A silver particle surface passivation treatment method

Abstract

The application belongs to the field of electronic packaging materials, and discloses a silver particle surface passivation treatment method. The method comprises the following steps: dispersing silver particles in a passivation solution, inserting an inert electrode as an anode and inserting a conductive porous network graphene electrode as a cathode, and making the silver particles adhere to the conductive porous network graphene electrode; electrifying the solution to make the silver particles on the conductive porous network graphene electrode deposit Cr on the surface and be passivated; applying ultrasonic oscillation or a high-frequency electric field to the conductive porous network graphene electrode to make the passivated silver particles fall off; then making new unpassivated silver particles re-attach to the conductive porous network graphene electrode, repeating the foregoing electrifying and applying ultrasonic oscillation or a high-frequency electric field steps until all the silver particles are passivated; and centrifugally drying the solution to obtain the passivated silver particles. The method can also use more than three conductive porous network graphene electrodes as cathodes and filter screens to process silver particles of different particle sizes.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electronic packaging materials, and particularly relates to a silver particle surface passivation treatment method. BACKGROUND

[0002] Nanoscale and microscale metal particles are key interconnection materials in electronic packaging, however, due to their small particle size, they are easily oxidized, which limits their further application. Passivating the metal to form a dense anti-oxidation film on its surface is an important solution and is widely used. The principle is to pass a current through the metal in the passivation solution and form a passivation film. However, for micro-nano metal particles, how to realize the electrification of the particles, how to realize uniform passivation, and how to collect the passivated metal particles are all problems to be solved. Therefore, there is no existing technology for surface passivation of metal particles. SUMMARY

[0003] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a silver particle surface passivation treatment method.

[0004] The purpose of the present application is achieved by the following technical solutions:

[0005] A silver particle surface passivation treatment method, when the silver particles are single-size or multi-size silver particles, the surface passivation treatment method comprises the following steps:

[0006] (1) dispersing the silver particles in a solution containing a passivation solution;

[0007] (2) mechanically stirring the solution, inserting an inert electrode as an anode and a conductive porous network graphene electrode as a cathode in the solution, the pore size D of the network on the conductive porous network graphene electrode and the maximum silver particle pore size d satisfy the relationship: D < 0.9d, so that the silver particles adhere to the conductive porous network graphene electrode;

[0008] (3) passing a current through the solution to deposit Cr on the surface of the silver particles on the conductive porous network graphene electrode to passivate; at intervals of 1-10 min, applying ultrasonic vibration or a high-frequency electric field to the conductive porous network graphene electrode to make the passivated silver particles fall off; then making new unpassivated silver particles re-attach to the conductive porous network graphene electrode, repeating the above current passing and applying ultrasonic vibration or high-frequency electric field steps until all the silver particles are passivated;

[0009] (4) centrifuging and drying the solution to obtain the passivated silver particles;

[0010] When the silver particles are multi-size silver particles, the surface passivation treatment method comprises the following steps:

[0011] (a) dispersing silver particles in a solution containing a passivation liquid, the solution being placed in a closed container;

[0012] (b) mechanically stirring the solution in the container, inserting an inert electrode as an anode into the solution from the side of the container, and arranging three or more conductive porous reticular graphene electrodes as cathodes and filters in the container, the conductive porous reticular graphene electrodes having the same shape as the cross section of the container; the conductive porous reticular graphene electrodes have different network pore sizes, and are arranged from top to bottom in order of decreasing network pore size, the network pore sizes satisfying the following relationship: D1 = (1.2-2)D2, D2 = (1.2-2)D3, and so on;

[0013] (c) arranging a pump in the container to drive the solution to flow circularly from top to bottom through the mesh holes of the conductive porous reticular graphene electrodes, so that silver particles of different sizes are deposited and attached to the conductive porous reticular graphene electrodes of corresponding sizes;

[0014] (d) applying electricity to the solution to cause the silver particles on the conductive porous reticular graphene electrodes to deposit Cr and be passivated; at intervals of 1-10 min, turning the conductive porous reticular graphene electrodes in the container by 180° as a whole and applying ultrasonic oscillation or a high-frequency electric field, so that the passivated silver particles fall off; then repeating steps (b) and (c) to make new silver particles that have not been passivated re-attach to the conductive porous reticular graphene electrodes, and repeating the foregoing steps of applying electricity and applying ultrasonic oscillation or a high-frequency electric field until all the silver particles are passivated;

