KR101116506B1 - Organic matrices containing nanomaterials to enhance bulk thermal conductivity - Google Patents

Abstract

The present invention relates to thermal interface compositions containing nanoparticles blended with a polymer matrix. Such compositions not only reduce the thermal interface resistance present between the thermal interface material and the corresponding mating surface, but also increase the bulk thermal conductivity of the polymeric composite. Formulations containing nanoparticles also show less phase separation of micron-sized particles compared to formulations without nanoparticles. In a particular embodiment, the thermal interface composition 2 is located between the heat generating element 3 and the heat sink.

Description

Organic matrix containing nanomaterials to improve bulk thermal conductivity {ORGANIC MATRICES CONTAINING NANOMATERIALS TO ENHANCE BULK THERMAL CONDUCTIVITY}

The present invention relates to the use of nanoparticles to increase the thermal conductivity of a polymer matrix.

Many electrical components generate heat during their operation. If this heat is not removed from the electrical component in an efficient manner, it will accumulate. This can lead to failure or permanent damage to the electrical components. Thus, thermal management techniques that promote heat removal during operation are often implemented in electrical circuits and systems.

Heat management techniques often involve the use of some form of heat sink to conduct heat from the high temperature region of the electrical system. A heat sink is a structure formed of a high thermally conductive material (eg, typically metal) that is mechanically coupled with an electrical component to aid in heat removal. In a relatively simple form, the heat sink may comprise a piece of metal (eg aluminum or copper) that contacts the electrical circuit during operation. Heat from the electrical circuits flows into the heat sink through the mechanical interface between the units.

In a typical electrical component, the flat surface of the heat sink is placed on the flat surface of the electrical component and mechanically couples the heat sink to the heat generating element during operation by holding the heat sink in place with some form of adhesive or fastener. . As can be seen, the surface of the heat sink and the surface of the element are rarely perfectly planar or smooth so that an air gap will generally be present between the surfaces. As is generally well known, the presence of an air gap between two opposing surfaces reduces the ability of heat to pass through the interface between the surfaces. Thus, these air gaps reduce the efficiency and value of the heat sink as a heat management device. To solve this problem, polymer compositions have been developed for placement between heat transfer surfaces to reduce the thermal resistance present between them. The bulk thermal conductivity of current thermal interface materials is greatly limited by the low thermal conductivity of the polymer matrix (about 0.2 W / m? K for thermal interface materials or polymers typically found in TIMs). According to some evaluations ("Thermally Conductive Polymer Compositions", DM Bigg., Polymer Composites, June 1986, Vol. 7, No. 3), the maximum bulk thermal conductivity achievable by electrically insulating polymer composites is only 20% of the base polymer matrix. To 30 times. This figure rarely changes, regardless of the type of filler, once the filler's thermal conductivity exceeds 100 times the base polymer matrix. In conclusion, the thermal conductivity of the polymeric material is low compared to the thermal conductivity of the heat sink, making the heat transfer from the heat producing element to the heat sink inefficient. In addition, the effective heat transfer capacity is inter-interface due to 1) micro or nano voids and 2) filler-free layers caused by the inability to penetrate micron-sized fillers into filler irregularities or surface irregularities smaller than filler size. Further reduced by imperfection.

Accordingly, there is a need for improved compositions for effectively transferring heat between heat sinks and heat producing elements.

Summary of the Invention

The thermal interface composition according to the present invention contains nanoparticles functionalized by one or more organic-functional groups blended into the organic matrix. In certain embodiments, the thermal interface composition also includes filler particles of micron size.

Also disclosed herein is an electrical component comprising a heat sink or heat spread and heat generating element in contact with a thermal interface composition containing organic-functionalized nanoparticles blended with an organic matrix, respectively.

The method of increasing the heat transfer efficiency according to the present invention comprises inserting a thermal interface composition containing organic-functionalized nanoparticles blended with an organic matrix between a heat generating element and a heat sink or heat spread.

1 is a representative schematic diagram of an electrical component according to the present invention.

The present invention provides a thermal interface composition containing functionalized nanoparticles blended with an organic matrix. Nanoparticles can be covalently bonded to the matrix, or dispersed through the matrix through non-covalent forces. In accordance with the present invention the matrix containing nanoparticles will have a higher thermal conductivity than the matrix without nanoparticles. Thus, functionalized nanoparticles increase the bulk thermal conductivity of the matrix while maintaining a viscosity that facilitates processing and manipulation.

