JPH0246076Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to electrical shielding of circuit boards, etc. that constitute high-frequency circuits, and particularly relates to a shielding structure suitable for circuit boards that are constituted of microstrip lines. .

[Background of the idea]

Figure 1 shows an example of shielding a high-frequency circuit board using a box-shaped shield structure in which a conductor layer is formed using plating technology on a heat-resistant synthetic resin.

Figure 1 is a cross-sectional view showing the shield structure, where 1 is a dielectric substrate, 2 is a microstrip line, 3 is a ground conductor, 4 is a synthetic resin box, 5 is a first conductor layer, and 6 is a first conductor layer. 2 represents a conductor layer, and 7 represents a solder layer.

In Figure 1, a high frequency circuit is constructed with a microstrip line 2 using a dielectric substrate such as alumina ceramic, a heat-resistant synthetic resin 4 is molded into a box shape, and then plating technology is used to form a high frequency circuit. This is to obtain an electrical shield by a shield structure in which the first conductor layer 5 is made of copper, and the second conductor layer is made of a metal having good solderability and corrosion resistance, such as chrome.

The conductors of the microstrip line 2, including the ground conductor 3, are made of metal with good conductivity to prevent circuit losses (conductor loss, loss due to radiation, etc.)
It is necessary to reduce it as much as possible. However, in the example shown in FIG. 1, since a metal with low conductivity such as chrome is used as the second conductor layer 6, the loss of the conductor having the same potential as the ground facing the high frequency circuit increases.
This causes increased loss in the circuit. Second
It is conceivable to use copper or silver as the conductor layer, but gold is not a suitable conductor material due to chemical changes such as corrosion resistance, and gold is cost-effective.

[Purpose of invention]

The purpose of this invention is to reduce loss in high frequency circuits,
The objective is to provide a shield structure with good corrosion resistance at a low price.

[Summary of the idea]

As a base when metal plating synthetic resin,
Focusing on the fact that a conductor layer is generally formed from electroless plated copper and a desired metal is formed on it by electroplating, etc., the copper used as the base is used as part of the conductor of the shield. It is.

[Example of idea]

An embodiment of the present invention is shown in FIG. 2 as a cross-section of the shield structure. Components having the same functions as those in FIG. 1 are given the same numbers, and explanations thereof will be omitted. 8 is a first conductor layer, and 9 is a second conductor layer.

The first and second conductor layers are different from the case shown in FIG. 1, and the shielding conductor is not disposed on the side of the box 4 molded from synthetic resin that faces the high frequency circuit where the microstrip line is formed. Instead, from the high-frequency circuit, the first conductor layer formed by electroless plating exists as a conductor of the same potential as the ground through the synthetic resin box 4. , Therefore, if the conductor thickness is sufficient to satisfy the skin thickness at the frequencies used in high-frequency circuits, the loss in the first conductor layer is sufficiently small;
Loss in high frequency circuits can be reduced. Note that since almost no high-frequency current flows through the second conductor layer, a conductor that is effective in various properties other than electrical properties such as corrosion resistance can be used. For the first conductor layer, if the thickness of the conductor formed by electroless plating is insufficient, further copper is formed by electroplating to increase the thickness of the conductor layer and the skin thickness. make sure that you are fully satisfied with the
This can be further electroplated with chrome or the like to protect the conductor surface.

To obtain the shield structure shown in Figure 2, the first
The portion of the shield structure shown in the figure facing the high frequency circuit may be selectively etched, or may be formed selectively when forming the conductor layer.

[Effect of idea]

According to the present invention, by shielding the high frequency circuit with a conductor layer formed on synthetic resin using plating technology and having low cost, low loss, and good corrosion resistance,
It is possible to improve the performance of high frequency circuits.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a conventional example of a shield structure.
FIG. 2 is a sectional view of a shield structure according to an embodiment of the present invention. 1... Dielectric substrate, 2... Microstrip line, 3... Ground conductor, 4... Synthetic resin, 5, 8
...First conductor layer, 6, 9...Second conductor layer, 7
...Solder.

Claims (1)

[Scope of utility model registration request] In a shield structure that electrically shields a circuit board on which a high frequency circuit is configured,
A shield structure comprising: a heat-resistant resin layer disposed on a side facing a high-frequency circuit; and a plurality of conductor layers disposed on the opposite side of the heat-resistant resin layer that does not face the high-frequency circuit.