Gold powder, preparation method thereof and gold conductor paste for LTCC

Abstract

The present application relates to the technical field of materials, and especially relates to a gold powder, a preparation method thereof and a gold conductor paste for LTCC. The preparation method of the gold powder comprises the following steps: dissolving a dispersing agent in water, then adding chloroauric acid, then adding ammonia water drop by drop until the pH value is greater than 9, then adding concentrated hydrochloric acid until the pH value is less than 1, and configuring a gold-containing solution; dissolving a reducing agent in water, then adding concentrated hydrochloric acid until the pH value is less than 1, and configuring a reducing solution; pouring the gold-containing solution into the reducing solution, stirring and reacting, then performing centrifugal water washing, drying, and obtaining the gold powder. The gold powder is applied to the gold conductor paste for LTCC, can form a fine and dense dendritic structure with nano platinum powder and nano palladium powder, promotes the capillary phenomenon of the glass phase in the substrate at the interface, has good matching with the LTCC substrate, and can prepare the gold conductor paste with good solderability and solder resistance, low square resistance and high adhesion.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a gold powder, a preparation method thereof and a gold conductor paste for LTCC. BACKGROUND

[0002] Low Temperature Co-fired Ceramic (LTCC) technology can achieve high integration, multi-layer wiring, three-dimensional circuit design, etc., and has adjustable characteristics such as low / high frequency microwave characteristics and strength, and is widely used in high-tech fields. LTCC can obtain appropriate electrical properties and strength according to different systems to meet the use requirements under different conditions. The gold-based electronic paste for LTCC has higher chemical inertness and stability than the silver-based electronic paste, and will not have defects such as diffusion, and is suitable for extremely harsh environments such as high humidity and high radiation. The solder resistance of ordinary surface layer gold conductor paste is very poor, and cannot meet the requirements of close connection between the substrate and external components. The surface layer solderable gold conductor paste can simultaneously achieve good solderability, solder resistance and high adhesion. At present, the surface layer solderable gold conductor paste for LTCC is prone to defects such as blistering, poor solderability, poor solder resistance, and low adhesion. Blistering is mostly caused by gold powder, and improper particle size and morphology of gold powder or organic residues in gold powder will cause mismatch between the shrinkage of the paste and the substrate; poor solderability, solder resistance and low adhesion to the substrate are caused by many factors such as the morphology of the paste after sintering and the interface bonding condition. The above defects will affect the use of the final LTCC product. SUMMARY

[0003] The present application provides a gold powder, a preparation method thereof and a gold conductor paste for LTCC to solve the above technical problems in the prior art.

[0004] According to a first aspect of the present application, the present application provides a preparation method of a gold powder, comprising the following steps:

[0005] (1) dissolving a dispersing agent in water, then adding chloroauric acid, and then adding ammonia water until the pH value is greater than 9, and then adding concentrated hydrochloric acid until the pH value is less than 1 to configure a gold-containing solution;

[0006] (2) dissolving a reducing agent in water, and then adding concentrated hydrochloric acid until the pH value is less than 1 to configure a reducing solution;

[0007] (3) pouring the gold-containing solution obtained in step (1) into the reducing solution obtained in step (2), stirring and reacting, then performing centrifugal water washing, drying, and obtaining a gold powder.

[0008] In the above scheme, the gold powder preparation method of the present application first configures a gold-containing solution and a reducing liquid with pH values less than 1, and then stirs and reacts the gold-containing solution and the reducing liquid. The low pH value can slow down the initial formation of the gold powder, and the reducing agent can control the particle size and internal structure of the gold powder, form a smooth surface, and make the gold powder have suitable sintering activity. When the gold powder is applied to the gold conductor paste for LTCC, it can form a fine and dense dendritic structure with nano platinum powder and nano palladium powder, promote the capillary phenomenon of the glass phase in the substrate at the interface, promote the transfer of the glass phase in the porcelain body to the interface during the sintering process, and form a strong interface bonding force. The prepared gold powder has good matching with other raw materials, and can prepare a gold conductor paste with good weldability and weld resistance, low square resistance, and high adhesion. The gold powder preparation process of the present application is simple, fast, safe, and easy to control, and can realize low cost and high batch stability.

