● Signal Layers
● Internal Planes Layers
● Mechanical Layers
● Solder Mask Layers
● Silkscreen Layers
● System Layers
In general there are 7 working layers in printed circuit board: Signal Layers, Internal Planes, Mechanical Layers, Solder Mask Layers, Silkscreen Layers, System Layers and Others Layers.
1. Signal Layers
Signal Layers include Top Layer, Bottom Layer, Mid Layer1, Mid Layer2……. Signal Layers are used to mount components and traces. It is also called circuit layer. These layers are positive.
2. Internal Planes Layers
The Internal Planes Layers are used to arrange the power and ground traces.These layers are negative. Every Internal Planes Layer can have two or more power suppliers, such as +5V, +l5V, etc.
3. Mechanical Layers
Mechanical Layers are generally used to place indicative information about the PCB board printing and the assembly methods, such as circuit board physical dimension lines, dimension markings, data sheets, vias information, assembly instructions, and so on.
4. Solder Mask Layers
Solder Mask Layers include Top Solder and Bottom Solder. Solder Paste Layers include Top Paste and Bottom Paste, which have similar functions with Solder Mask Layers. Solder Mask Layers and Solder Paste Layers are all negative.
5. Silkscreen Layers
Silkscreen Layers include Top Overlay and Bottom Overlay. It is used to place the text information like the components profile, the numbers of components.
6. Other Layers
Keep-Out Layer is used to define the area of printed circuit board.
Drill guide and Drill drawing are used to do the drill drawing and drill holes position. Drill Drawing is now more widely used.
7. System Layers
System Layers include Connections, Pad Holes, Via Holes, Visible Grid 1, and Visible Grid 2.