WO2018053802A1

WO2018053802A1 - Electrically conductive adhesive

Info

Publication number: WO2018053802A1
Application number: PCT/CN2016/099863
Authority: WO
Inventors: Minfang Mu; Fei Xiang; Tao Yang
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 2016-09-23
Filing date: 2016-09-23
Publication date: 2018-03-29
Anticipated expiration: 2019-03-23
Also published as: CN109790424A; CN109790424B

Abstract

Disclosed herein are adhesive compositions comprising : (a) a continuous insulating binder phase, (b) a plurality of conductive particles, (c) a first particulate non-conductive phase formed of a plurality of insulating particles, and (d) a second particulate non-conductive phase formed of a plurality of copolyetherester particles. Also disclosed herein are electrically conductive adhesives formed of the cured adhesive compositions, and electronic parts or articles comprising the electrically conductive adhesives.

Description

ELECTRICALLY CONDUCTIVE ADHESIVE

FIELD OF THE INVENTION

The present invention relates to an adhesive composition, an electrically conductive adhesive, and electronic parts or articles comprising the electrically conductive adhesive.

BACKGROUND OF THE INVENTION

Electrically conductive adhesives (ECAs) have been used widely in the electronic industry. Typically, ECAs are comprised of conductive particles dispersed in a polymeric binder system, which can provide bonding and conductivity between two electronic parts. And higher conductivity requires higher loading of the conductive particles. However, higher loading of conductive particles also negatively affects the mechanical strength of the ECAs. One solution is to include a particulate insulating phase in the ECAs, such as those disclosed in U.S. patent application publications US 2010/0221533； US 2014/0183715； and US 2010/0012358. However, there is still a need to develop ECAs with further improved bonding strength, while sufficient conductivity is maintained.

BRIEF SUMMARY OF THE INVENTION

Provided herein is an adhesive composition comprising: (a) a continuous insulating binder phase formed of a mixture of at least one fluoroelastomer and at least one ethylene/alkyl (meth) acrylate copolymer elastomer at a weight ratio of about 25: 75-90: 10, (b) a plurality of conductive particles； (c) a first particulate non-conductive phase comprising a plurality of insulating particles, and (d) a second particulate non-conductive phase comprising a plurality of copolyetherester particles, wherein, i) the conductive particles, the insulating particles, and the copolyetherester particles are dispersed in the continuous binder phase； ii) the volume ratio of the first particulate non-conductive phase to the second particulate non-conductive phase is about 60: 40-20: 80； iii) the copolyetherester particles comprised in the second particulate non-conductive phase have a melting point between 100-220℃； and iv) the insulating particles comprised in the first particulate non-conductive phase are formed of inorganic materials or cross-linked polymers or high melting point polymers having a melting point at least about 20℃ higher than that of the copolyetherester particles, have a standard deviation σp (expressed as D_84.13/D₅₀) value equals to about 1.7 or less, have a particle size distribution D₅₀ at least about 1.2 times that of the conductive particles, and have a particle size distribution D₉₉ range from about 10-80 μm.

In one embodiment of the adhesive composition, the continuous insulating binder phase is present at a level of about 5-45 wt％, the plurality of conductive particles is present at a level of about 30-80 wt％, and the first and second particulate non-conductive phase is present at a level of about 5-70 wt％, with the weight of all components totaling to 100 wt％.

In a further embodiment of the adhesive composition, the continuous insulating binder phase is present at a level of about 8-45 wt％, the plurality of conductive particles is present at a level of about 40-70 wt％, and the first and second particulate non-conductive phase is present at a level of about 7-60 wt％, with the weight of all components totaling to 100 wt％.

In a yet further embodiment of the adhesive composition, the volume ratio of the first particulate non-conductive phase to the second particulate non-conductive phase is about 55: 45-25: 75.

Further provided herein is an adhesive film formed of the adhesive composition disclosed above.

Yet further provided herein is an electrically conductive adhesive obtained by curing the adhesive composition described above.

In one embodiment of the electrically conductive adhesive, the adhesive composition is cured at a temperature of about 100-250℃ and a pressure of about 0.5-10 MPa.

In a further embodiment of the electrically conductive adhesive, the adhesive composition is cured at a temperature of about 120-250℃ and a pressure of about 1-10 MPa.

Yet further provided herein is an electronic part comprising the electrically conductive adhesive disclosed above.

DETAILED DESCRIPTION OF THE INVENTION

Disclosed herein are adhesive compositions comprising: (a) a continuous insulating binder phase, (b) a plurality of conductive particles, (c) a first particulate non-conductive phase formed of a plurality of insulating particles, and (d) a second particulate non-conductive phase formed of a plurality of copolyetherester particles.

Insulating Binder Phase

The continuous insulating binder phase is formed of or comprise a blend of at least one fluoroelastomer and at least one ethylene/alkyl (meth) acrylate copolymer elastomer (also known as AEM rubber) .

The fluoropolymers used herein may contain at least about 53 wt％of fluorine, or at least about 64 wt％of fluorine, based on the total weight of the fluoroestomer.

In particular, the fluoroelastomers used herein may be vinylidene fluoride-containing fluoroelastomers containing about 25-70 wt％of copolymerized units of vinylidene fluoride (VF₂) , based on the total weight of the fluoroelastomers. In such embodiments, the remaining units of the fluoroelastomers are comprised of one or more additional copolymerized monomers that are different from vinylidene fluoride. Such one or more additional polymerized monomers that are different from vinylidene fluoride may be selected from fluorine-containing olefins, fluorine-containing vinyl ethers, hydrocarbon olefins, and mixtures thereof.

Fluorine-containing olefins copolymerizable with the vinylidene fluoride include, but are not limited to, hexafluoropropylene (HFP) , tetrafluoroethylene (TFE) , 1, 2, 3, 3, 3-pentafluoropropene (1-HPFP) , chlorotrifluoroethylene (CTFE) , and vinyl fluoride.

Fluorine-containing vinyl ethers copolymerizable with vinylidene include, but are not limited to, perfluoro (alkyl vinyl) ethers (PAVE) . PAVE suitable for use as monomers include those of the formula

CF₂＝CFO (R_f’ O) _n (R_f” O) _mR_f (I)

wherein R_f’ and R_f” are different linear or branched perfluoroalkylene groups of 2-6 carbon atoms； m and n are independently integers of 0-10； and R_f is a perfluoroalkyl group of 1-6 carbon atoms.

A preferred class of perfluoro (alkyl vinyl) ethers includes those of the formula:

CF₂＝CFO (CF₂CFXO) _nR_f (II)

wherein X is F or CF₃； n is an integer of 0-5； and R_f is a perfluoroalkyl group of 1-6 carbon atoms.

A most preferred class of perfluoro (alkyl vinyl) ethers includes those ethers wherein n is 0 or 1 and R_f contains 1-3 carbon atoms. Examples of such perfluorinated ethers include perfluoro (methyl vinyl) ether (PMVE) and perfluoro (propyl vinyl) ether (PPVE) . Other useful monomers include compounds of the formula

CF₂＝CFO [ (CF₂) _mCF₂CFZO] _nR_f (III)

wherein R_f is a perfluoroalkyl group having 1-6 carbon atoms； m is 0 or 1； n is an integer of 0-5； and Z is F or CF₃. Preferred members of this class are those in which R_f is C₃F₇； m is 0； and n is 1.

