1. In the manufacturing of electronic products, as products continue to shrink in size and increase in complexity, the assembly density of circuit boards is rising significantly. The latest generation of SMT assembly processes, which have been developed and widely adopted, requires designers to prioritize manufacturability. If design inadequacies lead to poor manufacturability, modifications will be necessary, which can extend product introduction timelines and increase costs. Even minor adjustments to the PCB layout can result in the need for re-manufacturing the printed board and the SMT solder paste printing screen, with expenses reaching thousands or even tens of thousands of yuan. Additionally, analog circuits may require re-debugging. Delays in product rollout can cause companies to miss valuable market opportunities, placing them in a strategically disadvantaged position. Conversely, producing the product without making necessary modifications can lead to manufacturing defects or significantly increased costs, resulting in even greater repercussions. Thus, when a company designs a new product, considering manufacturability as early as possible is crucial for the successful introduction of new products.
2. Key Considerations When Designing PCBs
The manufacturability of PCB design can be categorized into two areas: one pertains to the processing technology for producing printed circuit boards, while the other involves the assembly technology of circuit and structural components with printed circuit boards. In terms of PCB processing technology, typical PCB manufacturers, due to their manufacturing capabilities, provide designers with detailed requirements, which is beneficial in practice. However, the author observes that the second category—design for electronic assembly—often receives insufficient attention. This article aims to address the manufacturability considerations that designers must keep in mind during the PCB design phase.
Design for electronic assembly necessitates that PCB designers take the following aspects into account early in the design process:
2.1 Appropriate Selection of Assembly Methods and Component Layout
Selecting the right assembly method and arranging components effectively are critical for PCB manufacturability, significantly influencing assembly efficiency, costs, and product quality. The author has encountered numerous PCBs and identifies some fundamental principles, though challenges remain.
(1) Choose a Suitable Assembly Method
Typically, based on the PCB’s assembly density, the following assembly methods are recommended:
To effectively design PCBs, circuit design engineers should have a clear understanding of the assembly process flow. This awareness helps avoid fundamental errors. When selecting an assembly method, it’s essential to consider the PCB’s assembly density, wiring complexity, the typical process flow of the method, and the company’s processing capabilities. For instance, if the company lacks an efficient wave soldering process, opting for the fifth assembly method listed may lead to significant complications. Additionally, if wave soldering is planned for the soldering surface, it is advisable to limit the number of SMDs in that area to prevent process complications.
(2) Component Layout
The arrangement of components on the PCB profoundly affects production efficiency and cost, serving as a key indicator of the design’s installability. Generally, components should be laid out as evenly, regularly, and neatly as possible, maintaining uniform direction and polarity. A systematic arrangement facilitates inspection, enhances patch/plug-in speed, and promotes optimal heat dissipation and soldering processes. Furthermore, PCB designers must recognize that only one group soldering process—either reflow or wave soldering—can be utilized on any side of the PCB. This is particularly important when assembly density is high, and the soldering surface accommodates numerous SMD components. Designers should decide on the appropriate group soldering process for components on the soldering surface. The ideal approach is to employ wave soldering after the patch has cured, allowing simultaneous soldering of the pins of through-hole devices on the component surface. However, wave soldering imposes strict limitations on SMD components; only chip resistors sized 0603 and larger, and SOT, SOIC packages (pin spacing ≥ 1mm and height < 2.0mm) are suitable for soldering. For components on the soldering surface, pin orientation should be perpendicular to the PCB's transmission direction during wave soldering to ensure that the solder pads or leads on both sides of the component are dipped simultaneously. The order and spacing between adjacent components must also comply with wave soldering requirements to avoid the "shading effect." When utilizing wave soldering for multi-pin components like SOIC, it is advisable to incorporate tin-stealing pads at the last two solder feet (one on each side) in the tin flow direction to prevent continuous soldering.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
2. Key Considerations When Designing PCBs
The manufacturability of PCB design can be categorized into two areas: one pertains to the processing technology for producing printed circuit boards, while the other involves the assembly technology of circuit and structural components with printed circuit boards. In terms of PCB processing technology, typical PCB manufacturers, due to their manufacturing capabilities, provide designers with detailed requirements, which is beneficial in practice. However, the author observes that the second category—design for electronic assembly—often receives insufficient attention. This article aims to address the manufacturability considerations that designers must keep in mind during the PCB design phase.
Design for electronic assembly necessitates that PCB designers take the following aspects into account early in the design process:
2.1 Appropriate Selection of Assembly Methods and Component Layout
Selecting the right assembly method and arranging components effectively are critical for PCB manufacturability, significantly influencing assembly efficiency, costs, and product quality. The author has encountered numerous PCBs and identifies some fundamental principles, though challenges remain.
(1) Choose a Suitable Assembly Method
Typically, based on the PCB’s assembly density, the following assembly methods are recommended:
To effectively design PCBs, circuit design engineers should have a clear understanding of the assembly process flow. This awareness helps avoid fundamental errors. When selecting an assembly method, it’s essential to consider the PCB’s assembly density, wiring complexity, the typical process flow of the method, and the company’s processing capabilities. For instance, if the company lacks an efficient wave soldering process, opting for the fifth assembly method listed may lead to significant complications. Additionally, if wave soldering is planned for the soldering surface, it is advisable to limit the number of SMDs in that area to prevent process complications.
(2) Component Layout
The arrangement of components on the PCB profoundly affects production efficiency and cost, serving as a key indicator of the design’s installability. Generally, components should be laid out as evenly, regularly, and neatly as possible, maintaining uniform direction and polarity. A systematic arrangement facilitates inspection, enhances patch/plug-in speed, and promotes optimal heat dissipation and soldering processes. Furthermore, PCB designers must recognize that only one group soldering process—either reflow or wave soldering—can be utilized on any side of the PCB. This is particularly important when assembly density is high, and the soldering surface accommodates numerous SMD components. Designers should decide on the appropriate group soldering process for components on the soldering surface. The ideal approach is to employ wave soldering after the patch has cured, allowing simultaneous soldering of the pins of through-hole devices on the component surface. However, wave soldering imposes strict limitations on SMD components; only chip resistors sized 0603 and larger, and SOT, SOIC packages (pin spacing ≥ 1mm and height < 2.0mm) are suitable for soldering. For components on the soldering surface, pin orientation should be perpendicular to the PCB's transmission direction during wave soldering to ensure that the solder pads or leads on both sides of the component are dipped simultaneously. The order and spacing between adjacent components must also comply with wave soldering requirements to avoid the "shading effect." When utilizing wave soldering for multi-pin components like SOIC, it is advisable to incorporate tin-stealing pads at the last two solder feet (one on each side) in the tin flow direction to prevent continuous soldering.
If you have any PCB manufacturing needs, please do not hesitate to contact me.Contact me
