JPH01210430A - Novel film having distribution in coefficient of thermal expansion and its production - Google Patents

Abstract

PURPOSE:To obtain a polymer film having distribution in the coefficient of thermal expansion, by applying precursor varnishes which can give polyamides of different coefficients of thermal expansion to a substrate in a state in contact with one another and imidating the precursor varnishes. CONSTITUTION:An aromatic diamine (A) (e.g., p-phenylene-diamine) or an aromatic isocyanate is reacted with a tetracarboxylic acid derivative (B) (e.g., 3,3',4,4'-biphenyltetracarboxylic dianhydride) at -20-200 deg.C in a solvent (e.g., N-methylpyrrolidone) to obtain a precursor varnish which can give a polyimide. Precursor varnishes of different coefficients of thermal expansion are applied to a substrate in a state in contact with one another and are imidated thermally or chemically to obtain the title film composed of the polymers of different coefficients of thermal expansion successively arranged in the direction of the face. This film is useful for bonding a material of a larger coefficient of thermal expansion to one of a smaller coefficient of thermal expansion.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a polymer film having a distribution of thermal expansion coefficients, particularly a polyimide film which is a highly heat-resistant insulating film, and a method for forming the same. This invention relates to a thermal expansion coefficient distribution type film suitable for joining many items with large thermal expansion coefficients to small items, such as flexible connectors for joining small semiconductor chips and wiring boards with large thermal expansion coefficients.

[Conventional technology]

Conventionally, the coefficient of thermal expansion of films has been almost uniform or has only been slightly variable depending on the molecular orientation during film production, and there are no known films in which the coefficient of thermal expansion has been intentionally varied sequentially within the film. .

The mainstream of heat-resistant flexible printed circuit boards is polyimide, and attempts have been made to bond resin printed circuit boards using this material, but it is impossible to bond materials with large differences in thermal expansion coefficient. In addition, up until now, LSIs (S chips) with a small coefficient of thermal expansion have been mounted on ceramic substrates such as alumina, 810, and mullite, which have a large coefficient of thermal expansion, organic glass epoxy laminates, metal substrates such as copper frames, etc. There was a similar problem when doing so. This was not much of a problem when the SL chip was small, but as the chip size increased, it became more of a problem.
Particularly in the case of the OOB method, breakage of solder joints is a major problem. 81 When bonding on the back side of the chip, silver paste,
Although this can be avoided to some extent by using stress-relaxing adhesives such as silicone rubber, problems such as a decrease in heat resistance arise. In the case of joining by the above-mentioned OOB method, it is necessary to use a material with low thermal expansion.

Furthermore, as one method of escaping thermal stress, a bin grid array method is known that utilizes relatively long lead pins and utilizes their deformation. However, this method is behind the times in terms of increasing density and simplifying the mounting process.

As described in Japanese Unexamined Patent Publication No. 60-243120, pest control is used to match the coefficients of thermal expansion of objects to be joined, but it is overwhelmingly impossible to do so. In computer mounting technology, semiconductor chips have a very small coefficient of thermal expansion, and it is extremely difficult to mount them on printed circuit boards or pancakes that have a large coefficient of thermal expansion.

Particularly recently, as the size of semiconductor chips has increased year by year, the issue of thermal stress caused by differences in thermal expansion coefficients has become increasingly important. 9. Increasingly, printed circuit boards with metal cores are often used to dissipate heat from semiconductor chips, and superconducting materials with relatively large coefficients of thermal expansion are used, but it is difficult to establish these connection methods. Very important.

[Problem to be solved by the invention]

The present invention eliminates the problems of the prior art described above and provides a method for joining materials having different coefficients of thermal expansion. For example, an 81 chip with a small coefficient of thermal expansion is mounted on a substrate with a large coefficient of thermal expansion, and it is used as a companion for bonding substrates with different coefficients of thermal expansion.

[Means to solve the problem]

To summarize the present invention, the first aspect of the present invention relates to a distributed coefficient of thermal expansion film, which is characterized in that polymers having different coefficients of thermal expansion are sequentially arranged in the plane direction.

