Recommendations For Specification & Qualification Of .

Proposed Scope of an Automotive PCB Spec1) Initial Focus on Complex/Critical/Safety Related Rigid PCBsoProposed Title:ooRecommend Practices for Specification & Qualification of Rigid Printed CircuitBoards for Automotive Electronic ApplicationsProposed Scope:ooThis document defines recommendations and specifications governing the classification,composition, test procedures and properties of RoHS compliant, Rigid Printed CircuitBoards (PCBs) used in vehicular applications.This document applies to PCBs used in complex vehicular electronic modules that are:o Essential to vehicle operation or safety,have more than 2 conductive layers,hold more that 25 E/E components total,or have hold more than 10 E/E component types.(Need to Refine)AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com16

Proposed Purpose of an Automotive PCB Spec2) Initial Focus on Complex/Critical/Safety Related Rigid PCBsoPurpose:o The purpose of this specification is to ensure that:oAn Automotive PCB is capable of enduring appropriatelead free soldering assembly processes,without damage or degradation.oAn automotive PCB is engineered to accommodate the E/E components itis required to carry, so that the resulting Printed Circuit Board Assembly(PCBA) is a Harmonized, Robust Design capable of:ooPassing (without failures) the accelerated durability/reliability demonstratedvalidation testing requirements of the application.Meeting the in service operating-storage, reliability-durability and warrantyobjectives of the vehicle application of the PCBA.AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com17

Examples of Proposed Content of an AEC PCB Spec3a) Parameters for Enduring Pb-Free Soldering: TgoTg - Glass Transition Temperature:oooTemperature where the PCB laminate changes from a hard,glass-like state with a low (CTE) (α1) to a soft, pliable,rubber-like state with a much larger CTE (α2)The larger CTE above the Tg creates higher stresses in the PCB and on theCu Plated Through Hold (PTH) vias that connect PCB’s conductive layersMeasured by 1 of 3 methodsooooooTMA - Thermo-Mechanical Analysis per IPC-TM-650-2.4.24 “Glass Transition Temperature and Z-AxisThermal Expansion by TMA”, (denoted as Tg (TMA).DSC - Differential Scanning Calorimetry per IPC-TM-650-2.4.25 “Glass Transition Temperature &Cure Factor by DSC”, (denoted as Tg (DSC)) (method typical cited on Laminate datasheets)DMA Dynamic Mechanical Analysis - IPC-TM-650-2.4.24.4 ““Glass Transition & Modulus of Materials- DMA Method”, (denoted as Tg (DMA)Pre RoHS Tin-Lead Soldering PCB Tg’s were as low as 115 CTg’s up to 260 C for Pb-Free LaminatesFor Complex PB-Free PCBs Tg of at least 170 C (DSC) is recommendedoTrade Offs: High Tg Laminates are harder & more brittle which:- Can increase the potential for pad cratering defects- May reduce copper peel strength &- Shorten times to delamination &- Higher Tg resins cost moreAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com18

Examples of Proposed Content of an AEC PCB Spec3b) Parameters for Enduring Pb-Free Soldering: TdoTd - Decomposition Temperature:oTemperature where substance starts to chemically decomposesas heat break chemical bonds and releases of volatile compoundswhich reduces the mass of the laminateooooThe laminate is basically burning upTd5% is the temperature where 5% of the PCB laminate sample is lossMeasured by IPC-TM-640 2.4.24.6 “Decomposition Temperature (Td)of Laminate Material Using Thermogravimetric Analyzer (TGA)Td is considered to be more critical to soldering degradation mitigation than TgoTypical values for Td5% range from 310 C to 400 C for Pb-Free assemblyoFor Complex PCBs in Pb-Free Soldering, a Td5% of at least 340 is recommendedAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com19

Examples of Proposed Content of an AEC PCB Spec3c) Parameters for Enduring Pb-Free Soldering: T260/T288/T300oTime-To-Delamination:oTime to PCB delaminate after exposure to aconstant temperature of either 260 C, 288 C or 300 C,Indicator of a PCB material’s ability to withstandmultiple soldering cycles without degradationoooDelamination is the separation of the laminate layersdetermined by monitoring the PCB thickness todetect layer separation expansion.Time-to-delamination & Decomposition Td are both measures of PCB thermal stability,material data sheets may list both or one or the other.Measured by IPC-TM-650 Method 2.4.24.1 “Time to Delamination (TMA Method)”,that can be combined with measuring the Tg & the Z axis CTEoooFor Tin-Lead soldering PCB T260 5 minutes are requiredFor low end Pb-free PCBs products, T280 5 minutes is the starting pointFor Complex PCBs in Pb-Free Soldering recommendT260 60 minutes, or a T288 30 minutesAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com20

