A method and system for online detection of curing properties of epoxy molding compound

Abstract

This invention provides an online detection method and system for the curing characteristics of epoxy molding compounds, belonging to the field of materials testing and analysis technology. The method includes: during the molding process, acquiring electrical response data of the epoxy molding compound within the mold cavity at at least two different excitation frequencies, and simultaneously acquiring equivalent temperature data of the mold cavity; calculating the complex impedance data corresponding to each excitation frequency based on the electrical response data, constructing a dielectric characteristic quantity to characterize the change in dielectric response of the epoxy molding compound, and performing temperature compensation processing on the dielectric characteristic quantity in conjunction with the equivalent temperature data of the mold cavity; based on the temperature-compensated dielectric characteristic quantity, obtaining online inversion information on the degree of curing change of the epoxy molding compound; based on the degree of curing change information, determining the gel determination time during the curing process of the epoxy molding compound, and outputting online detection results characterizing the curing state of the epoxy molding compound. This invention achieves real-time and stable detection of the curing process and gelation stage of epoxy molding compounds.

Description

Technical Field

[0001] This invention relates to the field of materials testing and analysis technology, specifically to an online detection method and system for the curing properties of epoxy molding compounds. Background Technology

[0002] Epoxy molding compounds are widely used in the molding and encapsulation of semiconductor devices and electronic components. Their curing state directly affects the mechanical strength, interface bonding reliability, and long-term service stability of the package structure. In the molding process, epoxy molding compounds are typically filled and cured under high temperature and high pressure conditions. The curing process exhibits significant non-linear characteristics and is affected by various factors such as material formulation differences, batch variations, mold cavity temperature distribution, and process parameter disturbances. Insufficient curing can easily lead to inadequate release of residual stress within the package, interface delamination, or void defects; over-curing can increase the risk of material embrittlement or warpage.

[0003] In current engineering practice, the determination of the curing characteristics of epoxy molding compounds largely relies on empirically set holding times or mold temperature profiles, or on offline detection methods such as differential scanning calorimetry to evaluate the material's curing behavior. However, offline detection methods are difficult to reflect the real-time curing state during the actual molding process and cannot adapt to dynamic changes under different molding cycles and operating conditions. Empirical determination methods based on fixed time or temperature parameters are also difficult to accurately characterize key state transitions in the curing process, especially to reliably identify important physical nodes such as the gelation stage.

[0004] Therefore, there is an urgent need for a method to detect the curing characteristics of epoxy molding compounds online during the molding process. This method should be able to reflect the evolution of the material's curing state in real time without interfering with the existing molding process, and provide objective and repeatable detection basis for determining the key states of the curing stage. Summary of the Invention

[0005] The purpose of this invention is to provide an online detection method and system for the curing characteristics of epoxy molding compounds, so as to at least solve the problem in the prior art that it is difficult to detect the curing state of epoxy molding compounds online during the molding process, thus making it impossible to reliably determine the curing process and gel stage.

[0006] To achieve the above objectives, the first aspect of the present invention provides an online detection method for the curing characteristics of epoxy molding compound. The method includes: during the molding process, acquiring electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies, and simultaneously acquiring equivalent temperature data of the mold cavity; calculating complex impedance data corresponding to each excitation frequency based on the electrical response data, constructing a dielectric characteristic quantity to characterize the dielectric response change of the epoxy molding compound based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, and performing temperature compensation processing on the dielectric characteristic quantity in conjunction with the equivalent temperature data of the mold cavity; obtaining the curing degree change information of the epoxy molding compound through online inversion based on the temperature-compensated dielectric characteristic quantity; determining the gel determination time during the curing process of the epoxy molding compound based on the curing degree change information, and outputting online detection results to characterize the curing state of the epoxy molding compound.

[0007] Optionally, during the molding process, electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies are acquired, and equivalent temperature data of the mold cavity is acquired simultaneously. This includes: after the mold cavity is filled, applying at least two AC excitation signals of different frequencies to the epoxy molding compound in the mold cavity; under the action of the AC excitation signals, collecting voltage and current signals corresponding to each excitation frequency as electrical response data; and simultaneously acquiring temperature signals characterizing the temperature state of the epoxy molding compound in the mold cavity, and determining equivalent temperature data of the mold cavity based on the temperature signals.

[0008] Optionally, calculating the complex impedance data corresponding to each excitation frequency based on the electrical response data includes: for each excitation frequency, under the AC excitation of the corresponding excitation frequency, acquiring the voltage signal time series and the current signal time series within the corresponding time period; based on the voltage signal time series and the current signal time series, calculating the amplitude ratio and phase difference between the voltage signal and the current signal; determining the amplitude ratio as the impedance amplitude information at the corresponding excitation frequency, and determining the phase difference as the impedance phase information at the corresponding excitation frequency, wherein the impedance amplitude information and the impedance phase information together constitute the complex impedance data at the corresponding excitation frequency.

