An ultra-low dielectric constant metal-clad laminate and circuit board

Abstract

The utility model discloses a super low dielectric constant metal-clad laminate and circuit board, include: at least one metal foil, at least one low dielectric low loss adhesive layer, at least one foamed plastic layer, wherein, between metal foil and foamed plastic layer, set at least one low dielectric low loss adhesive layer, metal foil, low dielectric low loss adhesive layer, foamed plastic layer constitute the layered structure with air cavity. The utility model discloses a circuit board made of laminate. The laminate can satisfy the performance of super low dielectric constant (DK <1.1) and low loss (Df <0.005), can reduce the refraction and reflection loss of high frequency signal between different layers, at the same time satisfies the firm adhesion (>3.0lbs / inch) of metal foil and base material, and the long-term reliability of adhesion - that is, does not appear the delamination of metal foil and base or the bubbling of metal foil under the influence of long-term use or use environment.

Description

Technical Field

[0001] This utility model relates to communication and antenna applications in the aerospace field, and in particular to an ultra-low dielectric constant metal foil laminate and circuit board. Background Technology

[0002] Antennas are key components of communication and radar systems, and antenna arrays fabricated using printed circuit boards (PCBs) are widely used due to their low cost, ease of fabrication, and high precision. However, the design, structure, size, and performance of an antenna are closely related to the dielectric properties of the PCB substrate material. For example, a low dielectric constant (DK<2) can effectively increase antenna bandwidth and reduce signal delay, while low dielectric loss (Df<0.005) can improve antenna gain and energy efficiency. Therefore, reducing the dielectric constant and dielectric loss of the substrate is an important research topic in this field.

[0003] However, in existing technologies, ordinary substrates generally consist of a base made primarily of one or more of the following resins: epoxy resin, polyphenylene ether resin, hydrocarbon resin, BT resin, and polytetrafluoroethylene, and an epoxy resin-based FR4 adhesive / sheet used for bonding. The dielectric constant of the base is generally greater than 2.10, and the dielectric constant of the FR4 adhesive / sheet is generally greater than 3.5. Furthermore, the molded ordinary substrate is typically a solid layered structure, resulting in generally high dielectric constants and dielectric losses. Even modified low-loss FR4 substrates generally still have dielectric constants greater than 3.8 and dielectric losses greater than 0.007, failing to meet the requirements for ultra-low dielectric constants (DK < 1.1) and low dielectric losses (Df < 0.005). Additionally, it should be noted that reducing the dielectric constant of the substrate to below 1.1 is quite difficult in existing technologies. Utility Model Content

[0004] The main objective of this invention is to provide an ultra-low dielectric constant metal foil laminate to at least partially solve the above-mentioned problems, and to provide a circuit board made from the aforementioned ultra-low dielectric constant metal foil laminate. Antennas made from this circuit board can effectively increase antenna bandwidth and reduce signal delay, while also improving antenna gain and energy efficiency.

[0005] As a first aspect of this utility model, in order to achieve the above-mentioned objective, the ultra-low dielectric constant metal foil laminate provided by this utility model includes: at least one metal foil, at least one low dielectric low loss adhesive layer, and at least one foamed plastic layer, wherein at least one low dielectric low loss adhesive layer is disposed between the metal foil and the foamed plastic layer; the metal foil, the low dielectric low loss adhesive layer, and the foamed plastic layer are configured into a layered structure, and the layered structure is provided with an air cavity.

[0006] Preferably, the metal foil comprises one or more of copper foil, aluminum foil, and stainless steel.

[0007] Preferably, the thickness of the metal foil is between 8 micrometers and 200 micrometers.

[0008] Preferably, the dielectric constant DK of the layered structure is <1.1, the dielectric loss Df is <0.005, and the metal foil peel strength is >3 lbs / inch.

[0009] Preferably, the low-dielectric-low-loss adhesive layer is characterized in that the dielectric constant of the low-dielectric-low-loss adhesive layer is between 2.0 and 3.1, and the dielectric loss of the low-dielectric-low-loss adhesive layer is less than 0.004.

