Flip chip replacement method and apparatus

Abstract

The application provides a flip chip replacement method and device, the method comprising: preheating the whole circuit board carrying a target chip to make the temperature of the circuit board reach a first predetermined temperature; locally heating the target chip to melt the solder bump array at the bottom of the target chip; vertically removing the target chip from the circuit board by applying an upward lifting force to the target chip in the state of melted solder bumps; cleaning the exposed pads on the circuit board to remove residual solder and underfill material residues; applying flux on the cleaned pads, and aligning and placing a new chip with the pads; reflow soldering the placed new chip, filling the bottom filling glue and performing thermal curing. Thus, the low-thermal-damage, high-success-rate and repeatable flip chip replacement operation is realized, which is of great significance to improving the maintainability and cost-effectiveness of high-density electronic assemblies.

Description

Technical Field

[0001] This invention relates to the field of electronic assembly and repair technology, and in particular to a method and apparatus for replacing flip-chips. Background Technology

[0002] Flip-chips are widely used in high-end electronic components such as CPUs, GPUs, RF modules, and MEMS sensors due to their excellent electrical performance and heat dissipation capabilities. Flip-chips are directly interconnected to the circuit board via solder bumps, with underfill filling the gap between the chip and the substrate to alleviate thermal stress and improve reliability. However, rework requires removing the soldered bare chip and replacing it with a new one, an operation facing multiple technical challenges: removing the underfill can easily damage surrounding components and pads; improper local heating can lead to chip overheating or substrate delamination; the timing and force of picking up the chip after the solder bumps melt are difficult to control, easily causing pad peeling or short circuits due to residual solder; and the alignment accuracy requirements during remounting are extremely high (the offset must typically be less than 10% of the pad diameter). Establishing a standardized rework method that can minimize thermal impact, protect the substrate and adjacent devices, and ensure soldering reliability after rework has become a critical issue that urgently needs to be addressed in the field of high-density electronic assembly. Summary of the Invention

[0003] This invention provides a flip chip replacement method and apparatus, which aims to solve the problems of damage to surrounding components and pads, as well as pad peeling or short circuits caused by residual solder when removing the soldered bare chip and replacing it with a new chip.

[0004] In a first aspect, the present invention provides a flip chip replacement method and apparatus, comprising: The circuit board carrying the target chip is preheated as a whole until the temperature of the circuit board reaches the first predetermined temperature. The target chip is locally heated to melt the solder bump array on the bottom of the target chip; While the solder bumps are molten, an upward lifting force is applied to the target chip to vertically remove the target chip from the circuit board. Clean the exposed pads on the circuit board to remove residual solder and underfill material residue; Apply flux to the cleaned pads and align the new chip with the pads; The placed new chip is reflow soldered, filled with underfill adhesive, and then thermoset.

[0005] In one embodiment, the first predetermined temperature is 10 to 20 degrees Celsius lower than the glass transition temperature of the chip bottom filler material.

[0006] In one embodiment, the local heating of the target chip includes: Position the hot air nozzle directly above the target chip to form a uniformly covered and clearly defined hot air surrounding area around the target chip. Based on the metallurgical properties of the solder alloy used in the original soldering of the target chip, the hot air temperature at the outlet of the hot air nozzle is preset to a second predetermined temperature, while the hot air volume flow rate is dynamically adjusted. The heating program is started to steadily raise the surface temperature of the target chip to the peak soldering temperature range at a controlled heating rate, and maintain the peak soldering temperature level for a preset time.

[0007] In one embodiment, the second predetermined temperature is 20 to 40 degrees Celsius greater than the melting point of the solder alloy.

[0008] In one embodiment, applying an upward lifting force to the target chip to vertically remove the target chip from the circuit board includes: Drive the vacuum nozzle to descend until the end face of the vacuum nozzle gently contacts the central area or edge non-functional area of ​​the upper surface of the target chip; The vacuum generator is activated, thereby establishing a stable negative pressure environment inside the vacuum nozzle. Upon receiving the adsorption confirmation signal, the servo lifting axis drives the vacuum nozzle to move upward in a direction perpendicular to the target chip at a preset constant speed, so as to peel the chip off from the pad array.

[0009] In one embodiment, cleaning the exposed pads on the circuit board includes: Lay the desoldering braid flat over the solder pad area and gently press the desoldering braid with a temperature-controlled soldering iron. The residual solder alloy on the surface of the pad is absorbed and transferred into the copper mesh openings of the solder-absorbing braided tape by utilizing the capillary adsorption effect; Immerse the circuit board partially in a specialized chemical cleaning agent, or apply the specialized chemical cleaning agent to the pad area using a precision spray valve, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening. After the special chemical cleaning agent has fully penetrated, use an antistatic brush to wipe the pad area and peel off the swollen and loosened underfill residue from the pad gaps and the surface of the solder mask. Perform a second final cleaning on the pads using a lint-free wiping cloth soaked in high-purity isopropyl alcohol to remove residual chemical cleaning agents and fine debris, and then use a clean compressed air stream to blow the surface of the pads until they are dry.

[0010] In one embodiment, applying flux to the cleaned pads and aligning the new chip with the pads includes: A pre-measured amount of flux is applied to the pad array area using a dip-type micro-transfer head or a piezoelectric jet dispensing valve to form a flux film. The replacement chip is obtained, and the coordinates of the circuit board reference alignment mark and the chip surface identification mark stored in the system database are called. The position deviation is calculated and the spatial attitude is calibrated by the vision alignment system to confirm whether the alignment accuracy meets the standard. After confirming that the alignment accuracy meets the standard, the placement head places the replacement chip on the pad array coated with flux, and ensures that the bottom bumps of the replacement chip and the circuit board pads form reliable physical contact and parallel alignment. After placement, check the offset between the edge contour of the replacement chip and the edge of the corresponding pad pattern on the circuit board, and determine whether the offset exceeds the preset allowable range; If the preset allowable range is exceeded, repeat the above steps.

