JP2000077969A - Surface acoustic wave device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a excellent unbalanced input-balanced output type or balanced input-unbalanced output type surface acoustic wave device which can be miniaturized with large specific band width. SOLUTION: This surface acoustic wave device S1 is obtained by successively arranging a balun element 2 which is put on a base 34 where an input electrode and output electrode are formed and then connected to either electrode to perform the balanced-unbalanced or unbalanced-balanced conversion and a surface acoustic wave element 1 which has an exciting electrode 11a connected to the element 2 on a piezoelectric substrate 15. Otherwise, a package which stores a surface acoustic wave element consisting of a piezoelectric substrate including an exciting electrode connected to a balun element can be placed on the balun element consisting of a laminated printed board.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave device such as a frequency band filter incorporated in mobile radio equipment such as a mobile phone and a mobile phone, and more particularly to an unbalanced input-balanced output type or a surface acoustic wave device. The present invention relates to a balanced input-unbalanced output type surface acoustic wave device.

[0002]

2. Description of the Related Art In recent years, a frequency band filter for mobile communication has been required to have a wide band, and a ratio of a pass band width to a center frequency (hereinafter, also referred to as a ratio band width) is as follows. For example, for a center frequency of 942 MHz,
It has increased to 35MHz (about 3.7%). In addition, in consideration of the shift of the filter characteristics due to the temperature and the variation of the filter characteristics due to the manufacturing, the pass band width usually needs to be set larger than the above requirement (for example, about 50 MHz, about 5.3%).

[0003] In addition, by reducing the number of parts used for reducing the size, weight, and cost of mobile communication devices and the like, new functions have been added to surface acoustic wave (SAW) devices. Have been requested, for example,
There is a demand for a device capable of supporting an unbalanced input-balanced output type or a balanced input-unbalanced output type.

Here, the balanced input or the balanced output is
A signal is a signal that is input or output as a potential difference between two signal lines. The signals on each signal line have the same amplitude,
The phases are out of phase. On the other hand, an unbalanced input or an unbalanced output means that a signal is one with respect to the ground potential.
It refers to what is input or output as the potential of this line.

A conventional SAW filter is generally an unbalanced input-unbalanced output type SAW filter (hereinafter referred to as an unbalanced type SW filter).
AW filter), if the circuit and electronic components downstream of the SAW filter are of the balanced input type, S
A circuit configuration in which a balun element as an unbalanced-balanced converter is inserted between the AW filter and the subsequent stage has been adopted.

Similarly, when the circuits and electronic components at the preceding stage of the SAW filter are of a balanced output type, the circuit configuration is such that a balun element which is also a balance-unbalance converter is inserted between the preceding stage and the SAW filter. .

At present, a so-called unbalanced input-balanced output type SA in which an SAW filter has an unbalanced-balanced conversion function or a balanced-unbalanced conversion function without using a balun element.
Practical use of a W filter or a balanced input-unbalanced output type SAW filter (hereinafter, abbreviated as a balanced type SAW filter) is in progress.

However, for example, the conventional balanced SAW filter J as shown in FIG. 7 is difficult to obtain a large fractional bandwidth due to its design. On the other hand, unbalanced S
Although the AW filter can obtain a large fractional bandwidth, it has a problem that a balun element is required and the entire device becomes large in area. In FIG. 7, D1 is a comb-shaped IDT electrode, D2 is a reflector electrode, I1 is an input terminal, and O1 and O2 are output terminals.

Accordingly, the present invention has been proposed in view of the above circumstances, and has as its object to provide an excellent unbalanced input-balanced output type or balanced input-unbalanced type having a large fractional bandwidth and capable of miniaturization. An object of the present invention is to provide an output type surface acoustic wave device.

[0010]

According to the present invention, there is provided a surface acoustic wave device comprising: a substrate on which an input electrode and an output electrode are formed; and a balanced-unbalanced conversion or an unbalanced-balanced connected to the input or output electrode. A balun element for performing conversion and a surface acoustic wave element having an excitation electrode connected to the balun element on a piezoelectric substrate are sequentially stacked and arranged.

