RU2793576C1 - Polyimides and copolyimides as dielectric materials with increased thermal and oxidative stability - Google Patents

Abstract

FIELD: dielectric materials.

SUBSTANCE: polyimides and copolyimides are intended for the manufacture of thermally stable dielectric materials with a set of high-performance characteristics that can be used in microelectronics. Polyimide is a compound of the general formula as follows

,

where x=1, 2; n=20÷100, m=80÷0.

EFFECT: resulting polyimides and copolyimides have increased thermal and oxidative stability, solubility, low yellowness index, and good optical transparency.

1 cl, 2 tbl, 2 ex

Description

The invention relates to new dielectric polymeric materials, specifically to polyimides and copolyimides based on dianhydride 2,3,3',4'-tetracarboxydiphenyl (non-DF) and unsymmetrical alicyclo-containing diamine 4-[4-(2-aminoethyl)tricyclo[3.3. 1.1 ^3,7 ]decan-1-yl]aniline (1) and 2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diamine (2), intended for the manufacture of dielectric materials, having a set of high performance characteristics (thermal-oxidative stability, solubility and optical transparency), which can be used in microelectronics.

Known polyimides based on aromatic, aliphatic, alicyclic diamines and dianhydrides of tetracarboxylic acids, which have high thermal and electrical properties [Bessonov MP. and others. Polyimides are a class of heat-resistant polymers. - L.; Science, 1983-328s.].

However, their disadvantage is low optical transparency and insolubility.

Known (co)polyimides based on 5,5'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(2-benzofuran-1,3-dione) (F6) and unsymmetrical alicyclo-containing diamines - 4-[4-(2-aminomethyl)tricyclo[3.3.1.1 ^3.7 ]decan-1-yl]aniline and 4-[4-(2-aminoethyl)tricyclo[3.3.1.1 ^3.7 ]decane -1-yl]aniline, and 9,9-bis-(4-aminophenyl)fluorene (AF) [US Pat. 2753691 RF, IPC C08G 73/10, C08L 79/08, publ. 08/19/2021]. These polymers have a sufficiently high solubility, optical transparency and a low yellowness index. However, these polyimides have relatively low thermal and oxidative stability.

The closest are adamantane-containing polyimides and copolyimides based on 3,4,3',4'-tetracarboxydiphenyl dianhydride (sim-DF) and adamantane series diamines based on 4-[4-(2-aminomethyl)tricyclo[3.3.1.1 ^3.7 ]decan-1-yl]aniline and 4-[4-(2-aminoethyl)tricyclo[3.3.1.1 ^3,7 ]decan-1-yl]aniline and 9,9-bis-(4-aminophenyl)fluorene (AF ) [Pat. 2751883 RF, IPC C08G 73/10, publ. 07/19/2021].

The disadvantages of these polyimides are the insufficiently high solubility of polyimides in a number of organic solvents, as well as their low transparency and relatively low thermal and oxidative stability [Novakov I.A., Orlinson B.S., Zavyalov D.V., Mednikov S.V., Saveliev E. .N., Potaenkova E.A., Nakhod M.A., Pichugin A.M., Kireeva A.V., Kovaleva M.N. Synthesis and study of the properties of new transparent (co)polyimides based on adamantane-containing diamines and aromatic tetracarboxylic acid dianhydrides. Izvestiya Akademii Nauk. Chemical series. - 2021. - No. 6. - C. 1141-1148.].

The objective of the invention is to develop new soluble thermally stable dielectric materials with a sufficiently low yellowness index and good optical transparency.

EFFECT: expansion of the range of dielectric materials, dielectric polyimides and copolyimides, having increased thermal-oxidative stability, solubility, low yellowness index and good optical transparency.

The technical result is achieved in polyimide and copolyimide by the general formula

,

,

where x=1, 2; n = 20÷100, m = 80÷0, as thermally stable dielectric materials.

The essence of the invention is dielectric polyimide and copolyimide, which have increased thermal-oxidative stability and solubility at a low level of yellowness index and good optical properties. Alicyclic fragments in the structure of aromatic polyimide, as well as the structure of the dianhydride fragment, increase the optical transparency, solubility, and reduce the yellowness index of polyimides and copolyimides, and the absence of a hinge atom in the dianhydride leads to an increase in the thermooxidative stability of the polymer.

