CN113549235B - A kind of preparation method of low dielectric constant polyimide film - Google Patents

Abstract

The invention discloses a preparation method of a low dielectric constant polyimide film, which comprises the following steps: the mesoporous silica with fluorine-grafted surface is added into the polyimide matrix to form a composite material, on one hand, the hollow filler is added to introduce air to reduce the dielectric constant of the polyimide composite film, and besides, the fluorine element on the surface has a strong electron-withdrawing effect, so that the discrete electron energy level of the polyimide film can be reduced, and the dielectric constant of the polyimide composite film can be further reduced. The dielectric constant of the composite film can be reduced to about 2.6 at the lowest, the thermal performance of the film is not obviously reduced, and the method is simple and feasible, has low economic cost and has wide application prospect in the electronic and microelectronic industries.

Description

A kind of preparation method of low dielectric constant polyimide film

technical field

The invention belongs to the field of polyimide films, and in particular relates to a preparation method of a low dielectric constant polyimide material.

Background technique

Polyimide has outstanding characteristics such as low dielectric constant, good processability, high mechanical properties, and good thermal stability. It is widely used in packaging materials and dielectric layers in the electronic and microelectronics industries. In electronic packaging, low-dielectric materials minimize crosstalk and the speed of signal propagation in the device. Therefore, polyimides with lower dielectric constants have been developed in recent years. Among the strategies to reduce the dielectric constant of polyimides, potential methods include: (1) adopting diamine and dianhydride monomers with the smallest polarizability; (2) constructing polyimides with high free volume; (3) adding fluorine to polymer chains; (4) introducing pores into the polyimide matrix to prepare foams. Due to the inherent characteristics of polyimide monomers, the methods of strategy (1) and strategy (2) cannot effectively further reduce the dielectric constant of polyimide. Although fluorine-containing polyimide can obtain polyimide with a dielectric constant in the range of 2.4-2.8, the limitations of this method lie in the difficulty of synthesis, solvent resistance and other reasons. Given the fact that air has the lowest dielectric constant of 1.0, foaming polyimide is an attractive and reasonable way to achieve low-k materials.

Contents of the invention

The invention provides a method for preparing a low dielectric constant film. The obtained polyimide film not only has good dielectric properties, but also can well preserve thermal properties and mechanical properties.

The low dielectric constant polyimide film prepared by the present invention is prepared by the following method:

(1) Firstly, silica is prepared by hydrolyzing tetraethyl orthosilicate.

(2) Etch silicon dioxide with potassium permanganate, so that silicon dioxide forms a hollow structure containing mesopores.

(3) Hydroxylation on the surface of mesoporous silica, and then connect all (17) fluorodecyltriethoxysilane on the surface of hydroxylated silica.

(4) Disperse the surface fluorinated mesoporous silica particles in N,N-dimethylformamide by ultrasonic waves, then add equimolar amounts of diamine and dianhydride monomers in sequence, and fully react for 4 to 6 hours.

(5) Pour out the reacted composite slurry, let it stand to remove the air bubbles in the slurry, and coat it into a film on a clean substrate.

⑹Put the coated film in a vacuum oven to program the temperature to remove the solvent in the film and perform thermal imidization on it.

In the present invention, the hydrolysis time of the tetraethyl orthosilicate is 6-10 hours.

In the present invention, the time for the potassium permanganate to etch silicon dioxide is 12 hours.

In the present invention, the surface of the silicon dioxide is hydroxylated with ethanol ammonia solution at 50° C. or with 0.3 mol/L sodium hydroxide solution.

In the present invention, the added amount of the silicon dioxide is 3% of the total mass of the monomers.

In the present invention, the temperature programming is 150° C., 250° C. and 330° C. for 1 hour respectively.

The low dielectric constant polyimide film prepared in the invention is used in aerospace, electronics and microelectronics.

