JP2504456B2 - Circuit board device - Google Patents

Description

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. And a high-frequency circuit board device capable of forming a feedthrough capacitor used as a shield element in the electromagnetic wave shield in a simple process.

(Prior Art) When electronic equipment such as audio / video equipment is equipped with high-frequency circuit board equipment such as tuners and high-frequency modulators, in order to prevent electromagnetic interference from surrounding circuits and electromagnetic wave leakage from the circuit itself, the entire circuit board Is housed in a shield case, and the input / output terminal portion is arranged so as to pass through a feedthrough capacitor installed on the shield case.
As a result, the noise component is guided to the shield case (earth) through the feedthrough capacitor, and the noise superposition on the voltage source and the signal is suppressed.

A commonly used feedthrough capacitor is constructed by using a ceramic dielectric body 2 formed in an annular shape having a through hole 1 at the center, as shown in FIGS. 7 (a) and 7 (b). As shown in FIG. 8 (a), the dielectric 2 shown in FIG. 7 has electrodes 3 and 3 formed on both surfaces orthogonal to the through hole 1 and, as shown in FIG. 8 (b), tin-plated. A lead wire 4 made of a conductive wire is inserted into the through hole 1 and its protruding portion is soldered to the electrode 3 with the solder 5. The feedthrough capacitor from which the lead wire 4 is drawn is constructed as shown in FIG. 2C by inserting the lead wire 4 into the side wall of the shield case 6 and soldering or adhering it with a conductive adhesive 7.

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

FIG. 9 shows a circuit device constructed by housing a thick film substrate in a shield case 6 to form a feedthrough capacitor. The same parts as those in FIG. 8 are designated by the same reference numerals.

Reference numeral 8 is an insulating substrate on which the wiring conductor 9 and the resistor 10 are formed by the thick film technique. A through hole 11 through which the lead wire 4 of the feedthrough capacitor is inserted is provided at a predetermined position of the insulating substrate 8.
Are formed. The lead wire 4 of the feedthrough capacitor attached to the shield case 6 as shown in FIG.
A terminal portion 12 is formed by being inserted into 11 and electrically connected to the wiring conductor 9 by the solder 5, and further penetrating the flat side wall of the shield case facing the mounting side.

However, since the feedthrough capacitor shown in FIG. 9 projects from the shield case 6, it is defective in appearance.

Further, in the manufacturing process, as shown in FIG. 8, after the feedthrough capacitor is formed (attached) to the shield case 6, as shown in FIG. This is a complicated work of connecting the wiring conductors.

Also, FIG. 10 is an equivalent circuit of the feedthrough capacitor of FIG. 9, but as can be seen from this circuit diagram, the feedthrough capacitor is
The feedthrough capacitor is provided on one side with the opposite side of the terminal portion 12, that is, the connection point between the lead wire 4 and the wiring conductor 9 as the center.
Twelve is split on the other side. Such a structure is not optimal in view of the electromagnetic wave shielding effect. In other words, the feedthrough capacitor has a higher electromagnetic wave shielding effect when it 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 technique has a structure in which the original purpose (electromagnetic wave shield) is not sufficiently achieved, and the forming process is complicated. There was an inconvenience.

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) The present invention is configured by accommodating a thick film circuit board in which a through capacitor portion is formed together with an ordinary bypass capacitor in a shield case.

(Operation) According to the present invention, since the feedthrough capacitor portion is formed on the side of the substrate housed in the shield case, it is projected from the connection point between one electrode of the feedthrough capacitor portion and the wiring conductor and from the shield case. The terminal section and the terminal section face each other with the feedthrough capacitor section sandwiched between them, and the electromagnetic wave shielding effect is optimized. Further, since the feedthrough capacitor can be formed simultaneously with other capacitors, no special process is required for forming the feedthrough capacitor.

(Embodiment) The embodiment of the present invention shown in FIG. 1 will be described below.

In FIG. 1, (a) is an insulating substrate such as an alumina substrate.
The insulating substrate 21 has a shaft hole 22 for inserting a lead wire of a feedthrough capacitor. The shaft hole 22 is formed by, for example, carbon dioxide laser beam.

Next, as shown in FIG. 1B, wiring conductors 23 and 23 'are formed on both surfaces of the insulating substrate 21 by a method such as screen printing using silver-palladium-based paste. After that, as shown in FIG. 1C, the thick film capacitor layers 24 and 24a are formed by a dielectric paste having a high dielectric constant.

Here, the wiring conductor 23 constitutes an ordinary wiring pattern, and the wiring conductor 23 'serves as the lower electrode of the feedthrough capacitor. The thick film capacitor layers 24, 24 are dielectric layers for feedthrough capacitors, and are formed in, for example, a square shape. Incidentally, 24a is a dielectric layer for another capacitor.

The insulating substrate 21 on which the thick film capacitor layers 24, 24a are formed in this manner is formed on the thick film capacitor layer 24 for feedthrough capacitors as an upper electrode on the wiring conductor 25, and on the thick film capacitor layers 24a for normal capacitors as well as the upper part. The wiring conductor 25a as an electrode is formed (see FIG. 1d). In the present embodiment, when the wiring conductors 25 and 25a shown in FIG.
Firing is performed in an atmosphere of 0 ° to 950 °.

In addition, with respect to the insulating substrate 21 of FIG. 1 (d), FIG.
Resistor 26 is formed as shown in, and firing is performed at 850 ° C.

