TWI827897B - Low dielectric loss polyimide film - Google Patents

Abstract

The invention is a polyimide film with low dielectric loss, which is prepared from copolymerized polyamide through a chemical cyclization method, wherein the copolymerized polyamide must have at least 3,3',4,4' -The composition of biphenyltetracarboxylic dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride; BPDA), p-phenylene diamine (p-PDA) and the diamine of the following chemical formula (A) :

Among them, the molar number of BPDA must account for more than 60% of the total molar number of the dianhydride of the copolymerized polyamic acid, and the molar number of p-PDA must account for the total molar number of the diamine of the copolymerized polyamic acid. The percentage of the molar number of chemical formula (A) must be more than 30% of the total molar number of diamines in the copolymerized polyamide acid; and the polyimide film has a glass transition temperature Tg greater than 280 ℃, the dielectric loss tangent Df (@ 10GHz) is less than 0.008 and the thermal expansion coefficient CTE is less than 12ppm/℃.

Description

Low dielectric loss polyimide film

The invention is a polyimide film with low dielectric loss, especially a polyimide film with a diameter of 25 microns or more produced by a chemical method, so that it has a low dielectric loss and a low linear expansion coefficient. .

Polyimide has excellent heat resistance, electrical properties and mechanical strength properties and is designed to have low dielectric loss. Polyimide films are often used in flexible circuit board applications with high-temperature processes, as well as in recent developments. Most of them are designed for 5G high-frequency and high-speed application components. In addition, the currently well-known compounds are composed of 1,2,4,5-pyromellitic anhydride (PMDA) and phenylenediamine (PDA) and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and Polyimide composed of p-phenylenediamine (PDA). Among them, although PMDA/PDA has excellent thermal properties, its film is very brittle and has poor mechanical and electrical properties. BPDA/PDA not only has excellent heat resistance, but also has excellent mechanical properties and dimensional stability. Therefore, It is preferably used in applications such as flexible printed circuit boards, protective films for semiconductor components, and interlayer insulating films for integrated circuits that require these characteristics. However, its high dielectric loss makes it unsuitable for 5G high-frequency materials. In addition, because it is rigid and has a straight main structure, the molecules are arranged and packed too densely, making it difficult for solvent vapor to penetrate during the production of the film, causing bubbles to be generated inside and on the surface.

Since this type of polyimide membrane is prone to bubbles, thermal cyclization was mostly used in the past. It is produced by a process method, because the thermal cyclization process is obtained by slowly heating and baking the polyamide precursor (PAA), and the baking temperature needs to be greater than 300 degrees. In this process, when the polyamide precursor (PAA) is in the plastic segment where the solvent is still present, its molecular chain segments are nonlinear, so the arrangement is less dense, so bubbles are less likely to occur, but when the film thickness There will still be bubbles when it is thicker (>25um). Patent Document 1 uses a co-solvent to produce the polyimide (BPDA-PDA). The co-solvent utilizes the azeotropic phenomenon produced by solvents with different boiling points to reduce the residual amount of solvent during the same baking process. A bubble-free polyimide membrane is obtained, but the disadvantage is that the waste liquid treatment after mass production is cumbersome and increases the cost.

In addition to thermal cyclization, chemical cyclization is also a common film-making process. Chemical cyclization uses dehydrating agents and catalysts to convert the polyamide precursor into polyimide at low temperatures. Therefore, In the plastic segment in the presence of solvent, since most of the nonlinear polyamide chain segments are converted into linear polyimide chain segments, the molecular chains are arranged regularly and closely, which is relatively easier and more Bubbles are generated, but therefore the chemical cyclization method of polyimide will have better mechanical and thermal properties than the thermal cyclization method. Patent Document 2 provides that a small amount of monomers with larger steric hindrances are added to form the polyimide. Imine allows the molecular chain segment to have space for the solvent to be discharged more easily without affecting too many mechanical and thermal properties. Although it can effectively eliminate bubbles, it will have a greater impact on electrical properties, resulting in increased dielectric loss and cannot be applied to 5G high-frequency materials.

Patent document 1: CN101802059B

Patent Document 2: TWI448487B

The invention is a polyimide film, which is prepared from copolymerized polyamide through a chemical cyclization method, wherein the copolymerized polyamide must have at least 3,3',4,4'-biphenyltetracarboxylic acid. dianhydride

(3,3’,4,4’-biphenyltetracarboxylic dianhydride; BPDA) and p-phenylenediamine (p- phenylene diamine; p-PDA) and the diamine of the following chemical formula (A).