Further, a package may be provided on a balun element composed of a laminated wiring substrate, in which a surface acoustic wave element composed of a piezoelectric substrate having excitation electrodes connected to the balun element is accommodated. That is, the package is configured such that the external terminal surface of the package accommodating the surface acoustic wave element composed of the piezoelectric substrate on which the excitation electrode is formed is mounted on the balun element composed of the laminated wiring substrate having the connection terminals on the upper surface.

[0012]

Embodiments of a surface acoustic wave device according to the present invention will be described below in detail with reference to the drawings.

FIGS. 1A and 1B are a longitudinal sectional view and a transverse sectional view, respectively, of a surface acoustic wave device S1. As shown in FIG. 1, the surface acoustic wave device S1 has input electrodes and output electrodes described later formed thereon, and is connected to the input electrodes or output electrodes on a base 34 constituting a package 3 made of ceramic or the like. A SAW composed of a balun element 2 composed of a laminated wiring board made of ceramic or the like for performing a balanced conversion or an unbalanced-balanced conversion, and an electrode 11 such as an excitation electrode electrically connected to the balun element 2 on a piezoelectric substrate 15. The element 1 is arranged by being sequentially superposed.

Here, the package 3 is configured by laminating a first frame 33, a second frame 32, and a lid 31 on the base 34. The balun element 2 is mounted and fixed at a predetermined position on the base 34 by a flip chip method. Further, the SAW element 1 is mounted and fixed on the balun element 2 with an adhesive member such as silicon resin. Note that w
Is a wire made of an Au wire or the like, and is wired between the SAW element 1 and the balun element 2, between the SAW element 1 and the package 3, and between the balun element 2 and the package 3. Also,
In the figure, 12 to 14 indicate electrode pads, respectively.

FIG. 2A shows a SAW element 1 and a balun element 2.
The vertical cross section of the composite device formed by
(C) illustrates the planar shape. FIG. 2B shows the cross-sectional shape of the insulator layer 41.

As shown in FIGS. 2A to 2C, the balun element 2 is a multilayer wiring board in which an insulating layer and a conductor pattern are stacked in multiple layers. Become. The upper layer 4 includes an insulator layer 42, a conductor pattern 43, and an opening 41a for exposing the conductor pattern 43 to the outside.
And an insulator layer 41 having The lower layer 5 is composed of an insulator layer 51 and a conductor pattern 52. The conductor pattern 52 is formed so as to be connectable to the outside through pinholes, and the output terminal sections 52a and 52b and the ground terminal section 52c are formed. Have. That is, these terminals are connected to the electrodes formed on the package 3.

The conductor pattern 43 is an electrode made of a metal such as Au, is designed to have an inductor component, and is formed in a spiral or meander shape or the like. In addition, connect both ends to the bonding pad, and through the wire,
One is connected to the SAW element 1 and the other is connected to a ground electrode to be described later on the package 3.

The conductor pattern 52 is also a conductor pattern 43.
It is designed to have the same material and characteristics as those described above, and both ends and an intermediate portion thereof are formed so as to be connected to pads formed on the back surface of the balun element through pin holes of the insulator layer 51. Pads 52a and 52b at both ends on the back surface side of the balun element 2 are connected to output 1 electrodes and output 2 electrodes described later on the package 3, respectively, and a pad 52c at an intermediate portion is provided.
Are connected to a ground electrode described later in the package 3.

FIGS. 3 (a) and 3 (b) are views showing planes of partial layers constituting a package. As shown in FIG. 3A, an input electrode 33a and ground electrodes 33b and 33c are formed in the first frame 33. FIG.
As shown in (b), the base 34 has input electrodes 34a,
An output 1 electrode 34b, an output 2 electrode 34c, and a ground electrode 34d are configured. Here, the composite element of the SAW element and the balun element is mounted and fixed at a position indicated by a broken line. The electrodes formed on the back surface of the composite element and the electrodes of the package are connected by a flip-chip method, respectively, so that conduction is obtained.

With the above configuration, the unbalanced signal input to the surface acoustic wave device S1 can pass through the SAW element 1 and the balun element 2 and be converted into a balanced signal and output. Further, since the SAW element has no problem even with an unbalanced SAW filter, it is possible to design a large fractional bandwidth. Further, the mounting area is less than 1/2 of that of the conventional surface acoustic wave device in which the balun elements are arranged and connected in a plane, and the size can be reduced.

