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New High Heat Conducting Materials and Manufacturing Processes for Improved Efficiency of Heat Management and Packaging Components in Electronics

Final Report Summary - HEATCONDUCTIVES (New High Heat Conducting Materials and Manufacturing Processes for Improved Efficiency of Heat Management and Packaging Components in Electronics)

Currently there are two major relevant problems to be solved in the electronic industry. In the short term, the first problem is the substitution of lead in all electronic components (mainly in solders). The second problem is the improvement of heat management in electronic devices. This is the best way to improve power, reliability and efficiency of existing products (Si, SiC and GaAs semiconductor technologies) while facing the challenge of the miniaturisation of electronic components (power microelectronics) and new developed semiconductors (GaN). Higher operating temperatures and frequencies are the main targets. Therefore the improvement of the housing of new electronic components is crucial for the near future of the electronic industry.

The electronic industry in Europe is a sector which is, on one hand, experiencing a strong competition from low-cost countries outside the European Union (mainly from the Far East) for the production of cheap components. On the other hand, Europe has a dependant position with respect to high-technology countries such as Japan and USA, these being the main providers of high-technology products such as new semiconductors, advanced materials for electronic packaging, etc. So, there is a clear need for the European industry, and more specifically to SMEs, to strengthen their competitiveness to compete advantageously with Far East countries while leaving step by step their dependant position from Japanese and American suppliers of strategic products. European SMEs of these sectors find the need to improve the quality of their products, to optimise the processes and to accept new challenges of new products developments, this way improving their competitiveness by offering higher quality products while reducing costs derived from a higher production rate of advanced components.

The HEATCONDUCTIVES project has focused on the improvement of the efficiency and reliability of electronic systems by the use of innovative highly heat-conducting materials and products formed by the combination of copper and new carbon nanofibres and nanotubes of outstanding thermal conductivity. Conventional and innovative manufacturing processes have been developed during the project to produce thin foils and three-dimensional (3D) near net-shape components. Through these methods, new highly heat-conductive composite materials have been produced with the target of improving the performance in comparison to those products available today.

The development of novel highly conductive low cost vapour grown carbon nanofibres (VGCNFs) and carbon nanotubes (CNTs) has been successfully carried out with products from both Grupo Antolin and Marion Technologies. The properties of these materials have been improved during the course of the project, particularly relating to the improvement of properties by graphitisation. The improvements seen when moving from laboratory to industry scale methods were very encouraging.

Production of feedstock for MIM proved to be difficult (due to issues with porosity and poor green strength) and the processing route had to be halted. However further work will continue outside of the HEATCONDUCTIVES project based on the findings of this work. The production of feedstock for tape casting with copper, VGCNFs and CNTs was successful. The copper coating method for both the VGCNFs and CNTs was improved during the project. The final products showed no visible interface between the copper and carbon fibres which was an essential step towards improving the thermal conductivity properties of the material. The best results were seen for the electroless plating technique developed at Inasmet.

Development of metal matrix composite two-dimensional (2D) and 3D manufacturing processes (tape casting and metal injection moulding). The MIM route proved to be difficult (due to issues with porosity and poor green strength) and the processing route had to be halted. However further work will continue outside of the HEATCONDUCTIVES project based on the findings of this work. The tape casting technique was successfully used to produce thin films that were used to construct the final demonstrators. In addition, hot pressing was successfully used to manufacture several of the components in place of the MIM process.

Validation of the technologies developed by the production of industrial components, mounting, assembling and evaluation of electronic devices. All three components were successfully mounted and tested. The IGBT baseplate tests carried out by Semelab showed a 14 % improvement of the thermal resistance of the copper / carbon nanofibres when compared to the standard AlSiC baseplate. This value was comparable with unfilled copper however the carbon fibre filled material has a closer CTE to the substrate material and is therefore more suitable than unfilled copper.

Overall the base plate materials did not show the large increases in thermal performance that were expected from this project. This is primarily due to the continuing problem of the interaction between copper and carbon. Whilst significant improvements have been made to improve the physical interface region between Cu and C, the lack of chemical interaction continues to prevent the optimum use of the good thermal properties of the carbon nanofibres. More work by the project partners is required to improve this interaction and this work will continue to be developed based upon the findings of the HEATCONDUCTIVES project.

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