Ultralow-hardness silver-copper conductive adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of conductive adhesives, and particularly relates to an ultralow-hardness silver-copper conductive adhesive and a preparation method thereof. The ultralow-hardness silver-copper conductive adhesive comprises the following components in parts by weight: 50-100 parts of liquid silicone rubber, 30-80 parts of a diluent, 1-10 parts of a chain extender, 0.1-5 parts of a heat-resistant agent, 0.1-5 parts of a coupling agent, 0.1-5 parts of an inhibitor and 100-400 parts of conductive filler. The shielding performance of the ultralow-hardness silver-copper conductive adhesive can reach 100 dB, the tensile strength is larger than 1 Mpa, the volume resistivity is smaller than 0.005 ohm.cm, and the hardness is smaller than 30 ShoreA. On the premise that the requirements of products for mechanical strength and shielding effectiveness are met, the ultralow-hardness silver-copper conductive adhesive has lower product hardness, the internal stress of the adhesive to electronic components is greatly reduced, and market requirements are met.

Description

Technical Field

[0001] The invention belongs to the technical field of conductive adhesives, and in particular relates to an ultra-low hardness silver-copper conductive adhesive and a preparation method thereof. Background Art

[0002] Conductive adhesive in the form-in-place (FIP) process is applied on the plate and then vulcanized at room temperature or high temperature to form a conductive sealing gasket to achieve electromagnetic interference (EMI) shielding and environmental sealing effects. This type of product must have appropriate viscosity and thixotropy before dispensing to meet dispensing speed and process requirements, and must have certain mechanical and electrical properties after dispensing. With the development of technology, the performance of electronic components continues to improve, while electronic devices continue to be miniaturized and lightweight. Different device units on electronic products are becoming more and more sensitive to contact stress. Large contact stress causes micro-deformation inside electronic devices, which slowly affects product performance and greatly reduces the service life and efficiency of terminal products.

[0003] In order to reduce the impact of internal stress on the performance of electronic products, it is imperative to continue to develop silver-copper conductive adhesives with lower hardness. Summary of the invention

[0004] In view of the above deficiencies in the prior art, the object of the present invention is to provide an ultra-low hardness silver-copper conductive adhesive and a preparation method thereof.

[0005] To achieve the above objectives, the technical solutions adopted are:

[0006] One of the purposes of the present invention is to provide an ultra-low hardness silver-copper conductive adhesive, comprising the following components in parts by weight:

[0007] Liquid silicone rubber 50-100 parts, diluent 30-80 parts, chain extender 1-10 parts, heat resistant agent 0.1-5 parts, coupling agent 0.1-5 parts, inhibitor 0.1-5 parts, conductive filler 100-400 parts;

[0008] Furthermore, the conductive filler is silver-copper powder; the silver-copper powder is obtained by plating silver on the surface of copper powder by a chemical plating method, and the copper powder is flaky copper powder.

[0009] Furthermore, the particle size of the silver-copper powder is 20-50 um.

[0010] Furthermore, the liquid silicone rubber is a two-component addition-type silicone rubber with a hardness of 0-5A and a tensile strength of >1.5 MPa, preferably a vinyl siloxane two-component addition-type silicone rubber.

[0011] The beneficial effect of adopting the above further technical solution is that the low-hardness and high-strength liquid silicone rubber is selected to further ensure the product's requirements for mechanical strength and hardness.

[0012] Furthermore, the diluent is kerosene with a flash point of 35-85°C.

[0013] Furthermore, the chain extender is a double-terminal vinyl silicone oil with a content of 50-500 cp and a vinyl content of 0.01% to 0.03%.

[0014] Furthermore, the heat-resistant agent is hexaphenoxycyclotriphosphazene (HPCTP).

[0015] The beneficial effect of adopting the above further technical solution is that the heat-resistant agent is selected as HPCTP, which has a unique phosphorus and nitrogen hybrid structure, exhibits excellent thermal stability and heat resistance, and can improve the flame retardancy and thermal stability of the product.

