Tape containing a conductive porous medium

Abstract

A tape containing a conductive porous medium is provided. [Solution] The tape comprises a first conductive adhesive layer having an outermost first main surface and a second main surface on opposite sides of each other, and first and second release liners disposed on each of the first and second main surfaces, wherein the first layer comprises a conductive porous medium and an adhesive disposed within the porous medium and extending through the thickness of the porous medium, defining a first area of ​​exposed adhesive and a first area of ​​exposed porous medium on the first main surface, and defining a second area of ​​exposed adhesive and a second area of ​​exposed porous medium on the second main surface, wherein in a plan view, the first main surface includes a first area of ​​exposed porous medium with an area percentage of P1, and the second main surface includes a second area of ​​exposed porous medium with an area percentage of P2, and 15% <P1<70%、30%<P2<95%、P2-P1> It is 5%.

Description

Background Art

[0001] The conductive tape can contain a plurality of conductive particles in its adhesive layer. The conductive particles can contact each other, thereby forming a conductive path.

Summary of the Invention

[0002] In some aspects of the present specification, a tape is provided that includes a first layer of conductive adhesive having outermost first and second main surfaces on opposite sides of each other. The first layer includes a conductive nonwoven layer containing metal-coated polymer fibers, and an adhesive disposed within the nonwoven layer and extending through the thickness of the nonwoven layer, defining a first region of exposed adhesive and a first region of exposed fibers of the nonwoven layer on the first main surface, and defining a second region of exposed adhesive and a second region of exposed fibers of the nonwoven layer on the second main surface. In a plan view, the first main surface includes a first region of exposed fibers at a P1 area percentage, the second main surface includes a second region of exposed fibers at a P2 area percentage, 15% < P1 < 70%, 30% < P2 < 95%, and P2 - P1 > 5%.

[0003] In some aspects of the present specification, a tape is provided that includes a first layer of conductive adhesive having outermost first and second main surfaces on opposite sides of each other. The first layer includes a conductive porous medium, and an adhesive disposed within the porous medium and extending through the thickness of the porous medium, defining a first region of exposed adhesive and a first region of exposed porous medium on the first main surface, and defining a second region of exposed adhesive and a second region of exposed porous medium on the second main surface. In a plan view, the first main surface includes a first region of exposed porous medium at a P1 area percentage, the second main surface includes a second region of exposed porous medium at a P2 area percentage, 15% < P1 < 70%, 30% < P2 < 95%, and P2 - P1 > 5%.

[0004] These and other aspects will become apparent from the detailed description below. However, in no case should this brief summary be construed as limiting the subject matter of the claims. [Brief explanation of the drawing]

[0005] [Figure 1] This is a schematic cross-sectional view of a tape according to several embodiments. [Figure 2] This is a schematic cross-sectional view of a tape, including layers on both sides of an adhesive layer, according to several embodiments. [Figure 3] This is a plan view image of a portion of the main surface of the conductive layer of an example tape. [Figure 4] This is a plan view of the main surface of a conductive layer divided into areas having a width W1 and a length L1, according to several embodiments. [Figure 5] The distribution of the area percentage of the exposed porous medium or exposed fibers relative to the area in Figure 4 is schematically shown in several embodiments. [Figure 6] This is a schematic cross-sectional view showing the coating of a porous medium, such as a nonwoven fabric, with an adhesive, according to several embodiments. [Figure 7] This is a schematic cross-sectional view of a tape, according to several embodiments, that is placed between two substrates and joins the two substrates together. [Figure 8] This is a schematic cross-sectional view showing 180-degree peeling of the tape from the substrate according to several embodiments. [Modes for carrying out the invention]

[0006] The following description refers to the accompanying drawings, which constitute part of this specification and illustrate various embodiments. The drawings are not necessarily to exact proportions. It should be understood that other embodiments can be conceived and implemented without departing from the scope or spirit of this specification. Therefore, the embodiments for carrying out the invention described below should not be construed as restrictive.

[0007] Conductive tapes utilize conductive nonwoven fabrics having an adhesive material containing conductive filler particles to bond adjacent substrates to each other, providing conductivity between substrates where the exposed portion of the nonwoven fabric provides electrical contact with the substrate. However, conventional tapes have had relatively small or relatively large exposure areas of the nonwoven fabric on the main surface(s) of the adhesive layer. This can lead to reduced and / or inconsistent performance in the end application. According to some embodiments of this specification, tapes can be formed by coating a conductive porous medium, such as a conductive nonwoven fabric, with an adhesive from one side of the porous medium so that the adhesive passes through the porous medium. According to some embodiments, this has been found to result in a tape having a higher area fraction of exposed conductive medium than conventional conductive tapes. Furthermore, according to some embodiments, the exposed area can have a sufficiently uniform distribution, and it has been found that there are substantially no areas of exposure that are too low for electrical contact or too high for proper bonding. In some applications, tapes are used between different substrates such that it is desirable for one side of the adhesive layer to have a higher porous medium exposure than the other side. According to some embodiments, the coating process described herein can naturally achieve this result. Furthermore, according to several embodiments, conductive tapes have been found to have improved electrical properties compared to conventional tapes. For example, according to some embodiments, conductive tapes can have low passive intermodulation (PIM) and / or low electrical resistance without the addition of conductive particles.

