TWI681035B - Multi-layered anisotropically piercing conductive adhesive tape and preparing method and fpc with shield-enhanced structure using the same - Google Patents

Abstract

The present invention provides a multi-layered anisotropically piercing conductive adhesive comprising an upper conductive adhesive layer, an ultrathin conductive fabric with two sides and a lower conductive adhesive layer; wherein both the upper conductive adhesive layer and the lower conductive adhesive layer comprises a plurality of metal conductive particles, and a metal plating layer is form on one side of the ultrathin conductive fabric. The present invention also provides a flexible printed circuit (FPC) with shield-enhanced structure using the conductive adhesive above. Even if no reserved grounding hole is form in the FPC, it also performs excellent grounding effect and good shielding. Therefore, the multi-layered anisotropically piercing conductive adhesive tape of the present invention has good electrical properties, good adhesive strength, better tin soldering, reliability and flame resistant. In additions, the method for producing multi-layered anisotropic conductive adhesive could simplify the process, and save cost.

Description

Multilayer anisotropic puncture type conductive adhesive tape, its manufacturing method, and flexible printed circuit board reinforcing shielding structure using the conductive adhesive tape

The invention relates to the technical field of conductive cloth for printed circuit boards, in particular to a multi-layer anisotropic puncture type conductive adhesive tape and a reinforced shielding structure.

With the development of electronic and communication products, circuit board components are becoming lighter, thinner, shorter, and more highly integrated. The frequency band of transmitted signals is becoming wider and wider, resulting in more and more serious electromagnetic interference. In addition, the safety of electronic circuit components is also included In consideration, new requirements have been put forward for the reliability of circuit component grounding in electronic products and the freedom of circuit board design. At present, the popular conductive adhesive products on the market often fill the grounding hole too much with conductive adhesive and affect the design and installation of other components. Or the conductive adhesive is not filled, resulting in gaps in the connection part during reflow soldering, and defects such as bursting.

FIG. 1 shows a prior art flexible printed circuit board (FPC) reinforced shielding structure, including a steel sheet 200; a flexible printed circuit board 300; a first ground hole 301 formed in the flexible printed circuit board 300; an electromagnetic wave shielding (EMI ) Film 400; and conductive adhesive film 600; wherein, the conductive adhesive film 600 covers the first grounding hole 301 and part of the flexible printed circuit board 300, and presses the steel sheet 200 on the conductive adhesive film 600, After hot pressing, the conductive adhesive film 600 melts and flows into the first ground hole 301 to form a connection with the flexible printed circuit board 300 for grounding and shielding. However, the FPC process in the current market requires smaller and smaller grounding apertures, and the downstream punching process technical requirements are becoming more and more stringent. However, due to the influence of factors such as the overflowing fluidity of the conductive adhesive, the conductive adhesive material has a very small aperture The conduction effect is not ideal. In view of this, there is an urgent need to provide a new material for the extremely small grounding hole (the diameter of which is less than or equal to 0.5 mm) to improve the grounding effect and stability. Although some existing new technologies and patents have disclosed that a thin metal coating is provided in the conductive adhesive layer to improve the conductivity of the conductive adhesive product to reduce the powder content and reduce the cost, in the actual production process, the flexibility of the metal itself Poor, resulting in the product's hole-filling after pressing is not as expected or even worse, and because of the poor permeability of the thin metal coating, there is an explosion in the SMT (surface mount technology) process of flexible printed circuit boards Board risk.

To this end, the present invention provides an anisotropic multilayer conductive tape with high conductivity including an ultra-thin conductive cloth layer and multiple metal particles of various shapes.

The main technical problem solved by the present invention is to provide a multi-layer anisotropic puncture type conductive adhesive tape. Applying the conductive adhesive tape of the present invention to a flexible printed circuit board, even if the FPC has no reserved ground hole, good grounding and electromagnetic wave shielding effects can still be obtained . Compared with the general conductive adhesive, the conductive adhesive tape of the present invention has good electrical characteristics, good adhesion strength, good solderability, high reliability and resistance It has good flammability and other characteristics, and its preparation method can reduce the production process and save production costs, and its market application prospects are broad.

