Optical Measurement for the Alarming Height of Silver Paste Overflow Surrounding APD Chip in Optical Component Packaging

The avalanche photodiode (APD) chip is the core component of the transistor outline (TO). The overflowing silver paste surrounding the APD that exceeds alarming height is frequently the main cause of suffering functional abnormalities of TO optical devices. With the relentless surge in demand for optical components, the traditional visual inspection of the overflow height of silver paste relying on a manual microscope has been unable to meet the requirements of scalable manufacturing for the accuracy and efficiency of measurement. Hereby, we propose an optical 3-D slice intelligent measurement system (O3D-SIMS) composed of an optical 3-D laser camera acquisition unit and a 3-D silver paste slice intelligent measurement unit. A blue line laser image acquisition scheme is proposed and experimentally verified, to meet the measurement requirements of the accuracy and efficiency of silver paste height, by analyzing the complex changes in the surface environment of both silver paste and APD chips. Additionally, a 3-D silver paste slice automatic measurement scheme has been demonstrated according to the physical characteristics of the overflow silver paste and the process quality control requirements of TO. Eventually, followed by introducing the ion migration mechanism leading to TO failure and the principle of 3-D laser imaging, the environmental factors that mainly affect the measurement accuracy and stability are analyzed and discussed in combination with the experimental results. The experimental results show that the relative error of the O3D-SIMS is >5% better, and with a single measurement time of less than 0.8 s, improving the efficiency by nearly 10 times compared to traditional methods. To the best of our knowledge, this is the first report on the realization of the optical measurement for the alarming height of the silver paste.