TW201813813A - Multi-layered anisotropic conductive film and the preparation thereof - Google Patents

Abstract

The present invention provides a multi-layered anisotropic conductive film comprising upper conductive adhesive layer, thin metal layer with thickness of 5-3000nm, lower conductive adhesive layer and release layer beneath the lower conductive adhesive layer; wherein, the upper and lower conductive adhesive layer include a plurality of metal conductive particles of various shapes. Since the metal conductive particles may pierce the thin metal layer to achieve the same conduction, the amounts of the metal conductive particles may be reduced, and also decrease metal powder pollution and operating cost. In addition, the isotropic flow of metal conductive particles exists as the conductive film become conductive; therefore, the multi-layered anisotropic conductive film of the present invention has good conductivity and high shielding performance. The invention further provides the method of producing multi-layered anisotropic conductive film.

Description

   Multilayer anisotropic conductive adhesive film and manufacturing method thereof   

The invention relates to a conductive adhesive for printed circuits, and more particularly to a multilayer anisotropic conductive adhesive film with high conductivity and excellent electromagnetic wave shielding properties.

In response to the development trend of electronic and communication products, circuit board components are becoming lighter, thinner, and more highly integrated. The frequency band of transmission signals is getting wider and wider, resulting in more and more serious electromagnetic interference. In addition, the use of electronic circuit components Safety is also taken into consideration, and new requirements have been put forward for the reliability of grounding of circuit components in electronic products. Currently, the popular conductive adhesive products on the market can connect to the grounding holes reserved in general printed circuit boards, but they also appear due to conductive adhesives. Filling the grounding hole is too full, which affects the design and installation of other components, or because the conductive glue does not fill the grounding hole, which causes gaps in the connection of electronic components during reflow soldering, resulting in a poor shielding effect. In addition, due to the current popularity on the market All conductive adhesive film products directly disperse conductive particles in conductive adhesive, and the conductive adhesive layer is usually too thick. If the curing is not sufficient and the pressing conditions are uneven, it will cause powder to appear on the printed circuit board. The uneven distribution affects the conduction performance. In addition, the metal conductive particles contained in the existing conductive glue are mostly spherical and shaped. First, it is difficult to have a good guide through different effect.

The technical problem mainly solved by the present invention is to provide a multilayer anisotropic conductive adhesive film with good processing fluidity, high continuity, good bonding strength, high electromagnetic wave shielding performance, low transmission loss, high transmission quality, and good reliability. Compared with general conductive adhesive film, it has better conduction effect, bonding strength and grounding effect.

In order to solve the above technical problems, the present invention provides a multilayer anisotropic conductive adhesive film including: an upper conductive adhesive layer having a thickness of 5 to 20 microns; a lower conductive adhesive layer having a thickness of 15 to 40 microns; and a thickness of 50 to 3000. A thin metal layer of nanometer is formed between the upper conductive adhesive layer and the lower conductive adhesive layer; and a release layer is attached under the lower conductive adhesive layer so that the lower conductive adhesive layer is located in the Between the thin metal layer and the release layer; wherein the upper conductive adhesive layer and the lower conductive adhesive layer each include a plurality of metal conductive particles having a particle diameter of 2 to 22 microns, and are selected from dendritic, needle-like, and sheet At least two shapes of the group consisting of a sphere and a sphere.

In a specific embodiment, the upper conductive adhesive layer and the lower conductive adhesive layer are both a thermosetting adhesive layer including an adhesive resin, and the plurality of metals in each of the upper conductive adhesive layer and the lower conductive adhesive layer are conductive. The particle content is 30 to 80% by weight, and the weight ratio of the plurality of metal conductive particles to the adhesive resin in the layer is 0.9: 1 to 6.67: 1.

In a specific embodiment, the thickness of the lower conductive layer is greater than or equal to the thickness of the cover film on the surface of the printed circuit board to be attached, and the thickness of the lower conductive adhesive layer and the cover of the surface of the printed circuit board to be attached The difference in film thickness is 0 to 5 microns.

