An electromagnetic shielding film, a shielded printed circuit board, and an electronic device

Abstract

The present invention provides an electromagnetic shielding film, which comprises an insulating layer, a shielding layer, a conductive adhesive layer and an electromagnetic wave absorbing filler; the shielding layer is located in the middle layer, the insulating layer is located on one side of the shielding layer, the conductive adhesive layer is located on the other side of the shielding layer, and the electromagnetic wave absorbing filler is located in the pores of the shielding layer; the shielding layer is a metallized polymer-based non-woven fabric with a porous structure. The electromagnetic shielding film of the present invention uses a metallized polymer-based non-woven fabric as the shielding layer. The porous structure of the shielding layer has the characteristic of air permeability, and can discharge water vapor and small molecule gases during the processes of thermal lamination and reflow soldering, avoiding the phenomenon of board explosion generated by the product at high temperature and improving the processing performance. The present invention also fills the pores of the shielding layer with an electromagnetic wave absorbing filler, further improving the electromagnetic shielding efficiency and being applicable to high-frequency and ultra-high-frequency application scenarios.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic shielding, and particularly to an electromagnetic shielding film, a shielded printed circuit board, and an electronic device. Background Art

[0002] With the accelerating development of 5G communication, electronic products are accelerating towards the direction of light weight and miniaturization. These characteristics have greatly promoted the development of flexible printed circuit boards, which have been widely used in industries such as mobile phones, display devices, communication fields, and aerospace fields. The resulting electromagnetic interference problems have become increasingly prominent. The electromagnetic interference inside and outside components caused by high-frequency and high-speed driving, as well as the problems of signal attenuation and insertion loss during transmission, have also become increasingly serious. Therefore, there is a wide demand for electromagnetic shielding films suitable for high-frequency scenarios.

[0003] In terms of the processing of electromagnetic shielding films, traditional electromagnetic shielding films use a metal thin layer as the shielding layer, and the metallized layer has good sealing performance. This will cause problems such as poor contact or even board explosion during processes such as thermal lamination and reflow soldering because water vapor, small molecule gases, etc. generated by water-absorbing resins under heating conditions cannot be discharged smoothly. Summary of the Invention

[0004] The purpose of the present invention is to provide an electromagnetic shielding film, a shielded printed circuit board, and an electronic device, which can avoid the phenomenon of board explosion generated by the product at high temperature while improving the electromagnetic shielding efficiency.

[0005] To achieve the above purpose, the present invention provides the following solutions:

[0006] An electromagnetic shielding film, comprising: an insulating layer, a shielding layer, a conductive adhesive layer, and an electromagnetic wave absorbing filler; the insulating layer is disposed on one side of the shielding layer, and the conductive adhesive layer is disposed on the other side of the shielding layer; the electromagnetic wave absorbing filler is filled in the shielding layer; the shielding layer is a metallized polymer-based non-woven fabric; the metallized polymer-based non-woven fabric has a porous structure.

[0007] Optionally, the polymer material used for the metallized polymer-based non-woven fabric is one or more of polyolefins, polyacetylenes, polyesters, polyamides, polyimides, polyethers, polyalcohols, polysulfones, polythionitrides, silicone polymers, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, and their derivatives, crosslinked products, and copolymers.

[0008] Optionally, the material used for the metallized layer of the metallized polymer-based non-woven fabric is one or more of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, iron, and cobalt.

[0009] Optionally, the metallization layer is a single-layer metal or a multi-layer metal; the thickness of the metallization layer is 0.01 μm - 20 μm.

[0010] Optionally, the particle size of the electromagnetic wave absorption filler is 0.001 μm - 25 μm.

[0011] Optionally, the electromagnetic wave absorption filler uses an electromagnetic wave absorbing material; the electromagnetic wave absorbing material is one or more of an iron-based absorbing material, a carbon-based absorbing material, a ceramic-based absorbing material, a composite absorbing material, metal powder, and metal oxide powder.

