| Customer: ESA/ESTEC (2007 – 2008) | |
 | Epoxy matrices in combination with carbon nano-material improves the thermal conductivity between an electronic chip and its substrate. In addition the thermal expansion coefficient will be reduced considerably. This study shall tailor the present material to that specific application. |
1. Application or Technical problem to be solved
While the continuous downscaling of transistor feature sizes in advanced semiconductor technologies (e.g. GaAs power MMICs, HBTs, SiC, GaN, etc.), leads to the desired increase in integration density, this result is not matched by an equivalent scaling of power density (which adversely affects the performance and reliability of such products). The resulting power dissipation problems are therefore becoming a limiting factor for the effective utilisation of these technologies in space applications. Some of these technology (like GaAs European HBT for example) are sufficiently mature to be submitted to space evaluation programmes but the assembly issues for such technology are still seen as the slow-down factor for space integration.
Conventional techniques such as using heat sinks are usually significantly increasing mass and volume of an assembly, thereby dramatically reducing or even exceeding the advantage of miniaturisation. Other techniques like CuW or diamond based packages or active cooling using MEMS fluidic loops are usually very expensive and require specific expertise during component assembly. It is therefore why Nanotechnology is considered as an interesting emerging candidate which may offer a short term solution to the technical problem described above.
2. Sought Innovation and Engineering Goals
Several pre-studies and papers (some of them presented during the 5th ESA MNT Round Table at ESTEC) tend to indicate that Nanotechnology and in particular nano-fibres or nano-powder or carbon nanotubes could be used in composite materials to modify the physical properties, such as the strength, the thermal conductivity and the CTE.
The engineering effort is expected to consist of 2 main tasks: The 1st task will aim at identifying possible nano-materials which could significantly improve the thermal dissipative properties of standard space qualified epoxy commonly used by the semiconductor industry while keeping them compatible with space requirements (outgassing, adhesion strength, etc). For each possible composite material, the expected performances improvement (in terms of thermal dissiopation) will be simulated and estimated.
The 1st task will be completed by the selection of one or two most promising composite materials to be developed during the 2nd task.
The 2nd task will include two main activities: Breadboarding: the composite materials will be developed and tested for their thermal and mechanical properties. Validation: the most performant modified die attach material will be validated through by the fabrication and measurement/characterisation of an hybrid circuit demonstrator. Standard space qualified conductive epoxy materials usually have a thermal conductivity close to 2 W.m-1.k-1. It is expected that nanomaterials when correctly processed and use can multiply at least by a factor 3 this average value.
Publications:
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Statement of Work:
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