Method for constructing constitutive model of high polymer material for packaging after accelerated temperature and humidity aging

Abstract

The invention discloses a method for constructing a constitutive model of a high polymer material for packaging after temperature and humidity aging acceleration, and relates to the technical field of mechanical property evaluation of packaging materials.The method comprises the steps that firstly, activation energy of the high polymer material for packaging under temperature and humidity aging acceleration stress is calculated through data obtained through an activation energy calculation test conducted on a test sample; therefore, an accurate temperature and humidity acceleration model is obtained, reasonable environment conditions of a test environment are obtained, then a strong acceleration steady-state damp-heat test and a tensile test are carried out according to the determined environment conditions, and the obtained test data can be used for fitting and deriving a constitutive model of the packaging high polymer material with viscoelastic characteristics after temperature and humidity aging acceleration. The constitutive model can accurately describe the dynamic response between physical quantities such as stress-strain after temperature and humidity aging acceleration of the high polymer material for packaging, and the accuracy of mechanical property evaluation of the high polymer material for packaging can be improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of evaluation of mechanical properties of packaging materials, in particular to a method for constructing a constitutive model of a packaging polymer material after temperature and humidity aging acceleration. BACKGROUND

[0002] The polymer material is widely used in the field of integrated circuit packaging due to its excellent specific strength, designability and corrosion resistance. With the wide application of plastic packaged integrated circuits, various complex application environments have put forward more severe challenges to the reliability of plastic packaged integrated circuits. Temperature and humidity are the two most common and key environmental loads, and the effects brought by them are as follows: (1) temperature effect: the packaging polymer material is prone to aging and deformation under high temperature environment, resulting in performance degradation or failure of the plastic packaged integrated circuit; (2) humidity effect: the effect of humidity on the plastic packaged integrated circuit mainly lies in moisture intrusion and popcorn phenomenon. In actual environment, the coupling effect of temperature and humidity will cause complex physical and chemical changes of the packaging polymer material, resulting in degradation of the mechanical properties of the packaging polymer material. Therefore, accurately predicting the mechanical properties of the packaging polymer material in long-term temperature and humidity environment is of great importance for evaluating the structural durability of the plastic packaged integrated circuit, ensuring the service safety and realizing the whole life cycle design.

[0003] The aging of the packaging polymer material in the temperature and humidity environment is a complex time-varying process. Since the natural aging period is long, it cannot meet the time requirement of engineering research and development and evaluation. Therefore, temperature and humidity aging acceleration test becomes an important means for verifying the long-term service reliability of the plastic packaged integrated circuit in the temperature and humidity environment, which can greatly shorten the test period in the temperature and humidity environment. The mathematical relationship provided by the constitutive model of the packaging polymer material can describe the dynamic response between stress-strain and other physical quantities, so as to evaluate the mechanical properties of the packaging polymer material after temperature and humidity aging acceleration test. However, the traditional constitutive model is constructed for the packaging polymer material in the original non-aged state. When the packaging polymer material is subjected to temperature and humidity aging, the microstructure and components thereof have undergone irreversible changes, resulting in a large error in the evaluation of the mechanical properties by using the constitutive model, which affects the accuracy of the evaluation of the mechanical properties of the packaging polymer material. SUMMARY

[0004] In view of the above problems and technical requirements, the application provides a method for constructing a constitutive model of a packaging polymer material after temperature and humidity aging acceleration. The method for constructing a constitutive model of a packaging polymer material after temperature and humidity aging acceleration comprises the following steps. Preparation of a test sample by using the packaging polymer material; Activation energy calculation experiments were conducted on the test samples to determine the activation energy of the encapsulation polymer material under accelerated stress of temperature and humidity aging. ; Activation energy of encapsulation polymer materials under accelerated stress of temperature and humidity aging Substitute the temperature and humidity acceleration model into the actual working environment and determine the environmental conditions of the test environment. After conducting HAST tests on the test samples according to the environmental conditions of the test environment and letting them stand for a predetermined time, tensile tests were carried out on the test samples to obtain multiple stress-strain curves. The constitutive model of the encapsulation polymer material after accelerated temperature and humidity aging was obtained by fitting multiple stress-strain curves based on a viscoelastic constitutive model.

