Thermally conductive silicone adhesive

Abstract

A thermally conductive silicone adhesive exhibiting both high thermal conductivity and high adhesive strength. This silicone adhesive is prepared from a curable composition comprising a reactive organosiloxane and thermally conductive particulate filler. This silicone adhesive can be used to dissipate excess heat in electronic packages.

Description

Technical Field

[0001] The present invention generally relates to thermally conductive adhesives for electronic components, and more specifically to curable silicone-based adhesives exhibiting high thermal conductivity and high adhesive strength. Background Technology

[0002] As electronic devices, such as semiconductors, are manufactured with increasing complexity and power density, there is a constant need for advancements in thermal management solutions. Typical thermal management solutions in electronic packages involve: thermally conductive sheets or pads pre-formed in a given shape and thickness; greases used as gap fillers; phase change polymers; in-situ molding materials; and adhesives that can be cured to create adhesion at the substrate interface. In all cases, thermal management solutions are positioned along a heat dissipation path to facilitate heat transfer originating from the heat-generating electronic components.

[0003] Thermal pads or heat spreaders can have relatively high thermal conductivity values ​​exceeding 2 W / m*K, but are limited by their pre-formed shape and thickness. For example, positioning a thermal pad along a heat dissipation path typically requires compressive loads on adjacent surfaces placed on either side of the pad. The loads required to achieve good contact between the adjacent surfaces and the thermal pad can damage electronic components and their connections.

[0004] Thermal grease has good contact properties and requires low to no load application to place it along the heat dissipation path. However, thermal grease is generally characterized as "tricky" and can be difficult to apply due to its high viscosity. During use, thermal grease also tends to flow out of its intended location due to compressive forces and elevated operating temperatures (which reduce shape stability). This can contaminate adjacent parts and also reduce the efficiency of heat transfer at the interface. Efforts to improve the surface adhesion and shape stability of thermal grease have had limited success, partly due to aging issues such as reduced elongation at break with operating time.

[0005] While some conventional thermally conductive materials exhibit high thermal conductivity, those that do tend to exhibit insufficient bond strength. For example, delamination can occur between the thermally conductive material and the heat-generating electronic components or heat sink, resulting in increased thermal resistance.

[0006] Thermally conductive adhesives can provide excellent mechanical bond strength and long-term reliability. However, thermal conductivity is often a sacrifice for adhesive strength, with high thermal conductivity values ​​in adhesives typically requiring high filler loading levels, which tend to harden the material and reduce bond strength. Despite efforts to improve both thermal conductivity and bond strength in a single solution, known adhesives have failed to achieve a combination of high thermal conductivity (>3 W / m*K) and high bond strength (>3 MPa). Data from the Dow literature demonstrate the difficulty of providing a curable thermally conductive silicone adhesive with both the desired thermal conductivity and bond strength.

[0007] Dow literature shows an inverse relationship between thermal conductivity and adhesive strength, where compositions with high thermal conductivity have low strength, while compositions with high strength have low thermal conductivity.

[0008] Therefore, there is a need for thermally conductive adhesive compositions that effectively bridge the large coefficient of thermal expansion (CTE) mismatch between surfaces along the heat dissipation path, while also exhibiting a high thermal conductivity of over 3 W / m*K.

[0009] The purpose of this invention is to provide a thermally conductive adhesive that exhibits improved stress and thermal management and can be applied in a variety of industries.

[0010] Another object of the present invention is to provide a curable silicone composition for preparing a thermally conductive silicone adhesive, the thermally conductive silicone adhesive having good thermal conductivity (>3 W / m*K) and adhesive strength (>3 MPa) for use in thermal management applications requiring stress buffering. Summary of the Invention

[0011] With the aid of this invention, components can be securely fixed within assemblies that facilitate efficient heat dissipation. Therefore, heat-generating components (such as electronic devices) can be encapsulated together with heat sinks that offer high durability and efficient heat transfer to excess heat. The encapsulation is assembled using the thermally conductive adhesive of this invention, which exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

[0012] In one embodiment, the curable composition for preparing a thermally conductive adhesive comprises an organosiloxane preparation comprising a first reactive organosiloxane having at least one unsaturated group and a second reactive organosiloxane comprising at least one silicon hydride functional group and at least one alkenyl group. In addition to the organosiloxane preparation, the curable composition further comprises an organosiloxane comprising an average of at least two silicon-bonded hydrogen atoms per molecule, in an amount sufficient to effectively cure the composition. The curable composition further comprises thermally conductive particulate fillers, such that the thermally conductive adhesive exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

[0013] In some embodiments, the first organosiloxane contains at least about one alkenyl group per molecule on average. In some embodiments, the first organosiloxane may contain at least 1.05 alkenyl groups per molecule on average.

