JP2585337B2 - High frequency circuit board device - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a high-frequency circuit board device in which a circuit board on which a printed circuit is mounted is housed in a shield case, and particularly to a signal input / output terminal. The present invention relates to a high-frequency circuit board device which is capable of forming a feedthrough capacitor used as an electromagnetic wave shielding element in the above-mentioned method with a high shielding effect and in a simple process.

(Prior Art) When a high frequency circuit board device such as a tuner or a high frequency module is mounted on an electronic device such as an audio video device,
The entire circuit board is housed in a shield case and the input / output terminals are placed in a state that penetrates through capacitors installed on the shield case to prevent electromagnetic waves leaking from the circuit frequency and electromagnetic waves leaking from the circuit itself. I do. Thereby, the noise component is guided to the shield case (earth) through the feedthrough capacitor, and the superimposition of the noise on the voltage source and the signal is suppressed.

As shown in FIGS. 4 (a) and 4 (b), a generally used feedthrough capacitor is formed by using an annularly formed ceramic dielectric 2 having a through hole 1 in the center. In the dielectric 2 shown in FIG. 4, electrodes 3 are formed on both surfaces orthogonal to the through hole 1 as shown in FIG. 5 (a), and tin is further formed as shown in FIG. 5 (b). A lead wire 4 made of a plated conductive wire is inserted into the through hole 1, and the protruding portion is soldered to the electrode 3 with solder 5. In the feedthrough capacitor from which the lead wire 4 has been drawn out, the lead wire 4 is inserted into the side wall of the shield case 6 and soldered or bonded with a conductive adhesive 7 to form a fifth capacitor.
The configuration is as shown in FIG.

When the present invention is applied to an actual circuit, it is attached to the shield case 6 as shown in FIG.

FIG. 6 shows a configuration in which the thick film substrate is housed in the shield case 6, and the same parts as those in FIG. 5 are denoted by the same reference numerals.

In FIG. 6, reference numeral 8 denotes an insulating substrate on which a wiring conductor 9 and a resistor 10 are formed by a thick film technique. At a predetermined position of the insulating substrate 8, a through hole 11 through which the lead wire 4 of the feedthrough capacitor is inserted is formed. As shown in FIG. 5, the lead wire 4 of the feedthrough capacitor attached to the shield case 6 is electrically connected to the wiring conductor 9 by the solder 5 inserted into the through hole 11 and further faces the mounting side. The terminal portion 12 is formed through the flat side wall of the shield case.

However, since the feedthrough capacitor shown in FIG. 6 protrudes from the shield case 6, it has a problem in appearance.

In the manufacturing process, as shown in FIG. 5, after the feedthrough capacitor is formed (attached) to the shield case 6, the lead wire is wired when the printed circuit board is housed in the shield case as shown in FIG. This is a complicated operation of connecting conductors.

FIG. 7 is an equivalent circuit diagram of the feedthrough capacitor of FIG. 6. As can be seen from this circuit diagram, the feedthrough capacitor is on the opposite side of the terminal portion 12. That is, the feedthrough capacitor is divided into one side, and the terminal portion 12 is divided into the other side around the connection point between the lead wire 4 and the wiring conductor 9. Such a structure is not optimal in view of the electromagnetic wave shielding effect. That is, the electromagnetic wave shielding effect is higher when the feedthrough capacitor is located between the terminal portion 12 and the connection point.

(Problems to be Solved by the Invention) As described above, the conventional feedthrough capacitor forming technology has a structure in which the original purpose (electromagnetic wave shielding) is not sufficiently achieved, and the forming process is complicated. was there.

An object of the present invention is to provide a high-frequency circuit board device which does not require a special process for forming a feedthrough capacitor and has a high electromagnetic wave shielding effect.

[Structure of the Invention] (Means for Solving the Problems) A high-frequency circuit board device according to the present invention includes an insulating substrate, at least a first conductor fixed to the insulating substrate, and the first conductor.
A dielectric layer formed on the first conductor, and a second conductor fixed to the dielectric layer while being opposed to the first conductor, wherein one of the first and second conductors is provided. Is connected to a signal line via a through hole from the front surface to the back surface of the insulating substrate, and the other is electrically grounded at least on the insulating substrate via a dielectric layer surrounding the through hole. And

(Function) According to the present invention, since the feedthrough capacitor portion is formed on the substrate side accommodated in the shield case, it protrudes from the connection point between one electrode of the feedthrough capacitor portion and the wiring conductor and from the shield case. The terminal portion is opposed to the terminal portion with the feedthrough capacitor portion interposed therebetween, and a circuit configuration having an excellent electromagnetic wave shielding effect is obtained. Further, since the feedthrough capacitor portion can be formed simultaneously with other capacitors, a special process is not required for forming the feedthrough capacitor. Moreover, by providing a through hole in the center of the feedthrough capacitor,
The signal lines can be routed from the front surface of the substrate to the back surface without taking up extra space.

