JPH10303689A - Surface acoustic wave device and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a surface acoustic wave device which is excellent in performance and can be reduced in size and thickness. An electrode pattern (1) is formed on a surface of a piezoelectric substrate (10).
A surface acoustic wave chip 3 provided with an electrode pattern 1 and conductive patterns 5 and 6 connected to the electrode pattern 11;
An insulating substrate 1 electrically connected to the surface acoustic wave chip 3 with a gap 19 between the insulating substrate 1 and a cap 4 for accommodating the surface acoustic wave chip 3 therein by fitting an opening to the insulating substrate 1. And the electrode pattern 1 of the surface acoustic wave chip 3
The surface acoustic wave chip 3 is fixed in the cap 4 so as not to cover at least the main part of the cap 1, and the joint between the peripheral portion of the insulating substrate 1 and the open end of the cap 4 is sealed from the inside of the cap 4. Adhesive seal layer 20
It is characterized by having.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication device (for example, a pager, a portable telephone, a PHS, a FPLMTS, a business radio, a portable radio for an amateur radio), an RF filter, a radio modem for a handy personal computer (CDPD). The present invention relates to a surface acoustic wave device used for RF, IF filters and the like, and more particularly to a surface acoustic wave device which can improve the frequency characteristics, is inexpensive, and can be made smaller and thinner, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Surface-mounted surface acoustic wave devices are used as RF and IF filters for mobile communication devices such as mobile phones, PHSs, and pagers. 16 to 19 show the structure of a conventional surface acoustic wave device.

FIG. 16 is an exploded perspective view of a surface acoustic wave device according to a first conventional example, and FIG. 17 is a longitudinal sectional view of the surface acoustic wave device. This conventional example is disclosed in Japanese Patent Application Laid-Open No. 61-245709, in which a surface acoustic wave (hereinafter abbreviated as SAW) chip 51 is mounted on an insulating substrate 50, and a conductive pattern of the insulating substrate 50 is formed. The electrodes of the SAW chip 51 are electrically connected by bonding wires 52. An insulating cap 53 is placed on the insulating substrate 50 from above the SAW chip 51, and the opening end of the cap 53 and the insulating substrate 50 are sealed with a sealing adhesive 54.

FIG. 18 is a longitudinal sectional view of a surface acoustic wave device according to a second conventional example. This conventional example is disclosed in JP-A-3-727.
08, in which the seal ring 55 is brazed to the insulating substrate 50 by silver brazing, and the metal cap 56 is sealed by seam welding to improve airtightness. Reference numeral 57 denotes a seam weld.

FIG. 19 is a sectional view of a surface acoustic wave device according to a third conventional example. This conventional example uses a ceramic multilayering technique and uses a multilayer ceramic case 58 to form a SAW.
A pocket 59 for accommodating a chip is formed, a SAW chip 51 is arranged in the pocket 59, and a pocket 59 is formed by a flat metal plate 60 via a seal ring 55 brazed with silver.
The opening is closed.

[0006]

However, in the conventional surface acoustic wave device having such a structure, the frequency characteristics inside and outside the band are not sufficient, and excellent characteristics as the surface acoustic wave device have not been exhibited.

In the first and second conventional examples, a space A for wire bonding is required, and there is a disadvantage that the package size is increased due to the presence of the space A.

In the second and third conventional examples, a seal ring is used. However, the seal ring type requires a high-level and complicated operation for brazing silver to an insulating substrate, and the material cost is high. And the productivity was poor.

Recent mobile communication devices, especially mobile phones, PH
There is a strong demand for ultra-small, ultra-thin, and low-price S and pagers, and in order to meet this demand, ultra-small, ultra-thin, and low-priced components are indispensable.

The present invention has been made in view of such a background, and an object of the present invention is to provide a surface acoustic wave device which is excellent in frequency characteristics and can be reduced in size, thickness, and cost, and a method of manufacturing the same. Aim.

[0011]

According to a first aspect of the present invention, there is provided a surface acoustic wave chip having an electrode pattern provided on a surface of a piezoelectric substrate, and a conductive pattern connected to the electrode pattern. An insulating substrate electrically connected to the surface acoustic wave chip with a gap between the electrode pattern and a cap for accommodating the surface acoustic wave chip inside by fitting an opening to the insulating substrate And fixing the surface acoustic wave chip in the cap so as not to cover at least the main part of the electrode pattern of the surface acoustic wave chip, and joining the peripheral portion of the insulating substrate to the opening end of the cap with the cap. And a sealing layer having an adhesive property for sealing from the inside, such as an epoxy resin.

