Flexible circuit board for microchip and preparation method thereof

Abstract

The present invention discloses a flexible circuit board for microchips and a method for preparing the same. The method comprises the following steps: selecting a composite flexible substrate to be processed and performing surface modification on the composite flexible substrate to produce a preliminary circuit board; sequentially coating the surface of the preliminary circuit board with a high-adhesion photoresist and a high-resolution photoresist, and using laser direct imaging technology to expose a pattern on the preliminary circuit board coated with the two layers of photoresist; curing the exposed photoresist layer through a hot pressing process; and forming a conductive layer in the circuit pattern area to produce the flexible circuit board. The present invention solves the technical problem of misaligned circuit processing in flexible circuit boards in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit board preparation, and in particular to a flexible circuit board for a microchip and a preparation method thereof. Background Art

[0002] Flexible printed circuit boards (FPCs) are highly reliable and flexible printed circuit boards made from polyimide or polyester film. They are often referred to as FPCs or FPCs and feature high wiring density, light weight, and thinness.

[0003] Conventional methods for manufacturing flexible circuit boards for microchips include substrate preparation, pattern transfer, etching, drilling, electroplating, solder masking, surface treatment, and packaging. However, due to the thermal expansion and contraction of the flexible substrate used in microchip flexible circuit boards, the manufacturing process can lead to mismatched dimensions between the mask and the substrate, resulting in misaligned circuitry and impacting fabrication accuracy. Summary of the Invention

[0004] The object of the present invention is to provide a flexible circuit board for microchips and a preparation method thereof, which solves the technical problem of misalignment in circuit processing of flexible circuit boards in the prior art.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] According to a first aspect, the present invention discloses a method for preparing a flexible circuit board for a microchip, comprising:

[0007] Step S1, selecting a composite flexible substrate to be processed and performing surface modification treatment on the composite flexible substrate to produce a preliminary circuit board; the composite flexible substrate is produced using a polyimide-liquid crystal polymer composite material;

[0008] Step S2, sequentially coating a high-adhesion photoresist and a high-resolution photoresist on the surface of the preliminary circuit board, and performing pattern exposure on the preliminary circuit board coated with the two layers of photoresist using laser direct imaging technology;

[0009] Step S3, curing the exposed photoresist layer through a hot pressing process;

[0010] Step S4: forming a conductive layer in the circuit pattern area to produce a flexible circuit board.

[0011] Optionally, step S1 includes:

[0012] Step S11, adjusting the composite ratio of polyimide and liquid crystal polymer according to the processing requirements of the flexible circuit board to obtain a processed composite flexible substrate;

[0013] Step S12, performing plasma treatment on the composite flexible substrate using a low-temperature plasma device to improve the surface properties of the composite flexible substrate and enhance the adhesion of subsequent photoresist;

[0014] Step S13, chemically treating the surface of the composite flexible substrate with an aluminum oxide solution or a fluoride solution;

[0015] Step S14: After the surface chemical treatment, the composite flexible substrate is dried to obtain a preliminary circuit board.

[0016] Optionally, step S14 includes:

[0017] S141, selecting a preset temperature and a preset humidity during the drying process; wherein the preset temperature is 80° C. to 100° C., and the preset humidity is 40% to 60%;

[0018] Step S142, gradually heating to a preset temperature at a rate of 2°C to 3°C per minute, and maintaining the temperature for 10 to 15 minutes after reaching the preset temperature;

[0019] Step S143: During the drying process, the air flow is kept uniform through the air circulation system, and the air flow speed is set to 0.5 meters to 1 meter per second.

[0020] Optionally, step S11 includes:

[0021] Step S111, determining the types and molecular structures of polyimide and liquid crystal polymer according to the processing requirements of the flexible circuit board; wherein the polyimide is a thermosetting polyimide or a soluble polyimide, and the liquid crystal polymer is a wholly aromatic liquid crystal polymer;

[0022] Step S112, based on the determined polyimide and liquid crystal polymer, regulating the mass ratio of the polyimide and the liquid crystal polymer to obtain target performance of the composite flexible substrate; wherein the mass percentage of the polyimide and the liquid crystal polymer is (70:30) to (50:50);

[0023] In step S113 , the polyimide and the liquid crystal polymer are processed into thin films respectively by hot pressing equipment, and then hot pressing and laminating them at a temperature of 200° C. to 300° C. to obtain a processed composite flexible substrate.

