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) elevates the process from manual stencil printing to a predictive, data-driven system. By measuring the three-dimensional geometry of each paste deposit—its volume, height, and area—SPI provides an early indicator for po...
- 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 boards for component placement accuracy and solder joi...
- 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 hidden solder joints. AXI is typically employed for p...
- 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 false alarm rate against the goal of zero escapes (f...
- 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 line, SPC enables early, minor corrections to proce...