A method for packaging optimization of a power module of a semiconductor etching apparatus

Abstract

This invention relates to the field of semiconductor etching technology, specifically to a method for optimizing the packaging of power modules in semiconductor etching equipment. The method includes the following steps: Pre-treatment of the packaging substrate: Mechanically polishing the heat sink and the mounting surface of the power device, controlling the surface roughness Ra to be between 0.8 μm and 1.6 μm. This method incorporates the thermal resistance test data after packaging into the setting of the thermal interface layer thickness, so that thermal testing is no longer just a screening at the end of a batch, but can be fed back to subsequent batches. The thermal interface layer thickness gradually approaches the target value based on the measured thermal resistance feedback, and the batch thermal resistance deviation gradually narrows in continuous production. The housing assembly is changed from pure torque control to adding a rotation angle after final tightening, and the assembly consistency index γ is used to uniformly evaluate the preload dispersion and flatness deviation. This improves the consistency of assembly gaps and sealant compression, correspondingly reducing the risk of electric field concentration and moisture intrusion, and decreasing the stress concentration points during potting compound curing.

Description

Technical Field

[0001] This invention relates to the field of semiconductor etching technology, and more specifically, to a method for optimizing the packaging of a power module in a semiconductor etching device. Background Technology

[0002] In semiconductor etching equipment, the power module provides radio frequency discharge high-frequency high-voltage power to the etching cavity. The internal power devices operate in a radio frequency high-voltage and high-temperature environment for a long time. The packaging must ensure effective heat dissipation and maintain sufficient insulation and mechanical strength. The packaging process involves key steps such as setting the thickness of the thermal interface layer, screw tightening, vacuum potting, and curing parameter adjustment. Improper control of any of these steps will affect the junction temperature, partial discharge level, and long-term reliability of the power devices.

[0003] In actual mass production, the thickness of the thermal interface layer is usually set once at the beginning of the batch and is not changed afterward. The deviation between the actual thermal resistance measured after packaging and the design target is only used for acceptance judgment and is not returned to the front end of the process. The deviation of the previous batch will not affect the stencil thickness or coating speed of the next batch. Each batch is repeated with the same parameters, and the thermal resistance fluctuation cannot be converged in the process. Modules that exceed the tolerance must be scrapped. The shell and heat sink base plate are fastened with screws by pure torque method. The dispersion of the thread friction coefficient causes the preload to fluctuate. The sealant compression is inconsistent, and the shell will have a certain degree of warping. The uniformity of the assembly gap decreases, which in turn causes electric field concentration, moisture intrusion and stress concentration of the potting layer. The above problems accumulate batch by batch in mass production. Especially when different material forms are used for the thermal interface layer, the lack of a unified feedback correction logic further aggravates the performance dispersion between batches.

[0004] Based on this, the present invention discloses a packaging optimization method for the power module of a semiconductor etching device. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention provides a method for optimizing the packaging of a power module in a semiconductor etching apparatus, comprising the following steps: Pre-treatment of the packaging substrate: The heat sink base plate and the mounting surface of the power device are mechanically polished to control the surface roughness Ra to 0.8μm to 1.6μm. Then, they are subjected to anhydrous ethanol ultrasonic cleaning, deionized water ultrasonic cleaning and nitrogen blowing, and then atmospheric pressure plasma treatment.

[0006] Thermal interface layer thickness control: A thermal interface layer is formed between the power device and the heat sink. For the initial batch, preset reference parameters are used: when the thermal interface layer is thermal grease, the reference value for stencil thickness is 0.20mm, and the reference value for scraping speed is 20mm / s; when the thermal interface layer is a thermal pad, the reference value for the thermal pad thickness is 0.25mm, and the compression rate is 20%. From the second batch onwards, the process parameters for this batch are corrected based on the thermal resistance deviation rate obtained from the thermal testing of the previous batch. The thermal resistance deviation rate is determined by dividing the difference between the measured thermal resistance of the previous batch and the reference thermal resistance by the reference thermal resistance. The reference thermal resistance is the target thermal resistance value specified in the product's thermal design specifications and is not updated with each batch. The deviation direction refers to the positive or negative direction of the thermal resistance deviation rate; a thermal resistance deviation rate greater than 0 is a positive deviation, and less than 0 is a negative deviation. For negative deviations, when the thermal interface layer is thermally conductive silicone grease, adjust the stencil thickness and scraping speed as follows: When the thermal resistance deviation rate is greater than 5%, reduce the stencil thickness by 0.01mm and increase the scraping speed by 5mm / s compared to the previous batch. When the thermal resistance deviation rate is less than -5%, increase the stencil thickness by 0.01mm and decrease the scraping speed by 5mm / s compared to the previous batch. When the absolute value of the thermal resistance deviation rate is not greater than 3%, maintain the stencil thickness and scraping speed of the previous batch and record the current batch as the "maintained" state. When the absolute value of the thermal resistance deviation rate is greater than 3% but not greater than 5%, if the previous batch was in the adjustment state and the deviation direction of the current batch is the same as that of the previous batch, then follow the same procedure as when the absolute value of the deviation is greater than 5%. The adjustment step size continues to be adjusted; otherwise, the current parameters remain unchanged. The "adjustment state" refers to the previous batch where process parameters were adjusted, and the "maintain state" refers to the previous batch where process parameters were not adjusted. After each adjustment, the current batch's state is recorded as the "adjustment state," and after each parameter maintenance, the current batch's state is recorded as the "maintain state." When the thermal interface layer is a thermal pad, the thermal pad compression ratio is corrected. The increase or decrease in compression ratio is achieved by replacing the thermal pad with one of different thicknesses, resulting in a corresponding increase or decrease in compression ratio for the same installation gap: when the thermal resistance deviation rate is greater than 5%, the thickness of the thermal pad in the previous batch is increased by 0.01 mm, increasing the compression ratio by approximately 3 percentage points; when the thermal resistance deviation rate is less than -5%, the thickness of the thermal pad in the previous batch is decreased by 0.01 mm. The compression ratio is reduced by approximately 3 percentage points. The initial batch thermal pad thickness is 0.25 mm. When the thermal resistance deviation rate is greater than 5%, the first adjustment is to replace it with 0.26 mm. When the thermal resistance deviation rate is less than -5%, the first adjustment is to replace it with 0.24 mm. When the absolute value of the thermal resistance deviation rate is not greater than 3%, the current compression ratio is maintained. When the absolute value of the thermal resistance deviation rate is greater than 3% but not greater than 5%, if the previous batch was in the adjustment state and the deviation direction of this batch is the same as that of the previous batch, the adjustment step size is the same as when the absolute value of the deviation is greater than 5%. Otherwise, the current compression ratio is maintained. The adjustment state and the maintenance state are recorded in the batch process parameters. The above judgment of the 3% to 5% range is used to avoid the thermal resistance deviation from oscillating due to frequent parameter adjustments within this range.

