Design method for thermal vibration comprehensive excitation intensification test profile of electronic products in full-scale test system

Abstract

The present invention relates to the technical field of reliability hardening testing for electronic products, and more specifically, to a method for designing a thermal-vibration-comprehensive excitation hardening test profile for electronic products in a full-scale test system. The method comprises: obtaining a target internal module of the electronic product in the full-scale test system where a failure occurs; obtaining the endpoint temperature and holding time of the target internal module during temperature cycling; obtaining the thermal damage value of the target internal module under temperature cycling excitation; obtaining the vibration damage value of the target internal module; obtaining the vibration termination stress, vibration start-up stress, and vibration stress step; and designing a thermal-vibration-comprehensive excitation hardening test profile. For products with slow heat transfer, the present invention significantly shortens test time by changing the temperature loading method without changing the failure mechanism.

Description

Technical Field

[0001] The present invention relates to the technical field of reliability enhancement testing of electronic products, and in particular to a thermal vibration comprehensive excitation enhancement test profile design method for electronic products in a full-scale test system. Background Art

[0002] Full-scale strength testing systems are used to test and evaluate the strength and durability of aircraft structures under realistic operating conditions. They are critical equipment in the aviation industry for ensuring aircraft structural safety and reliability. By simulating the various loading conditions found in actual flight environments, full-scale strength testing can identify and verify potential issues in aircraft structural designs.

[0003] Full-scale strength test systems typically consist of multiple complex mechanical, electrical, and hydraulic components, the reliability of which directly impacts the reliability of the entire system. Reliability hardening tests under combined thermal and vibration excitation analyze and predict the impact of the environment on the electronics of full-scale test systems, identify typical defects and failures, and ultimately improve their functional reliability.

[0004] At present, most traditional thermal vibration comprehensive excitation enhancement tests determine profile-related parameters based on relevant standards such as the national military standard. However, the traditional methods are not very targeted and do not consider the specific failure mechanism. Some scholars have also conducted research on the failure mechanism of electronic products under thermal vibration excitation, but have not combined it with the enhancement test profile design under thermal vibration comprehensive excitation, resulting in the problem that the basis of the enhancement test profile parameter design is not clear and the values ​​are not targeted.

[0005] Therefore, it is necessary to provide a thermal vibration comprehensive excitation enhancement test profile design method for electronic products in a full-scale test system to solve the above problems. Summary of the Invention

[0006] In order to overcome the problem of unclear correspondence between profile elements and failure mechanisms in the existing full-scale test system for electronic products with thermal vibration comprehensive excitation enhancement tests, the present invention provides a profile design method for the full-scale test system for electronic products with thermal vibration comprehensive excitation enhancement tests based on traditional profile design methods and thermal vibration excitation failure mechanisms.

[0007] The present invention provides a method for designing a thermal vibration comprehensive excitation reinforcement test profile for electronic products in a full-scale test system, which adopts the following technical solutions, including:

[0008] Based on the working principle of the electronic products in the full-scale test system and fault tree analysis, the target internal modules of the electronic products where failure occurs are obtained;

[0009] Apply a single-cycle temperature cycling excitation to the electronic products of the full-scale test system and perform thermal simulation analysis to obtain the temperature distribution field of the target internal module. The temperature variation range is obtained based on the temperature change rate preset in the temperature cycling excitation. Based on the temperature variation range and the extreme operating temperature range of the target internal module, the endpoint temperature of the target internal module during the temperature cycling is obtained.

[0010] The temperature hysteresis coefficient of each component is obtained based on the component mass, specific heat capacity, thermal conductivity, and effective area of ​​each component in the target internal module. The time when the temperature change rate of the component corresponding to the maximum temperature hysteresis coefficient meets the preset temperature change rate is used as the temperature stabilization time. The holding time of the endpoint temperature is obtained based on the temperature stabilization time and the time required for the test;

[0011] Based on the temperature distribution field, a thermal stress simulation analysis is performed on the target internal module to obtain the shear strain range and thermal stress of the target internal module under a single cycle of temperature cycling excitation. The thermal damage value of the target internal module under temperature cycling excitation is obtained based on the shear strain range, fatigue constant, and fatigue ductility index of the target internal module.

[0012] Modal analysis of the electronic products in the full-scale test system was performed using the thermal stress obtained from the thermal stress simulation analysis as prestress. Based on the modal analysis, vibration excitation was applied, and random vibration simulation analysis was performed to obtain three Von-Mises stresses. Based on these three Von-Mises stresses and combined with Miner's cumulative damage theory, the vibration damage value of the target internal module under vibration excitation was obtained.

[0013] The cumulative damage is obtained based on the vibration damage value and the thermal damage value. The vibration stress when the cumulative damage value is greater than or equal to the preset cumulative damage value threshold is used as the vibration termination stress, and 50% of the vibration termination stress is used as the vibration start-up stress. The stress difference between the vibration termination stress and the vibration start-up stress is divided equally according to the number of cycles to obtain the vibration stress step.

[0014] The vibration termination stress, vibration starting stress, vibration stress step, stable temperature, endpoint temperature and holding time of endpoint temperature are used as the design parameters of the thermal vibration comprehensive excitation strengthening test profile.

[0015] Preferably, the step of obtaining the thermal damage value of the target internal module under temperature cycle excitation is:

[0016] Obtain the failure time of the target internal module based on the shear strain range, fatigue constant, and fatigue ductility index;

[0017] The inverse of the failure time is taken as the thermal damage value of the target internal module under thermal-vibration combined excitation.

[0018] Preferably, the expression of the thermal damage value is:

[0019]

[0020] Where, is the thermal damage value of the target internal module under thermal-vibration comprehensive excitation; is the failure time of the target internal module, that is, the life of the target internal module under the comprehensive thermal vibration excitation; is the shear strain range of the target internal module under a single cycle of temperature cycling excitation; is the fatigue constant of the target internal module material; is the fatigue ductility index of the target internal module material.

[0021] Preferably, the expression of fatigue ductility index is:

[0022]

[0023] Where, is the fatigue ductility index; is the average temperature of the temperature cycle excitation; is the cycle frequency, which is the number of cycles performed by the target internal module in one day.