The claimed polyimide and copolyimide are obtained on the basis of unsymmetrical dianhydride 2,3,3',4'-tetracarboxydiphenyl (nes-DP), using unsymmetrical 1,4-substituted adamantane-containing diamine 4-[4-(2-aminoethyl)tricyclo [3.3.1.1 ^3,7 ]decan-1-yl]aniline (1) and 2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diamine (2):

,

,

where x= 1, 2; n = 20÷100, m = 80÷0.

Synthesis of polymers was carried out by the method of one-stage high-temperature polycyclization in solution. A mixture of 1,2-dichlorobenzene : sulfolane (80:20% vol.) was used as a solvent in the synthesis of polymers. The process temperature was gradually raised from 20 to 170-175°C. The chemical structure of the resulting polyimides was confirmed by IR spectroscopy data: the presence of absorption bands in the region of 750 and 1380 cm ^-1 characteristic of the five-membered imide cycle, as well as in the region of 1740 and 1780 cm ^-1 corresponding to vibrations of the carbonyl group of the imide cycle. IR spectra were taken on a Nicolet 6700 FT-IR spectrometer. The ratio of units in the polymers is determined from the molar ratio of loaded monomers and confirmed from the quantitative yield or by recalculation of unreacted monomers.

The dielectric properties of the resulting polyimides and copolyimides were determined by measuring the immittance, for which an E7-21 LCR meter was used. The basic error in measuring the capacitance and the tangent of the dielectric loss angle is not higher than 0.15%. To maintain a stabilized temperature within the specified range, an LBH-T02P automatic oven manufactured by Daihan Scientific Co, Korea was used. The error of maintaining the temperature during the measurement process is no more than 0.1 K. The sample temperature is recorded using a TSP-50 platinum thermal resistance connected to an MS-8226 DMM meter manufactured by Mustech, Hong Kong. The measurement error of the thermal resistance value is no more than ±0.5%. Conductive paste: manufacturer-Mechanic, brand - DJ912.

The optical properties of polyimide films were studied on an SF-56 spectrophotometer by measuring the optical transparency of the film depending on the wavelength in the range from 180 to 1100 nm.

The solubility of polyimide was evaluated by the ability to form 5% stable solutions at room temperature.

Thermal stability was evaluated by the temperature of 5% weight loss of the polymer sample. Dynamic thermogravimetric analysis of polymer samples was carried out on a Q-1200 derivatograph (MOM), the temperature rise rate was 10 deg/min, the sample weight was 50–70 mg.

The results of the study of dielectric, optical properties, solubility, as well as thermal-oxidative stability of the proposed polyimides and copolyimides based on non-DP dianhydrides, alicyclo-containing diamine (1) and 2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4, 4'-diamine (2) are presented in Table 1. For comparison, the results of studies of known (co)polyimides based on symmetric dianhydride 3,4,3',4'-tetracarboxydiphenyl (sim-DP) and alicyclo-containing diamine (1) were given. The table also presents data on industrial polyimide PM based on pyromellitic dianhydride (PMDA) and 4,4'-diaminodiphenyl ether (3).

Table 1 Alicyclo-containing diamine Content of diamine (2), m dianhydride Dielectric constant, ε Optical properties Temperature of 5% weight reduction, °C Diamine number n Yellowness index λ* _cut-off
(nm) 1 100 0 ness-df 2.60 2.84 375 495 1 50 50 carried DF 2.70 2.80 370 498 1** 100 0 sim-df 2.80 4.80 410 430 1** 50 50 sim-df 2.95 5.50 420 460 3*** 100 0 PMDA 3.50 93 470 530

* - cutoff wavelength

** - for comparison

*** - the film was obtained by a two-stage method.

The solubility of the proposed polyimides and copolyimides based on the dianhydrides of non-DF, alicyclo-containing diamine (1) and 2,2'-bis(trifluoromethyl)[1,1'-biphenyl]-4,4'-diamine (2) was studied and presented in the table 2. For comparison, the results of studies of known (co)polyimides based on 3,4,3',4'-tetracarboxydiphenyl dianhydride (sim-DP) and alicyclo-containing diamine (1) were given. The PI solubility was determined by the ability to form 5% stable solutions at room temperature or under heating conditions.