[0012] Optionally, the total thickness of the electromagnetic shielding film is between 1 μm and 60 μm.

[0013] A shielded printed circuit board includes: the electromagnetic shielding film and the circuit board body; the electromagnetic shielding film is disposed on the circuit board body, and the conductive adhesive layer of the electromagnetic shielding film is connected to the ground layer in the circuit board body.

[0014] Optionally, the circuit board body is a flexible printed circuit board or a rigid-flexible board.

[0015] An electronic device is assembled with the shielded printed circuit board.

[0016] According to the specific embodiments provided by the present invention, the following technical effects are disclosed:

[0017] The present invention provides an electromagnetic shielding film, including an insulating layer, a shielding layer, a conductive adhesive layer, and an electromagnetic wave absorption filler; the shielding layer is located in the middle layer, the insulating layer is located on one side of the shielding layer, the conductive adhesive layer is located on the other side of the shielding layer, and the electromagnetic wave absorption filler is located in the holes of the shielding layer; the shielding layer is a metallized polymer-based non-woven fabric with a porous structure. The electromagnetic shielding film of the present invention uses a metallized polymer-based non-woven fabric as the shielding layer, and the porous structure of the shielding layer has the characteristic of air permeability, which can discharge water vapor and small molecule gases during thermal lamination and reflow soldering processes, avoid the phenomenon of board explosion generated by the product at high temperature, and improve the processing performance. The present invention also fills the electromagnetic wave absorption filler into the holes of the shielding layer, further improving the electromagnetic shielding efficiency, and is applicable to high-frequency and ultra-high-frequency application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 Schematic structural diagram of the electromagnetic shielding film provided by the present invention;

[0020] Figure 2 Schematic structural diagram of the shielded printed circuit board provided by the present invention;

[0021] Figure 3 Comparison chart of shielding effectiveness of various embodiments and comparative examples of the electromagnetic shielding film provided by the present invention;

[0022] Symbol description: 10, electromagnetic shielding film; 100, insulating layer; 101, shielding layer; 102, electromagnetic wave absorbing filler; 103, conductive adhesive layer; 20, shielded printed circuit board; 200, circuit board body. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0024] The object of the present invention is to provide an electromagnetic shielding film, a shielded printed circuit board and an electronic device, which can improve the electromagnetic shielding effectiveness while avoiding the phenomenon of board explosion generated by the product at high temperature.

[0025] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0026] The object of the present invention is to provide an electromagnetic shielding film, a shielded printed circuit board and an electronic device. Figure 1 Schematic structural diagram of the electromagnetic shielding film provided by the present invention; Figure 2 Schematic structural diagram of the shielded printed circuit board provided by the present invention.

[0027] As Figure 1 shown, an electromagnetic shielding film 10 of the present invention includes: an insulating layer 100, a shielding layer 101, a conductive adhesive layer 103 and an electromagnetic wave absorbing filler 102. The insulating layer 100 is disposed on one side of the shielding layer 101, the conductive adhesive layer 103 is disposed on the other side of the shielding layer 101, and the electromagnetic wave absorbing filler 102 is filled in the shielding layer 101.

[0028] Specifically, the shielding layer 101 is a metallized polymer-based non-woven fabric, and the metallized polymer-based non-woven fabric has a porous structure with a porosity of 0.1%-99.9%. In the present invention, the porosity of the high-molecular-based non-woven fabric is characterized by the volume of gas passing vertically through a unit area of the metallized polymer-based non-woven fabric per unit time under a pressure difference of 125 Pa, and the range is 1 cc / cm 2 / sec - 1000 cc / cm 2 / sec; preferably, the porosity of the metallized polymer-based non-woven fabric ranges from 5 cc / cm 2 / sec - 500 cc / cm 2 / sec; more preferably, it is in the range of 10 cc / cm 2 / sec - 300 cc / cm 2 / sec.

