Low-viscosity high-thermal-conductivity epoxy underfill adhesive and preparation method thereof

Abstract

The invention belongs to the technical field of adhesives, and particularly relates to a low-viscosity high-thermal-conductivity epoxy underfill adhesive and a preparation method thereof.The low-viscosity high-thermal-conductivity epoxy underfill adhesive is prepared from, by weight, 13-20 parts of epoxy resin, 2-8 parts of epoxy diluent, 0.5-2 parts of silane coupling agent, 0.7-1.3 parts of wetting dispersant, 0.2-0.5 part of color paste, 55-65 parts of filler, 15-20 parts of curing agent and 0.5-2 parts of curing accelerator. The prepared epoxy underfill adhesive is a single-component epoxy resin adhesive, and has the characteristics of low viscosity, high flowing speed, high glass transition temperature, good high temperature resistance, small thermal expansion coefficient, high heat conductivity coefficient, high shear strength and the like; the method has an excellent application prospect in the aspect of underfill for packaging such as chip scale packaging (CSP) and ball grid array packaging (BGA).

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of adhesives, and particularly relates to a low-viscosity high-thermal-conductivity epoxy underfill adhesive and a preparation method thereof. BACKGROUND

[0002] Electronic products are gradually developing towards small size and high power at a high speed along with the change of market demand; in order to realize that small-size electronic products can have a longer service life while maintaining small size, the heat dissipation problem of electronic components has become the focus of the industry. In order to enable electronic products to achieve the purpose of high efficiency and long service life under the condition of smaller size, researchers have invested a lot of effort in improving the thermal conductivity of adhesives. Among them, epoxy resin (EP) as a relatively mature product, has the advantages of easy processing, excellent insulation performance and strong corrosion resistance, and has developed rapidly in the electronic packaging industry; due to the limitation of the non-crystalline chain structure of epoxy resin itself, the thermal conductivity is very low, only 0.2 W / (m·K), which cannot meet the demand for thermal conductivity in the electronic packaging industry. Therefore, researchers have invested a lot of effort in improving the thermal conductivity of epoxy adhesives.

[0003] Adding thermal conductive fillers is an effective way to improve the thermal conductivity of epoxy adhesives. However, the thermal conductive fillers themselves have strong polarity, and adding them to the matrix can easily cause uneven dispersion and agglomeration, which seriously affects the flowability of the adhesive, limits the increase of thermal conductivity, and also seriously affects the mechanical properties of the matrix. SUMMARY

[0004] The present application provides a low-viscosity high-thermal-conductivity epoxy underfill adhesive and a preparation method thereof, which not only has a fast flow speed, but also has the characteristics of high thermal conductivity and low thermal expansion coefficient.

[0005] The specific technical solutions are as follows: The first object of the present application is to provide a low-viscosity high-thermal-conductivity epoxy underfill adhesive, which comprises the following components by weight: 13-20 parts of epoxy resin, 2-8 parts of epoxy diluent, 0.5-2 parts of silane coupling agent, 0.7-1.3 parts of wetting dispersant, 0.2-0.5 parts of color paste, 55-65 parts of filler, 15-20 parts of curing agent, and 0.5-2 parts of curing accelerator.

[0006] Further, the epoxy resin is a mixture of biphenyl type epoxy resin and epoxy toughening agent, or the epoxy resin is a mixture of the biphenyl type epoxy resin and epoxy toughening agent and one or more of alicyclic type epoxy resin, phenolic type epoxy resin, and bisphenol F type epoxy resin.

[0007] Further, the epoxy resin is a mixture of a biphenyl type epoxy resin, an epoxy toughener and a bisphenol F type epoxy resin, or the epoxy resin is a mixture of the biphenyl type epoxy resin, the epoxy toughener and the bisphenol F type epoxy resin and one or both of an alicyclic type epoxy resin and a phenolic type epoxy resin.

[0008] Further, the biphenyl type epoxy resin is a self-synthesized biphenyl type epoxy resin, the structural formula of which is as follows:

[0009] The preparation method of the self-synthesized biphenyl type epoxy resin comprises the following steps: dissolving 3-methyl-4-hydroxybenzaldehyde and 3,3'-dimethylbenzidine in anhydrous ethanol, setting the temperature to 50-80°C, stirring for 6-8h, and then obtaining biphenyl diol I yellow crystals by a precipitation drying method; dissolving the obtained yellow crystals and 6-chloro-1-hexanol in a N,N-dimethylformamide (DMF) solution, setting the temperature to 110-130°C, stirring for 8-14h, and then obtaining biphenyl diol II by washing, filtering and vacuum drying; dissolving the biphenyl diol II completely at 70-90°C, reducing the temperature of the mixture to 50-60°C, slowly adding a 20-40% mass fraction sodium hydroxide solution, stirring at 60-70°C for 8-12h, and then obtaining a biphenyl type epoxy resin by washing in cold water, filtering and vacuum drying: .