In order to solve the above technical problems, the present invention uses a multi-layer anisotropic puncture type conductive adhesive tape, which includes: an upper conductive adhesive layer with a thickness of 15 to 25 microns; a lower conductive adhesive layer with a thickness of 35 to 45 microns, wherein , The upper conductive adhesive layer and the lower conductive adhesive layer both include a plurality of conductive metal particles with a particle size of 40 to 100 microns, and the plurality of conductive metal particles have a shape selected from dendritic, chain, needle, flake and At least two shapes of a group consisting of spheres; and an ultra-thin conductive cloth layer 5 to 15 microns thick with upper and lower sides, formed between the upper conductive adhesive layer and the lower conductive adhesive layer, wherein, At least one side of the ultra-thin conductive cloth layer has a metal plating layer.

In a specific embodiment, the upper conductive adhesive layer and the lower conductive adhesive layer are both thermosetting adhesive layers, and each includes an adhesive resin and the plurality of conductive metal particles, wherein each of the upper conductive adhesive The adhesive resin content of the adhesive layer and the lower conductive adhesive layer is 20 to 75% by weight, the content of the plurality of conductive metal particles is 25 to 70% by weight, and the plurality of conductive metal particles and the adhesive resin The weight ratio is 1:1 to 4:1.

In a specific embodiment, the ultra-thin conductive cloth layer is a fiber cloth, and the fiber cloth may be selected from a group consisting of mesh cloth, plain woven cloth, or non-woven cloth, wherein the fiber cloth Having a size allows the smallest conductive metal particles in the upper conductive adhesive layer and the lower conductive adhesive layer to pass through the plurality of micropores of the fiber cloth.

In another specific embodiment, the size of the plurality of micropores of the fiber cloth is not less than 5 microns.

In a specific embodiment, the metal plating layer on the surface of the ultra-thin conductive cloth layer may be a copper-nickel plating layer, a copper-cobalt plating layer, a copper-tin plating layer, a copper-silver plating layer, a copper-iron-nickel plating layer, a copper-plated gold layer Layer or copper layer.

In an embodiment, the plurality of conductive metal particles are composed of a plurality of needle-shaped conductive metal particles and a plurality of spherical conductive metal particles, and the plurality of needle-shaped conductive metal particles and the plurality of spherical conductive metal particles The weight ratio is 1:4 to 4:1.

In another embodiment, the material of the plurality of conductive metal particles includes alloy conductive particles.

In an embodiment, the conductive tape includes two release layers of 25 to 100 micrometers thick formed below the lower conductive adhesive layer and above the upper conductive adhesive layer, each of the release The layer can be a single-sided release film or a double-sided release film, and the release layer can be a fluorine-containing polyester release layer, a silicone oil-containing polyester release layer, a matte polyester release layer, and a polyethylene release layer Layer or polyethylene coated paper layer.

The invention further provides a flexible printed circuit board (FPC) reinforced shielding structure, which includes: a steel sheet with a thickness of 0.05 to 0.2 mm; an electromagnetic wave shielding (EMI) film with a thickness of 10 to 20 microns, which includes a thickness of 5 to 10 microns The conductive adhesive layer and the ink layer 5 to 10 microns thick on top of the conductive adhesive layer; the conductive adhesive tape of the present invention is located between the electromagnetic wave shielding film and the steel sheet; and the flexible printed circuit board is attached On the lower surface of the electromagnetic wave shielding film, the electromagnetic wave shielding film is located between the conductive tape and the flexible printed circuit board.

In a specific embodiment, the steel sheet is 0.05 to 0.2 mm thick Of nickel-plated steel.

The invention further provides a method for preparing the above-mentioned multi-layer anisotropic puncture type conductive adhesive tape, which comprises: mixing a plurality of conductive metal particles with a particle size of 40 to 100 microns and an adhesive resin in a weight ratio of 1:1 to 4:1, To form a mixture, wherein the plurality of conductive metal particles have at least two shapes selected from the group consisting of dendrite, chain, needle, flake, and sphere; the mixture is applied to the release layer The release surface forms the lower conductive adhesive layer; the ultra-thin conductive cloth layer is adhered and cured on the surface of the lower conductive adhesive layer; the other side of the ultra-thin conductive cloth layer is coated with 1:1 to 4:1 The weight ratio is to mix another mixture of a plurality of conductive metal particles with a particle size of 40 to 100 microns and an adhesive resin to form an upper conductive adhesive layer; and attach a release layer on the surface of the upper conductive adhesive layer.

