Accelerated life testing effects on CMOS microcircuit characteristics

Modifications and additions to the present process of making CMOS microcircuits which are designed to provide protective layers on the chip to guard against moisture and contaminants were investigated. High and low temperature Si3N4 protective layers were tested on the CMOS microcircuits and no conclusive improvements in device reliability characteristics were evidenced

Reliability Assessment of a Packaging Automatic Machine by Accelerated Life Testing Approach

Industrial competitiveness in innovation, the time of the market introduction of new machines and the level of reliability requested implies that the strategies for the development of products must be more and more efficient. In particular, researchers and practitioners are looking for methods to evaluate the reliability, as cheap as possible, knowing that systems are more and more reliable. This paper presents a reliability assessment procedure applied to a mechanical component of an automatic machine for packaging using the accelerated test approach. The general log-linear (GLL) model is combined based on a relationship between a number strains, in particular mechanical and time based. The complete Accelerated Life Testing - ALT approach is presented by using Weibull distribution and Maximum Likelihood verifying method. A test plan is proposed to estimate the unknown parameters of accelerated life models. Using the proposed ALT model, the reliability function of the component is evaluated and then compared with data from the field collected by customers referring to 8 years of real work on a fleet of automatic packaging machines. The results confirm that the assessment method through ALT is effective for lifetime prediction with shorter test times, and for the same reason it can improve the design process of automatic packaging machines

Accelerated Life Testing of Electronic Revenue Meters

Electricity meters are devices that continuously record electrical energy consumption. In the past, meters have been of electromechanical type and consisted windings and moving parts. Electromechanical meters tend to be bulky, less accurate and more susceptible to tampering. As with other aging power system infrastructure in the US, most electricity meters are around 40 years old and are nearing the end of their intended lifespan. Concerns over the accuracy of these electromechanical meters along with advances in technology have led to development of new electronic meters which have additional benefits such as light weight, tamper-proof mechanisms, harmonic detection and Advanced Metering Infrastructure (AMI) features. Utilities intend to spend millions of dollars over the next few years in replacing these aging electromechanical meters; however the new meters contain electronic parts that are typically more sensitive to environmental conditions and abnormal voltage conditions. The drive to replace older meters will not meet the expectations, either in terms of functionality or expected profits, if the new meters drift in accuracy or fail relatively quickly with respect to their electromechanical counterparts. In this thesis, reliability techniques that are used in the industry, for prediction of product quality information have been reviewed. Accelerated Life Test (ALT) plans have been developed to systematically study the effect of environmental stresses on electronic revenue meters by using degradation parameters, failure time distributions, and accelerating factors to predict their operational lifetime. A Human Machine Interface (HMI) was developed in LabVIEW to interface the data acquisition devices with software, and thus facilitate continuous monitoring of environmental parameters and the health of test specimens placed inside an environmental chamber. The HMI also has the capability of generating automated periodic reports and emails for review by management. Since the lab test data from accelerated life testing of electronic meters was yet to be obtained, the statistical analysis procedure, derived from literature review, was demonstrated with the help of ALT data from other electrical and electronic components. ALT data for cable insulation was obtained from literature and the failure data analysis was demonstrated, followed by an analysis of degradation data from LEDs. Finally, the causes of lack of data were analyzed and improvements in testing procedure were recommended

Imprecise Statistical Methods for Accelerated Life Testing

Accelerated Life Testing (ALT) is frequently used to obtain information on the lifespan of devices. Testing items under normal conditions can require a great deal of time and expense. To determine the reliability of devices in a shorter period of time, and with lower costs, ALT can often be used. In ALT, a unit is tested under levels of physical stress (e.g. temperature, voltage, or pressure) greater than the unit will experience under normal operating conditions. Using this method, units tend to fail more quickly, requiring statistical inference about the lifetime of the units under normal conditions via extrapolation based on an ALT model. This thesis presents a novel method for statistical inference based on ALT data. The method quantifies uncertainty using imprecise probabilities, in particular it uses Nonparametric Predictive Inference (NPI) at the normal stress level, combining data from tests at that level with data from higher stress levels which have been transformed to the normal stress level. This has been achieved by assuming an ALT model, with the relation between different stress levels modelled by a simple parametric link function. We derive an interval for the parameter of this link function, based on the application of classical hypothesis tests and the idea that, if data from a higher stress level are transformed to the normal stress level, then these transformed data and the original data from the normal stress level should not be distinguishable. In this thesis we consider two scenarios of the methods. First, we present this approach with the assumption of Weibull failure time distributions at each stress level using the likelihood ratio test to obtain the interval for the parameter of the link function. Secondly, we present this method without an assumed parametric distribution at each stress level, and using a nonparametric hypothesis test to obtain the interval. To illustrate the possible use of our new statistical method for ALT data, we present an application to support decisions on warranties. A warranty is a contractual commitment between consumer and producer, in which the latter provides post-sale services in case of product failure. We will consider pricing basic warranty contracts based on the information from ALT data and the use of our novel imprecise probabilistic statistical method

