PCB Design Guide to Via and Trace Currents and Temperatures

PCB Design Guide to Via and Trace Currents and Temperatures
	Contents
	Preface
	Technical Note: TRM
	Acknowledgments
	Chapter 1
Introduction and Historical Background
		1.1 Bottom Line
		1.2 Historical Background
		1.3 A Note about Consistency
		End Notes
	Chapter 2
Materials Used in PCBs
		2.1 Bottom Line
		2.2 Background
		2.3 Copper Used in PCBs
			2.3.1 Copper-clad laminates
			2.3.2 Copper Plating Manufacturing Step
			2.3.3 Copper Resistivity
			2.3.4 Summary
		2.4 Dielectrics Used in PCBs
			2.4.1 Thermal Conductivity (Tcon or k)
			2.4.2 Glass Transition Temperature (Tg)
			2.4.3 Decomposition Temperature (Td)
			2.4.4 Time to Delamination (T260/T288)
			2.4.5 Summary
		End Notes
	Chapter 3
Resistivity and Resistance
		3.1 Bottom Line
		3.2 Resistivity
		3.3 Resistance
		3.4 Thermal Coefficient of Resistivity (a)
		3.5 Measuring Resistivity
			3.5.1 Resistivity Investigation
			3.5.2 Nondestructive Measurements
		End Notes
	Chapter 4 Trace Heating and Cooling
		4.1 Bottom Line
		4.2 Overview
		4.3 Trace Heating
			4.3.1 Power and Energy
			4.3.2 Trace Heating
		4.4 Trace Cooling
			4.4.1 Conductive Cooling
		4.5 Mathematical Model of Trace Heating and Cooling
		4.6 Role of Current Density
		4.7 Measuring Trace Temperature
			4.7.1 IPC Procedure
			4.7.2 Infrared Measurement
			4.7.3 Thermocouple Measurement
			4.7.4 Point versus Average Measurements
		4.8 Trace Temperature Curves
			4.8.1 Typical Curve
			4.8.2 Heavy Overload
			4.8.3 Marginal Overload
		End Notes
	Chapter 5
IPC Curves
		5.1 Bottom Line
		5.2 IPC-2152
		5.3 Measuring the Temperature
		5.4 IPC Curves
			5.4.1 External Results
			5.4.2 External IPC Data Equations
			5.4.3 Internal IPC Data Equations
			5.4.4 IPC Vacuum Data
		End Notes
	Chapter 6
Thermal Simulations
		6.1 Bottom Line
		6.2 Background
		6.3 Modeling Traces
		6.4 The Modeling Process
		End Notes
	Chapter 7
Thermal Simulations
		7.1 Bottom Line
		7.2 Sensitivities: Layout Parameters
			7.2.1 Small Trace Widths
			7.2.2 Transient Response
			7.2.3 Thermal Gradients
			7.2.4 Changing Trace Length
			7.2.5 Dimensional Uncertainties
			7.2.6 Presence of Planes
			7.2.7 Adjacent Trace
			7.2.8 Adjacent Trace with Underlying Pla
			7.2.9 Parallel Power Traces
			7.2.10 Stacked Power Traces
			7.2.11 Air Flow
			7.2.12 Summary
		7.3 Sensitivities: Material Parameters
			7.3.1 Board Thickness and Planes
			7.3.2 Effect of Resistivity
			7.3.3 Effect of Heat Transfer Coefficien
			7.3.4 Effects of Thermal Conductivity Co
			7.3.5 Effect of Trace Thickness
			7.3.6 Summary
		7.4 Sensitivities: Trace Depth
		7.5 Conclusions
			7.5.1 Call to Action
		End Notes
	Chapter 7
Via Temperatures
		8.1 Bottom Line
		8.2 Background Information
		8.3 Thermal Simulation
			8.3.1 Simulation Strategy
			8.3.2 Board Model
			8.3.3 First Simulation
			8.3.4 Additional Simulations
			8.3.5 Two Vias
			8.3.6 Conclusion
		8.4 Experimental Verification
			8.4.1 Simulation
			8.4.2 Simulation Results
		8.5 Experimental Results
			8.5.1 Measured Results
			8.5.2 Conclusion
		8.6 Voltage Drop Across Trace and Via
			8.6.1 Summary
		8.7 Thermal Vias
			8.7.1 Special Via
			8.7.2 Conclusion
		End Notes
	Chapter 9
Current Densities in Vias
		9.1 Bottom Line
		9.2 Background
		9.3 Single Via
		9.4 Multiple Vias
		9.5 Multiple Vias and Turn
		9.6 Conclusions
		End Notes
	Chapter 10
Thinking Outside the Boxes
		10.1 Bottom Line
