JP2002208830A - Method for manufacturing surface acoustic wave device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To mass-produce a surface acoustic wave device easily and with good productivity without impairing electrical characteristics and reliability. SOLUTION: A grid-like V-shaped groove 6 for partitioning a plurality of squares into a flat plate package 2 and terminal conductors 8 are provided at predetermined positions of each square, and a surface acoustic wave chip 1 is mounted on each square. The terminal conductor 8 and the electrode of the surface acoustic wave chip 1 are connected by face-down bonding. After each surface acoustic wave chip 1 is covered with a cap-shaped cover 5 and hermetically sealed, the flat package 2 is divided along the V-groove 6, and each hermetically sealed surface acoustic wave chip is separated and elastically sealed. Obtain a surface acoustic wave device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a surface acoustic wave device mainly used as an electric circuit component of a communication device such as a mobile communication terminal.

[0002]

2. Description of the Related Art FIG. 8 is a cross-sectional view showing the configuration of a conventional surface acoustic wave device of this type disclosed in, for example, Japanese Patent Application Laid-Open No. Hei. In the figure, 1 is a surface acoustic wave chip, 21 is a package, 31 is a flat plate cover, and 4 is a wire. In this conventional surface acoustic wave device, after the surface acoustic wave chip 1 is fixed to the package 21, the surface acoustic wave chip 1 is connected to the terminals on the package 21 using the wires 4, and the device is further sealed. Therefore, it is manufactured by joining the flat plate cover 31 to the package 21.

Next, the operation will be described. The surface acoustic wave chip 1 has a required pattern formed by a metal thin film on the surface of a substrate having piezoelectricity. The surface acoustic wave chip 1 uses the piezoelectricity to convert an electric signal into a surface acoustic wave, and further converts the surface acoustic wave back into an electric signal, thereby processing the signal and operating as various electric elements. I do. The details of this operation principle are described in detail in, for example, the document “Surface Acoustic Wave Engineering” published in 1983 by the Institute of Electronics and Communication Engineers, and are omitted here.

The surface acoustic wave is generated by mechanical vibration on the surface acoustic wave chip 1. For this reason, if this mechanical vibration is hindered by the attachment of fine foreign matter such as dust and dirt on the surface acoustic wave chip 1 or the oxidation of the metal pattern, the characteristics of the surface acoustic wave device will change. It deteriorates remarkably. Therefore, in this type of device, the surface acoustic wave chip 1 is usually hermetically sealed with a package or the like. In this conventional example, the surface acoustic wave chip 1 is hermetically sealed by joining a flat cover 31 to the package 21. Further, in order to establish electrical continuity between the surface acoustic wave chip 1 and the outside, a wire 4 is provided between a pattern on the surface acoustic wave chip 1 and a terminal (not shown) provided on the package 21.
Connected by

[0005] Since this conventional surface acoustic wave device is configured as described above, separate packages 2 are provided.
It is necessary to mount the surface acoustic wave chip 1 on the substrate 1 and perform a process such as wiring and sealing to manufacture the chip. For this reason, there is a limit in productivity when mass-producing devices.

In such a surface acoustic wave device, the package 21 is usually made of ceramic. This is because ceramics are superior to other materials in electrical properties, airtightness, moisture absorption resistance, strength, and the like. However, depending on the ceramic material and the structure of the package 21, costs such as material costs and processing costs may increase.

Furthermore, in this conventional example, the package 21
A box-shaped structure is used. Also, wire 4
It is necessary to provide an internal terminal for connecting to the inside of the package 21. Therefore, the package 21 has a structure having a step inside. Therefore, when the package 21 is manufactured by the ordinary ceramic lamination firing process, it is necessary to have a structure in which at least three ceramic sheets are combined, so that the number of steps is increased and the manufacturing cost is complicated, that is, the price of the package 21 is reduced. Therefore, there is a problem that the manufacturing cost of the surface acoustic wave device increases.

FIG. 9 is a cross-sectional view showing another example of the configuration of a conventional surface acoustic wave device of this type disclosed in, for example, JP-A-9-148878. In the figure, 1 is a surface acoustic wave chip, 21 is a package, 31 is a flat plate cover, and 5 is a bump.

