An underfill adhesive with no filler, ultra-low viscosity and low CTE and its preparation method

Abstract

The present invention discloses a no-filler underfill with ultra-low viscosity and low CTE and a preparation method thereof. The no-filler underfill with ultra-low viscosity and low CTE comprises the following components in parts by weight: 12-18 parts of anthracene-type epoxy resin, 16-24 parts of bisphenol F epoxy resin, 15-17 parts of active epoxy resin diluent, 8-15 parts of acrylate, 22-30 parts of glycidyl methacrylate, 6-10 parts of liquid microcapsule latent curing agent, 1.5-2.5 parts of liquid polymerization initiator, and 0.5 part of defoaming agent; the no-filler underfill with ultra-low viscosity and low CTE prepared by this method has a low coefficient of thermal expansion, low viscosity, and good fluidity, can effectively eliminate the stress between the chip, solder balls, and PCB board after encapsulation, and has a high glass transition temperature Tg, excellent adhesion, and low water absorption after curing, can meet the requirements of the reliability of consumer electronics products, and realizes on-line curing, with high productivity and good use effect.

Description

Technical Field

[0001] The present invention relates to the technical field of filling adhesives, and particularly relates to an underfill adhesive without fillers, having ultra-low viscosity and low CTE, and a preparation method thereof. Background Art

[0002] With the continuous miniaturization and thinning of consumer electronic products, especially wearable electronic products such as mobile phones, bracelets, watches, earphones, tablets and other wearable consumer electronic products, it has promoted the increasing integration of integrated circuits, resulting in a sharp increase in the number of pins of integrated circuit chips, and the radius of pin solder balls (bumps) becoming smaller and smaller. When flip-chip packaging is performed, the gap between the chip and the PCB board becomes smaller and smaller. This requires that the underfill adhesive has good fluidity, can quickly flow through the narrow gap between the chip and the PCB board during packaging, reliably fill the entire gap without air bubbles or voids, and ensure the reliability of the device after packaging.

[0003] Ordinary underfill adhesives are difficult to meet this requirement because their viscosities are all above 1000 cps, the flow rate is not fast enough, and they contain inorganic fillers, but their CTE (coefficient of thermal expansion) is very low, reaching 25 ppm / K, which can well eliminate the stress between the chip, solder balls and PCB board after packaging. Driven by the above requirements for the narrow gap between the chip and the PCB board, the existing underfill adhesives without fillers have viscosities in the range of 100 - 500 cps and have good fluidity, but their CTE is usually relatively high and it is difficult to meet the actual use requirements. Therefore, other solutions need to be adopted to reduce the CTE of the encapsulation adhesive after curing, control the CTE within a lower range, so as to eliminate the stress between the chip, solder balls and PCB board after packaging as much as possible. At the same time, it should also have properties such as a relatively high glass transition temperature Tg, excellent adhesion and low water absorption to meet the reliability requirements of consumer electronic products, and achieve in-line curing, improve productivity, and reduce the unit cost of device processing.

[0004] In the existing solutions, the CTE is not ideal and relatively high, making it difficult to be popularized in the CSP and BGA chip packaging processes. Summary of the Invention

[0005] The purpose of the present invention is to provide an underfill adhesive without fillers, having ultra-low viscosity and low CTE, and a preparation method thereof. The underfill adhesive without fillers, having ultra-low viscosity and low CTE prepared by this method has a low coefficient of thermal expansion, low viscosity, good fluidity, can effectively eliminate the stress between the chip, solder balls and PCB board after packaging, and after curing, it has a relatively high glass transition temperature Tg, excellent adhesion and low water absorption, can meet the reliability requirements of consumer electronic products, and achieve in-line curing, with high productivity and good use effect.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] An underfill adhesive with no filler, ultra-low viscosity and low CTE comprises the following components in parts by weight:

[0008]

[0009] Preferably, the anthracene-type epoxy resin is dihydroanthracene epoxy resin; the structural formula of the dihydroanthracene epoxy resin is:

[0010]

[0011] Preferably, the active epoxy resin diluent is one or a mixture of two of CDMDG and p-tert-butylphenyl glycidyl ether;

[0012] The structural formula of the CDMDG is:

[0013]

[0014] The structural formula of the p-tert-butylphenyl glycidyl ether is:

[0015]

[0016] Preferably, the acrylate is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

[0017] Preferably, the liquid microcapsule latent curing agent is one or a mixture of any several of HX3613, HX3921HP, HX3941HP, HXA3922HP, and HXA3042HP.

[0018] Preferably, the liquid polymerization initiator is one or a mixture of two of tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide.

[0019] Preferably, the defoaming agent is one or a mixture of any several of BYK054, BYK535, BYK5790, BYK141, and TEGairex921.

