1、Scanning Acoustic Microscopy TrainingThis presentation and images are copyrighted by Sonix,Inc.They may not be copied,reproduced,modified,published,uploaded,posted,transmitted,or distributed in any way,without prior written permission from Sonix.Copyright Sonix,Inc2This presentation serves as a brie
2、f introduction into the theory and operation of scanning acoustic microscopes.Copyright Sonix,Inc3Ultrasound Inspection,Using an Acoustic Microscope UltrasoundNon-Destructive TestingExample ImagesWhat does this thing do?Copyright Sonix,Inc4University of California Medical CenterSan Francisco,Califor
3、niaMEDICALSONARWhat are Ultrasonic Waves?Ultrasonic waves refer to sound waves above 20 kHz(not audible to the human ear)Copyright Sonix,Inc5NDT utilizes various non-invasive measurement techniques,such as ultrasonics and radiography to determine the integrity of a component,structure,or material wi
4、thout destroying the usefulness of the item.Copyright Sonix,Inc6Failure Analysis ReliabilityProcess ControlVendor QualificationProductionQuality ControlResearchCopyright Sonix,Inc7Plastic encapsulated IC packagesFlip ChipsBonded WafersPrinted Circuit BoardsCapacitorsCeramicsMetallicPower Devices/Hyb
5、ridsMedical DevicesMaterial Characterization Copyright Sonix,Inc8Die CrackDelaminationBGA die attachLid seal voidsCopyright Sonix,Inc9Die Attach VoidsDie Tilt,B-ScanDie Pad delaminationMold compound voidsDie Top DelaminationFlip Chip Underfill VoidsCopyright Sonix,Inc10Ultrasound InspectionTheorySys
6、tem ComponentsTransducersCopyright Sonix,Inc11Characteristics of Ultrasonic WavesFreely propagate through liquids and solidsReflect at boundaries of internal flaws and change of materialCapable of being focused,straight transmissionSuitable for Real-Time processingHarmless to the human bodyNon-destr
7、uctive to materialUniversity of California Medical CenterSan Francisco,CaliforniaCopyright Sonix,Inc12H2OTransducerCouplingUltrasound A transducer produces a high frequency sound wave which interacts with the sample.High frequency sound waves can not propagate through air.Couplant-A material used to
8、 carry the high frequency sound waves.Water is the most common couplant for immersion testing.Inspection ModesPulse EchoThrough TransmissionReceiveCopyright Sonix,Inc13The scanner consists of a three axis system,X,Y,and Z.The motor controller directs the movement of these axes.ZAxisY-AxisStepX-AxisS
9、canFocusCopyright Sonix,Inc14High FrequencyShort FocusLow FrequencyLong Focus1.Higher resolution2.Shorter focal lengths3.Less penetration (Thinner packages)1.Lower resolution2.Longer focal lengths3.Greater penetration (Thicker packages)General rules:Ultra High Frequency(200+MHz)for flip chips and wa
10、fers.High Frequency(50-75 MHz)for thin plastic packages.(110MHz-UHF)for flip chips.Low Frequency(15 MHz)for thicker plastic packages.Copyright Sonix,Inc15Depth of FieldThe purple region is referred to as the focal area or depth of field of the transducer beam.Copyright Sonix,Inc16Sample Application
11、TransducerT/X Receiver10 MHz w/0.75”focusPLCC,QFP,PQFP15 MHz w/0.5”focusPower Pak15 MHz w/0.5”focusBGA Top50-75 MHz w/12mm focusCapacitors75 MHz w/12mm focusTSOP75 MHz w/12mm focusFlip Chip Underfill110 MHz w/8mm focusFlip Chip Interconnect UHF w/5.9 mm focusBonded Wafer110 MHz w/8mm focusBonded Waf
12、erUHF w/5.9 mm focusCopyright Sonix,Inc17ABCs Of AcousticsAcoustic ReflectionsAcoustic WaveformsImage DisplayCopyright Sonix,Inc18MaterialDensityLongitudinalWave Acoustic Impedance(g/cm3)Velocity(m/s)(kg/m2s)(x106)Water(200 C)1.0014831.48Alcohol(200 C)0.7911680.92Air(200 C)0.003440.00Silicon2.338600
13、20.04Gold19.3324062.53Copper8.90470041.83Aluminum2.70626016.90Epoxy Resin1.2026003.12Resin(for IC pkg)1.7239306.76Glass(Quartz)2.70557015.04Alumina(AL2O3)3.801041039.56Copyright Sonix,Inc19Acoustic Material Propertiesdensity()velocity of sound in material(c)acoustic impedance(Z=c)Copyright Sonix,Inc
14、20Whenever a sudden change in acoustic impedance is encountered,like at a material boundary,a portion of sound is reflected and the remainder propagates through the boundary.Copyright Sonix,Inc21Z1=C where:=1.00 gram/cm3C=1.5 x 106Z1=1.5 x 106Z2=C where:=2.00 gram/cm3C=2.00 x 106Z2=4.00 x 106Inciden
15、t EnergyTransmitted EnergyWater Z1Plastic Z2Reflected EnergyZ=C45%of the sound entering the boundary is reflected.Copyright Sonix,Inc22Measuring the reflected ultrasound can provide:Amplitude Information Polarity Information Time InformationCopyright Sonix,Inc23A-Scan-The raw ultrasonic data.It is t
16、he received RF signal from a single point(x,y).C-Scan-Data from a specified depth over the entire scan area.(Horizontal cross-section.B-Scan-A line of A-scans.(Vertical cross-section)Copyright Sonix,Inc24Initial PulseFront surfaceInterface of interestBack surfaceTransducerSampleCopyright Sonix,Inc25
17、The Black signal is commonly referred to as the initial pulse or the main bang.This signal occurs at Zero microseconds.The Red signal is commonly referred to as the front surface.This represents the first interface the sound encounters.The Green signal would be considered the area of interest.A data
