Test device and method for hard polymer encapsulation stress under constrained conditions

Abstract

The application discloses a testing device and method for hard polymer packaging stress under limited constraint structure. The device adopts a structure form of rigid structure covering hard polymer, flexible and deformable parts are designed in the local part of the rigid structure, a limited constraint structure is constructed, and the formation process of stress of the hard polymer in the curing process and under high and low temperature environments is reflected by monitoring the mechanical strain of the position of the measuring point. Meanwhile, the device takes the cylinder as a medium layer, ensures that the sensor and the hard polymer in the flowing state are not directly contacted, reduces the interaction between the sensor and the hard polymer, and thus reduces the interference signal in the testing process. The method deducts the influence of heat output in the strain testing, obtains accurate mechanical strain results, and improves the analysis precision of the hard polymer packaging stress. The application is suitable for electronic packaging stress analysis with the constraint degree between two-dimensional constraint and three-dimensional constraint, the testing method is simple and easy to implement, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electronic packaging, and particularly relates to a testing device and method for hard polymer packaging stress under restricted constraint structure. BACKGROUND

[0002] In reliability and temperature adaptability analysis of electronic products, the evaluation of hard polymer packaging stress is an important content. The packaging stress of hard polymer includes curing residual stress and thermal stress. The curing process of hard polymer is a complex phase change process from liquid to solid, which usually needs high temperature conditions. During the curing process, the chemical reaction shrinkage of hard polymer will generate shrinkage stress, and at the same time, due to the mismatch of thermal expansion coefficients between hard polymer and electronic product or supporting structure material, thermal stress will be formed during the temperature change process of the curing program. The sum of the chemical shrinkage stress and the thermal stress during the curing process is the curing residual stress of the hard polymer. If the temperature of the electronic product changes during use or storage, additional thermal stress will be generated, which will be superimposed with the curing residual stress. If the superimposed stress is too large, it will easily lead to performance cracking, electrical parameter drift, etc. of the electronic product, and even cause cracking or delamination of the packaging interface of the packaging material, solder joint or brittle materials (such as ceramics, silicon, etc.) in the electronic product, resulting in damage to the functional materials or interconnection structure of the electronic product; the cracking, delamination and other damages caused by the superimposed stress will also make the packaging structure vulnerable to environmental factors such as oxygen and water vapor, causing premature environmental-induced performance degradation failure. Therefore, the measurement of hard polymer packaging stress is very important for controlling packaging stress and reducing the risk of stress-induced failure.

[0003] During the curing reaction process of hard polymer, it will go through three phase state stages of transformation from viscous flow state to high-elastic state, and then from high-elastic state to glass state. Except that the viscous flow state does not form stress, both high-elastic state and glass state can form curing residual stress. The glass state Young's modulus and bulk modulus of hard polymer can reach GPa level, while the bulk modulus of high-elastic state reaches GPa level, and the Young's modulus is about 2 orders of magnitude lower. Based on the theory of elasticity, it can be analyzed that the packaging stress in one-dimensional and two-dimensional constraint structures is determined by the Young's modulus, and the packaging stress in three-dimensional constraint structure is determined by the bulk modulus. Therefore, the formation of packaging stress in high-elastic state stage has a strong structure constraint dependence. In one-dimensional and two-dimensional constraint structures, the curing chemical shrinkage and thermal expansion of hard polymer in high-elastic state only form weak stress, which can be ignored compared with the glass state thermal stress; while in three-dimensional constraint structure, the expansion or shrinkage of hard polymer in high-elastic state can form relatively significant stress, and the stress formation rate per unit temperature is even higher than that of glass state.

[0004] In addition to the above-mentioned ideal one-dimensional, two-dimensional and three-dimensional constraint structure forms, there is a constraint state between weak three-dimensional constraint and strong three-dimensional constraint, namely non-restricted constraint structure. This type of structure is a structure in which a hard polymer is wrapped with an electronic product or a structural material that does not match the thermal expansion coefficient, the expansion and contraction of the hard polymer is inhibited to a certain extent, and the free deformation is difficult. Typical restricted constraint structures include: electronic module potting with metal shell, impregnation or potting of metal coil winding forming structure, interlayer filling of multilayer stacked substrate containing ceramic-based devices, and bonding of non-planar adhesive joints. In the restricted constraint structure, not only is the high-elasticity stress formed significantly, but also the total solidification residual stress and thermal stress level is usually high. Various stress-induced failures can occur during the initial solidification shrinkage, solidification cooling stage and low temperature environmental conditions. Therefore, the stress regulation of the entire solidification process in the design of the restricted constraint structure packaging process is crucial. In particular, as the integration of electronic devices continues to improve, the packaging size continues to decrease, and the degree of constraint of the packaging structure gradually changes from two-dimensional constraint to three-dimensional constraint. For electronic packaging with high constraint degree, it is of great application value to develop a restricted constraint structure packaging stress measurement device and method.

