Packaging method for power semiconductor device and packaged power semiconductor device

Abstract

The invention relates to the technical field of packaging, and discloses a packaging method for a power semiconductor device and the packaged power semiconductor device. The method comprises the steps that a packaging tube shell is immersed in heat conduction liquid in an immersion bin, the temperature of the heat conduction liquid is larger than or equal to the junction temperature of the power semiconductor device, the heat conduction coefficient of the heat conduction liquid is larger than a preset coefficient, the heat conduction liquid is insulating liquid, and a gap exists between a cathode and a gate pole of the power semiconductor device; a packaging part is placed in the packaging tube shell; in the packaging tube shell, assembling the packaging parts for the power semiconductor device according to a packaging process sequence; and sealing and packaging the packaging tube shell. The heat dissipation efficiency of the gate cathode side can be improved, the heat dissipation balance of the cathode and the anode is improved, the junction temperature of the device is improved, the turn-off capacity is enhanced, the reliability of the device can be improved, the service life of the device can be prolonged, and meanwhile the advantages of being simple in process, low in cost, high in adaptability and the like are achieved.

Description

Technical Field

[0001] The present invention relates to the field of packaging technology, and in particular to a packaging method for a power semiconductor device and a packaged power semiconductor device. Background Art

[0002] Power semiconductor devices are core components of modern power electronic systems and are widely used in fields such as power regulation, control and conversion. As people pay more and more attention to energy transmission and environmental protection, power semiconductor devices have become increasingly important in the power industry, which also puts higher requirements on their performance. Integrated Gate Commutated Thyristor (IGCT) is a new type of power semiconductor device that can achieve high-voltage and large-capacity energy conversion. It has the advantages of high voltage resistance, high current resistance, low loss, high capacity density, fast switching speed, simple structure, high safety and high reliability. It can be widely used in high-voltage direct current transmission, new energy power generation, rail transportation and other fields.

[0003] Figure 1 It is a vertical cell structure of a power semiconductor device. There is a gap between the cathode and gate of the chip. The traditional thyristor packaging technology mainly adopts a press-fit packaging structure, and the gap is filled with air (such as Figure 1 or Figure 3a As shown). The thermal conductivity of air is low and its thermal conductivity is poor, and vacuum completely isolates the heat transfer along this path. On the cathode side of the chip, when the high current is turned off, the heat generated by the gate can only be conducted horizontally along the chip to the cathode table, and then longitudinally conducted to the molybdenum sheet through the cathode table in contact with the molybdenum sheet and the cathode electrode for heat dissipation. The cathode electrode in contact with the molybdenum sheet has a small area, usually less than 40% of the anode electrode, so the heat dissipation efficiency is extremely low. The heat dissipation capacity of the cathode and anode sides is inconsistent. During long-term use, the cathode will first experience problems such as aging and cracking. In addition, the heat dissipation on the cathode side seriously reduces the junction temperature and shutdown capability of the device, affecting the safety, reliability and service life of the device. Summary of the invention

[0004] The purpose of the present invention is to provide a packaging method for power semiconductor devices and a packaged power semiconductor device, which aims to solve the problems of uneven heat dissipation between the anode and cathode of the chip, low junction temperature of the device, and poor shutdown capability caused by the traditional packaging structure.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a packaging method for a power semiconductor device, the packaging method comprising: immersing a packaging tube shell into a thermally conductive liquid in an immersion chamber, wherein the temperature of the thermally conductive liquid is greater than or equal to the junction temperature of the power semiconductor device, the thermal conductivity of the thermally conductive liquid is greater than a preset coefficient, the thermally conductive liquid is an insulating liquid, and there is a gap between the cathode and the gate of the power semiconductor device; placing packaging components into the packaging tube shell; assembling the packaging components for the power semiconductor device inside the packaging tube shell according to the packaging process sequence; and sealing and packaging the packaging tube shell.

[0006] Preferably, after immersing the packaging tube shell into the thermal liquid in the immersion chamber, the packaging method further includes: after the temperature of the packaging tube shell rises to the temperature of the thermal liquid, performing ultrasound to eliminate bubbles in the packaging tube shell; and / or after placing the packaging component into the packaging tube shell, the packaging method further includes: after the temperature of the packaging component rises to the temperature of the thermal liquid, performing ultrasound to eliminate bubbles in the packaging component.

[0007] Preferably, inside the packaging tube shell, the packaging components are assembled with respect to the power semiconductor device according to the packaging process sequence, including: inside the packaging tube shell, in accordance with the packaging process sequence, the packaging components are sequentially aligned with the power semiconductor device; and the connection method and assembly sequence of the packaging components are detected.

[0008] Preferably, the viscosity of the thermal fluid is less than or equal to a preset viscosity and is non-corrosive.

[0009] Preferably, the thermal expansion coefficient of the thermal fluid is Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

[0010] Preferably, before immersing the packaging tube shell into the heat transfer liquid in the immersion chamber, the packaging method further comprises: cleaning and drying the packaging tube shell, the power semiconductor device and the packaging parts.

[0011] Preferably, the packaging method further comprises: testing the sealing and performance of the sealed and packaged power semiconductor device.

[0012] Preferably, the packaging tube shell is provided with guide grooves distributed along the longitudinal direction.

