CN113416066A

CN113416066A - LTCC substrate and preparation method and application thereof

Info

Publication number: CN113416066A
Application number: CN202110752365.XA
Authority: CN
Inventors: 陈涛; 黄国洪; 崔三川; 曹秀华; 沓世我; 付振晓
Original assignee: Guangdong Fenghua Advanced Tech Holding Co Ltd
Current assignee: Guangdong Fenghua Advanced Tech Holding Co Ltd
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2021-09-21

Abstract

The invention discloses an LTCC substrate and a preparation method and application thereof. The preparation method comprises the following steps: 1) mixing hollow spherical SiO₂With Al₂O₃Ball milling and calcining to obtain SiO₂@Al₂O₃Powder; 2) mixing KBS glass powder and SiO₂@Al₂O₃Mixing the powder and an additive, and performing ball milling to obtain ceramic slurry; 3) forming the ceramic slurry, laminating the membranes, carrying out isostatic pressing, and cutting into a ceramic blank; 4) sintering of ceramic bodyAnd obtaining the LTCC substrate. By adding hollow spherical SiO₂The dielectric constant of the LTCC ceramic is reduced, the dielectric constant of the material is as low as 3.5, and the dielectric loss is as low as 0.2%; hollow spherical SiO₂Surface coated with Al₂O₃Improving the glass and SiO content in the sintering process₂The surface bonding force of the LTCC substrate is improved to 220MPa, the ultralow dielectric constant LTCC substrate with good compactness and higher bending strength is obtained, and the LTCC substrate is suitable for the fields of high-frequency communication and radio frequency.

Description

LTCC substrate and preparation method and application thereof

Technical Field

The invention relates to the technical field of ceramic substrates, in particular to an LTCC substrate and a preparation method and application thereof.

Background

With the advent of the 5G communication and everything interconnection era, high frequency applications are becoming a trend. Low dielectric constant low temperature co-fired ceramic (LTCC) ceramic materials are receiving increasing attention to reduce signal transmission loss and increase signal transmission rate. The existing low dielectric ceramic powder with wide application mostly adopts glass and Al₂O₃System material, due to Al₂O₃The dielectric constant is higher than 9-11, the dielectric constant of the existing material system is generally higher than 5.0, and it is difficult to further reduce the dielectric constant of the porcelain powder. In the prior patent CN201910155188X, a material is disclosed, in which glass + Al₂O₃Adding SiO into the system₂The method reduces the dielectric constant and improves the compactness, but the dielectric constant in the method can only reach 4.3 at the lowest, and SiO₂The surface and glass have poor bonding performance, so that the LTCC substrate has low bending strength and is difficult to meet the requirement of high reliability. The dielectric constant of the developed organic-inorganic composite ceramic material can be lower than 4.0, but the organic polymer has poor temperature resistance, is incompatible with the current LTCC integration process, and cannot meet the requirement of high-density integration. Therefore, there is an urgent need to develop an LTCC substrate having an ultra-low dielectric constant and a high bending strength, which is compatible with the conventional LTCC process.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide the LTCC substrate which has an ultralow dielectric constant and higher bending strength.

Another object of the present invention is to provide a method for preparing the LTCC substrate.

The invention further aims to provide application of the LTCC substrate.

The purpose of the invention is realized by the following technical scheme: a preparation method of an LTCC substrate comprises the following steps:

(1) mixing hollow spherical SiO₂With Al₂O₃Mixing, ball milling to obtain mixed slurry, drying and calcining to obtain SiO₂@Al₂O₃Powder;

(2) mixing KBS glass powder and the SiO in the step (1)₂@Al₂O₃Mixing the powder, a solvent, a dispersant, a plasticizer, a defoaming agent and an adhesive, and performing ball milling to obtain ceramic slurry;

(3) and (3) forming the ceramic slurry in the step (2), laminating the obtained membrane, carrying out isostatic pressing, cutting into a ceramic blank, and sintering to obtain the LTCC substrate.

The hollow spherical SiO in step (1)₂The sphericity of the spherical particles is more than or equal to 98.

Al described in step (1)₂O₃Preferably Al₂O₃And (3) sol.

Al described in step (1)₂O₃The amount of the compound is preferably hollow spherical SiO₂3-8 wt% of (B).

