CN109651631B

CN109651631B - Polyimide film with low dielectric loss

Info

Publication number: CN109651631B
Application number: CN201810047796.4A
Authority: CN
Inventors: 李磊; 袁舜齐; 何志斌
Original assignee: Shenzhen Ruihuatai Film Technology Co ltd
Current assignee: Shenzhen Ruihuatai Film Technology Co ltd
Priority date: 2018-01-18
Filing date: 2018-01-18
Publication date: 2020-09-25
Anticipated expiration: 2038-01-18
Also published as: CN109651631A

Abstract

The invention provides polyimide and a polyimide film with ultralow dielectric loss, which is prepared from the polyimide, wherein the dielectric loss factor of the polyimide film is 0.0030-0.0060. The polyimide comprises structural units shown in a general formula (1), a general formula (2) and a general formula (3): wherein the structural unit represented by the general formula (1) accounts for more than 20 mol%, the structural unit represented by the general formula (2) accounts for more than 20 mol%, the structural unit represented by the general formula (3) accounts for more than 10 mol%, and n in the general formula (3) is an integer of 1-10; ar (Ar)₁、Ar₂、Ar₃Is a tetravalent aromatic radical, Ar₄Is a divalent aromatic group containing hetero atoms. The polyimides of the invention are mainly end-capped with amine groups.

Description

Polyimide film with low dielectric loss

Technical Field

The invention relates to a polyimide film material with low dielectric loss.

Background

The polyimide film (PIF for short) has excellent heat resistance, mechanical, electrical insulation and chemical resistance, is widely applied to manufacturing flexible copper clad laminates and plays a role in mechanical support and insulation of electronic circuits. The dielectric loss value is in direct proportion to the signal transmission loss, the common polyimide film dielectric loss is about 0.020-0.030 (10GHz frequency test), the frequency spectrum is widened along with the increase of the application frequency of electronic products, higher requirements are provided for the material dielectric loss, the traditional PIF product can not meet the requirements of the product on the aspect of signal transmission gradually, the dielectric loss value is large, and the integrity of the signal transmission can be hindered. Because of such market demands, extensive and intensive research has been conducted on low dielectric loss materials.

Fluorine element is introduced into diammonium or dianhydride monomer, the dielectric loss of polyimide is reduced to about 0.010-0.015 along with the increase of fluorine content of polyimide, the existing fluorine-containing polyimide is limited by synthetic monomer, the cost of the prepared film is higher, and the key is that the dielectric loss is only half of that of the existing traditional polyimide, and the cost performance is lower.

The Liquid Crystal Polymer (LCP) has outstanding dielectric property, the dielectric loss factor is less than 0.0035 in the frequency range of 1-40 GHz, and the problem of serious signal loss of a common packaging substrate in high frequency is solved due to the excellent high-frequency characteristic of the LCP. LCP has aroused high attention abroad as a novel high-frequency packaging material, but the LCP packaging technology is still in the starting stage, and some key problems such as weak bonding force of a metallization layer, immature packaging technology, packaging reliability and the like need to be solved.

Disclosure of Invention

The invention provides polyimide and a polyimide film with ultralow dielectric loss prepared from the polyimide.

The polyimide is formed by polymerizing a dianhydride monomer and a diamine monomer and comprises structural units shown in a general formula (1), a general formula (2) and a general formula (3):

wherein the structural unit represented by the general formula (1) accounts for more than 20 mol%, the structural unit represented by the general formula (2) accounts for more than 20 mol%, the structural unit represented by the general formula (3) accounts for more than 10 mol%, and n in the general formula (3) is an integer of 1-10; ar (Ar)₁、Ar₂、Ar₃Is a tetravalent aromatic radical, Ar₄Is a divalent aromatic group.

Preferably, Ar₁、Ar₂、Ar₃The aromatic tetracarboxylic dianhydride is a structural unit derived from an aromatic tetracarboxylic dianhydride selected from one or more of 3,3',4,4' -biphenyltetracarboxylic dianhydride, 2,3,3',4' -biphenyltetracarboxylic dianhydride, 3,3',4,4' -diphenylethertetracarboxylic dianhydride, 2,3,3',4' -diphenylethertetracarboxylic dianhydride, 4,4'- (hexafluoroisopropylidenedipropylene) tetracarboxylic dianhydride, 4,4' - (4,4 '-isopropyldiphenoxy) tetracarboxylic dianhydride, and 4,4' -diphenylsulfonetetracarboxylic dianhydride.

