阅读说明：本技术 一种改性银粉及包含该改性银粉的导电胶 (Modified silver powder and conductive adhesive containing same ) 是由 苏瑜 麦裕良 张磊 廖兵 庞浩 戴永强 贾康乐 张俊杰 于 2019-10-28 设计创作，主要内容包括：本发明公开了一种改性银粉及包含该改性银粉的导电胶。这种改性银粉为不饱和二元酸表面改性的银粉。这种导电胶的组分包括该改性银粉、树脂基体、固化剂、稀释剂和引发剂；其中,树脂基体由环氧树脂和不饱和基体组成。同时还分别公开了这种改性银粉和导电胶的制备方法。本发明采用不饱和二元酸处理银粉,得到一种新型的改性银粉,并将其应用于制备导电胶。这种包含改性银粉的导电胶具有良好的导电性能和机械性能,且工艺简单,应用前景十分广阔。(The invention discloses modified silver powder and conductive adhesive containing the same. The modified silver powder is silver powder with surface modified by unsaturated dibasic acid. The conductive adhesive comprises the modified silver powder, a resin matrix, a curing agent, a diluent and an initiator; wherein, the resin matrix consists of epoxy resin and unsaturated matrix. Simultaneously, also discloses a preparation method of the modified silver powder and the conductive adhesive respectively. According to the invention, silver powder is treated by using unsaturated dibasic acid to obtain novel modified silver powder, and the novel modified silver powder is applied to preparation of conductive adhesive. The conductive adhesive containing the modified silver powder has good conductivity and mechanical property, simple process and very wide application prospect.)

1. A modified silver powder characterized in that: the modified silver powder is silver powder with the surface modified by unsaturated dibasic acid.

2. The modified silver powder according to claim 1, characterized in that: the unsaturated dibasic acid is unsaturated dibasic acid containing double bonds.

3. The modified silver powder according to claim 2, characterized in that: the unsaturated dibasic acid containing double bonds is selected from at least one of maleic acid, citraconic acid and itaconic acid.

4. A method for producing the modified silver powder according to any one of claims 1 to 3, characterized in that: the method comprises the following steps: and dissolving unsaturated dibasic acid in a solvent, adding silver powder, mixing, and separating a solid product to obtain the modified silver powder.

5. The method for producing a modified silver powder according to claim 4, wherein: the molar ratio of the silver powder to the unsaturated dibasic acid is 1: (0.8 to 1.2).

6. A conductive adhesive is characterized in that: the conductive adhesive comprises the modified silver powder as defined in any one of claims 1 to 3, a resin matrix, a curing agent, a diluent and an initiator; the resin matrix is composed of epoxy resin and an unsaturated matrix.

7. The conductive paste according to claim 6, wherein: in the conductive adhesive, the using amount of the modified silver powder is 45-85% of the total mass of the conductive adhesive; the dosage of the resin matrix is 10-50% of the total mass of the conductive adhesive; the dosage of the epoxy resin is 20-80% of the mass of the resin matrix; the dosage of the curing agent is 10 to 80 percent of the mass of the epoxy resin; the dosage of the diluent is 1 to 10 percent of the mass of the epoxy resin; the dosage of the initiator is 0.5 to 2.5 percent of the mass of the unsaturated matrix.

8. The conductive paste according to claim 7, wherein: the unsaturated matrix is an unsaturated matrix containing double bonds.

9. The conductive paste according to claim 8, wherein: the unsaturated matrix containing double bonds is at least one of acrylic resin, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, butyl acrylate and isooctyl acrylate.

10. A method for preparing the conductive adhesive according to any one of claims 6 to 9, comprising the steps of: the method comprises the following steps: and mixing the epoxy resin, the unsaturated matrix and the diluent, adding the modified silver powder, mixing, adding the curing agent and the initiator, and mixing to obtain the conductive adhesive.

Technical Field

The invention relates to the technical field of conductive materials, in particular to modified silver powder and conductive adhesive containing the same.

Background

The conductive adhesive is an adhesive with conductive performance, is generally formed by compounding conductive fillers and a resin matrix, and is firstly seen in the U.S. patent. The conductive adhesive is used as a substitute of Pb-Sn solder, and has attracted attention and application since 1966 due to the advantages of high linear resolution, relatively low curing temperature, good mechanical properties, good wetting with most materials and the like. The research on the aspect of conductive adhesive in China is relatively late, the high-performance conductive adhesive required at present mainly depends on import, and most of the conductive adhesives used in some high-end fields in the market are imported from the following companies: ablistick, 3M, Sumitomo, and Three-Bond, etc., in the United states. The domestic conductive adhesive is mainly used for some middle and low-end products. The most important reason for limiting the application field of domestic conductive adhesives is poor conductivity.

The conductive performance of the conductive adhesive mainly comes from conductive fillers. The conductivity of the conductive adhesive can be increased by increasing the content of the conductive filler, but after the addition amount of the conductive filler exceeds the percolation threshold, the conductivity of the conductive adhesive cannot be obviously improved by continuously increasing the conductive filler, and the viscosity of the conductive adhesive is increased and the mechanical performance is reduced due to the excessive addition amount of the conductive filler.

