A flip chip solder joint defect detection method, system, medium and device

Abstract

The present invention relates to a flip chip solder joint defect detection method, system, medium and device, wherein the method comprises: step S1: obtaining a sample chip, wherein the sample chip has different solder joint defects; step S2: obtaining the ultrasonic signal of the sample chip through a focused ultrasonic transducer; step S3: converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal of a virtual non-focused ultrasonic transducer, and then converting the time domain wave field signal into a signal frequency domain wave field, and obtaining a two-dimensional focused image of the sample chip based on the signal frequency domain wave field; step S4: extracting a circular vector factor of the two-dimensional focused image, and using the circular vector factor to eliminate artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image; step S5: performing solder joint defect detection on the denoised two-dimensional focused image. The present invention can effectively detect solder joint defects of flip chips.

Description

Technical Field

[0001] The present invention relates to the technical field of flip chip defect detection, and in particular to a flip chip solder joint defect detection method, system, medium and equipment. Background Art

[0002] Flip chip is one of the popular packaging technologies currently. It uses bumps to directly connect the chip to the substrate, carrier or circuit board to achieve mechanical and electrical interconnection. Acoustic Micro Imaging (AMI), as a non-destructive testing technology, has been widely used to detect these micro defects. AMI uses a high-frequency focused ultrasonic transducer to generate ultrasonic waves. When the ultrasonic waves propagate to the defect interface, the acoustic impedance mismatch caused by the defect will affect the intensity of the reflected signal. By analyzing the echo signal, the defect can be effectively diagnosed. The ultrasonic detection echo signal contains information related to the defect location, size and characteristics, but due to the influence of material grains and detection system noise, the echo signal is often accompanied by noise interference, which affects the detection accuracy. Therefore, it is very important to denoise the echo signal to improve the detection accuracy.

[0003] Synthetic Aperture Focusing Technique (SAFT) is an ultrasonic imaging technology widely used in non-destructive testing, medical and other fields. The emergence of SAFT technology has broken through the limitations of traditional theory and achieved the effect of using a single ultrasonic transducer with a smaller aperture to simulate a large aperture array. However, due to the limitation of the effective aperture width, the resolution of traditional SAFT images is low, and it is often difficult to obtain detection images with sufficient signal-to-noise ratio, which can easily lead to incorrect judgments of defects or lesions. In addition, traditional SAFT is based on the time domain delay and sum (DAS) algorithm for image reconstruction. When processing large data sets, a large number of heavy iterative operations are required, so the image efficiency is obviously difficult to meet the requirements of online real-time imaging in low hardware environments. In summary, how to simultaneously improve the imaging quality and computational efficiency of SAFT has become an important technical problem that needs to be solved in the current field of non-destructive testing. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problem in the prior art that the imaging quality and operation efficiency of SAFT are low, which in turn leads to poor defect detection effect of flip-chip.

[0005] In order to solve the above technical problems, the present invention provides a flip chip solder joint defect detection method, comprising:

[0006] Step S1: obtaining a sample chip, wherein the sample chip has different solder joint defects;

[0007] Step S2: acquiring the ultrasonic signal of the sample chip by a focused ultrasonic transducer;

[0008] Step S3: converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal of a virtual unfocused ultrasonic transducer, and then converting the time domain wave field signal into a signal frequency domain wave field, and obtaining a two-dimensional focused image of the sample chip based on the signal frequency domain wave field;

[0009] Step S4: extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image;

[0010] Step S5: performing solder joint defect detection on the denoised two-dimensional focused image.

[0011] In one embodiment of the present invention, the method of acquiring the ultrasonic signal of the sample chip by using a focused ultrasonic transducer in step S2 includes:

[0012] Step S21: placing a sample chip with solder joint defects on a water immersion detection platform;

[0013] Step S22: moving the focused ultrasonic transducer to directly above the sample chip, and using the focused ultrasonic transducer to excite the sample chip to generate a vibration signal;

[0014] Step S23: converting the received vibration signal into an electrical signal through the focused ultrasonic transducer, and then filtering and amplifying the electrical signal to obtain an ultrasonic signal of the sample chip.

[0015] In one embodiment of the present invention, the method of step S3 includes:

[0016] Step S31: converting the ultrasonic signal of the sample chip, converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer;

[0017] Step S32: converting the time domain wavefield signal into a frequency domain wavefield signal, and performing wavefield extension on the frequency domain wavefield signal using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip.