[0024] Preferably, the step of obtaining the vibration damage value of the target internal module under vibration excitation is:

[0025]

[0026] Where, is the vibration damage value of the target internal module; is the cumulative damage life of the pins of the target internal module under the first Von-Mises stress 1σ; is the cumulative damage life of the pins of the target internal module under the second Von-Mises stress 2σ; is the cumulative damage life of the pins of the target internal module under the third Von-Mises stress 3σ; is the number of random vibration cycles of the pins of the target internal module under the first Von-Mises stress 1σ; is the number of random vibration cycles of the pins of the target internal module under the second Von-Mises stress 2σ; is the number of random vibration cycles of the pins of the target internal module under the third Von-Mises stress 3σ.

[0027] Preferably, the expression for the number of random vibration cycles is:

[0028]

[0029] Where,t Indicates vibration loading time; f 0 represents the statistical mean frequency of Von-Mises stress, where f 0 is equal to the average of the maximum and minimum values ​​of the vibration response frequency.

[0030] Preferably, the sum of the thermal damage value and the vibration damage value is used as the cumulative damage value of the target internal module under the combined thermal and vibration excitation.

[0031] Preferably, the step of obtaining the temperature variation range is:

[0032]

[0033] Where, is the temperature variation range; u is the preset temperature change rate; e is a natural constant.

[0034] Preferably, the step of obtaining the temperature hysteresis coefficient of the component is:

[0035]

[0036] Where, M is the component mass of the component; C is the specific heat capacity of the component; h is the thermal conductivity of the component; s is the effective area of ​​the component.

[0037] Preferably, the step of obtaining the endpoint temperature of the target internal module during temperature cycling is:

[0038] If the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range is less than or equal to the minimum value of the temperature change range, the temperature change rate during the applied temperature cycle excitation is increased until the minimum value of the temperature change range obtained according to the increased temperature change rate is less than the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range. The temperature difference is obtained by subtracting the halved temperature difference from the upper and lower limits of the extreme operating temperature range to obtain the highest endpoint temperature and the lowest endpoint temperature of the target internal module during temperature cycling.

[0039] The beneficial effects of the present invention are:

[0040] The value of each profile element is determined through independent temperature and vibration loading tests, simulation analysis, and related failure modeling. This allows temperature and vibration enhancement tests to be performed simultaneously or independently as a single stress test, which greatly reduces unnecessary time costs for testing. Unlike traditional profiles, the method of the present invention takes into account the influence of thermal modes in the design, and considers the change of modes with temperature in the analysis of vibration termination stress. The vibration failure stress level is predicted by the linear superposition of cumulative damage values, thereby reducing the error in the judgment of vibration termination stress in comprehensive testing of traditional profiles. For products with slow heat transfer, changing the temperature loading form without changing the failure mechanism greatly shortens the test time. Compared with traditional profiles, the design efficiency of product profiles is improved and the test time is greatly shortened. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 It is a flow chart of a method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products in a full-scale test system of the present invention;

[0043] Figure 2 This is a working principle diagram of the control system of an electronic product in an embodiment of a method for designing a thermal vibration comprehensive excitation enhancement test profile of an electronic product in a full-scale test system of the present invention;

[0044] Figure 3 A fault tree of a control system of an electronic product in an embodiment of a method for designing a thermal vibration comprehensive excitation reinforcement test profile for an electronic product of a full-scale test system of the present invention;

[0045] Figure 4 This is a schematic structural diagram of a detection module for electronic products in a full-scale test system according to an embodiment of the present invention;

[0046] Figure 5 for Figure 4 Schematic diagram of the distribution of components on the circuit board of the detection module;

[0047] Figure 6 for Figure 4 Reliability block diagram of the detection module;

[0048] Figure 7 for Figure 4 Temperature distribution diagram of the endpoint temperature of the detection module;

[0049] Figure 8 The stress-temperature variation curve in the embodiment of the present invention;

[0050] Figure 9 Schematic diagram of stress distribution of the circuit board of the detection module under 5Grms vibration load;

[0051] Figure 10 A schematic diagram of the constraints on the components of the detection module circuit board in various directions;

[0052] Figure 11 Schematic diagram of shear stress of pins in a detection module according to an embodiment of the present invention;

[0053] Figure 12 Schematic diagram of components used as thermal stability criteria in the detection module;

[0054] Figure 13 It is the structural schematic diagram of the optimized comprehensive test section;

[0055] Figure 14 Schematic diagram of stress distribution of the circuit board of the detection module under 45Grms vibration load;

[0056] Figure 15 Schematic diagram comparing the traditional cross-section design method and the cross-section design method of this embodiment;

[0057] Figure 16 This is a flow chart of implementing a reliability enhancement test in an embodiment of the present invention;

[0058] Figure 17 Schematic diagram of the cross section of a typical thermal vibration comprehensive excitation enhancement test. DETAILED DESCRIPTION

[0059] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0060] An embodiment of the present invention is a method for designing a thermal vibration comprehensive excitation strengthening test profile for electronic products of a full-scale test system, as shown in FIG. Figure 1 Shown, including:

[0061] S1. Obtain the target internal module where the electronic product of the full-scale test system fails;

[0062] Specifically, according to the working principle of the electronic product of the full-scale test system and the fault tree analysis, the target internal module where the electronic product fails is obtained.

[0063] In this embodiment, since the full-scale test system electronic products have the characteristics of long storage, short triggering and one-time operation, and need to ensure miniaturization and low-cost production, their circuits usually adopt a non-redundant solution, so their failure forms are mostly single-point failures. This embodiment takes a typical control system of a full-scale test system electronic product as an example. The working principle of the system is as follows: Figure 2 As shown in Figure 1, the external signal is received through the receiving module, and the control signal is finally output through a series of functional modules. The fault tree of the electronic products of the full-scale test system is as follows: Figure 3 As shown, the only logic gates in the fault tree are OR gates, representing a single series system. The fault tree indicates that each module is a single point of failure, and any failure in any component within the system module will cause a system failure. This paper utilizes the characteristics of the electronic product circuits in a full-scale test system for simulation analysis.

