A method for preparing a gold powder for matching low temperature co-fired ceramic

Abstract

The application provides a preparation method of gold powder for matching low-temperature co-fired ceramic, and submicron irregular gold powder is prepared in an aqueous solution of chloroauric acid through an oxidation-reduction method. In the preparation process, amino acid is used as a gold ion complexing agent and a pH buffer of a reaction solution, a small-molecule organic substance containing an imidazole functional group and having weak reduction is used as a reducing agent, and after the gold powder is washed with deionized water, ethanol is used to replace water in the powder, and the like, so that submicron irregular gold powder which is not agglomerated is prepared. The gold powder prepared by the application has a particle size range of 200nm-900nm, has good dispersibility in alcohol and ester solvents, and after sintering, a film layer is dense, can be matched with various green ceramic materials at home and abroad, and after sintering, a substrate is flat and has a warping degree less than 0.1mm. The preparation method of the application has high yield and is convenient in the preparation process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of noble metal electronic paste, in particular to a preparation method of gold powder for matching low temperature co-fired ceramic. BACKGROUND

[0002] Low temperature co-fired ceramic (LTCC) is a high-density circuit made by punching, printing conductor paste, laminating and sintering, which is a mainstream technology of passive integration. It has more wiring layers, which can improve the assembly density; it is easy to embed components and devices, which realizes the multifunctionalization of components; it is easy to form various structures of cavities or compatible with other wiring technologies, which realizes the application advantages of multifunctional and hybrid multi-chip components, and is widely used in various high-frequency communication components. The conductor in LTCC is mainly gold and alloy powder. Gold has the characteristics of high conductivity, high heat transfer, oxidation resistance, environmental erosion resistance and excellent reflection of electromagnetic radiation, and is made into various functional conductor paste, which plays a stable performance under high temperature and humidity, high corrosion and electromagnetic radiation conditions, especially in the fields of aviation and aerospace.

[0003] Abroad, the main manufacturers are Ferro and Dupont. Ferro company prepares LTCC gold inner electrode and hole paste, which uses flake powder mixed with nano irregular particle gold powder. Dupont company prepares LTCC gold inner electrode and hole paste, which uses submicron irregular particle gold powder. The paste of the two companies matches well with green ceramic, and the ceramic sheet is flat after sintering without bubbles. The domestic related reports mainly focus on the preparation of micron, nanometer spherical gold powder and flake mixed spherical gold powder. This type of gold powder is usually used for the preparation of post-sintering paste, which has poor matching with green ceramic when co-fired, and is easy to bubble or warp after sintering. The gold powder prepared by the present application has similar morphology and particle size to the gold powder used in Dupont's LTCC gold inner electrode and hole paste. At present, the gold powder and gold conductor paste for LTCC mainly depend on import, and the preparation of this type of gold powder has good market application prospect and key technology localization.

[0004] At present, the preparation of submicron irregular morphology gold powder mainly includes:

[0005] CN104275493A discloses a method for preparing gold nanodiscs using amino acid as reducing agent. Gold powder is prepared using amino acid as reducing agent, and the main product is flaky gold powder. The concentration of chloroauric acid is low, i.e. 0.03 mol / L, and the reaction time is 72 h. Under this condition, the oxidation-reduction reaction cycle is long, and the amount of prepared gold powder is small;

[0006] CN106112005A discloses a preparation method of monodisperse flaky gold powder, using ascorbic acid as a reducing agent and linear polyethylene imine as an additive to prepare flaky gold powder. The preparation method can obtain submicron irregular polygonal particle gold powder with a size of 500-800 nm, but the main product is flaky gold powder with a size of 4-6 microns. SUMMARY

[0007] The present application aims to provide a preparation method of gold powder for matching low-temperature co-fired ceramic, the prepared submicron irregular gold powder has the characteristics of uniform particle size, small specific surface area and no agglomeration, and the substrate warpage after sintering is less than 0.1 mm, which can be applied to low-temperature co-fired ceramic.

