Method for improving laminated plate thickness uniformity of multi-layer plate

Abstract

The invention discloses a method for improving the thickness uniformity of a laminated board of a multi-layer board, which is characterized in that the periphery of a copper-clad plate is connected with a copper ring, so that excessive glue can be effectively prevented from overflowing, the glue amount between layers is ensured to be more consistent, and the thickness uniformity of the laminated board is improved; the copper ring is provided with the exhaust groove, so that an effective exhaust channel is provided for gas between the plates in the pressing process, bubbles formed by gas residues are reduced, and the influence of the bubbles on the thickness uniformity and the electrical performance of the plates is avoided; the copper ring not only plays a role in blocking glue, but also enhances the mechanical strength of the edge of the copper-clad plate, thereby being beneficial to preventing the edge from being damaged or warped; by defining the exhaust grooves of each layer and automatically generating corresponding film data and laser data in the manufacturing process, the production process is more automatic, the possibility of human intervention is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of PCB boards, and in particular to a method for improving the uniformity of thickness of laminated multilayer boards. Background Art

[0002] As PCB boards develop towards high density, the architecture of multi-layer circuit boards is the most commonly used form. Each layer of a multi-layer circuit board is composed of an upper copper foil, a lower copper foil and a copper clad laminate in between, and each layer of material is pressed together with semi-cured glue as an adhesive.

[0003] During the lamination process of multi-layer boards, some technical challenges are often encountered, such as inconsistent bonding strength between layers of materials, residual bubbles, and uneven board thickness distribution. These problems not only affect the quality and reliability of the finished product, but also may cause positioning errors in subsequent processing steps, thereby reducing product yield.

[0004] Especially in the edge areas around the copper clad laminate, due to the fluidity of the glue, the edge thickness can easily exceed expectations, forming the so-called "glue overflow" phenomenon, which further aggravates the unevenness of the board thickness.

[0005] The present invention is made based on the above situation. Summary of the invention

[0006] The invention overcomes the shortcomings of the prior art and provides a method for improving the thickness uniformity of laminated multilayer boards.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for improving the uniformity of laminate thickness of a multilayer laminate comprises a copper-clad laminate, wherein the copper-clad laminate is surrounded by a copper ring for blocking glue, and the copper ring is provided with an exhaust groove for exhausting gas when the copper-clad laminate is pressed; the method comprises the following steps:

[0009] S1, cutting materials to prepare copper clad laminates;

[0010] S2. According to the design rules and preparation requirements, the original design files are processed using CAM software and files suitable for production are generated. According to the number of PCB layers and design requirements, the circuit information of each layer is separated and the exhaust slots of each layer are defined to generate the corresponding film data. The film is drawn by a photoplotter and converted into LDI laser data.

[0011] S3, micro-etching the surface of the copper clad laminate to remove the oxide layer and activate the copper surface to improve the adhesion of the photosensitive ink or dry film, and apply a layer of photosensitive ink on the copper clad laminate;

[0012] S4, using an LDI exposure machine to expose the copper clad laminate coated with photosensitive ink according to the converted laser data;

[0013] S5. The unexposed photosensitive ink is dissolved by a developer to expose the copper surface to be etched. A chemical etching solution is used to remove the exposed copper layer to form the required circuit pattern and generate the exhaust groove. After the etching is completed, the remaining photosensitive ink is removed to expose the complete circuit pattern.

[0014] S6. Check the inner layer circuit for open circuit, short circuit, notch, scratch and poor exposure through AOI, and remove defective products;

[0015] S7, browning the copper clad laminate, by cleaning the copper surface of the substrate, forming a browning film on the copper surface of the substrate, thereby enhancing the bonding force between the laminated substrate and the PP prepreg;

[0016] S8. Cut and cut the PP prepreg according to the design requirements;

[0017] S9. Pre-stack the copper clad laminate and the opened PP prepreg according to the requirements of the LOT card, with copper foil placed on the outermost layer and copper clad laminate and PP prepreg arranged alternately in the middle. Use an infrared positioning system to ensure the positioning of each layer of material.

