JPH04207094A - Flexible printed-circuit board and its manufacture - Google Patents

Abstract

PURPOSE:To enable dimensional change in an etching drying treatment process to be suppressed and dimensional stability to be improved by using a copolymerization polyimide film consisting of a repetition unit which is expressed by an expression (A) including a long-chain aromatic series diamine remaining group with a flexed group and that expressed by an expression (B) including an aromatic series diamine remaining group as an insulating material. CONSTITUTION:An aromatic series tetracarbonaciddianhydride (a) and one aromatic series diamine compound (b) are allowed to react within an organic polarity solvent using a more excessive mol than (a) and (b), a prepolymer with an acid anhydride at both edges is obtained, and then an aromatic series diamine compound (c) is added so that all aromatic series diamine [(a)+(c)] has a virtually equal mol as the aromatic series tetracarbon acid dianhydride in this copolymerization method, thus obtaining a copolymerizate where a length of a segment where either one repetition unit exists is constant within the copolymerizate molecule.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a flexible film with excellent dimensional stability, which is made by laminating a polyimide film with excellent water resistance and moisture resistance and a high modulus of elasticity with a metal conductor layer. The present invention relates to a method for manufacturing a flexible printed circuit board in which the yield is significantly improved by using a polyimide film having excellent water resistance, moisture resistance, and high elastic modulus for the insulating layer of the flexible printed circuit board.

[Conventional technology]

Polyimide generally has excellent heat resistance, electrical insulation, chemical resistance, and radiation resistance, is suitable as an insulating material for flexible printed circuit boards, and has been widely used. However, due to its chemical structure, conventional polyimide
It has the disadvantage of high water absorption and moisture absorption. For example, flexible printed circuit boards that use polyimide as an insulating material generally undergo dimensional changes due to water absorption in the insulating layer during the etching process, so when designing circuits, the dimensional changes in subsequent processes must be taken into consideration in advance. I needed to. The amount of change in this dimension varies depending on the type of pattern of the flexible printed circuit board, and is therefore a major cause of complicating the manufacturing process of the flexible printed circuit board and further reducing the product yield.

Therefore, in an attempt to lower the water absorption rate, we obtained a polyimide film with a low water absorption rate by using a long-chain aromatic diamine and reducing the proportion of imide rings in the total number, and using this to create flexible printed circuit boards. A method of manufacturing is being considered. However, since many long-chain diamines have several bending groups in their structure, polyimide films made using them have excellent water resistance and moisture resistance, but have low elastic modulus and distortion under tension. However, the dimensional stability of flexible printed circuit boards manufactured using this polyimide film cannot be sufficiently improved.

[Problem to be solved by the invention]

The present invention suppresses dimensional changes during the etching drying process and improves dimensional stability, which is an essential condition during microfabrication, by using a polyimide film with low water absorption and high elastic modulus for the insulating layer. The purpose is to provide flexible printed circuit boards.

[Means to solve the problem]

That is, the first aspect of the present invention is the following general formulas (A) and (B
) to a polyimide film having a repeating unit represented by
A flexible printed circuit board on which metal conductor layers are laminated with or without adhesive; (X is a hydrogen atom, a fluorine atom, R is a hydroxyl group, a methyl group,
Represents a methoxy group, chlorine atom or fluorine atom. ) The second aspect of the present invention is characterized in that a metal conductor layer is formed on a polyimide film having repeating units represented by the following general formulas (A) and (B), with or without an adhesive. Manufacturing method of flexible printed circuit board: (X is a hydrogen atom, a fluorine atom, R is a hydroxyl group, a methyl group,
Represents a methoxy group, chlorine atom or fluorine atom. ), respectively.

The flexible printed circuit board according to the present invention has a repeating unit represented by general formula (A) containing a long chain aromatic diamine residue having a bending group, and a general formula (B) containing a rigid aromatic diamine residue. It is characterized in that a copolymerized polyimide film consisting of the following repeating units is used as an insulating material. By using such a material with low water absorption and high elastic modulus as the insulating film, it is possible to improve the yield in each process of flexible printed circuit boards, and at the same time improve the physical properties of the manufactured flexible printed circuit boards. It will be excellent.