Next, FIG. 5A is a longitudinal sectional view, and FIG.
The surface acoustic wave device S2 shown in FIG. The surface acoustic wave device S2 includes a SAW device on a balun element 7 composed of a laminated wiring substrate having a connection terminal portion 7a formed on the upper surface.
A package 8 accommodating the element 6 and having a connection terminal portion (external terminal surface) 85 formed at a lower portion is provided. The balun element 7 has a comb-shaped excitation electrode 61 constituting the SAW element 6.
a, an electrode 61 such as a reflector electrode 61b, an input / output pad 62
To 64, which are formed on the piezoelectric substrate 65.

Here, the package 8 is configured by laminating a first frame 83, a second frame 82, and a lid 81 on a base 84, and the balun element 7 is electrically conductive on the lower surface of the package 8. Are bonded via an adhesive member and an electrode layer.
Note that w is a wire made of an Au wire or the like, and is wired between the SAW element 6 and the package 8. In the drawing, 62 to 64 are electrode pads, and 83 a to 83 c are electrode patterns formed on the first frame 83.

The SAW element 6 is mounted on the base 8 in the package 8 by face-up mounting or flip chip method.
4 is mounted and fixed at a predetermined position, and has a shape in which electrical wiring is provided by a wire such as an Au wire. The sheet of the package 8 and the sheet of the balun element 7 are mechanically and electrically connected and mounted and fixed by an adhesive resin such as epoxy or high-temperature solder.

FIG. 6A is a longitudinal sectional view for explaining the laminated structure of the balun element 7, and FIGS. 6B to 6E are transverse sectional views of each layer. As shown in FIG. 6, the balun element 7 is also a multilayer wiring board in which an insulator layer and a conductor pattern are stacked in multiple layers as described above, and includes an upper layer 9 and a lower layer 10. The upper layer 9 includes an insulator layer 92 and a conductor pattern 9.
3, composed of an insulator layer 91; The lower layer 10 is composed of an insulator layer 101 and a conductor pattern 102. The conductor pattern 102 is formed so as to be connected to the outside through pinholes, and the output terminal portions 102a, 102b,
It has a ground terminal portion 102c.

At least three or more pads electrically connected to the package 8 are formed on the upper surface of the insulator layer 91. Here, a pad 93a is for bonding to an input signal to the package 8, a pad 93b is for bonding to an unbalanced signal output from the package 8, pads 93c to 93e are for bonding to a ground electrode of the package 8, and a pad 93f. Is

When these pads are considered as a filter circuit, it is preferable to arrange a large number of these pads for the purpose of separating the input ground and the output ground and improving the quality of the ground.

A conductor pattern 93 made of a metal such as Au, Ag, or Cu is formed on the insulating layer 92. The conductor pattern is designed to have an inductor component, and has a spiral shape as described above. In particular, in the case of a high frequency, it is important to take care that the Q value of the inductance is not deteriorated due to the conductive loss due to the skin effect. In addition, both ends pass through vias, and pads and PK for electrode bonding of unbalanced signals from the package 8 are used.
Connected to G ground.

Via holes are formed at predetermined positions in the insulating layer 101, and a conductor pattern 102 is formed in the same manner as the conductor pattern 93. Further, both ends and an intermediate portion are formed so as to be connected to pads on the back surface side via via holes in the insulator layer 101. Here, the pads at both ends on the back side have balanced outputs, and become output 1 and output 2, respectively. The pad in the middle is connected to the ground electrode of the package 8 and serves as an electrical neutral point.

As described above, loss occurs in the balun element 7 due to conductor loss, dielectric loss, and the like. In order to reduce such loss, Ag, Au, Cu
It is desirable to use a low-temperature fired material that can be fired at about 850 ° C. to 1050 ° C. as the structural material of the balun element 7 because such a metal is preferable. Considering the impedance matching, the value of the inductance, and the optimization of the electrode capacitance, the relative permittivity of the material is preferably in the range of about 4 to 9. Further, since the connection between the balun element 7 and the package 8 is fixedly mounted with epoxy resin, the SAW element 6
Although no problem occurs due to the solder heat at the time of mounting, the connection uses a high-temperature solder having a melting point of about 320 ° C. which is higher than about 240 ° C. which is the solder temperature at the time of mounting the SAW element 6. It is suitable.

