A conductor paste for LED chip packaging and its preparation method

Abstract

This invention belongs to the field of conductor materials technology, and relates to a conductor paste for LED chip packaging and its preparation method. The invention provides a method for preparing a conductor paste, comprising: mixing copper powder and deionized water at a mass ratio of 1:5 to 1:7, dispersing evenly, adding triallyl citrate and sodium glyoxylate, and heating at 55-60°C for 1-2 hours; then adding γ-methacryloyloxypropyltrimethoxysilane and heating at 45-50°C for 1-2 hours; finally, vacuum drying to obtain antioxidant copper powder; and mixing the antioxidant copper powder, resin binder, solvent, and additives evenly to obtain the conductor paste. The conductor paste provided by this invention has excellent conductivity, good adhesion to LED chip substrates, and is not easily oxidized at high temperatures. This invention solves the technical problem of excessive sheet resistance in conductor pastes obtained by coating copper powder with γ-methacryloyloxypropyltrimethoxysilane to improve its antioxidant properties.

Description

Technical Field

[0001] This invention belongs to the field of conductor materials technology, and relates to a conductor paste for LED chip packaging and its preparation method. Background Technology

[0002] As a high-efficiency solid-state lighting and display device, the large-scale development of LEDs has placed comprehensive demands on conductor paste, a core material in the chip packaging process, requiring low resistance, high stability, high adhesion, and low cost. Conductor paste needs to provide the electrical connection between the LED chip and the substrate. It must not only have low sheet resistance to ensure current transmission efficiency but also withstand the high temperatures during packaging curing and long-term use. Simultaneously, it must maintain high adhesion to the substrate to prevent debonding failure under thermal cycling, and the raw material cost must be compatible with large-scale mass production requirements. Existing LED packaging conductor pastes are mainly divided into silver-based and copper-based categories. While silver-based pastes have excellent conductivity, they suffer from two major drawbacks: high raw material costs, driving up packaging costs; and the tendency for silver migration at high temperatures, leading to chip leakage or short circuits, making it difficult to meet high reliability requirements. Copper-based pastes, due to copper's room temperature resistivity being close to that of silver, low cost, and no migration risk, have become a key direction for replacing silver-based pastes. However, their industrialization is limited by the bottleneck of copper powder's easy oxidation.

[0003] During the preparation, storage, and encapsulation curing of slurry, copper powder readily reacts with oxygen to form an insulating oxide layer, directly causing a surge in the slurry's sheet resistance. This oxidation rate accelerates significantly, especially under high-temperature aging conditions, further deteriorating conductivity. To address the copper powder oxidation problem, existing technologies commonly employ organic coating modification. Among these, γ-methacryloyloxypropyltrimethoxysilane is a frequently used modifier because it can physically block oxygen by generating a siloxane layer through hydrolysis, and its organic functional groups can potentially enhance its bonding strength with resins. However, existing solutions contain irreconcilable contradictions. To enhance the antioxidant effect, the amount of γ-methacryloxypropyltrimethoxysilane needs to be increased to form a thicker coating layer. However, the thick siloxane layer blocks the direct metal-metal contact between copper powder particles, leading to a significant increase in the sheet resistance of the paste, which cannot meet the low-resistance requirements of LED packaging. At the same time, the interfacial bonding between the single γ-methacryloxypropyltrimethoxysilane coating layer and the resin binder is weak, resulting in generally low adhesion of the paste to the substrate. Furthermore, the adhesion decay rate is high after high-temperature aging, seriously affecting the reliability of the packaging. In summary, existing technologies cannot simultaneously achieve a balance between the core performance characteristics of low sheet resistance, high antioxidant properties, and high adhesion of copper-based conductor pastes, and cannot meet the actual application requirements of LED chip packaging. There is an urgent need to develop a conductor paste preparation technology that can overcome the above-mentioned technical bottlenecks. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem that while organic coating of copper powder in copper conductor paste can improve its oxidation resistance, it also leads to excessive sheet resistance. To address this, this invention provides a conductor paste for LED chip packaging and its preparation method to solve the aforementioned technical problem. The conductor paste provided by this invention exhibits excellent conductivity, good adhesion to LED chip substrates, and is not easily oxidized at high temperatures.

