A thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment

Abstract

The application discloses a thermocouple temperature measurement method suitable for a thin film vacuum evaporation device, and comprises the following steps: S1, a temperature module and a PLC controller are combined to measure a thermocouple original signal value; S2, dynamic front-end filtering: the original value of the thermocouple electromotive force collected is dynamically filtered with adjustable parameters at the PLC controller end, and the filtering strength is adjusted in real time according to different evaporation process stages; S3, standardized temperature conversion: based on the scale of the selected thermocouple, the conversion from the electromotive force to the temperature is completed in the PLC controller, and a thermocouple temperature measurement value is obtained. The thermocouple temperature measurement method suitable for the thin film vacuum evaporation device can improve the temperature measurement precision, optimize the thin film evaporation process quality, and has good compatibility.

Description

TECHNICAL FIELD

[0001] The present application relates to a temperature measurement method, in particular to a thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment. BACKGROUND

[0002] As the core preparation equipment of perovskite photovoltaic devices, the system architecture of thin film vacuum evaporation equipment usually includes film feeding chamber, buffer chamber and process chamber modules. The evaporation source mechanism is integrated in the process chamber, which can achieve precise co-evaporation of multi-metal (such as Au, Ag, Cu, etc.) in a high-temperature environment of 1500℃ or above. This technical feature is universal in perovskite device manufacturing (see literature DOI: 10.1039 / D2EE02023F). Under this working condition, C-type thermocouples (W5Re / W26Re) have excellent high-temperature stability (melting point 2340℃) and low thermoelectric potential drift characteristics (<0.1% @ 1800℃), and become the mainstream temperature sensing scheme. Other types of thermocouples (such as K-type, etc.) are also used for low-temperature evaporation processes.

[0003] In the field of industrial temperature measurement, the collection and processing of thermocouple signals usually adopt the following two types of technical schemes:

[0004] ① Temperature transmitter + PLC analog module architecture:

[0005] The original thermocouple signal is first converted into a standard analog signal (such as 4-20mA) by a special temperature transmitter, and then AD converted by a PLC analog input module. The transmitter needs to preset the corresponding cold end compensation algorithm and linearization processing module according to the thermocouple scale (such as K-type, J-type, C-type) (according to IEC 60584-1 standard).

[0006] Typical application cases include vacuum evaporation equipment temperature control systems, which use Rosemount 3144P transmitters and Siemens S7-1200 PLC 6ES7 231-4HD32 analog modules to realize continuous collection of C-type thermocouples.

[0007] ② Integrated PLC temperature module direct sampling scheme:

[0008] Connect the thermocouple directly through the PLC special temperature module (such as Omron CJ1W-TC001), and the module integrates scale selection switch, fixed parameter digital filter and cold end compensation circuit inside. For example:

[0009] The built-in hardware filter circuit based on Butterworth low-pass filter in the module has a fixed cutoff frequency of 10Hz (corresponding to a step response time of about 100ms)

[0010] The signal processing procedure is: thermocouple -> cold end compensation -> AD conversion -> fixed coefficient filtering -> temperature linearization calculation.

[0011] The core technical feature of the above scheme is:

[0012] Hardware matching dependency: the corresponding transmitter or the graduation number parameter of the PLC module needs to be selected according to the type of thermocouple (for example, the graduation table difference of C type).

[0013] Fixed filtering mechanism: pre-set filtering parameters (such as cutoff frequency and filter order) are used to ensure signal stability.

[0014] Signal processing: thermocouple signals (mV level) are susceptible to electromagnetic interference (EMI), ground loop noise, poor contact, temperature gradient mutation or cold end compensation error. Normal fluctuation: about 0.1-0.5 mV, corresponding to a temperature change of about 6.7-33.3℃ (C type sensitivity about 15 µV / ℃). In order to solve this problem, the temperature acquisition module or the temperature conversion module will have fixed software filtering processing. This processing method cannot completely adapt to the application occasion of the device, and the collected temperature will still have frequent fluctuations. The PLC will perform secondary filtering processing on the collected temperature to ensure the stability of the temperature control system.

[0015] As can be seen from the above, the prior art has the following defects:

[0016] (1) Fixed filtering temperature fluctuation

[0017] The software filtering processing of the temperature acquisition module is not suitable for the electromagnetic interference environment in the field, and the converted temperature will have large fluctuations.

[0018] (2) Secondary filtering increases temperature error

[0019] The PLC secondary filtering processing method cannot suppress noise from the front end of the signal chain, and has conversion error superposition, which also affects the process quality of the evaporation equipment.

