WO2016087613A1 - Composition adhésive conductrice - Google Patents

Composition adhésive conductrice Download PDF

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Publication number
WO2016087613A1
WO2016087613A1 PCT/EP2015/078580 EP2015078580W WO2016087613A1 WO 2016087613 A1 WO2016087613 A1 WO 2016087613A1 EP 2015078580 W EP2015078580 W EP 2015078580W WO 2016087613 A1 WO2016087613 A1 WO 2016087613A1
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WO
WIPO (PCT)
Prior art keywords
epoxy resin
formulation
conductive
formula
bisphenol
Prior art date
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PCT/EP2015/078580
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English (en)
Inventor
Manuel Arturo LOPEZ QUINTELA
Senén PAZ ABUÍN
Original Assignee
Nanogap Sub Nm Powder, S.A.
Galega De Impermeabilizaciones Y Revestimientos Especiales, S.A. (Gairesa)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Application filed by Nanogap Sub Nm Powder, S.A., Galega De Impermeabilizaciones Y Revestimientos Especiales, S.A. (Gairesa) filed Critical Nanogap Sub Nm Powder, S.A.
Priority to EP15805451.0A priority Critical patent/EP3227355A1/fr
Publication of WO2016087613A1 publication Critical patent/WO2016087613A1/fr

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J163/00—Adhesives based on epoxy resins; Adhesives based on derivatives of epoxy resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/14—Polycondensates modified by chemical after-treatment
    • C08G59/1433—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds
    • C08G59/1438—Polycondensates modified by chemical after-treatment with organic low-molecular-weight compounds containing oxygen
    • C08G59/145—Compounds containing one epoxy group
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/14—Polycondensates modified by chemical after-treatment
    • C08G59/1494—Polycondensates modified by chemical after-treatment followed by a further chemical treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used

Definitions

  • the present invention relates to single component epoxy based conductive adhesive compositions, and more particularly to a room stable conductive adhesive composition containing silver nanofibers as conductive additive.
  • ECAs Electrically conductive adhesives
  • Sn/Pb solders for surface mount applications.
  • conductive adhesive technology offers numerous advantages including environmental friendliness (no lead), low temperature processing conditions, fewer processing steps, low stress on the substrates, and fine pitch interconnect capability.
  • ICA isotropic conductive adhesive
  • AC A anisotropic conductive adhesive
  • ICAs contain conductive filler concentrations between 60 and 80% wt%, and the adhesives are conductive in all directions.
  • ACAs the volume fractions of conductive fillers are normally between 5 and 10 wt% and the electrical conduction is generally achieved only in the pressurization direction during curing.
  • ICAs materials consist of a polymer matrix containing electrically conductive fillers.
  • bisphenol-A based epoxies have been widely used in the electronic packing industry due to their excellent reliability, good thermal stability and high Young's modulus.
  • Silver is a widely used conductive filler, as it is the most conductive metal found in nature. Combinations of both components exist in a number of commercially available products, although they show some drawbacks as: the polymer matrix has to be loaded with large amounts of silver, often exceeding 60 wt% in order to achieve low resistivity values ( ⁇ 1 ⁇ 10 ⁇ 2 ⁇ ).
  • the authors of the present invention have developed a new water base epoxy resin formulation suitable for preparing a single-component isotropic conductive adhesive with improved properties based on Bisphenol A resin.
  • the formulation is characterized for comprising a mixture of two epoxy resins based on Bisphenol A diglycidylether, one is a liquid resin and the other one a waterborne liquid resin, in addition to an epoxy diluent and a latent curing agent.
  • the presence of water in the formulation allows the subsequent entire and homogeneous dispersion of conductive fillers within the resin formulation and also the incorporation of the curing agent therein, thus avoiding the use of a separate formulation containing the curing agent which has to be mixed-in prior to use, as well as preventing any potential quality problems associated with the effectiveness and accuracy of said mixing.
