High-adhesion heat-conducting polyimide film and preparation method thereof

Abstract

The invention provides a high-adhesion heat-conducting polyimide film and a preparation method thereof. The polyimide film is prepared by adding a special fluorine-containing anilino phosphonic acid derivative, a certain proportion of spherical silicon oxide, boron nitride and diatom ooze as inorganic modifiers in the polyimide preparation process. By utilizing a pi-pi conjugated structure and an amide group in the fluorine-containing anilino phosphonic acid derivative, the polyimide film has excellent deformation resistance; in addition, by adding the fluorine-containing anilino phosphonic acid derivative, not only can the water absorption of the polyimide film be reduced, but also the adhesive force of the film on the surface of a copper foil can be improved. In addition, due to a layered breathable structure of the nano-scale silicon oxide particles, the micron-scale flaky boron nitride and the diatom ooze, the defect that the heat conductivity is reduced due to the existence of the fluorine-containing anilino phosphonic acid derivative is overcome, and the heat conductivity coefficient of the obtained polyimide film is not lower than 1.0 W / (mk).

Description

Technical Field

[0001] The invention relates to the field of polymer materials, and in particular to a high-adhesion thermally conductive polyimide film and a preparation method thereof. Background Art

[0002] With the rapid improvement of semiconductor technology, the operation speed and corresponding design complexity are constantly increasing. In response to the needs of improved semiconductor technology, efficient semiconductor packaging technology has emerged, such as high-density packaging, Quad Flat Non-lead (QFN) packaging, etc. Among them, the QFN package is a popular low-pin-count high-density package type with relatively short signal wires and faster signal transmission speed. It has become the mainstream of low-pin-count chip packaging and is suitable for high-frequency chip packaging.

[0003] QFN is square or rectangular, with a large exposed pad in the center of the bottom of the package, which has a heat-conducting effect, and there are conductive pads on the periphery of the package for electrical connection. Since the QFN package does not have gull-wing leads like the traditional small outline integrated circuit package (SOIC) and thin small size package (TSOP) package, the conductive path between the internal pins and the pad is short, the self-inductance coefficient and the wiring resistance in the package are very low, so it can provide excellent electrical performance. In addition, it also provides excellent heat dissipation performance through the exposed lead frame pad, which has a direct heat dissipation channel for releasing heat in the package. Usually, the heat dissipation pad is directly soldered on the circuit board, and the heat dissipation vias in the PCB help to spread the excess power consumption into the copper ground plane, thereby absorbing excess heat.

[0004] The QFN package with exposed heat dissipation pads soldered on PCBs on the market is particularly suitable for any application that has requirements for size, weight and performance due to its small size, light weight, and outstanding electrical and thermal properties. However, the smaller the device, the smaller the heat dissipation space, which cannot dissipate heat well, resulting in warping, cracking, and peeling between the inorganic substrate (copper foil) and the polymer coating, and even plastic deformation and fracture of the solder joints, which seriously affects the reliability and stability of the QFN package. Therefore, the polyimide film needs to have high temperature resistance similar to that of copper foil, and it must also maintain effective conduction and release of heat after the copper foil resistor releases heat. This is the most important issue that needs to be paid attention to now. Summary of the invention

[0005] In order to solve some problems existing in the polyimide film used in the prior art, the present invention provides a high-adhesion thermally conductive polyimide film and a preparation method thereof. The polyimide film not only has high adhesion and high thermal conductivity, but also can resist chemical corrosion, has good high-temperature stability, and has strong structural support, and can ensure the safe, reliable and stable operation of the electronic equipment used.

[0006] A high-adhesion thermally conductive polyimide film comprises the following raw materials: biphenyltetracarboxylic acid dianhydride, p-phenylenediamine, acetic anhydride, fluorine-containing aniline phosphonic acid derivatives and inorganic modified particles; wherein the inorganic modified particles are obtained by mixing silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud in a mass ratio of 2-5:2-3:3-5, and the inorganic modified particles account for 30-35% of the mass of the total raw material system.

[0007] In some embodiments of the present invention, the fluorine-containing anilinophosphonic acid derivative is at least one of (2-(2-oxo-2-(2-(trifluoromethyl)anilino)ethoxy)phenyl)phosphonic acid (CAS=919741-28-9), (2-(2-oxo-2-(3-(trifluoromethyl)anilino)ethoxy)phenyl)phosphonic acid (CAS=919728-15-7), (2-(2-oxo-2-(2-chloro-5-(trifluoromethyl)anilino)-ethoxy)phenyl)phosphonic acid (CAS=920448-08-4), and 1-(3,5-bis(trifluoromethyl))-3-(2-(diethyl phosphate))-diphenylurea (CAS=674301-68-9).