[0016] Furthermore, the coupling agent is 3-glycidylpropyltrimethoxysilane.

[0017] Furthermore, the inhibitor is methylbutynol.

[0018] The second object of the present invention is to provide a method for preparing the ultra-low hardness silver-copper conductive adhesive, comprising the following steps:

[0019] Liquid silicone rubber, diluent, chain extender, heat resistant agent, coupling agent and inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 20-40r / min; then cooling circulating water is passed to control the material temperature below 30°C, and then conductive filler is added and stirred for 1 hour at a speed of 20-40rpm; then degassing and filling are performed to obtain the ultra-low hardness silver-copper conductive adhesive.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention provides an ultra-low hardness silver-copper conductive adhesive, which uses liquid silicone rubber, has good fluidity, fast vulcanization, is safer and more environmentally friendly, and ensures the requirements of the product on mechanical strength and hardness; a coupling agent is added to improve the bonding between the powder and the colloid, and at the same time improves the adhesion of the product to inorganic materials and metal materials when it is cured; a heat-resistant agent is added to improve the thermal stability of the product; the conductive filler is selected as silver-copper powder, and silver is plated on the surface of the copper powder by a chemical plating method to improve the bonding between the silver and the copper powder; a flaky copper powder with a large specific surface area is selected to make the silver-copper powder have a larger specific surface area, reduce the volume resistivity of the powder, increase the silver plating rate, make the silver layer on the surface of the copper powder more uniform, and the silver The layer is smoother and flatter, and the resistivity of the powder itself is reduced. The silver content can be reduced while ensuring that the resistance and shielding effectiveness are met, thereby reducing the powder filling amount, which can significantly reduce the product hardness and cost, reduce product resistance and improve product shielding effectiveness. The shielding effectiveness can reach 100dB (0.3HZ-10GHZ), the tensile strength is greater than 1Mpa, the volume resistivity is less than 0.005ohm.cm, and the hardness is less than 30ShoreA. Under the premise of meeting the product's requirements for mechanical strength and shielding effectiveness, it has a lower product hardness, greatly reducing the internal stress of the colloid on electronic components and meeting market demand. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below in conjunction with examples. The examples are only used to explain the present invention and are not used to limit the scope of the present invention.

[0023] Liquid silicone rubber: 0A vinyl siloxane two-component addition silicone rubber;

[0024] Diluent: kerosene with a flash point of 35-85°C;

[0025] Chain extender: 100cp double-terminated vinyl silicone oil, vinyl content 0.01%;

[0026] Heat-resistant agent: hexaphenoxy cyclotriphosphazene;

[0027] Coupling agent: 3-glycidylpropyltrimethoxysilane;

[0028] Inhibitor: methylbutynol;

[0029] Silver copper powder: Dendritic silver copper powder with a particle size range of 20-50um;

[0030] Unless otherwise specified, the above raw materials are applicable to the following embodiments and comparative examples.

[0031] Example 1

[0032] A preparation method of ultra-low hardness silver-copper conductive adhesive comprises the following steps:

[0033] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 280 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0034] Example 2

[0035] A preparation method of ultra-low hardness silver-copper conductive adhesive comprises the following steps:

[0036] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 240 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0037] Example 3

[0038] A preparation method of ultra-low hardness silver-copper conductive adhesive comprises the following steps:

[0039] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 200 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0040] Comparative Example 1

[0041] Except that the liquid silicone rubber is 10A silicone rubber, the remaining steps are the same as those in Example 2.

[0042] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 240 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0043] Comparative Example 2

[0044] Except that the chain extender is not added, the remaining steps are the same as those in Example 2.

[0045] 100 parts of liquid silicone rubber, 50 parts of diluent, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 240 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are performed to obtain the ultra-low hardness silver-copper conductive adhesive.

