ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES Walt Willing Mike Cascio Jonathan Fleisher.

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Transcript of ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES Walt Willing Mike Cascio Jonathan Fleisher.

  • ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUESWalt WillingMike CascioJonathan Fleisher

    2010 RAMS Tutorial 11B Cassady

    Importance of effective Failure AnalysisBasic Failure Analysis ProcessFailure Analysis TechniquesElectrical Testing / CharacterizationNon-Invasive TestsInvasive TestsSuggestions for your own failure analysis capabilitiesUnderstanding Electronic Part Failure MechanismsExcerpts from the 1997 Alan O. Plait Award for Tutorial Excellence

    Agenda*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Importance of Effective Failure AnalysisEffective root cause analysis helps assure proper corrective action can be implemented

    When electronic parts fail, its important to understand why - the Root Cause

    Accurate root cause assessment important for High Reliability systems where failures are very critical:Implantable medical devicesSpace satellite systemsDeep well drilling systems

    As well commercial high production products, where the cost of a single failure mode is replicated multiple times

    Common term for process of root cause determination and applying corrective actionFRACAS (Failure Reporting, Analysis and Corrective Action System)

    Failure Analysis is the crucial Analysis part of the FRACAS process *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Failure Analysis - CautionPreserve the Failure / Prevent RTOKsFailure Analysis has to be handled carefullyAssure the failure mechanism is preserved, not Lost due toCarelessnessBypassing important tests / measurements Performing destructive analyses in an incorrect sequence.

    Example: Once wirebonds are removed, the part may not be able to be electrically tested

    Many parts removed for failure analysis may Re-Test OK (RTOK)Possibly the wrong part was removedPart level testing performed did not properly capture the failure modeSubtle parameter shifts, etc.Peculiar failure sensitivity (e.g. gain vs temperature) exists

    Important to assure board level fault isolation / troubleshooting performed correctly*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Top Reasons for Component Failures (1 of 3)1) Electrical OverstressTransients related to test setups. Rapid switching to full amplitude voltage / lead to inrush or high transient Human body electrical static discharge (ESD)

    2) Solder joint failurePoor solder joints are the most common issue related to board fabricationCommonly responsible for latent failures due to joint fatigue driven by thermal cycling

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Top Reasons for Component Failures (2 of 3)3) ContaminationLeads to failures stemming from corrosion or electrical leakage paths Can rapidly destroy wire bond interconnects and metallization. Sources of contaminationHuman by-products (Spittle) Chemicals used in the assembly process. 4) Cracked Ceramic PackagesCeramics are used for the majority of high reliability military and space applicationsPackages are very brittle and are susceptible to cracking Stress risers from surface anomalies General mounting stresses (exacerbated by thermal cycling Root causes can be traced to either design implementation or process controls5) Timing IssuesIntermittent failures often due to Inadequate timing margins Through timing analysis should be part of any design when asynchronous signals are present

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Top Reasons for Component Failures (3 of 3)6) Power Sequencing IssuesMany IC technologies susceptible to damage if core bias voltages are not applied prior to control or data input voltages

    7) Poor Design Habits Lack of adequate derating (voltage, power, thermal)Most common of these is due to not managing component temperatureRunning parts outside their rated power dissipation specificationLeaving CMOS inputs floatingNot properly controlling resetsLow bias voltage / Step Load Droop*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Recommended Trouble ShootingPrior to Part Failure Analysis (1 of 3)Isolate and confirm part failure while still on the board to the extent possibleReview initial failure data Exonerate Test Equipment and if necessary:Use a known good reference unit to check test set-upConfirm failure on different test set and assembly levelsConfirm the following are within spec: Input conditions (bias, addressing, strobe, logic)Output parameters Take DC probe measurements on part (Use micro-clip probes if necessary)Look at all signals with an Oscilloscope to assure no AC oscillationsCheck Line-to-line & line-to-ground isolationLift solder joints as required to isolate part from circuitFor RF circuits, consider soldering a coax onto part before removing and confirm input/output is out-of-spec Use connectorized measurements as much as possible. Probe based RF measurements are typically not consistent and unreliable