[0020] (3) System compatibility problem

[0021] Taking C type thermocouple as an example, industry research data shows (based on HMI / SCADA Market Analysis Report 2024) that the native support rate of mainstream PLC modules for C type thermocouples is less than 19%. When selecting, in order to match the module that supports the type of thermocouple, it is necessary to select a heterogeneous module with thermocouple type across manufacturers, which leads to the discretization of hardware architecture; and further leads to the increase of time cost, fund cost and personnel cost. SUMMARY

[0022] The technical problem solved by the present application is to provide a thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment, which can improve temperature measurement accuracy, optimize thin film evaporation process quality, and has good compatibility.

[0023] To solve the above technical problems, the present application provides a thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment, comprising the following steps: S1, using a temperature module and a PLC controller to measure the original signal value of the thermocouple; S2, dynamic front-end filtering: adjusting the parameter dynamic filtering of the original value of the thermocouple electromotive force collected at the PLC controller end, and adjusting the filtering strength in real time according to different evaporation process stages; S3, standardized temperature conversion: based on the selected thermocouple scale, the conversion of electromotive force to temperature is completed in the PLC controller to obtain the thermocouple temperature measurement value.

[0024] Further, the PLC controller in step S1 is S7-1500.

[0025] Further, the temperature module in step S1 is beckhoff_KL3314, the thermocouple is connected to the KL3314 collection channel in step S1, the channel type is changed to mV type reading, and the data is fed back to the PLC controller through the DP coupler BK3150.

[0026] Further, the thermocouple in step S1 is a C-type thermocouple, which uses a quintic polynomial to output a nominal electromotive force; the quintic polynomial is used in step S3 to complete the conversion calculation of electromotive force to temperature by numerical iteration, the input range of electromotive force is 0-37mV, the temperature range is 32℉-4200℉, the Fahrenheit degree accuracy setting value is 0.01℉, and the worst time complexity O(log2n) is controlled by using binary search.

[0027] Further, the current filtering output in step S2 is the weighted sum of the original signal and the historical signal, and the weight of the historical data and the current input in the filtering output is adjusted by the filtering coefficient.

[0028] Further, the step S2 comprises: S21: initial value assignment, such that the last saved filtered value PreviousEMF and the original electromotive force RawEMF are equal; S22: reading the filter time dynamic parameter FilterTime and the PLC collection period DeltaT; S23: calculating the filter coefficient Alpha based on the filter time dynamic parameter, Alpha = e^(-DeltaT / FilterTime); obtaining the original electromotive force of the thermocouple RawEMF and the last saved filtered value PreviousEMF; S24: applying a first-order low-pass filter formula to obtain the current filtered electromotive force FilteredEMF, FilteredEMF = RawEMF(1-Alpha)+PreviousEMF·Alpha; S25: updating the historically saved electromotive force data; S26: outputting the filtered electromotive force data.

[0029] Further, the step S2 divides the evaporation process stage into a start-up stage, a rapid heating stage, a constant temperature maintaining stage and a cooling stage based on the temperature change rate, and controls the response speed by dynamically adjusting the time constant τ of the filter.

[0030] Further, the start-up stage corresponds to the cold start of the evaporation equipment, and the step S2 adjusts the filter time dynamic parameter in the start-up stage as follows: setting the initial time constant τ of the filter to 2 seconds to quickly suppress circuit noise, and then dynamically reducing the τ value according to the cavity vacuum degree, when the vacuum degree is detected to be 10^-4 Pa, τ is reduced to 0.5 seconds to improve the response speed, and the vacuum environment heat conduction mode is switched.

[0031] Further, the step S2 adjusts the filter time dynamic parameter in the rapid heating stage, the constant temperature maintaining stage and the cooling stage as follows: in the rapid heating stage, the temperature change rate is calculated in real time, and the gradient threshold is used to adjust the τ value between 0.1-0.5 seconds; in the constant temperature maintaining stage, the τ value is adjusted in real time according to the temperature error between 0.5-5.0 seconds; in the cooling stage, the τ value is adjusted in real time according to the evaporation source cooling rate between 0.5-2.0 seconds.

[0032] Further, in the rapid heating stage, for a metal source, when dT / dt≥15℃ / s, τ=0.1 seconds; for an organic source, when dT / dt≥8℃ / s, τ=0.2 seconds; in the constant temperature maintaining stage, when the temperature error exceeds ±0.3℃, τ is gradually increased; in the cooling stage, when the rapid cooling is ≥0.1℃ / s, τ is 0.5-1 seconds; when the curve cooling is ≤0.1℃ / s, τ is 1-2 seconds.

