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Topic: Thermal resistance


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In the News (Sat 1 Nov 14)

  
 SQUARE ONE : Thermal Resistance   (Site not responding. Last check: 2007-10-18)
The value of the thermal resistance of a piece of material can be thought of as the temperature difference across it required to produce one unit of heat flow per unit area.
Resistance on the other hand is an object property and depends on both the resistivity of the material and its overall thickness within that particular object.
Resistance is usually given as an "R" value which is the resistance of one square metre of the material subject to a one degree temperature difference.
www.squ1.com /thermal/resistance.html   (1384 words)

  
 Thermal Resistance
Thermal resistance is the opposition to flow of heat energy.
The thermal resistance of a plate of glass is 0.006 F°/(BTU/hr).
Using the table of thermal conductivity (Table II-1), find the thermal resistance of a 36" x 40" windowpane which is 0.125 in thick.
webpages.charter.net /griche/pt/u4s4prb.htm   (961 words)

  
 Electronics Cooling thermal interface materials   (Site not responding. Last check: 2007-10-18)
Thus, the thermal resistance of the joint is directly proportional to the joint thickness and inversely proportional to the thermal conductivity of the medium making up the joint and to the size of the heat transfer area.
Thermal resistance is minimized by making the joint as thin as possible, increasing joint thermal conductivity by eliminating interstitial air and making certain that both surfaces are in intimate contact.
Thermally conductive compounds are an improvement on thermal grease as these compounds are converted to a cured rubber film after application at the thermal interface.
www.electronics-cooling.com /Resources/EC_Articles/SEP96/sep96_01.htm   (1625 words)

  
 Ecliptek Tech Talk - Oscillator Thermal Resistance FAQ   (Site not responding. Last check: 2007-10-18)
The thermal resistance of an oscillator package is defined as the temperature difference that occurs between the semiconductor element within the package and the package's surface or ambient atmosphere when the device consumes 1 watt [W] of power.
Thermal resistance is an indication of the heat transfer from the semiconductor device through all of the package materials out to the open environment.
is defined as the thermal resistance from the semiconductor junction to the case of the oscillator (junction-to-case).
www.ecliptek.com /tech/faq_xothermal.html   (1171 words)

  
 Encyclopedia: Thermal resistance   (Site not responding. Last check: 2007-10-18)
The SI units of thermal resistance are: The International System of Units (abbreviated SI from the French phrase, Système International dUnités) is the most widely used system of units.
In physics, thermal conductivity, λ, is the quantity of heat transmitted, due to unit temperature gradient, in unit time under steady conditions in a direction normal to a surface of unit area, when the heat transfer is dependent only on the temperature gradient thermal conductivity = heat flow rate / (distance × temperature...
The R-value is a non-SI measure of thermal resistance used in housing insulation.
www.nationmaster.com /encyclopedia/Thermal-resistance   (1032 words)

  
 Thermal resistance -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-10-18)
The (A tetravalent nonmetallic element; next to oxygen it is the most abundant element in the earth's crust; occurs in clay and feldspar and granite and quartz and sand; used as a semiconductor in transistors) SI units of thermal resistance are:
where is the thermal resistance of the bond between the transistor's case and the metalwork.
We use the general principle that the temperature drop across a given thermal resistance with a given heat flow through it is:
www.absoluteastronomy.com /encyclopedia/t/th/thermal_resistance.htm   (620 words)

  
 ipedia.com: Thermal conductivity Article   (Site not responding. Last check: 2007-10-18)
The thermal conductivity of a material is equivalent to the quantity of heat that passes in unit time through unit area of a plate, when its opposite faces are subject to unit temperature gradient (e.g.
Since diamond has such a high thermal conductivity, natural blue diamond much higher still, one may test gems to determine if they are genuine diamonds using a thermal conductance tester, one of the instruments of gemology.
For general scientific use [2]class="external" target="_blank">[1, thermal conductance is the quantity of heat that passes in unit time through a plate of particular area and thickness when its opposite faces differ in temperature by one degree.
www.ipedia.com /thermal_conductivity.html   (557 words)

  
 thermal resistance: an oxymoron? - Article2.htm May, 1997   (Site not responding. Last check: 2007-10-18)
In practical circumstances, this resistance cannot be an invariant quantity designated by one number, because the orientation of internal conduction heat flow paths changes in response to changes in the thermal environment.
However, in doing so, the resulting 'thermal resistances' lose their physical meaning completely, as argued in Ref. 4, and one may wonder if the term 'thermal resistance' should be kept, on account of the persistence of the analogy in the minds of most scientists and designers for some time to come.
In all cases, a thermal resistance can be defined, but in many practical cases, the physical significance of the definition is meaningless, with the exception of those definitions which incorporate the ultimate heat sink (an ambient at uniform temperature) as one of the nodes.
www.electronics-cooling.com /Resources/EC_Articles/MAY97/article2.htm   (1537 words)

