JP2001244782A - Surface acoustic wave device and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cap-less surface acoustic wave device that prevents production of chipping or cracks and enhances reliability and yield. SOLUTION: A coating film 4 for protecting a non-electrode forming face is formed on the non-electrode forming face of a surface acoustic wave element 10. The coating film 4 is made of a resin or a silicon oxide film. Thus, occurrence of chipping or cracks of the element can be prevented and reliability and yield are enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface acoustic wave device and a method of manufacturing the same, and more particularly, to a surface acoustic wave device suitable as a frequency filter of a mobile communication terminal and a method of manufacturing the same.

[0002]

2. Description of the Related Art A surface acoustic wave device is composed of a comb-shaped electrode (IDT: InterDigital Transduce) made of a thin film metal on a piezoelectric body.
r) is a device that converts an electric signal to a surface acoustic wave (SAW) to transmit and receive signals, and is used for surface acoustic wave filters, surface acoustic wave resonators, delay circuits, etc. .

[0003] Such a surface acoustic wave device has an advantage that it can be made thinner and smaller.
In recent years, it has been widely used especially in the field of mobile communication such as a mobile phone.

[0004] With the downsizing of mobile phones and the like, demands for downsizing and thinning of surface acoustic wave devices have become more and more severe.

[0005] Therefore, a package of a surface acoustic wave device is constituted by a plate-like base substrate having substantially the same area as a piezoelectric body and a piezoelectric body to form a capless structure.

A conventional capless surface acoustic wave device has been manufactured by the following method.

[0007] As shown in FIG.
A comb-shaped electrode 22 and a terminal electrode 23 are formed thereon to form a surface acoustic wave device 30.

[0008] As shown in FIG.
3, a convex conductive material 25 such as a metal bump is formed by bonding, screen printing, or the like.

On the other hand, as shown in FIG. 6A, external connection terminals 33 and element connection terminals 32 are formed on a flat plate 31 to form a flat base substrate 40.

As shown in FIG. 6B, conductive adhesives 34 and 35 are applied on the element connection terminals 32 and the outer peripheral surface of the substrate by screen printing or the like.

As shown in FIG. 7A, the surface acoustic wave element 30 is face-down bonded to the base substrate 40 by the convex conductive material 25. Thereafter, by curing the conductive adhesives 34 and 35 by a heat process, the surface acoustic wave element 30 is fixed on the base substrate 40 and the element surface is sealed as shown in FIG. 7B.

Here, the surface acoustic wave element 30 is cut into individual pieces by dicing from a state in which a plurality of pieces are formed on the surface of the wafer, and then connected to the base substrate 40 by face-down bonding. .

On the other hand, after the base substrate 40 is formed in multiple pieces, the surface acoustic wave element 30 is mounted and then cut into individual pieces.

However, the dimensions of the surface acoustic wave element 30 and the base substrate 40 are the same. For this reason, the base substrate 40
Depending on the selection of the material and thickness of the device, after the multi-cavity element is connected to the multi-cavity base substrate 40 and fixed with an adhesive, the device 30 and the base substrate 40 are put together into individual devices. It may be cut.

As described above, the cutting of the element 30 and the base substrate 40 has been performed at a convenient stage according to the material, thickness and the like.

[0016]

However, the conventional surface acoustic wave device and its manufacturing method have the following problems.

As described above, the cap is not mounted on the back surface of the acoustic wave device 30 for miniaturization and thinning. Therefore, as shown in FIG. 8A, the back surface of the acoustic wave device 30 is exposed. Therefore, in the cutting step, the transporting step, the step of mounting the device on the printed circuit board, or the like, chip chipping occurs as shown in FIG. 8B, or cracks occur as shown in FIG. This has led to a decrease in reliability and yield.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a surface acoustic wave device capable of improving reliability and yield in a capless device and a method of manufacturing the same. With the goal.

[0019]

A surface acoustic wave device according to the present invention comprises a surface acoustic wave element having a comb-shaped electrode and a terminal electrode formed on a piezoelectric body, and an external connection terminal and an element connection terminal on the surface. A formed base substrate, a connection body for electrically connecting the terminal electrode of the surface acoustic wave element and the element connection terminal of the base substrate, and an outer peripheral portion of the surface acoustic wave element and the base substrate And a coating film formed on the non-electrode forming surface of the surface acoustic wave element.