Silver is hardly oxidized in the adhesive because of its characteristics of high electric and thermal conductivity, moderate price, easy processing and the like, and even the oxidized silver still has electric conductivity, the silver oxide is widely used as the conductive filler of the conductive adhesive. Commercial conductive paste silver powder usually has a layer of long-chain fatty acid on the surface thereof as a lubricant to prevent the silver particles from being oxidized and to prevent the silver particles from aggregating to be dispersed more uniformly in a resin matrix, but the layer of lubricant is substantially insulating, thereby affecting the conductive properties of the finally prepared conductive paste. Therefore, researchers have made many efforts on the aspect of silver powder surface modification for improving the conductivity of the conductive adhesive, for example, a saturated short-chain fatty acid is adopted to replace a silver surface lubricant in situ, the lubricant is thermally degraded at high temperature, silver halide is generated in situ to activate the silver surface, and the like, and the methods have a certain effect on improving the conductivity of the conductive adhesive. At the same time, however, the removal of the lubricant layer results in poor compatibility between the conductive filler and the resin matrix, poor interaction between the conductive filler and the resin matrix, increased viscosity of the conductive adhesive, and a significant decrease in tensile shear strength.

The conductive adhesive is a special adhesive, not only provides conductivity, but also needs a certain bonding strength. How to develop a conductive adhesive product with good conductivity and mechanical properties becomes a technical problem which needs to be solved urgently by researchers in the field.

Disclosure of Invention

In order to overcome the problems of the conductive paste in the prior art, the invention provides a modified silver powder, and a conductive paste containing the modified silver powder.

The invention concept of the invention is as follows: in order to remove the non-conductive lubricant on the surface of the silver powder, the surface of the silver powder is modified by using unsaturated dibasic acid, and then the modified silver powder is added into an unsaturated matrix and mixed to obtain the conductive adhesive. After the conductive adhesive is cured, unsaturated groups (such as double bonds) are polymerized, covalent bonds are formed between the surface of the silver powder and the resin matrix for connection, and the interaction between the silver powder and the resin matrix is increased, so that the conductive performance and the mechanical performance of the conductive adhesive are improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention provides modified silver powder, which is silver powder with an unsaturated dibasic acid surface modified.

Preferably, in the modified silver powder, the unsaturated dibasic acid is an unsaturated dibasic acid containing a double bond.

Preferably, in the modified silver powder, the unsaturated dibasic acid having a double bond is at least one selected from maleic acid (maleic acid), citraconic acid (citraconic acid), and itaconic acid (itaconic acid).

The invention also provides a preparation method of the modified silver powder.

The preparation method of the modified silver powder comprises the following steps: and dissolving unsaturated dibasic acid in a solvent, adding silver powder, mixing, and separating a solid product to obtain the modified silver powder.

Preferably, in the method for preparing the modified silver powder, the concentration of the solution of the unsaturated dibasic acid dissolved in the solvent is 16g/L to 135 g/L.

Preferably, in the preparation method of the modified silver powder, the solvent is an alcohol solvent; further preferably, the solvent is selected from at least one of methanol, ethanol, n-propanol and isopropanol; most preferably, the solvent is ethanol.

Preferably, in the preparation method of the modified silver powder, the molar ratio of the silver powder to the unsaturated dibasic acid is 1: (0.8 to 1.2); most preferably, the molar ratio of silver powder to unsaturated dibasic acid is 1: 1.

in the preparation method of the modified silver powder, the silver powder is a common conductive material, and any commercially available silver powder can be selected, such as at least one selected from micron-sized flaky silver powder, micron-sized spherical silver powder and nano-sized silver powder.

Preferably, in the preparation method of the modified silver powder, the mixing treatment is specifically ultrasonic treatment and then standing; more preferably, the mixing treatment is ultrasonic treatment for 0.5 to 2 hours and then standing for 5 to 20 hours.

Preferably, in the method for producing the modified silver powder, the method for separating the solid product is centrifugation.

Preferably, the method for preparing the modified silver powder further comprises the steps of washing and drying after the solid product is separated.

Preferably, in the preparation method of the modified silver powder, the washing is carried out by using ethanol, and the washing times are 1-3 times.

Preferably, in the method for preparing the modified silver powder, the drying is vacuum drying.

The invention provides a conductive adhesive containing the modified silver powder.

The conductive adhesive comprises the modified silver powder, a resin matrix, a curing agent, a diluent and an initiator; wherein, the resin matrix consists of epoxy resin and unsaturated matrix.

Preferably, in the conductive adhesive, the use amount of the modified silver powder is 45-85% of the total mass of the conductive adhesive.

Preferably, in the conductive adhesive, the amount of the resin matrix is 10-50% of the total mass of the conductive adhesive; more preferably, the dosage of the resin matrix is 13-39% of the total mass of the conductive adhesive.