[0009] Further, in step (1), after adding concentrated hydrochloric acid to pH 1, continue to add concentrated hydrochloric acid, wherein the volume of the added concentrated hydrochloric acid is 25%-35% of the volume of the water used to dissolve the dispersant.

[0010] In the above scheme, by limiting the volume of the added concentrated hydrochloric acid to be 25%-35% of the volume of the water used to dissolve the dispersant, the pH value of the gold-containing solution can be stabilized within a suitable range, which is more conducive to slowing down the initial formation of the gold powder, thereby better controlling the particle size and internal structure of the gold powder, forming a smoother surface, and making the gold powder have more suitable sintering activity.

[0011] Further, in step (2), after adding concentrated hydrochloric acid to pH 1, continue to add concentrated hydrochloric acid, wherein the volume of the added concentrated hydrochloric acid is 25%-35% of the volume of the water used to dissolve the reducing agent.

[0012] In the above scheme, by limiting the volume of the added concentrated hydrochloric acid to be 25%-35% of the volume of the water used to dissolve the reducing agent, the pH value of the reducing liquid can be stabilized within a suitable range, which is more conducive to slowing down the initial formation of the gold powder, thereby better controlling the particle size and internal structure of the gold powder, forming a smoother surface, and making the gold powder have more suitable sintering activity.

[0013] Further, in step (1), the dispersant is gum arabic; and / or, the concentration of the dispersant is 0.1 g / ml-0.2 g / ml.

[0014] In the above scheme, by selecting gum arabic which is easy to dissolve and hydrolyze as a dispersant, it can be ensured that there is no dispersant residue in the gold powder. At the same time, selecting a dispersant with a suitable concentration can achieve sufficient dispersion of the gold powder.

[0015] Further, in step (1), the concentration of the chloroauric acid is 2 times of the concentration of the dispersant.

[0016] Further, in step (2), the reducing agent is ascorbic acid or erythorbic acid; and / or, the concentration of the reducing agent is the same as the concentration of the chloroauric acid.

[0017] In the above scheme, by selecting ascorbic acid or erythorbic acid with moderate reducing ability as the reducing agent, a better synergistic effect can be achieved with the gold-containing solution, and the control of the gold powder particle size and internal structure can be better achieved. The same pH value of the gold-containing solution and the reducing solution is conducive to maintaining the uniformity of the reaction environment, and forming gold powder with uniform particle size.

[0018] Further, in step (3), the stirring reaction time is 20-40 min, preferably 30 min; and / or, the number of centrifugal water washing is 4-6 times, preferably 5 times; and / or, the drying temperature is 70-80℃.

[0019] In the above scheme, by controlling the stirring reaction time in step (3) within a reasonable range, the gold-containing solution and the reducing agent can be fully reacted to form better gold powder. By limiting the number of centrifugal water washing, an excellent washing effect can be achieved, thereby obtaining gold powder with better purity. By controlling the drying temperature, effective drying effect can be achieved while ensuring that the internal morphology of the gold powder does not change, thereby improving the quality of the gold powder.

[0020] According to a second aspect of the present application, the present application also provides a gold powder prepared by the above preparation method; the gold powder is micron-level spherical gold powder or quasi-spherical gold powder; the average particle size of the gold powder is 1.4-1.6 μm.

[0021] According to a third aspect of the present application, the present application also provides a gold conductor paste for LTCC, which is composed of the following components in mass percentage: gold powder 58-62%, platinum powder 9-12%, palladium powder 4.5-5.5%, oxide 1.8-2.2%, glass powder 1.8-2.2%, and organic carrier 18-24%; wherein the gold powder is prepared by the method of the present application.

