Conductive paste and preparation method and application thereof

Abstract

The invention relates to the technical field of new materials, in particular to conductive paste and a preparation method and application thereof. The conductive paste comprises 35 to 40 weight percent of conductive silver powder and 30 to 40 weight percent of composite resin; wherein the composite resin comprises epoxy resin, acrylic resin and TPU (thermoplastic polyurethane) resin in a mass ratio of (20-22): (7-10): (4-8). The invention provides the conductive paste with low silver content, and a conductive circuit formed by using the conductive paste has sheet resistance of less than 100 m omega / square / mil and has good stability.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and in particular to a conductive paste and a preparation method and application thereof. Background Art

[0002] In recent years, people in this field usually use conductive paste to form circuit patterns on substrates to obtain electronic devices; among them, conductive paste is a key factor in determining the performance of electronic devices. In the prior art, known conductive pastes mostly use conductive silver powder as conductive filler, and in order to make the conductive paste have good conductivity and stability, the content of conductive silver powder in the conductive paste is often very high. However, with the rising price of silver powder, the cost of conductive paste is also increasing; how to reduce the cost of conductive paste is imminent.

[0003] It can be seen that developing a conductive paste with low silver content and both conductivity and stability is a technical problem that people in this field need to solve urgently; in view of this, the present invention is specially proposed. Summary of the invention

[0004] The purpose of the present invention is to provide a conductive paste with a low silver content. The difficulty in its research and development lies in the difficulty in taking into account both the conductivity and stability of the product and the low silver content. After exploring and optimizing the key factors affecting the above effects, the present invention provides a conductive paste and a preparation method and application thereof.

[0005] Specifically, the present invention first provides a conductive paste, which includes 35-40wt% of conductive silver powder and 30-40wt% of composite resin;

[0006] Among them, the conductive silver powder is flaky silver powder and spherical silver powder according to (0.5-2):(2-4); the particle size of the flaky silver powder is 2-8μm; the particle size of the spherical silver powder is 1-5μm; the composite resin includes epoxy resin, acrylic resin and TPU resin in a mass ratio of (20-22):(7-10):(4-8).

[0007] The present invention finds that the above scheme is beneficial to improving the conductivity and stability of the slurry on the basis of low silver content.

[0008] Those skilled in the art can set other functional components in the formula and parameters in the process according to common knowledge, which can all obtain effects comparable to the above description of the present invention. However, there are also better technical solutions for other components and parameters, for which the present invention further explores and obtains the following preferred solutions.

[0009] Preferably, the epoxy resin is pre-treated, and the treatment comprises the following steps: mixing the epoxy resin and the first solvent in a mass ratio of (2-5): (6-9), and then stirring at 80-90° C. and 100-500 rpm for 6-12 hours.

[0010] Furthermore, the epoxy resin is selected from one or more of bisphenol A, EP4000, 1256, and PKHH.

[0011] Furthermore, the first solvent is selected from one or more of DEAC, diethyl ether, DBE, and diethylene glycol methyl ether.

[0012] Preferably, the acrylic resin is pre-treated, and the treatment comprises the following steps: mixing the acrylic resin and the second solvent in a mass ratio of (1-5): (6-9), and then stirring at 80-90° C. and 100-500 rpm for 6-12 hours.

[0013] Furthermore, the acrylic resin is selected from one or more of BR-85, BR-113, MB-2660, MB-7496, and S-70.

[0014] Furthermore, the second solvent is selected from one or more of DEAC, DBE, acetone, xylene, and ethyl acetate.

[0015] Preferably, the TPU resin is pre-treated, and the treatment comprises the following steps: mixing the TPU resin and the third solvent in a mass ratio of (3-4): (6-7), and then stirring at 80-90° C. and 100-500 rpm for 6-24 hours.

[0016] Furthermore, the TPU resin is selected from one or more of 5778, 5715, 5714, and 5713.

[0017] Furthermore, the third solvent is selected from one or more of DBE, ethylene glycol butyl ether acetate, DEAC, and diethylene glycol methyl ether acetate.

[0018] The present invention also finds that the composite resin composed of the epoxy resin, acrylic resin and TPU resin respectively pretreated as above can achieve the purpose of further improving the conductivity and stability of the entire slurry on the basis of low silver content.

[0019] Preferably, the conductive paste further comprises 9-10wt% of polyol;

[0020] The polyol is selected from one or more of 2420I, BMY-600 and 330ng.

[0021] Preferably, the conductive paste further comprises 9-11 wt % of a diluent and 3-5 wt % of a curing agent;

[0022] The diluent is selected from one or more of ethylene glycol, DEAC, isopropanol, and ethyl acetate; and the curing agent is isocyanate.