[0008] The fluorinated aniline phosphonic acid derivatives described above form hydrogen bonds with the imide groups of polyimide via the amide groups in the molecules, and form a hydrophobic protective layer around the polyimide molecular chains using the trifluoromethyl group, while also making the polyimide film denser.

[0009] In some embodiments of the present invention, in the inorganic modified particles, the mass ratio of silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud is 2:3:5.

[0010] In some embodiments of the present invention, in the inorganic modified particles, the mass ratio of silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud is 3:2:5.

[0011] In the present invention, a heat-conducting network is formed inside the polyimide by combining the spherical uniform body of silicon oxide nanoparticles, the flaky structure of micron-sized boron nitride, and the layered breathable structure of diatom mud. However, if the proportion of spherical silicon oxide nanoparticles increases, more gaps will appear in the film, which is not conducive to the construction of heat conduction paths, thereby affecting the thermal conductivity of the film; and too much flaky boron nitride will stack in the matrix, resulting in larger agglomerations, which is not conducive to heat transfer, and at the same time will increase the distance between molecular chains, weakening the interaction between molecular chains. Based on the above considerations, the inventors prefer that the mass ratio of silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud is 2:3:5 or 3:2:5.

[0012] The method for preparing the high-adhesion thermally conductive polyimide film described above comprises the following steps: S1: dissolving p-phenylenediamine and biphenyltetracarboxylic acid dianhydride in amide solvents respectively, then pouring the biphenyltetracarboxylic acid dianhydride solution into a reaction vessel containing p-phenylenediamine solution, filling with inert gas, and stirring at 35-40° C. for 4-6 hours to obtain polyamide acid glue; S2: adding the fluorinated aniline phosphonic acid derivative to the polyamic acid glue obtained in S1, and ultrasonically treating for 4-5 hours; S3: adding inorganic modified particles to the mixed system obtained in S2, stirring evenly at a temperature not higher than 25° C., and removing impurities by filter pressing; S4: The product obtained in S3 is mixed with acetic anhydride at -5-0°C, and the mixture is drooled on a steel belt through a coating die, and then sent into an oven for longitudinal stretching. After desolventizing and curing, the high-adhesion thermally conductive polyimide film is obtained.

[0013] Furthermore, in S1, the molar ratio of p-phenylenediamine to biphenyltetracarboxylic dianhydride is 1:1.12-1.25.

[0014] Furthermore, the amide solvent in S1 is at least one of dimethylformamide and dimethylacetamide.

[0015] Furthermore, in S2, the added mass of the fluorine-containing aniline phosphonic acid derivative is 30-50% of the mass of the polyamic acid glue.

[0016] The inventors found in the experiment that the hydrogen bonds between the molecules of the fluorinated anilinophosphonic acid derivatives make them have a strong tendency to aggregate, which will cause multi-layer stacking. Moreover, as the content of the fluorinated anilinophosphonic acid derivatives increases, the repulsive effect of the fluorinated groups will form a spherical structure in the polyimide film. The uniformly distributed spherical structure can play a role in strengthening and toughening, but it will also affect the thermal conductivity of the film. Therefore, after the experiment, it was found that the addition amount of the fluorinated anilinophosphonic acid derivatives accounted for 30-50% of the mass of the polyamide acid glue.

[0017] Furthermore, the added mass of the non-polar modified particles in S3 accounts for 30-35% of the total mass of the mixed system.

[0018] Furthermore, the added mass of acetic anhydride in S4 accounts for 10-18% of the total mass of the product obtained in S3.

[0019] Furthermore, in S4, the oven temperature is 175-195° C., and the running speed of the steel belt is 5-6 m / s.

