Investigating the effect of etching parameters on the porosification of LTCC with sodium hydroxide

Due to their outstanding material properties, low temperature co-fired ceramics (LTCC) have attracted a significant attention in highly integrated substrates and micromachined devices. However, LTCC are generally suffering... [ view full abstract ]

Due to their outstanding material properties, low temperature co-fired ceramics (LTCC) have attracted a significant attention in highly integrated substrates and micromachined devices. However, LTCC are generally suffering from high permittivity and we have introduced acidic wet-chemical etching to reduce their permittivity in the as-fired state without needing to alter the LTCC tape composition or the sintering process [1,2]. Also, very recently we have shown the potential of alkaline KOH solution as an alternative etchant for the surface-near porosification of Ceramtec GC LTCC [3]. The advantage of the proposed method is a surface quality for the etched LTCC which features an enhanced bearing plane allowing further metallization, being an essential pre-requirement for the reliable operation of compact devices or modules for high-frequency applications.

In this study, we have investigated the effect of important etching parameters on the etching behavior of commercially available Ferro L8 LTCC system with NaOH solution. Investigation of mass removal, porosification depth, and sample thickness change with regard to bath temperature, exposure time and etchant concentration is of utmost importance for optimization of the etching parameters, as the porosification can be tailored by altering these parameters.

In Figure 1 the mass removal for different etching conditions is shown.

Surface morphology and crystalline structure of the LTCC samples were investigated with SEM and XRD techniques, respectively. Figure 2 shows 3D reconstructed SEM images of the LTCC substrates etched at different tempeor 360 min.