CN117123793A - Mesoscopically structured micron silver, low-temperature sinterable solder paste and preparation method and application thereof - Google Patents

Abstract

The invention provides a micro-silver with a mesostructure, soldering paste capable of being sintered at low temperature, a preparation method and application thereof, wherein the micro-silver with the mesostructure is prepared by the following steps: preparing a precursor solution containing silver ions and a coating agent and a reducing solution containing a reducing agent respectively; mixing the precursor solution and the reducing solution, performing oxidation-reduction reaction for a period of time at 25-80 ℃, then dripping a surface etchant or a surface etchant solution for reaction, centrifuging the obtained solution, taking out precipitate, cleaning and drying to obtain micron silver particles with mesoscopic structures on the surfaces; the surface etchant is at least one of ferric chloride, ferrous chloride and sodium chloride. The surface of the micron silver particles obtained by the technical scheme of the invention has a shape structure with mesoscopic size, the obtained micron silver soldering paste can be uniformly dispersed without additional additives, and the low-temperature sintering and high Wen Fuyi can be realized.

Description

Micro-silver with mesoscopic structure, soldering paste capable of being sintered at low temperature, and preparation method and application thereof

Technical Field

The invention belongs to the technical field of electronic packaging materials, and particularly relates to a micro-silver soldering paste with a mesostructure, a soldering paste capable of being sintered at a low temperature, a preparation method and application thereof.

Background

The new generation of semiconductor materials such as SiC, gallium nitride, etc. can stably operate at higher temperatures and exhibit excellent performance, and at the same time, as electronic components continue to develop toward miniaturization and higher power, this puts higher demands on the electronic package interconnect material, i.e., it needs to stably operate in more extreme operating environments such as higher temperatures, higher current densities, etc. Although the conventional micron silver soldering paste can realize sintering interconnection at a certain temperature, a certain improvement space still exists for the performance of the conventional micron silver soldering paste.

Meanwhile, the existing micron silver soldering paste has relatively low sintering activity compared with nanometer and submicron silver particles because the size of the silver particles is micron-sized, so that higher temperature or pressure is often required to be applied in the actual sintering process, but the micron silver soldering paste can realize good dispersibility because the silver particles are micron-sized and depend on the steric hindrance effect brought by the micron size of the silver particles. For nano silver soldering paste, the nano silver particles have higher surface energy, and even though the coating agent exists on the surfaces of the nano silver particles, the agglomeration phenomenon is easy to occur, and the thicker coating layer is often unfavorable for the actual sintering process. Therefore, how to combine the advantages of nano-sized and submicron-sized silver solder paste and micron-sized silver solder paste, it is particularly important to provide a silver solder paste preparation process which has good dispersibility, is not easy to agglomerate, has high sintering activity and can be sintered at a low temperature or pressure.

Disclosure of Invention

Aiming at the technical problems, the invention discloses a micro-silver with mesoscopic structure, a low-temperature sinterable soldering paste, a preparation method and application thereof, wherein the steric hindrance effect generated by the micron-sized silver particles in the soldering paste can effectively solve the problem of silver particle agglomeration, and the mesoscopic structure on the surfaces of the particles can provide higher surface activity and higher sintering activity. On the other hand, the invention provides the application of the micron silver soldering paste with mesoscopic structure, which can realize the sintering at low temperature to form a compact sintered joint and has good performance without adding an additional binder.

In this regard, the invention adopts the following technical scheme:

a method for preparing micro silver with mesostructure, comprising the following steps:

step S1, respectively preparing a precursor solution containing silver ions and a coating agent, a reducing solution containing a reducing agent and a surface etching solution containing a surface etching agent; step S2, mixing the precursor solution and the reduction solution, carrying out oxidation-reduction reaction for a period of time at 25-80 ℃, then adding a surface etchant or a surface etchant solution, carrying out reaction, centrifuging the obtained solution, taking out precipitate, cleaning and drying to obtain micron silver particles with mesoscopic structures on the surfaces;

the surface etchant is at least one of ferric chloride, ferrous chloride and sodium chloride;

the ratio of the amount of silver ions to the amount of the substance of the surface etchant is 10 to 50.