[0013] Through the above technical solution, the present invention creatively immerses the package tube shell in a high thermal conductivity insulating heat-conducting liquid, so that the heat-conducting liquid fills the gaps between the package structures in the tube shell, thereby enhancing the heat dissipation capacity of heat on various paths, improving the heat dissipation efficiency on the cathode side of the gate, and improving the heat dissipation balance of the anode and cathode. The immersion liquid high thermal conductivity packaging technology can increase the junction temperature of the device and enhance the shutdown capability, improve the reliability and service life of the device, and at the same time, has the advantages of simple process, low cost, strong adaptability, etc.

[0014] A second aspect of the present invention provides a packaged power semiconductor device, comprising: a power semiconductor device, a packaging component, a packaging tube shell, and a thermal conductive liquid, wherein the thermal conductive liquid is filled between the power semiconductor device and the packaging tube shell, between the packaging component and the packaging tube shell, and between the cathode and gate of the power semiconductor device, the thermal conductivity of the thermal conductive liquid is greater than a preset value, the thermal conductive liquid is an insulating liquid, and there is a gap between the cathode and gate of the power semiconductor device.

[0015] Preferably, the viscosity of the thermal fluid is less than or equal to a preset viscosity and is non-corrosive.

[0016] Preferably, the thermal expansion coefficient of the thermal fluid is Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

[0017] Preferably, the packaging tube shell is provided with guide grooves distributed along the longitudinal direction.

[0018] For specific details and benefits of the packaged power semiconductor device provided by the embodiment of the present invention, please refer to the above description of the packaging method for the power semiconductor device, which will not be repeated here.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the embodiments of the present invention, but do not constitute a limitation on the embodiments of the present invention. In the accompanying drawings: Figure 1 It is a schematic diagram of the vertical structure of a cell of a power semiconductor device; Figure 2 is a flow chart of a packaging method for a power semiconductor device provided by an embodiment of the present invention; Figure 3a and Figure 3b They are schematic diagrams of the packaging structure of a power semiconductor device before and after being filled with a high thermal conductive liquid according to an embodiment of the present invention; Figure 4a It is a schematic diagram of an immersion packaging assembly based on a power semiconductor device provided by an embodiment of the present invention; Figure 4b It is a schematic diagram of an immersion packaging assembly based on a power semiconductor device provided by an embodiment of the present invention; Figure 5 is a top view of a package tube shell of a power semiconductor device provided by an embodiment of the present invention; and Figure 6 The present invention is a flowchart of an immersion packaging process for power semiconductor devices according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0022] Figure 2 FIG. 1 is a flow chart of a packaging method for a power semiconductor device provided by an embodiment of the present invention. Figure 2 As shown, the packaging method includes: step S201, immersing the packaging tube shell into the heat-conducting liquid in the immersion chamber, wherein the temperature of the heat-conducting liquid is greater than or equal to the junction temperature of the power semiconductor device, the thermal conductivity of the heat-conducting liquid is greater than a preset coefficient, the heat-conducting liquid is an insulating liquid, and there is a gap between the cathode and the gate of the power semiconductor device; step S202, placing the packaging components into the packaging tube shell; step S203, inside the packaging tube shell, assembling the packaging components for the power semiconductor device according to the packaging process sequence; and step S204, sealing and packaging the packaging tube shell.

[0023] The liquid immersion thyristor chip high thermal conductivity packaging technology proposed in this embodiment has the following advantages compared with the traditional packaging technology: (1) Improving the heat dissipation capacity of the device: The addition of high thermal conductivity fluid improves the phenomenon that the heat dissipation capacity on this path is weak due to the air filling between the gate and cathode. Because the device is wrapped in thermal conductive fluid, the path for the device to dissipate heat to the surrounding environment is increased, thereby enhancing the heat dissipation capacity of heat on each path, improving the heat dissipation efficiency on the gate cathode side, and improving the heat dissipation balance between the anode and cathode.

[0024] (2) Improve device reliability: The addition of high thermal conductivity fluid reduces the contact thermal resistance between the chip and the cathode molybdenum sheet. According to the junction temperature calculation relationship, the chip junction temperature is reduced, thereby increasing the junction temperature threshold and improving the reliability and service life of the device. At the same time, it provides a design possibility for further improving the turn-off voltage.

[0025] (3) Improving the shutdown capability of the device: The heat that cannot be dissipated causes the chip to heat up. Previously, under the normal operating temperature of 90°C and traditional double-sided water cooling, the device could only be shut down three times. After adding thermal conductive fluid, the maximum number of shutdown times can be increased to 5 times, significantly improving the shutdown capability of the device.

[0026] (4) Improve heat dissipation and electrical performance: Liquid immersion thyristor chip high thermal conductivity packaging technology has the advantages of simple process, low cost, and strong adaptability. The insulation of the thermal conductive liquid can eliminate the electrical stress breakdown caused by particles, burrs, etc. inside the device shell, which can effectively improve the heat dissipation and electrical performance of the thyristor.

[0027] The following explains and illustrates each of the above steps.

[0028] Step S201, immersing the package tube shell into the heat transfer liquid in the immersion chamber.

[0029] The temperature of the thermally conductive liquid is greater than or equal to the junction temperature of the power semiconductor device, the thermal conductivity of the thermally conductive liquid is greater than a preset coefficient, the thermally conductive liquid is an insulating liquid, and there is a gap between the cathode and the gate of the power semiconductor device.

[0030] Specifically, the thermal conductivity of the thermal conductive liquid should be greater than the thermal conductivity of the traditional solid packaging material (the thermal conductivity of the traditional solid packaging material ranges from 0.1 to 0.5 W / (m·K), for example, the preset coefficient can be 0.5 W / (m·K)) to improve the heat dissipation performance; and the insulation between the chip and the shell should be ensured to prevent leakage and short circuit, and a higher resistivity is required to ensure good insulation performance, for example, the resistivity should reach 10 8 Ω·m or more. For example, thermal conductive fluids include highly insulating electronic fluorinated fluids, highly thermally conductive organic fluids such as high-purity alcohol, nanofluids, and other highly thermally conductive insulating liquids.

