Method for testing shear modulus of polymer packaging material in curing process

Abstract

The invention relates to a method for testing the shear modulus of a polymer packaging material in a curing process, which comprises the following steps of: 1, obtaining polymer conversion rate data at different moments and clear curing process temperature parameters through attenuated total reflection Fourier infrared spectrum in-situ monitoring based on setting of curing process temperature parameters; step 2, based on the curing process temperature parameters determined in the step 1, obtaining associated data of shear modulus and time through a synchronous mechanical property test; and step 3, based on the conversion rate data in the step 1, the curing process temperature parameters and the shear modulus and time associated data in the step 2, obtaining corresponding polymer shear moduli under different conversion rates through multi-scale data fusion. The method has the beneficial effects that high synchronism and accuracy are achieved, full-period mechanical characterization is achieved, and a scientific basis is provided for internal stress prediction and demolding time determination in the composite material forming process.

Description

Technical Field

[0001] This invention belongs to the field of polymer shear modulus testing, specifically relating to a method for testing the shear modulus of polymer encapsulation materials during the curing process. Background Technology

[0002] In advanced semiconductor packaging technology, polymer packaging materials play a crucial role in mechanical support and environmental protection. Unlike macroscopic structural components that primarily bear tensile and compressive loads, the core challenge of packaging structures lies in the thermal mismatch at the interfaces of multilayer heterogeneous materials. Due to the significant differences in the coefficients of thermal expansion between the chip, substrate, and polymer packaging material, severe shear stresses are generated at the contact interfaces during curing, cooling, and subsequent thermal cycling. Shear modulus is a core parameter measuring a material's ability to resist shear deformation (i.e., shape change without volume change). In packaging reliability analysis, shear modulus directly determines the shear destructive force exerted by the polymer on solder joints and redistribution layers during thermal expansion and contraction. Once the shear modulus evolution and stress release mechanism during curing become unbalanced, it can easily lead to interface delamination, corner cracking, and solder ball shear fatigue failure. Therefore, accurately obtaining shear modulus data throughout the entire curing cycle is a prerequisite for establishing high-precision finite element simulation models to predict warpage and fatigue life.

[0003] Accurate measurement of shear modulus during polymer curing faces significant technical challenges related to "cross-scale" and "phase transitions," and existing testing methods have obvious measurement blind spots. The first method is rotational rheometer testing, currently the mainstream method for testing the rheological properties of liquid and gel polymers, applying a shear flow field through parallel plate or conical plate clamps. When the polymer cures into the high-modulus stage (glassy state), the material hardens and shrinks, easily causing wall slippage or interfacial debonding on the test clamp surface, resulting in a measured modulus value far lower than the true value; simultaneously, the instrument's own flexibility introduces significant errors when testing hard solids. The second method is dynamic thermomechanical analysis using shear / torsion modes, suitable for fully cured solid samples. This method cannot handle initial liquid polymers (due to the inability to form and clamp them), thus failing to obtain the shear modulus evolution curve of the complete continuous process from "liquid to gel point to solid," losing data on the crucial gelation transition stage that generates residual stress. The third method is the ultrasonic reflection method, calculating the shear modulus based on the transverse wave propagation velocity. Transverse waves attenuate extremely rapidly in liquid and viscous media, resulting in weak signals and low signal-to-noise ratios in the early stages of curing, making precise monitoring of the entire process difficult. In summary, traditional macroscopic mechanical testing primarily targets static tensile elastic modulus, failing to characterize the pure shear behavior of materials. Rheological and thermal analysis methods are limited to "soft" fluids or "hard" solids, respectively, lacking a continuous, slip-free, and highly precise method for measuring shear modulus throughout the entire transformation process of polymers from low-viscosity liquids to high-modulus solids. This lack of testing capability severely restricts a deeper understanding and precise control of the curing kinetics and residual shear stress evolution of advanced encapsulation materials. Summary of the Invention

[0004] In summary, the technical problem this invention aims to solve is to provide a method for testing the shear modulus of polymer encapsulation materials during the curing process. This method addresses the following technical issues: Traditional monitoring of polymer encapsulation material curing often faces the problem of a disconnect between microscopic chemical reactions and macroscopic mechanical property evolution. First, inconsistent testing conditions. Previous studies often measured conversion rate and modulus separately under different equipment and temperature programs, resulting in poor data matching. Second, difficulty in covering the entire curing process. Ordinary shear tests cannot adequately monitor the entire range from the initial liquid state to the hardened solid state. Third, lack of quantitative correlation models. It is difficult to accurately determine the precise shear modulus value corresponding to a specific conversion rate (degree of curing), leading to a lack of mechanical criteria for curing process optimization.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for testing the shear modulus of polymer encapsulation materials during the curing process, comprising the following steps:

[0006] Step 1: In-situ monitoring using attenuated total reflectance Fourier transform infrared spectroscopy based on the curing process temperature parameters was conducted to obtain polymer conversion rate data and specific curing process temperature parameters at different times.

