Dynamic hot-pressing leveling control method and yield improving system for high-density LED (light-emitting diode) packaging

Abstract

The invention discloses a dynamic hot-pressing leveling control method and a yield improving system based on high-density LED packaging, and relates to the technical field of LED packaging. A viscoplastic flow area is formed through counterpoint preheating and selective thermal activation, contact pressure is built between the flexible leveling device and the surface of the LED chip array, solder paste is heated to be in a viscoplastic flow state, the flexible leveling device conducts posture correction on the chip, the solder paste is suddenly dropped to be below the freezing point of the solder paste through the semiconductor thermoelectric cooling module array, and then the solder paste is heated to be in the viscoplastic flow state. And fixation of the chip position and rapid solidification forming of a welding spot are realized. The method is characterized in that solder paste is heated to a viscoplastic flow state through a targeted thermal activation technology, the inherent contradiction between the thermal damage risk and a narrow process window caused by the fact that a component must be exposed to a high-temperature environment in order to obtain enough surface tension is solved, and the yield, the performance consistency and the long-term reliability of a product are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of LED packaging technology, and in particular to a dynamic hot-pressing leveling control method and yield improvement system for high-density LED packaging. Background Technology

[0002] In the field of advanced semiconductor packaging and high-density integrated manufacturing, especially with the rapid development of technologies such as Micro-LED (micron-scale light-emitting diode) displays, high-bandwidth optical communication modules, and heterogeneous integrated chips, the efficient and precise transfer and bonding of tens of thousands or even millions of micron-scale functional components (typically smaller than 100 micrometers) onto a target substrate has become a core technological bottleneck restricting industrialization. Currently, the mainstream bonding method relies primarily on global heating reflow soldering. This process involves placing the entire substrate carrying components and solder paste in a reflow oven for overall heating, isothermal treatment, reflow, and cooling, utilizing the surface tension effect of the molten solder to achieve self-alignment and electrical connection of the components. However, this global heating method has inherent drawbacks: First, the thermal budget is extremely high, requiring the entire substrate and all components to withstand temperatures exceeding 230°C. For highly temperature-sensitive optoelectronic devices such as Micro-LEDs, this can easily lead to luminous efficiency degradation, wavelength drift, or even permanent failure. Second, the process cycle is long and energy consumption is enormous, limiting production efficiency. Third, the warping deformation caused by the mismatch in thermal expansion coefficients between the substrate and components at high temperatures severely affects the final alignment accuracy and bonding reliability. Therefore, developing a low-thermal-damage, high-precision, and high-efficiency microdevice precision alignment and curing technology is a key challenge that urgently needs to be addressed in this field.

[0003] In summary, the following technical problems still urgently need to be solved: First, there is a contradiction between the continuous risk of thermal damage and the narrow process window. To obtain an effective self-alignment driving force, the local temperature must be raised to the melting point that could damage the components, making it difficult to balance both. Second, there is a technical deficiency of a single and uncontrollable alignment driving force. Relying solely on passive surface tension has limited correction capabilities and cannot actively, accurately, and reliably guide and correct the chip's position and orientation. Finally, there is a fundamental problem of positional misalignment during the curing process. There is a lack of a mechanism to "lock" the chip in its ideal position the instantaneously. The slow, passive natural cooling process leaves hidden dangers of positional rebound and accuracy loss. Therefore, the field urgently needs a new technological paradigm that can completely eliminate the dependence on high-temperature melting and passive surface tension, achieving high-precision three-dimensional orientation correction and springback-free instantaneous in-situ curing of micron-level components through a low-temperature, active, and controllable method. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a dynamic hot-pressing leveling control method and yield improvement system for high-density LED packaging to solve the contradiction between the continuous risk of thermal damage and the narrow process window. That is, in order to obtain an effective self-alignment driving force, the local temperature has to be raised to the melting temperature that may damage the components, and it is difficult to balance the two.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a dynamic thermo-pressing leveling control method for high-density LED packaging, comprising the following steps:

[0008] Step 1: Alignment Preheating and Selective Thermal Activation. First, the substrate after die bonding is preheated at a low-temperature background to a first preset temperature below the critical point for plastic deformation of the solder paste. Then, a focused laser beam is controlled by a high-precision scanning galvanometer system to inject high-throughput energy into the solder paste area under each or each group of LED chips with positional deviations on the substrate. This allows the solder paste in this local area to be precisely heated to a second preset temperature that allows it to undergo viscoplastic flow in a very short time. The temperature increase of the chip itself and the surrounding substrate area is strictly controlled, thereby forming an isolated viscoplastic flow area working window that exists only in the area to be corrected.

[0009] Step 2: Acoustic fluidization coupling pressure leveling. After selective thermal activation, a flexible leveling device integrating a piezoelectric ceramic transducer array establishes a uniform initial contact pressure with the LED chip array surface during its descent. Subsequently, the piezoelectric transducer array within the flexible leveling device is excited, generating high-frequency acoustic waves. The high-frequency acoustic wave energy penetrates the chip and focuses on the liquid solder paste area that has been activated by the laser. Through the acoustic fluidization effect and the acoustic thinning effect, the local viscosity of the solder paste is greatly reduced. At this time, under the action of a precisely calibrated static normal pressure applied by the leveling head, the chip undergoes attitude correction on the almost frictionless liquid solder paste until it reaches the uniform physical plane defined by the leveling head.

[0010] Step 3: Integrated thermoelectric cooling and pressure curing. After the chip completes position and orientation correction, the high-frequency acoustic wave excitation is immediately stopped, but the normal pressure of the leveling head is kept unchanged or slightly increased. At the same time, the micro-semiconductor thermoelectric cooling module array integrated inside the flexible leveling device is activated. Through the Peltier effect, heat is actively and quickly pumped out from the contact surface of the flexible leveling device, so that the heat of the solder paste below is quickly extracted. The temperature drops sharply below its solidification point at an extremely high cooling rate, thereby fixing the chip position and rapidly solidifying the solder joints, preventing any position rebound caused by stress relaxation or thermal disturbance.

