JPH0837373A - Film bridging multilayered wiring board and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a film bridging multilayered wiring board on which wires can be wired at a high density by constituting the wiring board of a plurality of substrates and bridging sections and reinforcing the resin layers of the bridging sections by respectively sticking movable reinforcing layers to one surfaces of the resin layers at least within the extents of the bridging sections. CONSTITUTION:A film bridging multilayered wiring board is provided with a plurality of substrates 1 housing wiring and flexible bridging sections 2 which connect the substrates 1 to each other. Each bridging section 2 is constituted of wiring and a resin layer 4 which is composed mainly of an epoxy resin or phenol resin. In addition, the layer 4 is reinforced by sticking a flexible reinforcing layer to one surface of the layer 4 at least within the extent of the bridging section 2. The substrates 1 housing multilayered wiring have through holes 7, etc., for electrically connecting wiring layers to each other through the substrates 1. Therefore, IVH connection becomes possible and this multilayered wiring board can be applied to such a use that requires high- density wiring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density film bridging connection multilayer wiring board and a manufacturing method thereof.

[0002]

2. Description of the Related Art As electronic devices become lighter, thinner, shorter, smaller, and more sophisticated, the installation space for wiring boards is becoming narrower, and wiring boards are required to be even higher in density and thinner. A plurality of high-density and thin multilayer wiring boards are installed and connected to each other according to the size of the installation space.

As a method therefor, a method using a composite wiring board in which two rigid multilayer wiring boards are mechanically connected by a flexible wiring board is used, and a rigid flex wiring board in which a flexible wiring board is extended to a rigid multilayer wiring board portion. There was a method of using.

[0004]

By the way, in the method of the prior art, the cost of the flexible wiring board used only for connection is high, and both ends of the flexible wiring board are connected to the rigid wiring board. Therefore, there is a problem that the processing cost is high. In addition, in the case of the conventional technique, the material used for the conventional rigid flex wiring board has a problem that the price is high and the cost is high.

An object of the present invention is to provide a film bridge connection multilayer wiring board having an excellent wiring density and a method for economically producing such a multilayer wiring board.

[0006]

As shown in FIG. 4, a film bridging connection multilayer wiring board of the present invention has a plurality of substrates 1 in which multilayer wirings are accommodated and a flexible bridging connection connecting them. That the bridge connecting portion 2 is composed of the wiring 3 and the resin layer 4, and the resin layer 4 is provided with a flexible reinforcing layer on one surface at least in the range of the bridge connecting portion. Characterize.

As shown in FIG. 4, a through hole 31 for penetrating the substrate 1 to electrically connect each wiring layer to the substrate 1 in which the multi-layered wiring is accommodated, the wiring of the outermost layer and the wiring are formed. It is also possible to provide a via hole 32 for connecting only the wiring layer formed inside.

As a method of manufacturing such a multilayer wiring board,
1A, a step of making an inner wiring board 11, a step of making an adhesive metal foil 12 in which a metal foil and an adhesive resin layer are integrated, as shown in FIG. 1B, the inner wiring board 1 (c) to a step of laminating and bonding 11 and the adhesive metal foil 12 to a portion which will later become the bridging connection portion 2 via a release film.
As shown in (d), a step of forming wiring on the laminated and bonded product, a step of cutting the outer shape as shown in FIGS. 1 (e) and 1 (f), and a step shown in FIG. 1 (g). The method further comprises a step of cutting and removing a portion of the inner layer wiring board, which becomes the bridging connection portion 2, with the release film as a boundary.

At this time, a release metal foil may be used instead of the release film.

(Inner Layer Wiring Board) As the inner layer wiring shaped board, an inner layer wiring board in which inner layer wiring is formed on a base material mainly made of glass cloth and thermosetting resin can be used.

(Bridge Connection Portion) The bridge connection portion 2 of the present invention does not require the folding endurance of a general flexible wiring board, but does not crack when slightly bent. Flexibility is required. In the case of general epoxy resins and phenol resins, if they are made into a film and cured, they tend to crack, so it is necessary to mix a plasticizer and modify the resin. At this time, it is necessary to secure the heat resistance and electrical characteristics of the resin, and it is desirable that the resin be less expensive than the polyimide resin.

When a high molecular weight epoxy polymer is used as the resin of such an adhesive metal foil, it retains a certain degree of flexibility after curing without using a plasticizer or modification of the resin, and is laminated. The resin viscosity can be kept high even during heating during bonding. As such a high molecular weight epoxy polymer film, commercially available AS-3000 (trade name, manufactured by Hitachi Chemical Co., Ltd.) can be used.

