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Precision Solder Ball Analysis Using Ion Beam Polishing and SEM

Abstract

In contemporary semiconductor packaging, such as Ball Grid Arrays (BGAs), precise cross-sectional analysis of solder balls is crucial for assessing joint integrity and ensuring long-term reliability. Conventional mechanical polishing techniques often lead to surface damage or distortions, complicating accurate data acquisition. This study introduces an innovative approach utilizing the Coxem CP-8000+ Ion Beam Polisher combined with the EM-30N Tabletop SEM, providing non-destructive, high-resolution insights into solder ball cross-sections. A comparative evaluation highlights the enhanced surface finish and structural detail achieved through ion milling, establishing a new benchmark for semiconductor quality assurance and failure analysis.

Mechanical polish of BGA cross-section

The increasing miniaturization and complexity of semiconductor devices demand highly reliable interconnects, especially in BGA packages. Ensuring electrical performance and structural integrity requires precise evaluation of solder joints. However, traditional cross-section preparation techniques like mechanical polishing can cause deformation, making it difficult to observe internal features and reducing analysis accuracy. To overcome these limitations, COXEM developed a combined solution with the CP-8000+ Ion Beam Polisher and the EM-30N Tabletop SEM. This system enables precise, non-contact surface preparation and high-resolution imaging, making it ideal for advanced semiconductor packaging applications.

Materials and Methods

1. Argon Ion Milling with CP-8000+

The CP-8000+ employs high-energy argon ions to achieve contact-free polishing of
samples. This method ensures the creation of smooth, distortion-free
cross-sections, making it suitable for examining both flat and curved solder
joints. The milling process is carried out in a vacuum environment, minimizing
contamination and ensuring consistent results.

cp8000 brochure image
Ion Mill
After Ion Milling
2.  SEM Imaging with EM-30N

Following ion milling, the samples are examined using the EM-30N Tabletop SEM. Magnifications between 130X and 500X are utilized, with imaging performed in both SE and BSE modes. For enhanced analysis, optional EDS capabilities can provide detailed elemental composition, supporting material characterization and defect analysis.

Coxem EM-30 Tabletop Scanning Electron Microscope
Discussion

The combination of CP-8000+ and EM-30N provides a powerful and efficient method for solder ball cross-section analysis.

Key advantages include: –

  • Damage-free preparation: Ion milling eliminates mechanical stress and preserves internal features.
  • Enhanced clarity: High-resolution imaging reveals interfaces, voids, and defects with high contrast.
  • Workflow efficiency: From sample prep to imaging, the streamlined process ensures reproducibility.

The ability to observe internal structures clearly and without artifact enhances failure analysis, yield improvement, and quality assurance in semiconductor manufacturing.

Closeup After Ion Milling - SE Detector
Closeup After Ion Milling - BSE Composite
Conclusions

This study emphasizes the value of integrating an Ion Beam Polisher with a Scanning Electron Microscope (SEM) for advanced solder ball cross-section analysis in semiconductor packaging. This approach overcomes the challenges of traditional mechanical polishing, delivering distortion-free sample preparation and high-resolution imaging. The clarity and precision achieved through ion milling and SEM analysis enable detailed evaluation of internal structures, defects, and material interfaces. These innovations set a new benchmark for quality control and failure analysis, providing a dependable and efficient solution for maintaining the integrity of modern electronic interconnects.

Historically, scanning electron microscopy was limited to well-funded research facilities or analytical labs due to the high costs associated with the equipment. However, advancements in technology are driving affordability now making these tools accessible for routine use. This accessibility empowers manufacturing, materials, and sustaining engineers with enhanced process control and deeper insights into their operations. For more details, visit ION MILLING EQUIPMENT – JH Technologies and TABLETOP ELECTRON MICROSCOPES (SEM) – JH Technologies.

Acknowledgements

We would like to acknowledge Coxem corporation for providing the content in this study.  You can find this study on linkedin at (35) High-Precision Cross-Section Analysis of Solder Balls in Semiconductor Packages Using Ion Beam Polishing and Tabletop SEM | LinkedIn