Silver sintering composition comprising a copper alloy for metallic bonding

Abstract

The present invention relates to a silver sintering composition. Specifically, the present invention relates to a silver sintering composition comprising a copper alloy, which is capable of stably sintering on various metal substrates such as copper, gold or silver with good adhesion and sintering strength.

Description

TECHNICAL FIELD

[0001] The present invention relates to a silver sintering composition, in particular to a silver sintering composition comprising a copper alloy for metal bonding, and sintered products, assemblies and uses thereof. BACKGROUND

[0002] The electronics industry has an ever increasing demand for interconnect materials that can be applied at high processing and operating temperatures. Historically, lead (Pb) based solders have been used to connect components to electronic circuit boards or to connect external leads to electronic components. Recently, regulations such as the European RoHS legislation have limited the use of lead (Pb) in solders in electrical and electronic equipment, which has led the industry to seek various alternatives.

[0003] One of the current solutions is transient liquid phase sintering (TLPS). TLPS adhesives have been developed for many potential applications due to various advantages such as lead-free, flux-free, etc., especially their low temperature processability, which allows the use of heat sensitive components in the design. The following patents describe materials and processes for TLPS in forming electrically conductive joints.

[0004] U.S. Patent No. 5,853,622 discloses a TLPS formulation that combines a TLPS material with a cross-linked polymer to produce an electrically conductive adhesive that has improved electrical conductivity due to the intermetallic interface between the metal surfaces produced by the TLPS process.

[0005] U.S. Patent No. 5,964,395 discloses the spraying of two mating surfaces, one of which has a low temperature melting material, while the mating surface with a compatible higher melting temperature material forms a joint when heated to the melting point of the lower temperature material.

[0006] U.S. Patent No. 5,221,038 describes the use of SnBi or SnIn in a TLPS process to solder discrete components such as resistors, etc. to printed circuit boards.

[0007] U.S. Patent No. 6,241,145 discloses the use of Ag / SnBi coated onto two mating surfaces for mounting electronic modules to a substrate.

[0008] However, TLPS still has problems because it is brittle and creates voids in the cured product of the bonded substrate. Alternatively, silver sintering compositions including a resin and a conductive filler are used for the manufacture and assembly of semiconductor packages and microelectronic devices, both mechanically connecting and creating electrical and thermal conductivity between integrated circuit devices and their substrates. The most commonly used conductive filler is silver flake. Adhesive resins are used in the conductive compositions because silver flake generally does not adequately adhere the semiconductor or microelectronic devices to their substrates. However, the presence of the resin limits the high thermal and electrical conductivity of the silver.

[0009] Currently, conductive compositions with silver fillers in the absence of a resin can be adhered to silver or gold substrates by either thermal compression bonding or pressureless bonding. However, the bond strength is not satisfactory. In addition, the substrates commonly used in the manufacture of electronic devices are copper lead frames, and silver conductive compositions do not readily form intermetallic bonds with copper. They fail when they are cycled at temperatures close to their melting point in high power and high temperature applications. Another disadvantage is that such compositions require flux, which leaves flux residues after the intermetallic bond is formed, thus requiring a cleaning step of the substrates in the manufacturing process.

[0010] Therefore, silver sintering compositions with or without a resin have their limitations in the manufacture and assembly of semiconductor packages and microelectronic devices. Thus, there is still a need to develop a lead-free silver sintering composition that is capable of stably sintering on various metal substrates such as copper, gold or silver, particularly copper, with good adhesion and sintering strength. SUMMARY

[0011] Through intensive studies, the inventors have found that the above problems can be solved by a silver sintering composition comprising:

[0012] (A) at least one silver filler,

[0013] (B) at least one copper alloy in an amount of 0.01 to 20 wt% based on the total weight of the composition, and

[0014] (C) a matrix component selected from the group consisting of a resin, a solvent, and a combination thereof.

[0015] The silver sintering composition of the present application is capable of stably sintering on various metal substrates such as copper, gold or silver, particularly copper, with good adhesion and sintering strength.

[0016] In another aspect of the present application, there is provided a sintered product of the conductive composition according to the present application.

[0017] In an additional aspect of the present application, there is provided an assembly comprising a first silver substrate, a sintered product according to the present application, and a second substrate selected from the group consisting of copper, gold or silver, wherein the sintered product is distributed between the first and second substrates.

[0018] In yet another aspect of the application, there is provided the use of the conductive composition of the application in the manufacture of semiconductor packages and microelectronic device touch screens.

[0019] In yet another aspect of the application, there is provided the use of the sintered product of the application in semiconductor packages and microelectronic device touch screens. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 A scanning electron microscope (SEM) photograph at 5000x magnification showing the honeycomb structure of the silver sinter composition according to Example 1 is shown.

