1、ANSYS 电子产品可靠性仿真介绍电子产品可靠性仿真介绍Analyzing Printed Circuit Boards (PCBs) and PackagesGalileo Board3456 BodiesHow to prepare the board for analysis?Traditional ApproachExport step file from the board layout.The exported bodies are overlapping.Import into Design Modeler / Space ClaimPerform Boolean operati
2、on and share topologyImport Geometry into MechanicalMeshSpecify boundary conditionsSolveAnalyzing Printed Circuit Boards (PCBs) and PackagesGalileo Board3456 BodiesHow to prepare the board for analysis?Traditional ApproachExport step file from the board layout.30 minsImport into Design Modeler / Spa
3、ce Claim10 minsPerform Boolean operation and share topology24hrs and still runningImport Geometry into MechanicalMeshSpecify boundary conditionsSolveTraditional approach does not workTrace mapping provides a fast and efficient method to model such PCBs without incurring the inordinate cost of proces
4、sing geometry and mesh. Geometry is modeled by just the dielectric layers. Very simple geometry which can be easily generated and meshed. Effect of traces is modeled by checking for the presence of Metal Trace in each element, and assigning a new material with material properties calculated based on
5、 Metal fraction.What is Trace Mapping?Trace Mapping LayoutSimplified Geometry and MeshLayout representation as Metal MapMetal map on Target MeshSpaceClaim now has the ability to import ECAD files.Can import: Layout Geometry Layer Topology Supported File Formats: Cadence SPB (*.brd;*.mcm;*.sip) ANSYS
6、 Electronics Database (*.def) Other ECAD (*.tgz;*.xml;*.cvg;*.gds;*.sf;*.strm)Creating Simplified GeometryECAD Import in Space ClaimECAD Files can be imported into SpaceClaim using File - OpenECAD Import in Space Claim11 layersEach layer as a separate bodyShared TopologyDetails show Material Assignm
7、ent for each layerThe PCB 3D layout files can be specified in the External DataTransfer link from External Data Setup to Model cell in Mechanical system transfers the layout data to MechanicalFollowing formats are supported: Ansoft ANF Cadence BRD/MCM/SIP ODB+ TGZ ICEPAK BOOL+INFO ICEPAK COND+INFOFo
8、r each file user can specify: Rigid transforms to align the board outline with geometry.Importing Trace Data in MechanicalThe refresh operation on Model cell automatically inserts Imported Trace folder in the Tree. It automatically adds an Imported Trace object under the Imported Trace folder Additi
9、onal Imported Trace objects can be added by right click on Imported Trace folder and choosing Insert-TraceThe details view of the Imported Trace object allows user to specify Trace Import definition. Scoping: to specify the bodies representing the layer geometry for the PCB. External Data Identifier
10、: drop-down list of available ECAD files from the list of files specified in the External Data system.Importing Trace Data in Mechanical (contd.)The Data View allows the user to see (and modify) the layers specified in the PCB layout. The following information is available. Layer Names Layer Thickne
11、sses Trace material Activation / Deactivation of layers.Trace material is defined in the Engineering Data module Two sample materials have been added in General Materials library Copper Alloy (Metal) FR-4 (Dielectric)The dielectric material is assigned using Material field in body detailsImporting T
12、race Data in Mechanical (contd.)Once fully defined, the Import operation imports the Trace data and maps onto the Target mesh.Graphics Controls allow user to visualize the mapped dataAdditional Controls: Material-Modeling option allow user to control how material properties are calculated based on M
13、etal Fraction. X/Y-Discretization to you specify the grid density count to create the trace metal distribution of the board Importing Trace Data in Mechanical (contd.)22DisplacementDisplacement 2Uniform Temperature 50CBoundary ConditionsResultsX DeformationY DeformationResultsZ DeformationZ Deformat
14、ion (Full Fidelity)Good agreement between Full Fidelity and Trace Mapping analysisMore ResultsEquivalent StressEquivalent StrainMetal Trace mapping is also supported on shells for Structural AnalysisThe geometry is represented by a single shell bodyThe layers are modeled through layered elementsSmal
15、l differences are present in the definition of Imported Trace Activation/Deactivation is unavailable Dielectric material is specified in the data viewTrace Mapping on ShellsElectromigration AnalysisRelease 17.0Electromigration What? Displacement (movement) of metal atoms induced by intense electric
16、current through the conductor Diffusion controlled mass transport in the direction of electron flow (electron wind) Atoms move in the direction opposite to the electric current and form hillocksHillock or whisker failure Vacancies migrate in the direction of the electric current and form voidsIncrea
17、sed resistance Electric currentElectron flow Electromigration (EM) induced failure Key reliability issue for integrated circuits (IC)Electromigration Where? IC conductors On-chip interconnects and vias Micro-bumps, flip-chip solder joints, copper pillars Ball-grid-array (BGA) solder balls Through-si