Examples Proposed Content of an AEC PCB Spec4) PCB Durability/Reliability Robustness – Test & Field ConditionsoReliability/Durability of the PCB involves the capability of the PCB toendure the application’s loads & environmental stresses over therequired service life, involves:oooooStructural Integrity - Delamination, Swelling, Corrosion, Measling, Cratering Electrical Connections - Trace/Pad Integrity, Load Capability & Adhesion, PTH Via Fatigue .Electrical Isolation Current Leakage/shorts: Dendritic Growths, CAF, Dielectric Breakdown Signal Integrity for High Frequency PCBs - Dielectric Thickness & Relative PermittivityReliability/Durability of the Assembled PCB involvesselecting a PCB material with a (CTExy) that managesthe CTE mismatch between the board and its E/E Components,so that attachment fatigue does not occur overthe thermal cycling life profile of the test or field conditions.AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com21

Similar to SAE J1879 Robustness Validation Process Presented in AEC W.4 by W. KenertID MissionProfileID Critical FailureMechanismsApply FailureMechanism ModelsRun Durability Simulations to “Engineer”the Optimum PCB Design Solution forAchieving /Durability Reliability GoalsAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com22

Example of an Engineered Robustness Solution Calculations for4a) Cu Plated Through Holes (PTH) Via Fatigue EnduranceoPTH Via Fatigue Failure is a PCBDurability IssueoooooCTEx-y13-17 ppm/ CBarrel cracks form intermittent or open circuitsPCB Z axis CTE is higher than in plane CTExyWoven Glass Fiber constrain the PCB in theX-Y plane but not through the Z axis.Thermal cycling stresses will eventually fatiguethe Cu barrels resulting in cracking aroundthe center of the barrel.Key Factors:o Board Thickness & Overall CTEzo Number of Thermal Cycles & Delta To Drill Diameter, Plating Thickness & Qualityo Larger Dia. holes w/thicker plating havemore copper to resist fatigueo Smaller diameter holes are hard to plate.AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.comCTEz30-70 ppm/ C23

4a) Use IPC-TR-579 (1988) PTH Via Barrel Cracking Fatigue Life Modelto Identify Optimum PCB CTEz for Any Thermal Cycling Profile & Durationo Determineappliedstress (σ)oDetermine strainrange ( ε)oApply calibration constantsooStrain distribution factor, Kd(2.5 –5.0)PTH & Cu quality factor KQ(0 –10)oCalculate meancycles-to-failure (Nf50)oCalculate Distribution About the Meanto Determine the Time to First FailureAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com24

4a) Example of PCB Mechanical Stack Up Analysis Calculator– Calculates fabricated PCB Properties from Dimensions & Materials for IPC-TR-579 AnalysisCalculateso Thicknesso Densityo CTE x-yo CTE zo Modulus x-yo Modulus zo From thematerialpropertiesof each layero Using the Builtin LaminateData LibraryoFrom a Library of 48 Categories OfPCB Laminate Material Properties &Characteristics from 400 Circuit BoardLaminates Materials From 25 GlobalProducers.AEC-RW 20042014- 20102007 9000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com2525

4a) Example of Physics of Failure CAE App Calculator for PTH FatigueDurability/Reliability Risk AssessmentsCalculate the Mean Fatigue Lifethen use the Weibull Slope ofthe Failure Mechanism toCalculate the StatisticalDistribution about the MeanFirstFailuresAEC-RW 20042014- 20102007Identifies if theService Life Failure Risk ofa Specific PCB Material,PTH Dimensions &Plating Thickness isAcceptable or Excessive9000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com26