A second aspect of the present invention is an invention relating to a method for manufacturing a distributed thermal expansion coefficient film, in which precursor varnishes providing polyimides having different coefficients of thermal expansion are applied onto a substrate so as to be in contact with each other, and heated. Alternatively, it is characterized by being formed by chemical imidization.

The film of the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view showing an example of the structure of the distributed thermal expansion coefficient film of the present invention. In FIG. 1, numeral 1 means a low thermal expansion region of the film, 2 means a thermal expansion coefficient changing region, and 3 means a high thermal expansion region of the film.

Since the thermal expansion coefficient distribution type film of the present invention exhibits almost similar colors after curing, it is convenient to color the regions having a constant thermal expansion coefficient in advance. As a coloring method,
For example, a small amount of heat-resistant pigment such as alumina may be added.

Friend, the shape of the distribution of the thermal expansion coefficient of the present invention can be freely changed depending on the application. For example, striped shapes, concentric circles, square shapes, etc. are possible.

In the present invention, the materials used are aromatic polyamide,
Although liquid crystalline polymers are conceivable, low thermal expansion polyimides are preferred in terms of heat resistance, mechanical properties, ease of control of thermal expansion coefficient, and the like. Low thermal expansion polyimide was previously reported by the present inventors as follows (January 1985).
Proceedings of the 2nd International Conference on Polyimides (proc, 2) held in New York City from October 30th to November 1st.
ndInternatxonal Conference
e on Po1y1a+les, 5PE) Shun Numata-
"Chemical structures and properties of low thermal expansion polyimides J" published by Chamlaal et al.
dPropartzes or LoW The
r+mal 1cxpanszon Polylm
If a monomer that provides a polyimide with a low thermal expansion coefficient and a polyimide monomer that provides a polyimide with a large coefficient of thermal expansion are copolymerized, or each is mixed in the state of a polyamic acid precursor, Easily controllable.

Moreover, the thermal expansion coefficient distribution U film of the present invention can be produced by various methods. For example, using a coating device with multiple nozzles as shown in Section 2, a polyamic acid varnish with a viscosity and concentration that provides the thermal expansion coefficient of the crosspieces after curing is simultaneously applied onto the substrate, and heated or chemically applied. It can be obtained by imidization. FIG. 2 is a perspective view from below of an example of a varnish applicator used in the method of the present invention. In Fig. 2, reference numeral 4fi varnish tank, 5 are nozzles for low thermal expansion polyimide precursor, 6 to 9 are nozzles for intermediate thermal expansion polyimide precursor, 10 are nozzles for high thermal expansion polyimide precursor, and 11 are gaps for film thickness control. means. As shown in Figure 8g2, the varnish tank is partitioned so that polyimide precursor varnishes with different coefficients of thermal expansion can be arranged and applied at the same time.

In the case of 7xI thermal imidization, it is preferable to heat the film to a temperature equal to or higher than the glass transition temperature of the polyimide to be produced, in order to complete the imidization reaction and to relax thermal stress within the film.

Polyimides or precursors thereof that can be used in the present invention are generally polyamic acids, but other examples include esterified amic acids and reaction products of acid dianhydrides and diisocyanates.

Furthermore, many skeletons can be used. For example, there are polymers of aromatic aminocarboxylic acids, aromatic diamines or diincyanates, and aromatic tetracarboxylic acids as starting materials.

In the present invention, polyimide precursors include those having the following chemical structures.

In the formula, Ar is a divalent organic group, Ar2 is a tetravalent organic group,
R represents H or an alkyl group, and m and n represent arbitrary positive numbers.

Such polyimide precursors can be obtained by homopolymerization of aromatic aminodicarboxylic acid derivatives or by reaction of aromatic diamines or aromatic incyanates with tetracarboxylic acid derivatives. 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-methyl, pyrrolidone (N
MP), dimethylformamide (DMF), dimethylacetamide (DMAO), dimethyl sulfoxide (
DMSO), dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, norogenated phenol, cyclohexanone, dioxane, tetrahydrofuran, acetophenone, etc. at -20 to 200C.
It is carried out within the range of

Specific examples of aminodicarboxylic acid derivatives used in the present invention include 4-aminophthalic acid, 4-amino-5
-methylphthalic acid, 4-(1)-anilino)phthalic acid,
Examples thereof include 4-(3,5-dimethyl-4-anilino)7talic acid, and esters, acid anhydrides, and acid chlorides thereof.

