阅读说明：本技术 一种钛酸锶环形压敏电阻掺铋铜电极及其制备方法 (Bismuth-doped copper electrode of strontium titanate annular piezoresistor and preparation method thereof ) 是由 陈国新 于 2021-01-06 设计创作，主要内容包括：本发明提供一种钛酸锶环形压敏电阻掺铋铜电极及其制备方法,按以下具体成分配比混合：铜粉60-80％,铋粉1-20％,玻璃粉1-10％,有机载体10-20％。所述有机载体的具体成分配比为：乙基纤维素5-15％,松油醇30-50％,邻苯二甲酸二丁酯20-40％,油酸0.1-1％。预先将有机载体配料通过水浴90℃加热溶解乙基纤维素,再将各种粉体加入有机载体搅拌,再经过三辊研磨机研磨,再过滤得到浆料；再印刷在钛酸锶环形压敏电阻器上,最后放入烧结炉中烧结即成,本发明在浆料中掺入铋,使其烧结出来的铜浆形成铋铜合金,采用掺铋的方式来改善铜浆的烧结性能,烧结温度大大降低,烧出好后的电极,形成铋铜合金,电极更加致密,焊锡性能优秀。(The invention provides a bismuth-doped copper electrode of a strontium titanate annular piezoresistor and a preparation method thereof, wherein the bismuth-doped copper electrode is prepared by mixing the following specific components in proportion: 60-80% of copper powder, 1-20% of bismuth powder, 1-10% of glass powder and 10-20% of organic carrier. The organic carrier comprises the following specific components in percentage by weight: 5-15% of ethyl cellulose, 30-50% of terpineol, 20-40% of dibutyl phthalate and 0.1-1% of oleic acid. Heating and dissolving ethyl cellulose in organic carrier ingredients in a water bath at 90 ℃, adding various powders into the organic carrier, stirring, grinding by a three-roll grinder, and filtering to obtain slurry; the bismuth is doped into the slurry, so that the sintered copper slurry forms bismuth-copper alloy, the sintering performance of the copper slurry is improved by adopting a bismuth-doped mode, the sintering temperature is greatly reduced, the sintered electrode forms the bismuth-copper alloy, the electrode is more compact, and the soldering tin performance is excellent.)

1. The bismuth-doped copper electrode of the strontium titanate annular piezoresistor is characterized by being sintered by the following slurry in parts by weight:

2. the bismuth-doped copper electrode of the strontium titanate annular piezoresistor of claim 1, characterized in that: the granularity of the copper powder is 0.1-5 microns, the granularity of the bismuth powder is 0.5-20 microns, and the granularity of the glass powder passes through a 325-mesh screen.

3. The bismuth-doped copper electrode of the strontium titanate annular piezoresistor of claim 2, characterized in that: the granularity of the copper powder is 0.5-3 microns, and the granularity of the bismuth powder is 3-5 microns.

4. The bismuth-doped copper electrode of the strontium titanate annular piezoresistor according to claim 1, wherein the specific component ratio of the organic carrier is as follows:

5. a method for preparing the bismuth-doped copper electrode of the strontium titanate annular piezoresistor as claimed in claim 4, characterized by comprising the following steps: s1, heating the ingredients of the organic carrier in water bath at 90 ℃ in advance, and dissolving ethyl cellulose to obtain a uniform solution; s2: adding copper powder, bismuth powder and glass powder into the organic carrier and stirring; s3: grinding the mixture by a three-roll grinder until the granularity of the slurry is less than 10 microns; s4, filtering the mixture by a 300-mesh nylon net to obtain slurry; s5, screen-printing the slurry on the strontium titanate annular piezoresistor through 250 meshes, and drying the slurry at the temperature of 120-; and S6, finally, placing the mixture into a sintering furnace to be sintered.

6. The method for preparing the bismuth-doped copper electrode of the strontium titanate annular piezoresistor of claim 5, wherein in the step S6, the sintering temperature-time curve is as follows: the temperature is raised to 850 ℃ of 700-.

7. The method for preparing the bismuth-doped copper electrode of the strontium titanate annular piezoresistor of claim 5, wherein in the step S6, the sintering atmosphere is divided into two parts: the nitrogen atmosphere containing 20-100PPM oxygen is used before 450 deg.C, and pure nitrogen (purity greater than 99.99%) is used after 450 deg.C.

Technical Field

The invention belongs to the technical field of strontium titanate annular piezoresistors, and particularly relates to a bismuth-doped copper electrode of a strontium titanate annular piezoresistor and a preparation method thereof.

Background

The strontium titanate annular piezoresistor for the miniature direct current motor plays roles in weakening electric brush sparks and resisting electromagnetic interference. The resistor is connected with the motor and has electrodes, and the electrodes have two functions: soldering tin together to connect with the motor rotor coil; the two parts are connected with the resistor magnet to form ohmic contact, so that the electrical property is exerted. The mainstream electrodes are copper electrodes and silver electrodes. Silver is a precious metal, the cost is high, the technology is relatively simple, and most manufacturers adopt silver electrodes. The copper electrode technology difficulty is big, and the copper electrode of resistor has multiple advantage: the cost is low; the ohmic contact performance with the resistor magnet is good, and the performance is better; copper has no electron migration defect, so the performance is stable and durable; copper is more solder resistant and less prone to ablation of the electrodes. Copper electrodes are therefore a future trend for this resistor.

