JPH03129894A - Flexible printed wiring board and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a shielding layer which is excellent enough in shielding effect, flexibility, and hard to separate by a method wherein an intermediate adhesive layer is provided between the shielding layer formed through an evaporation method, a sputtering method, or an iron plating method and an insulating film. CONSTITUTION:A flexible printed wiring board A is formed in such a manner that a conductor circuit 4 is formed on a base film 6 through the intermediary of an adhesive layer 5, an insulating layer 3 is laminated on the conductor circuit 4 through the intermediary of an adhesive layer 5', and a shielding layer 1 formed through an evaporation method, a sputtering method, or an ion plating method is laminated on the insulating film 3 through the intermediary of an intermediate adhesive layer 2. By this setup, the shielding layer 1 is firmly bonded to the insulating film 3, hardly separated from it, and possessed of an enough shielding effect even if the layer 1 is thin. Moreover, as the shielding layer 1 is thin, a flexible printed wiring board is prevented from deteriorating in flexibility.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a shielded flexible printed wiring board suitable for use in electronic equipment, etc., and a method for manufacturing the same.

<Prior art and problems to be solved by the invention> Flexible printed wiring boards are smaller and lighter, have simpler wiring layouts, simpler wiring work, and have better circuit characteristics and reliability than ordinary electric wires and rigid boards. Because it is possible to improve the internal wiring of electronic desk calculators, telephones, and camera cameras,
Widely used in automotive wiring panels, etc.

In manufacturing the above-mentioned flexible printed wiring board, rolled copper foil or electrolytic copper foil is laminated on one or both sides of a base film made of a flexible insulating film via a base adhesive. Then, a conductor circuit is produced by etching, and an insulating film is laminated on the surface to protect the conductor circuit.

Furthermore, in order to improve the electromagnetic shielding properties of the flexible printed wiring board, a shield layer made of copper, nickel, aluminum, etc. is formed on the insulating film.

Such shield layers have been formed by methods such as applying conductive paint, laminating metal foil, metal vapor deposition, and metal plating.

When using conductive paint, the thickness of the shield layer must be 30 μm in order to provide sufficient shielding performance to the shield layer.
It is necessary to make it more than m.

However, when the thickness of the shield layer is 30 lines or more, there is a problem that the flexibility of the flexible printed wiring board is impaired and it becomes impossible to bend the board. Further, the shield layer formed by applying a conductive paint has a weak adhesion force to the insulating film, and is easily peeled off from the insulating film. Furthermore, there was also the problem that the shielding performance deteriorated over time.

In addition, when using metal foil, in order to give the shield layer sufficient shielding performance, the thickness of the shield layer must be 25 mm.
- Must be greater than or equal to

However, if the thickness of the shield layer is 25//1 or more,
There was a problem in that the flexibility of the flexible printed wiring board was impaired and it became impossible to bend it. In particular, there was a problem in that the shielding performance varied depending on how the metal foil was wrapped and how it was attached.

When using the metal vapor deposition method, the thickness of the shield layer should be 0.5 to 1
(The length may be 1 m, and there is no risk that the flexibility of the flexible printed wiring board will be impaired by the shield layer.

However, the shield layer has a problem in that it has a weak adhesive force to the insulating film and is easily peeled off.

When using the metal plating method, the thickness of the shield layer must be 0.5 μm in order to provide sufficient shielding performance to the shield layer.
m or more, and there is no risk that the flexibility of the flexible printed wiring board will be impaired by the shield layer.

However, in order to improve the adhesion of plating to the insulating film, it is necessary to perform a surface treatment such as etching on the surface of the insulating film, and there is a problem that the usable insulating film is limited to polypropylene or the like.

This invention was made in view of the above problems, and
It is an object of the present invention to provide a flexible printed wiring board having a shield layer that exhibits a sufficient shielding effect, has sufficient flexibility, and is difficult to peel off from an insulating film, and a method for manufacturing the same.

Means and Effects for Solving the Problems> In order to solve the above problems, the flexible printed wiring board of the present invention is provided with an intermediate adhesive layer between the shield layer and the insulating film, and the shield layer is formed by vapor deposition. , is characterized in that it is formed by a sputtering method or an ion plating method.

In the above flexible printed wiring board, an intermediate adhesive layer is provided between the shield layer and the insulating film, and this intermediate adhesive layer firmly adheres to both the shield layer and the insulating film, so that the shield layer can be insulated. It can firmly adhere to the film.

In addition, since the above-mentioned shield layer is formed by a vapor deposition method, a sputtering method, or an ion plating method, in order to provide a sufficient shielding effect to the shield layer, the thickness should be 0.5 to 10 μm. If so, there is no risk that the flexibility of the flexible printed wiring board will be impaired by the shield layer. The thickness of the above shield layer is 0°5I
If it is less than #, sufficient shielding performance cannot be obtained, and
If it is larger than 0ρ, there is a risk that the flexibility of the flexible wiring board may be impaired.

The above vapor deposition method deposits metal vapor onto the target surface to form a metal layer, while the sputtering method collides metal particles with the target surface to form a metal layer, and ion plating The method involves depositing the metal onto the target surface in an atmosphere of metal ions.