Aromatic diamines used in the present invention include p-phenylenediamine, 2.5-diaminotoluene, 2.5-
Diaminoxylene, diaminodurene (2,3,5,6-
titramethylphenylenediamine), 2,5-diaminopenzotrifluoride, 2,5-diaminoanisole,
2.5-diaminoacetophenone, 2.5-diaminobenzophenone, 2.5-diaminodiphenyl, 2,5-
Diaminofluorobenzene, benzidine, 〇-tolidine, m-)lysine, 5.3', 5. ”/-tetramethylbenzidine, 3.3'-dimethoxybenzidine, 5.5'
- Linear forms such as di(trifluoromethyl)benzidine, 5.5'-diacetylbenzidine, 5.3'-difluorobenzidine, octafluorobenzidine, 4.4'-diaminoter-7ale, 4.4"-diaminoquaterphenyl, etc. conformation, m-phenylenediamine, 4,4'-diaminodiphenylmethane,
1.2-bis(anilino)ethane, 4,4-diaminodiphelether, 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, diaminotoluene, diaminopenzotrifluoride, 1,4-bis(p-aminophenoxy)benzene, 4.4'-bis(p-aminophenoxy)biphenyl, hexafluoropropane, 2,2-bis(4-(
p-aminophenoxy)phenyl)propane, 2,2-
Bis(4-(m-aminophenoxy)phenyl)propane, 2.2-his(4-(p-aminophenoxy)phenyl)hexafluoropropane, 2.2-bis(4-(
tn-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(4-(p-aminophenoxy)
-3,5-dimethylphenyl)hexafluoropropane, 2,2-bis(4-(p-aminophenoxy) -
3,5-ditrifluoromethylphenyl)hexafluoropropane, p-bis(4-amine2-trifluoromethylphenoxy)benzene, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenyl,
4.4'-bis(4-amino-3-trifluoromethylphenoxy)biphenyl, 4,4'-bis(4-amino-2-trifluoromethylphenoxy)biphenylsulfone, 4.4'-bis(5- Amino-5-trifluoromethylphenoxy)biphenylsulfone, 2I2-bis(4-(p-amino-3-trifluoromethylphenoxy)phenyl)hexafluoropropane, diaminoanthraquinone, 4.4-bis(3-aminophenoxy) phenyl)diphenylsulfone, 1,3-his(anilino)hexafluoropropane, 1,4-bis(anilino)
Octafluorobutane, 1.5-bis(anilino)decafluorobentane, 1.7-bis(anilino)tetradecafluorohbutane, - Formula, 4R4 or (R5, R7 are divalent organic groups, R4, R6Vi1 Examples include di-aminosiloxanes represented by a valent organic group (p and q are integers greater than 1), and diisocyanate compounds thereof can also be used.

Examples of the tetracarboxylic acid derivatives used in the present invention include pyromellitic acid, methylpyromellitic acid, dimethylpyromellitic acid, di(trifluoromethyl)pyromellitic acid, 3.5',
4.1- and phenyltetracarboxylic acid, 5. dimethyl-5,5',4,4'-biphenyltetracarboxylic acid, p-(3,4-dicarboxyphenyl)benzene, 2,3.3',4'-tetracarboxydiphenyl,
3.5'4.4'-tetracarboxydiphenyl ether, 2,5.5'4'-tetracarboxydiphenyl ether, 5.3'4.4'-tetracarboxybenzophenone, 2.5.3'4'-tetracarboxy Benzophenone, 2,5,6,7-tetracarboxynaphthalene, 1,4,5,7-tetracarboxynaphthalene, 1,
2,5.6-tetracarboxynaphthalene, 5.3'4
．． 4'-tetracarboxydiphenylmethane, 2,3.
3'4'-tetracarboxydiphenylmethane, 2.2
-bis(3,4-dicarboxyphenyl)propane, 2
, 2-his(3,4-dicarboxyphenyl)hexafluoropropane, 3.3'4.4'-tetracarboxydiphenylsulfone, 3,4,9.10-tetracarboxyperylene, 2,2-bis( 4-(3,4-dicarboxyphenoxy)phenyl)furopane, 2,2-bis(
Examples include 4-(3,4-dicarboxyphenoxy)phenyl)hexafluoropropane, butanetetracarboxylic acid, and cyclopentanetetracarboxylic acid, and acid anhydrides, acid chlorides, and esters thereof can also be used.

