A lamination process for multilayer circuit boards

Abstract

This invention discloses a lamination process for multilayer circuit boards, relating to the field of multilayer circuit board lamination technology. The process includes the following steps: material preparation, preparing the materials required for lamination of the multilayer circuit board, including a substrate, a conductive layer, a non-conductive layer, and an insulating layer. The substrate can be copper foil, the conductive layer can be gold or silver, the non-conductive layer can be fiberglass cloth, and the insulating layer can be epoxy resin. This multilayer circuit board lamination process employs high-precision automated equipment and a precision control system, achieving precise control of the lamination process, improving interlayer alignment and lamination quality, reducing scrap rate, and minimizing problems such as poor interlayer alignment, residual bubbles, and resin voids. Furthermore, this process can well adapt to the needs of new materials and complex designs, supporting the manufacturing of circuit boards with higher layer counts and smaller line widths and spacings, and can promote the development of electronic products towards miniaturization, lightweighting, and high performance.

Description

Technical Field

[0001] This invention relates to the field of multilayer circuit board lamination technology, and particularly to a lamination process for multilayer circuit boards. Background Technology

[0002] The lamination process of multilayer circuit boards is a crucial step in PCB (Printed Circuit Board) manufacturing. Lamination refers to the process of bonding multiple layers of circuit boards according to design requirements. Under high temperature and pressure, the materials of each layer are tightly bonded together to form a complete multilayer circuit board. This process is the core step in PCB multilayer board manufacturing and is essential for improving the stability and reliability of the circuit board. While traditional multilayer circuit board lamination processes have been widely used in the past, they have some significant drawbacks. First, traditional processes often rely on manual operation and simple mechanical equipment, resulting in low lamination accuracy and problems such as poor interlayer alignment, air bubbles, and resin voids, which in turn affect the electrical performance and reliability of the circuit board. Second, traditional processes have low production efficiency, making it difficult to meet the needs of large-scale production, and the high scrap rate increases production costs. Furthermore, traditional processes are inadequate when dealing with new materials and complex designs, limiting the improvement of circuit board performance and the expansion of its application range. Summary of the Invention

[0003] The main objective of this invention is to provide a lamination process for multilayer circuit boards, which can effectively solve the problems in the background art.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A lamination process for a multilayer circuit board includes the following steps:

[0006] S1. Material preparation: Prepare the materials required for laminating the multilayer circuit board, including the substrate, conductive layer, non-conductive layer and insulating layer. The substrate can be made of copper foil, the conductive layer can be made of gold or silver, the non-conductive layer can be made of fiberglass cloth, and the insulating layer can be made of epoxy resin.

[0007] S2. Surface treatment: Clean the surface of the copper foil to remove impurities and oil. Then, lightly etch the surface of the copper foil to increase its roughness and adhesion. After that, coat the surface of the copper foil with an organic film to form an anti-oxidation film. Finally, dry the coating to improve its adhesion and stability.

[0008] S3. Inner layer fabrication: The inner layer circuit pattern is transferred onto the copper foil using photolithography. Then, the unprotected copper foil is etched away to form the inner layer circuit.

[0009] S4. Stacking: Stack the substrate, prepreg, and pre-made circuit board together in a certain order and fix them together with a riveting machine or hot melt machine.

[0010] S5. Hot pressing: The stacked multilayer circuit board is fed into the press and hot-pressed under high temperature and high pressure. During the hot pressing process, the resin in the prepreg melts and flows to fill the core board pattern. Then the resin gels and bonds the layers together.

[0011] S6. Cold pressing: After hot pressing, cold pressing is required to release stress and ensure product flatness. During cold pressing, mechanical pressure is mainly used to further bond the materials of each layer together.

[0012] S7. Inspection: Inspect the laminated multilayer circuit board to confirm whether its quality meets the requirements.

[0013] Preferably, in step S1, the thickness of the substrate copper foil is 0.5oz-2oz.

