1. **Definition of PCB Processing Technology and Assembly Process**
The first refers to the manufacturing technology involved in the production of printed circuit boards;
The second pertains to the assembly process of the circuit and structural components onto the printed circuit board.
When it comes to PCB production technology, most PCB manufacturers, based on their capabilities, typically provide designers with detailed requirements that are often quite practical and comprehensive.
From the author’s perspective, the second category focuses on manufacturability design for electronic assembly. This article specifically addresses manufacturability considerations that designers must keep in mind during the PCB design phase.
2. **Appropriate Selection of Assembly Method and Component Layout**
The selection of the assembly method and component layout plays a critical role in PCB manufacturability. It significantly impacts assembly efficiency, cost, and overall product quality. In the author’s experience with numerous PCBs, even while adhering to basic principles, there have been occasional oversights.
**Choosing the Right Assembly Method**
Generally, depending on the assembly density of the PCB, the recommended assembly methods are as follows:
**Understanding PCB Design Manufacturability**
As a circuit design engineer, it is essential to have a clear understanding of the PCB assembly process for the design you are working on. This awareness helps avoid common, fundamental mistakes. When selecting an assembly method, it is important not only to consider the PCB’s assembly density and routing complexity but also to evaluate the typical process flow for the chosen method and the capabilities of your company’s process equipment.
For instance, if your company lacks an advanced wave soldering process, selecting the fifth assembly method in the table above could lead to significant challenges.
Another important point to consider is that if wave soldering is part of the process, you should avoid placing SMD components on the soldering surface, as this could complicate the process unnecessarily.
3. **PCB Component Layout**
1. The component layout on the PCB significantly influences both production efficiency and cost, serving as a key indicator of the PCB design’s manufacturability.
2. In general, components should be arranged as evenly, regularly, and neatly as possible, with consistent orientation and polarity distribution.
3. A well-organized arrangement facilitates inspection, speeds up the placement and soldering processes, and helps optimize heat dissipation and the soldering process.
4. On the other hand, PCB designers must always remember that only one soldering process—either reflow soldering or wave soldering—can be used on any side of the PCB.
5. This consideration is especially important when dealing with high assembly densities, where the soldering side of the PCB must accommodate more SMD components.
6. Designers should evaluate which soldering process is most suitable for the components on the soldering side. The preferred approach is to use wave soldering after the SMD components are placed and cured, as this process can simultaneously solder the pins of through-hole components.
7. However, wave soldering has strict limitations for SMD components; only chip resistors and capacitors (size 0603 and larger), as well as SOT and SOIC packages (pin pitch ≥ 1mm, height < 2.0mm), are compatible with this method.
8. For components placed on the soldering side, it is critical to ensure the pin orientation is perpendicular to the PCB’s transmission direction during wave soldering, so that both ends of the component leads are dipped in solder simultaneously.
9. The arrangement order and spacing between adjacent components must also meet wave soldering requirements to prevent the “shading effect” (as illustrated in Figure 1).
10. When using wave soldering for multi-pin components like SOIC, tin-shunting pads should be added to the last two solder pads (one on each side) in the direction of the solder flow to prevent bridging.
11. What constitutes the manufacturability of PCB design?
12. Components of similar types should be aligned in the same direction on the PCB to facilitate component placement, inspection, and soldering.
13. For example, all radial capacitors’ negative poles should face the same side of the board, and the notch of all dual in-line packages (DIPs) should point in the same direction. This standardization accelerates insertion and error detection.
14. Using this method, it is easier to detect reverse polarity on board A, whereas board B would require more time for error identification.
15. In fact, a company can standardize the orientation of components across all PCBs it manufactures. While not all board layouts may allow for this, it is a goal worth striving for.
16. Moreover, components of the same type should, whenever possible, be grouped together, and the first pins of all components should align in the same direction.
17. What constitutes the manufacturability of PCB design?
18. However, the author has encountered numerous PCBs where high assembly densities demand the inclusion of taller components, such as tantalum capacitors, chip inductors, and fine-pitch devices like SOIC and TSOP. In such cases, only reflow soldering after double-sided solder paste printing can be used, and the placement of through-hole components should be concentrated in areas that accommodate manual soldering.
19. Another option is to distribute through-hole components along several main straight lines to facilitate the latest selective wave soldering process. This minimizes the need for manual soldering, enhancing both efficiency and soldering quality.
20. A scattered distribution of solder joints is detrimental to selective wave soldering, as it exponentially increases processing time.
21. When adjusting component positions in the PCB layout file, it is crucial to maintain a one-to-one correspondence between the components and their silkscreen symbols.
22. Moving components without adjusting the corresponding silkscreen symbols can introduce significant quality risks during manufacturing, as the silkscreen symbols serve as the universal industry language guiding production.
23. The PCB design must include clamping edges, positioning marks, and process holes for automated production. Currently, electronic assembly is one of the most automated industries, and the equipment used in production requires automatic PCB handling.
24. In the PCB transfer direction (typically along the long side of the board), a clamping edge of at least 3-5mm in width is necessary on both the top and bottom to enable smooth automatic transport and prevent assembly issues for components near the board’s edge.
25. Positioning marks are essential for modern optical assembly equipment, which requires at least two to three marks for the optical recognition system to accurately align the PCB and correct processing errors.
26. Of the commonly used positioning marks, two should be placed diagonally across the PCB. The marks should be standard shapes, such as solid round pads, and should be surrounded by an area free of other circuit features or markings for easy identification.
27. Ideally, the size of the positioning mark should be no smaller than its diameter, and the mark should be positioned at least 5mm from the board’s edge.