[0007] As a further improvement to this technical solution, the relationship between the adjustment direction of the thermal pad compression rate and the thermal resistance deviation rate is as follows: a thermal resistance deviation rate greater than 5% indicates that the measured thermal resistance is too high. In this case, replacing the thermal pad with a 0.26mm thermal pad increases the compression rate under the installation gap from 20% to approximately 23.1%, increasing the filling pressure of the thermal pad and reducing the interface thermal resistance. A thermal resistance deviation rate less than -5% indicates that the measured thermal resistance is too low. In this case, replacing the thermal pad with a 0.24mm thermal pad reduces the compression rate from 20% to approximately 16.7%. To avoid excessive compression that could lead to mechanical damage and increased interfacial stress in the thermal pad, this relationship was confirmed through calibration of the thermal pad's compression ratio-thermal resistance characteristics. The calibration conditions were: initial thermal pad thickness 0.25 mm, thermal conductivity 3.2 W / (m·K), hardness 70 Shore OO, heat source power 20 W, and cold plate temperature 20 °C. Different compression ratios were obtained by adjusting the installation gap. The calibration data were: at a compression ratio of 17.0%, the installation gap was 0.2075 mm, and the interfacial thermal resistance was 0.087 K·cm. 2 / W, with a compression ratio of 20.0%, an installation gap of 0.2000mm, and an interface thermal resistance of 0.083K·cm. 2 / W, with a compression ratio of 23.0%, the mounting gap is 0.1925mm, and the interface thermal resistance is 0.079K·cm. 2 / W, with a compression ratio of 26.0%, the mounting gap is 0.1850mm, and the interface thermal resistance is 0.075K·cm. 2 / W, the thermal resistance change rate corresponding to approximately 3 percentage point changes in compression ratio is in the range of 4.4% to 5.1%, not less than 4%, and the resolution of the thermal testing instrument is 0.001 K·cm. 2 / W, the change in thermal resistance is 3 times the instrument resolution, which meets the resolution requirement.

[0008] As a further improvement to this technical solution, the pre-fixation and interface bonding verification are performed as follows: the power device is pre-fixed to the thermal interface layer with a pre-tightening torque. After maintaining the pre-tightening state, the bonding area is detected by ultrasonic scanning. For areas where the bonding area does not meet the standard, the positioning fixture is kept in place, and only the pre-tightening screws corresponding to the non-compliant areas are loosened. The correspondence between the non-compliant areas and the pre-tightening screws is pre-determined by mapping the ultrasonic scanning image with the screw position: using the reference hole of the positioning fixture as the geometric reference, sub-regions corresponding to the positions of each pre-tightening screw are divided in the ultrasonic scanning image coordinate system. The sub-region into which the non-compliant area falls is the sub-region into which the corresponding pre-tightening screw needs to be loosened. Thermal interface material is then applied again, the pre-tightening torque is reapplied and the pre-tightening state is maintained until the bonding area meets the standard. When the thermal interface layer is a thermal pad and the thermal pad compression ratio is adjusted in the thermal interface layer thickness control step, the pre-fixation, ultrasonic scanning detection and bonding area verification steps are repeated.

[0009] Final locking of power device: After the bonding area meets the standard, perform final locking on the power device at a final torque of 0.8N·m, with the locking sequence being diagonal cross tightening. After final locking, re-perform ultrasonic scanning for re-inspection.

[0010] As a further improvement of this technical solution, insulation structure arrangement: Check the creepage distance and electrical clearance according to the peak voltage of radio frequency discharge superimposed with DC bias and high-frequency working conditions. Install an insulating sheet between the high-voltage node and the housing, perform fillet treatment on solder joints and sharp metal edges and coat with insulating varnish. Perform leakage current and partial discharge detection before potting, and reprocess the parts that fail the detection. The creepage distance is not less than 8.0mm, and the electrical clearance is not less than 3.0mm. The above values are determined according to the requirements for 1000V peak value and 400kHz working conditions in IEC60664-1 and GB / T16935.1, with consideration of pollution degree 2 and overvoltage category Ⅲ.

[0011] As a further improvement of this technical solution, torque-angle closed-loop control for housing assembly clearance: Control the flatness of the matching surface between the housing and the heat dissipation base plate within 0.05mm, apply sealant on the matching surface, and use screws for diagonal cross tightening in three times with torques of 0.6N·m, 1.0N·m and 1.5N·m in sequence. After the third tightening, apply a rotation angle of 15°±2° to each screw, measure the post-assembly flatness of a total of 6 measuring points at the four corners of the housing and the midpoints of the two long sides, determine the assembly consistency index γ, and perform graded closed-loop processing according to γ: γ≤0.10 is judged as qualified; 0.10<γ≤0.25, position and locally retighten before re-measurement; γ>0.25, re-apply sealant and perform overall rework. If the re-measured γ is still greater than 0.25, terminate the packaging process and perform repair. The local retightening refers to loosening the target screw by half a turn, retightening it at a torque of 1.5N·m and applying a 15° rotation angle, without applying additional actions to adjacent screws. Only when the re-measured γ still does not meet the standard, expand the retightening range or upgrade to overall rework. The screws are M4 carbon steel blackened screws with a quantity of 6, the housing is an engineering plastic housing, the heat dissipation base plate is an aluminum alloy heat dissipation base plate, and the calculation formula for the assembly consistency index γ is:

[0012] where is the standard deviation of the pre-tightening force of each screw, is the average value of the pre-tightening force of each screw, is the measured post-assembly flatness value of the i-th measuring point, is the flatness threshold, =0.05mm, represents the summation of i from 1 to 6, where i is the serial number of a total of 6 measuring points at the four corners of the housing and the midpoints of the two long sides. The flatness threshold and the flatness control value for matching surface machining adopt the same numerical value but have different physical meanings: the former is used for the flatness evaluation of the housing after assembly, and the latter is used for the machining accuracy control of the matching surface. Both the preload dispersion and flatness deviation are positively correlated. The larger the value, the worse the uniformity of the assembly gap.

[0013] The weighting coefficients 0.6 and 0.4 in the calculation formula were determined through statistical regression and multi-objective optimization verification using 9 sets of assembly test data. The test used the coefficient of variation of preload and the normalized value of average flatness as independent variables, and the leakage rate as the response variable. The 9 sets of test data are as follows:

[0014] Regression analysis and multi-objective optimization were performed on the above nine sets of data. Using the assembly qualification rate as the verification index, batch trial production comparisons were conducted with four weight combinations: 0.5 / 0.5, 0.6 / 0.4, 0.7 / 0.3, and 0.8 / 0.2. The results showed that the 0.6 / 0.4 weight combination... ≤0.10 batches pass the test on the first attempt, 1.10 < ≤0.25 batch partial rework pass rate, The overall rework pass rate of batches >0.25 was higher than that of other weight combinations. Based on this, the weight coefficients of the γ formula were determined to be 0.6 and 0.4.

[0015] according to Calculate the results of 9 trials Value, qualified group Range 0.059 to 0.086, maximum value 0.086, partial rework group Range 0.129 to 0.161, non-compliant group The range is 0.258 to 0.307, with a minimum value of 0.258. These three intervals are completely separate and do not overlap. A threshold of 0.10 is chosen between the maximum value of the acceptable group (0.086) and the minimum value of the partial rework group (0.129) as the acceptable threshold. A threshold of 0.25 is chosen between the maximum value of the partial rework group (0.161) and the minimum value of the unacceptable group (0.258) as the upper limit for the partial rework threshold. This forms... ≤0.10 qualified, 0.10< ≤0.25 Local re-tightening, The graded processing rules for overall rework of >0.25 have a clear correspondence between the threshold and the weight formula of 0.6 / 0.4.