[0014] Preferably, in step S2, the thickness of the organic film ranges from 1µm to 3µm, the drying temperature ranges from 60℃ to 120℃, and the drying time ranges from 30min to 90min.

[0015] Preferably, in step S3, during the fabrication of the inner layer, a dry film photosensitive film is attached to the surface of the copper foil. Then, the substrate with the attached dry film is placed in an exposure machine, and the inner layer circuit pattern is transferred onto the dry film through exposure. After exposure, the unexposed dry film portion is removed using a developing solution, leaving a dry film pattern corresponding to the inner layer circuit pattern. At the same time, after etching is completed, the remaining dry film is removed using a stripping solution, exposing the complete inner layer circuit.

[0016] Preferably, in step S5, the hot pressing temperature range can be set to 120℃-180℃, the hot pressing pressure is between 1.2MPa-1.6MPa, and the hot pressing time is between 60min-120min.

[0017] Preferably, during the hot pressing process, the hot pressing temperature can be divided into three stages: a heating stage, a constant temperature stage, and a cooling stage. The heating rate in the heating stage is controlled at 2-4℃ / min, the constant temperature in the constant temperature stage should match the curing temperature of the resin, and the cooling rate in the cooling stage is controlled within 10℃ / min.

[0018] Preferably, in step S6, the cold pressing time should be between 30 min and 120 min.

[0019] Preferably, in step S7, the detection method includes X-ray layer deviation detection and milling of target holes.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The lamination process of this multilayer circuit board employs high-precision automated equipment and a precision control system, achieving precise control of the lamination process, improving interlayer alignment and lamination quality, reducing scrap rate, and minimizing problems such as poor interlayer alignment, residual bubbles, and resin voids. Furthermore, this process can well adapt to the needs of new materials and complex designs, supporting the manufacturing of circuit boards with higher layer counts and smaller line widths and spacings. This drives the development of electronic products towards miniaturization, lightweighting, and high performance. Simultaneously, this multilayer circuit board lamination process has high production efficiency, meeting the needs of large-scale production, and a low scrap rate during production, reducing production costs. Ultimately, this leads to improved circuit board performance and expanded application range. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process flow for the lamination process of a multilayer circuit board according to the present invention. Detailed Implementation

[0023] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0024] like Figure 1 The lamination process of a multilayer circuit board shown includes the following steps:

[0025] S1. Material preparation: Prepare the materials required for laminating the multilayer circuit board, including the substrate, conductive layer, non-conductive layer and insulating layer. The substrate can be made of copper foil, the conductive layer can be made of gold or silver, the non-conductive layer can be made of fiberglass cloth, and the insulating layer can be made of epoxy resin.

[0026] Copper foil is an important component of multilayer circuit boards. As a conductive layer, it carries the signal transmission of the circuit. The insulating layer made of epoxy resin, also known as prepreg, is used to isolate the conductive layers and prevent signal interference. During the pressing process, the prepreg melts and fills the gaps between the copper foils. After cooling, it forms a strong insulating layer. The non-conductive layer is mainly used to enhance the mechanical strength and stability of the circuit board. It may also serve as a heat dissipation layer or a protective layer.

[0027] S2. Surface treatment: The copper foil surface is cleaned to remove impurities and oil. Then, the copper foil surface is slightly etched to increase its roughness and adhesion. After that, an organic film is coated on the copper foil surface to form an anti-oxidation film. Finally, the coating is dried to improve its adhesion and stability.

[0028] When cleaning the surface of copper foil, chemical cleaning agents can be used to remove impurities such as oil and oxides from the surface of the copper foil.

[0029] S3. Inner layer fabrication: The inner layer circuit pattern is transferred onto the copper foil using photolithography. Then, the unprotected copper foil is etched away to form the inner layer circuit.

[0030] The pattern transfer process includes dry film lamination, exposure, and development. Etching can only be performed after development is complete, and a film stripping operation is required after etching is completed.

