Moulded interconnect devices (MIDs) contain huge possibilities for many applications in micro electro-mechanical-systems because of their capability of reducing the number of components, process steps and finally in miniaturization of the product. Among the available MID process chains, two component injection moulding is one of the most industrially adaptive processes. However, the use of two component injection moulding for MID fabrication, with circuit patterns in the sub-millimeter range, is still a big challenge at the present state of technology. The scope of the current Ph.D. project is to explore and overcome the challenges associated with MID production by two component injection moulding. Fabrication of micro scale MIDs by two component injection moulding, calls for plastic materials suitable for two component micro injection moulding and requires optimization in injection moulding and selective metallization. Integrated knowledge about the materials, tooling, process conditions and product development is needed. The main issues to be taken into account for two component injection moulded MIDs are: • Two component injection moulding with a sharp interface between the two polymers and a reasonable adhesion between them. • Selective metallization of the two component plastic part (coating one polymer with metal and leaving the other one uncoated) To overcome these two main issues in MID fabrication for micro applications, the current Ph.D. project explores the technical difficulties associated with the processes mentioned above and makes attempts to overcome those challenges. In search of suitable polymer materials for MID applications, potential materials are characterized in terms of polymer-polymer bond strength, polymer-polymer interface quality and selective metallization. Several untraditional material pairs have been proven successful in the experiments. The experimental results find the factors which can effectively control the adhesion and interface quality between two polymers. Investigations on the selective metallization process, by two different methods (two component injection moulding and laser direct structuring process), present a comparative analysis of the two processes and find the factors which are important for successful selective metallization. The demonstrator MID fabricated at the final stage of the project proves that the multidisciplinary knowledge gained from the project about materials, tooling and process optimization can be linked for successful fabrication of the MIDs in precision applications. In conclusion, it can be stated that the main results of the Ph.D. project is the documented knowledge presented in the current thesis about two component injection moulding, selective metallization, MID process chains and the vast know-how about the effects of different factors on the final MIDs.
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Kjær, Erik Michael, Hansen, Hans Nørgaard, Tang, Peter Torben