Self-synthesized DA-structure epoxy resin, underfill adhesive and preparation method thereof

Abstract

The present invention provides a self-synthesized DA-structure epoxy resin, an underfill adhesive and a preparation method thereof. The underfill adhesive comprises the following components in parts by mass: 1 to 10 parts of the self-synthesized DA-structure epoxy resin, 10 to 30 parts of a liquid epoxy resin, 55 to 80 parts of a filler, 10 to 20 parts of a curing agent, 0.5 to 5 parts of a coupling agent and 0.1 to 5 parts of an auxiliary agent. The underfill adhesive product prepared from the self-synthesized DA-structure epoxy resin has better resistance to thermal shock, enabling the glue to have high reliability and self-healing function. Moreover, the preparation method is simple and has good feasibility, being suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the technical field of materials, and particularly to a self-synthesized DA-structured epoxy resin, an underfill adhesive, and a preparation method thereof. Background Art

[0002] Chip-level underfill adhesives are widely used as advanced packaging materials in chip-scale packaging (CSP) and ball grid array packaging (BGA). The glue is filled between the chip and the substrate to disperse the solder ball stress and reduce the difference in thermal expansion coefficients. With the high performance and intelligence of 3C electronics, the number of chips covered in electronic devices is increasing, the chip size used is getting larger, and the solder ball pitch is getting smaller, which puts higher reliability requirements on the underfill adhesive materials, especially the anti-cracking and anti-thermal shock performance.

[0003] Optimizing the performance of the glue is generally carried out by optimizing the molecular structure or adding a small amount of additives. On the one hand, more rigid benzene ring structures or flexible chain segments are used to balance the rigidity and toughness of the material, which helps to improve the impact resistance of the material. However, due to the use of a large amount of high molecular weight resin materials, the process performance is often difficult to balance, and the molding is relatively difficult. On the other hand, the material performance is improved by addition type, such as toughening agents (such as rubber particles and core-shell structures), antioxidants (such as hindered phenol antioxidants), etc. However, the addition type often brings compatibility problems to the product, and the industrial scale-up and large-scale use are restricted. Summary of the Invention

[0004] Aiming at the above deficiencies of the prior art, the present invention provides a self-synthesized DA-structured epoxy resin, an underfill adhesive, and a preparation method thereof, so that when applied to large-size chip devices, the glue has excellent impact resistance and anti-cracking performance.

[0005] To achieve the above object, the technical scheme adopted by the present invention is as follows:

[0006] In the first aspect of the present invention, a self-synthesized DA-structured epoxy resin is provided, and the structural formula of the self-synthesized DA-structured epoxy resin is:

[0007]

[0008] In the formula, R is one or more of an alkyl group, a sulfur group, benzene, biphenyl, polyether, and polyol. Further, R preferably has a diphenyl ether structure formed by combining a rigid benzene ring structure and a flexible ether bond structure. The beneficial effect of adopting the further scheme is that the rigid benzene ring can be connected by an ether bond to achieve a certain degree of free rotation, and the molecular structure has both rigidity and toughness, thereby improving the anti-cracking performance of the material under thermal shock.

[0009] The second aspect of the present invention provides a preparation method of self-synthesized DA-structured epoxy resin, which includes the following steps: Mix a compound with a bismaleimide structure and a toluene solvent, and heat it to 60°C to 120°C under nitrogen protection for dissolution to obtain a homogeneous solution after dissolution; then, while stirring the homogeneous solution, dropwise add glycidyl furfuryl ether, and control the temperature at 80°C for reaction for 24 h; after the reaction is completed, cool it, distill off the solvent under reduced pressure, and after vacuum drying, obtain the self-synthesized DA-structured epoxy resin.

[0010] Further, the compound with a bismaleimide structure is one of 4,4'-diphenyl ether dimaleimide, 1,2,3-bis(maleimide)heptanediol, and N,N'-(1,4-phenylene)bismaleimide; the toluene solvent is toluene or xylene.

