A Physics of Failure Approach to Component Placement

1992 ◽  
Vol 114 (3) ◽  
pp. 305-309 ◽  
Author(s):  
M. D. Osterman
Keyword(s):  
Operating Temperature ◽  
Threshold Temperature ◽  
Time To Failure ◽  
Failure Model ◽  
Physics Of Failure ◽  
Component Placement ◽  
Convection Cooling ◽  
The Individual ◽  
Component Temperature ◽  
Cycles To Failure

Traditionally, placement techniques have focused on improving rotability based on minimizing the total wire length between interconnected components. However, electronic card assembly (ECA) reliability, which is measured in terms of time to failure, cycles to failure, or the hazard rates of the individual components, the interconnections, and the PWB, is also affected by component placement. This paper discusses component placement for reliability based on a failure model which incorporates component temperature, a base operating temperature, a threshold temperature, and change in temperature. Placement procedures are developed so as to minimize the time to failure or the total hazard rate of the components on a PWB utilizing a forced convection cooling.

Comparative Reliability Prediction Using Physics of Failure Models

2011 ◽  
Vol 2011 (HITEN) ◽  
pp. 000189-000195
Author(s):  
Milton Watts ◽  
K. Rob Harker
Keyword(s):  
Circuit Complexity ◽  
High Impact ◽  
Reliability Prediction ◽  
Life Test ◽  
Physics Of Failure ◽  
Failure Models ◽  
The Individual ◽  
Aging Models ◽  
Device Test

Quartzdyne Electronics has invested millions of device test hours in life testing of circuits in both powered and un-powered tests. In addition to time at temperature, these tests include thermal cycling and high impact drop testing. Recent projects have required the use of larger packages and components as we have expanded the variety of circuits that we build. It is desirable to predict the effects of these changes on long-term reliability before investing in tooling. In this study we will compare a new design which contains these larger components to the simpler, smaller designs for which we have extensive life-test data. Using a physics-of-failure approach, component mounting stresses will be analyzed using finite element modeling. These results will be compared to pre and post-aging shear strengths of actual components of varying sizes. Aging models will then be developed to predict the reliability of the new design based on the comparative stress margins of the individual components coupled with circuit complexity. Once validated, the aging models will enable reliability prediction and trade-off analysis for future designs.

Thin Thermally Efficient ICECool Defense Semiconductor Power Amplifiers

2017 ◽  
Vol 14 (3) ◽  
pp. 77-93 ◽  
Author(s):  
Sumeer Khanna ◽  
Patrick McCluskey ◽  
Avram Bar-Cohen ◽  
Bao Yang ◽  
Michael Ohadi
Keyword(s):  
Heat Flux ◽  
Structural Reliability ◽  
Mechanical Design ◽  
Substrate Thickness ◽  
Time To Failure ◽  
Failure Model ◽  
High Concentration ◽  
Element Analysis ◽  
Analysis Technique ◽  
Compact Design

Abstract Traditional power electronics for military and fast computing applications are bulky and heavy. The “mechanical design” of electronic structure and “materials” of construction of the components have limitations in performance under very high temperature conditions. The major concern here is “thermal management.” To be more specific, this refers to removal of high-concentration hotspot heat flux >5 kW/cm2, background heat flux >1 kW/cm2, and “miniaturization” of device within a substrate thickness of <100 μm. We report on the novel applications of contact-based thermoelectric cooling (TEC) to successful implementations of high-conductivity materials - diamond substrate grown on gallium nitride (GaN)/AlGaN transistors to keep the hotspot temperature rise of device below 5 K. The requirement for smarter and faster functionality along with a compact design is considered here. These efforts have focused on the removal of higher levels of heat flux, heat transfer across interface of junction and substrate, advanced packaging and manufacturing concepts, and integration of TEC of GaN devices to nanoscale. The “structural reliability” is a concern and we have reported the same in terms of mean time to failure (cycles) of SAC305 (96.5% tin, 3% silver, 0.5% cu) solder joint by application of Engelmaier's failure model and evaluation of stresses in the structure. The mathematical equation of failure model incorporates the failure phenomena of fatigue and creep in addition to the dwell time, average solder temperature, and plastic strain accumulation. The approach to this problem is a nonlinear finite element analysis technique, which incorporates thermal, mechanical, and thermoelectric boundary conditions.

