IPC-D-279 EN.pdf - 第7页

A.3.8 Statistical Failure Distribution and Failure Probability .......................................................... 40 A-3.9 Multiple Cyclic Load Histories ......................... 41 A-3.10 System Reliability Eva…

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5.3 Package Lead Configuration Selection ............ 20
5.3.1 Gull Wing Components..................................... 20
5.3.2 J-Lead Components ........................................... 20
5.3.3 Pin Grid Arrays.................................................. 20
5.3.4 Fine Pitch Components...................................... 20
5.3.5 Plastic Surface Mount Components
(PSMC) .............................................................. 21
5.3.6 Component Termination Coplanarity and
Configuration...................................................... 21
5.3.7 Component Lead Configuration........................ 21
5.4 Component Termination Finishes...................... 21
5.4.1 Nickel Barrier Layer.......................................... 21
5.4.2 Tin and Tin-Lead Solder Termination
Finishes .............................................................. 21
5.4.3 Termination Recommendations When Using
Electrically Conductive Adhesives.................... 22
5.4.4 Gold, Palladium, Silver Termination Finishes.. 22
5.5 Solderability of Termination Finishes............... 22
5.6 Soldering Considerations................................... 22
5.7 CTE Mismatch Considerations.......................... 22
5.8 ESD Packaging Requirements........................... 23
5.9 Specials or Custom Devices Use Precaution.... 23
5.10 Components to Avoid or to Use with
Caution .............................................................. 23
5.11 Component Selection Considerations for
Military and Space Applications....................... 23
6.0 SOLDER MASK AND CONFORMAL COATING
CONSIDERATION
.................................................. 23
6.1 Solder Mask Considerations for SM................. 23
6.1.1 Solder Mask Selection....................................... 24
6.1.2 Solder Mask Thickness Issues........................... 24
6.2 Temporary Solder Mask and Tapes................... 24
6.3 Conformal Coatings........................................... 24
7.0 ASSEMBLY PROCESSES AND DESIGN FOR
MANUFACTURABILITY
......................................... 24
7.1
Solder Paste Application.................................... 26
7.2
Adhesive Application......................................... 26
7.3
Component Placement....................................... 26
7.4
Soldering............................................................ 27
7.4.1
Solder Paste Reflow........................................... 27
7.4.2
Wave Soldering.................................................. 27
7.5
Cleaning ............................................................. 27
7.6
Rework/Repair ................................................... 27
7.7
Depaneling ......................................................... 28
7.8
Design for Manufacturability ........................... 28
7.8.1
Components........................................................ 28
8.0 TESTING................................................................. 28
8.1
Design for Testability (DfT).............................. 29
8.2 Testing Philosophy............................................. 29
9.0 REFERENCE DOCUMENTS ................................ 29
9.1 General Books on SMT Process and Design .. 29
9.2 SMT Soldering Process Technical Details........ 30
9.3
SMT Solder Paste.............................................. 30
9.4
SMT Cleaning.................................................... 30
9.5
Solder Joint Reliability...................................... 30
9.6 Design of Electronic Packages and
Packaging .......................................................... 30
9.7 EMC, High Speed Transients and Electrical
Overstress........................................................... 31
9.8
ESD.................................................................... 31
9.9
Scanning Acoustic Microscopy ........................ 31
9.10
Plastic Package Cracking .................................. 31
9.11
Solder Joint Metallurgy and Etching................ 31
9.12
PWA Thermal Design........................................ 31
9.13
Substrate Fabrication Information..................... 32
9.14 Component Derating, Applications,
Qualification....................................................... 32
9.15
Testability, Manufacturability............................ 32
9.16
Vibration, Shock ................................................ 32
9.17
Accelerated Life Testing.................................... 33
9.18 Solder, Solderability, Soldered Assembly
Quality................................................................ 33
9.19
Solder Mask and Conformal Coating ............... 33
9.20
General Reliability............................................. 33
Appendix A Design for Reliability (DfR) of Solder
Attachments
A-1.0 SURFACE MOUNT SOLDER ATTACHMENT
RELIABILITY
...................................................... 34
A-2.0 DAMAGE MECHANISMS AND FAILURE......... 34
A-2.1
Solder Joints and Attachment Types................. 34
A-2.2
Global Expansion Mismatch ............................. 36
A-2.3
Local Expansion Mismatch............................... 36
A-2.4
Internal Expansion Mismatch............................ 36
A-2.5
Solder Attachment Failure................................. 36