[0022] In the above scheme, the gold conductor paste for LTCC is composed of the gold powder, the platinum powder, the palladium powder, the oxide, the glass powder and the organic carrier. The gold powder with specific shape and specific particle size can form fine dendritic structure with the platinum powder and the palladium powder, promote the capillary phenomenon of the glass phase in the substrate at the interface, promote the transfer of the glass phase in the porcelain body to the interface during the sintering process, and form strong interface bonding force. Further, the amount of the gold powder, the platinum powder, the palladium powder, the oxide, the glass powder and the organic carrier is limited in a reasonable range, so that the components can play a better synergistic effect. The gold conductor paste for LTCC has good flatness, small sheet resistance, good solderability, solder resistance and strong substrate adhesion after co-firing with the green porcelain, and reliable performance.

[0023] Further, the platinum powder is nano platinum powder with particle size < 30 nm.

[0024] Further, the palladium powder is nano palladium powder with particle size < 30 nm.

[0025] Further, the oxide is one or more of aluminum oxide and silicon oxide with average particle size of 4-6 μm.

[0026] Further, the glass powder is one of calcium boron lanthanum glass, lead boron silicon glass or calcium boron silicon glass with average particle size of 1.5-2 μm.

[0027] Further, the organic carrier is composed of 85-93% solvent and 7-15% binder. Preferably, the solvent is one or more of terpineol, butyl carbitol and butyl carbitol acetate, and the binder is ethyl cellulose.

[0028] In the above scheme, the nano platinum powder and the nano palladium powder can form finer dendritic structure with the gold powder, which is more conducive to promoting the capillary phenomenon of the glass phase in the substrate at the interface. The inert oxide with appropriate type and particle size can construct exhaust passages in the film layer and enhance the interface bonding. The glass powder with appropriate type and micron level can enhance the mechanical locking of the glass phase at the interface and achieve strong bonding force between the film layer and the LTCC substrate. The organic carrier with appropriate components and reasonable selection of component types can improve the rheological properties, printing properties and adhesion strength of the gold conductor paste, which is conducive to the improvement of the overall performance of the gold conductor paste.

[0029] Further, the viscosity of the gold conductor paste for LTCC is 180-230 Pa·s.

[0030] In the above scheme, the gold conductor paste for LTCC with appropriate viscosity can ensure the printing properties of the paste. The viscosity of the gold conductor paste for LTCC is realized by adjusting the content of the binder or the content of the organic carrier in the organic carrier.

[0031] The present application has at least the following advantages:

[0032] In the process of preparing gold powder, the present application can slow down the initial formation of gold powder at low pH value, and can realize the control of gold powder particle size and internal structure by combining with ascorbic acid or erythrocatechin with moderate reducing capacity, forming a smooth surface, so that the gold powder has suitable sintering activity, can form a fine and dense dendritic structure with nano platinum powder and nano palladium powder, promote the capillary phenomenon of the glass phase in the substrate at the interface, promote the transfer of the glass phase in the porcelain body to the interface during the sintering process, and form a strong interface bonding force. The selection of gum arabic which is easy to dissolve and hydrolyze can ensure that there is no dispersant residue in the gold powder, and the selection of high concentration dispersant can realize the full dispersion of the gold powder. The same pH value of the gold-containing solution and the reducing solution is conducive to maintaining the uniformity and consistency of the reaction environment, forming gold powder with uniform particle size, and avoiding defects such as blistering; the gold powder preparation process is simple, fast, safe and easy to control, and can realize lower cost and higher batch stability; the inert oxide with larger particle size can construct the exhaust passage in the film layer and enhance the interface bonding; the micron-level glass powder can enhance the mechanical locking of the glass phase at the interface and realize the strong bonding force of the film layer and the LTCC substrate. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0034] The following examples and comparative examples are as follows:

[0035] Melting of glass powder: after weighing and mixing the ingredients, melt at the corresponding temperature. After melting, quench and grind to obtain glass powder with an average particle size of 1.5 μm-2 μm.

[0036] Preparation of organic carrier: after weighing the solvent and binder, place them in a 90°C water bath, stir until completely dissolved, and cool for standby. The above organic carrier is composed of 85%-93% solvent and 7%-15% binder. The solvent is one or more of terpineol, butyl carbitol, butyl carbitol acetate. The binder is ethyl cellulose.