Preferably, Ar4 is one or more of phenylene ether type aromatic diamine selected from the group consisting of 4,4 '-diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 1, 3-bis (4 '-aminophenoxy) benzene, 1, 4-bis (3' -aminophenoxy) benzene, 1, 3-bis (2-trifluoromethyl-4-aminophenoxy) benzene, 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, 2, 2-bis [4- (4-aminophenoxy) phenyl ] hexafluoropropane, 2, 2-bis [4- (4-aminophenoxy) phenyl ] propane, and Ar4 accounts for 20 to 60 mol% of the total amount of diamine used in synthesizing the polyimide according to claim 1.

Preferably, the diamine monomer used for the structural unit represented by the general formula (2) includes one or more of biphenyldiamines having the general formula (4),

wherein R1-R8 are respectively and independently hydrogen atom, fluorine atom, trifluoromethyl and C_1～10Alkyl radical, C_2～4Alkenyl or C_1～8An alkoxy group, at least one of R1 to R8 being other than a hydrogen atom, and 20 to 40 mol% of biphenyldiamine represented by the general formula (4) based on the total amount of diamine used for synthesizing the polyimide according to claim 1.

Preferably, the diamine used for the structural unit represented by the general formula (3) includes one or more diamines having the general formula (5),

wherein n is an integer of 1 to 10, and when n is not less than 3 — (CH)₂)_nThe diamine represented by the general formula (5) is a linear or isomeric diamine and accounts for 10 to 40 mol% of the total amount of the diamines for synthesizing the polyimide according to claim 1.

Preferably, the molar ratio of the diamine monomer to the dianhydride monomer used for synthesizing the polyimide of the present invention is 1 (0.990-0.999), and the polyimide is mainly terminated with amine groups.

Preferably, the diamine monomer and the dianhydride monomer are polymerized in a solvent, wherein the solvent is one or more selected from N-methyl pyrrolidone, tetrahydrofuran, toluene, acetone, dimethylformamide and dimethylacetamide.

The dielectric loss factor of the polyimide film is 0.0030-0.0060.

Detailed Description

The present invention will be described in detail with reference to examples, which do not limit the scope of the present invention.

Synthesis of polyamic acid resin

Example 1.1

In a 500ml four-necked flask equipped with a heating, cooling and internal stirring device, nitrogen gas was continuously introduced, 220g of N-methylpyrrolidone was added after air was removed and heated to 60 ℃, 0.06mol of 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, 0.03mol of 4,4' -diaminooctafluorobiphenyl and 0.01mol of 1, 3-bis (4-aminophenoxy) neopentane were sequentially added, and the mixture was stirred to completely dissolve the diamine. 0.0995mol of 2,3,3',4' -biphenyl tetracarboxylic dianhydride is added step by step, the nitrogen environment is kept, the stirring reaction is carried out for 6 hours at the constant temperature of 60 ℃, and then the resin synthesis reaction is finished to obtain the polyamide acid resin.

Example 1.2

A polyamic acid resin was obtained by following the procedure of example 1.1, wherein 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene was used in an amount of 0.04mol, and 1, 3-bis (4-aminophenoxy) neopentane was used in an amount of 0.03mol, and the other conditions were kept constant.

Example 1.3

In a 500ml four-necked flask equipped with a heating, cooling and internal stirring device, nitrogen gas was continuously introduced, 220g of N, N-dimethylformamide was added after air was removed and heated to 80 ℃, 0.06mol of 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, 0.03mol of 4,4' -diaminooctafluorobiphenyl and 0.01mol of 1, 3-bis (4-aminophenoxy) neopentane were sequentially added, and the diamine was completely dissolved by stirring. 0.0998mol of 4,4' - (hexafluoro-isopropenyl) tetracarboxylic dianhydride is added step by step, a nitrogen environment is kept, stirring reaction is carried out at a constant temperature of 80 ℃ for 6 hours, and then resin synthesis reaction is finished to obtain the polyamide acid resin.

Example 1.4

A polyamic acid resin was obtained by following the procedure of example 1.3, wherein 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene was used in an amount of 0.04mol, and 1, 3-bis (4-aminophenoxy) neopentane was used in an amount of 0.03mol, and the other conditions were kept constant.

