JPH10126035A - Flexible printed board and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the dimensional stability of a flexible printed board by suppressing the elongation of a polyimide film by constituting the printed board so that the tension which acts on the film can become the necessary minimum to stably move the film straight until copper foil is stuck to the film. SOLUTION: In a process in which a thermosetting adhesive is applied to a polyimide film (a) and the adhesive is dried, the tension of the film (a) in a laminating section 6 is reduced as much as possible by bringing the film (a) into contact with through rolls 4 and 5. A rotating roll 8 which comes into contact with copper foil (b) and preheats the foil (b) is installed to efficiently heat the foil (b) in laminating the foil (b) upon the film (a). When the foil (b) is laminated upon the film (a), the elongation of the foil (a) is relatively reduced by reducing the difference between the thermal expansion of the film (a) and that of the foil (b) as much as possible by lowering the bonding temperature and efficiently elongating the foil (b) by preheating the foil (b).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible printed circuit board incorporated in an electronic product.

[0002]

2. Description of the Related Art In recent years,
There is an increasing demand for a flexible printed board formed by forming a copper foil circuit on an insulating film.

[0003] As a method of manufacturing this flexible printed circuit board, generally, a copper foil continuously supplied on an insulating film such as a polyimide film which is continuously supplied is continuously formed using a thermosetting adhesive. It is common to employ a manufacturing method in which a circuit is formed by applying means such as etching to this copper foil by laminating it in a heated state.

By the way, such a flexible printed circuit board is required to have dimensional stability, and in particular, a flexible printed circuit board to be incorporated in a high-precision product is required to have dimensional stability.

[0005] When this manufacturing method is adopted, the insulating film is stretched before the laminating step due to the influence of tension when the above-mentioned manufacturing method is adopted, and in this state, the flexible film is laminated with a copper foil (the copper foil hardly grows). Therefore, when a circuit is formed by performing an etching process to form a flexible printed circuit board, a portion of the copper foil is eluted during the etching process, so that the stretching strain of the insulating film is released and contracted, so that the flexible printed circuit board is contracted. There is a problem.

When the polyimide film and the copper foil are bonded together in a heated state, the polyimide film has a linear expansion coefficient larger than that of the copper foil. It is glued.
Therefore, when a circuit is formed by etching and a flexible printed board is formed, a part of the copper foil is eluted during the etching process, and the stretch strain of the polyimide film is released and shrunk, so that the flexible printed board shrinks. There is also.

In order to solve such shrinkage of the insulating film and shrinkage of the flexible printed circuit board, it is only necessary to solve the elongation of the insulating film at the time of bonding with the copper foil.

For example, Japanese Patent Publication No. 7-35106 proposes a technique for reducing the shrinkage of the flexible printed circuit board as much as possible and improving the dimensional stability.

However, Japanese Patent Publication No. 7-35106 describes
In addition to the costly plasma treatment, which is a plasma treatment, the plasma treatment is performed in a completely separate step from the step of laminating the insulating film and the copper foil. is there.

As a result of extensive studies by the present inventors, the main causes of the expansion of the insulating film are the tension applied to the insulating film during continuous supply of the insulating film, the linear expansion of the insulating film and the copper foil. It was confirmed that there was a difference between the coefficients.

The present invention is to provide a flexible printed circuit board having as high a dimensional stability as possible by removing a main cause of the elongation of the insulating film as much as possible.

[0012]

The gist of the present invention will be described with reference to the accompanying drawings.

Polyimide film a continuously supplied
After applying a thermosetting adhesive to the thermosetting adhesive and semi-curing the thermosetting adhesive by a drying process, a copper foil b continuously supplied is attached to the polyimide film a, and then the copper foil b A method for manufacturing a flexible printed circuit board for forming a circuit, in a continuous supply step of the polyimide film a until a copper foil b is bonded to the polyimide film a,
The present invention relates to a method for manufacturing a flexible printed circuit board, wherein the tension acting on the polyimide film a is configured so that the minimum tension required for the polyimide film a to travel straight and stably acts.

In the method for manufacturing a flexible printed circuit board according to the first aspect of the present invention, the rotating rolls 4 and 5 provided with a suction means capable of adjusting suction can be moved to a position where a thermosetting adhesive is applied to the polyimide film and the polyimide film a. The polyimide film a is disposed in contact with the copper film b between the positions where the copper foil b is bonded, and the minimum tension necessary for the polyimide film a to move straight and stably acts on the tension acting on the polyimide film a. The present invention relates to a method for manufacturing a flexible printed circuit board having the above-described configuration.