  • the first aspect of the present invention refers to a water base epoxy resin formulation comprising: a) the combination of a liquid epoxy resin of Bisphenol A diglycidylether of formula (I) and an aqueous dispersion of a liquid epoxy resin of Bisphenol A diglycidylether of formula (I):
  • n is a number ranging from 0 to 1 ; b) a glycidyl ether of formula (II):
  • R is an aliphatic or cycloaliphatic radical of valency m
  • R' is selected from H and methyl; and m is an integer from 1 to 3; c) a latent curing agent.
  • the water base epoxy resin formulation further comprises conductive fillers.
  • Another aspect of the invention relates to a process for the preparation of a water base epoxy resin formulation as defined above, said process comprising: a) mixing a liquid epoxy resin of Bisphenol A diglycidylether of formula (I) with a glycidyl ether of formula (II); b) adding the mixture resulting from step a) to an aqueous dispersion comprising an epoxy resin Bisphenol A diglycidylether of formula (I); c) adding the latent curing agent to the mixture resulting from step b).
  • a further aspect of the invention refers to a water base epoxy resin formulation obtainable by the process as defined above.
  • the process of the invention further comprises the addition of conductive fillers to the mixture resulting from step c). Accordingly, another aspect of the invention relates to a water base conductive epoxy resin formulation obtainable by this process.
  • the process of the invention further comprises the evaporation of at least 99.8 ⁇ 0.2 wt% of the water contained in the resulting water base conductive epoxy resin formulation mentioned above, thus providing a single- component isotropic conductive epoxy adhesive. Therefore, a further aspect of the invention relates to the single-component isotropic conductive adhesive obtainable by this process.
  • the conductive adhesive of the invention is characterized in that it can be stored at room temperature for prolonged periods.
  • Another aspect of the present invention relates to the use of the single-component isotropic conductive adhesive for surface mount applications and for bonding electronic components.
  • this refers to a water base epoxy resin formulation
  • a water base epoxy resin formulation comprising: a) the combination of a liquid epoxy resin of Bisphenol A diglycidylether of formula (I) and an aqueous dispersion of a liquid epoxy resin of Bisphenol A diglycidylether of formula (I):
  • n is a number ranging from 0 to 1 ; b) a glycidyl ether of formula (II):
  • R is an aliphatic or cycloaliphatic radical of valency m
  • R' is selected from H and methyl; and m is an integer from 1 to 3; c) a latent curing agent.
  • water base epoxy resin it is understood a formulation based on epoxy resins which is dispersed in an aqueous medium.
  • the water base epoxy resin formulation of the invention comprises the combination of two epoxy resins based on Bisphenol A diglycidyl ether (BADGE) of formula (I):
  • n is a number ranging from 0 to 1.
  • the Bisphenol A diglycidyl ether may be obtained by reaction between bisphenol A and epichlorohydrin according to any procedure known by a skilled person.
  • the reaction between bisphenol A and epichlorohydrin can be controlled to produce different molecular weights. Low molecular weight molecules tend to be liquids, whereas higher molecular weight molecules tend to be more viscous liquids or solids. This reaction can be carried out either continuously or discontinuously, and in the presence of an alkali metal hydroxide in the amount of two moles, or about two moles, for each mole of Bisphenol A (US2801227 and US3069434).
  • the Bisphenol A diglycidyl ether useful for the formulation of the present invention is liquid under ambient conditions, thus having a low molecular weight.
  • n ranges from 0 to 1, being preferred a Bisphenol A diglycidylether with a molecular weight lower than 700.
  • the liquid Bisphenol A diglycidyl ether is also commercially available, being supplied, for example, by Huntsman, Momentive or Dow Chemical.
  • the aqueous dispersion of the liquid resin is simply prepared by dispersing the liquid resin in water.
  • the resin is dispersed in a proportion ranging from 40 to 65 wt% with respect to the total weight of the aqueous dispersion.
  • the glycidyl ether of formula (II) is an epoxy diluent which is added to the formulation to impair flexibility, to reduce viscosity and improve adhesion.