[0008] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0009] A preparation method of gold powder for matching low-temperature co-fired ceramic, comprising the following steps:

[0010] (1) Dissolve 99.99% gold flakes, remove nitric acid and excess hydrochloric acid in the solution, and prepare a 1 mol / L chloroauric acid (HAuCl4) solution with deionized water;

[0011] (2) Dissolve the dispersant in deionized water, the mass ratio (dispersant: HAuCl4) is 1-5:100, and the volume ratio (deionized water: HAuCl4 solution) is 9:1;

[0012] (3) Dissolve the amino acid in deionized water to prepare an amino acid aqueous solution with a concentration of 1 mol / L, and the molar ratio (amino acid: HAuCl4) is 3:2;

[0013] (4) Dissolve the reducing agent containing imidazole functional groups in deionized water to prepare a reducing agent solution with a concentration of 1 mol / L, and the molar ratio (reducing agent: HAuCl4) is 2-3:2, and the solution is heated to 40℃;

[0014] (5) Under stirring conditions, pour the HAuCl4 solution prepared in step (1) into the dispersant solution prepared in step (2), after stirring for 15 minutes, add the amino acid aqueous solution prepared in step (3), adjust the pH to 1.3-1.5 using 0.1-1 mol / L HCl or NaOH solution, heat the reaction solution to 40℃, and add the reducing agent aqueous solution prepared in step (4), continue stirring until the reaction is complete;

[0015] (6) Let the reaction solution in step (5) stand and precipitate, pour out the supernatant, wash with deionized water for three times, wash with ethanol for two times, and dry in an 80℃ oven to prepare irregular submicron gold powder.

[0016] In the step (5), the reducing agent solution is added to the reaction solution by pouring method, and the temperature of the reaction solution and the reducing agent solution is 40℃;

[0017] In the step (5), about 1ml of the reaction solution is taken out, and hydrazine hydrate is used to test whether the reaction is complete. If the reaction solution becomes black or purple, the reaction is continued; if the color of the reaction solution does not change, the reaction is complete.

[0018] Preferably, the dispersing agent is one or more of polyvinylpyrrolidone (PVP, molecular weight 30000), sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, polyethylene glycol, and ethyl phenyl polyethylene glycol.

[0019] Preferably, the amino acid is one or more of glycine, alanine, valine, phenylalanine, glutamic acid, lysine, and arginine.

[0020] Preferably, the reducing agent is one or more of imidazole, 2-methyl-4-ethyl imidazole, indazole, benzimidazole, and histidine.

[0021] The present application has the following features:

[0022] 1. The amino acid is used as a gold ion complexing agent and a pH regulator of the reaction solution. The amino group in the amino acid is complexed with the gold ion, which can reduce the reaction rate of the gold ion and avoid the generation of other morphologies. The amino acid is amphoteric and can be used as a buffer to maintain the pH of the reaction solution and promote the stable progress of the reaction.

[0023] 2. The small-molecule organic compound with weak reducing property and imidazole functional group is used as a reducing agent to reduce the strong oxidizing chloroauric acid. The reaction process is controllable, and only irregularly shaped gold powder is obtained without the generation of flaky or spherical powder.

[0024] 3. After the gold powder is washed with deionized water, ethanol is used to replace the water in the powder, and the non-caking gold powder is obtained after drying, which is beneficial to the dispersion of the gold powder in the organic carrier.

[0025] 4. The present application provides a preparation method of gold powder for matching low-temperature co-fired ceramic. The gold powder is sub-micron irregularly shaped powder with a particle size range of 200nm-900nm.

[0026] 5. The gold powder prepared by the method has high yield, uniform particle size, and good dispersion in alcohol and ester solvents. After sintering, the film layer is dense, and the substrate is flat after sintering with a warping degree of less than 0.1mm.

[0027] 6. The preparation method of the present application is simple, the process is easy to control, the batch stability is high, it is easy to expand, and the environmental pollution is small.

[0028] In summary, the method of the present application can be used to prepare sub-micron irregular gold powder with particle size ranging from 200 to 900 nm, no agglomeration, good dispersibility in alcohol and ester solvents, dense film layer after sintering, and can match various domestic and imported green ceramic materials, the sintered substrate is flat with a warpage of less than 0.1 mm. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The scanning electron microscope photos of the gold powder prepared in Example 1.