[0021] Figure 2 A SEM photograph at 5000x magnification showing the honeycomb structure of the semi-sintered composition according to Example 6 is shown. DETAILED DESCRIPTION

[0022] It will be understood by those of ordinary skill in the art that the present application is merely an example of the illustrative embodiments and is not intended to limit the broader aspects of the present application. Each aspect described as such can be combined with any other aspect or aspects, unless explicitly indicated to the contrary. In particular, any feature indicated as preferred or advantageous can be combined with any other feature or features indicated as preferred or advantageous.

[0023] Unless otherwise indicated, in the context of the present application, the terms used are to be interpreted in accordance with the following definitions.

[0024] Unless otherwise indicated, as used herein, the terms "a," "an," and "the" include singular and plural referents.

[0025] The terms "comprising" and "comprises" as used herein are synonymous with "including," "includes," or "containing," "contains," and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or process steps.

[0026] The term "alloy" refers to a mixture comprising two or more metals and optionally additional non-metals, where the elements of the alloy fuse together or dissolve into one another upon melting. The nomenclature used herein for alloy compositions lists two or more elements, using their IUPAC symbols, separated by a forward slash (" / "). When given, the proportions of the elements in the alloy are indicated by the numbers following the elements, corresponding to the weight percent of the element in the alloy. For example, Cu / Sn represents an alloy of copper (Cu) and tin (Sn), which can be in any proportion. Cu75 / Sn25 represents a specific copper and tin alloy that contains 75 wt.% copper and 25 wt.% tin. In the case where a range is given for the weight percent of one or more elements in the alloy, the range indicates that the element can be present in any amount within the specified range. For example, Sn(70-90) / Bi(10-30) means an alloy containing 70 wt.% to 90 wt.% tin and 10 wt.% to 30 wt.% bismuth. Thus, the alloys encompassed within the "Sn(70-90) / Bi(10-30)" range include, but are not limited to: Sn70 / Bi30, Sn71 / Bi29, Sn72 / Bi28, Sn73 / Bi27, Sn74 / Bi26, Sn75 / Bi25, Sn76 / Bi24, Sn77 / Bi23, Sn78 / Bi22, Sn79 / Bi21, Sn80 / Bi20, Sn81 / Bi19, Sn82 / Bi18, Sn83 / Bi17, Sn84 / Bi16, Sn85 / Bi15, Sn86 / Bi14, Sn87 / Bi13, Sn88 / Bi12, Sn89 / Bi11, and Sn90 / Bi10. Furthermore, Sn(70-90) / Bi(10-30) represents an alloy in which the specific proportions of the elements Sn and Bi can vary from Sn70 / Bi30 to Sn90 / Bi10, including a variation in the proportion of Sn from 70 wt.% up to 90 wt.%, and conversely a variation in Bi from 30 wt.% down to 10 wt.%.

[0027] As used herein, the term "melting temperature" or "melting point" refers to the temperature (point) at which a solid becomes a liquid at atmospheric pressure.

[0028] Unless otherwise indicated, recitation of a number of endpoints includes all numbers and fractions subsumed within the corresponding range, as well as the recited endpoint.

[0029] All references cited in this specification are hereby incorporated by reference in their entirety.

[0030] Unless defined otherwise, all terms used in this application, including technical and scientific terms, have the meaning commonly understood by one of ordinary skill in the art to which this application belongs.

[0031] The present invention relates to a silver sintering composition comprising:

[0032] (A) at least one silver filler,

[0033] (B) at least one copper alloy in an amount of 0.01 to 20 wt% based on the total weight of the composition, and

[0034] (C) a matrix component selected from the group consisting of a resin, a solvent, and a combination thereof.

[0035] (A) silver filler

[0036] The silver sintering composition according to the present invention comprises at least one silver filler.

[0037] In a preferred embodiment, the silver filler has a D 50 particle size of 0.5 to 6.0 μm, preferably 0.8 to 5.0 μm, more preferably 1.0 to 5.0 μm, more preferably 1.1 to 1.4 μm, further preferably 1.1 to 3.0 μm. When the particle size of the silver filler is within the above range, the filler is more uniformly dispersed in the adhesive composition, which can improve the storage stability of the adhesive composition and provide uniform bonding strength. Here, the "D 50 particle size" of the silver filler refers to the median diameter in the volume-based particle size distribution curve obtained by a laser diffraction particle size analyzer.

[0038] In a preferred embodiment, the silver particles used in the adhesive composition include particles having a shape of a sheet. The filler having such a shape has a high contact area between the fillers, which can reduce voids in the cured product. The shape of the silver particles is analyzed by observation with a scanning electron microscope (SEM), and a Philips XL30 can be used as the observation device for the SEM. Examples of the sheet-shaped particles include particles having shapes called plate-like, disc-like, scale-like, and flaky. When the sheet-shaped silver particles are in contact with each other, the contact area increases compared to the case where the granular silver particles are in contact with each other. Therefore, if the adhesive composition including the sheet-shaped silver particles is heat-cured, the sintering density between the silver particles will increase, and thus it is presumed that not only the thermal and electrical conductivities of the cured product of the adhesive composition are improved, but also the adhesion strength to the surface of the base metal is improved.