According to a second aspect of the present invention, an electrode pattern of a surface acoustic wave chip is provided such that an electrode pattern of the surface acoustic wave chip and a conductive pattern of an insulating substrate face each other via a gap. Electrically connecting the conductive pattern with the conductive pattern of the insulating substrate, injecting a predetermined amount of a sealing agent such as an epoxy resin into the inside of the cap, and capping the insulating substrate with the surface acoustic wave chip. Fitting the surface acoustic wave chip inside the cap with the sealant, and sealing the joint between the peripheral portion of the insulating substrate and the open end of the cap from the inside of the cap. And characterized in that:

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, according to the present invention, a surface acoustic wave chip is fixed in a cap so that at least a main part of an electrode pattern of the surface acoustic wave chip is not covered by a seal layer, and an insulating substrate is provided. By forming a gap between the surface acoustic wave device and the surface acoustic wave device, there is no loss of the surface acoustic wave, the frequency characteristics outside the band and within the band are improved, and the surface acoustic wave device has excellent performance over a long period of time.

In addition, a complicated and complicated process of silver brazing of a seal ring required for seam welding, which is generally employed in the conventional structure, is not required, so that material costs can be reduced and working efficiency can be improved.

Further, by enclosing the sealing layer in the cap, the bottom area of the package can be made substantially the same size as the insulating substrate, and the device can be made smaller and thinner. In addition, the sealing layer sealed in the cap can simultaneously exhibit both the function of fixing the SAW chip and the function of hermetic sealing, and the cost can be reduced from this point as well.

Furthermore, by bump bonding the surface acoustic wave chip to the insulating substrate in a face-down state, a space for wire bonding becomes unnecessary, and as a result, the surface acoustic wave device can be reduced in size and thickness.

By using a conductive cap, electromagnetic interference with the outside can be eliminated. Further, by electrically connecting the cap and the conductive pattern of the insulating substrate, electromagnetic shielding from the outside can be further enhanced.

Hereinafter, embodiments of the present invention will be specifically described. 1 to 4 are views for explaining the surface acoustic wave device according to the first embodiment, FIG. 1 is an exploded perspective view thereof, FIG. 2 is a perspective view in a state where assembly is completed, and FIG. Is a longitudinal sectional side view, and FIG. 4 is an enlarged plan view showing an example of an electrode pattern of a SAW chip.

On an insulating substrate 1 made of glass epoxy resin or ceramic, a SAW chip 3 having a conductive lower surface bump 2 made of, for example, gold or solder (see FIG. 3) is mounted. And the cap 4 is fitted.

An input / output conductive pattern 5 and a ground conductive pattern 6 are formed on the insulating substrate 1, and these conductive patterns 5, 6 extend from the upper surface of the insulating substrate 1 to the lower surface via the side end surfaces. ing. Two groove-shaped recesses 7 having a depth substantially equal to the thickness of the cap 4 are formed on the long-side end surface of the insulating substrate 1 and at a place other than where the ground conductive pattern 6 is formed. 1).

The cap 2 is made of a metal or a synthetic resin such as an iron-nickel-cobalt alloy (trade name Kovar) or an iron-nickel alloy (trade name 42 alloy).
It has a box-like shape having an opening having substantially the same area as the insulating substrate 1 on one surface. A leg 8 is provided at the opening end so as to fit into the recess 7, and the opening end faces the input / output conductive pattern 5. Is formed with a notch 9 to avoid connection with the input / output conductive pattern 5.

As shown in FIG. 4, the SAW chip 3 has a first surface on a piezoelectric substrate 10 made of lithium niobate or the like.
The multi-electrode SAW 11a and the second multi-electrode SAW 11b are provided side by side.

In the first multi-electrode SAW 11a, the input electrode 12a and the output electrode 13a face each other with a predetermined gap therebetween to form a comb-shaped electrode, and reflectors 14 are provided on both sides of the comb-shaped electrode.
a, 14a are provided. Second multi-electrode SAW11
Similarly, the input electrode 12b and the output electrode 13b face each other to form a comb-shaped electrode, and reflectors 14b, 14b
b is provided.

