Intermetallic Bonding for High-Temperature Microelectronics and Microsystems: Solid-Liquid Interdiffusion Bonding

Solid-liquid interdiffusion (SLID) bonding for microelectronics and microsystems is a bonding technique relying on intermetallics. The high-melting temperature of intermetallics allows for system operation at far higher temperatures than what solder-bonded systems can do, while still using similar process temperatures as in common solder processes. Additional benefits of SLID bonding are possibilities of fine-pitch bonding, as well as thin-layer metallurgical bonding. Our group has worked on a number of SLID metal systems. We have optimized wafer-level Cu-Sn SLID bonding to become an industrially feasible process, and we have verified the reliability of Au-Sn SLID bonding in a thermally mismatched system, as well as determined the actual phases present in an Au-Sn SLID bond. We have demonstrated SLID bonding for very high temperatures (Ni-Sn, having intermetallics with melting points up to 1280°C), as well as SLID with low process temperatures (Au-In, processed at 180°C, and Au-In-Bi, processed at 90–115°C). We have verified experimentally the high-temperature stability for our systems, with quantified strength at temperatures up to 300°C for three of the systems: Cu-Sn, Au-Sn and Au-In

Interconnects based on metal coated polymer spheres for improved reliability

3D packaging and heterogeneous integration has revealed new opportunities with regard to where instrumentation can be applied. Extreme miniaturization of systems makes it possible to include sensors and electronics in regions where this was not possible earlier due to size or weight limitations. However, some of these new application areas represent a challenging combination of extreme demands for reliability in rough environments. Interconnects are known to be prone to failures as a result of thermo-mechanical stress and require a specific focus in any instrumentation system. In this presentation we will give three examples of cases where traditional interconnect technologies are replaced with solutions based on metal coated polymer spheres (MPS) in order to improve the reliability. The idea behind the work is that the larger compliance of the polymer core of MPS compared to solid metal will reduce the level of stress imposed on the interconnect during thermal cycling or shock loading. The interconnect challenges in the three cases were to mount a MEMS device onto a PCB, to mount a silicon planar sensor onto an ASIC, and to mount a ceramic carrier onto a PCB. In the first example silver epoxy was replaced with an isotropic conductive adhesive filled with 4-30 µm sized MPS. In the second example microbumps were replaced with an anisotropic conductive film filled with 6 µm sized MPS, and in the last example lead free solid solder BGA balls were replaced with 310 µm sized MPS. Results indicating increased reliability for the devices, especially with regard to thermal cycling and rough mechanical treatment, will be shown. All three technologies based on MPS are expected to represent valuable alternatives within several 3D packaging solutions, although 3D packing in itself is not the primary scope for the interconnect technology development at present

Interconnects based on metal coated polymer spheres for improved reliability

3D packaging and heterogeneous integration has revealed new opportunities with regard to where instrumentation can be applied. Extreme miniaturization of systems makes it possible to include sensors and electronics in regions where this was not possible earlier due to size or weight limitations. However, some of these new application areas represent a challenging combination of extreme demands for reliability in rough environments. Interconnects are known to be prone to failures as a result of thermo-mechanical stress and require a specific focus in any instrumentation system. In this presentation we will give three examples of cases where traditional interconnect technologies are replaced with solutions based on metal coated polymer spheres (MPS) in order to improve the reliability. The idea behind the work is that the larger compliance of the polymer core of MPS compared to solid metal will reduce the level of stress imposed on the interconnect during thermal cycling or shock loading. The interconnect challenges in the three cases were to mount a MEMS device onto a PCB, to mount a silicon planar sensor onto an ASIC, and to mount a ceramic carrier onto a PCB. In the first example silver epoxy was replaced with an isotropic conductive adhesive filled with 4-30 µm sized MPS. In the second example microbumps were replaced with an anisotropic conductive film filled with 6 µm sized MPS, and in the last example lead free solid solder BGA balls were replaced with 310 µm sized MPS. Results indicating increased reliability for the devices, especially with regard to thermal cycling and rough mechanical treatment, will be shown. All three technologies based on MPS are expected to represent valuable alternatives within several 3D packaging solutions, although 3D packing in itself is not the primary scope for the interconnect technology development at present

Integration of Carbon Nanotubes in Microsystems: Local Growth and Electrical Properties of Contacts

material

Joint International Master in Smart Systems Integrated Solutions

The Joint International Master in Smart Systems Integrated Solutions (SSIs) will graduate candidates for the ever-growing industry of Smart Systems, ubiquitous in all sectors of society including healthcare, transport, environment protection, energy and security. SSIs is given jointly by three universities in three European countries: Aalto University (Helsinki, Finland), University of South-Eastern Norway (USN), and Budapest University of Technology and Economics (BME) (Hungary), utilizing the complementary expertise and laboratory facilities of the three partners to create a unique programme with a more holistic approach than a single university could give. The programme collaborates closely with industry, and has EPoSS as Associated Partner, assuring its relevance. SSIs builds on the Joint International Master in Smart Systems Integration (SSI), which has been running since 2013 with Heriot-Watt University (Edinburgh, Scotland) co-ordinating a consortium with USN and BME. SSIs students benefit from the combined expertise of the consortium, as well as from the extended socio-cultural knowledge obtained by living in three different European countries that represent distinctively different aspects of the diverse Europe. The students in the programme show excellent performance, and the employability of graduates has proven to be very high