Electrogenerated failure reliability evaluation system for TSV-RDL wafer level packaging

Abstract

The invention relates to the technical field of failure evaluation, and discloses a TSV-RDL wafer level package electro-failure reliability evaluation system, which comprises an upper computer, a precision power supply, an editable controller, a direct current voltmeter and a relay array, the upper computer is connected with the precise power supply, the programmable controller and the direct-current voltmeter through a communication bus; the programmable controller is connected with the direct-current voltmeter and the relay array, the programmable controller responds to a control instruction and controls the on-off state of a current path at the connecting end of the TSV sample through the relay array, and the TSV sample receives current and voltage and responds to the current and the voltage in real time; the direct current voltmeter is used for measuring the voltage change of the TSV sample; the programmable controller judges whether a set condition is met or not based on data fed back by the direct-current voltmeter in real time, and then the on-off state of the relay is controlled. According to the invention, the current-voltage-resistance characteristics of the TSV sample can be comprehensively recorded, and the automation level of the test is improved, so that the requirements of the TSV electromigration failure test are met.

Description

Technical Field

[0001] The present invention relates to the technical field of failure assessment, and in particular to an electrical failure reliability evaluation system for TSV-RDL wafer-level packaging. Background Art

[0002] As an important component of three-dimensional integrated circuits, TSV technology plays a key role in achieving device miniaturization and functional enhancement. However, the thermomechanical reliability issues of TSV are becoming increasingly prominent, such as thermal stress (equivalent thermal stress, normal stress, shear stress, bending stress), elastic-plastic strain, fatigue life, creep, Cu convexity, cracks, etc. The main factors affecting TSV thermomechanical reliability include temperature gradient, thermal expansion coefficient mismatch, temperature rise or fall amplitude, and material yield strength. Taking TSV filled Cu material as an example, the thermal expansion coefficients of Cu, Si and SiO2 are 16.5, 2.3 and 0.5ppm / ℃ respectively. Under different temperature conditions (such as annealing process temperature of about 400-425℃, service temperature of about -25-125℃), the free expansion or contraction of Cu will be constrained by Si and SiO2. The resulting thermal stress will cause deformation of Cu and surrounding materials, resulting in increased thermal stress generated inside TSV-Cu and Si. The deformation forms of TSV-Cu are generally bulging (the height of TSV-Cu relative to Si substrate after annealing is higher than that before annealing) and shrinking (the height of TSV-Cu relative to Si substrate after annealing is lower than that before annealing).

[0003] like Figure 1 As shown, Figure 1 In (a), Dutta et al. analyzed the stress before and after using a scanning electron microscope and found that the Cu in the TSV-Cu had obvious expansion behavior under the 425℃ thermal load stress; and after the -25-125℃ temperature cycle, the filling material Cu showed a shrinkage phenomenon, such as Figure 1(b). Existing technologies have analyzed the protrusion phenomenon of TSV by scanning electron microscopy, atomic force microscopy, and electron backscatter diffraction, and found that the protrusion height increases linearly with the annealing temperature. In addition, nanoindentation technology was used to measure the material properties of TSV, and it was found that the hardness, yield strength, and elastic modulus decreased with the increase of annealing temperature; possible mechanisms of TSV protrusion were proposed through finite element analysis, including plastic deformation and diffusion creep; finally, solutions to minimize the protrusion effect were proposed, including copper annealing with the highest thermal budget after electroplating, and reducing the influence of creep mechanisms by increasing grain size. Existing technologies have estimated the fatigue life of TSV-Cu by establishing a finite element model and using the EN curve, and have conducted simulation analysis of stress, strain, and fatigue life under various load conditions. The research results show that the stress and strain responses of TSV-Cu under thermal load and vibration load are significantly different, and the fatigue life under thermal-vibration coupled load is much lower than that under single load conditions.

[0004] Research on TSV electrical stress reliability generally focuses on electromigration, resistance change and fatigue, dielectric breakdown of the insulating layer, etc. Among them, TSV electromigration is the key factor causing TSV electrical stress reliability. TSV electromigration refers to the electromigration phenomenon caused by electrical stress, which will lead to non-uniform distribution of current density inside the filling metal, which may cause overheating in local areas and trigger electrochemical reactions, thereby causing voids and lattice dislocations in the filling metal, damaging the conductivity and overall reliability of TSV. The electromigration phenomenon of TSV is affected by many factors, including but not limited to the current density, metal material properties and temperature. High current density and high temperature will aggravate the electron migration phenomenon of metals, and the electromigration effects of different metal materials are also inconsistent. In addition, the size, shape and layout of TSV, the stress generated during the preparation and operation process, and the preparation process parameters of TSV (such as electroplating conditions and annealing temperature) also have an important influence on the generation of electromigration effect.

[0005] Reliability research under TSV electromigration mainly focuses on life prediction, microscopic mechanism and failure analysis. Jiwoo et al. studied the electromigration problem of TSV structure and adjacent metal wires by finite element method. The results show that the size of TSV, the position of metal layer and wire relative to the center of TSV have an important influence on electromigration life. Based on these studies, conclusions and guidance on how to reduce electromigration-related failures in 3D chip design are proposed, including TSV size selection, wire position design and current density control. Chen Zhaohui et al. obtained the detailed distribution of TSV current density and temperature gradient through accelerated tests, and completed the calculation of relative atomic concentration distribution based on this distribution. The results show that the location where stress gradient causes TSV electromigration problem is distributed at the connection between pad and Cu column, or the edge of the former. Gousseau et al. found that grains and grain boundaries play an important role in the formation and evolution of voids based on electron backscatter diffraction and scanning electron microscopy. The grain boundaries on the TSV surface are often the location where voids are generated, and the grain boundaries and grain sizes will affect the expansion of voids. Some Cu “islands” appear in the middle position after the void is formed. These Cu “islands” are caused by electromigration and discontinuity of the insulating layer.

[0006] For circuit optimization of TSV structure, Xu et al. established TSV benchmark structure for simulation (using 3D full-wave electromagnetic (EM) simulator, SPICE simulator and empirical calculation formula to study the parasitic parameters of TSV. They found that the TSV parameter values ​​extracted by full-wave simulation and the parameter values ​​of empirical calculation formula were very close; the SPICE model had a good match for the amplitude and phase of return loss and insertion loss; at 20GHz, the thickness of the insulation layer played a major role in signal gain.

