Room-temperature self-repairing conductive adhesive film and preparation method thereof

Abstract

The invention relates to a room-temperature self-repairing conductive adhesive film and a preparation method thereof. The preparation method comprises the following steps: S1, preparing a urea-formaldehyde prepolymer; s2, preparing an emulsion; s3, preparing an epoxy resin microcapsule; s4, preparing a curing agent microcapsule; s5, preparing a mixed solution C; s6, preparing a mixed solution D; and S7, preparing the conductive adhesive film. According to the invention, self-repairing of a resin network in the conductive adhesive film is realized by introducing the urea formaldehyde microcapsule coated with the room-temperature curing agent, so that the material has a relatively long service life; urea formaldehyde microcapsules and conductive metal powder are added and mixed for use, the electric conductivity and thermal conductivity of the conductive adhesive film are greatly improved, stress between assemblies is reduced after acrylic acid copolymer is added, and the conductive adhesive film with excellent comprehensive performance is prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and in particular relates to a room temperature self-repairing conductive adhesive film and a preparation method thereof. Background Art

[0002] Conductive film is an adhesive that has certain electrical and thermal conductivity after curing. It is usually composed of a resin matrix, conductive fillers and additives. The resin matrix mainly plays a bonding role, and the conductive filler is used to form a conductive path. The resin matrix is ​​mainly thermosetting epoxy resin, silicone resin, polyimide resin, phenolic resin, polyurethane, acrylic resin, etc.; the conductive filler can be gold, silver, copper, aluminum, zinc, iron, nickel powder and silver-plated metal powder.

[0003] Conductive film is mainly used as an interconnect material in microelectronic packaging, which plays a role in heat and electricity conduction. However, with the further increase in the operating frequency of semiconductor devices, the increase in power capacity, and the improvement of efficiency and reliability, especially the increasing integration, the devices are required to be smaller and lighter, which will bring new changes to the electronic system. This leads to more and more heat generated on the device, and the conductive film is often used under high temperature conditions and then fails. At present, about 52% of packaging failures are attributed to mechanical problems under temperature and humidity loads. Therefore, the development of a conductive film that can be self-repaired at room temperature can meet the use requirements of high-density integrated circuit packaging and improve the service life and reliability of electronic components.

[0004] At present, there are two main ways to repair self-healing conductive adhesive films. One method is to use the reversibility of covalent bonds to prepare a dynamic network structure. After the conductive adhesive film is damaged, these dynamic covalent bonds are rearranged under external stimuli (such as light, heat, etc.) to generate new covalent bonds, thereby achieving repair. The other method is to add spherical microcapsules containing repair agents and catalysts to resin polymers. When the front end of the crack approaches the microcapsule, the microcapsule is squeezed and the repair agent flows out. The repair agent undergoes a polymerization reaction under the action of the catalyst to bond the two end faces of the crack to repair the crack, thereby achieving the repair process. However, this conductive adhesive has a high viscosity at room temperature. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a room temperature self-healing conductive adhesive film and a preparation method thereof. The interface delamination repair of high-power devices is achieved by introducing microcapsules into the conductive adhesive film. The addition of silver flakes and urea-formaldehyde microcapsules can effectively enhance the thermal conductivity of the conductive adhesive film. A room temperature self-healing epoxy silver paste is provided, thereby meeting the needs of high-power devices and enabling them to complete self-repair at room temperature, reducing the risk of high-temperature repair and reducing the manpower cost of troubleshooting defects.

[0006] The present invention solves the technical problem by the following technical solutions:

[0007] A method for preparing a room temperature self-repairing conductive adhesive film, the method comprising the following steps:

[0008] S1. Preparation of urea-formaldehyde prepolymer: adding urea and formaldehyde in a mass ratio of 3:2 into a beaker containing 90 ml of deionized water, adjusting the pH of the solution to 8-9 with triethanolamine, heating at 60-70° C. and stirring at 400 r / min for 1 h to obtain a urea-formaldehyde prepolymer;

[0009] S2, emulsion preparation: add water and alcohol to a beaker, add emulsifiers Span-80 and Tween-80 in proportion, pour in bisphenol F epoxy resin, and stir at 500r / min for 10min to obtain epoxy resin emulsion A; add water and alcohol to a beaker, add emulsifiers Span-80 and Tween-80 in proportion, pour in room temperature curing agent, and stir at 500r / min for 10min to obtain emulsion B;

