Conductive adhesive composition and electrically conductive article
Patent Information
- Authority / Receiving Office
- KR · KR
- Patent Type
- Applications
- Current Assignee / Owner
- 3M INNOVATIVE PROPERTIES CO
- Filing Date
- 2024-10-30
- Publication Date
- 2026-08-03
Smart Images
Figure PCT00008_ABST
Abstract
Description
Background Technology
[0001] It is desirable for electrically conductive adhesives to combine excellent electrical performance, adhesive performance, and resistance to thermal and humidity aging. Further development of electrically conductive adhesives would be desirable.
[0002] In a first embodiment, a conductive adhesive composition is provided. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; and electrically conductive particles dispersed within the matrix. The conductive adhesive composition further comprises an adhesion promoter comprising an alkyl alkoxysilane, an alkenyl alkoxysilane, an alkyl phosphonic acid, or an alkyl carboxylic acid; and optionally a non-functional dipodal alkoxysilane, provided that when the adhesion promoter comprises an alkyl alkoxysilane or an alkenyl alkoxysilane, the non-functional dipodal alkoxysilane is present.
[0003] In a second embodiment, another conductive adhesive composition is provided. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; an adhesion promoter comprising an organic molecule selected from a class of organic compounds capable of forming a bond with a metal oxide surface; and electrically conductive particles dispersed within the matrix.
[0004] In a third embodiment, an electrically conductive article is provided. The electrically conductive article comprises a substrate having a first main surface and a second main surface; and an electrically conductive adhesive layer disposed on at least a portion of the second main surface of the substrate. The electrically conductive adhesive comprises any conductive adhesive composition according to the first embodiment or the second embodiment.
[0005] The above "Description of the Invention" is not intended to describe each of the illustrated embodiments of the present disclosure or all embodiments of the present exemplary embodiments. The following "Brief Description of the Drawings" and "Detailed Description of the Invention" further illustrate specific preferred embodiments utilizing the principles disclosed in this specification. Brief explanation of the drawing
[0006] The present disclosure may be more fully understood by considering the following detailed description of various embodiments of the present disclosure in connection with the accompanying drawings, and in the accompanying drawings, FIG. 1 is a generalized schematic cross-sectional view of an exemplary electrically conductive article according to various embodiments disclosed herein; Figure 2 is a cross-sectional view of a device for testing the PIM (passive intermodulation) of an adhesive. In the drawings, similar reference numerals indicate similar elements. Although the foregoing drawings, which may not be drawn to a constant scale, disclose various embodiments of the invention, other embodiments are also considered as described in the specifics for carrying out the invention. In all cases, the present disclosure describes the disclosed content as an expression of exemplary embodiments rather than as an express limitation. It should be understood that many other modifications and embodiments falling within the scope and spirit of the present disclosure may be devised by those skilled in the art. Specific details for implementing the invention
[0007] In electronic assembly devices such as smartphones and tablets, there are many applications requiring conductive tapes and conductive gaskets that function as grounding and / or shielding materials. Among the components used in electronic devices are conductive pressure-sensitive adhesives (CPSA) and articles containing CPSA. These CPSAs are used not only to bond device components together (the general role of PSA) but are also required to perform additional roles within the device. Conductive PSAs have conflicting requirements; they typically must possess high electrical conductivity for grounding performance and adhere strongly to electrical components without adversely affecting them. Because electrical components (e.g., copper layers and conductive fabrics) often undergo corrosion and degradation, many typical materials used in pressure-sensitive adhesives (e.g., acidic or basic materials, or trace amounts of acid or basic impurities within CPSA components) are not optimal for use in CPSA.
[0008] One of the requirements for electronic devices is to reduce passive intermodulation (PIM). PIM is generated when two or more signals at different frequencies mix with each other due to electrical nonlinearity. In some cases, PIM signals originating from wireless transmission of signals may occur at frequencies within the receiving band of wireless communication or data devices, thereby causing undesirable signal interference. Methods for measuring PIM are described below and illustrated in the drawings. Therefore, there remains a need for conductive PSAs that maintain excellent PSA characteristics (such as peeling and shearing properties) and excellent conductivity, and provide low levels of PIM, even when aged at elevated temperature and humidity levels.
[0009] In the present disclosure, a conductive PSA is described that has and maintains excellent PSA properties (e.g., peel and shear properties), has and maintains excellent conductivity properties, and provides a low level of PIM. The conductive PSA comprises a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising aromatic terminal blocks and aliphatic elastomeric blocks, at least one hydrocarbon tackifying resin, at least one aromatic reinforcing resin, and electrically conductive particles dispersed within the matrix. Articles manufactured using such a conductive pressure-sensitive adhesive are also disclosed.
[0010] In the case of the following description of defined terms, these definitions shall apply to the entire application unless different definitions are provided in the claims or elsewhere in this specification.
[0011] terminology
[0012] Certain terms, most of which are well known but may require some explanation, are used throughout this specification and claims. The following should be understood:
[0013] As used herein, the term “adhesive” refers to a polymer composition useful for bonding two substrates together. An example of an adhesive is a pressure-sensitive adhesive.
[0014] Pressure-sensitive adhesive compositions are well known to those skilled in the art to possess properties including: (1) strong and permanent tackiness, (2) adhesion under pressure not greater than the pressure applied, (3) sufficient retention on a substrate, and (4) cohesiveness sufficient for clean removal from the substrate. Materials found to function well as pressure-sensitive adhesives are polymers designed and formulated to exhibit viscoelastic properties necessary to bring about the desired balance of tackiness, peel adhesion, and shear retention. Achieving the proper balance of properties is not a simple process.
[0015] The terms “room temperature” and “ambient temperature” are used interchangeably to mean temperatures in the range of 20°C to 25°C.
[0016] When referring to two layers, the term “adjacent” as used herein means that two layers are in close proximity to each other without interposing an open space between them. They may be in direct contact with each other (e.g., laminated together) or there may be an interposed layer.
[0017] The terms "polymer" and "macromolecule" are used herein in accordance with their common usage in chemistry. Polymers and macromolecules consist of a number of repeating subunits. The term "polymer" is used to describe a material produced by a polymerization reaction.
[0018] As used herein, "essentially absent" with respect to a component of a composition means that the component is present in an amount of less than 0.1 weight percent (weight%) based on the total weight of the composition, for example, less than 0.09 weight percent, 0.08 weight percent, 0.07 weight percent, 0.06 weight percent, or even less than 0.05 weight percent of the total weight of the composition.
