UHDI Fundamentals: UHDI Technology and Automated Inspection

Estimated reading time: 1 minute

Following up on the last article on integrating ultra high density interconnect (UHDI) PCB technologies and Quality 5.0, here we will do a deeper dive into the automated inspection component. UHDI applications demand extreme precision, with line/space dimensions below 25 µm and microvias below 30 µm. Automated inspection systems are essential to achieving the defect-free fabrication required at these scales, and legacy automated inspection systems are becoming obsolete and ineffective.

UHDI Inspection

UHDI technology pushes the boundaries of PCB design and manufacturing, introducing micron-scale features that demand extremely precise inspection methods. As line/space dimensions shrink below 25 µm and microvias drop under 30 µm, traditional inspection tools and practices become insufficient. Manual visual inspection and traditional AOI systems lack the resolution, speed, and accuracy to detect micron-scale defects. As a result, UHDI demands the integration of highly advanced, fully automated inspection systems capable of real-time analysis, defect classification, and process feedback.

Inspection Challenges in UHDI

• Sub-micron traces: UHDI designs may feature 15–25 µm line widths that challenge optical resolution
• Microvia defects: Blind/buried vias require specialized laser or X-ray inspection
• Layer registration: UHDI's multiple layers must be precisely aligned within <10 µm
• Material sensitivity: UHDI's advanced resins and films may be optically inconsistent or semi-transparent

To continue reading this article, which originally appeared in the October 2025 edition of Design007 Magazine, click here.