In this conventional example, similarly to the conventional example shown in FIG. 8, the surface acoustic wave chip 1 is hermetically sealed using a package 21 and a flat plate cover 31. However, the connection between the surface acoustic wave chip 1 and the terminals on the package 21 is performed by face-down bonding of the surface acoustic wave chip 1 to the package 21 via the bumps 5 without using the wires 4. Normally, the bump 5 is made of gold (A) having good bonding properties with the surface acoustic wave chip 1 and the package 21.
In many cases, u) is mainly used.

The operation principle of the conventional surface acoustic wave device is the same as that of the conventional example shown in FIG.

The package 21 includes a package 21
Since there is no need to form an internal step, a two-layer structure can be obtained even when a ceramic laminated structure is used. Therefore, the number of layers is smaller than that of the conventional package 21 shown in FIG. 8, and it can be manufactured at a slightly lower cost. However, it still has a multilayer structure.

Further, since it is necessary to bond the surface acoustic wave chips 1 to the individual packages 21 and perform processes such as sealing, the productivity in mass-producing devices is still limited.

[0013]

As described above, in this type of conventional surface acoustic wave device, since the devices are individually assembled, there is a limit in improving the productivity. Also,
Since the ceramic package 21 having a complicated structure is used,
There are problems that it takes time to produce and is complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a manufacturing method capable of easily mass-producing a surface acoustic wave device with good productivity without impairing electrical characteristics and reliability. And

[0015]

A first method of manufacturing a surface acoustic wave device according to the present invention is directed to a method of manufacturing a surface acoustic wave device, comprising a plurality of grids divided by a groove in a grid pattern, and terminals provided at predetermined positions of the grids. A step of forming a flat package having a conductor, a step of mounting a surface acoustic wave chip in each cell, and a step of connecting an electrode of the surface acoustic wave chip to a terminal conductor of each cell by face-down bonding; Covering each wave chip with a cap-shaped cover to hermetically seal each surface acoustic wave chip, and dividing the flat plate package along the groove and separating each surface acoustic wave chip individually hermetically sealed. Is applied.

In a second method for manufacturing a surface acoustic wave device according to the present invention, in the first method, the groove is provided on the upper surface and the lower surface of the flat plate package such that the bottom faces each other.

In a third method of manufacturing a surface acoustic wave device according to the present invention, in the first method, the groove is provided on only one of the upper surface and the lower surface of the flat package.

In a fourth method of manufacturing a surface acoustic wave device according to the present invention, a plurality of squares partitioned by imaginary lines in a grid pattern and terminal conductors provided at predetermined positions in each square are provided. A step of forming a planar package having, a step of mounting a surface acoustic wave chip for each cell, and a step of connecting an electrode of the surface acoustic wave chip to a terminal conductor of each cell by face-down bonding; A step of sealing each surface acoustic wave chip with a cap-shaped cover, and a step of dividing the flat package by a laser along the imaginary line and separating each of the individually hermetically sealed surface acoustic wave chips. Is applied.

In a fifth method of manufacturing a surface acoustic wave device according to the present invention, in any one of the first to fourth methods, a metal cover is used as the cap-shaped cover.

In a sixth method of manufacturing a surface acoustic wave device according to the present invention, in any one of the first to fifth methods, the flat plate package and the cover are joined by using a high melting point solder. is there.

In a seventh method of manufacturing a surface acoustic wave device according to the present invention, in the sixth method, a high melting point solder is previously attached to a joint between the flat plate package and the cover. .

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a cross-sectional view showing a state before dividing a flat package and separating each hermetically sealed surface acoustic wave chip according to the method for manufacturing a surface acoustic wave device according to Embodiment 1 of the present invention, and FIG. FIG. 3 is a perspective view showing the shape of the surface acoustic wave device finally obtained by dividing the flat plate package along the V-groove. In the drawing, 1 is a surface acoustic wave chip, 2 is a flat package, 3 is a cover, 5 is a bump, 6 is a V-groove carved in a vertical and horizontal lattice on both sides of the flat package 2, 8 is a pad portion 8a and a through-hole conductor. 8b.