[0011] In one embodiment, the reflow soldering of the placed new chip, filling with underfill adhesive, and thermal curing includes: The entire automatic temperature control thermal process is performed based on the standard temperature profile recommended in the datasheet of the replacement chip solder bump alloy, wherein the peak soldering temperature is a process overheat value of 20 to 30 degrees Celsius above the melting point of the solder alloy. After the soldering process is completed, the circuit board is transferred out of the furnace and allowed to cool naturally to room temperature in a clean environment; After the component temperature has fully returned to normal, use a non-contact gap measuring instrument or feeler gauge to measure the actual support gap height between the bottom surface of the chip and the top surface of the circuit board. Based on the aforementioned gap height, a dedicated bottom filler adhesive compatible with the rework process is selected. A precision dispensing needle is used to slowly inject adhesive along the adjacent two or one edge of the chip. The capillary effect generated by the tiny gap between the chip and the circuit board is used to drive the adhesive to automatically penetrate and flow from the chip edge to the center area of ​​the chip bottom until the adhesive overflows evenly from the remaining edges of the chip to form a complete encapsulation. The circuit board is transferred to a precision oven for constant temperature thermal curing, which allows the epoxy resin matrix inside the bottom filler to complete the cross-linking reaction and establish a stable three-dimensional network structure, thereby achieving effective stress buffering and mechanical protection for the solder joint connection area between the replacement chip and the circuit board.

[0012] Secondly, the present invention provides a flip chip replacement device, comprising: The preheating module is used to preheat the circuit board carrying the target chip as a whole, so that the temperature of the circuit board reaches the first predetermined temperature. A heating module is used to locally heat the target chip to melt the solder bump array on the bottom of the target chip; The removal module is used to apply an upward lifting force to the target chip while the solder bumps are molten, so as to vertically remove the target chip from the circuit board. The cleaning module is used to clean the exposed pads on the circuit board to remove residual solder and underfill material residue; A placement module is used to apply flux to the cleaned pads and align and place the new chip with the pads; The soldering module is used to reflow solder the placed new chips, fill the underfill adhesive, and perform heat curing.

[0013] Thirdly, the present invention provides an electronic device including a processor and a memory, the memory storing computer-readable instructions that, when executed by the processor, perform the steps of the method provided in the first aspect above.

[0014] Fourthly, the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the method provided in the first aspect above.

[0015] Fifthly, the present invention provides a computer program product comprising a computer program that, when executed by a processor, performs the steps of the method provided in the first aspect above.

[0016] As can be seen from the above technical solutions, the present invention has the following advantages: This invention provides a method and apparatus for flip chip replacement. The method includes: preheating a circuit board carrying a target chip to a first predetermined temperature; locally heating the target chip to melt the solder bump array on its underside; applying an upward lifting force to the target chip while the solder bumps are molten to vertically remove it from the circuit board; cleaning the exposed pads on the circuit board to remove residual solder and underfill material residue; applying flux to the cleaned pads and aligning the new chip with the pads; reflow soldering the placed new chip, filling with underfill adhesive, and thermally curing. This achieves low thermal damage, high success rate, and repeatable flip chip rework, which is of great significance for improving the maintainability and cost-effectiveness of high-density electronic components. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. 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.

[0018] Figure 1 This is a flowchart illustrating the steps of a first embodiment of the flip chip replacement method of the present invention; Figure 2 This is a flowchart illustrating the steps of a method for locally heating a target chip according to the present invention. Figure 3 This is a flowchart illustrating the steps of a method for vertically removing a target chip from a circuit board according to the present invention. Figure 4 This is a flowchart illustrating the steps of a method for cleaning exposed pads on a circuit board according to the present invention. Figure 5 This is a flowchart illustrating the steps of a method for aligning and placing a new chip with the pads according to the present invention. Figure 6 This is a flowchart illustrating the reflow soldering method for a newly placed chip according to the present invention. Figure 7 This is a structural block diagram of a second embodiment of the flip chip replacement device of the present invention. Detailed Implementation

[0019] This invention provides a flip chip replacement method and apparatus, which aims to solve the problems of damage to surrounding components and pads, as well as pad peeling or short circuits caused by residual solder when removing the soldered bare chip and replacing it with a new chip.

[0020] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0021] In existing technologies, flip-chip rework methods are mainly divided into the following two categories: The whole-board heating rework method involves placing the entire circuit board in a hot air reflow oven or infrared heating platform, raising the temperature of the entire board above the solder melting point to melt the solder bumps under the target chip. The chip is then removed using a vacuum nozzle. Its core drawback is that whole-board heating causes all solder joints on the circuit board (including other soldered chips and resistors / capacitors) to remelt, easily leading to displacement, bridging, or cold solder joints of adjacent components. Simultaneously, the underfill adhesive undergoes irreversible degradation at high temperatures, making it difficult to completely remove large areas of residual adhesive, and subsequent cleaning processes can easily damage the pads and solder resist layer. Furthermore, increased whole-board thermal cycling accelerates substrate aging and reduces long-term product reliability.

[0022] Manual hot air gun rework method: The operator holds a hot air gun and heats the target chip locally. After the solder melts, the chip is removed using tweezers or a simple suction pen. Although this method avoids heating the entire board area, it has the following significant drawbacks: the hot air gun temperature, airflow, and heating time are entirely dependent on the operator's experience, lacking real-time temperature monitoring and closed-loop control. This makes it extremely easy for excessively high temperatures or prolonged heating times to cause chip burnout, substrate carbonization, or deformation of adjacent plastic components; when removing the chip manually, it is difficult to ensure vertical lifting, which can easily generate lateral forces, causing pad lifting or substrate circuit breakage; cleaning the pads after rework usually involves manual operation with a soldering iron and desoldering wick, which can easily scratch the pads or cause missing pads, making it impossible to reliably solder new chips; during remounting, there is a lack of high-precision alignment methods, and the offset often exceeds the allowable range, causing open circuits or short circuits.

[0023] Existing flip-chip rework technologies have significant shortcomings in terms of process control precision and protection of the substrate and surrounding devices: the overall heating method easily causes disturbance to the solder joints and substrate aging; the manual hot air gun method is highly dependent on operator skills, lacks temperature monitoring and vertical removal control, and the pad cleaning and remounting precision cannot meet the requirements of fine pitch. To address these problems, this invention provides a flip-chip replacement method. By coordinating the thermal process with a preheating platform and local heating devices, monitoring the chip surface temperature in real time, vertically removing the chip with a vacuum nozzle, standardizing the pad cleaning process, and implementing high-precision alignment and underfill curing processes, a flip-chip bare chip rework method is established. This method achieves low thermal damage, high success rate, and repeatable flip-chip rework operations, which is of great significance for improving the maintainability and cost-effectiveness of high-density electronic components. Specific implementation methods are described in the following embodiments.