[0033] The application has the following beneficial effects compared with the prior art: the thermocouple temperature measurement method suitable for the thin film vacuum evaporation equipment provided by the application suppresses noise from the front end of the signal chain, reduces conversion error superposition, improves temperature measurement accuracy, and optimizes thin film evaporation process quality. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 a flow chart of thermocouple temperature measurement of the application;

[0035] Figure 2 a feedback principle diagram of thermocouple temperature measurement of the application;

[0036] Figure 3 a thermocouple filtering flow chart of the application;

[0037] Figure 4 a temperature calculation flow chart of the application. DETAILED DESCRIPTION

[0038] The application will be further described below in combination with the drawings and examples.

[0039] The application discloses a thin film vacuum evaporation equipment thermocouple temperature data reading method based on PLC. The original millivolt (mV) signal of the thermocouple is directly processed by the internal algorithm of the PLC, the traditional mode of relying on the embedded algorithm of the module is abandoned, the stability of temperature collection is improved by the more flexible processing mode, and the evaporation uniformity of the thin film evaporation equipment is improved. For specific implementation steps, please refer to Figure 1 , including:

[0040] S1. The temperature module and the PLC controller are combined to measure the thermocouple temperature.

[0041] S2. Dynamic front-end filtering: The mV signal collected at the PLC end is dynamically filtered with adjustable parameters, the filtering strength is adjusted in real time according to the evaporation process stage (such as preheating, deposition, and cooling), and the interference amplification problem of traditional secondary filtering is avoided.

[0042] S3. Standardized temperature conversion: Based on the C-type thermocouple scale, the mV-temperature conversion is completed in the PLC, the algorithm universality is ensured, and the collection module of different manufacturers is adapted.

[0043] The application improves the stability of the temperature system by dynamic filtering and real-time temperature calibration, and then improves the uniformity of the evaporation film layer and the consistency of the deposition rate. The technical advantages are as follows:

[0044] • Strong compatibility: the module only needs to output the original mV signal, reducing the dependence on hardware;

[0045] • Flexible and controllable: the front-end filtering parameters can be dynamically configured on site to adapt to complex working conditions.

[0046] • Performance improvement: reduce signal processing delay and noise interference, directly optimize the quality of evaporation process.

[0047] The technical problems to be solved by the thermocouple temperature measurement method suitable for the thin film vacuum evaporation equipment provided by the application are as follows:

[0048] 1. Improve compatibility:

[0049] According to the problems existing in the prior art, the thermocouple signal processing method designed by the application can read data using a temperature module that is not compatible with the type of thermocouple without using a matching thermocouple type module, and the temperature value can be obtained through a calculation method in the PLC, thereby improving system compatibility, not being restricted in selection, directly reducing costs.

[0050] 2. Dynamic noise suppression:

[0051] Unlike the noise suppression method of the temperature module, the application can adjust the noise suppression time parameter in real time according to the electromagnetic interference of the equipment, different stages of the temperature control system, etc., realize dynamic optimization and adjustment design, match the diversification of the equipment environment, and improve the precision and stability of the evaporation temperature control system.

[0052] 3. Avoid secondary signal processing:

[0053] The application can suppress noise from the front end of the signal chain, reduce conversion error superposition, improve temperature precision, and optimize thin film evaporation process quality.

[0054] The implementation process of the application will be described in detail below taking a C-type thermocouple as an example.

[0055] 1. Thermocouple temperature feedback principle:

[0056] To implement the technical method of the application, the thermocouple temperature feedback principle needs to be understood first. The thermocouple feedback principle is as shown in Figure 2 : The thermocouple is composed of two conductors or semiconductors of different materials (referred to as thermoelectric electrodes) represented by two colors. One end of the two thermoelectric electrodes is fused together to form a working end C (a measurement end) for directly contacting the medium to be measured; the other end is a free end A / B (a cold end) that is usually in a certain constant temperature environment.

[0057] Due to the thermoelectric effect, the temperature difference between the C end and the A / B end will generate a potential difference. Because the two different metal materials will cause the potential difference between the A end and the C end and the B end and the C end to be different, the final result is that there is a potential difference between the A end and the B end, and this potential difference is expressed in mV.

[0058] Adopt temperature collection module matching with thermocouple type, through mV value obtained by measurement, according to pre-stored algorithm of module, calculate known electromotive force (mV) and temperature, can calculate temperature value and feedback to control system;

[0059] 2 Hardware configuration

[0060] Use beckhoff_KL3314 temperature module, PLC controller (S7-1500) combination to read C type thermocouple as an example (other configuration can be replaced), technical document (manual KL3314 2022-05-24 | Version: 4.3).

[0061] The module does not support C type thermocouple type, when using, can change channel type to mV type reading, precision selection 2 μV corresponds to ± 60 mV (C type thermocouple voltage range 0~37 mV), analog module module setting uses KS2000 configuration software.

