Photo-curing damp-heat-resistant thiol epoxy resin adhesive

Abstract

The invention discloses a photocuring moisture and heat-resistant thiol epoxy resin adhesive which comprises the following components in parts by weight: 100 parts of epoxy resin, 60-100 parts of a polyfunctional group thiol (sulfydryl) silane coupling agent, 0.5-5 parts of a photobase generator and 0.5-5 parts of a photosensitizer. The adhesive disclosed by the invention cannot be cured immediately after UV illumination and can be completely cured by low-temperature heating, so that the adhesive has the characteristic of delayed curing. The structure of the adopted thiol compound coupling agent does not contain ester bonds, a cured product is elastic and excellent in heat and humidity resistance, and good bonding strength is still kept after high-temperature and high-humidity treatment.

Description

Technical Field

[0001] The invention relates to epoxy resin adhesive, in particular to a photocurable single-component epoxy resin, belonging to the technical field of adhesives. Background Art

[0002] Light-curing epoxy resins are widely used in semiconductor packaging and bonding applications because of their low curing shrinkage, high bonding strength, good corrosion resistance, excellent electrical insulation properties, high production efficiency, energy saving and environmental protection.

[0003] The photocuring mechanism of epoxy resin is generally based on the cationic reaction of photoacid generators. Although it does not have the surface oxygen inhibition effect of free radical curing mechanisms such as acrylate monomers or oligomer materials, it is easily affected by environmental humidity and does not cure. At the same time, the superacid generated by light initiation will also accelerate the corrosion of metal substrates, limiting its application in the field of electronic packaging.

[0004] Photobase generators are compounds that generate strong alkaline substances when exposed to ultraviolet light. They can be used in conjunction with photosensitizers to prepare single-component epoxy resin adhesives with excellent performance. Since the alkaline substances generated by light generally do not cause corrosion to the substrate, and the curing process is not affected by environmental humidity and surface oxygen inhibition, it is an ideal material for semiconductor electronic component packaging.

[0005] Epoxy groups and thiol (sulfhydryl) groups can undergo a click reaction in the presence of an alkaline catalyst, so photo-curable thiol epoxy resin adhesives can be prepared using photobase generators.

[0006] Li Zhiquan and others published the document "Synthesis and Performance Study of Reduced Amidine LED Photobase Generators" (Imaging Science and Photochemistry, Vol 38, No1, 2020). After ultraviolet light irradiation, the strong base DBN (amidine compound) released can effectively trigger the thiol-epoxy click reaction. However, the thiol used in the paper contains an ester bond structure, which is easily hydrolyzed in a high temperature and high humidity environment, resulting in a significant decrease in the bonding strength or even failure of the epoxy resin cured product after experiencing high temperature and high humidity (such as: 85℃85%RH), and it cannot be used for electronic and electrical components and other uses that require resistance to high temperature and high humidity environments.

[0007] Patent CN113736403A discloses a one-component heat-curing thiol epoxy resin composition, which includes 20-30 parts of bisphenol A epoxy resin, 20-30 parts of epoxy resin containing rigid ring, 30-50 parts of isocyanurate type polythiol compound (see molecular formula-1), 1-5 parts of latent curing agent, and 0.1-10 parts of auxiliary agent. It can achieve low-temperature rapid curing, and the cured product has good moisture and heat resistance and hot bonding strength. Since isocyanurate type polythiol compounds do not contain ester bond structures, they are not easy to hydrolyze and have good moisture and heat resistance. However, this type of polythiol compound is extremely expensive and difficult to obtain. At the same time, the cured product obtained is very brittle and lacks toughness and elasticity, is not resistant to falling, and is also prone to stress in cold and hot shock environmental tests, resulting in a decrease in bonding strength. Therefore, it is not ideal to use isocyanurate type polythiol compounds to prepare light-cured thiol epoxy.