[0024] Example 1 Please see Figure 1 , Figure 1 This is a flowchart illustrating a first embodiment of a flip chip replacement method according to the present invention; the flip chip replacement method includes: Step S101: Preheat the circuit board carrying the target chip as a whole until the temperature of the circuit board reaches the first predetermined temperature.

[0025] In one embodiment, the first predetermined temperature is 10 to 20 degrees Celsius lower than the glass transition temperature of the chip bottom filler material.

[0026] In a specific implementation, this step involves performing a controlled preheating treatment on the circuit board to be reworked, thus creating a thermodynamic buffer for the subsequent chip removal process.

[0027] Before initiating the flip-chip bare die rework operation, the circuit board assembly carrying the target chip to be reworked is precisely fixed onto the surface of a heating platform with precise temperature control capabilities. Vacuum adsorption or edge clamping mechanisms ensure the circuit board maintains stable flatness and positional repeatability throughout the entire operation cycle. The heating platform then initiates a preset low-temperature preheating program, raising the overall temperature of the circuit board to a safe critical range at a steady heating rate. This temperature is strictly limited to 10 to 20 degrees Celsius below the glass transition temperature of the chip's bottom filler material. The innovative significance of this preheating process lies in creating a thermal gradient buffer layer that runs through the thickness of the circuit board. Directly applying localized high-temperature heating to the circuit board at room temperature would create instantaneous temperature differences of up to several hundred degrees Celsius between the chip area and the surrounding substrate. The resulting thermal expansion mismatch stress could easily cause the initiation of interlayer microcracks or delamination failure at the interface between the solder pads and the substrate. By preheating the circuit board body temperature to a metastable range below the glass transition temperature of the underfill material, the thermal shock amplitude of the subsequent local heating stage is effectively reduced. This also avoids the underfill material from entering a highly elastic or even viscous flow state due to excessively high preheating temperature, thus losing its mechanical anchoring effect on the chip. This creates ideal thermodynamic conditions for the precise melting of solder bumps and the non-destructive removal of the chip.

[0028] Step S102: Locally heat the target chip to melt the solder bump array on the bottom of the target chip.

[0029] In a specific implementation, a localized hot air jet device is used to precisely control the temperature of the target chip, causing the bottom solder bump array to undergo a uniform phase transition. Once the overall circuit board temperature stabilizes at the preheating setpoint, the core heating module of the rework system is activated. Please refer to [link to relevant documentation]. Figure 2 , Figure 2 This is a flowchart illustrating the steps of a method for locally heating a target chip according to the present invention; the locally heating of the target chip includes: Step S1021: Position the hot air nozzle directly above the target chip to form a uniformly covered and clearly defined hot air surrounding area around the target chip.

[0030] This module uses a local hot air jet heating method, which precisely positions a hot air nozzle with a specific geometric configuration directly above the target chip. The inner diameter of the nozzle is adapted to the diagonal length or side length of the chip package to ensure that its inner diameter profile is 1 mm to 2 mm larger than the chip's outer dimensions, thereby forming a uniformly covered and clearly defined hot air surrounding area around the chip.

[0031] Step S1022: Based on the metallurgical properties of the solder alloy used in the original soldering of the target chip, the hot air temperature at the outlet of the hot air nozzle is preset to a second predetermined temperature, and the hot air volume flow rate is dynamically adjusted.

[0032] In an alternative embodiment, the second predetermined temperature is 20 to 40 degrees Celsius greater than the melting point of the solder alloy.

[0033] Based on the metallurgical properties of the solder alloy used for the original chip soldering, the system presets the hot air temperature at the nozzle outlet to the solder melting point plus a process overheating margin of 20 to 40 degrees Celsius. The hot air volume flow rate is dynamically adjusted within the range of 10 liters / minute to 30 liters / minute according to the chip size and heat capacity differences.

[0034] Step S1023: Start the heating program to steadily raise the surface temperature of the target chip to the peak welding temperature range at a controlled heating rate, and maintain the peak welding temperature level for a preset time.

[0035] After the heating program is initiated, the control system steadily raises the chip surface temperature to the peak soldering temperature range at a controlled heating rate of 2 to 5 degrees Celsius per second. This peak temperature is then maintained for a brief holding period of 10 to 30 seconds to ensure that all solder bumps on the bottom of the chip—including thermally hysteretic bumps in the central region and preferentially heated bumps at the edges—fully absorb latent heat and complete the phase transition from solid to liquid. Simultaneously, an infrared temperature sensor mounted on the off-axis of the heating head monitors the temperature change curve of the central region of the chip surface in real time using a non-contact method. When the monitored reading coincides with the preset peak temperature setpoint, the system automatically starts a holding timer to ensure that each solder bump receives sufficient and consistent melting energy input.

[0036] Step S103: While the solder bumps are molten, an upward lifting force is applied to the target chip to vertically remove the target chip from the circuit board.

[0037] In a specific implementation, the chip is removed vertically with low stress during the instantaneous window when the solder bumps are completely melted, using vacuum adsorption. Once the hold-up timer returns to zero, confirming that the solder bump array has reached a completely melted state, the chip pick-up mechanism of the rework system immediately intervenes to perform the removal operation. Please refer to [link to relevant documentation]. Figure 3 , Figure 3 This is a flowchart illustrating the steps of a method for vertically removing a target chip from a circuit board according to the present invention; the step of applying an upward lifting force to the target chip to vertically remove the target chip from the circuit board includes: Step S1031: Drive the vacuum nozzle to descend until the end face of the vacuum nozzle gently contacts the central area or edge non-functional area of ​​the upper surface of the target chip.

[0038] This can be understood as a vacuum nozzle with a matching inner diameter slowly descending under the drive of a precision servo motor until its end face gently contacts the central area or edge non-functional area of ​​the chip's upper surface.

[0039] Step S1032: Start the vacuum generator and establish a stable negative pressure environment in the inner cavity of the vacuum nozzle.