[0010] Further, the epoxy toughener is a mixture of one or more of MX125 (Kaneka), MX136 (Kaneka), MX139 (Kaneka), MX553 (Kaneka), E470 (EVONIK), E430 (EVONIK), E500 (EVONIK) and E601 (EVONIK).

[0011] Further, the alicyclic epoxy resin is a mixture of one or more of CELLOXIDE 2021P (Daicel), CELLOXIDE 2000 (Daicel), S-221 (Nantong, China, SYNASIA) and S-28E (Nantong, China, SYNASIA).

[0012] Further, the phenolic type epoxy resin is a mixture of one or more of EPALLOY 8240E (CVC Thermoset Specialties), EPALLOY 8250 (CVC Thermoset Specialties) and NPPN-631 (Nanya).

[0013] Further, the bisphenol F type epoxy resin is 830-S (DIC Corporation), EXA-835LVP (DIC Corporation), 370D (Huayi Resin).

[0014] Further, the curing agent is one or a combination of methylhexahydrophthalic anhydride (Yare Chemical), HN-2200 (HITACHI, Japan), methyl nadic anhydride (Puyang Hui Cheng).

[0015] Further, the curing accelerator is one or a combination of 2,4,6-tris-(dimethylaminomethyl) phenol, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-ethyl-4-methylimidazole, such as K-54 (Air, USA), 2E4MZ-CN (SHIKOKU, Japan), 2E4MZ (SHIKOKU, Japan).

[0016] Further, the epoxy diluent is one or a combination of AFG-90H (Huayi Resin), ED-509E (ADEKA), ED-506 (ADEKA), LITE 513E (Cardolite), HELOXY 8 (HELOXY).

[0017] Further, the silane coupling agent is one or a combination of Silquest A-187 (Momentive), KBE-403 (ShinEtsu), KBM-903 (ShinEtsu).

[0018] Further, the wet dispersing agent is one or a combination of Dynasylan-1124 (EVONIK), Tech-599 (Tego), Tech-5108 (Tego), Tech-6300 (Tego).

[0019] Further, the color paste is a low-halogen black color paste (Poly one, USA).

[0020] Further, the maximum particle size of the filler is 50 μm, and the average particle size is 7-10 μm; the filler is one or a combination of spherical aluminum oxide, spherical microsilica, spherical magnesium oxide, spherical boron nitride, including SE 6050-SQ (Admatechs, Japan), NQ1110H (Jiangsu Lianrui New Material Co., Ltd.), AO-502 (Admatechs, Japan), NAS-1.0-S3 (Jiangsu Lianrui New Material Co., Ltd.), MG-5 (STARMAG, Japan), PT-BN (Shanghai Pantian).

[0021] The second object of the present application is to provide a preparation method of the low-viscosity high-thermal-conductivity epoxy underfill adhesive, comprising the following steps: 1) preparing a primary mixture: adding epoxy resin, epoxy diluent, silane coupling agent and wetting dispersant into a reaction container according to the weight fraction, setting the stirring speed at 30-40 rpm, setting the rotation speed of the disperser at 200-300 rpm, vacuum stirring for 0.5-1 h, adding fillers, heating at 70-90°C, vacuum stirring for 12-18 h, and obtaining a primary mixture; 2) preparing a secondary mixture: taking out the primary mixture obtained in step 1) and putting it into a three-roll mill for over-roll processing, setting the minimum gap of the three-roll mill at 10 μm, and dispersing at an ambient temperature ≤ 30°C and an ambient humidity ≤ RH20%, to obtain a secondary mixture; 3) preparing a low-viscosity high-thermal-conductivity epoxy underfill adhesive: putting the secondary mixture obtained in step 2) into a reaction container again, adding color paste and curing agent, setting the stirring speed at 20-30 rpm and the rotation speed of the disperser at 100-200 rpm, vacuum stirring for 1-2 h, then adding a curing accelerator, and vacuum stirring for 0.5-1 h, to obtain the low-viscosity high-thermal-conductivity epoxy underfill adhesive.

