Micro-LED chip heterogeneous thermocompression bonding method and structure

Abstract

The invention discloses a Micro-LED chip heterogeneous thermocompression bonding method and structure, and the method comprises the steps: preparing a single Micro-LED chip and a single drive substrate, the Micro-LED chip comprises a substrate layer and a pixel layer, the substrate layer and the pixel layer are arranged back to back, and the drive substrate comprises a device layer; preparing a first AuSn alloy bump and a second AuSn alloy bump on the first surface of the pixel layer and the first surface of the device layer respectively, wherein the alloy mass ratio of Au to Sn is 80%: 20%; carrying out thermocompression bonding on the two electrodes through a flip-chip bonding process to form an electrode bonding region; filling gaps outside the electrode bonding areas to form sealing glue structure areas, and alternately distributing the electrode bonding areas and the sealing glue structure areas to form a bonding connection layer; and stripping the substrate layer to expose the second surface of the pixel layer, and preparing a fluorescence conversion layer on the surface by adopting a spraying process. Reliable heterogeneous integration can be achieved, the structural stability is enhanced, batch manufacturing is adapted, and the requirement for vehicle intelligent lighting is met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of display, in particular to a Micro-LED chip heterogeneous hot-press bonding method and structure. BACKGROUND

[0002] With the development of intelligent driving, vehicle-road cooperation and intelligent cockpit technology, automobile lighting is evolving from traditional lighting to intelligent, programmable and imaging. As a new generation of automotive light source, digital car light is the core platform for improving driving safety and human-computer interaction experience. In addition to basic lighting, it can also realize intelligent functions such as adaptive high and low beam, image projection, and has higher requirements for the integration, response speed, resolution and controllability of the light source. At present, the mainstream digital car light source is based on DMD (digital micro-mirror device), LCD (liquid crystal display) or LCOS (silicon-based liquid crystal) spatial light modulation technology, relying on laser or high-brightness LED as the main light source, and realizing image output through a complex optical system. However, there are problems such as large system size, complex heat dissipation, high response delay, and limited service life, which are difficult to meet the stringent requirements of vehicle-mounted systems for integration, miniaturization and reliability. Micro-LED (Micro Light Emitting Diode) as a new generation of self-luminous display technology, the size of the light emitting unit reaches micron level, has the advantages of high brightness, high efficiency, fast response, low power consumption and ultra-long service life, and has the ability of pixelization and array, which is extremely suitable for high-resolution projection and local controllable lighting of car lights, and is expected to break through the bottleneck of traditional solutions. However, its manufacturing still faces challenges such as array and heat dissipation cooperation, packaging reliability, CMOS drive integration, wide temperature stability and process consistency, and it is urgent to develop a batch manufacturing technology for vehicle environment to promote its application in the field of intelligent automobile lighting. SUMMARY

[0003] In order to solve the above technical problems, the present application provides a Micro-LED chip heterogeneous hot-press bonding method and a Micro-LED chip heterogeneous hot-press bonding structure.

[0004] In a first aspect, the present application provides a Micro-LED chip heterogeneous hot-press bonding method, which adopts the following technical scheme: S1: preparing a single Micro-LED chip and a single driving substrate, the Micro-LED chip comprising a substrate layer and a pixel layer, the substrate layer and the pixel layer being oppositely arranged, the driving substrate comprising a device layer, a first AuSn alloy bump is prepared on a first surface of the pixel layer, and a second AuSn alloy bump is prepared on a first surface of the device layer, wherein the mass ratio of the AuSn alloy is Au: Sn = 80%: 20%; the alloy bump S2: forming an electrode bonding area by thermocompression bonding the first AuSn alloy bump and the second AuSn alloy bump through a flip-chip bonding process; S3: filling a gap area outside the electrode bonding area to form an encapsulation structure area, and the electrode bonding area and the encapsulation structure area are alternately distributed to jointly constitute a bonding connection layer; S4: peeling off the substrate layer to expose a second surface of the pixel layer; S5: preparing a fluorescent conversion layer on the second surface of the pixel layer by a spraying process, and the fluorescent conversion layer comprises silica gel, fluorescent powder and a diluent. By adopting the above technical solution, the single Micro-LED chip and the single driving substrate are heterogeneously integrated with high reliability through the AuSn alloy bump with a specific proportion, the structure stability is enhanced to improve the heat dissipation efficiency by filling with epoxy resin, the substrate is peeled off to improve the light output efficiency, and the high-quality white light output is realized by spraying the fluorescent conversion layer. The overall process is suitable for batch manufacturing, and promotes the practical application of digital vehicle lamps in the direction of intelligence and imaging. Optionally, the conditions for thermocompression bonding the first AuSn alloy bump and the second AuSn alloy bump to form the electrode bonding area with the bump electrode include: a bonding temperature of 200-300°C, a bonding pressure of 5-20kgf, and a bonding time of 1-20min. By adopting the above technical solution, the specific parameter range of thermocompression bonding is limited, which ensures that the AuSn alloy bump can form a stable bond under suitable conditions, improves the bonding yield and stability, and reduces problems such as false welding caused by improper parameters. Optionally, the material of the encapsulation structure area comprises epoxy resin potting adhesive, and the epoxy resin potting adhesive comprises a first component A and a second component B, and the mass ratio of the first component A to the second component B is 2:1.