In another specific aspect, a particle diameter of the plurality of metal conductive particles is 10 to 18 microns.

In a specific embodiment, the plurality of metal conductive particles are a mixture of a plurality of dendritic metal conductive particles, a plurality of acicular metal conductive particles, and a plurality of sheet metal conductive particles, and the plurality of dendritic metal conductive particles and the The weight ratio of the plurality of acicular metal conductive particles is 1: 5 to 5: 1, and the weight ratio of the plurality of acicular metal conductive particles to the plurality of sheet metal conductive particles is 1: 4 to 4: 1. The weight ratio of the plurality of spherical metal conductive particles to the plurality of acicular metal conductive particles or the plurality of sheet metal conductive particles is 1: 4 to 4: 1.

In a specific embodiment, the material forming the plurality of metal conductive particles includes alloy conductive particles.

In a specific embodiment, the adhesive resin is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, polyparaxylylene resin, and bismaleimide. At least one of the group consisting of an imine-based resin, a phenol resin, a melamine resin, and a polyfluorene resin.

In a specific embodiment, the thin metal layer is a carrier metal layer after the carrier is peeled off, and the thin metal layer is one selected from the group consisting of a copper foil layer, a silver foil layer, and a nickel metal layer.

In another embodiment, the release layer is a single-sided release film or a double-sided release film with a thickness of 25 to 100 microns, and the release layer may be a fluorine-coated polyester release film layer. Silicone oil coated polyester release film, matte polyester release film, polyethylene release film or polyethylene coated paper.

The invention further provides a method for preparing a multilayer anisotropic conductive adhesive film, comprising: mixing a plurality of metal conductive particles having a particle diameter of 2 to 22 microns and an adhesive resin at a weight ratio of 0.9: 1 to 6.67: 1 to form a mixture. Wherein the plurality of metal conductive particles have at least two shapes selected from the group consisting of dendritic, needle-like, sheet-like, and spherical shapes; the mixture is coated on a specified release surface of a release layer to form A lower conductive adhesive layer; a thin metal layer having a thickness of 50 to 3000 nanometers is adhered to the lower conductive adhesive layer; and the other side of the thin metal layer is coated with a weight ratio of 0.9: 1 to 6.67: 1 and the mixed particle diameter is: Another mixture of a plurality of metal conductive particles of 2 to 22 microns and an adhesive resin to form an upper conductive adhesive layer; and pre-curing to form a lower conductive adhesive layer and an upper conductive adhesive layer.

In addition, the method for preparing a multilayer anisotropic conductive adhesive film further comprises cooling the pre-cured lower conductive adhesive layer and the upper conductive adhesive layer, and then performing a rewinding step.

The multilayer anisotropic conductive adhesive film according to the present invention has at least the following advantages:

1. The upper conductive adhesive layer and the lower conductive adhesive layer of the present invention include a plurality of metal conductive particles of at least two shapes. Because the plurality of metal conductive particles are of various shapes, they will tend to flow in multiple directions when the processing is deformed by hot pressing. , So that the distribution of the plurality of metal conductive particles in the conductive adhesive layer after lamination has multidirectionality and high dispersion, and then forms a conduction circuit with the ground hole on the flexible board, so that the upper conductive adhesive layer and the lower conductive adhesive layer have good Heterogeneity, greatly improves the conductive performance, and reduces the ground resistance value of the flexible board;

2. The thin metal layer of the present invention has a thickness of nanometer level. Since the particle diameter of some of the plurality of metal conductive particles is larger than the thickness of the thin metal layer, when pressed, metal conductive particles of various shapes will pierce the thin metal layer to form direct conduction It can greatly improve the conductive performance, so it can reduce the ground resistance value of the flexible board. In addition, due to the thin metal layer, the same amount of metal conductive particles in the upper conductive adhesive layer and the lower conductive adhesive layer can be used under the same conduction force. Corresponding reduction has the benefit of reducing dust pollution and cost.

