A method for real-time monitoring of temperature of power diode chip by infrared

Abstract

The application provides a method for monitoring the temperature of a power diode chip in real time through infrared rays, and has the characteristics that the method comprises the following steps: preparing a boron carbide-polyimide coating on the surface of a power diode chip to be measured; connecting the power diode chip to an aging circuit; and monitoring the temperature of the power diode chip in real time by using an emissivity calibration infrared method. The boron carbide-polyimide coating with uniform and consistent emissivity epsilon is prepared on the surface of the chip, so that the problem that the chip temperature cannot be accurately tested by using the traditional infrared method due to the inconsistent emissivity epsilon of the chip surface material is solved, and it is verified that the coating does not affect the distribution state of the current and temperature on the surface of the chip.

Description

TECHNICAL FIELD

[0001] The present application relates to the detection technology in the field of semiconductor, in particular to a method for real-time monitoring temperature of power diode chip by infrared. BACKGROUND

[0002] With the continuous reduction of the feature size of semiconductor chip, the packaging structure of semiconductor device is continuously miniaturized, complicated and refined. However, the reduction of the packaging structure makes the heat dissipation problem of the power diode become one of the important factors affecting its reliability and stability. When the chip temperature is significantly increased, if the generated heat cannot be effectively conducted out through the heat dissipation path, the heat will be accumulated at the bonding material, the bonding point, the passivation layer and the like, causing the chip debonding, the circuit ablation, the bonding point fracture and the like failure phenomenon.

[0003] In order to improve the heat dissipation performance of the power diode, it is necessary to monitor the chip temperature in real time, so as to determine the weak point of heat dissipation, shut down the device in time to avoid burning the whole single machine, and improve the design and packaging process of the chip. At present, there are various methods to monitor the temperature of diode chip, which can be mainly divided into thermocouple method, thermal resistance method and traditional infrared method:

[0004] The thermocouple method is a contact type temperature measurement method, and the spatial resolution is about 13-50 μm. Although the price is cheap, it needs to be in direct contact with the chip surface, and the pressure generated by the chip may damage the circuit structure of the chip. In addition, the thermocouple can only complete the test of one temperature point in a point contact way each time, and a temperature measurement point needs a set of wiring, so the test efficiency is low, and the chip temperature cannot be accurately tested.

[0005] The thermal resistance method is an indirect temperature measurement method, which mainly obtains the corresponding relationship between the electrical parameters of the chip and the temperature through the calibration of the temperature sensitive parameter. However, the thermal resistance method needs special fixtures and equipment to complete the indirect test of the chip temperature, the test cost is high, the process is complex, and the temperature can only be inversely calculated according to the electrical parameters, so the chip temperature cannot be obtained in real time. In addition, if the diode chip is welded in the hybrid integrated circuit, there is no independent temperature sensitive parameter lead-out end, so the diode chip temperature cannot be obtained by the thermal resistance method. The thermal resistance method also cannot obtain the temperature distribution of multiple diode chips in the hybrid integrated circuit at the same time.

[0006] The traditional infrared method is a non-contact temperature measurement method, and the maximum spatial resolution can reach 3 μm. The spatial resolution is much higher than that of the thermocouple, and the chip surface temperature distribution can be obtained in real time. However, the traditional infrared method obtains the radiation temperature distribution of the measured object surface, rather than the real temperature distribution of the object.

[0007] The radiation temperature is determined by the emissivity of the surface of the object, and according to the Stefan-Boltzmann law, the radiation energy E per unit area of the surface of the object is proportional to the fourth power of the temperature T of the object, that is, E = εσT 4 wherein ε is the emissivity, and σ is a proportional coefficient. Since the emissivity ε can vary between 0 and 1, the accuracy of the infrared temperature measurement is closely related to the emissivity ε of the surface material of the chip. When the emissivity ε of the surface of the object is consistent, the radiation temperature distribution of the surface of the object is basically the same as the real temperature distribution of the object; however, the emissivity ε of the surface material of the power diode chip has considerable difference, and the radiation temperature of the chip surface cannot reflect the real temperature of the chip. Although the infrared thermal imager has the function of calibrating the emissivity ε, it is necessary to input the emissivity ε of each temperature point respectively, and the test process is very tedious, and at the same time, the accuracy of the emissivity ε of each temperature point cannot be guaranteed, so the real temperature of the chip cannot be obtained.

