阅读说明：本技术 一种低温共烧陶瓷内导电银浆及其制备方法 (Low-temperature co-fired ceramic inner conductive silver paste and preparation method thereof ) 是由 姚英邦 胡永才 李毅 许一文 毕道广 焦志伟 郭劲 陈先义 鲁圣国 陶涛 梁波 于 2020-12-10 设计创作，主要内容包括：本发明公开了一种低温共烧陶瓷内导电银浆及其制备方法,所述导电银浆由如下质量百分比的原料制备得到：银粉75％～83％、玻璃粉1％～5％、氧化铝颗粒0.1％～1％、有机载体15％～20％；所述银粉为球状银粉,平均粒径为450～550nm；所述有机载体包括溶剂、添加剂、增塑剂、黏结剂以及分散剂。本发明的导电银浆与LTCC陶瓷基板具有优秀的共烧匹配性、印刷性以及优良的导电性,将银导电浆料经丝网印刷、烧结氧化铝陶瓷基板上,形成银导体电极,并测其电阻率,均符合LTCC技术的应用。(The invention discloses a low-temperature co-fired ceramic inner conductive silver paste and a preparation method thereof, wherein the conductive silver paste is prepared from the following raw materials in percentage by mass: 75-83% of silver powder, 1-5% of glass powder, 0.1-1% of alumina particles and 15-20% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 450-550 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant. The conductive silver paste and the LTCC ceramic substrate have excellent co-firing matching property, printing property and conductivity, the silver conductive paste is subjected to screen printing and sintering on the alumina ceramic substrate to form a silver conductor electrode, and the resistivity of the silver conductor electrode is measured, so that the silver conductor electrode and the LTCC ceramic substrate are all in accordance with the application of the LTCC technology.)

1. The conductive silver paste in the low-temperature co-fired ceramic is characterized by comprising the following components in percentage by mass: 75-83% of silver powder, 1-5% of glass powder, 0.1-1% of alumina particles and 15-20% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 450-550 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

2. The conductive silver paste in the low-temperature co-fired ceramic according to claim 1, wherein the glass powder comprises the following components in percentage by mass: 35 to 40 percent of silicon oxide, 35 to 40 percent of calcium oxide, 12 to 18 percent of aluminum oxide, 5 to 15 percent of barium oxide and 0.5 to 1.2 percent of lithium oxide.

3. The conductive silver paste in low-temperature co-fired ceramic of claim 1, wherein the solvent is one or more of terpineol, butyl carbitol acetate, butyl carbitol, ethylene glycol ethyl ether acetate and lecithin.

4. The conductive silver paste in the low-temperature co-fired ceramic according to claim 1, wherein the dispersant is one or more of castor oil, span 85, tributyl phosphate and polymethacrylic acid amine.

5. The low-temperature co-fired ceramic inner conductive silver paste of claim 1, wherein the plasticizer is one or both of dibutyl phthalate and dioctyl phthalate.

6. The low-temperature co-fired ceramic inner conductive silver paste of claim 1, wherein the binder is one or two of ethyl cellulose and hexadecanol; the additive is acetone.

7. The preparation method of the conductive silver paste in the low-temperature co-fired ceramic according to any one of claims 1 to 6, characterized by comprising the following steps:

s1, uniformly mixing silver powder, glass powder, an organic carrier and alumina particles in proportion;

and S2, carrying out ball milling and uniform dispersion on the uniformly mixed slurry to obtain the conductive silver paste.

8. The method for preparing the conductive silver paste in the low-temperature co-fired ceramic according to claim 7, wherein in step S2, the ball milling time is 12-18 h, and the ball milling speed is 400-600 rad/min.

9. The method for preparing the conductive silver paste in the low-temperature co-fired ceramic according to claim 7, wherein the method for preparing the silver powder comprises the following steps:

s11, mixing and stirring a silver nitrate solution and ammonia water to obtain a silver-ammonia solution;

s12, mixing and stirring an ascorbic acid solution and a dispersing agent to obtain a reducing solution;

s13, adding the silver-ammonia solution into the reducing solution to obtain the silver powder.

10. The method for preparing the conductive silver paste in the low-temperature co-fired ceramic according to claim 9, wherein the dispersant is one or more of gelatin, polyvinyl alcohol, polyvinylpyrrolidone and oleic acid.

Technical Field

The invention relates to the technical field of conductive paste, in particular to low-temperature co-fired ceramic inner conductive silver paste and a preparation method thereof.