[0008]

[0009] Molecular formula-1 (isocyanurate type polythiol compound TSIC)

[0010] Patent CN115029092A discloses a one-component epoxy resin adhesive resistant to moisture and heat and its preparation method and application, wherein the one-component epoxy resin adhesive comprises a combination of epoxy resin, toughening resin, mercaptan curing agent (molecular formula-2), curing accelerator and nano calcium carbonate, and by limiting the curing agent to a mercaptan curing agent that does not contain an ester bond, the hydrolysis resistance of the adhesive is greatly enhanced, and its moisture and heat aging resistance is improved. However, although the polyfunctional mercaptan containing ether bonds has excellent hydrolysis resistance, because the molecular weight is relatively small, the volatility is strong, and the smell is extremely unpleasant, it is difficult to accept the electronic and electrical applications used in a closed environment. Therefore, it is not suitable to prepare light-cured mercaptan epoxy with polyfunctional mercaptan compounds containing ether bonds.

[0011]

[0012] Molecular formula-2

[0013] Patent CN115232585A discloses a single-component epoxy resin composition resistant to wet and hot hydrolysis, and its preparation method and application. The composition comprises: 40-60 parts of epoxy resin, 20-60 parts of non-ester bond thiol compound (molecular formula-3), 0.5-10 parts of curing accelerator, 0.1-5 parts of stabilizer, 0.1-5 parts of silane coupling agent, and 0.1-40 parts of filler. Since the thiol compound structure does not contain ester bonds and contains two benzene ring structures, it has good wet and hot resistance after curing, and can still maintain good bonding strength after wet and hot treatment. However, the synthesis steps of the thiol compound used in this invention patent are extremely cumbersome, a large amount of solvent is used, the reaction time is very long, and complex process flows such as alkali washing, water washing, solvent extraction, distillation and purification are required, which produces a large amount of wastewater and waste solvents. The synthesis process is environmentally unfriendly, the yield of the target product is low, the cost is very high, and it is not suitable for packaging and bonding and sealing of ordinary electronic components. Therefore, it is not ideal to use this non-ester bond thiol compound to prepare light-cured thiol epoxy.

[0014]

[0015] Molecular formula-3. Summary of the invention

[0016] The invention aims to provide a multifunctional thiol silane coupling agent with simple synthesis process and low cost, and a light-cured moisture-heat-resistant thiol epoxy resin adhesive composition containing the coupling agent.

[0017] The technical solution to achieve the purpose of the present invention is:

[0018] In a first aspect, the present invention provides a multifunctional thiol (mercapto) silane coupling agent having the following structure:

[0019]

[0020] Wherein, R represents a methyl group or a methoxy group, and n is an integer of 0 to 100.

[0021] In a second aspect, the present invention provides a method for preparing the multifunctional thiol (mercapto) silane coupling agent described in the first aspect, which is synthesized by hydrolyzing a mercaptopropylmethyldimethoxysilane coupling agent and / or a mercaptopropyltrimethoxysilane coupling agent in the presence of a catalyst.

[0022] Preferably, the catalyst is selected from any one or more of inorganic acids, organic acids, organotin compounds, cation exchange resins, titanate compounds, α-silane coupling agents, Lewis acids or Lewis base compounds, preferably any one or more of inorganic acids, organic acids and organotin compounds, and the weight ratio of mercaptopropylmethyldimethoxysilane coupling agent and / or mercaptopropyltrimethoxysilane coupling agent to the catalyst is 100:0.05-2.

[0023] Specifically, the inorganic acid and organic acid are hydrochloric acid, sulfuric acid, phosphoric acid, methanesulfonic acid, trifluoromethanesulfonic acid, toluenesulfonic acid and the like.

[0024] Specifically, the organotin compound is dibutyltin dibutyl ketoxime silicon, dibutyltin diacetylacetonate, dibutyltin diacetylacetate, dibutyltin dilaurate, dibutyltin bistriethoxysilicate, dioctyltin bistriethoxysilicate, and a tetravalent tin compound which is the reaction product of diketoxime tin oxide and a silicate compound.

[0025] In a third aspect, the present invention provides a photocurable moisture-resistant thiol epoxy resin adhesive, which comprises, by weight: 100 parts of epoxy resin, 60 to 100 parts of multifunctional thiol (mercapto) silane coupling agent, 0.5 to 5 parts of photobase generator, and 0.5 to 5 parts of photosensitizer.

[0026] Preferably, the epoxy resin is selected from one or a mixture of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, oxetane, etc., preferably one or two of bisphenol A epoxy resin and bisphenol F epoxy resin.