[0009] Optionally, a dielectric characteristic quantity for characterizing the change in dielectric response of epoxy molding compound is constructed based on the amplitude difference and phase difference between complex impedance data at different excitation frequencies. This includes: for any set of different excitation frequencies, obtaining impedance amplitude information and impedance phase information in the complex impedance data at the corresponding excitation frequencies; based on the impedance amplitude information, calculating the difference between impedance amplitude information corresponding to different excitation frequencies to obtain an amplitude difference characteristic quantity characterizing the relationship between impedance amplitude and frequency; based on the impedance phase information, calculating the difference between impedance phase information corresponding to different excitation frequencies to obtain a phase difference characteristic quantity characterizing the relationship between impedance phase and frequency; and combining the amplitude difference characteristic quantity and the phase difference characteristic quantity as the dielectric characteristic quantity to characterize the change in dielectric response of epoxy molding compound during the molding process as the curing process progresses.

[0010] Optionally, temperature compensation processing is performed on the dielectric feature based on the cavity equivalent temperature data, including: during the construction of the dielectric feature, acquiring cavity equivalent temperature data within the time period corresponding to the dielectric feature; based on the cavity equivalent temperature data, correcting the frequency response offset in the dielectric feature caused by temperature changes to eliminate the influence of cavity temperature fluctuations on the dielectric feature, and obtaining the temperature-compensated dielectric feature.

[0011] Optionally, based on the temperature-compensated dielectric characteristics, online inversion is performed to obtain the curing degree change information of the epoxy molding compound, including: constructing a curing state inversion relationship to describe the curing process of the epoxy molding compound based on the temperature-compensated dielectric characteristics, wherein the curing degree is used as the state variable to be inverted in the curing state inversion relationship; during the continuous time period of the molding process, the temperature-compensated dielectric characteristics are used as the observation input to perform online update calculation on the curing state inversion relationship to obtain the curing degree estimate value at each time point; the curing degree estimate values ​​are arranged in chronological order to form a curing degree change sequence, which is output as curing degree change information.

[0012] Optionally, during the continuous time period of the molding process, the temperature-compensated dielectric characteristic is used as the observation input to perform online update calculation on the curing state inversion relationship to obtain the curing degree estimate for each time point. This includes: calculating the corresponding dielectric response increment based on the change in the temperature-compensated dielectric characteristic between adjacent time points; performing a recursive update on the curing degree estimate based on the dielectric response increment, and applying a monotonically increasing constraint to the curing degree estimate to limit the curing degree estimate from changing in the opposite direction over time; and performing consistency correction on the curing degree estimate at adjacent time points based on a preset change smoothing condition during the recursive update process to obtain the corrected curing degree estimate.

[0013] Optionally, based on the curing degree change information, the gel determination time during the epoxy molding compound curing process is determined, and an online detection result characterizing the curing state of the epoxy molding compound is output, including: calculating the curing rate information of curing degree change with time based on the curing degree change information; identifying the time interval in the curing rate information where the curing rate changes from a continuously increasing state to a non-continuously increasing state, and determining the time interval as the gel determination interval during the curing process; determining the time point that meets the preset time determination condition within the gel determination interval as the gel determination time; and outputting the gel determination time and the corresponding curing degree estimate as the online detection result characterizing the curing state of the epoxy molding compound.

[0014] Optionally, the preset time determination condition is as follows: within the gel determination interval, the curing rate information is discretely sampled with a preset time step; when the curing rate values ​​corresponding to multiple consecutive adjacent sampling times are not greater than the curing rate value corresponding to the previous sampling time, the first sampling time that satisfies this condition is determined as the candidate gel time; within a preset duration after the candidate gel time, if the curing rate value does not again exceed the curing rate value corresponding to the candidate gel time, the candidate gel time is determined as the gel determination time.

[0015] A second aspect of the present invention provides an online detection system for the curing characteristics of epoxy molding compound. The system includes: a response unit, configured to acquire electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies during the molding process, and simultaneously acquire equivalent temperature data of the mold cavity; a processing unit, configured to calculate complex impedance data corresponding to each excitation frequency based on the electrical response data, construct dielectric characteristic quantities for characterizing the dielectric response change of the epoxy molding compound based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, and perform temperature compensation processing on the dielectric characteristic quantities in conjunction with the equivalent temperature data of the mold cavity; an inversion unit, configured to obtain curing degree change information of the epoxy molding compound online based on the temperature-compensated dielectric characteristic quantities; and a result output unit, configured to determine the gel determination time during the curing process of the epoxy molding compound based on the curing degree change information, and output online detection results for characterizing the curing state of the epoxy molding compound.

[0016] Through the above technical solution, this invention simultaneously acquires multi-frequency electrical response data and mold cavity equivalent temperature data of the epoxy molding compound during the molding process, constructs a dielectric characteristic quantity that reflects the change of the material's dielectric response with the curing process, and applies temperature compensation processing to this dielectric characteristic quantity, thereby effectively reducing the impact of mold cavity temperature fluctuations on the detection results. Based on this, the temperature-compensated dielectric characteristic quantity is used to perform online inversion of the curing degree change of the epoxy molding compound, transforming the curing state from empirical time or offline inference into a continuously observable state quantity. Furthermore, by analyzing the curing degree change information, the gel determination time in the curing process is determined, achieving objective identification of key curing stages. Therefore, this solution can achieve online detection of the curing state of epoxy molding compounds without interfering with the molding process, providing stable and repeatable detection results for the state assessment of the curing process.