3. After a period of high-temperature curing and pressing, the multi-directional conductive metal particles can improve the electrical and mechanical properties of the adhesive resin after it is completely cross-linked and cured;

4. When using the conductive adhesive layer of the present invention and metal parts such as steel sheets to cover the printed circuit board to form a reinforcing part, it can effectively shield external electromagnetic wave interference due to its good grounding stability;

5. The metal particles of the present invention may include a plurality of alloy conductive particles, which have excellent oxidation resistance and conductivity, which is convenient for storage and transportation, does not affect the physical properties of the product, and has the characteristics of good stability and high reliability;

6. The thickness of the conductive adhesive layer under the present invention is greater than or equal to the thickness of the cover film on the surface of the printed circuit board to be attached, and the thickness of the lower conductive adhesive layer is different from the thickness of the cover film on the surface of the printed circuit board to be attached. 0 to 5 microns, suitable thickness, coupled with multiple shapes of multiple metal conductive particles in the lower conductive adhesive layer are evenly distributed, providing good fluidity in all directions during lamination, so that the conductive adhesive can be filled properly during lamination The grounding hole not only improves the shielding effect of external electromagnetic waves, but also facilitates the design and installation of other components, and avoids potential safety hazards.

The above description is only an overview of the technology of the present invention. In order to understand the technical means of the present invention more clearly and can be implemented in accordance with the content of the description, the following describes the detailed implementation of the present invention in conjunction with the drawings as follows.

100‧‧‧multilayer anisotropic conductive film

101‧‧‧ on conductive adhesive layer

102‧‧‧ thin metal layer

103‧‧‧ Lower conductive adhesive layer

104‧‧‧ Release layer

200‧‧‧ cover film

1011‧‧‧ metal conductive particles

1012‧‧‧Adhesive resin

The embodiments of the present invention will be described by way of example with reference to the accompanying drawings: FIG. 1 is a schematic diagram of the structure of the present invention; and FIG. 2 is a schematic diagram of the structure of the multilayer anisotropic conductive film of the present invention after the cover film is laminated.

The following is a description of specific embodiments of the present invention. Those skilled in the art can easily understand the advantages and effects of the present invention from the content disclosed in this specification.

It should be noted that the structures, proportions, sizes, etc. shown in the drawings in this specification are only used to match the content disclosed in the specification for the understanding and reading of those skilled in the art, and are not intended to limit the implementation of the present invention. The limited conditions are not technically significant. Any modification of the structure, change of the proportional relationship, or adjustment of the size shall still fall within the scope of this invention without affecting the effects and goals that the invention can produce. The technical content disclosed by the invention can be covered. At the same time, references such as “一”, “下” and “上” in this specification are for clarity only, and are not intended to limit the scope of the present invention. Substantially changing the technical content should also be regarded as the scope in which the present invention can be implemented. In addition, all ranges and values herein are inclusive and combinable. Any value or point that falls within the range described herein, for example, any integer can be used as the minimum or maximum value to derive the lower range, etc.

Referring to FIG. 1, a multilayer anisotropic conductive adhesive film 100 includes: an upper conductive adhesive layer 101 having a thickness of 5 to 20 microns; a lower conductive adhesive layer 103 having a thickness of 15 to 40 microns; a thin metal layer 102, Is formed between the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103, and the thickness of the thin metal layer 102 is 50 to 3000 nanometers; and a release layer 104 is attached to the lower conductive adhesive layer Under the layer 103, the lower conductive adhesive layer 103 is located between the thin metal layer 102 and the release layer 104; wherein the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 each include a plurality of metal conductive particles 1011, and the plurality The metal conductive particles 1011 have a particle diameter of 2 to 22 microns and include at least two shapes of metal conductive particles selected from the group consisting of dendritic, needle, sheet, and spherical.

