10/07/2026
A dispensed FIP gasket bead that drifts 0.20 mm off-path isn't a dimensional problem. It's a shielding effectiveness problem.
For defense EMI programs, process variation and mission performance are the same conversation. The physics isn't what fails programs at MRL gates — the manufacturing process is.
A few things worth knowing before your next MRL review:
- CHO-FORM bead height tolerances run ±0.10 mm (±0.004") for beads in the 0.46–0.86 mm range. Start/stop and T-joint zones carry wider allowance — and that's exactly where dispensing variation concentrates.
- Nolato TriShield 8800 (Ag/Ni filler, 15 mOhm·cm volume resistivity) targets 10–50% compression for rated performance. Average shielding effectiveness: 107 dB across 0.3–9 GHz on Ni/Sn plated aluminum. That number assumes the gasket is dispensed correctly and compressed to spec.
- Die-cut RF absorber tolerance for sponge/foam up to 6.3 mm thick runs ±0.81 mm (±0.032") at standard. If gap management is critical, tighter is achievable — but specify it only when the design actually demands it.
- The MRL 6-to-7 transition is where EMI programs lose schedule. "Documented process" has to become "demonstrated yield data." That gap requires production history, not just paperwork.
The DFM conversation on dispense path, compression stops, and adhesive coverage needs to happen at MRL 5 — not after qualification units reveal yield problems.
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