Design for Reliability: PCBs - DfR Solutions

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Electroless Nickel/Immersion Gold (ENIG)• Two material system.• Defined by IPC-4552 Specification forElectroless Nickel/Immersion Gold.• Electroless nickel.• 3 – 6 microns• Thin Immersion gold top coat• 0.08-0.23 microns• Benefits• Excellent flatness and long-term storage (shelf life).• Excellent oxidation resistance and wetting properties.• Robust for multiple reflow cycles,• Supports alternate connections (wirebond, separable connector) & electrical testability.• Moderate costs.• Gold readily dissolves into solder and does not tarnish or oxidizemaking it an excellent choice for a surface finish.• But gold cannot be directly plated onto copper, since copper diffuses into gold,which allows the Cu to reach the surface and oxidize which reduces solderability.• Nickel is serves as a barrier layer to copper,the thin gold coating protects the nickel from oxidizing.© 2004 - 2007 2010
Unreliability, F(t)ENIG: Mechanical Shock with SAC305 solder• ENIG Less Robust than OSP.• SAC less robust than SnPb• Plating is an important driver• SnNi vs. SnCu intermetallicsR eliaSoft's W eibull++ 6.0 - w w w .W eibull.c om99.0090.0050.00Probability - WeibullSAC305 on ENIGSAC305 on OSPW eibullPb-Free on ENIGW3 RR3 - SRM MEDF= 6 / S= 0Pb-Free on OSPW3 RR3 - SRM MEDF= 5 / S= 1SnPb on OSPW3 RR3 - SRM MEDF= 3 / S= 310.005.00SnPb on OSP1.001.00 10.00100.00Number of DropsCraig HillmanDfR Solutions7/29/2005 10:27 35x35mm, 312 I/O BGA© 2004 - 2007 2010
Page 1 and 2:
Design for Reliability: PCBsNorth T
Page 3 and 4:
Course OutlineINTRODUCTIONSooIntro
Page 5 and 6:
Why Design for Reliability (DfR)?o
Page 7 and 8:
Physics of Failure DefinitionsoFail
Page 9 and 10:
A Word on Quality, Reliability & Cl
Page 11 and 12:
PCB Materials / Laminate Selectiono
Page 13 and 14:
Laminate DatasheetsooOut-of-plane C
Page 15 and 16:
Glass StyleoooPCB laminates (and pr
Page 17 and 18:
Laminate Properties (cont.)oMore re
Page 19 and 20:
Thermal Parameters and IPC Slash Sh
Page 21 and 22:
PTV Degradation due to Assembly© 2
Page 23 and 24:
PCB Materials: StackupoMaximum stre
Page 25 and 26:
PCB ViasPlated Through Holes© 2004
Page 27 and 28:
How to Design a Reliable PTV?PTH Ar
Page 29 and 30:
PCB Industry PTV Capability95% of I
Page 31 and 32:
IPC TR-579oRound Robin Reliability
Page 33 and 34:
IPC TR-579 (cont.)oDetermine strain
Page 35 and 36:
IPC TR-579 (cont.)o Iteratively cal
Page 37 and 38:
The Effect of Design Parameters (He
Page 39 and 40:
Effect of Design Parameters (cont.)
Page 41 and 42:
Plating (Thickness and Material Pro
Page 43 and 44:
Case Study: Microvia Fill and PTV R
Page 45 and 46:
Plating Mechanical PropertiesoIndus
Page 47 and 48:
Cycles to FailureThe Reality of PTV
Page 49 and 50:
Post-Plating MeasurementsoHardness
Page 51 and 52:
Other Platings (cont.)oS. Neumann,
Page 53 and 54: Test / Qualify PTVoQualifying PTV i
Page 55 and 56: Simulation and ModelingoSecond step
Page 57 and 58: Initial Qualification (PCQR2)oQuali
Page 59 and 60: Lot QualificationoInterconnect stre
Page 61 and 62: ConclusionoThe base knowledge and u
Page 63 and 64: CAF: ExamplesInfluenced by electric
Page 65 and 66: Strain Flexure Issues & Pad Crateri
Page 67 and 68: Strain & Flexure: Pad CrateringoCra
Page 69 and 70: Potential Mitigations to Pad Crater
Page 71 and 72: Pad Geometry• Pad design influenc
Page 73 and 74: Future of Contamination / Cleanline
Page 75 and 76: Failure ModeoWhy do you care about
Page 77 and 78: ECM MechanismsoooSome ECM Mechanism
Page 79 and 80: Nominal Ionic LevelsooooBare printe
Page 81 and 82: Process Material Qualification - SI
Page 83 and 84: Importance of Surface FinishooooThe
Page 85 and 86: Surface Finish Selection Approachoo
Page 87 and 88: Surface Finish Selection GuidelineA
Page 89 and 90: OSP Issues: Plated Through-Hole Fil
Page 91 and 92: Surface Finish Selection GuidelineP
Page 93 and 94: ImAg Trace EtchingSolder maskGalvan
Page 95 and 96: Typical Creep Corrosion• Corrosio
Page 97 and 98: Wetting Force ( mN/mm)Impact of Tar
Page 99 and 100: Immersion Sn (ImSn)• A single mat
Page 103: ENIG - Ni Interface Issues w/ SACBr
Page 109 and 110: Pb-Free HASL: Ni-modified SnCuoAllo
Page 111 and 112: Newer Finishes to the MarketProduct
Page 113 and 114: Newer Finishes to the MarketProduct
Page 115 and 116: Examples of Best Application Fitsoo
Page 117 and 118: What to do if there is no SF fit?oo
Page 119 and 120: SummaryoooooThe surface finish you
Page 121 and 122: ConclusionsoooDesign for Reliabilit
Page 123: Contact Information• Questions?
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