A power device moisture absorption curve on-line measuring device and method

Abstract

The application discloses a kind of power device hygroscopic curve online measurement device and method, device includes: constant temperature and humidity environment box;Weighing unit is located outside constant temperature and humidity environment box, and the mass change signal of sample to be measured is obtained in real time;Rigid force transmission rod, through the wall surface of environment box, one end extends into the box, the other end is connected to weighing unit, for transmitting mass change to the weighing unit outside the box;Guide sleeve is fixed on the environment box and is sleeved on the outside of force transmission rod, for limiting its lateral deviation;Sealing assembly is arranged at the penetration of force transmission rod and environment box, for maintaining sealing while allowing vertical displacement of force transmission rod;Three-point tray type test tool is arranged inside the environment box and is connected with the extension end of force transmission rod, for supporting sample to be measured.Compared with prior art, the application realizes continuous online measurement of power device hygroscopic process by external weighing unit, rigid force transmission guide and three-point statically determinate bearing.

Description

Technical Field

[0001] This invention relates to the field of reliability testing and environmental adaptability evaluation of power electronic devices, and in particular to an online measurement device and method for the moisture absorption curve of power devices. Background Technology

[0002] Power semiconductor devices are widely used in offshore wind power, flexible DC transmission, high-power converters and new energy power generation. In actual service, the devices are often subjected to the coupling effects of complex environments such as high temperature, high humidity, high pressure and salt spray. Moisture can gradually penetrate into the device through the device shell, packaging materials and interfaces, which can lead to problems such as decreased insulation performance, interface peeling, electrochemical corrosion and reliability degradation, ultimately affecting the service life of the device and the stability of system operation. Especially in coastal, high humidity and strong corrosion conditions, humidity intrusion has become one of the important factors affecting the environmental adaptability and long-term reliability of power devices.

[0003] Currently, to study the moisture absorption characteristics of power device casings, packages, or related material samples under constant temperature and humidity conditions, the moisture absorption curve is usually obtained by manual intermittent weighing. Specifically, the sample is first placed in a constant temperature and humidity environment (e.g., 85°C or 85°F) for a moisture absorption test. Then, the sample is removed from the environmental chamber at preset time intervals and weighed using an electronic balance. Finally, a mass-time curve is plotted based on the mass changes at each moment, and the moisture absorption rate, equilibrium moisture absorption, and diffusion behavior of the sample are analyzed accordingly.

[0004] However, the above methods still have significant shortcomings in practical applications: First, the samples need to be repeatedly taken out and weighed from the constant temperature and humidity environment during the experiment, which can easily cause fluctuations in the temperature and humidity inside the environmental chamber, disrupting the original stable boundary conditions; Second, the samples are easily affected by external air disturbances, temperature differences, surface condensation, and human error during removal, transfer, and weighing, resulting in poor consistency of weighing results; Third, the existing methods are intermittent measurements, making it difficult to obtain complete and continuous moisture absorption curves, especially difficult to accurately characterize the rapid changes in the initial stage of moisture absorption; Fourth, the degree of automation in the experiment is low, the workload of manual labor is large, the testing efficiency is low, and it is also not conducive to subsequent analysis of moisture absorption patterns and fitting of related model parameters.

[0005] Furthermore, the few devices currently attempting to achieve online weighing, such as those employing a coaxial, vertically suspended balance structure, still face significant technical bottlenecks when practically applied to power device testing. Firstly, power device reliability testing requires circulating air within the environmental chamber to maintain uniform temperature and humidity in a large space. Traditional flexible coaxial suspension structures are highly susceptible to pendulum-like swaying caused by lateral wind loads within the chamber, leading to inaccurate high-precision weighing. Secondly, placing the balance directly above the chamber's opening exposes the sensor to escaping heat radiation and moisture, resulting in temperature drift. Finally, simple suspended trays struggle to stably support the heavy and irregularly shaped casings or packages of power devices, easily causing center of gravity shifts or tilting.

[0006] A search revealed that Chinese Patent Publication No. CN110595936A discloses a testing device and method for the coefficient of humid expansion of composite materials under humid conditions. This method involves suspending the sample with a quartz rod inside a vacuum chamber and using a load sensor and a displacement sensor to test the mass change and length change of the sample under constant humidity conditions, thereby obtaining the coefficient of humid expansion of the composite material. However, this scheme uses a quartz rod suspension method to support the sample, with the load sensor directly fixed to the top of the quartz rod and the entire assembly placed inside the vacuum chamber. Its weighing principle is suspension-based weighing. For power device samples with large self-weight and irregular shape, the suspension structure is prone to eccentric bending moments due to the sample's center of gravity shift, causing the sensor to bear a lateral component force and affecting weighing accuracy. Although the load sensor is located in the upper drying chamber, the sensor and the humidified environment chamber are isolated by a sealed heat insulation layer and dry airflow. During long-term humidification testing, there is still a potential risk that moisture will migrate upwards along the gaps in the quartz rod and interfere with the sensor's accuracy. In addition, the testing environment of this scheme is a sealed vacuum chamber, which is humidified by filling a small amount of constant humidity air. It is difficult to adapt to the circulating blower conditions and cannot meet the engineering requirements of actual power device testing.

