Alternatives Herstellungsverfahren von flexiblen Interconnects basierend auf dem Island-Bridge-Konzept
Internally funded project
Start date : 01.09.2021
Project details
Short description
The research project is used within a scope of a LEB PhD in collaboration with the Fraunhofer Institute for Integrated Systems and Device Technology (IISB).
The basis for many flexible conductor paths is the artificial extension of the initial length, for example by structuring them in serpentines or, in the case of the island bridge concept, by exploiting the trench depth. In the latter, the traces must be transferred or bonded to a pre-stretched substrate, whereby the traces, once the pre-stretch is removed, arc into the trench depth.
The question that arises is how the integration of the conductive traces into the trench depth can be realized by a less complex process. In this work, a new concept is implemented in which an arc-shaped connection is made directly on the three-dimensionally pre-patterned substrate. After its release, the approach also guarantees extensibility of the substrate. In this process, the trenches are filled in advance with a shaping polymer, on which the lithography for structuring the conductive tracks can then take place. The mechanics of these alternatively produced conductive tracks and stretching or bending processes are analyzed by numerical simulations and structural possibilities for optimizing the flexible structures are derived from this already without experimental effort. The final goal is to fabricate free-standing island bridge substrates with the developed traces and to demonstrate their electrical functionality under mechanical load
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Scientific Abstract
To built flexible electronics the structural engineering of the metallic interconnects is significantly important. Several concepts with different complexity are used. All concepts have in common to increase L0 and consequently reduce the strain. The island-bridge concept is one well known possibility and is often used with buckled, arc-shaped interconnects (bridge). The buckling of the bridge can be reached by mounting islands together with the metal structures onto are a pre-stretched flexible substrate and with releasing the stretch afterwards, so that the interconnects are partially lifted to form an arc shape. If the bridges have a sufficient height in the micrometer range, one design option is the buckling into the trench depth, which separates the islands from each other. Alternatively, before the actual process for the electronic devices starts, a stretchable substrate with a buckled surface is produced. This means a difficult transfer process or an extra manufacturing process is needed.
The aim of this work is to develop an alternative production route based on the island-bridge concept, where the free-standing interconnect is designed into the trench depth and the manufacturing is integrated into standard silicon planar technology.
The so produced arrays combine simple shape design with the advantages of the island bridge concept. For the first time the production of buckled metal structures is fully integrated into well known standard production steps without neither the need of a difficult transfer of the structure onto a stretchable substrate nor the additional pre-production of specific buckled substrate.