[0017] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0018] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0019] Figure 1 This is a flowchart of the steps of an online detection method for the curing properties of epoxy molding compound provided by one embodiment of the present invention;

[0020] Figure 2 This is a system structure diagram of an online detection system for the curing properties of epoxy molding compound provided in one embodiment of the present invention;

[0021] Figure 3 This is an internal structural diagram of a computer device provided in one embodiment of the present invention. Detailed Implementation

[0022] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] like Figure 1 As shown, this invention provides an online detection method for the curing properties of epoxy molding compounds, the method comprising:

[0024] Step S10: During the molding process, acquire the electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies, and simultaneously acquire the equivalent temperature data of the mold cavity.

[0025] Specifically, after the mold cavity is filled, at least two AC excitation signals of different frequencies are applied to the epoxy molding compound inside the mold cavity; under the action of the AC excitation signals, voltage signals and current signals corresponding to each excitation frequency are collected as electrical response data; while collecting the electrical response data, temperature signals characterizing the temperature state of the epoxy molding compound inside the mold cavity are collected, and the equivalent temperature data of the mold cavity is determined based on the temperature signals.

[0026] In this embodiment of the invention, the online detection process of epoxy molding compound curing characteristics occurs during the actual execution stage of the molding process. Considering that the epoxy molding compound begins a curing process dominated by chemical reaction after filling, this invention applies alternating current excitation to the epoxy molding compound within the mold cavity after filling and entering the curing stage to obtain electrical response information that reflects changes in the dielectric state of the material. The applied alternating current excitation signal includes at least two different excitation frequencies. The response of the epoxy molding compound to the applied electric field differs at different excitation frequencies, and this difference is closely related to the internal polarization behavior of the material and the curing process.

[0027] Under the action of an alternating current excitation signal, voltage and current signals corresponding to each excitation frequency are collected, and the collected voltage and current signals are recorded as electrical response data. In practical applications, voltage and current signals can be acquired synchronously to ensure the consistency of electrical response data in the time dimension under different excitation frequencies. It should be understood that this invention does not limit the specific sampling method or sampling frequency; as long as voltage and current information corresponding to the applied excitation frequency can be obtained, it should fall within the protection scope of this invention.

[0028] Simultaneously, during the acquisition of electrical response data, temperature signals characterizing the temperature state of the epoxy molding compound within the mold cavity are also acquired. These temperature signals can originate from temperature detection devices located inside or near the mold cavity, or they can be obtained by processing data from multiple temperature measurement points. Based on the acquired temperature signals, equivalent mold cavity temperature data that characterizes the overall thermal state of the epoxy molding compound under the current molding conditions is further determined. This equivalent temperature data reflects the temperature level of the epoxy molding compound within the mold cavity during the current time period. The specific determination method can be set according to the mold structure, the arrangement of temperature measurement points, or engineering needs; this invention does not limit this.

[0029] Through the above method, without changing the existing molding process, the simultaneous acquisition of multi-frequency electrical response data of epoxy molding compound and equivalent temperature data of mold cavity was achieved, providing a reliable data foundation for subsequent curing state analysis based on dielectric properties and temperature information.

[0030] Step S20: Calculate the complex impedance data corresponding to each excitation frequency based on the electrical response data, construct dielectric characteristic quantities to characterize the change of dielectric response of epoxy molding compound based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, and perform temperature compensation processing on the dielectric characteristic quantities in combination with the equivalent temperature data of the mold cavity.

[0031] Specifically, calculating the complex impedance data corresponding to each excitation frequency based on the electrical response data includes: for each excitation frequency, under the AC excitation of the corresponding excitation frequency, acquiring the voltage signal time series and the current signal time series within the corresponding time period; based on the voltage signal time series and the current signal time series, calculating the amplitude ratio and phase difference between the voltage signal and the current signal; determining the amplitude ratio as the impedance amplitude information at the corresponding excitation frequency, and determining the phase difference as the impedance phase information at the corresponding excitation frequency; the impedance amplitude information and the impedance phase information together constitute the complex impedance data at the corresponding excitation frequency.

[0032] Furthermore, based on the amplitude difference and phase difference between complex impedance data at different excitation frequencies, dielectric characteristic quantities for characterizing the change in dielectric response of epoxy molding compound are constructed, including: for any set of different excitation frequencies, obtaining impedance amplitude information and impedance phase information in the complex impedance data at the corresponding excitation frequencies; based on the impedance amplitude information, calculating the difference between impedance amplitude information corresponding to different excitation frequencies to obtain an amplitude difference characteristic quantity characterizing the relationship between impedance amplitude and frequency; based on the impedance phase information, calculating the difference between impedance phase information corresponding to different excitation frequencies to obtain a phase difference characteristic quantity characterizing the relationship between impedance phase and frequency; combining the amplitude difference characteristic quantity and the phase difference characteristic quantity as the dielectric characteristic quantity to characterize the change in dielectric response of epoxy molding compound during the molding process as the curing process progresses.

[0033] Furthermore, temperature compensation processing is performed on the dielectric feature based on the cavity equivalent temperature data, including: acquiring cavity equivalent temperature data within the time period corresponding to the dielectric feature during the construction of the dielectric feature; and correcting the frequency response offset caused by temperature changes in the dielectric feature based on the cavity equivalent temperature data to eliminate the influence of cavity temperature fluctuations on the dielectric feature, thereby obtaining the temperature-compensated dielectric feature.