[0008] Conductive tapes can be manufactured by laminating adhesive layers on one or both sides of a conductive porous (e.g., nonwoven) carrier. A problem with such tapes is their short shelf life. Because the porous carrier is laminated with adhesive layers after it has dried, the pores of the carrier are not immediately filled with adhesive. However, the adhesive can be slowly (e.g., over several months) pressed into the pores of the carrier, which can lead to problems with insufficient tape surface smoothness and adhesion. According to some embodiments, tapes described herein can be formed by coating a porous medium with adhesive from one side of the porous medium so that the adhesive passes through the porous medium. This allows the pores to be substantially filled with adhesive, improving the stability and performance of the tape. The processes described herein have also been found, according to some embodiments, to enable the manufacture of thinner tapes than those manufactured by conventional processes.

[0009] Conductive tapes typically contained conductive filler particles in the adhesive to achieve a desired electrical conductivity. According to some embodiments herein, even when the adhesive substantially does not contain conductive filler particles, a desired electrical conductivity can be achieved, at least in part, due to adequate exposure of the conductive porous medium on the main surface of the conductive adhesive layer.

[0010] FIG. 1 is a schematic cross-sectional view of a tape 100 including a first layer 110 of a conductive adhesive having outermost first and second major surfaces 112 and 114 on opposite sides of each other, according to some embodiments. The first layer 110 includes a conductive porous medium 120 and an adhesive 130 disposed within the porous medium 120 and extending through the thickness of the porous medium 120, defining at the first major surface 112 a first region 132 of exposed adhesive and a first region 126 of exposed porous medium, and at the second major surface 114 a second region 134 of exposed adhesive and a second region 128 of exposed porous medium. In some embodiments, in a plan view (see, e.g., FIGS. 3 and 4), the first major surface 112 includes a first region 126 of porous medium exposed at a P1 area percentage, and the second major surface 114 includes a second region 128 of porous medium exposed at a P2 area percentage, where 15% < P1 < 70% and 30% < P2 < 95%. In some embodiments, the first major surface 112 includes a substantially uniform distribution of the first region 126 of the exposed porous medium 120. In some embodiments, the second major surface 114 includes a substantially uniform distribution of the second region 128 of the exposed porous medium 120.

[0011] An exposed portion (e.g., exposed portions 132, 126, 134, or 128) of a major surface (e.g., major surface 112 or 114) of a layer (e.g., the first layer 110) refers to a portion that is exposed to any adjacent layer present on the major surface. The adjacent layer may be, for example, an air layer, in which case the exposed portion may be described as being exposed to air. The adjacent layer may be, for example, a release layer or a bonding substrate, in which case the exposed portion may be described as being exposed to the release layer or the bonding substrate.

[0012] In some embodiments, the porous medium 120 is or includes a nonwoven fabric containing polymer fibers 122 coated with a metal 123. In other embodiments, the porous medium is or includes different types of porous media, such as different types of fabrics (e.g., woven fabrics) coated with a metal or other conductor, or different types of open-cell polymer porous media coated with a metal or other conductor. In the embodiment schematically shown in Figure 1, the porous medium 120 is a nonwoven fabric containing metal-coated polymer fibers 122. The metal coating 123 may be, for example, copper, nickel, silver, gold, tin, cobalt, chromium, aluminum, or a combination thereof, or include them. The metal coating 123 can be applied, for example, by plating or sputtering. The polymer fibers 122 may be, for example, polyester, nylon, polyurethane, vinylon, polyvinyl acetate, acrylate, cellulosic polymer, or a combination thereof, or include them. The fibers may be metallized after the nonwoven fabric is formed, or the nonwoven fabric may be manufactured from the metallized fibers.

[0013] In an embodiment where the porous medium 120 is a non-woven fabric, the tape 100 may be described as including a first layer 110 of a conductive adhesive having outermost first and second main surfaces 112 and 114 on opposite sides of each other. The first layer 110 includes a conductive non-woven layer 120 containing metal-coated polymer fibers 122, and an adhesive 130 disposed within the non-woven layer 120 and extending through the thickness of the non-woven layer 120, defining at the first main surface 112 a first region 132 of exposed adhesive and a first region 126 of exposed fibers of the non-woven layer, and defining at the second main surface 114 a second region 134 of exposed adhesive and a second region 128 of exposed fibers of the non-woven layer 120. In some embodiments, in a plan view, the first main surface 112 includes a first region 126 of exposed fibers at a P1 area percentage, and the second main surface 112 includes a second region 128 of exposed fibers at a P2 area percentage, where 15% < P1 < 70% and 30% < P2 < 95%. In some embodiments, the first main surface 112 has a substantially uniform distribution of the first region 126 of exposed fibers. In some embodiments, the second main surface 114 has a substantially uniform distribution of the second region 128 of exposed fibers.

[0014] In some embodiments, the first and / or second main surface consists essentially of exposed porous medium (e.g., exposed fibers) and exposed adhesive. In other words, in some embodiments, in a plan view, the first (and / or second) main surface includes about 100 - P1 (or 100 - P2) area percentage of exposed adhesive at the main surface.

[0015] In some embodiments, as schematically shown in FIG. 1, for example, P2 > P1. In some embodiments, P2 - P1 > 5%, or P2 - P1 > 10%, or P2 - P1 > 15%, or P2 - P1 > 20%. In some such embodiments, or in other embodiments, 15% < P1 < 60%, 20% < P1 < 60%, or 20% < P1 < 50%, or 20% < P1 < 40%. In some such embodiments, or in other embodiments, 30% < P2 < 90%, or 35% < P2 < 85%, or 40% < P2 < 80%, or 40% < P2 < 75%, or 40% < P2 < 70%.

