A Terahertz Non-destructive Testing System for Electronic Circuits Based on Time-Domain Reflectometry

Abstract

This invention relates to the field of terahertz nondestructive testing technology, specifically to a terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry, comprising: a light source and beam splitting module, a strong-field terahertz pulse generation module, a terahertz collection and transmission module, a sample detection module, and a terahertz pulse detection module; the laser beam is split into a pump beam and a probe beam; the pump beam enters the strong-field terahertz pulse generation module to generate a strong-field terahertz pulse; the terahertz transmission and collection module collects the strong-field terahertz pulse and transmits it to the sample detection module; the sample detection module collects the reflection signal of the terahertz pulse from the electronic circuit sample; the probe beam enters the terahertz pulse detection module, and the terahertz pulse detection module performs coherent measurement on the reflected signal; this invention enables higher-performance nondestructive testing of internal defects in electronic circuits based on the generated strong-field terahertz pulse.

Description

Technical Field

[0001] This invention relates to the field of terahertz nondestructive testing technology, specifically to a terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry. Background Technology

[0002] Electronic circuits and semiconductor devices are increasingly moving towards higher integration and smaller package sizes, placing ever higher demands on their quality, cost, and reliability. Non-destructive testing (NDT) techniques can be used to inspect electronic circuits and semiconductor devices, and if defects are found, their location needs to be quickly and accurately pinpointed. Time-Domain Reflectometer (TDR) systems are a type of NDT system capable of detecting faults in semiconductor packages, electronic components, and printed circuit boards. However, traditional step-response-based analysis systems distinguish the presence and location of faults by analyzing the amplitude changes of the TDR waveform. This approach struggles to accurately determine the starting point of the signal change, introducing significant errors in fault location.

[0003] Terahertz waves have frequencies ranging from 0.1 THz to 10 THz, corresponding to wavelengths of 0.03 mm to 3 mm. Terahertz pulses have wavelengths in the picosecond range (ps). -12 Terahertz time-domain spectroscopy, on the order of s, allows for coherent measurement of terahertz wave waveforms and relative time delays. From the measured terahertz time-domain waveform, the internal information of the object under test can be inferred. Terahertz nondestructive testing utilizes this method to reconstruct the object's internal structure by measuring the transmitted or reflected signals and comparing them with a reference signal (typically from a defect-free location).

[0004] For objects that terahertz waves cannot penetrate or that have a multi-layered internal structure, the terahertz time-of-flight (THz-TOF) method can be used for detection. The basic principle is that if an object has internal defects or a multi-layered structure, an incident terahertz pulse will be reflected at the interfaces between the layers due to the difference in refractive index on both sides. By measuring the reflected terahertz time-domain waveform and considering the time delay of different reflected pulses, and if the refractive index of each layer is known, the thickness of the internal layered structure can be calculated. This method is commonly used for non-destructive testing of the internal structure of objects. If the object under test is moved in a two-dimensional scanning manner, and characteristic parameters of the terahertz pulse signal at different scanning positions (such as peak size, time delay, etc.) are extracted, terahertz imaging of the internal structure of the object can also be achieved. Introducing terahertz pulses into the non-destructive testing of electronic circuits and semiconductor packages allows for direct identification of defect locations through the pulse waveform.

[0005] Existing high-resolution time-domain reflectometers employ an asynchronous electro-optic sampling method using two femtosecond pulsed lasers. The first laser generates electrical pulses with a rise time of <10 ps, ​​which are coupled to the sample via an RF probe. The reflected signal is generated by internal damage. These electrical pulses are reflected to a photoconductive switch, which is then illuminated by the second laser. The measured current reflects the amplitude of the reflected signal. Due to the frequency difference Δf between the two lasers, the reflected wave can be recorded within 1 / Δf time, achieving high-resolution measurement. This technique requires two femtosecond lasers, and the repetition frequency of these two lasers needs precise control and locking. This necessitates more complex control technology and systems, complicating system construction and increasing costs due to the additional lasers and control devices. Furthermore, the time jitter between the laser pulses output by the two lasers affects the temporal resolution of the measurement, thus impacting the accuracy of defect location. Summary of the Invention