[0005] A further technical solution involves conducting activation energy calculation experiments on the test samples to determine the activation energy of the encapsulation polymer material under accelerated stress from temperature and humidity aging. include: Multiple activation energy calculation tests were conducted on the test samples. When conducting each activation energy calculation test on the test samples, the HAST test was conducted on the test samples first, followed by the quasi-static tensile test to obtain the fracture strength test value of the test samples under the current activation energy calculation test. The temperature and humidity conditions of the HAST test were different in any two sets of activation energy calculation tests. Based on the temperature and humidity accelerated aging model, the fracture strength test values ​​of the test samples under multiple activation energies were calculated to determine the activation energy of the encapsulation polymer material under temperature and humidity accelerated aging stress. .

[0006] A further technical solution involves determining the activation energy of the encapsulation polymer material under accelerated stress due to temperature and humidity aging. include: Accelerated model of temperature and humidity Taking the logarithm of both sides and transforming to obtain ;in, It is the expiration time. It is activation energy. It is Boltzmann's constant. It is absolute temperature. It refers to relative humidity. and These are known parameters; Substitute the fracture strength test value of the test sample under each group of activation energy calculation tests into... Substituting the absolute temperature of the HAST experiment into the current activation energy calculation experiment. Substituting the relative humidity parameter into the HAST experiment in the current activation energy calculation experiment. The activation energy of the encapsulation polymer material under accelerated stress due to temperature and humidity aging was obtained by solving the problem. .

[0007] A further technical solution involves conducting a HAST test on the test sample followed by a quasi-static tensile test to obtain the fracture strength test value of the test sample under the current activation energy calculation test, including: HAST tests were conducted on multiple test samples under corresponding temperature and humidity conditions, and variables were initialized. In the HAST experiment, Take out the first The quasi-static tensile test was conducted on the first test sample to determine the... The fracture strength of each test sample, let The calculation is repeated until the current activation energy test is completed. The average fracture strength of all test samples is then taken to obtain the fracture strength test value of the test sample under the current activation energy test. This refers to the duration of a single test group.

[0008] The further technical solution involves determining whether the current activation energy calculation experiment has been completed, including: When the first one is taken out If the deviation between the fracture strength of one test sample and the fracture strength of the first test sample does not reach the deviation threshold, it is determined that the current activation energy calculation test has not been completed. And again, the HAST test was performed to achieve... Take out the first The quasi-static tensile test was conducted on the first test sample to determine the... The steps for determining the fracture strength of a test sample; When the first one is taken out When the deviation between the fracture strength of the first test sample and the fracture strength of the second test sample reaches the deviation threshold, the current activation energy calculation test is considered complete.

[0009] The further technical solution involves determining the environmental conditions of the test environment based on the actual working environment conditions, including: Activation energy of encapsulation polymer materials under accelerated stress of temperature and humidity aging Substitute these known quantities into the temperature and humidity acceleration model; Determine the absolute temperature of the test environment. and relative humidity And combined with the absolute temperature of the real working environment and relative humidity The acceleration factor was calculated based on the temperature and humidity acceleration model. ; According to the acceleration factor and real working hours in a real work environment Determine the test time for the test environment. , the environmental conditions of the test environment include absolute temperature , relative humidity , and test time .

[0010] A further technical solution is to perform a tensile test on the test sample to obtain a plurality of stress-strain curves, including: performing a quasi-static tensile test on the test sample at least two different tensile rates to obtain a plurality of quasi-static tensile stress-strain curves; and performing a Hopkinson test on the test sample to obtain a Hopkinson stress-strain curve.