[0016] Adhesive 130 may be a pressure-sensitive adhesive (PSA). To achieve desired properties, the polymer(s) used in the adhesive may be adjusted to have a glass transition temperature (Tg) of less than about 0°C. Examples of suitable PSA materials include, for example, rubber-based PSAs, silicone-based PSAs, and acrylic-based PSAs. Particularly suitable pressure-sensitive adhesives are (meth)acrylate copolymers. Such copolymers are typically derived from monomers containing about 40% to about 98% by weight, often at least about 70% by weight, or at least about 85% by weight, or even at least about 90% by weight, of at least one alkyl (meth)acrylate monomer having a Tg of less than about 0°C as a homopolymer. Examples of such alkyl (meth)acrylate monomers include those in which the alkyl group contains about 4 to about 14 carbon atoms, such as n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, isodecyl acrylate, and mixtures thereof. Optionally, other vinyl monomers and alkyl (meth)acrylate monomers having a Tg greater than 0°C, such as methyl acrylate, methyl methacrylate, isobornyl acrylate, vinyl acetate, and / or styrene, may be used as homopolymers in combination with one or more low-Tg alkyl (meth)acrylate monomers and copolymerizable polar monomers. The term "(meth)acrylate" is used to refer to both acrylate and methacrylate materials. Other useful adhesives are described, for example, in U.S. Patent Application Publication No. 2016 / 0333232 (Choi et al.) and U.S. Patent No. 9,061,478 (Choi et al.).

[0017] It has been found that softer adhesives can provide better surface uniformity and have better aging properties than harder adhesives. In some embodiments, adhesive 130 has a Young's modulus E' at 25°C of less than about 1 MPa and / or a loss modulus E'' at 25°C of less than about 0.4 MPa and / or a loss tangent (tanδ) at 25°C of less than about 0.7. The elastic properties of the adhesive can be adjusted by a suitable selection of monomers in the adhesive formulation, as will be understood by those skilled in the art (for example, aliphatic monomers can result in a softer adhesive than aromatic monomers, and / or monomers that result in linear molecules can result in a softer adhesive compared to monomers that result in branched molecules).

[0018] In some embodiments, tape 100 further includes at least one release liner. Figure 2 is a schematic cross-sectional view of tape 200 according to some embodiments, which may correspond to tape 100, but includes a first layer 141 and a second layer 142 disposed on a first main surface 112 and a second main surface 114, respectively. In some embodiments, each of the first layer 141 and the second layer 142 is a release liner, and tape 200 may be described as a double-sided tape. In some embodiments, one of the first layer 141 and the second layer 142 is a release liner, and the other of the first layer 141 and the second layer 142 is a backing layer such as a metal foil, and tape 200 may be described as a single-sided tape.

[0019] The tape 100 and the first layer 110 in Figure 1 have an average thickness h1. The tape 200 in Figure 2 has an average thickness h2. In some embodiments, the tape 100 or 200 has an average thickness (h1 or h2) in the range of about 10 micrometers to about 200 micrometers, or 10 micrometers to about 100 micrometers, or about 15 micrometers to about 60 micrometers, or about 20 micrometers to about 50 micrometers. In some embodiments, the first layer 110 has an average thickness h1 in the range of about 10 micrometers to about 200 micrometers, or about 10 micrometers to about 100 micrometers, or about 15 micrometers to about 60 micrometers, or about 20 micrometers to about 50 micrometers, or about 20 micrometers to about 40 micrometers, or about 20 micrometers to about 35 micrometers.

[0020] The proportions of exposed adhesive and exposed porous media on the main surface can be determined using an optical microscope. Figure 3 is an image of a portion of the main surface of an exemplary first layer (corresponding to, for example, first layer 110), where the areas of exposed adhesive appear darker than the areas of exposed porous media. Line 160 is drawn around the areas of exposed adhesive. The area within line 160 can be determined using standard digital image processing techniques. The area percentage of exposed porous media on the main surface is obtained by subtracting the area percentage within line 160 from the area percentage of 100.

[0021] Machine learning models such as object detection, defect classification, segmentation detection, and customized image feature extraction computer vision algorithms and methods can be applied to determine the area fraction of exposed porous media. Both rule-based and deep learning-based models can be applied effectively and efficiently to, for example, the irregular shapes of protruding fibers. One type of preferred instance image segmentation model is known in the art as the mask-RCNN model. Such a model can detect objects (e.g., exposed fibers or other porous media) and accurately segment them from the background. Once the model is trained with a suitable set of similarly labeled images, objects can be segmented and covered with masks of the same size. An advantage of using mask-RCNN over conventional computer vision techniques is that mask-RCNN is not sensitive to background noise. For example, small dots with sizes very different from the target object will not be detected and segmented from the background in a mask-RCNN. Rule-based algorithms and non-neural network methods are also preferred methods for determining exposed area. Another preferred method is to use hybrid models, including deep neural network and non-neural network computer vision machine learning models.