First, a notch is made in the vertical and horizontal directions with a knife so that V-grooves 6 are formed in a lattice on the upper and lower surfaces of the green sheet before firing the ceramic. At that time, V
The bottoms of the grooves 6 are opposed to each other. Further, through holes for terminal conductors are respectively opened at predetermined positions in a plurality of squares divided by the grooves 6 in a grid pattern. This is fired to form a ceramic flat package 2 having a plurality of grids divided in a grid pattern by V-grooves. A terminal conductor 8 is formed at a predetermined position of each cell of the flat package 2. That is, a through-hole conductor 8b is formed in each through-hole, and connected to this.
Pad portions 8 a are formed on the upper and lower surfaces of the flat package 2. Next, the surface acoustic wave chip 1 is mounted on each cell of the flat package 2, and the electrodes of the surface acoustic wave chip 1 are connected to the terminal conductors 8 of each cell by face-down bonding. Thereafter, each of the surface acoustic wave chips 1 is covered with a cap-shaped cover 3, and each surface acoustic wave chip 1 is individually hermetically sealed. The cover 3 is stored in the cell so as not to straddle the V groove 6. Finally, a single flat package 2 on which a plurality of surface acoustic wave chips are mounted and hermetically sealed is divided along the V-groove 6 by the chocolate break method, and each cell, that is, each hermetically sealed Separation is performed for each surface acoustic wave chip 1 to obtain a surface acoustic wave device.

Next, the operation will be described. The surface acoustic wave chip 1 is obtained by forming a required pattern with a metal thin film on the surface of a substrate having piezoelectricity. By utilizing the piezoelectricity, an input electric signal is converted into a surface acoustic wave, and the surface acoustic wave is converted into an electric signal again to be an output signal, thereby operating as various electric elements. This operation principle is the same as that of the conventional surface acoustic wave device.

In the method of manufacturing a surface acoustic wave device according to the first embodiment, as described above, and as shown in FIGS. Can be assembled. For example, if a surface acoustic wave device of about 3 mm square is to be manufactured in a flat package 2 of about 100 mm square, about 1 mm
000 surface acoustic wave devices can be assembled at a time, and mass production can be easily performed.

Further, as compared with the assembly line in which the surface acoustic wave chip 1 is assembled into individual packages 21 one by one as in the device using the conventional package 21 shown in FIGS. Transport during assembly is facilitated. Therefore, especially when a large number of surface acoustic wave devices are manufactured, the productivity can be extremely increased.

Further, along the V groove 6 provided in advance,
By dividing the flat plate package 2 by the chocolate break method, it can be easily separated into individual devices.

Further, the surface acoustic wave chip 1 is hermetically sealed as in the prior art, and does not suffer from deterioration of characteristics due to entry of foreign matter or oxidation of the electrodes. A surface acoustic wave device having high reliability can be obtained.

As described above, the surface acoustic wave device according to Embodiment 1 has a simple and highly reliable package structure,
It has a structure that is easy to assemble and is suitable for mass production. With the manufacturing method of this embodiment, it is possible to obtain easily at low cost, with good productivity, without impairing electrical characteristics and reliability.

Embodiment 2 FIG. FIG. 4 is a cross-sectional view showing a state before splitting a flat package according to the method for manufacturing a surface acoustic wave device according to Embodiment 2 of the present invention. In the figure, 1
Denotes a surface acoustic wave chip, 2 denotes a flat plate package, 3 denotes a cover, 5 denotes a bump, and 6 denotes a V groove.

Also in the second embodiment, similarly to the first embodiment, a plurality of surface acoustic wave chips 1 are face-down bonded to a flat package 2 and the surface acoustic wave chip 1 is covered with a cap-shaped cover 3. Hermetically sealed, V
The surface acoustic wave device is obtained by dividing the flat plate package 2 along the groove 6 by the chocolate break method and separating the package. However, in the second embodiment, unlike the first embodiment, the V
A groove 6 is formed.

As described above, even if the V-groove 6 is only on the upper surface,
After assembling a plurality of devices at a time, separation into individual devices can be easily performed by using the same method as in the first embodiment. A surface acoustic wave device with good productivity and low cost can be obtained without impairing the surface acoustic wave device. Further, since the V-groove 6 is formed only on the upper surface of the flat package 2, the number of manufacturing steps of the flat package 2 is reduced as compared with the first embodiment, and a surface acoustic wave device at lower cost can be obtained.

