KR19990019503A - Package of Surface Acoustic Wave Filter - Google Patents

Abstract

A package of a surface acoustic wave filter for removing electromagnetic unwanted signal waves of a SAW filter package, the frame being surface-treated with a metal extending in a direction perpendicular to the base along the base and the edge of the base, and formed outside the base. A package of a surface acoustic wave filter comprising a plurality of metal pads, a ground portion of a metal plating layer formed inside the base, and to which a surface acoustic wave filter is attached, and a lid for sealing the surface acoustic wave filter. Has an input terminal IDT and an output terminal IDT formed on one surface of the piezoelectric body, and a blocking bar positioned between the input terminal IDT and the output terminal IDT, and the ground portion of the metal plating layer is electrically connected to a portion corresponding to the position where the blocking bar is installed. Ground part of the metal plating layer to which surface acoustic wave elements are attached so as to separate This dielectric waveguide function formed between the package and the mounting surface acoustic wave device as it is lost because they form the cut to be electrically isolated from a portion has electromagnetic-free signal can be significantly attenuated as it passed to the output at the input IDT IDT.

Description

Package of Surface Acoustic Wave Filter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package of a surface acoustic wave (SAW) filter, and more particularly, to a package of a surface acoustic wave filter having improved SWA filter characteristics by reducing the effects of electromagnetic feed-through.

The SAS filter is a piezoelectric filter, which enables direct multipoint driving and reception on the surface, and because the substrate is a support, it is excellent in shock resistance and impact resistance, and can be independently controlled in amplitude and phase. It is excellent and is widely used as an intermediate frequency filter.

In the typical SAW filter, as shown in FIG. 1, an input terminal IDT (inter-digital transducer) 12 and an output terminal IDT 13 are formed on a piezoelectric body 11, and an input impedance Rs is formed at the input terminal IDT 12. An input signal Vs having a signal is applied, and an output impedance Ro is connected to the output terminal IDT 13, and an absorber 14 for absorbing reflected waves is provided.

The detailed view of the input terminal IDT 12 and the output terminal IDT 13 is as shown in FIG. 2, and the IDT used for the input / output terminal is a withdrawal weighting type, the input terminal IDT 12 and the output terminal IDT. On one side of (13), an input port 15 and an output port 16 are provided, and on the other side, a ground terminal 17 is provided.

In order to reduce electromagnetic feed-through, a rod-shaped blocking bar 18 is disposed between the input terminal IDT 12 and the output terminal IDT 13 to have a slight inclination. Both ends of 18) are connected to the ground plane.

3A to 3D are detailed views of a typical SMD (Surface Mounted Device) package for mounting the SAW filter described above, where FIG. 3A is the back of the package, FIG. 3B is the side of the package, and FIG. 3C is the lid The plane of the package in the excited state, Figure 3d shows the plane of the package with the lid open, respectively.

The SMD package includes a base portion 20 formed of ceramic, a frame 21 extending in a vertical direction with the base portion 20 along the edge of the base portion 20 and plated on a surface thereof, and formed outside the base portion 20. Two gold plated pads 22, a ground portion 23 formed of a metal plating layer inside the base portion 20, and a lid 24 for sealing the mounted filter. The SAW filter is mounted on the ground 23 of the SMD package. Reference numeral 25 is a pad connection terminal.

In the conventional SAW filter, when a high frequency electric field is applied to the input terminal IDT 12, the surface acoustic wave is excited by a piezoelectric action, and the surface acoustic wave is transmitted to the output terminal IDT 13 via the surface of the piezoelectric body 11, The output stage IDT 13 converts the high frequency electric field back to the high frequency electric field by the anti-piezoelectric action to transmit the electric signal.

When a high frequency electric field is applied to the input terminal IDT 12 to generate a surface acoustic wave, and when the surface acoustic wave is transmitted via the piezoelectric body 11 surface, it is electrically or radiated energy from the input terminal IDT 12 to the output terminal IDT 13 side. Electromagnetic feed-through occurs, which is delivered directly in form.

This occurs because the input terminal IDT 12 and the output terminal IDT 13 are in close proximity. As the applied frequency increases, the generation of the electromagnetic unnecessary signal increases, and this electromagnetic unwanted signal is the sound wave which is the basic operating principle of the SAW filter. Unlike the energy transmitted by the light, it is transmitted at the speed of light, so this electromagnetic unwanted signal interferes with the surface acoustic wave and deteriorates the characteristics of the surface acoustic wave filter.