The effect of the present invention has at least the following points: 1. The multilayer conductive adhesive tape of the present invention includes a plurality of conductive metal particles of at least two shapes, and large-size conductive metal particles with a particle size of 40 to 100 microns. The conductive metal particles are in various shapes, and the thickness of the ultra-thin conductive cloth layer is extremely thin. Therefore, when the FPC reinforced shielding structure is formed by lamination, a plurality of conductive metal particles in the conductive tape are heated and pressed through the ultra-thin The plurality of micropores in the conductive cloth layer make the upper conductive adhesive layer and the lower conductive adhesive layer form a connection; on the other hand, when pressed, the conductive metal particles in the conductive adhesive cloth can pierce the ink layer of the EMI film Direct connection with the conductive adhesive layer of the EMI film, compared with the prior art, the process of reserving the ground hole in the FPC can be omitted, that is, the process of reinforcing the shielding structure through the FPC without punching, and also has the grounding and electromagnetic wave shielding Effect, effective solution In the FPC process, the defect of insufficient continuity and stability caused by the extremely small ground hole (the diameter of which is less than or equal to 0.5 mm), and the original punching process is saved, and the cost and cost of the FPC process are also saved. Manpower; of course, the present invention is also applicable to the case where a small-diameter grounding hole is reserved in the FPC process. In this case, the conduction effect is better than the ordinary conductive film; Second, the upper conductive adhesive layer and the lower of the present invention The conductive adhesive layer includes at least two shapes of plural conductive metal particles. Since the plural conductive metal particles are of various shapes, they tend to flow in multiple directions when deformed by hot pressing during processing. After pressing, the plural conductive metal particles The distribution of particles in the conductive adhesive layer has multi-directionality and high dispersion, and then forms a conductive circuit with the ground hole on the flexible board, so that the upper conductive adhesive layer and the lower conductive adhesive layer have good anisotropic conductivity, greatly Improve the conductive performance and reduce the grounding resistance value of the flexible board; 3. The ultra-thin conductive cloth layer of the present invention is beneficial to the plural conductive metal particles in the upper conductive adhesive layer and the lower conductive adhesive layer because of its fibrous or mesh structure Through its micro-holes, the conduction of the upper and lower conductive adhesive layers is achieved. At the same time, because the conductive cloth layer has good breathability, the board mounting technology process will not occur on the surface of the flexible printed circuit board, which can effectively solve the existing conductive The bursting problem faced by the adhesive and the conductive adhesive introduced into the thin metal layer; Fourth, because the conductive cloth layer of the present invention uses fiber cloth as the base material, it has good flexibility and wear resistance, so it can avoid the excessive hardness of the conductive adhesive When the flexible circuit board is deformed by heat and pressure, the performance is affected, and at the same time, the plurality of conductive metal particles of the upper conductive adhesive layer and the lower conductive adhesive layer are deformed by hot pressing to cause the adhesive resin material to deform and flow to achieve anisotropic conduction ,may have To avoid the defect of poor conduction effect of the traditional conductive adhesive of rabbit and the conductive adhesive introduced into the thin metal layer; Fifth, because the surface of the ultra-thin conductive cloth layer of the present invention is processed by electroplating metal plating to form a metal plating layer, it has the same conduction force. Under the circumstances, the use amount of the plurality of conductive metal particles of the upper conductive adhesive layer and the lower conductive adhesive layer can be correspondingly reduced, and reduce dust pollution, reduce costs, and greatly improve the product strength; six, after a period of high temperature aging pressure After closing, the multi-directional plural conductive metal particles can improve the electrical and mechanical properties of the adhesive resin to achieve complete cross-linking and curing; 7. When using the conductive adhesive tape and steel sheet and other metal parts of the present invention to cover the printed circuit When the reinforcing component is formed on the board, it can effectively shield the external electromagnetic wave interference due to its good grounding stability; 8. The conductive metal particles of the present invention can include a plurality of alloy conductive particles, which have excellent oxidation resistance and conductivity, which is beneficial to Product storage and transportation, does not affect the physical properties of the product, so that the product has the characteristics of good stability and high reliability; and Nine, the conductive adhesive tape of the present invention is attached to a steel sheet or other reinforcing parts to form a flexible printed circuit board (FPC) Reinforced shielding structure can effectively prevent the deformation of the installation site due to bending and other factors, and because the steel sheet has good stiffness, it is conducive to FPC parts installation, transportation and other operations; by pressing and inside the conductive tape The piercing effect of the conductive metal particles of multiple large particles, even if the FPC does not have a reserved ground hole, it also has a good grounding and shielding effect of external signal interference.