[0037] Preparation of gold conductor paste: Organic vehicle is mixed with nano platinum powder and nano palladium powder by stirring, then oxides, glass phase, gold powder and the above mixture are put into a mixer for mixing and rolling by a three-roll mill to uniformity, with a final fineness of ≤15 μm and a viscosity of 180 Pa·s-230 Pa·s. The oxides are one or more of alumina, silica, with an average particle size of 4 μm-6 μm. The paste component ratio is as follows: gold powder 58%-62%, platinum powder 9%-12%, palladium powder 4.5%-5.5%, oxide 1.8%-2.2%, glass powder 1.8%-2.2%, organic vehicle 20%-23%. The viscosity is controlled by adjusting the proportion of binder in the organic vehicle or the proportion of organic vehicle in the paste.

[0038] Sintering of gold conductor paste: The prepared paste is printed onto the LTCC green ceramic sheet by using a screen printer, with a printing screen of 325 mesh and printing patterns in accordance with GB / T 17473.3 and GB / T 17473.4. The printed paste is subjected to leveling, drying, lamination, hot pressing and sintering.

[0039] Test of gold conductor paste: The sintered surface-weldable gold conductor paste is observed under a microscope, with observation items being whether dense, flat, blistering; sheet resistance test is performed in accordance with GB / T 17473.3; weldability and solder resistance are performed in accordance with GB / T 17473.7; adhesion test is performed in accordance with GB / T 17473.4.

[0040] Example 1

[0041] This example provides a gold conductor paste for LTCC, which is composed of the following components in mass percentage: gold powder 58%, platinum powder 9%, palladium powder 5.5%, alumina 1.8%, glass powder 2.2%, and organic vehicle 23.5%.

[0042] The gold powder is prepared as follows: 5 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 10 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and has a bright yellow color. While stirring, concentrated ammonia is added dropwise, and the pH of the mixture is monitored using pH paper. A significant color deepening and turbidity are observed, and the addition of ammonia is stopped when the pH is greater than 9. After stirring for 45 s, concentrated hydrochloric acid is added to the mixture, and the color gradually changes to a light yellow color and remains turbid. When the pH is 1, 15 ml of concentrated hydrochloric acid is added to prepare a gold-containing solution, which is kept stirring to prevent settling before being added to the reducing solution. 10 g of erythorbic acid is added to 50 ml of deionized water, and the solution is stirred until the acid is dissolved. Concentrated hydrochloric acid is added to the solution, and when the pH is 1, 15 ml of concentrated hydrochloric acid is added to prepare a reducing solution. The gold-containing solution is added to the reducing solution while stirring, and the mixture is stirred for 30 min. After the reaction is complete, the mixture is poured into a centrifuge tube and centrifuged. The supernatant is decanted, and the gold powder is washed with deionized water and centrifuged again. This process is repeated five times. The gold powder is dried in a 70°C air oven until the weight is constant. The average particle size of the gold powder is 1.6 μm, and the particles are uniform and smooth.

[0043] The glass powder is a calcium-boron-lanthanum glass, and the average particle size is 1.7 μm.

[0044] The organic carrier is prepared as follows: 45% of terpineol, 45% of butyl carbitol, and 10% of ethyl cellulose are placed in a 90°C water bath, and the mixture is stirred until it is completely dissolved.

[0045] The gold conductor paste is printed on a LTCC green tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is measured to be 42 mΩ / sq, the adhesion is 2.5 kg, the failure mode is ceramic cracking, the film layer is dense, smooth, and free of bubbles, and the film has good solderability and solder resistance.

[0046] Example 2

[0047] The gold conductor paste for LTCC is prepared from the following components in the indicated proportions by mass: gold powder 60%, platinum powder 12%, palladium powder 4.5%, silicon oxide 2%, glass powder 2%, and organic carrier 22.5%.

