Reliability assessment method for thermal fatigue life of thermal interface materials

Abstract

This application provides a method for assessing the thermal fatigue life reliability of thermal interface materials. The method includes: applying boundary conditions and temperature loads to a simulation model of the thermal interface material; specifying the physical quantities of the thermal interface material to be output by the simulation model; and enabling the simulation model to perform simulation. Based on the simulation results, the method determines the thermal fatigue life reliability of the thermal interface material within a preset temperature variation range. This application solves the problem in related technologies where the assessment of the thermal fatigue life reliability of thermal interface materials relies on actual reliability testing after chip packaging, resulting in long processing times and high costs.

Description

Technical Field

[0001] This application relates to the field of thermal interface materials, and more specifically, to a method for assessing the thermal fatigue life reliability of thermal interface materials. Background Technology

[0002] With the increasing complexity of chip packaging and the diversification of operating environments, the requirements for the stability and reliability of chip packaging are becoming increasingly stringent. Thermal interface materials (TIMs) play a crucial role in chip packaging, situated between heat-generating components and heat sinks to effectively transfer heat and ensure chip operation within its normal operating temperature range. However, because chips are constantly subjected to temperature changes during operation, prolonged alternation between high and low temperatures can lead to thermal fatigue damage, thus affecting the reliability of the package. Specifically, the physical properties of the TIM in the packaging structure may degrade after repeated temperature cycles, resulting in reduced bond strength. This degradation is particularly pronounced under cyclic thermal loads because the differences in the coefficients of thermal expansion of different materials can easily lead to thermal fatigue failure of the TIM.

[0003] Currently, most assessments of the thermal fatigue reliability of thermal interface materials are based on experimental data, using accelerated temperature cycling tests to simulate temperature changes in actual working environments. However, reliability testing can only be conducted after chip packaging is complete, making it impossible to identify risks in advance during the design phase. Furthermore, testing is time-consuming and costly, and the cost of improvements after problems are discovered during testing is often prohibitive for the product.

[0004] Therefore, developing a more accurate, efficient, and comprehensive evaluation method to identify reliability risks of thermal interface materials in advance during the packaging design stage is of great significance for improving the reliability of chip packaging, extending its service life, and reducing product development costs. Summary of the Invention

[0005] This application provides a method for assessing the thermal fatigue life reliability of thermal interface materials, which at least solves the problem in related technologies that the assessment of the thermal fatigue life reliability of thermal interface materials depends on the actual reliability test after chip packaging, resulting in long time consumption and high cost.

[0006] According to one embodiment of this application, a method for assessing the thermal fatigue life reliability of a thermal interface material is provided, comprising: applying boundary conditions and temperature loads to a thermal interface material simulation model, specifying the physical quantities of the thermal interface material to be output by the thermal interface material simulation model, so that the thermal interface material simulation model can perform simulation; and determining the thermal fatigue life reliability of the thermal interface material within a preset temperature variation range based on the simulation results.

[0007] According to yet another embodiment of this application, a computer-readable storage medium is also provided, wherein a computer program is stored in the computer program, and the computer program is configured to execute the steps in the above method embodiments when it is run.

[0008] According to yet another embodiment of this application, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the steps in the above method embodiments.

[0009] According to yet another embodiment of this application, a computer program product is also provided, including a computer program that, when executed by a processor, implements the steps in the above method embodiments.

[0010] This application utilizes a thermal interface material simulation model, which significantly reduces cost and testing time compared to traditional physical experiments for assessing the reliability of thermal interface materials. Specifically, by applying boundary conditions and temperature loads to the thermal interface material simulation model, the model accurately reflects the key physical quantities of the thermal interface material under temperature cycling. Based on the simulation results, the thermal fatigue life of the thermal interface material within a preset temperature range can be evaluated, i.e., the time it takes for the material to maintain its functional integrity under specific temperature cycling conditions. This allows for reliability assessment of the thermal interface material during the packaging design stage, avoiding potential failure risks due to thermal fatigue after packaging. It solves the problem in related technologies where the reliability assessment of the thermal fatigue life of thermal interface materials relies on actual reliability testing after chip packaging, resulting in long processing times and high costs. Attached Figure Description

[0011] Figure 1 This is a hardware structure block diagram of a computer terminal for a thermal fatigue life reliability assessment method for thermal interface materials according to an embodiment of this application.