[0019] The term “alkenyl” refers to a monovalent group that is a radical of an alkene, which is a hydrocarbon having at least one carbon-carbon double bond. The alkenyl may be linear, branched, cyclic, or a combination thereof and typically contains 2 to 20 carbon atoms. In some embodiments, the alkenyl comprises 2 to 18, 2 to 12, 2 to 10, 4 to 10, 4 to 8, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkenyl groups include ethenyl, 1-propenyl, and 1-butenyl.
[0020] The term "alkyl" refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl group may be linear, branched, cyclic, or a combination thereof, and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, ethylhexyl, and octadecyl.
[0021] The term "alkylene" refers to a divalent group that is a radical of an alkane. An alkylene can be straight-chain, branched, cyclic, or a combination thereof. An alkylene often has 1 to 20 carbon atoms. In some embodiments, an alkylene contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. The radical center of an alkylene may be on the same carbon atom (i.e., alkylidene) or on different carbon atoms.
[0022] The term "alkoxy" refers to a monovalent group of the chemical formula -OR (where R is an alkyl group). The term "alkoxysilane" refers to a monovalent group of the chemical formula -Si(OR)n (where R is an alkyl group and n is an integer from 1 to 3).
[0023] The term "dipodal alkoxysilane" refers to a component having two sets of alkoxysilane groups.
[0024] The term “non-functional” refers to the absence of any functional group exhibiting reactivity or polymerizable reactivity with other functional groups, including hydroxyl groups, silanol groups, Si-H groups, vinyl groups, allyl groups, acrylic groups, methacrylic groups, epoxy groups, amino groups, and mercapto groups. Examples of non-functional groups include alkyl or aryl groups composed of carbon, hydrogen, and, in some embodiments, a halogen atom (e.g., a chlorine atom).
[0025] As used in this specification, the term “phosphonic acid” refers to a group having the chemical formula -P(=O)(OH)2 directly attached to a carbon atom.
[0026] As used in this specification, the term "carboxylic acid" refers to a group having the chemical formula -C(=O)(OH) directly attached to a carbon atom.
[0027] In relation to numerical values or features, the terms "about" or "approximately" mean + / - 5% of the numerical value or characteristic or feature, but clearly include the exact numerical value.
[0028] In relation to characteristics or features, the term "substantially" means that a characteristic or feature appears to a greater extent than its opposite.
[0029] As used in this specification and the appended embodiments, the singular forms (“a,” “an,” and “the”) include multiple referents unless the content clearly indicates otherwise. Thus, for example, a reference to “compound” includes a mixture of two or more compounds. As used in this specification and the appended embodiments, the term “or” is generally used to include “and / or” unless the content clearly indicates otherwise.
[0030] Unless otherwise indicated, all numbers expressing amounts of components, measurements of characteristics, etc., used in the specification and embodiments shall be understood in all cases to be modified by the term “about.” Accordingly, unless otherwise indicated, the numeric parameters presented in the foregoing specification and the appended list of embodiments may vary according to the desired characteristics that a person skilled in the art intends to obtain by utilizing the teachings of this disclosure. At a minimum, and not in an attempt to limit the application of the doctrine of equivalents to the scope of the claimed embodiments, each numeric parameter shall be interpreted at least in terms of the reported significant digits and by applying ordinary rounding techniques.
[0031] By definition, the total weight percentage of all components in the composition is equal to 100 weight percent.
[0032] Now, various exemplary embodiments of the present invention will be described. Exemplary embodiments of the present disclosure may be subject to various modifications and changes without departing from the spirit and scope of the present disclosure. Accordingly, it should be understood that embodiments of the present disclosure are not limited to the exemplary embodiments described below, but are subject to the limitations set forth in the claims and any equivalents thereof.
[0033] In a first embodiment, a conductive adhesive composition is provided. The conductive adhesive composition is,
[0034] A pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer including aromatic terminal blocks and aliphatic elastomeric blocks;
[0035] At least one hydrocarbon-based tackifying resin;
[0036] At least one aromatic reinforcing resin;
[0037] An adhesion promoter comprising an alkyl alkoxysilane, an alkenyl alkoxysilane, an alkyl phosphonic acid, or an alkyl carboxylic acid;
[0038] Optionally a non-functional dipodal alkoxysilane—provided that when the adhesion promoter comprises an alkyl alkoxysilane or an alkenyl alkoxysilane, the non-functional dipodal alkoxysilane is present—; and
[0039] It includes electrically conductive particles dispersed within the above matrix.
[0040] In a second embodiment, a different conductive adhesive composition is provided. The conductive adhesive composition is,
[0041] A pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer including aromatic terminal blocks and aliphatic elastomeric blocks;
[0042] At least one hydrocarbon-based tackifying resin;
[0043] At least one aromatic reinforcing resin;
[0044] An adhesion promoter comprising an organic molecule selected from a class of organic compounds capable of forming a bond with a metal oxide surface; and
[0045] It includes electrically conductive particles dispersed within the above matrix.
[0046] Various classes of organic compounds, including specified alkoxysilanes (e.g., alkyl alkoxysilanes, alkenyl alkoxysilanes), phosphonic acids (e.g., alkyl phosphonic acids), carboxylic acids (e.g., alkyl carboxylic acids), hydroxylic acids (i.e., N-hydroxy-amides), and phosphate esters, are suitable as adhesion promoters for the conductive adhesives disclosed herein.
[0047] It was unexpectedly found that the adhesion promoter according to the present disclosure provides improved clean removal of the conductive adhesive from the substrate compared to using an aminoalkoxysilane adhesion promoter.
[0048] Although it is possible to use a combination of an aminoalkoxysilane adhesion promoter and the adhesion promoter described herein, in some embodiments, the conductive adhesive composition essentially does not contain aminoalkoxysilane (i.e., contains less than 0.1 weight% of aminoalkoxysilane).
[0049] It is noted that certain classes of organic compounds, e.g. and without limitation, alkoxysilanes, phosphonic acids, phosphate esters, carboxylic acids, and hydroxyamic acids, can form bonds with metal oxide surfaces. In some cases, adhesion promoters form bonds with metal oxide surfaces, e.g., hydrogen bonds or covalent bonds. Adhesion promoters can form single or double bonds with metal oxide surfaces. Typical metal oxides include, e.g. and without limitation, nickel oxide, copper oxide, silver oxide, aluminum oxide, chromium oxide, iron oxide, and titanium oxide.