[0007] Bose et al. proposed a power distribution network design using a distributed layout of power and ground TSVs to mitigate the adverse effects of electromigration on the performance of a hybrid memory cube architecture, which can significantly improve the life of this architecture.

[0008] Regarding the reliability problem of the insulation layer of TSV under the action of electrical stress, Yao-Jen Chang et al. studied the TSV leakage current problem in the 3D integration scheme using Cu-filled TSV and Cu / Sn-BCB hybrid bonding technology. Through electrical testing and optical beam induced resistance change analysis technology, they identified that the metal semiconductor junction formed by the contact between titanium and silicon during the back processing is the source of leakage current. Therefore, an optimized back processing method was proposed, including measures such as reducing the opening and thickening the protective layer. After using the optimized process, the leakage current of TSV was significantly reduced, and the internal structure quality was verified by X-ray transmission electron microscopy observation, indicating that the optimized process effectively solved the TSV leakage problem in the 3D integration scheme. Li Kai et al. conducted a study on the reliability of the SiO2 insulation layer at the TSV interface. The mechanism of the influence of temperature cycling on TSV thermal leakage was clarified, the differences and influencing factors of the electrical breakdown failure mode of single blind hole TSV and double blind hole TSV under electrical stress were analyzed, and it was verified that the E model is the most suitable time-dependent dielectric breakdown (TDDB) life model for the SiO2 insulation layer at the TSV interface. Through experiments and simulation methods, they systematically studied the reliability of the SiO2 insulating layer at the TSV interface under different stress conditions, which is of great significance to improving the reliability of TSV technology.

[0009] Nakamura et al. studied the effect of TSV sidewall roughness on leakage current. Two TSV samples with different sidewall roughness were obtained by Bosch etching and direct etching. The experimental results show that the sidewalls of the TSV samples produced by Bosch etching have obvious step-like roughness, and their leakage currents are higher than those of the direct etching samples both at the beginning and after heat treatment. TEM observations found that there are periodic cracks in the SiON insulating layer of the Bosch etched samples, which are consistent with the sidewall roughness. FEM simulation results show that the sidewall roughness will produce stress concentration in the SiON layer, leading to crack formation, so the direct etching method can obtain smooth TSV sidewalls, which is more conducive to improving reliability.

[0010] Yunlong Li et al. compared the insulation layer reliability of two different copper barrier materials (tantalum film and titanium film prepared by physical vapor deposition technology) in TSV. They used two stress modes (copper confined mode and copper driven mode) to separate the effect of barrier integrity on insulation layer reliability. Through controlled IV and TDDB tests, they found that titanium film prepared by physical vapor deposition technology is superior to tantalum film as a barrier material. For tantalum film barriers, a bimodal distribution of TDDB lifetime was observed in the copper driven mode, which is related to the competition between insulation layer damage caused by barrier defects and intrinsic insulation layer damage.

[0011] TSV electromigration reliability evaluation methods generally focus on accelerated life testing, microstructure analysis, simulation modeling and simulation, and statistical analysis.

[0012] In the TSV electromigration test, ORIO et al. studied the fatal void volume growth rate caused by electromigration in the copper TSV structure. They observed through experiments that a fatal void was formed above the TSV. In most time windows, the volume growth rate of this void remained basically constant, but a significant increase was observed after a longer time. In order to explain this experimental result, they proposed a model. The model takes into account the influence of void size on the vacancy inflow rate caused by electromigration. The vacancy flow under different void volumes was calculated by numerical simulation, and the model formula was applied to calculate the relationship between the volume and time. The simulation results match the experimental data very well. In most time windows, the model can well describe the linear growth of the void volume and the constant volume growth rate. In longer time, the model can also describe the significant increase in the volume growth rate. This model takes into account the influence of void size on the vacancy flow caused by electromigration, and can well explain and describe the experimental observation of the change of fatal void volume over time, verifying the correctness of the model.

[0013] Xuewei Zhao et al. mainly studied the microstructural evolution and mechanism of copper-filled TSV structures under thermal and electrical load conditions. By analyzing the microscopic morphology changes of TSV structures under different thermal load conditions, the bulging forms of TSV-Cu were divided into overall bulging and local bulging, and a TSV-Cu surface grain growth model was established to explain the microscopic mechanisms of the two bulging forms. In addition, the location and mechanism of void generation in TSV structures under thermal load conditions were studied. By analyzing the critical void nucleation, the effects of thermal stress and interface energy on void formation were explored.

[0014] In terms of TSV electromigration simulation, Zhang et al. studied the electromigration performance through TSV in silicon interconnect applications. By comparing different TSV structural models through finite element simulation, it was found that moving the heat spreader to the top of the TSV can significantly reduce thermal stress, thereby greatly reducing the amount of electromigration. Therefore, it is concluded that the thermal stress generated by the temperature gradient is the main influencing factor of TSV electromigration, rather than the current density. In addition, when the top metal line only covers half of the TSV, a second electromigration failure point will appear, and the electromigration performance will be worse.

[0015] Ma Rui et al. studied the electromigration reliability problem in TSV interconnection structure, established TSV structural model by finite element method, and conducted electrothermal coupling analysis. They found that current density and ambient temperature are the main factors affecting TSV electromigration life. As they increase, the Joule heat of TSV will also increase, thus accelerating electromigration failure. Different filling materials generate different Joule heat under the same conditions. Carbon nanotubes generate the least Joule heat and are a better filling material. Changes in TSV length and aperture will also affect its temperature field and Joule heat distribution, and further affect the electromigration phenomenon. As the length of TSV increases, the heat generation rate per unit volume will decrease; as the aperture increases, the effect on Joule heat will be more obvious.

[0016] There is no research on TSV electromigration reliability evaluation system at home and abroad. Most of them are to build TSV electromigration reliability test platform while studying TSV electromigration reliability test and failure mechanism. Most of these test platforms are built with scattered instruments. Tan et al. built an electromigration test platform using source measurement unit and central processing unit with LabVIEW to conduct TSV electromigration test. The platform schematic diagram is as follows Figure 2 As shown. During the test, it was found that different connection methods between the equipment and TSV samples had a great influence on the results of the TSV electromigration test. Frank et al. used an electromigration test system to simulate the current density distribution under different conditions, and monitored the resistance change through a resistance tester. They used a scanning electron microscope to observe the TSV electromigration samples with high resolution and found that the voids were generated at the interface between the TSV and the metal layer. The test platform built by Frank can study the electromigration behavior from aspects such as microstructure, current density distribution and resistance change, but the equipment cost is high, the operation is complicated and the maintenance is difficult. Safonov et al. used a measurement platform consisting of an EM 6030A probe with a heating table and an Agilent4156C semiconductor analyzer to carry out constant temperature accelerated electromigration tests to evaluate the reliability of integrated circuit aluminum metallization tests, such as Figure 3 As shown in (a). Studies have shown that the resistance change of TSV presents three regions ( Figure 3 Middle (b)): Reaching the measurement range area ( Figure 3 In (b), mark 1), measure the main area ( Figure 3 Mark 2) in (b) and the electromigration failure area ( Figure 3 (b) (mark 3). Although the measurement system can effectively simulate different working environments and ensure the accuracy and applicability of the test, its high cost and professional requirements for operators limit its widespread application.

