JP4382945B2 - Surface acoustic wave device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface acoustic wave device for a resonator and a frequency band filter incorporated in a mobile wireless device such as an automobile phone and a cellular phone.
[0002]
[Prior art and its problems]
Conventionally, various surface acoustic wave devices have been used as elements such as filters, delay lines, oscillators and the like of electronic devices using radio waves.
[0003]
2. Description of the Related Art In recent years, surface acoustic wave filters that are particularly small and light and have high steep cut-off performance as filters have been widely used as RF stage and IF stage filters for mobile terminal devices in the field of mobile communication.
[0004]
In addition, the portable terminal device is reduced in size and weight, and in order to reduce the number of parts, the inductor component and the capacitive component mounted on the circuit board or the balance-unbalance conversion function is incorporated in the surface acoustic wave device. Therefore, there is a strong demand for downsizing that can be surface-mounted.
[0005]
At present, a can package type and a ceramic package type are put into practical use as the surface acoustic wave device, and the ceramic package type is widely used as a surface mountable and downsized device compared to the can package type.
[0006]
In the first generation ceramic package type surface acoustic wave device, the surface acoustic wave element bonded and fixed in the package and the internal electrode of the package are electrically connected by wire bonding. Therefore, the surface acoustic wave device has an occupied area five to six times that of the built-in surface acoustic wave element.
[0007]
In order to solve this problem and reduce the size, the second generation ceramic package type surface acoustic wave device has, as shown in FIG. 6, for example, comb-like electrodes 22 and wiring electrodes which are excitation electrodes on a piezoelectric substrate 21. The internal electrode 27a and the wiring electrode 23 formed on the surface acoustic wave device mounting surface of the conductor 27 (configured by 27a, 27b, 27c) wired to the package base 25 A surface acoustic wave device J that has been face-down bonded using metal bumps 24 for electrical connection has been put into practical use.
[0008]
As described above, since the electrical connection is made by connecting the metal bump 24 connected to the wiring electrode 23 and the internal electrode 27a formed on the package base 25, it is not necessary to use wire bonding. Compared to the first generation ceramic package type surface acoustic wave device, the size is reduced by about one half. In the figure, 28 is a package lid, 26 is a package frame, 27 b is a side electrode, 27 c is a bottom electrode, and 29 is a vibration space of the comb-like electrode 22.
[0009]
However, even in the above-mentioned second-generation face-down mounting type ceramic package type surface acoustic wave device, the package has about three times the size of the built-in surface acoustic wave device and is not sufficiently miniaturized. Met.
[0010]
Furthermore, the method of mounting the surface acoustic wave element on the package has a problem that it lacks mass productivity because it is assembled using individual packages after the device chip is cut from the wafer.
[0011]
In the second generation ceramic package type surface acoustic wave device, only the surface acoustic wave element and the wiring electrode on the ceramic package are configured, and the inductor component and the capacitance component for impedance adjustment mounted on the circuit board, Or, an electric circuit for adjusting an external circuit such as a balance-unbalance conversion function cannot be incorporated.
[0012]
Accordingly, the present invention has been made to cope with such a problem, and can be downsized to a surface acoustic wave element whose outer area occupies almost equal to that of a built-in surface acoustic wave element, and has high reliability. It is an object of the present invention to provide a surface acoustic wave device capable of combining a multi-functional electric circuit.
[0013]
[Means for Solving the Problems]
In order to solve the above problems, a surface acoustic wave device according to the present invention forms an excitation electrode for generating a surface acoustic wave on a piezoelectric substrate and a wiring electrode connected to the excitation electrode, and the excitation electrode and the wiring electrode are formed on the piezoelectric substrate. An external circuit adjustment electric circuit for covering the surface with an insulating protective body having external electrodes formed thereon and connecting the wiring electrodes and the external electrodes is provided in the insulating protective body.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a surface acoustic wave device according to the present invention will be described below in detail with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a similar member.
