1. Solder Paste Printing
Using a stencil and printer, solder paste is accurately applied to the PCB's pads, preparing for component placement. Precision at this stage directly impacts subsequent soldering quality.
2. SPI Inspection (Optional)
Solder Paste Inspection (SPI) utilizes optical or 3D measurement technology to verify paste quality—checking for missing prints, uneven thickness, or other anomalies. It serves as a quality gate before component placement.
3. Component Placement
Automated by Pick and Place Machines, this step acts like high-speed robotic arms, precisely positioning surface mount devices (SMDs) such as resistors, capacitors, and ICs onto designated PCB locations.
4. Reflow Soldering
The PCB enters a reflow oven, passing through four temperature zones: preheating, soaking, reflow (solder melting), and cooling—ensuring strong, reliable solder joint formation.
5. AOI Inspection
Automated Optical Inspection (AOI) uses cameras to capture and compare images, detecting visible post-assembly defects like missing components, wrong parts, misalignment, or short circuits.
6. X-Ray Inspection (AXI)
The linchpin for resolving "hidden" issues. For components with fully obscured bottom solder joints (e.g., BGA, QFN), X-Ray penetrates the PCB to reveal internal defects such as cold solder joints, bridges (shorts), insufficient solder, or voids.
7. Rework & Testing
Defective units undergo rework, followed by Functional Test (FCT) or In-Circuit Test (ICT) to ensure circuit board functionality.
二,Why X-Ray Inspection Is Indispensable
Also known as Automated X-ray Inspection (AXI), this technology addresses the limitations of visual inspection by using X-rays to penetrate PCBs and components, generating 2D or 3D images of internal structures—making hidden solder joints fully visible.
What It Inspects
Primarily targets defects in solder joints of BGA, QFN, and similar packages: cold solder joints, bridges, insufficient solder, and voids.
Its Critical Role
These hidden defects are potential "time bombs" for late-stage product failures. X-Ray inspection effectively intercepts such risks, serving as a cornerstone for ensuring high reliability in high-end electronics (e.g., smartphones, computers, automotive electronics).
Technological Advancements
Modern X-Ray inspection equipment is increasingly intelligent—delivering high-clarity imaging, AI-driven automatic defect recognition, and detailed inspection reports—dramatically boosting efficiency and accuracy.
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