[0005] By adopting the above technical solution, the material and proportion of the encapsulation structure area are specified, and the epoxy resin potting adhesive with the proportion can effectively fill the gap and enhance the mechanical strength and insulation performance of the bonding connection layer, thereby improving the reliability of the overall structure. Optionally, the encapsulation structure area is formed after first curing, and the first curing temperature is 25-100°C and the first curing time is 1-6h. By adopting the above technical solution, the curing parameters of the encapsulation structure area are specified, so that the epoxy resin potting adhesive can be fully cured to ensure its stable performance and further enhance the structural stability of the bonding connection layer. Optionally, the substrate layer is peeled off by laser, and the laser pulse energy used is 800-1000mJ. By adopting the above technical solution, the laser is used to peel off the substrate layer, and the energy parameter of the laser is specified, which can effectively peel off the substrate layer and reduce the damage to the pixel layer, thereby improving the light output efficiency of the Micro-LED.

[0006] Optionally, the mass ratio of the silica gel, the fluorescent powder and the diluent of the fluorescent conversion layer is 1:1.25:2.

[0007] By adopting the technical scheme, the ratio of the components of the fluorescent conversion layer is determined, which can make the fluorescent powder uniformly distributed, ensure the fluorescent conversion effect, and realize high-quality white light output. Optionally, the fluorescent conversion layer is formed by second curing, the second curing temperature is 100-150 DEG C, and the second curing time is 1-30 min. By adopting the technical scheme, the curing parameters of the fluorescent conversion layer are set, which promotes the full curing of the silica gel, improves the adhesion and stability of the fluorescent conversion layer, and ensures the long-term reliability of its optical performance.

[0008] Optionally, the substrate layer comprises sapphire.

[0009] By adopting the technical scheme, sapphire is selected as the substrate layer, and its excellent optical, mechanical and thermal properties are utilized to provide a good substrate for the growth of the Micro-LED chip, thereby ensuring the quality of the chip. Optionally, the process parameters of the thermal compression bonding in step S2 are determined by a multilayer perception machine model, including the following steps: S21: obtaining process parameters and value ranges related to bonding quality, randomly combining the process parameters within the value ranges, collecting bonding quality results under different process parameter conditions through experiments, and generating a data set; the process parameters include bonding temperature, bonding pressure, bonding time and glue material height, and the bonding quality results include bonding yield, brightness and AOI; S22: constructing a multilayer perception machine model, the multilayer perception machine model including an input layer, a hidden layer and an output layer; the input layer inputs the process parameters in S21, the hidden layer is connected to the input layer or the last layer of the hidden layer through weight and bias parameters, and the output layer outputs the bonding quality results; S23: training the multilayer perception machine model by using the data set in S21, optimizing the weight and bias of the multilayer perception machine model by using the stochastic gradient descent method, the adaptive time estimation method or the impulsive algorithm until the loss function value of the multilayer perception machine model meets the preset requirement, and the loss function represents the error between the predicted value and the actual value of the process parameters; S24: inputting the initial process parameter set into the trained multilayer perception machine model to obtain a prediction result and calculate the error between the prediction result and the target value; S25: Based on the error, a new set of process parameters is selected iteratively using a Bayesian optimization algorithm: the errors corresponding to the multiple sets of process parameters are substituted into the proxy function to calculate the updated prior distribution of the sample, and a new set of process parameters is optimized from the prior distribution by the acquisition function to balance the exploration and utilization proportion, the new process parameters are input into the multi-layer perception model to predict the bonding quality result, if the design requirements are met, the parameters are output, otherwise the step of updating the prior distribution is returned; S26: Repeat S24 and S25 until the error of the predicted result and the target value meets the design requirements, and the process parameters at this time are used as the parameters of the hot-press bonding. By using the above technical scheme, the multi-layer perception model and the Bayesian optimization algorithm are used to optimize the hot-press bonding process parameters, the optimal parameter combination can be quickly found, the stability and consistency of the bonding quality are improved, and the process development cost is reduced.

