In the printed circuit board (PCB) industry, advanced circuit boards require complex processes and high stability to ensure consistent quality. In Taiwan, in-spection and repair of polymer residues on PCBs still rely largely on imported equipment. Here, polymer residues refers to residual resin, epoxy, and other or-ganic polymeric contaminants remaining on PCB surfaces, particularly on copper surfaces, after processing.
With support from the National Science and Technology Council (NSTC), a research team led by Prof. Jeng-Rong Ho of the Department of Mechanical En-gineering at National Central University (NCU) has partnered with industry to develop a PCB Polymer Residue Inspection and Laser Repair System (Automat-ed Optical Inspection & Repair, AOIR). The system combines high-precision op-tical inspection with intelligent defect repair to improve yield and productivity. Its automated polymer-residue removal workflow reduces human error and enhances production line stability and consistency.
Prof. Ho’s interdisciplinary team brings together expertise in materials analy-sis, laser processing, automated optical inspection (AOI) and image recognition, mechatronic integration, and precision machinery. Based on the production re-quirements of Unimicron Technology Corp., Taiwan’s leading PCB manufacturer and one of the world’s top five PCB makers, and leveraging its engineering know-how, the team jointly developed a prototype AOIR system capable of au-tomatically detecting and removing polymer residues.
The prototype integrates a three-axis precision stage, a line-scan camera, and a coaxial vision system for image acquisition and processing to achieve targeted polymer-residue removal. Building on this prototype, the team and the company further implemented integrated mechatronic control, designed the line-scan cam-era and laser modules, and completed installation and calibration of the camera and laser hardware. They successfully migrated the AOIR prototype onto an ex-isting pick-and-place platform in the production line and improved system accu-racy to better than 5 µm.
Equipped with a self-developed human–machine interface, the system uses the line-scan camera to capture and analyze copper surface topography, accurately identifies polymer residue locations, and compares them with the original circuit layout. It then performs precisely positioned laser processing to remove residues at the designated sites.
Through extensive testing and parameter optimization, laser processing con-ditions were tailored for different types of polymer residues, enabling efficient and reliable removal. Verification using copper sulfate treatment, laser scanning confocal microscopy, and electron microscopy confirmed that the laser process can completely remove polymer residues without damaging the copper surface. This technology will be introduced to production lines for polymer-residue in-spection and removal on PCB panels up to 530 mm × 650 mm, further enhanc-ing process automation and precision.
The integrated use of AOI (Automated Optical Inspection) and AOR (Au-tomated Optical Repair) not only reduces equipment maintenance costs and boosts manufacturing efficiency, but also avoids the substantial expense of pur-chasing and servicing foreign machinery. At the same time, it supports the transi-tion of Taiwan’s semiconductor and PCB industries toward smart manufacturing, strengthening domestic supply-chain resilience and enhancing global competi-tiveness.
Looking ahead, the PCB Polymer Residue Inspection and Laser Repair Sys-tem can be extended to a broader range of semiconductor process applications, driving industrial upgrading and technological innovation and helping to secure Taiwan’s leading position in the global semiconductor and PCB sectors.
Media Contact：
Ming-Lun Tsai
Assistant Researcher
Department of Engineering and Technologies
National Science and Technology Council
Tel.: (02) 2737-7390
E-mail: mltsai@nstc.gov.tw