[0031] Wherein, the packaging tube shell can be a ceramic tube shell; and its sealing part can be stainless steel metal.

[0032] First, a thermal liquid is injected into the immersion chamber. To prevent the thermal liquid from expanding and contracting inside the tube shell after packaging, the thermal liquid is heated to the designed temperature (e.g., the designed junction temperature of the chip) and then kept at a constant temperature. Then, the package tube shell (e.g., a ceramic tube shell) is immersed in the thermal liquid in the immersion chamber. In this way, stress caused by thermal expansion in actual use after the packaging is completed can be avoided.

[0033] In one embodiment, the thermal conductive liquid also meets other conditions, for example, the viscosity of the thermal conductive liquid is less than or equal to a preset viscosity and is non-corrosive.

[0034] Low viscosity: easy to fill and flow, ensuring that the chip can be completely immersed in it, the viscosity is less than or equal to the preset viscosity (e.g., 10m² / s), for example, the viscosity (or kinematic viscosity) is selected between 5m² / s and 10m² / s. In this embodiment, the high thermal conductivity fluid has low requirements on fluidity in the device, but requires good thermal conductivity.

[0035] Good chemical stability: It is not easy to cause chemical reactions during long-term use, and will not corrode the chip and shell. In other words, it is non-corrosive: It is not corrosive to all metal materials and other organic and inorganic materials.

[0036] In addition, the thermal expansion and contraction coefficient of liquid at room temperature is generally small, and this change can usually be ignored. However, thyristor chips have high precision requirements and a corresponding stress tolerance range. The present invention considers the stress impact of the thermal expansion change of the high thermal conductivity liquid on the chip during operation after adding the high thermal conductivity liquid, and predicts the safety of the device.

[0037] Specifically, in a closed container, the thermal expansion of a liquid will cause an increase in pressure. According to the definition of the compressibility coefficient, we can get ,in is the initial volume, is the pressure change.

[0038] At the same time, according to the thermal expansion coefficient The volume change of the liquid can also be expressed as .

[0039] Since the volume of the liquid is unique, according to the compressibility So we can get = .

[0040] The above equation can be used to calculate the liquid thermal expansion pressure: .

[0041] In one embodiment, the thermal expansion coefficient of the thermal fluid is Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

[0042] The pressure range that the chip can withstand is 5~10MPa (i.e. =5 MPa), after adding high thermal conductivity fluid, the maximum temperature difference during the process of heating the device from room temperature to normal operating temperature At 30°C, the liquid is incompressible (i.e., the compressibility =1 / Pa). Design basis based on liquid thermal expansion pressure prediction , it can be concluded that when selecting high thermal conductivity, the thermal expansion coefficient α≤ / ℃.

[0043] Preferably, the thermal expansion coefficient of the heat transfer fluid is as small as possible to avoid thermal expansion and contraction of the heat transfer fluid in the sealed tube shell due to temperature changes, thereby affecting the device packaging stress.

[0044] Of course, in another embodiment, the thermal liquid can meet the above conditions. In addition, the boiling point of the thermal liquid should be higher than the limit temperature of the chip during the opening and closing process (for example, the boiling point is 128°C) to avoid the thermal liquid vaporizing inside the tube shell due to excessive temperature to form a high pressure, which affects the device packaging stress. The liquid density of the thermal liquid can be selected to be 880kg / m 3 .

[0045] In step S201, the liquid level of the heat transfer liquid must be high enough to completely immerse the tube shell, ensuring that the inside of the tube shell is filled with the heat transfer liquid.

[0046] In one embodiment, after immersing the package tube shell into the thermal liquid in the immersion chamber (ie step S201), the packaging method further includes: after the temperature of the package tube shell rises to the temperature of the thermal liquid, performing ultrasound to eliminate bubbles in the package tube shell.

[0047] Specifically, the immersion chamber containing the thermal liquid may have an ultrasonic function, the ceramic tube shell is immersed in the thermal liquid in the immersion chamber, and the ceramic tube shell is waited to be heated to the temperature of the thermal liquid, and ultrasonic treatment is performed to eliminate the bubbles remaining in the tube shell.

[0048] Since the heating temperature of the thermal fluid is the designed junction temperature of the chip, the ceramic tube shell immersed in the thermal fluid can be guaranteed to heat up to the thermal fluid temperature only if it is maintained for a sufficiently long time; alternatively, the temperature of the ceramic tube shell can also be easily obtained by using an infrared gun.

[0049] Optionally, the ultrasonic time is maintained at a range from tens of seconds to several minutes; optionally, the ultrasonic frequency is maintained at a range from 500 kHz to 2 MHz; optionally, the ultrasonic intensity is maintained at a range from 180 kPa to 570 kPa.

[0050] Step S202, placing the packaged components into the package shell.

[0051] The packaging components may include: a gate insulator, a gate contact ring, a cathode molybdenum sheet, an anode molybdenum sheet, and an anode electrode. The gate insulator is polyimide; the gate contact ring is metal molybdenum; and the anode electrode is a metal tube shell.

[0052] After placing the packaged component into the package shell (ie step S202 ), the packaging method further includes: after the temperature of the packaged component rises to the temperature of the thermal conductive liquid, performing ultrasound to eliminate bubbles in the packaged component.

