TW202225266A - Polyimide film with low dielectric loss having a glass transition temperature Tg of 280 DEG C or higher, a dielectric loss tangent Df (at 10GHz) of 0.008 or less, and a linear thermal expansion coefficient CTE of 12 ppm/DEG C or less - Google Patents

Abstract

The present invention is a polyimide film with low dielectric loss, which is prepared from copolymerized polyamic acid by a chemical cyclization method, wherein the copolymerized polyamic acid at least requires a composition having 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) and p-phenylene diamine (p-PDA) and a diamine of the following chemical formula (A): wherein, the number of moles of BPDA needs to account for 60 percent or more of the total number of moles of the dianhydrides of the copolymerized polyamic acid, the number of moles of p-PDA needs to account for 50 percent or more of the total molar number of the diamines of the copolymerized polyamic acid, and the number of moles of the chemical formula (A) needs to account for 30 percent or more of the total number of moles of the diamines of the copolymerized polyamide acid; in addition, the polyimide film has a glass transition temperature Tg of 280 DEG C or higher, a dielectric loss tangent Df (at 10GHz) of 0.008 or less, and a linear thermal expansion coefficient CTE of 12 ppm/DEG C or less.

Description

Polyimide Film with Low Dielectric Loss

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

Polyimide has excellent heat resistance, electrical properties and mechanical strength characteristics, and is designed to have low dielectric loss, so that polyimide films are often used in flexible circuit board applications with high temperature processes, and more recently. Most of them are designed on 5G high-frequency and high-speed application components. In addition, it is widely known that 1,2,4,5-benzenetetracarboxylic 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, while BPDA/PDA not only has excellent heat resistance, but also has excellent mechanical properties and dimensional stability, etc. Therefore, It is preferably used in flexible printed circuit boards, protective films for semiconductor elements, interlayer insulating films for integrated circuits, etc. that require these characteristics, but its high dielectric loss is not suitable for 5G high-frequency materials. In addition, because of its rigidity and the main structure of straight lines, the molecular arrangement is too dense, so that the film is not easily permeated by solvent vapor during the production, and bubbles are generated inside and on the surface.

Since such polyimide films are prone to bubble generation, thermally cyclized films are mostly used in the past. It is produced by the process method, because the thermal cyclization process is obtained by slowly heating and baking the polyamide acid precursor (PAA), and the baking temperature needs to be higher than 300 degrees. In this process, when the plastic segment of the polyamide acid precursor (PAA) still exists in the solvent, its molecular segment is non-linear, so the arrangement is less dense, so the occurrence of bubbles is less, but the film thickness There will still be bubbles in the case of thicker (>25um). In Patent Document 1, the polyimide (BPDA-PDA) is produced by using a co-solvent. The co-solvent uses the azeotropic phenomenon of solvents with different boiling points to reduce the residual amount of the solvent during the same baking process. A bubble-free polyimide membrane can be obtained, but the disadvantage is that the waste liquid treatment after mass production is cumbersome and increases cost.

In addition to thermal cyclization, chemical cyclization is also a common membrane-making process. Chemical cyclization uses dehydrating agents and catalysts to convert polyamide acid precursors into polyimide at low temperatures. Therefore, In the plastic segment in the presence of solvent, since most of the nonlinear polyimide segments are converted into linear polyimide segments, the molecular chains are arranged regularly and tightly, which is relatively easier and more 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 barriers are added to form polyimide. The imine can make the molecular segment have a space for the solvent to be easily discharged, and will not affect too much mechanical properties and thermal properties. Although it can effectively relieve the generation of 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 present invention relates to a polyimide film, which is prepared by a chemical cyclization method from a copolymerized polyamic acid, wherein the copolymerized polyamic acid 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 composition of the diamine of the following chemical formula (A).

Wherein in chemical formula (A), R can be -CF3 or -CH3;

Wherein the molar number of BPDA needs to account for more than 60% of the total molar number of dianhydride in the polyimide, and the molar number of p-PDA needs to account for the total molar number of diamine in the polyimide acid. More than 50, and the molar number of chemical formula (A) needs to account for more than 30 percent of the total molar number of diamines of the polyimide acid to form the reaction, so that the polyimide film has:

a. Glass transition temperature Tg greater than 280℃

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

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

The low dielectric loss polyimide film of the present invention, the thickness of the polyimide film is greater than 25 microns, is prepared by the chemical cyclization method of the copolymerized polyimide, wherein the copolymerized polyimide needs at least With 3,3',4,4'-biphenyltetracarboxylic dianhydride (3,3,4,4'-biphenyltetracarboxylic dianhydride; BPDA) and p-phenylene diamine (p-PDA) and the following The composition of the diamine of chemical formula (A), the 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/℃。

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

Wherein, in addition to the above-mentioned PDA, chemical formula (A) and aromatic diamine of chemical formula (A) and BPDA and aromatic dianhydride obtained by the reaction of the aromatic polyamide acid, the aromatic diamine and dianhydride can also include the following aromatic diamines and dianhydrides: 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 Diphenylene (44DDS), 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminobenzidine (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) .

