Anisotropic conductive adhesive film with improved pattern alignment precision

Abstract

An anisotropic conductive adhesive film according to the present invention is interposed between connection targets to electrically connect facing wiring patterns, and comprises: an adhesive resin film for bonding the connection targets to each other; and a plurality of conductive particles disposed in the adhesive resin film, wherein alignment parts, in which the conductive particles are disposed to correspond to an alignment mark provided on the connection targets, and pattern connection parts, in which the conductive particles are disposed in order to electrically connect the wiring patterns, are provided, and when the direction in which the wiring patterns are arranged is referred to as a wiring arrangement direction, the alignment parts and the pattern connection parts are repeatedly formed along the wiring arrangement direction.

Description

Anisotropic conductive adhesive film with improved pattern alignment precision

[0001] The present invention relates to a circuit connection technology using an anisotropic conductive adhesive, and more specifically, to an anisotropic conductive adhesive for circuit connection that can electrically conduct two electrodes that are opposite to each other in the thickness direction while simultaneously maintaining insulation between adjacent electrodes in the surface direction when interconnecting two circuit members that are opposite to each other.

[0002] As electronic devices become smaller and thinner, circuit components are becoming denser and more precise. Consequently, conventional methods such as welding or soldering have become difficult to use to connect microcircuits. To solve this problem, anisotropic conductive adhesives have been developed (Japanese Patent Laid-Open No. Sho-51-21192). Anisotropic conductive adhesives are circuit connection components that electrically conduct two electrodes facing each other in the thickness direction while maintaining insulation between adjacent electrodes in the plane direction by mixing conductive particles into an adhesive component including a cured resin and controlling the content thereof. Such anisotropic conductive adhesives are widely used for the purpose of electrically connecting and bonding various circuit components in the manufacturing of display devices, semiconductor devices, etc. For example, it is not only used in COG (Chip On Glass) mounting, FOG (Flex On Glass) mounting, and FOG (Flex On Board) mounting, but is also widely used as a material for circuit bonding in digital devices using panel displays such as tablet PCs and high-definition TVs.

[0003] In recent years, as the integration of electronic circuits has increased, the pitch between electrodes has become increasingly finer, and accordingly, the size (area) of circuit electrodes has also become smaller. Therefore, there is an urgent need for an anisotropic conductive adhesive that can maintain electrical connection reliability between circuit elements even when applied to electronic circuits with fine inter-electrode pitches and / or flexible circuit boards. Conventional anisotropic conductive adhesive films are manufactured in a form in which conductive particles are dispersed on a resin forming the adhesive layer. However, as the area of ​​the electrodes to be connected decreases and the gap between adjacent electrodes narrows, there is a problem that an area with a small number of conductive particles exists in the electrode connection area, or an area with too many conductive particles exists in the gap between the electrodes, resulting in electrical conduction between adjacent electrodes.

[0004] Meanwhile, the process of connecting two circuit elements using an anisotropic conductive adhesive film is described as follows. For example, when mounting an electronic component on a circuit board, the terminal electrodes of the electronic component must be electrically connected to the bumps of the circuit board by corresponding them. To this end, an anisotropic conductive adhesive film is first provisionally bonded to the area where the terminal electrodes of the electronic component are formed. Then, the electronic component with the anisotropic conductive adhesive film attached is aligned to the circuit board and pressed to bond the electronic component and the circuit board. At this time, the terminal electrodes provided on the electronic component are respectively matched to the corresponding circuit board bumps, and conductive particles are interposed between the terminal electrodes and the bumps to electrically conduct the two.

[0005] FIG. 1 illustrates a state in which an anisotropic conductive adhesive film is temporarily attached to a display panel. For convenience of explanation, (A) illustrates a plan view of a panel (200) so that a state in which a wiring pattern (210) used as an electrode is formed can be confirmed, and (B) illustrates a side cross-sectional view showing a state in which an anisotropic conductive adhesive film (100) is attached. Generally, an anisotropic conductive adhesive film (100; hereinafter referred to as ACF) is used by cutting it to a certain length to match the dimensions of a wiring pattern formed on an adherend (display panel, COF, etc.). For example, as shown in FIG. 2, an ACF having a certain width (W) of approximately several centimeters is used by slitting (S1) to a predetermined width (W1) from a roll (100) wound in the longitudinal direction (L) to fit an area to be attached. Slitting is typically performed with a width (W1) of several millimeters, and the slitting is performed by physically cutting the ACF fabric being fed using a knife positioned between the unwinder and the rewinder. Thereafter, an ACF segment (100a) cut (S2) to a length (L1) suitable for the bonding area of ​​the panel (200) is provisionally bonded according to the wiring pattern of the panel (200).

