Method for testing elastic modulus in polymer curing process

Abstract

The invention relates to the technical field of polymer elastic modulus testing, in particular to an elastic modulus testing method in a polymer curing process, an uncured sample is prepared by injecting a polymer into a pipe and inserting and sealing a metal wire, the problem that the sample cannot be applied to a quasi-static tensile test can be effectively improved, and the sample preparation and testing problems are solved. Wherein the metal wire not only has a sealing effect, but also provides a clamping area, so that the flowing of the polymer is effectively limited, the test error is reduced, and the clamping precision is improved. By applying the composite material elastic modulus calculation method, the calculation process is simplified. And finally, the curing process and the mechanical property of the polymer are associated from three dimensions of curing degree, curing time and elastic modulus, so that the calculation precision of the curing residual stress is improved, reference and basis are provided for the advanced packaging process of a semiconductor, and the research and development cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of polymer elastic modulus testing technology, and specifically to a method for testing the elastic modulus of a polymer during the curing process. Background Technology

[0002] Polymers are widely used in advanced semiconductor packaging, and accurately measuring the change in elastic modulus during the curing process is crucial for assessing and predicting the state of residual stress. Before the gel point, no residual stress can be generated because the elastic modulus is zero. After the gel point, the polymer viscosity increases rapidly, and the elastic modulus begins to change significantly. Residual stress can directly cause warping deformation of electronic packaging products, and may even generate small defects such as bubbles or cracks, altering mechanical, electrical, thermal, optical, and chemical bonds, thereby affecting the functionality, reliability, thermal performance, and signal integrity of the package.

[0003] Currently, the main methods for testing the elastic modulus of polymers include the following: The first method is the quasi-static tensile test, which applies a uniaxial load to the polymer and measures the slope of the initial elastic stage of the stress-strain curve, which is the elastic modulus. The second method is the compression test, which applies a compressive load to the sample and measures the stress and strain to calculate the elastic modulus. The third method is the nanoindentation test, which is suitable for measuring the mechanical properties of small areas. By applying and removing the load, the load-displacement curve is recorded to calculate the elastic modulus. The relevant standards are GB / T 1040.1-2025, GB / T 1040.2-2022, and GB / T 1040.3-2006. Of the three existing methods, only the first method conforms to the standard method for testing the elastic modulus in macroscopic static mechanics and can reflect the true elastic modulus. Polymers exist in viscous flow, gel, and viscoelastic states during curing, and currently there is no efficient method to accurately test the elastic modulus in these states. Summary of the Invention

[0004] The purpose of this invention is to provide a method for testing the elastic modulus of polymers during the curing process. This method is designed to be applied to different curing processes to determine the elastic modulus of polymers at different curing stages throughout the curing process, thereby solving the problem that existing elastic modulus sample preparation and testing methods are not suitable for accurately determining the elastic modulus of polymers during the curing process.

[0005] To achieve the above objectives, the present invention provides a method for testing the elastic modulus of a polymer during the curing process, comprising the following steps:

[0006] Step 1: Use a differential scanning calorimeter to test the heat release changes during the curing process, normalize the data to obtain the heat flow per unit mass, and statistically analyze the heat flow curve over time.

[0007] Step 2: Integrate the exothermic peak and baseline of the heat flow curve to obtain the heat of reaction, calculate the ratio of the cumulative released heat of reaction to the total released heat of reaction, and obtain the degree of curing at different times;

[0008] Step 3: Insert one end of the customized tubular container into the metal wire for sealing, insert a needle into the other end until it contacts the metal wire, inject the polymer, insert the metal wire again for sealing, and obtain an uncured composite sample;

[0009] Step 4: In a dynamic mechanical analyzer or a universal testing machine with a temperature chamber, use the temperature-time curve of the same curing process in a differential scanning calorimeter, clamp the area where the metal wire has been inserted, and immediately perform a quasi-static tensile test after the time required for the corresponding degree of curing is reached to obtain the stress-strain curve and calculate the elastic modulus of the composite specimen.

[0010] Step 5: Based on the composite material elastic modulus calculation method, combined with the elastic modulus of the composite sample and the known pipe and container, as well as the sample geometry, the elastic modulus of the polymer at different curing degrees is calculated.

[0011] Optionally, the formulas for calculating the heat of reaction and degree of cure in step 2 are as follows:

[0012]

[0013]

[0014] Where α is the degree of curing; ΔH t The integral of the heat flux, i.e., the cumulative heat of reaction released at present; ΔH total This represents the total heat of reaction released.

[0015] Optionally, in step 3, the core material is the polymer to be tested. The composite sample is sealed with metal wires at both ends. The metal wires provide a clamping area to ensure that the test can be performed in either a horizontal or vertical manner.

[0016] Optionally, the timing of the curing process in step 4 corresponds to the degree of curing. The slope of the stress-strain curve at the corresponding timing is the elastic modulus of the composite sample at the corresponding degree of curing. The calculation formula is as follows:

[0017]

[0018] Where E is the elastic modulus of the composite specimen; σ is the stress; ε is the strain; F is the applied force; A is the radial cross-sectional area of ​​the composite specimen; ΔL is the elongation; and L is the gauge length.