[0010] In existing technologies, the dielectric constant of the adhesive layer is often relatively high (e.g., ordinary epoxy resin has a dielectric constant of 3.7–4.0, thermosetting PI has a dielectric constant of 4.0, and modified polyphenylene ether and TAIC systems have a dielectric constant of 3.2–3.5), while the dielectric constant of the foamed material is often less than 2.0. Therefore, when using adhesive layers with high dielectric constants in existing technologies, the actual test results of microwave devices often differ significantly from the simulation results. For example, when using foamed plastic to fabricate Luneburg lenses, the epoxy resin bonding leads to the aforementioned problems, mainly due to the large difference in dielectric constant between the adhesive layer resin and the foamed layer, resulting in microwave refraction and reflection losses. (YAN Xiulin, SHI Yunqi, ZHU Lina. Design of Luneburg LensAntenna Based on Novel Foam Materials[J]. Journal of Electronics&InformationTechnology, 2022, 44(12): 4111-4115. doi: 10.11999 / JEIT220569).

[0011] Therefore, this disclosure reduces refraction and reflection losses when microwaves pass through the adhesive layer by controlling the dielectric constant and loss of the adhesive layer to be as close as possible to the dielectric constant of the foamed plastic. In particular, for foamed materials with a dielectric constant less than 2.0, the difference in dielectric constant between the adhesive layer and the substrate cannot be ignored in high-frequency and even millimeter-wave bands.

[0012] Preferably, the low-dielectric-low-loss adhesive layer is further characterized in that its glass transition temperature is greater than 240°C.

[0013] In existing technologies, rubber or hydrocarbon rubber is used as the adhesive layer. However, common rubber adhesives, such as butyl rubber and polyisobutyl rubber adhesives, have poor temperature and weather resistance. They are prone to blistering and delamination under long-term high temperature and high humidity conditions, especially in extreme environments. The adhesive layer of this invention has a glass transition temperature greater than 240 degrees Celsius, which is higher than the glass transition temperature of general cross-linked rubbers and resins. Therefore, the adhesive layer of this disclosure has better thermal stability.

[0014] Preferably, the low dielectric and low loss adhesive layer is characterized in that the water absorption rate of the low dielectric and low loss adhesive layer is less than 0.3% (tested by immersion in water at 50 degrees Celsius for 48 hours).

[0015] The low-dielectric, low-loss adhesive layer has a water absorption rate of less than 0.3%, effectively isolating the metal foil adhesion from changes in environmental humidity and ensuring adhesion stability. Existing technologies, such as epoxy resin, cyanate ester resin, and bismaleimide resin, have water absorption rates exceeding these requirements. For example, cyanate ester resin systems are widely used in radar radome materials, such as BASF's 5575-2, Fiberite's X54-2, Hexcel's HX 1584-3, and Dow Chemical's XU-71787. The 701 cyanate ester resin system developed by the Aerospace Materials and Processes Research Institute has the following process requirements: ε=2.8, tanδ=0.009, Tg=205℃. Its water absorption rate after immersion in water at 22℃ for 40 days is 0.73%, significantly higher than the water absorption rate of the low-dielectric, low-loss adhesive layer described in this invention.

[0016] The low-dielectric-low-loss adhesive layer of this invention can be described as follows: the main component of the low-dielectric-low-loss adhesive layer is one or a mixture of low-loss crosslinked hydrocarbon polymers or low-loss crosslinked polyphenylene ether polymers. The low-loss crosslinked hydrocarbon polymer includes one or more of the following: butadiene polymers, isoprene polymers, butadiene-styrene rubber, butadiene-styrene block polymers, styrene-isoprene block polymers, styrene-isoprene-styrene block polymers, styrene-polybutadiene-styrene block polymers, divinylbenzene polymers, styrene-divinylbenzene polymers, styrene-butadiene-divinylbenzene polymers, ethylene propylene diene monomer (EPDM) rubber, butyl rubber, and cycloolefin polymers (e.g., acenaphthene), crosslinked by free radical initiation. The low-loss crosslinked polyphenylene ether polymer comprises a polyphenylene ether polymer with vinyl or allyl active groups modified on the end groups or side groups of the polymer, crosslinked by free radical initiation.

