Heterostructure bonding quality evaluation method and device based on non-contact laser ultrasound

Abstract

The invention discloses a heterostructure bonding quality evaluation method and device based on non-contact laser ultrasound. The method comprises the following steps: aiming at a target multi-layer heterostructure, calculating all corresponding resonance modes by utilizing a computer finite element simulation method to obtain a multi-mode theoretical resonance frequency; carrying out laser ultrasonic multi-point scanning on a preset plane area of the target multilayer heterostructure based on a thermoelastic effect by utilizing the established detection device, and collecting an ultrasonic signal; performing time-frequency domain conversion on the ultrasonic signal to obtain a corresponding frequency spectrum signal, and further obtaining a multi-modal measurement resonance frequency; and comparing the multi-mode theoretical resonance frequency with the multi-mode measurement resonance frequency to obtain a heterostructure bonding quality evaluation result. According to the invention, the accuracy of bonding quality evaluation is improved, and the evaluation convenience is improved.

Description

Technical Field

[0001] The present invention relates to the field of ultrasonic testing technology, and more particularly to a method and device for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound. Background Art

[0002] Multilayer heterostructures are widely used in semiconductor devices, optoelectronic devices, aerospace and other fields because they can effectively exert material properties. Since multilayer heterostructures need to undergo a variety of coupling conditions during the production process, and the environment they are in during service is complex and changeable, it is easy for the adhesive material of the bonding layer to degrade in bonding performance or even debond, which seriously affects the structural performance and even causes catastrophic accidents. Therefore, there is an urgent need for a method to evaluate the bonding quality of multilayer heterostructures. However, traditional non-destructive testing methods, such as radiographic non-destructive testing, electromagnetic non-destructive testing and thermodynamic non-destructive testing, have the disadvantages of harsh testing conditions, inability to detect at a distance or difficulty in characterizing local features in actual applications.

[0003] Laser ultrasonic technology, as a non-contact ultrasonic nondestructive testing method, offers advantages such as the absence of coupling agents, high bandwidth, good repeatability, and flexible experimental conditions. It has been widely used in material performance testing and damage assessment. For example, the paper "Watzl G, Kerschbaummayr C, Schagerl M, et al. In situ laser-ultrasonic monitoring of Poisson's ratio and bulk sound velocities of steel plates during thermal processes [J]. Acta Materialia, 2022, 235: 118097" utilizes laser ultrasonic technology to perform in-situ, non-contact mechanical property testing of materials undergoing heat treatment. Patent application CN113588784A discloses a nondestructive testing method for debonding defects in thin-film coatings based on grating laser ultrasonic spectroscopy. This method utilizes the principle of laser ultrasonic excitation of materials of varying thicknesses to generate different types of ultrasonic waves, enabling qualitative detection of debonding defects within thin-film coatings. Laser ultrasonic technology meets the requirements for testing the bonding properties of multilayer heterogeneous structures and is crucial for the development of high-performance heterogeneous structures, production process optimization, and post-service performance testing.

[0004] In addition, the resonance modal analysis method can be used for ultrasonic testing of bonded structures and layered structures. Compared with the guided wave analysis method commonly used in material testing, the advantage of this method is that the high-order modes used in the analysis are more sensitive to minor damage to the material, especially in the early stages of damage. The basic principle of the resonance modal analysis method is that the material or structure has a natural frequency. When the frequency of the ultrasonic wave generated by external excitation is close to the natural frequency, resonance will occur. Since the ultrasonic wave has multiple modes, resonance may occur at multiple modes. In general structures, there are various resonance modes, including thickness resonance and zero group velocity resonance. At the resonance point, the ultrasonic wave stops propagating to form a non-propagating wave. The energy is concentrated here to form a strong resonance peak. Since the frequency of the resonance peak is related to the sample structure and material properties, it can be used for material performance characterization and damage detection.

[0005] At present, the resonance modal analysis method has been applied in ultrasonic testing of some specific structures. For example, patent application CN107037128A discloses a method and device for evaluating the degree of damage of bonded structures based on zero group velocity mode. This solution uses software to calculate the theoretical zero group velocity resonance frequency of the material, and then uses air-coupled ultrasonic technology to obtain the material dispersion information and compare it with the calculated resonance frequency, thereby achieving non-destructive testing of the bonded structure. However, when dealing with complex structures, this solution cannot accurately determine whether the zero group velocity resonance occurs in a specific mode, because complex structures such as multi-layer heterogeneous structures often have multiple resonance peaks in the dispersion spectrum, and these resonance peaks are difficult to correspond to the zero group velocity mode. In addition, when scanning the sample, this solution requires moving the operating tool to complete the operation.

