Phone Case & Screen Protector Inspection China: QC for Amazon FBA Sellers | $169

Why Phone Accessories Need Dedicated QC

Phone cases look simple, but they have surprisingly tight tolerances. A case that's 0.5 mm off at the charging port opening will generate negative reviews. Screen protectors with uneven adhesive layers bubble within days. Most suppliers in Shenzhen push high volume — the only way to catch fit and finish issues is on-site inspection before shipment.

Step 1: Dimensional Fit Test

The inspector uses a calibrated digital caliper to measure: overall case dimensions (length × width × height), button cutout alignment, camera bump clearance, charging port opening width, and speaker/mic hole placement. Each measurement is compared to the spec sheet. A tolerance of ±0.3 mm is typical for hard cases; ±0.5 mm for soft TPU. A sample phone model (the target device) is used to test actual fit — the case should snap on without forcing and stay secure during shake test.

Step 2: Material and Surface Quality

The inspector checks: no flash/mold lines on the edges, consistent texture across the back panel, no discoloration or oil spots on transparent cases, and correct hardness (Shore A for TPU, Shore D for polycarbonate). For tempered glass screen protectors: edge chamfer quality (no sharp edges), oleophobic coating uniformity (water bead test), and adhesive layer cleanliness (no dust specks trapped between layers).

Step 3: Functional Test

For phone cases: all buttons press smoothly (volume, power, silent switch), wireless charging works through the case (thickness ≤ 1.5 mm for MagSafe compatibility), and the case doesn't interfere with the camera flash. For screen protectors: the glass is placed on the phone screen — no halo effect (white edges), no bubbles after 30 seconds of pressing, and touch sensitivity is confirmed by tapping each quadrant of the screen.

Step 4: Packaging and Labeling Check

Each phone case or screen protector should be in a polybag or retail box with correct FNSKU barcode. The inspector scans every sample's barcode with a barcode verifier to confirm GS1 compliance. Carton labeling must show shipment ID, unit count, and product name in English. For FBA shipments, each outer carton must weigh under 50 lbs and have an FBA box label.

Common Phone Case Defects Caught by Inspection

After inspecting hundreds of phone case batches from Shenzhen and Guangdong factories, the most common defects are: (1) mold flash on the inner lip — causes loose fit; (2) misaligned camera cutout — covers corner of lens; (3) inconsistent matte finish — some units are shiny, some matte; (4) yellowing on clear TPU cases after 2-week hot box test (50°C for 14 days); (5) screen protector bubbles at the edges due to incomplete adhesive coverage near the 2.5D curved edge.

Sampling Level Recommendation

For phone cases and screen protectors, use AQL Level II normal inspection. The defect categories: critical (fit failure, cracked glass — AQL 0), major (misaligned cutout, bubble on screen protector — AQL 2.5), minor (slight mold flash, packaging blemish — AQL 4.0). For a batch of 5000 phone cases, sample size is 200 units (AQL 2.5, normal).

Frequently Asked Questions

Can you inspect with our actual phone model?

Yes. If you send a reference phone to the factory or our inspector, the fit test is performed on the actual device. For iPhone cases, we can use our own reference device (Apple iPhone 15/16, Samsung Galaxy S24/S25) if needed.

What causes screen protector bubbles?

There are three root causes: (1) the adhesive layer has trapped dust or manufacturing residue; (2) the 2.5D edge radius of the glass doesn't match the phone screen curvature; (3) the oleophobic coating is uneven, causing air pockets during installation. Our inspection checks all three.

Is TPU yellowing detectable during inspection?

Standard visual inspection catches existing yellowing. For prevention, we offer an optional hot box test (50°C for 14 days) that accelerates yellowing in low-quality TPU. Add this to your QC spec for clear phone cases.