2.5 Seals, Gaskets & Waterproofing
IPSealing ratingis practicesone of the most unforgiving aspects of electronics manufacturing—water and materialdust handling.
exploit Keepingthe watersmallest outoversight. isn’tThe justsuccess of an IP-rated build comes not from a final dunk test atbut from every detail upstream: choosing the end—it’sright agasket designmaterial, choice that touches materials, surfaces, and the sequence of assembly. Seals work only whenkeeping lands are clean and flat, the gasket type matches the environment, and compressiontightening isfasteners setwith bycontrolled numbers, not “feel.” IP (ingress protection) ratings turn that into proof, from spray checks to dunk or pressure-decay, so confidence is measured instead of guessed.compression. Adhesive-backed gasketsseals, FIPG beads, and FIPGcable (formed-in-placeglands gasket)extend bringflexibility, speedbut each demands precise handling, storage, and complexcure shapes,discipline. butWhen onlydone ifright, handling,sealing cure,doesn’t just block moisture; it reinforces EMC performance, prevents cosmetic flaws, and storage are treated like real specs. Done well, sealing supports EMC (electromagnetic compatibility) and customer-facing cosmetics too—no leaks, no light gaps, no lifted corners. The aim is simple: chooseprotects the rightcustomer’s gasket,trust applyin the rightproduct’s squeeze, and prove it right where the work happens.durability.
2.5.1 Why this matters (one sentence)
Water always finds the laziest path; your job is to make sure that path never reaches electronics—and to prove it on the line, not at the customer.
2.5.2 IP ratings in plain language (what you’re aiming for)
Your official test method comes from the product spec. On the floor, use representative checks (spray/dunk/decay) sized for tact and risk.
2.5.3 Gasket families & where they fit
Material quick picks
- Silicone: wide temp, UV-resistant; good for outdoor.
- EPDM: great vs water/steam; avoid oils.
- Neoprene/NBR: oil/fuel tolerant; check temp range.
Match chemistry to environment (cleaners, oils, UV).
2.5.4 Surface prep (seals love clean, flat, bare)
- Clean: lint-free + approved solvent; no silicone residue.
- Flatness: gasket lands within 0.3–0.5 mm across span (23.1).
- Bare where needed: EMI bond pads unpainted; no powder beads in grooves.
- No burrs: edges that touch seals must be smooth—install edge guards if harness routes nearby.
2.5.5 Compression—hit the number, not the feel
- Foam gaskets: 25–35% of thickness after closure.
- O-rings: 15–25% squeeze in the groove (don’t over-crush).
- Conductive foam: 20–30%; just enough for contact.
How to check quickly
- First article: place tape stack/feeler at corners → close → measure pullout thickness.
- Look for uniform witness (light contact line) all around; no “holidays.”
2.5.6 Order of operations (so nothing fights the seal)
- Prep lands (clean/inspect; bond pads exposed).
- Install brackets/frames (square the geometry, 23.4).
- Place gaskets (or dispense FIPG bead) and seat shields if shared fasteners exist.
- Apply TIM & mount heat sinks (23.4) without smearing into seal paths.
- Close the lid with a cross-pattern, two-pass torque (50% → 100%).
- Verify compression and run the chosen water/decay check.
2.5.7 Cable entries: glands, grommets, vents
- Glands: choose by cable OD range; tighten to maker torque; ensure strain relief is active; add 360° shield clamp ahead of the gland if EMC needs it.
- Grommets: slit faces downstream; seat fully; no sharp edges in panel cutout.
- Breather/vent membranes: equalize pressure (avoid “breathing” water); mount vertical; keep above splash line when possible.
2.5.8 Adhesive gaskets & FIPG (first-time right)
PSA gaskets (die-cut, with adhesive)
- Wipe surfaces; prime if the spec calls it.
- Align with a fixture/template; press with a roller for 3–5 s per section.
- Respect dwell: initial tack now, full bond after 24 h (typical).
FIPG (formed-in-place)
- Use meter-mix or syringe with nozzle gauge from the spec.
- Bead size consistent; avoid gaps/overlaps; radius corners.
- Skin/cure per chemistry before closure; log open time at the cell.
2.5.9 Storage & handling (gaskets are not immortal)
- Store flat, bagged, out of UV/ozone; temp 15–25 °C.
- Keep lot & date; many foams/adhesives have shelf life—scan at issue.
- Don’t stretch or pre-compress before install; avoid creasing corners.
- For lubed O-rings, use the right compatibility lube (silicone/fluorinated). Never flood PSA surfaces with oils.
2.5.10 Quick tests you can run on the line
- Spray check (IP54/65/66 proxy): 5–10 min multi-angle; towel inside stays dry.
- Dunk (IP67 proxy): 30 min at 1 m (or agreed depth/time for sampling).
- Pressure/vacuum decay: plug ports, apply low pressure; stable reading = good (great for high mix).
- Talc/witness tape: close on a dusted seal; open → continuous print = contact everywhere.
Tie the result to the unit SN (22.1/20.5).
2.5.11 Acceptance cues (fast eyes)
2.5.12 Common traps → smallest reliable fix
2.5.13 Pocket checklists
Before install
- Lands/grooves clean & bare where required; flatness OK
- Correct gasket type/thickness pulled by PN; lot/shelf life valid
- Glands/grommets sized to cable OD; vent present if spec’d
During
- Gasket seated (no stretch); corners tight; no overlaps/gaps
- FIPG/PSA bead continuous; cure/dwell timer started
- Lid closed with cross-pattern; two-pass torque; witness marks
Verify
- Compression within target (tape/feeler/witness)
- Quick spray/dunk/decay check per plan; PASS logged to SN
- Visual: no bead smears, no crushed foam, glands torqued
Rework rules (short)
- Never reuse a torn or permanently compressed gasket
- PSA gaskets: replace if lifted/contaminated
- O-rings: replace if nicked/twisted; re-lube with approved grease