The above description is only an overview of the technology of the present invention, in order to be more clear The technical means of the present invention can be understood and implemented in accordance with the contents of the description. The following is a detailed description of the present invention and the accompanying drawings in detail.

100‧‧‧ conductive tape

101‧‧‧Upper conductive adhesive layer

102‧‧‧Ultra-thin conductive cloth layer

103‧‧‧Lower conductive adhesive layer

104‧‧‧ Release layer

200‧‧‧Steel sheet

300‧‧‧flexible printed circuit board (FPC)

301‧‧‧First ground hole

302‧‧‧Second grounding hole

400‧‧‧Electromagnetic wave shielding (EMI) film

401‧‧‧Ink layer

402‧‧‧ conductive adhesive layer

500‧‧‧Single-sided copper clad laminate

600‧‧‧ conductive film

1011‧‧‧ conductive metal particles

1012‧‧‧adhesive resin

Exemplary embodiments of the present invention will be described with reference to the accompanying drawings: FIG. 1 is a cross-sectional view of a conventional FPC reinforced shielding structure including a common conductive film; FIG. 2 is a first embodiment of the present invention without release The cross-sectional view of the conductive tape of the layer; FIG. 3 is the cross-sectional view of the conductive tape containing the release layer of the first embodiment of the present invention; FIG. 4A is the FPC reinforced shielding structure of the second embodiment of the present invention Figure 4B is a cross-sectional view of the FPC reinforced shielding structure of the third embodiment of the present invention; Figure 5 is a schematic diagram of the test of the multilayered anisotropic puncture type conductive adhesive tape of the present invention; and Figure 6 is the present Invented a multi-layered anisotropic puncture type conductive adhesive tape for the second schematic test.

The following describes the implementation of the present invention by specific specific examples. Those skilled in the art can easily understand the advantages and effects of the present invention from the contents disclosed in this specification.

It should be noted that the structure, ratio, size, etc. shown in the drawings of this specification are only used to match the content disclosed in the specification, so as to familiarize yourself with this skill. The understanding and reading of the person is not used to limit the limitations of the invention, so it has no technical significance. Any structural modification, proportional relationship change or size adjustment does not affect what the invention can produce. Both the efficacy and the objectives that can be achieved should still fall within the scope of the technical content disclosed by the present invention. At the same time, the references such as "one", "lower" and "upper" in this specification are only for the convenience of description, and are not used to limit the scope of the invention. The relative relationship is changed or adjusted. Substantially changing the technical content should also be regarded as the scope of the invention. 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.

A multi-layer anisotropic puncture type conductive adhesive tape 100, as shown in FIGS. 2 and 3, includes: an upper conductive adhesive layer 101 with a thickness of 15 to 25 microns; a lower conductive adhesive layer 103 with a thickness of 35 To 45 microns, wherein the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 each include a plurality of conductive metal particles 1011 and an adhesive resin 1012 with a particle size of 40 to 100 microns, and the plurality of conductive metal particles 1011 It has at least two shapes selected from the group consisting of dendritic, chain-like, needle-like, lamellar and spherical; and an ultra-thin conductive cloth layer 5 of 5 to 15 microns thick with upper and lower sides, formed on the Between the conductive adhesive layer 101 and the lower conductive adhesive layer 103, wherein at least one side of the ultra-thin conductive cloth layer has a metal plating layer.

If the ultra-thin conductive cloth layer is too thick, it will cause the plurality of conductive metal particles 1011 in the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 to fail to contact, and the contact is poor; if the ultra-thin conductive cloth Layer 102 too Thinness is not conducive to production and increases production costs.