[0014] In some implementations, the thermally conductive particulate filler may be selected from metals such as nickel, copper, silver, gold, palladium, platinum, and mixtures and alloys thereof.

[0015] In some embodiments, the curable composition may include an adhesion promoter selected from organosilanes, organotitanates, and combinations thereof.

[0016] The catalyst may be present in a catalytic amount to promote the curing of the composition. In some embodiments, the catalyst may be selected from hydrosilylation catalysts, including platinum-based catalysts, ruthenium-based catalysts, palladium-based catalysts, osmium-based catalysts, iridium-based catalysts, titanium-based catalysts, and rhodium-based catalysts.

[0017] In some embodiments, a reaction inhibitor may be included to inhibit the hydrosilylation reaction of the curable composition. The reaction inhibitor may be selected from alkynyl alcohols, fumarate compounds, maleate compounds, and combinations thereof.

[0018] Curable compositions may be provided as one-component (1K) compositions or multi-component (2K) compositions. The one-component (1K) composition comprises all components in a single, commercially store-stable composition. The multi-component (2K) composition comprises a first portion and a second portion or more portions initially separate from the first portion, wherein the first portion does not contain organosiloxanes having an average of at least two silicon-bonded hydrogen atoms per molecule. In the multi-component composition, the portions are mixed immediately before use, and the mixture is not commercially store-stable.

[0019] In some implementations, the first organosiloxane may have the following formula: R1 a SiO (4-a) / 2 Where: each R 1 It is an alkenyl group or a hydrocarbon having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95.

[0020] In some embodiments, the first organosiloxane contains at least two unsaturated groups per molecule. The first organosiloxane can be [dissolved] at 25°C and 1 s [in a specific temperature range]. -1 It exhibits a viscosity ranging from 0.1 to 100,000 cP at various shear rates.

[0021] The second organosiloxane can have the following formula: R 2 a SiO (4-a) / 2 Where: each R 2 It is one of hydrogen, alkenyl, or hydrocarbons having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95.

[0022] The second organosiloxane can be used at 25°C and 1 second. -1 It exhibits a viscosity ranging from 0.1 to 100,000 cP at various shear rates.

[0023] In another embodiment, the thermally conductive adhesive comprises the reaction products of the following substances: (A) An organosiloxane formulation, said organosiloxane formulation comprising: (i) a first reactive organosiloxane having at least one reactive unsaturated group; and (ii) a second reactive organosiloxane comprising at least one hydride functional group and at least one alkenyl group; and (B) Organosiloxanes containing at least two silicon-bonded hydrogen atoms per molecule on average.

[0024] At least one of components (A) and (B) may contain thermally conductive particulate fillers, such that the thermally conductive adhesive exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

[0025] In some multi-part implementations, component (A) and component (B) may initially be separate.

[0026] The package of the present invention may include electronic components and a thermally conductive adhesive adhered to said electronic components. The thermally conductive adhesive may include components (A) and (B) above, as well as thermally conductive particulate filler. The package may also include a heat sink, wherein the thermally conductive adhesive may be adhered between the electronic components and the heat sink.

[0027] The method for manufacturing a package according to the present invention includes providing a composition having: (i) A first reactive organosiloxane comprising at least about one alkenyl group per molecule on average, and a second reactive organosiloxane comprising at least about one hydride functional group and at least about one alkenyl group; (ii) Unsaturated organosiloxanes; and Thermally conductive particulate filler in at least one of (iii), (i), or (ii).

[0028] The method further includes dispensing the composition onto the surface of at least one of a heat sink and an electronic component, and optionally reacting the first portion with the second portion in the presence of a catalytic amount of catalyst.

[0029] The electronic components can then be fixed to the heat sink using a composition arranged along a heat dissipation path originating from the electronic components.

