CN107511602B - A kind of nano Ag-Cu solder paste and its preparation method and application - Google Patents

Abstract

The invention discloses a nano-Ag-Cu solder paste, a preparation method and an application thereof. The nano-Ag-Cu solder paste is prepared from Ag powder, Cu powder and glycerol according to the following ratio: the mass ratio of Ag powder to Cu powder is 2～4:1; the sum of the mass of Ag powder and Cu powder The mass ratio to glycerol is 8-12:1. Wherein, the particle diameter of the Ag powder is 5-10 nm, and the particle diameter of the Cu powder is 20-60 nm. The preparation method of the nano-Ag-Cu solder paste is as follows: take Ag powder and Cu powder, add alcohol and grind to obtain Ag-Cu mixed powder, then add glycerol to make a viscous paste, and obtain nano-Ag-Cu solder paste . The nano-Ag-Cu solder paste can be used to prepare copper-copper connectors, and the specific steps are as follows: take an appropriate amount of nano-Ag-Cu solder paste, apply it evenly on the surfaces to be connected of two copper base materials, close the surfaces to be connected ,connect. The nano-Ag-Cu solder paste provided by the invention has strong oxidation resistance, good electrochemical migration resistance, high electrical conductivity and thermal conductivity, and the joint prepared by the connection thereof has ideal shear strength and high reliability.

Description

A kind of nano Ag-Cu solder paste and its preparation method and application

technical field

The invention belongs to the field of nano connection, and in particular relates to a nano Ag-Cu solder paste and a preparation method and application thereof.

Background technique

High-power electronic devices are often accompanied by high operating temperatures. In order to meet the requirements of electronic packaging, solder with a higher melting point is required. The corresponding melting points of Cu and Ag bulk materials are 1080°C and 960°C respectively, which are much higher than the melting point requirements of solder (usually around 200°C). In addition, both Cu and Ag are good conductors of electricity, which also ensures the stable transmission of electrical signals in electronic devices. At the same time, the addition of nano Cu particles can also reduce costs. Therefore, the preparation and application of nano-Ag-Cu solder is of great significance to the field of high-temperature electronic packaging.

However, the high melting points of Ag and Cu lead to difficulties in bonding, as excessive bonding temperatures can damage substrates and related components. Moreover, solders containing Ag and Cu in the prior art also have problems such as poor resistance to electrochemical migration and easy oxidation.

Contents of the invention

Aiming at the problems existing in the prior art, the object of the present invention is to provide a nano-Ag-Cu solder paste and its preparation method and application. The nano-Ag-Cu solder paste provided by the invention has strong oxidation resistance, good electrochemical migration resistance, high electrical conductivity and thermal conductivity, and has lower requirements on connection temperature when used for preparing joints, and the nano-Ag-Cu The solder paste connection has ideal joint shear strength and high reliability.

In order to achieve the above object, the technical scheme provided by the present invention is as follows:

A nano-Ag-Cu solder paste is characterized in that it is prepared from Ag powder, Cu powder and glycerol according to a certain ratio.

According to the above scheme, preferably, the mass ratio of the Ag powder to the Cu powder is 2-4:1; the mass ratio of the mass sum of the Ag powder and the Cu powder to glycerol is 8-12:1.

According to the above solution, preferably, the Ag powder has a particle size of 5-10 nm, and the Cu powder has a particle size of 20-60 nm.

According to the above scheme, preferably, the preparation method of the Ag powder with a particle size of 5-10 nm uses stearic acid, sodium hydroxide, and silver nitrate as raw materials, and is prepared by a liquid-phase chemical-thermal decomposition method, and the specific steps are as follows :

(1) Dissolve sodium hydroxide and stearic acid in deionized water and heat to 80°C, add AgNO ₃ , stir at constant temperature for 1 hour, then take the white waxy substance in the upper layer and centrifuge to clean it; more preferably, the speed of centrifugation is 7000r /min, the number of times of described cleaning is 4 times, and each cleaning time is 10min;

(2) Under the condition of blowing nitrogen, heat the white waxy substance after centrifugation and cleaning in step (1) to 250°C at a heating rate of 5°C/min and keep it warm for 90min to obtain nano-silver with a particle size of 5-10nm particles.