[0050] In some embodiments, an alkyl alkoxysilane is present, and the alkyl group of the alkyl alkoxysilane is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. In some cases, the alkyl group of the alkyl alkoxysilane is n-butyl. Often, a suitable alkoxy group of the alkyl alkoxysilane has 1 to 6 carbon atoms, 1 to 4 carbon atoms, 1 to 3 carbon atoms, or 1 to 2 carbon atoms. The alkoxy group is often methoxy or ethoxy. In some embodiments, the alkyl alkoxysilane comprises a dialkoxysilane or a trialkoxysilane. Exemplary alkyl alkoxysilanes include, for example and without limitation, n-butyltrimethoxysilane, n-decyltrimethoxysilane, n-octyltrimethoxysilane, n-butyldimethoxysilane, n-decyldimethoxysilane, and n-octyldimethoxysilane.
[0051] In some embodiments, an alkenyl alkoxysilane is present, and the alkenyl group of the alkenyl alkoxysilane is selected from the group consisting of ethenyl, 1-propenyl, 1-butenyl, and polybutadiene oligomers. The polybutadiene oligomer is not particularly limited and has a weight-average molecular weight of up to 5,000 g / mol, e.g., up to 4,500 g / mol, 4,000 g / mol, 3,500 g / mol, or up to 3,000 g / mol. The weight-average molecular weight (Mw) can be determined by gel permeation chromatography. In selected cases, the alkenyl group of the alkenyl alkoxysilane is polybutadiene. Exemplary alkenyl alkoxysilanes include, for example and without limitation, trimethoxyvinylsilane, allyltrimethoxysilane, trimethoxyoctenylsilane, dimethoxyvinylsilane, allyldimethoxysilane, dimethoxyoctenylsilane, and trimethoxy- or triethoxy-modified polybutadiene.
[0052] As mentioned above, when the adhesion promoter comprises alkyl alkoxysilane or alkenyl alkoxysilane, non-functional dipodal alkoxysilane is present. It has been found that a combination of non-functional dipodal alkoxysilane and either alkyl alkoxysilane or alkenyl alkoxysilane provides a synergistic effect in which the conductive adhesive is removed more cleanly upon peeling compared to when any of these materials are used alone in the conductive adhesive. Without being bound by theory, additional alkoxysilane groups of the non-functional dipodal alkoxysilane are believed to improve the interaction between the conductive adhesive and the substrate surface. In some embodiments, the alkyl alkoxysilane and the non-functional dipodal alkoxysilane are present in a weight ratio of 9:1 to 1:1, e.g., 8:1 to 1:1, 7:1 to 1:1, 6:1 to 1:1, or even 5:1 to 1:1. Exemplary suitable non-functional difodal alkoxysilanes include, for example and without limitation, 1,2-bistrimethoxysilylethane, 1,2-bistrimethoxysilylmethane, 1,2-bistrimethoxysilyloctane, 1,2-bistrimethoxysilylethane, 1,2-bistrimethoxysilylmethane, 1,2-bistrimethoxysilyloctane, 1,2-bisdimethoxysilylethane, 1,2-bisdimethoxysilylmethane, 1,2-bisdimethoxysilylethane, 1,2-bisdimethoxysilyloctane, and 1,2-bisdimethoxysilylmethane.
[0053] In some embodiments, an alkyl phosphonic acid is present, and the alkyl group of the alkyl phosphonic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. In the selected case, the alkyl group is n-butyl. Optionally, a second alkyl phosphonic acid may be added. Exemplary suitable alkyl phosphonic acids include, for example and without limitation, 1-butylphosphonic acid, 1,2-ethylenediphosphonic acid, methylphosphonic acid, ethylphosphonic acid, and 1,8-octanediphosphonic acid.
[0054] In some embodiments, an alkyl carboxylic acid is present, and the alkyl group of the alkyl carboxylic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. Where selected, the alkyl group is n-butyl or n-pentyl. Exemplary suitable alkyl carboxylic acids include, for example and without limitation, butanoic acid, pentanoic acid, and octanoic acid. In some cases, the alkyl carboxylic acid may also include at least one acrylate or vinyl group that can be reacted and introduced into the PSA, such as beta-carboxyethyl acrylate.
[0055] In some embodiments, the adhesion promoter comprises a phosphate ester. Exemplary suitable phosphate esters include, for example and without limitation, propyl phosphate, isopropyl phosphate, butyl phosphate, 2-ethylhexyl phosphate, dipropyl phosphate, diisopropyl phosphate, dibutyl phosphate, and bis(2-ethylhexyl) phosphate.
[0056] In some embodiments, the adhesion promoter comprises a hydroxyl acid. Exemplary suitable hydroxyl acids include, for example and without limitation, N-hydroxybutanamide, N-hydroxypentanamide, and N-hydroxyhexanamide.
[0057] The conductive adhesive may be tested for Passive Intermodulation (PIM) as described in more detail in the Examples section and drawings below. This method involves forming a tape, which comprises a conductive adhesive layer and an electrically conductive layer, such as a conductive woven or nonwoven layer. The tape is placed in a test fixture comprising a gold conductive surface. When first and second electrical signals of magnitude 30 dBm are propagated in the thickness direction of the conductive adhesive layer between the gold surfaces at frequencies F1 and F2, respectively, any intermodulation signal generated from the first and second electrical signals having a frequency F3 equal to nF1+mF2 (where m and n are positive or negative integers) has a power of less than about -60 dBm. It should be understood that "less than" a specific negative number refers to a larger negative number; for example, -70 dBm is less than -60 dBm.
[0058] It should be noted that adhesive properties such as 180° peel strength, DC resistance, and PIM are properties of the conductive adhesive. In the case of the 180° peel strength test, for example, the adhesive is formed into a tape by placing the conductive adhesive on a 50-micrometer PET backing; however, this property is a property of the adhesive itself and does not mean that the adhesive can only be used in tape form. Although the test method involves forming a tape to perform the test, the listed properties are properties of the adhesive itself.
[0059] The conductive adhesive comprises a pressure-sensitive adhesive matrix. The pressure-sensitive adhesive matrix comprises at least one nonlinear block copolymer comprising aromatic terminal blocks and aliphatic elastomeric blocks, at least one hydrocarbon-based tackifying resin, and at least one aromatic reinforcing resin.
