Wet chemical porosification with phosphate buffer solutions for permittivity reduction of LTCC substrates

  • The wireless high-frequency technology requires a robust, cost-effective, and highly integrated substrate technology offering the capability for areas of tailored permittivity. The wet-chemical porosification of low temperature co-fired ceramics (LTCC) substrates offers such an approach by locally embedding air. Porosification of LTCC in both extremely acidic and alkaline media has been investigated in previous works. However, for improving the available knowledge on the porosification of LTCC with H3PO4 as a standard and a widely used etching solution, the impact of solution concentration was systematically investigated and a substantial improvement in the etching performance was achieved. Moreover, in the present study, for the first time, the intermediate pH values, and the impact of pH as a key parameter on the etching process have been investigated. For this purpose, the applicability of phosphate buffer solution (PBS) as a prospective novel etchant mixture for the porosificationThe wireless high-frequency technology requires a robust, cost-effective, and highly integrated substrate technology offering the capability for areas of tailored permittivity. The wet-chemical porosification of low temperature co-fired ceramics (LTCC) substrates offers such an approach by locally embedding air. Porosification of LTCC in both extremely acidic and alkaline media has been investigated in previous works. However, for improving the available knowledge on the porosification of LTCC with H3PO4 as a standard and a widely used etching solution, the impact of solution concentration was systematically investigated and a substantial improvement in the etching performance was achieved. Moreover, in the present study, for the first time, the intermediate pH values, and the impact of pH as a key parameter on the etching process have been investigated. For this purpose, the applicability of phosphate buffer solution (PBS) as a prospective novel etchant mixture for the porosification of a commercially available LTCC tape (Ceramtape GC) was explored. Valuable information about surface morphology, crystalline composition, and the pore structure of the etched LTCCs was gathered employing scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and mercury porosimetry measurements. Based on these findings, the performance of PBS-based etchant systems towards the generation of porous LTCCs combining high depths of porosification with acceptable surface characteristics for subsequent metallization is demonstrated. Based on the obtained results, by application of a 0.2 mol L−1 solution of PBS, the effective relative permittivity of test samples with a thickness of approximately 600 µm and a porosification depth of 186 µm from each side, could be reduced up to 10% of its initial “as fired” value. Also, based on the measurement results and by measuring the depth of porosification, the permittivity of the etched layer was estimated to show a reduction of up to 22% compared to the initial “as fired” value.zeige mehrzeige weniger

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Metadaten
Autor*innen:A. Hajian, T. Konegger, K. Bielecki, Björn MiellerORCiD, Torsten Rabe, S. Schwarz, C. Zellner, U. Schmid
Dokumenttyp:Zeitschriftenartikel
Veröffentlichungsform:Verlagsliteratur
Sprache:Englisch
Titel des übergeordneten Werkes (Englisch):Journal of Alloys and Compounds
Jahr der Erstveröffentlichung:2020
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.4 Multimateriale Fertigungsprozesse
Verlag:Elsevier B.V.
Jahrgang/Band:863
Erste Seite:158059
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:LTCC; Permittivity reduction; Porosification; Wet chemical etching
Themenfelder/Aktivitätsfelder der BAM:Material
DOI:10.1016/j.jallcom.2020.158059
ISSN:0925-8388
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:14.12.2020
Referierte Publikation:Ja
Datum der Eintragung als referierte Publikation:01.04.2021
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