Example 1.5

In a 500ml four-necked flask equipped with a heating, cooling and internal stirring device, nitrogen gas was continuously introduced, 220g of N, N-dimethylformamide was added after air was removed and heated to 70 ℃, 0.06mol of 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, 0.03mol of 4,4' -diaminooctafluorobiphenyl and 0.01mol of 1, 3-bis (4-aminophenoxy) neopentane were sequentially added, and the diamine was completely dissolved by stirring. 0.0995mol of 4,4' -diphenyl sulfone tetracarboxylic dianhydride is added step by step, nitrogen environment is kept, stirring reaction is carried out for 6 hours at constant temperature of 80 ℃, and then resin synthesis reaction is finished to obtain the polyamide acid resin.

Example 1.6

A polyamic acid resin was obtained by following the procedure of example 1.5, wherein 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene was used in an amount of 0.04mol, and 1, 3-bis (4-aminophenoxy) neopentane was used in an amount of 0.03mol, and the other conditions were kept constant.

Preparation of polyimide film with low dielectric loss

Example 2.1

The polyamic acid resin obtained in example 1.1 was defoamed and then coated on a mirror-finished stainless steel plate, and the amount of the coating resin solution was controlled so that the film thickness of the final support was about 12. + -. 1. mu.m. The stainless steel is placed in an oven, and the temperature rise rate is 10 ℃/min, and the temperature rises from 60 ℃ to 390 ℃. And keeping for 5min after reaching the temperature to obtain the polyimide film with low dielectric loss.

Example 2.2

The polyamic acid resin obtained in example 1.2 was formed into a film by the method described in example 2.1 to obtain a low dielectric loss film.

Example 2.3

The polyamic acid resin obtained in example 1.3 was defoamed and then coated on a mirror-finished stainless steel plate, and the amount of the coating resin solution was controlled so that the film thickness of the final support was about 12. + -. 1. mu.m. The stainless steel is placed in an oven, and the film is prepared according to the film preparation method (II), wherein the heating rate is 10 ℃/min, and the temperature is increased from 60 ℃ to 330 ℃. And keeping for 5min after reaching the temperature to obtain the polyimide film with low dielectric loss.

Example 2.4

The polyamic acid resin obtained in example 1.4 was formed into a film by the method described in example 2.3 to obtain a low dielectric loss film.

Example 2.5

The polyamic acid resin obtained in example 1.5 was defoamed and then coated on a mirror-finished stainless steel plate, and the amount of the coating resin solution was controlled so that the film thickness of the final support was about 12. + -. 1. mu.m. Placing the stainless steel in an oven, and preparing the film according to the film preparation method (III), wherein the heating rate is 10 ℃/min, and the temperature is increased from 60 ℃ to 350 ℃. And keeping for 5min after reaching the temperature to obtain the polyimide film with low dielectric loss.

Example 2.6

The polyamic acid resin obtained in example 1.6 was formed into a film by the method of example 2.5 to obtain a low dielectric loss film.

Third, performance detection

3.1 measurement of tensile Strength and elongation

Measured using a universal tensile machine according to ASTM D882.

3.2 detection of dielectric loss

The test is carried out according to the ASTM D150 standard by using a network analyzer at a frequency of 10 GHz.

3.3 moisture absorption Rate

The test was carried out according to ASTM D750 standard 20 ℃ soak 24 Hr.

3.4 glass transition temperature

Using a dynamic thermomechanical analyzer (TA corporation): the temperature was raised to 450 ℃ at a temperature rise rate of 5 ℃/min under a nitrogen atmosphere at a vibration frequency of 1Hz, and the glass transition temperature was measured at the maximum value of the dielectric loss tangent.

3.5 test results

The test results of the low dielectric loss polyimide films (films having a thickness of 12. + -.1 μm) obtained in examples 2.1 to 2.6 are shown in Table 1.

TABLE 1

	Example 2.1	Example 2.2	Example 2.3	Example 2.4	Example 2.5	Example 2.6
							Tensile Strength (MPa)	132	105	125	98	145	129
Elongation at Break (%)	22.5	13.7	30.2	15.8	44.5	28.9
							Dielectric loss factor	0.0045	0.0034	0.0040	0.0031	0.0049	0.0037
Moisture absorption Rate (%)	0.82	0.65	0.45	0.36	0.77	0.55
							Glass transition temperature (. degree. C.)	335	302	291	270	305	287

The dielectric loss of the embodiments 2.2, 2.4 and 2.6 are respectively obviously lower than that of the embodiments 2.1, 2.2 and 2.3, so that the number of the phenyl ether bonds in the polyimide molecular chain is reduced, the number of the aliphatic chain structure is increased, and the dielectric loss value of the polyimide film is favorably reduced.

