JP2000332425A - Manufacture of resin film for multilayer interconnection board and the multilayer interconnection board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a rigid-flex interconnection board at high efficiency and accuracy, using a laser processing device, by projecting a swept continuous oscillation laser beam onto a resin film moving on a processing table, for providing an opening on the resin film. SOLUTION: Using a device with which a single-direction sweeping galvanometer mirror sweeping device 23 fitted to a carbon dioxide gas laser oscillator 20 which allows continuous oscillation, comprises a processing table 24 which moves in the direction almost orthogonal to the sweeping direction of the galvanometer mirror sweeping device 23, the resin film moving on the processing table 24 is irradiated with the swept continuous oscillation laser beam so that the resin film is provided with an opening. Thus the processing precision with an adhesive sheet is improved for suppressed infiltration of the adhesive sheet at pressing, resulting in manufacture at high efficiency and accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a resin film for a multilayer wiring board and a multilayer wiring board obtained by laminating the same as an insulating layer, particularly a rigid-flexible printed wiring board (also abbreviated as a rigid-flex wiring board). About).

[0002]

2. Description of the Related Art A rigid-flex wiring board has a rigid portion and a flex portion, and both ends of the flex portion are integrated with the rigid portion and are electrically connected. When such a wiring board is manufactured, a method is often used in which a substrate having a layer structure such as an integrated portion at both ends of a flex portion is prepared in advance, and then the rigid layer corresponding to the flex portion is removed. Further, the layer structure here is arranged between at least one flexible wiring board layer, at least one rigid wiring board layer, and at least one wiring board layer, and has at least one resin insulating layer also acting as an interlayer adhesive layer. have.

One example of the manufacturing method will be described. An insulating layer provided with an opening in a cable portion between rigid portions, that is, a portion corresponding to a flex portion, is formed on a flexible wiring board on which a circuit covered with a coverlay has been formed. Laminated, further provided with a conductor layer having a circuit formed on the surface, a rigid wiring board having a portion corresponding to the flex portion previously opened or a cut-out line is overlaid on this insulating layer, and the rigid wiring board After inserting an easy-to-remove resin into the opening as necessary, or after inserting a release spacer, pressurizing, heating and laminating and integrating, drilling,
Copper plating and outer layer circuit processing are performed. Thereafter, when a resin or a release spacer is fitted into the opening, it is removed, and when a cut line is made, the cut portion is removed.

[0004] As another example, the insulating layer is laminated on a flexible wiring board on which a circuit covered with a coverlay has been formed.
After arranging the rigid wiring board before opening processing and pressurizing and heating together with the flexible wiring board and laminating and integrating,
Open the rigid wiring board at the part corresponding to the flex part between the rigid wiring boards to expose the cable part of the flexible wiring board, and then perform drilling, copper plating and outer layer circuit processing, etc., to remove the rigid-flex wiring board To manufacture.

As described above, in the production of a normal rigid-flex wiring board, a portion where the flexible wiring board is exposed and becomes a flex portion is opened as an interlayer adhesive sheet and an insulating layer between the flexible wiring board and the rigid wiring board. It is necessary to use a resin film. According to a conventional method, in order to provide an opening of a predetermined shape at a predetermined position of a resin film used in the method of manufacturing such a rigid-flex wiring board, a method of punching with a die or a pin It was performed by a method such as punching using. However, such a method has a problem in that, for example, in the case of producing a small quantity of various kinds of wiring boards, a large number of dies must be produced in accordance with the production, and there is a problem that it cannot be manufactured at low cost. Also, with these methods, it is difficult to perform microfabrication corresponding to recent microcircuits, and it is hoped that a method for manufacturing a rigid-flex wiring board using a more accurate and efficient interlayer bonding layer processing method will be established. Was rare.

