The magnitude and the distribution of stresses in bi-metal thermostats subjected to uniform heating or cooling are determined. suggested approach enables one evaluate normal thermostat plates, as well shearing (“peeling”) interface. developed is applicable, generally speaking, any elongated lap shear assembly.

We have reconsidered the problem of critical layer thickness hc for growth strained heterolayers on lattice-mismatched substrates, using a new approach which allows us to determine spatial distribution stresses in bi-material assembly and include effects finite size sample. The possibility dislocation-free materials porous silicon substrates is discussed as an example more general heteroepitaxial small seed pads lateral dimension l, having uniform crystal orientation over entire substrate...

The magnitude and the distribution of interfacial stresses in thermostat-like structures are determined on basis an elementary beam theory, with consideration both longitudinal transverse (“through-thickness”) compliances thermostat strips. suggested approach is applicable, generally speaking, to any elongated lap shear assembly, subjected thermal or external loading.

The analysis contains an engineering method for the approximate evaluation of thermally induced stresses in single and multilayered heteroepitaxial structures fabricated on thick substrates, with consideration finite size structure. examined include normal stresses, acting film layers themselves responsible their ultimate fatigue strength, as well interfacial blistering peeling. developed formulas are simple, easy-to-use, clearly indicate how material structural characteristics affect...

Carbon nanotubes (CNTs), owing to their exceptionally high thermal conductivity, have a potential be employed in micro- and optoelectronic devices for integrated circuit (IC) cooling. In this study we describe photothermal metrology intended evaluate the conductivity of vertically aligned CNT array (VCNTA) grown on silicon (Si) substrate. Plasma-enhanced chemical vapor deposition, with nickel (Ni) as catalyst, was used grow CNT. The experimentally evaluated VCNTA contact resistance at...

The interfacial stresses in, and the curvature of, an elongated trimaterial assembly, subjected to change in temperature, are predicted based on approximate structural analysis (strength-of-materials) model. obtained results can be helpful stress–strain evaluations physical design of assemblies microelectronic photonic packaging.

An easy-to-use calculation procedure for the evaluation of thermally induced forces in single-coated optical fibers is discussed. The calculations show that increase lateral pressure at cladding-coating interface adequately reflects experimentally observed added transmission losses low temperatures. measurements were carried out on loose a test chamber, where mechanical effects other than shrinkage coating excluded. It suggested be used as tentative criterion temperature threshold expected...

We discuss the role and attributes of, as well state-of-the-art some major findings in, area of predictive analytical (“mathematical”) thermal stress modeling in electronic, opto-electronic, photonic engineering. The emphasis is on packaging assemblies structures simple meaningful practical models that can be (and actually have been) used mechanical (“physical”) design reliability evaluations assemblies, structures, systems. indicate role, objectives, attributes, merits, shortcomings its...

Boltzmann–Arrhenius–Zhurkov (BAZ) model enables one to obtain a simple, easy-to-use and physically meaningful formula for the evaluation of probability failure (PoF) material after given time in operation at temperature under stress (not necessarily mechanical). It is shown that degradation (aging, damage accumulation, flaw propagation, etc.) can be viewed, when BAZ considered, as Markovian process, obtained steady-state solution Fokker–Planck equation theory processes. also addresses worst...

Accelerated life tests (ALTs) are aimed at revealing and understanding the physics of expected or occurred failures, i.e., able to detect possible failure modes mechanisms. Another objective ALTs is accumulate representative statistics. Adequately designed, carefully conducted, properly interpreted provide a consistent basis for obtaining ultimate information reliability product—the predicted probability after given time service in conditions. Such can dramatically facilitate solution cost...

An analytical evaluation of the thermally induced microbending in dual-coated optical fibers is presented, with an emphasis on effect initial local curvatures. The analysis has shown that these curvatures could cause appreciable additional deflections glass fiber even at moderately low temperatures, thereby resulting added transmission losses. developed formulas are considered simple, easy-to-use, and to indicate clearly role various factors affecting prebuckling behavior fiber. They also...

An analytical (mathematical) thermal stress model has been developed for an electronic assembly comprised of identical components bonded at their end portions and subjected to different temperatures. The is used assess the effect size (dimension in x-direction) compliance regions (legs) on maximum interfacial shearing that supposedly responsible mechanical robustness assembly. numerical example carried out a simplified two-legged Bismuth-Telluride-Alloy (BTA)-based thermoelectric module...

The dynamic strength of structural elements micro- and portable electronic products is often evaluated on the basis measured maximum acceleration which these experience during shock or drop tests. It well known, however, that it stress, not acceleration, a true criterion strength. Using examples can be idealized as simply supported beam cantilever with concentrated mass at end, we show for given geometry weight, level stress indeed judged upon acceleration. However, application misleading if...

An analytical model is developed for the evaluation of thermally induced stresses in midportion an optical glass fiber soldered into a ferrule. The purpose analysis to select appropriate solder material and geometry joint. We show that ferrule has major effect on solder, that, conventional solders, low expansion ferrules (Invar) result high-tensile radial tangential both solder. On other hand, high-expansion (aluminum, nickel) excessive compressive therefore should also be avoided. However,...

The interfacial shearing and “peeling” stresses in an elongated bimaterial assembly, adhesively bonded at the ends subjected to change temperature, are predicted, based on approximate structural analysis (strength-of-materials) model. joints due thermal expansion (contraction) mismatch of adherend materials within areas (“local” mismatch), as well stresses, caused by unbonded midportion assembly (“global” considered. interaction “local” “global” is evaluated analyzed. It shown that if made...

We address some major trends in microelectronics, photonics, and other areas of "high-technology" engineering. discuss which the new directions emerging technologies this field engineering look most promising, what challenges a mechanical/materials/reliability engineer will likely encounter connection with these technologies.

Compliant external electrical leads are often utilized as strain buffers in surface-mounted device technology to provide the necessary stress relief for device, when substrate is subjected bending. A paradoxical situation was observed, however, during testing of compliant leaded hybrid integrated circuits (HIC): In some tests bending moment, applied printed wire board (PWB) and causing HIC fracture, turned out smaller (not greater), greater compliance were installed. We show that such a due...