JPS6160725A - Low-thermal expansion resin and composite molding - Google Patents

Abstract

PURPOSE:The title resin material having a coefficient of thermal expansion as low as that of an inorganic substance and excellent mechanical properties, comprising an oriented polyimide having a specified structure. CONSTITUTION:An aromatic aminodicarboxylic acid derivative is polymerized at 0-200 deg.C in a solvent such as N-methylpyrrolidone, or an aromatic diamine or an aromatic diisocyanate is reacted with an aromatic tetracarboxylic acid derivative to obtain a low-thermal expansion resin material comprising a polyimide having a chemical structure unit of an aromatic group which has at least one aromatic ring easily rotatable about the molecular axis but not flexible in other directions and is nearly linear within the region of 0+ or -40 deg. about the molecular axis and contains a region in which the polyamide molecules are uniaxially oriented at an order parameter >=0.07.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a low thermal expansion resin material having a specific chemical structure and made of oriented polyimide, and a composite molded article using the same.

[Background of the invention]

The thermal expansion coefficient (linear expansion coefficient) of most organic polymers is 4 x 10-3K or more even in the temperature range below the glass transition temperature, which is a much larger value than that of metals and inorganic materials. There are many problems caused by the large expansion coefficient of organic materials, and it is no exaggeration to say that lc4 is the reason why 5IC does not progress, considering the development of applications for organic polymers.For example, , a flexible printed circuit board (F
In PC), a film obtained by coating or heat-pressing a flexible film material on a metal foil is desired, but since it is necessary to cure, dry, or heat-press at a high temperature after coating, it is necessary to heat it after cooling to room temperature. There is a problem of curling due to thermal stress caused by the difference in expansion coefficients. usually,
In order to prevent this phenomenon from occurring, they are bonded together using an adhesive that can be cured at low temperatures. However, in the case of FPCs that require heat resistance, adhesives that can be cured at low temperatures generally have poor heat resistance, so even if a heat-resistant film such as a polyimide film is used as a base material, the original heat resistance cannot be exhibited.

In addition, in the case of coating films, when applied to metal plates or inorganic materials whose coefficient of thermal expansion is extremely small compared to ordinary organic polymers, thermal stress caused by the difference in coefficient of thermal expansion may cause deformation, cranking of the film, or Peeling off, destruction of the base material, etc. may occur. For example, if a coating film is formed on a silicon wafer as a protective film for LSI or IC, the wafer may warp, making it impossible to perform photolithography for patterning, or causing problems such as extremely poor resolution and thermal stress. If is large,
In some cases, the silicon wafer itself may undergo cleavage and rupture.

As described above, there are many problems due to the large coefficient of linear expansion of organic polymers, and organic polymers having a low coefficient of expansion have been strongly desired for a long time.

In view of these circumstances, the present inventors first attempted many synthesis experiments on heat-resistant resin materials, particularly polyimide, and studied in detail the relationship between raw material components and thermal expansion coefficients.

So far as polyimide ■U.S. Patent No. 317961
No. 4 (du Font) specification, ■C, E, 3ro
og, @polyimides”, J, pol
ym.

Sci, : Macromol, Rev, , 1
1, 161-208 (1976), ■N, A,
Adrova and M, M, Koton,
Dokl, Akad.

Nauk, 3 f3 f3B, 165.1069 (
1965), ■M, M.

Koton and Yu, N., 5azonov, J.
, Therm, human lys.

7 (1975), 165, ■M, M, Koton, p.
olym, Sci.

A wide variety of methods are available, as shown in U.S.S.R., 21, 2756 (1979). However, very few have been actually synthesized or put into practical use. So far, the synthesis of aromatic diamines such as diaminodiphenyl ether, diaminophenyl methane, diaminodiamine or diaminodiphenyl sulfide and pyromellitic dianhydride, which have been actually synthesized and reported or are commercially available, include There are only polyimides made from tetracarboxylic dianhydrides such as benzophenone tetracarboxylic dianhydride, tetracarpoxy diphenyl ether dianhydride, or butane tetracarbo/acid dianhydride.

However, the linear expansion coefficient of these polyimides is 4 to 6
It is extremely large at 10-IK-1.

However, as a result of further synthetic experiments, the inventors found that
The polyimide obtained from the specific aromatic diamine and tetracarboxylic dianhydride shown below has an abnormally small coefficient of linear expansion and extremely high tensile strength (compared to the polyimide mentioned above).
We have discovered a fact that has strength. The present invention has been made based on this discovery.