[0006] In view of the above problems, the present invention provides a terahertz non-destructive testing system for electronic circuits based on time-domain reflectometry, which solves the technical problem that the existing technology uses femtosecond lasers to pump photodiodes to generate electrical pulses, resulting in weak electrical pulse energy. For devices with long internal electronic circuits, transmission attenuation, interface reflection and other factors may lead to weak useful reflected signals at defects.

[0007] This invention provides a terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry, comprising a light source and beam splitting module, a strong-field terahertz pulse generation module, a terahertz pulse collection and transmission module, a sample detection module, and a terahertz pulse detection module; wherein,

[0008] The light source and beam splitting module includes: laser 1 and first beam splitter 2;

[0009] The strong field terahertz pulse generation module includes: a first reflector 3, an optical delay line 14, a first reflective grating 4, a second reflector 5, a first imaging system 6, a first half-wave plate 7, and a lithium niobate crystal 8;

[0010] The terahertz collection and transmission module includes: a third reflector 9, a first parabolic mirror 10, and a coupler 11;

[0011] The sample detection module includes: probe 12 and electronic circuit sample stage 13;

[0012] The laser 1 generates laser light, and the first beam splitter 2 splits the laser beam into a pump beam and a probe beam. The pump beam enters the strong-field terahertz pulse generation module to generate a strong-field terahertz pulse. The terahertz transmission and collection module collects the strong-field terahertz pulse and transmits it to the sample detection module. The sample detection module collects the reflection signal of the terahertz pulse from the electronic circuit sample. The probe beam enters the terahertz pulse detection module, and the terahertz pulse detection module performs coherent measurement on the reflection signal.

[0013] Preferably, the terahertz pulse detection module includes: a pulse width compressor 15, a third lens 16, a fourth lens 17, a fourth reflector 18, a step mirror 19, a fifth lens 20, a second beam splitter 21, a detector crystal 22, a sixth lens 23, a seventh lens 24, a quarter-wave plate 25, an eighth lens 26, a polarizing beam splitter prism 27, and a camera 28.

[0014] Preferably, for the terahertz pulse detection module: the optical path difference between the detection beam and the pump beam is adjusted by the optical delay line 14. The detection beam is reflected to the step mirror 19 by the pulse width compressor 15, the third lens 16, the fourth lens 17, and the fourth reflector 18. Then, it passes through the fifth lens 20 and the second beam splitter 21 and is collinearly focused on the detection crystal 22 with the reflected terahertz pulse sent by the coupler 11. After passing through the seventh lens 24, the quarter-wave plate 25, the eighth lens 26, and the polarizing beam splitter prism 27, it is imaged onto the detection array of the camera 28.

[0015] Preferably, the terahertz pulse detection module includes: a pulse width compressor 15, a fast delay line 29, a second half-wave plate 30, a detector crystal 22, a ninth lens 31, a quarter-wave plate 25, a Wollaston prism 32, and a balanced detector 33.

[0016] Preferably, for the terahertz pulse detection module: the detection beam passes through the pulse width compressor 15, the fast delay line 29, and the second half-wave plate 30, then through the small hole on the first parabolic mirror 10, and spatially coincides with the reflected terahertz pulse sent by the coupler 11 on the detection crystal 22. After passing through the ninth lens 31, the quarter-wave plate 25, and the Wollaston prism 32, it is incident on the balanced detector 33 for terahertz waveform detection.

[0017] Preferably, for the strong field terahertz pulse generation module: the pump beam irradiates the lithium niobate crystal 8 through the first reflector 3, optical delay line 14, first reflective grating 4, second reflector 5, first lens 61, first half-wave plate 7 and second lens 62 to generate a strong field terahertz pulse, and the first imaging system 6 includes the first lens 61 and the second lens 62.