[0011] A further technical solution is to use the plurality of stress-strain curves to fit a constitutive model of the high polymer material for packaging after temperature and humidity aging acceleration based on a viscoelastic constitutive model, including: integrating the viscoelastic constitutive model to obtain an integral expression ; wherein , , is the elastic constant of the nonlinear part, is the elastic constant of the viscoelastic part at low strain rate, is the relaxation time of the viscoelastic part at low strain rate, is the elastic constant of the viscoelastic part at high strain rate, is the relaxation time of the viscoelastic part at high strain rate, is the strain, is the stress at strain , is the tensile rate, denotes time; based on ignoring the high strain rate response term in the integral expression of the viscoelastic constitutive model, using the plurality of quasi-static tensile stress-strain curves to perform parameter fitting according to , and based on ignoring the low strain rate response term in the integral expression of the viscoelastic constitutive model, using the Hopkinson stress-strain curve to perform parameter fitting according to to determine the values of , , , , , , , and substituting them into the viscoelastic constitutive model to obtain the constitutive model of the high polymer material for packaging after temperature and humidity aging acceleration.

[0012] A further technical solution is to determine , , , 、 、 、 The value of the stress difference corresponding to the strain The quasi-static tensile test is carried out at a stretching rate of The strain The corresponding stress , and the quasi-static tensile test is carried out at a stretching rate of The strain The corresponding stress Subtracting the strain The corresponding stress difference ; the stress difference corresponding to different strains The stress difference corresponding to different strains According to Fitting obtains And The value of, wherein ; Substitute the values of And In , and based on the quasi-static tensile stress-strain curve fitting obtains the value of 、 、 ; Substitute the values of 、 、 And In , and based on the Hopkinson stress-strain curve fitting obtains the value of And .

[0013] Further, the technical scheme is to use the packaging polymer material to prepare the test sample, including: An injection molding machine and a compression molding process are used to form a sample semi-finished product on the surface of the substrate using the packaging polymer material. The sample semi-finished product is separated from the surface of the substrate and cut to obtain a thin test sample. The test sample includes a parallel reduction section and clamping sections located at both ends of the length direction of the parallel reduction section. The width of the clamping section is greater than that of the parallel reduction section, and the parallel reduction section and the clamping section are connected by an arc section.

[0014] The beneficial technical effects of the present application are: The application discloses a method for constructing a constitutive model of a high polymer material for packaging after temperature and humidity aging acceleration. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 is a flow chart of the method for constructing the constitutive model of the high polymer material for packaging after temperature and humidity aging acceleration in an embodiment of the application.

[0016] Figure 2 is a schematic diagram of a plane structure of a test sample prepared from the high polymer material for packaging.

[0017] Figure 3 is a stress-strain curve of a single test sample in an example after completing an activation energy calculation test.

[0018] Figure 4 is a corresponding relationship diagram of the fracture strength of each test sample and the test time of the HAST test experienced by the test sample in each activation energy calculation test when two groups of activation energy calculation tests are respectively carried out on the test sample by using a step test method in an example.

[0019] Figure 5 are two quasi-static tensile stress-strain curves obtained by carrying out quasi-static tensile tests at two tensile rates in an example.

[0020] Figure 6 is a Hopkinson stress-strain curve obtained by carrying out a Hopkinson test in an example. DETAILED DESCRIPTION

[0021] The specific embodiments of the application are further described below with reference to the accompanying drawings.

[0022] The application discloses a method for constructing a constitutive model of a high polymer material for packaging after temperature and humidity aging acceleration, which comprises the following steps, please refer to Figure 1 the flow chart shown in the figure: Step 110, using the encapsulation polymer material to prepare a test sample.

[0023] According to the relevant test standards, the test sample prepared in this application is a sheet-shaped bone rod type tensile member, and the planar structure of a single test sample is as shown in Figure 2 The test sample includes a parallel reduction section 210 and clamping sections 220 located at both ends of the length direction of the parallel reduction section 210, and the middle part of the parallel reduction section 210 has a gauge length, and the length of the parallel reduction section 210 is greater than the length of the gauge length, and the effective plastic deformation and the final fracture should occur in the parallel reduction section 210. The width of the clamping section 220 is greater than that of the parallel reduction section 210 to ensure firm clamping in the clamp, and the connection between the parallel reduction section 210 and the clamping section 220 is through a circular arc section to reduce stress concentration and prevent the test sample from being broken near the clamp. The dimensions of each part of the test sample are designed according to the actual situation, and in one embodiment, as shown in Figure 2 The thickness of the test sample is 1.5±0.02mm, the length of the test sample is 25mm, the width of the clamping section 220 is 4mm, and the length is 4.9mm. The length of the gauge length is 8.5+0.5mm, the length of the parallel reduction section 210 is 10±0.2mm, and the width of the parallel reduction section 210 is 1.5±0.02mm. The circular arc section between the parallel reduction section 210 and the clamping section 220 has a circular corner radius of 3mm.