[0020] Beneficial effects: Compared with the prior art, the present invention creatively adds fluorinated aniline phosphonic acid derivatives when preparing the polyimide film, thereby improving the high adhesion of the film to the copper foil, while also ensuring the mechanical strength of the film, so that it has excellent anti-deformation ability; combining silicon oxide nanoparticles, micron-sized boron nitride and diatom mud, the obtained polyimide film is endowed with good thermal conductivity; by adjusting the addition amounts of the four, the adhesion and thermal conductivity of the polyimide film are balanced, thereby meeting the requirements of electronic chip packaging processing. DETAILED DESCRIPTION

[0021] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0022] Example 1 S1: Dissolve 1 mol of p-phenylenediamine and 1.12 mol of biphenyltetracarboxylic anhydride in 1000 ml of dimethylformamide respectively, then pour the biphenyltetracarboxylic anhydride solution into a reaction vessel containing the p-phenylenediamine solution, fill with nitrogen, and stir at 35°C for 4 hours to obtain polyamic acid glue (yield 81.8%); S2: Add 107.3 g (2-(2-oxo-2-(2-(trifluoromethyl)anilino)ethoxy)phenyl)phosphonic acid to the polyamic acid glue obtained in S1 and treat with ultrasound for 4 h; S3: Add 139.5 g of inorganic modified particles (silicon oxide nanoparticles: micron-sized boron nitride flakes: diatom mud = 5:3:3) to the mixed system obtained in S2, stir evenly at 25°C, and remove impurities by filter pressing; S4: The product obtained in S3 is mixed with 55.4 g of acetic anhydride at -1°C, and the mixture is cast on a steel belt at a speed of 5 m / min through a coating die, and then sent into a 175°C casting oven for longitudinal stretching. After desolventizing and curing, the high-adhesion thermally conductive polyimide film is obtained.

[0023] Example 2 S1: Dissolve 1 mol of p-phenylenediamine and 1.20 mol of biphenyltetracarboxylic anhydride in 1000 ml of dimethylformamide respectively, then pour the biphenyltetracarboxylic anhydride solution into a reaction vessel containing the p-phenylenediamine solution, fill with nitrogen, and stir at 40°C for 5 hours to obtain polyamic acid glue (yield 80.5%); S2: Add 148.4 g of 2-(2-oxo-2-(2-chloro-5-(trifluoromethyl)anilino)-ethoxy)phenyl)phosphonic acid to the polyamic acid glue obtained in S1, and treat with ultrasound for 4.5 h; S3: Add 166.1 g of inorganic modified particles (silicon oxide nanoparticles: micron-sized boron nitride flakes: diatom mud = 2:3:5) to the mixed system obtained in S2, stir evenly at 20°C, and remove impurities by filter pressing; S4: The product obtained in S3 is mixed with 102.8 g of acetic anhydride at -3°C, and the mixture is cast on a steel belt at a speed of 5 m / min through a coating die, and then sent into a 185°C casting oven for longitudinal stretching. After desolventizing and curing, the high-adhesion thermally conductive polyimide film is obtained.

[0024] Example 3 S1: Dissolve 1 mol of p-phenylenediamine and 1.25 mol of biphenyltetracarboxylic anhydride in 1000 ml of dimethylformamide respectively, then pour the biphenyltetracarboxylic anhydride solution into a reaction vessel containing the p-phenylenediamine solution, fill with nitrogen, and stir at 40°C for 6 hours to obtain polyamic acid glue (yield 78.9%); S2: Add 187.6 g of 1-(3,5-bis(trifluoromethyl))-3-(2-(diethyl phosphate))-diphenylurea to the polyamic acid glue obtained in S1, and treat with ultrasound for 5 hours; S3: Add 197.0 g of inorganic modified particles (silicon oxide nanoparticles: micron-sized boron nitride flakes: diatom mud = 3:2:5) to the mixed system obtained in S2, stir evenly at 15°C, and remove impurities by filter pressing; S4: The product obtained in S3 is mixed with 136.8 g of acetic anhydride at -5°C, and the mixture is cast on a steel belt at a speed of 5 m / min through a coating die, and then sent into a 195°C casting oven for longitudinal stretching. After desolventizing and curing, the high-adhesion thermally conductive polyimide film is obtained.

[0025] Comparative Example 1 Similar to Example 3, except that boron oxide is used instead of micron-sized flake boron nitride.

[0026] Comparative Example 2 Similar to Example 3, except that micron-sized flake boron nitride is not added.

[0027] Comparative Example 3 Similar to Example 3, except that diatom mud is not added.

[0028] Comparative Example 4 Similar to Example 3, except that 1-(3,5-bis(trifluoromethyl))-3-(2-(diethylphospho))-diphenylurea was not added.

[0029] Performance Testing The polyimide films (thickness 12.5 μm) prepared in Examples 1-3 and Comparative Examples 1-4 were tested for tensile strength, elongation at break and Young's modulus according to ASTM D882; the thermal expansion coefficient at 200°C was tested according to ASTM D696; the thermal shrinkage was tested at 200°C for 2 hours according to ASTM D5213-04; the thermal conductivity of the thermally conductive PI film was tested by a flash thermal conductivity meter; and the peel strength was tested according to GB / T8808-1988.