According to the above scheme, preferably, the preparation method of the Cu powder with a particle size of 20 to 60 nm is to use sodium hypophosphite and copper sulfate as raw materials and prepare it by a liquid phase chemical reduction method. The specific steps are as follows:

(1) Add sodium hypophosphite and PVP into the diethylene glycol solution and heat to 80°C, add CuSO ₄ 5H ₂ O, stir at constant temperature for 1 hour, and take the purple-black precipitate in the reaction solution;

(2) Centrifugal cleaning and drying treatment of the purple-black precipitated substance obtained in step (1), finally obtaining nano-copper particles with a particle diameter of 20 to 60 nm; more preferably, the speed of the centrifugation is 7000r/min, and the The number of times of cleaning is 4 times, and the time of each cleaning is 10 minutes.

The present invention also provides a preparation method of the above-mentioned nano-Ag-Cu solder paste, which is characterized in that the specific steps are as follows: take Ag powder and Cu powder, add an appropriate amount of alcohol to grind until the alcohol is completely volatilized, and obtain uniform Ag-Cu mixed powder, Glycerol is then added to make a viscous paste to obtain a nano-Ag-Cu composite solder paste.

The present invention also provides the application of the nano-Ag-Cu solder paste, which is characterized in that it is used as solder to prepare copper-to-copper connectors.

The present invention also provides a copper-to-copper connecting piece, which is characterized in that it is prepared by using the above-mentioned nano-Ag-Cu solder paste for connection. The schematic diagram of the present invention using the nano-Ag-Cu solder paste to connect copper is shown in FIG. 1 .

According to the above scheme, preferably, the surfaces of the copper and the copper are plated with a Ni layer and an Ag layer, that is, the two base materials of the connecting piece between the copper and the copper are both plated with Ni/Ag copper.

The present invention also provides a method for preparing the above-mentioned copper-to-copper connector, which is characterized in that it comprises the following steps:

Take an appropriate amount of nano-Ag-Cu solder paste, apply it evenly on the surfaces to be connected of the two copper base materials, and then connect the surfaces to be connected of the two copper base materials, and connect under certain pressure conditions.

According to the above solution, preferably, the surfaces to be connected of the two copper base materials are cleaned and dried. More preferably, the cleaning is ultrasonic cleaning with alcohol for at least 30 minutes.

According to the above scheme, preferably, the pressure is 3-5 MPa.

According to the above solution, preferably, the connection temperature is 280-350° C., and the time for maintaining this temperature is 30-40 minutes.

According to the above scheme, more preferably, the following step is further included before reaching the connection temperature: keeping warm at 200-250° C. for 20-30 minutes.

Basic principle of the present invention is as follows:

The invention mainly prepares nano-Ag-Cu solder paste by adding nano-Cu particles to nano-Ag solder, so that the prepared solder paste has the excellent properties of nano-Ag and Cu at the same time. When the size of the particles reaches the nanoscale, the particles will have high surface energy, resulting in a significant decrease in melting point and sintering temperature. Utilizing the size effect of nano-Ag and Cu, the solder can complete the mission of "low temperature packaging, high temperature service". Utilizing the excellent electrochemical migration resistance of Cu and the good oxidation resistance of Ag, the nano-Ag-Cu solder paste has excellent characteristics that conventional solders do not have. These excellent properties can make nano-Ag-Cu solder paste better used in the field of microelectronic packaging.

Compared with the prior art, the beneficial effects of the present invention are:

(1) The nano-Ag-Cu solder paste provided by the present invention possesses the excellent properties of both Ag and Cu.

(2) The preparation method of the nano-Ag-Cu solder paste provided by the invention is simple, easy to use, safe and reliable.

(3) The production cost of the nano-Ag-Cu solder paste provided by the present invention is relatively low, and it has good anti-electrochemical mobility, excellent electrical conductivity and thermal conductivity while having excellent oxidation resistance, and can be directly used as Solder is used in the field of electronic packaging. (4) When the nano-Ag-Cu solder paste obtained in the present invention is used to connect copper base materials, the requirements for the connection temperature are relatively low, only 280-350° C., and the joint interface layer of the obtained connector is well bonded, and no cracks are observed And pores and other defects, the shear strength is greater than 20MPa.

Description of drawings

FIG. 1 is a schematic diagram of the present invention using nano-Ag-Cu solder paste to connect copper.

FIG. 2 is a SEM image of Ag nanoparticles with a particle diameter of 5-10 nm prepared in Example 1. FIG.

FIG. 3 is an SEM image of nano Cu particles with a particle diameter of 20-60 nm prepared in Example 1. FIG.