[0023] Preferably, the conductive paste further comprises 1-2wt% of an auxiliary agent;

[0024] The auxiliary agent is selected from one or more of a leveling agent, a dispersant, and a defoaming agent.

[0025] In the present invention, the selection of polyols, diluents, curing agents and additives as described above is beneficial to further improve the conductivity and stability of the conductive paste.

[0026] Those skilled in the art can combine the above technical solutions according to common sense to obtain preferred embodiments of the conductive paste of the present invention.

[0027] As a preferred embodiment of the present invention, the conductive paste comprises the following components in percentage by mass:

[0028] Epoxy resin 20-22wt%, acrylic resin 7-10wt%, TPU resin 4-8wt%, polyol 9-10wt%, diluent 9-11wt%, curing agent 3-5wt%, conductive silver powder 35-40wt%, auxiliary agent 1-2wt%; wherein,

[0029] The specific selection of each component is as described above.

[0030] The present invention also provides a method for preparing the conductive paste mentioned above, comprising: mixing the components uniformly and then grinding.

[0031] In a specific embodiment, grinding is performed using a triple roll mill.

[0032] The present invention also provides the use of the above-mentioned conductive paste in a circuit board, preferably in a flexible circuit board.

[0033] The present invention further provides an electronic device, comprising a substrate and a conductive circuit located on the substrate, wherein the conductive circuit is formed by printing the conductive paste described above and then heating and curing it.

[0034] Preferably, the printing method is pad printing, screen printing, electrostatic spinning or printing.

[0035] Preferably, the substrate is made of elastic material.

[0036] Based on the above scheme, the beneficial effects of the present invention are as follows:

[0037] The invention provides a conductive paste with low silver content. The conductive circuit formed by using the conductive paste has a square resistance of less than 100 mΩ / □ / mil and has good stability. DETAILED DESCRIPTION

[0038] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0039] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0040] The conductive silver powder involved in Examples 1-5 is a flaky silver powder and a spherical silver powder in a ratio of 1:1; the particle size of the flaky silver powder is 2-8 μm; the particle size of the spherical silver powder is 1-5 μm;

[0041] Example 1

[0042] This embodiment provides a conductive paste, and its formula is as follows in terms of mass percentage:

[0043] Epoxy resin 22wt%, acrylic resin 9.5wt%, TPU resin 4wt%, polyol 9wt%, diluent 10wt%, curing agent 4wt%, conductive silver powder 40wt%, auxiliary agent 1.5wt%; wherein,

[0044] The epoxy resin is pre-treated, and the treatment comprises the following steps: bisphenol A and DEAC are mixed in a mass ratio of 1:4, and then stirred at 80° C. and 400 rpm for 8 hours;

[0045] The acrylic resin is pre-treated, and the treatment comprises the following steps: BR-85 and DEAC are mixed in a mass ratio of 1:9, and then stirred at 80° C. and 300 rpm for 6 hours;

[0046] The TPU resin is pre-treated, and the treatment comprises the following steps: 5778 and DBE are mixed in a mass ratio of 3:7, and then stirred at 90° C. and 400 rpm for 7 hours;

[0047] The polyol is 2420I;

[0048] The diluent is ethylene glycol;

[0049] The curing agent is isocyanate.

[0050] This embodiment further provides a method for preparing the conductive paste, which is specifically: mixing the components uniformly, and then grinding them with a three-roll grinder at 200-400 rpm for 1 hour to obtain the conductive paste.

[0051] Example 2

[0052] This embodiment provides a conductive paste, and its formula is as follows in terms of mass percentage:

[0053] Epoxy resin 20wt%, acrylic resin 7.5wt%, TPU resin 8wt%, polyol 9wt%, diluent 10wt%, curing agent 4wt%, conductive silver powder 40wt%, auxiliary agent 1.5wt%; wherein,

[0054] The epoxy resin is pre-treated, and the treatment comprises the following steps: EP4000 and DBE are mixed in a mass ratio of 3:7, and then stirred at 80° C. and 500 rpm for 6 hours;

[0055] The acrylic resin is pre-treated, and the treatment comprises the following steps: BR-113 and DBE are mixed in a mass ratio of 2.5:7.5, and then stirred at 85° C. and 400 rpm for 10 hours;

[0056] The TPU resin is pre-treated, and the treatment includes the following steps: 5715 and ethylene glycol butyl ether acetate are mixed in a mass ratio of 3:7, and then stirred at 90° C. and 200 rpm for 10 hours;

[0057] The polyol is BMY-600;

[0058] The diluent is DEAC;

[0059] The curing agent is isocyanate.

[0060] This embodiment further provides a method for preparing the conductive paste, which is specifically: mixing the components uniformly, and then grinding them with a three-roll grinder at 200-400 rpm for 1 hour to obtain the conductive paste.