[0030] Figure 2 The scanning electron microscope photos of the gold powder prepared in Example 2. DETAILED DESCRIPTION

[0031] The method of the present application uses raw materials with the following purity: 99.99% gold sheet, deionized water, and the rest of the chemical reagents are all analytical pure.

[0032] The preparation steps are as follows:

[0033] 1. Dissolve the 99.99% gold sheet, remove nitric acid and excess hydrochloric acid in the solution, and prepare a 1 mol / L chloroauric acid (HAuCl4) solution using deionized water;

[0034] 2. Dissolve the dispersant in deionized water with a mass ratio (dispersant: HAuCl4) of 1-5:100 and a volume ratio (deionized water: HAuCl4 solution) of 9:1;

[0035] 3. Dissolve the amino acid in deionized water to prepare an amino acid aqueous solution with a concentration of 1 mol / L, and the molar ratio (amino acid: HAuCl4) is 3:2;

[0036] 4. Dissolve the reducing agent containing imidazole functional groups in deionized water to prepare a reducing agent solution with a concentration of 1 mol / L, and the molar ratio (reducing agent: HAuCl4) is 2-3:2, and the solution is heated to 40°C;

[0037] 5. Under stirring conditions, pour the HAuCl4 solution prepared in step (1) into the dispersant solution prepared in step (2), after stirring for 15 minutes, adjust the pH to 1.3-1.5 using 0.1-1 mol / L HCl or NaOH solution, add the amino acid aqueous solution prepared in step (3), heat the reaction solution to 40°C, add the reducing agent aqueous solution prepared in step (4), and continue stirring until the reaction is complete;

[0038] 6. Let the reaction solution of step (5) stand and precipitate, pour out the supernatant, wash with deionized water three times, wash with ethanol twice, and dry in an 80°C oven to prepare irregular sub-micron gold powder.

[0039] Example 1

[0040] 1. 10 g of gold flake with 99.99% purity was dissolved using aqua regia, and the nitric acid and excess hydrochloric acid in the solution were removed, and a 1 mol / L, about 50 ml of chloroauric acid (HAuCl4) solution was prepared using deionized water;

[0041] 2. 0.2 g of polyvinylpyrrolidone was dissolved in 450 ml of deionized water under stirring;

[0042] 3. 5.6 g of glycine was dissolved in 75 ml of deionized water;

[0043] 4. 3.4 g of imidazole was dissolved in 75 ml of deionized water, and the molar ratio (imidazole: HAuCl4) was 1:1, and heated to 40°C.

[0044] 5. The HAuCl4 solution prepared in step (1) was poured into the dispersant solution prepared in step (2) under stirring, and after stirring for 15 minutes, 0.1-1 mol / L of HCl or NaOH solution was used to adjust the pH to 1.3-1.5, the glycine aqueous solution prepared in step (3) was added, the reaction solution was heated to 40°C, the reducing agent aqueous solution prepared in step (4) was added, and the stirring was continued until the reaction was complete;

[0045] 6. The reaction solution of step (5) was allowed to stand and precipitate, the supernatant was poured out, and the precipitate was washed with deionized water three times and with ethanol twice, and was dried in an oven at 80°C to prepare irregularly shaped submicron gold powder.

[0046] Example 2

[0047] 1. 10 g of gold flake with 99.99% purity was dissolved using aqua regia, and the nitric acid and excess hydrochloric acid in the solution were removed, and a 1 mol / L, about 50 ml of chloroauric acid (HAuCl4) solution was prepared using deionized water;

[0048] 2. 0.5 g of sodium dodecyl sulfate was dissolved in 450 ml of deionized water under stirring;

[0049] 3. 11.02 g of glutamic acid was dissolved in 75 ml of deionized water;

[0050] 4. 11.6 g of histidine was dissolved in 75 ml of deionized water, and the molar ratio (histidine: HAuCl4) was 3:2, and heated to 40°C.

