CN104150766A - Microwave dielectric material with ultralow dielectric constant - Google Patents

Abstract

The ultra-low dielectric constant microwave dielectric material disclosed by the present invention has a crystal phase content of 0 or less than 5 mol%, a dielectric constant of 3.2 to 3.9, and an expression of xSiO ₂ -yB ₂ O ₃ -zLi ₂ O, wherein 40 mol %≤x≤90mol%, 10mol%≤y≤40mol%, 0mol%≤z≤20mol%, x+y+z=100mol%. The ultra-low dielectric constant microwave dielectric material has a high Qf value (40,000~80,000GHz) and a near-zero resonant frequency temperature coefficient (-9~-4ppm/ ^o C). Applying the ultra-low dielectric constant microwave dielectric material provided by the present invention to microwave substrates can significantly reduce the signal delay of microwaves in the substrate transmission process, thereby meeting the higher requirements for microwave substrate materials raised by the development trend of high-frequency microwave communications.

Description

A kind of ultra-low dielectric constant microwave dielectric material

technical field

The invention relates to a microwave dielectric material used in a communication system, in particular to a microwave dielectric material with an ultra-low dielectric constant.

Background technique

Low dielectric constant microwave dielectric materials are widely used in microwave substrates and are one of the key materials in the field of microwave communication. The basic performance requirements are: the lowest possible dielectric constant ε _r , the highest possible Qf value and Near-zero resonant frequency temperature coefficient τ _f . Microwave substrate materials mainly include polymer-based composite materials and ceramic materials, but the former usually has a low Qf value and poor thermal stability, while the latter generally has a high dielectric constant (>6). The signal delay of microwave transmission in the substrate increases with the increase of frequency and dielectric constant. Therefore, the development trend of high-frequency microwave communication puts forward higher and higher requirements for the low dielectric constant of the substrate material. How to further reduce the dielectric constant to below 5 or even 4 while maintaining a high Qf value and a near-zero resonant frequency temperature coefficient is the most critical issue in the development of new microwave substrate materials.

Contents of the invention

The object of the present invention is to provide a microwave dielectric material with a high Qf value and a near-zero resonant frequency temperature coefficient.

The ultra-low dielectric constant microwave dielectric material of the present invention has a crystal phase content of 0 or less than 5 mol%, a dielectric constant of 3.2 to 3.9, and an expression of xSiO ₂ -yB ₂ O ₃ -zLi ₂ O, wherein 40mol%≤x≤90mol%, 10mol%≤y≤40mol%, 0mol%≤z≤20mol%, x+y+z=100mol%.

The ultra-low dielectric constant microwave dielectric material of the present invention can be prepared by the following method.

First, mix SiO ₂ , B ₂ O ₃ , and Li ₂ O with a purity of 99.9% or more by wet ball milling for 24 hours according to the above ratio (the solvent is absolute ethanol). After drying, add a binder to the mixed powder and Granulate, then form by uniaxial pressure, prepare a green body with a diameter of 12mm and a thickness of 6mm under a pressure of 100MPa, and finally sinter at 850-1100°C for 3 hours in an atmospheric atmosphere to obtain the required microwave dielectric material.

The above-mentioned binder can be a polyvinyl alcohol solution with a concentration of 3-8%, and the dosage generally accounts for 5-10% of the total amount.

The ultra-low dielectric constant microwave dielectric material of the present invention has a dielectric constant of 3.2-3.9, a high Qf value (40,000-80,000 GHz) and a nearly zero resonant frequency temperature coefficient (-9-4ppm/°C). Applying the ultra-low dielectric constant microwave dielectric material provided by the present invention to microwave substrates can significantly reduce the signal delay of microwaves in the substrate transmission process, thereby meeting the higher requirements for microwave substrate materials put forward by the development trend of high-frequency microwave communication. Therefore, the present invention has great application value in industry.

Detailed ways

Table 1 shows several specific examples of the content of each component constituting the present invention and their microwave dielectric properties. Its preparation method is as described above. The phase analysis of the sintered sample was carried out by powder X-ray diffraction method, and the microwave dielectric properties at 15 GHz were tested by dielectric resonance method.

Table 1

It can be seen from Table 1 that the increase of B ₂ O ₃ and Li ₂ O content both contribute to the improvement of Qf value, the dielectric constant decreases with the increase of B ₂ O ₃ content, and increases with the increase of Li ₂ O content. The resonant frequency temperature coefficient is always maintained at a low level. Generally speaking, the Qf value decreases with the increase of crystal phase content in the sintered product. Therefore, completely eliminating the crystal phase in the sintered product or keeping it at a lower level (<5mol%) is the key to obtaining excellent comprehensive performance in the present invention.

Among all the ingredients in this example, the composition points of x=40mol%, y=40mol%, z=20mol% have the best microwave dielectric properties: _εr =3.55, Qf=79,400GHz, _τf =-8.9 ppm/°C.

Claims (2)

1. An ultra-low dielectric constant microwave dielectric material, characterized in that: the crystal phase content of the material is 0 or less than 5 mol%, its dielectric constant is 3.2-3.9, and the expression is xSiO ₂ -yB ₂ O ₃ - zLi ₂ O, wherein 40mol%≤x≤90mol%, 10mol%≤y≤40mol%, 0mol%≤z≤20mol%, x+y+z=100mol%. 2. The ultra-low dielectric constant microwave dielectric material according to claim 1, characterized in that: x=40mol%, y=40mol%, z=20mol%.