[0064] Specifically, step 11, thermal modal analysis of electronic products in full-scale test system:

[0065] Apply thermal vibration combined excitation (temperature cycle excitation and vibration excitation) to the electronic products of the full-scale test system, and perform modal analysis on the electronic products of the full-scale test system after the fault tree analysis in step S1. Its complex modular circuit can be regarded as a multi-degree-of-freedom system with limited degrees of freedom. The differential equation of its vibration system is:

[0066] (1)

[0067] Where, M is the structural mass matrix; C is the damping matrix; K is the stiffness matrix; and the structural mass matrix, damping matrix and stiffness matrix are n×n rank matrix; n is the number of discrete degrees of freedom of the structure; The acceleration response of the system n dimensional vector; The speed response of the system n dimensional vector; x is the displacement response of the system n dimensional vector, p ( t ) is the incentive received by the system.

[0068] In this embodiment, the influence of vibration damping is ignored during modal analysis, and the system is not loaded with any excitation. At this time, the differential equation of the vibration system is expressed as:

[0069] (2)

[0070] Assume that the equation of motion of the system is:

[0071] (3)

[0072] Where, is an n-dimensional constant column vector, is the structural vibration function with respect to time, Usually expressed as:

[0073] (4)

[0074] Where, is the vibration perimeter of the structure, is the phase angle, and combining the above equations (1), (2), (3), and (4) we can get:

[0075] (5)

[0076] The determinant of the system is 0, which is a necessary and sufficient condition for the existence of its non-zero solution:

[0077] (6)

[0078] The expanded form of formula (6) is:

[0079] (7)

[0080] In the equation matrix, Represents the system stiffness matrix The element represents the i Hedi j Stiffness coefficients between degrees of freedom; Represents the system mass matrix The element represents the i Hedi j The mass coupling between the degrees of freedom; the order of the eigenvalues ​​of the matrix in equation (7) is:

[0081] (8)

[0082] in, Represents the nth eigenvalue; the eigenvalue is used to characterize the natural frequency of the structural order vibration.

[0083] The process of solving the natural frequency shows that thermal-vibration coupling is not a simple linear superposition, but rather a temperature-induced change in the structural modal state. Under temperature cycling conditions, the structural modal state is primarily affected by changes in material parameters due to temperature changes and modal changes caused by internal thermal stresses in the structure. In this process, changes in the mass matrix M are negligible. The changes in the structural modal frequency and modal vibration modes caused by temperature changes are primarily caused by the stiffness matrix K, which is mainly reflected in the following two aspects:

[0084] 1. Temperature changes the elastic modulus of the structural material, and the thermal stress stiffness matrix of the additional temperature is recorded as K T The non-uniformity of the temperature field leads to different degrees of degradation of the mechanical properties of the materials in each part of the structure, and the thermal stress stiffness matrix K T for:

[0085] (9)

[0086] Where, B is a geometric matrix, D is the elastic modulus of the material E The elasticity matrix associated with Poisson's ratio μ, Indicates the temperature variation range, which is used to describe the temperature variation of the target internal module under temperature cycle stimulation.

[0087] 2. The temperature changes in the structure are uneven, and thermal deformation cannot proceed freely, which will generate tensile and compressive thermal stresses in the object, causing the local stiffness of the structure to increase or decrease, and changing the initial structural stiffness distribution. In this way, the vibration stress stiffness matrix of the two-dimensional solid unit considering the influence of thermal stress on vibration stress is obtained. K σ express:

[0088] (10)

[0089] Where, G is the shape function matrix, is the structural thermal stress matrix.

[0090] When solving structural modes in a thermal environment with temperature cycle excitation, it is generally necessary to consider the impact of changes in material parameters and thermal stresses caused by the thermal environment on the stiffness matrix. The stiffness matrix K of the structure is:

[0091] (11)

[0092] For three-dimensional solid units, the vibration stress stiffness matrix considering the influence of thermal stress on vibration stress K σ Denoted as:

[0093] (12)

[0094] Among them, the vibration stiffness coefficient considering the thermal stress at the initial temperature is Denoted as:

[0095] (13)

[0096] (14)

[0097] Where, represents the vibration stress state matrix taking into account the thermal stress at the initial temperature, Indicates x Normal stress in direction; Indicates xy In-plane shear stress; Indicates xz Shear stress in the plane.

[0098] (15)

[0099] Where, G 0 represents the shape function matrix related to the thermal stress state, which is used to describe the stress and deformation characteristics of the structure in a thermal environment. , ,..., The matrix elements represent the cumulative damage or fatigue life of the structure under thermal vibration loading and the coordinate x distribution relationship in different directions; these parameters are used to evaluate the fatigue damage of the structure at different locations and directions.

[0100] Thus, in the design of the profile for the thermal vibration combined excitation hardening test, for full-scale test system electronic products, most components are connected to the circuit board through pins. Table 1 shows the failure phenomenon of a full-scale test system electronic product during the hardening test. Ignoring the influence of materials and only considering the structural modal changes caused by thermal deformation, the component pins can be regarded as the weak link in the thermal vibration combined excitation hardening test.

[0101] Table 1

[0102]

[0103] Step 12: Failure mechanism analysis of electronic products in full-scale test system:

[0104] Based on the thermal modal analysis of the structure, the present invention uses the IDSA incremental damage superposition method to calculate the cumulative damage value under thermal-vibration combined excitation. That is, the cumulative damage value is the sum of the thermal damage value and the vibration damage value considering the temperature average stress. The specific expression is:

[0105] (16)

[0106] Where, D total is the cumulative damage value, D T is the thermal damage value; D R is the vibration damage value.

[0107] Step 13: Determine the target internal module where the failure occurs;

[0108] The thermal damage value is calculated using the Engelmeier model that takes into account the profile parameters of the thermal vibration strengthening test. The vibration damage value is calculated by combining the Miner cumulative damage theory and the three-bandwidth technology based on Gaussian distribution. When the cumulative damage value of the sum of the vibration damage value and the thermal damage value is greater than or equal to 1, the target internal module is considered to have failed.

[0109] S2, obtaining the endpoint temperature and holding time of the target internal module during temperature cycling;

[0110] Specifically, a single-cycle temperature cycling excitation is applied to the electronic products of the full-scale test system, and a thermal simulation analysis is performed to obtain the temperature distribution field of the target internal module. The temperature change range is obtained according to the temperature change rate preset in the temperature cycling excitation. According to the temperature change range and the extreme operating temperature range of the target internal module, the endpoint temperature of the target internal module during temperature cycling is obtained. According to the component mass, specific heat capacity, thermal conductivity and effective area of ​​each component in the target internal module, the temperature hysteresis coefficient of each component is obtained. The time when the component's own temperature change rate corresponding to the maximum temperature hysteresis coefficient meets the preset temperature change rate is used as the temperature stabilization time. According to the temperature stabilization time and the time required for the test, the holding time of the endpoint temperature is obtained.