The first multi-electrode SAW 11a includes a reflector 14a
-Comb-shaped electrodes 12a, 13a-Reflector 14a is second multi-electrode SAW 11b is reflector 14b-Comb-shaped electrode 12
b, 13b-reflector 14b are both arranged along the surface acoustic wave propagation direction. 15a is an input terminal, 16b
Is an output terminal, 17a and 17b are ground terminals, and 18 is a conductor.

As shown in FIG. 3, the SAW chip 3 is arranged on the insulating substrate 1 with the multi-electrode SAWs 11a and 11b facing down, and the input / output electrodes 15a and 16b of the SAW chip 3 are arranged.
Indicates that the input / output conductive pattern 5 of the insulating substrate 1 has a SAW
The ground electrode 17 of the chip 3 is connected to the ground conductive pattern 6 of the insulating substrate 1 by TAB bonding via the bump 2. Also,
The multi-electrode SAWs 11a and 11b do not directly contact the insulating substrate 1, but face the insulating substrate 1 with a gap 19 so that vibration of the multi-electrode SAWs 11a and 11b is not suppressed.

On the other hand, the cap 4 is made of an epoxy resin or a silicone rubber resin, for example, having a viscosity of about
A predetermined amount of a sealing agent 20 having a high viscosity of not less than 00 CPS and having an adhesive property is injected, and the cap 4 is covered with the insulating substrate 1 with the SAW chip 3, and as shown in FIG. 8 is fitted into the concave portion 7 of the insulating substrate 1, and the opening end 21 other than the leg 8 is in contact with the peripheral edge 22 of the insulating substrate 1. As a result, the insulating substrate 1 closes the opening of the cap 4 without excessively entering the inside, and the SAW chip 3 is accommodated inside the cap 4 as shown in FIG. 20
Is charged. Since the sealant 20 has a high viscosity, the sealant 20 does not penetrate into the gap 19 between the insulating substrate 1 and the SAW chip 3 and at least the main parts (comb-shaped electrodes 1213a and the reflector 14) of the multi-electrode SAWs 11a and 11b are formed. Sealant 2
The gap 19 is secured without being covered with zero. The notch 9 also has a function of discharging excess sealant to the outside when the sealant 20 is filled in the package.

In this manner, SAW is applied by the sealant 20.
The chip 3 is fixed in the cap 4, and the joint between the insulating substrate 1 and the cap 4 is hermetically sealed from the inside. In the case of the metal cap 4, a part of the opening end 21 is in contact with and electrically connected to the ground conductive pattern 6, so that electromagnetic interruption (electromagnetic interference) with the outside can be further enhanced. .

FIG. 5 is a diagram showing frequency characteristics when the SAW chip 3 is fixed (solid line) and when it is not fixed (dashed line). As is apparent from this figure, when the SAW chip 3 is not fixed, a longitudinal vibration in the thickness direction occurs at a frequency interval Δf determined by the chip volume, and the out-of-band and in-band frequency characteristics are deteriorated. Function is not fully exhibited. On the other hand, by firmly fixing the SAW chip 3 in the cap 4 as in the present invention, the out-of-band and in-band frequency characteristics are improved, and the function as a surface acoustic wave device can be sufficiently exhibited.

FIG. 6 is a view showing a second embodiment of the present invention, wherein laminated substrates 1a to 1c are used as an insulating substrate 1, and each laminated substrate 1a to 1c has an input / output conductive pattern 5 and a ground. A conductive pattern 6 is formed, and a part of the input / output conductive pattern 5 is electrically connected to the metal cap 4. The other configuration is the same as that of the first embodiment, and the description thereof is omitted.

FIG. 7 is a view showing a third embodiment of the present invention. In this embodiment, the injection amount of the sealant 20 is made smaller than that in the first embodiment to further reduce the weight. The SAW chip 3 is fixed on the back surface and the insulating substrate 1
And the cap 4 is sealed at the joint.

FIGS. 8 to 12 show a fourth embodiment of the present invention. FIGS. 8, 9, and 10 are a top view, a side view, and a bottom view of the insulating substrate 1, and FIG. 4 is a front view, and FIG. 12 is a longitudinal sectional view of the surface acoustic wave device.