[0006] In the conventional ACF, since the conductive particles (120) are manufactured in a dispersed and arranged form, pattern matching with the adherend is not required, and thus, when slitting, they are cut to a constant width (approximately 1 to 2 mm) and length (approximately 10 to 200 mm) and attached. Accordingly, in the cut ACF segment (100a), the conductive particles (120) are arranged regardless of the position or shape of the wiring pattern, and since the diameter of the conductive particles (120) is smaller than the width of the wiring pattern (210), the conductive particles may be captured between the opposing electrodes. However, as the pitch of the wiring pattern narrows, the number of conductive particles captured between the two opposing electrodes may not be constant depending on the position of the pattern, which may cause defects. In order to solve these problems, a method of regularly arranging conductive particles (120) at regular intervals to improve the capture rate of conductive particles captured in the wiring pattern has been attempted, but the reliability of the alignment process cannot be sufficiently secured due to the standard (straightness) tolerance and tilting that occur during the slitting process. In order to improve the accuracy of the alignment process for the cut ACF segment, a method of printing alignment marks at regular intervals on the ACF roll body (100) can be considered, but this not only increases the manufacturing cost, but also carries the risk of damaging the physical properties of the ACF itself by adding a printing material to the adhesive resin. In addition, in order to print an alignment mark on the surface of the resin film and match it with the alignment pattern (220) provided on the panel, it is necessary to be able to precisely control the slitting of the ACF roll (100). However, when slitting with a width of 1 mm or less, it is difficult to precisely control the straightness tolerance, so tilting is likely to occur, and as a result, problems such as positional changes or shape damage of the alignment mark may occur.

[0007] The present invention is intended to solve the problems of the above-described prior art, and aims to provide an anisotropic conductive adhesive film having excellent electrical connection reliability between circuit elements when applied to an electronic circuit having a fine inter-electrode pitch.

[0008] Another object of the present invention is to provide an anisotropic conductive adhesive film that can improve the precision of the alignment process for an adherend with respect to variables that may occur during the process, such as straightness tolerance and shape damage, when slitting a roll of anisotropic conductive adhesive film to a constant width.

[0009] The purposes of the present invention are not limited to the purposes mentioned above, and other purposes not mentioned can be clearly understood from the description below.

[0010] An anisotropic conductive adhesive film according to the present invention is an anisotropic conductive adhesive film that electrically conducts wiring patterns that are interposed between connection objects, the anisotropic conductive adhesive film comprising: an adhesive resin film that adheres the connection objects to each other; and a plurality of conductive particles arranged within the adhesive resin film; wherein an alignment portion in which the conductive particles are arranged corresponding to alignment marks provided on the connection objects, and a pattern connection portion in which the conductive particles are arranged for electrical connection of the wiring patterns are provided, and when the direction in which the wiring patterns are arranged is referred to as a wiring arrangement direction, the alignment portion and the pattern connection portion are formed repeatedly along the wiring arrangement direction.

[0011] Here, it is preferable that the conductive particles arranged in the alignment portion are arranged in a direction perpendicular to the wiring arrangement direction. In particular, it is preferable that the alignment portion in which the plurality of conductive particles are arranged has a straight shape in a direction perpendicular to the wiring arrangement direction.

[0012] In addition, the pattern connection portion may be formed as a plurality of pattern connection portions corresponding to each of a plurality of wiring patterns provided on the connection target.

[0013] In addition, the above-described anisotropic conductive adhesive film preferably has a plurality of connection areas formed along the longitudinal direction, each of the plurality of connection areas including: the pattern connection portion formed corresponding to the wiring pattern provided on the connection target; and a pair of alignment portions arranged at both ends of the pattern connection portion; and a dummy portion formed between the alignment portion formed in one connection area and the alignment portion formed in the other connection area, where no conductive particles are arranged.