In one embodiment, the particle diameter of the plurality of conductive metal particles is 40 to 80 microns; in another embodiment, the particle diameter of the plurality of conductive metal particles is 51 to 80 microns; wherein, the The plural conductive metal particles are composed of plural needle-shaped conductive metal particles and plural spherical conductive metal particles, and the weight ratio of the plural needle conductive metal particles to the plural spherical conductive metal particles is 1:4 to 4:1. If the weight ratio of the plural conductive metal particles to the adhesive resin is less than 1:1, the conductivity is not good, and too much adhesive resin causes problems such as sticking to the downstream operation of the plural conductive metal particles; If the weight ratio of the adhesive resin is higher than 4:1, it is not conducive to the dispersion of the powder, and the adhesion and subsequent strength of the conductive adhesive tape will also be affected by it.

If the conductive adhesive layer is too thin, the shielding effect is not good; if the conductive adhesive layer is too thick, it does not meet the requirements for thinning, and it is unfavorable for coating processability, which indirectly increases production costs.

Typically, there is only a single shape of conductive particles in the upper conductive adhesive layer and the lower conductive adhesive layer, which tend to flow and distribute in the same direction when dispersed and pressed together, so that the conductive adhesive layer tends to be conductive In the same direction, the conductivity of the entire conductive adhesive layer is poor, which further affects the shielding effect of the conductive adhesive layer. The multiple conductive metal particles of various shapes used in the present invention are dispersed in the conductive adhesive layer and subjected to hot pressing It is deformed and flows and distributes in multiple directions, so that the conductive adhesive layer has better anisotropic conductivity and improves the shielding performance.

The upper conductive adhesive layer and the lower conductive adhesive layer are both heat A solid adhesive layer, each including an adhesive resin and the plurality of conductive metal particles, wherein the adhesive resin content of each of the upper conductive adhesive layer and the lower conductive adhesive layer is 20 to 75% by weight, the The content of the plurality of conductive metal particles is 25 to 70% by weight, and the weight ratio of the plurality of conductive metal particles to the adhesive resin is 1:1 to 4:1. The upper conductive adhesive layer and the lower conductive adhesive layer of the present invention may include some auxiliary materials (such as hardener or thickener, etc.) and non-conductive metal particles (such as graphite or conductive compound, etc.).

In a specific embodiment, the content of the plurality of conductive metal particles in each of the upper conductive adhesive layer and the lower conductive adhesive layer is 35 to 55% by weight.

The adhesive resin is selected from epoxy resin, acrylic resin, urethane resin, silicone rubber resin, parylene resin, bismaleimide resin, phenol resin, At least one of the group consisting of melamine resin and polyimide resin, especially acrylic resin.

If the adhesive resin is too little, the viscosity is too low, which is not conducive to on-line production; if the adhesive resin is too much, the product produced has a strong viscosity, and the content of the plurality of conductive metal particles is relatively reduced, resulting in conductivity Not good.

The ultra-thin conductive cloth layer 102 is a fiber cloth, and the fiber cloth may be selected from a group consisting of mesh cloth, plain woven cloth, or non-woven cloth, wherein the fiber cloth has a plurality of micropores, and The size allows the smallest conductive metal particles in the upper conductive adhesive layer and the lower conductive adhesive layer to pass through the fiber cloth.

The metal plating layer on the surface of the ultra-thin conductive cloth layer may be a copper-nickel plating layer, a plating Copper-cobalt layer, copper-tin plated layer, copper-plated silver layer, copper-plated iron-nickel layer, copper-plated gold layer or copper-plated layer.

In a specific embodiment, the metal plating layer on the surface of the ultra-thin conductive cloth layer is a copper-plated nickel layer or a copper-plated silver layer.

The plural conductive metal particles are composed of plural needle-shaped conductive metal particles and plural spherical conductive metal particles, and the weight ratio of the plural needle conductive metal particles to the plural spherical conductive metal particles is 1:4 to 4 :1.

The material of the plurality of conductive metal particles includes alloy conductive particles. The material for forming the plurality of conductive metal particles includes at least one of single metal conductive metal particles and alloy conductive particles. Furthermore, the plurality of conductive metal particles are preferably alloy conductive particles.