In the chemical formula (A), R can be -CF3 or -CH3;

The molar number of BPDA must account for more than 60% of the total molar number of the dianhydride of the polyamic acid, and the molar number of p-PDA must account for the total molar number of the diamine of the polyamic acid. More than 50, and the molar number of chemical formula (A) needs to account for more than 30% of the total molar number of the diamines of the polyimide acid. The reaction composition makes the polyimide film have:

a. Glass transition temperature Tg is greater than 280℃

b. Dielectric loss tangent Df (@ 10GHz) is less than 0.008

c. The thermal expansion coefficient CTE is less than 12ppm/℃.

The polyimide film with low dielectric loss of the present invention, the thickness of the polyimide film is greater than 25 microns, and is prepared from copolymerized polyamide through a chemical cyclization method, wherein the copolymerized polyamide requires at least It has 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylenediamine (p-phenylene diamine; p-PDA) and the following The composition of the diamine of chemical formula (A), which chemical formula (A) is as follows:

其中BPDA的莫耳數需佔該共聚聚醯胺酸之二酸酐總莫耳數之百分比60以 上，以及p-PDA的莫耳數需佔該共聚聚醯胺酸之二胺總莫耳數之百分比50以上；化學式(A)的莫耳數需佔該共聚聚醯胺酸之二胺總莫耳數之百分比30以上反應組成；以及使該聚醯亞胺膜具有玻璃轉移溫度Tg大於280℃，介電損耗正切Df(@ 10GHz)小於0.008，熱線膨脹係數CTE小於12ppm/℃。

The molar number of BPDA must account for more than 60% of the total molar number of the dianhydride of the copolymerized polyamic acid, and the molar number of p-PDA must account for the total molar number of the diamine of the copolymerized polyamic acid. The percentage is more than 50; the molar number of chemical formula (A) needs to account for more than 30 molar percentage of the total molar number of the diamine of the copolymerized polyamide acid; and the polyimide film has a glass transition temperature Tg greater than 280°C. , the dielectric loss tangent Df (@ 10GHz) is less than 0.008, and the thermal expansion coefficient CTE is less than 12ppm/℃.

Wherein, in addition to the above-mentioned PDA, chemical formula (A) and BPDA aromatic diamine and aromatic dianhydride reaction, the aromatic polyamic acid may also include the following aromatic diamines and dianhydrides: wherein aromatic Diamines include 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2'-bis[4-(4-aminophenoxyphenyl)]propane (BAPP), 2 ,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane (HFBAPP), p-phenylenediamine (PDA), 4,4' -Bis(4-aminophenoxy)biphenyl (BAPB), 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA), 4,4'-diamino Diphenyl sulfide (44DDS), 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminobenzoanilide (44DABA), 2,2-bis(4-aminophenyl)hexafluoro Propane (Bis-A-AF), m-phenylenediamine (mPDA), 3,5-diaminobenzoic acid (35DABA), 2-(4-aminophenyl)-5-aminobenzoxazole (5BPOA), 1,4-bis(4-aminophenoxy)benzene (TPEQ), 4,4'-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline](FAPB) .

Among them, R in the chemical formula (A) can be CH3, so that the chemical formula (A) is 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB).

Wherein, R in the chemical formula (A) can be CF3, so that the chemical formula (A) is 2,2-bis(trifluoromethyl)diaminobiphenyl (TFMB).

Among them, the chemical cyclization method is formed by adding a dehydrating agent and a catalyst, wherein the dehydrating agent is acetic anhydride and the catalyst is methylpyridine and isoquinoline.

The dehydrating agent is added in an amount of at least 2 equivalents, and the catalyst is added in an amount of at least 1 equivalent.

Example

<Detection method>

The thermal properties and electrical properties of the polyimide films obtained in the following examples were measured using the following methods.

(1) Dk & Df @ 10GHz: Measured using the E5071C ENA Network Analyzer instrument produced by Keysight Technologies.

(2) CTE: Measured in accordance with ASTM D696 specifications using the model Q400 TMA instrument produced by TA Instruments. Measure the thermal expansion coefficient of the transparent polyimide film at 50~200℃, and set the heating rate to 10℃/min. In order to remove the stress caused by heat treatment, after removing the residual stress through the first measurement, the second measurement result is used as the actual value.

(3) Thickness: Measured using MiniTest 2100 instrument manufactured by Elektro Physik Company.

