A method for improving resin grinding depressions on high-multilayer server boards

Abstract

This invention discloses a method for improving resin grinding indentations on multilayer server boards, comprising the following steps: applying a dry film to one surface of a production board; the production board being a board that has already undergone resin plugging; then using at least one set of grinding components to grind the side of the production board without the dry film; the grinding components include grinding brushes and back pressure rollers arranged vertically, with a conveying gap formed between the grinding brushes and the back pressure rollers for the production board to pass through; during grinding, the side of the production board with the dry film is in contact with the back pressure rollers; after grinding, the film is removed, and a dry film is applied to the other surface of the production board; the grinding components are then used to grind the side of the production board without the dry film, and the film is removed after grinding; during grinding, the side of the production board with the dry film is in contact with the back pressure rollers. This invention uses a single-sided grinding method, and applies a dry film as a buffer layer to the un-grinded side of the production board to protect the board surface near the back pressure roller from indentations caused by foreign objects.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and specifically to a method for improving resin grinding depressions in high-multilayer server boards. Background Technology

[0002] High-multilayer server boards typically have 12-14 circuit layers and a board thickness of 3.0±0.2mm. To improve panel utilization, the panel size is generally 610*760mm, with a minimum line width / spacing of 89 / 100um. Server circuit boards are heavy and have dense circuitry, and the outer layer patterns have strict requirements on the quality of the incoming board surface, making it easy to produce quality defects during manufacturing. The main process for manufacturing high-multilayer communication boards is as follows: pre-processing → board electroplating → resin pretreatment → resin via plugging → resin grinding → outer layer patterning → post-processing.

[0003] The resin grinding process described above generally uses an "8-axis ceramic grinding brush + 4-axis non-woven fabric grinding brush". A back pressure roller is installed under the grinding brush. When grinding the board, the grinding brush and the back pressure roller squeeze the board surface against each other. The spray pipe is designed above the grinding brush. Each spray pipe is 810mm long and equipped with 6 nozzles.

[0004] However, the above grinding process has the following drawbacks:

[0005] 1. A back pressure roller is installed under the grinding brush. When grinding the board, the grinding brush and the back pressure roller squeeze the board surface against each other. If there are hard foreign objects or copper particles on the board surface, it will cause the board surface to be dented, which will easily cause the outer layer circuit to be open and scrapped in the later stage.

[0006] 2. The spray nozzles are designed on the grinding brush. Each spray nozzle is 810mm long and equipped with 6 nozzles. The water sprayed from the nozzles does not cover the entire grinding brush. Copper powder and foreign objects after grinding cannot be washed away and cleaned in time. This will cause the board surface to be concave during the subsequent grinding process, which will easily lead to open circuit gaps in the outer layer circuits and scrap. Summary of the Invention

[0007] To address the aforementioned technical deficiencies, this invention provides a method for improving resin grinding depressions on high-multilayer server boards. The method employs single-sided grinding and applies a dry film as a buffer layer to the un-ground side of the production board to protect the board surface near the back pressure roller from depressions caused by foreign objects.

[0008] To address the aforementioned technical problems, this invention provides a method for improving resin grinding depressions on high-multilayer server boards, comprising the following steps:

[0009] S1. Apply a dry film to one surface of the production board; the production board is a board that has already been resin-filled.

[0010] S2. Then, at least one set of grinding components is used to grind the side of the production board that is not covered with dry film; the grinding components include grinding brushes and back pressure rollers arranged vertically, and a conveying gap is formed between the grinding brushes and the back pressure rollers for the production board to pass through; during grinding, the side of the production board covered with dry film contacts the back pressure rollers.

[0011] S3. After grinding, remove the film and apply dry film to the other surface of the production board;

[0012] S4. Then, use the grinding assembly to grind the side of the production board that does not have the dry film attached. After grinding, remove the film. During grinding, the side of the production board with the dry film attached is in contact with the back pressure roller.

[0013] Furthermore, in steps S1 and S4, the thickness of the dry film is 50 μm.

[0014] Furthermore, in steps S1 and S4, the surface of the dry film is provided with a PET film.

[0015] Furthermore, in step S2, conveying components for forward conveying of production boards are provided on both the front and rear sides of the grinding assembly. The conveying components include two rows of roller groups arranged in the upper and lower positions, and a conveying gap is formed between the upper and lower roller groups for the production boards to pass through.

[0016] Furthermore, in step S2, before grinding the production plate, an acid and alkali resistant dust-adhesive plate is first passed through the conveying gap between the conveying assembly and the grinding assembly to remove debris from the roller assembly, grinding brush and back pressure roller.

[0017] Furthermore, a spray pipe extending along the length of the brush is provided on both sides above the brush, and a number of nozzles that spray downwards to the lower end of the spray pipe are provided at intervals. In steps S2 and S4, the nozzles are turned on simultaneously when grinding the production board so as to spray and clean the surface of the production board before and after grinding.

