Part 4. In-Line Optical & X-Ray Inspection (SPI recap, AOI, AXI, SPC)

Inspection is the data engine that makes your SMT line predictable. This chapter covers the tools that measure quality and drive process control.

Key technologies and their functions:

• SPI (Solder Paste Inspection): Measures paste volume/area to calculate process capability (Cp/Cpk) and predict reflow failures early.
• AOI (Automated Optical Inspection): Verifies component presence and orientation using optics.
• AXI (Automated X-ray Inspection): Sees hidden defects, like voiding under BGAs and QFNs.
• SPC: Unifies all inspection data into closed-loop control signals, stopping process drift.

This is how you move beyond simple checks to predictive process assurance.