IPC-D-279 EN.pdf - 第9页
F-8.3 Solid T antalum Capacitors................................. 89 F-8.4 Electrolytic Aluminum Capacitors .................... 89 F-8.5 V ariable Capacitors ............................................ 89 F-8.5.1 V ari…
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
vi
F-8.3 Solid Tantalum Capacitors................................. 89
F-8.4 Electrolytic Aluminum Capacitors .................... 89
F-8.5 Variable Capacitors............................................ 89
F-8.5.1 Variable Piston Capacitors................................. 89
F-9.0 INDUCTOR/TRANSFORMERS ......................... 90
F-10.0 SEMICONDUCTORS ........................................ 90
F-10.1 Light Emitting Semiconductor Diode (LED) ... 90
F-10.2 Digital Semiconductors...................................... 91
F-10.3 Digital Silicon Semiconductors
(MOS MSI/LSI)................................................. 91
F-10.4 Linear Semiconductors...................................... 91
F-11.0 OTHER COMPONENTS ................................... 91
F-11.1 Fuse.................................................................... 91
F-11.2 Separable Contacts (Relays, Switches,
Connectors, Sockets) ......................................... 91
F-11.2.1 Batteries.............................................................. 92
F-11.2.2 Separable Electrical Interconnections ............... 92
F-12.0 PRINTED BOARD............................................. 93
F-12.1 Printed Board PTH/Vias.................................... 93
F-12.2 Printed Board Conductor Design...................... 94
F-12.3 Solder Joints....................................................... 94
Appendix G Coefficient of Thermal Expansion
G-1.0 COEFFICIENT OF THERMAL EXPANSION
..... 96
G-2.0 CONSTRAINING CORES .................................. 96
Appendix H Electrostatic Discharge
H-1.0 INTRODUCTION
................................................. 99
H-1.1 ESD Susceptibility and Damage Prevention .... 99
H-1.2 Current Limiting (ESD)..................................... 99
H-1.3
Susceptible Parts and Workarounds.................. 99
H-1.4
Assembly Process and Handling....................... 99
H-2.0 ESD DESIGN AND CHECKLIST....................... 99
H-2.1
Hardware Design ............................................... 99
H-2.2
Assembly Process and Handling....................... 99
H-2.2.1
Firmware/Software ESD Design Guidelines .... 99
H-2.2.2
Printed Board Design Guidelines .................. 100
H-2.2.3
Components...................................................... 100
H-2.2.4
Cable ................................................................ 100
H-2.3 CLASS 1: Sensitivity Range 0 to
1,999 Volts ....................................................... 100
H-2.4 CLASS 2: Sensitivity Range 2,000 to
3,999 Volts ....................................................... 101
H-2.5 CLASS 3: Sensitivity Range 4,000 to
15,999 Volts ..................................................... 101
H-2.6 CLASS ‘‘4’’: Sensitivity Range 16,000 Volts
CONSIDERED NON-ESD SENSITIVE........ 101
APPENDIX I Solvents
I-1.0 INTRODUCTION
................................................. 102
I-2.0 MATERIALS AFFECTED................................... 102
I-3.0 COMMON CLEANING SOLVENT FAMILIES ... 103
I-4.0 HCFC BLEND AND OTHER DATA................... 103
Appendix J Design for Testability
J-1.0 DESIGN FOR TESTABILITY (DfT)
................... 105
J-1.1 Controllability.................................................. 105
J-1.2 Observability/Visibility.................................... 105
J-1.3 Partitioning....................................................... 105
J-2.0 STANDARDS..................................................... 105
J-2.1 General............................................................. 105
J-2.2 Testability......................................................... 105
J-3.0 SUBSTRATE TESTING..................................... 105
J-4.0 CHIP TESTING.................................................. 106
J-5.0 PROBLEMS AND ISSUES OF UNPACKED
ICs
...................................................................... 106
J-5.1 Availability....................................................... 106
J-5.2 Confidence Level............................................. 106
J-5.3 Vendor Concerns.............................................. 106
J-5.4 User Concerns.................................................. 106
J-5.5 Standards.......................................................... 106
J-6.0 ASSEMBLY TESTING....................................... 106
J-7.0 APPROACHES TO SMT TESTING.................. 106
J-7.1 Ad Hoc Techniques ......................................... 107
J-7.2 Structured Techniques...................................... 107
J-7.2.1 Boundary-Scan................................................. 107
J-7.2.2 BIST................................................................. 107
J-7.2.3 Boundary-Scan Coupled with BIST................ 107
J-7.3 Resistive Testing with Flying Probes.............. 107
J-7.4 Capacitance Testing ......................................... 107
J-7.5 Combined Resistance/Capacitance Testing..... 107
J-7.6 Glow Discharge ............................................... 107
J-7.7 Automatic Optical Inspection (AOI)............... 107
J-8.0 ISSUES AND CONCERNS OF TESTING........ 108
J-8.1
Test Equipment ................................................ 108
J-8.2
Test Points........................................................ 108
J-8.3