[0022] Compared with the prior art, the present application has the following advantages: (1) The present application uses 3-methyl-4-hydroxybenzaldehyde and 3,3'-dimethylbenzidine as raw materials to develop a biphenyl type epoxy resin, which contains biphenyl type liquid crystal units and can effectively control the order of the crosslinked network structure during the curing process of the epoxy resin, thereby further effectively improving the thermal conductivity of the system; in addition, due to the presence of benzene rings and biphenyl structures, the thermal stability of the underfill adhesive can be effectively improved, and the thermal expansion coefficient of the system can be reduced; (2) The biphenyl type epoxy resin of the present application uses aliphatic long-chain introduction, which can ensure high Tg while having good flexibility; (3) The present application uses the combination of biphenyl type epoxy resin, bisphenol F type epoxy resin and epoxy diluent to effectively reduce the viscosity of the system and improve the flow speed; the biphenyl type epoxy resin ensures rapid curing while having high Tg and high temperature resistance; (4) The present application uses an epoxy diluent with a rigid structure to effectively reduce the viscosity of the system, improve the flowability, and ensure high Tg of the system; (5) The present application uses the combination of different types and different particle sizes of fillers, which makes the fillers have high thermal conductivity under low filling amount, effectively prevents the settling of the fillers, reduces the influence on the viscosity and flowability of the system, and further reduces the thermal expansion coefficient of the system; (6) The curing agent used in the present application is a liquid curing agent, which has the advantages of low viscosity, high Tg, good high-temperature resistance and high reliability; (7) The epoxy underfill adhesive prepared by the present application is a single-component epoxy resin adhesive, which has the characteristics of low viscosity, fast flow speed, high glass transition temperature, good high-temperature resistance, small thermal expansion coefficient, high thermal conductivity and high shear strength, and has excellent application prospects in the aspects of underfilling for packaging such as chip size packaging (CSP) and ball grid array packaging (BGA). DETAILED DESCRIPTION

[0023] The principles and characteristics of the present application are described below in combination with examples, and the examples are only used to explain the present application and are not used to limit the scope of the present application. The parts described in the specific embodiments are weight parts.

[0024] Preparation Example A preparation method of a biphenyl type epoxy resin, comprising the following steps: 1) Synthesis of biphenyl diol I Dissolve 3-methyl-4-hydroxybenzaldehyde and 3,3'-dimethylbenzidine in a molar ratio of 2:1 in 400 mL of anhydrous ethanol, set the temperature to 60°C, stir for 8 h, and purify by a precipitation drying method to obtain yellow biphenyl diol I crystals;

[0025] 2) Synthesis of biphenyl diol II: Dissolve 6-chloro-1-hexanol and biphenyl diol I in a molar ratio of 2:1 in 400 mL of DMF solution, set the temperature to 130°C, stir for 12 h, and after cooling, wash and filter by pouring into cold water, place the obtained solid in a vacuum dryer at 70°C for 12 h, continue to wash and filter the obtained product with diethyl ether, and continue to place it in a vacuum dryer at 90°C for 24 h to obtain biphenyl diol II;

[0026] 3) Synthesis of biphenyl type epoxy resin III Dissolve biphenyl diol II and epichlorohydrin in a molar ratio of 1:2 at 90°C, stir for 6 h to completely dissolve the biphenyl diol II, reduce the temperature of the mixture to 60°C, slowly add a 20% sodium hydroxide solution by mass fraction, stir at 60°C for 12 h, and after cooling, wash and filter by pouring into cold water, place the obtained solid in a vacuum dryer at 70°C for 12 h, continue to wash and filter the obtained product with anhydrous ethanol repeatedly, and continue to place it in a vacuum dryer at 90°C for 24 h to obtain biphenyl type epoxy resin III.

[0027]