  • R is an aliphatic or cycloaliphatic radical of valency m
  • R' is selected from H and methyl; and m is an integer from 1 to 3;
  • aliphatic radical should be understood a straight or branched, saturated or unsaturated, hydrocarbon chain, interrupted in the chain by one or more oxygen or sulfur atoms or contains one or more carbonyl groups.
  • cycloaliphatic radical should be understood a saturated or unsaturated hydrocarbon cycle, that contains one or more ring systems and may contain a carbonyl group, wherein said rings may be substituted by and/or linked through alkyl groups.
  • R is an aliphatic radical of formula:
  • R" is H or a C 1 -C3 alkyl group and n is an integer from 1 to 20.
  • R" is H or methyl, and n ranges from 1 to 3.
  • the integer "m” is 1 or 2, more preferably Even more preferably is the use of a glycidyl ether of formula (Ha):
  • R" is H or a C1-C3 alkyl group; and n is an integer from 1 to 20.
  • C1-C3 alkyl group refers to a linear or branched alkyl group having from one to three carbon atoms, such as methyl, ethyl, propyl and iso-propyl.
  • R" is H or methyl
  • n ranges from 1 to 3. It is preferred the use of poly ethylenegly col diglycidyl ether or polypropylenglycol diglycidyl ether as epoxy diluent, even more preferably polypropylenglycol diglycidyl ether.
  • the polypropylenglycol diglycidyl ether is an aliphatic epoxy resin compatible with Bisphenol A-based epoxy resins at all proportions and, upon curing, becomes an integral part of the cured resin.
  • the glycidyl ether of formula (Ila) has a molecular weight ranging from 145 to 1200, even more preferably n ranges from 1 to 20.
  • Such glycidyl ether is liquid under ambient conditions.
  • the glycidyl ether of formula (II) useful for the purpose of the present invention can be obtained by reaction of the corresponding alcohol [R-(OH) m ] with an epihalohydrin of formula (III):
  • a catalyst such as a Lewis acid
  • a halohydrin ether intermediate is obtained.
  • the dehydrogenation of said intermediate is effected by contact with an inorganic base, generally an alkali metal hydroxide, such as sodium hydroxide.
  • an inorganic base generally an alkali metal hydroxide, such as sodium hydroxide.
  • the glycols useful for this purpose are chosen among ethyleneglycol, propylenglycol, butylenglycol, etc.
  • the glycidyl ether can also be commercially available.
  • a polypropylenglycol diglycidyl ether is manufactured under the name DER 732 by the Dow Cheical Company.
  • This liquid epoxy resin is a reaction product of epichlorohydrin and polypropylene glycol. It is a flexible, low viscosity, light color, epoxy resin which, in combination with Bisphenol A based epoxy resins, imparts flexibility, elongation and improves impact resistance.
  • latent curing agent is widely used in the art to define a curing agent which is active at high temperatures, generally at a temperature higher than 50°C. This component is the responsible of the subsequent curing of the epoxy resins.
  • curing has its ordinary meaning as known to those skilled in the art and may include polymerization and/or cross-linking of the epoxy resins which, in the case of the present invention, is performed by heating.
  • curing agent and "hardener” are used indistinctly.
  • the curing agent used in the formulation of the present invention is characterized for being water soluble as the formulation is a water base epoxy resin.
  • hardeners examples include low molecular weight polyamide- and polyamine-based compounds, aromatic amines, solid epoxy amine adducts, and solid anhydrides.
  • low molecular weight polyamide- and polyamine-based compounds examples include dicyanodiamide (DICY), isophthalic dihydrazide, and adipic dihydrazide, BC1 3 amine complex or BF 3 amine complex.
  • DICY dicyanodiamide
  • isophthalic dihydrazide examples include isophthalic dihydrazide, and adipic dihydrazide, BC1 3 amine complex or BF 3 amine complex.
  • Suitable aromatic amines include 4,4' diaminodiphenylsulfone and 3,3' diaminodiphenylsulfone.
  • Suitable solid anhydrides include trimel l it ic anhydride, pyromellitic dianhydridc 3,3',4,4'-Benzophenonetetracarboxylic dianhydride. maleic anhydride, giutaric anhydride, cis- 1 ,2-cyc!ohexane dicarboxylic anhydride, and 3,4,5,6 tetrahydrophtha! ic anhydride and mixtures thereof.