Background

With the rapid development of modern microelectronic information technology, people demand electronic components in the aspects of portability, miniaturization, digitalization, multifunction, high performance and high reliability, so that the requirements of integration, miniaturization and modularization of electronic components are increasingly urgent. Low temperature co-fired ceramic (LTCC) technology is a multi-disciplinary cross comprehensive integrated assembly technology emerging in recent decades and becomes a research hotspot of people in recent years, and due to good thermodynamics, electronics and corresponding mechanical properties, the LTCC technology has become a preferential development direction in the fields of future electronic component integrated devices and microwave technology, and has a good application prospect.

The invention discloses a conductive silver paste for a low-temperature co-fired ceramic substrate and a preparation method thereof (2018, 11, 2.8.8.11. 108735343A.8.3.3.3.3.3.3.3.3.3.3.3. the conductive silver paste takes silver powder, high polymer resin, glass powder and a solvent as raw materials, and the prepared silver paste is flat and compact in silver layer after being sintered, the binding force between the silver layer and a ceramic interface is strong, cracking and layering do not occur in the device, but the conductivity of the device is still to be improved.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide the low-temperature co-fired conductive silver paste in the ceramic. The conductive silver paste and the LTCC ceramic substrate have good co-firing matching performance and excellent conductivity.

The invention also aims to provide a preparation method of the conductive silver paste in the low-temperature co-fired ceramic.

In order to achieve the purpose, the invention adopts the scheme that:

the conductive silver paste in the low-temperature co-fired ceramic comprises the following components in percentage by mass: 75-83% of silver powder, 1-5% of glass powder, 0.1-1% of alumina particles and 15-20% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 450-550 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

As one of the main components of the silver paste, the particle size of the silver paste cannot be too large, which can cause poor screen printing performance of the silver paste, and the silver paste can agglomerate when the particle size is too small; furthermore, the conductivity of silver paste is mainly composed of two parts: one part is the resistance of pure silver itself and the other part is the contact resistance between silver powders, and too small particles of silver powders increase the contact resistance between silver powders. Through long-term research, the inventor finds that the silver powder with the particle size of 450-500 nm can avoid agglomeration, improve the screen printing performance, reduce the resistance and improve the conductivity of the silver paste.

In the low-temperature co-fired ceramic technology, a pattern is formed on a ceramic green tape by a screen printing mode through slurry, then the ceramic green tape and the slurry are sintered together, the sintering shrinkage behaviors of the ceramic and the silver slurry are required to be matched during co-firing, when mismatch occurs, stress can be generated at the interface of the two materials, so that a ceramic substrate is deformed, and the size precision of a circuit is difficult to control. If the shrinkage rate of the silver paste is larger than that of the ceramic, the ceramic tape can bear larger tension, and cracks can occur between interfaces to crack; if the shrinkage rate of the silver paste is smaller than that of the ceramic, the ceramic tape can bear larger pressure, and the interface will be warped and deformed. In order to reduce the mismatch of sintering shrinkage, under the condition that the composition and the particle size of the silver paste are fixed, the shrinkage behaviors of the silver paste and the aluminum oxide ceramic material are close to each other as much as possible by adjusting the parameters of the ceramic material, however, the adjustment space of the sintering shrinkage of the aluminum oxide ceramic material is limited. The aluminum oxide particles are added into the silver paste, so that the sintering shrinkage of the slurry can be effectively adjusted.

Preferably, the glass powder comprises the following components in percentage by mass: 35 to 40 percent of silicon oxide, 35 to 40 percent of calcium oxide, 12 to 18 percent of aluminum oxide, 5 to 15 percent of barium oxide and 0.5 to 1.2 percent of lithium oxide.

Preferably, the solvent is one or more of terpineol, butyl carbitol acetate, butyl carbitol, ethylene glycol ethyl ether acetate and lecithin.

Preferably, the dispersant is one or more of castor oil, span 85, tributyl phosphate and polymethacrylic acid amine.

Preferably, the plasticizer is one or two of dibutyl phthalate and dioctyl phthalate.

Preferably, the binder is one or two of ethyl cellulose and hexadecanol; the additive is acetone.

The preparation method of the conductive silver paste in the low-temperature co-fired ceramic comprises the following steps:

s1, uniformly mixing silver powder, glass powder, an organic carrier and alumina particles in proportion;

and S2, carrying out ball milling and uniform dispersion on the uniformly mixed slurry to obtain the conductive silver paste.

Preferably, in step S2, the ball milling time is 12 to 18 hours, and the ball milling speed is 400 to 600 rad/min.