[Purpose of the invention]

The purpose of the present invention is to provide a low thermal expansion resin material that has an extremely small coefficient of thermal expansion equivalent to that of inorganic materials such as metals, ceramics, or glass, and has excellent mechanical properties, and a composite molded product using the same. It is about providing.

[Summary of the invention]

The low thermal expansion resin material of the present invention has one or more aromatic rings, and the aromatic ring has a structure that allows easy rotation around the molecular axis but is inflexible in other directions (the molecular structure is The polyimide molecule is characterized by containing a portion in which the polyimide molecule is oriented in at least one axis, centered on an aromatic group having an aromatic group having a substantially linear shape in the range of 0±40° about the axis.

The degree of orientation is 0.07 as the order parameter (8)
The above is preferable. Note that S is expressed by the following formula.

E, y3 is E of infinite stretching and is approximately 4. OX 10” dyn
/c4) When looking at the thermal expansion coefficient ratio (α/α), there is a correlation between the uzg S value and α/α78gll (the inventor of the present application has studied the relationship between the fracture rate and the orientation). I confirmed this)
This is because when the S value is approximately 0.07 (7%), α is approximately halved.

Examples of the chemical structure of the low thermal expansion polyimide of the present invention include (R)t(R), n and or (12).

Examples include those consisting of. Here, 几 is an alkyl group,
Fluorinated alkyl group, alkoxyl group, fluorinated alkoxyl group, acyl group, halogen, t is O~4, m is 0~
2, n is O-3. The low thermal expansion resin material of the present invention has low thermal expansion, high strength, high elasticity, and high heat resistance compared to other polymers even when the molecular arrangement is random, but these properties are significantly improved by performing some kind of molecular orientation treatment. become.

Aromatic polymers such as polyphenylene are generally
Although it is straight, it has the disadvantage of being brittle. Between the aromatic rings, there is -0-1-8-9-+cH2+p.

Flexible bonds such as HsCH30H3-NH-C-0- are introduced to make the entire polymer flexible. Further, the bonding position of the aromatic ring is also made flexible by setting it to the 0- or m-position. The same is true for polyimides; all polyimides currently being industrialized have bonds selected from these. Therefore, the low thermal expansion polymer of the present invention has not been found.

Examples of the low thermal expansion polyimide of the present invention include the following. In addition, in each formula below, R,! ,,m,
n is as defined above, and k is the i number from O to 3.

(R)n Figure 1 shows the coefficient of thermal expansion of various materials. From this figure, it can be clearly seen that while the coefficient of thermal expansion of general organic polymers is larger than that of metals and ceramics, the coefficient of thermal expansion of the oriented polyimide of the present invention is small. If the coefficient of thermal expansion is as small as that of inorganic materials such as metals and ceramics, when these inorganic materials and organic materials are combined, dimensional changes will occur in the same way due to temperature changes, so thermal stress and warpage will not occur, making it suitable for industrial use. It is extremely useful. This 11. It is no exaggeration to say that the biggest drawback of organic materials up until now is that their coefficient of thermal expansion is much larger than that of inorganic materials.

The low thermal expansion polyimide of the present invention can be obtained by homopolymerization of an aromatic aminodicarboxylic acid derivative or by reaction of an aromatic diamine or an aromatic diincyanate with an aromatic tetracarboxylic acid derivative. Tetracarboxylic acid derivatives include esters, acid anhydrides, and acid chlorides. The use of acid anhydrides is preferable in terms of synthesis. The synthesis reaction generally involves N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamyl
'(DMAC), dimethyl sulfoxide (DM80)
, dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, 7-chlorohexanone, dioxane, etc., at a temperature ranging from 0 to 200C.

Specific examples of aminodicarboxylic acid derivatives used in the present invention include 4-7 minophthalic acid, 4-amino-5
-methyl phthalic acid, 4-(p-anilino)-phthalic acid,
Examples include 4-(3,5-dimethyl-4-anilino)phthalic acid, or esters, acid anhydrides, and acid chlorides thereof.

Examples of aromatic diamines used in the present invention include the following.

p-phinyl diamine, 2,5-diaminotoluene,
2.5-diaminoxylene, diaminoxylene (2*
3,5,6-tetramethyl-p-
phemylenediamine), 2, 5-
Diaminobencytrifluoride, 2,5-diaminoxinol, 2.5-diaminoacetophenone, 2.5-
Diaminobenzophenone, 2,5-diaminodiphenyl, 2,5-diaminofluorobenzene, benzidine, 0
-Tolidine, m-Tolidine, 3.3'.