[0014] By using the method for manufacturing an anisotropic conductive adhesive film according to the present invention, it is possible to more precisely align the ACF segment to the connection target despite the tolerance or tilting that occurs when slitting the ACF from the ACF roll at a fine width for provisional bonding the ACF to the circuit member. In particular, since alignment correction is possible when provisional bonding the ACF segment to the connection target despite the straightness tolerance or tilting that occurs when forming a fine-width ACF slit body having a width of 1 mm or less, the defect rate can be minimized. In addition, since it is easy to check the arrangement state, such as tilting or positional change, of the ACF segment when provisionally bonding to a circuit connection member having a fine line width, the alignment process can be performed with high precision with an error range of within several microns.

[0015] Figure 1 is a schematic diagram explaining a process of attaching a conventional anisotropic conductive adhesive film to an adherend.

[0016] Figure 2 is a schematic diagram explaining a process of cutting and attaching an ACF segment to be attached to an adherend from a conventional two-way conductive adhesive film roll.

[0017] FIG. 3 is a plan view of an ACF roll showing a state in which a connection area in which an alignment portion and a pattern connection portion are provided are repeatedly formed in an anisotropic conductive adhesive film according to the present invention.

[0018] FIG. 4 is a schematic diagram illustrating a process of cutting and attaching an ACF segment to be attached to an adherend from a roll of an anisotropic conductive adhesive film according to the present invention.

[0019] FIG. 5 is a cross-sectional view illustrating an alignment process for attaching an ACF according to the present invention to an adherend.

[0020] Fig. 6 is a cross-sectional view showing the arrangement of the conductive particles constituting the alignment portion in the ACF according to the present invention.

[0021] An anisotropic conductive adhesive film according to the present invention is an anisotropic conductive adhesive film that electrically conducts wiring patterns that are interposed between connection objects, the anisotropic conductive adhesive film comprising: an adhesive resin film that adheres the connection objects to each other; and a plurality of conductive particles arranged within the adhesive resin film; wherein an alignment portion in which the conductive particles are arranged corresponding to alignment marks provided on the connection objects, and a pattern connection portion in which the conductive particles are arranged for electrical connection of the wiring patterns are provided, and when the direction in which the wiring patterns are arranged is referred to as a wiring arrangement direction, the alignment portion and the pattern connection portion are formed repeatedly along the wiring arrangement direction.

[0022] Here, it is preferable that the conductive particles arranged in the alignment portion are arranged in a direction perpendicular to the wiring arrangement direction. In particular, it is preferable that the alignment portion in which the plurality of conductive particles are arranged has a straight shape in a direction perpendicular to the wiring arrangement direction.

[0023] In addition, the pattern connection portion may be formed as a plurality of pattern connection portions corresponding to each of a plurality of wiring patterns provided on the connection target.

[0024] In addition, the above-described anisotropic conductive adhesive film preferably has a plurality of connection areas formed along the longitudinal direction, each of the plurality of connection areas including: the pattern connection portion formed corresponding to the wiring pattern provided on the connection target; and a pair of alignment portions arranged at both ends of the pattern connection portion; and a dummy portion formed between the alignment portion formed in one connection area and the alignment portion formed in the other connection area, where no conductive particles are arranged.

[0025] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention. Furthermore, in describing the present invention, detailed descriptions of related known technologies will be omitted if they are deemed to unnecessarily obscure the gist of the present invention.

[0026] The anisotropic conductive adhesive film according to the present invention refers to an anisotropic conductive adhesive film that is interposed between opposing circuit elements to electrically connect circuit electrodes that face each other in the thickness direction while electrically insulating adjacent circuit electrodes in the surface direction. Here, the anisotropic conductive adhesive film may be configured to include an electrically insulating adhesive layer that can be cured by heat or a light source, and electrically conductive particles dispersed within the adhesive layer.

[0027] Hereinafter, the anisotropic conductive adhesive film according to the present invention will be described in detail with reference to FIGS. 3 to 5.

[0028] Figure 3 illustrates an anisotropic conductive adhesive film (300) according to the present invention. The anisotropic conductive adhesive film (300) can be used as an anisotropic conductive adhesive film that electrically conducts opposing wiring patterns interposed between connection objects.