Preferably, the method for preparing the silver powder comprises the following steps:

s11, mixing and stirring a silver nitrate solution and ammonia water to obtain a silver-ammonia solution;

s12, mixing and stirring an ascorbic acid solution and a dispersing agent to obtain a reducing solution;

s13, adding the silver-ammonia solution into the reducing solution to obtain the silver powder.

More preferably, in step S12, the dispersant is one or more of gelatin, polyvinyl alcohol, polyvinylpyrrolidone, and oleic acid.

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

the conductive silver paste prepared by the invention has no warpage and breakpoints after being sintered, has good co-firing matching with an LTCC ceramic substrate, and has excellent conductivity, and the resistivity of the formed silver conductor electrode is as low as 0.248m omega mm.

Drawings

Fig. 1 is a flow chart of the preparation of the conductive silver paste of the present invention.

Detailed Description

In order to more clearly and completely describe the technical scheme of the invention, the invention is further described in detail by the specific embodiments, and it should be understood that the specific embodiments described herein are only used for explaining the invention, and are not used for limiting the invention, and various changes can be made within the scope defined by the claims of the invention.

In the invention, the general preparation method of the glass powder comprises the following steps:

1) accurately weighing the oxides in proportion, putting the oxides into a corundum crucible, and fully and uniformly stirring the oxides by using a glass rod;

2) putting the prepared glass oxide into a high-temperature sintering furnace, and preheating the glass oxide by keeping the temperature at 400 ℃ for 10 minutes;

3) after the heat preservation, the temperature of the high-temperature sintering furnace is raised to 1400 ℃ at the speed of 10 ℃/min, and the heat preservation is carried out for 30 minutes;

4) taking out the molten glass powder by using a sampling clamp, and then quickly pouring the molten glass powder into an aluminum alloy lunch box filled with deionized water for water quenching;

5) and putting the cooled glass powder into a ball milling tank, adding 8cm, 5cm and 3cm zirconium balls in a ball-to-material ratio of 5:3:2, adding alcohol serving as a ball milling medium in a solid-to-liquid ratio of 3:2, performing ball milling for 30 hours, drying, grinding and sieving to obtain the glass powder.

In the invention, the general preparation steps of the silver powder comprise the following steps:

1) mixing 40ml of silver nitrate solution with the concentration of 50g/L and 3.5g of ammonia water, and stirring until the solution becomes colorless to obtain silver ammonia solution;

2) mixing and stirring 40ml of ascorbic acid solution with the concentration of 25g/L and 0.14g of dispersing agent until the ascorbic acid solution is completely dissolved to obtain a reducing agent solution;

3) adding the silver-ammonia solution into the reducing agent solution, stirring while dropwise adding, enabling the solution color to be changed into dark green, stirring for 1h, centrifuging, respectively cleaning with clear water and absolute ethyl alcohol for three times, and then performing ultrasonic dispersion to obtain the high-dispersibility silver powder for later use.

The compositions of oxides of glass frit A series A1-A5 are shown in Table 1.

TABLE 1

	Silicon oxide	Alumina oxide	Alumina oxide	Barium oxide	Lithium oxide
						A1	38％	38％	15％	8％	1％
A2	35％	40％	12％	11.8％	1.2％
						A3	40％	35％	18％	6.5％	0.5％
A4	37％	39％	18％	5％	1％
						A5	35％	35％	14.2％	15％	0.8％

In the present invention, the general preparation steps of the organic vehicle include the following steps:

1) accurately weighing each component of the organic carrier according to the proportion, mixing the components in a glass beaker, putting the glass beaker into a constant-temperature oil bath magnetic stirrer at the temperature of 60 ℃, uniformly stirring the mixture until insoluble matters such as ethyl cellulose, lecithin, hexadecanol and the like are completely dissolved, and storing the mixture at room temperature and ambient temperature.

Example 1

The utility model provides a low temperature fires electrically conductive silver thick liquid in pottery altogether, by mass percent, electrically conductive silver thick liquid includes the raw materials of following component: 78% of silver powder, 3% of glass powder (A1), 0.6% of alumina particles and 18.4% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 500 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

The composition of the glass frit described in this example is shown as a1 in table 1.

The composition of the organic vehicle described in this example is shown in table 2.

The silver powder described in this example was prepared using gelatin as the dispersing agent.