Wherein, the conductive metal particles of the single metal can be selected from at least one of the group consisting of gold particles, silver particles, copper particles and nickel particles, but not limited to this; the alloy conductive particles can be selected from silver-plated copper particles, At least one of the group consisting of silver-plated gold particles, silver-plated nickel particles, gold-plated copper particles, and gold-plated nickel particles, but is not limited thereto.

The conductive particles of the alloy 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 conductive adhesive tape 100 includes two release layers 104 formed below the lower conductive adhesive layer 103 and above the upper conductive adhesive layer 101 with a thickness of 25 to 100 microns, each of the release layers may be a single Surface release film or double-sided release film, and the release layer can be fluorine-containing polyester release layer, silicone oil-containing polyester Release layer, matt polyester release layer, polyethylene release layer or polyethylene coated paper layer.

In a specific embodiment, the release layer is preferably a double-sided release film with a thickness of 25 to 100 microns, and its thickness is too thin or too thick, which is not conducive to subsequent processing and punching.

The color of the release layer is pure white, milky white or transparent color, of which pure white release film or milky white release film is especially preferred, because when the CNC automatic equipment engraves the circuit, under infrared induction, the pure white release film or milky white The problem of the light reflection of the release film can be quickly and accurately positioned, and the processing operation, and during manual operation, pure white or milky white has a recognition effect, reducing the situation of artificial leakage.

The invention further provides a method for preparing the above-mentioned multi-layer anisotropic puncture type conductive adhesive tape, which comprises: Step 1: sieving the powder of conductive metal particles of various shapes to obtain a desired particle size, and then mixing the conductive metal particles of various shapes Uniform, the ball milling method can be selected during mixing, and the ball milling speed should not be too high (the speed is particularly preferably 200 to 300 rpm), otherwise the surface alloy layer of the metal particles will be destroyed, or the use of the stirring method (the speed is 700 to 2000 Rpm is better), the one with higher stirring speed has better mixing uniformity, and after mixing, a plurality of conductive metal particle mixtures are obtained; Step 2: Add the above-mentioned plurality of conductive metal particle mixtures to the adhesive resin in proportion and mix thoroughly and uniformly During the mixing, it is necessary to add a plurality of conductive metal particles while stirring and mixing, the mixing conditions are similar to step one; Step 3: Apply the mixture obtained in Step 2 to the designated release surface of the release layer to form the lower conductive adhesive layer; Step 4: Paste the ultra-thin conductive cloth layer with carrier on the lower conductive adhesive layer and pre-cure The pre-curing temperature of the lower conductive adhesive layer should not exceed the curing temperature of the adhesive resin itself. The pre-curing temperature selected in the present invention is between 80 and 100°C. After the pre-curing, the carrier is torn off to form an ultra-thin Conductive cloth layer; Step 5: Apply the mixture prepared in Step 2 on the other side of the ultra-thin conductive cloth layer to form an upper conductive adhesive layer. Of course, another mixture with different compositions and ratios can be additionally prepared; Step 6: The upper conductive adhesive layer is cured under the pre-curing conditions of Step 4 and then rolled up to obtain the finished product.

As shown in FIG. 4A, the present invention further provides a flexible printed circuit board (FPC) reinforced shielding structure, which includes: a steel sheet 200 with a thickness of 0.05 to 0.2 mm; and an electromagnetic wave shielding (EMI) film with a thickness of 10 to 20 microns 400, which includes an ink layer 401 with a thickness of 5 to 10 microns and a conductive adhesive layer 402 with a thickness of 5 to 10 microns. In this embodiment, the ink layer 401 is located on the conductive adhesive layer 402. Of course, the opposite can also be provided; The inventive conductive tape 100 is located between the electromagnetic wave shielding film 400 and the steel sheet 200, and the conductive tape is attached to the lower surface of the steel sheet 200; and the flexible printed circuit board 300 is attached to the electromagnetic wave shield The lower surface of the film 400.

In a specific embodiment, the steel sheet is a nickel-plated steel sheet with a thickness of 0.05 to 0.2 mm. In a specific embodiment, the total thickness of the nickel-plated steel sheet is 0.1 mm.

