Issue link: https://iconnect007.uberflip.com/i/1547450
NOVEMBER 2026 I SMT007 MAGAZINE 63 keep-outs, better to learn that at placement review than at tooling kickoff. A process sold as suitable for everything should be trusted for nothing. Summary Heat staking asks very little of a circuit designer, but it asks early. Table 1 is the short version of both parts: seven numbers worth bringing to the next layout review if a plastic housing is anywhere in the product's future. Get these onto the drawing while the drawing is still cheap to change. The alternative is the meeting mentioned earlier, and nobody enjoys that meeting, least of all the capacitors. SMT007 Alex Spurgeon is the owner of U.S. Heatstake. References 1. Handbook of Plastics Joining: A Practical Guide, 2nd ed., by M.J. Troughton, PDL Handbook Series, William Andrew/Elsevier, 2008. 2. IPC-A-610J, Acceptability of Electronic Assemblies, IPC, 2024. 3. IPC-2221B, Generic Standard on Printed Board Design, IPC. 4. IPC-2222B, Sectional Design Standard for Rigid Organic Printed Boards, IPC, 2020. 5. "Flexiterm: Guarding Against Capacitor Crack Fail- ures," Kyocera-AVX, technical paper. 6. IPC/JEDEC-9704A, Printed Circuit Assembly Strain Gage Test Guideline, IPC/JEDEC, 2012. 7. IPC/JEDEC-9702, Monotonic Bend Characterization of Board-Level Interconnects, IPC/JEDEC. 8. Board Flexure Initiative (BFI) Guide, Intel Corporation. 9. IPC-TM-650, Method 2.4.24C, Glass Transition Temperature and Z-Axis Thermal Expansion by TMA, IPC. 10. Polymer Property Database: glass transition and melting temperatures of thermoplastics, Omnexus/ SpecialChem. Table 1: Seven numbers to bring to the next layout review Design item Rule of thumb (D = stud diameter) Clearance hole D + 10–25%; top of range for FR-4; never under 0.10 mm total Hole finish Non-plated (NPTH), chamfered ~0.5 mm × 45° on the entry side Board-edge distance ≥ 2 × D from hole center Top-side keep-out ≥ 1.5 × D radius: no traces, vias, parts, or solder joints Bottom-side seating ring Bare laminate over the boss OD (2–3 × D) Stud protrusion above board 1.5–2.0 × D (head forms 2 × D wide, 0.5 × D tall) Standoff height Clears the tallest bottom-side component; ~3–25 mm typical