[0024] In one embodiment, the method for preparing the test sample includes: first using an injection molding machine and a mold process to form a sample semi-finished product on the surface of a substrate using the encapsulation polymer material, and then separating the sample semi-finished product from the surface of the substrate and cutting to obtain a test sample with a structure as shown in Figure 2 The substrate used here is, for example, an aluminum plate, and laser cutting process can be used when cutting.

[0025] Step 120, carrying out an activation energy calculation test on the test sample to determine the activation energy of the encapsulation polymer material under the temperature and humidity accelerated stress .

[0026] A set of activation energy calculation tests on the test sample includes: first carrying out a HAST test (highly accelerated stability test) on the test sample, and then carrying out a quasi-static tensile test to obtain the test sample to obtain the fracture strength test value under the current activation energy calculation test. In order to avoid accidents and improve the accuracy of the obtained fracture strength test value, when a set of activation energy calculation tests are carried out on the test sample, a step test method is used, which includes: According to the test requirements, set the temperature and humidity conditions of the HAST test, which can be set according to conventional experience. The absolute temperature and relative humidity of the HAST test are then set, and then a plurality of test samples are subjected to HAST tests under the corresponding temperature and humidity conditions. Initialize the variable , and the HAST test reaches Take out the first The quasi-static tensile test was conducted on the first test sample to determine the... The fracture strength of one test sample was determined, and the remaining test samples underwent HAST testing. The process is repeated until the current activation energy calculation test is completed. Finally, the average fracture strength of all multiple test samples is calculated to obtain the fracture strength test value of the test sample under the current activation energy calculation test. The test time for a single group can be customized, for example, set to 10 hours. Each test sample taken in sequence undergoes a HAST test under the same temperature and humidity conditions, but the test time is different. The test parameters for the quasi-static tensile test are the same for each test sample. The ambient temperature, humidity and tensile rate for the quasi-static tensile test can be customized.

[0027] For example, in one instance, multiple test samples were subjected to HAST tests under corresponding temperature and humidity conditions of 85°C and 85%RH. After 10 hours of HAST testing, the first test sample was removed and subjected to a quasi-static tensile test at an ambient temperature and humidity of 25°C and 65%RH at a tensile rate of 0.03 mm / s. The stress-strain curve of the test sample was obtained as shown in the figure. Figure 3 As shown in the figure, the fracture strength of the test sample is 42 MPa.

[0028] In the above process, after each quasi-static tensile test is conducted on the test sample, the first... The fracture strength of the first test sample is compared with the fracture strength of the second test sample. If the deviation between the fracture strength of one test sample and the fracture strength of the first test sample does not reach the deviation threshold, it is determined that the current activation energy calculation test has not been completed. And then repeat the above process for the next operation. When the first one is retrieved... When the deviation between the fracture strength of each test sample and the fracture strength of the first test sample reaches a deviation threshold, the current activation energy calculation test is considered complete. The fracture strength test value of the test sample under the current activation energy calculation test is calculated, and the cumulative duration of the HAST test at this time is recorded. The deviation threshold here can be customized.