[0020] A preparation method of an underfill adhesive with no filler, ultra-low viscosity and low CTE comprises the following steps:

[0021] S1. At room temperature, weigh 12 - 18 parts by weight of anthracene - type epoxy resin powder, 16 - 24 parts of bisphenol F epoxy resin, and 15 - 17 parts of reactive epoxy resin diluent and put them into a planetary reactor. Stir, and at the same time gradually raise the temperature of the reactor to 120 °C, then stir for 1 - 2 hours until the anthracene - type epoxy resin is completely dissolved and evenly dispersed in the atmosphere of bisphenol F epoxy resin and reactive epoxy resin diluent molecules, so that the anthracene - type epoxy resin molecules are surrounded by the molecules of this atmosphere, forming a stable thermodynamic system;

[0022] S2. When the temperature of the planetary reactor drops to room temperature, add 8 - 15 parts of acrylate and 22 - 30 parts of glycidyl methacrylate, and stir under full vacuum for 2 - 3 hours;

[0023] S3. Add 6 - 10 parts of liquid micro - capsule latent curing agent, 1.5 - 2.5 parts of liquid polymerization initiator, and 0.5 part of defoamer. Control the temperature below 15 °C and stir under full vacuum for 0.5 - 1 hour to obtain a bottom - filling adhesive without filler, with low viscosity and low CTE.

[0024] After adopting the above - mentioned technical solution, compared with the background technology, the present invention has the following beneficial effects:

[0025] 1. The present invention uses dihydroanthracene epoxy resin as the core material. Its molecular structure contains an anthracene ring (a fused ring of three benzene rings), and the anthracene - type epoxy resin molecules can be evenly dispersed in the atmosphere of bisphenol F epoxy resin and reactive epoxy resin diluent molecules, so that the anthracene - type epoxy resin molecules are surrounded by the molecules of this atmosphere and are not easily crystallized and precipitated. After curing, the anthracene rings are easily closely packed. Moreover, since the anthracene ring belongs to a two - dimensional planar structure, it is not easily rotated during molecular thermal motion. Therefore, due to the close packing between the anthracene rings in the molecule and the non - rotation of the two - dimensional planar structure of the anthracene ring, when the temperature rises, the volume is not easily expanded, so that the CTE can be controlled at a relatively low level, and the dependence on fillers can be effectively eliminated.

[0026] 2. The present invention utilizes the molecular structure characteristics of 9,9 - bis[4 - (2 - acryloyloxyethoxy)phenyl]fluorene. After the four benzene rings in the 9,9 - bis[4 - (2 - acryloyloxyethoxy)phenyl]fluorene (BPEFA) molecule are cured, they are not easily rotated, which can effectively reduce the CTE. In addition, since the viscosities of acrylates are relatively low, especially glycidyl methacrylate GMA (viscosity is only 2.7 cps at 25 °C), the viscosity of the adhesive system can be greatly reduced, making low viscosity possible.

[0027] 3. In the present invention, both the anthracene ring and the four benzene rings in the BPEFA molecule have relatively high glass transition temperatures Tg. After curing, glycidyl methacrylate (GMA) can serve as a crosslinking bridge between epoxy groups, between acrylate groups, and between epoxy groups and acrylate groups, forming an IPN (Interpenetrating Polymer Network, interpenetrating in space) crosslinked structure, which can further increase the glass transition temperature Tg. At the same time, the four benzene ring groups in the anthracene ring and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene (BPEFA) molecules are all strongly hydrophobic groups, which can significantly reduce the water absorption of the underfill adhesive after curing.

[0028] 4. Due to the reduction of CTE in the present invention, similarly, it also brings a low shrinkage rate of the underfill adhesive after curing, as well as good wettability of the epoxy groups and acrylate groups on the surface of the chip and the PCB board with solder balls (bumps), effectively improving the good adhesion of the underfill adhesive to the substrate. Detailed Embodiments

[0029] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0030] Example 1

[0031] An underfill adhesive with no filler, ultra-low viscosity and low CTE comprises the following components in parts by weight: 15 parts of dihydroanthracene epoxy resin, 20 parts of bisphenol F epoxy resin, 15 parts of CDMDG, 15 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, 25 parts of glycidyl methacrylate, 8 parts of HXA3922HP, 1.5 parts of tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of BYK054.

[0032] A preparation method of an underfill adhesive with no filler, ultra-low viscosity and low CTE comprises the following steps:

[0033] S1. At room temperature, weigh 15 parts of dihydroanthracene epoxy resin powder, 20 parts of bisphenol F epoxy resin, and 15 parts of CDMDG by weight and put them into a planetary reaction kettle, stir, and gradually raise the temperature of the reaction kettle to 120 °C, then stir for 1.5 hours until the dihydroanthracene epoxy resin is completely dissolved and uniformly dispersed in the atmosphere of bisphenol F epoxy resin and CDMDG molecules, so that the dihydroanthracene epoxy resin molecules are surrounded by the molecules in this atmosphere, forming a stable thermodynamic system;

[0034] S2. When the temperature of the planetary reactor drops to room temperature, add 15 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene and 25 parts of glycidyl methacrylate, and stir under full vacuum for 2 hours.

