Transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, preparation method and application

Abstract

The invention provides a transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, a preparation method and application. The epoxy adhesive composition comprises epoxy resin, an anhydride curing agent, a polyhydroxy compound, a surfactant and a filler. According to the present invention, the preparation method is simple, the raw materials are simple and easily available, and the adhesive has characteristics of high normal temperature bonding strength, high transparency and good yellowing resistance, and is suitable for the field of LED chip mounting solid crystal glue; compared with the prior art, the invention has the following technical effects: 1) the polyhydroxy compound is introduced as an accelerant to promote the curing reaction between the epoxy resin and acid anhydride, the yellowing resistance of a cured product is improved, and the yellowing resistance and the bonding strength of the epoxy glue are considered in a simple way; and 2) the nonionic surfactant is added, so that the normal-temperature activity of the polyhydroxy compound is reduced, and the normal-temperature storage performance of the epoxy glue is improved. And (3) the prepared epoxy glue is high in normal-temperature bonding strength, good in yellowing resistance and high in transparency.

Description

Technical Field

[0001] The present invention relates to the technical field of LED chip die bonding adhesives, and particularly relates to a transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, a preparation method and an application thereof. Background Art

[0002] LED (Light Emitting Diode) has the advantages of high brightness, low heat, low power consumption, small size, high stability, short response time, energy conservation and environmental protection, multi-color light emission, etc., and has become a typical green lighting source, which is widely used in the fields of display and lighting.

[0003] During the packaging process of LEDs, die bonding adhesives are used. The die bonding adhesives mainly play the role of fixing the chips, and at the same time play a certain function of conducting heat and dissipating heat. According to the difference in electrical conductivity, LED die bonding adhesives are divided into two categories: conductive adhesives and insulating adhesives. Chemically, there are two types: epoxy adhesives and silicone adhesives. Compared with the die bonding adhesives of the silicone system, the epoxy die bonding adhesives have strong adhesion, but poor temperature resistance and weather resistance, and are easy to turn yellow, which affects the light emission of LEDs. Although the silicone die bonding adhesives are not easy to turn yellow, their adhesion is very low.

[0004] In summary, how to balance the yellowing resistance and high adhesion of insulating transparent die bonding adhesives is a problem to be solved. In addition, when balancing the yellowing resistance and high adhesion of die bonding adhesives, it is also necessary to pay attention to the pursuit of low cost, more convenient raw material acquisition and the difficulty of the preparation process. Summary of the Invention

[0005] The first object of the present invention is to provide a transparent yellowing-resistant epoxy adhesive composition for LED chip mounting.

[0006] To this end, the above object of the present invention is achieved by the following technical solutions:

[0007] A transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, comprising an epoxy resin, an acid anhydride curing agent, a polyhydroxy compound, a surfactant and a filler;

[0008] The epoxy resin is an alicyclic epoxy resin with a saturated structure, and does not contain carbon-carbon double bonds and benzene rings;

[0009] The acid anhydride curing agent is a colorless transparent liquid acid anhydride, and the mass fraction of the acid anhydride curing agent in the epoxy resin is 70% - 100%;

[0010] The polyhydroxy compound is a mixture composed of a polyol and a liquid polymer containing a polyol hydroxyl structure. The total mass of the polyhydroxy compound accounts for 20% - 30% of the mass of the epoxy resin; the polyhydroxy compound needs to be soluble in the mixed solution of the epoxy resin and the acid anhydride, and the dissolved mixed solution is colorless and transparent;

[0011] The surfactant is a liquid non-ionic surfactant, and the mass fraction of the surfactant in the epoxy resin is 1% to 3%;

[0012] The filler is at least one of silica powder and fumed silica.

[0013] While adopting the above technical solution, the present invention can also adopt or combine the following technical solutions:

[0014] As a preferred technical solution of the present invention: The epoxy resin is a colorless transparent liquid.

[0015] As a preferred technical solution of the present invention: The epoxy resin is an alicyclic epoxy resin. By using a suitable alicyclic epoxy resin, the high-temperature resistance and UV yellowing resistance of the epoxy adhesive can be enhanced, and the requirements for curing agents and other additives can be reduced.