(Examples) Hereinafter, the present invention will be described based on examples shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of the high-frequency circuit board device of the present invention.

In this figure, reference numeral 24 denotes a lead terminal constituting an input / output terminal portion, 26 denotes a shield case for housing a high-frequency circuit board, and 28 denotes an insulating substrate such as an alumina substrate. Insulating substrate
On 28, a silver / palladium-based conductor paste is printed by a screen printing method and baked at 900 ° C. for 1 hour to form lower conductor layers 29 a and 29 b on both surfaces of the insulating substrate 2. At this time, a through-hole 33 is formed in the substrate 28 in advance, and a conductor layer 29c is also formed on the inner periphery of the through-hole 33 in order to make the both surfaces of the substrate conductive, thereby forming a through-hole.

Next, the dielectric layers 31a and 31b are formed using a high dielectric constant ceramic paste.At this time, the dielectric layer 31a for the high frequency circuit bypass capacitor and the dielectric layer 31b for the feedthrough capacitor are formed using the same material. Printing at the same time, 1 at 900 ℃
It was formed by firing in air for hours. Next, the dielectric layers 31a, 31
In b, the upper electrode 32 was formed by a screen printing method under the same conditions as above using a silver / palladium-based conductor paste of the same material as above. Thereafter, baking is performed at 850 ° C. for 1 hour using a ruthenium oxide-based resistor paste to form a thick-film resistor 30, and a chip component 34 such as a transistor is soldered and mounted on a substrate. Next, the lead terminal 24 having the holding portion is press-fitted into the end of the insulating substrate 28, and the upper portion of the terminal is soldered to the upper electrode 32 with solder 35.

Then, the high-frequency circuit board configured as described above is
A part of the lead terminal 24 is housed in the shield case 26 so as to be led out, and the lower electrode of the feedthrough capacitor is
29a and the shield case 26 are connected by solder 36. In addition,
The through-hole conductor layer 26c can be formed when the upper electrode 32 is printed.

In the above embodiment, the through hole is provided at the center of the feedthrough capacitor, and the signal line can be routed from the substrate surface to the rear surface without taking extra space. Further, since the through hole is provided at the center of the feedthrough capacitor, the electromagnetic shielding effect can be significantly improved in the electrical connection between the front surface and the back surface via the through hole. In addition, the bypass capacitor and the feedthrough capacitor can be formed at the same time, and the manufacturing process can be greatly simplified.

FIG. 2 is a plan view showing an example of the feedthrough capacitor section of the high-frequency circuit board. The feedthrough capacitor portion is formed, for example, in a rectangular shape, and a connection portion 29a 'for connecting to a shield case is formed at one end of the lower conductor layer 29a. At this time, for example, the upper electrode 32 has a size of 2.2 mm square,
The volume value was 3500 pF.

The mounting area of the feedthrough capacitor according to the present embodiment can be formed to be approximately half or less the area of the conventional one having the same capacity.

FIG. 3 shows an equivalent circuit diagram of the feedthrough capacitor corresponding to FIG. As is apparent from a comparison between the equivalent circuit diagram of FIG. 7 and the equivalent circuit diagram of FIG. 7, the feedthrough capacitor of FIG. 7 has the capacitor portion on the opposite side to the terminal portion 12, whereas the feedthrough capacitor of the present embodiment has the terminal portion. Since the feedthrough capacitor is located between the portion 24 and the wiring line 29b, the electromagnetic wave shielding performance is good.

[Effects of the Invention] As described above, the feedthrough capacitor forming process can be simplified, and the electromagnetic wave shielding effect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the high-frequency circuit board device of the present invention, FIG. 2 is a plan view showing a main part of the high-frequency circuit board in FIG. 1, and FIG. FIG. 4 is an explanatory view showing a ceramic dielectric used for a conventional feedthrough capacitor, FIG. 5 is an explanatory view showing a manufacturing process of a conventional feedthrough capacitor, and FIG. 6 is a conventional high frequency circuit board device FIG. 7 is an equivalent circuit diagram of the feedthrough capacitor of FIG. 24 Lead terminal, 26 Shield case, 28 Insulating substrate, 29a, 29b Lower conductor layer, 29c Through-hole conductor layer, 31a Dielectric layer of bypass capacitor, 31b Through capacitor Dielectric layer of 35,36 …… Solder.

Claims (1)

(57) [Claims] An insulating substrate, at least a first conductor fixed to the insulating substrate, a dielectric layer formed on the first conductor, and a dielectric layer arranged opposite to the first conductor and facing the first conductor. A second conductor fixed on a layer, wherein one of the first and second conductors is connected to a signal line via a through hole from the front surface to the back surface of the insulating substrate, and the other is at least the insulating material. A high-frequency circuit board device which is electrically grounded on a substrate via a dielectric layer surrounding the through hole.