There is only a single shape of conductive particles in the traditional conductive adhesive layer, which tends to flow and distribute in the same direction during dispersion and compression flow, so that the conductive adhesive layer tends to the same direction in terms of conductivity, resulting in an overall conductive adhesive layer. Poor continuity, which in turn affects the masking effect of the conductive adhesive layer. When multiple metal conductive particles of various shapes used in the present invention are dispersed in the adhesive layer, they are deformed by hot pressing to form multidirectional flow and high dispersion. Distribution, so that the conductive adhesive layer has better heteroconductivity and improves masking performance.

The thin metal layer 102 has a thickness of 50 to 3,000 nanometers and a suitable thickness. If the thickness is too thick, the hole filling performance will be poor. If the thickness is too thin, it will be detrimental to production and greatly increase production costs. In addition, since the thin metal layer has good conductivity, reliability and masking performance can be improved. Because when the multilayer anisotropic conductive film is laminated by a downstream pressing process, the plurality of metal conductive particles will pierce the thin metal layer, which greatly enhances the overall conduction effect of the multilayer anisotropic conductive film. The existing conductive adhesive film can effectively reduce the amount of the metal conductive particles in the upper conductive adhesive layer and the lower conductive adhesive layer, and achieve the same conduction effect.

The upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 are thermosetting adhesive layers including an adhesive resin 1012, and the content of the plurality of metal conductive particles in each of the upper conductive adhesive layer and the lower conductive adhesive layer is 30 to 80% by weight, and the weight ratio of the plurality of metal conductive particles to the adhesive resin in the layer is 0.9: 1 to 6.67: 1. In addition, the upper conductive adhesive layer and the lower conductive adhesive layer of the present invention include some auxiliary materials (such as a hardener or a thickener) and non-metal conductive particles (such as graphite or a conductive compound).

In a specific embodiment, the addition ratio of the adhesive resin is 30 to 60% by weight. If the adhesive resin is too small, the viscosity is too low, which is not conducive to production. If the adhesive resin is too large, the product produced is highly viscous, and the content of the plurality of metal conductive particles is relatively reduced, resulting in continuity. Not good.

In a specific embodiment, the mixing ratio of the plurality of metal conductive particles is 35 to 75% by weight. If the content of the metal conductive particles is too large, the problem of uneven dispersion of the powder will be caused; if the content of the metal conductive particles is too small, the conduction effect may be poor.

The thickness of the lower conductive adhesive layer 103 is greater than or equal to the thickness of the cover film 200 on the surface of the attached printed circuit board, and the thickness of the lower conductive adhesive layer is equal to the thickness of the cover film 200 on the surface of the attached printed circuit board. The difference is 0 to 5 microns.

The thickness of the lower conductive adhesive layer 103 can be selected according to the thickness of the cover film attached to the printed circuit board, so as to avoid its step difference from affecting the hole filling properties of the upper conductive adhesive layer and the lower conductive adhesive layer, resulting in conduction. Resistance is not good. As shown in Figure 2, for example: if the thickness of the cover film 200 is 37um, the thickness of the lower conductive adhesive layer can be selected as 40um, and if the thickness of the cover film is 27um, the thickness of the lower conductive adhesive layer can be selected 27um To ensure excellent hole filling.

In a specific embodiment, the particle size of the plurality of metal conductive particles is 10 to 18 microns, and the plurality of metal conductive particles are composed of a plurality of dendritic metal conductive particles, a plurality of acicular metal conductive particles, and a plurality of sheet metal. The conductive particles are mixed, and the weight ratio of the plurality of dendritic metal powders to the plurality of acicular metal conductive particles is 1: 5 to 5: 1. The weight ratio of the plurality of acicular metal conductive particles to the plurality of sheet metal conductive particles is: From 1: 4 to 4: 1. If the particle diameter of the plurality of metal conductive particles is too small, the filling effect of the via holes in the printed circuit board is not good. If the particle diameter of the plurality of metal conductive particles is too large, it will increase the difficulty of coating production and is not conducive to production.