table 2 Alicyclo-containing diamine Content of diamine (2), m dianhydride Solvent Diamine number n 1,2-DCB CHCl _{3 CH2Cl2 _} NMP DMAC DMSO DMF 2Me-THF THF Acetone bm SF 1 100 0 ness-df + + + + + + + +** - - + + 1 50 50 ness-df + + + + + + + + - - + + 1* 100 0 sim-df + - - +** + + + - - - - + 1* 50 50 sim-df + - - +** + + + - - - - +

SF - sulfolane, BM - 1-(methoxy)-2-(methoxyethoxy)ethane, 1,2-DCB - 1,2-dichlorobenzene, NMP - N-methyl-2-pyrrolidone, DMAC - N,N-dimethylacetamide, DMSO - dimethyl sulfoxide, DMF - N,N-dimethylformamide, 2Me-THF - 2-methyltetrahydrofuran, THF - tetrahydrofuran, * - for comparison; **- polymers dissolve when heated.

As follows from the data presented in the tables, polyimides and copolyimides based on 1,4-substituted adamantane-containing diamines are superior in thermal properties to known adamantane-containing polymers based on sim-DF, while possessing fairly good optical and dielectric properties. At the same time, they have good solubility in solvents such as CHCl ₃ , CH ₂ Cl ₂ , NMP (without heating), which contributes to their better processing compared to known polyimides based on diamine (1) and sim-DF dianhydride, and also higher solubility in solvents such as 2-MeTHF and BM, which makes it possible to cast films from these solvents and obtain polyimides with a lower yellowness coefficient.

Example 1. Synthesis of polyimides.

0.999⋅10 ^-3 mol of 1,4-substituted adamantane-containing diamine 1, 0.2937 g (0.999⋅10 ^-3 mol) of dianhydride 2,3,3',4 '-tetracarboxydiphenyl and 2.64 ml of 1,2-dichlorobenzene. The reaction mass is heated for 1 hour from 20 to 175°C, continuously blowing with an inert gas to remove the reaction water. After heating the reaction mass for 3-4 hours, 0.66 ml of sulfolane is added, the total concentration of the reagents is 0.30 mol/L, and kept under these conditions for another 9 hours. Then, after cooling, the reaction mass is dissolved in chloroform, poured into acetone, the precipitated polyimide is filtered off, washed with acetone, and reprecipitated from chloroform. Polymer yield 0.7731 g, 97% of theoretical, η _ex. = 1.20-1.40 dl/g.

Example 2 Synthesis of copolyimides.

n=20, m=80: Same as Example 1 except using 1.998 x 10 ^-4 mol 1,4-substituted adamantane-containing diamine 1, 0.2559 g (7.99 x 10 ^-4 mol), 2,2'-bis (trifluoromethyl)[1,1'-biphenyl]-4,4'-diamine and 0.2937 g (0.999×10 ^-3 mol) of 2,3,3',4'-tetracarboxydiphenyl dianhydride. The concentration of reagents is 0.30 mol/l. The reaction mass is heated for 1 hour from 20 to 175°C, continuously blowing with an inert gas to remove the reaction water, and kept under these conditions for 12 hours. Then, after cooling, the reaction mass is dissolved in chloroform, poured into acetone, the precipitated polyimide is filtered off, washed with acetone, and reprecipitated from chloroform. The yield of the polymer is quantitative, η _ex. =1.39 dl/g.

Polyimides, when changing the ratio of m and n, are obtained in a similar way, taking into account the recalculation of the loading of ingredients.

Polyimide films were obtained by pouring a 15% polymer solution in 2-MeTHF onto a glass substrate and then keeping the film at 80°C in a vacuum cabinet for 1 hour.

Thus, the dielectric polyimide and copolyimide of the claimed formula have increased thermal and oxidative stability, solubility, low yellowness index and good optical transparency.

Claims (3)

Polyimides and copolyimides of the general formula

, where x=1, 2; n=20÷100, m=80÷0, as thermally stable dielectric materials.