Thermal interface bonding method of copper-clad laminated board

Abstract

The invention relates to the technical field of printed circuit board manufacturing, in particular to a thermal interface bonding method of a copper-clad laminate, which comprises the following steps of: 1, cleaning the surfaces of a copper foil and an insulating base material, removing surface pollutants, and measuring the contact angle of water on the surfaces of the copper foil and the insulating base material through a contact angle measuring instrument; 2, performing low-temperature oxygen plasma activating treatment on the cleaned surfaces of the copper foil and the insulating base material; 3, forming a thermal stress buffer layer on the surfaces of the activated copper foil and the insulating base material; 4, carrying out thermocompression bonding, wherein temperature, pressure and time parameters of thermocompression bonding are dynamically optimized according to thickness data and surface energy data of the buffer layer; and step 5, carrying out post-curing treatment on the copper-clad laminated board subjected to primary bonding. Through cleaning, low-temperature oxygen plasma activation and the addition of the thermal stress buffer layer, the surface quality and thermal stability of the copper foil and the insulating base material are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a thermal interface bonding method for copper-clad laminates. Background Technology

[0002] Copper-clad laminates are the core basic material of printed circuit boards (PCBs), formed by hot-pressing bonding of an insulating substrate and copper foil. The insulating substrate typically uses epoxy resin, polyimide, or ceramic filler materials, while the copper foil provides the conductive path. In existing technologies, the thermal interface bonding method for copper-clad laminates is mainly achieved through a hot press, where the copper foil is pressed against the insulating substrate under specific temperature, pressure, and time conditions to form mechanical and electrical connections. However, this method has several technical problems, leading to unsatisfactory bonding quality and affecting the overall performance and reliability of the PCB.

[0003] First, in existing thermal bonding methods, the difference in thermal expansion coefficients between the copper foil and the insulating substrate easily leads to thermal stress concentration at the interface during hot pressing, causing warping, delamination, or microcracks in the bonded copper-clad laminate. These problems are particularly prominent in high-frequency or high-temperature applications, as thermal cycling exacerbates interface failure and reduces product lifespan. Second, existing methods lack sufficient control over surface cleanliness and roughness. The surfaces of the copper foil and the insulating substrate may contain oxides, grease, or dust contaminants. These contaminants can form interface defects such as bubbles or voids during bonding, increasing interface thermal resistance and electrical impedance, and affecting signal transmission efficiency and heat dissipation performance. Furthermore, existing thermal bonding process parameters (such as temperature, pressure, and time) are usually based on empirical settings, lacking real-time feedback and adaptive control, resulting in poor bonding uniformity and difficulty in ensuring consistency between different batches of products.

[0004] To improve bonding quality, existing technologies have explored various improvement methods. For example, some methods employ chemical treatment or plasma cleaning to pretreat the copper foil surface to remove contaminants and increase surface energy. However, chemical treatment may introduce residues, affecting interfacial insulation performance; plasma cleaning, on the other hand, is costly and its effectiveness is greatly affected by ambient humidity, making it difficult to apply stably in industrial production. Other methods add an adhesive layer during bonding, but the adhesive may increase interfacial thickness and thermal resistance, reducing heat dissipation efficiency. Furthermore, existing methods lack real-time monitoring of the bonding interface state and cannot dynamically adjust process parameters according to actual conditions, resulting in bonding quality that relies heavily on operator experience and has poor repeatability.

[0005] In summary, existing thermal interface bonding methods for copper-clad laminates have significant shortcomings in terms of bonding strength, thermal stability, and consistency, necessitating an innovative approach to address these issues. This invention addresses these technical deficiencies by proposing a highly innovative thermal interface bonding method that achieves more reliable and efficient bonding through the introduction of surface energy modulation and real-time parameter optimization. Summary of the Invention

[0006] To achieve the above objectives, the present invention provides a thermal interface bonding method for copper-clad laminates, comprising the following steps: Step 1: Provide copper foil and insulating substrate as copper-clad laminate assembly, clean the surface of copper foil and insulating substrate to remove surface contaminants, and measure the contact angle of water on the surface of copper foil and insulating substrate using a contact angle measuring instrument to ensure that the contact angle is less than or equal to a predetermined threshold, and output the cleaned surface of copper foil and insulating substrate. Step 2: Perform low-temperature oxygen plasma activation treatment on the cleaned copper foil and insulating substrate surface. The treatment time is dynamically adjusted according to the surface energy data. During the treatment, the surface energy change is monitored in real time by a surface energy analyzer. When the surface energy reaches the saturation value, the treatment is terminated and the activated copper foil and insulating substrate surface is output. Step 3: A thermal stress buffer layer is formed on the surface of the activated copper foil and insulating substrate. The thermal stress buffer layer is coated with nano-silica dispersion by spin coating. The spin coating speed is calculated based on the target thickness of the buffer layer. After coating, pre-curing is performed to output copper foil and insulating substrate with thermal stress buffer layer. Step 4: Align the copper foil with thermal stress buffer layer and the insulating substrate and place them in a hot press for hot pressing bonding. The temperature, pressure and time parameters of hot pressing bonding are dynamically optimized based on the buffer layer thickness data and surface energy data. During the bonding process, the interface temperature distribution is monitored by an infrared thermal imager, and the preliminary bonded copper-clad laminate is output. Step 5: Perform post-curing treatment on the initially bonded copper-clad laminate. Post-curing is carried out in an inert atmosphere. The post-curing temperature is determined based on the interface temperature data, and the post-curing time is adjusted based on the interface defect scanning results. The final bonded copper-clad laminate is then output.

[0007] Preferably, in step 1, cleaning the surfaces of the copper foil and insulating substrate includes mechanical wiping with anhydrous ethanol and microfiber cloth. After cleaning, the contact angle of water on the surfaces of the copper foil and insulating substrate is measured using a contact angle meter. The contact angle threshold is determined through experimental calibration to ensure that the surface energy meets the requirements. The thickness of the copper foil is determined according to the conductivity requirements of the target application. The thickness value is calculated by measuring the resistance value of the copper foil sample using a conductivity meter. The coefficient of thermal expansion of the insulating substrate is obtained by measuring the dimensional change of the insulating substrate sample during the heating process using a thermomechanical analyzer. During the cleaning process, if the contact angle is greater than a predetermined threshold, the cleaning steps are repeated until the contact angle is less than or equal to the predetermined threshold. The predetermined threshold is determined through a series of tests based on the surface energy requirements of the copper foil and insulating substrate. The tests include measuring the contact angle under different cleaning conditions and correlating the surface energy data.

[0008] Preferably, in step 2, the low-temperature oxygen plasma activation treatment is carried out in a plasma treatment chamber. The pressure of the plasma treatment chamber is maintained by a vacuum pump, and the pressure value is calculated based on the volume of the plasma treatment chamber and the gas flow rate. The oxygen plasma power is controlled by a radio frequency generator, and the power value is determined by experimental calibration based on surface energy data. The experimental calibration includes testing the surface energy after treatment at different powers and selecting the power value that maximizes the surface energy. The dynamic adjustment of the treatment time includes proportional adjustment based on the deviation between the real-time surface energy data and the target surface energy value, which is obtained through previous experiments. The surface energy saturation value is determined by monitoring the rate of change of surface energy in multiple treatment cycles using a surface energy analyzer. When the rate of change is lower than a set threshold, it is determined to be saturated.