[0048] The gold powder is prepared as follows: 7.5 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 15 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and has a bright yellow color. While stirring, concentrated ammonia is added dropwise, and the pH of the mixture is monitored using pH paper. A significant color deepening and turbidity are observed, and the addition of ammonia is stopped when the pH is greater than 9. After stirring for 45 s, concentrated hydrochloric acid is added to the mixture, and a gradual color change to light yellow and turbidity are observed. When the pH is 1, 17.5 ml of concentrated hydrochloric acid is added to prepare a gold-containing solution, which is kept stirring to prevent settling before being added to the reducing solution. 15 g of erythorbic acid is added to 50 ml of deionized water, and the solution is stirred until the acid is dissolved. Concentrated hydrochloric acid is added to the solution, and when the pH is 1, 17.5 ml of concentrated hydrochloric acid is added to prepare a reducing solution. The gold-containing solution is added to the reducing solution while stirring, and the mixture is stirred for 30 min. After the reaction is complete, the mixture is poured into a centrifuge tube and centrifuged. The supernatant is decanted, and the gold powder is washed with deionized water and centrifuged again. This process is repeated 5 times. The gold powder is dried in a forced air oven at 80°C to a constant weight. The average particle size of the gold powder is 1.6 μm, and the particles are uniform and smooth.

[0049] The glass powder is a lead borosilicate glass, and the average particle size is 1.9 μm.

[0050] The organic vehicle is prepared as follows: 93% butyl carbitol acetate and 7% ethyl cellulose are placed in a water bath at 90°C, and the mixture is stirred until it is completely dissolved.

[0051] The gold conductor paste is printed on a LTCC green tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is measured to be 46 mΩ / sq, the adhesion is 2.3 kg, the failure mode is ceramic cracking, the film layer is dense, smooth, and free of bubbles, and the film has good solderability and solder resistance.

[0052] Example 3

[0053] The gold conductor paste for LTCC is prepared from the following components in the indicated amounts by mass percentage: gold powder 62%, platinum powder 10%, palladium powder 5%, alumina 2.2%, glass powder 1.8%, and organic vehicle 19%.

[0054] The gold powder is prepared as follows: 10 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 20 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and has a bright yellow color. While stirring, concentrated ammonia is added dropwise, and the pH of the mixture is monitored using pH paper. A significant color deepening and turbidity are observed, and the addition of ammonia is stopped when the pH is greater than 9. After stirring for 45 s, concentrated hydrochloric acid is added to the mixture, and a gradual color change to light yellow and turbidity are observed. When the pH is 1, 12.5 ml of concentrated hydrochloric acid is added to prepare a gold-containing solution, which is kept stirring to prevent settling before being added to the reducing solution. 12 g of ascorbic acid is dissolved in 50 ml of deionized water, and concentrated hydrochloric acid is added dropwise to the solution. When the pH is 1, 12.5 ml of concentrated hydrochloric acid is added to prepare a reducing solution. The gold-containing solution is added to the reducing solution while stirring, and the mixture is stirred for 30 min. After the reaction is complete, the mixture is poured into a centrifuge tube and centrifuged. After centrifugation, the supernatant is poured off, and the gold powder is washed with deionized water and centrifuged again. This process is repeated 5 times. The gold powder is dried in a 70 °C air oven to a constant weight. The average particle size of the gold powder is 1.5 μm, and the particles are uniform and smooth.

[0055] The glass powder is a calcium borosilicate glass, and the average particle size is 1.6 μm.

[0056] The organic vehicle is prepared as follows: 36% of terpineol, 25% of butyl carbitol, 25% of butyl carbitol acetate, and 14% of ethyl cellulose are placed in a 90 °C water bath, and the mixture is stirred until it is completely dissolved.

[0057] The gold conductor paste is printed on a LTCC green tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is measured to be 37 mΩ / sq, the adhesion is 2.8 kg, the failure mode is ceramic cracking, the film layer is dense, smooth, and free of bubbles, and the film has good solderability and solder resistance.

[0058] Comparative Example 1

[0059] This comparative example provides a gold conductor paste for LTCC, which is composed of the following components by mass percentage: gold powder 58%, platinum powder 9%, palladium powder 5.5%, alumina 1.8%, glass powder 2.2%, and organic vehicle 23.5%.