[0007] Therefore, how to effectively resist the interference of cyclic blowing and the effects of temperature and humidity drift without destroying the constant temperature and humidity test environment, and achieve stable bearing and continuous online measurement of the moisture absorption process of irregular power device samples, is a technical problem that needs to be solved. Summary of the Invention

[0008] The purpose of this invention is to overcome the defects of the prior art by providing an online measurement device and method for the moisture absorption curve of power devices.

[0009] The objective of this invention can be achieved through the following technical solutions: According to a first aspect of the present invention, an online measurement device for the moisture absorption curve of a power device is provided, characterized in that it comprises: A constant temperature and humidity chamber is used to provide a constant temperature and humidity testing environment. The weighing unit is located outside the constant temperature and humidity chamber and is used to acquire the mass change signal of the sample to be tested in real time. A rigid force transmission rod passes through the wall of the constant temperature and humidity environment chamber, with one end extending into the interior of the environment chamber and the other end connected to the weighing unit, used to transmit the mass change of the sample to be tested to the weighing unit outside the chamber. A guide sleeve is fixedly installed on the constant temperature and humidity environment chamber and sleeved on the outside of the rigid force transmission rod to limit the lateral displacement of the force transmission rod. A sealing assembly is disposed at the point where the rigid force transmission rod passes through the constant temperature and humidity environment chamber, and is used to maintain the airtightness of the environment chamber while allowing the vertical displacement of the force transmission rod; The three-point tray-type testing fixture is set inside the constant temperature and humidity chamber and connected to the extension end of the rigid force transmission rod to fix and support the sample to be tested.

[0010] As a preferred technical solution, the three-point tray type testing fixture includes a three-point tray and a contact pad disposed on the three-point tray, and the sample to be tested is placed on the three-point tray through the contact pad.

[0011] As a preferred technical solution, the three-point tray-type testing fixture also includes an internal fixing frame, a sample clamping mechanism, and connecting parts; The internal fixing frame is fixed inside the constant temperature and humidity environment chamber and is used to guide and horizontally position the sample clamping mechanism; the three-point tray is connected to the rigid force transmission rod through the connector and the sample clamping mechanism to form a unique force transmission path to transmit the weight change of the sample to be tested to the weighing unit.

[0012] As a preferred technical solution, the contact pad is made of polytetrafluoroethylene, polyetheretherketone, or polyphenylene sulfide.

[0013] As a preferred technical solution, the weighing unit is positioned horizontally at the location where the rigid force transmission rod passes through the wall of the constant temperature and humidity chamber.

[0014] As a preferred technical solution, the rigid force transmission rod is also provided with a mechanical limiting component to restrict its overtravel displacement.

[0015] As a preferred technical solution, the sealing component is a flexible sealing component, with one end of the flexible sealing component sealed to the wall of the constant temperature and humidity environment chamber, and the other end sealed to the rigid force transmission rod.

[0016] As a preferred technical solution, the device further includes a temperature and humidity monitoring module, which is installed inside the constant temperature and humidity environment chamber and is used to synchronously collect temperature and humidity parameters inside the environment chamber.

[0017] As a preferred technical solution, the device further includes a data acquisition module and a data processing unit; The data acquisition module is connected to the weighing unit and the temperature and humidity monitoring module respectively, and is used to perform signal conditioning, analog-to-digital conversion, data acquisition and buffering on the mass signal output by the weighing unit and the temperature and humidity signal output by the temperature and humidity monitoring module. The data processing unit is specifically a host computer, which is communicatively connected to the data acquisition module. It is used to receive the mass signal and temperature and humidity signal transmitted by the data acquisition module, and to plot the mass-time curve, moisture absorption increment curve and moisture absorption rate curve based on the received mass signal and temperature and humidity signal, calculate the equilibrium moisture absorption, and set and adjust the temperature and humidity parameters of the constant temperature and humidity environment chamber.

[0018] According to a second aspect of the present invention, an online measurement method for the moisture absorption curve of a power device based on the aforementioned device is provided, comprising: Place the sample to be tested on the three-point tray-type test fixture and record the initial mass; Set the target temperature and target humidity of the constant temperature and humidity chamber so that the sample to be tested absorbs moisture under constant temperature and humidity conditions; During the moisture absorption process, the mass change of the sample to be tested is transmitted sequentially to the weighing unit through the three-point tray-type test fixture and the rigid force transmission rod, and the weighing unit outputs a mass signal in real time; the guide sleeve restricts the lateral displacement of the rigid force transmission rod during the transmission process; The data processing unit synchronously receives the quality signal and the temperature and humidity signals in the environmental chamber, processes them to generate a continuous moisture absorption curve, and calculates the moisture absorption increment, moisture absorption rate and equilibrium moisture absorption amount based on the moisture absorption curve.

[0019] Compared with the prior art, the present invention has the following advantages: 1. This invention, by placing the weighing unit outside the constant temperature and humidity environmental chamber, and in conjunction with a rigid force transmission rod passing through the chamber wall and a sealing component, achieves real-time continuous transmission and measurement of sample mass changes without compromising the airtightness of the environmental chamber. It eliminates the need for repeated opening of the chamber for sampling, thus avoiding the problems of environmental disturbance, human error, and measurement discontinuity in traditional methods.