[0024] Optionally, step S2 includes:

[0025] Step S21, coating a high-adhesion photoresist on the surface of the composite flexible substrate using a dynamic rheology controlled spin coating process, and coating a high-resolution photoresist using a plasma-assisted nano-spraying technology; wherein the thickness of the high-adhesion photoresist layer is 2-5 μm, and the thickness of the high-resolution photoresist layer is 1-3 μm;

[0026] Step S22 , using dual-mode laser direct imaging technology to perform pattern exposure to achieve the transfer of the circuit pattern.

[0027] Optionally, step S22 includes:

[0028] Step S221, pre-scanning the photoresist with a low-power laser to activate the photosensitive area in the photoresist;

[0029] Step S222: After the pre-exposure is completed, a high-power laser is used to perform a secondary exposure on the key areas of the circuit, the microscopic deformation of the substrate is detected in real time, and the laser trajectory is adjusted through a dynamic exposure compensation algorithm to achieve the transfer of the circuit pattern.

[0030] Optionally, step S3 includes:

[0031] Step S31, by performing zone control on the hot press, the temperature of each zone is monitored in real time, and the temperature is gradually adjusted using a nonlinear temperature ramp curve according to the thermal expansion characteristics of the substrate and the curing temperature of the photoresist;

[0032] Step S32 , curing the photoresist layer through a multi-stage temperature gradient heating process.

[0033] Optionally, step S4 includes:

[0034] Step S41 , using low-temperature chemical vapor deposition or physical vapor deposition technology to perform metal deposition at a temperature range of 60° C. to 80° C., and adding a nanoparticle reinforcement during the deposition process;

[0035] Step S42, dispersing the nanoparticles in the metal deposition solution using an ultrasonic dispersion method or a surfactant dispersion method, and controlling the deposition rate and nanoparticle concentration to ensure that the nanoparticles are evenly distributed in the metal layer;

[0036] In step S43, after the metal deposition is completed, the flexible circuit board is subjected to a low-temperature baking and curing treatment, and the baking temperature is controlled within the range of 80°C to 100°C.

[0037] Optionally, in step S42 , the concentration of the nanoparticles is 1% to 3%, and the deposition rate is 20-50 nm / min.

[0038] According to a second aspect, the present invention discloses a flexible circuit board for a microchip. The flexible circuit board for a microchip is manufactured using the method for manufacturing a flexible circuit board for a microchip as described in the first aspect.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a flexible circuit board for microchips and a method for preparing the same. By selecting a polyimide-liquid crystal polymer composite material as a composite flexible substrate and subjecting the substrate to surface modification, the flexible circuit board is adapted for the long-term, stable operating environment of the microchip. Laser exposure does not require a complex mask, reducing the cost and time of mask production and further improving production flexibility and efficiency. Hot press curing not only improves the adhesion and structural strength of the photoresist layer, but also ensures the stability of the photoresist layer in a high-temperature environment, providing a stable foundation for subsequent conductive layer deposition. This method is suitable for a variety of high-precision, high-reliability microchip applications, such as communications, medical equipment, consumer electronics, and other fields, meeting the needs of miniaturization, flexibility, and high performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present invention can be implemented and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size should still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and objectives that can be achieved by the present invention.

[0043] Figure 1 The present invention is a flowchart of a method for preparing a flexible circuit board for a microchip disclosed in the first embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, features, and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0045] In the description of the present invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. It should be noted that when a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally located component.

[0046] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0047] Example 1:

[0048] The embodiment of the present invention provides a method for preparing a flexible circuit board for a microchip, such as Figure 1 Shown, including:

[0049] Step S1, selecting a processed composite flexible substrate and performing surface modification on the composite flexible substrate to produce a preliminary circuit board; the composite flexible substrate is produced using a polyimide-liquid crystal polymer composite material; in this embodiment, by combining polyimide (PI) and liquid crystal polymer (LCP), the flexible circuit board not only has high mechanical strength but also provides excellent high temperature resistance and corrosion resistance, making it suitable for the long-term stable working environment of microchips.

[0050] Step S2, sequentially coating the surface of the preliminary circuit board with a high-adhesion photoresist and a high-resolution photoresist, and performing pattern exposure on the preliminary circuit board coated with two layers of photoresist using laser direct imaging technology; in this embodiment, the above-mentioned two photoresists have different functions. The high-adhesion photoresist can effectively enhance the adhesion of the photoresist to the substrate surface, preventing the photoresist from falling off or peeling in subsequent processes, while the high-resolution photoresist has a higher resolution and can provide a more refined circuit pattern during the pattern exposure process. Pattern exposure using laser direct imaging technology can accurately transfer the optimized circuit pattern to the photoresist layer. Compared with traditional photolithography processes, laser exposure has higher resolution and flexibility, and is particularly suitable for processing high-density, high-precision microchip circuit designs. At the same time, laser exposure does not require complex masks, reducing the cost and time of mask production, and further improving production flexibility and efficiency.