Further, in the method for manufacturing a flexible printed circuit board according to any one of claims 1 and 2, the rotating rolls 4 and 5 having suction means capable of adjusting a suction force are bonded to the polyimide film a by thermosetting. Between the position where the agent is applied and the inlet of the drying unit 3 for performing the drying process or / and the outlet of the drying unit 3 for performing the drying process and the polyimide film a
The polyimide film a is disposed in contact with the copper film b between the positions where the copper foil b is bonded, and the minimum tension necessary for the polyimide film a to move straight and stably acts on the tension acting on the polyimide film a. The present invention relates to a method for manufacturing a flexible printed circuit board having the above-described configuration.

Further, in the method for manufacturing a flexible printed circuit board according to any one of claims 1, 2 and 3, the tension on the polyimide film a after the drying step is set to 0.04 to 0.04.
The present invention relates to a method for manufacturing a flexible printed circuit board, wherein the pressure is 0.12 kg / mm ² .

In the method for manufacturing a flexible printed circuit board according to any one of claims 1, 2, 3, and 4, the temperature at the time of laminating the polyimide film a and the copper foil b is 50 to 120 ° C. The present invention relates to a method for manufacturing a flexible printed circuit board.

In the method for manufacturing a flexible printed circuit board according to any one of claims 1, 2, 3, 4, and 5, the copper foil b is preheated before the position where the polyimide film a is bonded. The present invention relates to a method of manufacturing a flexible printed circuit board characterized by having the above configuration.

Further, the present invention is a flexible printed circuit board formed by laminating a circuit formed of a copper foil b on a polyimide film a, wherein after removing the copper foil b, heating at 150.degree. The value is set to 0.05% or less in both the MD direction and the TD direction, which relates to a flexible printed circuit board.

[0020]

According to the present invention, the tension acting on the polyimide film is adjusted so that the minimum necessary tension for the polyimide film to travel stably is exerted. , When folded, without causing wrinkles, etc., the film is configured to be able to be transported, and when configured to pre-heat the copper foil when laminating the polyimide film and copper foil, polyimide Elongation due to film tension and difference in elongation with copper foil due to difference in linear expansion coefficient can be reduced.

Therefore, even if a circuit is formed by performing an etching process after bonding with a copper foil, a shrinkage of the polyimide film is small and a flexible printed board with high dimensional stability can be manufactured. .

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a manufacturing process according to the present invention, which will be described below.

In FIG. 1, reference numeral 1 denotes a polyimide film a.
(Kapton V type, 25 μm, manufactured by Dupont Toray Co., Ltd.), reference numeral 2 denotes a coater for applying a thermosetting adhesive to the polyimide film a, and reference numeral 3 denotes a drying unit (drying) for drying the thermosetting adhesive. Zone, 4 and 5 are rotating rolls equipped with a suction device, 6 is a laminating section, 7 is a raw material wound around copper foil b, 8 is abutting on copper foil b and preheating the copper foil b. Reference numeral 9 denotes a rolled product obtained by laminating a polyimide film a and a copper foil b. The remaining rolls are merely guide rolls.

Here, the characteristic portions of the above will be described in detail.

The rotary roll 4 with a suction device is a suction roll provided with a suction hole on the outer peripheral surface, and has a variable rotation speed to change the tension before and after the suction roll. Therefore, the thermosetting adhesive is applied to the polyimide film a by the coater 2 and the rotating roll 4 whose peripheral speed is slightly lower than the film transport speed to the coater 2 is applied.
After the contact, the tension applied to the polyimide film a in the drying zone 3 is reduced as much as possible.

Further, similarly, the tension applied to the polyimide film a after the contact with the rotating roll 5 and before the lamination with the copper foil b in the laminating section 6 is further reduced. Will be.

In the case of manufacturing a flexible printed circuit board by laminating the polyimide film a and the copper foil b, a certain amount of tension (approximately 0.1 mm) is required to stably transport the polyimide film a and uniformly apply the adhesive. 12kg / m
m ² ) is required. Therefore, heretofore, an adhesive was applied to the polyimide film a in a state where a tension of at least about 0.12 kg / mm ² or more was applied to the polyimide film a, and then the polyimide film a was conveyed to a drying zone.

However, the polyimide film a stretched due to the tension applied to the polyimide film a
After laminating, a circuit is printed on the copper foil b and the polyimide film a shrinks when etched and etched, so in the present embodiment, a thermosetting adhesive is applied to the polyimide film a and the drying step is performed. The rolls 4 and 5 are brought into contact with each other to reduce the tension of the polyimide film a in the laminating section 6 as much as possible, and thus the elongation of the polyimide film a is reduced.

