As experienced PCB design engineers, we often overlook 10 common design process defects when designing PCBs, which can lead to problems during subsequent production. In this article, we will take an in-depth look at these 10 common process defects in the PCB design process to provide guidance for young engineers just starting out in this field.
1. The processing levels are not clearly defined
In single-sided PCB design, if the manufacturing specifications for the top and bottom sides are not clearly specified, it may be difficult to solder the components once they are mounted on the PCB. Therefore, clearly defining the manufacturing layers is crucial for avoiding problems.
2. A large area of copper foil is too close to the outer frame
Large areas of copper foil should be spaced at least 0.2 mm away from the outer edge of the PCB. If the distance is too close, the copper foil may curl during contour milling, which could even cause the solder mask to peel off.
3. Draw pads using fill blocks
Although using solid blocks to draw pads passes DRC checks during circuit design, problems may arise during actual manufacturing. Such pads cannot be directly converted into solder mask data, and when the solder mask is applied, the solid block areas will be covered by the solder mask, thereby increasing the difficulty of component placement.
4. Electrical layers, with both patterned pads and interconnects
When designing power and ground planes, be sure to check whether their orientation is reversed compared to the actual layout on the printed circuit board. Avoid leaving gaps in the circuit to prevent short circuits between the two power supplies or blocking of connection areas.
5. Randomly placed characters
Improper placement of characters can cause problems during SMD soldering, continuity testing, and component mounting. The characters should be designed to be of a moderate size—not so small as to make screen printing difficult, nor so large as to cause them to overlap and become difficult to distinguish.
6. The pads on surface-mount devices are too short
For surface-mount devices, the length of the pads should be appropriate to allow for continuity testing. Pads that are too short can make it difficult to insert the test probes correctly.
7. Setting the Pad Hole Diameter for Single-Sided Boards
Single-sided pads generally do not require drilling; if drilling is not required, the hole diameter should be specified as zero. Otherwise, problems may arise when generating drilling data.
8. Pad Overlap
Overlapping pads can cause the drill bit to break during the drilling process, resulting in damaged holes. In multilayer printed circuit boards, overlapping pads can result in an isolation pad, rendering the board unusable.
9. The design contains too many filled blocks, or the filled blocks are filled with extremely thin lines.
Excessive fill blocks or the use of extremely thin lines for filling can result in the loss of light-painting data and make data processing more difficult.
10. Misuse of the Graphics Layer
Adding unnecessary connections to the layout layer can lead to misunderstandings, especially in multi-layer PCB designs. When designing, keep the layout layer clear and complete, and avoid unnecessary complexity.
By avoiding these manufacturing defects, you can improve the quality of your PCB design, reduce production issues, and ensure that your electronic products function properly.
FAQs:
1. Why should large areas of copper foil not be placed too close to the outer frame?
If large areas of copper foil are too close to the outer frame, it may cause the copper foil to curl and the solder mask to peel off.
2. Why is it important to be careful when placing characters?
Improper character placement may affect screen printing and component soldering.
3. Why should pad overlap be avoided?
Overlapping pads can cause damage to the circuit board and increase manufacturing costs.
4. Why limit the number of fill blocks?
Too many padding blocks can make data processing more difficult and may lead to data loss.
5. Why should you use graphic layers with caution?
Overuse of graphic layers increases design complexity and can easily lead to misunderstandings.