[0011] The third aspect of the present invention provides an underfill adhesive with both high reliability and self-healing function, which includes the following components in parts by mass: 1 to 10 parts of the self-synthesized DA-structured epoxy resin as described above, 10 to 30 parts of liquid epoxy resin, 55 to 80 parts of filler, 10 to 20 parts of curing agent, 0.5 to 5 parts of coupling agent, and 0.1 to 5 parts of auxiliary agent.

[0012] Further, the liquid epoxy resin is one or more of liquid bisphenol A, bisphenol F, aminophenol-type epoxy resin, glycidyl-type epoxy resin, and naphthalene-type epoxy resin, and the molecular weight of the liquid epoxy resin is below 500. Further, the liquid epoxy resin is preferably composed of one or any combination of low-viscosity bisphenol resin and heat-resistant benzene ring resin.

[0013] Further, the filler is spherical silica, and the particle size distribution range of the spherical silica is between 0.01 and 20 microns. Further, the filler particle size is preferably composed of a graded combination of small-size 10 to 500 nm filler and large-size 1 to 20 µm filler. The beneficial effect of adopting the further scheme is that the compounding of large and small ball fillers can improve the flow of the underfill adhesive and prevent the settlement of the filler.

[0014] Further, the curing agent is one or more of amine curing agents, phenolic curing agents, anhydride curing agents, and imidazole curing agents. Further, the preferred curing agent is a benzene ring structure amine curing agent with low moisture absorption and low stress.

[0015] Further, the coupling agent is one or more of epoxy groups, amino groups, mercapto groups, and vinyl groups. Further, the preferred coupling agent is an epoxy coupling agent containing active groups. The beneficial effect of adopting the further scheme is that the epoxy coupling agent has good compatibility with the resin system, can reduce the viscosity of the system, improve the flow, and achieve the rapid filling of large-size chips.

[0016] Further, the auxiliary agent is one or more of an antifoaming agent, a diluent, a leveling agent, an antioxidant, and a color paste.

[0017] The fourth aspect of the present invention provides a preparation method of the underfill adhesive with both high reliability and self-healing function as described above, including the following steps: sequentially adding the self-synthesized DA-structure epoxy resin, liquid epoxy resin, coupling agent, and auxiliary agent into a reaction kettle, and stirring evenly for 0.5 h to 1 h; after the above materials are premixed evenly, adding the filler into the reaction kettle in batches and dispersing it intensively for 1 h; after the filler is dispersed evenly, adding the curing agent and stirring for 0.5 h to 1 h to obtain the underfill adhesive.

[0018] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0019] 1. The self-synthesized DA-structure epoxy resin selects a benzene ring as the rigid backbone to improve the heat resistance and rigidity of the material. At the same time, an ether bond is preferably used to connect the benzene rings in the molecular design, enabling the benzene rings to rotate freely to a certain extent, improving the toughness of the material, and thus improving the high and low temperature cycle resistance and anti-cracking performance of the material itself under thermal shock.

[0020] 2. The self-synthesized DA-structure epoxy resin introduces a Diels-Alder group, and realizes the reversible reaction of the polymer material itself through intrinsic self-healing and molecular diffusion; the introduction of the DA structure is a cycloaddition reaction of a conjugated diene reactant (bismaleimide structure compound) and an active double bond reactant (glycidyl furfuryl ether), and the reaction mechanism diagram of the DA structure self-healing is as Figure 3 shown; this DA structure can realize the reversible chemical reaction of DA and r-DA at a relatively high temperature, realizing crosslinking self-healing, and further realizing the high reliability of the device.

[0021] Therefore, the molecular structure design and the specific DA structure enable the underfill adhesive product provided by the present invention with both high reliability and self-healing function to have better resistance to thermal shock, making the glue have high reliability and self-healing function. And the preparation method is simple, has good feasibility, and is suitable for industrial production. Description of the Drawings

[0022] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not limit the embodiments. Unless otherwise stated, the drawings in the figures do not constitute a proportional limitation.