  
 ESP - Heatsink design and transistor mounting
Terms such as 'thermal resistance' and 'degrees C / Watt' are a little daunting for the uninitiated, and the purpose of this article is to explain how thermal transfer works, from the transistor die until it is finally dispersed into the atmosphere.
Towards this end, an electrical analogue may be drawn, showing the thermal generator as a current source, thermal resistance as a resistor and the thermal inertia (or transient capacity) of the various materials as a capacitor.
Although the thermal resistances for each of the transistors remain the same, the resultant thermal resistances for a "parallel pair" are effectively halved.
sound.westhost.com /heatsinks.htm   (10976 words)

  
 Patents-Reducing The Thermal Resistance of CSPs and Flip-Chip ICs
The thermal resistance is obtained by taking the reciprocal of the sum of the kA factors where A is the cross-sectional area for each layer in the thermal path and k is the thermal conductivity of the material.
Because the intrinsic thermal resistance in the CPGA example is so poor, the external resistance of the heat sink to the ambient does not materially change the intrinsic thermal resistance.
Thermal resistance can be reduced by increasing the thermal conductivity of the various materials involved and/or by increasing the cross-sectional area.
www.chipscalereview.com /issues/1198/departmenti1.htm   (1042 words)

  
 High thermal resistance bonding material and semiconductor structures using same - Patent 4888634   (Site not responding. Last check: 2007-10-18)
A high thermal resistance bonding material for semiconductor chips includes a binder such as epoxy or polyimide and high thermal resistance material dispersed therein such as glass micropheres, glass beads, ceramic microspheres and ceramic beads.
High thermal resistance material such as glass and ceramic beads and microspheres of a generally uniform size are added to the binder.
The glass microspheres increase the thermal resistance of the adhesive, and the uniform distribution of the glass microspheres facilitates uniform thermal resistance between the semiconductor chip 10 and the substrate 12.
www.freepatentsonline.com /4888634.html   (1065 words)

  
 IngentaConnect Thermal resistance technique for measuring the thermal conductivi...   (Site not responding. Last check: 2007-10-18)
The thermal resistance technique for measurement of the thermal conductivity of microporous thin membranes is described.
A dependence of the thermal resistance on the thickness of the samples was observed.
The thermal conductivity of the membrane was deduced from a linear fit of the thermal resistance versus the number of membranes.
api.ingentaconnect.com /content/iop/jphysd/2004/00000037/00000021/art00011   (270 words)

  
 Low thermal resistance bearing assembly for x-ray device - US Patent 6693990   (Site not responding. Last check: 2007-10-18)
In particular, because thermal expansion is at least partially a function of temperature, the relatively greater temperature at the front bearing results in a relatively greater expansion of the front bearing, considered with respect to the expansion of the rear bearing.
A thermal expansion differential between the front and rear bearings, can cause unbalanced, or otherwise improper, rotation and operation of the shaft which is supported by the bearings.
Further, the extended surfaces permit a relative reduction in the thermal gradient along the length of the shaft, thereby contributing to improved heat distribution through the shaft, and reducing the operating temperatures in the front bearing.
www.patentstorm.us /patents/6693990.html   (9528 words)

  
 [No title]
Another is to compare the thermal resistance of pentane-blown PIR laminate boards aged in a laboratory environment since early 1998 to those obtained from the mathematical modeling and calculation algorithms developed by Huntsman Polyurethanes.
Another is to compare the thermal resistance of pentane blown PIR laminate boards aged in an uncontrolled ambient laboratory environment since early 1998 to those obtained from the mathematical modeling and calculation algorithms developed by Huntsman Polyurethanes.
Thermal Resistance Measurements and Foam Aging The foam thermal resistance was measured according to ASTM C518 with a mean plate temperature of 75oF and temperature difference of 40oF.
www.huntsman.com /pu/Media/singh_ntiru_dedecker_api_paper_2002.doc   (4831 words)

  
 Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride   (Site not responding. Last check: 2007-10-18)
Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride
Thermal-shock resistance of a ceramic comprising 60 percent boron carbide and 40 percent titanium diboride was investigated.
The material has thermal shock resistance comparable to that of NBS body 4811C and that of zirconia, but is inferior to beryllia, alumina, and titanium-carbide ceramals.
naca.larc.nasa.gov /reports/1953/naca-rm-e52l31   (100 words)

  
 Low resistance thermal   (Site not responding. Last check: 2007-10-18)
AOS Thermal Compounds is a leading innovator of dry-to-the touch thermal grease pads, that offer low thermal resistance without the mess of thermal grease.
Resistance is a linear function of temperature, affecting IR drop.
The thermal resistance RTH of the heat sink is known,...
www.vanforcar.com /low-resistance-thermal.html   (878 words)

  
 An Evaluation of the ThermoChill Radiators   (Site not responding. Last check: 2007-10-18)
For low air flow rates, the thermal resistance of the air side is much more important than the fluid side (except for low fluid flow rates).
Increasing the fluid flow rate leads to an improvement for the convection heat transfer, thus a lower thermal resistance, of the fluid side but this is negligible as compared to the air side thermal resistance.
Since the air flow resistance of the HE 120 series is the same per unit area, at the same backpressure the air flow volume of the HE 120.1 would be half of the HE 120.2, while the HE120.3 would be 50% more than the HE 120.2.
thermal-management-testing.com /ThermoChill.htm   (2141 words)