[0030] In some embodiments, the method further includes curing the composition by exposing it to a temperature of up to 300°C for a curing period. In some embodiments, the curing period is less than 2 hours. Attached Figure Description

[0031] Figure 1 This is a cross-sectional view of the electronic package of the present invention. Detailed Implementation

[0032] The objects and advantages listed above, as well as other objects, features, and advancements described in this invention, will now be described with reference to detailed embodiments. However, other embodiments and aspects of this invention are considered to be within the knowledge of those skilled in the art.

[0033] In general, thermally conductive adhesives can be prepared from curable compositions comprising the following components: (A) Organosiloxanes having at least about one alkenyl group per molecule on average; (B) An organosiloxane having at least one hydride functional group and at least one alkenyl group; (C) Organosiloxanes containing at least two silicon-bonded hydrogen atoms per molecule; (D) Thermally conductive filler; (E) Hydrosilylation catalyst; and (F) Optional additional components.

[0034] In some embodiments, the curable composition can be cured at temperatures up to 300°C for a curing period. In some embodiments, the curing period is less than 2 hours. The cured thermally conductive adhesive can exhibit a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

[0035] Component A In the implementation scheme, component (A) has the following formula: R 1 a SiO (4-a) / 2 Where: each R 1 It is an alkenyl group or a hydrocarbon having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95. “a” can be an integer, however, for branched molecules, “a” can have a decimal (non-integer) value.

[0036] R 1 Examples of alkenyl groups or hydrocarbons having 1 to 60 carbon atoms, 2 to 50 carbon atoms in some embodiments, and 2 to 20 carbon atoms in some embodiments include: alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and haloalkyl groups such as 3,3,3-trifluoropropyl. The alkenyl group may be bonded to silicon atoms present at the ends of the molecular chain and / or to silicon atoms present on the portion of the molecular chain other than at the ends.

[0037] Component A can have a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a three-dimensional network structure, such as an organosilicon resin having functional siloxane monomer units selected from Me3SiO, MeSiO3, SiO4, and combinations thereof. In an example, a linear diorganopolysiloxane has a backbone having repeating diorganosiloxane units, and both molecular chain ends are capped with triorganosiloxy groups.

[0038] Component A may be a polyorganosiloxane having an average of at least two aliphatic unsaturated organic groups per molecule, said aliphatic unsaturated organic groups being capable of hydrosilylation with silicon-bonded hydrogen atoms of components B and / or C. In some embodiments, component A comprises at least two reactive alkenyl groups, at least two reactive alkynyl groups, or at least one reactive alkenyl group and at least one reactive alkynyl group. In other embodiments, component A comprises at least one reactive unsaturated group and at least one silicon-bonded hydrogen atom. In some embodiments, component A comprises at least two reactive unsaturated groups and at least one silicon-bonded hydrogen atom.

[0039] Component (A) may have a viscosity of about 2 cps to 9,000,000 cps. In some embodiments, component (A) may have a viscosity of about 10 cps to 100,000 cps. In some embodiments, component (A) may have a viscosity of about 10 cps to 10,000 cps.

[0040] In some embodiments, component A may include polydiorganosiloxanes, such as dimethylvinylsiloxane-terminated polydimethylsiloxane; dimethylvinylsiloxane-terminated poly(dimethylsiloxane / methylvinylsiloxane); dimethylvinylsiloxane-terminated polymethylvinylsiloxane; trimethylsiloxane-terminated poly(dimethylsiloxane / methylvinylsiloxane), vinyl-terminated (phenylmethylsiloxane)vinylphenylsiloxane copolymer, vinyl-terminated (diphenylsiloxane)dimethylsiloxane copolymer, vinyl-terminated (diphenylsiloxane)-dimethylsiloxane copolymer, (phenylmethylsiloxane)vinylphenylsiloxane copolymer, (phenylmethylsiloxane)vinylmethylsiloxane copolymer, and combinations thereof.

[0041] Component B In the implementation scheme, component (B) has the following formula: R 2 a SiO (4-a) / 2 Where: each R 2 It is one of hydrogen, alkenyl, or hydrocarbons having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95. “a” can be an integer, however, for branched molecules, “a” can have a decimal (non-integer) value.

