Characterisation and Time Dependent Behaviour of Thermal Interface Materials

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Examensarbete för masterexamen
Master Thesis
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2009
Författare
Lundberg, Lisa
Fu, Tan-Xin
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Sammanfattning
Thermal interface materials (TIMs) are widely used in the electronics industry to facilitate heat conduction away from the working components. As the development in this industry is heading towards higher performances along with smaller components, heat density increases exponentially. This has imposed a demand for better TIMs. The aim of this master thesis is to characterise two commercial thermal interface materials, Material A and Material B, and investigate their time dependent properties. To predict the thermal performance of the two materials during their service life, knowledge of their time-dependent properties is vital. Material A and Material B serve as heat flow enhancers in Ericsson´s base stations all over the world and this master thesis is performed in collaboration with Ericsson AB, Göteborg. Characterisation of the two materials was performed at Chalmers University of Technology and Swerea IVF, using a number of analysing methods. It was found that both materials have an organo-siloxane matrix which is bimodally filled with highly thermally conductive particles. In order to investigate the long-term properties of the two materials, comparisons between test results from un-aged and aged specimen of both materials was made. It may be concluded that the shear and peel strength of Material A improved during ageing and its hardness increased. These results are believed to be associated with an increase in the amount of cross-links in the material introduced during the ageing process. Material A is superior to Material B for all test conditions in the shear and peel experiments and , in contrast to Material A, Material B weakened during ageing. The inferiority of Material B is thought to be due to embrittlement and dry-out during ageing. Results from the creep tests performed revealed that the aged samples of Material A is more creep resistant and showed a more solid-like behaviour. The thermal conductivity tests showed that Material A has better thermal performance and the performance is maintained after the ageing process. Material B showed an all over poorer performance and suffers from deteriorated thermal performance upon ageing. This is believed to be associated with an increased bond line thickness (BLT) and contact resistances of Material B. The thermal performance of both materials was recognised to be pressure dependent. However, above a certain threshold value of the pressure, the performance of Material A was shown to be independent of the pressure.
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Materialvetenskap, Konstruktionsmaterial, Materials Science, Construction materials
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