[0040] The vacuum generator then starts and establishes a stable negative pressure environment of -50 kPa to -80 kPa in the inner cavity of the suction nozzle. This negative pressure value has been precisely calibrated to be sufficient to overcome the adhesion force generated by the chip's own gravity and the surface tension of the molten solder, while being far below the critical stress threshold that may cause cracking in the thinned areas of the chip body.

[0041] Step S1033: Receive adsorption confirmation signal, and drive the vacuum nozzle to move upward in a direction perpendicular to the target chip at a preset constant speed to peel the chip off from the pad array.

[0042] Once the adsorption confirmation signal is established, the servo lifting axis drives the nozzle vertically upward at an extremely low constant speed of 0.1 mm to 0.5 mm per second, smoothly peeling the chip from the pad array. The innovation of this ultra-low-speed vertical lifting strategy lies in providing sufficient liquid flow relaxation time for the molten solder, allowing the solder to cohesively separate from the chip bump interface and the circuit board pad interface without being forcibly torn by mechanical force, thereby maximizing the protection of the geometric integrity of the circuit board side pads.

[0043] In one embodiment, while the chip rises to a safe height of 2 to 3 times its thickness, the system continuously monitors the negative pressure feedback signal in the vacuum circuit. If a sudden drop in adsorption force is detected, it is determined that adsorption has failed, and the rising process is immediately stopped to prevent the chip from accidentally falling and causing secondary damage. Successfully removed waste chips are then transferred to a dedicated waste collection box for centralized disposal.

[0044] Step S104: Clean the exposed pads on the circuit board to remove residual solder and underfill material residue.

[0045] In a specific implementation, a combined cleaning process is used on the exposed pads on the circuit board side to thoroughly remove residual solder, underfill residue, and surface oxides. After chip removal, the pad array on the circuit board surface inevitably retains excess solder of various shapes, fragments of semi-cured underfill material, and a thin film of metal oxide formed due to high-temperature exposure. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a flowchart illustrating the steps of a method for cleaning exposed pads on a circuit board according to the present invention; the cleaning of exposed pads on the circuit board includes: Step S1041: Lay the desoldering braid flat over the pad area and gently press the desoldering braid with a temperature-controlled soldering iron to absorb and transfer the residual solder alloy on the pad surface into the copper mesh of the desoldering braid using capillary adsorption effect.

[0046] The operator selects a suitable width of desoldering braided tape and lays it flat to cover the pad area. Using a temperature-controlled soldering iron, the operator gently presses the braided tape at a moderate temperature. The capillary effect is used to absorb and transfer most of the residual solder alloy on the pad surface into the copper mesh of the braided tape.

[0047] Step S1042: Immerse the circuit board partially in a special chemical cleaning agent, or apply the special chemical cleaning agent to the pad area using a precision spray valve, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening.

[0048] The circuit board is partially immersed in or a precision spray valve is used to apply a special chemical cleaning agent to the pad area. The cleaning agent formula is optimized for compatibility with the epoxy resin system of the underfill material and the characteristics of the anhydride curing agent. The immersion or wetting time is controlled between 1 and 3 minutes, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening.

[0049] Step S1043: After the special chemical cleaning agent has fully penetrated, use an antistatic brush to wipe the pad area and peel off the swollen and loosened underfill residue from the pad gaps and the surface of the solder resist layer.

[0050] Step S1044: Perform a second final cleaning of the pads using a lint-free cloth soaked in high-purity isopropyl alcohol to remove residual chemical cleaning agents and fine debris. Then, use clean compressed air to blow the surface of the pads until dry. This provides a clean interface with ideal solderability for subsequent new chip mounting.

[0051] Step S105: Apply flux to the cleaned pads and align the new chip with the pads.

[0052] In this specific implementation, precise flux application and high-precision chip alignment are performed before new chip mounting. After the pads are cleaned and dried, the new chip mounting preparation phase begins immediately. Please refer to [link to relevant documentation]. Figure 5 , Figure 5 This is a flowchart illustrating the steps of a method for aligning and placing a new chip with the pads according to the present invention; the step of applying flux to the cleaned pads and aligning and placing the new chip with the pads includes: Step S1051: Apply a preset amount of flux to the pad array area using a dip-type micro transfer head or a piezoelectric jet dispensing valve to form a flux film.

[0053] A uniform and complete flux film is formed within the pad array area using a dip-type micro-transfer head or a piezoelectric jet dispensing valve. The amount of flux applied is precisely metered and controlled to ensure sufficient oxide removal activity and promote solder wetting and spreading in the early stages of reflow soldering, while avoiding excessive application that could cause flux to boil and splash during reflow, contaminating the photosensitive areas of the chip or adjacent components.

[0054] Step S1052: Obtain the replacement chip, call the circuit board reference alignment mark coordinates and chip surface identification mark coordinates stored in the system database, and use the vision alignment system to calculate the position deviation and calibrate the spatial attitude to confirm whether the alignment accuracy meets the standard.

[0055] The placement equipment or high-precision manual placement tool picks up a brand-new, qualified Flip-chip bare chip from the tray, calls up the circuit board reference alignment mark coordinates and chip surface identification mark coordinates stored in the system database, and performs sub-micron level position deviation calculation and spatial attitude calibration through a beam splitter or dual-field vision alignment system.

[0056] Step S1053: After confirming that the alignment accuracy meets the standard, the placement head places the replacement chip on the pad array coated with flux, and ensures that the bottom bumps of the replacement chip and the circuit board pads form reliable physical contact and parallel alignment.

[0057] After confirming that the alignment accuracy meets the standard, the placement head uses a light contact force of 20 to 50 grams to place the new chip smoothly onto the pad array coated with flux, ensuring reliable physical contact and parallel alignment between the chip bottom bumps and the circuit board pads.

[0058] Step S1054: After placement, check the offset between the edge contour of the replacement chip and the edge of the corresponding pad pattern on the circuit board, and determine whether the offset exceeds the preset allowable range; if it exceeds the preset allowable range, repeat the above steps.

[0059] After placement, the offset between the four edge contours of the chip and the corresponding pad pattern edge on the circuit board is visually inspected using a high-magnification inspection microscope. This offset value must be strictly controlled within 10% of the pad design diameter. If it exceeds the tolerance, the chip must be picked up and re-aligned immediately.

