JPS60250031A - Low-thermal expansion resin material - Google Patents

Abstract

PURPOSE:A polyimide resin having a coefficient of thermal expansion as low as that of an inorganic substance such as a metal or a ceramic and good mechanical properties, containing specified two kinds of aromatic groups in the main chain. CONSTITUTION:A low-thermal expansion resin material containing unit structures of formula I, wherein Ar1 is a bivalent aromatic group of formula II, III, or IV (wherein R is a lower alkyl group, alkoxy, acyl, or a halogen, and n is 1-4) and Ar2 is a tetravalent aromatic group of formula V or VI. Said material is produced by reacting a benzidine derivative with an aromatic tetracarboxylic acid (derivative) in an organic solvent such as N-methylpyrrolidone.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a low thermal expansion resin material made of polyimide.

[Background of the invention]

The thermal expansion coefficient (linear expansion coefficient) of most organic polymers is 4, even in the temperature range below the glass transition temperature.
It has a value of more than 1 in X 10-6, which is much larger than that of metals and inorganic materials. There are many problems caused by the large coefficient of linear expansion of organic materials, and it is no exaggeration to say that these are all the reasons why the development of applications for organic polymers has not progressed as expected. For example, in a flexible printed circuit board (FPC) consisting of a film and a conductor, a film obtained by coating or thermocompression bonding a flexible film material on a metal foil is desired. Therefore, after cooling to room temperature, there is a problem of curling due to thermal stress caused by the difference in thermal expansion coefficients. Usually, to prevent this phenomenon from occurring, they are bonded together using an adhesive that can be cured at low temperatures. However, FPCs that require heat resistance
In this case, 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 the base material, it will not be able to exhibit its original heat resistance.

In addition, in the case of a film, if it is applied onto a metal plate or inorganic material whose coefficient of thermal expansion is much smaller than that of ordinary organic polymers, thermal stress caused by the difference in coefficient of thermal expansion may cause deformation, cracks in the film, etc. Otherwise, destruction of the base material, etc. will occur. For example, when a coating film is formed on a silicon wafer as a protective film for LSI or IC, the wafer warps, making it impossible to perform photolithography for buttering, or causing problems such as extremely poor resolution and high thermal stress. In such cases, the passivation film may be peeled off or the reconfirmation process itself may undergo cleavage failure.

As described above, there are many problems with organic polymers having large coefficients of linear expansion, and organic polymers with low coefficients of expansion have been strongly desired for some 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.

A wide variety of polyimides have been provided so far. However, very few have been actually synthesized or put into practical use. So far, the synthesis has actually been attempted, reported or commercially available: diaminodiphenyl ether, diaminocyphelmethane,
Aromatic diamines such as phenylene diamine or diaminodiphenyl sulfide and tetracarboxylic dianhydride such as pyromellitic dianhydride, benzophenone tetracarboxylic dianhydride, tetracarpoxy diphenylethyl dianhydride or butane tetracarboxylic dianhydride. There is only polyimide made from carboxylic dianhydride. However, the net expansion coefficient Vi4~6×1 of these polyimides
O-5K", which is extremely large. However, as a result of further synthesis experiments, the present inventors found that
A polyimide obtained from a specific aromatic diamine and an aromatic tetracarboxylic dianhydride as shown below has an abnormally small coefficient of thermal expansion that is inconceivable from the above-mentioned polyimide and other organic polymers, It was also discovered that it has significantly large values in terms of mechanical strength and elastic modulus.

The present invention has been made based on this discovery.

In addition, as a prior art of low expansion polyimide, JP-A-55-
Examples include polyimides described in Japanese Patent No. 7805.

[Purpose of the invention]

An object of the present invention is to provide a polyimide resin 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.

[Summary of the invention]

The low thermal expansion material of the present invention has the following formula [I] [where Arl is (IL) (R) (R) (i(,) (R)(R
几（几）1. (几)n (R) An aromatic group selected from (R) is a lower alkyl group, an alkoxy group, an acyl group, or a halogen, and n is 0 to 4.
, Ar2 is a tetravalent aromatic group. ].

