Preparation method of thick-copper high-multilayer board and thick-copper high-multilayer board

Abstract

The invention discloses a preparation method of a thick-copper high multilayer board and the thick-copper high multilayer board. The preparation method comprises the following steps: S1, material preparation: taking a substrate, a prepreg, an isolating membrane and a copper foil, and cutting the prepreg into a preset size; s2, cutting treatment is conducted, specifically, the base plate is cut into a preset size; s3, inner layer processing: conveying the cut substrate to an inner layer processing station, then carrying out coating and exposure operation, then printing a preset circuit pattern on the surface of the substrate, and then forming the circuit pattern through an etching process; s4, AOI maintenance: carrying out AOI detection on the substrate subjected to inner layer processing, and checking bad defects on the surface of the substrate; s5, a browning process: performing browning treatment on the substrate which is overhauled to be qualified, and forming a browning film on the surface of the substrate; s6, filling the fusion rivet and the prepreg; s7, carrying out plate arrangement operation; s8, pressing treatment is carried out; and S9, targeting and edge cutting. The method has the advantages of being high in interlayer positioning precision, capable of avoiding the problem of pressing height difference and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of printed circuit boards, and particularly relates to a preparation method of a thick-copper high-multilayer board and the thick-copper high-multilayer board. BACKGROUND

[0002] As a core interconnection component of electronic equipment, the performance of a printed circuit board (PCB) directly affects the stability and reliability of the electronic equipment. With the development of electronic technology in the direction of high power and high density, thick-copper high-multilayer boards are increasingly widely used in the fields of new energy vehicles, industrial power supplies, aerospace, etc. due to their excellent current-carrying capacity, heat dissipation performance and mechanical strength. A thick-copper high-multilayer board generally refers to a printed circuit board with a copper foil thickness of 30OZ and above and a number of layers of 6 and above. Its manufacturing process is complex, and the precision and stability of each process are extremely high.

[0003] In the manufacturing process of a thick-copper high-multilayer board, the pressing process is a key process that determines the interlayer bonding force and the uniformity of the board thickness. Due to the structural characteristics of the thick-copper high-multilayer board, some products are designed with large-area copper-free regions. These regions are prone to have obvious height differences in the pressing process due to the lack of support from the copper foil. Specifically, the coppered regions have a small compression amount under high temperature and high pressure due to the thickness support of the copper foil, while the large-area copper-free regions lack support and have a large compression amount, resulting in poor surface flatness of the pressed board and concave or convex defects. This height difference seriously affects the subsequent dry film pressing process, and the dry film cannot be tightly attached to the surface of the board, which is prone to have defects such as air bubbles and edge lifting. This further leads to problems such as open circuits, short circuits, and solder mask shedding in subsequent etching and solder mask processes, ultimately causing product scrap, seriously affecting production qualification rate, and increasing manufacturing cost.

[0004] In the prior art, to solve the pressing height difference problem of the thick-copper high-multilayer board, the pressing pressure or temperature is usually adjusted to improve the problem, but these methods have limited effect. Adjusting the pressing pressure or temperature can easily affect the interlayer bonding force, and even cause new quality problems such as core board deformation and resin loss. In addition, some processes use filling resin or other insulating materials, but these materials have poor compatibility with the substrate, are prone to have problems such as poor adhesion and interlayer peeling, and cannot fundamentally solve the subsequent process problems caused by the height difference.

[0005] Meanwhile, the multi-layer structure of the thick copper high multi-layer board is prone to layer deviation in the fusing process, and the layer deviation will cause the lines of each layer to be unable to be accurately aligned, affecting the electrical performance of the circuit board. The positioning methods used in the prior art are mostly mechanical positioning, and the positioning accuracy is limited, which is difficult to meet the strict requirements of the thick copper high multi-layer board on the layer deviation error (usually needs to be controlled within 2MIL). Therefore, how to solve the problem of high-low difference of the large-area non-copper area pressing while ensuring the interlayer positioning accuracy of the multi-layer structure has become a technical problem to be solved in the manufacturing process of the thick copper high multi-layer board. SUMMARY

[0006] In order to solve the problems in the prior art, a preparation method of a thick copper high multi-layer board with high interlayer positioning accuracy and capable of avoiding the problem of high-low difference of pressing is provided, and the thick copper high multi-layer board.