[0005] On the one hand, the present invention provides a method for preparing a conductor paste, which includes: mixing copper powder and deionized water in a mass ratio of 1:5 to 1:7, dispersing them evenly, adding triallyl citrate and sodium glyoxylate, keeping the mixture at 55 to 60°C for 1 to 2 hours, then adding γ-methacryloyloxypropyltrimethoxysilane, keeping the mixture at 45 to 50°C for 1 to 2 hours, and finally vacuum drying to obtain antioxidant copper powder;

[0006] The conductor paste is prepared by uniformly mixing the antioxidant copper powder, resin binder, solvent and additives.

[0007] Furthermore, in the method for preparing the conductor paste provided by the present invention, the amount of triallyl citrate is 0.8-1.5% relative to the mass percentage of copper powder, the amount of sodium glyoxylate is 0.4-0.8%, and the amount of γ-methacryloyloxypropyltrimethoxysilane is 1.8-2.0%.

[0008] Furthermore, in the method for preparing the conductor paste provided by the present invention, the particle size of the copper powder is not higher than 1 μm.

[0009] Furthermore, in the method for preparing the conductor paste provided by the present invention, the resin binder is at least one of polyurethane resin, polyacrylic resin, and epoxy resin.

[0010] Furthermore, in the method for preparing the conductor paste provided by the present invention, the solvent is at least one of ethylene glycol ethyl ether acetate, N-methylpyrrolidone, and isopropanol.

[0011] Furthermore, in the method for preparing the conductor paste provided by the present invention, the additives are curing agents, defoamers, and surfactants.

[0012] Furthermore, in the method for preparing the conductor paste provided by the present invention, the weight ratio of the curing agent, defoamer and surfactant in the additives is 3~5:0.5~1.5:0.1~3.

[0013] Furthermore, in the method for preparing the conductor paste provided by the present invention, the curing agent is at least one selected from dicyandiamide, diacetamide, and triethanolamine;

[0014] The defoamer is at least one of dimethyl silicone oil, polyoxypropylene glycerol ether, and sodium dodecyl sulfonate;

[0015] The surfactant is at least one of lecithin, glyceryl monostearate, and glycerol phosphate.

[0016] Furthermore, in the method for preparing the conductor paste provided by the present invention, the raw materials for preparing the conductor paste, by weight, consist of 70-80 parts of the antioxidant copper powder, 5-10 parts of the resin binder, 8-10 parts of the solvent and 1-10 parts of the additives.

[0017] On the other hand, the present invention relates to a conductor paste for LED chip packaging, which is prepared by the aforementioned method for preparing conductor paste.

[0018] Compared with the prior art, the technical solution provided by the present invention has at least the following beneficial effects or advantages:

[0019] This invention achieves a balance of key performance characteristics by synergistically modifying copper powder with three components. Firstly, it resolves the contradiction between oxidation resistance and low sheet resistance. Triallyl citrate (CTA) forms an anchoring layer with copper powder through its carboxyl groups, limiting the disordered growth of γ-methacryloyloxypropyltrimethoxysilane (KH570) during hydrolysis and condensation, thus preventing the formation of a continuous thick silane insulating layer. Simultaneously, its allyl double bond and the methacryloyloxy double bond of KH570 produce a synergistic π-π stacking effect. Sodium glyoxylate (SG) reduces the CuO / Cu2O on the copper powder surface to conductive Cu, cleaning the conductive interface. KH570 ultimately forms an ultrathin, discontinuous siloxane layer, which both hinders oxygen contact with the copper powder, improving oxidation resistance, and preserves direct metal-metal contact between copper powder particles, reducing sheet resistance. Secondly, it possesses… It exhibits excellent and stable adhesion. The synergistic effect of the double bonds of CTA and KH570 enhances the interfacial bonding force between copper powder and resin binder. Combined with curing agents, defoamers, and other additives, the adhesion of the slurry on LED aluminum nitride ceramic substrates reaches 16.2~17.1 N / mm², and the adhesion retention rate is still over 95% after aging at 150℃ for 24 hours. Thirdly, the process is highly controllable and applicable. By using a copper powder to deionized water mass ratio of 1:5~1:7 and staged heat preservation temperature, and by selecting various solvents such as ethylene glycol ethyl ether acetate and different resin combinations, it can be flexibly adapted to the LED chip packaging requirements. Moreover, the vacuum drying process avoids secondary oxidation of copper powder, further ensuring the stability of slurry performance. Detailed Implementation