[0006] Patent application CN113588784A discloses a nondestructive testing method for thin-film coating debonding defects based on grating laser ultrasonic spectroscopy. However, this method struggles to accurately determine damage in the early stages of debonding; accurate damage assessment requires a certain thickness (less than the ultrasonic wavelength) to be achieved. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a method and device for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound.

[0008] According to a first aspect of the present invention, a method for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound is provided. The method comprises the following steps:

[0009] For the target multi-layer heterogeneous structure, all corresponding resonance modes are calculated using computer finite element simulation method to obtain the multi-modal theoretical resonance frequency;

[0010] Using the established detection device, based on the thermoelastic effect, laser ultrasonic multi-point scanning is performed on the preset plane area of ​​the target multi-layer heterogeneous structure, and ultrasonic signals are collected;

[0011] The ultrasonic signal is converted into a corresponding spectrum signal by time-frequency domain, thereby obtaining a multimodal measurement resonance frequency;

[0012] By comparing the multimodal theoretical resonance frequency and the multimodal measured resonance frequency, a heterogeneous structure bonding quality evaluation result is obtained.

[0013] According to a second aspect of the present invention, a device for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound is provided. The device comprises:

[0014] Calculation unit: used to calculate all corresponding resonance modes of the target multi-layer heterogeneous structure using computer finite element simulation method to obtain the multi-modal theoretical resonance frequency;

[0015] Ultrasonic signal acquisition unit: used to perform laser ultrasonic multi-point scanning on a preset plane area of ​​the target multi-layer heterogeneous structure based on the thermoelastic effect using the established detection device and to collect ultrasonic signals;

[0016] Ultrasonic measurement unit: used to convert the ultrasonic signal into a corresponding spectrum signal through time-frequency domain conversion, and then obtain the multimodal measurement resonance frequency;

[0017] Evaluation unit: used for obtaining heterogeneous structure bonding quality evaluation results by comparing the multimodal theoretical resonance frequency and the multimodal measured resonance frequency.

[0018] Compared with existing technologies, the present invention offers an innovative, non-contact method for assessing the bond quality of multilayer heterogeneous structures. This method utilizes a multimodal resonance analysis method based on laser ultrasound technology to accurately assess the bond quality of multilayer heterogeneous structures. This improves the adaptability of ultrasonic testing methods to multilayer heterogeneous structures, simplifies scanning operations, and enhances detection accuracy. By leveraging the sensitivity of resonant frequency to thickness variations, the present invention can detect debonding damage in its earliest stages.

[0019] Further features and advantages of the present invention will become apparent from the following detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0021] Figure 1is a flow chart of a method for evaluating heterogeneous structure bonding quality based on non-contact laser ultrasound according to one embodiment of the present invention;

[0022] Figure 2 1. It is a schematic diagram of a dispersion curve and a resonance mode of a heterogeneous structure calculated by finite element simulation according to one embodiment of the present invention;

[0023] Figure 3 2 is a schematic diagram of a heterogeneous structure bonding quality assessment device based on non-contact laser ultrasound according to one embodiment of the present invention;

[0024] Figure 4 is a schematic diagram of a sample according to an embodiment of the present invention;

[0025] Figure 5 is an ultrasound signal amplitude diagram obtained by a signal acquisition device according to an embodiment of the present invention;

[0026] Figure 6 is a bonding quality distribution diagram obtained by multimodal resonance frequency of an ultrasonic signal according to one embodiment of the present invention;

[0027] Figure 7 is a schematic diagram of a transmission mode according to an embodiment of the present invention;

[0028] Figure 8 FIG. 1 is a schematic diagram of a reflection mode according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0030] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0031] Technologies, methods, and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered part of the specification.