The time for ball milling in step (1) is preferably 12 h.

The ball milling medium in the step (1) is preferably deionized water; the media is preferably zirconia balls.

The drying in step (1) is preferably spray drying, with the conditions: the inlet air temperature is 200-250 ℃, the outlet air temperature is 90-100 ℃, and the rotation speed of the atomizer is 16000-27000 rpm.

The calcination in the step (1) is preferably calcination at 1000-1200 ℃ for 1-2 h.

The time for ball milling in the step (2) is preferably 20 to 28 hours.

The mixture ratio of the raw materials in the step (2) is as follows: 35 to 45 percent of KBS glass powder and 55 to 65 percent of KBS glass powderSiO of (2)₂@Al₂O₃Powder; as follows in SiO₂@Al₂O₃Powder mass fraction additive: 90-110% of solvent, 1-3% of dispersant, 0.5-1% of plasticizer and 9-13% of adhesive;

the additive is preferably: 105% of solvent, 1.5% of dispersant, 0.8% of plasticizer and 11% of adhesive.

The binder is preferably polyvinyl butyral (PVB).

The solvent is preferably a mixture of ethanol and toluene in a volume ratio of 35: and 65 percent.

The preparation method of the KBS glass powder in the step (2) comprises the following steps:

(a) mixing SiO₂、H₃BO₃、K₂CO₃、Na₂CO₃、CaCO₃、BaCO₃Mixing, ball milling, drying, homogenizing glass liquid and quenching;

(b) and (2) ball-milling the glass quenched in the step (1) to obtain glass slurry, and drying to obtain the KBS glass powder.

SiO as described in step (a)₂、H₃BO₃、K₂CO₃、Na₂CO₃、CaCO₃、BaCO₃The mass ratio of (A) to (B) is 50-65: 30-45: 1-4: 0-0.5: 0.1-0.8: 0.1-0.7; preferably from 55 to 58: 40-43: 1.3-1.6: 0-0.2: 0.1-0.3: 0.1-0.3; more preferably 56.9: 41.1: 1.5: 0.1: 0.2: 0.2.

the ball milling in step (a) is preferably carried out for 2-4h by planetary ball milling.

The conditions for homogenizing the molten glass in step (a) are preferably 1300 ℃ for 1-2 h.

The quenching in step (a) is preferably with deionized water.

The ball milling medium in steps (a) and (b) is preferably deionized water.

The drying in steps (a) and (b) is preferably drying at 100 ℃ for 12 h.

The ball milling in the step (b) is preferably carried out for 12-24h by a planetary ball mill.

The ball milling medium in step (b) is preferably zirconia balls.

The molding in the step (3) is preferably a casting molding.

The isostatic pressing in step (3) is preferably: the pressure is 50-70MPa, the liquid temperature is 65-80 ℃, and the pressure maintaining time is 20-40 min.

The ceramic body in step (3) is preferably a ceramic body having a length and width of 5 x 10 mm.

The sintering in the step (3) is preferably performed at 850-900 ℃ for 30-120 min.

An LTCC substrate is prepared by the preparation method.

The LTCC substrate is applied to the preparation of microwave dielectric devices.

Compared with the prior art, the invention has the following beneficial effects:

the invention adds hollow spherical SiO₂The dielectric constant and the dielectric loss of the LTCC substrate are effectively reduced, the dielectric constant can be as low as 3.5, and the dielectric loss can be as low as 0.2%; by forming a hollow spherical SiO₂Surface coated with Al₂O₃Effectively improving the glass and SiO in the sintering process₂The surface bonding force of the LTCC substrate can improve the strength of the substrate to 220MPa, so that the LTCC substrate with high compactness, high bending strength and ultralow dielectric constant is obtained, and the LTCC substrate is suitable for the fields of high-frequency communication and radio frequency.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Examples

1. K-B-Si (KBS) glass preparation

1.1 weighing raw material SiO 56.9 wt%, 41.1 wt%, 1.5 wt%, 0.1 wt%, 0.2 wt%₂、H₃BO₃、K₂CO₃、Na₂CO₃、CaCO₃、BaCO₃. Performing planetary ball milling for 4 hours by using an agate ball milling tank and deionized water as a medium, discharging, and drying for 12 hours at 100 ℃ to obtain raw material powder;

