WO2003028070A2 - Compositions having controlled flowability and thermal properties - Google Patents

Abstract

Compositions having controlled flowability, coefficient of thermal expansion (CTE) and enhanced conductivity are provided. These compositions include a flowable matrix component, fluorosilane component and an inorganic filler component. The components work cooperatively to produce flowability, CTE and conductivity advantages.

Description

COMPOSITIONS HAVING CONTROLLED FLOWABILITY AND THERMAL PROPERTIES

FIELD OF THE INVENTION:

[0001] The present invention relates to flowable compositions which in their unsolidified or uncured state exhibit controlled flowability, and which exhibit controlled thermal expansion upon solidification or cure. This invention further relates to the use of filler compositions which provide controlled flowability to fluids and low thermal expansion properties to the solidified or cured forms of the fluids, e.g. their reactions products.

BACKGROUND OF RELATED TECHNOLOGY;

[0002] Controlled flowability of curable and non-curable compositions is an important property for many applications involving adhesives, sealants, coatings, casting materials and gap-filling products. For example, many commercial end-use applications in the machinery and electronic areas require controlled rheology to ensure application of the polymer composition only to the desired area. Developing a composition which suits the intended application, i.e. has the sufficient curing properties, barrier properties, adhesive properties and the like, while providing for controlled flowability, has proven a difficult task to achieve using conventional methods. This is particularly true when there is also a need for the solidified or cured composition to exhibit a low coefficient of thermal expansion (CTE), i.e. low amount of physical expansion when exposed to differing temperature conditions, in order to ensure better CTE matching to the substrates with which it is used.

[0003] Conventional methods of reducing CTE in curable compositions have focused on the addition of filler components, such as aluminas and silicas, which oftentimes may reduce CTE, but significantly increase the viscosity of the composition to which they are added. Consequently, the composition exhibits reduced flowability such that it may not be useful commercially in many applications. Sometimes, silica fillers are precoated with silanes prior to their addition as filler components, often times to modify chemical resistance or enhanced adhesive properties of the compositions into which the precoated silicas are incorporated. For example, U.S. Patent Nos. 5,607,744 and 5,614,250 (both to Drener et al.) disclose the use of fluorosilane precoatings of silica fillers for incorporation into Teflon or other fluorinated polymeric materials which can be then used as circuit board substrates. These compositions are solid, non-flowable materials and are reportedly designed to provide enhanced ductility, low dielectric constant, and improved alkali and moisture resistance. Other similar examples of silica fillers coated with fluorosilanes for incorporation in particulate or paste fluoropolymeric materials used for circuit board substrate manufacture are disclosed in U.S. Patent Nos. 4,849,284 and 5,614,250 (both to Arthur et al).

[0004] Alkoxy oligosiloxanes have also been used as coupling agents for inorganic fillers such as amorphous aluminum oxide powders, as disclosed in IP Kokai Tokkyo Koho JP 2001 139,582.

[0005] EP 0 167 163 A 1 is one example of an adhesive designed for semi-conductor chip attachment applications. Both inorganic and organic spherical fillers are disclosed, having a required average particle size of 10-100μm, for incorporation into various curable adhesives such as silicones, epoxies, polyimides and acrylics, to provide a material which can maintain a constant gap between the chip and the board upon which it is mounted.

[0006] U.S. Patent No. 6,169,142 discloses thermally conductive silicone compositions, useful as conductive rubber sheets, which contain an alkenyl-bearing organopolysiloxane having a viscosity up to about 500,000 centistokes at 25°C, 300-1,200 pbw of an aluminum oxide powder, 0.05-10 pbw of an alkoxy silane, a platinum catalyst and an organohydrogenpolysiloxane having at least two hydrogen atoms attached to a silicon atom in a molecule. This composition discloses that suppression of viscosity increases of the liquid silicone rubber composition due to heavy loading of the aluminum oxide can be achieved by including an alkoxysilane having a monovalent long-chain hydrocarbon group. The viscosity reductions of the resultant silicone compositions are shown to be only modestly reduced. [0007] Heat-conductive silicone rubber compositions are also disclosed in JP Kokai

Tokkyo Koho JP 2001 139,815. These compositions contain curable polyorganosiloxanes, hardners and heat-conductive fillers pretreated with oligomeric siloxanes. Other heat-conductive silicone rubber compositions are disclosed in JP Kokai Tokkyo Koho JP 2001 139,818. These compositions include large amounts of thermally conductive fillers which have been treated with silanes.

[0008] Fluoro treatment of powders for use in cosmetic formulations are disclosed in JP

Kokai Tokkyo Koho JP 201 139,413; JP Kokai Tokkyo 2001 131,013 and JP Kokai Tokkyo 2001 131,022. The fluoropolymer in each of these is a fluorine-containing (meth)acrylate derivative which is used in conjunction with a curable silicone monomer.

[0009] Micro-electronic applications, such as in gap- filling or coating of semi-conductor chips, circuit boards and related devices, often specify the use of materials which not only protect the device from the environment, but also provide for energy dissipation (thermal and/or electrical conductivity and/or dissipation), while having a relatively low CTE, or at least a CTE that is similar to both the underlying substrate and the semi-conductor chip to which it is applied. In use, micro-electronic devices of this kind, generate heat which is desirably dissipated as efficiently as possible from the surface of the micro-electronic device. Nonetheless, the device undergoes some degree of thermal expansion. If the adhesive, coating or gap-filling composition used has a CTE that is significantly different than the underlying substrate or semi-conductor chip, cracking of the substrate or chip or of the composition or delamination of the adhering layers may occur, rendering the device defective or unusable for the intended purpose. Compositions having the requisite flowability to be useful from a commercial standpoint, while also having other desired properties such as low CTE, adequate adhesive, sealing or gap-filling properties, have heretofore been elusive.

[0010] There is clearly a need for a composition which provides for controlled flowability and CTE. There is also a need for a composition which provides enhanced flowability, lower CTE and improved conductivity. There is a further need to achieve these properties without substantially detracting from other physical and chemical properties such as adhesive strength, barrier properties, cure properties, and other properties desired of their compositions.

SUMMARY OF THE INVENTION

[0011] Through the fluorosilane and inorganic filler, the present invention provides the ability to control the viscosity, and hence the degree of flowability, of compositions to which they are added, while achieving lower CTE values than compositions without an inorganic filler, or with an inorganic filler but without the fluorosilane. The fluorosilane component and inorganic filler component are separate and distinct components, as compared to prior compositions containing fillers which were pre-treated and pre-coated with silanes.

[0012] In contrast, the present invention has realized numerous unexpected properties due to the combination of fluorosilane and inorganic filler components, among which are controlled viscosity, particularly the ability to provide high loading of the filler to achieve the desired CTE, and consequently, reduce the overall viscosity; the ability to control the flowability of a composition through this unique component combination, for a wide variety of applications; the ability to control the thermal and/or electrical conductivity of the resultant composition; the ability to maintain or improve overall physical properties such as sealing ability and adhesive strength, without sacrificing flowability control or low CTE values; the ability to achieve these advantages over a range of different type of compositions, e.g., flowable matrix components, using a variety of different fluorosilane components and inorganic filler components; and a combination of two or more of these advantages and unexpected properties.

[0013] Thus, in one aspect of the invention there is provided a composition which includes: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; and c) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure.

[0014] In another aspect of the invention there is included a composition which includes: a) a flowable matrix component which can be solidified or cured; and b) a rheology modifying composition which includes a fluorosilane component and an inorganic filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof, the rheology modifying composition providing controlled flowability to the flowable matrix and controlled CTE and/or improved conductivity to the solidified or cured polymer composition.

