A high-temperature antioxidant copper paste and its preparation method

Abstract

This invention discloses a high-temperature antioxidant copper paste and its preparation method, belonging to the field of copper paste technology. The copper paste comprises: conductive copper powder: 80-92 wt%; glass powder: 1-5 wt%; organic carrier: 5-15 wt%; and a composite antioxidant-reduction system: 0.5-3 wt%. The copper paste preparation method includes the following steps: Copper powder pretreatment: Copper powder is dispersed in ethanol, an organophosphonic acid compound is added, and after reaction, the mixture is filtered and dried to obtain primary treated copper powder, which is dispersed in silica sol, ultrasonically treated, centrifuged, dried, and heat-treated at 300-400℃ to form conductive copper powder; Organic carrier preparation: Ethyl cellulose is dissolved in terpineol, and a leveling agent is added to form an organic carrier; Slurry preparation and mixing: The composite-coated conductive copper powder, glass powder, and composite antioxidant-reduction system are sequentially added to the organic carrier, mixed, and rolled to obtain a homogeneous copper paste.

Description

Technical Field

[0001] This invention relates to the field of copper paste technology, and in particular to a high-temperature antioxidant copper paste and its preparation method. Background Technology

[0002] Copper paste has become a key material to replace silver paste due to its excellent electrical and thermal conductivity and low cost. However, copper powder is easily oxidized during storage, processing and sintering, forming non-conductive copper oxide (CuO) or cuprous oxide (Cu2O), which leads to a sharp increase in the resistivity of the sintered film and a decrease in adhesion, severely restricting its application.

[0003] Existing technologies mainly employ two types of methods to prevent copper oxidation:

[0004] Harsh atmosphere protection: Sintering in pure nitrogen, hydrogen, or formic acid vapor. This method involves complex equipment, high costs, and is not suitable for atmosphere-sensitive environments or continuous production scenarios.

[0005] Adding reducing agents: Strong reducing agents such as hydrazine hydrate and sodium borohydride are added to the slurry. However, these reducing agents have low decomposition temperatures, high toxicity, and poor storage stability. Their violent reactions can easily lead to slurry bubbling and film cracking, making it impossible to provide continuous protection in the critical copper particle sintering neck temperature zone (500-800℃). Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-temperature antioxidant copper paste and its preparation method, which is a copper paste that does not require a harsh protective atmosphere, can continuously provide antioxidant protection in a wide temperature range, and is process-friendly.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows:

[0008] This invention discloses a high-temperature antioxidant copper paste, wherein the copper paste comprises the following components by weight percentage:

[0009] Conductive copper powder: 80-92 wt%, wherein the conductive copper powder is spherical or flake-shaped copper powder treated with a composite coating layer;

[0010] Glass powder: 1-5 wt%;

[0011] Organic carrier: 5–15 wt%

[0012] Composite antioxidant-reduction system: 0.5–3 wt%.

[0013] Preferably, the composite coating layer comprises an inner layer of organophosphonic acid compound and an outer layer of silica sol, wherein the organophosphonic acid compound is at least one of hexadecylphosphonic acid and phenylphosphonic acid.

[0014] Preferably, the content of the organophosphonic acid compound is 0.1 to 0.5% of the weight of the conductive copper powder; and the amount of silica sol coating is 0.5 to 2% of the weight of the conductive copper powder.

[0015] Preferably, the composite antioxidant-reduction system is a mixture of a low-temperature decomposition reducing agent and a high-temperature hydrogen-releasing protective agent in a weight ratio of 1:(0.2-0.5).

[0016] Preferably, the low-temperature decomposition reducing agent is a condensation product of formamide and citric acid, and the high-temperature hydrogen-releasing protective agent is surface-modified titanium hydride nanoparticles coated with a polyvinylpyrrolidone layer, with an initial decomposition temperature of 380–420°C.

[0017] Preferably, the thermal decomposition initiation temperature of the low-temperature decomposition reducing agent is 180–220°C, and the peak temperature is 280–320°C.

[0018] Preferably, the organic carrier includes ethyl cellulose, terpineol, and leveling agent.

[0019] A method for preparing the high-temperature antioxidant copper paste, the method comprising the following steps:

[0020] Copper powder pretreatment:

[0021] Copper powder is dispersed in ethanol, an organophosphonic acid compound is added, and the mixture is stirred and reacted at 60-80°C for 2-4 hours. After filtration and drying, primary processed copper powder is obtained. The primary processed copper powder is dispersed in silica sol with pH adjusted by ammonia water, ultrasonically treated, centrifuged, dried, and heat-treated at 300-400°C to form a dense silica coating layer, thus obtaining composite coated copper powder, which forms conductive copper powder.