[0032] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0033] It should be noted that like reference numerals and letters refer to like items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0034] The present invention proposes a method and device for evaluating the bonding quality of multilayer heterogeneous structures based on non-contact laser ultrasound. First, the theoretical dispersion curve of the structure is obtained through simulation calculation. Then, a laser is used to excite the surface of the multilayer heterogeneous structure to generate an ultrasonic signal, which is received by a laser vibrometer. The ultrasonic signal is processed to obtain a multimodal resonance spectrum. Finally, by extracting the frequency characteristics, two-dimensional visualization imaging of material bonding defects is achieved, thereby accurately evaluating the bonding quality.

[0035] See also Figure 1 As shown, the provided method for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound includes the following steps:

[0036] Step S1 : performing resonance modal analysis on the multi-layer heterogeneous structure using a computer finite element simulation method to obtain a multi-modal theoretical resonance frequency.

[0037] In one embodiment, a computer finite element simulation method is used to simulate and calculate all resonance modes corresponding to the multilayer heterostructure to be evaluated (or referred to as a target multilayer heterostructure or a multilayer heterostructure sample) to obtain the theoretical frequency of the resonance mode.

[0038] Traditional semi-analytical finite element analysis methods require excessive computational effort to approximate the complete dispersion curve, whereas finite element analysis can obtain complete dispersion curves for all modes. Because the resonant modes of multilayer heterostructures are difficult to predict, finite element analysis offers significant advantages for these structures. In general heterostructures, the structural characteristic frequencies and dispersion curves can be calculated using the Rayleigh-Lamb frequency equation to obtain resonant modal information.

[0039] According to the Rayleigh-Lamb frequency equation:

[0040] Symmetrical mode:

[0041]

[0042] Antisymmetric modes:

[0043]

[0044] Where h is the thickness of the thin plate, k is the wave number, V P is the phase velocity, ω represents angular velocity, q and p have no physical meaning, V T represents the shear wave velocity, V L Represents the longitudinal wave velocity.

[0045] Based on the above dispersion equation, combined with eigenfrequency analysis using finite element simulation software, the complete dispersion curve of the structure under test can be calculated, enabling performance analysis of complex multilayer heterostructure materials. Observing the equation, it is clear that the resonant modal frequency is very sensitive to changes in material thickness and properties. When debonding occurs, delamination or cavities form between the different components of the heterostructure, and the resonant modal frequency changes accordingly. This principle can be used to analyze and study the bonding performance of heterostructures.

[0046] Figure 2 This is a dispersion curve, or wavenumber-frequency curve, derived from finite element simulation of a multilayer heterogeneous structure. When the slope of the curve is zero, it indicates that the ultrasonic group velocity in that mode is zero, resulting in a zero group velocity resonance, with a corresponding resonant frequency. Resonance can occur in multiple modes within a single material or structure, all of which can be analyzed in the frequency domain. Therefore, this invention provides a multimodal resonance method.

[0047] Step S2: construct a detection device and set a test light path.

[0048] For example, the signal exciter, the signal acquisition device and the heterostructure sample are uniformly installed in the same plane at predetermined positions, and the signal exciter, the signal acquisition device and the heterostructure sample are placed in a specific test optical path, and the excitation laser and the detection laser emitted by the signal acquisition device act on the same point on the same side surface of the heterostructure sample.

[0049] Figure 3 Figure 1 is a schematic diagram of the detection device and optical path setup. The device primarily includes a display device 10, a signal driver 20, a processor 30, a laser vibrometer 40, a dichroic mirror 50, a reflector 60, a heterostructure sample 70, and a mobile platform 80. The signal driver 20 includes a laser pulse generator 21, a pulse width modulation module 22, a frequency modulation module 23, and an attenuator 24.

[0050] exist Figure 3 In the example, the test optical path primarily includes a dichroic mirror 50 and a reflector 60. The dichroic mirror 50 allows the detection laser light generated by the laser vibrometer 40 and its reflection on the surface of the heterostructure sample 70 to pass through, but prevents the excitation laser light generated by the laser pulser 21 from passing through, as the excitation laser light is reflected from the dichroic mirror 50. The signal exciter 20, laser vibrometer 40, and multilayer heterostructure sample 70 are uniformly mounted on the same plane at predetermined positions, and the optical path of the signal exciter 20 is adjusted so that the detection laser light and the excitation laser light act in parallel on the same point on the surface of the multilayer heterostructure sample 70.

[0051] Step S3: Using the constructed detection device, laser ultrasonic detection is performed on the multilayer heterogeneous structure based on the thermoelastic effect.