[0018] S10, first perform hot pressing to bond the layers of material together to form a solid whole, then transfer to cold pressing for cooling, take out the laminated multilayer board from the press, drill the target hole through X-RAY positioning technology, and then perform edge cutting on the multilayer board.

[0019] In the method for improving the thickness uniformity of laminated multilayer boards as described above, the copper ring is rectangular, and each side of the copper ring is provided with two exhaust grooves.

[0020] In the method for improving the thickness uniformity of laminated multilayer boards as described above, the width of the venting groove is 2.0 mm, and the angle between the extending direction of the venting groove and the length direction of the copper ring is 30°-60°.

[0021] As described above, a method for improving the uniformity of laminate thickness of a multilayer board is provided. In step S1, a copper clad board with a length of 622 mm and a width of 546 mm is cut out. The core board thickness of the copper clad board is 0.4 mm-0.6 mm, and the outer copper surface thickness of the copper clad board is 15 μm or H / HOZ or 1 / 1OZ.

[0022] In the method for improving the thickness uniformity of laminated multilayer boards as described above, there is also a step S1.2 between step S1 and step S2, wherein the copper clad board is baked in an oven for four hours at a baking temperature of 155°C.

[0023] In the method for improving the thickness uniformity of laminated multilayer boards as described above, in step S3, the processing speed is 4 m / min, the micro-etching amount is controlled at 0.80 μm, and the thickness of the ink is 11-13 μm.

[0024] In the above-mentioned method for improving the thickness uniformity of the laminated multilayer board, the line speed of the browning treatment in step S7 is 3.5 m / min, and the micro-etching amount is controlled at 1.5 μm.

[0025] 8. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, wherein in step S8, the model of the PP prepreg is 2116, the glue content is 56%, and the PP prepreg is cut into pieces with a length of 622 mm and a width of 546 mm.

[0026] In the above method for improving the thickness uniformity of a laminated multilayer board, in step S9, the length of the copper foil is 622 mm, the width is 546 mm, and the thickness is 15 μm.

[0027] A method for improving the thickness uniformity of laminated multilayer boards as described above, in step S10, steel plates are added to the top, middle and bottom of the laminated stack, two new kraft papers are placed between the steel plates, three layers of new kraft paper and eighteen layers of old kraft paper are used between the steel plates and the copper clad laminate, and the three layers of new kraft paper are located on the side close to the copper clad laminate.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] In this case, copper rings are connected around the copper clad laminate to effectively prevent excess glue from overflowing, ensuring a more consistent amount of glue between layers, thereby improving the uniformity of the thickness of the board after lamination; exhaust grooves are opened on the copper rings to provide an effective exhaust channel for the gas between the boards during the lamination process, reducing bubbles formed by residual gas, thereby avoiding the impact of these bubbles on the uniformity of board thickness and electrical performance; the copper rings not only play the role of blocking glue, but also enhance the mechanical strength of the edge of the copper clad laminate, helping to prevent edge breakage or warping; by defining the exhaust grooves for each layer and automatically generating the corresponding film data and laser data in the manufacturing process, the production process is made more automated, reducing the possibility of human intervention and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings, wherein:

[0031] Figure 1 It is a schematic diagram of the structure of the copper ring in the present invention;

[0032] Figure 2 It is a schematic diagram of the structure of the multilayer board in the present invention;

[0033] Figure 3 It is a diagram of the stacking structure of 4 layers of boards in the present invention;

[0034] Figure 4 It is a diagram of the stacking structure of 8 layers of boards in the present invention;

[0035] Figure 5 This is a distribution diagram of the thickness uniformity of the upper layer of the four-layer plate arrangement in the present invention;