With the above configuration, the unbalanced signal input to the surface acoustic wave device is filtered by the SAW element,
After passing through the balun element, it can be converted into a balanced signal and output. Further, since the SAW element has no problem even with an unbalanced SAW filter, it is possible to design a large fractional bandwidth. In addition, the mounting area is less than half the surface area of a conventional surface acoustic wave device in which balun elements are arranged and connected in a plane, so that downsizing can be realized.

The present invention is not limited to the above embodiment, and various changes may be made without departing from the scope of the present invention.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, more specific embodiments of the surface acoustic wave device according to the present invention will be described.

Example 1 A composite device was formed by using the SAW device and the balun device shown in FIG. 1 and mounted on a package.

More specifically, a piezoelectric substrate made of a 36 ° Y-cut LiTaO ₃ (lithium tantalate, hereinafter abbreviated as LT) single crystal by a photolithography method using a contact exposure apparatus using ultraviolet (Deep-UV). A negative pattern of a resist for a SAW filter was formed on the SAW in the propagation direction of the SAW at an angle θ = 0 ° with respect to the X axis of the single crystal.

Next, Al was formed on the negative pattern by an electron beam evaporator. Then, unnecessary Al was lifted off in the resist stripping solution to form a fine circuit pattern such as an IDT electrode.

Thereafter, a Si film for protecting the IDT electrode was formed on the entire surface of the piezoelectric substrate by an electron beam evaporation machine. Next, the piezoelectric substrate after the patterning was cut by a dicing method for each individual SAW filter to form individual SAW elements.

Next, pinholes having a diameter of about 0.2 mm were formed at predetermined locations on the ceramic substrate, and electrode patterns made of Au shown at 43 and 52 in FIG. 2 were formed. Next, each of the ceramic substrates is fired and bonded, and SiO ₂ is formed on portions other than the wire bonding pads shown in FIG.
Was formed. Next, the patterned ceramic substrate was cut into individual balun elements by a dicing method to form individual balun elements.

Next, a SAW element was bonded onto the balun element with a silicone resin, and was mounted and fixed to form a composite element of the SAW element and the balun element. Next, the composite device is
It was adhered and mounted and fixed in a package for MD (Surface Mounted Device) by a flip chip mounting method.

Next, for the composite element in the package, an Au wire of 30 μmφ (diameter 30 μm) was ultrasonically bonded so as to connect the electrode pad of the package to the composite element and the SAW element to the composite element. The cover was adhered, and the packaging of the SAW filter was completed.

The SAW filter was connected to a multi-port network analyzer, and the frequency characteristics of insertion loss were measured. As a result, as shown in FIG. 4, the pass band was large, and a balanced type characteristic was exhibited.

[Embodiment 2] Next, a package accommodating a SAW element composed of a piezoelectric substrate on which an excitation electrode connected to the balun element is formed is disposed on the balun element composed of the laminated wiring substrate shown in FIG. A specific example of the surface acoustic wave device thus configured will be described.

By a photolithography method using a contact exposure device using ultraviolet light (Deep-UV), a 36 ° Y-cut LiT
aO ₃ Lithium tantalate, abbreviated as LT) On a piezoelectric substrate made of a single crystal, an angle θ = 0 with respect to the X axis of the single crystal is formed.
A negative resist pattern for a SAW filter was formed in the direction of SAW propagation.

Next, Al was formed on the negative pattern by an electron beam evaporator. Then, unnecessary Al was lifted off in the resist stripping solution to form a fine circuit pattern such as an IDT electrode.

Thereafter, a Si film for protecting the IDT electrode was formed on the entire surface of the piezoelectric substrate by an electron beam evaporator. Next, the piezoelectric substrate after the patterning was cut by a dicing method for each individual SAW filter to form individual SAW elements.

