{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,27]],"date-time":"2026-01-27T21:15:20Z","timestamp":1769548520027,"version":"3.49.0"},"reference-count":28,"publisher":"MDPI AG","issue":"21","license":[{"start":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T00:00:00Z","timestamp":1635984000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Hyperspectral imaging and reflectance spectroscopy in the range from 200\u2013380 nm were used to rapidly detect and characterize copper oxidation states and their layer thicknesses on direct bonded copper in a non-destructive way. Single-point UV reflectance spectroscopy, as a well-established method, was utilized to compare the quality of the hyperspectral imaging results. For the laterally resolved measurements of the copper surfaces an UV hyperspectral imaging setup based on a pushbroom imager was used. Six different types of direct bonded copper were studied. Each type had a different oxide layer thickness and was analyzed by depth profiling using X-ray photoelectron spectroscopy. In total, 28 samples were measured to develop multivariate models to characterize and predict the oxide layer thicknesses. The principal component analysis models (PCA) enabled a general differentiation between the sample types on the first two PCs with 100.0% and 96% explained variance for UV spectroscopy and hyperspectral imaging, respectively. Partial least squares regression (PLS-R) models showed reliable performance with R2c = 0.94 and 0.94 and RMSEC = 1.64 nm and 1.76 nm, respectively. The developed in-line prototype system combined with multivariate data modeling shows high potential for further development of this technique towards real large-scale processes.<\/jats:p>","DOI":"10.3390\/s21217332","type":"journal-article","created":{"date-parts":[[2021,11,4]],"date-time":"2021-11-04T22:25:54Z","timestamp":1636064754000},"page":"7332","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":13,"title":["UV Hyperspectral Imaging as Process Analytical Tool for the Characterization of Oxide Layers and Copper States on Direct Bonded Copper"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6713-5669","authenticated-orcid":false,"given":"Mohammad","family":"Al Ktash","sequence":"first","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"},{"name":"Institute of Physical and Theoretical Chemistry, Eberhard Karls University T\u00fcbingen, Auf der Morgenstelle 18, 72076 T\u00fcbingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9459-0640","authenticated-orcid":false,"given":"Mona","family":"Stefanakis","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"},{"name":"Institute of Physical and Theoretical Chemistry, Eberhard Karls University T\u00fcbingen, Auf der Morgenstelle 18, 72076 T\u00fcbingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8622-917X","authenticated-orcid":false,"given":"Tim","family":"Englert","sequence":"additional","affiliation":[{"name":"Robert Bosch GmbH, Automotive Electronics, Postfach 1342, 72703 Reutlingen, Germany"},{"name":"Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Maryam S. L.","family":"Drechsel","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jan","family":"Stiedl","sequence":"additional","affiliation":[{"name":"Robert Bosch GmbH, Automotive Electronics, Postfach 1342, 72703 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Simon","family":"Green","sequence":"additional","affiliation":[{"name":"Robert Bosch GmbH, Automotive Electronics, Postfach 1342, 72703 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7777-2306","authenticated-orcid":false,"given":"Timo","family":"Jacob","sequence":"additional","affiliation":[{"name":"Institute of Electrochemistry, Ulm University, Albert-Einstein-Allee 47, 89081 Ulm, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Barbara","family":"Boldrini","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0492-0544","authenticated-orcid":false,"given":"Edwin","family":"Ostertag","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3577-2903","authenticated-orcid":false,"given":"Karsten","family":"Rebner","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5537-1448","authenticated-orcid":false,"given":"Marc","family":"Brecht","sequence":"additional","affiliation":[{"name":"Process Analysis and Technology PA & T, Reutlingen University, Alteburgstra\u00dfe 150, 72762 Reutlingen, Germany"},{"name":"Institute of Physical and Theoretical Chemistry, Eberhard Karls University T\u00fcbingen, Auf der Morgenstelle 18, 72076 T\u00fcbingen, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"319","DOI":"10.1007\/s11581-016-1894-8","article-title":"Nano-scale copper oxidation on leadframe surface","volume":"23","author":"Esa","year":"2017","journal-title":"Ionics"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"33503","DOI":"10.1007\/s11356-020-09517-2","article-title":"A review: Application of remote sensing as a promising strategy for insect pests and diseases management","volume":"27","author":"Marei","year":"2020","journal-title":"Environ. 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