[0034] In this embodiment of the invention, after obtaining the electrical response data of the epoxy molding compound and the equivalent temperature data of the mold cavity during the molding process, the present invention further processes the collected electrical response data to extract characteristic information that reflects the change of the dielectric state of the epoxy molding compound with the curing process. Since the internal polarization mechanism, carrier migration ability, and molecular chain segment motion state of the epoxy molding compound all undergo significant changes during the curing process, these changes are directly reflected in the differences in the material's response to electric field excitation at different frequencies. Therefore, constructing dielectric characteristic quantities through multi-frequency electrical responses can more effectively characterize the state evolution during the curing process.

[0035] In specific implementation, for each preset excitation frequency, under the AC excitation of the corresponding excitation frequency, a voltage signal time series and a current signal time series over a certain period are acquired. The time range can cover multiple excitation cycles to reduce the impact of instantaneous disturbances on the calculation results, but this invention does not impose specific limitations on this. Based on the acquired voltage signal time series... With current signal time series The amplitude and phase information can be extracted separately. For example, within one or more stable excitation cycles, the voltage and current signals can be represented as follows:

[0036] ;

[0037] in, and These represent the excitation frequency, respectively. The voltage and current amplitudes under these conditions Indicates the corresponding angular frequency. and These represent the phases of the voltage and current signals, respectively. Based on the amplitude and phase information mentioned above, the impedance amplitude and phase information at the corresponding excitation frequency can be calculated. The impedance amplitude information can be determined by the ratio of the voltage amplitude to the current amplitude, i.e.:

[0038] ;

[0039] The impedance phase information is determined by the phase difference between the voltage signal and the current signal, that is:

[0040] ;

[0041] In an embodiment of the present invention, the above impedance amplitude information is... With impedance phase information Together as excitation frequency The above-described form of complex impedance data representation. It should be understood that the above method of extracting amplitude and phase is only an example. In practical applications, equivalent frequency domain analysis methods, correlation analysis methods, or other methods that can obtain amplitude ratios and phase differences can also be used. As long as the impedance amplitude information and impedance phase information obtained can correspond one-to-one with the applied excitation frequency, they should be considered to fall within the protection scope of this invention.

[0042] After obtaining complex impedance data at different excitation frequencies, this invention further utilizes the relative relationships between the complex impedance data at different frequencies to construct dielectric characteristic quantities. Compared with directly using the impedance value at a single frequency, the difference characteristics between frequencies can effectively reduce the influence of factors such as mold cavity structure, filling state, and electrode contact conditions on the absolute value, and better highlight the intrinsic characteristics of the material's dielectric response changing with the curing process. Specifically, for any selected set of different excitation frequencies... and It can obtain impedance amplitude information at the corresponding frequency. , and impedance phase information , Based on this, amplitude difference characteristic and phase difference characteristic are constructed, for example:

[0043] ;

[0044] ;

[0045] The above amplitude difference characteristic quantity The phase difference characteristic is used to characterize the relative relationship between impedance amplitude and excitation frequency. This is used to characterize the relative relationship between impedance phase and excitation frequency. In practical applications, multiple frequency pairs can be selected to construct corresponding difference characteristic quantities according to engineering needs, or the difference characteristic quantities of multiple frequency pairs can be combined into a vector form as the input of dielectric characteristic quantities. This invention does not limit the number of excitation frequencies, the selection method of frequency pairs, or the combination form of characteristic quantities. As long as the constructed dielectric characteristic quantity can reflect the relative change relationship between dielectric response under different excitation frequencies, it should fall within the technical scope of this invention.

[0046] It should be noted that the dielectric response of epoxy molding compounds is not only related to the curing process but is also significantly affected by temperature changes. During the molding process, even if the mold temperature setpoint remains constant, the actual temperature inside the mold cavity may still change due to uneven heat conduction, exothermic reactions of the material, or process fluctuations, resulting in a general drift of dielectric characteristics with temperature. To reduce the interference of temperature factors on dielectric characteristics, this invention introduces equivalent mold cavity temperature data to perform temperature compensation processing on the dielectric characteristics while constructing them.

[0047] In practical implementation, the equivalent temperature data of the mold cavity within the time period corresponding to the dielectric characteristic quantity can be obtained. And based on this temperature data, the dielectric characteristics are corrected. For example, for a certain amplitude difference characteristic... A temperature compensation model of the following form can be constructed:

[0048] ;

[0049] in, This represents the characteristic quantity of the amplitude difference after temperature compensation. This represents the temperature sensitivity coefficient associated with the selected frequency. The reference temperature is indicated. Similarly, the phase difference characteristic can also be corrected using a corresponding temperature compensation form. It should be understood that the above compensation relationship is merely an example, and the present invention does not limit the specific form of the temperature compensation function. The compensation relationship can be in linear form, piecewise linear form, or other functional forms that can characterize the change of dielectric characteristics with temperature.

[0050] By performing temperature compensation processing on the dielectric characteristics, the influence of mold cavity temperature fluctuations on the dielectric response characteristics can be largely eliminated, making the temperature-compensated dielectric characteristics more accurately reflect the changing trend of the epoxy molding compound's curing process. This temperature-compensated dielectric characteristic is then used as input for subsequent cure degree inversion and state determination, providing a stable and reliable data foundation for online evaluation of the epoxy molding compound's curing state.