[0022] Organic carrier preparation:

[0023] Ethyl cellulose is dissolved in terpineol, a leveling agent is added, and the mixture is stirred and mixed evenly to form an organic carrier;

[0024] Configure a composite antioxidant-reduction system:

[0025] A composite antioxidant-reduction system was prepared by combining a low-temperature decomposition reducing agent and a high-temperature hydrogen-releasing protective agent in a specific weight ratio.

[0026] Slurry preparation and mixing:

[0027] The composite coated conductive copper powder, glass powder, and composite antioxidant system are sequentially added to the organic carrier. The mixture is first pre-mixed by planetary stirring, and then rolled by a three-roll mill to a fineness of less than or equal to 10 μm to obtain a homogeneous copper slurry.

[0028] The above technical solution has the following beneficial effects:

[0029] This application utilizes the above-mentioned components and preparation method to prepare a copper paste that does not require a harsh protective atmosphere, can continuously provide antioxidant protection over a wide temperature range, and is process-friendly. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Example 1

[0032] A high-temperature antioxidant copper paste, comprising the following components by weight percentage:

[0033] Conductive copper powder: 80-92 wt%

[0034] Glass powder: 1-5 wt%;

[0035] Organic carrier: 5–15 wt%

[0036] Composite antioxidant-reduction system: 0.5–3 wt%.

[0037] The total weight percentage of the conductive copper powder, glass powder, organic carrier, and composite antioxidant-reduction system in the preparation of the high-temperature antioxidant copper paste is 100 wt%. Specifically, the high-temperature antioxidant copper paste may include: 80 wt% conductive copper powder, 2 wt% glass powder, 15 wt% organic carrier, and 3 wt% composite antioxidant-reduction system, or it may include: 85.5 wt% conductive copper powder, 3 wt% glass powder, 10 wt% organic carrier, and 1.5 wt% composite antioxidant-reduction system.

[0038] The aforementioned conductive copper powder is spherical or flake-shaped copper powder treated with an organic-inorganic composite coating layer. The composite coating layer consists of an inner organic phosphonic acid compound and an outer silica sol. The organic phosphonic acid compound is selected from at least one of hexadecylphosphonic acid and phenylphosphonic acid, and its content is 0.1% to 0.5% of the weight of the conductive copper powder. The silica sol coating amount is 0.5% to 2% of the weight of the conductive copper powder. Specifically, the amount of the organic phosphonic acid compound is 0.1% or 0.5% of the weight of the conductive copper powder, and the amount of the silica sol coating amount is 0.5% or 2% of the weight of the conductive copper powder.

[0039] The composite antioxidant-reduction system is composed of a low-temperature decomposition reducing agent and a high-temperature hydrogen-releasing protective agent in a weight ratio of 1:(0.2-0.5). The low-temperature decomposition reducing agent is a condensation product of formamide and citric acid, with a thermal decomposition initiation temperature of 180-220℃ and a peak temperature of 280-320℃. The high-temperature hydrogen-releasing protective agent is surface-modified titanium hydride nanoparticles coated with a polyvinylpyrrolidone (PVP) layer, with an initiation decomposition temperature of 380-420℃. Specifically, the low-temperature decomposition reducing agent and the high-temperature hydrogen-releasing protective agent are compounded in a weight ratio of 1:0.2 or 1:0.5 to form the composite antioxidant-reduction system.

[0040] The organic carrier includes ethyl cellulose, terpineol, and leveling agent. Specifically, the organic carrier is formed by stirring and mixing ethyl cellulose, terpineol, and leveling agent evenly.

[0041] The technical solution of this application overcomes the shortcomings of existing copper pastes, such as easy oxidation during high-temperature sintering, dependence on harsh protective atmosphere, and mismatch of the operating temperature range of conventional reducing agents, and provides a high-performance copper paste with inherent continuous anti-oxidation ability that is suitable for sintering in air or weak reducing atmosphere.

[0042] Example 2

[0043] The present invention also provides a method for preparing the above-mentioned high-temperature antioxidant copper paste, comprising the following steps:

[0044] Copper powder pretreatment:

[0045] Copper powder is dispersed in ethanol, an organophosphonic acid compound is added, and the mixture is stirred at 60-80°C for 2-4 hours. After filtration and drying, primary processed copper powder is obtained. The primary processed copper powder is dispersed in a silica sol with pH adjusted by ammonia water, ultrasonically treated, centrifuged, dried, and heat-treated at 300-400°C for a short time to form a dense silica coating layer, thus obtaining composite coated copper powder.

[0046] Specifically, copper powder is dispersed in ethanol, an organophosphonic acid compound is added, and the mixture is stirred and reacted at 60°C or 80°C for 2 or 4 hours. After filtration and drying, primary processed copper powder is obtained. The pH of the silica sol is adjusted to 9 or 10 with ammonia water, and the primary processed copper powder is then dispersed in the silica sol. After ultrasonic treatment, centrifugation, drying, and short-term heat treatment at 300°C or 400°C, a dense silica coating layer is formed, resulting in composite coated copper powder, i.e., conductive copper powder.