According to certain embodiments disclosed hereinafter, polymeric composites composed of micron-sized fillers and organic matrices containing nanoparticles can achieve higher thermal conductivity compared to comparative blends of micron-sized fillers and organic matrices alone. . This allows for higher maximum achievable bulk thermal conductivity. In addition, nanoparticles can penetrate into surface voids and irregular areas that are inaccessible to micron sized fillers, thereby reducing the interfacial resistance effect.

Increased thermal conductivity in the polymer matrix is also advantageous in that it reduces the interfacial resistance when filler settling occurs and subsequently a "skin layer" (a layer with little or no microfiller) appears. If the skin layer has a higher thermal conductivity than can usually be achieved, the reduction in heat transfer will be much less severe. A further advantage of the incorporation of nanoparticles is that these small particles can prevent or reduce the sedimentation rate of micron sized fillers, thereby reducing the tendency for filler-free layers to form in the interface material.

Any nanoparticle that can be functionalized and has a higher thermal conductivity than the organic matrix can be used to prepare the compositions of the present invention. Suitable nanoparticles include colloidal silica, polyhedral oligomeric silsesquioxanes (“POSS”), nano-sized metal oxides (eg alumina, titania, zirconia), nano-sized metal nitrides (eg boron nitride, Aluminum nitride) and nano metal particles (eg silver, gold or copper nanoparticles), but are not limited to these. In particularly useful embodiments, the nanoparticles are organic-functionalized POSS materials or colloidal silica. Colloidal silica is present as a dispersion of submicron sized silica (SiO ₂ ) particles in an aqueous solution or other solvent medium. Colloidal silica contains up to about 85 weight percent silicon dioxide (SiO ₂ ), typically up to about 80 weight percent silicon dioxide. The particle size of the colloidal silica is typically about 1 nm to about 250 nm, more typically about 5 nm to about 150 nm.

Nanoparticles are functionalized to increase compatibility with organic matrices. Thus, the exact chemical nature of the functional groups added to the nanoparticles will depend on various factors including the chemical nature of the particular nanoparticles selected and the chemical composition of the matrix. In addition, the functional group may be reactive, non-reactive, or a combination of both. Reactive functional groups are those that can react with either the organic matrix in which the nanoparticles are dispersed or with the mating surface to which the final composition is to be dispensed. Subsequent chemical reactions will bind the nanoparticles to the organic matrix or mating surface via covalent bonds. Suitable functionalizing agents are organoalkoxysilanes, organochlorosilanes containing alkyl, alkenyl, alkynyl, silyl, siloxane, acrylate, methacrylates, epoxides, aryls, hydrides, amino, hydroxyl and other functional groups, Organoacetate silane and organosilazane. Schemes for adding functional groups to nanoparticles are within the range known to those skilled in the art. Functionalized nanoparticles are advantageously prepared in dispersions in compatible solvents to facilitate combination with the organic matrix. Particularly useful dispersions have a solids content of 20-50%, but any solids content can be used that allows the dispersion to be poured or flowed.

In a particularly useful embodiment, the functionalized nanoparticles are colloidal silica functionalized with an organofunctionalized POSS material or organoalkoxysilane.

Organoalkoxysilanes used to functionalize colloidal silica are included in the general formula:

(R ¹ ) _a Si (OR ² ) _4-a

Where

R ¹ , independently at each occurrence, may optionally be further functionalized by alkyl acrylate, alkyl methacrylate, epoxide, vinyl, allyl, styrene, silyl or siloxane groups or C _6-14 aryl radicals C _1-18 monovalent hydrocarbon radical,

R ² is independently at each occurrence a C _1-18 monovalent hydrocarbon radical or hydrogen radical,

"a" is an integer of 1 to 3 (including these).