[0061] Example 3

[0062] This embodiment provides a conductive paste, and its formula is as follows in terms of mass percentage:

[0063] Epoxy resin 20wt%, acrylic resin 7.5wt%, TPU resin 8wt%, polyol 9wt%, diluent 10wt%, curing agent 4wt%, conductive silver powder 40wt%, auxiliary agent 1.5wt%; wherein,

[0064] The epoxy resin is pre-treated, and the treatment comprises the following steps: 1256 and diethylene glycol methyl ether are mixed in a mass ratio of 2.8:7.2, and then stirred at 85° C. and 300 rpm for 8 hours;

[0065] The acrylic resin is pre-treated, and the treatment comprises the following steps: MB-2660 and acetone are mixed in a mass ratio of 1:4, and then stirred at 90° C. and 400 rpm for 8 hours;

[0066] The TPU resin is pre-treated, and the treatment includes the following steps: 5714 and DEAC are mixed in a mass ratio of 3:7, and then stirred at 85° C. and 400 rpm for 12 hours;

[0067] The polyol is 330ng;

[0068] The diluent is isopropanol;

[0069] The curing agent is isocyanate.

[0070] This embodiment further provides a method for preparing the conductive paste, which is specifically: mixing the components uniformly, and then grinding them with a three-roll grinder at 200-400 rpm for 1 hour to obtain the conductive paste.

[0071] Example 4

[0072] This embodiment provides a conductive paste, and its formula is as follows in terms of mass percentage:

[0073] Epoxy resin 20wt%, acrylic resin 7.5wt%, TPU resin 7.5wt%, polyol 10wt%, diluent 10wt%, curing agent 3.3wt%, conductive silver powder 40wt%, auxiliary agent 1.7wt%; wherein,

[0074] The epoxy resin is pre-treated, and the treatment comprises the following steps: PKHH and a first solvent (a mixture of ether and diethylene glycol methyl ether in equal proportions) are mixed in a mass ratio of 2:3, and then stirred at 80° C. and 200 rpm for 12 hours;

[0075] The acrylic resin is pre-treated, and the treatment comprises the following steps: MB-7496 and xylene are mixed in a mass ratio of 1:4, and then stirred at 90° C. and 100 rpm for 12 hours;

[0076] The TPU resin is pre-treated, and the treatment includes the following steps: 5713 and diethylene glycol methyl ether acetate are mixed in a mass ratio of 3:7, and then stirred at 90° C. and 500 rpm for 12 hours;

[0077] The polyol is BMY-600;

[0078] The diluent is ethyl acetate;

[0079] The curing agent is isocyanate.

[0080] This embodiment further provides a method for preparing the conductive paste, which is specifically: mixing the components uniformly, and then grinding them with a three-roll grinder at 200-400 rpm for 1 hour to obtain the conductive paste.

[0081] Example 5

[0082] This embodiment provides a conductive paste, and its formula is as follows in terms of mass percentage:

[0083] Epoxy resin 21wt%, acrylic resin 8wt%, TPU resin 7wt%, polyol 9.5wt%, diluent 10.5wt%, curing agent 3wt%, conductive silver powder 40wt%, auxiliary agent 1wt%; wherein,

[0084] The epoxy resin is pre-treated, and the treatment comprises the following steps: EP4000 and DEAC are mixed in a mass ratio of 3:7, and then stirred at 90° C. and 200 rpm for 7 hours;

[0085] The acrylic resin is pre-treated, and the treatment comprises the following steps: S-70 and ethyl acetate are mixed in a mass ratio of 1:9, and then stirred at 80° C. and 400 rpm for 10 hours;

[0086] The TPU resin is pre-treated, and the treatment comprises the following steps: 5778 and DBE are mixed in a mass ratio of 2:3, and then stirred at 80° C. and 200 rpm for 6-24 hours;

[0087] The polyol is 2420I;

[0088] The diluent is isopropanol;

[0089] The curing agent is isocyanate.

[0090] This embodiment further provides a method for preparing the conductive paste, which is specifically: mixing the components uniformly, and then grinding them with a three-roll grinder at 200-400 rpm for 1 hour to obtain the conductive paste.

[0091] Comparative Example 1

[0092] This comparative example provides a conductive paste, which is different from Example 1 in that in the formula, no TPU resin is added, the added amount of epoxy resin is 20wt%, and the added amount of acrylic resin is 15.5wt%.

[0093] Comparative Example 2

[0094] This comparative example provides a conductive paste, which is different from Example 1 in that the added amount of epoxy resin is 23wt%, the added amount of acrylic resin is 10.5wt%, and the added amount of TPU resin is 2wt%.

[0095] Comparative Example 3

[0096] This comparative example provides a conductive paste, which differs from Example 1 in that the polyol is replaced by 2120, and the conductive silver powder is replaced by spherical silver powder (with a particle size of 1-5 μm).

