Application Background
In PCB and IC substrate manufacturing, component height, flatness, and step height are key parameters affecting subsequent mounting, soldering, and packaging quality. Traditional contact-based measurements are inefficient and prone to damaging components. The ST-P series laser displacement sensors utilize laser triangulation for non-contact measurement, enabling high-speed, high-precision inspection of components on PCB surfaces, substrate pads, and chip packages, meeting the online quality control requirements of automated semiconductor production lines.
Inspection Objects and Purposes
Inspection Objects: Components on PCBs (e.g., resistors, capacitors, ICs), IC substrate surfaces, packages, wafer stages, etc.
Inspection Purposes: Measuring component height, substrate step height, flatness, warpage, and probe stage Z-axis position feedback to ensure assembly accuracy and yield.
Product Principle and Selection Guide
The ST-P series is based on laser triangulation. A laser beam is emitted to the surface being measured. The reflected light is imaged on a CMOS sensor through a lens, and displacement is calculated based on changes in the beam's position. For PCB/carrier board inspection, the model must be selected based on the installation distance and accuracy requirements:
Model | Reference Distance | Measurement Range | Repeatability | Linearity Error
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 0.2 5μm, linear error < ±4μm
ST-P80: Reference distance 80mm, measurement range ±15mm, repeatability 0.5μm, linear error < ±6μm
ST-P150: Reference distance 150mm, measurement range ±40mm, repeatability 1.2μm, linear error < ±16μm
For PCB component height detection, ST-P25 or ST-P30 are typically selected to achieve micron-level accuracy; for carrier board warping or large step differences, ST-P50 or ST-P80 can be selected. Specific selection needs to be confirmed based on the on-site installation space, the reflectivity of the measured object, and cycle time requirements.
Solution Recommendation
In automated production lines, the sensor can be fixed to a gantry crane or the end of a robotic arm, vertically aligned with the detection point. Measurement process: The sensor emits a laser, receives the reflected signal, calculates the height value through the controller, and outputs it to a PLC or host computer via Ethernet, RS485, or analog signal. For high-speed production lines, the ST-P series offers a maximum sampling frequency of 160kHz, meeting the requirements for in-line full inspection.
Installation and Commissioning Recommendations
Installation angle: Keep the laser beam perpendicular to the target surface to avoid spot deformation due to tilt.
Ambient light interference: Avoid direct strong light on the sensor window; use a light shield if necessary.
Target characteristics: For mirror-like metals, transparent encapsulants, or black chips, conduct sample testing to verify reflection signal quality. Different colors and surface roughness may affect measurement stability; on-site verification is recommended.
Mounting: Use rigid brackets to prevent vibration from affecting repeatability.
Frequently Asked Questions
Q: Can the sensor measure transparent adhesive surfaces?
A: Transparent materials may cause transmission and secondary reflections; testing is required. Consider applying matte paint or using a special model.
Q: What if measurement data fluctuates?
A: Check sensor mounting stability, clean the target surface from oil or dust, and adjust sampling frequency or filter parameters.
Q: How to integrate with existing PLC systems?
A: The ST-P series supports Ethernet, RS485, analog, and IO outputs. Choose the communication method based on the PLC interface. Refer to the product manual for wiring and protocol details.
Conclusion
The ST-P series laser displacement sensors, with high repeatability, high-speed sampling, and non-contact measurement, are suitable for PCB/substrate component height measurement, wafer flatness inspection, package height measurement, and other semiconductor automation applications. Selection should consider actual working conditions and be validated through sample testing. This article is for reference only; consult the manufacturer or conduct on-site tests for specific applications.