[0020] The technical solution of the present invention will be described below with reference to embodiments; however, the present invention is not limited to the following embodiments. Unless otherwise specified, the experimental and detection methods described in each embodiment are conventional methods; the reagents and materials described are commercially available unless otherwise specified. Unless otherwise specified, all percentages in the following embodiments refer to mass percentage content. Unless otherwise specified, all ratios in the following embodiments refer to mass ratios.

[0021] Example 1

[0022] This embodiment provides a process for preparing a conductor paste.

[0023] (1) Preparation of antioxidant copper powder:

[0024] Copper powder with a particle size of 0.8 μm was mixed with deionized water at a mass ratio of 1:6 and dispersed evenly. Triallyl citrate (1.2% of the copper powder mass) and sodium glyoxylate (0.6% of the copper powder mass) were added. The mixture was kept at 58 °C for 1.5 hours. γ-methacryloyloxypropyltrimethoxysilane (1.9% of the copper powder mass) was added. The mixture was kept at 48 °C for 1.5 hours. The mixture was then vacuum dried to obtain antioxidant copper powder.

[0025] (2) Raw material preparation:

[0026] Take the following raw materials in parts by weight:

[0027] Antioxidant copper powder: 75 parts;

[0028] Resin adhesive: 8 parts (epoxy resin, HT6302);

[0029] Solvent: 9 parts (ethylene glycol ethyl ether acetate);

[0030] Additives: 6 parts (curing agent: defoamer: surfactant = 4:1:1).

[0031] (3) Slurry preparation:

[0032] Mix the above-mentioned antioxidant copper powder, epoxy resin, solvent, and additives thoroughly. Among the additives:

[0033] Curing agent: dicyandiamide;

[0034] Defoamer: Dimethyl silicone oil;

[0035] Surfactant: lecithin.

[0036] After being processed by high-speed stirring and colloid milling to a fineness of less than 5μm, a conductor paste suitable for LED chip packaging is obtained.

[0037] Example 2

[0038] This embodiment provides a process for preparing a conductor paste.

[0039] (1) Preparation of antioxidant copper powder:

[0040] Copper powder with a particle size of 0.5 μm was mixed with deionized water at a ratio of 1:5; triallyl citrate (1.5%) and sodium glyoxylate (0.8%) were added; the mixture was kept at 60 °C for 1 hour; γ-methacryloyloxypropyltrimethoxysilane (2.0%) was added; the mixture was kept at 50 °C for 1 hour; and the mixture was vacuum dried to obtain antioxidant copper powder.

[0041] (2) Raw material preparation:

[0042] Take the following raw materials in parts by weight:

[0043] Antioxidant copper powder: 80 parts;

[0044] Resin adhesive: 5 parts (polyurethane resin, HT-600 Plus);

[0045] Solvent: 8 parts (N-methylpyrrolidone);

[0046] Additives: 5 parts (where curing agent: defoamer: surfactant = 5:0.5:0.5).

[0047] (3) Slurry preparation:

[0048] Antioxidant copper powder, polyurethane resin, solvent, and additives are mixed. Among the additives:

[0049] Curing agent: diacetamide;

[0050] Defoamer: Polyoxypropylene glycerol ether;

[0051] Surfactant: Glyceryl monostearate.

[0052] After being processed by high-speed stirring and colloid milling to a fineness of less than 5μm, a conductor paste suitable for LED chip packaging is obtained.

[0053] Example 3

[0054] This embodiment provides a process for preparing a conductor paste.

[0055] (1) Preparation of antioxidant copper powder:

[0056] Copper powder with a particle size of 1.0 μm was mixed with deionized water at a ratio of 1:7; triallyl citrate (0.8%) and sodium glyoxylate (0.4%) were added; the mixture was kept at 55°C for 2 hours; γ-methacryloyloxypropyltrimethoxysilane (1.8%) was added; the mixture was kept at 45°C for 2 hours; and the mixture was vacuum dried to obtain antioxidant copper powder.