Preferably, the organoalkoxysilane included in the present invention is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, phenyltrimethoxysilane, methacryloxypropyl Trimethoxysilane (MAPTMS), 1-hexenyl triethoxysilane, n-octyltriethoxy silane, n-dodecyl triethoxysilane and 2- (3-vinyl-tetramethyl disiloxane) -ethyl Trimethoxysilane. Combinations of functional groups are possible. Typically, the organoalkoxysilane is present in the range of about 2% to about 60% by weight based on the total weight of silicon dioxide contained in the colloidal silica. The resulting organofunctionalized colloidal silica is treated with acid or base to neutralize pH. Acids or bases may also be used to aid in the functionalization process, as well as other catalysts that promote condensation of silanol and alkoxysilane groups. Such catalysts include organo-titanium and organo-tin compounds such as tetrabutyl titanate, titanium isopropoxybis (acetylacetonate), dibutyltin dilaurate, dibutyl-tin diacetate or combinations thereof .

Functionalization of the colloidal silica can be carried out by adding an organoalkoxysilane functionalizing agent to an aqueous dispersion of colloidal silica commercially available at the weight ratios disclosed above, and adding an aliphatic alcohol thereto. The resulting composition comprising functionalized colloidal silica and organoalkoxysilane functionalizing agent in aliphatic alcohol is defined herein as a pre-dispersion. Suitable aliphatic alcohols include, but are not limited to, isopropanol, t-butanol, 2-butanol, 1-methoxy-2-propanol and combinations thereof. The amount of aliphatic alcohol typically ranges from about 1 to about 25 times the amount of silicon dioxide present in the aqueous colloidal silica pre-dispersion. In some cases, stabilizers such as 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxy (ie, 4-hydroxy TEMPO) may be added to the predispersion. In some cases, a small amount of acid or base may be added to adjust the pH of the clear predispersion.

The resulting predispersion is typically heated in a range from about 50 ° C. to about 140 ° C. for a period ranging from about 1 hour to about 5 hours to promote condensation of the alkoxysilane with OH groups on the surface of the colloidal silica, and colloidal silica. Functionalization was achieved.

The functionalized nanoparticles are combined with an organic matrix to form the compositions of the present invention. The organic matrix can be any polymeric material. Suitable organic matrices include polydimethylsiloxane resins, epoxy resins, acrylate resins, other organic-functionalized polysiloxane resins, polyimide resins, fluorocarbon resins, benzocyclobutene resins, fluorinated polyallyl ethers, polyamide resins, poly Imidoamide resins, phenol resol resins, aromatic polyester resins, polyphenylene ether (PPE) resins, bismaleimide triazine resins, fluororesins and any other polymer systems known to those skilled in the art, Not limited (for common polymers, see Polymer Handbook :, Branduf, J .; Immergut, E. H; Grulke, Eric A; Wiley Interscience Publication, New York, 4th ed. (1999)); "Polymer Data Handbook Mark, James Oxford University Press, New York (1999)". Preferred curable thermosetting matrices are acrylate resins, epoxy resins, polydimethyl siloxane resins, and free radical polymerization, atom transfer, radical polymerization ring-opening polymerization, ring-opening metathesis polymerization, anionic polymerization, cationic polymerization or those skilled in the art. Any other organic-functionalized polysiloxane resin capable of forming a crosslinking network by any other known method. Suitable curable silicone resins are described, for example, in "Chemistry and Technology of Silicone", Noll, W .; Addition curable and condensation curable matrices as disclosed in Academic Press 1968. If the polymer matrix is not a curable polymer, the resulting thermal interface composition may be formulated as a gel, grease or phase change material that holds the elements together during manufacture and transfers heat during operation of the device. In particularly useful embodiments, the organic matrix is functionalized to improve compatibility with functionalized nanoparticles.

In order to facilitate the combination of the functionalized nanoparticles with the organic matrix, one or more solvents may be optionally added to the composition. Suitable aliphatic solvents include, but are not limited to, isopropanol, 1-methoxy-2-propanol, 1-methoxy-2-propyl acetate, toluene, xylene, n-methyl pyrrolidone, dichlorobenzene and combinations thereof It doesn't work.

The manner in which the functionalized nanoparticles are combined with the organic matrix is not critical. If the nanoparticles are formulated in a pre-dispersion, the organic matrix and optional solvent can be added to the pre-dispersion.

The composition can be treated with an acid or a base or an ion exchange resin to remove acidic or basic impurities. The composition is advantageously treated with a vacuum in the range of about 0.5 Torr to about 250 Torr and a temperature in the range of about 20 ° C. to about 140 ° C. to substantially remove any low boiling components such as solvents, residues and combinations thereof. Can be removed with The result is a dispersion of functionalized nanoparticles in an organic matrix, referred to herein as the final dispersion. Substantially removing the low boiling component herein is defined as removing at least about 90% of the total amount of the low boiling component.