The input / output conductive pattern 5 and the ground conductive pattern 6 are formed on the upper surface of the insulating substrate 1 as shown in FIG. The lower surface is patterned as shown in FIG.

As shown in FIG. 8, a solder layer 23 is formed on the ground conductive pattern 6 at the four corners of the upper surface of the insulating substrate 1 by printing. Then, as shown in FIG. 12, the metal cap 4 is fitted to the insulating substrate 1 so that the open end 21 of the cap 4 comes into contact with the ground conductive pattern 6 and then reflows to form the solder layer. By melting 23, the electrical connection between the cap 4 and the ground conductive pattern 6 is further ensured.

FIGS. 13 to 16 show a fifth embodiment of the present invention. FIGS. 13 and 14 are top and bottom views of the insulating substrate 1, and FIG. FIG. 2 is a longitudinal sectional view of a conductive substrate 1.

The input / output conductive pattern 5 and the ground conductive pattern 6 are patterned on the upper surface of the insulating substrate 1 as shown in FIG. 13, and are patterned on the lower surface of the insulating substrate 1 as shown in FIG. The insulating substrate 1 is 2
There are two through holes 24, and the ground conductive pattern 6 on the upper surface side and the ground conductive pattern 6 on the lower surface side of the insulating substrate 1 are electrically connected through the through holes 24 (see FIG. 15). Thus, through hole 2
By providing 4, the electrical isolation between the input and the output is strengthened, so that the attenuation characteristics outside the band can be further improved.

Since the ground conductive pattern 6 is formed on the upper surface of the insulating substrate 1 as shown in FIG. 15, the metal cap 4 is fitted to the insulating substrate 1 so that the opening end of the cap 4 is opened. 21 is in contact with and electrically connected to the ground conductive pattern 6. If necessary, the open end 21 of the cap 4 and the ground conductive pattern 6 can be electrically connected by solder 23 as in the fourth embodiment. The electrical connection between the cap 4 and the ground conductive pattern 6 by soldering can also be made outside the package.

[0037]

As described above, according to the present invention, the surface acoustic wave chip is fixed in the cap so as not to cover at least the main part of the electrode pattern of the surface acoustic wave chip with the sealing layer, and the sealing substrate is in contact with the insulating substrate. By forming a gap between the two, it is possible to provide a surface acoustic wave device that has no loss of surface acoustic waves, improves out-of-band and in-band frequency characteristics, and has excellent performance over a long period of time.

Further, a complicated and complicated process of silver brazing of a seal ring required for seam welding, which is generally employed in the conventional structure, is not required, so that material costs can be reduced and work efficiency can be improved.

Further, by enclosing the sealing layer in the cap, the bottom area of the package can be made substantially the same size as the insulating substrate, and the device can be made smaller and thinner. In addition, the sealing layer sealed in the cap can simultaneously exhibit both the function of fixing the SAW chip and the function of hermetic sealing, and the cost can be reduced from this point as well.

By bump-bonding the surface acoustic wave chip to the insulating substrate in a face-down state as in the above embodiment, a space for wire bonding becomes unnecessary, and as a result, the surface acoustic wave device can be made smaller and thinner. Can be achieved.

Further, by using a conductive cap as in the above embodiment, electromagnetic interference with the outside can be eliminated. In addition, by electrically connecting the cap to the conductive pattern of the insulating substrate, electromagnetic shielding from the outside can be further enhanced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a surface acoustic wave device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the surface acoustic wave device in a state where assembly is completed.

FIG. 3 is a longitudinal sectional view of the surface acoustic wave device.

FIG. 4 is an enlarged plan view of an electrode pattern of a SAW chip in the surface acoustic wave device.

FIG. 5 is a frequency characteristic diagram of the surface acoustic wave device when a SAW chip is fixed and when it is not fixed.

FIG. 6 is a perspective view of a surface acoustic wave device according to a second embodiment of the present invention.

FIG. 7 is a sectional view of a surface acoustic wave device according to a third preferred embodiment of the present invention.

FIG. 8 is a top view of an insulating substrate used for a surface acoustic wave device according to a fourth embodiment of the present invention.

FIG. 9 is a side view of the insulating substrate.

FIG. 10 is a bottom view of the insulating substrate.

FIG. 11 is a front view of a cap used in the surface acoustic wave device.

FIG. 12 is a longitudinal sectional view of the surface acoustic wave device.

