PCB Layer Introduction

PCB Signal Layer
The signal layer is mainly used to be placed with the object associated with the signal, which is divided into top, bottom and middle layer . Typically, the top and bottom to place the components and wiring ; intermediate layer is mainly used for the wiring operation.

PCB Power / ground layer
Power / ground layer is mainly used to place the power and ground lines , power and ground circuit components power and ground pin does not need through any copper mold wire connected directly to the power supply and ground lines , and avoid some of the the emergence of design issues , such as ground loop interference.

PCB Mechanical Layer
The function of Mechanical layer is that this layer mainly used to describe the mechanical structure of the Multilayer pcb and place the label instructions, no specific electrical connection characteristics . For example , the mechanical layer may be used to define the physical boundaries of the circuit board in order to avoid Component placed outside the physical boundaries

PCB Mask Layer
The protective layer can be divided into two categories: Solder Mask layer and flux ( Paste Mask ) layer. Solder resist layer is used to protect the copper wire and to prevent the components are soldered to the right place , this layer commonly known as green ink. Generally, the surface of PCB board all covered with solder mask except the place where has pads. In this way to prevent the PCB surface soldered with tin. The flux layer is used to improve pad solderability characteristics. On PCB, the light-colored circular spot which is a little bigger than pad we usually see is the flux layer.

PCB Silkscreen Layer
Silkscreen layer is used to identify the specific location of the various components on the PCB, for example, the components package outline appearance and character , the purpose is to bring convenience to circuit installation and maintenance . Typically , white legends and symbols on the PCB is the silkscreen what often mentioned by human. In PCB field, silkscreen include includes components location , the nominal value , the outer contour of the components and manufacturers logo , production date and so on.