[0111] Among them, step 21, the step of obtaining the temperature change range according to the temperature change rate preset in the temperature cycle excitation is:

[0112] In this embodiment, the operating limit operating temperature range depends on the failure of the electronic component, and the failure of the electronic component can be represented by the Arrhenius model:

[0113] (17)

[0114] in, is the chemical reaction rate; A is a constant; E a is the activation energy of the failure mechanism; K is the Boltzmann constant; T is the absolute temperature; E a is the activation energy, which is a constant when the temperature is less than 500K. When the component exceeds the maximum / minimum allowable junction temperature, its failure process will be aggravated. In this embodiment, the maximum / minimum allowable junction temperature of the component is used as the failure boundary condition, that is, the maximum / minimum working limit prediction value.

[0115] Among the temperature cycle parameters, the temperature change range, temperature change rate and number of cycles have the greatest impact on the screening effect. Increasing the temperature change range and temperature change rate will increase the thermal expansion and contraction of the product, and the number of cycles will increase this cumulative effect. In this embodiment, the temperature cycle screening degree The calculation formula is:

[0116] (18)

[0117] Where, λ D is the failure rate; SS is the screening degree; N is the number of cycles; u is the preset temperature change rate.

[0118] Failure rate λ D Denoted as:

[0119] (19)

[0120] Assuming that at least one failure occurs within 5 cycles, λ D is 1, N is 5 times, and the temperature cycle screening degree formula (18) is substituted to obtain:

[0121] (20)

[0122] Simplifying the above formula (20) we can get the expression of temperature variation range:

[0123] (twenty one)

[0124] Where, is the temperature variation range; u is the preset temperature change rate; e is a natural constant; k Indicates the vibration mode number of different vibration modes. u =20℃ / min, the temperature change range is: R Greater than 139℃; when u When the speed is 25℃ / min, the temperature variation range is: R Greater than 102℃; when u When the temperature is 30℃ / min, the temperature change range is R Greater than 80℃.

[0125] Step 22: The steps for obtaining the endpoint temperature of the target internal module during temperature cycling are as follows:

[0126] If the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range is less than or equal to the minimum value of the temperature change range, the temperature change rate during the applied temperature cycle excitation is increased until the minimum value of the temperature change range obtained according to the increased temperature change rate is less than the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range. The temperature difference is obtained by subtracting the halved temperature difference from the upper and lower limits of the extreme operating temperature range to obtain the highest endpoint temperature and the lowest endpoint temperature of the target internal module during temperature cycling. Assuming the extreme operating temperature range is -50°C to 60°C, when the temperature change rate is 25°C / min, the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range (110°C) is greater than 102°C, meeting the requirement. At this time, the difference between 110°C and 102°C (8°C) is divided into two equal parts to obtain 4°C. The maximum endpoint temperature of the target internal module during temperature cycling is 56°C, and the minimum endpoint temperature is -46°C.

[0127] Step 23: Obtain the holding time of the endpoint temperature:

[0128] In this embodiment, the holding time is defined as the sum of the product's temperature stabilization time and the test time. According to the thermal stability regulations in GJB150.1A-2009, "Laboratory Environmental Test Methods Part 1: General Requirements," a product is considered to have achieved temperature stability when the rate of change of the functional component with the maximum temperature hysteresis effect during operation is no greater than a preset temperature change rate of 2.0°C / h.

[0129] Among them, the temperature hysteresis coefficient formula of the component is:

[0130] (twenty two)

[0131] Where, M is the component mass of the component; C s is the specific heat capacity of the component; h is the thermal conductivity of the component; s is the effective area of ​​the component. It should be noted that the heat transfer efficiency of different products is different. In this embodiment, the temperature change rate of the component with the largest temperature hysteresis coefficient in the product is selected as the temperature stability criterion. In the high-temperature insulation stage, the time when the temperature change rate of the component with the largest temperature hysteresis coefficient is less than or equal to the preset temperature change rate of 2.0℃ / h is used as the insulation time of the highest endpoint temperature; in the low-temperature insulation stage, the time when the temperature change rate of the component with the largest temperature hysteresis coefficient is less than or equal to the preset temperature change rate of 2.0℃ / h is used as the insulation time of the lowest endpoint temperature.

[0132] S3, obtaining the thermal damage value of the target internal module under temperature cycle excitation;

[0133] Specifically, a thermal stress simulation analysis is performed on the target internal module based on the temperature distribution field to obtain the shear strain range and thermal stress of the target internal module under a single cycle of temperature cycling excitation; the thermal damage value of the target internal module under temperature cycling excitation is obtained based on the shear strain range, fatigue constant, and fatigue ductility index of the target internal module.

[0134] In this embodiment, the Engelmeier model considering the profile parameters of the thermal vibration hardening test is used to calculate the thermal damage value of the target internal module under temperature cycle excitation. Specifically, the Engelmeier model is:

[0135] (twenty three)

[0136] Where, is the thermal damage value of the target internal module under thermal-vibration comprehensive excitation; is the failure time of the target internal module, that is, the life of the target internal module under the comprehensive thermal vibration excitation; is the shear strain range of the target internal module under a single cycle of temperature cycling excitation; is the fatigue constant of the target internal module material; is the fatigue ductility index of the target internal module material.

[0137] The expression of fatigue ductility index is:

[0138] (twenty four)

[0139] Where, is the fatigue ductility index; is the average temperature of the temperature cycle excitation; is the cycle frequency, which is the number of cycles performed by the target internal module in one day.

[0140] S4. Obtaining the vibration damage value of the target internal module;

[0141] Specifically, the thermal stress obtained from the thermal stress simulation analysis is used as prestress to perform modal analysis on the electronic products of the full-scale test system. Based on the modal analysis, vibration excitation is applied, and random vibration simulation analysis is performed to obtain three Von-Mises stresses. Based on the three Von-Mises stresses and combined with Miner's cumulative damage theory, the vibration damage value of the target internal module under vibration excitation is obtained.