[0029] Here, the ACF (300) is manufactured in a strip shape with a constant width (W), extended in the longitudinal direction (L), and wound into a roll shape. The ACF (300) may include an adhesive resin film (310) that bonds connection objects to each other, and a plurality of conductive particles (320) arranged within the adhesive resin film (310). Conductive particles (320) are embedded within the adhesive resin film (310), and an alignment portion (310a) in which the conductive particles (320a) are arranged corresponding to alignment marks (220) provided on the connection object (200), and a pattern connection portion (310b) in which the conductive particles (320b) are arranged corresponding to the wiring pattern (210) are provided.

[0030] The pattern connection portion (310b) may be formed in multiple numbers to correspond to each of the plurality of wiring patterns (210) provided on the connection target (200). Here, the pattern connection portion (310b) refers to a region of the resin film (310) and refers to a region where conductive particles (320b) that contribute to current conduction are arranged between the wiring patterns (210) that are connected vertically. It is advantageous for improving the insulation characteristics between the wiring patterns (210) that are adjacent in the plane direction that the conductive particles (320) are not arranged in the region between each pattern connection portion (310b) and the region between the pattern connection portion (310b) and the alignment portion (310a). The pattern connection portion (310b) may be designed in advance to correspond to the shape, position, number, and dimensions of the wiring patterns (210) formed on the connection target (200).

[0031] The alignment portion (310a) may be provided at both ends of the pattern connection portion (310b). The alignment portion (310a) refers to a region of the resin film (310) and refers to a region where conductive particles (320a) are arranged to correspond to alignment marks (220) provided on the connection target (200). The conductive particles (320a) arranged in the alignment portion (310a) do not contribute to the conduction of the wiring pattern, and are preferably arranged to be spaced apart from the conductive particles (320b) arranged in the neighboring pattern connection portion (310b) so as not to come into contact with each other. In addition, the conductive particles (320a) arranged in the alignment portion (310a) may use the same conductive particles as the conductive particles (320b) arranged in the pattern connection portion (310b).

[0032] In addition, it is preferable that the alignment portion (310a) and the pattern connection portion (310b) are repeatedly formed along the longitudinal direction (L) of the ACF (300). In particular, when the direction in which the wiring patterns (310) formed on the connection object are arranged is referred to as the wiring arrangement direction (P), it is preferable that the alignment portion (310a) and the pattern connection portion (310b) are repeatedly formed along the wiring arrangement direction (P). In addition, the alignment portion (310a) may include a pair of alignment portions arranged at each end in the longitudinal direction of the adhesive film (300), i.e., the wiring arrangement direction (P), with the pattern connection portion (310b) as the center. The pair of alignment portions (310a) and the pattern connection portion (310b) formed therebetween constitute one connection area. That is, the connection area is repeatedly formed in the longitudinal direction (L) of the ACF (300) along the wiring arrangement direction (P).

[0033] FIG. 4 schematically illustrates a process for temporarily bonding a conductive adhesive film according to the present invention to a connection target using a roll body (300) wound in a roll shape. As shown in FIG. 4, a slit body (300a) is formed by slitting (S1) from a roll body (300) to a predetermined width (W1). The slit body (300a) can be prepared in a strip shape in which a plurality of connection areas (R1, R2) are repeatedly formed along the wiring arrangement direction (P). An ACF segment (300b) prepared by cutting (S2) from the slit body (300a) to match the length of the connection area is temporarily bonded to the wiring pattern of the connection target (200). At this time, it is preferable that a dummy portion (310c) in which no conductive particles are arranged is formed between an alignment portion formed in one connection area (R1) and an alignment portion formed in another adjacent connection area (R2). That is, the dummy portion (310c) means a resin film region where no conductive particles are arranged between the connection regions (R1, R2), and the dimensions can be controlled more precisely when cutting the ACF segment (300b) through the dummy portion (310c) where no conductive particles are arranged.