[0005] However, the current restricted constraint structure packaging stress measurement faces the following two main problems:

[0006] First, the measurement device must be constructed in an intermediate state between two-dimensional constraint and three-dimensional constraint. The current reported hard polymer packaging stress measurement methods usually do not analyze and define the structural constraint of the measurement device, resulting in large differences in stress measurement results of different methods and often contradictory stress formation mechanisms. The electronic packaging industry usually uses a double-layer material configuration of depositing a thin layer of hard polymer on the surface of a thin layer of inorganic substrate to analyze packaging stress. This configuration is a two-dimensional constraint, which cannot effectively form high-elasticity stress and has a low packaging stress level. The stress mechanism research literature proposes a packaging stress test configuration of filling hard polymer in a closed metal ball or a tube with extremely high aspect ratio. This configuration aims to construct an ideal three-dimensional constraint, with high-elasticity stress being very large and the test being difficult to implement. However, the structural constraint formed by actual electronic product potting, filling, bonding and other working conditions is more between two-dimensional constraint and three-dimensional constraint, so the stress measurement results of the aforementioned two configurations cannot accurately reflect the packaging stress situation of these working conditions.

[0007] Second, the measuring device must be structured to produce a local structure that can be deformed / strained so that a strain sensor can be used to measure the local mechanical strain changes, which reflect the package stress level. Current stress testing methods are mostly achieved by embedding a strain sensor in a hard polymer matrix or attaching it to the surface of the electronic device structure material in two forms, which is difficult to obtain accurate mechanical strain. For the method of embedding the strain sensor in the hard polymer matrix, the measurement result is the total strain of the measurement object under the test conditions, and the mechanical strain can be obtained by deducting the non-mechanical strain (defined as thermal output) from the total strain. The composition of the thermal output includes solidification shrinkage strain and thermal expansion strain, both of which change with the reaction degree, temperature, time, etc. The embedded sensor is affected by the complex phase change and temperature change during the solidification process of the hard polymer, and it is difficult to evaluate the thermal output, so the mechanical strain cannot be obtained. For the method of attaching the strain sensor to the surface of the structural material, since the stiffness of the electronic device structure material is usually much greater than that of the hard polymer itself, the mechanical strain caused by the package stress is generally small (for example, <200με), which causes the regularity in the test results to be masked by the error signal.

[0008] Therefore, for electronic packaging applications such as pouring, filling, bonding, etc., which have a structure constraint between two-dimensional and three-dimensional constraints, it is necessary to develop a hard polymer package stress testing device and method with a limited constraint structure feature and a significant strain local structure, which is simple and easy to use, to accurately reflect the package stress during the solidification shrinkage, high-elasticity temperature change, and glass- state temperature change. SUMMARY

[0009] Therefore, for electronic packaging applications such as pouring, filling, bonding, etc., which have a structure constraint between two-dimensional and three-dimensional constraints, it is necessary to develop a hard polymer package stress testing device and method with a limited constraint structure feature and a significant strain local structure, which is simple and easy to use, to accurately reflect the package stress during the solidification shrinkage, high-elasticity temperature change, and glass- state temperature change.

[0010] The device adopts a rigid structure to cover the hard polymer, and uses flexible and easily deformed parts in the local structure, so as to construct a limited constraint on the hard polymer and form a strain measuring point with significant mechanical strain, reflect the limited constraint structure package stress to the deformation of the flexible and easily deformed part, and at the same time realize the physical isolation of the sensor and the hard polymer, thereby reducing the test interference and realizing the simple and accurate measurement of the mechanical strain; based on the linear relationship between the mechanical strain and the stress, the formation process of the package stress is reflected through the evolution process of the mechanical strain.

[0011] To achieve the above object, the application provides a test device for hard polymer packaging stress under limited constraint structure, which comprises a base, a cylinder, a metal sheet, a strain sensor and a temperature sensor.