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Recommended Trouble ShootingPrior to Part Failure Analysis (2 of 3)Inspect / Photograph / X-ray part on board Perform general examination under magnificationFocus on the following:Solder jointsConnectorsComponent (cracks, exterior finish)Foreign Object Debris (FOD)Suspect componentPhotograph guidelinesMinimum of four angles Solder interfaces to boardPhotograph each side of partX-ray on board prior to removal as required

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Recommended Trouble ShootingPrior to Part Failure Analysis (3 of 3)Part Removal GuidelinesReview removal process if new steps are requiredCut leaded wire connections when possible to remove partWitness removal as necessaryIf heat is required to remove partTake as much data as available, excessive solder heat may corrupt evidence

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Basic Failure Analysis TechniquesElectrical Testing / CharacterizationNon-Invasive TestsInvasive (Destructive) Tests*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Basic Failure Analysis Process Flow*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Electrical Testing / CharacterizationFirst FA Step - Fully Characterize Failure Mode

    Test / Characterize / Look for SensitivitiesOver temperatureVoltage rangeClock speed

    Perform Curve tracer assessments on all Inputs / OutputsCompare to known good devicesCan help isolate which pin may be damaged*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Non-Invasive TestsSecond FA Step - Perform Non-Invasive Tests External Microscopic Exam / PhotoX-ray (Film, Realtime, 3D)Fine & Gross seal tests for hermetic devicesVacuum Bake & RetestPIND Test XRF X-ray FluorescenceAcoustic tests (SAM / C-SAM)

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    External Microscopic Exam / PhotoThorough external visual examination of the suspect part using a stereo microscope should be performed early in the failure analysis processTypical inspection scopes range from 10X to 30X magnification Magnification levels up to 100X can be employed to further examine any anomalies identified. The following conditions should be specifically looked for:External contamination and/or solder balls Possibly shorting out pins on the deviceDamaged leads or package sealsSeal integrityLead integrityGross cracks in the packageCorrosionThermal or electrical damageRepresentative Photos should be taken of the part and any anomalies Crack

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    X-Ray - Film / Realtime / 3DX-Ray (Radiograph) is a very powerful tool for non-invasive failure analysisX-Ray examinations can detect actual or potential defects within enclosed packagesThere are multiple types of X-Ray equipment availableBasic film X-RaysReal time X-Ray3-D X-RayWhile film X-Rays can be useful, modern Real Time X-Ray provide extensive capabilities Resolution for film X-Ray = 1 mil particle size, or bond wires down to 1 mil diameterLimitation of film X-Ray - only one exposure level can be taken at a timeNot all characteristics can be observed at a single exposure levelReal time X-Rays typically have a resolution range from 1um to 0.4 umReal time allows for a continuous adjustment of exposure levels and conditions, as well as real time part rotation to obtain the most revealing X-Ray viewSpecial digital filtering / image processing can also be used to detect possible delinations in the image not otherwise observable on the image screen Refer to Mil-Std-883 Method 2012*RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    X-Ray ExaminationsX-Rays allow internal part examination looking for:Internal particlesInternal wire bond dress Make sure the wire bonds are not touching each other or package lidsDie attach quality (voiding, die attach perimeter)Solder joint quality for connectorsInsufficient or excessive solderSubstrate or printed wiring board trace integrityObvious voids in the lid sealForeign metallic particles within the packageInternal part orientation, etc.

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Real-Time X-ray of Coaxial ConnectorNormal X-ray View

    X-ray with Image Filtering

    *RAMS 2012 Tutorial 8B Willing, et al

    2010 RAMS Tutorial 11B Cassady

    Acoustic tests (SAM / C-SAM)Acoustic testing is popular for finding voids / delaminations / cracksPlastic Encapsulated Microcircuits (PEMS) Ceramic capacitors. Acoustic tests rely on acoustic energy transfer through the partIf there is a void, the acousti