Copper electrode has many advantages, but has a big disadvantage that the manufacturing technology is more complicated than silver electrode, which hinders the application of various manufacturers in China. Copper electrode needs to be sintered at high temperature, and copper is easy to oxidize at high temperature, so that the copper electrode needs to be sintered in inert gas in a protection manner, the sintering temperature of copper paste is higher than 800 ℃ according to the property of the copper powder, the copper powder with the particle size of about 1 micron of D50 needs to be sintered at a temperature higher than 800 ℃, and the particle size is larger, so that the particle size is smaller, the powder density is small, the number of sintering holes is large, and the densification is more difficult. Sintering copper slurry needs to be carried out in a nitrogen atmosphere, a sintering furnace needs to be good in air tightness and is often made of a stainless steel container, the sintering temperature is over 800 ℃, and the load of the stainless steel container is large. The higher the temperature is, the more the energy consumption is, the lower the sintering temperature is, the copper alloy is thought to be, the kinds of the alloy are many, the addition of zinc, aluminum, iron and other substances to the copper powder can reduce the sintering temperature to a certain extent, and the addition of zinc, aluminum, iron, silicon, titanium and other substances can affect the soldering performance of the copper electrode, so the electrode requirement of the resistor is not met.

In summary, the problems in the art are: copper is difficult to be burnt compactly, and the burnt electrode has many holes, so that the adhesion of the copper electrode and the magnet of the resistor is influenced; the copper electrode is sintered and has a thick oxide film on the surface, so the soldering performance is poor, the copper electrode of the resistor needs soldering tin to be connected with a rotor of a motor, and the application is hindered due to the difficulty of soldering.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a bismuth-doped copper electrode of a strontium titanate annular piezoresistor, bismuth is doped into slurry, so that the sintered copper slurry forms bismuth-copper alloy, the sintering performance of the copper slurry is improved by adopting a bismuth-doped mode, the sintering temperature is greatly reduced, the sintered electrode forms bismuth-copper alloy, the electrode is more compact, and the soldering tin performance is excellent.

In order to achieve the purpose, the invention provides a bismuth-doped copper electrode of a strontium titanate annular piezoresistor, which is characterized by being sintered by the following slurry in parts by weight:

furthermore, the granularity of the copper powder is 0.1-5 microns, the granularity of the bismuth powder is 0.5-20 microns, and the granularity of the glass powder passes through a 325-mesh screen.

Preferably, the particle size of the copper powder is 0.5-3 microns, and the particle size of the bismuth powder is 3-5 microns.

Further, the organic carrier comprises the following specific components in proportion:

the invention also provides a preparation method of the bismuth-doped copper electrode of the strontium titanate annular piezoresistor, which is characterized by comprising the following steps of: s1, heating the ingredients of the organic carrier in water bath at 90 ℃ in advance, and dissolving ethyl cellulose to obtain a uniform solution; s2: adding copper powder, bismuth powder and glass powder into the organic carrier and stirring; s3: grinding the mixture by a three-roll grinder until the granularity of the slurry is less than 10 microns; s4, filtering the mixture by a 300-mesh nylon net to obtain slurry; s5, screen-printing the slurry on the strontium titanate annular piezoresistor through 250 meshes, and drying the slurry at the temperature of 120-; and S6, finally, placing the mixture into a sintering furnace to be sintered.

Further, in step S6, the sintering temperature-time curve: the temperature is raised to 850 ℃ of 700-.

Further, in the step S6, the sintering atmosphere is divided into two parts: the nitrogen atmosphere containing 20-100PPM oxygen is used before 450 deg.C, and pure nitrogen (purity greater than 99.99%) is used after 450 deg.C.

The invention has the following beneficial effects:

the sintering temperature of copper powder can be reduced by doping bismuth into copper slurry, the melting point of bismuth is only 271.3 ℃, the bismuth belongs to a low-melting-point substance, the melting point of copper is 1083.4 ℃, the sintering liquid phase of the copper powder appears along with the fact that the particle size of the copper powder is 1 micron or less, the temperature is 700 plus one year of the sintering liquid phase and 850 ℃ is lower than the melting point, the low-melting-point doping sintering of bismuth is favorable for further reducing the sintering temperature of the copper powder, and a copper-bismuth alloy is formed, has good tin-coating performance and is extremely ideal as a strontium titanate annular piezoresistor bismuth-doped copper electrode.

Drawings

FIG. 1 is an enlarged view of the copper layer densification using a copper storage electrode;

FIG. 2 is an enlarged view of the copper layer densification of a bismuth-containing copper electrode;

FIG. 3 is a diagram of a tin-on sample using a copper-storing electrode;

FIG. 4 is a diagram of a tin-on sample of a bismuth-containing copper electrode.