[0017] Zhang Jicheng et al. used a self-built electromigration test platform to conduct multiple electromigration tests on samples by changing the current density and temperature conditions. They used a DC power supply to provide stable current, a data acquisition system to monitor the test parameters in real time, and a Zeiss Sigma field emission scanning electron microscope to conduct microscopic analysis to comprehensively study the electromigration failure law of the samples. However, due to the limited frequency of data acquisition, it is impossible to monitor the failure process in real time. Xun et al. used a scanning electron microscope to observe the structural changes of TSV at the microscopic scale in order to deeply analyze the failure mode, performance degradation trend and failure distribution of TSV microstructures under different stresses, and used high-resolution industrial micro-CT to provide three-dimensional microstructural information, providing a comprehensive perspective from micro to macro for TSV research, but it also brought higher testing costs and the need for professional operating skills.

[0018] In the prior art, the shortcomings are as follows:

[0019] (1) TSV electromigration reliability evaluation system

[0020] At present, most of the research on TSV electromigration is to build an electromigration test platform to conduct failure mechanism, life prediction, and device structure and material optimization. Due to the lack of a dedicated test system, it is often necessary to use a variety of equipment and instruments to meet different test requirements. This not only increases the complexity of the test, but also may introduce uncertain factors, affecting the accuracy and repeatability of the test results.

[0021] (2) Constructing TSV electromigration reliability life model

[0022] Although there have been extensive experiments and analyses in the field of TSV electromigration, there is currently no complete reliability life model to accurately predict the life of TSV in actual use. This not only restricts the in-depth analysis of TSV performance degradation, but also limits the reliability design in actual applications. Summary of the invention

[0023] The purpose of the present invention is to provide a TSV-RDL wafer-level packaging electrical failure reliability evaluation system to solve the problems that the accuracy and repeatability of existing test results are not high and a complete reliability life model has not yet been formed to accurately predict the life of TSV in actual use.

[0024] In order to achieve the above purpose, the technical solutions adopted are as follows:

[0025] The present invention provides a TSV-RDL wafer-level packaging electrical failure reliability evaluation system, comprising a host computer, a precision power supply, an editable controller, a DC voltmeter and a relay array;

[0026] The host computer is connected to the precision power supply, the programmable controller and the DC voltmeter via a communication bus, and is used to issue control instructions to the precision power supply, the DC voltmeter and the programmable controller; the control instructions are used to guide the test process;

[0027] The programmable controller is connected to the DC voltmeter and the relay array. The programmable controller responds to the control instruction and controls the switch state of the current path of the TSV sample connection end through the relay array. The TSV sample receives the current and voltage and responds in real time to form a closed-loop feedback system.

[0028] The DC voltmeter is used to measure the voltage change of the TSV sample and feed back the data to the programmable controller in real time; the programmable controller determines whether the set conditions are met based on the data fed back in real time by the DC voltmeter, and then controls the switching state of the relay. The programmable controller transmits the real-time updated data to the host computer.

[0029] Furthermore, the sample connection terminal is set to be multiple, each sample connection terminal serves as a workstation, each workstation forms a parallel circuit with the precision power supply, and each workstation is connected in series with a sampling resistor. The programmable controller controls the relay array to form an independent circuit with each sampling resistor and a DC voltmeter, and the current data change of each workstation is obtained through the DC voltmeter.

[0030] Furthermore, the sample connection terminal is set to be multiple, each sample connection terminal serves as a workstation, the precision power supply is connected in series with each workstation to form a series circuit, the current of each workstation is the same, the programmable controller controls the relay array to connect the DC voltmeter to both ends of each workstation, and the DC voltmeter inspects the workstations in sequence to obtain the voltage change of each workstation.

[0031] Furthermore, the host computer includes an interaction module, a data acquisition module and a life calculation module; wherein the interaction module is used to display a user interaction interface, the interaction module is connected to the data acquisition module, and is used to obtain the current and / or voltage data collected by the data acquisition module and control the data acquisition module, and the life calculation module is used to evaluate the TSV life and feed it to the interaction module.

[0032] Furthermore, the data acquisition module is used to determine whether the sample voltage and / or current data at the current moment has changed to the set value based on the set value fed by the interactive module and the sample voltage and / or current data collected in real time. If so, the test is exited; if not, the changes in the sample voltage and / or current data are continuously recorded until the set value is reached.

[0033] Furthermore, the life calculation module includes:

[0034] A database calling submodule is used to call a database containing sample failure evaluation results of historical tests and system historical data;

[0035] The data migration submodule is used to migrate the specified electromigration test data to the set data folder;

[0036] The life formula fitting submodule is used to fit the life formula according to the data in the database called by the database calling submodule and the data in the set data folder, and the life formula is used to evaluate the TSV life.

[0037] Furthermore, the life formula fitting submodule obtains the life formula by fitting in the following manner:

[0038] Extracting characteristic failure time, current and temperature of the sample from the sample failure evaluation results of the historical test and the system historical data;

[0039] The life model is constructed using the characteristic failure time, current and temperature of the sample, and the life model is expressed as:

[0040] MTTF=AJ -n e Ea / KT

[0041] Where MTTF represents the evaluated life, A, -n and Ea represent model parameters, e represents the natural constant, J represents the current density, and T represents the absolute temperature;

[0042] The slope and intercept of the failure curve in the TSV electromigration test are obtained by the least square method, and the slope and intercept of the failure curve are used to fit the life model A, -n and Ea to obtain the life formula.