[0029] Following the above process, multiple sets of activation energy calculation tests were conducted on the test samples to obtain the fracture strength values ​​of the test samples under each set of activation energy calculation tests. The temperature and humidity conditions of the HAST test in any two sets of activation energy calculation tests were different, while the test parameters of the quasi-static tensile test in each set of activation energy calculation tests were the same. The test parameters of the quasi-static tensile test included ambient temperature and humidity and tensile rate. In one example, two sets of activation energy calculation tests were conducted on the test samples. In the first set of activation energy calculation tests, the absolute temperature of the HAST test was 85℃ and the relative humidity was 85%RH. In the second set of activation energy calculation tests, the absolute temperature of the HAST test was 130℃ and the relative humidity was 85%RH. The ambient temperature and humidity of the quasi-static tensile test in both sets of activation energy calculation tests were 25℃ and 65%RH, and the tensile rate was 0.03 mm / s. The relationship between the test time of the HAST test and the corresponding fracture strength of each test sample taken sequentially from the two sets of activation energy calculation tests is as follows: Figure 4 As shown. The final fracture strength test value of the test sample under the first set of activation energy calculation tests was determined to be 34.7 MPa, and the fracture strength test value of the test sample under the second set of activation energy calculation tests was 16.7 MPa.

[0030] After completing multiple sets of activation energy calculation tests, the fracture strength test values ​​of the test samples under these tests can be obtained, and the temperature and humidity conditions of the HAST test in each set of activation energy calculation tests can be determined. Then, based on the temperature and humidity accelerated aging model and the fracture strength test values ​​of the test samples under the multiple sets of activation energy calculation tests, the activation energy of the encapsulation polymer material under temperature and humidity accelerated aging stress can be determined. .

[0031] The temperature and humidity acceleration model takes the following form: (1) in, It is the expiration time. It is the activation energy, and its unit is electron volt. It is Boltzmann's constant. The unit is electron volts per Kelvin. It is absolute temperature and the unit is Kelvin. It refers to relative humidity. These are known parameters, parameters for different chemical reactions. The values ​​can be different and can be pre-calibrated. The parameters are known and .

[0032] Taking the logarithm of both sides of the temperature and humidity acceleration model in equation (1) yields: (2) by For independent variable, As the dependent variable, equation (2) can be viewed as a function with a slope of The two-variable linear equation is then solved by substituting the fracture strength test values ​​of the test sample under each set of activation energy calculation tests into the equation. Substituting the absolute temperature of the HAST experiment into the current activation energy calculation experiment. Substituting the relative humidity parameter into the HAST experiment in the current activation energy calculation experiment. The activation energy of the encapsulation polymer material under accelerated stress due to temperature and humidity aging can then be calculated. .

[0033] Step 130: Activate the polymer material used for encapsulation under accelerated stress of temperature and humidity aging. Substitute the values ​​into the temperature and humidity acceleration model and combine them with the environmental conditions of the actual working environment to determine the environmental conditions of the test environment.

[0034] The activation energy of the encapsulation polymer material obtained in step 120 under accelerated stress of temperature and humidity aging. Substituting known quantities into the temperature and humidity acceleration model of equation (1), it can be determined that under the experimental environment, there are... , It is the failure time under test conditions. It is the absolute temperature of the test environment. This refers to the relative humidity of the test environment. And determining whether it exists in a real working environment. , This is the failure time under real working conditions. It is the absolute temperature of the real working environment. This refers to the relative humidity of the actual working environment. The actual working environment here refers to the environment in which the test sample is located under actual service conditions, while the test environment refers to the environment in which the test sample is subjected to accelerated testing using aging acceleration methods.

[0035] Based on the specific temperature and humidity aging acceleration requirements, the absolute temperature under the actual working environment can be determined. relative humidity and working hours Based on the HAST testing capabilities, the absolute temperature of the testing environment can be selected. and relative humidity However, the test environment and test duration still need to be determined. .

[0036] To determine the test duration for the test environment , making the acceleration factor We can obtain: (3) Then the already determined , 、 、 Substitute equation (3) to calculate the acceleration factor , and finally determine the test time of the test environment , thus obtaining all the environmental conditions of the test environment including absolute temperature , relative humidity and test time .

