Smartphone Back Cover Step Height Measurement

3C04.Smartphone Back Cover Step Height Measurement: Ensuring Perfect Assembly

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3C04.Smartphone Back Cover Step Height Measurement: Ensuring Perfect Assembly

Aug 15, 2025

1. Why Step Height Measurement Matters for Smartphone Back Covers

In modern smartphone manufacturing, the step height between the back cover and surrounding frame or components directly impacts:

Aesthetic quality: Even slight height differences can cause visible seams or gaps, reducing perceived quality.
Waterproofing & dust resistance: Uneven heights can compromise sealing performance.
Assembly precision: Consistent step height ensures reliable bonding and structural integrity.
User experience: Smooth transitions improve tactile feel and reduce snagging risks.

2. Common Step Height Measurement Methods

Measurement Method	Principle	Advantages	Limitations
Contact-type gauge	Physical probe touches the surface	Low cost, easy to operate	Risk of scratching; unsuitable for delicate or coated surfaces
Laser triangulation	Measures height based on reflection angle	Fast, non-contact	Accuracy affected by reflective/transparent smartphone covers
Vision-based measurement	Uses image analysis from a high-resolution camera	Inspects multiple points at once	Dependent on lighting; lower vertical resolution
Chromatic confocal measurement	Determines height from focused wavelength position	High precision; works on glossy, reflective, and transparent surfaces; non-contact	Higher equipment cost; requires proper setup

3. Principle and Process of Chromatic Confocal Measurement

Chromatic confocal displacement sensors measure height based on focused wavelength detection:

Step 1: White light passes through a chromatic lens, separating into different wavelengths along the optical axis.
Step 2: Only the wavelength perfectly focused on the target surface is reflected back into the sensor.
Step 3: The spectrometer analyzes the peak wavelength, converting it into an accurate height value.

Why it’s ideal for smartphone back cover step height measurement:

Non-contact and scratch-free, even on high-gloss or coated surfaces.
Works on both transparent glass and colored back covers.
High sampling speed up to 32kHz for inline inspection in high-volume production lines.

4. TronSight’s Solution

The TronSight TS-C Series Chromatic Confocal Displacement Sensor offers:

Up to 32kHz sampling rate with 16-channel fully synchronous acquisition.
EtherCAT compatibility for seamless integration into automated production lines.
±60° maximum measuring angle and 3.8mm minimum probe diameter for complex geometries.
Multi-layer glass measurement capability for covers with coatings or lamination.

Application example:
In a smartphone assembly environment, the TS-C chromatic confocal displacement sensor measures the height difference between the back cover and reference points on the fixture or surrounding parts. The measurement data can be used by the production system to evaluate step height consistency and support quality inspection processes.