[0060] A wide range of nonlinear block copolymers comprising aromatic terminal blocks and aliphatic elastomer blocks are suitable. Nonlinear block copolymers are not simple ABA block copolymers. In some embodiments, at least one nonlinear block copolymer comprises a star or comb copolymer. Star block copolymers are sometimes also referred to as radial block copolymers. Examples of commercially available radial styrene-farnesene-styrene block copolymers include SF902 from Kuraray, Tokyo, Japan.
[0061] In some embodiments of the block copolymer, the aromatic terminal block comprises a styrene block, and the aliphatic elastomer block comprises isoprene, farnesene, or a combination thereof. Particularly suitable polymers include radial styrene-isoprene-styrene block copolymers and styrene-farnesene-styrene block copolymers. Examples of commercially available radial styrene-isoprene-styrene block copolymers include those available from Kraton Polymers, Houston, Texas, under the trade names D1340KT and DL1124KT. Particularly suitable radial block copolymers include star copolymers having styrene terminal blocks and isoprene elastomer blocks, wherein the terminal blocks comprise 9 to 10 percent styrene based on the weight of the total polymer.
[0062] The pressure-sensitive adhesive matrix further comprises at least one hydrocarbon tackifying resin. The hydrocarbon tackifying resin comprises a hydrogenated or partially hydrogenated hydrocarbon resin. Various hydrogenated or partially hydrogenated hydrocarbon resins are suitable. Examples of commercially available hydrogenated or partially hydrogenated hydrocarbon resins include resins ARKON P100, ARKON P125, and ARKON P140 from Arakawa Chemical, Inc., Chicago, Illinois, USA.
[0063] The pressure-sensitive adhesive matrix further comprises at least one aromatic reinforcing resin. In some embodiments, the aromatic reinforcing resin comprises a thermoplastic aromatic copolymer having a Tg (glass transition temperature) greater than 100°C. A wide range of aromatic resins are suitable. Examples of commercially available aromatic reinforcing resins include ENDEX 160 from Eastman Chemical Company, Kingsport, Tennessee, USA.
[0064] The conductive adhesive further comprises electrically conductive particles dispersed within the pressure-sensitive adhesive matrix. A wide range of electrically conductive particles are suitable. The electrically conductive filler particles may be in the form of metal particles or metal-coated insulating (e.g., polymeric) particles or a combination thereof. In some embodiments, the electrically conductive particles comprise particles of nickel-coated graphite. The amount of electrically conductive particles present in the conductive adhesive may vary as described below. One particularly suitable conductive particle is the nickel-coated graphite particle “E-Fill #2806 Ni,” available for purchase from Oerlikon Metco, Westbury, New York, USA.
[0065] The conductive adhesive may optionally include at least one additive. Particularly suitable additives include conductive nanoparticles. Examples of suitable conductive nanoparticles include carbon nanotubes and metallic nanoparticles, including nanowires, nanoflakes, nanograins, and nanospheres.
[0066] The conductive adhesive matrix formulation may have a wide range of component compositions. In some embodiments, the conductive adhesive comprises a pressure-sensitive adhesive matrix, the pressure-sensitive adhesive matrix comprising: 40 to 70 parts by weight of at least one non-linear block copolymer; 30 to 60 parts by weight of a hydrocarbon tackifying resin; 2 to 8 parts by weight of an aromatic reinforcing resin; 0.1 to 5 parts by weight of an adhesion promoter; 0 to 2.5 parts by weight of a non-functional difodal alkoxysilane; and 15 to 30 parts by weight of electrically conductive particles. In selected embodiments, 0.1 to 5 parts by weight of the adhesion promoter comprises 0.2 to 5 parts by weight of an alkyl phosphonic acid. In selected embodiments, 0.1 to 5 parts by weight of the adhesion promoter comprises 0.5 to 5 parts by weight of an alkyl carboxylic acid. In selected embodiments, 0.1 to 5 parts by weight of the adhesion promoter comprises 0.1 to 4.5 parts by weight of an alkenyl alkoxysilane. In a selected embodiment, 0.1 to 5 parts by weight of the adhesion promoter comprises 0.1 to 4.5 parts by weight of alkyl alkoxysilane, and in this case, the pressure-sensitive adhesive matrix further comprises 0.02 to 2.5 parts by weight of non-functional dipodal alkoxysilane. Parts by weight are used instead of weight percent to describe this formulation, because the sum of the weight components does not necessarily equal 100.
[0067] As mentioned above, conductive adhesives possess a wide range of desirable properties. Among these properties are adhesive properties (180° peel strength) and electrical properties (DC resistance and PIM). Each of these properties is described below.
[0068] Conductive adhesives are pressure-sensitive adhesives, which means they possess the following characteristic properties of pressure-sensitive adhesives: (1) strong and permanent tack, (2) adhesion at pressure not greater than the pressure applied, (3) sufficient retention on the substrate, and (4) sufficient cohesion to be cleanly removed from the substrate. One test commonly used to measure the adhesive properties of pressure-sensitive adhesives is the 180° peel strength. In this test, the adhesive is placed on a backing and peeled off from the test surface as described in the test method of the Examples section. In some embodiments, the conductive adhesive has a 180° peel strength of at least 15.0 Newtons / decimeter (0.15 N / mm) at room temperature. In another embodiment, the conductive adhesive has a 180° peel adhesive strength at room temperature of at least 20.0 Newtons / decimeters (0.20 N / mm), 30 N / dm (0.3 N / mm), 40 N / dm (0.4 N / mm), 50 N / dm (0.5 N / mm), 60 N / dm (0.6 N / mm), 70 N / dm (0.7 N / mm), or even at least 80 N / dm (0.8 N / mm).
[0069] Conductive adhesives also possess desirable electrical properties. Among these properties are DC resistance and PIM. Conductive adhesives have a DC resistance of less than 0.4 ohms when measured by ETM-12. Test method ETM-12 is described in the Examples section below. In some embodiments, the conductive adhesive has a DC resistance of less than 0.35 ohms, 0.3 ohms, 0.25 ohms, 0.2 ohms, 0.15 ohms, 0.1 ohms, or even less than 0.05 ohms.
