What are the basic principles of PCBA manufacturability design? Let’s take a look with the editor of Dongguan SMT processing factory.
1. Preferred surface assembly and crimping components.
Surface mount components and crimping components have good manufacturability. With the development of component packaging technology, most components can be purchased in packaging types suitable for reflow soldering, including plug-in components that can be soldered by through-hole reflow soldering. If the design can achieve full surface assembly, it will greatly improve the efficiency and quality of assembly. Bed-connected components are mainly multi-pin connectors. This type of package also has good manufacturability and connection reliability. It is also a preferred category.
2. Targeted at PCBA assembly.
Overall consideration of package size and pin spacing. For the entire board I: The biggest impact on the craftsmanship is the package size and pin spacing. Under the premise of selecting surface mount components, you must select a set of I: a package with similar craftsmanship or a package suitable for solder paste printing on a certain thickness of stencil for the PCB of a specific size and assembly density. For example, for mobile phone boards, the selected packaging is suitable for welding and printing with 0.1mm thick steel mesh.”
3. Shorten the process path
The shorter the process path, the higher the production efficiency and the more reliable the quality.
The preferred process path design is:
(1) Single-sided reflow welding;
(2) Double-sided reflow welding;
(3) Double-sided reflow soldering + wave soldering;
(4) Double-sided reflow soldering + selective wave soldering;
(5) Double-sided reflow welding + manual welding.
4. Optimize the layout of components
Component layout design mainly refers to the layout and spacing design of components. The layout of the components must meet the requirements of the welding process. Scientific and reasonable layout can reduce the use of bad solder joints and tooling. It can optimize the design of steel mesh.
5. Consider the pad as a whole,
Design of solder mask and stencil opening. Design of pad, solder mask and stencil opening. Determine the actual distribution value of solder paste and the formation process of solder joints. Coordinating the design of pad, solder mask and stencil has a great effect on improving the welding pass-through rate.
6. Focus on new packages
The so-called new package does not completely refer to the packages that are newly available on the market, but to those packages that the company has no experience in using. For the introduction of new packages, small batch process verification should be carried out = others can use it, it does not mean that you can use it. The prerequisite for use must be that you have done a trial. Understand the process characteristics and potential problems, and master the countermeasures.
7. Focus on BGA, chip capacitors and crystal oscillators
BGAs, chip capacitors, and crystal oscillators are typical stress-sensitive components. During layout, avoid placing them in places where PCBs are prone to bending and deformation during soldering, assembly, workshop turnover, transportation, and use.
8. Study cases to improve design rules
Design rules for manufacturability are derived from production practices. Continuous optimization and improvement of design rules based on continuously emerging cases of poor assembly or failure are of great significance for improving design for manufacturability.