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ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES. Walt Willing Mike Cascio Jonathan Fleisher. Agenda. Importance of effective Failure Analysis Basic Failure Analysis Process Failure Analysis Techniques Electrical Testing / Characterization Non-Invasive Tests Invasive Tests

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ELECTRONIC PART FAILURE ANALYSIS TOOLS AND TECHNIQUES


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

    2. Agenda • Importance of effective Failure Analysis • Basic Failure Analysis Process • Failure Analysis Techniques • Electrical Testing / Characterization • Non-Invasive Tests • Invasive Tests • Suggestions for your own failure analysis capabilities • Understanding Electronic Part Failure Mechanisms Excerpts from the 1997 Alan O. Plait Award for Tutorial Excellence RAMS 2012 – Tutorial 8B – Willing, et al

    3. Importance of Effective Failure Analysis • Effective root cause analysis helps assure proper corrective action can be implemented • When electronic parts fail, it’s important to understand why - the Root Cause • Accurate root cause assessment important for High Reliability systems where failures are very critical: • Implantable medical devices • Space satellite systems • Deep 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 action • FRACAS (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

    4. Failure Analysis - Caution“Preserve the Failure” / Prevent “RTOKs” • Failure Analysis has to be handled carefully • Assure the failure mechanism is preserved, not “Lost” due to • Carelessness • Bypassing 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 removed • Part level testing performed did not properly capture the failure mode • Subtle 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

    5. Top Reasons for Component Failures (1 of 3) • 1) Electrical Overstress • Transients 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 failure • Poor solder joints are the most common issue related to board fabrication • Commonly responsible for latent failures due to joint fatigue driven by thermal cycling RAMS 2012 – Tutorial 8B – Willing, et al

    6. Top Reasons for Component Failures (2 of 3) • 3) Contamination • Leads to failures stemming from corrosion or electrical leakage paths • Can rapidly destroy wire bond interconnects and metallization. • Sources of contamination • Human by-products (Spittle) • Chemicals used in the assembly process. • 4) Cracked Ceramic Packages • Ceramics are used for the majority of high reliability military and space applications • Packages 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 controls • 5) Timing Issues • Intermittent 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

    7. Top Reasons for Component Failures (3 of 3) • 6) Power Sequencing Issues • Many 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 temperature • Running parts outside their rated power dissipation specification • Leaving CMOS inputs floating • Not properly controlling resets • Low bias voltage / Step Load “Droop” RAMS 2012 – Tutorial 8B – Willing, et al

    8. Recommended Trouble ShootingPrior to Part Failure Analysis (1 of 3) • Isolate and confirm part failure while still on the board to the extent possible • Review initial failure data • Exonerate Test Equipment and if necessary: • Use a known good reference unit to check test set-up • Confirm failure on different test set and assembly levels • Confirm 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 oscillations • Check Line-to-line & line-to-ground isolation • Lift solder joints as required to isolate part from circuit • For 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

    9. Recommended Trouble ShootingPrior to Part Failure Analysis (2 of 3) • Inspect / Photograph / X-ray part on board • Perform general examination under magnification • Focus on the following: • Solder joints • Connectors • Component (cracks, exterior finish) • Foreign Object Debris (FOD) • Suspect component • Photograph guidelines • Minimum of four angles • Solder interfaces to board • Photograph each side of part • X-ray on board prior to removal as required RAMS 2012 – Tutorial 8B – Willing, et al

    10. Recommended Trouble ShootingPrior to Part Failure Analysis (3 of 3) • Part Removal Guidelines • Review removal process if new steps are required • Cut leaded wire connections when possible to remove part • Witness removal as necessary • If heat is required to remove part • Take as much data as available, excessive solder heat may corrupt evidence RAMS 2012 – Tutorial 8B – Willing, et al

    11. Basic Failure Analysis Techniques • Electrical Testing / Characterization • Non-Invasive Tests • Invasive (Destructive) Tests RAMS 2012 – Tutorial 8B – Willing, et al

    12. Basic Failure Analysis Process Flow RAMS 2012 – Tutorial 8B – Willing, et al

    13. Electrical Testing / Characterization • First FA Step - Fully Characterize Failure Mode • Test / Characterize / Look for Sensitivities • Over temperature • Voltage range • Clock speed • Perform Curve tracer assessments on all Inputs / Outputs • Compare to known good devices • Can help isolate which pin may be damaged RAMS 2012 – Tutorial 8B – Willing, et al