Study on the Fabrication and Characterization of LAST and LASTT Based Thermoelectric Generators

2007 ◽  
Vol 1044 ◽  
Author(s):  
Chun-I Wu ◽  
Edward J. Timm ◽  
Fei Ren ◽  
Bradley D. Hall ◽  
Jennifer Ni ◽  
...  
Keyword(s):  
Operating Temperature ◽  
Thermoelectric Generators ◽  
Measurement Systems ◽  
Temperature Range ◽  
Fabrication And Characterization ◽  
The Individual ◽  
Contact Resistivities ◽  
Detailed Presentation ◽  
Operating Temperature Range

AbstractThermoelectric modules are of great interest for power generation applications where temperature gradients of approximately 500K exist, and hot side temperatures near 800K. The fabrication of such modules requires optimization of the material compositions, low contact resistivities, and low thermal loss.AgPbmSbTe2+m (LAST) and Ag(Pb1-xSnx)m SbTe2+m (LASTT) compounds are among the best known materials appropriate for this temperature range. Various measurement systems have been developed and used to characterize bulk samples in the LAST and LASTT systems within this operating temperature range. From the characterized data, modeling of modules based on these materials and segmented legs using LAST(T) with Bi2Te3 have been used to identify the optimal geometry for the individual legs, and the length of the Bi2Te3 segments. We have segmented LAST(T) with Bi2Te3 and achieved contact resistivities of less than 10 μΩ•cm2.Here we give a detailed presentation on the procedures used in the fabrication of thermoelectric generators based on LAST, LASTT, and segmented with Bi2Te3 materials. We also present the output data on these generators.

Physics of Failure Based Virtual Testing of Communications Hardware

2009 ◽  
Author(s):  
Elviz George ◽  
Diganta Das ◽  
Michael Osterman ◽  
Michael Pecht ◽  
Christopher Otte
Keyword(s):  
Thermal Cycling ◽  
High Reliability ◽  
Simulation Software ◽  
Circuit Board ◽  
Thermal Dissipation ◽  
Physics Of Failure ◽  
Printed Circuit ◽  
Operational Test ◽  
Reliability Systems ◽  
Cycles To Failure

Communications hardware for high reliability systems are starting to include modern low profile parts such as Quad Flat Pack No-lead (QFN) and Land Grid Array (LGA) packages to take advantage of their size and weight. In these parts, heat sinks often provide a conductive thermal dissipation path. Printed circuit assemblies with these parts will still need to meet the industry specific qualification requirements for thermal and vibration testing. It is beneficial to identify if the equipment will be able to meet the qualification test requirements during the design phase particularly when new technology insertions are being made. In this design, various surface mount packages like LGAs, QFNs and so on were used in a printed circuit board which included two stiffening layers with non-standard laminates. calcePWA is a simulation software which estimates the cycles to failure of components under various loading conditions using Physics of Failure (PoF). The cycles to failure simulation of this design using calcePWA software identified the critical interconnects that are at risk for failure under non-operational test conditions. The design was also evaluated under a long haul aircraft profile, with the assembly in operational state. In operational state simulation, the effectiveness of thermal shunts in reducing board to component thermal differentials was evaluated. Effects of degradations of the thermal shunts with time were used in the evaluation. Results showed that the vibration and shock reliability were less of a concern than thermal cycling for this board layout. Risk mitigation methods for thermal cycling durability were identified and recommended to be used in the system redesign.

IIIB-2 mean time to failure model for hot-carrier-induced degradation

1984 ◽  
Vol 31 (12) ◽  
pp. 1970-1971 ◽  
Author(s):  
K.L. Chen ◽  
S.A. Saller ◽  
I.A. Groves ◽  
D.B. Scott
Keyword(s):  
Time To Failure ◽  
Failure Model ◽  
Mean Time To Failure ◽  
Hot Carrier ◽  
Mean Time

scholarly journals DETERMINATION OF PEAT ASH FUSIBILITY OF KIROV REGION DEPOSITS

2019 ◽  
Vol 20 (11-12) ◽  
pp. 27-33
Author(s):  
V. A. Kuzmin ◽  
I. A. Zagrai ◽  
I. A. Desiatkov
Keyword(s):  
Fly Ash ◽  
Chemical Composition ◽  
Melting Temperature ◽  
Operating Temperature ◽  
Melting Characteristics ◽  
Steam Boilers ◽  
Ash Fusibility ◽  
The Individual ◽  
Individual Particles

