In the PCB (printed circuit board) assembly process, DFM (Design for Manufacturing, Design for Manufacturing) design rule inspection 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 DFM design rules during PCB assembly:
First, the preparation stage
Receive design data:
When the contract manufacturer (CM) receives design data for the first time, it shall confirm the completeness and accuracy of the data.
If the data is received in PCB design CAD database format, it will go directly into the engineering field for review.
If the data is received in a different format, it needs to be imported or converted to the tool used by CM, which takes a long time and is less reliable, so it is recommended to obtain the original CAD database as much as possible.
Set up inspection team:
Assemble inspection teams including component engineers, design engineers and manufacturing engineers.
Clear responsibilities and tasks to ensure the smooth conduct of inspection work.
2. Design data review
Check Bill of Materials (BOM) :
Component engineers check the BOM for parts that are not recommended for manufacturing, have long lead times, or are nearing the end of their useful life (EOL).
Make any recommendations for part replacement based on master component supplier inventory database.
Check the design document:
Design engineers use DFM inspection software, such as Huaqiu DFM, to conduct a thorough inspection of design documents.
Customize or use predefined DFM rules to check the manufacturability of your design.
Third, the specific steps of DFM design rules check
Component layout check:
Check whether the component spacing is reasonable to avoid solder bridging or short circuit during welding.
Check whether the layout of large-size components is reasonable to avoid affecting the structural stability of the PCB.
Ensure consistent component orientation and facilitate machine installation of components during production.
Wiring check:
Check whether the line width and line spacing meet the requirements of the production process to avoid line breakage or short circuit in the etching process.
Check the length, direction and number of holes of high-speed signal lines to ensure signal integrity.
The impedance matching design of key signals is carried out to ensure the quality of signal transmission.
Pad design check:
Make sure the pad size matches the pin size of the component to avoid weak welding.
Check the pad shape is correct, according to the component pin shape and the actual need to choose the appropriate pad shape.
Make sure that the solder pad is protected around the pad to prevent green oil from covering the pad and affecting the welding.
Hole design check:
Check that the diameter and position of the drill hole meet the manufacturing requirements.
Ensure that the hole spacing meets the requirements to prevent breakage or short circuit in the drilling process.
Check that the hole ring size is sufficient to avoid pad detachment during welding or maintenance.
Special process requirements check:
If the design includes special processes (such as blind burials, HDI, etc.), check that these processes match the process capabilities of the manufacturer.
For rigid and flexible bonding plates, check whether the special flexible materials and pressing processes required for their production are satisfied.
Testability design check:
Check that sufficient test points are set up and that the test points are located for easy access to the test equipment.
For complex PCBS, consider whether you need to design a test interface such as boundary Scan Test (JTAG).
Ensure that the test points are properly laid out to avoid being obscured by components and to maintain a certain distance from adjacent components.
Other checks:
Check whether the PCB material is suitable for the production process and the application environment of the product.
Ensure that the PCB board edge is left with a sufficient width of the process edge, and designed with sufficient positioning holes.
Check that the design meets other specific requirements (such as EMC, thermal design, etc.).
4. Generate inspection reports
Record the inspection results:
Record the problems found during the inspection, including the location of the problem, the description of the problem, and the recommended solution.
Generate inspection report:
A detailed inspection report is generated based on the inspection results for reference by design engineers and manufacturing engineers.
The report should clearly identify which design rules have been violated and provide recommendations for improvement.
5. Problem rectification and verification
Problem rectification:
Design engineers modify and optimize design documents based on inspection reports.
Once the changes are complete, verify with the DFM check software again to ensure that all issues have been resolved.
Production verification:
Before PCB production, small batch trial production is carried out to verify whether the modified design document meets the manufacturing process requirements.
Make final adjustment and optimization of the design document according to the results of trial production.
Through the above steps, you can ensure that the PCB design meets the manufacturing process requirements, improve production efficiency and product quality, and reduce production costs.
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