DFA (Design For Assembly) Checks: Ensuring Assembly Success
Muhammad Hanzala Iqbal
Master’s Candidate in IoT & Wireless Technologies | PCB CAM Engineer | Electrical Engineering Graduate ('23)
In the intricate world of electronics manufacturing, ensuring that boards pass through assembly without issues is crucial. Scrapping boards due to assembly errors not only wastes materials but also incurs significant costs and delays. This is where DFA (Design For Assembly) checks come into play. DFA checks are designed to identify and mitigate potential assembly issues early in the design phase, ensuring a smoother manufacturing process.
Key DFA Checks to Prevent Board Scrapping:
1. Body to Body:
This item checks the clearance of the component body to body. in this check we make insure two components will be placed at a specific distance, so that they cannot cause an issue of electric shorts. if the components are placed too closed to each other, it is difficult to perform a rework on that PCB.
Below given fig show spacing between different components.
2. Lead to Hole:
Checks the clearance between the PTH component lead and Hole. If there is not enough clearance, it result in soldering issues. to meet the IPC requirements for PTH component soldering there should be a clearance of 15 mils between lead and hole.
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3. PTH Lead Protrusion:
Check the length of PTH component lead. if a lead protrusion is negative, it will be assemble with SMD components during reflow soldering process. while if a lead protrusion is positive, it should be according to the IPC callouts. if it is much longer than the allowed length it can cause short circuits.
4. Package Pin and Footprint:
Check the distance between package lead and footprint pad. Inspects toe-print and heel-print of the SMD package, if the toe and heel are not according to the requirements. The solder past will not form a proper filet and cause an issue of cold solder joints.
5. Board edge to component:
Check the clearance between the component and board edge. All the components must have at least 125 mil clearances (air gap) from the board outline and 200mils from conveying edge (usually upper and lower edges of board).
Implementing these DFA checks early in the design process can significantly reduce the risk of board scrapping during assembly. By focusing on these critical areas, manufacturers can improve yield, reduce costs, and ensure a more reliable end product.