Thermal Management Solutions
ThermalManagementSolutionsCreated to perform when the heat is on
ThermalManagementSolutions Silicone & Non-Silicone Pastes RTVs and Bonding Products Phase Change Materials Encapsulation Resins Silicone & Non-Silicone Gap Pads 0.9 to 5.5W/m.KDuring use, some electronic components can generatesignificant amounts of heat. Failure to effectively dissipatethis heat away from the component and the device can leadto reliability concerns and reduced operational lifetimes.Newton’s law of cooling states that the rate of lossof heat is proportional to the temperature differencebetween the body and its surroundings. Therefore,as the temperature of the component increases andreaches its equilibrium temperature, the rate of heat lossper second will equate to the heat produced per secondwithin the component. This temperature may be highenough to significantly shorten the life of the componentor even cause the device to fail. It is in such cases thatthermal management measures need to be taken.The same considerations can be applied to a completecircuit or device which incorporates heat producingindividual components.Heat is lost from a component to its surroundings atthe surface of the component. The rate of loss of heatwill increase with the surface area of the component;a small device producing 10 watts will reach a highertemperature than a similar powered device with a largersurface area.This is where heat sinks are used – varying in sizeand shape, heat sinks can be designed to offer asignificantly increased surface area to maximise heatdissipation. They are typically connected to componentswhich generate a large amount of thermal energy whenused and therefore dissipate such energy away from thedevice to avoid failure due to over-heating.2Heat sinks have proven to be very effective over theyears however in order to ensure full contact andtherefore maximum efficiency, thermal managementproducts are used alongside.Metal surfaces, even when polished to a fine degree,have a certain amount of roughness. It can thereforebe deduced that when two metal surfaces are placedtogether contact is not 100% and there will alwaysbe an air gap between the two surfaces. The use ofa thermal interface material (TIM) between such gapsensures complete contact between the two surfacesand in turn more efficient heat conductance.The ongoing trend for product miniaturisation – coupledwith more modern, higher powered devices – hasensured that efficient thermal management is anessential part of both modern and future electronicsdesign, the LED lighting market being just oneexample. Thermal management products are alsooffering solutions for greater efficiency in green energydevelopment; photovoltaic inverters – which are knownto be particularly sensitive to temperature; connectionsbetween the heat-pipe and water storage tank for solarheating applications; hydrogen fuel cells; wind powergenerators, are just a few examples.
ThermalPastesThermally conductive pastes consist of thermallyconductive fillers in a carrier fluid. Thermal pastes do notcure; therefore, they offer the best solution when rework isimportant and provide versatility by avoiding geometricalrestrictions affecting cure.Silicone and Silicone-FreeElectrolube offers silicone and non-silicone thermalpastes. The silicone products offer a higher uppertemperature limit of 200 C and a lower viscosity system,due to the silicone base oil used.The use of products based on, or containing, siliconemay not be authorised in certain applications. Thiscould be due to a number of factors, for instance certainelectronic applications or where problems exhibited incleaning or adhesive processes are observed.Such issues are due to the migration of low molecularweight siloxanes; these volatile species can lower thesurface tension of a substrate, making them extremelydifficult to clean or adhere to. In addition, the migrationof low molecular weight siloxanes can lead to failuresin electronic applications, through the formation ofinsulative byproducts.Electrolube products are formulated from raw materialsspecifically designed for the electronics industry.Thus, silicone containing products are only utilisedwhere the low molecular weight fractions are monitoredand kept to an absolute minimum. As an alternative,a range of non-silicone products are also provided forcritical applications.The ‘Plus’ RangeElectrolube’s ‘Plus’ range contains a specialist blendof fillers carefully designed to achieve an optimisedparticle size combination and therefore can achievehigher thermal conductivity values than the Electrolubestandard range.3