[0010] In a second aspect, the application provides a Micro-LED chip heterogeneous hot-press bonding structure using the following technical scheme: A Micro-LED chip heterogeneous hot-press bonding structure, comprising: a single driving substrate, a device layer is arranged on the single driving substrate, a second AuSn alloy bump is arranged on a first surface of the device layer; a single Micro-LED chip, comprising a pixel layer, a first AuSn alloy bump is arranged on a first surface of the pixel layer; a bonding connection layer is arranged between the driving substrate and the pixel layer, the bonding connection layer comprises alternatingly distributed electrode bonding regions and encapsulation structure regions, the electrode bonding regions are formed by hot-press bonding of the first AuSn alloy bump and the second AuSn alloy bump; a fluorescent conversion layer is arranged on a second surface of the pixel layer; wherein the mass ratio of the AuSn alloy is Au: Sn = 80%: 20%.

[0011] By using the above technical scheme, the Micro-LED chip heterogeneous hot-press bonding structure of the application solves the problem of insufficient reliability of existing Micro-LED in batch manufacturing in vehicle environment, the electrode bonding region formed by the AuSn alloy bump with a specific ratio can realize reliable electrical connection, improve the integration degree and heat dissipation efficiency of the heterojunction structure, the encapsulation structure region enhances the mechanical stability, the fluorescent conversion layer guarantees the white light output quality, the overall structure has high integration degree, reliability and excellent optical performance, and is suitable for high-end scenes such as vehicles, and helps the intelligent and image development of digital vehicle lights.

[0012] In summary, the application has at least one of the following beneficial technical effects: 1. The high-reliability heterogeneous integration of a single Micro-LED and a single driving substrate is achieved by a specific ratio of AuSn alloy bumps, the structure stability is enhanced by epoxy resin filling to improve heat dissipation efficiency, the substrate is removed by peeling to improve light output efficiency, and high-quality white light output is achieved by spraying a fluorescent conversion layer. The overall process is suitable for batch manufacturing, and promotes the practical application of digital car lights in the direction of intelligence and imaging. 2. The specific parameter range of thermal compression bonding is defined to ensure that the AuSn alloy bumps can form stable bonding under suitable conditions, improve bonding yield and stability, and reduce problems such as false welding caused by improper parameters. 3. The material, ratio and curing parameters of the encapsulation structure area are specified, which can effectively fill the gap, enhance the mechanical strength and insulation performance of the bonding connection layer, and improve the reliability of the overall structure. BRIEF DESCRIPTION OF DRAWINGS Figure 1 is a cross-sectional structure schematic diagram of a Micro-LED chip heterogeneous thermal compression bonding structure provided by the embodiments of the present application; Figure 2 is a step flowchart of a Micro-LED chip heterogeneous thermal compression bonding method provided by the embodiments of the present application; Figure 3 is Figure 2 is a cross-sectional structure schematic diagram corresponding to step S1 of the method in Figure 4 is Figure 2 is a cross-sectional structure schematic diagram corresponding to the newly added step S1a between step S1 and step S2 of the method in Figure 5 is Figure 2 is a cross-sectional structure schematic diagram corresponding to step S2 of the method in Figure 6 is Figure 2 is a cross-sectional structure schematic diagram corresponding to step S3 of the method in Figure 7 is Figure 2 is a cross-sectional structure schematic diagram corresponding to step S4 of the method in

[0013] Explanation of reference signs: 1. Micro-LED chip; 10, substrate layer; 11, pixel layer; 12, fluorescent conversion layer; 2. Driving substrate; 20, device layer; 3. Bonding connection layer; 31, electrode bonding area; 311, first AuSn alloy bump; 312, second AuSn alloy bump; 32, encapsulation structure area; DETAILED DESCRIPTION The following will be described in detail in combination with the accompanying Figures 1-6 The present application is further described in detail.