The elongation rates of the embodiments 2.2, 2.4 and 2.6 are respectively obviously lower than those of the embodiments 2.1, 2.2 and 2.3, so that the elongation rate of the film can be reduced by increasing the number of the aliphatic chain structures in the polyimide molecular chain, the dianhydride structural unit is changed, and finally the polyimide film with good flexibility and low dielectric loss is obtained.

The polyimide film with low dielectric loss prepared by the invention is more suitable for a film preparation process of biaxial stretching or sizing. The elongation of the polyimide film with low dielectric loss can be further improved by biaxial stretching or sizing.

The polyimide film has excellent toughness and heat resistance on the premise of keeping low dielectric loss and low hygroscopicity, and is suitable for reducing signal transmission loss in the field of high-frequency electronic application.

Claims

1. A polyimide produced by polymerizing a dianhydride monomer and a diamine monomer, the polyimide comprising structural units represented by general formulae (1), (2) and (3):

wherein the structural unit represented by the general formula (1) accounts for more than 20 mol%, the structural unit represented by the general formula (2) accounts for more than 20 mol%, the structural unit represented by the general formula (3) accounts for more than 10 mol%, and n in the general formula (3) is an integer of 1-10; ar (Ar)₁、Ar₂、Ar₃Is a tetravalent aromatic radical, Ar₄Is a divalent aromatic group;

Ar₁、Ar₂、Ar₃is a structural unit formed by aromatic tetracarboxylic dianhydride selected from one or more of 3,3',4,4' -biphenyl tetracarboxylic dianhydride, 2,3,3',4' -biphenyl tetracarboxylic dianhydride, 3,3',4,4' -diphenyl ether tetracarboxylic dianhydride, 2,3,3',4' -diphenyl ether tetracarboxylic dianhydride, 4,4'- (hexafluoro-isopropenyl) tetracarboxylic dianhydride, 4,4' - (4,4 '-isopropyl-diphenoxy) tetracarboxylic dianhydride and 4,4' -diphenyl sulfone tetracarboxylic dianhydride;

Ar₄is an aromatic diamine of the phenylene ether type selected from 4,4 '-diaminodiphenyl ether, 3,4' -diaminodiphenyl ether, 1, 3-bis (4 '-aminophenoxy) benzene, 1, 4-bis (3' -aminophenoxy) benzene, 1, 3-bis (2-trifluoromethyl-4-aminophenoxy) benzene, 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, 2, 2-bis [4- (4-aminophenoxy) phenyl ] benzene]Hexafluoropropane, 2, 2-bis [4- (4-aminophenoxy) phenyl]One or more of propane, Ar₄20 to 60 mol% of the total diamine content of the synthesized polyimide;

the diamine monomer used for the structural unit represented by the general formula (2) includes one or more of biphenyldiamines represented by the general formula (4),

wherein R1-R8 are each independently a hydrogen atom, a fluorine atom, a trifluoromethyl group, a C1-10 alkyl group, a C2-4 alkenyl group or a C1-8 alkoxy group, at least one of R1-R8 is not a hydrogen atom, and biphenyldiamine represented by the general formula (4) accounts for 20-40 mol% of the total amount of diamine in the polyimide;

the diamine used for the structural unit represented by the general formula (3) includes one or more of diamines having the general formula (5),

wherein n is an integer of 1 to 10, and when n is not less than 3 — (CH)₂) n-is a straight chain or an isomer, and the diamine represented by the general formula (5) accounts for 10 to 40 mol% of the total amount of the diamines in the polyimide;

ar described in the reaction process₄The molar ratio to the diamine represented by the general formula (5) was 4: 3.

2. The polyimide of claim 1, wherein: ar is₄Is 1, 3-bis (3-trifluoromethyl-4-aminophenoxy) benzene, the biphenyldiamine represented by the general formula (4) is 4,4' -diaminooctafluorobiphenyl, and the diamine represented by the general formula (5) is 1, 3-bis (4-aminophenoxy) neopentane.

3. The polyimide of claim 1, wherein the molar ratio of diamine monomer to dianhydride monomer is 1 (0.990-0.999), and wherein the polyimide is terminated with predominantly amine groups.

4. The polyimide of claim 1, wherein the diamine monomer and the dianhydride monomer are polymerized in a solvent selected from one or more of N-methylpyrrolidone, tetrahydrofuran, toluene, acetone, dimethylformamide, and dimethylacetamide.

5. A polyimide film which is produced from the polyimide according to any one of claims 1 to 4 and has a dielectric loss factor of 0.0030 to 0.0060.