[0062] Hardware wiring mode, connect C type thermocouple into KL3314 collection channel, through DP coupler BK3150, feedback data to PLC controller (S7-1500).

[0063] 3 "C" type thermocouple selection

[0064] Reference file: "Tungsten-rhenium thermocouple graduation number equivalent products" from ASTM standard annual, copyright owned by American materials and testing association. The reference file describes that the nominal electromotive force of C thermocouple relative to temperature value is defined by a quintic polynomial. The electromotive force expressed in absolute millivolt value (IPTS68) is determined using the equation and coefficients shown below, temperature is expressed in Fahrenheit. Equation: EMF = AT + BT 2 + CT 3 + DT 4 + ET 5 + K, wherein EMF = electromotive force (mV), T = temperature (Fahrenheit), A\B\C\D\E\T = coefficient.

[0065] For example, graduation number G and C of tungsten-rhenium thermocouple, WN28R (G type) and WSRM28P (C type) thermocouple, the nominal electromotive force relative to temperature value is defined by a quintic polynomial. The electromotive force expressed in absolute millivolt value (IPTS68) is determined using the equation and coefficients shown below, temperature is expressed in Fahrenheit.

[0066] Normal form: EMF = AT + BT 2 + CT 3 + DT 4 + ET 5 + K

[0067] Temperature Range: 32°F to 4200°F (0 to 2315°C)

[0068]

[0069] 4 Signal Front-End Noise Suppression Processing

[0070] The PLC obtains the mV voltage value of the thermocouple, and performs noise suppression processing on the configurable time parameter through PLC calculation.

[0071] For example, using the theoretical filter coefficient formula: Alpha = e^{-DeltaT / tau}, other filtering methods can also be used, such as adaptive Kalman filtering, wavelet threshold denoising, etc.

[0072] This formula converts the filtering characteristics of continuous systems into discrete recursive algorithms through exponential decay weights, combining mathematical rigor and engineering practicality, and is widely used in real-time signal processing fields.

[0073] Formula composition and meaning:

[0074] e: natural constant ≈ 2.7182818

[0075] Alpha (α): filter coefficient, used to adjust the weight of historical data and current input in filter output.

[0076] DeltaT (ΔT): sampling time interval, i.e. the time difference between two data collections (unit: seconds).

[0077] tau (τ): time constant of filter, determines the response speed of system (unit: seconds).

[0078] Recursive filter formula: FilteredEMF = RawEMF(1-Alpha) + PreviousEMF·Alpha;

[0079] The current filter output is the weighted sum of the original signal and the historical signal, and the weights (1-Alpha) and Alpha are updated in real time to achieve dynamic noise suppression.

[0080] Please continue to see Figure 3 The thermocouple filter processing flow in the PLC of the present application is as follows:

[0081] Step 1: Assign initial value, so that the last saved filter value PreviousEMF is equal to the original electromotive force RawEMF;

[0082] Step 2: Read the filter time dynamic parameter number FilterTime and the PLC sampling period DeltaT;

[0083] Third step: Calculate filter coefficient Alpha based on dynamic parameters; Get raw electromotive force RawEMF and last saved filter value PreviousEMF;

[0084] Fourth step: Get current filtered electromotive force by applying first-order low-pass filter formula;

[0085] FilteredEMF = RawEMF(1-Alpha)+PreviousEMF·Alpha ;

[0086] Fifth step: Update historical saved electromotive force data;

[0087] Sixth step: Output filtered electromotive force data.

[0088] The application directly filters the electromotive force (mV) of the C-type thermocouple, only needs two multiplications and one addition, and has low calculation complexity (O(1)); by dynamically adjusting (FilterTime), the noise suppression and response speed can be balanced. The advantages of directly filtering the electromotive force (mV) of the C-type thermocouple vs. filtering after temperature conversion are as follows:

[0089] 1) Avoid noise amplification caused by nonlinear conversion

[0090] Nonlinear characteristics of C-type thermocouple:

[0091] The voltage-temperature relationship of C-type thermocouple (tungsten-rhenium 5-tungsten-rhenium 26) in the high-temperature section (such as 0-2320℃) is significantly nonlinear. For example:

[0092] At 1000℃: The sensitivity is about 0.033 mV / ℃ (i.e. 1mV ≈ 30.3℃)

[0093] At 2000℃: The sensitivity decreases to 0.017 mV / ℃ (i.e. 1mV ≈ 58.8℃)

[0094] Noise amplification effect:

[0095] If the original electromotive force signal has ±0.005mV noise:

[0096] i Directly filter mV signal: Noise is suppressed to ±0.001mV → Temperature error:

