A method for processing a macroporous resin plug hole

Abstract

The application discloses a processing method of macroporous resin hole plugging, comprising the following steps: drilling a through hole on a production plate and metalizing the through hole, the diameter of the through hole is greater than or equal to 0.8 mm; sticking a hard plate on one surface of the production plate to close one end of the through hole; drilling at least one air guide hole on the hard plate corresponding to the position of the through hole, the diameter of the air guide hole is 0.03-0.1 mm; performing resin hole plugging operation on the through hole; firstly, making the resin in a pre-solidification state through pre-baking, and then removing the hard plate on the production plate; removing the resin protruding from the plate surface after hole plugging through plate grinding; and completely solidifying the resin through baking. The method can effectively solve the resin hole plugging problem of a plate with a thickness greater than 1.0 mm and a hole diameter of 0.8-2.35 mm, ensure full hole plugging without obvious defects, meanwhile, the hard plate is easy to tear off during the post-processing process, and the reliability and stability of the macroporous resin hole plugging process are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, specifically to a method for processing large-diameter resin plugs. Background Technology

[0002] With the rapid development of electronic technology, printed circuit boards (PCBs) are playing an increasingly crucial role in electronic devices. Due to their increased functionality and higher quality requirements, manufacturers need to continuously develop new processing technologies to support PCB manufacturing. PCB resin via plugging is a common technology in the industry, widely used in blind vias, buried vias, and high-density interconnects. Commonly used via plugging methods include prepreg lamination, vertical vacuum resin plugging, selective resin plugging, and screen printing. Currently, PCB resin plugging technology for board thicknesses of 0.4–3.2 mm and via diameters of 0.25–0.40 mm is relatively mature, with a yield rate exceeding 99%. Some manufacturers have achieved resin plugging for via diameters <0.8 mm, but PCB resin plugging for via diameters ≥0.8 mm still presents many challenges.

[0003] To address the heat dissipation challenges of high-power, high-density electronic products, an increasing number of printed circuit board (PCB) manufacturers are opting for high thermal conductivity metal substrates. Common metal substrates are mostly single-sided. When manufacturing multi-layer metal substrates, holes larger than the finished product's aperture (0.8mm or larger in diameter) need to be drilled into the laminated metal substrate. These holes are then filled with high thermal conductivity resin before drilling again. In PCB manufacturing, vacuum plugging and semi-automatic screen printing are commonly used resin plugging methods. However, when the aperture exceeds a certain size (e.g., 0.8mm or larger), both methods have limitations. In actual production, it has been found that due to the larger aperture, the resin filling is not dense, resulting in noticeable voids and depressions at the hole openings. This fails to meet the PCB's quality requirements for holes, leading to decreased product yield and increased production costs.

[0004] The fundamental reason for the difficulty in plugging large-pore resins lies in the interaction between the physical properties of the resin itself and the plugging process conditions. Plugging resins have a certain degree of fluidity. For large pores, the surface tension between the freshly plugged resin and the pore wall is insufficient to support its adhesion to the pore wall. Especially in the initial stage of plugging, the resin is easily affected by gravity and its own flow characteristics, making it difficult to distribute evenly and adhere to the pore wall. In the low-temperature stage of the post-curing process, the resin fluidity remains strong, easily leading to resin loss during curing. This results in poor resin filling at the bottom of the pore and overall, failing to achieve effective pore plugging.

[0005] To address the problems associated with plugging large and medium-sized holes, the existing Chinese patent CN219514293U discloses a resin plugging structure for PCB printed circuit boards. First, after drilling through-holes on both sides or in multiple layers of the board, and after the holes are metallized and plated with copper, a barrier film is applied to one side before resin plugging. Then, a drilling machine or laser machine is used to drill vent holes in the barrier film at the hole locations. Vacuum plugging is then performed. After plugging, excess resin on the board surface is brushed off and the barrier film is removed. In this technical solution, the barrier film can be a commonly used photosensitive film for PCB etching, such as Hitachi's 1127 dry film. This barrier film is thin and flexible; its portion located at the through-hole will deform downwards under the influence of upward pressure (including the weight of the resin and the downward pressure of the scraper) during resin plugging, resulting in proper filling. The resin protrudes downwards from the lower end of the orifice. Even if the blocking film is made of cardboard or plastic, resin protrusions will form at the air vents of the blocking film after curing. Furthermore, the blocking film is only removed after the resin has cured and the plate has been sanded. Thus, during sanding, only the resin protruding from the orifice on the upper surface can be removed, while the lower surface is protected by the blocking film and is not sanded. In other words, the resin protruding from the orifice and the resin protrusions on the lower surface cannot be removed. As for the method of removing the blocking film, if the blocking film is dry film, it can be removed with a stripping solution without damaging the resin. However, if the blocking film is made of cardboard or plastic, firstly, it must be glued to the plate with adhesive. Removing it will generally leave adhesive residue on the plate, which will affect the quality of the plate. Secondly, the binding force between the blocking film and the cured resin is strong, and some resin is easily carried out during removal, which will affect the quality of the plugging. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for processing large-diameter resin plugging, which effectively solves the problem of resin plugging for boards thicker than 1.0 mm and with pore diameters between 0.8 and 2.35 mm. This method ensures full plugging without obvious defects, while also taking into account the ease of removal of the hardened board during post-processing, significantly improving the reliability and stability of the large-diameter resin plugging process.