[0022] Figures 4 and 5 schematically illustrate the determination of the mean and standard deviation of the area percentage of an exposed porous medium (e.g., exposed fibers) according to several embodiments. Figure 4 is a plan view of the main surface of a first layer 110 divided into a plurality of rectangular areas 178 having widths W1 and lengths L1. The plan view of the main surface of a layer is a view along a direction substantially perpendicular to the layer. The main surface in Figure 4 may correspond to a first main surface 112 or a second main surface 114. The width W1 and length L1 may be in the range of, for example, about 0.7 mm to about 5 mm, or about 1 mm to about 5 mm, or about 2 mm to about 5 mm, or about 3 mm to about 5 mm, or about 0.7 mm to about 3 mm, or about 0.7 mm to about 2 mm, respectively. Each rectangular area 178 may have the same width and length, or different lengths and widths may be used for different rectangular areas 178, each length and each width being in the range of about 0.7 mm to about 5 mm, or another range described elsewhere in this specification. A square is a special case of a rectangle, and in some embodiments, W1 and L1 are equal. In some embodiments, for each area 178, W1 and L1 are about 1 mm, or about 3 mm, or about 5 mm, respectively. Each area 178 may be labeled with an area number such that the i-th area contains area 126 or 128 in Pi area percentage. Figure 5 schematically shows the distribution of Pi values ​​for area 178. The average (mean) Pavg and standard deviation σ are shown. The analysis in Figures 4 and 5 can be applied separately to the first principal surface 112 and the second principal surface 114. The values ​​P1 and P2 for the first principal surface 112 and the second principal surface 114 can be approximated as the Pavg determined for these surfaces. The total number of areas 178 is selected such that the mean and standard deviation of the area percentage of the exposed porous medium (e.g., exposed fibers) determined using the areas 178 are sufficiently large to represent the mean and standard deviation of the principal surfaces. For example, the total number of areas 178 can be selected such that the mean and standard deviation of the area percentage of the exposed porous medium (e.g., exposed fibers) do not change significantly when more areas are included.In some embodiments, the total number of areas 178 is at least 10, or at least 15, or at least 20, and may be, for example, at most 100 or at most 50.

[0023] The distribution of the first regions 126 (each, the second regions 128) is such that when measured over the rectangular area 178 of the first major surface 112 (each, the second major surface 114), the standard deviation σ of the exposed porous medium area percentage or the exposed fiber area percentage is 0.35P1 (each, 0.35P2), and each rectangular area 178 can be described as being substantially uniform when having a length L1 and a width W1 each within a range of from about 0.7 mm to about 5 mm. The rectangular area should be understood to be rectangular in a plan view.

[0024] In some embodiments, the first major surface 112 has a substantially uniform distribution of the first region 126 of the exposed porous medium. In some embodiments, the first major surface has a standard deviation σ of less than about 15%, or less than about 10%, or less than about 7%, or less than about 5% of the exposed porous medium area percentage 112 when measured across the rectangular area of the first major surface such that each rectangular area has a length L1 and a width W1 within the range of about 0.7 mm to about 5 mm or another range described elsewhere in this specification. The standard deviation σ of the first major surface may be as low as about 3%, or about 2%, or about 1%, for example. In some embodiments, the second major surface 114 has a distribution of the second region 128 of the exposed porous medium 120 having a standard deviation σ of less than about 30%, or less than about 25%, or less than about 20%, or less than about 18% of the exposed porous medium area percentage of the second major surface 114 when measured across the rectangular area of the second major surface such that each rectangular area has a length L1 and a width W1 within the range of about 0.7 mm to about 5 mm or another range described elsewhere in this specification. The standard deviation σ of the first major surface may be as low as about 6%, or about 4%, or about 3%, for example. In some embodiments, the first major surface 112 has a distribution of the first region of the exposed porous medium 120 having a standard deviation σ of less than about 0.35P1, or less than about 0.3P1, or less than about 0.28P1, or less than about 0.26P1, or less than about 0.25P1, or less than about 0.24P1, or less than about 0.23P1 of the exposed porous medium area percentage when measured across the rectangular area of the first major surface 112 as further described elsewhere in this specification. In some embodiments, the second major surface 114 has a distribution of the second region 128 of the exposed porous medium 120 having a standard deviation σ of less than about 0.4P2, or less than about 0.38P2, or less than about 0.36P2, or less than about 0.35P2, or less than about 0.34P2, or less than about 0.33P2 of the exposed porous medium area percentage when measured across the rectangular area of the first major surface 112 as further described elsewhere in this specification.

[0025] In some embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the first principal surface 112 in a plan view, each rectangular area includes a first region 126 of exposed porous media 120 of about 15 area percent, or about 18 area percent, or about 20 area percent, or about 22 area percent, and each rectangular area has a length L1 and width W1 within the range of about 0.7 mm to about 5 mm or within the range described elsewhere herein. In some such embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the first principal surface 112 in a plan view, each rectangular area includes a first region 126 of exposed porous media 120 of less than about 70 area percent, or less than about 65 area percent, or less than 60 area percent. In some embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the second principal surface 114 in a plan view, each rectangular area includes a second region 128 of exposed porous media 120 of more than about 30 area percent, or more than about 35 area percent, or more than about 40 area percent, and each rectangular area has a length L1 and width W1 within the range of about 0.7 mm to about 5 mm or within the range described elsewhere herein. In some such embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the second principal surface 114 in a plan view, each rectangular area includes a second region 128 of exposed porous media 120 of less than about 95 area percent, or less than about 90 area percent, or less than about 85 area percent, or less than about 80 area percent. The regular arrangement of rectangular areas may be a two-dimensional periodic arrangement with no gaps between adjacent rectangular areas.