[0142] In this embodiment, the expression of the vibration damage value of the target internal module is:

[0143] (25)

[0144] Where, is the vibration damage value of the target internal module; is the cumulative damage life of the pins of the target internal module under the first Von-Mises stress 1σ; is the cumulative damage life of the pins of the target internal module under the second Von-Mises stress 2σ; is the cumulative damage life of the pins of the target internal module under the third Von-Mises stress 3σ; is the number of random vibration cycles of the pins of the target internal module under the first Von-Mises stress 1σ; is the number of random vibration cycles of the pins of the target internal module under the second Von-Mises stress 2σ; is the number of random vibration cycles of the pins of the target internal module under the third Von-Mises stress 3σ.

[0145] Among them, the expression of random vibration cycle number is:

[0146] (26)

[0147] Where, t represents the vibration loading time of the vibration excitation; f 0 represents the statistical average frequency of Von-Mises, where f 0 is equal to the average of the maximum and minimum values ​​of the vibration response frequency, , Indicates the maximum value of the vibration response frequency; It is necessary to note that the constant 0.6831 in formula (26) indicates that the probability of occurrence of the first Von-Mises stress of 1σ is 68.31%; the constant 0.271 indicates that the probability of occurrence of the second Von-Mises stress of 2σ is 27.1%; and the constant 0.0433 indicates that the probability of occurrence of the third Von-Mises stress of 3σ is 4.333%.

[0148] Among them, the cumulative damage life corresponding to each Von-Mises stress is:

[0149] (27)

[0150] Where, S 2 means S - N The fatigue stress of the material at the reference point of the curve (stress-life curve), S1 represents the calculated maximum stress, b represents the material S - N 2 curve materials, N express S - N The number of stress cycles required for fatigue damage to occur in the material at the reference point of the curve.

[0151] S5. Obtain vibration termination stress, vibration start-up stress, and vibration stress step;

[0152] Specifically, the cumulative damage value is obtained according to the vibration damage value and the thermal damage value. The vibration stress when the cumulative damage value is greater than or equal to the preset cumulative damage value threshold is used as the vibration termination stress, and 50% of the vibration termination stress is used as the vibration starting stress. The stress difference between the vibration termination stress and the vibration starting stress is equally divided according to the number of cycles to obtain the vibration stress step.

[0153] The cumulative damage value is calculated using formula (16). In this embodiment, the preset cumulative damage value threshold is defined as 1. When the cumulative damage value is greater than or equal to the preset cumulative damage value threshold, the product fails, and the vibration stress at this time is used as the vibration termination stress.

[0154] S6. Design the thermal vibration comprehensive excitation strengthening test profile;

[0155] Specifically, the vibration termination stress, vibration starting stress, vibration stress step, stable temperature, endpoint temperature and holding time of endpoint temperature are used as the design parameters of the thermal vibration comprehensive excitation strengthening test profile to design the thermal vibration comprehensive excitation strengthening test profile.

[0156] In addition, based on the design parameters of the thermal vibration comprehensive excitation strengthening test section, the loading design of temperature cycle excitation and vibration excitation is completed. The typical thermal vibration comprehensive excitation strengthening test section is as follows Figure 3 As shown in the figure, the vibration application time is generally 10 minutes. For full-scale test system electronic products, the thermal stabilization time is generally greater than 10 minutes. The timing of vibration application is an important factor in whether the profile can effectively stimulate faults. At present, there is no clear regulation on the timing of vibration excitation loading, and theoretical analysis is needed to maximize the ability of test excitation to stimulate faults. Therefore, according to the temperature strain formula, thermal deformation increases with the increase of temperature difference. When the structure reaches thermal stability, it reaches the maximum strain. At this time, the temperature strain for:

[0157]

[0158] Where, is the linear expansion coefficient of the material, T 0 is the initial temperature, TTo stabilize the temperature, the vibration loading should be carried out at the location with the largest thermal strain, i.e. the location with the largest thermal vibration cumulative damage.

[0159] The embodiments of the present invention are described in detail below with reference to the accompanying drawings:

[0160] Step 1: In this embodiment, the detection module of the electronic product of the full-scale test system is used as the research object. The appearance of the detection module is as follows: Figure 4 As shown, the internal structure of the detection module is as follows Figure 5 As shown in Table 2, the function names of the components corresponding to the detection module are shown in Table 2. The detection module can be simplified into two main functional module units: receiving and output. The functional modules of the internal circuit are independent of each other. Its reliability block diagram is shown in Figure 6 shown.

[0161] Table 2

[0162]

[0163] Based on the reliability block diagram of the detection module, FMEA analysis is performed on it. The analysis results are shown in Table 3. Table 3 clearly defines the product failure mode caused by the abnormality of the detection module and the local impact and final impact caused by the failure mode. Secondly, combined with Figure 6 The internal functional module design clearly defines the types of components connected in series with the detection module unit. Damage to the components will cause abnormal function of the detection module, which in turn will lead to product failure.

[0164] Table 3

[0165]

[0166] Step 2: Thermal modal analysis of electronic products under comprehensive thermal vibration excitation of full-scale test system:

[0167] After completing the working principle and fault tree establishment in step 1, thermal modal analysis is performed on the electronic products of the full-scale test system under thermal vibration comprehensive excitation. The complex modular circuit is regarded as a multi-degree-of-freedom system with limited degrees of freedom. The thermal stress stiffness matrix of the elastic modulus of the structural material is obtained through theoretical analysis to obtain the inhomogeneity of the temperature field. K T , the stress stiffness matrix of the additional stress caused by uneven temperature changes in the structure K σ When solving the structural modal under thermal environment, it is generally necessary to consider the influence of the changes in material parameters and thermal stress caused by the thermal environment on the stiffness matrix. The stiffness matrix of the structure .

[0168] First, a thermal simulation analysis is performed on the geometric model of the detection module of a certain test system in step 1 to determine the extreme operating temperature range. The temperature variation range during the thermal cycle is determined based on the temperature cycle screening degree. The maximum and minimum endpoint temperatures are determined based on the temperature variation range and the extreme operating temperature range. The temperature corresponding to each component is extracted and compared with the nominal temperature of the component. Because the product is a single point of failure, if a component overheats, the product will fail.