[0016] The preload of each screw is determined by the torque method and the correction for the rotation angle increment. The calculation formula is as follows: in, Apply a preload force to the i-th screw after the rotation. Let be the final tightening torque for the third diagonal tightening of the i-th screw, and let be the final tightening torque for each screw, which is 1.5 N·m. Let be the torque coefficient of the i-th screw. The nominal diameter of the thread is in meters, for M4 screws. =0.004m, The preload increment coefficient corresponding to the additional rotation angle is determined by calibration. The calibration conditions are: M4 carbon steel blackened screws, aluminum alloy heat sink base plate and engineering plastic housing, dry friction lubrication, tightening speed of 10 r / min, ambient temperature of 22℃±3℃, and rotation angle increment not exceeding 20°. If the usage conditions exceed the calibration conditions, recalibration is required. , The additional rotation angle applied to the i-th screw after the third torque tightening, and the torque coefficient. These are the measured values ​​obtained by calibrating each screw with a torque coefficient tester under the same lubrication conditions, tightening speed, and ambient temperature as the actual assembly before assembly. The unit is N / degree. The unit is degrees, and the torque term is... The formula for preload using the classical torque method can be found in Cheng Daxian (ed.), *Mechanical Design Handbook* (6th Edition), Volume 2, Chemical Industry Press, 2016, Part 5, Chapter 3, Threaded Connections, where the torque method preload formula is: Corner correction item This is a self-created modification in this invention, used to compensate for the increase in preload caused by the additional rotation angle.

[0017] The calibration method is as follows: Take 10 sets of M4 screws, 5 screws in each set, and screw them into the calibration fixture with a torque of 1.5 N·m. Record the initial preload. Then apply rotation angle increments of 5°, 10°, 15°, and 20° respectively, record the corresponding preload, calculate the preload increment, and plot the ΔF-rotation angle curve. Perform least squares fitting on the linear segment of the curve to obtain the result. The calibration results are as follows: the average preload increments for the entire group under each rotation angle increment are 0.170kN, 0.340kN, 0.520kN, and 0.701kN, respectively. Linear fitting yields... =0.035kN / ° = 35N / °, the linear fit goodness of fit meets the engineering calibration requirements. The calibration results exhibit low dispersion. In the preload estimation formula, the torque term characterizes the reference preload generated during the third torque control stage, and the rotation angle term characterizes the axial force increment caused by the additional angular displacement. The estimated value already includes the combined effects of the axial stiffness of the threaded pair, the elastic deformation of the mating surface, and the change in the torque coefficient on the axial force. This estimated value is mainly used to calculate the relative dispersion between each screw and is not used for absolute preload control. The coefficient of variation of the estimated preload of each screw is used to characterize the tightness consistency. This coefficient of variation is related to the uniformity of sealant compression and the flatness of the housing after assembly: the smaller the coefficient of variation, the more consistent the preload of each screw, the more uniform the sealant compression, and the closer the flatness of the housing after assembly is to the flatness threshold.

[0018] exist In the graded closed-loop processing, when 0.10 < γ ≤ 0.25, the screw with the largest deviation in positioning flatness and the largest contribution to the preload dispersion is locally retightened and γ is remeasured. If the remeasured γ is still within 0.10 < γ ≤ 0.25, positioning and local retightening continue. If γ is still within this range after two consecutive remeasurements, it is treated as γ > 0.25, the sealant is reapplied, and all three stages of diagonal cross tightening and corner remeasurement are performed. This processing rule is used to prevent the local tightening action from endlessly cycling in the 0.10 to 0.25 range, and to provide a clear upgrade path for γ closed-loop judgment.

[0019] As a further improvement to this technical solution, vacuum-assisted potting is performed: the pre-fixed module is evacuated and degassed, and potting compound is injected under vacuum so that the potting compound level is 12mm higher than the highest charged body. If the level is lower than 12mm, the compound is added to bring it above 12mm, and the vacuum is evacuated again. Then, the pressure is restored to normal at a rate of 5L / min. The potting compound level is measured by a liquid level sensor.

[0020] Segmented Curing and Shrinkage Stress Control: After standing at room temperature, heat according to the segmented heating curve and maintain the temperature segment by segment. Then cool down to room temperature at a rate of 0.8℃ / min. After curing, loosen the shell screws by half a turn, stand for 5 minutes, and then tighten again with a torque of 1.5 N·m and a rotation angle of 15°±2°. The sealant is an organic silicone elastic sealant with an elongation at break of not less than 200% after curing. After loosening by half a turn, the sealant compresses and rebounds. After tightening again, the sealing performance is maintained. After tightening again, re-measure the flatness of the four corners of the shell and the midpoint of the two long sides and calculate γ. If 0.10<γ≤0.25, locally tighten according to rule S5 and re-measure. If γ>0.25, remove the sealant and the cured potting compound, reapply the sealant, and repeat the steps of segmented curing and shrinkage stress control of shell assembly clearance torque-rotation angle, except for the airtightness test. After the gamma treatment, an airtightness test is performed on the joint between the housing and the heat sink base plate to confirm that the sealing performance is qualified. If the airtightness test fails, the sealant and cured potting compound are removed, the sealant is reapplied, and the steps of housing assembly gap torque-angle closed-loop control to segmented curing and shrinkage stress control, except for the airtightness test, are repeated. The steps of device pre-fixation, interface bonding verification, and final locking of power devices are not repeated. Then, the airtightness test is performed again. If the airtightness test still fails, the encapsulation is deemed a failure and the module encapsulation process is terminated. During the airtightness test, 0.2MPa compressed air is applied to the housing joint and held for 5 minutes. The pressure drop should not exceed 0.01MPa. This test pressure is determined based on a safety factor of 1.5 times the housing design pressure. The holding time and allowable pressure drop are determined based on the creep characteristics of the sealant and batch testing.

[0021] As a further improvement to this technical solution, post-packaging testing and thermal verification are performed: ultrasonic scanning, insulation testing, partial discharge testing, and rated power thermal testing are conducted on the cured module to obtain the measured thermal resistance. The measured thermal resistance is compared with the reference thermal resistance to calculate the thermal resistance deviation rate, which is used for the control of the thermal interface layer thickness in the next batch. If the absolute value of the measured thermal resistance deviation rate in this batch is greater than 5%, the thermal performance of this batch is deemed unqualified and it is disposed of as a non-conforming product, not flowing into subsequent delivery and use processes. The thermal test data of this batch is still used to calculate the thermal resistance deviation rate and fed back to the next batch. In the thermal test, the steady-state judgment condition is that the junction temperature change of the power device does not exceed ±1℃ within 30 minutes. The measured thermal resistance is determined by dividing the difference between the junction temperature of the power device and the ambient temperature by the power consumption of the power device. The power consumption is determined by the difference between the input power and the output power.

[0022] As a further improvement to this technical solution, the packaging completion and process recording are as follows: the packaging process parameters are recorded to form a batch record. The packaging process parameters include the thermal resistance deviation rate, γ value, preload of each screw, adjustment status and maintenance status records of this batch, as well as the stencil thickness and scraping speed, thermal pad thickness and compression rate determined according to the thermal interface layer type.