[0026] In some embodiments, the porous medium is a nonwoven fabric. In some embodiments, the first main surface 112 has a substantially uniform distribution of first areas 126 of exposed fibers 122. In some embodiments, the first main surface has a distribution of first areas 126 of exposed fibers 122 having a standard deviation σ of exposed fiber area of ​​less than about 15%, or less than about 10%, or less than about 7%, or less than 5%, when measured across a rectangular area of ​​the first main surface, and each rectangular area has a length L1 and width W1 within the range of about 0.7 mm to about 5 mm or within the range described elsewhere herein. In some embodiments, the second principal surface 114 includes a distribution of second regions 128 of exposed fibers 122 having a standard deviation of exposed fiber area of ​​less than about 30%, less than about 25%, less than about 20%, or less than about 18% when measured over a rectangular area of ​​the second principal surface, and each rectangular region has a length L1 and width W1 within the range of about 0.7 mm to about 5 mm or within the range described elsewhere in this specification. In some embodiments, the first principal surface 112 has a distribution of first regions 126 of exposed fibers 122 having a standard deviation σ of exposed fiber area of ​​less than about 0.35P1%, less than about 0.30P1%, less than about 0.28P1%, less than about 0.26P1%, less than about 0.25P1%, less than about 0.24P1%, or less than 0.23P1 when measured over a rectangular area, as further described elsewhere in this specification. In some embodiments, the second principal surface 114 includes a distribution of second regions 128 of exposed fibers 122 having a standard deviation of exposed fiber area of ​​less than about 0.4P2, or less than about 0.38P2, or less than about 0.36P2, or less than about 0.35P2, or less than about 0.34P2, or less than about 0.33P2, when measured over a rectangular area, as further described elsewhere in this specification.

[0027] In some embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the first principal surface 112 in total in a plan view, each rectangular area includes a first area 126 of exposed fibers 122 of more than about 15 area percent, or more than about 20 area percent, or more than about 25 area percent, or more than about 30 area percent, and each rectangular area has a length L1 and width W1 in the range of about 0.7 mm to about 5 mm or in the range described elsewhere herein. In some such embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the first principal surface 112 in total in a plan view, each rectangular area includes a first area 126 of exposed fibers 122 of less than about 70 area percent, or less than about 65 area percent, or less than 60 area percent. In some embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the second principal surface 114 in a plan view, each rectangular area includes a second area 128 of exposed fibers 122 of more than about 30 area percent, or more than about 35 area percent, or more than about 40 area percent, and each rectangular area has a length L1 and width W1 in the range of about 0.7 mm to about 5 mm or in the range described elsewhere herein. In some such embodiments, with respect to a regular arrangement of at least 20 rectangular areas of the second principal surface 114 in a plan view, each rectangular area includes a second area 128 of exposed fibers 122 of less than about 95 area percent, or less than about 90 area percent, or less than about 85 area percent, or less than 80 area percent. The regular arrangement of rectangular areas may be a two-dimensional periodic arrangement with no gaps between adjacent rectangular areas.

[0028] The tapes described herein can be formed by coating a porous medium with an adhesive from one side of the porous medium so that the adhesive penetrates into the porous medium. Any preferred coating method can be used. One preferred method is to use a Meyer rod. A Meyer rod includes a wire wound around a cylinder and is characterized by a Meyer rod size number that gives the wire diameter in mills. Figure 6 is a schematic cross-sectional view of coating a porous medium 120, such as a nonwoven fabric, with an adhesive 130 using a Meyer rod 222 at a winding angle α, according to several embodiments. It has been found that using a Meyer rod with a lower Meyer rod size number (e.g., 15-26) provides better coating uniformity and results in higher peeling force than using a Meyer rod with a higher Meyer rod size number (e.g., 30-33). Furthermore, it has been found that increasing the winding angle α can improve the penetration of the adhesive through the porous medium so that when the porous medium is coated from the first main surface 112, a sufficient amount of adhesive is present on the second main surface 114. When the porous medium is a nonwoven fabric, it has also been found that the tension of the fabric near the Meyer rod can be adjusted to further control how the adhesive is deposited. For example, higher tension keeps the fabric in closer contact with the Meyer rod, resulting in greater fiber exposure. The coated side typically has a lower percentage of exposed porous medium area than the opposite side. A backing layer, such as a release liner, can be applied to the side of the porous medium 120 that is opposite each other from the Meyer rod. The adhesive can be applied in a solvent, followed by evaporation of the solvent in an oven. The solids percentage of the adhesive in the solvent may be in the range of 30–45 weight percent and can be adjusted to give the coating the appropriate rheology.

[0029] Tapes manufactured by coating a porous medium with an adhesive from one side so that the adhesive penetrates the porous medium have been found to offer improved electrical properties (e.g., lower electrical resistance and / or lower passive intermodulation) and / or improved adhesion compared to conventional tapes.

