JPH046892A - Flexible printed wiring board - Google Patents

Abstract

PURPOSE:To get excellent processability and productivity and besides a favorable flexibility property by forming a flexible printed wiring board, which has mechanical properties, using an aromatic polyamide film. CONSTITUTION:The polymerization of an aromatic polyamide is performed by the low temperature solution polymerization method within amido solvent, the interface polymerization method using an aqueous solvent, or other method, and the polymer solution or polymer obtained with polymerization is isolated once, and then it is redissolved to make a film from polymer solution. This aromatic polyamide film shall be 5mum or more and 50mum or less in thickness, 30% or more and 150% or less in breaking elongation, 150g/mm or more and 400g/mm or less in tear propagation resistance, 300kg/mm or more and 1500kg/mm or less in end tear resistance. Next, an electrolytic copper foil is laminated to make it into a plate lined with a copper, and then the copper foil is etched, and an aromatic polyamide film, to which an adhesive is applied, is laminated as a cover film, and through boring and punching processes, FPC is made.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a flexible printed circuit board (hereinafter abbreviated as FPC), and more specifically, a flexible printed wiring board (hereinafter abbreviated as FPC), which has excellent flexibility and processability and uses an aromatic polyamide film as a substrate film. F.P.
This is related to C.

[Background Art] The use of FPCs is increasing in the electrical and electronic industries as equipment becomes smaller and lighter and required functions become more sophisticated. F.P.
The general structure of C is that an electric circuit is formed on one or both sides of a substrate film, and a cover film or an insulating resist is further laminated on the circuit. Conventionally, polyimide films or polyester films have been used as substrate films, and particularly when solder resistance is required, polyimide films having excellent heat resistance have been used.

[Problems to be Solved by the Invention] Although polyimide films have excellent heat resistance, it is difficult to manufacture thin films due to the polymer and manufacturing method, which poses a problem in improving bending resistance.

On the other hand, aromatic polyamide film has heat resistance second only to polyimide, and it is easy to obtain high mechanical properties, making it easy to manufacture thin films. It is hoped that this will become a reality, and many FPCs using aromatic polyamide films as substrate films have been proposed.

However, even though FPCs made of aromatic polyamide film show good characteristics at the prototype level, there are problems with production yields at the mass production level, and currently no significant progress has been made in expanding the range of practical use. be. The biggest problem in manufacturing FPCs using aromatic polyamide films as substrate films is that the films tend to tear or tear during the FPC punching or hole-drilling process, as well as during component mounting or assembly into equipment.

It is an object of the present invention to solve these problems and provide an FPC using an aromatic polyamide film with excellent processing characteristics and productivity, and in addition, to realize an FPC with good flexibility.

[Means for Solving the Problems] The present invention provides a flexible printed wiring board in which an electric circuit is formed on at least one side of an aromatic polyamide film, wherein the aromatic polyamide film has a thickness of 5 μm or more and 50 μm or less and a breaking elongation. 30% or more and 150% or less, tear propagation resistance of 150g/mm or more and 400g/mm or less, end tear resistance of 300kg/mm or more and 1500kg/mm
It is characterized by a flexible printed wiring board having a size of 1 mm or less.

The aromatic polyamide film in the present invention has the general formula: NH-Art -NHC-Ar2 CNH-Ar
A film made of an aromatic polyamide polymer containing repeating structural units represented by 3-C either singly or in copolymerized form, and containing 70 mol% or more, preferably 90 mol% or more of the above-mentioned structural units. Here, Art, Ar2, and Ar3 contain at least one aromatic ring, and may be the same or different, and representative examples include the following.

These aromatic rings include those in which some of the hydrogen atoms on the ring are substituted with a substituent selected from a halogen group, a nitro group, an 01-C3 alkyl group, and a C-C3 alkoxy group, and is selected from 0-, -CH2-, -8o2-, -3OCH3 -C--C- CH3.

Among the aromatic polyamides mentioned above, those in which benzene rings with amide bonds bonded at the para position account for 50% or more, preferably 70% or more of the total aromatic rings, have improved heat resistance and mechanical properties, and have improved thermal expansion. Polymers are preferred in that the coefficient is small, and in which benzene rings in which some of the hydrogen atoms on the benzene rings are substituted with halogen groups, particularly chloro groups, account for 30% or more, preferably 50% or more of the total aromatic rings. , is preferably used to reduce the humidity expansion coefficient and moisture absorption rate.

The thickness of the aromatic polyamide film used in the present invention is 5
μm or more and 50μm or less, preferably 10μm or more and 25μm
If it is thinner than 5 μm, the film will be weak, resulting in poor workability, and it is not preferable because it will cause cracks during the punching and hole punching process. If it is thicker than 50 μm, the flexibility of the FPC will be impaired, and the mechanical strength of the film will be too high, so the life of the punching blade will be short (which is not preferable).