[0016] As a preferred technical solution of the present invention: The anhydride curing agent is at least one of methylhexahydrophthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride, methyltetrahydrophthalic anhydride, benzoic anhydride, pivalic anhydride, and glutaric anhydride.

[0017] As a preferred technical solution of the present invention: The polyhydroxy compound can be dissolved in the epoxy resin at room temperature, and the resulting mixed liquid is colorless and transparent.

[0018] As a preferred technical solution of the present invention: The mass fraction of the polyol in the total polyhydroxy compound is 80% to 95%.

[0019] As a preferred technical solution of the present invention: The polyol is at least one of diethylene glycol, ethylene glycol, 2-propanediol, 1,5-pentanediol, glycerol, triethanolamine, 3-methyl-1,3-butanediol, 1,2-pentanediol, dipropylene glycol, 1,4-butanediol, butanetriol, pentanetriol, and hexanediol.

[0020] As a preferred technical solution of the present invention: The liquid polymer containing a polyol hydroxyl structure is at least one of polyether polyol, polypropylene glycol, liquid polyethylene glycol, and polytetrahydrofuran ether diol.

[0021] The polyhydroxy compound can promote the reaction between the anhydride and the epoxy resin, improve the toughness and yellowing resistance of the cured product, reduce internal stress, and improve reliability.

[0022] As a preferred technical solution of the present invention: The surfactant is at least one of fatty acid glyceride, sorbitan fatty acid ester, polysorbate, low molecular weight polyvinyl alcohol, and fatty alcohol polyoxyethylene ether.

[0023] The second object of the present invention is to provide a preparation method of a transparent yellowing-resistant epoxy adhesive for LED chip mounting.

[0024] For this purpose, the above object of the present invention is achieved by the following technical solutions:

[0025] A preparation method of a transparent yellowing-resistant epoxy adhesive for LED chip mounting includes the following steps:

[0026] Stir the epoxy resin, acid anhydride curing agent, polyhydroxy compound, and surfactant in the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting as described above in proportion, then add the filler in the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting as described above, mix evenly, perform vacuum defoaming treatment (the vacuum degree of defoaming ≤ -0.098 MPa, and the defoaming time is 10 min to 20 min), and discharge to obtain the transparent yellowing-resistant epoxy adhesive for LED chip mounting.

[0027] While adopting the above technical solutions, the present invention can also adopt or combine the following technical solutions:

[0028] As a preferred technical solution of the present invention: the mixing device is a double planetary hybrid stirring kettle.

[0029] The third object of the present invention is to provide a transparent yellowing-resistant epoxy adhesive for LED chip mounting prepared by the preparation method as described above.

[0030] Another object of the present invention is to provide the application of the transparent yellowing-resistant epoxy adhesive for LED chip mounting as described above in LED chip mounting.

[0031] The present invention provides a transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, a preparation method, and an application. The preparation method is simple, and the raw materials are simple and easy to obtain. It has the characteristics of high room temperature shear strength, high room temperature bonding strength, high transparency, and good yellowing resistance. It is suitable for the field of LED chip mounting die bonding glue. Specifically, compared with the prior art, the present invention has the following technical effects:

[0032] 1) Introduce a polyhydroxy compound as an accelerator to promote the curing reaction between the epoxy resin and the acid anhydride, improve the yellowing resistance of the cured product, and balance the yellowing resistance and bonding strength of the epoxy adhesive in a simple way.

[0033] 2) Add a non-ionic surfactant to reduce the room temperature activity of the polyhydroxy compound and improve the room temperature storage performance of the epoxy adhesive.

[0034] 3) The prepared epoxy adhesive has high room temperature bonding strength, good yellowing resistance, and high transparency. Specific embodiments

[0035] A transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, comprising: epoxy resin, acid anhydride curing agent, polyhydroxy compound, surfactant and filler;

[0036] The epoxy resin is an alicyclic epoxy resin without carbon-carbon double bonds and benzene rings; in the present invention, the epoxy resin is preferably S-186 (Hubei Xinjing New Materials), 2021P (Daicel of Japan), etc. well-known to those skilled in the art.

