Microwave dielectric substrate and multilayer microwave dielectric substrate

Abstract

The present application relates to a kind of microwave dielectric substrates, the microwave dielectric substrate includes foam matrix, first resin composition layer and metal foil are sequentially stacked on the two opposite surfaces of the foam matrix, the roughness of the side of the foam matrix is less than or equal to 20 μm, alternatively, the side of the foam matrix is coated with second resin composition layer, and the roughness of the second resin composition layer is less than or equal to 50 μm.The present application also relates to a kind of multilayer microwave dielectric substrate, including at least two layers of the microwave dielectric substrate, and the adhesive layer is arranged between adjacent two layers of the microwave dielectric substrate.The microwave dielectric substrate of the present application is low in density, and has low dielectric constant, low dielectric loss, high wave-transmitting performance and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of electronic industry technology, and in particular to microwave dielectric substrates and multilayer microwave dielectric substrates. Background Technology

[0002] Traditional microwave dielectric substrates are mainly divided into glass fiber reinforced polytetrafluoroethylene resin series, ceramic powder filled polytetrafluoroethylene resin series, and ceramic powder filled thermosetting resin series. However, glass fiber and ceramic powder have disadvantages such as high density, high dielectric constant and low transmittance. Therefore, these microwave dielectric substrates cannot meet the requirements of lightweighting, nor can they achieve the performance requirements of low dielectric constant, low dielectric loss and high transmittance. Summary of the Invention

[0003] Therefore, it is necessary to provide a microwave dielectric substrate and a multilayer microwave dielectric substrate to address the above problems. The microwave dielectric substrate has low density and features low dielectric constant, low dielectric loss, high wave transmission performance, and excellent mechanical properties.

[0004] A microwave dielectric substrate includes a foam substrate, wherein a first resin composition layer and a metal foil are sequentially stacked on two opposite surfaces of the foam substrate, and the roughness of the side surface of the foam substrate is less than or equal to 20 μm; or, the side surface of the foam substrate is covered with a second resin composition layer, and the roughness of the second resin composition layer is less than or equal to 50 μm.

[0005] In one embodiment, the foam matrix has a closed-cell structure.

[0006] In one embodiment, the pore size of the bubble is 20μm-500μm.

[0007] In one embodiment, the thickness of the first resin composition layer is 10 μm-700 μm.

[0008] In one embodiment, the foam matrix is ​​activated to generate a first active functional group, which includes at least one of alkenyl, alkynyl, formyl, carbonyl, and methacrylic acid groups.

[0009] In one embodiment, the foam matrix is ​​selected from at least one of polyamide foam matrix, hydrocarbon resin foam matrix, polyurethane foam matrix, phenolic foam matrix, and high-energy adhesive foam matrix.

[0010] In one embodiment, the raw materials of the first resin composition layer include a first resin and a first curing agent. The molecular chain of the first resin includes a second active functional group. The second active functional group includes at least one of vinyl, amino, methacrylate, sulfhydryl, carboxyl, and cyano groups. The first active functional group and the second active functional group can form chemical bonds.

[0011] The raw materials of the second resin composition layer include a second resin and a second curing agent. The molecular chain of the second resin includes a third active functional group, which includes at least one of vinyl, amino, methacrylate, sulfhydryl, carboxyl, and cyano groups. The first active functional group and the third active functional group can form a chemical bond.

[0012] In one embodiment, the first resin and the second resin are each independently selected from at least one of epoxy resin, cyanate ester resin, phenolic resin, benzoxazine resin, bismaleimide resin, hydrocarbon resin, and polyphenylene ether resin.

[0013] In one embodiment, the metal foil has a modified surface with a silane coupling agent, the first resin composition layer is stacked on the modified surface side, and the second active functional group can form a chemical bond with the silane coupling agent.

[0014] In one embodiment, the metal foil is selected from at least one of nickel foil, tin foil, copper foil, silver foil, and gold foil.