[0031] S4. Stacking: Stack the substrate, prepreg, and pre-formed core board together in a certain order and fix them together with a riveting machine or hot melt machine.

[0032] During the stacking process, it is necessary to ensure that each layer of material is accurately aligned and free from offset or misalignment.

[0033] S5. Hot pressing: The stacked multilayer circuit board is fed into the press and hot-pressed under high temperature and high pressure. During the hot pressing process, the resin in the prepreg melts and flows to fill the core board pattern. Then the resin gels and bonds the layers together.

[0034] The hot pressing process relies on the unique state transformation of the resin, which changes from a soluble and fusible state to a semi-cured state at high temperatures, and then further to a fully cured state. This transformation is irreversible, ensuring the stability and reliability of the multilayer circuit board after pressing.

[0035] S6. Cold pressing: After hot pressing, cold pressing is required to release stress and ensure product flatness. During cold pressing, mechanical pressure is mainly used to further bond the materials of each layer together.

[0036] During the cold pressing process, it is necessary to closely monitor the changes in the multilayer circuit board to avoid problems such as over-pressing or under-pressing.

[0037] S7. Inspection: Inspect the laminated multilayer circuit board to confirm whether its quality meets the requirements.

[0038] By inspecting the laminated multilayer circuit board, potential problems can be identified and corrected in a timely manner, thereby ensuring that the quality and performance of the product meet the design requirements.

[0039] Furthermore, in step S1, the thickness of the copper foil substrate is 0.5oz-2oz; in step S2, the thickness of the organic film ranges from 1um to 3um; the drying temperature range for the organic film is 60°C-120°C; and the drying time ranges from 30min-90min. In step S3, during the inner layer fabrication, a dry film photosensitive film is attached to the surface of the copper foil. This film undergoes a chemical reaction during exposure, making the exposed portion soluble or insoluble. The substrate with the attached dry film is then placed in an exposure machine, and the inner layer circuit pattern is transferred onto the dry film through exposure. During the exposure process, the intensity of the light source, the exposure time, and the exposure accuracy must be strictly controlled to ensure the accuracy of the pattern transfer. For clarity, after exposure, a developer is used to remove the unexposed dry film, leaving a dry film pattern corresponding to the inner layer circuit pattern. During etching, the developed substrate is placed in an etching machine, and a chemical reaction is used to etch away the copper foil parts not protected by the dry film, forming the inner layer circuit. During the etching process, the concentration, temperature, and etching time of the etching solution need to be controlled to ensure the uniformity and depth of etching. After etching, a stripping solution is used to remove the remaining dry film, exposing the complete inner layer circuit. The stripping process needs to ensure that the dry film is completely removed while avoiding damage to the inner layer circuit. In step S5, the hot pressing temperature range can be set to 120℃-180℃, and the hot pressing pressure is 1.2MPa-1.The pressure is between 6 MPa, and the hot pressing time is between 60 min and 120 min. During the hot pressing process, the hot pressing temperature can be divided into three stages: heating stage, constant temperature stage, and cooling stage. The heating rate in the heating stage is controlled at 2-4℃ / min, the constant temperature in the constant temperature stage should match the curing temperature of the resin, and the cooling rate is controlled within 10℃ / min. In step S6, the cold pressing time should be between 30 min and 120 min. In step S7, the detection methods include X-ray layer deviation detection and milling target holes. The purity, thickness, and surface roughness of the copper foil need to be strictly controlled. High-purity copper foil can reduce resistance and signal attenuation, and improve the electrical performance of the circuit board. Appropriate thickness can balance conductivity and mechanical strength. Surface roughness affects the bonding force between the copper foil and the insulating layer. The material of the insulating layer should have good insulation properties. The heat resistance and chemical stability of the multilayer circuit board are crucial, and its thickness and uniformity also require strict control to ensure the insulation effect between conductive layers and the flatness of the circuit board. This multilayer circuit board lamination process employs high-precision automated equipment and a precision control system, achieving precise control of the lamination process, improving interlayer alignment and lamination quality, reducing scrap rates, and minimizing problems such as poor interlayer alignment, residual bubbles, and resin voids. Furthermore, this process can well adapt to the needs of new materials and complex designs, supporting the manufacturing of circuit boards with higher layer counts and smaller line widths and spacings, driving the development of electronic products towards miniaturization, lightweighting, and high performance. Simultaneously, this multilayer circuit board lamination process has high production efficiency, meeting the needs of large-scale production, and a low scrap rate during production reduces production costs, ultimately leading to improved circuit board performance and expanded application range.