[0028] Example 1 A method for preparing a low-viscosity, high-thermal-conductivity epoxy underfill adhesive includes the following steps: 1) Preparation of primary mixture: 5 parts of biphenyl type epoxy resin III (prepared in the preparation example), 4.5 parts of bisphenol F type epoxy resin EXA-835LVP (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 3 parts of epoxy diluent ED-509E (ADEKA), 3 parts of alicyclic epoxy resin CELLOXIDE 2021P (Daicel), 0.8 parts of silane coupling agent SilquestA-187 (Momentive), and 1 part of wetting and dispersing agent Tech-6300 (Tiger Additives) were added to the reactor in sequence. The stirring speed was set to 40 rpm and the disperser to 300 rpm, and the mixture was stirred under vacuum for 1 h. Then, 38.2 parts of filler NAS-1.0-S3 (Lianrui), 16.4 parts of PT-BN (Shanghai Pantian), and 5.4 parts of AO-502 (Admatechs Japan) were added. The mixture was heated to 80°C and stirred under vacuum for 18 h to obtain the primary mixture. 2) Preparation of secondary mixture: Take out the primary mixture obtained in step 1) and put it into a three-roll mill for passing through the mill. Set the minimum gap of the three-roll mill to 10μm and disperse it under the conditions of ambient temperature ≤30℃ and ambient humidity ≤RH20% to obtain the secondary mixture. 3) Preparation of low-viscosity, high-thermal-conductivity epoxy underfill: The secondary mixture obtained in step 2) is put back into the reactor, and 0.4 parts of low-halogen black pigment paste (Poly One, USA) and 19 parts of curing agent methylhexahydrophthalic anhydride (Yarui Chemical) are added. The stirrer speed is set to 30 rpm and the disperser rotation speed is set to 200 rpm. After vacuum stirring for 2 hours, 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) are added and vacuum stirred for 1 hour to obtain the low-viscosity, high-thermal-conductivity epoxy underfill.

[0029] Example 2 A method for preparing a low-viscosity, high-thermal-conductivity epoxy underfill adhesive includes the following steps: 1) Preparation of a primary mixture: 5 parts of biphenyl type epoxy resin III (prepared in the preparation example), 4.5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 6 parts of epoxy diluent ED-509E (ADEKA), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), 1 part of wet dispersant Tech-6300 (Tegoseal) are sequentially added to a reaction kettle, the stirring speed is set to 40 rpm, the disperser is set to 300 rpm, vacuum stirring is carried out for 1 h, 5.4 parts of filler AO-502 (Japan Admatechs), 38.2 parts of NAS-1.0-S3 (Lianrui), 16.4 parts of PT-BN (Shanghai Pantian) are added, heated at 80°C, vacuum stirring for 18 h to obtain a primary mixture; 2) Preparation of a secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll treatment, the minimum gap of the three-roll mill is set to 10 μm, dispersion is carried out under the condition that the ambient temperature is ≤30°C and the ambient humidity is ≤RH20%, to obtain a secondary mixture; 3) Preparation of a low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black paste (Poly one, USA), 19 parts of curing agent methyl hexahydrophthalic anhydride (Yarui Chemical) are added, the stirring speed is set to 30 rpm, the self-rotation speed of the disperser is set to 200 rpm, vacuum stirring is carried out for 2 h, then 0.8 parts of curing accelerator 2E4MZ-CN (Japan SHIKOKU) is added, vacuum stirring for 1 h, to obtain the low-viscosity high-thermal-conductivity epoxy underfill adhesive.

[0030] Example 3 A preparation method of a low-viscosity high-thermal-conductivity epoxy underfill adhesive, comprising the following steps: 1) Preparation of a primary mixture: 5 parts of biphenyl type epoxy resin III (prepared in the preparation example), 4.5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 6 parts of epoxy diluent ED-509E (ADEKA), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), 1 part of wet dispersant Tech-6300 (Tegoseal) are sequentially added to a reaction kettle, the stirring speed is set to 40 rpm, the disperser is set to 300 rpm, vacuum stirring is carried out for 1 h, 5.4 parts of filler AO-502 (Japan Admatechs), 38.2 parts of NAS-1.0-S3 (Lianrui), 16.4 parts of PT-BN (Shanghai Pantian) are added, heated at 80°C, vacuum stirring for 18 h to obtain a primary mixture; 2) Preparation of secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll processing, the minimum gap of the three-roll mill is set to 10 μm, and dispersion is carried out at an ambient temperature ≤ 30 ℃ and an ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) Preparation of low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black color paste (Poly one, USA), 19 parts of curing agent methyl hexahydrophthalic anhydride (Yaray Chemical Industry) are added, the stirring speed of the stirrer is set to 30 rpm, the self-rotation speed of the disperser is set to 200 rpm, vacuum stirring is carried out for 2 h, 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) is added, vacuum stirring is carried out for 1 h, and the low-viscosity high-thermal-conductivity epoxy underfill adhesive is obtained.