[0039] In a preferred embodiment, the silver filler has a tap density of 2 g / cm 3 to 15 g / cm 3 , preferably 3 g / cm 3 to 7.5 g / cm 3 .

[0040] The silver filler used in the present application can be manufactured by a known method such as a reduction method, a milling method, an electrolytic method, an atomization method, or a heat treatment method.

[0041] In certain embodiments, the surface of the silver filler can be coated with an organic substance.

[0042] Here, the state in which the silver filler is "coated with an organic substance" includes a state in which an organic solvent adheres to the surface of the silver filler by dispersing the silver filler in the organic solvent.

[0043] Examples of the organic substance coating the silver filler can include a hydrophilic organic compound such as an alkyl alcohol having 1 to 5 carbon atoms, an alkyl mercaptan having 1 to 5 carbon atoms, and an alkane polyol having 1 to 5 carbon atoms, or a lower aliphatic acid having 1 to 5 carbon atoms; and a hydrophobic organic compound such as a higher aliphatic acid having 15 or more carbon atoms and a derivative thereof, a middle fatty acid having 6 to 14 carbon atoms and a derivative thereof, an alkyl alcohol having 6 or more carbon atoms, an alkyl amine having 16 or more carbon atoms, or an alkyl mercaptan having 6 or more carbon atoms.

[0044] Examples of the higher aliphatic acid include straight-chain saturated fatty acids such as pentadecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, 12-hydroxyoctadecanoic acid, eicosanoic acid, docosanoic acid, tetracosanoic acid, hexacosanoic acid (lignoceric acid), or octacosanoic acid; branched-chain saturated fatty acids such as 2-pentylnonanoic acid, 2-hexyldecanoic acid, 2-heptyldodecanoic acid, or isostearic acid; and unsaturated fatty acids such as palmitoleic acid, oleic acid, vaccenic acid, elaidic acid, linoleic acid, linolenic acid, ricinoleic acid, gadoleic acid, erucic acid, and shark oil acid.

[0045] Examples of the middle fatty acid include straight-chain saturated fatty acids such as hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, or tetradecanoic acid; branched-chain saturated fatty acids such as isohexanoic acid, isoheptanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, 2-propylheptanoic acid, isodecanoic acid, isoundecanoic acid, 2-butyloctanoic acid, isododecanoic acid, and isotridecanoic acid; and unsaturated fatty acids such as 10-undecylenic acid.

[0046] Examples of the method of manufacturing the silver filler coated with the organic substance on the surface include, but are not particularly limited to, a method of manufacturing the silver filler by a reduction method in the presence of an organic solvent. Specifically, the silver filler can be obtained by mixing a silver salt of carboxylic acid with a primary amine and depositing a conductive filler using a reducing agent in the presence of an organic solvent.

[0047] Commercially available silver fillers can be used in the present application. Examples thereof include TC-505C available from Tokuriki Chemical Research Co., Ltd. and FA-SAB-238 available from Dowa Hightech.

[0048] When the surface of the silver filler is coated with an organic substance, the aggregation of the silver filler in the adhesive composition can be further prevented or reduced.

[0049] The silver filler can be used alone, or two or more silver fillers can be used in combination. The combination of fillers of different shapes or different sizes can reduce the porosity of the cured product. Examples of the combination include, but are not limited to, a mixture of flaky silver fillers and approximately spherical silver fillers having a center particle diameter smaller than that of the flaky silver fillers.

[0050] Particularly preferably, the silver filler can be incorporated in the silver sintering composition in an amount of 80 to 96% by weight, preferably 85 to 95% by weight, based on the total weight of the composition.

[0051] (B) copper alloy

[0052] The silver sintering composition includes at least one copper alloy in an amount of 0.01 to 20% by weight, based on the total weight of the composition. The inventors have surprisingly found that the incorporation of a copper alloy in the sintering composition can greatly improve the adhesion properties of the silver sintering adhesive on metal, such as copper, surfaces.

[0053] In a preferred embodiment, the silver sintering composition comprises a copper alloy having a melting point of 200 to 1000°C, preferably 300 to 900°C, more preferably 400 to 800°C.

[0054] In a preferred embodiment, the silver sintering composition comprises a copper alloy having a melting point of 200 to 1000°C, preferably 300 to 900°C, more preferably 400 to 800°C. 50 a copper alloy having a particle size of 100 nm to 100 μm, preferably 0.5 μm to 50 μm, more preferably 1 μm to 25 μm.

[0055] The type of copper alloy is not limited, as long as it comprises not more than 95% by weight of copper (Cu), preferably 20 to 90% by weight of copper (Cu), more preferably 28 to 90% by weight of copper (Cu), more preferably 73 to 90% by weight of copper (Cu), even more preferably 60 to 90% by weight of copper (Cu), based on the weight of the alloy.

