A pressing method and pressing plate structure for AI high-performance computing PCB

Abstract

The application discloses a kind of AI high-performance computing PCB's compression method and compression plate structure, the compression method is: before compression, the copper foil with thickness ≤9 μm is adhered to the aluminum sheet of same size by epoxy resin, as outer layer compression piece;After the outer layer compression piece and the inner layer plate are pre-laminated together by PP, compression is formed into production plate;When compression, aluminum sheet is located at the outer side away from the inner layer plate, and the epoxy resin glue on the outer layer compression piece fails under the high temperature of compression, so as to realize the separation of aluminum sheet and copper foil.The copper foil is adhered to aluminum sheet together as compression piece for use in the application, solves the quality problems such as wrinkle and plate surface depression of 9 μm or less ultra-thin copper foil compression.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, specifically to a lamination method and lamination layout structure for a PCB used in AI high-performance computing. Background Technology

[0002] First, the thinnest copper foil that can be stacked during reflow line lamination is currently 12μm. This means that copper foil with a thickness of less than 12μm cannot be produced using reflow line lamination. This is mainly because the copper foil is too thin, and quality problems such as copper wrinkling and board surface dents are prone to occur during the cutting, stacking, and lamination processes. In recent years, AI high-performance computing has experienced explosive growth. To meet the physical demand of "computing power hunger," AI chips (such as GPUs) often have thousands of pins. A massive number of signal lines and power lines must be arranged on PCBs of limited size. This directly drives the continuous reduction of PCB line width / spacing. Only in this way can stable computing power output be guaranteed in the harsh environment of high speed, high density, and high heat. This requirement for the fine circuitry of PCBs can be described as "extreme". The realization of ultra-fine PCB circuitry necessitates increasingly thinner copper foil layers. Typically, the thickness of the copper layer on the laminated board cannot exceed 9μm. The common practice in the industry is to use 12μm thick copper foil for lamination, followed by an additional copper reduction process to thin the copper layer to ≤9μm. However, this method increases both the production cost of the copper reduction process and the raw material cost of the copper foil. Furthermore, the unevenness of the copper reduction process increases the difficulty of subsequent production processes, making it prone to problems such as incomplete etching and abnormal line width in the patterning process.

[0003] Secondly, during the PCB lamination and stacking process, when multiple PCB boards are laminated at once, steel plates are used to separate the PCB boards. The normal stacking sequence from bottom to top is: chassis - kraft paper - steel plate - PCB board - steel plate - PCB board - steel plate... kraft paper - cover plate. This stacking method has the following problems: The steel plate is in direct contact with the copper surface. For every 600 PNL boards produced, 5 PNL steel plates will have scratches on their surface, resulting in a defect rate of 0.83%. Scratches on the steel plate surface can easily lead to bulges on the PCB board after lamination, and open circuit gaps in the circuit. During repeated use, foreign objects easily adhere to the surface of the steel plate. These foreign objects can cause dents on the PCB board after lamination and open circuit gaps after etching. The steel plates require regular maintenance, cleaning, and polishing, which increases maintenance costs. The thickness tolerance of the steel plate is relatively large, generally within ±0.05mm, which leads to uneven thickness of the PCB board after lamination and uneven control of the dielectric layer thickness, which can easily cause problems such as abnormal impedance and differences in dielectric loss. The large amount of steel plates used increases the procurement cost of steel plates, and the large volume and weight of steel plates often increase the labor intensity of personnel during the stacking process. When the pressing height inside the press is constant, steel plates are used to isolate adjacent PCB boards. Because the thickness of the steel plates is relatively large (usually 1-2mm), the overall number of PCB boards stacked during pressing is reduced, which reduces the unit production capacity and efficiency. Summary of the Invention

[0004] In response to the aforementioned technical deficiencies, this invention provides a lamination method and lamination layout structure for PCBs used in AI high-performance computing, which solves quality problems such as wrinkling and surface depressions when laminating ultra-thin copper foils below 9μm.

[0005] In the first aspect, in order to solve the above-mentioned technical problems, the present invention provides a lamination method for a PCB for AI high-performance computing. Before lamination, a copper foil with a thickness ≤9μm is bonded to an aluminum sheet of the same size with epoxy resin adhesive to serve as an outer lamination component. After the outer lamination component and the inner layer board are pre-stitched together with PP, they are laminated to form a production board. During lamination, the aluminum sheet is located on the outside away from the inner layer board, and the epoxy resin adhesive on the outer lamination component fails at the high temperature of lamination, thereby achieving the separation of the aluminum sheet and the copper foil.

