1. A preparation method of a ceramic composite polytetrafluoroethylene microwave composite medium substrate is characterized by comprising the following specific steps:

(1) firstly, carrying out surface modification on a porcelain powder filler by using a silane coupling agent, wherein the using amount of the silane coupling agent is 1-5% of the mass of the filler;

(2) respectively weighing the modified porcelain powder and the polytetrafluoroethylene emulsion according to the mass ratio of the surface modified porcelain powder to the polytetrafluoroethylene emulsion A (1-A), wherein A is 25-50%;

(3) adding deionized water into the weighed modified porcelain powder for dispersion, wherein the mass of the deionized water is 3-5 times that of the modified porcelain powder, adding one or more of glacial acetic acid and hydrochloric acid, adjusting the pH value of the solution to be 4-6, fully stirring to form modified porcelain powder aqueous dispersion, and adding polytetrafluoroethylene emulsion for full mixing to prepare mixed emulsion;

(4) performing high-temperature demulsification on the mixed emulsion by using a spray drying device by adopting a high-temperature and high-speed rotary demulsification method, wherein the inlet temperature of the spray drying device is 200-260 ℃, the outlet temperature of the spray drying device is 100-130 ℃, and the rotating speed of an atomizer is 5000-8000 r/min; the mixed emulsion is transmitted to a high-speed rotary atomizing device by using a vacuum transmission device, the emulsion is quickly thrown out by the high-speed rotary atomizing device, and quick emulsion breaking is realized under the action of centrifugal force and high temperature;

(5) demulsifying by a spray drying process to prepare polytetrafluoroethylene/filler composite dough, and pressing the prepared composite dough into a sheet-shaped membrane by a pressing forming device;

(6) and carrying out hot-pressing sintering on the prepared flaky membrane to prepare the microwave composite medium substrate.

2. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate as claimed in claim 1, wherein the filler is one or more of silicon dioxide, titanium dioxide, calcium titanate and barium nonatitanate.

3. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate as claimed in claim 1, wherein the particle size of the filler is 6 μm to 10 μm.

4. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite medium substrate as claimed in claim 1, wherein the temperature range of the high-temperature demulsification is 200-260 ℃.

5. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate according to claim 1, wherein the spray drying device is a spray drying tower.

6. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate according to claim 1, wherein the vacuum transmission device is a vacuum pump.

7. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate according to claim 1, wherein the adopted press forming device is a calender or a molding press.

8. The method for preparing a ceramic composite polytetrafluoroethylene microwave composite dielectric substrate according to claim 1, wherein the temperature range of the hot-pressing sintering is 350 ℃ to 390 ℃, and the pressure is 5Mpa to 10 Mpa.

9. The preparation method of the ceramic composite polytetrafluoroethylene microwave composite medium substrate as claimed in claim 1, wherein the specific preparation method of the composite medium substrate is as follows:

selecting silicon dioxide as a filler, and carrying out surface treatment on the silicon dioxide by using a silane coupling agent, wherein the silane coupling agent accounts for 2% of the mass of the silicon dioxide;

mixing the surface-modified ceramic powder and polytetrafluoroethylene emulsion according to the mass ratio of 60% of silicon dioxide and 40% of polytetrafluoroethylene, stirring for 4 hours, pumping the mixed solution to an atomizer of a spray drying tower by using a vacuum pump while stirring the mixed solution, wherein the rotating speed of the atomizer is 6000r/min, the inlet temperature is 250 ℃, and the outlet temperature is 110 ℃, and preparing a composite dough;

and performing calendaring molding on the prepared composite dough, and finally performing hot-pressing sintering at the temperature of 370 ℃ and under the pressure of 7Mpa for 2 hours to prepare the silicon dioxide composite polytetrafluoroethylene high-frequency microwave composite dielectric substrate.

10. The preparation method of the ceramic composite polytetrafluoroethylene microwave composite medium substrate as claimed in claim 1, wherein the specific preparation method of the composite medium substrate is as follows:

selecting titanium dioxide as a filler, and treating the surface of the titanium dioxide by using a silane coupling agent, wherein the silane coupling agent accounts for 1.5 percent of the mass of the titanium dioxide;

mixing the ceramic powder with the modified surface with polytetrafluoroethylene according to the mass ratio of 66% of titanium dioxide and 34% of polytetrafluoroethylene;

demulsifying, rolling, hot-pressing and sintering according to the method of claim 9 to prepare the titanium dioxide composite polytetrafluoroethylene type high-frequency microwave composite dielectric substrate.