[0031] Example 4 A preparation method of a low-viscosity high-thermal-conductivity epoxy underfill adhesive, comprising the following steps: 1) Preparation of primary mixture: 7 parts of biphenyl type epoxy resin III (prepared in the preparation example), 5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3 parts of epoxy toughening agent MX553 (Kaneka), 4 parts of epoxy diluent ED-509E (ADEKA), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), and 1 part of wetting dispersant Tech-6300 (Tiger Auxiliary Agent) are sequentially added to a reaction kettle, the stirring speed is set to 40 rpm, the disperser speed is set to 300 rpm, vacuum stirring is carried out for 1 h, 5.4 parts of filler AO-502 (Admatechs, Japan), 38.2 parts of NAS-1.0-S3 (Lianrui), and 16.4 parts of PT-BN (Shanghai Pantian) are added, heating is carried out at 80 ℃, and vacuum stirring is carried out for 18 h, to obtain a primary mixture; 2) Preparation of secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll processing, the minimum gap of the three-roll mill is set to 10 μm, and dispersion is carried out at an ambient temperature ≤ 30 ℃ and an ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) Preparation of low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black color paste (Poly one, USA), 19 parts of curing agent methyl hexahydrophthalic anhydride (Yaray Chemical Industry) are added, the stirring speed of the stirrer is set to 30 rpm, the self-rotation speed of the disperser is set to 200 rpm, vacuum stirring is carried out for 2 h, 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) is added, vacuum stirring is carried out for 1 h, and the low-viscosity high-thermal-conductivity epoxy underfill adhesive is obtained.

[0032] Comparative Example 1 A preparation method of an epoxy underfill adhesive, comprising the following steps: 1) preparing a primary mixture: 8 parts of bisphenol F type epoxy resin EXA-835LVP (DIC Corporation), 3 parts of epoxy diluent ED-509E (ADEKA), 8 parts of alicyclic epoxy resin CELLOXIDE 2021P (Daicel), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), and 1 part of wet dispersant Tech-6300 (Tegos) are sequentially added to a reaction kettle, a stirring speed of 40 rpm and a disperser speed of 300 rpm are set, vacuum stirring is performed for 1 h, 5.4 parts of filler AO-502 (Japan Admatechs), 38.2 parts of NAS-1.0-S3 (Lianrui), and 16.4 parts of PT-BN (Shanghai Pantian) are added, heating is performed at 80°C, and vacuum stirring is performed for 18 h to obtain a primary mixture; 2) preparing a secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll treatment, the minimum gap of the three-roll mill is set to 10 μm, and dispersion is performed under the condition that the ambient temperature is ≤ 30°C and the ambient humidity is ≤ RH 20% to obtain a secondary mixture; 3) preparing an epoxy underfill adhesive with low viscosity and high thermal conductivity: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black paste (Poly one, USA) and 19 parts of curing agent methylhexahydrophthalic anhydride (Yaer Chemical) are added, the stirring speed is set to 30 rpm, the self-rotation speed of the disperser is set to 200 rpm, vacuum stirring is performed for 2 h, 0.8 parts of curing accelerator 2E4MZ-CN (Japan SHIKOKU) is added, and vacuum stirring is performed for 1 h to obtain the epoxy underfill adhesive.

[0033] Comparative Example 2 A preparation method of an epoxy underfill adhesive, comprising the following steps: 1) preparing a primary mixture: 8 parts of bisphenol F type epoxy resin EXA-835LVP (DIC Corporation), 3 parts of epoxy diluent ED-509E (ADEKA), 8 parts of alicyclic epoxy resin CELLOXIDE 2021P (Daicel), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), and 1 part of wet dispersant Tech-6300 (Tegos) are sequentially added to a reaction kettle, a stirring speed of 40 rpm and a disperser speed of 300 rpm are set, vacuum stirring is performed for 1 h, 5.4 parts of filler AO-502 (Japan Admatechs), 38.2 parts of NAS-1.0-S3 (Lianrui), and 16.4 parts of PT-BN (Shanghai Pantian) are added, heating is performed at 80°C, and vacuum stirring is performed for 18 h to obtain a primary mixture; 2) Preparation of secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll processing, the minimum gap of the three-roll mill is set to 10 μm, and dispersion is carried out at an ambient temperature ≤ 30 ℃ and an ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) Preparation of low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black color paste (Poly one, USA), 19 parts of curing agent methyl hexahydrophthalic anhydride (Yaray Chemical Industry), the stirring speed is set to 30 rpm, the rotation speed of the disperser is set to 200 rpm, vacuum stirring is carried out for 2 h, then 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) is added, vacuum stirring is carried out for 1 h, and the epoxy underfill adhesive is obtained.

