5.1 Cleaning & Cosmetic Inspection

Shiny hardware and sharp electronics mean little if the final product looks careless. Cleaning and cosmetic inspection form the bridge between technical build quality and customer perception, where residues, smears, or lifted labels can undo the trust earned by precision assembly. This step is more than presentation: it safeguards optics, protects surfaces, and ensures every unit communicates competence the moment it’s unboxed. Consistent methods, approved materials, and honest inspection lighting turn finishing work into a controlled, repeatable process rather than an afterthought.

5.1.1 Why this step matters (the one-liner)

Customers judge with their eyes and hands. Clean, even, fingerprint-free surfaces reduce returns and make the rest of your build look competent.

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5.1.2 What “clean” means here

• No loose stuff: dust, fibers, metal fines (FOD).
• No films: flux haze, adhesive smear, gasket crumbs, TIM/grease mist.
• No marks: fingerprints, water spots, label squeegee lines.
• No damage: scratches, rubs, lifted paint, light leaks around windows.
• Ready to ship: protective caps on, films removed where required, labels stuck hard.
  

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5.1.3 Tools & consumables (use the right ones)

• Gloves: powder-free nitrile (no silicone).
• Wipes: low-lint microfiber or cellulose-poly (class: lens-safe).
• Swabs: foam-tip, ESD-safe handles for tight spots.
• Air: filtered, dry blow-off; ionizer on for plastics/lenses.
• Brush: ESD-safe soft bristle for vents/knurls.
• Chemicals (plant-approved only):
• • IPA 70–99% (general degrease; avoid on some polycarbonate/anti-glare)
  • DI water or neutral aqueous cleaner (smears/salts)
  • Adhesive remover (citrus/acetone-free grade) for label bleed—test first
  • Panel/lens cleaner specified by the display/paint vendor
  • No silicone polishes unless customer spec says so (label fish-eye risk)

Rule: if the finish is unknown, spot test on a hidden area.

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5.1.4 Cleaning playbook (fast, safe sequence)

1. Prep the area: bright diffuse light, clean mat, ionizer on, fresh gloves.
2. Dry clean first: filtered air → soft brush → tack wipe on seams/vents.
3. Wet clean next (smallest effective amount): dampen wipe (don’t flood), wipe in one direction, flip to a clean face each pass.
4. Detail: swabs for bezel corners, screw heads, logo relief, connector shells.
5. Specials:
6. • Lenses/windows: use the approved lens cleaner, not IPA if coating is anti-glare/hard-coat sensitive.
   • Labels: roll with a clean squeegee; if edges lift, re-press with heat per spec or replace—never glue.
   • Adhesive ooze: remove carefully with approved remover; re-wipe with IPA/DI to de-scent.
   • TIM/threadlocker smear: lift with dry wipe first, then minimal solvent; keep away from seals.
6. Dry & de-static: final microfiber wipe; short ionized air burst.
7. Final touch: fit dust caps, port plugs, and protective films only where the customer expects them (don’t hide defects).
   

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5.1.5 Materials & what they like (and hate)

Surface	OK cleaners	Avoid	Notes
Powder coat / paint	IPA, aqueous neutral	Strong ketones	Light pressure; circular then straight pass
Anodized AL / bare metal	IPA, mild degreaser	Acidic/alkaline	Watch water spots—DI final wipe
Polycarbonate / acrylic windows	Vendor lens cleaner, DI	Neat IPA/acetone	Use microfiber only; no paper towels
Rubber gaskets/foams	DI wipe	Solvents	Don’t swell; keep cleaners off edges
Labels/PSA	IPA edge wipe	Soaking	After 24 h dwell, edges should not lift
Stainless/EMI fingers	IPA	Oily polishes	Brush along grain; avoid lint caught in fingers

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5.1.6 Cosmetic inspection setup (make it repeatable)

• Lighting: bright diffuse overhead (~1000–1500 lx) + optional grazing light to reveal scratches.
• Distance/angle: arm’s length (≈ 500–600 mm) for Grade-A; closer only for Grade-B internals.
• Background: matte neutral; cut reflections.
• Reference: golden sample or photo card at station.

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5.1.7 Acceptance cues (starter criteria—tune to your spec)

Zone	Accept	Reject
Grade-A faces (bezels, lids)	No scratches visible at arm’s length; color/gloss uniform	Obvious scratches, rubs, paint chips, swirl haze
Windows/lenses	Clear, no lint under film, no light leaks	Dust specks under lens, edge light leaks, wipes streaks
Labels	Aligned to map ±0.5–1.0 mm, no bubbles, edges sealed	Skew >1°, bubbles, lifted corners, smears
Ports & shields	Clean, centered, no burr/dust	Metal lip in port, debris, fingerprints on shells
Seals	Even compression imprint, no squeeze-out on face	Crushed foam, visible glue/grease on gasket line
Hardware	Heads even, witness marks tidy	Scuffed heads, paint shear, tool tracks

Light leaks check: dim room, backlight on max—no glowing seams at windows/bezel joints.

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5.1.8 What to record (short and useful)

• If your customer/spec demands: cosmetic release tick (Grade-A/labels/windows), photo of front panel, and any exceptions with location.
• For rework: note method/chemical, area, and final PASS check. Attach to the SN.
  

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5.1.9 Common residues → best removal

Residue	Source	Fix
Fingerprints/oils	Handling	IPA or lens cleaner; fresh gloves
Dust/fibers	Packaging, cloth	Ionized air + microfiber; avoid paper wipes
Adhesive bleed	Labels/foam tape	Edge with adhesive remover → IPA rinse; replace if edge won’t seal
Flux haze	Late solder touch-ups	IPA with light brush; avoid flooding near seals
TIM/paste smudge	Heat sink install	Dry lift → minimal solvent; keep off gaskets/labels
Threadlocker stain	Torque ops	Dry wipe quickly; if cured, leave if cosmetic spec allows—don’t smear

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5.1.10 Common traps → smallest reliable fix

Trap	Symptom	First move
“Polish” with silicone	Later label lift/fish-eye	Ban silicone polish; re-clean with IPA; re-label
Over-wet cleaning	Streaks, seep under bezels	Damp, not dripping; edge-wipe only
IPA on coated lens	Crazing/film damage	Use vendor lens cleaner; replace if damaged
Paper towels	Micro-scratches, lint	Switch to low-lint microfiber
Cleaning before film peel	Trapped dust	Peel late, ionize, then final clean
Ignoring dwell on PSA	Edges lift in pack	Respect 24 h dwell; warm press if spec’d

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5.1.11 Pocket checklists

Before

• Ionizer on; bright diffuse light; clean mat
• Approved wipes/chemicals at hand; fresh nitrile gloves
• Label map & golden photo card visible

Clean

• Dry: filtered air → brush → tack wipe
• Wet: minimal solvent; one-direction strokes; swap faces often
• Lenses with approved cleaner only; labels rolled and sealed

Inspect

• Grade-A faces: no visible scratches at arm’s length
• Windows: no dust/leaks; LEDs clean; light-leak check
• Labels: position ±0.5–1.0 mm, no bubbles, edges sealed
• Hardware & seals tidy; witness marks clean

Closeout

• Caps/plugs fitted; required films applied/removed per spec
• Cosmetic release ticked; photos (if required) bound to SN
• Place on clean rack or straight to pack cell

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A disciplined approach to cleaning and cosmetic inspection keeps defects from slipping through and prevents costly rework or returns. By respecting materials, following a structured playbook, and inspecting with rigor, products leave the line polished, protected, and ready to represent the brand at its best.