[0027] Preferably, the photobase generator (PBG) is selected from one or more of cobalt ammonia complexes, carbamates, ketoxime esters, formamides, quaternary ammonium salts, triphenylmethanol, and tetraphenylborate of organic amines such as triethylamine, tributylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazidobicyclo[4.4.0]dec-5-ene (TBD) and their organic amine derivatives, and preferably tetraphenylborate of organic amines.

[0028] Preferably, the photosensitizer is selected from any one or more of benzoin and its derivatives, benzil derivatives, dialkoxyacetophenone, α-hydroxyalkyl phenone, α-aminoalkyl phenone, acylphosphine oxide, benzophenone and its derivatives, thioxanthone compounds, anthraquinone compounds, fluorenone compounds, etc., preferably thioxanthone compounds, and isopropyl thioxanthone ITX is more preferred in terms of ease of use and economy.

[0029] Preferably, the adhesive may also contain a silane coupling agent, including but not limited to: one or more of γ-methacryloxypropyltrimethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltrimethoxysilane, vinyltriethoxysilane, anilinemethyltriethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and γ-ureapropyltriethoxysilane.

[0030] Preferably, the adhesive may also contain various fillers, including but not limited to: one or more of fused silica, glass fiber powder, and glass microspheres.

[0031] Preferably, the adhesive may further include antioxidants, flame retardants, diluents, adhesion promoters, dyes, pigments, defoamers, leveling agents, etc., which are well known to those skilled in the art and will not be elaborated herein.

[0032] In a fourth aspect, the present invention provides a method for using the photocurable moisture-resistant and heat-resistant thiol epoxy resin adhesive described in the third aspect, wherein after dispensing, ultraviolet irradiation is first performed, and then the bonded specimens are aligned and bonded, and then cured.

[0033] Preferably, according to the production process requirements, it can be further heated for a short time for curing, or left to cure at room temperature.

[0034] Compared with the prior art, the advantages of the present invention are:

[0035] (1) The photocurable heat-resistant mercaptan epoxy resin adhesive of the present invention cannot be cured immediately after exposure to light, but has a delayed curing characteristic, and can also be photocured and bonded to opaque materials.

[0036] (2) The photocurable heat-resistant thiol epoxy resin adhesive of the present invention has excellent heat-resistant properties and maintains the original bonding strength without decreasing after high temperature and high humidity tests. DETAILED DESCRIPTION

[0037] The epoxy resin of the present invention is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, oxetane, etc. to achieve the required viscosity, hardness or reaction speed.

[0038] The initiation efficiency of the photobase generator is usually lower than that of the free radical and cationic photoinitiators, so it is necessary to cooperate with a photosensitizer to achieve a sufficiently high initiation efficiency. Different from the free radical polymerization mechanism of acrylates, which cures quickly after illumination, the photobase generator generates a strong alkaline group after UV (ultraviolet) illumination, which promotes the click reaction of the thiol-epoxy group and initiates anionic polymerization, but it will not cure immediately. It generally requires a short time of heating or a period of time at room temperature to be completely cured, that is, it has a delayed curing effect. Therefore, the thiol epoxy adhesive of the present invention can also be used for the bonding of opaque materials. Different from the traditional free radical curing or cationic curing adhesives that are first bonded and then illuminated after dispensing, the method of using the light-cured thiol epoxy adhesive of the present invention is to first irradiate with ultraviolet light after dispensing, and then align and bond the bonded samples. According to the production process requirements, it can be further heated for a short time for curing, or placed at room temperature for curing. The ultraviolet irradiation dose will affect the heating and curing speed of the next step. The greater the irradiation dose, the lower the temperature required for heating in the next step or the shorter the heating time required for the same heating temperature.

[0039] The following are the synthesis methods of the multifunctional thiol silane coupling agent and the formulation examples of the photocurable moisture-heat-resistant thiol epoxy resin adhesive.

