Accelerated Reliability Testing Research Articles

Quantitative evaluation of PI-RDL interfacial delamination in fan-out wafer-level packaging during unbiased highly accelerated stress test

Fan-Out Wafer-Level Packaging (FOWLP) is increasingly utilized for its superior performance, facilitated by flexible heterogeneous integration. Despite its advantages, the interface between Polyimide (PI) and Redistribution Layers (RDL) is susceptible to significant vulnerabilities, notably delamination. This study introduces a quantitative method to assess PI-RDL interface delamination in FOWLP under unbiased Highly Accelerated Stress Tests (uHAST), a standard approach in accelerated reliability testing characterized by high humidity and temperature. Central to our methodology is the development of a time–temperature-moisture equivalence-based creep constitutive model, which significantly enhances our understanding of the impact of temperature and moisture on creep behavior. Furthermore, we have developed an innovative “open moisture absorption” method for preparing samples for four-point bending tests, enabling precise quantification of the time-induced degradation of PI-RDL interfacial fracture toughness under saturated conditions. Our comprehensive finite element model integrates moisture diffusion, the newly developed creep constitutive model, and solid mechanics to accurately simulate the accumulation of strain energy release rate during uHAST, facilitating precise predictions of delamination initiation times in FOWLP. Experimental validation under two uHAST conditions—130 °C/85 %RH for 96 h and 110 °C/85 %RH for 264 h—demonstrates the effectiveness of our approach, predicting the delamination initiation time at the PI-RDL interface with over 80 % accuracy. This predictive methodology is pivotal in enhancing the structural optimization and extending the service life of FOWLP in varied environmental conditions.

Simplifying finite elements analysis of four-point bending tests for flip chip microcomponents

PurposeThe purpose of this study is to propose a simplifying approach for modelling a reliability test. Modelling the reliability tests of printed circuit board (PCB)/microelectronic component assemblies requires the adoption of several simplifying assumptions. This study introduces and validates simplified assumptions for modeling a four-point bend test on a PCB/wafer-level chip scale packaging assembly.Design/methodology/approachIn this study, simplifying assumptions were used. These involved substituting dynamic imposed displacement loading with an equivalent static loading, replacing the spherical shape of the interconnections with simplified shapes (cylindrical and cubic) and transitioning from a three-dimensional modelling approach to an equivalent two-dimensional model. The validity of these simplifications was confirmed through both quantitative and qualitative comparisons of the numerical results obtained. The maximum principal plastic strain in the solder balls and copper pads served as the criteria for comparison.FindingsThe simplified hypotheses were validated through quantitative and qualitative comparisons of the results from various models. Consequently, it was determined that the replacement of dynamic loading with equivalent static loading had no significant impact on the results. Similarly, substituting the spherical shape of interconnections with an equivalent shape and transitioning from a three-dimensional approach to a two-dimensional one did not substantially affect the precision of the obtained results.Originality/valueThis study serves as a valuable resource for researchers seeking to model accelerated reliability tests, particularly in the context of four-point bending tests. The results obtained in this study will assist other researchers in streamlining their numerical models, thereby reducing calculation costs through the utilization of the simplified hypotheses introduced and validated herein.

Design and Simulation of Reliability Test System of a Charging Generator

The DC voltage pulsation factor of twelve-phase rectification is much smaller than that of three- and six-phase rectification. Twelve-phase rectifier charging generators are often used where a high quality DC power supply is required. The probability of failure of charging generator is gradually increasing due to its complex structure and function. The reliability test of charging generator can provide a scientific basis for the operation condition, maintenance and determination of the repair cycle of this type of motor. The article combines the basic theory of reliability test, analyses the charging generator constant stress accelerated reliability test scheme, designs the energy feedback test drag system with the generator output as the power source of DC motor, and carries out the dynamic performance simulation and analysis of the reliability test system based on PSCAD/EMTDC. The simulation results show that the energy feedback reliability test system has fast response and good stability.