[0012] Figure 2 This is a flowchart of a method for assessing the thermal fatigue life reliability of thermal interface materials according to an embodiment of this application;

[0013] Figure 3 It is a finite element three-dimensional structural simulation model according to the embodiments of this application;

[0014] Figure 4 These are stress-strain curves according to embodiments of this application;

[0015] Figure 5 This is a structural block diagram of a thermal fatigue life reliability assessment device for thermal interface materials according to an embodiment of this application;

[0016] Figure 6This is a schematic diagram of the chip structure according to an embodiment of this application;

[0017] Figure 7 This is a flowchart of a method for assessing the thermal fatigue life reliability of a thermal interface material according to another embodiment of this application. Detailed Implementation

[0018] The embodiments of this application will be described in detail below with reference to the accompanying drawings and examples.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0020] The methods and embodiments provided in this application can be executed on a mobile terminal, a computer terminal, or a similar computing device. Taking running on a computer terminal as an example, Figure 1 This is a hardware structure block diagram of a computer terminal for a thermal fatigue life reliability assessment method for thermal interface materials according to an embodiment of this application. Figure 1 As shown, a computer terminal may include one or more ( Figure 1 Only one is shown in the diagram. A processor 102 (which may include, but is not limited to, a microprocessor MCU or a programmable logic device FPGA, etc.) and a memory 104 for storing data are also shown. The computer terminal may further include a transmission device 106 for communication functions and an input / output device 108. Those skilled in the art will understand that... Figure 1 The structure shown is for illustrative purposes only and does not limit the structure of the computer terminal described above. For example, the computer terminal may also include components that are more complex than those described above. Figure 1 The more or fewer components shown, or having the same Figure 1 The different configurations shown.

[0021] The memory 104 can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the thermal fatigue life reliability assessment method for thermal interface materials in this embodiment. The processor 102 executes various functional applications and data processing by running the computer program stored in the memory 104, thus implementing the above-described method. The memory 104 may include high-speed random access memory and may also include non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory 104 may further include memory remotely located relative to the processor 102, and these remote memories can be connected to a computer terminal via a network. Examples of such networks include, but are not limited to, the Internet, corporate intranets, local area networks, mobile communication networks, and combinations thereof.

[0022] The transmission device 106 is used to receive or send data via a network. Specific examples of the network described above may include a wireless network provided by a communication provider for the computer terminal. In one example, the transmission device 106 includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device 106 may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0023] This embodiment provides a method for assessing the thermal fatigue life reliability of thermal interface materials used in the aforementioned computer terminal. Figure 2 This is a flowchart of a method for assessing the thermal fatigue life reliability of thermal interface materials according to an embodiment of this application, such as... Figure 2 As shown, the process includes the following steps:

[0024] Step S202: Apply boundary conditions and temperature loads to the thermal interface material simulation model, and specify the physical quantities of the thermal interface material to be output by the thermal interface material simulation model so that the thermal interface material simulation model can perform simulation.

[0025] In one embodiment, the steps of simulating the thermal interface material simulation model include applying defined boundary conditions to the chip on the thermal interface material simulation model, applying a temperature load to the chip under the applied boundary conditions, and specifying the physical quantities of the thermal interface material that need to be output.

[0026] In an exemplary embodiment of this application, the boundary conditions include symmetrical boundary conditions and fixed boundary conditions, and the temperature load is consistent with the temperature range of the actual product reliability test.

