Conductive silicone adhesive

Abstract

An electrically conductive silicone adhesive exhibiting high electrical conductivity and high adhesive strength useful for providing adhesion and electrical paths in electronic packages, and a method of making the electrically conductive silicone adhesive from a curable composition comprising a reactive organosiloxane and an electrically conductive particulate filler.

Description

Technical Field

[0001] The present invention generally relates to conductive adhesives for electronic components, and more specifically to curable silicone-based adhesives that exhibit high electrical 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 pursuit of advancements in conductive adhesive solutions. While some conventional conductive materials exhibit high conductivity (low resistance), they often demonstrate lower-than-expected adhesive strength. For example, delamination can occur between the conductive material and the electronic component, leading to increased resistance.

[0003] Typically, there is a trade-off between electrical conductivity and adhesive strength, where high electrical conductivity values ​​in adhesives often require high filler levels, which tend to cause the material to harden and reduce adhesive strength. Despite efforts to improve both conductivity and adhesive strength in a single solution, known adhesive materials have failed to achieve the desired combination of high conductivity and high adhesive strength. Data from the literature demonstrate the difficulty in providing curable conductive silicone adhesives that offer both the desired high conductivity and the desired high adhesive strength.

[0004] Literature indicates an inverse relationship between electrical conductivity and adhesive strength; compositions with higher conductivity (lower resistance) exhibit lower strength, while high-strength compositions have lower conductivity (higher resistance). There is a trade-off between conductivity and adhesive strength, making it very difficult to provide a curable adhesive that simultaneously possesses excellent conductivity and strong adhesion.

[0005] Electrical components can be securely fixed within the assembly. Such components, such as electronic devices, may require adhesives to hold the components in place while allowing efficient transfer of electrical energy between selected components.

[0006] Therefore, there is a need for a conductive adhesive composition that effectively bridges large coefficient of thermal expansion (CTE) mismatches between surfaces while exhibiting high electrical conductivity and high adhesive strength. Summary of the Invention

[0007] One embodiment provides a curable silicone composition for preparing a conductive silicone adhesive with good electrical conductivity and adhesive strength.

[0008] One embodiment provides a curable silicone composition for preparing a conductive silicone adhesive having a good electrical conductivity of 0.01 Ω-cm or less and an adhesive strength greater than 3 MPa.

[0009] One embodiment provides a curable silicone composition for preparing a conductive silicone adhesive having a good electrical conductivity of 0.001 Ω-cm or less and an adhesive strength greater than 3 MPa.

[0010] One embodiment provides a curable composition for preparing a conductive curable adhesive, comprising an organosiloxane preparation having a first reactive organosiloxane having at least one unsaturated group, and a second reactive organosiloxane having at least one silane-hydrogen functional group and at least one alkenyl group. In addition to the organosiloxane preparation, the curable composition further comprises an organosiloxane containing an average of at least two silicon-bonded hydrogen atoms per molecule, in an amount effective for curing the composition. The curable composition further comprises conductive particulate filler such that the conductive adhesive exhibits a conductivity of 0.01 Ω-cm, preferably 0.001 Ω-cm or less, and an adhesive strength of at least 3 MPa.

[0011] In some embodiments, the first organosiloxane comprises at least about one alkenyl group per molecule on average. In some embodiments, the first organosiloxane may comprise at least 1.05 alkenyl groups per molecule on average.

[0012] In some embodiments, the conductive particulate filler comprises particles having at least one outer surface made of a metal such as nickel, copper, silver, gold, palladium, platinum, and mixtures and alloys thereof. The conductive particles can have any desired shape, such as spherical or sheet-like, or any aspect ratio in between.

[0013] In some embodiments, the curable composition may include an adhesive additive selected from organosilanes, organotitanates, and combinations thereof.

[0014] A catalytic amount of catalyst may be present 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.

[0015] 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.

[0016] The curable composition may be provided as a one-component (1K) composition comprising all components in a single, commercially stable composition, or as a multi-component (2K) composition comprising a first component and a second or more components initially separate from the first component, wherein the first component does not include an organosiloxane having an average of at least two silicon-bonded hydrogen atoms per molecule. In the multi-component composition, the components are mixed only before use, and the mixture is not commercially stable.

