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DFM's Key Role in PCB Manufacturing

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DFM's Key Role in PCB Manufacturing

May 7, 2024

DFM design in PCB stands for Design for Manufacturability in Printed Circuit Board.

In today's highly digital and electronic era, printed circuit boards (PCBs) serve as a backbone and crucial foundation for connecting and supporting electronic components. The quality and efficiency of PCB manufacturing are essential. The impact of design on manufacturing lies in DFM (Design for Manufacturing) – that is, designing for manufacturing. Design for Manufacturing (DFM) plays a crucial role in PCB manufacturing by enhancing manufacturing efficiency, reducing costs, and guaranteeing the quality and reliability of the final product. This article will explore the critical role of Design for Manufacturability (DFM) in PCB manufacturing.

Application of DFM in PCB Production

PCB Production

1. Material Selection

DFM technology can assist designers in selecting materials suitable for PCB production. Choosing the appropriate material is crucial for ensuring the stability and durability of the PCB board itself, as well as for meeting various process requirements during the PCB manufacturing process.

2. Design Optimization

Through Design for Manufacturing (DFM) technology, designers can optimize PCB board layout and component placement to minimize line length and complexity, thereby enhancing circuit performance and reliability. In addition, optimized design can also reduce energy consumption, thermal issues and costs.

3. Manufacturing Process Optimization

DFM technology can assist manufacturers in optimizing production processes and enhancing production efficiency. By optimizing the process flow and equipment configuration, the production cycle can be shortened, production costs reduced, and product quality improved.

4. Troubleshooting

Troubleshooting is an essential aspect of the PCB production process. DFM technology can assist designers in predicting potential manufacturing problems and making corresponding corrections during the design stage. This can help reduce failure rates and enhance product reliability.

5. Quality Control

Through Design for Manufacturing (DFM) technology, more stringent quality control can be achieved. By considering various factors in the manufacturing process during the design stage, the defect rate in production can be reduced, ensuring that product quality meets standard requirements.

pcb manufacturing

Key DFM Inspection Guide Before PCB Fabrication

DFM (Design for Manufacturability) inspection is an essential step in PCB design to ensure that the circuit board can be manufactured smoothly. Here are some key considerations when it comes to Design for Manufacturability (DFM) inspections.

Line Width and Line Spacing Check

Line width/line spacing check: The line width size is closely related to the current carrying capacity. The smaller the line width, the lower the current-carrying capacity. When routing multiple high-speed signal lines over long distances, it is important to follow the 3W principle. This principle ensures that the line spacing meets specifications, which helps to minimize signal interference and crosstalk.

PCB line width

Choosing the right PCB manufacturer is crucial to avoid manufacturing quality risks caused by line width and line spacing. If the line width is too small, it may cause excessive etching or even open circuit problems. Conversely, if the line spacing is too small, the sandwich film may not be etched cleanly, or the etching may not reach the trace spacing, resulting in a short circuit.

A Hole-To-Hole Inspection

Insufficient hole spacing may affect the quality and yield of manufacturing, and could even lead to drill breakage during the drilling process.

Insufficient hole spacing between different networks may cause the Conductive Anodic Filament (CAF) effect and increase the risk of electrical short circuits.

If the distance between plug-in holes is too small, it may increase the risk of soldering short circuits.

Hole-To-Hole Inspection

On-Hole Pad Inspection

The term "pad on the hole" refers to the hole on the patch pad, similar to the concept of a "hole in the plate" in the design. The presence of holes on the patch pad will cause the pad to be concave and uneven, thereby affecting the welding quality. To ensure the reliability of welding, the holes on the pads need to be plated flat, but this will increase manufacturing costs. In the design, it is important to minimize the occurrence of pads on holes to prevent higher manufacturing costs and welding quality issues, particularly problems like virtual soldering.

On-Hole Pad Inspection

Component Packaging Inspection

Selecting Component and Package Size: It is crucial to determine the size of components and packages by thoroughly studying the Bill of Materials (BOM). If space permits, larger resistor and capacitor sizes may be selected. For example, a 0603 or 0805 size capacitor/resistor could be used instead of a 0402 or 0201. By doing so, assembly fault tolerance is enhanced, and problems during assembly are reduced

Component Packaging Inspection

If possible, choose smaller packages. While small packages can save space, excessive use of them can complicate board assembly and make cleaning and rework more challenging. Therefore, a trade-off should be made between size and performance. It is important to select an appropriately sized package to ensure the simplicity and reliability of the assembly process.

Silk Screen Inspection

The silkscreen layer contains a lot of important information. Some examples include component orientation markings, pin 1 markings, polarity markings, cathode markings, etc.

It is crucial to ensure that the information on the silkscreen layer is clearly legible. In the worst-case scenario, if the silkscreen incorrectly labels data such as polarity, the assembler may install the component accordingly, leading to potential board to malfunction.

Therefore, before assembly begins, it is important to ensure that the information on the silk screen layer is accurate and clearly readable to guarantee proper assembly and reliable board functionality.

PCB Footprint Creation Guidelines

Check the Spacing Between Components

Insufficient component spacing is a common Design for Manufacturability (DFM) error that requires special attention in PCB design. Ensuring that there is adequate clearance between components during component placement is critical to prevent overlapping parts, the formation of solder bridges, and to facilitate manual soldering and rework.

It is even more important for sensitive components, such as QFP/QFN, POP, or BGA, to be handled with care. These components typically have higher pin densities and more complex soldering requirements. Therefore, it is important to ensure that there is sufficient clearance between them to avoid any soldering issues or shorts.

Sometimes components may be placed closely to achieve a smaller form factor, but doing so may cause subsequent manufacturing or repair issues. Therefore, it is best to follow spacing guidelines and ensure that you provide appropriate clearance for each element in your design to ensure a zero-error layout.

The image below shows the preferred component layout on the PCB.

preferred component layout on the PCB

Pad Size and Spacing Inspection

Choosing a smaller pad size may result in poor solder joints in SMT components and could potentially lead to breakage when applied to through-hole parts.

Making the pad size as large as possible may not be the solution. A wider pad will occupy more space and may displace the SMT component from its original position during soldering.

Similar to pad size, pad spacing cannot be too close or too far apart, as this can lead to issues during component placement.

Pad Size and Spacing

Overall, the crucial role of Design for Manufacturability (DFM) in PCB manufacturing cannot be ignored. It lays a solid foundation for PCB manufacturing by considering manufacturing requirements during the design stage, optimizing layout and process selection, and enhancing production efficiency and quality.

With the continuous development of technology and the changing market, the significance of Design for Manufacturability (DFM) will become increasingly prominent. Only by fully understanding and applying Design for Manufacturability (DFM) can we better meet customer needs, maintain competitive advantages, and promote the sustainable development of the PCB manufacturing industry.