The paper deals with the issues related to the effect of slagging within the steam boilers furnaces and shows the determination results on peat ash fusibility of Kirov region deposits. Fusibility properties of peat ash (temperatures of deformation, sphere, hemisphere and flow) from the four industrial areas (Dymny, Pishchalsky, Karinsky, Gorokhovsky) depending on its chemical composition are presented. Melting temperature of the mineral part of the peat, determined by GOST, is averaged and does not reflect the actual melting temperature of the individual particles in fly ash. The existence of such separate particles having a melting temperature below the average melting temperature of the ash makes it difficult to find the operating temperature of the torch to reach the minimum of the furnace slagging during peat combustion. The comparison of melting characteristics of peat ash with the reference literature data is performed. The initial slagging temperature is calculated depending on the ratio of the acidic and basic oxides in peat ash.

scholarly journals Application of resettable elements for electrical protection of solar batteries

2018 ◽  
pp. 43-49 ◽  
Author(s):  
A. S. Tonkoshkur ◽  
A. V. Ivanchenko ◽  
L. V. Nakashydze ◽  
S. V. Mazurik
Keyword(s):  
Operating Temperature ◽  
Photovoltaic Cells ◽  
Threshold Temperature ◽  
Temperature Range ◽  
Emergency Situations ◽  
Local Overheating ◽  
Carbon Fillers ◽  
Multiple Switching ◽  
Solar Batteries ◽  
Operating Temperature Range

The manifestation and formation of various defects in the process of exploitation in real photovoltaic cells and their compounds as well as their work in the regime of changing non-uniform illumination lead to the so-called series and parallel inconsistencies (differences of electrical characteristics) between separate cells and their groups. This results in local overheating and intensifying of degradation processes. In some cases temporary disconnection (isolation) of the corresponding elements of the solar batteries is more appropriate in order to increase their service life. In this work additional devices for insulation of overheating cells (and/or components) of solar batteries such as “PolySwith” resettable fuses are proposed to be used as a perspective solution of such problems. These structures are polymer composites with nanosized carbon fillers. Electrical resistance of such a fuse increases abruptly by several orders of magnitude when certain threshold temperature is reached, and when the temperature decreases the fuse returns to its initial high-conductivity state. This study investigates the possibilities of using the specified type of fuses for electrical insulation of «overheated» photovoltaic cells. Particular attention is paid to the research of the effect of fuses on the working of the solar batteries in the operating temperature range and their functional applicability in emergency situations associated with overheating. The studies were carried out using a model structure of several series of parallel connected photovoltaic cells and specified fuses. Attention is paid to the influence of such factors as the ambient temperature and the drift of the fuses resistance in the conducting state in the process their multiple switching. It has been established that such protection elements do not influence the work of solar batteries in operating temperature range and are functionally applicable for the electrical isolation of local regions and components of solar batteries with increased temperature.

Sliding Failure Model for Magnetic Head-Disk Interface

1990 ◽  
Vol 112 (2) ◽  
pp. 299-303 ◽  
Author(s):  
P. A. Engel ◽  
B. Bhushan
Keyword(s):  
Friction And Wear ◽  
Time To Failure ◽  
Failure Model ◽  
Head Disk Interface ◽  
Magnetic Head ◽  
Disk Interface ◽  
Damage Rate ◽  
Debris Particles ◽  
Physical Variables ◽  
Topographic Parameters

A mechanical model is presented for the “time to failure” of a sliding magnetic head-disk interface system. The principal physical variables include the sliding speed, surface topography, elastic mechanical properties, coefficient of friction, and wear rate. Surface protrusions, such as asperities and debris particles, induce impact and sliding encounters which represent a damage rate. Failure occurs when a specific damage rate, a characteristic for the system, is reached. Modeling uses a set of topographic parameters describing the changing, wearing surface.

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