Wherein, 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).

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 picoline and isoquinoline.

The addition amount of the dehydrating agent is at least 2 equivalents or more, and the catalyst addition amount is at least 1 equivalent or more

Example

<Detection method>

The thermal 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 model E5071C ENA Network Analyzer produced by Keysight Technologies.

(2) CTE: According to ASTM D696 specification, use the model Q400 TMA instrument of TA Instruments company to measure. The thermal expansion coefficient of the transparent polyimide film was measured at 50-200 °C, and the heating rate was set to 10 °C/min. In order to remove the stress caused by the heat treatment, after removing the residual stress by the first measurement, the second measurement result is used as the actual value.

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

<Example 1>

Production of Polyamide

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

Fabrication of Polyimide Film

Take out 58.5 g of the above-mentioned copolymerized polyamic acid solution, and add 6.5 g of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride to DMAc is 5 The weight ratio of 1 was diluted, and 3-picoline and DMAc were diluted with a weight ratio of 1:1, and then 6.3 ml of acetic anhydride diluent and 5.3 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated sample in Bake in an oven at 80°C for 20 minutes, then raise the temperature to 170°C for 20 minutes at a rate of 1.8°C/min, and then raise the temperature to 350°C for 20 minutes at a rate of 2.0°C/min as the final treatment.

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

Example 2

Production of Polyamide

Add 11.898 grams of p-phenylene diamine (PDA, 0.0110mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 16.186 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride(BPDA, 0.055mole), stirred for 1 hour and the temperature was maintained at 25°C, then added 23.358 g of 2,2'-diMethyl-4,4'-diaMinobiphenyl(m-Tolidine, 0.110mole), stirred until Completely dissolve, then slowly add 47.586 grams of BPDA, 0.1161 mole, stir for 12 hours to dissolve and react, and the temperature of the solution is maintained 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% solution of copolyamide.

Fabrication of Polyimide Film

Take out 58.5 g of the above-mentioned copolymerized polyamic acid solution, and add 6.5 g of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride to DMAc is 5 1 for dilution, and then 3-picoline and DMAc were diluted with a 1:1 weight ratio, and then 6.0 ml of acetic anhydride diluent and 5.1 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment.

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

Example 3

Production of Polyamide

Add 12.514 grams of p-phenylene diamine (PDA, 0.0116mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 17.064 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.058mole), stirred for 1 hour and the temperature was maintained at 25°C and then added 24.60 g of 2,2'-diMethyl-4,4'-diaMinobiphenyl (mTB, 0.116mole), stirred until completely dissolved , and then slowly add 15.156 grams of 1,2,4,5-benzenetetracarboxylic anhydride (PMDA, 0.0695mole), stir for 0.5 hours and then slowly add 30.001 grams of BPDA, 0.102mole, stir for 12 hours until it dissolves and reacts , and the temperature of the solution was maintained at 25 °C, and then the viscosity was adjusted to 200,000±30,000 cps with a trace amount of BPDA, and finally a copolymerized polyamide solution with a solid content of 20% was obtained.

Fabrication of Polyimide Film

Take out 58.5 grams of the above-mentioned copolymerized polyamic acid solution, add 6.5 grams of N,N-dimethylacetamide (DMAc), dilute the solid content to 18%, stir for 10 minutes, and mix acetic anhydride and DMAc in a weight ratio of 5 to 1. After diluting 3-picoline and DMAc at a weight ratio of 1:1, 6.3 ml of acetic anhydride diluent and 5.3 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min. 20 minutes for final treatment.

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

Example 4

Production of Polyamide

Add 11.123 grams of p-phenylene diamine (PDA, 0.103mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 15.151 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.052mole), stirred for 1 hour and the temperature was maintained at 25°C and then added 24.60 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.103mole), stirred To complete dissolution, slowly add 13.472 grams of 1,2,4,5-benzenetetracarboxylic anhydride (PMDA, 0.062mole), stir for 0.5 hours, then slowly add 26.666 grams of BPDA, 0.091mole, and stir for 12 hours until it progresses Dissolved and reacted, and the temperature of the solution was maintained at 25 °C, and then the viscosity was adjusted to 200,000±30,000 cps with a trace amount of BPDA, and finally a copolymerized polyamic acid solution with a solid content of 20% was obtained.