Additional perfluoro (alkyl vinyl) ether monomers include those of the formula

CF₂＝CFO [ (CF₂CF {CF₃} O) _n (CF₂CF₂CF₂O) _m (CF₂) _p] C_xF_2x+i (IV)

wherein m and n are independently integers of 0-10； p is an integer of 0-3； and x is an integer of 1-5.

Preferred members of this class include compounds wherein n is 0 or 1； m is 0 or 1； and x is 1.

Other examples of useful perfluoro (alkyl vinyl ethers) include

CF₂＝CFOCF₂CF (CF₃) O (CF₂O) _mC_nF_2n+i (V)

wherein n is an integer of 1-5； m is an integer of 1-3； and wherein, preferably, n is 1.

If copolymerized units of PAVE are present in the fluoroelastomers used herein, the PAVE content generally ranges from about 25 wt％to about 75 wt％, based on the total weight of the fluoroelastomer. If PMVE is used, then the fluoroelastomer used herein preferably contains between about 30 wt％and about 55 wt％copolymerized PMVE units.

The fluoroelastomers used herein may also, optionally, comprise units of one or more cure site monomers. Examples of suitable cure site monomers include, without limitation, i) bromine-containing olefins； ii) iodine-containing olefins； iii) bromine-containing vinyl ethers； iv) iodine-containing vinyl ethers； v) 1, 1, 3, 3, 3-pentafluoropropene (2-HPFP) ； and vi) non-conjugated dienes.

Brominated cure site monomers may contain other halogens, preferably fluorine. Examples of brominated olefin cure site monomers are CF₂＝CFOCF₂CF₂CF₂OCF₂CF₂Br； bromotrifluoroethylene； 4-bromo-3, 3, 4, 4-tetrafluorobutene-1 (BTFB) ； vinyl bromide； 1-bromo-2, 2-difluoroethylene； perfluoroallyl bromide； 4-bromo-1, 1, 2-trifluorobutene-1； 4-bromo-1, 1, 3, 3, 4, 4, -hexafluorobutene； 4-bromo-3-chloro-1, 1, 3, 4, 4-pentafluorobutene； 6-bromo-5, 5, 6, 6-tetrafluorohexene； 4-bromoperfluorobutene-1； and 3, 3-difluoroallyl bromide. Brominated vinyl ether cure site monomers useful herein include 2-bromo-perfluoroethyl perfluorovinyl ether, fluorinated compounds of the class CF₂Br-Rf-O-CF＝CF₂ (wherein Rf is a perfluoroalkylene group, such as CF₂BrCF₂O-CF＝CF₂) , and fluorovinyl ethers of the class ROCF＝CFBr or ROCBr＝CF₂ (wherein R is a lower alkyl group or fluoroalkyl group, such as CH₃OCF＝CFBr or CF₃CH₂OCF＝CFBr) .

Suitable iodinated cure site monomers include iodinated olefins of the formula: CHR＝CH-Z-CH₂CHR-I, wherein R is -H or -CH₃； Z is a C₁-C₁₈ (per) fluoroalkylene radical, linear or branched, optionally containing one or more ether oxygen atoms, or a (per) fluoropolyoxyalkylene radical as disclosed in U.S. Patent 5,674,959. Other examples of useful iodinated cure site monomers are unsaturated ethers of the formula: l (CH₂CF₂CF₂) _nOCF＝CF₂ and ICH₂CF₂O [CF (CF₃) CF₂O] _nCF＝CF₂, and the like, wherein n is an integer of 1-3, such as disclosed in U.S. Patent 5,717,036. In addition, suitable iodinated cure site monomers including iodoethylene, 4-iodo-3, 3, 4, 4-tetrafluorobutene-1 (ITFB) ； 3-chloro-4-iodo-3, 4, 4-trifluorobutene； 2-iodo-1, 1, 2, 2-tetrafluoro-1-(vinyloxy) ethane； 2-iodo-1- (perfluorovinyloxy) -l, 1, -2, 2-tetrafluoroethylene； 1, 1, 2, 3, 3, 3-hexafluoro-2-iodo-1- (perfluorovinyloxy) propane； 2-iodoethyl vinyl ether； 3, 3, 4, 5, 5, 5-hexafluoro-4-iodopentene； iodotrifluoroethylene, and those disclosed in U.S. Patent 4,694,045. Allyl iodide and 2-iodo-perfluoroethyl perfluorovinyl ether are also useful cure site monomers.

Examples of non-conjugated diene cure site monomers include, but are not limited to, 1, 4-pentadiene； 1, 5-hexadiene； 1, 7-octadiene； 3, 3, 4, 4-tetrafluoro-1, 5-hexadiene； and others, such as those disclosed in Canadian Patent 2,067,891 and European Patent 0784064A1. A suitable triene is 8-methyl-4-ethylidene-1, 7-octadiene. Of the cure site monomers listed above, preferred compounds, for situations wherein the fluoroelastomer will be cured with peroxide, include 4-bromo-3, 3, 4, 4-tetrafluorobutene-1 (BTFB) ； 4-iodo-3, 3, 4, 4-tetrafluorobutene-1 (ITFB) ； allyl iodide； and bromotrifluoroethylene. When the fluoroelastomer will be cured with a polyol, 2-HPFP is the preferred cure site monomer. However, a cure site monomer is not required in copolymers of vinylidene fluoride and hexafluoropropylene in order to cure with a polyol.

Units of cure site monomer, when present in the fluoroelastomers used herein, are typically present at a level of about 0.05-10 wt％, or about 0.05-5 wt％, or about 0.05-3 wt％, based on the total weight of fluoroelastomers.

Additionally, iodine-containing end groups, bromine-containing end groups or mixtures thereof may optionally be present at one or both of the fluoroelastomer polymer chain ends as a result of the use of chain transfer or molecular weight regulating agents during preparation of the fluoroelastomers. The amount of chain transfer agent, when employed, is calculated to result in an iodine or bromine level in the fluoroelastomer in the range of about 0.005-5 wt％, or about 0.05-3 wt％.

Examples of chain transfer agents include iodine-containing compounds that result in incorporation of bound iodine at one or both ends of the polymer molecules. Methylene iodide； 1, 4-diiodoperfluoro-n-butane； and 1, 6-diiodo-3, 3, 4, 4, tetrafluorohexane are representative of such agents. Other iodinated chain transfer agents include 1, 3-diiodoperfluoropropane； 1, 6-diiodoperfluorohexane； 1, 3-diiodo-2-chloroperfluoropropane； 1, 2-di (iododifluoromethyl) -perfluorocyclobutane； monoiodoperfluoroethane； monoiodoperfluorobutane； 2-iodo-1-hydroperfluoroethane, etc. Also included are the cyano-iodine chain transfer agents disclosed in European Patent 0868447A1. Particularly preferred are diiodinated chain transfer agents. Examples of brominated chain transfer agents include 1-bromo-2-iodoperfluoroethane； 1-bromo-3-iodoperfluoropropane； 1-iodo-2-bromo-1, 1-difluoroethane and others such as disclosed in U.S. Patent 5,151,492.

