CN117542945B - Bonding method of flip MICRO LED chip and substrate - Google Patents
Bonding method of flip MICRO LED chip and substrate Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/48—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor body packages
- H01L33/62—Arrangements for conducting electric current to or from the semiconductor body, e.g. lead-frames, wire-bonds or solder balls
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
- H01L24/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
- H01L24/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
- H01L2224/80—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected
- H01L2224/85—Methods for connecting semiconductor or other solid state bodies using means for bonding being attached to, or being formed on, the surface to be connected using a wire connector
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Abstract
The invention discloses a bonding method of flip MICRO LED chips and a substrate, which comprises the following steps: establishing a three-dimensional entity model and a finite element model of the bonding head, performing model analysis, and determining characteristic parameters of the bonding head; determining a weak part of the bonding head and optimizing the structural mechanical characteristics of the weak part based on the characteristic parameters of the bonding head; the flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, and then gold wire bonding is performed on the flip-chip MICRO LED chip placed on the substrate. Preliminary bonding is carried out based on an optimized bonding head, so that larger deformation and/or residual vibration generated under the action of impact load and periodic excitation force is reduced, bonding precision of chips is improved, gold wire bonding is carried out on flip MICRO LED chips placed on a substrate, bonding precision is further improved, and reliable connection is realized.
Description
Technical Field
The invention relates to the technical field of chip bonding, in particular to a bonding method of a flip MICRO LED chip and a substrate.
Background
Currently, microLED display technology is widely focused on due to the advantages of high response speed, low power consumption, long lifetime, high luminous efficiency and the like, and is considered as the next generation display technology following an LCD. MicroLED the technology requires bonding MicroLED chips on a substrate for electrical connection, thereby realizing drive control.
In the prior art, bonding of a MICRO LED chip and a substrate is performed through a bonding head, for example, chinese patent application with publication number CN107134427a and publication date 2017, 09, 05, and name of "chip bonding device and method" provides a chip bonding device, which comprises a carrier table, a bonding head structure and a bonding table, and the existing flip chip bonding process comprises the steps of providing a plurality of chips and substrates to be bonded, wherein the chips comprise device surfaces; then, placing a plurality of chips on a bearing table in a mode that devices face upwards, and grabbing the chips by utilizing a grabbing and overturning structure and overturning; and then, the chips are handed over to the bonding head structure through the handing-over structure, the bonding head structure adsorbs a plurality of chips through the chip bearing assembly, when the chips are moved to the upper part of the substrate positioned on the bonding table by the bonding head structure, the alignment marks of the chips and the alignment marks of the substrate are aligned through the CCD image sensor, and finally, the chips on the bonding head structure are bonded to the substrate at one time.
The technical problems existing in the prior art are as follows: when the MICRO LED chip is packaged in a flip-chip manner, the bonding head often generates larger deformation and/or residual vibration under the action of impact load and periodic excitation force due to insufficient structural rigidity, and the bonding precision of the chip is directly affected.
Disclosure of Invention
The present invention aims to solve, at least to some extent, one of the technical problems in the above-described technology. Therefore, the invention aims to provide a bonding method for flip-chip MICRO LED chips and a substrate, which improves the bonding precision of the MICRO LED chips.
To achieve the above objective, an embodiment of the present invention provides a bonding method of a flip-chip MICRO LED chip and a substrate, including:
Establishing a three-dimensional entity model and a finite element model of the bonding head, performing model analysis, and determining characteristic parameters of the bonding head;
Determining a weak part of the bonding head and optimizing the structural mechanical characteristics of the weak part based on the characteristic parameters of the bonding head;
The flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, and then gold wire bonding is performed on the flip-chip MICRO LED chip placed on the substrate.
According to some embodiments of the present invention, a three-dimensional solid model and a finite element model of a bond head are established, and model analysis is performed to determine characteristic parameters of the bond head, including:
Acquiring the bonding process characteristics of the flip chip and the overall entity structure of the bonding head, and establishing a three-dimensional entity model of the bonding head;
setting a bonding head finite element simplification principle, and establishing a finite element model of the bonding head;
For the three-dimensional solid model and the finite element model, the static deformation of the bonding head under the static load effect and the dynamic deformation of the bonding head under the dynamic load effect are calculated through the model analysis, the first constraint mode characteristics of the bonding head provided with the pick-up head component under the braking and non-braking working conditions are analyzed, and the second constraint mode characteristics of the bonding head not provided with the pick-up head component under the braking and non-braking working conditions are analyzed;
And determining characteristic parameters of the bonding head according to the static deformation, the dynamic deformation, the first constraint mode characteristics and the second constraint mode characteristics.