[0037] The acid anhydride curing agent is a colorless transparent liquid acid anhydride, and the mass of the acid anhydride curing agent is 70% - 100% of the epoxy resin; in the present invention, the acid anhydride curing agent is preferably one or more of methylhexahydrophthalic anhydride, 1,2-cyclohexanedicarboxylic anhydride, methyltetrahydrophthalic anhydride, benzoic anhydride, pivalic anhydride, glutaric anhydride well-known to those skilled in the art, and the optional mass parts are 70 parts by mass, 85 parts by mass, 100 parts by mass.

[0038] The polyhydroxy compound is a mixture composed of polyhydric alcohol and a liquid polymer containing a polyol hydroxyl structure. The total mass of the polyhydroxy compound is 20% - 30% of the mass of the epoxy resin, and the polyhydric alcohol is 80% - 95% of the total mass of the polyhydroxy compound.

[0039] The present invention has no special restrictions on the source of the above polyhydric alcohol, and commercially available products or self-made products well-known to those skilled in the art can be used. In the present invention, the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting includes 16 - 28 parts by mass of polyhydric alcohol, and the optional mass parts are 17 parts by mass, 20 parts by mass, 23 parts by mass, 25 parts by mass. It is preferably one or more of diethylene glycol, ethylene glycol, 2-propanediol, 1,5-pentanediol, glycerol, triethanolamine, 3-methyl-1,3-butanediol, 1,2-pentanediol, dipropylene glycol, 1,4-butanediol, butanetriol, pentanetriol, hexanediol well-known to those skilled in the art.

[0040] The present invention has no special restrictions on the source of the liquid polymer containing a plurality of alcohol hydroxyl structures, and commercially available products or self-made products well-known to those skilled in the art can be used. It is preferably one or more of polyether polyol, polypropylene glycol, liquid polyethylene glycol, polytetrahydrofuran ether glycol, such as PTMG2000, DL-1000D, PPG-3000. In the present invention, the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting includes 1 - 5 parts by mass of the polymer containing a polyhydroxy structure, and the optional mass parts are 1 part by mass, 3 parts by mass, 5 parts by mass.

[0041] The surfactant is a liquid non-ionic surfactant, and the mass fraction of the surfactant in the epoxy resin is 1% - 3%;

[0042] The present invention has no special restrictions on the source of the above-mentioned surfactants, and commercially available products or self-made products well-known to those skilled in the art can be used. One or several of fatty acid glycerides, sorbitan fatty acids, polysorbates, low molecular weight polyvinyl alcohol, and fatty alcohol polyoxyethylene ethers are preferred, such as Tween 40 and Tween 80.

[0043] The filler is at least one of silica powder and fumed silica.

[0044] The present invention has no special restrictions on the sources of the above-mentioned silica powder and fumed silica, and commercially available products well-known to those skilled in the art can be used, such as TS-720 from Cabot in the United States and SO-C5 from ADMATECHS Co., Ltd. in Japan.

[0045] The present invention uses an alicyclic epoxy resin as the main resin, a polyhydroxy compound to promote the reaction of the acid anhydride with the epoxy resin, a surfactant to reduce the change in viscosity at room temperature, and fumed silica as the main filler to prepare a colorless and transparent epoxy adhesive for LED chip mounting, taking into account the yellowing resistance, storage stability, and room temperature bonding strength. The implementation method is simple, and the raw materials are easy to obtain and the preparation process is easy.

[0046] The present invention also provides a method for preparing a transparent yellowing-resistant epoxy adhesive for LED chip mounting, which includes the following steps:

[0047] Stir the epoxy resin, acid anhydride curing agent, polyhydroxy compound, and surfactant in the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting as described above in proportion, then add the filler in the transparent yellowing-resistant epoxy adhesive composition for LED chip mounting as described above, mix evenly, and perform vacuum degassing treatment (the vacuum degree for degassing is ≤ -0.098 MPa, and the degassing time is 10 min to 20 min), and discharge to obtain the transparent yellowing-resistant epoxy adhesive for LED chip mounting.

[0048] The mixing equipment is a double planetary hybrid stirring kettle.

[0049] The preparation method provided by the present invention has a simple process, mild and easy-to-control conditions, and good process adaptability.

[0050] To further illustrate the present invention, the following examples are used for detailed description.

