A method, system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance

Abstract

The present application belongs to the technical field of thermal conductivity and interface thermal resistance testing, and discloses a method and system for nondestructive in-situ testing of solder thermal conductivity and interface thermal resistance. The test sample in the present application is sequentially composed of a chip, a metal layer, solder and a substrate from top to bottom. The present application focuses a pulse laser beam on the surface of the metal layer in the test sample and heats it. The detection laser beam is focused on the surface of the metal layer, and the reflected detection beam formed after being reflected by the test sample is transmitted to a signal processing unit to obtain reflected light intensity information. Based on a heat conduction theoretical model and the reflected light intensity information, the thermal conductivity of the solder and the interface thermal resistance between the solder and the chip are obtained through fitting calculation. The present application can realize in-situ testing of the thermal conductivity of the solder and the interface thermal resistance between the solder and the chip in an actual device. The present application is ingeniously designed, directly uses the metal layer between the chip and the solder as a sensing layer, does not need to perform metal plating treatment on the device, and can realize nondestructive testing.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of thermal conductivity and interfacial thermal resistance testing, and more particularly relates to a method and system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance. BACKGROUND

[0002] With the continuous reduction in the size of electronic devices, rapid increase in integration density and power density, the heat problem is becoming more and more serious, and heat dissipation has become a key factor restricting the performance and reliability of devices. High-power electronic devices need to be welded to the substrate by solder such as indium (In), sintered silver (Ag) or gold-tin (AuSn). When the solder and the chip and the substrate are directly contacted and welded, there are problems such as poor adsorption and large thermal stress. In order to improve the weldability, a layer or more of transition metal (such as Au, Al, Cu, Ag, etc.) is usually covered on the bottom of the chip before welding. Due to the huge difference in material properties between the metal and the solder and the poor interface quality, a large interfacial thermal resistance is generated between the solder and the chip, which seriously hinders the heat dissipation of the device. In addition, due to process problems during preparation, impurities, voids and other defects often exist inside the solder, which leads to the actual thermal conductivity of the solder being often lower than the expected value provided by the manufacturer. Therefore, the testing of the thermal conductivity and interfacial thermal resistance of the solder is of great significance to the heat dissipation of electronic devices.

[0003] The current traditional testing methods for the thermal conductivity of materials include steady-state heat flow method, transient hot wire method, laser flash method, etc. However, these methods are direct tests for the thermal conductivity of single-layer bulk materials. However, in actual devices, the solder and the chip are often a complex structure containing multiple layers of metal (such as Figure 1 As shown), and the above testing methods cannot obtain the thermal conductivity of the solder and cannot realize the testing of the interfacial thermal resistance.

[0004] Laser thermal reflection testing technology is a new type of material thermal property characterization technology, as shown in Figure 2 The technology needs to first deposit a layer of metal film (such as Au, Al, etc.) on the surface of the sample as a measurement sensing layer before testing, and then focus a pulse laser on the metal surface of the sample to heat the sample and make it produce temperature changes. According to the formula:

[0005]

[0006] Where ΔR / R represents the change in reflectivity of the material, ΔT represents the change in temperature of the material, C thThe thermal reflectance coefficient of a material is represented. When the temperature rise is small, the reflectivity change (ΔR / R) of the sample surface metal is proportional to the temperature change (ΔT), at this time, the change (ΔR / R) of the reflected light intensity of the sample surface metal is tested by using a probe laser, so that the temperature change (ΔT) can be obtained. Then, by fitting algorithm, the thermal conduction theoretical model and the measured transient temperature signal are fitted to obtain the thermal physical property parameters (thermal conductivity, interface thermal resistance, etc.) of the measured sample. However, since the solder is embedded in a multilayer structure in a real device, and the pulse laser and the probe laser beams need to be focused on the surface of the sample during testing, the direct use of the technology cannot realize the in-situ testing of the thermal conductivity of the solder in the real device. SUMMARY

[0007] The present application provides a method and system for non-destructive in-situ testing of solder thermal conductivity and interface thermal resistance, which solves the problem that the prior art cannot test the thermal conductivity of the solder in the real device and the interface thermal resistance between the solder and the chip.