[0027] In one embodiment, symmetric boundary conditions are used in the simulation of chip package structures to simplify calculations and improve efficiency. Specifically, if the package structure is symmetrical about a certain axis or plane, the model can be simplified to a model of the symmetrical portion, such as a 1 / 4, 1 / 2, or 1 / 8 symmetric model. Symmetric boundary conditions ensure that physical quantities such as displacement, stress, or temperature on one side or edge of the model correspond to the other side of the symmetry plane or axis. This not only reduces the consumption of computational resources but also ensures the accuracy of the simulation results.

[0028] In one embodiment, a fixed boundary condition refers to setting boundaries in certain parts of the model that do not allow any displacement. This is typically used to simulate the connection between the package structure and the external frame or substrate. The fixed boundary condition ensures the stability of the model during simulation and prevents unrealistic results caused by excessive displacement at the boundaries.

[0029] In one embodiment, the temperature load setting in the simulation model must closely match the actual temperature cycling range experienced by the product. This includes determining the upper and lower limits of the temperature cycles, the number of cycles, the cycle rate, and any nonlinear or discontinuous temperature changes. Ensuring the consistency of the temperature load with actual reliability test conditions makes the simulation results closer to the real environment and improves the credibility of the evaluation. Extending the traditional static temperature load setting to dynamic adjustment, that is, optimizing the temperature load spatially and temporally based on the heat conduction path and heat dissipation characteristics of the package structure. For example, considering the uneven heat distribution in different areas of the chip during operation, the temperature load in local areas can be set to better reflect reality, thereby more accurately predicting the thermal fatigue behavior of the thermal interface material.

[0030] In an exemplary embodiment of this application, before applying boundary conditions and temperature loads to the thermal interface material simulation model, the method further includes: constructing a thermal interface material simulation model based on the chip packaging structure, the material parameters of the thermal interface material used in the chip, and the packaging reliability test conditions.

[0031] In an exemplary embodiment of this application, the thermal interface material simulation model is a finite element three-dimensional structural simulation model, which includes multiple discrete elements formed by partitioning.

[0032] In one embodiment, the encapsulated structure is divided into many small discrete elements during the creation of a finite element three-dimensional structural simulation model; this is known as meshing. These elements form the "skeleton" of the model, each possessing its own physical properties, such as material properties, geometric dimensions, and boundary conditions. Through meshing, the complex encapsulated structure is decomposed into thousands of simple small elements, each capable of independent thermal and thermodynamic analysis. The size and shape of the elements can be optimized based on the required accuracy and computational efficiency. In high-stress or high-strain regions, the mesh elements can be finer; while in regions with relatively gradual temperature or stress changes, the elements can be larger to reduce computational load.

[0033] In one embodiment, the finite element three-dimensional structural simulation model is as follows: Figure 3 As shown. In Figure 3 As can be seen, the model is divided into multiple small units, i.e., a mesh. This meshing is for the purpose of accurately calculating physical quantities such as stress and strain in each small region during finite element analysis. The size and shape of the mesh are adjusted according to the required accuracy and computational efficiency, and finer meshes are usually used at structural boundaries or stress concentration regions.

[0034] Step S204: Determine the thermal fatigue life reliability of the thermal interface material within the preset temperature variation range based on the simulation results.

[0035] In an exemplary embodiment of this application, determining the thermal fatigue life reliability of the thermal interface material within a preset temperature variation range based on simulation results includes: determining the maximum value of the equivalent plastic strain of the thermal interface material based on simulation results; determining the coverage degradation value of the thermal interface material after a preset number of temperature cycles based on the coverage degradation calculation formula of the thermal interface material, the maximum value of the equivalent plastic strain, and the preset number of temperature cycles of the thermal interface material; and determining the thermal fatigue life reliability of the thermal interface material based on the coverage degradation value.

[0036] It should be noted that the coverage degradation value can directly reflect the degree of degradation of the thermal interface material performance with temperature cycling. A low coverage degradation value means that the thermal interface material maintains good performance after temperature cycling, and the thermal conductivity and stability of the encapsulation structure are high, which in turn indicates that the thermal interface material has high reliability in thermal fatigue life.

