JPH07240601A - Connection method for high frequency circuit board - Google Patents

Abstract

PURPOSE:To perform connection stable against temperature fluctuation regardless of the thermal expansion coefficients of a substrate and a metallic base, etc., by forming a conductor for connecting dielectric substrates in a projecting shape on the side of the metallic base to be a circuit common ground. CONSTITUTION:In a high frequency circuit constituted of the metallic base 3 for the circuit common ground, the dielectric substrates 1 for which a conductor pattern for high frequency signal connection is formed and the conductor 4 for the connection for connecting the dielectric substrates 1, the connection is performed by the conductor 4 for the connection formed in a projecting semicircular shape on the side of the metallic base 3. Thus, stress applied to a connection part by the difference of the thermal expansion coefficients of the substrates 1 and the metallic base 3 due to the temperature fluctuation is absorbed at the semicircular part of the conductor 4 for the connection and the connection stable against the temperature fluctuation is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting high frequency circuit boards.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional method of connecting a high frequency circuit board. Substrate 1 which is a dielectric, high frequency signal conductor pattern 2 formed on the substrate, metal base 3, and connecting conductor 4
It is composed by. The board is fixed to the metal base by soldering or screws so that the board electrically connects with the metal base. Both ends of the connecting conductor are fixed to a conductor pattern on the substrate by soldering or a conductive adhesive material.

In such a conventional mounting method, by matching the thermal expansion coefficients of the substrate, the metal base, and the connecting conductor, the stress of the connecting portion caused by the temperature fluctuation is reduced.

[0004]

In the above conventional technique, it is necessary to match the thermal expansion coefficients of the substrate, the metal base, and the connecting conductor. Substrates used for high-frequency circuits are required to have small propagation loss in the high-frequency region, and Teflon, alumina ceramics, etc. are used to meet the demand. Alumina ceramics are often used for high-frequency circuit boards because they are easy to process and suitable for mass production. The coefficient of thermal expansion of this alumina ceramics is 7 × 10
~ A ^{4 K-1,} there is Kovar metal having the same thermal expansion coefficient. However, since the coefficient of thermal expansion of Kovar varies from 5 to 11 × 10 ⁴ K to ¹ depending on the composition ratio, it is necessary to adjust the composition ratio. Therefore, there is a problem that such a material becomes expensive and is difficult to process.

An object of the present invention is to provide a connection method which is stable with respect to temperature fluctuations in the connection of a high frequency circuit board regardless of the thermal expansion coefficients of the board, the metal base and the connecting conductor.

[0006]

In order to achieve the above object, substrates are connected by using a conductor for connection which is formed in a convex shape on the metal base side.

[0007]

In the present invention, the variation in the distance between the substrates, which is caused by the difference in the thermal expansion coefficient between the substrate, the metal base, and the connecting conductor, is absorbed by the convex portion formed in a part of the connecting conductor. It is possible to reduce stress applied to the fixed portion of the board and the conductor for connection, and to realize stable connection with respect to temperature fluctuations.

As a conventional example, the projection of the connecting conductor is shown in FIG.
It is also possible to connect to the metal base side as shown in FIG. This is shown in FIG. However, from the viewpoint of impedance mismatch at the connection portion of the substrate, which is important in the high frequency circuit, it is advantageous to make the convex portion of the connecting conductor on the metal base side. In Figure 4,
A thickness of 0.1 parallel to the ground plane at 10 GHz.
When a conductor for connection having a size of mm, a width of 0.6 mm, and a length of 1.0 mm is provided, the height of the conductor is varied to calculate the VSWR. From the figure, it is understood that the closer the distance between the connecting conductor and the ground plane is, the smaller the VSWR becomes, and hence the impedance mismatch can be reduced. Therefore, when the convex portion of the connecting conductor 4 is on the metal base side, the impedance mismatch is smaller, and it is suitable for connecting the high frequency circuit board.

[0009]

FIG. 1 shows an embodiment of the present invention. Dielectric 1
0, a substrate 1 made of ceramics having a thickness of 0.635 mm
In a configuration in which a high-frequency circuit board formed of a microstrip line 2 having a width of 0.6 mm formed on the metal base 3 is mounted on the metal base 3, a plate-shaped connecting conductor having a width of 0.6 mm, which is the same as the microstrip line This is a method of connecting the substrates by forming a part of 4 into a semicircular shape.
In this embodiment, the stress applied to the connecting portion due to the difference in the thermal expansion coefficient between the substrate and the metal base due to the temperature fluctuation can be absorbed by the semicircular portion of the connecting conductor 4. Further, in order to reduce the impedance mismatch of the connecting portion, the connecting conductor 4 is formed in a plate shape and its width is adjusted to the width of the microstrip line. Further, the convex portion is mounted on the metal base side so that the connecting conductor is close to the ground.

Further, in this embodiment, the shape of the convex portion of the connecting conductor 4 is a semi-circle, but there is no problem as long as it can absorb the expansion and contraction of the substrate due to heat.

[0011]

According to the present invention, it is possible to sufficiently secure the reliability of the connection portion between the substrates due to the temperature fluctuation.
Further, there is an effect that it is possible to suppress the impedance mismatch at the connection portion between the substrates to be small.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a method of connecting a first conventional high-frequency circuit board.

FIG. 3 is a diagram showing a second conventional high-frequency circuit board connection method.

FIG. 4 is a diagram showing a result of calculation of VSWR when a connecting conductor is provided on a ground surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... High frequency circuit board, 2 ... Microstrip line, 3 ... Metal base, 4 ... Conductor for connection.

Claims (1)

[Claims] 1. A metal base serving as a circuit common ground, at least one dielectric substrate having at least one conductor pattern for high-frequency signal connection, and for connecting between the dielectric substrates. In a high-frequency circuit composed of at least one or more connecting conductors, the connecting method is performed by using a connecting conductor formed in a convex shape on the metal base side.