[0043] Furthermore, the programmable controller sequentially controls the relay of each station, so that the DC voltmeter is connected to each station one by one to measure the voltage; wherein the programmable controller sequentially controls the relay of each station through the following steps:

[0044] Step 1, wait for the start signal;

[0045] Step 2, controlling the relay of each station in turn to open the wiring path of the corresponding station;

[0046] Step 3, start the voltage measurement function and wait for the measurement to be completed;

[0047] Step 4, turn off the relay of the current station and prepare to enter the next station;

[0048] Step 5: Repeat steps 2 to 4 until the voltages of all stations are measured.

[0049] Furthermore, a plurality of logic operation networks are configured in the programmable controller, the logic operation networks include contactors, coils and timers, and the plurality of logic operation networks are used to control the voltage measurement of each workstation.

[0050] Further, the plurality of logic operation networks include a first network, a second network, a third network and a fourth network; wherein:

[0051] In the first network, contactor R50 and contactor R0 are connected in series to control the activation of timer TMX0. When contactor R50 triggers a rising edge, contactor R0 is always triggered, and timer TMX0 starts timing. Coil K1 triggers contactor T0 signal once after timer TMX0 delays 0.1s. Relay R200 is used to assist contactor T0 in maintaining self-locking. When contactor R50 is triggered, the timing of contactor T0 has not been reached, and the timing of contactor T0 is maintained through relay R00. When the timing is reached, contactor T0 is triggered, the normally closed point of contactor T0 is disconnected, the coil of relay R200 is disconnected, and contactor T0 no longer times. Contactor T0 will not start timing until the next rising edge of contactor R50 is triggered.

[0052] In the second network, contactor T0 is used to control the activation of timer TMX1 after the first test starts. When the normally open contact of contactor R54 and contactor R20 is satisfied, contactor T1 starts timing, and the duration is the time setting of DT0. When contactor T1 starts timing, the internal coil and external coil Y0 of contactor R1 are energized at the same time. The energization duration is consistent with the timing duration of contactor T1, which is used to maintain the voltage measurement of the current station. When the timing time is reached, contactor T1 is normally closed and disconnected, and the internal coil of contactor R1 no longer maintains the energization of contactor T1. The falling edge of contactor R1 triggers the delay timing before measurement of the next station. When all other stations are not checked, or In the case of failure, the internal relay R201 is always energized. When the measurement signal is triggered, the internal coil of contactor R1 and the external coil Y0 are always energized for a long time. At this time, the timer no longer works until the stop button is manually clicked or the test time is reached, and the internal coil of contactor R1 and the external coil Y0 are disconnected to stop the test of the current station; when other stations have selective tests, coil R27 is always energized. When it is the turn of other stations to measure and the timing is completed, the falling edge of contactor R157 triggers the re-measurement of the current station, or when other stations are not selected for measurement, when the previous station of other stations is finished measuring, the other stations are skipped and the measurement starts again from the current station;

[0053] In the third network, contactor R117 is controlled by T0 and R0. If R110 is energized, the current station is skipped to judge the next station. T0 is when the test starts, the flag coil R20 of the current station is not energized, indicating that the current station has not selected the test. If these two conditions are met at the same time, R110 will be energized. When R110 is energized, it is used to trigger the measurement judgment of the next station.

[0054] In the fourth network, the falling edge of contactor R1 is used to trigger the timing of timer T2, and R0 and T2 timers are connected in series to control the power supply of R150 coil. If T2 timer completes 0.3 seconds of timing, T2 triggers a rising edge for measurement judgment of the next workstation.

[0055] The beneficial effects of the present invention are:

[0056] According to the TSV-RDL wafer-level package electrical failure reliability evaluation system provided by the present invention, first, the overall architecture scheme is designed according to the requirements of the TSV electromigration life test; then, the hardware part is built using the test source meter, test voltmeter, relay array, and programmable controller according to the design scheme; then the system host terminal software part, such as user interaction, parameter setting, data recording, life model parameter fitting calculation program, etc., is edited, and the functional verification of the system is completed using the test data obtained by the system and the life algorithm of the test system. Fit the TSV electromigration Black life model parameters, complete the TSV electromigration life test, and thus obtain an improved TSV electromigration Black life model. The present invention can comprehensively record the current-voltage-resistance characteristics of the TSV sample, improve the level of test automation, and meet the needs of the TSV electromigration failure test. At the same time, by introducing the life model program algorithm, the TSV electromigration Black life model is improved and perfected according to the test data recorded by the system, so that the test system can not only perform electromigration tests, but also have the ability to automatically calculate the life model parameters of the TSV sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of Cu deformation under thermal stress in a TSV-Cu structure according to the prior art is shown; wherein (a) is expansion; and (b) is shrinkage.

[0058] Figure 2 FIG. 4 shows a schematic diagram of a TSV electromigration platform according to the prior art.

[0059] Figure 3 The electromigration measurement scheme according to the prior art and a schematic diagram of the variation of sample resistance over time during electromigration are shown; wherein, (a) is the electromigration measurement scheme; and (b) is the sample resistance during electromigration.

[0060] Figure 4 A schematic diagram of functional structural modules of a TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to an embodiment of the present invention is shown.

[0061] Figure 5 The hardware structure diagram of a TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to an embodiment of the present invention is shown; wherein, (a) is a structural schematic diagram; (b) is a prototype design diagram; and (c) is a physical diagram of the system.

[0062] Figure 6 The working principle diagram of the programmable controller, the sample connection terminal and the voltmeter according to the embodiment of the present invention is shown.

[0063] Figure 7 A schematic diagram of parallel and series connection ends of workstations according to an embodiment of the present invention is shown; wherein, (a) workstations are connected in parallel; and (b) are connected in series.

[0064] Figure 8 A physical diagram of a sample connection end according to an embodiment of the present invention is shown; wherein (a) is a series connection mode; and (b) is a parallel connection mode.

[0065] Fig. 9 The overall structure diagram of the software functional module part of a TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to an embodiment of the present invention is shown.

[0066] Fig.10 A functional flow chart of a data acquisition module according to an embodiment of the present invention is shown.

[0067] Fig.11 A software fitting flow chart of a TSV electromigration Black lifetime model according to an embodiment of the present invention is shown.

[0068] Fig.12 A functional flow chart of a life parameter calculation module according to an embodiment of the present invention is shown.

[0069] Fig.13 A schematic diagram of a VISA serial port communication connection between a LabVIEW module and a programmable controller according to an embodiment of the present invention is shown.

[0070] Fig.14 A schematic diagram of a parameter instruction issued to a programmable controller according to an embodiment of the present invention is shown.