[0014] The embodiment of the application discloses a Micro-LED chip heterogeneous thermal compression bonding structure. Referring to Figure 1 and Figure 3 , the Micro-LED chip heterogeneous thermal compression bonding structure sequentially comprises a single driving substrate 2, a bonding connection layer 3 and a single Micro-LED chip 1 from bottom to top, wherein a large number of driving circuits such as driving transistors, driving chips and the like are arranged on the single driving substrate 2, the driving transistors comprise at least one of field effect transistors such as amorphous silicon thin film transistors, polycrystalline silicon thin film transistors, indium gallium zinc oxide thin film transistors or CMOS transistors, and in a preferred embodiment, the CMOS transistors are taken as an example for description, a layer where the CMOS transistors are located constitutes a device layer 20, the device layer 20 comprises a CMOS transistor array, and the CMOS transistors are used to provide driving signals for the Micro-LED chip 1, as shown in Figure 3 , a plurality of second AuSn alloy bumps 312 are arranged on a first surface (a direction facing the Micro-LED chip 1) of the device layer 20, the plurality of second AuSn alloy bumps 312 are arranged in correspondence with the CMOS transistor array, each second AuSn alloy bump 312 is connected with an output end of a corresponding CMOS transistor; the Micro-LED chip 1 comprises a pixel layer 11 and a fluorescent conversion layer 12, the pixel layer 11 is used to realize generation of a light signal, and an array of Micro-LED light emitting units (i.e. a pixel array) is integrated in the pixel layer 11, each light emitting unit can be independently controlled to emit light, a first AuSn alloy bump 311 is arranged on a first surface (a direction facing the driving substrate 2) of the pixel layer 11, the first AuSn alloy bump 311 is also arranged in an array and corresponds to each Micro-LED light emitting unit in the pixel array one by one, and is used to receive a driving signal; after the first AuSn alloy bump 311 and the second AuSn alloy bump 312 are connected through thermal compression bonding, an electrode bonding area 31 is formed, a second surface (arranged opposite to the first surface) of the pixel layer 11 is provided with the fluorescent conversion layer 12, which is used to realize white light output, and the driving substrate 2 can transmit an electric signal to a corresponding Micro-LED light emitting unit in the pixel layer 11 through the electrode bonding area 31, so as to accurately control the light emitting brightness, on-off state and the like of each pixel, thereby realizing driving of the entire pixel array and completing display and dynamic regulation of an image.

[0015] It should be noted that the alloy bump in the application is a functional structure with both electric conduction and welding functions, which is made into a protruding form through evaporation, electroplating or printing process, and can be used as a welding material to realize heterogeneous connection.

[0016] In an embodiment, the mass ratio of AuSn alloy in the first AuSn alloy bump 311 and the second AuSn alloy bump 312 is Au:Sn = 80%:20%.

[0017] It is understandable that since the Micro-LED chip 1 is mostly based on compound semiconductor materials of sapphire substrate, the thermal expansion coefficient is about 7.5×10 -6 / ℃, and the driving substrate 2 is mainly based on silicon material, with a corresponding thermal expansion coefficient of about 2.6×10 -6 / ℃, the two belong to different material systems, forming a typical heterogeneous integration, with significant thermal expansion differences, which can easily generate interface stress during temperature cycling, leading to problems such as cracking of the bonding interface and electrical connection failure. In this application, the thermal expansion coefficient of the AuSn alloy with a mass ratio of 80%:20% is about 16×10 -6 / ℃, the same as the two -6 / °C, this order of magnitude matching significantly reduces the severe stress shock that may be caused by the cross-order-of-magnitude difference in thermal expansion coefficient. More importantly, the AuSn alloy of the present application has excellent plasticity. When temperature changes cause the substrate to deform, it can adapt to the interface stress changes through its own plastic deformation, effectively absorbing and buffering the deformation difference between sapphire and silicon. At the same time, its high thermal conductivity (about 57W / (m・K)) can accelerate the transfer of heat at the heterogeneous interface, reduce the stress concentration caused by local temperature differences, further reduce the risk of cracking at the bonding interface, and improve the stability of the integration.

[0018] In one embodiment, to further enhance heterogeneous bonding stability, a sealing structure region 32 is provided in the bonding connection layer 3 between the Micro-LED chip 1 and the driver substrate 2. The sealing structure region 32 is filled between the plurality of electrode bonding regions 31 and is alternately distributed with the electrode bonding regions 31. The filling setting of the sealing structure region 32 can cooperate with a specific proportion of AuSn alloy bumps to jointly ensure the high reliability of heterogeneous integration.