[0018] In one embodiment of the present invention, the method of converting the ultrasonic signal of the sample chip in step S31, converting the ultrasonic signal of the sample chip from a focused ultrasonic transducer to a time domain wave field signal corresponding to a virtual unfocused ultrasonic transducer, includes:

[0019] Step S311: Extend the focusing angle of the focused ultrasonic transducer to the inside of the sample chip by Snell's law to obtain the angle between the focused sound wave of the ultrasonic signal and each interface inside the sample chip, and then calculate the displacement distance of the focused sound wave in the horizontal direction:

[0020] ;

[0021] in, and Indicates the number of Layer and Sound velocity of layer material, and Indicates the focused sound wave and the sample chip Layer and The angle between the layers, Indicates the focused sound wave and the sample chip The angle between the layer interfaces and Indicates the last layer inside the sample chip. Indicates the number of Layer material thickness, It indicates the distance between the focal point formed when the focused sound wave reaches the inside of the sample chip and the interface of the previous layer. Indicates the horizontal displacement distance of the focused sound wave;

[0022] Step S312: Calculate the time required for the focused ultrasonic transducer sound wave to reach the focus: is equal to half of the probe width of the focused ultrasonic transducer, then the position of the focus is obtained, and according to the reversibility of the acoustic path, the position of the focus is regarded as a virtual unfocused ultrasonic transducer, and then the sample chip ultrasonic signal is converted into a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer. The sample chip ultrasonic signal is a time domain wave field signal of a focused ultrasonic transducer, and then satisfies:

[0023] ;

[0024] in, Indicates the number of Sound velocity of layer material, represents the time domain wave field signal corresponding to the focused ultrasonic transducer, represents the time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer, represents the time domain wave field signal, Indicates the signal conversion symbol, Represents the width matrix of the time domain wave field signal generated by the focused ultrasonic transducer in the transverse direction, represents the depth matrix in the longitudinal direction of the time domain wave field signal generated by the focused ultrasound transducer, for The flip matrix, is the time from the focused ultrasound transducer to the focal point, include and also includes the time from the virtual non-focused ultrasonic transducer to the starting point, where the starting point is the position of the focused ultrasonic transducer.

[0025] In one embodiment of the present invention, the method of converting the time domain wavefield signal into a frequency domain wavefield signal in step S32, and performing wavefield extension on the frequency domain wavefield signal using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip includes:

[0026] Step S321: For the time domain wave field signal ,make And perform two-dimensional Fourier transform to obtain the frequency domain wave field signal in the frequency domain-wave number domain , is the frequency domain, for Directional wave vector component;

[0027] Step S322: The frequency domain wave field signal Through the wave field extrapolation formula, we can get the wave field depth increment Frequency domain wave field signal:

[0028] ;

[0029] in, is the wave field depth increment The frequency domain wave field signal, is the phase shift factor;

[0030] Step S323: To increase the computing speed, the frequency domain wave field signal From the frequency domain-wave number domain to the two-dimensional wave number domain, the two-dimensional dispersion relation is obtained about Expression, insert And perform inverse Fourier transform and convert Substitute it to get the reconstructed image:

[0031] ;

[0032] in, represents the wave speed, is the reconstructed image;

[0033] Step S324: The value of , the process of step S321 to step S324 is repeated, and the wave field depth is increased continuously. To reconstruct the image until From the virtual unfocused ultrasound transducer reaching the sample chip surface, all reconstructed images are acquired and stitched together to obtain the final two-dimensional focused image.

[0034] In one embodiment of the present invention, the method of extracting the ring vector factor of the two-dimensional focused image in step S4 and using the ring vector factor to remove artifact noise of the two-dimensional focused image to obtain the denoised two-dimensional focused image is:

[0035] The PCI algorithm is used to extract phase information of the two-dimensional focused image of the sample chip, and the ring vector factor of the two-dimensional focused image is obtained from the phase information. The ring vector factor is used to eliminate artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image.

[0036] In one embodiment of the present invention, the ring vector factor is defined as:

[0037] ;

[0038] in, The two-dimensional signal form representing the two-dimensional focused image, yes The abbreviation of represents a two-dimensional focused image, To find the modulo symbol, is an imaginary unit, is the phase information of the two-dimensional signal, is the width matrix of the time domain wave field signal in the transverse direction generated by the focused ultrasound transducer The number of signals in represents a unit complex signal consisting of phase information and , represents the ring vector factor, and represents the real and imaginary parts of a unit complex signal and , .