A method using a laser is known as a method for removing and opening a resin layer constituting a laminated member.
For example, as a method of forming a fine hole, Japanese Patent Application Laid-Open No. 5-3054
As disclosed in JP-A-68-68, a method using a pulse laser is known. However, in such a method,
In the case of processing a continuous area larger than the irradiation area of the pulse laser beam 1 pulse on the processing surface, for example, when processing an elongated continuous area, it is necessary to irradiate the pulse laser beam without gaps. For example, Japanese Patent Application Laid-Open No. Hei 9-22
No. 3456, it takes a long time to irradiate a plurality of pulses because the pulse repetition frequency is as low as about 10 kHz or less, that is, it takes a long time to remove a continuous wide range of resin. Therefore, there is a problem that the resin cannot be removed efficiently.
Specifically, the range in which the resin is to be removed corresponds to the standard irradiation range of one pulse of the pulsed laser beam.
In the case of cm ² or more, there was a problem that the resin could not be removed efficiently.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for processing a resin film used for a multilayer wiring board with high efficiency and high accuracy by using a laser. In particular, it is an object of the present invention to provide a method for manufacturing a rigid-flex wiring board with high efficiency and high accuracy.

[0008]

The inventors of the present invention have conducted intensive studies and have found that if a continuous oscillation laser beam is used as a laser beam to be swept, it is difficult to obtain a laser beam having a diameter of 0.2 cm ² , which has been difficult with conventional laser processing techniques. The above-described resin removal processing has become possible, and it has been found that the above-mentioned problems can be solved, and the present invention has been completed.

That is, the present invention relates to a sweeping device capable of sweeping a laser beam in one direction and a resin film moving in a direction substantially perpendicular to the sweeping direction of the laser beam in processing a resin film for a multilayer wiring board using a laser beam. Using a laser processing apparatus having a processing table for moving the laser beam, irradiating the swept continuous oscillation laser beam to the moving resin film on the processing table, and opening the resin film. This is a method for producing a resin film for a plate. The area of at least one of the openings is preferably 0.2 cm ² or more, and the resin film is advantageously a polyimide resin having a silicon unit or an uncured or semi-cured resin thereof. Further, the present invention provides a rigid material having at least one resin film obtained by the above-mentioned manufacturing method as an insulating layer.
-It is a flexible printed wiring board.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In general, a multilayer wiring board is manufactured by sequentially stacking conductor layers such as an insulating layer and a rigid wiring board on a printed wiring board or a flexible wiring board on which a circuit is formed. In the present invention, at the time of manufacturing a multilayer wiring board, a resin film provided with an opening in a predetermined range of at least one layer for adhesion and insulation, laminated with a rigid board also provided with a predetermined opening,
This is to produce a multilayer wiring board by heating and pressing.

The type of the resin film for the multilayer wiring board is not particularly limited as long as it has insulating properties, and known resin films can be widely used. Examples of the material used for such an insulating resin film include an epoxy resin, a polyimide resin, a polyester resin, and a resin composition containing these. Preferably, it is a polyimide resin or a resin composition containing a polyimide resin. Among the polyimide resins, a silicon-modified polyimide resin having a silicon unit is preferable. For example, a resin composition comprising 70 to 99% by weight of a polyimide resin having a silicon unit and 1 to 30% by weight of an epoxy resin, which is disclosed in JP-A-6-200216, is preferred.

In the case of a polyimide resin composition containing an epoxy resin, it is preferably an uncured or semi-cured resin, and particularly preferably a B-staged resin.

The thickness of the resin film is not particularly limited, but is preferably 1 μm or more and 1000 μm or less.
It is difficult to prepare a resin film having a thickness of less than 1 μm.
In the case of a resin film having a thickness of more than 000 μm, it is difficult to process the resin film in terms of energy even in laser processing, and the thickness of the multilayer wiring board becomes large, which is not practical.

In the present invention, in order to provide an opening in a predetermined range in the resin film, a laser which is oscillated from a laser oscillator and is swept is applied to a portion to be opened.
As a laser to be used, a carbon dioxide gas laser which does not require large equipment and is relatively easy to handle and maintain is preferable. The opening in the predetermined range may include at least a part corresponding to the flex part or a part or all of the part and the peripheral part, and may include other parts as necessary.