[0020] 2. This invention utilizes the cooperation between a rigid force transmission rod and a guide sleeve to effectively resist the lateral wind load disturbance generated by the circulating air in the environmental chamber by leveraging the high bending stiffness of the rigid rod itself. At the same time, the guide sleeve limits the lateral offset of the force transmission rod, eliminating the pendulum swaying phenomenon that is prone to occur in traditional flexible suspension structures, and ensuring the stability of high-precision weighing under circulating air conditions.

[0021] 3. By placing the weighing unit outside the environmental chamber, the weighing sensor is removed from the high temperature and high humidity environment, thus eliminating the sensor temperature drift effect caused by thermal and humidity interference. At the same time, the weighing unit is offset in the horizontal direction at the position where the force transmission rod passes through the chamber wall, avoiding the direct impact of the airflow escaping from the perforation on the sensor, further improving the long-term stability of weighing.

[0022] 4. This invention uses a three-point tray-type testing fixture to statically bear the sample under test, eliminating the problem of uneven force caused by excessive constraint of multi-point support. It effectively avoids the problem of center of gravity shift and tilting that easily occurs in power device samples due to their large self-weight and irregular shape, and improves the stability and reliability of continuous weighing.

[0023] 5. Through the coordinated operation of the weighing unit, temperature and humidity monitoring module, data acquisition module and data processing unit, this invention achieves synchronous acquisition and real-time processing of mass signals and environmental parameters, generates a complete and continuous moisture absorption curve and automatically calculates the moisture absorption rate and equilibrium moisture absorption, thereby improving the degree of automation of the test and the efficiency of data analysis. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the online measurement device for the moisture absorption curve of power devices according to the present invention; Figure 2 This is a schematic diagram of the three-point tray-type test fixture structure of the present invention; Figure 3 This is a flowchart of the data acquisition and control process of the present invention; Figure 1 The components listed are: 1. Constant temperature and humidity chamber; 2. Weighing unit; 3. Weighing unit mounting bracket; 4. Rigid force transmission rod; 5. Sealing assembly; 6. Guide sleeve; 7. Mechanical limiting component; 8. Internal fixing frame; 9. Sample clamping mechanism; 10. Sample to be tested; 11. Temperature and humidity monitoring module; 12. Data acquisition module; 13. Data processing unit. Figure 2 The following items are indicated by their designations: 14. Three-point tray; 15. Contact pad; 16. Connector. Detailed Implementation

[0025] 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0026] Example 1: like Figure 1As shown, this invention provides an online measurement device for the moisture absorption curve of power devices, used for online measurement of the moisture absorption process of power device shells, power module packages, or related material samples under constant temperature and humidity conditions. The device mainly includes a constant temperature and humidity environment chamber 1, a weighing unit 2, a weighing unit mounting bracket 3, a rigid force transmission rod 4, a sealing assembly 5, a guide sleeve 6, a mechanical limiting component 7, an internal fixing frame 8, a sample clamping mechanism 9, a three-point tray 14, a connecting component 16, a temperature and humidity monitoring module 11, a data acquisition module 12, and a data processing unit 13.

[0027] The constant temperature and humidity environmental chamber 1 is used to provide a stable temperature and relative humidity environment required for testing. It has a settable and adjustable temperature control system and humidity control system, which can set the target temperature and target relative humidity according to the test requirements and maintain the stability of environmental parameters during the test. In the reliability testing of power devices, it is usually necessary to turn on the circulating air in the environmental chamber to maintain uniform temperature and humidity in a large space. The resulting airflow disturbance is one of the main factors affecting the weighing accuracy.

[0028] Weighing unit 2 is located outside the constant temperature and humidity chamber 1 and is used to acquire the mass change signal of the sample 10 under test during the moisture absorption process in real time. Weighing unit 2 adopts a high-precision electronic balance with an accuracy better than 0.1mg and has a continuous real-time data output function. Weighing unit 2 is fixedly installed outside the constant temperature and humidity chamber 1 by weighing unit mounting bracket 3, so that the weighing unit 2 maintains an appropriate distance from the wall of the chamber and ensures that the position of the weighing unit 2 is stable during the test and is not affected by the vibration of the chamber.

[0029] like Figure 1 As shown, the weighing unit 2 is horizontally offset at the position where the rigid force transmission rod 4 passes through the wall of the constant temperature and humidity chamber 1, so that the weighing unit 2 and the sample 10 to be tested are not coaxially arranged in the vertical direction. Since the moisture absorption test of power devices is usually carried out under high temperature and high humidity conditions, a large amount of high temperature and high humidity airflow accumulates in the top area of ​​the chamber due to the natural rise of hot and humid air. If the weighing unit is placed directly above the top of the chamber, the hot and humid airflow escaping from the opening of the chamber will directly act on the sensitive element of the weighing sensor, causing the sensor temperature drift effect, resulting in measurement data drift, affecting the accuracy and stability of long-term continuous measurement. This invention, by horizontally offsetting the weighing unit 2, avoids the hot and humid airflow outlet area at the top of the chamber, physically isolating the hot and humid interference path, ensuring that the weighing unit works in a normal temperature and humidity environment, and eliminating the risk of temperature drift.

[0030] The rigid force transmission rod 4 passes through the wall of the constant temperature and humidity environment chamber 1, with one end extending into the interior of the environment chamber and the other end connected to the weighing unit 2. The rigid force transmission rod 4 is used to transmit the mass change of the sample 10 to be tested during the moisture absorption process to the weighing unit 2 outside the chamber. The rigid force transmission rod 4 is made of stainless steel or alloy material and has sufficient rigidity and strength so that it does not bend or twist when transmitting gravity signals.

