Workshop - Voorkomen van faling door vibraties - mechanical interaction


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Workshop - Voorkomen van faling door vibraties - mechanical validation - mechanical interaction

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Workshop - Voorkomen van faling door vibraties - mechanical interaction

  1. 1. ProsperitaVibration guidelineRob van Tol30 Mei 2012
  2. 2. © Sirris 2012 © imec 2012 | www.edmp.beContent21. Sirris and the Prosperita project2. The need for guidelines for mechanical integration3. Current version of the guideline4. Present and foreseen capabilities of the “vibration tool”
  3. 3. © Sirris 2012 © imec 2012 | www.edmp.beSirris & Agoria identified this themeas highly important for the technology industrybecause of its disruptive potentialto create new innovative productsand so creating sustainable growth1. Focus on SMART products31-5-© Sirris | | | 3Make theProduct moreAmbient-ConsciousProductMake theProduct moreEco-SystemConsciousMake theProduct moreSelf-ConsciousMake theProduct moreUser-ConsciousIncreasing need tointroduce electronicsinto products
  4. 4. © Sirris 2012 © imec 2012 | 31-5-42. Why is there a need ?World record: 102.68 m (men) , 53.52 m (women)Belgian record: 70.94 m (men)
  5. 5. © Sirris 2012 © imec 2012 | www.edmp.be2. Failure of electronic equipment“Field failures related to the operating environments of electronicequipment reveal that about fifty-five percent of failures aredue to high temperature and temperature cycling, twentypercent are related to vibration and shock, and anothertwenty percent are due to humidity .”D. Steinberg, Vibration Analysis for Electronic Equipment,third edition, John Wiley & Sons, Inc. 2000.31-5-5
  6. 6. © Sirris 2012 © imec 2012 | www.edmp.be2. What causes the problem ?6Common practice:- Design a product and order electronics (OEM)- Design Layout (ODM)- Production of PBA (EMS)- Integration of the electronics in a product (OEM)- Use-life of the productMoment a problemshould be detectedMoment a problemis detected
  7. 7. © Sirris 2012 © imec 2012 | www.edmp.be2. Mechanical guidelines in VIS-PROSPERITAPBA realization: DfM-DfR-DfTD1: PCB SpecificationD2: Component SpecificationD3: Assembly materialD4: Design-for-AssemblyD5: PCB density classesD6: PCB LayoutD7: Design-for-Test PBA integrationI1: Mechanical interactionI2: Thermal interactionI3: EMC interactionI4: integrationVIS-traject PROSPERITA2011-20147
  8. 8. © Sirris 2012 © imec 2012 | www.edmp.be2. Questions and challenges• Will a board meet the requirements to prevent failure ?Prior to the PBA layout!– What frequencies, amplitudes, curvatures can be expected ?– How to fix the PBA in the product ?– Are stiffeners needed and where to place them ?– In what locations should heavy components be placed/avoided ?• Answers should be communicated throughout theproduction chain.⇒ Guidelines for mechanical interaction⇒ Tool to support the guidelines8
  9. 9. © Sirris 2012 © imec 2012 | www.edmp.be3. Vibration guidelines EDM-0019• The objective of the guideline is to provide amethodology to estimate early in the design phase –prior to PCB layout – where fixation points, stiffeners orglued components are required.“Vanos” isBMW’s namefor itsvariablevalve timingunits on6- cylinderengine S54. Old design New design
  10. 10. © Sirris 2012 © imec 2012 | www.edmp.be3. The guideline10
  11. 11. © Sirris 2012 © imec 2012 | www.edmp.be3. Estimating the mechanical loading11• Rigid suspensions– Measure the loading• acceleration/displacement vs. frequency spectra at the fixationpoints• Alternativelly at or close to the compartment– Use standardized mechanical vibration application specificqualification spectra• Eg. ETS 30019 (telecom), IEC 60721 (environmentalconditions), ISO-16750 (road vehicles), ….• Non-rigid suspension of the PBA– Measure vibrations spectrum on the PBA itself– Incorporate a transmissibility function to determine the externalloading transferred by the suspension system to the PBA
  12. 12. © Sirris 2012 © imec 2012 | www.edmp.beExample of standards for mechanicalloading12Fig. 1: ETS 300 19-1-5 example of mechanical loading conditions for ground vehicle installation of telecommunication electronics.
