ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
AlSi7Mg/SiC/70p (AlSiC) is used for heat sinks because of its good thermal conductivitycombined with a low coefficient of thermal expansion (CTE). These properties are important forpower electronic devices where heat sinks have to provide efficient heat transfer to a coolingdevice. A low CTE is essential for a good surface bonding of the heat sink material to the insulatingceramics. Otherwise mismatch in thermal expansion would lead to damage of the bondingdegrading the thermal contact within the electronic package. Therefore AlSiC replaces increasinglycopper heat sinks. The CTE mismatch between insulation and a conventional metallic heat sink istransferred into the MMC heat sink. The stability of the interface bonding within a MMC is criticalfor its thermal properties.In situ thermal cycling measurements of an AlSi7Mg/SiC/70p MMC are reported yielding thevoid volume fraction and internal stresses between the matrix and the reinforcements in function oftemperature. The changes in void volume fractions are determined simultaneously by synchrotrontomography and residual stresses by synchrotron diffraction at ESRF-ID-15. The measurementsshow a relationship between thermal expansion, residual stresses and void formation in the MMC.The results obtained from the in situ measurements reveal a thermoelastic range up to 200 °Cfollowed by plastic matrix deformation reducing the volume of voids during heating. A reverseprocess takes place during cooling. Thus the CTE becomes smaller than according to thermoelasticcalculations. Damage could be observed after multiple heating cycles, which increase the volumefraction and the size of the voids.The consequence is localdebonding of the matrix from thereinforcement particles, whichleads to an irreversible reductionof the thermal conductivity aftermultiple heating cycles
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/18/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.571-572.413.pdf
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