[0097] At 1000℃: ±0.001mV × 30.3℃ / mV = ±0.03℃

[0098] At 2000℃: ±0.001mV × 58.8℃ / mV = ±0.05℃

[0099] ii Filtered temperature signal after conversion: ±0.005 mV raw noise directly converted to temperature fluctuation:

[0100] 1000℃: ±0.005 mV × 30.3℃ / mV = ±0.15℃

[0101] 2000℃: ±0.005 mV × 58.8℃ / mV = ±0.29℃

[0102] From the above: In the mV stage filtering, the non-linear interval noise can be avoided to be amplified by 5 times, the measurement stability is significantly improved, and the temperature fluctuation is reduced by 0.12℃ at 1000℃ and 0.24℃ at 2000℃.

[0103] 2) Improve the uniformity of thin film deposition

[0104] Evaporation rate stability:

[0105] Temperature fluctuation directly affects the evaporation rate. ±1℃ deviation can cause the evaporation rate to change by 5%~10% (depending on the material), which in turn causes the thin film thickness distribution to be uneven (such as the difference between the edge and the center).

[0106] Taking 1000℃ as an example, the front-end filtering temperature detection stability is improved by 0.12℃, and the evaporation rate fluctuation can be reduced by 1.2% at most, which significantly improves the stability and uniformity of thin film deposition;

[0107] 3) Reduce the consumption of computing resources

[0108] Reduce real-time computing pressure:

[0109] Temperature conversion may involve floating point operations or table lookup operations. In resource-limited PLCs, filtering before conversion can reduce repeated processing of dirty data.

[0110] Data volume comparison:

[0111] Original voltage signal filtering: 1 floating point filtering calculation per cycle.

[0112] Temperature signal filtering: needs to be converted (may involve multiple operations) and then filtered → calculation volume increased by more than 30%.

[0113] 5 Temperature calculation method

[0114] PLC obtains the mV voltage value of the thermocouple (after noise suppression processing), and the actual temperature can be obtained through PLC calculation.

[0115] The analysis equation is a quintic equation, which needs to be calculated by numerical iteration. The equation can be derived as: (A·T +B·T 2 + C·T3 + D·T 4 + E·T 5 + K)–EMF = 0,

[0116] Temperature T = 32-4200℉, EMF = real-time value, A\B\C\D\E\K = fixed coefficient

[0117] The result is compared with 0, and the result is iteratively transformed T value (32-4200℉). This iterative calculation method needs to set the accuracy of the temperature, and the T value in the accuracy range can be calculated to obtain the current temperature.

[0118] Take the binary search method as an example (other search methods can be used instead, such as interpolation search, exponential search, etc.), in computer science, binary search (binary search), also known as half-interval search, is a search algorithm for finding a specific element in a sorted array. The search process starts from the middle element of the array. If the middle element is the element to be searched, the search process ends. If a certain element is greater than or less than the middle element, search in the half of the array greater than or less than the middle element, and start from the middle element as before. If the array is empty at a certain step, it means that it cannot be found. This search algorithm reduces the search range by half each time.

[0119] Adopting binary search program:

[0120] ① Variable setting initial value:

[0121] Input variable:

[0122] T_low:=32.0 (lower limit of Fahrenheit)

[0123] T_high:=4200.0 (upper limit of Fahrenheit)

[0124] T_tol:= 0.01 (Fahrenheit accuracy setting value)

[0125] T_mid:=0.0 (binary search middle temperature value)

[0126] A:= 0.7190027 x 10 -2 (coefficient fixed value)

[0127] B:= 0.3956443 x 10 -5 (coefficient fixed value)

[0128] C:= -0.1842722 x 10 -8 (coefficient fixed value)

[0129] D:= 0.3471851 x 10 -12 (coefficient fixed value)

[0130] E:= -0.2616792 x 10 -16 (coefficient fixed value)

[0131] K:= -0.234471(coefficient fixed value)

[0132] EMF:=0~37mV (collect the current electromotive force, the value after noise processing)

[0133] Output variables:

[0134] T_C:= 0.0; (output temperature value ℃)

[0135] Internal variables:

[0136] T_F:= 0.0; (intermediate temperature value ℉)

[0137] ② The temperature processing flow is shown in Figure 4 , including:

[0138] First, new variables are created and initial values are set;

[0139] Second, determine whether the current selected temperature meets the accuracy requirements;

[0140] Third, if the accuracy requirements are not met, calculate the intermediate temperature of the selected iteration;

[0141] Fourth, calculate the electromotive force difference value of the lower limit temperature and the intermediate temperature under the current selected iteration;

[0142] Fifth, conditionally determine the temperature of the selected iteration at the bisection judgment position;

[0143] Sixth, update the upper or lower limit temperature value to the intermediate value;

[0144] Seventh, if the accuracy is met, obtain the current iteration temperature (℉);

[0145] Eighth, convert ℉ to ℃;

[0146] Ninth, output the temperature value.

