Processing method for realizing zero glue overflow of blind slot and blind slot PCB (Printed Circuit Board) thereof

Abstract

The invention provides a processing method for realizing zero glue overflow of a blind slot and a blind slot PCB (Printed Circuit Board) thereof. The processing method comprises the following steps: S1, firstly, manufacturing a core board; s2, coating a glue blocking coating: accurately coating a layer of glue blocking coating which is uniform in thickness and free of defects on the blind groove needing to be protected and a peripheral bonding pad area at the position, needing to be provided with the blind groove, of the core plate, so as to form a temporary protective layer, and physically isolating the contact between resin and the bonding pad; s3, high-temperature-resistant adhesive tape is pasted, and the high-temperature-resistant adhesive tape located on the upper side of the adhesive blocking coating is attached to the core plate layer above the position, where the blind groove needs to be formed, of the core plate; s4, mother board pressing: pressing a plurality of core boards into a mother board; s5, grooving is carried out, normal grooving is carried out on the mother board, and the high-temperature-resistant adhesive tape corresponding to the blind groove is removed together; s6, washing is removed, the temporary glue blocking coating at the blind groove is removed through a chemical cleaning line, and the excessive glue of the blind groove is fundamentally prevented; the processing method completely eradicates the phenomenon of glue overflow at the bottom of the blind groove.

Description

Technical Field

[0001] This invention relates to PCB manufacturing technology, and more particularly to a manufacturing method for achieving zero adhesive overflow in blind slots and a blind slot PCB board thereof. Background Technology

[0002] Currently, as electronic products develop towards high performance, miniaturization, and high density, the structure of printed circuit boards (PCBs) is becoming increasingly complex. PCBs are no longer simply flat surfaces; they have evolved into diverse and multi-dimensional products. One type of product features a pit design with circuitry and holes at the bottom. This type of product has complex manufacturing processes and low yield rates. In the PCB industry, this type of product is commonly referred to as a blind slot.

[0003] In printed circuit boards, blind slot structures have been widely used in high-end communications and integrated circuit packaging fields because they can meet the requirements of thinness and high-density interconnection. In the traditional manufacturing process of blind slot PCBs, after lamination, the uncontrolled flow of prepreg or filling resin often causes glue overflow at the edge of the blind slot. In order to clean up the overflow, the precision pattern at the bottom of the blind slot can be easily damaged, which seriously affects the final performance and reliability of the product.

[0004] Currently, the industry mainly relies on embedding high-temperature tape in the inner layer sub-board for adhesive resistance. However, this method has inherent drawbacks, including inconsistent quality of the high-temperature tape, a narrow process window, and high tape leakage and operating costs. Furthermore, the tape's thickness is incompatible with the prepreg, leading to pressure loss after lamination and adhesive overflow from the lamination gaps, ultimately requiring cleaning. Chemical or mechanical cleaning methods suffer from narrow process windows and are prone to pad damage. Moreover, existing technologies are all "end-of-pipe treatments," failing to effectively "prevent" adhesive overflow at its source.

[0005] In view of this, and in light of the shortcomings of existing technologies, there is an urgent need for a processing method that can fundamentally prevent the generation of adhesive overflow in blind grooves. Summary of the Invention

[0006] The present invention provides a processing method for achieving zero glue overflow in blind slots and a blind slot PCB board thereof. Throughout the entire processing, the bottom pattern of the blind slot remains intact, completely eliminating glue overflow at the bottom of the blind slot.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A processing method for achieving zero adhesive overflow in blind grooves includes the following steps: S1. First, make the core board; S2. Apply a resist coating. At the location where blind slots need to be opened on the core board, accurately apply a layer of resist coating with uniform thickness and no defects to the blind slots and surrounding pad areas that need protection, and avoid covering other areas that need resin filling and bonding, forming a temporary protective layer to physically isolate the resin from contact with the pads. S3. Apply high-temperature resistant tape. Apply high-temperature resistant tape above the adhesive-resistant coating on the core board layer above the location where blind grooves need to be made in the core board. This is used to fill the PP cutouts. S4. Motherboard pressing: Pressing several core boards together to form a motherboard; S5. Grooving: Grooving is done normally on the motherboard, and the high-temperature resistant tape corresponding to the blind groove is removed at the same time. S6. Removal and washing: After passing through the chemical cleaning line, the temporary adhesive-resistant coating on the blind tank is removed, fundamentally preventing adhesive overflow from the blind tank.

[0008] Further, step S2 specifically includes: selecting a modified photosensitive polyimide as the resist material for the resist coating, and accurately printing it onto the blind groove area of ​​the blind groove layer using a screen printing machine; baking it in a pre-baking oven for a period of time to form a dry film-like protective layer, and then exposing and developing it to form a pattern the same size as the blind groove area.

[0009] Furthermore, the modified photosensitive polyimide material has a wavelength of 365-405nm, is curable, and is resistant to high temperatures.

