JP2002121381A - Paste of polyimide precursor containing inorganic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems such as viscosity increase and gellation of a paste containing an inorganic powder and a polyimide precursor. SOLUTION: In a paste containing an inorganic powder and a polyimide precursor, the concentration of a carboxylic acid in a polyimide precursor is less than 3.8 mmol/g, and the difference between the ionization potential of a diamine and the electronic affinity of a carboxylic anhydride, both constituting the polyimide precursor, is at least 5.4 eV but less than 5.8 eV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inorganic powder-dispersed paste for forming a magnetic layer or the like by printing on a ceramic substrate or a conductor.

[0002]

2. Description of the Related Art As a method of forming a small coil component or a capacitor component, a conductive thin film is formed on a ceramic substrate by sputtering or the like, an electrode pattern is formed by etching, and a resin insulating layer is formed thereon. And a so-called thin film method in which a multilayer structure is formed by repeating conductor layer sputtering and resin insulating layer formation. This method is easy to miniaturize and has high productivity.

[0003] In order to obtain more reliable parts,
It is necessary to use a resin having excellent mechanical strength, electrical insulation and heat resistance as a resin used for the insulating layer. Among them, polyimide resin is particularly excellent in these characteristics. As the polyimide resin, a polyimide resin film obtained by applying a polyimide precursor resin solution, drying and then imidizing by heating to obtain a polyimide resin film is well known.

[0004] Polyimide resin has excellent properties as known so far, but when used as an insulating layer of a coil component or a capacitor component, it has a satisfactory dielectric constant and magnetic permeability for the component. May not be obtained. Therefore, in order to obtain a polyimide insulating layer having a high dielectric constant or magnetic permeability, there is a method of dispersing a ferromagnetic or ferroelectric inorganic powder in a polyimide precursor resin solution to form a paste.

[0005]

However, a method of dispersing an inorganic powder such as a ferromagnetic substance or a ferroelectric substance into a polyimide precursor resin solution to form a paste improves the magnetic permeability and dielectric constant of the polyimide insulating film. Although this method is an excellent method, when these inorganic powders are dispersed in a polyimide precursor resin solution, these powders and the resin often react with each other, resulting in a noticeable thickening of the paste, and further gelation. Could cause.

An object of the present invention is to provide a paste containing an inorganic powder and a polyimide precursor, which suppresses the reaction between the powder and the resin, suppresses gelation, and has a stable viscosity.

[0007]

That is, according to the present invention, in a paste containing an inorganic powder and a polyimide precursor, the carboxylic acid concentration of the polyimide precursor is 3.8 mmol.
1 / g, wherein the difference between the ionization potential of the diamine constituting the polyimide precursor and the electron affinity of the carboxylic anhydride is 5.4 eV.
This is a paste characterized by being less than 5.8 eV.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The present invention provides an inorganic powder and a paste containing a polyimide precursor, wherein the carboxylic acid concentration of the polyimide precursor is less than 3.8 mmol / g. A paste characterized in that a difference between an ionization potential and an electron affinity of a carboxylic anhydride is 5.4 eV or more and less than 5.8 eV.

The carboxylic acid concentration of the polyimide precursor of the present invention is preferably less than 3.8 mmol / g.
If the amount is 8 mmol / g or more, the viscosity increases remarkably, which is not preferable. The carboxylic acid concentration here is the number of moles of carboxylic acid contained per gram of the substance.
In the present invention, the concentration of the carboxylic acid was determined from the structural formula. For example, when the acid dianhydride is A (unit molecular weight a), the diamine is B (unit molecular weight b), and C (unit molecular weight c), the polymerization ratio is A / B / C = 96/95/5. Assuming that the carboxylic acid concentration is 2 × 0.96 / (0.
96 × a + 0.95 × b + 0.05 × c).

It is known that the acid affinity Ea used as a parameter of the polyimide precursor is an electron affinity Ea and the ionization potential Ip is a parameter of a diamine. The difference Ip-Ea greatly affects the properties of the polyimide. . The present inventors have now found that this difference also affects the dispersion stability of the inorganic powder. In the range, the difference between the ionization potential of the diamine and the electron affinity of the carboxylic acid anhydride is preferably 5.4 eV or more and less than 5.8 eV, and more preferably 5.5 eV or more and less than 5.8 eV. The ionization potential and electron affinity are described in the literature CONSULTANTS BUREAU POLYIMIDES The
rmally Stable Polymers (MIBessonov, MM Koton, V.
V. Kudryavtsev, by LALaius).