Accelerated Reliability Tests of Characteristics of Off-Road Vehicles and Their Parts

Accelerated Reliability Tests of Characteristics of Off-Road Vehicles and Their Parts

FEATURES OF ISSUING APPLICATION AUTHORIZATION PROTOCOLS FOR QUARTZ OSCILLATORS

The article deals with questions on the use of quartz oscillators in equipment in conditions and modes other than those specified in the technical specifications. Options are considered in which it is possible to obtain permission to increase the shelf life or gamma-percentage operating time specified in the technical specifications. Recommendations are given on which data sources should be relied upon when calculating the duration of accelerated reliability tests of piezoelectronic products. An example of calculating the duration of accelerated reliability tests of quartz oscillators in the GK108-P SMD package is given to justify obtaining permission to expand the scope (use) of the equipment during the gamma-percentage operating time when using one accelerating factor – elevated temperature for a period of 150,000 hours at a temperature of 70 °C. The results of the calculation are analyzed and the procedure after the tests is indicated to justify obtaining permission to use generators in conditions other than those specified in the technical specifications.

The approval protocols for application of the crystal oscillators

An example of calculating the accelerated reliability tests duration of quartz oscillators in the GK108-P in SMD package for justify permission to expand the scope (application) quartz oscillators in equipment during the gamma-percentage operating time when using one accelerating factor — an elevated temperature of 70 °C for a period of 150000 hours is given. The results of the calculation are analyzed and the order of actions after testing to justify the permission of generators application in conditions other than specified technical specifications is indicated. Issues related to the application of quartz oscillators in equipment under conditions and modes other than those specified in the technical specifications are considered. Options in which it is possible to obtain permission to increase the shelf life or gamma-percentage operating time specified in the technical specifications are considered. Recommendations on which data sources should be relied upon when calculating the duration of accelerated reliability tests of piezoelectronic products are given. Keywords crystal oscillator, application permission protocol, increased ambient temperature, accelerated reliability calculation

Development of test methods for electromechanical sensors of vehicles used for operation in regions with a hot climate

Currently, there are various methods of testing vehicles and its components used by different car manufacturing companies. Also, these methods are given in the UNECE regulatory documents in the field of transport, but these documents do not take into account the separate operating conditions of cars in different regions. In this regard, the paper presents the road and climatic conditions of Central Asia characterized by peculiar characteristics. Based on the climatic features of the operation in a hot region, technical requirements have been developed for electromechanical sensors of cars for operation in hot climatic conditions, which should ensure the reliability of these components when the car runs at least 250,000 km. The method of testing electromechanical sensors of cars has been presented. It is established that in order to ensure the normal operability of sensors operating in hot climates, it is necessary to conduct tests at a nominal ambient temperature 45 ± 5 °C. The test procedure is built based on this parameter. All developed test methods are consistent with current standards in the field of electromagnetic, electromechanical and other electrical parameters of the automotive industry. Schematic diagrams of stands for testing have been given. The paper reflects the methodology of accelerated reliability tests, in which the temperature is set as the accelerating factor. The tests fully reflect the operational characteristics of the movement of cars in a sharply continental climate with a hot slope of ambient temperature with sharp temperature changes. After each test, it is determined that the nominal parameters of the sensors are checked for compliance with the established requirements. Conclusions reflecting the results of the work carried out have been made.

Perspective estimation of light emitting diode reliability measures based on multiply accelerated long run stress testing backed up by stochastic diffusion process

Light emitting diodes (LEDs) are currently a key element of many systems. They provide main, informational, safety, support and other functions. Their design, size and low-cost production make them increasingly popular. The relatively long technical life of electronic components is not always easy to prove and properly estimate, and the correlations between luminance, luminous flux intensity and other electrical characteristics of an LED (e.g. voltage) are not usually available. To ensure that their operation is correct and safe, LEDs must have a suitable level of reliability; LEDs are examined in service to detect their degradation and the deterioration of their technical condition. This article is devoted to estimating and demonstrating some LED reliability measures, such as the time during which the LED operation is failure-free and at the required luminance level. Existing research is typically based on short testing periods, one stress factor and more traditional models for analysing recorded data. In contrast, our approach is based on multiply accelerated reliability testing with very long experiment runs supported by degradation modelling using a stochastic diffusion process. Multiple acceleration is provided by intensifying environmental climatic effects (heat exposure) and simultaneously increasing the stress of operating conditions (increased current load). The parameters for degradation models based on stochastic diffusion processes are estimated for the studied LEDs by a specific form of the maximum likelihood estimation (MLE) method, including parameter confidence intervals. Based on the results, a novel correlation between luminance level, luminous flux intensity and voltage magnitude is also determined. The aim is to estimate and demonstrate key LED reliability measures.