18、 gate would be positioned over this signal or group of signals for evaluation.The Blue signal is commonly referred to as a back wall echo or back surface.Just as the name implies it is the back or bottom of the sample.1212Copyright Sonix,Inc26A-Scans provide the following information:1.Amplitude/%of
19、 full screen height (FSH)2.Phase/positive or negative peak3.Time/DepthAmplitude%FSH0%100%-100%_+PhasePhaseTime /DepthCopyright Sonix,Inc27IPFront surfaceArea of interestBack surfaceThe red box(data gate)indicates the depth of information.Copyright Sonix,Inc28Front surfaceBack surfaceFront surfaceSig
20、nal from indicationBack surfaceThe blue line(B-scan gate)represents the depth of information recorded.Signal from indicationCopyright Sonix,Inc29Inspection ModesPulse EchoThrough TransmissionCopyright Sonix,Inc30Pulse-Echo-One Transducer Ultrasound reflected from the sample is used.Can determine whi
21、ch interface is delaminated.Requires scanning from both sides to inspect all interfaces.Provides images with high degree of spatial detail.Peak Amplitude,Time of Flight(TOF)and Phase Inversion measurementThrough Transmission-Two Transducers Ultrasound transmitted through the sample is used.One Scan
22、reveals delamination at all interfaces.No way to determine which interface is delaminated.Less spatial resolution than pulse-echo.Commonly used to verify pulse-echo results.Pulse-EchoThrough TransmissionTransmit&ReceiveTransmitReceiveCopyright Sonix,Inc31Pulse-EchoTransmit&Receive2211Front SurfaceFr
23、ont SurfaceBack surfaceAir GapAir GapCopyright Sonix,Inc32Through TransmissionReceiveTransmit332211Copyright Sonix,Inc33Focusing SoundCopyright Sonix,Inc341231223Focusing an ultrasonic transducer is similar to focusing an optical microscope.When optimum focus is reached the signal will reach a maxim
24、um peak.(See the A-scans images to the left)Too CloseToo FarFocusedToo CloseFocusedToo FarCopyright Sonix,Inc35De-focused-too closeCorrect focusDe-focused-too far1.Note the time in microseconds of the signal at the different focus locations.(Red arrow)2.Also note the amplitude of the signal.(white b
25、ox)When the signal is not in focus the amplitude is lower compared to that of correct focus.Water path28%85%33%*The ultrasound is focused on the surface of the penny.Copyright Sonix,Inc36De-Focused-Too Far AwayFocused on DieDe-Focused-Too CloseAmplitude=42%Time=10.5 usAmplitude=82%Time=14.5 usAmplit
26、ude=55%Time=18.5 usCopyright Sonix,Inc37Practical ApplicationDigital OscilloscopeFront Surface FollowerData GatesCopyright Sonix,Inc38Initial pulse2nd Echo3rd EchoMultiple Echoes 1st EchoThe 1st set of echoes is the area of interest,gate placement will be on this group.Copyright Sonix,Inc39Gates are
27、 used to collect information at desired interfaces within the sample.The gate is placed over the signal or signals of interest.The absolute value of the highest amplitude signal which breaks the gate threshold within the gated region is recorded.(Figure 1)If no signal breaks the gate threshold no da
28、ta is recorded.(Figure 2)Signal amplitude can be increased or decreased by adjusting gain.Highest Amplitude signalNo data recordedGate Threshold12Copyright Sonix,Inc40Practical ApplicationImage DataPeak AmplitudeTime of Flight(TOF)Phase InversionCopyright Sonix,Inc41Peak amplitude imaging is used wh
29、en defects result in changes in the amount or strength of ultrasound reflected.It is the most common type of imaging technique.Copyright Sonix,Inc42Peak AmplitudeX1Amplitude 78%Signal height is measured in absolute value for Peak Amplitude images.100755025078Copyright Sonix,Inc43Time of Flight(TOF)i
30、maging works by measuring changes in the time it take sound to reflect off a particular interface.Most commonly used to measure die tilting.Copyright Sonix,Inc44X2X1Time of Flight images provide a relative depth within a sample.Structures which appear white or light gray are closer to the surface of
31、 the sample.Structures which appear darker shades of gray or black are deeper within sample.12The peak signal for location 1 occurs at 14.2 microseconds(light gray)while the peak signal for location 2 occurs at 14.6 microseconds(dark gray).Copyright Sonix,Inc45Peak AmplitudeTime of FlightX1X2Amplitu
32、de=67%Time=14.6 microsecondsX1X2Amplitude=73%Time=14.2 microsecondsCopyright Sonix,Inc46Phase Inversion imaging is used when defects cause changes in polarity(phase)of the signal.Most commonly used for top and back side imaging of plastic encapsulated devices.Do not use phase inversion imaging for f
33、lip chip,bonded wafer or die attach imaging.Copyright Sonix,Inc47NormalPhase InvertedCopyright Sonix,Inc48XXXREDYellowSonix uses a proprietary algorithm to detect phase inversion.This method is independent of signal amplitude as long as the signal is not saturated(100%screen height).Copyright Sonix,Inc49Phase Inversion Image of Die TopPeak Amplitude Image of Die AttachThrough TransmissionPeak Amplitude Image of Die Top
