Building PCBs with a high production yield requires a thorough evaluation of the design and assembly processes. You may have to tick multiple checklists before submitting your PCB design for manufacturing. Adhering to the DFM (Design for Manufacturability) guidelines is crucial. The reliability of a circuit operation depends on the manufacturing processes. If counterfeit components are mounted, the board will fail prematurely adding debug costs to your account. An accurate PCB BoM (Bill of Materials) and an approved vendor list is vital in procuring genuine components.
The PCB material chosen should be based on the operating temperature and the design functionality. During the fabrication process, the physical construction of the PCB impacts its structural integrity. Sharing comprehensive design data with your contract manufacturer can avoid delays in PCB manufacturing. Starting from design to assembly, each stage must meet the necessary quality requirements for building a successful PCB product. You can create a suitable design checklist to verify these critical aspects before handing it over to your CM.
PCB quality checklist can avert possible errors during the design or manufacturing stages. They can track any negligence or unnoticed mistakes in PCB development. The latest EDA tools come with in-built design and layout guidelines that support effective PCB fabrication. If any new component is introduced in the design, it is important to obtain its manufacturer’s datasheet to create a precise footprint. Developing the 3D model and simulating the component placement on the board can avoid assembly issues or respin. We will list out and discuss important checkpoints to consider while you are placing online PCB order and proceed to its manufacturing as a final product.
Things to Check Before Placing Online PCB Manufacturing Order
1. Design Specification
An initial schematics review is done to validate the circuit functionality to be aligned with the design specifications. A DRC (Design Rule Check) is run on the schematics and errors are cleaned. All components used in the schematics should be updated with the latest library files to avoid any placement issues during assembly.
PCB prototype testing reports are analysed and design modifications are completed for the final product. Understanding the end product and its main objectives is the first checkpoint in the PCB design.
2. Component placement and layout verifications
PCB layout involves stack-up design, strategic component placement, and routing. Signal integrity depends largely on the power and ground planes in the stack-up. Logical component placement with enough clearance from board edges is important. Check for visible reference designators on the board for connectors and other main components.
Layout tools can recommend necessary placement and routing requirements for the PCB design. Some of the critical layout guidelines to check before PCB manufacturing are:
- Avoid 90° trace bends as they can trap residual acid during the fabrication process. This will further etch out copper from the traces and can create open connections.
- Copper pour near the board edges may cause short in adjacent layers. Maintain enough clearance to avoid such mistakes.
- Ensure through-hole/ via diameter matches with the board’s aspect ratio. This can prevent production issues wherein vias may crack due to thermal expansion.
- Check for any void in the thermals used to provide enough heat during soldering. The void can cause irregular soldering during the reflow process and may lead to functional failures.
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3. Mechanical dimensions and drill details
Board dimensions and hole/via details should be checked in the Gerber files before sharing with the CM. 3D models of the PCB components can assist in identifying mounting issues, connector mating errors, etc. So, generating 3D models and simulating the assembly is a critical checkpoint before going for PCB manufacturing.
4. Silkscreen and Solder mask
Legible PCB silkscreen is used to identify the components’ location and orientation on the PCB. During the circuit design, it is important to ensure enough spacing between the silkscreen and the component outline. Also, the silkscreen should not be placed on a copper layer without a solder mask as the ink may melt in the solder joints. Follow uniform silkscreen size throughout the PCB design.
A solder mask is applied to isolate the copper traces from incorrect soldering. Applying solder masks in high-density designs is cumbersome. In such cases follow the clearance restrictions to avoid solder bridges. EDA tools can be configured to set the required distance between the solder mask and the surface components. A DRC check and a detailed layout review are mandatory checkpoints before proceeding with the PCB fabrication process.
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5. PCB Fabrication checks
A fab drawing provides the manufacturing requirements of a PCB design. It includes the board outline, layer stack up, drill file, title block, etc. It is different from assembly drawing which is used to provide component assembly details. It is important to check that all necessary fabrication data is included in the package.
6. Production file compatibility
Open database (ODB) ++ is the commonly used CAD-to-CAM exchange file format that conveys the required design information to a PCB manufacturer. While a Gerber file alone doesn’t provide complete information, it is necessary to share the centroid (X-Y placement) file, drill file, netlist, and readme text also. IPC-2581 file format and ODB ++ are the intelligent formats for design data delivery. Ensure that your production file package is compatible with your CM’s system.
7. BoM check
Before going ahead with the PCB manufacturing, you must check your Bill of Material for component availability. Look for Do Not Install (DNI) components and obsolete parts in the BoM. Provide an approved vendor list to procure alternate parts for your CM.
8. Obtain Certifications
It is important to acquire all the required certifications for your design before going ahead with bulk production. Based on the end application, list the industry certifications required for your product. Your CM can assist you in getting those certificates.
Conclusion
DFM checklists will help you to optimize your product cost and minimize potential failures during PCB manufacturing. These checkpoints will ensure product quality and high manufacturing output. Neglecting these checks may result in reliability issues and delay in your product delivery.
If you want to prevent potential issues and streamline the process while saving both time and cost, choosing Mermar Electronics is the smartest move. We offer comprehensive PCB services including PCB assembly, fabrication, and design, all in one place. Simply complete the form below to request a complimentary quote or email sales@mermarinc.com .
