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Innovation day 2013 2.5 joris vanderschrick (verhaert) - embedded system development


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  • 1. CONFIDENTIAL When first time right embedded system developments need to become cost effective 1
  • 2. Joris Vanderschrick Business Development Embedded Systems 2
  • 3. Risk based development methods Cut Tangible Risk focus Early Options • Development phases • Functional subsystems • Visualize • Simulate • Test • Review • Roadshow • Criticalities • Added value • 360° • Rapid prototyping • First time right • Backup • Buffer • Requirements vs. design Reliability 3
  • 4. Introduction Reliability: The measure of a product’s ability to …perform the specified function …at the customer (within their use environment) …over the desired lifetime 4
  • 5. Customer satisfaction vs reliability 17% 6% 5
  • 6. Cost of changes (ifo Reliability) NJIT by Rishi R Persad 6
  • 7. Objectives of a reliability approach Objectives: • Early identification of weak points in design to: • Limit the risk/cost of modifications in production or deployment phase • Reduce product failures/returns/recalls during the product lifecycle • Improve time to market by early detection of weakness and flaws • Minimize number of dead-on-arrivals • Increase customer satisfaction 7
  • 8. Different methods to define reliability 3 methods: 1. 2. 3. Theoretical Approach: Standards/Norms & Simulations Pragmatic Approach: Accelerated Testing Analytical Approach (PoF) 8
  • 9. Example of a Verhaert approach Step 1: Inventarisation & scoping Define Subsytems Explore Norms & Guidelines Step 2: Calculations & Simulations Failure Rate calculations following the selected Norm/Standard Step 3: Detailing of tests HALT vs Traditional Testing Step 4: Implementation of test plan Execution Pragmatic approach FMECA, FTA,… Simulations (Mech., Electr, SW,…) Define acceleration factors Optimize analytical models Theoretical Approach FMMEA Define Failure Mechanisms Analytical Models PoF Approach 9
  • 10. CONFIDENTIAL Theoretical Approach Inventarisation & Scoping 10
  • 11. Inventarisation The definition of the Reliability approach starts with the inventarisation by subsystem: • • • • System breakdown in subsystems-assembly-subassembly-components Typical systems: Electronic & electrical systems, mechanical, hydraulic, process systems,… Which critical topics are relevant (FMECA: Failure modes)? How will these critical topics be evaluated ifo life-time. (via which norm or guideline) This will invlove the inventarisation of the norms or guidelines that are the most relevant for the application or intended purpose. 11
  • 12. How? Example: FMECA RPN = Severity x Occurrence x Detection The RPN can then be used to compare issues within the analysis and to prioritize problems for corrective Action. The ratings are defined by: • • Main published standards for this type of analysis, like SAE J1739, AIAG FMEA-3 and MIL-STD1629A. Industries and companies have developed their own procedures to meet the specific requirements of their products/processes 12
  • 13. Why use a FMECA FMECA/FMEA is useful as a survey method to identify effects of major failure modes in a system It can contribute to improved designs for products and processes, resulting in higher reliability, better quality, increased safety, enhanced customer satisfaction and reduced costs. • • • Avoid time and cost consuming design changes at a late stage in the development The tool can also be used to establish and optimize maintenance plans, control plans and other quality assurance procedures. In addition, an FMEA or FMECA is often required to comply with safety and quality requirements, such as ISO 9001, QS 9000, ISO/TS 16949, 13485, FDA,… Remarks: • • • • Complex systems & processes makes the task of defining a detailed FMEA/FMECA time-consuming Assumes the causes of problems are all single event in nature (combinations of events = 1 event) The process relies on the right participants & open communication & cooperation Human error sometimes overlooked It’s just a tool. Without a follow-up plan & actions, It will not improve the reliability of your system 13