[0051] I. Experimental part

[0052] The basic information of the raw materials used in the following examples and comparative examples of the present invention is shown in Table 1.

[0053] Table 1 Basic information of the raw materials used in the examples and comparative examples

[0054]

[0055]

[0056] Examples 1 - 6 and Comparative Examples 1 - 4

[0057] (1) Raw material dosage:

[0058] The raw material dosages of Examples 1 - 6 and Comparative Examples 1 - 4 are shown in Table 2. In the following table, all are in parts by mass.

[0059] Table 2 Raw material dosages of Examples 1 - 6 and Comparative Examples 1 - 4

[0060]

[0061] (2) Preparation method (taking Example 1 as an example):

[0062] Weigh 100 g of epoxy resin S - 186, 70 g of anhydride curing agent methylhexahydrophthalic anhydride, 20 g of polyol diethylene glycol, 3 g of polyhydroxy polymer DL - 1000D, and 2 g of surfactant Tween 80 according to the ratio, stir evenly until it is uniformly clear and transparent, then add 5 g of filler TS720 and stir evenly to obtain a semi - finished epoxy adhesive. Stir and degas at a vacuum degree ≤ - 0.098 MPa for 20 min, and then discharge at normal pressure to obtain a colorless and transparent epoxy adhesive for LED chip mounting.

[0063] II. Testing part

[0064] (1) Performance characterization and testing methods:

[0065] Chip thrust: The testing method refers to "HG / T 5912 - 2021 Conductive Adhesives". The silicon wafer size is: 2 mm × 2 mm; the substrate is a silver - plated copper sheet, and the curing condition is 175 °C × 1.0 h in a forced - air oven; the testing equipment is a DAGE - 4000P multi - functional push - pull force tester, manufactured by Nordson DAGE Precision Industries LTD, USA. The thrust unit is kgF; the number of test samples is 10, and the average value is taken. For each type of adhesive, 10 samples are taken and the average value is taken. When measuring the high - temperature thrust, after the temperature - controlled heating stage reaches the target temperature and stabilizes for 5 min, the test is carried out.

[0066] Light transmittance: The sample is optically tested using a UV - visible spectrophotometer Cary 5000. The sample thickness is 2 mm, the scanning range is 400 - 800 nm, and the resolution is 1 nm.

[0067] Viscosity: The viscosity value is tested using a Brookfield rotational viscometer. The viscometer rotor is 51#, the rotation speed is 5 rpm, and the test temperature is 25 °C; after the sample is placed at room temperature of 25 °C for 24 h, the viscosity value is tested using the same method.

[0068] High temperature and UV yellowing: After the sample is cured, it is further heated in an oven at 175°C for 24 hours, and then placed in a UV aging chamber for 7 days. The sample is observed with the naked eye to see if it turns yellow.

[0069] (2) Test results

[0070] The performance and test results are shown in Table 3 below.

[0071] Table 3 Performance test results of Examples 1-6 and Comparative Examples 1-4

[0072]

[0073] III. Analysis of experimental results

[0074] Compared with Example 1, in Comparative Example 1, other components are the same, and the mass fraction of the anhydride curing agent is reduced from 70 parts to 40 parts. The bonding strength at room temperature and high temperature drops sharply (the strength drops by more than 60%), it turns yellow after the action of high temperature and UV, and the yellowing resistance performance deteriorates.

[0075] Compared with Example 2, in Comparative Example 2, the added polyhydroxy compound is mainly a polyol hydroxyl liquid polymer. The bonding strength at room temperature and high temperature decreases (the strength drops by 40%), the viscosity change at room temperature for 24 hours exceeds 30%, the light transmittance drops by about 10%, and it turns yellow after the action of high temperature and UV.

[0076] Compared with Example 2, in Comparative Example 3, no surfactant is added. The viscosity change at room temperature for 24 hours increases from 12% to 41%. Adding a certain amount of surfactant can reduce the viscosity change at room temperature and improve the sizing stability.

[0077] Compared with Example 2, in Comparative Example 4, no polyhydroxy compound is added. It still does not cure after heating at 175°C for 1.0 h, and the chip thrust and light transmittance cannot be measured. The polyhydroxy compound has a promoting effect on curing.