Further, the bridging connection portion 2 can be formed with a reinforced layer 5 of a flexible resin film or a metal foil.

In the present invention, the resin layer of the adhesive metal foil is
It is also possible to form a multi-layered structure with a plurality of resins, and in that case, a resin layer having no adhesive force (for example, cured) can be used as the resin layer other than the outermost layer.

(Adhesive Metal Foil) As the adhesive metal foil, an adhesive metal foil with holes in which holes for interlayer connection are preliminarily drilled can be used. For making holes in the adhesive metal foil, known methods such as drilling and punching can be used.

The type of resin used for the resin layer of the adhesive metal foil is not particularly limited, but epoxy resin, phenol resin, and modified resins thereof are preferable. Among these, epoxy resins having excellent properties such as heat resistance, mechanical properties, electrical properties, and chemical resistance are preferred.
In terms of characteristics, resin is cheap,
Phenolic resins, which are often used for wiring board applications, are economical. The resin layer may contain an organic filler or an inorganic filler, and the resin layer may be impregnated in paper, woven cloth or non-woven cloth.

When the resin used for the resin layer has too low a viscosity during heating, the interlayer insulation becomes insufficient, and when a pre-drilled adhesive metal foil with holes is used, the via layer to be described later is used. There is a problem that the resin oozes into the holes for holes and it becomes impossible to conduct electricity.Therefore, in order to maintain an appropriate viscosity, the addition of fillers such as those mentioned above and the use of paper, woven fabric, or non-woven fabric is used. Then, a method of adjusting the apparent viscosity by reducing the proportion of the resin contained in the resin layer may be used.

Further, when laminating and bonding the inner wiring board and the adhesive metal foil, it is preferable to insert a cushion material between the end plate and the laminate to laminate and bond them.

(Release Layer) When a release metal foil is used, a laser can be used for cutting and removing the portion which becomes the bridging connection portion 2 of the inner layer wiring board, as will be described later.

A copper foil, an aluminum foil, or the like can be used as the release metal foil which is inserted for the purpose of preventing the adhesion between the inner layer wiring formed product and the adhesive metal foil at the time of lamination and adhesion. If the thickness of these release metal foils is too thick, a step difference becomes large at the time of laminating and bonding, and the laminating and bonding becomes incomplete. If it is too thin, it will be difficult to handle. From these, the thickness is preferably 15 to 80 microns, more preferably 15 to 80 microns.
~ 40 microns.

A normal method of arranging a desired laminate between the end plates can be used for the lamination adhesion, but if the resin layer of the adhesion metal foil is not sufficiently embedded in the gap portion of the inner layer wiring. In many cases, the peripheral portion of the release metal foil has poor adhesion due to the unevenness of the release metal foil. To prevent this, it is desirable to insert a cushion material between the end plate and the laminate. As the cushion material, a silicone rubber having a thickness of 0.2 mm to 1 mm, a polyethylene film having a thickness of 30 μm to 100 μm, or the like can be used.

In a step after the lamination adhesion, a specific portion of the inner layer wiring formed product is cut and removed with the release metal foil as a boundary. The timing of this cutting and removal is not particularly limited, but it is desirable to carry out after the outer shape processing. For the cutting, V cutting may be performed in advance on the cut portion of the inner layer wiring formation product, or V cutting may be performed after stacking and a specific portion may be broken off at the V cutting portion. Further, it is also possible to cut by cutting with a knife to a certain depth from the unnecessary portion side (inner layer wiring formation side). From the viewpoint of productivity, a method of irradiating a laser beam from the unnecessary portion side and cutting the release metal foil as a stopper is excellent.

The release metal foil is preferably left for strengthening the bridging connection. A conventional through-hole connection can be used for the connection between the wiring layers. Further, if an adhesive metal foil that has been punched in advance is used, IVH (interstitial via hole) connection can be performed at the same time when the through hole is connected. As the connection method, in addition to the method of connecting by plating, a method of filling and connecting a conductive material such as a copper paste or a silver paste can also be used.

[0024]

In the present invention, after the release metal foil or release film is interposed and the layers are once laminated and adhered, the unnecessary portions of the inner layer wiring formation are cut and removed with the release metal foil or release film as a boundary. Therefore, when laminated and bonded, it can be handled and manufactured in the same manner as a general multilayer wiring board. Further, according to the object of the present invention, when a resin having a high viscosity is used, it is difficult to sufficiently fill the gap between the inner layer wirings and the step due to the release metal foil with the resin by a press using an ordinary mirror plate, which may cause a void. Occurrence or cracking may occur during the heat cycle, but such a problem does not occur because the cushion material is inserted between the end plate and the one to be laminated according to the present invention.

