ST-P Series Laser Displacement Sensor for Online PCB Component Height Inspection

Measurement Solution

Industry Background In the 3C electronics manufacturing industry, PCBs (Printed Circuit Boards) are core components, and their component mounting quality directly affects product performance. With the miniaturization and high integration of electronic products, the dimensional requirements for components, solder joints, and flatness on PCBs are becoming increasingly stringent. Online inspection has become a crucial step in ensuring yield rates. Traditional contact-based measurements are inefficient, prone to damaging components, and cannot meet the demands of high-speed production lines. Inspection Requirements PCB component height inspection mainly includes: * Component body height measurement to confirm whether the mounting height is within tolerance limits * Solder joint height inspection to assess soldering quality * PCBA warpage inspection to ensure subsequent assembly accuracy * Connector pin height consistency inspection * FPC (Flexible Printed Circuit) warpage inspection Inspection needs to be non-contact, high-speed, and high-precision, and adaptable to PCB surface colors, reflectivity, and component diversity. Measurement Challenges: * The PCB surface contains various materials such as metal pads, black plastic encapsulation, and ceramic substrates, resulting in significant differences in reflectivity. * Component heights range from 0.1mm to 10mm, requiring a balance between high accuracy for small measurement ranges and adaptability for large ranges. * Fast production line cycle times necessitate high sensor sampling frequency and fast response. * The online detection environment is susceptible to interference from vibration and temperature changes. Recommended Sensor Solution: * The ST-P series laser displacement sensor uses laser triangulation for non-contact measurement, suitable for PCB component height detection. Based on measurement distance and accuracy requirements, the following models are recommended: Model | Reference Distance | Measurement Range | Repeatability | Linearity Error | Applicable Scenarios * ST-P25 | Detection range 25mm±1mm, repeatability 0.05μm, linearity error <±0.6μm | Suitable for small component heights and solder joint heights * ST-P30 | Detection range 30mm±5mm, repeatability 0.15μm, linearity error <±3μm | Suitable for general component heights and connector pins * ST-P50 | Detection range 50mm±10mm, repeatability 0.25μm m, linear error < ±4μm for larger components, FPC warpage ST-P80, detection range 80mm±15mm, repeatability 0.5μm, linear error < ±6μm for PCBA warpage, flatness ST-P150, detection range 150mm±40mm, repeatability 1.2μm, linear error < ±16μm for large height differences, assembly gaps The sensor has a maximum sampling frequency of 160kHz, supports Ethernet, RS485, analog and IO outputs, and can be connected to PLC, host computer and vision system. Implementation Method: The sensor is installed above the PCB conveyor line and adjusted to a suitable reference distance using a fixed bracket. During measurement, the sensor is vertically aligned with the component being measured. The laser spot illuminates the surface, and the reflected light is imaged onto the CMOS sensor through a lens. The height is calculated using triangulation. Multiple sensors can be combined to achieve multi-point synchronous measurement. Data is uploaded to the industrial control computer via Ethernet or RS485 for real-time judgment and feedback. Selection Considerations: Select the measurement range based on the component height range. Choose ST-P25 for small components and ST-P150 for larger ranges. Consider the reflective properties of the PCB surface: Test on highly reflective surfaces such as metal and glass; adjust the installation angle or use a polarizer if necessary. Confirm sensor sensitivity for low-reflective surfaces such as black plastic and FPC flexible boards. Evaluate light spot penetration for transparent materials (such as adhesives); sample testing is recommended. The sampling frequency is determined by the production line cycle time; a 160kHz model is recommended for high-speed production lines. Application Value: Non-contact measurement, avoiding component damage. High repeatability (up to 0.05μm), meeting precision testing requirements. High-speed sampling, suitable for online full inspection. Multiple output interfaces for easy system integration. Reduced manual sampling costs and improved yield. Precautions: Sensor parameters must be confirmed based on the specific model; sample testing is required before selection. Avoid direct laser light on the eyes during installation; a protective cover is required. Clean the lens regularly to prevent dust from affecting measurements. Consider temperature compensation or constant temperature installation when there are large ambient temperature variations.