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    上传于:2014-09-14

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    内容提示: John IsaacJohn IsaacDesigning Your PCB for High ReliabilityDirector of Market DevelopmentSystems Design Division Reliability – What Makes Electronic Systems Fail? Heat Vibration Electromagnetic interferenceHigh Temperatures© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com PCB assembly faults PCB fabricationEMIVibration & ShockPCB Assembly Faults The Issues with Testing for Reliability Reliability problems do not manifest themselves as quality issues in manufacturing— A syste...

    亚博足球app下载格式:PDF| 浏览次数:5| 上传日期:2014-09-14 17:03:18| 亚博足球app下载星级:
    John IsaacJohn IsaacDesigning Your PCB for High ReliabilityDirector of Market DevelopmentSystems Design Division Reliability – What Makes Electronic Systems Fail? Heat Vibration Electromagnetic interferenceHigh Temperatures© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com PCB assembly faults PCB fabricationEMIVibration & ShockPCB Assembly Faults The Issues with Testing for Reliability Reliability problems do not manifest themselves as quality issues in manufacturing— A system could pass final test after manufacturing — This system could fail in the field due to prolonged stress© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Creating prototypes and testing does not always work— The test could pass on the prototype given a small but unacceptable failure rate— Very difficult to simulate years of stress in test chambers— Multiple prototypes & testing increase time-to-market and cost The Answer – “Virtual Prototyping” During Design Software can predict reliability issues — Avoid design practices that may lead to failures— Can simulate months in a test chamber— Predict product failures in hours that can take years to fail in the field© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Mentor’s Virtual Prototyping Products for Increased ReliabilityRe-spinsRe-spinsReducesPrototypes& Re-spinsResults in HigherReliabilityProducts,FasterX© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comSystems DesignPrototypesNPIManufacturingCompetitive ProductLow CostReliableHigh PerformanceSmall form factorFunctionalityVirtual Prototyping Here AVOIDING PCB ASSEMBLY RELIABILITY ISSUES © 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com DFM (with reliability checks) Can Avoid Design Issue that may Cause Field Failures© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comNumber of DFM Categories AvailableFabrication277Assembly270Packaging Substrate105Microvia45Panel38 Reliability issues are those that may not manifest themselves as being issues until they have undergone some level of field testing or usageUnderstanding the Reliability Risks8810Manufacturing violationsReliability issues© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com02463.00 -3.493.50 -3.994.00 -4.494.50 -4.995.00 -5.495.50 -5.996.00 -6.496.50 -6.997.00 -7.497.50 -8.00 Acute angles create acid traps. While these may not cause failure at test, the acid continues to etch continues to etch even after lamination, weakening the circuit.Design Issues which Affect ReliabilityFabrication ExamplesNon-plated thru holes too close to holes too close to copper puts stress on the prepreg, causing a possible fracture in the circuit.© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comSilkscreen on pads will create problems with solder quality which may not manifest as a problem until it is put into use.Starved thermal vias prevent proper heat containment and may effect quality of hole plating, resulting in a potential cracked barrel. Assembly ExamplesTraces under low-lying components can cause the component to rock, creating a weak solder joint. It can solder joint. It can be sufficient to pass ICT, but no robust enough to withstand vibration.Different trace widths connecting pads can cause tombstoning. Partial tombstoningmakes the connection susceptible to field failure.Design Issues which Affect Reliability© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comVias drilled through SMD pads need to be plugged. Otherwise they can have voids in the vias which can show up as intermittent opens.Tall components too close to adjacent components can cause shadowing at wave solder. A poor solder joint cannot easily be checked. THERMAL ANALYSIS FOR THERMAL ANALYSIS FOR INCREASED RELIABILITY© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Reliability Issue – Excessive Heat Increasing IC power dissipation driven by speed and density— Boards exceeding 300W— Systems exceeding 1000sW— Smaller form factors driving heat densitydensity© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comAlcatel-Lucent , >300W per blade Systems Performance Degrades and Components Fail with too Much Heat Examples of the importance of heat sinks© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Above critical junction temperature— More powerful ICs in a smaller space increases heat density— Reliability decreases exponentially— Performance degrades Mechanical Analysis Thermal Simulation Capabilities - IC Package, PCB, & SystemPackagePackagePCBPCBSystemSystemDesign Design FlowFlowFlowFlowFacilityFacility© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com1 4Heat Heat FlowFlowAmbient Ambient Mentor Graphics’ Unique Technologies Across the Complete Thermal Design FlowDesignDesignIC Package IC Package DesignDesignPCB DesignPCB DesignExpedition EnterpriseExpedition EnterpriseMechanical Mechanical DesignDesign© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com1 5Thermal Thermal SimulationSimulationThermal Thermal TestingTesting FloTHERM® - Thermal Management of Electronic SystemsPCB Designer for PCB-Level Thermal ManagementMCAD Designer for Systems Level/ Complete EnclosurePCB DesignEnclosureDesign© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comPCB DesignPCB ThermalElectrical DesignerEnclosure ThermalMechanical Designer Identifying Thermal