[0007] To address the aforementioned technical problems, this invention provides a method for processing large-diameter resin plugs, comprising the following steps: S1. Drill through holes on the production board and metallize the through holes, wherein the diameter of the through holes is ≥0.8mm; S2. A rigid board is attached to one surface of the production board to seal one end of the through hole. S3. Drill at least one air guide hole at the position corresponding to the through hole on the hard plate, wherein the diameter of the air guide hole is 0.03-0.1mm; S4. Perform resin plugging operation on the through hole; S5. First, pre-bake the resin to put it in a pre-cured state, and then remove the hardboard from the production board. S6. Remove the resin protruding from the plate surface after plugging the hole using a grinding plate; S7. The resin is fully cured by baking.

[0008] Furthermore, when the diameter of the through hole is 0.8 mm, the diameter of the air guide hole is 0.03 mm; when the diameter of the through hole is 1 mm, the diameter of the air guide hole is 0.05 mm.

[0009] Furthermore, the diameter of the through hole is ≤2.35mm, and when the diameter of the through hole is ≥2.3mm, the diameter of the air guide hole is 0.1mm.

[0010] Furthermore, when there is only one vent hole at each through hole, the vent hole is located at the center of the through hole.

[0011] Furthermore, when there are multiple air guide holes at each through hole, one of the air guide holes is located at the center of the through hole, and the other air guide holes are arranged in a ring array around the central air guide hole.

[0012] Furthermore, when there are multiple air guide holes at each through hole, the multiple air guide holes are arranged in a ring array or a square array.

[0013] Furthermore, in step S1, after drilling through holes in the production board, the through holes are metallized by copper plating and electroplating in sequence, and the thickness of the copper layer on the board surface is increased by 3-6 μm beyond the design after electroplating.

[0014] Furthermore, in step S2, a rigid board is adhered to one surface of the production board using an adhesive, and the size of the rigid board is consistent with the size of the production board. The rigid board is an epoxy resin board. In step S3, air vents are drilled into the rigid board using mechanical drilling or laser drilling. In step S6, the adhesive on the surface of the production board and the pre-excess portion of the copper layer on the board are removed during the grinding process.

[0015] Furthermore, in step S5, a staged heating method is used during baking; the staged heating includes two stages, with the first stage baking temperature being 90°C and the second stage baking temperature being 120°C; after the second stage baking, the resin of the production board is in a pre-cured state; in step S7, the baking temperature is 150°C.

[0016] Furthermore, the production board is a metal substrate.

[0017] Furthermore, the production board is a multilayer board in which an inner core board and an outer copper foil are laminated together by a prepreg, and the inner core board has been fabricated with inner layer circuitry before lamination.

[0018] Compared with the prior art, the present invention has the following beneficial effects: In this invention, a rigid plate is used to seal one end of the through-hole to support the resin entering the through-hole during subsequent resin plugging. This prevents excessive resin loss due to gravity caused by an overly large orifice, which could lead to incomplete plugging. Small-diameter vent holes are drilled in the rigid plate to guide air and facilitate resin flow downwards during plugging, ensuring the resin can flow downwards and fill the through-hole. The filled resin can only flow out through the small-diameter vent holes, preventing significant loss and ensuring complete filling of the through-hole. Furthermore, the rigid plate is removed when the resin has cured to a preliminary cured state. At this point, the rigid plate, the resin surface of the plug, and the surface of the production board all have good tear resistance, minimizing residue and resin loss during removal. Therefore, this method effectively solves the problem of board thicknesses greater than 1.0 mm. This process addresses the resin plugging issue for pores with diameters ranging from 0.8 to 2.35 mm, ensuring full plugging without significant defects while also considering the ease of removal of the hardened board during post-processing. This significantly improves the reliability and stability of the large-diameter resin plugging process.