[0010] S3, Preparation of epoxy resin microcapsules: Slowly pour the urea-formaldehyde prepolymer of S1 into the epoxy resin emulsion A of S2, stir for 30 min, add 14 ml of 10% NaCl solution and 5 ml of 10% NH 4 Cl solution, adjust the pH to 1-1.5 with HCl, stir for 2 h, and add 10% Na 2 CO 3 The solution was adjusted to neutral, allowed to stand for more than 12 hours, and then filtered to obtain white epoxy urea-formaldehyde microcapsules;

[0011] S4, preparation of curing agent microcapsules: slowly pour the urea-formaldehyde prepolymer of S1 into the emulsion B of S3, stir for 30 minutes, then add 14 ml of 10% NaCl solution and 5 ml of 10% NH 4 Cl solution, adjust the pH to 1-1.5 with HCl, stir for 2 h, and add 10% Na 2 CO 3 The solution was adjusted to neutral, allowed to stand for more than 12 hours, and then filtered to obtain white curing agent urea-formaldehyde microcapsules;

[0012] S5, mixing the epoxy resin and the epoxy diluent at room temperature for 3 to 30 minutes, adding the coupling agent to the mixture, and mixing at room temperature until uniform, to obtain a mixed solution C;

[0013] S6, adding the epoxy resin microcapsules and curing agent microcapsules prepared in S3 and S4 to the mixed solution C of S4 in a certain proportion, and ultrasonically dispersing for 1 to 5 hours to obtain a mixed solution D;

[0014] S7. Add the high temperature curing agent and curing accelerator to the mixed solution D obtained in S5 and mix until uniform, then add the conductive filler and mix until uniform, remove bubbles by vacuum stirring at 20-40° C., and use a coating machine to prepare a conductive adhesive film.

[0015] Moreover, the epoxy resin is preferably one or more of glycidyl ether bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

[0016] Moreover, the epoxy diluent is preferably one or more of benzyl alcohol, benzene, alcohol, and ketone.

[0017] Moreover, the room temperature curing agent is preferably one or more of polyetheramine MA2200, diethylenetriamine, ethylenediamine, and aminoethylethanolamine; and the high temperature curing agent is preferably JH5200.

[0018] Moreover, the curing accelerator is preferably one or more of benzyl dimethylamine, DMP-30, and N,N-dimethylaniline.

[0019] Moreover, the conductive filler is preferably one or more of metal powder, silver-plated powder, graphite or carbon black.

[0020] Moreover, the coupling agent is preferably KH-550.

[0021] A room temperature self-repairing conductive adhesive film is prepared by adopting the preparation method.

[0022] The advantages and beneficial effects of the present invention are:

[0023] The present invention realizes self-repair of the resin network in the conductive film by introducing urea-formaldehyde microcapsules containing a room temperature curing agent, so that the material has a longer service life; the urea-formaldehyde microcapsules and conductive metal powder are mixed and used to greatly improve the electrical and thermal conductivity of the conductive film. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0025] A method for preparing a room temperature self-repairing conductive adhesive film, the innovation of which lies in the following steps:

[0026] (1) Preparation of epoxy resin microcapsules: Urea and formaldehyde were added into a beaker containing 90 ml of deionized water in a mass ratio of 3:2, the solution pH was adjusted to 8-9 with triethanolamine, and the solution was heated at 60-70°C and stirred at 400 r / min for 1 h to obtain a urea-formaldehyde prepolymer.

[0027] Add water and alcohol into a beaker, then add Span-80 and Tween-80 in proportion, pour in bisphenol F epoxy resin, and stir at 600 r / min for 10 min to obtain epoxy resin emulsion;

[0028] The obtained prepolymer was slowly poured into the emulsion and stirred for 30 minutes, then 14 ml of 10% NaCl solution and 5 ml of 10% NH 4 Cl solution, adjust the pH to 1-1.5 with HCl and stir for 2h, then add 10% by mass Na 2 CO 3 The solution was adjusted to neutral, allowed to stand for more than 12 hours, and then filtered to obtain white epoxy urea-formaldehyde microcapsules.

[0029] (2) Preparation of curing agent microcapsules: urea and formaldehyde were added into a beaker containing 90 ml of deionized water in a mass ratio of 3:2, the pH of the solution was adjusted to 8-9 with triethanolamine, and the solution was heated at 60-70°C and stirred at 400 r / min for 1 h to obtain a urea-formaldehyde prepolymer;

[0030] Add water and alcohol into a beaker, then add Span-80 and Tween-80 in proportion, pour in room temperature curing agent, and stir at 1200 r / min for 10 min to obtain a curing agent emulsion;

[0031] The obtained prepolymer was slowly poured into the emulsion and stirred for 30 minutes, then 14 ml of 10% NaCl solution and 5 ml of 10% NH 4 Cl solution, adjust the pH to 1-1.5 with HCl and stir for 2h, then add 10% by mass Na 2 CO 3 The solution was adjusted to neutral, allowed to stand for more than 12 hours, and then filtered to obtain white curing agent urea-formaldehyde microcapsules.

