JP2003060324A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesion between an electrically conductive resin material and the wall surface of a through-hole in a substrate or a copper-foil circuit part on the substrate in a printed wiring board, constituted by filling and hardening the electrically conductive resin material (electrically conductive paste) in the through-hole. SOLUTION: Through-holes 3A, 3A divided and partitioned into a plurality of slots are made by laser processing using holes 2C, 2C formed in a conductor pattern 2 of a surface layer as a mask. The electrically conductive resin material (electrically conductive paste) 4 is filled and is made to harden in respective slots 3A, 3A.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a double-sided flexible printed board, a double-sided printed board, a multilayer printed board, a multilayer printed board, etc. (hereinafter referred to as a printed wiring board).

[0002]

2. Description of the Related Art In recent years, electronic devices such as portable information terminals and notebook computers have been widely used for flexible printed boards and multilayer printed wiring boards for the purpose of space saving as the electronic devices have become smaller and higher in density. ing.

In a conventional multilayer printed wiring board, copper-clad laminated substrates are integrally laminated, wiring patterns are formed on both surfaces thereof, and inner layer wiring patterns are provided between insulating layers.

In these wiring patterns, the through holes formed in the thickness direction of the laminated substrate are plated with conductive metal through holes to electrically connect the inner layer wiring patterns to each other or between the inner layer wiring patterns and the surface wiring patterns. Are configured to connect together.

However, a multilayer printed wiring board having a through-hole structure has a problem that it is difficult to cope with miniaturization of portable electronic equipment because it is necessary to secure a region for forming a through-hole.

For this reason, recently, it is not necessary to specially provide a region for forming a through hole in place of the above-mentioned multilayer printed wiring board having a through hole structure, and it is easy to miniaturize and increase the density of electronic equipment. A printed wiring board having a structure having a via hole that can be realized is adopted.

As this type of printed wiring (1)
7-170046, (2) JP-A-8-316598, (3)
As disclosed in JP-A-2000-40862, a substrate laminated with copper foil and / or a through hole formed in a laminate of these substrates is filled with a conductive resin composition (conductive paste),
It has a cured structure.

[0008]

However, in the structure in which the through hole is filled with the conductive resin composition (conductive paste) and cured, the conductive resin composition and the through hole wall surface of the substrate and / or Or, the adhesion to the copper foil circuit portion on the board is poor. Therefore, in the above-mentioned (1) Japanese Patent Application Laid-Open No. 7-170046, unevenness is formed on the wall surface of the through hole of the substrate to improve the adhesion with the conductive resin composition. Further, in the above (2) Japanese Patent Application Laid-Open No. 8-316598, a third insulating resin having good adhesion to the conductive resin composition is provided on the substrate to improve mutual adhesion. .

Further, in the above (3) Japanese Patent Application Laid-Open No. 2000-40862, a large number of depressions are provided in the land portion of the metal foil circuit on the surface of the substrate, and the depressions are utilized to form a conductive resin composition. To improve the adhesion.

According to the present invention, the conductive resin composition filled in the through hole, the through hole, and the through hole can be formed without special processing of the wall surface of the through hole, adoption of the third resin, or special processing of the circuit land portion. It is an object of the present invention to provide a printed wiring board with improved adhesion to a circuit on a board.

[0011]

A first problem solving means according to the present invention is formed by laminating one or a plurality of substrates each having a wiring pattern on one side or both sides, and the wiring patterns are electrically connected to each other. A through hole communicating with a selected portion to be formed is punched, a conductive resin composition is filled in the through hole, and the selected portions of the wiring pattern are electrically connected to each other. It is configured to be divided into a plurality of elongated holes along the axial direction.

The second means for solving the problem is constructed so that the tip portions of the plurality of elongated holes reach the surface of at least one wiring pattern.