[0051] Step S3, curing the exposed photoresist layer through a hot pressing process; in this embodiment, curing the exposed photoresist layer through a hot pressing process helps to enhance the stability of the photoresist and avoid pattern deviation or damage in subsequent processing.

[0052] In step S4, a low-temperature deposition process is used to form a conductive layer in the circuit pattern area to produce a flexible circuit board. In this embodiment, low-temperature deposition technology can complete the deposition of conductive materials at a relatively low temperature, effectively avoiding the damage that high-temperature processes can cause to the flexible substrate, such as deformation and softening. In addition, low-temperature deposition can control the thickness and uniformity of the conductive layer, ensuring accurate transmission of the circuit pattern and good electrical conductivity. This process is particularly suitable for the high-precision requirements of flexible materials and microelectronic products, and can further improve the electrical performance and reliability of the circuit board.

[0053] It should be noted that the present invention provides a method for preparing a flexible circuit board for microchips, which selects a polyimide-liquid crystal polymer composite material as a composite flexible substrate and performs surface modification on the substrate to make the flexible circuit board suitable for the long-term stable working environment of the microchip; laser exposure does not require a complex mask, which reduces the cost and time of mask production and further improves the flexibility and efficiency of production. Hot pressing curing can not only improve the adhesion and structural strength of the photoresist layer, but also ensure the stability of the photoresist layer in a high-temperature environment, providing a stable foundation for the subsequent deposition of the conductive layer. This method is suitable for a variety of high-precision, high-reliability microchip applications, such as communications, medical equipment, consumer electronics and other fields, meeting the needs of miniaturization, flexibility and high performance.

[0054] In an optional embodiment, step S1 includes:

[0055] Step S11, adjusting the composite ratio of polyimide and liquid crystal polymer according to the processing requirements of the flexible circuit board to obtain a processed composite flexible substrate; in this embodiment, polyimide has excellent high temperature resistance, chemical stability and mechanical strength, while liquid crystal polymer has low dielectric loss, high dimensional stability and low hygroscopicity. By adjusting the ratio of polyimide and liquid crystal polymer, an optimal balance can be found between mechanical flexibility, heat resistance and electrical properties. In flexible circuit boards for microchips, it is necessary to consider both the bending ability and structural support of the circuit board. Reasonable regulation of the ratio of polyimide and liquid crystal polymer can improve the overall mechanical properties, so that it can meet the bending requirements without affecting the stability of the electrical connection due to excessive flexibility.

[0056] In step S12, the composite flexible substrate is subjected to plasma treatment using a low-temperature plasma device to improve the surface properties of the composite flexible substrate and enhance the adhesion of the subsequent photoresist. In this embodiment, plasma treatment removes organic contaminants from the material surface, allowing the formation of more polar functional groups (such as hydroxyl and carboxyl groups), thereby improving the adhesion of the photoresist and reducing delamination caused by poor interface properties. After plasma modification, the substrate surface becomes more uniform, facilitating uniform coating of the photoresist, improving the accuracy of the photolithography process, and reducing the possibility of circuit breakage or failure. Low-temperature plasma treatment does not damage the main structure of the polyimide-liquid crystal polymer composite material while achieving efficient surface modification. Compared to traditional mechanical polishing or chemical etching processes, it is more gentle and environmentally friendly.

[0057] Specifically, the low-temperature plasma equipment uses oxygen, nitrogen, or argon as the gas source, and the gas flow rate is set between 10 cubic centimeters per minute and 200 cubic centimeters per minute. The vacuum pressure of the low-temperature plasma equipment is controlled between 0.1 Torr and 1 Torr. Excessive pressure will reduce the excitation effect of the plasma, resulting in insufficient surface modification; while too low a pressure may cause the plasma to be unstable and unable to produce sufficient ions and active molecules. In order to effectively modify the surface of the composite flexible substrate, the excitation power of the low-temperature plasma equipment is 50W to 150W, the treatment time is set between 30 seconds and 5 minutes, and the treatment temperature is 25°C to 60°C.