Other chain transfer agents suitable for use in the fluoroelastomers used herein include those disclosed in U.S. Patent 3,707,529. Examples of such agents include isopropanol, diethylmalonate, ethyl acetate, carbon tetrachloride, acetone, and dodecyl mercaptan.

Specific fluoroelastomers which may be used herein include, but are not limited to those having at least about 53 wt％fluorine and comprising copolymerized units of i) vinylidene fluoride and hexafluoropropylene； ii) vinylidene fluoride, hexafluoropropylene, and tetrafluoroethylene； iii) vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, and 4-bromo-3, 3, 4, 4-tetrafluorobutene-1； iv) vinylidene fluoride, hexafluoropropylene, tetrafluoroethylene, and 4-iodo-3, 3, 4, 4-tetrafluorobutene-1； v) vinylidene fluoride, perfluoro (methyl vinyl) ether, tetrafluoroethylene, and 4-bromo-3, 3, 4, 4-tetrafluorobutene-1； vi) vinylidene fluoride, peril uoro (methyl vinyl) ether, tetrafluoroethylene, and 4-iodo-3, 3, 4, 4-tetrafluorobutene-1； or vii) vinylidene fluoride, peril uoro (methyl vinyl) ether, tetrafluoroethylene, and 1, 1, 3, 3, 3-pentafluoropropene.

The fluoroelastomers used herein are typically prepared in an emulsion polymerization process, which may be a continuous, semi-batch, or batch process.

The fluoroelastomers useful herein are commercially available from various vendors. For example, suitable fluoroelastomers may be obtained from E.I. du Pont de Nemours and Company (U.S.A. ) (hereafter “DuPont” ) under the trade name

or from 3M (U.S.A. ) under the trade name 3M^TM Dyneon^TM, or from Daikin Industries, Ltd. (Japan) under the trade name DAI-EL^TM, or from Tetralene Elastomer, Inc. (U.S.A. ) under the trade name FluoTrex^TM.

The fluoroelastomers used herein may be cross-linked with a cross-linking agent. For example, the cross-linking agents used herein include, without limitation, bisphenol compounds, diamino compounds, aminophenol compounds, amino-siloxane compounds, amino-silanes, phenol-silanes, and peroxides. Exemplary diamine-based cross-linking agents include, N, N'-dicinnamal-1, 6-hexamethylenediamine； hexamethylene diamine carbomate； N, N-Bis (salicylidene) -1, 3-propanediamine； etc. Exemplary bisphenol-based cross-linking agents include, 2, 2-bis (4-hydroxyphenyl) hexafluoropane； 4’, 4-(Hexafluoroisopropylidene) diphenol； benzyltriphenylphosphonium chloride； 2, 4-dihydroxybenzophenone； bisphenol AF； etc. Exemplary peroxide-based cross-linking agents include, tert-butylcumyl peroxide； α, α-bis (tert-butylperoxy-isopropyl) benzene； 2, 5-dimethyl-2, 5-di (t-butyl-peroxy) hexane； etc. Suitable cross-linking agents also are available commercially from various vendors, which include, without limitation, those available from 3M under the trade name of 3M^TM Dynamar^TM Rubber Curative RC, or from R.T. Vanderbilt Company, Inc. (U.S.A. ) under the trade name VAROX^TM, or from AkzoNobel Corporate (The Netherlands) under the trade names Trigonox^TM or Perkadox^TM, or from DuPont under the trade names

CURATIVE 20, CURATIVE 30, or CURATIVE 50.

The ethylene/alkyl (meth) acrylate copolymer elastomers used herein are derived from copolymerization of polymerized units of ethylene and about 45-90 wt％, or about 50-80 wt％, or about 50-75 wt％of polymerized units of at least one alkyl (meth) acrylate, based on the total weight of the ethylene/alkyl (meth) acrylate copolymer elastomer. The term " (meth) acrylate" is used herein to refer to esters of methacrylic acids and/or esters of acrylic acids, and the term “meth” is used herein to refer to -H or branched or non-branched groups C₁-C₁₀ alkyl, and the term “alkyl” is used herein to refer to -H or branched or non-branched groups of C₁-C₁₂ alkyl, C₁-C₂₀ alkoxyalkyl, C₁-C₁₂ cyanoalkyl, or C₁-C₁₂ fluoroalkyl. The alkyl (meth) acrylate groups used herein include, without limitation, alkyl acrylate, alkyl methacrylates, alkyl ethacrylates, alkyl propacrylates, alkyl hexacrylates, alkoxyalkyl methacrylates, alkoxyalkyl ethacryates, alkoxyalkyl propacrylates, and alkoxyalkyl hexacrylates. The alkyl groups may be substituted with cyano groups or one or more fluorine atoms. That is, the alkyl group may be a C₁-C₁₂ cyanoalkyl group or a C₁-C₁₂ fluoroalkyl group. The ethylene/alkyl (meth) acrylate copolymers may also comprise copolymerized units of more than one species of the alkyl (meth) acrylates, for example two different alkyl acrylate monomers. For example, the ethylene/alkyl (meth) acrylate copolymers used herein include, without limitation, ethylene/methyl acrylate copolymers (EMA) , ethylene/ethyl acrylate copolymers (EEA) , and ethylene/butyl acrylate copolymers (EBA) .

Moreover, the ethylene/alkyl (meth) acrylate copolymer elastomers used herein may optionally further comprise up to about 5 wt％of a functionalized comonomer, based on the total weight of the ethylene/alkyl (meth) acrylate copolymer elastomer. The optional functionalized comonomers used herein, include, without limitation, (meth) acrylate glycidyl esters (such as glycidyl methacrylate) , chlorovinyl ether, maleic acids, and other comonomers having one or more reactive groups including acid, hydroxyl, anhydride, epoxy, isocyanates, amine, oxazoline, chloroacetate, carboxylic ester moieties, or diene functionality. Also conceivable is that the ethylene/alkyl (meth) acrylate copolymer elastomers used herein are made by copolymerizing ethylene and more than one (e.g., two) alkyl (meth) acrylate monomers. Examples are ethylene/alkyl (meth) acrylate copolymer elastomers made by polymerizing ethylene, methyl acrylate, and a second acrylate (such as butyl acrylate) .

The ethylene/alkyl (meth) acrylate copolymer elastomers may be prepared by various processes well known in the polymer art. For example, the copolymerization can be run as a continuous process in an autoclave reactor. Or alternatively, the ethylene/alkyl (meth) acrylate copolymers used herein may be produced at high pressure and elevated temperature in a tubular reactor or the like. The copolymer can be separated from the product mixture with the un-reacted monomers and solvent (if used) by conventional means, e.g., vaporizing the non-polymerized materials and solvent under reduced pressure and at an elevated temperature.

The ethylene/alkyl (meth) acrylate copolymer elastomers used herein are also available commercially. Exemplary ethylene/alkyl (meth) acrylate copolymer elastomers may include those available from DuPont under the trade name

The ethylene/alkyl (meth) acrylate copolymer elastomers used herein may be cross-linked with cross-linking agents.