FIG. 13 is a top view of an insulating substrate used for a surface acoustic wave device according to a fifth embodiment of the present invention.

FIG. 14 is a bottom view of the insulating substrate.

FIG. 15 is a sectional view of the insulating substrate taken along line XX of FIG. 13;

FIG. 16 is an exploded perspective view of a surface acoustic wave device according to a first conventional example.

FIG. 17 is a longitudinal sectional view of the surface acoustic wave device.

FIG. 18 is a longitudinal sectional view of a surface acoustic wave device according to a second conventional example.

FIG. 19 is a longitudinal sectional view of a surface acoustic wave device according to a third conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Bump 3 SAW chip 4 Cap 5 Input / output conductive pattern 6 Ground conductive pattern 7 Concave portion 8 Leg 9 Notch 10 Piezoelectric substrate 11 Multi-electrode SAW 19 Gap 20 Sealant 21 Opening end 22 Peripheral edge 23 Solder layer 24 Through hole

Claims (14)

[Claims] 1. A surface acoustic wave chip having an electrode pattern provided on a surface of a piezoelectric substrate, and a conductive pattern connected to the electrode pattern, wherein the surface acoustic wave chip is electrically connected to the electrode pattern with a gap between the electrode pattern. An insulating substrate connected to the surface acoustic wave chip, a cap for accommodating the surface acoustic wave chip inside by fitting an opening to the insulating substrate, and covering at least a main part of an electrode pattern of the surface acoustic wave chip. And a sealing layer having an adhesive property for sealing a joint between a peripheral portion of the insulating substrate and an opening end of the cap from inside the cap, while fixing the surface acoustic wave chip in the cap. Surface acoustic wave device. 2. The surface acoustic wave device according to claim 1, wherein an electrode pattern of the surface acoustic wave chip and a conductive pattern of an insulating substrate are connected via a bump. 3. The surface acoustic wave device according to claim 1, wherein the cap has conductivity. 4. The surface acoustic wave device according to claim 3, wherein the cap is electrically connected to a conductive pattern provided on the insulating substrate. 5. The insulating substrate according to claim 1, wherein a first engaging portion is provided on the insulating substrate, a second engaging portion is provided on the cap, and the insulating substrate is fitted to an opening end of the cap. The surface acoustic wave device is characterized in that the first engagement portion and the second engagement portion engage with each other to position the insulating substrate at the opening end of the cap. 6. The surface acoustic wave device according to claim 1, wherein a relief portion is provided at a part of the cap to allow excess sealant to escape outward. 7. The elastic substrate according to claim 1, wherein a through hole for electrically connecting the conductive pattern inside and the conductive pattern outside the insulating substrate is provided in the insulating substrate. Surface wave device. 8. The electrode pattern of the surface acoustic wave chip and the conductive pattern of the insulating substrate are electrically connected so that the electrode pattern of the surface acoustic wave chip and the conductive pattern of the insulating substrate face each other via a gap. And a step of injecting a predetermined amount of a sealant inside the cap; fitting the insulating substrate with the surface acoustic wave chip to an open end of the cap; and capping the surface acoustic wave chip with the sealant. And a step of sealing the joint between the peripheral portion of the insulating substrate and the opening end of the cap from the inside of the cap. 9. The method according to claim 8, wherein the electrode pattern of the surface acoustic wave chip and the conductive pattern of the insulating substrate are connected via a bump. 10. The method for manufacturing a surface acoustic wave device according to claim 8, wherein said cap has conductivity. 11. The method according to claim 10, wherein the cap is electrically connected to a conductive pattern provided on an insulating substrate. 12. The insulating substrate according to claim 8, wherein a first engaging portion is provided on the insulating substrate, and a second engaging portion is provided on the cap, and the insulating substrate is fitted to an opening end of the cap. The method for manufacturing a surface acoustic wave device, wherein the first and second engaging portions engage with each other to position the insulating substrate at the open end of the cap. 13. The method for manufacturing a surface acoustic wave device according to claim 8, wherein an escape portion for allowing excess sealant to escape to the outside is provided in a part of the cap. 14. The elastic substrate according to claim 8, wherein a through hole for electrically connecting the conductive pattern inside and the conductive pattern outside the insulating substrate is provided in the insulating substrate. A method for manufacturing a surface acoustic wave device.