[0019] By adopting the above-mentioned technical solution, the heterogeneous hot-pressing bonding structure of the Micro-LED chip of the present application can solve the problem of insufficient reliability of heterogeneous integration in the existing Micro-LED mass production in the automotive environment. The electrode bonding area 31 formed by the AuSn alloy bumps with a specific ratio can achieve reliable electrical connection, improve the structural integration and heat dissipation efficiency, the sealing structure area 32 enhances the mechanical stability, and the fluorescent conversion layer 12 ensures the quality of white light output. The overall structure has high integration, reliability and excellent optical performance, which is suitable for high-end scenarios such as automotive use, and helps the intelligent and image-based development of digital car lights.

[0020] Reference Figure 2 Based on the above-mentioned Micro-LED chip heterogeneous thermal compression bonding structure, another embodiment of the present application further discloses a Micro-LED chip heterogeneous thermal compression bonding method, comprising the following steps: S1: If Figure 3As shown, a single Micro-LED chip 1 and a single driving substrate 2 are prepared, the Micro-LED chip 1 comprises a substrate layer 10 and a pixel layer 11, the substrate layer 10 and the pixel layer 11 are oppositely arranged, the driving substrate 2 comprises a device layer 20, a first AuSn alloy bump 311 is prepared on a first surface of the pixel layer 11 and a second AuSn alloy bump 312 is prepared on a first surface of the device layer 20, wherein the mass ratio of the AuSn alloy is Au:Sn = 80%:20%, after the alloy electrode is prepared, the surfaces of the two are cleaned respectively using acetone and ethanol to remove organic contaminants and particulate matter, and then dried by nitrogen gun to keep the surface clean and dry. It can be understood that the thermal expansion coefficient of the AuSn alloy with a mass ratio of 80%:20% adopted in the embodiment of the present application is about 16x10 -6 / ℃, which is of the same order of magnitude as the sapphire substrate and the silicon driving substrate, and the matching of this order of magnitude greatly reduces the severe stress impact that may be caused by the cross-order difference of the thermal expansion coefficient. More importantly, the AuSn alloy of the present application has excellent plasticity, and when the substrate is deformed due to temperature change, it can conform to the interface stress change by its own plastic deformation, effectively absorbing and buffering the deformation difference between sapphire and silicon; at the same time, its high thermal conductivity (about 57 W / (m・K)) can accelerate the heat transfer at the heterojunction interface, reduce the stress concentration caused by local temperature difference, further reduce the risk of bonding interface cracking, and improve the stability of integration.

[0021] In an embodiment, after S1 and before S2, further comprising a step S1a: as Figure 4 shown, a metal transition layer 4 is formed in advance in the electrode preparation area of the Micro-LED chip 1 and the driving substrate 2. Specifically, first, a Ti metal layer 41 is prepared on the first surface of the electrode area of the pixel layer 11 and the first surface of the electrode area of the device layer 20 respectively, the Ti metal layer serves as an adhesion layer, which can enhance the bonding force of the subsequent metal and the substrate, preventing the subsequent metal layer from falling off; then, a Ni metal layer 42 is prepared on the surface of the two Ti metal layers 41 respectively, the Ni metal layer serves as a transition layer, which can prevent Ti from diffusing with Au in the subsequent AuSn alloy, and also form a good transition interface with Au; after the Ti and Ni metal layers are prepared, the operations of preparing the first AuSn alloy bump 311 on the first surface of the pixel layer 11 and the second AuSn alloy bump 312 on the first surface of the device layer 20 in S1 are performed, that is, the first AuSn alloy bump 311 is prepared on the surface of the Ni metal layer 42 on the pixel layer 11 side, and the second AuSn alloy bump 312 is prepared on the surface of the Ni metal layer 42 on the device layer 20 side.

[0022] It should be noted that in the technical solution of the present application, step S1a is not a necessary step. When the application scenario has low requirements for the long-term stability of the bonding structure and intermetallic diffusion control, or the base material of the Micro-LED chip and the driving substrate itself has good bonding force with the AuSn alloy, step S1a can be omitted, and the AuSn alloy bumps are directly prepared on the surfaces of the pixel layer 11 and the device layer 20 to simplify the process flow, reduce the production cost, and adapt to batch manufacturing scenarios with high requirements for production efficiency; when the application scenario has strict requirements for bonding reliability and environmental aging resistance, the step S1a is introduced to form the Ti / Ni metal transition layer, which can further improve the performance stability of the bonding structure and meet the high reliability requirements.