  • latent curing agents are solid epoxy amine adducts as those commercially available under the trade name AJICURE PN-23 and MY-24 from AJIMOTO or EPIKURE P-101 and P- 103 from MOMENTIVE which also act as curing accelerators.
  • the latent curing agent is a low molecular weight polyamide- and polyamine-based compound or an aliphatic amine curing agent.
  • the choice of the proper curing agent is determined by its solubility in water and by its low reactivity at low temperature (i.e., a long pot life).
  • the latent curing agent is dicyanodiamide which has the following formula:
  • Formulations comprising dicyanodiamide as latent curing agent have excellent storage stability, but they should be heated at high temperature to allow the curing of the epoxy resin.
  • accelerators such as ureas, imidazoles, urethans, biurets, allophanates, amides and lactames can be added to the formulation, said accelerators also may impair storage stability.
  • the amount of the cure accelerator to be added is selected to be within the range of the catalytic quantity to the epoxy components. In a particular embodiment, the amount of the cure accelerator to be added is desirably selected to be within the range of 0.01 to 1 moles per epoxy equivalent of the formulation.
  • the cure accelerator that may be used in the present invention remains intact in the cured conductive product obtained after heat curing.
  • the amount of the epoxy-functional resins in the epoxy resin formulation can vary depending in part upon the intended application. In a typical embodiment, the epoxy- functional resins are present in an amount ranging from 45 to 95 percent by weight, based on the total weight of the components of the formulation excluding water.
  • the ratio of the epoxy groups to the curing agent is selected so that the curing agent is within the equivalents ratio range between 0.7 and 1.2, more preferably between 0.8 and 1.1 equivalents, with respect to the epoxy equivalent of the epoxy resins. Thereby, the amount of unreacted curing agent remaining in the final cured product can be kept in a very low level.
  • the water base epoxy resin formulation of the invention further comprises conductive fillers.
  • conductive fillers may include, but are not limited to, metals and metal alloys, metal-coated particles, surface functionalized metals, conductive veils, non-metals, polymers and nano-scale materials.
  • the morphology of the conductive fillers may include one or more of flakes, powders, particles, fibers and the like.
  • Metals and their alloys may be employed as effective conductive fillers, owing to their relatively high electrical conductivity.
  • Examples of metals and alloys for use with embodiments of the present disclosure may include silver, gold, nickel, copper, aluminium and alloys and mixtures thereof.
  • the morphology of the conductive filler may include one or more of flakes, powders, fibers, wires, microspheres and nanospheres, singly or in combination.
  • metals such as gold and silver are preferred due to their stability and effectiveness. Even more preferable is the use of silver.
  • the conductive fillers may comprise metal coated particles.
  • metal-coated particles include metal coated glass balloons, metal coated graphite, and metal-coated fibers.
  • metals which may be used as substrates or coatings may include silver, gold, nickel, copper, aluminum, and mixtures thereof.
  • Embodiments of non-metals suitable for use as conductive fillers may include conductive carbon black, graphite or carbon fiber.
  • Embodiments of nanomaterials suitable for use as conductive fillers may include carbon nanotubes, carbon nanofibers, metal nanofibers or metal nanowires, metal-coated nanofibers, metal nanoparticles and graphite in the form of nanoplatelets.
  • the conductive fillers are nanowires or nanofibers. Both terms are used indistinctly in the present disclosure.
  • Examples of nanowires or nanofibers suitable for use as conductive fillers may include nickel, iron, silver, copper, aluminum and alloys thereof. More preferably, the conductive fillers are silver nanowires, more preferably anisotropic silver nanowires as silver is the most conductive metal.
  • the length of the nanowires may be greater than about 1 ⁇ , greater than about 5 ⁇ , greater than about 10 ⁇ , and about 10 to 25 ⁇ .
  • the diameter of the nanowires may range from 20 to 150 nm. In a particular embodiment, said diameter is greater than about 10 nm, greater than about 40 nm, greater than about 70 nm, and about 80 to 100 nm.