Next, a via hole having a diameter of about 0.2 mm was formed in a predetermined position shown in FIG. 6 on a glass ceramic substrate made of a low-temperature fired substrate material, and an electrode pattern made of Ag shown in 93 and 102 in FIG. 6 was formed. Next, each of the ceramic substrates was fired at a temperature of about 900 ° C. and laminated.

Next, the SAW chip is replaced with a sheet-like SM.
It was adhered by face-up in a package for D (Surface Mounted Device) and mounted and fixed.
Further, an epoxy adhesive and a solder paste were applied to the upper surface of the balun element sheet, and the package sheets were laminated in a matched pattern, and were electrically and mechanically joined in a furnace at 350 ° C.

Next, the SAW element was mounted in the package cavity of the sheet with a silicon-based adhesive member and cured at 150 ° C. for 1 hour. Thereafter, the electrical connection between the SAW element and the package is made 30 μmφ (diameter 30 μm).
After ultrasonic bonding using an Au wire, a package lid was put on and bonded, and the packaging of the SAW filter was completed.

Thereafter, the package was divided by a dicing saw to complete a surface acoustic wave device comprising about 300 balun elements and a surface acoustic wave filter from one sheet.

The surface acoustic wave device was connected to a multi-port network analyzer, and the frequency characteristics of insertion loss were measured. As a result, as in the case of the first embodiment, the pass band was large and the characteristics of the balanced type were exhibited.

[0050]

According to the surface acoustic wave device of the present invention, a composite element is formed by bonding and wiring a surface acoustic wave element on a balun element, and the composite element is mounted on a package by flip-chip mounting. Accordingly, the bandwidth ratio can be designed to be larger than that of a conventional balanced filter, and the size can be significantly reduced compared to a surface acoustic wave device in which a conventional balun element is wired.

A surface acoustic wave device having the same effect as described above can also be obtained by mounting the external terminal surface of the package containing the surface acoustic wave element on a balun element composed of a laminated wiring board having connection terminals on the upper surface. Can be provided.

[Brief description of the drawings]

1A and 1B are diagrams illustrating an example of a surface acoustic wave device according to the present invention, wherein FIG. 1A is a longitudinal sectional view and FIG. 1B is a transverse sectional view.

FIGS. 2A and 2B are diagrams illustrating an example of a SAW element and a balun element according to the present invention, wherein FIG.
(C) is a plan view.

FIGS. 3A and 3B are plan views each illustrating a layer structure of a package according to the present invention.

FIG. 4 is a graph showing a measured frequency characteristic of insertion loss of the surface acoustic wave device according to the present invention.

5A and 5B are diagrams illustrating an example of another surface acoustic wave device according to the present invention, wherein FIG. 5A is a longitudinal sectional view and FIG. 5B is a transverse sectional view.

6A and 6B are diagrams illustrating an example of another balun element according to the present invention, in which FIG. 6A is a longitudinal sectional view, and FIGS. 6B to 6E are plan views illustrating respective layers.

FIG. 7 is a plan view illustrating a conventional balanced SAW filter.

[Explanation of symbols]

 1, 6: SAW element 11, 61: electrode 2, 7: balun element 3, 8: package 32, 82: second frame 33, 83: first frame 34, 84: base 4, 9: upper layer 41 : Insulator layer 43: Conductor pattern 5, 10: Lower layer 51, 101: Insulator layer 52, 102: Conductor pattern 15, 65: Piezoelectric substrate S1, S2: Surface acoustic wave device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5J097 AA12 AA19 AA29 BB11 GG03 HA02 HA04 HA07 HA08 JJ09 KK04 KK10 LL01

Claims (2)

[Claims] A balun element connected to the input electrode or the output electrode for performing a balanced-unbalanced conversion or an unbalanced-balanced conversion, on a substrate on which an input electrode and an output electrode are formed; and A surface acoustic wave device in which surface acoustic wave elements each having an excitation electrode connected to a balun element are sequentially superposed. 2. A surface acoustic wave device in which an external terminal surface of a package accommodating a surface acoustic wave element formed of a piezoelectric substrate having excitation electrodes formed thereon is mounted on a balun element formed of a laminated wiring substrate having connection terminals on an upper surface. .