What is the structure of PCB

PCB is made of different components and a variety of complex processing technology. The structure of PCB includes single-layer, double-layer and multi-layer structure. Different hierarchical structures have different manufacturing methods.

Structure of circuit board

The circuit board is mainly composed of pads, vias, mounting holes, wires, components, connectors, fillers, electrical boundaries, etc. Common board structures include single layer PCB, double layer PCB and multi layer PCB.

Structure of printed circuit board

Printed circuit board is mainly composed of pad, via, mounting hole, wire, component, connector, filling, electrical boundary, etc

Pad: a metal hole used to weld pins of components.

Vias: there are metal vias and nonmetal vias. Metal vias are used to connect component pins between layers.

Mounting hole: used to fix the circuit board.

Wire: copper film of electrical network used to connect component pins.

Connector: used for connecting components between circuit boards.

Filling: used for copper coating of ground wire network, which can effectively reduce the impedance.

Electrical boundary: used to determine the size of the circuit board, all components on the circuit board can not exceed the boundary.

Through hole, installation hole, wire, component, connector, filling, electrical boundary, etc.

Internal structure of PCB

Multilayer circuit board, there are usually through-hole board, first-order board, second-order board, second-order stacked hole board. The higher-order boards, such as the third-order board and the interconnection board of any layer, are usually very few and expensive, so I won't discuss them much first.

Generally, 8-bit MCU products use 2-layer through-hole plate; 32-bit MCU level intelligent hardware, using 4-6 layer through-hole board; Linux and Android level intelligent hardware, using 6-layer through-hole to 8-level HDI board; Smart phones, such as compact products, generally use 8-layer first-order to 10 layer second-order circuit board.

The most common through hole

There is only one kind of via, from the first layer to the last layer. Whether it's the external circuit or the internal circuit, the hole is pierced. It's called through-hole plate.

The through-hole board has nothing to do with the number of layers. At ordinary times, the two layers we use are all through-hole boards, while many switches and military circuit boards, which are made of 20 layers, are still through-hole boards.

Drill through the circuit board with a drill, and then copper the hole to form a path.

It should be noted here that the inner diameters of through holes are usually 0.2mm, 0.25mm and 0.3mm, but generally 0.2mm is much more expensive than 0.3mm. Because the drill bit is too thin, it is easy to break, and the drilling speed is slower. The extra time and cost of the drill are reflected in the rising price of the circuit board.

Laser hole of HDI board

Both the surface layers are laser holes with an inner diameter of 0.1 mm. The inner layer is a mechanical hole

It is equivalent to a 4-layer through-hole plate, covered with another 2 layers.

Laser can only penetrate glass fiber plate, not metal copper. So the outer surface drilling will not affect the other internal lines.

After laser drilling and copper plating, laser through-hole is formed.

Second order HDI board with two laser holes

The so-called second order is that there are two laser holes

The so-called staggered hole is that the two laser holes are staggered.

Why stagger? Because the copper plating is not enough, the hole is empty, so it can not be straight

Layer structure classification of printed circuit board

The common layer structures of printed circuit board include single layer PCB, double layer PCB and multi layer PCB

(1) Single layer board: that is, only one side of the circuit board with copper and the other side without copper. Components are usually placed on the side without copper, which is mainly used for wiring and welding.

(2) Double layer board: that is, the circuit board with copper on both sides, which is usually called top layer on one side and bottom layer on the other side. Generally, the top layer is used as the placement surface of components, and the bottom layer is used as the welding surface of components.

(3) Multilayer board: it is a circuit board that contains multiple working layers. In addition to the top and bottom layers, it also contains several intermediate layers. Generally, the intermediate layer can be used as wire layer, signal layer, power layer, grounding layer, etc. The layers are insulated from each other, and the layer to layer connection is usually realized through vias.

Structure of circuit board

Printed circuit board (PCB proofing production) includes many types of working layers, such as signal layer, protective layer, screen printing layer, internal layer, etc

(1) Signal layer: mainly used to place components or wiring. Protel DXP usually consists of 30 middle layers, namely mid layer 1 ~ mid layer 30. The middle layer is used to lay signal lines, and the top and bottom layers are used to place components or copper.

(2) Protective layer: it is mainly used to ensure that the parts on the circuit board that do not need to be tinned are not tinned, so as to ensure the reliability of the circuit board. Top paste and bottom paste are top layer and bottom layer respectively; Top and bottom solders are solder paste protective layer and bottom solder paste protective layer respectively.

(3) Screen printing layer: mainly used to print the serial number, production number and company name of the component on the printed circuit board.

(4) Internal layer: mainly used as signal wiring layer, PROTEL DXP contains 16 internal layers.

(5) Other layers: mainly including four types of layers.

Drill guide: it is mainly used for drilling position on printed circuit board.

okay. The above is about the PCB circuit board structure of the detailed information, I hope to help you; Need to know more about: circuit board proofing, circuit board proofing, double-sided circuit board information, please contact us!