Conductor

What Is A Conductor in PCB?

 

PCB Conductor, Trace or Track, is a copper or constantan area on a PCB surface or internal layer, usually composed of lands (to which component leads are connected) and paths (traces).

 

The following table shows the maximum allowed conductor trace width with the minimum conductor trace spacing, depending on the respective copper thickness.

 

Conductor Width in Inner Layers

Copper thickness	min. conductor trace width / space	min. annular ring
12µm	75µm/100µm**	90µm
18µm	90µm	90µm
35µm	100µm	100µm
70µm	150µm	150µm
105µm	250µm	250µm
140µm	300µm	300µm
210µm	500µm	500µm

 

Conductor Width in Outer Layers

Final copper*	min. conductor trace width / space	min. annular ring
30µm	75µm/100µm** 90µm	90µm 90µm
35µm	100µm	100µm
70µm	150µm	150µm
105µm	250µm	250µm
140µm	300µm	300µm
210µm	500µm	500µm
400µm	900µm**	900µm

* After electroplating / ** prior data check necessary

 

Current Carrying Capacity of Conductors according to IPC-2221

Maximum current [A] subject to the temperature increase in degrees [°]

2 Layers – 35µm copper

Trace Width		10°	20°	30°	40°	50°	60°
0.1mm	4mil	0.4A	0.6A	0.8A	0.9A	1.0A	1.1A
0.2mm	8mil	0.7A	1.0A	1.2A	1.4A	1.6A	1.7A
0.3mm	12mil	0.9A	1.3A	1.6A	1.8A	2.0A	2.2A
0.4mm	16mil	1.1A	1.5A	1.9A	2.2A	2.4A	2.7A
0.5mm	20mil	1.3A	1.8A	2.2A	2.5A	2.8A	3.1A
0.6mm	24mil	1.4A	2.0A	2.4A	2.8A	3.1A	3.4A
0.7mm	28mil	1.6A	2.2A	2.7A	3.1A	3.5A	3.8A
0.8mm	32mil	1.7A	2.4A	2.9A	3.4A	3.8A	4.1A
0.9mm	36mil	1.8A	2.6A	3.2A	3.7A	4.1A	4.5A
1.0mm	40mil	2.0A	2.8A	3.4A	3.9A	4.4A	4.8A
1.5mm	60mil	2.5A	3.6A	4.4A	5.1A	5.7A	6.2A
2.0mm	80mil	3.0A	4.3A	5.3A	6.1A	6.8A	7.5A
3.0mm	120mil	3.9A	5.6A	6.8A	7.9A	8.8A	9.7A
4.0mm	160mil	4.7A	6.7A	8.2A	9.5A	10.6A	11.6A
5.0mm	200mil	5.5A	7.7A	9.5A	10.9A	12.2A	13.4A
6.0mm	240mil	6.1A	8.7A	10.6A	12.3A	13.7A	15.1A
7.0mm	280mil	6.8A	9.6A	11.7A	13.6A	15.2A	16.6A
8.0mm	320mil	7.4A	10.4A	12.8A	14.8A	16.5A	18.1A
9.0mm	360mil	8.0A	11.3A	13.8A	15.9A	17.8A	19.5A
10.0mm	400mil	8.5A	12.1A	14.8A	17.0A	19.1A	20.9A

The calculation of the values is an approximation from the derived formulas of the IPC-2221 (see below). Deviation from DIN IEC 326 is due to the complexity of the topic. A rough estimate should always be possible.

The design guideline IPC-2221 (predecessor document: MILSTD 275) is the default data source for the DC temperature resistance of conductors. The measurements thereto come from the National Bureau of Standards (NBS) from the 1950s and refer to a 1.6mm thick PCB with a straight current-carrying conductor (thickness 35µm) and a 35µm Cu solid area on the back. They do not consider the surrounding medium (air pressure, motion), or the layout density.

In the 1960s the American magazine Design News published amended recommendations. In the mid-80s, in Germany the DIN IEC 326 comes out, which attends to this topic – the values obtained are quite similar to those from the Design News (with all advantages and disadvantages).

The tables specified here can therefore only be used to roughly estimate the temperature development.