O'Reilly logo

Power Over Ethernet Interoperability Guide by Sanjaya Maniktala

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

Separations in Inner Layers
Let us first understand basic multilayer PCB construction. There are two basic elements: (a) copper foil of varying thicknesses, and (b) FR-4 (“fire-resistant 4” category, as per IEC). The FR-4 may be in the form of prepreg (preimpregnated) material, or in the form of a core. The core material is cured fiberglass-epoxy resin (i.e., hardened to start with). Prepreg however consists of thin sheets of fiberglass impregnated with uncured epoxy resin. Several layers of prepreg may be combined to achieve a desired final prepreg thickness. Finally, the entire assembly is pressed together, and under heat, the uncured epoxy also gets cured (it hardens).
We can have many variations of thicknesses, and finally, the distance ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required