1.2, putting the dried raw material powder into a platinum crucible, putting the platinum crucible into a high-temperature furnace, preserving heat for 2 hours at 1300 ℃ to homogenize molten glass, taking out the molten glass at high temperature, and quenching the molten glass in deionized water;

1.3, placing the quenched glass in an agate ball milling tank, carrying out planetary ball milling for 12 hours by using zirconia balls as a medium and deionized water as a medium to obtain glass slurry, and drying the glass slurry at 100 ℃ for 12 hours to obtain KBS glass powder;

2、Al₂O₃coated SiO₂Core-shell Structure (SiO)₂@Al₂O₃) Preparation of powder

2.1 with hollow spherical SiO₂As raw material, hollow spherical SiO₂The sphericity is more than or equal to 98 percent. Weighing a certain amount of Al₂O₃Sol of Al₂O₃Is SiO₂The proportion of (B) is 3-10 wt%. Using deionized water as medium and zirconia ball as medium to make hollow spherical SiO₂And Al₂O₃Ball-milling the sol in a ball mill for 12h to obtain uniform SiO₂With Al₂O₃Mixing the slurry;

2.2, carrying out spray drying on the mixed slurry, wherein the air inlet temperature of a drying tower is 200 ℃, the air outlet temperature is 100 ℃, the rotation speed of an atomizer is 20000rpm, and drying to obtain Al₂O₃Coated SiO₂Core-shell structure powder;

2.3, mixing Al₂O₃Coated SiO₂Placing the core-shell structure powder in a muffle furnace, calcining for 2h at 1050 ℃ to obtain Al₂O₃With SiO₂The surface reacts to form a Si-Al-O compound to obtain SiO₂@Al₂O₃And (3) powder. The calcination temperature is too low, the reaction is not sufficient, and the Si-Al-O compound and the SiO₂The combination is not compact, the calcination temperature is too high, the activity of the Si-Al-O compound is low, and the combination compatibility with glass is not facilitated during the co-firing.

3. LTCC substrate preparation

3.1 weighing the KBS glass powder and SiO in percentage by mass₂@Al₂O₃Powder, wherein the KBS glass powder accounts for 35-45 wt% and SiO₂@Al₂O₃The powder accounts for 55-65 wt%, and SiO accounts for the following addition₂@Al₂O₃Powder mass fraction additive: 105% of solvent (ethanol and toluene are mixed according to a volume ratio of 35: 65), 1.5% of dispersant (AKM0531), 0.8% of plasticizer (diisooctyl phthalate, DOP) and 11% of PVB (Butvar-B76), placing the mixture into a horizontal ball milling tank, and carrying out ball milling for 24 hours by taking zirconia balls with the diameter of 5mm as media to obtain uniform and stable ceramic slurry;

3.2 carrying out tape casting on the ceramic slurry to obtain a uniform diaphragm, laminating the diaphragm, carrying out isostatic pressing, keeping the isostatic pressing pressure at 60MPa, the liquid temperature at 75 ℃, keeping the pressure for 30min, and cutting the diaphragm into a ceramic blank with the length and width of 5 x 10 mm;

and 3.3, sintering the ceramic blank at 860 ℃, preserving heat for 60min, and then cooling along with the furnace to obtain the LTCC substrate with a smooth surface.

And coating an Ag electrode on the obtained LTCC substrate, and carrying out performance test after silver burning. The dielectric property is obtained by testing with a precision capacitance tester (HP 4286A); the bending strength is obtained by a three-point bending method according to the test of national standard GBT 6569-one 2006 of the people's republic of China.

Table 1 gives the dielectric properties and flexural strength of several examples of the components of the invention, comparative examples and the resulting substrates. In comparative example 1, the KBS glass content is 30 wt% which is lower than the required 35-45 wt%, and sintering is not dense, resulting in a lower bending strength of the substrate; SiO in comparative example 2₂@Al₂O₃The calcination temperature of the powder is 950 ℃ which is lower than the required 1000-1200 ℃, resulting in insufficient formation of Al-Si-O compounds, Al₂O₃In SiO₂The surface bonding is not firm, and the KBS glass can not be bonded with SiO in the sintering process₂Good wetting and bonding are formed on the surface, so that the bending strength of the substrate is low; al in comparative example 3₂O₃The content of 10 wt% exceeding the required 3-8 wt% results in a substrate having a high dielectric constant.