[0017] Preferably, the low-dielectric-low-loss adhesive layer includes a filler. The filler comprises one or a mixture of silica particles, hollow silica, porous silica, hollow glass microspheres, zeolite, molecular sieve, diatomaceous earth, boron nitride, and silicon nitride.

[0018] Preferably, the low-dielectric-low-loss adhesive layer has a thickness of 20 micrometers to 200 micrometers.

[0019] Preferably, the foamed plastic layer is characterized in that its dielectric constant is less than 2.00.

[0020] Preferably, the foamed plastic layer, in a second characteristic, is a low-loss resin foamed plastic layer, comprising one or more of polymethacrylamide foam material, porous / foamed polyimide material, and foamed polyester material.

[0021] Preferably, the air cavity is located between two foamed plastic layers arranged vertically in the layered structure. The layered structure also has a middle foamed plastic layer located between the two foamed plastic layers and situated on both sides of the air cavity. The air cavity is allowed to penetrate through one end, both ends, or neither end penetrates the end of the layered structure.

[0022] Preferably, the layered structure includes a first metal foil, a second metal foil, a first foamed plastic layer disposed near the first metal foil, a second foamed plastic layer disposed near the second metal foil, and an intermediate foamed plastic layer located between the first and second foamed plastic layers and situated on both sides of the layered structure. The first foamed plastic layer, the second foamed plastic layer, and the intermediate foamed plastic layers situated on both sides together form the air cavity. Low-dielectric-low-loss adhesive layers are provided between the first metal foil and the first foamed plastic layer, between the second metal foil and the second foamed plastic layer, between the first foamed plastic layer and the intermediate foamed plastic layers situated on both sides, and between the second foamed plastic layer and the intermediate foamed plastic layers situated on both sides.

[0023] Preferably, the first and second metal foils are copper foils, the first foamed plastic layer, the second foamed plastic layer, and the middle foamed plastic layer located on both sides are foamed PMI, and the low dielectric and low loss adhesive layer is a semi-cured adhesive sheet made of a low-loss cross-linked hydrocarbon polymer as the main resin.

[0024] In another aspect, this utility model also provides an electrical and electronic component, preferably a circuit board, made from the aforementioned ultra-low dielectric constant metal foil laminate.

[0025] The advantages of this utility model are: The ultra-low dielectric constant metal foil laminate and the circuit board made from the ultra-low dielectric constant metal foil laminate of this invention can meet the performance requirements of ultra-low dielectric constant (DK<1.1), low dielectric loss (Df<0.005), and metal foil peel strength >3 lbs / inch. It can reduce the refraction and reflection loss of high-frequency signals at the interface between the low dielectric and low loss adhesive layer and the foamed plastic layer. It can meet the requirements of strong adhesion between the metal foil and the substrate (>3 lbs / inch) and long-term reliability of the adhesion, that is, there will be no delamination of the metal foil and the substrate or blistering of the metal foil due to long-term use or the influence of the use environment.

[0026] Meanwhile, the antenna fabricated using the aforementioned circuit board can effectively increase antenna bandwidth and reduce signal delay, while also improving antenna gain and energy efficiency. Attached Figure Description

[0027] Figure 1 This is a three-dimensional schematic diagram of the layered structure involved in this embodiment.

[0028] Figure 2 This is an enlarged schematic diagram of the layered structure involved in this embodiment.

[0029] Figure 3 A schematic diagram of a series-fed patch antenna fabricated on an ultra-low dielectric substrate with an air cavity. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0031] This utility model discloses an ultra-low dielectric constant metal foil laminate, the design of which is that the laminate includes: at least one metal foil, at least one low dielectric low loss adhesive layer, and at least one foamed plastic layer, wherein at least one low dielectric low loss adhesive layer is provided between the metal foil and the foamed plastic layer; the metal foil, the low dielectric low loss adhesive layer, and the foamed plastic layer are constructed into a layered structure, and an air cavity is provided in the layered structure.

[0032] Specifically, the metal foil can be made of one or more of copper foil, aluminum foil, stainless steel, or embedded copper foil, and the thickness can be limited to 8 micrometers to 200 micrometers.

[0033] For the low dielectric and low loss adhesive layer, regarding the limitation of thickness, the thickness of the low dielectric and low loss adhesive layer is defined as 20 micrometers to 200 micrometers.

