During the assembly process of PCB (Printed Circuit Board), the inspection of DFM (Design for Manufacturing, Design for Manufacturing) design rules is a key step to ensure that the PCB design meets the manufacturing process requirements and improves production efficiency and product quality. The following are the detailed steps for checking the DFM design rules during the PCB assembly process:
First, the preparation stage
Receive design data
When the contract manufacturer (CM) receives the design data for the first time, it should confirm the completeness and accuracy of the data.
If the data is received in the format of the PCB design CAD database, it will directly enter the engineering field for review.
If the data is received in other formats, it needs to be imported or converted into a tool used by CM. This process is time-consuming and less reliable. Therefore, it is recommended to obtain the original CAD database as much as possible.
Form an inspection team:
Form an inspection team including component engineers, design engineers and manufacturing engineers.
Each party should clearly define their responsibilities and tasks to ensure the smooth progress of the inspection work.
Second, design data review
Check the Bill of Materials (BOM) :
Component engineers check the BOM table to look for parts that are not recommended for manufacturing, have long delivery times, or are approaching the end of their service life (EOL).
Based on the inventory database of the main component suppliers, put forward any suggestions required for part replacement.
Check the design documents:
Design engineers use DFM inspection software (such as Huaqiu DFM) to conduct a comprehensive inspection of design documents.
Check the manufacturability of the design by customizing or using predefined DFM rules.
Third, the specific steps for checking the DFM design rules
Component layout check:
Check whether the component spacing is reasonable to avoid solder bridging or short circuit during the soldering process.
Check whether the layout of large-sized components is reasonable to avoid affecting the structural stability of the PCB.
Ensure the consistency of component directions to facilitate the installation of components on the machine during production.
Wiring inspection
Check whether the line width and line spacing meet the production process requirements to avoid line breaks or short circuits during the etching process.
Check the length, direction and number of vias of the high-speed signal line to ensure signal integrity.
Impedance matching design is carried out for key signals to ensure the quality of signal transmission.
Pad design inspection
Make sure the size of the pad matches the size of the component pins to avoid loose soldering.
Check whether the pad shape is correct and select the appropriate pad shape based on the shape of the component pins and actual needs.
Make sure that the solder pads are treated with solder mask to prevent green oil from covering the pads and affecting the welding.
Design inspection of holes:
Check whether the diameter and position of the drill holes meet the manufacturing requirements.
Ensure that the hole spacing meets the requirements to prevent broken drill bits or short circuits during the drilling process.
Check whether the size of the hole ring is sufficient to prevent the solder pad from coming off during welding or maintenance.
Inspection of special process requirements
If the design includes special processes (such as blind buried holes, HDI, etc.), check whether these processes match the process capabilities of the manufacturer.
For rigid-flexible composite boards, check whether the special flexible materials and lamination processes required for their production are met.
Testability design check
Check whether sufficient test points have been set up and ensure that the positions of the test points are accessible to the test equipment.
For complex PCBS, consider whether it is necessary to design test interfaces such as boundary scan test (JTAG).
Ensure that the layout of the test points is reasonable, avoiding being blocked by components and maintaining a certain distance from adjacent components.
Other examinations:
Check whether the PCB material is suitable for the production process and the application environment of the product.
Ensure that the edge of the PCB board is left with a sufficiently wide process edge and that sufficient positioning holes are designed.
Check whether the design meets other specific requirements (such as EMC, thermal design, etc.).
Fourth, generate inspection reports
Record the inspection results:
Record in detail the problems found during the inspection process, including the location of the problem, the problem description and the suggested modification plan.
Generate the inspection report:
Generate detailed inspection reports based on the inspection results for the reference of design engineers and manufacturing engineers.
The report should clearly indicate which design rules have been violated and provide suggestions for improvement.
Fifth, problem rectification and verification
Problem rectification:
The design engineer modifies and optimizes the design documents based on the inspection report.
After the modification is completed, use the DFM inspection software again for verification to ensure that all problems have been solved.
Production verification
Before PCB production, a small-scale trial production is conducted to verify whether the modified design documents meet the manufacturing process requirements.
Make final adjustments and optimizations to the design documents based on the trial production results.
Through the above steps, it can be ensured that the PCB design meets the manufacturing process requirements, improving production efficiency and product quality, and reducing production costs.