[0023] In this invention, the γ weight experiment, γ threshold derivation, The calibration and thermal pad compression ratio-thermal resistance calibration data are all from actual engineering test records, and the complete original data are kept on file by the applicant for future reference.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This method incorporates post-encapsulation thermal resistance test data into the setting of the thermal interface layer thickness. This allows thermal testing to extend beyond batch-end screening to subsequent batches. The thermal interface layer thickness gradually approaches the target value based on measured thermal resistance feedback, resulting in a gradual narrowing of batch thermal resistance deviations during continuous production. The housing assembly process has been changed from pure torque control to adding a rotation angle after final tightening. The assembly consistency index γ is used to uniformly evaluate preload dispersion and flatness deviations. This improves the consistency of assembly gaps and sealant compression, thereby reducing the risk of electric field concentration, moisture intrusion, and stress concentration points during potting compound curing.

[0025] 2. Vacuum degassing and segmented curing processes reduce air bubbles inside the potting layer, gradually release cross-linking exothermics, relax shrinkage stress at low temperatures, reduce potting layer cracking and interface peeling, reduce stress on power device pins and solder joints, and improve the long-term mechanical reliability of the module under temperature cycling. All of the above improvements are achieved through process parameters and process control without introducing complex irregular parts. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the packaging optimization method of the present invention; Figure 2 Block diagram of thermal resistance feedback control logic for cross-batch thermal interface layer thickness; Figure 3 This is a flowchart of the γ-level judgment process in the closed-loop control of the assembly clearance torque-angle of the housing. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 Therefore, this invention provides a method for optimizing the packaging of power modules in semiconductor etching equipment, see [link to relevant documentation]. Figures 1 to 3As shown, this embodiment optimizes the packaging of the power module of a semiconductor etching equipment. This power module is used to provide high-frequency, high-voltage power for radio frequency discharge to the etching cavity. The rated operating voltage of the power device is 1000V peak, the switching frequency is 400kHz, the heat dissipation base plate is made of aluminum alloy, the shell material is engineering plastic, the screws are standard M3 and M4 screws, all of which are standard parts, and the potting compound is a commercially available two-component addition-curing silicone potting compound with typical parameters as follows: viscosity after mixing 4000mPa·s, dielectric constant 3.0, volume resistivity 1×10^15Ω·cm, thermal conductivity 0.9W / (m·K), electrical strength 22kV / mm, and batch-to-batch viscosity fluctuation ±10%. The sealant is a silicone elastic sealant with an elongation at break of 220%.

[0029] Pre-treatment of the packaging substrate: The heat sink base plate and the mounting surface of the power device are mechanically polished, and the surface roughness Ra is controlled between 0.8μm and 1.6μm. After polishing, the surface is ultrasonically cleaned with anhydrous ethanol for 5 min, ultrasonically cleaned with deionized water for 3 min, dried with nitrogen, and then subjected to atmospheric pressure plasma treatment with a processing power of 300W, a scanning speed of 10mm / s, and a processing time of 30s.

[0030] Thermal interface layer thickness control: A thermal interface layer is formed between the power device and the heat sink. In this embodiment, thermal grease is used. For the initial batch, a stencil is used for application. The stencil thickness is 0.20 mm, the stencil angle is 60°, the application speed is 20 mm / s, and the coating thickness is controlled to be 0.15 mm ± 0.02 mm. From the second batch onwards, the thickness is adjusted based on the thermal resistance deviation rate of the previous batch. The thermal conductivity of the thermal interface material is not less than 3.0 W / (m·K), and the thermal resistance is not greater than 0.05 K·cm. 2 / W, with a breakdown voltage of not less than 10kV / mm, for every 0.01mm change in the steel mesh thickness, the thermal grease coating thickness changes from 0.008mm to 0.012mm. According to thermal testing and calibration, the corresponding thermal resistance change rate is approximately 1.0% to 1.5%. For every 5mm / s change in the scraping speed, the wet film thickness changes from 0.005mm to 0.010mm, corresponding to a thermal resistance change rate of approximately 0.5% to 1.0%. Therefore, a steel mesh thickness of 0.01mm and a scraping speed of 5mm / s are selected as the feedback adjustment step size to ensure distinguishability while avoiding over-adjustment.

[0031] Device pre-fixation and interface bonding verification: The power device is placed on the thermally conductive interface layer, and the displacement of the device in the X and Y directions is restricted using a positioning fixture. The power device fixing screws are M3 screws, and the pre-tightening torque is 30% of the final torque, i.e., 0.24 N·m. The pre-tightening state is maintained for 10 minutes. Then, the bonding area is detected by ultrasonic scanning. The bonding area is not less than 95%. In this embodiment, the bonding area is 96.5%, which is qualified. If there is a substandard area, the positioning fixture constraint is maintained, and only the pre-tightening screw corresponding to the substandard area is loosened. The correspondence is established as follows: with the reference hole of the positioning fixture as the geometric reference, the coordinate system of the ultrasonic scanning image is divided into sub-regions corresponding to the positions of each pre-tightening screw. The substandard area falls into which the pre-tightening screw corresponding to that sub-region needs to be loosened. The thermally conductive interface material is applied again, the pre-tightening torque of 0.24 N·m is applied again and maintained for 10 minutes, and then the test is performed again.

[0032] Final locking of power devices: After the bonding area meets the standard, the power devices are finally locked with a final torque of 0.8 N·m. The locking sequence is diagonal cross-tightening. After final locking, an ultrasonic scan is performed again for re-inspection. The bonding area is not less than 95% after re-inspection.

[0033] Insulation Structure Arrangement: Based on a peak operating voltage of 1000V and a high-frequency operating condition of 400kHz, the creepage distance is determined to be no less than 8.0mm, and the clearance is no less than 3.0mm. These values ​​are determined according to IEC60664-1 and GB / T16935.1, taking into account pollution degree 2 and overvoltage category III. A 0.5mm thick polyimide insulating sheet is installed between the high-voltage power device pins, DC busbars, AC busbars, and the housing. Solder joints and sharp metal edges are rounded with a radius of curvature of no less than 1mm and coated with a 0.1mm thick insulating varnish. Before potting, weak points in the insulation are tested: Applying DC 1500V for 60s, the leakage current does not exceed 10μA; applying AC 750V, the partial discharge does not exceed 10pC. In this embodiment, the leakage current is 6μA and the partial discharge is 7pC, which is acceptable.

[0034] Housing assembly clearance torque-angle closed-loop control: The flatness of the mating surfaces of the housing and the heat sink base plate is controlled within 0.05mm, and the clearance between the housing and the heat sink base plate is 0.1mm to 0.3mm. Sealant is applied to the mating surfaces with a width of 3mm ± 0.5mm and a height of 0.5mm ± 0.1mm, forming a closed loop. Six M4 carbon steel blackened screws are used, tightened diagonally in three stages with torques of 0.6N·m, 1.0N·m, and 1.5N·m respectively, with a 5-minute interval between each tightening. The final tightening torque for the third tightening of each screw is 1.5N·m. After the third tightening, a 15° ± 2° rotation angle is applied to each screw. The flatness of the assembled housing is measured at six points: the four corners and the midpoints of the two long sides. Each measuring point corresponds to a screw position. The assembly consistency index γ is calculated. The preload of each screw is calculated using the formula: Calculations, where M4 screws =0.004m, The final tightening torque for the third diagonal cross tightening is 1.5 N·m. Each piece was calibrated individually using a torque coefficient tester. Pre-calibrated to 35 N / ° This is an additional 15° rotation angle applied after the third torque tightening. The unit is N / degree. The unit is degrees. In this embodiment, the preload of the six screws are 2.45kN, 2.32kN, 2.56kN, 2.28kN, 2.44kN, and 2.38kN, respectively. The average preload is... =2.405kN, Sample standard deviation coefficient of variation 0.042. In this embodiment, the measured flatness values ​​of each measuring point after assembly in a certain assembly corresponding to batch 4 were 0.01mm, 0.02mm, 0.02mm, 0.01mm, 0.01mm, and 0.01mm, respectively, with an average of 0.042. After normalization, 0.0133 / 0.05 = 0.267. Substituting this into the formula, we get γ = 0.6 × 0.042 + 0.4 × 0.267 = 0.0252 + 0.1067 = 0.132. This value is in the range of 0.10 < γ ≤ 0.25. Loosen the screw with the largest deviation in flatness and the screw with the largest contribution to the preload dispersion. Then, tighten the screw by half a turn and apply a torque of 1.5 N·m with a 15° rotation. Do not apply any additional action to adjacent screws. If the remeasured γ is 0.07, it is considered qualified. If the remeasured γ is still in the range of 0.10 < γ ≤ 0.25, continue positioning and local retightening. If the γ is still in this range after two consecutive remeasurements, it is treated as γ > 0.25. Reapply sealant and rework the entire product.