[0039] In order to solve the above technical problems, the present invention provides a flip chip solder joint defect detection system, comprising:

[0040] A first acquisition module: used to acquire a sample chip, wherein the sample chip has different solder joint defects;

[0041] A second acquisition module: used for acquiring the ultrasonic signal of the sample chip through a focused ultrasonic transducer;

[0042] A conversion module: used to convert the ultrasonic signal of the sample chip from a focused ultrasonic transducer into a time domain wave field signal of a virtual non-focused ultrasonic transducer, and then convert the time domain wave field signal into a signal frequency domain wave field, and obtain a two-dimensional focused image of the sample chip based on the signal frequency domain wave field;

[0043] Denoising module: used for extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove the artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image;

[0044] Detection module: used to perform solder joint defect detection on the denoised two-dimensional focused image.

[0045] To solve the above technical problems, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above flip chip solder joint defect detection method when executing the computer program.

[0046] In order to solve the above technical problems, the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the above flip chip solder joint defect detection method are implemented.

[0047] The above technical solution of the present invention has the following advantages compared with the prior art:

[0048] The present invention studies the noise phenomenon of high-frequency ultrasonic signals of flip chips and the problem of low image resolution caused by probe limitations. A virtual non-focused ultrasonic transducer is constructed to perform phase shift imaging on the signal, and the artifact noise of the focused two-dimensional focused image is eliminated to improve the quality of the two-dimensional focused image. Based on the obtained two-dimensional focused images of different defects, solder joint defects can be identified quickly and efficiently.

[0049] The detection result of the present invention has better objectivity and accuracy, and provides a new idea for realizing fast and efficient flip chip solder joint defect detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0051] Figure 1 is a flow chart of the method of the present invention;

[0052] Figure 2 It is a multi-layer schematic diagram of a sample chip in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0054] Reference Figure 1 As shown, the present invention relates to a flip chip solder joint defect detection method, comprising:

[0055] Step S1: obtaining a sample chip, wherein the sample chip has different solder joint defects, and the solder joint defects include but are not limited to solder joint missing, solder joint cold solder joint and solder joint crack;

[0056] Step S2: acquiring the ultrasonic signal of the sample chip by a focused ultrasonic transducer;

[0057] Step S3: converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal of a virtual unfocused ultrasonic transducer, and then converting the time domain wave field signal into a signal frequency domain wave field, and obtaining a two-dimensional focused image of the sample chip based on the signal frequency domain wave field;

[0058] Step S4: extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image;

[0059] Step S5: performing solder joint defect detection on the denoised two-dimensional focused image.

[0060] Furthermore, the method for obtaining the sample chip in step S1 includes:

[0061] The bare chip size of the sample chip used in this embodiment is , there are 184 solder joints on the lower surface, evenly distributed on the four sides. Each solder joint is made of alloy, with a diameter of 120um and a solder joint spacing of 200um. Using the MC001-YR2010 auxiliary equipment, and with the help of fine-tipped tweezers, some solder joints and pads are manually removed to create two typical defects, cold solder joints and missing solder joints, and the locations of solder joint defects are marked. In order to create crack defects, a thermal cycle experiment is carried out on the sample chip using a device that can simulate temperature changes, and the solder joint condition is observed by an acoustic scanning microscope. Finally, sample chips with different solder joint defects are obtained.

[0062] Furthermore, the method of acquiring the ultrasonic signal of the sample chip by using a focused ultrasonic transducer in step S2 includes:

[0063] Step S21: placing a sample chip with solder joint defects on a water immersion detection platform;

[0064] Step S22: moving the focused ultrasonic transducer to directly above the sample chip, and using the focused ultrasonic transducer to excite the sample chip to generate a vibration signal;

[0065] Step S23: converting the received vibration signal into an electrical signal through the focused ultrasonic transducer, and then filtering and amplifying the electrical signal to obtain an ultrasonic signal of the sample chip.

[0066] Further, the method of step S3 includes:

[0067] Step S31: converting the ultrasonic signal of the sample chip, converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer;

[0068] Step S32: converting the time domain wavefield signal into a frequency domain wavefield signal, and performing wavefield extension on the frequency domain wavefield signal using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip.