[0030] Figure 7 is a schematic cross-sectional view of a tape 100' placed between substrates 252 and 251 to bond them together, according to several embodiments. Tape 100' and the first layer 110' may correspond to tape 100 and the first layer 110', respectively, except that the first layer 110' contains optional conductive filler particles 333. The conductive filler particles 333 may be included to reduce electrical resistance, or they may be included in a volume filler amount that has only a negligible effect on the electrical properties of tape 100'. If included, the conductive filler particles 333 may be, for example, metal particles or metal-coated insulating (e.g., polymer) particles or a combination thereof. The first layers 110, 110' may be described as substantially free of conductive filler particles 333 if removing the conductive filler particles 333 and replacing them with an equal volume of adhesive 130 changes the electrical resistance Rz of the first layers 110, 110' in the thickness direction (z direction in Figure 7, see illustrated xyz coordinate system) by less than about 10%. In some embodiments, removing the conductive filler particles 333 and replacing them with an equal volume of adhesive 130 changes the electrical resistance Rz of the first layers 110, 110' in the thickness direction (z direction) by less than about 5%, less than about 3%, or less than about 2%. In some embodiments, the conductive filler particles 333 are included in an amount of less than about 5 volume percent, less than about 3 volume percent, or less than about 2 volume percent. In some embodiments, the first layers 110, 110' have an electrical resistance Rz in the thickness direction (z-direction) of the first layer of less than about 300 mΩ, or less than about 200 mΩ, or less than about 100 mΩ, or less than about 50 mΩ, or less than about 35 mΩ, or less than about 30 mΩ, or less than about 29 mΩ, or less than about 28 mΩ. In some such embodiments, or in other embodiments, the first layers 110, 110' do not contain or substantially contain conductive filler particles 333. The electrical resistance Rz may be as low as, for example, about 24 mΩ, or about 20 mΩ, or about 16 mΩ. The electrical resistance generally decreases, for example, as the exposure rate of the porous conductive medium increases.

[0031] In some embodiments, the tape has low passive intermodulation (PIM). PIM occurs when two or more signals of different frequencies mix with each other due to electrical nonlinearity. In some cases, the PIM signal may have a frequency close to the input frequency, which can cause undesirable interference. Substrates 251 and 252 have respective main surfaces 261 and 262 facing the first layer 110'. Substrate 252 may be gold and / or may include a gold main surface 262 (e.g., by being gold-plated). Substrate 251 may be stainless steel and / or may include a stainless steel main surface 261. The first layer 110' can be arranged such that a second main surface 114 faces the gold surface 262 and a first main surface 112 faces the stainless steel surface 261. In some embodiments, when the first electrical signal 401 and the second electrical signal 402 propagate in the thickness direction (z direction) of the first layer 110, 110' between the gold surface 262 and the stainless steel surface 261 at their respective frequencies F1 and F2, an arbitrary intermodulation signal 403 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 -88 dB, or less than about -90 dB, or less than about -94 dB, or less than about -95 dB, or less than about -97 dB, or less than about -98 dB, or less than about -99 dB, or less than about -100 dB, or less than about -101 dB relative to the total power of the first signal 401 and the second signal 402. The power may be as low as approximately -110 dB or approximately -105 dB relative to the total power of the first signal 401 and the second signal 402. F1 and F2 are each selected from the frequency range fa to fb. The frequency fa may be, for example, approximately 100 MHz, 200 MHz, 300 MHz, 500 MHz, 700 MHz, 800 MHz, or 850 MHz, and the frequency fb may be approximately 10 GHz, 5 GHz, 3 GHz, 1 GHz, or 900 MHz.In some embodiments, each of F1 and F2 is in the range of about 100 MHz to 10 GHz, and the difference between F1 and F2 is in the range of about 5 MHz to about 1 GHz, or about 10 MHz to about 800 MHz, or about 10 MHz to about 700 MHz, or about 10 MHz to about 100 MHz, or about 20 MHz to about 40 MHz, or about 25 MHz to about 35 MHz. In some embodiments, each of F1 and F2 is in the range of about 850 MHz to about 900 MHz. For example, in some embodiments, F1 may be 869 MHz and F2 may be 894 MHz. When these signals are combined to form a third-order product (where the sum of the absolute values ​​of m and n is 3), a PIM signal with frequencies such as 2F1-F2=844 MHz and 2F2-F1=919 MHz may be generated.

[0032] Figure 8 is a schematic cross-sectional view showing 180-degree peeling of tape 100 from a substrate 270 having a main surface 273, according to several embodiments. The substrate 270 may be, for example, a stainless steel substrate. In some embodiments, tape 100, or any tape described herein, may have a 180-degree peel strength of at least about 0.1 N / mm, or at least about 0.2 N / mm, or at least about 0.25 N / mm, or at least about 0.3 N / mm from the stainless steel surface 273. The peel strength can be determined using, for example, a peeling rate of about 300 mm / min (e.g., 304.8 mm / min). The peel strength may be any of these ranges for at least one of the first main surface 112 and the second main surface 114 facing the stainless steel surface 273. In some embodiments, the peel strength is in any of these ranges when the first main surface 112 faces the stainless steel surface 273 and when the second main surface 114 faces the stainless steel surface 273. The peel strength can be determined, for example, according to ASTM D3330 / D3330M-04 (re-approved in 2018), "Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape". Test method C of this standard can be used when the tape is double-sided, and test method A of this standard can be used when the tape is single-sided (for example, when layer 142 is the backing layer of tape 200).