[0042] R 2Examples of alkenyl groups or hydrocarbons having 1 to 60 carbon atoms, 2 to 50 carbon atoms in some embodiments, and 2 to 20 carbon atoms in some embodiments include: alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; alkenyl groups such as vinyl and allyl; aryl groups such as tolyl; aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl; and haloalkyl groups such as 3,3,3-trifluoropropyl. The alkenyl group may be bonded to silicon atoms present at the ends of the molecular chain and / or to silicon atoms present on the portion of the molecular chain other than at the ends. Component B may have a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a three-dimensional network structure, such as organosilicon resins having functional siloxane monomer units selected from Me3SiO, MeSiO3, SiO4, and combinations thereof. In the example, the linear diorganopolysiloxane has a main chain having repeating diorganosiloxane units, and the ends of the two molecular chains are capped with triorganosiloxy groups.

[0043] Component B may be a polyorganosiloxane having, on average, at least one reactive hydride and at least one alkenyl group per molecule. In some embodiments, each molecule of component B contains at least one silicon-bonded hydrogen atom and at least one reactive unsaturated group. In some embodiments, each molecule of component B contains at least one silicon-bonded hydrogen atom and at least two reactive unsaturated groups. Typically, the alkenyl group is located at the terminal position of the molecule, and the hydride group may be terminal or side-mounted.

[0044] Component (B) may have a viscosity of about 2 cps to 9,000,000 cps. In some embodiments, component (B) may have a viscosity of about 10 cps to 100,000 cps. In some embodiments, component (B) may have a viscosity of about 10 cps to 10,000 cps.

[0045] Component C In the implementation scheme, component (C) has the following formula: R 3 a SiO (4-a) / 2 Where: each R 3 It is one of hydrogen or a hydrocarbon having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95. “a” can be an integer, however, for branched molecules, “a” can have a decimal (non-integer) value.

[0046] R 3Examples of hydrocarbons having 1 to 60 carbon atoms, 2 to 50 carbon atoms in some embodiments, and 2 to 20 carbon atoms in some embodiments include: alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, phenyl, dodecyl, tetradecyl, hexadecyl, and octadecyl; and cycloalkyl groups such as cyclopentyl and cyclohexyl.

[0047] Component C can have a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a three-dimensional network structure, such as organosilicon resins having functional siloxane monomer units selected from Me3SiO, MeSiO3, SiO4, and combinations thereof. In an example, a linear diorganopolysiloxane has a backbone having repeating diorganosiloxane units, and the ends of both molecular chains are capped with triorganosiloxy groups.

[0048] Component C may be a polyorganosiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule, typically 2 to 300 silicon-bonded hydrogen atoms, and preferably 2 to 100 silicon-bonded hydrogen atoms. The hydrogen atoms in component C may be bonded to silicon atoms present at the ends of the molecular chain and / or to silicon atoms present in the portion of the molecular chain other than at the ends.

[0049] Organic groups other than hydrogen atoms can also be bonded to silicon atoms. Examples of such organic groups include: alkyl groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl; aryl groups, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups, such as benzyl and phenethyl; and haloalkyl groups, such as chloromethyl.

[0050] In some embodiments, components A, B, and C together are present in an amount of 1% to 50% by weight of the curable composition. In some embodiments, components A, B, and C together are present in an amount of 2% to 30% by weight of the curable composition. In some embodiments, components A, B, and C together are present in an amount of 5% to 20% by weight of the curable composition. In some embodiments, components A, B, and C together are present in an amount of 10% to 15% by weight of the curable composition.

[0051] In some embodiments, component C is present in an amount of 0.5% to 99.5% relative to the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount of 0.5% to 50% relative to the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount of 0.5% to 10% relative to the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount of 1% to 5% relative to the total amount of components A, B, and C together in the curable composition.

[0052] In some embodiments, the reaction products of the silicone resins of components A, B, and C are thermosetting. In some embodiments, thermosetting is a hydrolysis-polymerization reaction at a temperature of up to 300°C. Therefore, the electronic device of the encapsulation of the present invention can be adhered to the substrate at a temperature of 300°C or lower.

[0053] In some embodiments, the ratio of silicon-bonded hydrogen atoms to vinyl groups in the curable composition is from 0.1:1 to 100:1. In some embodiments, the ratio is from 0.5:1 to 50:1. In some embodiments, the ratio is from 1:1 to 10:1. In some embodiments, the ratio is from 1.2:1 to 5:1.