Fabrication of Polyimide Film

Take out 58.5 g of the above-mentioned copolymerized polyamic acid solution and add 6.5 g of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. Dilute by weight ratio, and then dilute 3-picoline and DMAc at a weight ratio of 1:1, and then add 5.6 ml of acetic anhydride diluent and 4.7 ml of 3-picoline diluent, respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment.

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

Example 5

Production of Copolymerized Polyamide

Add 10.623 grams of p-phenylene diamine (PDA, 0.098mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 14.470 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.049mole), stirred for 1 hour and the temperature was maintained at 25°C, then added 31.498 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.098mole), stirred To complete dissolution, slowly add 42.831 grams of BPDA, 0.146 moles, stir for 12 hours to dissolve and react, and the temperature of the solution is maintained at 25 ° C, then use a trace amount of BPDA to adjust the viscosity to 200,000 ± 30,000cps, and finally obtain Copolyamide solution with 20% solids content.

Fabrication of Polyimide Film

Take out 58.5 g of the above-mentioned copolymerized polyamic acid solution and add 6.5 g of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. Dilute by weight ratio, and then dilute 3-picoline and DMAc at a weight ratio of 1:1, and then add 5.3 ml of acetic anhydride diluent and 4.5 ml of 3-picoline diluent, respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment.

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

Example 6

Production of Polyamide

Add 11.123 grams of p-phenylene diamine (PDA, 0.103mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 15.151 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.052mole), stirred for 1 hour and the temperature was maintained at 25°C and then added 24.60 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.103mole), stirred To complete dissolution, slowly add 13.472 grams of 1,2,4,5-benzenetetracarboxylic 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 Dissolved and reacted, and the temperature of the solution was maintained at 25 °C, and then the viscosity was adjusted to 200,000±30,000 cps with a trace amount of BPDA, and finally a copolymerized polyamic acid solution with a solid content of 20% was obtained.

Fabrication of Polyimide Film

Take out 58.5 mg of the above-mentioned copolymerized polyamic acid solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. After diluting 3-picoline and DMAc in a weight ratio of 1:1, 6.1 ml of acetic anhydride diluent and 5.2 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment.

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

Comparative Example 1

Preparation of polyamide solution

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

Fabrication of Polyimide Film

Take out 58.5 mg of the above-mentioned copolymerized polyamic acid solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. The weight ratio was diluted, and then 3-picoline and DMAc were diluted in a weight ratio of 1:1, and then 6.4 ml of acetic anhydride diluent and 5.4 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment.

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

Comparative Example 2

Add 10.175 grams of p-phenylene diamine (PDA, 0.094mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 13.859 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.0471mole), stir the reaction for 1 hour and the temperature is maintained at 25°C and then add 10.036 g of 2,2'-bis(trifluoromethyl)diaminobiphenyl (TFMB, 0.047mole), stir To complete dissolution, slowly add 12.323 grams of 1,2,4,5-benzenetetramethyl Acid anhydride (PMDA, 0.057 mole), stirred for 0.5 hours and then slowly added 19.614 g of 4,4'-(4,4'-isopropyldiphenoxy) diphthalic anhydride (BPADA, 0.038 mole) and 13.028 g of BPDA (0.044mole), stirred for 12 hours until it was dissolved and reacted, and the temperature of the solution was maintained at 25°C, and then the viscosity was adjusted to 200,000±30,000cps with a small amount of BPDA, and finally a copolymerized polyamide with a solid content of 20% was obtained. Amino acid solution.

Fabrication of Polyimide Film

Take out 58.5 mg of the above-mentioned copolymerized polyamic acid solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. The weight ratio was diluted, and then 3-picoline and DMAc were diluted in a weight ratio of 1:1, and then 5.1 ml of acetic anhydride diluent and 4.3 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated sample in an oven at 80°C for 20 minutes, then raise the temperature to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min. 20 minutes for final treatment.

Comparative Example 3

Preparation of polyamide solution

Add 12.695 grams of p-phenylene diamine (PDA, 0.118mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 17.293 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride (BPDA, 0.059mole), stirred for 1 hour and the temperature was maintained at 25°C and then added 23.510 g of 4,4'-diaminodiphenyl ether (ODA, 0.118mole), stirred until completely dissolved and then slowly added 15.375 grams of 1,2,4,5-benzenetetracarboxylic acid anhydride (PMDA, 0.071 mole) was stirred for 0.5 hours and then slowly added 30.089 grams of BPDA (0.102 mole), stirred for 12 hours until it was dissolved and reacted, and the solution was The temperature was maintained at 25 °C, and then the viscosity was adjusted to 200,000 ± 30,000 cps using a small amount of BPDA, and finally a copolymerized polyamide solution with a solid content of 20% was obtained.