[0017] In some embodiments, the first organosiloxane may have the following formula: R 1 a SiO (4-a) / 2 Where: each R 1 It is an alkenyl group or a hydrocarbon group having 1 to 60 carbon atoms; and “a” is a positive number between 1.05 and 3.95.

[0018] In some embodiments, the first organosiloxane contains at least two unsaturated groups per molecule. The first organosiloxane can be [determined] at 25°C and 1 s [time / time]. -1 It exhibits a viscosity between 0.1 and 100,000 cP at shear rates.

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

[0020] The second organosiloxane can be used at 25°C for 1 second. -1 It exhibits a viscosity between 0.1 and 100,000 cP at a given shear rate. The second organosiloxane may be different from the first organosiloxane.

[0021] In another embodiment, a conductive adhesive comprises the reaction product of the following substances: (A) Organosiloxane preparations, including: (i) a first reactive organosiloxane having at least one reactive unsaturated group; and (ii) A second reactive organosiloxane comprising at least one silane functional group and at least one alkenyl group; and (B) Organosiloxanes containing, on average, at least two hydrogen atoms bonded to silicon per molecule.

[0022] At least one of components (A) and (B) may include conductive particulate fillers, such that the conductive adhesive exhibits a conductivity of 0.001 Ω-cm or less, preferably 0.0001 Ω-cm or less, more preferably 0.00001 Ω-cm or less, and an adhesive strength of at least 3 MPa.

[0023] In some multi-component implementations, components (A) and (B) may be initially separate.

[0024] The encapsulation of the present invention may include electronic components and a conductive adhesive adhered to the electronic components. The conductive adhesive may include the components (A) and (B) described above, as well as conductive particulate fillers.

[0025] A method for manufacturing a package according to the invention includes providing a composition having: (i) a first reactive organosiloxane comprising at least one alkenyl group per molecule on average, and a second reactive organosiloxane comprising at least one silane-hydrogen functional group and at least one alkenyl group; (ii) Unsaturated organosiloxanes; and (iii) The conductive particulate filler in at least one of (i) or (ii).

[0026] The method further includes dispensing the composition onto the surface of at least one of a substrate and an electronic component, and optionally reacting the first component with the second component in the presence of a catalytic amount of catalyst.

[0027] The electronic components can then be fixed to the substrate using the composition arranged along the electrical path from the electronic components.

[0028] 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

[0029] Figure 1 This is a schematic cross-sectional view of the electronic package of the present invention. Detailed Implementation

[0030] The objectives and advantages listed above, as well as other objectives, features, and advancements of the invention, will now be described in detail with reference to specific embodiments. However, other embodiments and aspects of the invention are considered to be within the knowledge of those skilled in the art.

[0031] Typically, 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 silane functional group and at least one alkenyl group; (C) Organosiloxanes containing at least two hydrogen atoms bonded to silicon per molecule; (D) Conductive filler; (E) Hydrosilylation catalyst; and (F) Optional additional components.

[0032] In some embodiments, the curable composition can be cured at a temperature of up to 300°C for a curing period. In some embodiments, the curing period is less than 2 hours. The cured conductive adhesive can exhibit a conductivity of 0.01 Ω-cm or less, preferably 0.001 Ω-cm or less, and an adhesive strength of at least 3 MPa.

[0033] Component A In one implementation, 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 group 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 numerators, “a” can have a fractional (non-integer) value.

[0034] R 1 Examples of alkenyl or hydrocarbon groups 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 portions of the molecular chain other than the ends.

[0035] Component A can have a linear structure, a partially branched linear structure, a branched structure, a ring structure, and a three-dimensional network structure, for example, it can have a structure selected from Me3SiO, MeSiO3、 Silicone resins comprising functional siloxane monomer units of SiO4 and combinations thereof. In one example, it is a linear diorganopolysiloxane with repeating diorganosiloxane units in the main chain and both ends of its molecular chain being capped with triorganosiloxy groups.