[0007] Step 2: Based on the curing process temperature parameters defined in Step 1, obtain the correlation data between shear modulus and time through simultaneous mechanical property testing;

[0008] Step 3: Based on the conversion rate data and curing process temperature parameters from Step 1 and the shear modulus-time correlation data from Step 2, the polymer shear modulus corresponding to different conversion rates can be obtained through multi-scale data fusion.

[0009] Based on the above technical solution, the present invention can be further improved as follows:

[0010] Furthermore, step 1 specifically involves:

[0011] Step 1.1: Accurately weigh the polymer and curing agent according to the stoichiometric ratio, mix them evenly in a vacuum mixer to obtain a mixture and degas it;

[0012] Step 1.2: Take 10–20 mg of the mixture and coat it on the surface of the attenuating total internal reflection crystal, ensuring complete coverage of the central optical path area of ​​the crystal;

[0013] Step 1.3: Using a Fourier transform infrared spectrometer equipped with a heating accessory, set the temperature change curve of the heating stage according to the curing process requirements, with the spectral range set to 600–4000 cm⁻¹. -1 4 cm resolution -1 The number of scans per spectrum is set to 16, 32 or 64 depending on the reaction rate. The acquisition mode is selected as serial acquisition or kinetic mode, and the acquisition interval is 1 spectrum per minute.

[0014] Step 1.4: First, acquire the background spectrum in an empty stage to remove the interference from water vapor and carbon dioxide in the air. Then, quickly add the polymer to be tested and immediately acquire the first spectrum as the reference data at t = 0. Start the acquisition program to allow the software to automatically record the spectra at different time points.

[0015] Step 1.5: After the attenuated total reflectance Fourier transform infrared spectroscopy test is completed, the characteristic peaks are baseline corrected and integrated using software. The conversion rate at different times is calculated using the following formula:

[0016] ;

[0017] ;

[0018] Where, α t Let A be the conversion rate at time t. t R represents the absorbance of the characteristic peak at time t. tLet A0 be the absorbance of the internal standard peak at time t, and R0 be the absorbance of the characteristic peak and the internal standard peak before the reaction starts, respectively. Let A' be the normalized absorbance ratio.

[0019] Furthermore, if the mixture in step 1.2 is a solid powder coating, it needs to be compacted and then coated onto the surface of the attenuating total reflection crystal.

[0020] Furthermore, the attenuating total internal reflection crystal mentioned in step 1.2 is a diamond or ZnSe crystal.

[0021] Furthermore, step 2 specifically involves:

[0022] Step 2.1: Prepare the customized mold. In a dynamic mechanical analyzer or a universal testing machine with a temperature chamber, use tensile clamps to clamp the upper and lower molds of the mold in the vertical direction respectively.

[0023] Step 2.2: Inject a predetermined amount of the polymer to be tested into the mold cavity using a pipette, so that the polymer to be tested forms a ring within the mold cavity, using the curing process temperature change parameters defined in Step 1:

[0024] If the dynamic mode is used, the frequency is set to 1 Hz, a fixed sinusoidal strain amplitude of 0.1% is applied, and the relationship between shear storage modulus and time is directly obtained after the test is started.

[0025] If a constant rate mode is used, the displacement rate is set to 1% of the strain / min. The test is started at the critical time point corresponding to the conversion rate determined in step 1. The shear force F perpendicular to the cross-section and the displacement Δx of the movable fixture are recorded. The shear modulus G is calculated using the following formula:

[0026] ;

[0027] ;

[0028] ;

[0029] Where τ is the shear stress, A is the area of ​​the stressed surface, γ is the shear strain, θ is the shear angle, Δx is the displacement of the movable fixture, and h is the radius of the annular polymer to be tested.

[0030] Furthermore, the mold described in step 2 is made of polytetrafluoroethylene.

[0031] Furthermore, step 3 specifically involves:

[0032] Using the time axis as an intermediary, the conversion rate data at different times obtained in step 1, the specific curing process temperature parameters, and the correlation data between shear modulus and time obtained in step 2 are precisely aligned to construct a four-dimensional mapping relationship model of curing temperature, time, conversion rate, and shear modulus. Through this model, the corresponding shear modulus at a specific conversion rate can be directly queried or derived.