[0019] Optionally, the formula for calculating the elastic modulus of the polymer at different degrees of curing in step 5 is as follows:

[0020]

[0021]

[0022] Among them, E total E represents the elastic modulus of the composite specimen. s E represents the elastic modulus of the pipe. c R is the elastic modulus of the core material. s R is the outer radius of the pipe or container. c The core material radius is equal to the inner radius of the pipe.

[0023] This invention provides a method for testing the elastic modulus of a polymer during the curing process. By injecting polymer into a tube and sealing it with a metal wire, an uncured sample is prepared. This effectively addresses the problem that samples cannot be used for quasi-static tensile testing, solving the challenges of sample preparation and testing. The metal wire serves both as a seal and provides a clamping area, effectively restricting polymer flow, reducing testing errors, and improving clamping accuracy. The application of composite material elastic modulus calculation methods simplifies the calculation process. Finally, the polymer curing process is correlated with mechanical properties from three dimensions: degree of curing, curing time, and elastic modulus. This improves the accuracy of calculating residual stress after curing, providing a reference and basis for advanced semiconductor packaging processes and reducing R&D costs. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram illustrating the execution steps of a polymer curing process elastic modulus testing method according to the present invention.

[0026] Figure 2 This is an isometric view of the composite sample in a specific embodiment of the present invention.

[0027] Figure 3 This is a schematic axial cross-sectional view of the composite sample in a specific embodiment of the present invention. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] The following is an explanation of the relevant English terminology:

[0030] Differential scanning calorimeter (DSC): Differential scanning calorimeter;

[0031] Dynamic Mechanical Analyzer (DMA): Dynamic Mechanical Analyzer;

[0032] Fluorinated ethylene propylene, FEP: Fluorinated ethylene propylene.

[0033] This invention provides a method for testing the elastic modulus of a polymer during the curing process, comprising the following steps:

[0034] Step 1: Use a differential scanning calorimeter to test the heat release changes during the curing process, normalize the data to obtain the heat flow per unit mass, and statistically analyze the heat flow curve over time.

[0035] Step 2: Integrate the exothermic peak and baseline of the heat flow curve to obtain the heat of reaction, calculate the ratio of the cumulative released heat of reaction to the total released heat of reaction, and obtain the degree of curing at different times;

[0036] Step 3: Insert one end of the customized tubular container into the metal wire for sealing, insert a needle into the other end until it contacts the metal wire, inject the polymer, insert the metal wire again for sealing, and obtain an uncured composite sample;

[0037] Step 4: In a dynamic mechanical analyzer or a universal testing machine with a temperature chamber, use the temperature-time curve of the same curing process in a differential scanning calorimeter, clamp the area where the metal wire has been inserted, and immediately perform a quasi-static tensile test after the time required for the corresponding degree of curing is reached to obtain the stress-strain curve and calculate the elastic modulus of the composite specimen.

[0038] Step 5: Based on the composite material elastic modulus calculation method, combined with the elastic modulus of the composite sample and the known pipe and container, as well as the sample geometry, the elastic modulus of the polymer at different curing degrees is calculated.

[0039] Execution process as follows Figure 1 As shown.

[0040] The following provides further explanation with reference to specific embodiments and execution flow:

[0041] Step 1: DSC Test

[0042] The polymer was brought to room temperature for approximately 30 minutes after being removed from storage conditions. 5–10 mg of polymer sample was weighed using a high-precision balance and placed in a dedicated crucible for DSC (DSC 25, TA, USA), ensuring sample homogeneity and avoiding air bubbles or impurities that could affect the test results. A temperature profile for the curing process was established. The DSC was then used in dry nitrogen at a flow rate of 50 ml / min, and the exothermic changes of the sample were recorded. Normalization was performed to obtain the heat flow rate per unit mass, and the heat flow rate over time was statistically analyzed.

[0043] Step 2: Calculation of reaction heat and degree of cure

[0044] The degree of curing of the polymer is linearly related to the heat of reaction. The exothermic peak and baseline of the heat flow curve are integrated and defined by the following formulas (1) and (2):

[0045] (1)

[0046] (2)

[0047] Where α is the degree of curing; ΔH t The integral of the heat flux, i.e., the cumulative heat of reaction released at present; ΔH total The total heat of reaction released is used. Time nodes are extracted uniformly within the entire curing process time range. At the corresponding time, the ratio of the cumulative heat of reaction released to the total heat of reaction released is calculated according to formulas (1) and (2) to obtain the degree of curing at that time, and then the degree of curing is correlated with the curing process time.

[0048] Step 3: Preparation of composite samples

[0049] Prepare a custom-made tubing container, typically made of transparent fluorinated ethylene propylene, a polymer in the Teflon family, which can be used long-term at temperatures ranging from -85°C to 200°C. Seal one end of the tubing container by inserting a metal wire (usually copper wire). Insert a needle into the other end of the container until it contacts the wire, then inject the polymer to be tested. Seal the container again by inserting the wire, thus obtaining an uncured composite sample, preventing the polymer from spilling out. Figure 2 and Figure 3 As shown, the core material is the polymer to be tested. The metal wire provides the clamping area, and testing can be performed horizontally or vertically.

