JPH10224174A - Package for high-frequency device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a SAW filter satisfactory in out-of-band attenuating characteristic by forming an LC filter inside of a package on which the SAW filter is mounted, thereby suppressing signal leakage caused by the effects of the package. SOLUTION: A ground electrode 11 is provided by connecting with inter-layer connecting electrodes 5, 7, 8 and 19, LC filter patterns 12 and 13 are provided to be connected with respective inter-layer connecting electrodes 6 and 9, a SAW filter chip 2 is mounted as an upper layer, and terminals 14 and 15 constituting a wire-bonding electrode for a signal and terminals 17 and 19 constituting a wire bonding electrode for the ground are provided. In addition, an upper-layer sealing pattern 30 is provided and the respective layer of these are laminated and integrally baked to constitute a package 1. Then the filter patterns 12 and 13 are designed to make themselves provided with proper inductance L and a capacitance C. Sufficient attenuation characteristic is obtained by a passing out-of-band frequency of a surface acoustic wave filter in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package for a high-frequency device, and more particularly to a package for a high-frequency device for housing elements such as a surface acoustic wave filter.

[0002]

2. Description of the Related Art Conventionally, as a filter for microwave communication used in a wireless communication device or the like, a dielectric filter or SAW has been used.
A filter or the like is used. Particularly, since the SAW filter is small and has a sharp frequency selection characteristic, the demand for the filter corresponding to the miniaturization of the wireless communication device or the like is rapidly increasing at present.

[0003] Here, the SAW filter has an input comb electrode for converting an electric signal input from an input terminal into a surface acoustic wave, and an output for converting the surface acoustic wave into an electric signal and outputting it to an output terminal. The side comb electrode is a surface acoustic wave filter formed on a piezoelectric substrate.
A structure disclosed in Japanese Patent Publication No. 96 is known.

[0004] With the miniaturization of wireless communication devices and the like, devices such as filters used in these devices are becoming more and more chips, and are mounted on surface mount type packages using ceramics such as alumina and LFC. Supplied as

[0005]

However, the conventional SAW filter has the following problems. FIG. 4 shows the frequency characteristics of the SAW filter mounted on the ceramic package. In the figure, the signal level S ₂₁ (dB) is displayed on the vertical axis with respect to the frequency (GHz) on the horizontal axis, and it can be seen that signal transmission is observed in a band slightly smaller than 1 GHz. On the other hand, in the attenuation band on the high frequency side, high frequency signals are transmitted due to the influence of the package, and the attenuation characteristics on the high frequency side are not sufficient.

[0006] This is because a package is usually composed of a ceramic substrate laminated on a conductor pattern formed on each ceramic substrate and electrodes for electrically connecting the laminated substrates. It is considered that the signal was leaked. The mechanism of the signal leakage can be inferred as follows.

FIG. 5 shows an electrical equivalent circuit of the electrode structure provided on the package. Electrical signal entering from the input terminal through an inductance L ₁ of the signal terminals, but to reach the SAW filter, the stray capacitances C ₁ and C ₃ in the middle, partially leaks to the ground terminal. Since the ground electrode is directly connected to the output terminal, the leakage signal is C ₂ and C ₄
To the output terminal. The electrical signal input from the input terminal leak even through the stray capacitance C ₅ to the output terminal.

As described above, the conventional SAW filter has a problem that the out-of-band attenuation characteristics are not sufficient because the electric signal partially leaks due to the electrode structure inside the package.

[0009] Even in the prior art, in order to prevent the deterioration of the attenuation characteristic of a SAW filter caused by mounting on a package, for example, as disclosed in JP-A-5-259793, a part of the electrode structure itself is used. It is proposed to change.

[0010]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem by removing the above-described leakage signal seen in a SAW filter using a filter provided inside a package.

That is, according to the present invention, in order to solve the above-described problems of the prior art, an LC filter using a conductor pattern is inserted into the input terminal and the output terminal inside the package.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the present invention, L
Since the C filter is configured inside the package, the out-of-band frequency component of the input signal is removed by the LC filter on each of the input side and the output side, so that leakage is prevented by the electrode structure provided in the package, The out-of-band attenuation characteristics of the SAW filter can be improved.

[0013]

1 (a) to 1 (f) are structural views of a high frequency device package showing an embodiment of the present invention.

The package 1 is formed by laminating an alumina ceramic, glass ceramic substrate or a plastic substrate, and forming a conductor pattern on each substrate by printing or etching a conductor paste.

As shown in a schematic perspective view in FIG.
In the W filter, the SAW filter chip 2 is die-bonded to the package 1, and the SAW filter chip 2 and the package 1 are bonded to the bonding wires 4-1, 4-2, 4-3, 4-4.
And the package 1 is sealed with a cap 31. FIG. 1B is a bottom view of the package 1.
External terminals 24-26 and external terminals 27-29 are interlayer connection electrodes 5-10
Is provided.

FIGS. 1 (c) to 1 (f) are plan views of the respective laminated portions from the lower side to the upper side. FIG. 1 (c) shows the ground electrode 11
Are connected to the interlayer connection electrodes 5, 7, 8, and 10. In FIG. 1D, LC filter patterns 12, 13 are provided, and are connected to the interlayer connection electrodes 6, 9, respectively. FIG. 1E shows the SAW filter chip 2 as an upper layer.
(Not shown), and are provided with terminals 14 and 15 constituting a wire bonding electrode for signals and terminals 17 and 19 constituting a wire bonding electrode for grounding. FIG. 1F shows a sealing pattern 30 of the uppermost layer. These layers are stacked and integrally fired to form the package 1.