[0046] Comparative Example 3

[0047] Except for adding a chain extender with a viscosity of 5000 cp, the remaining steps are the same as those in Example 2.

[0048] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 240 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0049] Comparative Example 4

[0050] Except for adding silver copper powder with a particle size of 5 μm, the remaining steps are the same as those in Example 2.

[0051] 100 parts of liquid silicone rubber, 50 parts of diluent, 5 parts of chain extender, 2 parts of heat-resistant agent, 1 part of coupling agent and 0.2 parts of inhibitor are sequentially added into a stirring kettle and stirred for 1 hour at a speed of 30 rpm; cooling circulating water is passed, the material temperature is controlled below 30°C, 240 parts of silver-copper powder are added and stirred for 1 hour at a speed of 30 rpm; then degassing and filling are carried out to obtain the ultra-low hardness silver-copper conductive adhesive.

[0052] The performance test results of the ultra-low hardness silver-copper conductive adhesives of Examples 1-3 and Comparative Examples 1 to 4 are shown in Table 1.

[0053] Table 1. Material performance test results of Examples 1-3 and Comparative Examples 1 to 4

[0054]

[0055]

[0056] By comparing with Examples 1 to 3, it can be found that the conductive adhesive product prepared by using high-hardness silicone rubber in Comparative Example 1 has a relatively large hardness, and Examples 1 to 3 use low-hardness silicone rubber, and the hardness of the conductive adhesive product can be greatly reduced; at the same time, it can be found from Comparative Examples 2 and 3 that the viscosity of the conductive adhesive product can be reduced to a large extent by adding a chain extender, and the hardness reduction is more obvious when adding a low-viscosity chain extender; at the same time, it can be found from Comparative Example 4 that the conductive adhesive with large particle size has better conductive performance under the premise of the same filling amount.

[0057] It can be seen that the ultra-low hardness silver-copper conductive adhesive prepared by the present invention improves the conductivity of the powder itself and reduces the silver content of the silver-copper powder, so that the product performance can be met with less powder filling amount, while greatly reducing the hardness of the product to meet the market demand.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultra-low hardness silver-copper conductive adhesive, characterized in that: The invention comprises the following components in parts by weight: 50-100 parts of liquid silicone rubber, 30-80 parts of diluent, 1-10 parts of chain extender, 0.1-5 parts of heat-resistant agent, 0.1-5 parts of coupling agent, 0.1-5 parts of inhibitor and 100-400 parts of conductive filler.

2. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The conductive filler is silver copper powder.

3. The ultra-low hardness silver-copper conductive adhesive according to claim 2, characterized in that: The particle size of the silver copper powder is 20-50 um.

4. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The chain extender is 50-500cp double-terminal vinyl silicone oil with a vinyl content of 0.01% to 0.03%.

5. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The liquid silicone rubber is a two-component addition-type silicone rubber with a hardness of 0-5A and a tensile strength of more than 1.5 MPa.

6. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The heat-resistant agent is hexaphenoxy cyclotriphosphazene.

7. The ultra-low hardness silver-copper conductive adhesive according to claim 6, characterized in that: The diluent is kerosene with a flash point of 35-85°C.

8. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The coupling agent is 3-glycidylpropyltrimethoxysilane.

9. The ultra-low hardness silver-copper conductive adhesive according to claim 1, characterized in that: The inhibitor is methylbutynol.

10. A method for preparing the ultra-low hardness silver-copper conductive adhesive according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding liquid silicone rubber, diluent, chain extender, heat resistant agent, coupling agent and inhibitor into a stirring kettle in sequence and stirring for 1 hour at a rotation speed of 20-40 r / min; then passing cooling circulating water to control the material temperature below 30°C, then adding conductive filler and stirring for 1 hour at a rotation speed of 20-40 rpm; then degassing and filling are performed to obtain the ultra-low hardness silver-copper conductive adhesive.

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