The cross-linking agents used herein include, without limitation, amino compounds and peroxides. Exemplary peroxide type cross-linking agents that are suitable herein include, without limitation, methylethylketone peroxide； dicumyl peroxide； 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane； 1, 1-bis (t-butylperoxy) -3, 3, 5-tr-imethylcyclohexane； 1, 1-di- (t-butylperoxy) cyclohexane； 2, 2'-bis (t-butylperoxy) diisopropylbenzene； 4, 4'-bis (t-butylperoxy) butyl valerate； ethyl 3, 3-bis (t-butylperoxy) butyrate； t-butyl cumyl peroxide； di [ (t-butylperoxy) -isopropyl] benzene； t-butyl peroxide； 6, 6, 9, 9-tetramethyl-3-methyl-3, n-butyl-1, 2, 4, 5-tetraoxycyclononane； 6, 6, 9, 9-tetramethyl-3-methyl-3-ethyl carbonylmethyl-1, 2, 4, 5-tetraoxy-cyclononane； ethyl 3, 3-di (t-butylperoxy) -butyrate； dibenzoyl peroxide； 2, 4-dichlorobenzoyl peroxide； OO-t-butyl-O- (2-ethylhexyl) mono peroxycarbonate； 2, 5-dimethyl-2, 5-di- (t-butylperoxy) -3-hexyne； and combinations of two or more thereof.

The peroxide type cross-linking agents used herein also are available commercially. Exemplary peroxide type cross-linking agents may include those available from AkzoNobel Corporate under the trade name Perkadox^TM； or from Arkerma, Inc. under the trade name Luperox^TM. Suitable dicumyl peroxide (DCP) cross-linking agents may be obtained from Shanghai Fangruida Chemical Co. Ltd. (China) or Hangzhou Hi-Tech Fine Chemical Co. Ltd. (China) .

Exemplary amino compounds that are suitable herein include, without limitation, hexamethylene diamine carbamate, triethylene tetramine, and methylene dianiline. Suitable amino compounds as cross-linking agents are available commercially, such as, hexamethylene diamine carbamate, available from DuPont under the trade name Diak^TM No. 1； triethylene tetramine, available from Huntsman Corporation (USA) ； methylene dianiline, available from Sigma-Aldrich Co. LLC (USA) .

It is understood that, when peroxide type cross-linking agent (s) are used, suitable cross-linking co-agents also may be used. Exemplary cross-linking co-agents used herein include, without limitation, trifunctional methacrylate ester (TMA) , zinc diacrylate (ZDA) , high vinyl polybutadiene (HVPBD) , triallyl cyanurate (TAC) , and triallyl isocyanurate (TAIC) . Suitable TMA may be obtained from DSM-AGI Corporation (Taiwan) under the tradename Agisyn^TM 2817 (TMPTMA) or Agisyn^TM 2811 (TMTPA) ； Suitable ZDA may be obtained from Sartomer Company (France) under the tradename SR633； suitable HVPBD may be obtained from Cray valley USA, LLC (USA) under the trade name Ricon^TM154； Suitable TAIC may be obtained from DuPont under the trade name of Diak^TM7.

The blend of the at least one fluoroelastomer and the at least one at least one ethylene/alkyl (meth) acrylate copolymer elastomer forms a continuous binder phase in the adhesive composition and all other components are uniformly dispersed in the continuous binder phase. Within the insulating binder phase, the weight ratio of the at least one fluoroelastomer to the at least one ethylene/alkyl (meth) acrylate copolymer elastomer may be in range of about 25:75-90:10, or from about 30:70-90:10, or from about 35:65-85:15.

Based on the adhesive composition, the continuous insulating binder phase may be present at a level of about 5-45 wt％, or about 8-45 wt％.

Conductive Particles

The conductive particles may include metal particles, metal coated particles, and combinations thereof. Suitable metal particles include, without limitation, particles of Au, Ag, Ni, Cu, Al, Sn, Zn, Ti, Sn, Bi, W, Pb, and alloys of two or more thereof. The metal coating material used in the metal coated particles may include, without limitation, Au, Ag, Ni, and combinations of two or more thereof. Suitable metal coated particles include, without limitation, Ag-coated glass beads, Ag-coated polystyrene particles, Ag-coated Cu particles, Ni-coated Cu particles, and combinations of two or more thereof.

The particle size distribution D₅₀ of the conductive particles may range from about 1-20 μm, or about 2-10 μm. Particle size distribution D₅₀ is also known as the median diameter or the medium value of the particle size distribution, it is the value of the particle diameter at 50 volume％in the cumulative distribution. For example, if D₅₀＝5.4 μm, then 50 volume％of the particles in the sample have diameters larger than 5.4 μm, and 50 volume％of the particles have diameters smaller than 5.4 μm. Likewise, particle size distribution D₁₀ is the value of the particle diameter at 10 volume％in the cumulative distribution； particle size distribution D_84.13 is the value of the particle diameter at 84.13 volume％in the cumulative distribution； and particle size distribution D₉₉ is the value of the particle diameter at 99 volume％in the cumulative distribution. Particle size distributions of a group of particles can be determined using light scattering methods following, for example, ASTM B822-10.

Based on the total weight of the adhesive composition, the conductive particles may be present at a level of about 30-80 wt％, or about 40-70 wt％, or about 45-65 wt％.

First Particulate Non-conductive Phase

The first particulate non-conductive phase comprised in the adhesive composition comprises or is formed of a plurality of insulating particles that are not deformable under proper process conditions. In particular, as, when in use in electronic parts, the binder phase of the adhesive composition will be cross- linked into a binder matrix, it is understood that the polymeric particles will not melt or deform during such cross-linking (or curing) process.

The inorganic particles used herein include, without limitation, metal oxide particles, silica particles, sand particles, mineral particles, ceramic particles, and mixture thereof.

The polymeric particles disclosed herein comprise or are formed of high melting point polymers or cross-linked polymers.

The cross-linked polymers used herein include, without limitation, cross-linked poly (methyl methacrylate) (PMMA) , cross-linked polydimethylsiloxane (silicone) , cross-linked polystyrene (PS) , cross-linked polyvinyl acetate (PVA) , cross-linked glycidyl methacrylate/methyl methacrylate (GMA/MMA) , and combinations of two or more thereof.

The high melting point polymers used herein have a melting point at least about 20℃ higher than that of the copolyetherester particles. The high melting point polymers used herein include, without limitation, polyamide 6, polyamide 66, polytetrafluoroethylene (PTFE) , polyether ketone (PEK) , polyether ether ketone (PEEK) , polyphenylene sulfite (PPS) , polyimide (PI) , polyethersulfone (PES) , polyphenylsulfone (PPSU) , and combinations of two or more thereof.

In accordance with the present disclosure, the high melting point polymers have a melting point ranging from about 150-450℃, or about 170-400℃. More specifically, the high melting point polymers used herein need to have a melting point at least 20℃ higher than that of the copolyetheresters used in forming the copolyetherester particles.