Optionally, the pre-dispersion or final dispersion of the functionalized colloidal silica can be further functionalized. The low boiling component is at least partially removed and then a suitable capping agent to react with the residual hydroxy functional groups of the functionalized colloidal silica is about 0.05 times to about the amount of silicon dioxide present in the pre-dispersion or final dispersion. Add in amounts of 10 times the range. Partial removal of the low boiling component as used herein means removal of at least about 10% of the total amount of the low boiling component, preferably at least about 50% of the total amount of the low boiling component. The capped functionalized colloidal silica is said to have at least 10%, preferably at least 20%, more preferably at least 35% of the free hydroxyl groups present in the total composition functionalized by reaction with the capping agent. Is defined. Effective capping of the functionalized colloidal silica can in some cases improve the room temperature stability of the final dispersion.

Preferred capping agents include hydroxyl reactive materials such as silylating agents. Examples of silylating agents include hexamethyldisilazane (HMDZ), tetramethyldisilazane, divinyltetramethyldisilazane, diphenyltetramethyldisilazane, N- (trimethylsilyl) diethylamine, 1- ( Trimethylsilyl) imidazole, trimethylchlorosilane, pentamethylchlorodisiloxane, pentamethyldisiloxane and combinations thereof, but is not limited thereto. The final dispersion is then heated in the range of about 20 ° C. to about 140 ° C. for a period of about 0.5 hour to about 48 hours. The resulting mixture is then filtered. When the pre-dispersion is reacted with a capping agent, one or more organic matrix compositions are added to add the final dispersion. The mixture of functionalized colloidal silica in the organic material is concentrated at a pressure ranging from about 0.5 Torr to about 250 Torr to form the final concentrated dispersion. During this process, lower boiling components such as solvents, residues, by-products of the capping and hydroxyl groups, excess capping and combinations thereof are substantially removed.

Optionally, the total final dispersion composition can be blended with micron sized filler. Micron sized fillers may be added to substantially increase the thermal conductivity of the composition. Thus, the effect of functionalized nanoparticles on the thermal conductivity of the polymer matrix is greatly doubled by the addition of microfillers. For example, if the polymer matrix has a thermal conductivity of 0.2 W / m-K, the addition of 80-90% by weight of suitable microfillers can increase the thermal conductivity to 2.0 W / m-K. However, by the addition of the functionalized nanoparticles according to the invention, the initial thermal conductivity of the polymer matrix can be increased to 0.3 W / m-K or more, and the addition of the same amount of micron sized filler leads to about 3 W of thermal conductivity. Increasing to / m? K increases the thermal conductivity by 50% compared to compositions that do not contain nanoparticles. In many cases, adding only microparticles to a thermal conductivity of 3 W / m? K will make the composition very sticky and difficult to process and will not flow as needed for the manufacture of electrical devices, especially flip / chip devices. . On the other hand, when using the nanoparticles according to the present invention, the thermal conductivity is increased while maintaining a sufficiently low viscosity to facilitate processing.

Fillers are thermally conductive materials of micron size and may be reinforced or non-reinforced. Fillers are, for example, fumed silica, fused silica, finely divided quartz powder, amorphous silica, carbon black, graphite, diamond, metals (eg silver, gold, aluminum and copper), silicon carbide, aluminum hydrate, metal nitride (For example boron nitride and aluminum nitride), metal oxides (eg aluminum oxide, zinc oxide, titanium dioxide or iron oxide) and combinations thereof. When present, fillers are typically present in the range of about 10 to about 95 weight percent based on the weight of the total final composition. More typically, the filler is present in the range of about 20 to about 90 weight percent based on the weight of the total final dispersion composition.

The presence of nanoparticles in the composition of the present invention improves the stability of the composition when microfillers are present. The nanoparticles have been found to inhibit the settling of microparticles into the bottom of the container containing the composition, compared to a composition containing the same amount of microfiller but no nanoparticles.