[0037] In an exemplary embodiment of this application, determining the maximum value of the equivalent plastic strain of the thermal interface material based on simulation results includes: determining the equivalent plastic strain distribution cloud map of the thermal interface material based on simulation results; determining the region of maximum reliability risk of the thermal interface material based on the equivalent plastic strain distribution cloud map; and determining the maximum value of the equivalent plastic strain based on the region of maximum reliability risk.

[0038] In one embodiment, the maximum value of the equivalent plastic strain ΔPEEQ is substituted into formula (1), where C is the degradation rate, that is, how much the thermal interface material has degraded relative to the initial state coverage after the reliability test, in percentage, and K1 and K2 are coefficients. For example, if the reliability test temperature cycle is specified as 500 cycles, then N = 500. After substituting ΔPEEQ obtained from the simulation, if C = 10 is calculated, it means that after 500 temperature cycles, the TIM coverage of the chip has degraded by 10% relative to the initial time.

[0039]

[0040] In one embodiment, the equivalent plastic strain distribution cloud map is a commonly used visualization tool in finite element analysis to show the distribution of plastic strain in a material under stress. The equivalent plastic strain distribution cloud map is a color-coded graphical representation, where different colors represent different equivalent plastic strain values. Typically, the colors transition from cool colors (such as blue) to warm colors (such as red), representing a change in strain value from low to high. In the equivalent plastic strain distribution cloud map, the color of each discrete element (i.e., a small element in the finite element mesh) represents the equivalent plastic strain value of that element. By observing the cloud map, regions of strain concentration or severe damage in the thermal interface material can be easily identified. These regions are usually displayed as darker or brighter colors, indicating that they may become the starting points for thermal fatigue failure. The equivalent plastic strain distribution cloud map is particularly important in the thermal fatigue reliability assessment of thermal interface materials, providing a visual understanding of the degree and distribution of damage to the thermal interface material during temperature cycling.

[0041] Equivalent plastic strain refers to the total strain accumulated in a material during the plastic deformation stage. Regardless of the stress state causing this deformation, equivalent plastic strain normalizes the plastic strain in all directions and represents it as a scalar value. During temperature cycling, due to differences in the thermal expansion coefficients of the materials and the thermal cycling load, plastic strain will be generated in different regions of the thermal interface material. This strain accumulation will accelerate the aging and damage of the material.

[0042] In an exemplary embodiment of this application, the material parameters of the thermal interface material are determined based on the stress-strain curve of the thermal interface material, wherein the material parameters cover the elastoplastic parameters within the temperature range of the packaging reliability test.

[0043] Material parameters, including but not limited to elastic modulus, Poisson's ratio, yield strength, and coefficient of thermal expansion, are crucial for constructing finite element models. In particular, elastoplastic parameters encompass the material's properties during both elastic and plastic deformation stages, and these properties are essential for understanding the damage accumulation and reliability degradation of thermal interface materials during temperature cycling.

[0044] In an exemplary embodiment of this application, the stress-strain curve is used to indicate the transition of the thermal interface material from the elastic region to the plastic region, the elastic modulus, the yield point, and the stress-strain relationship in the plastic region.

[0045] In one embodiment, the stress-strain curve is as follows: Figure 4As shown, the stress-strain curve can be divided into several key stages: the elastic stage, where there is a linear relationship between stress and strain, represented by a straight line. The elastic modulus of the material can be directly calculated from the slope of the curve, reflecting the material's ability to resist elastic deformation; the yield point, where the stress-strain curve begins to deviate from the linear relationship, indicating that the material has entered the plastic deformation stage. The yield point is usually defined by a specific stress value, which corresponds to the beginning of permanent deformation; the plastic stage, after which the increase in stress is no longer proportional to the strain, and the material exhibits plastic flow or permanent deformation. Plastic parameters, such as the plastic modulus and hardening curve, can be extracted from the shape of the curve in the plastic stage, describing the material's behavior after exceeding the elastic limit; and final failure, where, with increasing strain, the material eventually reaches a point beyond which it can no longer maintain its structural integrity, leading to fracture or failure. Although this point may not be reached in thermal fatigue assessment, it defines the material's ultimate performance.