FIG. 1 is a sectional view showing an example of a flexible printed wiring board A according to the present invention. In this flexible printed wiring board A, a conductor circuit 4 is formed on a base film 6 via an adhesive layer 5, and an insulating film 3 is laminated on the conductor circuit 4 with an adhesive layer 5''. Further, a shield layer 1 is laminated on the insulating film 3 with an intermediate adhesive layer 2 interposed therebetween.

Examples of the shield layer 1 include those made of silver, copper, aluminum, nickel, or a composite system (for example, a laminate, an alloy, etc.) of these metals.

Examples of the insulating film 3 include conventionally known flexible films such as polyester, polyimide, glass epoxy, glass Teflon, polyamideimide, and polyvinyl chloride.

As the intermediate adhesive layer 2, polydimethylsiloxane,
Examples include polydialkylsiloxanes such as polydiethylsiloxane and polymethylethylsiloxane, or compounds having high adhesiveness to both the shield layer 1 and the insulating film 3, such as polyacrylonitrile.

Metal materials constituting the conductor circuit 4 include copper, silver,
Examples include nickel, aluminum, or a composite system of these metals. The thickness of the conductor circuit should be the same as the conventional one (f
Generally, it is preferably within the range of 18 to 75 I#.

The base film 6 can be made of the same material as the insulating film 3, and its thickness is usually 25 to 125 mm.
Preferably within the range of sin.

As the adhesive constituting the adhesive layer 5.5'', it is possible to use a urethane-based, polyester-based, or epoxy-based adhesive that does not hinder the flexibility of the flexible printed wiring board A and is resistant to thermal stress. can.

Furthermore, in the flexible printed wiring board A of the present invention, a protective film made of the same material as the insulating film 3 may be laminated on the shield layer 1 in order to prevent corrosion of the shield layer 1.

The method for manufacturing the flexible printed wiring board A of the present invention includes:
After forming the intermediate adhesive layer 2 on the insulating film 3 by a plasma polymerization method, the shield layer 1 is formed on the intermediate adhesive layer 2 in the same chamber by a vapor deposition method, a sputtering method, or an ion plate method. do.

The plasma polymerization method described above involves bringing plasma of a compound into contact with a target surface to form a layer of the compound.

According to this method of manufacturing flexible printed wiring board A, the intermediate adhesive layer is formed by plasma polymerization, and the shield layer is formed by vapor deposition, sputtering, or ion plate method. Since the plasma polymerization method, the vapor deposition method, the sputtering method, and the ion plate method can be performed in the same chamber, the intermediate adhesive layer 2 and the shield layer 1 can be continuously formed in the same chamber.

The method for forming the conductor circuit 4 includes a so-called substrative method in which unnecessary parts of the thin film made of the metal material laminated on the surface of the base film 6 are removed by etching, and a method for forming the conductor circuit 4 on the surface of the base film 6. Conventionally known methods can be applied, such as an additive method in which a metal material is deposited only on a portion, and a semi-stratative method in which a substrative method and an additive method are combined.

Note that the flexible printed wiring board according to the present invention is not limited to the above embodiments.

For example, as in the flexible printed wiring board A1 shown in FIG. 2, an intermediate adhesive layer 21 is formed on the surface of the base film 6 opposite to the surface on which the conductor circuit 4 is formed, by a method similar to that described above. It is also possible to provide a shield layer 11 on the intermediate adhesive layer 21.

In this flexible printed wiring board A1, shield layers 1.11 are provided on both the upper and lower sides of the conductor circuit 4, so that
It has particularly good shielding performance.

<Example> Example 1 Base film thickness 25I#, width 2a*, length 1
A 3'll thick copper foil was placed on the surface of a long belt-shaped polyimide film of 831, and a 25' thick layer of urethane adhesive was applied.
It was adhered through the μmaro adhesive layer.

Next, this copper foil was etched to form two conductor circuits with a line width of 0.5 mm and one conductor circuit with a line width of 0.1 mm parallel to the longitudinal direction of the base film.

Then, a 25 μm thick polyimide film was laminated as an insulating film on this conductor circuit via a 25 μm thick adhesive layer made of a urethane adhesive.

Next, the above laminate was placed in a plasma generator with a distance of 30 mm, and the pressure inside the device was adjusted to 0.4 torr while acrylonitrile vapor was introduced together with nitrogen gas at a flow rate of 20 w1/min. Then, an intermediate adhesive layer made of polyacrylonitrile having a thickness of 2 μm was formed on the insulating film by plasma polymerization using an interelectrode power of 20 W.

Furthermore, copper vapor was flowed into the same plasma generator, the voltage between the electrodes was set to 60 V, and a shield layer made of copper with a thickness of 5 μm was formed on the intermediate adhesive layer by vapor deposition.

Then, a 25-thick polyimide film coated with a urethane adhesive was laminated on the shield layer by press-bonding to obtain a flexible printed wiring board.

Example 2 In the same manner as in Example 1, an intermediate adhesive layer made of polydimethylsiloxane with a thickness of 3 μm was formed, and a shield layer made of copper with a thickness of 5 μm was formed on the intermediate adhesive layer.