The ‘Xtra’ RangeElectrolube’s ‘Xtra’ range of thermal products areenhanced versions of the non-silicone products HTCand HTCP. These ‘X’ versions are manufacturedusing one of the company’s proprietary technologiesand possess the following benefits with almost nocompromise in usability and viscosity: an increase in thecomparative thermal conductivity, lower oil bleed andlower evaporation weight loss. HTCPX is mainly usedas a gap filler and has been approved by one of the topmanufacturers in the automotive industry.The following graph shows the effects of humidity (168hours, 25 C, 90% RH) and thermal cycling (25 cyclesbetween -25 C and 65 C) on HTC and HTCX.The results show that the rheology of HTC changes afterexposure to such conditions and as a result the viscosityalso increases with increasing shear rate, exhibitingdilatant behaviour.HTCX however shows greater stability under suchconditions with the rheology and viscosity remainingunchanged after the exposure. HTCX exhibitspseudoplastic behaviour; decreasing viscosity withincreasing shear rate.The ‘Xtra’ range of products are also more resistant tohumidity and thermal cycling (rapid changes in heatingand cooling) than the standard range.RHEOLOGY OF HTC AND HTCX BEFORE AND AFTER HUMIDITYAND THERMAL CYCLING TESTING500450400350250T(Pa)20015010050000.511.5D (1/s)HTC BEFORE4HTCX BEFOREHTC AFTERHTCX AFTER2
Phase-ChangeMaterialsPhase-Change MaterialPhase change materials have been designed to combinethe very low thermal resistance achieved using a thermalpaste, with the stability of a cured or solid material, suchas an RTV or gap pad. Their name is derived from theirproperties during use, changing state from a solid to aliquid and back again depending on the temperature ofthe application. Each phase change material will have its’own softening temperature, at which the change of stateoccurs. Once this temperature is reached, the ability ofthe phase change material to become softer allows theproduct to fully conform to the contours of the substrate,filling in the interface at a minimal bond line thickness.This in turn, results in very low thermal resistance andmaximise the efficiency of heat transfer.ProductBulk Thermal Conductivity(W/m K)Thermal Resistance( C in2 /W)TPM3503.500.026TPM5505.500.012Normalised Thermal ResistancePhase change materials can be applied in a numberof ways; the most convenient being a screen printingtechnique. In this application method, a phase changematerial containing a small amount of solvent is spreadacross a screen to deposit the desired thickness ofmaterial to the substrate. The solvent quickly evaporatesleaving a firm paste behind at the interface. As thetemperature increases, the material absorbs heat untilit reaches its softening point and upon cooling revertsback to a firm paste again. Due to the stability ofphase change materials during frequent temperaturechanges, the materials are resistant to problems suchas pump-out, commonly seen with non-curing thermalmanagement materials.The stability of Electrolube’s phase change product,TPM350, during thermal cycling is shown in the graphbelow. This test was conducted on a Thermal TestVehicle (TTV) using a Power Cycle Test, delivering achange in temperature from room temperature to 95 C.Each cycle includes 12 min power heating and 8mincooling. A total of 1000 cycles were conducted andresults showed good stability of the TPM350 throughoutthe duration of this test.TPM Thermal Reliability Result By TTV Power Cycle TestCycles5
GapPadsThermal gap pads are used in place of traditionalthermal interface materials (TIMs) such as a thermalpaste or RTV. The main benefit of gap pads is that theyoffer a quick and easy application method, requiringminimal training for the operator and without the messsometimes associated with a paste, grease or bondingproduct. In addition, they do not require the use ofexpensive dispensing machines and can easily beapplied via a manual process.Gap pads are often cut to size to fit the requirements ofthe specific interface application. They work in a similarmanner to other TIMs, filling the small gaps and pocketsbetween the two surfaces. As they cannot be appliedin such a thin film as a thermal paste for example, theyoften provide a much thicker interface; pads thus workbest for applications where there is a pressure exertedon the interface, minimising the bond line and ensuringProductSimilar to thermal pastes, Electrolube’s gap pads areavailable in both silicone and non-silicone options,offering a range of performance requirements andmeeting the demand for high temperature applications.Despite