[0052] In this step, the signal exciter 20 is used to output an excitation laser to generate an ultrasonic signal on the surface of the multilayer heterostructure sample 70, and a signal receiver (or signal acquisition device) is used to receive the ultrasonic signal from the surface of the multilayer heterostructure sample 70.

[0053] The principle of laser-induced ultrasonic waves is the thermoelastic effect. When a laser beam irradiates the surface of the material being tested, the material absorbs the laser energy and converts it into its own heat, causing the surface temperature to rise rapidly. Due to uneven thermal diffusion, the temperature gradient causes varying degrees of thermal expansion and large stress differences on the surface, which in turn form elastic stress waves in the material, known as ultrasonic waves. This excitation mechanism is called the thermoelastic effect. The signal receiver operates on the Doppler effect. The detection beam calculates the optical path difference between the reference beam and the actual reflected beam, generating vibration information on the test sample's surface, known as the ultrasonic signal.

[0054] Specifically, the detection laser is adjusted to focus on the sample surface, and an ultrasonic signal is generated through the thermoelastic effect. The device uses a Nd:YAG laser with a wavelength of 1064nm, a pulse width of 10ns, and a maximum frequency of 400Hz as the laser pulser. The pulse width adjustment module and the frequency adjustment module are devices built into the laser pulser and are electrically connected to the laser pulser. The laser pulser is connected to the processor signal and can be directly controlled by the display device. The attenuator is an external device that can be used to control the energy of the excitation laser generated by the signal exciter. The excitation laser generated by the laser pulser is attenuated by the attenuator, and the excitation laser is output by the signal exciter to generate an ultrasonic signal on the surface of the heterostructure sample, and the ultrasonic signal from the surface of the heterostructure sample is received by the signal receiver.

[0055] The signal receiver primarily collects ultrasonic signals generated by the thermoelastic effect on the surface of heterogeneous samples, filters them through the processor's built-in filter, and displays and stores them on the display device. Using the built-in filter during signal acquisition improves the signal-to-noise ratio in the frequency domain.

[0056] S4, performing laser ultrasonic multi-point scanning on a preset plane area of ​​the multilayer heterogeneous structure and collecting ultrasonic signals.

[0057] Specifically, a multi-layer heterostructure sample is placed on a three-axis movable platform, and the movement of the mobile platform is controlled to complete multi-point scanning of the heterostructure sample surface. The mobile platform includes a mobile platform base and a sample placement structure fixed to the mobile platform. The sample can be fixed on the mobile platform perpendicular to the direction of the incident laser and can move along the three axes with the mobile platform. The mobile platform is connected to the processor signal, and the mobile platform can be directly controlled through the display device to move the mobile platform with precise three-axis positioning. In addition, the mobile platform can be positioned in real time, and its movement path can be edited to complete point-by-point scanning of a specified planar area on the surface of the heterostructure sample.

[0058] Step S5 , performing time-frequency conversion on the collected ultrasonic signal to obtain a multi-modal measured resonance frequency, and then evaluating the heterogeneous structure bonding quality by comparing the multi-modal theoretical resonance frequency with the measured resonance frequency.

[0059] In this step, during the scanning process, the signal obtained by the signal acquisition device is analyzed and processed to evaluate the bonding quality of the heterogeneous structure.

[0060] Specifically, during the scanning process, the collected ultrasonic signal is displayed as an electrical signal on the oscilloscope of the display device. The original signal data is a time domain signal. After Fourier transform, a spectrum signal is obtained. Multiple resonance mode information can be obtained on the spectrum. By comparing it with the multi-modal theoretical resonance frequency calculated in step S1, it can be determined whether debonding occurs.

[0061] Step S6: draw a cloud map of the heterogeneous structure bonding quality distribution to perform bonding defect imaging analysis.

[0062] In one embodiment, the features of the scanning data at each point are extracted, and a cloud map of the bonding quality distribution of the heterogeneous structure sample, i.e., bonding defect imaging, is formed by plotting the frequency domain data.

[0063] For example, by extracting the characteristics of each scan data point, multiple resonance peaks may exist within a certain frequency range. These resonance peaks correspond to the resonant modes of the ultrasound. By selecting the frequency characteristics of the resonance peaks, a cloud diagram of the bonding quality distribution of multilayer heterostructure samples can be drawn. In addition, the scan data of each point can be exported to a computer for further processing.