The above-mentioned flexible printed circuit board refers to one in which an insulating layer and a conductive layer are laminated with or without an adhesive, and one in which a patterning, etching treatment, etc. is applied to this.

When an adhesive is used, an adhesive used in the manufacture of ordinary flexible printed circuit boards can be used as the adhesive.

Further, the conductor layer referred to in the present invention is typified by metal such as copper, iron, aluminum, or metal foil, but
It may be anything other than this.

The polyimide copolymer of the insulating material used in the present invention may be a random copolymer, an alternating copolymer, or a block copolymer. Further, the repeating number of the repeating units represented by general formulas (A) and (B) is preferably in the range of 100 to 1oooo, and the molar ratio (A)/(B) is 20/80 to
It is preferably in the range of 80/20, more preferably in the range of 40/60 to 60/40. If the ratio of (A) is smaller than this, the water absorption rate of the film will be high and the dimensional change will be large during a process in which the film is exposed to water such as an etching process. On the other hand, if the ratio of (A) is larger than this, the elastic modulus will be low and the elongation due to tension will be large, which will also cause large dimensional changes. Also, the general formula (
The molecular weight of the polyimide molecule consisting of the repeating units A) and (B) is preferably between 50.000 and 1,000,000.The insulating material contains various organic additives, inorganic fillers, and various other materials. It is also possible to use reinforcing materials alone or in combination.

Next, a method for manufacturing this polyimide insulating material will be explained. This aromatic polyimide copolymer insulating material is obtained from a polyamic acid copolymer solution which is its precursor, and this polyamic acid copolymer solution can be produced by a known method. That is, it is obtained by using substantially equimolar amounts of tetracarboxylic dianhydride and diamine component and polymerizing them in an organic polar solvent.

A specific example of the method for producing this polyamic acid copolymer solution is shown below.

(1) Aromatic tetracarboxylic dianhydride (a), aromatic,
A copolymerization method in which a mixture of aromatic diamine compounds (b) and (c) is used in substantially equimolar amounts and reacted in an organic polar solvent,
This method yields random copolymers.

(2) Aromatic tetracarboxylic dianhydride (a) and one aromatic diamine compound (b) are reacted in an organic polar solvent using a molar excess of (a) over (b), and both ends are reacted. A prepolymer having an acid anhydride group is obtained, and then an aromatic diamine compound (e) is added thereto, and a wholly aromatic diamine C (b
) + (c)) is aromatic tetracarboxylic dianhydride (a
), a copolymerization method in which the copolymerization method is added in a substantially equimolar amount with
By this method, a copolymer can be obtained in which the length of the segment in which one of the repeating units is present is constant within the copolymer molecule.

(3) React the aromatic tetracarboxylic dianhydride (a) with the aromatic diamine compound (b) in such a manner that (b) is in excess of (a), and prepare a compound having amino groups at both ends. After obtaining a polymer and subsequently adding an aromatic diamine component (c) thereto, the total diamine component C(b) + (c
)) A copolymerization method in which an insufficient amount of aromatic tetracarboxylic dianhydride (a) is added and reacted so as to be substantially equimolar.

A block copolymer can be obtained by this method.

Other methods may be used to obtain the polyamic acid copolymer, and it is also possible to obtain the polyamic acid copolymer by mixing different types of polyamic acid solutions. It is preferable to use the method (2) because it yields products with excellent properties.

When pyromellitic dianhydride is used as the aromatic tetracarboxylic dianhydride to obtain the above-mentioned polyamic acid, the polyamic acid has excellent properties.

The aromatic diamine component has the general formula (1) CX3 [X represents a hydrogen atom or a fluorine atom. ) and the aromatic diamine component represented by the general formula (It) (R represents a hydroxyl group, methyl group, methoxy group, chlorine atom, or fluorine molecule). It can be suitably used as b) and (c).