The material forming the plurality of metal conductive particles includes at least one of a single metal conductive particle and an alloy conductive particle, and the plurality of metal conductive particles are particularly preferably an alloy conductive particle. The single metal conductive particle may be selected from at least one of the group consisting of gold particles, silver particles, copper particles, and nickel particles, but is not limited thereto. The alloy conductive particle may be selected from silver-plated copper particles and silver-plated particles. At least one of the group consisting of gold particles, silver-plated nickel particles, gold-plated copper particles, and gold-plated nickel particles, but is not limited thereto. The alloy conductive particles have good oxidation resistance and conductivity, and the product is convenient for storage and transportation, and does not affect the physical properties of the product, so that the product has the characteristics of good stability and high reliability.

The adhesive resin is selected from the group consisting of epoxy resin, acrylic resin, urethane resin, silicone rubber resin, parylene resin, bismaleimide resin, phenol resin, At least one of the group consisting of a melamine resin and a polyimide resin, among which an acrylic resin is particularly preferred.

The thin metal layer is a carrier metal layer after the carrier is peeled off, and the thin metal layer may be one selected from the group consisting of a copper foil layer, a silver foil layer, and a nickel metal layer.

The thickness of the release layer is 25 to 100 microns, and the release layer may be a fluorine-coated polyester release film layer, a silicone oil-coated polyester release film layer, a matte polyester release film layer, Polyethylene release film or polyethylene coated paper. The color of the release film of the release layer is pure white, milky white, or transparent. Among them, a pure white release film or milky white release film is preferred. When the CNC automated equipment sculpts the circuit, it is pure white release under infrared induction. Film or milky white release film does not have the problem of light reflection. It can be quickly and accurately positioned and processed. In addition, pure white or milky white can be identified during manual operation to reduce human leakage.

The invention further provides a method for preparing a multi-layer anisotropic conductive adhesive film, which includes the following steps: Step 1: sieving the powder of metal conductive particles of various shapes to obtain a desired particle diameter, and mixing the metal conductive particles of various shapes uniformly, The ball milling method can be selected during mixing, and the ball milling speed should not be too high (especially 200 to 300 rpm is preferred), otherwise the surface alloy layer of the metal particles will be damaged, or the stirring method (700 to 2000 rpm) Minutes are better). However, the higher the stirring speed is, the better the mixing uniformity is. After mixing, a plurality of metal conductive particle mixtures are obtained. Step 2: Add the above-mentioned heterogeneous metal particle mixture in proportion to the adhesive resin and mix thoroughly. Add a plurality of metal conductive particle mixtures, the mixing conditions are similar to step one; step three: apply the mixture obtained in step two on the specified release surface of the release layer to form a lower conductive adhesive layer; step four: apply the lower conductive adhesive layer The carrier metal layer is adhered and pre-cured, and its pre-curing temperature should not exceed the curing temperature of the adhesive resin itself. The pre-curing selected in the present invention The temperature is between 80 and 100 ° C. After the pre-curing, the carrier is peeled off to form a thin metal layer. Step 5: Apply the mixture of Step 2 to the other side of the thin metal layer to form an upper conductive adhesive layer, or apply Another mixture of a plurality of metal conductive particles and an adhesive resin is used to form an upper conductive adhesive layer; Step 6: The upper conductive adhesive layer is cured under the pre-curing condition of Step 4 and rolled up to obtain a finished product.

Test Method 1: Continuity Analysis

Conduct the continuity test on the multilayer anisotropic conductive adhesive film after peeling the double-sided release film with a Takahashi tester. After the nickel-plated steel sheet and the printed circuit board are falsely pasted on the surface of the upper conductive adhesive layer and the lower conductive adhesive layer, respectively, After curing (pressure 100 kg, temperature 180 ° C, pre-pressing 10 seconds, pressing 120 seconds) after curing (temperature 160 ° C, time 1 hour), test the continuity resistance of the sample before and after reflow soldering three times. The present invention is taken as an example, in which the composition ratios of the conductive metal particles and the adhesive resin of the upper conductive adhesive layer and the lower conductive adhesive layer are the same. The same method is used to test the conductivity of a general product as a comparative example. The measured conduction is Sexual results are recorded in Table 1.