[0015] A multilayer microwave dielectric substrate includes at least two microwave dielectric substrates, with an adhesive layer disposed between adjacent microwave dielectric substrates.

[0016] The microwave dielectric substrate of the present invention has the following beneficial effects:

[0017] First, the low density of the foam matrix allows for the lightweighting of microwave dielectric substrates.

[0018] Secondly, the foam matrix has a low dielectric constant (Dk), low dielectric loss (Df), and excellent wave transmission performance. At the same time, by using a foam matrix with a side roughness of less than or equal to 20 μm, or by using a second resin composition to seal the side of the foam matrix to make its roughness less than or equal to 50 μm, the moisture absorption rate of the foam matrix can be reduced. Therefore, the microwave dielectric substrate of the present invention has a dielectric constant of less than or equal to 4.0, a dielectric loss of less than or equal to 0.005, and a wave transmission rate of greater than or equal to 80% at 10 GHz, exhibiting low dielectric constant, low dielectric loss, and high wave transmission performance. Attached Figure Description

[0019] Figure 1This is a cross-sectional schematic diagram of the microwave dielectric substrate of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of the multilayer microwave dielectric substrate of the present invention.

[0021] In the figure: 10, microwave dielectric substrate; 20, adhesive layer; 101, foam matrix; 102, first resin composition layer; 103, metal foil; 104, second resin composition layer. Detailed Implementation

[0022] The microwave dielectric substrate and multilayer microwave dielectric substrate provided by the present invention will be further described below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, the microwave dielectric substrate 10 provided by the present invention includes a foam substrate 101. A first resin composition layer 102 and a metal foil 103 are sequentially stacked on both opposite surfaces of the foam substrate 101. The roughness of the side surface of the foam substrate 101 is less than or equal to 20 μm. Alternatively, the side surface of the foam substrate 101 is covered with a second resin composition layer 104, and the roughness of the second resin composition layer 104 is less than or equal to 50 μm.

[0024] In the microwave dielectric substrate 10 of the present invention, the foam matrix 101 has a low density and at the same time has a low dielectric constant, low dielectric loss and excellent wave transmission performance. Thus, on the one hand, the microwave dielectric substrate 10 can be made lightweight, and on the other hand, the microwave dielectric substrate 10 has a low dielectric constant, low dielectric loss and high wave transmission performance at a wide bandwidth and high frequency of operation.

[0025] Specifically, the microwave dielectric substrate 10 of the present invention has a dielectric constant of less than or equal to 4.0, a dielectric loss of less than or equal to 0.005, and a transmittance of greater than or equal to 80% at 10 GHz.

[0026] However, the foam matrix 101 has a high moisture absorption rate, which will reduce the dielectric and wave transmission properties of the microwave dielectric substrate 10 after moisture absorption, affecting the normal use of the microwave dielectric substrate 10. Therefore, this invention uses a foam matrix 101 with a side surface roughness of less than or equal to 20 μm, or a second resin composition layer 104 is used to seal the side surface of the foam matrix 101, making its roughness less than or equal to 50 μm, so that the moisture absorption rate of the microwave dielectric substrate 10 is controlled within 3%, thereby effectively reducing the moisture absorption rate of the foam matrix 101 and improving the dielectric and wave transmission properties of the microwave dielectric substrate 10.

[0027] To further reduce the moisture absorption rate of the microwave dielectric substrate 10 and control it to within 1.5%, the present invention uses a foam matrix 101 with a side roughness of less than or equal to 10 μm, or uses a second resin composition layer 104 to seal the side surface of the foam matrix 101, making its roughness less than or equal to 20 μm.

[0028] In this invention, the foam cells in the foam matrix 101 are preferably closed-cell structures, that is, the foam matrix 101 preferably adopts a closed-cell structure, wherein the pore size of the foam cells is preferably 20μm-500μm, more preferably 30μm-200μm. On the one hand, this can further reduce the moisture absorption rate of the foam matrix 101, and on the other hand, it can also improve the strength of the foam matrix 101.

