Case 1

The determination of the maximum allowed current by graphical methods is based on the relations current – temperature known by many decades. The standard which represented the milestone in this determination was/is IPC–D–275 (“Design Standard for Rigid Printed Boards and Rigid Printed Board Assemblies”, figure 3–4, page 10, IPC, September edition 1991). IPC comes from the name of the American Institute of Standardization for Printed Circuits (IPC – Institute of Printed Circuits, institution which now is named Institute Connecting Electronics Industries). In this standard can be found out diagrams by which it can be determined the maximum allowed current through different track configurations or relations between the track width and the area of the crossing section, function of the thickness of the copper foil which is applied on the isolating substrate. These diagrams are considered sufficiently… acceptable but it cannot be said that they are extremely precised and sometimes, in special cases, it is recommended the specialist not to base on them “with the eyes closed”.

 

Fig.1 Graphic for determination of maximum admitted current function of the track width (in accordance with “IPC-The National Roadmap for Electronic Interconnections 2000/2001”).