[0008] In summary, the point contact thermocouple method cannot accurately test the temperature of the chip, and the thermal resistance method cannot obtain the temperature of the chip in real time; the accuracy of the traditional infrared method is affected by the emissivity ε of the surface material of the chip, so it is urgent to develop a new method to improve the emissivity ε of the surface material of the chip, so as to accurately and timely monitor the temperature of the diode chip. SUMMARY

[0009] The purpose of the present application is to provide a method for real-time monitoring of the temperature of a power diode chip by infrared, which solves the problem that the traditional infrared method cannot be used to accurately test the temperature of the chip due to the inconsistent emissivity ε of the surface material of the chip.

[0010] In order to achieve the above purpose, the present application provides a method for real-time monitoring of the temperature of a power diode chip by infrared, characterized in that it comprises: preparing a boron carbide-polyimide coating on the surface of the power diode chip to be tested; connecting the power diode chip to an aging circuit, and using an emissivity calibration infrared method to monitor the temperature of the power diode chip in real time.

[0011] Further, the boron carbide-polyimide coating on the surface of the power diode chip to be tested is prepared by a spin coating method.

[0012] Further, the spin coating method comprises: uniformly mixing boron carbide particles and polyimide by ball milling, and then coating on the surface of the power diode chip to be tested; fixing the power diode chip to be tested in a spin coating machine; controlling the centrifugal force by changing the rotation speed of the spin coating machine to obtain a suitable coating thickness L; heating to solidify the coating, and then naturally cooling to room temperature.

[0013] Furthermore, the real-time monitoring of the power diode chip temperature using the emissivity calibrated infrared method includes: using an infrared thermal imager to test the chip temperature, then calibrating it according to the coating emissivity ε, and monitoring the chip temperature in real time using the emissivity calibrated infrared method.

[0014] Furthermore, the coating emissivity ε is obtained by using a heating tube to increase the temperature of the diode chip, and the actual chip temperature of the coating upper surface temperature and the coating lower surface temperature are equal to the heating tube temperature T b ; Use infrared thermal imager to obtain the surface radiation temperature T of the chip coated with coating r ; Chip surface radiation temperature T tested by infrared thermal imager r The actual chip temperature T b Satisfaction relationship The coating emissivity ε is calculated from this.

[0015] Furthermore, the diameter of the boron carbide particles ranges from 30 to 50 nm.

[0016] Furthermore, the coating thickness L ranges from 4 to 8 μm.

[0017] Furthermore, the power diode chip is replaced by a test device housing, a substrate, or a PCB copper-clad plate.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention solves the problem of inability to accurately measure chip temperature using traditional infrared methods due to inconsistent emissivity ε of chip surface materials by preparing a boron carbide-polyimide coating with uniform emissivity ε on the chip surface. At the same time, it verifies that the coating does not affect the distribution of current and temperature on the chip surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention provides a method for real-time infrared monitoring of the temperature of a power diode chip by the following embodiments and accompanying drawings.

[0021] Figure 1 A flow chart of a method for real-time infrared monitoring of power diode chip temperature according to a preferred embodiment of the present invention;

[0022] Figure 2 This is a schematic diagram of a Pt thin film resistor temperature sensor deposited on a copper-clad PCB according to a preferred embodiment of the present invention;

[0023] Figure 3 A schematic diagram of converting the resistance and temperature of a Pt thin film resistor temperature sensor according to a preferred embodiment of the present invention;

[0024] Figure 4Pt thin film resistance temperature sensor resistance and Pt thin film resistance temperature sensor temperature curve of the preferred embodiment of the present application;

[0025] Figure 5 Schematic diagram of preparing boron carbide-polyimide coating on the surface of PCB copper-clad plate by spin coating method of the preferred embodiment of the present application;

[0026] Figure 6 Schematic diagram of testing coating thickness by ellipsometer of the preferred embodiment of the present application;

[0027] Figure 7 Schematic diagram of testing coating resistivity by four-point probe method of the preferred embodiment of the present application;

[0028] Figure 8 Schematic diagram of testing coating thermal conductivity by laser flash method of the preferred embodiment of the present application;

