JPH03123093A - Manufacture of copper plated laminated board - Google Patents

Abstract

PURPOSE:To prevent a film from curing and to improve it in reliability as to dimensional stability, adhesive force, and the like by a method wherein polymide resin layers different from each other in thermal linear expansion coefficient are applied onto a conductor making the resin layer of higher thermal expansion coefficient face outward, which is dried up to be set in a pressure reduced and/or a reducing atmosphere to form a multilayered insulator. CONSTITUTION:A copper plated laminated board is manufactured in such a method that at least two types of polyimide resin compositions or their precursor compositions different from each other in thermal linear expansion coefficient are applied onto a conductor making a resin layer of higher thermal expansion coefficient located outside, which is dried up to be set in a pressure reduced and/or a reducing atmosphere. It is preferable that the linear expansion coefficient difference between the high thermal linear expansion resin layer and the low thermal linear expansion resin layer is larger than 510(1/K) or above. It is also preferable that a resin applying method is carried out in such a manner that two more kinds of polyimide resin or their precursor solutions are applied onto a conductor at the same time using a multilayered die. By this setup, even if a heat hysteresis is given to a copper plated laminated board of this design, it is free from curling, torsion, warpage, and the like, can be secured enough in adhesion, flexibility, dimensional stability, and the like, and can be made small in curling after the etching of a conductor so as to be improved in workability.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a flexible printed circuit that is free from curling, twisting, warping, etc. after circuit formation, and has excellent heat resistance, dimensional stability, adhesiveness, and bending resistance. The present invention relates to a method for manufacturing copper-clad laminates for use in industrial applications.

[Prior Art] Conventionally, copper-clad laminates for flexible printed circuits have generally been manufactured by bonding a conductor and an organic polymer insulator with an adhesive such as epoxy resin or urethane resin.

However, 1. If a thermal history such as thermocompression bonding is added at this time, there is a drawback that curling, twisting, warping, etc. of the substrate occurs during cooling, making subsequent patterning of the conductor etc. impossible. These problems are caused by the difference in coefficient of linear expansion between conductors and insulators. Further, there were other problems such as the flame retardance being lowered due to the adhesive layer, the polyimide film used being expensive, and the flexible printed circuit board requiring a great deal of effort to bond together.

JP-A-56-23-791 and other publications propose a method in which a polyamide-imide solution is applied to a metal foil, and after drying, the curl that occurs due to the difference in linear expansion coefficient is alleviated by heat treatment in a post-goni culm. However, this method is still unsatisfactory as it requires time and effort to manufacture and curls when reheated in a soldering bath due to different coefficients of linear expansion.

Also, JP-A-60-157.286 and JP-A-60
Publication No. 243120 proposes a method in which a polyamide-imide solution is applied to a metal foil, and after drying, curls that occur due to the difference in linear expansion coefficient are relaxed by heat treatment. However, problems such as the fact that manufacturing is time-consuming and the linear expansion coefficients are different, resulting in curling during reheating in a soldering bath, etc., have not yet been solved and have not been satisfactory.

Also, JP-A-60-157.286 and JP-A-60
-243.120 proposes a method of applying polyimide having a specific structure or a polyimide precursor solution onto a conductor to obtain a low thermal expansion resin, thereby obtaining a flexible printed circuit board with less curl. The adhesive force may be insufficient, or when the conductor is bonded to form a circuit, the film may curl significantly with the side that was in contact with the conductor facing inward, making it difficult to perform subsequent work such as protecting the circuit. The problem was that it was difficult.

In addition, in conventional types using an adhesive layer, the adhesive layer maintains physical properties that polyimide films lack, such as hardness and tear strength. However, there were problems in various aspects such as the workability of hammering and handling.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to have a material that does not curl, twist, warp, etc. even when subjected to heat history, and has sufficient adhesive strength, bending resistance, dimensional stability, etc. Moreover, it was an object of the present invention to provide an industrially useful flexible printed circuit board 1 which has a small curl after etching a conductor and which impairs workability.

[Means for Solving the Problems 1] As a result of extensive research in view of the above, the present inventor has developed an insulator with a plurality of polyimide resin layers having different linear expansion coefficients, and a high thermal expansion resin layer. By coating the conductor as the outside and drying and curing under reduced pressure and/or a reducing gas atmosphere to form a multilayer film, it prevents the film from curling after etching the conductor and provides excellent resistance to temperature changes.
The inventors have discovered that it is possible to obtain a flexible printed circuit board with excellent reliability in terms of legal stability, adhesive strength, etc., and have completed the present invention.