[0050] Step 4: Testing and Calculation of the Elastic Modulus of the Composite Specimen

[0051] In a DMA (DMA Q800, TA, USA) or a universal testing machine with a temperature chamber, set the same temperature and time conditions as the DSC test for the curing process. Clamp the part containing the metal wire and use the part containing the polymer to be tested as the gauge length. After reaching the required curing degree, perform a quasi-static tensile test according to GB / T 1040.2-2022. The slope of the stress-strain curve calculated according to formula (3) is the elastic modulus of the composite specimen. Repeat this step to obtain the elastic modulus of the composite specimen at different target curing degrees.

[0052] (3)

[0053] Where E is the elastic modulus of the composite specimen; σ is the stress; ε is the strain; F is the applied force; A is the radial cross-sectional area of ​​the composite specimen; ΔL is the elongation; and L is the gauge length.

[0054] Step 5: Calculation of polymer elastic modulus

[0055] Assuming perfect bonding at the interface of the composite specimen between gauge lengths, consisting of a tubular container and an inner core material (the polymer to be tested), the elastic modulus of the core material is obtained using the composite elastic modulus calculation formulas (4) and (5) based on the obtained elastic modulus of the composite specimen, the known elastic modulus of the tubular container, and the specimen geometry. The curing process of the polymer is then linked to its mechanical properties from three dimensions: degree of curing, curing time, and elastic modulus.

[0056] (4)

[0057] (5)

[0058] Among them, E total V represents the elastic modulus of the composite specimen. s E represents the volume fraction of the pipe material. s V is the elastic modulus of the pipe. c E represents the volume fraction of the core material. c Let be the elastic modulus of the core material. Formulas (4) and (5) can be transformed into the following formulas (6) and (7) using the cylinder volume formula:

[0059] (6)

[0060] (7)

[0061] Among them, R s R is the outer radius of the pipe or container. c Let be the core material radius, and assume that the core material radius is equal to the inner radius of the tube.

[0062] The above description discloses only one or more preferred embodiments of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art can understand that implementing all or part of the above embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for testing the elastic modulus of a polymer during the curing process, characterized in that, Includes the following steps: Step 1: Use a differential scanning calorimeter to test the heat release changes during the curing process, normalize the data to obtain the heat flow per unit mass, and statistically analyze the heat flow curve over time. Step 2: Integrate the exothermic peak and baseline of the heat flow curve to obtain the heat of reaction, calculate the ratio of the cumulative released heat of reaction to the total released heat of reaction, and obtain the degree of curing at different times; Step 3: Insert one end of the customized tubular container into the metal wire for sealing, insert a needle into the other end until it contacts the metal wire, inject the polymer, insert the metal wire again for sealing, and obtain an uncured composite sample; Step 4: In a dynamic mechanical analyzer or a universal testing machine with a temperature chamber, use the temperature-time curve of the same curing process in a differential scanning calorimeter, clamp the area where the metal wire has been inserted, and immediately perform a quasi-static tensile test after the time required for the corresponding degree of curing is reached to obtain the stress-strain curve and calculate the elastic modulus of the composite specimen. Step 5: Based on the composite material elastic modulus calculation method, combined with the elastic modulus of the composite sample and the known pipe and container, as well as the sample geometry, the elastic modulus of the polymer at different curing degrees is calculated.

2. The method for testing the elastic modulus of a polymer during curing as described in claim 1, characterized in that, The formulas for calculating the heat of reaction and degree of cure in step 2 are as follows: ； ； Where α is the degree of curing; ΔH t The integral of the heat flux, i.e., the cumulative heat of reaction released at present; ΔH total This represents the total heat of reaction released.

3. The method for testing the elastic modulus of a polymer during curing as described in claim 1, characterized in that, In step 3, the core material is the polymer to be tested. The composite sample is sealed with metal wires at both ends. The metal wires provide a clamping area to ensure that the test can be performed in either a horizontal or vertical manner.

4. The method for testing the elastic modulus of a polymer during curing as described in claim 1, characterized in that, In step 4, the timing of the curing process corresponds to the degree of curing. The slope of the stress-strain curve at the corresponding timing is the elastic modulus of the composite sample at the corresponding degree of curing. The calculation formula is as follows: ； Where E is the elastic modulus of the composite specimen; σ is the stress; ε is the strain; F is the applied force; A is the radial cross-sectional area of ​​the composite specimen; ΔL is the elongation; and L is the gauge length.

5. The method for testing the elastic modulus of a polymer during curing as described in claim 1, characterized in that, The formula for calculating the elastic modulus of the polymer at different degrees of curing in step 5 is as follows: ； ； Among them, E total E represents the elastic modulus of the composite specimen. s E represents the elastic modulus of the pipe. c R is the elastic modulus of the core material. s R is the outer radius of the pipe or container. c The core material radius is equal to the inner radius of the pipe.

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