[0035] Vacuum-assisted potting: Place the pre-fixed module into a vacuum potting chamber, evacuate to 150Pa (allowable range 100Pa to 200Pa), and maintain for 10 minutes. Inject two-component addition-type silicone potting compound under vacuum. The liquid level is measured by a liquid level sensor and should be 12mm above the highest charged part. If it is below this value, add more potting compound to bring it above 12mm. After adding more potting compound, evacuate again to 150Pa and maintain for 5 minutes. Then restore to normal pressure at a rate of 5L / min (allowable range 1L / min to 10L / min).

[0036] Segmented curing and shrinkage stress control: The potting module was left to stand at room temperature for 2 hours, then heated to 60℃ at a rate of 1.5℃ / min and held for 2 hours, then heated to 80℃ at a rate of 1.5℃ / min and held for 2 hours, then heated to 100℃ at a rate of 1.5℃ / min and held for 1 hour, and finally cooled to the allowable range of 0.5℃ / min to 1.5℃ / min at a rate of 0.8℃ / min. After curing, the potting compound had a Shore hardness of 50A, an elongation at break of 60%, and an elastic modulus of 3MPa. The sealant had an elongation at break of 220% after curing. After loosening half a turn, the sealant compressed and rebounded. After curing, the housing screws were loosened half a turn and held for 5 minutes. Then, they were tightened again with a torque of 1.5 N·m and a rotation angle of 15°±2°. After tightening again, the flatness of the four corners of the housing and the midpoints of the two long sides was re-measured and γ was calculated. If 0.10 < γ ≤ 0.25, the flatness was locally tightened according to rule S5 and then re-measured. If γ > 0.25, remove the sealant and cured potting compound, reapply the sealant, and repeat all steps except for the airtightness test in the housing assembly gap torque-angle closed-loop control to segmented curing and shrinkage stress control. After completing the above γ treatment, perform an airtightness test on the housing joints by applying 0.2 MPa compressed air and holding it for 5 minutes. The pressure drop should be 0.005 MPa, not exceeding 0.01 MPa, indicating a successful seal. If the airtightness test fails, remove the sealant and cured potting compound, reapply the sealant, and repeat all steps except for the airtightness test in the housing assembly gap torque-angle closed-loop control to segmented curing and shrinkage stress control. Do not repeat the device pre-fixation, interface bonding verification, and final locking steps of the power devices. Then perform the airtightness test again. If the airtightness test still fails, the encapsulation is deemed a failure, and the module encapsulation process is terminated.

[0037] Post-packaging testing and thermal verification: Ultrasonic scanning showed a void area ratio of 2.5%, a maximum single void diameter of 1.1 mm, an insulation resistance of 515 MΩ at DC 500V, no breakdown flashover at AC 3000V, 50Hz for 1 minute, a partial discharge of 6 pC at AC 1500V, continuous operation at rated power for 30 minutes, and steady-state determination based on junction temperature change not exceeding ±1℃ within 30 minutes. The measured thermal resistance was determined by dividing the difference between junction temperature and ambient temperature by power dissipation. The highest temperature of the power device was 119℃, the maximum temperature difference on the housing surface was 10K, and the highest temperature rise on the housing surface was 32K. The calculated thermal resistance deviation rate was 2.8%, which was used for the next batch. If the absolute value of the measured thermal resistance deviation rate of this batch is greater than 5%, the thermal performance of this batch is deemed unqualified and disposed of as a non-conforming product, not flowing into subsequent delivery and use processes. The thermal test data of this batch is still used to calculate the thermal resistance deviation rate and fed back to the next batch.

[0038] Packaging completion and process record: Record the thermal resistance deviation rate, γ value, preload of each screw, adjustment status and maintenance status of this batch, as well as the stencil thickness and coating speed used in this batch, to form a batch record.

[0039] Example 2 The difference between this embodiment and Embodiment 1 is that a thermal pad is used as the thermal interface layer. The initial batch thickness is 0.25mm, the compression rate is 20%, and the closed-loop feedback rule for the thermal pad is as follows: when the thermal resistance deviation rate is greater than 5%, the first adjustment is to increase the compression rate by about 3 percentage points by replacing the thermal pad with a thickness of 0.26mm; when it is less than -5%, the first adjustment is to decrease the compression rate by about 3 percentage points by replacing the thermal pad with a thickness of 0.24mm; when the absolute value is not greater than 3%, the compression rate is maintained; when it is between 3% and 5%, if the previous batch was recorded as being in an adjustment state and the direction of the thermal resistance deviation rate in this batch is the same as that of the previous batch, then the thickness of the thermal pad in this batch is adjusted by 0.01mm based on the previous batch. The compression ratio changes by about 3 percentage points. If the previous batch is in the maintenance state or the deviation direction of this batch changes, the current compression ratio is maintained. In this embodiment, the thermal resistance deviation rate of the current batch is 4.2%, and the previous batch is in the maintenance state. Therefore, the compression ratio of this batch is maintained and recorded as the maintenance state. The remaining steps are the same as in Embodiment 1. In the packaging completion and process record, the thermal resistance deviation rate, γ value, preload of each screw, adjustment state and maintenance state record of this batch are recorded, as well as the thickness of the thermal pad and the compression ratio used in this batch. Finally, the highest temperature of the module power device is 121°C, the partial discharge is 7pC, and the insulation resistance is 510MΩ, all of which meet the specifications.

[0040] Comparative Example The comparative example uses traditional encapsulation technology: the mounting surface is only wiped with solvent, the thermal grease is used to fix the stencil thickness at 0.20mm and the scraping speed is 20mm / s, the thermal test results are not used for parameter correction, the power devices are tightened at 0.8N·m in one go, without pre-tightening grading or ultrasonic testing, the insulation structure is checked according to the power frequency withstand voltage, the sharp edges of the solder joints are not rounded, the shell screws are tightened by pure torque method, the three torques are 0.6N·m, 1.0N·m and 1.5N·m respectively, without corners, the potting is injected at normal pressure, without degassing, the curing is carried out by curing at 80℃ for 4 hours in one go, without staged heating and stress release.