[0023] S2: The first AuSn alloy bump 311 and the second AuSn alloy bump 312 are thermocompression bonded by flip-chip bonding process to form an electrode bonding area 31 with a bump electrode, specifically, as shown in Figure 3 and Figure 5 The first AuSn alloy bump 311 and the second AuSn alloy bump 312 are thermocompression bonded by flip-chip bonding equipment to form the electrode bonding area 31, and in a preferred embodiment, the bonding temperature is 200-300°C, the bonding pressure is 5-20kgf, and the bonding time is 1-20min. By limiting the specific parameter range of thermocompression bonding, it can be ensured that the AuSn alloy bump can form a stable bond under suitable conditions, improve the bonding yield and stability, and reduce the problem of false welding caused by improper parameters. S3: Fill the gap area outside the electrode bonding area 31 to form an encapsulation structure area 32, and the electrode bonding area 31 and the encapsulation structure area 32 are alternately distributed to jointly constitute the bonding connection layer 3, specifically, as shown in Figure 6As shown, after the bonding is completed, the gap area in the bonding interface is filled with an epoxy resin to form a sealing structure area 32. The filling material is a two-component transparent epoxy resin sealant, mainly including component A and component B. Component A is an epoxy resin, and component B is a curing agent. The mass ratio of the two is 2:1. Component A is the main component of the sealant and determines the basic properties of the sealant, such as bonding performance, mechanical strength, electrical insulation performance, etc. Common types of epoxy resins include bisphenol A type and phenolic type. In the sealant, the epoxy resin in component A is in a liquid state before being mixed with component B and has a certain viscosity, which can preliminarily adhere to the electronic components and other objects to be sealed. After being mixed with the curing agent in component B and undergoing a curing reaction, the molecular chains of the epoxy resin are crosslinked with each other through the action of the curing agent to form a three-dimensional network structure, thereby curing the sealant and providing mechanical protection and electrical insulation for the electronic components to be sealed. Component B is a curing agent that chemically reacts with the epoxy resin to promote the crosslinking and curing of the epoxy resin to form a stable three-dimensional network structure. Common curing agents include amines and acid anhydrides. Different types of curing agents affect the curing speed of the sealant and the properties of the sealant after curing, such as hardness and heat resistance. In an embodiment, component B is mixed with component A in a mass ratio of 2:1, and then undergoes a first curing process. The first curing temperature is 25-100°C, and the first curing time is 1-6 hours, which can convert the sealant from a liquid state to a solid state, thereby packaging and protecting the first AuSn alloy bump 311 and the second AuSn alloy bump 312, effectively filling the gap, and enhancing the mechanical strength and insulation performance of the bonding layer 3.

[0024] S4: Peel off the substrate layer 10 to expose the second surface of the pixel layer 11; as Figure 7 As shown, in an embodiment, the substrate layer 10 is made of sapphire material. Sapphire has excellent optical, mechanical and thermal properties and can provide a good substrate for the growth of the Micro-LED chip 1 to ensure quality. After the filling process, the substrate layer 10 can be peeled off by laser peeling, mechanical peeling, chemical etching, wet etching, etc. Preferably, the sapphire substrate on the top of the Micro-LED chip 1 (the second surface of the pixel layer 11) is removed by laser peeling. The laser energy used is 800-1000 mJ, preferably 900 mJ.

[0025] Understandably, sapphire's high hardness and stable chemical properties create weak van der Waals forces or heterojunction bonding at the interface with the Micro-LED pixel layer (typically a GaN-based material). Laser light of a specific wavelength penetrates the sapphire and is absorbed by the GaN layer at the interface, causing the local temperature to instantly rise to thousands of degrees Celsius, generating a gas explosion-like shockwave that severs the interfacial bonding. An energy range of 800-1000mJ ensures sufficient laser heat accumulation at the interface, effectively separating the sapphire from the pixel layer. Energy levels below 800mJ can lead to incomplete separation, leaving residual sapphire fragments that could affect subsequent light performance. Energy levels above 1000mJ can easily cause excessive vaporization at the interface, leading to pixel edge cracking or lattice damage. 900mJ is the preferred value, achieving the optimal balance between energy threshold and safety.