[0023] Figure 1 It is the synthesis reaction route diagram of the self-synthesized DA-structure epoxy resin;

[0024] Figure 2Synthesis route diagram of epoxy resin with DA structure;

[0025] Figure 3 Reaction mechanism diagram of self-healing of DA structure;

[0026] Figure 4 Optical microscope image of typical crack of Comparative Example 1. Detailed implementation manners

[0027] The inventors found that during the use of electronic devices, individual chips fail. If the entire main board is replaced, the cost is very high. Therefore, it is necessary to repair the failed chips, which requires the glue to have a certain repair function or a certain self-healing ability. At present, epoxy adhesives with repair functions in the industry mainly focus on some PCB board-level underfills. These board-level underfill glues are generally low-temperature cured and have a low Tg point. Therefore, the performance of the glue is poor and the reliability is average. They are suitable for board-level packaging structures with relatively macroscopic structural dimensions and not strict performance requirements. In view of the high-reliability requirements of underfill glue for chip-level applications, the purpose of the present invention is to provide a chip-level bottom filling glue with both high reliability and self-healing function and a preparation method thereof. Epoxy resin with optimized molecular structure design is introduced to achieve high strength and high toughness of the bottom filling glue, and the specific DA structure in the resin can achieve thermoreversible covalent bond self-healing to repair fine cracks, meeting the anti-cracking and anti-thermal shock application requirements of the bottom filling glue under large-size chips.

[0028] The first aspect of the present invention provides a self-synthesized epoxy resin with DA structure, and the structural formula of the self-synthesized epoxy resin with DA structure is:

[0029]

[0030] In the formula, R is one or more of alkyl, sulfhydryl, benzene, biphenyl, polyether, and polyol. Further, R preferably has a diphenyl ether structure combining a rigid benzene ring structure and a flexible ether bond structure. The beneficial effect of adopting the further scheme is that the rigid benzene ring connected by an ether bond can achieve a certain degree of free rotation, and the molecular structure has both rigidity and toughness, thereby improving the anti-cracking performance of the material under thermal shock.

[0031] The second aspect of the present invention provides a preparation method of the self-synthesized epoxy resin with DA structure, as Figure 1 shown, including the following steps: Mix a compound with a bismaleimide structure and a toluene solvent, and heat it to 60°C to 120°C under nitrogen protection for dissolution to obtain a homogeneous solution after dissolution; then dropwise add glycidyl furfuryl ether to the homogeneous solution while stirring, and control the temperature at 80°C for reaction for 24 h; after the reaction is completed, cool it, and remove the solvent by reduced pressure distillation. After vacuum drying, the self-synthesized epoxy resin with DA structure is obtained. Among them, the preferred synthesis route diagram of the self-synthesized epoxy resin with DA structure is asFigure 2 as shown

[0032] The third aspect of the present invention provides a underfill adhesive with both high reliability and self-healing function, including the following components by mass: 1-10 parts of the self-synthesized DA-structure epoxy resin as described above, 10-30 parts of liquid epoxy resin, 55-80 parts of filler, 10-20 parts of curing agent, 0.5-5 parts of coupling agent, and 0.1-5 parts of auxiliary agent.

[0033] The fourth aspect of the present invention further provides a preparation method of the underfill adhesive with both high reliability and self-healing function, including the following steps:

[0034] Add the self-synthesized multi-functional group epoxy resin with DA structure, liquid resin, coupling agent, and auxiliary agent into the reaction kettle in sequence, and stir evenly for 0.5 h-1 h;

[0035] After the above materials are premixed evenly, add spherical silica with a particle size of 0.01-20 microns into the reaction kettle in batches and disperse them intensively for 1 h;

[0036] After the filler is dispersed evenly, add the curing agent and stir for 0.5 h-1 h to obtain the underfill adhesive.

[0037] The present invention also provides the application of the underfill adhesive with both high reliability and self-healing function as described above in the field of encapsulation materials.

[0038] The present invention has been verified by experiments and the results are good. For the convenience of understanding the present invention, the present invention will be described more comprehensively and detailedly below in combination with embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments, and the protection scope of the present invention is subject to the claims.