[0019] Secondly, using a rigid plate as the air guide template can effectively support the resin in the hole, preventing downward deformation that could cause resin to protrude. Furthermore, after removing the rigid plate, the protruding resin and adhesive on the board surface can be removed together, ensuring the flatness of the board surface. In addition, the thickness of the copper layer on the board surface is increased during electroplating, which increases the amount of wear during subsequent grinding, further ensuring the removal of adhesive and resin from the board surface and improving the flatness of the board surface. Attached Figure Description

[0020] Figure 1 This is a schematic diagram showing the air duct hole drilled in the rigid plate in the embodiment. Figure 2 This is a schematic diagram showing the through-hole filled with resin in the embodiment; Figure 3 This is a schematic diagram of an embodiment where multiple air guide holes are provided at the through hole and a central air guide hole is present. Figure 4 This is a schematic diagram of another embodiment in which multiple air guide holes are provided at the through hole and the multiple air guide holes are arranged in a ring array. Figure 5 This is a schematic diagram of another embodiment where multiple air guide holes are provided at the through hole and the multiple air guide holes are arranged in a square array. Detailed Implementation

[0021] To better understand the technical content of this invention, the technical solution of this invention will be further introduced and explained below in conjunction with specific embodiments.

[0022] Example 1 This embodiment illustrates a method for manufacturing a circuit board, which includes a process of resin plugging large-diameter through-holes, comprising the following processing steps in sequence: (1) Cutting: Cut the core board according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm, and the copper layer thickness on both surfaces of the core board is 0.5oz.

[0023] (2) Inner layer circuit fabrication (negative film process): Inner layer pattern transfer, photosensitive film is coated using a vertical coating machine, and the film thickness of the photosensitive film is controlled at 8μm. The inner layer circuit is exposed using a fully automatic exposure machine with 5-6 exposure rulers (21 exposure rulers). After development, the inner layer circuit pattern is formed; Inner layer etching, the inner layer circuit is etched out on the core board after exposure and development. The inner layer line width is measured to be 3mil; Inner layer AOI, and then the inner layer circuit is inspected for defects such as open circuits, short circuits, line gaps, and line pinholes. Defective products are scrapped, and defect-free products are sent to the next process.

[0024] (3) Pressing: The browning speed is based on the thickness of the bottom copper. The core board, prepreg, and outer copper foil are stacked in sequence as required. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the stacked board to form the production board. The thickness of the production board is greater than 1mm.

[0025] (4) Drilling: According to the existing drilling technology, drilling is carried out on the production board 1 according to the design requirements to drill through holes 2 with a diameter ≥ 0.8 mm.

[0026] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole walls using chemical copper plating to metallize the holes. The backlight test is level 10, and the copper plating thickness in the holes is 0.5μm.

[0027] (6) Full-board electroplating: The production board is electroplated to thicken the copper layer in the holes and on the board surface. After full-board electroplating, the thickness of the copper layer on the board surface is increased by 3-6 μm beyond the design.

[0028] (7) Resin plugging: Specifically includes the following steps: a. A rigid board 3 is glued to one surface of the production board 1 using adhesive, so as to seal one end of the through hole 2 (e.g., Figure 1 (As shown); the dimensions of this rigid board are consistent with those of the production board; b. Drill at least one vent hole 4 at the position corresponding to the through hole on the rigid plate 3 (e.g., Figure 1 As shown in the figure, the air guide hole 4 is located within the range of the through hole 2, and the diameter of the air guide hole 4 is 0.03-0.1mm; c. The through-hole 3 is filled with resin 5 using vacuum plugging or semi-automatic screen printing plugging methods, i.e., the through-hole 3 is filled with resin 5 (e.g., resin 5). Figure 2 (as shown) d. First, pre-baking is used to bring the resin to a pre-cured state (i.e., preliminary curing state), and then the hardboard on the production board is removed. e. Remove the resin protruding from the board surface after plugging by using a ceramic grinding plate or abrasive belt grinding plate. During grinding, remove the adhesive on the board surface and the pre-large portion of the copper layer on the board surface. f. The resin is fully cured by baking at a temperature of 150°C.

[0029] In one embodiment, the diameter of the through hole 2 is ≤2.35mm.