Solder heat resistance: Nickel-plated steel sheet 200 and printed circuit board 300 are affixed on the surfaces of upper conductive adhesive layer 101 and lower conductive adhesive layer 103, respectively, after compression bonding (pressure 100 kg, temperature 180 ° C, pre-pressing for 10 seconds) , Pressing for 120 seconds) after curing (temperature 160 ° C, time 1 hour), in a high temperature soldering furnace, observe whether there are bubbles, patterns, melting and other phenomena, refer to the solder test method of IPC-TM650 2.4.13.

Test Method 2: Peel Force Analysis

A universal tensile machine was used to test the peeling force of the multilayer anisotropic conductive film after peeling the double-sided release film. After the nickel-plated steel sheet and the single-sided copper foil substrate were falsely pasted on the surface of the upper conductive adhesive layer and the lower conductive adhesive layer, respectively, After pressing and curing, the sample is taken out to test the peel force value. The present invention is taken as an example, in which the composition ratio of the plurality of conductive metal particles and the adhesive resin of the upper conductive adhesive layer and the lower conductive adhesive layer is the same. The peeling force of the product is used as a comparative example, and the measured peeling force results are recorded in Table 1.

Example 1: Preparation of multilayer anisotropic conductive film

The sieving screened out the copper-plated spherical, silver-plated nickel needle-shaped metallic conductive particles with a particle diameter of about 12 microns, and then stirred and mixed the metallic conductive particles with a ball milling speed of 250 rpm. The weight ratio of the spherical metal particles to the plurality of acicular metal conductive particles is about 4: 1, and a special-shaped metal particle mixture is prepared.

Next, the aforesaid heterogeneous metal particle mixture was added to the acrylic adhesive resin (RD0351 and RD0352, Asia Electric Materials Co., Ltd.) and thoroughly mixed uniformly at a ball mill speed of 250 rpm, and the heterogeneous metal particle mixture was added while mixing. 45% of the acrylic adhesive resin, 45% of the above-mentioned special-shaped metal particle mixture, and the remaining coating composition containing an auxiliary agent (RD0326, Asia Electric Materials Co., Ltd.) were prepared.

The coating mixture is coated on a specified surface of a fluorine-coated polyester release layer, that is, a conductive adhesive layer with a thickness of less than 20 microns is formed, and the lower conductive adhesive layer is bonded to the carrier copper foil metal layer and pre-cured. The pre-curing temperature is 80 ° C. After the pre-curing, the carrier is peeled off to form a thin metal layer with a thickness of 2 μm.

On the other side of the thin metal layer, a conductive adhesive layer having a thickness of 20 micrometers having the same composition as that of the lower conductive adhesive layer is formed in the same coating and pre-curing manner. After molding, it is rolled up, that is, a multi-layer anisotropic conductive adhesive film product.

The physical properties of the multilayer anisotropic conductive film were tested and recorded in Table 1.

The method for preparing the multilayer anisotropic conductive film of Examples 2 to 7 and Comparative Examples 1 to 5 is the same as that of Example 1, except that only the ratio of the metal powder and the adhesive resin, the type of metal powder, the weight ratio of the metal powder mixture, and The thickness of the upper and lower conductive adhesive layers is shown in Table 1. The physical properties of the multilayer anisotropic conductive adhesive film were tested and recorded in Table 1.

As can be seen from the above table, the multilayer anisotropic conductive adhesive film of the present invention has good puncture effect, conductive effect, and electromagnetic wave shielding property, and has good mechanical strength.