[0025]

【Example】

(Preparation of Inner-Layer Wiring Formed Product) An inner-layer wiring was formed by etching, in which a core was formed by laminating copper foils on both sides of a base material impregnated with epoxy resin on a glass cloth, and lands were provided at necessary portions of the IVH connection portion.

(Preparation of Adhesive Metal Foil with Holes) A high-molecular-weight epoxy polymer film AS3000 (trade name, manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 50 μm and copper foil were superposed on each other and heated and adhered. The adhesion at this time was carried out in a short time (about 5 minutes) so that the B-stage state of the high molecular weight epoxy polymer film was maintained. An adhesive metal foil with holes was prepared by drilling a hole (0.3 mm diameter) for IVH connection in this adhesive metal foil (copper foil).

(Example) A copper foil for mold release is arranged on a portion of an inner layer wiring formed product which is a specific portion of a wiring board, and a trace amount of an adhesive is applied to a portion (cutting margin) which is not finally the wiring board. I used it and made a temporary stop. An adhesive metal foil with holes was placed on this product and laminated and adhered. Next, a hole was drilled for connecting the through hole with a drill. After performing processing such as hole cleaning, thick copper plating for interlayer connection at the through hole connection portion and the IVH connection portion was performed. Then, surface wiring was formed by a tenting method. After the V-cut process and the outer shape cutting process were performed on the boundary portion of the specific portion (planned bridge connection portion), unnecessary portions of the inner layer wiring formation were cut and removed from the V-cut portion.

[0028]

According to the present invention, it is possible to manufacture a film bridge connecting wiring board in which rigid wiring boards have a bridge connecting structure without using an expensive material and in a small number of steps. In addition, IVH connection is possible and it can be applied to applications requiring high density, and the cost increase at this time is smaller than that of the conventional method. As described above, the present invention is low cost,
This contributes to higher density of electronic devices.

[Brief description of drawings]

1A to 1G are cross-sectional views in each step for explaining an embodiment of the present invention.

FIG. 2 is a schematic top view for explaining an embodiment of the present invention.

FIG. 3 is a top view for explaining an embodiment of the present invention.

FIG. 4 is a sectional view showing a usage state of a wiring board according to an embodiment of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Haruo Ogino 1500 Ogawa, Shimodate City, Ibaraki Prefecture Shimodate Factory, Hitachi Chemical Co., Ltd. Shimodate Research Center (72) Inventor Yoshihiro Tamura 1500 Ogawa, Shimodate City, Ibaraki Prefecture Hitachi Chemical Co., Ltd. Shimodate Factory

Claims (27)

