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PCB Tech

PCB Tech

PCB Tech

PCB Tech

Five common senses you must know in the PCB industry
2021-10-06
View:35
Author:Downs

PCB (PrintedCircuitBoard), the Chinese name is printed circuit board, also known as printed circuit board, which is the support of electronic components and the carrier of electrical connection of electronic components. In the electronics industry, almost every electronic device, from electronic watches, calculators, to computers, communication electronic equipment, military weapon systems, as long as there are electronic components such as integrated circuits, in order to make the electrical interconnection between the various components, To use PCB.

PCB Industry Chain

The PCB industry chain from top to bottom is: upstream raw materials-midstream manufacturing-downstream PCB applications.

A notable feature of PCB is its extensive coverage of downstream applications, covering computer, communications, consumer electronics, industrial medical, military, semiconductor, and automotive industries, and almost all electronic information products. Among them, computers, communications and consumer electronics are the three main application areas, accounting for about 70% of the PCB industry's output value.

Classification of copper clad laminates

pcb board

Copper Clad Laminate (Copper Clad Laminate, CCL) is the upstream core material for PCB manufacturing. It is a plate-like material made by impregnating electronic fiberglass cloth or other reinforcing materials with resin, and covering one or both sides with copper foil and hot pressing. . It accounts for about 20% to 40% of PCB production cost, and has a strong interdependence with PCB.

1) According to the mechanical rigidity of the copper clad laminate, it can be divided into rigid copper clad laminate (RigidCopperCladLaminate) and flexible copper clad laminate (FlexibleCopperCladLaminate).

2) According to different insulating materials and structures, it can be divided into organic resin-based copper clad laminates, metal-based copper clad laminates, and ceramic-based copper clad laminates.

3) According to the thickness of the copper clad laminate, it can be divided into thick plates (the thickness range is 0.8~3.2mm (including Cu)) and thin plates (the thickness range is less than 0.78mm (excluding Cu)).

4) According to the reinforcing material of the copper clad laminate, it is divided into glass cloth-based copper clad laminate, paper-based copper clad laminate, and composite-based copper clad laminate (CME-1, CME-2).

5) Divided into flame-retardant and non-flame-retardant boards according to the flame-retardant grade: According to UL standards (UL94, UL746E, etc.), the CCL flame-retardant grade is divided, and rigid CCL can be divided into four different flame-retardant grades : UL-94V0 level; UL-94V1 level; UL-94V2 level and UL-94HB level.

PCB design

PCB design is a development link of product hardware design. It is an important research and development work that connects hardware circuit board schematic design and circuit board processing and manufacturing. The project process is as follows:

1) At the beginning of the project, it is necessary to check whether all the materials required by the project are complete: including schematic diagrams, structure diagrams, package libraries, signal flow diagrams of complex products, power tree diagrams, key signal descriptions, power supply currents, design requirements, etc.

2) Design information input: including the import of netlists and structural diagrams. After importing the structure diagram, pay special attention to the size of the screw holes and some positioning holes, the forbidden area of the device and wiring, the height limit area, and the position of the connector.

3) Layout: Based on comprehensive consideration of signal quality, EMC, thermal design, DFM, DFT, structure, safety regulations, etc., the components are placed on the board reasonably. The basic idea of the layout is generally to combine the signal flow direction and the power flow direction to lay out in addition to the structural restrictions.

4) Wiring constraints: Wiring constraints are mainly divided into line width, spacing, and equal length. Some rules need to be guided by pre-simulation, such as line length, impedance size, topological structure, stacked structure, etc.

5) Wiring: Wiring is one of the most important aspects of PCB design, and there are many points to pay attention to. Such as line impedance, continuity of reference plane, EMC, SI/PI, DFM, etc.

6) Review + post-simulation verification: After the wiring is completed, review and inspection by senior staff in the department and simulation of key signals and power supplies are required.

7) Processing: After the PCB design is no problem, the gerber file can be output for production.

PCB processing

There are many processes in PCB processing and manufacturing. Whether it is circuit processing, solder mask processing, or silk screen processing, they are all similar to the "printing" method, which is why PCB is called "printed circuit board" or "printed circuit board".