[0056] In preferred embodiments, the copper alloy comprises at least one metal selected from the group consisting of tin (Sn), silver (Ag), zinc (Zn), gold (Au), bismuth (Bi), lead (Pb), manganese (Mn), iron (Fe), nickel (Ni), indium (In), cadmium (Cd), cobalt (Co), arsenic (As), aluminum (Al), silicon (Si), and antimony (Sb), preferably comprises at least one metal selected from the group consisting of Sn, Ag, Pb, and Zn.

[0057] Commercially available products can be used in the present application. Examples thereof include Cu (20-97) / Sn (3-80), such as Cu90 / Sn10, Cu75 / Sn25, Cu60 / Sn40, and Sn80 / Cu20; Cu (57-65) / Pb (35-43), such as Cu62 / Pb38; Cu (20-60) / Pb (40-80), such as Ag72 / Cu28; Cu (64-70) / Zn (24-31) / Ni (5-6), such as Cu64 / Zn31 / Ni5, Cu70 / Zn24 / Ni6; Cu (60-70) / Zn (25-38) / Ni (2-5), such as Cu73 / Sn23 / Ag4, all of which are available from 5N Plus Inc.

[0058] According to the present application, the amount of copper alloy incorporated into the silver sintering composition is from 0.01 wt% to 20 wt%, preferably from 0.01 wt% to 10 wt%, preferably from 1.5 wt% to 7.0 wt%, more preferably from 2.5 wt% to 5.0% wt%, based on the total weight of the composition.

[0059] (C) matrix component

[0060] The silver sintering composition further includes a matrix component selected from the group consisting of a resin, a solvent, and combinations thereof.

[0061] resin

[0062] In some embodiments, the silver sintering composition includes at least one resin to improve one or more performance properties of the composition of the present application, such as tack, wetting ability, flexibility, service life, high temperature adhesion, and / or resin-filler compatibility. Further, the resin component is provided in the compositions described herein to improve one or more performance properties of the composition of the present application, such as rheology, dispensability.

[0063] If present, the resin can be a thermoset resin or a thermoplastic resin capable of imparting one or more of the above-mentioned properties to the composition. Such thermoset resins or thermoplastic resins include, but are not limited to, acetals, (meth)acrylic monomers, oligomers or polymers, acrylonitrile-butadiene-styrene (ABS) polymers or copolymers or polycarbonate / ABS alloys, alkyd resins, butadiene, styrene-butadiene, cellulose, coumarone-indene, cyanate ester, diallyl phthalate (DAP), epoxy monomers, oligomers or polymers, flexible epoxy resins or polymers having epoxy functionality, fluoropolymers, melamine-formaldehyde, neoprene, nitrile resins, phenolic resins, nylon, petroleum resins, phenol resins, polyamide-imides, polyarylate and polyarylate ether sulfone or polyarylate ether ketone, polybutene, polycarbonate, polyester and copolyester carbonate, polyether ester, polyethylene, polyimide, maleimide, nadimide, itaconamide, polyketone, polyolefin, polyphenylene ether, sulfide, ether, polypropylene and polypropylene-EPDM blends, polystyrene, polyurea, polyurethane, vinyl polymers, rubber, silicone polymers, siloxane polymers, styrene acrylonitrile, styrene butadiene latex and other styrene copolymers, sulfone polymers, thermoplastic polyesters (saturated), phthalate, unsaturated polyesters, urea-formaldehyde, polyacrylamide, polyglycol, polyacrylic acid, polyethylene glycol, intrinsically conductive polymers, fluoropolymers, and the like, as well as combinations of any two or more thereof.

[0064] Exemplary maleimides, nadimides or itaconamides contemplated for use herein include 4,4'-diphenylmethane bismaleimide, 4,4'-diphenyl ether bismaleimide, 4,4' diphenyl sulfone bismaleimide, phenylmethane maleimide, m-phenylene bismaleimide, 2,2'-bis[4-(4-maleimidophenoxy)phenyl]propane, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimido-(2,2,4-trimethyl)hexane, 1,3-bis(3-maleimidophenoxy)benzene, 1,3-bis(4-maleimidophenoxy)-benzene, and the like.

[0065] In preferred embodiments, the resin is selected from the group consisting of epoxy resins, acrylates, isocyanates, cyanate esters, maleimides, polyurethane silicones and mixtures thereof, more preferably an epoxy resin.

[0066] In some embodiments, the epoxy resin can be a liquid epoxy resin or a solid epoxy resin containing aromatic and / or aliphatic backbones, such as a diglycidyl ether of bisphenol F or a diglycidyl ether of bisphenol A, preferably a liquid epoxy resin. Optionally, the epoxy resin is a flexible epoxy resin. The flexible epoxy resin can have a variable length chain length (e.g., short chain or long chain), such as a short chain length or a long chain length polyethylene glycol diepoxide liquid resin. In the adhesive composition with the epoxy resin, the epoxy resin self-crosslinks and cures when the composition is heated at a temperature of about 150 °C. The composition can be heated by any known heating mechanism, including but not limited to conventional furnaces and ovens and microwave ovens, such as those that rely on variable frequency microwave radiation. Those skilled in the art will appreciate that other chemical components including but not limited to amine- and / or carboxyl-containing compounds can be incorporated into the adhesive component to crosslink with the epoxy resin.