[0060] Step S106: Reflow soldering is performed on the placed new chip, bottom filler is filled and then thermosetting is performed.

[0061] In a specific implementation, the process involves reflow soldering of the new chip, capillary filling of the underfill adhesive, and thermosetting. After the new chip is mounted and alignment accuracy is confirmed, the circuit board assembly is placed into the reflow oven chamber. Please refer to [link to relevant documentation]. Figure 6 , Figure 6 This is a flowchart illustrating the reflow soldering method for a newly placed chip according to the present invention; the reflow soldering of the placed new chip, including filling with underfill adhesive and thermal curing, comprises: Step S1061: Perform a fully automatic temperature control thermal process based on the standard temperature curve recommended in the datasheet of the replacement chip solder bump alloy, wherein the peak soldering temperature is a process overheat value of 20 to 30 degrees Celsius above the melting point of the solder alloy.

[0062] The reflow soldering equipment performs a fully automatic temperature-controlled thermal process according to the standard temperature profile recommended in the datasheet of the solder bump alloy for this chip model. The peak soldering temperature is precisely set to an additional 20 to 30 degrees Celsius above the melting point of the solder alloy, ensuring that all solder bumps can be fully melted and form a continuous and dense intermetallic compound metallurgical bonding layer with the circuit board pads and the metal layer under the chip bumps.

[0063] Step S1062: After the soldering process is completed, the circuit board is transferred out of the furnace and naturally cooled to room temperature in a clean environment.

[0064] Step S1063: After the component temperature has fully returned to normal, use a non-contact gap measuring instrument or feeler gauge to measure the actual support gap height between the bottom surface of the chip and the top surface of the circuit board.

[0065] Step S1064: Based on the gap height, select a special bottom filler adhesive compatible with the rework process. Use a precision dispensing needle to slowly inject adhesive along the adjacent two or one edge of the chip. Utilize the capillary effect generated by the tiny gap between the chip and the circuit board to drive the adhesive to automatically penetrate and flow from the chip edge to the center area of ​​the chip bottom until the adhesive overflows evenly from the remaining edges of the chip to form a complete encapsulation.

[0066] Step S1065: Transfer the circuit board to a precision oven for constant temperature thermal curing, so that the epoxy resin matrix inside the bottom filler adhesive can complete the full cross-linking reaction and establish a stable three-dimensional network structure, thereby achieving effective stress buffering and mechanical protection for the solder joint connection area between the replacement chip and the circuit board.

[0067] After the underfill is applied, the circuit board is transferred to a precision oven for constant temperature curing. The curing temperature is set between 150 and 165 degrees Celsius according to the underfill technical specifications, and the continuous heat treatment time is controlled between 30 and 60 minutes. This allows the epoxy resin matrix inside the underfill to complete the full cross-linking reaction and establish a stable three-dimensional network structure, ultimately achieving effective stress buffering and mechanical protection for the solder joint connection area between the chip and the circuit board.

[0068] The flip-chip replacement method provided in this embodiment has the following significant advantages compared with the prior art: 1) This embodiment employs a synergistic thermal control strategy of "overall preheating + localized precise heating". Overall preheating elevates the circuit board to a metastable temperature plateau, significantly reducing the thermal shock amplitude during localized heating and preventing interlayer delamination and thermal stress damage to surrounding components. Compared to existing whole-board heating methods, this method does not cause other solder joints to remelt; compared to manual hot air gun methods, this method achieves closed-loop temperature control, eliminating the risk of overheating.

[0069] 2) Each step in this embodiment employs precise and controllable process parameters, rather than relying on operational experience. For example, the "ultra-low speed vertical lift" strategy in the removal step provides relaxation time for the molten solder, greatly improving the pad integrity rate; the vision alignment system in the mounting step ensures sub-micron level alignment accuracy, meeting the rework requirements of fine-pitch chips. This makes the entire rework process standardized and repeatable, significantly improving the rework success rate.

[0070] 3) By using the vacuum nozzle for gentle contact adsorption, low constant speed vertical peeling, and a combination of non-destructive cleaning processes (chemical softening + soft brush, rather than scraping with hard tools), this invention maximizes the protection of sensitive pads and solder mask layers on the circuit board, preventing pad lifting, missing parts, or broken circuits.

[0071] 4) The new chip is precisely aligned and placed with controlled force. Reflow soldering and underfill curing are performed under optimized conditions to ensure the metallurgical quality of the new solder joints and the full cross-linking of the underfill. The final reworked product can approach the original factory level in terms of electrical performance and mechanical reliability.

[0072] 5) By achieving maintainability of high-value flip-chip components, this method significantly reduces the cost of scrapping an entire module due to the failure of a single chip. Simultaneously, the standardized and automated process reduces human error and material waste, demonstrating good economic benefits and application prospects.

[0073] Example 2 This embodiment provides a flip chip replacement device. Please refer to [link / reference]. Figure 7 , Figure 7 This is a structural block diagram of a second embodiment of the flip chip replacement device of the present invention. The flip chip replacement device is used to implement the method described in the first embodiment.

[0074] The replacement device comprises six core modules: a preheating module 10, a heating module 20, a removal module 30, a cleaning module 40, a placement module 50, and a soldering module 60. The preheating module 10 preheats the circuit board carrying the target chip to a predetermined temperature. The heating module 20 locally heats the target chip to melt the solder bump array on its underside. The removal module 30 applies an upward lifting force to the target chip while the solder bumps are melted, vertically removing it from the circuit board. The cleaning module 40 cleans the exposed pads on the circuit board to remove residual solder and underfill material. The placement module 50 applies flux to the cleaned pads and aligns the new chip with them. The soldering module 60 reflows the placed chip, fills it with underfill adhesive, and heat-cures it.