The low thermal expansion material used in the present invention is benzidine, 3.3'
-dimethylbenzidine, 3,3'-bis(trifluoromethyl)benzidine, 3,3'-dimethquinpenzidine, 3,3'-bis(trifluoromethoxybenzidine, 3+ 3' + 5+ 5'-tetramethyl Benzidine, 2.2'-dimethylbenzidine, 3.3'-diacetylbenzidine, 4.4'-diaminooctafluorobiphenyl, 3.3',5.5'-tetrachlorobenzidine, 4.4"-diaminoterphenyl ,4,4/
It can be obtained by reacting //-diaminoquataphenyl or an incyanate thereof with an aromatic tetracarboxylic acid selected from pyromellitic acid, benzophenonetetracarboxylic acid, and biphenyltetracarboxylic acid or a derivative thereof.

Tetracarboxylic acid derivatives include esters, acid anhydrides, and acid chlorides. It is preferable to use acid anhydrides because they are synthetically reactive and free from harmful by-products.

The synthesis reaction is generally performed using N-methylpyrrolidone (NM
P), dimethylformamide (DMF), dimethylacetamide (DMAC), dimethylsulfoxide (DM
SO), dimethyl sulfate, sulfolane, butyrolactone,
It is carried out in a solution of cresol, phenol, halogenated phenol, cyclohexanone, dioxane, tetrahydrofuran, etc. in the range of θ to 200C. Even if it is reacted at a relatively low temperature to form a film and coat it as a polyamic acid varnish, it will be imidized at the same time as it is heated and dried.
If there is no problem with solubility, it may be reacted at high temperature in the fest stage to form a polyamide fest.

The low thermal expansion polyimide can also be modified by introducing other aromatic diamines, aromatic diincyanates, tetracarboxylic acids, or derivatives thereof within a permissible range.

To give specific examples, p-phenyl diamine, m-
fluorinatediamine, diaminotoluene, diaminobensitrifluoride, diaminoxylene, diaminodurene, 4.4'-diaminodiphenylmethane, 1.2
-bis(anilino)etha 7.4.4'-diaminodiphenyl ether, diaminodiphenylsulfone, 2.2-
Bis(p-aminophenyl)propane, 2,2-bis(
p-aminophenyl)hexafluoropropane, 3゜3
'-Dimethyl-4,4'-diaminodiphenyl ether, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 1,4-bis(p-aminophenoxy)benzene, 4,4'-bis(p-amino phenoxy)biphenyl, 2,2-bis(4-(p-aminophenoxy)phenyl)propane, diaminoanthraquinone, 4.4'
-bis(3-aminophenoxyphenyl)diphenylsulfone, 1,3-bis(anilino)hexafluoropropane, 1,4-bis(anilino)octafluorobutane, 1,5-bis(anilino)decafluorobencune, 1
．． 7-bis(anilino)tetradecafluorohebutane,
Diaminocloxane, 2.2-bis(4 -(p-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)
Benzene, 4. ．． 4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl, 4,4'-bis(4-amino-3-trifluoromethylphenoxy7)
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 diinocyanates obtained by reacting these diamines with phosgene, such as tolylene diiso7anate, diphenylmethane diisocyanate, naphthalene diisocyanate, There are aromatic diisocyanates such as diphenyl ether diisocyanate and phenylene-1,3-diisocyanate. In addition, examples of tetracarboxylic acids and derivatives thereof include the following. Although the tetracarboxylic acid is exemplified here, its esterified products, acid anhydrides, and acid chlorides can of course also be used. 2,
3.3'.

4'2 Tetracarboxydiphenyl% 313' 14
．． 4'-Tetracarboquine diphenyl ether, 2.3
．． 3', 4'-tetracarboxydiphenyl ether, 2.3.3', 4'-tetracarboxybenzophenone, 2,3,6.7-titracarboxynaphthalene,
1.4,5.7-titracarboxynaphthalene, 1,2
, 5.6-titracarboxynaphthalene, 3.3',
4.4'-tetracarboxydiphenylmethane, 2.
2-bis(3,4-dicarboxyphenyl)propane,
2゜2-bis(3,4-dicarboxyphenyl)hexafluoropropane, 3.3',4.4'-tetracarboxydiphenylsulfone, 3,4,9゜10-tetracarboxyperylene, 2.2-bis (4-(3,4-
dicarboxyphenoxy)phenyl)propane, 2.2
-bis(4-(3,4-dicarboxyphenyl7)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) A pyrrolone ring, isoindoquinazolinedione ring, or the like is introduced by modifying with a compound represented by the general formula (I[[).