[0070] As mentioned above, an important feature of current conductive adhesives is their stability when exposed to heat and moisture, particularly when the adhesive comes into contact with a conductive substrate such as a conductive fabric. In some embodiments, the 180° peel strength of the conductive adhesive changes by 25% or less after aging on a conductive fabric substrate at 85°C and 85% relative humidity for at least one week.
[0071] An adhesive layer is generally described as having length and width in the xy plane and thickness along the z-axis. The conductive adhesive of the present disclosure is generally a "z-axis conductive adhesive." This means that the adhesive layer is conductive along the z-axis, which is the thickness of the adhesive layer, and is not necessarily conductive in the xy plane of the adhesive layer.
[0072] The adhesive layer of the present disclosure may be manufactured from a conductive adhesive composition. The layer may be manufactured by placing the adhesive composition on the surface of a substrate, such as a release liner. The adhesive layer may be provided in various forms, such as a sheet or a roll, wherein the roll may be self-winded for transport or storage and unfolded for use.
[0073] In a third embodiment, an electrically conductive article is provided. The electrically conductive article comprises a substrate having a first main surface and a second main surface; and an electrically conductive adhesive layer disposed on at least a portion of the second main surface of the substrate. The electrically conductive adhesive comprises any electrically conductive adhesive composition according to the first embodiment or the second embodiment, as described in detail herein.
[0074] Referring to FIG. 1, a generalized schematic cross-sectional view of an electrically conductive article (100) is provided. The article (100) comprises a substrate (110) having a first main surface (112) and a second main surface (114) on the opposite side. An electrically conductive adhesive (120) is disposed on the second main surface (114) (at least a portion of) of the substrate (110). In this embodiment, an optional second layer of electrically conductive adhesive (130) is disposed on the first main surface (112) (at least a portion of) of the substrate (110).
[0075] A wide variety of substrates are suitable. In some embodiments, the substrate comprises an electrically conductive substrate. Such embodiments may be described as “single-sided tape” because they have a single side of exposed adhesive. A wide range of electrically conductive substrates are suitable. Examples of suitable conductive substrates include a nonwoven layer comprising metal-coated polymer fibers, a woven fabric layer comprising metal-coated polymer fibers, a film layer having metal-coated surface(s), or a metal foil. The metal can be deposited on the fiber or film in a wide variety of ways, such as coating, sputtering, electroplating, or chemical vapor deposition.
[0076] In another embodiment, the substrate includes a release liner. In this embodiment, the conductive adhesive layer is a freestanding adhesive layer with both surfaces of the adhesive layer exposed. This freestanding adhesive layer can be used in various ways. The exposed adhesive surfaces can be laminated to a conductive substrate to form a single-sided tape as described above. The freestanding adhesive layer can be laminated to a surface using it as is, or the release liner can be removed to expose a second surface of the pressure-sensitive adhesive, and the substrate or surface can be adhered to the newly exposed surface. The freestanding adhesive layer can also be laminated to the opposite surface of the single-sided adhesive tape as described above to form a double-sided adhesive tape.
[0077] Release liners are well known in the field of adhesive technology as films from which an adhesive composition or coating can be easily removed. Exemplary release liners include those made from paper (e.g., kraft paper) or polymeric materials (e.g., polyolefins, such as polyethylene or polypropylene, ethylene vinyl acetate, polyurethane, polyesters, such as polyethylene terephthalate, etc., and combinations thereof). At least some release liners are coated with a layer of release agent, such as silicone, fluorosilicone-containing materials, or fluorocarbon-containing materials.
[0078] Another important feature of the conductive adhesive of the present disclosure is a relatively low PIM (passive intermodulation). PIM can be tested as illustrated in FIG. 2 using a double-sided tape comprising two conductive adhesive layers with a conductive intermediate layer disposed between them. The conductive intermediate layer may be various conductive layers, such as a metallic layer or a conductive woven or nonwoven layer. Samples of the double-sided tape are placed on the gold portion of the PIM board, and a conductive bridge connects the samples. In FIG. 2, the PIM test board (200) has a gold portion (210) and a wire (240). The test sample comprises an adhesive layer (220) having a conductive bridge (230). The adhesive layer (220) has sublayers, these sublayers being an adhesive sample sublayer (221), a conductive intermediate layer sublayer (222), and an adhesive sample sublayer (223).
[0079] It should be understood that the adhesive test method for PIM does not limit the articles that can be manufactured with the conductive adhesive, and that regardless of how PIM is measured, the characteristic is that of the conductive adhesive, not that of the adhesive article (e.g., single-sided tape, double-sided tape, etc.). When first and second electrical signals of magnitude 30 dBm propagate in the thickness direction (z-axis) of the conductive adhesive layer at frequencies F1 and F2, respectively, any intermodulated signal generated has a frequency F3 equal to nF1+mF2 (where m and n are positive or negative integers). When measured in this manner, the PIM has a power of less than approximately -60 dBm.
[0080] Additionally, electrically conductive articles are disclosed herein. In some embodiments, the electrically conductive article comprises a substrate having a first main surface and a second main surface; and an electrically conductive adhesive layer disposed on at least a portion of the second main surface of the substrate. The electrically conductive adhesive is described in detail above. In some embodiments, the conductive adhesive comprises a pressure-sensitive adhesive matrix and electrically conductive particles dispersed within the matrix. The pressure-sensitive adhesive matrix comprises at least one non-linear block copolymer comprising aromatic end blocks and aliphatic elastomeric blocks, at least one hydrocarbon tackifying resin, and at least one aromatic reinforcing resin. The conductive adhesive is a pressure-sensitive adhesive and has a 180° peel adhesion force at room temperature of at least 30.0 Newtons / decimeters (0.3 N / mm) when disposed on a 50 micrometer-thick PET (polyethylene terephthalate) backing, and a DC resistance of less than 0.3 ohms as measured by ETM-12 when disposed on a copper foil backing. Optionally, the 180° peel adhesion changes by 25% or less after aging on a conductive fabric substrate at 85°C and 85% relative humidity for at least one week.
[0081] List of exemplary embodiments
[0082] In a first embodiment, the present disclosure provides a conductive adhesive composition. The conductive adhesive composition comprises a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon tackifying resin; at least one aromatic reinforcing resin; and electrically conductive particles dispersed within the matrix. The conductive adhesive composition further comprises an adhesion promoter comprising an alkyl alkoxysilane, an alkenyl alkoxysilane, an alkyl phosphonic acid, or an alkyl carboxylic acid; and optionally a non-functional dipodal alkoxysilane, provided that when the adhesion promoter comprises an alkyl alkoxysilane or an alkenyl alkoxysilane, the non-functional dipodal alkoxysilane is present.