[0006] Furthermore, the two surfaces of the copper foil are a smooth surface and a rough surface, respectively; before pressing, an epoxy resin adhesive is first coated around one surface of the aluminum sheet, and then the smooth surface of the copper foil is aligned and bonded to the aluminum sheet using the epoxy resin adhesive.

[0007] Furthermore, the location of the epoxy resin adhesive on the aluminum sheet corresponds to the waste area on the edge of the production board.

[0008] Furthermore, the epoxy resin adhesive has a ring width of 3mm, and the vertical distance between the outer periphery of the epoxy resin adhesive and the edge of the aluminum sheet is 3mm.

[0009] Furthermore, the inner layer board consists of at least one core board, and the core board has been fabricated with inner layer circuitry before lamination.

[0010] Furthermore, when the inner layer includes at least two core boards, the two adjacent core boards are separated by PP, and the core boards and the PP between the core boards are riveted and fixed by rivets to form a multi-layer core board.

[0011] Furthermore, when there are at least two inner layer boards stacked on top and bottom during the pressing process, a copper foil needs to be laminated on the adjacent sides between two adjacent inner layer boards. The two copper foils between two adjacent inner layer boards are bonded to the two surfaces of the same aluminum sheet with epoxy resin. That is, after the two copper foils are bonded to the same aluminum sheet, they serve as the intermediate pressing component that separates the two adjacent inner layer boards. At the outermost part of the top and bottom of the stacked board structure, the outer pressing component is stacked and pressed with the inner layer board. After pressing, at least two production boards are produced simultaneously.

[0012] Furthermore, the thickness of the aluminum sheet is 0.4-0.5mm.

[0013] Furthermore, the aluminum sheet is a double-sided smooth aluminum sheet.

[0014] Secondly, the present invention also provides a lamination and stacking structure for a PCB for AI high-performance computing, comprising an outer lamination component, a PP, an inner layer board, another PP, and an outer lamination component arranged sequentially from bottom to top; wherein a copper foil with a thickness ≤9μm is bonded to an aluminum sheet of the same size with epoxy resin as the outer lamination component, and the aluminum sheet is located on the outside when the boards are stacked; the thickness of the aluminum sheet is controlled at 0.4-0.5mm.

[0015] Furthermore, on the outer side of the upper outer layer press-fit component, steel plates, cushioning material, and cover plates are stacked sequentially from bottom to top, while on the outer side of the lower outer layer press-fit component, steel plates, cushioning material, and chassis are stacked sequentially from top to bottom.

[0016] Furthermore, the cushioning material consists of several layers of kraft paper.

[0017] Furthermore, the aluminum sheet is a double-sided smooth aluminum sheet.

[0018] Thirdly, the present invention also provides another lamination and stacking structure for a PCB for high-performance AI computing, characterized in that it includes an outer lamination component, a PP, an inner layer board, a PP, an intermediate lamination layer, a PP, an inner layer board, a PP, and an outer lamination component arranged sequentially from bottom to top; wherein, a copper foil with a thickness ≤9μm is bonded to one surface of an aluminum sheet of the same size with epoxy resin adhesive as an outer lamination component, and the aluminum sheet in the outer lamination component is located on the outside when the boards are stacked; two copper foils with a thickness ≤9μm are respectively bonded to the two surfaces of the aluminum sheet with epoxy resin adhesive as intermediate lamination components; and the thickness of the aluminum sheet is controlled at 0.4-0.5mm.

[0019] Furthermore, on the outer side of the upper outer layer press-fit component, steel plates, cushioning material, and cover plates are stacked sequentially from bottom to top, while on the outer side of the lower outer layer press-fit component, steel plates, cushioning material, and chassis are stacked sequentially from top to bottom.

[0020] Furthermore, the cushioning material consists of several layers of kraft paper.