[0034] Regarding the material selection of the low dielectric and low loss adhesive layer, the main component is limited to one or a mixture of low loss crosslinked hydrocarbon polymer or low loss crosslinked polyphenylene ether polymer. Wherein: the low loss crosslinked hydrocarbon polymer can comprise one or more of butadiene polymer, isoprene polymer, butadiene-styrene rubber, butadiene-styrene block polymer, styrene-isoprene block polymer, styrene-isoprene-styrene block polymer, styrene-polybutadiene-styrene block polymer, divinylbenzene polymer, styrene-divinylbenzene polymer, styrene-butadiene-divinylbenzene polymer, ethylene propylene diene monomer rubber, butyl rubber and cyclic olefin polymer, which is crosslinked by free radical initiation; the low loss crosslinked polyphenylene ether polymer can comprise polyphenylene ether polymer with vinyl or allyl reactive groups modified at the end groups or side groups of the polymer, which is crosslinked by free radical initiation.

[0035] Further, the low dielectric and low loss adhesive layer may comprise a filler, and when comprising the filler, the filler may comprise one or a mixture of silica particles, hollow silica, porous silica, hollow glass microspheres, zeolite, molecular sieve, diatomite, boron nitride and silicon nitride.

[0036] After the aforementioned material selection, the dielectric constant of the low dielectric and low loss adhesive layer at a frequency of 10 GHz satisfies 2.0 < DK < 3.1, the dielectric loss of the low dielectric and low loss adhesive layer at a frequency of 10 GHz can be less than 0.004, the glass transition temperature of the low dielectric and low loss adhesive layer is greater than 240 °C, and the water absorption of the low dielectric and low loss adhesive layer is less than 0.3% (tested by soaking in water at 50 °C for 48 hours).

[0037] It should be noted that in the prior art, rubber or hydrocarbon rubber is used as the adhesive layer, but common rubber adhesives, such as butyl rubber and polyisobutyl rubber adhesives, have poor temperature resistance and weather resistance, and are prone to blistering and delamination under long-term use in high temperature and high humidity environments, especially in extreme environments. In the present utility model, the glass transition temperature of the low dielectric and low loss adhesive layer is greater than 240 °C, which is higher than the glass transition temperature of common crosslinked rubbers and resins, therefore, the adhesive layer has good thermal stability.

[0038] The aforementioned low-dielectric, low-loss adhesive layer has a water absorption rate of less than 0.3%, which can effectively isolate the influence of environmental humidity changes on the metal foil adhesion and ensure adhesion stability. In contrast, existing technologies such as epoxy resin, cyanate ester resin, and bismaleimide resin have water absorption rates exceeding these requirements. For example, cyanate ester resin systems are widely used in radar radome materials, such as BASF's 5575-2, Fiberite's X54-2, Hexcel's HX 1584-3, and Dow Chemical's XU-71787. The 701 cyanate ester resin system developed by the Aerospace Materials and Processes Research Institute has the following process requirements: ε=2.8, tanδ=0.009, Tg=205℃. Its water absorption rate after immersion in water at 22℃ for 40 days is 0.73%, significantly higher than the water absorption rate of the low-dielectric, low-loss adhesive layer described in this disclosure.

[0039] Regarding the selection of materials for the foamed plastic layer, the foamed plastic layer can be one or more of polymethacrylamide foam material, porous / foamed polyimide material, and foamed polyester material. After selecting the aforementioned materials, the dielectric constant of the foamed plastic layer can be less than 2.00, while the dielectric constant of the low-dielectric-low-loss adhesive layer is between 2.0 and 3.1, and the dielectric constants of the two are close.

[0040] It should be noted that in existing technologies, the dielectric constant of the adhesive layer is often relatively high (e.g., the dielectric constant of ordinary epoxy resin is 3.7–4.0, that of thermosetting PI is 4.0, and that of modified polyphenylene ether and TAIC systems is 3.2–3.5), while the dielectric constant of the foamed material is often less than 2.0. Therefore, when using adhesive layers with high dielectric constants in existing technologies, the actual test results of microwave devices often differ significantly from the simulation results. For example, when using foamed plastic to fabricate Luneburg lenses, the epoxy resin bonding leads to the aforementioned problems, mainly due to the large difference in dielectric constant between the adhesive layer resin and the foamed layer, resulting in microwave refraction and reflection losses. (YAN Xiulin, SHI Yunqi, ZHU Lina. Design ofLuneburg Lens Antenna Based on Novel Foam Materials[J]. Journal of Electronics&Information Technology, 2022, 44(12): 4111-4115. doi: 10.11999 / JEIT220569).