According to the technical scheme, the surface etchant is added on the basis of the reaction of the precursor solution and the reduction solution, wherein the surface etchant plays a role in etching away the coating agent on the surface of the silver particles and reacting with part of silver ions on the surface of the silver particles formed by the reaction, so that a fractal structure with a mesoscopic size (100-150 nm) is formed on the surface of the obtained micron silver particles, the micron silver can provide higher surface activity, and the silver paste prepared by adopting the micron silver particles has higher sintering activity.

Further, the average particle diameter of the obtained silver microparticles is 1 to 2. Mu.m.

Further, in the precursor solution, the ratio of the silver ions to the substances of the coating agent is 0.5-2.5;

further, in step S2, after the precursor solution and the reducing solution are mixed with each other, the ratio of the amount of the silver ions to the amount of the reducing agent is 0.1 to 1.5.

As a further improvement of the present invention, the silver ions in the precursor solution are derived from one or more of silver nitrate, silver bromate, silver bromide, silver chloride, silver citrate, silver fluoride, silver iodate, silver iodide, silver nitrite, silver phosphate, silver chlorate, silver perchlorate, and silver tetrafluoroborate; the coating agent is at least one of citric acid, sodium citrate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, dodecyl mercaptan, polyethylene glycol and polyacrylic acid.

As a further improvement of the invention, the reducing agent is at least one of sodium borohydride, citric acid, formic acid, sodium citrate, disodium citrate, ferrous sulfate, ascorbic acid, sodium ascorbate, hydroxylamine, aniline, glucose, ethylene glycol, polyethylene glycol, glycerol, polyvinylpyrrolidone and sodium sulfite.

As a further improvement of the present invention, step S1 further comprises preparing a surface etchant solution, wherein the solvent of the surface etchant solution is one or a mixture of more than two of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol and diethylene glycol.

As a further improvement of the invention, the surface etchant is at least one of ferric chloride and ferrous chloride.

As a further improvement of the invention, in the step S2, after the oxidation-reduction reaction, a surface etchant solution is dripped for reaction.

As a further improvement of the invention, in the step S2, the speed of dripping the surface etching agent solution is 1-5 mL/min, and the reaction is 0.5-1 h.

As a further improvement of the present invention, the solvent of the precursor solution includes at least one of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, diethylene glycol.

As a further improvement of the present invention, the solvent of the reducing solution includes at least one of water, methanol, ethanol, ethylene glycol, propanol, isopropanol, butanol, isobutanol, pentanol, isopentanol, diethylene glycol.

As a further improvement of the invention, in the step S2, the stirring speed is 250 r/min-1200 r/min when the oxidation-reduction reaction is carried out, and the oxidation-reduction reaction time is 0.5-2.5 h.

As a further improvement of the invention, in the step S2, the washing comprises washing with deionized water, absolute ethyl alcohol or acetone, and then centrifugally washing at least 3 times at 3000-4500 r/min.

Further, after the cleaning is finished, drying is carried out at 50 ℃ for 10 hours under the condition that the vacuum degree is less than 0.01MPa, and the micron silver particles are obtained.

The invention also discloses a micro-silver with a mesostructure, which is prepared by adopting the preparation method of the micro-silver with the mesostructure.

The invention also discloses a low-temperature sinterable soldering paste, which comprises the micro silver with mesostructure and an organic solvent; the organic solvent is one or a mixture of at least two of ethanol, ethylene glycol, propylene glycol, terpineol, n-amyl ether and isoamyl ether.

As a further improvement of the invention, the mass ratio of the micro silver with mesostructure to the organic solvent is 8-9:1-2.

The invention also discloses application of the low-temperature sinterable soldering paste, which is used in the electronic component welding interconnection packaging.