[0029] In one embodiment, the thickness of the foam substrate 101 is preferably 0.5 mm to 20 mm, and the thickness of the metal foil 103 is 10 μm to 100 μm.

[0030] In one embodiment, the foam matrix 101 is selected from foam matrices that have undergone activation treatment to generate a first active functional group, wherein the first active functional group includes at least one selected from alkenyl, alkynyl, formyl, carbonyl, and methacrylic acid groups. Optionally, the foam matrix 101 is selected from at least one selected from polyamide foam matrix, hydrocarbon resin foam matrix, polyurethane foam matrix, phenolic foam matrix, and high-energy adhesive foam matrix.

[0031] In one embodiment, the activation treatment employs plasma treatment because plasma treatment of the foam matrix 101 can also improve the compressive strength of the pore walls on the surface of the foam matrix 101. Specifically, the compressive strength of the pore walls can reach more than 1.5 MPa, thereby reducing the possibility of pore wall breakage.

[0032] In this invention, the raw materials of the first resin composition layer 102 include a first resin and a first curing agent. The molecular chain of the first resin includes a second active functional group, which includes at least one of vinyl, amino, methacrylate, sulfhydryl, carboxyl, and cyano groups. The first active functional group and the second active functional group can form chemical bonds.

[0033] Similarly, the raw materials of the second resin composition layer 104 include a second resin and a second curing agent, wherein the molecular chain of the second resin includes a third active functional group, the third active functional group including at least one of vinyl, amino, methacrylate, sulfhydryl, carboxyl, and cyano groups, and the first active functional group and the third active functional group can form a chemical bond.

[0034] Optionally, the first resin and the second resin are each independently selected from at least one of epoxy resin, cyanate ester resin, phenolic resin, benzoxazine resin, bismaleimide resin, hydrocarbon resin, and polyphenylene ether resin, specifically selected based on their ability to react with the first active functional group to form a chemical bond.

[0035] The function of the first curing agent is to promote the curing of the first resin. Therefore, the first curing agent can be selected according to the specific first resin. Similarly, the function of the second curing agent is to promote the curing of the second resin. The second curing agent can be selected according to the specific second resin.

[0036] Optionally, the first resin composition layer 102 may further include a first dielectric filler, thereby adjusting the dielectric properties of the first resin composition layer 102, and the second resin composition layer 104 may further include a second dielectric filler, thereby adjusting the dielectric properties of the second resin composition layer 104.

[0037] Optionally, the first dielectric filler and the second dielectric filler are each independently selected from at least one of hollow silica filler or fused silica. Based on 100 parts by weight of the first resin, the amount of the first dielectric filler is less than or equal to 60 parts by weight, and based on 100 parts by weight of the second resin, the amount of the second dielectric filler is less than or equal to 100 parts by weight.

[0038] It should be noted that the first resin composition layer 102 and the second resin composition layer 104 in this invention can be the same resin composition layer or different resin composition layers. Similarly, the first resin composition layer 102 on the two opposite surfaces of the foam matrix 101 can be the same or different resin composition layers, and the second resin composition layer 104 on different sides of the foam matrix 101 can also be the same or different resin composition layers.

[0039] In order to achieve chemical bonding between the metal layer 103 and the first resin composition layer 102, the metal foil 103 is modified with a silane coupling agent in this invention. Therefore, the metal foil 103 of this invention has a modified surface with a silane coupling agent. The first resin composition layer 102 is stacked on the modified surface side, and the second active functional group can form a chemical bond with the silane coupling agent.

[0040] Optionally, the metal foil 103 is selected from at least one of nickel foil, tin foil, copper foil, silver foil, and gold foil, and the silane coupling agent is selected based on its ability to react with the second active functional group to form a chemical bond.

