JPH05235688A - Surface acoustic wave device and mobile radio terminal using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] Built-in peripheral circuits such as impedance matching circuit and demultiplexing circuit without expanding the overall area, and enables high-precision adjustment of the entire module, which causes problems before mounting on the circuit board. A surface acoustic wave device that is modularized and a mobile wireless terminal using the same can be miniaturized. [Structure] A surface acoustic wave element chip is mounted on the backside of a sub-board on which a peripheral circuit such as an impedance matching circuit and a branching circuit is mounted, and the sub-board is mounted on a planar mounting type package board. The surface acoustic wave device is modularized and hermetically sealed with a metallic lid.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device which is compact, lightweight and thin and can be mounted on a plane, and a mobile radio terminal using the same.

[0002]

2. Description of the Related Art Since mobile radio terminals are advantageous for miniaturization,
Surface wave (SAW) for the duplexer, interstage filter, etc.
Equipment is used.

Conventionally, as shown in, for example, Hitachi Review Vol. 72, No. 9, p57-62, p79-86, etc., they are packaged for each integral filter and then an impedance matching element, if necessary. Accordingly, it has been attached to a circuit board provided with a demultiplexing circuit element and used as a module. Alternatively, for example, JP-A-2-179
As disclosed in No. 017, a surface acoustic wave element chip is placed on a ceramic substrate on which an impedance matching pattern is formed, and the surface acoustic wave element chip is sealed with a metallic cap to form a package. The electromagnetic wave shielding property was secured.

[0004]

However, the above-mentioned conventional surface acoustic wave device or module has the following problems. That is, in the former case, since each individual chip is packaged and the matching element is provided on the external circuit board, the entire module requires a large area and is thick. On the other hand, in the latter, the impedance matching pattern is SAW, although it is made slightly smaller than the former.
Since it is formed on the same plane as the element chip, the entire area does not become small. Further, it is difficult to adjust the performance with high precision. Further, in the conventional example, if there is a problem, there is a waste of having to discard both the SAW device and the circuit board that have been packaged.

In order to solve the above problems, an object of the present invention is to mount an impedance matching circuit and a demultiplexing circuit on the circuit board without expanding the overall area, and to enable highly accurate adjustment of the entire module to be mounted on a circuit board. It is possible to remove a defective one before, and thereby to downsize a modularized surface acoustic wave device and a mobile radio terminal using the same.

[0006]

In order to achieve the above object, according to the present invention, an elastic surface is formed on a portion of the back surface of a sub-board on which a peripheral circuit such as an impedance matching circuit or a branching circuit is mounted and where a metal film is formed. Place the wave element chip. And
The characteristics of the module are measured using the sub-board, and trimming correction is performed. After that, the sub-board is attached to a flat mount package, and the package is hermetically sealed with a metallic lid.

[0007]

By mounting the surface acoustic wave device chip on the back surface of the sub-board on which the peripheral circuit is mounted as described above, the area of the entire module can be suppressed even if the peripheral circuit is built in.

The sub-board on which the surface acoustic wave element chip is mounted can measure its own frequency characteristics, and it is easy to judge whether it is good or bad and to perform trimming correction while monitoring the surface acoustic wave element. Since the chip is on the back side, contamination during trimming can be avoided.

Further, the transmitting / receiving electrode of the surface acoustic wave element chip and the peripheral circuit element are separated by the surface acoustic wave substrate, the metal film on the back surface of the sub-substrate, and the sub-substrate, and the metal film is grounded. Thus, mutual interference can be sufficiently suppressed.

[0010]

1 is a perspective conceptual view showing a preferred embodiment as a duplexer of a mobile radio terminal of the present invention, FIG. 2 is a view showing an electrical equivalent circuit of the embodiment of FIG. 1, and FIG. FIG. 2 is a central sectional view in the long side direction of the embodiment of FIG. 1.

In FIGS. 1 and 3, reference numeral 3 denotes a sub-board, on the surface of which transmission lines S1 and S2 as a demultiplexing circuit on the receiving side and a transmitting side are provided, and a matching inductor L1 of the receiving-side first-stage surface acoustic wave filter. L2, L3, L4, matching inductors L5, L6, L7, L of the transmission-side final-stage surface acoustic wave filter
8 is formed, and a uniform metallic film 15 is formed on the back surface thereof in the portions corresponding to the transmission lines S1 and S2, and the surface acoustic wave filter chips T1 and R1 and the inductors L1, L3 and L are formed.
Pads for wire bonding with 5, 5 and L7, a wiring pattern, and wiring patterns of inductors L2, L4, L6, L8 are formed. These inductor pads and wiring patterns are connected to the inductors on the front side through through holes.