  • 14. Scoping Evaluation & definition of the appropriate calculation methods of the failure rate • For the defined building blocks (sub-systems) & specific parts, we will analyze which norm or standard provides the best method for the evaluation & calculation of the failure rate. Work packages Reliability Electronic components Reliability Mechanical parts Software reliability General Approach & Study logic ifo reliability design & production 1.1. Voorbereiding met AGFA ECSS-E-ST-33-01C Space Mechanisms oScope of the standard: requirements applicable to the: concept definition, design, analysis, development, production, test verification and operation of space mechanisms to meet the mission performance requirements 14
  • 15. CONFIDENTIAL Theoretical Approach Step 2: Calculations & Simulations 15
  • 16. MTBF, FIT calculations (Prediction Method) To obtain high product reliability, consideration of reliability issues should be integrated from the very beginning of the design phase. This leads to the concept of reliability prediction. • • • • • MTBF: Mean Operating Time Between Failures The failure rate of the system is calculated by summing up the failure rates of each component in each category (based on probability theory). This applies under the assumption that a failure of any component is assumed to lead to a system failure. Constant failure rate  Relevant for Useful life-time Fault is repairable MIL-HDBK-217F is probably the most internationally recognized empirical prediction method, by far. Parts Stress Parts count 16
  • 17. Example 17
  • 18. Simulations FEA Simulations FEM Analysis: (FEA) FEA consists of a computer model (2D, 3D)of a material or design that is stressed and analyzed for specific results. It is used in new product design, and existing product refinement. A company is able to verify a proposed design and will be able to perform to the client's specifications prior to manufacturing or construction. What can you check at an early stage? Point, pressure, thermal, gravity, and centrifugal static loads Thermal loads from solution of heat transfer analysis Enforced displacements Heat flux and convection Point, pressure and gravity dynamic loads Examples: • • • • • Drop/shock Bending, load Vibration Thermal cross points … 18
  • 19. Simulations DESTECS (Design Support and Tooling for Dependable Embedded Control Software) • Inspiration o Use collaborative multidisciplinary design of Embedded Systems o Rapid construction and evaluation of system models o Evaluated on industrial applications • Need because of Embedded Systems o More demanding requirements for Reliability, Fault Tolerance o Increasingly distributed: more complex design possibilities  more fault scenario’s 19
  • 20. Example 20
  • 21. Conclusions Advantages of empirical methods: • • • Easy to use, and a lot of component models exist. Relatively Indicators of inherent reliability. Provide an approximation of field failure rates. Disadvantages of empirical methods: • Based on statistical data & sometimes out-dated • Not all components from new designs are described in the Standard. • Failure of the components is not always due to component-intrinsic mechanisms but can be caused by the system design. Simulations • • • • • Early validation of your system More and faster iterations Parallel hw & sw development Early full system validation and risk mitigation without hw Less real-life testing (= the poor man’s approach) 21
  • 22. CONFIDENTIAL Pragmatic Approach Slide 22
  • 23. Not Traditional Testing!! • Traditional (QA) testing is done before product release but after the design & development phase (ex. Burn-in test, environmental testing, drop testing, shock & vibration testing,…) • Many of today's products are capable of operating under extremes of environmental stress and for thousands of hours without failure. Traditional test methods are no longer sufficient to identify design weaknesses or validate life predictions. Disadvantages • • • • Test under operating conditions  Takes too long Testing is costly! (equipment, time-consuming,…) Will not tell you anything about the realiability during useful life. Just about infant failures. (DOA) Too late in NPD process,  Design corrections will be very expensive 23
  • 24. Highly accelerated testing HALT = Highly Accelerated Life Time Test What? • • • Highly accelerated life testing (HALT) techniques are important in uncovering many of the weak links of a product DURING THE DESIGN PHASE These discovery tests rapidly find weaknesses using accelerated stress conditions Stresses are applied in a controlled, incremental fashion while the unit under test is continuously monitored for failures Why? HALT reveals product failure modes in a matter of hours or days Traditional test methods that can take weeks or even months to find, if at all The purpose of HALT is to determine the operating and destruct limits of a design – why those limitations exist and what is required to increase those margins. HALT, therefore, stresses products beyond their design specifications. 24