[0009] Preferably, in step 3, the concentration of the nano-silica dispersion in the thermal stress buffer layer is determined by measuring the flow characteristics of the dispersion using a viscometer; the spin coating speed is calculated based on the target thickness of the buffer layer, and the calculation process includes establishing a curve showing the relationship between the spin coating speed and the thickness of the buffer layer through experiments, and then selecting the target thickness based on the difference in the coefficients of thermal expansion between the copper foil and the insulating substrate; pre-curing is carried out in a low-temperature oven, and the pre-curing temperature is determined based on the glass transition temperature of the thermal stress buffer layer material, which is obtained by measuring the thermal stress buffer layer sample using a differential scanning calorimeter; the pre-curing time is calculated based on the thickness of the thermal stress buffer layer and the pre-curing temperature using a thermal conduction model, which is constructed based on the material's thermal conductivity and specific heat capacity parameters.

[0010] Preferably, in step 4, the temperature parameters of hot-press bonding are monitored in real time by thermocouples and adjusted using a step-by-step heating strategy based on the buffer layer thickness data. The step-by-step heating strategy includes first raising the temperature to a lower level to allow the thermal stress buffer layer to flow, and then raising it to the bonding temperature. The pressure parameters are monitored by a pressure sensor and adjusted gradually based on surface energy data. The gradual pressure adjustment includes using a lower initial pressure to avoid interface deformation, and then gradually increasing the pressure. The time parameters are controlled by a timer and adjusted according to the real-time interface temperature curve to ensure that the bonding interface reaches thermal equilibrium. The interface temperature distribution is monitored by an infrared thermal imager, and the temperature uniformity data is used as a bonding quality evaluation index. The temperature uniformity is obtained by calculating the temperature standard deviation of different regions of the interface.

[0011] Preferably, in step 5, the composition of the inert atmosphere for post-curing is monitored by a gas analyzer, and the inert atmosphere includes nitrogen or argon; the post-curing temperature is determined based on interface temperature data, using a slow heating to a value higher than the bonding temperature, and the heating rate is obtained by measuring the reaction kinetics of the copper-clad laminate material using a thermal analyzer; the post-curing time is adjusted based on the interface defect scanning results, and the interface defect scanning uses an ultrasonic scanner to detect interface bubbles or delamination, and the defect area threshold is determined by statistical analysis of historical bonding quality data; during the post-curing process, if the defect area exceeds the threshold, the post-curing time is extended, and the extension time is calculated based on an experimental model of the relationship between defect area and time.

[0012] Preferably, the dynamic optimization in step 4 includes adjusting the hot-press bonding parameters using a feedback control algorithm. The feedback control algorithm calculates the optimal values ​​of temperature, pressure, and time in real time based on buffer layer thickness data and surface energy data. The feedback control algorithm includes a proportional-integral-derivative controller, and the parameters of the proportional-integral-derivative controller are determined through experimental debugging. The dynamic optimization process also includes recording historical bonding data for parameter prediction in subsequent bonding processes. The historical bonding data includes buffer layer thickness, surface energy, temperature, pressure, and time.

[0013] Preferably, the formation of the thermal stress buffer layer in step 3 further includes ultrasonic dispersion of the nano-silica dispersion, the ultrasonic dispersion time being determined according to the concentration and viscosity of the dispersion; after coating, the thickness of the buffer layer is verified using a thickness measuring instrument, including a laser thickness gauge; if the thickness of the buffer layer deviates from the target value, the spin coating speed is adjusted and the coating is reapplied; after pre-curing, the adhesion strength between the thermal stress buffer layer and the copper foil and insulating substrate is checked using an adhesion tester, the adhesion tester using the cross-cut test method, and the adhesion strength value is used to verify the quality of the buffer layer.

[0014] Preferably, the post-curing process in step 5 further includes cooling the copper-clad laminate after post-curing. The cooling rate is determined based on the thermal expansion coefficient and bonding interface structure of the copper-clad laminate. The cooling process is carried out in a controlled environment, with the ambient temperature maintained by an ambient temperature control chamber. The cooling rate is obtained by monitoring the temperature change of the copper-clad laminate using thermocouples. After cooling, the bonding strength is measured using a tensile tester. The bonding strength value is used for final quality acceptance. The tensile tester uses a peel test method, and the peel speed is set according to the standard protocol.

[0015] Preferably, all parameter measurements and data acquisitions during the entire bonding process are achieved through an automated system, which includes sensors, data acquisition cards, and control units. The automated system collects contact angle, surface energy, buffer layer thickness, temperature, pressure, and defect data in real time, and dynamically adjusts the parameters of each step based on the collected data. The automated system also integrates data recording and alarm functions for production quality tracking and fault diagnosis.

[0016] The beneficial effects of this invention are: 1. Due to the enhanced interfacial chemical bonding resulting from the surface energy activation treatment, the thermal stress buffer layer reduces thermal stress concentration, and the bonded copper-clad laminate exhibits higher peel strength in tensile tests, which is an improvement over existing technologies.

[0017] 2. Through dynamic parameter control and post-curing, the interfacial thermal resistance is reduced, and the copper-clad laminate does not delaminate or warp during high and low temperature cycling tests, making it suitable for high-frequency and high-temperature applications.

[0018] 3. Real-time monitoring and parameter optimization ensured bonding uniformity, resulting in small bonding quality deviations between different batches of products, thus improving production efficiency and product yield. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0020] Figure 1 This is a flowchart of the steps of the method of the present invention. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0022] Please see Figure 1 This invention provides a thermal interface bonding method for copper-clad laminates. In step 1, the surfaces of the copper foil and insulating substrate are first cleaned to remove contaminants such as oxides, grease, or dust, which may affect the subsequent bonding quality. Next, a contact angle meter is used to measure the contact angle of water on the surface. By ensuring that the contact angle is less than or equal to a predetermined threshold, sufficient surface wettability can be guaranteed, increasing surface energy and thus improving the effectiveness of subsequent processing. This step ensures surface cleanliness and appropriate wettability, providing ideal surface conditions for subsequent activation and bonding.

[0023] In step 2, after surface cleaning, a low-temperature oxygen plasma activation treatment is performed. This process removes residual contaminants from the surface using oxygen plasma and further increases the surface energy, making the copper foil and insulating substrate surfaces more hydrophilic and enhancing the adhesion between the surface and the thermal stress buffer layer. The treatment time is dynamically adjusted based on real-time monitored surface energy data to ensure that the treatment is terminated immediately once the surface energy reaches saturation, avoiding over-activation or damage to the substrate surface. This step, by precisely controlling the activation time and surface energy, avoids the potential side effects of chemical treatment, such as contaminant residue or material performance degradation.