[0034] Comparative Example 3 A preparation method of an epoxy underfill adhesive comprises the following steps: 1) Preparation of primary mixture: 5 parts of biphenyl type epoxy resin III (prepared in Preparation Example), 4.5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 6 parts of epoxy diluent ED-509E (ADEKA), and 0.8 parts of silane coupling agent Silquest A-187 (Momentive) are sequentially added to a reaction kettle, the stirring speed is set to 40 rpm, the rotation speed of the disperser is set to 300 rpm, vacuum stirring is carried out for 1 h, 5.4 parts of filler AO-502 (Admatechs, Japan), 38.2 parts of NAS-1.0-S3 (Lianrui), and 16.4 parts of PT-BN (Shanghai Pantian) are added, heating is carried out at 80 ℃, and vacuum stirring is carried out for 18 h, to obtain a primary mixture; 2) Preparation of secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll processing, the minimum gap of the three-roll mill is set to 10 μm, and dispersion is carried out at an ambient temperature ≤ 30 ℃ and an ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) Preparation of low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black color paste (Poly one, USA), 19 parts of curing agent methyl hexahydrophthalic anhydride (Yaray Chemical Industry), the stirring speed is set to 30 rpm, the rotation speed of the disperser is set to 200 rpm, vacuum stirring is carried out for 2 h, then 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) is added, vacuum stirring is carried out for 1 h, and the epoxy underfill adhesive is obtained.

[0035] Comparative Example 4 A preparation method of an epoxy underfill adhesive comprises the following steps: 1) Preparation of a primary mixture: 5 parts of biphenyl type epoxy resin YX-4000H (Japan MITSUBISHI), 4.5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 6 parts of epoxy diluent ED-509E (ADEKA), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), 1 part of wet dispersant Tech-6300 (Tegos) were sequentially added to a reaction kettle, the stirring speed was set to 40 rpm, the disperser was set to 300 rpm, vacuum stirring was carried out for 1 h, 5.4 parts of filler AO-502 (Japan Admatechs), 38.2 parts of NAS-1.0-S3 (Lianrui), 16.4 parts of PT-BN (Shanghai Pantian) were added, heated at 80°C, vacuum stirring for 18 h to obtain a primary mixture; 2) Preparation of a secondary mixture: the primary mixture obtained in step 1) was taken out and put into a three-roll mill for over-roll treatment, the minimum gap of the three-roll mill was set to 10 μm, and the dispersion was carried out under the conditions of ambient temperature ≤ 30°C and ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) Preparation of a low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) was again put into a reaction kettle, 0.4 parts of low-halogen black paste (Poly one, USA), 19 parts of curing agent methylhexahydrophthalic anhydride (Yarui Chemical Industry) were added, the stirring speed was set to 30 rpm, the self-rotation speed of the disperser was set to 200 rpm, vacuum stirring was carried out for 2 h, then 0.8 parts of curing accelerator 2E4MZ-CN (Japan SHIKOKU) was added, vacuum stirring for 1 h, to obtain the epoxy underfill adhesive.

[0036] Comparative Example 5 A preparation method of an epoxy underfill adhesive, comprising the following steps: 1) Preparation of a primary mixture: 5 parts of biphenyl type epoxy resin III (prepared in Preparation Example), 4.5 parts of bisphenol F type epoxy resin 830-S (DIC Corporation), 3.5 parts of epoxy toughening agent MX553 (Kaneka), 6 parts of epoxy diluent ED-509E (ADEKA), 0.8 parts of silane coupling agent Silquest A-187 (Momentive), 1 part of wet dispersant Tech-6300 (Tegos) were sequentially added to a reaction kettle, the stirring speed was set to 40 rpm, the disperser was set to 300 rpm, vacuum stirring was carried out for 1 h, 42 parts of filler NAS-1.0-S3 (Lianrui), 18 parts of PT-BN (Shanghai Pantian) were added, heated at 80°C, vacuum stirring for 18 h to obtain a primary mixture; 2) Preparation of secondary mixture: the primary mixture obtained in step 1) is taken out and put into a three-roll mill for over-roll treatment, the minimum gap of the three-roll mill is set to 10 pm, and dispersion is carried out at an ambient temperature of ≤30°C and an ambient humidity of ≤RH20%, to obtain a secondary mixture; 3) Preparation of low-viscosity high-thermal-conductivity epoxy underfill adhesive: the secondary mixture obtained in step 2) is again put into a reaction kettle, 0.4 parts of low-halogen black paste (Poly one, USA) and 19 parts of curing agent methyl hexahydrophthalic anhydride (Yaray Chemical) are added, the stirring speed of the stirrer is set to 30 rpm, the rotation speed of the disperser is set to 200 rpm, and vacuum stirring is carried out for 2 h, then 0.8 parts of curing accelerator 2E4MZ-CN (SHIKOKU, Japan) is added, and vacuum stirring is carried out for 1 h, to obtain the epoxy underfill adhesive.

