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Failure-Oriented-Accelerated-Testing and Its Role in Making a Device into a Product
... In the analysis that follows another alternative is proposed-a modification of the recently suggested Boltzmann-Arrhenius-Zhurkov (BAZ) model [23][24][25][26]. This model and particularly its multi-parametric version have been developed as an essential part, the core, of the probabilistic design-for-reliability (PDfR) concept [27][28][29][30][31][32][33][34][35][36][37]. The BAZ model is used in our analysis for the evaluation of the remaining useful lifetime (RUL) of solder joint material in a situation, when it experiences inelastic strains. ...
... A highly focused and highly cost effective FOAT is the ''heart'' of the probabilistic design for reliability (PDfR) concept [31][32][33][34][35][36]. FOAT should be conducted in addition to and, in some cases, even instead of HALT. ...
... It should be emphasized that the temperature T in the formula (39) is, unlike in the Boltzmann's statistics (34) or in the Arrhenius formula (32), a parameter, not an argument. It is the threshold of the low temperature, below which the inelastic strains in the peripheral solder joints occur. ...
Although there exist promising ways to avoid inelastic strains in solder joints of the second level interconnections in IC package designs, it still appears more typical than not that the peripheral joints of a package/PCB assembly experience inelastic strains. This takes place at low temperature conditions, when the deviation from the high fabrication temperature is the largest and the induced thermal stresses are the highest. On the other hand, it is well known that it is the combination of low temperatures and repetitive dynamic loading that accelerate dramatically the propagation of fatigue cracks, whether elastic or inelastic. Accordingly, a modification of the recently suggested Boltzmann–Arrhenius–Zhurkov model is developed for the evaluation of the remaining useful lifetime of the second level solder joint interconnection whose peripheral joints experience inelastic strains. The experimental basis of the approach is the highly focused and highly cost-effective failure-oriented-accelerated-testing (FOAT). The FOAT specimens are subjected in our methodology to the combined action of low temperatures (not to elevated temperatures, as in the classical Arrhenius model) and random vibrations with the given input energy spectrum. The suggested methodology is viewed as a possible, effective and attractive alternative to temperature cycling. As long as inelastic deformations take place, it is assumed that it is these deformations that determine the fatigue lifetime of the solder material, and the state of stress in the elastic mid-portion of the assembly does not have to be accounted for. The roles of the size and stiffness of this mid-portion have to be considered, however, when determining the very existence and establishing the size of the inelastic zones at the peripheral portions of the designs. The general concept is illustrated by a numerical example. Although this example is carried out for a ball-grid-array design, it is applicable to highly popular column-grid-array (CGA) and quad-flat-no-lead (QFN) designs as well. It is noteworthy that it is much easier to avoid inelastic strains in CGA and QFN structures than in the addressed BGA design. The random vibrations are considered in the developed methodology as a white noise of the given (m/s²)²/Hz—the ratio of the acceleration amplitudes squared to the vibration frequency.
... LCD un LC šūnas verificē dažādi, piemēram, veic funkcionālo parametru izmain , u pārbaudes, produktu izstrādes pārbaudes (PDT ), paātrinātu ilgtermin , a pārbaudi (HALT ), kvalifikācijas pārbaudes (QT ), neveiksmēm orientētu paātrinātu pārbaudi (FOAT ), sadegšanas/sabrukšanas parabaudes (BIT ) [14][15][16] un tamlīdzīgi. Dažādi ražotāji un pētniecības laboratorijas ir rūpīgi analizējušas un uzlabojušas šīs metodolo ' gijas. ...
... 16. att. ...