SUATU STUDI TENTANG UJI HIDUP DIPERCEPAT TEGANGANBERTINGKAT: PERKEMBANGAN MUTAKHIR

This paper is reviewing the development of life testing data analysis of lie testing conducted in normal stress condition; stronger than normal stress (or constant stress accelerated life testing); and step stress accelerated life testing. It used exponential life test distribution model, log-normal accelerated model and tempered failure rate step stress model. It is completed by describing several problem for the future research

Accelerated Life Testing to Predict Service Life and Reliability for an Appliance Door Hinge

Appliance manufacturers have traditionally performed physical testing using prototypes to assess reliability and service integrity of new product designs. However, for white goods where service lives are measured in years or decades, the use of endurance testing to analyze long time reliability is uneconomical. As accelerated life testing (ALT) is more efficient and less costly than traditional reliability testing, the methodology is finding increased usage by appliance manufacturers. In the present study, a simulation-based ALT approach was used to predict the service life of a polyacetal hinge cam from a consumer refrigerator. A predictive life stress model based on cumulative surface wear under accelerated stress conditions was developed and used to predict time to failure under consumer use. Results show that the life stress model demonstrated good agreement with performance testing data and reasonably predicts hinge life

Bootstrap-based confidence intervals in partially accelerated life testing

Accelerated life testing (ALT) is utilized to estimate the underlying failure distribution and related parameters of interest in situations where the components under study are designed for long life and therefore will not yield failure data within a reasonable test period. In ALT, life testing is carried out under two or more higher than normal stress levels, with the resulting acceleration of the failure process yielding a sufficient amount of un-censored life-span data within a practical test duration. Usually one (or more) parameters of the life distribution is linked to the stress level through a suitably selected model based on a well-understood relationship. The estimate of this model is then utilized to determine the life distribution of the components under normal use (design use) conditions. Partially accelerated life testing (PALT) is preferable over accelerated life testing (ALT) in situations where such a model linking the stress to the distribution parameters is unavailable. In this study, parametric and nonparametric bootstrap based methods for obtaining confidence intervals for the parameters of the life distribution as well as a the lower confidence bound for the mean life under normal conditions are developed for both the Weibull and Generalized exponential life distributions under Type I censoring. Monte-Carlo simulation studies are carried out to study the performance of the confidence intervals based on the proposed methods against those of intervals obtained using the traditional delta method. Results show that the bootstrap-based methods performs as well as or better than asymptotic distribution-based methods in most cases --Abstract, page iii

Accelerated Life Testing Of Subsea Equipment Under Hydrostatic Pressure

Accelerated Life Testing (ALT) is an effective method of demonstrating and improving product reliability in applications where the products are expected to perform for a long period of time. ALT accelerates a given failure mode by testing at amplified stress level(s) in excess of operational limits. Statistical analysis (parameter estimation) is then performed on the data, based on an acceleration model to make life predictions at use level. The acceleration model thus forms the basis of accelerated life testing methodology. Well established accelerated models such as the Arrhenius model and the Inverse Power Law (IPL) model exist for key stresses such as temperature and voltage. But there are other stresses like subsea pressure, where there is no clear model of choice. This research proposes a pressure-life (acceleration) model for the first time for life prediction under subsea pressure for key mechanical/physical failure mechanisms. Three independent accelerated tests were conducted and their results analyzed to identify the best model for the pressure-life relationship. The testing included material tests in standard coupons to investigate the effect of subsea pressure on key physical, mechanical, and electrical properties. Tests were also conducted at the component level on critical components that function as a pressure barrier. By comparing the likelihood values of multiple reasonable candidate models for the individual tests, the exponential model was identified as a good model for the pressure-life relationship. In addition to consistently providing good fit among the three tests, the exponential model was also consistent with field data (validation with over 10 years of field data) and demonstrated several characteristics that enable robust life predictions in a variety iv of scenarios. In addition the research also used the process of Bayesian analysis to incorporate prior information from field and test data to bolster the results and increase the confidence in the predictions from the proposed model

Accelerated life testing effects on CMOS microcircuit characteristics

This report covers the time period from May 1976 to December 1979 and encompasses the three phases of accelerated testing: Phase 1, the 250 C testing; Phase 2, the 200 C testing; and Phase 3, the 125 C testing. The duration of the test in Phase 1 and Phase 2 was sufficient to take the devices into the wear out region. The wear out distributions were used to estimate the activation energy between the 250 C and the 200 C test temperatures. The duration of the 125 C test, 20,000 hours, was not sufficient to bring the test devices into the wear out region; consequently the third data point at 125 C for determining the consistency of activation energy could not be obtained. It was estimated that, for the most complex of the three device types, the activation energy between 200 C and 125 C should be at least as high as that between 250 C and 200 C. The practicality of the use of high temperature for the accelerated life tests from the point of view of durability of equipment was assessed. Guidelines for the development of accelerated life test conditions were proposed. The use of the silicon nitride overcoat to improve the high temperature accelerated life test characteristics of CMOS microcircuits was explored in Phase 4 of this study and is attached as an appendix to this report