That is, the present invention provides a method for manufacturing a copper-clad laminate for a flexible printed circuit, which is formed by directly coating a polyimide resin on a conductor, in which at least two types of polyimide resin compositions or precursors thereof having different coefficients of linear expansion are used. A copper-clad laminate characterized in that a body composition is coated on a conductor so that the resin layer with a high coefficient of linear expansion is on the outside, and then dried and cured under reduced pressure and/or in a reducing gas atmosphere. This is a method of manufacturing a board.

In the present invention, a copper-clad laminate for flexible printed circuits formed by direct coating refers to a method in which a resin solution or its precursor resin solution is directly applied onto a conductor, dried, and further cured. A substrate for a flexible wiring body or its material formed by forming a composite material with.

Moreover, the polyimide resin referred to in the present invention is a heat-resistant resin such as polyimide, polyamide, polybenzimidazole, and polyimide ester.

In the present invention, an insulator is formed by combining a high thermal expansion resin layer and a low thermal expansion resin layer with different linear expansion coefficients, and the thickness of the high thermal expansion resin layer (tl
) and the thickness (tl) of the low thermal expansion resin layer (t2/l
l) (However, tl and tl are the sum of the thicknesses of each resin layer), 0°01 to 20,000,
Preferably 2-100. More preferably, it is necessary to satisfy 3 to 25 rows A'↑.

Here, the high thermal expansion resin layer and the low thermal expansion resin layer are:
A resin layer having a linear thermal expansion coefficient higher than the simple average value of the linear thermal expansion coefficients of each component resin layer of an insulator forming a multilayer structure is called a high thermal expansion resin layer. A resin layer having a lower coefficient of linear expansion is referred to as a low thermal expansion resin layer.

If the value of the thickness ratio (t2/11) is too small, the linear expansion coefficient of the insulator as a whole will become large, and the difference in linear expansion coefficient with the conductor will cause the board to curl with the insulator inside, making it difficult to form circuits. When etching the conductor, the distortion may be released and the dimensions may change significantly. On the other hand, if the value of the thickness ratio (t2/ll>) is too large, it becomes difficult to prevent the film from curling after conductor etching, which is the object of the present invention.

In the present invention, the total thickness (tl+t2>) of the insulator is usually 5 to 100 μs, preferably 10 to 50 μs. Also, the linear expansion coefficient of the high thermal expansion resin layer constituting this insulator is 30×1O− 6 (1/K) or more, preferably (40 to 100) x 1O-6 (1/K), and the linear expansion coefficient of the low thermal expansion resin layer is 30 x 10' (1/K).
less than (0 to 25) xlO' (1/K), and the linear expansion coefficient between the high thermal expansion resin layer and the low thermal expansion resin layer is 5 x 10' (1/K).
It is desirable that there is a difference of at least IOX K), preferably at least IOX 10' (1/K). 5 x 10-6 (1/K)
If it is less than that, it will be difficult to prevent the film from curling after etching.

In order to prevent film curl, it is necessary to provide a high thermal expansion resin layer as the outer layer.

In this manufacturing method, it is necessary to provide at least two polyimide resin layers with different coefficients of thermal expansion. There is no problem even if a resin layer is provided.

The high thermal expansion resin may be any polyimide resin, but from the viewpoint of heat resistance, it is preferably one whose main component is a polyamide-imide resin or a polyimide resin having a structural unit represented by the following general formula. .

In addition, as the above Ar2, for example, (However, in each of the above general formulas, Ar1 is a divalent aromatic group having 12 or more carbon atoms, and Ar2 is a tetravalent aromatic group. Here, the above Ar1 is, for example, oOo, oSo
, 0S02-0-1, etc. However, due to its low cost and excellent flexibility, polyimide resins preferably having such a structure usually have a linear expansion coefficient of 30x 1O. -6 (1ha shows a relatively high value of 0 or more.

In particular, polyimide having a structural unit represented by the following general formula (I [I) F3 Go-G-G-oG, GOGO (O-) has thermoplasticity, and when provided in the outermost layer, the circuit 1111 construction It is sometimes suitable for multi-layering by thermocompression bonding.

In addition, there are no particular restrictions on the low thermal expansion resin as long as it is a polyimide resin with a low coefficient of linear expansion, but polyimide resins having a structural unit represented by the following general formula (i) or (TI) may be used. preferable.