Preferably, in the conductive adhesive, the using amount of the epoxy resin is 20-80% of the mass of the resin matrix; the amount of unsaturated matrix is the balance of the resin matrix.

Preferably, in the conductive adhesive, the amount of the curing agent is 10-80% of the mass of the epoxy resin; more preferably, the amount of the curing agent is 15 to 80% by mass of the epoxy resin.

Preferably, in the conductive adhesive, the using amount of the diluent is 1-10% of the mass of the epoxy resin; more preferably, the amount of the diluent is 2 to 5% by mass of the epoxy resin.

Preferably, in the conductive adhesive, the amount of the initiator is 0.5-2.5% of the mass of the unsaturated matrix.

In the conductive adhesive, the epoxy resin is a common epoxy resin, and any one of commercially available epoxy resins, such as at least one selected from bisphenol a type epoxy resin and bisphenol F type epoxy resin, can be selected.

Preferably, in the conductive paste, the unsaturated matrix is an unsaturated matrix containing double bonds.

Preferably, in the conductive adhesive, the unsaturated matrix containing double bonds is at least one selected from acrylic resin, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, butyl acrylate and isooctyl acrylate; more preferably, the unsaturated matrix containing double bonds is at least one selected from the group consisting of acrylic resin, acrylic acid, and methacrylic acid.

Preferably, in the conductive adhesive, the curing agent is at least one selected from amine curing agents and anhydride curing agents; more preferably, the curing agent is at least one selected from triethanolamine, triethylamine, methylhexahydrophthalic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, and dodecylmaleic anhydride; still more preferably, the curing agent is at least one selected from triethanolamine and methylhexahydrophthalic anhydride.

Preferably, in the conductive adhesive, the diluent is selected from at least one of acetone, ethyl acetate, 1, 4-butanediol diglycidyl ether and ethylene glycol diglycidyl ether; further preferably, the diluent is at least one selected from the group consisting of acetone and 1, 4-butanediol diglycidyl ether.

Preferably, in the conductive adhesive, the initiator is an azo initiator; further preferably, the initiator is selected from at least one of Azobisisobutyronitrile (AIBN), Azobisisoheptonitrile (ABVN).

Preferably, when the curing agent of the conductive adhesive is an acid anhydride curing agent, the conductive adhesive further comprises an accelerator. When the curing agent of the conductive adhesive is an amine curing agent, no accelerator may be added.

Preferably, in the conductive adhesive, the using amount of the accelerator is 1-10% of the mass of the anhydride curing agent; more preferably, the amount of the accelerator is 4 to 7% by mass of the acid anhydride curing agent.

Preferably, in the conductive adhesive, the accelerator is an imidazole compound; further preferably, the accelerator is a methyl imidazole derivative; still more preferably, the accelerator is 2-ethyl-4-methylimidazole.

The invention also provides a preparation method of the conductive adhesive.

The preparation method of the conductive adhesive comprises the following steps: and mixing the epoxy resin, the unsaturated matrix and the diluent, adding the modified silver powder, mixing, adding the curing agent and the initiator, and mixing to obtain the conductive adhesive.

Preferably, in the preparation method of the conductive adhesive, the mixing is carried out in a planetary gravity mixer.

The invention has the beneficial effects that:

according to the invention, silver powder is treated by using unsaturated dibasic acid to obtain novel modified silver powder, and the novel modified silver powder is applied to preparation of conductive adhesive. The conductive adhesive containing the modified silver powder has good conductivity and mechanical property, simple process and very wide application prospect.

Specifically, compared with the prior art, the invention has the following advantages:

1. according to the invention, the silver powder is treated by using the unsaturated dibasic acid for the first time to obtain the novel modified silver powder, and the novel modified silver powder is used for preparing the conductive adhesive to obtain the novel conductive adhesive.

2. When the silver powder surface lubricant is processed, unsaturated dibasic acid is adopted to replace common saturated dibasic acid, double bonds can be introduced to the surface of the silver powder, and after the silver powder surface lubricant is added into a resin matrix containing the double bonds and cured, the double bonds of the unsaturated dibasic acid on the surface of the silver powder and the double bonds in the resin matrix can be polymerized to form covalent bond connection between the surface of the silver powder and the resin matrix, so that the interaction between the silver powder and the resin matrix is enhanced, and the conductivity and the mechanical property of the conductive adhesive are improved.

3. The conductive adhesive prepared by the invention has better application performance, such as low volume resistivity, good bonding performance and the like. Meanwhile, the comprehensive performance of the conductive adhesive can be adjusted by adjusting the types of the raw materials and the proportion of the raw materials, so that different application requirements are met.

4. The method has the advantages of simple process, easily controlled reaction conditions, low cost and environmental protection.

Detailed Description

The present invention will be described in further detail with reference to specific examples. The starting materials, reagents or apparatus used in the examples and comparative examples were obtained from conventional commercial sources unless otherwise specified. The same kinds of raw materials, for example, the same epoxy resins as used in the examples and comparative examples were used unless otherwise specified. Unless otherwise indicated, the testing or testing methods are conventional in the art.