In the present invention, even though polyimide is used, it is preferable to use a material that is not completely imidized from the viewpoint of adhesive properties. The polyimide precursor film can be obtained by applying a polyimide precursor solution uniformly by lath spin coating or the like, and drying preferably at a temperature in the range of about 50 to 250C. When using a polyimide precursor, after removing the mask, it is desirable to heat it to a high temperature to convert it into polyimide or to immerse it in an imidizing agent solution to almost imidize it. In the case of thermal imidization, it is desirable to heat the polyimide to a temperature higher than the glass transition temperature of the polyimide to be produced.

In the present invention, when a diamine component having a linear conformation is used and a pyromellitic acid derivative or a biphenyltetracarboxylic acid derivative is used as the natracarboxylic acid, a rod-like polyimide is obtained, and they have a low thermal expansion property. become.

In the present invention, it is possible to form a film in advance and then form a conductor film thereon, but it is also possible to apply varnish on a conductor such as metal foil in advance and form a pattern on the conductor after curing. .

In the case of powder, the adhesion between polyimide and various substrates is reduced. It is preferable that the surface of the inorganic material be treated with a roughened material, a silane coupling agent, a titanate coupling agent, an aluminum alcoholate, an aluminum chelate, a zirconium chelate, an aluminum acetylacetone, or the like. Further, these surface treating agents may be added to the polyimide.

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

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 p-phenyl diamine (p-PDA) and 4,4'-diaminodiphenyl ether (DDIC) and 5,3'
, 4,4'-biphenyltetracarboxylic dianhydride (s-BPDa) was reacted at room temperature in N-methyl-2-pyrrolidone (NMP) at the following blending ratio to obtain a high viscosity polyamic acid. friend. Furthermore, the mixture was heated and stirred at a temperature of 80 to 85C until the viscosity at 25C reached 50P, yielding 6 types of copolyamic acids with uniform viscosity (sap) and concentration (15%). As shown in Table 1, JP6
Fine particle alumina powder was added to varnishes 2 and 5 so that the gradient region of the coefficient of thermal expansion could be seen at a glance.

Table 1 Each polyamic acid was placed in a varnish container equipped with a coating nozzle as shown in Figure 2 and coated on a glass plate.

The coating thickness was adjusted to approximately 50 μm after curing.

After drying at 100C/1h, it was removed from the glass plate, fixed with an iron frame, heated from 100C to 400C in 2 hours, held at 400C for 30 minutes, and then cooled to room temperature to obtain the desired coefficient of thermal expansion. A distributed film was obtained. The distribution of the thermal expansion coefficient in the width direction of the obtained film is as shown in FIG.

That is, FIG. 3 shows the measurement results of the distribution of the thermal expansion coefficient of the film produced in Example 1 in terms of the film width direction dimension (W
It is a graph showing the relationship between I11 (horizontal axis) and thermal expansion coefficient (X10-5 -1, vertical axis).

Example 2 4.4#-diaminoterphenyl (DATP) and 5-B
Polyamic acid varnish 47 was obtained by reacting with PDA in NMP at a molar ratio of 1:1 in the same manner as in Example 1.
P, DDE and s-BPDA: 0.75:0.25
: Copolyamic acid A8 was obtained by reacting in the same manner at a molar ratio of 1.0.

These polyamic acid varnishes were mixed in the proportions shown in Table 2 below, and carbon black was added to A9 and A12 to color them black.