[0097] Test example

[0098] In this test example, the viscosity of the conductive paste of each embodiment and comparative example was first tested using a viscosity tester, and then the conductive paste of each embodiment and comparative example was respectively formed into a conductive circuit on the surface of the PI film substrate by screen printing, and cured at 200° C. for 15 minutes to obtain several flexible circuit boards, and then the performance of each flexible circuit board was tested, as follows:

[0099] 1. Perform square resistance test on each flexible circuit board respectively. The specific test method is: use a resistance tester to detect the resistance, and then calculate it into square resistance.

[0100] 2. Conduct adhesion test on the conductive circuits on each flexible circuit board respectively. The specific test method is: use 3M600# adhesive tape to adhere to the surface of the conductive circuit. After standing for 1 minute, use external force to quickly remove the 3M 600# adhesive tape and observe whether the appearance of each conductive circuit is falling off; if there is no falling off, the adhesion is good; if there is falling off (including partial falling off), the adhesion is poor.

[0101] 3. Conduct stability tests on each flexible circuit board separately. The specific test method is as follows: place the flexible circuit board at room temperature (25°C) for 3 months, use a resistance tester to detect the resistance, and calculate the square resistance; continue to place each flexible circuit board for 6 months, use a resistance tester to detect the resistance, and calculate the square resistance.

[0102] 4. The test results are shown in Table 1.

[0103] Table 1 Test results

[0104]

[0105] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A conductive paste, characterized in that: It includes 35-40wt% of conductive silver powder and 30-40wt% of composite resin; Among them, the conductive silver powder is flaky silver powder and spherical silver powder according to (0.5-2):(2-4); the particle size of the flaky silver powder is 2-8μm; the particle size of the spherical silver powder is 1-5μm; the composite resin includes epoxy resin, acrylic resin and TPU resin in a mass ratio of (20-22):(7-10):(4-8).

2. The conductive paste according to claim 1, characterized in that: The epoxy resin is pre-treated, and the treatment comprises the following steps: mixing the epoxy resin and the first solvent in a mass ratio of (2-5): (6-9), and then stirring at 80-90° C. and 100-500 rpm for 6-12 hours; Preferably, the epoxy resin is selected from one or more of bisphenol A, EP4000, 1256, and PKHH; More preferably, the first solvent is selected from one or more of DEAC, diethyl ether, DBE, and diethylene glycol methyl ether.

3. The conductive paste according to claim 1, characterized in that: The acrylic resin is pre-treated, and the treatment comprises the following steps: mixing the acrylic resin and the second solvent in a mass ratio of (1-5): (6-9), and then stirring at 80-90° C. and 100-500 rpm for 6-12 hours; Preferably, the acrylic resin is selected from one or more of BR-85, BR-113, MB-2660, MB-7496, and S-70; More preferably, the second solvent is selected from one or more of DEAC, DBE, acetone, xylene, and ethyl acetate.

4. The conductive paste according to claim 1, characterized in that: The TPU resin is pre-treated, and the treatment comprises the following steps: mixing the TPU resin and the third solvent in a mass ratio of (3-4): (6-7), and then stirring at 80-90° C. and 100-500 rpm for 6-24 hours; Preferably, the TPU resin is selected from one or more of 5778, 5715, 5714, and 5713; More preferably, the third solvent is selected from one or more of DBE, ethylene glycol butyl ether acetate, DEAC, and diethylene glycol methyl ether acetate.

5. The conductive paste according to any one of claims 1 to 4, characterized in that: The conductive paste further comprises 9-10wt% of a polyol; The polyol is selected from one or more of 2420I, BMY-600 and 330ng.

6. The conductive paste according to any one of claims 1 to 5, characterized in that: The conductive paste also includes 9-11 wt% of a diluent and 3-5 wt% of a curing agent; The diluent is selected from one or more of ethylene glycol, DEAC, isopropanol, and ethyl acetate; and the curing agent is isocyanate.

7. The conductive paste according to any one of claims 1 to 6, characterized in that: The conductive paste also includes 1-2wt% of an auxiliary agent; The auxiliary agent is selected from one or more of a leveling agent, a dispersant, and a defoaming agent.

8. The method for preparing the conductive paste according to any one of claims 1 to 7, characterized in that: include: Mix all ingredients well and then grind.

9. Use of the conductive paste according to any one of claims 1 to 7 in a circuit board, preferably in a flexible circuit board.

10. An electronic device comprising a substrate and a conductive circuit located on the substrate, characterized in that: The conductive circuit is formed by printing the conductive paste according to any one of claims 1 to 7 and heating and curing; Preferably, the printing method is pad printing, screen printing, electrostatic spinning or printing; More preferably, the material of the substrate is elastic material.

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