[0015] In still another aspect of the invention there is provided a composition which includes a rheology modifying composition which includes a fluorosilane component and an inorganic filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof, the rheology modifying composition providing controlled flowability to the flowable matrix and controlled CTE and/or improved conductivity to the solidified or cured polymer composition.

[0016] In yet another aspect of the invention there is included a composition which includes: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; c) a filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof; and d) an agent which aids in solidification or cure of said matrix component.

[0017] The reaction product of the recited components exhibits a lower CTE as compared to the reaction products in the absence of components b) and c), and the composition exhibits controlled flowability prior to solidification or cure and controlled CTE and/or improved conductivity subsequent to solidification or cure. [0018] In still another aspect of the invention there is included a composition which includes: a) a curable polymer component; b) a fluorosilane component; c) a metal filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof; and d) a curing agent.

The reaction product of a), b) and c) lowers the CTE and/or provides improved conductivity of the curable polymer component.

[0019] In an additional aspect of the invention there is included a composition which includes: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; and c) a filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof.

[0020] The composition exhibits controlled flowability prior to solidification or cure and lower CTE and/or improved conductivity subsequent to solidification or cure as compared to the polymer component without components b) and c).

[0021] In a further aspect of the invention there is included a composition which includes: a) a fluid carrier component; b) a fluorosilane component; and c) a filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof.

[0022] In yet another aspect of the invention there is included a composition which includes: a) a fluorosilane component; and b) a component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof.

[0023] In a further aspect of the invention there is included a composition which includes: a) a flowable reactive silicone component which can be solidified or cured; b) a fluorosilane component; and c) an inorganic filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof.

The composition exhibits controlled flowability prior to solidification or cure.

[0024] In another aspect of the invention there is included a composition which includes: a) a fluorosilane component; and b) an inorganic filler component selected from metals, metal oxides, metal nitrides, silicas and combinations thereof.

[0025] In an additional aspect of the invention there is included a method of controlling the flowability of a fluid carrier composition which includes the steps of: a) providing a fluid carrier composition; and b) combining the fluid carrier composition with a flow-control composition comprising a fluorosilane and filler components selected from metals, metal oxides, metal nitrides, silicas and combinations thereof, said flow-control composition being present in amounts selected to effect the desired amount of flowability.

[0026] In a further aspect of the invention there is included a method of controlling the flowability of a fluid carrier composition which includes the steps of adding to said fluid carrier composition: a) a fluorosilane component; and b) a component selected from metals, metal oxides, silicas and combinations thereof. [0027] In still another aspect of the invention there is included an electronic microchip assembly which includes: a) a chip-on-board component; and b) a composition having controlled flowability and which serves as underfill and/or sealant around component (a), said composition comprising:

(i) a flowable matrix component which can be solidified or cured; (ii) a fluorosilane component; and

(iii) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a graph showing the low CTE values of the inventive compositions as a function of increased inorganic filler content, while maintaining controlled flowability of the compositions.

[0029] Figure 2 is a perspective view of a chip-on-board micro-electronic device showing the components encapsulated with the inventive silicone composition in a "glob top" application.

[0030] Figure 3 is a perspective view of a chip-on-board micro-electronic device showing the components encapsulated with the inventive silicone composition in a "dam and fill" application.

[0031] Figure 4 is a perspective view of a flowability test apparatus and shows the inventive composition flowing between two glass plates. [0032] Figure 5 is a perspective view showing the results of a flowability test conducted on an inventive composition after 1 minute.

[0033] Figure 6 is a perspective view showing the results of a flowability test conducted on an inventive composition after 3 minutes.

DETAILED DESCRIPTION OF THE INVENTION

Flowable Matrix Components

[0034] The compositions of the present invention include a flowable matrix component which can be solidified or cured. The flowable matrix component may be a material which is already in the fluid or flowable state, or one which can be rendered flowable by subjecting it to heat or solvent. A variety of flowable matrix components may be used in the present invention, including materials which are thermoplastic or thermosetting. Moreover, use of the term "solidified" includes those materials, such as latexes, and other such materials which solidify without crosslinking, but unlike thermoplastic resins, are not necessarily thermo-reversible. Flowable matrix materials which contain latent curable groups, such as latent curing latex materials, may also be employed.

[0035] In addition to flowable matrix components which can be solidified or cured, controlled flowability of other fluid materials, such as mineral oil, can be achieved by incorporation of the fluorosilane component and the inorganic filler component into the oil.

[0036] In one aspect of the invention there is provided flowable compositions which have the following components in the recited amounts: INVENTIVE COMPOSITIONS

*metals, metal oxides, silicas, metal nitrides, ceramics

[0037] In those compositions which are designed intended to be cured or cross-linked, appropriate selection of curing agents such as free radial initiators, accelerators and promoters may be employed. The choice of the curing system is dictated by the particular choice of flowable matrix component employed.

[0038] Thermosetting and thermoplastic materials which are useful as flowable matrix components may be selected from a wide variety of materials. For example, silicones, (meth)acrylates, epoxies, polyesters, polyethers, urethanes, latexes and copolymers thereof may be employed. Combinations of these materials are also useful.

[0039] The silicones useful and flowable matrix components in the present invention desirably, but do not necessarily, have at least two unsaturated functional groups to permit cross- linking of the composition. While the unsaturated groups are desirably vinyl, other unsaturated groups may be employed. Useful reactive silicones may be generally represented by the following formula:

R^> R¹ R*

R⁵- Si - O - (Si- O)„ — Si— R⁵

R⁴ R^ R⁴ where R¹, R², R³, R⁴ and R⁵ may be the same or different and may be hydrogen, alkyl, alkenyl, aryl, alkoxy, alkenyloxy, aryloxy, (meth)acryl or (meth)acryloxy provided that at least two of R , R², R³, R⁴ and R⁵ have up to 12 carbon atoms (Cι-ι₂) and include an unsaturated group; and n is an integer between about 100 and 1,200.

[0040] Desirably, the reactive silicone is a vinyl terminated polydimethylsiloxane, which may be represented by the following formula:

R R' R'

H₂C = CH- Si — O — (Si-O)_n — Si— CH=CH₂

R⁴ R^z R*

where R¹, R², R³ and R⁴ may be selected from alkyl, alkoxy, alkenyloxy, aryloxy, aryl, methacryl, methacryloxy and combinations thereof and n is between 100 and 1,200.

[0041] The reactive silicone is generally present in amounts sufficient to achieve the structural integrity required of the specific application chosen. In general, the reactive silicone may be present in amounts of about 15% to about 90%, and desirably about 20% to about 50% by weight of the total composition. For example, the following compositions may be employed:

INVENTIVE SILICONE COMPOSITIONS

[0042] The reactive organopolysiloxanes of the present invention may optionally contain one or more hydrolyzable groups, in addition to the two unsaturated groups. In such cases, the silicone composition can then be made to cure using a mechanism other than heat. For example, moisture curing groups can be placed on the reactive silicone to impart moisture cure properties. Such hydrolyzable groups include amino, oxime, hydroxyl, alkoxy, aroloxy, alkaroloxy, aralkoxy and the like.

[0043] Curable polyolefinically unsaturated monomers may also be used as the flowable matrix component including acrylic and methacrylic resins, and mixtures thereof. The term (meth)acrylic is used to refer to both types of resins.

[0044] In particular, anaerobic curing monomers have been found to be desirable flowable matrix components.

[0045] Useful anaerobic curing monomers include the alkylene glycol diacrylates having the general formula:

wherein R⁴ is selected from the group consisting of hydrogen, halogen, and lower alkyl of 1-4 carbon atoms; R⁵ is selected from the group consisting of hydrogen, -OH and

O II — O— C— C=CH₂

R⁴

R⁶ is a radical selected from the group consisting of hydrogen, lower alkyl of 1-4 carbon atoms, hydroxyalkyl of 1-4 carbon atoms, and m is an integer equal to at least 1, desirably 1-8 and more desirably from 1 to 4; n is an integer equal to at least 1, desirably, 1 to 20; and p is 0 or 1.