The elongation at break of the film is 30% or more and 150% or less, preferably 100% or less, and the tear propagation resistance is 150g/m
m or more and 400 g/anus or less, preferably 200 g/mm
The end tear resistance is 300kg/m or more and 1500k.
g/anus or less, preferably 1000 kg/mm or less. When a thin aromatic polyamide film is used as a substrate film as in the present invention, the elongation at break, tear propagation resistance, and end tear resistance closely influence each other, and each value must be within the above range. It has been discovered that FPC can be manufactured with a good yield and that problems when using FPC can be solved. If each characteristic value is too small, the film will often tear during the punching process or the FPC will tear when parts are mounted on the FPC.On the other hand, if the characteristic values are too large, the punching process will fail. The film may be torn or cracked, and the blade used for punching may be subject to considerable wear and tear.

In addition, the surface roughness of the film is 0°005μ in average roughness Ra.
It is preferable that the thickness is not less than m and not more than 1.0 μm. 0.00
If it is less than 5 μm, the slipperiness of the film is poor and wrinkles are likely to occur when laminating the film with copper foil or the like, and if it exceeds 1.0 μm, the insulation reliability will be lowered, which is not preferable.

Next, a method for manufacturing an FPC according to the present invention will be explained.

Polymerization of the aromatic polyamide can be carried out by a known polymerization method such as a low-temperature solution polymerization method in an amide solvent or an interfacial polymerization method using an aqueous medium. A film is formed from a polymer solution obtained by polymerization or a polymer solution in which the polymer is once isolated and then redissolved. The solvent used here is an amide solvent such as dimethylacetamide or N-methylpyrrolidone, but sulfuric acid may also be used.

Film formation can be carried out by a solution film forming method, and there is no particular limitation, although distinctions such as dry method, wet method, dry-wet method, etc. are made depending on the type of solvent removal. During the film forming process, the film usually has a
0. at 350°C. The film is heat treated for about 1 to 10 minutes and stretched by about 0.9 to 5.0 times in the longitudinal and width directions of the film. These heat treatment conditions and stretching conditions are important together with the composition of the polymer in determining the properties of the final film, and are determined depending on each polymer so as to obtain predetermined property values. In general, when applying a large amount of heat to a film during heat treatment, elongation tends to be higher, tear propagation resistance is higher, and end tear resistance tends to be lower. The resistance tends to be small and the end-splitting resistance tends to be large. In particular, in the wet and wet-dry method of film production, the film contains a large amount of water after the solvent is extracted in a water bath, and the final film is obtained by drying the water and then performing a heat treatment. here,
We considered that stretching the film with water still contained in the film is effective in improving tear propagation resistance, rather than performing the film stretching operation after moisture drying, but before or at the same time as drying. I discovered it in the process. The degree of polymerization of the polymer also affects the characteristic values, and the higher the degree of polymerization, the higher the elongation and tear propagation resistance.The intrinsic viscosity of the polymer, ηinh, is preferably 2.5 or more, but it is more than a certain degree. The larger the value, the smaller the influence on characteristic values.

Furthermore, the surface roughness of the film can be easily controlled by adding inorganic or organic fine particles to the polymer solution for film formation.

To manufacture an FPC using the obtained film as a substrate film, the same method as in the case of conventional polyimide films can be carried out. Methods for forming an electric circuit on a substrate film include laminating copper foil, aluminum foil, etc. with adhesive, plating method, vapor deposition method to layer copper, etc., and then forming the circuit by etching method, copper paste, etc. The method is not particularly limited, and may include a method of screen printing silver paste, carbon paste, etc., or a combination thereof.

After forming the electric circuit, through-hole processing is performed as necessary, lamination of cover film, application of resist ink,
An FPC can be obtained by drilling holes and punching out the outer shape.

[Applications] The FPC obtained in the above manner is commonly used in conventional FPCs.
It can be used in electrical and electronic equipment, and is particularly suitable for use in FPCs that require bending resistance.

Further, there is a film connector which has a similar structure to the FPC, and of course it can be suitably used for this as well.

[Characteristics evaluation method] The method for evaluating characteristic values of the present invention is as follows.

(1) Elongation at break The method for measuring elongation at break specified in JIS C2318 was followed.

(2) Tear propagation resistance According to the method for measuring tear propagation resistance specified in JIS P8116, and assuming that the tear propagation resistance value is proportional to the film thickness, it was converted into a numerical value in terms of a thickness of 1.0 mm.

(3) End tear resistance According to the method for measuring end tear resistance specified in JIS C2318, further assuming that the end tear resistance value is proportional to the film thickness,
It was converted into a numerical value of 1.0 normal thickness.

(4) Surface roughness (Ra) Using a thin film step measuring instrument (ET-10) manufactured by Koita Institute,
Stylus tip radius: 0.5 μm, stylus load: 5 mm, cutoff value: 0.008 mm, measurement length: 0. Measurement was carried out 10 times under the condition of 5 mm, and the average values were expressed as Ra and Rp. In addition, Rp
The definition of is given, for example, in "Surface Roughness Measurement and Evaluation Method" by J. Nara (Sogo Technological Center 1983).