[0041] Nine batches of power modules were prepared for comparison. One batch was rejected due to excessive partial discharge caused by voids in the potting layer. The test results of the other eight batches are as follows: the highest temperatures of the power devices were 132℃, 125℃, 127℃, 138℃, 148℃, 129℃, 123℃, and 141℃, respectively; the module thermal resistances were 0.62K / W, 0.59K / W, 0.61K / W, 0.66K / W, 0.74K / W, 0.61K / W, 0.60K / W, and 0.70K / W, respectively; the partial discharge amounts were 18pC, 16pC, 22pC, 20pC, 33pC, 17pC, 15pC, and 24pC, respectively; and the insulation resistances were 96MΩ, 78MΩ, 82MΩ, 80MΩ, and 68MΩ, respectively. The resistance values ​​are 88MΩ, 94MΩ, and 76MΩ, respectively. The flatness of the four corners of the shell are 0.10mm, 0.09mm, 0.11mm, 0.14mm, 0.17mm, 0.10mm, 0.08mm, and 0.15mm, respectively. The percentage of void area in the potting layer is 6.5%, 5.8%, 7.0%, 7.2%, 9.5%, 6.2%, 5.6%, and 8.5%, respectively. The batch thermal resistance deviations are 8%, 5%, 9%, 10%, 16%, 6%, 5%, and 12%, respectively. The preload fluctuations are 17%, 15%, 18%, 20%, 26%, 16%, 14%, and 23%, respectively. The comparison shows that the maximum temperature, partial discharge, and insulation resistance of the power devices in each batch vary greatly, indicating poor batch consistency.

[0042] Example 1 yielded 9 batches of power modules, of which 8 were qualified and 1 was rejected. The process is as follows: Batch 1 had a thermal resistance deviation rate of 2.8% and γ=0.08, which was qualified; Batch 2 had a thermal resistance deviation rate of 3.1% and γ=0.06, which was qualified; Batch 3 had a thermal resistance deviation rate of 5.6%. Following the rules, the steel mesh was thinned by 0.01mm and the coating speed was increased by 5mm / s, and this batch passed the test; Batch 4's thermal resistance deviation rate decreased to 2.5% and γ=0.132, falling within the range of 0.10 < γ ≤ 0.25. After local re-tightening, γ was retested and found to be 0.07, which was qualified; Batch 5 had a thermal resistance deviation rate of 3.8%. After encapsulation, the DC500V insulation resistance did not meet the requirement of not less than 100MΩ, so it was judged as unqualified and rejected. Its thermal test data was still valid and used to calculate the thermal resistance deviation rate of 3.8%, which was fed back to batch 6. The thermal resistance deviation rate of batch 6 was 2.9%, and the initial measurement of the void area ratio by ultrasonic scanning was 3.1%, exceeding the factory's internal control value of 2.5%. After local removal and refilling of the excess area, the retest showed 2.3%, which was qualified. The thermal resistance deviation rate of batch 7 was 3.4%, γ=0.09, which was qualified. The thermal resistance deviation rate of batch 8 was 2.7%, γ=0.28. After recoating the sealant and reworking the whole batch, the retest showed γ=0. .09, qualified. Batch 9 has a thermal resistance deviation rate of 3.0% and a partial discharge quantity of 9pC, meeting the final indicators and is judged as qualified. The highest temperatures of the 8 qualified batches of power devices obtained in Example 1 were 119℃, 118℃, 121℃, 124℃, 117℃, 122℃, 120℃, and 123℃, respectively, all below 125℃. The module thermal resistances were 0.52K / W, 0.53K / W, 0.51K / W, 0.54K / W, 0.50K / W, 0.53K / W, 0.53K / W, and 0.52K / W, respectively, and the partial discharge quantities were 6pC and 7pC, respectively. The insulation resistances of the batches 5pC, 8pC, 6pC, 7pC, 7pC, and 6pC were 510MΩ, 520MΩ, 500MΩ, 530MΩ, 505MΩ, 525MΩ, 512MΩ, and 508MΩ, respectively. The maximum deviation of the flatness of the four corners of the shell was 0.05mm. The proportion of void area in the potting layer was 2.5%, 2.8%, 2.2%, 3.0%, 2.4%, 2.6%, 2.7%, and 2.5%, respectively. All eight qualified batches in Example 1 met the preset threshold. Batches not included in the qualified statistics were excluded. Closed-loop feedback and assembly control maintained the consistency of qualified batches.

[0043] The results above show that the power module prepared in the embodiment is superior to the comparative example in terms of thermal performance, insulation performance, assembly accuracy, and batch consistency. Moreover, all qualified batches meet the preset threshold requirements. The data of each batch in the comparative example fluctuates greatly and the batch consistency is poor. In the embodiment, batch 5 was not included in the qualified statistics due to unqualified insulation resistance, but its thermal test data still participated in the thermal resistance deviation rate feedback, and the closed loop was not interrupted. The remaining batches remained qualified through closed loop feedback and assembly control, which shows that the technical solution of the present invention is effective under actual engineering fluctuation conditions.