When a resin film is processed using a carbon dioxide laser, a known carbon dioxide laser processing apparatus as described later can be used as the processing apparatus. The carbon dioxide laser oscillation device used for processing the resin film may use a known carbon dioxide laser device capable of continuous oscillation having an oscillation wavelength of 9 to 11 μm, and preferably has an average output of 100 W or more, more preferably 500 W or more. It is preferable to use a carbon dioxide gas laser device.

In order to irradiate a continuous wave laser beam oscillated from a laser oscillator to a portion of the resin film to be removed, it is necessary to sweep the laser beam. The sweeping method can be performed by using a mirror device used in known laser processing. As such a sweepable driving mirror device, a galvano mirror scanner capable of rotating a plane mirror back and forth at an angle with respect to an axis including a plane and a polygon mirror scanner rotating a polygon mirror are known. And any of them can be used.

Normally, when laser processing is performed continuously, the processing object is performed using a processing table that can be moved at a constant speed in a fixed direction. That is, the laser beam swept as described above is applied to the resin film moving in a certain direction on the processing table. Here, the laser beam is moved in the moving direction (the Y direction) of the resin film. ) Is irradiated in the direction (X direction).

When condensing the swept laser beam, an optical lens may be used. When a carbon dioxide laser is used, the optical lens used is made of ZnSe due to the high transmittance to the laser beam. Is preferred.

In processing the resin film, when a laser beam is incident on the resin film provided with a conformal mask or a contact mask (by combining a driving mirror sweeping device and an optical lens), the laser beam is incident on the mask surface. A part of the laser beam is reflected without being absorbed by the mask, and may return to the laser oscillator through substantially the same optical path. Once the oscillated laser beam returns to the laser oscillator, the returned laser beam causes stimulated emission irrespective of laser oscillation, and decreases the gain, which is the amplification factor of laser oscillation.
As a result, it is possible that the laser oscillation output is reduced. Further, there is a possibility that the returned laser beam is irradiated to the resonator wall surface of the laser oscillator and the like, and the resonator itself is destroyed. Therefore, it is desirable to prevent the laser beam reflected on the mask surface from returning to the oscillator.

As a method of preventing the laser beam from returning to the oscillator, there is a method of disposing an optical system combining a circular deflecting mirror or the like utilizing the deflection of the laser beam between the laser oscillator and the resin film. However, in this case, a part of the oscillated laser beam is reflected or absorbed by these optical systems, causing a decrease in the energy of the laser beam applied to the resin film, resulting in a decrease in efficiency.

In order to prevent such a reduction and prevent the laser beam from returning, it is necessary to arrange the driving mirror sweeping device so that the incident angle of the laser beam applied to the resin film exceeds 0 °. I just need. Specifically, the drive mirror sweeping device is tilted in the range of 2 to 20 °, and the incident angle of the laser beam on the resin film is set to 2 to 2
By controlling the angle to 0 °, it is possible to prevent the laser beam reflected on the mask surface from returning to the oscillator without reducing the incident energy of the laser beam. When the inclination angle is less than 2 °, a part of the laser beam reflected by the mask returns to the laser oscillator, and when the inclination angle exceeds 20 °, the laser beam does not return, but the resin film after the laser processing does not return. The processed cross-sectional shape is undesirably tilted according to the tilt angle.

The processing table for moving and fixing the resin film to be processed is provided with a mechanism for moving at a constant speed in a direction (Y direction) orthogonal to a sweep direction (X direction) by a driving mirror sweeping device. I just need. The shape of the working table is not particularly limited, and may be a flat shape or a cylindrical shape. When the processing table is cylindrical, the cylinder must be arranged so that the sweep direction of the laser beam by the drive mirror sweeping device matches the height direction of the cylinder. Also, the method of fixing the resin film to the processing table is not particularly limited, and when the processing table is planar, a method using vacuum suction through fine holes provided in the processing table or a method using a magnet may be used.
When the processing table is cylindrical, a method using a tension roll or the like may be used. In any case, the moving speed of the resin film is at least 0.1 (cm / s) in the range of 0.1 to 2 (cm / s).
It can be variably controlled in increments, preferably 0.01 to 10 (cm / s)
It is only necessary to be able to variably control in the range of 0.01 cm / s.

