JPH03214787A - High-frequency circuit board - Google Patents

Abstract

PURPOSE:To contrive to make it possible to obtain a good adhesion between a substrate made of a synthetic resin and a case by a method wherein the title circuit board is provided with the substrate, which is bonded to the surface on the other side of a ceramic substrate with a microwave integrated circuit formed on its surface and is provided with mounting parts to the case and the like outside of its bonding parts to the ceramic substrate. CONSTITUTION:A substrate 5 made of a synthetic resin consisting of a glass fiber fluorine plastic, which consists of such a fluorine plastic as Teflon or the like, and a glass fiber, a glass epoxy resin and the like is bonded to the rear of a ceramic substrate 1 mounted with such components as an IC and the like on its surface side and at the same time, wired with a microstrip conductor on its surface side. The area of the substrate 5 is larger than that of the substrate 1, mounting parts are respectively formed at parts, which protrude from the substrate 1, of the substrate 5, threaded holes 5a for screwing the substrate 5 on a metal case 3 are constituted and the substrate 5 is bonded to the substrate 1 on its surface side with a bonding agent or the like and is fixed on the case 3 on its rear side in such a way as to closely adhere to the case 3 by screwing. Thereby, a crack and peeling are never generated in the substrate 1 and a good adhesion can be reliably obtained between the substrate 5 and the case 3.

Description

Detailed Description of the Invention [Object of the Invention] (Industrial Application Field) The present invention relates to a high frequency circuit board used for signal amplification in the microwave band.

(Prior Art) Generally, in order to reduce the size of the circuit configuration, a high frequency circuit is formed on a high dielectric constant ceramic substrate and housed in a metal case.

The high frequency circuit is constructed by wiring components such as ICs mounted on one surface 1 of the ceramic substrate using microstrip conductors, and forming a ground conductor made of a metal film on the other back surface.

However, the ceramic substrate itself is mechanically fragile, so if it is fixed in a metal case by screws, etc., the mechanical stress applied directly to the substrate during tightening and fixing may cause cracking or peeling. .

Conventionally, as shown in FIG. 3, a ceramic substrate 1 is bonded and fixed to a metal plate 2 called a carrier plate, which has high mechanical strength and also serves as a ground plate, by soldering or the like.
Then, the metal plate 2 was fixed to the metal case 3 with screws 4.

However, since the metal plate 2, which also serves as a grounding plate, is required to have good conductivity, the materials used are limited and the weight is large. Further, due to the rigidity of the metal plate 2 itself, the distortion force generated when fixing with screws directly affects the ceramic substrate 1, causing cracking or peeling, so the size of the substrate 1 itself to which it can be attached is also limited.

2. As shown in FIG. 4, there is also a method in which the ceramic substrate 1 is directly fixed to the bottom of the metal case 3 by soldering or adhesive without using a metal plate. However, even if the ceramic substrate 1 is fixed in the metal case 3, cracks and peeling tend to occur on the substrate l side due to the difference in materials between ceramic and metal. Furthermore, since the fragile ceramic substrate 1 itself is directly bonded to the bottom of the box-shaped metal case 3, there is a drawback that the assembly work is troublesome.

Alternatively, as shown in FIG. 5, there is a method of attaching and fixing the ceramic substrate 1 to the bottom of the metal case 3 via screws 4 using a stopper 4a. However, with this method, it is not easy to obtain sufficient planar accuracy for bonding at the bonding surface between the substrate 1 and the case 3, and also due to aging, mechanical vibration, etc. Since gaps tend to occur between the two, improvements have been requested. If there is a gap between the substrate 1 and the case 3, it will cause an electrical resonance phenomenon or change the impedance characteristics, which will adversely affect the electrical performance of the high frequency circuit.

(Issue 8 to be solved by the invention) When conventional high-frequency circuit boards are housed and fixed in a metal case, due to the unique properties of ceramic substrates, the board may crack or peel when mounted inside the case. However, there was a drawback that good adhesion with the case could not be obtained.

It is an object of the present invention to provide a high frequency circuit board that eliminates the above-mentioned conventional drawbacks, does not cause cracking or peeling of the ceramic board, and can ensure good adhesion to the metal case.

[Structure of the Invention] (Means for Solving the Problems) A high-frequency circuit board according to the present invention includes a ceramic substrate on which a microwave integrated circuit is formed on one substrate surface, and a ceramic substrate bonded to the other surface of the ceramic substrate. The present invention is characterized by comprising a synthetic resin substrate having a mounting portion to the metal case outside the bonding portion of the substrate.