[0083] In a second embodiment, the present disclosure provides a conductive adhesive composition according to a first embodiment, wherein the adhesive composition essentially does not contain amino alkoxysilane.
[0084] In a third embodiment, the present disclosure provides a conductive adhesive composition according to a first or second embodiment, wherein an alkyl alkoxysilane is present, and the alkyl group of the alkyl alkoxysilane is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.
[0085] In the fourth embodiment, the present disclosure provides a conductive adhesive composition according to any of the first to third embodiments, wherein an alkyl alkoxysilane is present, and the alkyl group of the alkyl alkoxysilane is n-butyl.
[0086] In the fifth embodiment, the present disclosure provides a conductive adhesive composition according to any of the first to fourth embodiments, wherein an alkyl alkoxysilane is present, and the alkyl alkoxysilane comprises a diallkoxysilane or a trialkoxysilane.
[0087] In the sixth embodiment, the present disclosure provides a conductive adhesive composition according to any of the first to fifth embodiments, wherein an alkyl alkoxysilane is present, and the alkyl alkoxysilane and the non-functional dipodal alkoxysilane are present in a weight ratio of 9:1 to 1:1.
[0088] In the seventh embodiment, the present disclosure provides a conductive adhesive composition according to the first or second embodiment, wherein an alkenyl alkoxysilane is present, and the alkenyl group of the alkenyl alkoxysilane is selected from the group consisting of ethenyl, 1-propenyl, 1-butenyl, and polybutadiene oligomer.
[0089] In the eighth embodiment, the present disclosure provides a conductive adhesive composition according to the first embodiment, the second embodiment, or the seventh embodiment, wherein an alkenyl alkoxysilane is present, and the alkenyl group of the alkenyl alkoxysilane is polybutadiene.
[0090] In the ninth embodiment, the present disclosure provides a conductive adhesive composition according to the first or second embodiment, wherein an alkyl phosphonic acid is present, and the alkyl group of the alkyl phosphonic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.
[0091] In the 10th embodiment, the present disclosure provides a conductive adhesive composition according to the 9th embodiment, wherein the alkyl group is n-butyl.
[0092] In the 11th embodiment, the present disclosure provides a conductive adhesive composition according to the 10th embodiment, further comprising 1,2-ethylenediphosphonic acid.
[0093] In the 12th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 9th to 11th embodiments, comprising 40 to 70 parts by weight of at least one nonlinear block copolymer; 0 to 60 parts by weight of at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of at least one aromatic reinforcing resin; 0.2 to 5 parts by weight of alkyl phosphonic acid; and 15 to 30 parts by weight of electrically conductive particles.
[0094] In the 13th embodiment, the present disclosure provides a conductive adhesive composition according to the first or second embodiment, wherein an alkyl carboxylic acid is present, and the alkyl group of the alkyl carboxylic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl.
[0095] In the 14th embodiment, the present disclosure provides a conductive adhesive composition according to the 13th embodiment, wherein the alkyl carboxylic acid comprises butanoic acid, pentaic acid, or beta-carboxyethyl acrylate.
[0096] In the 15th embodiment, the present disclosure provides a conductive adhesive composition according to the 13th or 14th embodiment, comprising 40 to 70 parts by weight of at least one non-linear block copolymer; 30 to 60 parts by weight of at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of at least one aromatic reinforcing resin; 0.5 to 5 parts by weight of alkyl carboxylic acid; and 15 to 30 parts by weight of electrically conductive particles.
[0097] In the 16th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 15th embodiments, wherein at least one non-linear block copolymer comprises a star-shaped or comb-shaped copolymer.
[0098] In the 17th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 16th embodiments, wherein the aromatic terminal block comprises a styrene block and the aliphatic elastomer block comprises isoprene, farnesene, or a combination thereof.
[0099] In the 18th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 17th embodiments, wherein the nonlinear block copolymer comprises a star-shaped copolymer having styrene terminal blocks and isoprene elastomer blocks, and the styrene terminal blocks constitute 9 to 10 weight percent of the total polymer.
[0100] In the 19th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 18th embodiments, wherein at least one hydrocarbon tackifying resin comprises a hydrogenated or partially hydrogenated hydrocarbon resin.
[0101] In the 20th embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 19th embodiments, wherein at least one aromatic reinforcing resin comprises a thermoplastic aromatic copolymer having a Tg greater than 100°C.
[0102] In the 21st embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 20th embodiments, wherein the electrically conductive particles comprise nickel-coated graphite particles.
[0103] In the 22nd embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 6th embodiments, comprising: 40 to 70 parts by weight of at least one nonlinear block copolymer; 30 to 60 parts by weight of at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of at least one aromatic reinforcing resin; 0.1 to 4.5 parts by weight of alkyl alkoxysilane or alkenyl alkoxysilane; 0.02 to 2.5 parts by weight of non-functional dipodal alkoxysilane; and 15 to 30 parts by weight of electrically conductive particles.
[0104] In the 23rd embodiment, the present disclosure provides a conductive adhesive composition according to any of the 1st to 22nd embodiments, further comprising a conductive nanoparticle comprising at least one of carbon nanotubes, metallic nanowires, metallic nanoflakes, metallic nanograins, or metallic nanospheres.
[0105] In the 24th embodiment, the present disclosure provides a conductive adhesive composition according to any of the first to 23 embodiments, wherein the conductive adhesive composition can be tested for passive intermodulation by forming a tape comprising a layer of the conductive adhesive composition and an electrically conductive layer according to a PIM test method, and by placing the tape in a test fixture comprising one gold conductive surface and one stainless steel conductive surface, and when first and second electrical signals of magnitude 30 dBm are propagated in the thickness direction of the conductive adhesive layer between the gold surfaces at frequencies F1 and F2, respectively, any intermodulation signal generated from the first and second electrical signals having a frequency F3 equal to nF1+mF2 (where m and n are positive or negative integers) has a power of about -60 dBm or less.
[0106] In the 25th embodiment, another conductive adhesive composition is provided. The conductive adhesive composition comprises: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; an adhesion promoter comprising an organic molecule selected from a class of organic compounds capable of forming a bond with a metal oxide surface; and electrically conductive particles dispersed within the matrix.