[0007] To solve the above technical problems, the technical scheme is as follows: The preparation method of the thick copper high multi-layer board comprises the following steps: S1, material preparation: taking a substrate, a prepreg, an isolation film and a copper foil, and cutting the prepreg into a predetermined size; S2, cutting processing: cutting the substrate into a predetermined size; S3, inner layer processing: conveying the cut substrate to an inner layer processing station, then performing coating and exposure operations, then printing a predetermined line pattern on the surface of the substrate, and then forming the line pattern by etching process; S4, AOI inspection: performing AOI detection on the substrate after the inner layer processing, checking the defects on the surface of the substrate, repairing and supplementing the lines of the substrate with defects, and confirming the qualified substrate to enter S5; S5, brown process: performing brown processing on the qualified substrate, and forming a brown film on the surface of the substrate; S6, fusing rivet and prepreg filling: using a fusing machine to fuse multiple substrates in S5 at high temperature, controlling the layer deviation error in the fusing process within a predetermined range, and using a rivet to reinforce the fused substrate. During the fusing rivet operation, the prepreg is placed in the corresponding non-copper area according to the size of the large-area non-copper area on the substrate, and the prepreg is ensured not to move during the placement process; S7, plate arranging operation: according to the requirements of the operation instruction book, confirming the thickness of the copper foil, and sequentially and neatly stacking the substrate after fusing the rivet and filling the prepreg, the copper foil and the isolation film on the steel plate; S8, pressing processing: conveying the stacked structure after the plate arranging operation to an oil press, and pressing the multi-layer board to a predetermined thickness; S9, target cutting: after the pressing is completed, a positioning hole is drilled by using an X-RAY machine, and the excess material on the edge of the substrate is cut off to obtain the thick copper high multi-layer board.

[0008] Preferably, the prepreg is an adhesive insulating material composed of resin and glass fiber cloth.

[0009] Preferably, the thickness of the copper foil is 30OZ or 40OZ.

[0010] Preferably, the fusion temperature in S6 is 280°C-325°C, the fusion time is 15S-50S, the cooling time is 3S-6S, and the layer deviation error is less than 2MIL.

[0011] Preferably, in S3, the coating adopts photosensitive ink coating, the exposure adopts ultraviolet light exposure, and the etching adopts acid etching liquid etching.

[0012] Preferably, in S7, the order of sequentially and neatly stacking is first taking a steel plate, then placing a separation film, then placing a copper foil, then placing a substrate filled with prepreg, then placing a copper foil again, then placing a separation film again, and finally placing a steel plate again.

[0013] The application further discloses a thick copper high multilayer board prepared by the preparation method of the thick copper high multilayer board.

[0014] By adopting the technical scheme, the application has the following beneficial effects: (1) The application can effectively solve the pressing height difference problem. In the fusion rivet process, the prepreg is filled in the large-area copper-free area of the thick copper high multilayer board, so that the prepreg melts and fills the gap of the copper-free area in the pressing process, accurately compensates the thickness difference between the copper area and the copper-free area, significantly improves the flatness of the substrate surface after pressing, and controls the height difference within 0.05mm, thereby fundamentally solving the problem of dry film pressing caused by the height difference; (2) The application adopts the fusion rivet process. The substrate is preliminarily bonded through high-temperature fusion, and then is reinforced through rivets, so that the stability of the multilayer structure in the subsequent process is ensured through double positioning, the layer deviation error is strictly controlled within 2MIL, the requirements of the thick copper high multilayer board on the alignment accuracy of the circuit are met, the electrical performance of the product is improved, and the interlayer positioning accuracy is improved; (3) The application adopts the prepreg filling mode, which can reduce the loss of waste products, and the prepreg has low cost and small process transformation difficulty, so that the problem of high cost caused by the pressing height difference problem can be effectively reduced; In summary, the application has the advantages of high interlayer positioning accuracy and can avoid the pressing height difference problem. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flowchart of the application. DETAILED DESCRIPTION

[0016] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0017] The components of the embodiments of the invention described and shown in the accompanying drawings can typically be arranged and designed in a variety of different configurations. Therefore, the following detailed description of the embodiments of the invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0018] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0019] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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 limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] Example 1 In this embodiment, a method for preparing a thick copper high-multilayer board and the thick copper high-multilayer board are provided. By selectively filling small-sized prepreg sheets (small PP sheets) in the fusion riveting process, combined with precise fusion positioning and optimized process parameters, the problem of uneven lamination caused by large areas without copper in the thick copper high-multilayer board is fundamentally solved. At the same time, the interlayer positioning accuracy is ensured and the product qualification rate is improved. In this invention, the number of layers in the thick copper high-multilayer board is 6, 8, or 10 or more.

