Issue link: https://resources.pcb.cadence.com/i/1541046
39. Reviewing Design for Manufacturability (DFM) and Assembly Constraints How To Implement 1. Obtain and review your fabricator's and assembler's capability documents: f Collect the latest specs for minimum trace/space, via sizes, annular ring, component spacing, copper-to-edge, stencil/paste specs, component orientation, and board thickness constraints. f Check guidelines for double-sided assembly, fine-pitch/ BGA handling, selective wave solder, and process-specific rules. 2. Apply DFM rules in your CAD tool and constraint manager: f Set up all manufacturability constraints: part-to-part, part-to-board edge, via and trace rules, minimum mask/ paste openings, component keepouts for automated assembly and inspection, and fiducial requirements for pick-and-place and AOI. f Use part orientation standards to optimize pick-and-place sequencing and reflow profile. 3. Use automated DFM checks and validation tools: f Run built-in or third-party DFM checks to flag violations: minimum feature size, solder mask slivers, insufficient paste, component spacing, polarity errors, and fiducial placement. f Pay special attention to fine-pitch parts, dense clusters, and "hybrid" assembly zones (mix of SMD, TH, BGA, connectors). 4. Review component orientation, accessibility, and handling: f Place components with consistent orientation (e.g., pin 1 all in the same direction) where possible for assembly efficiency. f Ensure no parts are shadowed by taller components or located under mechanical constraints (heatsinks, enclosures) that block pick-and-place heads or inspection cameras. f Avoid placing fragile parts (crystals, large electrolytics) at the board edge or near breakaway tabs. 5. Check for cleaning, rework, and test accessibility: f Maintain clearances for cleaning under low-profile parts or BGAs if the board will be washed. f Ensure there is probe access to all required test points. f Provide rework space around BGAs, FPGAs, and high-pin-count ICs as recommended by your assembler. 6. Engage with your CM (contract manufacturer) for feedback: f Submit design for DFM/DFT (Design for Test) review before final release. f Address feedback quickly; iterate as needed to resolve manufacturability or assembly risks. Common Pitfalls, Their Impact, and How to Avoid Them Common Pitfall How to Avoid it Ignoring CM guide- lines or assembly constraints Leads to rejected builds, costly rework, or "design-locked" issues – Incorporate CM assembly and design rules in your DRC/DFM checks. Inadequate spacing for high-density or tall parts Causes pick-and-place or soldering problems, high defect rates – Set minimum clearance rules. Missing DFM check for new/complex parts New packages or process flows can require special handling – Perform a DFM review with your CM or update your design rules library. Not planning for test, cleaning, or rework Makes future servicing difficult or impossible – Incorporate test features from the start and provide adequate component spacing.