[0011] As a preferred embodiment of the dynamic hot-pressing leveling control method for high-density LED packaging described in this invention, the alignment preheating and selective thermal activation steps include:

[0012] First, a global heating device is used to preheat the substrate as a whole, so that it uniformly reaches a first stable background temperature that is lower than the solidus temperature of the solder paste, but sufficient to significantly reduce the thermal shock required for subsequent local heating and to moderately pre-activate the flux. Then, a high energy density beam directional projection system executes a preset, dynamic energy projection scanning path on the solder paste area under each LED chip with positional deviation, based on the pre-acquired positional deviation data of each or each group of LED chips. By accurately integrating and controlling the projected energy in the time and space dimensions, heat is injected into the solder paste area under the LED chip in a targeted manner, so that it is rapidly heated to the second preset temperature within a millisecond time scale to form the viscoplastic flow region. At the same time, it is ensured that the temperature increase of the chip body and the surrounding non-target area is strictly controlled within a safe threshold that will not cause material damage or deterioration of solder joint performance.

[0013] As a preferred embodiment of the dynamic hot-pressing leveling control method for high-density LED packaging described in this invention, the acoustic fluidization coupling pressure leveling step specifically comprises:

[0014] A leveling actuator integrating an acoustic energy generation unit and a conformal contact interface first establishes physical contact with the top surface of the LED chip array. An initial contact pressure sufficient to ensure effective acoustic coupling without causing chip displacement is applied through the conformal contact interface. Then, under the initial contact pressure, the acoustic energy generation unit is activated to emit high-frequency acoustic energy into the solder paste area, which is already in a viscoplastic flow state, to reduce its viscosity and make it present a fluid-like state. Synchronously or immediately following this acoustic excitation, a pressure control system smoothly and controllably increases the pressure applied to the chip array to a final leveling pressure. Thus, under the synergistic effect of acoustic fluidization and increased mechanical pressure, all LED chips are driven to adjust their posture in a low-resistance state until their top surfaces collectively abut against the unified physical reference plane defined by the leveling actuator.

[0015] As a preferred embodiment of the dynamic thermo-pressing leveling control method for high-density LED packaging described in this invention, the integrated thermoelectric cooling and pressure curing step specifically comprises:

[0016] After the acoustic fluidization coupling pressure leveling step is completed and all LED chips are mechanically held in place on the unified physical reference plane, the emission of high-frequency acoustic energy is immediately terminated. Simultaneously, a semiconductor thermoelectric cooling unit array integrated inside the leveling execution end and forming a high-efficiency heat conduction path with its conformal contact interface is activated. Driven by a high transient response power supply, the thermoelectric cooling unit array actively pumps heat through the LED chip body, forcibly and unidirectionally extracting heat from the solder paste area that is already in a viscoplastic flow state. Under a preset pressure control program synchronized with the heat extraction process, the final leveling pressure applied to the chip array is further slightly increased and maintained to actively counteract the stress generated by the volume shrinkage of the solder paste during the phase change curing process. This achieves in-situ rapid quenching at an ultra-high cooling rate of over 100 degrees Celsius per second while maintaining precise physical positioning. All LED chips are solidified in their corrected positions and orientations, ultimately forming micron-level precision solidified solder joints with no positional rebound, no orientation deflection, and dense internal structure.

[0017] As a preferred embodiment of the dynamic hot-pressing leveling control method for high-density LED packaging described in this invention, the leveling step further includes:

[0018] An external energy field is applied to the solder to significantly reduce its viscosity, causing it to enter a highly fluid fluidized state, thereby achieving coplanarization under the static pressure;

[0019] And after the solder achieves coplanarity, the leveling device is actively cooled to a cooling rate sufficient to suppress the solder from shrinking due to surface tension, thereby rapidly solidifying the solder and fixing the coplanar shape.

[0020] As a preferred embodiment of the dynamic hot-pressing leveling control method for high-density LED packaging described in this invention, the application of an external energy field includes:

[0021] The leveling device is excited to generate a preset acoustic vibration, which is coupled with the static pressure applied by the leveling device and acts synergistically on the solder particles. By generating high-frequency normal and tangential alternating stress between the particles, the static friction and cohesion between them are effectively destroyed, thereby stimulating and maintaining the highly fluid fluidized state.

[0022] As a preferred embodiment of the dynamic hot-pressing leveling control method for high-density LED packaging described in this invention, the method of utilizing acoustic vibration further includes:

[0023] During the application of the acoustic vibration, a physical feedback parameter characterizing the fluidization degree of the solder is monitored in real time, and a closed-loop control loop is established based on the parameter to dynamically and adaptively adjust at least one operating parameter of the acoustic vibration, thereby precisely maintaining the highly fluid fluidization state within a preset target range.

[0024] Furthermore, this invention also provides a yield improvement system for high-density LED packaging, wherein the system integrates the following mutually cooperating units within a unified process chamber:

[0025] Thermal field generation unit: configured to project high-resolution, dynamically adjustable energy into a local area below one or more target components on the substrate during reflow soldering, thereby artificially and controllably establishing a non-uniform temperature distribution field in the molten solder.

[0026] Potential field constraint unit: configured to synchronously generate a spatial potential well field in the process atmosphere medium surrounding the target element within the process cavity, the potential well field being able to apply a passive restoring force to the element that is related to its spatial pose deviation and directed towards the center of the potential well;

[0027] The collaborative control unit is electrically connected to the programmable thermal field generation unit and the non-contact potential field constraint unit, respectively. Its core function is to integrate and control the gradient, direction and intensity of the non-uniform temperature distribution field, as well as the position, shape and depth of the spatial potential well field, in real time according to the preset component target pose data. In this way, it can comprehensively utilize the surface tension driving force generated by the temperature field gradient on the liquid solder and the non-contact restoring force generated by the potential well field to actively and accurately guide the component to the predetermined target position and achieve stable posture maintenance in the liquid phase stage of reflow soldering until the solder solidifies.

[0028] As a preferred embodiment of the yield improvement system for high-density LED packaging described in this invention, the step of generating a controllable surface tension gradient driving force by applying a dynamic asymmetric thermal field is specifically implemented as follows:

[0029] By using programmable optical modulation devices, the intensity of an energy beam is spatially modulated to generate a structured energy pattern that can be changed in real time, corresponding to the desired surface tension gradient distribution.

[0030] The structured energy pattern is then precisely projected onto the surface of the molten solder. By dynamically changing the asymmetry and intensity distribution of the pattern, the magnitude and direction of the driving force acting on the component are controlled in real time to achieve precise guidance and final stabilization of its position.

[0031] As a preferred embodiment of the yield improvement system for high-density LED packaging described in this invention, the step of simultaneously applying a non-contact potential field to provide passive restoring force is specifically implemented as follows:

[0032] By arranging a controllable non-contact field source array above or around the component, and by having a cooperative control unit selectively drive one or more field sources in the field source array according to the target alignment position of the component, a localized potential field with the lowest potential energy point centered on the target alignment position is generated in the molten solder area where the component is located.