[0058] In step S13, the surface of the composite flexible substrate is chemically treated using an aluminum oxide solution or a fluoride solution. In this embodiment, chemical treatment further removes any residual oxides or contaminants on the surface while forming a uniform activation layer, ensuring more stable adhesion of subsequent metal layers (such as copper or other conductive materials) and avoiding localized uneven deposition caused by surface defects. Appropriate chemical treatment can adjust the surface roughness of the material at the nanometer level, enhancing the adhesion of the photoresist without affecting the precision of the final circuit. Chemical modification can optimize the wetting properties of the substrate surface, resulting in better flowability in subsequent coating processes (such as photoresist and conductive layers), reducing defects, and improving yield.

[0059] In the specific implementation process, the mass concentration of the aluminum oxide solution is 0.1-5%, and the composite flexible substrate is immersed in the aluminum oxide solution for 1 to 10 minutes. The aluminum oxide particles are stirred to promote uniform dispersion and ensure uniform surface modification. Alternatively, the concentration of the fluoride is 0.5% to 3%, and the composite flexible substrate is immersed in the fluoride solution for 1 to 3 minutes. Light stirring is used to enhance the uniformity of the treatment. Immediately after treatment, the substrate surface is thoroughly rinsed with deionized water to remove residual aluminum oxide solution or fluoride solution.

[0060] Step S14, after the surface chemical treatment, the composite flexible substrate is dried to produce a preliminary circuit board. In this embodiment, after the chemical treatment, a small amount of solvent or moisture may remain on the surface of the material. If it is not removed in time, it may cause defects such as blistering and delamination in subsequent processes such as photolithography and deposition. Drying treatment can effectively remove these adverse factors and improve process stability. Appropriate preheating can release the stress inside the polyimide-liquid crystal polymer composite material and reduce warping or deformation caused by temperature changes during subsequent processing. The dried material has better surface cleanliness and consistency, providing a more stable substrate for subsequent processes such as photolithography and conductive layer deposition, thereby improving the yield rate.

[0061] It should be noted that through the rational proportioning of polyimide-liquid crystal polymer composite materials, key properties such as high flexibility, high mechanical strength, high temperature resistance and low dielectric loss are taken into account, enabling the circuit board to operate stably in microchip applications. The combined effect of low-temperature plasma treatment and chemical modification improves the adhesion of the substrate surface, optimizes the adhesion performance of the photoresist and conductive layer, reduces the production defect rate, and improves the overall yield rate. After drying, the internal stress of the material is released and the dimensional stability is enhanced, so that the flexible circuit board will not deform or fail due to environmental changes during long-term use. Low-temperature plasma treatment is an environmentally friendly and efficient surface modification method. Compared with traditional mechanical roughening or strong acid etching processes, it is environmentally friendly, while reducing manufacturing costs and improving the feasibility of industrial applications.

[0062] Specifically, step S11 includes:

[0063] Step S111: Determine the types and molecular structures of polyimide and liquid crystal polymer based on the processing requirements of the flexible circuit board; wherein the polyimide is a thermosetting polyimide or a soluble polyimide, and the liquid crystal polymer is a wholly aromatic liquid crystal polymer. In this embodiment, when the operating temperature of the flexible circuit board is required to exceed 300° C., thermosetting polyimide is selected; when the operating temperature of the flexible circuit board is required to be no more than 300° C., or when the composite flexible substrate needs to be coated over a large area, soluble polyimide is selected.

[0064] Step S112: Based on the determined polyimide and liquid crystal polymer, the mass ratio of the polyimide and the liquid crystal polymer is adjusted to obtain target performance of the composite flexible substrate; wherein the mass percentage of the polyimide and the liquid crystal polymer is (70:30) to (50:50). In this embodiment, the target performance includes heat resistance, flexibility, mechanical strength, dimensional stability, and electrical properties. When the mass content of the polyimide is greater than 70%, the heat resistance of the composite flexible substrate can be improved, but the flexibility is reduced. When the mass content of the liquid crystal polymer is greater than 50%, the flexibility of the composite flexible substrate can be enhanced, but the thermal stability and adhesion are affected.

[0065] In step S113, the polyimide and liquid crystal polymer are processed into thin films using a hot press, and then hot-pressed at a temperature of 200°C to 300°C to form a composite flexible substrate. In this embodiment, the thickness of the composite flexible substrate is within a range of 10 to 50 μm, depending on the requirements of the flexible circuit board.

[0066] It should be noted that by controlling the liquid crystal polymer content to 30% to 50%, the composite material can maintain good morphological stability in high-temperature environments, while taking into account the interfacial bonding strength of polyimide and liquid crystal polymer, ensuring that the reliability of the flexible circuit board will not be affected by the decrease in adhesion. Through high-temperature hot pressing, the molecular segments of polyimide can be cross-linked and cured, improving the heat resistance of the substrate. Liquid crystal polymer can form an oriented structure at high temperatures, enhancing the mechanical strength and flexibility of the material. Since the composite thickness of polyimide and liquid crystal polymer is in the range of 10 to 50 μm, the material ensures a balance between flexibility and mechanical strength, making it both sufficient to support and adapt to the development needs of miniaturized flexible circuit boards.