[0060] The gold powder was prepared as follows: 5 g gum arabic and 50 ml deionized water were placed in a beaker with magnetic stirring at room temperature, and the mixture was stirred until the solution was clear and free of white particles. 10 g chloroauric acid was added to the above mixture, and the solution was stirred until it was uniform and had a bright yellow color. While stirring, concentrated ammonia was added dropwise, and the pH of the mixture was monitored using pH paper. A significant color deepening and turbidity were observed, and the addition was stopped when the pH was greater than 9. After stirring for 45 s, concentrated hydrochloric acid was added dropwise to the mixture, and the color gradually changed to a light yellow color and remained turbid. The addition was stopped when the pH was 1, and the gold-containing solution was prepared. The solution was stirred to prevent settling before it was added to the reducing solution. 10 g erythorbic acid was added to 50 ml deionized water, and the solution was stirred until it dissolved. Concentrated hydrochloric acid was added dropwise to the solution, and the addition was stopped when the pH was 1. The reducing solution was prepared. The gold-containing solution was added to the reducing solution while stirring, and the mixture was stirred for 30 min. After the reaction was complete, the mixture was poured into a centrifuge tube and centrifuged. The supernatant was decanted, and the gold powder was washed with deionized water and centrifuged again. This washing process was repeated five times. The gold powder was dried in a forced air oven at 70 °C until the weight was constant. The average particle size of the gold powder was 0.9 μm, and the particles were uniform and smooth.

[0061] The glass powder was calcium-boron-lanthanum glass, and the average particle size was 1.7 μm.

[0062] The organic vehicle was prepared as follows: 45% terpineol, 45% butyl carbitol, and 10% ethyl cellulose were placed in a 90 °C water bath, and the mixture was stirred until it dissolved completely.

[0063] The surface layer solderable gold conductor paste was printed on a LTCC green tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance was 40 mΩ / sq, the adhesion was 1.3 kg, and the failure mode was delamination of the film.

[0064] Comparative Example 2

[0065] A gold conductor paste for LTCC was prepared from the following components in the indicated amounts by weight: gold powder 58%, platinum powder 9%, palladium powder 5.5%, alumina 1.8%, glass powder 2.2%, and organic vehicle 23.5%.

[0066] The gold powder is prepared as follows: 5 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 10 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and has a bright yellow color. Concentrated hydrochloric acid is added dropwise to the above mixture, and the addition is stopped when the pH is 1, to form a gold-containing solution. 10 g of erythorbic acid is added to 50 ml of deionized water, and the solution is stirred until it dissolves quickly. Concentrated hydrochloric acid is added dropwise to the above solution, and the addition is stopped when the pH is 1, to form a reducing solution. The gold-containing solution is added to the reducing solution under stirring, and the mixture is stirred for 30 min. After the reaction is completed, the mixture is poured into a centrifuge tube and centrifuged. The supernatant is poured out, and the gold powder is washed with deionized water and centrifuged again. This process is repeated 5 times. The gold powder is dried in a blast oven at 70°C until the weight is constant. The average particle size of the gold powder is 0.7 μm, the particle size is uniform, the surface is rough, and there are many linear protrusions.

[0067] The glass powder is calcium-boron-lanthanum glass, and the average particle size is 1.7 μm.

[0068] The organic carrier is prepared as follows: 45% of terpineol, 45% of butyl carbitol, and 10% of ethyl cellulose are placed in a water bath at 90°C, and the mixture is stirred until it dissolves completely.

[0069] The gold conductor paste is printed on a LTCC green ceramic tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is measured to be 47 mΩ / sq, the adhesion is 0.6 kg, and the failure mode is film peeling.

[0070] Comparative Example 3

[0071] A gold conductor paste for LTCC is prepared from the following components in the indicated proportions by mass: gold powder 58%, platinum powder 9%, palladium powder 5.5%, alumina 1.8%, glass powder 2.2%, and organic carrier 23.5%.