[0033] The potential field applies a restoring force pointing back to the center to components that are off-center, and a restoring torque to components that have undergone attitude deflection, thereby forming a three-dimensional potential field constraint to actively suppress the position drift and attitude rotation of the components on the liquidus line, and works in conjunction with the surface tension gradient driving force to ensure the dynamic stability of the components during the alignment process and prevent overshoot.

[0034] The beneficial effects of this invention are as follows: This invention uses targeted thermal activation technology to heat the solder paste to a viscoplastic flow state far below its melting point, rather than a completely molten liquid state. This solves the inherent contradiction between the risk of thermal damage and the narrow process window caused by the requirement to expose components to high-temperature environments (such as above 230°C) in order to obtain sufficient surface tension in the prior art.

[0035] Secondly, this invention constructs an active, highly controllable three-dimensional correction system based on "sound pressure coordination." The active intervention of high-frequency acoustic energy transforms viscous solder paste into near-frictionless solder paste through the "acoustic fluidization" effect, creating unprecedented ideal conditions for the free movement of chips, thereby greatly improving the yield, performance consistency, and long-term reliability of the final product. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of a dynamic hot-pressing leveling control method for high-density LED packaging.

[0038] Figure 2 This is a flowchart of the para-preheating and selective thermal activation process.

[0039] Figure 3 This is a flowchart of acoustic fluidization coupling pressure leveling.

[0040] Figure 4 This is a flowchart of an integrated thermoelectric cooling and pressure curing process.

[0041] Figure 5 This is a flowchart of a system for improving yield in high-density LED packaging. Detailed Implementation

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0043] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0044] Secondly, the term "one embodiment" or "example" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The appearance of an embodiment in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that mutually excludes other embodiments.

[0045] Example 1

[0046] This invention proposes a dynamic thermo-pressing leveling control method for high-density LED packaging, applied to the process stage after die bonding and before reflow soldering. The method is characterized by the following steps:

[0047] Step 1: Alignment Preheating and Selective Thermal Activation. First, the substrate after die bonding is preheated at a low-temperature background to a first preset temperature below the critical point for plastic deformation of the solder paste. Then, a focused laser beam is controlled by a high-precision scanning galvanometer system to inject high-throughput energy into the solder paste area under each or each group of LED chips with positional deviations on the substrate. This allows the solder paste in this local area to be precisely heated to a second preset temperature that allows it to undergo viscoplastic flow in a very short time. The temperature increase of the chip itself and the surrounding substrate area is strictly controlled, thereby forming an isolated viscoplastic flow area working window that exists only in the area to be corrected.

[0048] In this step, the solder used can be the widely used SAC305 lead-free solder, with a liquidus temperature of approximately 220°C. Accordingly, the first preset temperature is set within the range of 235°C to 250°C, for example, 240°C, to ensure complete melting of the solder. After component alignment, the solder is cooled to a second preset temperature, below its solidus temperature, typically ambient room temperature (e.g., 25°C), by stopping localized heating, thereby achieving final component fixation.

[0049] In this invention, considering the assembly requirements of the heat-sensitive element, Sn42Bi58 low-temperature solder, with a melting point of 138°C, can be selected. At this time, the first preset temperature can be set to 150°C, while the second preset temperature is also room temperature. This allows the entire alignment and fixing process to be completed at a lower temperature, effectively protecting the heat-sensitive element.

[0050] In this invention, the device for achieving precise local heating is a high-precision scanning galvanometer system. This system is a key component for realizing the high-speed, flexible self-alignment process of this invention. To meet the precision requirements of micro-nano device assembly, the high-precision scanning galvanometer system in this embodiment achieves a repeatability of 2μm and a scanning speed of up to 7000mm / s. The laser used in conjunction with it is a fiber laser, whose focused spot diameter can be controlled between 30μm and 100μm. This configuration enables this invention not only to rapidly heat individual pads but also to perform complex path scanning (such as circular or spiral scanning), thereby rapidly heating the solder to a first preset temperature within 100 milliseconds while ensuring highly concentrated heat to avoid thermal damage to adjacent components or substrate areas.

[0051] In this invention, a precision scanning galvanometer system accurately focuses a laser beam onto the target pad, heating it. This heating process is completed in a very short time. In a preferred embodiment of the invention, this very short time is typically in the range of 50 to 500 milliseconds, for example, 100 milliseconds. The purpose of choosing this time range is to ensure that the input energy is sufficient to rapidly heat the solder to a molten state (i.e., a first preset temperature) before the heat significantly diffuses to the surrounding substrate and components. This not only greatly improves assembly efficiency, but more importantly, it achieves true localized heating, effectively avoiding thermal damage to heat-sensitive components and ensuring the overall assembly yield and reliability.

[0052] Example 2

[0053] In a preferred embodiment of the invention, the laser power used is P = 20 watts (W). After focusing by the scanning galvanometer system and field lens, the diameter of the spot formed on the pad is d = 50 micrometers (μm).

[0054] The area of ​​the light spot was calculated to be A = π(d / 2).2 ≈3.14(25x10 -6 m) 2 ≈1963μm 2 .

[0055] At this point, the energy flux injected into the pads is as high as: Flux = P / A = 20W / (1963x10⁻¹⁰). -12 m 2 )≈1.02x10 10 W / m 2

[0056] In contrast, traditional global heating reflow ovens, while having a higher total power (e.g., 5000W), have their heating power distributed across the entire heating chamber and large circuit boards (e.g., a 30cm x 30cm area, with an area of ​​0.09m²). 2 Its average energy flux is only 5000W / 0.09m. 2 ≈5.6 x 10 4 W / m 2 .

[0057] As can be seen, the high-throughput energy injection method used in this invention has an energy density that is nearly six orders of magnitude higher than that of traditional reflow soldering. It is this huge difference in energy that enables this invention to complete local melting within milliseconds, while the heat does not have time to dissipate, thus achieving a high-precision, damage-free, and high-efficiency assembly effect that is unattainable by traditional technologies.