In the specific embodiment shown in FIG. 4A, the flexible printed circuit board 300 located below the conductive tape does not have a reserved ground hole, which is different from the typical flexible printed circuit board (FPC) in FIG. 1 Reinforce the shielding structure.

In the FPC reinforced shielding structure, after the conductive tape 100 is pressed against the steel sheet 200, the conductive metal particles 1011 in the adhesive resin 1012 pierce the ink layer 401 of the EMI film and directly communicate with the conductive adhesive layer 402 of the EMI film , And transmitted through the conductive adhesive layer 402 to the second ground hole 302 of the large aperture of the flexible printed circuit board 300 that is not covered by the conductive tape 100 and the EMI film, and then is grounded, compared with the typical FPC reinforced shielding structure, As shown in FIG. 1, the process of reserving the first ground hole 301 with a small aperture under the EMI film coverage of the typical FPC reinforced shielding structure can be omitted, that is, the process of reinforcing the shielding structure through the FPC without punching is also required. The effect of grounding and electromagnetic wave shielding effectively solves the defect of insufficient conductivity and stability caused by the extremely small grounding hole (the diameter of which is less than or equal to 0.5 mm) in the FPC process, and because the original punching process is omitted, at the same time It also saves the cost and manpower of the FPC process.

In another embodiment, a flexible printed circuit board (FPC) reinforced shielding structure, as shown in FIG. 4B, includes: a steel sheet 200; an electromagnetic wave shielding (EMI) film 400, which includes an ink layer 401 and a conductive adhesive layer 402, wherein the ink layer 401 is located on the conductive adhesive layer 402; the flexible printed circuit board 300 includes a first ground hole 301 and a second ground hole 302; and the above-mentioned conductive tape 100 is covered on the first A ground hole 301 and part of the flexible printed circuit board 300, and the steel is pressed against the conductive tape 100 片200.

After hot pressing, the upper conductive adhesive layer and the lower conductive adhesive layer of the conductive tape melt into the first ground hole 301 to form a connection with the FPC for grounding shielding. Compared with the prior art, the present invention can The overflowing fluidity of the ordinary conductive adhesive film is avoided, and the conduction effect of the present invention is better than that of using the ordinary conductive film.

Test Method 1: Continuity Analysis

As shown in Figure 5, conduct a continuity analysis test on the multi-layer anisotropic puncture type conductive adhesive tape after the release layer is removed by using a Takahashi tester, and respectively adhere to the surfaces of the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 After the nickel-plated steel sheet 200 and the flexible printed circuit board 300 are pressed and cured, the continuity resistance values of the samples before and after reflow soldering are tested separately. The present invention is used as an example to test the conductivity of general products in the same way as a comparison For example, record the measured continuity results in Table 1.

Test Method 2: Peeling force analysis

As shown in Figure 6, the multi-layer anisotropic puncture type conductive adhesive tape after peeling the double-sided release film was tested with a universal tensile machine, and the surfaces of the upper conductive adhesive layer 101 and the lower conductive adhesive layer 103 were false. After the nickel-plated steel sheet 200 and the single-sided copper clad laminate 500 are pressed and cured, the sample is taken out to test the peeling force value. The present invention is used as an example, and the peeling force of a general product is tested in the same way as a comparative example. The results of the peel force obtained are reported in Table 1.

It can be seen from Table 1 that the multi-layer anisotropic puncture type conductive adhesive tape of the present invention does have a good conductive effect, stability and good adhesive strength compared to general products. In contrast, the general conductive adhesive is not conductive because the FPC has no holes and no piercing effect.

The above-mentioned embodiments are only illustrative and not intended to limit the present invention. Any equivalent structure made by using the description and drawings of the present invention, or directly or indirectly used in other related technical fields, is also included in the patent protection scope of the present invention.

