxygen-evolving titanium mesh, the distance between the anode and cathode is 12 cm, and the plating solution temperature is 40℃. The pulse electroplating parameters and formula are shown in Table 1. This makes the copper plating in the middle of the hole wall thicker, forming a waist-shaped structure. After electroplating, the copper thickness in the middle of the hole wall is 0.0381 mm, and the copper thickness on both sides of the hole wall is 0.025 mm, resulting in the hole diameter being reduced from 0.2 mm to 0.1238 mm (as shown in process III in the figure). (4) Using a solder resist ink machine, ordinary liquid photosensitive solder resist ink is filled into the through hole (as shown in step IV in the figure). (5) The solder resist ink is cured so that the ink is tightly bonded to the interior of the through hole.

[0079] Table 1: Pulse Electroplating Parameters

[0080] The plating solution comprises, by mass concentration: 270 g / L copper sulfate pentahydrate, 60 g / L 98% sulfuric acid, 0.07 g / L chloride ions, 10 g / L ferrous sulfate hexahydrate, 4 g / L ferric ions generated by electrolysis, 0.002 g / L sodium dithiopropane sulfonate, 0.1 g / L polyethylene glycol with a molecular weight of 10,000, 0.75 g / L polyethylene oxide polypropylene oxide monobutyl ether with a molecular weight of 1,000, and 0.005 g / L phenyltetraazapentacyclic compound.

[0081] Example 2 Unlike Example 1, by controlling the ratio and duration of the forward and reverse currents, as well as the electroplating temperature, the copper plating in the middle of the hole wall is made thicker, forming a tapered structure. After electroplating, the copper thickness in the middle of the hole wall is 0.045 mm, and the copper thickness on both sides of the hole wall is 0.020 mm, resulting in a reduction in hole diameter from 0.2 mm to 0.11 mm.

[0082] Example 3 like Figure 6 As shown, a method for manufacturing an LED PCB board includes: (1) Provide copper-clad laminates (as shown in process I in the figure); (2) First, use a drill bit with a diameter of 0.1-0.2 mm to open a through hole on the PCB substrate (as shown in step II in the figure). Then, use a drill bit with a diameter of 0.2-0.4 mm to drill holes on both sides of the copper-clad board (as shown in step III in the figure). Control the drilling depth to be 40% of the board thickness to form a through hole with large and small holes. (3) Electroplating process is used to deposit copper on the surface of the copper-clad laminate and the via (as shown in process IV in the figure). (4) Using a solder resist ink machine, ordinary liquid photosensitive solder resist ink is filled into the through hole (as shown in step V in the figure); (5) The solder resist ink is cured so that the ink is tightly bonded to the interior of the through hole.

[0083] Example 4 like Figure 7 As shown, a method for manufacturing an LED PCB board includes: (1) Provide copper-clad laminates (as shown in process I in the figure); (2) First, use a drill bit with a diameter of 0.2-0.4 mm to drill a depth control hole on the front side of the copper-clad board (as shown in step II in the figure), with a depth of 80% of the board thickness. Then, use a drill bit with a diameter of 0.1-0.2 mm to drill a depth control hole on the back side of the copper-clad board (as shown in step III in the figure), with a depth of 20% of the board thickness, to form a through hole with large and small holes. (3) Electroplating process is used to deposit copper on the surface of the copper-clad laminate and the via (as shown in process IV in the figure). (4) Using a solder resist ink machine, ordinary liquid photosensitive solder resist ink is filled into the through hole (as shown in step V in the figure); (5) The solder resist ink is cured so that the ink is tightly bonded to the interior of the through hole.

[0084] Comparative Example 1 (1) Provide copper-clad laminates; (2) Drill a cylindrical through hole on the PCB substrate; (3) Copper is uniformly deposited on the surface of the copper-clad laminate and the via using an electroplating process; (4) Use a solder resist ink machine to fill the through holes with ordinary liquid photosensitive solder resist ink; (5) The solder resist ink is cured so that the ink is tightly bonded to the interior of the through hole.

[0085] The LED PCB boards obtained in Examples 1-4 were subjected to technical testing, and the results are as follows: (1) The test method is as follows: To verify the reliability of the LED PCB board of this invention, a high-temperature and high-pressure molding simulation test was conducted. The test method is as follows: the cured sample was placed in a molding machine, and a pressure of 1.5 tons (approximately 14.7 MPa) was applied at a temperature of 185°C for 30 minutes. After the test, metallographic section analysis was used to observe whether the ink in the through-holes was squeezed out, whether it separated from the hole wall to create voids, and to check whether there were any traces of molding adhesive leakage on the board surface.

[0086] (2) Test results:

[0087] (3) Analysis of test results: This invention replaces the existing through holes with narrowed sections. The convex surface at the narrowed section can provide a strong stress point for the cured ink. After molding, the ink will not be squeezed out or displaced, and there will be no gaps between the ink and the hole wall. The molding adhesive will not leak, greatly improving the reliability of the PCB.