Detailed Description

The invention will now be further described with reference to specific examples:

example 1:

slurry of a bismuth-doped copper electrode of a strontium titanate annular piezoresistor is mixed according to the following specific component proportions: 60% of copper powder, 15% of bismuth powder, 10% of glass powder and 15% of organic carrier, wherein the particle size of the copper powder is 0.1-0.5 micron, the particle size of the bismuth powder is 0.5-3 micron, the surface of the bismuth powder is allowed to be naturally oxidized, the melting point of the glass powder is 450-700 ℃, and the specific component ratio of the organic carrier is as follows: 10% of ethyl cellulose, 50% of terpineol, 39% of dibutyl phthalate and 1% of oleic acid, and the preparation method comprises the following steps: heating the ingredients of the organic carrier in a water bath at 90 ℃ in advance, and dissolving ethyl cellulose to obtain a uniform solution; s2: adding copper powder, bismuth powder and glass powder into the organic carrier and stirring; s3: grinding the mixture by a three-roll grinder until the granularity of the slurry is less than 10 microns; s4, filtering the mixture by a 300-mesh nylon net to obtain slurry; s5, screen-printing the slurry on the strontium titanate annular piezoresistor through 250 meshes, and drying the slurry at the temperature of 120-; s6, finally placing the mixture into a sintering furnace for sintering, wherein the sintering temperature-time curve is as follows: the temperature is raised to 850 ℃ of 700-: the nitrogen atmosphere containing 20-100PPM oxygen is used before 450 ℃, pure nitrogen (purity is more than 99.99%) is used after 450 ℃ to finish, and the oxygen is mainly used for removing glue by decomposing ethyl cellulose in the slurry through oxygen.

Example 2:

the difference from example 1 is that:

slurry of a bismuth-doped copper electrode of a strontium titanate annular piezoresistor is mixed according to the following specific component proportions: 64% of copper powder, 12% of bismuth powder, 7.5% of glass powder and 16.5% of organic carrier, wherein the granularity of the copper powder is 0.5-3 microns, the granularity of the bismuth powder is 3-5 microns, and the specific component ratio of the organic carrier is as follows: 15% of ethyl cellulose, 44.5% of terpineol, 40% of dibutyl phthalate and 0.5% of oleic acid.

The preparation method is the same as that of example 1.

Example 3:

the difference from example 1 is that:

slurry of a bismuth-doped copper electrode of a strontium titanate annular piezoresistor is mixed according to the following specific component proportions: 74% of copper powder, 5% of bismuth powder, 5% of glass powder and 16% of organic carrier, wherein the particle size of the copper powder is 3-5 microns, the particle size of the bismuth powder is 5-20 microns, and the specific component ratio of the organic carrier is as follows: 13% of ethyl cellulose, 48% of terpineol, 38.7% of dibutyl phthalate and 0.3% of oleic acid.

The preparation method is the same as that of example 1.

For further comparison with pure copper, the present invention provides the following example 4: the difference from example 1 is that:

slurry of a bismuth-doped copper electrode of a strontium titanate annular piezoresistor is mixed according to the following specific component proportions: 70% of copper powder, 10% of bismuth powder, 3% of glass powder and 17% of organic carrier, wherein the organic carrier comprises the following specific components in percentage by weight: ethyl cellulose accounts for 10 percent of the total mass of the whole organic carrier, terpineol 50 percent, dibutyl phthalate 39.5 percent and oleic acid 0.5 percent.

The preparation method is the same as that of example 1.

Comparative example: the differences from example 4 are: slurry of a strontium titanate annular piezoresistor copper electrode is mixed according to the following specific component proportions: 80% of copper powder, 3% of glass powder and 17% of organic carrier, wherein the organic carrier comprises the following specific components in percentage by weight: ethyl cellulose accounts for 10 percent of the total mass of the whole organic carrier, terpineol accounts for 50 percent, dibutyl phthalate accounts for 39.5 percent, and oleic acid accounts for 0.5 percent. The preparation method is the same as example 4.

Example 4 and comparative examples were prepared using the same batch of resistor magnets and the same process, and the results of electrode comparison were as follows:

and (4) conclusion: as seen from the above table, the electrode of example 4 has good denseness, easy tin application, and strong adhesion as compared with the pure copper electrode.

And (4) conclusion: from the above table, there is no difference in the basic electrical properties of the resistor produced by the two electrodes compared to pure copper electrodes.

Therefore, the bismuth is doped into the copper paste for the strontium titanate annular piezoresistor, the sintered copper paste forms bismuth-copper alloy, the bismuth is doped to improve the sintering performance of the copper paste, the sintering temperature can be reduced, and the bismuth-copper alloy is formed by sintering the good electrode, so that the electrode is more compact and has excellent soldering performance.

The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that variations based on the shape and principle of the present invention should be covered within the scope of the present invention.