General formula (i) (However, in the formula, ``Nuki'' represents a tetravalent aromatic group, and ``R2'' and ``R2'' represent either a lower alkyl group, a lower alkoxy group, or a halogen, which may be the same or different from each other. ,
[beta] and ... are integers of O to 4 and have at least one lower alkoxy group) A polyamide-imide resin containing a structural unit represented by [beta], preferably the following]14 monomer.

1 General formula (If) A polyimide resin containing the structural unit shown below.

These polyimide resins are synthesized using N-methylpyrrolidone (NHP) and dimethylformamide (DH) for boat fishing.
F), dimethyl acetamide (D to 1 to c), dimethyl sulfur oxide (SO), dimethyl sulfate, sulfolane, butyrolactone, cresol, phenol, halogenated phenol, cyclohexanone, diochirin, tetrahydrofuran, diglyme, etc. in a solvent such as the above. A diamine compound and an acid anhydride compound corresponding to each general formula are mixed in approximately equimolar ratios, and the reaction temperature is O~'200°C.
Preferably, by reacting in the range of 0 to 100°C, a polyimide resin precursor solution is obtained, and the resin solution is further coated onto a conductor and the drying process is repeated, or a multilayer die is formed. A polyimide resin layer or a polyimide precursor resin layer with a multilayer structure is formed on the conductor by simultaneously applying multiple layers using a knife coat, etc., and drying. 200'C or more, preferably 300'
The imidization reaction is performed by heat treatment at a temperature of C or higher.

Examples of tetracarboxylic acids and derivatives thereof include the following. Although tetracarboxylic acids are exemplified here, esterified products, acid anhydrides, and acid chlorides thereof can of course also be used. Pyromellitic acid, 3.3', 4.4 biphenyltetracarboxylic acid, 3,3°, 4,4-benzophenonetetracarboxylic acid, 3,3°, 4.4'-diphenylsulfonetetracarboxylic acid, 2, 3,3°,4°-diphenyl ethertetracarboxylenetetracarboxylic acid, 2,3,6.7-naphthalenetetracarboxylic acid, 1,4,5.7-naphthalenetetracarboxylic acid, 1,2,5.6 -naphthalenetetracarboxylic acid, 3,3°,4,4°-Schiff1nylmethanetetracarboxylic acid, 2,2-bis(3,4-dicarboxyphenyl)propane, 2,2-his(3,4- Dicarboxyphenyl 3 Hexafluoropropane, 3,4,9.10-tetracarboxyperylene, 2,2-bis[4-(3.4-dicarboxyphenoxy)phenyl]propane, 2.2-bis[4(3 , 4-dicarboxyphenoxy)phenyl]hexafluoropropane, butanetetracarboxylic acid, cyclopentanetetracarboxylic acid, etc. Also, trimellitic acid and its derivatives can be mentioned.

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.

(2) By modifying with a compound represented by the following general formula, a pyrrolone ring, isoindoquinazolinedione ring, etc. are introduced.

[However, in the formula, R7 represents an aromatic organic group with a valence of 2+z (2 is 1 or 2), 8 is a 1Nl+2 group, -CONII
A substituent selected from 2 groups or -S02N112 groups, which is ortho to the amino group] 4. Modified with a derivative of amine, diamine, dicarboxylic acid, tricarboxylic acid, or tetracarboxylic acid having a polymerizable unsaturated bond. to form a cross-linked structure upon curing. As the unsaturated compound, maleic acid, nadic acid, tetrahydrophthalic acid, edinylaniline, etc. can be used.

(2) Modify with an aromatic amine having a phenolic hydroxyl group or carboxylic acid, and form a network structure using a bridging agent that can react with the hydroxyl group or carboxyl group.

The linear expansion coefficient of the low thermal expansion resin of the present invention can be adjusted by modifying it using each of the above-mentioned components. That is, a polyimide resin consisting only of the structure of general formula (I) or (l[>) has 1X10-
Although it is possible to form an insulator having a linear expansion coefficient of 5 (to -1) or less, the linear expansion coefficient can be increased arbitrarily by modifying the insulator using each of the above-mentioned components.

Furthermore, even a polyimide resin containing a structural unit of general formula (I> or (II>) can be made into a high thermal expansion resin by modifying it using each of the above components.

Any coating method that performs multilayer coating can be used as the coating method, but the following three methods are preferred from the viewpoint of coating accuracy.

(2) Coating two or more polyimide resins or their precursor solutions onto the conductor at the same time using a multilayer die.

■After coating by any method, further coat by knife coating method on the undried coated surface.

■ After coating by any method and drying, further coat by any method on the dried coated surface.