18、licon vias (TSV) Under bump metallization (UBM) Copper redistribution layers (RDL)Electromigration Why? Miniaturization of electronic components Smaller interconnect sizes Increased current density Higher temperatures and mechanical stresses Dimension mismatches among interconnects New interconnect
19、materials Cu or Cu-Al interconnects Pb-free (”green”) solder joints New joint designs Cu pillar vs solder bumpNew under bump metallization (UBM) Thickness and stacking order of Cu and NiElectromigration Who? Leading providers of semiconductor packaging design, assembly and test services Flip chip pa
20、ckaging Copper pillar bumping and packaging Copper wire interconnects Through Silicon Via (TSV) technologyElectromigration Reliability The goal of EM reliability analysis is to determine the Mean-time-to-failure (MTTF) of the interconnect Safe (maximum allowable) electric currents Role of other fact
21、ors affecting the interconnect reliability Temperature, stresses Metallurgy (UBM stacking and materials, solder alloy composition) Relative performance of different designsThe goal of EM reliability simulation is to determine the Change of electrical resistance as a function of void formation and pr
22、opagation when local concentration reached a threshold value, the elements are EKILLed temperature, electric current, geometry intermetallic compounds (IMC) growth in solder bumps, grain orientation and surface finish Electromigration Modeling Atomic fluxGoverning EquationTkTDCQkTDCVkTeDCZCDJH2*Elec
23、tromigrationStress migrationDiffusionThermomigrationFor more details, see section “4.26 Migration Model” of the Material Reference D=D0exp(-Ea/kT) diffusivityC concentrationT temperatureV electric potentialH local hydrostatic stress = (11+ 22+ 33)/3 Parameters are input using the new TB,MIGR table E
24、a activation energyZ* effective charge numbere elementary charge, 1.602e-19 C atomic volumeQ* heat of transportCoupled-Field Analyses Fully coupled diffusion (atomic flux) and electric, structural, thermal analyses For more details, see sections “10.10 Structural-Diffusion Coupling,” “10.11 Thermal-
25、Diffusion Coupling,” “10.12 Electric-Diffusion Coupling” of the Theory ReferenceGradientFluxDisplacementThermalElectricConcentrationStressElasticityPlasticityThermal expansion TDiffusion expansion CHeatPiezocaloric effectPlastic heatThermal conductionJoule heatPeltier effectCurrentPiezoresistive eff
26、ectSeebeck effectElectric conductivityAtomicStress migration-(D/kT)cHThermomigration-(D/kT2)cQ*TElectromigration-(D/kT)cZ*e?Diffusion-DcH=trace(c(u- T- C)/3D=D0exp(-Ea/kT)Coupled-Field Elements New analyses Electric-diffusion (KEYOPT(1)=100100) Thermal-electric-diffusion (KEYOPT(1)=100110) Structura
27、l-electric-diffusion (KEYOPT(1)=100101) Structural-thermal-electric-diffusion (KEYOPT(1)=100111) Enhanced analyses Stress migration with structural and diffusion DoFs (KEYOPT(1)=100 xx1) Can also be used to model hydrogen or oxygen migration in metals Thermomigration with thermal and diffusion DoFs
28、(KEYOPT(1)=100 x1x)For more details, see sections “PLANE223,” “SOLID226,” “SOLID227” of the Element Reference 22x Coupled-Field ElementsPLANE223 2-D 8-node quadrilateralSOLID2263-D 20-node brickSOLID2273-D 10-node tetrahedron Solder Ball - Model A transient structural-thermal-electric-diffusion anal
29、ysis of a solder joint subject is performed to determine the atomic density distribution symmetry modelSOLID227, KEYOPT(1)=100111Current load I=2.85 AInitial normalized concentration C0=1SnAgCu (SAC)kB=1.3806488e-23*1.e12 ! Boltzmann constant, pJ/KkB_e=8.6173324e-5 ! Boltzmann constant, eV/KR=8.3144
30、5 ! Universal gas const, J/(K*mol)V_SAC=2.71e-29*1e18 ! atomic volume, um3Ea=0.98 ! activation energy, eVZ=-23 ! charge numberQ=0.0094 ! heat of transport, eVtb,migr,2 ! migration model for SACtbdata,1,Ea/kB_e ! diffusivitytbdata,2,V_SAC/kB ! stress migrationtbdata,3,Q/kB_e ! thermomigration tbdata,
31、4,Z/kB_e ! electromigrationCuFor more details, see sections “2.15 Thermal-Electric-Diffusion Analysis” and “2.16 Structural-Electric-Diffusion Analysis” of the Coupled-Field User Guide Simulation results after 100 hoursStress intensityNormalized concentrationElectric current densitySolder Ball - Res
32、ultsCopper Interconnect - Model A transient structural-thermal-electric-diffusion analysis is performed to determine the back stress build-up due to the electromigration of vacancies in a copper wireL = 2 mm x H =0.05 mmSOLID226, KEYOPT(1)=100111Initial normalized concentration C0=1Voltage load V =
33、0.01 VFor more details, see section “2.17 Structural-Thermal-Electric-Diffusion Analysis of the Coupled-Field User GuideCuZe=4*1.6e-19 ! POSITIVE effective charge, CkB=1.38e-23 ! Boltzmann constant, m2*kg/(s2*degK)Va=1.66e-29 ! atomic volume, m3Ceq=6e21 ! equilibrium vacancy concentration, m(-3)f=0.
34、6 ! vacancy volume relaxation factorbet=-Ceq*f*Va*1e-3 ! NEGATIVE diffusion expansionmp,betx,1,bet ! diffusion expansion - back-stressmp,cref,1,1 ! reference concentration for tb,migr,1,1 ! migration model, vacancy fluxtbdata,2,Va/kB ! stress migration tbdata,4,Ze/kB ! electromigration tbdata,8,f ! relaxation factorCopper Interconnect - ResultsNormalized Concentration atTime=1 hourBack Stress vs TimeElectric currentVacancy migration 谢谢聆听！谢谢聆听！