[0054] Component D Component (D) is a particulate packing with a thermal conductivity of not less than 10 W / m*K, preferably at least 20 W / m*K. In some embodiments, the average particle size (d) of the particulate packing is... 50 The average particle size (d) of the particulate filler ranges from 0.1 μm to 250 μm. In some embodiments, the average particle size (d) of the particulate filler is... 50 The average particle size (d) of the particulate filler ranges from 0.1 μm to 100 μm. In some embodiments, the average particle size (d) of the particulate filler is... 50 The particle size ranges from 0.2 μm to 100 μm. In some embodiments, the distribution of the thermally conductive particulate filler is not monodisperse but rather a particle size distribution. In some embodiments, the particle size distribution is multimodal, comprising a mixture of relatively small and relatively large particles within the aforementioned size range. For the purposes of this document, the term "average particle size" refers to the cumulative weight average (d). 50 The particle size distribution is such that 50% of the particles are larger than this value and 50% are smaller than this value, as determined by laser diffraction. Component D can be dispersed in a polymer matrix and can be conductive or electrically insulating depending on the application requirements. Examples of thermally conductive particulate fillers include particles or powders of the following substances: nickel, copper, silver, gold, platinum, palladium, aluminum, diamond, carbon, indium, gallium, zinc oxide, titanium oxide, magnesium oxide, aluminum oxide, aluminum hydroxide, boron nitride, aluminum nitride, and mixtures and alloys thereof. In some embodiments, the particulate filler can be conductive by having at least a metallic outer surface, said metal being selected from nickel, copper, silver, gold, platinum, palladium, and alloys thereof. The shape of the particulate filler can be spherical, non-spherical, or a combination thereof. Exemplary non-spherical shapes include sheets, plates, rods, etc. Spherical particulate fillers can have an aspect ratio of 0.8 to 1.2.

[0055] The presence of thermally conductive particulate filler is sufficient to provide the adhesive with high thermal conductivity. In some embodiments, the adhesive exhibits a thermal conductivity of at least 3 W / m*K. In some embodiments, the adhesive exhibits a thermal conductivity of at least 5 W / m*K. In some embodiments, the adhesive exhibits a thermal conductivity of at least 7 W / m*K. In some embodiments, the adhesive exhibits a thermal conductivity of at least 9 W / m*K.

[0056] To achieve the high thermal conductivity value of this invention, the thermally conductive particulate filler may be present in an amount of at least 80% by weight of the binder. In some embodiments, the thermally conductive filler may be present in an amount of 80% to 95% by weight of the binder. In some embodiments, the thermally conductive filler may be present in an amount of 85% to 95% by weight of the binder.

[0057] If necessary, component D can also be hydrophobized with, for example, organosilanes, organozanes, organopolysiloxanes, and organofluorine compounds.

[0058] Component E Component (E) is a catalyst that effectively catalyzes the hydrosilylation reaction. The catalyst for component E can be selected from platinum-based, ruthenium-based, palladium-based, osmium-based, iridium-based, titanium-based, and rhodium-based catalysts. In some embodiments, the compositions of the present invention can be converted into curable compositions in the presence of the catalyst of component E. However, it is contemplated that the curable compositions of the present invention do not require component E to carry out the reaction.

[0059] In the compositions of the present invention, component E is present in an amount required to cure the composition, said amount being referred to as the catalytic amount. In some embodiments, the amount of component E present may be from 0.1 to 1000 ppm by mass of the organosiloxane. In some embodiments, the amount of component E present may be from 0.1 to 500 ppm by mass of the organosiloxane. In some embodiments, the amount of component E present may be from 0.1 to 100 ppm by mass of the organosiloxane. In some embodiments, the amount of component E present may be from 1 to 50 ppm by mass of the organosiloxane. In some embodiments, the amount of component E present may be from 15 to 35 ppm by mass of the organosiloxane.

[0060] To control the curing rate of the compositions of the present invention, a curing reaction inhibitor may be included in the curable composition. Inhibitors that can be used in the present invention include hydrosilylation inhibitors, such as acetylene-based compounds (including alkynols), fumarate-based compounds, and maleate-based compounds. Although there is no limitation on the amount of curing reaction inhibitor used in the compositions of the present invention, exemplary amounts include 2 to 20,000 ppm by mass of organosiloxane. In some embodiments, the amount of curing reaction inhibitor present is 20 to 5,000 ppm by mass of organosiloxane. In some embodiments, the amount of curing reaction inhibitor present in the compositions of the present invention is 300 to 3,500 ppm by mass of organosiloxane.