A curing catalyst can be added to the final dispersion to promote curing of the final composition. Typically, the catalyst is present in the range of about 10 ppm to about 10 weight percent of the total curable composition. Examples of cationic curing catalysts are onium catalysts, for example bisaryl iodonium salts (e.g. bis (dodecylphenyl) iodonium hexafluoroantimonate, (octyloxyphenyl, phenyl) iodonium hexa Fluoroantimonates, bisaryliodonium tetrakis (pentafluorophenyl) borate), triarylsulfonium salts, and combinations thereof. Examples of radical curing catalysts include various peroxides (eg t-butyl peroxy benzoate), azo compounds (eg 2,2'-azo bis-isobutyl nitrile) and nitroxides (eg 4 -Hydroxy TEMPO), but is not limited to such. In the case of further curable silicone resins, preferred catalysts are various Group 8-10 transition metal (eg ruthenium, rhodium, platinum) complexes. In the case of condensation curable silicones, preferred catalysts are organo-tin or organo-titanium composites. The detailed structure of the catalyst is known to those skilled in the art.

Optionally, for cationic curable matrices, an effective amount of free-radical generating compound can be added as an optional reagent, examples of which are aromatic pinacol, benzoinalkyl ethers, organic peroxides and combinations thereof. Free radical generating compounds promote the decomposition of onium salts at low temperatures.

In the case of epoxy resins, a curing agent, for example an organic compound containing a carboxylic acid-anhydride curing agent and a hydroxyl moiety, can be added together with the curing catalyst as an optional reagent. In this case, the curing catalyst may be selected from amines, alkyl-substituted imidazoles, imidazolium salts, phosphines, metal salts, triphenyl phosphines, alkyl-imidazoles and aluminum acetyl acetonates and combinations thereof, but It is not limited. In the case of epoxy resins, a curing agent, for example a polyfunctional amine, can optionally be incorporated as a crosslinking agent. Exemplary amines include ethylene diamine, propylene diamine, 1,2-phenylenediamine, 1,3-phenylene diamine, 1,4-phenylene diamine, and any other compound containing two or more amino groups. Including but not limited to.

For epoxy resins, exemplary anhydride curing agents are typically methylhexahydrophthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride, bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic anhydride, methyl Bicyclo [2.2.1] hept-5-ene-2,3-dicarboxylic anhydride, phthalic anhydride, pyromellitic dianhydride, hexahydrophthalic anhydride, dodecenyl succinic anhydride, dichloromaleic anhydride, chloric anhydride And tetrachlorophthalic anhydride. Combinations comprising two or more anhydride curing agents can also be used. Illustrative examples include "Chemistry and Technology of the Epoxy Resins" B. Ellis (Ed.) Chapman Hall, New York, 1993 and "Epoxy Resins Chemistry and Technology", edited by CA May, Marcel Dekker, New York, 2nd edition, 1988.

In the case of addition curable silicone resins, crosslinking agents, for example polyfunctional Si-H containing silicone fluids, are incorporated such that the molar ratio of Si-H to vinyl in the final formulation is in the range of 0.5 to 5.0, preferably 0.9 to 2.0. can do.

In the case of addition curable silicone resins, inhibitors may optionally be included to modify the curing profile and achieve desirable shelf life. Inhibitors include, but are not limited to, phosphine compounds, amine compounds, isocyanurates, alkynyl alcohols, maleic esters, and any other compounds known to those skilled in the art.

Reactive organic diluents can be added to the total curable composition to reduce the viscosity of the composition. Examples of reactive diluents include 3-ethyl-3-hydroxymethyl-oxetane, dodecylglycidyl ether, 4-vinyl-1-cyclohexane diepoxide, di (beta- (3,4-epoxycyclohexyl ) Ethyl) -tetramethyldisiloxane, various dienes (e.g. 1,5-hexadiene), alkenes (e.g. n-octene), alkenes, styrene compounds, acrylates or methacrylate-containing compounds (e.g. Methacryloxypropyltrimethoxysilane) and combinations thereof, but is not limited thereto. Non-reactive diluents can also be added to the composition to reduce the viscosity of the formulation. Examples of non-reactive diluents include, but are not limited to, low boiling aliphatic hydrocarbons (eg octane), toluene, ethyl acetate, butyl acetate, 1-methoxy propyl acetate, ethylene glycol, dimethyl ether, and combinations thereof. .