[0072] The gold powder is prepared as follows: 5 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 10 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and has a bright yellow color. Concentrated hydrochloric acid is added dropwise to the above mixture, and the addition is stopped when the pH is 1, to form a gold-containing solution. 10 g of oxalic acid is added to 50 ml of deionized water, and the mixture is stirred until it dissolves quickly. Concentrated hydrochloric acid is added dropwise to the above solution, and the addition is stopped when the pH is 1, to form a reducing solution. The gold-containing solution is added to the reducing solution under stirring, and the mixture is stirred for 30 min. After the reaction is completed, the mixture is poured into a centrifuge tube and centrifuged. The supernatant is poured out, and the gold powder is washed with deionized water and centrifuged again. This process is repeated 5 times. The gold powder is dried in a blast oven at 70°C until the weight is constant. The average particle size of the gold powder is 1.1 μm, the particle size uniformity is poor, the surface is rough, and there are many protrusions.

[0073] The glass powder is calcium-boron-lanthanum glass, and the average particle size is 1.7 μm.

[0074] The organic carrier is prepared as follows: 45% of terpineol, 45% of butyl carbitol, and 10% of ethyl cellulose are placed in a water bath at 90°C, and the mixture is stirred until it is completely dissolved.

[0075] The gold conductor paste is printed on a LTCC green ceramic tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is measured to be 44 mΩ / sq, the adhesion is 0.9 kg, and the failure mode is film peeling.

[0076] Comparative Example 4

[0077] A gold conductor paste for LTCC is prepared from the following components in the indicated proportions by mass: gold powder 58%, platinum powder 9%, palladium powder 5.5%, alumina 1.8%, glass powder 2.2%, and organic carrier 23.5%.

[0078] The gold powder is prepared as follows: 5 g of gum arabic and 50 ml of deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixture is stirred until the solution is clear and free of white particles. 10 g of chloroauric acid is added to the above mixture, and the solution is stirred until it is uniform and clear. Concentrated hydrochloric acid is added dropwise to the above mixture, and the addition is stopped when the pH is 1. A gold-containing solution is prepared. 10 g of sodium sulfite is dissolved in 50 ml of deionized water, and concentrated hydrochloric acid is added dropwise to the above solution, and the addition is stopped when the pH is 1. A reducing solution is prepared. The gold-containing solution is added to the reducing solution under stirring, and the mixture is stirred for 30 min. After the reaction is completed, the mixture is poured into a centrifuge tube and centrifuged. The supernatant is discarded, and the gold powder is washed with deionized water and centrifuged again. This process is repeated 5 times. The gold powder is dried in a blast oven at 70°C to constant weight. The average particle size of the gold powder is 1.0 μm, and the gold powder is composed of a large amount of spherical gold powder and a small amount of flaky powder. The surface of the spherical gold powder is rough, with lumps and protrusions, and contains organic impurities that are difficult to remove.

[0079] The glass powder is calcium-boron-lanthanum glass, and the average particle size is 1.7 μm.

[0080] The organic carrier is prepared as follows: 45% of terpineol, 45% of butyl carbitol, and 10% of ethyl cellulose are placed in a water bath at 90°C, and the mixture is stirred until it is completely dissolved.

[0081] The gold conductor paste is printed on a LTCC green tape, and after flow leveling, drying, lamination, hot pressing, and sintering, the sheet resistance is 16 Ω / sq, the adhesion is 0.8 kg, and the failure mode is film peeling.

[0082] Comparative Example 5

[0083] The comparative example is compared with example 1, the difference is that the gold powder preparation process is as follows: 5g gum arabic and 50ml deionized water are placed in a beaker with magnetic stirring at room temperature, and the mixed solution is stirred until it is clear and free of white small particles. 10g chloroauric acid is poured into the above mixed solution, and stirred until the solution is uniform and presents a clear bright yellow color. Under stirring, concentrated ammonia is added dropwise, and the pH of the mixture is monitored using pH paper. A significant color deepening and turbidity are observed, and the dropwise addition is stopped when the pH is greater than 9. After stirring for 45s, concentrated hydrochloric acid is added dropwise into the above mixture until the pH value is 3, and a gold-containing solution is prepared. The gold-containing solution is kept stirring to avoid sedimentation before it is added to the reducing solution. 10g erythorbic acid is added to 50ml deionized water, and stirred to dissolve quickly. Concentrated hydrochloric acid is added dropwise into the above solution until the pH value is 3, and a reducing solution is prepared. Under stirring, the above gold-containing solution is poured into the above reducing solution, and stirred for 30min. After the reaction is completed, the mixture is poured into a centrifuge tube and centrifuged. After centrifugation, the upper solution is poured out, and the gold powder is washed with deionized water and centrifuged again. The water washing is repeated for 5 times, and the gold powder is placed in a blast oven at 70℃ and dried to constant weight. The average particle size of the gold powder is 0.6μm, and the particle size uniformity is poor, and the surface is smooth.

