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 …

If you would like more information, contact IPC by e-mail at

perrjo@ipc.org.