100‧‧‧ conductive tape

101‧‧‧Upper conductive adhesive layer

102‧‧‧Ultra-thin conductive cloth layer

103‧‧‧Lower conductive adhesive layer

104‧‧‧ Release layer

1011‧‧‧ conductive metal particles

Claims (9)

A multi-layer anisotropic puncture type conductive adhesive tape, comprising: a conductive adhesive layer above 15-25 microns thick; a conductive adhesive layer below 35-45 microns thick, wherein the upper conductive adhesive layer and the lower conductive adhesive The layers are all thermosetting adhesive layers, and each includes an adhesive resin and a plurality of conductive metal particles with a particle size of 40 to 100 microns, wherein the plurality of conductive metal particles have a shape selected from dendritic, chain, needle, flake and At least two shapes of the group consisting of spheres; the adhesive resin content of each of the upper conductive adhesive layer and the lower conductive adhesive layer is 20 to 75% by weight, and the content of the plurality of conductive metal particles is 25 to 70% by weight, and the weight ratio of the plurality of conductive metal particles to the adhesive resin is 1:1 to 4:1; and an ultra-thin conductive cloth layer 5 to 15 microns thick with upper and lower sides is formed on the Between the conductive adhesive layer and the lower conductive adhesive layer, wherein at least one side of the ultra-thin conductive cloth layer has a metal plating layer. The conductive tape as described in item 1 of the patent application range, wherein the ultra-thin conductive cloth layer is a fiber cloth, and the fiber cloth may be selected from one of the group consisting of mesh cloth, plain woven cloth or non-woven cloth , Wherein the fiber cloth has a size that allows the smallest conductive metal particles in the upper conductive adhesive layer and the lower conductive adhesive layer to pass through the plurality of micropores of the fiber cloth. The conductive adhesive tape as described in item 1 of the patent application scope, wherein the metal plating layer on the surface of the ultra-thin conductive cloth layer may be a copper-nickel plating layer, a copper-cobalt plating layer, a copper-tin plating layer, a copper-plating silver layer, a copper-plating iron layer Nickel layer, copper-plated gold layer or copper-plated layer. As mentioned in the first paragraph of the patent scope of conductive adhesive tape, where the plural The conductive metal particles are composed of a plurality of needle-shaped conductive metal particles and a plurality of spherical conductive metal particles, and the weight ratio of the plurality of needle-shaped conductive metal particles to the plurality of spherical conductive metal particles is 1:4 to 4:1. The conductive adhesive tape as described in item 1 of the patent application range, wherein the material of the plurality of conductive metal particles includes alloy conductive particles. The conductive adhesive tape as described in item 1 of the patent application range includes two release layers of 25 to 100 microns thick formed below the lower conductive adhesive layer and above the upper conductive adhesive layer, each The release layer can be a single-sided release film or a double-sided release film, and the release layer can be a fluorine-containing polyester release layer, a silicone oil-containing polyester release layer, a matte polyester release layer, and a polyethylene release layer Type layer or polyethylene coated paper layer. A flexible printed circuit board (FPC) reinforced shielding structure includes: a steel sheet with a thickness of 0.05 to 0.2 mm; an electromagnetic wave shielding (EMI) film with a thickness of 10 to 20 microns, which includes a conductive adhesive layer with a thickness of 5 to 10 microns and is located An ink layer of 5 to 10 microns thick above the conductive adhesive layer; the conductive adhesive tape as described in item 1 of the patent application scope is located between the electromagnetic wave shielding film and the steel sheet; and the flexible printed circuit board is attached Combined with the lower surface of the electromagnetic wave shielding film, the electromagnetic wave shielding film is located between the conductive tape and the flexible printed circuit board. The flexible printed circuit board (FPC) reinforced shielding structure as described in item 7 of the patent application scope, wherein the steel sheet is a nickel-plated steel sheet. A method for preparing conductive tape as described in item 6 of patent application The method includes: mixing a plurality of conductive metal particles with a particle size of 40 to 100 microns and an adhesive resin in a weight ratio of 1:1 to 4:1 to form a mixture, wherein the plurality of conductive metal particles have At least two shapes of the group consisting of shape, chain, needle, flake and sphere; apply the mixture to the designated release surface of the release layer to form a lower conductive adhesive layer; apply ultra-thin conductive cloth The layer is adhered and cured on the surface of the lower conductive adhesive layer; the other side of the ultra-thin conductive cloth layer is coated with a plurality of conductive metal particles with a mixed particle size of 40 to 100 microns in a weight ratio of 1:1 to 4:1 And another mixture of adhesive resin to form an upper conductive adhesive layer; and a release layer is attached to the surface of the upper conductive adhesive layer.

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