[0036] 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 undergoing a hydrosilylation reaction 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.

[0037] Component (A) may have a viscosity of about 2 cp to 9,000,000 cp. In some embodiments, component (A) may have a viscosity of about 10 cp to 100,000 cp.

[0038] In some embodiments, component A may include polydiorganosiloxanes, such as dimethylvinylsiloxy-terminated polydimethylsiloxane; dimethylvinylsiloxy-terminated poly(dimethylsiloxane / methylvinylsiloxane); dimethylvinylsiloxy-terminated polymethylvinylsiloxane; trimethylsiloxy-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.

[0039] Component B In one implementation, component (B) has the following formula: R 2 a SiO (4-a) / 2 Where: each R 2 It is one of hydrogen, alkenyl, or hydrocarbon groups 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 numerators, “a” can have a fractional (non-integer) value.

[0040] Component B may be different from component A.

[0041] R 2 Examples of alkenyl or hydrocarbon groups 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 portions of the molecular chain other than 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 silicone resins having functional siloxane monomer units selected from Me3SiO, MeSiO3, SiO4, and combinations thereof. In one example, it is a linear diorganopolysiloxane with repeating diorganosiloxane units in the main chain and both ends of its molecular chain being capped with triorganosiloxy groups.

[0042] Component B may be a polyorganosiloxane having, on average, at least one reactive silane and at least one alkenyl group per molecule. In some embodiments, component B comprises at least one silicon-bonded hydrogen atom and at least one reactive unsaturated group per molecule. In some embodiments, component B comprises at least one silicon-bonded hydrogen atom and at least two reactive unsaturated groups per molecule. Typically, the alkenyl group will be located at the terminal position of the molecule, while the hydrogen group may be terminal or side-mounted.

[0043] Component (B) may have a viscosity of about 2 cp to 9,000,000 cp. In some embodiments, component (B) may have a viscosity of about 10 cp to 100,000 cp.

[0044] Component C In one implementation, component (C) has the following formula: R 3 a SiO (4-a) / 2 Where: each R 3 It is either hydrogen or a hydrocarbon group 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 numerators, “a” can have a fractional (non-integer) value.

[0045] Component C may be different from component A and / or component B.

[0046] R 3 Examples of hydrocarbon groups 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 a silicone resin having functional siloxane monomer units selected from Me3SiO, MeSiO3, SiO4, and combinations thereof. In one example, it is a linear diorganopolysiloxane having repeating diorganosiloxane units in its main chain and both ends of its molecular chains being capped with triorganosiloxy groups.

[0048] Component C may be a polyorganosiloxane having an average of at least two hydrogen atoms bonded to silicon per molecule, typically 2 to 300 hydrogen atoms bonded to silicon, preferably 2 to 100 hydrogen atoms bonded to silicon. The hydrogen atoms in component C may be bonded to silicon atoms located at the ends of the molecular chain and / or to silicon atoms located on 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 are present together in an amount between 1 and 50% by weight of the curable composition. In some embodiments, components A, B, and C are present together in an amount between 2 and 30% by weight of the curable composition. In some embodiments, components A, B, and C are present together in an amount between 5 and 20% by weight of the curable composition. In some embodiments, components A, B, and C are present together in an amount between 10 and 15% by weight of the curable composition.

[0051] In some embodiments, component C is present in an amount between 0.5% and 99.5% of the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount between 0.5% and 50% of the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount between 0.5% and 10% of the total amount of components A, B, and C together in the curable composition. In some embodiments, component C is present in an amount between 1% and 5% of 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 devices of the package 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 between 0.1:1 and 100:1. In some embodiments, the ratio is between 0.5:1 and 50:1. In some embodiments, the ratio is between 1:1 and 10:1. In some embodiments, the ratio is between 1.2:1 and 5:1.