[0040] [Mercaptosilane coupling agent-1] In a three-necked glass flask with a reflux condenser, add 100 g of mercaptopropylmethyldimethoxysilane coupling agent (commercially available chemical reagent), 5 g of deionized water, 50 g of ethanol, and 0.5 g of dibutyltin bistriethoxysilicate. Stir and heat to 60°C for 5 h. Rotary evaporate to remove unreacted water, ethanol solvent and generated methanol to obtain a multifunctional mercaptosilane coupling agent-1 with a viscosity of 5.8 mPas.

[0041] [Mercaptosilane coupling agent-2] In a three-necked glass flask with a reflux condenser, add 100g of mercaptopropylmethyldimethoxysilane coupling agent, 15g of deionized water, 50g of ethanol, and 0.1g of trifluoromethanesulfonic acid. Stir and heat to 60°C for 5h, then cool to room temperature. Add excess sodium carbonate to neutralize the residual trifluoromethanesulfonic acid, filter out the solid sodium carbonate by sedimentation, and remove the ethanol solvent and the generated methanol by rotary evaporation to obtain a multifunctional thiol silane coupling agent-2 with a viscosity of 45mPas.

[0042] [Mercaptosilane coupling agent-3] Add 100g of mercaptopropylmethyldimethoxysilane coupling agent, 10g of deionized water, and 0.5g of dibutyltin dilaurate to a three-necked glass flask with a reflux condenser, stir and heat to 60°C for reaction for 5h, and remove the unreacted water and generated methanol by rotary evaporation to obtain a multifunctional mercaptosilane coupling agent-3 with a viscosity of 90mPas. [Mercaptosilane coupling agent-4] Add 90g of mercaptopropylmethyldimethoxysilane coupling agent, 10g of mercaptopropyltrimethoxysilane coupling agent, 10g of deionized water, and 0.5g of dibutyltin dilaurate to a three-necked glass flask with a reflux condenser, stir and heat to 60°C for reaction for 5h, and remove the unreacted water and generated methanol by rotary evaporation to obtain a multifunctional mercaptosilane coupling agent-4 with a viscosity of 155mPas.

[0043] [Example 1] - [Example 4] The formula is shown in Table 1, and the preparation process is the same. Epoxy resin, thiol silane coupling agent, photobase generator, photosensitizer, etc. are added to a planetary mixer and stirred in vacuum to mix evenly.

[0044] [Comparative Example 1] - [Comparative Example 3] The formulas are shown in Table 1, and the preparation processes are the same.

[0045] The test results of various embodiments and comparative examples are shown in Table 1.

[0046] Table 1

[0047] Example-1 Example-2 Example-3 Example-4 Comparative Example-1 Comparative Example-2 Comparative Example-3 850S 100 100 100 100 830S 100 100 100 Mercaptan silane coupling agent-1 90 Thiol silane coupling agent-2 90 Thiol silane coupling agent-3 90 Thiol silane coupling agent-4 90 PEMP 70 70 TSIC 70 Photobase Generator WPBG-300 2.5 3.0 2.5 3.0 Photobase Generator WPBG-345 3.0 2.0 2.0 ITX 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Fe / Fe shear strength (MPa) <![CDATA[Irradiation dose: 1000 mJ / cm 2 + 60 °C * 20 min]]> 5.5 6.1 6.8 7.1 18.1 25.1 18.3 85℃85%RH*500h 5.5 6.2 6.9 7.4 3.6 14.3 1.5 <![CDATA[Irradiation dose 1000 mJ / cm 2 + 25 °C * 24 h]]> 5.2 5.8 6.2 6.4 15.4 21.2 16.5 85℃85%RH*500h 5.8 5.7 6.6 6.9 2.8 13.4 2.3

[0048] Note: 850S is bisphenol A epoxy resin of China Bluestar International Chemical, 830S is bisphenol F epoxy resin of China Bluestar International Chemical, PEMP is pentaerythritol tetrakis(3-mercaptopropionic acid), TsIC is an isocyanurate type polythiol compound of molecular formula -1, photobase generator WPBG-300 and 345 are commercial products of Wako Pure Chemical Industries, Japan, belonging to tetrakis(3-fluorophenylborate) of organic guanidine, which generates strong base biguanide under light irradiation. ITX is commercially available isopropylthioxanthone.