[0075] In a specific implementation, the preheating module 10 is also used to perform controllable preheating of the circuit board to be reworked, building a thermodynamic buffer for the subsequent chip removal process. Before starting the flip-chip bare chip rework operation, the circuit board assembly carrying the target chip to be reworked is first precisely fixed on the surface of a heating platform with precise temperature control capabilities. Vacuum adsorption or edge clamping mechanisms ensure that the circuit board maintains stable flatness and positional repeatability throughout the entire operation cycle. The heating platform then starts a preset low-temperature preheating program, raising the overall temperature of the circuit board to a safe critical range at a steady heating rate. This temperature value is strictly limited to 10 to 20 degrees Celsius below the glass transition temperature of the chip's bottom filler material. The ingenious significance of this preheating process lies in constructing a thermal gradient buffer layer that runs through the thickness direction of the circuit board. If the circuit board at room temperature is directly subjected to local high-temperature heating, an instantaneous temperature difference of up to several hundred degrees Celsius will be generated between the chip area and the surrounding substrate. The resulting thermal expansion mismatch stress can easily cause the initiation of interlayer microcracks in the circuit board or the delamination failure of the interface between the pads and the substrate. By preheating the circuit board body temperature to a metastable range below the glass transition temperature of the underfill material, the thermal shock amplitude of the subsequent local heating stage is effectively reduced. This also avoids the underfill material from entering a highly elastic or even viscous flow state due to excessively high preheating temperature, thus losing its mechanical anchoring effect on the chip. This creates ideal thermodynamic conditions for the precise melting of solder bumps and the non-destructive removal of the chip.

[0076] In a specific implementation, the heating module 20 includes: A moving unit is used to position the hot air nozzle directly above the target chip to form a uniformly covered and clearly defined hot air surrounding area around the target chip.

[0077] This module uses a local hot air jet heating method, which precisely positions a hot air nozzle with a specific geometric configuration directly above the target chip. The inner diameter of the nozzle is adapted to the diagonal length or side length of the chip package to ensure that its inner diameter profile is 1 mm to 2 mm larger than the chip's outer dimensions, thereby forming a uniformly covered and clearly defined hot air surrounding area around the chip.

[0078] The temperature setting unit is used to preset the hot air temperature at the hot air nozzle outlet to a second predetermined temperature based on the metallurgical properties of the solder alloy used in the original soldering of the target chip, while dynamically adjusting the hot air volume flow rate.

[0079] In an alternative embodiment, the second predetermined temperature is 20 to 40 degrees Celsius greater than the melting point of the solder alloy.

[0080] Based on the metallurgical properties of the solder alloy used for the original chip soldering, the system presets the hot air temperature at the nozzle outlet to the solder melting point plus a process overheating margin of 20 to 40 degrees Celsius. The hot air volume flow rate is dynamically adjusted within the range of 10 liters / minute to 30 liters / minute according to the chip size and heat capacity differences.

[0081] The heating unit is used to start the heating program to steadily raise the surface temperature of the target chip to the peak welding temperature range at a controlled heating rate, and maintain the peak welding temperature level for a preset time.

[0082] After the heating program is initiated, the control system steadily raises the chip surface temperature to the peak soldering temperature range at a controlled heating rate of 2 to 5 degrees Celsius per second. This peak temperature is then maintained for a brief holding period of 10 to 30 seconds to ensure that all solder bumps on the bottom of the chip—including thermally hysteretic bumps in the central region and preferentially heated bumps at the edges—fully absorb latent heat and complete the phase transition from solid to liquid. Simultaneously, an infrared temperature sensor mounted on the off-axis of the heating head monitors the temperature change curve of the central region of the chip surface in real time using a non-contact method. When the monitored reading coincides with the preset peak temperature setpoint, the system automatically starts a holding timer to ensure that each solder bump receives sufficient and consistent melting energy input.

[0083] In a specific implementation, the removal module 30 includes: The nozzle driving unit is used to drive the vacuum nozzle to descend until the end face of the vacuum nozzle gently contacts the central area or edge non-functional area of ​​the upper surface of the target chip.

[0084] This can be understood as a vacuum nozzle with a matching inner diameter slowly descending under the drive of a precision servo motor until its end face gently contacts the central area or edge non-functional area of ​​the chip's upper surface.

[0085] The negative pressure unit is used to start the vacuum generator and establish a stable negative pressure environment in the inner cavity of the vacuum nozzle.

[0086] The vacuum generator then starts and establishes a stable negative pressure environment of -50 kPa to -80 kPa in the inner cavity of the suction nozzle. This negative pressure value has been precisely calibrated to be sufficient to overcome the adhesion force generated by the chip's own gravity and the surface tension of the molten solder, while being far below the critical stress threshold that may cause cracking in the thinned areas of the chip body.

[0087] The stripping unit is used to receive an adsorption confirmation signal. The servo lifting axis drives the vacuum nozzle to move upward in a direction perpendicular to the target chip at a preset constant speed, so as to strip the chip from the pad array.

[0088] Once the adsorption confirmation signal is established, the servo lifting axis drives the nozzle vertically upward at an extremely low constant speed of 0.1 mm to 0.5 mm per second, smoothly peeling the chip from the pad array. The innovation of this ultra-low-speed vertical lifting strategy lies in providing sufficient liquid flow relaxation time for the molten solder, allowing the solder to cohesively separate from the chip bump interface and the circuit board pad interface without being forcibly torn by mechanical force, thereby maximizing the protection of the geometric integrity of the circuit board side pads.

[0089] In one embodiment, while the chip rises to a safe height of 2 to 3 times its thickness, the system continuously monitors the negative pressure feedback signal in the vacuum circuit. If a sudden drop in adsorption force is detected, it is determined that adsorption has failed, and the rising process is immediately stopped to prevent the chip from accidentally falling and causing secondary damage. Successfully removed waste chips are then transferred to a dedicated waste collection box for centralized disposal.

[0090] In a specific implementation, the cleaning module 40 includes: The residual removal unit is used to lay the desoldering braid flat over the pad area and use a temperature-controlled soldering iron to gently press the desoldering braid to absorb and transfer the residual solder alloy on the pad surface into the copper mesh of the desoldering braid using capillary adsorption effect.

[0091] The operator selects a suitable width of desoldering braided tape and lays it flat to cover the pad area. Using a temperature-controlled soldering iron, the operator gently presses the braided tape at a moderate temperature. The capillary effect is used to absorb and transfer most of the residual solder alloy on the pad surface into the copper mesh of the braided tape.

[0092] The cleaning unit is used to partially immerse the circuit board in a special chemical cleaning agent, or to apply a special chemical cleaning agent to the pad area using a precision spray valve, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening.

