3C Electronics
ST-P Series Laser Displacement Sensor for PCBA Warpage Detection
This application outlines a non-contact displacement measurement approach for st-p series laser displacement sensor for pcba warpage detection, including installation, acquisition, and result verification.
Background
This article introduces the application of ST-P series laser displacement sensors in PCBA warpage detection, covering industry background, measurement requirements, challenges, sensor selection, implementation, and precautions, providing a high-precision non-contact measurement solution for 3C electronics manufacturing.
Pain Points
- • Maintaining a stable measurement reference while the target moves through the process.
- • Separating real height change from vibration, tilt, and surface-reflection effects.
- • Synchronizing measurement output with line speed and quality-control logic.
Measurement Solution
Industry Background: In 3C electronics manufacturing, PCBAs (Printed Circuit Board Assemblies) are prone to warping after reflow soldering, wave soldering, and other processes due to thermal stress, material shrinkage, or improper clamping. Excessive warping can lead to poor component soldering, incomplete soldering, assembly interference, and even affect product reliability. Therefore, online PCBA warping detection is a critical aspect of quality control. Detection Requirements: PCBA warping detection primarily measures the height deviation of the board surface relative to a reference plane, typically requiring micron-level accuracy, with the measurement range covering the entire board surface or a localized area. Detection objects include the PCB substrate, solder joints, and component surfaces, requiring adaptability to different colors, materials, and reflective properties.
Measurement Challenges: Surface Diversity: PCBA surfaces include green solder mask, white silkscreen printing, metal pads, black IC packages, etc., resulting in significant differences in reflectivity, which can easily lead to unstable measurement signals. High Accuracy Requirements: Warping is typically required to be controlled within ±0.1 mm, and the sensor must possess high repeatability and linearity. Online high-speed measurement: High production line cycle times require sensors with high-speed sampling capabilities to achieve full-board scanning in conjunction with motion mechanisms. Non-contact measurement: To avoid scratching or contaminating the PCBA, a non-contact method must be used. Recommended sensor solution: The ST-P series laser displacement sensor uses laser triangulation for non-contact measurement, suitable for PCBA warpage detection.
Based on installation distance and accuracy requirements, the following models are recommended: Model | Reference Distance | Measurement Range | Repeatability | Linearity Error | Applicable Scenarios ST-P25: Reference distance 25mm, measurement range ±1mm, repeatability 0.05μm, linearity error < ±0.6μm ST-P30: Reference distance 30mm, measurement range ±5mm, repeatability 0.15μm, linearity error < ±3μm ST-P50: Reference distance 50mm, measurement range ±10mm, repeatability 0.25μm, linearity error < ±4μm ST-P80: Reference distance 80mm, measurement range ±15mm, repeatability 0.5μm, linearity error < ±6μm ST-P150: Reference distance 150mm, measurement range ±40mm, repeatability 1.2μm, linearity error < ±16μm
The sensor has a maximum sampling frequency of 160kHz and supports Ethernet, RS485, analog output, and IO output. It can be connected to a PLC or host computer. Implementation: The sensor is fixed to a gantry or robotic arm, mounted perpendicular to the PCBA surface. During measurement, the PCBA is positioned by a conveyor belt or fixture. The sensor scans along the X/Y directions, collecting height data at multiple points. Software calculates the warpage (e.g., maximum height difference or curvature). The signal is uploaded to the control system via Ethernet or RS485 for real-time pass/fail determination. Selection Considerations: Measurement Range and Accuracy: Select an appropriate range based on the PCBA warpage amplitude to ensure accuracy meets requirements.
Surface Adaptability: For highly reflective pads or black components, sample testing is recommended. Adjust the mounting angle or select a special spot size model if necessary. Sampling Speed: Match the production line cycle time; a high sampling frequency model is required for high-speed scanning. Output Interface: Ensure compatibility with existing control systems; Ethernet or RS485 is recommended. Application Value: The ST-P series sensors enable online non-contact detection of PCBA warpage, improving yield, reducing manual sampling costs, supporting data traceability, and facilitating smart manufacturing. Precautions: For highly reflective metals, transparent adhesives, black plastics, etc., sample testing is required to verify measurement stability. Ambient light interference should be avoided during installation, and the lens should be cleaned regularly.
Parameters need to be confirmed based on the specific model; please contact technical support before selection.
| 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 |
| ST-P150 | 150 mm | ±40 mm | 1.2 μm | <±16 μm |
Technical Advantages
- • Non-contact measurement avoids mechanical wear on the target.
- • High-speed acquisition supports in-line trend and transient analysis.
- • Industrial output options support integration with control and data systems.