[0046] Typical of these anaerobic monomers are mono-, di-, tri- tetra- and polyethylene glycol dimethacrylate and the corresponding diacrylates; di(pentamethylene glycol) dimethacrylate; tetraethylene glycol di(chloroacrylate); diglycerol diacrylate; diglycerol tetramethacrylate; butylene glycol dimethacrylate; neopentyl glycol diacrylate; and trimethylopropane triacrylate.

[0047] Particularly useful polymerizable crosslinkable anaerobic monomers are ethoxylated trimethylolpropane triacrylate, trimethylol propane trimethacrylate, dipentaerythritol monohydroxypentacrylate, pentaerythritol triacrylate, ethoxylated trimethylolpropane triacrylate, 1,6-hexanedioldiacrylate, neopertyl glycoldiacrylate, pentaerythritol tetraacrylate, 1,2-butylene glycoldiacrylate, trimethylopropane ethoxylate tri(meth)acrylate, glyceryl propoxylate tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol monohydroxy penta(meth)acrylate, tri(propylene glycol) di(meth)acrylate, neopentylglycol propoxylate di(meth)acrylate, 1,4-butanediol di(meth)acrylate, polyethyleneglycol di(meth)acrylate, triethyleneglycol di(meth)acrylate, butylene glycol di(meth) acrylate, ethoxylated bisphenol A di(meth)acrylate and combinations thereof.

[0048] The flowable matrix component may also include urethane and urethane-acrylate type monomers, such as those described in U.S. Patent No. 3,925,988 to Gorman, and U.S. Patent No. 4,309,526 to Baccei, each of which are incorporated herein by reference. The monomers disclosed in the '526 patent may be viewed as one-component polymerizable block copolymers (prepolymers) having rigid and flexible segments. This is achieved by the chemical linking of precursor "prepolymers" which are subsequently "capped" with (meth)acrylate, functionality.

[0049] Other useful flowable matrix component monomers include those acrylates derived from bisphenol- A, such as bisphenol-A dimethacrylate, hydrogenated bisphenol-A dimethacrylate, and ethoxylated bisphenol-A dimethacrylate.

[0050] While di- and other polyacrylate esters have been found particularly desirable, for many purposes, the flowable matrix component may include monofunctional acrylate esters (esters containing one acrylate group). When dealing with monofunctional acrylate esters, it is desirable to use an ester which has a relatively polar alcoholic moiety. Such materials are less volatile than low molecular weight alkyl esters and, more importantly, the polar group tends to provide intermolecular attraction during and after cure, thus producing more desirable cure properties, as well as a more durable sealant or adhesive. Particularly desirable are the polar groups selected from labile hydrogen, heterocyclic ring, hydroxy, amino, cyano, and halogen polar groups. Useful examples of compounds within this category include cyclohexyl methacrylate, tetrahydrofurfuryl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, t-butylaminoethyl methacrylate, cyanoethylacrylate, and chloroethyl methacrylate. The materials are often incorporated as reactive diluents which are capable of copolymerizing with the various other polymerizable materials. Other unsaturated reactive diluents, such as styrene and acrylonitrile, can also be used. [0051] Epoxy resins useful in the compositions of the present invention include polyepoxides curable at room temperature or by elevated temperature. Examples of these polyepoxides include polyglycidyl and poly(β-methylglycidyl) ethers obtainable by reaction of a compound containing at least two free alcoholic hydroxyl and/or phenolic hydroxyl groups per molecule with the appropriate epichlorohydrin under alkaline conditions or, alternatively, in the presence of an acidic catalyst and subsequent treatment with alkali. These ethers may be made from acyclic alcohols such as ethylene glycol, diethylene glycol, and higher poly(oxyethylene) glycols, propane- 1,2-diol and poly(oxypropylene) glycols, propane- 1, 3 -diol, butane- 1,4-diol, poly(oxytetramethylene) glycols, pentane-l,5-diol, hexane-2,4,6-triol, glycerol, 1,1,1- trimethylolpropane, pentaerythritol, sorbitol, and poly(epichlorohydrin); from cycloaliphatic alcohols such as resorcinol, quinitol, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4- hydroxycyclohexyl)propane, and l,l-bis(hydroxymethyl)-cyclohex-3-ene; and from alcohols having aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline and p,p'-bis(2- hydroxyethylamino)diphenylmethane. Or they may be made from mononuclear phenols, such as resorcinol and hydroquinone, and from polynuclear phenols, such as bis(4- hydroxyphenyl)methane, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl) sulphone, 1,1,2,2- tetrabis(4-hydroxyphenyl)ethane, 2,2,-bis(4-hydroxyphenyl)propane (otherwise known as bisphenol A), 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, and novolaks formed from aldehydes such as formaldehyde, acetaldehyde, chloral, and furfuraldehyde, with phenols such as phenol itself, and phenols substituted in the ring by chlorine atoms or by alkyl groups each containing up to nine carbon atoms, such as 4-chlorophenol, 2-methylphenol, and 4-t- butylphenol.

[0052] Poly(N-glycidyl) compounds may also be used and include, for example, those obtained by dehydrochlorination of the reaction products of epichlorohydrin with amines containing at least two amino-hydrogen atoms, such as aniline, n-butylamine, bis(4- aminophenyl)methane, and bis(4-methylaminophenyl)methane; triglycidyl isocyanurate; and N,N'-diglycidyl derivatives of cyclic alkylene ureas, such as ethyleneurea and 1,3- propyleneureas, and of hydantoins such as 5,5-dimethylhydantoin. [0053] Epoxide resins having the 1,2-epoxide groups attached to different kinds of hetero atoms maybe employed, e.g., the N,N,O-triglycidyl derivative of 4-aminophenol, the glycidyl ether-glycidyl ester of salicylic acid, N-glycidyl-N'-(2-glycidyloxypropyl)-5,5- dimethylhydantoin, and 2-glycydyloxy-l,3-bis(5,5-dimethyl-l-glycidylhydantoin-3-yl)propane.

[0054] Such epoxies are available from a variety of commercial sources, such as the

EPON series from Shell Chemical Co., the EPI-REZ series from Rhόne-Poulenc, the Araldite series from Vantico, the D.E.R. series from Dow Chemical Co., and the EPOTUF series from Reichhold.

[0055] Also useful are halogenated epoxy resins such as the brominated epoxides available from the sources shown above. Halogenated epoxy resins in combination with other fire retardant materials may be suitable for use as fire retardant additives in the compositions of the present invention.

[0056] Especially preferred epoxy resins useful in the present invention are the diglycidyl ethers of bisphenol A marketed under the tradenames EPON 825 and EPON 828 available from Shell Chemical Co., D.E.R. 331 and 332 available from Dow Chemical Co., and the cycloaliphatic epoxy resin marketed as ERL-4221 by Union Carbide Co.

[0057] Various epoxies such as the glycidyl ethers marketed as the EPODIL series by

Pacific Anchor Chemical Corporation, a division of Air Products and Chemicals Inc., may also be added as epoxy diluents.

[0058] It will be understood that the foregoing list of epoxy compounds is intended only to be illustrative in character, and that other compounds having 1,2 epoxide functionality and curable at room temperature or by heat may potentially be employed. Other optional epoxy compounds may be present which have both epoxy functionality and olefinically unsaturated functionality ("dual-functional" resins). [0059] Other useful flowable matrix components which are curable include cyanoacrylate compositions, such as those disclosed in U.S. Patent Nos. 3,742,018; 4,102,945; 5,922,783, among others, all of which are incorporated herein by reference.