[0061] In some embodiments, the mass ratio of the curing reaction inhibitor to the reaction catalyst can be from 10:1 to 500:1. In some embodiments, the mass ratio of the curing reaction inhibitor to the reaction catalyst can be from 20:1 to 200:1. In some embodiments, the mass ratio of the curing reaction inhibitor to the reaction catalyst can be from 35:1 to 100:1.

[0062] The thermally conductive composition of the present invention may further comprise one or more additional components, such as adhesion promoters, silicone diluents, reactive diluents, colorants, corrosion inhibitors, acid acceptors, silica black, glass beads, metal particles, and combinations thereof. In some embodiments, the presence of one or more adhesion promoters can effectively establish a chemical bond at the interface between the thermally conductive adhesive and the substrate to be adhered. The adhesion promoter may be present in the composition of the present invention in an amount of 0 to 5% by weight. In some embodiments, the presence of the adhesion promoter is 0 to 2% by weight of the composition. In some embodiments, the presence of the adhesion promoter is 0.1% to 0.5% by weight of the composition.

[0063] Examples of suitable adhesion promoters include organosilanes, including: monosilanes; dipodal silanes; tripopodal silanes; and oligomeric silanes having methoxy, ethoxy, and / or propoxy structures. Exemplary alkoxysilanes are epoxy-functionalized alkoxysilanes. Other suitable adhesion promoters include organotitanates and mercapto-functionalized compounds.

[0064] In some embodiments, a solvent may optionally be used. Preferably, the composition is solvent-free (such as an organic solvent) to minimize the content of volatile organic compounds (VOCs).

[0065] The thermally conductive compositions of the present invention can be used after curing. In some embodiments, the thermally conductive compositions of the present invention can be cured at a temperature of about room temperature to about 300°C. In some embodiments, the thermally conductive compositions of the present invention can be cured by heating to a temperature of about 70°C to about 200°C. In some embodiments, the thermally conductive compositions of the present invention can be cured by heating to a temperature of about 125°C to 190°C.

[0066] The curing time can be at least one minute. In some embodiments, the curing time is less than 250 minutes. In some embodiments, the curing time is 1 to 200 minutes. In some embodiments, the curing time is 1 to 150 minutes.

[0067] The curable compositions of the present invention can be provided as single-component (1K) compositions or multi-component compositions (which include components in two or more portions, provided that components B, C, and E are not present in the same portion). For single-component compositions, the components are mixed with sufficient reaction inhibitors to give the resulting composition a commercially acceptable shelf life of several weeks to a year or more while remaining usable. For multi-component compositions, component E cannot be present in the same portion as component B or component C. Typically, in multi-component compositions, any catalyst is present in the alkenylsilane component and is separate from any hydride component.

[0068] The curable silicone compositions of the present invention exhibit tunable rheological properties and curing kinetics adapted to different processes in encapsulation applications, as well as low volatile organic compound (VOC) content. Furthermore, the silicone compositions of the present invention can be cured to form silicone adhesives that combine excellent adhesion and thermal conductivity (and optionally electrical conductivity), as well as good reliability. Additionally, the silicone compositions of the present invention can be cured to form silicone adhesives that exhibit excellent stress management by buffering differences in the coefficients of thermal expansion of the adhered portions, and a substantially void-free adhesive layer.

[0069] The cured adhesive of the present invention preferably exhibits an adhesive strength of at least 3 MPa. In some embodiments, the cured adhesive exhibits an adhesive strength of at least 5 MPa. In some embodiments, the cured adhesive exhibits an adhesive strength of at least 10 MPa. In some embodiments, the cured adhesive exhibits an adhesive strength of at least 20 MPa. The adhesive strength of the adhesive of the present invention is measured by a die shear test. In some embodiments, the die shear test can be performed using Mil-Std-883 method 2019.

[0070] The silicone compositions of the present invention can be used to prepare thermally conductive adhesives, which can be used in a variety of applications (such as thermal interface materials in semiconductor packaging, die attach adhesives, and solder alternatives). In specific embodiments, the adhesives of the present invention can be used to bond electronic components to flexible or rigid substrates, particularly sandwiched between the surface of a heat-generating electronic component and a heat sink.