[0010] Furthermore, in step S3, the thickness of the high-temperature resistant tape material is 50-180 μm.

[0011] Furthermore, step S4 specifically includes: stacking the core board, prepreg, and blind groove layer together, and completing the pressing under conditions of 210°C and 350psi, while ensuring that the adhesive resist coating still completely covers the bottom of the blind groove after high temperature and high pressure pressing.

[0012] Further, step S5 specifically includes: opening windows in the upper layer of the blind slot after lamination, then immersing the entire laminated board in an alkaline aqueous solution with a concentration of 5%-7% for 3-5 minutes at a temperature of 70-80℃, and using slight ultrasonic waves to clean the residue on the surface of the solder pads.

[0013] A blind slot PCB board employs the aforementioned processing method to achieve zero adhesive overflow in the blind slots.

[0014] The beneficial effects of this invention are: This invention applies the resist layer process from microelectronics and photolithography to PCB manufacturing. By using a combination of temporary physical blocking and subsequent chemical stripping, it solves the long-standing problem of adhesive overflow in the industry. Before lamination, a temporary resist coating is applied to the critical areas of the blind slots. This resist coating is applied only to the blind slots and surrounding pads that need protection, avoiding coverage of other areas that require resin filling and bonding. It also ensures uniform coating thickness and no defects. After lamination, the resist coating is completely removed, effectively ensuring selective removal of the layer without affecting the entire board. This physically isolates the resin from the pads, fundamentally preventing adhesive overflow in the blind slots and effectively improving product yield and reliability.

[0015] The entire processing method is simple and physically blocks the path of resin overflow, realizing a fundamental shift from "passive glue removal" to "active prevention," completely eliminating soldering defects and performance risks caused by glue overflow in blind slots; during processing, the resist coating can be precisely applied through pattern transfer, and the protected area is controllable; the stripping solution has high selectivity for the resist coating, and the stripping process will not damage other parts of the PCB board, achieving a wide process window and high safety.

[0016] Moreover, this processing method is compatible with existing PCB production lines, eliminating the need for large and expensive equipment, and enabling the blind slot bottom design of PCBs to move towards greater integration. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the blind slot of the core board coated with an adhesive-resistant coating in this invention; Figure 2 This is a schematic diagram of the structure of the core board, prepreg, and blind groove layer after being laminated together in this invention; Figure 3 This is a schematic diagram of the PCB board after mechanical window opening and washing in this invention. Detailed Implementation

[0018] This section will describe in detail specific embodiments of the present invention. Preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0020] In the description of this invention, "several" means one or more, "more than" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0021] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0022] A processing method for achieving zero adhesive overflow in blind grooves includes the following steps: S1. First, make the core board; S2. Apply an adhesive-resistant coating, such as Figure 1 As shown, at the location where blind slots 2 need to be opened on the core board 1, a layer of uniform and defect-free resist coating 3 is precisely applied to the blind slot 2 and the surrounding pad area that needs to be protected, and avoids covering other areas that need to be filled and bonded with resin, forming a temporary protective layer to physically isolate the resin from contact with the pads 4. In the specific coating process: a modified photosensitive polyimide is selected as the resist material for the resist coating 3, and it is precisely printed onto the blind groove 2 area of ​​the blind groove layer using a screen printing machine; it is baked in a pre-baking oven for a period of time to form a dry film-like protective layer, and then exposed and developed to form a pattern the same size as the blind groove 2 area; wherein, the wavelength of the modified photosensitive polyimide material is 365-405nm, which can be cured and is resistant to high temperature.

[0023] S3. Apply high-temperature resistant tape 5. Apply high-temperature resistant tape 5 above the core board layer above the position where the blind groove 2 needs to be opened in the core board 1. This tape is used to fill the PP cutout. The thickness of the high-temperature resistant tape material is 50-180μm.

[0024] S4. Mother plate pressing, such as Figure 2 As shown, several core boards are pressed together to form a mother board; during the pressing process, the core boards, prepreg and blind groove layer are stacked together and pressed at 210°C and 350psi, while ensuring that the adhesive resist coating still completely covers the bottom of the blind groove after high temperature and high pressure pressing.

[0025] S5. Grooving: Grooving is performed normally on the motherboard, and the high-temperature resistant tape 5 corresponding to blind groove 2 is removed at the same time. S6, rinsing, such as Figure 3As shown, after passing through the chemical cleaning line, the temporary adhesive-resistant coating 3 at blind tank 2 is removed, thus fundamentally preventing adhesive overflow from blind tank 2.

[0026] During processing, after lamination, mechanical or laser windowing is performed on the upper layer of the blind slot. Then, the entire laminated board is immersed in a 5%-7% alkaline aqueous solution at a temperature of 70-80℃ for 3-5 minutes, and slight ultrasonic cleaning is used to remove residues from the solder pad surface.

