A method for modifying silica fillers for use in underfill adhesives and their applications.

Abstract

This invention discloses a method for modifying silica fillers used in bottom filler adhesives and its application. The chemical structure of the bifunctional amine modifier used in the process is as follows: [Formula omitted for brevity]. Where R and R' are independently methyl or ethyl; n is an integer from 1 to 3; m is an integer from 1 to 5; a is 0 or 1; b is 0 or 1; c is 0 or an integer from 1 to 3; d is 0 or 1; and e is 0 or an integer from 1 to 3. This amine modifier, containing both aromatic rings and double bonds, is used to modify the surface of silica via spraying. This replaces traditional aliphatic chain or single-benzene-ring amine modifiers for modifying silica micropowder, resulting in silica micropowder with low viscosity, low coefficient of thermal expansion, and high adhesion. When added to resin, it does not react rapidly, increasing adhesion without increasing viscosity and reducing the coefficient of thermal expansion.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering technology, and in particular to a method for modifying silica fillers for use in bottom-filling adhesives and their applications. Background Technology

[0002] With the miniaturization of electronic devices, advanced flip-chip packaging requires continuously reducing the spacing between solder joints, which has driven the application of nano-silica fillers in underfill adhesives. Nano-silica fillers, due to their low coefficient of thermal expansion and excellent chemical stability, have been widely used in resins to reduce the coefficient of thermal expansion of composite materials and improve adhesion. However, the reduction in the coefficient of thermal expansion of composite materials is achieved by increasing the amount of nano-silica filler, but with increased nano-silica filler content, silica tends to agglomerate and cannot be uniformly dispersed in the resin, causing a series of problems. To reduce silica agglomeration, silane coupling agents can be used to modify the surface of silica, thereby greatly improving its dispersibility. A key reason for the improved dispersibility after modification is that a layer of functional groups similar to those in the resin is grafted onto the silica surface. Based on the principle of "like dissolves like," silica can be well dispersed in the resin matrix.

[0003] However, the amine coupling agents commonly used in existing surface modification technologies are usually aliphatic chains or contain a single benzene ring. If aliphatic amines are grafted onto the silica surface, after complete grafting modification, the silica powder is added to the resin and a rapid reaction begins, resulting in increased viscosity, decreased adhesive strength, and an increased coefficient of thermal expansion. Alternatively, grafting amine coupling agents containing a single benzene ring onto the silica surface may slightly improve performance, but it still results in an increased coefficient of thermal expansion, reduced adhesive strength, and, at high grafting rates, increased viscosity of the encapsulation material. Summary of the Invention

[0004] To address the aforementioned problems, this invention employs amine modifiers containing aromatic rings and double bonds (bifunctional groups) to replace traditional aliphatic chain or single-benzene-ring amine modifiers for modifying silica micropowder. This achieves the desired effect of maintaining viscosity, increasing adhesive strength, and reducing the coefficient of thermal expansion. The specific technical solution is as follows:

[0005] A method for modifying silica fillers for use in underfill adhesives includes the following steps:

[0006] Modified silica micro powder is prepared by adding a bifunctional amine modifier to preheated silica micro powder, heating and stirring to react.

[0007] The chemical structural formula of the bifunctional amine modifier is shown in Formula I:

[0008]

[0009] Where R and R' are independently methyl or ethyl; n is an integer from 1 to 3; m is an integer from 1 to 5; a is 0 or 1; b is 0 or 1; c is an integer from 0 to 1 to 3; d is 0 or 1; e is an integer from 0 to 1 to 3.

[0010] Preferably, the bifunctional amine modifier accounts for 0.1% to 5% of the weight of the silica micropowder.

[0011] Preferably, the preheating is carried out by stirring at 110-150°C for 0.5-3 hours.

[0012] Preferably, the reaction conditions are: 110-150℃, stirring speed of 200-500 rpm, and reaction time of 0.5-2h.

[0013] Preferably, the average particle size of the silica micro powder is 0.3–5 μm.

[0014] Preferably, the bifunctional amine modifier is added to the silica micro powder by spraying.

[0015] The present invention also provides modified silica micro powder obtained by the above modification method.

[0016] This invention also provides the application of the modified silica micropowder obtained by the above modification method in the preparation of bottom filler adhesive, including the following steps:

[0017] Modified silica micro powder was added to epoxy resin in batches. First, the mixture was mixed at 1500 rpm for 2 minutes, then at 2000 rpm for 2 minutes. Then, the curing agent was added, and the mixture was mixed evenly and degassed under vacuum. The mixture was then cured at 165℃ for 2 hours to make a bottom filler.

[0018] Preferably, the modified silica micro powder accounts for 50% to 80% of the epoxy resin by weight.