    14. Non-Invasive Tests • Second FA Step - Perform Non-Invasive Tests • External Microscopic Exam / Photo • X-ray (Film, Realtime, 3D) • Fine & Gross seal tests for hermetic devices • Vacuum Bake & Retest • PIND Test • XRF X-ray Fluorescence • Acoustic tests (SAM / C-SAM) RAMS 2012 – Tutorial 8B – Willing, et al

    15. External Microscopic Exam / Photo • Thorough external visual examination of the suspect part using a stereo microscope should be performed early in the failure analysis process • Typical 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 device • Damaged leads or package seals • Seal integrity • Lead integrity • Gross cracks in the package • Corrosion • Thermal or electrical damage • Representative Photos should be taken of the part and any anomalies Crack RAMS 2012 – Tutorial 8B – Willing, et al

    16. X-Ray - Film / Realtime / 3D • X-Ray (Radiograph) is a very powerful tool for non-invasive failure analysis • X-Ray examinations can detect actual or potential defects within enclosed packages • There are multiple types of X-Ray equipment available • Basic film X-Rays • Real time X-Ray • 3-D X-Ray • While 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 diameter • Limitation of film X-Ray - only one exposure level can be taken at a time • Not all characteristics can be observed at a single exposure level • Real time X-Rays typically have a resolution range from 1um to 0.4 um • Real 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 view • Special 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

    17. X-Ray Examinations • X-Rays allow internal part examination looking for: • Internal particles • Internal wire bond dress • Make sure the wire bonds are not touching each other or package lids • Die attach quality (voiding, die attach perimeter) • Solder joint quality for connectors • Insufficient or excessive solder • Substrate or printed wiring board trace integrity • Obvious voids in the lid seal • Foreign metallic particles within the package • Internal part orientation, etc. RAMS 2012 – Tutorial 8B – Willing, et al

    18. Real-Time X-ray of Coaxial Connector Normal X-ray View X-ray with Image Filtering RAMS 2012 – Tutorial 8B – Willing, et al

    19. Acoustic tests (SAM / C-SAM) • Acoustic testing is popular for finding voids / delaminations / cracks • Plastic Encapsulated Microcircuits (PEMS) • Ceramic capacitors. • Acoustic tests rely on acoustic energy transfer through the part • If there is a void, the acoustic energy is blocked, and therefore voids can be detected • The acoustic tests can also be tuned to attempt to determine the depth of any void • Acoustic tests involve either reflected acoustic energy, or transmitted energy through the part • The energy transmission medium is typically DI water • Parts to be examined need to be able to withstand exposure to water RAMS 2012 – Tutorial 8B – Willing, et al

    20. Acoustic Scan of a Discoidal Ceramic Capacitor CSAM identified significant void Confirmed to exist via cross-sectioning RAMS 2012 – Tutorial 8B – Willing, et al

    21. Invasive (Destructive) Tests - Last but Not Least • Internal Package Exam / DIE Exam • Cross Sectioning • Die Probing • IR Microscopic • Liquid Crystal die thermal mapping • SEM • Auger • EDS/EDX • FIB • FTIR • SIMS (TOF SIMS / D-SIMS) • TEM (transmission electron microscopy • STEM (scanning transmission electron microscopy) • ESD Testing RAMS 2012 – Tutorial 8B – Willing, et al

    22. Microscopic Internal / Die Exam • Look for: • Damaged metal traces • Die cracks • Broken or damaged wirebonds • Typically performed using a microscope at magnifications of 100X up to 1000X • Deep UV optical microscopes can reach 16,000 X magnification and are capable of resolving 10 microns • Microscopes equipped with both dark and light field illumination are helpful, as changing the lighting conditions can help reveal issues. • Photographs should be taken to document the condition of the die and to record any anomalies Open Wire Bond Disturbed Bonds RAMS 2012 – Tutorial 8B – Willing, et al

    23. Cross Sectioning • Cross-Sectioning is a very important means of failure analysis • Often used for: • Connectors • Printed wiring board • Substrates • Solder joints • capacitors, resistors, transformer • Semiconductors • Prior to cross-sectioning, samples are potted in a hard setting acrylic or polyester rosin • Failed item is literary cut in a cross-sectioned fashion then highly polished for detailed microscopic examination • The potted sample can be cut in half initially to find target the failure site, or the cross-section can commence at one end of the sample and then progressively cross-section up to and through the failure site. • This progressive cross-sectioning can provide a “3D” view of the failure site. • Photograph at all steps Solder Joint RAMS 2012 – Tutorial 8B – Willing, et al