The inorganic powder in the present invention includes gold, silver,
Includes metal powders such as copper, platinum, and palladium, glass powders, ceramic powders, ferromagnetic powders, ferroelectric powders, and the like, but are preferably magnetic substances, and particularly have high reactivity with polyimide precursors. The present invention is effective for metals such as copper, lead and iron, or those containing them, such as glass containing lead and ferrite containing a lot of iron.
If a ferromagnetic material or a ferroelectric material is used as the inorganic powder, the magnetic permeability and the dielectric constant of the polyimide film obtained by applying the paste can be controlled. In the present invention, ferrite is preferably used as the inorganic powder, and the magnetic permeability of the polyimide resin can be increased. Among the ferrites, more preferably, a nickel / zinc system or a manganese / zinc system is used.

The average particle size of the inorganic powder is as follows: dispersibility,
In order to improve the applicability and fluidity of the paste, the thickness is preferably 0.01 μm or more and less than 5 μm, more preferably 0.05 μm or more and less than 2 μm, and even more preferably 0.1 μm or more and less than 1 μm. If the powder is too small, the fluidity at the time of forming a paste is poor, and if it is too large, the flatness at the time of application is reduced. As a method for measuring the average particle size of the inorganic powder, for example, the particle size distribution and particle size distribution are measured by a light scattering method, and the 50% particle size (D5
0), that is, the average particle diameter can be defined as the particle diameter in which 50% of the particles are included in total.

The amount of the inorganic powder to be added is preferably 50% by weight or more and less than 95% by weight based on the total solid weight of the paste. If the amount is small, sufficient electrical and magnetic properties cannot be obtained, and if it is too large, the mechanical strength of the polyimide film and the adhesion to the substrate decrease. In the present invention, the total solid content weight of the paste is defined as the weight remaining after the paste is applied and dried, and further heated to imidize the polyimide precursor. As a measurement method, take a small amount of paste, perform the same heating step as the imidation step of the polyimide precursor,
There is a method of measuring the residual weight. Alternatively, simply, the same result can be obtained by measuring the residue after heating for 1 hour to 2 hours at the same constant temperature as the highest temperature in the imidization step. The amount of the inorganic powder means that the paste is
The organic component is completely decomposed and volatilized by treating at a high temperature of 0 ° C. for 1 to 2 hours, and the weight of the inorganic powder is obtained by measuring the weight of the residue.

The polyimide precursor used in the present invention preferably includes a polyamic acid and its ester obtained by reacting tetracarboxylic dianhydride with a diamine in an aprotic polar solvent. As the tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylethertetracarboxylic dianhydride, 3,3 ′,
4,4'-diphenylhexafluoropropanetetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride Anhydride, pyromellitic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, 2,3 ′,
3,4′-biphenyltetracarboxylic dianhydride, 3,
3 ', 4,4'-diphenylmethanetetracarboxylic dianhydride, 3,3', 4,4'-terphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride And the like, but are not limited thereto. From the viewpoint of the heat resistance of the polyimide precursor, particularly preferred specific examples include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 3,3 ′, 4,4′-diphenylethertetracarboxylic dianhydride. Anhydride, 3,3 ',
4,4'-diphenylhexafluoropropanetetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride Anhydride, pyromellitic dianhydride, 2,3 ′, 3,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-diphenylmethanetetracarboxylic dianhydride, 3,3 ′ , 4,
4'-terphenyltetracarboxylic dianhydride, 1,
4,5,8-naphthalenetetracarboxylic dianhydride and the like can be mentioned. Also preferably, 3,3 ', 4,4'
-Benzophenone tetracarboxylic dianhydride is preferred from the viewpoint of viscosity stability.

As the diamine, paraphenylene diamine, metaphenylene diamine, methyl paraphenylene diamine, methyl metaphenylene diamine, dimethyl paraphenylene diamine, dimethyl metaphenylene diamine, trimethyl paraphenylene diamine, trimethyl metaphenylene diamine, tetramethyl paraphenylene diamine , Tetramethylmetaphenylenediamine, trifluoromethylparaphenylenediamine, trifluoromethylmetaphenylenediamine, bis (trifluoromethyl) paraphenylenediamine, bis (trifluoromethyl) metaphenylenediamine, methoxyparaphenylenediamine, methoxymetaphenylenediamine , Trifluoromethoxy paraphenylenediamine, trifluoromethoxymetaphenyl Diamine, fluoroparaphenylenediamine, fluorometaphenylenediamine, chloroparaphenylenediamine, chlorometaphenylenediamine, bromoparaphenylenediamine, bromometaphenylenediamine, carboxyparaphenylenediamine, carboxymetaphenylenediamine, methoxycarbonylparaphenylenediamine, methoxycarbonyl Metaphenylenediamine, diaminodiphenylmethane, bis (aminomethylphenyl) methane, bis (aminotrifluoromethylphenyl) methane, bis (aminoethylphenyl) methane, bis (aminochlorophenyl) methane, bis (aminodimethylphenyl) methane, bis ( Aminodiethylphenyl) methane, diaminodiphenylpropane, bis (aminomethylphenyl) p Bread, bis (aminotrifluoromethylphenyl) propane, bis (aminoethylphenyl) propane, bis (aminochlorophenyl) propane, bis (aminodimethylphenyl) propane, bis (aminodiethylphenyl) propane, diaminodiphenylhexafluoropropane, bis (Aminomethylphenyl) hexafluoropropane, bis (aminotrifluoromethylphenyl) hexafluoropropane, bis (aminoethylphenyl) hexafluoropropane, bis (aminochlorophenyl) hexafluoropropane, bis (aminodimethylphenyl) hexafluoropropane, Bis (aminodiethylphenyl) hexafluoropropane, diaminodiphenylsulfone, bis (aminomethylphenyl) sulfone, bis (aminoethyl Phenyl) sulfone, bis (aminotrifluoromethylphenyl) sulfone, bis (aminodimethylphenyl) sulfone, bis (aminodiethylphenyl) sulfone, diaminodiphenylether, bis (aminomethylphenyl) ether, bis (aminotrifluoromethylphenyl) ether , Bis (aminoethylphenyl) ether, bis (aminodimethylphenyl) ether, bis (aminodiethylphenyl) ether, and 3,3'-diaminodiphenylsulfone. Particularly preferred is 4,4'-diaminodiphenyl ether from the viewpoint of viscosity stability.