FIG. 4 is the XRD spectrum of the nano-Ag-Cu mixed powder prepared in Example 1.

FIG. 5 is a microscopic topography diagram of the interface area of copper/copper joints connected by nano-Ag-Cu solder paste prepared in Example 1. FIG.

Detailed ways

In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

Example 1

The preparation of nanometer Ag-Cu solder paste, concrete steps are as follows:

1. Preparation of Ag powder (nano-silver particles with a particle size of 5-10nm):

First, dissolve 0.6g of sodium hydroxide and 4.65g of stearic acid in 600mL of deionized water, heat to 80°C, add 2.5g of AgNO ₃ , stir at constant temperature for 1 hour, then take the white waxy substance in the upper layer and centrifuge to clean it at a speed of 7000r /min, cleaning 4 times (including 3 times with deionized water and 1 time with alcohol), each cleaning time is 10min. Subsequently, the white waxy substance was heated in a tube furnace with nitrogen gas, the heating rate of the tube furnace was 5°C/min, and when it was heated to 250°C, it was kept for 90 minutes, and finally silver nanoparticles with a particle size of 5-10nm were obtained. . Fig. 2 is the SEM image of the silver nano particles prepared in this embodiment.

2. Preparation of Cu powder (copper nanoparticles with a particle size of 20-60nm):

First, add 0.7433g of sodium hypophosphite and 0.16g of PVP into 60ml of diethylene glycol solution and heat to 80°C, then add 1.9974g of CuSO ₄ 5H ₂ 0, stir at constant temperature for 1 hour, and take the purple-black color in the reaction solution. The precipitated matter was centrifugally cleaned at a centrifugal rate of 7000r/min for 4 times (including 3 times with deionized water and 1 time with alcohol), and the time for each cleaning was 10 minutes. Then, the purple-black precipitated substance is dried to finally obtain nano-copper particles with a particle diameter of 20-60 nm. FIG. 3 is a SEM image of the nano-copper particles prepared in this embodiment.

3. Preparation of nano-Ag-Cu solder paste: Mix the nano-Ag powder with a particle size of 5-10nm and the nano-Cu powder with a particle size of 20-60nm obtained in steps 1 and 2 respectively in a mass ratio of 3:1 , add alcohol and grind until the alcohol is completely volatilized to obtain a uniformly mixed nano-Ag-Cu mixed powder, and then add glycerin whose mass is one-tenth of the total mass of the nano-Ag-Cu mixed powder to make a viscous paste. Nano Ag-Cu solder paste.

Fig. 4 is the XRD spectrum of the nano-Ag-Cu mixed powder obtained in step 3 of this embodiment.

Example 2

The preparation of nanometer Ag-Cu solder paste, concrete steps are as follows:

Step 1, 2 are with embodiment 1;

Step 3, preparation of nano-Ag-Cu solder paste: the nano-Ag powder with a particle size of 5-10nm and the nano-Cu powder with a particle size of 20-60nm obtained in steps 1 and 2 respectively in a mass ratio of 4:1 Mix, add alcohol and grind until the alcohol is completely volatilized to obtain uniformly mixed nano Ag-Cu powder, then add glycerol whose mass is one-eighth of the total mass of nano Ag-Cu powder, and make a viscous paste to obtain nano Ag -Cu solder paste.

Application Example 1

The nanometer Ag-Cu solder paste that adopts embodiment 1 preparation is connected to plate Ni/Ag copper, and concrete steps are as follows:

1. Ultrasonic clean two pieces of Ni/Ag-plated copper in alcohol for 30 minutes, and dry them for later use.

2. Get a small amount of nano-Ag-Cu solder paste prepared in Example 1, apply it evenly on the surface to be connected of Ni/Ag copper, close the surface to be connected, and obtain Ni/Ag copper/nano-Ag-Cu soldering Paste/plated Ni/Ag copper to be connected.

3. Put Ni/Ag-plated copper/nano-Ag-Cu solder paste/Ni/Ag copper-plated parts to be connected into the hot press, set the pressure to 5MPa, first keep it at 200°C for 20min, and then heat it at 350°C The temperature is kept at a temperature of 30 minutes, and then cooled to room temperature with the furnace to obtain the final product Ni/Ag copper/nano-Ag-Cu solder paste/Ni/Ag copper joint.

The joints prepared in this embodiment were tested for shear strength on a universal testing machine, and the results showed that the average shear strength of the joints exceeded 20 MPa.

