Issue link: https://resources.pcb.cadence.com/i/1541046
40. Designing for Reliability in Harsh Mechanical, Thermal, and Environmental Conditions How To Implement 1. Select appropriate materials and finishes: f Use high-Tg, low-CTE PCB laminates (e.g., FR-4 TG170+, polyimide, or ceramic) for high-temperature/vibration exposure. f Specify heavy copper (2 oz or more) for power or high-current circuits. f Choose corrosion-resistant finishes: ENIG, immersion silver/tin, or hard gold; avoid bare copper or standard HASL in corrosive environments. 2. Design for thermal management and cycling: f Use larger copper pours for heat spreading; add thermal vias under hot parts. f Space out high-power components and keep sensitive analog/RF parts away from heat sources. f Ensure sufficient copper balance on all layers to minimize board warpage. f Simulate or measure hotspot and temperature gradients under worst-case conditions. 3. Mitigate vibration and shock risk: f Place large or heavy components (e.g., relays, connectors, electrolytic caps) near mounting points or support with adhesive, brackets, or staking. f Use underfill, corner gluing, or edge bonding for BGA, QFN, or chip-on-board, where specified by package datasheet or standards. f Avoid tall components on unsupported board regions; consider a thicker PCB or mechanical stiffeners if necessary. 4. Protect against humidity, condensation, and contaminants: f Define conformal coating or encapsulation for the whole board or critical zones; specify keepout/no-coat regions for test pads or connectors. f Design proper spacing/creepage between high-voltage nets and use conformal coating to further increase breakdown strength. f Use sealed or gasketed connectors and keep sensitive nodes away from exposed edges. 5. Prevent corrosion and chemical damage: f Avoid silver or copper exposed on the edge or in cutouts; use a proper mask and finish coverage. f For boards exposed to salt spray or industrial chemicals, use high-grade coatings and sealants, and test for compatibility. 6. Plan for board expansion/contraction: f Use large mounting holes with slots for boards mounted on metal or in environments with large temperature swings. f Route differential pairs and sensitive nets with expansion in mind; avoid routing over large cutouts or between isolated sections that may move differently. 7. Validate with reliability and stress testing: f Prototype and subject boards to thermal cycling, vibration, humidity, and salt fog per relevant industry standards. f Use test coupons and monitoring points for ongoing quality and reliability tracking. Common Pitfalls, Their Impact, and How to Avoid Them Common Pitfall How to Avoid it Relying on standard FR-4 for high-temp, high-power, or high-vi- bration designs Risks delamination, board warpage, and cracked joints – Check material specifications against operating conditions. Neglecting thermal simulation and balance Hot spots and uneven copper lead to expansion, drift, and failure – Include thermal validation in sign-off. Skipping conformal coating or not defining keepout zones Exposes sensitive nets and contacts to corrosion or electrical leakage – Specify requirements in assembly notes. Mounting or assembling in a way that introduces stress Causes long-term cracking, solder joint fatigue, or trace breakage – Review mechanical constraints with ECAD/MCAD teams.