Single-component flexible heat-conducting structural adhesive as well as preparation method and application thereof

Abstract

The invention discloses a single-component flexible heat-conducting structural adhesive and a preparation method and application thereof.The single-component flexible heat-conducting structural adhesive is prepared from, by weight, 25-37 parts of epoxy resin, 2-8 parts of curing agent, 4-10 parts of flexibilizer, 0.08-0.13 part of rheological agent and 50-63 parts of heat-conducting filler, the single-component flexible heat-conducting structural adhesive has the characteristics of high heat conductivity coefficient, high shear strength and high bonding strength. The cured single-component flexible heat-conducting structural adhesive can be applied to the fields of bonding and heat dissipation of electronic elements, bonding of battery modules of new energy electric vehicles and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of thermal conductive structural adhesives, and in particular to a single-component flexible thermal conductive structural adhesive and a preparation method and application thereof. Background Art

[0002] With the expansion of emerging markets such as new energy vehicles and smart homes, the demand for high-performance and high-reliability integrated circuit packaging adhesives is also increasing.

[0003] Single-component electronic packaging adhesive plays an important role in integrated circuit packaging. It can effectively protect the chip from the influence of the external environment while ensuring stable signal transmission. Specific applications include: ① Chip packaging, where the single-component electronic packaging adhesive is injected around the chip and forms a sealing layer after curing to protect the chip from moisture, dust and other contaminants. ② Pin connection, where the single-component electronic packaging adhesive is used to reinforce and seal the pin connection to ensure the stability and reliability of the connection. ③ Overall packaging, for some special requirements of integrated circuits, single-component electronic packaging adhesive can be used for overall packaging to improve their protection level and reliability. Therefore, single-component electronic packaging adhesive is widely used in the field of integrated circuit packaging due to its excellent electrical properties, heat and cold resistance, weather resistance and shock resistance.

[0004] The common problems with epoxy thermal conductive structural adhesives at present are low thermal conductivity, a hard solid state after curing, and a flexibility that cannot meet the needs of actual use. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a one-component flexible thermally conductive structural adhesive and a preparation method and application thereof.

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

[0007] The invention provides a one-component flexible thermal conductive structural adhesive, comprising the following components in parts by weight: 25-37 parts of epoxy resin, 2-8 parts of curing agent, 4-10 parts of toughening agent, 0.08-0.13 parts of rheological additive and 50-63 parts of thermal conductive filler.

[0008] The present invention provides a method for preparing the above-mentioned one-component flexible thermal conductive structural adhesive, which comprises: mixing epoxy resin, curing agent, toughening agent, rheological additive and thermal conductive filler in proportion to prepare the one-component flexible thermal conductive structural adhesive.

[0009] The present invention provides an application of the above-mentioned single-component flexible thermally conductive structural adhesive in the packaging of electronic components and the bonding of battery modules of new energy electric vehicles.

[0010] The present invention has the following beneficial effects:

[0011] The present invention provides a one-component flexible thermally conductive structural adhesive, its preparation method, and application. The one-component flexible thermally conductive structural adhesive comprises the following components in parts by weight: 25-37 parts epoxy resin, 2-8 parts curing agent, 4-10 parts toughening agent, 0.08-0.13 parts rheological additive, and 50-63 parts thermally conductive filler. The one-component flexible thermally conductive structural adhesive exhibits high thermal conductivity, high shear strength, and high bond strength. The cured one-component flexible thermally conductive structural adhesive can be used in bonding and heat dissipation of electronic components, as well as bonding battery modules for new energy electric vehicles. DETAILED DESCRIPTION

[0012] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0013] The following is a detailed description of a one-component flexible thermally conductive structural adhesive provided by an embodiment of the present invention, and its preparation method and application.

[0014] In a first aspect, an embodiment of the present invention provides a one-component flexible thermally conductive structural adhesive, comprising the following components in parts by weight: 25-37 parts of epoxy resin, 2-8 parts of curing agent, 4-10 parts of toughening agent, 0.08-0.13 parts of rheological additive and 50-63 parts of thermally conductive filler.