  • 25. Procedure? • • Using a test environment that is more severe than that experienced during normal equipment use. Done on early prototypes & different design concepts Since higher stresses are used, accelerated testing must be approached with caution to avoid introducing failure modes that will not be encountered in normal use. Accelerating factors used, either singly or in combination, include: • • • • • More frequent power cycling Higher vibration levels High humidity More severe temperature cycling Higher temperatures ‘ It’s not a Pass/Fail test but a discovery process! ’ 25
  • 26. Results • • • • Structural weaknesses Electronic weaknesses • Component failures • Component dislocation • PCB delamination, via-cracking, … • Solder failure • Software failures due to component degradation • Connector problems • ... Information on product limits and product capabilities outside the limits Product weaknesses & design errors 26
  • 27. Goals HALT provides engineers with the opportunity to improve product design, increasing its robustness and minimizing possibility of costly warranty services and expensive product recalls after release Once the weaknesses of the product are uncovered and corrective actions taken, the limits of the product are clearly understood and the operating margins have been extended as far as possible. A much more mature product can be introduced much more quickly with a higher degree of reliability. 27
  • 28. Taking It a step further… • Define the S-N curve for the specific failure mechanisms • Use test data in a model relating the reliability (or life) measured under high stress conditions to that which is expected under normal operation to determine length of life • Accelerated test models relate the failure rate or the life of a component to a given stress such that measurements taken during accelerated testing can then be extrapolated back to the expected performance under normal operating conditions  Design for Reliability!!!  PoF 28
  • 29. CONFIDENTIAL EXAMPLE: Central Heating sensor Slide 30
  • 30. Thermal cycle vs measurement errors Goal: Life-time expectancy necessary for product = 10years Verify the reliability of measurements with HALT test setup Discover design weakness, improve & repeat test Setup: • • • • acceleration : cycle 1x/day => 1x/hour acceleration : min-max temperatures & high transient statistical number of test samples (one is not enough) Identify & measure performance parameter(s) 31
  • 31. CONFIDENTIAL Slide 32
  • 32. Test data 33
  • 33. Conclusions • • • • • • Upfront definition of evaluation criteria are important. Multiple failure modes Early failures Non-constant (random) failures Performance degradation over time: Quality of the measurements will degrade in time. Temperature induced (thermo-mechanical stress) 34
  • 34. HALT vs Field & Traditional testing HALT Field testing • Faster results (accelerated stress) • Correct & increase design reliability throughout the test procedures • Control over test conditions • Main costs: Fabrication of samples, test setup, assembly, testing,… •Time-consuming •Network •Costly Installations •More spread on the test results •Same test conditions cannot be guaranteed: Difficult for quatative comparison Traditional testing •Time-consuming (operational stress) • Expensive setups • Expensive corrective actions • Too late in design cycle • Only for infant failures (DOA) 35
  • 35. CONFIDENTIAL PoF approach Slide 36
  • 36. Current approaches = not sufficient? • • • Mostly only FMECA executed. Rarely identifies design issues because of limited focus on the failure mechanism Incorporation of HALT and failure analysis (HALT is test, not DfR; failure analysis is too late) MTBF/MTTF calculations tend to assume that failures are random in nature Provides no motivation for failure avoidance • Easy to manipulate numbers Tweaks are made to reach desired MTBF E.g., quality factors for each component are modified • Often misinterpreted 50K hour MTBF does not mean no failures in 50K hours Source: Loughborough University Alternative = Physics-of-Failure principle: The use of science (physics,chemistry, etc.) to capture an understanding of failure mechanisms and evaluate useful life under actual operating conditions 37