[0035] S3. Add 8 parts of HXA3922HP, 1.5 parts of tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of BYK054. Control the temperature below 15°C and stir under full vacuum for 0.5 hour to obtain a bottom filling adhesive without filler, having low viscosity and low CTE.

[0036] Example 2

[0037] A bottom filling adhesive without filler, having ultra-low viscosity and low CTE, comprises the following components in parts by weight: 12 parts of dihydroanthracene epoxy resin, 24 parts of bisphenol F epoxy resin, 17 parts of CDMDG, 8 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene (BPEFA), 30 parts of glycidyl methacrylate, 6 parts of HXA3922HP, 2.5 parts of tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of BYK535.

[0038] A preparation method of a bottom filling adhesive without filler, having ultra-low viscosity and low CTE, comprises the following steps:

[0039] S1. At room temperature, weigh 12 parts of dihydroanthracene epoxy resin powder, 24 parts of bisphenol F epoxy resin, and 17 parts of CDMDG by weight, put them into a planetary reactor, stir, and gradually raise the temperature of the reactor to 120°C, then stir for 1 hour until the dihydroanthracene epoxy resin is completely dissolved and uniformly dispersed in the atmosphere of bisphenol F epoxy resin and the active epoxy resin diluent molecules, so that the dihydroanthracene epoxy resin molecules are surrounded by the molecules in this atmosphere to form a stable thermodynamic system.

[0040] S2. When the temperature of the planetary reactor drops to room temperature, add 8 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene and 30 parts of glycidyl methacrylate, and stir under full vacuum for 2 - 3 hours.

[0041] S3. Add 6 parts of HXA3922HP, 2.5 parts of tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of BYK535. Control the temperature below 15°C and stir under full vacuum for 0.5 hour to obtain a bottom filling adhesive without filler, having low viscosity and low CTE.

[0042] Example 3

[0043] An underfill adhesive with no filler, ultra-low viscosity and low CTE, comprising the following components by weight parts: 18 parts of anthracene dihydroxide epoxy resin, 16 parts of bisphenol F epoxy resin, 16 parts of CDMDG, 15 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene, 22 parts of glycidyl methacrylate, 8 parts of HXA3042HP, 2.5 parts of di-tert-butyl peroxide, and 0.5 part of TEGAirex9210.

[0044] A preparation method of an underfill adhesive with no filler, ultra-low viscosity and low CTE, comprising the following steps:

[0045] S1. At room temperature, weigh 18 parts of anthracene dihydroxide epoxy resin powder, 16 parts of bisphenol F epoxy resin, and 16 parts of CDMDG, and put them into a planetary reactor, stir, and gradually raise the temperature of the reactor to 120 °C, then stir for 2 hours until the anthracene dihydroxide epoxy resin is completely dissolved and evenly dispersed in the atmosphere of bisphenol F epoxy resin and active epoxy resin diluent molecules, so that the anthracene dihydroxide epoxy resin molecules are surrounded by the molecules of this atmosphere to form a stable thermodynamic system;

[0046] S2. When the temperature of the planetary reactor drops to room temperature, add 15 parts of 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene and 22 parts of glycidyl methacrylate, and stir under full vacuum for 3 hours;

[0047] S3. Add 8 parts of HXA3042HP, 2.5 parts of di-tert-butyl peroxide, and 0.5 part of TEGAirex9210, control the temperature below 15 °C, and stir under full vacuum for 1 hour to obtain an underfill adhesive with no filler, low viscosity and low CTE.

[0048] Comparative example

[0049] An underfill adhesive with no filler, comprising the following components by weight parts: 35 parts of bisphenol F epoxy resin, 15 parts of active epoxy resin diluent CDMDG, 15 parts of butyl methacrylate, 25 parts of glycidyl methacrylate, 8 parts of liquid microcapsule latent curing agent HXA3922HP, 1.5 parts of liquid polymerization initiator tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of defoamer BYK054.

[0050] A preparation method of an underfill adhesive with no filler, comprising the following steps:

[0051] S1. At room temperature, weigh 35 parts of bisphenol F epoxy resin and 15 parts of active epoxy resin diluent CDMDG, put them into a planetary reactor, stir, and gradually raise the temperature of the reactor to 80 °C, then stir for 1 hour.

[0052] S2. When the temperature of the planetary reactor drops to room temperature, add 15 parts of butyl methacrylate, 25 parts of glycidyl methacrylate, and stir under full vacuum for 2 hours.