[0015] In some optional embodiments, the epoxy resin is a compound of one or more of bisphenol A epoxy resin, polyether modified epoxy resin, organosilicon modified epoxy resin, rubber modified epoxy resin, and polyurethane modified epoxy resin. Commonly used materials with good flexibility include polyurethane and silicone rubber. Organosilicon has a series of excellent properties such as high and low temperature resistance, excellent mechanical properties, weather resistance and good electrical insulation due to its special silicon-oxygen bond main chain structure, and is also widely used. The polyether segment in the polyether modified resin forms a molecular-level "elastic hinge", which absorbs energy through segment rotation under external force impact and prevents crack propagation. Preferably, the present invention selects bisphenol A epoxy resin, or a compound of bisphenol A epoxy resin and polyether modified epoxy resin as the matrix resin of the encapsulating glue. As the proportion of polyether-modified epoxy resin in the compounded resin increases, the flexibility of the encapsulant increases and the bonding strength decreases. The present invention explores the optimal ratio, and preferably the mass ratio of bisphenol A epoxy resin to polyether-modified epoxy resin is 3.0 / 0.8 to 3.0 / 2.0.

[0016] In some optional embodiments, the curing agent is a latent epoxy curing agent, including one or more compounds of dicyandiamide curing agent, HAA curing agent, boron amine curing agent, and modified imidazole curing agent. Boron amine curing agent has a long curing time but the cured encapsulation adhesive has excellent flexibility. The encapsulation adhesive cured by dicyandiamide curing agent and HAA has good flexibility and high shear strength. Among them, HAA curing agent is both an epoxy curing agent and an accelerator for amine curing agents. Preferably, the present invention mixes HAA curing agent with dicyandiamide to play the role of HAA accelerator. At the same time, the low-temperature activation characteristics of HAA can be used to reduce the curing temperature and extend the storage period. The mass ratio is preferably 1 / 0.2 to 1 / 0.9.

[0017] In some optional embodiments, the toughening agent includes one or more of liquid carboxyl-terminated nitrile rubber (CTBN), core-shell resin, hyperbranched polymer, thermotropic liquid crystal polymer (TLCP), etc., and the above toughening agents can be used alone or in combination for toughening. The present invention preferably uses a core-shell resin as the toughening agent, wherein the core material of the core-shell resin is selected from a rubber elastomer and the shell material is selected from a thermoplastic resin, more preferably the core material is butadiene-styrene copolymer and the shell material is polymethyl methacrylate.

[0018] The present invention preferably uses a core-shell structure resin as a toughening agent for a single-component flexible thermal conductive structural adhesive, which has the following advantages: (1) Good structural designability: After the core-shell structure resin and the epoxy resin are cured, the original structure, size, distribution state, etc. of the particles can be maintained unchanged, and it has good designability. The core-shell structure resin is a multi-layer polymer, including a thermoplastic resin shell with good compatibility with the matrix epoxy resin, and a core with good toughness such as a rubber elastomer material. The monomers constituting the core-shell structure can be prepared by emulsion polymerization. (2) Good toughening effect: When the core-shell structure resin present in a large amount in the resin matrix is ​​subjected to stress, due to the significant difference in modulus between the core-shell particles and the rigid epoxy matrix, stress concentration will occur near the equatorial region of the particles, thereby inducing local plastic deformation of the surrounding epoxy matrix. At the same time, under high triaxial stress, the soft shell may undergo cavitation (cavities are generated inside). The generation of cavitation is a process that consumes energy and releases the hydrostatic tension of the matrix, promoting more extensive shear yield plastic deformation of the surrounding epoxy matrix, reducing the energy that causes the material to crack, and thus increasing the flexibility of the structural adhesive. (3) Good compatibility: Due to the good compatibility of the core-shell polymer with the resin matrix, it can be evenly dispersed in the cured cross-linked network of the system, thereby achieving a stronger toughening effect. At the same time, the addition of core-shell particles will not cause too much loss of the system's glass transition temperature. In addition, the core-shell toughening agent works synergistically with the polyether epoxy, making the toughness of the adhesive layer more superior, suitable for the dynamic working conditions of new energy vehicle modules.

