Anisotropic conductive adhesive and composition thereof

Abstract

The present invention provides an adhesive resin composition comprising a substituted or unsubstituted dicyclopentadiene and a substituted or unsubstituted acrylic compound, and having a storage modulus of 100 Pa or more and 1000 Pa or less at 100° C. or more and 300° C. or less, and a self-assembling anisotropic conductive adhesive comprising the adhesive resin composition, thereby providing the effect of having excellent adhesive strength even to flexible displays or semiconductor substrates.

Description

[Technical Field]

[0001] The present invention relates to an anisotropically conductive adhesive, and more particularly to an anisotropically conductive adhesive used in flexible circuit boards. [Background technology]

[0002] As information and communication devices have become more advanced in the 21st century, semiconductor packages have become increasingly more highly integrated, functional, cost-effective, and compact. Flexible displays, which have recently attracted attention as next-generation displays, have the advantage of being highly flexible and can be folded or rolled. As a result, research into the stable electrical and mechanical properties and high integration of the attached micro-components is progressing rapidly.

[0003] As a result, the development of high-density electronic packaging technology is progressing vigorously, and among the bonding technologies for such electronic packaging technology, bonding methods using anisotropic conductive adhesives (ACAs) have significant advantages such as lower process temperatures and simplified processes.

[0004] Generally, in most cases, a chip attachment process in manufacturing a semiconductor package is performed face-up, and the chip is attached to a printed circuit board (CB). Therefore, when attaching a chip to a flexible display or flexible circuit board, the adhesive film or adhesive for attaching the chip needs to have not only hard properties but also flexible properties.

[0005] However, resins that generally have flexible properties tend to have a high storage modulus and no hard properties, resulting in a low storage modulus and poor adhesive strength. Therefore, there is a need for the development of flexible adhesives that have flexible properties and high adhesive strength without being inferior in adhesive strength.

[0006] Meanwhile, dicyclopentadiene (DCPD) is commonly used as a raw material for polyester resins and has good compatibility with other base resins, so it is used in a variety of industrial fields, such as in adhesives and inks, and methods for using it to solve the above technical problems can be explored. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Republic of Korea Patent Publication No. 10-2020-0068204 Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem that the present invention aims to achieve is to provide an anisotropic conductive adhesive that combines flexible properties with hard properties due to a high storage modulus, and can be used in the mounting process of flexible substrates or displays.

[0009] The technical problems that the present invention aims to achieve are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present invention pertains from the following description. [Means for solving the problem]

[0010] In order to achieve the above technical objectives, one embodiment of the present invention provides an adhesive resin composition comprising a substituted or unsubstituted dicyclopentadiene and a substituted or unsubstituted acrylic compound, and characterized in that the composition has a storage modulus (E") of 100 Pa or more and 1000 Pa or less at 100°C or more and 300°C or less.

[0011] In one embodiment of the present invention, the acrylic compound may be an adhesive resin composition, characterized by including at least one selected from the group consisting of methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, acrylamide, hydroxyalkyl acrylate, glycidyl methacrylate, isononyl acrylate, 2-ethylhexyl acrylic acid, methyl methacrylate, methyl acrylic acid, and acrylonitrile.

[0012] In addition, in one embodiment of the present invention, the adhesive resin composition may be characterized in that the weight ratio of the dicyclopentadiene to the acrylic compound is 1:0.5 or more and 1:50 or less.

[0013] In order to achieve the above technical objectives, another embodiment of the present invention provides a self-assembling anisotropic conductive adhesive, characterized by comprising the adhesive resin composition of the above embodiment and conductive solder particles.

[0014] In one embodiment of the present invention, the solder particles may be a self-assembling anisotropic conductive adhesive, characterized in that they include at least one selected from the group consisting of tin (Sn), indium (In), silver (Ag), bismuth (Bi), and copper (Cu).

[0015] In addition, in an embodiment of the present invention, the solder particles may be a self-assembling anisotropic conductive adhesive characterized in that the melting point is 70°C or more and 250°C or less.

[0016] In an embodiment of the present invention, the solder particles may be a self-assembling anisotropic conductive adhesive, characterized in that an oxide film has been removed.