[0040] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A lamination process for multilayer circuit boards, characterized in that, Includes the following steps: S1. Material preparation: Prepare the materials required for laminating the multilayer circuit board, including the substrate, conductive layer, non-conductive layer and insulating layer. The substrate can be made of copper foil, the conductive layer can be made of gold or silver, the non-conductive layer can be made of fiberglass cloth, and the insulating layer can be made of epoxy resin. S2. Surface treatment: Clean the surface of the copper foil to remove impurities and oil. Then, lightly etch the surface of the copper foil to increase its roughness and adhesion. After that, coat the surface of the copper foil with an organic film to form an anti-oxidation film. Finally, dry the coating to improve its adhesion and stability. S3. Inner layer fabrication: The inner layer circuit pattern is transferred onto the copper foil using photolithography. Then, the unprotected copper foil is etched away to form the inner layer circuit. S4. Stacking: Stack the substrate, prepreg, and pre-made circuit board together in a certain order and fix them together with a riveting machine or hot melt machine. S5. Hot pressing: The stacked multilayer circuit board is fed into the press and hot-pressed under high temperature and high pressure. During the hot pressing process, the resin in the prepreg melts and flows to fill the core board pattern. Then the resin gels and bonds the layers together. The hot pressing temperature range can be set to 120℃-180℃, the hot pressing pressure is between 1.2MPa-1.6MPa, and the hot pressing time is between 60min-120min. During the hot pressing process, the hot pressing temperature can be divided into three stages: heating stage, constant temperature stage, and cooling stage. The heating rate in the heating stage is controlled at 2-4℃ / min, the constant temperature in the constant temperature stage should match the curing temperature of the resin, and the cooling rate is controlled within 10℃ / min. S6. Cold pressing: After hot pressing, cold pressing is required to release stress and ensure product flatness. During cold pressing, mechanical pressure is mainly used to further bond the materials of each layer together. The cold pressing time should be between 30min and 120min. S7. Inspection: Inspect the laminated multilayer circuit board to confirm whether its quality meets the requirements.

2. The lamination process for a multilayer circuit board according to claim 1, characterized in that, In step S1, the thickness of the substrate copper foil is 0.5oz-2oz.

3. The lamination process for a multilayer circuit board according to claim 1, characterized in that, In step S2, the thickness of the organic film ranges from 1µm to 3µm, the drying temperature ranges from 60℃ to 120℃, and the drying time ranges from 30min to 90min.

4. The lamination process for a multilayer circuit board according to claim 1, characterized in that, In step S3, during the inner layer fabrication, a dry film photosensitive film is attached to the surface of the copper foil. Then, the substrate with the attached dry film is placed in an exposure machine. The inner layer circuit pattern is transferred onto the dry film through exposure. After exposure, the unexposed dry film portion is removed using a developing solution, leaving a dry film pattern corresponding to the inner layer circuit pattern. At the same time, after etching is completed, the remaining dry film is removed using a stripping solution, exposing the complete inner layer circuit.

5. The lamination process for a multilayer circuit board according to claim 1, characterized in that, In step S7, the detection methods include X-ray layer deviation detection and milling of target holes.

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