Further, in order to improve the adhesiveness of the paste of the present invention, it is possible to copolymerize an aliphatic group having a siloxane bond as long as the heat resistance is not reduced. Preferred specific examples include, but are not limited to, bis (3-aminopropyl) tetramethyldisiloxane. The polyimide precursor in the present invention may be one type or a copolymer composed of two or more types.

Further, preferably used aprotic polar solvents include N-methyl-2-pyrrolidone, N, N'-dimethylacetamide and the like.

Next, a method for producing a paste according to the present invention and a method for forming a polyimide film from the obtained paste will be described, but the present invention is not limited thereto.

The polyimide precursor is a polyamic acid synthesized by selectively combining and reacting tetracarboxylic dianhydride and diamine, or after reacting with tetracarboxylic dianhydride and an alcohol compound, and then reacting with thionyl chloride. The polyamic acid ester is synthesized by selectively combining with an appropriate diamine after synthesizing an acid chloride using the method described above, or by selectively combining and reacting with a diamine using an appropriate dehydrating agent such as dicyclohexylcarbodiimide. For example, it is synthesized by a known method.

A solution of the polyimide precursor and the inorganic powder are mixed in a predetermined amount. At this time, in order to improve the dispersibility of the powder, a dispersant, preferably a polyester-based polymer, a Si-based polymer, a sorbitan fatty acid ester, and the like may be added as necessary, but the invention is not limited thereto. Further, a leveling agent may be added for the purpose of improving the smoothness of the coating film. This mixture is stirred until it becomes a slurry. The obtained slurry is kneaded using an apparatus such as a three-roll mill or a ball mill to obtain a paste.

The obtained paste is uniformly applied on a substrate such as an alumina substrate by a screen printer or a spin coater. Thereafter, by heating and drying with a hot plate, a hot air oven, or the like, a coating film containing an inorganic powder in a polyimide precursor is obtained. The drying temperature is 80
C. to 120.degree. C. for 10 to 60 minutes to dry.

The obtained polyimide precursor coating film is heated to obtain a polyimide film containing inorganic powder.
The heating temperature profile at this time is, for example, 1 from room temperature.
The temperature is raised from 20 ° C. to 180 ° C. in 30 minutes, held for 30 minutes, then raised again to 300 ° C. to 400 ° C. in 1 hour, held for 1 hour, and then cooled. By this heating step, the residual solvent in the coating film is completely removed, and the polyimide precursor is imidized through a dehydration ring-closing reaction to form a polyimide film.

The paste according to the present invention has a very good dispersion of the inorganic powder in the polyimide precursor and a stable viscosity. Furthermore, the inorganic powder-dispersed polyimide film obtained from the paste of the present invention has a high insulating property and mechanical strength inherent to polyimide, and can be freely controlled in dielectric constant and magnetic permeability, so that it is very suitable as a material for electronic components. .

[0024]

EXAMPLES The present invention will be described in detail with reference to the following examples, but the present invention is not limited by these examples.

A. B. Inorganic powder (1) Ferrite Ni / Zn system: monodisperse granular average particle size (D50) 1.4 μm (2) Ferrite Mn / Zn system: monodisperse granular average particle size (D50) 4.7 μm Polyimide precursor Abbreviations of carboxylic dianhydride and diamine used are as follows.