As a further improvement of the invention, the method comprises the following steps:

the low-temperature sinterable soldering paste is coated on materials, substrates or parts to be sealed which need to be connected through a dispensing or printing method, and then the materials, the substrates or the parts to be sealed are placed in an oven for glue discharging treatment at the temperature of 90-110 ℃ for 20-40 min;

and placing the chips to be connected on a material or a substrate subjected to glue discharging, and performing hot-pressing sintering, wherein the hot-pressing sintering temperature is 150-250 ℃, and the hot-pressing pressure is 5-20 MPa. Further, the sintering time is 10-30min. Further, the temperature of the adhesive discharge is 100 ℃ and the time is 30 mm.

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

by adopting the technical scheme, the micron silver particles with mesostructures are prepared through oxidation-reduction reaction, organic matters and part of silver ions on the surfaces of the silver particles can be etched by the surface etchant through the addition of the surface etchant, and chloride ions contained in the etchant can be combined with the silver ions to generate etching action, so that submicron-level mesostructure shape structures are grown and etched on the surfaces of the prepared micron silver particles. Further, the micron silver particles and the organic solvent are mixed with each other to obtain the micron silver soldering paste which can be sintered at low temperature and has a mesoscopic structure, and even dispersion of the micron silver particles can be realized without additional additives. The fractal structure with mesoscopic size on the surface of the micron silver soldering paste improves sintering activity, so that sintering can be realized under the auxiliary action of 160 ℃ and pressure at the lowest, and the obtained soldering joint has high shearing strength, good oxidation resistance and conductivity, and can be stably served at high temperature, thereby realizing low-temperature sintering and high Wen Fuyi ". Meanwhile, the welding spot prepared by using the micron silver paste has good performance, the shearing strength can reach more than 50MPa at the highest, and the micron silver paste can be well applied to the field of electronic packaging.

Drawings

Fig. 1 is a field emission scanning electron micrograph (SEM, ×50000) of micrometer silver particles of example 1 of the present invention.

Fig. 2 is a field emission scanning electron micrograph (SEM, ×5000) of micrometer silver particles of example 1 of the present invention.

Fig. 3 is an XRD pattern of the micro silver particles in example 1 of the present invention.

Fig. 4 is a DSC-TG image of the micro silver solder paste in example 1 of the present invention.

FIG. 5 is a field emission scanning electron micrograph (SEM, ×5000) of a sintered weld shear fracture in example 1 of the present invention.

Fig. 6 is a field emission scanning electron microscope (SEM, ×50000) image of the micro silver particles in comparative example 1 of the present invention.

Detailed Description

Preferred embodiments of the present invention are described in further detail below.

Example 1

The micron silver particles with mesoscopic structures on the surfaces are prepared by the following steps:

6.8g of silver nitrate and 2.35g of polyvinylpyrrolidone are dispersed in 150mL of deionized water and stirred uniformly to obtain a precursor solution. 7.04g of ascorbic acid was dispersed in 50mL of deionized water and stirred uniformly to obtain a reducing solution. 0.20g of ferric chloride solution was dissolved in 20mL of deionized water to obtain a surface etchant solution, ferric chloride solution. The reducing solution was added dropwise to the precursor solution at a rate of 1mL/s with stirring at 75℃at 500r/min, and after 45min of reaction, the ferric chloride solution was added dropwise to the reaction solution at a rate of 2.5mL/min, followed by a further 1h of reaction. Centrifuging to obtain precipitate after the end of the waiting reaction, centrifuging and washing with 3500r/min deionized water for 3 times, washing with absolute ethyl alcohol once again, and then drying the precipitate at 50 ℃ for 10 hours under the condition that the vacuum degree is less than 0.01MPa to obtain the micron silver particles with mesoscopic structures on the surfaces.

And (3) placing 8 parts of the micrometer silver particles and 2 parts of terpineol into a planetary stirrer for uniformly stirring according to the parts by mass, so as to prepare the micrometer silver soldering paste capable of being sintered at low temperature.

