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5.19 Cleaning and Cosmetic Inspection

Final cleaning and cosmetic inspection are the final quality checkpoints performed just before packaging. This stage ensures the product not only functions correctly but also meets the customer's aesthetic standards (Grade-A surface integrity) and is free of contaminants that could cause long-term reliability issues (e.g., flux residue, fingerprints). This is the last opportunity to address flaws that can result in customer rejection or field failure due to degradation.

5.1.19.1 Cleaning Protocol and Contaminant Removal

Cleaning must be targeted to remove manufacturing residues without damaging sensitive components or cosmetic finishes.

A) Target Contaminants and Tools

  • Contaminants: Loose particulates (dust, metal fines, fibers - FOD), films (flux haze, adhesive smear, thermal grease mist), and handling marks (fingerprints, water spots).
  • Mandatory Tools: Powder-free nitrile gloves (no silicone), low-lint microfiber wipes, and ESD-safe foam-tip swabs for tight spots. Air must be filtered and dry.

B) Cleaning Playbook

    • Dry Clean First: Remove loose material using filtered air and a soft ESD-safe brush. Use a tack wipe on seams/vents.
    • Wet Clean (Surface): Dampen a low-lint wipe with IPA 70%–99% (general degrease) or neutral aqueous cleaner (for salts/smears). Wipe in one direction, flipping the cloth for each pass.
    • Detail: Use swabs for bezel corners, screw heads, and logo relief.
      • Lenses/Windows: Prohibited: Neat IPA on anti-glare coatings. Use the approved lens cleaner specified by the vendor.
    • Specials (Residue Removal): Use dry lift first, then minimal adhesive remover (citrus/acetone-free grade) for label bleed; rinse with IPA/DI water.
      • Fixes: Threadlocker stain or TIM smudge must be lifted with a dry wipe first, then minimal solvent; keep solvent away from seals and labels.
    • Dry & Finalize: Final microfiber wipe; short burst of ionized air (for plastics) to dissipate static.

5.1.19.2 Cosmetic Inspection and Acceptance Cues

Cosmetic inspection verifies that the final assembly meets the aesthetic specification, categorized by surface visibility.

A) Inspection Setup

  • Lighting: Inspection must be performed under bright, diffuse overhead lighting (~1000 – 1500 lx). Optional grazing light can be used to reveal scratches.
  • Distance: Inspection is performed at arm’s length (≈ 500 – 600 mm) for Grade-A surfaces.
  • Reference: A golden sample or photo card must be present at the station.

B) Acceptance Criteria (Grade A Mandates)

  • Grade-A Faces: Mandate: Zero scratches or rubs visible at arm’s length. Color/gloss must be uniform.
  • Windows/Lenses: Must be clear; zero lint under film; no wipes streaks or dust specks.
  • Ports/Shields: Clean, centered; no burr/dust; no fingerprints on shells.

Feature

Accept

Reject

Labeling

Aligned to map ± 0.5 – 1.0 mm; no bubbles; edges sealed.

Skew > 1˚; bubbles; lifted corners near radii.

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 around holes.

Light Leaks

No glowing seams at windows/bezel joints (check dim room, backlight max).

Visible light leak or specks under the lens.

5.1.19.3 Labeling, Rework, and Traceability

Final inspection verifies the permanence of identification and logs any necessary exceptions.

A) Label Application Final Check

  • Adhesion: Labels must be checked for full adhesion. If the label is new, roll with a clean squeegee for 3 – 5 seconds (per spec). If edges lift, the label must be replaced, not glued.
  • Protection: Protective films must be removed only where required; protective caps and port plugs must be fitted for shipping.

B) Traceability and Rework Record

  • Data Capture: The final cosmetic release (PASS/FAIL) must be recorded by the inspector. Any exceptions (e.g., Grade B blemishes) must be noted with the location.
  • Rework Record: If rework is performed (e.g., using adhesive remover), the method/chemical, area, and final PASS check must be logged and attached to the Serial Number (SN) record.

Final Checklist

Mandate

Criteria

Verification Action

FOD Removal

Interior enclosure vacuumed; zero metal chips/snippings remain.

Final inspection using filtered air confirms no loose material.

Grade A Standard

No scratches, gouges, or rubs visible at arm's length.

Inspection performed under bright, diffuse overhead lighting.

Cleaning Integrity

Exterior surfaces wiped with approved solvent; zero adhesive residue.

Audit confirms no neat IPA used on anti-glare/sensitive coatings.

Label Adhesion

External labels verified for full adhesion; alignment ± 1.0 mm.

Clean squeegee used to press labels; no bubbles or lifted corners.

Functional Cleanliness

Flux residue, thermal grease, and fingerprints removed.

Interior visual check confirms no process contamination.

Cosmetic Final

Protective caps/plugs fitted; labels adhered; no light leaks.

Final release requires inspector sign-off on Grade-A cosmetic status.


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