[0015] (e) centrifuging and drying the solution to obtain the passivated silver particles;

[0016] The solution containing the passivation liquid has a pH value of 2-9, the solvent therein is water, methanol or ethanol, and the solute is one or more of H2O2, diaminotriazole, acrylic resin, epoxy resin, tannic acid, phytic acid and organic molybdate, and a mixture of Cr 3+ , Cr 6+ , SO4 2- , Cl - , NO3 - ions and alkali metal ions.

[0017] The silver particles have a size of 10 nm-100 μm.

[0018] The inert electrode in step (2) and step (b) is graphite.

[0019] In the process of step (3) and step (d) for passivation, the temperature is kept at -20℃-100℃, and the voltage is kept at 0-100 V.

[0020] In the passivation process described in steps (3) and (d), air or oxygen is introduced while the solution is subjected to ultrasonic and stirring treatment.

[0021] The frequency f of the ultrasonic vibration or high-frequency electric field in steps (3) and (d) has multiple options (f1, f2, f3) and satisfies the following relationship:

[0022] (0.5+n)c i / f i =L i , i = 1, 2, 3

[0023] where n is any natural number, c1 is the surface transverse wave speed of the conductive porous reticular graphene electrode, L1 is the characteristic size of the conductive porous reticular graphene electrode, c2 is the bulk wave speed of the silver particle, L2 is the characteristic size of the silver particle, c3 is the bulk wave speed of the solution, and L3 is the distance between the anode electrode and the conductive porous reticular graphene electrode.

[0024] After the passivation process described in steps (3) and (d) is completed, the conductive porous reticular graphene electrode is removed and placed in another solution, which contains cetyltrimethylammonium bromide (CTAB) and a fatty acid salt small molecule surfactant to reduce the surface energy of the silver particles and promote the shedding of the silver particles. Ultrasonic vibration is applied to make the passivated silver particles shed, and then the solution is centrifuged and dried to obtain the passivated silver particles.

[0025] The present application has the following advantages and effects compared to the prior art: The present application proposes a new method for passivating the surface of metal particles, which can achieve the passivation and collection of micro-nano silver particles and is suitable for passivating particles of different sizes at one time. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Process flow chart of silver particle surface passivation treatment method A;

[0027] Figure 2 Process flow chart of silver particle surface passivation treatment method B;

[0028] Where 1 is a silver particle, 2 is a solution containing a passivation solution, 3 is an anode, 4 is a conductive porous reticular graphene electrode, 5 is a passivation layer, 6 is mechanical stirring, 7 is ultrasonic waves of a specific frequency, 8 is water circulation generated by a pump, 9 is a large-pore reticular graphene electrode, 10 is a medium-pore reticular graphene electrode, 11 is a small-pore reticular graphene electrode, and 12 is a flipped graphene electrode. DETAILED DESCRIPTION

[0029] The present application will be further described in detail below in conjunction with the embodiments and drawings, but the embodiments of the present application are not limited thereto.

[0030] The frequency f of the ultrasonic oscillation or high frequency electric field in the following examples has multiple choices (f1, f2, f3) and satisfies the following relationship:

[0031] (0.5 + n)c i / f i = L i , i = 1, 2, 3

[0032] wherein n is any natural number, c1 is the transverse wave speed of the surface of the conductive porous reticulated graphene electrode, L1 is the characteristic size of the conductive porous reticulated graphene electrode, c2 is the bulk wave speed of the silver particle, L2 is the characteristic size of the silver particle, c3 is the bulk wave speed of the solution, and L3 is the distance between the anode electrode and the conductive porous reticulated graphene electrode.

[0033] The temperature in the passivation process in the following examples is kept at -20°C to 100°C.

[0034] Example 1 Silver particle surface passivation treatment method A, the process flow is shown in Figure 1 , wherein 1 is a silver particle, 2 is a solution containing a passivation solution, 3 is an anode, 4 is a conductive porous reticulated graphene electrode, 5 is a passivation layer, 6 is mechanical stirring, and 7 is ultrasonic wave of a specific frequency.