And performing interconnection welding test on the micron silver soldering paste prepared by the method, obtaining an interconnection joint through printing, glue discharging and hot-pressing sintering, wherein the shearing strength of the interconnection joint obtained when the sintering temperature is 175 ℃ and the heat preservation time is 10min and the auxiliary pressure is 15MPa reaches more than 50 MPa.

Taking the obtained micron silver particles with mesoscopic structures on the surfaces, observing the morphology of the particles by using a field emission Scanning Electron Microscope (SEM), carrying out phase-spectrum analysis on the particles by using an X-ray diffractometer (XRD), carrying out thermogravimetric and differential thermal analysis on the obtained micron silver soldering paste by using a synchronous thermal analysis instrument, and observing and shearing by using the field emission scanning electron microscope to obtain the section of the interconnection joint. The results are shown in fig. 1, 2, 3, 4 and 5, respectively. As can be seen from fig. 1, the surface of the micro silver particles has a plurality of mesoscale structures, and the mesoscale structures are uniformly distributed on the surface of the micro silver particles; as can be seen from FIG. 2, the micron silver particles have good dispersibility, no obvious agglomeration phenomenon, uniform particle size and uniform shape. The characteristic peaks of elemental metallic silver can be seen from fig. 3, where there are no characteristic peaks of silver oxide or second phase species. From fig. 4, it can be seen that the thermal weight change and the heat absorption and release conditions of the micron silver paste in the heating process can be seen that the micron silver paste can be sintered at a lower temperature of about 175 ℃. Figure 5 shows a cross-section of the interconnect after shear testing, and shows the formation of a sintered neck between particles under low temperature hot pressure sintering.

Example 2

The micron silver particles with mesoscopic structures on the surfaces are prepared by the following steps:

10g of silver nitrate and 7.0g of sodium citrate are dispersed in 250mL of deionized water and stirred uniformly to form a precursor solution, 10g of sodium ascorbate is dispersed in 75mL of deionized water and stirred uniformly to form a reducing solution, and 0.16g of ferrous chloride solution is dissolved in 25mL of deionized water.

The reducing solution was added dropwise to the precursor solution at a rate of 1mL/s at 60℃with stirring at 500r/min, and after 45min of reaction, the ferrous chloride solution was added dropwise to the reaction solution at a rate of 2.5mL/min, followed by a further 1h of reaction. Centrifuging to obtain precipitate after the end of the waiting reaction, washing with 3500r/min deionized water for 3 times, washing with absolute ethyl alcohol for one time, and then drying the precipitate at 50 ℃ for 10 hours under the condition that the vacuum degree is less than 0.01MPa to obtain the micron silver particles with mesoscopic structures on the surfaces.

The SEM image, XRD image and internal structure of the prepared micron silver particles are similar to those of the example 1, which shows that the micron silver particles are metallic silver simple substance, have no other impurities, have no agglomeration phenomenon, are well dispersed and have uniform particle size.

Comparative example 1

This example differs from example 1 in that the amount of iron chloride added in example 1 was changed to 0.67g, and the other conditions were exactly the same as those in example 1.

SEM images of the prepared micro silver particles are shown in fig. 6, and it can be seen that the spherical particles are completely etched into plate-like particles due to the excessive addition of the surface etchant for this comparative example.

Comparative example 2

This example differs from example 1 in that the amount of iron chloride added in example 1 was changed to 0.12g, and the other conditions were exactly the same as those in example 1.

The surface of the silver particles prepared was not etched, i.e., for this comparative example, the lower content did not produce an etching effect due to the small addition of the surface etchant.

Example 3

A low-temperature sinterable micro-silver solder paste comprises 8 parts by mass of micro-silver particles and 2 parts by mass of ethylene glycol, wherein the micro-silver particles are prepared in the same manner as in example 1.

The preparation method of the low-temperature sintered micro silver paste is the same as that of example 1.