In accordance with the present disclosure, the particle size distribution D₅₀ of the insulating particles may be at least about 1.2 times that of the conductive particles and may range from about 1.5-80 μm and particle size distribution D₉₉ of the insulating particles may range from about 10-80 μm. In addition, the standard deviation σ_p of the insulating particles may be about 1.7 or less. Standard deviation σ_p, which is expressed as D_84.13/D₅₀, is use to describe the diversity of particles sizes of a group of particles. A group of particles having a broad range of particle sizes has a larger standard deviation σ_p than those having a narrow range of particle sizes. Obtaining particles with various size distribution can be achieved by any suitable methods, such by sieving.

Second Particulate Non-conductive Phase

The second particulate non-conductive phase comprised in the adhesive composition comprises or is formed of a plurality of copolyetherester particles.

The copolyetheresters used herein may be copolymers having a multiplicity of recurring long-chain ester units and recurring short-chain ester units joined head-to-tail through ester linkages, the long-chain ester units being represented by formula (I) :

and the short-chain ester units being represented by formula (II) :

wherein,

G is a divalent radical remaining after the removal of terminal hydroxyl groups from poly (alkylene oxide) glycols having a number average molecular weight of about 400-6000；

R is a divalent radical remaining after the removal of carboxyl groups from a dicarboxylic acid having a number average molecular weight of about 300 or less；

D is a divalent radical remaining after the removal of hydroxyl groups from a glycol having a number average molecular weight of about 250 or less, and

wherein,

the at least one copolyetherester contains about 1-85 wt％of the recurring long-chain ester units and about 15-99 wt％of the recurring short-chain ester units.

In one embodiment, the copolyetherester used in the composition disclosed herein contains about 5-80 wt％of the recurring long-chain ester units and about 20-95 wt％of the recurring short-chain ester units.

In a further embodiment, the copolyetherester used in the composition disclosed herein contains about 10-75 wt％of the recurring long-chain ester units and about 25-90 wt％of the recurring short-chain ester units.

In a yet further embodiment, the copolyetherester used in the composition disclosed herein contains about 40-75 wt％of the recurring long-chain ester units and about 25-60 wt％of the recurring short-chain ester units.

As used herein, the term “long-chain ester units” refers to reaction products of a long-chain glycol with a dicarboxylic acid. Suitable long-chain glycols are poly (alkylene oxide) glycols having terminal hydroxyl groups and a number average molecular weight of about 400-6000, or about 600-3000, which include, without limitation, poly (tetramethylene oxide) glycol, poly (trimethylene oxide) glycol, poly (propylene oxide) glycol, poly (ethylene oxide) glycol, copolymer glycols of these alkylene oxides, and block copolymers such as ethylene oxide-capped poly (propylene oxide) glycol. The long-chain glycols used herein may also be combinations of two or more of the above glycols.

As used herein, the term “short-chain ester units” refers to reaction products of a low molecular weight glycol or an ester-forming derivative thereof with a dicarboxylic acid. Suitable low molecular weight glycols are those having a number average molecular weight of about 250 or lower, or about 10-250, or about 20-150, or about 50-100, which include, without limitation, aliphatic dihydroxy compounds, alicyclic dihydroxy compounds, and aromatic dihydroxy compounds (including bisphenols) . In one embodiment, the low molecular weight glycol used herein is a dihydroxy compound having 2-15 carbon atoms, such as ethylene glycol； propylene glycol； isobutylene glycol； 1, 4-tetramethylene glycol； pentamethylene glycol； 2, 2-dimethyltrimethylene glycol； hexamethylene glycol； decamethylene glycol； dihydroxycyclohexane； cyclohexanedimethanol； resorcinol； hydroquinone； 1, 5-dihydroxynaphthalene； or the like. In a further embodiment, the low molecular weight glycol used herein is a dihydroxy compound having 2-8 carbon atoms. In a yet further embodiment, the low molecular weight glycol used herein is 1, 4-tetramethylene glycol. Bisphenols that are useful herein include, without limitation, bis (p-hydroxy) diphenyl, bis (p-hydroxyphenyl) methane, bis (p-hydroxyphenyl) propane, and mixtures of two or more thereof.

The ester-forming derivatives of low molecular weight glycols useful herein include those derived from the low molecular weight glycols described above, such as ester-forming derivatives of ethylene glycol (e.g., ethylene oxide or ethylene carbonate) or ester-forming derivatives of resorcinol (e.g., resorcinol diacetate) . As used herein, the number average molecular weight limitations pertain to the low molecular weight glycols only. Therefore, a compound that is an ester-forming derivative of a glycol and has a number average molecular weight more than 250 can also be used herein, provided that the corresponding glycol has a number average molecular weight of about 250 or lower.

The “dicarboxylic acids” useful for reaction with the above described long-chain glycols or low molecular weight glycols are those low molecular weight (i.e., number average molecular weight of about 300 or lower, or about 10-300, or about 30-200, or about 50-100) aliphatic, alicyclic, or aromatic dicarboxylic acids.

The term “aliphatic dicarboxylic acids” used herein refers to those carboxylic acids having two carboxyl groups each attached to a saturated carbon atom. If the carbon atom to which the carboxyl group is attached to is saturated and is in a ring, the acid is referred to as an “alicyclic dicarboxylic acid” . The term “aromatic dicarboxylic acids” used herein refers to those dicarboxylic acids having two carboxyl groups each attached to a carbon atom in an aromatic ring structure. It is not necessary that both functional carboxyl groups in the aromatic dicarboxylic acid be attached to the same aromatic ring. Where more than one ring is present, they can be joined by aliphatic or aromatic divalent radicals or divalent radical such as -O-or -SO₂-.

The aliphatic or alicyclic dicarboxylic acids useful herein include, without limitation, sebacic acid； 1, 3-cyclohexane dicarboxylic acid； 1, 4-cyclohexane dicarboxylic acid； adipic acid； glutaric acid； 4-cyclohexane-1, 2-dicarboxylic acid； 2-ethyl suberic acid； cyclopentane dicarboxylic acid； decahydro-1, 5-naphthylene dicarboxylic acid； 4, 4’-bicyclohexyl dicarboxylic acid； decahydro-2, 6-naphthylene dicarboxylic acid； 4, 4’-methylenebis (cyclohexyl) carboxylic acid； 3, 4-furan dicarboxylic acid； and mixtures of two or more thereof. In one embodiment, the dicarboxylic acids used herein are selected from cyclohexane dicarboxylic acids, adipic acids, and mixtures thereof.

The aromatic dicarboxylic acids useful herein include, without limitation, phthalic acids； terephthalic acids； isophthalic acids； dibenzoic acids； dicarboxylic compounds with two benzene nuclei (such as bis (p-carboxyphenyl) methane； p-oxy-1, 5-naphthalene dicarboxylic acid； 2, 6-naphthalene dicarboxylic acid； 2, 7-naphthalene dicarboxylic acid； or 4, 4’-sulfonyl dibenzoic acid) ； and C₁-C₁₂ alkyl and ring substitution derivatives of the aromatic dicarboxylic acids described above (such as halo, alkoxy, and aryl derivatives thereof) . The aromatic dicarboxylic acids useful herein may also be, for example, hydroxyl acids such as p- (β-hydroxyethoxy) benzoic acid.