[0067] In certain embodiments, the epoxy resins contemplated for use herein include diglycidyl ethers of bisphenol A epoxy resins, diglycidyl ethers of bisphenol F epoxy resins, epoxy novolac resins, epoxy cresol resins, and the like.

[0068] In some embodiments, the epoxy resin can be a toughened epoxy resin, such as an epoxidized carboxyl-terminated butadiene-acrylonitrile (CTBN) oligomer or polymer, an epoxidized polybutadiene diglycidyl ether oligomer or polymer, a heterocyclic epoxy resin (such as an isocyanate-modified epoxy resin), and the like.

[0069] In certain embodiments, the epoxy resins contemplated for use herein include rubber or elastomer-modified epoxy resins. Rubber or elastomer-modified epoxy resins include epoxidized derivatives of:

[0070] (a) a homopolymer or copolymer of a conjugated diene containing 4 to 11 carbon atoms per molecule (e.g., 1,3-butadiene, isoprene, etc.) having a weight average molecular weight (Mw) of 30,000 to 400,000 or more, as described in U.S. Patent No. 4,020,036 (the entire contents of which are incorporated herein by reference);

[0071] (b) a homopolymer of an epihalohydrin, a copolymer of two or more epihalohydrin monomers, or a copolymer of one or more epihalohydrin monomers and one or more oxide monomers having a number average molecular weight (Mn) of about 800 to about 50,000, as described in U.S. Patent No. 4,101,604 (the entire contents of which are incorporated herein by reference);

[0072] (c) a hydrocarbon polymer including an ethylene / propylene copolymer and an ethylene / propylene copolymer with at least one non-conjugated diene, such as ethylene / propylene / hexadiene / norbornadiene, as described in U.S. Patent No. 4,161,471; or,

[0073] (d) conjugated diene butyl elastomers, such as copolymers consisting of 85 to 99.5 weight percent of C4-C5 olefins and about 0.5 to about 15 weight percent of conjugated polyolefins having 4-14 carbon atoms, copolymers of isobutylene and isoprene, wherein the majority of isoprene units incorporated have conjugated diene unsaturation (see, e.g., U.S. Patent No. 4,160,759; the entire contents of which are incorporated herein by reference).

[0074] In certain embodiments, the epoxy resin is an epoxidized polybutadiene diglycidyl ether oligomer or polymer.

[0075] In some embodiments, the additional epoxy resin material can be a variety of epoxy-functionalized resins contemplated for use herein, such as bisphenol A-based epoxy resins (e.g., Epon resin 834), bisphenol F-based epoxy resins (e.g., RSL-1739 or JER YL980), thermoplastic phenol-formaldehyde resin-based multifunctional epoxy resins, dicyclopentadiene-type epoxy resins (e.g., Epiclon HP-7200L), naphthalene-type epoxy resins, and the like, as well as mixtures of any two or more thereof.

[0076] Optionally, the epoxy resin can be a copolymer having a backbone that is a mixture of monomeric units (i.e., a hybrid backbone). The epoxy resin can include linear or branched chain segments. In certain embodiments, the epoxy resin can be an epoxidized organosilicon monomer or oligomer. Optionally, the epoxy resin can be a flexible epoxy-silicone copolymer. Exemplary flexible epoxy-silicone copolymers contemplated for use herein include ALBIFLEX 296 and ALBIFLEX 348, both of which are commercially available from Evonik Industry (Germany).

[0077] In some embodiments, one epoxy monomer, oligomer, or polymer is present in the composition. In certain embodiments, a combination of multiple epoxy monomers, oligomers, or polymers is present in the composition. For example, two or more, three or more, four or more, five or more, or six or more epoxy monomers, oligomers, or polymers are present in the composition. A combination of multiple epoxy resins can be selected and used to achieve desired properties of a film or paste prepared from the composition. For example, a combination of multiple epoxy resins can be selected such that a film prepared from the composition exhibits one or more of the following improved properties: film quality, tack, wet-out ability, flexibility, service life, high temperature adhesion, resin-filler compatibility, sintering ability, and the like. A combination of multiple epoxy resins can be selected such that a paste prepared from the composition exhibits one or more improved properties, such as rheology, dispensability, service life, sintering ability, and the like.

[0078] The compositions described herein can also include an acrylic monomer, polymer, or oligomer. Acrylic esters contemplated for use in the practice of the present application are well known in the art. See, for example, U.S. Patent No. 5,717,034, the entire contents of which are incorporated herein by reference.