PMDA: pyromellitic dianhydride (electron affinity: Ea = 1.90 eV) BTDA: 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride (Ea = 1.55 eV) BPDA: 3 , 3 ', 4,4'-biphenyltetracarboxylic dianhydride (Ea = 1.38 eV) ODPA: 4,4'-oxydiphthalic dianhydride (Ea
= 1.30 eV) DAE: 4,4′-diaminodiphenyl ether (ionization potential: Ip = 7.22) BAPS: 4,4 ′-[sulfonylbis (4,1-phenylenoxy)] dianiline SiDA: bis (3-amino) Propyl) tetramethyldisiloxane polyamic acid and polyamic acid ester: copolymer composition (1) PMDA / DAE / SiDA = 96/95/5
(Carboxylic acid concentration 4.66 mmol / g) (2) BTDA / DAE / SiDA = 96/95/5
(Carboxylic acid concentration 3.75 mmol / g) (3) BTDA / BAPS / SiDA = 96/95/5
(Carboxylic acid concentration 2.62 mmol / g) (4) BPDA / DAE / SiDA = 96/95/5
(Carboxylic acid concentration 3.95 mmol / g) (5) ODPA / DAE / SiDA = 96/95/5
(Carboxylic acid concentration 3.83 mmol / g) (6) BTDA / ethanol / DAE / SiDA = 99
/ 10/95/5 (carboxylic acid concentration 3.75 mmol /
g) C.I. Solvent N-methyl-2-pyrrolidone.

Preparation of paste (1) The polyimide precursor solution, the dispersant and the inorganic powder were mixed and stirred until a slurry was obtained. (2) The obtained slurry was rolled into three rolls (EXACT m
odel 50) to obtain a paste.

Viscosity measurement The viscosity was measured using a Brookfield viscometer DV-II +. The measurement condition was a measurement temperature of 25 ° C.

The yield value was determined from the paste one week after storage at room temperature. The yield value is the minimum shear stress required to cause the flow, and in the present invention, the viscosity was measured by changing the shear rate, and plotted by taking the square root of the shear rate on the horizontal axis and the square root of the shear stress on the vertical axis. , The square of the intercept of the so-called Casson plot.

Film formation (1) Paste the alumina substrate (96% white plate 75 m
It was printed on a 60 mm square solid pattern screen mask (SUS # 325 mesh) on an m square with a thickness of 0.65 mm) and dried at 90 ° C. for 30 minutes using a hot air oven. (2) The coating film was heat-treated in a nitrogen atmosphere under the following conditions to obtain a polyimide film. Heating conditions: temperature rise from room temperature to 140 ° C. in 30 minutes, 140
The temperature was kept at 30 ° C. for 30 minutes, the temperature was raised from 140 ° C. to 350 ° C. for 1 hour, the temperature was kept at 350 ° C. for 1 hour, and the cooling was performed in this order.

Measurement of Coating Film Adhesion Strength (1) A 100 mm square was formed in the coating by making a 10 mm cut with a width of 1 mm, and a peeling test was performed with a cellophane tape. Was evaluated. (2) It was placed in a PCT (pressure cooker tester) at 120 ° C. and 2 atm, and the adhesive strength after 100 hours was similarly evaluated. The results are summarized in Table 1.

[0032]

[Table 1]

In all of Examples 1 to 4, the viscosity was changed even one week after the preparation, but the gel was not formed, the paste was a stable paste having a low yield value, and the adhesion was good. On the other hand, in Comparative Examples 1 to 3, the viscosity and yield value of the paste increased one week after the preparation.

[0034]

According to the present invention, an inorganic powder-containing polyimide precursor paste having good viscosity stability and an inorganic powder-containing polyimide film having excellent mechanical strength can be obtained by having the above-described structure.

Claims (7)

[Claims] 1. A paste containing an inorganic powder and a polyimide precursor, wherein the carboxylic acid concentration of the polyimide precursor is less than 3.8 mmol / g. 2. In the paste containing the inorganic powder and the polyimide precursor, the difference between the ionization potential of the diamine constituting the polyimide precursor and the electron affinity of the carboxylic anhydride is 5.4 eV or more and less than 5.8 eV. A polyimide precursor paste containing an inorganic powder, characterized by comprising: 3. An inorganic powder-containing polyimide precursor paste according to claim 1, wherein the amount of the inorganic powder is from 50 wt% to less than 95 wt% based on the total solid content of the paste. 4. The inorganic powder-containing polyimide precursor paste according to claim 1, wherein the average particle size of the inorganic powder is 0.01 μm or more and less than 5 μm. 5. The inorganic powder-containing polyimide precursor paste according to claim 1, wherein the inorganic powder is a magnetic material. 6. The inorganic powder-containing polyimide precursor paste according to claim 1, wherein the inorganic powder is ferrite. 7. The inorganic powder-containing polyimide precursor paste according to claim 1, wherein the inorganic powder is nickel / zinc-based or manganese / zinc-based ferrite.