[0169] After simulation analysis, the schematic diagram of the temperature distribution field of the detection module is as follows Figure 7 As shown in the figure, the extreme operating temperature range is -60℃~70℃. When the preset temperature change rate is 23℃ / min in the temperature cycle excitation, the corresponding temperature change range is R greater than 118℃ and 118℃ less than 130℃. The difference (12℃) between 130℃ and 118℃ is divided into two equal parts, and the highest endpoint temperature of the temperature cycle is 64℃ and the lowest endpoint temperature is -54℃. The stress change curve of the entire module is obtained by transient thermal analysis and thermodynamic analysis, and the stress change curve at the component pins is extracted. Based on the stress change curve, the temperature-stress change curve is obtained as shown in the figure. Figure 8 As shown, from Figure 8 As can be seen from the figure, due to component self-heating, the component and pin temperature T1 is much lower than the board temperature T2 before 150.7 minutes. As the temperature continues to rise, the temperature difference between T1 and T2 gradually decreases, and the thermal stress also decreases accordingly. After 150.7 minutes, T1 briefly exceeds T2, and as the temperature difference increases, the thermal stress also increases. After 161.3 minutes, the board temperature gradually stabilizes, and the temperature difference between T1 and T2 gradually decreases. At this point, the thermal stress then shows a downward trend. Although the high-temperature thermal stress reaches its maximum at 161.3 minutes, for experimental operability, this time point is not set as the vibration stress loading point.

[0170] During the temperature cycle, thermal stress generated by the thermal expansion and contraction of the structural material gradually accumulates. After one temperature cycle, the stress state tends to stabilize when the temperature reaches a stable state. At this time, the thermal stress obtained from the thermal stress analysis is used as the prestress for modal analysis to obtain the first six modes of the structure, as shown in Table 4. Compared with the modes without prestress, the modal natural frequency under prestress is significantly lower. This is because thermal stress separates the components from the circuit board structure, resulting in a decrease in the component load-bearing capacity and ultimately a decrease in the modal natural frequency.

[0171] Table 4

[0172]

[0173] Apply a vibration load of 5~40Grms to the detection module and perform vibration simulation analysis, such as Figure 9 The figure shows the stress distribution contours under a 5 Grms load. The stress distribution contours derived from vibration simulation analysis show that the vibration stress is highest at the pins on the detection module, while the vibration stress at other locations is within the safe range. Because the maximum thermal and vibration stresses are both located at the circuit pins, the thermal and random vibration simulation results were combined with the linear superposition cumulative damage method to predict the module's failure limit and develop a thermal-vibration coupled test profile.

[0174] Step 3: Analysis of the failure mechanism of electronic products under thermal vibration comprehensive excitation in the full-scale test system:

[0175] After completing the thermal modal analysis in step 2, the failure mechanism of the electronic product under thermal vibration comprehensive excitation of the full-scale test system is analyzed. When the cumulative damage value is greater than or equal to 1, the structure is considered to have failed. Since the pins of the detection module components are all made of the same material, the cumulative damage value is calculated using formula (16). The pin with the maximum stress value is x The damage values ​​under the vibration stress value of 5~40Grms are shown in Table 5; the component pins with the maximum stress value are at y The corresponding damage values ​​for the vibration stress values ​​of 5~40Grms in the direction are shown in Table 6; the component pins with the maximum stress value are at z The corresponding damage values ​​for vibration stress values ​​of 5~40Grms in the direction are shown in Table 7.

[0176] Table 5

[0177]

[0178] Table 6

[0179]

[0180] Table 7

[0181]

[0182] From Tables 5, 6, and 7, we can see that the cumulative damage value of the pin is y The cumulative damage value in the axial direction is larger. x 、 z The damage value in the axial direction is smaller, which is related to the arrangement of the components. Figure 10 As shown, the components are z The axial direction is constrained by both the circuit board and the pins, so the cumulative damage value in this direction is the smallest. x The axial direction is limited by the pins on both sides. y Compared with the shaft, the overall damage is within the safe range. When the vibration load reaches 40Grms, yThe cumulative damage value in the axial direction is greater than 1, and there is a risk of fracture. However, the vibration termination stress in the temperature-vibration comprehensive test needs to be selected by comprehensively considering the thermal stress.

[0183] Extract the shear strain range of the pin in the simulation, such as Figure 11 As shown. The maximum positive strain is 1.1337e-4, and the maximum negative strain is -9.4071e-5. Substituting it into the thermal damage model, the cumulative thermal damage value of the temperature cycle is 3.21e-18, which is approximately 0. Therefore, the cumulative thermal damage value of the temperature cycle is ignored, and only the cumulative vibration damage value caused by the vibration stress is considered. According to the linear superposition cumulative damage formula, when the vibration stress is 40Grm, D T =0, D total =1.0107, D =1.107>1, it is considered that the pins are damaged, the component function is lost, and the test system function is invalid. Therefore, 40Grms is the vibration termination stress of the detection module of the test system.

[0184] Step 4: Design a full-scale test system for electronic product thermal vibration comprehensive excitation enhancement test profile:

[0185] This embodiment determines the profile elements through comprehensive thermal vibration simulation. Unlike traditional profiles, the test profile obtained in this embodiment is based on simulation deterministic analysis and product characterization, which is more effective in stimulating product failures. The specific elements are determined as follows:

[0186] (1) Endpoint temperature of the temperature cycle: The highest endpoint temperature is 76°C and the lowest endpoint temperature is -63°C, which are calculated through thermal simulation.

[0187] (2) Insulation time: According to the temperature hysteresis coefficient formula, the temperature change curve of the component with the largest temperature hysteresis coefficient is selected as the thermal stability time criterion, such as Figure 12 As shown in the figure, the component's temperature change curve was obtained through transient thermal analysis, and the stabilization time was determined based on the description of thermal stability in GJB150.1A. The stabilization time at the lowest temperature was 92.2 minutes, and the stabilization time at the highest temperature was 99.1 minutes. This means that the holding time at the lowest endpoint temperature was 92.2 minutes, and the holding time at the highest endpoint temperature was 99.1 minutes.