[0041] Therefore, one beneficial effect of this invention is that by controlling the dielectric constant and loss of the low-dielectric, low-loss adhesive layer to be as close as possible to the dielectric constant of the foamed plastic, the refraction and reflection losses when microwaves pass through the adhesive layer are reduced. Especially for foamed materials with a dielectric constant less than 2.0, the difference in dielectric constant between the adhesive layer and the substrate cannot be ignored in high-frequency and even millimeter-wave bands.

[0042] The following specific embodiments illustrate the detailed preparation method of the aforementioned ultra-low dielectric constant metal-coated laminate, which includes the following steps: S1. Prepare a low-dielectric-low-loss adhesive layer; S2. Place the low dielectric and low loss adhesive layer between the metal foil and the foamed plastic layer to form a multi-layer structure, and leave an air cavity in the multi-layer structure. S3. Place the above multi-layer structure in a laminator or molding machine. Under certain temperature and pressure, the adhesive layer cross-links, and at the same time, the metal foil and the foamed plastic layer are bonded together.

[0043] In this embodiment, the method for preparing the low dielectric and low loss adhesive layer described in S1 can be exemplified as follows: for example, a horizontal coating method can be used, in which a composition of resin, initiator, filler and other materials is selected to prepare a slurry, which is then coated on a base film, the solvent is removed, partial curing occurs, and a semi-cured adhesive sheet is prepared to serve as a low dielectric and low loss adhesive layer in the laminate.

[0044] It should be noted that in this embodiment: a low-loss cross-linked hydrocarbon polymer is selected as the main resin to fabricate the semi-cured adhesive sheet. Specifically, HM30S semi-cured adhesive sheet from Ningbo Turbulent Electronic Materials Co., Ltd. can be selected, which does not contain reinforcing materials but contains silica filler, has a thickness of 50 micrometers, a dielectric constant of 3.00 at 10 GHz, a dielectric loss of 0.0026 at 10 GHz, a glass transition temperature greater than 280 degrees Celsius, and a water absorption rate of 0.01% (50 degrees Celsius, 48 ​​hours). The metal foil is selected as copper foil, specifically TWL-HP Hoz copper foil from Luxembourg Circuit Copper Foil Factory. The foamed plastic layer is made of foamed PMI foam board, specifically ROHACELL 71HF from Yingchuang, with a thickness of 2.0 mm.

[0045] The temperature in S3 satisfies the following two conditions: (A) it can initiate the cross-linking reaction of the low dielectric and low loss adhesive layer; (B) it will not cause irreversible deformation of the foamed plastic layer.

[0046] The pressure described in S3 is not limited in this invention, provided that it effectively bonds the material without causing irreversible deformation of the foamed plastic layer or affecting the deformation of the air cavity. It should be noted that when manufacturing the laminate with the above structure, since the air cavity needs to be preserved, the pressing can be done by flat plate pressing or mold pressing, preferably by mold pressing. Alternatively, the pressure can be controlled by flat plate pressing, thereby ensuring that the air cavity is not affected during pressing.

[0047] Meanwhile, crosslinking and bonding can be carried out within the range of temperature: 80℃~300℃, pressure: 0.1kg / cm²~200kg / cm², and time: 1 minute~10 hours. More preferably, it can be carried out within the range of temperature: 150℃~250℃, pressure: 1kg / cm²~30kg / cm², and time: 1 minute~2 hours.

[0048] The materials prepared by the above method can also be used to manufacture electrical and electronic components. Specifically, circuit boards can also be made using low dielectric constant metal foil laminates as raw materials.