In one embodiment of the compositions disclosed herein, the dicarboxylic acids used to form the copolyetheresters component may be selected from aromatic dicarboxylic acids. In a further embodiment, the dicarboxylic acids may be selected from aromatic dicarboxylic acids having about 8-16 carbon atoms. In a yet further embodiment, the dicarboxylic acids may be terephthalic acid alone or a mixture of terephthalic acid with phthalic acid and/or isophthalic acid.

In addition, the dicarboxylic acids useful herein may also include functional equivalents of dicarboxylic acids. In forming the copolyetheresters, the functional equivalents of dicarboxylic acids react with the above described long-chain and low molecular weight glycols substantially the same way as dicarboxylic acids. Useful functional equivalents of dicarboxylic acids include ester and ester-forming derivatives of dicarboxylic acids, such as acid halides and anhydrides. As used herein, the number average molecular weight limitations pertain only to the corresponding dicarboxylic acids, not the functional equivalents thereof (such as the ester or ester-forming derivatives thereof) . Therefore, a compound that is a functional equivalent of a dicarboxylic acid and has a number average molecular weight more than 300 can also be used herein, provided that the corresponding dicarboxylic acid has a number average molecular weight of about 300 or lower. Moreover, the dicarboxylic acids may also contain any substituent groups or combinations thereof that do not substantially interfere with the copolyetherester formation and the use of the copolyetherester in the compositions disclosed herein.

The long-chain glycols used in forming the copolyetherester component of the composition disclosed herein may also be mixtures of two or more long-chain glycols. Similarly, the low molecular weight glycols and dicarboxylic acids used in forming the copolyetherester component may also be mixtures of two or more low molecular weight glycols and mixtures of two or more dicarboxylic acids, respectively. In a preferred embodiment, at least about 70 mol％of the groups represented by R in Formulas (I) and (II) above are 1, 4-phenolene radicals, and at least 70 mol％of the groups represented by D in Formula (II) above are 1, 4-butylene radicals. When two or more dicarboxylic acids are used in forming the copolyetherester, it is preferred to use a mixture of terephthalic acid and isophthalic acid, while when two or more low molecular weight glycols are used, it is preferred to use a mixture of 1, 4-tetramethylene glycol and hexamethylene glycol.

The at least one copolyetherester comprised in the fire-retardant copolyetherester composition disclosed herein may also be a blend of two or more copolyetheresters. It is not required that the copolyetheresters comprised in the blend, individually meet the weight percentages requirements disclosed hereinbefore for the short-chain and long-chain ester units. However, the blend of two or more copolyetheresters must conform to the values described hereinbefore for the copolyetheresters on a weighted average basis. For example, in a blend that contains equal amounts of two copolyetheresters, one copolyetherester may contain about 10 wt％of the short-chain ester units and the other copolyetherester may contain about 80 wt％of the short-chain ester units for a weighted average of about 45 wt％of the short-chain ester units in the blend.

In one embodiment, the at least one copolyetherester component comprised in the fire-retardant copolyetherester composition disclosed herein is obtained by the copolymerization of a dicarboxylic acid ester selected from esters of terephthalic acid, esters of isophthalic acid, and mixtures thereof, with a lower molecular weight glycol that is 1, 4-tetramethylene glycol and a long-chain glycol that is poly (tetramethylene ether) glycol or ethylene oxide-capped polypropylene oxide glycol. In a further embodiment, the at least one copolyetherester is obtained by the copolymerization of an ester of terephthalic acid (e.g., dimethylterephthalate) with 1, 4-tetramethylene glycol and poly (tetramethylene ether) glycol.

The copolyetheresters useful in the compositions disclosed herein may be made by any suitable methods known to those skilled in the art, such as by using a conventional ester interchange reaction.

In one embodiment, the method involves heating an dicarboxylic acid ester (e.g., dimethylterephthalate) with a poly (alkylene oxide) glycol and a molar excess of a low molecular weight glycol (e.g., 1, 4-tetramethylene glycol) in the presence of a catalyst, followed by distilling off methanol formed by the interchange reaction and continuing the heat until methanol evolution is complete. Depending on the selection of temperatures and catalyst types and the amount of the low molecular weight glycols used, the polymerization may be completed within a few minutes to a few hours and results in formation of a low molecular weight pre-polymer. Such pre-polymers can also be prepared by a number of alternate esterification or ester interchange processes, for example, by reacting a long-chain glycol with a short-chain ester homopolymer or copolymer in the presence of catalyst until randomization occurs. The short-chain ester homopolymer or copolymer can be prepared by the ester interchange either between a dimethyl ester (e.g., dimethylterephthalate) and a low molecular weight glycol (e.g, 1, 4-tetramethylene glycol) as described above, or between a free acid (e.g., terephthalic acid) and a glycol acetate (e.g., 1, 4-butanediol diacetate) . Alternatively, the short-chain ester homopolymer or copolymer can be prepared by direct esterification from appropriate acids (e.g., terephthalic acid) , anhydrides (e.g., phthalic anhydride) , or acid chlorides (e.g., terephthaloyl chloride) with glycols (e.g., 1, 4-tetramethylene glycol) . Or, the short-chain ester homopolymer or copolymer may be prepared by any other suitable processes, such as the reaction of dicarboxylic acids with cyclic ethers or carbonates.

Further, the pre-polymers obtained as described above can be converted to high molecular weight copolyetheresters by the distillation of the excess low molecular weight glycols. Such process is known as "polycondensation" . Additional ester interchange occurs during the polycondensation process to increase the molecular weight and to randomize the arrangement of the copolyetherester units. In general, to obtained the best results, the polycondensation may be run at a pressure of less than about 1 mmHg and a temperature of about 240-260℃, in the presence of antioxidants (such as 1, 6-bis- (3, 5-di-tert-butyl-4-hydroxyphenol) propionamido] -hexane or 1, 3, 5-trimethyl-2, 4, 6-tris [3, 5-di-tert-butyl-4-hydroxybenzyl] benzene ) , and for less than about 2 hours. In order to avoid excessive holding time at high temperatures with possible irreversible thermal degradation, it is advantageous to employ a catalyst for ester interchange reactions. A wide variety of catalysts can be used herein, which include, without limitation, organic titanates (such as tetrabutyl titanate alone or in combination with magnesium or calcium acetates) , complex titanates (such as those derived from alkali or alkaline earth metal alkoxides and titanate esters) , inorganic titanates (such as lanthanum titanate) , calcium acetate/antimony trioxide mixtures, lithium and magnesium alkoxides, stannous catalysts, and mixtures of two or more thereof.

In accordance with the present disclosure, the copolyetheresters used herein have a melting point between about 100-220℃. Also, the process conditions are selected in a way such that the copolyetherester particles are deformed after the insulating binder phase is cured into a binder matrix.

Based on the total weight of the adhesive composition, the combined weight of the first and second particulate non-conductive phase is present at a level of about 5-70 wt％or about 7-60 wt％.