[0039] Example 1:

[0040] Example 1 provides an underfill adhesive with both high reliability and self-healing function and its preparation method. The preparation method includes the following steps:

[0041] Step 1, the DA-structure epoxy resin and its preparation method include the following process: Mix 71 parts by mass of 1,23-bis(maleimide)heptanediol with 100 mL of toluene, carry out mechanical stirring and dispersion under the condition of not less than 120 °C. After the dispersion is completed, add 61 parts by mass of glycidyl furfuryl ether, control the temperature at 80 °C and react for 24 h, filter and dry to obtain the DA-structure epoxy resin with flexible chain segments.

[0042] Step 2: The preparation of the underfill glue contains the following components and processes by mass fraction: Add 5 parts by mass of self-synthesized DA-structured epoxy resin with flexible segments, 17.5 parts by mass of liquid resin, 1 part by mass of coupling agent, 1 part by mass of diluent, and 0.5 part by mass of carbon black into the reaction kettle in sequence and mix evenly, stir for 1 h; then add 65 parts by mass of spherical silica filler in four batches and stir intensively for dispersion for 1 h; finally, add 10 parts by mass of amine curing agent and stir for 0.5 h to obtain the underfill glue.

[0043] Among them, the liquid resin is selected as bisphenol F epoxy resin with an epoxy equivalent of 160 g / mol, the coupling agent is KH560, the diluent is polypropylene glycol glycidyl ether with an epoxy equivalent of 180 g / mol, the average particle size of the filler is 1.5 microns, the maximum particle size is 10 microns, and the curing agent is diethyl toluene diamine.

[0044] Example 2:

[0045] Example 2 provides an underfill glue with both high reliability and self-healing function and its preparation method. The preparation method includes the following steps:

[0046] Step 1: The DA-structured epoxy resin and its preparation method include the following processes: Mix 54 parts by mass of N,N'-(1,4-phenylene) bismaleimide with 100 mL of xylene, carry out mechanical stirring and dispersion at 110 °C, add 61 parts by mass of glycidyl furfuryl ether after the dispersion is completed, control the temperature at 80 °C and react for 24 h, filter by suction and dry to obtain the DA-structured epoxy resin with rigid segments.

[0047] Step 2: The preparation of the underfill glue contains the following components and processes by mass fraction: Add 5 parts by mass of self-synthesized DA-structured epoxy resin with flexible segments, 17.5 parts by mass of liquid resin, 1 part by mass of coupling agent, 1 part by mass of diluent, and 0.5 part by mass of carbon black into the reaction kettle in sequence and mix evenly, stir for 1 h; then add 65 parts by mass of spherical silica filler in four batches and stir intensively for dispersion for 1 h; finally, add 10 parts by mass of amine curing agent and stir for 0.5 h to obtain the underfill glue.

[0048] Among them, the materials and processes are the same as those in Example 1.

[0049] Example 3:

[0050] Example 3 provides an underfill glue with both high reliability and self-healing function and its preparation method. The preparation method includes the following steps:

[0051] Step 1. The DA-structured epoxy resin and its preparation method include the following process: Mix 72 parts by mass of 4,4'-diphenyl ether dimaleimide with 100 mL of xylene, conduct mechanical stirring and dispersion at 110 °C. After the dispersion is completed, add 61 parts by mass of glycidyl furfuryl ether, control the temperature at 80 °C and react for 24 h. Then, perform suction filtration and drying to obtain the DA-structured epoxy resin with rigidity and a certain degree of flexibility.

[0052] Step 2. The preparation of the underfill adhesive includes the following components and process by mass: Add 5 parts by mass of the self-synthesized DA-structured epoxy resin with flexible chain segments, 17.5 parts by mass of liquid resin, 1 part by mass of coupling agent, 1 part by mass of diluent, and 0.5 part by mass of carbon black into the reaction kettle in sequence and mix evenly, and stir for 1 h; then add 65 parts by mass of spherical silica filler in four batches, and conduct centralized stirring and dispersion for 1 h; finally, add 10 parts by mass of amine curing agent and stir for 0.5 h to obtain the underfill adhesive.