A-3.0 RELIABILITY PREDICTION MODELING.......... 36
A-3.1
Creep-Fatigue Modeling.................................... 36
A-3.2
Damage Modeling.............................................. 37
A-3.3
CAVEAT 1 — Solder Joint Quality.................. 38
A-3.4 CAVEAT 2 — Large Temperature
Excursions.......................................................... 38
A-3.5 CAVEAT 3 — High-Frequency/
Low-Temperatures ............................................. 39
A-3.6
CAVEAT 4 — Local Expansion Mismatch...... 39
A.3.7 CAVEAT 5 — Very Stiff Leads/Very Large
Expansion Mismatches ..................................... 40
IPC-D-279 July 1996
iv
A.3.8 Statistical Failure Distribution and Failure
Probability.......................................................... 40
A-3.9
Multiple Cyclic Load Histories......................... 41
A-3.10
System Reliability Evaluation........................... 41
A-4.0 DfR-PROCESS ................................................... 42
A-5.0 CRITICAL FACTORS FOR EMERGING
ADVANCED TECHNOLOGIES
.......................... 42
A-5.1
Flip Chip on Laminate ...................................... 42
A-5.2
Area Arrays (BGA, CGA)................................. 43
A-5.3
Thin Packages (TSOP)...................................... 43
A-6.0 VALIDATION AND QUALIFICATION TESTS.... 44
A-7.0 SCREENING PROCEDURES ............................ 44
A-7.1
Solder Joint Defects........................................... 44
A-7.2
Screening Recommendations............................. 45
A-8.0 STEP-BY-STEP NUMERICAL EXAMPLE
RELATING REQUIRED DESIGN LIFE TO
ACCELERATED RELIABILITY TEST
RESULTS
............................................................ 45
A-9.0 REFERENCES.................................................... 47
Appendix B Design for Reliability (DfR) of
Plated-Through Via (PTV) Structures
B-1.0 PLATED-THROUGH VIA (PTV) RELIABILITY
ISSUES
............................................................... 50
B-1.1
Copper Plating Process...................................... 50
B-1.1.1
Acid Copper Plating.......................................... 50
B-1.1.2
Pyrophosphate Copper Plating.......................... 51
B-1.2
Material Properties............................................. 51
B-1.2.1
Tensile Properties............................................... 51
B-1.2.2
Ductility.............................................................. 51
B-1.2.3
Fatigue Behavior................................................ 51
B-1.3
Damage Mechanisms and Failure..................... 52
B-1.3.1
PTV Quality....................................................... 52
B-1.3.2 Impact of Assembly Processes and ESS
Procedures.......................................................... 53
B-1.3.3 Impact of Test Procedures and Cyclic
Operating Environments.................................... 54
B-2.0 RELIABILITY PREDICTION MODELING.......... 54
B-3.0 DfR-PROCESS ................................................... 56
B-4.0 CRITICAL FACTORS FOR EMERGING
ADVANCED TECHNOLOGIES
.......................... 57
B-5.0 VALIDATION AND QUALIFICATION TESTS.... 57
B-6.0 SCREENING PROCEDURES ............................ 57
B-7.0 REFERENCES.................................................... 57
Appendix C Design for Reliability (DfR) of Insulation
Resistance
C-1.0 INSULATION RESISTANCE DAMAGE
MECHANISMS AND FAILURE
.......................... 59
C-1.1
Surface Insulation Resistance (SIR).................. 59
C-1.2
Electrochemical Corrosion ................................ 59
C-1.3
Dendrite Growth................................................ 60
C-1.4
Conductive Anodic Filaments (CAF)................ 60
C-2.0 INSULATION RESISTANCE MODELING.......... 60
C-2.1
Insulation Resistance Degradation .................... 60
C.2.2
Conductive Anodic Filament Failure ................ 61
C-3.0 DfR-PROCESS ................................................... 61
C-4.0 CRITICAL FACTORS FOR EMERGING
ADVANCED TECHNOLOGIES
.......................... 62
C-5.0 VALIDATION AND QUALIFICATION TESTS.... 62
C-5.1
SIR Test Procedures........................................... 62
C-5.1.1
Factors Affecting SIR Readings Geometry....... 62
C-6.0 SCREENING PROCEDURES ............................ 63
C-7.0 REFERENCES ................................................... 63
Appendix D Thermal Considerations
D-1.0 GENERAL
........................................................... 65
D-2.0 THERMAL ANALYSIS AT THE DEVICE
LEVEL
................................................................. 65
D-2.1 The Ambient Temperature of an Electronic
System (T
a
)........................................................ 65
D-2.2 The Temperature Rise of the Cooling Agent
at the Device Level (∆T
CA
)............................... 66
D-2.3 The Temperature Rise Inside the Device
Boundary Layer (∆T
BL
)..................................... 66
D-2.4 The Temperature Rise Inside the Device
Package (∆T
P
).................................................... 66
D-2.5
Thermal Wake (∆T
TW
) ...................................... 66
D-3.0 DETERMINING THE SOLDER JOINTS
TEMPERATURE SWINGS
.................................. 66
D-4.0 COOLING OF ELECTRONIC EQUIPMENT...... 67
D-4.1
Radiation............................................................ 67
D-4.2
Free Convection................................................. 67
D-4.3
Direct Forced Convection.................................. 67
D-4.4
Conduction Cooling........................................... 67
D-4.5
Heat Pipes.......................................................... 67
D-4.6