[0029] In practical applications, the polymer material used for the metallized polymer-based non-woven fabric can be one or more of polyolefins, polyacetylenes, polyesters, polyamides, polyimides, polyethers, polyalcohols, polysulfones, polythionitrides, silicone polymers, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, and their derivatives, crosslinked products, and copolymers. Preferably, the polymer material used for the metallized polymer-based non-woven fabric is one or more of polyacetylenes, polyesters, polyamides, polyimides, polyethers, and aromatic ring polymers; more preferably, the polymer material used for the metallized polymer-based non-woven fabric is one or more of polyesters, polyamides, and polyimides.

[0030] In practical applications, the material used for the metallized layer of the metallized polymer-based non-woven fabric can be one or more of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, iron, and cobalt. Preferably, the metallized layer is made of one or more of copper, nickel, titanium, and silver; more preferably, it is made of one or more of copper, nickel, and silver. The metallized layer is a single-layer metal or a multi-layer metal; the thickness of the metallized layer is 0.01 μm - 20 μm; preferably, the thickness of the metallized layer is 0.1 μm - 10 μm; more preferably, the thickness of the metallized layer is 0.5 μm - 5 μm.

[0031] The electromagnetic wave absorbing filler 102 can be one or more of iron-based wave absorbing materials, carbon-based wave absorbing materials, ceramic-based wave absorbing materials, composite wave absorbing materials, metal powders, and metal oxide powders. Exemplarily, the electromagnetic wave absorbing filler 102 can be one or more of metal powders, metal oxide powders, carbon black, graphite, carbon nanotubes, conductive polymers, graphene, silicon carbide, barium titanate, conductive fibers, alloy powders, and nano iron fibers. Preferably, the electromagnetic wave absorbing filler 102 can be one or more of metal powders, metal oxide powders, ferrites, silicon carbide, graphite, carbon nanotubes, conductive fibers, and nano iron fibers; more preferably, it can be one or more of metal powders, metal oxide powders, ferrites, silicon carbide, carbon nanotubes, and nano iron fibers. The particle size range of the electromagnetic wave absorbing filler 102 is 0.001 μm - 25 μm; preferably, the particle size range of the electromagnetic wave absorbing filler 102 is 0.01 μm - 10 μm; more preferably, the particle size range of the electromagnetic wave absorbing filler 102 is 0.1 μm - 5 μm.

[0032] Here, the shape of the electromagnetic wave absorbing filler 102 is not particularly limited and can be spherical, cluster-shaped, strip-shaped, sheet-shaped, dendritic, etc.

[0033] The insulating layer 100 can be an insulating material such as a polyimide film PI or a polyethylene terephthalate film PET.

[0034] The conductive adhesive of the conductive adhesive layer 103 can be a gold-based conductive adhesive, a silver-based conductive adhesive, a copper-based conductive adhesive, a carbon-based conductive adhesive, etc.

[0035] The total thickness of the electromagnetic shielding film 10 is 1 μm - 60 μm; preferably, it is 5 μm - 45 μm; more preferably, it is 10 μm - 35 μm.

[0036] Specific examples are used below to comparatively illustrate the shielding effectiveness of each example and the comparative example of the electromagnetic shielding film of the present invention.

[0037] In each example of the electromagnetic shielding film of the present invention, the polymer material of the metallized polymer-based non-woven fabric is a liquid crystal polymer (LCP). The liquid crystal polymer (LCP) has advantages such as low hygroscopicity, small expansion, high strength, low dielectric constant, and small tangent angle.

[0038] Example 1

[0039] As Figure 1The electromagnetic shielding film 10 shown has an insulating layer 100 disposed on one side of the shielding layer 101, and a conductive adhesive layer 103 disposed on the other side of the shielding layer 101. The insulating layer 100 is made of a 7-μm thick polyimide film, the shielding layer 101 is made of metallized liquid crystal polymer non-woven fabric, the material of the metallized layer is copper with a thickness of 1 μm, and the porosity of the metallized liquid crystal polymer non-woven fabric is 90 cc / cm 2 / sec. The conductive adhesive layer 103 is an isotropic conductive adhesive. The electromagnetic wave absorbing filler 102 is made of titanium dioxide powder. The total thickness of the insulating layer 100, the shielding layer 101, and the conductive adhesive layer 103 is 33 μm, and the thickness after thermocompression bonding is 28 μm.

