1. Common errors in schematic
(1) There is no signal connected to the ERC report pin:
b. Inconsistent grid attributes are modified when components are created or placed, and the pins and lines are not connected;
c. When creating the component, the pin direction is reversed, and the non-pin name end must be connected.
d. The most common reason is that there is no project file, which is the most common mistake for beginners.
2) The component goes outside the drawing boundary: no component is 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, do not use annotate.
Two, common errors in PCB
(1) It is reported that NODE is not found when the network is loaded
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 use packages with inconsistent pin numbers in the PCB library.
For example, a triode: the pin numbers in sch are e, b, and c, and the pin numbers in pcb are 1, 2, 3.
(2) Can not always 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. Select to show all hidden characters, reduce the pcb, and then move the characters to the boundary.
(3) The DRC reporting network is divided into several parts:
It means that this network is not connected. Look at the report file and use CONNECTED COPPER to find it.
If you make a more complicated design, try not to use automatic wiring.
Three, common errors in the PCB manufacturing process
After years of practice and exploration, China Strong PCB is China’s top model and small batch circuit board manufacturer under Shenzhen Huaqiang Jufeng Group. It has been focusing on the production of multi-layer precision circuit boards for many years. Technical Director Liu shared with us a few Some experience in the perfect integration of PCB manufacturing and design.
(1) Pad overlap
a. Causes heavy holes, and breaks the drill and damages the holes due to multiple drilling in one place during drilling.
b. In the multi-layer board, there is both a connecting plate and an isolating plate at the same position, and the board behaves as • isolation and connection errors.
(2) Irregular use of graphics layer
a. Violation of conventional design, such as component surface design in the Bottom layer, welding surface design in the TOP layer, causing misunderstandings.
b. There are a lot of design rubbish on each layer, such as broken lines, useless borders, labels, etc.
(3) Unreasonable characters
a. The characters cover the SMD solder tabs, which brings inconvenience to PCB on-off detection and component soldering.
b. The characters are too small, which makes screen printing difficult. If the characters are too large, they will overlap each other and be difficult to distinguish. The font is generally >40mil.
(4) Setting aperture of single-sided pad
a. Single-sided pads are generally not drilled, and the hole diameter should be designed to be zero, otherwise the coordinates of the hole will appear at this position when the drilling data is generated. Special instructions should be given for drilling.
b. If a single-sided pad needs to be drilled, but the aperture is not designed, the software treats this pad as an SMT pad when outputting electrical and ground data, and the inner layer will lose the isolation disk.
(5) Draw pads with filler blocks
Although it can pass the DRC inspection, the solder mask data cannot be directly generated during processing. The pad is covered with solder mask and cannot be soldered.
(6) The electrical ground layer is designed with both a heat sink and a signal line. The positive and negative images are designed together, and errors occur.
(7) Large area grid spacing is too small
Grid line spacing
(8) The graphics are too close to the frame
At least 0.2mm or more spacing should be ensured (V-cut 0.35mm or more), otherwise the copper foil will be warped and the solder resist will fall off during the exterior processing, which will affect the appearance quality (including the inner copper skin of the multilayer board).
(9) The outline frame design is not clear
Many layers are designed with frames and do not overlap, which makes it difficult for PCB manufacturers to judge which line to use. The standard frame should be designed on the mechanical layer or the BOARD layer, and the internal hollowed out parts should be clear.
(10) Uneven graphic design
When the pattern is electroplated, the current distribution is uneven, which affects the uniformity of the coating, and even causes warpage.
(11) Short shaped hole
The length/width of the shaped hole should be> 2:1 and the width> 1.0mm, otherwise the CNC drilling machine cannot process it.
(12) Milling profile positioning hole is not designed
If possible, design at least two positioning holes with a diameter> 1.5mm in the PCB board.
(13) The aperture is not clearly marked
a. The aperture marking should be marked in metric system as much as possible, and in increments of 0.05.
b. Combine the apertures that may be combined into one reservoir area as much as possible.
c. Whether the tolerances of metallized holes and special holes (such as crimp holes) are clearly marked.
(14) Unreasonable wiring inside the multilayer board
a. The heat dissipation pad is placed on the isolation tape, and it is easy to fail to connect after drilling.
b. The design of the isolation belt has gaps, which is easy to misunderstand.
c. The isolation band design is too narrow to accurately judge the network
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