Cadence Ebooks

38. Specifying and Checking Solder Mask and Paste Mask Clearances Solder mask and paste mask layers control solderability, bridging, and assembly yield. Solder mask keeps solder confined to pads, prevents bridging and corrosion, and reduces the risk of shorts. Paste mask (stencil opening) controls the amount of solder deposited during assembly. Incorrect mask clearance can cause shorts, opens, tombstoning, or poor wetting. For fine- pitch parts, BGAs, and dense areas, proper mask control is absolutely critical for manufacturability and field reliability. When And Where To Apply Check and specify solder mask and paste mask clearances after all footprints are finalized, before outputting Gerbers or ODB++ files, especially for fine-pitch ICs, BGAs, dense passives, and any part with nonstandard pad or pitch. Visualizing solder and paste mask in ORCAD X

• Cover
• I. Project Planning, Requirements, and Documentation
• 1.Establishing a Clean Design Rule Set
• 2. Preventing Floating or Unused Inputs and Outputs
• 3. Finalizing the PCB Stackup Early
• 4. Validating Symbol-to-Footprint Mapping
• 5. Using Descriptive Net and Component Naming
• 6. Confirming Component Availability and Avoiding Obsolete Parts
• 7. Archiving and Documenting the Complete Design for Future Reuse and Support
• II. Placement, Floorplanning, and Mechanical Integration
• 8. Including Mechanical References Early in the PCB Layout
• 9. Prioritizing Placement of Fixed and Critical Components
• 10. Planning BGA and Fine-Pitch Fanout Before Surrounding Placement
• 11. Grouping by Functional Blocks and Signal Flow
• 12. Respecting Assembly Spacing and Rework Access
• 13. Keeping Height and Keep-In/Keep-Out Constraints Visible
• 14. Reviewing Silkscreen and Markings for Readability and Clarity
• 15. Confirming Board Edge Clearances for Copper, Vias, and Components
• 16. Reviewing and Optimizing Via Types, Sizes, and Counts
• III. Power, Grounding, and Thermal
• 17. Using a Continuous Ground Plane
• 18. Optimizing Regulator and Power Converter Current Loops
• 19. Keeping Analog, Digital, and Power Domains Isolated
• 20. Preventing Ground Loops and Unintentional Return Paths
• 21. Pouring Copper with Electrical Intent, Not Just for Fill
• 22. Building Ground Via Fences and Edge Stitching
• 23. Managing Split Planes and Power Islands Correctly
• 24. Planning for Thermal Management: Heat Sinks, Vias, and Copper Pours
• IV. Signal Integrity and High-Speed Routing
• 25. Minimizing Crosstalk by Managing Parallelism and Trace Spacing
• 26. Routing Differential Pairs with Consistent Geometry and Return Paths
• 27. Avoiding Right-Angle and Acute Trace Corners
• 28. Minimizing Layer Transitions on Critical Nets
• 29. Eliminating Stubs and Dead-End Tees
• 30. Treating Length and Skew Matching as Numeric Constraints
• 31. Isolating Clocks, Resets, and Sensitive References from Noise Sources
• 32. Using Guard Traces and Shielding for Ultra-Sensitive or High-Speed Nets
• 33. Optimizing Decoupling and Bulk Capacitor Placement
• 34. Specifying Controlled Impedance and Reference Plane Requirements
• V. Manufacturability, Test, Reliability
• 35. Performing Design Rule Checks (DRC) and Electrical Rule Checks (ERC) Iteratively
• 36. Designing for Effective Test Point Access and Coverage
• 37. Verifying All Pad, Hole, and Footprint Sizes for Manufacturing
• 38. Specifying and Checking Solder Mask and Paste Mask Clearances
• 39. Reviewing Design for Manufacturability (DFM) and Assembly Constraints
• 40. Designing for Reliability in Harsh Mechanical, Thermal, and Environmental Conditions