[0107] In the 26th embodiment, the present disclosure provides an electrically conductive article. The electrically conductive article comprises a substrate having a first main surface and a second main surface; and an electrically conductive adhesive layer disposed on at least a portion of the second main surface of the substrate. The electrically conductive adhesive comprises any electrically conductive adhesive composition according to any of the first to 25 embodiments.
[0108] In the 27th embodiment, the present disclosure provides an electrically conductive article according to the 26th embodiment, wherein the material comprises an electrically conductive material.
[0109] In the 28th embodiment, the present disclosure provides an electrically conductive article according to the 27th embodiment, wherein the electrically conductive substrate comprises a nonwoven layer comprising metal-coated polymer fibers, a woven fabric layer comprising metal-coated polymer fibers, a film layer having a metal-coated surface, or a metal foil.
[0110] In the 29th embodiment, the present disclosure provides an electrically conductive article according to the 27th or 28th embodiment, wherein the article further comprises a second layer of a conductive adhesive disposed on a first main surface of an electrically conductive substrate.
[0111] In the 30th embodiment, the present disclosure provides an electrically conductive article according to the 26th embodiment, wherein the substrate comprises a release liner.
[0112] Examples
[0113] Unless otherwise stated or not evident from the context, all parts, percentages, ratios, etc. in the Examples and the remainder of this specification are on a weight basis.
[0114] Materials used in the examples
[0115]
[0116]
[0117] Static shear test
[0118] The test was performed at 70°C. The adhesive sample was laminated onto a 50 μm thick PET film. A test specimen was cut from the sample material having dimensions of 12.7 mm × 175 mm. Subsequently, the liner was removed, and the adhesive was bonded to a stainless steel plate with an overlap of 12.7 mm × 25.4 mm. A loop was prepared at the end of the test strip to hang the specified weight. Then, the test sample was rolled four times using a standard FINAT test roller (weighing 2 kg) at a speed of approximately 10 mm / sec to obtain close contact between the adhesive and the surface. Prior to testing, the test sample was left at ambient room temperature (23°C + / - 2°C, 50% relative humidity + / - 5%) for 24 hours.
[0119] Next, each sample was placed in a vertical shear stand (+2° alignment) at 70°C equipped with an automatic time logging function. After a 10-minute settling time in the oven, a 500 g weight was attached to the hook. The time to failure was measured and recorded in minutes. The target value was 10,000 minutes. Two samples were measured for each structure. A time recorded as “>10,000” indicates that the adhesive did not fail after 10,000 minutes. The failure modes were given as follows: PO for pop-off, AT for adhesive transfer, and CF for cohesive failure.
[0120] Double-sided coated tape manufacturing
[0121] Using a seam roller, two sheets of 17.8 cm × 17.8 cm samples, each 20 μm thick, were laminated onto a 22 μm thick nickel / copper coated fabric. Each fabric sample was passed through a laminator (ChemInstruments Hot Roll Laminator, HL-200) equipped with a rubber roller on the bottom and a steel roller on the top at room temperature and a pressure of 0.34 MPa (50 psi, controlled by an air regulator). After lamination, the samples were annealed in an oven at 40°C for 4 days prior to measurement.
[0122] Peel test
[0123] ASTM D3330 / D3330M was complied with. Double-sided coated tape structures were prepared by laminating some samples onto both sides of a conductive fabric. After removing the release liner, the adhesive samples were laminated onto a 50 μm thick PET film. Subsequently, the adhesive was applied to a stainless steel substrate and left to stand at room temperature for 20 minutes (RT 20 min) or 72 hours (RT 72 hours), after which it was peeled at 180° at 30.5 cm / min. Three measurements were performed, and the average peel value was recorded. The peel failure mode was also recorded (clean or 2-bond).
[0124] Passive Intermodulation (PIM) Test
[0125] The PIM of the sample was measured using a test fixture consisting of a 50-ohm microstrip test board and a mechanically connected coaxial cable. The test board was a 50 mm x 80 mm x 60 mil (1.52 mm) FR-4 dielectric with 1 oz copper finished with ENIG (electroless nickel, dipping gold). The microstrip line was 3 mm wide, with a 10 mm gap in the center along the length of the board to break the circuit. Two 3 mm x 15 mm adhesive samples were manually bonded (by pressure) to both sides of the 10 mm gap within the microstrip line. A 40 mm x 3 mm x 1 mm stainless steel 316L bridge was aligned with the sample and the gap, and the electrical circuit was completed by connecting it using a pressure of 0.103 MPa (15 psi). The sample was left standing for at least 20 minutes prior to measurement. Measurements were performed by connecting a Rosenberger desktop PIM analyzer (Tittmoning, Germany) to a test fixture. Two frequency signals of 30 dBm (1 W) at 729 to 758 MHz were swept across the LTE700L cellular band, and the maximum reflection third (IM3) value was recorded.
[0126] ETM-12, DC resistance via PSA, Z-axis test
[0127] A sample of double-sided coated tape was cut into 10 mm x 10 mm pieces, and two pieces were placed at the center of each electrode on a 3M ETM-7 board (St. Paul, Minnesota, USA) with the adhesive side facing down. After initial manual lamination and liner removal, a 3M ETM-12-SUS316L (stainless steel) plate (50 mm x 10 mm x 1 mm) (Cheil Technology, Seoul, South Korea) was placed on the tape with the metal side facing down, and then a 2 kg rubber roller was applied across the ETM-12 board. After a settling time of 20 minutes, the DC resistance between the electrodes was measured using a micro-ohm meter.
[0128] Formulation
[0129] After adding the amounts (in grams) of the materials listed in Table 1 to a glass vial, a 3:1 mixture of HEP and EA was added to prepare a 30% solids solution. The vial was rolled under a heat lamp for 12 hours to form a homogeneous solution. Subsequently, the solution was coated onto RL-1 (50 μm thick) using a knife coater with a gap of 63.5 μm (2.5 mil). The coated samples were placed in an oven set to 70°C for 15 minutes. Then, RL-2 (50 μm thick) was laminated onto each dried sample.
[0130] [Table 2]
[0131]
[0132] A peel adhesion test was performed, and the results are shown in Table 3. An electrical test was performed, and the results are shown in Table 4. Note that a more negative PIM value indicates better performance. A static shear test was performed, and the results are shown in Table 5.