A third problem-solving means is that the tips of the plurality of elongated holes reach the surface of at least one of the wiring patterns, and a part of the surface of the wiring pattern is covered with the conductive resin composition. Further, the conductive resin composition and its wiring pattern are integrally joined.

The function of the first problem solving means is that the conductive resin composition is filled in the elongated holes divided into a plurality of sections, so that the contact area between the conductive resin composition and the wall surface of the through hole is increased. Then, the conductive resin composition is more securely fixed to the through holes.

Further, even if one of the plurality of long holes has a poor electrical contact state, it is possible to ensure the electrical continuity of the other long holes.

The operation of the second means for solving the problem is effective for the structure of the via hole.

The operation of the third means for solving the problems can make the mechanical and electrical contact between the wiring pattern and the conductive resin composition more reliable.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

1 and 2 show a first embodiment of the present invention, which is an epoxy resin, a polyimide resin, a ceramic, a glass cloth epoxy resin, a glass nonwoven cloth epoxy resin, a glass cloth bismaleimide triazine resin. A metal foil 2 laminated on both sides of an insulating substrate 1 obtained by curing an aramid nonwoven fabric epoxy resin or the like into a plate shape is subjected to a surface treatment such as etching, and the first wiring pattern 2A and the second wiring pattern 2A of a predetermined conductor circuit are formed. The wiring pattern 2B is formed.
At this time, it is necessary to electrically connect the first wiring pattern 2A and the second wiring pattern 2B to each other, and the metal foil is removed by etching at the selected connection portion to form the fine hole 2C.

The shape of the fine holes 2C has a shape in which a circle or a rectangle is divided into a plurality of sections as a whole, as described later.

Further, the through holes 3 are formed in the insulating substrate 1 by a laser drilling method using an excimer laser, a carbon dioxide gas laser or the like with a copper foil of a wiring pattern surrounding the fine holes 2C as a mask (conformal mask). Is perforated.

As shown in FIG. 6, the through hole 3 has a partition wall 1A having a rectangular or circular shape such as a square or a rectangle as a whole.
Is divided into a plurality of long holes 3A.

For example, the through hole 3 may be partitioned by a partition wall 1A having a cross shape to form four independent long holes 3A. In addition, the shape of the partition is
It can be divided into two and Y shapes and can be divided into two and three. Further, as shown in FIGS. 6 (h) and 6 (i), it may be constituted by a curved partition wall 1A.

On the other hand, since the copper foil has a large reflection coefficient for laser light, it functions as a mask and the fine holes 2
When the through hole 3 (long hole 3A) is dug from C, the second wiring pattern 2B acts as a stopper, so that the second wiring pattern 2B is not perforated by the laser light.

A conductive resin composition 4, for example, a conductive paste of copper, silver, gold, carbon or the like is applied by a printing method to each of the plurality of long holes 3A forming the through holes 3 punched as described above. Filled and cured. At this time, by appropriately selecting the shape and size of the holes of the printing screen of the electrically conductive resin composition 4, the electrically conductive resin composition 4 becomes the fine holes 2
It can be applied so as to cover a part of the copper foil of the wiring pattern surrounding C. That is, as shown in FIG. 1D, the conductive resin composition 4 covers a part of the copper foil surrounding the fine holes 2C to form a via hole.

In the above embodiments, a double-sided printed wiring board having a single substrate has been described, but the invention can also be applied to a well-known multilayer printed wiring board, a multilayer flexible printed circuit board or the like in which a large number of these are laminated. Can be done. In this case, the conventional through-hole and IVH (Interst
It can be used instead of itial via hole) plating.

FIG. 3 shows a second embodiment of the present invention, in which the second wiring pattern 2B at the bottom of the elongated hole 3A in the first embodiment also communicates with the elongated hole 3A. 2C is perforated and the conductive resin composition 4 is applied to the substrate 1
Via holes are formed by extending and filling the inside of each long hole 3A until the height substantially coincides with the height of the outer surface of the wiring pattern on both surfaces. Therefore, the conductive resin composition in this portion has a plurality of via holes formed by partition walls 2D formed in the wiring patterns 2A and 2B.

