JPH07240659A - Surface mount saw filter - Google Patents

Abstract

PURPOSE:To provide a surface mount SAW filter where sufficient attenuation can be secured outside the pass and without the generation of spurious resonance. CONSTITUTION:In a surface mount SAW filter 10 where an SAW filter of a package type with a lead terminal and a printed board 11 having connection holes 12a to 12d into which the lead terminal is inserted are included, the printed board 11 is provided with external connection terminal 13a to 13f of the terminal end connected with each connection hole via conductive patterns 14a to 14d formed on the rear surface and the areas except the connection holes on the upper surface are covered with conductive material 15, the printed board 11 is provided with shield parts 16a to 16c extending among each connection hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is constructed by mounting a package type electronic component with lead terminals on a printed circuit board by cutting the lead terminals short.
The present invention relates to the structure of surface mount electronic components.

[0002]

2. Description of the Related Art Conventionally, so-called surface mount SAW filters are
For example, it is configured as shown in FIG. That is, FIG.
In the surface mount SAW filter 1, the package type SAW filter 2 with lead terminals is formed by cutting the lead terminals shortly and then mounting the SAW filter 2 on the printed circuit board 3 slightly larger than the SAW filter 2. There is.

The printed circuit board 3 is constructed as shown in FIGS. 8 and 9. That is, the printed circuit board 3 is
Corresponding to the lead terminals extending downward from the SAW filter 2, a plurality of, in the illustrated case, four connection holes 3a, 3b, 3c, 3d are formed so as to penetrate vertically. The inner surface of each of the connection holes 3a to 3d is covered with a conductive material as a through hole.

A plurality of semi-circular cross-sections are provided at the edges of the printed circuit board 3, in the illustrated case, the left and right edges and the upper edges.
In the case shown, the six slits 4a, 4b, 4c, 4d,
4e and 4f are formed. Here, each of the connection holes 3
a, 3b, 3c and 3d are conductive patterns 5a, 5b, 5c and 5d formed on the back surface of the printed circuit board 3, respectively.
Connected to each of the conductive patterns 5a, 5b, 5c,
5d extends to the inner surfaces of the slits 4a, 4b, 4c, 4d, respectively.

Further, the surface of the printed circuit board 3 is covered with solder plating except the regions of the connection holes 3a to 3d, as shown in FIG. Further, as shown in FIG. 9, the back surface of the printed circuit board 3 is covered with solder plating except the region of the conductive pattern. Then, these solder platings extend into the above-mentioned slits 4e, 4f.

As a result, the slits 4a to 4f are formed.
Can be used as an input terminal, an intermediate matching terminal, an intermediate matching terminal, an output terminal, a ground terminal, and a ground terminal, respectively.

[0007]

However, in the surface mount SAW filter 1 configured as described above,
When a multi-stage filter is configured, if an inductor 5 is connected in series between the intermediate matching terminals 4b and 4c as shown in FIG. 10 for matching, the characteristics of the SAW filter 2 may vary depending on the frequency. Connection hole 3a,
Due to the parasitic capacitance generated between the through holes forming 3b, 3c and 3d and the resonance of the inductance 5, there is a problem that spurious is generated in the vicinity of the pass band as indicated by a symbol A in FIG. . Therefore, the inductor 5 is connected in series to the intermediate matching terminals 4b and 4c.
Couldn't get a match by connecting.

In addition, when an inductor is connected in parallel to the SAW filter 2 to obtain matching, there is a problem that a sufficient amount of attenuation outside the pass band cannot be secured.

In view of the above points, the present invention has as its object to provide a surface mount SAW filter capable of ensuring a sufficient amount of attenuation outside the pass band without causing spurious resonance.

[0010]

According to the present invention, the above object includes a package type SAW filter with lead terminals and a printed circuit board having a connection hole into which the lead terminals are inserted. The printed circuit board is provided with the external connection terminals at the edges connected to the connection holes through the conductive pattern formed on the back surface, and the region on the upper surface except the connection holes is covered with the conductive material. ,
The surface mount SAW filter is achieved by the surface mount SAW filter, wherein the printed circuit board includes a shield portion extending between the connection holes.

The surface mount SAW filter according to the present invention comprises:
Preferably, the shield part is composed of a long and thin through hole.