<Example 1>

Production of polyamide

Add 17.458 grams of p-phenylene diamine (PDA, 0.0161 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 27.174 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.092 mole), stir for 1 hour and keep the temperature at 25°C, then add 14.688 grams of 2,2'-diMethyl-4,4'-diaMinobiphenyl (m-Tolidine, 0.069 mole), stir until Completely dissolve, then slowly add 40.034 grams of BPDA, 0.136 mole, stir for 12 hours to dissolve and react, and maintain the temperature of the solution at 25°C, then use a trace amount of BPDA to adjust the viscosity to 200,000cps±30,000cps, and finally get A solution of copolymerized polyamide with a solids content of 20%.

Production of polyimide membrane

Take out 58.5 grams of the above copolymerized polyamide solution and add 6.5 grams of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, mix acetic anhydride and DMAc at a ratio of 5. Dilute the mixture at a weight ratio of 1, dilute 3-methylpyridine and DMAc at a weight ratio of 1 to 1, and then add 6.3 ml of acetic anhydride diluent and 5.3 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample on Bake in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min and bake for 20 minutes, then raise the temperature to 350°C and bake for 20 minutes at a rate of 2.0°C/min as the final treatment.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 9.7ppm/°C, a dielectric loss of Df 0.0069, and a Tg of 335°C.

Example 2

Production of polyamide

Add 11.898 grams of p-phenylene diamine (PDA, 0.0110 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 16.186 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.055 mole), stir for 1 hour and keep the temperature at 25°C, then add 23.358 grams of 2,2'-diMethyl-4,4'-diaMinobiphenyl (m-Tolidine, 0.110 mole), stir until Completely dissolve, then slowly add 47.586 grams of BPDA, 0.1161 mole, stir for 12 hours to dissolve and react, and maintain the temperature of the solution at 25°C, then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally obtain a solid A 20% copolymerized polyamide solution.

Production of polyimide membrane

Take out 58.5 grams of the above copolymerized polyamide solution and add 6.5 grams of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, mix acetic anhydride and DMAc at a ratio of 5. Dilute the mixture at a weight ratio of 1, dilute 3-methylpyridine and DMAc at a weight ratio of 1 to 1, and add 6.0 ml of acetic anhydride diluent and 5.1 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 7.7ppm/°C, a dielectric loss of Df 0.0065, and a Tg of 315°C.

Example 3

Production of polyamide

Add 12.514 grams of p-phenylene diamine (PDA, 0.0116 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 17.064 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.058 mole), stir for 1 hour and keep the temperature at 25°C, then add 24.60 grams of 2,2'-diMethyl-4,4'-diaMinobiphenyl (mTB, 0.116 mole), stir until completely dissolved , then slowly add 15.156 grams of pyromellitic anhydride (PMDA, 0.0695 mole), stir for 0.5 hours, then slowly add 30.001 grams of BPDA, 0.102 mole, stir for 12 hours until it dissolves and reacts , and the temperature of the solution was maintained at 25°C, and then a trace amount of BPDA was used to adjust the viscosity to 200,000±30,000cps, and finally a copolymerized polyamide solution with a solid content of 20% was obtained.

Production of polyimide membrane

Take 58.5 grams of the above copolymerized polyamide solution and add 6.5 grams of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Then dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 6.3 ml of acetic anhydride diluent and 5.3 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 8.5ppm/°C, a dielectric loss of Df 0.008, and a Tg of 342°C.

Example 4

Production of polyamide

Add 11.123 grams of p-phenylene diamine (PDA, 0.103 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 15.151 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.052 mole), stir for 1 hour and keep the temperature at 25°C, then add 24.60 grams of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.103 mole), stir Until it is completely dissolved, slowly add 13.472 grams of pyromellitic anhydride (PMDA, 0.062 mole), stir for 0.5 hours, then slowly add 26.666 grams of BPDA, 0.091 mole, and stir for 12 hours until it completes. Dissolve and react, and maintain the temperature of the solution at 25°C. Then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally obtain a copolymerized polyamide solution with a solid content of 20%.

Production of polyimide membrane

Take 58.5 grams of the above copolymerized polyamide solution and add 6.5 grams of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 5.6 ml of acetic anhydride diluent and 4.7 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 11.9ppm/°C, a dielectric loss of Df 0.007, and a Tg of 328°C.

Example 5

Preparation of copolymerized polyamide

Add 10.623 grams of p-phenylene diamine (PDA, 0.098 mole) to 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 14.470 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.049 mole), stir for 1 hour and keep the temperature at 25°C, then add 31.498 grams of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.098 mole), stir Until it is completely dissolved, slowly add 42.831 grams of BPDA, 0.146 mole, stir for 12 hours to dissolve and react, and maintain the temperature of the solution at 25°C. Then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally get A solution of copolymerized polyamide with a solids content of 20%.