Promocijas darba mērķis ir noskaidrot, vai Smectic-A šķidrais kristāls var būt nākamās paaudzes produkts, kas spētu uzlabot cilvēku ikdienu. Šī šķidrā kristāla optiskās īpašības, salīdzinot ar tirgū pieejamajiem produktiem, ir krietni labākas, t. i., gaismas caurlaidība vienā stāvoklī ir > 85 %, otrā < 2 %. Tas paver iespējas produktu izmantot dažādiem nolūkiem, piemēram, viedajiem logiem, lai izkliedētu gaismu saulainā dienā vai sniegtu privātuma sajūta atklātā ofisa telpā. Veikta padziļināta Smectic-A šķidrā kristāla iepriekšējo pētījumu, iegūto eksperimentālo datu un mēģinājumu izstrādāt funkcionālus produktus analīze. Iegūtā informācija detalizēti aprakstīta, izceļot galvenās neatrisinātās problēmas un piedāvājot to risinājumus. Lai saprastu Smectic-A šķidrā kristāla potenciālu viedo logu tehnoloģijā, veikta esošo produktu analīze, sniegts kopsavilkums par aktīvajiem viedajiem logiem un to savstarpējais salīdzinājums. Eksperimentāli izpētīta Smectic-A šķidrā kristāla gaismas caurlaidības un pārslēgšanās ātruma atkarība no pārslēgšanas frekvences, kā arī jaudas patēriņš, balstoties uz pārslēdzamo šķidrā kristāla šūnas laukumu. Izstrādāta metodika, kā noteikt šķidrā kristāla elektriskos parametrus, lai varētu izveidot elektrisko simulācijas modeli un atvieglotu elektronisko sistēmu izstrādi.
... LCDs and LC cells go through various stages of testing, e. g., functional, parameter variation testing, Product Development Testing (PDT ), Highly Accelerated Life Testing (HALT ), Qualification Tests (QT ), Failure Oriented Accelerated Testing (FOAT ), Burn In Test (BIT ) [16], [17], [18]. All of the testing methodologies have been thoroughly analysed and improved by some manufacturers and research laboratories. ...
... 18. Unswitchable (stuck) LC cluster zones in inner state before testing cycle and parameter optimization. ...
The Thesis focuses on Smectic-A (SmA) liquid crystals' (LCs) functional behaviour in order to understand if this will be the next generation product that could improve the daily life of the society. The optical properties of this liquid crystal are by far the best compared to the products available in the market, i.e., the light transmittance in transparent state is >85 % and in scatter state <2 %. Enabling the LC to be used for a variety of purposes, such as smart windows to scatter light on a sunny day or provide a sense of privacy in an open type office space. An in-depth literature review discusses the existing studies, obtained experimental data and attempts to develop functional products. The main unresolved problems are highlighted, described in detail and solutions are offered. In order to understand the potential of SmA LC in the smart glass/window technology, analysis of existing products was performed, a summary of an active smart glass/windows provided, and a comparative study between them was made. In addition, an in-depth study of long-term functional stability was performed during which the most popular types of defects were listed and analysed. Solutions for defect elimination and recommendations for optimization of switching systems and production processes are provided. A methodology for determining the electrical parameters of an LC has been developed in order to create an electrical simulation model and facilitate the development of electronic switching systems.
... Results show that the maximum peeling stress is applied to the solders at the corners of the board. A hybrid model consisting of Boltzmann-Arrhenius-Zhukov has been presented to test the fatigue of the solder layer in a PCB [20]. The results of this study illustrate that the mechanical oscillations and thermal loadings quicken the proliferation of the fatigue splits. ...
... A suitable fatigue indicator of the elements can help to assess a proper view for the vibration tests. As has been shown in many similar studies [15][16][17][18][19][20][21][22][23][24][25], the root means square of the peeling stress has been introduced as the proper indicator [24,25]. Test results show that the interconnection points between the MOSFETs and the PCB are the weakest regions under the vibration. ...
This paper presents the simulation and hardware test results for determining the fatigue life of the solder joints of a printed circuit board (PCB) including a DC to AC inverter circuit with six power metal oxide semiconductor field effect transistors (MOSFETs) by using the finite element method (FEM) under different vibration effects. This board is exposed under different angles by a vibration machine. The selected angles were performed on the power module to find the maximum stress points of the power module for different vibration frequencies. The results indicate that the maximum stress is observed at the corners of the solder layer. The stress of the solder joints significantly increases when the input frequency increases, and the failure, voids generation and crack formation and propagation are more observable under this condition. Furthermore, the loading direction changes show that the peeling stress of the solder layer is directly affected by lower angles. The shear stress occurs in lower angles of loading directions, and this situation results in the peeling stress. The simulation investigations are proved by the experimental results in the study. According to the observations, the fatigue effects result in the coalescence and the void growths in lower angles of vibration loadings. The paper also investigates the normal loading condition of the power inverter circuit, and the highest reliability is obtained compared to all other experimental tests.