[0015]
1 and 2 schematically show a cross-sectional view of a main part of the surface acoustic wave devices S1 and S2 according to the present invention. The surface acoustic wave devices S1 and S2 include, for example, a lithium tantalate single crystal, a lithium niobate single crystal, a lithium tetraborate single crystal, a single crystal having a langasite type crystal structure, a piezoelectric ceramic such as PZT or ZnO, and the like. An excitation electrode 2 made of at least one pair of comb-like electrodes and generating a surface acoustic wave and a wiring electrode 3 connected to the excitation electrode 2 are arranged on the piezoelectric substrate 1 made of the material. 3 is covered with an insulating protective body 6.
[0016]
Here, the excitation electrode 2 is made of a metal such as aluminum or an alloy thereof, and reflector electrodes may be disposed at both ends thereof, or a plurality of these may be connected in series and / or in parallel. The wiring electrode 3 is connected to the excitation electrode 2 and is made of the same metal material as the excitation electrode 2. The insulating protective body 6 may be a thermosetting resin (epoxy, silicone, phenol, polyimide, or polyurethane resin), a thermoplastic resin (polyphenylene sulfide resin), an ultraviolet curable resin, or a low-temperature resin. It shall consist of melting point glass etc.
[0017]
Insulating protector 6 is laminated with members of insulating protector 6, and columnar conductor 5 made of metal (single or alloy of copper, gold, nickel, etc.) or conductive resin (external circuit adjusting electricity) Circuit: In the surface acoustic wave device S1, the first columnar portion 5a, the second columnar portion 5b, the flat plate portion 5c, the third columnar portion 5d, the flat plate portion 5e, and the dielectric 12. The surface acoustic wave device. In S2, a first columnar portion 5a, a second columnar portion 5b, a flat plate portion 5c, a third columnar portion 5d, and a flat plate portion 5e are disposed. This columnar conductor 5 is connected to both a wiring electrode 3 made of the same material as the excitation electrode 2 and an external electrode 7 made of a metal material such as a solder bump formed on the surface of the insulating protective body 6. Yes.
[0018]
In the laminated structure of the insulating protective body 6, by providing the columnar conductor 5 with a plurality of divided portions A and bent portions B, an inductor component and / or a capacitance component for impedance adjustment can be formed. Furthermore, a balance-unbalance conversion function unit (balun) using a mutual inductor can also be formed.
[0019]
That is, for example, like the surface acoustic wave device S1 shown in FIG. 1, the columnar conductor 5 is divided by a part A thereof, and a parallel plate type capacitive component is generated by the dielectric 12 between the columnar conductor 5 and the plate. Circuit can be formed.
[0020]
FIG. 3 shows a schematic equivalent electric circuit diagram of the configuration shown in FIG. In the circuit diagram, the capacitor 15 is shown in parallel with the signal line 13, but this may be connected in series with the signal line 13. In the figure, 17 is a surface acoustic wave element, and 14 is a ground wire.
[0021]
Further, as shown in FIG. 2, a circuit in which an inductor component is generated can be formed by bending the columnar conductor 5 so that the inside of the insulating protective body 6 is a meandering (meander-like) pattern or a spiral conductive pattern. is there.
[0022]
FIG. 4 shows a schematic equivalent electric circuit diagram of the configuration shown in FIG. Although the inductor 16 is illustrated in series with the signal line 13 in the circuit diagram, it may be connected in parallel to the signal line 13. In addition, although an example in which the inductor 16 and the capacitor 15 are connected in parallel to the ground line 14 is shown, an electric circuit that can be produced by the divided portion A and the bent portion B of the columnar conductor in the insulating protective body 6 is shown. It doesn't matter.
[0023]
FIG. 5 shows a schematic equivalent electric circuit diagram of another embodiment. In the circuit diagram, the conversion is performed by using a mutual inductor as the balance-unbalance conversion circuit 18. However, as described above, the insulating protective body 6 can be produced by the divided portion A and the bent portion B of the columnar conductor. Any electrical circuit may be used.
[0024]
In order to secure the vibration space 11 of the excitation electrode 2, a cover body 4 made of metal, resin, glass or the like is disposed between the insulating protective body 6 and the excitation electrode 2.