The knife coating method referred to herein is a method in which a resin solution is leveled and applied using a bar, squeegee, knife, or the like.

Any method can be used for drying and curing, but in consideration of work efficiency, yield, etc., the polyimide resin is coated and pre-dried, then wound into a roll and then heated at a high temperature. A batch processing method in which drying and curing is performed is preferred. At this time, in order to prevent oxidation of the conductor, it is preferable to perform heat treatment at a high temperature (2060° C. or higher) under reduced pressure and/or in a reducing gas atmosphere.

Flexible print 1 of the present invention - copper temporary laminate for substrates includes:
It has at least a conductor and an insulator, and examples of the conductor include copper, aluminum, iron, silver, palladium, nickel, chromium, molybdenum, tungsten, and alloys thereof, and copper is preferable.

In addition, the surface of these conductors is coated with siding, nickel plating, and copper-plating to improve adhesion.
Chemical or mechanical surface treatment may be performed using zinc alloy plating, aluminum alcoholade, aluminum chelate, silane coupling agent, or the like.

The insulating layer can also be modified with a coupling agent such as trimethoxysilylaniline to improve the adhesion direction.

U Examples] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but it goes without saying that the present invention is not limited thereto.

The coefficient of linear expansion is determined using a thermomechanical analyzer (TMA) using a sample that has undergone sufficient imidization reaction.
After heating to 250'C, cool at 10°C/min for 24 hours.
The average coefficient of linear expansion from 0''C to 100°C was calculated.

The curl of the film after etching is determined by etching the entire surface of the conductor with a ferric chloride aqueous solution,
A film with a size of 25 mm x thickness was heated at 100'C for 10 minutes.
After drying for a minute, the radius of curvature of the curls generated was determined and quantified.

The strength and elastic modulus of the film after etching are JIS
Measured according to Z-1702 and ASTHD-882-87.

The abbreviations on each side are as follows.

PMDA: Pyromellitic dianhydride BPDA: 3.3°, 4,4°-biphenyltetracarboxylic dianhydride BTDA: 3.3°, 4,4°-benzophenonetetracarboxylic dianhydride DDE: 4, 4'-diaminodiphenyl ether 8) IABA: 2°-methyl-4,4'-diaminobenzanilide PPD: paraphenylenediamine DO3: 3.3°-diaminodiphenylsulfone BAPP: 2.2-bis(4-(4 -aminophenoxy)fer]propane DD) f:4,4°-diaminodiphenylmethane DHA
c Nidimethylacetamide N) IP: N-methyl-2-pyrrolidone Synthesis Example 1 200 d/mi in a 500 mff four-loop flask equipped with a thermometer, calcium chloride tube, stirrer and nitrogen inlet
While flowing nitrogen at a rate of n, 0.1 = Ele and 300 °C of DMAc were added, stirred and dissolved, and the solution was cooled to 10 °C or less in a water cooling bath while 0.10 °C was added. Moles of BTDA were added slowly. The reaction mixture was polymerized while generating heat, and a viscous polyamic acid (polyimide precursor solution) was obtained.

This polyamic acid solution was coated with an applicator onto the rough surface of a commercially available 35 IU electrolytic copper foil (manufactured by Nippon Mining Co., Ltd.) fixed on a stainless steel frame to a film thickness of approximately 25 IU. , 130℃
Then, the mixture was left in a hot air oven at 150°C for 10 minutes to dry, and then the temperature was raised to 360°C over 15 minutes to perform an imidization reaction.

The resulting copper-clad product had the resin largely curled inward.

When this copper-clad product was etched with an aqueous ferric chloride solution and the linear expansion coefficient of the obtained film was measured, it was found to be 55X.
It was 10' (1/K).

Synthesis Examples 2 to 6 In the same manner as in Synthesis Example 1, a polymerization reaction was carried out using various diamine compounds and acid anhydrides to prepare a high thermal expansion polyimide precursor solution. A film with a thickness of 25 mm was obtained by coating. The linear expansion coefficient was measured in the same manner as in Synthesis Example 1. The results are shown in Table 1.

0 Table 1 Synthesis Example 7 In the same manner as in Synthesis Example 1, 0.055 mol of IABA and 0.045 mol of DDE were dissolved in 300 d of DHAc, and then 0.10 mol of PMOA was added and reacted. A viscous polyamic acid was obtained.

The linear expansion coefficient of the polyamideimide film obtained using this polyamic acid was 13x 1O-6 (1/K). Also, the curl was noticeable.