The rotating roll 8 which is in contact with the copper foil b and performs preheating is provided for efficiently heating the copper foil b when laminating the polyimide film a and the copper foil b. When laminating the polyimide film a and the copper foil b, a certain temperature (usually 100 ° C. or higher) is required to soften the semi-cured adhesive applied to the polyimide film a and laminate the copper foil b. is necessary.

However, when the temperature is high, the linear expansion coefficient of the polyimide film a is larger than that of the copper foil b, so that the polyimide film a is stretched (attached in a state larger than the copper foil b). Therefore, after bonding the polyimide film a stretched due to this temperature to the copper foil b, and then printing and etching a circuit on the copper foil b, the polyimide film a shrinks. In the step of laminating the polyimide film a and the copper foil b, the difference in linear expansion is made as small as possible by lowering the laminating temperature, and the copper foil b is preheated and the copper foil b is efficiently stretched. Thus, the elongation of the polyimide film a was relatively reduced.

Although the polyimide film a has high hygroscopicity and is likely to be stretched by moisture absorption, in the case of this embodiment, since the moisture of the polyimide film a is removed by the drying zone, the polyimide film a is also used in this respect. a can be suppressed.

The present inventors conducted various experiments and found that the polyimide film a before the laminating section 6
Dimensional stability is extremely by preheating temperature 80 to 140 ° C. temperature of 50 to 120 ° C. cemented before the copper foil b in laminating tension 0.04~0.12kg / mm ² copper foil b and the polyimide film a to We have produced excellent flexible printed circuit boards.

This embodiment is shown in Table 1 below.

[0034]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a manufacturing process of the present embodiment.

[Explanation of symbols]

 a polyimide film b copper foil 3 drying unit 4 rotating roll 5 rotating roll

Claims (7)

[Claims] 1. A thermosetting adhesive is applied to a continuously supplied polyimide film a, and the thermosetting adhesive is semi-cured by a drying process, and then a copper foil b continuously supplied.
To the polyimide film a, and then the copper foil b
In the method for manufacturing a flexible printed circuit board to form a circuit, in the continuous supply step of the polyimide film a until the copper foil b is bonded to the polyimide film a, the tension acting on the polyimide film a,
A method for manufacturing a flexible printed circuit board, characterized in that a minimum tension required for the polyimide film (a) to move straight and stably acts. 2. The method for manufacturing a flexible printed circuit board according to claim 1, wherein a rotating roll provided with a suction means capable of adjusting suction is provided at a position where a thermosetting adhesive is applied to the polyimide film and a copper foil is provided at the polyimide film a. b is disposed in contact with the polyimide film a between the bonding positions, and the tension acting on the polyimide film a is configured so that the minimum necessary tension for the polyimide film a to go straight and stably acts. A method for manufacturing a flexible printed circuit board. 3. The method for manufacturing a flexible printed circuit board according to claim 1, wherein a rotating roll provided with a suction means capable of adjusting a suction force is provided by applying a thermosetting adhesive to the polyimide film a. Abutting on the polyimide film a between the position where the copper foil b is bonded to the polyimide film a and / or between the entrance of the drying unit for performing the drying process or / and the exit of the drying unit for performing the drying process and the polyimide film a. A method for manufacturing a flexible printed circuit board, comprising: arranging a tension acting on the polyimide film (a) so that a minimum necessary tension for the polyimide film (a) to move straight and stably acts. 4. The method according to claim 1, wherein the tension on the polyimide film a after the drying step is 0.04 to 0.1.
A method for manufacturing a flexible printed circuit board, wherein the pressure is ² kg / mm ² . 5. The method for manufacturing a flexible printed circuit board according to claim 1, wherein the temperature at the time of laminating the polyimide film a and the copper foil b is 5 or more.
A method for manufacturing a flexible printed circuit board, which is performed at 0 to 120 ° C. 6. The method for manufacturing a flexible printed circuit board according to claim 1, wherein the copper foil b is preheated before the position where the polyimide film a is bonded. A method for manufacturing a flexible printed circuit board, comprising: 7. A flexible printed board formed by laminating a circuit formed by a copper foil b on a polyimide film a, wherein after removing the copper foil b, heating at 150 ° C. for 30 minutes to obtain an absolute dimensional change. A flexible printed circuit board, wherein the value is set to 0.05% or less in both the MD and TD directions.