[0018] Preferably, for the terahertz collection and transmission module: the strong field terahertz pulse is reflected by the third reflecting mirror 9 to the first parabolic mirror 10, the first parabolic mirror 10 collects the strong field terahertz pulse and couples it to the coupler 11, the coupler 11 transmits the free space terahertz pulse to the sample detection module, and transmits the reflected terahertz pulse detected by the sample detection module to free space.

[0019] Preferably, for the sample detection module: the probe 12 transmits a strong-field terahertz pulse from the coupler to the electronic circuit sample to be tested, the electronic circuit sample being mounted on the electronic circuit sample stage 13; the movement of the electronic circuit sample stage 13 is controlled to align the probe 12 with the position to be tested.

[0020] Preferably, the laser 1 is a femtosecond laser or a picosecond laser, and the pulse width compressor 15 compresses the pulse width to within 100 fs.

[0021] Preferably, the detector crystal 22 is an electro-optic crystal.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] (1) The electronic circuit terahertz non-destructive testing system based on time-domain reflection method provided by the present invention uses only one laser to drive it, which reduces the complexity of the system and lowers the requirements for control technology and control system.

[0024] (2) The strong field terahertz pulse generation module provided by the present invention uses tilted wavefront technology. The laser pumps the lithium niobate crystal to generate strong field terahertz pulses for defect detection. The generated terahertz pulses have strong absolute energy. In the case of multiple interface reflections and long-distance transmission losses, the terahertz pulses reflected by the defects have even stronger energy, which is convenient for detection.

[0025] (3) In the system provided by the present invention, the pump beam and the probe beam are obtained by splitting the same laser beam through a beam splitter and adopting synchronous optical sampling technology, so that there is no laser pulse time jitter between the pump beam and the probe beam, which reduces the impact of time jitter on the accuracy of the probe signal.

[0026] (4) The present invention uses a stepped mirror to realize a spatial coding single sampling device to detect each individual terahertz pulse waveform at once; or uses a fast delay line, which has a fast detection capability. Attached Figure Description

[0027] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] Figure 1A schematic diagram of a terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry provided in an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of a fast delay line device provided in an embodiment of the present invention.

[0030] Figure reference numerals: 1-Laser, 2-First beam splitter, 3-First reflecting mirror, 4-First grating, 5-Second reflecting mirror, 6-First imaging system, 61-First lens, 62-Second lens, 7-First half-wave plate, 8-Lithium niobate crystal, 9-Third reflecting mirror, 10-First parabolic mirror, 11-Coupler, 12-Probe, 13-Sample stage, 14-Optical delay line, 15-Pulse width compressor, 16-Third lens, 17-Fourth lens, 18-Fourth reflecting mirror, 19-Step mirror, 20-Fifth lens, 21-Second beam splitter, 22-Detector crystal, 23-Sixth lens, 24-Seventh lens, 25-Quarter-wave plate, 26-Eighth lens, 27-Polarizing beam splitter prism, 28-Camera, 29-Fast delay line, 30-Second half-wave plate, 31-Ninth lens, 32-Wollaston prism, 33-Balanced detector. Detailed Implementation

[0031] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0032] This invention provides a terahertz non-destructive testing system for electronic circuits based on time-domain reflectometry. It employs synchronous optical sampling technology, using a laser-pumped lithium niobate crystal to generate strong-field terahertz radiation, achieving the generation and coherent detection of terahertz electromagnetic pulses with pulse widths on the order of picoseconds, for non-destructive testing of electronic circuit fault locations. Furthermore, it utilizes a staircase mirror to achieve spatially encoded single-shot sampling, or employs a fast optical delay line for rapid detection.