[0012] The base is a stepped hollow structure.

[0013] The cylinder is a hollow cylinder, one end of which is fixedly connected with the base.

[0014] The metal sheet is located at the connecting position of the base and the cylinder, and the metal sheet and the cylinder enclose a cavity for filling hard polymer packaging material.

[0015] The strain sensor and the temperature sensor are arranged on the surface of the metal sheet which does not contact with the hard polymer packaging material.

[0016] Preferably, the thickness of the metal sheet is 0.5-1.0 mm.

[0017] Preferably, the base, the cylinder and the metal sheet are made of aluminum alloy.

[0018] Preferably, the strain sensor and the temperature sensor are arranged adjacently in pairs.

[0019] Preferably, the strain sensor and the temperature sensor are arranged at the central position of the metal sheet.

[0020] Preferably, the temperature sensor is a thermocouple.

[0021] Preferably, the strain sensor is any one of a strain sheet, a strain rosette and a fiber Bragg grating sensor.

[0022] Preferably, the temperature sensor is fixed by polyimide tape, and the strain sensor is fixed by glue.

[0023] The application provides a test method for hard polymer packaging stress under limited constraint structure, which is based on the above test device and comprises testing of hard polymer packaging material curing residual stress and testing of hard polymer packaging material packaging thermal stress.

[0024] (I) The testing of hard polymer packaging material curing residual stress is as follows:

[0025] S1-1: Paste the strain sensor and the temperature sensor at the central position of the metal sheet.

[0026] S1-2: Place the metal sheet with the attached strain sensor and temperature sensor in the environmental test chamber, and zero the strain sensor at room temperature T0; start the temperature control of the environmental test chamber, first cool down and then warm up, and in the whole process, collect the strain ε(t) and temperature data T(t) of the metal sheet at different time t by using the strain sensor and the temperature sensor; fit the strain ε(t) and temperature data T(t) to obtain the functional relationship ε(T) between the strain ε(t) and the temperature T(t) of the metal sheet, and draw the thermal output temperature curve with the abscissa as T(t) and the ordinate as ε(t). i i,rsc i i i i,rsc i i i i,rsc i i i i,rsc i i i i,rsc i

[0027] S1-3: Assemble the metal sheet in S1-1 with the base and the cylinder, and fill the hard polymer packaging material in the hollow part of the cylinder;

[0028] S1-4: Start the temperature control of the environmental test chamber, and perform the curing process of the hard polymer packaging material, and collect the indicated strain and temperature data of the metal sheet at different time t during the curing process of the hard polymer packaging material. j

[0029] S1-5: Obtain the strain of the metal sheet at different temperature data from the thermal output temperature curve obtained in S1-2 by using the interpolation method.

[0030] S1-6: Calculate the curing residual stress of the hard polymer packaging material:

[0031] (II) The test of the packaging thermal stress of the hard polymer packaging material is as follows:

[0032] First, obtain the thermal output temperature curve and fill the hard polymer packaging material to be tested, and the operation steps are the same as S1-1-S1-3 in the test of the curing residual stress of the hard polymer packaging material.

[0033] ​​​​​​​​​​​​​​​​​​​​​​Then, set high and low temperature cycle conditions, start the temperature control of the environmental test chamber, and perform temperature cycle loading of the hard polymer packaging material. Collect the strain of the metal sheet at different times t j during the high and low temperature cycle test and temperature data

[0034] Then, use interpolation method to obtain the strain of the metal sheet at different temperature data from the heat output temperature curve obtained in S1-2

[0035] Finally, calculate the thermal stress of the hard polymer packaging material to be tested:

[0036] Preferably, S1-2 further includes eliminating the zero drift of the strain sensor when it is first subjected to high and low temperatures, specifically including:

[0037] First, set multiple temperature rising and falling cycles, and collect strain data and temperature data during the temperature rising and falling process. Record the starting time and ending time of the last temperature rising cycle as t k and t l , respectively.

[0038] Next, after the temperature rising and falling cycle is completed, the temperature is restored to room temperature T0 and is kept for a certain period of time. Record the ending time of the keeping as t n .

[0039] Then, use the strain data ε i,rsc (t i ) and temperature data T i (t i ) collected in the time period t k ~ t l to calculate the functional relationship ε i,rsc (T i ) between the strain ε i,rsc (t i ) and the temperature T i (t i ).