[0029] Figure 9 Temperature rise curve of the lower surface of the coating tested by Pt thin film resistance temperature sensor resistance meter panel of the preferred embodiment of the present application;

[0030] Figure 10 Schematic diagram of preparing boron carbide-polyimide coating on the surface of power diode chip by spin coating method of the preferred embodiment of the present application;

[0031] Figure 11 Schematic diagram of testing chip temperature by infrared thermal imager after preparing coating on the surface of diode chip of the preferred embodiment of the present application;

[0032] Figure 12 Schematic diagram of testing diode temperature sensitive parameter K coefficient by transient thermal resistance method of the preferred embodiment of the present application;

[0033] Figure 13 Schematic diagram of testing diode chip temperature by transient thermal resistance method and emissivity calibration infrared method respectively of the preferred embodiment of the present application;

[0034] Figure 14 Chip temperature curve T rz tested by transient thermal resistance method and chip temperature curve T hw tested by emissivity calibration infrared method of the preferred embodiment of the present application;

[0035] Figure 15 Schematic diagram of testing power diode chip temperature by emissivity calibration infrared method during aging process of the preferred embodiment of the present application. DETAILED DESCRIPTION

[0036] The following will be combined with Figures 1-15The present invention provides a method for infrared real-time monitoring of power diode chip temperature in further detail.

[0037] Figure 1 This is a flow chart of a method for real-time infrared monitoring of power diode chip temperature according to a preferred embodiment of the present invention. Figure 1 A method for infrared real-time monitoring of the temperature of a power diode chip in an embodiment of the present invention includes the following steps: preparing a boron carbide-polyimide coating on the surface of the power diode chip to be tested; connecting the power diode chip to an aging circuit, and using an emissivity calibrated infrared method to monitor the temperature of the power diode chip in real time.

[0038] The method of using the emissivity calibration infrared method to monitor the power diode chip temperature in real time includes: using an infrared thermal imager to test the chip temperature, then calibrating it according to the coating emissivity ε, and monitoring the chip temperature in real time by the emissivity calibration infrared method.

[0039] The steps for obtaining the coating emissivity ε include: using a heating tube to increase the temperature of the diode chip, and the actual temperature of the chip on the upper surface of the coating and the lower surface of the coating are both equal to the heating tube temperature T b ; Use infrared thermal imager to obtain the surface radiation temperature T of the chip coated with coating r ; Chip surface radiation temperature T tested by infrared thermal imager r The actual chip temperature T b Satisfaction relationship The coating emissivity ε is calculated from this.

[0040] The present invention is described in further detail below.

[0041] This invention solves the problem of the conventional infrared method being unable to accurately measure chip temperature due to the inconsistent emissivity ε of the chip surface material. In order to verify whether the emissivity ε of the prepared surface material is consistent, the following preliminary experiments were conducted:

[0042] Experiment 1: Setting up a Pt thin film resistor temperature sensor

[0043] The purpose of this experiment is to prepare a Pt thin film resistor temperature sensor on a PCB copper clad board, obtain a PCB copper clad board with a Pt thin film resistor temperature sensor, and test the relationship between the resistance and temperature of the Pt thin film resistor temperature sensor as a conversion M coefficient.

[0044] Figure 2 This is a schematic diagram of a Pt thin film resistor temperature sensor deposited on a copper-clad PCB surface according to a preferred embodiment of the present invention. Figure 2Pt thin film resistance temperature sensor mask plate 112 of specific shape is used to cover PCB copper clad plate 111 with size of 20mm*20mm*2mm, Ti layer with thickness of 5-20nm is selectively evaporated on the surface of PCB copper clad plate 111 as bottom layer to improve bonding strength, then Pt layer with thickness of 300-1000nm is selectively evaporated on the same area as surface layer and completely covers Ti layer, then the area not covered by Pt thin film resistance temperature sensor mask plate 112 will form Pt thin film resistance temperature sensor with Ti as bonding bottom layer. The first and last ends of the Pt thin film resistance temperature sensor are rectangular pad area positive electrode 113 and pad area negative electrode 114, and the middle wiring area 115 is in snake shape, and the resistance of the middle wiring area 115 is taken as the resistance of the Pt thin film resistance temperature sensor. The middle wiring area 115 is designed in snake shape to increase the contact area with the coating, improve the temperature measurement stability of the Pt thin film resistance temperature sensor, and reduce the surface temperature test error of the coating.

