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锣嗣别
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1 Reliability Physics Theory and Application (Concepts) (Fall 2017) 15

2 About Failure 16

3 About Failure Failure: the event, or inoperable state, in which any item or part of an item does not, or would not, perform as previously specified Failure mode: observable way of failure Failure site: location of failure Failure mechanisms: the physical, chemical, electrical, thermal or other processes that results in failure Root cause of failure: cause of failure that can lead to corrective or preventive actions Fault and failure 17

4 Failure and Time Time-to-Failure Mean-Time-to-Failure (MTTF) Mean-Time-Between-Failure (MTBF) Lifetime 18

5 Failure Mode vs. Failure Mechanism Failure mode defines the primary characteristic of a failure, and therefore, identifies a category or a sub-category of failures. Failure mechanism describes a failure process. Different failure mechanisms can result in the same failure mode. Failure criteria is failure-mode-dependent, but is independent of failure mechanism. Understanding failure mode and its effect is essential to the reliability and quality assurance effort in industry, but understanding failure mechanism may not be (e.g. FA, FMEA, FMECA, FTA, trouble-shooting) Understanding failure mechanism can significantly help with, but may not be necessary for, the determination of root cause of failure. 19

6 Failure Rate and Hazard Rate () t t () t Rt () Rt ( t) t R() t t hazard function R() t R( t t) 1 dr() t ht () lim t 0 t R() t R() t dt R() t f () t ht () f () t R() t Rt () f( sds ) e t t hsds ( ) 0 20

7 Early, Random and Wearout Failures 21

8 Failure Distribution 22

9 A Failure Mechanism Hypothesis Early failure: Random failure: Wearout failure: 23

10 About Reliability and Reliability Assurance Practice 24

11 Reliability and Failure Reliability is the ability of an item to perform its intended function without failure. Reliability is correspondent to certain failure Reliability can be different for different failures; Failure is defined by failure criteria Failure is not necessarily permanent or catastrophic ; Reliability is dependent upon the definition of failure Failure criteria are determined based on required function and/or application. 25

12 What is Reliability? -A Performance Ability of an item to perform its intended function for a specified interval under stated conditions Reliability as a performance Degradation in functional/parametric performance Service life and warranty claim Number of field failures and product return Requirement on maintenance and repair 26

13 What is Reliability? - The Quantitative Measure The probability that an item can perform its intended function for a specified interval under stated conditions. Reliability as the measure Failure probability/reliability 27

14 What is Reliability? -A Practice IQC: incoming quality control SPC: statistical process control ORT: on-going reliability test Corrective and preventive actions Auditing Specifications on product and component reliability and reliability testing FA (failure analysis)/fmea (failure mode and effect analysis)/ FMECA (failure mode, effect, and criticality analysis) and troubleshooting Reliability Assessment Customer service DfR 28

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16 Concept of Intrinsic and Extrinsic Reliability Early failure is a Quality failure, is of an extrinsic failure mechanism; Random failure is of an intrinsic failure mechanism; This directly implies that manufacturing quality cannot increase the inherent reliability of a design in a given use environment; however, inadequate manufacturing quality can reduce this inherent designed-in reliability by increasing infant mortality failures. / 30

17 Quality is the totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs. (ISO ) 31

18 Concept of Quality and Reliability Quality issues Quality- products meet their workmanship requirements. (fundamental, patent quality) Quality- products, in a general sense, have an acceptable margin in terms of application conditions and life span. (integrity, latent quality) Reliability issues 32

19 Concept of Quality and Reliability Quality (validation and verification) (assessment) (qualification) Reliability (reliability assessment) 33

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22 A Definition of DfR Given by ReliaSoft Design for Reliability, however, is more specific than these general ideas. It is actually a process. Specifically, DFR describes the entire set of tools that support product and process design (typically from early in the concept stage all the way through to product obsolescence) to ensure that customer expectations for reliability are fully met throughout the life of the product with low overall life-cycle costs. In other words, DFR is a systematic, streamlined, concurrent engineering program in which reliability engineering is weaved into the total development cycle. It relies on an array of reliability engineering tools along with a proper understanding of when and how to use these tools throughout the design cycle. This process encompasses a variety of tools and practices and describes the overall order of deployment that an organization needs to follow in order to design reliability into its products. 36

23 DfR Tools 37

24 Use of Tools in DfR Phases DfR Tools DfR Phases 38

25 About Physics of Failure 39

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27 Driving Force of taking the PoF Approach in DfR A technical tool to achieve quantitative requirements Eliminating human factors Solid and sound scientific basis Sensitive to design features, and even to manufacturing Push up the envelop on precision to catch up with requirements on both cost efficiency and performance 41

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Arrhenius' Equation Arrhenius' equation is a simple, but remarkably accurate, formula for the temperature dependence of

van't Hoff who had noted in 1884 that van't Hoff's equation for the temperature dependence of equilibrium constants

Arrhenius provided a physical justification and interpretation for the formula.

30 Arrhenius' Equation Arrhenius' equation is a simple, but remarkably accurate, formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist J. H. van't Hoff who had noted in 1884 that van't Hoff's equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and reverse reactions. Arrhenius provided a physical justification and interpretation for the formula. Currently, it is best seen as an empirical relationship. It can be used to model the temperature variation of diffusion coefficients, population of crystal vacancies, creep rates, and many other thermallyinduced processes/reactions. 44

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32 SoP: System on Package? 46?

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34 About Reliability Assessment and Reliability Prediction 48

35 Reliability Prediction Reliability Prediction: an operation to quantitatively estimate reliability or the probability that an item can perform required functions for a specified interval under stated conditions Prediction of failure rate Prediction of mean value Reliability analysis: any operation to either quantitatively or qualitatively estimate or evaluate an item on its reliability-dependent performance or factors, such as service life, functional performance, degradation performance, field failure record, etc. 49

36 Reliability Prediction Approach Data Approach Handbook Approach Testing Approach Physics of Failure (PoF) Approach 50

37 Uncertainty Inherent variations: Material properties Geometry (Environmental conditions) Consequence: Stress Performance Lifetime 51

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45 Mathematical Problem of Classic Reliability Given the distribution of design parameters (geometry, materials etc.) Given correspondent failure functions or reliability functions To obtain the probability of the failure or the reliability function, based upon the defined failure criteria 59

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47 y () x x fx ( x) y fy ( y) y xn ( n 1,2,...) ( )... ( )... y x1 x n fy f ( y) f ( x ) f ( x ) x 1 x n y ( y) ( x1 ) ( xn ) ( x ) ( x) x 61

48 b a N b a f ( xdx ) f( xi ) N i 1 x [, ] i ab 4 (, ) p( x, y ) 1 1 N p x y dxdy 1 1 N i 1 i i pxy (, ) x y 0, otherwise 2 2 1, 1 62

LH_Series_Rev2014.pdf

LH_Series_Rev2014.pdf REMINDERS Product information in this catalog is as of October 2013. All of the contents specified herein are subject to change without notice due to technical improvements, etc. Therefore, please check