[0079] Exemplary (meth)acrylates contemplated for use herein include monofunctional (meth)acrylates, difunctional (meth)acrylates, trifunctional (meth)acrylates, polyfunctional (meth)acrylates, and the like, as well as mixtures of any two or more thereof.

[0080] Other thermoset or thermoplastic resin components contemplated for use in the compositions described herein can include polyurethanes, cyanate esters, polyvinyls, polyesters, polyureas, polyvinyl acetal resins, and phenoxy resins. In some embodiments, the compositions can include imide-containing monomers, oligomers, or polymers, such as maleimides, nadimides, itaconimides, bismaleimides, or polyimides.

[0081] In one particular embodiment, the thermoset or thermoplastic resin component is selected from the group consisting of epoxy monomers, epoxy oligomers, epoxy polymers, (meth)acrylic monomers, (meth)acrylic oligomers, (meth)acrylic polymers, phenolic resins, polyurethanes, cyanate esters, polyvinyls, polyesters, polyureas, polyvinyl acetal resins, phenoxy resins, maleimides, bismaleimides, nadimides, itaconimides, polyimides, and mixtures thereof. Preferably, the thermoset or thermoplastic resin component is selected from the group consisting of epoxy monomers, epoxy oligomers, epoxy polymers, (meth)acrylic monomers, (meth)acrylic oligomers, (meth)acrylic polymers, maleimides, bismaleimides, and mixtures thereof.

[0082] Commercially available products can be used in the present application. Examples thereof include dodecenyl succinic anhydride, cycloaliphatic glycidyl ester, available from Broadview Technologies, ERISYS RDGE, available from CVC Specialties, Poly 605E, Silquest A-186 silane, Silquest A-187, available from Momentive Performance Materials.

[0083] solvent

[0084] When the silver sintering composition includes a resin, a solvent is not an essential component in the present application, but a solvent can be added to reduce the viscosity of the binder composition. When the silver sintering composition does not contain a resin, a solvent is required to disperse the silver filler in the binder composition.

[0085] Most silver fillers are provided with an organic coating when purchased to prevent clumping. The organic material impedes sintering, which means that higher temperatures will be required for sintering. The solvent acts to dissolve or displace the organic material from the surface of the silver filler. The solvent must have a polarity balance to effectively remove the coating and disperse the silver in the solvent until dispensing and sintering. Typical organic materials used by silver flake manufacturers include stearic acid, isostearic acid, lauric acid, capric acid, capric acid, oleic acid, palmitic acid, or fatty acids neutralized with amines such as imidazole. Effective solvents are those that will remove these and other similar lubricants from the surface of the silver filler.

[0086] There is no limitation on the type of solvent as long as it has a flash point greater than 70 °C, preferably greater than 90 °C, more preferably greater than 120 °C. The solvent can be selected from the group consisting of 2-(2-ethoxy-ethoxy)ethyl acetate, propylene glycol monoethyl ether, butyl ethoxy ethyl acetate, propylene carbonate, cyclooctenone, cycloheptanone, cyclohexanone, straight or branched alkanes, and mixtures thereof.

[0087] Commercially available products can be used in the present application. Examples thereof include diisobutyl adipate available from Sinopharm Chemical Reagent Co., Ltd and ethyl 2-(2-butoxyethoxy)acetate available from BASF.

[0088] In a preferred embodiment, the silver sintering composition comprises a matrix component comprising a resin and a solvent.

[0089] Particularly preferably, the matrix component selected from the group consisting of a resin, a solvent, and combinations thereof can be incorporated into the silver sintering composition in an amount of no more than 15 wt.%, preferably 2 wt.% to 10 wt.%, based on the total weight of the composition.

[0090] (D) additive

[0091] Other commonly used additives can be further added to the silver sintering composition. Such commonly used additives include fluxing agents, peroxides, flow additives, adhesion promoters, rheology modifiers, toughening agents, and mixtures thereof.

[0092] Particularly preferably, the additives can be incorporated into the silver sintering composition in an amount of no more than 2 wt.%, based on the total weight of the composition.

[0093] In another aspect of the present application, there is provided a sintered product of the conductive composition according to the present application.

[0094] The sintering compositions described herein are prepared at room temperature. When used in semiconductor manufacturing, these compositions have sufficient adhesion upon sintering to adhere a metal-coated die to a metal-coated substrate. In particular, the compositions can be used to adhere silver or gold-coated semiconductor dies to copper lead frames. In some embodiments, the compositions of the present invention will sinter at temperatures from 150°C to 300°C, preferably from 200°C to 250°C. No pressure is required to induce sintering. At the sintering temperature, the solvent, if any, additives such as peroxide, or fluxing agent, if any, and organic species contained in the silver filler used in the composition are burned off, leaving a sintered product comprising sintered silver and copper alloy.