[0030] The test results are detailed in Table 1: Table 1-1 Performance test results of the films obtained in Examples 1-3 Table 1-2 Performance test results of the films obtained in Comparative Examples 1-4 From the data obtained in Table 1-1 and Table 1-2, it can be seen that the polyimide film provided by the present invention has excellent performance: the thermal expansion coefficient similar to that of copper foil, coupled with higher peel strength and lower thermal shrinkage, enables the film to adhere well to the copper foil, and has good deformation resistance when subjected to high temperature, reducing the possibility of warping, cracking, peeling and other manifestations; the thermal conductivity coefficient of not less than 1.0W / ((m·k)) makes it have excellent thermal conductivity. It can be seen that the various properties of the high-adhesion thermally conductive polyimide film provided by the present invention are greatly optimized, providing a good packaging material for QFN.

Claims

1. A high-adhesion thermally conductive polyimide film, characterized in that: The invention comprises the following raw materials: biphenyltetracarboxylic acid dianhydride, p-phenylenediamine, acetic anhydride, fluorine-containing aniline phosphonic acid derivatives and inorganic modified particles; wherein the inorganic modified particles are silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud mixed in a mass ratio of 2-5:2-3:3-5.

2. The high-adhesion thermally conductive polyimide film according to claim 1, characterized in that: The fluorine-containing anilinophosphonic acid derivative is at least one of (2-(2-oxo-2-(2-(trifluoromethyl)anilino)ethoxy)phenyl)phosphonic acid, (2-(2-oxo-2-(3-(trifluoromethyl)anilino)ethoxy)phenyl)phosphonic acid, (2-(2-oxo-2-(2-chloro-5-(trifluoromethyl)anilino)-ethoxy)phenyl)phosphonic acid, and 1-(3,5-bis(trifluoromethyl))-3-(2-(diethyl phosphate))-diphenylurea.

3. The high-adhesion thermally conductive polyimide film according to claim 1, characterized in that: In the inorganic modified particles, the mass ratio of silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud is 2:3:

5.

4. The high-adhesion thermally conductive polyimide film according to claim 1, characterized in that: In the inorganic modified particles, the mass ratio of silicon oxide nanoparticles, micron-sized flaky boron nitride and diatom mud is 3:2:

5.

5. The method for preparing the high-adhesion thermally conductive polyimide film according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: dissolving p-phenylenediamine and biphenyltetracarboxylic anhydride in amide solvents respectively, then adding the biphenyltetracarboxylic anhydride solution into a reaction vessel containing p-phenylenediamine solution in batches for multiple times, filling with inert gas, and stirring at 35-40° C. for 4-6 hours to obtain polyamide acid glue; S2: adding the fluorinated aniline phosphonic acid derivative to the polyamic acid glue obtained in S1, and ultrasonically treating for 4-5 hours; S3: adding inorganic modified particles to the mixed system obtained in S2, stirring evenly at a temperature not higher than 25° C., and removing impurities by filter pressing; S4: adding acetic anhydride to the product obtained in S3 in batches for multiple times, mixing, and then drooling on a steel belt through a coating die, and sending it into an oven to perform dehydration cyclization and thermal imidization in sequence, so as to obtain the high adhesion thermal conductive polyimide film.

6. The method for preparing the high-adhesion thermally conductive polyimide film according to claim 5, characterized in that: In S1, the molar ratio of p-phenylenediamine to biphenyltetracarboxylic dianhydride is 1:1.12-1.

25.

7. The method for preparing the high-adhesion thermally conductive polyimide film according to claim 5, characterized in that: The amide solvent in S1 is at least one of dimethylformamide and dimethylacetamide.

8. The method for preparing the high-adhesion thermally conductive polyimide film according to claim 5, characterized in that: In S2, the added mass of the fluorinated aniline phosphonic acid derivative is 30-50% of the mass of the polyamic acid glue.

9. The method for preparing the high-adhesion thermally conductive polyimide film according to claim 5, characterized in that: The added mass of the inorganic modified particles in S3 accounts for 30-35% of the total mass of the mixed system.

10. The method for preparing the high-adhesion thermally conductive polyimide film according to claim 5, characterized in that: The added mass of acetic anhydride in S4 accounts for 10-18% of the total mass of the product obtained in S3.

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