Distributed Optical Inspection for PCB Assembly Lines
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Solution Overview
Problem
Conventional automated optical inspection systems for printed circuit boards are inefficient in initial programming, provide limited insight into manufacturing errors, and struggle to detect defects in components with hidden electrical connections, such as ball grid array or flip chip packages, due to the need for expensive and slow X-ray systems.
Innovation Solution
A high-speed optical inspection system with a camera array and integrated illuminator that uses pulsed strobed illumination and multiple illumination field types to generate high contrast images, allowing for real-time inspection of printed circuit boards without the need for expensive motion control hardware, and enabling the detection of defects like stray components and solder paste issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional automated optical inspection systems are used, then inspection can be performed, but inspection time is excessive and productivity is low
Solution Approach 1:
The inspection system is divided into multiple distributed optical sensors positioned at different locations along the production line, each performing specialized inspections. This segmentation allows parallel processing of different inspection tasks simultaneously, dramatically increasing overall inspection speed and productivity while reducing total inspection time.
Solution Approach 2:
The system performs preliminary inspections at multiple stages before final completion, including pre-inspection before component placement and post-inspection after assembly. By conducting inspections preliminarily at strategic points, defects are detected early when they can be addressed without rework, improving productivity by preventing downstream issues.
2Loss of information
If conventional optical inspection systems are used, then manufacturing errors can be identified, but root cause analysis is limited
Solution Approach 1:
The distributed sensors provide continuous feedback about manufacturing conditions and defects at each stage. This feedback loop enables real-time monitoring and automatic adjustment of process parameters, providing complete error information including root causes. The system tracks defects back to their source operations, enabling comprehensive root cause analysis without increasing programming complexity.
3Measurement precision
If X-ray systems are used to detect hidden defects, then detection accuracy is improved, but system cost and inspection speed deteriorate
Solution Approach 1:
Instead of using expensive X-ray systems for all inspections, the patent applies different inspection methods to different locations and defect types. Distributed optical sensors with specialized illumination and imaging capabilities are positioned at specific locations to detect particular defect types with high accuracy. This local quality approach achieves detection precision comparable to X-ray for visible defects while maintaining high inspection speed and low cost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system significantly reduces inspection time, enhances defect detection accuracy, and provides insight into the root cause of manufacturing errors, improving the quality and reliability of printed circuit board production while minimizing scrap and rework costs.
Implementation Method 1
A first optical inspection sensor disposed over the conveyor before the inlet of the second electronics assembly machine and providing first sensor inspection image data relative to a substrate passing beneath the first optical inspection sensor in a non-stop fashion
Data Source
AI summary
An electronics assembly line includes a first electronics assembly machine and a second electronics assembly machine. The first electronics assembly machine has a first electronics assembly machine outlet. The second electronics assembly machine has a second electronics assembly machine inlet and outlet. The inlet of the second electronics assembly machine is coupled to the outlet of the first electronics assembly machine by a conveyor. A first optical inspection sensor is disposed over the conveyor before the inlet of the second electronics assembly and is configured to provide first sensor inspection image data relative to a substrate that passes beneath the first optical inspection sensor in a non-stop fashion. A second optical inspection sensor is disposed over the conveyor after the outlet of the second electronics assembly machine and is configured to provide second sensor inspection image data relative to a substrate that passes beneath the second optical inspection sensor in a non-stop fashion. A computer is operably coupled to the first and second optical inspection sensors and is configured to provide an inspection result based upon at least one of the first and second inspection image data.