[0030] In one embodiment, when the diameter of the through hole 2 is 0.8 mm, the diameter of the air guide hole 4 is 0.03 mm.

[0031] In another embodiment, when the diameter of the through hole 2 is 1 mm, the diameter of the air guide hole 4 is 0.05 mm.

[0032] In another embodiment, when the diameter of the through hole 2 is ≥2.3mm, the diameter of the air guide hole 4 is 0.1mm.

[0033] Therefore, the larger the through hole, the larger the corresponding air guide hole diameter, which improves the air guiding and exhaust function and avoids the difficulty of plugging the hole due to untimely exhaust.

[0034] In one embodiment, when there is only one air guide hole 4 at each through hole 2 (e.g.) Figure 1 As shown), the air guide hole 4 is located at the center of the through hole 2, so that the resin flows toward the center.

[0035] In another embodiment, when there are multiple air guide holes 4 at each through hole 2, one air guide hole 4 is located at the center of the through hole 2, and the other air guide holes 4 are arranged in a ring array around the central air guide hole (e.g., Figure 3 (As shown).

[0036] In another embodiment, when there are multiple air guide holes 4 at each through hole 2, the multiple air guide holes 4 are arranged in a ring array or a square array (e.g., Figure 4 and Figure 5 (As shown).

[0037] Understandably, for larger through holes, more small-diameter air guide holes can be set. For example, when the diameter of the through hole is ≥2.3mm, the diameter of the air guide hole can also be designed to be 0.05mm. The air guide holes are also set in a ring array around the central air guide hole. Compared with the previous scheme where the diameter of the air guide hole is 0.1mm, because the diameter is smaller, more air guide holes can be set within the same through hole range to achieve the same exhaust effect, and the problem of resin flowing downward can be further reduced.

[0038] In one embodiment, in step b, air vents are drilled into the rigid plate by mechanical drilling or laser drilling, preferably by laser drilling.

[0039] In one embodiment, step d involves a staged heating method for resin baking and curing. This staged heating includes two phases: a first stage baking temperature of 90°C, a second stage baking temperature of 120°C, and a third stage baking temperature of 150°C. After the first stage baking, the resin on the production board is in a flow state. Removing the hardener at this point can easily lift the resin from the holes, causing blockage and depressions. Therefore, the hardener cannot be removed in this state. After the second stage baking, the resin is in a pre-cured state (initial curing state). In this state, the hardener... The hard board has good tearability with both the resin on the plugging surface and the production board surface. It is not easy to leave residue or take away the resin in the hole when removing the hard board. Therefore, the hard board is removed in the pre-cured state after the second stage baking. Then, it is baked at a high temperature of 150°C in step f to make the resin completely cured. If the hard board is removed after the resin is completely cured, firstly, the bonding force between the hard board and the resin on the plugging surface and the printed circuit board surface increases due to the high temperature baking, which makes it easy to leave residue and take away the resin in the hole during removal. Secondly, it is not easy to grind the board after the resin is completely cured.

[0040] In one embodiment, the rigid board is an epoxy resin board.

[0041] In one embodiment, the thickness of the rigid plate is 0.2-0.5 mm.

[0042] (8) Fabrication of outer layer circuits (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuit film. The outer layer circuit is exposed using an exposure ruler of 5 to 7 divisions (21 divisions). After development, the outer layer circuit pattern is formed on the production board. The outer layer pattern is electroplated, and then copper and tin are plated on the production board respectively. The electroplating parameters are set according to the required copper thickness. Copper plating is performed at a current density of 1.8 ASD for 60 minutes, and tin plating is performed at a current density of 1.2 ASD for 10 minutes, with a tin thickness of 3 to 5 μm. Then, the film is removed, etched, and tin is removed in sequence to etch the outer layer circuit on the production board. The outer layer AOI is performed using an automatic optical inspection system. By comparing with the CAM data, the outer layer circuit is checked for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0043] (9) Solder resist and screen printing: After screen printing solder resist ink on the surface of the production board, it is then subjected to pre-curing, exposure, development and heat curing treatment in sequence to cure the solder resist ink into a solder resist layer; specifically, the solder resist ink on the TOP side and the characters on the TOP side are added with "UL mark", thereby coating a layer on the lines and substrates that do not need to be soldered to prevent bridging between lines during soldering, provide a permanent electrical environment and chemical corrosion resistance, and at the same time beautify the appearance.