Here, the function of the package 1 according to the present invention, on which the above-described SAW filter chip 2 is mounted and which further includes the LC filter patterns 12 and 13, will be described as follows.

First, as shown in FIG. 1A, the SAW filter chip 2 has an input comb electrode 3-1 for converting an electric signal input from an input terminal 20 onto a piezoelectric substrate into a surface acoustic wave.
And an output-side comb-shaped electrode 3-2 for converting a surface acoustic wave into an electric signal and outputting the electric signal to the output terminal 22.

The input electrode 20 of the SAW filter chip 2
21, output side electrodes 22 and 23 are bonding wires 4-
1, 4-2, 4-3, and 4-4 are connected to terminals 14, 17, 15, and 19 provided on the package 1, respectively. Of these terminals, signal terminals 14 and 15 are connected to filter patterns 12 and 13 provided inside the package 1 through through holes and the like of the package 1, respectively. 1 are connected to external terminals 25 and 28 provided outside. The grounding terminals 16, 17, 18, and 19 are connected to the interlayer connection electrodes 5,
External terminals 2 of the package 1 via 7, 8, and 10 respectively
4, 26, 27 and 29 are connected. Filter pattern 1
2 and 13 are designed to have appropriate inductance L and capacitance C themselves.

FIG. 2 is a detailed view of an example of the filter pattern shown in FIG. 1D. For example, a width W = 0.2 mm, a = 1.0 mm, and b = on a ceramic substrate having a thickness h = 0.2 mm. 1.0 m
m, c = 0.6 mm, d = 0.6 mm filter patterns 12, 13
As a result, an LC low-pass filter having an input / output impedance Z of 50Ω and a cutoff frequency of 1 GHz can be formed as described later.

It goes without saying that the filter pattern is not limited to this shape, and an optimum one can be selected according to the shape and size of the package. The position where the package 1 is arranged is not limited, and the package 1 may be arranged above or below the package 1 via a through hole. In that case, the filter pattern shape is 3
Efficient design can be achieved by calculating the characteristics in advance by a three-dimensional electromagnetic field simulation or the like. The method of deriving the values of L and C of the LC filter provided according to the present invention is performed as follows.

FIG. 3 shows an electrical equivalent circuit of a package electrode structure in which an LC filter is formed inside a package according to the present invention. By adding capacitances C ₇ and C ₆ and inductances L ₁ and L ₂ on the input side and the output side, respectively, they function as LC filters.
As can be seen, for example, on the input side, the values of the inductance L ₁ , the stray capacitance C _1, and the capacitance C ₇ are

[0023]

(Equation 1)

An LC low-pass filter having a cutoff frequency f and an input / output impedance Z can be formed by appropriately selecting the above formulas. The same can be calculated for the output side terminal.

For such an LC low-pass filter, the cut-off frequency f is set higher than the pass band frequency and inserted into the input / output terminals, whereby the out-of-band attenuation characteristics can be improved.

Here, for example, the input / output impedance Z is
Considering 50Ω and 1GHz cutoff frequency,
Calculated from the above equations (1) and (2), L = 8nH, C =
(C ₁ + C ₇ ) = 3 pF. A filter pattern having such values of L and C can be obtained by a three-dimensional electromagnetic field simulation or the like. In this case, for example, FIG.
In the shape as shown in the figure, width W = 0.2 mm, a = 1.0 mm, b = 1.0 on a ceramic substrate having a thickness h = 0.2 mm.
A pattern of mm, c = 0.6 mm and d = 0.6 mm may be formed.

The same applies to the output side. Generally, by forming a filter pattern symmetrically on the input / output side, C ₇
= C ₆ , but may be configured so that C ₇ ≠ C ₆ to further improve the attenuation characteristics.

[0028]

As described in detail above, according to the present invention in which an LC filter is formed inside a package on which a SAW filter is mounted, signal leakage caused by the influence of the package is suppressed, and the SAW having good out-of-band attenuation characteristics A filter can be provided.

[Brief description of the drawings]

FIG. 1 (a) is a schematic perspective view showing a high-frequency device package according to the present invention with a cap removed.
1B is a bottom view, and FIGS. 1C to 1F are development views of the layer structure.

FIG. 2 is a detailed view of a filter pattern of the high-frequency device package according to the present invention.

FIG. 3 is an electrical equivalent circuit when a LC filter is incorporated in a high-frequency device package according to the present invention and a SAW filter element is mounted.

FIG. 4 shows frequency characteristics of a conventional SAW filter element.

FIG. 5 is an electric equivalent circuit when a SAW filter element is mounted on a conventional high-frequency device package.

[Explanation of symbols]

1: Package, 2: SAW filter chip 3: Comb-shaped electrode 4-1,4-2,4-3,4-4: Bonding wire 5,6,7,8,9,10: Interlayer connection electrode 11: Ground Electrodes 12, 13: Filter pattern 14, 15: Terminals constituting signal wire bonding electrodes 16, 17, 18, 19: Terminals constituting ground wire bonding electrodes 20, 21, 22, 23: Terminals of SAW filter chip 24, 25, 26, 27, 28, 29: Package external terminal 30: Seal ring pattern, 31: Cap

Claims (1)

[Claims] 1. A package for a high-frequency device in which a high-frequency device is mounted, in order to obtain sufficient attenuation characteristics at a frequency outside a pass band of the surface acoustic wave filter, an LC filter is built in the package.