The invention has the advantages that the hollow spherical SiO is adopted₂The low-temperature co-fired ceramic is used as a raw material, so that the dielectric constant of the LTCC substrate is effectively reduced and can be reduced to 3.5; in hollow spherical SiO₂Surface coated with Al₂O₃Calcining to form Si-Al-O compound on the surface and increase Al₂O₃With SiO₂The surface bonding force is improved, and the KBS glass and SiO during sintering are improved₂The bonding force of the surface improves the bending strength of the LTCC substrate, and the LTCC substrate with ultralow dielectric constant and high strength is obtained.

TABLE 1 specific examples and resulting samples dielectric Properties and flexural Strength

While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A preparation method of an LTCC substrate is characterized by comprising the following steps:

2. The method of preparing an LTCC substrate according to claim 1,

the hollow spherical SiO in step (1)₂The sphericity of the spherical particles is more than or equal to 98;

al described in step (1)₂O₃Is Al₂O₃Sol;

the mixture ratio of the raw materials in the step (2) is as follows: 35 to 45 percent of KBS glass powder and 55 to 65 percent of SiO₂@Al₂O₃Powder; as follows in SiO₂@Al₂O₃Powder mass fraction additive: 90-110% of solvent, 1-3% of dispersant, 0.5-1% of plasticizer and 9-13% of adhesive.

3. The method of preparing an LTCC substrate according to claim 2,

the additive is as follows: 105% of solvent, 1.5% of dispersant, 0.8% of plasticizer and 11% of adhesive;

the adhesive is polyvinyl butyral;

the solvent is prepared by mixing ethanol and toluene according to a volume ratio of 35: and 65 percent.

4. The method of preparing the LTCC substrate of claim 1, wherein the Al in the step (1)₂O₃The dosage of the hollow spherical SiO₂3-8 wt% of (B).

5. The method of preparing an LTCC substrate according to claim 1,

in the step (1), the calcination is carried out at 1000-1200 ℃ for 1-2 h;

in the step (3), the sintering is carried out at the temperature of 850-900 ℃ for 30-120 min.

6. The method of preparing an LTCC substrate according to claim 1,

the ball milling time in the step (1) is 12 h;

the drying in the step (1) is spray drying, and the conditions are as follows: the air inlet temperature is 200-250 ℃, the air outlet temperature is 90-100 ℃, and the rotation speed of the atomizer is 16000-27000 rpm;

the ball milling time in the step (2) is 20-28 h;

the forming mode in the step (3) is casting forming;

the isostatic pressing in the step (3) is as follows: the pressure is 50-70MPa, the liquid temperature is 65-80 ℃, and the pressure maintaining time is 20-40 min.

7. The method for preparing the LTCC substrate according to claim 1, wherein the KBS glass frit is prepared by the method comprising the steps of (2):

(b) ball-milling the glass quenched in the step (1) to obtain glass slurry, and drying to obtain KBS glass powder;

SiO as described in step (a)₂、H₃BO₃、K₂CO₃、Na₂CO₃、CaCO₃、BaCO₃The mass ratio of (A) to (B) is 50-65: 30-45: 1-4: 0-0.5: 0.1-0.8: 0.1-0.7;

homogenizing the molten glass in the step (a) at 1300 ℃ for 1-2 h;

the drying in the steps (a) and (b) is drying for 12 hours at the temperature of 100 ℃;

the ball milling in the step (a) is carried out for 2-4h by planet ball milling;

and (b) performing planetary ball milling for 12-24 h.

8. The method of claim 7, wherein the SiO in step (a) is in the form of a SiO solid₂、H₃BO₃、K₂CO₃、Na₂CO₃、CaCO₃、BaCO₃The mass ratio of (A) to (B) is 55-58: 40-43: 1.3-1.6: 0-0.2: 0.1-0.3: 0.1-0.3.

9. An LTCC substrate produced by the production method according to any one of claims 1 to 8.

10. Use of the LTCC substrate of claim 9 in the manufacture of a microwave dielectric device.