Copper is the PCB conductive material that forms the connections between components, and serves as power and ground planes if the product is designed to take advantage of them. Copper also distributes heat, and becomes part of the mechanical strength for component attachment to the board.
Electrodeposited (ED) copper foil is the standard copper used in the laminate industry. ED foil is deposited from solution onto a moving titanium or steel drum, from which it is subsequently stripped. The grain structure formed by this process forms the dendritic "tooth" of the copper foil on the bath side PCB of the copper. The drum side takes the smooth texture of the polished drum surface onto which it is plated.
Rolled copper is made by running a copper strip through successively smaller and smaller gaps in a rolling mill until it reaches the desired thickness. Rolled copper is smoother and can be made very flexible by annealing (The acronym "RA" means "Rolled Annealed"). Much of the RA foil in the laminate industry is used in flexible circuitry, typically bonded to a polyimide film with an acrylic adhesive, used in applications where ductility is essential.
As a circuit board designer, the primary attribute of the copper in a board will be its thickness. Copper thickness is often specified in ounces; where one ounce copper would be the thickness resulting from taking one ounce of copper and spreading it evenly over a one square foot surface. Referring to copper thickness in ounces is a tradition dating back to when many roofs were covered with copper, and the tradesmen specified copper in this way. Although you need to know what people are talking about if they use phrases like "half-ounce copper" or "two ounce copper", it would probably be better for the circuit board industry to move towards specifying actual copper thickness, either in inch or metric units.
HERE IS A CHART SHOWING THE DIMENSIONS OF THE MOST COMMON COPPER THICKNESSES:
Using thinner copper makes it easier to control trace widths, but thicker copper can carry more current without as much heat. You may have to evaluate the current-carrying requirements of your design before selecting your material, but the most common copper weights range from half ounce to two ounce. A detailed tutorial on the relationship between trace geometry, current, and temperature rise (including a free spreadsheet-based calculator) can be found in the section called Trace&Space.
If you look at a cross-section of copper clad material, you will notice that the outside surface is relatively smooth, but the side bonded to the insulating material has more "tooth". In other words, the bonded surface is more rough than the smooth exposed surface.
There are two things you should be aware of regarding the copper TOOTH:
When measuring the dielectric thickness (the amount of insulating material), the PCB distance is measured from peak to peak.
The skin effect of high-speed signal propagation may be affected by the copper tooth, and there are "low-profile" materials available to reduce this effect (materials with smoother copper, i.e. less tooth).
Finally, you should understand the fact that copper is specified with a theoretically exact thickness, but the actual thickness in any particular board construction can vary with accepted tolerances and as the result of certain processing steps in bare board fabrication.
