Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-04-30
2001-12-11
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S348000
Reexamination Certificate
active
06329739
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of Applications No. H10-168041 and No. H10-168042, both filed Jun. 16, 1998 in Japan, the subject matter of which is incorporated herein by reference.
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface-acoustic wave (SAW) device package, which is effectual to miniaturize itself. The present invention also relates to a method for packaging a surface-acoustic-wave device, which is effectual to miniaturize the package.
BACKGROUND OF THE INVENTION
In recent years, personal communication devices, such as mobile phones, have been remarkably improved. For personal communication devices, high frequency analog devices became more important than ever. For manufacturing a personal communication device to be small in size, surface-acoustic-wave (SAW) devices are useful. For example, surface-acoustic-wave devices are used for filters, resonator and the like.
A conventional surface-acoustic-wave (SAW) device includes a transducer, which converts an electric signal into acoustic waves or converts acoustic waves into an electric signal. Such a transducer may be made of a piezoelectric material. The piezoelectric material produces a mechanical distortion in response to application of voltage. In reverse, the piezoelectric material generates electric polarization as a result of the application of mechanical stress. Usually, as piezoelectric crystal, quartz, lithium niobate (LiNbO
3
) and lithium tantalate (LiTaO
3
) is used.
A conventional SAW transversal filter includes a piezoelectric substrate and IDTs (Interdigital Transducers). When an input signal is applied to one IDT, a mechanical distrotion is generated with a certain frequency and surface-acoustic-waves are generated on the surface of the piezoelectric substrate. The surface-acoustic waves travel on the surface of the piezoelectric substrate to another IDT, and aer converted into an electrical signal.
The surface-acoustic-wave device can be mounted on a base substrate in the same manner as an LSI, using wire-bonding technique. In packaging process, it is required to have an air gap around the functional surface of the piezoelectric substrate. For example, the piezoelectric substrate is mounted in a cavity of a base substrate, and a seal lid is provided to make the air gap above the piezoelectric substrate.
According to the above described conventional technology, it is difficult to package a surface-acoustic-wave device in a small space with lower cost.
OBJECTS OF THE INVENTION
Accordingly, an object of the present invention is to provide a surface-acoustic-wave device package which can be miniaturized easily.
Another object of the present invention is to provide a method for packaging a surface-acoustic-wave device in a small space.
Additional objects, advantages and novel features of the present invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, a surface-acoustic-wave device package includes a cover film which covers a surface-acoustic-wave device to provide an air gap around the functional surface thereof. The air gap allows surface acoustic waves travel on the functional surface securely. The surface-acoustic-wave device package also includes a seal material which is provided over the cover film to seal the surface-acoustic-wave device.
According to another aspect of the present invention, a method for packaging a surface-acoustic-wave device including the steps of: mounting the surface-acoustic-wave device on a base substrate; covering the surface-acoustic-wave device with a cover film to make an air gap around the functional surface; and sealing the surface-acoustic-wave device covered with the cover film.
According to a further aspect of the present invention, a surface-acoustic-wave device package includes first to Nth surface-acoustic-wave (SAW) device layers, which are piled up. The first SAW device layer is mounted on the base substrate. The first SAW device layer includes a first SAW device that is provided with a functional surface, on which surface acoustic waves travel along, and with a bottom surface connected to the base substrate. The Nth SAW device layer, in which “N” represents a whole number larger than one, is piled up on the (N−1)th SAW device layer. The Nth SAW device layer includes an Nth SAW device that is provided with a functional surface, on which surface acoustic waves travel along. The SAW device package further includes a seal lid which is arranged over the Nth SAW device layer to provide a sealed air gap above the functional surface of the Nth SAW device. The bottom surface of the Nth surface-acoustic-wave device functions as a seal to provide a sealed air gap above the functional surface of the (N−1)th SAW device.
According to the present invention, a surface-acoustic-wave device can be packaged in a small space easily with low costs.
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patent: 4628146 (1986-12-01), Schmotz et al.
patent: 4656385 (1987-04-01), Tanaka
patent: 5390401 (1995-02-01), Shikata et al.
patent: 5818145 (1998-10-01), Fukiharu
patent: 5920142 (1999-07-01), Onishi et al.
patent: 5969461 (1999-10-01), Anderson et al.
Medley Peter
OKI Electric Industry Co., Ltd.
Rabin & Berdo P.C.
Ramirez Nestor
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