JPH0969688A - Multilayered circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively connect two interconnections disposed via an insulating film in a viahole. SOLUTION: The multilayered circuit board is formed by sequentially covering a board 1 with first interconnection group made of a plurality of interconnections 2 and a second interconnection group made of an insulating film 3 and a plurality of interconnections 4, and electrically connecting the interconnections 2 of the first group and the interconnections 4 of the second group through a viahole conductor (part of the interconnections 4) filled in a viahole 3a provided at a predetermined position of the film 3. The interconnection width w1 of the first group disposed directly under the viahole 3a provided at the film 3 is narrowed as compared with the diameter ϕ of the viahole 3a to provide a gap between the inner wall of the viahole 3a and the end of the interconnection 2 of the first group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a multilayer wiring board in which a plurality of wiring groups are laminated with an insulating film interposed therebetween.

[0002]

2. Description of the Related Art A conventional multilayer wiring board is shown in FIG.
As shown in (a) and (b), a first wiring group composed of a plurality of wirings 22 and a second wiring group composed of a plurality of wirings 24 are provided on a substrate 21 made of glass, ceramics or the like with an insulating film 23 interposed therebetween. While being deposited, a predetermined position of the insulating film 23,
A via hole 23a having a diameter of 0.1 mm to 0.25 mm is provided in the thickness direction, and the wiring 22 and the wiring 24 are electrically connected through the via hole 23a.

As a material of the insulating film 23, for example, a photosensitive resin such as a photosensitive epoxy resin is known, and when the photosensitive epoxy resin is used, the wiring 22 is first deposited. A photosensitive epoxy resin which has been liquefied by adding and mixing an organic solvent or the like is applied to a predetermined thickness on the substrate 21 by a spin coating method or a roll coater method, and then the liquid photosensitive epoxy resin is applied. The insulating film 23 having the via holes 23a is formed by irradiating ultraviolet rays through the exposure mask, photo-curing the irradiated portion, and removing the non-photo-cured portion with an alkaline developing solution. In this case, a photoresist for separately forming the via hole 23a is deposited on the insulating film 23, or the insulating film 23 is formed by using a drill or the like.
Since it is not necessary to perforate the holes, there is an advantage that the manufacturing process of the multilayer wiring board is simplified.

Further, the wirings 22 and 24 are the via holes 2
Lands 22a and 24a, which are slightly larger than the via holes 23a, are provided at the locations where the via holes 3a are provided. By doing so, they are electrically connected.

[0005]

However, in this conventional multilayer wiring board, when the insulating film 23 is formed of a photosensitive epoxy resin or the like, the organic solvent 23b contained in the photosensitive epoxy resin is replaced by the via hole 23a. Permeates from the inner periphery of the via hole 23a and adheres to the upper surface of the land 22a forming the bottom surface of the via hole 23a. Therefore, even if an attempt is made to deposit the wiring 24 on the wiring 22 (land 22a) in the via hole 23a in a later step, the wirings 22 and 24
The organic solvent 23b intervenes in most of the spaces between them, and the area where they are adhered becomes small. As a result, there is a drawback that the wiring 22 and the wiring 24 cannot be reliably connected.

[0006]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks. The first invention is composed of a plurality of wirings on a substrate.
A second wiring group consisting of a wiring group, an insulating film, and a plurality of wirings is sequentially deposited, and each wiring of the first wiring group and the second wiring group are deposited.
A multilayer wiring board electrically connected to each wiring of a wiring group via a via-hole conductor filled inside a via hole provided at a predetermined position of the insulating film, wherein the via hole provided in the insulating film is It is characterized in that the wiring width of the first wiring group located immediately below is narrower than the diameter of the via hole, and a gap is provided between the inner wall of the via hole and the end of the wiring of the first wiring group.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing an embodiment in which the multilayer wiring board of the present invention is applied to an LED head.
The head is on a substrate 1 made of glass, ceramic, etc.
LED array L1 consisting of 64 LED elements mounted on each
~ L40, a shift register 5 for serially transferring the image signal from the printer body in the LED head, a latch 6 for holding the image signal stored in the shift register 5 for a predetermined period, and a strobe signal Is supplied, a predetermined power is supplied to the gates A1 to A64 which generate a predetermined output according to the image signal of the latch 6 and the respective LED elements of the LED arrays L1 to L40 according to the outputs of the gates A1 to A64. Constant current circuits B1 to B64 to be supplied, and switching transistors T1 to T40 for controlling on / off of currents flowing through the LED arrays L1 to L40 according to a selection signal from the printer body.
It has a structure in which and are arranged. Further, such an LED head includes a drive circuit (shift register 5, latch 6, gate
In order to integrate A1 to A64 and constant current circuits B1 to B64) and to simplify the bus line used for supplying data, LED elements are blocked in array units and time-division driven. First connected to constant current circuits B1 to B64
The wiring 2 of the wiring group X and the wiring 4 of the second wiring group Y1 to Y40 connected to the LED elements of the LED arrays L1 to L40 are multi-layered, and these are electrically connected to each other at a predetermined position in the thickness direction to obtain a desired shape. The wires are electrically connected. still,
In the case of the LED head shown in the figure, the above-mentioned connection points reach a total of 2560 points.

Next, the above-mentioned first wiring group X and second wiring group Y1
The connection structure with Y40 will be described with reference to FIG.