[0049] The low dielectric constant metal foil laminate is described below with a specific layered structure. The ultra-low dielectric constant metal foil laminate is plate-shaped and has a metal foil, a low dielectric low loss adhesive layer, and a foamed plastic layer. The metal foil, the low dielectric low loss adhesive layer, and the foamed plastic layer are stacked to form a layered structure, and the layered structure has an air cavity.

[0050] Specifically, refer to Figure 1 , Figure 2 In this embodiment, the layered structure includes a first metal foil 1, a second metal foil 2, a first foamed plastic layer 3 disposed near the first metal foil 1, a second foamed plastic layer 4 disposed near the second metal foil 2, and an intermediate foamed plastic layer 5 located between the first foamed plastic layer 3 and the second foamed plastic layer 4 and situated on both sides of the layered structure. The first foamed plastic layer 3, the second foamed plastic layer 4, and the intermediate foamed plastic layers 5 situated on both sides together form the air cavity 6. Low dielectric and low loss adhesive layers 7 are provided between the first metal foil 1 and the first foamed plastic layer 3, between the second metal foil 2 and the second foamed plastic layer 4, between the first foamed plastic layer 3 and the intermediate foamed plastic layers 5 situated on both sides, and between the second foamed plastic layer 4 and the intermediate foamed plastic layers 5 situated on both sides. It should be noted that the specific shape, size and distribution of the air cavity 6 are not limited. In addition to forming a long rectangle in this embodiment, other shapes are allowed. In addition to the air cavity 6 shown in this embodiment having both ends penetrating the ends of the layered structure, in other embodiments, the air cavity 6 is also allowed to have one end penetrating or not penetrating the ends of the layered structure. That is to say, the air cavity 6 can be a closed cavity or an open cavity.

[0051] Regarding the material selection of metal foils, foamed plastic layers, and low-dielectric low-loss adhesive layers, in this embodiment, the details are as follows: the first metal foil 1 and the second metal foil 2 are both copper foils; the first foamed plastic layer 3, the second foamed plastic layer 4, and the intermediate foamed plastic layer 5 disposed on two separate sides are all foamed PMI; the low-dielectric low-loss adhesive layers 7 are all prepreg adhesive sheets made of low-loss crosslinked hydrocarbon polymer as the main resin, preferably HM30S prepreg adhesive sheet from Ningbo Turbulence Electronic Material Co., Ltd., so that it contains no reinforcing material but includes silica filler.

[0052] For conventional existing substrates and conventional existing adhesive films, the conventional adhesive film is generally an FR4 adhesive sheet with epoxy resin as the main component (DK>3.5), and the conventional substrate refers to a substrate with one or more of epoxy resin, polyphenylene ether resin, hydrocarbon resin, BT resin, and polytetrafluoroethylene as the main resin, and the dielectric constant of the conventional substrate is generally greater than 2.10. In contrast, the foamed material in this embodiment (DK<2.0) and the adhesive material of the low-dielectric low-loss adhesive layer in this embodiment (2.0<DK<3.1) both have extremely low dielectric constants. In addition, in the layered laminate of the above structure, an air cavity 6 is provided, after the air cavity 6 is disposed, the dielectric constant in the thickness direction in the area of the air cavity 6 can be further reduced to be close to that of air. Therefore, the laminated board in this embodiment can reduce the comprehensive dielectric constant in the thickness direction to 1.03-1.05, so that the laminated board in this embodiment forms an ultra-low dielectric constant metal-clad laminate (DK<1.1). Manufacturing transmission lines and antennas with this foamed substrate can effectively reduce the insertion loss of the transmission lines, and the prepared patch antenna with an air cavity has unique advantages in terms of gain and radiation efficiency.

[0053] Reference Figure 3 , which is a schematic diagram of a series-fed patch antenna fabricated from an ultra-low dielectric substrate with an air cavity 6.

[0054] The above description is only a preferred embodiment of the present utility model, and is not intended to limit the patent scope of the present utility model. Any equivalent structural transformation made by using the description and accompanying drawings of the present utility model under the inventive concept of the present utility model, or direct / indirect application to other related technical fields, shall be included in the patent protection scope of the present utility model.