Then, a 25 μm thick polyimide film coated with a urethane adhesive was laminated on the shield layer by press-bonding, to obtain a flexible printed wiring board.

Example 3 In the same manner as in Example 1, an intermediate adhesive layer made of polydimethylsiloxane with a thickness of four layers was formed, and a shield layer made of aluminum with a thickness of 5 μm was formed on the intermediate adhesive layer.

Then, a 25 μm thick polyimide film coated with a urethane adhesive was laminated on the shield layer by press-bonding, to obtain a flexible printed wiring board.

Comparative Example 1 A flexible printed wiring board was obtained in the same manner as in Example 1, except that a shield layer made of copper with a thickness of 51 m was formed without forming an intermediate adhesive layer on the insulating film.

Comparative Example 2 Instead of forming an intermediate adhesive layer and a shield layer on an insulating film, a 30% Ag base was formed on the insulating film.
A flexible printed wiring board was obtained in the same manner as in Example 1, except that the coating was applied to a thickness of - and dried at 150° C. for 30 minutes.

Comparative Example 3 Instead of forming an intermediate adhesive layer and a shield layer on the insulating film, a 5-thickness adhesive layer was formed on the insulating film.
A flexible printed wiring board was obtained in the same manner as in Example 1, except that 0μ iron foil was laminated.

For each of the flexible printed wiring boards obtained in Evaluation Test Examples 1 to 4 and Comparative Examples 1 to 2,
The presence or absence of cracks in the shield layer during bending was investigated. ■ Adhesion of the shield layer to the insulating film. ■ Shielding effect against electromagnetic waves at room temperature and in an atmosphere of 80° C. was investigated.

Note that the evaluation test (■) was evaluated by a T-peel test.

In addition, regarding the evaluation test (2), evaluation was made using the attenuation rate of 30 MHz electromagnetic waves measured using a spectrum analyzer.

The results are shown in Table 1.

(Margin below) Table 1 From Table 1, the flexible printed wiring boards of Examples 1 to 3 in which an intermediate adhesive layer was provided between the shield layer and the insulating film were compared with those in which the shield layer was provided directly on the insulating film. It can be seen that, compared to the flexible printed wiring board of Example 1, the shield layer adheres more firmly to the insulating film. Moreover, it can be seen that, compared to those obtained in Comparative Examples 2 and 3, despite the thickness of the shield layer being thinner, an excellent shielding effect was exhibited, and an excellent shielding effect was exhibited even in a high-temperature environment. Furthermore, it can be seen that it has high flexibility.

<Effects of the Invention> As described above, in the flexible printed wiring board of the present invention, since the intermediate adhesive layer is provided between the shield layer and the insulating film, the shield layer is firmly adhered to the insulating film. There is no risk of it peeling off. Further, since the shield layer is formed by a vapor deposition method, a sputtering method, or an ion plating method, a sufficient shielding effect can be obtained with a thin shield layer. Furthermore, since the shield layer is thin, there is no risk of loss of flexibility.

Further, according to the method for manufacturing a flexible printed wiring board of the present invention, the intermediate adhesive layer is formed by a plasma polymerization method,
Since the shield layer is formed by a vapor deposition method, a sputtering method, or an ion plating method, the intermediate adhesive layer and the shield layer can be formed continuously in the same chamber, and the above flexible printed wiring board can be easily manufactured. It has the effect of being able to.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing one embodiment of the flexible printed wiring board of the present invention, and FIG. 2 is a sectional view showing another embodiment. A, Al...Flexible printed wiring board, 1.11
... Shield layer, 2.21 ... Intermediate adhesive layer, 3...
- Insulating film, 4... conductor circuit. A, Al...Flexible printed wiring board 1, 11.
...Shield layer 2.21...Intermediate adhesive layer 3...Insulating film 4...Conductor circuit No.

Claims (5)

[Claims] 1. Consists of a conductive thin film on a base film Conductor circuit, insulating film, shield layer and are formed in this order. A component wiring board, Between the above shield layer and insulating film An intermediate adhesive layer is provided to seal The layer is formed by vapor deposition, sputtering or Formed by ion plating method flexi, which is characterized by Bull printed wiring board. 2. The intermediate adhesive layer is made of polyacrylonite. Lyle or polydialkylsiloxane? The flexible preform according to claim 1, consisting of component wiring board. 3. If the above shield layer is silver, copper, or aluminum Is it aluminum, nickel or a combination of these? The flexible preform according to claim 1, consisting of component wiring board. 4. The thickness of the above shield layer is 0.5~ The flexible according to claim 1, which has a diameter of 10 μm. printed wiring board. 5. Consists of a conductive thin film on a base film Conductor circuit, insulating film, shield layer and are formed in this order. A method for manufacturing a component wiring board, the method comprising: Plasma polymerization method on the above insulation film After forming the intermediate adhesive layer by Seal onto the intermediate adhesive layer above in the chamber Deposit layer by vapor deposition method, sputtering method or Formed by ion plating method Flexible printing characterized by Method of manufacturing wiring boards.