3 (Function) In this invention, a synthetic resin substrate having a mounting portion to a metal case is bonded to the other surface of the ceramic substrate, so the ceramic substrate is bonded to a substrate that has the flexibility inherent to synthetic resin. Therefore, it has the characteristic that it is less subject to mechanical stress such as distortion at the joint site. Also,
Mounting to the metal case is also done by fixing the synthetic resin board, so it can be mounted without directly touching the ceramic board, making the mounting process easy and reducing the chance of torsion or other forces being applied to the ceramic board. A lightweight high-frequency circuit board can be obtained.

(Example) Hereinafter, a first example of a high frequency circuit board according to the present invention will be described.
This will be explained in detail with reference to the figures and FIG.

Components that are the same as the conventional configurations shown in FIGS. 3 to 5 will be described with the same reference numerals.

That is, FIG. 1 is a cross-sectional view showing one embodiment of a high frequency circuit board according to the present invention. A ceramic substrate 1 has components 5 4 such as ICs mounted on the front side, and microstrip conductors are wired on the back side of the ceramic substrate 1. A synthetic resin substrate 5 made of a glass fiber fluororesin made of glass fiber, a glass fiber epoxy resin, or the like is bonded to a fluororesin such as (trade name).

The synthetic resin substrate 5 has a larger area than the ceramic substrate 1, and a mounting portion is formed in a portion protruding from the ceramic substrate 1, and a screw hole 5a for screwing to the metal case 3 is formed.

The outer peripheral surface of the synthetic resin substrate 5 is covered with a good conductive metal film, and it also functions as a conventional carrier plate, and is bonded to the ceramic substrate 1 with an adhesive or the like on the front side, and with screws on the back side. It is fixed in close contact with the metal case 3 by a stopper. The synthetic resin substrate 5 is lightweight and flexible due to the inherent properties of the material, absorbs distortions etc. that occur at the bonding site, and achieves good bonding with the ceramic substrate 1.

Furthermore, even if torsional stress is generated when the synthetic resin substrate 5 is screwed to the metal case 3, it is absorbed by the flexible synthetic resin substrate 5 itself, and the stress is not applied to the ceramic substrate 1 itself. This can prevent the occurrence of cracking, peeling, etc.

Note that the through hole 5b is formed in order to make the ground potential of the ceramic substrate 1 itself more reliable at high frequencies.

Further, the high frequency circuit board according to the present invention is convenient not only for forming only a high frequency circuit, but also for incorporating, for example, a DC bias supply circuit at the same time.

That is, FIG. 2 is a sectional view showing another embodiment of the high frequency circuit board according to the present invention.

The difference from the embodiment shown in FIG. 1 is that the synthetic resin substrate 5
Of these, the area of the portion where the ceramic substrate 1 is not bonded is slightly increased, and bias supply circuit components 6 such as resistors and capacitors are incorporated in that portion.

As a result, conventionally, such DC bias supply circuits, low frequency circuits, etc. were formed on separate printed circuit boards 7, but as in this embodiment, they are formed on synthetic resin substrates 5 in the same case. High-density packaging can be achieved by attaching the device, which is effective for downsizing the entire device.

In addition, 3a is a four part with a space provided to prevent the tip of the terminal from punching through when the bias supply circuit component is attached to the synthetic resin board 5, and the tip coming into contact with the metal case 3, resulting in a short circuit. be.

In addition to the DC bias circuit, other substrates such as synthetic resin substrates may be assembled in multiple layers on the synthetic resin substrate 5 in the same metal case, or multiple ceramic substrates may be assembled and mounted. You may place

In addition, although the ceramic substrate 1 is bonded to only one side of the synthetic resin substrate 5, it is bonded to both sides, and the synthetic resin substrate is mounted and fixed parallel to the bottom surface of the metal case with a gap to achieve high-density mounting. be able to.

[Effects of the Invention] As described above, the high-frequency circuit board according to the present invention is constructed by bonding a synthetic resin board to a ceramic board, so it is lightweight and does not suffer from mechanical stress when mounted on a metal case. Since this is rare, it can be used in various communication devices to achieve remarkable effects.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the high frequency circuit board according to the present invention, FIG. 2 is a sectional view showing another embodiment of the high frequency circuit board according to the present invention, and FIGS. 3 to 5 are respectively conventional FIG. 2 is a sectional view showing a high frequency circuit board of FIG. 1...Ceramics substrate, 2...Metal plate, 3...
・Metal case, 4... Screw, 4a... Fastener, 5... Synthetic resin board, 5a...
・Screw hole, 5b...Through hole, 6・
・Bias supply circuit parts.

Claims (1)

[Claims] It is equipped with a ceramic substrate on which a microwave integrated circuit is formed on one substrate surface, and a synthetic resin substrate that is bonded to the other surface of the ceramic substrate and has an attachment part to a case, etc. outside the bonded part of the ceramic substrate. High frequency circuit board.