Claims

1. A metal foil-coated laminate with ultra-low dielectric constant, characterized in that, Comprising: at least one layer of metal foil, at least one layer of low-dielectric low-loss adhesive layer, and at least one layer of foamed plastic layer, wherein at least one layer of low-dielectric low-loss adhesive layer is arranged between the metal foil and the foamed plastic layer; the metal foil, the low-dielectric low-loss adhesive layer and the foamed plastic layer are constructed into a layered structure, and the layered structure is provided with an air cavity.

2. The ultra-low dielectric constant metal foil laminate as described in claim 1, characterized in that: the metal foil comprises one of copper foil, aluminum foil and stainless steel; the thickness of the metal foil is 8 micrometers to 200 micrometers.

3. The ultra-low dielectric constant metal foil laminate as described in claim 2, characterized in that: the layered structure has a dielectric constant DK<1.1, a dielectric loss Df<0.005, and a peeling strength of the metal foil>3 lbs / inch; the dielectric constant of the low-dielectric low-loss adhesive layer satisfies 2.0<DK<3.1, and the dielectric loss of the low-dielectric low-loss adhesive layer is less than 0.004; the glass transition temperature of the low-dielectric low-loss adhesive layer is higher than 240°C; the water absorption of the low-dielectric low-loss adhesive layer is less than 0.3%.

4. The ultra-low dielectric constant metal foil laminate as described in claim 3, characterized in that: the main component of the low-dielectric low-loss adhesive layer is a low-loss crosslinked hydrocarbon polymer.

5. The ultra-low dielectric constant metal foil laminate as described in claim 3, characterized in that: the main component of the low-dielectric low-loss adhesive layer is a low-loss crosslinked polyphenylene ether polymer; the low-loss crosslinked polyphenylene ether polymer is formed by subjecting a polyphenylene ether polymer with vinyl or allyl active groups modified at the terminal groups or side groups of the polymer to free radical initiated crosslinking.

6. The ultra-low dielectric constant metal foil laminate as described in claim 4 or 5, characterized in that: the thickness of the low-dielectric low-loss adhesive layer is 20 micrometers to 200 micrometers; the low-dielectric low-loss adhesive layer comprises a filler.

7. The ultra-low dielectric constant metal foil laminate as described in claim 1, characterized in that: the dielectric constant of the foamed plastic layer is less than 2.00; the foamed plastic layer comprises one of polymethacrylimide foam materials, porous / foamed polyimide materials and foamed polyester materials.

8. The ultra-low dielectric constant metal foil laminate as described in claim 7, characterized in that: the air cavity is located between two upper and lower foamed plastic layers arranged in the layered structure, the layered structure is further provided with intermediate foamed plastic layers located between the two upper and lower foamed plastic layers and respectively arranged at two sides of the air cavity, and the air cavity can penetrate through the end part of the layered structure at a single end, penetrate through at both ends, or not penetrate through at both ends.

9. The ultra-low dielectric constant metal foil laminate as described in claim 8, characterized in that: the layered structure comprises a first metal foil, a second metal foil, a first foamed plastic layer arranged close to the first metal foil, a second foamed plastic layer arranged close to the second metal foil, and intermediate foamed plastic layers located between the first foamed plastic layer and the second foamed plastic layer and respectively arranged at two sides of the layered structure, the first foamed plastic layer, the second foamed plastic layer and the intermediate foamed plastic layers respectively arranged at two sides jointly enclose to form the air cavity, and low-dielectric low-loss adhesive layers are respectively arranged between the first metal foil and the first foamed plastic layer, between the second metal foil and the second foamed plastic layer, between the first foamed plastic layer and the intermediate foamed plastic layers respectively arranged at two sides, and between the second foamed plastic layer and the intermediate foamed plastic layers respectively arranged at two sides.

10. The ultra-low dielectric constant metal foil laminate as described in claim 9, characterized in that: the first metal foil and the second metal foil are copper foils, the first foamed plastic layer, the second foamed plastic layer and the intermediate foamed plastic layers respectively arranged at two sides are foamed PMI, and the low-dielectric low-loss adhesive layer is constructed by a semi-cured adhesive sheet prepared with a low-loss crosslinked hydrocarbon polymer as a main resin.

11. A circuit board, characterized in that, manufactured from the ultra-low dielectric constant metal-clad laminate according to any one of claims 1 to 10 as a raw material.

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