not meeting the same levels of efficiency oninitial application, a gap pad may outperform a thermalpaste under certain conditions. As the gap pad is aformed material, it does not move during thermal cyclingand therefore does not experience the same pump-outissues that can be seen with some thermal pastes inrapidly changing thermal environments.Bulk Thermal Conductivity(W/m K)Thermal Resistance( C in2 /W)GP3003.000.990GP5005.000.700In some applications, thermal dissipation is requiredto remove air gaps much larger than those found ina typical TIM application. Thermal pastes, such asHTSX for example, are not designed to be applied athigh thicknesses. When gaps are in excess of a fewhundred microns, it is advised to switch to a stablegap filling material. The most common air gaps to fillcan be between a component and its metal housing,where it is imperative that a non-electrically conductivematerial is used. Non-curing options include the highviscosity HTCPX paste, proven to be stable duringtypical automotive thermal and vibrational cycling.6maximum contact with the gap pad. The pressureforces the pad material into the air pockets, moreeffectively reducing the thermal resistance. The thermalresistance achieved will not match that of a thermalpaste however.Curing options include two-part systems, such asElectrolube gap filling ‘GF’ range, graded dependentupon their thermal conductivity values. These productsare designed to fill gaps in a vast array of applications,including heat dissipation within electric vehiclebatteries.
Adhesives &EncapsulantsAdhesives and RTVsElectrolube offer a thermal bonding adhesive calledTBS, as well as two RTV (room temperature vulcanising)products: TCOR and TCER.TBS (Thermal Bonding System) is a two-part, highstrength epoxy adhesive designed to bond a heat sinkto the component. In addition to the mineral fillers,the adhesive contains small glass beads of controlleddiameter: these allow for a set thickness of 200 micronsto be achieved, providing optimal performance.TCOR and TCER are Electrolube’s silicone RTVproducts. TCOR is an oxime-cure RTV, and TCER is anethanol-cure version. TCER has the advantage that it isvery low in viscosity and higher in thermal conductivitycompared to TCOR; however, TCOR exhibits improvedbond-strength properties.Encapsulation ResinsFor certain types of heat generating circuitry, it maybe beneficial to encapsulate the device in a heatsink enclosure using a thermally conductive pottingcompound. This method offers both heat dissipationand protection from the surrounding environment,such as high humidity or corrosive conditions.ER2183 is a lower viscosity version of ER2220(5000 mPa s). The reduced filler content required toachieve this viscosity has little effect on the thermalconductivity performance: ER2183 is 67% lower inviscosity, but only exhibits a 28% decrease in thermalconductivity as a result (1.10 W/m.K).Electrolube produces a variety of two-partencapsulation solutions utilising epoxy, polyurethaneand silicone technologies:UR5633 is a polyurethane encapsulation resin thatoffers very good thermal conductivity of 1.24 W/m.K.This is ideal for applications where thermal conductivityand a degree of flexibility are required.ER2220 provides the highest level of thermalconductivity combined with environmental protectionafforded from the encapsulation process. Thishighly-filled epoxy resin possesses very high thermalconductivity (1.54 W/m.K), resulting in a high viscosity(15,000 mPa s).SC4003 is a silicone encapsulation resin, offeringa good level of thermal conductivity (0.70 W/m.K)over an exceptionally wide temperature range (-60 to 200 C). The product is thixotropic, making it ideal forapplications where the resin should not flow throughsmall gaps.7
ApplicationOptionsThermal PastesAs highlighted previously and with the exception of gapfilling products, it is important that thermal interfacematerials (TIM) are applied in the thinnest layer possibleto reduce the effects of thermal resistance. Therefore,the application of thermal pastes can be as important asthe product selection stage.Thermal pastes can be applied via a range of methods,either manual or automated.RTVsElectrolube RTVs are supplied in ready-to-usecartridges and should be used with the TCR Gunapplicator. Please contact Electrolube regardingbulk quantities.These materials are often used for combined thermaltransfer and fixing, therefore a thin layer should beapplied and tests conducted to ensure the level ofbonding achieved is sufficient for the application.i. M anual applications can be carried out using a roller,squeegee