[0024] In step 3, following the coating of the thermal stress buffer layer, a thermal stress buffer layer is coated onto the surfaces of the copper foil and the insulating substrate using a nano-silica dispersion. The buffer layer is uniformly coated onto the surface using a spin-coating method, with the spin-coating speed calculated based on the target thickness to ensure precise control of the buffer layer thickness. After coating, pre-curing is performed to enhance the structural stability of the buffer layer. The function of this buffer layer is to effectively reduce the thermal stress caused by the difference in thermal expansion coefficients between the copper foil and the substrate during hot pressing, thereby avoiding problems such as warping, delamination, or microcracks, and significantly improving the thermal stability and structural strength of the copper-clad laminate.

[0025] In step 4, hot-press bonding involves placing the copper foil with a thermal stress buffer layer and the insulating substrate into a hot press for hot-press bonding. During the hot-pressing process, temperature, pressure, and time parameters are dynamically optimized based on buffer layer thickness and surface energy data to achieve the best bonding effect. Simultaneously, an infrared thermal imager monitors the interface temperature distribution to ensure uniform temperature distribution during bonding, avoiding interface defects caused by excessively high or low temperatures. This step, through precise control of hot-pressing parameters, ensures high-quality bonding of the copper-clad laminate and improves the stability of the production process.

[0026] In step 5, the final post-curing process, the initially bonded copper-clad laminate undergoes post-curing in an inert atmosphere to prevent oxidation or other adverse reactions. The post-curing temperature is determined based on interface temperature data, and the post-curing time is adjusted according to the interface defect scanning results. This step ensures the final strength and stability of the bonding interface, while further eliminating minor defects generated during hot pressing, thus improving the reliability and long-term performance of the copper-clad laminate.

[0027] By employing cleaning, low-temperature oxygen plasma activation, and the addition of a thermal stress buffer layer, the surface quality and thermal stability of the copper foil and insulating substrate are effectively improved, reducing warping and cracking issues caused by thermal stress. Secondly, dynamically optimized hot-pressing parameters and a real-time monitoring system ensure the uniformity and consistency of the bonding process, avoiding quality fluctuations caused by improper experience in traditional processes. Furthermore, post-curing treatment guarantees the structural strength and stability of the final product, significantly improving the overall performance of the copper-clad laminate, especially in high-temperature and high-frequency environments, where product reliability and service life are significantly enhanced.

[0028] In one possible implementation, when cleaning the surface of copper foil and insulating substrate, mechanical wiping is first performed using anhydrous ethanol and microfiber cloth to remove oil, oxides, and other contaminants from the surface. This mechanical wiping method, combined with anhydrous ethanol as a solvent, effectively cleans the surface without introducing additional contaminants. Anhydrous ethanol has good solubility and volatility, allowing it to evaporate rapidly and avoiding the impact of residual solvent on subsequent processes. The microfiber cloth, with its excellent softness and cleaning properties, ensures that the material surface is not scratched or damaged. Surfaces cleaned in this way provide ideal conditions for subsequent processing.

[0029] After cleaning, the copper foil and insulating substrate surfaces need to have their contact angles measured using a contact angle meter to assess surface energy. The contact angle is a crucial indicator of surface energy; a smaller contact angle indicates higher surface energy and a greater susceptibility to adhesion reactions with other substances. A contact angle threshold, calibrated experimentally, ensures that the surface energy of the copper foil and insulating substrate meets process requirements. This threshold is determined through a series of experiments, covering contact angle measurements under different cleaning conditions and calibrated in conjunction with changes in surface energy. If the measured contact angle exceeds the predetermined threshold, the cleaning process must be repeated until the contact angle meets the requirements. This measure ensures surface energy stability, avoids the residual effects of surface contaminants, and improves the reliability of subsequent activation and thermal interface bonding processes.

[0030] The thickness of the copper foil is determined based on the conductivity requirements of the target application. In practical applications, the thickness of the copper foil needs to meet conductivity requirements to ensure the normal functioning of the circuit. The resistance value of the copper foil sample is measured using a conductivity meter, and the thickness of the copper foil is calculated based on the results. This measure ensures that the copper foil meets conductivity requirements without affecting subsequent bonding processes and structural stability.

[0031] The coefficient of thermal expansion (CTE) of the insulating substrate is a crucial parameter affecting the thermal performance of copper-clad laminates. Precise CTE data can be obtained by measuring the dimensional changes of the insulating substrate sample during heating using a thermomechanical analyzer (TMA). This data is critical for the subsequent thermal interface bonding process, as a mismatch in CTEs can lead to bonding instability or interface cracking. Therefore, understanding the CTE, in conjunction with the properties of other materials, helps optimize subsequent hot pressing and curing processes.

[0032] By using anhydrous ethanol and microfiber cloth for cleaning, along with precise contact angle measurement and surface energy monitoring, sufficient wettability of the copper foil and insulating substrate surfaces can be effectively ensured. This increases adhesion during the thermal interface bonding process, reduces interference from surface contamination, and ensures high-quality bonding results.

[0033] In one possible implementation, the oxygen plasma activation process is carried out within a plasma processing chamber. During this process, a low-pressure environment is maintained within the processing chamber using a vacuum pump; pressure control is crucial. The pressure is calculated based on the volume of the plasma processing chamber and the gas flow rate. Oxygen is introduced into the processing chamber, and oxygen molecules are excited by a radio frequency generator to produce oxygen plasma. The plasma, through its high energy, reacts with the surface of the copper foil and insulating substrate, removing surface contaminants and activating the surface to achieve higher surface energy.

[0034] The power of the oxygen plasma was controlled by a radio frequency generator, and this power value was experimentally calibrated using surface energy data. In the experiment, researchers processed the plasma at different powers and measured the surface energy values ​​to determine the power value that maximized the surface energy. This experimental calibration process is a crucial step in ensuring the stability and consistency of the activation effect, as the power value directly affects the degree of surface activation, and consequently, the quality of subsequent bonding.

[0035] Dynamically adjusting the processing time is also crucial during the process. Specifically, the processing time ratio is adjusted based on the deviation between real-time surface energy data and the target surface energy value to ensure that the surface energy consistently reaches the target value. The target surface energy value is obtained through preliminary experiments and is set according to the material type and application requirements. Dynamic adjustment ensures that the surface energy can quickly reach and remain at the required optimal state under different processing conditions.

[0036] The change in surface energy requires multiple plasma treatment cycles, and the rate of change is monitored using a surface energy analyzer. After a period of treatment, the rate of change in surface energy gradually decreases. If the rate of change falls below a set threshold, it can be determined that the surface energy has reached saturation, and further treatment is discontinued. This criterion helps avoid over-treatment, reduces unnecessary energy consumption, and ensures both high efficiency and cost control in the treatment process.

[0037] Through precise process control and dynamic adjustment, not only has the quality and efficiency of thermal interface bonding of copper clad laminates been improved, but a sustainable and stable solution has also been provided for large-scale production.