The above-mentioned embodiments are merely illustrative and not intended to limit the present invention. Anyone skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the rights of the present invention is defined by the scope of the patent application attached to the present invention, as long as it does not affect the effect and implementation purpose of the present invention, it should be covered in this disclosed technical content.

Claims (10)

    A multilayer anisotropic conductive adhesive film includes: an upper conductive adhesive layer having a thickness of 5 to 20 microns; a lower conductive adhesive layer having a thickness of 15 to 40 microns; and a thin metal layer having a thickness of 50 to 3000 nanometers. Between the upper conductive adhesive layer and the lower conductive adhesive layer; and a release layer is attached under the lower conductive adhesive layer so that the lower conductive adhesive layer is located between the thin metal layer and the release layer. Wherein the upper conductive adhesive layer and the lower conductive adhesive layer each include a plurality of metal conductive particles having a particle diameter of 2 to 22 microns, and are selected from the group consisting of dendritic, needle, sheet, and spherical At least two shapes.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of the patent application, wherein the upper conductive adhesive layer and the lower conductive adhesive layer are both thermosetting adhesive layers including an adhesive resin, and the upper conductive adhesive layer and the lower conductive adhesive The content of the plurality of metal conductive particles in each layer of the layer is 30 to 80% by weight, and the weight ratio of the plurality of metal conductive particles to the adhesive resin in the layer is 0.9: 1 to 6.67: 1.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of the patent application, wherein the particle diameter of the plurality of metal conductive particles is 10 to 18 microns.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of the patent application, wherein the plurality of metal conductive particles are a mixture of a plurality of dendritic metal conductive particles, a plurality of acicular metal conductive particles, and a plurality of sheet metal conductive particles. The weight ratio of the plurality of dendritic metal conductive particles to the plurality of acicular metal conductive particles is 1: 5 to 5: 1, and the weight ratio of the plurality of acicular metal conductive particles to the plurality of sheet metal conductive particles is 1: 4. To 4: 1.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of the patent application, wherein the material forming the plurality of metal conductive particles includes alloy conductive particles.         The multilayer anisotropic conductive adhesive film according to item 2 of the scope of the patent application, wherein the adhesive resin is selected from epoxy resin, acrylic resin, urethane resin, silicone rubber resin, At least one selected from the group consisting of cycloxylene-based resin, bismaleimide-based resin, phenol resin, melamine resin, and polyimide resin.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of the patent application, wherein the thin metal layer is a carrier metal layer after the carrier is peeled off, and the thin metal layer is selected from a copper foil layer, a silver foil layer, and a nickel metal layer. One of the groups formed in.         The multilayer anisotropic conductive adhesive film according to item 1 of the scope of patent application, wherein the release layer is a single-sided release film or a double-sided release film with a thickness of 25 to 100 microns, and the release layer may be fluorine Plain coated polyester release film layer, silicone oil coated polyester release film layer, matte polyester release film layer, polyethylene release film layer or polyethylene coated paper layer.         A method for preparing a multilayer anisotropic conductive adhesive film as described in item 1 of the scope of patent application, comprising: mixing a plurality of metal conductive particles with a particle size of 2 to 22 microns in a weight ratio of 0.9: 1 to 6.67: 1 and adhesive Agent resin to form a mixture, wherein the plurality of metal conductive particles have at least two shapes selected from the group consisting of dendritic, needle-like, sheet-like, and spherical shapes; and the mixture is applied to a specified release layer The release surface, that is, the lower conductive adhesive layer is formed; a thin metal layer with a thickness of 50 to 3000 nanometers is attached to the lower conductive adhesive layer; and the other surface of the thin metal layer is coated with 0.9: 1 to 6.67: 1. A mixture of a plurality of metal conductive particles having a particle size of 2 to 22 microns and another mixture of an adhesive resin is formed in a weight ratio to form an upper conductive adhesive layer; and pre-curing and coating to form a lower conductive adhesive layer and an upper conductive adhesive layer.         The method as described in claim 9 of the scope of patent application, wherein the mixture and the other mixture are the same.