HzN -R' N H2 (DI) (where R' is a 2+X-valent aromatic organic group, 2 is N H2
The group is selected from a group consisting of a C0 NHz group and an 802 NHz group, and is in the ortho position with respect to an acyl group and an amino group. 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 prepped structure upon curing. As the unsaturated compound, maleic acid, nadic acid, tetrahydrophthalic acid, ethynylaniline, etc. can be used.

QID is modified with an aromatic amine having a phenolic hydroxyl group or a carboxylic acid, and a network structure is formed using a crosslinking agent that can react with the hydroxyl group or carboxyl group.

The coefficient of thermal expansion can be adjusted by modifying with each of the above components. That is, the modification components detailed above are included in the general formula (Il), and by increasing the content of this structural unit, the thermal properties of the polymer consisting only of the structural units represented by the general formula [■] The coefficient of linear expansion can be larger than the coefficient of expansion, and can be set arbitrarily depending on the purpose or use.For example, the coefficient of linear expansion of a polymer consisting only of structural units represented by the general formula CD is approximately 1×1.
-1 to 0-', but 3,3'-dimethylbenzidine (A r t of general formula [■], abbreviated as DMBZD)
Diaminodiphenyl ether (Ar* of general formula [■])
5DDE), the linear expansion coefficient of the polyimide produced is as shown in Figure 1. In addition, the carboxylic acid component used at this time was one using only biphenyltetracarboxylic dianhydride, which was reacted with the reed and wholly aromatic diamine components in equimolar amounts. Furthermore, if you look at Figure 1, D
It can be seen that when the DE content is 75 mol, the expansion coefficient decreases rapidly.In the present invention, when integrating with a low thermal expansion polyimide inorganic material, adhesiveness is important. be. It is preferable to roughen the surface of the inorganic material or subject it to surface treatment using a silane coupling agent, a titanate coupling agent, aluminum alcoholate, aluminum chelate, zirconium chelate, aluminum acetylacetone, or the like. These surface treating agents may be added to the low thermal expansion polyimide.

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

The low thermal expansion polyimide of the present invention is extremely useful for the following uses.

(1) Film carrier type IC, LSI (2) Insulated coil using heat-resistant film (3) L with multilayer wiring
SI (4) Semiconductor device having a passivation film made of organic polymer (5) Semiconductor device having an α-ray blocking film (6)
Flexible printed board (7) Printed circuit board formed on metal plate (8) Solar cell (9) Organic filler αG Organic fiber Next, a detailed explanation will be given with reference to FIGS. 2 to 4.

FIG. 2 shows a cross-sectional view of a memory element having an α-ray shielding film. 1 is a silicon substrate, 2 is a wiring layer, and 5 is a lead wire. When the low thermal expansion polyimide is used as the α-ray shielding film 4, the difference in thermal expansion coefficient between the silicon substrate 1 and the wiring layer 2 is small, resulting in cracks caused by thermal stress, which was a problem when conventional polymers were used. In addition, problems such as curving of the wafer and deterioration of resolution during turning of the photoresist do not occur. Furthermore, it has extremely superior heat resistance compared to conventional polyimide, making it suitable for use in glass-sealed semiconductor devices. 450υ
The thermal decomposition rate is about 1/10 that of the conventional type.

Part 3 shows a cross-sectional view of a printed wiring board based on a metal plate with LSI mounted thereon. 6 is a metal substrate, 7 is an LSI chip manufactured by a film carrier method, 8 is a carrier film using the low thermal expansion polyimide, and 9 is a terminal. Since low thermal expansion polyimide is used as the carrier film 8, a high-precision, high-density LSI 7 can be obtained, and the stress applied to the bonding solder balls 10 is significantly reduced, thereby reducing the problem of fatigue breakage. Furthermore, by employing low thermal expansion polyimide for the insulating film 4 of the wiring section 3 formed on the metal substrate 6, a printed wiring board without curvature can be obtained.
This enables high-precision, high-density mounting.