[0051] In another possible implementation, considering that during the molding process, the epoxy molding compound may experience incomplete filling, localized air inclusions, or uneven material distribution in individual mold passes, these factors can cause changes in the equivalent electric field distribution at different locations within the mold cavity, thereby affecting the stability of the electrical response data. To address this scenario, this invention introduces a time-consistent feature validity discrimination mechanism during the construction of dielectric characteristics.

[0052] Specifically, during the molding and curing stage, time consistency analysis is performed on dielectric characteristics obtained at multiple consecutive time points under the same set of excitation frequencies to calculate the magnitude and direction of change of dielectric characteristics within adjacent time periods. When a dielectric characteristic deviates significantly from its historical trend within a short period and fails to gradually revert over time, the corresponding time period is marked as an abnormal observation interval. Within the abnormal observation interval, the weight of the dielectric characteristics in the curing degree inversion process during that time period can be reduced, or the update calculation of the curing state inversion relationship can be temporarily suspended.

[0053] By adopting the above method, without introducing additional sensors or changing the original detection process, the robustness of the online detection method to abnormal electrical responses under complex working conditions is improved, and the curing degree inversion results can more stably reflect the overall curing process of epoxy molding compound, thereby avoiding interference from local anomalies on the gel determination time and online detection results.

[0054] Step S30: Based on the dielectric characteristics after temperature compensation, obtain the curing degree change information of the epoxy molding compound through online inversion.

[0055] Specifically, based on the temperature-compensated dielectric characteristics, a curing state inversion relationship is constructed to describe the curing process of the epoxy molding compound, wherein the degree of curing is used as the state variable to be inverted in the curing state inversion relationship; during the continuous time period of the molding process, the temperature-compensated dielectric characteristics are used as the observation input to perform online update calculations on the curing state inversion relationship to obtain the degree of curing estimate for each time point; the degree of curing estimate is arranged in chronological order to form a degree of curing change sequence, which is output as degree of curing change information.

[0056] Furthermore, during the continuous time period of the molding process, the temperature-compensated dielectric characteristics are used as observation inputs to perform online update calculations on the curing state inversion relationship to obtain the curing degree estimate for each time point. This includes: calculating the corresponding dielectric response increment based on the change in the temperature-compensated dielectric characteristics between adjacent time points; performing a recursive update on the curing degree estimate based on the dielectric response increment, and applying a monotonically increasing constraint to the curing degree estimate to limit the curing degree estimate from changing in the opposite direction over time; and performing consistency correction on the curing degree estimate at adjacent time points based on a preset change smoothing condition during the recursive update process to obtain the corrected curing degree estimate.

[0057] In this embodiment of the invention, after obtaining the temperature-compensated dielectric characteristics, the present invention further performs online inversion of the curing state of the epoxy molding compound based on these dielectric characteristics. The curing process of the epoxy molding compound during molding is continuous and irreversible, and its curing state can be characterized by the degree of curing, a state variable. Since the degree of curing cannot be obtained through direct measurement, this invention constructs a curing state inversion relationship, mapping observable dielectric characteristics to estimated degrees of curing, thereby achieving online characterization of the curing process.

[0058] In this embodiment of the invention, the temperature-compensated dielectric characteristics are expressed as a time function:

[0059] ;

[0060] in, Indicates at time The dielectric characteristic vector obtained under these conditions can have components that correspond to the amplitude difference characteristic and phase difference characteristic under different combinations of excitation frequencies. (Based on curing degree) As the state variables to be inverted, a solidification state inversion relationship is constructed to describe the solidification process, which can be abstractly represented as:

[0061] ;

[0062] in, This represents the inverse mapping relationship between dielectric characteristics and degree of cure. This mapping relationship can be obtained through calibration based on the material system and process conditions, and its specific mathematical form is not limited.

[0063] During the continuous time period of the molding process, the temperature-compensated dielectric characteristics are continuously input into the curing state inversion relationship in the form of a time series to estimate the degree of curing online. To improve the responsiveness of the inversion process to dynamic changes, this invention adopts an incremental recursive update method. At adjacent time points... and Between these points, calculate the change in dielectric characteristic:

[0064] ;

[0065] And based on this dielectric response increment, the curing degree estimate is recursively updated, for example:

[0066] ;

[0067] in, Indicates time The corresponding estimated degree of cure, This represents the mapping function of dielectric response increment to curing degree change, which is used to characterize the relationship between changes in dielectric characteristic quantity and the progress of curing process.

[0068] Considering the physical characteristics of the epoxy molding compound curing process, this invention applies a monotonically increasing constraint to the curing degree estimate during the recursive update process to prevent the curing degree estimate from changing inversely over time. Specifically, when the curing degree prediction value obtained from the recursive update satisfies... At that time, the current curing degree estimate will be corrected to This ensures the physical consistency of the curing degree change sequence over time.

[0069] Furthermore, to avoid excessive influence of local dielectric response fluctuations or measurement noise on the curing degree inversion results, this invention introduces a change smoothing condition during the recursive update process to perform consistency correction on the curing degree estimates at adjacent time points. For example, when the curing degree change between adjacent time points exceeds a preset range, a weighted smoothing method can be used to correct the curing degree estimate.

[0070] ;

[0071] in, This is a preset smoothing coefficient used to adjust the weighting relationship between the current update result and the historical estimate.