[0035] (1) Disperse silver particles with an average size of 100 nm in a solution containing a passivation solution; the pH value of the solution containing the passivation solution is 3, the solvent is ethanol, and the solute is a mixture of H2O2, Cr 3+ , Cr 6+ , SO4 2- , Cl - , NO3 - ions and alkali metal ions;

[0036] (2) Perform mechanical stirring on the solution, insert graphite as an anode and insert a conductive porous reticulated graphene electrode with a pore size of 80 nm as a cathode in the solution, so that the silver particles are attached to the conductive porous reticulated graphene electrode;

[0037] (3) Apply electricity to the solution with a voltage of 5V, so that the silver particles on the conductive porous reticulated graphene electrode are deposited with Cr to be passivated; at intervals of 1 min, apply ultrasonic oscillation of 12.5 MHz to the conductive porous reticulated graphene electrode, so that the passivated silver particles are detached; then make new unpassivated silver particles reattach to the conductive porous reticulated graphene electrode, repeat the above steps of applying electricity and applying ultrasonic oscillation or high frequency electric field, until all the silver particles are passivated;

[0038] (4) Centrifugal dry the solution to obtain the passivated silver particles.

[0039] Example 2 Silver particle surface passivation treatment method B, process flow as shown in Figure 2 Figure 1, wherein 1 - silver particles, 2 - solution containing passivation solution, 3 - anode, 5 - passivation layer, 6 - mechanical stirring, 7 - ultrasonic wave of specific frequency, 8 - water circulation made by pump, 9 - large pore size reticular graphene electrode, 10 - medium pore size reticular graphene electrode, 11 - small pore size reticular graphene electrode, 12 - flip graphene electrode.

[0040] (a) Disperse 140 nm, 110 nm, 80 nm silver particles in a solution containing passivation solution, and place the solution in a closed container; the pH value of the solution containing passivation solution is 7, the solvent is methanol, and the solute is a mixture of acrylic resin, Cr 3+ , Cr 6+ , SO4 2- , Cl - , NO3 - ions and alkali metal ions;

[0041] (b) Mechanically stir the solution in the container, insert an inert electrode as an anode into the solution from the side of the container, and set three conductive porous reticular graphene electrodes as cathodes and filters in the container, the shape of the conductive porous reticular graphene electrodes is the same as the cross section of the container; the network pore sizes of the three conductive porous reticular graphene electrodes are 120 nm, 90 nm, and 60 nm respectively, and they are arranged from top to bottom in the order of network pore size from large to small;

[0042] (c) Set a pump in the container to drive the solution to circulate and flow from top to bottom through the mesh holes of the conductive porous reticular graphene electrodes, so that silver particles of different particle sizes are deposited and attached to the conductive porous reticular graphene electrodes of corresponding sizes;

[0043] (d) Apply electricity to the solution with a voltage of 5 V to make the silver particles on the conductive porous reticular graphene electrodes deposit Cr and be passivated; every 1 min, flip the conductive porous reticular graphene electrodes in the container by 180° as a whole and apply ultrasonic oscillation of 12.5 MHz to make the passivated silver particles fall off; then repeat steps (b) and (c) to make new silver particles that have not been passivated reattach to the conductive porous reticular graphene electrodes, and repeat the above steps of applying electricity and applying ultrasonic oscillation or high frequency electric field until all the silver particles are passivated;

[0044] (e) Centrifugal dry the solution to obtain passivated silver particles.

[0045] Example 3

[0046] Other steps are the same as example 1, the difference is that after the passivation process in step (3) is completed, the conductive porous reticular graphene electrode is taken out and placed in another solution, and hexadecyl trimethyl ammonium bromide (CTAB) and a fatty acid salt small molecule surfactant are added to the other solution to reduce the surface energy of the silver particles and promote the shedding of the silver particles; ultrasonic oscillation is applied to make the passivated silver particles fall off; the operation is repeated until all the silver particles are passivated; and then the other solution is centrifuged and dried to obtain the passivated silver particles.

