Combined 3D Micro Structuring of Ceramic Green Tape Using Punching, Embossing and Laser Processing

Abstract

Multilayer ceramics technology, as LTCC, offers several advantages for the fabrication of miniaturized three-dimensional structures, e.g. for microsystem applications, where electrical, mechanical and fluidic functions can be combined in robust and compact packages. 3D features, required by those applications, are e.g. vias for electrical and thermal interconnection, cavities for chip integration and channels for fluidic functions. They can be realized, in principle, in the sintered, as well as in the green state, but structuring in the green state dominates due to the then far better machinability of the material. Ceramic green tape structuring is usually accomplished by mechanical or laser machining. Punching is the standard process for realizing vias or cavities in LTCC. By nature, only through tape features can be realized, but 3D features can be realized by stacking of several layers. Embossing can be used for the realization of quite complex 3D structures with high resolution. It can be carried out either at elevated temperature, at which the binder of the tape is softened (hot embossing) or at room temperature (cold embossing). Laser structuring is a quite flexible method, which allows both through-cutting and engraving without any specific tool. However, a certain roughness of ablated areas cannot be avoided, and depth control and uniformity of laser engraved features remain challenging. In the present paper, the different techniques will be compared regarding their appropriateness for different structuring tasks. A combined use of punching, embossing and laser processing is described, which has been made possible by a novel machine and tool concept.