  13. 13. © Sirris 2012 © imec 2012 | www.edmp.be3. Mechanical Failure Mitigation: SMD• For SMD’s board bending is the dominant load on thesolder joints• Largest vibration amplitude when the external loadingexites the eigenfrequencies of the PCB• Procedure to eliminate exitations of eigenfrequencies– Determine the upper eigenfrequency to be eleiminated, based onthe mechanical loading– Estimate the lower eigenfrequencies of the PCB (“Vibration tool”)– Eliminate these eigenfrequencies by fixing at antinodes of theeigenmode lower than the upper eigenfrequency– Alternativelly place a stiffener along antinodes and fix it to theframe ( multiple eigenmodes can be eliminated )– Recheck the eigenfrequencies of the mechanically addapted PBA13
  14. 14. © Sirris 2012 © imec 2012 | www.edmp.be3. Example of failure Mitigation: SMD14PCB type: FR-4Length: 150mmWidth: 100mmThickness:2.5mmMode1 (00) (164Hz) Mode 2 (01) (399Hz) Mode 3 (10) (481Hz)Mode1 (01) (468Hz) Mode 2 (02) (739Hz) Mode 3 (11) (1212Hz)Only fixed at cornersAdd fixed stiffener toeliminate mode 1 and 3Re-checkeigenfrequency
  15. 15. © Sirris 2012 © imec 2012 | www.edmp.be3. Extended approach for SMD’s (1)• To prevent overfixation by the basic approach– If the curvature due to removed eigenmodes would be within thelimits• Eliminate eigenmodes that exceed a specified bendinglimit– Calculation tool for bending limit in development (IMEC)• Larger uncertainties in damping and thus curvature dueto uncertainties in materials and components– Larger safety margins• Procedure for the extended approach– Based on the required product lifetime and the Wöhler relationshipbetween number of vibration cycles and solder strain, determinethe maximum strain as a function of frequency for the SMD solderjoints. (“Tool for bending limit”)– Estimate the lower eigenmodes, eigenfrequencies and curvatruredistribution as a response to mechanical loading (“Vibration tool”)15
  16. 16. © Sirris 2012 © imec 2012 | www.edmp.be3. Extended approach for SMD’s (2)– Based on the maximum allowed strains determine the acceptableminimal bending radius for the most critical components of the PBABill-of-Material –• e.g. large, small pitch BGA, large low stand-off components.– If ceramic SMD components are present that are susceptible tocracking, determine minimum bending radius for these componentsfrom their datasheets.– Eliminate all eigenmodes with bending radii at component locationsthat are smaller than those minima specified above by positioningof the fixation points at or near the antinodes– Alternatively – when fixation to the system frame is not possible atthe desired location– the curvature can be reduced with one ormore stiffeners.– Re-check mechanical response of the mechanically adapted PBA– Flexible, damped electronics suspension is required if this approachdoes not provide satisfactory results16
  17. 17. © Sirris 2012 © imec 2012 | www.edmp.be3. Example extended approach SMD’s1700. 200 400 600 800 1000Centre pointPoint 1Point 2Frequency (Hz) 200 400 600 800 1000Centre pointPoint 1Point 2Frequency (Hz)Curvature x Curvature y Curvature x Curvature yPCB type: FR-4Vibration type: SinusoidalLength: 150mmWidth: 100mmFrequency range: 50-1000 HzThickness:2.5mmAcceleration: g=60m/s2Direction: Z directionDamping: ζ=0.05