[0049] Comparing the results of Examples 1 to 4 in Table 1, it can be found that for the multifunctional thiol silane coupling agent synthesized by hydrolysis, the photobase generator and the photosensitizer ITX are irradiated with a high-pressure mercury lamp at 1000 mJ / cm 2After that, it can be cured at room temperature at 25°C, or it can be cured quickly by heating at 60°C*20min. Regardless of whether it is cured at room temperature or heated, the shear strength after high temperature and high humidity will not decrease, and the shear strength of some formulations will increase, which may be due to further cross-linking reactions at high temperatures. The formula of the multi-functional thiol silane coupling agent of the present invention has excellent moisture and heat resistance, which may also be partly due to its alkoxysilane structure and the strong chemical anchoring effect produced by the bonded substrate. Although the initial shear strength of Comparative Examples 1 and 3 is relatively large, the shear strength drops sharply after high temperature and high humidity, indicating that the thiol compound containing an ester bond structure is severely hydrolyzed under high temperature and high humidity conditions, resulting in molecular chain breakage, and it is difficult to be used for applications that require harsh moisture resistance, such as bonding or sealing of electronic and electrical components. The thiol compound of Comparative Example 2 does not contain an ester bond structure, and the shear strength decreases much less after high temperature and high humidity than Comparative Examples 1 and 3 containing an ester bond structure, but there will still be a relatively large decrease. In addition, the cured product is very hard and brittle, which is not conducive to anti-drop experiments.

Claims

1. A multifunctional thiol (mercapto) silane coupling agent, characterized in that: It has the following structure: Wherein, R represents a methyl group or a methoxy group, and n is an integer of 0 to 100.

2. A method for preparing a multifunctional thiol (mercapto) silane coupling agent as claimed in claim 1, characterized in that: The method comprises the steps of hydrolyzing and synthesizing a mercaptopropylmethyldimethoxysilane coupling agent and / or a mercaptopropyltrimethoxysilane coupling agent in the presence of a catalyst.

3. The method according to claim 2, characterized in that The catalyst is selected from any one or more of inorganic acid, organic acid, organotin compound, cation exchange resin, titanate compound, α-silane coupling agent, Lewis acid or Lewis base compound, preferably any one or more of inorganic acid, organic acid and organotin compound.

4. The method according to claim 2, characterized in that The weight ratio of the mercaptopropylmethyldimethoxysilane coupling agent and / or the mercaptopropyltrimethoxysilane coupling agent to the catalyst is 100:0.05-2.

5. A photocurable heat-resistant thiol epoxy resin adhesive, characterized in that: The invention comprises, by weight: 100 parts of epoxy resin, 60-100 parts of the multifunctional thiol (mercapto) silane coupling agent as claimed in claim 1, 0.5-5 parts of photobase generator, and 0.5-5 parts of photosensitizer.

6. The adhesive according to claim 5, characterized in that The epoxy resin is selected from one or a mixture of bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, glycidyl ester epoxy resin, alicyclic epoxy resin, and oxetane, preferably one or two of bisphenol A epoxy resin and bisphenol F epoxy resin.

7. The adhesive according to claim 5, characterized in that The photobase generator is selected from one or more of tetraphenylborate of cobalt ammonia complex, carbamate, ketoxime ester, formamide, quaternary ammonium salt, triphenylmethanol, and triethylamine, tributylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5,7-triazidobicyclo[4.4.0]dec-5-ene (TBD) and organic amine derivatives thereof, preferably tetraphenylborate of organic amine.

8. The adhesive according to claim 5, characterized in that The photosensitizer is selected from any one or more of benzoin and its derivatives, benzil derivatives, dialkoxyacetophenone, α-hydroxyalkyl phenone, α-aminoalkyl phenone, acylphosphine oxide, benzophenone and its derivatives, thioxanthone compounds, anthraquinone compounds, and fluorenone compounds, preferably thioxanthone compounds, and more preferably isopropylthioxanthone ITX.

9. A method for using the adhesive according to any one of claims 5 to 8, characterized in that: After dispensing, the glue is first irradiated with ultraviolet light, then the bonded specimens are aligned and bonded, and then cured.

10. The method of use according to claim 9, characterized in that: The curing mentioned herein refers to heating curing or room temperature curing.

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