[0057] (2) Raw material preparation:

[0058] Take the following raw materials in parts by weight:

[0059] Antioxidant copper powder: 70 parts;

[0060] Resin binder: 10 parts (polyacrylic resin, HumiSeal 1B31EPA).

[0061] Solvent: 10 parts (isopropanol);

[0062] Additives: 8 parts (of which curing agent: defoamer: surfactant = 3:1.5:3).

[0063] (3) Slurry preparation:

[0064] Antioxidant copper powder, polyacrylic acid resin, solvent, and additives are mixed. Among the additives:

[0065] Curing agent: triethanolamine;

[0066] Defoamer: Sodium dodecyl sulfonate;

[0067] Surfactant: Glycerol phosphate.

[0068] The slurry is obtained by processing it with a colloid mill to a fineness of less than 5 μm.

[0069] Example 4

[0070] This embodiment provides a process for preparing a conductor paste.

[0071] (1) Preparation of antioxidant copper powder:

[0072] Copper powder with a particle size of 0.6 μm was mixed with deionized water at a ratio of 1:6; triallyl citrate (1.0%) and sodium glyoxylate (0.5%) were added; the mixture was kept at 57 °C for 1.5 hours; γ-methacryloyloxypropyltrimethoxysilane (1.9%) was added; the mixture was kept at 47 °C for 1.5 hours; and the mixture was vacuum dried to obtain antioxidant copper powder.

[0073] (2) Raw material preparation:

[0074] Take the following raw materials in parts by weight:

[0075] Antioxidant copper powder: 78 parts;

[0076] Resin adhesive: 7 parts (epoxy resin and polyurethane resin mixed in a 1:1 ratio);

[0077] Solvent: 9 parts (ethylene glycol ethyl ether acetate and isopropanol mixed in a 2:1 ratio);

[0078] Additives: 5 parts (of which curing agent: defoamer: surfactant = 4.5:1:2).

[0079] (3) Slurry preparation:

[0080] Antioxidant copper powder, epoxy resin, polyurethane resin, mixed solvent, and additives are mixed. Among the additives:

[0081] Curing agent: a mixture of dicyandiamide and diacetamide in equal mass;

[0082] Defoamer: Dimethyl silicone oil;

[0083] Surfactant: A mixture of lecithin and glyceryl monostearate in equal mass;

[0084] After being processed by high-speed stirring and colloid milling to a fineness of less than 5μm, a conductor paste suitable for LED chip packaging is obtained.

[0085] Comparative Example 1

[0086] This comparative example is the same as Example 1, except that triallyl citrate is replaced with γ-methacryloyloxypropyltrimethoxysilane.

[0087] Comparative Example 2

[0088] This comparative example is the same as Example 1, except that sodium glyoxylate is replaced with γ-methacryloyloxypropyltrimethoxysilane.

[0089] Comparative Example 3

[0090] This comparative example is the same as Example 1, except that triallyl citrate and sodium glyoxylate are replaced with γ-methacryloyloxypropyltrimethoxysilane.

[0091] The conductor pastes prepared in Examples 1-4 and Comparative Examples 1-3 were printed on LED aluminum nitride ceramic substrates (thickness 30 μm), dried and cured (200℃ for 10 min), and then subjected to sheet resistance (0.6 mm × 60 mm), aging sheet resistance (0.6 mm × 60 mm, 150℃ for 24 hrs), adhesion (2 mm × 2 mm tensile testing machine, refer to GB / T 17473.4-2008), and aging adhesion (2 mm × 2 mm tensile testing machine, 150℃ for 24 hrs, refer to GB / T 17473.4-2008). The test results are shown in Table 1.