This electromagnetic unwanted signal is mainly caused by two causes. One of the causes is that the upper and lower surfaces of the package are generally conductors, and the piezoelectric material formed by the SAW filter is a steel dielectric. A strong dielectric exists between the formed input / output IDT and the package to have a dielectric waveguide shape, thereby generating an electromagnetic unnecessary signal.

At this time, since the signal transmitted through the dielectric waveguide is a close wave (leaky wave) or the input terminal IDT and the output terminal IDT are very close, the energy transmitted by the electromagnetic unnecessary signal is relatively large compared to other secondary effects.

Another cause is due to radiation occurring between the IDT and the bonding wire of the input / output terminal.

Since the junction line and the input / output terminal IDTs actually act as antennas, electromagnetic unwanted signals are generated by radiating electromagnetic waves within the package of the SAW filter.

As a prior art for increasing or decreasing the electromagnetic unnecessary signal, as shown in FIG. 2, a blocking rod 18 of a metal conductor is provided at a predetermined angle on the surface of the piezoelectric body 11 between the input terminal IDT 12 and the output terminal IDT 13. And to ground both ends of the blocking bar (18).

According to such a configuration, the electromagnetic unnecessary signal transmitted from the input terminal IDT 12 to the output terminal IDT 13 via the piezoelectric body 11 surface is absorbed by the blocking bar 18 to attenuate the electromagnetic unnecessary signal. .

However, since the SAW filter package according to the prior art installs only a blocking bar, only some of the electromagnetic unnecessary signals flowing through the surface of the piezoelectric body can be removed, which causes some of the electromagnetic unnecessary signals to interfere with the surface acoustic wave, thereby lowering the filter characteristics. There is this.

Accordingly, it is an object of the present invention to provide a package of surface acoustic wave filters that improves filter characteristics by completely attenuating electromagnetic unwanted signals.

1 is a view schematically showing a conventional surface acoustic wave filter,

2 is a detailed view of an input terminal IDT and an output terminal IDT of the surface acoustic wave filter;

3a to 3d is a view showing a package of a conventional surface acoustic wave filter,

4A to 4D are views showing a package of the surface acoustic wave filter of the first embodiment of the present invention;

5 is a view schematically showing a second embodiment of the present invention;

6A and 6B schematically show a third embodiment of the present invention.

* Explanation of symbols for main parts of the drawings

10 surface acoustic wave filter 11 piezoelectric body

12: input terminal IDT 13: output terminal IDT

14: sound absorbing material 15: input port

16: output port 17: ground terminal

18: blocking bar 20,30: bottom

21,31: frame 22,32: pad

23,33: ground portion 24,34: lid

35: pad connection part 36: cutting part

40: surface acoustic wave 41: input terminal IDT

42: output stage IDT 43: blocking bar

44: blocking wire 50: measuring jig

51: input stage 52: output stage

53: ground plane 54: cutout

The package of the surface acoustic wave filter of the present invention includes a frame surface-treated with a metal extending in a direction perpendicular to the base portion along a base portion and an edge of the base portion, a plurality of metal pads formed outside the base portion, and formed inside the base portion. And a ground portion of the metal plating layer to which the surface acoustic wave filter is attached, and a cover body for sealing the surface acoustic wave filter, wherein the surface acoustic wave filter comprises an input terminal IDT and an output terminal formed on one surface of the piezoelectric body. An IDT and a blocking bar positioned between the input terminal IDT and the output terminal IDT are provided, and the ground portion of the metal plating layer is configured to electrically separate a portion corresponding to the position where the blocking bar is installed.

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described concretely based on an accompanying drawing.

4A to 4D schematically show a package of the surface acoustic wave filter of the first embodiment of the present invention, in which FIG. 4A is a back side of the package, FIG. 4B is a side view of the package, FIG. 4C is a plan view of the package, and FIG. 4D is The plane of the package with the lid open is shown respectively.

The surface acoustic wave filter package of the first embodiment of the present invention has a base portion 30 which is a dielectric such as ceramic, and extends perpendicularly to the base portion 30 along the edge of the base portion 30, as shown in FIGS. 4A to 4D. The surface 31 is plated with a metal such as a metal, a plurality of metal pads 32 for grounding and signal connection in the outer direction of the base part 30, and a metal plating layer formed inside the base part 30, and the surface acoustic wave device A ground portion 33 to which a SAW filter (not shown) is attached, a pad connection portion 35 for connecting the ground portion 33 to the pad 32 formed outside the package, and sealing the SAW element. A lid 34 is provided, wherein the ground portion 33 is a central portion corresponding to an installation position of the blocking bar 18 formed between the input terminal IDT 12 and the output terminal IDT 13 of the SAW element described above. A cutout 36 is formed which is electrically separated from each other.