Table 2 Next, in the same manner as in Example 1, the mixture was coated on a glass plate and dried and cured to obtain a thermal expansion coefficient distribution type film having a thickness of about 50 μm. Furthermore, a rubber-dispersed epoxy adhesive was applied to a thickness of approximately 15 μm, a copper foil was pasted, and the adhesive was cured at 100C/1h.The copper foil was patterned using conventional photolithography to create a thermal expansion coefficient distributed type flexible adhesive. Get the circuit board. Using the flexible circuit board obtained here, as shown in Fig. 4, a liquid crystal display gray on a glass substrate with a thermal expansion coefficient of 3 x 10 K and a glass epoxy printed board with a thermal expansion coefficient of 15 x 10-'K-' were fabricated. connection was made.

That is, FIG. 4 is a plan view of the liquid crystal display manufactured in Example 2. In FIG. 4, reference numeral 21 indicates a thermal expansion coefficient distribution type flexible film, 22 indicates a liquid crystal display, 23 indicates a glass epoxy printed board, and 24 indicates a joint portion.

Example 3 Using the varnish of Example 2 and the formulation shown in Table 3, a distributed thermal expansion film with a small coefficient of thermal expansion in the center and large at both ends was obtained, and a copper foil was further applied using sifodringraphy. The foil was patterned to obtain a flexible circuit board.

Table 3 Using this, we can create a new semiconductor (7) as shown in Figure 5.
I got Hara Cage. There was no mismatch in the coefficient of thermal expansion, and it was highly reliable.

FIG. 5 is a cross-sectional view of the semiconductor device manufactured in Example 5, in which reference numeral 25 is a semiconductor chip, 26 is a thermal expansion coefficient distributed type flexible circuit board, 27 is a ceramic substrate, and 28f'
i Copper/polyimide high-density wiring board, 29-piece ceramic case, 30 means lead pins, 31 means solder.

〔Effect of the invention〕

The present invention is applicable to many electronics substrates with different coefficients of thermal expansion, such as semiconductor devices such as IC, f, and SI, high-density wiring boards, glass epoxy printed boards, wiring boards for thermal heads, and substrates for liquid crystal display elements. It is extremely convenient for joining.

[Brief explanation of the drawing]

Figure 1 shows one of the configurations of the distributed thermal expansion coefficient film of the present invention.
A perspective view showing an example, FIG. 2 is a perspective view of an example of a varnish coating device used in the method of the present invention, viewed from below, and FIG. 3 is a distribution of the coefficient of thermal expansion of the film produced in Example 1 of the present invention. FIG. 4 is a plan view of an FC liquid crystal display manufactured in Example 2 of the present invention, and FIG. 5 is a cross-sectional view of a semiconductor device manufactured in Example 3 of the present invention. 1: Low thermal expansion region of the film, 2: Thermal expansion coefficient changing region, 3: High thermal expansion region of the film, 4: Varnish tank, 5
: Nozzle for low thermal expansion polyimide precursor, 6 to 9: Nozzle for intermediate thermal expansion polyimide precursor, 10: Nozzle for high thermal expansion polyimide precursor, 11: Gap for film thickness control, 21: Thermal expansion coefficient distribution type flexible film, 2
2: i-crystal display, 23 glass epoxy printed board, 25: semiconductor chip, 26: thermal expansion coefficient distribution type flexible circuit board, 27: ceramic substrate, 28: copper/polyimide high-density wiring board Patent applicant Hitachi, Ltd. between Hitachi Chemical Co., Ltd.

Claims (3)

[Claims] 1. A thermal expansion coefficient distribution film characterized by sequentially arranging polymers with different thermal expansion coefficients in the plane direction. 2. 2. The thermal expansion coefficient distribution type film according to claim 1, wherein the portions having different thermal expansion coefficients are colored with different colors. 3. Thermal expansion according to claim 1, characterized in that it is formed by applying precursor varnishes that provide polyimides with different coefficients of thermal expansion onto the substrate so as to be in contact with each other, and thermally or chemically imidizing the substrates. A method for producing a coefficient distribution film.