[0038] In one possible implementation, one of the main components of the thermal stress buffer layer is a nano-silica dispersion, the concentration of which is measured using a viscometer. The viscometer measures the flow characteristics of the dispersion, helping to determine its concentration. This measurement reveals the relationship between the dispersion's viscosity and concentration, ensuring that the dispersion's viscosity is suitable during coating and avoiding uneven flow caused by unsuitable concentration, thereby guaranteeing the uniformity and stability of the buffer layer.

[0039] The thickness of the thermal stress buffer layer is a key parameter affecting its performance; therefore, the spin coating speed needs to be calculated based on the target thickness. To accurately determine the spin coating speed, a curve showing the relationship between spin coating speed and buffer layer thickness was first established experimentally. This curve can help quickly select a suitable spin coating speed based on the target thickness in actual production. Furthermore, the selection of the target thickness also needs to consider the difference in the coefficients of thermal expansion between the copper foil and the insulating substrate. Due to the differences in thermal expansion and contraction between different materials, an appropriate buffer layer thickness can effectively reduce deformation and damage caused by thermal stress.

[0040] Pre-curing in a low-temperature oven ensures the initial curing of the thermal stress buffer layer material after coating. The pre-curing temperature is determined by the glass transition temperature (GLT) of the thermal stress buffer layer material, which is the temperature at which the material changes from a softened to a hardened state. The GLT of the thermal stress buffer layer sample is measured using differential scanning calorimetry (DSC) to provide a basis for determining the pre-curing temperature. Precise control of the pre-curing temperature and time is necessary to ensure that the adhesion and performance of the buffer layer material are not affected by excessive heat treatment.

[0041] The pre-curing time is calculated using a thermal conductivity model based on the thickness of the thermal stress buffer layer and the pre-curing temperature. This model, based on physical parameters such as the material's thermal conductivity and specific heat capacity, can accurately calculate the required curing time for different thicknesses and temperatures. A reasonable pre-curing time not only ensures complete curing of the material but also avoids thermal damage caused by excessive curing time, thereby improving the quality and stability of the final product.

[0042] By precisely controlling each step, the quality stability of the copper-clad laminate is ensured, especially the thermal interface bonding effect under high-temperature conditions, providing reliable technical support for high-precision fields such as electronic packaging.

[0043] In one possible implementation, the temperature parameters of the thermocompression bonding are monitored in real time using thermocouples. As high-precision temperature sensors, thermocouples accurately reflect temperature changes at the bonding interface and ensure precise temperature control. Based on the thickness data of the buffer layer, a stepped heating strategy is employed for temperature regulation. First, the temperature is raised to a lower level to encourage flow in the thermal stress buffer layer, preventing excessive thermal stress and uneven flow at excessively high temperatures. Next, the temperature is raised to the target bonding temperature; this step helps avoid interface defects or material damage caused by rapid heating. Therefore, the stepped heating strategy effectively improves material compatibility during the bonding process and reduces the impact of thermal stress on material properties.

[0044] Pressure parameters are monitored in real time using pressure sensors, and progressive pressure adjustments are made based on surface energy data. Initially, a lower pressure is used to begin the bonding process to avoid interface deformation or copper foil damage that may occur under high pressure. As the bonding process progresses, the pressure is gradually increased. This progressive adjustment ensures uniform stress on the interface throughout the bonding process, thereby achieving the desired bonding effect. Precise pressure control avoids interface quality problems caused by excessive or insufficient pressure, improving bond strength and reliability.

[0045] During the bonding process, the time parameter is precisely controlled by a timer and adjusted according to the real-time interface temperature profile. By monitoring changes in the interface temperature in real time, thermal equilibrium at the bonding interface is ensured. This method guarantees sufficient heat transfer within a certain time frame, avoiding poor bonding caused by uneven temperature distribution.

[0046] To ensure uniform temperature distribution during the bonding process, an infrared thermal imager is used to monitor the interface temperature distribution. Temperature uniformity data, as an important evaluation indicator of bonding quality, can be obtained by calculating the standard deviation of temperature in different regions of the interface. The smaller the temperature standard deviation, the more uniform the interface temperature, and the better the bonding effect. By monitoring and adjusting the temperature distribution in real time, localized uneven thermal expansion caused by excessive temperature differences can be effectively avoided, reducing thermal stress damage to the material and ensuring the overall quality and stability of the bonded layer.

[0047] By using stepped heating and temperature uniformity control, the distribution of thermal stress can be better controlled, reducing thermal damage caused by excessively rapid temperature changes or large local temperature differences, thereby improving the long-term stability of copper-clad laminates.

[0048] In one possible implementation, during the post-curing process, an inert atmosphere (such as nitrogen or argon) is used to provide a stable environment, preventing oxidation or other unwanted chemical reactions. To ensure the purity and correct composition of the inert atmosphere, a gas analyzer is used for real-time monitoring. The gas analyzer can accurately detect the proportions of each component in the atmosphere, ensuring the stability of the material during curing and avoiding any possible gas contamination or compositional deviations, which is crucial for improving the thermal interface quality of the laminate.

[0049] The post-curing temperature is precisely controlled by real-time monitoring of the interface temperature. In practice, the temperature is slowly increased until it exceeds the set bonding temperature. The heating rate is derived from the reaction kinetics data of the copper-clad laminate material obtained by a thermal analyzer. By gaining a thorough understanding of the material's thermal behavior and reaction rate, the heating rate is optimized to ensure smooth and uniform temperature changes, avoiding stress concentration or interlayer inhomogeneity caused by excessively rapid heating.

[0050] The post-curing time is dynamically adjusted based on the interface defect scanning results. An ultrasonic scanner is used to detect defects such as bubbles or delamination at the interface, especially in the bonding interface area. Interface defect scanning accurately detects minute defects, such as bubbles, delamination, or other structural instabilities, ensuring the interface remains intact. Whenever a defect is detected, the system compares the defect area with historical bonding quality data to set a defect area threshold. If the detected defect area exceeds the set threshold, the post-curing time is extended to ensure sufficient time for repair. The specific extension time is calculated using an experimental model based on the relationship between defect area and required time.

[0051] By precisely controlling the atmosphere, adjusting the temperature rise rate and curing time, and dynamically detecting interface defects, the post-curing quality of copper-clad laminates has been significantly improved, ensuring the stability and reliability of their thermal interface bonding.

[0052] In one possible implementation, a feedback control algorithm is the core of dynamic optimization, calculating the optimal values ​​of temperature, pressure, and time in real time based on buffer layer thickness and surface energy data. This process automatically adjusts the parameters at each stage of the hot-press bonding process, thereby avoiding errors caused by manual operation and ensuring that temperature, pressure, and time are always within the most suitable range, guaranteeing consistent bonding quality.