[0017] In addition, in an embodiment of the present invention, the anisotropic conductive adhesive may be a self-assembling type, characterized in that the solder particles are contained in a proportion of 10% by volume to 70% by volume relative to the total amount of the anisotropic conductive adhesive.

[0018] In this case, the self-assembling anisotropic conductive adhesive may be characterized in that the solder particles are contained in a proportion of 50% by volume to 60% by volume with respect to the total amount of the anisotropic conductive adhesive.

[0019] In the embodiment of the present invention, the anisotropic conductive adhesive may be a self-assembling anisotropic conductive adhesive that is in the form of a film or a paste. [Effects of the Invention]

[0020] According to an embodiment of the present invention, an anisotropic conductive adhesive can be provided that combines flexible properties with hard properties due to a high storage modulus, and can be used in the mounting process of flexible substrates or displays.

[0021] The effects of the present invention are not limited to the above effects, but include all effects that can be inferred from the configuration of the invention described in the detailed description of the present invention or the claims. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram illustrating the operating principle of a conventional self-assembling anisotropic conductive adhesive. [Figure 2] 1 is a diagram illustrating the operating principle of a conventional self-assembling anisotropic conductive adhesive. [Figure 3] 1 is a diagram illustrating the operating principle of a conventional self-assembling anisotropic conductive adhesive. [Figure 4] 1A and 1B are diagrams showing the configuration of substrates when the self-assembling anisotropic conductive adhesive of the present invention is used to bond the substrates together. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will now be described with reference to the accompanying drawings. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein. In addition, to clearly illustrate the present invention in the drawings, parts that are not relevant to the description are omitted, and similar parts are designated by similar reference numerals throughout the specification.

[0024] Throughout this specification, when a part is said to be "connected (connected, contacted, or coupled)" to another part, this includes not only "directly connected" but also "indirectly connected" via another member therebetween. Furthermore, when a part is said to "comprise" a certain component, this does not mean that it excludes other components, but that it may further comprise other components, unless otherwise specified.

[0025] The terms used in this specification are merely used to describe specific embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise. In this specification, the terms "comprise" or "have" specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0026] Flexible displays, which have recently been attracting attention as next-generation displays, have excellent flexibility, and adhesives used in such displays must maintain adhesive strength to the flexible substrate. However, conventional adhesives have not been able to maintain adhesive strength to the flexible substrate.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0028] In one embodiment of the present invention, in order to solve the above technical problems, there is provided a self-assembly anisotropic conductive adhesive (hereinafter referred to as "SACA") characterized by comprising an adhesive resin composition of an embodiment described below and conductive solder particles.

[0029] 1 to 3 are diagrams illustrating the operating principle of a conventional self-assembling anisotropic conductive adhesive.

[0030] FIG. 4 is a diagram showing the configuration of substrates when the self-assembling anisotropic conductive adhesive of the present invention is used to bond the substrates together.

[0031] As can be seen from Figures 1 to 3, when using conventional self-assembling anisotropic conductive adhesives, the substrate or display was not flexible. Therefore, even after the self-assembling anisotropic conductive adhesive hardened, the substrate became flexible and no external force could be applied to the hardened conductive adhesive.

[0032] On the other hand, when the substrate has a flexible function, as can be seen from FIG. 4, when the substrate is bonded using the self-assembling anisotropic conductive adhesive of the present invention, the substrate corresponds to a flexible display or substrate and can have various curved surfaces. In this case, the cured adhesive also has various curves accordingly, and at this time, the adhesive strength of the cured adhesive must be maintained without weakening.

[0033] As described above, the self-assembling anisotropic conductive adhesive of the present invention provides an anisotropic conductive adhesive containing an adhesive resin composition having a controlled storage modulus by mixing a dicyclopentadiene compound and an acrylic compound, and can be used in the component mounting process or contact process steps of a flexible display or flexible circuit board.

[0034] In this case, the degree of flexibility of the self-assembling anisotropic conductive adhesive of the present invention used by the user may also vary depending on the degree of flexibility of the flexible display or flexible circuit board, and the processing temperature and use temperature of the flexible display or flexible circuit board.