[0031] Compared to traditional flexible suspension structures, the design of rigid force transmission rod 4 is based on the following considerations: First, in order to maintain uniform temperature and humidity in the large space, the constant temperature and humidity environment chamber 1 must turn on the internal circulating blower system. Under this condition, there is a continuous lateral wind load in the chamber. The flexible connecting rope will generate a continuous swing similar to a pendulum under the action of the lateral wind load. This swing will directly generate a noise signal on the weighing unit. Its amplitude may far exceed the small mass change during the moisture absorption process of the power device, causing the effective signal to be submerged in the noise. The rigid force transmission rod 4 itself has a large bending stiffness and hardly undergoes lateral displacement under the action of lateral wind load, thus fundamentally eliminating the source of sway.

[0032] Second, the casing or package of power devices is usually heavy. When the flexible connecting rope carries heavy samples, it needs to be made of thicker diameter or high-strength material. Even so, the inherent swing period is extended and the damping is reduced due to the heavy weight suspension, which further deteriorates the wind load resistance. After the rigid force transmission rod 4 is combined with the guide sleeve 6, its lateral constraint stiffness is independent of the sample weight. No matter the sample weight, the wind load resistance performance remains stable.

[0033] Third, the rigid force transmission rod 4 has a clear force transmission path and no elastic hysteresis, and the mass signal can be transmitted to the weighing unit 2 in real time without delay, which is conducive to capturing the rapid mass change process in the early stage of moisture absorption. When the flexible connecting rope transmits small mass changes, its own nonlinear factors such as stretching and twisting will introduce non-negligible measurement errors.

[0034] The guide sleeve 6 is fixedly installed on the constant temperature and humidity environment chamber 1 and sleeved on the outside of the rigid force transmission rod 4. The inner wall of the guide sleeve 6 and the outer wall of the rigid force transmission rod 4 are provided with appropriate clearance fit, which allows the rigid force transmission rod 4 to move freely in the axial direction and constrains its radial swing. The guide sleeve 6 is used to limit the lateral displacement of the rigid force transmission rod 4 to resist the lateral wind load disturbance generated by the circulating air inside the constant temperature and humidity environment chamber 1.

[0035] Specifically, the guide sleeve 6 is made of a self-lubricating material to reduce friction with the rigid force transmission rod 4, ensuring that small force changes in the vertical direction can be transmitted without obstruction. The guide sleeve 6 is fixedly installed at the opening on the wall of the environmental chamber, and its axis is perpendicular to the wall of the environmental chamber. When the rigid force transmission rod 4 is subjected to lateral wind load and generates lateral force, the lateral force is transmitted to the inner wall of the guide sleeve 6 through the outer wall of the force transmission rod, and is borne by the guide sleeve 6 and the fixed environmental chamber wall, thereby effectively constraining the radial swing of the force transmission rod. At the same time, the force transmission rod still maintains free movement along the axial direction, and the small displacement and force changes caused by the sample mass change are transmitted to the weighing unit 2 without obstruction.

[0036] Existing solutions involve adding wind shields or sealing the samples in sealed bottles. Wind shields can only reduce wind speed but cannot eliminate the swaying effect of wind load on the suspension structure. While sealed bottles can isolate airflow, they are only suitable for lightweight, small samples, and the temperature and humidity equilibrium time inside the bottle is relatively long. The guide sleeve constraint of this invention acts directly on the force transmission rod itself, eliminating the conditions for swaying from the mechanical source. It does not rely on additional shielding structures, does not affect the uniformity of the temperature and humidity field inside the chamber, and does not limit the size and weight of the samples, thus having wider applicability.

[0037] A sealing assembly 5 is positioned at the point where the rigid force transmission rod 4 passes through the constant temperature and humidity environment chamber 1. The sealing assembly 5 is a flexible sealing assembly, with one end sealed to the wall of the environment chamber and the other end sealed to the rigid force transmission rod 4. The flexible sealing assembly maintains the airtightness of the environment chamber while allowing vertical displacement of the rigid force transmission rod 4. The flexible sealing assembly 5 is preferably a bellows-type seal or a rubber diaphragm-type seal, possessing sufficient axial flexibility to follow the minute displacements of the force transmission rod, while also exhibiting good radial sealing performance to prevent high-temperature, high-humidity gas inside the chamber from escaping along the gap between the force transmission rod and the opening.

[0038] In existing technologies, when a balance is placed inside a box, there is no need to consider the sealing of the box. However, the risk of moisture damage to the sensor is very high. In external balance solutions, the position where the force transmission rod protrudes from the box is usually statically sealed with a simple sealing ring or sealant. However, this sealing method does not allow any displacement of the force transmission rod. When the balance is used for high-precision weighing, the force transmission rod is affected by the friction or jamming force of the sealing ring, and the signal of minute mass change cannot be accurately transmitted, resulting in a significant decrease in weighing accuracy. This invention introduces a flexible sealing component, which achieves complete sealing and isolation between the box and the outside world, while allowing the force transmission rod to move freely in the vertical direction. The low friction ensures the accurate transmission of weak mass change signals.