[0045] Figure 3 The figure is a schematic diagram for testing the resistance of Pt thin film resistance temperature sensor and the conversion M coefficient of temperature of the preferred embodiment of the present application. As shown in the figure, Figure 3 Pt thin film resistance temperature sensor resistance instrument panel 116 is connected with Pt thin film resistance temperature sensor pad area positive electrode 113 and pad area negative electrode 114 respectively, and the resistance of Pt thin film resistance temperature sensor is measured through Pt thin film resistance temperature sensor resistance instrument panel 116. Thermocouple sensor 117 is in close contact with Pt thin film resistance temperature sensor wiring area 115, and the temperature of Pt thin film resistance temperature sensor wiring area 115 is monitored by thermocouple sensor temperature instrument panel 119 as the temperature of Pt thin film resistance temperature sensor. Heating tube 118 is used to heat PCB copper clad plate 111, and when the reading of thermocouple sensor temperature instrument panel 119 no longer changes obviously, the resistance value measured by Pt thin film resistance temperature sensor resistance instrument panel 116 and the temperature of Pt thin film resistance temperature sensor measured by thermocouple sensor temperature instrument panel 119 are determined. The temperature of heating tube 118 is kept constant at 20, 40, 80 and 100℃ respectively, and the resistance (r1, r2, r3, r4) measured by Pt thin film resistance temperature sensor resistance instrument panel 116 and the temperature (t1, t2, t3, t4) of Pt thin film resistance temperature sensor measured by thermocouple sensor temperature instrument panel 119 are recorded respectively.

[0046] Figure 4 The figure is a Pt thin film resistance temperature sensor resistance and Pt thin film resistance temperature sensor temperature curve diagram of the preferred embodiment of the present application. As shown in the figure, Figure 4The Pt thin film resistance temperature sensor resistance and the Pt thin film resistance temperature sensor temperature curve is drawn. The curve presents a linear relationship, and the conversion M coefficient is determined. According to the conversion M coefficient, the Pt thin film resistance temperature sensor temperature t can be monitored in real time as long as the Pt thin film resistance temperature sensor resistance r is obtained.

[0047] Experiment 2: Preparation of boron carbide-polyimide coating

[0048] The purpose of this experiment is to prepare a boron carbide-polyimide coating on the surface of the PCB copper-clad plate with a Pt thin film resistance temperature sensor obtained in Experiment 1 by using a spin coating method.

[0049] The boron carbide particles with a diameter range of 30-50 nm are mixed with polyimide, and the mixture is subjected to ball milling treatment so that the boron carbide particles can be uniformly distributed in the polyimide. The uniformly distributed boron carbide particles can ensure that the boron carbide-polyimide mixture has good radiation and uniform and consistent surface emissivity ε, and the results obtained by the infrared testing method are more accurate. The boron carbide particles with a diameter range of 30-50 nm can make the temperature resolution obtained by the infrared method higher.

[0050] Figure 5 The schematic diagram of the preferred embodiment of the present application for preparing a boron carbide-polyimide coating on the surface of a PCB copper-clad plate by using a spin coating method. As shown in Figure 5 The boron carbide-polyimide mixture coating 121 is coated on the surface of the PCB copper-clad plate 111 with a Pt thin film resistance temperature sensor, and the coating size is 20 mm x 20 mm. The positive electrode 113 and the negative electrode 114 in the Pt thin film resistance temperature sensor pad area are not completely covered. The PCB copper-clad plate 111 containing the coating 121 and the Pt thin film resistance temperature sensor is fixed in a spin coating machine, and the centrifugal force is controlled by changing the rotation speed of the spin coating machine to obtain a suitable coating thickness L range of 4-8 μm.

[0051] When the thickness is too large, there will be a large temperature difference between the upper and lower surfaces of the coating, and the temperature of the upper surface of the coating measured by the infrared method cannot represent the temperature of the lower surface of the coating. When the thickness is too small, it is not possible to ensure that the coating has a uniform emissivity ε. The heating pipe 118 is used to heat the PCB copper-clad plate 111 to solidify the coating 121, and then naturally cool to room temperature.