[0067] In summary, surface modification of the composite flexible substrate improves photoresist adhesion, prevents photoresist peeling and uneven coating, and ensures accurate pattern transfer. The substrate's surface microstructure is optimized, enhancing photoresist coating uniformity and reducing pattern distortion. This surface-modified composite flexible substrate is more suitable for high-precision pattern transfer, ensuring the high-resolution requirements of applications such as microchips. The modified surface enhances compatibility between the photoresist and other materials, such as the conductive layer, preventing subsequent process issues and ultimately improving the overall quality and stability of flexible circuit board manufacturing.

[0068] Specifically, step S14 includes:

[0069] S141, set the preset temperature and preset humidity during the drying process; wherein, the preset temperature is 80°C to 100°C, and the preset humidity is 40% to 60%; in this embodiment, the temperature range of 80°C to 100°C is selected, which can not only effectively remove the solvent and moisture that may remain on the surface of the composite flexible substrate, but also avoid thermal damage to the substrate caused by excessively high temperatures. Excessively high temperatures may cause material deformation, thermal stress concentration, or loss of some physical properties, while this temperature range helps to improve the stability of the material. The humidity is set between 40% and 60%, which can avoid excessive drying of the substrate surface caused by too low humidity, thereby causing problems such as cracks and embrittlement, and prevent the softening of the substrate or uneven surface drying due to excessive humidity. This humidity condition helps to dry the material evenly and ensure the stability of the substrate after drying.

[0070] In step S142, the temperature is gradually raised to a preset temperature at a heating rate of 2°C to 3°C per minute. After reaching the preset temperature, the temperature is maintained constant for 10 to 15 minutes. In this embodiment, the temperature is gradually raised to the preset temperature at a heating rate of 2°C to 3°C per minute, which can effectively avoid the accumulation of thermal stress caused by a sudden temperature rise.

[0071] Step S143, during the drying process, the air flow is maintained uniform through the air circulation system, and the air flow speed is set to 0.5 meters to 1 meter per second; in this embodiment, the air flow speed is controlled within the range of 0.5 meters to 1 meter per second, which can not only ensure the efficiency of air flow, but also avoid damage to the surface caused by excessive airflow.

[0072] It's important to note that controlling temperature, humidity, and heating rate can prevent uneven thermal stress and surface damage during the drying process, ensuring the long-term reliability of the flexible circuit board substrate. Precisely controlled airflow velocity and a real-time feedback adjustment system ensure uniform airflow during the drying process, preventing localized drying unevenness and ensuring high-precision execution of subsequent processes such as photolithography and conductive layer deposition. Real-time monitoring and feedback adjustment of temperature and humidity ensure stable temperature and humidity throughout the drying process, improving the automation level of the production process, reducing the need for manual intervention, and ensuring consistent production efficiency and finished product quality.

[0073] In an optional embodiment, step S2 includes:

[0074] In step S21, a high-adhesion photoresist is applied to the surface of the composite flexible substrate using a dynamic rheologically controlled spin-coating process, and a high-resolution photoresist is applied using a plasma-assisted nanospraying technique. The high-adhesion photoresist has a thickness of 2-5 μm, while the high-resolution photoresist has a thickness of 1-3 μm. In this embodiment, the dynamic rheologically controlled spin-coating process dynamically adjusts the photoresist coating method based on the substrate's characteristics, ensuring a uniform adhesive layer and improving the accuracy of the photolithographic pattern. The plasma-assisted nanospraying technique enhances the film quality of the high-resolution photoresist, enabling it to support ultra-fine circuit processing.

[0075] It should be noted that high-adhesion photoresist, with a layer thickness of 2-5μm, enhances adhesion to the substrate and improves overall heat resistance and chemical corrosion resistance. High-resolution photoresist, with a layer thickness of 1-3μm, provides ultra-fine photolithographic patterns. Its thinner layer enables higher exposure resolution, ensuring high-precision pattern formation and enabling submicron circuit processing.

[0076] Step S22 uses dual-mode laser direct imaging technology for pattern exposure to achieve circuit pattern transfer. In this embodiment, dual-mode exposure effectively reduces alignment errors and enables submicron-level circuit pattern transfer. This significantly increases exposure speed, making flexible circuit boards suitable for large-scale production and particularly suitable for high-precision microchip applications.

