Introduction to Design for Reliability (DfR) and Design for Manufacturability (DfM) SMTA North Texas Chapter November 4, 2016 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com © 2004 – 2010 What is Design for Reliability (DfR)? o Reliability is the measure of a product’s ability to o …perform the specified function o …at the customer (with their use environment) o …over the desired lifetime o Design for Reliability is a process for ensuring the reliability of a product or system during the design stage before physical prototype o Often part of an overall Design for Excellence (DfX) strategy 2 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Why Design for Reliability (DfR)? o The foundation of a successful product is a robust design o Provides margin o Mitigates risk from defects o Satisfies the customer 3 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com When Do Mistakes Occur? o Insufficient exchange of information between electrical design and mechanical design o Poor understanding of supplier limitations o Customer expectations (reliability, lifetime, use environment) are not incorporated into the new product development (NPD) process There can be many things that “you don’t know you don’t know” 4 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com List of DfR Tools and Techniques 5 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com List of DfR Tools and Techniques o Failure Mode Analysis o Failure Mode Effect Analysis (FMEA), Fault Tree/Tolerance Analysis (FTA), Design Review by Failure Mode (DRBFM), Sneak Circuit Analysis (SCA) o Reliability Prediction - Empirical o Design Rules o Design for Excellence o Design for Manufacturability (DfM), Design for Testability (DfT) o Tolerancing (Mechanical, Electrical) o Simulation and Modeling (Stress) o Thermal, Mechanical, Electrical/Circuit o Simulation and Modeling (Damage) o EMI/EMC, EOS/ESD, Physics of Failure, Derating 6 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Failure Mode Analysis o A process of identifying potential failure modes and appropriate mitigations early in the design process o Likely the most common DfR tool for reliability engineers o These are generic DfR tools o A Strength and Weakness o Strength: Can provide amazing insight o Weakness: Can be a boring, monotonous, no-value, check-the-box activity 7 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Concept / Block Diagram o Can DfR mistakes occur at this stage? o No………..and Yes o Failure to capture and understand product specifications at this stage lays the groundwork for mistakes at schematic and layout o Important specifications to capture at concept stage o Reliability goals o Use environment o Dimensional constraints 8 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Limitations of MTTF/MTBF o MTBF/MTTF calculations tend to assume that failures are random in nature o Provides no motivation for failure avoidance o Easy to manipulate numbers o Tweaks are made to reach desired MTBF o E.g., quality factors for each component are modified o Often misinterpreted o 50K hour MTBF does not mean no failures in 50K hours o Better fit towards logistics and procurement, not failure avoidance 9 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Field Environment (Best Practice) o Use standards when… o Certain aspects of your environment are common o No access to use environment o Measure when… o Certain aspects of your environment are unique o Strong relationship with customer o Do not mistake test specifications for the actual use environment o Common mistake with vibration loads 10 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Electrical Environments o Often very well defined in developed countries o Introduction into developing countries can sometimes cause surprises o Rules of thumb o China: Can have issues with grounding (connected to rebar?) o India: Numerous brownouts (several a day) o Mexico: Voltage surges 11 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Know Your Environment (Case Study) o Leader in surgical systems for eyecare o Released latest system with foot pedal for ease of use o Failed to realize how customers would use foot pedal o Moving system across carpet without lifting up foot pedal created large static charges o Using foot pedal to pull system caused cable/connector failures 12 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Thermal Environments (Case Study): Closed Containers Container and Ambient Temperature 75.0 Temp. Container Temp (°C) Outdoor Temp (°C) Variation 65.0 Trucking 55.0 Container 45.0 Temperature Temperature (°C) 35.0 25.0 15.0 0 50 100 150 200 250 300 350 400 450 Hours 13 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Dimensions o Keep dimensions loose at this stage o Large number of hardware mistakes driven by arbitrary size constraints o Examples include poor interconnect strategies and poor choices in component selection o Case study: Use of 0201 chip components o Tight dimensional requirements push designer towards wholesale placement of 0201 components o 0201 is not yet an appropriate technology for systems requiring reliability o Result: Major issues at customers 14 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Part Selection o The process of creating the bill of materials (BOM) during the ‘virtual’ design process o Before physical layout o For some companies, this is during the creation of the approved vendor list (AVL) o Design-independent 15 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Part Selection (cont.) o KIS: Keep it Simple o New component technology can be very attractive o Not always appropriate for high reliability embedded systems o Be conservative o Reality: Marketing hype FAR exceeds actual implementation o Component manufacturers typically use portable sales to boost numbers o Claim: We have built 100’s of millions of these components without a single return! o Actuality: All sales were to two cell phone customers with lifetimes of 18 months 16 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Part Selection (cont.) o Even when used by hi-rel companies, some modifications may have been made o Example: State-of-the-art crystal oscillator required specialized assembly to avoid failures one to three years later in the field o Prior examples of where care should have been taken o New technologies: X5R dielectric, SiC diodes, etc. o New packaging: Quad flat pack no lead (QFN), 0201, etc. 17 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Part Selection (cont.) o As technology progresses, functional performance has become a limited aspect of the part selection process o Other concerns are increasingly taking center stage o Moisture sensitivity level (MSL) o Temperature sensitivity level (PSL) o Electrostatic discharge (ESD) classification o Manufacturability (Design for Assembly) o Plating material o Lifetime / Long-term reliability o Sometimes Physics of Failure is required 18 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Critical Components o Most small to mid-size organizations do not have the resources to perform a thorough part selection assessment on every part o Does not excuse performing this activity o Requires focusing on components critical to the design o Critical Components: A narrowed list of components of most concern to the OEM o Sensitivity of the circuit to component performance o Number of components within the circuit o Output from FMEA / FTA o Past experiences o Complexity of the component o Industry-wide experiences 19 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com When to do Simulation and Modeling? o With recent improvements in model development (typically biggest time sink), there are few limitations to rapid and robust electrical/thermal/mechanical/reliability simulations of electronic products o Simulation and modeling allows organizations to o Obtain deeper insight earlier in the design process o Quantify price vs. performance for supplier and material selection o Iteration and optimization at minimal cost o Avoid ‘opinioneering’ o Substitute or replace test requirement o Accurately predict field performance o Faster time to market 20 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com Simulation & Modeling Case Study – Virtual Power Cycling 3D Sherlock Model Thermal Analysis Results Lifetime Prediction o EDA → Sherlock → Flotherm → Sherlock → Prediction: 8 hours 21 9000 Virginia Manor Rd Ste 290, Beltsville MD 20705 | 301-474-0607 | www.dfrsolutions.com DfR Conclusions o To avoid design mistakes, be aware that functionality is only the beginning o Mechanical and thermal are just as important as electrical o Maximize knowledge of your design as early in the product development process as possible o Be aware of industry best practices o Do not overly rely on supplier statements o Their view: Reliability is