Example 4

A low-temperature sinterable micro-silver solder paste comprises 9 parts by mass of micro-silver particles and 1 part by mass of n-amyl ether, wherein the micro-silver particles are prepared in the same manner as in example 1.

The preparation method of the low-temperature sintered micro silver paste is the same as that of example 1.

Example 5

A low-temperature sinterable micro-silver solder paste comprising 9 parts by mass of micro-silver particles and 2 parts by mass of glycerol, wherein the micro-silver particles are prepared in the same manner as in example 1.

The preparation method of the low-temperature sintered micro silver paste is the same as that of example 1.

Example 6

A low-temperature sinterable micro-silver solder paste comprises 8 parts by mass of micro-silver particles and 1 part by mass of isoamyl ether, wherein the micro-silver particles are prepared in the same manner as in example 1.

The preparation method of the low-temperature sintered micro silver paste is the same as that of example 1.

Example 7

A method for preparing a low temperature sinterable micro-silver solder paste was the same as in example 1, except that the pressure during the thermocompression sintering was 5MPa.

Example 8

A method for preparing a low temperature sinterable micro-silver paste was the same as in example 1, except that the time for the thermocompression sintering process was 30min.

Example 9

A method for preparing a low temperature sinterable micro-silver paste was the same as in example 1, except that the pressure during the thermocompression sintering was 10MPa.

Example 10

A method for preparing a low temperature sinterable micro-silver solder paste was the same as in example 1, except that the temperature of the thermocompression sintering process was 225 ℃.

The micron silver soldering paste prepared in each example is placed between a silver-plated copper plate, a copper substrate and a silver-plated silicon chip and then hot-pressed and sintered, and specific sintering conditions are shown in the following table 1:

table 1 application of the micro silver paste of each of examples and comparative examples

	Sintering temperature (. Degree. C.)	Pressure (MPa)	Sintering time (min)
				Example 1	175	15	10
Example 3	200	10	10
				Example 4	225	5	10
Example 5	250	20	10
				Example 6	160	20	10
Example 7	175	5	10
				Example 8	175	15	30
Example 9	175	10	10
				Example 10	225	15	10

The welded joint was tested for shear strength at room temperature using a Try Precision MFM1200 push-pull tester at a shear rate of 300 μm/s. The test results are shown in Table 2.

Table 2 application properties and test results of the micro silver solder paste prepared in each example and comparative example

	Shear Strength (MPa) of welded Joint
		Example 1	56.2
Example 3	63.3
		Example 4	59.0
Example 5	112.5
		Example 6	38.5
Example 7	21.7
		Example 8	78.2
Example 9	40.7
		Example 10	90.7

As can be seen from table 2, the sintered solder joint prepared from the micro silver soldering paste with mesostructure on the surface prepared by the method has higher shear strength after sintering at low temperature, and successfully realizes low-temperature connection and high Wen Fuyi. The invention takes the raw materials with lower cost as reactants, has low reaction condition, low consumption and environmental protection, and has simple preparation flow. Meanwhile, the prepared micron silver particles have good dispersibility, the surfaces of the micron silver particles have consistent mesoscale structures, and the micron silver particles can be produced in batches and applied to the field of electronic packaging materials.

The foregoing is a further detailed description of the invention in connection with the preferred embodiments, and it is not intended that the invention be limited to the specific embodiments described. It will be apparent to those skilled in the art that several simple deductions or substitutions may be made without departing from the spirit of the invention, and these should be considered to be within the scope of the invention.

Claims (10)

1. A method for preparing micro silver with mesostructure, comprising the following steps:

step S1, preparing a precursor solution containing silver ions and a coating agent and a reducing solution containing a reducing agent respectively;

step S2, mixing the precursor solution and the reduction solution, carrying out oxidation-reduction reaction for a period of time at 25-80 ℃, then adding a surface etchant or a surface etchant solution for reaction, centrifuging the obtained solution, taking out precipitate, cleaning and drying to obtain micrometer silver particles with mesoscopic structures on the surfaces;

the surface etchant is at least one of ferric chloride, ferrous chloride and sodium chloride;

the ratio of the amount of silver ions to the amount of the substance of the surface etchant is 10 to 50.

