JPH077219U - Surface wave filter mounting structure - Google Patents

Abstract

(57) [Summary] [Object] To provide a surface acoustic wave filter mounting structure capable of surely grounding a surface acoustic wave filter and not deteriorating the characteristics of the surface acoustic wave filter. [Structure] A surface acoustic wave filter 3 is mounted on a filter mounting portion 1a provided integrally with the shield frame 1, and the surface acoustic wave filter 3 is grounded directly to the shield frame 1 via the filter mounting portion 1a, so that a separate grounding is performed. It is possible to reliably prevent deterioration of the characteristics of the surface acoustic wave filter 3 without generating characteristic impedance as in the case of using a member.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a mounting structure of a surface wave filter used in a filter circuit for high frequency signals.

[0002]

[Prior art]

 Conventionally, when mounting a surface acoustic wave filter on a circuit board incorporated in a shield frame, the input terminal, output terminal, and ground terminal of the surface acoustic wave filter are inserted into the through holes of the circuit board, and each of these terminals is connected to the conductor on the back side of the board. Soldered to the pattern. In that case, it is not possible to secure sufficient and stable out-of-band attenuation simply by connecting the ground terminal to the ground pattern of the circuit board, so the surface wave filter case must be grounded separately. Therefore, conventionally, a protrusion for grounding is projected from the shield frame to the surface side of the circuit board to connect to the case of the surface acoustic wave filter, or a part of the surface of the circuit board contacts the bottom surface of the case of the surface acoustic wave filter. There is a dedicated ground pattern for this, or a surface wave filter is mounted on a metal mounting base, and the mounting base is connected to the ground of the circuit board.

[0003]

[Problems to be solved by the device]

 However, when the grounding protrusion is projected from the shield frame, there is a problem that such a grounding member has a high-frequency characteristic impedance and deteriorates the characteristics of the surface acoustic wave filter. This also applies to the dedicated ground pattern provided on the surface of the circuit board and the surface wave filter mounting base. In particular, when the surface wave filter mounting base is used, the number of parts increases and the cost increases. There were also problems.

The present invention has been made in view of the above problems, and an object of the present invention is to reliably ground a surface wave filter without deteriorating the characteristics of the surface wave filter. It is to provide a mounting structure of a surface acoustic wave filter.

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention provides a structure in which a surface wave filter is mounted on a circuit board incorporated in a shield frame, wherein the surface wave filter is integrally formed with the shield frame on the front surface side of the circuit board. A filter mounting part is provided, and the surface wave filter is directly grounded to this filter mounting part.

Further, in claim 2, a space capable of accommodating other components is formed between the filter mounting portion and the circuit board.

[0007]

[Action]

 According to the first aspect, since the surface wave filter is directly grounded to the shield frame through the filter mounting portion, characteristic impedance unlike when a separate grounding member is used does not occur.

According to the second aspect, in addition to the effect of the first aspect, it is possible to accommodate other components in the space formed between the filter mounting portion and the circuit board.

[0009]

【Example】

 1 to 3 show a first embodiment of the present invention. FIG. 1 is a perspective view showing a structure for mounting a surface acoustic wave filter 3 on a circuit board 2 incorporated in a shield frame 1.

The shield frame 1 is made of a conductive plate material formed so as to surround the periphery of the circuit board 2, and shields electromagnetic waves generated in the circuit board 2 from the outside. The shield frame 1 is provided with a filter mounting portion 1a extending horizontally on the surface side of the circuit board 2, and the filter mounting portion 1a is provided with a total of four terminal holes 1b. The filter mounting portion 1a is formed by cutting and raising a part of the shield frame 1 at a right angle from below, and a bent piece 1c extending downward is formed at the tip thereof.

The circuit board 2 constitutes a filter circuit for high frequency signals and the like, and in FIGS. 1 and 2, only a portion where the surface wave filter 3 is mounted is shown, and this portion includes the filter mounting portion 1a. A total of four terminal holes 2a corresponding to the terminal hole 1b and a long hole 2b corresponding to the bent piece 1c are provided.

The surface acoustic wave filter 3 has an outer surface covered with a conductive case 3 a, and a filter element is incorporated therein. The case 3a has a flat lower surface, and two input terminals 3b and two output terminals 3c are provided on the lower surface. The case 3a itself is a ground terminal.