[0018] Furthermore, each of the spray pipes is provided with 12 nozzles at its lower end.

[0019] Furthermore, the spray pressure of the nozzle is 3 kg / cm². 2 .

[0020] Furthermore, both ends of the back pressure roller are rotatably mounted on a rotating seat, and one of the rotating seats has a side nozzle that sprays horizontally toward the surface of the production board.

[0021] Furthermore, the side nozzle has a flat structure, and the side nozzle has a plurality of spray holes arranged in a row on the side facing the production plate.

[0022] Furthermore, the production board is a multilayer board in which the inner core board and the outer copper foil are pressed together by a prepreg, and the multilayer board has successively undergone drilling, copper plating, full-board electroplating and resin plugging processes.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] In this invention, a single-sided grinding method is adopted, that is, only one side of the production board is ground each time, and the other side is ground after one side is ground. A dry film is attached to the unground side of the production board as a buffer layer to protect the board surface near the back pressure roller from being squeezed by foreign objects and causing dents.

[0025] Secondly, the number of nozzles on a single spray pipe will be increased from the existing 6 to 12, expanding its spray range so that the entire board surface can be sprayed, while controlling the spray pressure at 3 kg / cm². 2 This effectively cleans copper powder and foreign objects generated on the board surface after grinding, preventing the ground surface from being affected by copper powder and foreign objects after grinding and causing the board surface to dent. Before grinding, a dust-removing board is used to pass through the grinding line to clean the debris and foreign objects on the grinding brush, back pressure roller, and roller, so as to avoid the problem of board surface dent caused by debris and foreign objects on the grinding brush, back pressure roller, and roller.

[0026] In addition, a side nozzle is set at one end of the back pressure roller to spray the surface of the production board horizontally. This can better clean the copper powder and other foreign matter generated on the board surface after grinding, and further avoid the problem of board surface dents during the grinding process. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the grinding lines in the embodiment;

[0028] Figure 2 This is a side view of the grinding assembly in the embodiment;

[0029] Figure 3 This is a schematic diagram of the side nozzle in the embodiment. Detailed Implementation

[0030] 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.

[0031] Example

[0032] This embodiment illustrates a method for manufacturing a circuit board, which can improve the problem of resin grinding depressions in high-multilayer server boards. The method includes the following processing steps:

[0033] (1) Cutting: Cut the core board according to the panel size of 610mm×760mm. The thickness of the core board is 0.5mm, and the copper layer thickness on both surfaces of the core board is 0.5oz.

[0034] (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 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 as 3μm; 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.

[0035] (3) Lamination: 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 laminated board to form the production board.

[0036] (4) Drilling: Drilling is performed on the production board according to the design requirements based on existing drilling technology.

[0037] (5) Copper plating: A thin layer of copper is deposited on the board surface and hole walls using chemical copper plating. The backlight test is level 10, and the copper plating thickness in the hole is 0.5μm.

[0038] (6) Full-board electroplating: Electroplating the entire board for 120 minutes at a current density of 18ASF to thicken the copper layer in the holes and on the board surface.

[0039] (7) Resin plugging: Resin is plugged into the holes in the production board where resin is to be plugged and cured by baking.

[0040] (8) Grinding plate: This includes the following steps:

[0041] a. Apply a dry film to one surface of the production board. The surface of the dry film is covered with a PET film. That is, after applying the dry film, there is no need to peel off the PET film on the surface of the dry film, and the dry film does not need to be exposed.

[0042] In the above, the thickness of the dry film is 50 μm, which increases the buffer thickness and improves the buffering performance.

[0043] b. Then, at least one set of grinding components is used to grind the side of the production board that is not covered with dry film; as shown in the figure, the grinding components include a grinding brush 1 and a back pressure roller 2 arranged at the top and bottom, and a conveying gap 3 is formed between the grinding brush 1 and the back pressure roller 2 for the production board to pass through; during grinding, the side of the production board covered with dry film contacts the back pressure roller 2.

[0044] In one embodiment, such as Figure 1As shown, in order to realize the conveying of the production board in the grinding assembly, conveying assemblies for forward conveying of the production board are provided on both the front and rear sides of the grinding assembly. The conveying assemblies include two rows of roller groups arranged in the upper and lower positions. Each row of roller groups consists of several rollers 4. A conveying gap is formed between the upper and lower rows of roller groups for the production board to pass through. The grinding assembly and the conveying assemblies together form the grinding line for grinding the production board.

[0045] In the above process, before grinding the production plate, an acid and alkali resistant dust-adhesive plate is first passed through the conveying gap between the conveying assembly and the grinding assembly to remove debris from the roller assembly, grinding brush, and back pressure roller; preferably, the dust-adhesive plate is made of silicone.