[0035] Considering the specific conditions and methods of use described above, the flexibility of the self-assembling anisotropic conductive adhesive of the present invention preferably has a storage modulus (E") of 100 Pa or more and 1000 Pa or less at a temperature of 100°C or more and 300°C or less.

[0036] Before describing the SACA provided in the above embodiment, an adhesive resin composition provided in another embodiment of the present invention will be described below.

[0037] One embodiment of the present invention provides an adhesive resin composition comprising a substituted or unsubstituted dicyclopentadiene and a substituted or unsubstituted acrylic compound, and having a storage modulus (E") of 100 Pa or more and 1,000 Pa or less at 100°C or more and 300°C or less.

[0038] The substituted or unsubstituted dicyclopentadiene and the substituted or unsubstituted acrylic compound are polymerized to form a polymer mixture, which can be used as a flexible adhesive resin composition.

[0039] In this case, the adhesive resin composition has flexibility and can be used in various flexible displays or flexible circuit boards, and the flexibility of the flexible displays or flexible circuit boards is also diverse.

[0040] Therefore, in order to be used in the various flexible displays or flexible circuit boards, the adhesive resin composition preferably has a storage modulus (E") of 100 Pa to 1000 Pa at 100°C to 300°C, as described above.

[0041] The components of the adhesive resin composition will be described below.

[0042] The substituted or unsubstituted dicyclopentadiene in the adhesive resin composition has the property of extremely high cohesive strength between polymer chains, and is added to the adhesive resin composition for the purpose of imparting high toughness and adhesive strength to the bonding material when bonding flexible circuit boards together, and in this case, the adhesive resin composition containing the dicyclopentadiene preferably has a tensile strength of 1.0 kgf / cm or more.

[0043] By adding the dicyclopentadiene, a strong bond is formed when the adhesive resin composition is cured, and the initial tensile strength is increased.

[0044] However, when the adhesive resin composition is repeatedly exposed to external shocks such as high temperature, low temperature, and humidity, the adhesive may break down at the interface between the flexible circuit board and the adhesive resin composition due to the extremely high cohesive strength between polymer chains due to the characteristics of the dicyclopentadiene material. Therefore, it is necessary to complement the adhesive resin composition by polymerization with a material that can compensate for the drawback of the possibility of adhesive break down at the interface without compromising the advantage of high cohesive strength.

[0045] The substituted or unsubstituted acrylic compound in the adhesive resin composition has low chain fluidity and is flexible, and is added to the adhesive resin composition to impart flexibility to the bonding material when bonding flexible circuit boards together, so that when the adhesive resin composition is repeatedly exposed to external shocks such as high temperature, low temperature, and humidity, the adhesion does not break down at the interface between the flexible circuit board and the adhesive resin composition, which is relatively vulnerable to external shocks, but rather cohesive failure occurs within the adhesive resin composition, which is relatively resistant to external shocks. The addition of the acrylic compound has the effect of improving long-term reliability.

[0046] Therefore, the acrylic compound may be, for example, any one selected from the group including methyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, styrene, acrylamide, hydroxyalkyl acrylate, glycidyl methacrylate, isononyl acrylate, 2-ethylhexyl acrylic acid, methyl methacrylate, methyl acrylic acid, and acrylonitrile, but is not limited to the above examples.

[0047] The solder particles will be described below.

[0048] The structure of the solder particles will be described below.

[0049] The solder particles are conductive particles that are positioned between adherends after the component mounting process and act as electrical wires to transmit electricity. Therefore, the solder particles may be conductive metal particles, including at least one selected from the group consisting of tin (Sn), indium (In), silver (Ag), bismuth (Bi), and copper (Cu), and preferably have a melting point of 70°C to 250°C. However, the present invention is not limited to metal particles, and any other configuration that can be easily modified and adopted by a person skilled in the art to achieve the effects of the present invention, such as a conjugated polymer conductive polymer, should be considered to be within the scope of the present invention.

