SMTA International Conference Proceedings


X-ray Inspection for PCBA – Challenges and New Developments

Authors: David Geiger, Elbert Suen, Zhen (Jane) Feng, Ph.D., Weifeng Liu, Ph.D., Anwar Mohammed, Ph.D., Mike Doiron, Evstatin Krastev, Ph.D., Peter Chipman
Company: Flex, Nordson Dag, Optimum Design
Date Published: 9/17/2017   Conference: SMTA International


Abstract: X-ray inspection systems are key tools for quality control, yield enhancement, and failure analysis of advanced printed circuits board assemblies (PCBA). The electronics industry has witnessed significant improvements in the X-ray inspection capabilities (AXI, 2DX, 3D CT, Large Board CT) during the last twenty years. These advancements have aided in the development of new high performance packages and PCBA processes. In many cases, X-Ray inspection is the only non-destructive technique to inspect optically hidden components and solder joints such as BGA, POP, QFN, flip chips, through holes, etc.

Automated X-Ray inspection (AXI) has been available since 1999 at our manufacturing sites, and plays very important role to assure high quality SMT process. Along the way, manual X-ray systems (2DX and 3D CT) have been providing invaluable testing capabilities for verifying the AXI results, fine tuning the AXI parameters, process development, and X-ray inspection that is out of the scope of the AXI equipment.

Through the years these capabilities have been significantly improved and best practices have been developed on how to jointly use the AXI, 2DX(MXI), and 3D CT X-ray equipment to achieve best possible testing results and speed. In this paper, we will summarise the extensive experience we have accumulated while working on real problems together with our customers, X-ray inspection vendors and R&D teams. These projects include BGA HIP (head in pillow), solder charge connector, Package on Package, package 03015. In addition, we will discuss how to optimize test coverage and eliminate defect escapes during PCBA testing. These studies have been performed using variety of X-ray inspection systems at several production sites and lasted several years.

We will also discuss the X-ray inspection capabilities that are considered most important to the PCBA manufacturing process including: 1. Highest resolution X-ray images and clear distinction between good and defective pins; 2. Measurement data from inspection output; 3. Operator independent automated results for pass/fail condition; 4. Non-destructive e-cross section; 5. Easy and intuitive operation and programing; 6. Real time data feedback; 7. Flexible automated algorithms that are easily adjustable by the machine operator; 8. Zero defect escape with reasonable false call PPM.

Key Words: 

X-ray technology, AXI, 2DX(MXI), 3D CT, Large Board CT, pCT, Optimization.



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