According to some embodiments of the invention, optimizing structural mechanical properties of the weakpoint component comprises:
The design parameters based on sensitivity analysis are preferably optimized by an optimization method combining the optimal solution extraction based on analytic hierarchy process to optimize the structural mechanical characteristics of the weak component.
According to some embodiments of the present invention, gold wire bonding a flip-chip MICRO LED chip placed on a substrate includes:
implanting gold balls at the PAD position of the flip-chip MICRO LED chip based on the first gold wires;
and (5) connecting the gold ball with the gold finger of the substrate based on the second gold wire to finish gold wire bonding.
According to some embodiments of the invention, the gold finger of the substrate and the gold ball are connected by a second gold wire, which is one of gold wire ball bonding, ultrasonic wedge bonding, thermocompression bonding, and thermosonic bonding.
According to some embodiments of the invention, the bonding mode of the second gold wire to the gold ball is ball bonding.
According to some embodiments of the invention, before the flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, further comprising:
Detecting a first thickness of the flip-chip MICRO LED chip and a second thickness of the substrate;
Acquiring attribute information of the flip MICRO LED chip, inquiring a preset data table, and determining a first preset distance between the upper surface of the flip MICRO LED chip and the lower surface of the substrate and a second preset distance between the lower surface of the flip MICRO LED chip and the upper surface of the substrate;
according to the first preset distance, the first thickness and the second thickness, calculating to obtain the actual distance between the flip MICRO LED chip and the substrate;
And judging whether the actual distance is consistent with the second preset distance, and moving a bonding head for placing the flip MICRO LED chip to enable the actual distance to be consistent with the second preset distance when the actual distance is inconsistent with the second preset distance.
According to some embodiments of the invention, detecting a first thickness of a flip-chip MICRO LED chip includes:
Generating a ranging signal for flip-chip MICRO LED chips;
Transmitting laser according to the ranging signal;
Performing phase modulation on laser based on a phase modulator to generate positive and negative frequency sidebands, and generating a target optical signal related to the free spectral range of an optical filter after the modulated laser signal passes through the optical filter;
Measuring a time difference between the emission and return of the target optical signal; and determining the first thickness of the flip-chip MICRO LED chip according to the time difference and the light speed information.
According to some embodiments of the invention, before the flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, further comprising:
Acquiring a scene image of the upper surface of the substrate;
preprocessing the scene image to obtain a preprocessed image;
Processing the preprocessed image based on a Gaussian Laplace function with 0 as a center and a Gaussian standard deviation sigma, determining discrete points and removing the discrete points to obtain a target image;
carrying out graying treatment and region division on the target image, and determining a plurality of local regions;
Determining the absolute value of the difference value between the gray value of each pixel point in each local area and the gray value of each adjacent pixel point, taking the maximum absolute value as the flat value of the corresponding pixel point, and judging whether the maximum absolute value is in a preset flat value range;
Calculating the ratio of the number of pixel points with the flat value not in the preset flat value range in each local area to the total pixel points in the local area, and judging whether the ratio is larger than the preset ratio;
and when the determined ratio is larger than the preset ratio, determining the corresponding local area as the area to be processed, and carrying out planarization processing on the area to be processed.
According to some embodiments of the invention, the preprocessing includes image noise reduction and image enhancement processing.
The invention provides a bonding method of a flip MICRO LED chip and a substrate, which is based on a three-dimensional entity model and a finite element model of a bonding head, and performs model analysis to determine characteristic parameters of the bonding head; determining a weak part of the bonding head and optimizing the structural mechanical characteristics of the weak part based on the characteristic parameters of the bonding head; preliminary bonding is carried out based on an optimized bonding head, so that larger deformation and/or residual vibration generated under the action of impact load and periodic excitation force is reduced, bonding precision of chips is improved, gold wire bonding is carried out on flip MICRO LED chips placed on a substrate, bonding precision is further improved, and reliable connection is realized.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and drawings.