[0058] Example 3

[0059] Step 2 of this invention is acoustic fluidization coupling pressure leveling. After selective thermal activation, a flexible leveling device integrating a piezoelectric ceramic transducer array establishes a uniform initial contact pressure with the LED chip array surface during the descent of the flexible leveling device. Subsequently, the piezoelectric transducer array in the flexible leveling device is excited to generate high-frequency acoustic waves. The high-frequency acoustic wave energy penetrates the chip and focuses on the liquid solder paste area that has been activated by laser. Through the acoustic fluidization effect and the acoustic thinning effect, the local viscosity of the solder paste is greatly reduced. At this time, under the action of a precisely calibrated static normal pressure applied by the leveling head, the chip performs attitude correction on the almost frictionless liquid solder paste until it reaches the uniform physical plane defined by the leveling head.

[0060] Specifically, this invention employs a special flexible leveling device—an acoustic leveling head.

[0061] The key feature of this acoustic flattening head is its flexible conformal contact surface on its working end face. Flexible conformality refers to the macroscopic compliance of this contact surface, allowing it to adaptively conform to the overall warpage profile of the chip caused by its manufacturing process when in contact with it. This characteristic ensures that the applied pressure is evenly distributed across the entire chip surface, avoiding the risk of chip damage caused by pressure concentration at the highest point of warpage.

[0062] At the same time, this flexible surface is designed to effectively transmit the high-frequency acoustic vibration energy generated by the flattening head body. Therefore, based on achieving uniform pressure distribution, acoustic energy can act indiscriminately on each micro-protrusion, prompting it to efficiently and uniformly achieve coplanarization.

[0063] Therefore, this flattening head, through its unique flexible conformal contact surface, cleverly acts as an adapter between rigid acoustic energy and non-ideal warped surfaces, thus solving the problem of balancing flattening effect and chip security in existing technologies.

[0064] In this embodiment, the initial contact pressure is set to a value sufficient to ensure that the flexible conformal contact surface fully conforms to and fits the overall warp profile of the chip. The aim is to eliminate any air gaps between the flattening head and the back of the chip, ensuring that subsequently applied acoustic energy is delivered through a continuous, uniform medium to every microbump beneath the chip.

[0065] Specifically, it is generally appropriate to set the initial contact pressure in the range of 10 kPa to 200 kPa. However, those skilled in the art should understand that this specific numerical range is not a limitation of the present invention, and the optimal value can be adaptively adjusted according to the chip size, warpage, geometry and material of the microbumps, and the specific mechanical properties of the flexible contact surface.

[0066] In this embodiment, the acoustic thinning effect primarily acts on the liquid matrix of the solder, while the acoustic fluidization effect primarily acts on the solid particles within it. The two work synergistically, complementing each other, to cause a sudden and significant reduction in the overall local viscosity of the solder during ultrasonic treatment. This quasi-liquid characteristic allows the solder to spontaneously flow and redistribute itself based solely on its surface tension without the need for additional high pressure, thereby achieving rapid self-leveling of the solder at the tips of all micro-bumps and ultimately forming a highly consistent coplanarity. When the acoustic energy is no longer applied, the internal structure of the solder rapidly recovers, and the viscosity rebounds, thus fixing the perfect coplanar morphology.

[0067] In this embodiment, the pressure provides an ideal coplanar reference for solder reshaping. The working end face of the acoustic flattening head has extremely high flatness. When it is applied to the back of the chip and transmitted to each microbump through the chip as a whole, this flat surface constitutes the target geometric plane that all solder bumps should ultimately achieve.

[0068] Secondly, this pressure is the direct physical force driving the controlled redistribution of the fluidized solder. Although the solder is already in a quasi-liquid state under the influence of acoustic energy, a gentle external force is still needed to guide its flow. This static normal pressure adaptively acts on individual solder bumps with varying initial heights: for bumps with higher initial heights, the pressure causes excess solder volume to flow until their height is reduced to be flush with the coplanar reference plane; while for bumps with lower heights, it simply ensures they are in contact with the reference plane. This is a self-terminating process that ultimately and efficiently brings all solder tops to the same height.

[0069] Most importantly, the precise calibration of this pressure ensures the absolute non-destructive nature of the entire process. The pressure value is carefully set within an optimized process window: its lower limit is sufficient to overcome the surface tension of the fluidized solder to achieve effective shaping, while its upper limit is far below any mechanical threshold that could damage the internal structure of the chip (such as the low-k dielectric layer), circuitry, or pads. Furthermore, the static and normal characteristics of this pressure eliminate the risks of impact damage and shear damage, respectively, guaranteeing a high degree of controllability and safety in the leveling process.

[0070] Example 4

[0071] Step 3 of this invention is integrated thermoelectric cooling and pressure curing. After the chip completes position and orientation correction, the excitation of high-frequency acoustic waves is immediately stopped, but the normal pressure of the leveling head is kept unchanged or slightly increased. At the same time, the micro-semiconductor thermoelectric cooling module array integrated inside the flexible leveling device is activated. Through the Peltier effect, heat is actively and quickly pumped out from the contact surface of the flexible leveling device, so that the heat of the solder paste below is rapidly removed, and the temperature drops sharply below its solidification point at an extremely high cooling rate. This achieves the fixation of the chip position and the rapid solidification of the solder joint, preventing any position rebound caused by stress relaxation or thermal disturbance.

[0072] In this step, active cooling is preferably achieved by integrating a thermoelectric cooling module based on the Peltier effect inside the flattening head.

[0073] Specifically, the internal structure of the acoustic flattener integrates one or more thermoelectric cooling modules. These thermoelectric cooling modules are solid-state active heat pumps based on the Peltier effect.

[0074] Structurally, the cooling end of the thermoelectric cooling module is coupled to the working contact surface of the flattened head, which is used to contact the back surface of the chip, through efficient heat conduction. The heat dissipation end is connected to a heat dissipation system (e.g., a micro fan radiator or a water cooling device).

[0075] Once the solder coplanarization process is complete, the control system applies direct current to the thermoelectric cooling module, activating the Peltier effect. At this point, the cold end of the thermoelectric cooling module actively consumes electrical energy, pumping heat away from its surface. This causes the temperature of the working contact surface of the flattening head coupled with it to drop rapidly within a very short time (typically milliseconds). This drastic cooling is rapidly conducted through the chip substrate to the solder on the front side, quickly quenching the quasi-liquid solder, which is already in a perfectly coplanar state, causing it to solidify instantly. This precisely fixes the ideal geometry after flattening, effectively preventing surface tension shrinkage or shape destruction that might occur due to slow cooling.