[0071] Figure 1 The package 10 of the present invention is schematically illustrated. The package 10 includes: a substrate 12, such as a printed circuit board; an electronic component 14, such as a semiconductor, processor, etc.; a thermally conductive adhesive 16; and a heat sink 18, such as a heat sink or cover. The thermally conductive adhesive 16 is adhered between the electronic component 14 and the heat sink 18. In some embodiments, the thermally conductive adhesive 16 can adhere the heat sink 18 to the electronic component 14.

[0072] In one embodiment, the curable composition of the present invention is dispensed onto the surface of at least one of electronic component 14 and heat sink 18, and electronic component 14 is secured to the heat sink such that the composition is disposed along a heat dissipation path originating from electronic component 14. In some embodiments, the encapsulation 10 is formed by curing the composition for a curing time to produce a cured adhesive exhibiting shape-stable product. The composition can be cured by exposing it to a temperature of up to 300°C for a curing period of less than 2 hours.

[0073] Example The following test methods are used in the examples.

[0074] Viscosity was measured using a parallel plate viscometer at 5 rpm and room temperature.

[0075] The bond strength of silicon wafers and nickel-plated copper substrates was measured at both room temperature and high temperature (260°C) using the Dage Series 4000 wafer shear tester.

[0076] The thermal conductivity of the solidified material was measured using a thermal conductivity meter (LFA 447 NanoFlash, commercially available from NETZSCH-Geratebau GmbH, Germany).

[0077] Example 1: Prepare single-component formulations according to the table below:

[0078] * Trimethoxysilanes described by the manufacturer as methacryloyloxy functional.

[0079] The methylhydrosiloxane-dimethylsiloxane copolymer contains an average of 5.55 mmol / g of Si-H, while the vinylmethyldimethylsiloxane copolymer contains an average of 1.1 mmol / g of vinyl functional groups. The tap density of the silver sheet is ~5.1 g / cm³. 3 Its specific surface area is ~0.16 m². 2 / g, with an average diameter of ~11.8 μm (of which D50 is ~10.3), and surface treated with fatty acids.

[0080] The components were mixed under vacuum in a dual planetary mixer for 10 minutes and then cooled with cold water. The mixed composition was cured by exposure to 150°C for 2 hours. The cured silicone adhesive exhibited an adhesion strength of 6.1 MPa between the silicon wafer and the nickel substrate at room temperature and 4.9 MPa at 260°C. The cured silicone adhesive exhibited a thermal conductivity of 5.7 W / m*K.

[0081] Example 2: Prepare single-component formulations according to the table below:

[0082] The methylhydrosiloxane-dimethylsiloxane copolymer contains an average of 5.55 mmol / g of Si-H, while the vinylmethyldimethylsiloxane copolymer contains an average of 1.1 mmol / g of vinyl functional groups. The tap density of the silver sheet is ~3.7 g / cm³. 3 Its specific surface area is ~0.14 m². 2 / g, with an average diameter of ~13.7 μm (where D50 is ~12.1), and surface treated with PEG silane.

[0083] The components were mixed under vacuum in a dual planetary mixer for 10 minutes and then cooled with cold water. The mixed composition was cured by exposure to 150°C for 2 hours. The cured silicone adhesive exhibited an adhesion strength of 7 MPa between the silicon wafer and the nickel substrate at room temperature and 4.7 MPa at 260°C. The cured silicone adhesive exhibited a thermal conductivity of 5.5 W / m*K.

Claims

1. A curable composition for preparing a thermally conductive adhesive, said curable composition comprising: Organosiloxane formulations, wherein the organosiloxane formulations comprise: (i) a first reactive organosiloxane having at least one unsaturated group; and (ii) A second reactive organosiloxane comprising at least one hydride functional group and at least one alkenyl group; An organosiloxane comprising, on average, at least two silicon-bonded hydrogen atoms per molecule, wherein the organosiloxane is present in an amount sufficient to effectively cure the composition; and Thermally conductive particulate filler, wherein the thermally conductive adhesive exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

2. The curable composition according to claim 1, wherein the first organosiloxane comprises, on average, at least about one alkenyl group per molecule.

3. The curable composition according to claim 2, wherein the first organosiloxane comprises an average of at least 1.05 alkenyl groups per molecule.

4. The curable composition according to claim 2, wherein the first organosiloxane has no hydrogenated silicon functional groups.