Improvement Opportunities: “Shortcut” Classic Temperature Plot – You have a problem© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comThermal Shortcut Displayed – Guidance to Solution Thermal Design Change: Introduce a Gap Pad?GAP PAD Thermal Opportunities: Shortcut Original Temperature© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comNew Temperatures – 74% Reduction in Junction Temperature Identifying Thermal Improvement Opportunities: “Bottlenecks”Temperatures with Gap Pad installed – You still have a problem© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comGAP PADEXTRUSIONEXTRUSIONThermal Bottlenecks Displayed – Guidance to SolutionThermal Design Change: Replace Gap Pad with Chassis extrusion? We Have Solved Our Thermal Problem74% Drop© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com58% Drop T3Ster Value to IC/Package Suppliers Accelerates package design process Enables better designs, more “what-ifs” Manufacturing quality checking, defect identification Fast, accurate thermal model creation© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com“We chose the T3Ster because of its compactness and ease of use, allowing us to improve data acquisition and processing of the transient thermal data.”IBM Zurich Research Laboratory“In our lab the T3Ster is used to measure the thermal resistance of our packages in customer specific environments. Thanks to the T3Ster, our measurements are quick and easy to perform.”NXP-Semiconductors VIBRATION AND STRESS VIRTUAL PROTOTYPING© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Design for ReliabilityThe Classic Highly Accelerate Life Testing (HALT) Process Time – testing can take months per passLimited availability Limited availabilityPhysical Lifecycle (Chamber HALT) Testing Takes Weeks!© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Very long term failure risks not exposed Re-design/prototype is expensive and time consuming Physical HALT vs. Virtual HALTReduce Re-spins, Faster Time-to-ResultsCircuit Design & SchematicLayoutFabricationAssemblyHALTMass ProductionPhysical Prototype & TestingCycle Spin of Weeks/Months© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comCircuit Design & SchematicLayoutHALTFabricationAssemblyMass ProductionVirtual Prototype & TestingCycle Spin of Hours/DaysReduced Design CyclesReduced Design Cycles xRobust®Virtual HALT AnalysisxRobust®Virtual HALT Results© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comPatented Technology Mentor’s xRobust® HALT Simulation Virtual prototyping of vibration— Reduces prototypes— Reduces design re-spins— Increases product reliability reliability – More design scenarios– Long term failures — Reduces TTM and development costsor© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com263 Months3 Hours“We have used Mentor’s HALT product now for five designs that will go into our new Infantry Combat Vehicle. Being able to analyze these PCBs using Mentor’s HALT technology has significantly improved our design cycle times while identifying possible reliability issues.” Israeli Ministry of Defense AVOIDING FAILURES CAUSED BY CAUSED BY ELECTROMAGNETIC INTERFERENCE© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Subtle Layout Practices Can Cause EMI Reliability Issues Layout could be electrically correct but raise risk of EMI Examples of EMI causing layout practices:— Nets crossing plane gapNets crossing plane gap— Reference plane changes— Differential pair routing— I/O nets with coupling— Via to pin ratio on connectors— ICs over splits— Exposed critical trace routingIIIcm© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Expedition’s EMI Checking During Layout PCB Expert System — Rules-based verification tool— User customizable to reflect your best practices— Enables designers to avoid compromising EMI— Reduces need for prototypes and test chamber testing© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Same Analysis for Layout DesignerSignal© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comProblem: Clock net crosses more than maximum allowable number of gaps (1 )Advice: Look at gap crossing areas (markers) and reroute net to reduce number of crossingsGround AVOIDING FAILURES CAUSED BY POWER DISTRIBUTION NETWORKS© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com System-Level Power OptimizationTrading-off Cost and Performance IC design for low power is driving need for complex Power Distribution Networks (PDNs)— Multiple voltage rails to supply lower voltages and tolerances— Increased current requirements Downstream impact on PCB/system design— More power distribution networks (PDNs)— CAD Designer must create complex area fills© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comIC requiring powerVoltage source (voltage regulator module) High Current Densities in Power Distribution Networks Common problems:— High current densities in plane neck-downs and vias— Leads to dielectric or via breakdown, board failure, fires— Causes increase in PCB and System heat dissipation© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.comICs requiring powerVoltage source (voltage regulator module) Real World Customer Example Analysis of a power rail shows cut-outs that create a current density problem.© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com Design for Reliability – Thermal Analysis Including Power Distribution Networks 3 problems exist:— Excessive heat can cause PCB de-lamination and fusing— Heat raises copper resistance and can reduce PDN voltages— PDN heat contributes to PCB and system thermal management challengesthermal management challenges© 201 0 Mentor Graphics Corp. Company Confidentialwww.mentor.com The challenge:— Analysis requires iterations to a convergent solution– Current density through copper creates heat– Heat dissipation changes the PCB/system temperature– Temperature changes resistivity of copper– Changing resistivity changes PDN current density

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