[0147] ③ Advantage analysis of the algorithm

[0148] The total data amount of 0.01 precision temperature values in the range of 32-4200 is:

[0149] (4200-32) / 0.01+1=4168 / 0.01+1=416800+1=416801 (total data amount)

[0150] Efficiency comparison of search algorithm:

[0151] Sequential search: average time complexity O(n / 2) ≈ 207,900 operations;

[0152] Binary search: worst time complexity O(log2n) ≈ 19 operations;

[0153] The above data analysis shows that the efficiency of binary search is greatly improved compared to the ordinary sequential algorithm, saving CPU computing resources and reducing the overall scanning period of PLC. In the PLC temperature closed-loop control of C-type thermocouple, this algorithm can meet the stringent real-time requirements of millisecond-level of industrial temperature control system.

[0154] 6 Dynamic adjustment of noise suppression special processing of thin film evaporation equipment

[0155] Temperature filtering of evaporation equipment needs to cope with special challenges such as dynamic changes in vacuum environment, thermal sensitivity of thin film materials, and high precision requirements of thin film uniformity process (nanometer level film thickness control). The filtering parameter adjustment strategy is significantly different from traditional industrial temperature control. The specific special processing is as follows:

[0156] ① Start-up phase (cold initialization)

[0157] Noise characteristics: vacuum chamber thermal inertia mutation, evaporation equipment cold start, residual gas adsorption / desorption in vacuum chamber, heating wire cold resistance jump, etc. will introduce non-stationary noise (conventional equipment is mostly stationary noise).

[0158] Filtering requirements: use larger τ value to enhance noise suppression ability and avoid false triggering of control action.

[0159] Adjustment logic: (τ=0.5~2 seconds) initial τ=2 seconds to quickly suppress circuit noise, then dynamically reduce τ value according to chamber vacuum degree (pressure sensor feedback) (vacuum degree reaches 10^-4 Pa, τ reduces to 0.5 seconds to improve response speed), and match the switching of vacuum environment heat conduction mode.

[0160] Exceeding influence: τ<0.5 seconds, leading to noise penetration filtering, triggering heating false action power fluctuating frequently, actual temperature curve fluctuating; if τ>2 seconds, system response is too slow, prolonging the acquisition time leading to temperature control overshoot phenomenon.

[0161] Core principle: temperature change rate is small during start-up phase, response speed requirement is low, appropriately increase τ filtering time to sacrifice response speed (but can meet), prioritize noise suppression (large τ), and ensure control stability.

[0162] ② Rapid heating phase

[0163] Noise characteristics: The thermal capacity of the evaporation source is nonlinear, and the thermal capacity of metal evaporation sources (such as Au, Ag, and Cu) drops sharply in the high-temperature zone. The temperature detection delay is required to be less than or equal to 0.3 seconds, otherwise the film thickness uniformity will be deteriorated due to overshoot. The radiation interference is enhanced, and the radiation noise (infrared band) of the heating body in a vacuum environment increases exponentially with temperature, so a fine balance between noise suppression and response speed is required.

[0164] Filtering requirements: A small τ value (τ = 0.1-0.5 seconds) is used to reduce the filtering strength and ensure that the filtered output closely follows the actual temperature changes.

[0165] Adjustment logic: Gradient threshold control, real-time calculation of temperature change rate (frac{dT}{dt}), and adjustment of temperature change rate threshold according to the type of evaporation source (metal source: τ = 0.1 seconds when dT / dt ≥ 15 ℃ / s; organic source: τ = 0.2 seconds when dT / dt ≥ 8 ℃ / s), dynamically reducing τ to meet the response requirements.

[0166] Exceeding influence: τ > 0.5 seconds will cause filtering delay and temperature overshoot; τ < 0.1 seconds will amplify high-frequency noise and interfere with PID control.

[0167] Core principle: In the rapid heating stage, the temperature change rate is large, and in order to ensure stable PID output, τ is dynamically adjusted in a small value range, and if necessary, the filtering strength is sacrificed to ensure the response requirements.

[0168] ③PID stable stage (constant temperature maintenance)

[0169] Noise characteristics: Sensitive period of film growth, small fluctuations (> ± 0.5 ℃) in the constant temperature stage will cause changes in film crystallinity (such as lattice distortion of metal oxide thin films).