As the aromatic diamine represented by this general formula (1), 2
,2-bis(4-(4-aminophenoxy)phenyl)
Examples include propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, and these may be used alone or in combination of two or more.

Further, as the aromatic diamine represented by the general formula (ff), 3,3'-dihydroxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'- Examples include dimethoxy-4,4'-diaminobiphenyl, 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-difluoro-4,4'-diaminobiphenyl, etc., which may be used alone or in combination. 2
Used in combination of more than one species.

In addition, as the organic polar solvent used in the production reaction of the polyamic acid copolymer, sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide-based solvents such as N,N-dimethylformamide, N,N-diethylformamide, etc. Acetamide solvents such as N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-vinyl-
Pyrrolidone solvents such as 2-pyrrolidone, phenol,
Examples include 0-1m-1 or p-cresol, xylenol, halogenated phenol, phenolic solvents such as catechol, hexamethylphosphoramide, γ-butyrolactone, etc., which may be used alone or in a mixture of two or more. It is preferable to use aromatic hydrocarbons such as xylene and toluene.

Further, this polyamic acid copolymer is contained in the organic polar solvent in an amount of 5 to 40% by weight, preferably 10 to 30% by weight.
From the viewpoint of handling, it is desirable that the material be dissolved.

Next, a conventionally known method can be used to manufacture an organic insulating film made of polyimide from this polyamic acid solution. i.e. thermal methods of thermal dehydration;
Although any chemical method using a dehydrating agent and a catalyst may be used, the chemical method is preferred because the resulting polyimide polymer has excellent mechanical properties such as elongation and tensile strength.

Note that the dehydrating agent mentioned here includes, for example, aliphatic acid anhydrides such as acetic anhydride, aromatic acid anhydrides such as phthalic anhydride, and the like. Examples of catalysts include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as N,N-dimethylaniline, and heterocyclic tertiary amines such as pyridine, picoline, isoquinoline, and quinoline. can be mentioned.

In this way, an insulating material having both low water absorption and high elastic modulus can be obtained.

The thickness of the insulating material is preferably 7 to 150 μm. The flexible printed circuit board of the present invention is obtained by laminating the above-mentioned insulating material and conductor. A typical example will be described next, but the method is not limited to this method.

First, apply adhesive to the insulation material, and after drying, the thickness is about 10 to 70 μm.
A metal foil such as copper is thermally laminated under pressure, and a predetermined bonding process is performed to obtain a flexible board. Further, a desired circuit is patterned on the metal surface, and then a patterned flexible substrate can be obtained through etching, water washing and drying steps. As the adhesive, adhesives such as epoxy adhesives that are commonly used in the manufacture of flexible printed circuit boards can be used. Further, as a lamination method that does not use an adhesive, a method can be used in which a thin conductive layer is formed on the insulating material by sputtering or electroless plating, and then a conductive layer of a constant thickness is obtained by electrolytic plating.

〔Example〕

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited only to these Examples.

In the examples, ODA is 4,4'-diaminodiphenyl ether, p-PDA is phenylene diamine, PMDA
is pyromellitic dianhydride, BAPP is 2,2-bis(
4-(4-aminophenoxy)phenyl]propane, D
MB represents 3,3'-dimethyl-4,4'-diaminobiphenyl, and DMF represents dimethylformamide.

Dehydrated and purified DMF815 in the separable flask of Comparative Example 21
g, here 0DA49.75 g (0°248
mol) and stirred until homogeneous.

Next, 108.38 g (0,497 mol) of PMDA was added thereto and reacted for 2 hours. During this time, the reaction system was
Cooled with ice water at C. Next, p-pDA26.
87 g (0,248 mol) was added thereto, and the reaction was further continued for 4 hours to obtain a polyamic acid solution with a solid content of 18.5% by weight.

