Introduction For The Five Things You Must Know About The PCB Industry

PCB (Printed circuit board), is the support body of electronic components, and the carrier of electrical connection of electronic components. In the electronic industry, almost every kind of electronic equipment, from small electronic watches and calculators to large computers, communication electronic equipment and military weapon systems, as long as there are electronic components such as integrated circuits, to make the electrical interconnection between each component, PCB should be used.

PCB industry chain

The PCB industry chain from top to bottom is: upstream raw materials — midstream manufacturing — downstream PCB application, as shown in the figure below.

A notable feature of PCB is that its downstream applications cover a wide range of fields, covering computer, communication, consumer electronics, industrial medical, military, semiconductor and automotive industries and almost all electronic information products. Among them, computer, communication and consumer electronics are the three main application areas, accounting for about 70% of the output value of PCB industry.

Classification of copper clad plates

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

1) according to the mechanical rigidity can be divided into Rigid Copper Clad sheet (it Rigid Copper Clad Laminate) and flexible Copper Clad (FlexibleCopperCladLaminate).

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

3) According to the thickness of the copper clad plate can be divided into thick plate (plate thickness range of 0.8 ~ 3.2mm (including Cu)), thin plate (plate thickness range of less than 0.78mm (not including Cu)).

4) According to the reinforcement materials of the copper clad panels, the panels are divided into glass cloth copper clad panels, paper copper clad panels and composite copper clad panels (CME-1, CME-2).

5) according to the flame retardant grade is divided into flame retardant board and non-flame retardant board: according to the UL standard (UL94, UL746E, etc.), the flame retardant grade of CCL is divided, the rigid CCL can be divided into four different flame retardant grade: namely UL-94V0 grade; UL – 94 v1 level; The UL-94V2 class and the UL-94HB class.

PCB design

As a product hardware design development link, PCB design is an important research and development work connecting hardware circuit board schematic design with circuit board processing and manufacturing. The project flow is as follows:

1) At the beginning of the project, it is necessary to check whether the required materials are complete, including schematic diagram, structure diagram, packaging library, signal flow diagram of complex products, power tree diagram, key signal description, power supply current size, design requirements, etc.

2) Design information input: including network list and structure drawing import.

After the structure drawing is imported, special attention should be paid to the size of the screw holes and some positioning holes, the forbidden cloth area of the device and the wiring, the height limit area, and the position of the connector.

3) Layout: Base on comprehensive consideration of signal quality, EMC, thermal design, DFM, DFT, structure, safety regulations and other requirements, the device should be reasonably placed on the board. In addition to the limitation of structure, the basic idea of the layout is to combine the signal flow direction and the power flow direction to the layout.

4) Wiring constraints: Wiring constraints are mainly divided into line width, spacing, equip length, etc. Some of the rules need to be guided by pre-stimulation, such as line length, impedance, topology, stack structure, etc.

5) Wiring: Wiring is a link with the largest workload in PCB design, and many points need attention. Such as line impedance, reference surface continuity, EMC, SI/PI, DFM, etc.

6)Review + post-simulation verification: after wiring is completed, the department’s senior staff are required to review and inspect and simulate key signals and power supplies.

7) Processing: after the PCB design is no problem, the light drawing file can be output for production.

PCB processing

PCB processing and manufacturing processes are many, whether it is line processing, soldering ink processing, screen printing processing, are similar to the way of “printing”, which is also the reason why PCB is called “printed circuit board” or “printed circuit board”.