[0072] Through the aforementioned online inversion and constraint update process, a set of curing degree estimates evolving over time can be obtained within a continuous time period of the molding process. These estimates are then arranged in chronological order to form a curing degree change sequence, which serves as the output curing degree change information characterizing the curing process of the epoxy molding compound. This curing degree change information maintains sensitivity to changes in dielectric response while possessing good temporal continuity and physical rationality, providing a stable and reliable state input for subsequent gel determination.

[0073] Step S40: Based on the curing degree change information, determine the gel determination time during the curing process of the epoxy molding compound, and output the online detection results used to characterize the curing state of the epoxy molding compound.

[0074] Specifically, based on the curing degree change information, the curing rate information of the curing degree changing with time is calculated; in the curing rate information, the time interval from the curing rate changing from a continuously increasing state to a non-continuously increasing state is identified, and the time interval is determined as the gel determination interval in the curing process; within the gel determination interval, the time point that meets the preset time determination condition is determined as the gel determination time; the gel determination time and the corresponding curing degree estimate are used together as the online detection result output to characterize the curing state of the epoxy molding compound.

[0075] Furthermore, the preset time determination condition is as follows: within the gel determination interval, the curing rate information is discretely sampled with a preset time step; when the curing rate values ​​corresponding to multiple consecutive adjacent sampling times are not greater than the curing rate value corresponding to the previous sampling time, the first sampling time that satisfies this condition is determined as the candidate gel time; within a preset duration after the candidate gel time, if the curing rate value does not again exceed the curing rate value corresponding to the candidate gel time, the candidate gel time is determined as the gel determination time.

[0076] In this embodiment of the invention, after obtaining information on the curing degree change of the epoxy molding compound, the present invention further identifies key state nodes in the curing process based on this curing degree change information. The gelation stage is a key physical stage in which the epoxy molding compound transforms from a viscous flow state to an elastic network structure. Its corresponding chemical reaction kinetics typically manifest as a change in the curing reaction rate from continuous acceleration to a state limited by diffusion or network formation. Therefore, compared to directly using the absolute value of the curing degree as the criterion, the present invention identifies the gelation determination moment based on the characteristics of the curing rate change.

[0077] Specifically, based on the aforementioned curing degree change sequence The curing rate can be obtained by calculating the relationship between the degree of curing and time. The curing rate can be expressed as the rate of change of the degree of curing with respect to time; for example, under discrete-time conditions, it can be expressed as:

[0078] ;

[0079] in, Indicates at time The estimated curing rate at the location. By continuously calculating the curing rate information throughout the molding process, a curing rate change sequence reflecting the characteristics of the curing reaction progression can be obtained.

[0080] In the curing rate information, this invention focuses on the trend of curing rate change over time. In the early stages of curing, due to the abundance of active groups in the reaction system, the curing reaction rate typically shows a continuous increasing trend. As the reaction proceeds, the system gradually forms a spatial network structure, restricting molecular movement, and the increasing trend of the curing reaction rate gradually weakens and reverses. Based on this physical characteristic, this invention identifies the time interval in the curing rate information where the curing rate transitions from a continuously increasing state to a non-continuously increasing state, and defines this time interval as the gel determination interval. This interval is used to limit the reasonable time range for gel determination, thereby avoiding misjudgments in the early or late stages of curing.

[0081] After determining the gel determination interval, this invention further introduces regularized timing conditions within this interval to select a stable and physically meaningful gel determination time from multiple possible candidate time points. Specifically, within the gel determination interval, the curing rate information is discretely sampled according to a preset time step to form a regularized sampling sequence. This time step can be set according to the molding process cycle or data acquisition frequency, and this invention does not limit it.

[0082] When the curing rate values ​​corresponding to multiple consecutive adjacent sampling times are not greater than the curing rate value corresponding to the previous sampling time, it indicates that the curing rate no longer maintains a monotonically increasing trend. In this case, the first sampling time that satisfies this condition is determined as the candidate gelation time. To avoid misjudgment due to local noise or short-term fluctuations, this invention further introduces a preset duration constraint after the candidate gelation time. Within this duration, if the curing rate value does not again exceed the curing rate value corresponding to the candidate gelation time, the trend change in the curing rate is considered stable, and this candidate gelation time is ultimately determined as the gelation determination time.

[0083] By combining the aforementioned partitioning and rule-based determination methods, this invention can stably identify the gel stage in the epoxy molding compound curing process without relying on empirical thresholds. Finally, the determined gel determination time and the corresponding estimated degree of cure are output as the online detection result, thus providing an engineering-interpretable detection basis for characterizing the overall curing state of the epoxy molding compound.

[0084] In one specific implementation, taking the curing process of a certain epoxy molding compound under standard molding conditions as an example, the online detection process for determining the gelation time is explained. After the molding process is completed, the curing degree change information is inverted online at a fixed time step during the curing stage, and the corresponding curing rate information is further calculated. The time step is set to 10 seconds, and the estimated curing degree values ​​corresponding to several time points are continuously obtained during the molding curing stage, as shown in Table 1 for specific examples.

[0085] Table 1. Example data on degree of cure and cure rate

[0086] ;

[0087] As shown in Table 1, the curing rate continuously increases with time from 60s to 120s; after 120s, the curing rate no longer increases and gradually shows a decreasing trend. Based on this change characteristic, the time interval from 120s to 150s, in which the curing rate changes from a continuously increasing state to a non-continuously increasing state, is determined as the gel determination interval.

