2. **Design Software Tools**: Modern circuit board design software usually includes design specifications for parameters such as line width, line spacing, and via hole sizes. During the design process, these tools can automatically execute the specifications, saving time, reducing workload, and minimizing errors.
3. **Double-Sided Boards**: Double-sided boards are often used for applications requiring high reliability or high wiring density. They offer a balance of moderate cost and high reliability, making them suitable for most applications.
4. **Multi-Layer Boards**: Some power supply modules use multi-layer boards to integrate transformers, inductors, and other power components, optimizing routing and cooling. These boards provide excellent workmanship, consistency, and heat dissipation but come with higher costs, reduced flexibility, and are best suited for large-scale industrial production.
5. **Single-Sided Boards**: Most market-circulating universal switching power supplies use single-sided boards due to their low cost. Despite the lower cost, design and production measures are taken to ensure performance.
6. **Single-Sided PCB Design**: Single-sided printed circuit boards are widely used in switched power lines due to their low cost and ease of manufacture. With copper on only one side, device electrical connections and mechanical fixation rely on that copper layer, so careful handling is essential.
1. To ensure optimal structural performance of the welding machine, the single-panel bonding pad should be slightly larger to maintain a strong bond between the copper sheet and the base plate, preventing the copper sheet from peeling off or breaking under vibration. Typically, the weld ring width should exceed 0.3mm. The pad hole diameter should be slightly larger than the pin diameter of the device, but not excessively so. Ensure that the distance between the pin and the pad is minimal and that the pad hole size does not hinder normal inspection. The pad hole diameter is generally 0.1-0.2mm larger than the pin diameter. Multi-pin devices may require larger pads to facilitate smooth inspection.
2. Electrical connections should be as wide as possible, with the width ideally exceeding the pad diameter. In special cases, the line must be widened (commonly called a tear drop) when connecting to the pad to avoid breakage between certain conditional lines and the pad. The line width should be at least 0.5mm.
3. Components on a single panel should be firmly attached to the circuit board. For devices requiring overhead heat dissipation, adding sleeves to the pins between the devices and the circuit board can support the devices and improve insulation, minimizing or avoiding impacts on the bond pad-to-pin connection and enhancing welding solidity. Heavy components, such as transformers and power device radiators, can benefit from increased support connection points to enhance the connection strength with the circuit board.
4. The pin of a single-panel welded surface can be kept longer without affecting the distance from the outer shell. This approach increases the strength and area of the weld and helps quickly detect virtual welding issues. A longer pin means less force on the welded part. In Taiwan and Japan, bending the pin at a 45-degree angle to the circuit board before welding is a common practice for the same reason.
5. Now, let’s delve into double-panel design issues. In high-requirement or high-line-density environments, double-sided PCBs perform better than single panels. Since the holes are metallized to a higher strength, the ring can be smaller compared to a single panel. The hole diameter on a double panel can be slightly larger than the pin diameter, which aids in tin solution penetration during welding, improving weld reliability. However, if the hole is too large, some device parts may float under jet tin impact during peak soldering, potentially causing defects.
6. For high-current lines, the width can be treated as previously mentioned. If the width is insufficient, tin plating can generally be used to increase thickness. Various solutions exist:
1. Design the route as a bonding pad to avoid solder coverage during circuit board manufacturing and ensure tin plating during hot air conditioning.
2. Place the pad in the wiring and set it to the desired shape, ensuring the pad hole is zero.
3. This method is flexible for placing wires in the solder-resistant layer but may require clear instructions to manufacturers, as not all will understand your intentions. No solder should be applied where the wire is placed on the solder layer.
7. As noted, if a wide line is completely tin-plated, it may bond unevenly after soldering, affecting appearance. Generally, long, thin tin-plated strips with a width of 1–1.5mm are used, with length determined by the line. Double-sided circuit boards with 0.5–1mm spacing between tin-plated parts provide more layout flexibility, making wiring more efficient. For grounding, power ground must be separated from signal ground, and they can be joined at the filter capacitance to avoid instability from large pulsed currents. Signal control circuits should use point grounding where possible. It’s beneficial to place non-grounded lines on one layer and ground wires on another. Typically, the output line passes through filter capacitance before reaching the load, and the input line must pass through capacitance before reaching the transformer. This setup ensures ripple current passes through the filter capacitance.
8. For voltage feedback sampling, to avoid the impact of large currents, place the feedback voltage sampling point at the power output end to improve the load effect index of the entire unit.
9. Wiring between layers is usually done through holes, which should not be placed through pin pads to avoid damaging the connection when inserting the device. At least two holes per 1A current are recommended, with a hole size greater than 0.5mm, typically 0.8mm, to ensure processing reliability.
10. In small power sources, circuit board wiring can also serve as heat dissipation. The wiring should be as wide as possible to increase heat dissipation area, with no solder applied. If conditions permit, evenly spaced holes can enhance thermal conductivity.