FIG. 2A is an enlarged plan view of the Z portion of FIG.
2B is a sectional view taken along the line A′-A ′ of FIG. 2A, in which 1 is a substrate, 2 is wiring of the first wiring group X, 3 is an insulating film, 3a is a via hole, and 4 is a second wiring group. Wiring for Y1 to Y40.

A wiring 2, an insulating film 3 and a wiring 4 are sequentially deposited on the substrate 1, and the wiring 2 and the wiring 4 are filled in a via hole 3a provided at a predetermined position of the insulating film 3. They are electrically connected via a via hole conductor (a part of the wiring 4).

The wiring 2 and the wiring 4 are arranged in directions orthogonal to each other, and the wiring 2 is formed to have a constant width (50 μm).

Each of the wirings 2 and 4 adopts a thick film method such as a well-known plating method or screen printing, and is made of a metal material with a predetermined thickness (the thickness of the wiring 2 is 1 to 4 μm).
m, the thickness of the wiring 4 is 1 to 4 μm).

On the other hand, the insulating film 3 interposed between the two wirings 2 and 4 has a via hole 3 having a diameter φ (0.4 mm) larger than the width w1 of the wiring 2 at the intersection of the wirings 2 and 4.
a is provided, and the wiring 2 and the wiring 4 are electrically connected through the via hole 3a.

Further, as the insulating film 3, a photosensitive resin such as a photosensitive epoxy resin, or a sheet processed from such a resin is used. For example, when the photosensitive epoxy resin is used, Substrate 1 to which wiring 2 is attached
A photosensitive epoxy resin, which has been liquefied by adding and mixing an organic solvent or the like, is applied to the upper surface of the coating to a predetermined thickness (50 μm) by a spin coat method or a roll coater method, and then the liquid photosensitive epoxy resin is applied. By irradiating ultraviolet rays through an exposure mask to photo-cure the irradiated portion and removing the non-photo-cured portion with an alkaline developing solution to form a via hole 3a.

At this time, the width w1 of the wiring 2 located immediately below the via hole 3a is smaller than the diameter φ of the via hole 3a, and a gap is provided between the inner wall of the via hole 3a and the end of the wiring 2. Therefore, a recess surrounded by the upper surface of the substrate 1, the peripheral surface of the via hole 3a, and the side surface of the wiring 2 is formed on the bottom of the via hole 3a, so that the organic solvent 3b contained in the photosensitive epoxy resin is formed. Even if the organic solvent 3b oozes out from the inner circumference of the via hole 3a, these organic solvents 3b are effectively prevented from accumulating in the above-mentioned depression and adhering to the upper surface of the wiring 2. As a result, when the wiring 4 is deposited on the wiring 2 in the via hole 3a in a later step, the wirings 2, 4
Almost no organic solvent 3b is interposed between the wiring 4 and
Can be satisfactorily adhered to the upper surface of the wiring 2 over a wide area. Thereby, the wiring 2 and the wiring 4
Can be reliably and satisfactorily electrically connected via the via hole 3a.

In this case, it is not necessary to separately deposit a photoresist for forming the via hole 3a on the insulating film 3 or to perforate the insulating film 3 with a drill or the like. Therefore, it is possible to simplify the manufacturing process of the multilayer wiring board.

The effect of the present invention becomes greater as the number of via holes formed on the substrate, such as the LED head described above, is greater. However, the present invention is not limited to such an embodiment, and the present invention is not limited thereto. Various modifications and improvements can be made without departing from the spirit of the invention.

Further, in the above embodiment, the description has been given by taking the example of the multilayer wiring board having the two-layer wiring in which the two wiring groups are interconnected via the insulating film, but the insulating film is interposed between the three or more wiring groups. It is also applicable to a multilayer wiring board having a laminated structure of three or more layers in which these are interconnected.

Further, in the above-mentioned embodiment, the wiring width of the first wiring group is made constant and equalized inside and outside the via hole. However, the wiring width of the first wiring group located immediately below the via hole is smaller than the diameter of the via hole. As long as it is narrower, the wiring width of the first wiring group inside and outside the via hole is not specified at all. For example, the wiring width of the first wiring group may be wider outside the via hole than inside. Absent.

[0021]

According to the multilayer wiring board of the present invention, even if the organic solvent or the like contained in the insulating film oozes out from the inner periphery of the via hole, these hardly adhere to the wiring in the via hole. The plurality of wiring groups can be reliably and satisfactorily electrically connected through the via holes of the insulating film.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an LED head to which the present invention is applied.

2A is an enlarged plan view of a Z portion of FIG. 1, and FIG. 2B is a sectional view taken along the line A′-A ′ of FIG.

3A is a partially enlarged plan view of a conventional multilayer wiring board, and FIG. 3B is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Wiring of 1st wiring group 3 ... Insulating film 3a ... Via hole 3b ... Organic solvent 4 ... Wiring of 2nd wiring group

Claims (1)

[Claims] 1. A first wiring group consisting of a plurality of wirings, a second wiring group consisting of an insulating film and a plurality of wirings are sequentially deposited on a substrate, and each wiring of the first wiring group and a second wiring. A multilayer wiring board electrically connected to each wiring of the group via a via hole conductor filled in a via hole provided at a predetermined position of the insulating film, which is directly below the via hole provided in the insulating film. A multilayer wiring board characterized in that the wiring width of the first wiring group located at is narrower than the diameter of the via hole to provide a gap between the inner wall of the via hole and the end of the wiring of the first wiring group.