[0047] Example 4

[0048] Other steps are the same as example 2, the difference is that after the passivation process in step (d) is completed, the conductive porous reticular graphene electrode is taken out and placed in another solution, and hexadecyl trimethyl ammonium bromide (CTAB) and a fatty acid salt small molecule surfactant are added to the other solution to reduce the surface energy of the silver particles and promote the shedding of the silver particles; ultrasonic oscillation is applied to make the passivated silver particles fall off; the operation is repeated until all the silver particles are passivated; and then the other solution is centrifuged and dried to obtain the passivated silver particles.

[0049] The above examples are the preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A silver particle surface passivation treatment method, characterized in that: when the silver particles are single-size or multi-size silver particles, the surface passivation treatment method comprises the following steps: (1) dispersing the silver particles in a solution containing a passivation liquid; (2) mechanically stirring the solution, inserting an inert electrode as an anode and a conductive porous mesh graphene electrode as a cathode into the solution, the pore size D of the network of the conductive porous mesh graphene electrode and the maximum silver particle pore size d satisfy the relationship: D < 0.9d, so that the silver particles adhere to the conductive porous mesh graphene electrode; (3) electrifying the solution to make the silver particles on the conductive porous mesh graphene electrode deposit Cr on the surface and be passivated; after 1-10 minutes, ultrasonic oscillation is applied to the conductive porous mesh graphene electrode to make the passivated silver particles fall off; then new unpassivated silver particles adhere to the conductive porous mesh graphene electrode again, and the above-mentioned electrification and ultrasonic oscillation steps are repeated until all the silver particles are passivated; (4) centrifugal drying the solution to obtain the passivated silver particles; when the silver particles are multi-size silver particles, the surface passivation treatment method comprises the following steps: (a) dispersing the silver particles in a solution containing a passivation liquid, and placing the solution in a closed container; (b) mechanically stirring the solution in the container, inserting an inert electrode as an anode into the solution from the side of the container, and arranging three or more conductive porous mesh graphene electrodes as cathodes and filter screens in the container, the shape of the conductive porous mesh graphene electrode is the same as the cross section of the container; the conductive porous mesh graphene electrodes have different network pore sizes, and are arranged from top to bottom in the order of network pore size from large to small, and the network pore sizes satisfy the following relationship: D1 = (1.2~2)D2, D2 = (1.2~2)D3, and so on; (c) arranging a pump in the container to drive the solution to flow circularly from top to bottom through the mesh holes of the conductive porous mesh graphene electrodes, so that silver particles of different sizes are deposited and adhered to the conductive porous mesh graphene electrodes of corresponding sizes; (d) electrifying the solution to make the silver particles on the conductive porous mesh graphene electrodes deposit Cr on the surface and be passivated; after 1-10 minutes, the conductive porous mesh graphene electrodes in the container are turned over by 180º and ultrasonic oscillation is applied to make the passivated silver particles fall off; then the steps (b) and (c) are repeated to make new unpassivated silver particles adhere to the conductive porous mesh graphene electrodes again, and the above-mentioned electrification and ultrasonic oscillation steps are repeated until all the silver particles are passivated; (e) centrifugal drying the solution to obtain the passivated silver particles; after the passivation process in steps (3) and (d) is completed, the conductive porous mesh graphene electrodes are taken out and placed in another solution, bromohexadecyltrimethylammonium and a fatty acid salt small molecule surfactant are added to the other solution to reduce the surface energy of the silver particles and promote the falling off of the silver particles; ultrasonic oscillation is applied to make the passivated silver particles fall off, and then the solution is centrifugally dried to obtain the passivated silver particles; the size of the silver particles is 10 nm-100 μm. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The pH value of the solution containing the passivation solution is 2-9, wherein the solvent is water, methanol or ethanol, and the solute is one or more of H2O2, diaminotriazole, acrylic resin, epoxy resin, tannic acid, phytic acid and organic molybdate. 3+ Cr 6+ 、SO4 2- 、Cl - 、NO3 - A mixture of ions and alkali metal ions.

2. The method for passivating the surface of silver particles according to claim 1, characterized in that: ​ 3. The method of claim 1, wherein the silver particles are treated with a passivation agent. The inert electrode in step (2) and step (b) is graphite.

4. The method of claim 1, wherein the silver particles are treated with a passivation agent. In the passivation process in step (3) and step (d), air or oxygen is introduced, and the solution is treated by ultrasonic and stirring.

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