[0022] like Figure 1 As shown, in one embodiment of the present invention, the method for preparing a thick copper multilayer board includes the following steps: S1, material preparation: take the substrate, prepreg, separator and copper foil and cut the prepreg to the preset size, the prepreg is an adhesive insulating material composed of resin and glass fiber cloth, the main function of the prepreg is to melt and fill the interlayer gap during pressing to realize the bonding of each layer of the substrate; the copper foil is selected to be a thick copper foil with a thickness of 30Z or 40Z to meet the current carrying requirement of thick copper high multilayer board; the substrate is selected to be a core plate suitable for thick copper high multilayer board, and the material and thickness of the core plate are determined according to the product design requirement; S2, cutting processing: cutting the substrate into a preset size, that is, cutting the substrate into the design panel size specified in the engineering data, during the cutting process, the cutting speed and pressure of the cutting machine are controlled to ensure that the edge of the cut substrate is flat, without burrs and broken corners, and the size accuracy meets the design requirement (error not more than ±0.1mm), after the cutting is completed, the substrate is cleaned to remove dust, oil stains and other impurities on the surface to avoid affecting the processing quality of the subsequent process; S3, inner layer processing: the cut substrate is transported to the inner layer processing station, then coating, exposure operation is performed, then the preset circuit pattern is printed on the surface of the substrate, and then the circuit pattern is formed by etching process, in S3, the coating adopts photosensitive ink coating, the exposure adopts ultraviolet light exposure, and the etching adopts acid etching liquid for etching, specifically, the photosensitive ink is uniformly coated on the surface of the substrate by the coating machine, the coating thickness is controlled to be 10-20μm according to the line precision requirement to ensure that the ink layer is uniform without bubbles, sagging and other defects; then, the coated substrate is aligned with the preset circuit film and put into the exposure machine for ultraviolet light exposure, the exposure energy is adjusted to 80-120mJ / cm² according to the type of photosensitive ink to transfer the circuit pattern on the film to the photosensitive ink layer; after exposure, the substrate is developed to remove the unexposed photosensitive ink to expose the copper foil area to be etched; finally, the developed substrate is put into the etching machine, and acid etching liquid (main components are copper chloride and hydrochloric acid) is used for etching, the etching temperature is controlled at 45-55℃, and the etching time is adjusted according to the thickness of the copper foil to ensure that the copper foil not protected by the ink is completely etched and removed to form the preset inner layer circuit pattern; S4, AOI repair: AOI detection is performed on the substrate after inner layer processing to check the defects (notch, open circuit, etc.) on the surface of the substrate, the substrate with defects is repaired and the line is supplemented, and after confirmation, it enters S5, the AOI equipment collects the surface image of the substrate through high-definition camera and compares it with the preset standard circuit pattern to automatically check out the defects such as circuit gap, open circuit, short circuit and residual copper, the defective substrate detected is repaired by manual repair, and the line is supplemented and the residual copper is scraped off for rectification, and after rectification, AOI reinspection is performed again, and after confirmation (defect rate is less than 0.1%), it can enter the next process to ensure the integrity and accuracy of the inner layer circuit; S5, a brown process: the substrate is subjected to a brown process to form a brown film on the surface of the substrate. The purpose of the brown process is to form a uniform brown film on the surface of the substrate to enhance the adhesion between the substrate and the prepreg and prevent interlayer peeling. The brown process is performed in a dedicated brown equipment. The brown solution is composed of sulfuric acid, hydrogen peroxide, copper ions and other additives. The control range of each component is as follows: the concentration of 98% sulfuric acid is 4-6%, the concentration of hydrogen peroxide is 2-3%, the content of copper ions is ≤30g / L, and the concentration of additives is adjusted according to the actual production situation. The brown process parameters are strictly controlled as follows: pickling pressure 1.0-2.0 kg / cm², cleaner concentration 3-7%, oil removal pressure 1.0-2.0 kg / cm², pre-dip concentration 1-3%, pre-dip temperature 35±2℃, pre-dip pressure 1.0-2.0 kg / cm², brown temperature 35±2℃, drying temperature 90±5℃, DI water conductivity ≤10 us / cm, overflow water washing pressure 2.0±0.5 kg / cm², and overflow water flow 4-8 L. During the brown process, the copper foil on the surface of the substrate reacts with the brown solution to form a rough brown film. The thickness of the brown film is controlled at 0.5-1.0 μm to ensure that the adhesion is enhanced without affecting the electrical performance of the circuit. After the brown process is completed, the substrate is thoroughly washed with water and dried to remove the residual solution on the surface and prevent contamination of the subsequent processes; S6, fusion rivet and prepreg filling: multiple substrates in S5 are fused at high temperature using a fusion machine. The layer deviation error is controlled within a predetermined range during the fusion process. Meanwhile, a rivet is used to reinforce the fused substrate. In addition, during the fusion rivet operation, according to the size of the large-area copper-free area on the substrate, a prepreg is placed in the corresponding copper-free area. During the placement process, it is ensured that the prepreg does not move. In S6, the fusion temperature is 280°C-325°C, the fusion time is 15S-50S, the cooling time is 3S-6S, and the layer deviation error is less than 