[0088] Within the gel determination interval, the curing rate information is discretely sampled according to preset time determination conditions. When the curing rate value is not greater than the curing rate value corresponding to the previous sampling time in multiple consecutive adjacent sampling times (120s, 130s, 140s), the first sampling time of 120s that meets the condition is determined as the candidate gel time. Furthermore, within a preset duration after the candidate gel time 120s, the curing rate value does not exceed the curing rate value corresponding to 120s again. Therefore, 120s is finally determined as the gel determination time of the epoxy molding compound in this molding process. Finally, the determined gel determination time 120s and the corresponding estimated degree of cure of 0.48 are output as online detection results to characterize the curing state of the epoxy molding compound in this molding process.

[0089] In another possible implementation, within multiple consecutive molding cycles, the gel determination time and corresponding estimated degree of cure for each molding cycle are recorded, and a statistical distribution of gel determination under the molding cycle sequence is constructed. When the gel determination time obtained in the current molding cycle shows a continuous shift relative to the statistical mean of historical molding cycles, and this shift trend remains consistent across multiple adjacent molding cycles, it is determined that a systematic change has occurred in the initial state of the material. In this case, the initial conditions for the curing state inversion relationship in subsequent molding cycles can be adaptively corrected to make the degree of cure inversion process more closely match the current material state.

[0090] like Figure 2 As shown, this invention provides an online detection system for the curing characteristics of epoxy molding compound. The system includes: a response unit, used to acquire electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies during the molding process, and simultaneously acquire equivalent temperature data of the mold cavity; a processing unit, used to calculate the complex impedance data corresponding to each excitation frequency based on the electrical response data, construct a dielectric characteristic quantity to characterize the dielectric response change of the epoxy molding compound based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, and perform temperature compensation processing on the dielectric characteristic quantity in combination with the equivalent temperature data of the mold cavity; an inversion unit, used to obtain the curing degree change information of the epoxy molding compound online based on the temperature-compensated dielectric characteristic quantity; and a result output unit, used to determine the gel determination time during the curing process of the epoxy molding compound based on the curing degree change information, and output the online detection result to characterize the curing state of the epoxy molding compound.

[0091] In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 3As shown, the computer device includes a processor A01, a network interface A02, a memory (not shown), and a database (not shown) connected via a system bus. The processor A01 provides computing and control capabilities. The memory includes internal memory A03 and a non-volatile storage medium A06. The non-volatile storage medium A06 stores an operating system B01, a computer program B02, and a database (not shown). The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 stored in the non-volatile storage medium A06. The network interface A02 is used for communication with an external terminal (not shown) via a network connection (double arrows indicate bidirectional communication with the external terminal). When the processor A01 executes the computer program B02, it implements online detection of the curing characteristics of an epoxy molding compound.

[0092] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware. This program is stored in a storage medium and includes several instructions to cause a microcontroller, chip, or processor to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as a USB flash drive, a portable hard drive, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0093] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details described above. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention. It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe the various possible combinations.

[0094] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the embodiments of the present invention, they should also be regarded as the content disclosed by the embodiments of the present invention.

Claims

1. An online detection method for the curing properties of epoxy molding compounds, characterized in that, The method includes: During the molding process, electrical response data of the epoxy molding compound in the mold cavity at at least two different excitation frequencies are acquired, and the equivalent temperature data of the mold cavity is acquired simultaneously. Based on the electrical response data, the complex impedance data corresponding to each excitation frequency is calculated. Based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, a dielectric characteristic quantity is constructed to characterize the change in dielectric response of epoxy molding compound. The dielectric characteristic quantity is then subjected to temperature compensation processing in conjunction with the equivalent temperature data of the mold cavity. Based on the dielectric characteristics after temperature compensation, the curing degree change information of epoxy molding compound is obtained through online inversion; Based on the curing degree change information, the gel determination time in the epoxy molding compound curing process is determined, and online detection results for characterizing the curing state of the epoxy molding compound are output.

2. The online detection method for curing properties of epoxy molding compound according to claim 1, characterized in that, During the molding process, electrical response data of the epoxy molding compound inside the mold cavity at at least two different excitation frequencies are acquired, and equivalent temperature data of the mold cavity are acquired simultaneously, including: After the mold cavity is filled, at least two AC excitation signals of different frequencies are applied to the epoxy molding compound in the mold cavity. Under the action of the AC excitation signal, voltage and current signals corresponding to each excitation frequency are collected respectively as electrical response data; While acquiring the electrical response data, a temperature signal characterizing the temperature state of the epoxy molding compound inside the mold cavity is acquired, and the equivalent temperature data of the mold cavity is determined based on the temperature signal.

3. The online detection method for curing properties of epoxy molding compound according to claim 2, characterized in that, Based on the electrical response data, the complex impedance data corresponding to each excitation frequency is calculated, including: For each of the aforementioned excitation frequencies, under the AC excitation of the corresponding excitation frequency, the voltage signal time series and current signal time series within the corresponding time period are obtained; Based on the voltage signal time series and the current signal time series, calculate the amplitude ratio and phase difference between the voltage signal and the current signal; The amplitude ratio is determined as the impedance amplitude information at the corresponding excitation frequency, and the phase difference is determined as the impedance phase information at the corresponding excitation frequency. The impedance amplitude information and the impedance phase information together constitute the complex impedance data at the corresponding excitation frequency.

