Ampacity

Ampacity, conductor cross-section and temperature are decisive factors in the design of printed circuit boards, especially in electronic applications. Correct dimensioning and consideration of these parameters play a key role in the performance and reliability of printed circuit boards.

In this context, the following charts and diagrams provide valuable insights and findings that illustrate the importance of these factors. These visual aids make it possible to better understand the interactions between current carrying capacity, trace cross-section and temperature and help to develop optimized PCBauch: gedruckte Schaltung, engl.: PCB – Printed circuit boar… More layouts that meet the requirements of electronic circuits in terms of performance and reliability. In the following sections, we will explain these key aspects in more detail and use the information from the accompanying charts and diagrams to deepen our understanding.

Conductor cross-section, temperature

Example

With a conductor track width of 5.5 mm and a copper thickness of 35 µm, a current load of 13 A results in a temperature increase of around 30°C.

Click to enlarge.

Temperature increase

The adjacent diagram is used to estimate the temperature increase as a function of current and conductor width with a copper thickness of 35µm.

These apply to a nominal board thickness of 1.6-3.0 mm.

Additional metallization (nickel, gold, tin) is not taken into account.

Empirically determined values of the ampacity of printed conductors as a function of the conductor width of 35µm and 70µm at a limit temperature of ~60°C.

Temperature coefficients

for copper thicknesses 35µm and 70µm

35µm

70µm

Insulation distances

Minimum electrical distances for internal distances “conductor track to conductor track” and “conductor track to plated-through hole” depending on sea level are shown in the following table.
The voltage values apply to DC voltage or peak/peak for AC voltage. With AC voltage, the frequency can lead to a reduction in the dielectric strength of materials, so various design parameters should be taken into account.

PCB					Electronic device
Voltage	L1	L2	L3	L4	FB1	FB2
0-15V	0,10mm	0,64mm	0,64mm	0,13mm	0,13mm	0,13mm
16-30V	0,10 mm	0,64mm	0,64mm	0,13mm	0,25mm	0,13mm
31-50V	0,10mm	0,64mm	0,64mm	0,13mm	0,38mm	0,13mm
51-100V	0,10mm	0,64mm	1,50mm	0,13mm	0,50mm	0,13mm
101-150V	0,20mm	0,64mm	3,18mm	0,38mm	0,75mm	0,38mm
151-170V	0,20mm	1,27mm	3,18mm	0,38mm	0,75mm	0,38mm
171-250V	0,20mm	1,27mm	6,40mm	0,38mm	0,75mm	0,38mm
251-300V	0,20mm	1,27mm	12,70mm	0,38mm	0,75mm	0,38mm
301-500V	0,25mm	2,54mm	12,70mm	0,75mm	1,50mm	0,75mm
>500V (per volt)	0,0025mm	0,0050mm	0,0254mm	0,00305mm	0,00305mm	0,00305mm

L1
L2
L3
L4
FB1
FB2

Internal conductor
External conductor, without coating, sea level < ≤3048m (10000 ft)
External conductor, without coating, sea level > ≥3048m (10000 ft)
External conductors, with durable polymer coating
External component connection, without coating
External component connection, with permanent coating (over the assembly)