Adhesion promoters such as trialkoxyorganosilanes (e.g., γ-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, bis (trimethoxysilylpropyl) fumarate) are also typically used in the final final dispersion. It can be used with the total final dispersion in an effective amount in the range of about 0.01% to about 2% by weight of the weight of.

Flame retardants may optionally be used in the total final dispersion in the range of about 0.5% to about 20% by weight of the total final dispersion amount. Examples of flame retardants include phosphoramide, triphenyl phosphate (TPP), resorcinol diphosphate (RDP), bisphenol-A-disphosphate (BPA-DP), organic phosphine oxide, halogenated epoxy resins (tetrabromobisphenol A), metal oxides, metal hydroxides and combinations thereof.

The final dispersion composition may be mixed by hand or in a standard mixing device, such as a dough mixer, chain can mixer, rotary mixer, twin screw extruder, two or three roll mill, or the like. Mixing of the dispersing components can be carried out batchwise, continuously or semi-continuously by any means used by those skilled in the art.

The curing process can be carried out by any process known to those skilled in the art. Curing can be performed by methods such as thermal curing, UV light curing, microwave curing, e-beam curing and combinations thereof. Curing typically occurs at temperatures in the range of about 20 ° C. to about 250 ° C., more typically in the range of about 20 ° C. to about 150 ° C. Curing typically occurs at a pressure in the range of about 1 atmosphere ("atm") to about 5 tons / in ² , more typically in the range of about 1 atmosphere to about 100 pounds / in ² ("psi"). Curing may also occur for a period ranging from about 30 seconds to about 5 hours, more typically from about 90 seconds to about 60 minutes. Optionally, the cured composition may be post-cured for a period of about 1 hour to about 4 hours at a temperature in the range of about 100 ° C to about 150 ° C.

The addition of functionalized nanoparticles is used to increase the bulk thermal conductivity of the base polymer matrix to provide improved thermal conductivity when placed between any two objects, in particular components of electrical components. In addition, the thermal interface composition of the present invention reduces the interface resistance to heat flow essentially present on the surface of any two elements to which heat is transferred, as disclosed above. The thermal interface composition of the present invention can be used in devices of electronic products such as computers, semiconductors, or any device that requires heat transfer between elements. As shown in FIG. 1, for example, the thermal interface composition 2 of the present invention is inserted between the semiconductor chip 3 and the heat sink 1 to fill any air gaps and to promote heat transfer. The layer 2 of the thermal interface composition of the present invention can be as thin as 20 to 150 microns and still provide the desired effect. Application of the thermal interface composition of the present invention can be accomplished by any method known in the art. Conventional methods include screen printing, stencil printing, syringe dispensing and pick-and-place devices.

In other embodiments, the compositions of the present invention may be formed into sheets and cut into any desired form. In this embodiment, the compositions of the invention can advantageously be used for thermal interface pads to be placed between electrical components.

Although preferred and other embodiments of the invention are disclosed herein, those skilled in the art can recognize additional embodiments without departing from the scope of the invention as defined by the following claims.

Example 1

4.95 g of the dispersing composition consisted of methacryloxypropyl-trimethoxysilane (“MAPTMS”) functionalized colloidal SiO ₂ (20 nm by weight, based on unfunctionalized colloidal SiO ₂ by weight). ) Acryloxy-terminated polydimethylsiloxane (Gelest, DMSU22, molecular weight about 1000-1200). In addition, 2 g of MAPTMS, 0.13 g of iodonium salt (GE silicones, UV9380c) and 45.6 g of alumina (Showa Denka AS 10) were blended into the dispersion composition. The added alumina was 86.5% by weight of the total formulation. The dispersion composition was cured at 120 ° C. The thermal conductivity of the dispersion composition was measured, which was found to be 2.6 W / m K ± 0.05 at room temperature and 2.55 W / m K at 100 ° C. In comparison, the thermal conductivity of acrylate alone, when filled with 86.5% by weight of alumina (average size = 38 microns), is about 1.4 to 1.9 W / m · K at 100 ° C. See Table 1 below.