When the resin film is processed by the laser beam, decomposition by-products of the insulating layer such as soot are generated, which may adhere to the wiring board or to the optical lens constituting the processing apparatus. . Each of these causes a decrease in the quality of the resin film and a decrease in the performance of the processing apparatus, and is not preferable. Therefore, a so-called assist gas device, which is a gas blowing device for removing decomposition by-products such as soot generated,
Alternatively, it is preferable to dispose an air curtain device, a dust collecting device for collecting soot, and the like. Each device may be a generally known device, and the type of gas used for the assist gas device and the air curtain device is not particularly limited.
Air pressurized to about 5 kg / cm ² may be used.

When processing is performed by irradiating a resin film with a laser using such a laser processing apparatus, the average output of the laser beam, the cross-sectional area of the laser beam bundle on the resin film surface, and the resin beam of the laser beam by the drive mirror sweeping device Energy density φ ₀ (J / cm ² ) of the laser beam applied to the resin film controlled by the sweep speed on the film
Is the processing threshold φ in resin film processing by laser
_th (J / cm ² ), and desirably in the range of 2φ _th <φ ₀ <20φ _th . In particular, when the resin film is composed mainly of a polyimide resin or epoxy resin, 3J / cm ² or more and an energy density of 50 J / cm ² or less.

The moving speed v (cm / s) of the processing table on which the resin film is fixed is determined by the absorption coefficient α (cm ^-1 ) of the resin film, the thickness L (cm) for processing the film,
Section diameter d (c) of the laser beam bundle on the resin film surface
m) and the sweep frequency G (H
z), and it is desirable that the range is 0.5 × (dG / αL) <v <4.0 × (dG / αL).

In the present invention, the method of laminating a resin film to be a laser-processed adhesive layer and insulating layer and a wiring board is as follows.
Although not particularly limited, a hot press, a hot roll or the like is used to apply a hot press forming method at a temperature range of 160 to 220 ° C. and a pressure range of about ²⁰ to 40 kg / cm ² by a hot press forming method. The lamination method is preferred.

The above-mentioned laminate may be subjected to a drilling process or the like by a known method such as NC drilling. Also, when a plated portion is plated with copper to form a through hole, A known electroless plating or electrolytic plating method may be used. Further, the circuit processing of the conductor layer of the surface layer is performed by applying a photosensitive resin or laminating a usual photosensitive dry film, then placing a desired mask pattern thereon and exposing the photosensitive resin layer by ultraviolet irradiation to develop. After that, a known method such as etching with an etchant such as ferric chloride may be used.

[0028]

EXAMPLES The following will explain the rigidity of the present invention based on examples.
The method for manufacturing the flex wiring board will be described in detail.

Example 1 A bonding sheet SPB05 manufactured by Nippon Steel Chemical Co., Ltd. was used for a resin film for interlayer adhesion and insulation between a flexible wiring board of a rigid-flex wiring board and a rigid wiring board.
OA (thickness: 50 μm, epoxy-modified silicone-modified polyimide resin composition: B stage) was used.

As shown in FIG. 2, a unidirectional sweeping galvanomirror sweeping device 23 is attached to a continuously oscillating carbon dioxide laser 20 and a processing table 24 is provided which moves in a direction substantially perpendicular to the sweeping direction of the galvanomirror sweeping device. The resin film was processed using the apparatus. A metal mask contact method was used for the opening formed by laser processing in a predetermined range where the flexible wiring board was exposed to become a flex portion. Opening of contact mask is 100mm × 50
mm and an opening area of 50 cm ² . In the drawing, reference numeral 21 denotes a laser beam, and reference numeral 22 denotes a condenser lens.