[0040] Finally, take the strain at the ending time t n of the keeping as the strain zero point ε n,rsc (t n ), and correct the functional relationship ε i,rsc (T i ) to obtain the functional relationship between the corrected strain ε i,rsc (t i ) and the temperature T i (t i ): ε i ′ ,rsc(T i ) = ε i,rsc (T i ) - ε n,rsc (t n ), and a heat output temperature curve is plotted according to the corrected function relationship.

[0041] The beneficial effects of the present application are: the test device and method for testing the stress of hard polymer encapsulation under limited constraint structure disclosed by the present application: (1) by designing a rigid structure, the structure form of pouring encapsulation material in a thick-walled sleeve, using the characteristics of large rigidity and low expansion coefficient of the thick-walled sleeve, simulating the scene that the deformation of high-temperature expansion and low-temperature shrinkage of polymer encapsulation material is strongly suppressed, that is, forming the characteristics of three-dimensional limited constraint structure; (2) by designing a flexible and variable part that is well bonded with the encapsulation material, that is, a metal sheet, the deformation of hard polymer encapsulation material during solidification and the thermal expansion and contraction deformation under high and low temperature environment are reflected on the metal sheet, and the measurement of hard polymer solidification residual stress and thermal stress is realized by monitoring the mechanical strain of the metal sheet, in addition, by adjusting the thickness of the metal sheet, the problem of strain level observation can be realized; (3) using the metal sheet as a medium layer, the sensor is pasted to the outer surface of the metal sheet, which ensures that the sensor and the flowing hard polymer do not directly contact, and the monitoring of the hard polymer solidification strain evolution process can be realized, and the influence of hard polymer on the sensor test signal is avoided; (4) the method proposed by the present application excludes the influence of heat output in strain measurement, the strain sensor and the temperature sensor are pasted to the outside of the metal sheet, and the heat output data of the strain sheet is obtained through the experiment in the unencapsulated state, then the heat output data is deducted from the indicated strain of the strain sensor in the solidification process and the high and low temperature environment, so as to obtain the mechanical strain of the measuring point, and the influence of temperature factor on stress test is excluded.

[0042] The test device and method provided in the present application have the following uses: (1) for hard polymer material analysis, using the method described in the present application, the packaging stress of different types and different performance packaging materials under limited constraint structure can be obtained, and the quantitative basis for packaging material selection can be obtained without complicated material performance analysis; (2) for hard polymer packaging process parameter analysis, using the method described in the present application, the influence of different curing procedures, temperature change rates and other parameters on the packaging stress can be compared, so as to optimize the parameter design and reduce the packaging stress; (3) for hard polymer packaging stress formation mechanism research, using the method described in the present application, the formation and evolution data of the curing residual stress and thermal stress of the limited constraint structure can be obtained, which supports the stress formation mechanism analysis; (4) for hard polymer stress simulation model checking, using the method described in the present application, the packaging stress evolution data of the limited constraint structure covering the gelation stage, the high-elasticity temperature rising and falling stage and the glass state temperature rising and falling stage can be obtained, which supports the verification of the stress simulation model precision; (5) for release agent selection and process research, using the method described in the present application, by coating the release agent on the side of the flexible variable part (i.e. metal sheet) contacting the hard polymer, and measuring the stress condition causing delamination, the quantitative basis for release agent selection and process research can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 It is a structural schematic diagram of the hard packaging material curing residual stress test device of the limited constraint structure in the present application.

[0044] Figure 2 It is a top view of the hard packaging material curing residual stress test device of the limited constraint structure in the present application.

[0045] Figure 3 It is a top view of the hard packaging material curing residual stress test device of the limited constraint structure in the present application. Figure 2 It is a sectional view of the A-A plane of the top view of the hard packaging material curing residual stress test device of the limited constraint structure in the present application.

[0046] Wherein: 1, base; 2, thick-walled sleeve; 3, metal sheet; 4, hard polymer packaging material; 5, strain sensor; 6, temperature sensor.

[0047] Figure 4 It is a typical test result of the hard polymer curing residual stress measurement under the limited constraint structure in the embodiment of the present application. DETAILED DESCRIPTION

[0048] Those skilled in the art will appreciate that the embodiments described herein are presented for the purpose of aiding the reader in understanding the principles of the present application and should be construed as not limiting the scope of the present application to such specifically recited embodiments and examples. Those skilled in the art can make various other specific modifications and combinations according to the technical spirit disclosed in the present application without departing from the scope of the present application, and such modifications and combinations are still within the scope of the present application.