[0053] Specifically, the packaged components are placed in the package tube shell in the thermal liquid in turn. Similarly, after the components are heated to the temperature of the thermal liquid, the bubbles remaining in the packaged components are eliminated by ultrasonic treatment one by one. Since the heating temperature of the thermal liquid is the junction temperature designed for the chip, only by keeping it for a long enough time can the packaged components immersed in the thermal liquid be heated to the temperature of the thermal liquid; alternatively, the temperature of the packaged components can also be easily obtained by using an infrared gun.

[0054] The liquid level of the thermal transfer fluid must be able to completely immerse the packaged components to ensure that the gaps on the surface of the packaged components and between the components are filled with thermal transfer fluid without bubbles.

[0055] Optionally, the ultrasonic time is maintained at a range from tens of seconds to several minutes; optionally, the ultrasonic frequency is maintained at a range from 500kHz to 2MHz; optionally, the ultrasonic intensity is maintained at a range from 180kPa to 570kPa.

[0056] Of course, in another embodiment, after executing step S201 and step S202, ultrasonic treatment may be performed in the above manner to eliminate bubbles in the packaging tube shell and the packaging component.

[0057] Step S203 , assembling the packaging components for the power semiconductor device inside the packaging shell according to the packaging process sequence.

[0058] Inside the packaging tube shell, the packaging components are assembled with respect to the power semiconductor device according to the packaging process sequence, that is, step S203 may include: inside the packaging tube shell, according to the packaging process sequence, the packaging components are sequentially aligned with the power semiconductor device; and the connection method and assembly sequence of the packaging components are detected.

[0059] Specifically, according to the packaging process sequence of the internal components of the device, the components are aligned in sequence (such as Figure 4a As shown in the figure), and check whether the connection method and assembly sequence of parts meet the packaging structure design.

[0060] Among them, all packaged components must be assembled and interconnected before packaging below the liquid level of the thermal fluid immersion chamber.

[0061] Optionally, after the components are arranged and interconnected according to the packaging design structure, ultrasound needs to be performed again to ensure that there are no residual bubbles; optionally, after the internal components of the device are assembled according to the packaging design structure, they need to be rotated at multiple angles and ultrasound is added to avoid residual bubbles in the gaps, micro grooves, micro holes and other areas of the components, ensuring that the components inside the packaging tube shell are filled with thermal transfer fluid; optionally, the assembly and interconnection process between the packaged components is kept as slow and smooth as possible to avoid splashing of the thermal transfer fluid and the formation of bubbles inside the thermal transfer fluid.

[0062] Step S204: sealing and packaging the packaging shell.

[0063] Specifically, the package tube shell after the previous step is sealed and packaged using an appropriate packaging method and sealing material, so that the interior of the package tube shell can be fully filled with the thermal conductive liquid (such as Figure 3b The gap between the cathode and gate of the chip shown is filled with thermal fluid). The packaging process must ensure that the thermal fluid inside the shell cannot leak to prevent bubbles from forming inside the shell. The package shell must have high sealing to avoid leakage of thermal fluid; the packaging process can be carried out below the thermal fluid level.

[0064] Optionally, the packaging method is compression packaging, bonding packaging, or welding packaging.

[0065] Before immersing the packaging tube shell into the heat transfer liquid in the immersion chamber (ie step S201 ), the packaging method further includes: cleaning and drying the packaging tube shell, the power semiconductor device and the packaging parts.

[0066] Specifically, the package shell, power semiconductor devices, and package components (such as electrodes) are cleaned to remove surface oil, impurities, etc. When cleaning the chip, the chip surface is ensured to be free from dissolution, corrosion, etc. by the cleaning solution as much as possible. All the above-mentioned cleaned components must be dried after cleaning to keep them dry.

[0067] Optionally, the cleaning solution includes deionized water, organic cleaning solution, ethanol, acetone, hydrogen peroxide, etc.; optionally, to further ensure the cleaning effect, ultrasonic cleaning, heating cleaning, vibration cleaning, etc. can be selected.

[0068] After executing step S204, the packaging method further comprises: testing the sealing and performance of the sealed and packaged power semiconductor device.

[0069] Specifically, the packaged device is tested, and the testing scope includes the sealing of the tube shell (whether there is leakage of thermal transfer fluid) and device performance.

[0070] Optionally, the detection methods include naked eye observation, vibration detection, thermal-electrical-mechanical and other parameter detection.

[0071] First, based on the theoretical model of immersion packaging design, the stress impact of the thermal expansion change of the high thermal conductivity fluid on the chip is verified to verify the safety of the device; the reduction in thermal resistance before and after replacing the high thermal conductivity fluid is compared. (1) Liquid expansion coefficient verification Furthermore, the liquid expansion pressure and pressure of power semiconductor devices (such as IGCT devices) are calculated. The temperature difference between the device working in the extreme working condition (120°C) and the normal working condition (90°C) is 30°. At 90°C, the liquid expansion pressure is 0Pa. When the device works in the extreme working condition (120°C), the liquid expansion pressure is 0.36Pa.

[0072] The pressure that the Si chip side can withstand is 5MPa-10MPa. Therefore, when the device works under extreme conditions (120°C), the pressure generated by the liquid on the chip side is much smaller than the chip's withstand pressure.

[0073] (2) Thermal resistance reduction Taking the IGCT device as an example, the IGCT junction temperature calculation method is to first calculate its junction temperature at any time. t Power p ( t ), and then according to t Thermal resistance and power p ( t ) relationship, the junction temperature is obtained , as follows: .