[0033] In some embodiments, the tape 300 has a peel strength within any of the ranges described herein and an electrical resistance within any of the ranges described herein. In some such embodiments, or in other embodiments, the adhesive is substantially free of conductive fillers. In some such embodiments, or in other embodiments, the tape provides intermodulation within any of the ranges described herein. [Examples]

[0034] Sample preparation Various samples were prepared by coating a 30-micrometer thick conductive nonwoven fabric (obtained from Jiaxin Purification Equipment Co. Ltd.) with an acrylate pressure-sensitive adhesive composition containing approximately 40% by weight of solids. The acrylate pressure-sensitive adhesive composition contained a bisamide crosslinking agent and was similar to that described in U.S. Patent No. 6,893,718 (Melancon et al.). The conductive nonwoven fabric was a polyethylene terephthalate (PET) nonwoven fabric with a sputtered multilayer nickel / copper / nickel coating. The conductive nonwoven fabric was coated with the adhesive composition from one side using a Meyer rod without a supporting liner or roll underneath. The coated nonwoven fabric was then sent to an oven for solvent evaporation. Samples with a total thickness of approximately 40 micrometers were prepared using various Meyer rods (characterized by Meyer rod size number), and the peel strength was measured as described in "Test Method". The results are shown in the table below. [Table 1]

[0035] Various other samples (Examples 1-3) were prepared in the same manner as described above, but with thinner coatings. The conductive adhesive layer of Example 1 had an average thickness of approximately 35 micrometers (e.g., corresponding to the average thickness h1 in Figure 1). The conductive adhesive layers of Examples 2 and 3 each had an average thickness of approximately 30 micrometers (e.g., corresponding to the average thickness h1 in Figure 1). The coating conditions (total coating weight and nonwoven fabric tension) were varied for Examples 1-3 to obtain different thicknesses and distributions of exposed fibers, as shown under "Test Results". The total coating weight decreased in Examples 2-3 compared to Example 1, resulting in thinner adhesive layers. In Examples 2-3, a higher tension was used on the nonwoven fabric near the coater compared to Example 1, resulting in increased fiber exposure.

[0036] Comparative Example CE1 was 3M 5113DF, a double-sided conductive tape available from 3M Company (St. Paul, MN).

[0037] Comparative Example CE2 was 3M Conductive Transfer Tape 9701, a double-sided tape available from 3M Company (St. Paul, MN), which has a nickel / copper coated conductive nonwoven fabric carrier. Comparative Example CE2 had a conductive adhesive layer with a thickness of 50 micrometers.

[0038] Test method Peel test sample preparation: A stainless steel panel was wiped three times with a tissue dampened with isopropanol using firm hand pressure. The cleaned panel was air-dried for 10 minutes. A 25.4 mm x 200 mm adhesive tape sample was placed on the stainless steel panel, and a 1 kg rubber roller was rotated back and forth once over the tape to adhere the tape sample to the surface of the stainless steel panel.

[0039] 180° Peel Strength Test (23°C, 60% Relative Humidity): All samples were held at 23°C and 60% relative humidity for 20 minutes prior to the peel strength test at room temperature (approximately 23°C). The procedure for the room temperature peel strength test was as described in ASTM D3330 / D3330M-04 (re-approved in 2018), "Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape". The peel strength test was performed using an INSTRON tensile testing machine (available from Instron (Norwood, MA, US)) at a peel speed of 304.8 mm / min. Samples were tested on the coated side facing the stainless steel panel (first main surface) and the opposite side facing the stainless steel panel (second main surface).

[0040] Conductivity (Z-axis electrical resistance through adhesive): Two strips of conductive tape were placed 10mm x 10mm in the center of the electrodes on a PCB substrate. The PCB substrate size was 50mm (X-axis) x 75mm (Y-axis) and the thickness was 1.6mm. The electrodes on the substrate were 10mm wide. The distance between electrodes was 30mm. After initial hand lamination to provide a 10mm x 10mm contact area between the tape and electrodes, another PCB substrate was attached to the opposite side of the tape, with dimensions of 10mm x 50mm. A 2kg rubber roller was then applied to the entire substrate to simulate a typical manufacturing process that can be used to apply tape to the surface. After setting for 20 minutes, the DC resistance between electrodes was measured with a microohmmeter.

[0041] Passive Intermodulation (PIM) Test: A conductive tape was placed between a gold surface and a stainless steel surface within a test fixture. Two currents with frequencies of 860 MHz and 890 MHz were transmitted through the thickness of the conductive tape from the gold surface to the stainless steel surface, and the reflected third-order intermodulation signal was measured. The test was performed as generally described for CCIF3 IMD in Hongwei's "Measurements of Various Intermodulation Distortions (IMD, TD+N, DIM) using Multi-Instrument," Virtins Technology, August 2020.

[0042] Exposed fiber area percentage: Using an optical microscope (Keyence VHX-5000 with VH-100R lens, available from Keyence Corporation (Osaka, Japan)), digital images of the outermost principal surface of the conductive tape were acquired, and the exposed fiber area percentage of each surface was determined, as generally described in relation to Figure 3. The average and standard deviation were determined from measurements of at least 10 approximately 3-4 mm × approximately 3-4 mm areas on each surface.

[0043] Test results The conductive tape was measured as described in the "Test Method" section. The results for electrical properties and peel strength are reported in the table below. [Table 2]

[0044] The results regarding the exposed fiber area are reported in the table below. [Table 3]

[0045] Terms such as “about” will be understood by those skilled in the art in the context in which they are used and described herein. Where the use of “about” in relation to the size, quantity, and physical properties of a feature is not otherwise obvious to those skilled in the art in the context in which it is used and described herein, “about” will be understood to mean within 10 percent of a particular value. A quantity given as about or approximately of a particular value may be exactly that particular value. For example, where it is not otherwise obvious to those skilled in the art in the context in which it is used and described herein, a quantity having a value of about 1 means that the quantity has a value between 0.9 and 1.1, and that the value may also be 1.

[0046] All references, patents, or patent applications cited above are incorporated herein by reference in their entirety. In the event of any inconsistency or contradiction between any part of the incorporated references and this application, the information in the foregoing description shall prevail.