[0034] FIG. 5 is a schematic diagram illustrating a process of performing pattern matching using an alignment portion (310a) when temporarily bonding an ACF segment (300b) to a connection target (200). As shown in FIG. 5, an alignment mark (220) provided on a connection target (200) and a conductive particle (320a) of an alignment portion (310a) formed on an ACF segment (300b) are aligned. At this time, the work can be performed while confirming through a camera (400) whether the alignment portions (310a) at both ends are accurately matched to the corresponding alignment marks (220). It is preferable that the alignment portion (310a) formed on the ACF (300) have a straight shape in a direction perpendicular to the longitudinal direction (L) of the ACF (300). The width of the slit body (300a) is slit to a dimension of approximately 2 mm or less, and since the diameter of the conductive particles has a dimension of several microns, up to 1,000 conductive particles can be arranged in the width (W1) direction. It is preferable that the conductive particles (320a) arranged in the alignment portion (310a) are arranged such that the interval between adjacent conductive particles (320a) is along the width (W) direction. It should be possible to confirm through the camera (400) that the conductive particles (320a) arranged in the alignment portion (310a) are arranged to overlap with the alignment mark (220).

[0035] FIG. 6 schematically illustrates a state in which conductive particles (320a) are arranged in the alignment portion (310a). The alignment portion (310a) in which a plurality of conductive particles (320a) are arranged has a straight line shape in a direction perpendicular to the longitudinal direction (L) of the ACF (300). Here, “having a straight line shape” means that the conductive particles (320a) are arranged along an imaginary vertical line (H) perpendicular to the longitudinal direction (L) along the width (W) of the ACF roll body (300), as shown in FIG. 6. In particular, in order to secure visibility of the camera (400) for the alignment portion (310a) while at the same time making it easy to check the tilting angle of the alignment portion (310a) through overlapping with the alignment mark (220), it is preferable that the conductive particles (320a) are arranged in an area with a width of 10 μm or more and 200 μm or less centered on the imaginary vertical line (H). If the width (w) of the alignment portion (310a) is less than 10 ㎛, the visibility of the alignment portion (310a) by the camera (400) may be reduced when the ACF segment (300b) is temporarily bonded. In addition, if the width (w) of the alignment portion (310a) exceeds 200 ㎛, it may be difficult to confirm the tilting angle of the ACF segment (300b) through the orientation of the alignment portion (310a) and the alignment mark (220). The conductive particles (320a) may be arranged in close proximity to each other. In addition, when arranging the conductive particles (320a), a method of transferring them to the resin film (310) through a transfer film may be used. However, if the spacing between the conductive particles (320a) is one or more times the particle diameter, unintended conductive particles may be caught between neighboring conductive particles (320a), which may cause deformation of the shape of the alignment portion (310a). For this purpose, it is preferable that the conductive particles (320a) placed in the alignment portion (310a) are placed so that the gap between adjacent conductive particles is less than one time the particle diameter.

[0036] The alignment portion (310a) is formed from one edge to the other edge across the width (W) of the ACF roll body (300). Even if straightness tolerance or tilting that may occur when forming the slit body (300a) occurs, the alignment portion (310a) formed at both ends can be precisely controlled to match the orientation of the wiring pattern. In addition, when temporarily bonding a circuit connection member having a fine line width, it is easy to check the arrangement state such as tilting or positional change of the ACF segment, so that the alignment process can be performed with high precision with an error range of several microns. In addition, even after temporary bonding, it is easy to verify misalignment of the ACF segment by checking the alignment state of the alignment portion (310a) and the alignment mark (220).

[0037] As the resin composition constituting the resin film (310) in the anisotropic conductive adhesive film according to the present invention described above, a polymerizable material having a functional group polymerizable by radicals, for example, a compound such as acrylate, methacrylate, maleimide, or a thermosetting resin such as epoxy resin, can be used. In addition, the resin composition may include a curing agent. As the curing agent, a curing agent that generates free radicals by heating or light can be used, and for example, compounds such as organic peroxides, azo compounds, imidazoles, or the like can be used. In addition, as the curing agent, a latent curing agent coated with a polymer resin can be used so that the storage life can be further improved. In particular, in order to check the alignment status of the alignment part (310a) and the alignment mark (220) through the camera (400), it is preferable to use a resin composition made of a transparent material with excellent visibility, but any material that allows the positions of the alignment mark (220) and the conductive particle (320a) to be checked through the camera (400) is possible.