[0074] According to the relevant parameters in the RB-IGCT device manual, the device thermal resistance relationship can be extracted as follows: , In the formula, is the transient thermal resistance of the device; is the equivalent thermal resistance (in K / kW) of the i-th layer of medium (such as air or thermal fluid) from the bottom to the top of the device, and n is the total number of equivalent thermal resistances (such as Figure 3b The n shown is 13, which includes the sum of the total volume thermal resistance formed by the medium of each structural layer and the total contact thermal resistance formed by the medium between adjacent structural layers); is the time constant (in s).

[0075] The main verification device is under normal working steady state, the absolute value of the device thermal resistance reduction before and after adding high thermal conductivity liquid and the relative value of the overall thermal resistance reduction of the device. Under steady state working state, the thermal resistance has nothing to do with time t. The thermal resistance of the cathode and anode sides can be simplified to the above formula: , The device thermal resistance is obtained by connecting the cathode and anode side thermal resistances in parallel. The overall device thermal resistance can be expressed as: , in, is the total thermal resistance on the cathode side, is the total thermal resistance on the anode side.

[0076] Calculate the reduction ratio of the contact thermal resistance between Si and Mo: When the gap is filled with air, it is assumed that the heat conduction path is only conducted through the cathode comb bars, and the air-filled area is a thermal insulation channel. The contact thermal resistance of the layer is replaced by the body thermal resistance of the layer. Substituting the physical property parameters, it can be obtained as 0.000037 K·m 2 / W.

[0077] After the gap is filled with high thermal conductivity liquid, the bulk thermal resistance of the cathode comb heat conduction path and the high thermal conductivity liquid heat conduction path in parallel is 0.0000317 K·m 2 / W.

[0078] Therefore, after the gap is filled with high thermal conductivity liquid, the absolute value of the contact thermal resistance between the Si chip and the Mo chip is reduced by 14%.

[0079] Calculate the proportion of the reduction in the thermal resistance of the entire IGCT device due to the reduction in the contact thermal resistance between Si_Mo after adding the high thermal conductive fluid.

[0080] When the gap is filled with air, according to the above assumption, the contact thermal resistance between Si_Mo is replaced by the thermal resistance of the layer. According to the above thermal resistance model, substituting the physical parameters and empirical values, the overall thermal resistance of the device is calculated to be 0.75 K·m 2 / W.

[0081] After the gap is filled with high thermal conductivity liquid, according to the above theoretical assumptions, the contact thermal resistance between Si_Mo is replaced by the parallel body thermal resistance. According to the above thermal resistance model, the physical parameters and empirical values ​​are substituted to calculate the overall thermal resistance of the device to be 1.17 K·m 2 / W.

[0082] Therefore, after the gap is filled with high thermal conductive liquid, the reduction in contact thermal resistance between Si_Mo accounts for 56% of the reduction in thermal resistance of the entire IGCT device.

[0083] In one embodiment, the package tube shell is provided with flow guide grooves distributed along the longitudinal direction, such as Figure 5 shown.

[0084] In order to ensure the smooth flow of the internal coolant, it is preferred that some longitudinal guide grooves be provided on the tube shell, with the inner diameter unchanged. Figure 5 The guide groove structure inside the tube shell of a power semiconductor device is schematically shown from a top view.

[0085] The packaging process of power semiconductor devices (such as IGCT devices) is described below. Figure 6 shown.

[0086] Step 1: Clean the parts.

[0087] Clean the immersion chamber, IGCT chip ceramic tube shell, IGCT chip, electrodes and other components to remove surface oil, impurities, etc.

[0088] During the production and transportation of parts, the surface may be contaminated with various impurities (such as dust, organic matter, metal particles, etc.). The immersion chamber, IGCT chip ceramic tube shell, selected IGCT chip, electrodes and other components are cleaned, and ultrasonic cleaning is used to remove impurities from the chip surface.

[0089] After cleaning, nitrogen is used to blow dry the chip to ensure that the chip surface is dry and clean, preparing for the subsequent packaging process.

[0090] Step 2: inject high thermal conductivity liquid into the immersion chamber, heat the thermal conductivity liquid to the designed temperature and maintain the constant temperature.

[0091] The size of the immersion chamber should be larger than the package size of the device, so as to be suitable for placing and removing the packaged components and for portable activities inside the chamber; the thermal fluid should be selected from materials that meet the selection requirements described in 6.2; the heating temperature of the thermal fluid should be the designed junction temperature of the chip (80°C).

[0092] Perform a sealing check to ensure that it is well sealed. Use an inflator to fill the immersion chamber with 1.2 atmospheres of gas, which can be dry nitrogen or other inert gas, close the air inlet valve, and record the initial pressure. After 24 hours, if the pressure drop is within the allowable range (generally not more than 5%-10% of the specified pressure, depending on the requirements), it means that the sealing performance is good.

[0093] Injecting high thermal conductivity liquid into the immersion chamber: Vacuum injection can ensure that no air bubbles enter the immersion chamber, thereby ensuring the good performance of the thermal fluid. Moreover, this method of injection is relatively uniform, which enables the thermal fluid to better fill every corner of the immersion chamber. First, the interior of the immersion chamber is evacuated to a vacuum state, and then the thermal fluid is sucked into the immersion chamber by vacuum suction. This equipment mainly includes a vacuum pump and a liquid injection system. The vacuum pump first vacuums the immersion chamber, and then opens the liquid injection valve. The thermal fluid is sucked into the immersion chamber under the pressure difference formed by the external atmospheric pressure and the vacuum in the immersion chamber.