[0077] It's important to note that traditional mask lithography (such as contact or projection lithography) is limited by factors such as mask accuracy and optical distortion, making it difficult to achieve ultra-high-precision circuit patterns. Dual-mode laser direct imaging technology, on the other hand, uses a computer to directly control laser beam exposure, eliminating the need for a mask. This technology achieves submicron exposure accuracy, making it ideal for the manufacture of high-density flexible circuit boards. Laser direct imaging eliminates the need for masks and allows software-based modification of exposure data, allowing for rapid adaptation to varying design requirements. This significantly increases production flexibility and reduces manufacturing costs.

[0078] Specifically, step S22 includes:

[0079] In step S221, a low-power laser is used to pre-scan the photoresist to activate the photosensitive areas in the photoresist. In this embodiment, the photosensitive areas include the photosensitizer in the photoresist and its reaction area after stimulation. The pre-scanning of the low-power laser is used to activate the photosensitive areas of the photoresist, ensuring that the photoresist surface can uniformly respond to subsequent high-power laser exposure. This process helps to remove any non-uniformities or over-cured areas that may exist on the photoresist surface, enhance the uniformity of the photoresist layer, and thus improve the accuracy of pattern transfer. In the specific implementation process, the power range of the low-power laser is 0.1mW / cm² to 10mW / cm², and the scanning speed of the low-power laser is 1μm / s to 10μm / s.

[0080] In step S222, after the pre-exposure is completed, a high-power laser is used to perform a secondary exposure on the critical circuit areas. Microscopic deformation of the substrate is detected in real time, and the laser trajectory is adjusted using a dynamic exposure compensation algorithm to achieve circuit pattern transfer. In this embodiment, the high-power laser secondary exposure targets the critical circuit areas, ensuring that the accuracy of these critical circuit sections is fully guaranteed and avoiding pattern blurring or distortion in complex circuit patterns. This precise high-power laser secondary exposure can effectively process fine line widths and spacings, ensuring high-precision pattern transfer, making it particularly suitable for high-density and complex microchip circuit designs. In specific implementations, the dynamic exposure compensation algorithm is commonly used in the field and will not be described in detail here. Critical circuit areas include the core functional areas of the microchip, areas with fine line widths, vias, and metal interconnects. The core functional areas of the microchip include logic gates, memory cells, power distribution networks, and high-speed signal transmission channels. In specific implementations, the high-power laser power ranges from 10mW / cm² to 200mW / cm², and the scanning speed ranges from 0.1μm / s to 1μm / s.

[0081] In an optional embodiment, step S3 includes:

[0082] Step S31, by performing zoning control on the hot press, the temperature of each zone is monitored in real time, and a nonlinear temperature ramp curve is used to gradually adjust the temperature based on the thermal expansion characteristics of the substrate and the curing temperature of the photoresist. In this embodiment, the polyimide-liquid crystal polymer composite material may expand to varying degrees when heated. If the temperature changes unevenly in each zone, it can easily lead to local stress concentration, affecting the circuit accuracy. Zoning control can ensure that the entire substrate is heated evenly, reducing deformation and improving dimensional accuracy. The curing of photoresist generally requires precise temperature control. The nonlinear temperature ramp curve can provide slow heating or cooling at appropriate stages to ensure uniform curing of the photoresist layer and reduce cracking or delamination caused by rapid changes in temperature gradients.

[0083] Step S32: Curing the photoresist layer using a multi-stage temperature gradient heating process. In this embodiment, the curing process of the present invention utilizes a precise temperature control strategy and multi-stage temperature gradient heating technology to ensure uniform curing of the photoresist while reducing substrate deformation and internal stress, thereby improving the overall quality and long-term reliability of the flexible printed circuit board. This process solution is particularly suitable for high-precision microchip applications, meeting stringent manufacturing requirements and providing a high-quality substrate foundation for subsequent processing.

[0084] Specifically, step S32 includes:

[0085] Step S321, slowly raise the temperature to 50-70°C, control the heating rate at 1-2°C / min, and maintain it for 5-10 minutes; in this embodiment, this step is a preheating stage, which starts thermal activation of the photoresist and releases stress inside the substrate.

[0086] In step S322, the temperature is raised to the photoresist's primary curing temperature, which ranges from 100°C to 130°C, and maintained for 20 to 30 minutes. In this embodiment, this step is the primary curing stage, during which the chemical crosslinking of the photoresist is fully completed, resulting in higher heat resistance and mechanical stability. This optimizes the curing rate, avoids thermal decomposition or localized overcuring, and improves the stability of the circuit pattern.