Description of drawings

Figure 1 _N2 adsorption and desorption curves before and after potassium permanganate etching of silicon dioxide

Figure 2 Pore size distribution before and after etching silicon dioxide with potassium permanganate

Figure 3 Dielectric constant of polyimide film

Figure 4 Dielectric loss of polyimide film

Figure 5 thermal weight loss diagram of polyimide film

Fig.6 Partial enlarged view of thermal weight loss of polyimide film

Fig. 7 Mechanical tensile diagram of polyimide film

Detailed ways

The technical scheme of the present invention is described in further detail below, but the scope of protection of the present invention is not limited to the scope shown in the examples, and the selection of processing conditions such as temperature and time in the preparation method can be adjusted to local conditions and have no substantial impact on the results.

Example 1

(1) Dissolve 1.2g of cetyltrimethylammonium bromide in 40mL of ethanol and 30mL of deionized water, then add 0.8mL of ammonia water, after the above solution is mixed evenly, slowly add 1.6mL of tetraethyl orthosilicate dropwise, then stir at a constant speed for ten hours at room temperature, then centrifuge, wash and dry. denoted as HMS-1

(2) Ultrasonically disperse 1g of the above-mentioned dried silica particles in 150mL of deionized water, then dissolve 0.5g of potassium permanganate in 50mL of deionized water, add the aqueous solution of potassium permanganate into the silica dispersion, and react at room temperature for 12 hours, and finally reduce the potassium permanganate in the silica particles with hydrogen peroxide solution under acidic conditions, centrifuge, wash, and dry. Denoted as HMS-2

(3) Take the above 0.5g of etched silicon dioxide particles in 50mL of ethanol and 10mL of ammonia water, react at 50°C for 2 hours, filter and wash, then disperse the washed particles in 50mL of ethanol and 5mL of water, add 0.1g of per(17)fluorodecyltriethoxysilane to the reflux at 80°C, react for 3 hours, filter with suction, wash, and dry.

(4) Ultrasonically disperse 0.075g of the silica particles in step (3) in 100mL of N,N-dimethylformamide, then add 5.7488g of 4,4-diaminodiphenyl ether under nitrogen and a cold water bath, wait until the 4,4-diaminodiphenyl ether is completely dissolved, add 9.2512g of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride in three times, fully react for 4 to 6 hours, pour it out and let it stand to remove air bubbles, Coating a film on a clean glass plate, and finally keeping it in a vacuum oven at 150°C, 250°C and 330°C for 1 hour respectively, and cooling to room temperature to obtain a polyimide film with low dielectric constant.

Example 2

(1) Dissolve 1.2g of cetyltrimethylammonium bromide in 40mL of ethanol and 30mL of deionized water, then add 0.8mL of ammonia water, after the above solution is mixed evenly, slowly add 1.6mL of tetraethyl orthosilicate dropwise, then stir at a constant speed for ten hours at room temperature, then centrifuge, wash and dry. denoted as HMS-1

(2) Ultrasonically disperse 1g of the above-mentioned dried silica particles in 150mL of deionized water, then dissolve 0.5g of potassium permanganate in 50mL of deionized water, add the aqueous solution of potassium permanganate into the silica dispersion, and react at room temperature for 12 hours, and finally reduce the potassium permanganate in the silica particles with hydrogen peroxide solution under acidic conditions, centrifuge, wash, and dry. Denoted as HMS-2

(3) Take the above 0.5g of etched silicon dioxide particles in 50mL of ethanol and 10mL of ammonia water, react at 50°C for 2 hours, filter and wash, then disperse the washed particles in 50mL of ethanol and 5mL of water, add 0.1g of per(17)fluorodecyltriethoxysilane to the reflux at 80°C, react for 3 hours, filter with suction, wash, and dry.

(4) Take 0.15 g of the silica particles in step (3) and ultrasonically disperse them in 100 mL of N,N-dimethylformamide, then add 5.7488 g of 4,4-diaminodiphenyl ether under nitrogen and a cold water bath, wait until the 4,4-diaminodiphenyl ether is completely dissolved, add 9.2512 g of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride in three times, fully react for 4 to 6 hours, pour it out and let it stand to remove air bubbles, A clean glass plate is coated into a film, and finally kept in a vacuum oven at 150°C, 250°C and 330°C for 1 hour respectively, and cooled to room temperature to obtain a polyimide film with a low dielectric constant.