[0041] In this invention, when the first resin composition layer 102 and the foam matrix 101, and the first resin composition layer 102 and the metal foil 103 are connected by chemical bonds, the peel strength of the microwave dielectric substrate 10 can be effectively improved compared with the physical bonding method, thereby giving the microwave dielectric substrate 10 excellent mechanical properties.

[0042] Furthermore, while ensuring peel strength, the thickness of the first resin composition layer 102 can be reduced. In one embodiment, the thickness of the first resin composition layer 102 is 10μm-700μm, preferably 10μm-400μm, to reduce the influence of the first resin composition layer 102 on the dielectric properties and wave transmission properties of the microwave dielectric substrate 10.

[0043] Furthermore, the microwave dielectric substrate of the present invention can achieve a dielectric constant of less than 3.0 at 10 GHz, a dielectric loss of less than or equal to 0.003, and a transmittance of more than 90% at vertical incidence, exhibiting low dielectric constant, low dielectric loss, and high transmittance performance.

[0044] In one embodiment, the microwave dielectric substrate 10 of the present invention is prepared in the following steps:

[0045] (1) First, the foam matrix 101 is subjected to plasma treatment;

[0046] (2) The first resin composition is coated on two opposite surfaces of the foam matrix 101, and the second resin composition is coated on the side surface of the foam matrix 101;

[0047] (3) The metal foil 103 is modified by using a silane coupling agent to give the metal foil 103 a modified surface of the silane coupling agent. Then the modified surface of the metal foil 103 is applied to the two first resin compositions to obtain a preform.

[0048] (4) The precast plate is solidified and formed by hot press molding or vacuum bag autoclave molding to obtain microwave dielectric substrate 10.

[0049] like Figure 2 As shown, the multilayer microwave dielectric substrate provided by the present invention includes at least two microwave dielectric substrates 10, and an adhesive layer 20 is provided between two adjacent microwave dielectric substrates 10.

[0050] In one embodiment, the adhesive of the adhesive layer is selected from at least one of polyphenylene ether resin, epoxy resin, cyanate ester resin, phenolic resin, benzoxazine resin, bismaleimide resin, and hydrocarbon resin.

[0051] Therefore, it can meet the usage requirements of more scenarios, and the number of layers of microwave dielectric substrate 10 can be adjusted as needed.

[0052] When preparing a multilayer microwave dielectric substrate, the microwave dielectric substrate 10 and the adhesive layer 20 can be pressed and formed by hot press molding or vacuum bag autoclave molding.

[0053] The microwave dielectric substrate and the multilayer microwave dielectric substrate will be further described below through specific embodiments.

[0054] Example 1

[0055] In this embodiment, the foam matrix 101 is a polymethacrylimide (PMI) foam matrix. The PMI foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1.0 mm.

[0056] A first resin composition layer 102 with a thickness of 20 μm is stacked on both opposite surfaces of the PMI foam matrix. The raw materials of the first resin composition layer 102 include a first resin, which is a modified polyphenylene ether resin, a first curing agent, which is triallyl isocyanate, and a first dielectric filler, which is hollow silica. The mass ratio of the first resin, the first curing agent, and the first dielectric filler is 50:45:5. The vinyl functional groups of the first resin react with the vinyl functional groups generated by plasma treatment of the PMI foam matrix to form a first chemical bond.

[0057] The side of the PMI foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is a modified polyphenylene ether resin, the second curing agent is triallyl isocyanurate, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The vinyl functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the PMI foam matrix to form a third chemical bond.

[0058] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 facing away from the PMI foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional groups of the vinyl silane coupling agent react with the vinyl functional groups of the first resin to form a second chemical bond.

[0059] Example 2

[0060] In this embodiment, the foam matrix 101 is a polymethacrylimide (PMI) foam matrix. The PMI foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1.0 mm.