[0076] During this process, heat pumped from the cold end and superimposed with the module's own Joule heat is collected at the hot end and efficiently dissipated by the rear-end cooling system. Therefore, this invention utilizes the Peltier effect to achieve an active, controllable, and extremely high-rate cooling process for the solder, which is a key step in ensuring that the final leveling effect is perfectly maintained.

[0077] In a preferred embodiment of the invention, the cooling rate is crucial for achieving the quenching treatment of the solder. This rate must be high enough to ensure that the time from the quasi-liquid state to complete solidification is extremely short, thereby overcoming the surface tension effect of the solder itself and preventing it from shrinking or changing shape during slow cooling, which would destroy the perfect coplanarity already formed.

[0078] Research and experimental verification have shown that, in order to achieve the above objectives, the cooling rate should preferably be higher than 1,000 K / s, and more preferably in the range of 5,000 K / s to 50,000 K / s.

[0079] By achieving high cooling efficiency, the microcrystalline structure of the solder is rapidly frozen, ensuring that the micron-level or even submicron-level flatness obtained during the leveling operation is perfectly maintained. This invention, through the use of active cooling technologies such as the Peltier effect, reliably achieves and controls the cooling rate within the aforementioned range.

[0080] The para-preheating and selective thermal activation steps include:

[0081] First, a global heating device is used to preheat the substrate as a whole, so that it uniformly reaches a first stable background temperature that is lower than the solidus temperature of the solder paste, but sufficient to significantly reduce the thermal shock required for subsequent local heating and to moderately pre-activate the flux. Then, a high energy density beam directional projection system executes a preset, dynamic energy projection scanning path on the solder paste area under each LED chip with positional deviation, based on the pre-acquired positional deviation data of each or each group of LED chips. By accurately integrating and controlling the projected energy in the time and space dimensions, heat is injected into the solder paste area under the LED chip in a targeted manner, so that it is rapidly heated to a second preset temperature within a millisecond time scale to form a viscoplastic flow region. At the same time, it is ensured that the temperature increase of the chip body and the surrounding non-target areas is strictly controlled within a safe threshold that will not cause material damage or deterioration of solder joint performance.

[0082] In this embodiment, the combination of targeting and transience allows energy to be injected in a spatiotemporally focused manner. This injection method creates a transient, localized low-viscosity region within the target solder paste micro-area.

[0083] In this embodiment, the acoustic fluidization coupling pressure leveling step is specifically as follows:

[0084] A leveling actuator integrating an acoustic energy generation unit and a conformal contact interface first establishes physical contact with the top surface of the LED chip array. An initial contact pressure sufficient to ensure effective acoustic coupling without causing chip displacement is applied through the conformal contact interface. Then, the acoustic energy generation unit is activated under the initial contact pressure to emit high-frequency acoustic energy into the solder paste area, which is already in a viscoplastic flow state, to reduce its viscosity and make it present a fluid-like state. Synchronously or immediately following this acoustic excitation, a pressure control system smoothly and controllably increases the pressure applied to the chip array to a final leveling pressure. Under the synergistic effect of this acoustic fluidization and increased mechanical pressure, all LED chips are driven to adjust their posture in a low-resistance state until their top surfaces collectively abut against the unified physical reference plane defined by the leveling actuator.

[0085] Physical contact specifically refers to the operation method in which any solid mechanical tool (such as a probe, gripper, push rod, nozzle, etc.) directly interacts with the electronic component body during the precise calibration of the position or orientation of electronic components on the substrate.

[0086] In this embodiment, the integrated thermoelectric cooling and pressure curing steps are specifically as follows:

[0087] After the acoustic fluidization coupling pressure leveling step is completed and all LED chips are mechanically held in a uniform physical reference plane, the emission of high-frequency acoustic energy is immediately terminated. Simultaneously, a semiconductor thermoelectric cooling unit array integrated inside the leveling execution end and forming an efficient heat conduction path with its conformal contact interface is activated. Driven by a high transient response power supply, the thermoelectric cooling unit array actively pumps heat through the LED chip body, forcibly and unidirectionally extracting heat from the solder paste area that is already in a viscoplastic flow state. Under a preset pressure control program synchronized with the heat extraction process, the final leveling pressure applied to the chip array is further slightly increased and maintained to actively counteract the stress generated by the volume shrinkage of the solder paste during the phase change curing process. This achieves in-situ rapid quenching at an ultra-high cooling rate of over 100 degrees Celsius per second under pressure to maintain precise physical positioning, solidifying all LED chips in their corrected positions and orientations, ultimately forming micron-level precision solidified solder joints with no positional rebound, no orientation deflection, and dense internal structure.

[0088] This step maintains a constant temperature in the working area: by directing >95% of the waste heat from its source to a location away from the operating area for dissipation, heat conduction and radiation to the substrate and microelectronic components are effectively prevented. This is crucial for preventing the solder paste from altering its rheological properties due to temperature changes.

[0089] Eliminating thermally induced displacement errors: All materials have a coefficient of thermal expansion. If heat diffuses to the fixture, positioning stage, or substrate, it will cause micron-level thermal expansion and contraction. This unpredictable deformation is the enemy of precision positioning. This approach fundamentally eliminates the source of thermally induced displacement errors by maintaining the isothermal state of the system's key components, which is a basic prerequisite for achieving sub-micron positioning accuracy.

[0090] Improve system reliability and lifespan: Ensure that the acoustic transducer operates within a safe temperature range, preventing performance degradation, frequency drift, or even damage due to overheating, thereby ensuring the ability of the entire system to operate stably for a long time.

[0091] In this embodiment, the leveling step further includes:

[0092] An external energy field is applied to the solder to significantly reduce its viscosity, causing it to enter a highly fluid fluidized state, thereby achieving coplanarization under static pressure;

[0093] Furthermore, after the solder achieves coplanarity, the solder is rapidly solidified by actively cooling the leveling device at a cooling rate sufficient to suppress the solder's retraction due to surface tension, thereby fixing the coplanar shape.

[0094] In this step, the external energy field introduces a new control dimension independent of acoustic fluidization and mechanical pressure. Its core purpose is to apply non-contact, controllable physical force and / or torque to micro-electronic components (such as Micro-LED chips) to achieve precise adjustment of their spatial attitude (especially rotation angle), thereby solving the orientation problem that is difficult to achieve by mechanical thrust alone.

[0095] In this invention, under the technical background of this invention, the reason why it is difficult to precisely fine-tune micro-components in the initial bonding medium (such as solder paste) is due to two different but synergistic resisting forces: interfacial static friction and bulk cohesion.

