PCB substrate design performance most with a single PCB or double PCB substrate similar, that is to avoid too much of the circuit plug too small space, resulting in unrealistic tolerances, high inner-layer capacity, and may even endanger the safety of product quality. Therefore, the performance specification should consider the internal circuit of the thermal shock, insulation resistance, welding resistance, such as the complete evaluation. The following article describes the important factors that should be considered in PCB substrate design.
I. Mechanical design factors
Mechanical design includes the choice of the appropriate plate size, plate thickness, plate cascade, inner layer copper tube, aspect ratio and so on.
1 Board Size
The board size should be optimized according to application requirement, System box size, PCB manufacturer's limitation and manufacturing capability. Large circuit boards have many advantages, such as less PCB substrate, many components between the shorter circuit path, so that can have higher operating speed, well and each PCB board can have more input and output connections, so in many applications should be preferred large circuit boards, such as in the personal computer, see the larger motherboard. However, the design of large PCB board signal line layout is more difficult, need more signal layer or internal wiring or space, heat treatment is also greater difficulty. Therefore, designers must consider a variety of factors, such as standard board size, production equipment size and the limitations of the production process. Some guiding principles for the selection of standard printed circuit/board dimensions are given in 1pc-d-322.
2 Board Thickness
Multi-PCB substrate thickness is determined by a variety of factors, such as the number of signal layers, the number and thickness of the power supply board, the aperture and thickness required for high quality punching and electroplating, automatic insertion of the desired component pin length and the type of connection used. The thickness of the whole circuit board is composed of conductive layer, copper layer, PCB substrate thickness and prepreg material thickness on both sides of PCB board. It is difficult to obtain strict tolerances on synthetic PCB substrates, and about 10% of the tolerance criteria are considered reasonable.