5.5'-tetramethylbenzidine, 7benzidine in 3.3'-diphtho, 3.3'-di(trifluoromethyl)
Benzidine, 3.3'-Diacetylbenzidine, 3.3
'-difluorobenzidine, octafluorobenzidine, 4.4"-diaminoterphenyl, 4.4"-diaminoquarterphenyl.

Further, these diisocyanate compounds can also be used in the same manner.

Examples of the tetracarboxylic acid derivatives used in the present invention include pyromellitic acid, methylpyromellitic acid, dimethylpyromellitic acid, di(trifluoromethyl)pyromellitic acid,
．． 3', 4.4'-biphenyltetracarboxylic acid, 5
．． Examples include 5'-dimethyl-3°3', 4,4'-biphenyltetracarboxylic acid, p-(3,4-dicarboxyphenyl)benzene, and acid anhydrides, acid chlorides, and esters thereof.

The polyimide of the present invention has low thermal expansion, high strength, and high elasticity compared to other polymers even without particular molecular orientation, but it exhibits its effectiveness significantly by orienting the molecular chains. I can do it. For example, molecular chains can be aligned by uniaxially or biaxially stretching a film-like molded product. Although it is known that aromatic polyimides generally have low thermal expansion, high elasticity, and high strength through orientation treatment, these effects are quite small compared to the polyimide of the present invention. Orientation of polymer chains can be achieved not only by stretching a normal film using a stretching machine, but also by utilizing the curing reaction and shrinkage caused by solvent volatilization during the process of turning polyimide or its precursor face into a polyimide molded product. I can do it. That is, applying the face and curing rlAK
By suppressing s-contraction, it is possible to orient the molecular chains. Although the amount of stretching due to curing shrinkage is very small compared to conventional stretching methods, the polyimide of the present invention is sufficiently effective even with such an orientation treatment.

In addition, when stretching a film-like molded product, if you try to stretch a completely cured product, it must be stretched at a very high temperature because the glass transition temperature of polyimide is extremely high. However, since the intermolecular cohesive force is extremely strong, it is difficult to align the molecules. In order to easily achieve orientation, it is preferable to orient the molecules by stretching the polyamic acid in a state containing a certain amount of solvent or in a state of polyamic acid having a low glass transition temperature, and then completely harden.

The reason why the polyimide of the present invention exhibits behavior that is completely different from the common sense of conventional polymers is considered to be as follows. That is, the polyimide main chain of the present invention has a substantially linear structure. However, in the state of polyamic acid or polyamide foam, it becomes solvated and becomes a random coil shape, and even when cured, a linear structure cannot be obtained. It is thought that when orientation treatment is applied, this polyimide molecule is able to assume the most stable linear structure.

The low thermal expansion polyimide of the present invention does not lose its properties even if it is blended or copolymerized with a polymer that does not have low thermal expansion. Some of the polyimides of the present invention are mechanically fragile, and it may be preferable to blend or copolymerize such polyimides with flexible polymers that do not have low thermal expansion. Examples of polymers that can be blended or copolymerized include polyimides obtained from the following diamines and tetracarboxylic acid derivatives. Specific examples of aromatic diamines include m-phenylenediamine, 4.4'-diaminodiphenylmethane, 1.2-bis(anilino)ethane, 4.4'-diaminodiphenyl ether, diaminodiphenyl sulfone, and 2.2-bis. (p-aminophenyl)propane, to 2,2-bis(p-aminophenyl)-
? l fluoropropane, 3,37-cymethyl-4,4'
-Diaminodiphenyl ether, 3,3'-dimethyl-
4,4'-diaminodiphenylmethane, diaminotoluene, diaminobensitrifluoride, 1,4-bi2(
p-aminophenoxy)benzene, 4,4'-bis(p
-aminophenoxy)biphenyl, 2,2-bis(4-
(p-aminophenoxy)phenyl)propane, diaminoanthraquinone, 4,4'-bis(3-aminophenoxyphenyl)diphenylsulfony/, 1,3-bis(
Anilino) to? Tefluoropropane, 1,4-bis(
Anilino)octafluorobuta/, 1.5-bis(anilino)decafluoropentane, 1.7-bis(anilino)tetradecafluorohbutane, general formula % formula % (Rs, Rr is a divalent organic group, R4 , Rs is a monovalent organic group, p and q are integers larger than 1), 2,2-bis(4-(+)-aminophenoxy)phenyl)hexafluoropropane, 2,2 −
Bis(4-(3-aminophenoxy)phenyl)hexafluoropropane, 2゜2-bis(4-(2-aminophenoxy)phenyl-hexafluoropropane, 2.2
-bis(4-(4-aminophenoxy)-3,5-dimethylphenyl)hexafluoropropane, 2,2-bis(4-(4-aminophenoxy)-3,5-ditrifluoromethylphenyl)hexafluoropropane Fluoropropane, p-bis(4-amino-2-trifluoromethylphenoxy)
be/zene, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 4,4'-bis(
4-amino-3-) 17fluoromethylphenoxy)
Biphenyl, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)diphenylsulfone, 4.4
'-bis(3-amino-5-trifluoromethylphenoxy)diphenylsulfone, 2,2-bis(4-(4-
Diamines such as amino-3-trifluoromethylphenoxy)phenyl)hexafluoropropane, and diisocyanates obtained by reacting these diamines with phosgene, etc. For example, tolylene diinocyanate, diphenylmethane diisocyanate, naphthalenedi ink There are aromatic diisocyanates such as annate, diphenyl ether diincyanate, and phenylene-1,3-diisocyanate. Examples of tetracarboxylic acids and their derivatives include the following. Although tetracarboxylic acids are exemplified here, esterified products, acid anhydrides, and acid chlorides thereof can of course also be used. 2
, 3.3'.