[0008] The present application provides a method for non-destructive in-situ testing of solder thermal conductivity and interface thermal resistance, and the test sample is sequentially composed of a chip, a metal layer, solder and a substrate from top to bottom. The method comprises the following steps:

[0009] A pulse laser is used to emit a pulse laser beam, and the pulse laser beam is focused on the surface of the metal layer in the test sample to heat the surface of the metal layer;

[0010] A probe laser is used to emit a probe laser beam, and the probe laser beam is focused on the surface of the metal layer. The centers of the light spots of the probe laser beam and the pulse laser beam coincide on the surface of the metal layer;

[0011] The reflected probe laser beam formed after the probe laser beam is reflected by the test sample is transmitted to the signal processing unit, and the reflected light intensity information is obtained based on the signal processing unit;

[0012] Based on the thermal conduction theoretical model and the reflected light intensity information, the thermal conductivity of the solder and the interface thermal resistance between the solder and the chip are calculated by fitting.

[0013] Preferably, the working wavelengths of the pulse laser and the probe laser are selected based on the material of the chip and the metal material contained in the metal layer.

[0014] Preferably, the photon energy corresponding to the working wavelengths of the pulse laser and the probe laser is lower than the band gap width of the material of the chip, and the working wavelength of the probe laser makes the thermal reflectance coefficient of the metal material contained in the metal layer greater than a preset thermal reflectance coefficient threshold.

[0015] Preferably, the material of the chip is one of bulk material, semiconductor hetero-epitaxy or homo-epitaxy thin film material; the bulk material is one of GaN, SiC, Si, Ge, GaAs; the semiconductor hetero-epitaxy or homo-epitaxy thin film material is one of GaN-SiC, GaN-Si, GaAs-Si; the metal layer comprises one or more layers of transition metal.

[0016] In another aspect, the present application provides a system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance, comprising: a pulsed laser, a probe laser and a signal processing unit; the pulsed laser is used to emit a pulsed laser beam, which is focused to the surface of a metal layer between a chip and solder in a test sample and heats the surface of the metal layer; the probe laser is used to emit a probe laser beam, which is focused to the surface of the metal layer; the center of the spot of both the probe laser beam and the pulsed laser beam coincide on the surface of the metal layer; the reflected probe laser beam formed after the probe laser beam is reflected by the test sample is transmitted to the signal processing unit, which is used to obtain reflected light intensity information.

[0017] Preferably, the working wavelength of the pulsed laser and the probe laser corresponds to photon energy lower than the band gap width of the material of the chip, and the working wavelength of the probe laser makes the thermal reflectance of the metal material contained in the metal layer greater than a preset thermal reflectance threshold.

[0018] Preferably, the pulsed laser and the probe laser are both wavelength-adjustable lasers, or the pulsed laser and the probe laser are both fixed-wavelength lasers.

[0019] Preferably, the system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance further comprises: a dichroic mirror, an objective lens, a beam splitter and a sample stage; the sample stage is used to carry the test sample; the pulsed laser beam is transmitted through the dichroic mirror and focused to the surface of the metal layer by the objective lens; the probe laser beam is transmitted through the beam splitter and then incident to the dichroic mirror, and the probe laser beam is reflected by the dichroic mirror and coaxial with the pulsed laser beam, and then focused to the surface of the metal layer by the objective lens; the reflected probe laser beam is transmitted to the signal processing unit after being reflected by the dichroic mirror and the beam splitter in sequence.

[0020] Preferably, the system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance further comprises: a beam expander, a mirror and a filter; the beam expander is located between the pulsed laser and the dichroic mirror, and is used for expanding the pulsed laser beam emitted by the pulsed laser; the mirror is located between the probe laser and the beam splitter, and is used for making the probe laser beam incident on the beam splitter; the filter is located between the beam splitter and the signal processing unit, and is used for filtering the reflected probe beam; and the signal processing unit comprises a photodetector and an oscilloscope connected with the photodetector.

[0021] Preferably, the system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance further comprises: a fitting calculation unit; the fitting calculation unit is used for fitting calculation of the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip based on a heat conduction theoretical model and the reflected light intensity information.