[0032] (3) mixing the epoxy resin and the epoxy diluent at room temperature for 3 to 30 minutes to obtain a mixture of the epoxy resin and the epoxy diluent, then adding the coupling agent to the mixture of the epoxy resin and the epoxy diluent, and mixing at room temperature until the mixture is uniform;

[0033] (4) adding the microcapsules prepared in steps (1) and (2) to the mixture obtained in (3) in a certain proportion, and dispersing by ultrasonication for 1 to 5 hours;

[0034] (5) Add a high-temperature curing agent and a curing accelerator to the mixture obtained in step (4) and mix until uniform, then add a conductive metal powder and mix until uniform, remove bubbles by vacuum stirring at 20 to 40° C., and use a coating machine to prepare a conductive adhesive film.

[0035] Examples 1 to 3

[0036] The epoxy diluent I, epoxy resin II, curing accelerator, emulsifier and deionized water required for preparing the microcapsule powder are weighed according to the masses given in Table 1, and mixed to form a uniform epoxy resin emulsion; then the obtained epoxy resin emulsion is heated to 50-85° C. in a constant temperature water bath and stirred evenly, and the corresponding number of prepolymer liquids of capsule wall materials are added according to Table 1, and after stirring evenly, the deionized water is removed by centrifugation and vacuum drying to obtain microcapsule powder. Then, the room temperature curing agent, emulsifier, and deionized water required for preparing the microcapsule powder are weighed according to the mass given in Table 2, mixed, and mixed to form a uniform curing agent emulsion; then the obtained curing agent emulsion is heated to 50-85°C in a constant temperature water bath and stirred evenly, and the corresponding number of prepolymer liquids of the capsule wall material are added according to Table 2. After stirring evenly, the deionized water is removed by centrifugation and vacuum drying to obtain microcapsule powder. Next, the microcapsule powder, epoxy diluent I, epoxy resin I, curing agent, flaky silver powder, and coupling agent are weighed according to the number of parts given in Table 3, and mixed evenly at room temperature, and a self-healing conductive adhesive film is obtained using a coating machine.

[0037] Embodiments 4 to 6

[0038] The epoxy resin II, emulsifier and deionized water required for preparing the microcapsule powder are weighed according to the masses given in Table 1 and Table 2, and mixed to form a uniform epoxy resin emulsion; then the obtained epoxy resin emulsion is heated to 50-85° C. in a constant temperature water bath and stirred evenly, and the corresponding number of prepolymer liquids of capsule wall materials are added according to Table 1, and after stirring evenly, the deionized water is removed by suction filtration and vacuum drying to obtain microcapsule powder. Then, the room temperature curing agent, emulsifier, and deionized water required for preparing the microcapsule powder are weighed according to the mass given in Table 2, mixed, and mixed to form a uniform curing agent emulsion; then the obtained curing agent emulsion is heated to 50-85°C in a constant temperature water bath and stirred evenly, and the corresponding number of prepolymer liquids of capsule wall materials are added according to Table 2. After stirring evenly, the deionized water is removed by suction filtration and vacuum drying to obtain microgel powder. Then, the microcapsule powder (epoxy resin), microcapsule powder (curing agent), epoxy diluent I, epoxy resin I, high temperature curing agent, flaky silver powder, and coupling agent are weighed according to the number of parts given in Table 3, and mixed evenly at room temperature, and a self-healing conductive adhesive film is obtained using a coating machine.

[0039] Table 1 Content of each raw material component of microcapsule powder (epoxy resin)

[0040]

[0041] Table 2 Content of each raw material component of microcapsule powder (curing agent)

[0042]

[0043] Table 3 Content of each raw material component of conductive adhesive film

[0044]

[0045] The self-healing conductive adhesive film obtained in Examples 1 to 6 was cured at 90°C to 120°C for 4 hours to obtain a cured product. The initial volume resistivity of the conductive adhesive film was tested and calculated by the four-point probe method, and the initial fracture strength was tested by the ASTMD5045-99 standard. The tested specimens were aligned and cured at room temperature for 4d-7d. The volume resistivity of the conductive adhesive film after self-healing was then calculated by the four-point probe method, and the fracture strength after self-healing was determined by the ASTM D5045-99 standard. The ratio of the volume resistivity after self-healing to the initial resistivity, as well as the ratio of the fracture strength after self-healing to the initial fracture strength are listed in Table 4.