[0064] Accordingly, the present invention also provides a non-contact laser ultrasound-based heterostructure bonding quality assessment device for implementing one or more aspects of the above-mentioned method. For example, the device includes: a calculation unit for calculating all corresponding resonance modes of a target multi-layer heterostructure using a computer finite element simulation method to obtain a multi-modal theoretical resonance frequency; an ultrasonic signal acquisition unit for performing a laser ultrasonic multi-point scan of a preset planar area of ​​the target multi-layer heterostructure based on the thermoelastic effect using an established detection device and collecting ultrasonic signals; an ultrasonic measurement unit for converting the ultrasonic signal into a corresponding spectrum signal through time-frequency domain conversion, thereby obtaining a multi-modal measured resonance frequency; and an evaluation unit for obtaining a heterostructure bonding quality assessment result by comparing the multi-modal theoretical resonance frequency with the multi-modal measured resonance frequency. Each unit can exist as an independent module or a separate module, or can be implemented in combination with hardware such as a dedicated processor, a general-purpose processor, or an FPGA.

[0065] In order to further verify the effectiveness of the present invention, a specific scenario embodiment was selected for numerical simulation and experimental verification.

[0066] High-performance thermal interface materials are key to solving chip heat dissipation issues. Thermal interface materials (TIMs), a thermal management material commonly used in chip packaging, are located between the chip and the vapor chamber, as well as between the vapor chamber and the heat sink. They are primarily used to fill the micro-gaps and uneven holes created when two hard materials are combined, thereby reducing heat transfer contact resistance and improving the device's heat dissipation capabilities. During the TIM R&D stage, stacked electronic packaging devices are typically simplified into a multi-layer heterogeneous structure of "copper package cover (top) - thermal interface material (center) - silicon chip (bottom)" (Cu-TIM-Si), using this as a carrier for various performance tests and research.

[0067] During chip operation, they must withstand thousands of cyclic loads such as temperature and stress, and must operate stably in extreme temperatures (-55 to 150°C) and humidity environments. These factors can cause the mechanical properties and micromorphology of thermal interface materials to evolve, leading to poor adhesion between the material and the chip surface and debonding. Debonding increases the interlayer contact thermal resistance, ultimately inducing thermal failure and malfunction of the chip. Therefore, it is necessary to effectively characterize the bonding quality of thermal interface materials and their upper and lower interfaces to optimize the thermal interface material preparation process and improve service performance. Furthermore, the uncertainty in the relationship between the material's chemical composition, properties, and service environment poses unprecedented challenges to the development of thermal interface materials and the optimization of chip packaging processes. Therefore, both the development of thermal interface materials and the optimization of chip packaging processes urgently require a non-contact, in-situ detection method and technology for the bonding quality of thermal interface materials in multi-layer heterogeneous packaging structures.

[0068] In order to verify whether the non-contact laser ultrasonic detection method proposed in this invention can accurately characterize the bonding quality of multilayer heterogeneous structures, laser ultrasonic tests were carried out on Cu-TIM-Si simplified structure samples to verify the proposed method.

[0069] In the experimental verification, the test was completed using a Cu-TIM-Si three-layer heterostructure thin plate sample as an example. A total of two samples were prepared, one of which was artificially processed to simulate debonding, and the other was a well-bonded sample for comparison. The sample size was 2.5cm×2.5cm. The thickness and material properties of each layer of the heterostructure sample were known, but the interlayer bonding condition was unknown. Figure 4 Schematic diagram of the two three-layer thin plate samples. Figure 4 (a) is the silicon side debonding sample 1, Figure 4 (b) is sample 2 where no debonding occurred.

[0070] Using the present invention Figure 4 The two samples were tested and the typical ultrasonic spectrum signal diagram of the samples was obtained, as shown in Figure 5As shown, the original signal data is a time domain signal, and the spectrum signal is obtained after Fourier transform. Figure 5 (a) is the signal of a typical debonding defect. Figure 5 (b) is the ultrasonic signal amplitude of the well-bonded part obtained by the signal acquisition device. By comparing the ultrasonic signals, it can be seen that there are obvious differences in their resonance peak characteristics, which can be used to determine whether the bonding is damaged.