Further, in the surface mount SAW filter according to the present invention, preferably, the shield part is made of a metal material inserted in a notch formed in an elongated shape.

[0013]

According to the above structure, since the connection holes of the printed circuit board to which the lead terminals extending from the package of the SAW filter are connected are shielded from each other by the shield portion, the SAW filters connected to the connection holes are connected. The direct wave between the lead terminals can be suppressed and the capacitance can be reduced. Therefore, even when an inductor is connected in series to the intermediate matching terminal, spurious resonance does not occur and a sufficient amount of attenuation outside the pass band can be secured.

Even when the external matching inductor is unnecessary, the direct wave between the input terminal and the output terminal is suppressed by shielding the input terminal and the output terminal with the shield part. Therefore, a sufficient amount of attenuation outside the pass band can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the embodiments shown in the drawings. 1 and 2 show an embodiment of a surface mount SAW filter according to the present invention. Here, the surface mount SAW filter 10 according to the present invention is shown in FIG.
As in the case of the conventional surface mount SAW filter 1 shown in FIG. 1, the package type SAW filter 2 with lead terminals is cut into short lead terminals, and then the S
It is configured by being mounted on a printed circuit board 11 which is slightly larger than the AW filter 2.

Here, as shown in FIGS. 1 and 2, a plurality of the printed circuit boards 11 are formed so as to vertically penetrate corresponding to the lead terminals extending downward from the SAW filter 2. In this case, four connection holes 12a, 12
It has b, 12c, and 12d. The inner surface of each of the connection holes 12a to 12d is covered with a conductive material as a through hole.

A plurality of slits 13a, 13b, 13 having a semi-circular cross section are provided at the edges of the printed circuit board 11, that is, the left and right edges and the upper edges in the case shown in the figure.
c, 13d, 13e, 13f are formed. Here, the respective connection holes 12a, 12b, 12c, 12d are
The conductive patterns 14a, 14b, 14c, 14d formed on the back surface of the printed circuit board 11 are connected to the respective conductive patterns 14a, 14b, 14c, 14d.
Are slits 13a, 13b, 13c, 13d, respectively.
Extends to the inner surface of.

Further, as shown in FIG. 1, the surface of the printed board 11 is covered with a conductive material 15 such as copper foil or solder plating except for the regions of the connection holes 12a to 12d. In addition, the back surface of the printed circuit board 12 is
As shown in FIG. 2, the conductive patterns 14a, 14b,
Except for the regions 14c and 14d, it is similarly covered with a conductive material 15 such as copper foil or solder plating. And
These conductive materials 15 are the slits 13e, 1 described above.
It extends into 3f.

As a result, the slits 13a to 13 are formed.
f can be used as an input terminal, an intermediate matching terminal, an intermediate matching terminal, an output terminal, a ground terminal, and a ground terminal, respectively.

The above-mentioned structure is similar to the printed circuit board 3 of the conventional surface mount SAW filter 1 shown in FIGS. 8 and 9, but the surface mount SAW filter 1 according to the present invention is used.
At 0, the printed circuit board 11 is further provided with elongated slits 16a, 16b and 16c formed so as to extend between the connecting portions 12a, 12b, 12c and 12d. These slits 16a, 16b and 16c
Like the front and back surfaces of the printed circuit board 11, is covered with a conductive material such as copper foil or solder plating, so that it is configured as a through hole and can function as a shield portion. .

The surface-mounted SAW filter 10 according to the embodiment of the present invention is constructed as described above, and in the case of constructing a multi-stage filter, in order to obtain matching, the intermediate matching terminals 13b and 13c are connected to each other as shown in FIG. As shown, the inductor 17 is connected in series. In this case, since the shield portion due to the slit 16b exists between the intermediate matching terminals 13b and 13c, the direct wave between the intermediate matching terminals 13b and 13c can be suppressed, and the intermediate matching terminals 13b and 13c can be suppressed. Capacity can be reduced.

As a result, the spurious resonance of the inductance 17 does not occur, and therefore the characteristic of the SAW filter is that sufficient attenuation outside the pass band is obtained as shown in FIG. Thus, it is possible to achieve matching by connecting the inductor 17 in series to the intermediate matching terminals 13b and 13c.