Fabrication of Polyimide Film

Take out 58.5 mg of the above-mentioned copolymerized polyamic acid solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. The weight ratio was diluted, and then 3-picoline and DMAc were diluted in a weight ratio of 1:1, and then 6.4 ml of acetic anhydride diluent and 5.4 ml of 3-picoline diluent were added respectively. After uniform stirring, a centrifugal defoamer was used for defoaming, and the defoamed solution was applied to a glass plate and then applied using a doctor blade with a gap of 900 μm. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment. The polyimide film prepared above has a thermal expansion coefficient of 10.0ppm/°C between 50 and 200°C, a dielectric loss of Df of 0.012, and a Tg of 340°C.

Comparative Example 4

Preparation of polyamide solution

Add 26.851 grams of p-phenylene diamine (PDA, 0.249mole) to 400 grams of N,N-dimethylacetamide (DMAc), and after all dissolved, add 71.686 grams of 3,3',4,4' -biphenyltetracarboxylic dianhydride(BPDA, 0.244mole), the temperature was controlled at 25°C during the addition, the reaction was stirred for 24 hours and the temperature was maintained at 25°C, and then the viscosity was adjusted to 200,000±30,000cps with a small amount of BPDA, and the solid content was finally obtained It is a 20% solution of copolyamide.

Fabrication of Polyimide Film

Take out 58.5 mg of the above-mentioned copolymerized polyamic acid solution and add 6.5 mg of N,N-dimethylacetamide (DMAc) to dilute the solid content to 18%. After stirring for 10 minutes, the ratio of acetic anhydride and DMAc is 5:1. Dilute by weight ratio, and then dilute 3-picoline and DMAc at a weight ratio of 1:1, and add 6.8 ml of acetic anhydride diluent and 5.7 ml of 3-picoline diluent, respectively. After uniform stirring, the defoaming machine is used for defoaming, and the defoamed solution is applied After reaching the glass plate, use a doctor blade with a gap of 900 μm for coating. Place the coated samples in an oven at 80°C for 20 minutes, then heat up to 170°C for 20 minutes at a rate of 1.8°C/min, and then bake at 350°C at a rate of 2.0°C/min 20 minutes for final treatment. The polyimide film prepared above has a thermal expansion coefficient of 3.5ppm/°C between 50 and 200°C, a dielectric loss of Df of 0.013, and a Tg of 360°C.

Example \ and comparative example table

The contents of the above-mentioned specific embodiments 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 skilled in the art can understand that, Various changes or modifications made to the present invention without departing from the scope defined by the appended claims are part of the present invention.

Claims (6)

A polyimide film with low dielectric loss, the thickness of the polyimide film is greater than 25 microns, which is prepared by a chemical cyclization method from a copolymerized polyamide, wherein the copolymerized polyamide must have at least 3,3',4,4'-biphenyltetracarboxylic dianhydride (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), this chemical formula (A) is as follows:

Wherein the molar number of BPDA needs to 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 needs to account for the total molar number of the diamine of the copolymerized polyamic acid. The percentage is more than 50; the molar number of the chemical formula (A) needs to account for more than 30 percent of the total molar number of the diamine in the copolymerized polyamide acid. Reaction composition; and make the polyimide film have a glass transition temperature Tg greater than 280 ° C , the dielectric loss tangent Df (@10GHz) is less than 0.008, and the thermal linear expansion coefficient CTE is less than 12ppm/℃. According to the low dielectric loss polyimide film described in item 1 of the claimed scope, R in the chemical formula (A) can be CH3, so that the chemical formula (A) is 2,2'-dimethyl- 4,4'-Diaminobiphenyl (m-TB). The polyimide film with low dielectric loss as described in item 1 of the claimed scope, wherein R in the chemical formula (A) can be CF3, so that the chemical formula (A) is 2,2-bis(trifluoromethyl) base) diaminobiphenyl (TFMB). The polyimide film with low dielectric loss as described in item 1 of the scope of the application, wherein the aromatic polyimide is in addition to the above-mentioned PDA, chemical formula (A) and aromatic diamide of BPDA In addition to the reaction of amine and aromatic dianhydride, it can also include the following aromatic diamines and dianhydrides: wherein the aromatic diamine includes 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'-diaminodiphenyl ether (44DDS), 4,4'-diaminodiphenyl ether (ODA), 4,4'-diaminodiphenyl ether (ODA) 4'-Diaminobenzidine (44DABA), 2,2-bis(4-aminophenyl)hexafluoropropane (Bis-A-AF), m-phenylenediamine (mPDA), 3,5-diamino Benzoic 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). The polyimide film with low dielectric loss as described in item 1 of the patent application scope, 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 picoline, isoquinoline. The polyimide film with low dielectric loss according to item 5 of the scope of the application, wherein the addition amount of the dehydrating agent is at least 2 equivalents or more, and the catalyst addition amount is at least 1 equivalent or more