Paradigm Shift in Design Assurance and Reliability Prediction

Transcription

1 Paradigm Shift in Design Assurance and Reliability Prediction Ed Dodd, Clayton Bonn, and Craig Hillman DfR Solutions, College Park, MD Yizhak Bot BQR Reliability Engineering, Rishon Lezion, Israel

2 Reliability and Design The foundation of a reliable product is a robust design Provides margin Mitigates risk from defects Satisfies the customer 2

3 Reliability and Design (cont.) Assessing and ensuring reliability during the design phase maximizes return on investment (ROI) Caught during design: 1x; Caught during engineering: 10x; Caught during production: 100x Caught at the customer: 1000x Electronic OEMs that use design analysis tools Hit development costs 82% more frequently Average 66% fewer re-spins Save up to $26,000 in re-spins Aberdeen Group, Printed Circuit Board Design Integrity: The Key to Successful PCB Development,

4 Leverage in Product Design Actual Cost 30% Overhead 5% 5% 20% Labor 15% Material 50% 70% 5% Design 70% of a Product s Total Cost is Determined by its Design Source: Six Sigma by M. Harry and R. Schroeder (Published by Doubleday) 4

5 Reality of Design for Reliability Assuring reliability of electronic designs is becoming increasingly difficult Increasing complexity of electronic circuits Increasing power requirements Introduction of new component technologies Introduction of less robust components Results in multiple potential drivers for failure 5

6 Reality (cont.) Predicting reliability is becoming problematic Standard MTBF calculations can tend to be inaccurate A physics-of-failure (PoF) approach can be timeintensive and not always definitive (limited insight into performance during operating life) 6

7 Component Stress Analysis A critical aspect of all three activities (design assurance, MTBF, PoF) is component stress analysis and stress derating Component stresses: The voltage, current, and power experienced by a component during operation Derating: The practice of limiting the stress on electronic components to levels below the manufacturer s specified ratings Due to the overly manual process required, these activities have been constrained by time and money 7

8 Component Stress (cont.) Companies responses Performing component stress analysis only once in the new product development (NPD) process Limiting the scope of component stress analysis Making assumptions so as to provide input into MTBF calculations Relying on test-in reliability during prototyping What is the problem with these approaches? 8

9 Case Studies: Field Failures Example 1: Telecommunications OEM experiences multiple tantalum polymer capacitor failures during turn-on at the customers Failure history All failures are 4V rated parts on a 3.3V line Exceeds manufacturer s recommended derating of 70% No failures on 2.5V, 1.8V, or 1.3V lines Failures to date: 1500 Material costs: $15 million+ 9

10 Case Studies (cont.) Example 2: Power supply OEM experiences 10% failure rate at customers after Failure history 30V rated Schottky diode periodically experiences 30V stress Failures eliminated by replacing with 40V Zener diode Latent behavior; failures did not occur during testing or screening at OEM Material costs: $1 million Cost of Quality: Much higher! 10

11 Case Studies (cont.) Example 3: Customers of industrial controls OEM experiencing intermittent failures Failure history Parametric drift measured on output control lines Intensive failure analysis effort ($) Root-cause identified as excessive power levels on a chip resistor during operation Periodic overheating resulted in a gradual increase in resistance Five months of root-cause analysis to find the problem and fix it! 11

12 A Solution is Needed Tools that will allow circuit designers and reliability practitioners to perform component stress analysis, derating, and MTBF calculations by simplifying and automating the process 12

13 fixtress Mentor: BOM, Netlist, External Sources & Loads Stress Calculator Applied Values Option 1 Option 2 Stress Derating CARE-SDTA Overstressed components! No overstressed components Design Approved! CARE Parts Library Thermal Analysis Thermal Mapping Reliability Prediction CARE-MTBF MTBF Option 1: Automatic stress w/o Thermal mapping Option 2: Automatic stress with Thermal mapping 13

14 fixtress Stress Calculator The fixtress stress calculator tool leverages a broad range of sophisticated algorithms. fixtress component stress analysis is not SPICE fixtress does not require SPICE models. Information found in standard data sheets is sufficient Use of standard parametric data opens up component stress analysis to automation, allows for quicker assessment and what-if scenarios Breaking free of SPICE allows for more flexibility and faster results Unlike SPICE, fixtress can handle large PCB's with thousands of components, including FPGAs with more than 1,000 pins SPICE simulation can be slow for transient simulation analysis Not all SPICE simulators are not always fully compatible because of differences in default simulator options and the need for simulatorspecific models 14

15 Importing Design Information Use of standard parametric data allows for the easy import of design information in multiple formats Bill of materials (BOM) Net list Pin library for digital integrated circuits (ICs) Information on external sources and loads Software performs an iterative check on the BOM and netlist to ensure all connections are complete 15

16 Components Library Component s electrical parameters retrieved from a direct link to the Datasheet PDF 16

17 Stress Derating Curves Two options available to the user Software provides standard stress-derating curves (MIL-Std, NAVSEA, etc.) User can define stress-derating curves (internal specifications or those provided by the manufacturer) For example: Derating Curves for Types of Capacitors (C6A- CFR type) 17

18 Specify External Sources and Loads Wide variety of sources and loads Wave forms (sinusoidal, rectangular, trapezoidal, etc.) DC, AC (1 Harmonic), Advanced AC (Multi-Harmonics) Range of frequencies Voltage, Current, Resistance, Capacitance and Inductive 18

19 Final Data Specifications Additional required information Parameters of voltage regulators Parameters of DC/DC converters Frequencies of RF components Parameters of attenuator IC operating frequencies Internal frequency Percentage of use Frequency distributions This information requirement is clearly defined in the wizard 19

20 Circuit Simulation Run DC Calculations Run AC Calculations Single or multi-harmonics Select and run Bus simulations 20

21 Stress Analysis Results Review stresses on all parts Identify parts that exceed manufacturer s ratings Identify parts that exceed specified derating curves 21

22 SDTA Results Degrees) Result from Stress Calculator 22

23 SDTA Results Degrees) Result from Stress Calculator Derated Factor for Degrees was 80% 23

24 Stress Recommendations - C139 24

25 Stress Recommendations U8 25

26 Component Stress Analysis MTBF 26

27 Return on Investment (Stress De-Rating) Example: 7000 pad PCB Design Manual 200 man-hours (5 weeks!) How much does this cost you? Internal Personnel $100/hr; $20K Consultant $200/hr; $40K Loss of revenue OEM s generate $350K to $600K of revenue per year per employee $175 to $300/hr; $35K to $60K fixtress fixtress can reduce turn time on stress analysis by 50-80% 10 new PCB designs per year? Save $10K to $40K 20 new PCB designs per year? Save $20K to $80K 50 new PCB designs per year? Save $50K to $200K Earn a ROI of >10:1 in the first year! Manual analysis can t cover all components, requires assumptions, typically not accurate, difficult to redo after a design change 27

28 fixtress Summary Improves the accuracy of MTBF calculations Get it right the first time by capturing the effect of electrical stresses Reduces risk of escapes to the customer Effective tool for managing original design manufacturers (ODMs) Accelerates PCB design cycles for rapid time to market Captures problems early in the design stage Faster than trial and error testing Democratizes circuit analysis Short-term training, easy-to-use 28

29 Conclusion The resource reductions provided by fixtress demonstrate that stress and derating analyses no longer exist outside the boundaries of viable business models Customers, especially in the high-rel marketplace, should expect full stress analysis from their suppliers and suppliers will be made aware that this is no longer an unreasonable expectation 29