In the above structure, as shown in FIG. 2, the edge of the circuit board 2 contacts the shield frame 1 and the filter mounting portion 1 a of the shield frame 1 is attached to the surface of the circuit board 2. . At this time, the terminal holes 1b and 2a are aligned with each other, and the bent piece 1c of the filter mounting portion 1a is inserted into the elongated hole 2b of the circuit board 2. In this state, the surface acoustic wave filter 3 is mounted on the filter mounting portion 1a, and the terminals 3b, 3c thereof are inserted into the terminal holes 1b, 2a. Then, on the back surface of the circuit board 2, the terminals 3b and 3c and the bent piece 1c of the filter mounting portion 1a are soldered to a predetermined conductive pattern. As a result, the surface acoustic wave filter 3 is directly grounded to the shield frame 1 via the filter mounting portion 1a, and the characteristic impedance that would occur when a separate grounding member is used does not occur.

As described above, according to this embodiment, the surface acoustic wave filter 3 is mounted on the filter mounting portion 1a provided on the shield frame 1, and the surface acoustic wave filter 3 is directly connected to the shield frame 1 via the filter mounting portion 1a. Since it is grounded at the same time, characteristic impedance unlike the case where a separate grounding member is used does not occur, and deterioration of the characteristics of the surface wave filter 3 can be reliably prevented. Further, since the filter mounting portion 1a is formed integrally with the shield frame 1, no other parts are required, which is advantageous in terms of cost. The bent piece 1c may be provided if necessary.

FIG. 3 is an example of a plan view showing the entire circuit board 2. The circuit board 2 is divided into a total of four places by the shield frame 1, one of which is a dedicated space for the surface wave filter 3. It has become. In this case, the filter mounting portion 1a is provided over the entire area within the section in which the surface acoustic wave filter 3 is housed.

4 to 8 show a second embodiment of the present invention, in which a space for accommodating other components is provided between the circuit board 2 and the filter mounting portion 1a. .

That is, the filter mounting portion 1 a is located above the circuit board 2 with a predetermined space, and a space A is formed between the lower surface and the surface of the circuit board 2 as shown in FIG. There is. Along with this, the terminals 3b and 3c of the surface acoustic wave filter 3 and the bent pieces 1c of the filter mounting portion 1a are formed longer than in the above-described embodiment.

Therefore, since the other electronic components B and the like arranged on the circuit board 2 can be accommodated in the space A, the overall size of the circuit board 2 can be reduced.

FIG. 6 shows that a partition 1d integrally formed with the filter mounting portion 1a is provided at substantially the center of the space A. By the partition 1d, the input terminal 3b side and the output terminal 3c side of the surface acoustic wave filter 3 are provided. Since and are isolated at high frequencies, the input and output can be reliably isolated.

7 and 8 show a modification of the filter mounting portion in the second embodiment. The filter mounting portion 1e shown in FIG. 7 is a protrusion provided on the upper end of the shield frame 1. The filter mounting portion 1f shown in FIG. 8 is formed by cutting a part of the shield frame 1 and bending the protruding piece provided at the lower end of the shield frame 1.

[0021]

[Effect of device]

 As described above, according to the surface acoustic wave filter mounting structure of the first aspect, characteristic impedance is not generated unlike the case where a separate member for grounding is used. This can be surely prevented, and the out-of-band attenuation can be sufficiently and stably secured.

According to the surface acoustic wave filter mounting structure of the second aspect, the effect of the first aspect can be achieved, and the overall size of the circuit board can be reduced, so that the circuit device can be downsized. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view of a surface acoustic wave filter mounting structure showing a first embodiment of the present invention.

FIG. 2 is a side sectional view of a surface acoustic wave filter mounting structure.

FIG. 3 is a plan view of a circuit board showing an example of division by a shield frame.

FIG. 4 is a perspective view of a surface acoustic wave filter mounting structure showing a second embodiment of the present invention.

FIG. 5 is a side sectional view of a surface acoustic wave filter mounting structure.

FIG. 6 is a side sectional view of a surface acoustic wave filter mounting structure showing an example in which a partition wall is provided.

FIG. 7 is a perspective view showing a modified example of a filter mounting portion.

FIG. 8 is a perspective view showing another modification of the filter mounting portion.

[Explanation of symbols]

1 ... Shield frame, 1a, 1e, 1f ... Filter mounting part, 2 ... Circuit board, 3 ... Surface wave filter, A ... Space,
B: Electronic component.

Claims (2)

[Scope of utility model registration request] 1. A structure for mounting a surface wave filter on a circuit board assembled in a shield frame, wherein a filter mounting portion integrally formed with the shield frame is provided on a front surface side of the circuit board, and the filter mounting portion has a surface. Surface acoustic wave filter mounting structure characterized in that the wave filter is directly grounded. 2. The surface acoustic wave filter mounting structure according to claim 1, wherein a space capable of accommodating other components is formed between the filter mounting portion and the circuit board.