FIG. 7 shows a metal substrate module mounted using the lead wire bonding method. 11 is a lead wire bonding type LSI chip.

Although not particularly shown in the drawings, it is also useful for the following uses.

As a substrate for solar cells using amorphous silicon,
When a metal foil such as stainless steel coated with the low thermal expansion polyimide thin film is used, the occurrence of cracks in the amorphous silicon thin film is significantly reduced compared to when conventional polyimide is used.

When the above-mentioned low thermal expansion polyimide is used as a film for flexible printed circuit boards, it has a small coefficient of linear expansion with metal wiring materials, so a flat flexible printed circuit board that does not curl like when conventional polyimide is used can be obtained. It will be done. Moreover, since there is no such problem, it is possible to adopt a manufacturing method in which the face is applied directly onto the metal foil without using an adhesive. Therefore, the number of steps is reduced by more than half compared to the conventional method of bonding metal foil and pre-prepared films with adhesives, and there is no significant drop in heat resistance due to low-temperature curing adhesives.

Furthermore, since this flexible printed circuit board has a small coefficient of thermal expansion, when used as a multilayer wiring board, the thickness of each layer is extremely small, allowing high-density mounting.

When the low thermal expansion polyimide is used as a matrix resin for a fiber-reinforced laminate, not only the coefficient of thermal expansion in the longitudinal direction due to fiber reinforcement but also the coefficient of thermal expansion in the through-layer direction perpendicular to the fiber reinforcement can be made small. Furthermore, since the difference in coefficient of thermal expansion with the fiber material is small, there is no local thermal stress, and problems such as cracking of the interface due to heat yokes do not occur.

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

[Embodiments of the invention]

Examples 1-12. Comparative Examples 1 and 2 Diamines in amounts shown in Table 1 were placed in a four-bottle flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and dissolved in 850 g of N-methyl-2-pyrrolidone (NMP). 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 cloth shown in Table 1. If the festival viscosity becomes very high, heat at 80-85C until the viscosity at 25C reaches 50 poise.
The mixture was heated and stirred at .

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 for 30 to 60 minutes at C to form a film, peel it off from the glass plate and fix it on an iron frame.
Each was held at 0C for 60 minutes to obtain a polyimide film with a thickness of 30 to 200 μm. This is 3 rtan
It was cut out to a length of 80 m, sandwiched between two glass plates, heated again to 350 C, slowly cooled to remove residual strain, and then measured for dimensional changes using a thermomechanical testing machine at a rate of 5 C/m. , based on the amount of dimensional change below the glass transition point. In this way,
An accurate coefficient of thermal expansion cannot be measured unless the hygroscopic moisture of the film, the solvent, and the residual strain caused by the imidization reaction are sufficiently removed, and the imidization reaction is not substantially completed. Due to moisture absorption, the thermal expansion coefficient of the upper film is observed to be apparently small due to dehumidification in the range of RT to 150C. Also, if residual strain or imidization reaction is not completed, T
At around g, shrinkage occurs due to removal of residual strain or dehydration due to imidization reaction, and the apparent linear expansion coefficient is often observed to be small.

Next, Table 2 shows the tensile strength, elastic modulus, thermal decomposition characteristics, and glass transition point of the polyimide film.

These results show that it is excellent in various physical properties.

Example 13 Polyamic acid fabric shown in Example 1 (sample A in Table 1)
1) was directly applied onto the roughened surface of a 35 μm thick copper foil that had been roughened on one side so that the film thickness after curing would be 50 μm. Dry and harden at 100C/1 while fixed on an iron frame.
The test was carried out under the following conditions: 200C/30 minutes and 350C/15 minutes. After cooling to room temperature, the iron frame was removed to obtain a flexible copper-clad board. This flexible copper clad board was slightly curved with the copper foil inside, but the radius of curvature was 92 square meters, which was substantially negligible. Furthermore, it was placed in a 260T:' solder bath for 30 seconds and left in a hot air oven at 300C for 30 minutes in a free (not fixed or supported) state, then cooled to room temperature. There was no change. Furthermore, printed circuit boards were made by etching copper foil into various patterns, but there were no abnormalities in this case either.
In fact, the curvature was slightly reduced. Furthermore, the beer strength between the copper foil and the polyimide film was impossible to measure because the adhesive strength was too strong and the copper foil itself broke.