Background

With the development of the communication field towards higher frequency bands, the requirement of high integration and high frequency of integrated circuits is required, the requirement of a core material microwave composite medium substrate for preparing the integrated circuits is gradually improved, at present, mainstream copper clad plate manufacturers in China still use glass fiber cloth to dip polytetrafluoroethylene emulsion, and the glass fiber cloth is dried to prepare a prepreg, has obvious directionality, and has cross nodes, so that the node constants of the plate in the X and Y directions have obvious difference, attenuation with different degrees exists in the high-frequency signal transmission process, and the signal transmission stability is poor, and the ceramic is filled, the production mode is that a high-speed dispersion machine is used for carrying out high-speed dispersion on the polytetrafluoroethylene emulsion and ceramic powder after surface treatment, and then materials such as flocculating agent, alcohol, ether and the like are added to break emulsion and precipitate the polytetrafluoroethylene emulsion, so as to obtain composite dough required by preparing the high-frequency microwave composite medium substrate, according to the method, on one hand, other materials need to be introduced, after the green body is prepared, the green body needs to be baked for a long time to volatilize, part of the materials are not volatilized completely, and are carbonized in a hot-pressing sintering stage, so that the loss of the dielectric substrate is increased, and on the other hand, in the precipitation process, coarse-particle ceramic powder is easy to precipitate firstly, and fine-particle ceramic powder is easy to precipitate later, so that the parameter distribution of the density and the dielectric property of the microwave composite dielectric substrate is easy to be uneven. The whole production process has long time consumption and poor uniformity, and is not suitable for batch production and product quality control.

In view of the above, the present invention is particularly proposed.

Disclosure of Invention

The purpose of the invention is: solves the problems of uniform mixing and unsuitability for continuous batch production of the existing ceramic-filled polytetrafluoroethylene composite material.

The technical conception adopted by the invention is as follows: the composite material is prepared by a spray drying process and a high-temperature and high-speed rotary demulsification method. The method has the advantages that micromolecule materials such as flocculating agents and the like are not introduced, the problem that the dielectric loss of the composite material is influenced by high-temperature carbonization of the micromolecules does not exist, the emulsion is thrown out after high-speed rotation atomization, resin fully wraps the porcelain powder under the action of centrifugal force, the dispersion uniformity of the composite material is better, the emulsion breaking process is quicker than that of flocculating agents, the standing and filtering mode is faster, and the production efficiency is higher.

The technical scheme of the invention is as follows:

therefore, the invention provides a preparation method of a ceramic composite polytetrafluoroethylene microwave composite medium substrate, which comprises the following steps as shown in a process flow schematic diagram shown in figure 1:

(1) firstly, carrying out surface modification on a filler by using a silane coupling agent, wherein the filler can be one or more of silicon dioxide, titanium dioxide, calcium titanate and barium nonatitanate, the filler is commercially available ceramic powder, the particle size D50 of the filler is 6-10 mu m, and the using amount of the silane coupling agent is 1-5% of the mass of the filler;

(2) respectively weighing the modified porcelain powder and the polytetrafluoroethylene emulsion according to the mass ratio of the surface modified porcelain powder to the polytetrafluoroethylene emulsion A (1-A), wherein A is 25-50%;

(3) adding deionized water into the weighed modified porcelain powder for dispersion, wherein the mass of the deionized water is 3-5 times that of the modified porcelain powder, adding one or more of glacial acetic acid and hydrochloric acid, adjusting the pH value of the solution to be 4-6, fully stirring to form modified porcelain powder aqueous dispersion, and adding polytetrafluoroethylene emulsion for full mixing to prepare mixed emulsion;

(4) and (3) performing high-temperature demulsification on the mixed emulsion by using a spray drying device by adopting a high-temperature and high-speed rotary demulsification method, wherein the inlet temperature of the spray drying device is 200-260 ℃, the outlet temperature of the spray drying device is 100-130 ℃, and the rotating speed of an atomizer is 5000-8000 r/min. Use vacuum transmission device to transmit the mixed emulsion to high-speed rotatory atomizing device, the emulsion is thrown away through high-speed rotatory atomizing device fast, under centrifugal force and high temperature effect, realizes quick breakdown of emulsion, and whole production process is controllable in succession, and other materials are not introduced to whole breakdown of emulsion process, and under the effect of centrifugal force, and polytetrafluoroethylene is inseparabler to the parcel of porcelain powder, and the dispersion is more even.