After adding acetic anhydride as a dehydrating agent and pyridine as a catalyst to this polyamic acid solution, it was cast onto a glass plate, dried at about 100°C for about 90 seconds, and then the polyamic acid coating was peeled off from the glass plate. , the coating was fixed to a support frame.

After that, it was heated to about 110°C for about 90 seconds, and then heated to about 200°C for about 6 seconds.
After heating at about 300° C. for about 60 seconds and then at about 400° C. for about 60 seconds, dehydration, ring closure, and drying, the film was removed from the support frame to obtain a polyimide film of about 25 μm. The initial elastic modulus of this insulating material was 630 kg/mm'', and the water absorption rate was 4.2%.

Next, a nylon/epoxy adhesive was applied to this insulating material and dried, and then a copper foil was laminated under pressure and heat, and this was subjected to a boss cure to obtain a flexible copper clad board.

Subsequently, two points A and B were stamped on the insulating material of this flexible copper clad board, and the lengths of the distances A and B were measured and were set as 10.

Furthermore, this flexible net cladding board is patterned according to a conventional method, and then after going through an etching, washing and drying process,
A patterned flexible substrate was obtained. In this flexible printed circuit board, the distance between A and 8 above was measured, and this was defined as l. The dimensional change rate was calculated using the following formula.

l.

As a result, the dimensional change rate of this flexible printed circuit board was 0.3%.

Comparative Example 2 BAPP 120.81 g (0,294 mol) and P
MDA64.19g (0,294 mol) DMF81
Polymerization was carried out in 5 g to obtain a 18.5% by weight polyamic acid solution. Thereafter, a polyimide insulating material having a thickness of about 25 μm was obtained by the same operation as in Comparative Example 1.

The initial elastic modulus of this insulation material was 280 kg/lan'' and the water absorption rate was 0.5%.

Next, this insulating material was subjected to the same operation as in Comparative Example 1, and the dimensional change was determined to be 0.1%.

Example 1 BAPP71 was added to 815 g of DMF in the same manner as in Comparative Example 1.
．． 72g (0,175mol), PMDAT6゜21g
(0,35 mol L DMB37.08g (0,175
mol) were added in order for polymerization to obtain a 18.5% by weight polyamic acid solution. Thereafter, a polyimide insulating material having a thickness of about 25 μm was obtained by the same operation as in the comparative example. The initial elastic modulus of this insulation material is 660 kg/+u+”,
The water absorption rate was 1.3%.

Next, this insulating material was subjected to the same operation as in Comparative Example 1, and the dimensional change was determined to be 0.1%.

The above results are shown in Table 1.

Table 1 [Effects of the Invention] According to the present invention, by using an insulating material that has a high initial elastic modulus and a low water absorption rate, a flexible printed circuit board with little loss during the manufacturing process and very small dimensional change can be produced. can be provided.

Claims (4)

[Claims] 1. A flexible printed circuit board in which a metal conductor layer is laminated with or without an adhesive on a polyimide film having repeating units represented by the following general formulas (A) and (B). (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (B) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (X is a hydrogen atom, a fluorine atom, R is a hydroxyl group, a methyl group,
Represents a methoxy group, chlorine atom or fluorine atom. ) 2. The flexible printed circuit board according to claim 1, which uses a polyimide film in which the ratio (A)/(B) of the repeating units represented by the general formulas (A) and (B) is in the range of 40/60 to 60/40. . 3. A method for producing a flexible printed circuit board, comprising forming a metal conductor layer on a polyimide film having repeating units represented by the following general formulas (A) and (B), with or without an adhesive. (A) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (B) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (X is a hydrogen atom, a fluorine atom, R is a hydroxyl group, a methyl group,
Represents a methoxy group, chlorine atom or fluorine atom. ) 4. The flexible printed circuit board according to claim 1, wherein a polyimide film having a ratio (A)/(B) of repeating units represented by the above general formulas (A) and (B) is in the range of 40/60 to 60/40. Production method.