[0033] The beneficial effects of this invention are as follows: By strictly unifying the temperature control procedures and sampling times of ATR-FTIR and DMA, experimental errors are eliminated, ensuring a one-to-one correspondence between conversion rate and shear modulus, exhibiting high synchronization and accuracy. The customized PTFE mold and shear calculation model solve the clamping and testing challenges caused by the drastic changes in viscoelasticity during the polymer's transition from fluid to solid, achieving full-cycle mechanical characterization. It can accurately provide the shear modulus at specific conversion rates (such as gel point or final curing point), effectively guiding the process and providing a scientific basis for predicting internal stress and determining demolding time during composite material molding. Attached Figure Description

[0034] Figure 1 This is a flowchart of the present invention;

[0035] Figure 2 A schematic diagram illustrating the injection of a preset amount of polymer to be tested into a designated location in the mold;

[0036] Figure 3 for Figure 2 A sectional view.

[0037] The attached diagram lists the components represented by each number as follows:

[0038] 1. Lower mold, 2. Upper mold, 3. Polymer to be tested. Detailed Implementation

[0039] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0040] like Figure 1 As shown, a method for testing the shear modulus during the curing process of a polymer encapsulation material includes the following steps:

[0041] Step 1: In-situ monitoring based on attenuated total reflectance Fourier transform infrared spectroscopy (including setting curing process temperature parameters) yielded polymer conversion rate data and specific curing process temperature parameters at different times. Details are as follows:

[0042] Step 1.1: Attenuated Total Reflection–Fourier Transform Infrared Spectroscopy (ATR–FTIR) is suitable for monitoring the entire process from liquid to solid due to its simple sample preparation and the ability to accurately simulate the curing process temperature using a temperature control accessory. The polymer and curing agent are precisely weighed according to stoichiometric ratios, mixed uniformly in a vacuum mixer to obtain a homogeneous mixture, and then degassed.

[0043] Step 1.2: Take 10–20 mg of the mixture (solid powder coating needs to be compacted) and apply it directly to the surface of the attenuating total internal reflection crystal (such as diamond or ZnSe crystal), ensuring complete coverage of the central optical path area of ​​the crystal;

[0044] Step 1.3: Using a Fourier transform infrared spectrometer equipped with a heating attachment, set the temperature change curve of the heating stage according to the curing process requirements (this temperature parameter serves as the benchmark for subsequent mechanical testing), with the spectral range set to 600–4000 cm⁻¹. -1 4 cm resolution -1 The number of scans per spectrum is set to 16, 32 or 64 depending on the reaction rate. The acquisition mode is selected as "Series Acquisition" or "Kinetics" mode, and the acquisition interval is 1 spectrum per minute.

[0045] Step 1.4: First, acquire the background spectrum in an empty stage to subtract the interference from water vapor and carbon dioxide in the air. Then, quickly add the polymer to be tested and immediately acquire the first spectrum as the reference data at t = 0. Start the acquisition program to allow the software to automatically record the spectra at different time points.

[0046] Step 1.5, the core principle of calculating conversion using infrared spectroscopy is the internal standard method. It requires comparing a characteristic peak that is consumed during the reaction (reaction peak) with a characteristic peak that remains unchanged (reference / internal standard peak). After the ATR-FTIR test is completed, the characteristic peak is baseline-corrected and integrated using software, and the conversion rate at different times is calculated using the following formula:

[0047] ;

[0048] ;

[0049] Where, α t Let A be the conversion rate at time t. t R represents the absorbance (peak area or peak height) of the characteristic peak at time t. tLet A0 be the absorbance (peak area or peak height) of the internal standard peak at time t, and let R0 be the absorbance of the characteristic peak and the internal standard peak before the reaction starts (t = 0, not cured), respectively. Let A' be the normalized absorbance ratio (i.e., A / R).

[0050] Step 1 utilizes the in-situ heating function of ATR-FTIR to simulate the real curing environment by presetting and fixing the curing process temperature parameters, ensuring the stability of the test environment; using the internal standard method, the conversion rate is calculated in real time and accurately by monitoring the absorbance changes of the reaction peak and the internal standard peak, while clarifying the curing process temperature parameters, providing consistent temperature conditions for subsequent synchronous mechanical testing.