  18. 18. © Sirris 2012 © imec 2012 | www.edmp.be3. Failure mitigation of through-holecomponents (1)• The main cause of through-hole component failure of thecomponent leads, is the vibrational motion of thecomponent body relative to the PCB• Similar procedure to basic SMD approach:– Determine the upper eigenfrequency to be eliminated, based onthe mechanical loading– Determine the eigenfequency of the critical components• Ie. Two leaded, large mass and large stand-off– For a leaded component with n in-plane leads the eigenfrequencyof the fundamental vibration mode is given by:18with with644dIπ=RectilinearleadCircularlead
  19. 19. © Sirris 2012 © imec 2012 | www.edmp.be3. Failure mitigation of through-holecomponents (v)• Determine the upper eigenfrequency to be eliminated, based on themechanical loading• Higher modes of the in-plane multi-leaded component can becalculated with the “vibration tool”• Eliminate the low eigenfrequency component-PCB modes by fixatingcomponent body to the PCB, see, e.g., J-STD-001DS for guidelines.19Mode 1 Mode 2 Mode 3
  20. 20. © Sirris 2012 © imec 2012 | www.edmp.be3. Failure mitigation of high profile SMD’s(1)• High profile SMD components may suffer from additionalmechanical stress/strain loading on the solder jointscoming from the vibration acceleration working on theSMD body mass.• Mitigation procedure:– For two-leaded SMD components the through-hole mitigationmethod shall be applied to eliminate the eigenmodes by fixation• Use an adhesive that has a small thermal mismatch withrespect to solder.– For multi-leaded SMD components method the extended approachfor SMD’s shall be used.• Derive the stress/strains in the solder joints from theacceleration momentum working on the component relative tothe PCB taking into account staking adhesives present.Subtract this from the maximum strain obtained for the givenlifetime objective.20
  21. 21. © Sirris 2012 © imec 2012 | www.edmp.be3. Failure mitigation of high profile SMD’s(2)• Correct the strain to determine the minimal bending radius.• If the strain induced by the acceleration momentum to thecomponent body exceeds the maximum allowable strainwithout bending one needs to:• Provide component body fixation that reduces the momentumon the solder joints.• Reduce mechanical loading on the electronics by externalmeans such as a vibration damping suspension21
  22. 22. © Sirris 2012 © imec 2012 | www.edmp.be3. Transfer functions (dampers)• When dampers are used the loadon the PCB depends on thetransmissibility of the dampers• Transmissibility function• With22PCBkmC0.010.11101000.1 1 10ζ=0.02ζ=0.10ζ=0.25ζ=0.40Frenquency RatioExample of transmissibilityvs. frequency ratio (f/fn)
  23. 23. © Sirris 2012 © imec 2012 | www.edmp.be3. Concluding remarks• The EDM- 001 Vibration guideline provides a procedureto substantially mitigate the risk of problems duringproduction or during life time• Tools are available to obtain necessary data• After revision the guideline and tools will be madeavailable for Sirris and EDM members23
  24. 24. © Sirris 2012 © imec 2012 | www.edmp.be4. Present capabilities of the “Vibrationtool”24• Modal analysis• Calculate eigenfrequencies and display mode shapes• for simple and more complex shaped boards• Reads *.emn files• Heavy components• Facilitates addition of fixations and stiffeners• PBA response to loading• Sinusoidal vibration loading• Shock• Plots• Eigen frequency• Local displacements• Curvature in x or y direction• Component analysis• Modal analysis• Shock• Heavy components• local mass increase
  25. 25. © Sirris 2012 © imec 2012 | www.edmp.be4. Foreseen implementations25• Improve the input of stiffeners• Fixed – non fixed• Curvature plots• At a point picked• Maximum• At the location of a component• Response to loading• Random vibration loading• Extend the choice of response spectra• Dampers• Transfer through rubbers at a given torque