    24. Cross-Sectioning of PWB Blister area above electrically stressed signal traces caused un-expected resistance <10ohms Deformation/ Delamination due to excessive heating RAMS 2012 – Tutorial 8B – Willing, et al

    25. Signs of Overheating of Center Trace Distorted signal trace, Evidence of high current thru trace Damage located above the trace +28V Trace maintains shape, No evidence of over-current Material appears carbonized RAMS 2012 – Tutorial 8B – Willing, et al

    26. Scanning Electron Microscope (SEM) • SEM is an important tool for semiconductor die failure analysis, as well as metallurgical failure analysis • SEM can provide detailed images of up to 120,000X magnification • Typical magnifications of 50,000X to 100,000X • Resolve features down to 25 Angstroms • NANO SEMs can resolve features down to 10 Angstroms • With a SEM image, the depth of field is fairly large, providing a better overall three-dimensional view of the sample • SEM examinations are often used to verify semiconductor die metallization integrity and quality • Refer to Mil-Std-883 Method 2018 RAMS 2012 – Tutorial 8B – Willing, et al

    27. Auger Electron Spectroscopy (AES) • Sample surfaces are exposed to an electron beam designed to dislodge secondary electrons (Auger electrons) • Materials identified by energy level spectra unique to each material’s valence bands • Auger useful for detecting organic materials on surfaces • Depth profiling can occur, useful to 2000 Angstroms deep Auger profile of contamination on the surface of a wire bond pad RAMS 2012 – Tutorial 8B – Willing, et al

    28. Energy Dispersive X-ray analysis (EDS, EDAX or EDX) • EDX is a technique used along with an SEM to identify the elemental composition of a sample • During EDX, a sample is exposed to an electron beam inside the SEM • SEM electrons collide with the electrons within the sample, causing some of them to be knocked out of their orbits • The vacated positions are filled by higher energy electrons which emit X-rays in the process • By a spectrographic analysis of the emitted X-rays, the elemental composition of the sample can be determined • EDS is a powerful tool for microanalysis of elemental constituents RAMS 2012 – Tutorial 8B – Willing, et al

    29. Energy Dispersive X-ray (EDX, EDAX, EDS) EDS maps of a Cadmium particle RAMS 2012 – Tutorial 8B – Willing, et al

    30. Secondary Ion Mass Spectrometry (SIMS) • SIMS is a technique which can detect very low concentrations of dopants and impurities in semiconductors • By ion milling deeper into the sample, SIMS provides elemental depth profiles from a few angstroms to tens of microns • SIMS works by sputtering the sample surface with a beam of primary ions • Secondary ions formed during the sputtering are analyzed using a mass spectrometer • These secondary ions can range down to sub-parts-per-million trace levels • Advanced SIMS analyses such as Time-of-Flight SIMS (TOF-SIMS) and Dynamic SIMS (D-SIMS) provide additional means of elemental detection and resolution RAMS 2012 – Tutorial 8B – Willing, et al

    31. Focused Ion Beam FIB • FIB uses an ion beam to microscopically mil / ablate material away to allow for cross-sectioning of semiconductor die (ion milling) • Gallium or Tungsten ion sources are used • FIB cross-sections are examined by SEM to see features such as • Die metallization construction • Pinhole in dielectrics (oxides/nitrides) • EOS or ESD damage sites • FIB cross sections are very “polished” revealing features down to 200 to 250 Angstroms • FIB can also be used to cut semiconductor metallization lines to isolate circuitry on the die, and if necessary, a Platinum ion beam can be used to actually deposit metallization creating new circuit traces • In this case, die level design changes (known as “Device Editing”) can be implemented to allow for a design “try-out” RAMS 2012 – Tutorial 8B – Willing, et al

    32. Focused Ion Beam (FIB) FIB cross-section of a Schottky diode FIB cross-section of a MOSFET GATE RAMS 2012 – Tutorial 8B – Willing, et al

    33. Transmission Electron Microscopy (TEM/STEM)TEM (Transmission Electron MicroscopySTEM (Scanning Transmission Electron Microscopy) • TEM and STEM use a high energy electron beam to image through an ultra-thin sample allowing for image resolutions on the order of 1 - 2 Angstroms • S/TEM has better spatial resolution then a standard SEM and is capable of additional analytical measurements • S/TEM and requires significantly more sample preparation as very thin samples need to be prepared, often using FIB techniques • S/TEM provides outstanding image resolution and it is possible to characterize crystallographic phase and orientation as well as produce elemental maps RAMS 2012 – Tutorial 8B – Willing, et al

