PCB Tech - Summarize the principles of PCBA manufacturability design

1. Optimizing 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 categories 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.

Crimping components are mainly multi-pin connectors. This type of package also has good manufacturability and connection reliability, and is also a preferred category.

2. Taking the PCBA assembly surface as the object, considering the package size and pin spacing as a whole

The biggest impact on the overall board manufacturability is the package size and pin spacing. On the premise of selecting surface mount components, a set of packages with similar processability or a package suitable for solder paste printing on a certain thickness of stencil must be selected for a PCB of a specific size and assembly density. For example, for mobile phone boards, the selected packages are suitable for solder paste 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:

Single-sided reflow welding;

Double-sided reflow welding;

Double-sided reflow soldering + wave soldering;

Double-sided reflow soldering + selective wave soldering;

Double-sided reflow welding + manual welding.

4. Optimize the layout of components

Principle 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, and can optimize the design of steel mesh.

5. Consider the design of pads, solder masks and steel mesh windows as a whole

The design of pads, solder mask and stencil opening determines the actual distribution of solder paste and the formation process of solder joints. Coordinating the design of pad, solder mask and steel mesh has a great effect on improving the straight-through rate of welding.

6. Focus on new packaging

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, a small batch of process verification should be carried out. Others can use it, it doesn't mean you can use it. The prerequisite for using it is to have done experiments, understand the process characteristics and problem spectrum, and master the countermeasures.

7. Focus on BGA, chip capacitors and crystal oscillators

BGA, chip capacitors, and crystal oscillators are typical stress-sensitive components. When layout, avoid placing PCBs in places where the PCB is prone to bending and deformation during welding, 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 poor assembly or failure cases is of great significance for improving design for manufacturability.