Light-blocking tapes for phone camera modules
Black light-blocking tape prevents flare and light leakage between the image sensor and the cover glass in smartphone camera modules, helping preserve contrast and accurate colors in photos.
Modern smartphones have clusters of multiple cameras placed close together, next to the flash and proximity sensor. Even a tiny gap can let light from the flash or strong external light sources enter the lens along unintended paths, causing light streaks or reduced contrast.
Light leakage defects are often hard to detect in standard functional testing and only show up when users shoot against the light or at night under streetlights. That is why a strong light source test should be included in the inspection process.
Characteristics of light-blocking tape
Light-blocking tape uses a black-dyed PET or foam carrier combined with black acrylic adhesive. The key requirements are near-zero light transmission and a low-reflectance surface so that no additional reflected light enters the lens.
- Light transmission below 0.1% across the visible and near-infrared range.
- Matte black surface with low gloss.
- Total thickness of 30–150 microns depending on position.
- May include a thin foam layer to fill uneven gaps.
Application points in the camera module
Between the cover glass and the camera frame
A ring of black tape both bonds the glass and blocks light entering from the glass edge. The cut outline must precisely match the lens aperture.
Around the proximity sensor and flash
Prevents light from the flash from spreading laterally through the glass layer, which would disturb the sensor or cause halos.
Wrapping the edge of the sensor board
In some designs, light can pass through a thin circuit board substrate. Black tape applied to the back side solves this problem.
Testing light-blocking effectiveness
- Photograph a point light source in a dark chamber to detect halos.
- Measure the material's light transmission with a spectrophotometer.
- Inspect cut edges under a microscope to avoid adhesive strings or burrs.
- Run damp heat tests to ensure the tape edges do not lift and create gaps.
Light-blocking tape must also generate little dust, because any particle that lands on the sensor leaves a spot on the image.
Coordinating optical design and materials
Light-blocking effectiveness depends heavily on the design stage. The optics team should simulate stray light paths to identify areas that need masking, after which the mechanical team selects a tape thickness suited to the assembly gap. Changing the tape drawing at this stage is very cheap, but once the housing mold is frozen, the options become significantly limited.
AMS supplies black light-blocking tapes and precision die-cutting services for camera modules. Contact AMS Vietnam to receive samples.