or spatula; often a roller is the best methodto ensure a thin even film is deposited across theentire surface.ii. Automated applications involve the use of specialistequipment. This usually consists of an applicatorhead where the material is fed to the applicator viadispensing equipment. Due to the viscosities ofthese materials, the dispensing equipment is usuallya follower-plate system which connects to thethermal paste container as supplied. Please contactElectrolube where container dimensions are required.As these are moisture cure products, ambient humiditymust be considered during application. Extremeconditions (very dry or very wet) will inhibit the cure andelevated temperatures will not speed up the process,unless humidity is also increased.Encapsulation ResinsEncapsulation resins are two part systems which canbe applied manually or through automated equipment.In all cases, the mixing procedure used should avoidthe introduction of air; the introduction of air or moisturecan affect the cure process of these materials as wellas leave air voids in the cured product, which willsignificantly reduce the thermal conductivity.i. Electrolube supply encapsulation resins in resinpack form; a pouch divided by a clip and rail whichseparates the Part A and B until the time of mixing.These packs are ideal for air-free mixing and areadvised for all manual application of encapsulationresins. When supplied in an aluminium outer,this outer material should not be removed untilimmediately before use.ii. Automated mixing and dispensing machines arealso available either in benchtop or large scalemodels. Electrolube work with a number of localand international equipment manufacturers, pleasecontact us for further information.8
TypicalPropertiesThermal ConductivityThermal conductivity, measured in W/m.K, representsa materials’ ability to conduct heat. Bulk thermalconductivity values give a good indication of the levelof heat transfer expected, allowing for comparisonbetween different materials. Some techniques onlymeasure the sum of the materials’ thermal resistanceand the material/instrument contact resistance.Electrolube utilise a Modified Transient Plane Source(MTPS) method amongst others, providing accuratecomparisons of bulk thermal conductivity. The followinggraph shows the comparative thermal conductivities ofElectrolube’s thermal .00.51.01.52.02.53.03.54.04.55.05.56.0THERMAL CONDUCTIVITY (W/m.K)BULK THERMAL CONDUCTIVITY (W/m.K)NOTE: Thermal Conductivity of air 0.024 W/m.K9
Thermal ConductivityRelying on bulk thermal conductivity values alone willnot necessarily result in the most efficientheat transfer, however.Thermal resistance, measured in K cm2/W, is thereciprocal of thermal conductivity. It takes into accountthe interfacial thickness and although it is dependenton the contact surfaces and pressures applied, somegeneral rules can be followed to ensure thermalresistance values are kept to a minimum and thusmaximising the efficiency of heat transfer.As discussed, a thermal interface material (TIM)would be used between a heat generating device andits associated heat sink. As the heat sink will havea significantly higher thermal conductivity than theinterface material, it is important that only a thin layerof the interface material is used; increasing thicknesswill only increase the thermal resistance in this case.Therefore, lower interfacial thicknesses and higherthermal conductivities give the greatest improvementin heat transfer. In some cases, however, utilising amaterial with a higher bulk thermal conductivity couldbe to the detriment of contact resistance and thus, noimprovement will be accomplished.10An example of this difference can be drawn from thecomparison of thermal pastes and thermal pads.Thermal gap pads are solid, polymerised materials of afixed thickness which are available in a variety of thermalconductivities. Initially a thermal paste can be appliedat a very low bond line thickness, ie. 100 microns, asthey are non-curing compounds and as a result, theirviscosity can alter slightly as the temperature increases.This allows for a further reduction in interfacialresistance. In the case of thermal pads, high pressuresare needed to achieve an adequate interface, thus, apaste and pad of similar bulk thermal conductivity mayhave very different thermal resistance measurements inuse, and as such a difference in the efficiency of heattransfer will be observed.Users must address bulk thermal conductivity values,contact resistance and application thicknesses andprocesses in order to successfully achieve the optimumin heat transfer efficiency.