[0033] To illustrate the effectiveness of the method proposed in this invention, the following detailed description of the above technical solution is provided through a specific embodiment, such as... Figure 1 As shown, a terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry is disclosed, comprising a light source and beam splitting module, a strong-field terahertz pulse generation module, a terahertz collection and transmission module, a sample detection module, and a terahertz pulse detection module; wherein:

[0034] The light source and beam splitting module includes: laser 1 and first beam splitter 2;

[0035] The strong field terahertz pulse generation module includes: a first reflector 3, an optical delay line 14, a first reflective grating 4, a second reflector 5, a first imaging system 6, a first half-wave plate 7, and a lithium niobate crystal 8;

[0036] The terahertz collection and transmission module includes: a third reflector 9, a first parabolic mirror 10, and a coupler 11;

[0037] The sample detection module includes: probe 12 and sample stage 13;

[0038] The terahertz pulse detection module includes: a pulse width compressor 15, a third lens 16, a fourth lens 17, a fourth reflector 18, a step mirror 19, a fifth lens 20, a second beam splitter 21, a detector crystal 22, a sixth lens 23, a seventh lens 24, a quarter-wave plate 25, an eighth lens 26, a polarizing beam splitter prism 27, and a camera 28.

[0039] The laser 1 generates laser light, and the first beam splitter 2 splits the laser beam into a pump beam and a probe beam. The pump beam enters the strong-field terahertz pulse generation module to generate a strong-field terahertz pulse. The terahertz transmission and collection module collects the strong-field terahertz pulse and transmits it to the sample detection module. The sample detection module collects the reflection signal of the terahertz pulse from the sample. The probe beam enters the terahertz pulse detection module, and the terahertz pulse detection module performs coherent measurement on the reflection signal.

[0040] In some embodiments, the pump beam, after passing through the first reflecting mirror 3, the first reflecting grating 4, the second reflecting mirror 5, the first lens 61 and the second lens 62 in the first imaging system 6, and the first half-wave plate 7, illuminates the lithium niobate crystal 8 to generate a terahertz signal. The pump beam undergoes negative first-order diffraction by the first reflecting grating 4 to achieve wavefront tilting, and is guided by the second reflecting mirror 5 into the first imaging system 6. The first lens 61 and the second lens 62 image the lithium niobate crystal 8 to satisfy the tilted wavefront phase matching angle. The first half-wave plate 7 is used to adjust the polarization state of the pump beam to match the optimal polarization direction for the terahertz radiation generated by the pumping lithium niobate crystal. Under the pumping of the pump beam, the lithium niobate crystal 8 generates strong-field terahertz pulse radiation through optical rectification. This strong-field terahertz pulse radiation results in a high absolute energy of the terahertz pulses that can be used for defect detection. After interface reflection and transmission loss during testing, the absolute energy of the pulse reflected at the defect is even higher, improving the defect detection capability.

[0041] In some embodiments, the strong-field terahertz pulse radiation generated by the lithium niobate crystal 8 is collected by the terahertz collection and transmission module. The terahertz pulse radiation generated by the lithium niobate crystal 8 is a diverging beam, which is reflected by the third reflector 9 to the first parabolic mirror 10. The first parabolic mirror 10 collects the diverging terahertz pulse radiation and couples it to the coupler 11.

[0042] In some embodiments, the coupler 11 transmits free-space terahertz pulses to the sample detection module and transmits reflected terahertz pulses detected by the sample detection module to free space.

[0043] In some embodiments, probe 12 transmits terahertz pulses from the coupler to the sample under test, which is mounted on sample stage 13. The precise movement of the sample stage controls the detection position, achieving alignment between the probe and the test location. The terahertz pulses transmitted to the probe are then transmitted through the probe to the electronic circuitry of the sample under test. The reflected signals from the electronic circuitry inside the sample are transmitted back to the probe and then back to the coupler, generating terahertz radiation into free space.