4'-f tracarboxydiphenyl, a, 3/14.
4'-f tracarboxydiphenyl ether, 2.3.
3',4'-tetracarboxydiphenyl ether,
3.3', 4.4'-tetracarboxybenzophenone, 2,3.3', 4'-tetracarboxybenzophenone, 2,3,6.7-titracarboxynaphthalene, 1,4,5.7-titracarboxy naphthalene, 1
．． 2,5.6=tetracarboxynaphthalene, 3.3'
, 4゜4'-tetracarboxydiphenylmethane, 2
゜2-bis(3,4-dicarboxyphenyl)propane, 2.2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 3.3', 4゜4'-tetracarboxydiphenyl sulfone, 3゜4.9.10-tetracarboxyperylene, 2゜2-bis(4-(3,4-
dicarboxyphenoxy)phenyl)furopane, 2.2
-bis(4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, and the like.

Furthermore, it is also possible to introduce a crosslinked structure or ladder structure by modifying with a compound having a reactive functional group. For example, there are the following methods.

(1) By modifying with a compound represented by general formula (III), a pyrrolone ring, isoindoquinazoline di/ring, etc. are introduced.

Here, 几′ is a 2+X-valent aromatic organic group, 2 is N H2
It is a group selected from a group, a CONHz group, and a 5OzNHz group, and is in the orn position with respect to the eagle and amino groups. X is 1 or 2.

(11) Amine, diamine having a polymerizable unsaturated bond,
It is modified with dicarboxylic acid, tricarboxylic acid, and tetracarboxylic acid derivatives to form a crosslinked structure upon curing. As the unsaturated compound, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline, etc. can be used.

(liD The phenolic hydroxyl group, certain b, is modified with an aromatic amine having a carboxylic acid, and a network structure is formed using a crosslinking agent that can react with this hydroxyl group or carboxyl group.

In the present invention, adhesiveness is important when integrating with a low thermal expansion polyimide inorganic material. It is preferable to roughen the surface of the inorganic material or to treat the surface with a silane coupling agent, a titanate coupling agent, an aluminum alcoholate, an aluminum chelate, a zirconium chelate, an aluminum acetylacetate, or the like. These surface treating agents may be added to the low thermal expansion polyimide.

In the present invention, inorganic, organic, or metal powders, fibers, chopped strands, etc. may be mixed in order to lower the coefficient of thermal expansion, increase the elastic modulus, and control fluidity. I can do it.

The composite molded article of the present invention is a product in which the above-described low thermal expansion resin and inorganic material are integrated. That is, the above-described low thermal expansion polyimide of the present invention takes advantage of its characteristics of low thermal expansion, high strength, and high elasticity, and is extremely useful for the following uses.

α) IC, LSI carrier film (2) Flat cable (3) Flexible printed circuit board (4) L8I wiring insulation film (5) L, 9I moisture-resistant protective film (6) LSI α-ray shielding film (7) Film Insulated coil (8) Semiconductor passivation film (9) Metal-core printed board αO solar cell with polyimide insulating film (6) Organic fiber @ Low thermal expansion polyimide fiber reinforcement FP (2) Organic filler [Embodiment of the invention ] Figure 2 shows a cross section of a flexible printed circuit board obtained by applying a precursor face of low thermal expansion polyimide 2 directly to copper foil 1, curing while suppressing curing shrinkage, and then buttering the copper foil. . Due to its low thermal expansion, even when cooled to room temperature after curing, there is no curling due to differences in thermal expansion coefficients, and a flat flexible printed circuit board can be obtained. normal FPC
In this case, adhesives are used, but there is no significant decrease in heat resistance due to adhesives, and the adhesive strength is also very strong.