Fluorosilanes

[0060] The addition of a separate fluorosilane component in the inventive compositions allows for substantial control of the viscosity and hence the flowability of the inventive compositions as a whole. Control of the flowability is important in applications where too much or not enough flow is undesirable. In compositions which are designed to have low CTE, flowability has not been controllable in conventional compositions. As mentioned above, this is largely due to the high loading of filler components which substantially increase the viscosity, regardless of lubricating agents and/or precoating agents designed to make the filler particles less interactive, i.e. remove or neutralize the hydrophilic groups. Hence, prior low CTE compositions resulted in non- flowable compositions. Moreover, while the high loading of filler components, such as metal particles, increased the thermal and/or electrical conductivity of conventional compositions, viscosity increases were so substantial that flowability was either minimized or non-existent.

[0061] The ability to control the rheology, i.e. the deformation and flow of the composition, is controlled in the present invention by the incorporation of the fluorosilane component in combinations with the inorganic filler component. The relative amount of the fluorosilane component to the inorganic filler component can be varied, thus providing for viscosity control and subsequent flow control. Extremely large quantities of inorganic filler component can be added, e.g. up to about 90% by weight of the total composition, with the addition of only a minor amount, e.g. about 0.01% to about 10% by weight fluorosilane. The resultant compositions are not only flowable under their own weight when acted upon by gravity, but also are flowable by capillary action in the small interstices of parts, e.g. electronic microchip bonding, sealing and/or filling applications. [0062] The following equation is useful for purposes of the present invention:

Viscosity = stress (force/area) shear rate (velocity/thickness)

[0063] One method of measuring the flowability of the compositions of the present invention was to measure the viscosity on a cone and plate instrument such as the Haake machine. A sample of the composition was placed in-between the cone and the plates of the Haake machine at a controlled temperature, such as 25°C. The plate was stationary, but the cone (which can be 2-5 cm in diameter, with an angle of 1° to 4°) rotated at controlled, programmable rate. The stress required to turn the cone was then accurately measured. The thicker and less flowable a sample composition was, the more force was required to turn the cone. For example, the viscosity reported at shear rate of 0.5 1/S indicated the flowability of the sample composition at that speed of turning of the cone. If the cone speed was increased for samples that undergo shear thinning, the viscosity become less. The viscosity measurements on the Haake machine give the flowability of a sample composition at a particular shear rate, and the viscosity at infinite shear and 0 shear can then be predicted mathematically.

[0064] The value of a 0.5 shear rate is fairly slow and correlates well with the flow rate of a flowable material which is disturbed only slightly. In many applications in the electronic industry this in fact what happens.

[0065] Many of the compositions of the present invention will also have thixotropic characteristics. That is, the composition may require an initial shear force to begin movement of the material, but once movement begins, the material readily flows at a given rate. These compositions may regain their original fixed structure when left unsheared for a while. A common example of a thixotropic material is ketchup. Typically, ketchup will not pour out of the bottle until sufficient shearing is introduced, i.e. shaking, in order to reduce its viscosity sufficiently so that it can flow. When the ketchup is left for a few hours, however, the structure rebuilds and becomes non-flowable.

[0066] Another measurement technique used in the present invention for determining flowability was to observe the flow of a sample composition as a droplet spreads out over a flat surface over time. For example, a predetermined volume of the sample composition was placed at the center of a planar grid, and observed over time. This is a simple flow method, where the distance the composition travels along the grid for a given time period can be measured. Materials which are more flowable will travel a further distance than less flowable materials for a given time period. Additionally, the flowability of compositions which are thixotropic may also be observed. These compositions may only flow once sufficient shear is introduced, and may also gradually slow down and even completely stop due to the rebuilding and thickening of the composition over time. For the most part, very small amounts of shear force, i.e. small movements with a spatula were required with the inventive thixotropic compositions. The incorporation of various amounts of fillers with the fluorosilane component allows for the production of a substantially reduced viscosity notwithstanding high filler content, as well as the production of compositions which have a graduated thixotropic character.

[0067] Another method used to demonstrate the flowability of the present invention uses two glass slides or surfaces which can be placed in a spaced apart relationship and which provide a flow path for the composition to move therebetween. In this measurement technique, in addition to the flow of the composition due to gravitational forces, there is also a slight capillary force acting on the sample which not only pulls it along, but contributes to shear thinning.

[0068] Useful fluorosilanes in the present invention include, without limitation fluoroalkylalkoxysilanes such as trifluoropropyltrimethoxysilane, trifluoropropyldimethoxymethylsilane, pentafluorophenyl-propyltrimethoxysilane, heptadecafluoro 1,2,2-tetra-hydrodecyltriethoxysilane and combinations thereof. For example, trifluoropropyltrimethoxysilane (TFPTMS) as well as tridecafluorooctyltriethoxy silane (TDFPTES) are among the commercially available fluorosilanes found to be particularly useful. The fluorosilanes may be present of amounts of about 0.01 % to about 10% by weight of the total composition. In general, at least two fluoro groups are desirably present per molecule of silane. The alky portion of the silane desirably contains a carbon chain length of is Cι_-32 and the alkoxy portion may have a carbon chain length of C_1-5. [0069] In certain applications, the compositions of the present invention may also include non-fluorinated silanes in combination with the fluorinated silanes. Mixtures of silanes are contemplated.

[0070] Through the addition of the fluorosilane component in combination with the inorganic filler component, the flowability of compositions can be rendered more or less flowable through the control of viscosity. For example, flowability has been imparted to compositions which due to extremely high viscosities are not flowable when placed even under significant shear forces. Moreover, as mentioned above, the addition of the inorganic filler component and fluorosilane component to fluids such as mineral oil produced similar controlled flow results. Thus, the advantages of the present invention are apparent in a host of different compositions, including those which are curable, non-curable, fluid or solidifiable.

Inorganic Fillers

[0071] Inorganic fillers useful in the present invention include metals, metal oxides, metal nitrides, silicas and combinations thereof. Various ceramic materials are also useful. The filler component can be used up to about 95% by weight of the total composition, and desirably in amounts of about 60 to about 90% by weight. Lower amounts of filler, for example about 1 to about 60% by weight, are also useful. The amount of inorganic filler used for a particular application will depend in part on the density of the chosen inorganic filler.

[0072] The addition of the filler component allows for controlled CTE, as well as improved thermal and/or electrical conductivity. These properties are particularly useful in electronic applications, such as semi-conductors and other computer-related applications.

[0073] Examples of useful inorganic filler components include, without limitation aluminum, zinc, nickel, copper, boron, silica, oxides of any of these, as well as nitrides of any of these. Combinations of the inorganic filler components are also useful.

[0074] The inorganic filler component may be a variety of shapes and sizes. For example, the filler component may be a particulate having a relatively dendritic or irregular shape. Alternatively, the inorganic filler component may be substantially spherical in shape. Combinations of spherical and non-spherical inorganic filler components may also be employed. Additionally, a combination of different density inorganic fillers is also desirable. Using a combination of different density particles, assists in prevention of the inorganic filler component from settling out over time. The less dense particles tend to interfere with the settling out of the more dense inorganic filler components, thereby maintaining the desired properties over time. One example of such a combination is alumina and silica. When these filler components are combined, regardless of whether they are of different sizes, the more dense alumina particles are prevented from settling out by the less dense silica particles.

[0075] In addition to the aforementioned inorganic filler components, other ceramic filler components may also be incorporated. Conventional filler components such as calcium carbonate, magnesium oxide, talc, among others, may be added, but generally result in the reduction of certain advantages of the present invention. However, in applications where specific tailoring is desired, such additions may be made.

[0076] The particle size of the inorganic filler component may also vary widely. For example, particles ranges from about 0.1 μm to about 100 μm are particularly desirable. It should be noted, however, that particle sizes outside of these ranges have been found to be useful in specific applications.