Here, the coating film may be formed using a resin, or may be formed using a material having a higher hardness than the piezoelectric body.

According to the method of manufacturing a surface acoustic wave device of the present invention, a step of providing a comb-shaped electrode and a terminal electrode on a piezoelectric body to form a surface acoustic wave element, and a step of coating the non-electrode forming surface of the piezoelectric body Forming a film, providing a connection body on the terminal electrode of the surface acoustic wave element, and having conductivity on the element connection terminal of the base substrate on which the external connection terminal and the element connection terminal are formed. Applying an adhesive, a step of applying an adhesive having conductivity or insulation in the outer peripheral region,
In a state where the terminal electrode of the surface acoustic wave element and the element connection terminal of the base substrate are connected via the connection body, the surface acoustic wave element and the base substrate are fixed and sealed with the adhesive. Here, the step of stopping is provided. The coating film may be formed by screen printing of a resin, or may be formed by spin coating of a resin. Alternatively, a thin film may be formed by sputtering or vapor deposition.

As described above, the surface acoustic wave device of the present invention protects the back surface of the element with the coating film to prevent chipping and cracking of the element in a state where the element is small and thin without caps. Can be prevented. Such a surface acoustic wave device can be obtained by the manufacturing method of the present invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a configuration of a surface acoustic wave device according to an embodiment of the present invention and a method of manufacturing the same will be described.
A description will be given with reference to element cross-sectional views for each process.

As shown in FIG. 1A, a comb-shaped electrode 2 and a terminal electrode 3 are formed on a piezoelectric body 1 to form a surface acoustic wave device 10.

As shown in FIG. 1B, a resin is applied to the back surface of the piezoelectric body 1 on which the electrodes 2 and 3 are not formed by screen printing or spin coating to a thickness of 1 to 50 μm. 4 is formed. As a resin to be applied and formed, a resin material such as a silicon-based resin, an epoxy-based resin, and polyimide can be used.

As shown in FIG. 1C, a convex conductive material 5 such as a metal bump is formed on the terminal electrode 3 by bonding or screen printing.

On the other hand, as shown in FIG. 2A, an external connection terminal 13 and an element connection terminal 12 are formed on a flat plate 11 to form a flat base substrate 20.

As shown in FIG. 2B, conductive adhesives 14 and 15 are applied on the element connection terminals 12 and the outer peripheral surface of the substrate by screen printing or the like.

As shown in FIG. 3A, the surface acoustic wave device 10 is face-down bonded to the base substrate 20 by the convex conductive material 5. Thereafter, by curing the conductive adhesives 14 and 15 by a heat process,
As shown in FIG. 3B, the surface acoustic wave element 10 is
The surface of the element is fixed on the substrate and the surface of the element is sealed to obtain a surface acoustic wave device.

Here, it is necessary to apply a conductive adhesive 14 to the element connection terminals 12, but the adhesive 15 applied to the outer peripheral region of the substrate is not necessarily required to be a conductive adhesive. An adhesive may be used. In this case, the application of the adhesives 14 and 15 can be realized by performing the application twice.

Here, the surface acoustic wave device 10 may be cut into individual pieces by dicing from a state of being formed in multiple pieces on the surface of the wafer, and then connected to the base substrate 20 by face-down bonding.

On the other hand, after the base substrate 20 is formed in multiple pieces, the surface acoustic wave element 10 may be mounted and then cut into individual pieces.

However, the dimensions of the element 10 and the base substrate 20 are the same. For this reason, depending on the selection of the material and thickness of the base substrate 20, after the multi-piece device 10 is face-down bonded and fixed to the multi-piece base substrate 20, the device 10 and the base substrate 20 are combined. Can be cut into individual pieces. By adopting such a process, manufacturing efficiency is improved.

Further, the efficiency of the process of forming the coating film 4 on the surface acoustic wave element 10 is improved by performing the process before cutting the wafer by cutting a large number of wafers.

According to the present embodiment, as shown in FIG. 4A, the coating film 4 is formed on the back side of the device.
Accordingly, even when stress is applied in the steps of transporting, cutting, mounting, and the like, the occurrence of cracks, chips, and the like as shown in FIG. 4B is prevented.