FIG. 1 (f) shows a finished product of the high-frequency circuit board device according to this embodiment, in which each thick film layer is formed as shown in FIG. 1 (f).
Discrete parts 32 such as chip parts are soldered to the baked insulating substrate 21 and housed in the shield case 27. However, the lead wire 28 is inserted into the shaft hole 22 and connected to the wiring conductor 23 by the solder 29 before the insulating substrate 21 is housed in the shield case 27. Also, the lead wire 28 and the wiring conductor 25
Is also soldered as the other electrode of the feedthrough capacitor, and the shield case 27 and the wiring conductor 23 'are soldered by the wire L. Furthermore, when the insulating substrate 21 is housed in the shield case 27, the lead wire 28 is projected to the outside of the case through the terminal portion projecting hole 30 formed in the shield case 27, and the projecting portion constitutes the terminal portion 31. ing.

The high frequency circuit board device according to this embodiment is configured as described above. As described above, since the feedthrough capacitor can be formed simultaneously with the formation of another capacitor by using the thick film technique, the forming process is simplified, and the feedthrough capacitor portion (the lower electrode 23 ', the thick film capacitor layer 24, the upper electrode 25) is housed inside the shield case 27 and does not project as in the conventional case.

FIG. 2 is an explanatory view for explaining the planar shape of the feedthrough capacitor, and a plurality of feedthrough capacitors are formed assuming an actual high frequency circuit. The same parts as those in FIG. 1 are designated by the same reference numerals. As shown in FIG. 2, the present embodiment does not have a circular ring shape as in the prior art, but has a well shape, but of course, it may have a circular ring shape. Incidentally, using a high dielectric constant paste as in this embodiment, the area of the lower electrode 23 'is 2.0 m
m ^□ , plane area of thick film capacitor layer 24 is 2.4 mm ^□ , upper electrode
When the area of 25 and 2.2 mm ^□, capacity after calcination of FIG. 1 (d) are obtained those 2500~3500P F.

Further, FIG. 3 shows an equivalent circuit of the present feedthrough capacitor corresponding to FIG. As is clear from comparison between this equivalent circuit diagram and the equivalent circuit diagram of FIG. 10, in the feedthrough capacitor of FIG. 10, the capacitor portion is on the opposite side of the terminal portion 12,
In the feedthrough capacitor according to the present embodiment, the feedthrough capacitor is located between the terminal portion 31 and the wiring line 33, and the electromagnetic wave shielding performance is good.

Moreover, 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. 4 is a sectional view showing another embodiment of the present invention.
4, the same members as those in FIG. 1 are designated by the same reference numerals, and the characteristic configuration is that the embodiment of FIG.
While 31 is extended from the upper flat portion of the shield case 27, in this embodiment, the terminal portion 31 is extended from the end side surface of the shield case 27. In this case, the lead wire 41 supports the insulating substrate 21 inside the shield case, and the terminal portion 31 through the terminal portion projecting hole 30 formed on the end side surface.
The part that becomes is protruding. In addition, the upper electrode 25 of the feedthrough capacitor part should not come into contact with the lead wire 41 in the case.
The insulating layer 43 is formed.

The second characteristic of this embodiment is that the lead wire 41 is not directly connected to the insulating substrate 21 with the wiring conductor 23 '(lower electrode). Therefore, it is not necessary to form a shaft hole for inserting the lead wire 41 in the insulating substrate 21, and instead, the lead wire 41 is formed so that the solder 42 enters the center of the square shape and the wiring conductor 23 ′. Connected to.

The upper electrode 25 of the feedthrough capacitor is soldered to the shield case 27 by a wire L from the end of the substrate.

FIG. 5 shows the planar shape of the feedthrough capacitor of FIG.
The part surrounded by the two-dot chain line part is the insulating layer 43, the part surrounded by the one-dot chain line is the thick film capacitor layer 24, the dotted line part shown as these lower members is the lower electrode 23 ', and the solid line part is the upper electrode 25. .

Further, FIG. 6 shows an equivalent circuit of the feedthrough capacitor of FIG. 4, and it can be seen that the circuit structure is the same as that of FIG. 3 and the electromagnetic wave shielding effect is enhanced.

As described above, according to the present invention, the feedthrough capacitor forming process can be simplified.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram showing an embodiment of a high-frequency circuit board device according to the present invention, and FIGS. 2 and 3 are plan views and equivalent circuit diagrams for illustrating the device of FIG. 1 in detail. FIG. 4 is a sectional view showing another embodiment of the present invention, FIGS. 5 and 6 are plan views and an equivalent circuit diagram for explaining the apparatus of FIG. 4 in detail, and FIGS. 7 and 8 are conventional. 9 and 10 are explanatory views for explaining the method of forming the feedthrough capacitor of FIG.
It is sectional drawing and an equivalent circuit diagram which show an example of the conventional high frequency circuit board device in which the feedthrough capacitor was formed by the method of the figure. 21 ... Insulating substrate, 23, 23 ', 25 ... Wiring conductor, 24 ... Thick film capacitor layer, 27 ... Shield case, 30 ... Hole for projecting terminal part, 31 ... Lead wire.

Claims (1)

(57) [Claims] 1. An inorganic insulating substrate, a first film conductor formed on the insulating substrate, a film dielectric formed on the first film conductor, and a first film conductor that are arranged to face the first film conductor. A second film conductor formed on the film dielectric layer, wherein one of the first and second film conductors is connected to a signal line and the other is the dielectric layer on the insulating substrate. A circuit board device characterized in that a part of a signal line is surrounded by an electric ground.