Synthesis Example 8 In the same manner as in Synthesis Example 1, 0.090 mol of PPD and 0
．． After dissolving 0.10 moles of D-leaf in 300 moles of DHAc, o,io moles of BPDA were added and reacted.
A viscous polyamic acid was obtained.

The linear expansion coefficient of the polyimide film obtained using this polyamic acid was IOX 1O-6 (1/K). Also, the curl was noticeable.

Examples 1 to 6 Thickness 3 in which the resin solution obtained in Synthesis Example 7 was fixed to a metal frame
The resin solution obtained in Synthesis Examples 1 to 6 was coated with a bar to a film thickness of 23 μs on electrolytic copper foil for 5 μs and dried at 130°C for 5 minutes. Coat with a bar so that
After drying for 0 minutes, the temperature was raised to 360° C. over 15 minutes to perform an imidization reaction.

The resulting copper-clad product was flat, and the film obtained by etching copper with an aqueous ferric chloride solution was also flat.

Examples 7 to 12 Two copper-clad products were obtained in the same manner as Examples 1 to 6 using the resin solution of Synthesis Example 8 and the resin solution of Synthesis Examples 1 to 6. There was no curling of the copper-clad product or the film, and it was fully usable.

Comparative Examples 1 to 6 Using only the resin solutions obtained in Synthesis Examples 1 to 6, Example 1
A copper-clad product was obtained in the same manner as in steps 6 to 6.

The curl of the copper-clad product was too large, and the curl of the film after etching the copper was so large that it had a radius of curvature of about 20 m, making it unusable.

Comparative Examples 7-8 Using only the resin solutions obtained in Synthesis Examples 7-8, Example 7
A copper-clad product was obtained in the same manner as in 8.

Although there was no curling in the copper-clad product, the obtained film had a radius of curvature of 10 m and was unusable.

Example 13 After applying the resin solution of Synthesis Example 7 in the same manner as Example 1,
Apply the resin solution of Synthesis Example 1 on the undried coated surface using a bar]
Then, the same heat treatment was performed.

There were no copper-clad crystals or curling of the film, and the result was good.

3 Example 14 Using a multilayer die, the resin solution of Synthesis Example 1 and the resin solution of Synthesis Example 7 were simultaneously extruded in a curtain shape in a coating device having a part of a dryer with a line length of 7 m, and the final resin was applied onto the copper foil surface. Coating was carried out so that the thickness was 23 μs and 2 μs, respectively, and the line speed was 0.2 m/min from 130°C to 360°C.
Heat treatment was performed by continuously raising the temperature to .

The resulting copper-clad product had no curls, the film after etching was flat, and it was fully usable.

Example 15 In the same manner as in Example 1, the resin solutions of Synthesis Examples 7 and 1 were applied, dried at 130°C, and dried in a vacuum dryer.
, the temperature was gradually raised from 130°C in an atmosphere of 2 torr,
Heat treatment was carried out to 360°C over 10 hours. In the copper-clad product obtained after cooling, there was no oxidation of the copper foil, and there was no curling of the copper-clad product or film.

Example 16 4 In the same manner as in Example 15, an uncured copper-clad product was heat-treated to 360° C. in an inert oven in a nitrogen gas atmosphere.

The obtained copper clad crystal was useful as in Example 15, free from oxidation of the copper foil, copper clad product curl, and film curl.

[Effects of the Invention] The manufacturing method of the present invention is extremely useful for manufacturing industrially useful copper-clad laminates for flexible printed circuits.

Claims (4)

[Claims] (1) In a method for manufacturing a copper-clad laminate for a flexible printed circuit, which is formed by directly coating a polyimide resin on a conductor, at least two types of polyimide resin compositions or precursor compositions thereof having different coefficients of linear expansion are used. is coated on a conductor so that the resin layer with a high coefficient of linear expansion is on the outside, and then dried and cured under reduced pressure and/or a reducing gas atmosphere. Method. (2) Claim 1 in which at least two polyimide layers having a difference in linear expansion coefficient of 5×10^-^6 (1/K) or more are formed.
The method for manufacturing the copper-clad laminate described above. (3) At least two different coefficients of linear expansion depending on the multilayer die
2. The method for producing a copper-clad laminate according to claim 1, wherein the polyimide resin composition or its precursor composition is simultaneously coated onto the conductor. (4) The copper clad according to claim 1, wherein at least one polyimide resin having a high coefficient of linear expansion is a polyimide resin containing a constituent unit represented by the following general formula (III) ▲ Numerical formula, chemical formula, table, etc. ▼ Method of manufacturing laminates.