[0022] The one or more technical solutions provided in the present application have at least the following technical effects or advantages:

[0023] The test sample in the present application is sequentially composed of a chip, a metal layer, solder and a substrate from top to bottom. The present application focuses the pulsed laser beam emitted by a pulsed laser on the surface of the metal layer in the test sample, and heats the surface of the metal layer. The probe laser beam emitted by a probe laser is focused on the surface of the metal layer. The reflected probe beam formed after the probe laser beam is reflected by the test sample is transmitted to a signal processing unit, and the reflected light intensity information is obtained based on the signal processing unit. The thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip are fitted and calculated based on a heat conduction theoretical model and the reflected light intensity information. The present application selects the working wavelengths of the pulsed laser and the probe laser based on the materials of the chip and the metal materials contained in the metal layer, focuses the beams of the pulsed laser and the probe laser on the surface of the metal layer, and realizes the in-situ testing of the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip in the actual device. The present application is ingeniously designed, directly uses the metal layer between the chip and the solder as a sensing layer, does not need to perform metal plating treatment on the device, and can realize non-destructive testing. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 FIG. 1 is a structural schematic diagram of an actual device, i.e., a test sample of the present application;

[0025] Figure 2 FIG. 2 is a schematic diagram of a laser thermal reflection testing technology;

[0026] Figure 3 FIG. 3 is a schematic diagram of a system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance provided in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0027] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with the drawings of the specification and specific embodiments.

[0028] Referring to Figure 1 , the actual device, i.e., the structure of the test sample of the present application, is sequentially from top to bottom a chip 101, a metal layer 102, a solder 103, and a substrate 104. The present application is to test the thermal conductivity of the solder 103 and the interfacial thermal resistance between the solder 103 and the chip 101.

[0029] The conventional laser thermal reflection test technology is described in Figure 2 . This technology generally needs to deposit a layer of metal film on the surface of the sample 204 as a metal sensing layer 203 (i.e., a measurement sensing layer) before testing, and then uses a pulse laser 201 to focus on the surface of the metal sensing layer 203 to heat the sample 204 to cause temperature changes, and uses a probe laser 202 to test the change in the intensity of the reflected light from the surface of the sample, i.e., the temperature change.

[0030] Since the solder in the test sample studied by the present application is actually embedded in a multilayer structure as shown in Figure 1 , the laser thermal reflection test technology as shown in Figure 2 cannot be directly used for testing. To solve this problem, the present application ingeniously uses the metal layer between the chip and the solder as the sensing layer, without the need for metal plating treatment of the device, and can achieve non-destructive testing.

[0031] The non-destructive in-situ test method and system for solder thermal conductivity and interfacial thermal resistance provided by the present application will be described in detail below.

[0032] Embodiment 1

[0033] Embodiment 1 provides a system for non-destructive in-situ test of solder thermal conductivity and interfacial thermal resistance, which is described in Figure 3 , and mainly includes a pulse laser 1, a probe laser 9, and a signal processing unit. The pulse laser 1 is used to emit a pulse laser beam 3, which is focused on the surface of the metal layer between the chip and the solder in a test sample 6 and heats the surface of the metal layer. The probe laser 9 is used to emit a probe laser beam 10, which is focused on the surface of the metal layer. The centers of the light spots of the probe laser beam 10 and the pulse laser beam 3 coincide on the surface of the metal layer. The reflected probe laser beam 12 formed after the probe laser beam 10 is reflected by the test sample 6 is transmitted to the signal processing unit, and the signal processing unit is used to obtain reflected light intensity information.

[0034] The working wavelengths of the pulse laser 1 and the probe laser 9 correspond to photon energies lower than the band gap width of the material of the chip, and the working wavelength of the probe laser 9 is such that the thermal reflectance coefficient of the metal material contained in the metal layer is greater than a preset thermal reflectance coefficient threshold.

[0035] Specifically, the wavelengths selected by the pulse laser 1 and the probe laser 9 correspond to photon energies lower than the band gap width of the material of the chip. The material of the chip refers to the semiconductor substrate used to make the device, including bulk materials such as GaN, SiC, Si, Ge, GaAs, and semiconductor heteroepitaxial or homoepitaxial thin film materials (such as GaN-SiC, GaN-Si, GaAs-Si, etc.). Taking a GaN chip as an example, the band gap width of GaN is about 3.4 eV. According to the formula:

[0036]

[0037] where λ represents the wavelength of light, h represents Planck's constant, C represents the speed of light, and E represents the photon energy corresponding to the wavelength λ. Therefore, the absorption cutoff wavelength of GaN is about 365 nm; for a laser with a wavelength greater than 365 nm, it is transparent to GaN, i.e., a laser with a wavelength greater than 365 nm can penetrate GaN. Therefore, when the wavelengths of the pulse laser 1 and the probe laser 9 are both greater than 365 nm, the pulse laser beam 3 and the probe laser beam 10 can penetrate the GaN chip and focus on the surface of the metal layer between the chip and the solder, thereby realizing in-situ testing of the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip.