[0071] By performing multi-point scanning imaging on the sample surface within a range of 1.5cm×1.5cm, we can obtain Figure 6 The bonding quality distribution cloud diagram of the two different samples is shown in Figure 2. Figure 6 (a) corresponds to sample 1, Figure 6 (b) corresponds to sample 2. Figure 6 The experimental results show that the non-contact laser ultrasound detection method and device proposed in this invention can detect the bonding quality of multi-layer heterogeneous structures and effectively distinguish between well-bonded areas and debonded areas.

[0072] It should be noted that, without violating the spirit and scope of the present invention, appropriate changes or modifications may be made to the above embodiments. For example, when performing defect detection based on a laser ultrasonic system, all unit devices, optical path settings, original devices, etc. in the system may adopt different models. When using multimodal resonance for defect detection, a variety of methods can be used to calculate the multimodal resonance frequency. The defect imaging method or the sample scanning method can adopt other methods, such as scanning by an optical galvanometer. In addition, the optical path construction can adopt the transmission mode (see Figure 7 ) and reflection mode ( Figure 8 There are two methods (shown), of which the transmission mode has a simple optical path and is easier to generate signals. In practical applications, in order to meet the requirements of in-situ non-contact non-destructive testing, the transmission mode is often not applicable to detect the target, and the reflection mode is more often used. Figure 8 The lens placed between the dichroic mirror and the reflector can be used to control the excitation laser spot size.

[0073] In summary, compared with the prior art, the present invention has the following advantages:

[0074] 1) The present invention uses laser ultrasonic testing technology to achieve long-distance, non-contact testing. Compared with local precision testing, it is closer to actual engineering requirements and can be completed during production and service.

[0075] 2) The present invention uses a multi-modal resonance method for detection, which can avoid the problems of difficulty in identifying the zero group velocity mode and difficulty in distinguishing multiple resonance modes;

[0076] 3) The present invention realizes the bonding quality detection of multi-layer heterogeneous structures with high accuracy, and can identify and detect damage in the early stage;

[0077] 4) The present invention proposes a scanning method based on a three-axis mobile platform, which can avoid moving operating tools and is more convenient to operate.

[0078] The present invention may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present invention.

[0079] Computer-readable storage medium can be a tangible device that can keep and store the instructions used by the instruction execution device.Computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device or any suitable combination thereof.More specific examples (non-exhaustive list) of computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, for example, a punch card or a convex structure in a groove having instructions stored thereon, and any suitable combination thereof.Computer-readable storage medium used herein is not interpreted as a transient signal itself, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagated by waveguides or other transmission media (for example, light pulses by fiber optic cables), or electrical signals transmitted by wires.

[0080] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0081] The computer program instructions for performing the operation of the present invention can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, Python, and conventional procedural programming languages ​​such as "C" language or similar programming languages. The computer readable program instructions can be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), is personalized by utilizing the state information of the computer readable program instructions, and the electronic circuit can execute the computer readable program instructions, thereby realizing various aspects of the present invention.

[0082] Various aspects of the present invention are described herein with reference to flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowcharts and / or block diagrams, and combinations of blocks in the flowcharts and / or block diagrams, can be implemented by computer-readable program instructions.

[0083] These computer-readable program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, thereby producing a machine, so that when these instructions are executed by the processor of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, where these instructions cause the computer, programmable data processing device, and / or other device to operate in a specific manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0084] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0085] The flowcharts and block diagrams in the accompanying drawings show the possible implementation architecture, functions and operations of the systems, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flowchart or block diagram can represent a module, program segment or part of an instruction, and the module, program segment or part of the instruction contains one or more executable instructions for implementing the specified logical function. In some alternative implementations, the functions marked in the box can also occur in an order different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system that performs the specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions. It is well known to those skilled in the art that implementation by hardware, implementation by software, and implementation by a combination of software and hardware are all equivalent.

[0086] While various embodiments of the present invention have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein. The scope of the present invention is defined by the appended claims.