[0071] Fig.15 A flow chart of automatic detection control of a programmable controller according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0072] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0073] The specific implementation of the present invention is further described in detail below in conjunction with the drawings and examples.

[0074] The current TSV electromigration reliability test platform generally has significant limitations, which are manifested in the scattered and independent hardware equipment and poor overall stability, which affects the consistency and accuracy of the test results. At the same time, the high cost and complex operation process of the existing platform limit its possibility of widespread application in the industry. Moreover, the existing test methods are limited by the insufficient frequency of data collection and cannot continuously and real-time monitor the electromigration behavior of TSV samples, thus failing to capture potential transient failure modes and subtle parameter change trends.

[0075] Therefore, in order to overcome the above problems, the embodiment of the present invention provides a TSV-RDL wafer-level packaging electrical failure reliability evaluation system, which determines the functional requirements and performance indicators of the system through the demand analysis of the TSV electromigration test, so as to build the overall hardware architecture of the system. The programmable controller and industrial computer are used as the core control unit, and the hardware such as the precision power supply, high-precision DC voltmeter, relay array, and sample connection terminal are combined to realize the automatic control and data acquisition monitoring of the test process of the TSV electromigration reliability evaluation system.

[0076] like Figure 4As shown in the figure, the electrical failure reliability evaluation system of TSV-RDL wafer-level packaging is divided into software and hardware parts. The software part includes modules such as data acquisition, user operation, data storage, and life model. The hardware part consists of a precision power supply (model: B2901B), a programmable controller (model: FP-XHC38AT), a high-precision DC voltmeter (model: DM7275), a relay array (model: FP-X E14YR), and a TSV sample test connection terminal. The VISA (Virtual Instrument Software Architecture, VISA) serial port function of LabVIEW software and the communication bus RS232 realize the precise control of the host computer over the precision power supply, voltmeter, and programmable controller. While applying electrical load to the TSV sample, it can also complete the real-time data acquisition, display, and storage of current-voltage data. The combined control of the host computer and the programmable controller enables the relay array to switch back and forth between different test modes. The user interface of the software part provides interactive information such as device status, parameter setting, and data recording. Users can use LabVIEW software and the host computer to fully control hardware such as precision power supplies, programmable controllers, high-precision DC voltmeters, and relay arrays. Other modules of the software part can be used to comprehensively evaluate TSV reliability. The synergy of software and hardware modules forms a complete test control system, providing an efficient and reliable tool for TSV electromigration research.

[0077] For hardware components, the hardware structure of the TSV-RDL wafer-level packaging electrical failure reliability evaluation system is as follows: Figure 5As shown in the figure, it consists of a host computer, a precision power supply, a programmable controller, a voltmeter and a relay array. First, the host computer is connected to the precision power supply, programmable controller and voltmeter through the RS232 communication bus, and then the serial communication of the above devices is configured through the LabVIEW software of the host computer to realize the host computer's full control over the precision power supply, voltmeter and programmable controller. Through the instructions of LabVIEW, detailed control instructions can be sent to the precision power supply, voltmeter and programmable controller to accurately guide the test process. As the main control unit, the programmable controller controls the switch state of the current path of the TSV sample connection end (16 sample stations) through the relay according to the instructions. On this basis, the TSV sample receives current and voltage and responds in real time to form a closed-loop feedback system. The DC voltmeter is used to measure the voltage change of the TSV sample and feeds the data back to the programmable controller in real time. The programmable controller analyzes the measurement data with an efficient algorithm to determine whether the set conditions are met, and then controls the switch state of the relay. The cycle process is carried out continuously to achieve precise regulation and comprehensive monitoring of the current-voltage characteristics of the TSV sample. Finally, the real-time updated data is transmitted to the host computer, providing researchers with detailed experimental data and laying a reliable foundation for in-depth analysis and research on TSV electromigration.

[0078] The prototype design diagram of the TSV electromigration reliability evaluation test system is shown in the figure below. Figure 5 (b), the actual picture is as follows Figure 5 As shown in (c). The dimensions of the equipment are 1600mm in height, 600mm in width, and 800mm in depth. The display (computer interface) is assembled at the top of the cabinet, and all parameter information is displayed on the display. From top to bottom, the layout is the display, keyboard drawer, high-precision DC power supply and voltmeter, and the programmable controller and relay array are installed inside the chassis. Considering the TSV electromigration test conditions and the characteristics of the TSV samples, the high-precision DC power supply uses Keysight's B2901B precision power supply, the programmable controller uses Panasonic Group's FP-XHC38AT controller, and the high-precision DC voltmeter uses Hioki's DM7275 voltmeter.

[0079] The precision power supply selected is the Keysight precision power supply model B2901B, and its specific parameters are shown in Table 1. The Keysight precision power supply is mainly used for the measurement of electronic components, circuits and devices, with extremely low noise and drift to ensure the provision of stable current and voltage. The Keysight precision power supply also has high-precision voltage and current measurement functions, and can calculate the resistance in the circuit. The Keysight precision power supply can also be used for material property testing, such as the electrical properties and conductivity of semiconductor materials. It is integrated with the automatic test system to perform large-scale automated testing.

[0080] Table 1 Keysight B2901B precision power supply main technical parameters

[0081]

[0082]

[0083] The DC voltmeter selected is the DM7275 high-precision DC voltmeter from HOKI. The main technical parameters are shown in Table 2. It has high precision and high resolution, can accurately measure the DC-voltage value in the circuit, and automatically select the most appropriate range according to the measured voltage range; can save measurement data and provide recording function; allows the user to capture the peak value of the voltage signal, that is, the highest voltage value, which helps to detect transient voltage peaks or instantaneous events; supports relative measurement function, allowing the user to set the current measurement value to zero and then measure the change relative to this value; is equipped with a clear LCD display so that users can easily read the measurement results.

[0084] Table 2 Technical parameters of DM7275 high-precision DC voltmeter

[0085]

[0086] The programmable control logic device selected is Panasonic's FP-XHC38AT programmable controller, which not only realizes intelligent management of various hardware devices, but also has the ability to quickly respond to instructions, adjust power supply in real time, and accurately control current paths. At the same time, the controller also provides users with efficient real-time data transmission and monitoring capabilities by working in collaboration with different devices, improving the intelligence and production efficiency of the production line. It plays a key role in the TSV electromigration test system, cooperating with power supplies, voltmeters, and relays to complete the system's real-time reception and processing of voltage data, ensuring the accuracy and stability of the test.