[0038] In addition, the thermal reflectance coefficients C th of different metals in different wavelength ranges are quite different. For example, Au has a large C th (~2×10 -4 K -1 ) in the range of 400-600 nm, and Al has a large C th (~1.5×10 -4 K -1 ) in the range of 700-900 nm. In laser thermal reflectance testing, it is required that the metal has a large C th , so as to improve the signal-to-noise ratio and reduce the uncertainty of measurement. Therefore, the wavelength of the probe laser 9 is selected not only to correspond to a photon energy lower than the band gap width of the chip material, but also to have a large C th according to the type of metal (Au, Cu, Ag, Al, etc.) at the interface between the chip and the solder.

[0039] That is, the present application comprehensively considers the material of the chip and the kind of metal material contained in the metal layer, and designs the laser wavelength, so as to achieve the purpose of in-situ testing the thermal conductivity of solder and interface thermal resistance.

[0040] In summary, the working wavelength of the pulse laser 1 needs to meet the following conditions: (1) penetrating the chip. The working wavelength of the probe laser 9 needs to meet the following conditions: (1) penetrating the chip; (2) having a large thermal reflection coefficient C to the corresponding metal material th .

[0041] Wherein, the pulse laser 1 and the probe laser 9 are both wavelength-adjustable lasers, or the pulse laser 1 and the probe laser 9 are both fixed-wavelength lasers.

[0042] Specifically, the system for non-destructive in-situ testing of thermal conductivity of solder and interface thermal resistance can further include: a beam expander 2, a dichroic mirror 4, an objective lens 5, a sample stage 7, a beam splitter 8, a mirror 11 and a filter 13.

[0043] The sample stage 7 is used to carry the test sample 6; the beam expander 2 is located between the pulse laser 1 and the dichroic mirror 4, and is used to expand the pulse laser beam 3 emitted by the pulse laser; the pulse laser beam 3 is transmitted through the dichroic mirror 4 and focused to the surface of the metal layer through the objective lens 5; the mirror 11 is located between the probe laser 9 and the beam splitter 8, and is used to make the probe laser beam 10 incident to the beam splitter 8; the probe laser beam 10 is transmitted through the beam splitter 8 and then incident to the dichroic mirror 4, and the probe laser beam 10 is reflected by the dichroic mirror 4 and coaxial with the pulse laser beam 3, and is focused to the surface of the metal layer through the objective lens 5; the reflected probe beam 12 is transmitted to the signal processing unit after being reflected by the dichroic mirror 4 and the beam splitter 8 in turn after passing through the objective lens 5; the filter 13 is located between the beam splitter 8 and the signal processing unit, and is used to filter the reflected probe beam 12; the signal processing unit can specifically include a photodetector 14 and an oscilloscope 15 connected with the photodetector 14. That is, the reflected probe beam 12 carrying the temperature change signal is finally received and amplified by the photodetector 14, and the reflected light intensity signal of the reflected probe beam 12 is read on the oscilloscope 15, and finally the thermal conduction theoretical model is fitted with the data read from the oscilloscope 15 through a fitting algorithm, and the measured thermal conductivity and interface thermal resistance are analyzed.

[0044] After the reflected light intensity information is obtained, the thermal conductivity of the solder and the interface thermal resistance between the solder and the chip can be directly fitted and calculated based on a heat conduction theoretical model.

[0045] Alternatively, the fitting calculation can also be realized by means of an additional tool, that is, the system for nondestructive in-situ testing of the thermal conductivity of solder and the interface thermal resistance can further comprise a fitting calculation unit, which is configured to fit and calculate the thermal conductivity of the solder and the interface thermal resistance between the solder and the chip based on a heat conduction theoretical model and the reflected light intensity information.

[0046] The fitting calculation of the thermal physical parameters (thermal conductivity, interface thermal resistance, etc.) of the measured sample based on the heat conduction theoretical model and the reflected light intensity information can be realized by using existing algorithms, and the present application does not involve specific improvements of the algorithms, so the algorithms will not be described in detail.

[0047] The selection of the pulsed laser and the probe laser will be described below.

[0048] (1) Select a pulsed laser and a probe laser with adjustable wavelength.