[0019] In some optional embodiments, the thermally conductive filler includes any one or a mixture of aluminum oxide, aluminum hydroxide, aluminum nitride or boron nitride, and the surface of the thermally conductive filler is modified by a silane coupling agent, and the D50 of the thermally conductive filler is preferably 1.5-30 μm. Preferably, the present invention selects a compound of spherical aluminum oxide whose surface is modified by a silane coupling agent and flaky aluminum nitride as the thermally conductive filler. The thermally conductive filler is compounded with spherical aluminum oxide and aluminum nitride in a certain proportion, which can form a three-dimensional thermal conductive network in the structural adhesive. The micron-level spherical aluminum oxide plays the role of filling the gaps, and the flaky aluminum nitride constructs the main path, which can ultimately ensure that the single-component flexible thermally conductive structural adhesive has a high thermal conductivity coefficient.

[0020] In some optional embodiments, the rheological additive includes one or more of GARAMITE-1958, 4740, and HL-380+R606. The single-component encapsulant is required to have high thixotropy and basically does not flow at low shear rates. This requires the addition of a rheological additive to change its rheological properties and meet the technical requirements of high thixotropy. Since the encapsulant requires a thermal weight loss rate of less than 1% and low moisture and carbon dioxide residues, the rheological additive cannot contain solvents. The rheological additive selected in the present invention is 4740, and the preferred dosage is 0.05%-0.15%.

[0021] In a second aspect, an embodiment of the present invention further provides a method for preparing the above-mentioned one-component flexible thermally conductive structural adhesive, comprising the following steps:

[0022] S1. Add 25-37 parts of epoxy resin and 2-8 parts of toughening agent by weight into a reactor and stir for 30 minutes.

[0023] S2. Add 50-63 parts of thermal conductive filler in batches, stirring under vacuum every 10 minutes.

[0024] S3. Add 2-8 parts of curing agent and 0.08-0.13 parts of auxiliary agent into the reactor and stir, and finally vacuum degas for 30 minutes.

[0025] During the preparation process of the above-mentioned one-component flexible thermal conductive structural adhesive, a multi-stage dispersion process is used to evenly disperse the raw materials, and a latent curing system is used to achieve the storage stability of the one-component flexible thermal conductive structural adhesive.

[0026] In a third aspect, embodiments of the present invention further provide applications of the above-mentioned single-component flexible thermally conductive structural adhesive in the packaging of electronic components and the bonding of battery modules of new energy electric vehicles.

[0027] The present invention will be further described below with reference to the embodiments.

[0028] Example 1:

[0029] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 50 g of bisphenol A epoxy resin E-44, 10 g of WD510 toughening agent, and 6 g of MX-125 core-shell rubber toughening agent into a reactor and stirring for 20 minutes; adding 99 g of aluminum nitride with a D50 of 30 μm in batches after uniform distribution; stirring under vacuum at intervals of 10 minutes; subsequently adding 1.8 g of dicyandiamide curing agent, 1.5 g of HAA-1021 curing agent, and 1.5 g of rheological additive and stirring for 20 minutes; and finally evacuating the reactor for 30 minutes.

[0030] Example 2:

[0031] A single-component flexible thermally conductive structural adhesive is prepared by the following steps:

[0032] 46.5 g of bisphenol A epoxy resin E-44, 16 g of polyether-modified epoxy resin ZK-2819, and 8 g of MX-125 toughening agent were added to a reactor and stirred for 20 minutes. After uniform distribution, 108 g of aluminum nitride with a D50 of 5 μm was added in batches and stirred. Subsequently, 3 g of dicyandiamide curing agent, 1.8 g of HAA-1021 curing agent, and 1.8 g of rheological additive were added and stirred for 20 minutes. Finally, vacuum was applied for 30 minutes.