In the second embodiment, the case where the V groove 6 is formed only on the upper surface of the flat package 2 has been described. However, the V groove 6 may be formed only on the lower surface of the flat package 2. In this case, Obviously, the same effect can be obtained.

Embodiment 3 FIG. 5 is a perspective view showing a surface acoustic wave device obtained according to the third embodiment of the present invention. In the figure, reference numeral 2 denotes a flat package, and 32 denotes a metal cover.

Although not shown in FIG. 5, the surface acoustic wave chip 1 face-down bonded inside the package is hermetically sealed as shown in FIGS. In the third embodiment, a metal cover 32 is used as a cover for hermetically sealing the surface acoustic wave chip 1.

In general, in a surface acoustic wave device, an input electric signal is once converted into a surface acoustic wave, converted into an electric signal again, and output. At this time, a so-called feed-through occurs in which a part of the input electric signal propagates in the space inside and outside the package as an electromagnetic wave without being converted into a surface acoustic wave, and is output as an electric signal as it is. In general, if the level of feedthrough is large, the out-of-band attenuation of the filter deteriorates, which is not preferable in terms of electrical characteristics. For this reason, in the surface acoustic wave device, it is desirable to minimize the level of feedthrough. In order to reduce the level of the feedthrough, it is effective to cover the surface acoustic wave device with a metal shield as much as possible.

In the third embodiment, the metal cover 32 is used as a cover for sealing the surface acoustic wave device. For this reason, the level of the feedthrough described above can be reduced, and a surface acoustic wave device having good electric characteristics can be obtained.

Further, since the metal cover 32 is in the form of a cap, the ratio of covering the device is larger than that in the case of using the flat cover 31 as in the conventional surface acoustic wave device. Therefore, the level of feed-through can be reduced as compared with the conventional surface acoustic wave device.

As described above, in the method of manufacturing a surface acoustic wave device according to the third embodiment of the present invention shown in FIG. 5, a surface acoustic wave device having low cost, good productivity, and excellent electric characteristics can be obtained. Can be.

Embodiment 4 FIG. FIG. 6 is a cross-sectional view showing a state before a flat package is divided and before each surface acoustic wave chip is separated according to the method for manufacturing a surface acoustic wave device according to the fourth embodiment of the present invention. In the figure, 1 is a surface acoustic wave chip, 2 is a flat package, 3 is a cover, 5 is a bump, 6
Is a V groove, and 7 is a high melting point solder.

In the fourth embodiment, as in the first embodiment, a plurality of surface acoustic wave chips 1 are
The surface acoustic wave chip 1 is covered with a cap-shaped cover 3 and hermetically sealed. In the hermetic sealing, the flat package 2 and the cover 3 are joined with a high melting point solder 7. ing.

The cover 3 has a cap-like shape, and the simultaneous joining of a plurality of covers 3 to the flat package 2 can be more easily performed by using solder than by seam welding or the like. Further, since the high melting point solder 7 is used as the solder, when the completed surface acoustic wave device is soldered to an electric circuit board of a communication device such as a mobile communication terminal, a solder having a lower melting point than the high melting point solder 7 is used. , That is, at a normal soldering temperature, the high melting point solder 7 does not melt, so that the surface acoustic wave device can be mounted without causing sealing destruction.

As described above, in the method of manufacturing a surface acoustic wave device according to the fourth embodiment, a surface acoustic wave device with higher productivity can be obtained.

As a material of the high melting point solder 7, gold tin (A
uSn), lead tin 10 (Pb-Sn10), lead silver tin (Pb-Ag-Sn), tin silver (Sn-Ag), tin copper (Sn-Cu) and the like. May be selected.

Embodiment 5 FIG. FIG. 7 is a cross-sectional view showing a state before airtight sealing of each surface acoustic wave chip according to the method for manufacturing a surface acoustic wave device according to the fifth embodiment of the present invention.
In the drawing, 1 is a surface acoustic wave chip, 2 is a flat package, 3 is a cover, 5 is a bump, 6 is a V groove, and 7 is a high melting point solder. In this embodiment, when the cover 3 is joined to the flat package 2 using the high melting point solder 7, the high melting point solder 7 is previously attached to the joint between the flat package 2 and the cover 3. In actual assembly, the surface acoustic wave chip 1 is hermetically sealed by joining the cover 3 to which the high melting point solder 7 is attached to the flat package 2 to which the high melting point solder 7 is attached.