[0054] Component D Component (D) is a particulate filler having an electrical conductivity of 0.01 Ω-cm or less, preferably 0.001 Ω-cm or less. In some embodiments, the particulate filler has an average particle size (d) between 0.1 and 250 µm. 50 In some embodiments, the particulate filler has an average particle size (d) between 0.1 and 100 µm. 50 In some embodiments, the particulate filler has an average particle size (d) between 0.2 and 100 µm. 50 In some embodiments, the 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). 50The particle size distribution is determined by laser diffraction, where 50% of the particles are larger than this value and 50% are smaller than this value. Component D can be dispersed in a polymer matrix. Examples of conductive particulate fillers include particles or powders composed at least partially of a metal, such as nickel, copper, silver, gold, platinum, palladium, aluminum, diamond, carbon, indium, gallium, and mixtures and alloys thereof. In some embodiments, the particulate filler may be conductive by having at least one outer surface made of a metal 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. Examples of non-spherical shapes include sheets, plates, rods, wires, etc. Spherical particulate fillers can have an aspect ratio between 0.8 and 1.2.

[0055] The conductive particulate filler is present in an amount sufficient to provide a current path between the adhered parts. In some embodiments, the adhesive exhibits a conductivity of 0.001 Ω-cm or less. In some embodiments, the adhesive exhibits a conductivity of 0.0001 Ω-cm or less. In some embodiments, the adhesive exhibits a conductivity of 0.00001 Ω-cm or less.

[0056] To achieve high electrical conductivity values, conductive particulate fillers may be present in an amount of at least 60% by weight of the adhesive. In some embodiments, the conductive filler may be present in an amount between 60% and 95% by weight of the adhesive. In some embodiments, the conductive filler may be present in an amount between 70% and 90% by weight of the adhesive. In some embodiments, the conductive filler may be present in an amount between 75% and 85% by weight of the adhesive.

[0057] If necessary, component D can also be hydrophobized, for example, with organosilanes, organosilazanes, 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 disclosed herein, component E is present in an amount required to cure the composition, referred to as the catalytic amount. In some embodiments, component E may be present in an amount between 0.1 and 1000 ppm by mass relative to the organosiloxane. In some embodiments, component E may be present in an amount between 0.1 and 500 ppm by mass relative to the organosiloxane. In some embodiments, component E may be present in an amount between 0.1 and 100 ppm by mass relative to the organosiloxane. In some embodiments, component E may be present in an amount between 1 and 50 ppm by mass relative to the organosiloxane. In some embodiments, component E may be present in an amount between 15 and 35 ppm by mass relative to the organosiloxane.

[0060] To control the curing rate of the compositions of this disclosure, a curing reaction inhibitor may be included in the curable composition. Inhibitors that can be used in this invention include inhibitors for hydrogen silanization, 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 composition, example amounts include 2 to 20,000 ppm by mass relative to the organosiloxane. In some embodiments, the curing reaction inhibitor is present in an amount between 20 and 5,000 ppm by mass relative to the organosiloxane. In some embodiments, in the compositions of this invention, the curing reaction inhibitor is present in an amount between 300 and 3,500 ppm by mass relative to the organosiloxane.

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

[0062] The conductive compositions disclosed herein may further comprise one or more additional components, such as adhesion promoters, silicone diluents, reactive diluents, colorants, corrosion inhibitors, acid acceptors, silica, carbon black, glass beads, metal particles, and combinations thereof. In some embodiments, one or more adhesion promoters may be present in an amount sufficient to effectively establish chemical bonding at the interface between the conductive adhesive and the substrate being adhered. Adhesion promoters may be present in the compositions of the present invention in an amount between 0 and 5% by weight. In some embodiments, adhesion promoters are present in an amount between 0 and 2% by weight. In some embodiments, adhesion promoters are present in an amount between 0.1 and 0.5% by weight.

[0063] Suitable examples of adhesion promoters include organosilanes, including monosilanes, bipodial silanes, tripodial silanes, and oligomeric silanes having methoxy, ethoxy, and / or propoxy structures. An example of alkoxysilanes is an epoxy-functionalized alkoxysilane. 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 conductive compositions disclosed herein can be used after curing. In some embodiments, the conductive compositions disclosed herein can be cured at a temperature from about room temperature to about 300°C. In some embodiments, the conductive compositions disclosed herein can be cured by heating to a temperature between 70°C and about 200°C. In some embodiments, the conductive compositions disclosed herein can be cured by heating to a temperature between 125°C and 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 between 1 and 200 minutes. In some embodiments, the curing time is between 1 and 150 minutes.