In the laser processing of the resin film, the average output of laser oscillation is 720 W, and the laser beam focusing area is 9.
62 × 10 ^-4 cm ² , laser beam sweep width 100 m
m, the moving speed of the wiring board was 12 mm / s, and the sweep frequency by the galvanomirror sweeping device was 50 Hz.

Next, as shown in FIG. 1, a double-sided copper-clad laminate (SB
35-50-35WE), laminating a commercially available photosensitive dry film, placing a desired mask pattern on it, exposing it to ultraviolet light, developing it, etching it with an etchant such as ferric chloride, etc. The circuit processing of the layer is performed, and a coverlay film (SPC35A2) manufactured by Nippon Steel Chemical Co., Ltd.
5A) to form a flexible wiring board 5. The coverlay is heated from room temperature at 3 ° C / min.
After holding for a time, the coating was performed by pressing with a pressing pressure of 30 kg / cm ² under a temperature condition of cooling to room temperature in 20 minutes by a water cooling method.

Next, the rigid wiring boards 3 and 7 having predetermined openings which are to be flex portions are opened, and the openings 10, 11, 12 so that the openings of the rigid wiring board overlap with the openings.
And 13, and the copper foils 1 and 9 forming the outer layer were simultaneously laminated by hot pressing. The laminating press is heated from room temperature at 3 ° C./min.
After maintaining at 80 ° C. for 1 hour, the mixture was cooled to room temperature by a water cooling method in 20 minutes, and the pressure was set to 20 kg / cm ² .

Next, a perforated hole and copper plating are applied to the laminated multilayer wiring board, a photosensitive dry film is laminated, a pattern mask is applied, and the photosensitive dry film is exposed to ultraviolet rays to expose the photosensitive dry film. An outer layer circuit was processed through a development and etching process to produce a rigid-flex wiring board.

The manufactured rigid-flex wiring board is
Since the processing accuracy of the adhesive sheet was improved, bleeding of the adhesive sheet at the time of pressing was suppressed, and it was confirmed that in addition to a highly efficient manufacturing method, high-precision manufacturing was possible.

[0036]

According to the present invention, it is possible to manufacture a highly reliable multi-layer wiring board which can process openings and holes of an adhesive sheet to be an insulating resin layer of the multi-layer wiring board with high accuracy and high efficiency. Can be.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a layer structure of a multilayer wiring board.

FIG. 2 is a schematic diagram of a continuous wave carbon dioxide laser processing apparatus.

[Explanation of symbols]

 1, 9 Outer layer copper foil 2, 4, 6, 8 Resin film 3, 7 Rigid wiring board 5 Flexible wiring board 20 Carbon dioxide laser oscillator 21 Laser beam 22 Condensing lens 23 Unidirectional galvanometer mirror 24 Processing table

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 26/10 104 G02B 26/10 104 H05K 3/00 H05K 3/00 N // B23K 101: 42 (72 Inventor Shoichi Ii 1 Tsukiji, Kisarazu City, Chiba Prefecture, within the Electronic Materials Development Center of Nippon Steel Chemical Co., Ltd. F-term in development center (reference) 2H045 AA01 AB01 DA31 4E068 AF00 CD12 CE01 DA11 5E346 AA41 CC10 EE44 GG15

Claims (4)

[Claims] In a processing of a resin film for a multilayer wiring board using a laser beam, a sweeping device capable of sweeping a laser beam in one direction and a resin film moving in a direction substantially perpendicular to the laser beam sweeping direction are moved. Using a laser processing apparatus having a processing table for irradiating a resin film on a moving processing table with a continuous oscillation laser beam swept in one direction to open the resin film. A method for producing a resin film for a board. 2. The area of at least one opening is 0.2.
^{2. The} method for producing a resin film for a multilayer wiring board according to claim 1, wherein the thickness is not less than cm ² . 3. The method according to claim 1, wherein the resin film is a polyimide resin having a silicon unit or an uncured or semi-cured resin thereof. 4. A rigid-flexible printed multi-layer wiring board comprising at least one resin film obtained by the method according to claim 1, 2 or 3 as an insulating layer.