[0039] Mechanical limiter 7 is installed on the stroke path of rigid force transmission rod 4 to limit the over-travel displacement of rigid force transmission rod 4. When the force transmission rod is displaced beyond the normal range due to accidental impact, sample loading and unloading operation error, etc., mechanical limiter 7 will contact the mating structure on the force transmission rod to prevent it from continuing to move, thereby protecting the weighing unit 2 from damage caused by over-range impact.

[0040] The three-point tray-type testing fixture is installed inside the constant temperature and humidity chamber 1 to fix and support the sample 10 to be tested. The three-point tray-type testing fixture is connected to the extension end of the rigid force transmission rod 4 to form a unique force transmission path from the sample 10 to the weighing unit 2.

[0041] Specifically, such as Figure 1 and Figure 2 As shown, the three-point tray type test fixture includes an internal fixing frame 8, a three-point tray 14, a contact pad 15, a sample clamping mechanism 9, and a connector 16.

[0042] The internal fixing frame 8 is fixed inside the constant temperature and humidity environment chamber 1, used to guide and horizontally position the sample clamping mechanism 9, and to position the three-point tray 14. The internal fixing frame 8 is made of stainless steel or aluminum alloy profile and is fixed to the inner wall of the environment chamber by bolts or welding. The internal fixing frame 8 is flexibly connected to the inner wall of the environment chamber or vibration isolation pads are installed to reduce the transmission of vibration from the environment chamber to the test fixture.

[0043] The three-point tray 14 supports the sample 10 to be tested using a three-point contact method. The three support points of the three-point tray 14 are not on the same straight line, forming a statically determinate support plane. The specific structure of the three-point tray 14 is as follows: three support arms extend outward from the center, and a support point is set at the end of each support arm. The three support points are located in the same horizontal plane and are distributed in an equilateral triangle. The three support points together determine a support plane, on which the sample 10 to be tested is placed.

[0044] This invention employs a three-point tray-type statically determinate bearing structure, specifically designed for the unique requirements of power device samples: the shapes of power device shells or packages are highly irregular, often featuring complex three-dimensional structures such as heat dissipation substrates, electrode leads, and ceramic shells. Furthermore, the center of gravity varies significantly between different device models. In traditional single-point suspension bearing methods, the sample is suspended by only one point. For irregularly shaped samples, the center of gravity deviates from the vertical line of the suspension point, generating an eccentric torque that causes the sample to tilt or even tip over, resulting in highly unstable weighing results. In traditional planar tray-type bearing methods, the sample bottom surface is in surface contact with the tray plane. When the sample bottom surface is uneven or has protruding structures, the actual contact state is uncontrollable, sometimes with one contact point, sometimes with two or more. The number and position of contact points may randomly change during moisture absorption due to sample expansion, introducing unpredictable support errors. According to the principle of statics, three support points that are not on the same straight line can determine a plane, and this plane is unique. No matter how irregular the shape of the bottom surface of the sample 10 is, as long as its center of gravity is located within the triangular area enclosed by the three support points (by adjusting the support radius and angle of the three-point tray 14, it can adapt to devices of different sizes), the sample can obtain a stable and unique support posture. The contact state of the three support points remains unchanged during the moisture absorption process and will not change the number or position of the contact points due to the slight expansion or contraction of the sample. The support error has a high degree of consistency over time, thereby ensuring the stability and repeatability of continuous measurement of mass change.

[0045] The contact pad 15 is set at the three support points of the three-point tray 14. The sample to be tested 10 contacts the three-point tray 14 through the contact pad 15. The contact pad 15 is made of a low moisture-absorbing material, such as polytetrafluoroethylene (PTFE), polyetheretherketone (PEEK) or polyphenylene sulfide (PPS).

[0046] In a constant temperature and humidity testing environment, any material in contact with the environment exhibits varying degrees of moisture absorption. If the contact pad 15 is made of common engineering plastics, such as PA or POM, which have high moisture absorption rates, it will continuously absorb moisture and increase in weight during the test. This causes the total mass of the three-point tray 14 and its upper load-bearing structure to increase over time. This mass increment will be added to the measurement signal of the online weighing unit 2, becoming a systematic error and causing the final calculated moisture absorption of the sample to be too high. The moisture absorption rate of materials such as PTFE, PEEK, and PPS is usually less than 0.1%, and the moisture absorption under 85℃ / 85%RH conditions is also extremely limited. The interference of the moisture absorption of the fixture body on the weighing results can be reduced to a negligible level, thereby ensuring that the change in the weighing signal mainly reflects the moisture absorption behavior of the sample 10 itself and improving the accuracy of the test. In practical use, the shape of the contact pad 15 can be processed into a suitable shape according to the local geometry of the contact surface of the sample 10 to ensure reliable contact with the sample and avoid load path deviation caused by poor contact.

[0047] The sample clamping mechanism 9 and the connector 16 realize the mechanical connection between the three-point tray 14 and the lower end of the rigid force transmission rod 4, forming a complete force transmission link from the sample to be tested 10 to the force transmission rod 4. All connection nodes in the entire force transmission link adopt a rigid connection method, avoiding gaps, loosening or nonlinear deformation that may be introduced by flexible connection, and ensuring the accurate transmission of quality signals.

[0048] The temperature and humidity monitoring module 11 is installed inside the constant temperature and humidity chamber 1 to synchronously collect temperature and humidity parameters inside the chamber during the test. The temperature and humidity monitoring module 11 includes a temperature probe and a humidity probe, which are located near the sample 10 to be tested, such as about 50 mm above the sample surface, to monitor the air temperature and humidity of the sample surface in real time, so as to ensure the traceability of test data and the controllability of environmental conditions. The output of the temperature and humidity monitoring module 11 is connected to the data acquisition module 12.

