3C Electronics
ST-P Series Laser Displacement Sensor for Mobile Phone Battery Compartment Flatness Inspection
For flatness and local-deformation inspection of a mobile battery-compartment floor, this article explains ST-P multipoint layout, datum fitting, occlusion avoidance, and validation on different recessed surfaces.
Background
This article introduces the application of ST-P series laser displacement sensors in mobile phone battery compartment flatness inspection, covering inspection requirements, measurement challenges, sensor selection, installation, and precautions, providing a high-precision non-contact measurement solution for 3C electronics manufacturing.
Pain Points
- • The battery compartment is recessed, and sidewalls, steps, and ribs can block emitted or received light and create optical shadow zones.
- • The floor may be reflective metal, black plastic, or a coated surface, with material boundaries changing return intensity and stability.
- • Ribs, bosses, and local pockets are not part of the datum plane; including them in a scan can bias the fitted flatness result.
- • Fixture support, thin-wall deformation, mechanism vibration, and temperature change can introduce drift and reduce batch-to-batch comparability.
Measurement Solution
Industry Background In 3C electronics manufacturing, the flatness of the mobile phone battery compartment directly affects the fit and safety of battery assembly. Excessive flatness deviation can lead to battery bulging, poor contact, or even safety hazards. With the trend of thinner phones, the machining accuracy of the battery compartment is increasingly demanding. Traditional contact measurement methods are inefficient and prone to surface scratches, unable to meet the needs of online full inspection. Inspection Requirements Inspection Object: Bottom surface of mobile phone battery compartment (metal or plastic material) Inspection Purpose: Measure battery compartment flatness to ensure assembly gap meets design tolerance Accuracy Requirement: Repeatability better than 1μm, linearity error < ±5μm Cycle Time Requirement: Online inspection, single point measurement time < 10ms
Measurement Challenges Battery compartment surface may be reflective (metal) or black light-absorbing (plastic), affecting laser reflection Complex internal structure with steps and grooves requires multi-point scanning to fit a plane Production line vibration and ambient light interference affect measurement stability Recommended Sensor Solution ST-P series laser displacement sensors use laser triangulation non-contact measurement, suitable for precision inspection in 3C electronics. Based on installation distance and accuracy requirements, the following models are recommended: Model | Reference Distance | Measurement Range | Repeatability | Linearity Error | Application Scenario ST-P25 | 25 mm | ±1 mm | 0.05 μm | < ±0.6 μm | High precision, small range ST-P30 | 30 mm | ±5 mm | 0.15 μm | < ±3 μm | General high precision ST-P50 | 50 mm | ±10 mm | 0.25 μm | < ±4 μm | Medium distance
ST-P80 | 80 mm | ±15 mm | 0.5 μm | < ±6 μm | Larger installation space The sensor supports a maximum sampling frequency of 160kHz and outputs via Ethernet, RS485, analog, and IO, which can be connected to PLC or host computer. Implementation Method Installation Layout: Arrange multiple sensors (e.g., 4-6) above the battery compartment to cover key areas of the bottom, or use a single sensor with an XY motion platform for scanning. Measurement Process: Sensors synchronously collect height data from multiple points, fit a plane through algorithms, and calculate flatness deviation. Signal Output: Transmit data to the host computer via Ethernet, or output to PLC via analog/IO for sorting control.
Selection Considerations Measurement Range: Select appropriate range based on battery compartment depth and tolerance to avoid exceeding range. Accuracy and Repeatability: Must be confirmed according to specific model to ensure flatness inspection requirements are met. Surface Adaptability: For highly reflective metal or black plastic, sample testing is recommended; adjust installation angle or use special spot if necessary. Environmental Factors: Production line vibration and temperature changes may affect measurement; consider compensation or protective measures. Application Value ST-P series sensors achieve non-contact high-speed measurement, avoiding workpiece scratches and improving inspection efficiency. High repeatability and linearity ensure reliable flatness inspection, supporting quality control in 3C electronics manufacturing.
Precautions Ensure the sensor optical axis is perpendicular to the measured surface during installation to avoid tilt error. For transparent adhesives or highly transparent materials, evaluate laser penetration effects; testing is recommended. Regularly clean the sensor lens to prevent dust from affecting measurement accuracy.
| Model | Reference Distance | Measuring Range | Repeatability | Linearity Error |
|---|---|---|---|---|
| ST-P25 | 25 mm | ±1 mm | 0.05 μm | < ±0.6 μm |
| ST-P30 | 30 mm | ±5 mm | 0.15 μm | < ±3 μm |
| ST-P50 | 50 mm | ±10 mm | 0.25 μm | < ±4 μm |
| ST-P80 | 80 mm | ±15 mm | 0.5 μm | < ±6 μm |
Technical Advantages
- • Non-contact multipoint measurement from above the opening avoids inserting a probe into the restricted space and reduces scratch risk.
- • Defining the valid floor area and excluding ribs, openings, and steps allows a plane fit and maximum local-deviation output.
- • Mounting position can be selected around pocket depth and wall direction to keep both optical paths clear, with metal and plastic samples validated separately.
- • ST-P data can be integrated with a PLC or host for flatness decisions, defect-location records, and process-trend monitoring.