4b) Example of a Thermal Cycling Solder Fatigue Model– Calculates Fatigue Life from Geometry & CTE MismatchoModified EngelmaieroooooooEnergy based fatigueDetermine the strain range (Dg)LDDaDThsWhere: C is a function of activation energy, temperature and dwell time,LD is diagonal distance, a is CTE, DT of temperature cycle & h is solder joint height Determine the shear force a 2 a1 DT LD F LD LD hs hc 2 applied at the solder joint E1 A1 E2 A2 AsGs AcGc 9 Gb a oWhere: F is shear force, LD is length, E is elastic modulus, A is the area, h is thickness,G is shear modulus, and a is edge length of bond pad.oSubscripts: 1 is component, 2 is board, s is solder joint, c is bond pad, and b is boardoTakes into consideration foundation stiffness and both shear and axial loads(Models of Leaded Components factor in lead stiffness / compliancy)FDetermine the strain energyDW 0.5 Dg Asdissipated in the solder jointCalculate Mean cycles-to-failure using: N f 0.0019 DW 1oooSemi-empirical analytical approach Dg CAn Energy Based model for SnPbThe Syed-Amkor model for SACN f 0.0006061 DW 1Calculate Distribution About the Meanto Determine the Time to First FailureAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com27

Comparison of PCB-IC Package Thermal Cycling ReliabilityLeaded IC, BGA & Flat No Lead Chip Scale Packages (CSP)oWithout a flexible terminal lead to absorb thermal Expansion/Contract motions,a high amount of thermal expansion stress is applied to the small, low profileunder body solder joints, which accelerate solder fatigue failure.oSolder Attachment Cycles to FailureoOrder of magnitude (10X) reduction from QFPso3X reduction from BGAsGull Wing Leaded QFPsTTCL: 10,000Laminated BGAs:TTCL: 3,000 to 8,000Package TypeTypical Thermal Cycles to Failure(-40C to 125C)QFP 10,000BGA3,000 – 8,000QFN1,000-3,000FNL CSP:TTCL: 1,000 to 3,000Typical Thermal Cycle Life-40 to 125 CVariations Due to IC Package Size and PCB CTE Mis-Match DifferencesAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com28

5) PCB Surface Finishes - Post Pb-FreeoA circuit board surface finish is a coating over exposedPCB copper that prevents copper oxidation.Surface Finishes, WorldwideoooPrior to RoHS Tin-Lead Hot Air Solder Leveling (HASL)was the most popular surface finish due to:ooo2003Application Ease, Material Compatibility, Low Cost.Since RoHS Multiple Pb-Free Surface Finish Several OptionsNow widely used, but none dominate.oEach PCB surface has advantages & disadvantages forfabrication, solderability, testability, reliability, shelf life.2007The 5 most popular Pb-Free Surface Finishes are:1.2.3.4.5.oTo ensure good solderability.Must dissolves away during solder to enable bondingElectroless nickel/immersion gold (ENIG)Immersion silver (ImAg)Immersion tin (ImSn)Organic Solderability Preservative (OSP)Pb-free HASL.18%No “Best Finish” - Not possible to universally require a single finish.oInstead propose an Appendix to define trade offs of eachfinish and the appropriate compensating measures.AEC-RW 2920042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.comRef: J. BeersGold Circuits29

6) Validation/Qualification of Bare PCBsoQualification, Stress Testing & Durability Characterization of PCB Materials &Design Feature is Performed on Daisy Chained Test Coupons.ooDurability Stress Testing of Design Specific Bare PCBs is not practical- No easy way to detect failures on a Bare PCBDurability Testing of an assembled PCBA that can be activated and monitored todetect failure is more practical.AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com30

6) Validation/Qualification of Bare PCBsoHowever material properties and fabrication quality can beevaluated and certified by First Article Inspections (FAI) &Direct QRD Assessments.ooA durability life test is a Indirect QRD Assessment where passing a lifetest is an indirect indicator that the item being tested has adequateQRD for the application.Direct QRD assessments use IPC & PoF material science evaluations to:ooDirectly Measures or Evaluates If Critical to QRD Material Properties andFabrication Parameter Have Been AchievedOnce the QRD of the formulation has been achieved,Evaluations to verify that the Formula is being followed are sufficientto verify the QRD will be achieved.oThis is a foundation of the Materials & Chemical Industries- Verification that a proven fundamental formulation is being followedfor each application of the technology.AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com31