[0188] (3) Vibration termination stress V e : Based on the damage limit, the vibration termination stress is expected to be 40Grms:

[0189] (4) Vibration initial stress V s : According to the vibration termination stress calculation, the vibration starting stress is 20Grms:

[0190] (5) Vibration stress step: based on V e 、V s Calculation, each step should be 5Grms:

[0191] (6) Timing of vibration loading: The vibration should be loaded after the temperature stabilizes, that is, 113 minutes after the test temperature changes and insulation.

[0192] Step 5: Full-scale test system electronic product thermal vibration comprehensive excitation loading design, according to the thermal vibration comprehensive excitation strengthening test section parameters designed in step 4, according to the temperature strain formula when the structure reaches thermal stability Complete the loading design of temperature cycle excitation and vibration excitation.

[0193] It should be noted that

[0194] It can be seen from step three that in the comprehensive test of the test system, the thermal fatigue damage caused by temperature in a single cycle is extremely small, and since the number of cycles in the reliability enhancement test is small, the failures that occur in the comprehensive test are fatigue damage caused by vibration stress. Comparing the modal and vibration stress at high and low temperatures, the test system has a greater impact on vibration stress at low temperatures. Therefore, in this paper, the comprehensive test profile is optimized, and the temperature cycle is changed to a constant low temperature and vibration step stress loading after the temperature is stabilized. The optimized comprehensive test profile is as follows Figure 13 As shown. For specimens requiring long holding times, this integrated test profile can significantly improve efficiency. The profile proposed in this invention eliminates the holding time and additional testing time required for each cycle without changing the failure mechanism. Through simulation analysis, the present invention determined the traditional and optimized profiles, and conducted tests to verify that the optimized profile not only significantly reduced the time required, but also maintained the failure mechanism.

[0195] In order to compare the advantages of the optimized profile design method, the traditional profile design method is used for the same product. According to the simulation results, for a single vibration load, the product is damaged at 45Grms, and the stress cloud diagram is as follows: Figure 14 As shown, assuming that the simulation data is accurate and consistent with the experimental results, Figure 14 It can be seen that damage occurs at 45 Grms. According to traditional comprehensive test profile design requirements, the vibration end stress is the failure limit of the vibration test, set at 45 Grms. The starting stress and each step length are 1 / 5 of the end stress, set at 9 Grms. The holding time is determined through testing, and the temperature endpoints are selected at 80% of the operating limit of the temperature cycle test. Assuming the temperature simulation data is accurate, the high and low temperature endpoints are set at 64°C and -54°C, respectively. The test profile is shown in Table 8.

[0196] Table 8

[0197]

[0198] For a single comprehensive test: Compared with traditional methods, MDP-TVS (the method of the present invention) has a smaller step size, higher test accuracy, and more accurate judgment of the degree of product failure. For example, through MDP-TVS simulation analysis, this article can reasonably increase the starting stress and improve the prediction accuracy of the product destruction limit from the original 9G to 5G. In theory, the error can be reduced by up to 44%, and the excitation of the fault is more accurate. While the failure mechanism and the fault excitation intensity remain unchanged, change the loading mode of the temperature excitation from temperature cycle to constant low temperature. This method is suitable for large products or products with good insulation, and can greatly reduce the test time. For a certain type of test system detection module, the total test time was reduced from 956.5min to 142.2min, saving 85.1% of the test time. The test profile comparison is as follows: Figure 15 shown.

[0199] For the overall test: Compared with the traditional method, this method clarifies the simulation determination principles of the six cross-section elements, namely, endpoint temperature, temperature stabilization time, vibration end stress, initial stress, and vibration excitation loading timing. In the traditional method, the endpoint temperature, vibration end stress, initial stress, and stress step need to be obtained through preliminary tests. The test process is as follows: Figure 16 As shown. Assume that the low temperature step test time is T1, the high temperature step test time is T2, the temperature cycle test time is T3, the vibration step test time is T4, and the temperature-vibration comprehensive test time is T5. Considering that there are sufficient test equipment, the total test time of the traditional method is T1+T2+T3+T4+T5 at the longest, and the shortest test time is Max(T1, T2)+T3+T4. The test time can be shortened to the shortest Max(T1, T 2, T3, T4 and T5), that is, the test time is determined by the longest test among these five tests.

[0200] The method proposed in the present invention clarifies the specific values ​​of the stabilization time and the vibration excitation loading time through simulation analysis, which has not been mentioned in traditional methods. The excitation loading time should be in the insulation stage, when the temperature stability of the thermal stress is the greatest. Compared with the traditional profile regarding the excitation loading time, the present invention has made clear provisions for this to increase the excitation intensity of the test fault; the specific value of the temperature stabilization time is clarified. This value is obtained by detecting the internal components of the circuit. In actual testing, it is difficult to detect the temperature of the internal components, which makes it difficult for traditional profiles to achieve temperature stability during insulation. For products with a large temperature variation range and severe thermal shock, it is difficult to achieve the maximum thermal stress, which ultimately leads to the failure to achieve the expected test results.

[0201] In summary, the accuracy and efficiency of the traditional profile and the profile designed in this paper were compared, and the main conclusions were drawn as follows:

[0202] (1) In the embodiment, based on the traditional profile design method, the profile design is improved and a multi-stress step-hardening test (MDP-TVS) for profile design is proposed. The design process of the proposed method and the principle of determining each profile element are explained. The method of this embodiment improves the defects of traditional profile design, that is, the need for independent temperature and vibration tests, and the value of each profile element is determined through simulation analysis and related failure modeling. As a result, the temperature and vibration enhancement tests can be performed simultaneously or independently of a single stress test, which greatly reduces unnecessary time and cost costs of testing.

[0203] (2) Unlike traditional profiles, this embodiment takes into account the influence of thermal modes in the design and considers the change of modes with temperature in the analysis of vibration termination stress. The vibration failure stress level is predicted by linear superposition of cumulative damage, thereby reducing the error in the vibration termination stress judgment of traditional profiles in comprehensive testing. For products with slow heat transfer, changing the temperature loading form without changing the failure mechanism greatly shortens the test time, and the test time is shortened by 85.1% compared with traditional profiles.