[0094] Liquid level control: The liquid level of the high thermal conductivity liquid needs to be controlled so that it can completely immerse the semiconductor device, but it cannot be too high or too low. If the liquid level is too high, the liquid may overflow, while if the liquid level is too low, the device cannot be completely immersed in the liquid, affecting the heat dissipation effect.

[0095] Then, the temperature of the thermal fluid was raised to 80°C and maintained at a constant temperature.

[0096] Step 3: immerse the ceramic shell in the thermal fluid.

[0097] The cleaned and dried ceramic shell is immersed in the heat transfer liquid in the immersion chamber, and the temperature of the ceramic shell is waited to be raised to the temperature of the heat transfer liquid, and the remaining bubbles in the shell are eliminated by ultrasonic.

[0098] Quality inspection of ceramic shell: Before immersion, the appearance of the ceramic shell needs to be checked again to ensure that there are no defects such as cracks and missing corners, so as not to affect the sealing of the package and the performance of the device. At the same time, it is necessary to confirm whether the dimensional accuracy of the ceramic shell meets the requirements, which is crucial for its adaptability in the immersion chamber and subsequent coordination with other package components.

[0099] Inspection of thermal fluid: The purity and quality of the thermal fluid must be checked to avoid impurities or moisture that may affect the heat dissipation effect or cause corrosion to the device.

[0100] Debugging of the immersion chamber: The temperature control system, liquid level monitoring system, etc. of the immersion chamber need to be debugged to ensure that they can work normally and provide a stable immersion environment for the ceramic shell.

[0101] Slow immersion: Slowly place the cleaned and dried ceramic shell into the thermal fluid in the immersion chamber to avoid splashing or bubbles due to rapid placement. The presence of bubbles will affect the heat dissipation effect of the thermal fluid, because the thermal conductivity of bubbles is much lower than that of the thermal fluid itself.

[0102] Immersion depth control: The immersion depth of the ceramic shell must be precisely controlled to ensure that it is completely covered by the thermal fluid and that all parts are in full contact with the thermal fluid to achieve the best heat dissipation effect. At the same time, care must be taken to avoid collision between the shell and the inner wall of the immersion chamber or other components to prevent damage to the shell.

[0103] Prevent static electricity: During operation, measures should be taken to prevent static electricity. Operators can wear anti-static wristbands and use anti-static tools. Static electricity may damage semiconductor devices and affect their performance and reliability.

[0104] Bubble removal: After immersion, if bubbles are found in the thermal fluid, gently shake the immersion chamber to eliminate the bubbles visible to the naked eye, and then use ultrasonic equipment to remove them to ensure good thermal contact between the thermal fluid and the ceramic tube shell.

[0105] Sealing check: Use the pressure test (mentioned above) to check the sealing of the immersion chamber to ensure that the sealing performance of the immersion chamber is still good and there is no leakage after the ceramic shell is immersed.

[0106] Temperature balance: Allow enough time for the ceramic shell and the thermal fluid to reach temperature balance, so that the thermal fluid can fully exert its heat dissipation effect and stabilize the operating temperature of the IGCT device.

[0107] Step 4: Place the packaged components in turn into the packaged ceramic tube shell in the thermal fluid.

[0108] Place the other packaged components that have been cleaned and dried into the package tube shell (such as Figure 4b Similarly, after the temperature of the parts is raised to the temperature of the thermal fluid, the bubbles remaining in the packaged parts are eliminated by ultrasonic treatment one by one.

[0109] Specifically, quality inspection of other packaged components: Before immersion, the appearance of each packaged component needs to be checked again to ensure that there are no defects such as cracks and missing corners, so as not to affect the sealing of the package and the performance of the device. At the same time, it is necessary to confirm whether the dimensional accuracy of each packaged component meets the requirements, which is crucial for its adaptability in the immersion chamber and subsequent coordination with other packaged components.

[0110] Then repeat the immersion steps such as checking the thermal fluid, debugging the immersion chamber, slow immersion, controlling the immersion depth, preventing static electricity, exhausting bubbles, sealing inspection, temperature balance, etc.

[0111] Then, put the cathode molybdenum sheet, gate contact ring, gate insulation, etc. in sequence (such as Figure 4a After alignment, align according to the package design structure and eliminate bubbles with ultrasound.

[0112] Next, put the IGCT chip in. There are micro grooves inside the gate cathode of the chip. After placing it, it needs to be ultrasonicated for a short time to eliminate bubbles, but not for a long time. At the same time, the temperature of the thermal conductive liquid should not be too high to avoid the red glue and other insulating materials on the surface of the chip from being peeled off.

[0113] Place the anode molybdenum sheet and the anode electrode (such as a metal tube shell) in sequence, align, interconnect and seal according to the packaging design structure.

[0114] The installation of the above components needs to be encapsulated inside the thermal fluid.

[0115] The packaging pressure parameter is 80kN, which can promote the tight assembly of components in the thermal fluid environment. Appropriate pressure helps to compact the components and make the connection between them more stable. For example, it can make the gap between the components that fit each other smaller and enhance the tightness of the physical connection. For some components connected by crimping, fitting, etc., this pressure can ensure that the connection effect meets the packaging expectations. The pressure needs to be precisely controlled at 80kN. If the pressure is too high, it may cause damage to some fragile components. For example, it may cause internal structural deformation and pin breakage of precision components such as chips, affecting their normal functions. If the pressure is too low, a good assembly effect cannot be achieved, and there may be looseness between components, which will affect the stability of the entire device and subsequent performance.