[0052] Experiment 3: Testing the coating thickness by using an ellipsometer

[0053] Figure 6 The schematic diagram of the preferred embodiment of the present application for testing the coating thickness by using an ellipsometer. As shown in Figure 6The incident light generated by the ellipsometer light source generator 131 is deflected after passing through the rotating polarizer 132, and the deflected incident light is decomposed into polarization p light and polarization s light parallel and perpendicular to the incident plane. The amplitude and phase of the p light and s light will change after being reflected on the surface of the coating to be measured, and the change degree is related to the thickness L of the coating to be measured. The reflected light with changed polarization state passes through the compensator 133 and the analyzer 134 in turn, and then reaches the detector 135. Through data processing, the ellipsometric experimental curve with X axis as Δ and Y axis as ψ is obtained. The ellipsometric experimental curve of the coating to be measured with a known thickness is compared with the ellipsometric curve of the coating with a known thickness, and the thickness L of the coating to be measured is obtained. The coating thickness tested by the ellipsometer is 6 μm.

[0054] Test the resistivity of the coating in Experiment 4

[0055] The purpose of this experiment is to test the resistivity of the coating by the four-point probe method, and to verify that the coating does not affect the current distribution state of the sample to be measured on the lower surface.

[0056] Figure 7 The schematic diagram of the four-point probe method for testing the resistivity of the coating of the preferred embodiment of the present application is shown in FIG. 1. Figure 7 According to the principle of testing the resistivity of thin layer material by the four-point probe method, at room temperature, four probes (No. 141, No. 142, No. 143, and No. 144) are arranged perpendicular to the coating 121 and located in the same plane, and the distance between adjacent two probes is S, that is, No. 141 and No. 142, No. 142 and No. 143, and No. 143 and No. 144 are separated by S. Along the direction perpendicular to the coating 121, pressure is applied to the four probes to form ohmic contact with the coating 121. The IM test current 149 is connected to the outer probes No. 141 and No. 144 and a small current I (mA) is applied. The VF voltage sensor 147 is connected to the inner probes No. 142 and No. 143, and the voltage drop V (mV) is tested.

[0057] Since the side length of the coating (20 mm) is much larger than the thickness L of the coating (4-8 μm), and the distance S between the probes is also much larger than the thickness L of the coating (4-8 μm), the four-point probe method for testing the resistivity of the coating meets the test conditions of the resistivity of the thin layer material, and the resistivity of the coating The four-point probe method for testing the resistivity of the coating does not need to be calibrated, which is very convenient.

[0058] The resistivity of the coating measured at room temperature is e 5.6 Ω·m, which is significantly larger than the resistivity of the silicon wafer (2.5 × 10 -4 Ω·m) and the resistivity of aluminum (2.5 × 10 -8 Ω·m), indicating that the coating has very poor conductivity and will not affect the current distribution state of the sample to be measured on the lower surface of the coating, nor will it cause short circuit and open circuit of the sample to be measured on the lower surface of the coating.

[0059] Test the thermal conductivity of the coating in Experiment 5

[0060] The purpose of this experiment is to test the thermal conductivity of the coating by laser flash method, and to verify that the coating does not affect the temperature distribution state of the sample to be measured on the lower surface.

[0061] Figure 8 The schematic diagram of the laser flash method for testing the thermal conductivity of the coating of the preferred embodiment of the present application. As shown in Figure 8 Place the PCB copper-clad plate 111 containing the boron carbide-polyimide coating 121 and the Pt thin-film resistance temperature sensor under the laser pulser 151. The Pt thin-film resistance temperature sensor resistance meter panel 116 is connected to the positive electrode 113 and the negative electrode 114 of the Pt thin-film resistance temperature sensor pad area.

[0062] As shown in Figure 8 , a uniform pulsed light is vertically irradiated onto the upper surface of the coating 121 by the laser pulser 151, so that the coating 121 is raised to a certain temperature (≤5℃); the temperature rise curve of the lower surface of the coating 121 is tested by the Pt thin-film resistance temperature sensor resistance meter panel 116. Since the size of the coating (20mm×20mm) is much larger than the thickness of the coating (4-8μm), it meets the condition of one-dimensional heat dissipation path, and the radial heat flow of the coating is significantly reduced.

