Rigid-Flex PCB design seems to be complicated, considering both the direction of various signals and the energy transfer, the disturbance and the pain caused by heat are always present. But in fact, the summary is very clear, can be started from two aspects: put it bluntly: “how to put” and “how to connect.”
- In accordance with the “first big after small, first difficult after easy” layout principle, that is, important unit circuit, core components should be priority layout. This and eat buffet principle is the same: buffet appetite is limited to choose the favorite to eat, PCB space is limited to choose the important place.
- The layout should refer to the principle block diagram and arrange the main components according to the flow pattern of the main signal of the single board. The layout should meet the following requirements as far as possible: the total connection as short as possible, the key signal line is the shortest; The layout of the decoupling capacitor should be as close to the IC power supply pin as possible, and the circuit formed between it and the power supply and the ground should be the shortest; Reduce the signal to run the wrong way, to prevent accidents on the road.
- The arrangement of components should be convenient for debugging and maintenance, that is, large components should not be placed around small components, and there should be enough space around components to be debugged so that the situation will often become awkward if it is too crowded.
- The same structure of the circuit part, as far as possible using the “symmetric” standard layout; Optimize the layout according to the standard of uniform distribution, balanced center of gravity and beautiful layout.
- Plug-in components of the same type shall be placed in one direction in X or Y direction.Polar discrete components of the same type should also strive to maintain the same X or Y direction to facilitate production and inspection.
- Heating components should generally be evenly distributed to facilitate the heat dissipation of the single board and the whole machine. In addition to temperature detection components, temperature-sensitive components should be kept away from those with high heat.
- High voltage, high current signal and small current, low voltage signal is completely separated; The analog signal is separated from the digital signal; High frequency signal and low frequency signal are separated; High frequency components should be adequately spaced. When laying out components, proper consideration should be given to putting devices using the same power source together as far as possible to facilitate future power separation.
The above is about the “how to place” that is the layout of the main matters needing attention. As for “how to connect”, it is relatively more complicated, which is basically as follows:
Key signal line priority: simulation small signal, high-speed signal, clock signal and synchronization signal and other key signals priority wiring;
Density first principle: start wiring from the components with the most complex connections on the veneer. Start wiring from the most densely wired area on the veneer.