[0067] The curable compositions disclosed herein can be provided as single-component (1K) compositions or multi-component compositions, wherein the multi-component compositions comprise each component in two or more components, provided that components B, C, and E are not present in the same component. For single-component compositions, each component is mixed with a sufficient amount of reaction inhibitor, such that the resulting composition has a commercially acceptable shelf life of several weeks to a year or longer while maintaining availability. For multi-component compositions, component E cannot be present in the same component as components B or C. In multi-component compositions, typically any catalyst will be present in the alkenylsilane component and separate from any hydride component.

[0068] The curable silicone compositions disclosed herein can exhibit tunable rheological properties and curing kinetics to accommodate different processing methods in encapsulation applications, as well as low volatile organic compound (VOC) content. Furthermore, the silicone compositions of this invention can be cured to form silicone adhesives with excellent adhesion and electrical conductivity, as well as good reliability.

[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 according to Mil-Std-883 Method 2019.

[0070] The silicone compositions of the present invention can be used to prepare conductive adhesives, which can be used in a variety of applications, such as adhesives in semiconductor packaging, chip mounting adhesives, and solder substitutes. In one particular embodiment, the adhesives disclosed herein can be used to bond electronic components to flexible or rigid substrates.

[0071] Figure 1 The package 10 of the present invention is schematically illustrated, comprising a substrate 12, such as a printed circuit board; an electronic component 14, such as a semiconductor, processor, etc.; a conductive adhesive 16; and leads 18. The conductive adhesive 16 is adhered between the substrate 12 and the leads 18. Once cured, the adhesive bonds the substrate 12 and the leads 18 while providing electrical contact between the substrate 12 and the leads 18. In other embodiments, the conductive adhesive 16 may replace solder to provide a secure and electrically conductive connection between two or more electrical components. The conductive adhesive can cure at low temperatures and will be useful in applications where the temperatures required to melt solder are problematic.

[0072] In one embodiment, the curable composition of the present invention is dispensed onto the surface of at least one of a substrate 12 and a lead 18, and the lead 18 is secured to the substrate 12 with the curable composition disposed therebetween, such that the composition bonds the substrate 12 and the lead 18 while providing a conductive path from the substrate 12 to the lead 18. In some embodiments, the package 10 is formed by curing the composition for a curing time to form a cured adhesive exhibiting shape-stable properties. The composition can be cured by exposing the composition to a temperature of up to 300°C for a curing period of less than 2 hours.

[0073] Example The following test methods were used in the examples. Viscosity was measured at 5 rpm and room temperature using a Brookfield viscometer with a cone plate CP-51. Adhesion strength was measured at room temperature using a Dage Series 4000 die shear tester with a 3 mm × 3 mm silicon die and a nickel-coated copper substrate. The conductivity of the bulk-cured material was measured as volume resistivity using a four-point probe on a megohm bridge.

[0074] Example 1: Prepare single-component formulations according to the table below:

[0075] The methylhydrosiloxane-dimethylsiloxane copolymer contains an average of 5.55 mmol / g of Si-H, and the vinylmethyldimethylsiloxane copolymer contains an average of 0.36 mmol / g of vinyl functional groups. The silver sheet has ~3.2 g / cm³. 3 The tap density is ~0.47 m. 2 Specific surface area per g, average diameter ~ 8 µm (D 50 ~ 5.8), with fatty acid surface treatment.

[0076] The components were mixed for 10 minutes in a dual planetary mixer under vacuum and cooled with chilled water. The final viscosity was ~22 Pa·s at 5 rpm. The mixed composition was cured by exposure to 150°C for two hours. The cured silicone adhesive exhibited an adhesion strength of 4.7 MPa between a silicon wafer and a nickel substrate at room temperature. The cured silicone adhesive exhibited a volume resistivity of 0.0003 Ω-cm.

