Design Guidelines for Reliable Surface Mount Technology ...

1 IPC-D-279 Design Guidelines for ReliableSurface Mount TechnologyPrinted Board AssembliesIPC-D-279 July 1996 The Institute forInterconnectingand PackagingElectronic Circuits2215 Sanders RoadNorthbrook, Illinois60062-6135 TelFaxURL:847 of .. Philosophy .. the Design Team .. Reliability Requirements .. the Product Life the Product Organization .. for Reliability of SM Assemblies .. Materials and Coatings .. Processes and .. and for Interconnecting and PackagingElectronic Circuits (IPC) .. Industries Association .. Industry Standards .. FOR RELIABILITY FOR SURFACEMOUNT Cycle Environment .. Processes .. Temperature Excursions .. and Environmental Stress Screening(ESS) .. Temperature Swings .. Shock .. Shock and Vibration .. Resistance .. Compatibility .. Radiation .. Environment .. Board Design and Design and Layout .. Design and Conformal Coating .. Patterns.

2 About Neutral Axis .. Board Trace Widths and Spaces .. and PTV Thermal Isolation/Relief .. Pads .. Between Parts .. Pads-Only with Reduced Clearances(Traces Under) .. with Reduced Clearance andOpen of Thermal Expansion (CTE)and Joint Reliability .. Design Parameters .. Design Parameters .. Hole and Via Reliability .. of SM Solder Attachments .. of Insulation Resistance .. Substrate Categories .. and Their Functions: .. and its Effects on PolymerSubstrates .. of Thermal Expansion (CTE) ofPolymer Cores in Substrates .. Board Stiffness and Printed Board with MetalSupport Plane .. Wire Structures with Metal SupportPlane .. of Polymer Substrates .. Process Effects on PolymerSubstrates .. Board Solderability .. for Reliability of Plated-Through-HoleVias (PTVs).. COMPONENT Selection Strategy .. Leadframe and Local Materials .. 20 July Lead Configuration Selection .. Wing Components.

3 Components .. Grid Pitch Surface Mount Components(PSMC) .. Termination Coplanarity Lead Configuration .. Termination Barrier and Tin-Lead Solder TerminationFinishes .. Recommendations When UsingElectrically Conductive , Palladium, Silver Termination Finishes .. of Termination Finishes .. Considerations .. Mismatch Packaging or Custom Devices Use Precaution .. to Avoid or to Use withCaution .. Selection Considerations forMilitary and Space Applications .. MASK AND CONFORMAL Mask Considerations for Mask Selection .. Mask Thickness Solder Mask and Coatings .. PROCESSES AND Design Paste Placement .. Paste Soldering .. for Manufacturability .. for Testability (DfT).. Books on SMT Process and Design .. Soldering Process Technical Solder Paste .. Cleaning .. Joint Reliability .. of Electronic Packages andPackaging .. , High Speed Transients and ElectricalOverstress.

4 Acoustic Microscopy .. Package Cracking .. Joint Metallurgy and Etching .. Thermal Design .. Fabrication Information .. Derating, Applications,Qualification .. , Manufacturability .. , Shock .. Life , Solderability, Soldered Mask and Conformal Coating .. Reliability .. 33 Appendix ADesign for Reliability (DfR) of Mount SOLDER MECHANISMS AND Joints and Attachment Types .. Expansion Mismatch .. Expansion Mismatch .. Expansion Attachment Failure .. PREDICTION Modeling .. 1 Solder Joint 2 Large TemperatureExcursions .. 3 High-Frequency/Low-Temperatures .. 4 Local Expansion Mismatch .. 5 Very Stiff Leads/Very LargeExpansion Mismatches .. 40 IPC-D-279 July Failure Distribution and FailureProbability .. Cyclic Load Histories .. Reliability Evaluation .. FACTORS FOR EMERGINGADVANCED Chip on Laminate .. Arrays (BGA, CGA).. Packages (TSOP) .. AND QUALIFICATION Joint NUMERICAL EXAMPLERELATING REQUIRED Design LIFE TOACCELERATED RELIABILITY 47 Appendix BDesign for Reliability (DfR) ofPlated-Through Via (PTV) VIA (PTV) Plating Copper Plating.

5 Copper Plating .. Mechanisms and Failure .. Quality .. Impact of Assembly Processes and ESSP rocedures .. Impact of Test Procedures and CyclicOperating Environments .. PREDICTION FACTORS FOR EMERGINGADVANCED AND QUALIFICATION 57 Appendix CDesign for Reliability (DfR) of RESISTANCE DAMAGEMECHANISMS AND Insulation Resistance (SIR).. Corrosion .. Growth .. Anodic Filaments (CAF).. RESISTANCE Resistance Degradation .. Anodic Filament Failure .. FACTORS FOR EMERGINGADVANCED AND QUALIFICATION Test Affecting SIR Readings 63 Appendix DThermal ANALYSIS AT THE Ambient Temperature of an ElectronicSystem (Ta) .. Temperature Rise of the Cooling Agentat the Device Level ( TCA).. Temperature Rise Inside the DeviceBoundary Layer ( TBL).. Temperature Rise Inside the DevicePackage ( TP) .. Wake ( TTW) .. THE SOLDER JOINTSTEMPERATURE OF ELECTRONIC .. Convection.