... The recently suggested, mostly in application to avionics and automotive electronics and photonics, probabilistic design for reliability (PDfR) concept [6][7][8][9][10][11] is based on the highly focused and highly cost-effective failure-oriented-accelerated-testing (FOAT) [12][13][14][15][16][17] aimed, first of all, at understanding and confirming the anticipated physics of failure. This type of testing should be conducted, when developing a new technology, in addition to the widely used today, in different modifications, highly-accelerated-life-testing (HALT). ...
... • And how such a lifetime should be related to the acceptable (adequate and, if appropriate, even specifi ed) probability of failure for a particular product and application [16,17]? ...
... The PDfR concept quantifies, on the probabilistic basis and using BAZ model, the lifetime of an E&P product from highly focused and highly cost-effective failure-oriented-accelerated-testing (FOAT) [14][15][16]. The τ value is viewed in the BAZ model (1) as the mean-time-to-failure (MTTF). ...
... Frequency-Domain (FD) and Monte-Carlo (MC) models are the most common techniques for fatigue estimation for the solder joints under the vibration and according to the [20][21][22], the FD approach is more accurate. For the Plastic Quad Flat (PQF)-based Printed Circuit Boards (PCBs), based on the Boltzmann-Arrhenius-Zhukov (BAZ) model [23][24], the cracks in the solder joints is started from the solder to the copper lead under the vibration. Based on presented researches, the fatigue life of the solder joints is analyzed separately under vibration and thermal cycling and there is a limited number of studies that present the fatigue of the solder joints under both thermal and vibration effects. ...
This study presents the effects of the vibration and thermal cycling on the fatigue life of a power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) in a power converter circuit. The fatigue mechanism in per loading mode was investigated separately and based on the overlap approach, the synchronous effects were analyzed. The solder creeps’ attitudes are depended on the fatigue life for the thermal loops. The success of the deposited strain per thermal loop is in direct relation with the fatigue lifetime. The main source of the stress in the packaging process is the differences between the components’ thermal coefficients. To evaluate the effects of the vibration on the fatigue life for the solder layers, the RMS value of the peeling stress was considered. According to the results, the maximum stress and main affected points realized at the corners of the layers. It has been identified that the assembling of the thermal effects and mechanical loads are quickened the failure rate at the solder joints for this device. The Finite Element Method (FEM) is used for the simulation and the results confirm the estimated crack formation places in the layers.
Astronaut's performance is critical to assure success and safety of an outer space mission. For the given mental workload (MWL), astronaut's long-term performance is affected by his/hers human capacity factor (HCF), while the astronaut's short-term performance depends also on his/hers current state of health (SoH). It is suggested that the roles of these human factors (HFs) are quantified by using the double-exponential-probability-distribution function (DEPDF). The underlying physics and attributes of this function in the problem in question are addressed and explained. The general concepts are illustrated by a numerical example.
Three practically important reliability-related questions for solder joint interconnections (SJIs) in automotive electronics, and particularly in its actuator and sensor electron devices, are addressed in this analysis: Could inelastic strains in the solder material be avoided by a rational physical design of the IC package, and, if not, could the sizes of the peripheral inelastic strain areas be predicted and minimized? It is clear that the low cycle fatigue lifetime is inversely proportional to the sizes of the inelastic zones and that the material's fatigue lifetime could be improved dramatically, if the induced strains remain within the elastic range. The Palmgren-Miner rule of linear accumulation of damages can be used, instead of Coffin-Manson relationships, in such a situation. Realizing that, because of the inevitable uncertainties, the difference between highly reliable and an insufficiently robust electronic products is “merely” in the levels of their never-zero probabilities of failure, could these probabilities be assessed, and could this be done at the design stage? A possibility of doing that is particularly critical for SJIs, the most vulnerable structural elements in the today's IC package designs. Reliability of an electronic material or a product cannot be assured, if it is not quantified, and, because of the inevitable and critical uncertainties, this should be done on the probabilistic basis. Should SJI accelerated testing based on costly, time- and labor-consuming and, because of temperature dependency of material properties, possibly even misleading temperature cycling, be replaced by a more physically meaningful, less expensive and more trustworthy accelerated test vehicle, and could low-temperature/random-vibrations bias be employed in this capacity? The rationale behind such a question has to do with the facts that the highest thermal stresses take place at the lowest temperature conditions, and that fatigue cracks, whether elastic or inelastic, propagate most rapidly, when the material experiences random vibrations. This technique has been already reduced to practice in an industrial lab two years ago.