[0037] The formulations of examples 1-4 and comparative examples 1-5 are shown in Table 1.

[0038] Table 1 Formulation table of examples and comparative examples

[0039] Test: The performance of the epoxy underfill adhesives of examples 1-4 and comparative examples 1-5 is tested by the following tests: Test Test 1 Viscosity test The samples obtained from examples 1-4 and comparative examples 1-5 are tested for viscosity using cp35 20s-1 according to standard ASTM D2196-05.

[0040] Test Test 2 Flow speed test The samples obtained from examples 1-4 and comparative examples 1-5 are tested for flow speed using a device consisting of a gap slide and a cover glass, a glass slide, and a gap of 0.15 mm (simulating the gap between packaged components), according to the semiconductor industry standard J-STD-030 test method.

[0041] Test Test 3 Glass transition temperature test The samples obtained from examples 1-4 and comparative examples 1-5 are tested according to standard ASTM D696-79.

[0042] Test Test 4 Linear thermal expansion coefficient test The samples obtained from examples 1-4 and comparative examples 1-5 are tested according to standard ASTM D696-79.

[0043] Test Test 5 Thermal conductivity test The samples obtained in Examples 1-4 and Comparative Examples 1-5 were tested for thermal conductivity according to ASTM D5470 using a Hot Disk TPS 2500S thermal conductivity meter.

[0044] Test Test 6: Elongation at break test The samples obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to standard ASTM D638.

[0045] Test Test 7: Shear strength test The samples obtained in Examples 1-4 and Comparative Examples 1-5 were bonded with Cu-Cu plates and tested according to standard GB / T 7124-2008.

[0046] Test Test 8: High temperature resistance test The samples obtained in Examples 1-4 and Comparative Examples 1-5 were tested for temperature resistance according to semiconductor industry standard J-STD-030 using a QHL 360SMT lead-free reflow soldering machine from Beijing Qingyun Innovation Co., Ltd.

[0047] Test Test 9: Double 85 reliability test The samples obtained in Examples 1-4 and Comparative Examples 1-5 were tested according to standard GB / T 5170.5-2008.

[0048] The test data for Examples 1-4 and Comparative Examples 1-5 are shown in Table 2.

[0049] Table 2: Test data for Examples and Comparative Examples

[0050] As can be seen from the data in Table 2, the epoxy underfill adhesive prepared in the examples of the present application has low viscosity, fast flow speed, high glass transition temperature, good high temperature resistance, small thermal expansion coefficient, high thermal conductivity, and high shear strength, and has excellent application prospects in the field of underfill for packaging such as chip size packaging (CSP) and ball grid array packaging (BGA).

[0051] Comparing the data of Examples 1-4 and Comparative Example 1, it can be seen that the self-synthesized biphenyl epoxy resin of the present application has a higher glass transition temperature, a lower linear thermal expansion coefficient, and can effectively improve the thermal conductivity and shear strength of the system, and effectively improve the temperature resistance and reliability of the system, and effectively improve the comprehensive performance of the system.

[0052] The data comparison of example 1 and comparative example 2 shows that the example has more excellent elongation at break, and the addition of the epoxy toughening agent MX553 with core-shell structure can make the formula have certain toughening effect on the system while keeping the original strength, so that the system can have better performance.

[0053] The data comparison of example 2 and comparative example 3 shows that the example has lower viscosity and faster flow rate, and the dispersant Tech-6300 has good wettability and strong viscosity reduction ability, so that the filler can be more uniformly dispersed in the system.

[0054] The data comparison of example 2 and comparative example 4 shows that the example has more excellent elongation at break while ensuring higher shear strength, and the self-synthesized biphenyl epoxy resin has excellent bonding performance and can make the system have more excellent flexibility.

[0055] The data comparison of example 2 and comparative example 5 shows that the viscosity of the example is further reduced, the flow rate is further improved, and the thermal conductivity is effectively improved, which shows that the addition of small-size AO-502 can fill the gap of large-size filler and form a heat conduction path to improve the thermal conductivity; at the same time, it can play the role of gear in the gap of large-size filler, so that the viscosity is effectively reduced and the flow rate is improved.

[0056] The data comparison of example 3 and example 4 shows that the viscosity of example 3 is further reduced, the flow rate is further improved, and the elongation at break is more excellent, which shows that the addition of the epoxy diluent HELOXY 8 with long chain structure can effectively improve the flexibility of the system while further reducing the viscosity and improving the flow rate.