(5) And demulsifying by a spray drying process to prepare polytetrafluoroethylene/filler composite dough, and performing compression molding on the prepared composite dough by using a compression molding device, wherein the compression molding device can be a calender or a molding press, and the dough is subjected to the compression molding process to prepare the sheet-shaped membrane.

(6) And carrying out hot-pressing sintering on the prepared sheet diaphragm, wherein the hot-pressing sintering temperature is 350-390 ℃, and the pressure is 5-10 Mpa, so as to prepare the microwave composite medium substrate, and the dielectric constant of the microwave composite medium substrate is 3.0-11.

The temperature range of the high-temperature demulsification is 200-260 ℃.

The spray drying device is a spray drying tower.

The vacuum transmission device is a vacuum pump.

The adopted pressing device is a calender or a molding press.

The temperature range of the hot-pressing sintering is 350-390 DEG C

The invention has the main advantages that:

(1) and small molecular materials such as flocculant and the like are not introduced, so that the problem that the dielectric loss of the composite material is influenced by the high-temperature carbonization of the small molecules is solved.

(2) The emulsion breaking mode is that the emulsion is thrown out after high-speed rotation atomization, the resin fully wraps the porcelain powder under the action of centrifugal force, and the dispersion uniformity of the composite material is better.

(3) Compared with the modes of flocculating agent demulsification and standing filtration, the demulsification process is quicker and has higher production efficiency.

(4) The prepared composite dough has good uniformity and can be produced continuously in batches.

(5) The dielectric constant of the microwave composite dielectric substrate is 3.0-11.

(6) The method is of great importance to the development of the high-frequency microwave composite dielectric substrate industry.

The ceramic composite polytetrafluoroethylene microwave composite dielectric substrate is widely applied to the fields of modern microwave electronic communication such as aerospace electronic equipment, mobile communication, electronic countermeasure, satellite communication, a Beidou system (GPS), a Bluetooth technology, a wireless local area network (MLAN) and the Internet of things.

Drawings

FIG. 1 is a schematic view of a production process.

Detailed Description

A preparation method of a ceramic composite polytetrafluoroethylene microwave composite medium substrate comprises the following specific implementation modes:

example 1:

selecting silicon dioxide as a filler, carrying out surface treatment on the silicon dioxide by using a silane coupling agent, wherein the silane coupling agent accounts for 2% of the mass of the silicon dioxide, mixing the surface-modified porcelain powder and polytetrafluoroethylene emulsion according to the mass ratio of 60% of the silicon dioxide to 40% of the polytetrafluoroethylene, stirring the mixture for 4 hours, pumping the mixture to an atomizer by using a vacuum pump while stirring the mixture, wherein the rotation speed of the atomizer is 6000r/min, the inlet temperature is 250 ℃, the outlet temperature is 110 ℃, preparing a composite dough, carrying out calendaring molding on the prepared composite dough, and finally carrying out hot-press sintering at the hot-press sintering temperature of 370 ℃, the pressure position is 7MPa and the time is 2 hours, thus preparing the silicon dioxide composite polytetrafluoroethylene type high-frequency microwave composite dielectric substrate, wherein the dielectric constant is 3.0.

Example 2:

titanium dioxide is selected as a filler, the surface of the titanium dioxide is treated by using a silane coupling agent which accounts for 1.5 percent of the mass of the titanium dioxide, the ceramic powder with the modified surface and polytetrafluoroethylene are mixed according to the mass ratio of 66 percent of the titanium dioxide to 34 percent of the polytetrafluoroethylene, and then emulsion breaking, rolling and hot-pressing sintering are carried out according to the method in the embodiment 1, so that the titanium dioxide composite polytetrafluoroethylene type high-frequency microwave composite dielectric substrate is prepared, and the dielectric constant is 11.

Finally, it should be noted that: the above examples are merely examples for clarity of illustration, and the present invention includes but is not limited to the above examples, which are not necessarily exhaustive of all embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. Embodiments that meet the requirements of the present invention are within the scope of the present invention.