[0087] In step S323, a nonlinear cooling curve is used to slowly reduce the temperature to 70-80°C and maintain it for 5-10 minutes; wherein the cooling rate is 1-2°C / min; in the present embodiment, this step is a temperature slow-down stage, which can gradually eliminate the thermal stress of the photoresist and the substrate. In the present embodiment, the nonlinear cooling curve means that the cooling rate during the temperature reduction process is not a constant value, but varies according to specific process requirements and material properties. Specifically, the cooling rate may gradually slow down over time, or be adjusted in certain specific temperature ranges. Compared with linear cooling, nonlinear cooling allows for more precise temperature control, allowing the photoresist and substrate to better adapt to temperature changes during the cooling process and avoid excessive thermal stress.

[0088] Step S324: Lower the temperature to room temperature and allow the substrate to cool naturally for 10-15 minutes; room temperature is 25°C. In this embodiment, this step is a cooling phase, allowing the substrate and photoresist layer to reach thermal equilibrium, ensuring stability of the cured photoresist layer and preventing deformation or stress release during subsequent processing. This enhances the reliability of the flexible circuit board and prevents microcracks or delamination caused by residual internal stress.

[0089] In an optional embodiment, step S4 includes:

[0090] In step S41, metal deposition is performed in a temperature range of 60°C to 80°C using low-temperature chemical vapor deposition or physical vapor deposition technology, and a nanoparticle enhancer is added during the deposition process. In this embodiment, the nanoparticle enhancer can be metal nanoparticles, carbon nanotubes, aluminum oxide, etc.

[0091] In step S42, the nanoparticles are dispersed in the metal deposition liquid using an ultrasonic dispersion method or a surfactant dispersion method, and the deposition rate and nanoparticle concentration are controlled to ensure that the nanoparticles are evenly distributed in the metal layer. In this embodiment, the concentration of the nanoparticles is 1% to 3%, and the deposition rate is 20-50 nm / min.

[0092] In step S43, after the metal deposition is completed, the flexible circuit board is subjected to a low-temperature baking and curing treatment, and the baking temperature is controlled within the range of 80°C to 100°C.

[0093] It should be noted that low-temperature deposition technology avoids high-temperature damage to the substrate, ensuring the stability of the flexible circuit board. The addition of nanoparticles not only improves the conductivity of the metal layer, but also enhances its adhesion and durability, meeting the electrical requirements of high-precision microchips. The low-temperature curing process further strengthens the bond between the metal layer and the substrate, improving the long-term reliability of the metal layer and ensuring the stability of the flexible circuit board in complex applications.

[0094] Example 2:

[0095] The present invention discloses a flexible circuit board for a microchip. The flexible circuit board for a microchip is manufactured by adopting the method for preparing the flexible circuit board for a microchip as described in the first embodiment.

[0096] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a flexible circuit board for a microchip, characterized in that: include: Step S1, selecting a composite flexible substrate to be processed, and performing surface modification treatment on the composite flexible substrate to produce a preliminary circuit board; The composite flexible substrate is made of a polyimide-liquid crystal polymer composite material; Step S2, sequentially coating a high-adhesion photoresist and a high-resolution photoresist on the surface of the preliminary circuit board, and performing pattern exposure on the preliminary circuit board coated with the two layers of photoresist using laser direct imaging technology; Step S3, curing the exposed photoresist layer through a hot pressing process; Step S4, forming a conductive layer in the circuit pattern area to produce a flexible circuit board; The step S2 comprises: Step S21, coating a high-adhesion photoresist on the surface of the composite flexible substrate using a dynamic rheology controlled spin coating process, and coating a high-resolution photoresist using a plasma-assisted nano-spraying technology; wherein the thickness of the high-adhesion photoresist layer is 2-5 μm, and the thickness of the high-resolution photoresist layer is 1-3 μm; Step S22, using dual-mode laser direct imaging technology to perform pattern exposure to achieve circuit pattern transfer; The step S22 includes: Step S221, pre-scanning the photoresist with a low-power laser to activate the photosensitive area in the photoresist; Step S222: After the pre-exposure is completed, a high-power laser is used to perform a secondary exposure on the key areas of the circuit to detect the microscopic deformation of the substrate in real time. The laser trajectory is adjusted using a dynamic exposure compensation algorithm to achieve the transfer of the circuit pattern. The power range of low-power lasers is 0.1mW / cm² to 10mW / cm², and the scanning speed is 1μm / s to 10μm / s. The power range of high-power lasers is 10mW / cm² to 200mW / cm², and the scanning speed is 0.1μm / s to 1μm / s. The photosensitive area includes the photosensitizer in the photoresist and its reaction area after stimulation. The secondary exposure of the high-power laser targets the key areas of the circuit, which include the core functional areas of the microchip, small line width areas, through-holes and metal interconnect areas. The core functional areas of the microchip include logic gates, storage units, power distribution networks and high-speed signal transmission channels. The step S3 comprises: Step S31, by performing zone control on the hot press, the temperature of each zone is monitored in real time, and the temperature is gradually adjusted using a nonlinear temperature ramp curve according to the thermal expansion characteristics of the substrate and the curing temperature of the photoresist; Step S32, curing the photoresist layer through a multi-stage temperature gradient heating process; Step S32 includes: Step S321, slowly increase the temperature to 50-70°C, control the heating rate at 1-2°C / min, and maintain it for 5-10 minutes; Step S322, raising the temperature to the main curing temperature of the photoresist, which is in the range of 100-130°C, and maintaining it for 20-30 minutes; Step S323: using a nonlinear cooling curve, slowly lower the temperature to 70-80°C and maintain it for 5-10 minutes; wherein the cooling rate is 1-2°C / min; Step S324, lowering the temperature to room temperature and naturally cooling for 10 to 15 minutes; wherein the room temperature is 25°C.