[0047] Unless otherwise indicated, the descriptions of elements in the drawings should be understood to apply equally to the corresponding elements in other drawings. While specific embodiments are illustrated and described herein, it will be understood by those skilled in the art that these specific embodiments may be replaced by various alternative and / or equivalent embodiments without departing from the scope of this disclosure. This application is intended to encompass all adaptations, modifications, or combinations of the specific embodiments discussed herein. Therefore, this disclosure is intended to be limited only by the claims and their equivalents.

Claims

1. A tape comprising a first conductive adhesive layer having an outermost first main surface and a second main surface on opposite sides, wherein the first layer is A conductive nonwoven fabric layer containing metal-coated polymer fibers, The adhesive comprises an adhesive disposed within the nonwoven fabric layer, extending through the thickness of the nonwoven fabric layer, defining a first region of exposed adhesive and a first region of exposed fibers of the nonwoven fabric layer on the first main surface, and defining a second region of exposed adhesive and a second region of exposed fibers of the nonwoven fabric layer on the second main surface, In a plan view, the tape has a first main surface that includes a first region of exposed fibers with area percentage P1, and a second main surface that includes a second region of exposed fibers with area percentage P2, where 15% < P1 < 70%, 30% < P2 < 95%, and P2 - P1 > 5%.

2. The tape according to claim 1, wherein the first main surface includes a distribution of first areas of exposed fibers, which, when measured over a rectangular area of ​​the first main surface, includes a standard deviation of less than 10% of the exposed fiber area percentage, and each rectangular area has a length and width in the range of about 0.7 mm to about 5 mm.

3. The tape according to claim 1, wherein the first main surface includes a distribution of first areas of exposed fibers, which, when measured over a rectangular area of ​​the first main surface, includes a standard deviation of exposed fiber area of ​​less than approximately 0.28P1, and each rectangular area has a length and width in the range of approximately 0.7 mm to approximately 5 mm.

4. The tape according to claim 1, wherein the second main surface includes a distribution of the second region of exposed fibers, which, when measured over a rectangular area of ​​the second main surface, includes a standard deviation of less than 25% of the exposed fiber area percentage, and each rectangular area has a length and width in the range of about 0.7 mm to about 5 mm.

5. The tape according to claim 1, wherein the second main surface includes a distribution of the second region of exposed fibers, which, when measured over a rectangular area of ​​the second main surface, includes a standard deviation of less than approximately 0.35P2 of the percentage of exposed fiber area, and each rectangular area has a length and width in the range of approximately 0.7 mm to approximately 5 mm.

6. The tape according to claim 1, wherein, in a plan view, with respect to a regular arrangement of at least 20 rectangular areas of the first main surface in total, each rectangular area includes a first area of ​​exposed fibers exceeding about 15 area percent, and each rectangular area has a length and width in the range of about 0.7 mm to about 5 mm.

7. The tape according to claim 1, wherein, in a plan view, with respect to a regular arrangement of at least 20 rectangular areas of the second main surface in total, each rectangular area includes a second area of ​​exposed fibers exceeding about 30 area percent, and each rectangular area has a length and width in the range of about 0.7 mm to about 5 mm.

8. A tape comprising a first conductive adhesive layer having an outermost first main surface and a second main surface on opposite sides, wherein the first layer is A conductive porous medium, The adhesive comprises an adhesive disposed within the porous medium, extending through the thickness of the porous medium, defining a first region of exposed adhesive and a first region of exposed porous medium on the first main surface, and defining a second region of exposed adhesive and a second region of exposed porous medium on the second main surface. In a plan view, the first main surface includes a first region of the exposed porous medium with area percentage P1, and the second main surface includes a second region of the exposed porous medium with area percentage P2, where 15% < P1 < 70%, 30% < P2 < 95%, and P2 - P1 > 5%.

9. The tape according to claim 8, wherein the first main surface includes a distribution of first areas of exposed porous media, which, when measured over a rectangular area of ​​the first main surface, includes a standard deviation of less than about 10% of the exposed porous media area percentage, and each rectangular area of ​​the first main surface has a length and width in the range of about 0.7 mm to about 5 mm, and the second main surface includes a distribution of second areas of exposed porous media, which, when measured over a rectangular area of ​​the second main surface, includes a standard deviation of less than about 25% of the exposed porous media area, and each rectangular area of ​​the second main surface has a length and width in the range of about 0.7 mm to about 5 mm.

10. The tape according to any one of claims 1 to 9, wherein 20% < P1 < 40% and P2 - P1 > 15%.

11. The tape according to any one of claims 1 to 9, wherein the first layer has an electrical resistance of less than about 300 mΩ in the thickness direction of the first layer, and the first layer is substantially free of conductive filler particles.

12. The tape according to any one of claims 1 to 9, wherein the first layer has an electrical resistance of less than about 30 mΩ in the thickness direction of the first layer.

13. The tape according to claim 12, wherein the first layer substantially does not contain conductive filler particles.

14. The tape according to any one of claims 1 to 9, having a 180° peel strength of at least about 0.25 N / mm from a stainless steel surface.

15. The tape according to any one of claims 1 to 9, wherein when the first electrical signal and the second electrical signal propagate in the thickness direction of the first layer between the gold surface and the stainless steel surface at their respective frequencies F1 and F2, an arbitrary intermodulation signal generated from the first electrical signal and the second electrical signal having a frequency F3 equal to nF1 + mF2, where m and n are positive or negative integers, has a power of less than about -95 dB relative to the total power of the first electrical signal and the second signal.

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