  • silver nanowires may include SNW-A60, SNW-A90, SNW-A300 and SNW-A900 from Filigree Nanotech, Inc.
  • nanowires Due to the high aspect ratio of the nanowires and therefore low percolation threshold, a low concentration of nanowires is required to achieve good electrical conductivity in comparison to micro sized flakes and particles.
  • the presence of water in the epoxy resin formulation of the invention allows the entire and homogeneous dispersion of the conductive fillers within the resin formulation, thus also contributing to the reduction in the content of these fillers.
  • the proportion of conductive fillers in the water base epoxy resin formulation ranges from 0.1 to 75 wt% with respect to the total weight of the resin formulation excluding water, more preferably from 0.5 to 45 wt%, even more preferably from 5 to 30 wt%.
  • Other ingredients ranges from 0.1 to 75 wt% with respect to the total weight of the resin formulation excluding water, more preferably from 0.5 to 45 wt%, even more preferably from 5 to 30 wt%.
  • the curable compositions of the present invention can include a variety of optional ingredients and/or additives that are usually employed in epoxy adhesives composition, such as pigments including carbon black or graphite, reinforcements, thixotropes, accelerators, surfactants, plasticizers, extenders, oligomers such as urethane and acrylates stabilizers, corrosion inhibitors, diluents, antioxidants, and chemical blowing agents.
  • optional ingredients and/or additives that are usually employed in epoxy adhesives composition, such as pigments including carbon black or graphite, reinforcements, thixotropes, accelerators, surfactants, plasticizers, extenders, oligomers such as urethane and acrylates stabilizers, corrosion inhibitors, diluents, antioxidants, and chemical blowing agents.
  • Process Another aspect of the present invention relates to a process for the preparation of the water base epoxy resin formulation as defined above, said process comprising: a) mixing the liquid epoxy resin of Bisphenol A diglycidylether of formula (I) with the glycidyl ether of formula (II); b) adding the mixture resulting from step a) to an aqueous dispersion comprising a liquid epoxy resin Bisphenol A diglycidylether of formula (I); c) adding the water soluble hardener to the mixture resulting from step b).
  • Step a) of the process of the invention involves the mixture of the liquid epoxy resin of Bisphenol A diglycidylether of formula (I) with the glycidyl ether resin of formula (II).
  • the glycidyl ether is mixed in a proportion ranging from 0.5 to 50 wt% with respect to the weight of the liquid epoxy resin of Bisphenol A diglycidyl ether (I).
  • the mixture is allowed to stir at room temperature untill a homogeneous blend is formed.
  • an aqueous dispersion of a liquid epoxy resin Bisphenol A diglycidylether of formula (I) is added.
  • Said aqueous dispersion is prepared by dispersing the liquid epoxy resin Bisphenol A diglycidylether in water in the amounts mentioned hereinbefore.
  • the liquid epoxy resin is added to the water in a proportion ranging from 40 to 65 wt% with respect to the total weight of the dispersion.
  • the aqueous dispersion of the liquid epoxy resin of Bisphenol A diglycidylether of formula (I) is added to the resulting mixture so as the proportion of the liquid epoxy resin dispersed in the water ranges from 20 to 150 parts in weight per 100 parts of the liquid epoxy resin Bisphenol A diglycidylether of formula (I) used in step a) of the process of the invention, more preferably from 50 to 100 parts in weight.
  • the resulting mixture is also allowed to stir at room temperature till a homogenous aqueous dispersion is formed.
  • the latent curing agent is added.
  • the latent curing agent is water soluble, such as dicyandiamide, it is first dissolved in water and the aqueous solution formed is added to the mixture resulting from step b) of the process of the invention.
  • the latent curing agent is added to the water in a proportion ranging from 10 to 50 wt% depending on the solubility of the curing agent.
  • the aqueous dispersion of the latent curing agent is added to the resulting mixture so as the proportion of the latent curing agent ranges from 5 to 70 parts in weight per 100 parts of the resins contained in the mixture obtained after conducting step b) of the process of the invention, more preferably from 10 to 50 parts in weight.
