Application Background
IC substrates are critical substrates for chip packaging, and their step differences and flatness directly affect the yield of subsequent mounting, bonding, and packaging processes. Traditional contact-based measurements are inefficient, prone to surface damage, and unsuitable for high-speed automated production lines. The ST-P series laser displacement sensors employ non-contact measurement using laser triangulation, effectively addressing the accuracy and speed requirements of online IC substrate inspection.
Inspection Objects and Objectives
Inspection Objects: Height differences (step differences) and overall flatness of various areas on the IC substrate surface. Inspection Objectives: To ensure the flatness of the substrate is within the process tolerances, preventing chip misalignment and poor soldering due to warping or localized unevenness.
On-site Pain Points
IC substrate surfaces may exhibit reflectivity, translucency, or color variations, affecting the stability of laser measurements.
High production line cycles require sensors with high-speed sampling capabilities (typically above 10kHz).
Limited installation space necessitates compact sensors that are easy to integrate.
Environmental vibration and temperature variations may affect measurement accuracy.
Product Principles and Selection Guide
The ST-P series is based on laser triangulation, calculating displacement by receiving changes in the position of the reflected light spot using a CCD/CMOS sensor. For IC carrier board inspection, model selection should be based on measurement range, accuracy, and installation distance:
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 IC carrier board step detection (typically within ±1mm), ST-P25 or ST-P30 are recommended; if simultaneous detection of larger warpage is required, ST-P50 or ST-P80 can be selected. The specific model needs to be confirmed based on the actual installation distance and accuracy requirements.
Solution Recommendation
Use multi-sensor array or single-sensor scanning method:
Multi-sensor array: Arrange multiple ST-P series sensors across the substrate width to measure heights at multiple points simultaneously and calculate flatness. Suitable for high-speed online inspection.
Single-sensor scanning: Move the sensor or substrate via a motion stage to measure point by point. Suitable for offline sampling or low-cycle production lines.
Signal output options include Ethernet, RS485, analog, and IO, facilitating integration with PLCs or host computers. Sampling frequency up to 160 kHz meets high-speed production line requirements.
Installation and Commissioning Suggestions
Avoid direct strong light on the sensor and ensure the laser spot is perpendicular to the measured surface.
For highly reflective IC substrates, adjust the sensor angle or use a polarizer; sample testing is recommended.
In high-vibration environments, add vibration damping or use averaging filter algorithms.
During commissioning, perform zero-point calibration first, then verify linearity using standard gauge blocks.
Frequently Asked Questions
Q: Can the sensor measure IC substrates with transparent encapsulation glue?
A: Transparent materials may cause multiple reflections; sample testing is recommended. The ST-P series has some adaptability to transparent materials, but actual results should be verified.
Q: Can the sensor measure both step height and flatness simultaneously?
A: Yes. Step height and flatness can be calculated from multi-point measurement data, but the measurement points must cover the entire substrate area.
Q: Is measurement accuracy affected by temperature?
A: The ST-P series features temperature compensation, but extreme temperature changes still require on-site verification.
Conclusion
The ST-P series laser displacement sensors provide a non-contact, high-precision, high-speed solution for IC substrate step height and flatness measurement. Selection should be confirmed based on specific working conditions, and sample testing is recommended to verify surface adaptability. This solution effectively improves semiconductor packaging inspection efficiency and yield.