JPH07307548A - Method of processing flexible printed wiring board - Google Patents

Abstract

PURPOSE:To obtain a flexible printed wiring board which less emits gas in a high-temperature environment by a method wherein the flexible printed wiring board is subjected to a thermal treatment at a prescribed temperature for a specific time and isolated from emitted gas even at the prescribed temperature. CONSTITUTION:Base adhesive agent 2 is applied onto a base film 1 and dried out, a copper foil is pasted on the base film 1 and subjected to a laminating process at a temperature of 180 deg.C for 15 minutes and then an etching process for the formation of a conductor circuit 3, adhesive agent 5 is applied onto an insulating/protecting coverlay film 4 and dried out, and holes are bored in a circuit section of the coverlay film 4. The coverlay film 4 is pasted on the base film 1 where a circuit is formed and pressed for lamination, adhesive agent 7 is applied onto a reinforcing Al plate 6 and dried out, and the Al plate 6 is pasted on the rear of the base film 1 for lamination. Therefore, a flexible printed wiring board is subjected to a thermal treatment at a temperature of 300 deg.C or below for 10 minutes or above and then isolated as kept at a temperature of 300 deg.C or below so as to previously remove residual solvent, so that the printed wiring board less emits gas even if it is used in a high-temperature environment such as in a hard disc drive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a flexible printed wiring board (FPC), and more particularly to improving the amount of gas generated from FPC constituents in a high temperature environment such as in a hard disk drive.

[0002]

2. Description of the Related Art In recent years, FPCs have been widely used in various electronic devices. As a typical example, a copper foil is attached to a base film such as a polyimide film via an adhesive, and a circuit is formed on the copper clad film. There is one in which a cover lay film is formed and then bonded with an adhesive.
As described above, various adhesives and resins are used in the FPC, but these contain various solvents, and the solvents are also used in substrate cleaning and the like. FP
Since the adhesive or resin portion used for C is generally bonded or formed by thermocompression bonding, most of the contained solvent evaporates or volatilizes at this point. However, in general, pressing and heating in FPC production are carried out at the lowest possible temperature and in a short period of time in order to improve efficiency, and it is difficult to completely remove the contained solvent.

On the other hand, the FPC is also used as an internal component in a hard disk drive such as an optical disk or a magnetic disk. In the hard disk drive,
It is possible that the temperature during operation will reach 100 ° C,
Under such an environment, the residual solvent or the like is gasified from the adhesive or resin used in the FPC. As a result, gas adheres to the surface of the hard disk, and the adhered gas promotes adsorption of foreign matter such as dust, which may cause reading failure. In particular, in recent years, as the density of hard disks increases, the distance between the disk surface and the read head tends to become closer, and the above-mentioned gas generation has become a more serious problem. Therefore, an object of the present invention is to provide an FPC that generates less gas even in a high temperature environment.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to achieve such an object, and is characterized by FPC.
In order to remove the solvent of the adhesive or resin used in the above in advance, the heat treatment is performed at 300 ° C. or lower for 10 minutes or longer. After this treatment, when the FPC is separated from the generated gas, it is preferable to perform it while keeping the heat treatment temperature substantially. By such a treatment, the amount of gas generated when the FPC is exposed to a temperature of 120 ° C. for 5 hours can be reduced to 1000 ppm or less, and the occurrence of read failures and the like can be suppressed even when used in a high temperature environment such as a hard disk drive.

[0005]

In general, it is preferable to carry out the above heat treatment after heat-curing or pressure-bonding an adhesive or resin containing a solvent, or after processing as an FPC for a hard disk. At this time, using a heat treatment device such as a dryer or a vacuum dryer, the temperature is set to 300 ° C. or lower, more preferably 15
Heat to a temperature of 0 ° C. or higher and 200 ° C. or lower. The reason why the temperature is 300 ° C. or less is that the thermal damage to the FPC is taken into consideration.
Further, if the temperature is lower than 150 ° C., the residual solvent cannot be removed in a short period of time, and if the temperature exceeds 200 ° C., thermal deterioration of the FPC may be accelerated.