[0133] [Table 3]
[0134]
[0135] [Table 4]
[0136]
[0137]
[0138] [Table 5]
[0139]
[0140] Although specific embodiments have been illustrated and described herein, it will be recognized by those skilled in the art that various alternative and / or equivalent embodiments may substitute for the specific embodiments illustrated and described without departing from the scope of the present disclosure. The present application is intended to include any modification or variation of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and their equivalents.
[0141] Additionally, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as specifically and individually indicated where each individual publication or patent is incorporated by reference. In the event of any discrepancy or contradiction between the incorporated references and parts of this application, the information in the foregoing description shall prevail. Various exemplary embodiments have been described. These and other embodiments are within the scope of the following claims.
Claims
Claim 1 A conductive adhesive composition comprising: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; an adhesion promoter comprising an alkyl alkoxysilane, an alkenyl alkoxysilane, an alkyl phosphonic acid, or an alkyl carboxylic acid; optionally a non-functional dipodal alkoxysilane—provided that when the adhesion promoter comprises an alkyl alkoxysilane or an alkenyl alkoxysilane, the non-functional dipodal alkoxysilane is present—; and electrically conductive particles dispersed within the matrix. Claim 2 A conductive adhesive composition according to claim 1, wherein the adhesive composition essentially does not contain amino alkoxysilane. Claim 3 A conductive adhesive composition according to claim 1 or 2, wherein the alkyl alkoxysilane is present, and the alkyl group of the alkyl alkoxysilane is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. Claim 4 A conductive adhesive composition according to any one of claims 1 to 3, wherein the alkyl alkoxysilane is present and the alkyl group of the alkyl alkoxysilane is n-butyl. Claim 5 A conductive adhesive composition according to any one of claims 1 to 4, wherein the alkyl alkoxysilane is present, and the alkyl alkoxysilane comprises a diallkoxysilane or a trialkoxysilane. Claim 6 A conductive adhesive composition according to any one of claims 1 to 5, wherein the alkyl alkoxysilane is present, and the alkyl alkoxysilane and the non-functional dipodal alkoxysilane are present in a weight ratio of 9:1 to 1:
1. Claim 7 A conductive adhesive composition according to claim 1 or 2, wherein the alkenyl alkoxysilane is present, and the alkenyl group of the alkenyl alkoxysilane is selected from the group consisting of ethenyl, 1-propenyl, 1-butenyl, and polybutadiene oligomer. Claim 8 A conductive adhesive composition according to claim 1, 2, or 7, wherein the alkenyl alkoxysilane is present and the alkenyl group of the alkenyl alkoxysilane is polybutadiene. Claim 9 A conductive adhesive composition according to claim 1 or 2, wherein the alkyl phosphonic acid is present, and the alkyl group of the alkyl phosphonic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. Claim 10 A conductive adhesive composition according to claim 9, wherein the alkyl group is n-butyl. Claim 11 A conductive adhesive composition according to claim 10, further comprising 1,2-ethylenediphosphonic acid. Claim 12 A conductive adhesive composition according to any one of claims 9 to 11, comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 30 to 60 parts by weight of the at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.2 to 5 parts by weight of the alkyl phosphonic acid; and 15 to 30 parts by weight of electrically conductive particles. Claim 13 A conductive adhesive composition according to claim 1 or 2, wherein the alkyl carboxylic acid is present, and the alkyl group of the alkyl carboxylic acid is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, and ethylhexyl. Claim 14 A conductive adhesive composition according to claim 13, wherein the alkyl carboxylic acid comprises butanoic acid, pentaic acid, or beta-carboxyethyl acrylate. Claim 15 A conductive adhesive composition according to claim 13 or 14, comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 30 to 60 parts by weight of the at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.5 to 5 parts by weight of the alkyl carboxylic acid; and 15 to 30 parts by weight of electrically conductive particles. Claim 16 A conductive adhesive composition according to any one of claims 1 to 15, wherein the electrically conductive particles comprise nickel-coated graphite particles. Claim 17 A conductive adhesive composition according to any one of claims 1 to 6, comprising: 40 to 70 parts by weight of the at least one non-linear block copolymer; 30 to 60 parts by weight of the at least one hydrocarbon tackifying resin; 2 to 8 parts by weight of the at least one aromatic reinforcing resin; 0.1 to 4.5 parts by weight of the alkyl alkoxysilane or the alkenyl alkoxysilane; 0.02 to 2.5 parts by weight of the non-functional dipodal alkoxysilane; and 15 to 30 parts by weight of electrically conductive particles. Claim 18 A conductive adhesive composition according to any one of claims 1 to 17, wherein the conductive adhesive composition can be tested for passive intermodulation by forming a tape comprising a layer of the conductive adhesive composition and an electrically conductive layer according to a PIM test method, and placing the tape in a test fixture comprising one gold conductive surface and one stainless steel conductive surface, wherein when first and second electrical signals of magnitude 30 dBm are propagated in the thickness direction of the conductive adhesive layer between the gold surfaces at respective frequencies F1 and F2, any intermodulation signal generated from the first and second electrical signals having a frequency F3 equal to nF1+mF2 (where m and n are positive or negative integers) has a power of less than about -60 dBm. Claim 19 A conductive adhesive composition comprising: a pressure-sensitive adhesive matrix comprising at least one non-linear block copolymer comprising an aromatic terminal block and an aliphatic elastomeric block; at least one hydrocarbon-based tackifying resin; at least one aromatic reinforcing resin; an adhesion promoter comprising an organic molecule selected from a class of organic compounds capable of forming a bond with a metal oxide surface; and electrically conductive particles dispersed within the matrix. Claim 20 An electrically conductive article comprising: a substrate having a first main surface and a second main surface; and an electrically conductive adhesive layer disposed on at least a portion of the second main surface of the substrate; wherein the electrically conductive adhesive comprises an electrically conductive adhesive composition of any one of claims 1 to 19. Claim 21 In paragraph 20, the above description is an electrically conductive article comprising an electrically conductive material. Claim 22 In claim 21, the electrically conductive substrate comprises a nonwoven layer comprising metal-coated polymer fibers, a woven fabric layer comprising metal-coated polymer fibers, a film layer having a metal-coated surface, or a metal foil, an electrically conductive article. Claim 23 An electrically conductive article according to claim 21 or 22, wherein the article further comprises a second layer of conductive adhesive disposed on the first main surface of the electrically conductive substrate.