The objective of the analysis is to shed light, by using analytical (“mathematical”) modeling, rather than widely spread computer simulation, on the mechanical behavior and the underlying physics of failure in the SJI. Future work should focus primarily on experimentations to confirm theoretical findings and recommendations.
The recently suggested probabilistic design for reliability (PDfR) concept of electronics and photonics (EP) products is based on 1) highly focused and highly cost-effective failure oriented accelerated testing (FOAT), aimed at understanding the physics of the anticipated failures and at quantifying, on the probabilistic basis, the outcome of FOAT conducted for the most vulnerable element(s) of the product of interest, for the most likely applications and for the most likely and meaningful combination of possible stressors (stimuli); 2) simple and physically meaningful predictive modeling (PM), both analytical and computer-aided, aimed at bridging the gap between the obtained FOAT data and the most likely actual operation conditions; and 3) subsequent FOAT-and-PM-based sensitivity analysis (SA) using the methodologies and algorithms developed as important by-products at the two previous steps. The PDfR concept proceeds from the recognition that nothing is perfect, and that the difference between a highly reliable and an insufficiently reliable product is 'merely' in the level of the probability of its field failure. If this probability (evaluated for the anticipated loading conditions and the given time in operation) is not acceptable, then a SA can be effectively employed to determine what could/should be changed to improve the situation. The PDfR analysis enables one also to check if the product is not 'over-engineered', i.e., is not superfluously robust. If it is, it might be too costly. The operational reliability cannot be low, but it does not have to be higher than necessary either. It has to be adequate for the given product and application. When reliability and cost-effectiveness are imperative, ability to optimize reliability is a must, and no optimization is possible if reliability is not quantified. We show that optimization of the total cost associated with creating a product with an adequate (high enough) reliability and acceptable (low enough) cost can be interpreted in terms of an adequate level of the availability criterion. The major PDfR concepts are illustrated by practical examples. Although some advanced PDfR predictive modeling techniques have been recently developed, mostly for aerospace applications, the practical examples addressed in this talk employ more or less elementary analytical models. In this connection we elaborate on the roles and interaction of analytical (mathematical) and computer-aided (simulation) modeling. We show also how the recently suggested powerful and flexible Boltzmann-Arrhenius-Zhurkov (BAZ) model and particularly its multi-parametric extension could be successfully employed to predict, quantify and assure operational reliability. The model can be effectively used to analyze and design EP products with the predicted, quantified, assured, and, if appropriate and cost-effective, even maintained and specified probability of operational failure. It is concluded that these concepts and methodologies can be accepted as an effective means for the evaluation of the operational reliability of EP materials and products, and that the next generation of qualification testing (QT) specifications and practices for such products could be viewed and conducted as a quasi-FOAT, an early stage of FOAT that adequately replicates the initial non-destructive segment of the previously conducted comprehensive 'full-scale' FOAT.
The recently suggested probabilistic design for reliability (PDfR) concept proceeds from the recognition that nothing is perfect, and that the difference between a highly reliable and an insufficiently robust product is 'merely' in the level of the probability of its failure. The PDfR effort includes: 1) Highly focused and highly cost-effective failure oriented accelerated testing (FOAT) aimed at understanding the reliability physics underlying of the occurred or anticipated failures; 2) Simple and physically meaningful predictive modeling (PM) effort geared to a particular FOAT model and aimed at bridging the gap between the obtained FOAT information and what will supposedly take place in the field; and 3) Extensive sensitivity analysis (SA) that should be carried out, if necessary, to determine what could possibly be done to change the predicted probability of failure. The general concepts are illustrated by practical examples.