[0038] In addition, as the conductive particle (320), metal particles such as silver (Ag), gold (Au), platinum (Pt), tin (Sn), cobalt (Co), iron (Fe), nickel (Ni), aluminum (Al), titanium (Ti), zinc (Zn), copper (Cu), and indium (In) may be used, and one or a mixture of two or more selected from these metal materials may be used. In addition, as the conductive particle (320), a conductive metal plating layer formed on the surface of a spherical polymer core may be used. Here, the polymer core is one or more selected from allyl compounds such as divinylbenzene, 1,4-divinyloxybutane, divinylsulfone, diallyl phthalate, diallylacrylamide, triallyl(iso)cyanurate, and triallyl trimellitate, and (poly)alkylene glycol di(meth)acrylate compounds such as (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol di(deta)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, and glycerol tri(meth)acrylate. A mixed material can be used. In addition, the metal plating layer is formed by plating a metal layer on the surface of the polymer core (210a) particle, for example, nickel, gold, copper, etc., to exhibit electrical properties. In addition, the conductive particle (320) can be formed in various shapes, such as spherical, square, and spike-shaped.

[0039] As a method for evenly arranging the conductive particles (320) in the alignment portion (310a) and the pattern connection portion (310b), a method may be used in which the conductive particles are arranged through a transfer mold having a concave groove formed therein and then transferred to a resin film using a transfer film; a method may be used in which the conductive particles are arranged through a transfer film having a locally high viscosity formed in the area where the conductive particles are to be arranged and then transferred to the resin film; and a method may be used in which the conductive particles are arranged at a fixed position within the resin composition through a mold having an opening through which the conductive particles pass. Since a known technology can be used as a method for arranging the conductive particles at a fixed position, a detailed description thereof will be omitted here.

[0040] While preferred embodiments of the present invention have been described so far, those skilled in the art will appreciate that modifications and variations can be implemented without departing from the essential characteristics of the present invention. Therefore, the embodiments of the present invention described herein should be considered illustrative rather than restrictive. The scope of the present invention is defined by the claims, not the foregoing description, and all differences within the scope equivalent thereto should be construed as being encompassed by the present invention.

Claims

1. An anisotropic conductive adhesive film that electrically conducts the opposing wiring patterns interposed between the objects to be connected. An adhesive resin film for bonding objects to each other; and a plurality of conductive particles arranged within the adhesive resin film; An alignment portion in which the above-mentioned conductive particles are arranged in correspondence to alignment marks provided on the above-mentioned connection target, and a pattern connection portion in which the above-mentioned conductive particles are arranged for electrical connection of the above-mentioned wiring pattern are provided, An anisotropic conductive adhesive film, characterized in that the alignment portion and the pattern connection portion are formed repeatedly along the longitudinal direction of the adhesive film.

2. In paragraph 1, An anisotropic conductive adhesive film characterized in that the alignment portion and the pattern connection portion are formed repeatedly along the wiring arrangement direction, when the direction in which the above wiring patterns are arranged is referred to as the wiring arrangement direction.

3. In paragraph 1, An anisotropic conductive adhesive film, characterized in that the alignment portion in which the plurality of conductive particles are arranged has a straight line shape in a direction perpendicular to the longitudinal direction of the adhesive film.

4. In paragraph 3, An anisotropic conductive adhesive film, characterized in that the plurality of conductive particles arranged in the alignment portion are arranged in an area having a width of 10 µm or more and 200 µm or less centered on an imaginary vertical line perpendicular to the longitudinal direction of the adhesive film.

5. In paragraph 1, An anisotropic conductive adhesive film, characterized in that the above pattern connection portion is formed as a plurality of pattern connection portions corresponding to each of a plurality of wiring patterns provided on the connection target.

6. In paragraph 1, Multiple connection areas are formed along the length direction, Each of the plurality of connection areas includes: the pattern connection portion formed corresponding to the wiring pattern provided on the connection target; and a pair of alignment portions arranged at both ends of the pattern connection portion; An anisotropic conductive adhesive film characterized in that a dummy portion is formed between an alignment portion formed in one connection area and an alignment portion formed in another connection area, in which no conductive particles are arranged.

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