Example 2

Dispersion composition octakis of 1.82g (dimethyl siloxy -T8- silse quinolyl Noksan) (T ₈ ^OSiMe2H, Gelest), 0.73g of 1,5- hexamethyl-tri-siloxane (M ^{H H} DM GE Silicones) , 1.53 g of 1,3-divinyltetramethyldisiloxane (GE Silicone), 1.04 g of vinyl-terminated polydimethylsiloxane (Gelest, MW 9400) DMSV22, a suitable catalyst and 20 g of alumina (show And a blend of Denka, AS-40 and Sumitomo AA04). Alumina was added at about 80% by weight of the total formulation. The dispersion composition was cured at 80 ° C. The thermal conductivity of the dispersion composition was measured, which was found to be 1.99 W / m-K ± 0.15 at room temperature and 1.70 W / m-K ± 0.10 at 100 ° C. By comparison, the thermal conductivity of polydimethylsiloxane (“PDMS”) is about 1.00 W / m · K when filled with 80% by weight of alumina (average size = 10 μm for AS40 and 0.4 μm for AA04). See Table 1 below.

Example 3

7 g of GE Silicone FCS100 (containing 40 wt% MAPTMS-functionalized colloidal SiO ₂ in 1,6-hexanediol diacrylate), 0.14 g of iodonium salt (GE silicon, UV9380c) and 43 g of Dispersion compositions containing alumina (Showa Denka, AS50 and Sumitomo AA04) were blended. Alumina added was 86% by weight of the total formulation. The thermal conductivity of the dispersion was measured, which was found to be 3.35 W / m K ± 0.20 W / m K at room temperature and 3.25 W / m K 0.15 at 100 ° C. In comparison, the thermal conductivity of the acrylate when filled with 86.5% by weight of alumina (average size = 10 μm for AS40 and 0.4 μm for Sumitomo) is about 1.4 to 1.9 w / m · K. See Table 1 below.

Example 4

The final dispersion is 56% by weight of phenyltrimethoxysilane functionalized colloidal silica (based on SiO ₂ content and functional group) in cycloaliphatic epoxy resin (UVR6105, DOW), 1% by weight of iodo as catalyst It is composed of a nium salt (GE Silicones UV9392c) and 0.5% by weight of benzoyl pinacol (Aldrich). The dispersion is cured at 156 ° C. for 5 minutes and has a thermal conductivity of 0.37 W / m · K at 25 ° C. Typical epoxides without nanoparticles have a thermal conductivity of 0.2 to 0.25 W / m-K at 25 ° C.

Example 5

The final dispersion was colloid functionalized with phenyltrimethoxysilane and further end capped with hexamethyldisilazine (HMDZ) in vinyl-terminated polydimethyl-co-diphenyl-siloxane (Gelest, PDV1625). It consists of 22% by weight of silica. The weight percent of colloidal silica + condensed functional group is about 27%. 5.33 g of this final dispersion was mixed with 0.04 g of platinum catalyst package ([Pt] = 7.5 ppm in the final formulation) and 0.14 g of polydimethyl-co-methylhydride-siloxane (GE silicone, 88466). The final blend produces a flowable material. The composition was cured at 150 ° C. for 1 hour to produce a material having a bulk thermal conductivity of 0.17 W / m · K.

Example 6

10.06 g of vinyl-terminated polydimethyl-co-diphenyl-siloxane (Gelest, PDV1625), 0.38 g of polydimethyl-co-methylhydride-siloxane (GE silicone, 88466), 1.10 g of phenyltrime A stock solution consisting of oxysilane and 0.10 g of catalyst package (subject ([Pt] = 7.5 ppm in the final blend) was made up. 2.76 g of this stock solution consisted of 0.44 g of fused silica (Denka, average size). = 5 microns) and 0.35 g of double treated fumed silica (GE silicone, 88318) This mixture was a non-flowing thick paste.

The composition was cured at 150 ° C. for 1 hour. Bulk thermal conductivity was 0.17 W / m · K at 25 ° C., similar to Example 5.

Example 7

Appropriate amounts of final dispersion as disclosed in Example 5 were dispensed by hand using a syringe in an X pattern on an 8 × 8 mm aluminum coupon. A second aluminum coupon was then placed on top and the resulting sandwich structure was placed in a 150 ° C. oven for 1 hour to complete curing. The bond-line-thickness of the TIM layer is 16.8 microns. The effective thermal conductivity of the TIM layer is 0.18 W / m · K at 25 ° C. The total thermal resistance across the TIM layer is 94 mm ² –K / W.