  
 2003_February_calccorner   (Site not responding. Last check: 2007-10-18)
Using these equations it is possible to estimate heat sink thermal performance in terms of the thermal resistance from the temperature at the base of the fins to the temperature of the air entering the fin passages.
For purposes of illustration these equations were used to estimate heat sink thermal resistance for a 50 x 50 mm aluminum heat sink.
Effect of fin height and number of fins on heat sink thermal resistance at an air velocity of 2.5 m/s (492 fpm).
www.electronics-cooling.com /html/2003_february_calccorner.html   (851 words)

  
 Thermal resistance form pads to inner layers of a PCB   (Site not responding. Last check: 2007-10-18)
Thermal resistance form pads to inner layers of a PCB
Online calculator for the thermal resistance between pads and the first inner layer of a PCB.
There thermal resistance for the pads are calculated with the 45-deg rule.
www.frigprim.com /online/pad_ground.html   (148 words)

  
 Soldering method capable of providing a joint of reduced thermal resistance - Patent 4927069
The soldering method of claim 13 wherein the heating apparatus has an entrance end and an exit end, and wherein the first and second push members are both disposed intermediate the entrance end and exit end of the heating apparatus for allowing the solder paste layers to re-increase their thickness before being allowed to solidify.
The thermal resistance of a soldered joint is known to decrease approximately in proportion with its thickness or with the amount of gas bubbles that are generated by the flux in use with the solder and entrapped in the joint.
Although there was a corresponding increase in thermal resistance, all such increase could be compensated for by the decrease in the total area of the remaining gas bubbles.
freepatentsonline.com /4927069.html   (4746 words)

  
 Satellite, Thermal Design for the MAX2116 and MAX2118 - Maxim/Dallas
Maximum ambient temperature is found to be 105°C. The thermal resistance from case to ambient is 66.3°C/Watt.
ja is a measure of the resistance to heat flow from chip to the surrounding air.
Apply thermal grease to the resistor and pad so the heat flow is directed to the pad.
www.maxim-ic.com /appnotes.cfm/appnote_number/1758   (1107 words)

  
 IngentaConnect Estimating thermal resistance of the bedding assembly from thickn...   (Site not responding. Last check: 2007-10-18)
IngentaConnect Estimating thermal resistance of the bedding assembly from thickn...
Thermal resistance was measured using a guarded-hotplate similar to that specified in ISO 11092:1993(E).
While it was possible to predict thickness and thermal resistance of flat bedding from estimated values, extrapolation to bedding during simulated use was considered inappropriate, with significant differences of over 1,000 per cent.
api.ingentaconnect.com /content/mcb/058/1999/00000011/00000005/art00002   (225 words)

  
 The whole picture | February 2002 | Professional Roofing Magazine
Although based on the same thin-slicing and accelerated-aging concept as ASTM C1303, this method accounts for the effect of permeable facings, or skins, on the long-term thermal resistance of foam insulation in addition to a number of other factors.
Before measuring the thermal performance of a closed-cell foam product, a manufacturer was directed to condition the product for 180 days at 75 F (24 C).
For at least 35 years, the long-term thermal resistance of polyisocyanurate rigid foam insulation has been studied and debated.
www.professionalroofing.net /past/feb02/polyisofeature.asp   (1073 words)

  
 Thermal resistance probes - DirectIndustry.com   (Site not responding. Last check: 2007-10-18)
COOLSCAN 20 is a unique 2-dimension scan thermal imager with exceptionally large field of view (70°x180°).
The extended temperature measurement range (200°C to 1600°C) makes it suitable for various industries such as cement where it is used for controlling air flows of grate clinker coolers.
This broader spectral response is particularly important for applications requiring excellent sensitivity at infrared wavelengths to 2500 nm, such as the water absorption band at 1.95 micron.
www.directindustry.com /find/thermal-resistance-probes.html   (980 words)

  
 Directed Evolution of beta -Glucosidase A from Paenibacillus polymyxa to Thermal Resistance -- González-Blasco ...
Protein thermal resistance is an important issue beyond its obvious industrial interest, because the understanding of the
gene caused a remarkable increase in the thermal resistance of
Increased Thermal Resistance and Modification of the Catalytic Properties of a beta -Glucosidase by Random Mutagenesis and in Vitro Recombination
www.jbc.org /cgi/content/full/275/18/13708   (3199 words)

  
 Water sensor - dynamic thermal resistance sensor   (Site not responding. Last check: 2007-10-18)
After some time the power is turned off and the NTC resistor is used to measure the temperature and more importantly the negative slope of the temperature when the power is off.
A high slope indicates that water is present to cool off the NTC through the thermal resistance of the NTC/steel connection, the steel itself and finally the water.
Thats all fine because a sensor like this may not be as sensitive as the capacitive one because the impedance levels are lower and in case of water that penetrates the enclosure the effect of the volume conductivity will be minimal.
www.cabling-design.com /forums/Water-sensor--dynamic-thermal-resistance-sensor-article96695-46.htm   (1061 words)

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