  • the mixture resulting from step c) is also stir till a homogenous aqueous dispersion of all components is obtained.
  • a cure accelerator in the particular case when a cure accelerator is used, this can be added to the aqueous solution where the curing agent is dissolved, provided that said cure accelerator has an activation temperature higher than 100°C. If the cure accelerator has an activation temperature lower than 100°C, this is added in a subsequent step, once the water has been evaporated.
  • This process provides a water base epoxy resin formulation which is also a further aspect of the present invention.
  • the process of the invention further comprises the addition of conductive fillers to the water base epoxy resin formulation obtained according to the process mentioned above to form a conductive water base epoxy resin formulation wherein the conductive fillers are homogeneously dispersed in said formulation.
  • the conductive fillers are previously dispersed in water and subsequently, the aqueous dispersion formed is added to the water base epoxy resin formulation.
  • the conductive fillers are dispersed in the water in a proportion ranging from 2 to 25 wt%, more preferably at 15 wt%, with respect to the total weight of the aqueous dispersion.
  • the conductive fillers are nano wires or nano fibers selected from materials such as nickel, iron, silver, copper, aluminum and alloys thereof. In a more preferred embodiment, the conductive fillers are silver nanowires.
  • water base epoxy resin formulation of the invention as precursor of a conductive adhesive allows the entire conductive fillers to be evenly distributed within the epoxy resin, thus avoiding the formation of agglomerates and, therefore, enhancing the physical contact between said fillers even when lower amount of fillers is added.
  • another aspect of the invention refers to the conductive water base epoxy resin formulation obtainable by the process as defined above, wherein the conductive fillers are homogeneously distributed within the formulation.
  • the process of the invention further comprises a step of evaporation of at least 99.8 ⁇ 0.2 wt% of the water contained in the resulting conductive water base epoxy resin formulation to form a single component conductive adhesive.
  • the water can be evaporated by any method known by a skilled person.
  • said method includes the use of rotatory vacuum evaporators, so as a more homogenous evaporation is obtained.
  • Another aspect of the invention relates to the single component conductive adhesive obtainable by the process as defined above in which the water has been evaporated in the proportions mentioned above.
  • the term "single-component” is used to refer to a formulation which comprises therein the hardener or curing agent and, therefore, it does not require the addition of the hardener or curing agent to be mixed- in just prior its use.
  • the single component conductive adhesive according to the present invention is a dispersion-type conductive adhesive wherein the conductive fillers, used as a conductive medium, are evenly dispersed in a single-component epoxy resin composition used as a binder resin component.
  • the electric conduction paths between conductive fillers are constructed by the formation of dense physical contact between the fillers being bound to each other with the epoxy resin.
  • the amount of the epoxy- functional resins in the curable composition can vary depending in part upon the intended application of the composition. In a typical embodiment, the epoxy-functional resins are present in an amount ranging from 45 to 95 percent by weight, based on the total weight of the curable composition.
  • the ratio of the epoxy groups to the curing agent is selected so that the curing agent is within the equivalents ratio range between 0.7 and 1.1 , more preferably between 0.8 and 0.95 equivalents, with respect to the epoxy equivalent of the epoxy resins. Thereby, the amount of unreacted curing agent remaining in the obtained cured product can be kept in a very low level.
  • the content of the conductive fillers in the single component conductive adhesive of the invention is lower than 45 wt%, more preferably ranges from 0.5 to lower than 45 wt%, even more preferably from 5 to 30 wt%.
  • Existing products load over 50% of silver fillers to achieve comparable results.
  • the conductive fillers are preferably nanowires or nanofibers. More preferably, the conductive fillers are silver nanowires, more preferably anisotropic silver nanowires.
  • the conductive adhesive according to the present invention is used by applying it onto the surface of one metal surface in a predetermined thickness, when a junction is formed therewith. Therefore, when applying, it is required to adjust the viscosity of the conductive adhesive within a predetermined viscosity range in order to maintain the film thickness of the applied film. For example, in such a case that the target thickness of the applied film is within the range of 100 ⁇ or less, as the applying method, a printing method using a metal mask or dispense applying method may be used, and its viscosity should be adjusted within the range suited to each of the applying method.