[0087] The working principle diagram between the programmable controller, sample connection terminal (sample station) and voltmeter is as follows: Figure 6 . As the core component of the system, the sample test connection terminal is responsible for accessing and managing 16 sample stations. These stations are connected to the voltmeter and programmable controller through relays to achieve reliability testing of TSV electromigration. The relay array used in the system is the FP-X E14YR electromagnetic relay of Xiamen Hongfa Electroacoustics Co., Ltd. In the system, the relay acts as a switch between the test connection terminal and the voltmeter. Through the control signal sent by the programmable controller, the relay can open or close the corresponding station. At the same time, the programmable controller controls the on and off state of the relay in sequence according to the preset test process and procedure, so that the voltmeter can measure the voltage of each station according to the set time interval.

[0088] In order to meet the requirements of applying voltage and current loads to 16 stations, and considering the limited power of the precision power meter, two connection modes, series and parallel, are designed for the sample connection end, such as Figure 7 shown. Figure 7 In (a), 16 stations and a precision power meter form a parallel circuit. When the power of the precision power meter is constant, the 16 station samples can meet the constant voltage electric stress test at the same voltage. Each station is connected in series with a sampling resistor. The programmable controller controls the relay array to form an independent circuit with each sampling resistor and the voltmeter, so that the current data change of each station can be obtained arbitrarily. The setting of the sampling resistor should be much smaller than the sample resistance of the station. Figure 7 In (b), the precision power meter and the workstation form a series circuit, and the current of the 16 workstations is the same. Similarly, the programmable controller controls the relay array to connect the voltmeter to both ends of each workstation. The voltmeter inspects the workstations in sequence, thereby obtaining the voltage change of each workstation. The series mode provides a batch test method for TSV electromigration reliability testing. The actual pictures of the sample connection ends of the two modes are shown in the figure below. Figure 8 .

[0089] The host computer is selected as an industrial computer, which refers to a computer specially designed for industrial environments. It has all the functions of a standard personal computer, but is optimized in structure to adapt to the harsh conditions of industrial sites, such as high temperature, dust, vibration, etc. The general functions include: running control software, such as programming of programmable control logic, motion control, visual processing, etc.; it can also serve as the host of the host computer software. The industrial computer used in this embodiment is the Yanxiong IPC-310 industrial computer, and the parameter specifications are shown in Table 3. This industrial computer is the core control center of the system, with stable performance and reliable industrial-grade characteristics, suitable for the control and data processing of the TSV electromigration reliability evaluation system; it is mainly responsible for managing and controlling the operation of the entire TSV electromigration reliability evaluation system to ensure the coordinated work of each module; it is also equipped with a powerful processor and large-capacity memory, which can collect and process a large amount of data generated during the TSV electromigration test in real time to ensure the accuracy and integrity of the data.

[0090] Table 3 EVOC IPC-310 technical parameters

[0091]

[0092] The design of the software part of the system directly determines the intelligence level of the system and the user experience. Through reasonable user interface design, researchers can easily master the operation method of the system and realize intuitive monitoring of the experimental process. In the design of the underlying control logic, a reasonable software architecture enables the system to automatically execute complex experimental steps and improve the experimental efficiency. After the hardware system was built, this study used LabVIEW as the main software development platform. According to the experimental requirements, experimental process, and parameter control, the overall structure of the software system is as follows: Fig. 9 The design of the software system is mainly composed of the user and system interaction interface (main interface), data acquisition module and life model parameter calculation module. The design of the user interaction interface module is equivalent to the brain of the entire system, and all instructions are issued through it; the data acquisition module is equivalent to the bridge of the entire system, completing the information exchange between samples and users; the life model parameter calculation module is the ultimate goal of TSV electromigration reliability evaluation in this paper.

[0093] The specific process of the data acquisition module is as follows Fig.10 As shown. First, the user sets the test sample parameters, and then the data acquisition module is responsible for detecting whether the sample voltage and current data have changed to the set value during the test. If the sample data reaches the set value, it is recorded and stored, and the test is exited. If it does not reach the set value before the test, the data acquisition module continues to record the sample data changes until it reaches the set value.

[0094] The life parameter calculation module process is as follows Fig.11As shown. The life parameter evaluation module process is a key step in TSV performance evaluation. The task is to apply a specific life parameter calculation algorithm based on test data to quantitatively evaluate the TSV life. The module design needs to consider the TSV reliability life model to ensure the applicability of the test conditions, which covers multiple variables in the electromigration test, such as current density and temperature. In the process of life parameter calculation, the system first needs to call a database containing sample failure evaluation results of historical tests, system historical data, and other related information. The purpose of calling the database is to compare and verify the results of the current test and provide more comprehensive data support. Next, the user needs to select a specific data folder to provide the sample with a test data set that needs to be evaluated for life to ensure the accuracy and reliability of the life calculation. The user specifies specific electromigration test data by selecting a data folder to ensure that only relevant data is included in the life evaluation range. After that, the life model formula algorithm is fitted to establish a mathematical relationship between TSV life and test data. The process of fitting the life model formula includes curve fitting and regression analysis to find the best fitting result, thereby improving the accuracy of life evaluation. In general, the design of the lifetime parameter calculation module takes into account the entire process from test data collection to lifetime evaluation, ensuring the system's scientific evaluation and comprehensive understanding of TSV electromigration test results.

[0095] In the entire process of the above-mentioned life parameter calculation module, fitting the life formula is an important part. This process conducts in-depth analysis of TSV electromigration test data to accurately evaluate TSV life. The specific flow chart of the fitting life formula is as follows: Fig.12 As shown in the figure, the characteristic failure time of TSV samples is a key parameter in TSV electromigration test, which directly affects the shape and slope of the failure curve, and is also the core step of fitting the TSV electromigration Black life model. Through the designed scheme, the system can record the failure time of TSV samples in the test and then convert it into a characteristic failure time algorithm. The TSV electromigration Black life model widely used in reliability analysis is introduced into the software system. The model describes the change trend of TSV life by considering the characteristic failure time of the sample and the key parameters in its electromigration process. It has strong applicability and accuracy. Then, the characteristic failure time, current and temperature parameters of the TSV sample are imported into the TSV electromigration Black life model by calling the database. Finally, the slope and intercept of the failure curve in the TSV electromigration test are obtained by using the least squares method commonly used in statistics, and the slope and intercept of the curve are used to fit the parameters of the TSV electromigration Black life model, so as to establish a Black life model dedicated to the TSV. The model will specifically describe the life characteristics of the TSV sample in the electromigration process, which can be used to predict the life changes of TSV in future tests.