The resin film formed by coating acts to relieve stress when an external force is applied to the chip, so that damage to the chip can be prevented. Further, this resin film is formed smoothly on the back surface of the chip by a film forming method such as screen printing or spin coating. Therefore, during face-down bonding, pressure can be uniformly applied to each of the bumps to be bonded, and a good connection state can be obtained. The thickness of the resin film is preferably 1 μm in order to reduce the stress applied to the chip. In addition, in order to separate chips after film formation, the thickness is preferably 50 μm or less in consideration of easiness of dicing.

Further, as the coating film, an inorganic film such as a silicon oxide film or a silicon nitride film can be used. That is, by using a material having a higher hardness than the piezoelectric substrate, the chip can be reinforced to prevent breakage. These films are formed by a film formation method such as a sputtering method or an evaporation method. At this time, the thickness of the coating film is preferably 50 nm or more in order to improve the external force resistance of the chip.
The following is preferred.

[0038]

As described above, according to the present invention, a coating film is formed on a non-electrode forming surface of a capless surface acoustic wave device, so that the device can be reduced in size and thickness while maintaining a small size. It is possible to prevent breakage such as cracking and chipping, and to improve reliability and yield.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an element showing a configuration of a surface acoustic wave device according to an embodiment of the present invention and a method for manufacturing the same in each step.

FIG. 2 is a vertical cross-sectional view of an element showing a configuration of the surface acoustic wave device according to the embodiment and a method of manufacturing the same in each step.

FIG. 3 is a vertical cross-sectional view of the element showing the configuration of the surface acoustic wave device according to the embodiment and a method of manufacturing the same in each step.

FIG. 4 is a longitudinal sectional view showing that occurrence of cracks and chips is prevented even when stress is applied to the surface acoustic wave device according to the embodiment.

FIG. 5 is a longitudinal sectional view of an element showing a configuration of a conventional surface acoustic wave device and a method of manufacturing the same in each step.

FIG. 6 is a longitudinal sectional view of the element showing the configuration of the surface acoustic wave device and the method of manufacturing the same for each process.

FIG. 7 is a longitudinal sectional view of an element showing the configuration of the surface acoustic wave device and a method of manufacturing the same for each process.

FIG. 8 is a longitudinal sectional view showing that cracking and chipping occur when stress is applied to the surface acoustic wave device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric body 2 Comb-shaped electrode 3 Terminal electrode 4 Coating film 5 Conductor 10 Surface acoustic wave element 11 Flat plate 12 Element connection terminal 13 External connection terminal 14, 15 Adhesive 20 Base substrate

Claims (7)

[Claims] A surface acoustic wave element having a comb-shaped electrode and terminal electrodes formed on a piezoelectric body; a base substrate having external connection terminals and element connection terminals formed on a surface; A connection body for electrically connecting the terminal electrode and the element connection terminal of the base substrate; a sealing body for sealing the surface acoustic wave element and an outer peripheral portion of the base substrate; And a coating film formed on the non-electrode forming surface of the wave element. 2. The surface acoustic wave device according to claim 1, wherein said coating film is formed using a resin. 3. The surface acoustic wave device according to claim 1, wherein said coating film is formed using a material having a higher hardness than a piezoelectric material. 4. A step of forming a surface acoustic wave element by providing a comb-shaped electrode and a terminal electrode on a piezoelectric body; a step of forming a coating film on a non-electrode forming surface of the piezoelectric body; Providing a connector on the terminal electrode of the surface acoustic wave element; applying an adhesive having conductivity to the element connection terminal on the base substrate on which the external connection terminal and the element connection terminal are formed; Applying an adhesive having a property or an insulating property, and the surface acoustic wave in a state where the terminal electrode of the surface acoustic wave element and the element connection terminal of the base substrate are connected via the connection body. Fixing and sealing the element and the base substrate with the adhesive. A method for manufacturing a surface acoustic wave device, comprising: 5. The method for manufacturing a surface acoustic wave device according to claim 4, wherein in the step of forming the coating film, a resin is formed by screen printing. 6. The method for manufacturing a surface acoustic wave device according to claim 4, wherein in the step of forming the coating film, a resin is formed by spin coating. 7. The method for manufacturing a surface acoustic wave device according to claim 4, wherein in the step of forming the coating film, a thin film is formed by sputtering or vapor deposition.