Example 3

(1) Dissolve 1.2g of cetyltrimethylammonium bromide in 40mL of ethanol and 30mL of deionized water, then add 0.8mL of ammonia water, after the above solution is mixed evenly, slowly add 1.6mL of tetraethyl orthosilicate dropwise, then stir at a constant speed for ten hours at room temperature, then centrifuge, wash and dry. denoted as HMS-1

(2) Ultrasonically disperse 1g of the above-mentioned dried silica particles in 150mL of deionized water, then dissolve 0.5g of potassium permanganate in 50mL of deionized water, add the aqueous solution of potassium permanganate into the silica dispersion, and react at room temperature for 12 hours, and finally reduce the potassium permanganate in the silica particles with hydrogen peroxide solution under acidic conditions, centrifuge, wash, and dry. Denoted as HMS-2

(3) Take the above 0.5g of etched silicon dioxide particles in 50mL of ethanol and 10mL of ammonia water, react at 50°C for 2 hours, filter and wash, then disperse the washed particles in 50mL of ethanol and 5mL of water, add 0.1g of per(17)fluorodecyltriethoxysilane to the reflux at 80°C, react for 3 hours, filter with suction, wash, and dry.

(4) Take 0.3g of the silica particles in step (3) and ultrasonically disperse them in 100mL of N,N-dimethylformamide, then add 5.7488g of 4,4-diaminodiphenyl ether under the conditions of nitrogen and cold water bath, wait until the 4,4-diaminodiphenyl ether is completely dissolved, add 9.2512g of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride in three times, fully react for 4~6 hours, pour it out and let it stand to remove air bubbles, Coated a thin film on a glass plate, and finally kept it in a vacuum oven at 150°C, 250°C and 330°C for 1 hour respectively, and cooled to room temperature to obtain a polyimide film with low dielectric constant.

Example 4

(1) Dissolve 1.2g of cetyltrimethylammonium bromide in 40mL of ethanol and 30mL of deionized water, then add 0.8mL of ammonia water, after the above solution is mixed evenly, slowly add 1.6mL of tetraethyl orthosilicate dropwise, then stir at a constant speed for ten hours at room temperature, then centrifuge, wash and dry. denoted as HMS-1

(2) Ultrasonically disperse 1g of the above-mentioned dried silica particles in 150mL of deionized water, then dissolve 0.5g of potassium permanganate in 50mL of deionized water, add the aqueous solution of potassium permanganate into the silica dispersion, and react at room temperature for 12 hours, and finally reduce the potassium permanganate in the silica particles with hydrogen peroxide solution under acidic conditions, centrifuge, wash, and dry. Denoted as HMS-2

(3) Take the above 0.5g of etched silicon dioxide particles in 50mL of ethanol and 10mL of ammonia water, react at 50°C for 2 hours, filter and wash, then disperse the washed particles in 50mL of ethanol and 5mL of water, add 0.1g of per(17)fluorodecyltriethoxysilane to the reflux at 80°C, react for 3 hours, filter with suction, wash, and dry.

(4) Ultrasonic dispersion of 0.45g of silica particles in step (3) into 100mL N,N-dimethylformamide, and then adding 5.7488g of 4,4-diaminodiphenyl ether under nitrogen and a cold water bath. After the 4,4-diaminodiphenyl ether is completely dissolved, add 9.2512g of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride in three times. A clean glass plate is coated into a film, and finally kept in a vacuum oven at 150°C, 250°C and 330°C for 1 hour respectively, and cooled to room temperature to obtain a polyimide film with a low dielectric constant.

Example 5

Add 5.7488g 4,4-diaminodiphenyl ether to 100mL N,N-dimethylformamide under the condition of nitrogen and cold water bath. After the 4,4-diaminodiphenyl ether is completely dissolved, add 9.2512g 3,3’,4,4’-benzophenone tetracarboxylic dianhydride three times. After fully reacting for 4~6 hours, pour it out and let it stand to remove air bubbles. 250 DEG C and 330 DEG C respectively for 1 hour, cooled to room temperature to obtain a polyimide film with low dielectric constant.