[0096] In order to realize the automatic control of TSV electromigration reliability life test, LabVIEW module is configured in the host computer, and communication is established with the programmable logic controller through the RS232 serial port. LabVIEW provides powerful serial port communication functions, which can easily interact and control data with the programmable controller. Through the VISA library function of LabVIEW, the RS232 serial port is successfully configured, and the correct communication parameters such as baud rate, data bit and check bit are set. The serial port configuration between LabVIEW and the programmable controller is as follows: Fig.13 shown. Fig.13 In the tutorial, the "VISA Configure Serial Port" virtual instrument is introduced, and then the "VISA Resource Name", "Baud Rate", "Parity" and "Data Bit" configurations are completed. Then it is introduced into the programmable controller, and finally the serial port communication between LabVIEW and the programmable controller is completed through the "VISA Close" virtual instrument.

[0097] Fig.14 This is a schematic diagram of issuing parameter instructions to a programmable controller. The issuance of parameter instructions is realized through sub-virtual instruments such as "controller sends parameters", "controller sends coils", "controller reads status" and "controller reads register data". Based on the parameter instructions and LabVIEW modules, the communication and control between LabVIEW and the programmable controller are jointly realized.

[0098] In order to realize the automation of voltage measurement, the control process of the programmable controller is as follows Fig.15 As described. Based on the control of the programmable controller, 16 workstations are connected to the voltmeter, so that the programmable controller controls the relay to connect the voltmeter to any workstation at any time to measure the voltage of the workstation. After the user checks the 16 workstations in the parameter setting interface, the programmable controller program controls the relay of each workstation in turn, so that the voltmeter can be connected to each workstation one by one to measure the voltage and complete the inspection of the 16 workstations. Specifically, the program loops through the following steps:

[0099] Step 1, wait for the start signal;

[0100] Step 2, controlling the relay of each station in turn to open the wiring path of the corresponding station;

[0101] Step 3, start the voltage measurement function and wait for the measurement to be completed;

[0102] Step 4, turn off the relay of the current station and prepare to enter the next station;

[0103] Step 5: Repeat steps 2 to 4 until the voltages of all stations are measured.

[0104] Based on the control of the programmable controller, the TSV electromigration reliability life test is automatically tested on the host computer, and the voltage data of each workstation can be automatically recorded. Fig.15 This is the inspection program diagram for station 1, which consists of a series of horizontal logic operation networks, each of which can independently implement a control logic function. The network consists of contactors (equivalent to logic gates or switches) and coils (control output devices). They are usually executed in order from top to bottom and from left to right. The following elements are in the diagram: contactors (such as T0, R0, X0, etc.), representing input signals such as buttons, switches, sensor signals, etc.; coils (such as K1, Y0, K3, etc.), representing control outputs, such as starting motors, opening valves, etc.; timers (such as TMX0, TMX1, TMX2), used to introduce time delays in logic control. The control logic of this programmable controller has the following parts:

[0105] (1) Network 2: R50 (normally open contact, test start button 0) and R0 (normally open contact, always set after the test starts) are connected in series to control the activation of TMX0 (0.1 second unit timer). When R50 triggers a rising edge, the R0 coil is always triggered and the timer starts timing. K1 triggers the T0 signal once after the timer delays 0.1S. R200 is a relay that assists T0 to maintain self-locking. After R50 is triggered, if T0 timing has not arrived, R200 is required to maintain the timing of T0 in network 2. When the timing arrives, T0 is triggered, the normally closed point of T0 is disconnected, and the coil of R200 is also disconnected. T0 no longer times, and it is necessary to wait until the next rising edge of R50 is triggered before T0 starts timing again.

[0106] (2) Network 4: Similar to Network 2, T0 (normally open contact) is used to control the activation of the TMX1 timer after the first test starts. When the normally open contacts of R54 and R20 are satisfied, T1 starts timing, and the duration is the time setting of DT0. When T1 starts timing, the internal coil of R1 and the external coil of Y0 are energized at the same time. The energization duration is consistent with the timing duration of T1, which is used to maintain the voltage measurement of the current station 1. When the timing time is reached, T1 is normally closed and disconnected, and R1 no longer maintains the power supply of T1. The falling edge of R1 triggers the delay timing before the measurement of the next station. When all other stations are not checked or have failed, the internal relay R201 is always energized. When the measurement signal is triggered, the internal coil of R1 and the external coil of Y0 will remain energized for a long time. At this time, the timer will no longer work until the stop button is manually clicked or the test time is reached, and then the internal coil of R1 and the external coil of Y0 will be disconnected to stop the test of the current station. When station 8 has a selection test, the R27 coil is always energized. When it is station 8's turn to measure and the timing is completed, the falling edge of R157 triggers the re-measurement of station 1. Or when station 8 has not selected for measurement, station 7 finishes the measurement and skips station 8, and starts the measurement again from station 1.

[0107] (3) Network 6: R117 is also controlled by T0 and R0. This is to determine whether the current station needs to be measured. If R110 is energized, the current station is skipped and the next station is determined. T0 is when the test starts, and the R20 mark coil of station 1 is not energized, indicating that the current station 1 has not selected the test. If these two conditions are met at the same time, R110 will be energized. When R110 is energized, it is used to trigger the measurement judgment of station 2.

[0108] (4) Network 8: The falling edge of R1 (normally open contact) is used to trigger the timing of T2. R0 (normally open contact) is connected in series with the T2 timer to control the power supply of the R150 coil. If the T2 timer completes the timing of 0.3 seconds, T2 triggers a rising edge for the measurement judgment of the next station.

[0109] The above implementation modes are only used to illustrate the present invention, but not to limit the present invention. Ordinary technicians in the relevant technical field can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions also belong to the scope of the present invention. The patent protection scope of the present invention should be defined by the claims.

