Large-depth photocuring epoxy adhesive and preparation method thereof

Abstract

The invention relates to the technical field of epoxy adhesives, in particular to a great-depth photocuring epoxy adhesive and a preparation method thereof.The great-depth photocuring epoxy adhesive is at least prepared from, by weight, 15-25 parts of epoxy resin, 5-10 parts of reactive diluent, 0.2-2 parts of cationic photoinitiator, 1-3 parts of coupling agent, 3-6 parts of thixotropic agent and 60-70 parts of filler. The product overcomes the problem that the existing photocuring epoxy adhesive cannot realize large curing depth under the condition of filling a large amount of filler, meets the requirements of BGA device edge fixing glue on high bonding strength and high reliability, and has higher market application value.

Description

Technical Field

[0001] The invention relates to the technical field of epoxy adhesives, in particular to a large-depth light-curing epoxy adhesive and a preparation method thereof. Background Art

[0002] Traditional ball grid array (BGA) device packaging uses bottom filler to protect solder joints to achieve good reliability. However, as the size of chips increases, the shrinkage of traditional underfill during the curing process may cause stress concentration between BGA solder joints and the substrate, resulting in welding failure and service life that does not meet expectations. In addition, the underfill has compatibility issues with solder paste residue during the curing process, making traditional underfill no longer suitable for large chip packaging.

[0003] At present, the packaging solution for large chips includes edge fixing glue, which refers to applying "L"-shaped glue strips on the four corners of the edge of the chip to bond the chip and the substrate. After curing, the edge fixing effect is achieved, thereby protecting the solder joints at the bottom of the chip and improving product reliability.

[0004] The existing BGA device edge fixing glue is mostly heat-curing epoxy adhesive and light-curing epoxy adhesive. Heat-curing epoxy adhesive has a long curing time and requires additional heating equipment, which is costly, energy-intensive and inefficient. However, light-curing epoxy adhesive has the characteristics of fast curing speed and low shrinkage, which shortens the curing time from tens of minutes to tens of seconds or even seconds, greatly improving production efficiency. Most of the traditional light-curing adhesives are acrylic resin systems, but there are two problems that cannot be completely solved: 1. The oxygen inhibition phenomenon is serious; 2. The curing shrinkage rate of the system is large, usually greater than 5%, and some even exceed 10%; ultimately resulting in low bonding strength, internal stress concentration, and poor reliability testing. The dual-stage bottom filling glue for chips disclosed in the Chinese patent (authorization announcement number CN1946795B) introduces epoxy resin into the light-curing acrylate system to ensure the stability of the subsequently obtained integrated circuit chips at ambient temperature.

[0005] However, after the edge fixing glue is cured, it is necessary to match the thermal expansion coefficient (CTE, including CTE1 and CTE2) of the chip and the circuit board. Therefore, the general requirement for the CTE1 of the glue is less than 30ppm / K. In this way, a large amount of inorganic fillers need to be added to the adhesive to reduce the CTE of the product. However, with the addition of fillers, the light transmittance of the adhesive deteriorates, so that the bottom of the glue cannot be completely cured or even not cured. After curing, the bonding strength of the glue is very poor and cannot meet the reliability requirements of BGA devices. At present, most of the light-curing epoxy adhesives on the market use phosphates or antimonates as photoinitiators, and the curing depth is generally low, which cannot meet customers' needs for deep curing. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a large-depth photocuring epoxy adhesive, which overcomes the problem that existing photocuring epoxy adhesives cannot achieve a large curing depth when a large amount of fillers are filled, meets the requirements of BGA device edge fixing glue for high bonding strength and high reliability, and has high market application value.

[0007] On one hand, the present invention provides a deep-depth photocuring epoxy adhesive, which comprises at least the following raw materials by weight: 15-25 parts of epoxy resin, 5-10 parts of active diluent, 0.2-2 parts of cationic photoinitiator, 1-3 parts of coupling agent, 3-6 parts of thixotropic agent and 60-70 parts of filler.

[0008] As a preferred technical solution, the cationic photoinitiator is selected from onium salts.