[Example code] The present invention will be explained based on examples.

Example 1 2-chloroparafendiamine corresponding to a molar ratio of 0.85 and 4,4'-diaminodiphenyl ether corresponding to a molar ratio of 0.15 are dissolved in N-methylpyrrolidone (NMP). 2-chloro-terephthalic acid chloride corresponding to 1.0 molar ratio was added to the mixture and stirred for 2 hours to complete the polymerization.

This was neutralized by adding lithium carbonate in an amount equivalent to the generated hydrogen chloride to obtain an aromatic polyamide solution with a polymer concentration of 10.5% by weight. 0.5% silica particles (based on polymer weight)
Added.

This polymer solution was cast onto a stainless steel endless belt and heated with hot air at 180°C for 1.5 minutes to dry the solvent, and the film that had achieved self-retention properties was continuously peeled off. The polymer concentration at this time was 37% by weight. The peeled film was continuously introduced into a water bath at 50°C, stretched 1°05 times in the longitudinal direction while extracting the residual solvent and inorganic salts generated during neutralization, and then continuously introduced into a tenter. After drying the moisture and simultaneously stretching the film by 1.15 times in the width direction, heat treatment was performed to obtain an aromatic polyamide film having a thickness of 15 μm. Here, the heat treatment was at 320° C. for 161 minutes.

The physical properties of the obtained film were as follows: elongation at break, 48%, 51%, tear propagation resistance, 275 g/mm, 280 g/mm, end tear resistance, 6 in the film longitudinal direction and width direction, respectively.
The roughness was 70 kg/mm, 690 kg/mm, and the average roughness Ra was 0.05 μm.

Next, after laminating 35 μm thick electrolytic copper foil with a thermosetting epoxy adhesive (adhesive thickness 15 μm) to make a copper clad board,
Etched copper foil. Next, the above-mentioned aromatic polyamide film coated with the above-mentioned adhesive was laminated as a cover film, and an FPC was created through a hole punching process.

Ten holes with a diameter of 1°0 mm were made, and a rectangular FPC was made using a Thomson blade. Although 50 FPCs of the same shape were produced, there were no problems such as film tearing due to hole punching.

Comparative Example 1 Same as Example 1 except that the polymer solution prepared in Example 1 was used, the stretching ratio was 1.25 times and 1°35 times in the longitudinal direction and width direction, respectively, and the heat treatment temperature was 300 ° C. An aromatic polyamide film with a thickness of 16 μm was prepared using the method described above. The physical properties of the obtained film were: elongation at break of 25% and 28%, tear propagation resistance of 210 g/mm and 240 g/mm, and edge tear resistance of 7 in the film longitudinal direction and width direction, respectively.
50kg/mm, 780kg/mm, average roughness is 0.0
It was 5 μm.

When this film was punched and punched in the same manner as in Example 1, 3 out of 50 samples were torn, and the film had poor workability, with cracks appearing at the edges after punching. there were.

Comparative Example 2 The diamine components were 2-chloro-paraphenylenediamine corresponding to a 0.95 molar ratio and 4゜4'-diaminodiphenyl ether corresponding to a 0.05 molar ratio, and an equivalent amount of 2-chloro-terephthalic acid chloride. An aromatic polyamide film was prepared using the same polymerization and film forming method as in Example 1 from a monomer having acid chloride component. However, the stretching during film formation was 1.20 times and 1.28 times in the longitudinal direction and width direction, and the heat treatment temperature was 300°C.

The physical properties of the obtained film were elongation at break of 23% and 27% in the longitudinal and width directions, and tear propagation resistance of 105 g.
/mm, 110g/mm, end tear resistance 1090kg/mm
, 1010 kg/mm.

When this film was punched and punched in the same manner as in Example 1, 28 out of 50 samples were torn, and the degree of cracking after punching and punching was even worse than in Comparative Example 1.

[Effects of the invention] In the present invention, by manufacturing an FPC using a thin aromatic polyamide film having specific mechanical properties as a substrate film, the delay in practical application has been avoided due to problems in processability despite conventional heat resistance. It is possible to manufacture FPC using aromatic polyamide in a small amount of time, and also has excellent bending resistance.
It became possible to obtain a PC.

Claims (1)

[Claims] A flexible printed wiring board in which an electric circuit is formed on at least one side of an aromatic polyamide film,
The aromatic polyamide film has a thickness of 5 μm or more and 50 μm
Hereinafter, a flexible printed wiring board characterized by having a breaking elongation of 30% or more and 150% or less, a tear propagation resistance of 150 g/mm or more and 400 g/mm or less, and an end tear resistance of 300 kg/mm or more and 1500 kg/mm or less.