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Epoxy molding compounds are among the most widely used materials in the semiconductor industry. These molds interact with semiconductors, which can greatly affect the reliability and average lifespans of electronic devices. The tools involved must characterize and classify materials properly to ensure the right ones are used and that the properties do not deviate from those of previous batches.
Usually, FT-IR and Raman spectroscopy are used in this process, but since molding compounds are dyed with carbon black, the processes are hindered due to high IR absorption and high fluorescence backgrounds caused by the dying process.
To bypass these limitations, a team of scientists headed by Lukas Brunnbauer, a postdoctoral scientist at the Vienna University of Technology, tested how effective Tandem LA-ICP-MS/LIBS would be on different types of molding compounds. LIBS allows for simultaneous multi-element analysis while providing information on major, minor, and organic sample constituents (1). LA-ICP-MS enables analysis for trace element content, which provides information about raw material impurities and contaminations introduced during the manufacturing process. In combination with each other, Tandem LA-ICP-MS/LIBS can help analyze the elemental fingerprints and polymer signals of the epoxy molding compounds.
The study, published in the Journal of Chromatography A, involved 29 samples of 20 different molding compound types from 4 different suppliers. Each sample was categorized by shape and analyzed by the Tandem LA-ICP-MS/LIBS system. Using principal component analysis (PCA) and hierarchical cluster analysis (HCA), the scientists measured the spectral fingerprints of each sample before a model was characterized and constructed using a Random Decision Forest-classifier. From there, the model was tested with samples independent of those used for training, showing how it would function in everyday production.
The system was able to classify most of the samples properly. However, some samples that were very similar to each other were not correctly identified. For samples that form well-separated clusters during PCA and HCA, Tandem LA-ICP-MS/LIBS was effective at classifying them.
The scientists wrote that they think this system can be improved, namely by analyzing more samples of different molding compounds and having systems with better washouts and settling times. Tandem LA-ICP-MS/LIBS could help further our understanding of semiconductor production and lead to more powerful and durable electronics.
(1) Brunnbauer, L.; Zeller, V.; Gajarska, Z.; Larisegger, S.; Schwab, S.; Lohninger, H.; Limbeck, A. Classification of epoxy molding compounds by Tandem LA-ICP-MS/LIBS to enhance the reliability of electronic devices. J. Chromatogr. A. 2023, 207, 106739. DOI: https://doi.org/10.1016/j.sab.2023.106739