FIG. 3 shows a cross section of a multilayer wiring section of an LSI.

3 is a silicon wafer, 4 is a thermally cured film, 5 is aluminum (A4) wiring, and 6 is an insulating thin film of low thermal expansion polyimide. When an insulating thin film is formed using a spin cord, the level difference in the At wiring is greatly reduced, providing a flat and highly reliable wiring structure.
In addition, due to its low thermal expansion, stress on the element is extremely low. If the thermal stress is large, cracks will occur in the device.

Furthermore, the low thermal expansion material used in the present invention can be easily processed using Hydrazi 7 or the like. The etching speed is about twice as fast as that of conventional polyimide.

FIG. 4 shows a cross-sectional view of a memory element having an α-ray shielding film. 7 is a wiring layer, and 8 is a lead wire. α
When the low thermal expansion polymer is used as the wire shielding film 9, the difference in thermal expansion coefficient between the silicon wafer 1 and the wiring layer 7 is small, so that cranking due to thermal stress, which was a problem when using conventional polymers, is avoided. In addition, problems such as deterioration of resolution in photoresist patterning due to curving of the wafer do not occur. Furthermore, it has extremely superior heat resistance compared to conventional polyimide, making it suitable for glass-sealed semiconductor devices. The thermal decomposition rate at 450C is about 1/10 that of the conventional type.

When the low thermal expansion polyimide of the present invention is used as the insulating film for the LSI shown in FIGS. 3 and 4, the shrinkage upon curing is as follows.
It exhibits low thermal expansion suppressed by silicon wafer.

FIG. 5 shows a cross-sectional view of a printed wiring board based on an LSI-mounted metal plate. 10 is a metal substrate, 11 is an LSI chip manufactured by a film carrier method, 12 is a carrier film using the low thermal expansion polyimide, and 13 is a terminal. Since a low thermal expansion polyimide is employed as the carrier film 12, a high precision and high density adhesive, 9111, can be obtained, and the stress applied to the bonding solder balls 14 is significantly reduced, thereby reducing the problem of fatigue breakage. In addition, by employing low thermal expansion polyimide for the insulating film 16 of the wiring section 15 formed on the metal substrate 10, a printed wiring board without curvature can be obtained, which enables high-precision, high-density mounting.

FIG. 6 shows a metal substrate module mounted using the lead wire bonding method. 17 is a lead wire bonding type LSI chip.

Further, although the drawings are not particularly shown, the present invention is effective for the following uses.

As a substrate for solar power and other devices using amorphous silicon,
When using a metal foil such as stainless steel coated with the aforementioned low thermal expansion polyimide thin film, when used as an amorphous silicon resin, the coefficient of thermal expansion in the longitudinal direction due to fiber reinforcement is lower than when using conventional polyimide. , the coefficient of thermal expansion in the translayer direction perpendicular to this can also be made smaller. Furthermore, since the difference in thermal expansion coefficient with the fiber material is small, there is no local thermal stress, and problems such as interface peeling due to heat shock and the like do not occur.

When used as a molding material, when the embedding material is metal or ceramic, the problems of cranking and cracking and deformation of the embedding do not occur.

In addition, when low thermal expansion polyimide is made into fibers and used as reinforcing fibers for FRP, it becomes lighter than glass cloth or the like. For multilayer wiring boards for computers, it has advantages such as a lower dielectric constant than those using glass cloth.

In this way, the composite molded article of the present invention is made by integrating the low thermal expansion polyimide and the inorganic material directly or through an adhesive or a binder.

The synthesis of the resin of the present invention will be illustrated in detail below.

Examples 1-8. Comparative Examples 1 to 1G A four-bottle flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet was charged with diamine in the amount shown in Table 1, and N-methyl-2-pyrrolidone (NMP) 850
It was dissolved in g. Next, the flask was immersed in a water bath at 0 to 50 C, and tetracarboxylic dianhydride was added while suppressing heat generation.

After the tetracarboxylic dianhydride was dissolved, the water bath was removed and the reaction was continued for about 5 hours at around room temperature to obtain the polyamic acid varnish shown in Table 1. If the varnish viscosity becomes very high, heat at 80-85C until the viscosity at 25C is 50 poise.
The mixture was heated and stirred at a high temperature.