[0021] Furthermore, the aluminum sheet is a double-sided smooth aluminum sheet.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention improves the strength of the copper foil during stacking and lamination by first bonding a copper foil with a thickness ≤9μm to an aluminum sheet using epoxy resin adhesive, forming an integral outer lamination component. The aluminum sheet serves as a support component. This solves the quality problems such as copper foil wrinkling and board surface dents that occur during the stacking and lamination of ultra-thin copper foils below 9μm. Furthermore, epoxy resin adhesive has good adhesion at room temperature, which can bond the copper foil and aluminum sheet together. Ordinary epoxy resin adhesives typically maintain stable adhesion between -60℃ and 150℃, but will fail if the temperature exceeds this range. The highest temperature during the lamination process is generally ≥200℃. Therefore, this epoxy resin adhesive gradually fails and loses its adhesion at the high temperature of lamination, thus achieving the separation of the aluminum sheet and copper foil during the lamination process to form the production board. This eliminates the need for a subsequent step of peeling off the aluminum sheet, making the entire process simple and convenient.

[0023] Compared to the existing method of laminating 12μm copper foil and then reducing copper, this method reduces the copper reduction process, improves the linewidth abnormality caused by uneven copper thickness after etching and copper reduction, and also reduces processing costs, copper foil procurement costs, and material loss costs.

[0024] Applying epoxy resin only to the outer periphery of the aluminum sheet and the non-working area corresponding to the edge of the copper foil reduces the contamination of the copper foil by the epoxy resin. After lamination, the epoxy resin loses its adhesiveness due to the high temperature, making it easy to clean the residual epoxy resin on the copper foil.

[0025] Furthermore, the aluminum sheet acts as an isolation barrier, preventing the steel plate used during lamination from contacting the copper surface. This avoids quality issues such as bulges or depressions on the board surface after lamination caused by scratches or foreign objects on the steel plate. This solves the problem of open circuit gaps that appear after subsequent etching. Moreover, by improving the issue of board surface depressions, thinner dry film can be used for circuit fabrication in the later stages, reducing dry film procurement costs. It also improves the resolution of pattern fabrication, which is beneficial for the production of fine circuits.

[0026] The thickness tolerance of aluminum sheets (generally ±0.005mm) is smaller than that of steel sheets (generally ±0.05mm). In existing methods, the thickness tolerance of the sheet after lamination by directly contacting the steel sheet with the copper foil is ±0.1mm. However, the thickness tolerance of the production sheet after lamination using aluminum sheets in this invention is ±0.05mm, which meets the requirement of ±5% thickness tolerance. Furthermore, aluminum sheets have a large coefficient of expansion and good toughness, ductility, and thermal conductivity. During the lamination process, aluminum sheets can better transmit pressure to the copper-free areas in the inner layer, making the pressure distribution in the copper-free and copper-containing areas of the inner layer consistent. The resin is subjected to uniform stress and can completely fill the copper-free areas of the inner layer, thereby preventing the problem of insufficient filling and improving the impedance abnormalities and dielectric loss differences caused by uneven sheet thickness and uneven dielectric layer thickness.

[0027] Two copper foils are bonded to the two surfaces of an aluminum sheet to form an intermediate pressing component. This component isolates the two production boards of the upper and lower stacked boards and achieves the purpose of pressing the two inner layers of the boards with the copper foil to form the production board. Here, aluminum sheets are used instead of the steel plates between the upper and lower PCB boards in the existing stacked structure. Only one steel plate is needed at the top and one at the bottom of the stacked structure. Compared with the traditional process, this reduces the number of steel plates used, saves steel plate usage costs, reduces the cost of regular maintenance and daily cleaning and polishing of the steel plates, and also reduces the labor intensity of operators during the stacking and pressing process. In addition, the aluminum sheet is thinner than the steel plate, which can increase the number of production boards stacked in a single pressing, improve unit capacity and production efficiency, ensure product delivery time, and reduce outsourced pressing processing costs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the press-fit plate structure in Example 1; Figure 2 This is a schematic diagram of the press-fit plate structure in Example 2. Detailed Implementation

[0029] 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.

[0030] Example 1 This embodiment illustrates a method for manufacturing a PCB for AI high-performance computing, including a lamination method for the PCB, comprising the following processing steps: Material cutting: Cut the core board, copper foil, aluminum sheet and PP according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm and the copper layer thickness on both surfaces of the core board is 9μm. The thickness of the copper foil is ≤9μm and the thickness of the aluminum sheet is 0.4-0.5mm.