According to the surface acoustic wave filter package of the present invention, the surface acoustic wave filter 10 is attached to the ground portion 33 thereof, and then, the surface acoustic wave filter is packaged using the lid 34.

According to the configuration of the present invention, when the electromagnetic unnecessary signal is transmitted from the input terminal IDT 12 of the surface elastic filter to the output terminal IDT 13, the electromagnetic unwanted signal is not only absorbed by the blocking bar 18, but also the blocking. Waveguide function is lost by the cutout portion 36 provided near the rod 18 and cut to electrically separate the ground portion 33 forming part of the waveguide, and to the output terminal IDT 13 side. It is possible to block the propagation of the electromagnetic unnecessary signal by further increasing the attenuation of the electromagnetic unnecessary signal to be propagated.

FIG. 5 shows a second embodiment of the present invention, in which the second embodiment of the surface acoustic wave filter 40 has both ends just above the blocking bar 43 positioned between the input terminal IDT 41 and the output terminal IDT 42. Except for further providing a grounding shielding wire 44, the same reference numerals are given to the same parts, and the detailed description thereof will be omitted.

According to the second embodiment of the present invention configured as described above, when the electromagnetic unnecessary signal propagates from the input terminal IDT 41 of the surface acoustic wave filter 40 to the output terminal IDT 42, as in the above-described first embodiment, 43) and the cut-off portion not only attenuate the propagation of the electromagnetic unnecessary signal, but also the electromagnetic unnecessary signal propagated to the output terminal IDT 42 through the air by the antenna action of the bonding wire 44 or the like to the blocking wire 44. Absorption can further attenuate the propagation of electromagnetic unnecessary signals.

6A and 6B illustrate a third embodiment of the present invention, in which the present invention is applied to a measuring jig for measuring a surface acoustic wave filter, which is typically used when measuring the characteristics of a surface acoustic wave filter or adapting to a system. The ground surface 53 formed on the back surface of the measuring jig substrate 50 having the input terminal 51 and the output terminal 52 is shared by the input terminal 51 and the output terminal 52, and thus the input terminal 51 and the output terminal 52 are shared. The ground plane 53 of) is electrically connected.

Therefore, the "-" current on the input side flowing through the ground plane 53 of the measuring jig flows to the output side to generate an induced current, and an electromagnetic unnecessary signal is generated by the induced current.

Therefore, the present embodiment is configured to electrically cut the ground plane of the input terminal and the output terminal by forming a cut portion 54 for electrically separating the central portion of the ground plane 53.

In this configuration, since the above-described induction current is not generated, propagation of the electromagnetic unnecessary signal can be greatly attenuated.

As described above, according to the present invention, since the cutout portion is formed to electrically disconnect a part of the ground portion of the metal plating layer to which the surface acoustic wave element is attached, the electromagnetic unnecessary signal propagated through the dielectric waveguide function between the surface acoustic wave element and the package mounted thereon It can greatly attenuate the transmission from the input terminal IDT to the output terminal IDT. Moreover, when a blocking wire is installed on the blocking bar, it can also attenuate the propagation of electromagnetic unnecessary signals propagated through the air, thereby preventing the filter from passing through the filter. The surface acoustic wave filter having excellent performance can be realized by increasing attenuation in a band and reducing ripple that may occur in a pass band.

Claims (2)

A frame surface-treated with a metal extending in a direction perpendicular to the base portion along the base portion and the edge of the base portion, a plurality of metal pads formed outside the base portion, and a metal plating layer formed inside the base portion and to which a surface acoustic wave filter is attached. In the package of the surface acoustic wave filter comprising a grounding portion and a lid for sealing the surface acoustic wave filter, The surface acoustic wave filter includes an input terminal IDT and an output terminal IDT formed on one surface of the piezoelectric body, and a blocking rod positioned between the input terminal IDT and the output terminal IDT. The ground portion of the metal plating layer package of the surface acoustic wave filter, characterized in that configured to be electrically separated from the portion corresponding to the position where the blocking rod is installed. The method of claim 1, Package of a surface acoustic wave filter characterized in that it further comprises a blocking wire which is spaced apart at a predetermined interval on the blocking bar and both ends are grounded.