Fig. 5 is the microscopic appearance diagram of the joint interface area of the plated Ni/Ag copper/nanometer Ag-Cu solder paste/plated Ni/Ag copper joint that this application example adopts nano-Ag-Cu solder paste to make, as can be seen from the figure, The interface between the base metal and the connection layer is well bonded, and the solder layer is relatively uniform and dense.

Application Example 2

The nano-Ag-Cu solder paste prepared in Example 2 is used to connect plated Ni/Ag copper under different processes, and the specific steps are as follows:

1. Ultrasonic clean two pieces of Ni/Ag-plated copper in alcohol for 30 minutes, and dry them for later use.

2, get the nano Ag-Cu solder paste that a small amount of embodiment 2 makes, smear evenly on the surface to be connected of plated Ni/Ag copper base material, close the surface to be connected, obtain plated Ni/Ag copper/nanometer Ag-Cu Solder paste/Ni/Ag copper plated parts to be connected.

3. Put Ni/Ag-plated copper/nano-Ag-Cu solder paste/Ni/Ag copper-plated parts to be connected into the hot press, set the pressure to 4MPa, first keep it at 250°C for 25min, and then heat it at 320°C Keep it warm for 35 minutes at a certain temperature, and then cool to room temperature with the furnace to obtain the final product copper/copper joint.

The connection layer of the obtained joint is uniform and dense, and is well combined with the base material.

Claims (8)

1. A nanometer Ag-Cu soldering paste is characterized by being prepared from Ag powder, Cu powder and glycerol according to a certain proportion, wherein the grain diameter of the Ag powder is 5-10 nm, the grain diameter of the Cu powder is 20-60 nm,

The preparation method of the Ag powder with the particle size of 5-10 nm comprises the following steps:

(1) dissolving sodium hydroxide and stearic acid in deionized water, heating to 80 ℃, and adding AgNO₃Stirring at constant temperature for 1h, and centrifuging and cleaning the upper white waxy substance;

(2) heating the white waxy substance centrifugally cleaned in the step (1) to 250 ℃ at a heating rate of 5 ℃/min and preserving heat for 90min under the condition of introducing nitrogen to obtain nano silver particles with the particle size of 5-10 nm;

The preparation method of the Cu powder with the particle size of 20-60 nm comprises the following steps:

(1) Adding sodium hypophosphite and PVP into diethylene glycol solution, heating to 80 ℃, and adding CuSO₄·5H₂o, stirring at constant temperature for 1h, and taking the purple black substances in the reaction solution;

And (2) centrifugally cleaning and drying the purple black substance obtained in the step (1) to finally obtain the nano copper particles with the particle size of 20-60 nm.

2. The nano Ag-Cu solder paste as claimed in claim 1, wherein the mass ratio of Ag powder to Cu powder is 2-4: 1; the mass ratio of the sum of the mass of the Ag powder and the mass of the Cu powder to the mass of the glycerol is 8-12: 1.

3. The preparation method of the nano Ag-Cu soldering paste as claimed in any one of claims 1 to 2, which is characterized by comprising the following steps:

and adding a proper amount of alcohol into the Ag powder and the Cu powder, grinding until the alcohol is completely volatilized to obtain uniform Ag-Cu mixed powder, and adding glycerol to prepare a viscous paste to obtain the nano Ag-Cu composite soldering paste.

4. use of a nano Ag-Cu solder paste according to any one of claims 1 to 2 as a solder for the preparation of copper-to-copper connectors.

5. A copper-to-copper connector, which is manufactured by using the nano Ag-Cu paste according to any one of claims 1 to 2, wherein the surfaces of the copper and the copper are plated with a Ni layer and an Ag layer.

6. the method of making a copper-to-copper interconnect of claim 5, comprising the steps of:

Taking a proper amount of nano Ag-Cu soldering paste, uniformly coating the nano Ag-Cu soldering paste on the surfaces to be connected of the two copper base metals, butting the surfaces to be connected of the two copper base metals, and connecting under a certain pressure.

7. the method for preparing a copper-copper connecting piece according to claim 6, wherein the pressure is 3 to 5 MPa; the temperature of the connection is 280-350 ℃, and the time for keeping the temperature is 30-40 min.

8. The method of making a copper to copper connection according to claim 7, further comprising the steps of, prior to reaching the temperature of said connection: keeping the temperature at 200-250 ℃ for 20-30 min.