[0050] Furthermore, when the solder particles are metal elements, they easily form an oxide film on their surfaces upon contact with oxygen in the atmosphere. When an anisotropic conductive adhesive containing solder particles is used to mount electronic components such as semiconductor chips, the oxide film can cause problems such as unstable contact resistance, low conductivity, and unstable bonding strength, resulting in poor electrical characteristics. To address this issue, solder particles with improved wetting properties due to the addition of a reducing agent such as a carboxylic acid during the step of mixing and dispersing the solder particles and binder resin can be used to strengthen the bond with wiring or signal line contacts.

[0051] That is, when the solder particles are metal elements, there is a possibility that an oxide film may be formed on the solder particles, and therefore it is preferable that the oxide film on the solder particles has been removed or controlled by a reducing agent.

[0052] The particle size of the solder particles will be described below.

[0053] The size of the solder particles can be selected depending on the size (egpitch) of the conductive pattern to be applied, and as the size of the conductive pattern increases, solder particles with larger particle sizes can be used.

[0054] The mixing ratio of the solder particles will be explained below.

[0055] The solder particles may be contained in a proportion of 10 to 70% by volume of the total amount of the anisotropic conductive adhesive, taking into consideration fluidity and wettability. If the proportion is less than 10% by volume, there is a risk that a lack of solder particles will prevent connection between terminals, and if the proportion is more than 70% by volume, there is a risk that excessive solder particles will remain, causing a bridge due to the connection between adjacent terminals and resulting in a short circuit.

[0056] The physical properties and characteristics of the self-assembling anisotropic conductive adhesive will now be described.

[0057] The anisotropic conductive adhesive of the present invention includes the conductive solder particles and the adhesive resin composition as described above. The anisotropic conductive adhesive of the present invention can have a viscosity of 10,000 cps or more and 500,000 cps or less in a temperature range of 100°C or more and 250°C or less.

[0058] The anisotropic conductive adhesive can be used in film or paste form. However, when mounting a substrate, it is preferable to use a film-type conductive adhesive. This is because a film-type conductive adhesive is superior to a paste-type adhesive in terms of mounting costs for electronic components, thickness control, and quality control such as adhesive reliability.

[0059] Furthermore, in the case of the film form, it can be manufactured taking into consideration the width of the adherend, and when it is manufactured to the same width as the adherend, adhesion is possible without any additional processing, which is advantageous in terms of process.

[0060] Furthermore, as will be seen from the experiments described below, the anisotropic conductive adhesive has an adhesive strength of 2.0 to 3.0 kgf / cm and excellent contact resistance, and compared to previously proposed anisotropic conductive adhesives, it has a high potential for use as a mounting conductive adhesive in a variety of industrial fields, such as substrates, displays, and semiconductors.

[0061] The present invention will be described in more detail below with reference to Production Examples and Experimental Examples, but the present invention is not limited to the following Production Examples and Experimental Examples.

[0062] Manufacturing Example 1 In Production Example 1, a dicyclopentadiene compound and a hydroxyalkyl acrylate compound as an acrylic compound were mixed to produce an anisotropic conductive adhesive.

[0063] The specific process steps are as follows:

[0064] 10 g of dicyclopentadiene epoxy and 15 g of hydroxyalkyl acrylate epoxy were mixed at 30° C. for 30 minutes to form a mixture.

[0065] 1 g of a silane coupling agent was mixed with the mixture at 25° C. for 10 minutes.

[0066] 25 g of solder particles containing In and Sn and 1 g of a reducing agent were further mixed with the mixture at 25° C. for 10 minutes, and finally 5 g of a curing agent was further mixed at 25° C. for 1 minute.

[0067] According to the above process, in Preparation Example 1, an adhesive resin composition was successfully prepared.

[0068] Experimental Example 1 In Experimental Example 1, the storage modulus of various anisotropic conductive adhesives prepared in Preparation Example 1 above was measured.

[0069] As a specific experimental method, the storage modulus was measured in the temperature range of 100 to 300°C using a rheometer.

[0070] As a result of the above experiment, it was found that the storage modulus was in the range of 500 Pa to 5,000 Pa in the temperature range of 100°C to 300°C. As can be seen from Experimental Example 2 described below, a storage modulus in the range of 100 Pa to 1,000 Pa in the temperature range of 100°C to 300°C exhibits the best adhesive strength in flexible displays.