[0044] In some embodiments, depending on the sample to be tested, a laser 1 with different pulse widths can be selected as the pump source, such as a femtosecond laser or a picosecond laser. At the same time, a coupler 11 and a terahertz waveguide adapted to different frequencies are selected to transmit the terahertz pulse to the probe 12. In addition, different pulse compressors 15 can be selected to compress the pulse width of the probe beam with different pulse widths.

[0045] The probe beam enters the terahertz pulse detection module, and the optical path between the probe beam and the pump beam can be adjusted by the optical delay line 14 on the pump beam path. The probe beam passes through the pulse width compressor 15 to compress the pulse width, preferably to within 100 fs, for subsequent electro-optic sampling and detection of the terahertz waveform. Subsequently, the probe beam is expanded by the third lens 16 and the fourth lens 17, and reflected by the fourth mirror 18 to the step mirror 19.

[0046] The step mirror 19 is a reflector whose surface is composed of many narrow steps. When the probe beam is incident on the step mirror 19 at different spatial positions, the optical path is different at different spatial positions due to the existence of the steps. Therefore, a time delay distribution is introduced into the spatial distribution of the probe beam spot.

[0047] The probe beam is focused by the fifth lens 20 and reflected by the second beam splitter 21, collinearly focusing with the terahertz pulse onto the probe crystal 22. The time delay corresponding to different spatial positions of the probe beam coincides with the terahertz pulse at different times, realizing spatial encoding of the probe beam on the probe crystal. The sixth lens 23 and the fifth lens 20 form a 4f imaging system, and the seventh lens 24 and the eighth lens 26 form a 4f imaging system. The two 4f imaging systems distribute and image the beam information of the step mirror 19 onto the camera 28.

[0048] In some embodiments, the reflected terahertz pulse radiation is collected by the terahertz collection and transmission module and focused onto the detector crystal 22. The detector crystal 22 is an electro-optic crystal, which may be GaAs (gallium arsenide), KTiOPO4 (potassium titanium oxyphosphate), NH4H2PO4 (ammonium dihydrogen phosphate), ZnTe (zinc telluride) or KNbO3 (potassium niobate).

[0049] Preferably, the detector crystal 22 can be selected to have a thickness of 2 mm and a crystal orientation of [missing information]. <110> ZnTe crystals.

[0050] The probe beam passes through a quarter-wave plate 25, an imaging system consisting of a seventh lens 24 and an eighth lens 26, and a polarizing beam splitter prism 27 before being imaged onto the detector array of the camera 28. The camera reads out the intensity of the detected probe beam and extracts the terahertz pulse waveform, enabling single-shot diagnosis of the terahertz pulse waveform.

[0051] This invention also provides another implementation of the terahertz pulse detection module, such as... Figure 2 As shown, in this implementation, a fast delay line 29 is used in the terahertz pulse detection module to rapidly change the optical path of the detection beam. After passing through the second half-wave plate 30, the beam passes through a small hole on the first parabolic mirror 10, spatially coinciding with the terahertz pulse on the detection crystal 22. The position of the fast delay line 29 is changed to achieve temporal coincidence between the detection beam and the terahertz pulse. Scanning the fast delay line, detection beams with different time delays carry terahertz waveform information and pass through the ninth lens 31, the quarter-wave plate 25, and the Wollaston prism 32 before being incident on the balanced detector 33 for terahertz waveform detection.

[0052] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0053] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0054] In this invention, the terms "first," "second," "third," and "fourth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The term "multiple" refers to two or more unless otherwise expressly defined.