The heating time is not particularly limited as long as the residual solvent can be sufficiently removed, but is preferably 10 minutes or more and 50 hours or less. If the temperature is high, it takes only a short time, but if the temperature is low, there is a tendency that a long treatment is required. Therefore, the amount of adhesive used depends on the thermal damage to the FPC and the time required for the heat treatment, or the difference in the FPC configuration. It may be set appropriately in consideration of the above. After the heat treatment, the generated gas is FP again.
It must be stored in such a way that it does not adhere to C. For example, FPC may be taken out at the heating temperature and then stored in a desiccator so that the gasified residual solvent does not condense again.

By such heat treatment, the FPC is 120
The amount of gas generated when exposed to a temperature of ℃ for 5 hours is 100
It can be 0 ppm or less. This temperature environment and the amount of gas generated are
FP under high temperature environment such as hard disk drive
It is assumed that C is used. That is, in this temperature environment, with such a gas generation amount, it is presumed that the generated gas adheres less to the hard disk surface, and even if the gas adheres, it is possible to suppress malfunction such as reading failure. In addition, the FPC that is the target of the processing method of the present invention
The structure and the manufacturing method are not particularly limited.

[0008]

EXAMPLES Examples of the present invention will be described below. (FPC manufacturing process) The FPC shown in FIGS. The manufacturing process of each FPC is as follows. (1) The base adhesive 1 for the FPC flexible insulating film shown in FIG. 1 is coated with the base adhesive 2 and dried to form a 40 μm thick adhesive layer. A copper foil is attached to this and laminated at 180 ° C. for 15 minutes to obtain a copper clad film. Next, the copper foil portion is subjected to an etching treatment to form the conductor circuit 3
To form. An adhesive 5 is applied to the insulating and protective coverlay film 4, dried to a thickness of 30 μm, and a portion corresponding to a circuit portion to be exposed is perforated. The cover lay film is laminated on the circuit-formed base film, and pressed at 150 ° C. for 10 minutes to be laminated. Further, an adhesive 7 was applied to the Al plate 6 for reinforcement and dried to a thickness of 40 μm, which was attached to the back surface of the base film 1 and pressed at 170 ° C. for 10 minutes to be laminated.

(2) Copper is directly laminated on the base film 1 made of the FPC flexible insulating film shown in FIG. 2 by electrolysis to form a copper clad film. Hereinafter, an FPC is formed according to the FPC manufacturing process (-) shown in FIG.

(3) FPC shown in FIG. 3 Similar to the FPC shown in FIG. 2, copper is directly laminated by electrolysis on the base film 1 made of a flexible insulating film to form a copper clad film, which is then etched. Then, the conductor circuit 3 is formed. Resin is cast on the surface of the film on which the circuit is formed.
Heat treatment at 0 ° C. for 2 hours is performed to obtain polyimide insulation layer 8
To form. Further, an Al plate 6 is attached to the back surface of the base film 1 for reinforcement by means of an adhesive 7 to form an FPC.

(Constituent Material of FPC) The constituent materials used in the above FPC are as follows. Base film 1: Polyimide, 25 μm thick Coverlay film 4: Polyimide, 25 μm thick Copper foil: Rolled copper foil, 35 μm thick Base adhesive 2: AR-51 (Nippon Zeon Co., Ltd., trade name), Epicoat 828 (Okaka) Adhesive consisting of Shell Epoxy, trade name), YH-30 (Okaka Shell Epoxy, trade name), Curezol 2MZ-A (Shikoku Kasei Co., trade name), xylene, methyl ethyl ketone. Coverlay Adhesive 5: Aron S-1511 (trade name, manufactured by Toagosei Co., Ltd.), SG-80 (manufactured by Teikoku Chemical Industry Co., Ltd.,
Product name), Coronate L (product name of Nippon Polyurethane, product name), 4,4 diaminodiphenylmethane (Sumitomo Chemical Co., Ltd.)
Made, trade name), toluene 300 parts, ethyl acetate 150
Part, an adhesive consisting of 100 parts of methyl cellosolve. Adhesive 7 for Al plate: SG-90 (manufactured by Teikoku Chemical Industry Co., Ltd.,
Trade name), Epicoat 1004 (made by Yuka Shell Epoxy Co.,
Product name), 4, 4 diaminodiphenylmethane (Sumitomo Chemical Co., Ltd., trade name), Curezol 2PHZ (Shikoku Kasei Co., Ltd. trade name), toluene, xylene, methyl ethyl ketone adhesive. Resin for insulating layer 8: Upicoat (manufactured by Ube Industries, trade name)