5. The curable composition according to claim 2, wherein the first organosiloxane is present in an amount sufficient to effectively cure the organosiloxane formulation.

6. The curable composition according to claim 1, wherein the thermally conductive particulate filler is selected from nickel, copper, silver, gold, palladium, platinum, and mixtures and alloys thereof.

7. The curable composition according to claim 1, comprising an adhesion promoter selected from organosilanes, organotitanates, and combinations thereof.

8. The curable composition according to claim 1, comprising a catalyst present in a catalytic amount, said catalyst being selected from hydrosilylation catalysts, said hydrosilylation catalysts including platinum-based catalysts, ruthenium-based catalysts, palladium-based catalysts, osmium-based catalysts, iridium-based catalysts, titanium-based catalysts, and rhodium-based catalysts.

9. The curable composition according to claim 1, comprising a reaction inhibitor that effectively inhibits the hydrosilylation reaction.

10. The curable composition according to claim 9, wherein the reaction inhibitor is selected from alkynyl alcohols, fumarate compounds, maleate compounds, and combinations thereof.

11. The curable composition of claim 1, comprising a first portion and a second portion initially separate from the first portion, wherein one of the first portion and the second portion does not contain the organosiloxane comprising an average of at least two silicon-bonded hydrogen atoms per molecule.

12. The curable composition according to claim 1, wherein the first organosiloxane has the following formula I: R 1 a SiO (4-a) / 2 (I) in: Each R 1 It is an alkenyl group or a hydrocarbon having 1 to 60 carbon atoms; and "a" is a positive number between 1.05 and 3.

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13. The curable composition of claim 12, wherein each molecule of the first organosiloxane comprises at least two reactive unsaturated groups.

14. The curable composition according to claim 13, wherein the organosiloxane is cured at 25°C and 1 s. -1 It exhibits a viscosity ranging from 0.1 to 100,000 cP at various shear rates.

15. The curable composition according to claim 12, wherein the second organosiloxane has the following formula (II): R 2 a SiO (4-a) / 2 (II) in: Each R 2 It is one of hydrogen, alkenyl, or hydrocarbons having 1 to 60 carbon atoms; and "a" is a positive number between 1.05 and 3.

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16. The curable composition according to claim 15, wherein the second organosiloxane is cured at 25°C and 1 s. -1 It exhibits a viscosity ranging from 0.1 to 100,000 cP at various shear rates.

17. A thermally conductive adhesive, wherein the thermally conductive adhesive comprises the reaction products of the following substances: (A) An organosiloxane formulation, said organosiloxane formulation comprising: (iii) A first reactive organosiloxane having at least one reactive unsaturated group; and (iv) A second reactive organosiloxane comprising at least one hydride functional group and at least one alkenyl group; and (B) Organosiloxanes containing, on average, at least two silicon-bonded hydrogen atoms per molecule. At least one of components (A) and (B) comprises thermally conductive particulate filler, such that the thermally conductive adhesive exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

18. The thermally conductive adhesive of claim 17, wherein component (A) and component (B) are initially separate.

19. A package, the package comprising: Electronic components; as well as The thermally conductive adhesive according to claim 15 adheres to the electronic component.

20. The package of claim 17, comprising a heat sink, wherein the thermally conductive adhesive is adhered between the electronic component and the heat sink.

21. A method for manufacturing a package, the method comprising: (a) Providing a composition comprising: (iv) A first portion comprising a first reactive organosiloxane comprising an average of at least about one alkenyl group per molecule, and a second reactive organosiloxane comprising at least about one hydride functional group and at least about one alkenyl group; (v) Part two, wherein the second part comprises an unsaturated organosiloxane; and (vi) Thermally conductive particulate filler in at least one of the first portion and the second portion; (b) Dispensing the composition onto the surface of at least one of a heat sink and an electronic component; (c) Optionally, in the presence of a catalytic amount of catalyst, the first portion reacts with the second portion; as well as (d) The electronic component is attached to the heat sink using the composition arranged along a heat dissipation path originating from the electronic component.

22. The method of claim 21, wherein the composition exhibits a thermal conductivity of at least 3 W / m*K and an adhesive strength of at least 3 MPa.

23. The method of claim 21, further comprising curing the composition by exposing the composition to a temperature of up to 300°C for a curing period of time.

24. The method according to claim 23, wherein the curing time period is less than 2 hours.

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