[0055] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry, characterized in that, The system includes a light source and spectrometer module, a strong-field terahertz pulse generation module, a terahertz pulse collection and transmission module, a sample detection module, and a terahertz pulse detection module; wherein... The light source and beam splitting module includes: a laser (1) and a first beam splitter (2); The strong field terahertz pulse generation module includes: a first reflector (3), an optical delay line (14), a first reflective grating (4), a second reflector (5), a first imaging system (6), a first half-wave plate (7), and a lithium niobate crystal (8); The terahertz collection and transmission module includes: a third reflector (9), a first parabolic mirror (10), and a coupler (11); The sample detection module includes: a probe (12) and an electronic circuit sample stage (13); The laser (1) generates laser light, and the first beam splitter (2) splits the laser beam into a pump beam and a probe beam; the pump beam enters the strong field terahertz pulse generation module to generate a strong field terahertz pulse; the terahertz collection and transmission module collects the strong field terahertz pulse and transmits it to the sample detection module; the sample detection module collects the reflection signal of the terahertz pulse from the electronic circuit sample; the probe beam enters the terahertz pulse detection module, and the terahertz pulse detection module performs coherent measurement on the reflection signal; The terahertz pulse detection module includes: a pulse width compressor (15), a third lens (16), a fourth lens (17), a fourth reflector (18), a step mirror (19), a fifth lens (20), a second beam splitter (21), a detector crystal (22), a sixth lens (23), a seventh lens (24), a quarter-wave plate (25), an eighth lens (26), a polarizing beam splitter prism (27), and a camera (28); Alternatively, the terahertz pulse detection module may include: a pulse width compressor (15), a fast delay line (29), a second half-wave plate (30), a detector crystal (22), a ninth lens (31), a quarter-wave plate (25), a Wollaston prism (32), and a balanced detector (33).

2. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 1, characterized in that, For the terahertz pulse detection module: The optical path difference between the probe beam and the pump beam is adjusted by an optical delay line (14). The probe beam is reflected by a pulse width compressor (15), a third lens (16), a fourth lens (17), and a fourth mirror (18) to a step mirror (19). Then, it passes through a fifth lens (20) and a second beam splitter (21) and is collinearly focused on the probe crystal (22) with the reflected terahertz pulse sent by the coupler (11). After passing through a seventh lens (24), a quarter-wave plate (25), an eighth lens (26), and a polarizing beam splitter prism (27), it is imaged onto the probe array of the camera (28).

3. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 2, characterized in that, For the terahertz pulse detection module: The probe beam passes through the pulse width compressor (15), the fast delay line (29), the second half-wave plate (30), and then through the small hole on the first parabolic mirror (10). It spatially coincides with the reflected terahertz pulse sent by the coupler (11) on the probe crystal (22). After passing through the ninth lens (31), the quarter-wave plate (25), and the Wollaston prism (32), it is incident on the balanced detector (33) to detect the terahertz waveform.

4. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to any one of claims 1-3, characterized in that, For the strong-field terahertz pulse generation module: The pump beam passes through the first reflector (3), optical delay line (14), first reflective grating (4), second reflector (5), first lens (61), first half-wave plate (7) and second lens (62) to irradiate the lithium niobate crystal (8) to generate a strong field terahertz pulse. The first imaging system (6) includes the first lens (61) and the second lens (62).

5. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 4, characterized in that, Regarding the terahertz collection and transmission module: The strong-field terahertz pulse is reflected by the third mirror (9) to the first parabolic mirror (10). The first parabolic mirror (10) collects the strong-field terahertz pulse and couples it to the coupler (11). The coupler (11) transmits the free-space terahertz pulse to the sample detection module and transmits the reflected terahertz pulse detected by the sample detection module to free space.

6. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 5, characterized in that, For the sample detection module: The probe (12) transmits a strong-field terahertz pulse from the coupler to the electronic circuit sample to be tested, which is mounted on the electronic circuit sample stage (13); the movement of the electronic circuit sample stage (13) is controlled to align the probe (12) with the position to be tested.

7. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 6, characterized in that: The laser (1) is a femtosecond laser or a picosecond laser, and the pulse width compressor (15) compresses the pulse width to within 100 fs.

8. The terahertz nondestructive testing system for electronic circuits based on time-domain reflectometry according to claim 7, characterized in that: The detector crystal (22) is an electro-optic crystal.

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