Testing Electromechanical Sensors to Ensure Reliability in Hot Environments

In the world there are various methods of testing vehicles and its components used by various car manufacturing companies. Many methods are given in the UNECE regulatory documents in the field of transport, but these documents do not take into account the hot and climatic conditions of car operation. This article presents the road and climatic conditions of Central Asia, which is characterized by peculiar characteristics. The test methods are designed in such a way that, when operating cars in hot climatic conditions, the reliability of the sensors should be ensured when the car runs at least 250,000 km. It is established that in order to ensure the normal operability of sensors operating in hot climates, it is necessary to conduct tests at a nominal ambient temperature 45±5 °C, based on this parameter, a test procedure is built. The test methods are designed in such a way that all tests are carried out in accordance with the current standards in the field of electromagnetic, electromechanical and other electrical parameters of the automotive industry. Schematic diagrams of test benches are also given. The scientific work substantiates the methodology of accelerated reliability tests, in which the temperature is set as the accelerating factor. The tests fully reflect the operational characteristics of the movement of cars in a sharply continental climate with a hot slope of ambient temperature with sharp temperature changes, i. e. the impact of cyclical temperature changes. Based on the conducted research, conclusions are drawn, which reflects the results obtained.

From lab to lamp: Understanding downconverter degradation in LED packages

Downconverters, primarily inorganic phosphors, are critical components in white solid-state LED-based lighting and liquid crystal display backlights. Research efforts have led to a fundamental understanding of a downconverter's absorption, photoluminescence, and efficiency as a function of composition, structure, and processing conditions. However, considerably less work has focused on the reliability of phosphors once they are incorporated into LED packages. Solving these issues is often the final step before the commercialization of new materials, but the significant resources and time required to evaluate and mitigate materials failure are rarely discussed in the literature. In this Perspective, we discuss the need for conducting downconverter reliability testing and the potential of accelerating, screening, and understanding downconverter failure modes. Our focus highlights the mechanisms of failure and discusses how this influences materials selection and the design of different LED packages. We also stress the potential for accelerated reliability testing protocols and note the potential role first-principles calculations and data-driven models could play in establishing the compositional-processing trends for different aspects of downconverter reliability. We close with possible research directions that could improve downconverter reliability and emphasize the importance of assessing a material's (chemical) stability where multiple manufacturing and processing steps can dictate system performance.

Cardinal and Ordinal Directions Approach in Investigating Arrayed Solder Joints Crack Propagation of Ball Grid Array Semiconductor Packages

An accelerated reliability testing via thermal cycling test (TCT) was used to test ball grid array (BGA) components’ reliability. Five variables were observed; control sample J and samples K, L, M, and N were BGA component samples that have been exposed to TCT between 500 and 1250 cycles with the TCT profile in the range of 0 °C–100 °C. The crack orientation of the individual solder joint was analyzed along with the propagation path pattern on the solder array of the BGA component pad by analyzing the dye and pull test results that were then mapped and analyzed using the cardinal and ordinal directions approach. This is to determine the crack propagation path direction in the solder array and track the potential of warpage on the BGA package as the TCT cycles progressed. A cross section was performed on sample M with the 3-D X-ray and scanning electron microscopy (SEM) analysis to observe the solder joints’ fracture lines and surface topographies. The results showed that individual solder joint crack orientation is correlated to the crack propagation location on the BGA package. The solder joint from northwest (NW), northeast (NE), southeast (SE), and southwest (SW) of the BGA package is prone to solder crack compared to the solder joint array in the middle. A solder grain structure coarsening occurred at the crack propagation due to the high cyclic strain from the TCT.