Costs................................................................. 108
J-8.4
CAD/CAE Software ........................................ 108
Appendix K Design for Manufacturability and
Assembly Checklist
K-1.0 SUMMARY
........................................................ 109
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vii
Appendix L Corrision Basics and Checklist
L-1.0 CORROSION BASICS
...................................... 111
L-2.0 CORROSION OF THE PWA............................. 111
L-3.0 CORROSION IN COMPONENTS..................... 111
L-4.0 OTHER EFFECTS OF WATER AND WATER
VAPOR
............................................................... 111
L-5.0 FRETTING ‘‘CORROSION’’.............................. 112
L-6.0 CORROSION DESIGN CHECKLIST................ 112
L-6.1 Galvanic Corrosion.......................................... 114
Appendix M Solder Joint Variability
M-1.0 SOLDER JOINT VARIABIALITY
..................... 116
Appendix N Adhesives, Solder Mask and Conformal/
Other Coatings
N-1.0 ADHESIVES
...................................................... 119
N-1.1 Electrically Conductive Attachment
Materials........................................................... 119
N-1.2 Thermally Conductive Adhesives.................... 119
N-1.3 Mechanical Attachment Adhesives.................. 119
N-2.0 SOLDER MASK................................................ 119
N-2.1 Types of Solder Masks.................................... 120
N-2.1.1 Liquid Screenprinted Solder Mask.................. 120
N-2.1.2 Dry Film........................................................... 120
N-2.1.3 Liquid Photoimageable.................................... 121
N-3.0 TEMPORARY MASKS AND STOPS............... 121
N-4.0 CONFORMAL COATING.................................. 121
N-4.1 Selection of Coating ....................................... 122
N-4.2 Thermal Stress Design Considerations ........... 122
N-4.3 Chemical Stress Design Considerations.......... 122
N-4.4 Space Environment Design Considerations.... 122
N-4.5 Manufacturing Considerations......................... 122
N-4.6 Other Design Considerations........................... 122
N-5.0 COMMON CRITICAL PROPERTIES OF
SOLDER MASK AND CONFORMAL
COATINGS
........................................................ 123
N-6.0 JUNCTION COATINGS, ‘‘GLOB-TOPS’’......... 124
Appendix O Aerospace and High Altitude Concerns
O-1.0 INTRODUCTION
............................................... 125
O-2.0 THERMAL DESIGN.......................................... 125
O-3.0 LARGE THERMAL EXCURSIONS.................. 125
O-4.0 CONTAMINATION ............................................ 125
O-5.0 RADIATION ENVIRONMENT........................... 126
O-6.0 ELECTRICAL PROPERTIES OF GASES....... 126
O-7.0 GRAVITY (OR LACK OF)................................ 126
Appendix P Technical Acronyms and Abbreviations
Figures
Figure 1−1
General Design Steps.......................................... 3
Figure 1−2
Flow Chart for Reliability Assurance Processes.. 4
Figure 3−1
SMT Assembly Response to Thermal Shock ...... 8
Figure 3−2
Thermal Relief in Ground Planes....................... 12
Figure 3−3
Spacing Between Parts...................................... 13
Figure 6−1 Impact of Solder Mask Thickness on
Stenciling............................................................ 25
Figure 7−1
Type 1B Assembly − All SMT Components....... 25
Figure 7−2 Type 1C Assembly − Mixed Technology
Assembly............................................................ 25
Figure 7−3
Type 2B − All SMT Components........................ 25
Figure 7−4
Type 2C − Mixed Technology............................. 26
Figure A−1 Depiction of the Effects of the Accumulating
Fatigue Damage in Solder
Joint Structure.................................................... 35
Figure A−2 Solder Joint Pull Strengths for Gullwing Leads
Consisting of Alloy 42 from Different Vendors
and Copper......................................................... 39
Figure A−3 Effect of Component Offsets on the Fatigue
Reliability of Three Capacitor
Chip (CC) Sizes ................................................. 44
Figure B−1 Cross-Section Schematic of a PTV With a
Barrel Fracture Near the Center of the MLB..... 52
Figure B−1 Cross-Section Schematic of a PTV With a
Barrel Fracture Near the Centerof the MLB ...... 52
Figure B−2 Schematic Cross-Sectional View of a PTV with
a Shoulder Fracture in a printed board.............. 53
Figure B−3 Reduction of Available Copper Ductility Due to
Localized Nicks Reducingthe Width of the
FlexCircuit Conductors [Ref. B-7: 25] and PTV
Stress Concentration Factor, K
c
......................... 56
Figure D−1
Thermal Vias and Planes................................... 70
Figure D−2
Other Methods of Conductive Heat Transfer..... 70
Figure D−3
Use of Heat Slug................................................ 71
Tables
Table 1−1
The Design Team................................................. 1
Table 3−1 Realistic Representative
(1)
Use Environments,
Service Lives, and Acceptable Failure
Probabilities for Surface Mounted Electronics
Attachments by Use Categories .......................... 6
Table 4−1 Advantages and Disadvantages of Various
Types of Substrates ........................................... 18
Table 6−1
Solder Mask Guidelines..................................... 24
Table A−1 Realistic Representative
(1)
Use Environments,
Service Lives, and Acceptable Failure
Probabilities for Surface Mounted Electronics
Attachments by Use Categories ........................ 35
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