    34. TEM of a gold ball bond on an Aluminum pad confirmed Good Bond Intermetallics TEM analysis of a gold/aluminum interface of a wire bond Data from the TEM provided assurance that the gold/aluminum stoichiometry was correct even after extensive life aging RAMS 2012 – Tutorial 8B – Willing, et al

    35. Suggestions for Your Own Failure Analysis Capabilities • Suggestions are provided for Failure Analysis capabilities for a typical electronics firm • Three levels of Failure Analysis capabilities are suggested • Basic • Moderate • Advanced • Beyond these three levels, one might consider using commercial failure analysis laboratories for the more esoteric capabilities such as • TEM / STEM • SIMS • Usually its more cost effective to subcontract out those types of analyses vs. establishing them in-house RAMS 2012 – Tutorial 8B – Willing, et al

    36. Basic Failure Analysis Lab • Basic Meters (DVMMs) • Stereo Microscope (10X to 30X) (Preferably with digital camera) • Cross Sectioning Equipment • Power Supplies / Signal generator • Curve Tracer Curve Tracer showing I/V Curve Cross-Section Equipment RAMS 2012 – Tutorial 8B – Willing, et al

    37. Moderately Equipped Failure Analysis lab • Metallurgical Microscope (1000X) (Preferably with digital camera) • Film X-Ray • SEM • Chemical Hood with De-capsulating chemicals • Die Probe Station • Liquid Crystal • Acoustic Scan Metallurgical Microscope with Digital Camera RAMS 2012 – Tutorial 8B – Willing, et al

    38. SEM and Acoustic Testing (CSAM) Acoustic Testing (CSAM) Scanning Electron Microscope RAMS 2012 – Tutorial 8B – Willing, et al

    39. Advanced Failure Analysis lab • Real-time X-ray • SEM/EDS • Auger Analysis System • FIB • IR Thermal Imaging • RF Test Equipment (If necessary) RAMS 2012 – Tutorial 8B – Willing, et al

    40. Real-time X-ray Comparison Between Film & Real-time X-ray Film X-ray Real Time X-ray RAMS 2012 – Tutorial 8B – Willing, et al

    41. Scanning Electron Microscope with EDS EDX used for Spectral Element Analysis RAMS 2012 – Tutorial 8B – Willing, et al

    42. Focused Ion Beam (FIB) Cross-Sectioning FIB Cross-Section – Contact Windows FIB Cross-Section – MOSFET Gates RAMS 2012 – Tutorial 8B – Willing, et al

    43. Thermal Imaging A hotspot in a CMOS gate is indicated by the liquid crystal technique at 1000X IR Thermal Imaging System RAMS 2012 – Tutorial 8B – Willing, et al

    44. Understanding Electronic Part Failure MechanismsExcerpts from the 1997 Alan O. Plait Award for Tutorial Excellence • Five subjects covered: • Interconnects • Semiconductor elements • Passive elements • Substrates • Packages. RAMS 2012 – Tutorial 8B – Willing, et al

    45. Purpose of Failure Mechanisms Section • Understanding common part failure mechanisms for various technologies necessary to provide effective corrective action to avoid failures Typical Hybrid, Transistor, and IC RAMS 2012 – Tutorial 8B – Willing, et al

    46. Wire Bonds • ISSUES: • Bond placement • Wire dress • Bonding energy • Bonding temperature • Bondability • Dissimilar metals • Corrosion • Contamination • Electrical overstress Mis-Placed bonds caused shorts RAMS 2012 – Tutorial 8B – Willing, et al

    47. Wire Bonds Poor Stress Relief • ISSUES: • Bond placement • Wire dress • Bonding energy • Bonding temperature • Bondability • Dissimilar metals • Corrosion • Contamination • Electrical overstress RAMS 2012 – Tutorial 8B – Willing, et al

    48. Wire Bonds • ISSUES: • Bond placement • Wire dress • Bonding energy • Bonding temperature • Bondability • Dissimilar metals • Corrosion • Contamination • Electrical overstress RAMS 2012 – Tutorial 8B – Willing, et al

    49. Wire Bonds • ISSUES: • Bond placement • Wire dress • Bonding energy • Bonding temperature • Bondability • Dissimilar metals • Corrosion • Contamination • Electrical overstress RAMS 2012 – Tutorial 8B – Willing, et al

    50. Wire Bonds • ISSUES: • Bond placement • Wire dress • Bonding energy • Bonding temperature • Bondability • Dissimilar metals • Corrosion • Contamination • Electrical overstress Gold / Aluminum Intermatallic“Purple Plague” RAMS 2012 – Tutorial 8B – Willing, et al