[0025]
Further, by providing a large number of divided portions and bent portions, the stress acting on the external electrode 7 is relaxed and transmitted to the columnar conductor, so that the influence on the piezoelectric substrate 1 can be suppressed as much as possible. As a result, when the surface acoustic wave device is mounted on a circuit board with solder or the like, the stress due to thermal strain or temperature change during the transmission is transmitted to the piezoelectric substrate 1 via the columnar electrode 5 and the characteristics are remarkably deteriorated. In some cases, the problem that cracks occur in the piezoelectric substrate can be prevented as much as possible, and a highly reliable surface acoustic wave device can be obtained.
[0026]
In any case, by providing a plurality of bent portions, the external stress applied to the external electrode 7 connected to the printed board or the like by solder or the like acts on the piezoelectric substrate 1 through the columnar conductor to prevent damage as much as possible. Can do.
[0027]
The number of pairs of the excitation electrodes 2 is about 50 to 200, the width of the electrode fingers is about 0.1 to 10.0 μm, the distance between the electrode fingers is about 0.1 to 10.0 μm, and the cross width of the electrode fingers is 10 to 80 μm. The thickness of the IDT electrode 2 is preferably about 0.2 to 0.4 μm in order to obtain desired characteristics as a resonator or a filter. Further, if a piezoelectric material such as ZnO or Al2O3 is formed on the excitation electrode 2, it is preferable because the resonance efficiency of the SAW is improved.
[0028]
As the piezoelectric substrate 1, a 42 ° or 36 ° Y-cut-X propagation LiTaO 3 crystal, a 64 ° Y-cut-X propagation LiNbO 3 crystal, and a 45 ° X-cut-Z propagation LiB 4 O 7 crystal have a large electromechanical coupling coefficient and a group. This is preferable because the delay time temperature coefficient is small. The thickness of the piezoelectric substrate 1 is preferably about 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost increases.
[0029]
In addition, this invention is not limited to said embodiment, A various change does not interfere in the range which does not deviate from the summary of this invention.
[0030]
【Example】
Next, more specific examples of the present invention will be described.
[0031]
An embodiment will be described by taking the configuration shown in FIG. 1 as an example.
[0032]
The general flow of manufacturing is to form a large number of cover bodies on a wafer, and then to form a large number of surface acoustic wave element regions on a separately prepared piezoelectric wafer. After removal by such means, sealing with an insulating protective body, and further, external electrodes are formed on the insulating protective body and finally separated into individual chips to complete the surface acoustic wave device.
[0033]
First, as shown in FIG. 1, the excitation electrode 2 and the wiring electrode 3 were formed on the piezoelectric substrate 1. A 42 ° Y-cut lithium tantalate substrate having a thickness of 350 μm was used as the piezoelectric substrate 1, and an aluminum alloy (copper content 1%) was used for the excitation electrode 2 and the wiring electrode 3 of the first layer of the wiring electrode 3. The electrode thickness was 2000 to 4000 mm. The second-layer wiring electrode 3 is a nickel / copper two-layer electrode having a thickness of 1000 mm or 2000 mm and selectively formed by photolithography.
[0034]
Here, the cover body 4 is prepared separately.
[0035]
A plating cover body 4 is formed on the main surface of a silicon wafer of the same size as the piezoelectric substrate wafer on which the surface acoustic wave element is to be formed. As this wafer, a piezoelectric substrate, a silicon substrate, or a glass substrate can be used, and a material that can be easily removed in a later process is used. The cover body 4 is formed to a thickness of about 0.2 μm to 1 μm by sputtering film formation using a metal material such as copper.
[0036]
Next, a plating guide corresponding to the vibration space of the cover body 4 is formed by photolithography. The thickness of the photoresist is 50 μm to 100 μm.
[0037]
Next, a portion corresponding to the upper portion of the cover body is formed by electrolytic plating of copper. For this electrolytic solution, copper sulfate 0.5 to 1.0 × 10 ³ mol / m ³ and sulfuric acid 1.5 to 2 × 10 ³ mol / m ³ were used, and the standard electrode of potassium chloride / silver chloride was used for the reference electrode. Use electrodes.
