I. Technical Principle: Accurate Measurement Advantages of Spectral Confocal

Spot spectral confocal sensors realize non-contact three-dimensional topographic measurements by emitting white light (composite light) and analyzing the position of the focal point of the reflected light of different wavelengths on the surface of the object. Its core advantages are:

1. Multi-wavelength coverage: white light contains continuous wavelengths, even if the measured surface exists curved or transparent materials (such as the glue in the threaded blind hole of a cell phone), the complete contour can be restored by the reflected signals of different wavelengths of light.

2. Strong anti-interference ability: traditional laser sensors are prone to signal loss due to refraction from transparent materials or deviation from the reflection angle of curved surfaces, while spectral confocal can penetrate the transparent layer and capture the data of curved edges through the synergistic work of multiple wavelengths.

3. High-speed sampling: Sampling frequency up to thousands of times per second, suitable for automated production lines of high-speed inspection needs.

II. Typical scenarios of cell phone threaded blind hole detection

1.1 Camera Module Blind Hole Thread Inspection Challenges:

In the blind hole process, the camera is placed under the screen and the threaded holes need to be precisely aligned with the internal structure. Traditional inspection methods (e.g., vernier calipers) are susceptible to interference from hole depth and thread inclination, and are unable to measure the transparent adhesive filler layer.

1.2 Solutions:

① Scan the inner wall of the threaded hole with a point spectrum confocal sensor, and calculate the thread depth, pitch and tooth angle by wavelength-distance algorithm.

② Combined with transparent glue detection mode, synchronized measurement of glue height and width to ensure sealing (e.g. waterproof cell phones require glue layer thickness error ≤ 0.02mm).

2.1 Blind Hole Thread Inspection Challenges for Fingerprint Recognition Modules:

The fingerprint module needs to be embedded into the blind hole of the screen, and the threaded hole needs to be precisely fixed with the fingerprint chip. Traditional contact measurement may scratch the surface of the chip.

2.2 Solutions:

① Non-contact spectral confocal measurement, avoiding physical contact damage.

② Through the design of “avoidance hole”, only the threaded area is scanned, avoiding the sensitive part of the fingerprint chip.

③ The detection accuracy is ±1μm, which meets the fingerprint module's requirement of thread perpendicularity ≤0.1°.

III. Recommended Solution: POMEAS SFS-8012 in Blind Hole Inspection

• Model: POMEAS SFS-8012 Color Spectral Confocal Displacement Sensor

• Core parameters：

  • Measuring range: ±1mm

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    Resolution: 0.01μm

     

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    Sampling frequency: 20kHz

     

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    Wavelength range: 400nm~1000nm

     

• Advantage:

  • For the transparent glue in the blind holes of cell phone threads, a dual-wavelength thickness measurement mode is used to simultaneously acquire the height of the glue and the surface topography of the substrate in a single scan.

  • Support IP67 protection level, adapt to the high dust environment of cell phone production line.

  • Provide SDK development kit, can be seamlessly connected to the MES system, realizing real-time upload and traceability of inspection data.