Printed circuit board is an important electronic component, the support of electronic components and the carrier of electrical connection in the electronic components.
After the electronic equipment adopts the printed board, the error of manual wiring is avoided due to the consistency of the same kind of printed board, and the electronic components can be automatically inserted or pasted, automatically soldered and detected, ensuring the quality of the electronic equipment, improving the labor productivity, reducing the cost, and facilitating the maintenance.
1. High density
For decades, the high density of PCB has been developing with the improvement of IC integration and installation technology.
2. High reliability
Through a series of inspections, tests and aging tests, PCB can be guaranteed to work reliably for a long time (generally 20 years).
3. Designability
For PCB performance (electrical, physical, chemical, mechanical, etc.), PCB design can be realized through design standardization, standardization, etc., having short time and high efficiency.
4. Producibility
With modern management, standardization, scale (quantity), automation and other production can be carried out to ensure the consistency of product quality.
5. Testability
A relatively complete test method, test standard, various test equipment and instruments are established to test and identify PCB product qualification and service life.
6. Assembly ability
PCB products are not only convenient for standardized assembly of various components, but also for automatic and large-scale mass production. At the same time, PCB and various component assembly parts can also be assembled to form larger parts, systems, and even the whole machine.
7. Maintainability
Because PCB products and various component assembly parts are produced in standardized design and scale, these parts are also standardized. Therefore, once the system breaks down, it can be replaced quickly, conveniently and flexibly, and the system can be recovered quickly. Of course, there are more examples, such as miniaturization, lightweight, high-speed signal transmission and so on.
Solder: it refers to the part on the board that needs to be painted green; because it is a negative output, the actual effect of the part with solder is not painted green, but tinned and silvery white.
Paste: it is used for machine mounting, which corresponds to the pad of all chip components. Its size is the same as that of the toplayer / bottomlayer layer, and it is used to open the steel mesh for tin leakage.
1. Signal layer
The signal layer is mainly used to arrange the wires on the circuit board.
2. Internal plane layer
This type of layer is only used for multi-layer boards, mainly for the layout of power lines and grounding wires. We call it double-layer board, four layer board and six layer board, which generally refers to the number of signal layer and internal power / ground layer.
3. Mechanical layer
The mechanical layer is generally used to set the overall dimensions, data marks, alignment marks, assembly instructions and other mechanical information of the circuit board. This information varies according to the requirements of the design company or PCB manufacturer. Execute the menu command Design|Mechanicallayer to set more mechanical layers for the circuit board. In addition, the mechanical layer can be attached to other layers to output the display together.
4. Solder mask layer
Apply a coat of paint, such as anti soldering paint, to all parts outside the pad to prevent tin application. The solder mask is used to match the pad in the design process and is generated automatically.
5. Paste mask layer
It is similar to the function of the solder mask layer, but different from the pad of the corresponding surface bonding element when the machine is welded.
6. Keep out layer
It is use to define areas on the board where components and wiring can be effectively placed. Draw a closed area in this layer as the effective area of routing. It cannot be automatically laid out and routed outside this area.
7. Silkscreen layer
The silk screen layer is mainly used to place printed information, such as outline and annotation of components, various annotation characters, etc. Protel 99 SE provides two screen printing layers: top overlay and bottom overlay. Generally, all kinds of marking characters are in the top screen layer, and the bottom screen layer can be closed.
8. MulTI layer
The pad and through-hole on the circuit board should penetrate the whole circuit board, and establish the electrical connection relationship with different conductive graphic layers, so the system specially set up an abstract layer multilayer. Generally, pads and vias should be set on multiple layers. If this layer is closed, pads and vias cannot be displayed.
9. Drill layer
The drilling layer provides the drilling information during the manufacturing process of the circuit board (For example, drilling is required for pad and through hole).