Development of accelerated reliability test cycle for electric drive system based on vehicle operating data

For the current traditional vehicle, reliability test specification is difficult to effectively cover the actual service load intensity of the electric drive system (EDS), the existing specification has the problems of insufficient evaluation of extreme operating conditions, the inaccurate definition of the whole life cycle damage target, and weak user relevance. Therefore, this paper proposes a method to construct an accelerated reliability test cycle for EDS based on 300 users' one-year operation data. By extracting the running fragments and constructing the characteristic parameters associated with the dominant failure load of the EDS. Principal component analysis and clustering algorithms identify the running fragments and obtain five typical operating conditions. Based on the unit damage intensity distribution model, the accelerated testing condition for simultaneous assessment of multiple components is selected, and each component's whole life cycle damage target is determined. To further consider the loading sequence of the fragments, a state transfer probability matrix for each condition is established based on the Markov chain model, which implements the condition combination. Using the multi-objective optimization algorithm determines the number of cycles for each condition and eventually compiles the accelerated reliability test cycle of the EDS. In addition, by conducting rig tests to verify the validity of the accelerated test load spectrum and determine the accelerated factor by the testing data. This study provides specific references and technical support for developing and validating the EDS.

Acetic acid detection in photovoltaic modules during ultraviolet irradiation and damp-heat combined tests

In this study, we evaluated the acetic acid generation in photovoltaic (PV) modules during an accelerated reliability test that combines ultraviolet (UV) irradiation and damp-heat (DH) using tin film sensors. We employed a tin film to detect acetic acid through the change in optical reflectance due to the chemical reaction from metallic tin to transparent tin tetraacetate. The relative reflectance of the tin film sensors laminated in a PV module was measured and used as an indicator of acetic acid generated during the reliability test. Consequently, we achieved non-destructive detection of a small amount of acetic acid generated during the UV irradiation stage of the UV+DH combined test with high spatial and temporal resolution using tin film sensors.

Reliability testing for product return prediction

Return of products within the warranty coverage induces additional cost and loss of reputation to manufacturers. It is of practical interest to predict the return rate by experimental means before introducing a product to the market. In this paper, we propose to optimize accelerated reliability tests to achieve the goal within limited time. To describe the heterogeneity in the customers’ usage mode, a discrete random variable is employed to model the degradation rate in addition to the continuous stress variable. To further characterize the heterogeneity in the customers’ behavior, two models of product return are investigated: one assumes that customers return products once the degradation level reaches the minimum eligible return threshold and the other assumes that the threshold varies among different customers. Optimal reliability tests are planned under the large-sample assumption with two novel test schemes: global optimal planning and stress constrained planning. Insights regarding the optimal plans are gleaned to ameliorate the test planning procedure and verify the optimality. A real example from the battery industry is then presented along with the simulation study and sensitivity analysis to demonstrate the methods. We find that the randomness in return level results in different test plans. Furthermore, the constrained optimal plans offer more robustness to the compromise plans.

Accelerated reliability tests of n+ and p+ poly-Si passivated contacts

We report on the stability of encapsulated, low-pressure chemical vapor-deposited phosphorus ( n + poly-Si) doped and boron ( p + poly-Si) doped poly-Si/SiO x passivated contacts by exposing the samples to three different accelerated tests: damp heat test, thermal cycling and ultraviolet exposure, adhering closely to the IEC 61215 standard. Outdoor testing was also performed by exposing the samples in the outdoor testing field at the National Renewable Energy Laboratory, and preliminary data accumulated for 1000 h from February to April of 2021 is reported. We studied non-metallized, thermally-metallized, and screen-printed n + and p + poly-Si by monitoring the effective minority carrier lifetime at the implied maximum power point using a Sinton lifetime tester, and recorded photoluminescence images before and after the exposure. The samples were found to be stable under all test conditions, which is encouraging for incorporation of these contacts in next-generation industrial silicon solar cells. • Three accelerated tests performed on encapsulated LPCVD n + and p + poly-Si/SiO x , adhering closely to IEC 61215 standard. • Samples include non-metallized, thermally metallized, and screen-printed n + and p + poly-Si/SiO x . • Effective minority carrier lifetime and PL images of the sample monitored. • All samples found to be stable after the exposure to accelerated and outdoor tests.