[0036] Figure 6 This is a distribution diagram of the thickness uniformity of the middle layer of the four-layer board arrangement in the present invention;

[0037] Figure 7 This is a distribution diagram of the thickness uniformity of the upper layer of the eight-layer board arrangement in the present invention;

[0038] Figure 8 This is a distribution diagram of the uniformity of the thickness of the middle layer of the eight-layer board row in the present invention. DETAILED DESCRIPTION

[0039] The present invention will be further described below in conjunction with the accompanying drawings:

[0040] like Figures 1 to 8 A method for improving the thickness uniformity of a laminated multilayer board is shown, comprising a copper clad board 1, wherein the copper clad board 1 is connected with a copper ring 2 surrounding it and used for blocking glue, and the copper ring 2 is provided with an exhaust groove 21 for exhausting gas when the copper clad board 1 is pressed; the copper clad board 1 comprises a core board 11 in the middle and a copper layer 12 arranged on the surface of the core board 11, and the method comprises the following steps:

[0041] S1, cutting and preparing copper clad laminate 1;

[0042] S2. According to the design rules and preparation requirements, the original design file is processed using CAM software and a file suitable for production is generated. According to the number of layers of the PCB and the design requirements, the circuit information of each layer is separated and the exhaust slots 21 of each layer are defined. The corresponding film data is generated and converted into LDI laser data by a photoplotter;

[0043] S3, performing micro-etching on the surface of the copper clad laminate 1 to remove the oxide layer and activate the copper surface to improve the adhesion of the photosensitive ink or dry film, and coating a layer of photosensitive ink on the copper clad laminate 1;

[0044] S4. Use an LDI exposure machine to expose the copper clad laminate 1 coated with photosensitive ink according to the converted laser data; the exposure energy is set to 6 full grids based on the standard of a 21-grid exposure scale to ensure that the image is clear and consistent, thereby improving the accuracy of the final circuit pattern.

[0045] S5, the unexposed photosensitive ink portion is dissolved by a developer to expose the copper surface to be etched, and a chemical etching solution is used to remove the exposed copper layer to form the required circuit pattern and generate the exhaust groove 21. After the etching is completed, the remaining photosensitive ink is removed to expose the complete circuit pattern;

[0046] S6. Check the inner layer circuit for open circuit, short circuit, notch, scratch and poor exposure through AOI, and remove defective products;

[0047] S7, performing browning treatment on the copper clad laminate 1, by cleaning the copper surface of the substrate, forming a browning film on the copper surface of the substrate, thereby enhancing the bonding force between the pressed substrate and the PP prepreg;

[0048] S8. Cut and cut the PP prepreg 3 according to the design requirements;

[0049] S9. Pre-stack the copper clad laminate 1 and the opened PP prepreg 3 according to the requirements of the LOT card, place the copper foil 4 on the outermost layer, and alternately arrange the copper clad laminate 1 and the PP prepreg 3 in the middle. Use an infrared positioning system to ensure the positioning of each layer of material.

[0050] S10, first perform hot pressing to bond the layers of material together to form a solid whole, then transfer to cold pressing for cooling, take out the laminated multilayer board from the press, drill the target hole through X-RAY positioning technology, and then perform edge cutting on the multilayer board.

[0051] In this case, copper rings 2 are connected around the copper clad laminate 1, which can effectively prevent excess glue from overflowing, ensure that the amount of glue between each layer is more consistent, and thus improve the uniformity of the thickness of the board after lamination; an exhaust groove 21 is opened on the copper ring 2, thereby providing an effective exhaust channel for the gas between the boards during the lamination process, reducing bubbles formed by residual gas, and thus avoiding the influence of these bubbles on the uniformity of the thickness and electrical properties of the board; the copper ring 2 not only plays the role of blocking glue, but also enhances the mechanical strength of the edge of the copper clad laminate 1, which helps to prevent edge damage or warping; by defining the exhaust grooves 21 of each layer and automatically generating corresponding film data and laser data in the manufacturing process, the production process is made more automated, the possibility of human intervention is reduced, and production efficiency is improved.