[0204] (3) By enumerating six profile elements, MDP-TVS is compared with traditional profiles from three dimensions. The results show that in terms of time cost, MDP-TVS is lower than traditional profiles. When the test equipment is sufficient, MDP-TVS only needs Max(T1, T 2, T3, T4 and T5) can complete a series of tests such as high temperature stepping, low temperature stepping, temperature cycling, vibration, temperature and vibration combination; MDP-TVS has a clearer standard for the value of profile elements, defines the standard for the thermal stabilization time of the product, the selection method of the thermal stability curve and the simulation analysis method of the thermal stabilization time, and also clarifies the value standard for the thermal stability element. MDP-TVS makes the standard for the value of profile elements clearer, determines the standard for the thermal stabilization time of the product, the selection method of the thermal stability curve and the analysis method of the thermal stabilization time. It stipulates that the loading timing of the vibration excitation in the comprehensive test should be after the temperature stabilizes; MDP-TVS reduces the stress step size to improve the accuracy of the magnitude judgment during the test fault excitation. For example, in the comparison in this article, after reducing the stress step size from 9 Grms to 4 Grms, the test error can be reduced by up to 44%

[0205] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products in a full-scale test system, characterized in that: include: Based on the working principle of the electronic products in the full-scale test system and fault tree analysis, the target internal modules of the electronic products where failure occurs are obtained; Apply a single-cycle temperature cycling excitation to the electronic products of the full-scale test system and perform thermal simulation analysis to obtain the temperature distribution field of the target internal module. The temperature variation range is obtained based on the temperature change rate preset in the temperature cycling excitation. Based on the temperature variation range and the extreme operating temperature range of the target internal module, the endpoint temperature of the target internal module during the temperature cycling is obtained. The temperature hysteresis coefficient of each component is obtained based on the component mass, specific heat capacity, thermal conductivity, and effective area of ​​each component in the target internal module. The time when the temperature change rate of the component corresponding to the maximum temperature hysteresis coefficient meets the preset temperature change rate is used as the temperature stabilization time. The holding time of the endpoint temperature is obtained based on the temperature stabilization time and the time required for the test; Based on the temperature distribution field, a thermal stress simulation analysis is performed on the target internal module to obtain the shear strain range and thermal stress of the target internal module under a single cycle of temperature cycling excitation. The thermal damage value of the target internal module under temperature cycling excitation is obtained based on the shear strain range, fatigue constant, and fatigue ductility index of the target internal module. Modal analysis of the electronic products in the full-scale test system was performed using the thermal stress obtained from the thermal stress simulation analysis as prestress. Based on the modal analysis, vibration excitation was applied, and random vibration simulation analysis was performed to obtain three Von-Mises stresses. Based on these three Von-Mises stresses and combined with Miner's cumulative damage theory, the vibration damage value of the target internal module under vibration excitation was obtained. The cumulative damage is obtained based on the vibration damage value and the thermal damage value. The vibration stress when the cumulative damage value is greater than or equal to the preset cumulative damage value threshold is used as the vibration termination stress, and 50% of the vibration termination stress is used as the vibration start-up stress. The stress difference between the vibration termination stress and the vibration start-up stress is divided equally according to the number of cycles to obtain the vibration stress step. The vibration termination stress, vibration starting stress, vibration stress step, stable temperature, endpoint temperature and holding time of endpoint temperature are used as the design parameters of the thermal vibration comprehensive excitation strengthening test profile.

2. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1 is characterized in that: The steps to obtain the thermal damage value of the target internal module under temperature cycling excitation are: Obtain the failure time of the target internal module based on the shear strain range, fatigue constant, and fatigue ductility index; The inverse of the failure time is taken as the thermal damage value of the target internal module under thermal-vibration combined excitation.

3. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 2 is characterized in that: The expression of thermal damage value is: Where, is the thermal damage value of the target internal module under thermal-vibration comprehensive excitation; is the failure time of the target internal module, that is, the life of the target internal module under the comprehensive thermal vibration excitation; is the shear strain range of the target internal module under a single cycle of temperature cycling excitation; is the fatigue constant of the target internal module material; is the fatigue ductility index of the target internal module material.

4. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 3 is characterized in that: The expression of fatigue ductility index is: Where, is the fatigue ductility index; is the average temperature of the temperature cycle excitation; is the cycle frequency, which is the number of cycles performed by the target internal module in one day.

5. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1 is characterized in that: The steps to obtain the vibration damage value of the target internal module under vibration excitation are as follows: Where, is the vibration damage value of the target internal module; is the cumulative damage life of the pins of the target internal module under the first Von-Mises stress 1σ; is the cumulative damage life of the pins of the target internal module under the second Von-Mises stress 2σ; is the cumulative damage life of the pins of the target internal module under the third Von-Mises stress 3σ; is the number of random vibration cycles of the pins of the target internal module under the first Von-Mises stress 1σ; is the number of random vibration cycles of the pins of the target internal module under the second Von-Mises stress 2σ; is the number of random vibration cycles of the pins of the target internal module under the third Von-Mises stress 3σ.

6. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 5, characterized in that: The expression for the number of random vibration cycles is: Where, t Indicates vibration loading time; f 0 represents the statistical mean frequency of Von-Mises stress, where f 0 is equal to the average of the maximum and minimum values ​​of the vibration response frequency.

7. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1 is characterized in that: The sum of the thermal damage value and the vibration damage value is taken as the cumulative damage value of the target internal module under the combined thermal and vibration excitation.

8. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1 is characterized in that: The steps to obtain the temperature variation range are: Where, is the temperature variation range; u is the preset temperature change rate; e is a natural constant.

9. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1 is characterized in that: The steps to obtain the temperature hysteresis coefficient of a component are: Where, M is the component mass of the component; C is the specific heat capacity of the component; h is the thermal conductivity of the component; s is the effective area of ​​the component.

10. The method for designing a thermal vibration comprehensive excitation enhancement test profile for electronic products of a full-scale test system according to claim 1, characterized in that: The steps to obtain the endpoint temperature of the target internal module during temperature cycling are: If the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range is less than or equal to the minimum value of the temperature change range, the temperature change rate during the applied temperature cycle excitation is increased until the minimum value of the temperature change range obtained according to the increased temperature change rate is less than the sum of the absolute values ​​of the upper and lower limits of the extreme operating temperature range. The temperature difference is obtained by subtracting the halved temperature difference from the upper and lower limits of the extreme operating temperature range to obtain the highest endpoint temperature and the lowest endpoint temperature of the target internal module during temperature cycling.

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