PCB Design Information.
Here is some useful information for designing general-use printed circuit boards. For other designs and materials, a good source for information is: Design Standard for Rigid Printed Boards and Rigid Printed Board Assemblies IPC-D-275 published by the Institute for Interconnecting and Packaging Electronic Circuits (IPC) 7380 Lincolnwood Avenue Lincolnwood, IL 60646
Environmental Factors
The environment in which a PCB is to be used will change a number of factors needed to design and test it. The ambient temperature is one of these important factors.
Worst Case Environments
Cat
USE
Min Temp
Max Temp
Service
1
Consumer
0°C
+60°C
1-3 Yrs
2
Computer
+15°C
~5 Yrs
3
Telecomm
-40°C
+85°C
7-20 Yrs
4
Civ Aircraft
-55°C
+95°C
~10 Yrs
5
Industrial
+55°C
Auto Pass Cmp
6
Mil Gnd/Ship
7
Space
5-20 Yrs
8
Mil Aircraft
9
Auto Engine
+125°C
PCB Base Material
The base material a PCB is made of also affects it's design. Here are some examples materials.
PCB Base Laminate Data
Designation
Dielectric Thickness
ANSI
MIL-P-13949
-
PX
105°C
GE
125°C
FR-4
GF
.004-.014"
120°C
.015 +
130°C
FR-5
GH
.025-.054"
140°C
.055 +
170°C
Trace width calculation
Trace width calculations are derived from a paper presented at IPCWorks '97, "Emperical equation for sizing copper PWB traces" by John McHardy and Mehendra Gandhi, Hughes Aircraft. Technical paper SO6-2-1.
Thanks to:
Ralph Hersy at
Ralph Hersey & Associates
3885 Mills Way
Livermore, CA 94550-3319
PHN: 510.454.9805
FAX: 510.454.9805
e-mail: rjhersey@ix.netcom.com
The formula is:
I = kT0.44A0.725
where:
I = maximum current in Amps
k = derating constant (.024 for inner, .048 for outer)
T = maximum temperature rise above ambient in °C
A = cross-sectional area in square mils (NOT millimeters)
Trace Spacing Guidelines
Conductor Spacing
Voltage Between Conductors (VDC or Peak)
Minimum Spacing (inches)
Bare Board
Assembly
B1
B2
B3
B4
A5
A6
A7
0 thru 15
.004
.025
.005
16 thru 30
.010
31 thru 50
.015
51 thru 100
.060
.020
101 thru 150
.008
.125
.030
151 thru 170
.050
171 thru 250
.250
251 thru 300
.500
301 thru 500
.100
More than 500
.0001 /Volt
.0002 /Volt
.001 /Volt
.00012 /Volt
B1 - Internal Conductors B2 - External Conductors, uncoated, sea level to 10,000 ft. B3 - External Conductors, uncoated, over 10,000 ft. B4 - External Conductors, with permanent polymer coating (soldermask). A5 - External Conductors, with conformal coating over assembly. A6 - External Component lead/termination, uncoated. A7 - External Component lead/termination, with conformal coating.
NOTE: This information is provided as a guideline only. All efforts have been made to ensure it is correct, but it is the responsibility of the user to verify the data is correct for their application.
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