[0019] Compared with the prior art, the present invention has the following innovations and beneficial effects:

[0020] This invention employs an amine modifier containing both aromatic rings and double bonds with dual functional groups to replace traditional aliphatic chain or single benzene ring amine modifiers for modifying silica micropowder. When applied to the preparation of bottom filler adhesives, it can increase adhesion and reduce the coefficient of thermal expansion without increasing viscosity. Detailed Implementation

[0021] The following disclosure provides many different implementations or examples for carrying out various aspects of the invention. To simplify the disclosure, specific examples are described below. Of course, these are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0022] In this invention, unless otherwise specified, all equipment and raw materials can be purchased from the market or are commonly used in this industry.

[0023] Unless otherwise specified, the methods described in the following embodiments are conventional methods in the art.

[0024] The amine modifier containing aromatic rings and double bonds with bifunctional groups used in this invention was prepared by Shenzhen Zhengan Organosilicon Materials Co., Ltd., and its specific chemical structural formula is shown in Formula I.

[0025]

[0026] Where R' can be methyl or ethyl; R can be methyl or ethyl; n is an integer from 1 to 3; m is an integer from 1 to 5; a is 0 or 1, b is 0 or 1, c is 0 or an integer from 1 to 3; d is 0 or 1; e is 0 or an integer from 1 to 3.

[0027] Comparative Example 1:

[0028] 1) Preheat 100g of silica micro powder with an average particle size of 1μm at 130℃ for 1h;

[0029] 2) Add 0.2% by weight of N-2-(aminoethyl)-3-aminopropyltrimethoxysilane amine modifier to the heat-pretreated silica micro powder by spraying;

[0030] 3) At 140℃, the stirring speed was 300 rpm for 1 hour to obtain silica micro powder modified with amine modifier;

[0031] 4) Add 60% by weight of the above-mentioned amine modifier-modified silica micro powder to bisphenol F epoxy resin, mix at 1500 rpm for 2 min and 2000 rpm for 2 min in a mixer, add curing agent, mix evenly and degas under vacuum conditions, and test the room temperature viscosity (shear rate 50 / sec) with a rheometer.

[0032] 5) The slurry obtained above is cured at 165°C for 2 hours to prepare a cured sample. The coefficient of thermal expansion is tested on a TMA and the adhesion is tested on the substrate.

[0033] Comparative Example 2:

[0034] 1) Preheat 100g of silica micro powder with an average particle size of 1μm at 130℃ for 1h;

[0035] 2) Add 0.2% by weight of N-phenyl-3-aminopropyltrimethoxysilane amine modifier to the heat-pretreated silica micro powder by spraying;

[0036] 3) At 140℃, the stirring speed was 300 rpm for 1 hour to obtain silica micro powder modified with amine modifier;

[0037] 4) Add 60% by weight of the above-mentioned amine modifier-modified silica micro powder to bisphenol F epoxy resin, mix at 1500 rpm for 2 min and 2000 rpm for 2 min in a mixer, add curing agent, mix evenly and degas under vacuum conditions, and test the room temperature viscosity (shear rate 50 / sec) with a rheometer.

[0038] 5) The slurry obtained above is cured at 165°C for 2 hours to prepare a cured sample. The coefficient of thermal expansion is tested on a TMA and the adhesion is tested on the substrate.

[0039] Example 1:

[0040] The bifunctional amine modifier provided in this embodiment is compound 1 as shown in Formula II (e is 1, c is 1, m is 1, d is 0, b is 0, a is 0).

[0041] application:

[0042] 1) Preheat 100g of silica micro powder with an average particle size of 1μm at 130℃ for 1h;

[0043] 2) 0.2% by weight of the amine modifier of compound 1 was added to the heat-pretreated silica micro powder by spraying.

[0044] 3) At 140℃, the stirring speed was 300 rpm for 1 hour to obtain silica micro powder modified with amine modifier;

[0045] 4) Add 60% by weight of the above-mentioned amine modifier-modified silica micro powder to bisphenol F epoxy resin, mix at 1500 rpm for 2 min and 2000 rpm for 2 min in a mixer, add curing agent, mix evenly and degas under vacuum conditions, and test the room temperature viscosity (shear rate 50 / sec) with a rheometer.

[0046] 5) The slurry obtained above is cured at 165°C for 2 hours to prepare a cured sample. The coefficient of thermal expansion is tested on a TMA and the adhesion is tested on the substrate.

[0047]

[0048] Example 2:

[0049] The bifunctional amine modifier provided in this embodiment is compound 2 as shown in Formula III (e is 2, d is 1, b is 0, c is 0, m is 3).

