PCB Visual Inspection
PCB visual inspection, especially automated optical inspection (AOI), is a core technology for ensuring product quality in modern electronics manufacturing. It utilizes optical imaging and computer analysis to efficiently and accurately detect various defects that may occur during the PCB manufacturing process.
To help you quickly build a comprehensive understanding, the table below outlines the core tasks, mainstream technical solutions, and value of PCB visual inspection at different stages of production.
| Inspection Stage | Main Defect Types Detected | Common Technologies and Equipment | Core Value of this Inspection Stage |
| Post-Solder Paste Printing | Solder paste bridging, misalignment, excessive/insufficient solder, no solder paste | 2D AOI, 3D SPI (Solder Paste Inspection Machine) | Problem Prevention: Ensure the accuracy of the "raw materials" for soldering, avoiding defects at the source. |
| Post-Placement/Pre-Reflow Soldering | Component omission, incorrect component, offset, skew, reverse polarity, bent leads | 2D/3D AOI | Process Tracking: Confirm component placement quality before soldering, facilitating quick correction of placement machine parameters. |
| Post-Reflow Soldering (Final Quality) | Solder joint quality issues (insufficient/excessive solder, bridging, cold solder joint, solder balls), missing/offset/incorrect polarity | 2D AOI, 3D AOI, AI Vision, X-Ray (for hidden solder joints such as BGA) Problem Detection: As the final checkpoint before shipment, ensuring 100% product qualification upon delivery. | Key Technologies and Development Trends: Traditional visual inspection relies primarily on 2D images and algorithms with pre-defined rules. However, the industry is moving towards smarter and more precise methods to address more complex challenges. |
3D Visual Inspection: By acquiring 3D point cloud data of solder joints, the height, volume, and shape of the solder joints can be accurately measured. This fundamentally solves the problems that 2D technology struggles to accurately identify, such as "cold solder joints" and the amount of solder, achieving blind-spot-free inspection.
AI and Deep Learning:
Traditional algorithms often require extensive adjustments and are prone to false alarms when facing varied defects or new product line changes. Visual systems integrating AI technology possess self-learning capabilities. Even with only a small number of defect samples (small sample training), the model can be continuously optimized through training, significantly improving the accuracy and adaptability in identifying complex defects (such as cold solder joints of various shapes).
Multimodal Fusion:
Visual inspection is ineffective for bottom-hidden solder joints such as BGA and CSP. At this point, a multimodal fusion solution, such as "X-Ray + Vision," is needed. X-rays' penetrating power is used to detect internal defects, achieving comprehensive quality control.
Advantages over manual inspection:
Compared to traditional manual visual inspection, automated optical inspection demonstrates significant advantages in modern production lines:
High efficiency and stability:
Inspection speeds can reach millisecond levels, operating 24/7 without fatigue, with extremely high consistency.
High precision and reliability:
It can stably detect defects as small as 0.1mm or even smaller, with an accuracy rate exceeding 95%, far exceeding the limits of the human eye, effectively reducing missed and false detections.
Data-driven process optimization:
The inspection process generates a large amount of data, which can be used for Statistical Process Control (SPC) to help engineers analyze defect trends and optimize process parameters such as printing, placement, and reflow soldering from the source, continuously improving overall yield.
Summary:
In conclusion, PCB visual inspection has evolved from an "automated tool" replacing the human eye to an "intelligent quality control system" empowering the entire manufacturing process. It's not just a "keen eye" for spotting defects, but also a "smart brain" for continuous process improvement.
Hopefully, the above information helps you gain a comprehensive understanding of PCB visual inspection. If you are particularly interested in a specific inspection环节 (such as AOI on an SMT production line) or a particular technology (such as how AI algorithms are trained), we can discuss it further.