[0053] Feedback control algorithms include proportional-integral-derivative (PID) controllers. The PID controller precisely adjusts various parameters during the hot pressing process using three control parameters (proportional, integral, and derivative). Proportional control adjusts the output based on the current error, integral control adjusts for accumulated errors, and derivative control optimizes the control process by predicting future errors. Through the combination of these three methods, the PID controller can finely regulate temperature, pressure, and time, ensuring it remains in optimal condition throughout the hot pressing process.

[0054] The parameters of the PID controller are determined through experimental tuning. This step is crucial because each material and process has different optimal control parameters. Through experimentation, the most suitable proportional, integral, and derivative values ​​can be found, enabling the control system to adjust the hot-pressing parameters more accurately and efficiently in actual operation.

[0055] Dynamic optimization also includes recording historical data from each bonding process for subsequent parameter prediction. This historical data includes key parameters such as buffer layer thickness, surface energy, temperature, pressure, and time. By accumulating and analyzing this historical data, a scientific basis for predicting future bonding processes can be provided, allowing for the pre-setting of optimal process parameters and avoiding instability caused by environmental factors or material variations. The use of historical data not only improves the accuracy of each operation but also provides data support for long-term process optimization.

[0056] The dynamic optimization technology of this invention, through the use of feedback control algorithms, PID controllers, and historical data prediction, can adjust key parameters in real time during the thermal interface bonding process of copper-clad laminates, ensuring process stability and improving product quality and production efficiency.

[0057] In one possible implementation, to improve the performance of the thermal stress buffer layer, the nano-silica dispersion first needs to be ultrasonically dispersed. The dispersibility of the nano-silica material is crucial to the uniformity and stability of the buffer layer. Ultrasonic dispersion can effectively break up the aggregation between nanoparticles, ensuring a uniform distribution of nano-silica particles in the dispersion, thereby giving the buffer layer consistent physical properties. The ultrasonic dispersion time is determined based on the concentration and viscosity of the dispersion; higher concentrations and viscosities generally require longer dispersion times to ensure all particles are fully dispersed and to avoid the negative impact of particle agglomeration on the buffer layer performance.

[0058] After the nano-silica dispersion is coated onto the substrate surface, it is essential to ensure that the thickness of the thermal stress buffer layer meets the design requirements. Thickness measurement is performed using a laser thickness gauge, which provides accurate non-contact measurement to ensure uniform coating thickness. If the measured buffer layer thickness deviates from the target value, recoating is necessary by adjusting the spin coating speed. Adjusting the spin coating speed controls the coating's flowability and deposition rate during the coating process, thereby ensuring the desired thickness is achieved. Thickness measurement is then performed again after adjustment until the predetermined standard is met.

[0059] After the thermal stress buffer layer is coated and its thickness is verified, a pre-curing treatment is performed to enhance the adhesion and structural stability of the buffer layer. Following pre-curing, the bond strength between the thermal stress buffer layer and the copper foil and insulating substrate is checked using an adhesion tester. The adhesion test employs the cross-cut test, a standard method that assesses the adhesion between the buffer layer and the substrate by creating a grid pattern on the buffer layer and then peeling it off with adhesive tape. The cross-cut test accurately reflects the adhesion of the buffer layer, ensuring that it will not detach or separate due to weak adhesion during subsequent thermosetting bonding.

[0060] The thermal stress buffer layer formation process of the present invention improves the overall performance and stability of the copper-clad laminate, effectively prevents thermal stress from damaging the material, and enhances its adaptability under complex working conditions.

[0061] In one possible implementation, the core objective of the cooling process is to restore the copper-clad laminate from its high-temperature curing state to room temperature, while avoiding thermal stress concentration or interlayer delamination caused by uneven or excessively rapid cooling. The cooling rate is determined based on the thermal expansion coefficient of the copper-clad laminate and the structural characteristics of the bonding interface. The differences in thermal expansion between different materials and structures necessitate precise control of the cooling rate to avoid material damage or interface delamination due to differences in thermal stress.

[0062] Cooling must be performed in a controlled environment to ensure accuracy and consistency. Maintaining the required ambient temperature within an environmental temperature-controlled chamber ensures stable temperature changes and prevents external temperature fluctuations from affecting the cooling rate. The environmental temperature-controlled chamber provides stable temperature and humidity conditions, which are crucial for managing temperature variations during the cooling process.

[0063] The cooling rate is monitored using thermocouples. Thermocouples can monitor the temperature changes of the copper-clad laminate in real time, thereby precisely controlling the cooling rate. By observing the relationship with temperature changes, the temperature variations in the cooling environment can be accurately adjusted, ensuring a smooth cooling process and preventing thermal stress problems caused by sudden temperature drops or excessive temperature gradients.

[0064] After the cooling process is complete, the copper-clad laminate needs to undergo a bond strength test to confirm the quality of the thermal interface bonding. A tensile tester is used to measure the bond strength; this test employs a peel test method, applying tension until the bond layers separate, thus testing the bond strength. To ensure the accuracy of the test results, the peel speed is set according to a standard protocol, which is typically matched to the material properties and application scenario. Standardized peel speeds ensure the repeatability and comparability of the test, guaranteeing reliable results for each test.

[0065] By employing cooling treatment, precise temperature control, and standardized tensile testing during the post-curing process, the thermal interface bonding quality and reliability of copper-clad laminates are significantly improved.

[0066] In one possible implementation, the automation system comprises three key components: sensors, data acquisition cards, and control units.

[0067] The role of sensors is to monitor and measure various key parameters in real time, such as contact angle, surface energy, buffer layer thickness, temperature, pressure, and defect data. Different sensors are used to monitor different physical quantities. For example, temperature sensors are used to measure temperature changes, pressure sensors are used to monitor the pressure applied during bonding, and contact angle sensors are used to assess the wettability of material surfaces.

[0068] The data acquisition card is responsible for converting the signals collected by the sensors into digital signals and transmitting them to the control unit. It acts as a "bridge" in the automation system, ensuring smooth data transmission and analysis within the control unit.

[0069] The control unit is responsible for real-time data processing and analysis, and dynamically adjusts the production process based on the collected data. The control unit can automatically optimize various step parameters, such as adjusting process conditions like coating, heating, and pressure, thereby ensuring that each stage of the process is carried out under optimal conditions.

[0070] The automated system can collect data on multiple key parameters in real time. These data include: Contact angle: used to evaluate the wettability of a material surface, directly affecting the coating effect of thermal interface materials.

[0071] Surface energy: Surface energy reflects the interaction between the surface of a material and other materials, and directly affects the bonding quality of the thermal interface.

[0072] Buffer layer thickness: Affects the thermal stress buffering effect. Precise control of the thickness helps prevent thermal stress from damaging the material.

[0073] Temperature and pressure: These are the core parameters in the bonding process, affecting the plastic deformation and bond strength of the material.

[0074] Defect data: The collection of defect data helps to monitor potential problems that occur in the production process in real time, such as bubbles and peeling, and can make timely adjustments to prevent defective products from being shipped out.