The thermal expansion coefficient of polyimide obtained by heating these polyamic acids was measured as follows. That is, apply it uniformly to a glass plate using an applicator, and
Dry at C for 30-60 minutes, hold for 60 minutes, dry at 30-2
A polyimide film with a thickness of 0.00 μm was obtained. This is 3mX
Cut it out to 80m, sandwich it between the second glass plate and cut it again to 40m.
After heating to 0CK and slowly cooling to remove residual strain, dimensional changes were measured using a thermomechanical testing machine under conditions of 5C/-, and determined from the amount of dimensional change below the glass transition point. Unless hygroscopic moisture in the film, solvent, and residual strain caused by the imidization reaction are sufficiently removed, and the imidization reaction is not substantially completed, a proper coefficient of thermal expansion cannot be measured. Due to moisture absorption, the thermal expansion coefficient of the upper film appears to be small due to dehumidification in the range of T to 150t: ±40°. In addition, if the residual strain or imidization reaction is not completed, shrinkage may occur near Tg due to removal of residual strain or dehydration due to the imidization reaction, and the linear expansion coefficient above may appear to be small. many. Furthermore, even if it is fixed to an iron frame and cured, if it breaks during curing, the orientation treatment will be insufficient and the coefficient of thermal expansion will increase somewhat, so care must be taken.

Next, Tables 1 and 2 show the thermal expansion coefficients of the polyimide film after fixed curing and free curing.

In addition, the results of plotting the data in Tables 1 and 2 with the linear expansion coefficient for fixed hardening on the horizontal axis and the thermal expansion coefficient for free hardening on the vertical axis, t-
It is shown in Figure 717. It can be seen that the polyimide of the present invention has a very small coefficient of thermal expansion compared to general polyimide.

Looking at the common points in chemical structure, among these diamines that have low heat properties are I)-PDA and DA'rP.

o-TOLID, p-DATOL. As for the tetracarboxylic dianhydride, PMD is BPDA. That is, based on these experimental data, the conditions under which low thermal expansion is exhibited are as follows.

■ The skeleton consists of a benzene nucleus and an imide ring ■ The bond between the benzene nucleus is a para bond ■ The benzene nucleus may have a substituent such as a methyl group as a side chain.

Examples 9 to 14 It is also possible to appropriately control the thermal expansion coefficient of the low thermal expansion polyimide of the present invention by copolymerizing it with a general polyimide having a large thermal expansion coefficient or copolymerizing it at the polyamic acid stage. .

Table 3 shows the thermal expansion coefficients of the copolymers and blends. It can be seen that there is a nearly linear relationship between the coefficient of thermal expansion and the ratio of copolymerization or blending, making it easy to control.

Example 15 (Study of properties) α) Sample: Aromatic diamine shown in Table 4 and aromatic tetracarboxylic dianhydride were reacted in N-methyl-2-pyrrolipan at room temperature to produce polyamic acid. Made with varnish.

This varnish was applied onto a glass plate, dried at 100C for 1 hour, then the film was removed and dried at 200C for 1 hour.
It was further cured in nitrogen gas at 350C for 1 hour to obtain a polyimide film.

In addition, when curing shrinkage is allowed to occur during curing (pre
e cure), and when shrinkage is suppressed in one or two directions with an iron frame (Unlz f ix, Bi fix).
It was found that the thermal expansion behavior changes depending on the temperature (cure).

(2) Coefficient of thermal expansion...width 51Ili1 thickness 20~
100pm.

Using a thermophysical testing machine (TMA1500, Shinku Riko) as a test piece, a film with a length of 65 m + (between chucks) was used.
It was measured under the condition of 5C/-. Since the coefficient of thermal expansion has temperature dependence, it was decided to use an average value between 50 and 250 C as a representative value.

(3) Wide-angle X-ray diffraction...Geigerflex Ordinary D as a 30w x 40m, approximately 40μm thick test piece
(Rigaku Denki).

(4) Results and Discussion It was found that the thermal expansion behavior of polyimide varies depending on whether curing shrinkage is suppressed during the heat curing process from polyamic acid film to polyimide. Fig
, 8 is polyimide AD from DATP and PMDA
This is the thermal expansion behavior of 1. The coefficient of thermal expansion of polyimide is usually 4-6 x 10-'K'', and there is a dimensional change of 0.8-12% for a temperature change of 50-250C.

In comparison, /FLD1 has a temperature range of 50 to 250C, a precure one of 0.2 俤, and a Bifi
In the case of x cure, the dimension change was only about 0.1. Fig. 9 is also made of low thermal expansion polyimide (AA2)
This is an example. In this case as well, the Bifix cure is less than 0.1.
e has a relatively large coefficient of thermal expansion, 50~
It is about 0.4 inch in the range of 250C. In this sample,
We also investigated products in which curing shrinkage was suppressed in only one axis. According to this result, in the suppression direction (UFX-X), the coefficient of thermal expansion becomes even smaller, and the dimensional change is almost 0 degrees up to around 250C. However, in the direction perpendicular to the suppression direction (UFX-Y), it exhibited almost the same behavior as pre-Cure. In other words, slight curing shrinkage (linear shrinkage of about 10
%), the same effect as when stretching a general prepolymer film several times to several tens of times was obtained. Similarly, black people 3. Fig. shows the thermal expansion behavior of each sample of F3.