[0093] The circuit board is partially immersed in or a precision spray valve is used to apply a special chemical cleaning agent to the pad area. The cleaning agent formula is optimized for compatibility with the epoxy resin system of the underfill material and the characteristics of the anhydride curing agent. The immersion or wetting time is controlled between 1 and 3 minutes, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening.

[0094] The wiping unit is used to wipe the pad area with an antistatic brush after the special chemical cleaning agent has fully penetrated, so as to peel off the swollen and loosened underfill residue from the gap between the pads and the surface of the solder mask.

[0095] The cleaning and drying unit uses a lint-free cloth soaked in high-purity isopropyl alcohol to perform a secondary final cleaning of the pads, removing residual chemical cleaning agents and fine debris. Then, clean compressed air is used to blow the pad surface dry. This provides a clean interface with ideal solderability for subsequent chip mounting.

[0096] In a specific implementation, the placement module 50 includes: The coating unit is used to apply a preset amount of flux to the pad array area using a dip-type micro-transfer head or a piezoelectric jet dispensing valve to form a flux film.

[0097] A uniform and complete flux film is formed within the pad array area using a dip-type micro-transfer head or a piezoelectric jet dispensing valve. The amount of flux applied is precisely metered and controlled to ensure sufficient oxide removal activity and promote solder wetting and spreading in the early stages of reflow soldering, while avoiding excessive application that could cause flux to boil and splash during reflow, contaminating the photosensitive areas of the chip or adjacent components.

[0098] The alignment unit acquires the replacement chip, calls the circuit board reference alignment mark coordinates and chip surface identification mark coordinates stored in the system database, and performs position deviation calculation and spatial attitude calibration through the vision alignment system to confirm whether the alignment accuracy meets the standard.

[0099] The placement equipment or high-precision manual placement tool picks up a brand-new, qualified Flip-chip bare chip from the tray, calls up the circuit board reference alignment mark coordinates and chip surface identification mark coordinates stored in the system database, and performs sub-micron level position deviation calculation and spatial attitude calibration through a beam splitter or dual-field vision alignment system.

[0100] The alignment unit is used to place the replacement chip onto the flux-coated pad array after confirming that the alignment accuracy meets the standard, and to ensure that the bottom bumps of the replacement chip and the circuit board pads form reliable physical contact and parallel alignment.

[0101] After confirming that the alignment accuracy meets the standard, the placement head uses a light contact force of 20 to 50 grams to place the new chip smoothly onto the pad array coated with flux, ensuring reliable physical contact and parallel alignment between the chip bottom bumps and the circuit board pads.

[0102] After placement, the judgment unit checks the offset between the edge contour of the replacement chip and the edge of the corresponding pad pattern on the circuit board, and determines whether the offset exceeds a preset allowable range; if it exceeds the preset allowable range, the above steps are repeated.

[0103] After placement, the offset between the four edge contours of the chip and the corresponding pad pattern edge on the circuit board is visually inspected using a high-magnification inspection microscope. This offset value must be strictly controlled within 10% of the pad design diameter. If it exceeds the tolerance, the chip must be picked up and re-aligned immediately.

[0104] In a specific implementation, the welding module 60 includes: The temperature control unit is used to perform a fully automatic temperature control thermal process based on the standard temperature profile recommended in the datasheet of the replacement chip solder bump alloy, wherein the peak soldering temperature is a process overheat value of 20 to 30 degrees Celsius above the melting point of the solder alloy.

[0105] The reflow soldering equipment performs a fully automatic temperature-controlled thermal process according to the standard temperature profile recommended in the datasheet of the solder bump alloy for this chip model. The peak soldering temperature is precisely set to an additional 20 to 30 degrees Celsius above the melting point of the solder alloy, ensuring that all solder bumps can be fully melted and form a continuous and dense intermetallic compound metallurgical bonding layer with the circuit board pads and the metal layer under the chip bumps.

[0106] The cooling unit is used to transfer the circuit board out of the furnace after the welding process is completed and allow it to cool naturally to room temperature in a clean environment.

[0107] After the component temperature has fully returned to normal, the measuring unit uses a non-contact gap measuring instrument or feeler gauge to measure the actual support gap height between the bottom surface of the chip and the top surface of the circuit board.

[0108] The dispensing unit is used to select a special underfill adhesive compatible with the rework process based on the gap height. It uses a precision dispensing needle to slowly dispense adhesive along the adjacent two or one edge of the chip. Utilizing the capillary effect generated by the tiny gap between the chip and the circuit board, the adhesive is driven to automatically penetrate and flow from the chip edge to the center area of ​​the chip bottom until the adhesive overflows evenly from the remaining edges of the chip to form a complete encapsulation.

[0109] The curing unit transfers the circuit board to a precision oven for constant-temperature thermal curing, allowing the epoxy resin matrix inside the bottom filler to complete a full cross-linking reaction and establish a stable three-dimensional network structure, thereby achieving effective stress buffering and mechanical protection for the solder joint connection area between the replacement chip and the circuit board.

[0110] After the underfill is applied, the circuit board is transferred to a precision oven for constant temperature curing. The curing temperature is set between 150 and 165 degrees Celsius according to the underfill technical specifications, and the continuous heat treatment time is controlled between 30 and 60 minutes. This allows the epoxy resin matrix inside the underfill to complete the full cross-linking reaction and establish a stable three-dimensional network structure, ultimately achieving effective stress buffering and mechanical protection for the solder joint connection area between the chip and the circuit board.

[0111] Example 3 This invention also provides an electronic device, including a memory and a processor. The memory stores a computer program, and when the computer program is executed by the processor, the processor performs the steps of a flip chip replacement method according to any embodiment.

[0112] Example 4 This invention also provides a computer storage medium storing a computer program thereon, wherein the computer program, when executed by the processor, implements the steps of a flip chip replacement method according to any embodiment.

[0113] Example 5 This invention also provides a computer program product having a computer program stored thereon, wherein the computer program, when executed by the processor, implements the steps of a flip chip replacement method according to any embodiment.

