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IPC Current Carrying Capacity Task Group (1-10b)
August 2008
Michael R. Jouppi, Thermal Man, Inc., Task Group Chair
IPC-2152, Standard for Determining Current-Carrying Capacity in
Printed Board Design
Mike Jouppi is a mechanical engineer who specializes in heat transfer. He has a bachelor’s of science in mechanical engineering from the University of Arizona and a master’s of science in computer information systems from Regis University.
Mike has been a thermal analyst since 1982. He has been a team member on projects such as the International Space Station, satellites, airships, missiles systems and, most recently, the Mars Lander.
Mike started with the IPC-1-10b task group in 1999 and has chaired the group since 2000.
IPC-2152
Introduction- The amount of current that can be applied to a conductor
and its resulting temperature rise is a printed circuit board (PCB) design concern.• Design constraints have created a need for more
precise guidelines for sizing conductors than those currently found in IPC-2221.
- Simple and accurate design guidelines, with an explanation to their origin, is the vision for IPC-2152.
Vision: Simple and Accurate Design Guidelines
Standard for Determining Current Carrying Capacity in Printed Board Design
IPC-2152 Introduction- The temperature rise of a PCB conductor is a complex
problem, yet the desire is to have general guidelines.- A compromise has resulted that provides general
guidelines in a main document and detailed guidelines in an attached appendix.
IPC-2152 is divided into two sections, a main document with simple charts and an appendix that discusses details that impact the temperature rise of a conductor and more.
IPC-2152 Introduction- The new standard is based on testing that was
performed following IPC-TM-650, Method 2.5.4.1a, Conductor Temperature Rise Due to Current Changes in Conductors.
- Computer simulations were also used to improve the understanding of the impact that certain variables have on the temperature rise of a conductor.
IPC-2152 is based on industry standards test procedures and correlated computer simulations.
IPC-2152 Test Considerations
- Environment• Testing was performed in air and vacuum
- Internal and external conductors- PCB thickness
• 0.038-inch, 0.059-inch and 0.07-inch thick test vehicles- Copper thickness/weight (1/2-oz, 1-oz, 2-oz and 3-oz)- PCB material
• Polyimide and FR4 test vehicles
Current carrying capacity testing considered multiple environments, conductor width and thickness, PCB thickness
and PCB materials.
IPC-2152
Test ResultsEnvironment: Still air vs. vacuum
- Internal conductors in a board tested in vacuum are 55 percent higher in temperature rise than the same conductors in a still air environment.
- External conductors in a board tested in vacuum are 35 percent higher in temperature rise than the same conductors in a still air environment.
Conductors run hotter in a vacuum than in air by as much as 55% or more.
Test ResultsConductors: Comparing internal vs. external conductors
- An external conductor designed for a 10oC rise will operate 20 percent higher in temperature than the same size internal conductor in a still air environment.
- Identical external and internal conductors in a vacuum experience the same increase in temperature for the same applied current.
External conductors run hotter than internal traces in a still air environment.
IPC-2152
Test Results
Board Thickness: Conductor temperature and PCB thickness
- Conductors in a 0.965 mm (0.038 in.) thick PCB are approximately 30 to 35 percent higher in temperature than in a 1.78 mm (0.07 in.) thick PCB.
- Conductors in a 1.498 mm (0.059 in.) thick PCB are approximately 20 percent higher in temperature than in a 1.78 mm (0.07 in.) thick PCB.
- Test boards thicker than 1.78 mm have not been evaluated.
Conductors in thin PCBs run hotter than thesame size conductor in thicker PCBs.
IPC-2152
Test Results
Comparing Copper Weights:- Half-ounce copper conductors are similar in temperature rise for the
same size cross-sectional area as 1 oz. conductors.
- Two ounce copper conductors increase in temperature by 10 to 15 percent above 1 oz. conductors for the same size trace and applied current.
- Three ounce copper conductors increase in temperature by 15 to 20 percent above 1 oz. conductors for the same size trace and applied current.
- The higher percentages are related to a 45oC delta T and the lower percentages are related to a 10oC rise.
For the same cross-sectional area a wider conductor (1 oz.) will run 15 to 20 percent cooler than a narrow conductor (3 oz).
IPC-2152
Main Document- Designed to be as simple as possible with
conservative guidelines for sizing conductors.- The IPC-2221 internal conductor sizing chart will be
kept as the most conservative chart to use for sizing conductors.
- A single chart is included that envelopes both internal and external conductors in air environments• External conductor heating data from a 1.78 mm (0.07 in.)
thick PCB, 3 oz. copper, in an air environment
- A single chart is included that envelopes both internal and external conductors in a vacuum environment• Based on external conductors heating data for a 1.78 mm
(0.07 in.) thick PCB, 3 oz. copper, in a vacuum environment
IPC-2152
AppendixPurpose:
A place in the document to add clarity on topic areas and a place for expanding on current carrying capacity in electrical conductors.
• Example problems• New research: PCB materials, embedded resistors, high
current, etc.
IPC-2152
AppendixTopics Discussed:
- New and Old Conductor Sizing Charts- PCB Thickness- Parallel Conductors- Perpendicular Conductors- Flex circuits- PCB Material- Environments
IPC-2152
AppendixTopics Discussed (Continued)
- Vias- Neck down of conductors- High Density Interconnect
• Fine line and space conductors• Microvias
- Copper thickness- Thermal analysis of conductors, vias, odd shaped
geometries
IPC-2152
New Charts- Multiple charts and chart formats- Charts for air and vacuum- Charts specifically for 1/2 oz., 1 oz., 2 oz. and 3 oz.
copper weights (thicknesses)- Internal and external conductors- Linear charts and log-log charts- Charts showing finer resolution - SI (metric) and English (inch) units
IPC-2152
IPC-2152
0
5
10
15
20
25
30
0 100 200 300 400 500 600 700 800
Area (Sq-Mils)
100 C
75 C
60 C
2 C
45 C
30 C
20 C
10 C
5 C
1 C
Chart Format Example
IPC-2152
0.1
1
10
100
1 10 100 1000
Area (Sq-Mils)
100 C
75 C
60 C
2 C
45 C
30 C
20 C
10 C
5 C
1 C
Chart Format Example
Thermal Modeling (Computer Simulations)- Thermal models developed and correlated
to test data- Thermal models were used to investigate
the influence of variables on conductor temperature rise: • Copper planes • Distance from conductor to copper plane • Board level details
IPC-2152
PCB Level Details- Conductors
• Parallel conductors
- Vias- Thermals- Odd-shaped geometries- Neck-down
IPC-2152
Summary- IPC-2152 will replace the conductor sizing charts
that currently exist in IPC-2221.- IPC-2152 is a document that will be updated over
time (embedded devices, microvias, etc.) as task group members continue adding to the knowledge base regarding current carrying capacity in printed board design.
- IPC-2152 is the result of volunteer efforts that started in 1998.
IPC-2152
For more information …
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