JPH03241790A - Multilayer circuit substrate - Google Patents

Abstract

PURPOSE:To obtain a shield effect for a multilayer circuit substrate itself by providing a simple conduction pattern at an inner layer substrate. CONSTITUTION:A circuit pattern is formed on circuit pattern formation surfaces 1a-1d and conduction patterns for grounding 2a-2d are formed at each outer periphery, thus forming a grounding wire for circuits by a circuit pattern. Also, a specified number of through-holes 3 are provided from a part where the conduction pattern for grounding 2a-2d of the circuit pattern formation surfaces 1a-1d in each inner-layer substrate and the conduction patterns for grounding 2a and 2b, the conduction patterns for grounding 2b and 2c, and the conduction patterns 2c and 2d for grounding are connected one another, thus enabling the conduction pattern for grounding to be placed with a narrow gap which is equal to the thickness of an inner-layer base at the outer periphery of the outer-layer circuit substrate and enabling these to operate as a shield member in a direction which is in parallel to the surface of the multilayer circuit base.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multilayer circuit board suitable for use in thin electronic devices such as semiconductor memory cards.

[Conventional technology]

In electronic devices such as semiconductor memory cards that have a built-in multilayer circuit board with electronic components and memory mounted inside the housing, it is necessary to prevent the generation of static electricity due to the intrusion of electromagnetic waves from the outside and the release of unnecessary radiation from the inside to the outside. Shielding measures are taken to prevent this.

As a conventional shielding method, a metal nameplate is heat-bonded to a plastic side wall member of the casing as a top plate and a bottom plate, and these metal nameplates are fixed to a ground potential. However, even with this method,
A considerable amount of unnecessary radiation was emitted from the inside through the side wall member between the metal nameplates, and a sufficient shielding effect could not be obtained.

In contrast, a method has also been proposed in which the outer periphery of one or both of the metal cotton material serving as the top plate and the metal cotton material serving as the bottom plate is bent toward the side wall member.

2 According to this, the bent portion of the metal nameplate partially shields the top of the casing and between the bottom plates, thereby reducing the emission of unnecessary radiation from the side surface of the casing.

[Problem to be solved by the invention]

However, the above method of increasing the shielding effect by bending the metal nameplate requires bending the metal nameplate, which complicates the structure of the casing, increasing costs and reducing productivity. was there.

Furthermore, in semiconductor memory cards, characters and patterns such as product names and manufacturing company names are printed on the surface of a metal cotton material having a large area. By the way, when manufacturing a casing by bending a metal nameplate, the new curved part is integrally molded by inserting it into the plastic side wall member, but this molding simply involves folding the flat metal nameplate into the side wall member. This is done by heating at a sufficiently higher temperature than when adhering to a surface.

Therefore, if an attempt is made to integrally mold the printed metal nameplate and the side wall member, the printing will be blown off due to high temperature heating, resulting in a poor appearance. Therefore, it is conceivable to print on the metal nameplate of the manufactured casing, but this printing is extremely difficult and would lead to an increase in cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer circuit board that solves these problems and can enhance the shielding effect with a simple structure.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a multilayer circuit board in which a plurality of inner layer base materials each having a circuit pattern formed thereon are laminated, and a grounding conductive pattern is provided on the outer periphery of each of the inner layer base materials.

[For production]

On the outer periphery of the multilayer circuit board, grounding conductive patterns are arranged at narrow intervals equal to the thickness of the inner layer base material, and these conductive patterns act as a shield member in a direction parallel to the surface of the multilayer circuit base material.

Therefore, when this multilayer circuit board is installed in a case with a metal nameplate adhered to a plastic side wall member, the arrangement of the above-mentioned grounding conductive patterns acts as a shielding member for the side wall of the case, and together with the metal nameplate. , shielding of the entire interior of the casing is achieved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing an embodiment of a multilayer circuit board according to the present invention, in which 1a to 1d are circuit pattern forming surfaces of an inner layer base material, 2a to 2d are conductive patterns for grounding, 3 are through holes, and 4a -4d is a cutting part.

This example will be explained assuming that four inner layer substrates are laminated. However, for the sake of simplicity, only the surface on which the circuit pattern is formed (circuit pattern forming surface) of the inner layer substrate will be explained. It shows.

In FIG. 1, circuit pattern forming surface 1a+1b+lc
, ld have a circuit pattern (not shown) formed thereon, and a grounding conductive pattern 2a on the outer periphery of each.
, 2b, 2c, and 2d are formed, and serve as grounding lines for the circuit formed by the circuit patterns on the circuit pattern forming surfaces 1a, lb, lc, and Id. In addition, a predetermined number of through holes 3 are provided in each inner layer board from the portions of the circuit pattern forming surface 1a+1b+1c+1d where the grounding conductive patterns 2a, 2b, 2c, and 2d are formed. Filled with a conductive material, the grounding conductive patterns 2a and 2b, the grounding conductive patterns 2b and 2c, and the grounding conductive patterns 2c and 2d are electrically connected, respectively.