[0027] In this embodiment, a temporary resist coating 3 is applied to the critical area of ​​the blind slot 2 before lamination. The resist coating 3 can be precisely applied by pattern transfer, and the protected area is controllable. The stripping solution has high selectivity for the resist coating 3, and the stripping process will not damage other parts of the PCB board, achieving a wide process window and high safety. It physically isolates the resin from the pads and completely removes the resist coating 3 after lamination, thereby fundamentally preventing the overflow of adhesive in the blind slot 2 and effectively improving product yield and reliability.

[0028] In a second aspect, a blind slot PCB board is provided, which applies the processing method described in the first aspect of the present invention to achieve zero glue overflow in the blind slot.

[0029] In this embodiment, the resist layer process from microelectronics and photolithography is applied to the PCB manufacturing process. By using a combination of temporary physical blocking and subsequent chemical stripping, the long-standing problem of resin overflow in the industry is solved. By applying the resist coating only to the blind slots and surrounding pad areas that need protection, avoiding covering other areas that require resin filling and bonding, the coating is effectively selectively removed after lamination without affecting the entire board. The entire processing method is simple and physically blocks the path of resin overflow, achieving a fundamental shift from "passive resin removal" to "active prevention," completely eliminating soldering defects and performance risks caused by resin overflow in the blind slots. Moreover, this processing method is compatible with existing PCB production lines, eliminating the need for large and expensive equipment, and enabling the design of the bottom of the blind slots on PCBs to move towards higher integration.

[0030] Compared to existing blind slot manufacturing methods in the industry, this method offers high precision and selectivity: the coating can be precisely applied using a patterned approach, and the protected area is controllable; the stripping process will not damage the rest of the PCB, the process window is wide, and safety is high. It also effectively solves problems such as difficulty in repairing adhesive inside the blind slot after lamination, scratches on the precision patterns at the bottom of the blind slot, and scratches on the pads at the bottom of the blind slot. It is compatible with existing PCB production lines and suitable for manufacturing various high-density, small-pitch PCBs.

[0031] The above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Except for the cases listed in the specific embodiments, all equivalent changes made in accordance with the shape, structure and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A processing method for achieving zero adhesive overflow in blind grooves, characterized in that, Includes the following steps: S1. First, make the core board; S2. Apply a resist coating. At the location where blind slots need to be opened on the core board, accurately apply a layer of resist coating with uniform thickness and no defects to the blind slots and surrounding pad areas that need protection, and avoid covering other areas that need resin filling and bonding, forming a temporary protective layer to physically isolate the resin from contact with the pads. S3. Apply high-temperature resistant tape. Apply high-temperature resistant tape above the adhesive-resistant coating on the core board layer above the location where blind grooves need to be made in the core board. This is used to fill the PP cutouts. S4. Motherboard pressing: Pressing several core boards together to form a motherboard; S5. Grooving: Grooving is done normally on the motherboard, and the high-temperature resistant tape corresponding to the blind groove is removed at the same time. S6. Removal and washing: After passing through the chemical cleaning line, the temporary adhesive-resistant coating on the blind tank is removed, fundamentally preventing adhesive overflow from the blind tank.

2. The processing method for achieving zero glue overflow in blind grooves according to claim 1, characterized in that, Step S2 specifically includes: selecting a modified photosensitive polyimide as the resist material for the resist coating, and accurately printing it onto the blind groove area of ​​the blind groove layer using a screen printing machine; baking it in a pre-baking oven for a period of time to form a dry film-like protective layer, and then exposing and developing it to form a pattern the same size as the blind groove area.

3. The processing method for achieving zero glue overflow in blind grooves according to claim 2, characterized in that, The modified photosensitive polyimide material has a wavelength of 365-405nm, is curable, and is resistant to high temperatures.

4. The processing method for achieving zero glue overflow in blind grooves according to claim 1, characterized in that, In step S3, the thickness of the high-temperature resistant tape material is 50-180 μm.

5. The processing method for achieving zero glue overflow in blind grooves according to claim 1, characterized in that, Step S4 specifically includes: the core board, the prepreg, and the blind groove layer are stacked together and pressed together at 210°C and 350psi, while ensuring that the adhesive resist coating still completely covers the bottom of the blind groove after high temperature and high pressure pressing.

6. The processing method for achieving zero glue overflow in blind grooves according to claim 1, characterized in that, Step S5 specifically includes: opening windows in the upper layer of the blind slot after lamination, then immersing the entire laminated board in an alkaline aqueous solution with a concentration of 5%-7% for 3-5 minutes at a temperature of 70-80℃, and using slight ultrasonic waves to clean the residue on the surface of the solder pads.

7. A blind slot PCB board, characterized in that, The processing method for achieving zero glue overflow in blind grooves, as described in any one of claims 1 to 6, is applied.

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