Claims

1. A TSV-RDL wafer-level packaging electrical failure reliability evaluation system, characterized in that: It includes a host computer, a precision power supply, an editable controller, a DC voltmeter and a relay array; The host computer is connected to the precision power supply, the programmable controller and the DC voltmeter via a communication bus, and is used to issue control instructions to the precision power supply, the DC voltmeter and the programmable controller; the control instructions are used to guide the test process; The programmable controller is connected to the DC voltmeter and the relay array. The programmable controller responds to the control instruction and controls the switch state of the current path of the TSV sample connection end through the relay array. The TSV sample receives the current and voltage and responds in real time to form a closed-loop feedback system. The DC voltmeter is used to measure the voltage change of the TSV sample and feed back the data to the programmable controller in real time; the programmable controller determines whether the set conditions are met based on the data fed back in real time by the DC voltmeter, and then controls the switching state of the relay. The programmable controller transmits the real-time updated data to the host computer.

2. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 1, characterized in that: The sample connection terminals are arranged in a plurality, each of which serves as a workstation, each of which forms a parallel circuit with the precision power supply, and each of which is connected in series with a sampling resistor. The programmable controller controls the relay array to form an independent circuit between each sampling resistor and a DC voltmeter, and obtains the current data change of each workstation through the DC voltmeter.

3. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 1, characterized in that: The sample connection terminals are arranged in a plurality, each of which serves as a workstation. The precision power supply is connected in series with each workstation to form a series circuit. The current of each workstation is the same. The programmable controller controls the relay array to connect the DC voltmeter to both ends of each workstation. The DC voltmeter inspects the workstations in sequence to obtain the voltage change of each workstation.

4. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 1, characterized in that: The host computer includes an interaction module, a data acquisition module and a life calculation module; wherein the interaction module is used to display a user interaction interface, the interaction module is connected to the data acquisition module, and is used to obtain the current and / or voltage data collected by the data acquisition module and control the data acquisition module, and the life calculation module is used to evaluate the TSV life and feed it to the interaction module.

5. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 4, characterized in that: The data acquisition module is used to determine whether the sample voltage and / or current data at the current moment has changed to the set value based on the set value fed by the interactive module and the sample voltage and / or current data collected in real time. If so, the test is exited; if not, the changes in the sample voltage and / or current data are continuously recorded until the set value is reached.

6. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 4, characterized in that: The life calculation module comprises: A database calling submodule is used to call a database containing sample failure evaluation results of historical tests and system historical data; The data migration submodule is used to migrate the specified electromigration test data to the set data folder; The life formula fitting submodule is used to fit the life formula according to the data in the database called by the database calling submodule and the data in the set data folder, and the life formula is used to evaluate the TSV life.

7. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 6, characterized in that: The life formula fitting submodule obtains the life formula by fitting in the following way: Extracting characteristic failure time, current and temperature of the sample from the sample failure evaluation results of the historical test and the system historical data; The life model is constructed using the characteristic failure time, current and temperature of the sample, and the life model is expressed as: MTTF=AJ -n e Ea / KT Where MTTF represents the evaluated life, A, -n and Ea represent model parameters, e represents the natural constant, J represents the current density, and T represents the absolute temperature; The slope and intercept of the failure curve in the TSV electromigration test are obtained by the least square method, and the slope and intercept of the failure curve are used to fit the life model A, -n and Ea to obtain the life formula.

8. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 2 or 3, characterized in that: The programmable controller sequentially controls the relay of each station, so that the DC voltmeter is connected to each station one by one to measure the voltage; wherein the programmable controller sequentially controls the relay of each station through the following steps: Step 1, wait for the start signal; Step 2, controlling the relay of each station in turn to open the wiring path of the corresponding station; Step 3, start the voltage measurement function and wait for the measurement to be completed; Step 4, turn off the relay of the current station and prepare to enter the next station; Step 5: Repeat steps 2 to 4 until the voltages of all stations are measured.

9. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 2 or 3, characterized in that: The programmable controller is configured with a plurality of logic operation networks, the logic operation networks including contactors, coils and timers, and the plurality of logic operation networks are used to control the voltage measurement of each workstation.

10. The TSV-RDL wafer-level packaging electrical failure reliability evaluation system according to claim 9, characterized in that: The plurality of logic operation networks include a first network, a second network, a third network and a fourth network; wherein: In the first network, contactor R50 and contactor R0 are connected in series to control the activation of timer TMX0. When contactor R50 triggers a rising edge, contactor R0 is always triggered, and timer TMX0 starts timing. Coil K1 triggers contactor T0 signal once after timer TMX0 delays 0.1s. Relay R200 is used to assist contactor T0 in maintaining self-locking. When contactor R50 is triggered, the timing of contactor T0 has not been reached, and the timing of contactor T0 is maintained through relay R00. When the timing is reached, contactor T0 is triggered, the normally closed point of contactor T0 is disconnected, the coil of relay R200 is disconnected, and contactor T0 no longer times. Contactor T0 will not start timing until the next rising edge of contactor R50 is triggered. In the second network, contactor T0 is used to control the activation of timer TMX1 after the first test starts. When the normally open contact of contactor R54 and contactor R20 is satisfied, contactor T1 starts timing, and the duration is the time setting of DT0. When contactor T1 starts timing, the internal coil and external coil Y0 of contactor R1 are energized at the same time. The energization duration is consistent with the timing duration of contactor T1, which is used to maintain the voltage measurement of the current station. When the timing time is reached, contactor T1 is normally closed and disconnected, and the internal coil of contactor R1 no longer maintains the energization of contactor T1. The falling edge of contactor R1 triggers the delay timing before measurement of the next station. When all other stations are not checked, or In the case of failure, the internal relay R201 is always energized. When the measurement signal is triggered, the internal coil of contactor R1 and the external coil Y0 are always energized for a long time. At this time, the timer no longer works until the stop button is manually clicked or the test time is reached, and the internal coil of contactor R1 and the external coil Y0 are disconnected to stop the test of the current station; when other stations have selective tests, coil R27 is always energized. When it is the turn of other stations to measure and the timing is completed, the falling edge of contactor R157 triggers the re-measurement of the current station, or when other stations are not selected for measurement, when the previous station of other stations is finished measuring, the other stations are skipped and the measurement starts again from the current station; In the third network, contactor R117 is controlled by T0 and R0. If R110 is energized, the current station is skipped to judge the next station. T0 is when the test starts, the flag coil R20 of the current station is not energized, indicating that the current station has not selected the test. If these two conditions are met at the same time, R110 will be energized. When R110 is energized, it is used to trigger the measurement judgment of the next station. In the fourth network, the falling edge of contactor R1 is used to trigger the timing of timer T2, and R0 and T2 timers are connected in series to control the power supply of R150 coil. If T2 timer completes 0.3 seconds of timing, T2 triggers a rising edge for measurement judgment of the next workstation.

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