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Current Carrying Capacity
Revision 3, July 2004
Please note that a new standard IPC - 2152 : Standard for determining current carrying capacity in Printed Board Design, is in preparation. The information in this document has been prepared for use in determining current carrying capacity and sizes of etched copper conductors for various temperature rises above ambient. It is a tabular version of the graphical information contained in MIL-STD-275E. The notes from this specification are quoted below.
Please note that the maximum current values are for conductors on outer layers, for conductors on inner layers the values shall be reduced by 50%.
|
TEMP. |
Rise °C |
10 |
20 |
30 |
||||||
|
COPPER |
||||||||||
|
oz. |
0,5 |
1 |
2 |
0,5 |
1 |
2 |
0,5 |
1 |
2 | |
|
Micron |
18 |
35 |
70 |
18 |
35 |
70 |
18 |
35 |
70 | |
|
Trace Width Inches |
Trace Width microns |
Maximum Current in Amperes |
||||||||
|
0,0025 |
63,5 |
0,13 |
0,30 |
0,60 |
0,17 |
0,35 |
0,45 |
0,35 |
0,55 |
0,75 |
|
0,005 |
127 |
0,25 |
0,60 |
1,10 |
0,40 |
0,55 |
1,10 |
0,50 |
0,75 |
1,20 |
|
0,010 |
254 |
0,50 |
1,00 |
1,40 |
0,60 |
1,20 |
1,60 |
0,70 |
1,50 |
2,20 |
|
0,015 |
381 |
0,70 |
1,20 |
1,60 |
0,80 |
1,30 |
2,40 |
1,00 |
1,60 |
3,00 |
|
0,020 |
508 |
0,70 |
1,30 |
2,10 |
1,00 |
1,70 |
3,00 |
1,20 |
2,40 |
3,60 |
|
0,025 |
635 |
0,90 |
1,70 |
2,50 |
1,20 |
2,20 |
3,30 |
1,50 |
2,80 |
4,00 |
|
0,030 |
762 |
1,10 |
1,90 |
3,00 |
1,40 |
2,50 |
4,00 |
1,70 |
3,20 |
5,00 |
|
0,050 |
1270 |
1,50 |
2,60 |
4,00 |
2,00 |
3,60 |
6,00 |
2,60 |
4,40 |
7,30 |
|
0,075 |
1905 |
2,00 |
3,50 |
5,70 |
2,80 |
4,50 |
7,80 |
3,50 |
6,00 |
10,00 |
|
0,100 |
2540 |
2,60 |
4,20 |
6,90 |
3,50 |
6,00 |
9,90 |
4,30 |
7,50 |
12,50 |
|
0,200 |
5080 |
4,20 |
7,00 |
11,50 |
6,00 |
10,00 |
11,00 |
7,50 |
13,00 |
20,50 |
|
0,250 |
6350 |
5,00 |
8,30 |
12,30 |
7,20 |
12,30 |
20,00 |
9,00 |
15,00 |
24,5 |
NOTES:
1: The design chart has been prepared as an aid in estimating temperature rises (above ambient) vs current for various cross sectional areas of etched copper conductors. It is assumed that for normal design conditions prevail where the conductor surface area is relative small compared to the adjacent free panel area. The curves (tabular values) as presented include a nominal 10% derating (on a current basis) to allow for normal variations in etching techniques, copper thickness, conductor width estimates, and cross sectional area.
2: Additional derating of 15% (current wise) is suggested under the following conditions:
(a) For panel thickness of 1/32 inch (0,8mm) or less.
(b) For conductor thickness of 0,0042 inch (100 micron) (3oz/feet2) or thicker.
3: For general use the permissible temperature rise is defined as the difference between the maximum safe operating temperature of the laminate and the maximum ambient temperature in the location where the panel will be used.
4: For single conductor applications, the chart may be used directly for determining conductor widths, conductor thickness, cross sectional area, and current carrying capacity for various temperature rises.
5: For groups of similar parallel conductors, if closely spaced the temperature rise may be found by using equivalent cross section and an equivalent current. The equivalent cross section is equal to the sum of the cross sections of the parallel conductors, and the equivalent current is the sum of the currents in the conductors.
6: The effect of heating due to attachment of power dissipation parts is not included.
7: The final conductor thickness in the design do not include conductor over plating with metals other than copper.