FIG. 4 shows a third embodiment of the present invention, in which a through hole is formed only in the portion of the substrate 1 sandwiched between the first wiring pattern and the second wiring pattern to be electrically connected. 3 is perforated, the conductive resin composition 4 is filled in this portion, and the wiring pattern itself is not filled with the conductive resin composition.

FIG. 5 shows a fourth embodiment of the present invention, in which a through hole is formed only in the portion of the substrate 1 sandwiched between the first wiring pattern and the second wiring pattern to be electrically connected. 3 is perforated, and at the end portion of at least one side of each long hole 3A, each long hole is communicated.
That is, the end of each long hole is communicated with the vicinity of the back surface of one wiring pattern, and the communicated portion is enlarged in diameter to form a via hole.

[0030]

According to the first aspect of the invention, since the conductive resin composition is filled in the plurality of elongated holes, the contact area between the conductive resin composition and the wall surface of the through hole is increased, The conductive resin composition is more reliably fixed to the through holes.

Furthermore, even if the electric contact state of one long hole becomes defective, the electric conduction state of the other long hole can be secured, so that the reliability of the product is increased.

According to the second invention, there is an effect that a via hole can be formed by the wiring pattern and the conductive resin composition.

According to the third invention, there is an effect that a mechanical and electrical contact state between the wiring pattern and the conductive resin composition becomes more reliable.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a manufacturing process of a printed wiring board according to a first embodiment of the present invention.

FIG. 2A is a longitudinal sectional view showing a printed wiring board according to a first embodiment of the present invention. FIG. 2B is a plan view showing a printed wiring board according to the first embodiment of the present invention. AA cross section

FIG. 3A is a vertical sectional view showing a printed wiring board according to a second embodiment. FIG. 3B is a plan view showing a printed wiring board according to the second embodiment.

FIG. 4A is a vertical sectional view showing a printed wiring board according to a third embodiment. FIG. 4B is a plan view showing a printed wiring board according to the third embodiment.

5A is a longitudinal sectional view showing a printed wiring board according to a fourth embodiment; FIG. 5B is a sectional view taken along line AA in FIG. 5A; and FIG. 5C is a sectional view taken along line BB in FIG. 5A.

FIG. 6 is a cross-sectional view showing an example of a large number of long holes used in the present invention.

[Explanation of symbols]

1 --- insulating substrate 2 ---- metal foil 2A --- First wiring pattern 2B --- Second wiring pattern 2C --- Micropore 3--through hole 4--Conductive resin composition

Continued front page    F term (reference) 5E317 AA21 AA24 BB02 BB03 BB04                       BB12 BB22 CC25 CD32 GG03                 5E346 AA22 AA43 CC04 CC05 CC09                       CC10 CC16 CC32 DD02 DD12                       DD32 EE04 FF18 GG15 GG22                       GG28 HH11

Claims (3)

[Claims] 1. A single or a plurality of substrates each having a wiring pattern on one or both sides thereof are laminated, and a through hole communicating with a selected portion where the wiring pattern is to be electrically connected to each other is punched. A printed wiring board in which holes are filled with a conductive resin composition and selected portions of the wiring pattern are electrically connected to each other, and the through holes are divided into a plurality of long holes (3A) along the axial direction thereof. A printed wiring board characterized by being partitioned. 2. The printed wiring board according to claim 1, wherein the tips of the plurality of elongated holes (3A) reach the outer surface of at least one of the wiring patterns. 3. The end portions of the plurality of elongated holes (3A) reach the outer surface of at least one wiring pattern, and a part of the outer surface of the wiring pattern is formed by the conductive resin composition (4). The printed wiring board according to claim 1, wherein the printed wiring board is covered and the conductive resin composition and its wiring pattern are integrally joined.