A numerical analysis on the effect of point-support methods on the fatigue performance of thermally cycled electronic assemblies

This paper aims to investigate the effect of the point fixation properties on the fatigue life characteristics of electronic assemblies subjected to thermal cycling loadings. In this investigation, several point-support patterns and placement properties were considered. Solder characteristic thermal fatigue life predictions are calculated using finite element analysis data and Darveaux's model. The results showed that the support schematic can highly affect not just the fatigue life performance, but also the crack initiation locations. Finally, design recommendations of support systems are suggested for the use in electronic packages in real-life applications as well as in accelerated reliability tests.

Accelerated Reliability Test of Li Battery

Accelerated Reliability Test of Li Battery

Accelerative reliability tests for Sn3.0Ag0.5Cu solder joints under thermal cycling coupling with current stressing

The lead‑tin solder has already been replaced by the lead-free solder gradually in most industrial applications according to the RoHS restriction. However, the reliability test duration and the failure mechanism of lead-free solders are always a concerned problem that must be addressed when designing a new electronic product. In this paper, a thermo-electric accelerated test (TEC) method, as well as its corresponding failure mechanism, was discussed to consider the feasibility of reducing the reliability test duration. Compared with the traditional thermal cycling (TC) test, the lifetime of the component boards decreased apparently in the thermo-electric accelerated test, including both the time-to-failure and the cycles-to-failure based on the Weibull distribution. The main failure mode in TEC test is the cracks propagating along the boundaries of the recrystallized grains at the corner of a solder joint, similar as the TC test. The higher acceleration rate of TEC test might be related to the intermetallic evolution both at the interface and in the solder bulk. Thus, it could be concluded that the thermo-electric test would be a valuable option to achieve highly accelerated reliability test for electronic products.

MATHEMATICAL MODELS OF RELIABILITY OF POWER SUPPLY SYSTEMS

Ensuring reliability is one of the most important issues in the creation and operation of any technical system. This is especially important for complex systems, such as power supply systems with internal and external connections consisting of many elements. The task of ensuring the reliability of power supply systems includes a whole set of technical, economic and organizational measures aimed at reducing damage caused by violations of the normal mode of operation of electricity consumers. To obtain information about the reliability of elements of power supply systems, it is necessary to study a fairly large number of identical elements over a long period of time. In the real conditions of an industrial enterprise, this creates certain difficulties, so it is possible to conduct an accelerated reliability test using mathematical modeling [3].
 The article discusses some ways to solve the main problem of reliability theory - building a mathematical model and obtaining criteria for selecting optimal options for power supply systems. In this paper, the main materials for calculating the reliability of power supply systems using the mathematical apparatus of probability theory are presented.

Accelerated reliability testing of Cu-Al bimetallic contact by a micropattern corrosion testing platform for wire bond device application

Accelerated reliability testing of integrated circuit (IC) packages, such as wire-bonded devices, is a useful tool for predicting the lifetime corrosion behavior of real-world devices. Standard tests, such as highly accelerated stress test, involves subjecting an encapsulated device to high levels of humidity and high temperature (commonly 85–121 ⁰C and 85–100% relative humidity). A major drawback of current reliability tests is that mechanistic information of what occurs between t = 0 and device failure is not captured. A novel method of in-situ investigation of the device corrosion process was developed to capture the real time mechanistic information not obtained in standard reliability testing [1]. The simple, yet effective methodology involves:•Immersing a micropattern or device directly into contaminant-spiked aqueous solution, and observing its morphological changes under optical microscope paired with a camera.•Short (2–48 h) time required for testing (compared to 24–300 h of standard tests).•No need for humidity chambers.