Examples 14-17. Comparative Example 3 In the same manner as in Example 2, a copper-clad board was produced using the polyamic acids of Samples A2 to A5 in Table 1. The bending radius of the flexible printed circuit board is as shown in Table 3.

Table 3 A value of - indicates that it is along the Cu foil side.

Comparative Example 4 Using the polyamic acid of Comparative Example 1 in Table 1, a 50 μm thick polyimide film was prepared in advance for casting onto a glass plate.

This film was coated with a nitrile rubber-modified epoxy adhesive to a thickness of approximately 20 μm, and one side was nickel plated to a thickness of 35 μm.
The copper foil was bonded to the nickel-plated surface) and molded for 30 minutes using a hot press (pressure: 40 Kf/d, 150 C). After cooling to room temperature, it was greatly curved. Then 300C
As a result of dipping in a solder bath for 5 minutes, peeling occurred between the copper foil and the polyimide film.

As described above, the flexible 7 pulled flint substrate in the above example does not require an adhesive treatment process, so it is extremely easy to manufacture, and also has strong beer strength and excellent heat resistance.

Example 18 and Comparative Example 5 The polyamic acids of Example 9 and Comparative Example 1 in Table 1 were used to form protective films for a large number of memory elements formed on wafers having a diameter of 41 nch. First, a 1% toluene solution of aluminum alcoholate (surface treatment agent) was applied onto the wafer, and the wafer was treated at 350C for 1 hour. Next, each of the polyamic acid varnishes was spin-coded at 600 r% for 30 seconds so that the thickness after curing was 50 μm. The curing conditions were 100C/30 minutes + 150G/30 minutes. A negative photoresist was coated on this to a thickness of 2 μm, and a pattern was formed so that the resist film remained only on the memory area. Polyimide in areas other than the memory cells was removed by etching with a mixture of hydrazine and ethylenediamine. Furthermore, after removing the photoresist using an oxygen plasma asher, imidization was completed under the conditions of 400C for 130 minutes, and an α-ray shielding film was formed on the memory area.

As a result, when the polyamic acid of Example 9 was used, production was possible without any abnormality, but when the polyamic acid of Comparative Example 1 was used, the polyimide film was significantly curved when the entire surface of the wafer was coated, so the photo There were problems such as inability to vacuum suction during mask alignment in one lithography process and difficulty in aligning with the mask. Furthermore, when the polyimide film was etched, a serious problem arose in that the memory element was peeled off from the Uchiha substrate due to thermal expansion.

〔Effect of the invention〕

As explained above, according to the present invention, a polyimide resin having an extremely small coefficient of thermal expansion and excellent mechanical properties can be obtained.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the blending amount of DDE and the linear expansion coefficient of polyimide, Figure 2 is a cross-sectional view of a memory element with an α-ray shielding film, and Figure 3 is a metal plate on which a film carrier type LSI is mounted. FIG. 4 is a sectional view of a metal plate pace printed circuit board mounted with a lead wire bonding type L8 It-. DESCRIPTION OF SYMBOLS 1... Noricon wafer, 2... Wiring layer, a... Aluminum wiring, 4... Low thermal expansion polyimide, 5...
・Lead wire, 6... Metal substrate, 7... Film carrier type LSI, 8... Carrier film, 9...
・Terminal, 10...Solder pole, 11...Lead wire bonding method % type % Perforation 1 Figure DDE/l ml■ ((IL,/; ) 30th funeral 4z

Claims (1)

[Claims] 1. A low thermal expansion resin material characterized by containing a unit structure represented by the following formula. In the formula c, Arl is an aromatic group selected from and, and R is selected from a lower alkyl group, an alkoxy group, an acyl group, and a norogen. )