Basic classification of PCBS

 

PCB (Printed Circuit Board), the Chinese name is a printed circuit board, also known as a printed circuit board, is the support body of electronic components, and is a carrier for electrical connections of electronic components. Its basic classification is:

1. According to the number of layers: based on the number of layers of copper foil

One-piece panel: The wires only appear on one side, and there are many strict limits on the design line (because there is only one side, the path that cannot cross the wiring room must be around alone), so only this type of board is used in the early circuit.

Double panels: There is wiring on both sides of this circuit board. Double panels solve the problem of single panels because of staggered wiring (can be guided to the other side). It is more suitable for more complex circuits than a single panel.

Multi-layer PCB: Use one double-sided as the inner layer, two single-sided for the outer layer or two double-sided as the inner layer, and the two single-sided on the outer printing line board. Together conductive graphics are interconnected according to design requirements. The six-layer printed circuit board is also known as a multilayer printed circuit board. Usually the number of layers is even, and contains the two outermost layers. Most motherboards are 4 to 8 layers.

2. Pressing hardness performance

（1）.Rigid PCB

FR-4 is a PCB substrate, glass napkin board.

FR4-free plate materials: Halogen-free refers to substrate materials that do not contain halogen (fluoroproba iodine and other elements), because bromine will produce toxic gases when burning, mainly environmental protection requirements.

The common core boards are yellow core and white core.

（2）.Flexible PCB

FPC soft board is a flexible circuit board with the simplest structure, which is mainly used to connect with other circuit boards.

Structure: Generally divided into single-layer boards, double-layer boards, multi-layer boards, etc.

Structure of single-layer soft board:

The flexible board of this structure is the most flexible board of the simplest structure.

Usually substrate+ transparent glue+ copper foil is a set of raw materials purchased. Protective film+ transparent glue is another raw material purchased.

Double-sided soft board structure:

There are pads on both sides of the double panel, which are mainly used to connect with other circuit boards.

Although it is similar to a single-layer plate structure, the production process is very different. Its raw materials are copper foil, protective film+ transparent glue.

The most typical difference between multilayer board and single-layer board is to increase the perforated structure to connect the copper foil of each layer.

The first processing process of general substrate+ transparent glue+ copper foil is to make holes.

（3）.Rigid-Flex PCB

The hard and hard combination board is the flexible circuit board and the hard line board. After the pressing process, the line board with FPC and PCB characteristics is combined according to the requirements of the relevant process.

Advantages: The hard and hard combination board has the characteristics of FPC and PCB. Therefore, it can be used in some products with special requirements. There are both deflection areas and a certain rigid area. Reduce the volume of the finished product and improve product performance.

Disadvantages: There are many production processes in the combination of software and hardware, the production difficulty, the low rate of good products, and the materials invested, and there is more manpower. Therefore, its price is relatively expensive and the production cycle is relatively long.

3. Press the piano out of the hole

（1）. Through Hole: The holes that run through the entire board.

（2）. BLIND HOLE: starts from the surface (outer layer), ends in the inner layer, and holes that are not penetrated through the entire plate.

（3）.Buried Via: Without two layers of outer surface, only pores that penetrate into some inner layers. According to whether there are copper categories in the holes: there are copper holes PTH and copper-free NPTH NPTH

（4）. PTH: Plating through holes: There is copper in the inner wall of the holes, and the role of guide;

（5）.NPth: No playing through holes:

The inner wall of the hole has no copper and no pitching effect. It is usually a hole for positioning.

4. Press the surface

Because the copper surface is easily oxidized in the general environment, it cannot be used as tin (poor weld, so it will be protected on the copper surface). The method of protection is collectively called surface treatment.

1. Hot Air Level Soldering

2. Hot Air Level Soldering Lead Free

3.Electroless nickel/Immersion Gold/Immersion AU/Enig

4.Tin/Chemical Sn Immersion

5.Silver/Chemical Ag Immersion

6.OSP: ORGANICSORABILITY PRESERVATIVES

7.Gold Plating/Flash Gold

8.Carbon Oil

9. PELABLE SOLDER MASK

10. Plating Gold Finger/EDGEDContact/Connecting Finger

IPC-6012 Class 2 requires the smallest gold finger thickness: 0.80um (30U), nickel thick (ni): minimum 2um;