[0084] The above gold conductor paste is printed on the LTCC green ceramic tape, and after leveling, drying, lamination, hot pressing and sintering, the sheet resistance is measured to be 41mΩ / sq, the adhesion is 0.6kg, and the failure mode is film peeling.

[0085] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A gold powder, characterized by, The gold powder is micron-level spherical gold powder or quasi-spherical gold powder; the average particle size of the gold powder is 1.4-1.6 μm; The preparation method of the gold powder comprises the following steps: (1) dissolving a dispersing agent in water, adding chloroauric acid, then adding ammonia water drop by drop until the pH value is greater than 9, and then adding concentrated hydrochloric acid until the pH value is less than 1 to prepare a gold-containing solution; (2) dissolving a reducing agent in water, then adding concentrated hydrochloric acid until the pH value is less than 1 to prepare a reducing solution; (3) pouring the gold-containing solution obtained in step (1) into the reducing solution obtained in step (2), stirring and reacting, then performing centrifugal water washing, drying to obtain the gold powder; In step (1), after adding the concentrated hydrochloric acid until the pH value is equal to 1, the concentrated hydrochloric acid is continuously added, wherein the volume of the continuously added concentrated hydrochloric acid is 25%-35% of the volume of the water used for dissolving the dispersing agent; In step (2), after adding the concentrated hydrochloric acid until the pH value is equal to 1, the concentrated hydrochloric acid is continuously added, wherein the volume of the continuously added concentrated hydrochloric acid is 25%-35% of the volume of the water used for dissolving the reducing agent.

2. The gold powder according to claim 1, characterized by In step (1), the dispersing agent is gum arabic; and / or the concentration of the dispersing agent is 0.1-0.2 g / ml.

3. The gold powder of claim 1, wherein In step (1), the concentration of the chloroauric acid is 2 times the concentration of the dispersing agent.

4. The gold powder of claim 1, wherein In step (2), the reducing agent is ascorbic acid or isoascorbic acid; and / or the concentration of the reducing agent is the same as the concentration of the chloroauric acid.

5. The gold powder of claim 1, wherein In step (3), the stirring and reacting time is 20-40 min; and / or the centrifugal water washing time is 4-6 times; and / or the drying temperature is 70-80 ℃.

6. The gold powder according to claim 5, wherein In step (3), the stirring and reacting time is 30 min.

7. The gold powder of claim 5, wherein The centrifugal water washing time is 5 times.

8. A gold conductor paste for LTCC, characterized by, The gold powder is prepared by using the gold powder according to any one of claims 1-7.

9. The gold conductor paste for LTCC according to claim 8, characterized in that, The platinum powder is nano platinum powder with a particle size of <30 nm; The palladium powder is nano palladium powder with a particle size of <30 nm; The oxide is one or more of alumina and silica with an average particle size of 4-6 μm; The glass powder is one of calcium-boron-lanthanum glass, lead-boron-silicon glass or calcium-boron-silicon glass with an average particle size of 1.5-2 μm; The organic carrier is composed of 85%-93% of a solvent and 7%-15% of a binder.

10. The gold conductor paste for LTCC according to claim 9, characterized in that, The solvent is one or more of terpineol, butyl carbitol and butyl carbitol acetate, and the binder is ethyl cellulose.

11. The gold conductor paste for LTCC according to claim 8, characterized in that, The viscosity of the gold conductor paste for LTCC is 180-230 Pa·s.