[0053] Among them, both the materials and the process are the same as those in Example 1.

[0054] Comparative Example 1:

[0055] Comparative Example 1 provides a conventional chip-level underfill adhesive and its preparation method. The preparation method includes the following steps:

[0056] The preparation of the underfill adhesive in Comparative Example 1 includes the following components and process by mass: Add 5.5 parts by mass of naphthalene ring resin, 17.5 parts by mass of liquid resin, 1 part by mass of coupling agent, 1 part by mass of diluent, and 0.5 part by mass of carbon black into the reaction kettle in sequence and mix evenly, and stir for 1 h; then add 65 parts by mass of spherical silica filler in four batches, and conduct centralized stirring and dispersion for 1 h; finally, add 9.5 parts by mass of amine curing agent and stir for 0.5 h to obtain the underfill adhesive. The optical microscope image of the device using the underfill adhesive prepared in Comparative Example 1 is as Figure 4 shown.

[0057] Among them, the epoxy equivalent of the naphthalene ring resin is 145 g / mol, and other materials and processes are the same as those in Example 1.

[0058] Testing method

[0059] (1) Viscosity measurement: Use a DV2T HB Brookfield viscometer, control the temperature at 25 °C, select the SC4-14 rotor, and measure at a speed of 50 rpm to obtain the viscosity value by reading after 60 s;

[0060] (2) Fluidity measurement: At a temperature of 110 °C, inject the glue into two parallel glass plates with a gap of 50 μm, and record the time when the glue flows to a position of 30 mm.

[0061] (3)Modulus measurement: The glue was cured into a block, polished into a long block with a length, width, and thickness of 60 mm * 11.5 mm * 3.5 mm, and a programmed temperature rise was carried out in the double cantilever mode of the DMA850 device at a heating rate of 5 °C / min, and the test temperature range was 20 °C to 270 °C; the room temperature modulus and high temperature modulus were taken as the modulus values at 25 °C and 240 °C;

[0062] (4)Elongation at break measurement: The glue was cured into dumbbell-shaped specimens using a mold and tensile tested using a universal testing machine at a tensile rate of 5 mm / min.

[0063] (5)Coefficient of thermal expansion measurement: The glue was cured into a block, cut and polished into a cube of a fixed shape, and tested using a TMA450 thermomechanical analyzer at a heating rate of 5 °C / min, and the test temperature range was 20 °C to 300 °C.

[0064] (6)High and low temperature cycling: The underfill was filled into the electronic device of a large-size chip. The electronic device was pre-conditioned according to MSL3 in the JEDES-STD-22 standard. The pre-conditioning condition was to keep the temperature constant at 125 °C for 24 h, and the device was hygroscopic at 85 °C and 60% RH in an aging oven for 168 h, and then subjected to high-temperature treatment by three reflow solders. The reflow soldering furnace program was set to ensure that the device was heated at a temperature above 220 °C for 300 s; after pre-conditioning, the device was placed in a TCC-151W aging oven for TCT cycling from -55 °C to 125 °C, with 700 cycles. The microscope was used to observe whether there were cracks in the underfill around the device and in the corners, and the number of cracks was used for evaluation. The optical microscope image of the typical cracks of the underfill prepared by Application Comparative Example 1 for the device is as Figure 4 shown.

[0065] (7)Thermal shock: The underfill was filled into the large-size chip device. The electronic device was pre-conditioned according to MSL3 in the JEDES-STD-22 standard. After pre-conditioning, the device was placed in a TSE-12-A thermal shock test chamber for TSE thermal cycling from -55 °C to 125 °C, with 700 cycles. The microscope was used to observe whether there were cracks in the underfill around the device and in the corners, and the number of cracks was used for evaluation.

