Aluminum Silicon Carbide (AlSiC) Microprocessor Lids and Heat Sinks for Integrated Thermal Management Solutions

摘要

The next generation microprocessor assemblies will require integrated thermal management design solutions as the device density and clock speeds increase. These solutions will include a heat spreader, or lid, that is in contact with the heat generating microprocessor in the total packaging assembly. The materials choice for these integrated heat spreader solutions must provide the following material property attributes. 1. High bulk thermal conductivity 2. CTE compatibility with the Device and/or Microprocessor Assembly 3. EMI/RFI Shielding 4. Light weight 5.Dimensional Stability/Flatness (minimize bond line length resulting in a decreased Θ_(JC)). 6. Competitive Pricing AJSiC, Aluminum Silicon Carbide, metal matrix composite materials meet the material property, design and pricing demands for microprocessor assemblies that require integrated heat sink thermal management solutions. The CTE of AJSiC material and components can be tuned to be compatible with the specific heatsink application by controlling the SiC volume fraction in the AlSiC composite. AlSiC products with CTE values 7 ― 9 ppm/°C (30 ― 250°C) are suitable for direct attachment to GaAs and Si devices and ceramic substrate. Higher CTE materials 10 ―12 ppm/°C are used for attachment to printed circuit boards. The AlSiC thermal conductivity value is 180 ― 200 W/mK (compositional dependent) similar to CuMo and CuW materials. The material density of AJSiC is 1/3rd to 1/5th that of CuMo and CuW making AlSiC more suited to weight sensitive applications. The Ceramics Process Systems AlSiC components are cost-effectively fabricated to net-shape attaining close dimensional tolerances with minimal machining. The AlSiC material composition (hence CTE) is controlled by monitoring the SiC volume fraction of a tightly toleranced SiC preform fabricated with the QuickSet~(TM) injection molding process. The pore structure of the SiC preform is infiltrated with molten Al-metal (termed the QuickCast~(TM) process) to form the AlSiC composite material to the exact product dimensions defined by the infiltration mold. The combined processes form a fully dense, hermetic material of discrete SiC paniculate in a continuous Al-metal matrix phase. This process is currently used for high volume production for a number of product geometries and thermal management applications including MPU integrated heat spreading lid solutions. The ideal material properties coupled with AlSiC fabrication process provide low-cost high-performance functional integrated thermal management heat spreading solutions for microprocessor applications. This paper will illustrate the AlSiC material/design capabilities through microprocessor heat spreader examples.