A similar three layer sandwich structure was constructed using the formulation disclosed in Example 6. The bond line thickness is 23 microns and the effective thermal conductivity of the TIM layer is 0.13 W / m · K at 25 ° C. The total thermal resistance across the TIM layer is 173 mm ² –K / W.

Although preferred and other embodiments of the invention are disclosed herein, those skilled in the art can recognize additional embodiments without departing from the scope of the invention as defined in the following claims.

Claims (10)

A thermal interface composition comprising a blend of capped functionalized nanoparticles and a curable polymer matrix selected from the group consisting of capped functionalized colloidal silica and capped functionalized polyhedral oligomeric silsesquioxanes (POSS) The capped functionalized nanoparticles are colloidal silica or POSS functionalized by organoalkoxysilane represented by the following formula and further functionalized by silylating agent, Thermal interface composition: (R ¹ ) _a Si (OR ² ) _4-a Where R ¹ is independently at each occurrence a C _1-18 monovalent hydrocarbon radical functionalized by alkyl acrylate, alkyl methacrylate, epoxide, vinyl, allyl, styrene, silyl or siloxane groups, R ² is independently at each occurrence a C _1-18 monovalent hydrocarbon radical or hydrogen radical, "a" is an integer of 1-3. The method of claim 1, Wherein said curable polymer matrix is an acrylate resin and R ¹ is a C _1-18 monovalent hydrocarbon radical functionalized with alkyl acrylate or alkyl methacrylate. delete The method of claim 1, A thermal interface composition further comprising a micron sized filler. The method of claim 2, A thermal interface composition further comprising a micron sized filler. Positioning the heat generating element 3 in contact with the thermal interface composition 2 comprising a blend of the curable polymer matrix and the capped functionalized nanoparticles; And Positioning a heat sink 1 in contact with the thermal interface composition 2 In a method of increasing heat transfer, comprising: The capped functionalized nanoparticles are colloidal silica or polyhedral oligomeric silsesquioxanes (POSS) functionalized by organoalkoxysilanes represented by the following formula and further functionalized by silylating agents: How to increase heat transfer: (R ¹ ) _a Si (OR ² ) _4-a Where R ¹ is independently at each occurrence a C _1-18 monovalent hydrocarbon radical functionalized by alkyl acrylate, alkyl methacrylate, epoxide, vinyl, allyl, styrene, silyl or siloxane groups, R ² is independently at each occurrence a C _1-18 monovalent hydrocarbon radical or hydrogen radical, "a" is an integer of 1-3. delete Heat generating element 3; Heat sink 1; And An electrical component comprising a thermal interface composition (2) inserted between the heat generating element (3) and the heat sink (1) and comprising a blend of a curable polymer matrix and capped functionalized nanoparticles, The capped functionalized nanoparticles are colloidal silica or polyhedral oligomeric silsesquioxanes (POSS) functionalized by organoalkoxysilanes represented by the following formula and further functionalized by silylating agents: Electrical parts: (R ¹ ) _a Si (OR ² ) _4-a Where R ¹ is independently at each occurrence a C _1-18 monovalent hydrocarbon radical functionalized by alkyl acrylate, alkyl methacrylate, epoxide, vinyl, allyl, styrene, silyl or siloxane groups, R ² is independently at each occurrence a C _1-18 monovalent hydrocarbon radical or hydrogen radical, "a" is an integer of 1-3. The method of claim 8, Electrical component wherein the thermal interface composition (2) comprises a pre-molded pad. A method of slowing phase separation of a polymer composition filled with a micron sized filler comprising blending capped functionalized nanoparticles with a curable polymer composition, The capped functionalized nanoparticles are colloidal silica or polyhedral oligomeric silsesquioxanes (POSS) functionalized by organoalkoxysilanes represented by the following formula and further functionalized by silylating agents: Way: (R ¹ ) _a Si (OR ² ) _4-a Where R ¹ is independently at each occurrence a C _1-18 monovalent hydrocarbon radical functionalized by alkyl acrylate, alkyl methacrylate, epoxide, vinyl, allyl, styrene, silyl or siloxane groups, R ² is independently at each occurrence a C _1-18 monovalent hydrocarbon radical or hydrogen radical, "a" is an integer of 1-3.

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