[0063] Figure 9 The graph of the temperature rise curve of the lower surface of the coating tested by the Pt thin-film resistance temperature sensor resistance meter panel of the preferred embodiment of the present application. As shown in Figure 9 , after the upper surface of the coating is heated by the laser pulse, the heat is diffused to the lower surface of the coating through the one-dimensional heat dissipation path, and the temperature is raised from the initial temperature T0 to the maximum temperature T max . According to the temperature rise curve, the midpoint 152 when the temperature rise reaches half is determined. The time corresponding to the midpoint 152 is the characteristic time t 0.5 , combined with the thickness L of the coating, the thermal diffusivity of the coating is calculated.

[0064] The specific heat capacity c of the boron carbide-polyimide coating is tested by DSC differential scanning calorimeter, and the density of the coating is tested by the mass m and volume V of the boron carbide-polyimide coating The thermal conductivity of the coating is

[0065] The thermal conductivity of the coating measured by the coating thermal conductivity formula is 0.4 W / (m·K); since the thickness of the coating is only 4-8μm, the temperature gradient and heat loss in the vertical direction of the coating are small and can be ignored, so the temperature of the upper surface of the coating is approximately equal to the temperature of the lower surface of the coating, and the coating does not affect the temperature distribution state of the sample to be measured on the lower surface.

[0066] It can be seen from Experiments 4 and 5 that the boron carbide-polyimide coating has extremely poor conductivity and does not affect the current distribution state of the sample to be tested on the lower surface of the coating, nor does it cause short circuit and open circuit of the sample to be tested on the lower surface of the coating, nor does it affect the temperature distribution state of the sample to be tested on the lower surface. Therefore, it can be used for coating the surface of power diode chips without affecting the function and temperature distribution of the power diode chips.

[0067] For practical use, the present invention further carried out the following experiments:

[0068] Experiment 6: Testing the emissivity ε of the surface coating on the power diode chip

[0069] The purpose of this experiment is to prepare a boron carbide-polyimide coating on the surface of a power diode chip using a spin coating method, test the coating's emissivity ε using an infrared contrast method, and verify the uniformity of the emissivity ε distribution.

[0070] Figure 10 Schematic diagram of a preferred embodiment of the present invention using a spin coating method to prepare a boron carbide-polyimide coating on the surface of a power diode chip. Figure 10 Reference numeral 171 denotes a power diode substrate, reference numeral 172 denotes a diode chip 172 soldered to power diode substrate 171, and reference numerals 173 and 174 denote the positive and negative lead terminals 173 and 174 of diode chip 172 soldered to power diode substrate 171, respectively. Reference numeral 175 denotes the bonding wires connecting the positive and negative lead terminals 173 and 174 to the chip. Using a method similar to that used in Experiment 2, a boron carbide-polyimide coating 121 was deposited on the surface of power diode chip 172, with a coating thickness ranging from 4 to 8 μm.

[0071] Figure 11 This is a schematic diagram of the temperature of the diode chip tested by an infrared thermal imager after a coating is prepared on the surface of the diode chip according to a preferred embodiment of the present invention. Figure 11 , do not power on the device, and set the temperature of the heating tube 118 to T b1 The heating tube 118 is used to raise the temperature of the diode chip and maintain it for a long enough time so that the chip temperature is equal to the temperature of the heating tube. Since Experiment 5 has proved that the coating does not affect the temperature distribution of the sample under test, the temperature of the chip under the coating is consistent with the temperature of the upper surface of the coating, both of which are T b1 The infrared thermal imager 176 is used to obtain the surface radiation temperature T of the chip coated with the coating. r1 Since the temperature measured by the infrared thermal imager is affected by the emissivity ε of the sample surface material, the infrared method measures the chip surface radiation temperature T r1 And the actual chip temperature T b1 There are differences.