[0170] Filtering requirements: A large τ value (τ = 0.5-5 seconds) is used to strengthen noise suppression and avoid PID oscillation caused by high-frequency noise.

[0171] Adjustment logic: Real-time adjustment of temperature error, gradually increasing τ when the error (|T_{text{set}} - T_{text{actual}}| < epsilon ) (± 0.3 ℃) to strengthen noise suppression and ensure stable PID output.

[0172] Exceeding influence: τ > 5 seconds will excessively smooth the signal, causing PID response to be sluggish; τ < 0.5 seconds will not be able to filter out high-frequency noise, causing control oscillation.

[0173] Core principle: In the PID stable stage, the temperature is basically unchanged, and the response speed requirement is low. This is also the most critical stage of the process, and small temperature fluctuations will have a great impact on film quality. τ is dynamically adjusted in a large value range to prioritize filtering strength.

[0174] ④Cooling stage (natural or curve cooling)

[0175] Noise characteristics: thermal stress release interference, substrate cooling shrinkage after evaporation ends can cause cavity structure micro-vibration, produce low-frequency mechanical noise, traditional filtering is easy to misjudge it as temperature drop signal.

[0176] Filtering requirements: dynamically adjust tau according to the cooling rate: moderately increase tau (tau = 0.5-2 seconds) to suppress environmental interference.

[0177] Adjustment logic: dynamically adjust tau according to the evaporation source temperature drop rate (frac{dT}{dt}), when the cooling rate is greater than or equal to 0.1℃ / s: reduce tau (such as tau = 0.5-1 second) to avoid filter lag hiding the real temperature change. When the curve cooling rate is less than or equal to 0.1℃ / s: moderately increase tau (such as tau = 1-2 seconds) to suppress environmental interference.

[0178] Exceeding influence: tau < 0.5 seconds may amplify the noise of cooling medium flow; tau > 2 seconds will mask the real temperature drop trend.

[0179] Core principle: the temperature change rate is small during the cooling stage, the response speed requirement is low, the tau filtering time is appropriately increased to sacrifice the response speed (but it can meet the requirements), noise suppression is prioritized (large tau), and control stability is ensured.

[0180] ⑤Summary

[0181] Noise-response speed trade-off: high dynamic stage (heating up): prioritize response speed (small tau), sacrifice part of noise suppression ability. Low dynamic stage (start / cooling): moderate response speed, dynamically adjust tau value in a reasonable range, while considering response speed and filtering strength. Steady state stage (PID maintenance): prioritize noise suppression (large tau), ensure control stability.

[0182] By dynamically adjusting the filtering time constant tau, the present application can achieve the best balance between noise suppression and response speed throughout the heating process, and the specific strategies include:

[0183] Stage identification: based on temperature change rate and error size to divide heating stages.

[0184] Parameter self-adaptation: design the functional relationship between tau and dynamic parameters to realize smooth switching.

[0185] Engineering verification: optimize tau adjustment logic through step response test, spectrum analysis and other means to ensure robustness.

[0186] The thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment provided by the present application mainly improves the following points:

[0187] ① Hardware structure innovation, the electromotive force (mV) signal of the thermocouple is collected and calculated in the PLC, which does not depend on the algorithm of the module itself, and the temperature module of the original type not supported can be selected.

[0188] ② Thermocouple noise suppression mode innovation, the original value of the electromotive force of the thermocouple is dynamically suppressed, and the suppression parameter can be dynamically optimized in real time according to the diversification of the use environment.

[0189] ③ For the process flow of the thin film evaporation equipment, the effective temperature filtering method and parameter are customized, and the stability of the evaporation temperature collection is improved.

[0190] The thermocouple temperature measurement method suitable for thin film vacuum evaporation equipment provided by the application has the following beneficial effects:

[0191] ① The compatibility of the module does not need to be considered in design and selection, the efficiency and selection range of system design are improved, the system selection is discretized due to the incompatibility of the thermocouple type is avoided, and the cost of procurement is reduced by using the cost-effective product.

[0192] ② The system compatibility is improved, different types of thermocouple sensors are temporarily expanded in the system, and system components are not replaced or supplemented due to hardware compatibility problems.

[0193] ③ The original value of the electromotive force of the thermocouple can be dynamically suppressed, which is different from the fixed noise suppression mode of the temperature collection module, the filter parameter can be dynamically adjusted according to the requirements of different heating stages, the secondary filtering work of the control system is avoided, and the temperature feedback precision is also greatly improved.

[0194] ④ The customized temperature filtering method of the thin film evaporation equipment is applied to the evaporation source temperature detection system of the equipment, the temperature noise is effectively suppressed in each process stage, the dynamic adjustment also guarantees the response requirement, the stability of the temperature control system is optimized, and the evaporation uniformity is improved.