  • 37. Focus on failure mechanisms Failure Mode: o The EFFECT by which a failure is OBSERVED, PERCEIVED or SENSED. Failure Mechanism: o The PROCESS (elect., mech., phy., chem. ... etc.) that causes failures. FMMEA: Add failure mechanisms to FMEA 39
  • 38. Example FMMEA Infusion Pump Center for Advanced Life Cycle Engineering (CALCE), University of Maryland 40
  • 39. Further break-down to PBA level Failure site = CBGA IC broken-off from PCB Solder-joint = Surface mount solder attachment. Electrical interconnection & mechanical attachment of electronic component on the PCB  but also critical heat transfer in between Failure Mode = Solder-joint fatigue Failure effect: Solder-Joint crack 41
  • 40. Example: Solder-joint cracks Failure Mechanism: Solder-joint fatigue by CTE mismatch Caused by the local thermal mismatches between the different material characteristics of IC, PCB and solder itself = CTE mismatch. (Coeficient of Thermal expansion) Result: Different thermal expansions, due to thermal energy dissipated  stress on solder joints  fatigue Fatigue leads to growing of the grains inside the solder  Result: Cracks! 42
  • 41. S-N curve of solder-joint fatigue • • For each failure mode a S-N curve can be defined Solder-joint fatigue = Function of Thermal strain vs N cycles to failure Established out of: • Test data • Statistics • FE simulation • Physical modeling 43
  • 42. Acceleration Acceleration: Thermal swings (dT) in the operational environment  accelerating the thermal strain  accelerating solder-joint fatigue  accelerating failure effect: Solder-joint crack Acceleration test: Thermal cycling test requirements: • Heat/cool rate limited (transient) • Allow for minimal dwell times at extreme temperatures: time is essential. • Materials set limits to temperature extremes  Establish accelerating factor = Thermal strain (accelerated temp conditions)/Thermal strain (normal temp conditions) Acceleration Model: These are mathematical models that can extrapolate the Number cycles to failure under accelerated Temp conditions to the number of cycles to failure under operational Temp conditions 44
  • 43. Example: Solder-joint cracks Test Point Operation Point Establish test failure distribution and predict operational failure distribution using the acceleration factors and the operational use of the product Use test data in a model relating the reliability (or life) measured under high stress conditions to that which is expected under normal operation to determine length of life 45
  • 44. Characteristics, benefits and limitations: • • • • Physics not statistics. The only way to predict long term wearout lifetime. Testing is in general done on specially designed test samples, not on the actual product. It is input for the design process. Can be established independent from design cycle. Time-to– market! • Requires profound understanding of technologies used in the product and the wearout physics involved. Limitation: Establishing the S-N curves and acceleration factors is a tedious, time-consuming and expensive job with a lot of pitfalls. Therefore, for many relevant failure mechanisms S-N or acceleration factor information is not available. Still subject of scientific research. • • 46
  • 45. CONFIDENTIAL General Conclusion 47
  • 46. Cost for design changes FMECA FMMEA Calculations MTBF, FiT,… Simulations HALT Traditional testing PoF Field Testing Reliability 48
  • 47. Traditional testing FMECA FMMEA Calculations MTBF, FiT,… Field Testing Simulations HALT PoF Infant failures Useful Life (Normal Operation) 49
  • 48. 50
  • 49. VERHAERT MASTERS IN INNOVATION® Headquarters Hogenakkerhoekstraat 21 9150 Kruibeke (B) tel +32 (0)3 250 19 00 fax +32 (0)3 254 10 08 More at VERHAERT MASTERS IN INNOVATION® MASTERS IN INNOVATION® is a platform set up by VERHAERT to train, stimulate and incubate you as an innovator. We provide an extensive training program with different tracks and covering critical areas of new products and business innovation. Furthermore we manage the VERHAERT venturing program and organize our Innovation Day, an annual conference on best practices and insights on new products & business innovation. 51 Netherlands ESIC European Space Innovation Centre Kapteynstraat 1 2201 BB Noordwijk (NL) Tel: +31 (0)618 12 19 19 More at