Broadband wave-absorbing packaging structure based on alternation of magnetic layers and dielectric layers and preparation method

Abstract

The invention discloses a broadband wave-absorbing packaging structure based on alternation of magnetic layers and dielectric layers, and the structure comprises a substrate, and the magnetic layers and the dielectric layers are alternately stacked on the substrate. The magnetic layer is formed by compounding Fe3O4 nanoparticles and a polyimide precursor; the dielectric layer is formed by hot pressing silicon carbide nanowires and boron nitride powder; oxygen plasma treatment is adopted between the magnetic layer and the dielectric layer, and a silane coupling agent is adopted to enhance the interface bonding force. The full frequency band of 1-100 GHz can be covered through the magnetic layers and the dielectric layers which are stacked alternately, and meanwhile the high temperature of 200 DEG C and the high-humidity environment of 85% RH can be tolerated at the same time.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers and a preparation method thereof. Background Art

[0002] Single absorbing material: Traditional absorbing layers use a single magnetic material (Fe3O4) or dielectric material (carbon-based). Low frequencies (1-10GHz) rely on magnetic loss, and high frequencies (>30GHz) rely on dielectric loss. A single material cannot cover the entire frequency band.

[0003] Planar structure limitations: The use of a planar mixed material layer leads to enhanced reflection of high-frequency electromagnetic waves, and the measured shielding effectiveness (SE) at 28GHz is only 25-35dB.

[0004] Insufficient thermal stability: The dielectric properties of polymer-based absorbing materials (such as CNT / epoxy resin) deteriorate at high temperatures (>150°C), and the absorption rate decreases by >30%.

[0005] Therefore, it is necessary to design an absorbing structure that can achieve SE > 45 dB and absorptivity > 95% in a wide frequency band of 1-100 GHz, while being resistant to high temperature (200° C.) and high humidity (85% RH) environments.

[0006] To this end, a broadband wave-absorbing packaging structure and a preparation method based on alternating magnetic layers and dielectric layers are proposed. Summary of the Invention

[0007] The object of the present invention is to provide a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers and a preparation method thereof, so as to solve the problems raised in the above-mentioned background technology.

[0008] To achieve the above-mentioned object, the present invention provides the following technical solution: a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers, comprising a substrate on which magnetic layers and dielectric layers are alternately stacked;

[0009] The magnetic layer is a composite of Fe3O4 nanoparticles and polyimide precursor;

[0010] The dielectric layer is formed by hot pressing of silicon carbide nanowires and boron nitride powder;

[0011] The magnetic layer and the dielectric layer are treated with oxygen plasma and a silane coupling agent is used to enhance the interface bonding force.

[0012] Preferably, the thickness of the magnetic layer is 50±5 μm, and the thickness of the dielectric layer is 30±3 μm.

[0013] Preferably, the stacking period of the magnetic layer and the dielectric layer is 4 to 8 layers.

[0014] Preferably, the silicon carbide nanowires have a diameter of 100±10 nm and a length of 5 to 10 μm.

[0015] A method for preparing a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers as described above comprises the following steps:

[0016] S1, Fe3O4 nanoparticles and polyimide precursor were mixed in a volume ratio of 3:7 and dispersed by ball milling for 4 hours;

[0017] S2. Spin coating on the substrate surface with a thickness of 50±5μm, and step curing: 80℃ / 30min→180℃ / 2h→250℃ / 1h. After curing, the surface roughness Ra is less than 0.1μm, forming a magnetic layer;

[0018] S3, growing silicon carbide nanowires on the surface of the magnetic layer by chemical vapor deposition at a temperature of 1100°C, CH3SiCl3 / H2 / Ar=50 / 200 / 1000 sccm, for 1 h;

[0019] S4, mixing silicon carbide nanowires and boron nitride powder in a mass ratio of 2:1, and hot pressing to form a dielectric layer at a hot pressing pressure of 20 MPa and a temperature of 300°C;

[0020] S5. Oxygen plasma treatment was used between each layer with a power of 100 W and a time of 30 s, followed by silane coupling agent KH-550 to enhance the interfacial bonding strength.

[0021] Preferably, the purity of the Fe3O4 nanoparticles is 99.9%, the particle size is 20 nm, and the particle size of the boron nitride powder is 1 μm.

[0022] Preferably, the Fe3O4 nanoparticles are pretreated by an oleic acid coating process, and the polyimide precursor is PMDA-ODA.

[0023] Compared with the prior art, the present invention has the following advantages: the entire frequency band of 1-100 GHz can be covered by alternately stacked magnetic layers and dielectric layers, while also being able to withstand high temperatures of 200°C and high humidity environments of 85% RH. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention.

[0025] In the figure: 1, substrate; 2, magnetic layer; 3, dielectric layer; 31, silicon carbide nanowires; 32, boron nitride powder. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention.

[0027] See also Figure 1 The present invention provides a technical solution: a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers, comprising a substrate 1, on which magnetic layers 2 and dielectric layers 3 are alternately stacked, wherein the stacking period of the magnetic layers 2 and the dielectric layers 3 is 4 to 8 layers;

[0028] The magnetic layer 2 is a composite of Fe3O4 nanoparticles and polyimide precursors. The thickness of the magnetic layer 2 is 50±5 μm, the magnetic permeability μ'=2.5 (1 GHz), and the dielectric constant ε'=8.3;

[0029] The dielectric layer 3 is formed by hot pressing silicon carbide nanowires 31 and boron nitride powder 32. The diameter of the silicon carbide nanowires 31 is 100±10nm and the length is 5-10μm. The thickness of the dielectric layer 3 is 30±3μm, the dielectric constant ε' is 12.7, and the loss tangent tanδ is 0.15 (40GHz).

