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Suhir E.,Physical science and Engineering Research Division | Suhir E.,University of California at Santa Cruz | Suhir E.,University of Maryland University College | Suhir E.,Vienna University of Technology | Suhir E.,ERS Co.
Advancing Microelectronics | Year: 2012

Here are the major messages of this paper: reliability of an electronic (opto-electronic, photonic, MEMS) product cannot be low, should not be higher than necessary for a particular application, but has to be adequate; understanding the reliability physics is crucial, if one intends to create a product with an adequate reliability level; when reliability is imperative, ability to quantify it is a must; the best product is the best compromise between the needs for adequate reliability, cost effectiveness and time-to-market (completion); reliability evaluations and assurances cannot be delayed until the product is made and shipped to the customer, i.e., cannot be left to the prognostics and health monitoring/management (PHM) stage; design, fabrication, qualification and PHM efforts should consider the most likely (anticipated) application(s) of the product; probabilistic design for reliability (PDfR) approach is an effective means for improving the state-of-the-art in electronics reliability: the difference between an unreliable product and a highly robust one is "just" the level of the probability of failure (PoF); highly focused and highly cost effective failure oriented accelerated testing (FOAT) is an important part of the PDfR effort; FOAT cannot do without simple and physically meaningful predictive modeling (PM), both analytical ("mathematical") and computer-aided (simulation); PM using FOAT data and sensitivity analyses is a powerful means to understand the underlying physics, to quantify reliability and prevent failures; consistent and comprehensive PDfR effort can lead to the most feasible qualification test (QT) methodologies, practices and specifications; the PDfR approach complements the existing system-related and human-psychology-related efforts, when there is an intent to assess the likelihood of the success and safety of a mission; PDfR concept enables one to bridge the gap between the three critical areas responsible for a vehicular (airor spacecraft, boat, car, etc.) mission performance - reliability engineering, vehicular technology and human factor, with consideration of various critical uncertainties. It is concluded that the highly promising and fruitful PDfR concept enables one to improve dramatically the existing practice by quantifying reliability. Extensive further research and validation effort will be needed, of course, to make the approach widely used in various practical situations. Source


Suhir E.,Physical science and Engineering Research Division | Suhir E.,University of California at Santa Cruz | Suhir E.,University of Maryland University College | Suhir E.,Vienna University of Technology | Suhir E.,ERSCo. LLC
Microelectronics Reliability | Year: 2012

Some major features and attributes of the probabilistic design-for-reliability (PDfR) approach in aerospace electronics are indicated and discussed. The general concepts are illustrated by practical examples. The incentives for using PDfR methods and techniques are addressed, as well as the importance to consider the physics of failure and, when possible and appropriate, the most likely application(s) of the product of interest. © 2012 Elsevier Ltd. All rights reserved. Source


Suhir E.,Physical science and Engineering Research Division | Suhir E.,University of California at Santa Cruz | Suhir E.,University of Maryland University College | Suhir E.,Vienna University of Technology | And 3 more authors.
Journal of Applied Mechanics, Transactions ASME | Year: 2013

Low-temperature thermally induced stresses in a trimaterial assembly subjected to the change in temperature are predicted based on an approximate structural analysis (strength-of-materials) analytical ("mathematical" ) model. The addressed stresses include normal stresses acting in the cross-sections of the assembly components and determining their short- and long-term reliability, as well as the interfacial shearing and peeling stresses responsible for the adhesive and cohesive strength of the assembly. The model is applied to a preframed crystalline silicon photovoltaic module (PVM) assembly. It is concluded that the interfacial thermal stresses, and especially the peeling stresses, can be rather high, so that the structural integrity of the module could be compromised, unless appropriate design for reliability measures are taken. The developed model can be helpful in the stress analysis and physical (structural) design of the PVM and other trimaterial assemblies. Copyright © 2013 by ASME. Source


Suhir E.,Physical science and Engineering Research Division | Suhir E.,University of California at Santa Cruz | Suhir E.,University of Maryland University College | Suhir E.,Vienna University of Technology | Suhir E.,ERS Co.
Journal of Applied Mechanics, Transactions ASME | Year: 2013

A simple and physically meaningful analytical (mathematical) predictive model is developed using two-dimensional (plane-stress) theory-of-elasticity approach (TEA) for the evaluation of the effect of the circular configuration of the substrate (wafer) on the elastic lattice-misfit (mismatch) stresses (LMS) in a semiconductor and particularly in a gallium nitride (GaN) film grown on such a substrate. The addressed stresses include (1) the interfacial shearing stress supposedly responsible for the occurrence and growth of dislocations, for possible delaminations, and for the cohesive strength of the intermediate strain buffering material, if any, as well as (2) normal radial and circumferential (tangential) stresses acting in the film cross-sections and responsible for the short-and long-term strength (fracture toughness) of the film. The TEA results are compared with the formulas obtained using strength-of-materials approach (SMA). This approach considers, instead of the actual circular substrate, an elongated bi-material rectangular strip of unit width and of finite length equal to the wafer diameter. The numerical example is carried out, as an illustration, for a GaN film grown on a silicon carbide (SiC) substrate. It is concluded that the SMA model is acceptable for understanding the physics of the state of stress and for the prediction of the normal stresses in the major midportion of the assembly. The SMA model underestimates, however, the maximum interfacial shearing stress at the assembly periphery and, because of the very nature of the SMA, is unable to address the circumferential stress. The developed TEA model can be used, along with the author's earlier publications and the (traditional and routine) finite-element analyses (FEA), to assess the merits and shortcomings of a particular semiconductor crystal growth (SCG) technology, as far as the level of the expected LMS are concerned, before the actual experimentation and/or fabrication is decided upon and conducted. © 2013 American Society of Mechanical Engineers. Source

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