[0046] In one embodiment, such as Figure 1 As shown, a spray pipe 5 extending along the length of the brush is provided on both sides above the brush. Several nozzles 51 that are inclined downwards and spray onto the lower end of the brush 1 are provided at intervals at the lower end of the spray pipe 5. The nozzles are turned on simultaneously when grinding the production board so that the surface of the production board is sprayed and cleaned before and after grinding to remove impurities from the board surface.

[0047] Preferably, each spray pipe 5 has 12 nozzles 51 at its lower end, and more nozzles can better cover the entire brushing range.

[0048] In the above, the spray pressure of the nozzle is 3 kg / cm². 2 .

[0049] In one embodiment, such as Figure 2 As shown, both ends of the back pressure roller 2 are rotatably mounted on a rotating seat 6; in order to improve the cleaning ability, a side nozzle 7 is provided on the upper side of one of the rotating seats 6, which sprays horizontally toward the surface of the production board. The side spraying method can better clean the debris on the surface of the production board.

[0050] In one embodiment, such as Figure 2 and Figure 3 As shown, the side nozzle 7 has a flat structure, and its front and rear range covers the area in front of and behind the contact point between the grinding brush and the production board. Several horizontally arranged spray holes 71 are provided on the side of the side nozzle 7 facing the production board. These spray holes 71 can be used to spray and clean the surface of the production board before and after grinding. The spray pressure of the spray holes is controlled at 3-5 kg / cm². 2 .

[0051] c. After grinding the first surface, remove the film and apply dry film to the other surface of the production board.

[0052] d. Then, use the grinding assembly to grind the side of the production board that does not have the dry film attached. After grinding, remove the film. During grinding, the side of the production board with the dry film attached is in contact with the back pressure roller. The control during the grinding process is the same as in step b.

[0053] (9) Fabrication of outer layer circuitry (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuitry. The outer layer circuitry is exposed using an exposure ruler of 5 to 7 divisions (or 21 divisions). After development, the outer layer circuitry 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 circuitry 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 circuitry is inspected for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0054] (10) 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.

[0055] (11) 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.

[0056] (12) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0057] (13) Molding: Based on existing technology and design requirements, the circuit board is made with a shape tolerance of + / -0.05mm.

[0058] (14) FQC: Inspect the appearance of the circuit board according to the customer's acceptance standards and our company's inspection standards. If there are any defects, repair them in time to ensure excellent quality control for customers.

[0059] (15) 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.

[0060] (16) Packaging: The circuit boards are sealed according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0061] 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 improving resin grinding depressions on high-multilayer server boards, characterized in that, Includes the following steps: S1. A dry film is attached to one surface of the production board, and the surface of the dry film is covered with a PET film; the production board is a board that has been resin-filled. S2. Then, at least one set of grinding components is used to grind the side of the production board that is not covered with dry film. The grinding components include grinding brushes and back pressure rollers arranged vertically. A conveying gap is formed between the grinding brushes and the back pressure rollers for the production board to pass through. A spray pipe extending along the length of the grinding brush is provided on both sides above the grinding brush. The lower end of the spray pipe is provided with 12 nozzles that spray downwards to the lower end of the grinding brush. Both ends of the back pressure roller are rotatably mounted on a rotating base. One of the rotating bases has a side nozzle that sprays horizontally towards the surface of the production board. The grinding assembly has conveying components on both the front and rear sides for forward conveying of the production board. The conveying components include two rows of rollers arranged in upper and lower positions, with a conveying gap between the upper and lower rollers for the production board to pass through. Before grinding the production board, an acid and alkali resistant dust-adhesive plate passes through the conveying gap between the conveying assembly and the grinding assembly to remove debris from the rollers, brushes, and back pressure rollers. During grinding, the side of the production board with the dry film attached contacts the back pressure roller. The nozzles are opened simultaneously during grinding to spray and clean the surface of the production board before and after grinding. S3. After grinding, remove the film and attach a dry film to the other surface of the production board. The surface of the dry film is covered with a PET film. S4. Then, the grinding assembly is used to grind the side of the production board that is not covered with dry film. After grinding, the film is removed. During grinding, the side of the production board covered with dry film is in contact with the back pressure roller. The nozzle is turned on simultaneously while grinding the production board so that the surface of the production board is sprayed and cleaned before and after grinding.

2. The method for improving resin grinding depressions in high-multilayer server boards according to claim 1, characterized in that, In steps S1 and S4, the thickness of the dry film is 50 μm.

3. The method for improving resin grinding depressions in high-multilayer server boards according to claim 1, characterized in that, The spray pressure of the nozzle is 3 kg / cm². 2 .

4. The method for improving resin grinding depressions on high-multilayer server boards according to claim 1, characterized in that, The side nozzle has a flat structure, and the side nozzle has several spray holes arranged in a row on the side facing the production plate.

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