[0057] In summary, the synergistic effect of the self-synthesized biphenyl epoxy resin and different thermal conductive fillers through various raw materials such as diluents and additives is an effective method to adjust the comprehensive performance of the adhesive.

[0058] The above only describes the preferred embodiments of the present application, and does not limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A low viscosity high thermal conductive epoxy underfill adhesive, characterized in that, By weight parts, including the following components: epoxy resin 13~20 parts, epoxy diluent 2~8 parts, silane coupling agent 0.5~2 parts, wet dispersing agent 0.7~1.3 parts, color paste 0.2~0.5 parts, filler 55~65 parts, curing agent 15~20 parts, curing accelerator 0.5~2 parts.

2. The low viscosity high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The epoxy resin is a mixture of a biphenyl type epoxy resin and an epoxy toughening agent, or the epoxy resin is a mixture of the biphenyl type epoxy resin and the epoxy toughening agent and one or more of alicyclic epoxy resin, phenolic type epoxy resin, bisphenol F type epoxy resin. 3.The low viscosity high thermal conductivity epoxy underfill adhesive of claim 2, wherein, The biphenyl type epoxy resin is a self-synthesized biphenyl type epoxy resin, and its preparation method comprises the following steps: dissolving 3-methyl-4-hydroxybenzaldehyde and 3,3'-dimethylbenzidine in anhydrous ethanol, setting the temperature to 50~80℃, stirring for 6~8h, and then obtaining biphenyl dihydric alcohol I yellow crystals by precipitation drying method; dissolving the obtained yellow crystals and 6-chloro-1-hexanol in N,N-dimethylformamide solution, setting the temperature to 110~130℃, stirring for 8~14h, and obtaining biphenyl dihydric alcohol II by washing, filtering, and vacuum drying; dissolving biphenyl dihydric alcohol II in 70~90℃, and then reducing the temperature of the mixture to 50~60℃, slowly adding a 20~40% mass fraction sodium hydroxide solution, stirring at 60~70℃ for 8~12h, and obtaining the biphenyl type epoxy resin by washing in cold water, filtering, and vacuum drying: 。 4. The low viscosity high thermal conductivity epoxy underfill adhesive of claim 2, wherein, The epoxy toughening agent is selected from one or more of MX125, MX136, MX139, MX553, E470, E430, E500, E601.

5. The low viscosity, high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The curing agent is selected from one or more of methylhexahydrophthalic anhydride, HN-2200, methyl nadic anhydride.

6. The low viscosity, high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The curing accelerator is selected from one or more of 2,4,6-tris-(dimethylaminomethyl)phenol, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-ethyl-4-methylimidazole.

7. The low viscosity high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The epoxy diluent is selected from one or more of AFG-90H, ED-509E, ED-506, LITE 513E, HELOXY 8.

8. The low viscosity, high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The wet dispersing agent is a compound of one or more of Dynasylan-1124, Tech-599, Tech-5108, Tech-6300. 9.The low viscosity and high thermal conductivity epoxy underfill adhesive of claim 1, wherein, The maximum particle size of the filler is 50μm, and the average particle size is 7~10μm; the filler is a compound of one or more of spherical aluminum oxide, spherical microsilica, spherical magnesium oxide, and spherical boron nitride.

10. A method for preparing a low viscosity high thermal conductive epoxy underfill adhesive according to any one of claims 1 to 9, characterized in that, The method comprises the following steps: 1) preparing a first mixture: adding epoxy resin, epoxy diluent, silane coupling agent, and wet dispersing agent into a reaction container according to weight parts, setting the stirring speed to 30~40rpm, setting the self-rotation speed of the disperser to 200~300rpm, vacuum stirring for 0.5~1h, adding filler, heating at 70~90℃, and vacuum stirring for 12~18h to obtain a first mixture; 2) preparing a secondary mixture: taking out the primary mixture obtained in step 1) and putting it into a three-roll mill for over-roll treatment, setting the minimum gap of the three-roll mill to 10 μm, and dispersing at ambient temperature ≤ 30 °C and ambient humidity ≤ RH 20%, to obtain a secondary mixture; 3) preparing a low-viscosity high-thermal-conductivity epoxy underfill adhesive: putting the secondary mixture obtained in step 2) into a reaction vessel again, adding color paste and a curing agent, setting the stirring speed of the stirrer to 20-30 rpm and the rotation speed of the disperser to 100-200 rpm, vacuum stirring for 1-2 h, then adding a curing accelerator, and vacuum stirring for 0.5-1 h, to obtain the low-viscosity high-thermal-conductivity epoxy underfill adhesive.

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