Production of polyimide membrane

Take 58.5 grams of the above copolymerized polyamide solution and add 6.5 grams of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 5.3 ml of acetic anhydride diluent and 4.5 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 11ppm/°C, a dielectric loss of Df 0.0075, and a Tg of 300°C.

Example 6

Production of polyamide

Add 11.123 grams of p-phenylene diamine (PDA, 0.103 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 15.151 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.052 mole), stir for 1 hour and keep the temperature at 25°C, then add 24.60 grams of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.103 mole), stir Until it is completely dissolved, slowly add 13.472 grams of pyromellitic anhydride (PMDA, 0.062 mole), stir for 0.5 hours, then slowly add 26.666 grams of BPDA, 0.091 mole, stir for 0.5 hours and wait for it to proceed. Dissolve and react, and maintain the temperature of the solution at 25°C. Then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally obtain a copolymerized polyamide solution with a solid content of 20%.

Production of polyimide membrane

Take 58.5 mg of the above copolymerized polyamide solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 6.1 ml of acetic anhydride diluent and 5.2 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 9.0ppm/°C, a dielectric loss of Df 0.0080, and a Tg of 325°C.

Comparative example 1

Preparation of polyamide solution

Add 20.422 grams of p-phenylene diamine (PDA, 0.189 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 27.817 grams of 3,3’,4,4’ -biphenyltetracarboxylic dianhydride (BPDA, 0.0945 mole), stir for 1 hour and keep the temperature at 25°C, then add 10.036 grams of 2,2'-diMethyl-4,4'-diaMinobiphenyl (mTB, 0.047 mole), stir until completely dissolved Then slowly add 40.682 grams of BPDA (0.138 mole), stir for 12 hours to dissolve and react, and maintain the temperature of the solution at 25°C. Then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally obtain a solid content of 20% copolymerized polyamide solution.

Production of polyimide membrane

Take 58.5 mg of the above copolymerized polyamide solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 6.4 ml of acetic anhydride diluent and 5.4 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 9.5ppm/°C, a dielectric loss of Df 0.011, and a Tg of 340°C.

Comparative example 2

Add 10.175 grams of p-phenylene diamine (PDA, 0.094 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 13.859 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.0471 mole), stir for 1 hour and keep the temperature at 25°C, then add 10.036 grams of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.047 mole), stir Until it is completely dissolved, slowly add 12.323 grams of 1,2,4,5-benzene tetramethyl acid anhydride (PMDA, 0.057 mole), stir for 0.5 hours and then slowly add 19.614 grams of 4,4'-(4,4'-isopropyl diphenoxy) diphthalic anhydride (BPADA, 0.038 mole) and 13.028 grams of BPDA (0.044 mole), stir for 12 hours to dissolve and react, and maintain the temperature of the solution at 25°C. Then use a trace amount of BPDA to adjust the viscosity to 200,000±30,000cps, and finally obtain a copolymer with a solid content of 20%. Amino acid solution.

Production of polyimide membrane

Take 58.5 mg of the above copolymerized polyamide solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 5.1 ml of acetic anhydride diluent and 4.3 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing.

Comparative example 3

Preparation of polyamide solution

Add 12.695 grams of p-phenylene diamine (PDA, 0.118 mole) to 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 17.293 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.059 mole), stir for 1 hour and keep the temperature at 25°C, then add 23.510 grams of 4,4'-diaminodiphenyl ether (ODA, 0.118 mole), stir until completely dissolved and then add slowly 15.375 grams of pyromellitic anhydride (PMDA, 0.071 mole), stir for 0.5 hours, then slowly add 30.089 grams of BPDA (0.102 mole), stir for 12 hours until it dissolves and reacts, and the solution The temperature was maintained at 25°C, and then a trace amount of BPDA was used to adjust the viscosity to 200,000±30,000cps, and finally a copolymerized polyamide solution with a solid content of 20% was obtained.

Production of polyimide membrane

Take 58.5 mg of the above copolymerized polyamide solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 6.4 ml of acetic anhydride diluent and 5.4 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, apply the degassed solution to the glass plate and use a spatula with a gap of 900 μm for coating. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing. The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 10.0ppm/°C, a dielectric loss of Df 0.012, and a Tg of 340°C.