[0009] Preferably, the onium salt is thionium phosphate, model number is CPI-210S, and is sourced from Sanyo Chemical.

[0010] As a preferred technical solution, the epoxy resin includes at least one of alicyclic epoxy resin, bisphenol A epoxy resin or bisphenol F epoxy resin.

[0011] Preferably, the epoxy resin is a combination of alicyclic epoxy resin and bisphenol A epoxy resin or bisphenol F epoxy resin.

[0012] Preferably, the mass ratio of the alicyclic epoxy resin to the bisphenol A epoxy resin or bisphenol F epoxy resin is (12-18):(4-10).

[0013] As a preferred technical solution, the alicyclic epoxy resin is 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexylcarboxylate, with a CAS number of 2386-87-0, and commercially available brands include Daicel CELLOXIDE 2021P or Tytel TTA21.

[0014] As a preferred technical solution, the bisphenol A epoxy resin has an epoxy equivalent of 170-200 g / eq and a viscosity of 10000-20000 mPa·s at 25°C.

[0015] Preferably, the bisphenol A epoxy resin has an epoxy equivalent of 180-200 g / eq and a viscosity of 10000-15000 mPa·s at 25° C. The commercially available brands include at least one of Nan Ya NPEL-128, Dow DER-331, Shell 828EL or DIC 850.

[0016] As a preferred technical solution, the bisphenol F epoxy resin has an epoxy equivalent of 150-190 g / eq and a viscosity of 10000-15000 mPa·s at 25°C.

[0017] Preferably, the bisphenol F epoxy resin has an epoxy equivalent of 160-185 g / eq and a viscosity of 2000-6000 mPa·s at 25° C. The commercially available brands include at least one of Nan Ya NPEF-170, Dow DER-354 or DIC830.

[0018] As a preferred technical solution, the active diluent includes at least an oxetane monomer, and the commercially available brands include at least one of East Asia Synthesis OTX-101, East Asia Synthesis OXT-221, Changzhou Qiangli Electronics TCM-201, Changzhou Qiangli Electronics TCM-207, Hubei Gurun OXT-1 or Hubei Gurun OXT-3.

[0019] As a preferred technical solution, the coupling agent includes at least an epoxysilane coupling agent, and the epoxysilane coupling agent is preferably at least one of γ-glycidyloxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexane)ethyltrimethoxysilane, and commercially available brands include Shin-Etsu KBM-403 or Maitu A-186.

[0020] As a preferred technical solution, the thixotropic agent is fumed silica.

[0021] Preferably, the BET specific surface area of ​​the fumed silica is 80-120 m 2 / g.

[0022] As a preferred technical solution, the filler is silicon powder.

[0023] The photocurable epoxy adhesive system provided by the present invention overcomes the problems of low bonding strength and low reliability of the adhesive product when the filler addition amount is ≥60wt% by optimizing the alicyclic epoxy resin and bisphenol A epoxy resin or bisphenol F epoxy resin in the system in combination with oxetane monomers, and in the presence of a sulfonium phosphate photoinitiator, the curing depth of the product can reach more than 5mm.

[0024] The photocurable epoxy adhesive system provided by the present invention overcomes the problems of severe oxygen inhibition and large curing shrinkage in the existing acrylic photocurable adhesive system, and is suitable for packaging of large chips.

[0025] The light-curing epoxy adhesive provided by the present invention has low requirements on curing conditions, fast curing speed, high reaction degree, no need to add additional heating equipment, low cost, low energy consumption, high efficiency, and better meets practical application needs.

[0026] Another aspect of the present invention provides a method for preparing a deep-depth photocurable epoxy adhesive, comprising at least the following steps:

[0027] (1) premixing an epoxy resin, a reactive diluent, a cationic photoinitiator, and a coupling agent; adding a thixotropic agent and a filler and continuing to mix to obtain an epoxy adhesive mixture;

[0028] (2) The epoxy adhesive mixture is ground, dispersed, homogenized, degassed, and filtered to obtain a deep-depth light-curing epoxy adhesive.

[0029] As a preferred technical solution, the premixing speed is 500-800 rpm and the time is 3-8 min.