By assembling in this manner,
At the time of the hermetic sealing assembly process, the joining property between the flat package 2 and the cover 3 can be further enhanced, and a surface acoustic wave device with high hermeticity can be obtained. In the fifth embodiment, a surface acoustic wave device can be favorably manufactured with higher productivity and reliability.

Embodiment 6 FIG. In the method for manufacturing a surface acoustic wave device according to the sixth embodiment, assembling is performed on the assumption that the flat plate package 2 is not formed with a groove, but is divided into a grid by virtual lines, and a plurality of grids are formed. Things.
That is, the terminal conductors 8 are respectively provided at predetermined positions of a plurality of grids divided by imaginary lines of the flat package 2, and the same process as in the above-described embodiment is performed. The chips 1 are hermetically sealed. Thereafter, the flat plate package is divided by irradiating a laser along the imaginary line, and the surface acoustic wave chips individually hermetically sealed are separated to obtain a surface acoustic wave device. As in the above-described embodiment, a surface acoustic wave device can be obtained easily at low cost and with good productivity without impairing the electrical characteristics and reliability. The terminal conductors can be collectively formed at predetermined positions of the flat plate package by plating, etching, and the like, and the laser beam can be accurately scanned along the imaginary line by numerical control, so that there is no problem even if there is no groove.

In the above embodiment, the case where the V-groove 6 is used as a groove for partitioning the flat package 2 in a grid pattern has been described, but the shape of the groove is not limited to the V-shape, but may be other shapes. May be. For example, a shape that can be easily divided by the chocolate break method is desirable.

Further, in the above-described embodiment, the description has been given of the case where the flat package 2 is made of ceramic material. However, other materials may be used. In this case, the flat package has a simpler structure than the conventional example. Therefore, the same effect as the present invention can be obtained.

Further, in the above embodiment, each surface acoustic wave chip 1 is covered with one independent cap one by one. However, one in which a plurality of caps are connected may be used, and workability may be improved. improves. When the flat plate package is divided by the chocolate break method, one that can be easily divided together with the flat plate package is used. For example, a cap that is connected and integrated so that the caps are not separated by a bridge, or a cap that is integrally formed by opening a perforation for separation between adjacent caps is used.

[0051]

As described above, in the first method for manufacturing a surface acoustic wave device according to the present invention, a plurality of squares partitioned in a grid pattern by grooves and a plurality of squares are provided at predetermined positions of each square. A step of forming a flat package having terminal conductors, a step of mounting a surface acoustic wave chip for each cell, and a step of connecting electrodes of the surface acoustic wave chip to the terminal conductors of each cell by face-down bonding,
A step of covering each surface acoustic wave chip with a cap-shaped cover, and sealing each surface acoustic wave chip, and dividing the flat plate package along the grooves, and individually sealing each surface acoustic wave chip. Since the separation step is performed, the surface acoustic wave device can be easily mass-produced with high productivity without impairing the electrical characteristics and reliability.

Further, the second surface acoustic wave device of the present invention
In the manufacturing method of (1), since the groove is provided in the first method such that the bottom faces the upper surface and the lower surface of the flat package, the flat package can be divided more easily.

Further, the third surface acoustic wave device of the present invention
In the manufacturing method of (1), in the first method, the grooves are provided on only one of the upper surface and the lower surface of the flat plate package. Therefore, the number of manufacturing steps is reduced, and the productivity can be further increased.

Further, the fourth surface acoustic wave device of the present invention
In the manufacturing method, a step of forming a flat package having a plurality of squares partitioned in a grid pattern by imaginary lines and terminal conductors provided at predetermined positions in each square, respectively, an elastic surface for each square Mounting the surface acoustic wave chip and connecting the electrodes of the surface acoustic wave chip to the terminal conductors of each cell by face-down bonding, covering each surface acoustic wave chip with a cap-shaped cover, and sealing each surface acoustic wave chip The step of stopping and the step of dividing the flat package along the imaginary line by a laser and separating each surface acoustic wave chip which is individually hermetically sealed, thereby impairing electrical characteristics and reliability. Therefore, the surface acoustic wave device can be easily mass-produced with high productivity.