[0037] Step 140, carry out HAST test on the test sample according to the environmental conditions of the test environment, including carrying out HAST test on the test sample at the absolute temperature , relative humidity of the test environment and lasting for the test time . Then take out the test sample that has completed the warm and humid aging accelerated HAST test and stand for a predetermined length of time, and carry out tensile test on the test sample to obtain a plurality of stress-strain curves. The standing time can be set by the user, such as the commonly used standing time of 8 hours.

[0038] When carrying out tensile test on the test sample that has completed the warm and humid aging accelerated HAST test, two types of tensile test are included: 1. Quasi-static tensile test under low strain rate test condition including carrying out quasi-static tensile test on the test sample at least at two different tensile rates to obtain quasi-static tensile stress-strain curves at each tensile rate. The environmental temperature and humidity conditions of each quasi-static tensile test are the same but the tensile rates are different. In order to reduce the contingency and improve the data quality, quasi-static tensile test can also be carried out on multiple test samples at the same tensile rate, and the sample data with test error is removed, so as to obtain the quasi-static tensile stress-strain curve with the best data quality at the tensile rate.

[0039] The tensile rate of each quasi-static tensile test can be set by the user. In one example, quasi-static tensile test is carried out on the test sample at two different tensile rates, and the environmental temperature and humidity conditions of the two quasi-static tensile tests are both 25℃ / 65%RH. The tensile rate of one quasi-static tensile test is 0.03mm / s, and the tensile rate of the other quasi-static tensile test is 0.003mm / s. The quasi-static tensile stress-strain curves obtained by the two quasi-static tensile tests are shown in Figure 5 .

[0040] 2. Hopkinson test under high strain rate test condition Hopkinson tests are conducted on test samples to obtain Hopkinson stress-strain curves. Similarly, multiple test samples can be subjected to Hopkinson tests at the same tensile rate, and data from samples with experimental errors can be discarded to obtain the Hopkinson stress-strain curves with optimal data quality. The environmental temperature and humidity conditions for Hopkinson tests are generally the same as those for quasi-static tensile tests, typically 25℃ / 65%RH. The tensile rate in Hopkinson tests is much higher than that in quasi-static tensile tests; for example, in one instance, the tensile rate was 2000 mm / s, and the resulting Hopkinson stress-strain curve is as follows... Figure 6 As shown.

[0041] Step 150: Using multiple stress-strain curves, a constitutive model of the encapsulation polymer material after accelerated temperature and humidity aging is obtained by fitting a viscoelastic constitutive model.

[0042] Encapsulation polymers are typically molding compounds with viscoelastic constitutive properties. Therefore, a viscoelastic constitutive model is used to fit the constitutive model of the encapsulation polymer after accelerated temperature and humidity aging. The form of the viscoelastic constitutive model is as follows: (4) in, , , It is the elastic constant of the nonlinear part. These are the elastic constants of the viscoelastic component at low strain rates. It is the relaxation time of the viscoelastic portion under low strain rate. These are the elastic constants of the viscoelastic component under high strain rates. It is the relaxation time of the viscoelastic portion under high strain rate. It is a response. It is a strain The stress under, It is the stretching rate. Indicates time.

[0043] Integrating the viscoelastic constitutive model of equation (5) yields: (5) In the quasi-static tensile test under low strain rate conditions, the high strain rate response term in the integral expression of the viscoelastic constitutive model shown in equation (7) can be ignored, and the integral expression of the viscoelastic constitutive model under low strain rate conditions can be obtained: (6) In the Hopkinson test under high strain rate conditions, the low strain rate response term in the integral expression of the viscoelastic constitutive model shown in equation (7) can be ignored, and the integral expression of the viscoelastic constitutive model under high strain rate conditions can be obtained: (7) Then, by using multiple quasi-static tensile stress-strain curves at different tensile rates according to equation (6), and by using the Hopkinson stress-strain curves at the corresponding tensile rates according to equation (7), the parameters can be fitted to determine the... , , , , , , The values ​​of and specific parameter fitting methods include: At a stretching rate of The strain obtained by quasi-static tensile test Corresponding stress , and at a stretching rate of The strain obtained by quasi-static tensile test Corresponding stress Subtraction yields strain Corresponding stress difference Then, different strains were applied. Corresponding stress difference By fitting the parameters according to equation (6), we can obtain... and The possible values ​​of , where, The specific parameter fitting method can be the least squares method.