[0044] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0045] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for optimizing the packaging of a power module in a semiconductor etching apparatus, wherein the power module is used to provide radio frequency discharge high-frequency high-voltage power to the etching cavity of the semiconductor etching apparatus, characterized in that... Includes the following steps: S1. Pre-treatment of the packaging substrate: Mechanical grinding is performed on the heat sink base plate and the mounting surface of the power device to control the surface roughness Ra to 0.8μm to 1.6μm. Then, anhydrous ethanol ultrasonic cleaning, deionized water ultrasonic cleaning and nitrogen blowing are performed in sequence, followed by atmospheric pressure plasma treatment. S2. Thermal Interface Layer Thickness Control: A thermal interface layer is formed between the power device and the heat sink. For the initial batch, preset reference parameters are used: when the thermal interface layer is thermal grease, the reference value for stencil thickness is 0.20mm, and the reference value for application speed is 20mm / s; when the thermal interface layer is a thermal pad, the thermal pad thickness is 0.25mm, and the compression rate is 20%. From the second batch onwards, the process parameters for this batch are corrected based on the thermal resistance deviation rate obtained from the thermal testing of the previous batch. The thermal resistance deviation rate is determined by dividing the difference between the measured thermal resistance of the previous batch and the reference thermal resistance by the reference thermal resistance. The reference thermal resistance is the target thermal resistance value specified in the product's thermal design specifications and is not updated with each batch. The deviation direction is the positive or negative side of the thermal resistance deviation rate. For thermal resistance deviation rates, a value greater than 0 is considered a positive deviation, and a value less than 0 is considered a negative deviation. When the thermal interface layer is thermally conductive silicone grease, the stencil thickness and scraping speed are adjusted as follows: When the thermal resistance deviation rate is greater than 5%, the stencil thickness is reduced by 0.01 mm from the previous batch, and the scraping speed is increased by 5 mm / s. When the thermal resistance deviation rate is less than -5%, the stencil thickness is increased by 0.01 mm from the previous batch, and the scraping speed is decreased by 5 mm / s. When the absolute value of the thermal resistance deviation rate is not greater than 3%, the stencil thickness and scraping speed of the previous batch are maintained, and the current batch is recorded as the "maintained" state. When the absolute value of the thermal resistance deviation rate is greater than 3% but not greater than 5%, if the previous batch was in the "adjustment" state... If the deviation direction of this batch is the same as that of the previous batch, then continue adjusting with the same adjustment step size as when the absolute value of the deviation is greater than 5%. Otherwise, maintain the current parameters unchanged. The adjustment state refers to the previous batch having performed process parameter adjustments, and the maintenance state refers to the previous batch not having adjusted process parameters. After each adjustment, the status of this batch is recorded as the adjustment state, and after each parameter maintenance, the status of this batch is recorded as the maintenance state. When the thermal interface layer is a thermal pad, correct the thermal pad compression ratio. The increase or decrease in the compression ratio is achieved by replacing the thermal pad with one of different thicknesses, so that the compression ratio increases or decreases accordingly under the same installation gap. When the thermal resistance deviation rate is greater than 5%, increase the thickness of the thermal pad by 0.01mm based on the previous batch, so that the compression ratio... Increase by approximately 3 percentage points. When the thermal resistance deviation rate is less than -5%, reduce the thickness of the thermal pad by 0.01mm based on the previous batch, thereby reducing the compression rate by approximately 3 percentage points. The initial batch thermal pad thickness is 0.25mm. When the thermal resistance deviation rate is greater than 5%, the first adjustment is to replace it with 0.26mm. When the thermal resistance deviation rate is less than -5%, the first adjustment is to replace it with 0.24mm. When the absolute value of the thermal resistance deviation rate is not greater than 3%, maintain the current compression rate. When the absolute value of the thermal resistance deviation rate is greater than 3% but not greater than 5%, if the previous batch was in an adjustment state and the deviation direction of this batch is the same as that of the previous batch, continue to adjust according to the same compression rate adjustment step size as when the absolute value of the deviation is greater than 5%. Otherwise, maintain the current compression rate unchanged. S3. Device Pre-fixation and Interface Adhesion Verification: The power device is pre-fixed to the thermal interface layer with a pre-tightening torque. After maintaining the pre-tightening state, the adhesion area is detected by ultrasonic scanning. For areas where the adhesion area does not meet the standard, the positioning fixture is maintained, and only the pre-tightening screws corresponding to the non-standard areas are loosened. The correspondence between the non-standard areas and the pre-tightening screws is pre-determined by mapping the ultrasonic scanning image with the screw position: Using the reference hole of the positioning fixture as the geometric reference, sub-regions corresponding to the positions of each pre-tightening screw are divided in the ultrasonic scanning image coordinate system. The sub-region into which the non-standard area falls is determined to be the pre-tightening screw that needs to be loosened. Thermal interface material is applied again, the pre-tightening torque is reapplied and the pre-tightening state is maintained until the adhesion area meets the standard. When the thermal interface layer is a thermal pad and the thermal pad compression ratio is adjusted in S2, the pre-fixation, ultrasonic scanning detection and adhesion area verification of this step are repeated. S3a. Final locking of power devices: After the bonding area meets the standard, the power devices are finally locked with a final torque of 0.8 N·m. The locking sequence is diagonal cross-tightening. S4. Insulation structure arrangement: The creepage distance and electrical clearance are checked according to the peak voltage of the RF discharge superimposed DC bias and the high frequency operating conditions. An insulating sheet is set between the high voltage node and the shell. The solder joints and sharp metal edges are rounded and coated with insulating varnish. Leakage current and partial discharge are tested before potting. Any parts that fail are reprocessed. S5. Closed-loop control of housing assembly clearance torque-rotation angle: The flatness of the mating surface between the housing and the heat dissipation base plate is controlled within 0.05mm, sealant is applied on the mating surface, screws are used for diagonal cross tightening in three times, with torques of 0.6N·m, 1.0N·m and 1.5N·m in sequence. After the third tightening, a rotation angle of 15°±2° is applied to each screw, the post-assembly flatness of a total of 6 measuring points at the four corners of the housing and the midpoints of the two long sides is measured, the assembly consistency index γ is determined, and graded closed-loop processing is performed according to γ: it is judged as qualified when γ≤0.10, when 0.10<γ≤0.25, the target position is located, partially retightened and then re-measured, when γ>0.25, the sealant is re-applied for overall rework, and when the re-measured γ is still greater than 0.25, the packaging process is terminated for rework. The partial retightening refers to loosening the target screw by half a turn, retightening it at a torque of 1.5N·m and applying a 15° rotation angle, without applying additional actions to the adjacent screws. The screws are 6 pieces of M4 carbon steel blackened screws, the housing is an engineering plastic housing, the heat dissipation base plate is an aluminum alloy heat dissipation base plate, and the calculation formula of the assembly consistency index γ is: in , where represents the standard deviation of the preload force of each screw. This is the average preload of all screws. The measured flatness value of the i-th measuring point after assembly. For flatness threshold, =0.05mm, This indicates the summation of i from 1 to 6, where i is the index of one of the six measuring points (four corners and the midpoints of the two longer sides) of the shell. The flatness threshold and the flatness control value for mating surfaces use the same value but have different physical meanings. The former is used to evaluate the flatness of the shell after assembly, while the latter is used to control the machining accuracy of the mating surfaces. Both the preload dispersion and flatness deviation are positively correlated. A larger value indicates a poorer uniformity of assembly clearance. The preload of each screw is determined by the torque method and correction for the rotation angle increment. The calculation formula is as follows: ,in Apply a preload force to the i-th screw after the rotation. Let be the final tightening torque for the third diagonal tightening of the i-th screw, and let be the final tightening torque for each screw, which is 1.5 N·m. Let be the torque coefficient of the i-th screw. The nominal diameter of the thread is in meters, for M4 screws. =0.004m, The preload increment coefficient corresponding to the additional rotation angle is determined by calibration. The calibration conditions are: M4 carbon steel blackened screws, aluminum alloy heat sink base plate and engineering plastic housing, dry friction lubrication, tightening speed of 10 r / min, ambient temperature of 22℃±3℃, and rotation angle increment not exceeding 20°. If the usage conditions exceed the calibration conditions, recalibration is required. , The torque coefficient is the additional rotation angle applied to the i-th screw after the third torque tightening. The measured values ​​of each screw were obtained by a torque coefficient tester before assembly, under the same lubrication conditions, tightening speed and ambient temperature as the actual assembly. The coefficient of variation of the estimated preload of each screw is used to characterize the fastening consistency. This coefficient of variation is related to the uniformity of sealant compression and the flatness of the housing after assembly. S6. Vacuum-assisted potting: Vacuum the pre-fixed module to remove gas, and inject potting compound under vacuum so that the potting compound level is 12mm higher than the highest charged body. If the level is lower than 12mm, add more compound to bring it above 12mm, and then vacuum and remove gas again, and restore normal pressure at a rate of 5L / min. S7. Segmented Curing and Shrinkage Stress Control: After standing at room temperature, heat according to the segmented heating curve and maintain the temperature segment by segment. Then cool down to room temperature at a rate of 0.8℃ / min. After curing, loosen the shell screws by half a turn, stand for 5 minutes, and then tighten them again with a torque of 1.5 N·m and an angle of 15°±2°. The sealant is an organic silicone elastic sealant with an elongation at break of not less than 200% after curing. After loosening by half a turn, the sealant compresses and rebounds. After tightening again, the sealing performance is maintained. After tightening again, re-measure the flatness of the four corners of the shell and the midpoints of the two long sides and calculate... If 0.10 < ≤0.25, re-tighten locally according to rule S5 and retest. If >0.25, remove the sealant and cured potting compound, reapply the sealant, and repeat steps S5 to S7 except for the airtightness test. After completing the above γ treatment, perform an airtightness test on the joint between the housing and the heat sink base plate to confirm that the sealing performance is qualified. If the airtightness test is unqualified, remove the sealant and cured potting compound, reapply the sealant, and repeat steps S5 to S7 except for the airtightness test. S3 and S3a are not repeated. Then perform the airtightness test again. If the airtightness test is still unqualified, the encapsulation is determined to be unsuccessful and the module encapsulation process is terminated. S8. Post-packaging inspection and thermal verification: Perform ultrasonic scanning, insulation testing, partial discharge testing, and rated power thermal testing on the cured module to obtain the measured thermal resistance. Calculate the thermal resistance deviation rate by comparing the measured thermal resistance with the reference thermal resistance. This deviation rate is used for controlling the thermal interface layer thickness in step S2 of the next batch. If the absolute value of the measured thermal resistance deviation rate of this batch is greater than 5%, the thermal performance of this batch is deemed unqualified and it is disposed of as a non-conforming product, not flowing into subsequent delivery and use processes. The thermal test data of this batch is still used to calculate the thermal resistance deviation rate and is fed back to the next batch. S9. Packaging Completion and Process Recording: Record the packaging process parameters to form a batch record. The packaging process parameters include the thermal resistance deviation rate, γ value, preload of each screw, adjustment status and maintenance status records of this batch, as well as the stencil thickness and scraping speed, thermal pad thickness and compression rate determined according to the thermal interface layer type.

2. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that: In step S1, the ultrasonic cleaning time with anhydrous ethanol is 5 min, the ultrasonic cleaning time with deionized water is 3 min, the atmospheric pressure plasma treatment power is 300W, the scanning speed is 10 mm / s, and the treatment time is 30 s.

3. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S2, when thermal grease is used as the thermal interface layer, it is applied using a stencil. The stencil thickness is 0.20 mm, the scraper angle is 60°, the scraping speed is 20 mm / s, and the coating thickness is controlled at 0.15 mm ± 0.02 mm. The 0.20 mm stencil thickness corresponds to a coating thickness of 0.15 mm ± 0.02 mm. The relationship between the coating thickness and the stencil thickness is calibrated through a scraping test. When a thermal pad is used as the thermal interface layer, the thermal pad thickness is 0.25 mm and the compression rate is 20%. For the first adjustment of the thermal pad compression rate, the thermal pad is replaced with one of corresponding thickness according to the deviation direction, with thicknesses of 0.24 mm and 0.26 mm respectively. The compression rate adjustment step size is determined based on the thermal resistance-compression rate characteristic curve of the thermal pad. Approximately 3 percentage points correspond to a thermal resistance change rate of not less than 4%, which can be distinguished by thermal testing.

4. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S3, the power device fixing screw is M3, and the pre-tightening torque is 30% of the final torque, i.e., 0.24 N·m. The pre-tightening state is maintained for 10 minutes, and the ultrasonic scanning bonding area is not less than 95%. When this step is repeated due to the adjustment of the thermal pad compression ratio, the ultrasonic scanning bonding area requirement remains unchanged. In step S3a, the final locking torque is 0.8 N·m. After final locking, an ultrasonic scan is performed again for re-inspection.

5. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S4, the creepage distance is determined to be no less than 8.0 mm and the electrical clearance is no less than 3.0 mm based on a peak operating voltage of 1000 V and a high-frequency operating condition of 400 kHz. The insulating sheet is a 0.5 mm thick polyimide insulating sheet with a corner radius of curvature of no less than 1 mm and an insulating varnish thickness of 0.1 mm. Before potting, DC 1500 V is applied for 60 s, and the leakage current does not exceed 10 μA. When AC 750 V is applied, the partial discharge does not exceed 10 pC.

6. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S5, the clearance between the housing and the heat dissipation base plate is 0.1mm to 0.3mm, the width of the sealant line is 3mm ± 0.5mm, the height of the sealant line is 0.5mm ± 0.1mm, the sealant line is a closed loop, and the tightening interval is 5 minutes each time. The number of measuring points at the four corners and the midpoints of the two long sides of the housing is the same as the number of screws, and the position of each measuring point corresponds one-to-one with the position of the screw.

7. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 6, characterized in that, In step S5, if γ > 0.25, the sealant is reapplied and all three stages of diagonal cross tightening and cornering are performed before retesting. If the retested γ is still greater than 0.25, the encapsulation process is terminated and the screw is reworked. If 0.10 < γ ≤ 0.25, the screw with the largest deviation in positioning flatness and the screw with the largest contribution to preload dispersion is locally retightened and γ is retested. If the retested γ is not greater than 0.10, it is considered qualified. If the retested γ is still within 0.10 < γ ≤ 0.25, positioning and local retightening continue. If the retested γ is still within this range for two consecutive times, it is treated as γ > 0.

25. The screw with the largest contribution to preload dispersion is the screw with the largest absolute value of deviation from the mean preload among all screws.

8. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S6, the vacuum degree is 100 Pa to 200 Pa, preferably 150 Pa. Vacuum degassing is maintained for 10 min. The potting compound is a two-component addition-type silicone potting compound with a viscosity of 4000 mPa·s after mixing, a dielectric constant of 3.0, a volume resistivity of 1×10^15 Ω·cm, a thermal conductivity of 0.9 W / (m·K), and an electrical strength of 22 kV / mm. After potting, the vacuum is maintained at 150 Pa for 5 min, and then atmospheric pressure is restored at a rate of 1 L / min to 10 L / min, preferably 5 L / min. The potting compound level is measured by a level sensor. When the level is below 12 mm, the potting compound is added to bring it above 12 mm. After adding the potting compound, the vacuum is re-evacuated to 150 Pa and maintained for 5 min to allow air bubbles in the added compound to rise and burst. Then atmospheric pressure is restored at a rate of 5 L / min.

9. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S7, the room temperature standing time is 2 hours, the heating rate is 1.5℃ / min, and the temperature is successively increased to 60℃ and held for 2 hours, 80℃ and held for 2 hours, and 100℃ and held for 1 hour. The cooling rate is 0.5℃ / min to 1.5℃ / min, preferably 0.8℃ / min. After curing, the potting compound has a Shore hardness of 50A, an elongation at break of not less than 50%, and an elastic modulus of 3MPa. During the airtightness test, 0.2MPa of compressed air is applied to the shell joint and held for 5 minutes. The pressure drop does not exceed 0.01MPa. This test pressure is determined based on a safety factor of 1.5 times the shell design pressure. The holding time and allowable pressure drop are determined based on the creep characteristics of the sealant and batch tests.

10. The packaging optimization method for a power module of a semiconductor etching equipment according to claim 1, characterized in that, In step S8, the ultrasonic scanning test sets the void area ratio to be no more than 5%, the diameter of a single void to be no more than 2mm, the insulation resistance to be no less than 100MΩ under DC500V, no breakdown flashover under AC3000V, 50Hz, for 1min, the partial discharge quantity to be no more than 10pC under AC1500V, continuous operation under rated power for 30min, the maximum temperature of the power device to be no more than 125℃, the maximum temperature difference on the shell surface to be no more than 15K, and the maximum temperature rise on the shell surface to be no more than 40K. In the thermal test, the steady-state judgment condition is that the junction temperature change of the power device to be no more than ±1℃ within 30min. The measured thermal resistance is determined by dividing the difference between the junction temperature of the power device and the ambient temperature by the power consumption of the power device. The power consumption is determined by the difference between the input power and the output power.

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