Reliability integration across the product life cycle
Reliability IntegrationAcross the Product Life Cycle Mike Silverman Fred Schenkelberg from Ops A La Carte www.opsalacarte.com (408) 472-3889
Introduction♦ “Reliability? Oh, that’s 50,000 hour MTBF!”♦ “We design for a 5 year life.”♦ “Every project passes HALT, no problem.” A successful product reliability program is the collection of goals, plans, tools, and skills focused on the cost-effective and timely creation of products that meet business objectives.
Agenda♦ Introduction and Agenda♦ Overview♦ Reliability Goals♦ Reliability Plan♦ Reliability Execution FMEA and HALT Prediction and RDT/ALT♦ Integration♦ Wrap-up
Overview Goal Plan FMEA PredictionHALT RDT/ALT Verification Review
Vocabulary♦ Reliability♦ Goal♦ Plan♦ FMEA♦ HALT♦ Prediction♦ RDT♦ ALT
Reliability Goal1. Function2. Probability3. Duration4. Environment5. Customer Expectation♦ Example: Our Power Supply will provide 5V with a 90% reliability at 2 years in a home and office environment.
Reliability Goal – How?♦ Business objectives♦ Warranty period♦ Useful or expected functional life♦ What is it supposed to do?♦ Where and under what conditions?♦ Estimated cost of product failure
Reliability Plan♦ Goals, apportionment and metrics♦ Selected tools for discovery♦ Selected tools for analysis♦ Selected tools for verification♦ Procurement activities and critical parts♦ Field service, maintenance, call centers
Reliability Plan Engineering Review Determine Reliability Targets Initial Design FMEA Apportion Target & Determine Gaps Initial Design (Prototype #1) Subsystem ALTs HALT Competitive Competitive & drop testing HALT Teardown Improve Design (Prototype #2)Revise Apportion Update DOE Derating HALTTargets and Gaps FMEA (if needed) Analysis Improve Design (Prototype #3 or Production) HALT Benchtop Identity CTQ Lifecycle testing Final System Establish Reliability Control Plans Reliability Analysis Demonstration Review Results Monitor Metrics Product Launch Monitor CTQ parameters
Reliability Execution♦ Two distinct reliability schools Measurement techniques • Prediction • RDT and ALT Improvement techniques • FMEA • HALT
Reliability Execution♦ Which should we use? Both, of course... but how do we integrate them together? FMEA Prediction HALT RDT/ALT
Reliability Measurement Techniques♦ Prediction in Design Phase♦ RDT in Prototype Phase Prediction RDT/ALT
Reliability Prediction♦ Reliability Prediction Definition: A method of calculating the reliability of a product or piece of a product from the bottom up by assigning a failure rate to each individual component and then summing all of the failure rates.
Reliability Prediction♦ Reliability Predictions are used to: help calculate spares provide input to system-level reliability models assist in deciding which product to purchase drive design trade-off studies set achievable in-service performance standards help set test parameters for RDTs/ALTs
Reliability Prediction♦ Limitations of a Prediction Predictions have inaccuracies due to: • Data is from outdated standards • Data is from different environments • Data is from different applications • Data is from unclean field data • Technology is too new – no good models So what can we do?
Reliability Prediction♦ Getting Around Prediction Limitations We use relative failure rate values rather than absolute values and feed to a FMEA. We fill in gaps of inaccuracy with RDTs and ALTs.
Prediction Integrated with FMEA♦ Use results of Prediction for a FMEA In a FMEA, we are looking for high risk areas. To quantify these risks, we need to assess the probability of the risk occurring. Predictions can supply this probability. Usually, a probability relative to other risks is all that is necessary, and a prediction is good for this.
Prediction Integrated with RDT/ALT♦ Use results of Prediction to plan an RDT/ALT Predictions will identify where a product is vulnerable to help decide which RDT/ALT to run. Predictions can give you sensitivity of components to thermal and electrical stress – key accelerants in the RDT/ALT models. Predictions can help determine stress limits of components when choosing accelerated stress levels for a test.
Reliability Demonstration Test (RDT)♦ RDT: Definition A sample of units are tested to validate reliability requirements. The test is usually performed at accelerated stresses to compress time. The accelerated stresses can be environmental, electrical, or mechanical.
Accelerated Life Test (ALT)♦ ALT: Similar to RDT but also used: to characterize dominant failure mechanisms, often due to wearout. usually at the assembly level rather than system level to target specific areas of design.
RDT and ALT Parameters♦ In order to set up an ALT, we must know (or derive) several different parameters: Length of test Number of samples Goal of test Confidence desired Accuracy desired Cost Acceleration Factor • Field Environment • Test Environment • Acceleration Factor Calculation Slope of Weibull Distribution (Beta factor)
RDT and ALT Parameters♦ Keys to a Good RDT/ALT Accelerants must be valid Acceleration factors must be measurable Failure region must be well understood • (infant mortality, steady state, wearout) Note that the lead-free transition will change all our old acceleration models.
RDT and ALT Parameters♦ If we don’t have a good formula for acceleration factor, we can determine through experimentation.♦ When wearout is a dominant failure mode, we cannot substitute units for time.♦ If we cannot find environmental or electrical accelerants, we can resort to duty cycle acceleration.