[0026] S5: A fluorescent conversion layer 12 is prepared on the second surface of the pixel layer by spraying. The fluorescent conversion layer 12 includes silica gel, fluorescent powder and diluent. Specifically, the fluorescent powder is sprayed on the stripped Micro-LED light-emitting surface (the second surface of the pixel layer 11) to form the fluorescent conversion layer 12. Finally, the following is formed: Figure 1 In the heterogeneous hot-compression bonding structure of the Micro-LED chip shown, the phosphor conversion layer 12 comprises phosphor, two-component silicone, and a diluent. The materials are thoroughly mixed in a mass ratio of silicone A:B = 10:1 and silicone:phosphor:diluent = 1:1.25:2. After mixing, the mixture is evenly sprayed onto the light-emitting surface and then subjected to a second curing process. In a preferred embodiment, the second curing temperature is 100-150°C and the second curing time is 1-30 minutes, thereby forming a uniform phosphor conversion layer. By setting the mixing and curing parameters of the phosphor conversion layer 12, the silicone can be fully cured, improving the adhesion and stability of the phosphor conversion layer and ensuring its long-term optical performance and reliability.

[0027] By adopting the above technical solution, highly reliable heterogeneous integration of a single Micro-LED and a single driver substrate is achieved through AuSn alloy bumps with a specific ratio. Epoxy resin filling is combined to enhance structural stability to improve heat dissipation efficiency. The substrate is stripped and removed to improve light output efficiency. The fluorescent conversion layer is sprayed to achieve high-quality white light output. The overall process is suitable for mass production, promoting the practical application of digital car lights in the direction of intelligence and imaging. In one embodiment, the process parameters of the thermocompression bonding in step S2 can be determined by optimizing the multi-layer perceptron model. The specific optimization steps are as follows: S21: Obtain process parameters related to bonding quality and value ranges, randomly combine process parameters within the value ranges, collect bonding quality results under different process parameter conditions through experiments, and generate a data set; the process parameters include bonding temperature, bonding pressure, bonding time, and adhesive height, and the bonding quality results include bonding yield, brightness, and AOI; S22: Construct a multi-layer perception model, which includes an input layer, a hidden layer, and an output layer; the input layer inputs the process parameters in S21, the hidden layer is connected to the input layer or the previous layer of the hidden layer through weight and bias parameters, and the output layer outputs the bonding quality results; S23: Train the multi-layer perception model using the data set in S21, and optimize the weights and biases of the multi-layer perception model through a stochastic gradient descent method, an adaptive time estimation method, or an impulsive algorithm until the loss function value of the multi-layer perception model meets a preset requirement, and the loss function represents the error between the predicted value and the actual value of the process parameters; S24: Input the initial process parameter set into the trained multi-layer perception model, obtain the predicted results, and calculate the error between the predicted results and the target value; S25: Based on the error, a new process parameter set is iteratively selected using a Bayesian optimization algorithm: the errors corresponding to multiple sets of process parameters are substituted into a proxy function to calculate the updated prior distribution of the samples, and a new process parameter set is optimized from the prior distribution through a sampling function to balance the exploration and utilization ratio, the new process parameter is input into the multi-layer perception model to predict the bonding quality results, if the design requirements are met, the parameter is output, otherwise the step of updating the prior distribution is returned; S26: Repeat S24 and S25 until the error between the predicted results and the target value meets the design requirements, and the process parameter at this time is used as the parameter of hot-press bonding. By using the above technical solutions, the multi-layer perception model and the Bayesian optimization algorithm are used to optimize the hot-press bonding process parameters, the optimal parameter combination can be quickly found, the stability and consistency of the bonding quality are improved, and the process development cost is reduced.

[0028] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, therefore: any equivalent changes made according to the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for heterogeneous thermal compression bonding of Micro-LED chips, characterized in that: The following steps are involved: S1: preparing a single Micro-LED chip (1) and a single driving substrate (2), wherein the Micro-LED chip (1) comprises a substrate layer (10) and a pixel layer (11), wherein the substrate layer (10) and the pixel layer (11) are arranged in a back-to-back manner, and the driving substrate (2) comprises a device layer (20), and respectively preparing a first AuSn alloy bump (311) on a first surface of the pixel layer (11) and a second AuSn alloy bump (312) on a first surface of the device layer (20), wherein the mass ratio of the AuSn alloy is Au:Sn=80%:20%; S2: bonding the first AuSn alloy bump (311) and the second AuSn alloy bump (312) through a heterogeneous hot-press bonding process to form an electrode bonding region (31); S3: filling the gap area outside the electrode bonding area (31) to form a sealing structure area (32), wherein the electrode bonding area (31) and the sealing structure area (32) are alternately distributed to form a bonding connection layer (3); S4: peeling off the substrate layer (10) to expose the second surface of the pixel layer (11); S5: preparing a fluorescent conversion layer (12) on the second surface of the pixel layer (11) by a spraying process, wherein the fluorescent conversion layer (12) comprises silica gel, fluorescent powder and a diluent.

2. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, characterized in that: The first AuSn alloy bump (311) and the second AuSn alloy bump (312) are hot-pressed and bonded to form an electrode bonding area (31). The conditions include: a bonding temperature of 200-300° C., a bonding pressure of 5-20 kgf, and a bonding time of 1-20 min.

3. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, wherein: The material of the sealing structure area (32) includes epoxy resin potting glue, and the epoxy resin potting glue includes a first component A and a second component B, and the mass ratio of the first component A to the second component B is 2:

1.

4. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 3, wherein: The sealing structure area (32) is formed by a first curing process, wherein the first curing temperature is 25-100° C. and the first curing time is 1-6 hours.

5. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, wherein: The substrate layer (10) is peeled off by laser, and the laser pulse energy used is 800-1000 mJ.

6. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, wherein: The mass ratio of the silica gel, the phosphor and the diluent in the fluorescent conversion layer (12) is 1:1.25:

2.

7. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 6, wherein: The fluorescent conversion layer (12) is formed by a second curing process, wherein the second curing temperature is 100-150° C. and the second curing time is 1-30 minutes.

8. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, wherein: The substrate layer (10) comprises sapphire.

9. The method for heterogeneous thermal compression bonding of Micro-LED chips according to claim 1, wherein: The process parameters of the hot pressing bonding in step S2 are determined by optimizing a multi-layer perceptron model, including the following steps: S21: Obtaining process parameters and value ranges related to bonding quality, randomly combining process parameters within the value range, and experimentally collecting bonding quality results under different process parameter conditions to generate a data set; the process parameters include bonding temperature, bonding pressure, bonding time, and adhesive material height; and the bonding quality results include bonding yield, brightness, and AOI; S22: constructing a multilayer perceptron model, the multilayer perceptron model including an input layer, a hidden layer, and an output layer; the input layer inputs the process parameters in S21, the hidden layer is connected to the input layer or the upper layer node of the hidden layer through weight and bias parameters, and the output layer outputs the bonding quality result; S23: using the data set in S21 to train the multilayer perceptron model, optimizing the weights and biases of the multilayer perceptron model by a stochastic gradient descent method, an adaptive time estimation method, or an impulse algorithm, until a loss function value of the multilayer perceptron model meets a preset requirement, wherein the loss function represents an error between a predicted value and an actual value of a process parameter; S24: Inputting the initial process parameter set into the trained multi-layer perceptron model to obtain a prediction result and calculating the error between the prediction result and the target value; S25: Based on the error, a new set of process parameters is iteratively selected using a Bayesian optimization algorithm: the errors corresponding to the multiple sets of process parameters are substituted into a proxy function to calculate a prior distribution after sample update, a new set of process parameters is optimized from the prior distribution through an acquisition function to balance the proportion of exploration and utilization, the new process parameters are input into the multi-layer perceptron model to predict the bonding quality result, and if the parameters meet the design requirements, the parameters are output; otherwise, the process returns to the step of updating the prior distribution; S26: Repeat S24 and S25 until the error between the predicted result and the target value meets the design requirement, and use the process parameters at this time as the parameters of the thermal compression bonding.

10. A Micro-LED chip heterogeneous thermal compression bonding structure, characterized in that: include: A single drive substrate (2), wherein a device layer (20) is provided on the drive substrate (2), and a second AuSn alloy bump (312) is provided on a first surface of the device layer (20); A single Micro-LED chip (1), the Micro-LED chip (1) comprising a pixel layer (11), a first AuSn alloy bump (311) being provided on a first surface of the pixel layer (11); a bonding connection layer (3) disposed between the driving substrate (2) and the pixel layer (11), the bonding connection layer (3) comprising alternately distributed electrode bonding areas (31) and sealing structure areas (32), the electrode bonding areas (31) being formed by hot-press bonding of the first AuSn alloy bump (311) and the second AuSn alloy bump (312); A fluorescent conversion layer (12) is provided on the second surface of the pixel layer (11); The mass ratio of the AuSn alloy is Au:Sn=80%:20%.

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