[Claims] 1. A plurality of substrates accommodating multilayer wiring and a flexible bridging connection portion connecting them, the bridging connection portion comprising:
A film bridging connection multilayer wiring board comprising a wiring and a resin layer, wherein the resin layer is provided with a flexible reinforcing layer on one surface at least in the range of the bridging connection portion. 2. The substrate portion excluding the bridging connection portion and its extended portion is mainly made of a material obtained by impregnating a fiber-reinforced material such as glass cloth with a thermosetting resin. The described film bridge connection multilayer wiring board. 3. A wiring formed in a film bridging connection portion or a wiring formed on the same surface as the wiring has an interlayer connection hole for electrically connecting with a wiring formed in a layer immediately below the wiring. The film bridge connection multilayer wiring board according to claim 1 or 2, characterized in that. 4. The resin layer of the bridge connection portion is a resin layer mainly composed of an epoxy resin.
The film wiring bridged multilayer wiring board according to any one of 1. 5. The film bridging connection multilayer wiring board according to claim 4, wherein the resin of the resin layer containing an epoxy resin as a main component is a resin containing a high molecular weight epoxy polymer as a main component. 6. The film bridge connection multilayer wiring board according to claim 4, wherein the resin of the resin layer containing an epoxy resin as a main component is a resin containing an amide epoxy resin as a main component. 7. The film bridging connection multilayer wiring board according to claim 1, wherein the resin layer of the bridging connection portion is a resin layer mainly composed of a phenol resin. 8. The bridging connection portion is reinforced with a flexible resin film, wherein the bridging connection portion is reinforced with a flexible resin film.
The film wiring bridged multilayer wiring board according to any one of 1. 9. The multilayer film wiring board according to claim 1, wherein the flexible resin film is one of a polyimide film and a polyester film. 10. The multilayer wiring board for film bridge connection according to claim 1, wherein the bridge connection portion is reinforced with a metal foil. 11. A step of producing an inner wiring board, a step of producing an adhesive metal foil in which a metal foil and an adhesive resin layer are integrated, the inner layer wiring formed product and the adhesive metal foil are connected to each other via a film bridging connection portion. At the location where at least a release film that does not adhere to the inner layer wiring board is laminated and bonded, a process of forming wiring on the laminated and bonded product, a step of cutting the outer shape, an inner layer wiring with the release film as a boundary A method for producing a film-bridge-connected multilayer wiring board, which comprises a step of cutting and removing the board to form a film-bridge connecting section connecting a plurality of multilayer wiring board sections. 12. The production of a film-bridge-connected multilayer wiring board according to claim 11, wherein the inner wiring board is formed by forming the inner wiring on a base material mainly composed of a glass cloth and a thermosetting resin. Law. 13. The adhesive metal foil according to claim 11, wherein the adhesive metal foil is an adhesive metal foil with holes which is preliminarily punched.
2. The method for manufacturing a film bridge connection multilayer wiring board according to 2. 14. The laminated bonding of the inner layer wiring board and the adhesive metal foil, wherein a cushioning material is inserted between the end plate and the laminated body to carry out the laminated bonding. The method for producing a film-bridge-connected multilayer wiring board according to. 15. The adhesive resin layer is a resin layer containing an epoxy resin as a main component, according to claim 11.
5. The method for producing a film bridge connection multilayer wiring board according to any one of 4 above. 16. The method for producing a film bridging connection multilayer wiring board according to claim 15, wherein the resin of the resin layer containing an epoxy resin as a main component is a resin containing a high molecular weight epoxy polymer as a main component. . 17. The method for producing a film bridging connection multilayer wiring board according to claim 15, wherein the resin of the resin layer mainly containing epoxy resin is a resin mainly containing amide epoxy resin. 18. The method for producing a film bridging connection multilayer wiring board according to claim 11, wherein the adhesive resin layer is a resin layer mainly composed of a phenol resin. 19. A step of forming an inner layer wiring board, a step of forming an adhesive metal foil in which a metal foil and an adhesive resin layer are integrated, and the inner layer wiring board and the adhesive metal foil are at least film-bridged later. A step of laminating and adhering a release metal foil to a portion to be a part, a step of forming wiring on the laminated and adhering object,
A film bridge characterized by having a step of cutting the outer shape, a step of cutting and removing the inner layer wiring board with the release metal foil as a boundary, and forming a bridge connection portion connecting a plurality of multilayer wiring board sections. Manufacturing method of connection multilayer wiring board. 20. The film bridge according to claim 19, wherein the inner layer wiring formed product is an inner layer wiring formed product in which the inner layer wiring is formed on a substrate mainly composed of glass cloth and a thermosetting resin. Manufacturing method of multi-layered wiring board. 21. The film bridging connection multilayer wiring board according to claim 19 or 20, wherein the adhesive metal foil is an adhesive metal foil with holes in which holes for interlayer connection are preliminarily drilled. Manufacturing method. 22. The laminated bonding of the inner layer wiring formed product and the adhesive metal foil is performed by laminating and bonding a cushion material between the end plate and the laminated product.
A method for manufacturing a film bridge-connection multilayer wiring board according to any one of 1. 23. A laser is used to cut and remove a specific portion of the inner layer wiring formed product with the release metal foil as a boundary, and the cutting is performed. Manufacturing method of film bridge connection multilayer wiring board. 24. The adhesive resin layer is a resin layer containing an epoxy resin as a main component.
4. The method for producing a film bridge connection multilayer wiring board according to any one of 3 above. 25. The method for producing a film bridging connection multilayer wiring board according to claim 24, wherein the resin of the resin layer containing an epoxy resin as a main component is a resin containing a high molecular weight epoxy polymer as a main component. . 26. The method for producing a film bridge connection multilayer wiring board according to claim 24, wherein the resin of the resin layer containing an epoxy resin as a main component is a resin containing an amide epoxy resin as a main component. 27. The method for producing a film bridging connection multilayer wiring board according to claim 19, wherein the adhesive resin layer is a resin layer containing a phenol resin as a main component.