[0116] Step 5: Align and inspect the components in turn.

[0117] According to the packaging process sequence of the components inside the device ( Figure 4a The IGCT chip, cathode molybdenum sheet, anode molybdenum sheet, gate contact ring, gate insulator, and metal tube shell shown in the figure are aligned in turn, and the connection method and assembly sequence of the components are checked to see if they meet the packaging structure design.

[0118] First, make sure that the foundation's load-bearing structural components are accurately placed and fixed in their initial positions as required, so as to provide an accurate reference for the subsequent assembly of other components.

[0119] Next, for functional core components such as IGCT chips, they must be accurately aligned to the corresponding positions based on their connection relationships with peripheral components and the spatial layout in the entire packaging structure. They must also be accurately connected to corresponding pins and circuits to ensure that electrical connections are in line with the design plan.

[0120] After that, the parts for sealing or reinforcement should be aligned to their respective positions in sequence, and the sealing gaskets should be completely and accurately stuck in the corresponding interfaces.

[0121] Aligning the components in sequence in this way helps to ensure the integrity and accuracy of the entire packaging structure, allowing the components to work together as expected, laying a good foundation for subsequent connection, testing and normal operation of the entire device, and avoiding problems such as electrical failures, poor heat dissipation or structural instability due to component position deviations.

[0122] The assembly and interconnection process between the packaged components should be kept as slow and smooth as possible, mainly to prevent splashing of the thermal fluid and formation of bubbles inside the thermal fluid. This is a better operating suggestion.

[0123] After the internal components of the device are assembled according to the packaging design structure, they are rotated at multiple angles. This operation plays an important role.

[0124] Multi-angle rotation can make the position distribution of components in the package more reasonable and uniform, ensuring that the fit between components meets design expectations and avoiding unreasonable local assembly.

[0125] Finally, combined with additional ultrasonic operation, the bubbles remaining in the gaps, micro grooves, micro holes and other areas of each component can be effectively discharged, so that the interior of the package shell can be fully filled with thermal transfer fluid, ensuring that the thermal transfer fluid can better play its role in heat dissipation and other aspects, improve the performance and stability of the entire device, and avoid potential problems such as local overheating and impact on electrical performance caused by residual bubbles.

[0126] Step 6: sealing the package shell.

[0127] The packaged tube shell after the previous step is sealed and packaged with a suitable packaging method and sealing material. The packaging process must ensure that the thermal conductive liquid inside the tube shell cannot leak to prevent bubbles from forming inside the tube shell.

[0128] Optionally, the packaging tube shell must have high sealing performance to avoid leakage of the thermal fluid; optionally, the packaging process can be carried out below the liquid level of the thermal fluid; optionally, the packaging method is crimping packaging, bonding packaging, and welding packaging.

[0129] Afterwards, take out the IGCT tube shell from the thermal fluid for drying. The drying methods include blowing dry, wiping dry, and spinning dry.

[0130] Use a special drying device to properly place the IGCT tube shell in it and start the equipment. Use the centrifugal force through rapid rotation to make it rotate at high speed for a certain period of time. At the same time, perform appropriate rotation and shaking movements manually. Pay attention to the strength and stability during manual operation to avoid the tube shell from falling and being damaged.

[0131] Use clean, soft wiping tools such as cotton balls and dust-free cloth to gently wipe the surface of the tube shell to remove the thermal fluid. Be gentle when wiping, and wipe different parts in a certain order to avoid scratching the tube shell. The corners and other parts should be handled more carefully.

[0132] Use the airflow generated by a hair dryer or other equipment to dry the thermal fluid on the surface of the tube shell and any gaps, holes, etc. The airflow can accelerate the evaporation of the liquid and take away the moisture. When operating, the hair dryer should be kept at a suitable distance from the tube shell and moved evenly so that all parts of the tube shell can be fully exposed to the airflow to ensure comprehensive drying.

[0133] Step 7: testing the packaged IGCT device.

[0134] Conduct thermal, electrical and mechanical tests.

[0135] Thermal detection: Semiconductor devices generate heat during operation, and whether the heat can be effectively dissipated directly affects the performance and service life of the device. Thermal detection is to evaluate the heat dissipation capacity of the device and the internal heat distribution to ensure that there is no local overheating that leads to performance degradation or even damage. Measure the thermal resistance of the device from the heat source to the heat dissipation end. The smaller the thermal resistance, the smoother the heat conduction and the better the heat dissipation effect. Generally, temperature sensors are installed at the heating and heat dissipation parts of the device, combined with certain heating conditions and calculation formulas to obtain the thermal resistance value.

[0136] Electrical testing: It is mainly to verify whether the various electrical properties of the device meet the design requirements, including conductivity, insulation, accuracy of electrical parameters (such as resistance, capacitance, voltage, current and other indicators), etc., to ensure that the device can function normally in the circuit. First, use the different function gears of the multimeter, such as the resistance gear to detect the resistance of the device to determine whether there is a short circuit or open circuit problem; the voltage gear and current gear can be used to measure the corresponding working voltage and current and other parameters. The operation is simple and convenient, and is often used for preliminary electrical performance inspection. Then, the oscilloscope can be used to observe the waveform changes of voltage, current and other signals of the device during operation. By analyzing the shape, frequency, amplitude and other characteristics of the waveform, the electrical characteristics of the device can be deeply understood, such as whether there is signal distortion, interference, etc., which is very effective for the electrical performance detection of some high-frequency and complex semiconductor devices. Finally, for the tester specializing in IGCT devices, multiple electrical parameters of the device are accurately measured and compared with the standard parameters to accurately determine whether the electrical performance of the device is qualified.