[0072] The temperature of the heating pipe 118 is set to T b2 and T b3 Similarly, the surface radiation temperature T r2 and T r3 of the coated chip are obtained respectively;

[0073] According to the principle of the infrared thermal imager, the surface radiation temperature T r of the chip tested by the infrared thermal imager 176 satisfies the relationship with the real temperature T b of the chip surface Where ε is the emissivity, and C is a constant; substituting T b1 , T b2 , T b3 , T r1 , T r2 , T r3 , we have Through derivation, the emissivity of the chip surface coating is calculated respectively The error of different emissivities is calculated It is shown that the emissivity ε is uniform.

[0074] Experiment 7 verifies the accuracy of the emissivity calibration infrared method

[0075] The purpose of this experiment is to test the temperature of the diode chip by using the transient thermal resistance method and the emissivity calibration infrared method respectively, and to verify the accuracy of the emissivity calibration infrared method.

[0076] Figure 12 The schematic diagram of the transient thermal resistance method for testing the temperature sensitive parameter K coefficient of the diode of the preferred embodiment of the present application is shown in FIG. 7. Figure 12 The power diode is connected to the transient thermal resistance test circuit, and the positive and negative lead-out ends 173 and 174 of the diode chip 172 are connected to the VF voltage sensor 147, the IH heating current 148, and the IM test current 149 respectively; since the actual directions of the VF voltage sensor 147, the IH heating current 148, and the IM test current 149 are the same, all of them are displayed as positive (+). The T3ster device is used to load only 5mA of the IM test current 149 to the diode, without loading the IH heating current 148, and the VF voltage sensor 147 is used to monitor the voltage drop change of the diode chip 172 in real time.

[0077] As shown in FIG. 8, the transient thermal resistance test circuit is shown in FIG. 8. Figure 12Heating tube 118 is used to heat power diode substrate 171 for a certain period of time until the temperature of heating tube 118 equals the temperature of diode chip 172. The temperature of heating tube 118 is adjusted to gradually increase the temperature of diode chip 172 from 25°C to 140°C at a heating rate of 5°C / minute. The voltage drop-temperature curve of the diode chip is recorded in real time to determine its temperature-sensitive parameter, the K coefficient.

[0078] Figure 13 Schematic diagram of the transient thermal resistance method and the emissivity calibration infrared method respectively testing the diode chip temperature in a preferred embodiment of the present invention. Figure 13 The power diode connected to the transient test circuit is placed under the infrared thermal imager 176, with the diode chip 172 coated with the boron carbide-polyimide coating 121 facing the infrared thermal imager 176. A 0.5A IH heating current 148 is applied to the diode chip 172. After the VF voltage sensor 147 stabilizes, the chip temperature is measured using the infrared thermal imager 176. The chip temperature is then calibrated according to the emissivity ε of Experiment 6 to obtain the chip temperature T measured by the emissivity calibration infrared method. hw1 .

[0079] like Figure 13 , quickly switch from IH heating current 148 to IM test current 149, use transient thermal resistance method to test diode chip voltage drop, and obtain chip temperature T through the above K coefficient rz1 .

[0080] like Figure 13 , change the IH heating current 148, and obtain the chip temperature T of the transient thermal resistance method test at different IH heating currents (1.0, 1.5, 2.0A) rz2 、T rz3 、T rz4 and the chip temperature T of the infrared test with emissivity calibration hw2 、T hw3 、T hw4 .

[0081] Figure 14 The chip temperature curve T is measured by the transient thermal resistance method of the preferred embodiment of the present invention. rz Chip temperature curve T of infrared method test with emissivity calibration hw Overlay graph. Figure 14 , draw and superimpose the chip temperature curve T tested by transient thermal resistance method rz Chip temperature curve T tested by 179 and emissivity calibration infrared method hw 178. Curve T rz 179 and T hw The overlap of 178 is good, indicating that the emissivity-calibrated infrared method can accurately test the chip temperature.

[0082] Based on the experimental demonstration results, the method for monitoring the temperature of the power diode chip in real time by the infrared method provided by the application comprises the following steps: preparing a boron carbide-polyimide coating on the surface of the power diode chip to be measured; connecting the power diode chip to an aging circuit, and monitoring the temperature of the power diode chip in real time by the emissivity calibration infrared method.