A preparation method of conductive silver paste in low-temperature co-fired ceramic is shown in figure 1 and comprises the following steps:

s1, accurately weighing silver powder, glass powder, an organic carrier and alumina particles according to a proportion, and placing the silver powder, the glass powder, the organic carrier and the alumina particles in a high-power constant-temperature stirrer for pre-stirring for 5 hours;

s2, taking out the slurry of the stirrer, and performing ball milling for 15 hours at a rotating speed of 500rad/min to obtain the conductive silver paste.

TABLE 2

Example 2

The utility model provides a low temperature fires electrically conductive silver thick liquid in pottery altogether, by mass percent, electrically conductive silver thick liquid includes the raw materials of following component: 75% of silver powder, 4.9% of glass powder (A2), 0.1% of alumina particles and 20% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 450 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

The composition of the glass frit described in this example is shown as a2 in table 1.

The composition of the organic vehicle in this example was substantially the same as in example 1, except that the dispersant was span 85.

The silver powder described in this example was prepared using polyvinyl alcohol as the dispersant.

The preparation method of the low-temperature co-fired ceramic inner conductive silver paste in the embodiment is basically the same as that in the embodiment 1, and the difference is that the ball milling time is 12 hours, and the ball milling rotating speed is 400 rad/min.

Example 3

The utility model provides a low temperature fires electrically conductive silver thick liquid in pottery altogether, by mass percent, electrically conductive silver thick liquid includes the raw materials of following component: 83% of silver powder, 1% of glass powder (A3), 1% of alumina particles and 15% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 550 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

The composition of the glass frit described in this example is shown as a3 in table 1.

The composition of the organic vehicle of this example was substantially the same as that of example 1, except that the dispersant was polymethacrylamide.

The silver powder described in this example was prepared using polyvinylpyrrolidone as the dispersant.

The preparation method of the low-temperature co-fired ceramic inner conductive silver paste in the embodiment is basically the same as that in the embodiment 1, and the difference is that the ball milling time is 18h, and the ball milling rotating speed is 600 rad/min.

Example 4

The utility model provides a low temperature fires electrically conductive silver thick liquid in pottery altogether, by mass percent, electrically conductive silver thick liquid includes the raw materials of following component: 78% of silver powder, 5% of glass powder (A4), 1% of alumina particles and 16% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 500 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

The composition of the glass frit described in this example is shown as a4 in table 1.

The composition of the organic vehicle in this example was essentially the same as in example 1 except that the dispersant was tributyl phosphate.

The silver powder described in this example was prepared using oleic acid as the dispersant.

The preparation method of the low-temperature co-fired ceramic inner conductive silver paste in the embodiment is basically the same as that in the embodiment 1, and the difference is that the ball milling time is 15 hours, and the ball milling rotating speed is 550 rad/min.

Example 5

The utility model provides a low temperature fires electrically conductive silver thick liquid in pottery altogether, by mass percent, electrically conductive silver thick liquid includes the raw materials of following component: 78% of silver powder, 3% of glass powder (A5), 0.6% of alumina particles and 18.4% of organic carrier; the silver powder is spherical silver powder, and the average particle size is 500 nm; the organic vehicle includes a solvent, an additive, a plasticizer, a binder, and a dispersant.

The composition of the glass frit described in this example is shown as a5 in table 1.

The composition of the organic vehicle described in this example was consistent with example 1.

The silver powder described in this example was prepared using gelatin as the dispersing agent.

The preparation method of the low-temperature co-fired ceramic inner conductive silver paste in the embodiment is basically the same as that in the embodiment 1, and the difference is that the ball milling time is 15 hours, and the ball milling rotating speed is 500 rad/min.

Performance testing

The conductive silver paste prepared in examples 1 to 5 was printed on an alumina ceramic substrate through a stainless steel wire mesh, dried at 120 ℃ for 10 minutes, and then sintered in a high temperature sintering furnace for 120 minutes at a peak temperature of 870 ℃ for 10 minutes. Thereafter, each sample was tested for resistivity and shrinkage. The calculation formula of the resistivity ρ is as follows:

where L is the length of the material, S is the cross-sectional area (S ═ w × h), w is the width of the electrode wire, and h is the thickness of the electrode.

The calculation formula of the shrinkage rate is as follows:

wherein L is₁For the width of the electrode after baking, L₂Is the width of the electrode after sintering.

The test results are shown in table 3.

TABLE 3

As can be seen from table 3, the resistivity of the silver conductor electrode formed by the silver paste of the present invention is as low as 0.248m Ω · mm, which indicates that it has excellent conductivity; after sintering, the silver paste has no warpage or breaking point, and the shrinkage rate is lower than 10%, which shows that the silver paste and the LTCC ceramic substrate have good co-firing matching property.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.