[0069] Furthermore, in step S31, the method of converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer to a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer includes:

[0070] Step S311: Please combine Figure 2 , the focusing angle of the focused ultrasonic transducer is extended to the inside of the sample chip by Snell's law, the angle between the focused acoustic wave of the ultrasonic signal and each interface inside the sample chip is obtained, and then the displacement distance of the focused acoustic wave in the horizontal direction is calculated:

[0071] ;

[0072] in, and Indicates the number of Layer and Sound velocity of layer material, and Indicates the focused sound wave and the sample chip Layer and The angle between the layers, Indicates the focused sound wave and the sample chip The angle between the layer interfaces and Indicates the last layer inside the sample chip. Indicates the number of Layer material thickness, It indicates the distance between the focal point formed when the focused sound wave reaches the inside of the sample chip and the interface of the previous layer. Represents the horizontal displacement of the focused sound wave. Please note that Figure 2 Displacement of the focused acoustic wave in each layer of the sample chip The sum is equal to .

[0073] Step S312: Calculate the time required for the sound wave of the focused ultrasonic transducer to reach the focus: is equal to half of the probe width of the focused ultrasonic transducer, then the position of the focus is obtained, and according to the reversibility of the acoustic path, the position of the focus is regarded as a virtual unfocused ultrasonic transducer, and then the ultrasonic signal of the sample chip (i.e., the time domain wave field signal of the focused ultrasonic transducer) is converted into the time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer, then:

[0074] ;

[0075] in, Indicates the number of Sound velocity of layer material, Indicates the number of Layer material thickness, represents the time domain wave field signal corresponding to the focused ultrasonic transducer, represents the time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer, represents the time domain wave field signal, Indicates the signal conversion symbol, Represents the width matrix of the time domain wave field signal generated by the focused ultrasonic transducer in the transverse direction, represents the depth matrix in the longitudinal direction of the time domain wave field signal generated by the focused ultrasound transducer, for The flip matrix ( arrive The essence is to convert the signal from the form of ultrasound focused ultrasound transducer to the form of virtual non-focused ultrasound transducer). is the time from the focused ultrasound transducer to the focal point, include The time from the virtual unfocused ultrasound transducer to the starting point ( The time periods at both ends are included because the ultrasonic signal is considered to be a back and forth process). The starting point is the location of the focused ultrasonic transducer.

[0076] Furthermore, in step S32, the time domain wavefield signal is converted into a frequency domain wavefield signal, and the frequency domain wavefield signal is subjected to wavefield extension using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip. The method includes:

[0077] Step S321: For the time domain wave field signal ,make And perform two-dimensional Fourier transform to obtain the frequency domain wave field signal in the frequency domain-wave number domain , is the frequency domain, for Directional wave vector component;

[0078] Step S322: The frequency domain wave field signal Through the wave field extrapolation formula, we can get the wave field depth increment Frequency domain wave field signal:

[0079] ;

[0080] in, For the depth increment The frequency domain wave field signal, is the phase shift factor, For the sound field depth increment, you can Simply understood as a very small increment, the purpose is to make subsequent images clearer;

[0081] Step S323: To increase the computing speed, the frequency domain wave field signal From the frequency domain-wave number domain to the two-dimensional wave number domain, the two-dimensional dispersion relation is obtained about Expression, insert And perform inverse Fourier transform and convert Substitute it to get the reconstructed image:

[0082] ;

[0083] in, represents the wave speed, is the reconstructed image;

[0084] Step S324: The value of , the process of step S321 to step S324 is repeated, and the wave field depth is increased continuously. To reconstruct the image until From the virtual unfocused ultrasound transducer to the sample chip surface, all reconstructed images are acquired and stitched together to obtain the final two-dimensional focused image.

[0085] Furthermore, in step S4, the ring vector factor of the two-dimensional focused image is extracted, and the artifact noise of the two-dimensional focused image is eliminated by using the ring vector factor to obtain the denoised two-dimensional focused image.

[0086] The PCI (Phase Contrast Imaging) algorithm (i.e., phase coherent imaging algorithm) is used to extract the phase information of the two-dimensional focused image of the sample chip, and the ring vector factor of the two-dimensional focused image is obtained from the phase information. The artifact noise of the two-dimensional focused image is eliminated using the ring vector factor to obtain a denoised two-dimensional focused image.