[0083] Figure 15 The figure is a schematic diagram of the temperature of the power diode chip tested by the emissivity calibration infrared method in the aging process of the preferred embodiment of the application. As shown in the figure, Figure 15 For the power diode chips 172 of different packaging structures and different types, the boron carbide-polyimide coating 121 with a thickness ranging from 4 to 8 microns is coated on the surface of the power diode chip 172 to be measured by the spin coating method.

[0084] As shown in the figure, Figure 15 The power diode is connected to the aging circuit 181, the temperature of the chip 172 is tested by the infrared thermal imager 176, and then the temperature of the chip is monitored in real time by the emissivity calibration infrared method according to the coating emissivity ε obtained in Experiment 6.

[0085] The application has the following beneficial effects:

[0086] First, the conventional infrared method is affected by the emissivity ε of the surface material of the diode chip to be measured, and the test accuracy is poor. In the application, the boron carbide-polyimide coating is prepared on the surface of the diode chip to be measured by the spin coating method, so that the emissivity ε of the surface material of the diode chip to be measured is uniform; and the emissivity ε is tested by the infrared contrast method, so that the temperature of the diode chip to be measured is accurately calculated.

[0087] Second, for power diode chips of different types, the transient thermal resistance method needs to test the temperature sensitive parameters of the diode each time, and the test cost is high. In the application, the boron carbide-polyimide coating is prepared on the surface of the diode chip to be measured by the spin coating method, and the temperature of the diode chip can be monitored in real time by the emissivity calibration infrared method, and the coating will not affect the distribution of the temperature and current on the surface of the diode chip.

[0088] Third, for power diodes of different packaging structures, special fixtures need to be prepared for testing by the transient thermal resistance method, the power diode needs to be powered, and the one-dimensional conduction path needs to be met, the design cost of the fixture is high, and the preparation process is complex. In the application, the transient thermal resistance test is not repeated, and the temperature of the power diode chip can be monitored in real time by verifying the accuracy of the emissivity calibration infrared method by the transient thermal resistance method.

[0089] Fourth, the thermocouple method needs to be in direct contact with the chip surface to complete temperature measurement, and the temperature measurement accuracy is low, and a group of flat cables can only test one temperature point. The chip temperature measured by the application is very close to the chip temperature measured by the transient thermal resistance method, and is more accurate than the thermocouple method; at the same time, the test steps of the application are fast and convenient, and the complex flat cable of the thermocouple method is avoided.

[0090] Fifth, the application can not only be used for testing chip temperature, but also for testing the temperature of device shell, substrate, PCB copper clad plate and other packaging structures, and the test range is wide, and the temperature distribution state of the whole device can be presented.

[0091] The above specific embodiments can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the application, the protection scope of the application is subject to the claims and is not limited by the above specific embodiments, and each implementation scheme within the scope is subject to the constraints of the application.

Claims

1. A method for real-time infrared monitoring of power diode chip temperature, characterized in that: include: The spin coating method is used to prepare the boron carbide-polyimide coating on the surface of the power diode chip to be tested, and the coating thickness L ranges from 4 to 8 μm; Connect the power diode chip to the aging circuit and use the emissivity calibration infrared method to monitor the power diode chip temperature in real time. The spin coating method comprises: mixing boron carbide particles and polyimide by ball milling and uniformly coating the mixture on the surface of a power diode chip to be tested, wherein the diameter of the boron carbide particles ranges from 30 to 50 nm; fixing the power diode chip to be tested in a spin coating machine; controlling the centrifugal force by changing the speed of the spin coating machine to obtain a suitable coating thickness L; heating the coating to solidify the coating, and then naturally cooling the coating to room temperature; The method of using an emissivity-calibrated infrared method to monitor the power diode chip temperature in real time includes: using an infrared thermal imager to test the chip temperature, then calibrating it according to the coating emissivity ε, and monitoring the chip temperature in real time by using the emissivity-calibrated infrared method; The steps for obtaining the coating emissivity ε include: using a heating tube to increase the temperature of the diode chip, and the actual temperature of the chip on the upper surface of the coating and the lower surface of the coating are both equal to the heating tube temperature T b ; Use infrared thermal imager to obtain the surface radiation temperature T of the chip coated with the coating r ; Chip surface radiation temperature T tested by infrared thermal imager r The actual chip temperature T b Satisfaction relationship The coating emissivity ε is calculated from this, and C is a constant.

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