High operational reliability of an electronic material or a device intended for aerospace applications is critical, and, in the author’s opinion, cannot be assured, if the underlying physics of failure is not well understood and the never-zero probability of failure is not predicted and made adequate for the particular material, device and application. The situation is the same in some other areas of electronics materials engineering, such as military, medical, or long-haul communications, where high level of reliability is required. The situation is different in today’s commercial electronics, where cost and time-to-market are typically more important than high reliability. Failure-oriented-accelerated-testing (FOAT) of aerospace electronics materials and products and its role in making a viable device into a reliable product is addressed and discussed vs. very popular today highly-accelerated-life-testing (HALT). The differences of the two accelerated test procedures and objectives is briefly discussed. FOAT is an essential part of the recently suggested probabilistic design for reliability (PDfR) approach in electronics engineering. It is argued that high (adequate) reliability level of aerospace electronics materials and devices cannot be achieved and assured, if their never-zero probability-of-failure is not quantified for the given (anticipated) combination of the loading conditions (stresses, stimuli) and time in operation. It is the application of the FOAT, the heart of the highly effective and highly flexible PDfR concept, that should be employed and mastered, when high reliability of a material or a device is imperative. The general concepts are illustrated by numerical examples. They are based on an analytical modeling approach, as the FOAT models are.
The recently suggested probabilistic design-for-reliability (PDfR) concept and particularly its physically meaningful and flexible Boltzmann–Arrhenius–Zhurkov (BAZ) model, can be effectively employed as an attractive replacement of the widely used today purely empirical and physically unsubstantiated power law relationship for assessing the static fatigue (delayed fracture) lifetime of optical silica fibers. In this analysis the BAZ model is employed to estimate the static fatigue lifetime of an optical silica fiber under the combined action of tensile loading and an elevated temperature. The PDfR concept has its experimental basis in the highly-focused and highly-cost-effective failure-oriented accelerated testing (FOAT). Accordingly, it is shown how the PDfR concept, BAZ model and FOAT data can be effectively used, when there is a need to assess the long-term tensile strength (static fatigue life) of a coated optical fiber subjected to the combined action of tensile loading and elevated temperature. Although the role of elevated humidity might be insignificant owing to the elevated temperature conditions, this role can be accounted for, if there is a need for that, as well, by using multi-parametric BAZ model. Since the principle of superposition does not work in reliability engineering, all the three stressors, namely, the elevated temperature, tensile stress and relative humidity, should be applied concurrently to the specimen under test, and their coupling, if any, should and could be considered by the FOAT based on the BAZ model. The numerical example is carried out, however, for the case when only the elevated temperature and tensile stress are applied. The results of the analysis can be employed in the design and testing of optical silica fibers.
A simple and physically meaningful analytical stress model is developed in application to shear-off testing with an objective to evaluate the interfacial shearing stress in the bonding material from the measured shear off force. The model can be used also for the evaluation of the shear modulus of the bonding material, if the interfacial displacement is also measured. The general concept is illustrated by a numerical example. In the authors’ opinion, the suggested methodology, based on the concept of the interfacial compliance, suggested by the first author in his 1986 ASME J. Appl. Mech. paper, could become a basis for a new effective experimental method for assessing the interfacial shearing strength and elastic moduli of the bonding material in electronics. The methodology can be used particularly in application to the recently suggested sintered silver bonding materials to evaluate their bonding strength from the measured force-at-failure and shear modulus from the measured shearing force and displacement.