[0096] Static friction and cohesive force together constitute the total resistance to the movement of components. The former defines the difficulty of initiating motion, while the latter defines the resistance during the motion process.

[0097] In this embodiment, utilizing acoustic vibration further includes:

[0098] During the application of acoustic vibration, a physical feedback parameter characterizing the fluidization degree of the solder is monitored in real time, and a closed-loop control loop is established based on this parameter to dynamically and adaptively adjust at least one operating parameter of the acoustic vibration, thereby precisely maintaining the highly fluid fluidization state within a preset target range.

[0099] This step includes a high-performance closed-loop control loop, which is the core of achieving ultra-high precision and robust positioning and orientation of micro-components.

[0100] Example 5

[0101] In this embodiment, the application of an external energy field in the above embodiment is further explained. The application of an external energy field includes: exciting the leveling device to generate a preset acoustic vibration. The acoustic vibration is coupled with the static pressure applied by the leveling device and acts synergistically on the solder particles. By generating high-frequency normal and tangential alternating stress between the particles, the static friction and cohesion between them are effectively destroyed, thereby stimulating and maintaining a highly fluid fluidized state.

[0102] Example 6

[0103] Another object of the present invention is to provide a yield improvement system for high-density LED packaging, which is based on the above-described invention and includes the following mutually cooperating units:

[0104] Thermal field generation unit: configured to project high-resolution, dynamically adjustable energy into a local area below one or more target components on the substrate during reflow soldering, thereby artificially and controllably establishing a non-uniform temperature distribution field in the molten solder.

[0105] Potential field constraint unit: configured to synchronously generate a spatial potential well field in the process atmosphere medium surrounding the target element within the process cavity, which can apply a passive restoring force to the element that is related to its spatial pose deviation and points towards the center of the potential well.

[0106] The collaborative control unit is electrically connected to the programmable thermal field generation unit and the non-contact potential field constraint unit, respectively. Its core function is to integrate and control the gradient, direction and intensity of the non-uniform temperature distribution field, as well as the position, shape and depth of the spatial potential well field, in real time according to the preset component target pose data. In this way, it can comprehensively utilize the surface tension driving force generated by the temperature field gradient on the liquid solder and the non-contact restoring force generated by the potential well field to actively and accurately guide the component to the predetermined target position in the liquid phase stage of reflow soldering and achieve stable posture maintenance until the solder solidifies.

[0107] The integrated advantage of this system in this invention lies in its ability to instantly generate a customized energy formula for each manipulated component. Based on machine vision feedback, the system can simultaneously or sequentially project energy fields of varying shapes, sizes, intensities, and durations at multiple different locations on the substrate. This unprecedented flexibility and precision enables large-scale parallel processing, adaptive repair, and complex, non-uniform assembly processes, thereby significantly improving the efficiency, yield, and process window of micro-assembly technology.

[0108] In this invention, a non-uniform temperature distribution field refers to a controlled thermodynamic state with a spatially non-constant temperature, intentionally created and maintained on the surface or bulk phase of a target workpiece (such as a semiconductor substrate) using a high-resolution, dynamically adjustable energy projection system. This technology is a core prerequisite for realizing selective, localized, and parallel micro-assembly processes.

[0109] The non-uniform temperature distribution field is not a passively generated side effect, but rather an advanced process condition actively pursued and precisely controlled by this invention. It elevates thermal management from a macroscopic, uniform dimension to a microscopic, programmable, and designable dimension, providing a key physical means for the next generation of high-density, heterogeneous integrated micro-assembly technology.

[0110] The specific implementation method of generating a controllable surface tension gradient driving force by applying a dynamic asymmetric thermal field is as follows:

[0111] By using programmable optical modulation devices, the intensity of an energy beam is spatially modulated to generate a structured energy pattern that can be changed in real time, corresponding to the desired surface tension gradient distribution.

[0112] The structured energy pattern is then precisely projected onto the surface of the molten solder. By dynamically changing the asymmetry and intensity distribution of the pattern, the magnitude and direction of the driving force acting on the component are controlled in real time to achieve precise guidance and final stabilization of its position.

[0113] In this step, the dynamic asymmetric thermal field is typically generated in the following way and used to achieve complex manipulation tasks:

[0114] Generation method:

[0115] Single-point scanning: A single focused energy point (such as a laser beam) is moved on a substrate by scanning a galvanometer or moving platform.

[0116] Array timing activation: For spatial light modulators such as DMD or VCSEL arrays, a moving energy pattern is formed by sequentially illuminating adjacent pixels or units according to a preset timing sequence.

[0117] Core functions:

[0118] Programmable transport: This is its most important function. By pre-planning the path, this mechanism can precisely transport components from any initial position on the substrate to any target position.

[0119] Path planning and obstacle avoidance: Due to its dynamic controllability, the transport path can be designed as a complex curve to bypass other components or surface defects that are already fixed on the substrate, which greatly improves the flexibility and success rate of assembly.

[0120] Speed ​​and acceleration control: By adjusting the movement speed and energy intensity (i.e. the magnitude of the temperature gradient) of the energy pattern in real time, the movement speed and acceleration of the components can be precisely controlled. For example, smooth deceleration can be achieved when approaching the target position to achieve a soft landing, avoid collision damage, and improve the final positioning accuracy.

[0121] The driving force in this invention ranges from 10 piconewtons (pN) to 500 micronewtons (μN).

[0122] Quick Reference Table of Core Performance Parameters

[0123]

[0124]

[0125] The specific implementation method of simultaneously applying a non-contact potential field to provide a passive restoring force is as follows:

[0126] By arranging a controllable non-contact field source array above or around the component, and by having a cooperative control unit selectively drive one or more field sources in the field source array according to the target alignment position of the component, a localized potential field with the lowest potential energy point centered on the target alignment position is generated in the molten solder area where the component is located.

[0127] This potential field applies a restoring force pointing back to the center to components that are off-center, and a restoring torque to components that have undergone attitude deflection, thereby forming a three-dimensional potential field constraint. This constraint is used to actively suppress the position drift and attitude rotation of components on the liquidus line, and works in conjunction with the surface tension gradient driving force to ensure the dynamic stability of components during the alignment process and prevent overshoot.