[0046] Table 4 Performance table

[0047] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Ratio of initial resistivity to volume resistivity after self-healing 0.8 0.85 0.87 0.9 0.91 0.95 Ratio of fracture strength after self-repair to initial fracture strength 0.2 0.34 0.5 0.66 0.79 0.85 Room temperature curing time 7d 7d 7d 7d 5d 4d

[0048] It can be concluded from Table 4 that as the amount of microcapsule powder increases, its resistivity after self-healing will gradually decrease, and its fracture strength will also be significantly improved. In addition, the room temperature curing time required will also be reduced without affecting its resistivity and fracture strength.

[0049] Although the embodiments of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments.

Claims

1. A method for preparing a room temperature self-healing conductive adhesive film, characterized in that: The steps of the method are: S1. Preparation of urea-formaldehyde prepolymer: adding urea and formaldehyde in a mass ratio of 3:2 into a beaker containing 90 ml of deionized water, adjusting the pH of the solution to 8-9 with triethanolamine, heating at 60-70° C. and stirring at 400 r / min for 1 h to obtain a urea-formaldehyde prepolymer; S2, emulsion preparation: add water and alcohol to a beaker, add emulsifiers Span-80 and Tween-80 in proportion, pour in bisphenol F epoxy resin, and stir at 500r / min for 10min to obtain epoxy resin emulsion A; add water and alcohol to a beaker, add emulsifiers Span-80 and Tween-80 in proportion, pour in room temperature curing agent, and stir at 500r / min for 10min to obtain emulsion B; S3, preparation of epoxy resin microcapsules: slowly pour the urea-formaldehyde prepolymer of S1 into the epoxy resin emulsion A of S2, stir for 30 minutes, add 14 ml of 10% NaCl solution and 5 ml of 10% NH4Cl solution, adjust the pH to 1-1.5 with HCl, stir for 2 hours, adjust to neutral with 10% Na2CO3 solution, let stand for more than 12 hours and filter to obtain white epoxy urea-formaldehyde microcapsules; S4, preparation of curing agent microcapsules: slowly pour the urea-formaldehyde prepolymer of S1 into the emulsion B of S3, stir for 30 minutes, add 14 ml of 10% NaCl solution and 5 ml of 10% NH4Cl solution, adjust the pH to 1-1.5 with HCl, stir for 2 hours, adjust to neutral with 10% Na2CO3 solution, let stand for more than 12 hours and filter to obtain white curing agent urea-formaldehyde microcapsules; S5, mixing the epoxy resin, epoxy diluent and acrylic copolymer at room temperature for 3 to 30 minutes, adding the coupling agent to the mixture, and mixing at room temperature until uniform, to obtain a mixed solution C; S6, adding the epoxy resin microcapsules and curing agent microcapsules prepared in S3 and S4 to the mixed solution C of S4 in a certain proportion, and ultrasonically dispersing for 1 to 5 hours to obtain a mixed solution D; S7. Add the high temperature curing agent and curing accelerator to the mixed solution D obtained in S5 and mix until uniform, then add the conductive filler and mix until uniform, remove bubbles by vacuum stirring at 20-40° C., and use a coating machine to prepare a conductive adhesive film.

2. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The epoxy resin is one or more of glycidyl ether bisphenol A epoxy resin, bisphenol F epoxy resin, and bisphenol S epoxy resin.

3. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The epoxy diluent is preferably one or more of benzyl alcohol, benzene, alcohol, and ketone.

4. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The room temperature curing agent is preferably one or more of polyetheramine MA2200, diethylenetriamine, ethylenediamine, and aminoethylethanolamine; the high temperature curing agent is preferably JH5200.

5. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The curing accelerator is preferably one or more of benzyl dimethylamine, DMP-30, and N,N-dimethylaniline.

6. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The conductive filler is preferably one or more of metal powder, silver-plated powder, graphite or carbon black.

7. The method for preparing a room temperature self-healing conductive adhesive film according to claim 1, characterized in that: The coupling agent is preferably KH-550.

8. A room temperature self-healing conductive film, characterized in that: The method is prepared by the method according to any one of claims 1 to 7.

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