With this configuration, on the outer periphery of this multilayer circuit board, the grounding conductive patterns 2 are arranged at narrow intervals equal to the thickness d of the inner layer base material.
a, 2b, 2c, and 2d are arranged, and by fixing them to the ground potential, these circuit patterns are eliminated from unnecessary radiation generated from the circuit patterns on the circuit pattern forming surfaces 1b, lc, and ld. Surface 1b, Ic, Id
A shielding effect is obtained that blocks the emission of components parallel to the outside.

Therefore, such a multilayer circuit board, like the previous conventional example,
Even when a flat metal nameplate is installed in a housing made by adhering to a plastic side wall member, the shielding effect of these grounding conductive patterns 2a, 2b, 2c, and 2d prevents unnecessary radiation from the side wall member. release to the body will be suppressed.

In addition, regarding unnecessary radiation generated from the circuit pattern on the circuit pattern forming surface 1a, the grounding conductive pattern 2a,
2b, 2c, and 2d have no shielding effect, but when this multilayer circuit board is placed in the above-mentioned case, the gap between the metal cotton material as the top plate and the metal nameplate as the bottom plate is smaller than the distance between the metal nameplates as the top plate and the bottom plate. Since the distance from the circuit pattern forming surface 1a (therefore, the grounding conductive pattern 2a) becomes narrower, due to the shielding effect caused by this, the circuit pattern generated from the circuit pattern forming surface 1a passes through the plastic side wall member. The emitted unnecessary radiation is reduced to some extent.

Further, each of the grounding conductive patterns 28 to 2d has a U-shape, but may be formed over the entire surface of the circuit pattern forming surfaces 1a to 1d. However, when a connector pattern is provided on one side of the uppermost circuit pattern forming surface 1a, it goes without saying that the grounding conductive pattern 2a is formed around the area other than this part.

By the way, these grounding conductive patterns 28 to 2d have a shielding effect as described above, but because of their U-shaped shapes, they also produce an antenna effect, which causes electromagnetic waves from the outside to be treated as noise. There is a risk of receiving it. When noise is received in this way, the grounding conductive pattern 28
The potential at ~2d varies from the ground potential, and distortion may occur in No. 18 processed by the circuits on the circuit pattern forming surfaces 1a~ld.

In order to prevent this, cutting portions 4a to 4d are provided in each of the U-shaped grounding conductive patterns 28 to 2d, for example, at positions that are symmetrical points of shape.

As a result, each of the grounding conductive patterns 2a to 2d consists of two parts each having a shape different from the U-shape.
Antenna effects are significantly reduced.

In addition, cutting portions 4 are provided on each of the grounding conductive patterns 28 to 2d.
When 8 to 4d are provided, the above-mentioned unnecessary radiation generated inside is emitted to the outside through these cutting parts 48 to 4d, reducing the shielding effect. In order to compensate for this, as shown in FIG.
What is necessary is to short-circuit the cut portion 4a.

Here, cut portions 41) on the grounding conductive patterns 28 to 2d.
4d means that the resistance value of the portion where these cutting portions 48 to 4d are provided is almost zero, and the shielding effect is maximized, but the antenna effect is also maximized. In addition, cut portions 4 are provided on the grounding conductive patterns 28 to 2d.
Providing the cutting portions 4a to 4d means that the cutting portions 4a to 4d are
Since d is an infinite resistance value, the antenna effect is minimized, but the shielding effect at the cut portion is also minimized.

Therefore, as shown in FIG. 2, a grounding conductive pattern 2a
When the cut portion 4a of
The antenna effect and shielding effect are increased compared to when only 4d is provided. Therefore, by appropriately setting the resistance value of the resistive element 5 in consideration of the balance between the antenna effect and the shielding effect, it is possible to suppress the antenna effect and obtain a good shielding effect.

- Although the resistive element 5 is provided only in the grounding conductive pattern, it may be provided in other grounding conductive patterns as well.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a simple conductive pattern on the inner layer board, the multilayer circuit board itself can have a shielding effect, and the shielding means for the casing in which the multilayer circuit board is built. This increases the degree of freedom in designing the casing, improving productivity, and greatly easing restrictions on pasting and printing decorative stickers on the outside of the casing. .

[Brief explanation of drawings]

FIGS. 1 and 2 are block diagrams showing embodiments of a multilayer circuit board according to the present invention, respectively. ■a to 1d...Circuit pattern forming surface, 2a to 2d...
・Grounding conductive pattern, 3...Through hole, 48~
4d... Cutting portion, 5... Resistance element. 10

Claims (4)

[Claims] (1) A multilayer circuit board formed by laminating a plurality of inner layer base materials provided with circuit patterns, characterized in that a grounding conductive pattern is provided on the outer periphery of each of the inner layer base materials. (2) In claim (1), a through hole is provided on the outer periphery of each of the inner layer base materials, and the grounding conductive patterns on the inner layer base materials are electrically connected to each other via the through holes. Multilayer circuit board. (3) The multilayer circuit board according to claim (1) or (2), wherein the grounding conductor pattern has one or more cutting portions. (4) The multilayer circuit board according to claim (3), wherein the cut portion is short-circuited via a resistive element.