10.11.

Fig. 12 shows the relationship between the chemical structure of polyimide and the coefficient of thermal expansion. Based on these results, polyimide types can be roughly classified into the following four types.

■ Both Free and Bifix cure have small thermal expansion coefficients. This group includes 〇-TLD
Or a combination of DATP and PMDA is included.

■ In the case of precure, the coefficient of thermal expansion is somewhat large, but it becomes very small when bifix cured. This group includes people with pPD.

o Includes TLDs or a combination of DATP and BPDA.

■ In the case of pre-cure, it has a fairly large coefficient of thermal expansion, but with Bifix cure, the coefficient of thermal expansion is reduced to about half.This group includes p-PDA, o-TL, etc.
D, DATP, combination of m-PDA and BTD person, DD
Combination of E and PMDA, 2.4-DA'I'O and BP
Includes combinations with DA.

■ pre cure, 13ifix cure
All of these have a large coefficient of thermal expansion, and most other polyimides are included in this group.

It is well known that the coefficient of thermal expansion of polymers is reduced by stretch crystallization. Therefore, the crystallinity of polyimide was investigated using wide-angle X-ray diffraction. Measurement results l11
g, aP'g shown in 13 and 14.

From No. 13, it can be seen that Dl included in the group (■) exhibits sharp reflection and is crystalline.

C1 is also considered to be crystalline to some extent. Compared to these, ■
Person A2 in the group ``Group'' and person 3 in the ``Group ■'' are considered to have some orientation compared to F3 in the ``Group'', but
It is thought that it does not have crystallinity like Dl or C1.

Also, from the results of Fig. 14, pre-
cure, Bifix cure, UFX, and UF
Although we investigated the difference in Y, there was almost no difference in the wide-angle Xa1 diffraction data. If I had to say, Free c
In the case of ure, the size of the mountain seems to be small. These results clearly show that the stronger the crystallinity, the smaller the coefficient of thermal expansion, but this alone cannot explain the effect of suppressing curing shrinkage. Orderliness over long distances is thought to be important.

Next, when we examined the conformation of the polyimide in each group, we found that there was some commonality in texture, as shown in Fig. 15. In the group (2), both diamine and tetracarboxylic acid components can only take conformations that are linearly aligned on almost the same plane. Therefore, it is thought that it is rod-shaped in the direction of the molecular axis, rigid and rigid, and easily crystallized. ■The ones in the group are BP
D's biphenyl creates a somewhat zigzag structure, but
It has a fairly straight conformation. The group (■) is separated by two additional I/Cs. One is a p-PD person.

It consists of o-TLD, DATP and BTD people, (I
Although they are arranged on almost the same plane as shown in II), it is difficult to arrange them in a straight line due to the benzophenone skeleton. The other is (■
), the folds at the ether bonds are not lined up on the same plane, but the skeletons between the ether bonds are lined up on a straight line. PMDA and DDM.

The combination with DDS is also of the same type. Most other polyimides, like (V), lose their regularity due to ether, thioether, methylene, ketone, etc.

〔Effect of the invention〕

As explained above, according to the present invention, a resin material having an extremely small coefficient of thermal expansion equivalent to that of an inorganic material can be obtained, and therefore, a composite molded article using this material can be made thermally stable.

It has the effect of being mechanically superior.

[Brief Description of the Drawings] Figure 1 is a graph showing the thermal expansion coefficients of various materials, Figure 2 is a cross-sectional view of a flexible printed circuit board obtained by direct coating, and Figure 3 is a graph showing the coefficient of thermal expansion of various materials. 4 is a sectional view of a memory element having an α-ray shielding film, FIG. 5 is a sectional view of a metal core wiring board on which a film carrier type LSI is mounted, and FIG. 6 is a sectional view of a lead wire box. FIG. 7 is a characteristic diagram of the resin of the present invention. FIGS. 8 to 11 are temperature characteristic diagrams of example materials of the present invention. 12
The figure is also a custom-made diagram arranging the thermal expansion coefficients of the material of this example, Figures 13 and 14 are diffraction diagrams of the material of this example, and Figure 15 is a schematic diagram showing the molecular structure of the material of this example. Illustrated.