Cure Systems

[0077] As previously mentioned, the type of cure system chosen, if any, will be dictated largely by the type of flowable matrix component selected.

[0078] When the flowable matrix component is a heat-curable silicone composition, there is generally included a silicone having at least two reactive silicon hydride functional groups. This component functions as a cross-linker for the reactive silicon. In the presence of the hydrosylization catalyst, the silicon-bonded hydrogen atoms in the cross-linking component undergo an addition reaction, which is referred to as hydrosilation with the silicon-bonded alkenyl or unsaturated groups in the reactive silicone component. This results in cross-linking and curing of the compositions. Since the reactive silicone component contains at least two unsaturated functional groups, the silicone cross-linking component should also contain at least two silicon-bonded hydrogen atoms to achieve the final cross-linked structure in the cured product. The silicon-bonded organic groups present in the silicone cross-linking component may be selected from the same group of substituted and unsubstituted monovalent hydrocarbon radicals as set forth above for the reactive silicone component, with the exception that the organic groups in the silicone cross-linker should be substantially free of ethylenic or acetylenic unsaturation. The silicone cross-linker may have a molecular structure that can be straight chained, branched straight chained, cyclic or networked.

[0079] The silicone cross-linking component may be selected from a wide variety of compounds, that desirably conforms to the formula below:

wherein at least two of R , R and R are H; otherwise R , R and R can be the same or different and can be a substituted or unsubstituted hydrocarbon radical from Cι_₂₀ such hydrocarbon radicals including those as previously defined for formula I above; thus the SiH group may be terminal, pendent or both; R can also be a substituted or unsubstituted hydrocarbon radical from Cι_-2o such hydrocarbon radicals including those as previously defined for R⁷, R⁸ and R , and desirably is an alkyl group such as methyl; x is an integer from 10 to 1,000; and y is an integer from 1 to 20. Desirably R groups which are not H are methyl. The silicon hydride crosslinker should be present in amounts sufficient to achieve the desired amount of crosslinking and desirably in amounts of about 1 to about 10% by weight of the composition. [0080] When silicones are employed as the flowable matrix material, the inventive compositions may include a rhodium catalyst, which is effective for catalyzing the addition reaction between the silicon-bonded hydrogen atoms in the silicon crosslinker and the unsaturated groups in the reactive silicone. Useful rhodium catalysts include, but are not limited to, rhodium hydrocarbon complexes, such as tris(tributylsulfιde) rhodium trichloride, (acetylacetonato)di-carbonylrhodium, tri(triphenylphosphine) rhodium chloride having the formula (Ph P) RhCl, rhodium acetate dimer having the formula [(CH₃COO)₂Rh]₂, and rhodium acetylacetonate having the formula Rh(acac)₂ in which acac is the acetylacetonato group forming a ring structure with the rhodium atom.

[0081] For instance, a rhodium- or platinum-containing transition metal complex may be used and chosen from a variety of organometallic materials or metallocenes. Those materials of particular interest herein may be represented by metallocenes within structure II:

M_β

II where Ri and R₂ may be the same or different and may occur at least once and up to as many four times on each ring in the event of a five-membered ring and up to as many as five times on each ring in the event of a six-membered ring;

[0082] R_Ϊ and R₂ may be selected from H; any straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms, such as CH₃, CH₂CH₃, CH₂CH₂CH₃, CH(CH₃)₂, C(CH )₃ or the like; acetyl; any straight- or branched-chain alkenyl constituent having from 2 to about 8 carbon atoms; vinyl or allyl; halogen; hydroxyl; carboxyl; -(CH₂)„-OH, where n may be an integer in the range of 1 to about 8; -(CH₂)_n-COOR₃, where n may be an integer in the range of 1 to about 8 and R₃ may be any straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; H; Li; or Na; -(CH₂)_n-OR , wherein n may be an integer in the range of 1 to about 8 and R₄ may be any straight- or branched-chain alkyl constituent having from 1 to about 8 carbon atoms; or -(CH₂)_nN⁺(CH₃)₃ X^", where n may be an integer in the range of 1 to about 8 and X may be halogen, ClO₄ ^" or BF ^";

[0083] Yι and Y₂ may not be present at all, but when at least one is present they may be the same or different and may be selected from H, halogen, cyano, methoxy, acetyl, hydroxy, nitro, trialkylamines, triaryamines, trialkylphosphines, triphenylamine, tosyl and the like; A and A' may be the same or different and may be C or N; m and m' may be the same or different and may be 1 or 2; and M_e is Rh, or Pt.

[0084] Of course, depending on valence state, the element represented by M_e may have additional ligands ~ Yi and Y₂ — associated therewith beyond the carboxylic ligands depicted above.

[0085] Alternatively, metallocene structure II may be modified to include materials such as those within structure III below:

III

where Ri, R₂, Yi, Y₂, A, A', m, m' and M_e are as defined above. [0086] A particularly desirable example of such a material is where Ri and R₂ are each

H; Yi and Y₂ are each halogen, such as Cl; A and A' are each N; m and m' are each 2 and Me is Rh.

[0087] Within metallocene structure II, well-suited metallocene materials may be chosen from within metallocene structure IV:

IV where Ri, R₂ and M_e are as defined above.

[0088] Other used rhodium complexes are those disclosed in U.S. Patent No. 3,890,359, the subject matter of which is incorporated herein by reference. For example, such complexes include RhCl₃(EtSCH₂SiMe₃)₃, RhCl₃(n-BuSCH₂SiMe₃)₃, RhCl₃(PhSCH₂SiMe₃)₃ and RhCl₃[(Me₃SiCH₂)₂S]₃, wherein Me, Et, Bu and Ph represent methyl, ethyl, butyl and phenyl radicals respectively.

[0089] The rhodium catalysts should be used in an amount effective to induce curing at an appropriate temperature, which is lower than that which is ordinarily required with non- rhodium heat cure catalysts. Desirably, the catalyst is present in amounts of about 0.0001% to about 1.0% by weight, and more desirably about 0.0002% to about 0.001% and even more desirably in amounts of about 0.0005% to about 0.003 % by weight of the total composition. [0090] Useful platinum catalysts include platinum or platinum-containing complexes such as the platinum hydrocarbon complexes described in U.S. Patent Nos. 3,159,601 and 3,159,662; the platinum alcoholate catalysts described in U.S. Patent No. 3,220,970, the platinum complexes described in U.S. Patent No. 3,814,730 and the platinum chloride-olefin complexes described in U.S. Patent No. 3,516,946. Each of these patents relating to platinum or platinum- containing catalysts are hereby expressly incorporated herein by reference.

[0091] The relative amounts of rhodium-based catalyst to platinum-based catalyst may range from about 1 : 100 to about 10: 1.

[0092] In addition to the aforementioned catalysts, other catalysts may be used in combination with the rhodium and rhodium/platinum catalyst combinations. For example, complexes of ruthenium, palladium, oznium and arridium are also contemplated.

[0093] Other useful metallocenes which may be included in combination with the inventive catalyst system include ferrocenes (i.e., where M_e is Fe), such as ferrocene, vinyl ferrocenes, ferrocene derivatives, such as butyl ferrocenes or diarylphosphino metal-complexed ferrocenes [e.g., 1,1 -bis (diphenylphosphino) ferrocene-palladium dichloride], titanocenes (i.e., where M_e is Ti), such as bis(2-2,4-cyclopentadien-l-yl)-bis-[2,6-difluoro-3-(lH-pyrrol-l- yl)phenyl] titanium which is available commercially from Ciba Specialty Chemicals, Tarrytown, New York under the tradename "IRGACURE" 784DC, and combinations thereof. A particularly desirable metallocene is ferrocene.

[0094] And bis-alkylmetallocenes, for instance, bis-alkylferrocenes (such as diferrocenyl ethane, propanes, butanes and the like) are also desirable for use herein.

