Pressfit technology for 3-D molded interconnect devices (MID) - A lead-free alternative to solder joints - challenges and solutions concepts

The continuous trend in electronics production towards new substrate materials, the development of the third dimension by molded interconnect devices (3-D MID) and the constantly rising integration of functions and miniaturization of electronic products leads to new challenges for interconnection technology. Compared to interconnections established by solder materials the pressfit technology offers many advantages. Most important is that no temperature is needed which results in a thermal stress-free situation for the base substrate. Seen from the ecological side, no fumes, gases or cleaning fluids which may reduce the contact reliability of the connector come into existence. This kind of interconnection is also completely lead-free due to the fact that no lead containing solders are needed. Also undesirable effects like cold solder joints, bridges or opens do not occur. And finally, recycling of connectors can be made easily by disassembly of connector and base material. This paper shows, how these advantages can be made accessible for 3-D MID-Technology, too. The thermoplastic base materials covered within this project are: PC/ABS-Blend, Polyamide 66, Polyetherimide and Liquid Crystal Polymer (reference: standard FR-4). With this four different substrates almost the whole field of thermoplastics can be covered (commodity, technical and high temperature materials). Based on a test vehicle with various hole diameters and forms it is the aim to show the best combinations between hole diameter, used compliant press-fit connector (four pins with different geometries) and type of thermoplastic base material. The main intention of the investigations described in this paper is to make pressfit technology be useable for molded interconnect devices.