Also in accordance with the present disclosure, the volume ratio of the first particulate non-conductive phase to the second particulate non-conductive phase may be in the range of about 60:40-20:80, or about 55:45-25:75.

The copolyetheresters used herein can also be obtained commercially from DuPont under the trade name

Adhesive Compositions

The adhesive compositions disclosed herein may be prepared by any suitable process. For example, the adhesive composition may be prepared by first dissolving the binder material (blend of fluoroelastomer and ethylene/alkyl (meth) acrylate copolymer elastomer) in a solvent (e.g., methyl isobutyl ketone (MIBK) and diisobutyl ketone (DIBK) ) and then mixing or kneading the other constituent materials in the solution. Again, it is understood that in the adhesive solution, both the polymeric particles and the copolyetherester particles retain their original particulate forms and remain distinct.

Adhesive films

Further disclosed herein are adhesive films made of the adhesive compositions disclosed above. Any suitable process may be used in forming the films, which include, without limitation, coating, rolling, casting, extrusion, etc. The extrusion temperature of the blend of fluoroelastomer and ethylene/alkyl (meth) acrylate copolymer elastomer may be in the range of about 60-110℃. In addition, as stated above, the process conditions are selected in such a way that, within the adhesive films, polymeric particles and the copolyetherester particles retain their original particulate forms and remain distinct.

Electrically Conductive Adhesives and Electronic Parts Comprising the Same

The adhesive compositions disclosed herein may be used in forming electronic parts. When in use, the adhesive compositions are heated to their cured form. In such cured form, the elastomer blend is cross-linked and the continuous insulating binder phase turned into a binder matrix； the first insulating particles retain their original particulate form and remain dispersed within the binder matrix； the copolyetherester particles are melted and blended in the binder matrix； and the conductive particles are connected into a network so that the cured adhesive composition becomes conductive. Such cured adhesive composition also may be called electrically conductive adhesives.

The electrically conductive adhesives disclosed above may be used for various applications, for example, as the material for forming electrically connection between conductive members (e.g., electrodes) ； for forming mounted electric components； for forming a circuit-wiring pattern on a circuit board； and for forming conductive connections among a plurality of circuit-wiring patterns on a plurality of circuit boards.

The electronic parts comprising the electrically conductive adhesives disclosed above include, without limitation, CMOS camera module, fingerprint module, SIM card seat, charge connector, antenna connector, etc.

In one embodiment, the electronic part disclosed herein is a flexible printed circuit module. The flexible printed circuit module disclosed herein comprise a flexible printed circuit board, the electrically conductive adhesives bonded to one or more target regions of the flexible printed circuit board, and one or more reinforcement members mounted over the electrically conductive adhesive. The flexible printed circuit board typically comprises a flexible base film (board or base material) made of polyimide or the like and wiring pattern provided thereon. The adhesive composition as disclosed herein is first applied over target regions of flexible printed circuit board. The application of the adhesive may be conducted by ink jet printing, casting, dispensing, etc. Or, the application of the adhesive may be conducted by simply placing the adhesive film over the target regions of flexible printed circuit board. Then, the one or more reinforcement members are press against the adhesives, followed by lamination under heat and optional pressure. The adhesive composition or adhesive film is cured during the lamination process and therefore provide a bond between the reinforcement members and the flexible printed circuit board. The reinforcement member may be made of insulating materials, such as, polyimide, polyethylene terephthalate (PET) , liquid crystal polymer (LSP) , glass epoxy, or the like. When the electrically conductive adhesive is connected with grounding electrode of the flexible printed circuit, it provides electromagnetic interference shielding effect. In another embodiment, the reinforcement member is made of conductive materials, such as, stainless steel, copper, aluminum, or the like and the electrically conductive adhesive provided electrical connection between the conductive reinforcement member and the electrode in the flexible printed circuit. When the conductive reinforcement member is connected with grounding electrode of the flexible printed circuit, it also works as electromagnetic interference shielding layer.

The pressure applied during the lamination process may be in the range of about 0.5-15 MPa or about 1-10 MPa, while the lamination temperature may be set in the range of about 100-250℃, or about 120-250 ℃ . And it is important that the lamination process is applied under a condition such that the polymeric particles forming the first particulate non-conductive phase of the adhesive composition remain un-deformed, while the copolyetherester particles forming the second particulate non-conductive phase of the adhesive composition are melted and deformed.

Yet further disclosed herein are articles comprising the electronic parts disclosed herein, which include, without limitation, cellular phone, notebook PCs and medical devices, etc.

EXAMPLES

Materials:

· FE-1 (fluoroelastomer-1) : vinylidene

fluoride/hexafluoropropylene/tetrafluoroethylene terpolymer obtained from the Chemours Company (U.S.A. ) under the trade name

GF 200s；

· FE-2 (fluoroelastomer-2) : vinylidene

fluoride/hexafluoropropylene/tetrafluoroethylene terpolymer obtained from the Chemours Company under the trade name

GBL600；

· AEM (ethylene/alkyl (meth) acrylate copolymer elastomer) : ethylene/alkyl (meth) acrylate dipolymer elastomer obtained from DuPont under the trade name

DP；

· Cu/Ag: a powder mixture of (i) Cu/Ag-s (spherical copper particles coated with silver obtained from Join M Co. Ltd. (Korea) under the product name TCSP0415 (D₅₀＝4.2～4.6 μm, data provided by vendor) and (ii) Cu/Ag-f (flaky copper particles coated with silver obtained from Join M Co. Ltd. under the product name TCFL0713 (D₅₀＝6.5～7.3 μm, data provided by vendor) at a weight ratio of 3:2 and having a D₅₀ of the powder mixture was measured to be 9.54 μm；

· Ag-f: silver flakes obtained from Kunming Nobel Metal Electronic Materials Co., Ltd (China) under the product name HC-02 (D₅₀＝3.56 μm) ；

· PMMA-1: half-crosslinked PMMA beads obtained from Heyo Enterprise Co., Ltd. (Taiwan) with the product name AC15-F (D₅₀＝14.7； D_84.13＝24.24； D₉₉＝37.8； σ_p＝1.65； density＝1.2 g/cm³) ；

· PMMA-2: half-crosslinked PMMA beads obtained from J Color Chemicals Corp., Ltd (China) with the product name NMT-20 (D₅₀＝20.9； D_84.13＝32.22； D₉₉＝44.1； σ_p＝1.54； density＝1.2 g/cm³) ；

· PA 6T/XT: polyamide powder obtained by pulverizing polyamide 6T/XT resin (from DuPont under the trade name

HTN501) and collected using a 500 mesh sieve (melting point＝370℃； D₅₀＝16.24； D_84.13＝28.52； D₉₉＝46.7； σ_p＝1.76； density＝1.2 g/cm³) ；

· Silicone: crosslinked silicone beads obtained from Shenzhen Hayond Powder Techonology Co., Ltd. (China) with grade name HY-610 (D₅₀＝14.18； D_84.13＝23.24； D₉₉＝69.2； σ_p＝1.64； density＝1.2 g/cm³) ；