6a) PCB Qualification & CoC’sCertificate of Conformance or Compliance to RequirementsoMore Than One Way to Skin theQualification Cat!ooStress Life Tests are not the onlytype of Qualification MethodsCoC - A document certified bya competent authority that thesupplied goods or service meetsrequired industry of customer specificationsooCoCs are a foundation of the Materials, Chemical and Fabrication IndustriesSome CoCs are competent, others are notooWhat Specs are reference?,Check marks or Listing of measured values compared to the requiremento Depends on competence of procurement specs, customer expectations,scrutiny & diligenceAn AEC PCB Spec Could Include Defining a RecommendedAuto Industry Common PCB CoC Format, Content & ProceduresAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com32

Redacted PCB Certificate of Conformance Example:AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com33

6a) Examples of Micro Sectioning Per IPC-IPC-TM-650-2.1.1.2a for PCB PTH QualityAssessments “First Article Inspection” - Since PCB Drill & Cu Plating Defects Will Weaken theCopper Barrel Which Will Hasten PTH Via Barrel FailureoDrilling Quality Issues & DefectsoGlass Fiber Protrusion into CopperooIrregular Drill Hole WallsooFrom Rough Drilling/Dull Drill BitNail Head SeparationooFrom Rough Drilling/Dull Drill BitFrom Drilling DamageTo Inner CopperLayersCopper Pull Away From Drill Hole Wallsor Inner Layer Connection SeparationoFrom Drill Smear Residue/ImproperDe-Smearing Cleaning ProcessAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com34

6a) Examples of Micro Sectioning Per IPC-IPC-TM-650-2.1.1.2a for PCB PTH QualityAssessments “First Article Inspection” - Since PCB Drill & Cu Plating Defects Will Weaken theCopper Barrel Which Will Hasten PTH Via Barrel FailureoPlating Quality Issues & DefectsoInsufficient Plating ThicknessooPlating VoidsooFrom Low Electroplating Current,Weak Plating Solution,Time in Solution too shortFrom Air Bubbles &Plating Solution Quality IssuesDifferences/Defects in Plating LayersoUse of Different Types of Plating Methods& Solutions can produces multiple copperstratification layers. Differences instrength, porosity, brittleness . . , etc.between the layer can lead to crackingfailures .AEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com35

6a) Examples of Micro Sectioning Per IPC-IPC-TM-650-2.1.1.2a for PCB PTH QualityAssessments “First Article Inspection” - Since PCB Drill & Cu Plating Defects Will Weaken theCopper Barrel Which Will Hasten PTH Via Barrel FailureoDamage to Via Copper PlatingoEtch Pits Holes in Barrel PlatingooEtchant Residues Trapped in Vias From ImproperOuter Layer Etching or Rework Process and FollowUp Cleaning.Copper DissolutionoCopper Dissolved into Lead Free Solder due toExcessive Exposure to Liquid Lead Free SolderAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com36

Conclusions:oThere is no universal Circuit Board SpecoPCBs need to be a cost effective, solution engineered for the applicationand the E/E components the PCB carries, to achieve:oooDegradation free endurance of Assembly Soldering Thermal StressesFor Durability/Reliability of the PCB and the PCB AssemblyThere is an Rich Foundation of Existing PCB Specifications that can beLeveraged/Referenced in an AEC Spec for Selecting and QualifyingPCB for various types of automotive applications.oTo provide guidance for specifying a PCB with optimum critical to QRDparameters for each of the wide range of automotive E/E applications.ooUnder hood, Passenger Compartment, Infotainment, Hybrid-Elect . . .Focus of a PCB Qualification SpecooMaterials PropertiesVerification of PCB Fabrication Quality (Absence of Defects)by Direct Assessments, documented in an auto industry common CoCooImpractical to Life Stress Test a Design Specific, Bare PCBFaster & Lower Cost than Stress Life TestingAEC-RW 20042014- 201020079000 Virginia Manor Rd. Suite 290, Beltsville MD 20705 301-474-0607 www.dfrsolutions.com37

Discussion - Moving ForwardoAssemble a team of PCB Experts from AEC Memberand Interested CompaniesooTo meet monthly via conf. call and/or face to face meetingto refine the proposal and develop the

o IPC-2221A is the foundation design standard for the IPC-2220 series. o Establishes the generic requirements for the design of printed boards o IPC-2222- Design Standard for Rigid Organic Printed Boards o A supplement to IPC-2221 that establishes specific requirements for the design of rigid PCBs o IPC-