2. The method for preparing a flexible circuit board for a microchip according to claim 1, wherein: The step S1 comprises: Step S11, adjusting the composite ratio of polyimide and liquid crystal polymer according to the processing requirements of the flexible circuit board to obtain a processed composite flexible substrate; Step S12, performing plasma treatment on the composite flexible substrate using a low-temperature plasma device; Step S13, chemically treating the surface of the composite flexible substrate with an aluminum oxide solution or a fluoride solution; Step S14: After the surface chemical treatment, the composite flexible substrate is dried to obtain a preliminary circuit board.

3. The method for preparing a flexible circuit board for a microchip according to claim 2, wherein: The step S14 includes: S141, setting a preset temperature and a preset humidity during the drying process; wherein the preset temperature is 80° C. to 100° C., and the preset humidity is 40% to 60%; Step S142, gradually heating to a preset temperature at a rate of 2°C to 3°C per minute, and maintaining the temperature for 10 to 15 minutes after reaching the preset temperature; Step S143: During the drying process, the air flow is kept uniform through the air circulation system, and the air flow speed is set to 0.5 meters to 1 meter per second.

4. The method for preparing a flexible circuit board for a microchip according to claim 2, wherein: The step S11 includes: Step S111, determining the types and molecular structures of polyimide and liquid crystal polymer according to the processing requirements of the flexible circuit board; wherein the polyimide is a thermosetting polyimide or a soluble polyimide, and the liquid crystal polymer is a wholly aromatic liquid crystal polymer; Step S112, based on the determined polyimide and liquid crystal polymer, regulating the mass ratio of the polyimide and the liquid crystal polymer to obtain target performance of the composite flexible substrate; wherein the mass percentage of the polyimide and the liquid crystal polymer is (70:30) to (50:50); In step S113 , the polyimide and the liquid crystal polymer are processed into thin films respectively by hot pressing equipment, and then hot pressing and laminating them at a temperature of 200° C. to 300° C. to obtain a processed composite flexible substrate.

5. The method for preparing a flexible circuit board for a microchip according to claim 1, wherein: The step S4 comprises: Step S41 , using low-temperature chemical vapor deposition or physical vapor deposition technology to perform metal deposition at a temperature range of 60° C. to 80° C., and adding a nanoparticle reinforcement during the deposition process; Step S42, dispersing the nanoparticles in the metal deposition solution using an ultrasonic dispersion method or a surfactant dispersion method, and controlling the deposition rate and nanoparticle concentration to ensure that the nanoparticles are evenly distributed in the metal layer; In step S43, after the metal deposition is completed, the flexible circuit board is subjected to a low-temperature baking and curing treatment, and the baking temperature is controlled within the range of 80°C to 100°C.

6. The method for preparing a flexible circuit board for a microchip according to claim 5, wherein: In step S42 , the concentration of the nanoparticles is 1% to 3%, and the deposition rate is 20-50 nm / min.

7. A flexible circuit board for a microchip, characterized in that: The flexible circuit board for microchip is manufactured by the method for manufacturing a flexible circuit board for microchip according to any one of claims 1 to 6.

Images