[0061] A first resin composition layer 102 with a thickness of 50 μm is stacked on both opposite surfaces of the PMI foam matrix. The raw materials of the first resin composition layer 102 include a first resin, which is a modified polyphenylene ether resin, a first curing agent, which is triallyl isocyanurate, and a first dielectric filler, which is hollow silica. The mass ratio of the first resin, the first curing agent, and the first dielectric filler is 50:45:5. The vinyl functional groups of the first resin react with the vinyl functional groups generated by plasma treatment of the PMI foam matrix to form a first chemical bond.

[0062] The side of the PMI foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is a modified polyphenylene ether resin, the second curing agent is triallyl isocyanurate, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The vinyl functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the PMI foam matrix to form a third chemical bond.

[0063] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 facing away from the PMI foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional groups of the vinyl silane coupling agent react with the vinyl functional groups of the first resin to form a second chemical bond.

[0064] Example 3

[0065] In this embodiment, the foam matrix 101 is a PMI foam matrix. The PMI foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1.0 mm.

[0066] A first resin composition layer 102 with a thickness of 20 μm is stacked on both opposite surfaces of the PMI foam matrix. In the raw materials of the first resin composition layer 102, the first resin is cyanate ester, the first curing agent is dicyandiamide, and the first dielectric filler is hollow silica. The mass ratio of the first resin, the first curing agent and the first dielectric filler is 50:45:5. The cyano functional groups of the first resin react with the vinyl functional groups generated by plasma treatment of the PMI foam matrix to form the first chemical bond.

[0067] The side of the PMI foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is cyanate ester, the second curing agent is dicyandiamide, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The cyano functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the PMI foam matrix to form a third chemical bond.

[0068] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 facing away from the PMI foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional group of the vinyl silane coupling agent reacts with the cyano functional group of the first resin to form a second chemical bond.

[0069] Example 4

[0070] In this embodiment, the foam matrix 101 is a PMI foam matrix. The PMI foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1 mm.

[0071] A first resin composition layer 102 with a thickness of 50 μm is stacked on both opposite surfaces of the PMI foam matrix. The raw materials of the first resin composition layer 102 include a first resin, a cyanate ester, a first curing agent, a dicyandiamide, and a first dielectric filler, which are hollow silica. The mass ratio of the first resin, the first curing agent, and the first dielectric filler is 50:45:5. The cyano functional groups of the first resin react with the vinyl functional groups generated by plasma treatment of the PMI foam matrix to form a first chemical bond.

[0072] The side of the PMI foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is cyanate ester, the second curing agent is dicyandiamide, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The cyano functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the PMI foam matrix to form a third chemical bond.

[0073] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 facing away from the PMI foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional group of the vinyl silane coupling agent reacts with the cyano functional group of the first resin to form a second chemical bond.

[0074] Example 5

[0075] In this embodiment, the foam matrix 101 is a polyimide foam matrix. The polyimide foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1.0 mm.

[0076] A first resin composition layer 102 with a thickness of 20 μm is stacked on both opposite surfaces of the polyimide foam matrix. The raw materials of the first resin composition layer 102 include a first resin, which is a modified polyphenylene ether resin, a first curing agent, which is triallyl isocyanurate, and a first dielectric filler, which is hollow silica. The mass ratio of the first resin, the first curing agent, and the first dielectric filler is 50:45:5. The vinyl functional groups of the first resin react with the vinyl functional groups of the polyimide foam matrix generated by plasma treatment to form a first chemical bond.

[0077] The side surface of the polyimide foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is a modified polyphenylene ether resin, the second curing agent is triallyl isocyanurate, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the polyimide foam matrix to form a third chemical bond.

[0078] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 that are away from the polyimide foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional groups of the vinyl silane coupling agent react with the vinyl functional groups of the first resin to form a second chemical bond.

[0079] Example 6

[0080] In this embodiment, the foam matrix 101 is a polyimide foam matrix. The polyimide foam matrix is ​​plasma treated and has a closed-cell structure with a pore size of 50 μm and a thickness of 1.0 mm.