[0051] 5. Under stirring, pour the HAuCl4 solution prepared in step (1) into the dispersant solution prepared in step (2), after stirring for 15 minutes, adjust the pH to 1.3-1.5 using 0.1-1 mol / L HCl or NaOH solution, add the aqueous glycine solution prepared in step (3), heat the reaction solution to 40°C, and add the aqueous reducing agent prepared in step (4), continue stirring until the reaction is complete;

[0052] 6. Allow the reaction solution prepared in step (5) to stand and precipitate, pour out the supernatant, wash repeatedly with deionized water three times, wash with ethanol twice, and dry in an oven at 80°C to prepare irregularly shaped submicron gold powder.

[0053] By Figure 1 and Figure 2 It can be seen that, compared with Example 1, Example 2 increases the molar ratio of reducing agent to chloroauric acid, and the particle size of the prepared gold powder increases. As a reducing agent containing an imidazole functional group, imidazole contains two nitrogen atoms, which can complex gold ions, reduce the reaction rate, and prolong the particle size growth process, so the particle size of the gold powder prepared in Example 2 increases.

Claims

1. A method for preparing gold powder for matching low-temperature co-fired ceramics, characterized in that: The following steps are involved: (1) Dissolve 99.99% gold flakes in aqua regia, remove nitric acid and excess hydrochloric acid in the solution, and prepare a 1 mol / L HAuCl4 solution in deionized water; (2) dissolving the dispersant in deionized water, with the mass ratio of the dispersant to HAuCl4 being 1 to 5:100, and the volume ratio of deionized water to HAuCl4 solution being 9:1; (3) dissolving amino acids in deionized water to prepare an amino acid aqueous solution with a concentration of 1 mol / L, wherein the molar ratio of amino acids to HAuCl4 is 3:2; the amino acids serve as gold ion complexing agents and pH regulators of the reaction solution to reduce the reaction rate of gold ions, avoid the formation of other morphologies, and regulate the pH to promote stable reaction. (4) Dissolve the reducing agent containing imidazole functional groups in deionized water to prepare a reducing agent solution with a concentration of 1 mol / L and a molar ratio of the reducing agent to HAuCl4 of 2 to 3:

2. Appropriately increase the solution temperature; (5) Pour the HAuCl4 solution prepared in step (1) into the dispersant solution prepared in step (2) under stirring conditions, stir for a period of time, add the amino acid aqueous solution prepared in step (3), adjust the pH to 1.3-1.4 using HCl or NaOH solution with a concentration of 0.1-1 mol / L, appropriately increase the solution temperature, then add the reducing agent aqueous solution prepared in step (4), and continue stirring until the reaction is complete; (6) The reaction solution of step (5) was allowed to settle, the supernatant was poured out, and the powder was washed repeatedly with deionized water and then washed with ethanol to replace the water in the powder. The powder was dried in an oven to prepare gold powder with irregular morphology, no agglomeration, a particle size range of 200nm to 900nm, and a warpage of less than 0.1mm.

2. The preparation method according to claim 1, wherein: The dispersant is one or more of polyvinyl pyrrolidone, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, polyethylene glycol or ethylphenyl polyethylene glycol.

3. The preparation method according to claim 1, wherein: The amino acid is one or more of glycine, alanine, valine, phenylalanine, glutamic acid, lysine or arginine.

4. The preparation method according to claim 1, wherein: The reducing agent is one or more of imidazole, 2-methyl-4-ethylimidazole, benzimidazole or histidine.

5. The preparation method according to claim 1, wherein: In steps (4) and (5), the solution temperature is raised to 40°C.

6. The preparation method according to claim 1, wherein: In step (5), about 1 ml of the reaction solution is taken out and tested with hydrazine hydrate to see if the reaction is complete. If the reaction solution turns black or purple, continue stirring the reaction; if the color of the reaction solution does not change, the reaction is complete.

7. The preparation method according to any one of claims 1 to 6, wherein: In step (6), the product is washed repeatedly with deionized water for more than three times and with ethanol for more than two times; the oven drying temperature is 80°C.

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