2. The method for preparing the mesostructured micro-silver according to claim 1, wherein: in the precursor solution, silver ions are from one or more of silver nitrate, silver bromate, silver bromide, silver chloride, silver citrate, silver fluoride, silver iodate, silver iodide, silver nitrite, silver phosphate, silver chlorate, silver perchlorate and silver tetrafluoroborate; the coating agent is at least one of citric acid, sodium citrate, polyvinylpyrrolidone, cetyltrimethylammonium bromide, sodium dodecyl benzene sulfonate, dodecyl mercaptan, polyethylene glycol and polyacrylic acid;

in the precursor solution, the ratio of the silver ions to the substances of the coating agent is 0.5-2.5.

3. The method for preparing the mesostructured micro-silver according to claim 1, wherein: the reducing agent is at least one of sodium borohydride, citric acid, formic acid, sodium citrate, disodium citrate, ferrous sulfate, ascorbic acid, sodium ascorbate, hydroxylamine, aniline, glucose, glycol, polyethylene glycol, glycerol, polyvinylpyrrolidone and sodium sulfite; in step S2, after the precursor solution and the reducing solution are mixed with each other, the ratio of the amounts of the silver ions to the reducing agent is 0.1 to 1.5.

4. The method for preparing the mesostructured micro-silver according to claim 1, wherein: step S1 also comprises preparing a surface etchant solution, wherein the solvent of the surface etchant solution is one or more than two of water, methanol, ethanol, glycol, propanol, isopropanol, butanol, isobutanol, amyl alcohol, isoamyl alcohol and diethylene glycol; in the step S2, after the oxidation-reduction reaction is carried out for 30min, a surface etchant solution is dripped, and the reaction is continued for 0.5 to 1h;

the solvent of the precursor solution is at least one of water, methanol, ethanol, glycol, propanol, isopropanol, butanol, isobutanol, amyl alcohol, isoamyl alcohol and diethylene glycol;

the solvent of the reducing solution is at least one of water, methanol, ethanol, glycol, propanol, isopropanol, butanol, isobutanol, amyl alcohol, isoamyl alcohol and diethylene glycol.

5. The method for preparing the mesostructured micro-silver according to claim 1, wherein: in the step S2, when the oxidation-reduction reaction is carried out, the stirring speed is 250 r/min-1200 r/min, and the reaction time is 0.5-2.5 h.

In the step S2, the cleaning comprises the steps of washing with deionized water, absolute ethyl alcohol or acetone, and then centrifugally washing at least 3 times at 3000-4500 r/min.

6. A mesostructured micro silver, characterized by: the method for preparing the mesostructured micro-silver according to any one of claims 1 to 5.

7. A soldering paste capable of being sintered at low temperature is characterized in that: comprising the mesostructured micro silver of claim 6 and an organic solvent; the organic solvent is one or a mixture of at least two of ethanol, ethylene glycol, propylene glycol, terpineol, n-amyl ether and isoamyl ether.

8. The low temperature sinterable solder paste of claim 7, wherein: the mass ratio of the micro silver with the mesostructure to the organic solvent is 8-9:1-2.

9. Use of a low temperature sinterable solder paste according to claim 7, wherein: the low-temperature sinterable solder paste is used in electronic component soldering interconnection packaging.

10. Use of a low temperature sinterable solder paste according to claim 9, comprising the steps of:

the low-temperature sinterable soldering paste is coated on materials, substrates or parts to be sealed which need to be connected through a dispensing or printing method, and then the materials, the substrates or the parts to be sealed are placed in an oven for glue discharging treatment at the temperature of 90-110 ℃ for 20-40 min;

and placing the chips to be connected on a material or a substrate subjected to glue discharging, and performing hot-pressing sintering, wherein the hot-pressing sintering temperature is 150-250 ℃, and the hot-pressing pressure is 5-20 MPa.