[0075] By monitoring these parameters in real time, the control unit can automatically adjust various aspects of the production process based on data changes. For example, when the temperature changes beyond the preset range, the automatic system can promptly adjust the operating status of the heating equipment to ensure that the temperature is maintained within the ideal range; if the pressure deviates from the standard value, the control unit will automatically adjust the pressure of the press.

[0076] The automated system integrates data logging capabilities, enabling real-time recording of process parameters, quality data, and any potential fault information for each production batch. This data not only helps trace the production process of each product but also provides detailed reference information for subsequent quality control and improvement.

[0077] In addition, the automated system also has an alarm function. When the system detects abnormal data or production parameters deviating from the standard, it immediately issues an alarm and automatically stops production or makes corresponding adjustments. This function ensures that every step of the production process is within a controllable range, preventing quality problems caused by operational errors or equipment malfunctions in a timely manner.

[0078] The introduction of automation systems has greatly improved the accuracy, stability and efficiency of the thermal interface bonding process, ensuring that each batch of copper-clad laminates meets the expected quality standards, while providing strong support for quality control, production traceability and fault diagnosis. Example

[0079] This embodiment is applied to the manufacturing scenario of copper-clad laminate for high-frequency circuit boards, specifically for printed circuit board substrates in 5G communication equipment. Step 1: Preparation and surface cleaning of copper-clad laminate assembly; We provide copper foil and an insulating substrate as components for copper-clad laminates. The copper foil is electrolytic copper foil, and its thickness is determined based on the conductivity requirements of the target application. First, the resistance of the copper foil sample is measured using a conductivity meter (a four-probe resistance meter). During measurement, a constant current is applied to the copper foil surface, and the voltage drop is measured. The resistivity is calculated using Ohm's law, and then the thickness is calculated based on the geometric dimensions of the copper foil (length and cross-sectional area). The target thickness ensures that the conductivity meets the low-loss requirements of high-frequency circuits. The insulating substrate is an epoxy resin-based composite material, and its coefficient of thermal expansion (CTE) is measured using a thermomechanical analyzer (TMA). The insulating substrate sample is cut to standard dimensions, placed in the TMA, and heated at a constant heating rate while monitoring the length change. The CTE value is calculated based on the definition of the CTE (the rate of change of length per unit temperature change), ensuring it matches the CTE of the copper foil to reduce thermal stress.

[0080] Clean the surfaces of the copper foil and insulating substrate using anhydrous ethanol and a microfiber cloth for mechanical wiping. During wiping, the microfiber cloth applies uniform pressure in a circular motion to remove surface contaminants (such as oxides, grease, and dust). After cleaning, the contact angle of water on the copper foil and insulating substrate surfaces is measured using a contact angle meter (using the seated drop method): a drop of deionized water is placed on the surface, the droplet shape is captured by a high-speed camera, and the contact angle value is calculated using image analysis software. The contact angle threshold is determined through experimental calibration: the contact angle is measured under a series of cleaning conditions (including different wiping times and ethanol amounts), and correlated with surface energy data (measured using a surface energy analyzer), to select a contact angle threshold that ensures the surface energy meets the standard; specifically, the threshold is set to a contact angle less than or equal to 30 degrees. This value is based on historical data statistics; when the contact angle is greater than 30 degrees, insufficient surface energy may lead to bonding defects. During the cleaning process, if the contact angle is greater than the threshold, the cleaning steps are repeated until the contact angle is less than or equal to the threshold. This step outputs the cleaned copper foil and insulating substrate surfaces, and the surface energy data is used as input for step 2.

[0081] Step 2: Surface energy activation treatment; The cleaned copper foil and insulating substrate surfaces undergo low-temperature oxygen plasma activation treatment to increase surface energy and chemical activity. The activation treatment is performed in a plasma treatment chamber, with the chamber pressure maintained by a vacuum pump. First, the pressure value is calculated based on the chamber volume and gas flow rate using the formula: Pressure = (Gas Flow Rate × Gas Density) / Chamber Cross-sectional Area, where the gas density is calculated based on the gas constant of oxygen and temperature. The actual pressure value is monitored in real-time by a pressure sensor to ensure it remains stable near the calculated value. The oxygen plasma power is controlled by a radio frequency generator, and the power value is determined experimentally based on surface energy data. First, the surface energy after treatment is tested at different powers (from 50W to 300W) (measured using a surface energy analyzer). The power value that maximizes the surface energy (e.g., 200W) is selected, and this calibration process is repeated multiple times to ensure reliability.

[0082] The processing time is dynamically adjusted based on surface energy data: Surface energy data is monitored in real time using a surface energy analyzer. The analyzer uses the pendant drop method to measure surface tension and calculate the surface energy value. The dynamic adjustment logic is as follows: when the real-time surface energy value deviates significantly from the target surface energy value (obtained through previous experiments, e.g., 72 mN / m), the processing time is increased; when the deviation is small, the processing time is decreased. The specific adjustment formula is: Change in processing time = Kp × Deviation + Ki × Integral Deviation + Kd × Deviation Change Rate, where Kp, Ki, and Kd are proportional, integral, and derivative coefficients, determined through experimental debugging (e.g., Kp=0.5, Ki=0.1, Kd=0.2). The surface energy saturation value is determined by monitoring the surface energy change rate through multiple processing cycles using the surface energy analyzer: when the surface energy change rate is lower than a set threshold (e.g., 0.5 mN / mpersecond), saturation is determined, and the processing is terminated. This step outputs the activated copper foil and insulating substrate surface; the surface energy data serves as the input for step 3.

[0083] Step 3: Formation of thermal stress buffer layer; A thermal stress buffer layer is formed on the surface of the activated copper foil and the insulating substrate to compensate for the difference in thermal expansion coefficients. The thermal stress buffer layer is coated with a nano-silica dispersion, the concentration of which is determined by measuring its flow characteristics using a viscometer (rotational viscometer): the viscosity of the dispersion at different shear rates is measured, and the concentration value is determined based on the rheological curve. The target concentration ensures that the dispersion has appropriate flowability and coverage.

[0084] The coating method is spin coating, and the spin coating speed is calculated based on the target thickness of the buffer layer. First, an experimental curve relating spin coating speed to buffer layer thickness is established. The dispersion is coated at different spin coating speeds (from 1000 rpm to 5000 rpm), and the thickness is measured using a laser thickness gauge. A speed-thickness curve is plotted and fitted to a quadratic function model: Thickness = a × speed^2 + b × speed + c, where a, b, and c are fitting coefficients (determined using the least squares method). The target thickness of the buffer layer is selected based on the difference in thermal expansion coefficients between the copper foil and the insulating substrate. This difference is calculated using the measurement data from step 1, and the target thickness is directly proportional to the difference. The proportionality coefficient is determined through thermal stress simulation experiments.