· PTFE: polytetrafluoroethylene powder obtained from the Chemours Company (U.S.A. ) under the trade name Zonyl^TM MP1300 (melting＝327-342 ℃； D₅₀＝9.95； D_84.13＝20.39； D₉₉＝71.2； σ_p＝2.05； density＝2.2 g/cm³) ；

· Al₂O₃ : spherical Al₂O₃ particle obtained from Xiamen Zhanfan Trading Co. Ltd., under the product name ZF-KK01 (D₅₀＝24.92； D_84.13＝35.38； D₉₉＝48.9； σ_p＝1.42； density＝3.9 g/cm³) ；

· Glass: glass microspheres obtained from Potters Industries LLC (U.S.A. ) under the trade name Sheriglass^TM 3000cp (D₅₀＝34.89； D_84.13＝53.93； D₉₉＝82.1； σ_p＝1.59) ；

· CoP: copolyetherester powder obtained by pulverizing copolyetherester resin (from DuPont under the trade name

3078) and collected using a 300 mesh sieve (melting point＝177℃； density＝1.2 g/cm³) ；

· DBPH: 2, 5-dimethyl-2, 5-di (t-butylperoxy) hexane obtained from Aladdin Industrial Corporation (U.S.A. ) ；

· DCP: dicumyl peroxide purchased obtained from Sinopharm Group Co. Ltd. (China) ；

· TMPH: 1, 1-bis (t-butylperoxy) -3, 3, 5-trimethylcyclohexane obtained from Sinopharm Chemical Reagent Co., Ltd. ；

· TAIC: triallyl isocyanurate obtained from DuPont under the trade name of Diak^TM7；

· Glymo: γ-glycidylpropyltrimethoxysilane purchased from Sinopharm Group Co., Ltd；

· The particles size distribution D₅₀, D_84.13, and D₉₉ of the above materials (unless specified otherwise) were measured using a Mastersizer 2000 (manufactured by Malvern Instruments Ltd (UK) ) as analyzer, a Hydro 2000SM (A) (provided by Malvern Instruments Ltd (UK) ) as accessory, and an ethanol as dispersant. And prior to measurement, the powder mixture was dispersed in dispersant and ultrasonic treated for half hour.

Adhesive Films:

In each of Examples E1-E11 and Comparative Examples CE1-CE23, an adhesive composition was prepared as follows (components are tabulated in Tables 1-4) : dissolving binder material in MIBK/DIBK (1/3) mixture to form a solution； (ii) adding the cross-linking agents in the solution and mixing at 2000 rpm for 1 min； (iii) adding conductive particles, insulation particles, and copolyetherester particles into the solution and mixing at 2000 rpm for 1 min； (v) slot-die coating the solution over a PET release film followed by drying at 100℃for about 5-30 minutes.

Electrically Conductive Adhesives

In each of E1-E11 and CE1-CE23, (i) cut the adhesive films prepared above into 4x40 mm pieces； (ii) applied a layer of polyimide film over the adhesive film by hot-roll at 100℃ and 0.4 MPa for 1 min； (iii) peeled of the PET release film； and (iv) laminated the “polyimide/adhesive film” bilayer film in a vacuum press (manufactured by VIGOR MACHINERY CO., LTD., Model No. VLP-150～60) at 2.55 MPa and 170℃ for 60 min, thus the adhesive film is cured into an electrically conductive adhesive (ECA) film.

Then, the sheet resistance of the cured ECA film was measured by four probe method using

QT-70 (manufactured by QUATEK INC. ) , while the thickness of the cured ECA film was measured using Dektal XT stylus profiler. The resistivity of the cured ECA bar was calculated by the equation below and tabulated in Tables 1-4:

ρ (Resistivity) ＝ sheet resistance x thickness x geometry correction

＝ sheet resistance x thickness x 3.2248/4.5324

Also in each of E1-E11 and CE1-E23, under similar conditions, cut a piece of the adhesive film and applied a layer of polyimide over each side of the adhesive film by hot-roll, followed by lamination. Thus, a tri-layer film with electrically conductive adhesives laminated inbetween two layers of polyimide was obtained. The “polyimide/ECA/polyimide” tri-layer film was then cut into 10x100 mm test samples, and the 90° peel strength (@a rate of 50.8 mm/min) for each samples was measured using LF PLUS universal test machine (manufactured by Lloyd Instruments Ltd. ) . The results are tabulated in Tables 1-4.

As demonstrated in Table 1, when insulating particles were included in the composition, the cured ECA exhibited low peeling strength, while the inclusion of copolyetherester particles (with the volume ratio of the insulating particles to the copolyetherester particles ranges from about 60:40-20:80) could increase the peeling strength while maintaining low resistivity.

Claims

An adhesive composition comprising: (a) a continuous insulating binder phase formed of a mixture of at least one fluoroelastomer and at least one ethylene/alkyl (meth) acrylate copolymer elastomer at a weight ratio of about 25: 75-90: 10, (b) a plurality of conductive particles； (c) a first particulate non-conductive phase comprising a plurality of insulating particles, and (d) a second particulate non-conductive phase comprising a plurality of copolyetherester particles, wherein,

i) the conductive particles, the insulating particles, and the copolyetherester particles are dispersed in the continuous binder phase；

ii) the volume ratio of the first particulate non-conductive phase to the second particulate non-conductive phase is about 60: 40-20: 80；

iii) the copolyetherester particles comprised in the second particulate non-conductive phase have a melting point between 100-220℃； and

iv) the insulating particles comprised in the first particulate non-conductive phase are formed of inorganic materials or cross-linked polymers or high melting point polymers having a melting point at least about 20℃ higher than that of the copolyetherester particles, have a standard deviation σ_p (expressed as D_84.13/D₅₀) value equals to about 1.7 or less, have a particle size distribution D₅₀ at least about 1.2 times that of the conductive particles, and have a particle size distribution D₉₉ range from about 10-80 μm.
The adhesive composition of Claim 1, wherein, the continuous insulating binder phase is present at a level of about 5-45 wt％, the plurality of conductive particles is present at a level of about 30-80 wt％, and the first and second particulate non-conductive phase is present at a level of about 5-70 wt％, with the weight of all components totaling to 100 wt％.
The adhesive composition of Claim 1, wherein, the continuous insulating binder phase is present at a level of about 8-45 wt％, the plurality of conductive particles is present at a level of about 40-70 wt％, and the first and second particulate non-conductive phase is present at a level of about 7-60 wt％, with the weight of all components totaling to 100 wt％.
The adhesive composition of Claim 3, wherein, the volume ratio of the first particulate non-conductive phase to the second particulate non-conductive phase is about 55: 45-25: 75.
An adhesive film formed of the adhesive composition recited in any one of Claims 1-4.
An electrically conductive adhesive obtained by curing the adhesive composition recited in any one of Claims 1-4.
The electrically conductive adhesive of Claim 6, wherein the adhesive composition is cured at a temperature of about 100-250℃ and a pressure of about 0.5-10 MPa.
The electrically conductive adhesive of Claim 7, wherein the adhesive composition is cured at a temperature of about 120-250℃ and a pressure of about 1-10 MPa.
An electronic part comprising the electrically conductive adhesive of any one of Claims 6-8.