Claims

1. A method for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound, comprising the following steps: For the target multi-layer heterogeneous structure, all corresponding resonance modes are calculated using computer finite element simulation method to obtain the multi-modal theoretical resonance frequency; Using the established detection device, based on the thermoelastic effect, laser ultrasonic multi-point scanning is performed on the preset plane area of ​​the target multi-layer heterogeneous structure, and ultrasonic signals are collected; The ultrasonic signal is converted into a corresponding spectrum signal by time-frequency domain, thereby obtaining a multimodal measurement resonance frequency; By comparing the multimodal theoretical resonance frequency and the multimodal measured resonance frequency, a heterogeneous structure bonding quality evaluation result is obtained.

2. The method according to claim 1, characterized in that The detection device includes a signal exciter, a processor, a laser vibrometer, a dichroic mirror, a reflector, a mobile platform and a display device, wherein: The mobile platform is used to carry the target multi-layer heterostructure, and the target multi-layer heterostructure can move along three axes with the mobile platform; The signal exciter is used to generate an excitation laser, which is reflected on the surface of the dichroic mirror and then acts on the target multilayer heterostructure to generate an ultrasonic signal on the surface of the target multilayer heterostructure; The laser vibrometer is used to generate a detection laser, which acts on the target multilayer heterostructure via the dichroic mirror; The signal exciter, the laser vibrometer and the target multilayer heterostructure are uniformly installed in predetermined positions on the same plane, and the optical path is adjusted so that the detection laser and the excitation laser act in parallel on the same point on the surface of the target multilayer heterostructure; The processor is configured to control the mobile platform, the signal actuator, and the laser vibrometer in response to a user operation; The mobile platform is configured to be capable of real-time positioning and to complete point-by-point scanning of a preset plane area of ​​a target heterostructure sample by editing its movement path; The display device is used to receive user operations, transmit them to the processor, and display heterogeneous structure bonding quality evaluation results to the user.

3. The method according to claim 2, characterized in that The signal exciter 20 includes a laser pulser, a pulse width adjustment module, a frequency adjustment module and an attenuator, wherein the laser pulser is used to generate a laser with a preset frequency and pulse width; the pulse width adjustment module is built into the laser pulser and is used to adjust the pulse width of the laser; the frequency adjustment module is built into the laser pulser and is used to adjust the frequency of the laser; the attenuator is external to the laser pulser and is used to control the energy of the laser generated by the laser pulser.

4. The method according to claim 2, characterized in that The mobile platform includes a base and a sample placement structure, wherein the sample placement structure is used to fix the target multilayer heterostructure on the mobile platform perpendicular to the direction of the incident laser, and the mobile platform is configured to perform desired positioning movement in response to a user operation, which is transmitted to the processor via the display device.

5. The method according to claim 2, characterized in that A lens is further provided between the dichroic mirror and the reflector, and the lens is used to control the spot size of the excitation laser.

6. The method according to claim 1, characterized in that The multimodal measurement resonance frequency is obtained according to the following steps: During the scanning process, the original ultrasonic signal is collected, and the original ultrasonic signal is a time domain signal; The original ultrasonic signal is subjected to Fourier transformation to obtain a spectrum signal, and based on multiple resonance mode information represented by the spectrum signal, the multi-modal measurement resonance frequency is obtained.

7. The method according to claim 6, characterized in that The method further includes using a filter to perform filtering when acquiring the original ultrasonic signal.

8. The method according to claim 3, characterized in that The laser pulser is a Nd:YAG laser with a wavelength of 1064 nm, a pulse width of 10 ns, and a maximum frequency of 400 Hz.

9. A device for evaluating the bonding quality of heterogeneous structures based on non-contact laser ultrasound: Calculation unit: used to calculate all corresponding resonance modes of the target multi-layer heterogeneous structure using computer finite element simulation method to obtain the multi-modal theoretical resonance frequency; Ultrasonic signal acquisition unit: used to perform laser ultrasonic multi-point scanning on a preset plane area of ​​the target multi-layer heterogeneous structure based on the thermoelastic effect using the established detection device and to collect ultrasonic signals; Ultrasonic measurement unit: used to convert the ultrasonic signal into a corresponding spectrum signal through time-frequency domain conversion, and then obtain the multimodal measurement resonance frequency; Evaluation unit: used for obtaining heterogeneous structure bonding quality evaluation results by comparing the multimodal theoretical resonance frequency and the multimodal measured resonance frequency.

10. A computer-readable storage medium having a computer program stored thereon, wherein: When the computer program is executed by a processor, the steps of the method according to claim 9 are implemented.

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