[0081] A first resin composition layer 102 with a thickness of 50 μm is stacked on both opposite surfaces of the polyimide foam matrix. The raw materials of the first resin composition layer 102 include a first resin, which is a modified polyphenylene ether resin, a first curing agent, which is triallyl isocyanurate, and a first dielectric filler, which is hollow silica. The mass ratio of the first resin, the first curing agent, and the first dielectric filler is 50:45:5. The vinyl functional groups of the first resin react with the vinyl functional groups of the polyimide foam matrix generated by plasma treatment to form a first chemical bond.

[0082] The side surface of the polyimide foam matrix is ​​coated with a second resin composition layer 104 with a surface roughness of 10 μm. In the raw materials of the second resin composition layer 104, the second resin is a modified polyphenylene ether resin, the second curing agent is triallyl isocyanurate, and the second dielectric filler is fused silica. The mass ratio of the second resin, the second curing agent and the second dielectric filler is 50:40:10. The vinyl functional groups of the second resin react with the vinyl functional groups generated by the plasma treatment of the polyimide foam matrix to form a third chemical bond.

[0083] Copper foil with a thickness of 35 μm is stacked on the surfaces of the two first resin composition layers 102 that are away from the polyimide foam matrix. The copper foil has a modified side with a vinyl silane coupling agent. The modified side of the copper foil is stacked on the first resin composition layer 102. The vinyl functional groups of the vinyl silane coupling agent react with the vinyl functional groups of the first resin to form a second chemical bond.

[0084] Example 7

[0085] The only difference between Example 7 and Example 1 is that the PMI foam matrix in Example 7 is coated with a second resin layer 104 with a roughness of 30 μm.

[0086] Example 8

[0087] The only difference between Example 8 and Example 1 is that the side of the PMI foam matrix in Example 8 is not covered with the second resin composition layer, and the surface roughness of the foam matrix side is 5 μm.

[0088] Example 9

[0089] The only difference between Example 9 and Example 1 is that the side of the PMI foam matrix in Example 9 is not covered with the second resin composition layer, and the surface roughness of the foam matrix side is 15 μm.

[0090] Example 10

[0091] The only difference between Example 10 and Example 1 is that the PMI foam matrix in Example 10 has an open-cell structure.

[0092] Example 11

[0093] The only difference between Example 11 and Example 1 is that the PMI foam matrix in Example 11 was not subjected to plasma treatment.

[0094] Example 12

[0095] The difference between Example 12 and Example 1 is that in Example 12, the first resin in the first resin composition layer 102 is an unmodified polyphenylene ether resin. The first resin cannot react with the vinyl functional groups generated by plasma treatment of the PMI foam matrix to form the first chemical bond, and the first resin composition layer is physically bonded to the PMI foam matrix.

[0096] Example 13

[0097] The only difference between Example 13 and Example 1 is that the thickness of the first resin composition layer 102 in Example 13 is 600 μm.

[0098] Example 14

[0099] The only difference between Example 14 and Example 13 is that the pore size of the foam matrix 101 in Example 14 is 300 μm.

[0100] Example 15

[0101] The only difference between Example 15 and Example 13 is that the pore size of the foam matrix 101 in Example 15 is 600 μm.

[0102] Example 16

[0103] The only difference between Example 16 and Example 13 is that the pore size of the foam matrix 101 in Example 16 is 600 μm and the thickness of the first resin layer is 1200 μm.

[0104] Example 17

[0105] The difference between Example 17 and Example 1 is that in Example 17, the first resin in the first resin composition layer 102 is a modified polyphenylene ether resin, the metal foil 103 is not modified with a coupling agent, the first resin cannot react with the metal foil to form a second chemical bond, and the first resin composition layer 102 and the metal foil 103 are physically bonded.

[0106] Example 18

[0107] The only difference between Example 18 and Example 1 is that the second resin composition layer 104 in Example 18 is made of unmodified polyphenylene ether resin, which prevents it from being chemically bonded to the foam matrix.