Although there exist promising ways to avoid inelastic strains in solder joints of the second level interconnections in IC package designs, it still appears more typical than not that the peripheral joints of a package/PCB assembly experience inelastic strains. This takes place at low temperature conditions, when the deviation from the high fabrication temperature is the largest and the induced thermal stresses are the highest. On the other hand, it is well known that it is the combination of low temperatures and repetitive dynamic loading that accelerate dramatically the propagation of fatigue cracks, whether elastic or inelastic. Accordingly, a modification of the recently suggested Boltzmann–Arrhenius–Zhurkov model is developed for the evaluation of the remaining useful lifetime of the second level solder joint interconnection whose peripheral joints experience inelastic strains. The experimental basis of the approach is the highly focused and highly cost-effective failure-oriented-accelerated-testing (FOAT). The FOAT specimens are subjected in our methodology to the combined action of low temperatures (not to elevated temperatures, as in the classical Arrhenius model) and random vibrations with the given input energy spectrum. The suggested methodology is viewed as a possible, effective and attractive alternative to temperature cycling. As long as inelastic deformations take place, it is assumed that it is these deformations that determine the fatigue lifetime of the solder material, and the state of stress in the elastic mid-portion of the assembly does not have to be accounted for. The roles of the size and stiffness of this mid-portion have to be considered, however, when determining the very existence and establishing the size of the inelastic zones at the peripheral portions of the designs. The general concept is illustrated by a numerical example. Although this example is carried out for a ball-grid-array design, it is applicable to highly popular column-grid-array (CGA) and quad-flat-no-lead (QFN) designs as well. It is noteworthy that it is much easier to avoid inelastic strains in CGA and QFN structures than in the addressed BGA design. The random vibrations are considered in the developed methodology as a white noise of the given (m/s²)²/Hz—the ratio of the acceleration amplitudes squared to the vibration frequency.
When encountering a particular reliability problem at the design, fabrication, testing, or an operation stage of a product's life, and considering the use of predictive modeling to assess the seriousness and the likely consequences of the a detected failure, one has to choose whether a statistical, or a physics-of-failure-based, or a suitable combination of these two major modeling tools should be employed to address the problem of interest and to decide on how to proceed. A three-step concept (TSC) is suggested as a possible way to go in such a situation. The classical statistical Bayes' formula can be used at the first step in this concept as a technical diagnostics tool. Its objective is to identify, on the probabilistic basis, the faulty (malfunctioning) device(s) from the obtained signals ("symptoms of faults"). The recently suggested physics-of-failure-based Boltzmann-Arrhenius-Zhurkov's (BAZ) model and particularly the multi-parametric BAZ model can be employed at the second step to assess the remaining useful life (RUL) of the faulty device(s). If the RUL is still long enough, no action might be needed; if it is not, corrective restoration action becomes necessary. In any event, after the first two steps are carried out, the device is put back into operation (testing), provided that the assessed probability of its continuing failure-free operation is found to be satisfactory. If the operational failure nonetheless occurs, the third, technical diagnostics step should be undertaken to update reliability. Statistical beta-distribution, in which the probability of failure is treated as a random variable, is suggested to be used at this step. While various statistical methods and approaches, including Bayes' formula and beta-distribution, are well known and widely used in numerous applications for many decades, the BAZ model was introduced in the microelectronics reliability (MR) area only several years ago. Its attributes are addressed and discussed therefore in some detail. The suggested concept is illustrated by a numerical example geared to the use of the prognostics-and-health-monitoring (PHM) effort in actual operation, such as, e.g., en-route flight mission.
Boltzmann–Arrhenius–Zhurkov (BAZ) model enables one to obtain a simple, easy-to-use and physically meaningful formula for the evaluation of the probability of failure (PoF) of a material after the given time in operation at the given temperature and under the given stress (not necessarily mechanical). It is shown that the material degradation (aging, damage accumulation, flaw propagation, etc.) can be viewed, when BAZ model is considered, as a Markovian process, and that the BAZ model can be obtained as the steady-state solution to the Fokker–Planck equation in the theory of Markovian processes. It is shown also that the BAZ model addresses the worst and a reasonably conservative situation, when the highest PoF is expected. It is suggested therefore that the transient period preceding the condition addressed by the steady-state BAZ model need not be accounted for in engineering evaluations. However, when there is an interest in understanding the physics of the transient degradation process, the obtained solution to the Fokker–Planck equation can be used for this purpose.
Random events discrete random variables continuous random variables systems of random variables functions of random variables entropy and information random processes - correlation theory random processes - spectral theory extreme value distributions reliability Markovian processes random fatigue geometric tolerance random loads and responses in some engineering systems processing of experimental data.
IEEE CPMT ASTR tutorials, 2012
- M Silverman
Probabilistic Design for Reliability (PDfR) of Medical Electronic Devices (MEDs): When Reliability is Imperative, Ability to Quantify it is a Must
- suhir