[0052] In one embodiment, the copper clad board 1 and the copper ring 2 are rectangular, and each side of the copper ring 2 is provided with two exhaust grooves 21, thereby ensuring that the gas generated during the pressing process can be evenly discharged from four directions. This helps to prevent the formation of bubbles due to gas accumulation in local areas, thereby improving the uniformity of the board thickness and the quality of the finished product. Furthermore, the exhaust grooves 21 are evenly distributed on each side of the copper ring 2. At the same time, the copper ring 2 can serve as a shielding layer, effectively reducing the impact of external electromagnetic interference on the internal circuit, and also reducing the electromagnetic radiation of the PCB board itself to the external environment.

[0053] Furthermore, the width of the exhaust groove 21 is 2.0 mm, and the angle a between the extension direction of the exhaust groove 21 and the length direction of the copper ring 2 is 30°-60°. Since the fluidity of glue is not as good as that of gas, it tends to move along the shortest path, that is, flow in a direction perpendicular to the edge of the copper ring 2. By setting the exhaust groove 21 at a certain inclination angle, the glue can be effectively prevented from overflowing along the groove without affecting the discharge of gas.

[0054] In one embodiment, in step S1, a copper clad laminate 1 having a length of 622 mm and a width of 546 mm is cut out, the core board 11 of the copper clad laminate 1 has a thickness of 0.4 mm-0.6 mm, and the thickness of the outer copper layer 12 of the copper clad laminate 1 is 15 μm or H / HOZ or 1 / 1OZ. The size of 622 mm*546 mm is one of the common standard sizes for PCB manufacturing. This standardized size can use existing production equipment and process flow, reduce the complexity and cost of customized production, and help improve production efficiency. The core board 11 has a thickness range of 0.4 mm-0.6 mm, which is suitable for most conventional applications, ensuring sufficient mechanical strength without being too thick to increase weight or occupy too much space. For circuit boards that require a multi-layer structure, this thickness range is also convenient for the subsequent pressing process to ensure good bonding between the layers.

[0055] In step S8, the model of the PP prepreg 3 is 2116, and the glue content is 56%, which helps to provide sufficient fluidity during the lamination process, ensures that the layers are fully bonded, and fills any small gaps that may exist. The PP prepreg 3 with a length of 622 mm and a width of 546 mm is cut out.

[0056] In step S9 , the copper foil 12 has a length of 622 mm, a width of 546 mm, and a thickness of 15 μm.

[0057] In one embodiment, step S1.2 is provided between step S1 and step S2, wherein the copper clad laminate 1 is baked in an oven for four hours at a baking temperature of 155°C. The copper clad laminate 1 may absorb moisture from the environment during storage and transportation. If the moisture is not discharged in time during the subsequent high-temperature process, the dimensional stability of the laminate may be reduced, and the moisture can be removed by baking the laminate. At the same time, pre-baking can help stabilize the size of the copper clad laminate 1, reduce the impact of thermal expansion and contraction, and improve the yield rate.

[0058] In one embodiment, in step S3, the processing speed is 4 m / min, and the micro-etching amount is controlled at 0.80 μm to ensure uniform surface treatment without excessive corrosion of the copper surface; the thickness of the ink is 11-13 μm.

[0059] In step S6, open circuit: detect whether there are broken or discontinuous wires. Short circuit: check whether there is accidental contact between different circuits, resulting in electrical connection errors. Notch: look for missing parts on the wire or pad. Scratches: identify surface damage caused by mechanical operation or other reasons. Poor exposure: evaluate possible problems in the exposure process, such as overexposure or underexposure, which affects the quality of pattern transfer. Inspection method: scan the PCB using a high-resolution camera and optical inspection conditions. The image processing software compares the actual image with the preset standard template and automatically identifies any deviations or defects. If the AOI system detects any of the above-mentioned defects, the PCB will be marked as unqualified and usually scrapped to avoid waste in subsequent processes.