[0095] Other materials well-suited for use herein include M_e[CW₃-CO-CH=C(O^")-

CW₃]₂, where M_e is as defined above, and W and may be the same or different and may be selected from H, and halogens, such as F and Cl. Examples of such materials include platinum (II) acetylacetonate ("PtACAC"), cobalt (II) acetylacetonate ("Co(II)ACAC"), cobalt (III) acetylacetonate ("Co(III)ACAC"), nickel (II) acetylacetonate ("NiACAC"), iron (II) acetylacetonate ("Fe(II)ACAC"), iron (III) acetylacetonate ("Fe(III)ACAC"), chromium (II) acetylacetonate ("Cr(II)ACAC"), chromium (III) acetylacetonate ("Cr(III)ACAC"), manganese (II) acetylacetonate ("Mn(II)ACAC"), manganese (III) acetylacetonate ("Mn(III)ACAC") and copper (II) acetylacetonate ("CuACAC").

[0096] When the flowable matrix is a moisture-curing and/or photo-curing compound, suitable moisture catalysts and photoinitiators may be chosen. When the flowable matrix component cures through generation of a free radical, a number of well known initiators of free radical polymerization may be incorporated in the present invention. Among those particularly useful in conjunction with anaerobic curing monomers include, without limitation, hydroperoxides, such as cumene hydroperoxide (CHP), paramenthane hydroperoxide, tertiary butyl hydroperoxide (TBH) and tertiary butyl perbenzoate. While the useful amounts of peroxide compounds typically range from about 0.1 to about 10% by weight of the total composition, the present invention achieves its speed of cure when about 1% by weight of the peroxide is used along with a substantially equal amount of the reducing agent, e.g., saccharin. Thus, for the cure speed advantages discussed herein, the ratio of peroxide to peroxide reducing agent (e. g., saccharin) is desirably about 1:1, and the ratio of peroxide to accelerator is desirably about 2:1.

[0097] Useful accelerators for the anaerobic curing flowable matrix components of the present invention include compounds having the following formula:

O

R — N-N— C— R² I I H H

wherein R¹ is selected from alkyl from 2 to 6 carbon atoms, cycloalkyl, aryl, alkenyl, and cycloalkenyl and R² is selected from hydrogen, alkyl, cycloalkyl, alkenyl and cycloalkenyl, aryl, alkoxy, aryloxy, carbonyl, amino, and the following groups:

and

wherein R¹⁰ is selected from alkyl groups containing one to about 10 carbon atoms, alkenyl groups containing two to about 10 carbon atoms, and aryl groups containing up to about 10 carbon atoms. Examples of useful accelerator compounds include l-acetyl-2-phenyl hydrazine, l-acetyl-2(p-tolyl) para-toluene sulfonyl hydrazide, l-formyl-2-phenyl hydrazine and combinations thereof. As previously noted, the ratio of peroxide to accelerator is desirably about 2:1. While the amount of accelerator can be proportionately varied to the amount of peroxide present, to achieve the aforementioned desired physical properties of the anaerobic composition the accelerator is desirably present in about 0.5% by weight of the total composition.

[0098] Stabilizers and inhibitors may also be employed as well as chelating agents to control and prevent premature peroxide decomposition and polymerization. Among those useful inhibitors include phenols such as hydroquinone and quinones. Chelating agents may be used to remove trace amounts of metal contaminants. An example of a useful chelating agent is the tetrasodium salt of ethylenediamine tetraacetic acid (EDTA).

[0099] Other agents such as thickeners, plasticizers, fillers, elastomers, thermoplastics, and other well-known additives may be incorporated where functionally desirable.

[0100] Various conventional heat-activated curing agents for epoxies are useful in the present invention including imidazoles, preferably 2-ethyl-4-methyl imidazole, l-(2- cyanomethyl)-2-ethyl-a-4-methylimidazole and 2-phenyl-4,5-dihydroxymethyl imidazole; aliphatic cycloaliphatic amines, preferably 2,2'-dimethyl-4,4'-methylene-bis(cyclohexylamine) (Ancamine 2049); aromatic amines, preferably 4,4'-diaminodiphenyl sulfone (Ancamine S and Ancamine SP); a blend of aromatic and aliphatic amines (Ancamine 2038); Lewis Acid catalysts such as boron trifluoride: amine complexes, preferably BF₃:benzyl amine (Anchor 1907), BF₃:monoethyl amine (Anchor 1948) and liquid BF₃:amine complex (Anchor 1222); Lewis Base catalysts such as t-amines, preferably tris(dimethyl-aminomethyl)phenol (Ancamine K.54), dimethylaminomethyl phenol (Ancamine 1110); dicyandiamides, preferably dicyandiamide (Amicure CG). The Ancamine, Anchor, and Amicure series are tradenames for heat activated curing agents marketed by Pacific Anchor Performance Chemicals Division of Air Products and Chemicals, Inc.

[0101] Preparation of the inventive compositions can be made by adding the fluorosilane component to a pre-combined portion of the filler and flowable matrix component. Alternatively the filler and/or silane components can be added separately to the flowable matrix component and then mixed until uniform.

[0102] A fluorosilane/inorganic premix may also be made using dry blending, solvent or slurry techniques. In the first instance, where the fluorosilane is added to the filler component prior to addition to the flowable matrix component, this premixture is desirably allowed to undergo a conditioning time. For example, maintaining the fluorosilane/inorganic filler premix at a temperature of about 80°-100°C for about 8 to about 16 hours. Such conditioning, however, is distinct from conventional precoating of filler materials with hexamethyl disilazane which requires removal of by-product generally using a vacuum.

[0103] The compositions of the present invention have been found to be particularly useful as encapsulants for chip-on-board devices. Figure 2 shows a perspective view of a chip- on-board device. In this figure, substrate 10, also commonly referred to as a circuit board, is shown having a central area 12 for attaching a semi-conductor chip 14, also commonly referred to as a die. Electrical wires or leads 16 connect the circuit board to the semi-conductor chip 14 at connections 18 and 18a. The chip and wire connections are then encased or encapsulated with the inventive silicone composition, which is then subjected to relatively low heat to cure. The cured composition serves to protect the electronic components. This configuration is often referred to as a "glob top" application. [0104] Figure 3 is also a perspective view of a chip-on-board electronic device, with a configuration commonly referred to as a "dam and fill" application. The semi-conductor chip 14' is located on circuit board 10', which in turn are connected to each other by wire leads 16' at locations 18' and 18a'. A reservoir or dam area having walls 20 is shown about semi-conductor chip 14'. This dam area provides a volume in which the inventive composition can be applied or filled.

[0105] Referring now to Figure 4, the apparatus shown is a test device to demonstrate flowability of the inventive compositions. Using a glass base 22 as a platform, two aluminum spacers 26 and 26' are placed at each end of the glass base. These spacers were about 50 microns thick. A thin glass plate 24 is then placed over the spacers to create a flow path section 27. The inventive composition 30 is then placed at one end of the flow path and a dam 28 is positioned so that the composition may only flow in one direction, i.e. through the flow path 27 between the glass plates. The flow of the composition is measured as function of the distance traveled over time.

[0106] Figure 5 is a photograph of another measurement device for flowability. A mylar sheet having an X and Y axes (grid) with marked distances was used as the substrate. The mylar sheet was kept flat (parallel to the ground) and 5 ml of inventive Composition 1 was placed at the intersection of the X-Y axes. The flow of the composition was measured over time. Figure 5 represents the flow after one minute. Figure 6 is the same test composition after three minutes. As can be seen, the flow of the material has increased as shown by the distance traveled as evidenced by the larger surface area of the composition as it spread out.