Claims (1)

[Claims] An aromatic group having one or more aromatic rings, which rotates around the molecular axis but is inflexible in other directions, is defined as a chemical structural unit. 1. A low thermal expansion resin material comprising a polyimide having polyimide molecules oriented in at least one axis. 2. The low thermal expansion resin material according to claim 1, wherein the degree of orientation has an order parameter of 0.07 or more. 3. The low thermal expansion resin material according to claim 1, wherein the polyimide has a molecular structure exhibiting a substantially linear molecular structure within a range of 0±40° around the molecular axis. 4. In claim 1, the main chain of the polyimide has ▲a mathematical formula, a chemical formula, a table, etc.▼, ▲a mathematical formula, a chemical formula,
There are tables, etc. ▼ and/or ▲ There are mathematical formulas, chemical formulas, tables, etc. An integer of ~4, m is an integer of 0 to 2,
n is an integer of 0 to 3). 5. The low thermal expansion resin material according to claim 1, wherein the unit structure of the polyimide molecule is selected from the following formula. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ( 4) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (5) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (6) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (7) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼(8) (wherein R is selected from an alkyl group, a fluorinated alkyl group, an alkoxyl group, a fluorinated alkoxyl group, an acyl group, and a halogen, k is an integer of 0 to 3, l is an integer of 0 to 4,
m is an integer of 0 to 2, and n is an integer of 0 to 3. 6. The low thermal expansion resin material according to claim 1, which is made by blending or copolymerizing the polyimide molecule with another polymer. 7. Claim 1, wherein the polyimide is a homopolymerization of an aromatic aminodicarboxylic acid derivative, or a reaction product of an aromatic diamine or an aromatic diisocyanate and an aromatic tetracarboxylic acid derivative. Low thermal expansion resin material. 8. The low thermal expansion resin material according to claim 1, characterized in that when the low thermal expansion resin material is molded into a coated film or fiber, the orientation direction is uniaxial or biaxial. 9. A low thermal expansion resin material according to claim 6, characterized in that the other polymer is a polyimide obtained from a diamine and a tetracarboxylic acid derivative. 10. In a composite molded product made by integrating an inorganic material and a polyimide resin, the polyimide resin has an aromatic group having a structure that rotates around the molecular axis and is not flexible in other directions as a chemical structural unit. What is claimed is: 1. A composite molded article comprising a portion oriented in at least one axis. 11. The low thermal expansion resin material according to claim 10, wherein the polyimide has a molecular structure in which the molecular axis is approximately linear in the range of 0±40°. 12. The low thermal expansion resin material according to claim 11, wherein the degree of orientation has an order parameter of 0.07 or more. 13. The composite molded product according to claim 10, which is a flexible printed board in which metal wiring is provided as the inorganic material on the substrate made of the polyimide resin. 14. A composite molded product according to claim 10, which is an LSI in which the polyimide resin is provided as a wiring insulating film between a silicon wafer and wiring, or between wirings. . 15. The composite molded product according to claim 10, which is an LSI formed by covering a silicon wafer with wiring with the polyimide resin. 16. In claim 10, the main chain of the polyimide has: ▲a mathematical formula, a chemical formula, a table, etc.▼, ▲a mathematical formula, a chemical formula,
There are tables, etc. ▼ and/or ▲ There are mathematical formulas, chemical formulas, tables, etc. An integer of ~4, m is an integer of 0 to 2,
n is an integer of 0 to 3). 17. The composite molded article according to claim 10, wherein the unit structure of the polyimide molecule is selected from the following formula. ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (2) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (3) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ ( 4) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (5) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (6) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (7) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼(8) (wherein R is selected from an alkyl group, a fluorinated alkyl group, an alkoxyl group, a fluorinated alkoxyl group, an acyl group, and a halogen, k is an integer of 0 to 3, l is an integer of 0 to 4,
m is an integer of 0 to 2, and n is an integer of 0 to 3. 18. The composite molded article according to claim 10, which is obtained by blending or copolymerizing the polyimide molecule with another polymer. 19. Claim 10, wherein the polyimide is a homopolymerization of an aromatic aminodicarboxylic acid derivative, or a reaction product of an aromatic diamine or an aromatic diisocyanate and an aromatic tetracarboxylic acid derivative. Composite molded product. 20. The composite molded article according to claim 10, characterized in that when the low thermal expansion resin material is molded into a coat-like film shape or a fiber shape, the orientation direction is uniaxial or biaxial. 21. The composite molded article according to claim 20, wherein the other polymer is a polyimide obtained from a diamine and a tetracarboxylic acid derivative.