[0092] Table 1: Test Results of Conductor Paste

[0093]

[0094] As shown in Table 1, the conductor pastes prepared in Examples 1-4 exhibit excellent overall performance, with sheet resistance of 9.5-11.1 mΩ / □ and aging sheet resistance (150℃ for 24 hours) of 10.8-12.3 mΩ / □. The sheet resistance is low and the increase after high-temperature aging is small. The adhesion reaches 16.2-17.1 N / mm² and aging adhesion is 15.5-16.2 N / mm², demonstrating high adhesion and good retention at high temperatures. In contrast, Comparative Examples 1-3 show significantly deteriorated performance, with sheet resistance of 21.3-38.7 mΩ / □, aging sheet resistance of 30.6-51.2 mΩ / □, and adhesion of 12.1-14.2 N / mm² and aging adhesion of 11.0-13.1 N / mm². Comparative Example 1, by replacing triallyl citrate with γ-methacryloxypropyltrimethoxy In Comparative Example 1, the use of silane (KH570) resulted in the loss of the anchoring and restraining effect of triallyl citrate on KH570 coating. This led to the formation of a thick insulating layer by KH570, which blocked the conductive path of copper powder and was prone to cracking at high temperatures, exacerbating oxidation. At the same time, the loss of double bond synergy reduced adhesion. In Comparative Example 2, the replacement of sodium glyoxylate with KH570 resulted in the loss of the reducing and cleaning effect of sodium glyoxylate on the oxide layer of copper powder surface. The residual insulating oxide layer increased the contact resistance, and the lack of sodium glyoxylate to assist the coordination of triallyl citrate reduced the stability of the modified layer, thus affecting adhesion. In Comparative Example 3, the replacement of both triallyl citrate and sodium glyoxylate with KH570 resulted in the absence of anchoring restraint, leading to the formation of a thicker insulating layer by KH570. The lack of reducing and cleaning resulted in residual oxide layer, and the loss of double bond synergy also resulted in the worst performance, failing to achieve the technical effect of the embodiments.

[0095] As described above, the basic principles, main features, and advantages of the present invention have been well described. The above embodiments and specifications are merely descriptions of preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit and scope of the present invention should fall within the protection scope defined by the present invention.

Claims

1. A method for preparing a conductor paste, characterized by, The application relates to a conductor paste and a preparation method thereof. The copper powder and deionized water are mixed in a mass ratio of 1:5-1:7, and after being uniformly dispersed, triallyl citrate and sodium glyoxylate are added, and the mixture is preserved at 55-60 DEG C for 1-2 hours; then gamma-methacryloxypropyl trimethoxysilane is added, and the mixture is preserved at 45-50 DEG C for 1-2 hours; finally, the antioxidant copper powder is prepared through vacuum drying; The antioxidant copper powder, a resin binder, a solvent and an additive are uniformly mixed to prepare the conductor paste.

2. The method of claim 1, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The amount of triallyl citrate is 0.8-1.5% by mass percentage of the copper powder, the amount of sodium glyoxylate is 0.4-0.8%, and the amount of gamma-methacryloxypropyl trimethoxysilane is 1.8-2.0%.

3. The method of claim 1, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The particle size of the copper powder is not higher than 1 mu m.

4. The method of claim 1, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The resin binder is at least one of polyurethane resin, polyacrylic resin and epoxy resin.

5. The method of claim 1, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The solvent is at least one of ethylene glycol ether acetate, N-methyl pyrrolidone and isopropyl alcohol.

6. The method of claim 1, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The additive is a curing agent, a defoaming agent and a surfactant.

7. The method of claim 6, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The weight ratio of the curing agent, the defoaming agent and the surfactant in the additive is 3-5:0.5-1.5:0.1-3.

8. The method of claim 6, wherein the conductive paste is prepared by mixing the conductive filler, the binder, and the solvent. The curing agent is at least one of dicyandiamide, diacetamide and triethanolamine; The defoaming agent is at least one of dimethyl silicone oil, polyoxypropylene glycerol ether and sodium dodecyl sulfonate; The surfactant is at least one of lecithin, glycerol monostearate and glycerol phosphate.

9. The method of claim 1, wherein the conductive paste is prepared by the steps of: The preparation raw materials of the conductor paste are composed of 70-80 parts of the antioxidant copper powder, 5-10 parts of the resin binder, 8-10 parts of the solvent and 1-10 parts of the additive.

10. A conductor paste for LED chip packaging, characterized by, The conductor paste is prepared by the preparation method of any one of claims 1-9.

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