[0077] Example 2: Prepare single-component formulations according to the table below:

[0078] The methylhydrosiloxane-dimethylsiloxane copolymer contains an average of 5.55 mmol / g of Si-H, while the vinylmethyldimethylsiloxane copolymer contains an average of 0.36 mmol / g of vinyl functional groups. The silver sheet has a density of ~6.3 g / cm³. 3 The tap density is ~0.31 m. 2 Specific surface area per g, with diameter ranging from ~0.7 to 20 µm (D 50 ~ 2.2), treated with fatty acid surface.

[0079] The components were mixed for 10 minutes in a dual planetary mixer under vacuum and cooled with chilled water. The final viscosity was ~15 Pa·s at 5 rpm. The mixed composition was cured by exposure to 150°C for two hours. The cured silicone adhesive exhibited an adhesion strength of 5.4 MPa between a silicon wafer and a nickel substrate at room temperature. The cured silicone adhesive exhibited a volume resistivity of 0.00015 Ω-cm.

Claims

1. A curable composition for preparing a conductive adhesive, the curable composition comprising: Organosiloxane preparations, including: (i) a first reactive organosiloxane having at least one unsaturated group; and (ii) A second reactive organosiloxane comprising at least one silane functional group and at least one alkenyl group; An organosiloxane comprising, on average, at least two hydrogen atoms bonded to silicon per molecule, wherein the organosiloxane is present in an amount sufficient to effectively cure the composition; and Conductive particulate fillers, wherein the conductive adhesive exhibits a conductivity of 0.01 Ω-cm or less and an adhesive strength of at least 3 MPa.

2. The curable composition according to claim 1, wherein the first organosiloxane comprises an average of 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 is free of silane-hydrogen 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 preparation.

6. The curable composition according to claim 1, wherein the conductive particulate filler is at least partially composed of particles of nickel, copper, silver, gold, palladium, platinum, and mixtures and alloys thereof.

7. The curable composition according to claim 1, comprising an adhesive additive 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, 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 component and a second component initially separate from the first component, wherein one of the first component and the second component does not contain an 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: R 1 a SiO (4-a) / 2 in: Each R 1 It is an alkenyl group or a hydrocarbon group having 1 to 60 carbon atoms; and "a" is a positive number between 1.05 and 3.

95.

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

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

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

95.

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 between 0.1 and 100,000 cP at shear rates.

17. A conductive adhesive comprising a reaction product of the following substances: (A) Organosiloxane preparations, the preparations comprising: (i) A first reactive organosiloxane having at least one reactive unsaturated group; and (ii) A second reactive organosiloxane comprising at least one silane functional group and at least one alkenyl group; and (B) Organosiloxanes containing, on average, at least two hydrogen atoms bonded to silicon per molecule. At least one of components (A) and (B) includes conductive particulate filler, such that the conductive adhesive exhibits a conductivity of 0.001 Ω-cm or less, preferably 0.0001 Ω-cm or less, more preferably 0.00001 Ω-cm or less, and an adhesive strength of at least 3 MPa.

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

19. A package comprising: Electronic components; and The conductive adhesive of claim 15 adheres to the electronic component.

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

21. A method for manufacturing a package, the method comprising: (a) A composition comprising: (i) A first component comprising a first reactive organosiloxane and a second reactive organosiloxane, the first reactive organosiloxane comprising an average of at least about one alkenyl group per molecule, and the second reactive organosiloxane comprising at least about one silane-hydrogen functional group and at least about one alkenyl group. (ii) A second component comprising unsaturated organosiloxanes; and (iii) a conductive particulate filler in at least one of the first component and the second component; (b) Dispensing the composition onto the surface of at least one of a substrate and an electronic component; (c) Optionally, in the presence of a catalytic amount of catalyst, react the first component with the second component; and (d) The electronic component is fixed to the substrate using the composition disposed along the electrical path from the electronic component.

22. The method of claim 21, wherein the composition exhibits an electrical conductivity of 0.001 Ω-cm or less, preferably 0.0001 Ω-cm or less, more preferably 0.00001 Ω-cm or less, 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.

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

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