[0071] Experimental Example 2 In Experimental Example 2, the anisotropic conductive adhesive of Production Example 1 was used to mount components on a flexible display.

[0072] The specific experimental method is as follows:

[0073] First, an anisotropic conductive adhesive film was temporarily attached to a flexible lower substrate at a temperature of 60° C. under a pressure of 1 MPa, and then the flexible lower substrate to which the film was temporarily attached and the corresponding upper substrate were all-in-one.

[0074] Thereafter, the lower substrate-film-upper substrate state was bonded at 180° C. for 10 seconds under a pressure of 1 kg, and then an adhesive strength test was performed. 1.Equipment used: UTM (Universal Testing Machine) 2. Substrates used: PCB and FPCB adhesive (200 pitch) 3. Experimental conditions: Tensile speed 50 mm / min, 90° peel

[0075] As a result of the above experiment, it was found that an anisotropic conductive adhesive containing an adhesive resin composition having a storage modulus in the range of 100 Pa to 1,000 Pa in the temperature range of 100°C to 300°C exhibited the most excellent effect.

[0076] Experimental Example 3 In Experimental Example 3, an experiment was conducted to confirm the types of flexible adherends to which the anisotropic conductive adhesive synthesized in Production Example 2 above can be applied.

[0077] The specific experimental method was the same as that of Experimental Example 2 above, except that the type of flexible adherend was changed.

[0078] The four types of adherends used in the experiment in Experimental Example 3 were PI, PET, PCT, and ultra-thin glass.

[0079] As a result of the above experiments, excellent effects were observed on various types of flexible adherends.

[0080] Manufacturing Example 2 In Preparation Example 2, only the ratio of solder particles in Preparation Example 1 was changed to 10 / 15 / ... / 65 / 70 volume %, and various anisotropic conductive adhesives were prepared using the same method.

[0081] As a result, anisotropic conductive adhesives containing solder particles with various component ratios were successfully prepared. The effect of changing the ratio of the solder particles was confirmed in Experimental Example 4 described below.

[0082] Experimental Example 4 In Experimental Example 4, the adhesive strength was confirmed using anisotropic conductive adhesives manufactured in Manufacturing Example 2 above, in which the ratio of solder particles was varied.

[0083] As a result, as shown in Table 1, it was found that the adhesive strength was best when the solder particle content was about 50% to 60% by volume.

[0084] [Table 1]

[0085] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting. For example, each component described as a single component may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

[0086] The scope of the present invention is defined by the claims that follow, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents are included within the scope of the present invention. [Explanation of symbols]

[0087] 10: Second board 11: Connection terminal 20: First board 21: Electrode terminal 30: Self-assembling anisotropic conductive adhesive 31: Solder particles 32: Binder resin (or adhesive resin composition) 33: Hardener 40:Connector 50: Cured resin layer

Claims

1. A self-assembling anisotropic conductive adhesive comprising dicyclopentadiene, an acrylic compound, a coupling agent, and solder particles, The solder particles are contained in an amount of 40% by volume to 70% by volume relative to the total amount of the self-assembling anisotropic conductive adhesive; The self-assembling anisotropic conductive adhesive has a storage modulus of 500 Pa or more and 5,000 Pa or less in a temperature range of 100° C. or more and 300° C. or less, The solder particles are conductive solder particles. A self-assembling anisotropic conductive adhesive characterized by:

2. The solder particles include at least one selected from the group consisting of tin (Sn), indium (In), silver (Ag), bismuth (Bi), and copper (Cu). The self-assembling anisotropic conductive adhesive according to claim 1 .

3. The solder particles have a melting point of 70°C or more and 250°C or less. The self-assembling anisotropic conductive adhesive according to claim 1 .

4. The solder particles have had their oxide film removed. The self-assembling anisotropic conductive adhesive according to claim 1 .

5. The anisotropic conductive adhesive is in the form of a film or a paste. The self-assembling anisotropic conductive adhesive according to claim 1 .

Images