[0087] The ring vector factor is defined as:

[0088] ;

[0089] in, The two-dimensional signal form representing the two-dimensional focused image, yes The abbreviation of represents a two-dimensional focused image, To find the modulo symbol, is an imaginary unit, is the phase information of the two-dimensional signal, is the width matrix of the time domain wave field signal in the transverse direction generated by the focused ultrasound transducer The number of signals in represents a unit complex signal consisting of phase information and , represents the ring vector factor, and represents the real and imaginary parts of a unit complex signal and , . Embodiment 2

[0090] This embodiment provides a flip chip solder joint defect detection system, including:

[0091] A first acquisition module: used to acquire a sample chip, wherein the sample chip has different solder joint defects;

[0092] A second acquisition module: used for acquiring the ultrasonic signal of the sample chip through a focused ultrasonic transducer;

[0093] A conversion module: used to convert the ultrasonic signal of the sample chip from a focused ultrasonic transducer into a time domain wave field signal of a virtual non-focused ultrasonic transducer, and then convert the time domain wave field signal into a signal frequency domain wave field, and obtain a two-dimensional focused image of the sample chip based on the signal frequency domain wave field;

[0094] Denoising module: used for extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove the artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image;

[0095] Detection module: used to perform solder joint defect detection on the denoised two-dimensional focused image. Embodiment 3

[0096] This embodiment provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the flip chip solder joint defect detection method described in Embodiment 1 are implemented. Embodiment 4

[0097] This embodiment provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the flip chip solder joint defect detection method described in the first embodiment are implemented.

[0098] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present application may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0099] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0100] These computer program instructions may also be stored in a computer readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0101] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0102] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0103] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from them are still within the protection scope of the invention.

Claims

1. A flip chip solder joint defect detection method, characterized in that: include: Step S1: obtaining a sample chip, wherein the sample chip has different solder joint defects; Step S2: acquiring the ultrasonic signal of the sample chip by a focused ultrasonic transducer; Step S3: converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal of a virtual unfocused ultrasonic transducer, and then converting the time domain wave field signal into a signal frequency domain wave field, and obtaining a two-dimensional focused image of the sample chip based on the signal frequency domain wave field; The method of step S3 comprises: Step S31: converting the ultrasonic signal of the sample chip, converting the ultrasonic signal of the sample chip from the focused ultrasonic transducer into a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer; The method of converting the ultrasonic signal of the sample chip in step S31, and converting the ultrasonic signal of the sample chip from a focused ultrasonic transducer into a time domain wave field signal corresponding to a virtual unfocused ultrasonic transducer, comprises: Step S311: Extend the focusing angle of the focused ultrasonic transducer to the inside of the sample chip by Snell's law to obtain the angle between the focused sound wave of the ultrasonic signal and each interface inside the sample chip, and then calculate the displacement distance of the focused sound wave in the horizontal direction: ； in, and Indicates the number of Layer and Sound velocity of layer material, and Indicates the focused sound wave and the sample chip Layer and The angle between the layers, Indicates the focused sound wave and the sample chip The angle between the layer interfaces and Indicates the last layer inside the sample chip. Indicates the number of Layer material thickness, It indicates the distance between the focal point formed when the focused sound wave reaches the inside of the sample chip and the interface of the previous layer. Indicates the horizontal displacement distance of the focused sound wave; Step S312: Calculate the time required for the focused ultrasonic transducer sound wave to reach the focus: is equal to half of the probe width of the focused ultrasonic transducer, then the position of the focus is obtained, and according to the reversibility of the acoustic path, the position of the focus is regarded as a virtual unfocused ultrasonic transducer, and then the sample chip ultrasonic signal is converted into a time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer. The sample chip ultrasonic signal is a time domain wave field signal of a focused ultrasonic transducer, and then satisfies: ； in, Indicates the number of Sound velocity of layer material, represents the time domain wave field signal corresponding to the focused ultrasonic transducer, represents the time domain wave field signal corresponding to the virtual unfocused ultrasonic transducer, represents the time domain wave field signal, Indicates the signal conversion symbol, Represents the width matrix of the time domain wave field signal generated by the focused ultrasonic transducer in the transverse direction, represents the depth matrix in the longitudinal direction of the time domain wave field signal generated by the focused ultrasound transducer, for The flip matrix, is the time from the focused ultrasound transducer to the focal point, include The time also includes the time from the virtual non-focused ultrasonic transducer to the starting point, where the starting point is the position of the focused ultrasonic transducer; Step S32: converting the time domain wavefield signal into a frequency domain wavefield signal, and performing wavefield extension on the frequency domain wavefield signal using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip; The method of converting the time domain wave field signal into a frequency domain wave field signal in step S32, and performing wave field extension on the frequency domain wave field signal using a wave field extrapolation formula to obtain a two-dimensional focused image of the sample chip includes: Step S321: For the time domain wave field signal ,make And perform two-dimensional Fourier transform to obtain the frequency domain wave field signal in the frequency domain-wave number domain , is the frequency domain, for Directional wave vector component; Step S322: The frequency domain wave field signal Through the wave field extrapolation formula, we can get the wave field depth increment Frequency domain wave field signal: ； in, is the wave field depth increment The frequency domain wave field signal, is the phase shift factor; Step S323: To increase the computing speed, the frequency domain wave field signal From the frequency domain-wave number domain to the two-dimensional wave number domain, the two-dimensional dispersion relation is obtained about Expression, insert And perform inverse Fourier transform and convert Substitute it to get the reconstructed image: ； in, represents the wave speed, is the reconstructed image; Step S324: The value of , the process of step S321 to step S324 is repeated, and the wave field depth is increased continuously. To reconstruct the image until From the virtual unfocused ultrasound transducer reaching the sample chip surface, all reconstructed images are acquired and stitched together to obtain a final two-dimensional focused image; Step S4: extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image; In step S4, the method of extracting the annular vector factor of the two-dimensional focused image and using the annular vector factor to remove the artifact noise of the two-dimensional focused image to obtain the denoised two-dimensional focused image is: Extracting phase information of the two-dimensional focused image of the sample chip by using the PCI algorithm, obtaining a ring vector factor of the two-dimensional focused image from the phase information, and removing artifact noise of the two-dimensional focused image by using the ring vector factor to obtain a denoised two-dimensional focused image; The ring vector factor is defined as: ； in, The two-dimensional signal form representing the two-dimensional focused image, yes The abbreviation of represents a two-dimensional focused image, To find the modulo symbol, is an imaginary unit, is the phase information of the two-dimensional signal, is the width matrix of the time domain wave field signal in the transverse direction generated by the focused ultrasound transducer The number of signals in represents a unit complex signal consisting of phase information and , represents the ring vector factor, and represents the real and imaginary parts of a unit complex signal and , ; Step S5: performing solder joint defect detection on the denoised two-dimensional focused image.