[0031] Fabrication of the outer lamination component: A copper foil is bonded to one surface of an aluminum sheet using epoxy resin adhesive, serving as the outer lamination component 1. This epoxy resin adhesive has good adhesion at room temperature, which can bond the copper foil and the aluminum sheet together. The adhesion of ordinary epoxy resin adhesive can usually remain stable between -60℃ and 150℃. Exceeding this temperature range will lead to failure. The highest temperature during the lamination process is generally ≥200℃. Therefore, the epoxy resin adhesive gradually fails and loses its adhesion at the high temperature of lamination, thereby achieving the separation of the aluminum sheet and copper foil during the lamination process. This eliminates the need for a subsequent step of peeling off the aluminum sheet, making the whole process simple and convenient.

[0032] Specifically, the two surfaces of the copper foil are a smooth surface and a rough surface, respectively. First, an epoxy resin adhesive is coated around one side of an aluminum sheet, and then the smooth surface of the copper foil is aligned and bonded to the aluminum sheet using the epoxy resin adhesive.

[0033] Specifically, the position of the epoxy resin adhesive on the aluminum sheet corresponds to the waste area on the edge of the production board, reducing the contamination of the copper foil by the epoxy resin adhesive. After lamination, the epoxy resin adhesive loses its adhesiveness due to the high temperature, which also makes it easy to clean the residual epoxy resin adhesive on the copper foil.

[0034] Specifically, the epoxy resin adhesive has a ring width of 3mm, and the vertical distance between the outer periphery of the epoxy resin adhesive and the edge of the aluminum sheet is 3mm.

[0035] In one embodiment, the aluminum sheet is a flat, double-sided bright aluminum sheet.

[0036] (3) Inner layer circuit fabrication (negative film process): Inner layer pattern transfer, photosensitive film is coated with a vertical coating machine, the film thickness of the photosensitive film is controlled at 8μm, and the inner layer circuit is exposed with a fully automatic exposure machine using 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, and the inner layer line width is measured to be 3mil; Inner layer AOI, and then the inner layer circuit is inspected for defects such as open circuits, short circuits, line gaps, and line pinholes. Defective products are scrapped, and defect-free products are sent to the next process.

[0037] (4) Pressing: The browning speed is based on the thickness of the base copper layer, such as... Figure 1 As shown, outer laminating component 1, PP2, core board 3, PP2, and outer laminating component 1 are stacked sequentially, with the copper foil in the outer laminating component in contact with PP. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the stacked board to form a production board. At the same time, the epoxy resin adhesive on the outer laminating component fails under the high temperature of the pressing, realizing the separation of the aluminum sheet and the copper foil, that is, achieving the purpose of separating the aluminum sheet and the production board.

[0038] In the above-mentioned press-fit plate structure, such as Figure 1As shown, steel plates 5, buffer material 6 and cover plate 7 are stacked sequentially from bottom to top on the outer side of the upper outer layer pressing component 1, and steel plates 5, buffer material 6 and chassis 8 are stacked sequentially from top to bottom on the outer side of the lower outer layer pressing component 1.

[0039] Specifically, the cushioning material consists of several layers of kraft paper.

[0040] Functions of the chassis and cover plate: heat transfer, direct contact with the hot press, and load-bearing function.

[0041] The function of kraft paper: to balance the pressure during the pressing process.

[0042] The function of steel plates is to transfer heat and pressure downwards.

[0043] In one embodiment, a stepped heating and cooling method is used for pressing, and the highest temperature during pressing is ≥200°C.

[0044] (5) Drilling: Drilling is performed on the production board according to the design requirements based on existing drilling technology.

[0045] (6) 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.

[0046] (7) Full-board electroplating: The production board is electroplated according to the design requirements to increase the thickness of the copper layer in the holes and the copper layer on the board surface.