[0033] Example 3:

[0034] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 37.5 g of bisphenol A epoxy resin E-44 and 8 g of MX-125 toughening agent into a reactor and stirring for 20 minutes; adding 89 g of aluminum nitride with a D50 of 30 μm in batches and stirring after uniform distribution; then adding 7 g of dicyandiamide curing agent, 4.2 g of HAA-1021 curing agent, and 1.8 g of rheological additive and stirring for 20 minutes; and finally vacuuming for 30 minutes.

[0035] Example 4:

[0036] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 50 g of bisphenol A epoxy resin E-44 and 18.7 g of WD510 toughening agent into a reactor and stirring for 20 minutes; adding 101 g of aluminum nitride with a D50 of 30 μm in batches and stirring after uniform distribution; then adding 3 g of dicyandiamide curing agent, 1.8 g of HAA-1021 curing agent, and 1.8 g of rheological additive and stirring for 20 minutes; and finally vacuuming for 30 minutes.

[0037] Example 5:

[0038] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 32g of bisphenol A epoxy resin E51, 13g of polyether-modified epoxy resin ZK-2819, and 6g of MX-125 toughening agent into a reactor and stirring for 20 minutes; adding 60g of spherical aluminum oxide with a D50 of 5 μm and 40g of flaky aluminum nitride with a D50 of 1.5 μm in batches after uniform distribution for dispersion; stirring under vacuum for 10 minutes; subsequently adding 4.5g of dicyandiamide curing agent, 1.8g of HAA-1021 curing agent, and 1.8g of rheological additive and stirring for 20 minutes; and finally evacuating the mixture for 30 minutes.

[0039] Example 6:

[0040] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 50 g of bisphenol A epoxy resin E-44 and 10 g of WD510 toughening agent into a reactor and stirring for 20 minutes; adding 99 g of aluminum nitride with a D50 of 30 μm in batches after uniform distribution; stirring under vacuum at intervals of 10 minutes; subsequently adding 1.8 g of dicyandiamide curing agent, 1.5 g of HAA-1021 curing agent, and 1.5 g of rheological additive and stirring for 20 minutes; and finally evacuating the reactor for 30 minutes.

[0041] Example 7:

[0042] A one-component flexible thermally conductive structural adhesive is prepared by the following steps: adding 32g of bisphenol A epoxy resin E51, 13g of polyether-modified epoxy resin ZK-2819, and 6g of MX-125 toughening agent into a reactor and stirring for 20 minutes; adding 100g of aluminum nitride with a D50 of 30μm in batches for dispersion after uniform distribution; stirring under vacuum for 10 minutes; subsequently adding 4.5g of dicyandiamide curing agent, 1.8g of HAA-1021 curing agent, and 1.8g of rheological additive and stirring for 20 minutes; and finally evacuating the reactor for 30 minutes.

[0043] Performance testing:

[0044] Thermal conductivity: tested using the TPS2500S thermal conductivity tester from Hot Disk.

[0045] Peel strength: tested according to GB / T 7122-1996 method.

[0046] Elongation at break: tested according to GB / T 1040.3-2006 method.

[0047] The above test specifications were used to test Examples 1-7, and the test results are shown in Table 1.

[0048] Table 1

[0049]

[0050] It can be seen from Table 1 above that the one-component flexible thermally conductive structural adhesive provided by the embodiment of the present invention has the characteristics of high thermal conductivity, high shear strength and bonding strength. For example, in Example 2, the proportion of polyether modified resin and core-shell rubber added is appropriately increased compared with other embodiments, which has a double toughening effect, and its flexibility is optimal and the elongation at break is the highest. The comprehensive performance of the structural adhesive provided by Example 5 is the best. The addition of polyether modified resin and core-shell rubber toughening agent in Example 5 makes the structural adhesive show good flexibility and better elongation at break, and the compounding of spherical alumina and flaky aluminum nitride as thermally conductive fillers ensures that the structural adhesive in Example 5 has excellent thermal conductivity (relative to other embodiments, the thermal conductivity of the structural adhesive provided in Example 5 can reach 3.0W / (m·K)). In general, the one-component flexible thermally conductive structural adhesive provided by the embodiment of the present invention has excellent overall performance and is expected to be widely used in the fields of bonding and heat dissipation of electronic components and bonding of battery modules of new energy electric vehicles.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A one-component flexible thermally conductive structural adhesive, characterized by: The invention comprises the following components in parts by weight: 25-37 parts of epoxy resin, 2-8 parts of curing agent, 4-10 parts of toughening agent, 0.08-0.13 parts of rheological additive and 50-63 parts of thermal conductive filler.