[0046] Because the properties of thermal interface materials change with temperature, material parameters covering the entire temperature range for package reliability testing must be used when constructing simulation models. This means that the material's elastic modulus, Poisson's ratio, coefficient of thermal expansion, and other parameters must be accurately measured or determined experimentally under low-temperature, room-temperature, and high-temperature conditions, and then input into the simulation software. Using these temperature-related parameters in the model ensures that the simulation results accurately reflect the behavior of the thermal interface material under actual thermal cycling conditions, thereby enabling a more accurate assessment of the thermal fatigue reliability of the thermal interface material.

[0047] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0048] This embodiment also provides a thermal fatigue life reliability assessment device for thermal interface materials. This device is used to implement the above embodiments and preferred embodiments, and details already described will not be repeated. As used below, the term "module" can be a combination of software and / or hardware that performs a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0049] Figure 5 This is a structural block diagram of a thermal fatigue life reliability assessment device for thermal interface materials according to an embodiment of this application, such as... Figure 5 As shown, the device includes a simulation module 10 and a determination module 20.

[0050] Simulation module 10 is used to apply boundary conditions and temperature loads to the thermal interface material simulation model, and to specify the physical quantities of the thermal interface material that the thermal interface material simulation model needs to output, so that the thermal interface material simulation model can perform simulation.

[0051] The determination module 20 is used to determine the thermal fatigue life reliability of the thermal interface material within a preset temperature variation range based on the simulation results.

[0052] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0053] To facilitate understanding of the technical solutions provided in the application embodiments, the following description is based on specific scenario embodiments.

[0054] In this application embodiment, the thermal interface material plays a key role in chip packaging. The thermal interface material is located between the heat-generating element and the heat sink to effectively transfer heat and ensure that the chip operates within its normal operating temperature range. Figure 6 This is a schematic diagram of the chip structure according to an embodiment of this application, such as... Figure 6 As shown, 1 is the cover plate (Lid), 2 is the thermal interface material (TIM), 3 is the chip (Die), 4 is the underfill, 5 is the bump, 6 is the substrate, 7 is the solder ball, and 8 is the printed circuit board (PCB).

[0055] Figure 7 This is a flowchart of a method for assessing the thermal fatigue life reliability of a thermal interface material according to another embodiment of this application, as shown below. Figure 7 As shown, the process includes the following steps:

[0056] Step S701: Determine the chip structure dimensions;

[0057] Step S702: Establish a simulation model based on the actual chip structure and specifications;

[0058] Step S703: Determine material parameters;

[0059] Step S704: Determine the fixed, symmetrical boundary;

[0060] Step S705: Apply temperature load according to the actual reliability test specifications;

[0061] Step S706: Determine if the simulation calculation is error-free;

[0062] Specifically, if the judgment result is yes, proceed to step S707; if the judgment result is no, proceed to step S708.

[0063] Step S707: Determine the maximum value of the equivalent plastic strain of the thermal interface material;

[0064] Step S708: Check if the network, material parameters, boundaries, and loads are correct;

[0065] Step S709: Calculate the degradation rate of the thermal interface material;

[0066] Step S710: Determine whether the chip meets the reliability specifications;

[0067] Step S711: Design optimization and simulation iterative analysis.

[0068] Embodiments of this application also provide a computer-readable storage medium storing a computer program, wherein the computer program is configured to execute the steps in any of the above method embodiments when run.

[0069] In one exemplary embodiment, the aforementioned computer-readable storage medium may include, but is not limited to, various media capable of storing computer programs, such as a USB flash drive, read-only memory (ROM), random access memory (RAM), portable hard disk, magnetic disk, or optical disk.

