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4. In-Line Optical & X-Ray Inspection: SPI, AOI, AXI, SPC

A fundamental manufacturing principle dictates that processes cannot be managed without measurement. In modern PCBA, components are too small and densely packed for reliable human visual inspection at production speeds.

Automated Optical Inspection (AOI) and Automated X-Ray Inspection (AXI) provide empirical data necessary for effective Statistical Process Control (SPC). This chapter details programming these systems to minimize false calls while assuring reliable defect capture.

  • 4.1 SPI Recap & Cₚ/Cₚₖ

    Solder Paste Inspection (SPI) bridges the gap between manual stencil printing and a predictive, data-driven system. By measuring the three-dimensional geometry of each paste deposit—its volume, height...

  • 4.2 AOI Fundamentals

    Automated Optical Inspection (AOI) serves as a primary visual quality gate for the SMT line. Utilizing high-resolution cameras and advanced pattern-matching algorithms, AOI automatically inspects boar...

  • 4.3 AXI Techniques

    Automated X-ray Inspection (AXI) is a valuable non-destructive testing method that uses X-ray radiation to penetrate components and the PCB, providing clear visibility into internal structures and hid...

  • 4.4 Programming & Tuning

    Inspection programming involves translating raw component and solder data into actionable pass or fail criteria. The primary operational goal of tuning an inspection system is balancing a minimized fa...

  • 4.5 SPC & Dashboards

    Statistical Process Control (SPC) is the operational discipline that converts raw machine data into useful predictive intelligence. By continuously charting the key performance indicators of the SMT l...