[0044] (10) Surface treatment (immersion nickel and gold): The copper surface of the solder pads of the solder mask opening position is uniformly deposited with a nickel layer and a gold layer of a certain required thickness through chemical principle. The thickness of the nickel layer is 3-5μm; the thickness of the gold layer is 0.05-0.1μm.

[0045] (11) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0046] (12) Molding: Based on existing technology and design requirements, the circuit board is made with a shape tolerance of + / -0.05mm.

[0047] (13) FQC: In accordance with the customer's acceptance standards and the applicant's inspection standards, inspect the appearance of the circuit board, and repair any defects in a timely manner to ensure excellent quality control for the customer.

[0048] (14) FQA: Re-test the appearance of the circuit board, the thickness of the copper in the holes, the thickness of the dielectric layer, the thickness of the solder mask, the thickness of the inner copper layer, etc. to see if they meet the customer's requirements.

[0049] (15) Packaging: The circuit boards are sealed and packaged according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0050] Example 2 The method for manufacturing a metal substrate shown in this embodiment is basically the same as the method described in Embodiment 1, except that the lamination process in step (3) is as follows: (3) Lamination: The browning speed is based on the thickness of the bottom copper. The outer copper foil, prepreg, core board, prepreg and metal substrate are stacked sequentially from top to bottom as required. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the laminated board to form a metal substrate. The thickness of the metal substrate is greater than 1mm.

[0051] In one embodiment, the metal base is copper-based or aluminum-based.

[0052] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The descriptions of the embodiments above are only for helping to understand the principles of the embodiments of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for processing large-pore resin plugs, characterized in that, Includes the following steps: S1. Drill through holes on the production board and metallize the through holes, wherein the diameter of the through holes is ≥0.8mm; S2. A rigid board is attached to one surface of the production board to seal one end of the through hole. S3. Drill at least one air guide hole at the position corresponding to the through hole on the hard plate, wherein the diameter of the air guide hole is 0.03-0.1mm; S4. Perform resin plugging operation on the through hole; S5. First, pre-bake the resin to put it in a pre-cured state, and then remove the hardboard from the production board. S6. Remove the resin protruding from the plate surface after plugging the hole using a grinding plate; S7. The resin is fully cured by baking.

2. The processing method for large-pore resin plugs according to claim 1, characterized in that, When the diameter of the through hole is 0.8 mm, the diameter of the air guide hole is 0.03 mm; when the diameter of the through hole is 1 mm, the diameter of the air guide hole is 0.05 mm.

3. The processing method for large-pore resin plugs according to claim 1, characterized in that, The diameter of the through hole is ≤2.35mm. When the diameter of the through hole is ≥2.3mm, the diameter of the air guide hole is 0.1mm.

4. The method for processing large-pore resin plugs according to any one of claims 1-3, characterized in that, When there is only one air guide hole at each through hole, the air guide hole is located at the center of the through hole.

5. The method for processing large-pore resin plugs according to any one of claims 1-3, characterized in that, When there are multiple air guide holes at each through hole, one of the air guide holes is located at the center of the through hole, and the other air guide holes are arranged in a ring array around the central air guide hole.

6. The method for processing large-pore resin plugs according to any one of claims 1-3, characterized in that, When there are multiple air guide holes at each through hole, the multiple air guide holes are arranged in a ring array or a square array.

7. The method for processing large-pore resin plugs according to claim 1, characterized in that, In step S1, after drilling through holes in the production board, the through holes are metallized by copper plating and electroplating in sequence, and the thickness of the copper layer on the board surface is increased by 3-6 μm beyond the design after electroplating.

8. The method for processing large-pore resin plugs according to claim 7, characterized in that, In step S2, a rigid board is attached to one surface of the production board using an adhesive, and the size of the rigid board is the same as that of the production board. The rigid board is an epoxy resin board. In step S3, air vents are drilled into the rigid board using mechanical drilling or laser drilling. In step S6, the adhesive on the surface of the production board and the pre-excess portion of the copper layer on the board are removed during the grinding process.

9. The method for processing large-pore resin plugs according to claim 1, characterized in that, In step S5, a staged heating method is used during baking; the staged heating includes two stages, with the first stage baking temperature at 90°C and the second stage baking temperature at 120°C; after the second stage baking, the resin of the production board is in a pre-cured state; in step S7, the baking temperature is 150°C.

10. The processing method for large-pore resin plugs according to claim 1, characterized in that, The production board is a metal substrate or a multilayer board in which the inner core board and the outer copper foil are laminated together by prepreg, and the inner core board has been fabricated with inner layer circuitry before lamination.

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