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Thermal Solution using Nanowires Disclosure Number: IPCOM000033152D
Original Publication Date: 2004-Nov-30
Included in the Prior Art Database: 2004-Nov-30
Document File: 2 page(s) / 46K

Publishing Venue



A method is disclosed using nanowires to efficiently transfer heat from a component at higher temperature to a component at lower temperature. The approach demonstrates a thermal solution for future processors and ICs.

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Thermal Solution using Nanowires

With improving processor performance the power density on the chip is rising dramatically thus increasing the requirement to efficiently remove the heat from the chip. Using the current chip package the thermal power generated by future processors will not be removed sufficiently leading to a temperature rise on the chip which is not tolerable and would destroy the chip. Therefore new thermal solutions with increased total thermal conductance are required.

The typical power density of today's processors during operation is in the range of 40 W/cm2 and 140 W/cm2 at the hot spot leading to an operation temperature of about 85 degree Celsius and 105 degree Celsius, respectively. Driving the chip at higher operation temperature would lead to degraded reliability and reduced transistor performance. Excessive leakage current would increase the power density even further.

In the package currently used the Si chip is connected to the copper thermal hat by a high viscosity thermal paste. The thermal paste is compensating for the different thermal expansion of the thermal hat (Cu) and the processor (Si). The typical thickness of the paste material used is in the range of 10 micrometer resulting in a thermal resistance of less than 5 W/(K m).

During thermal cycling, the components (thermal hat and Si processor) show different thermal expansion and the paste-filled gap expands and contracts. The lateral expansion during power on/off cycling is in the range of 12 micrometer. One disadvantage in today's package is that this leads to paste pumping and air intrusion into the gap therefore deteriorating the thermal contact between thermal hat and chip. One possible approach to increase the thermal heat transfer from the Si chip to the thermal hat is to reduce the thermal resistance of the paste layer by reducing its thickness. However, with decreasing thickness of the paste layer the paste pumping becomes worse. A direct connection between chip and thermal hat by soldering would give a much better thermal contact but is due to the different thermal expansion coefficients so far not possible.

The approach presented addresses the problem of connecting two components comprising materials with different thermal expansion. Disclosed is an approach in which nanowires (NWs) are used to significantly improve the heat removal from one component at higher temperature to a second component at lower temperature which might be a heat sink or might be connected to a heat s...