Further, the surface mount SAW filter 10 described above.
In the above, even if the inductor 17 for external matching is unnecessary, the input terminal 13a and the output terminal 1
The spaces 3d are shielded by the slits 16a, 16b, 16c. Therefore, since the direct wave between the input terminal 13a and the output terminal 13d is suppressed, a sufficient amount of attenuation outside the pass band can be obtained.

In the embodiment described above, the shield portion between the connection holes 12a, 12b, 12c and 12d is provided with a conductive material on the inner surface so that the slits 16a, 16b and 16c are formed as through holes. Consists of
The configuration is not limited to this, and may be configured as shown in FIGS. 5 and 6, for example.

That is, in FIG. 5 and FIG. 6, the printed circuit board 11 has the respective connection holes 12a, 12b, 12c, 1 thereof.
Slits 16a, 16b and 16 extending between 2d
A metal plate 18 of copper, aluminum or the like is inserted into c,
The printed circuit board 11 is electrically connected to a copper foil covering the front and back surfaces and a conductive material such as solder plating by solder plating or the like.

As a result, the slits 16a, 16b,
16c can act as a shield portion in the same manner as when it is configured as a through hole.

Thus, also in the embodiment shown in FIGS. 5 and 6, as in the case of the embodiment shown in FIGS. 1 and 2, spurious resonance does not occur and a sufficient amount of attenuation outside the pass band is obtained. Thus, a surface mount SAW filter can be constructed.

[0028]

As described above, according to the present invention, S
Since the connection holes of the printed circuit board to which the lead terminals extending from the package of the AW filter are connected are shielded from each other by the shield portion, direct waves between the lead terminals of the SAW filter connected to the connection holes are suppressed. And the capacity can be reduced. Therefore, even when an inductor is connected in series to the intermediate matching terminal, spurious resonance does not occur and a sufficient amount of attenuation outside the pass band can be secured.

Further, even when the inductor for external matching is unnecessary, the direct wave between the input terminal and the output terminal is suppressed by shielding the input terminal and the output terminal with the shield part. Therefore, a sufficient amount of attenuation outside the pass band can be obtained.

Thus, according to the present invention, it is possible to provide a surface mount SAW filter which can secure a sufficient amount of attenuation outside the pass band without causing spurious resonance.

[Brief description of drawings]

FIG. 1 is a plan view of a printed circuit board in an embodiment of a surface mount SAW filter according to the present invention.

FIG. 2 is a bottom view of the printed circuit board shown in FIG.

FIG. 3 is a plan view showing a state in which an inductor is connected to the printed board of FIG.

FIG. 4 is a graph showing characteristics of the SAW filter having the configuration of FIG.

FIG. 5 is a plan view of a printed circuit board in various embodiments of the surface mount SAW filter according to the present invention.

FIG. 6 is a bottom view of the printed circuit board shown in FIG.

FIG. 7 is a schematic perspective view showing an example of a conventional surface mount SAW filter.

8 is a plan view of a printed circuit board in the surface mount SAW filter of FIG.

9 is a bottom view of the printed circuit board of FIG.

10 is a plan view showing a state in which an inductor is connected to the printed board of FIG.

11 is a graph showing the characteristics of the SAW filter having the configuration of FIG.

[Explanation of symbols]

2 SAW filter 10 Surface mount SAW filter 11 Printed circuit board 12a, 12b, 12c, 12d Connection hole 13a, 13b, 13c, 13d, 13e, 13f, 1
6a, 16b, 16c Slit (shield part) 14a, 14b, 14c, 14d Conductive pattern 15 Conductive material 17 Inductor 18 Metal plate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayoshi Kashiwagi 1601 Sakai, Atsugi-shi, Kanagawa Mitsumi Electric Co., Ltd. Atsugi Plant

Claims (3)

[Claims] 1. A package type S with lead terminals
It includes an AW filter and a printed circuit board having a connection hole into which the lead terminal is inserted, and the printed circuit board has an edge connected to each of the connection holes via a conductive pattern formed on the back surface. In the surface mount SAW filter, which is provided with an external connection terminal and whose region on the upper surface excluding the connection hole is covered with a conductive material, the printed circuit board is provided with a shield portion extending between the connection holes. A surface mount SAW filter, characterized in that 2. The surface mount SAW filter according to claim 1, wherein the shield part is an elongated through hole. 3. The shield part is made of a metal material inserted in a notch formed in an elongated shape.
The surface mount SAW filter according to claim 1.