[0066] (8)Thermal shock + MSL3: The electronic device that had undergone 700 cyc thermal shock was further subjected to enhanced reliability treatment according to the reliability MSL3 standard. Similarly, the microscope was used to observe whether there were cracks in the underfill around the device and in the corners, and the number of cracks was used for evaluation.

[0067] The performance parameters of the above Examples 1-3 and Comparative Example 1 are shown in Table 1

[0068] The underfill adhesives prepared in Examples 1 to 3 and the underfill adhesive prepared in Comparative Example 1 were tested according to the above test methods, and the performance parameters and reliability results are shown in Table 1.

[0069] Table 1: Performance parameters and reliability results in Examples 1-3 and Comparative Example 1

[0070]

[0071] From Examples 1-3 and Comparative Example 1, it can be found that for the underfill adhesive added with the self-synthesized DA-structure epoxy resin provided by the present invention, the number of cracks during the reliability experiment can be effectively reduced, and the process performance and mechanical properties are not attenuated, which can ensure that the adhesive has good workability and mechanical strength.

[0072] From the reliability results, it can be seen that by introducing the self-synthesized DA-structure epoxy resin in the present invention, rigid groups and flexible chain segments are introduced into the underfill adhesive, which can effectively resist the generation of cracks and has good reliability. On the other hand, the DA structure can realize the reversible chemical reaction of DA and r-DA under the high temperature condition of reflow soldering to achieve self-repair of small cracks. Therefore, the underfill adhesive in the present invention has high reliability and self-repair function, and will have broad application value and development prospect in electronic devices in the future.

[0073] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent changes made by using the content of this specification are included in the patent protection scope of the present invention.

Claims

1. A self-synthesized DA-structured epoxy resin, characterized in that, The structural formula of the self-synthesized DA-structured epoxy resin is as follows: 。 2. The preparation method of the self-synthesized DA structure epoxy resin according to claim 1, characterized in that, It includes the following steps: Mix 4,4'-diphenyl ether dimaleimide and toluene solvent, and heat it to 60°C - 120°C under nitrogen protection for dissolution to obtain a homogeneous solution after dissolution; Then, while stirring the homogeneous solution, dropwise add glycidyl furfuryl ether, and control the temperature at 80°C for reaction for 24 h; After the reaction is completed, cool it, remove the solvent by reduced pressure distillation, and obtain the self-synthesized DA-structured epoxy resin after vacuum drying.

3. A underfill adhesive, characterized in that, It includes the following components by mass: 1 - 10 parts of the self-synthesized DA-structured epoxy resin as described in claim 1, 10 - 30 parts of liquid epoxy resin, 55 - 80 parts of filler, 10 - 20 parts of curing agent, 0.5 - 5 parts of coupling agent, and 0.1 - 5 parts of additive.

4. The underfill adhesive according to claim 3, wherein, The liquid epoxy resin is one or more of liquid bisphenol A, bisphenol F, aminophenol-type epoxy resin, glycidyl-type epoxy resin, and naphthalene-type epoxy resin, and the molecular weight of the liquid epoxy resin is below 500.

5. The underfill glue according to claim 3, characterized in that, The filler is spherical silica, and the particle size distribution range of the spherical silica is between 0.01 - 20 microns.

6. The underfill adhesive according to claim 3, wherein The curing agent is one or more of amine curing agents, phenolic curing agents, anhydride curing agents, and imidazole curing agents.

7. The underfill adhesive according to claim 3, characterized in that, The additive is one or more of defoaming agents, diluents, leveling agents, antioxidants, and color pastes.

8. A method for preparing the underfill adhesive according to any one of claims 3-7, characterized in that It includes the following steps: Add the self-synthesized DA-structured epoxy resin, liquid epoxy resin, coupling agent, and additive into the reaction kettle in sequence, and stir evenly for 0.5 h - 1 h; After the above materials are premixed evenly, add the filler into the reaction kettle in batches and disperse it intensively for 1 h; After the filler is dispersed evenly, add the curing agent and stir for 0.5 h - 1 h to obtain the underfill adhesive.

Images