[0049] The data acquisition module 12 is connected to the weighing unit 2 and the temperature and humidity monitoring module 11 for synchronous acquisition of mass signals and environmental parameter signals. The data acquisition module 12 includes a signal conditioning unit for amplifying and filtering the sensor output signal; an analog-to-digital conversion unit for converting analog signals to digital signals; an acquisition buffer unit for temporarily storing acquired data; and a communication transmission unit for transmitting data to the data processing unit 13. The sampling frequency of the data acquisition module 12 can be set according to experimental needs. Periodic acquisition at intervals on the order of minutes is usually sufficient to meet the time resolution requirements of moisture absorption curve measurement, but shorter sampling intervals can also be set to capture rapid changes in the initial stage of moisture absorption.

[0050] Data processing unit 13 is communicatively connected to data acquisition module 12 and is used to receive, process, store, and display acquired data. Data processing unit 13 is a general-purpose computer running data processing software. The functions of the data processing software include: (1) Data reception: Receives quality signal data, temperature data and humidity data from data acquisition module 12 through the communication interface; (2) Data processing: Perform preprocessing operations such as digital filtering, zero-point correction, and unit conversion on the raw data; (3) Curve plotting: Based on the preprocessed data, plot the mass-time curve, moisture absorption increment curve, and moisture absorption rate curve, and display them on the user interface in real time; (4) Parameter calculation: Calculate the moisture absorption rate, equilibrium moisture absorption, and other parameters of the sample based on the drawn moisture absorption curve; (5) Storage: Store the raw data and calculation results on a hard disk or external storage medium for easy analysis and report generation.

[0051] Figure 3 This is a flowchart of the data acquisition and control process of the present invention, as shown below. Figure 3 As shown, the mass signal output by the external online weighing unit 2 and the environmental parameter signal output by the temperature and humidity monitoring module 11 are uniformly sent to the data acquisition module 12. After signal conditioning, analog-to-digital conversion, acquisition buffering and communication transmission, the data is input to the data processing unit 13. The host computer completes the data reception, processing, calculation, storage and curve plotting, and outputs the mass-time curve, moisture absorption increment curve, moisture absorption rate curve, equilibrium moisture absorption amount and data report, etc. At the same time, the data processing unit 13 can also set and adjust the temperature and humidity parameters of the constant temperature and humidity environment chamber 1 through the control interface of the environment chamber according to the test requirements.

[0052] This invention enables real-time continuous measurement of the moisture absorption mass of power device samples without disrupting the constant temperature and humidity environment. The rigid force transmission rod, in conjunction with the guide sleeve, effectively resists the lateral wind load disturbance generated by the circulating airflow inside the chamber and eliminates the pendulum swaying that is prone to occur in flexible suspension structures. The external non-coaxial arrangement isolates the temperature drift interference from the hot and humid airflow at the top of the chamber. The three-point tray-type statically determinate load-bearing structure can stably support the power device samples, which have a large self-weight and irregular shape, and avoid the center of gravity shift, thereby ensuring the long-term stability and data accuracy of high-precision continuous weighing.

[0053] Example 2: This invention provides a method for online measurement of the moisture absorption curve of power devices, using the online measurement device for the moisture absorption curve of power devices described in Example 1. The method includes: Step S1: Sample pretreatment and initial quality recording.

[0054] The sample 10 to be tested is pretreated to eliminate the influence of adsorbed moisture and processing residues on the sample surface on the measurement results. Specifically, when the sample 10 is a power device casing, power module package, or related material sample, the sample is placed in a drying oven and dried under standard environmental conditions until the sample mass no longer changes. If the difference between two consecutive weighings does not exceed 0.01% of the sample mass, after drying, the sample is taken out and placed in a desiccator to cool to room temperature.

[0055] After cooling to room temperature, the three-point tray 14 is connected and fixed to the extension end of the rigid force transmission rod 4 through the sample clamping mechanism 9 and the connector 16. The initial mass m0 of the sample 10 to be tested is recorded. The initial mass record is completed by the weighing unit 2 and transmitted through the data acquisition module 12 and stored by the data processing unit 13.

[0056] Step S2: Set the test environment parameters.

[0057] Set the target temperature and target relative humidity for the constant temperature and humidity chamber 1. Depending on the testing standards or research needs, you can select dual 85 conditions (temperature 85℃, relative humidity 85%) or other temperature and humidity combinations. Once the constant temperature and humidity chamber 1 reaches the set temperature and humidity and stabilizes, maintain these conditions to allow the sample 10 to begin absorbing moisture. During the operation of the chamber, its internal circulating air system remains on to maintain temperature and humidity uniformity within the large space.

[0058] Step S3: Continuous online measurement during the moisture absorption process.

[0059] The constant temperature and humidity environment chamber 1 maintains constant temperature and humidity conditions inside. The sample 10 to be tested continuously absorbs moisture in the high temperature and high humidity environment. During the moisture absorption process, the mass of the sample 10 to be tested gradually increases. Its mass change is transmitted sequentially through the three-point tray 14, contact pad 15, connector 16, sample clamping mechanism 9 and rigid force transmission rod 4 to the weighing unit 2 set outside the environment chamber. The weighing unit 2 outputs the mass signal in real time.

