1. If the two ends of the PCB chip components are not connected to the plug-in components, test points must be added. The diameter of the test points should be between 1.0 mm and 1.5 mm to facilitate online tester testing. The edge of the test point pad should be at least 0.4 mm away from the edge of the surrounding pad. The test pad diameter must exceed 1 mm and should possess network properties. The center-to-center distance between two test pads should be equal to or greater than 2.54 mm. If a via is used as a measurement point, a pad must be added outside the via, with a diameter greater than 1 mm (inclusive).

2. PCB pads must be added at positions where holes with electrical connections are located. All pads must exhibit network attributes. For networks lacking connected components, the network names cannot be identical. The distance between the center of the positioning hole and the center of the test pad should exceed 3 mm. Other irregular shapes, such as slots with electrical connections, must be uniformly placed on mechanical layer 1 (referring to single-insertion, fuse, and other slotted holes).

3. For components with dense pin spacing (less than 2.0 mm), such as ICs and socket swings, if their pin pads are not connected to manual plug-in unit pads, test pads must be added. The diameter of the test point should range between 1.2 mm and 1.5 mm to facilitate online tester testing.

4. If the distance between pads is less than 0.4mm, apply solder mask to prevent solder bridging when the wave crest is exceeded.

5. The ends of SMT components involved in the glue dispensing process should use lead-tinning. A recommended lead-tinning width is 0.5mm wire, with a length generally of 2 or 3mm.

6. For hand-soldered components on a single panel, remove excess solder in the opposite direction of the solder flow, ensuring hole widths between 0.3mm to 0.8mm.

7. The spacing and dimensions of conductive rubber buttons must precisely match those of the actual components. PCBs connected to these should be designed with gold fingers, specifying a gold plating thickness generally greater than 0.05um to 0.015um.

8. PCB pad sizes and spacing should correspond to the dimensions of SMD components.

a. Unless specified otherwise, ensure symmetry between component holes, pads, and component leads. Square component leads should have square holes and pads, while round components should have circular holes and pads. Keep adjacent pads independent to prevent solder bridging.

b. Adjacent pins of components within the same circuit or compatible devices with different pin pitches should have separate pad holes. This is especially critical for compatible relay package pads. Ensure each pad hole is surrounded by solder mask.

9. When designing multi-layer boards, consider metal shell components carefully. These shells must be in contact with the PCB during assembly. Top layer pads beneath these shells should not be exposed and must be covered with green or silkscreen mask.

10. Minimize PCB slotting and cutting openings during design to maintain board strength.

11. Avoid placing valuable components near corners, edges, mounting holes, slots, or cutting openings on the PCB. These areas are prone to high stress during handling and may lead to solder joint cracks.

12. Heavier components like transformers should be positioned near positioning holes to avoid board deformation and maintain strength. Place these components under the PCB during layout, especially when entering the wave soldering process.

13. Components and circuits that emit electromagnetic energy, such as transformers and relays, should be placed away from sensitive devices like amplifiers, microcontrollers, crystal oscillators, and reset circuits to ensure reliable operation.

14. QFP packaged ICs requiring wave soldering should be placed at a 45-degree angle, and additional solder pads should be provided.