PCB News - Common mistakes in PCB (experience summary)

1. Common errors in schematic diagrams:
   (1) There is no signal connected to the ERC report pin:
   a. I/O attributes are defined for the pins when the package is created;
   b. Inconsistent grid attributes are modified when components are created or placed, and the pins and wires are not connected;
   c. When creating the component, the pin direction is reversed, and the non-pin name end must be connected.
   (2) The component went out of the drawing boundary: no component was created in the center of the diagram paper of the component library.
   (3) The network table of the created project file can only be partially imported into the PCB: when the netlist is generated, global is not selected.
   (4) When using multi-part components created by yourself, never use annotate.

   

   
   2. Common errors in PCB board:
   (1) It is reported that NODE is not found when loading the network:
   a. The components in the schematic diagram use packages that are not in the PCB library;
   b. The components in the schematic diagram use packages with inconsistent names in the PCB library;
   c. The components in the schematic diagram use packages with inconsistent pin numbers in the PCB library. For example, a triode: the pin number in sch is e, b, c, and the pin number in PCB is 1, 2, 3.
   (2) It is always impossible to print on one page when printing:
   a. It is not at the origin when creating the PCB library;
   b. The components have been moved and rotated many times, and there are hidden characters outside the boundaries of the PCB board. Choose to show all hidden characters, shrink the PCB, and then move the characters to the boundary.
   (3) The DRC reporting network is divided into several parts:
   Indicates that this network is not connected. Look at the report file and use CONNECTED COPPER to find it.
   In addition, remind friends to use WIN2000 as much as possible to reduce the chance of blue screen; export the file several times to make a new DDB file to reduce the file size and the chance of PROTEL freezing. If you make a more complicated design, try not to use automatic routing.

In PCB design, wiring is an important step to complete product design. It can be said that the previous preparations are done for it. In the entire PCB, the wiring design process has the highest limit, the finest skills, and the largest workload. PCB wiring includes single-sided wiring, double-sided wiring and multilayer wiring. There are also two ways of wiring: automatic wiring and interactive wiring. Before automatic wiring, you can use interactive to pre-wire the more demanding lines. The edges of the input end and the output end should be avoided adjacent and parallel to avoid reflection interference. If necessary, ground wire should be added for isolation, and the wiring of two adjacent layers should be perpendicular to each other. Parasitic coupling is easy to occur in parallel.

The routing rate of automatic routing depends on a good layout. The routing rules can be preset, including the number of bending times, the number of vias, and the number of steps. Generally, explore the warp wiring first, quickly connect the short wires, and then perform the labyrinth wiring. First, the wiring to be laid is optimized for the global wiring path. It can disconnect the laid wires as needed. And try to re-wire to improve the overall effect.

The current high-density PCB design has felt that the through-hole is not suitable, and it wastes a lot of valuable wiring channels. In order to solve this contradiction, blind and buried hole technologies have emerged, which not only fulfill the role of the through-hole It also saves a lot of wiring channels to make the wiring process more convenient, smoother, and more complete. The PCB board design process is a complex and simple process. To master it well, a vast electronic engineering design is required. Only when personnel experience it by themselves can they get the true meaning of it.