[0047] (8) Fabrication of outer layer circuits (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuit film. The outer layer circuit is exposed using an exposure ruler of 5 to 7 divisions (21 divisions). After development, the outer layer circuit pattern is formed on the production board. The outer layer pattern is electroplated, and then copper and tin are plated on the production board respectively. The electroplating parameters are set according to the required copper thickness. Copper plating is performed at a current density of 1.8 ASD for 60 minutes, and tin plating is performed at a current density of 1.2 ASD for 10 minutes, with a tin thickness of 3 to 5 μm. Then, the film is removed, etched, and tin is removed in sequence to etch the outer layer circuit on the production board. The outer layer AOI is performed using an automatic optical inspection system. By comparing with the CAM data, the outer layer circuit is checked for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0048] (9) Solder resist and screen printing: After screen printing solder resist ink on the surface of the production board, it is then subjected to pre-curing, exposure, development and heat curing treatment in sequence to cure the solder resist ink into a solder resist layer; specifically, the solder resist ink on the TOP side and the characters on the TOP side are added with "UL mark", thereby coating a layer on the lines and substrates that do not need to be soldered to prevent bridging between lines during soldering, provide a permanent electrical environment and chemical corrosion resistance, and at the same time beautify the appearance.

[0049] (10) Surface treatment (immersion nickel and gold): The copper surface of the solder pads of the solder mask opening position is uniformly deposited with a nickel layer and a gold layer of a certain required thickness through chemical principle. The thickness of the nickel layer is 3-5μm; the thickness of the gold layer is 0.05-0.1μm.

[0050] (11) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0051] (12) Molding: Based on existing technology and design requirements, the PCB is made with a tolerance of + / -0.05mm.

[0052] (13) FQC: Inspect the appearance of the PCB according to the customer's acceptance standards and the applicant's inspection standards. If there are any defects, repair them in time to ensure excellent quality control for the customer.

[0053] (14) FQA: Re-test the appearance of the PCB, the thickness of the hole copper, the thickness of the dielectric layer, the thickness of the green solder mask, the thickness of the inner copper layer, etc. to see if they meet the customer's requirements.

[0054] (15) Packaging: The PCBs are sealed and packaged according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0055] Example 2 This embodiment illustrates a method for manufacturing a PCB for AI high-performance computing, including a lamination method for the PCB, comprising the following processing steps: Material cutting: Cut the core board, copper foil, aluminum sheet and PP according to the panel size of 520mm×620mm. The thickness of the core board is 0.5mm and the copper layer thickness on both surfaces of the core board is 9μm. The thickness of the copper foil is ≤9μm and the thickness of the aluminum sheet is 0.4-0.5mm.

[0056] Fabrication of the pressed parts: A copper foil is bonded to one surface of an aluminum sheet using epoxy resin adhesive, serving as the outer pressed part 1; two copper foils are bonded to the two surfaces of the aluminum sheet respectively using epoxy resin adhesive, serving as the intermediate pressed part 4; the epoxy resin adhesive has good adhesion at room temperature, which can bond the copper foil and aluminum sheet together. The adhesion of ordinary epoxy resin adhesive can usually remain stable between -60℃ and 150℃. Exceeding this temperature range will cause failure. The highest temperature during the pressing process is generally ≥200℃. Therefore, the epoxy resin adhesive gradually fails and loses its adhesion at the high temperature of pressing, thereby achieving the separation of the aluminum sheet and copper foil during the pressing process. This eliminates the need for a subsequent step of peeling off the aluminum sheet, making the whole process simple and convenient.

[0057] Specifically, the two surfaces of the copper foil are a smooth surface and a rough surface, respectively. First, an epoxy resin is coated around one or both surfaces of the aluminum sheet, and then the smooth surface of the copper foil is aligned and bonded to the aluminum sheet using the epoxy resin.

[0058] Specifically, the position of the epoxy resin adhesive on the aluminum sheet corresponds to the waste area on the edge of the production board, reducing the contamination of the copper foil by the epoxy resin adhesive. After lamination, the epoxy resin adhesive loses its adhesiveness due to the high temperature, which also makes it easy to clean the residual epoxy resin adhesive on the copper foil.

[0059] Specifically, the epoxy resin adhesive has a ring width of 3mm, and the vertical distance between the outer periphery of the epoxy resin adhesive and the edge of the aluminum sheet is 3mm.

[0060] In one embodiment, the aluminum sheet is a flat, double-sided bright aluminum sheet.

[0061] (3) Inner layer circuit fabrication (negative film process): Inner layer pattern transfer, photosensitive film is coated with a vertical coating machine, the film thickness of the photosensitive film is controlled at 8μm, and the inner layer circuit is exposed with a fully automatic exposure machine using 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, and the inner layer line width is measured to be 3mil; Inner layer AOI, and then the inner layer circuit is inspected for defects such as open circuits, short circuits, line gaps, and line pinholes. Defective products are scrapped, and defect-free products are sent to the next process.