[0095] In another aspect of the present invention, there is provided an assembly comprising a first substrate, a sintered product of the present invention, and a second substrate selected from copper, gold or silver, wherein the sintered product is disposed between the first and second substrates.

[0096] In yet another aspect of the present invention, there is provided the use of a sintering composition of the present invention in the manufacture of a semiconductor package or touch screen.

[0097] In yet another aspect of the present invention, there is provided the use of a sintered product of the present invention in a semiconductor package and microelectronic device touch screen.

[0098] Examples

[0099] The following examples are intended to assist the person of skill in the art to better understand and practice the present invention. The scope of the present invention is not limited by the examples, but is defined in the appended claims. Unless otherwise indicated, all parts and percentages are by weight.

[0100] Raw materials:

[0101] TC-505C silver powder is available from Tokuriki Chemical Research Co., Ltd.

[0102] Silver powder FA-SAB-238 is available from Dowa Hightech.

[0103] Dodecenyl succinic anhydride is an anhydride resin available from Broadview Technologies.

[0104] Epalloy TM 5200 is a cycloaliphatic glycidyl ester available from CVC Specialties.

[0105] ERISYS RDGE is an epoxy resin available from CVC Specialties.

[0106] Poly 605E is an epoxy-functional polybutadiene resin available from Total Group.

[0107] Silquest A-186 silane is a silane resin available from Momentive Performance Materials.

[0108] Silquest A-187 silane is a silane resin available from Momentive Performance Materials.

[0109] Diisobutyl adipate is a solvent available from Sinopharm Chemical Reagent Co., Ltd.

[0110] Ethyl 2-(2-butoxyethoxy)acetate is a solvent available from BASF.

[0111] Cu75 / Sn25 is a copper alloy consisting of 75 wt% Cu and 25 wt% Sn with a melting point of about 800 °C, available from 5N Plus Inc.

[0112] Ag72 / Cu28 is a copper alloy consisting of 28 wt% Cu and 72 wt% Ag with a melting point of about 780 °C, available from 5N Plus Inc.

[0113] Cu90 / Sn10 is a copper alloy consisting of 90 wt% Cu and 10 wt% Sn with a melting point of about 860 °C, available from 5N Plus Inc.

[0114] Cu60 / Sn40 is a copper alloy consisting of 60 wt% Cu and 40 wt% Sn with a melting point of about 725 °C, available from 5N Plus Inc.

[0115] Cu73 / Sn23 / Ag4 is a copper alloy consisting of 72.5 wt% Cu, 3.5 wt% Ag, 22.5 wt% Sn, 0.1 wt% Fe, 0.3 wt% As, 0.3 wt% Sb, 0.3 wt% Bi, and 0.5 wt% O with a melting point of about 645 °C, available from 5N Plus Inc.

[0116] Sn80 / Cu20 is a copper alloy consisting of 20 wt% Cu and 80 wt% Sn with a melting point of about 480 °C, available from 5N Plus Inc.

[0117] Preparation method:

[0118] In the following examples, samples were prepared by mixing and stirring at a temperature lower than 30°C, preferably at room temperature, at 1000 rpm in order to obtain a homogeneous composition paste. The samples were then sintered under N2 atmosphere at a rate of 5°C / min to 130°C for 30 minutes and then at a rate of 5°C / min to 220°C for 60 minutes. No pressure was used.

[0119] Test method:

[0120] Chip shear strength:

[0121] The die shear strength (DSS) was measured using a DAGE 4000 with a heater adapter board capable of reaching 260°C. The compositions were coated onto 2x2 mm 2 silver coated die and on a commercial type of copper lead frame (CDA151) used in the semiconductor industry. The samples were sintered according to the sintering profile described above. Each sample was tested eight times under the same conditions and the average die shear strength was calculated and recorded using the simple average method to eliminate errors. The average die shear strength target was greater than or equal to 4.0 Kg / mm 2 .

[0122] Examples 1-4 and Comparative Example 1

[0123] In this set of examples, a silver sintering composition not including resin and not including copper alloy (CE.2) and a silver sintering composition with a copper alloy according to the application (EX.5) were prepared based on the weight percentages specified in the table below. The die shear strength of samples for type 2 Cu lead frame was tested.

[0124]

[0125] Example 5 and Comparative Example 2

[0126] In this set of examples, a silver sintering composition not including resin and not including copper alloy (CE.2) and a silver sintering composition with a copper alloy according to the application (EX.5) were prepared based on the weight percentages specified in the table below. The die shear strength of samples for type 2 Cu lead frame was tested.

[0127]

[0128] Examples 6-11 and Comparative Example 3

[0129] In this set of embodiments, a silver sintered composition (CE.3) excluding resin and copper alloy and six silver sintered compositions (EX.6-EX.11) having different types of copper alloys according to the invention were prepared based on the weight percentages specified in the table below. The chip shear strength of the samples used for the type 2 Cu leadframe was tested.