[0088] The technical features of the embodiments described above can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing an LED PCB board, characterized in that, include: Provide PCB substrates; A via is formed on the PCB substrate, and a narrowing portion is formed inside the via; The ink is filled into the through hole; The ink is cured to ensure that it is tightly bonded to the interior of the through hole.

2. The method for preparing an LED PCB board according to claim 1, characterized in that, The via includes a through hole penetrating the PCB substrate and a metal layer formed on the inner wall of the through hole; Along the thickness direction of the PCB substrate, the thickness of the metal layer is not equal or the inner diameter of the via is not equal, so that the via forms a narrowing portion.

3. The method for preparing an LED PCB board according to claim 2, characterized in that, Along the thickness direction of the PCB substrate, the thickness of the metal layer increases from both ends of the via towards the middle, so that the via forms a waist-shaped narrowing portion; or Along the thickness direction of the PCB substrate, the inner diameter of the through hole decreases from both ends toward the middle, or the inner diameter of the through hole decreases from top to bottom, so that the through hole forms a narrowing portion.

4. The method for preparing an LED PCB board according to claim 2, characterized in that, Along the thickness direction of the PCB substrate, the height of the via is H, and the height of the narrowing portion is h, where h = (1 / 5~1 / 2) * H; The maximum inner diameter of the through hole is R, and the minimum inner diameter of the narrowing part is r. r and R satisfy: r = (40% - 90%) * R.

5. The method for preparing an LED PCB board according to claim 1, characterized in that, The inner diameter of the through hole is 0.1~0.5mm, and the inner diameter of the narrowing portion is 0.04~0.45mm; the height H of the through hole is 0.2-3.0mm, and the height h of the narrowing portion is 0.04-1.5mm.

6. The method for preparing an LED PCB board according to claim 1, characterized in that, The inner wall of the through hole protrudes in the axial direction to form a protrusion; The protrusion includes at least one inclined or curved surface, which provides a force point for the cured ink filling the via to be mounted toward the mounting surface of the PCB substrate.

7. The method for preparing an LED PCB board according to claim 1, characterized in that, The via formed on the PCB substrate, wherein the via forms a narrowing portion therein, includes: Through holes are formed on the PCB substrate; The PCB substrate is placed in a pulse electroplating bath for electroplating. By controlling the ratio of positive and negative currents, the duration of positive and negative currents, and the electroplating temperature, the surface of the PCB substrate and the vias are electroplated to form a narrowing portion in the vias.

8. The method for preparing an LED PCB board according to claim 7, characterized in that, The forward current density of the electroplating is 1~10 A / dm. 2 ; The reverse current density of the electroplating is 25~35A / dm. 2 ; The positive pulse width of the electroplating is 200~400ms; The reverse pulse width of the electroplating is 1~10ms; The positive current time for the electroplating is 50-88 minutes; The reverse current time for the electroplating is 0.3~1.8 minutes; The electroplating temperature is 35~50℃; The ink is a solder resist ink with a surface tension of 10~50mN / m.

9. The method for preparing an LED PCB board according to claim 7, characterized in that, The electroplating solution used for electroplating comprises the following components, based on mass concentration: Copper sulfate 180~300g / L, sulfuric acid 40~100g / L, chloride ion 0.03~0.12g / L, iron source 5~10g / L, accelerator 0.0005~0.02g / L, carrier 0.05~1.5g / L, brightener 0.0001~0.01g / L, and leveling agent 0.0005~0.015g / L; The accelerator includes any one or a combination of at least two of sodium polydithiopropane sulfonate, sodium 3-mercapto-1-propane sulfonate, or sodium N,N-dimethyldithiopropane sulfonate. The carrier includes any one or a combination of at least two of polyethylene glycol and EO / PO polyether; The leveling agent includes any one or a combination of at least two of the following: a phenyltetrazopentane group compound, a thiazole derivative, or a compound containing a phenyltetrazopentane group.

10. An LED PCB board prepared by the method according to any one of claims 1 to 9, characterized in that, Including PCB substrate; A via is formed on the PCB substrate, and a narrowing portion is formed inside the via; The through hole is filled with ink, and after the ink is cured, it is tightly bonded to the interior of the through hole.

11. The LED PCB board according to claim 10, characterized in that, The via includes a through hole penetrating the PCB substrate and a metal layer formed on the inner wall of the through hole; Along the thickness direction of the PCB substrate, the thickness of the metal layer is not equal or the inner diameter of the via is not equal, so that the via forms a narrowing portion.

12. The LED PCB board according to claim 10, characterized in that, Along the thickness direction of the PCB substrate, the height of the via is H, and the height of the narrowing portion is h, where h = (1 / 5~1 / 2) * H; The maximum inner diameter of the through hole is R, and the minimum inner diameter of the narrowing part is r. r and R satisfy: r = (40% - 90%) * R.

13. The LED PCB board according to claim 10, characterized in that, The inner wall of the through hole protrudes in the axial direction to form a protrusion; The protrusion includes at least one inclined or curved surface, which provides a force point for the cured ink filling the via to be mounted toward the mounting surface of the PCB substrate.

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