[0049] According to the chip material (GaN, SiC, Si, Ge, GaAs, etc.) and the type of transition metal (Au, Cu, Ag, Al, etc.) in the metal layer, the wavelength of the pulsed laser and the probe laser is adjusted in real time, and after the wavelength is adjusted, the thermal conductivity and the interface thermal resistance are tested.

[0050] For example, the chip is GaN, and the transition metal is Au. According to the band gap width of GaN (-3.4 eV), the corresponding cut-off wavelength is about 365 nm, and at this time, the wavelength of the pulsed laser and the probe laser should be adjusted to be greater than 365 nm. At the same time, Au as a transition metal has a large C th Therefore, the wavelength of the probe laser should be further adjusted to between 400-600 nm.

[0051] When selecting a laser with adjustable wavelength, for a variety of different test samples, it is not necessary to replace the laser, but only to adjust the wavelength to measure the related parameters of a variety of materials, which can improve the testing efficiency.

[0052] (2) Select a pulsed laser and a probe laser with fixed wavelength.

[0053] According to the chip material (GaN, SiC, Si, Ge, GaAs, etc.) and the type of transition metal (Au, Cu, Ag, Al, etc.) in the metal layer, the wavelength of the pulsed laser and the probe laser is adjusted in real time, and after the wavelength is adjusted, the thermal conductivity and the interface thermal resistance are tested.

[0054] For example, the chip is SiC, the transition metal is Au, and according to the band gap width of SiC (about 3.23 eV), the corresponding cut-off wavelength is about 384 nm, at which time the pulse laser and the probe laser should both be selected to have a wavelength greater than 384 nm. Meanwhile, Au as a transition metal has a relatively large C th Therefore, the wavelength of the probe laser should be further adjusted to between 400-600 nm. Based on the above considerations, a fixed-wavelength pulse laser and a probe laser are selected, and then the thermal conductivity and the interfacial thermal resistance are tested.

[0055] When selecting a fixed-wavelength laser, the laser needs to be replaced according to different test occasions.

[0056] Embodiment 2

[0057] Embodiment 2 provides a method for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance, which can be implemented by using the system provided in Embodiment 1.

[0058] The test sample is sequentially arranged from top to bottom as a chip, a metal layer, solder, and a substrate. Embodiment 2 provides a method for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance, which includes the following steps:

[0059] Step 1, placing the test sample on the sample stage of the test system designed with the wavelengths of the pulse laser and the probe laser.

[0060] Specifically, based on the material of the chip and the metal material contained in the metal layer, the operating wavelength of the pulse laser and the probe laser is selected. The operating wavelength of the pulse laser and the probe laser corresponds to a photon energy that is lower than the band gap width of the material of the chip, and the operating wavelength of the probe laser makes the thermal reflection coefficient of the metal material contained in the metal layer greater than a preset thermal reflection coefficient threshold.

[0061] The material of the chip is a bulk material, a semiconductor heteroepitaxy or a homoepitaxy thin film material, etc. The bulk material is GaN, SiC, Si, Ge, GaAs, etc. The semiconductor heteroepitaxy or homoepitaxy thin film material is GaN-SiC, GaN-Si, GaAs-Si, etc. The metal layer contains one or more transition metals.

[0062] Step 2, using the pulse laser to emit a pulse laser beam, focusing the pulse laser beam to the surface of the metal layer in the test sample, and heating the surface of the metal layer; using the probe laser to emit a probe laser beam, focusing the probe laser beam to the surface of the metal layer; the centers of the light spots of the probe laser beam and the pulse laser beam coincide on the surface of the metal layer.

[0063] Specifically, the pulsed laser beam generated by the pulsed laser passes through a series of optical components such as an expander, a dichroic mirror, and an objective lens, and is focused on the surface of the metal layer between the chip and the solder. The probe laser beam generated by the probe laser passes through a series of optical components such as a mirror, a beamsplitter, a dichroic mirror, and an objective lens, and is focused on the surface of the metal layer between the chip and the solder. Through the dichroic mirror, the probe laser beam and the pulsed laser beam are coaxial, and the centers of the light spots of the two beams coincide on the surface of the metal layer.

[0064] Step 3: The reflected probe laser beam formed after the probe laser beam is reflected by the test sample is transmitted to the signal processing unit, and the reflected light intensity information is obtained based on the signal processing unit.

[0065] Specifically, the reflected probe laser beam carrying the temperature change signal is received and amplified by a photodetector after being guided and filtered by a beamsplitter and a filter, and then data is read from an oscilloscope.