[0062] (4) Pressing: The browning speed is based on the thickness of the base copper layer, such as... Figure 2 As shown, outer laminating component 1, PP2, core board 3, PP2, intermediate laminating component 4, PP2, core board 3, PP2, and outer laminating component 1 are stacked sequentially, with the copper foil in the outer laminating component in contact with the PP. Then, according to the Tg of the board material, appropriate lamination conditions are selected to press the stacked boards together to form two production boards. At the same time, the epoxy resin adhesive on the outer laminating component and the intermediate laminating component fails under the high temperature of the pressing, realizing the separation of the aluminum sheet and the copper foil, that is, achieving the purpose of separating the aluminum sheet and the production board, thus obtaining two separated production boards.

[0063] In the above-mentioned press-fit plate structure, such as Figure 2 As shown, steel plates 5, buffer material 6 and cover plate 7 are stacked sequentially from bottom to top on the outer side of the upper outer layer pressing component 1, and steel plates 5, buffer material 6 and chassis 8 are stacked sequentially from top to bottom on the outer side of the lower outer layer pressing component 1.

[0064] Specifically, the cushioning material consists of several layers of kraft paper.

[0065] Functions of the chassis and cover plate: heat transfer, direct contact with the hot press, and load-bearing function.

[0066] The function of kraft paper: to balance the pressure during the pressing process.

[0067] The function of steel plates is to transfer heat and pressure downwards.

[0068] In one embodiment, a stepped heating and cooling method is used for pressing, and the highest temperature during pressing is ≥200°C.

[0069] (5) Drilling: Drilling is performed on the production board according to the design requirements based on existing drilling technology.

[0070] (6) 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.

[0071] (7) Full-board electroplating: The production board is electroplated according to the design requirements to increase the thickness of the copper layer in the holes and the copper layer on the board surface.

[0072] (8) Fabrication of outer layer circuits (positive film process): The outer layer pattern is transferred using a fully automatic exposure machine and positive film circuit film. The outer layer circuit is exposed using an exposure ruler of 5 to 7 divisions (21 divisions). After development, the outer layer circuit pattern is formed on the production board. The outer layer pattern is electroplated, and then copper and tin are plated on the production board respectively. The electroplating parameters are set according to the required copper thickness. Copper plating is performed at a current density of 1.8 ASD for 60 minutes, and tin plating is performed at a current density of 1.2 ASD for 10 minutes, with a tin thickness of 3 to 5 μm. Then, the film is removed, etched, and tin is removed in sequence to etch the outer layer circuit on the production board. The outer layer AOI is performed using an automatic optical inspection system. By comparing with the CAM data, the outer layer circuit is checked for defects such as open circuits, gaps, incomplete etching, and short circuits.

[0073] (9) Solder resist and screen printing: After screen printing solder resist ink on the surface of the production board, it is then subjected to pre-curing, exposure, development and heat curing treatment in sequence to cure the solder resist ink into a solder resist layer; specifically, the solder resist ink on the TOP side and the characters on the TOP side are added with "UL mark", thereby coating a layer on the lines and substrates that do not need to be soldered to prevent bridging between lines during soldering, provide a permanent electrical environment and chemical corrosion resistance, and at the same time beautify the appearance.

[0074] (10) Surface treatment (immersion nickel and gold): The copper surface of the solder pads of the solder mask opening position is uniformly deposited with a nickel layer and a gold layer of a certain required thickness through chemical principle. The thickness of the nickel layer is 3-5μm; the thickness of the gold layer is 0.05-0.1μm.

[0075] (11) Electrical test: Test the electrical conductivity of the finished board. The test method used for this board is: flying probe test.

[0076] (12) Molding: Based on existing technology and design requirements, the PCB is made with a tolerance of + / -0.05mm.

[0077] (13) FQC: Inspect the appearance of the PCB according to the customer's acceptance standards and the applicant's inspection standards. If there are any defects, repair them in time to ensure excellent quality control for the customer.

[0078] (14) FQA: Re-test the appearance of the PCB, the thickness of the hole copper, the thickness of the dielectric layer, the thickness of the green solder mask, the thickness of the inner copper layer, etc. to see if they meet the customer's requirements.