[0047] Carrier preparation:

[0048] Ethyl cellulose is dissolved in terpineol, a leveling agent is added, and the mixture is stirred until homogeneous to obtain an organic carrier. Specifically, the leveling agent can be hydrogenated castor oil, polyether-modified siloxane, or lecithin. 15 wt% of ethyl cellulose can be dissolved in 80 wt% liquid terpineol, and then 5 wt% of leveling agent is added and stirred until homogeneous to obtain an organic carrier.

[0049] Preparation of a composite antioxidant-reduction system:

[0050] A composite antioxidant system was formed by mixing formamide-citric acid condensate with titanium hydride nanoparticles coated with polyvinylpyrrolidone (PVP).

[0051] Slurry preparation and mixing:

[0052] The composite coated copper powder, glass powder, and composite antioxidant system are sequentially added to the organic carrier. They are first mixed by planetary stirring, and then rolled by a three-roll mill to a fineness of less than or equal to 10 μm to obtain a homogeneous copper slurry.

[0053] Specifically, the above-prepared coated copper powder, composite antioxidant and reduction system, and glass powder are added to an organic carrier. The glass powder is a white, amorphous, hard, ultrafine powder obtained by melting glass raw materials at high temperature, quenching, and pulverizing. It is first pre-mixed by planetary stirring, and then rolled by a three-roll mill to a fineness of less than or equal to 10 μm. The fineness can be 10 μm or 8 μm to obtain a homogeneous copper paste.

[0054] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A high-temperature antioxidant copper paste, characterized in that, The copper paste comprises the following components by weight percentage: Conductive copper powder: 80-92 wt%, wherein the conductive copper powder is spherical or flake-shaped copper powder treated with a composite coating layer; Glass powder: 1-5 wt%; Organic carrier: 5–15 wt% Composite antioxidant-reduction system: 0.5–3 wt%.

2. The high-temperature antioxidant copper paste according to claim 1, characterized in that, The composite coating layer comprises an inner layer of organophosphonic acid compound and an outer layer of silica sol, wherein the organophosphonic acid compound is at least one of hexadecylphosphonic acid and phenylphosphonic acid.

3. The high-temperature antioxidant copper paste according to claim 2, characterized in that, The content of the organophosphonic acid compound is 0.1 to 0.5% of the weight of the conductive copper powder; the amount of silica sol coating is 0.5 to 2% of the weight of the conductive copper powder.

4. The high-temperature antioxidant copper paste according to claim 1, characterized in that, The composite antioxidant-reduction system is a mixture of a low-temperature decomposition reducing agent and a high-temperature hydrogen-releasing protective agent in a weight ratio of 1:(0.2-0.5).

5. The high-temperature antioxidant copper paste according to claim 4, characterized in that, The low-temperature decomposition reducing agent is a condensation product of formamide and citric acid, and the high-temperature hydrogen-releasing protective agent is surface-modified titanium hydride nanoparticles coated with a polyvinylpyrrolidone layer, with an initial decomposition temperature of 380–420°C.

6. The high-temperature antioxidant copper paste according to claim 5, characterized in that, The thermal decomposition initiation temperature of the low-temperature decomposition reducing agent is 180–220°C, and the peak temperature is 280–320°C.

7. The high-temperature antioxidant copper paste according to claim 4, characterized in that, The organic carrier includes ethyl cellulose, terpineol, and a leveling agent.

8. A method for preparing a high-temperature antioxidant copper paste as described in any one of claims 1-7, characterized in that, The preparation method includes the following steps: Copper powder pretreatment: Copper powder is dispersed in ethanol, an organophosphonic acid compound is added, and the mixture is stirred and reacted at 60-80°C for 2-4 hours. After filtration and drying, primary processed copper powder is obtained. The primary processed copper powder is dispersed in silica sol with pH adjusted by ammonia water, ultrasonically treated, centrifuged, dried, and heat-treated at 300-400°C to form a dense silica coating layer, thus obtaining composite coated copper powder, which forms conductive copper powder. Organic carrier preparation: Ethyl cellulose is dissolved in terpineol, a leveling agent is added, and the mixture is stirred and mixed evenly to form an organic carrier; Configure a composite antioxidant-reduction system: A composite antioxidant-reduction system was prepared by combining a low-temperature decomposition reducing agent and a high-temperature hydrogen-releasing protective agent in a specific weight ratio. Slurry preparation and mixing: The composite coated conductive copper powder, glass powder, and composite antioxidant system are sequentially added to the organic carrier. The mixture is first pre-mixed by planetary stirring, and then rolled by a three-roll mill to a fineness of less than or equal to 10 μm to obtain a homogeneous copper slurry.