[0044] Then the fitted determination and Substitute the value of into equation (6), and perform parameter fitting based on the quasi-static tensile stress-strain curve at one of the tensile rates, for example, using the tensile rate The quasi-static tensile stress-strain curve is fitted to obtain... , , The value of .

[0045] Then the fitted determination , , and Substituting the value of into equation (7), and obtaining the result based on the Hopkinson stress-strain curve fitting. and The value of .

[0046] It should be noted that the above parameter fitting process takes two quasi-static tensile stress-strain curves and one Hopkinson stress-strain curve as an example. However, those skilled in the art will understand that when more stress-strain curves are included, the above method can be used to combine more stress-strain curves to obtain more accurate parameter values.

[0047] The final determined value of , , , , , , The value of is substituted into the viscoelastic constitutive model (4), and the constitutive model of the high polymer material after temperature and humidity aging acceleration for packaging can be obtained.

[0048] The above only describes the preferred embodiments of the present application, and the present application is not limited to the above embodiments. It can be understood that other improvements and changes directly derived or thought by those skilled in the art without departing from the spirit and concept of the present application should be considered to be included in the protection scope of the present application.

Claims

1. A method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging, characterized in that, The method for constructing the constitutive model of the encapsulation polymer material after accelerated temperature and humidity aging includes: Experimental samples were prepared using encapsulation polymer materials; Activation energy calculation experiments were conducted on the test samples to determine the activation energy of the encapsulation polymer material under accelerated stress of temperature and humidity aging. ; Activation energy of encapsulation polymer materials under accelerated stress of temperature and humidity aging Substitute the temperature and humidity acceleration model into the actual working environment and determine the environmental conditions of the test environment. After conducting HAST tests on the test samples according to the environmental conditions of the test environment and letting them stand for a predetermined time, tensile tests were carried out on the test samples to obtain multiple stress-strain curves. The constitutive model of the encapsulation polymer material after accelerated temperature and humidity aging was obtained by fitting multiple stress-strain curves based on a viscoelastic constitutive model.

2. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 1, characterized in that, Activation energy calculation experiments were conducted on the test samples to determine the activation energy of the encapsulation polymer material under accelerated stress of temperature and humidity aging. include: Multiple activation energy calculation tests were conducted on the test samples. When conducting each activation energy calculation test on the test samples, the HAST test was conducted on the test samples first, followed by the quasi-static tensile test to obtain the fracture strength test value of the test samples under the current activation energy calculation test. The temperature and humidity conditions of the HAST test were different in any two sets of activation energy calculation tests. Based on the temperature and humidity accelerated aging model, the fracture strength test values ​​of the test samples under multiple activation energies were calculated to determine the activation energy of the encapsulation polymer material under temperature and humidity accelerated aging stress. .

3. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 2, characterized in that, Determine the activation energy of the polymer material used for packaging under accelerated stress of temperature and humidity aging. include: Accelerated model of temperature and humidity Taking the logarithm of both sides and transforming to obtain ;in, It is the expiration time. It is activation energy. It is Boltzmann's constant. It is absolute temperature. It refers to relative humidity. and These are known parameters; Substitute the fracture strength test value of the test sample under each group of activation energy calculation tests into... Substituting the absolute temperature of the HAST experiment into the current activation energy calculation experiment. Substituting the relative humidity parameter into the HAST experiment in the current activation energy calculation experiment. The activation energy of the encapsulation polymer material under accelerated stress due to temperature and humidity aging was obtained by solving the problem. .

4. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 2, characterized in that, The test samples were subjected to HAST tests followed by quasi-static tensile tests to obtain the fracture strength values ​​of the test samples under the current activation energy calculation conditions. HAST tests were conducted on multiple test samples under corresponding temperature and humidity conditions, and variables were initialized. In the HAST experiment, Take out the first The quasi-static tensile test was conducted on the first test sample to determine the... The fracture strength of each test sample, let The calculation is repeated until the current activation energy test is completed. The average fracture strength of all test samples is then taken to obtain the fracture strength test value of the test sample under the current activation energy test. This refers to the duration of a single test group.

5. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 4, characterized in that, Determining whether the current activation energy calculation experiment has been completed includes: When the first one is taken out If the deviation between the fracture strength of one test sample and the fracture strength of the first test sample does not reach the deviation threshold, it is determined that the current activation energy calculation test has not been completed. And again, the HAST test was performed to achieve... Take out the first The quasi-static tensile test was conducted on the first test sample to determine the... The steps for determining the fracture strength of a test sample; When the first one is taken out When the deviation between the fracture strength of the first test sample and the fracture strength of the second test sample reaches the deviation threshold, the current activation energy calculation test is considered complete.

6. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 3, characterized in that, The environmental conditions for determining the test environment, based on the actual working environment conditions, include: Activation energy of encapsulation polymer materials under accelerated stress of temperature and humidity aging Substitute these known quantities into the temperature and humidity acceleration model; Determine the absolute temperature of the test environment. and relative humidity And combined with the absolute temperature of the real working environment and relative humidity The acceleration factor was calculated based on the temperature and humidity acceleration model. ; According to the acceleration factor and real working hours in a real work environment Determine the test time for the test environment. The environmental conditions for obtaining the test environment include absolute temperature. relative humidity and test time .

7. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 1, characterized in that, Tensile tests were conducted on the test samples, yielding multiple stress-strain curves, including: Quasi-static tensile tests were conducted on the test samples at at least two different tensile rates to obtain multiple quasi-static tensile stress-strain curves; and Hopkinson tests were conducted on the test samples to obtain Hopkinson stress-strain curves.

8. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 7, characterized in that, The constitutive model of the encapsulation polymer material after accelerated temperature and humidity aging was obtained by fitting multiple stress-strain curves based on a viscoelastic constitutive model, including: For viscoelastic constitutive models Integral expression ;in, , , It is the elastic constant of the nonlinear part. These are the elastic constants of the viscoelastic component at low strain rates. It is the relaxation time of the viscoelastic portion under low strain rate. These are the elastic constants of the viscoelastic component under high strain rates. It is the relaxation time of the viscoelastic portion under high strain rate. It is a response. It is a strain The stress under, It is the stretching rate. Indicates time; Ignoring the high strain rate response term in the integral expression of the viscoelastic constitutive model, multiple quasi-static tensile stress-strain curves are used according to... Parameter fitting was performed, and, ignoring the low strain rate response term in the integral expression of the viscoelastic constitutive model, the Hopkinson stress-strain curve was used to... Perform parameter fitting to determine , , , , , , The value of is taken and substituted into the viscoelastic constitutive model to obtain the constitutive model of the polymer material for packaging after accelerated temperature and humidity aging.

9. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 8, characterized in that, Sure , , , , , , The possible values ​​include: At a stretching rate of The strain obtained by conducting quasi-static tensile tests Corresponding stress , and at a stretching rate of The strain obtained by conducting quasi-static tensile tests Corresponding stress Subtraction yields strain Corresponding stress difference For different strains Corresponding stress difference according to Fitting and The possible values ​​of , where, ; Will and Substitute the value In the middle, and based on the fitting of the quasi-static tensile stress-strain curve, it is obtained , , The value of ; Will , , and Substitute the value And based on the Hopkinson stress-strain curve fitting, it was obtained and The value of .

10. The method for constructing a constitutive model of a polymer material for encapsulation after accelerated temperature and humidity aging according to claim 1, characterized in that, The preparation of test samples using encapsulation polymers includes: A sample semi-finished product is formed on the surface of a substrate using an injection molding machine and compression molding process with a polymer material for packaging. The sample semi-finished product is separated from the substrate surface and cut into a thin sheet-like test sample. The test sample includes a parallel reduction section and clamping sections located at both ends of the parallel reduction section along its length. The width of the clamping section is greater than that of the parallel reduction section, and the parallel reduction section and the clamping section are connected by an arc segment.

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