Reliability Improvement Techniques♦ FMEA in the Design Phase♦ HALT in the Prototype Phase FMEA HALT
Failure Modes Effects Analysis (FMEA)♦ FMEA is a systematic technique to analyze a system for all potential failure modes.♦ FMEA’s are used to identify highest risk items and mitigate them to reduce overall product risk.
FMEA Integrated with HALT♦ When planning a HALT, FMEA’s can be used for: identifying failure modes that HALT is likely to uncover. identifying failure modes that require extra planning to find. identifying non-relevant failure modes. Identifying wearout mechanisms that HALT will not be able to find. helping to decide on the number of samples.
Highly Accelerated Life Testing (HALT)♦ HALT is a method of applying progressively higher levels of environmental, electrical, and mechanical stresses to a product to the point of failure in order to assess and improve design robustness and margin above its intended operation.
Highly Accelerated Life Testing (HALT)♦ HALT is used to: Quickly discover design issues. Evaluate and improve design margins. Release mature product at market release. Reduce development time and cost. Evaluate cost reductions made to product.
Highly Accelerated Life Testing (HALT) HALT, How It Works Fa ilu sse ea se) re (in r cr St is Im s pr ov aly An e
Highly Accelerated Life Testing (HALT) HALT, Why It Works Classic S-N Diagram (stress vs. number of cycles) S2 S0= Normal Stress conditions N0= Projected Normal LifeStress S1 S0 N2 N1 N0 Number of Cycles
Highly Accelerated Life Testing (HALT) Limitations of HALT Classic S-N Diagram (stress vs. number of cycles) Point at which failures become non-relevant S2 S0= Normal Stress conditions N0= Projected Normal LifeStress S1 S0 N2 N1 N0 Number of Cycles
Reliability IntegrationBetween HALT and RDT/ALT Goal Plan FMEA Prediction HALT RDT/ALT Verification Review
Reliability Integration Between HALT and RDT/ALT♦ Often times we will run a product through HALT and then run the subassemblies through ALT that were not good candidates for HALT. HALT on System ALT on System Fan
Reliability Integration Between HALT and RDT/ALT♦ And at other times, we may develop an RDT based on HALT limits, using the same accelerants but lowering the acceleration factors to measurable levels. HALT on System RDT on System
Reliability Integration Back to Goals Goal Plan FMEA Prediction HALT RDT/ALT Verification Review
Reliability Integration Back to Goals♦ Field Data will tell us: if our goals were accurate. If our plan was complete. If our individual tools were effective.♦ If not, make adjustments for next program.
Wrap Up♦ A successful product reliability program is the collection of goals, plans, tools, and skills focused on the cost-effective and timely creation of products that meet business objectives.♦ To minimize total Life Cycle Costs, we: create clear goals. choose the best tools. properly integrate the tools forwards and back.
Presenter’s Biographical Sketch♦ Fred Schenkelberg, (408) 710-8248, firstname.lastname@example.org♦ Fred Schenkelberg is a Senior Reliability Engineering Consultant at Ops A La Carte. He is currently working with clients using reliability assessments as a starting point to develop and execute detailed reliability plans and programs. Also, he exercises his reliability engineering and statistical knowledge to design and conduct accelerated life tests.♦ Fred joined HP in February 1996 in Vancouver, WA. He joined ESTC, Palo Alto, CA., in January 1998 and co-founded the HP Product Reliability Team. He was responsible for the community building, consulting and training aspects of the Product Reliability Program. He was also responsible for research and development on selected product reliability management topics.♦ Prior to joining ESTC, he worked as a design for manufacturing engineer on DeskJet printers. Before HP he worked with Raychem Corporation in various positions, including research and development of accelerated life testing of polymer based heating cables.♦ He has a Bachelors of Science in Physics from the United States Military Academy and a Masters of Science in Statistics from Stanford University. Fred is an active member of the RAMS Management Committee and currently the IEEE Reliability Society Santa Clara Valley Chapter Vice President.
Presenter’s Biographical Sketch♦ Mike Silverman, (408) 472-3889, email@example.com♦ Mike is founder and managing partner at Ops A La Carte, a Professional Business Operations Company that offers a broad array of expert services in support of new product development and production initiatives. The primary set of services currently being offered are in the area of reliability. Through Ops A La Carte, Mike has had extensive experience as a consultant to high-tech companies, and has consulted for over 200 companies including Cisco, Ciena, Apple, Siemens, Intuitive Surgical, Abbott Labs, and Applied Materials. He has consulted in a variety of different industries including telecommunications, networking, medical, semiconductor, semiconductor equipment, consumer electronics, and defense electronics.♦ Mike has 20 years of reliability, quality, and compliance experience, the majority in start-up companies. He is also an expert in accelerated reliability techniques, including HALT and HASS. He set up and ran an accelerated reliability test lab for 5 years, testing over 300 products for 100 companies in 40 different industries. Mike has authored and published 7 papers on reliability techniques and has presented these around the world including China, Germany, and Canada. He has also developed and currently teaches 8 courses on reliability techniques.♦ Mike has a BS degree in Electrical and Computer Engineering from the University of Colorado at Boulder, and is both a Certified Reliability Engineer and a course instructor through the American Society for Quality (ASQ), IEEE, Effective Training Associates, and Hobbs Engineering. Mike is a member of ASQ, IEEE, SME, ASME, PATCA, and IEEE Consulting Society and currently the IEEE Reliability Society Santa Clara Valley Chapter President.