[0137] In each of the above embodiments, the power semiconductor device includes: an IGCT device, an IGBT device, a MOSFET device, and a GTO device.

[0138] The IGCT chip in each embodiment of the present invention includes a GCT device (ie, a whole wafer structure), surface metal aluminum, PI glue, edge red glue, and silicon oxide.

[0139] In summary, the novel liquid immersion thyristor chip high thermal conductivity packaging technology provided by the present invention mainly immerses the packaging tube shell in a high thermal conductivity insulating thermal conductive liquid, so that the thermal conductive liquid fills the gaps between the packaging structures in the tube shell, enhances the heat dissipation capacity of heat on various paths, improves the heat dissipation efficiency on the gate cathode side, and improves the heat dissipation balance of the anode and cathode. The immersion liquid high thermal conductivity packaging technology can increase the junction temperature of the device and enhance the shutdown capability, improve the reliability and service life of the device, and at the same time, has the advantages of simple process, low cost, strong adaptability, etc.

[0140] An embodiment of the present invention provides a packaged power semiconductor device, the packaged power semiconductor device comprising: a power semiconductor device, a packaging component, a packaging tube shell, and a thermal conductive liquid, wherein the thermal conductive liquid is filled between the power semiconductor device and the packaging tube shell, between the packaging component and the packaging tube shell, and between the cathode and gate of the power semiconductor device, the thermal conductivity of the thermal conductive liquid is greater than a preset value, the thermal conductive liquid is an insulating liquid, and there is a gap between the cathode and the gate of the power semiconductor device.

[0141] In one embodiment, the viscosity of the thermal conductive fluid is less than or equal to a preset viscosity and is non-corrosive.

[0142] In one embodiment, the thermal expansion coefficient of the thermal fluid is Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

[0143] In one embodiment, the package tube shell is provided with guide grooves distributed along the longitudinal direction.

[0144] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0145] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0146] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A packaging method for a power semiconductor device, characterized in that: The packaging method comprises: Immersing the package tube shell into the heat-conducting liquid in the immersion chamber, wherein the temperature of the heat-conducting liquid is greater than or equal to the junction temperature of the power semiconductor device, the thermal conductivity of the heat-conducting liquid is greater than a preset coefficient, the heat-conducting liquid is an insulating liquid, and there is a gap between the cathode and the gate of the power semiconductor device; placing the packaged components into the package shell; Inside the packaging tube shell, assembling the packaging components for the power semiconductor device according to the packaging process sequence; and The packaging tube shell is sealed and packaged.

2. The packaging method according to claim 1, characterized in that: After immersing the package tube shell into the heat transfer liquid in the immersion chamber, the packaging method further includes: performing ultrasound to eliminate bubbles in the package tube shell after the temperature of the package tube shell rises to the temperature of the heat transfer liquid; and / or After placing the packaged component into the packaged tube shell, the packaging method further includes: after the temperature of the packaged component rises to the temperature of the thermal conductive liquid, performing ultrasound to eliminate bubbles in the packaged component.

3. The packaging method according to claim 1, characterized in that: Inside the packaging tube shell, the packaging components are assembled for the power semiconductor device according to the packaging process sequence, including: Inside the packaging tube shell, sequentially aligning the packaging components with respect to the power semiconductor device according to the packaging process sequence; and The connection mode and assembly sequence of the packaged components are detected.

4. The packaging method according to claim 1, characterized in that: The viscosity of the thermal conduction fluid is less than or equal to a preset viscosity and the thermal conduction fluid is non-corrosive.

5. The packaging method according to claim 1, characterized in that: The thermal expansion coefficient of the thermal fluid Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

6. The packaging method according to claim 1, characterized in that: Before immersing the package tube shell into the heat transfer liquid in the immersion chamber, the packaging method further includes: The packaging tube shell, the power semiconductor device and the packaging parts are cleaned and dried.

7. The packaging method according to claim 1, characterized in that: The packaging method further comprises: Test the sealing and performance of power semiconductor devices after sealing and packaging.

8. The packaging method according to any one of claims 1 to 7, characterized in that: The packaging tube shell is provided with guide grooves distributed along the longitudinal direction.

9. A packaged power semiconductor device, characterized in that: The packaged power semiconductor device comprises: a power semiconductor device, a packaged component, a packaged tube shell, and a thermal conductive liquid. The thermal conductive liquid is filled between the power semiconductor device and the packaging tube shell, between the packaging component and the packaging tube shell, and between the cathode and gate of the power semiconductor device. The thermal conductivity of the thermal conductive liquid is greater than a preset value. The thermal conductive liquid is an insulating liquid, and there is a gap between the cathode and gate of the power semiconductor device.

10. The packaged power semiconductor device according to claim 9, characterized in that: The viscosity of the thermal conduction fluid is less than or equal to a preset viscosity and the thermal conduction fluid is non-corrosive.

11. The packaged power semiconductor device according to claim 9, characterized in that: The thermal expansion coefficient of the thermal fluid Depend on Determine, among which, is the compressibility coefficient of the thermal fluid, is the temperature difference between the junction temperature of the power semiconductor device and the normal temperature, and is the voltage difference that the power semiconductor device can withstand.

12. The packaged power semiconductor device according to any one of claims 9 to 11, characterized in that: The packaging tube shell is provided with guide grooves distributed along the longitudinal direction.

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