The technical scheme of the invention is further described in detail through the drawings and the embodiments.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
Fig. 1 is a flow chart of a method of bonding a flip-chip MICRO LED chip to a substrate according to one embodiment of the present invention;
FIG. 2 is a flow chart of determining characteristic parameters of a bond head in accordance with one embodiment of the present invention;
fig. 3 is a flow chart of gold wire bonding a flip-chip MICRO LED chip placed on a substrate according to one embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, it being understood that the preferred embodiments described herein are for illustration and explanation of the present invention only, and are not intended to limit the present invention.
As shown in fig. 1, an embodiment of the present invention provides a bonding method of flip-chip MICRO LED chip and substrate, comprising steps S1-S3:
S1, establishing a three-dimensional entity model and a finite element model of a bonding head, and carrying out model analysis to determine characteristic parameters of the bonding head;
s2, determining a weak part of the bonding head based on characteristic parameters of the bonding head and optimizing structural mechanical properties of the weak part;
s3, fixing the flip-chip MICRO LED chip on the substrate based on the optimized bonding head, and performing gold wire bonding on the flip-chip MICRO LED chip placed on the substrate.
The working principle of the technical scheme is as follows: in this embodiment, the characteristic parameters include a static deformation of the bond head under a static load, a dynamic deformation of the bond head under a dynamic load, a first constraint mode characteristic of the bond head with the pick-up head assembly installed under braking and non-braking conditions, a second constraint mode characteristic of the bond head without the pick-up head assembly installed under braking and non-braking conditions, and the like.
In this embodiment, the weak part of the bond head is determined based on the characteristic parameters of the bond head, and the part that most affects the bond head to generate larger deformation and/or residual vibration under various working conditions is determined as the weak part. And the structural mechanical property of the weak part is optimized, so that the integral mechanical property of the bonding head is improved.
In the embodiment, the flip MICRO LED chip is fixed on the substrate based on the optimized bonding head, and preliminary bonding is performed based on the optimized bonding head, so that larger deformation and/or residual vibration generated under the action of impact load and periodic exciting force are reduced, and the bonding precision of the chip is improved.
In the embodiment, gold wire bonding is performed on the flip-chip MICRO LED chip placed on the substrate, so that bonding precision is further improved, bonding technology can be guaranteed, connection stability is guaranteed, circuit signals on the chip can be transmitted to pins of the substrate, connection quality is improved, and packaging reliability is improved.
The beneficial effects of the technical scheme are that: based on a three-dimensional entity model and a finite element model of the bonding head, carrying out model analysis, and determining characteristic parameters of the bonding head; determining a weak part of the bonding head and optimizing the structural mechanical characteristics of the weak part based on the characteristic parameters of the bonding head; preliminary bonding is carried out based on an optimized bonding head, so that larger deformation and/or residual vibration generated under the action of impact load and periodic excitation force is reduced, bonding precision of chips is improved, gold wire bonding is carried out on flip MICRO LED chips placed on a substrate, bonding precision is further improved, and reliable connection is realized.
As shown in fig. 2, according to some embodiments of the present invention, a three-dimensional solid model and a finite element model of a bond head are established, and model analysis is performed to determine characteristic parameters of the bond head, including steps S11-S14:
S11, acquiring the bonding process characteristics of the flip chip and the overall entity structure of the bonding head, and establishing a three-dimensional entity model of the bonding head;
s12, setting a bonding head finite element simplification principle, and establishing a finite element model of the bonding head;
S13, analyzing the static and dynamic structural mechanical properties of the bonding head through the three-dimensional solid model and the finite element model, calculating the static deformation of the bonding head under the static load, the dynamic deformation under the dynamic load, analyzing the first constraint modal properties of the bonding head provided with the pick-up head component under the braking and non-braking working conditions, and analyzing the second constraint modal properties of the bonding head not provided with the pick-up head component under the braking and non-braking working conditions;
s14, determining characteristic parameters of the bonding head according to the static deformation, the dynamic deformation, the first constraint mode characteristics and the second constraint mode characteristics.