2. The flip chip solder joint defect detection method according to claim 1, characterized in that: The method for acquiring the ultrasonic signal of the sample chip by using a focused ultrasonic transducer in step S2 comprises: Step S21: placing a sample chip with solder joint defects on a water immersion detection platform; Step S22: moving the focused ultrasonic transducer to directly above the sample chip, and using the focused ultrasonic transducer to excite the sample chip to generate a vibration signal; Step S23: converting the received vibration signal into an electrical signal through the focused ultrasonic transducer, and then filtering and amplifying the electrical signal to obtain an ultrasonic signal of the sample chip.

3. A flip chip solder joint defect detection system, used to implement the flip chip solder joint defect detection method as described in any one of claims 1-2, characterized in that: include: A first acquisition module: used to acquire a sample chip, wherein the sample chip has different solder joint defects; A second acquisition module: used for acquiring the ultrasonic signal of the sample chip through a focused ultrasonic transducer; A conversion module: used to convert the ultrasonic signal of the sample chip from a focused ultrasonic transducer into a time domain wave field signal of a virtual non-focused ultrasonic transducer, and then convert the time domain wave field signal into a signal frequency domain wave field, and obtain a two-dimensional focused image of the sample chip based on the signal frequency domain wave field; The conversion module comprises: Converting the ultrasonic signal of the sample chip, converting the ultrasonic signal of the sample chip from a focused ultrasonic transducer into a time domain wave field signal corresponding to a virtual unfocused ultrasonic transducer; Converting the time domain wavefield signal into a frequency domain wavefield signal, and performing wavefield extension on the frequency domain wavefield signal using a wavefield extrapolation formula to obtain a two-dimensional focused image of the sample chip; Denoising module: used for extracting the annular vector factor of the two-dimensional focused image, and using the annular vector factor to remove the artifact noise of the two-dimensional focused image to obtain a denoised two-dimensional focused image; The ring vector factor is defined as: ； in, The two-dimensional signal form representing the two-dimensional focused image, yes The abbreviation of represents a two-dimensional focused image, To find the modulo symbol, is an imaginary unit, is the phase information of the two-dimensional signal, is the width matrix of the time domain wave field signal in the transverse direction generated by the focused ultrasound transducer The number of signals in represents a unit complex signal consisting of phase information and , represents the ring vector factor, and represents the real and imaginary parts of a unit complex signal and , ; Detection module: used to perform solder joint defect detection on the denoised two-dimensional focused image.

4. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the flip chip solder joint defect detection method according to any one of claims 1 to 2 are implemented.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the flip chip solder joint defect detection method according to any one of claims 1 to 2 are implemented.

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