一、Common errors in the schematic diagram of the PCB board
(1) The ERC report pin does not have access to the signal:
a. Define the I/O properties for the pins when creating the package;
b. When creating a component, the pin direction is, and the non-pinname end must be connected;
c. When creating components or placing components, the inconsistent grid properties are modified, and the pins and lines are not connected;
d. The most common reason is that no project file has been created, which is the most common mistake for beginners.
2) The component goes out of the drawing boundary: the component is not created in the center of the drawing paper of the component library.
3) When using self-created multi-part components, never use annotate.
4) The netlist of the created project file can only be partially transferred to the pcb: when generating the netlist, global is not select.
二、Common mistakes in PCB board
(1) When the network is loaded, it is reported that NODE is not found
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 pinnumbers in the pcb library.
Such as triode: the pinnumber in sch is e, b, c, and 1, 2, 3 in pcb board.
(2) It is always impossible to print on one page when printing
a. 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. Select Show All Hidden Characters, shrink the pcb, and move the characters within the bounds.
(3) The DRC reporting network is divided into several parts:
It means that the network is not connected, look at the report file, use CONNECTEDCOPPER to search, if you make a more complicated design, do not use automatic routing.
High precision multilayer PCB board
(4) Single-side pad setting aperture
a. Single-sided pads are generally not drilled, and the aperture should be designed to be zero, otherwise when generating drilling data, the coordinates of the hole appear at this position. If drilling, special instructions should be given;
b. If a single-side pad needs to be drilled, but the aperture is not designed, the software will treat this pad as an SMT pad when outputting electrical and stratum data, and the inner layer will lose the isolation pad.
(5) Draw pads with filler blocks
Although it can pass the DRC inspection in this way, it cannot directly generate solder mask data during processing, and the pad is covered with solder mask and cannot be soldered.
(6) The heat sink and the signal line are designed for the electric stratum, and the positive image and the negative image are designed together, and errors occur.
(7) Large area grid spacing is too small
The grid line spacing is less than 0.3mm. During the PCB manufacturing process, the pattern transfer process produces broken films after development and causes disconnection, which increases the difficulty of processing.
(8) The graphic is too close to the outer frame
At least 0.2mm spacing should be guaranteed (0.35mm or more at the V-cut), otherwise the copper foil will warp and the solder resist will fall off during exterior processing, which will affect the appearance quality (including the inner copper skin of the multilayer board).
(9) The shape frame design is not clear
Frames are designed for many layers, and they do not overlap, making it difficult for PCB manufacturers to judge which line to form. The standard frame should be designed in the mechanical layer or the hollowed out part of the BOARD layer.
(10) Uneven graphic design
When the pattern is electroplated, the current distribution is uneven, which affects the uniformity of the coating and even causes warping.
(11) short shaped hole
The length/width of the special-shaped hole should be >2:1, and the width >1.0mm, otherwise the CNC drilling machine cannot process it. (12) The milling shape positioning hole is not designed
If possible, design at least two positioning holes with a diameter >1.5mm in the PCB board. (13) Aperture mark is not clear
a. Merge the apertures that may be merged into one reservoir area as much as possible;
b. The hole diameter should be marked in metric system as much as possible, and it should be incremented by 0.05;
c. Whether the tolerances of metallized holes and special holes (such as crimping holes) are clearly marked.
(14) Unreasonable wiring in the inner layer of the multilayer circuit board
a. There is a gap in the design of the isolation belt, which is easy to misunderstand;
b. The design of the isolation zone is too narrow to accurately judge the network;
c. Put the heat dissipation pad on the isolation belt, and it is easy to fail to connect after drilling.