[0049] The present application will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0050] The testing device for residual stress of hard polymer encapsulation under restricted constraint structure proposed in the present application, referring to Figures 1-3 , comprises a base 1, a cylinder 2, a metal sheet 3, a hard polymer encapsulation material 4, a strain sensor 5 and a temperature sensor 6, wherein the base 1 is a stepped hollow structure and is located at the bottom end, the cylinder is a hollow cylindrical thick-walled sleeve, and the hard polymer is encapsulated inside during testing, the metal sheet 3 is in a sheet structure and is located at the connecting position of the base 1 and the cylinder 2, the metal sheet 3 and the cylinder 2 form a restricted constraint structure for encapsulating the hard polymer encapsulation material 4, and the strain sensor 5 and the temperature sensor 6 are arranged on the surface of the metal sheet 3 which does not contact the hard polymer encapsulation material.

[0051] The principle of the testing device and method for residual stress of hard polymer encapsulation under restricted constraint structure is as follows: considering the phase change of hard polymer during the curing process and the difficulty of directly pasting strain gauges for strain measurement, the chemical shrinkage deformation characteristics of hard polymer during the curing process and the mismatching characteristics of the thermal expansion coefficient between hard polymer and metal material are utilized, and the first constraint structure surrounded by the thick-walled cylinder and the metal sheet is designed according to the characteristics of small rigidity and easy deformation of the metal sheet, the deformation of the hard polymer is reflected on the deformation of the metal sheet, during the curing process and in the low-temperature environment, the chemical shrinkage and thermal shrinkage of the hard polymer occur, the thermal expansion coefficient of the hard polymer is much larger than that of the metal material, the hard polymer shrinks inward during the curing shrinkage and the cooling process, the compression strain is generated on the outer surface of the metal sheet, and the hard polymer expands outward during the heating process, the tensile strain is generated on the metal sheet, so that the residual stress of the hard polymer during the curing process is tested by measuring the strain of the metal sheet.

[0052] According to the test principle of the strain sensor, the device and method also consider the influence of the thermal output of the strain sensor. The indicated strain of the strain sensor is related to the mechanical strain and temperature of the measuring point, wherein only the mechanical strain reflects the size of the residual stress and the thermal induced stress, and the strain after deducting the strain related to the temperature, i.e. the thermal output, is the mechanical strain. The method provided in the application realizes the deduction of the influence of the thermal output in the mechanical stress test, which firstly pastes the strain sensor to the outer side of the metal sheet, and obtains the thermal output data of the strain sheet through the experiment in the unpackaged state, and then deducts the thermal output data from the indicated strain of the strain sensor in the solidification process and the high and low temperature environment, so as to obtain the mechanical strain of the measuring point.

[0053] As an example, the metal sheet 3 is in the form of a sheet, and the thickness is 0.6mm-1.0mm. If the strain is too small in the test, the wall thickness can be appropriately reduced to reduce the rigidity of the metal sheet, so as to ensure that the deformation of the metal sheet in the solidification process reaches the measurable order of magnitude of the strain sheet. Otherwise, the wall thickness can be appropriately increased to reduce the risk of plastic deformation of the metal sheet.

[0054] As an example, the base, the cylinder and the metal sheet are made of aluminum alloy, and can also be made of other metals with a thermal expansion coefficient smaller than that of the hard polymer.

[0055] As an example, the strain sensor and the temperature sensor are arranged in pairs adjacent to each other and at the center position of the metal sheet, wherein the temperature sensor is pasted by using a high and low temperature resistant adhesive tape, preferably a polyimide adhesive tape, and the strain sensor is fixed by using a high and low temperature resistant adhesive.

[0056] As an example, the type of the sensing device can be selected according to actual needs. For example, the temperature sensor can be selected as a thermocouple; the strain sensor can be selected as a strain sheet or a fiber Bragg grating sensor, and can also be selected as a strain rosette, multiple strain sheets or multiple fiber Bragg grating sensors.

[0057] As an example, FBG (fiber Bragg grating) can be used to replace the thermocouple and the resistance strain sheet to collect the strain and temperature signals, and the interpretation of the strain and temperature signals can be based on the working principle of the FBG.