The technical scheme has the working principle and beneficial effects that: the constrained modal characteristics (Constrained Modal Characteristics) are typically related to structural dynamics and engineering vibration analysis. In the case of unconstrained free vibration, the structure will exhibit a range of natural frequencies and corresponding modal shapes. In constrained modal analysis, the structure is constrained to vibrate at certain boundaries or constraints, which may affect or change its natural frequency and modal shape. Constrained modality analysis is mainly used in several cases: the vibration characteristics of the structure under certain constraints are determined. For example, if the structure is fixed at both ends, then its vibration characteristics will be different from the unconstrained free vibration characteristics. The vibrational response of the structure under certain constraints is predicted during the design process. In structural optimization, the constraint mode characteristics can be used as objective functions or constraint conditions. Constrained modal property analysis is typically calculated using a Finite Element Method (FEM), finite Difference Method (FDM), or other numerical method. These methods are capable of handling complex boundary conditions and nonlinear dynamics.
In the embodiment, when the three-dimensional entity model of the bonding head is built, not only the overall entity structure of the bonding head but also the characteristics of the flip chip bonding process are considered, so that the accuracy of building the three-dimensional entity model of the bonding head is improved. And setting a bonding head finite element simplification principle, and establishing a finite element model of the bonding head, so that analysis of relevant parameters is facilitated. In the embodiment, for a three-dimensional solid model and a finite element model, static and dynamic structural mechanical properties of a bonding head are analyzed through the models, including data acquisition under various working condition scenes, including calculation of static deformation of the bonding head under the action of static load, dynamic deformation under the action of dynamic load, analysis of first constraint modal properties of the bonding head provided with a pick-up head assembly under braking and non-braking working conditions, and analysis of second constraint modal properties of the bonding head provided with no pick-up head assembly under braking and non-braking working conditions; comprehensive and accurate model analysis is realized comprehensively, so that the static and dynamic structural mechanical characteristics of the bonding head can be accurately determined, and further, the accurate characteristic parameters of the bonding head can be determined.
According to some embodiments of the invention, optimizing structural mechanical properties of the weakpoint component comprises:
The design parameters based on sensitivity analysis are preferably optimized by an optimization method combining the optimal solution extraction based on analytic hierarchy process to optimize the structural mechanical characteristics of the weak component.
The technical scheme has the working principle and beneficial effects that: the structural mechanical characteristics of the weak component are optimized by combining sensitivity analysis and analytic hierarchy process, key design parameters can be effectively determined, and the optimal solution is extracted to improve the performance of the component. The steps can be as follows: determining an objective function: first, it is necessary to specify the goals of weak component optimization. This may be a characteristic such as maximum strength, minimum compliance, minimum weight, etc. The objective function may be defined based on these criteria. Selecting design variables: there are many parameters that can affect the performance of the component during the design process. By sensitivity analysis it can be determined which parameters have the most pronounced effect on the objective function. These parameters become design variables. And (3) constructing a model: finite Element Analysis (FEA) or other numerical modeling methods are used to build models to predict the effect of design variables on the objective function. Converting the physical problem into a mathematical problem. Sensitivity analysis: sensitivity analysis is used to evaluate the extent of influence of each design variable on the objective function. By differentiating the model or using special software tools. Hierarchical analysis: based on the results of the sensitivity analysis, the design variables are separated into different layers. The most important variable is at the top layer, the next most important variable is at the next layer, and so on. Optimizing: at each level, an optimization algorithm (e.g., genetic algorithm, particle swarm optimization, etc.) is used to find the optimal solution. This is to take the variables of each layer into account simultaneously, looking for a combination of variables that will bring the objective function to an optimal value. Evaluation and feedback: after finding the optimal solution for each level, the solution is evaluated. This includes checking whether the solution meets certain constraints (e.g., feasibility, economy, etc.), and comparing the optimal solutions at different levels to determine an overall optimal solution. And finally, feeding back the optimal solution to the original problem, and performing a new round of optimization. The optimization method combining design parameter optimization based on sensitivity analysis and optimal solution extraction based on analytic hierarchy process is convenient for realizing accurate and rapid optimization of structural mechanical characteristics of the weak component.
As shown in fig. 3, according to some embodiments of the present invention, gold wire bonding is performed on a flip-chip MICRO LED chip placed on a substrate, including steps S31-S32:
s31, implanting gold balls at the PAD position of the flip MICRO LED chip based on the first gold wires;
s32, connecting the gold ball based on the second gold wire and completing gold wire bonding by the gold finger of the substrate.
The working principle of the technical scheme is as follows: in this embodiment, the specification of first gold thread is unanimous with the second gold thread, is 4N gold thread, because the resistivity of 4N gold thread is little, is convenient for realize the high-efficient transmission of signal. One end of the second gold wire is fixed on the gold ball, and the other end of the second gold wire is fixed on the gold finger of the substrate for connection.