Further, the fifth surface acoustic wave device of the present invention
In the manufacturing method of (1), in the first to fourth methods, since a cover made of metal is used as the cap-shaped cover, a surface acoustic wave device having more excellent electric characteristics can be obtained.

Further, the sixth surface acoustic wave device of the present invention
In the manufacturing method of (1), in the first to fifth methods, the flat plate package and the cover are joined using the high melting point solder, so that a surface acoustic wave device can be obtained with higher productivity.

The seventh surface acoustic wave device of the present invention
In the manufacturing method of (1), since the high melting point solder is previously attached to the joint between the flat plate package and the cover in the sixth method, a surface acoustic wave device with higher airtightness can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a manufacturing process of a surface acoustic wave device according to Embodiment 1 of the present invention, showing a state before separation.

FIG. 2 is a perspective view showing a manufacturing process of the surface acoustic wave device according to Embodiment 1 of the present invention, showing a state before separation.

FIG. 3 is a perspective view showing a surface acoustic wave device obtained according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing process of the surface acoustic wave device according to Embodiment 2 of the present invention, showing a state before separation.

FIG. 5 is a perspective view showing a surface acoustic wave device obtained according to a third embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a manufacturing process of the surface acoustic wave device according to Embodiment 4 of the present invention, showing a state before separation.

FIG. 7 is a cross-sectional view showing a manufacturing process of the surface acoustic wave device according to Embodiment 5 of the present invention, in a state before hermetic sealing.

FIG. 8 is a cross-sectional view illustrating a configuration of a conventional surface acoustic wave device.

FIG. 9 is a cross-sectional view illustrating a configuration of another conventional surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface acoustic wave chip 2 Plate package 3 Cover 4 Wire 5 Bump 6 V groove 7 High melting point solder 21 Package 31 Plate cover 32 Metal cover.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukio Yoshida 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Koji Morishima 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F term in Ryo Denki Co., Ltd. (reference) 5J097 AA25 AA31 AA34 HA04 HA07 HA08 KK10

Claims (7)

[Claims] 1. A step of forming a flat plate package having a plurality of squares partitioned by a groove in a grid pattern and terminal conductors provided at predetermined positions in each square, and a surface acoustic wave chip for each square. Is mounted, and the electrodes of the surface acoustic wave chip are connected to the terminal conductors of each cell by face-down bonding. Each surface acoustic wave chip is covered with a cap-shaped cover, and each surface acoustic wave chip is hermetically sealed. A method of manufacturing a surface acoustic wave device, comprising the steps of: dividing the flat plate package along the groove, and separating each of the hermetically sealed surface acoustic wave chips. 2. The method for manufacturing a surface acoustic wave device according to claim 1, wherein said groove is provided on an upper surface and a lower surface of said flat plate package so that a bottom portion thereof is opposed. 3. The method for manufacturing a surface acoustic wave device according to claim 1, wherein the groove is provided on only one of an upper surface and a lower surface of the flat package. 4. A step of forming a flat plate package having a plurality of squares partitioned by imaginary lines in a grid pattern and terminal conductors provided at predetermined positions in each square, wherein a surface acoustic wave is provided for each square. A step of mounting the chip and connecting the electrodes of the surface acoustic wave chip to the terminal conductors of each cell by face-down bonding, covering each surface acoustic wave chip with a cap-shaped cover, and hermetically sealing each surface acoustic wave chip And a step of dividing the flat package by a laser along the imaginary line and separating the individual hermetically sealed surface acoustic wave chips. 5. The method for manufacturing a surface acoustic wave device according to claim 1, wherein a cover made of metal is used as said cap-shaped cover. 6. The method for manufacturing a surface acoustic wave device according to claim 1, wherein the flat plate package and the cover are joined by using a high melting point solder. 7. The method for manufacturing a surface acoustic wave device according to claim 6, wherein a high melting point solder is previously attached to a joint between the flat package and the cover.