Temperature RangeElectrolube’s thermal management products cover anextensive operating temperature range. It is importantthat the temperature extremes experienced duringapplication fall within the operating temperature rangeof the product selected.Depending on the type of product and chemistrychosen, the temperature range will differ. Someproducts may be suitable for short-term excursionsoutside of the recommended operating temperatureranges. Testing in representative end-use conditionsis always PHTSHTCPXHTCPHTCXHTC-70-203080130180230OPERATING TEMPERATURE RANGE ( C)11
Dielectric StrengthThermal management products are used withinelectrical applications and therefore must not have anydetrimental effect on the performance of the device.Measurements of the electrical properties of suchproducts can assist in proving suitability for use.For example, the dielectric strength is the maximumelectric field strength that a product can withstandintrinsically without breaking down, i.e. withoutexperiencing a failure of its electrical properties.This is sometimes also referred to as the dielectricwithstanding voltage. Conversely, the breakdownvoltage is the minimum voltage that causes a portionof an insulator to become electrically HTSPHTSHTCPXHTCPHTCX
manufacturers in the automotive industry. The ‘Xtra’ range of products are also more resistant to humidity and thermal cycling (rapid changes in heating and cooling) than the standard range. The following graph shows the effects of humidity (168 hours, 25 C, 90% RH) and thermal cycling (25 cycles between -25 C and 65 C) on HTC and HTCX. The results show that the rheology of HTC changes .
Energies 2018, 11, 1879 3 of 14 R3 Thermal resistance of the air space between a panel and the roof surface. R4 Thermal resistance of roof material (tiles or metal sheet). R5 Thermal resistance of the air gap between the roof material and a sarking sheet. R6 Thermal resistance of a gabled roof space. R7 Thermal resistance of the insulation above the ceiling. R8 Thermal resistance of ceiling .
Thermal Control System for High Watt Density - Low thermal resistance is needed to minimize temperature rise in die-level testing Rapid Setting Temperature Change - High response thermal control for high power die - Reducing die-level test time Thermal Model for New Thermal Control System - Predict thermal performance for variety die conditions
thermal models is presented for electronic parts. The thermal model of an electronic part is extracted from its detailed geometry configuration and material properties, so multiple thermal models can form a thermal network for complex steady-state and transient analyses of a system design. The extracted thermal model has the following .
Thermal Transfer Overprinting is a printing process that applies a code to a flexible film or label by using a thermal printhead and a thermal ribbon. TTO uses a thermal printhead and thermal transfer ribbon. The printhead comprises a ceramic coating, covering a row of thermal pixels at a resolution of 12 printing dots per mm
Transient Thermal Measurements and thermal equivalent circuit models Title_continued 2 Thermal equivalent circuit models 2.1 ntroduction The thermal behavior of semiconductor components can be described using various equivalent circuit models: Figure 6 Continued-fraction circuit, also known as Cauer model, T-model or ladder network
The electrical energy is transformed into thermal energy by the heat sources. The thermal energy has to meet the demand from the downstream air-conditioning system. Thermal en-ergy storage systems can store thermal energy for a while. In other words the storages can delay the timing of thermal energy usage from electricity energy usage. Fig. 1 .
using the words kinetic energy, thermal energy, and temperature. Use the space below to write your description. 5. Brainstorm with your group 3 more examples of thermal energy transfer that you see in everyday life. Describe where the thermal energy starts, where the thermal energy goes, and the results of the thermal energy transfer.
changes to thermal energy. Thermal energy causes the lamp's bulb to become warm to the touch. Using Thermal Energy All forms of energy can be changed into thermal energy. Recall that thermal energy is the energy due to the motion of particles that make up an object. People often use thermal energy to provide warmth or cook food. An electric space