Embodiment 1～5 of above-mentioned gained is carried out dielectric property, thermal property and mechanical property test, and the result is as shown in table 1 below:

index Example 1 Example 2 Example 3 Example 4 Example 5 Dielectric constant 3.36 2.83 2.61 3.28 3.56 Dielectric loss 0.0043 0.0045 0.0049 0.0073 0.0037 Td5% (℃) 554.914 549.895 544.463 547.067 555.402 Tensile strength 68.66 56.31 48.22 36.99 87.2 (MPa) 2 Elongation at break (%) 11.47 11 8.77 8.29 12.5

The specific surface areas of silicon dioxide before and after etching with potassium permanganate were 880.9225 m²/g and 1,489.6125 m²/g, respectively. The sizes of the pores are 1.6166 nm and 3.3491 nm, respectively, which shows that the mesoporous silica particles are formed by potassium permanganate etching. As shown in Table 1 above, doping a small amount of fluorinated mesoporous silica particles into polyimide can significantly reduce the dielectric constant of the film without affecting the thermal properties of the film. However, the tensile strength and elongation at break of the film decreased by 57.59% and 33.68%, which may be due to the two-phase separation of silica particles in the polyimide matrix to generate pores. In addition, it is also possible that the silica is agglomerated in the polyimide matrix, thereby reducing the mechanical properties of the film. Because the addition of mesoporous silica particles into the polyimide matrix will increase the free volume fraction of polyimide. Therefore, the introduction of fluorinated mesoporous silica in polyimide lowered the dielectric constant. In addition, due to the strong electron-withdrawing properties of fluorine atoms, fluorinated mesoporous silica may reduce the discrete electronic energy levels of the composite film, which reduces the electronic polarization of the composite film and further reduces the dielectric constant of the film. The lowest dielectric constant of the composite film can be reduced to 2.61. In addition, the degree of electronic polarization of fluorinated mesoporous silica is reduced, and the hydrophobicity is enhanced, which is not conducive to the moisture absorption of the polymer, and also reduces the water absorption rate of the polymer. Therefore, the polyimide composite film prepared by the present invention can meet the requirements for low dielectric materials in the fields of integrated circuits, 5G communication antenna materials and flexible copper clad laminates.

Claims (7)

1. The preparation method of the low dielectric constant polyimide film is characterized by comprising the following steps of:

firstly, preparing silicon dioxide by hydrolysis of tetraethyl orthosilicate;

etching silicon dioxide by potassium permanganate so that the silicon dioxide forms a hollow structure containing mesopores;

hydroxylating the surface of mesoporous silica, and then connecting full (seventeen) fluorodecyl triethoxysilane on the surface of the hydroxylated silica;

dispersing mesoporous silica particles with fluorinated surfaces in N, N-dimethylformamide by ultrasonic, sequentially adding diamine and dianhydride monomers with equal molar weight, and fully reacting for 4-6 hours;

pouring out the reacted composite slurry, standing to remove bubbles in the slurry, and coating the clean substrate with the slurry to form a film;

sixth, the coated film is placed in a vacuum oven, the temperature is raised in a procedure to remove the solvent in the film, and thermal imidization is carried out on the solvent.

2. The method for preparing a low dielectric constant polyimide film according to claim 1, wherein the time for hydrolysis of tetraethyl orthosilicate is 6-10 hours.

3. The method for preparing a low dielectric constant polyimide film according to claim 1, wherein the time for etching the silicon dioxide by the potassium permanganate is 12 hours.

4. The method for producing a low dielectric constant polyimide film according to claim 1, wherein the silica surface is hydroxylated with an aqueous ammonia solution of ethanol at 50 ℃ or with a 0.3mol/L sodium hydroxide solution.

5. The method for preparing a low dielectric constant polyimide film according to claim 1, wherein the silica is added in an amount of 3% of the total mass of the monomers.

6. The method for preparing a polyimide film with low dielectric constant according to claim 1, wherein the temperature programming is 150 ℃, 250 ℃ and 330 ℃ for 1 hour.

7. The use of the low dielectric constant polyimide film prepared according to the method of claim 1 in aerospace, electronics and microelectronics.