2MIL. Specifically, the parameters of the fusion process are adjusted according to the number of layers of the substrate. For 6-8 layers of substrate, the fusion temperature is 285±5℃, the fusion time is 15-30 seconds, and the cooling time is 3-4 seconds. For 8-10 layers of substrate, the fusion temperature is 300±5℃, the fusion time is 35-40 seconds, and the cooling time is 4-5 seconds. For more than 10 layers of substrate, the fusion temperature is 320±5℃, the fusion time is 40-50 seconds, and the cooling time is 5-6 seconds. S6 is the core process of this invention for solving the problem of unevenness in the lamination of thick copper multilayer boards. First, multiple substrates after browning are stacked on the worktable of the fusion and riveting equipment. The process parameters of the fusion mechanism are adjusted according to the number of layers of the substrate: the fusion temperature of 6-8 layer boards is 285±5℃, the fusion time is 15-30 seconds, and the cooling time is 3-4 seconds; the fusion temperature of 8-10 layer boards is 300±5℃, the fusion time is 35-40 seconds, and the cooling time is 4-5 seconds; the fusion temperature of boards with more than 10 layers is 320±5℃, the fusion time is 40-50 seconds, and the cooling time is 5-6 seconds. The fusion mechanism slightly melts the resin on the surface of the substrate by heating it at high temperature to achieve initial bonding, while controlling the layer deviation error within 2 mil. Subsequently, the riveting mechanism uses copper rivets or stainless steel rivets to reinforce the fused substrate. The rivets are evenly distributed on the edges and key positions of the substrate to further prevent layer deviation in subsequent processes. While the fusion riveting operation is underway, a small PP sheet (prepreg) filling operation is performed: Based on the size and shape of the large copper-free area on the substrate in the engineering data, the prepreg (PP) is pre-cut into corresponding small-sized prepreg (small PP sheet) using a cutting device. The size of the small PP sheet is slightly larger than the size of the copper-free area by 0.5 to 1.0 mm to ensure that it can completely fill the copper-free area. The material of the small PP sheet is the same as that of the prepreg used in the lamination process to ensure compatibility and bonding effect. The operator accurately places the small PP sheet in the large copper-free area of ​​the substrate. During the placement process, it is necessary to ensure that the small PP sheet does not move or shift. When picking up and placing the substrate, keep it stable and handle it gently to avoid the small PP sheet falling or being misaligned. The function of the small PP sheet is to accurately compensate for the thickness difference of the large copper-free area by melting it under high temperature and high pressure in the subsequent lamination process, so that the surface of the laminated board remains flat. S7. Laying out the panels: Confirm the copper foil thickness according to the work instruction. After fusing the rivets and filling with prepreg, neatly stack the substrate, copper foil, and release liner onto the steel plate, ensuring a pre-set spacing between each layer. The stacking order in S7 is as follows: first, place the steel plate; then place the release liner; then place the copper foil; next, place the substrate filled with prepreg; then place the copper foil again; then place the release liner; and finally, place the steel plate. The work instruction (MI) is a detailed production operation document that clearly specifies the number of product layers, copper foil thickness, prepreg type, laying out order, and pressing... To meet all production requirements, including parameters, during the board layout process, a layer of steel plate is first placed on the board layout rack. The steel plate surface is flat and free of scratches. Then, the release film, copper foil, substrate (filled with prepreg) are laid out in sequence... substrate (filled with prepreg), copper foil, release film, steel plate. This ensures that the stacking order of each layer of material is accurate. A gap of 5-10mm is reserved between the boards to allow the resin to flow smoothly during the pressing process and to prevent adhesion between adjacent substrates. During the board layout process, positioning pins are used for precise positioning to ensure the alignment accuracy of each layer of substrate and copper foil, and to further control the layer deviation error. S8. Lamination Process: The completed laminated structure is fed into a hydraulic press to press the multilayer boards to the preset thickness. The hydraulic press provides high pressure through a hydraulic system and high temperature through a heating system, causing the prepreg (including small PP sheets for filling) to melt and undergo a cross-linking reaction, firmly bonding each layer of substrate and copper foil together to form a complete thick copper multilayer board. The lamination parameters are adjusted according to the number of layers, copper foil thickness, and board thickness requirements of the product. The lamination temperature is usually 170-190℃, the lamination pressure is 20-40 kg / cm², and the lamination time is 90-150 minutes. The lamination process is divided into three stages: heating, constant temperature, and cooling. In the heating stage, the temperature is increased slowly to allow the resin to melt gradually and avoid resin loss. In the constant temperature stage, the set temperature and pressure are maintained to ensure that the resin undergoes a full cross-linking reaction and improves the interlayer bonding force. In the cooling stage, the temperature is naturally or forcibly lowered to avoid internal stress caused by excessive temperature difference in the board. After pressing is completed, the hydraulic press automatically releases pressure and removes the pressed board. At this time, the small PP sheet has completely melted and filled the copper-free area. The surface of the board is flat and there is no obvious height difference. S9. Targeting and trimming: After lamination, use an X-RAY machine to drill positioning holes, and then trim off the excess board material at the edge of the substrate to obtain a thick copper multilayer board.