[0050] application:

[0051] 1) Preheat 100g of silica micro powder with an average particle size of 1μm at 130℃ for 1h;

[0052] 2) 0.2% by weight of the amine modifier of compound 2 was added to the heat-pretreated silica micro powder by spraying;

[0053] 3) At 140℃, the stirring speed was 300 rpm for 1 hour to obtain silica micro powder modified with amine modifier;

[0054] 4) Add 60% by weight of the above-mentioned amine modifier-modified silica micro powder to bisphenol F epoxy resin, mix at 1500 rpm for 2 min and 2000 rpm for 2 min in a mixer, add curing agent, mix evenly and degas under vacuum conditions, and test the room temperature viscosity (shear rate 50 / sec) with a rheometer.

[0055] 5) The slurry obtained above is cured at 165°C for 2 hours to prepare a cured sample. The coefficient of thermal expansion is tested on a TMA and the adhesion is tested on the substrate.

[0056]

[0057] Example 3:

[0058] The bifunctional amine modifier provided in this embodiment is compound 3 as shown in Formula IV (e is 0, c is 1, d is 0, b is 1, a is 0, m is 1).

[0059] application:

[0060] 1) Preheat 100g of silica micro powder with an average particle size of 1μm at 130℃ for 1h;

[0061] 2) Add 0.2% by weight of the amine modifier of compound 3 to the heat-pretreated silica micro powder by spraying;

[0062] 3) At 140℃, the stirring speed was 300 rpm for 1 hour to obtain silica micro powder modified with amine modifier;

[0063] 4) Add 60% by weight of the above-mentioned amine modifier-modified silica micro powder to bisphenol F epoxy resin, mix at 1500 rpm for 2 min and 2000 rpm for 2 min in a mixer, add curing agent, mix evenly and degas under vacuum conditions, and test the room temperature viscosity (shear rate 50 / sec) with a rheometer.

[0064] 5) The slurry obtained above is cured at 165°C for 2 hours to prepare a cured sample. The coefficient of thermal expansion is tested on a TMA and the adhesion is tested on the substrate.

[0065]

[0066] Table 1 (Room temperature viscosity, coefficient of thermal expansion, and adhesive strength of Comparative Examples 1-2 and Examples 1-2)

[0067]

[0068] In summary, this invention employs an amine modifier containing aromatic rings and double-bonded bifunctional groups, which is added to pretreated silica micropowder via spray to modify the surface of silica. Chemical grafting is then completed under high temperature and high-speed stirring, resulting in amine-modified silica micropowder with low viscosity, low coefficient of thermal expansion, and high adhesion. Due to the high rigidity of the aromatic rings and the low molecular mobility of the modifier, coupled with the protection of the double-bonded functional groups, the modifier exhibits excellent stability. Therefore, upon addition to the resin, it does not react rapidly, the viscosity does not increase, and the adhesion is enhanced while the coefficient of thermal expansion is reduced.

[0069] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0070] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for modifying a silica filler for use in underfill adhesive, characterized by, The method comprises the following steps: Preheating silica powder, adding bifunctional amine modifier into the silica powder, and heating and stirring to react, to obtain modified silica powder; The chemical structure of the bifunctional amine modifier is shown in formula I: wherein, R and R' are independently methyl or ethyl; n is an integer of 1-3; m is an integer of 1-5; a is 0 or 1; b is 0 or 1; c is 0 or an integer of 1-3; d is 0 or 1; and e is 0 or an integer of 1-3.

2. The modification method according to claim 1, characterized in that, The weight percentage of the bifunctional amine modifier in the silica powder is 0.1-5%.

3. The modification method of claim 1, wherein, The preheating is specifically stirring preheating at 110-150℃ for 0.5-3h.

4. The modification method of claim 1, wherein, The heating and stirring condition is 110-150℃, the stirring speed is 200-500rpm, and the reaction time is 0.5-2h.

5. The modification method of claim 1, wherein, The average particle size of the silica powder is 0.3-5μm.

6. The modification method of claim 1, wherein, The bifunctional amine modifier is added into the silica powder in the form of spraying.

7. Modified silica powder obtained by the modification method according to any one of claims 1-6.

8. Use of the modified silica fine powder obtained by the modification method according to any one of claims 1 to 6 in the production of an underfill adhesive, characterized in that, The method comprises the following steps: The modified silica powder is added into epoxy resin in batches, stirring at 1500rpm for 2min, then stirring at 2000rpm for 2min, then adding curing agent, mixing uniformly under vacuum and defoaming, and curing at 165℃ for 2h, to obtain the underfill adhesive.

9. Use according to claim 8, characterized in that, The weight percentage of the modified silica powder in the epoxy resin is 50%-80%.

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