4. The online detection method for curing characteristics of epoxy molding compound according to claim 3, characterized in that, Dielectric characteristic quantities for characterizing the dielectric response changes of epoxy molding compounds are constructed based on the amplitude and phase differences between complex impedance data at different excitation frequencies, including: For any set of different excitation frequencies, the impedance amplitude information and impedance phase information in the complex impedance data at the corresponding excitation frequency are obtained respectively; Based on the impedance amplitude information, the difference between the impedance amplitude information corresponding to different excitation frequencies is calculated to obtain the amplitude difference characteristic quantity that characterizes the relationship between impedance amplitude and frequency. Based on the impedance phase information, the difference between the impedance phase information corresponding to different excitation frequencies is calculated to obtain the phase difference characteristic quantity that characterizes the relationship between impedance phase and frequency. The amplitude difference characteristic and the phase difference characteristic are combined as the dielectric characteristic, which is used to characterize the change of the dielectric response of the epoxy molding compound during the curing process.

5. The online detection method for curing characteristics of epoxy molding compound according to claim 4, characterized in that, Temperature compensation processing is performed on the dielectric characteristics based on the equivalent temperature data of the mold cavity, including: During the construction of the dielectric characteristic, the equivalent temperature data of the mold cavity within the time period corresponding to the dielectric characteristic is obtained; Based on the equivalent temperature data of the mold cavity, the frequency response offset caused by temperature change in the dielectric characteristic is corrected to eliminate the influence of mold cavity temperature fluctuation on the dielectric characteristic, and the temperature-compensated dielectric characteristic is obtained.

6. The online detection method for curing properties of epoxy molding compound according to claim 1, characterized in that, Based on the temperature-compensated dielectric characteristics, online inversion is used to obtain information on the curing degree changes of the epoxy molding compound, including: Based on the dielectric characteristics after temperature compensation, a curing state inversion relationship is constructed to describe the curing process of epoxy molding compound, wherein the degree of curing is used as the state variable to be inverted in the curing state inversion relationship. During the continuous time period of the molding process, the temperature-compensated dielectric characteristics are used as observation inputs to perform online update calculations on the curing state inversion relationship to obtain the curing degree estimate for each time point. The estimated curing degree values ​​are arranged in chronological order to form a curing degree change sequence, which is then output as curing degree change information.

7. The online detection method for curing characteristics of epoxy molding compound according to claim 6, characterized in that, During the continuous time period of the molding process, the temperature-compensated dielectric characteristics are used as observation inputs to perform online update calculations on the curing state inversion relationship, in order to obtain the estimated degree of curing at each time point, including: Between adjacent time points, the corresponding dielectric response increment is calculated based on the change in dielectric characteristics after temperature compensation. Based on the dielectric response increment, the curing degree estimate is recursively updated, and a monotonically increasing constraint is applied to the curing degree estimate to limit the curing degree estimate from changing in the opposite direction over time. During the recursive update process, based on a preset change smoothing condition, the curing degree estimates at adjacent time points are corrected for consistency to obtain corrected curing degree estimates.

8. The online detection method for curing characteristics of epoxy molding compound according to claim 1, characterized in that, Based on the curing degree change information, the gel determination time during the epoxy molding compound curing process is determined, and online detection results characterizing the curing state of the epoxy molding compound are output, including: Based on the curing degree change information, calculate the curing rate information of curing degree change over time; In the curing rate information, the time interval between the curing rate changing from a continuously increasing state to a non-continuously increasing state is identified, and the time interval is determined as the gel determination interval in the curing process; Within the gel determination interval, the time point that meets the preset time determination condition is determined as the gel determination time. The gel determination time and the corresponding curing degree estimate are used together as the online detection result output to characterize the curing state of the epoxy molding compound.

9. The online detection method for curing properties of epoxy molding compound according to claim 8, characterized in that, The preset time determination condition is: Within the gel determination interval, the curing rate information is discretely sampled at a preset time step; When the curing rate values ​​corresponding to multiple consecutive adjacent sampling times are not greater than the curing rate value corresponding to the previous sampling time, the first sampling time that meets this condition is determined as the candidate gelation time. If, within a preset duration following the candidate gelation time, the curing rate value does not again exceed the curing rate value corresponding to the candidate gelation time, then the candidate gelation time is determined as the gelation determination time.

10. An online detection system for the curing properties of epoxy molding compounds, characterized in that, The system includes: The response unit is used to acquire electrical response data of epoxy molding compound in the mold cavity at at least two different excitation frequencies during the molding process, and simultaneously acquire the equivalent temperature data of the mold cavity. The processing unit is used to calculate the complex impedance data corresponding to each excitation frequency based on the electrical response data, construct dielectric characteristic quantities to characterize the change of dielectric response of epoxy molding compound based on the amplitude difference and phase difference between the complex impedance data at different excitation frequencies, and perform temperature compensation processing on the dielectric characteristic quantities in combination with the equivalent temperature data of the mold cavity. The inversion unit is used to obtain information on the curing degree change of epoxy molding compound online based on the dielectric characteristics after temperature compensation; The result output unit is used to determine the gel determination time in the curing process of epoxy molding compound based on the curing degree change information, and output online detection results to characterize the curing state of epoxy molding compound.

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