		10.2 Start Thinking Outside Our Boxes
		10.3 Test Board
		10.4 Copper Under the Trace
			10.4.1 Discussion
		10.5 Adding Additional Copper to Traces
			10.5.1 Discussion
		10.6 Dealing with Connecting Links
			10.6.1 Discussion
		10.7 Conclusions
		End Notes
	Chapter 11
Fusing Currents: Background
		11.1 Bottom Line
		11.2 Background
		11.3 W. H. Preece
		11.4 I. M. Onderdonk
			11.4.1 Cautions
		End Notes
	Chapter 12
Fusing Currents: Analyses
		12.1 Bottom Line
		12.2 Background
		12.3 Fusing Time and Temperature
		12.4 Assumptions and Cautions
		12.5 Simulation Models
			12.5.1 Simulation Results, TRM Fuse
			12.5.2 Simulation Results, TRM Trace
			12.5.3 Short-time Effects
			12.5.4 Final Conclusions
		12.6 Experimental Results:
			12.6.1 Heating Uncertainties
			12.6.2 Cooling Uncertainties
		12.7 The Fusing Process
			12.7.1 Strong Overload
			12.7.2 Slight Overload
		12.8 Experimental Results
			12.8.1 Case A: Fast Fusing
			12.8.2 Case B: Slow Fusing
			12.8.3 Other Cases
		12.9 Summary
		End Notes
	Chapter 13
Do Traces Heat Uniformly?
		13.1 Bottom Line
		13.2 Background
		13.3 Thermal Gradients on Traces
			13.3.1 Thermal Gradients on Narrow Trace
			13.3.2 Does Trace Thickness Matter?
			13.3.3 Is Trace Thickness Uniform?
			13.3.4 What Causes Thermal Nonuniformity
			13.3.5 Conclusion
		13.4 Thermal Gradients Around Corners
			13.4.1 Software Simulation
			13.4.2 Experimental Verification
			13.4.3 Conclusions
		End Notes
	Chapter 14
Stop Thinking about Current Density
		14.1 Bottom Line
		14.2 Background
		14.3 Current Density Is Not an Independe
		14.4 IPC Curves
		14.5 Copper Type
		14.6 Dielectric Type
		14.7 Right-Angle Corners
		14.8 Trace Form Factor
		14.9 Via Current Densities
		14.10 Conclusion
	Chapter 15 AC Currents
		15.1 Bottom Line
		15.2 Digital Simulation Models
			15.2.1 Preliminary Results
		15.3 Experimental Verification
			15.3.1 Conclusions
		15.4 Analog AC Currents
			15.4.1 Test Circuit
			15.4.2 RMS Signal Levels
			15.4.3 Nonlinearities
			15.4.4 Results
			15.4.5 Conclusion
		End Notes
	Chapter 16
Industrial CT (X-Ray) Scanning
		16.1 Bottom Line
		16.2 Background
		16.3 The Promise
		16.4 The Microsectioning Process
		16.5 Industrial CT Scanning
			16.5.1 Results
		16.6 Comparison of the Processes
		16.7 Conclusion
		End Notes
	Appendix A Measuring Thermal Conductivity
		A.1 Measurement
		End Notes
	Appendix B
Measuring Resistivity
		B.1 Resistance versus Resistivity
		B.2 How to Measure PCB Trace Resistivity
		B.3 Problem with Ohmmeter Measurement
		B.4 Sources of Measurement Error
			B.4.1 Trace Width
			B.4.2 Trace Length
			B.4.3 Trace Thickness
			B.4.4 Roughness
		B.5 An Experimental Study
			B.5.1 What Is Expected Resistivity?
		B.6 Summary
		End Notes
	Appendix C
IPC Internal and Vacuum Curves Fitted wi
	Appdendix D 
Detailed Set of Equations for the Curves
	Appendix E
Current/Temperature Curves, 0.25 to 5.0
	Appendix F
Current Density in Vias
		F.1 Interpretations
			F.1.1 Caution
			F.1.2 Symmetry
		F.2 Single Via Model
		F.3 Single Via Model with Core 1 Broken
		F.4 Simulation of Four Vias, Proceeding
		F.5 Simulation of Four Vias, Traces at R
	Appendix G Derivation of Onderdonk’s Equation
		G.1 Onderdonk’s Equation
		G.2 Background
			G.2.1 Basic Equation
			G.2.2 Solving the Equation
		G.3 Proof that α * ρ = ρ * α
		End Notes
	Appendix H
Results of All Six Fusing Configuration
	Appendix I 
Nonuniform Heating Patterns
	About the Authors
	Index