Realisation of Large Cavities in Multilayer Ceramics by Cold Low Pressure Lamination and Their Characterisation by μCT

Abstract

In microelectronics the ceramic multilayer technology is frequently used as it allows a precise and yet flexible production of MEMS, microelectronic devices, micro reactors or devices for micro fluidics. During production of those multilayer structures the single layers are typically laminated by thermo-compression. However, large cavities cannot be realised using thermo-compression without adding sacrificial fillings. In contrast, the cold low pressure lamination (CLPL) technique allows lamination at room temperature without applying a high pressure. As in this lamination technique no mass flow occurs, internal cavities are not destroyed during the lamination step. In this study, commercially available LTCC green tapes were structured using a milling plotter with a high frequency spindle. Different process parameters (milling speed, spindle frequency) were evaluated regarding the accuracy of shape and quality of the channel edge. Channels with various dimensions (2.5 - 15 mm width and 30 mm length) were milled into the green tapes. Subsequently, the green tapes were laminated using the CLPL technique. With CLPL adjacent ceramic green tapes are joined by a double sided adhesive tape, which is applied by a soft roller. By alternately applying green (structured or unstructured) and adhesive tapes multilayer structures with internal cavities are formed. For characterisation of the sintered LTCC structures μCT (computed tomography) was used to analyse the internal structure without destroying the sample. Influence of sintering regime on deformation was evaluated. It was shown that milling of green tapes in combination with CLPL is a suitable method to fabricate internal cavities in LTCC multilayer structures.