[0195] Although the application has been disclosed as above with the preferred embodiments, it is not intended to limit the application, and any person skilled in the art can make some modifications and improvements without departing from the spirit and scope of the application, therefore the protection scope of the application should be defined by the claims.

Claims

1. A thermocouple temperature measurement method for thin film vacuum evaporation equipment, characterized by, It comprises the following steps: S1, a temperature module and a PLC controller combination is used to measure the thermocouple original signal value; S2, dynamic front-end filtering: the original value of the thermocouple electromotive force collected is dynamically filtered with adjustable parameters at the PLC controller end, and the filtering strength is adjusted in real time according to different evaporation process stages; S3, standardized temperature conversion: based on the selected thermocouple scale, the conversion of electromotive force to temperature is completed in the PLC controller to obtain the thermocouple temperature measurement value.

2. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 1, wherein, The PLC controller in step S1 is S7-1500.

3. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 1, wherein, The temperature module in step S1 is beckhoff_KL3314, the thermocouple is connected to the KL3314 collection channel in step S1, the channel type is changed to mV type reading, and the data is fed back to the PLC controller through the DP coupler BK3150.

4. The thermocouple temperature measurement method for thin film vacuum deposition equipment as claimed in claim 1, wherein, The thermocouple in step S1 is a C-type thermocouple, which uses a quintic polynomial to output the nominal electromotive force; the quintic polynomial is used in step S3 to complete the conversion calculation of electromotive force to temperature through numerical iteration, the input range of electromotive force is 0-37mV, the temperature range is 32℉-4200℉, the Fahrenheit degree accuracy setting value is 0.01℉, and the worst time complexity O(log2n) is controlled by using binary search.

5. The thermocouple temperature measurement method for thin film vacuum deposition equipment as claimed in claim 1, wherein, The current filtering output in step S2 is the weighted sum of the original signal and the historical signal, and the weights of the historical data and the current input in the filtering output are adjusted by the filtering coefficient.

6. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 5, wherein, The step S2 comprises: S21: initial value assignment, so that the last saved filtering value PreviousEMF and the original electromotive force RawEMF are equal; S22: read the filtering time dynamic parameter FilterTime and the PLC collection period DeltaT; S23: calculate the filtering coefficient Alpha based on the filtering time dynamic parameter, Alpha = e^(-DeltaT / FilterTime); obtain the thermocouple original electromotive force RawEMF and the last saved filtering value PreviousEMF; S24: apply a first-order low-pass filter formula to obtain the current filtered electromotive force FilteredEMF, FilteredEMF = RawEMF(1-Alpha) + PreviousEMF·Alpha; S25: update the historical saved electromotive force data; S26: output the filtered electromotive force data.

7. The thermocouple temperature measurement method for thin film vacuum deposition equipment as claimed in claim 1, wherein, The evaporation process stage is divided into start-up stage, rapid heating stage, constant temperature holding stage and cooling stage based on the temperature change rate, and the response speed is controlled by dynamically adjusting the time constant τ of the filter.

8. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 7, wherein, The start-up stage corresponds to the cold start of the evaporation equipment, and the filtering time dynamic parameter is adjusted in the start-up stage as follows: the time constant τ of the initial filter is set to 2 seconds to quickly suppress circuit noise, then τ value is dynamically reduced according to the cavity vacuum degree, when the vacuum degree reaches 10^-4 Pa, τ is reduced to 0.5 seconds to improve the response speed and match the vacuum environment heat conduction mode switching.

9. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 7, wherein, The step S2 adjusts the filtering time dynamic parameter in the fast heating stage, the constant temperature keeping stage and the cooling stage as follows: In the fast heating stage, the temperature change rate is calculated in real time, and the gradient threshold is adopted to adjust the τ value between 0.1 and 0.5 seconds; In the constant temperature keeping stage, the τ value is adjusted in real time according to the temperature error between 0.5 and 5.0 seconds; In the cooling stage, the τ value is adjusted in real time according to the evaporation source cooling rate between 0.5 and 2.0 seconds.

10. The thermocouple temperature measurement method for the thin film vacuum deposition equipment as claimed in claim 9, wherein, In the fast heating stage, for the metal source, when dT / dt≥15℃ / s, τ=0.1 second; for the organic source, when dT / dt≥8℃ / s, τ=0.2 second; In the constant temperature keeping stage, when the temperature error exceeds ±0.3℃, τ is gradually increased; In the cooling stage, when the fast cooling is ≥0.1℃ / s, τ is 0.5-1 second; when the curve cooling is ≤0.1℃ / s, τ is 1-2 seconds.

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