[0040] Example 2

[0041] As Figure 1 shown, for the electromagnetic shielding film 10, the insulating layer 100 is disposed on one side of the shielding layer 101, and the conductive adhesive layer 103 is disposed on the other side of the shielding layer 101. The insulating layer 100 is made of a 7-μm thick polyimide film, the shielding layer 101 is made of metallized liquid crystal polymer non-woven fabric, the material of the metallized layer is copper with a thickness of 1 μm, and the porosity of the metallized liquid crystal polymer non-woven fabric is 94 cc / cm 2 / sec. The conductive adhesive layer 103 is an isotropic conductive adhesive. The electromagnetic wave absorbing filler 102 is made of carbon nanotubes. The total thickness of the insulating layer 100, the shielding layer 101, and the conductive adhesive layer 103 is 33 μm, and the thickness after thermocompression bonding is 28 μm.

[0042] Example 3

[0043] As Figure 1 shown, for the electromagnetic shielding film 10, the insulating layer 100 is disposed on one side of the shielding layer 101, and the conductive adhesive layer 103 is disposed on the other side of the shielding layer 101. The insulating layer 100 is made of a 7-μm thick polyimide film, the shielding layer 101 is made of metallized liquid crystal polymer non-woven fabric, the material of the metallized layer is copper with a thickness of 1 μm, and the porosity of the metallized liquid crystal polymer non-woven fabric is 92 cc / cm 2 / sec. The conductive adhesive layer 103 is an isotropic conductive adhesive. The electromagnetic wave absorbing filler 102 is made of silicon carbide powder. The total thickness of the insulating layer 100, the shielding layer 101, and the conductive adhesive layer 103 is 33 μm, and the thickness after thermocompression bonding is 28 μm.

[0044] Comparative Example 1

[0045] Taking the traditional electromagnetic shielding film as a comparison, the insulating layer is made of a 7-μm thick polyimide film. The shielding layer is made of a 2-μm thick copper foil, and the shielding layer is adhered to one side of the insulating layer. The conductive adhesive layer is a 17-μm thick isotropic conductive adhesive, which is adhered to the other side of the shielding layer. The total thickness of the insulating layer, the shielding layer, and the adhesive film layer is 26 μm, and the thickness after thermocompression bonding is 25 μm.

[0046] As Figure 3 shown, the comparison chart of the shielding effectiveness of each example and Comparative Example 1 measured by the KEC method. From Figure 3 the shown comparison chart, it can be seen that the shielding effectiveness of Examples 1-3 using the method of the present invention is better than that of Comparative Example 1 in high-frequency application scenarios. At 1 GHz, the shielding effectiveness of the electromagnetic shielding film of the present invention measured by the KEC method reaches 76.6 dB, which is especially suitable for high-frequency and ultra-high-frequency application scenarios.

[0047] As Figure 2 shown, a shielding printed circuit board 20 provided by the present invention includes an electromagnetic shielding film 10 and a circuit board body 200. The conductive adhesive layer 103 of the electromagnetic shielding film 10 is connected to the ground layer in the circuit board body 200, and the electromagnetic shielding film 10 is thermally pressed and adhered to the printed circuit board 20.

[0048] In practical applications, the circuit board body 200 can be a flexible printed circuit board or a rigid-flexible board. The shielding printed circuit board 20 is heated to 260 °C and then cooled to room temperature. This heating and cooling process is carried out a total of 5 times, and it is visually inspected whether the electromagnetic shielding film bulges or cracks. The experimental results show that since the electromagnetic shielding film of the present invention uses a metallized polymer-based non-woven fabric as the shielding layer, the porous structure of the shielding layer has the characteristic of air permeability and can discharge water vapor and small molecule gases during thermal lamination and reflow soldering processes. Therefore, it can effectively avoid the phenomenon of board explosion generated by the product at high temperature and improve the processing performance.