[0078] Referring to the changing trend of the chip thrust of Examples 1, 2, and 3, as the addition amount of the anhydride curing agent increases, the bonding force gradually increases. However, in the process of increasing the anhydride curing agent from 70 parts to 100 parts, the bonding force at room temperature only increases by about 1 kgF, while other properties remain almost unchanged.

[0079] Compared with Examples 4, 5, and 6, in the polyhydroxy compound, the proportion of polyol in the total amount of polyhydroxy compounds gradually decreases (the mass ratio of polyol is more than 80% in all cases). The chip thrust and light transmittance gradually decrease, but the cured product still remains colorless and transparent.

[0080] In summary, the colorless and transparent epoxy adhesive for LED chip mounting provided by the present invention has the following beneficial effects:

[0081] (1) Excellent working performance; the viscosity change does not exceed 20% after standing at room temperature for 24 hours;

[0082] (2) High shear strength at room temperature; manifested as the shear strength at 25°C: the thrust of a 2mm×2mm chip is greater than 8.0 kgF;

[0083] (3) The cured product has high light transmittance, good high-temperature resistance and UV yellowing resistance.

[0084] The above specific embodiments are used to explain the present invention, which are only the preferred embodiments of the present invention, rather than limiting the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and scope of the claims of the present invention fall within the protection scope of the present invention.

Claims

1. A transparent yellowing-resistant epoxy adhesive composition for LED chip mounting, characterized in that: Including epoxy resin, anhydride curing agent, polyol, surfactant and filler; The epoxy resin is an alicyclic epoxy resin; The acid anhydride curing agent is a colorless transparent liquid acid anhydride, and the mass fraction of the acid anhydride curing agent in the epoxy resin is 70% to 100%; The polyhydroxy compound is a mixture of polyols and liquid polymers containing polyol hydroxyl structures, and the total mass of the polyhydroxy compound accounts for 20% to 30% of the mass fraction of the epoxy resin; The surfactant is a liquid nonionic surfactant, and the mass fraction of the surfactant in the epoxy resin is 1% to 3%; The filler is at least one of silicon micropowder and fumed silica.

2. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1, characterized in that: The epoxy resin is a colorless transparent liquid.

3. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1, characterized in that: The polyhydroxy compound is miscible with the epoxy resin at room temperature to form a colorless transparent liquid.

4. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1, characterized in that: The mass fraction of the polyol in the total polyhydroxy compounds is 80% to 95%.

5. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1 or 4, characterized in that: The polyol is at least one of diethylene glycol, ethylene glycol, 2-propylene glycol, 1,5-pentanediol, glycerol, triethanolamine, 3-methyl-1,3-butanediol, 1,2-pentanediol, dipropylene glycol, 1,4-butanediol, butanetriol, pentanetriol, and hexanediol.

6. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1, characterized in that: The liquid polymer containing a polyol hydroxyl structure is at least one of polyether polyol, polypropylene glycol, liquid polyethylene glycol, and polytetramethylene glycol.

7. The transparent yellowing-resistant epoxy adhesive composition for LED chip mounting according to claim 1, characterized in that: The surfactant is at least one of fatty acid glyceride, fatty acid sorbitan, polysorbate, low molecular weight polyvinyl alcohol, and fatty alcohol polyoxyethylene ether.

8. A method for preparing a transparent yellowing-resistant epoxy adhesive for LED chip mounting, characterized in that: The steps include: The epoxy resin, anhydride curing agent, polyhydroxy compound and surfactant in the transparent anti-yellowing epoxy adhesive composition for LED chip mounting as claimed in claim 1 are mixed evenly according to a proportion, and then the filler in the transparent anti-yellowing epoxy adhesive composition for LED chip mounting as claimed in claim 1 is added, mixed evenly, vacuumed and degassed, and the transparent anti-yellowing epoxy adhesive for LED chip mounting is obtained; The vacuum degree of degassing is ≤-0.098MPa, and the degassing time is 10min~20min.

9. The transparent yellowing-resistant epoxy adhesive for LED chip mounting prepared by the preparation method according to claim 8.

10. Use of the transparent yellowing-resistant epoxy adhesive for LED chip mounting according to claim 9 in LED chip mounting.

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