[0038]
Next, a plating guide corresponding to the wall portion of the cover body is formed by photolithography. The thickness of the photoresist is 50 μm to 100 μm, and the width of the groove corresponding to the wall thickness is about 50 μm to 100 μm.
[0039]
Next, a portion corresponding to the wall portion of the cover body is formed by electrolytic plating of copper, and then the low melting point glass 8 is formed on the cover body with a thickness of 5 to 10 μm by screen printing. Finally, the photoresist is removed to complete the substrate on which the cover bodies are arranged.
[0040]
Here, the cover body 4 separately formed on the silicon substrate is bonded to the piezoelectric substrate wafer on which the surface acoustic wave element is manufactured with the low melting point glass 8, and thereafter, the silicon substrate and the cover body 4 are combined using a polishing machine. Part was removed. The polishing liquid at this time was performed by using colloidal silica mixed in an aqueous alkali solution such as an aqueous sodium hydroxide solution.
[0041]
Next, a guide for forming the first columnar portion 5a by plating was formed of a photoresist, and the first columnar portion 5a was formed by electrolytic plating of copper. The diameter of the first columnar part 5a at this time was 100 μm and the height was 200 μm.
[0042]
Next, after removing the photoresist for plating guide, a part of the insulating protective body 6 was formed by transfer molding using a thermosetting molding resin. Further, by attaching a heat-resistant resin film having a thickness of 100 μm to a die for pressing the resin from above, the upper part of the first columnar part 5a is exposed from the first resin layer. The thickness of the first resin layer was about 200 μm.
[0043]
Similarly, the flat plate portion 5c, the dielectric 12 between the flat plates, the flat plate portion 5e, and the columnar portion 5b were sequentially formed.
[0044]
As the flat plate portion, a single-layer electrode of copper and a double-layer electrode of nickel and copper were used, and the thicknesses thereof were 1 μm, 1000 mm, and 2000 mm, respectively. Copper plating was used for the columnar portion, and the thickness was 100 μm.
[0045]
Next, cream solder was screen-printed on the top of the columnar conductor 5 with a thickness of 10 μm, and then reflowed at 270 ° C. to form solder bumps to be the external electrodes 7.
[0046]
Finally, the surface acoustic wave devices (chips) were separated into one by one by dicing the substrate to complete the surface acoustic wave device. In the obtained surface acoustic wave device, the comb-like electrode is protected by a sealing resin that is a cover body and an insulating protective body, and a columnar conductor is provided with a dividing portion and a bent portion for stress relaxation. As a result, even in the temperature cycle test of −40 ° C. to 85 ° C., the piezoelectric substrate was not damaged and no characteristic deterioration was observed. Further, it was possible to realize a reduction in size and a reduction in height of 0.8 mm, almost the same occupied area as the surface acoustic wave filter element (1 mm × 1.5 mm).
[0047]
【The invention's effect】
As described above in detail, according to the surface acoustic wave device of the present invention, an inductance component is provided by providing a plurality of divided portions and bent portions on the conductor connecting the wiring electrode and the external electrode of the surface acoustic wave element. It is possible to arbitrarily configure an external circuit adjustment electric circuit having a capacitance component, so that a multi-functional electronic circuit such as an inductor, a capacitor, or a balun that has been mounted on a circuit board for impedance adjustment in the past can be used. A surface acoustic wave device that can be incorporated can be provided.
[0048]
In addition, since the conductor is provided with a plurality of divided portions and bent portions, the stress applied to the external electrode can be sufficiently relaxed, so that a highly reliable surface acoustic wave device that does not deteriorate due to a temperature change or the like can be provided.
[0049]
In addition, the piezoelectric substrate can be used as the lower housing and sealed by resin molding to be used as the upper housing, eliminating the need for a conventional ceramic package, etc. It is possible to provide a surface-mountable surface wave device that can be mounted on the surface and is ultimately miniaturized in that the size of the surface wave device is substantially equal to that of the built-in surface acoustic wave device.