[0128] In this step, one or more field sources refer to one or more physical devices or apparatuses responsible for generating and projecting the required energy onto the surface of the target substrate to form a structured energy pattern. This field source is the energy supply and spatial modulation execution unit for implementing the non-contact manipulation method of this invention. This description is intended to cover a variety of feasible hardware implementation schemes to ensure a broad scope of technical protection.

[0129] The core function of the field source is to receive digital instructions (i.e., data from structured energy patterns) from the control system and transform them into a physical energy field with a specific spatial distribution and temporal intensity. This energy field interacts with the medium (such as a thin liquid film) on the substrate surface, thereby generating the desired physical effects (such as a temperature gradient).

[0130] In this invention, the restoring force pointing back to the center is a net force field with specific directionality and functionality generated by a structured energy pattern. The core feature of this force is that, within its effective range, its force vector always points to a predefined, stable equilibrium point (i.e., the geometric center of the pattern).

[0131] This restoring force is a specific manifestation of the controllable surface tension gradient driving force under a particular spatial configuration. A potential well can be constructed on the liquid film on the substrate surface by projecting a structured energy pattern with centrosymmetry (e.g., a ring or polygonal frame).

[0132] Potential well construction: The energy map itself constitutes a low surface tension region (potential barrier), while the un-energy-irradiated central region it surrounds becomes a high surface tension region (bottom of the potential well).

[0133] Directionality of force: the resulting surface tension gradient The components exhibit a radially inward distribution within the potential well. Therefore, any component located within the potential well but off-center will experience a net driving force F_restore pointing towards the geometric center of the potential well. The mathematical expression for this force satisfies... The form is , where U is the potential energy field of the component, and its minimum value is located at the center of the potential well.

[0134] Equilibrium condition: When the component is driven to the exact center of the potential well, the surface tension gradient forces from all directions reach perfect equilibrium, and the net force acting on the component is zero (F_restore = 0). This position is a stable equilibrium point.

[0135] This embodiment also provides a computer device applicable to the dynamic hot-pressing leveling control method and yield improvement system for high-density LED packaging, including: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to realize the dynamic hot-pressing leveling control method and yield improvement system for high-density LED packaging as proposed in the above embodiment.

[0136] The computer device can be a terminal, comprising a processor, memory, communication interface, display screen, and input devices connected via a system bus. The processor provides computing and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The communication interface is used for wired or wireless communication with external terminals; wireless communication can be achieved through Wi-Fi, carrier networks, NFC (Near Field Communication), or other technologies. The display screen can be an LCD screen or an e-ink screen. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad on the computer device's casing, or an external keyboard, touchpad, or mouse.

[0137] This embodiment also provides a storage medium storing a computer program. When executed by a processor, the program implements the dynamic hot-pressing leveling control method and yield improvement system for high-density LED packaging as proposed in the above embodiments. The storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0138] In summary, this invention, through targeted thermal activation technology, heats solder paste to a viscoplastic flow state far below its melting point, rather than a completely molten liquid state. This solves the inherent contradiction between the risk of thermal damage and the narrow process window caused by the requirement to expose components to high temperatures (such as above 230°C) in order to obtain sufficient surface tension in existing technologies.

[0139] Secondly, this invention constructs an active, highly controllable three-dimensional correction system based on "sound pressure coordination." The active intervention of high-frequency acoustic energy transforms viscous solder paste into a near-frictionless fluid-like medium through the "acoustic fluidization" effect, creating unprecedented ideal conditions for the free movement of the chip, thereby greatly improving the yield, performance consistency, and long-term reliability of the final product.

[0140] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A dynamic thermo-pressing leveling control method for high-density LED packaging, applied in the process stage after die bonding and before reflow soldering, characterized in that, Includes the following steps: Step 1: Alignment preheating and selective thermal activation. First, the substrate after die bonding is preheated at a low temperature background to bring it to a first preset temperature below the critical point of plastic deformation of the solder paste. Subsequently, a high-precision scanning galvanometer system is used to control a focused laser beam to inject high-throughput energy into the solder paste area under each or each group of LED chips with positional deviations on the substrate. This allows the solder paste in this local area to be precisely heated to a second preset temperature that allows it to undergo viscoplastic flow in a very short time. Meanwhile, the temperature increase of the chip itself and the surrounding substrate area is strictly controlled, thereby forming an isolated viscoplastic flow area working window that exists only in the area to be corrected. Step 2: Acoustic fluidization coupling pressure leveling. After selective thermal activation, a flexible leveling device integrating a piezoelectric ceramic transducer array establishes a uniform initial contact pressure with the LED chip array surface during its descent. Subsequently, the piezoelectric transducer array within the flexible leveling device is excited, generating high-frequency acoustic waves. The high-frequency acoustic wave energy penetrates the chip and focuses on the liquid solder paste area that has been activated by the laser. Through the acoustic fluidization effect and the acoustic thinning effect, the local viscosity of the solder paste is greatly reduced. At this time, under the action of a precisely calibrated static normal pressure applied by the leveling head, the chip undergoes attitude correction on the almost frictionless liquid solder paste until it reaches the uniform physical plane defined by the leveling head. Step 3: Integrated thermoelectric cooling and pressure curing. After the chip completes position and orientation correction, the high-frequency acoustic wave excitation is immediately stopped, but the normal pressure of the leveling head is kept unchanged or slightly increased. At the same time, the micro-semiconductor thermoelectric cooling module array integrated inside the flexible leveling device is activated. Through the Peltier effect, heat is actively and quickly pumped out from the contact surface of the flexible leveling device, so that the heat of the solder paste below is quickly extracted. The temperature drops sharply below its solidification point at an extremely high cooling rate, thereby fixing the chip position and rapidly solidifying the solder joints, preventing any position rebound caused by stress relaxation or thermal disturbance.

2. The dynamic hot-pressing leveling control method for high-density LED packaging according to claim 1, characterized in that, The preheating and selective thermal activation steps include: First, a global heating device is used to preheat the substrate as a whole, so that it uniformly reaches a first stable background temperature that is lower than the solidus temperature of the solder paste, but sufficient to significantly reduce the thermal shock required for subsequent local heating and to moderately pre-activate the flux. Then, a high energy density beam directional projection system executes a preset, dynamic energy projection scanning path on the solder paste area under each LED chip with positional deviation, based on the pre-acquired positional deviation data of each or each group of LED chips. By accurately integrating and controlling the projected energy in the time and space dimensions, heat is injected into the solder paste area under the LED chip in a targeted manner, so that it is rapidly heated to the second preset temperature within a millisecond time scale to form the viscoplastic flow region. At the same time, it is ensured that the temperature increase of the chip body and the surrounding non-target area is strictly controlled within a safe threshold that will not cause material damage or deterioration of solder joint performance.