2. The one-component flexible thermally conductive structural adhesive according to claim 1, characterized in that: The epoxy resin includes one or more of bisphenol A epoxy resin, polyether modified epoxy resin, silicone modified epoxy resin, rubber modified epoxy resin, and polyurethane modified epoxy resin; Preferably, the epoxy resin is selected from bisphenol A epoxy resin, or bisphenol A epoxy resin and polyether modified epoxy resin in a mass ratio of 3.0 / 0.8 to 3.0 / 2.

0.

3. The one-component flexible thermally conductive structural adhesive according to claim 1, characterized in that: The curing agent is a latent epoxy curing agent, including one or more of dicyandiamide curing agent, HAA curing agent, boron amine curing agent, and modified imidazole curing agent; Preferably, the curing agent is selected from dicyandiamide curing agent and HAA in a mass ratio of 1 / 0.2 to 1 / 0.

9.

4. The one-component flexible thermally conductive structural adhesive according to claim 1, characterized in that: The toughening agent includes one or more of liquid carboxyl-terminated nitrile rubber (CTBN), core-shell structure resin, hyperbranched polymer, and thermotropic liquid crystal polymer (TLCP); Preferably, the toughening agent is selected from core-shell structure resin, and the core material of the core-shell structure resin is selected from rubber elastomer, and the shell material is selected from thermoplastic resin. More preferably, the core material is butadiene-styrene copolymer, and the shell material is polymethyl methacrylate.

5. The one-component flexible thermally conductive structural adhesive according to claim 1, characterized in that: The rheological additive includes one or more of GARAMITE-1958, 4740, and HL-380+R606; Preferably, the rheological additive is selected from rheological additive 4740.

6. The one-component flexible thermally conductive structural adhesive according to claim 1, characterized in that: The thermally conductive filler comprises one or more of aluminum oxide, aluminum hydroxide, aluminum nitride or boron nitride, and the surface of the thermally conductive filler is treated with a silane coupling agent; Preferably, the D50 of the thermally conductive filler is 1.5-50 μm; Preferably, the thermally conductive filler is selected from spherical aluminum oxide and flaky aluminum nitride whose surfaces are treated with a silane coupling agent.

7. A method for preparing the one-component flexible thermally conductive structural adhesive according to any one of claims 1 to 6, characterized in that: It includes: The epoxy resin, curing agent, toughening agent, rheological additive and thermal conductive filler are mixed in proportion to prepare the one-component flexible thermal conductive structural adhesive.

8. The method for preparing the one-component flexible thermally conductive structural adhesive according to claim 7, characterized in that: The following steps are involved: First, the epoxy resin and the toughening agent are added to a reaction kettle and stirred, and then the thermal conductive filler is added in batches. Then, the curing agent and the rheological additive are added and stirred evenly. Finally, vacuum degassing is performed and the mixture is filled.

9. The method for preparing a one-component flexible thermally conductive structural adhesive according to claim 8, characterized in that: The epoxy resin and the toughening agent are added to the reaction kettle and stirred for 20 minutes. The thermal conductive filler is added in 3-5 batches with an interval of 10-15 minutes between batch additions. The mixture is stirred until there is no dry powder, no agglomeration, and no obvious granularity or streaks.

10. Use of the one-component flexible thermally conductive structural adhesive according to any one of claims 1 to 6 or the one-component flexible thermally conductive structural adhesive prepared by the preparation method according to any one of claims 7 to 9 in the packaging of electronic components and the bonding of battery modules of new energy electric vehicles.

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