If your have any questions about PCB ,please contact me info@wellcircuits.com
The first refers to the manufacturing technology involved in the production of printed circuit boards;
The second pertains to the assembly process of the circuit and structural components onto the printed circuit board.
When it comes to PCB production technology, most PCB manufacturers, based on their capabilities, typically provide designers with detailed requirements that are often quite practical and comprehensive.
From the author’s perspective, the second category focuses on manufacturability design for electronic assembly. This article specifically addresses manufacturability considerations that designers must keep in mind during the PCB design phase.
2. **Appropriate Selection of Assembly Method and Component Layout**
The selection of the assembly method and component layout plays a critical role in PCB manufacturability. It significantly impacts assembly efficiency, cost, and overall product quality. In the author’s experience with numerous PCBs, even while adhering to basic principles, there have been occasional oversights.
**Choosing the Right Assembly Method**
Generally, depending on the assembly density of the PCB, the recommended assembly methods are as follows:
**Understanding PCB Design Manufacturability**
As a circuit design engineer, it is essential to have a clear understanding of the PCB assembly process for the design you are working on. This awareness helps avoid common, fundamental mistakes. When selecting an assembly method, it is important not only to consider the PCB’s assembly density and routing complexity but also to evaluate the typical process flow for the chosen method and the capabilities of your company’s process equipment.
For instance, if your company lacks an advanced wave soldering process, selecting the fifth assembly method in the table above could lead to significant challenges.
Another important point to consider is that if wave soldering is part of the process, you should avoid placing SMD components on the soldering surface, as this could complicate the process unnecessarily.
3. **PCB Component Layout**
1. The component layout on the PCB significantly influences both production efficiency and cost, serving as a key indicator of the PCB design’s manufacturability.
2. In general, components should be arranged as evenly, regularly, and neatly as possible, with consistent orientation and polarity distribution.
3. A well-organized arrangement facilitates inspection, speeds up the placement and soldering processes, and helps optimize heat dissipation and the soldering process.
4. On the other hand, PCB designers must always remember that only one soldering process—either reflow soldering or wave soldering—can be used on any side of the PCB.
5. This consideration is especially important when dealing with high assembly densities, where the soldering side of the PCB must accommodate more SMD components.
6. Designers should evaluate which soldering process is most suitable for the components on the soldering side. The preferred approach is to use wave soldering after the SMD components are placed and cured, as this process can simultaneously solder the pins of through-hole components.
7. However, wave soldering has strict limitations for SMD components; only chip resistors and capacitors (size 0603 and larger), as well as SOT and SOIC packages (pin pitch ≥ 1mm, height < 2.0mm), are compatible with this method.
8. For components placed on the soldering side, it is critical to ensure the pin orientation is perpendicular to the PCB’s transmission direction during wave soldering, so that both ends of the component leads are dipped in solder simultaneously.
9. The arrangement order and spacing between adjacent components must also meet wave soldering requirements to prevent the “shading effect” (as illustrated in Figure 1).
10. When using wave soldering for multi-pin components like SOIC, tin-shunting pads should be added to the last two solder pads (one on each side) in the direction of the solder flow to prevent bridging.
11. What constitutes the manufacturability of PCB design?
12. Components of similar types should be aligned in the same direction on the PCB to facilitate component placement, inspection, and soldering.
13. For example, all radial capacitors’ negative poles should face the same side of the board, and the notch of all dual in-line packages (DIPs) should point in the same direction. This standardization accelerates insertion and error detection.
14. Using this method, it is easier to detect reverse polarity on board A, whereas board B would require more time for error identification.
15. In fact, a company can standardize the orientation of components across all PCBs it manufactures. While not all board layouts may allow for this, it is a goal worth striving for.
16. Moreover, components of the same type should, whenever possible, be grouped together, and the first pins of all components should align in the same direction.
17. What constitutes the manufacturability of PCB design?
18. However, the author has encountered numerous PCBs where high assembly densities demand the inclusion of taller components, such as tantalum capacitors, chip inductors, and fine-pitch devices like SOIC and TSOP. In such cases, only reflow soldering after double-sided solder paste printing can be used, and the placement of through-hole components should be concentrated in areas that accommodate manual soldering.
19. Another option is to distribute through-hole components along several main straight lines to facilitate the latest selective wave soldering process. This minimizes the need for manual soldering, enhancing both efficiency and soldering quality.
20. A scattered distribution of solder joints is detrimental to selective wave soldering, as it exponentially increases processing time.
21. When adjusting component positions in the PCB layout file, it is crucial to maintain a one-to-one correspondence between the components and their silkscreen symbols.
22. Moving components without adjusting the corresponding silkscreen symbols can introduce significant quality risks during manufacturing, as the silkscreen symbols serve as the universal industry language guiding production.
23. The PCB design must include clamping edges, positioning marks, and process holes for automated production. Currently, electronic assembly is one of the most automated industries, and the equipment used in production requires automatic PCB handling.
24. In the PCB transfer direction (typically along the long side of the board), a clamping edge of at least 3-5mm in width is necessary on both the top and bottom to enable smooth automatic transport and prevent assembly issues for components near the board’s edge.
25. Positioning marks are essential for modern optical assembly equipment, which requires at least two to three marks for the optical recognition system to accurately align the PCB and correct processing errors.
26. Of the commonly used positioning marks, two should be placed diagonally across the PCB. The marks should be standard shapes, such as solid round pads, and should be surrounded by an area free of other circuit features or markings for easy identification.
27. Ideally, the size of the positioning mark should be no smaller than its diameter, and the mark should be positioned at least 5mm from the board’s edge.
If your have any questions about PCB ,please contact me info@wellcircuits.com