The beneficial effects of the technical scheme are that: and one end of the second gold wire is fixed on the gold ball, so that the problem of growth of metal compounds is avoided, gold wire bonding is completed based on the gold finger of the second gold wire connected with the gold ball and the substrate, bonding precision is further improved, and meanwhile, signal transmission is performed based on the second gold wire, so that high efficiency and reliability of signal transmission are realized.
According to some embodiments of the invention, the gold finger of the substrate and the gold ball are connected by a second gold wire, which is one of gold wire ball bonding, ultrasonic wedge bonding, thermocompression bonding, and thermosonic bonding.
The beneficial effects of the technical scheme are that: the second gold wire is convenient to realize stable connection with the gold ball and the gold finger of the substrate, and the reliability is improved.
According to some embodiments of the invention, the bonding mode of the second gold wire to the gold ball is ball bonding.
The beneficial effects of the technical scheme are that: and stable and accurate bonding is facilitated.
According to some embodiments of the invention, before the flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, further comprising:
Detecting a first thickness of the flip-chip MICRO LED chip and a second thickness of the substrate;
Acquiring attribute information of the flip MICRO LED chip, inquiring a preset data table, and determining a first preset distance between the upper surface of the flip M ICRO LED chip and the lower surface of the substrate and a second preset distance between the lower surface of the flip M ICRO LED chip and the upper surface of the substrate;
Calculating to obtain the actual distance between the flip M ICRO LED chip and the substrate according to the first preset distance, the first thickness and the second thickness;
And judging whether the actual distance is consistent with the second preset distance, and moving a bonding head for placing the flip MI CRO LED chip to enable the actual distance to be consistent with the second preset distance when the actual distance is inconsistent with the second preset distance.
The working principle of the technical scheme is as follows: in this embodiment, the attribute information includes the shape, size, etc. of the flip-chip MICRO LED chip. The preset data table is a corresponding table of preset attribute information, namely a first preset distance and a second preset distance, and is used as a bonding process parameter table.
In this embodiment, the actual distance is a value obtained by subtracting the first thickness and the second thickness from the first preset distance.
The beneficial effects of the technical scheme are that: judging whether the actual distance is consistent with the second preset distance, and moving a bonding head for placing the flip-chip MICRO LED chip to enable the actual distance to be consistent with the second preset distance when the actual distance is inconsistent with the second preset distance, so that the fact that the thickness of the MICRO LED chip and the thickness of the substrate are inconsistent with the corresponding preset thickness due to the influence of the process for manufacturing the MICRO LED chip and the substrate is eliminated, and deviation occurs in the bonding process. Deformation amount of the flip-chip MICRO LED chip and the substrate when being bonded is consistent with preset deformation amount, so that good electrical connectivity between the flip-chip MICRO LED chip and the substrate is ensured, and the signal transmission rate is ensured.
According to some embodiments of the invention, detecting a first thickness of a flip-chip MICRO LED chip includes:
Generating a ranging signal for flip-chip MICRO LED chips;
Transmitting laser according to the ranging signal;
Performing phase modulation on laser based on a phase modulator to generate positive and negative frequency sidebands, and generating a target optical signal related to the free spectral range of an optical filter after the modulated laser signal passes through the optical filter;
Measuring a time difference between the emission and return of the target optical signal; and determining the first thickness of the flip-chip MICRO LED chip according to the time difference and the light speed information.
The technical scheme has the working principle and beneficial effects that: in the embodiment, the laser is subjected to phase modulation based on a phase modulator to generate positive and negative frequency sidebands, and the modulated laser signal passes through an optical filter to generate a target optical signal related to the free spectral range of the optical filter; the method is convenient for realizing filtering, eliminating irrelevant signals, obtaining stable and consistent target optical signals and realizing unification of the signals. Measuring a time difference between the emission and return of the target optical signal; and determining the first thickness of the flip-chip MICRO LED chip according to the time difference and the light speed information. The first thickness of the flip-chip MICRO LED chip is conveniently and accurately calculated.
In an embodiment, the principle of detecting the second thickness of the substrate is consistent with the principle of detecting the first thickness of the flip-chip MICRO LED chip, and will not be described herein.