6 Forced Cooling .. Pipes .. Liquid Natural Convection Liquid Cooling .. Forced Liquid Cooling .. THERMAL 69 July Level Cooling .. Parts .. 69 Appendix EEnvironmental of Rework and Repair .. Transition Temperature for PrintedBoards .. Compound Transition Temperature for PlasticEncapsulating .. Vapor Pressure Effects on PlasticEncapsulated Components .. Vapor Pressure Effects on PrintedBoards .. Melt Temperature Excursion ( T) and TemperatureRate of Change ( T/ t).. Flexure .. Impact .. Discharge (ESD).. FAILURES/STRESS Derating Reference Conditions .. Most Important Stress and SomePrecautions .. Modes/Failure Mechanisms .. OF Stresses and Component Responseto OF TEMPERATURE AS ACOMPONENT STRESS Reversible/TemporaryChanges in Component Parameters .. Irreversible/PermanentChanges in Component Parameters .. of Low Temperature .. of Temperature Shock .. AND CURRENT (Electrostatic Discharge/Electrical Overstress).

7 AND GAS AND SUSCEPTIBILITY, RADIATION, ATMOSPHERICPRESSURE/HIGH 82 Appendix LEADLESS CHIP CARRIER(CLLCC).. ELECTRODE FACE BONDED(MELFs).. ABOVE SM PICK AND PLACE FEEDER WITH RUBBER SM COMPONENTS, MOISTURE,AND SM REFLOW and Resistive Shorts in PSMCs .. and Intermittent Opens in PSMCs .. Delamination and Thermal Resistance( jcDegradation).. Checklist for Power Resistors .. Resistors .. Film Resistor Networks .. Oxide Film Resistors .. chips .. Resistors .. Variable Resistor Reliability .. Ceramic Chip Capacitors .. Film 88 IPC-D-279 July Tantalum Aluminum Capacitors .. Capacitors .. Variable Piston Light Emitting Semiconductor Diode (LED) .. Digital Digital Silicon Semiconductors(MOS MSI/LSI) .. Linear Semiconductors .. Fuse .. Separable Contacts (Relays, Switches,Connectors, Sockets) .. Separable Electrical Interconnections.

8 Printed Board PTH/Vias .. Printed Board Conductor Design .. Solder 94 Appendix GCoefficient of Thermal OF THERMAL 96 Appendix HElectrostatic Susceptibility and Damage Prevention .. Limiting (ESD).. Parts and Workarounds .. Process and Handling .. Design AND Design .. Process and Handling .. ESD Design Guidelines .. Board Design Guidelines .. 1: Sensitivity Range 0 to1,999 Volts .. 2: Sensitivity Range 2,000 to3,999 Volts .. 3: Sensitivity Range 4,000 to15,999 Volts .. 4 : Sensitivity Range 16,000 VoltsCONSIDERED NON-ESD SENSITIVE.. 101 APPENDIX CLEANING SOLVENT BLEND AND OTHER 103 Appendix JDesign for FOR TESTABILITY (DfT).. AND ISSUES OF .. Level .. TO SMT Hoc Techniques .. Boundary-Scan .. BIST .. Boundary-Scan Coupled with Testing with Flying Testing .. Resistance/Capacitance Testing .. Discharge .. Optical Inspection (AOI).

9 AND CONCERNS OF Equipment .. Points .. Software .. 108 Appendix KDesign for Manufacturability andAssembly 109 July 1996 IPC-D-279viiAppendix LCorrision Basics and OF THE IN EFFECTS OF WATER AND CORROSION .. Design Corrosion .. 114 Appendix MSolder Joint JOINT 116 Appendix NAdhesives, Solder Mask and Conformal/Other Conductive AttachmentMaterials .. Conductive Attachment of Solder Masks .. Liquid Screenprinted Solder Dry Liquid Photoimageable .. MASKS AND of Coating .. Stress Design Considerations .. Stress Design Environment Design Considerations .. Design CRITICAL PROPERTIES OFSOLDER MASK AND COATINGS, GLOB-TOPS .. 124 Appendix OAerospace and High Altitude THERMAL PROPERTIES OF (OR LACK OF).. 126 Appendix PTechnical Acronyms and AbbreviationsFiguresFigure 1 1 General Design Steps .. 3 Figure 1 2 Flow Chart for Reliability Assurance Processes.

10 4 Figure 3 1 SMT Assembly Response to Thermal Shock .. 8 Figure 3 2 Thermal Relief in Ground 12 Figure 3 3 Spacing Between 13 Figure 6 1 Impact of Solder Mask Thickness onStenciling .. 25 Figure 7 1 Type 1B Assembly All SMT Components .. 25 Figure 7 2 Type 1C Assembly Mixed TechnologyAssembly .. 25 Figure 7 3 Type 2B All SMT 25 Figure 7 4 Type 2C Mixed 26 Figure A 1 Depiction of the Effects of the AccumulatingFatigue Damage in SolderJoint Structure .. 35 Figure A 2 Solder Joint Pull Strengths for Gullwing LeadsConsisting of Alloy 42 from Different Vendorsand 39 Figure A 3 Effect of Component Offsets on the FatigueReliability of Three CapacitorChip (CC) Sizes .. 44 Figure B 1 Cross-Section Schematic of a PTV With aBarrel Fracture Near the Center of the MLB .. 52 Figure B 1 Cross-Section Schematic of a PTV With aBarrel Fracture Near the Centerof the MLB .. 52 Figure B 2 Schematic Cross-Sectional View of a PTV witha Shoulder Fracture in a printed 53 Figure B 3 Reduction of Available Copper Ductility Due toLocalized Nicks Reducingthe Width of theFlexCircuit Conductors [Ref.]