[0085] After coating, pre-curing is performed in a low-temperature oven. The pre-curing temperature is determined based on the glass transition temperature of the thermal stress buffer layer material. The glass transition temperature is obtained by measuring the thermal stress buffer layer sample using differential scanning calorimetry (DSC). During measurement, the sample is scanned at a constant heating rate, and the heat flow change is recorded. The glass transition temperature is taken as the inflection point on the heat flow curve. The pre-curing time is calculated based on the thermal stress buffer layer thickness and pre-curing temperature using a thermal conduction model. The thermal conduction model is based on Fourier's law, considering the material's thermal conductivity and specific heat capacity parameters. The model equation is ∂T / ∂t=α∇²T, where α is the thermal diffusivity, obtained through material testing. The pre-curing time is calculated as the time required to reach the target degree of cure, which is determined by measuring the heat of reaction using DSC. After pre-curing, an adhesion tester (using the cross-cut test method) is used to check the adhesion strength between the thermal stress buffer layer and the copper foil and insulating substrate to ensure the quality of the buffer layer. This step outputs the copper foil and insulating substrate with the thermal stress buffer layer. The buffer layer thickness data is used as input for step 4.

[0086] Step 4: Hot-press bonding and dynamic parameter control; After aligning the copper foil with a thermal stress buffer layer and the insulating substrate, they are placed in a hot press for hot-press bonding. The temperature, pressure, and time parameters for hot-press bonding are dynamically optimized based on buffer layer thickness and surface energy data. Dynamic optimization uses a feedback control algorithm (proportional-integral-derivative controller), which calculates the optimal values ​​for temperature, pressure, and time in real time based on buffer layer thickness and surface energy data. The controller's input is the deviation between the buffer layer thickness and surface energy, and the output is the parameter adjustment amount. The parameters of the proportional-integral-derivative controller (proportional coefficient Kp, integral coefficient Ki, and derivative coefficient Kd) are determined through experimental debugging, for example, testing the impact of different parameter combinations on bonding quality during trial production to select the optimal combination.

[0087] Temperature parameters are monitored in real time via thermocouples and adjusted using a stepped heating strategy based on buffer layer thickness data. This strategy involves initially raising the temperature to a lower level (e.g., 150°C) to allow the thermal stress buffer layer to flow, then gradually increasing it to the bonding temperature (e.g., 200°C). Specific temperature values ​​are calculated based on the buffer layer thickness; a larger thickness results in a lower initial temperature and a slower heating rate. Pressure parameters are monitored via pressure sensors and adjusted progressively based on surface energy data. This involves using a lower initial pressure (e.g., 0.5 MPa) to avoid interface deformation, followed by a gradual increase in pressure (e.g., to 2 MPa). The pressure adjustment is based on the surface energy value; a higher surface energy results in a slower pressure increase rate. Time parameters are controlled by a timer and adjusted based on the real-time interface temperature curve. The interface temperature curve is monitored by an infrared thermal imager, and time adjustment ensures the bonding interface reaches thermal equilibrium, i.e., the interface temperature standard deviation is below a threshold (e.g., 2°C). The infrared thermal imager monitors the interface temperature distribution, and temperature uniformity data serves as a bonding quality evaluation indicator. Temperature uniformity is obtained by calculating the temperature standard deviation of different regions of the interface. This step outputs a preliminarily bonded copper-clad laminate, with the interface temperature data serving as input for step 5.

[0088] Step 5: Post-curing and interface strengthening; Post-curing is performed on the initially bonded copper-clad laminate to strengthen the interfacial bonding. Post-curing is carried out in an inert atmosphere, the composition of which is monitored by a gas analyzer: the gas analyzer uses infrared spectroscopy to detect the oxygen and moisture content in the atmosphere in real time, ensuring an inert atmosphere (e.g., nitrogen purity greater than 99.99%). The post-curing temperature is determined based on the interfacial temperature data, using a slow heating process to a value above the bonding temperature (e.g., 220°C). The heating rate is obtained by measuring the reaction kinetics of the copper-clad laminate material using a thermal analyzer: the thermal analyzer measures the reaction heat flux using DSC, calculates the activation energy, and then determines the heating rate according to the Arrhenius equation.

[0089] The post-curing time is adjusted based on the interface defect scanning results: Interface defect scanning uses an ultrasonic scanner (using the pulse-echo method) to detect interface bubbles or delamination, and the defect area is calculated using image processing software. The defect area threshold is determined through statistical analysis of historical bonding quality data: Defect area data of qualified and defective products from past production are collected, distribution curves are plotted, and the threshold is set as the upper limit of the defect area of ​​qualified products (e.g., 0.1% of the total area). If the defect area exceeds the threshold, the post-curing time is extended. The extension time is calculated based on an experimental model of the relationship between defect area and time: the model is a linear relationship, and the extension time = k × defect area, where k is a proportionality coefficient, determined through regression analysis.

[0090] After post-curing, the copper-clad laminate undergoes a cooling process. The cooling rate is determined based on the thermal expansion coefficient of the copper-clad laminate and the bonding interface structure. The cooling rate is obtained by monitoring the temperature change of the copper-clad laminate using thermocouples, and the target cooling rate ensures minimal thermal stress. Cooling is performed in a controlled environment, with the ambient temperature maintained by an environmental temperature control chamber. After cooling, the bond strength is measured using a tensile tester employing a peel test method. The peel speed is set according to a standard protocol (such as IPC-TM-650). The bond strength value is used for final quality acceptance. This step outputs the final bonded copper-clad laminate.

[0091] In this embodiment, through the above steps, the copper-clad laminate exhibits excellent bonding strength, thermal stability, and consistency in high-frequency circuit board applications. Bonding strength, measured by a tensile tester, shows an average peel strength that is more than 20% higher than existing technologies. Thermal stability is verified through high and low temperature cycling tests (-40°C to 125°C, 1000 cycles), showing no delamination or warping. Consistency is demonstrated through statistical process control (SPC) analysis, with bonding quality deviations less than 5%.

[0092] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for thermal interface bonding of a copper-clad laminate, characterized in that, Includes the following steps: Step 1: Provide copper foil and insulating substrate as copper-clad laminate assembly, clean the surface of copper foil and insulating substrate to remove surface contaminants, and measure the contact angle of water on the surface of copper foil and insulating substrate using a contact angle measuring instrument to ensure that the contact angle is less than or equal to a predetermined threshold, and output the cleaned surface of copper foil and insulating substrate. Step 2: Perform low-temperature oxygen plasma activation treatment on the cleaned copper foil and insulating substrate surface. The treatment time is dynamically adjusted according to the surface energy data. During the treatment, the surface energy change is monitored in real time by a surface energy analyzer. When the surface energy reaches the saturation value, the treatment is terminated and the activated copper foil and insulating substrate surface is output. Step 3: A thermal stress buffer layer is formed on the surface of the activated copper foil and insulating substrate. The thermal stress buffer layer is coated with nano-silica dispersion by spin coating. The spin coating speed is calculated based on the target thickness of the buffer layer. After coating, pre-curing is performed to output copper foil and insulating substrate with thermal stress buffer layer. Step 4: Align the copper foil with thermal stress buffer layer and the insulating substrate and place them in a hot press for hot pressing bonding. The temperature, pressure and time parameters of hot pressing bonding are dynamically optimized based on the buffer layer thickness data and surface energy data. During the bonding process, the interface temperature distribution is monitored by an infrared thermal imager, and the preliminary bonded copper-clad laminate is output. Step 5: Perform post-curing treatment on the initially bonded copper-clad laminate. Post-curing is carried out in an inert atmosphere. The post-curing temperature is determined based on the interface temperature data, and the post-curing time is adjusted based on the interface defect scanning results. The final bonded copper-clad laminate is then output.

2. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, In step 1, cleaning the surface of the copper foil and insulating substrate includes mechanical wiping with anhydrous ethanol and microfiber cloth. After cleaning, the contact angle of water on the surface of the copper foil and insulating substrate is measured by a contact angle measuring instrument. The contact angle threshold is determined by experimental calibration to ensure that the surface energy meets the standard. The thickness of the copper foil is determined according to the conductivity requirements of the target application. The thickness value is calculated by measuring the resistance value of the copper foil sample with a conductivity meter. The coefficient of thermal expansion of the insulating substrate was obtained by measuring the dimensional changes of the insulating substrate sample during the heating process using a thermomechanical analyzer. If the contact angle is greater than the predetermined threshold during the cleaning process, the cleaning steps are repeated until the contact angle is less than or equal to the predetermined threshold. The predetermined threshold, based on the surface energy requirements of the copper foil and insulating substrate, was determined through a series of tests, including measuring the contact angle and correlating the surface energy data under different cleaning conditions.

3. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, In step 2, the low-temperature oxygen plasma activation treatment is carried out in the plasma treatment chamber. The pressure in the plasma treatment chamber is maintained by a vacuum pump, and the pressure value is calculated based on the volume of the plasma treatment chamber and the gas flow rate. The oxygen plasma power is controlled by a radio frequency generator. The power value is determined by experimental calibration based on surface energy data. The experimental calibration includes testing the surface energy after treatment at different powers and selecting the power value that maximizes the surface energy. The dynamic adjustment of processing time includes proportional adjustment based on the deviation between real-time surface energy data and the target surface energy value, which is obtained through preliminary experiments. The surface energy saturation value is determined by monitoring the rate of change of surface energy in multiple processing cycles using a surface energy analyzer. When the rate of change is lower than a set threshold, it is determined to be saturated.

4. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, In step 3, the concentration of the nano-silica dispersion in the thermal stress buffer layer is determined by measuring the flow characteristics of the dispersion using a viscometer. The spin coating speed is calculated based on the target thickness of the buffer layer. The calculation process includes establishing a curve showing the relationship between the spin coating speed and the thickness of the buffer layer through experiments, and then selecting the target thickness based on the difference in the coefficients of thermal expansion between the copper foil and the insulating substrate. Pre-curing was carried out in a low-temperature oven. The pre-curing temperature was determined based on the glass transition temperature of the thermal stress buffer layer material. The glass transition temperature was obtained by measuring the thermal stress buffer layer sample using a differential scanning calorimeter. The pre-curing time is calculated based on the thickness of the thermal stress buffer layer and the pre-curing temperature using a thermal conduction model, which is constructed based on the material's thermal conductivity and specific heat capacity parameters.

5. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, In step 4, the temperature parameters of hot-press bonding are monitored in real time by thermocouples and adjusted using a step heating strategy based on the buffer layer thickness data. The step heating strategy includes first raising the temperature to a lower temperature to allow the thermal stress buffer layer to flow, and then raising it to the bonding temperature. Pressure parameters are monitored by a pressure sensor and a gradual pressure adjustment is performed based on surface energy data. The gradual pressure adjustment involves using a low initial pressure to avoid interface deformation, and then gradually increasing the pressure. The time parameter is controlled by a timer and adjusted according to the real-time interface temperature curve to ensure that the bonding interface reaches thermal equilibrium. The interface temperature distribution was monitored by an infrared thermal imager, and the temperature uniformity data was used as an indicator for evaluating the bonding quality. The temperature uniformity was obtained by calculating the temperature standard deviation of different regions of the interface.

6. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, In step 5, the composition of the inert atmosphere for the post-curing treatment is monitored by a gas analyzer, and the inert atmosphere includes nitrogen or argon. The post-curing temperature is determined based on the interface temperature data. The temperature is slowly increased to a value higher than the bonding temperature. The heating rate is obtained by measuring the reaction kinetics of the copper-clad laminate material using a thermal analyzer. The post-curing time is adjusted based on the interface defect scanning results. The interface defect scanning uses an ultrasonic scanner to detect interface bubbles or delamination. The defect area threshold is determined by statistical analysis of historical bonding quality data. During the post-curing process, if the defect area exceeds the threshold, the post-curing time is extended. The extension time is calculated based on an experimental model of the relationship between defect area and time.

7. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, The dynamic optimization in step 4 includes adjusting the hot-press bonding parameters using a feedback control algorithm, which calculates the optimal values ​​of temperature, pressure, and time in real time based on buffer layer thickness data and surface energy data. The feedback control algorithm includes a proportional-integral-derivative controller, and the parameters of the proportional-integral-derivative controller are determined through experimental debugging. The dynamic optimization process also includes recording bonding history data for parameter prediction in subsequent bonding processes. The bonding history data includes buffer layer thickness, surface energy, temperature, pressure, and time.

8. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, The formation of the thermal stress buffer layer in step 3 also includes ultrasonic dispersion of the nano-silica dispersion, the ultrasonic dispersion time of which is determined according to the concentration and viscosity of the dispersion. After coating, the thickness of the buffer layer is verified using a thickness measuring instrument, including a laser thickness gauge. If the thickness of the buffer layer deviates from the target value, the spin coating speed is adjusted and the coating is reapplied. After pre-curing, the adhesion strength between the thermal stress buffer layer and the copper foil and insulating substrate is checked using an adhesion tester. The adhesion tester uses the cross-cut test method, and the adhesion strength value is used to verify the quality of the buffer layer.

9. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, The post-curing process in step 5 also includes cooling the copper-clad laminate after post-curing. The cooling rate is determined based on the thermal expansion coefficient and bonding interface structure of the copper-clad laminate. The cooling process is carried out in a controlled environment, the ambient temperature is maintained by an ambient temperature control chamber, and the cooling rate is obtained by monitoring the temperature change of the copper-clad laminate using thermocouples. After cooling, the bond strength is measured using a tensile tester. The bond strength value is used for final quality acceptance. The tensile tester uses the peel test method, and the peel speed is set according to the standard protocol.

10. The thermal interface bonding method for a copper-clad laminate according to claim 1, characterized in that, Throughout the bonding process, all parameter measurements and data acquisition are performed through an automated system, which includes sensors, data acquisition cards, and control units. The automated system collects data on contact angle, surface energy, buffer layer thickness, temperature, pressure, and defects in real time, and dynamically adjusts the parameters of each step based on the collected data; The automated system also integrates data logging and alarm functions for production quality tracking and fault diagnosis.

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