[0058] In another preferred embodiment, a compensation sheet method (the compensation sheet can be pasted on a non-expanding alloy or a compensation block with the same material as the measuring point) can be used.

[0059] The test method for the packaging stress of the hard polymer under the limited constraint structure provided in the application is based on the above-mentioned test device, and the method includes the test of the solidification residual stress of the hard polymer packaging material and the test of the thermal induced stress of the hard polymer packaging material.

[0060] (a) The test results for residual stress after curing of rigid polymer encapsulation materials are as follows:

[0061] S1-1: Attach the strain sensor and temperature sensor to the center of the metal sheet;

[0062] S1-2: Place the metal sheet containing the strain sensor and temperature sensor in an environmental test chamber and zero the strain sensor at room temperature (T0). Start the temperature control of the environmental test chamber, first cooling and then heating. Throughout the process, use the strain sensor and temperature sensor to collect data on the metal sheet at different times (t). i strain ε i,rsc (t i ) and temperature data T i (t i ); utilizing strain ε i,rsc (t i ) and temperature data T i (t i The strain ε of the metal sheet was obtained by fitting. i,rsc (t i ) and temperature T i (t i The functional relationship between ε i,rsc (T i ), and with the x-axis as T i (t i ), with the ordinate being ε i,rsc (t i Plot the heat output temperature curve;

[0063] As another embodiment, the above process can also eliminate zero-point drift caused by the strain sensor when it first experiences high and low temperatures, specifically including:

[0064] First, multiple heating and cooling cycles were set up, and strain and temperature data were collected during the heating and cooling processes. The start and end times of the last heating cycle were recorded as t1 and t2, respectively. k and t l ;

[0065] Next, after the heating and cooling cycle is completed, the temperature is restored to room temperature T0 and held at that temperature. The end time of the holding period is recorded as t. n ;

[0066] Then, using the time period t k ~t l Strain ε collected internally i,rsc (t i ) and temperature data T i (t i The strain ε was calculated. i,rsc (t i ) and temperature T i (ti ) between the function relationship ε i,rsc (T i );

[0067] Finally, the strain at the end of the heat preservation time t n is taken as the strain zero point ε n,rsc (t n ), and the function relationship ε i,rsc (T i ) is corrected to obtain the function relationship between the corrected strain ε i,rsc (t i ) and the temperature T i (t i ): ε i ′ ,rsc (T i ) = ε i,rsc (T i ) - ε n,rsc (t n ), and the heat output temperature curve drawn according to the corrected function relationship.

[0068] S1-3: Assemble the metal sheet in S1-1 with the base and the cylinder, and fill the hard polymer packaging material in the hollow part of the cylinder;

[0069] S1-4: Start the temperature control of the environmental test chamber, perform the curing process of the hard polymer packaging material, and collect the indicated strain and temperature data of the metal sheet at different time tj during the curing process of the hard polymer packaging material

[0070] S1-5: Obtain the strain of the metal sheet at different temperature data from the heat output temperature curve obtained in S1-2 by using the interpolation method

[0071] S1-6: Calculate the curing residual stress of the hard polymer packaging material:

[0072] (II) The test of the packaging thermal stress of the hard polymer packaging material is as follows:

[0073] First, obtain the heat output temperature curve and fill the hard polymer packaging material to be tested, and the operation steps are the same as S1-1-S1-3 in the test of the curing residual stress of the hard polymer packaging material.

[0074] Then, set the high-low temperature cycle conditions, start the temperature control of the environmental test chamber, perform the temperature cycle loading of the hard polymer packaging material, and collect the indicated strain and temperature data of the metal sheet at different time tj during the high-low temperature cycle test

[0075] Then, using interpolation method, obtain different temperature data from the heat output temperature curve obtained in S1-2 Strain of the metal sheet under

[0076] Finally, calculate the thermal stress of the hard polymer to be measured:

[0077] Figure 4 A schematic diagram of the result of measuring the residual stress of the hard polymer cured by using the limited constraint structure in the embodiment of the application.

Claims

1. A test device for hard polymer encapsulation stress under restricted constraint structure, characterized in that, The test device comprises a base, a cylinder, a metal sheet, a strain sensor and a temperature sensor; The base is a stepped hollow structure; The cylinder is a hollow cylinder, one end of which is fixedly connected with the base; The metal sheet is located at the connecting position of the base and the cylinder, and the metal sheet and the cylinder enclose a cavity for filling hard polymer packaging material; the thermal expansion coefficient of the hard polymer is greater than that of the metal sheet; The strain sensor and the temperature sensor are arranged on the surface of the metal sheet which does not contact the hard polymer packaging material.

2. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The thickness of the metal sheet is 0.5mm-1.0mm.

3. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The base, the cylinder and the metal sheet are all made of aluminum alloy.

4. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The strain sensor and the temperature sensor are arranged adjacently in pairs.

5. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The strain sensor and the temperature sensor are arranged at the center position of the metal sheet.

6. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The temperature sensor is a thermocouple.

7. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The strain sensor is any one of a strain gauge, a strain rosette and a fiber Bragg grating sensor.

8. The test device for encapsulation stress of hard polymer under restricted constraint structure according to claim 1, characterized in that, The temperature sensor is fixed by polyimide tape, and the strain sensor is fixed by glue.

9. A method of testing the stress of a hard polymer package under a restricted constraint structure, characterized by, The method is based on the test device of any one of claims 1-8, and the method comprises testing of the curing residual stress of the hard polymer packaging material and testing of the packaging thermal-induced stress of the hard polymer packaging material; (I) The testing of the curing residual stress of the hard polymer packaging material is as follows: S1-1: Paste the strain sensor and the temperature sensor at the center position of the metal sheet; S1-2: Place the metal sheet with the pasted strain sensor and temperature sensor in the environmental test chamber, and zero the strain sensor under room temperature T0 conditions; start the temperature control of the environmental test chamber, first perform temperature reduction and then temperature increase, and collect the strain ε i (t i,rsc ) and temperature data T i (t i ) of the side wall cylinder at different times t i during the whole process by using the strain sensor and the temperature sensor; according to the time synchronization relationship of the strain ε i,rsc (t i ) and the temperature T i (t i ), the curve ε i,rsc (T i ) between the strain ε i (t i ) and the temperature T i,rsc (t i ), i.e. the thermal output temperature curve, can be obtained; S1-3: Assemble the metal sheet in S1-1 with the base and the cylinder, and fill the hard polymer packaging material in the hollow part of the cylinder; S1-4: Start the environmental test chamber temperature control, perform the hard polymer encapsulant curing process, and collect the metal sheet's indicative strain j and temperature data at different times t during the hard polymer encapsulant curing process S1-5: Obtain different temperature data T from the heat output temperature curve obtained in S1-2 using an interpolation method j GH (t j ) of the metal sheet S1-6: Calculate the curing residual stress of the hard polymer encapsulation material: (ii) The encapsulation thermal induced stress of the hard polymer encapsulation material is tested as follows: First, obtain the heat output temperature curve and fill the hard polymer packaging material to be tested, and the operation steps are the same as S1-1-S1-3 in the testing of the curing residual stress of the hard polymer packaging material; Then, set high and low temperature cycle conditions, start the environmental test chamber temperature control, and perform temperature cycle loading of the hard polymer packaging material. The metal sheet at different times t j indicated strain and temperature data Then, using interpolation, different temperature data are obtained from the heat output temperature curve obtained in S1-2 Strain of the metal sheet under Finally, the thermal induced stress of the hard polymer package under test is calculated:

10. The test method for stress in hard polymer encapsulated parts under restrained constraint of claim 9, wherein, The S1-2 further comprises eliminating the zero-point drift of the strain sensor when it is first subjected to high and low temperatures, which specifically comprises: First, a plurality of temperature rising and falling cycles are set, and strain data and temperature data during the temperature rising and falling cycles are collected. The starting time and the ending time of the last temperature rising cycle are recorded as t k and t l , respectively. Then, after the temperature recovery to room temperature T0 and the temperature recovery, record the time t n ; then, using the strain ε k (t l ) and temperature data T i,rsc (t i ) collected in the time period t i ~t i , calculate the functional relationship ε i,rsc (T i ) between the strain ε i (t i ) and the temperature T i,rsc (t i ); Finally, the strain at the end of the holding period t n is used as the strain zero point ε n,rsc (t n ) to correct the function relationship ε i,rsc (T i ) to obtain the function relationship between the corrected strain ε i,rsc (t i ) and the temperature T i (t i ): ε i ′ ,rsc (T i ) = ε i,rsc (T i ) - ε n,rsc (t n ), and a thermal output temperature curve is plotted using the corrected function relationship.

Images