3. The dynamic hot-pressing leveling control method for high-density LED packaging as described in claim 2, characterized in that, The acoustic fluidization coupling pressure leveling step is specifically as follows: A leveling actuator integrating an acoustic energy generation unit and a conformal contact interface first establishes physical contact with the top surface of the LED chip array. An initial contact pressure sufficient to ensure effective acoustic coupling without causing chip displacement is applied through the conformal contact interface. Then, under the initial contact pressure, the acoustic energy generation unit is activated to emit high-frequency acoustic energy into the solder paste area, which is already in a viscoplastic flow state, to reduce its viscosity and make it present a fluid-like state. Synchronously or immediately following this acoustic excitation, a pressure control system smoothly and controllably increases the pressure applied to the chip array to a final leveling pressure. Thus, under the synergistic effect of acoustic fluidization and increased mechanical pressure, all LED chips are driven to adjust their posture in a low-resistance state until their top surfaces collectively abut against the unified physical reference plane defined by the leveling actuator.

4. The dynamic hot-pressing leveling control method for high-density LED packaging as described in claim 3, characterized in that, The integrated thermoelectric cooling and pressure curing steps are specifically as follows: After the acoustic fluidization coupling pressure leveling step is completed and all LED chips are mechanically held in place on the unified physical reference plane, the emission of high-frequency acoustic energy is immediately terminated. Simultaneously, a semiconductor thermoelectric cooling unit array integrated inside the leveling execution end and forming a high-efficiency heat conduction path with its conformal contact interface is activated. Driven by a high transient response power supply, the thermoelectric cooling unit array actively pumps heat through the LED chip body, forcibly and unidirectionally extracting heat from the solder paste area that is already in a viscoplastic flow state. Under a preset pressure control program synchronized with the heat extraction process, the final leveling pressure applied to the chip array is further slightly increased and maintained to actively counteract the stress generated by the volume shrinkage of the solder paste during the phase change curing process. This achieves in-situ rapid quenching at an ultra-high cooling rate of over 100 degrees Celsius per second while maintaining precise physical positioning. All LED chips are solidified in their corrected positions and orientations, ultimately forming micron-level precision solidified solder joints with no positional rebound, no orientation deflection, and dense internal structure.

5. The dynamic hot-pressing leveling control method for high-density LED packaging as described in claim 4, characterized in that, The leveling step further includes: An external energy field is applied to the solder to significantly reduce its viscosity, causing it to enter a highly fluid fluidized state, thereby achieving coplanarization under the static pressure; And after the solder achieves coplanarity, the leveling device is actively cooled to a cooling rate sufficient to suppress the solder from shrinking due to surface tension, thereby rapidly solidifying the solder and fixing the coplanar shape.

6. The dynamic hot-pressing leveling control method for high-density LED packaging as described in claim 5, characterized in that, The application of the external energy field includes: The leveling device is excited to generate a preset acoustic vibration, which is coupled with the static pressure applied by the leveling device and acts synergistically on the solder particles. By generating high-frequency normal and tangential alternating stress between the particles, the static friction and cohesion between them are effectively destroyed, thereby stimulating and maintaining the highly fluid fluidized state.

7. The dynamic hot-pressing leveling control method for high-density LED packaging as described in claim 6, characterized in that, The utilization of acoustic vibration further includes: During the application of the acoustic vibration, a physical feedback parameter characterizing the fluidization degree of the solder is monitored in real time, and a closed-loop control loop is established based on the parameter to dynamically and adaptively adjust at least one operating parameter of the acoustic vibration, thereby precisely maintaining the highly fluid fluidization state within a preset target range.

8. A yield improvement system for high-density LED packaging, based on the dynamic hot-pressing leveling control method for high-density LED packaging as described in any one of claims 1 to 7, characterized in that, The system integrates the following mutually cooperating units within a unified process chamber: Thermal field generation unit: configured to project high-resolution, dynamically adjustable energy into a local area below one or more target components on the substrate during reflow soldering, thereby artificially and controllably establishing a non-uniform temperature distribution field in the molten solder. Potential field constraint unit: configured to synchronously generate a spatial potential well field in the process atmosphere medium surrounding the target element within the process cavity, the potential well field being able to apply a passive restoring force to the element that is related to its spatial pose deviation and directed towards the center of the potential well; The collaborative control unit is electrically connected to the programmable thermal field generation unit and the non-contact potential field constraint unit, respectively. Its core function is to integrate and control the gradient, direction and intensity of the non-uniform temperature distribution field, as well as the position, shape and depth of the spatial potential well field, in real time according to the preset component target pose data. In this way, it can comprehensively utilize the surface tension driving force generated by the temperature field gradient on the liquid solder and the non-contact restoring force generated by the potential well field to actively and accurately guide the component to the predetermined target position and achieve stable posture maintenance in the liquid phase stage of reflow soldering until the solder solidifies.

9. The yield improvement system for high-density LED packaging as described in claim 8, characterized in that, The step of generating a controllable surface tension gradient driving force by applying a dynamic asymmetric thermal field is specifically implemented as follows: By using programmable optical modulation devices, the intensity of an energy beam is spatially modulated to generate a structured energy pattern that can be changed in real time, corresponding to the desired surface tension gradient distribution. The structured energy pattern is then precisely projected onto the surface of the molten solder. By dynamically changing the asymmetry and intensity distribution of the pattern, the magnitude and direction of the driving force acting on the component are controlled in real time to achieve precise guidance and final stabilization of its position.

10. The yield improvement system for high-density LED packaging as described in claim 9, characterized in that, The specific implementation method of the step of synchronously applying a non-contact potential field to provide a passive restoring force is as follows: By arranging a controllable non-contact field source array above or around the component, and by having a cooperative control unit selectively drive one or more field sources in the field source array according to the target alignment position of the component, a localized potential field with the lowest potential energy point centered on the target alignment position is generated in the molten solder area where the component is located. The potential field applies a restoring force pointing back to the center to components that are off-center, and a restoring torque to components that have undergone attitude deflection, thereby forming a three-dimensional potential field constraint to actively suppress the position drift and attitude rotation of the components on the liquidus line, and works in conjunction with the surface tension gradient driving force to ensure the dynamic stability of the components during the alignment process and prevent overshoot.

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