[0060] If the PCB board is made of 6 to 8 layers of material, the required hole diameter can be accurately punched at the specified position according to the optical positioning system by using the OPE punching machine.

[0061] In one embodiment, the browning treatment is to form a uniform oxide layer on the surface to enhance the bonding between the copper surface and the PP prepreg 3. Speed: The processing line speed is 3.5 m / min to ensure that there is enough residence time during the treatment to form a stable oxide layer. Microetching amount: controlled at 1.5 microns, which helps to remove the slight oxide layer and contaminants on the copper surface without excessively corroding the copper surface, ensuring the subsequent bonding effect. After the browning treatment, the surface of the copper clad laminate 1 appears brown, indicating that an ideal oxide layer has been formed, which enhances the bonding with the PP prepreg 3.

[0062] In one embodiment, in step S10, steel plates are added to the top, middle and bottom of the pressed stack, two new kraft papers are placed between the steel plates, three layers of new kraft papers and eighteen layers of old kraft papers are used between the steel plates and the copper clad laminate 1, and the three layers of new kraft papers are located on the side close to the copper clad laminate 1. The new kraft paper is unused kraft paper or kraft paper without impurities or residues on the surface: it is mainly used for pressure buffering to ensure that no impurities or residues affect the quality of the final product. They have good flatness and thermal conductivity and can buffer the balance of pressure. The old kraft paper refers to the used kraft paper: it is used to further enhance the thermal conductivity, increase the buffering effect, and also reduce the cost. Although the old paper is not brand new, it can still provide the necessary buffering and thermal conductivity. By using multiple layers of kraft paper and steel plates, it is ensured that the pressure is evenly distributed during the entire pressing process, and the quality and flatness of the finished product are improved. Hot pressing, cold pressing, X-RAY positioning technology and gong edge are all conventional technical means for pressing PCB boards, which will not be repeated here.

[0063] Test the thickness uniformity of the laminated PCB:

[0064] Thickness uniformity distribution data of the upper layer of four-layer board arrangement:

[0065]

[0066] Thickness uniformity distribution data of the middle layer of four-layer board row:

[0067]

[0068] Thickness uniformity distribution data of the upper layer of eight-layer board row:

[0069]

[0070]

[0071] Thickness uniformity distribution data of the middle layer of eight-layer board row:

[0072]

[0074]

[0075] Experimental data analysis: Analyze the plate thickness data obtained from the above pressing;

[0076] Take the upper layer data, middle layer data and analysis data of the pressed board.

[0077] According to the data analysis of the thickness of the upper layer, the thickness uniformity of the four layers is extremely poor within 0.06mm.

[0078] According to the thickness range data of the laminated middle layer, the thickness uniformity of the four-layer board is within 0.06mm.

[0079] The thickness of the laminated eight-layer board is extremely poor, with the uniformity of the upper layer within 0.06mm.

[0080] The thickness of the laminated eight-layer board is extremely poor, with the uniformity in the middle within 0.06mm.

[0081] Due to the design of the flow-blocking grooves on the four sides of the board, the thickness uniformity of the pressed board is extremely poor, which meets the requirements.

[0082] The PCB industry standard is in the range of 0.06mm for four-layer boards and 0.08mm for eight-layer boards. The four-layer and eight-layer boards are qualified for lamination.

[0083] This embodiment is verified by combining a large number of experiments. By connecting the copper ring 2 and the exhaust groove 21 around the copper clad board 1, the loss of the glue distribution in the board is reduced. The thickness uniformity data of the test board is significantly improved, which can greatly reduce the defects of large thickness difference after pressing, optimize the process flow, and greatly improve the production quality.

