Current Carrying Capacity of PCB Traces

The current carrying capacity of PCB traces could be different than the value presented in standards and datasheets or obtained after solving thermal equations. According to IPC standards, the current carrying capacity of PCB traces represents the maximum electrical current that can be carried continuously by a trace without causing an objectionable degradation of electrical or mechanical properties of the product.

Temperature Rise in PCB Traces

When a PCB trace is powered, current flowing through it generates heat, creating a temperature rise between the trace and the surrounding environment. The temperature rise depends upon the trace cross sectional area and various factors such as PCB thickness, dielectric material, amount and adjacency of copper in the board.

Additionally, the environmental factors affect significantly the current capacity and fusing aspects, which are under interest. Usually, equations, graphs and tables present general design concerns that bound normally all the PCB designs. Unfortunately, the various contributions to the board temperature rise may occur in particular applications and are not detailed in standards. When considering the ambient temperature, with respect to the charts, one must evaluate all the contributions to the overall temperature rise of the board in the worst case conditions in which it is required to operate.

How to Analyse PCB Traces

Because the printed circuit boards can be extremely different from one design to another, the PCB testing/design engineer has to investigate the fusing aspects based on some important PCB parameters (type of dielectric, trace width (W), copper thickness, etc.) and environment conditions in which the board operates.

Based on the experimental results in the case of traces/tracks fusing, in order to avoid failures of electronic systems during the operation and, the PCB design engineer has to follow thermal design guidelines of PCBs.

Finite element modelling and simulation – To obtain the thermal solution, for example the temperature map, a coupled-field analysis is required. For this type of analysis the interaction (coupling) between two or more types of physical phenomena (fields) is considered. Such an analysis may involve direct or indirect coupling of fields.