[0050]
Furthermore, all the manufacturing processes can be performed in a wafer process, and a large number of surface acoustic wave devices can be formed simultaneously by processing in units of wafers. That is, individual surface acoustic wave devices can be formed in a dicing process on a wafer that has been completely sealed with a resin. Since the finished product can be obtained by cutting, it is not necessary to assemble the surface acoustic wave element individually after the conventional dicing process, and assembly equipment such as a die bonder, wire bonder, seam welder, etc. with low processing capacity is available. This eliminates the need for it, greatly simplifies the process, and provides a surface acoustic wave device with high mass productivity.
[Brief description of the drawings]
FIG. 1 is a schematic end view illustrating an embodiment of a surface acoustic wave device according to the present invention.
FIG. 2 is a schematic end view illustrating an embodiment of another surface acoustic wave device according to the present invention.
FIG. 3 is a schematic equivalent circuit diagram of a surface acoustic wave device according to the present invention.
FIG. 4 is a schematic equivalent circuit diagram of another surface acoustic wave device according to the present invention.
FIG. 5 is a schematic equivalent circuit diagram of another surface acoustic wave device according to the present invention.
FIG. 6 is a schematic end view illustrating a conventional surface acoustic wave device.
[Explanation of symbols]
1: Piezoelectric substrate 2: Excitation electrode (a pair of comb-shaped electrodes)
3: Wiring electrode 4: Cover body 5: Columnar conductor (electric circuit for external circuit adjustment)
5a: first columnar portion 5b: second columnar portion 5c: flat plate portion 5d: third columnar portion 5e: flat plate portion 6: resin layer (insulating protector)
7: External electrode 8: Low melting point glass 9: Vibration space 10: Resin layer 11: Second wiring electrode 12: Dielectric between plates 13: Signal line 14: Ground line 15: Capacitor 16: Inductor 17: Surface acoustic wave element 18: Balance-unbalance conversion circuit S1, S2: Surface acoustic wave device according to the present invention J: Conventional surface acoustic wave device

Claims (6)

A piezoelectric substrate ;
An excitation electrode disposed on the piezoelectric substrate,
A wiring electrode disposed on the piezoelectric substrate and connected to the excitation electrode ;
A cover body that constitutes a vibration space of the excitation electrode and is bonded to the piezoelectric substrate such that an outer peripheral edge is located in a region immediately above the piezoelectric substrate;
An insulating protective body made of a resin covering the cover body ;
An external electrode disposed on the insulating protective body;
The insulating protection provided in the body, the surface acoustic wave device and a capacitive component that is connected to the wiring electrode. The surface acoustic wave device according to claim 1, wherein the capacitive component is formed of a columnar conductor having two opposing flat plate-like portions. A piezoelectric substrate;
An excitation electrode disposed on the piezoelectric substrate;
A wiring electrode disposed on the piezoelectric substrate and connected to the excitation electrode;
A cover body that constitutes a vibration space of the excitation electrode and is bonded to the piezoelectric substrate such that an outer peripheral edge is located in a region immediately above the piezoelectric substrate;
An insulating protective body made of a resin covering the cover body;
An external electrode disposed on the insulating protective body;
A surface acoustic wave device provided with an inductor component for impedance adjustment provided in the insulating protective body and connected to the wiring electrode. The surface acoustic wave device according to claim 3, wherein the inductor component is formed of a columnar conductor having a bent portion. The surface acoustic wave device according to claim 3, wherein the inductor component is formed of a columnar conductor having at least one of a meandering pattern or a spiral pattern. A piezoelectric substrate;
An excitation electrode disposed on the piezoelectric substrate;
A wiring electrode disposed on the piezoelectric substrate and connected to the excitation electrode;
A cover body that constitutes a vibration space of the excitation electrode and is bonded onto the piezoelectric substrate such that an outer peripheral edge is located in a region directly above the piezoelectric substrate;
An insulating protective body made of a resin covering the cover body;
An external electrode disposed on the insulating protective body;
A surface acoustic wave device comprising: a balance-unbalance conversion function unit provided in the insulating protective body and connected to the wiring electrode.

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