[0051] Step 2, as follows Figure 2 and 3 As shown, based on the curing process temperature parameters defined in step 1, the correlation data between shear modulus and time was obtained through simultaneous mechanical property testing. Specifically:

[0052] Step 2.1: Prepare a custom mold (to make the polymer 3 to be tested into a ring shape), generally made of polytetrafluoroethylene. In a dynamic mechanical analyzer (DMA, Q800, TA, USA) or a universal testing machine with a temperature chamber, clamp the upper mold 1 and lower mold 2 of the mold vertically using tensile clamps.

[0053] Step 2.2: Inject a preset amount of the polymer to be tested into the designated position of the mold using a pipette (without overflowing the lower mold), so that the polymer to be tested 3 forms a ring within the mold cavity. Strictly follow the curing process temperature change parameters specified in Step 1.

[0054] In dynamic mode, with the frequency set to 1 Hz and a fixed sinusoidal strain amplitude of 0.1%, the relationship between shear storage modulus (equivalent to shear modulus) and time can be directly obtained after the test is started. The relationship between shear modulus and curing process can be obtained with just one dynamic shear test. Based on the obtained relationship between conversion rate and time, the relationship between shear modulus and conversion rate can be established. During dynamic tensile shear testing (i.e., testing at a certain frequency), the shear storage modulus can be directly obtained, which is equivalent to shear modulus.

[0055] If a constant rate mode is used, the displacement rate is set to 1% of the strain per minute. The test begins when the target conversion rate is reached. Repeating the test at different times yields the shear test results at the corresponding conversion rate. The test is started at the critical time point corresponding to the conversion rate determined in step 1. The shear force F perpendicular to the cross-section and the displacement Δx of the movable fixture are recorded. During the constant rate tensile shear test, the shear modulus G needs to be calculated using the following formula based on the test data of shear stress and shear strain:

[0056] ;

[0057] ;

[0058] ;

[0059] Where τ is the shear stress, A is the area of ​​the stressed surface, γ is the shear strain, θ is the shear angle, Δx is the displacement of the movable fixture, and h is the radius of the annular polymer being tested. When the deformation of the polymer being tested is extremely small... In this case, θ is calculated in radians.

[0060] Step 2 follows the curing process temperature parameters defined in Step 1 to ensure environmental synchronization between mechanical testing and conversion rate monitoring, eliminating data errors caused by temperature differences; a customized mold is used to ensure uniform sample thickness and pure shear stress, adapting to the phase change of the polymer from liquid to solid state; the storage modulus is directly obtained through dynamic mode or the shear modulus is calculated by combining mechanical formulas with constant rate mode, establishing the correlation between shear modulus and time.

[0061] Secondly, step 2 shapes the polymer to be tested into a ring shape, ensuring uniform sample thickness and guaranteeing the purity of shear stress and the applicability of the small deformation assumption (tanθ ≈ θ). The mold is compatible with testing polymers in their uncured state, allowing for the detection of shear modulus during the curing process. The test method remains effective for fully cured polymer samples.

[0062] Finally, step 2 sets the temperature variation conditions for the same curing process as the ATR-FTIR test. In the dynamic tensile shear test, the shear modulus of the curing process can be obtained with a single start, while also being compatible with multiple tests in the constant-rate tensile mode. Combining dynamic oscillation testing (measuring storage modulus) and constant-rate tensile shear testing (measuring static / instantaneous modulus), the dual-mode shear test complements each other, covering different application scenarios for polymer encapsulation materials.

[0063] Step 3: Based on the conversion rate data and curing process temperature parameters from Step 1, and the shear modulus versus time correlation data from Step 2, the polymer shear modulus corresponding to different conversion rates is obtained through multi-scale data fusion. Specifically:

[0064] Using the time axis as an intermediary, the conversion rate data at different times obtained in step 1 and the specific curing process temperature parameters are precisely aligned with the correlation data between the shear modulus (energy storage modulus in dynamic mode or modulus calculated in constant rate mode) and time obtained in step 2. A four-dimensional mapping relationship model of curing temperature, time, conversion rate and shear modulus is constructed. Through this model, the corresponding shear modulus at a specific conversion rate (such as gel point, final curing point) can be directly queried or derived.

[0065] Step 3 establishes a one-to-one correspondence between microscopic conversion rate, curing temperature and macroscopic shear modulus based on the time axis, eliminates errors caused by different test conditions, and realizes the quantitative derivation from "temperature-time-conversion rate" to "shear modulus" through a four-dimensional mapping model, and finally obtains the shear modulus data of the entire polymer curing process.