[0030] The magnetic layer 2 and the dielectric layer 3 are treated with oxygen plasma and a silane coupling agent is used to enhance the interface bonding strength.

[0031] A method for preparing any of the above-mentioned broadband wave-absorbing packaging structures based on alternating magnetic layers and dielectric layers comprises the following steps:

[0032] S1. Mix Fe3O4 nanoparticles and a polyimide precursor in a volume ratio of 3:7 and disperse by ball milling for 4 hours. The Fe3O4 nanoparticles have a purity of 99.9% and a particle size of 20 nm. The Fe3O4 nanoparticles are pretreated with oleic acid coating, and the polyimide precursor is PMDA-ODA.

[0033] S2. Spin-coat the substrate surface to a thickness of 50±5μm and perform step-curing: 80℃ / 30min→180℃ / 2h→250℃ / 1h. After curing, the surface roughness Ra is less than 0.1μm, forming a magnetic layer.

[0034] S3. Grow silicon carbide nanowires on the surface of the magnetic layer by chemical vapor deposition at a temperature of 1100° C., CH 3 SiCl 3 / H 2 / Ar=50 / 200 / 1000 sccm, and for 1 h.

[0035] S4. Mix silicon carbide nanowires and boron nitride powder in a mass ratio of 2:1. The boron nitride powder has a particle size of 1 μm and is hot-pressed to form a dielectric layer. The hot-pressing pressure is 20 MPa and the temperature is 300°C. A Carver 3850 hot press is used with a temperature control accuracy of ±1°C.

[0036] S5. Oxygen plasma treatment was used between each layer with a power of 100 W and a time of 30 s, followed by silane coupling agent KH-550 to enhance the interfacial bonding strength.

[0037] Technical effects:

[0038] 1. Broadband absorbing performance:

[0039] SE>45dB in the full frequency band of 1-100GHz, absorption rate at 40GHz is 98.2%;

[0040] Standing wave ratio (VSWR) <1.5, energy reflectivity <5%.

[0041] 2. Environmental reliability:

[0042] High temperature test: After aging at 200℃ for 500h, SE attenuation is less than 1dB;

[0043] Damp heat test: 1000h at 85℃ / 85%RH, absorption rate remains>94%.

[0044] 3. Performance testing:

[0045] Shielding effectiveness: 45-52dB (1-100GHz, ASTM D4935 standard);

[0046] Absorption rate: 98.2% @ 40GHz (waveguide method test, IEEE 299 standard).

[0047] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers, comprising a substrate (1), characterized in that: Magnetic layers (2) and dielectric layers (3) are alternately stacked on the substrate (1); The magnetic layer (2) is a composite of Fe3O4 nanoparticles and a polyimide precursor; The dielectric layer (3) is formed by hot pressing silicon carbide nanowires (31) and boron nitride powder (32); Oxygen plasma treatment is adopted between the magnetic layer (2) and the dielectric layer (3), and a silane coupling agent is adopted to enhance the interface bonding force.

2. The broadband microwave absorbing packaging structure based on alternating magnetic and dielectric layers according to claim 1, characterized in that: The thickness of the magnetic layer (2) is 50±5 μm, and the thickness of the dielectric layer (3) is 30±3 μm.

3. The broadband microwave absorbing packaging structure based on alternating magnetic and dielectric layers according to claim 1, wherein: The stacking period number of the magnetic layer (2) and the dielectric layer (3) is 4 to 8 layers.

4. The broadband microwave absorbing packaging structure based on alternating magnetic and dielectric layers according to claim 1, wherein: The silicon carbide nanowire (31) has a diameter of 100±10 nm and a length of 5 to 10 μm.

5. The method for preparing a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1, Fe3O4 nanoparticles and polyimide precursor were mixed in a volume ratio of 3:7 and dispersed by ball milling for 4 hours; S2. Spin coating on the substrate surface with a thickness of 50±5μm, and step curing: 80℃ / 30min→180℃ / 2h→250℃ / 1h. After curing, the surface roughness Ra is less than 0.1μm, forming a magnetic layer; S3, growing silicon carbide nanowires on the surface of the magnetic layer by chemical vapor deposition at a temperature of 1100°C, CH3SiCl3 / H2 / Ar=50 / 200 / 1000 sccm, for 1 h; S4, mixing silicon carbide nanowires and boron nitride powder in a mass ratio of 2:1, and hot pressing to form a dielectric layer at a hot pressing pressure of 20 MPa and a temperature of 300°C; S5. Oxygen plasma treatment was used between each layer with a power of 100 W and a time of 30 s, followed by silane coupling agent KH-550 to enhance the interfacial bonding strength.

6. The method for preparing a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers according to claim 5, characterized in that: The purity of the Fe3O4 nanoparticles is 99.9%, the particle size is 20 nm, and the particle size of the boron nitride powder is 1 μm.

7. The method for preparing a broadband wave-absorbing packaging structure based on alternating magnetic layers and dielectric layers according to claim 5, characterized in that: The Fe3O4 nanoparticles are pretreated by adopting an oleic acid coating process, and the polyimide precursor adopts a PMDA-ODA type.

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