Difference Between AOI and SPI Inspection Machines | SMTFullLine
2026-04-01 10:12
Difference Between AOI and SPI Inspection Machines
Both AOI and SPI are optical inspection systems used in SMT, but they serve different purposes and are placed at different process stages. Understanding the difference between AOI and SPI helps you build a complete quality strategy. SMTFullLine provides both technologies.
Comparison Table
| Feature | SPI (Solder Paste Inspection) | AOI (Automated Optical Inspection) |
|---|---|---|
| Inspection point | After solder paste printing | After reflow soldering (or after placement in some cases) |
| What it measures | Paste volume, height, area, alignment | Component presence, position, polarity, solder joint quality |
| Defects caught | Insufficient/excess paste, bridging, shift | Missing components, tombstoning, bridging, misalignment, wrong polarity |
| Typical technology | 3D phase shift or laser | 2D color + optional 3D for height |
| Correction action | Re‑print or adjust printer settings | Rework or scrap board |
| Outcome | Prevents defects from moving downstream | Final quality verification |
Why You Need Both
SPI stops paste defects before component placement, saving costly rework.
AOI ensures the finished board meets quality standards.
Together, they form a closed‑loop quality system.
SMTFullLine’s Integrated Solutions
We offer 3D SPI systems and inline/offline AOI that can share data for process control. Our support team helps you set up inspection parameters for both machines.
Combine SPI and AOI for zero‑defect SMT.
Learn about our inspection packages at SMTFullLine.com.
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