(Heat Treatment) The obtained FPC was heated at 100 ° C. for 1 hour.
Heat at 20 ℃ for 24, 76, 200 hours respectively, 15
Degassing was performed by heating at 0 ° C., 170 ° C. and 190 ° C. for 1, 5 and 10 hours, respectively. Then, after the heat treatment, the FPC was taken out at the heating temperature and stored in a desiccator so that the generated gas did not adhere to the FPC again. Among the degassed products, the FPC shown in FIG. 1 is referred to as Example 1, the FPC shown in FIG. 2 is referred to as Example 2, and the FPC shown in FIG. 3 is referred to as Example 3. In addition, a sample not subjected to such heat treatment was used as a comparative example, the FPC shown in FIG. 1 was used as a comparative example 1, the FPC shown in FIG. 2 was used as a comparative example 2, and the FPC shown in FIG. 3 was used as a comparative example 3.

(Test Example) Each of the FPCs obtained above is
It was put in a vial bottle of ml, covered with a rubber stopper and covered with an aluminum cap from above to prevent the generated gas from leaking to the outside. Then, this vial was heated at 150 ° C. for 5 hours to generate a gas, the generated gas was extracted with a syringe, and the gas was directly injected into gas chromatography and analyzed to quantify the gas. The results are shown in Tables 1 and 2.

[0014]

[Table 1]

[0015]

[Table 2]

As shown in the table, the comparative examples which did not undergo the heat treatment produced a large amount of gas, whereas the examples which carried out the degassing treatment produced a small amount of gas. It was confirmed. Particularly, 150 ° C to 190
It can be said that the one that has been subjected to the heat treatment at ℃ is suitable for use in an electronic device that requires a high degree of cleanliness, such as a hard disk drive, in which the amount of generated gas is extremely small. Of course, it is expected to be used not only for hard disks, but also for all electronic devices in which residual solvent gas is a problem under high temperature environments.

[0017]

As described above, by removing the residual solvent of the adhesive or resin constituting the FPC by the treatment method of the present invention in advance, it is generated even when used in a high temperature environment such as in a hard disk drive. The amount of gas can be reduced. Also,
By such a treatment, it is possible to obtain an FPC having a generated gas amount of 1000 ppm or less when exposed to a temperature of 120 ° C. for 5 hours. Therefore, even when used in a high temperature environment such as a hard disk drive, it is possible to suppress malfunctions such as reading defects.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an FPC obtained by laminating a copper foil on a base film via an adhesive.

FIG. 2 is a cross-sectional view of an FPC obtained by directly laminating copper on a base film.

FIG. 3 is a cross-sectional view of an FPC in which an insulating layer is directly formed on a circuit.

[Explanation of symbols]

1 Base Film 2 Adhesive for Base 3 Circuit 4 Coverlay Film 5 Adhesive for Coverlay 6
Al plate 7 Adhesive for Al plate 8 Insulating layer

Claims (2)

[Claims] 1. A method for treating a flexible printed wiring board, which comprises subjecting the flexible printed wiring board to heat treatment at 300 ° C. or lower for 10 minutes or longer. 2. A method for treating a flexible printed wiring board, characterized in that the heat treatment according to claim 1 is performed to generate a gas, and the flexible printed wiring board is isolated from the generated gas while substantially maintaining the heat treatment temperature.