[0079] (15) Packaging: The PCBs are sealed and packaged according to the packaging method and quantity required by the customer, and desiccant and humidity card are placed in the packaging before shipment.

[0080] In other embodiments, according to the stacked structure of Embodiment 2, stacking and pressing operations of three or more production boards can be completed simultaneously as needed. It is only necessary to use intermediate pressing between adjacent production boards to separate and press them.

[0081] 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 lamination method for a PCB used in AI high-performance computing, characterized in that, Before lamination, copper foil with a thickness of ≤9μm is bonded to an aluminum sheet of the same size with epoxy resin to serve as the outer lamination component. After the outer lamination component and the inner layer board are pre-stitched together with PP, they are laminated to form the production board. During lamination, the aluminum sheet is located on the outside away from the inner layer board, and the epoxy resin on the outer lamination component fails under the high temperature of lamination, thereby achieving the separation of the aluminum sheet and copper foil.

2. The lamination method for a PCB used in AI high-performance computing according to claim 1, characterized in that, The two surfaces of the copper foil are a smooth surface and a rough surface, respectively. Before pressing, an epoxy resin adhesive is first coated around one side of the aluminum sheet, and then the smooth surface of the copper foil is aligned and bonded to the aluminum sheet using the epoxy resin adhesive.

3. The lamination method for a PCB used in AI high-performance computing according to claim 2, characterized in that, The location of the epoxy resin adhesive on the aluminum sheet corresponds to the waste area on the edge of the production board.

4. The lamination method for a PCB used in AI high-performance computing according to claim 3, characterized in that, The epoxy resin adhesive has a ring width of 3mm, and the vertical distance between the outer periphery of the epoxy resin adhesive and the edge of the aluminum sheet is 3mm.

5. The lamination method for a PCB used in AI high-performance computing according to claim 1, characterized in that, The inner layer board consists of at least one core board, and the inner layer circuitry has been fabricated on the core board before lamination.

6. The lamination method for a PCB used in AI high-performance computing according to claim 5, characterized in that, When the inner layer includes at least two core boards, the two adjacent core boards are separated by PP, and the core boards and the PP between the core boards are riveted and fixed by rivets to form a multi-layer core board.

7. The lamination method for a PCB for AI high-performance computing according to any one of claims 1-6, characterized in that, When there are at least two inner layer boards stacked on top and bottom during the pressing process, a copper foil needs to be laminated on the adjacent sides between two adjacent inner layer boards. The two copper foils between two adjacent inner layer boards are bonded to the two surfaces of the same aluminum sheet with epoxy resin. That is, after the two copper foils are bonded to the same aluminum sheet, they serve as the intermediate pressing part that separates the two adjacent inner layer boards. The outer pressing part is laminated with the inner layer board at the outermost top and bottom of the stacked board structure. At least two production boards are produced simultaneously after pressing.

8. The lamination method for a PCB used in AI high-performance computing according to claim 1, characterized in that, The thickness of the aluminum sheet is 0.4-0.5mm.

9. A laminated board structure for a PCB used in AI high-performance computing, characterized in that, The assembly includes, from bottom to top, an outer laminating component, a PP, an inner plate, another PP, and an outer laminating component; wherein, a copper foil with a thickness ≤9μm is bonded to the surface of an aluminum sheet of the same size using epoxy resin adhesive, serving as the outer laminating component, and the aluminum sheet is located on the outer side when the plates are stacked; the thickness of the aluminum sheet is controlled between 0.4-0.5mm.

10. A laminated board structure for a PCB used in AI high-performance computing, characterized in that, The assembly includes, from bottom to top, an outer laminating component, a PP layer, an inner plate, a PP layer, an intermediate laminating layer, another PP layer, another inner plate, another PP layer, and an outer laminating component. A copper foil with a thickness ≤9μm is bonded to one surface of an aluminum sheet of the same size using epoxy resin adhesive, serving as the outer laminating component, with the aluminum sheet located on the outer side during stacking. Two copper foils with a thickness ≤9μm are bonded to the two surfaces of the aluminum sheet respectively using epoxy resin adhesive, serving as the intermediate laminating component. The thickness of the aluminum sheet is controlled between 0.4-0.5mm.

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