According to some embodiments of the invention, before the flip-chip MICRO LED chip is fixed on the substrate based on the optimized bonding head, further comprising:
Acquiring a scene image of the upper surface of the substrate;
preprocessing the scene image to obtain a preprocessed image;
Processing the preprocessed image based on a Gaussian Laplace function with 0 as a center and a Gaussian standard deviation sigma, determining discrete points and removing the discrete points to obtain a target image;
carrying out graying treatment and region division on the target image, and determining a plurality of local regions;
Determining the absolute value of the difference value between the gray value of each pixel point in each local area and the gray value of each adjacent pixel point, taking the maximum absolute value as the flat value of the corresponding pixel point, and judging whether the maximum absolute value is in a preset flat value range;
Calculating the ratio of the number of pixel points with the flat value not in the preset flat value range in each local area to the total pixel points in the local area, and judging whether the ratio is larger than the preset ratio;
and when the determined ratio is larger than the preset ratio, determining the corresponding local area as the area to be processed, and carrying out planarization processing on the area to be processed.
The working principle of the technical scheme is as follows: in this embodiment, prior to affixing the flip-chip MICRO LED chip on the substrate based on the optimized bond head, further comprising acquiring an image of the scene of the upper surface of the substrate; preprocessing the scene image to obtain a preprocessed image; the method is convenient for acquiring accurate images, eliminating the influence of noise and improving the accuracy of image processing.
In this embodiment, processing the preprocessed image based on a laplacian gaussian function centered on 0 and having a standard deviation of gaussian sigma, determining discrete points and removing, to obtain a target image, includes:
Wherein LoG (x, y) is a laplace gaussian function; x and y are coordinates of pixel points in the preprocessed image, sigma represents standard deviation, pi represents circumference ratio, and e represents natural constant.
The area with the intensity changed rapidly in the image can be highlighted based on the Gaussian Laplace function, so that discrete points are determined accurately, the influence of noise pixel points is eliminated, a target image is obtained, and whether the noise pixel points are flat or not is detected conveniently.
In the embodiment, the target image is subjected to graying treatment and region division, and a plurality of local regions are determined; determining the absolute value of the difference value between the gray value of each pixel point in each local area and the gray value of each adjacent pixel point, taking the maximum absolute value as the flat value of the corresponding pixel point, and judging whether the maximum absolute value is in a preset flat value range; calculating the ratio of the number of pixel points with the flat value not in the preset flat value range in each local area to the total pixel points in the local area, and judging whether the ratio is larger than the preset ratio; and when the determined ratio is larger than the preset ratio, determining the corresponding local area as the area to be processed, and carrying out planarization processing on the area to be processed. The method is convenient for accurately determining the area to be processed, namely the non-flat area, and carrying out planarization on the area to be processed, so that the planarization on all areas is avoided, and the speed and pertinence of the planarization are improved.
The beneficial effects of the technical scheme are that: the planarization treatment is carried out on the region to be treated, the planarization treatment is avoided on all the regions, the speed and pertinence of the planarization treatment are improved, and the bonding accuracy is improved when the flip MICRO LED chip is fixed on the substrate based on the optimized bonding head.
According to some embodiments of the invention, the preprocessing includes image noise reduction and image enhancement processing.
The beneficial effects of the technical scheme are that: image noise reduction and image enhancement are realized, and the accuracy of the image is ensured.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (9)
1. A bonding method of flip-chip MICRO LED chip and substrate, comprising:
Establishing a three-dimensional entity model and a finite element model of the bonding head, performing model analysis, and determining characteristic parameters of the bonding head;
Determining a weak part of the bonding head and optimizing the structural mechanical characteristics of the weak part based on the characteristic parameters of the bonding head;
fixing the flip MICRO LED chip on a substrate based on an optimized bonding head, and performing gold wire bonding on the flip MICRO LED chip placed on the substrate;
Establishing a three-dimensional entity model and a finite element model of the bonding head, performing model analysis, and determining characteristic parameters of the bonding head, wherein the method comprises the following steps:
Acquiring the bonding process characteristics of the flip chip and the overall entity structure of the bonding head, and establishing a three-dimensional entity model of the bonding head;
setting a bonding head finite element simplification principle, and establishing a finite element model of the bonding head;
For the three-dimensional solid model and the finite element model, the static deformation of the bonding head under the static load effect and the dynamic deformation of the bonding head under the dynamic load effect are calculated through the model analysis, the first constraint mode characteristics of the bonding head provided with the pick-up head component under the braking and non-braking working conditions are analyzed, and the second constraint mode characteristics of the bonding head not provided with the pick-up head component under the braking and non-braking working conditions are analyzed;
determining characteristic parameters of the bonding head according to the static deformation, the dynamic deformation, the first constraint mode characteristics and the second constraint mode characteristics;
optimizing structural mechanical properties of a weak part, comprising:
The design parameters based on sensitivity analysis are preferably optimized by an optimization method combining the optimal solution extraction based on analytic hierarchy process to optimize the structural mechanical characteristics of the weak component.