  • the conductive adhesive according to the invention is applied in a predetermined film thickness onto one surface of a metal forming junction, the other metal surface is arranged on the upper surface thereof, and then treatment for pressure welding is performed so as to achieve a dense contact between the metal surface and the conductive filler dispersed in the conductive adhesive. After that, heating treatment is carried out to cure the epoxy resin contained therein. In such a process, the adhesion between the metal surface and the obtained cured conductive layer, and the binding between the conductive fillers, are accomplished by the cured product of the epoxy resin that is formed therein.
  • the conductive joint fabricated using the conductive adhesive according to the present invention is excellent in long-term reliability in a high-temperature environment of at least 150°C, long-term reliability under high humidity conditions and long-term reliability in cooling-heating temperature cycle environment.
  • the conductive adhesive of the present invention can be used as means for the surface mounting of electronic parts on a substrate circuit which are intended for in- vehicle electronic devices, modules and the like. It can also be used as a conductive adhesive suited for the purpose of substituting soldering, being capable of forming a conductive joint under a low-temperature condition, at least not exceeding 200°C, in the fabrication of electronic parts. Examples
  • a mixture of 30 pbw (parts by weight) of liquid epoxy resin of Bisphenol A and 6 pbw of polypropyleneglycol diglycidyl ether was prepared.
  • the resulting mixture was added to a reactor equipped with mechanical stirring and containing 30 pbw of an aqueous dispersion of a liquid epoxy resin of Bisphenol A (54% content of resin).
  • 34.2 pbw of an aqueous solution of dicyanodiamide (10 wt%) were added to the reactor.
  • the evaporation of water was conducted in a rotary evaporator at a temperature of 45 ⁇ 2 °C and at a pressure from 10 to 110 bar.
  • the resulting conductive formulation has a density of 2.1 g/cm 3 and a viscosity at room temperature of 22000 ⁇ 3000 Pa.s (at 0.01s "1 ), 2000 ⁇ 200 Pa.s (at 1 s "1 ) and 400 ⁇ 40 Pa.s (at 10 s "1 ).
  • the resulting conductive adhesive After subjecting the formulation to a curing process during 30 minutes at 180°C, the resulting conductive adhesive has an electrical conductivity (bulk) of 2 ⁇ 1 xlO "3 ohm cm, a glass transition temperature of 80 ⁇ 5 °C, thermal conductivity of 4.5 ⁇ 0.5 W/mK, Young modulus of 4.5 ⁇ 0.5 GPa and a coefficient of thermal expansion (CTE) of 75 ppm/°C (T ⁇ Tg) and of 152 ppm/°C.
  • electrical conductivity bulk
  • a glass transition temperature 80 ⁇ 5 °C
  • thermal conductivity 4.5 ⁇ 0.5 W/mK
  • Young modulus of 4.5 ⁇ 0.5 GPa
  • CTE coefficient of thermal expansion

Abstract

La présente invention concerne une formulation de résine époxyde à base d'eau qui comprend la combinaison d'une résine époxyde liquide d'éther diglycidylique de bisphénol A et d'une dispersion aqueuse d'une résine époxy liquide d'éther diglycidylique de bisphénol A, une résine d'éther glycidylique et un agent de durcissement latent, ladite formulation étant appropriée pour l'élaboration d'un adhésif conducteur à composant unique ayant des charges conductrices dispersées de manière uniforme à l'intérieur de la résine époxyde.
PCT/EP2015/078580 2014-12-04 2015-12-03 Composition adhésive conductrice WO2016087613A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP15805451.0A EP3227355A1 (fr) 2014-12-04 2015-12-03 Composition adhésive conductrice

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP14196251.4 2014-12-04
EP14196251 2014-12-04

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WO2016087613A1 true WO2016087613A1 (fr) 2016-06-09

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