[0070] Embodiments of this application also provide an electronic device including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the steps in any of the above method embodiments.

[0071] In one exemplary embodiment, the electronic device may further include a transmission device and an input / output device, wherein the transmission device is connected to the processor and the input / output device is connected to the processor.

[0072] Specific examples in this embodiment can be found in the examples described in the above embodiments and exemplary implementations, and will not be repeated here.

[0073] This application's embodiments enable the prediction and evaluation of product reliability during the product design and development stages, eliminating the need for extensive actual physical experiments and significantly shortening the evaluation cycle. It allows for rapid iterative design optimization; through simulation technology, potential problems in the product design can be quickly identified and iteratively optimized, improving product reliability. The reliability of thermal interface materials determined by simulation methods in this application's embodiments overcomes the drawbacks of long experimental cycles and high costs. Existing evaluation methods mostly focus on qualitative descriptions of thermal fatigue damage, making it difficult to accurately predict the thermal fatigue life and reliability of electronic packaging structures. However, this application's embodiments can obtain the fatigue life of thermal interface materials through simulation.

[0074] Obviously, those skilled in the art should understand that the modules or steps of this application described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. They can be implemented using computer-executable program code, and thus can be stored in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented here, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, this application is not limited to any particular combination of hardware and software.

[0075] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the principles of this application should be included within the protection scope of this application.

Claims

1. A method for assessing the reliability of thermal fatigue life of a thermal interface material, characterized in that, include: Apply boundary conditions and temperature loads to the thermal interface material simulation model, and specify the physical quantities of the thermal interface material that the thermal interface material simulation model needs to output, so that the thermal interface material simulation model can perform simulation. The thermal fatigue life reliability of the thermal interface material within the preset temperature variation range is determined based on the simulation results. The determination of the thermal fatigue life reliability of the thermal interface material within the preset temperature variation range based on simulation results includes: The maximum value of the equivalent plastic strain of the thermal interface material is determined based on the simulation results; The coverage degradation value of the thermal interface material after a preset number of temperature cycles is determined based on the coverage degradation calculation formula of the thermal interface material, the maximum value of the equivalent plastic strain, and the preset number of temperature cycles of the thermal interface material. The thermal fatigue life reliability of the thermal interface material is determined based on the coverage degradation value.

2. The method according to claim 1, characterized in that, The boundary conditions include symmetrical boundary conditions and fixed boundary conditions, and the temperature load is consistent with the temperature range of the actual product reliability test.

3. The method according to claim 1, characterized in that, The determination of the maximum value of the equivalent plastic strain of the thermal interface material based on simulation results includes: The equivalent plastic strain distribution cloud map of the thermal interface material is determined based on the simulation results; The region of maximum reliability risk for the thermal interface material is determined based on the equivalent plastic strain distribution cloud map, and the maximum value of the equivalent plastic strain is determined based on the region of maximum reliability risk.

4. The method according to claim 1, characterized in that, Before applying boundary conditions and temperature loads to the thermal interface material simulation model, the following steps are also included: The thermal interface material simulation model is constructed based on the chip packaging structure, the material parameters of the thermal interface material used in the chip, and the packaging reliability test conditions.

5. The method according to claim 1, characterized in that, The method further includes: The material parameters of the thermal interface material are determined based on the stress-strain curve of the thermal interface material, wherein the material parameters cover the elastoplastic parameters within the temperature range of the packaging reliability test.

6. The method according to claim 5, characterized in that, in, The stress-strain curve is used to indicate the transition of the thermal interface material from the elastic region to the plastic region, and the stress-strain relationship of the elastic modulus, yield point, and plastic region.

7. The method according to claim 1, characterized in that, in, The thermal interface material simulation model is a finite element three-dimensional structural simulation model, which includes multiple discrete elements formed by division.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of the method described in any one of claims 1 to 7.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method described in any one of claims 1 to 7.

10. A computer program product comprising a computer program that, when executed by a processor, implements the steps of the method described in any one of claims 1 to 7.

Images