[0060] During this test, the circulating blower inside the constant temperature and humidity chamber 1 remained on. The lateral airflow generated by the circulating blower acted on the part of the rigid force transmission rod 4 that extended into the chamber. However, due to the high bending stiffness of the rigid force transmission rod 4 and the limiting effect of the guide sleeve 6 on the lateral displacement of the force transmission rod, the airflow could not cause any perceptible swaying or bending of the force transmission rod. Similarly, the stable support and static stability of the sample 10 provided by the three-point tray 14 ensured that the sample itself was not affected by the airflow and would not be displaced or shaken, further guaranteeing the stability of the force transmission path.

[0061] Meanwhile, the weighing unit 2 is located outside the constant temperature and humidity environment chamber 1. The weighing unit 2 is offset in the horizontal direction at the position where the rigid force transmission rod 4 passes through the wall of the environment chamber, so that the sensor element of the weighing unit 2 avoids the rising channel of the hot and humid airflow escaping from the opening at the top of the chamber. The sensor is always at the laboratory ambient temperature and is not affected by heat radiation and humidity, thus avoiding the influence of temperature drift effect on measurement accuracy.

[0062] The mass signal output by the weighing unit 2 is an analog voltage or digital signal, the amplitude of which is proportional to the mass of the sample 10 to be tested. The weighing unit 2 continuously outputs the mass signal to the data acquisition module 12 at a preset sampling frequency.

[0063] Step S4: Synchronous acquisition of environmental parameters.

[0064] While the moisture absorption process is underway, the temperature and humidity monitoring module 11 simultaneously collects the temperature and humidity parameters inside the constant temperature and humidity environment chamber 1. The temperature sensor and humidity sensor of the temperature and humidity monitoring module 11 are preferably set close to the sample 10 to be tested, so as to truly reflect the actual temperature and humidity conditions of the microenvironment in which the sample is located. The temperature and humidity monitoring module 11 outputs temperature and humidity signals to the data acquisition module 12 at the same sampling frequency as the weighing unit 2.

[0065] The data acquisition module 12 simultaneously receives the mass signal from the weighing unit 2 and the temperature and humidity signal from the temperature and humidity monitoring module 11, and performs signal conditioning, analog-to-digital conversion, and acquisition buffering. The data acquisition module 12 realizes the synchronous acquisition of mass signal and environmental parameter signal, ensuring that the correspondence of each physical quantity on the time axis is accurate during subsequent data analysis, and providing a reliable raw data foundation for temperature drift correction, humidity influence analysis, etc.

[0066] Step S5: Data processing and moisture absorption curve generation.

[0067] The data acquisition module 12 transmits the acquired quality signal and temperature and humidity signal to the data processing unit 13, which then processes the received data as follows: Preprocessing: The mass signal is digitally filtered to remove measurement noise; the nominal weighing value is corrected for temperature drift and humidity based on the temperature and humidity signals to eliminate the residual influence of environmental parameter fluctuations on the mass reading. Curve generation: Arrange the preprocessed mass data in chronological order and plot the mass-time curve, i.e., the moisture absorption curve. The horizontal axis of the curve is time, and the vertical axis is the sample mass, or the change in mass relative to the initial mass Δm. Since this invention realizes continuous online acquisition of mass signals, the obtained moisture absorption curve is a continuous curve, which can fully present the details of the entire process from the start of moisture absorption to moisture saturation, especially the rapid mass change process of the sample in the early stage of moisture absorption. Incremental calculation: Calculate the moisture absorption increment Δm(t) = m(t) - m0 at each time point based on the moisture absorption curve, and plot the moisture absorption increment curve; Rate calculation: The moisture absorption increment curve is numerically differentiated to calculate the moisture absorption rate v(t)=d(Δm) / dt, and the moisture absorption rate curve is plotted. The moisture absorption rate curve can intuitively reflect the speed of moisture absorption of the sample at different stages and can be used to identify the control mechanism of the moisture absorption process. Equilibrium determination and parameter calculation: When the moisture absorption curve becomes flat and the moisture absorption rate approaches zero, the sample is considered to have reached moisture absorption equilibrium. The corresponding increase in moisture absorption at this point is the equilibrium moisture absorption amount. The host computer automatically determines the equilibrium point. For example, if the mass change rate of N consecutive data points is less than a preset threshold, equilibrium is determined, and the equilibrium moisture absorption amount is calculated and output.

[0068] Step S6: Output and application of results.

[0069] The data processing unit 13 outputs mass-time curves, moisture absorption increment curves, moisture absorption rate curves, equilibrium moisture absorption, and data reports based on the processing results. These results can be displayed graphically on the host computer screen or saved or printed in document form. Test personnel can analyze the moisture absorption patterns, diffusion behavior, and environmental adaptability of power device samples based on the above results, providing data support for the analysis of humidity intrusion patterns of power devices, packaging reliability assessment, and service life prediction.

[0070] The method of this invention places the sample on a three-point tray inside an environmental chamber, allowing the sample to absorb moisture under constant temperature and humidity conditions. The mass change is transmitted in real time to the weighing unit outside the chamber through a rigid force transmission rod, and temperature and humidity signals are collected simultaneously to generate a continuous moisture absorption curve and calculate the moisture absorption rate and equilibrium moisture absorption. This method can achieve continuous monitoring throughout the entire process without opening the chamber to take samples, capture the rapid change characteristics in the early stage of moisture absorption, avoid environmental disturbances and human errors, and the rigid force transmission combined with the guide limit effectively overcomes the influence of circulating air load, improving test efficiency and data reliability.