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for testing the shear modulus during the curing process of a polymer encapsulation material, characterized in that... The steps include the following: Step 1: In-situ monitoring using attenuated total reflectance Fourier transform infrared spectroscopy based on the curing process temperature parameters was conducted to obtain polymer conversion rate data and specific curing process temperature parameters at different times. Step 2: Based on the curing process temperature parameters defined in Step 1, obtain the correlation data between shear modulus and time through simultaneous mechanical property testing; Step 3: Based on the conversion rate data and curing process temperature parameters from Step 1 and the shear modulus-time correlation data from Step 2, the polymer shear modulus corresponding to different conversion rates can be obtained through multi-scale data fusion.

2. The method for testing the shear modulus during the curing process of polymer encapsulation materials according to claim 1, characterized in that, Step 1 is as follows: Step 1.1: Accurately weigh the polymer and curing agent according to the stoichiometric ratio, mix them evenly in a vacuum mixer to obtain a mixture and degas it; Step 1.2: Take 10–20 mg of the mixture and coat it on the surface of the attenuating total internal reflection crystal, ensuring complete coverage of the central optical path area of ​​the crystal; Step 1.3: Using a Fourier transform infrared spectrometer equipped with a heating accessory, set the temperature change curve of the heating stage according to the curing process requirements, with the spectral range set to 600–4000 cm⁻¹. -1 4 cm resolution -1 The number of scans per spectrum is set to 16, 32 or 64 depending on the reaction rate. The acquisition mode is selected as serial acquisition or kinetic mode, and the acquisition interval is 1 spectrum per minute. Step 1.4: First, acquire the background spectrum in an empty stage to remove the interference from water vapor and carbon dioxide in the air. Then, quickly add the polymer to be tested and immediately acquire the first spectrum as the reference data at t = 0. Start the acquisition program to allow the software to automatically record the spectra at different time points. Step 1.5: After the attenuated total reflectance Fourier transform infrared spectroscopy test is completed, the characteristic peaks are baseline corrected and integrated using software. The conversion rate at different times is calculated using the following formula: ； ； Where, α t Let A be the conversion rate at time t. t R represents the absorbance of the characteristic peak at time t. t Let A0 be the absorbance of the internal standard peak at time t, and R0 be the absorbance of the characteristic peak and the internal standard peak before the reaction starts, respectively. Let A' be the normalized absorbance ratio.

3. The method for testing the shear modulus during the curing process of polymer encapsulation materials according to claim 1, characterized in that, If the mixture in step 1.2 is a solid powder coating, it needs to be compacted and then coated on the surface of the attenuating total reflection crystal.

4. The method for testing the shear modulus during the curing process of polymer encapsulation materials according to claim 1, characterized in that, The attenuating total internal reflection crystal mentioned in step 1.2 is a diamond or ZnSe crystal.

5. The method for testing the shear modulus during the curing process of polymer encapsulation materials according to claim 1, characterized in that, Step 2 is as follows: Step 2.1: Prepare the customized mold. In a dynamic mechanical analyzer or a universal testing machine with a temperature chamber, use tensile clamps to clamp the upper and lower molds of the mold in the vertical direction respectively. Step 2.2: Inject a predetermined amount of the polymer to be tested into the mold cavity using a pipette, so that the polymer to be tested forms a ring within the mold cavity, using the curing process temperature change parameters defined in Step 1: If the dynamic mode is used, the frequency is set to 1 Hz, a fixed sinusoidal strain amplitude of 0.1% is applied, and the relationship between shear storage modulus and time is directly obtained after the test is started. If a constant rate mode is used, the displacement rate is set to 1% of the strain / min. The test is started at the critical time point corresponding to the conversion rate determined in step 1. The shear force F perpendicular to the cross-section and the displacement Δx of the movable fixture are recorded. The shear modulus G is calculated using the following formula: ； ； ； Where τ is the shear stress, A is the area of ​​the stressed surface, γ is the shear strain, θ is the shear angle, Δx is the displacement of the movable fixture, and h is the radius of the annular polymer to be tested.

6. The method for testing the shear modulus during the curing process of polymer encapsulation materials according to claim 5, characterized in that, The mold mentioned in step 2 is made of polytetrafluoroethylene.

7. The method for testing the shear modulus of polymer encapsulation materials during the curing process according to any one of claims 1 to 6, characterized in that, Step 3 specifically involves: Using the time axis as an intermediary, the conversion rate data at different times obtained in step 1, the specific curing process temperature parameters, and the correlation data between shear modulus and time obtained in step 2 are precisely aligned to construct a four-dimensional mapping relationship model of curing temperature, time, conversion rate, and shear modulus. Through this model, the corresponding shear modulus at a specific conversion rate can be directly queried or derived.

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