[0049] The present invention also provides an electronic device, and the electronic device is assembled with the shielding printed circuit board 20.

[0050] In an electromagnetic shielding film, a shielding printed circuit board and an electronic device provided by the present invention, the shielding layer of the electromagnetic shielding film 10 uses a metallized polymer-based non-woven fabric. After the selected polymer-based non-woven fabric is metallized, it has the advantages of being porous, bend-resistant, high in tensile strength, low in water absorption rate, high in dimensional stability, low in dielectric constant, etc., and is an ideal carrier for the shielding layer of the electromagnetic shielding film; the electromagnetic wave absorbing material 102 is filled into the shielding layer, further increasing the reflection and absorption of electromagnetic waves between the shielding layer and the filler, and increasing the shielding effectiveness.

[0051] At the same time, the metallized polymer-based non-woven fabric is used as the shielding layer, and the porous structure of the shielding layer has the characteristic of air permeability, which can discharge water vapor and small molecule gases during thermal lamination and reflow soldering processes, avoiding the phenomenon of board explosion generated by the product at high temperature; and it can relieve the stress shrinkage during the processing process. The shielding film 10 has the characteristics of high shielding effectiveness and good processing performance.

[0052] In the present specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference can be made to each other.

[0053] Specific examples are used herein to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. An electromagnetic shielding film, characterized in that, Comprising: An insulating layer, a shielding layer, a conductive adhesive layer, and an electromagnetic wave absorbing filler; the insulating layer is disposed on one side of the shielding layer, and the conductive adhesive layer is disposed on the other side of the shielding layer; the electromagnetic wave absorbing filler is filled in the shielding layer; the shielding layer is a metallized polymer-based nonwoven fabric; the metallized polymer-based nonwoven fabric has a porous structure; The polymer material used for the metallized polymer-based nonwoven fabric is one or more of polyolefins, polyacetylenes, polyesters, polyamides, polyimides, polyethers, polyalcohols, polysulfones, polythionitrides, silicone polymers, polysaccharide polymers, amino acid polymers, aromatic ring polymers, aromatic heterocyclic polymers, epoxy resins, phenolic resins, and their derivatives, crosslinked products, and copolymers; The total thickness of the electromagnetic shielding film is 1 μm - 60 μm; The thickness of the metallized layer of the metallized polymer-based nonwoven fabric is 0.5 μm - 5 μm.

2. An electromagnetic shielding film according to claim 1, wherein The material used for the metallized layer of the metallized polymer-based nonwoven fabric is one or more of aluminum, aluminum alloy, copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, iron, and cobalt.

3. An electromagnetic shielding film according to claim 2, wherein The metallized layer is a single-layer metal or a multi-layer metal.

4. The electromagnetic shielding film according to claim 1, wherein The particle size of the electromagnetic wave absorbing filler is 0.001 μm - 25 μm.

5. An electromagnetic shielding film according to claim 1, characterized in that, The electromagnetic wave absorbing filler uses an electromagnetic wave absorbing material; the electromagnetic wave absorbing material is one or more of iron-based absorbing materials, carbon-based absorbing materials, ceramic-based absorbing materials, composite absorbing materials, metal powders, and metal oxide powders.

6. A shielded printed circuit board, characterized in that, Comprising: The electromagnetic shielding film as claimed in claim 1 and a circuit board body; the electromagnetic shielding film is disposed on the circuit board body, and the conductive adhesive layer of the electromagnetic shielding film is connected to the ground layer in the circuit board body.

7. The shielded printed circuit board according to claim 6, wherein The circuit board body is a flexible printed circuit board or a rigid-flexible printed circuit board.

8. An electronic device, characterized in that, The electronic device is assembled with the shielded printed circuit board as claimed in claim 6.

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