ST-P Series Laser Displacement Sensor for PCBA Warpage Detection

Measurement Solution

Industry Background In 3C electronics manufacturing, PCBA (Printed Circuit Board Assembly) boards are prone to surface warpage following processes such as reflow and wave soldering due to factors like thermal stress, material shrinkage, or improper clamping. Excessive warpage can lead to issues such as cold solder joints, poor soldering quality, and assembly interference, potentially compromising product reliability. Consequently, in-line inspection of PCBA warpage has become a critical step in quality control. Inspection Requirements PCBA warpage inspection primarily involves measuring the height deviation of the board surface relative to a reference plane. It typically requires micron-level precision and must cover either the entire board surface or specific localized areas. Targets for inspection include the PCB substrate, solder joints, and component surfaces, necessitating compatibility with a wide range of colors, materials, and reflective properties. Measurement Challenges Surface Diversity: PCBA surfaces feature a mix of elements—such as green solder masks, white silkscreen printing, metal pads, and black IC packages—that exhibit significant differences in reflectivity, which can lead to unstable measurement signals. High Precision Requirements: Warpage must typically be controlled within a range of ±0.1 mm, requiring sensors with high repeatability and linearity. High-Speed ​​In-Line Measurement: Fast production line cycle times require sensors capable of high-speed sampling, integrated with motion mechanisms to enable full-board scanning. Non-Contact Measurement: To prevent scratching or contaminating the PCBA, a non-contact measurement method is mandatory. Recommended Sensor Solution The ST-P series laser displacement sensors utilize non-contact laser triangulation technology, making them ideal for PCBA warpage inspection. The following models are recommended based on installation distance and accuracy requirements: Model | Reference Distance | Measurement Range | Repeatability | Linearity Error | Suitable Scenarios 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 The sensors feature a maximum sampling frequency of 160 kHz and support Ethernet, RS485, analog, and I/O outputs, allowing for integration with PLCs or host computers. Implementation Method Mount the sensor onto a gantry frame or robotic arm, positioned perpendicular to the PCBA surface. During measurement, the PCBA is positioned via a conveyor belt or fixture; the sensor scans along the X/Y axes to collect height data at multiple points, and software calculates the warpage (e.g., maximum height difference or curvature). Signals are transmitted to the control system via Ethernet or RS485 for real-time pass/fail determination. Selection Considerations Measurement Range and Accuracy: Select a model with an appropriate range based on the magnitude of PCBA warpage to ensure accuracy requirements are met. Surface Adaptability: For highly reflective pads or black components, sample testing is recommended; adjust the installation angle or select a model with a specialized beam spot if necessary. Sampling Speed: Match the production line cycle time; select a model with a high sampling frequency 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 in-line, non-contact detection of PCBA warpage, improving yield rates, reducing manual inspection costs, supporting data traceability, and facilitating smart manufacturing. Precautions For surfaces such as highly reflective metal, transparent adhesive, or black plastic, sample testing is required to verify measurement stability. Avoid ambient light interference during installation and clean the lens regularly. Specifications depend on the specific model; please contact technical support before selecting a model.