[0030] As a preferred technical solution, the rotation speed of the continued mixing is 500-800 rpm and the time is 3-5 min.

[0031] As a preferred technical solution, the speed of the homogenizing and degassing is 500-800 rpm, and the vacuum pressure is -0.1 MPa.

[0032] As a preferred technical solution, the grinding and dispersing equipment is a three-roller mill, and the fineness after grinding and dispersing is ≤10 μm.

[0033] As a preferred technical solution, the grinding and dispersing includes: using a three-roller machine to grind and disperse the epoxy adhesive mixture three times, the first grinding gap is 40-20 (feed gap 40μm, discharge gap is 20μm), and the speed is 200-500rpm; the second grinding gap is 20-10 (feed gap 20μm, discharge gap is 10μm), and the speed is 200-500rpm; the third grinding gap is 20-10 (feed gap 20μm, discharge gap is 10μm), and the speed is 200-500rpm.

[0034] As a preferred technical solution, the filtering equipment is a sieve, and the aperture of the sieve is 200 meshes.

[0035] The entire preparation process of the deep-depth light-curing epoxy adhesive provided by the present invention is carried out under a yellow light lamp to avoid light-induced reaction, and the finished product must be stored away from light.

[0036] The adhesive provided by the present invention ensures the dispersion effect of high-added amount of fillers and other powders in the resin system by optimizing the grinding and dispersing process, thereby ensuring the bonding performance of the product.

[0037] Beneficial Effects

[0038] 1. The present invention provides a large-depth photocuring epoxy adhesive, which overcomes the problem that the existing photocuring epoxy adhesive cannot achieve a large curing depth when a large amount of fillers are filled, meets the requirements of BGA device edge fixing glue for high bonding strength and high reliability, and has a high market application value.

[0039] 2. The photocurable epoxy adhesive system provided by the present invention overcomes the problems of low bonding strength and low reliability of the adhesive product when the filler addition amount is ≥60wt% by optimizing the alicyclic epoxy resin and bisphenol A epoxy resin or bisphenol F epoxy resin in the system in combination with oxetane monomer, and in the presence of a sulfonium phosphate photoinitiator, the product curing depth can reach more than 5mm.

[0040] 3. The photocurable epoxy adhesive system provided by the present invention overcomes the problems of severe oxygen inhibition and large curing shrinkage in the existing acrylic photocurable adhesive system, and is suitable for packaging of large chips.

[0041] 4. The curing conditions of the light-curing epoxy adhesive provided by the present invention are not high, the curing speed is fast, the reaction degree is high, no additional heating equipment is required, the cost is low, the energy consumption is low, the efficiency is high, and it can better meet the actual application needs.

[0042] 5. The adhesive provided by the present invention ensures the dispersion effect of high-added fillers and other powders in the resin system by optimizing the grinding and dispersion process, thereby ensuring the bonding performance of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram of the grinding gap in Example 1, where 1 is the feed gap and 2 is the discharge gap. DETAILED DESCRIPTION

[0044] Examples 1-9

[0045] On the one hand, Examples 1-9 of the present invention provide a deep-depth photocuring epoxy adhesive, and the formula is shown in Table 1 in parts by weight.

[0046] Table 1

[0047]

[0048] On the other hand, embodiments 1-9 of the present invention provide a method for preparing a deep-depth photocurable epoxy adhesive, comprising the following steps:

[0049] (1) premixing epoxy resin, reactive diluent, cationic photoinitiator, and coupling agent using a planetary homogenizer; adding thixotropic agent and filler and continuing to mix to obtain an epoxy adhesive mixture;

[0050] (2) The epoxy adhesive mixture is ground, dispersed, homogenized, degassed, and filtered to obtain a deep-depth light-curing epoxy adhesive.

[0051] The rotation speed of the premixing is 600 rpm, and the time is 5 min. The rotation speed of the continued mixing is 600 rpm, and the time is 5 min.

[0052] The speed of the homogenization degassing is 600 rpm, and the vacuum pressure is -0.1 MPa.