[0114] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0115] In the several embodiments provided in this application, it should be understood that the methods, apparatuses, electronic devices, and storage media disclosed in this invention can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0116] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0117] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0118] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a readable storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned readable storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0119] The above-described 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for replacing a flip chip, characterized in that, include: The circuit board carrying the target chip is preheated as a whole until the temperature of the circuit board reaches the first predetermined temperature. The target chip is locally heated to melt the solder bump array on the bottom of the target chip; While the solder bumps are molten, an upward lifting force is applied to the target chip to vertically remove the target chip from the circuit board. Clean the exposed pads on the circuit board to remove residual solder and underfill material residue; Apply flux to the cleaned pads and align the new chip with the pads; The placed new chip is reflow soldered, filled with underfill adhesive, and then thermoset.

2. The flip chip replacement method according to claim 1, characterized in that, The first predetermined temperature is 10 to 20 degrees Celsius lower than the glass transition temperature of the filler material at the bottom of the chip.

3. The flip chip replacement method according to claim 1, characterized in that, The local heating of the target chip includes: Position the hot air nozzle directly above the target chip to form a uniformly covered and clearly defined hot air surrounding area around the target chip. Based on the metallurgical properties of the solder alloy used in the original soldering of the target chip, the hot air temperature at the outlet of the hot air nozzle is preset to a second predetermined temperature, while the hot air volume flow rate is dynamically adjusted. The heating program is started to steadily raise the surface temperature of the target chip to the peak soldering temperature range at a controlled heating rate, and maintain the peak soldering temperature level for a preset time.

4. The flip chip replacement method according to claim 3, characterized in that, The second predetermined temperature is 20 to 40 degrees Celsius higher than the melting point of the solder alloy.

5. The flip chip replacement method according to claim 1, characterized in that, Applying an upward lifting force to the target chip to vertically remove the target chip from the circuit board includes: Drive the vacuum nozzle to descend until the end face of the vacuum nozzle contacts the central region or edge non-functional area of ​​the upper surface of the target chip; Start the vacuum generator and establish a stable negative pressure environment inside the vacuum nozzle; Upon receiving an adsorption confirmation signal, the vacuum nozzle is driven to move upward in a direction perpendicular to the target chip at a preset constant speed to peel the chip off from the pad array.

6. The flip chip replacement method according to claim 1, characterized in that, The cleaning of exposed pads on the circuit board includes: Lay the desoldering braid flat over the pad area and gently press the desoldering braid with a temperature-controlled soldering iron to absorb and transfer the residual solder alloy on the pad surface into the copper mesh of the desoldering braid using capillary adsorption effect. Immerse the circuit board partially in a specialized chemical cleaning agent, or apply the specialized chemical cleaning agent to the pad area using a precision spray valve, so that the cross-linked and cured underfill residue undergoes controlled swelling and softening. After the special chemical cleaning agent has fully penetrated, use an antistatic brush to wipe the pad area and peel off the swollen and loosened underfill residue from the pad gaps and the surface of the solder mask. Use a lint-free wiping cloth soaked in isopropyl alcohol to perform a second cleaning of the pads, removing any residual chemical cleaning agent and fine debris, and then use a clean compressed air stream to blow the surface of the pads until they are dry.

7. The flip chip replacement method according to claim 1, characterized in that, The step of applying flux to the cleaned pads and aligning the new chip with the pads includes: A pre-measured amount of flux is applied to the pad array area using a dip-type micro-transfer head or a piezoelectric jet dispensing valve to form a flux film. The replacement chip is obtained, and the coordinates of the circuit board reference alignment mark and the chip surface identification mark stored in the system database are called. The position deviation is calculated and the spatial attitude is calibrated by the vision alignment system to confirm whether the alignment accuracy meets the standard. After confirming that the alignment accuracy meets the standard, the placement head places the replacement chip on the pad array coated with flux, and ensures that the bottom bumps of the replacement chip and the circuit board pads form reliable physical contact and parallel alignment. After placement, check the offset between the edge contour of the replacement chip and the edge of the corresponding pad pattern on the circuit board, and determine whether the offset exceeds the preset allowable range; If the preset allowable range is exceeded, repeat the above steps.

8. The flip chip replacement method according to claim 1, characterized in that, The process of reflow soldering the placed new chip, filling the underfill adhesive, and heat curing includes: The entire automatic temperature control thermal process is performed based on the standard temperature profile recommended in the datasheet of the replacement chip solder bump alloy, wherein the peak soldering temperature is a process overheat value of 20 to 30 degrees Celsius above the melting point of the solder alloy. After the soldering process is completed, the circuit board is transferred out of the furnace and allowed to cool naturally to room temperature in a clean environment; After the component temperature has fully returned to normal, use a non-contact gap measuring instrument or feeler gauge to measure the actual support gap height between the bottom surface of the chip and the top surface of the circuit board. Based on the aforementioned gap height, a dedicated bottom filler adhesive compatible with the rework process is selected. A precision dispensing needle is used to slowly inject adhesive along the adjacent two or one edge of the chip. The capillary effect generated by the tiny gap between the chip and the circuit board is used to drive the adhesive to automatically penetrate and flow from the chip edge to the center area of ​​the chip bottom until the adhesive overflows evenly from the remaining edges of the chip to form a complete encapsulation. The circuit board is transferred to a precision oven for constant temperature thermal curing, which allows the epoxy resin matrix inside the bottom filler to complete the cross-linking reaction and establish a stable three-dimensional network structure, thereby achieving effective stress buffering and mechanical protection for the solder joint connection area between the replacement chip and the circuit board.

9. A flip chip replacement device, characterized in that, include: The preheating module is used to preheat the circuit board carrying the target chip as a whole, so that the temperature of the circuit board reaches the first predetermined temperature. A heating module is used to locally heat the target chip to melt the solder bump array on the bottom of the target chip; The removal module is used to apply an upward lifting force to the target chip while the solder bumps are molten, so as to vertically remove the target chip from the circuit board. The cleaning module is used to clean the exposed pads on the circuit board to remove residual solder and underfill material residue; A placement module is used to apply flux to the cleaned pads and align and place the new chip with the pads; The soldering module is used to reflow solder the placed new chips, fill the underfill adhesive, and perform heat curing.

10. An electronic device, characterized in that, It includes a processor and a memory, the memory storing computer-readable instructions that, when executed by the processor, perform the method as described in any one of claims 1-8.

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