[0023] The present invention also discloses a thick copper multilayer board, which is prepared by the above-described method for preparing a thick copper multilayer board.

[0024] This embodiment does not impose any limitation on the shape, material, structure, etc. of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a thick copper multilayer board, characterized in that, Includes the following steps: S1. Material preparation: Take the substrate, prepreg, release film and copper foil and cut the prepreg to the preset size; S2. Cutting process: Cut the substrate into the preset size; S3, Inner Layer Processing: The cut substrate is transported to the inner layer processing station, where coating and exposure operations are performed. Then, the preset circuit pattern is printed on the surface of the substrate, and the circuit pattern is shaped by etching. S4, AOI Inspection: Perform AOI inspection on the substrate that has completed the inner layer processing, check for defects on the substrate surface, repair and fill in the defects on the substrate, and proceed to S5 after confirming that it is qualified. S5. Browning process: The inspected and qualified substrates are subjected to browning treatment to form a browning film on the substrate surface. S6. Fusion Rivets and Prepreg Filling: Multiple substrates from S5 are fused together at high temperature using a fusion machine. During the fusion process, the layer deviation error is controlled within a preset range. At the same time, rivets are used to reinforce the fused substrates. During the fusion rivet operation, the prepreg is placed in the corresponding copper-free area according to the size of the large copper-free area on the substrate. During the placement process, it is ensured that the prepreg does not move. S7. Laying out the board: Confirm the copper foil thickness according to the requirements of the work instruction, and neatly stack the substrate, copper foil and release film after fusion rivets and filling with prepreg on the steel plate. S8. Pressing process: The stacked structure with the finished plates is sent into the hydraulic press to press the multi-layer plates to the preset thickness. S9. Targeting and trimming: After lamination, use an X-RAY machine to drill positioning holes, and then trim off the excess board material at the edge of the substrate to obtain a thick copper multilayer board.

2. The method for preparing a thick copper multilayer board according to claim 1, characterized in that: The semi-cured sheet is an adhesive insulating material composed of resin and fiberglass cloth.

3. The method for preparing a thick copper multilayer board according to claim 1, characterized in that: The thickness of the copper foil is 3 oz or 4 oz.

4. The method for preparing a thick copper multilayer board according to claim 1, characterized in that: The fusion temperature in S6 is 280°C to 325°C, the fusion time is 15S to 50S, the cooling time is 3S to 6S, and the layer deviation error is less than 2MIL.

5. The method for preparing a thick copper multilayer board according to claim 1, characterized in that: In S3, the coating is done with photosensitive ink, the exposure is done with ultraviolet light, and the etching is done with an acidic etching solution.

6. The method for preparing a thick copper multilayer board according to claim 1, characterized in that: The orderly stacking order in S7 is as follows: first, take the steel plate, then place the release film, then place the copper foil, then place the substrate filled with the prepreg, then place the copper foil, then place the release film, and finally place the steel plate.

7. A thick copper multilayer board, characterized in that: It is prepared by the method of any one of claims 1 to 6 for thick copper multilayer boards.

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