Comparative example 4

Preparation of polyamide solution

Add 26.851 grams of p-phenylene diamine (PDA, 0.249 mole) and 400 grams of N,N-dimethylacetamide (DMAc). After all is dissolved, add 71.686 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.244 mole), the temperature is controlled at 25°C when added, the reaction is stirred for 24 hours and the temperature is maintained at 25°C, and then a trace amount of BPDA is used to adjust the viscosity to 200,000±30,000cps, and the solid content is finally obtained It is a 20% copolymerized polyamide solution.

Production of polyimide membrane

Take 58.5 mg of the above copolymerized polyamide solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, add acetic anhydride and DMAc at a ratio of 5 to 1. Dilute 3-methylpyridine and DMAc at a weight ratio of 1:1, then add 6.8 ml of acetic anhydride diluent and 5.7 ml of 3-methylpyridine diluent respectively. After evenly stirring, use a centrifugal degassing machine to degas, and apply the degassed solution After reaching the glass plate, use a 900μm gap spatula to apply. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C at a rate of 1.8°C/min, bake for 20 minutes, and then raise the temperature to 350°C at a rate of 2.0°C/min. 20 minutes for final processing. The polyimide film produced above has a thermal expansion coefficient between 50 and 200°C of 3.5ppm/°C, a dielectric loss of Df 0.013, and a Tg of 360°C.

Table of Examples and Comparative Examples

The specific embodiments described above are intended to illustrate the present invention in detail. However, these embodiments are only for illustration and are not intended to limit the present invention. Those familiar with the art in this field can understand, Various changes or modifications made to the present invention without departing from the scope defined in the appended patent application are part of the present invention.

Claims (4)

A polyimide film with low dielectric loss. The thickness of the polyimide film is greater than 25 microns. It is prepared from copolymerized polyamide through a chemical cyclization method, wherein the copolymerized polyamide must have at least 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylene diamine (p-PDA) and the following chemical formula The composition of the diamine of (A), the chemical formula (A) is as follows:

, where R is CH3, so that chemical formula (A) is 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB), or R is CF3, so that chemical formula (A) is 2 , 2-bis(trifluoromethyl)diaminobiphenyl (TFMB); the molar number of BPDA must account for more than 60% of the total molar number of the dianhydride of the copolymerized polyamide acid, and the molar number of p-PDA must be The molar number of chemical formula (A) needs to account for more than 50% of the total molar number of the diamines of the copolymerized polyamide acid; the molar number of the chemical formula (A) needs to be estimated to be more than 30% of the total molar number of the diamines of the copolymerized polyamic acid. The composition; and the polyimide film has a glass transition temperature Tg greater than 280°C, a dielectric loss tangent Df (@10GHz) less than 0.008, and a thermal expansion coefficient CTE less than 12ppm/°C. The polyimide film with low dielectric loss as described in item 1 of the patent application, wherein the aromatic polyamide contains, in addition to the aromatic diamine and aromatic dianhydride of the above-mentioned PDA, chemical formula (A) and BPDA. In addition to those obtained by reaction, the following aromatic diamines may also be included: wherein the aromatic diamines include 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB), 2,2'-bis[4 -(4-Aminophenoxyphenyl)]propane (BAPP), 2,2-bis[4-(4-aminophenoxyphenyl)]-1,1,1,3,3,3-hexa Fluoropropane (HFBAPP), p-phenylenediamine (PDA), 4,4'-bis(4-aminobenzene) Oxy)biphenyl (BAPB), 2,2'-bis(trifluoromethyl)-4,4'-diaminophenyl ether (6FODA), 4,4'-diaminodiphenyl sulfone (44DDS), 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminobenzoanilide (44DABA), 2,2-bis(4-aminophenyl)hexafluoropropane (Bis-A-AF ), m-phenylenediamine (mPDA), 3,5-diaminobenzoic acid (35DABA), 2-(4-aminophenyl)-5-aminobenzoxazole (5BPOA), 1,4-bis(4 -Aminophenoxy)benzene (TPEQ) or 4,4'-[1,4-phenylbis(oxy)]bis[3-(trifluoromethyl)aniline] (FAPB). The polyimide film with low dielectric loss as described in item 1 of the patent application, wherein the chemical cyclization method is formed by adding a dehydrating agent and a catalyst, wherein the dehydrating agent is acetic anhydride and the catalyst is methylpyridine or Isoquinoline. For the low dielectric loss polyimide membrane described in item 3 of the patent application, the dehydrating agent is added in an amount of at least 2 equivalents, and the catalyst is added in an amount of at least 1 equivalent.