[0107] In addition to the aforementioned semiconductor encapsulant applications, other electronic applications, such as the filling of gaps or the wicking of the silicone composition into voids are also contemplated.

[0108] The following non-limiting examples are intended to be illustrative of various embodiment of the present invention, but are not intended to restrict the scope of the invention. EXAMPLES

[0109] All viscosity (CPS) measurements, unless otherwise specified, were measured at ambient temperature (approximately 25°C), using a Haake C20/2 shear rate 0.5. Unless otherwise specified, all compositions were prepared by adding the flowable matrix, fluorosilane and inorganic filler as separate components.

Example 1

[0110] This example demonstrates the profound effect the inventive compositions have on viscosity as compared to compositions without the inclusion of the fluorosilane component.

[0111] The following Compositions 1-4 (Table 1) were prepared by combining the recited components in a mixer.

[0112] The vinyl terminated polydimethylsiloxanes (PDMS) components are representative of the flowable matrix components in accordance with the present invention; alumina is representative of the inorganic filler component; and trifluoropropyltrimethoxy silane component is representative of the fluorosilane component.

[0113] Compositions 1 and 3 are representative of invention compositions.

Compositions 2 and 4 are comparative examples which are substantially identical to the inventive Compositions, but without the fluorosilane component.

[0114] As shown in Table I, below, inventive Compositions 1 and 3 show substantially lower viscosity measurements (43, 670 cps and 92,920 cps) as compared to Compositions 2 and 4 (103, 200 and 612,900). These differences in viscosity are indeed remarkable, particularly in view of the fact that the only compositional differences relate to the addition of a minor amount of fluorosilane component. TABLE 1

Example 2

[0115] This example demonstrates the effect of different filler types in combination with the fluorosilane component in a silicone composition. Silica, carbon black, zinc oxide, spherical nickel, magnesium and calcium carbonate were each chosen as fillers for respective silicone compositions. Each composition included as the flowable matrix component, a combination of two vinyl terminated PDMS reactive polymers (5 gram, 8,500-10,500 cps and 1 gram, 150-250 CSt) and the recited amounts of filler and fluorosilane components shown in Table 2 below.

TABLE 2

Haake C20/2 Shear rate 0.5, cps

* in Vinyl terminated PDMS (8500-10500 cps) only

** Measurements determined to be problematic

*** Trifluoropropyltrimethoxysilane

1 Particle size approximately 300 nanometers

[0116] As indicated by Table 2, when each of silica, zinc oxide, aluminum nitride, boron nitride, non-spherical alumina C and spherical nickel powder provide fillers where incorporated in a reactive silicone (vinyl terminated PDMS) composition which contained a fluorosilane component, and subjected to viscosity measurements, the results showed a drastic reduction in viscosity as compared to the same composition without the fluorosilane.

[0117] This example also demonstrates that viscosity reductions are not obtained when either carbon black or calcium carbonate fillers are used in combination with the fluorosilane components in vinyl terminated PDMS flowable matrix component. Example 3

[0118] This example demonstrates inventive compositions which incorporate different flowable matrix components in combination with an alumina filler component and a fluorosilane component.

[0119] Table 3, below, shows the effect of the fluorosilane and inorganic filler components in combination on the viscosity of various flowable matrix components as compared to the same flowable matrix components with only the filler component. Diverse flowable matrix components were chosen to demonstrate the wide breadth and applicability of the invention. As the results indicate, viscosity reductions were remarkably lower, often more than 50% lower in the invention compositions regardless of the chosen flowable matrix component.

[0120] This example further demonstrates its operability on fluids such as uncurable mineral oil, in addition to curable (meth)acrylates, reactive silicones and epoxies.

Table 3

Haake C20/2 Shear rate 0.5, cps * Trifluoropropyltrimethoxy silane 0.15g **Alumina Filler

The results indicate that the fluorosilane can affect viscosity in non-silicone polymer systems. Example 4

[0121] Inventive compositions which included mineral oil as the flowable matrix component, spherical silica as the inorganic filler component and trifluoropropyltrimethoxysilane as the fluorosilane component were prepared as uniform mixtures in accordance with the present invention. Comparable compositions containing the identical amount and type of flowable matrix and filler components were also prepared. Viscosity measurements were then taken on each of the uniformly mixed compositions. The resultant viscosity of the invention compositions as compared to the same composition without the fluorosilane component are a magnitude of over 100 times lower.

Table 4

Viscosity Versus Fluorosilane Incorporation into Non- Alumina, Non- Silicone Polymer Systems

Flowable Matrix Without Fluorosilane With Fluorosilane Component*

Component /Inorganic Component 0.15 g

Filler Component (Composition) (Viscosity) (Composition) (Viscosity)

Mineral oil 5g/ 27 3,623,000 28 31,990 Spherical silica 20g*

Haake C20/2 Shear rate 0.5,cps *Tri fluoropropyltrimethoxysilane

Example 5

[0122] This example demonstrates the effect of the fluorosilane component on reactive silicone compositions which incorporate silica as the filler.

[0123] Compositions 29-32 were prepared by uniformly admixing each of the selected components. As shown in Table 5 below, Compositions 30 and 32 are representative of the inventive compositions. Compositions 29 and 31 represent identical compositions, but without the fluorosilane component. Viscosity measurements were taken on each of the compositions and the results are indicated in Table 5. The inventive compositions exhibited viscosities of 120,150 cps (Composition 30) and 203,050 cps (Composition 32) as compared to Compositions 29 and 31 (1,024,00 cps and 1,797,000, respectively). Table 5

Haake C20/2 Shear rate 0.5, cps

Example 6

[0124] This example demonstrates that when a fluorosilane component is added to a flowable matrix component without the incorporation of an inorganic filler component, only a slight reduction in viscosity occurs. However, this reduction in the base flowable matrix component is negligible as compared to the inventive compositions which can include extremely high amounts of the inorganic filler component. This example, demonstrates therefore, the significance of the combination of the inorganic filler component and the fluorosilane component for the reduction of viscosity, and the resultant controlled flow of the overall composition. It should be noted that the relative amounts of fluorosilane component and flowable matrix component used in this example are comparable to the amounts shown in the inventive compositions in prior examples.

Table 6

*TFPTMS is an abbreviation for trifluoropropyltrimethoxysilane.

Example 7

[0125] This example demonstrates the effect of the inventive compositions on CTE values as a function of increased filler loading. Inventive reactive silicone compositions containing the fluorosilane component and various amounts of spherical alumina were prepared by combining each of the components in admixture until a uniform mixture is achieved.

[0126] These inventive compositions 41-51 are set forth in Table 7 below.

[0127] The compositions were cured and CTE measurements were taken on each of the following two instruments:

l.)ψ Measured on a thermal analysis (TA) instrument (Thermal Analysis Instrument Company, New Castle, DE, with an expansion probe and a 5mN load. Temperature program form -100°C to 150°C at 10°C/min.

2.)d Measured on Perkin Elmer DMA 7e used in TMA (static) mode with an expansion probe, helium purge and a lOmN load. Temperature program from -50°C at 10°C/min. These measurements were based on ASTM E831 and El 545 standard test methods for measuring coefficients of linear expansion and glass transition temperatures. [0128] The results, as shown in Figure 1, show a remarkable decrease in CTE as the filler content increased. It is significant that these reductions in CTE were obtained while concurrently controlling the viscosity and resultant flowability of the overall compositions.

Table 7

The thermal conductivity of Composition 51 (70g filler) when cured was measured to be 2.4Wm/K.