2. The bonding method of the flip-chip MICRO LED chip to the substrate according to claim 1, wherein the gold wire bonding of the flip-chip MICRO LED chip placed on the substrate comprises:
implanting gold balls at the PAD position of the flip-chip MICRO LED chip based on the first gold wires;
and (5) connecting the gold ball with the gold finger of the substrate based on the second gold wire to finish gold wire bonding.
3. The bonding method of flip-chip MICRO LED chip and substrate according to claim 2, wherein the second gold wire is connected to the gold ball and the gold finger of the substrate by one of ultrasonic wedge bonding, thermocompression bonding, and thermosonic bonding.
4. The bonding method of flip-chip MICRO LED chip and substrate according to claim 2, wherein the bonding method of the gold ball and the gold finger of the substrate is gold ball bonding.
5. The bonding method of flip-chip MICRO LED chip and substrate according to claim 2, wherein the bonding mode of the second gold wire to the gold ball is ball bonding.
6. The method of bonding a flip-chip MICRO LED chip to a substrate of claim 1, further comprising, prior to securing the flip-chip MICRO LED chip to the substrate based on the optimized bond head:
Detecting a first thickness of the flip-chip MICRO LED chip and a second thickness of the substrate;
Acquiring attribute information of the flip MICRO LED chip, inquiring a preset data table, and determining a first preset distance between the upper surface of the flip MICRO LED chip and the lower surface of the substrate and a second preset distance between the lower surface of the flip MICRO LED chip and the upper surface of the substrate;
according to the first preset distance, the first thickness and the second thickness, calculating to obtain the actual distance between the flip MICRO LED chip and the substrate;
And judging whether the actual distance is consistent with the second preset distance, and moving a bonding head for placing the flip MICRO LED chip to enable the actual distance to be consistent with the second preset distance when the actual distance is inconsistent with the second preset distance.
7. The method of bonding a flip-chip MICRO LED chip to a substrate of claim 6, wherein detecting the first thickness of the flip-chip MICRO LED chip comprises:
Generating a ranging signal for flip-chip MICRO LED chips;
Transmitting laser according to the ranging signal;
Performing phase modulation on laser based on a phase modulator to generate positive and negative frequency sidebands, and generating a target optical signal related to the free spectral range of an optical filter after the modulated laser signal passes through the optical filter;
Measuring a time difference between the emission and return of the target optical signal; and determining the first thickness of the flip-chip MICRO LED chip according to the time difference and the light speed information.
8. The method of bonding a flip-chip MICRO LED chip to a substrate of claim 1, further comprising, prior to securing the flip-chip MICRO LED chip to the substrate based on the optimized bond head:
Acquiring a scene image of the upper surface of the substrate;
preprocessing the scene image to obtain a preprocessed image;
Processing the preprocessed image based on a Gaussian Laplace function with 0 as a center and a Gaussian standard deviation sigma, determining discrete points and removing the discrete points to obtain a target image;
carrying out graying treatment and region division on the target image, and determining a plurality of local regions;
Determining the absolute value of the difference value between the gray value of each pixel point in each local area and the gray value of each adjacent pixel point, taking the maximum absolute value as the flat value of the corresponding pixel point, and judging whether the maximum absolute value is in a preset flat value range;
Calculating the ratio of the number of pixel points with the flat value not in the preset flat value range in each local area to the total pixel points in the local area, and judging whether the ratio is larger than the preset ratio;
and when the determined ratio is larger than the preset ratio, determining the corresponding local area as the area to be processed, and carrying out planarization processing on the area to be processed.
9. The method of bonding a flip-chip MICRO LED chip to a substrate of claim 8, wherein the preprocessing includes image noise reduction and image enhancement processing.
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