Direct Liquid Cooling........................................ 68
D-4.6.1
Direct Natural Convection Liquid Cooling ...... 68
D-4.6.2
Direct Forced Liquid Cooling........................... 68
D-5.0 PRODUCT THERMAL DESIGN......................... 69
July 1996 IPC-D-279
v
D-5.1
Component Level Cooling ................................ 69
D-5.2
Hot Parts ............................................................ 69
Appendix E Environmental Stresses
E-1.0 THERMAL
........................................................... 72
E-1.1
Effects of Rework and Repair........................... 72
E-1.2 Glass Transition Temperature for Printed
Boards ............................................................... 72
E-1.3
Intermetallic Compound Growth....................... 72
E-1.4 Glass Transition Temperature for Plastic
Encapsulating..................................................... 72
E-1.5 Water Vapor Pressure Effects on Plastic
Encapsulated Components................................. 73
E-1.6 Water Vapor Pressure Effects on Printed
Boards ................................................................ 73
E-1.7
Solder Melt Temperature Effects....................... 73
E-1.8 Temperature Excursion (∆T) and Temperature
Rate of Change (∆T/∆t)..................................... 73
E-2.0 CHEMICAL.......................................................... 74
E-2.1
PWA Cleanliness................................................ 74
E-3.0 MECHANICAL..................................................... 74
E-3.1
PWA Flexure...................................................... 74
E-3.2
Tooling Impact................................................... 74
E-4.0 ELECTRICAL...................................................... 74
E-4.1
Electrostatic Discharge (ESD)........................... 74
E-5.0 SMT FAILURES/STRESS CONDITIONS........... 74
E-5.1
Component Derating Reference Conditions ..... 74
E-5.2 The Most Important Stress and Some
Precautions......................................................... 74
E-5.3
Failure Modes/Failure Mechanisms .................. 74
E-6.0 OVERVIEW OF STRESSES............................... 74
E-6.1 Common Stresses and Component Response
to Stress.............................................................. 74
E-7.0 IMPORTANCE OF TEMPERATURE AS A
COMPONENT STRESS FACTOR
...................... 75
E-7.1 Temperature-Related Reversible/Temporary
Changes in Component Parameters .................. 75
E-7.2 Temperature-Related Irreversible/Permanent
Changes in Component Parameters .................. 75
E-7.3
Effects of Low Temperature.............................. 76
E-7.4
Effects of Temperature Changes........................ 76
E-7.5
Thermal Shock................................................... 77
E-8.0 POWER............................................................... 77
E-9.0 VOLTAGE............................................................ 77
E-10.0 CURRENT AND CURRENT DENSITY ............ 78
E-11.0 ESD/EOS (Electrostatic Discharge/
Electrical Overstress)
...................................... 78
E-12.0 MOISTURE AND HUMIDITY............................ 79
E-13.0 CORROSIVE GAS AMBIENT .......................... 79
E-14.0 TEMPERATURE/HUMIDITY/BIAS.................... 80
E-15.0 SAND AND DUST ............................................ 80
E-16.0 MECHANICAL SHOCK .................................... 80
E-17.0 MECHANICAL VIBRATION.............................. 80
E-18.0 MECHANICAL OVERLOAD............................. 81
E-19.0 EM SUSCEPTIBILITY, RADIATION,
INTERFERENCE
............................................... 81
E-20.0 LOW ATMOSPHERIC
PRESSURE/HIGH ALTITUDE/VACUUM
.......... 81
E-21.0 IONIZING RADIATION...................................... 81
E-22.0 SOLVENTS........................................................ 82
Appendix F Components
F-1.0 CERAMIC LEADLESS CHIP CARRIER
(CLLCC)
.............................................................. 83
F-2.0 METAL ELECTRODE FACE BONDED
(MELFs)
............................................................... 83
F-3.0 SPACING ABOVE BOARD ................................ 83
F-4.0 ALL SM PICK AND PLACE FEEDER PARTS.. 83
F-5.0 COMPONENTS WITH RUBBER SEALS........... 83
F-6.0 PLASTIC SM COMPONENTS, MOISTURE,
AND SM REFLOW PROCESSING
.................... 83
F-6.1
Shorts and Resistive Shorts in PSMCs............. 84
F-6.2
Opens and Intermittent Opens in PSMCs ....... 84
F-6.3 PSMC Delamination and Thermal Resistance
(θ
jc
Degradation)................................................ 85
F-7.0 RESISTORS........................................................ 85
F-7.1
A Checklist for Power Resistors....................... 85
F-7.2
Trimmed Resistors............................................. 86
F-7.3
Fixed Resistors................................................... 86
F-7.3.1
Metal Film Resistors.......................................... 86
F-7.3.2
Thick-Film Resistor Networks.......................... 86
F-7.3.3
Metal Oxide Film Resistors .............................. 86
F-7.3.4
Resistor chips .................................................... 86
F-7.4
Variable Resistors ............................................. 87
F-7.4.1
Enhancing Variable Resistor Reliability ........... 87
F-8.0 CAPACITORS...................................................... 88
F-8.1
Multilayer Ceramic Chip Capacitors ................ 88
F-8.2
Plastic Film Capacitors...................................... 88
IPC-D-279 July 1996
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