[0066] Step 4: Based on the heat conduction theoretical model and the reflected light intensity information, the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip are fitted and calculated.

[0067] Specifically, after obtaining the reflected light intensity information, the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip can be directly fitted and calculated by combining the heat conduction theoretical model. Alternatively, additional tools can be used to realize the fitting calculation.

[0068] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced equivalently without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A method for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance, characterized in that, The test sample, from top to bottom, consists of a chip, a metal layer, solder, and a substrate; the method includes the following steps: A pulsed laser beam is emitted using a pulsed laser, and the pulsed laser beam is focused onto the surface of the metal layer in the test sample to heat the surface of the metal layer; A probe laser beam is emitted using a probe laser, and the probe laser beam is focused onto the surface of the metal layer; the centers of the probe laser beam and the pulsed laser beam coincide on the surface of the metal layer. The reflected detection beam formed by the detection laser beam after being reflected by the test sample is transmitted to the signal processing unit, and the reflected light intensity information is obtained based on the signal processing unit. Based on the thermal conduction theoretical model and the reflected light intensity information, the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip are calculated by fitting. The operating wavelengths of the pulsed laser and the probe laser are selected based on the material of the chip and the metal material contained in the metal layer. The photon energies corresponding to the operating wavelengths of the pulsed laser and the probe laser are both lower than the bandgap of the chip material, and the operating wavelength of the probe laser makes the thermal reflectivity of the metal material contained in the metal layer greater than a preset thermal reflectivity threshold.

2. The method for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance according to claim 1, characterized in that, The chip is made of one of the following materials: bulk material, semiconductor heteroepitaxial or homoepitaxial thin film material; the bulk material is one of GaN, SiC, Si, Ge, GaAs; the semiconductor heteroepitaxial or homoepitaxial thin film material is one of GaN-SiC, GaN-Si, GaAs-Si; and the metal layer comprises one or more transition metals.

3. A system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance, characterized in that, include: Pulsed laser, probe laser, signal processing unit, and fitting calculation unit; The pulsed laser is used to emit a pulsed laser beam, which is focused onto the surface of a metal layer located between the chip and the solder in the test sample, and heats the surface of the metal layer. The probe laser is used to emit a probe laser beam, which is focused onto the surface of the metal layer; the centers of the probe laser beam and the pulsed laser beam coincide on the surface of the metal layer. The reflected detection beam formed by the detection laser beam after being reflected by the test sample is transmitted to the signal processing unit, and the signal processing unit is used to obtain the reflected light intensity information. The fitting calculation unit is used to calculate the thermal conductivity of the solder and the interfacial thermal resistance between the solder and the chip based on the thermal conduction theoretical model and the reflected light intensity information. The photon energies corresponding to the operating wavelengths of the pulsed laser and the probe laser are both lower than the bandgap of the chip material, and the operating wavelength of the probe laser makes the thermal reflectance coefficient of the metal material contained in the metal layer greater than a preset thermal reflectance coefficient threshold.

4. The system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance according to claim 3, characterized in that, Both the pulsed laser and the probe laser are wavelength-tunable lasers, or both the pulsed laser and the probe laser are fixed-wavelength lasers.

5. The system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance according to claim 3, characterized in that, Also includes: Dichroic mirror, objective lens, beam splitter, and sample stage; The sample stage is used to hold the test sample; The pulsed laser beam, after being transmitted through the dichroic mirror, is focused onto the surface of the metal layer by the objective lens; the probe laser beam, after being transmitted through the beam splitter, is incident on the dichroic mirror, and after being reflected by the dichroic mirror, is coaxial with the pulsed laser beam and focused onto the surface of the metal layer by the objective lens; the reflected probe beam, after passing through the objective lens, is reflected by the dichroic mirror and then by the beam splitter before being transmitted to the signal processing unit.

6. The system for non-destructive in-situ testing of solder thermal conductivity and interfacial thermal resistance according to claim 5, characterized in that, Also includes: Beam expander, mirror, and filter; The beam expander is located between the pulsed laser and the dichroic mirror, and is used to expand the pulsed laser beam emitted by the pulsed laser; the reflector is located between the probe laser and the beam splitter, and is used to allow the probe laser beam to be incident on the beam splitter; the filter is located between the beam splitter and the signal processing unit, and is used to filter the reflected probe beam; the signal processing unit includes a photodetector and an oscilloscope connected to the photodetector.

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