[0108] Comparative Example 1

[0109] The only difference between Comparative Example 1 and Example 1 is that the surface roughness of the second resin composition layer 104 in Comparative Example 1 is 85 μm.

[0110] Comparative Example 2

[0111] The only difference between Comparative Example 2 and Example 1 is that the side of the PMI foam matrix in Comparative Example 2 is not covered with the second resin composition layer, and the surface roughness of the foam matrix side is 35 μm.

[0112] The performance of the microwave dielectric substrates of Examples 1-18 and Comparative Examples 1-2 was tested. The specific test contents and standards are shown below, and the test results are shown in Table 1.

[0113] The dielectric constant testing method adopts IEC61189-2-721-2015;

[0114] The dielectric loss detection method adopts IEC61189-2-721-2015;

[0115] The transmittance testing method adopts GJB 7945-2012;

[0116] The peel strength (N / mm) test method adopts GB / T 4722-2017 7.2.1;

[0117] The moisture absorption rate test method is as follows: place the board in a 110℃ oven to dry for 2 hours, weigh the mass m1, place the dried board in an environment with 80% humidity for 12 hours, weigh the mass m2, and the moisture absorption rate = (m2-m1) / m1;

[0118] Table 1

[0119]

[0120] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0121] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A microwave dielectric substrate, characterized in that, The substrate includes a foam matrix, on which a first resin composition layer and a metal foil are sequentially stacked on both opposite surfaces. The roughness of the side surface of the foam matrix is ​​less than or equal to 20 μm, so that the moisture absorption rate of the microwave dielectric substrate is controlled within 3%. Alternatively, the side surface of the foam matrix is ​​covered with a second resin composition layer, the roughness of which is less than or equal to 50 μm, so that the moisture absorption rate of the microwave dielectric substrate is controlled within 3%. The thickness of the first resin composition layer is 10μm-700μm; the foam matrix is ​​selected from polymethacrylamide foam matrix or polyimide foam matrix; The pore size of the foam matrix is ​​20μm-500μm. The raw material of the first resin composition layer includes a first resin, which is selected from cyanate ester resin and / or polyphenylene ether resin. The raw material of the second resin composition layer includes a second resin, which is selected from cyanate ester resin and / or polyphenylene ether resin.

2. The microwave dielectric substrate according to claim 1, characterized in that, The foam matrix has a closed-cell structure.

3. The microwave dielectric substrate according to any one of claims 1-2, characterized in that, The foam matrix is ​​activated to generate a first active functional group, which includes at least one of alkenyl, alkynyl, formyl, carbonyl, and methacrylic acid groups.

4. The microwave dielectric substrate according to claim 3, characterized in that, The compressive strength of the pore walls of the foam matrix is ​​greater than or equal to 1.5 MPa.

5. The microwave dielectric substrate according to claim 3, characterized in that, The raw materials of the first resin composition layer include a first curing agent, and the molecular chain of the first resin includes a second active functional group, which includes at least one of vinyl, amino, methacrylate, carboxyl, and cyano groups. The first active functional group and the second active functional group can form chemical bonds. The raw materials of the second resin composition layer include a second curing agent, and the molecular chain of the second resin includes a third active functional group, which includes at least one of vinyl, amino, methacrylate, carboxyl, and cyano groups, and the first active functional group and the third active functional group can form a chemical bond.

6. The microwave dielectric substrate according to claim 5, characterized in that, The metal foil has a modified surface with a silane coupling agent, and the first resin composition layer is stacked on the modified surface side. The second active functional group can form a chemical bond with the silane coupling agent.

7. The microwave dielectric substrate according to claim 6, characterized in that, The metal foil is selected from at least one of nickel foil, tin foil, copper foil, silver foil, and gold foil.

8. A multilayer microwave dielectric substrate, characterized in that, It comprises at least two microwave dielectric substrates as described in any one of claims 1-7, wherein an adhesive layer is provided between two adjacent microwave dielectric substrates.

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