Claims

1. A method for improving the thickness uniformity of laminated multilayer boards, characterized in that: The invention comprises a copper-clad laminate, wherein the copper-clad laminate is connected with a copper ring surrounding the copper-clad laminate and used for blocking glue, and the copper ring is provided with an exhaust groove for exhausting gas when the copper-clad laminate is pressed; the method comprises the following steps: S1, cutting materials to prepare copper clad laminates; S2. According to the design rules and preparation requirements, the original design files are processed using CAM software and files suitable for production are generated. According to the number of PCB layers and design requirements, the circuit information of each layer is separated and the exhaust slots of each layer are defined to generate the corresponding film data. The film is drawn by a photoplotter and converted into LDI laser data. S3, micro-etching the surface of the copper clad laminate to remove the oxide layer and activate the copper surface to improve the adhesion of the photosensitive ink or dry film, and apply a layer of photosensitive ink on the copper clad laminate; S4, using an LDI exposure machine to expose the copper clad laminate coated with photosensitive ink according to the converted laser data; S5. The unexposed photosensitive ink is dissolved by a developer to expose the copper surface to be etched. A chemical etching solution is used to remove the exposed copper layer to form the required circuit pattern and generate the exhaust groove. After the etching is completed, the remaining photosensitive ink is removed to expose the complete circuit pattern. S6. Check the inner layer circuit for open circuit, short circuit, notch, scratch and poor exposure through AOI, and remove defective products; S7, browning the copper clad laminate, by cleaning the copper surface of the substrate, forming a browning film on the copper surface of the substrate, thereby enhancing the bonding force between the laminated substrate and the PP prepreg; S8. Cut and cut the PP prepreg according to the design requirements; S9. Pre-stack the copper clad laminate and the opened PP prepreg according to the requirements of the LOT card, with copper foil placed on the outermost layer and copper clad laminate and PP prepreg arranged alternately in the middle. Use an infrared positioning system to ensure the positioning of each layer of material. S10, first perform hot pressing to bond the layers of material together to form a solid whole, then transfer to cold pressing for cooling, take out the laminated multilayer board from the press, drill the target hole through X-RAY positioning technology, and then perform edge cutting on the multilayer board.

2. A method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: The copper ring is rectangular, and each side of the copper ring is provided with two exhaust grooves.

3. The method for improving the thickness uniformity of laminated multilayer boards according to claim 2, characterized in that: The width of the exhaust groove is 2.0 mm, and the angle between the extension direction of the exhaust groove and the length direction of the copper ring is 30°-60°.

4. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: In step S1, a copper clad laminate having a length of 622 mm and a width of 546 mm is cut out, the core board thickness of the copper clad laminate is 0.4 mm-0.6 mm, and the outer copper surface thickness of the copper clad laminate is 15 μm or H / HOZ or 1 / 1OZ.

5. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: Between step S1 and step S2, there is also step S1.2 of baking the copper clad laminate in an oven for four hours at a baking temperature of 155°C.

6. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: In step S3, the processing speed is 4 m / min, the micro-etching amount is controlled at 0.80 μm, and the thickness of the ink is 11-13 μm.

7. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: The line speed of the browning treatment in step S7 is 3.5 m / min, and the micro-etching amount is controlled at 1.5 μm.

8. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: In step S8, the model of the PP prepreg is 2116, the glue content is 56%, and the PP prepreg with a length of 622 mm and a width of 546 mm is cut out.

9. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: In step S9, the copper foil has a length of 622 mm, a width of 546 mm, and a thickness of 15 μm.

10. The method for improving the thickness uniformity of laminated multilayer boards according to claim 1, characterized in that: In step S10, steel plates are added to the top, middle and bottom of the pressed stack, two new kraft papers are placed between the steel plates, three layers of new kraft paper and eighteen layers of old kraft paper are used between the steel plates and the copper clad laminate, and the three layers of new kraft paper are located on the side close to the copper clad laminate.

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