[0053] S3. Add 8 parts of liquid microcapsule latent curing agent HXA3922HP, 1.5 parts of liquid polymerization initiator tert-butyl peroxy-2-ethylhexanoate, and 0.5 part of defoamer BYK054. Control the temperature below 15°C and stir under full vacuum for 0.5 hour to obtain a filler-free underfill adhesive.

[0054] Performance Testing

[0055] 1. Viscosity Test:

[0056] Test according to ASTM D2196-1999.

[0057] 2. Coefficient of Thermal Expansion (CTE) Test:

[0058] TMA (Dynamic Mechanical Analyzer), nitrogen atmosphere, 10°C / min.

[0059] 3. Glass Transition Temperature (Tg) Test:

[0060] Test according to ASTM D3418—2015.

[0061] 4. Shear Strength Test:

[0062] Test according to ASTM D1002.

[0063] 5. Water Absorption Test:

[0064] Immerse in water at 25°C for 24 HRS and measure the weight difference before and after immersion.

[0065] (Weight after water absorption - Dry weight) / Dry weight * 100%

[0066] The test results of Examples 1-3 and Comparative Example are shown in Table 1.

[0067] Table 1 Test Results of Examples 1-3 and Comparative Example

[0068] Index Example 1 Example 2 Example 3 Comparative Example Viscosity (cps, 25°C) 355 342 387 343 CTE (ɑ1, ppm / K) 59 66 54 93 CTE (ɑ2, ppm / K) 165 191 162 237 Tg (°C, TMA) 125 117 129 91 Shear Strength (Mpa) 16.2 15.7 16.8 14.1 Water Absorption Rate (%) 0.42 0.50 0.46 0.81

[0069] As can be seen from the test results in Table 1, the bottom filling adhesive with no filler, ultra-low viscosity and low CTE prepared by the present invention has very low viscosity, good fluidity, CTE controlled at a relatively low level, a relatively high glass transition temperature, good adhesion and very low water absorption. For the bottom filling adhesive with no filler prepared in the comparative example, since the anthracene-type epoxy resin and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene (BPEFA) were deleted, the CTE increased sharply, the Tg decreased and the water absorption increased.

[0070] As mentioned above, the above are only the preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An underfill adhesive with no filler, ultra-low viscosity, and low CTE, characterized in that Comprising the following components by weight parts: The anthracene-type epoxy resin is dihydroanthracene epoxy resin; the structural formula of the dihydroanthracene epoxy resin is: The active epoxy resin diluent is one or a mixture of two of CDMDG and p-tert-butylphenyl glycidyl ether; The structural formula of the CDMDG is: The structural formula of the p-tert-butylphenyl glycidyl ether is: The acrylate is 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene.

2. The underfill adhesive with ultra-low viscosity and low CTE without filler as described in claim 1, wherein: The liquid microcapsule latent curing agent is one or any mixture of several of HX3613, HX3921HP, HX3941HP, HXA3922HP, and HXA3042HP.

3. The underfill adhesive with ultra-low viscosity and low CTE without filler as described in claim 1, wherein: The liquid polymerization initiator is one or a mixture of two of tert-butyl peroxy-2-ethylhexanoate and di-tert-butyl peroxide.

4. The underfill adhesive with ultra-low viscosity and low CTE without filler according to claim 1, wherein: The defoaming agent is one or any mixture of several of BYK054, BYK535, BYK5790, BYK141, and TEGAirex921.

5. A method for preparing an underfill adhesive with no filler, ultra-low viscosity, and low CTE as described in any one of claims 1 to 4, characterized in that, Including the following steps: S1. At room temperature, weigh 12-18 parts by weight of anthracene-type epoxy resin powder, 16-24 parts of bisphenol F epoxy resin, and 15-17 parts of active epoxy resin diluent and put them into a planetary reaction kettle, stir, and gradually raise the temperature of the reaction kettle to 120°C, then stir for 1-2 hours until the anthracene-type epoxy resin is completely dissolved and evenly dispersed in the atmosphere of bisphenol F epoxy resin and active epoxy resin diluent molecules, so that the anthracene-type epoxy resin molecules are surrounded by the molecules in this atmosphere to form a stable thermodynamic system; S2. When the temperature of the planetary reaction kettle drops to room temperature, add 8-15 parts of acrylate and 22-30 parts of glycidyl methacrylate, and stir under full vacuum for 2-3 hours; S3. Add 6-10 parts of liquid microcapsule latent curing agent, 1.5-2.5 parts of liquid polymerization initiator, and 0.5 part of defoaming agent, control the temperature below 15°C, and stir under full vacuum for 0.5-1 hour to obtain a bottom filling adhesive with no filler, low viscosity, and low CTE.

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