[0130]

[0131]

[0132] The results of the above three sets of embodiments show that, regardless of whether it is a pure silver sintering binder without resin or a silver sintering binder containing resin, the average chip shear strength of the copper lead frame composition containing copper alloy is higher than that of the composition without copper alloy.

[0133] As can be seen from the figure, for silver sintered matrix ( Figure 1 ) and semi-sintered matrix ( Figure 2 The copper alloy increases the diffusion of silver particles, which can improve adhesion on the metal substrate.

[0134] Although some preferred embodiments have been described, many modifications and variations can be made to them based on the above teachings. Therefore, it should be understood that the invention can be practiced in ways different from those specifically described without departing from the scope of the appended claims.

Claims

1. A silver sintering composition comprising: (A) at least one silver filler in an amount of 80 to 96 wt.%, based on the total weight of the composition, (B) at least one copper alloy in an amount of 1.5 to less than 7.5 wt.%, based on the total weight of the composition, and (C) a matrix component selected from a resin, a solvent, and combinations thereof, in an amount of no more than 15 wt.%, based on the total weight of the composition, wherein the copper alloy comprises at least one metal selected from tin (Sn), silver (Ag), zinc (Zn), gold (Au), bismuth (Bi), lead (Pb), manganese (Mn), iron (Fe), nickel (Ni), indium (In), cadmium (Cd), cobalt (Co), arsenic (As), aluminum (Al), silicon (Si), and antimony (Sb), and wherein the copper alloy comprises 20 to 90 wt.% Cu, based on the total weight of the copper alloy.

2. The composition of claim 1, wherein, The silver filler has a D 50 The particle size is 0.5 to 6.0 μm.

3. The composition of claim 1, wherein, The silver filler has a D 50 The particle size is 0.8 to 5.0 μm.

4. The composition of claim 1, wherein, The silver filler has a D 50 The particle size is 1.0 μm to 5.0 μm.

5. The composition of claim 1, wherein, The silver filler has a D 50 The particle size is 1.1 to 1.4 μm.

6. The composition of claim 1, wherein, The silver filler has a D 50 The particle size is 1.1 to 3.0 μm.

7. The composition according to any one of claims 1 to 6, wherein, The silver filler has a tap density of 2 g / cm 3 up to 15 g / cm 3 .

8. The composition according to any one of claims 1 to 6, wherein, The silver filler has a tap density of 3 g / cm 3 to 7.5 g / cm 3 .

9. The composition according to any one of claims 1 to 6, wherein, The copper alloy comprises at least one metal selected from Sn, Ag, Pb, and Zn.

10. The composition according to any one of claims 1 to 6, wherein, The resin is selected from a thermoplastic resin or a thermoset resin.

11. The composition according to any one of claims 1 to 6, wherein, The solvent has a flash point of greater than 70 °C.

12. The composition according to any one of claims 1 to 6, wherein, The solvent has a flash point of greater than 90 °C.

13. The composition according to any one of claims 1 to 6, wherein, The solvent has a flash point of greater than 120 °C.

14. The composition according to any one of claims 1 to 6, wherein, The silver filler is present in an amount of 85 to 95 wt.%, based on the total weight of the composition.

15. The composition according to any one of claims 1 to 6, wherein, The copper alloy is present in an amount of 1.5 to 7.0 wt.%, based on the total weight of the composition.

16. The composition according to any one of claims 1 to 6, wherein, The copper alloy is present in an amount of 2.5 to 5.0 wt.%, based on the total weight of the composition.

17. The composition according to any one of claims 1 to 6, wherein, The copper alloy comprises 28 to 90 wt.% Cu, based on the total weight of the copper alloy.

18. The composition according to any one of claims 1 to 6, wherein, The copper alloy comprises 73 to 90 wt.% Cu, based on the total weight of the copper alloy.

19. The composition according to any one of claims 1 to 6, wherein, The copper alloy comprises 60 to 90 wt.% Cu, based on the total weight of the copper alloy.

20. The composition according to any one of claims 1 to 6, wherein, The matrix component is present in an amount of 2 to 10 wt.%, based on the total weight of the composition.

21. The composition according to any one of claims 1 to 6, wherein, The composition further comprises an additive selected from a fluxing agent, a peroxide, a flow additive, an adhesion promoter, a rheology modifier, a toughener, and mixtures thereof.

22. The composition of claim 21, wherein, The additive is present in an amount of no more than 2 wt.%, based on the total weight of the composition.

23. The composition of claim 21, wherein, The additive is present in an amount of 0.5 to 2 wt.%, based on the total weight of the composition.

24. A sintered product of the silver sintering composition according to any one of claims 1 to 23.

25. An assembly comprising a first substrate of silver, the sintered product according to claim 24, and a second substrate selected from copper, gold, or silver, wherein the sintered product is distributed between the first substrate and the second substrate.

26. Use of the silver sintering composition according to any one of claims 1 to 23 or the sintered product according to claim 24 in the manufacture of a semiconductor package or a touch screen.

Images