[0071] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An online measurement device for the moisture absorption curve of a power device, characterized in that, include: A constant temperature and humidity chamber (1) is used to provide a constant temperature and humidity test environment; a weighing unit (2) is located outside the constant temperature and humidity chamber (1) to acquire the mass change signal of the sample (10) to be tested in real time; a rigid force transmission rod (4) passes through the wall of the constant temperature and humidity chamber (1), with one end extending into the interior of the chamber and the other end connected to the weighing unit (2) to transmit the mass change of the sample (10) to the weighing unit; and a guide sleeve (6) is fixedly installed in the constant temperature and humidity chamber. (1) It is sleeved on the outside of the rigid force transmission rod (4) to limit the lateral displacement of the force transmission rod; the sealing assembly (5) is located at the penetration position of the rigid force transmission rod (4) and the constant temperature and humidity environment chamber (1) to maintain the sealing of the environment chamber while allowing the vertical displacement of the force transmission rod; the three-point tray-type test fixture is located inside the constant temperature and humidity environment chamber (1) and connected to the extension end of the rigid force transmission rod (4) to fix and support the sample to be tested (10).

2. The online measurement device for the moisture absorption curve of a power device according to claim 1, characterized in that, The three-point tray type test fixture includes a three-point tray (14) and a contact pad (15) disposed on the three-point tray (14). The sample to be tested (10) is placed on the three-point tray (14) through the contact pad (15).

3. The online measurement device for the moisture absorption curve of a power device according to claim 2, characterized in that, The three-point tray-type test fixture also includes an internal fixing frame (8), a sample clamping mechanism (9), and a connector (16). The internal fixing frame (8) is fixed inside the constant temperature and humidity environment chamber (1) and is used to guide and horizontally position the sample clamping mechanism (9); the three-point tray (14) is connected to the rigid force transmission rod (4) through the connector (16) and the sample clamping mechanism (9) to form a unique force transmission path to transmit the weight change of the sample to be tested (10) to the weighing unit (2).

4. The online measurement device for the moisture absorption curve of a power device according to claim 2, characterized in that, The contact pad (15) is made of polytetrafluoroethylene, polyetheretherketone or polyphenylene sulfide.

5. The online measurement device for the moisture absorption curve of a power device according to claim 1, characterized in that, The weighing unit (2) is positioned horizontally at the location where the rigid force transmission rod (4) passes through the wall of the constant temperature and humidity chamber (1).

6. The online measurement device for the moisture absorption curve of a power device according to claim 1, characterized in that, The rigid force transmission rod (4) is also provided with a mechanical limiter (7) to limit its overtravel displacement.

7. The online measurement device for the moisture absorption curve of a power device according to claim 1, characterized in that, The sealing component (5) is a flexible sealing component. One end of the flexible sealing component is sealed to the wall of the constant temperature and humidity environment chamber, and the other end is sealed to the rigid force transmission rod (4).

8. The online measurement device for the moisture absorption curve of a power device according to claim 1, characterized in that, The device also includes a temperature and humidity monitoring module (11), which is located inside the constant temperature and humidity environment chamber (1) and is used to synchronously collect temperature and humidity parameters inside the environment chamber.

9. The online measurement device for the moisture absorption curve of a power device according to claim 8, characterized in that, The device also includes a data acquisition module (12) and a data processing unit (13). The data acquisition module (12) is connected to the weighing unit (2) and the temperature and humidity monitoring module (11) respectively, and is used to perform signal conditioning, analog-to-digital conversion, data acquisition and buffering on the mass signal output by the weighing unit (2) and the temperature and humidity signal output by the temperature and humidity monitoring module (11); The data processing unit (13) is specifically a host computer, which is connected to the data acquisition module (12) for receiving the quality signal and temperature and humidity signal transmitted by the data acquisition module (12), and plotting the quality-time curve, moisture absorption increment curve and moisture absorption rate curve according to the received quality signal and temperature and humidity signal, calculating the equilibrium moisture absorption, and setting and adjusting the temperature and humidity parameters of the constant temperature and humidity environment chamber (1).

10. A method for online measurement of the moisture absorption curve of a power device based on the apparatus described in any one of claims 1-9, characterized in that, include: Place the sample to be tested (10) on the three-point tray-type test fixture and record the initial mass; Set the target temperature and target humidity of the constant temperature and humidity chamber (1) so that the sample to be tested (10) absorbs moisture under constant temperature and humidity conditions; During the moisture absorption process, the mass change of the sample to be tested (10) is transmitted sequentially to the weighing unit (2) through the three-point tray-type test fixture and the rigid force transmission rod (4), and the weighing unit (2) outputs a mass signal in real time; the guide sleeve (6) restricts the lateral displacement of the rigid force transmission rod (4) during the transmission process; The data processing unit synchronously receives the quality signal and the temperature and humidity signals in the environmental chamber, processes them to generate a continuous moisture absorption curve, and calculates the moisture absorption increment, moisture absorption rate and equilibrium moisture absorption based on the moisture absorption curve.

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