In FIGS. 1 and 3, reference numeral 1 denotes a package substrate, on which a so-called hot side wiring pattern 7, a ground side wiring pattern 14 and a through hole 8 are formed, and a frame 6 is formed.
It is laminated with. It should be noted that the package substrate 1 has a step inside the frame 6, and the wiring patterns 7 and 14 are exposed on the step and serve as pads for connection with the wiring pattern of the sub-board 3. The plane under the step is connected to the ground side wiring pattern 14 by a uniform metallic film.

As shown in FIG. 3, the transmitting-side final-stage surface acoustic wave filter chip T1 and the receiving-side first-stage surface acoustic wave filter chip R1 are mounted on the metallic film 15 on the back surface of the sub-substrate 3 using an adhesive. There is. The hot pads of T1 and R1 are respectively wire-bonded to the corresponding wire-bonding pads on the back surface of the sub-board 3.
The ground-side pads of T1 and R1 are wire-bonded to the metallic film 15. However, wires and pads are omitted in the drawings. The sub-board 3 is placed on the step of the package board 1 with its back surface in contact, and its wiring pattern and the corresponding connection pad on the step are connected by a conductive adhesive or solder. On top of that, the metallic cap 5 is the seam welding ring 1
3 is welded to the frame 6 and hermetically sealed to form a duplexer module. The metallic cap 5 is electrically connected to the ground-side wiring pattern 14 through the through hole 8 on the outer surface of the frame 6 and has an electromagnetic shield.

The wiring of the duplexer module shown in FIGS. 1 and 3 has an equivalent circuit as shown in FIG. 2, in which the receiving-side first-stage surface acoustic wave filter chip R1 is connected to the receiving output Rx via matching inductors L3 and L4. And matching inductors L1 and L
2 is connected to one end of the transmission line S1 via one end of the transmission line S1, one of the transmission-side final-stage surface acoustic wave filter chips T1 is connected to the transmission input Tx via the matching inductors L7 and L8, and is connected via the matching inductors L5 and L6. Are connected to one end of the transmission line S2, and the other ends of the transmission lines S1 and S2 are connected to the antenna terminal ANT. As is apparent from FIG. 3, the filter chips R1 and T1 are spaced apart so that the reception output Rx and the transmission input Tx are not coupled.

When the alumina substrate having a dielectric constant of 10 is used as the sub-substrate 3, the thickness can be 250 to 300 μm. In the mobile radio terminal of 800-900 MHz band, the transmission lines S1 and S2 are copper patterns, and Width and spacing are 250
-300μm, thickness can be 5μm or more (when the characteristic impedance is 50Ω), the resistance can be sufficiently small, and the length can be bent at a quarter wavelength (about 40mm), so the size can be suppressed. The dimensions of the duplexer module are 14 mm x 7 mm and the thickness is 2 mm.
The volume can be reduced to about 0.2 cc.

In the embodiment, the demultiplexing circuit is formed by using the distributed constant transmission line of the microstrip line as described above. However, depending on the design of the surface acoustic wave filter chip, a lumped constant type inductor or capacitor may be used. Alternatively, a combination of them can be used as a branching circuit.

[0017]

According to the present invention, a modularized surface acoustic wave device can be housed in a package mounted on a plane without increasing the overall area and thickness of the device. As a module, it has the effect of being smaller and thinner. Therefore, it is possible to reduce the size and weight of the mobile wireless terminal using the above module.

[Brief description of drawings]

FIG. 1 is a perspective conceptual view showing an embodiment as a duplexer of a mobile radio terminal of the present invention.

FIG. 2 is a diagram showing an electrical equivalent circuit of an embodiment.

FIG. 3 is a central cross-sectional view in the long side direction of the embodiment.

[Explanation of symbols]

1 ... Package substrate, 3 ... Sub substrate, 5 ... Cap, 6
... frame, 7 ... hot side wiring pattern, 8 ... through hole, 13 ... seam welding ring, 14 ... grounding side wiring pattern, 15 ... metallic film, T1 ... transmitting side final stage filter chip, R1 ... receiving side first stage filter chip , S1, S2 ... Transmission line, L1, L2, L3, L4, L5, L6, L7,
L8 ... inductor, Tx ... transmission input, Rx ... reception output,
ANT ... Antenna terminal.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Kobayashi 1410 Inada, Katsuta City, Ibaraki Prefecture Inside the Tokai Plant, Hiritsu Manufacturing Co., Ltd.

Claims (2)

[Claims] 1. A surface acoustic wave device chip is mounted on the back surface of a sub-board on which a peripheral circuit is mounted, the sub-board is mounted on a planar mounting type package board, and hermetically sealed with a metallic lid. Characteristic surface acoustic wave device. 2. A mobile radio terminal using the surface acoustic wave device according to claim 1 as a demultiplexer or a filter.