Heat sink thermal resistance

TABLE 10.2 Case to Heat Sink Thermal Resistance, Scs. for Various Packages... 

Thermal Conductivity. The value of 2000 W/(m-K) at room temperature for Type Ila natural stones is about five times that of Cu, and recent data on 99.9% isotopicaHy pure Type Ila synthesized crystals ate in the range of 3300—3500 W/(m-K) (35). This property combined with the high electrical resistance makes diamond an attractive material for heat sinks for electronic devices. 

Heat flows from a heat source at temperature 6 t) through a wall having ideal thermal resistance Ri to a heat sink at temperature 62(1) having ideal thermal capacitance Ct as shown in Figure 2.14. Find the differential equation relating 6 t) and 02(0-... 

It was demonstrated that for a fixed pumping power, the overall thermal resistance for a two-layered micro-channel stack is 30% less than for a one-layered micro-channel due to doubling of the heat transfer area. Methods for optimizing the thermal performance of micro-channel heat sinks were discussed by Kim (2004). 

Such a program should be used in small signal circuits where the values of the components are constant. For this reason, we supplied a very small test energy AE in order to produce very small change AT and considered the thermal resistance and heat capacities constant in the calculations for each heat sink temperature. 

Let us remember that the bolometer noise consists of two contributions [82] the phonon noise caused by fluctuations in the transfer of thermal energy between the bolometer and the heat sink and the Johnson noise due to the thermistor resistance. 

Other approaches for measuring thermal resistance or conductivity of fibers and fabrics include the use of calorimetry (28), thermal flow through a heat sink of known emissivity (2 ), immersion of fibers or fabrics in liquids of known thermal conductivity (30), and measurement of the rate of cooling of textiles or insulating materials by a Cenco-Fitch apparatus (2). 

Combined natural convection and radiation thermal resistance of various heat sinks used in the cooling of electronic devices between the beat sink and the surroundings. All fins are made of aluminum 6063T-5, are black anodized, and are 76 mm (3 in) long. ... 

Specially dc.signcd finned surfaces called heat sinks, which are commonly used in the cooling of electronic equipment, involve one-of-a-kind complex geometries, as shown in Tabic 3-6. The heat transfer performance of heat sinks is usually expressed in terms of their thermal resistances R in CAV, wliich is defined as... 

A small value of thermal resistance indicates a small temperature drop across the heat sink, and thus a high fin efficiency. 

Discussion This transistor can be used at higher power levels by attaching it to a heat sink (which lowers the thermal resistance by increasing the heat transfer surface area, as discussed in the next example) or by using a fan (vrhich lowers the thermal resistance by increasing the convection heal transfer coefficient). 

Analysis The rate of heat transfer from a 60-W transistor at full power is Q = 60 W. The thermal resistance between the transistor attached to the heat sink and the ambient air for the specified temperature difference is determined to be... 

Therefore, the thermal resistance of the heat sink should he below 1.0°C/W. An examination of Table 3-6 reveals that the HS 5030, whose thermal resistance is 0.9°C/W in the vertical position, is the only heat sink that will fneet this requirement. 

Choquette et al. [10] performed analyses to obtain momentum and thermal characteristics in microchannel heat sinks. A computer code was developed to evaluate the performance capabilities, power requirements, efficiencies of heat sinks, and for heat sink optimization. Significant reductions in the total thermal resistance were found not to be achieved by designing for turbulent flows, mainly due to the significantly higher pumping power requirements realized, which offset the slight increase in the thermal performance. 

In the absence of any electrical input, it is clear that the temperature of the sample cavity will decrease until the total heat flux, qa, from the room to the sample cavity is balanced by heat flow, qs, from the cavity to the liquid nitrogen. The vast majority of this latter flux is carried by the thermal shunt and the heat sink. To a good approximation the thermal resistance of the heat sink is negligible compared to the shunt. If we lump the effective thermal conductance of the... 

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