[0053] The grinding and dispersing comprises: grinding and dispersing the epoxy adhesive mixture three times with a three-roller machine, wherein the first grinding gap is 40-20 (the feeding gap is 40 μm, and the discharging gap is 20 μm), and the speed is 300 rpm; the second grinding gap is 20-10 (the feeding gap is 20 μm, and the discharging gap is 10 μm), and the speed is 300 rpm; and the third grinding gap is 20-10 (the feeding gap is 20 μm, and the discharging gap is 10 μm), and the speed is 300 rpm.

[0054] Grinding gap diagram Figure 1 , Figure 1 The feed gap 1 is 40 μm and the discharge gap 2 is 20 μm.

[0055] The filtering device is a sieve, and the aperture of the sieve is 200 meshes.

[0056] The entire preparation process of the deep-depth light-curing epoxy adhesive provided by the present invention is carried out under a yellow light lamp to avoid light-induced reaction, and the finished product must be stored away from light.

[0057] Performance Testing

[0058] 1. The deep-depth photocurable epoxy adhesive product provided in Examples 1-9 is used for bonding between FR4-FR4 (epoxy glass cloth laminate-epoxy glass cloth laminate) and Glass-PCB (glass-PCB). 2 The film was irradiated under an LED light and cured for 40 seconds. The thickness of the adhesive layer was 0.2 mm. The tensile shear strength was tested after 2 hours (refer to GBT_7124-2008). The test results are shown in Table 2.

[0059] 2. Fill the deep-depth photocurable epoxy adhesive product provided in Examples 1-9 into a 10 mm deep mold and heat it at 1000 mW / cm 2 The parts were irradiated under an LED light and cured for 40 seconds. After 2 hours, the cured parts were dug out and the curing depth was tested. The test results are shown in Table 2.

[0060] Table 2

[0061]

[0062]

Claims

1. A deep-depth light-curing epoxy adhesive, characterized in that: Calculated by weight, it at least includes the following raw materials: 15-25 parts of epoxy resin, 5-10 parts of active diluent, 0.2-2 parts of cationic photoinitiator, 1-3 parts of coupling agent, 3-6 parts of thixotropic agent and 60-70 parts of filler.

2. The deep depth light curing epoxy adhesive according to claim 1, characterized in that: The cationic photoinitiator is selected from onium salts.

3. The deep depth light curing epoxy adhesive according to claim 1, characterized in that: The epoxy resin includes at least one of alicyclic epoxy resin, bisphenol A epoxy resin or bisphenol F epoxy resin.

4. The deep depth light curing epoxy adhesive according to claim 3, characterized in that: The bisphenol A epoxy resin has an epoxy equivalent of 170-200 g / eq and a viscosity of 10000-20000 mPa·s at 25° C.

5. The deep depth light curing epoxy adhesive according to claim 3, characterized in that: The bisphenol F epoxy resin has an epoxy equivalent of 150-190 g / eq and a viscosity of 10000-15000 mPa·s at 25° C.

6. The deep depth light curing epoxy adhesive according to claim 1, characterized in that: The reactive diluent includes at least an oxetane monomer.

7. The deep depth light-curing epoxy adhesive according to claim 1, characterized in that: The coupling agent at least includes an epoxy silane coupling agent.

8. A method for preparing a deep depth light-curing epoxy adhesive according to any one of claims 1 to 7, characterized in that: At least the following steps are included: (1) premixing an epoxy resin, a reactive diluent, a cationic photoinitiator, and a coupling agent; adding a thixotropic agent and a filler and continuing to mix to obtain an epoxy adhesive mixture; (2) The epoxy adhesive mixture is ground, dispersed, homogenized, degassed, and filtered to obtain a deep-depth light-curing epoxy adhesive.

9. The method for preparing a deep-depth light-curing epoxy adhesive according to claim 8, characterized in that: The rotation speed of the premixing is 500-800 rpm, and the time is 3-8 min; the rotation speed of the continued mixing is 500-800 rpm, and the time is 3-5 min.

10. The method for preparing a deep-depth light-curing epoxy adhesive according to claim 8, characterized in that: The grinding and dispersing equipment is a three-roller mill, and the fineness after grinding and dispersing is ≤10 μm.

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