Example 8

[0129] The following table demonstrates the effect of several surface modifiers used in an amount of 0.15g on the viscosity of a base composition containing 20g spherical alumina (AO-809), and 5g divinyl polydimethylsiloxane (8,500-10,500 cps):

Table 8

[0130] As indicated in Table 8, many of the conventional non-fluorinated silanes, such as various non-fluorinated alkoxy silanes, significantly increased the viscosity of the alumina/PDMS base composition, as opposed to decreasing it. In some cases, this increase is 10- 20 times greater than the same composition without the alkoxy silane. In contrast, addition of the same amount of fluorosilane brought the viscosity of the base composition from 114,250 cps to 29,535 cps in the case of TFPTMS and to 74,060 cps in the case of TDFOTES. Example 9

[0131] Table 9 illustrates the viscosity lowering effect of trifluoropropyltrimethoxysilane

(0.15g) on a base composition containing 30g alumina (AO-809) and 5g divinyl PDMS 8,500- 10,500 cps:

Table 9

As indicated in Table 9, the addition of the fluorosilane component to the inorganic filler and flowable matrix base composition lowered the viscosity 7.5 times.

Example 10

[0132] Table 10 demonstrates the impact of several different fillers on reactive silicone di(vinyl) PDMS compositions (5g):

The above table confirms that:

• Spherical particles increase viscosity less than irregular shaped particles

• Alumina appears to afford lower viscosity than silica

• Below 1 micron particle size impacts more on viscosity than larger particle sizes Example 11

[0133] This example demonstrates the impact of different inorganic fillers and amounts of these fillers upon the viscosity of the composition. Inventive Compositions 76, 78,80, 82 and 84 all exhibited remarkable viscosity reductions as compared to the same compositions without the fluorosilane component.

Table 11

Tetrafluoropropyltrimethoxysilane ² acetylacetonato (dicarbonyl) rhodium cps (Haacke C20/2 1/s = = 0.5)

Claims

WHAT IS CLAIMED IS:

1. A composition comprising: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; and c) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure.

2. The composition of claim 1 wherein said composition when solidified or cured exhibits controlled CTE and/or improved conductivity.

3. The composition of claim 1, wherein said filler inorganic component is selected from the group consisting of aluminum, zinc, nickel, copper, boron, silica, their oxides and nitrides and combinations thereof.

4. The composition of claim 1, wherein the filler is spherical.

5. The composition of claim 1, wherein the fluorosilane is selected from the group consisting of trifluoropropyltrimethoxysilane, trifluoropropyldimethoxymethylsilane, pentafluorophenyl-propyltrimethoxysilane, heptadecafluoro 1 ,2,2-tetra- hydrodecyltriethoxysilane and combinations thereof.

6. The composition of claim 1, wherein said flowable matrix component is selected from the group consisting of silicones, (meth)acrylates, epoxies, polyesters, polyethers, cyanoacrylates, urethanes, latexes and combinations thereof.

7. The composition of claim 1, wherein said flowable matrix component is crosslinkable.

8. The composition of claim 7, wherein said flowable matrix component comprises a silicone.

9. The composition of claim 1, wherein said flowable matrix component comprises a thermoset material.

10. The composition of claim 1, wherein said flowable matrix component comprises a thermoplastic material.

11. The composition of claim 1 , wherein said flowable matrix component comprises a latex material.

12. The composition of claim 1, wherein said composition is thermally or electrically conductive.

13. The composition of claim 1, wherein said filler component is present in amounts of about 1 to about 95.

14. The composition of claim 1, wherein said filler has a particle size of about O.lμ to about lOOμ.

15. The composition of claim 1, wherein said fluorosilane is present in amounts of about 0.01% to about 10% by weight.

16. The composition of claim 1, wherein said fluorosilane and filler components are present in amounts sufficient to achieve a lower CTE of the polymer component in the solidified or cured state without a substantial increase in viscosity.

17. The composition of claim 1, wherein said fluorosilane and filler components are present in amounts sufficient to achieve (i) a decrease in viscosity of the composition in the unsolidified or uncured state; and (ii) in the solidified or cured state a property selected from the group consisting of lower CTE, improved conductivity and combinations thereof.

18. A composition comprising: a) a flowable matrix component which can be solidified or cured; and b) a rheology modifying composition comprising a fluorosilane component and an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof, said rheology modifying composition providing controlled flowability to said flowable matrix and controlled CTE and/or improved conductivity to the solidified or cured polymer composition.

19. A composition having controlled flowability, comprising: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; c) a filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure and controlled CTE and/or improved conductivity subsequent to solidification or cure; and d) an agent which aids in solidification or cure of said matrix component; wherein the reaction product of the recited components exhibits a lower CTE as compared to the reaction products in the absence of components b) and c).

20. A sealant, coating or gap-filling composition comprising: a) a curable polymer component; b) a fluorosilane component; c) a metal filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; d) a curing agent; wherein the reaction product of a), b) and c) lowers the CTE and/or provides improved conductivity of the curable polymer component.

21. The product formed from a composition comprising: a) a flowable matrix component which can be solidified or cured; b) a fluorosilane component; and c) a filler component selected from the group consisting of metals, metal oxides, silicas and combinations thereof; wherein the product exhibits controlled flowability prior to solidification or cure and lower CTE and/or improved conductivity subsequent to solidification or cure as compared to the polymer component without components b) and c).

22. A method of controlling the flowability of a fluid carrier composition comprising the steps of: a) providing a fluid carrier composition; and b) combining said fluid carrier composition with a flow-control composition comprising a fluorosilane and filler components selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof, said flow-control composition being present in amounts selected to effectuate the desired amount of flowability.

23. A fluid carrier composition having controlled flowability comprising: a) a fluid carrier component; b) a fluorosilane component; and c) a filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof.

24. A method of providing controlled flowability to a viscous, substantially non-flowable carrier fluid comprising the step of admixing into said carrier fluid a composition comprising: a) a fluorosilane component; and b) a component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof.

25. A composition useful for providing controlled flowability to a fluid carrier comprising: a) a fluorosilane component; and b) a component selected from the group consisting of metals, metal nitrides, metal oxides, silicas and combinations thereof.

26. A composition which imparts a controlled CTE and/or improved conductivity to a polymer which has been solidified or cured, said composition comprising: a) a fluorosilane component; and b) a component selected from the group consisting of metals, metal oxides, silicas and combinations thereof.

27. A method of increasing the amount of filler in a flowable composition while retaining flowability comprising the step of incorporation into said flowable composition a fluorosilane component and a filler member selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof.

28. A composition comprising: a) a flowable reactive silicone component which can be solidified or cured; b) a fluorosilane component; and c) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure.

29. The composition of claim 28, wherein said composition when solidified or cured exhibits controlled CTE and/or improved conductivity.

30. The composition of claim 28, wherein said filler component is selected from the group consisting of aluminum, zinc, nickel, copper, boron and combinations and oxides thereof.

31. The composition of claim 28, wherein the filler is spherical.

32. The composition of claim 28, wherein the fluorosilane is selected from the group consisting of trifluoropropyltrimethoxysilane, pentafluorophenyl-propyltrimethoxysilane, heptadecafluoro 1,2,2-tetra-hydrodecyltriethoxysilane and combinations thereof.

33. The composition of claim 28, wherein said composition is thermally or electrically conductive.

34. A composition useful as an additive for controlling the flowability of a flowable material comprising: a) a fluorosilane component; and b) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof.

35. An electronic assembly comprising:

(a) a chip-on-board component;

(b) a composition having controlled flowability and which serves as an underfill for and/or sealant around component (a), said composition comprising:

(i) a flowable matrix component which can be solidified or cured;

(ii) a fluorosilane component; and

(iii) an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof; wherein the composition exhibits controlled flowability prior to solidification or cure.

36. A rheology modifying composition comprising a fluorosilane component and an inorganic filler component selected from the group consisting of metals, metal oxides, metal nitrides, silicas and combinations thereof, said rheology modifying composition providing controlled flowability to said flowable matrix and controlled CTE and/or improved conductivity to the solidified or cured polymer composition.