JP4514572B2 - Surface acoustic wave device and communication device - Google Patents

Description

  The present invention relates to a surface acoustic wave device, a manufacturing method thereof, and a communication device. More specifically, it is a surface acoustic wave device having a face-down mounting structure used as a surface acoustic wave filter, and in particular, a surface acoustic wave device having improved out-of-passband attenuation, a manufacturing method thereof, and the surface acoustic wave device. The present invention relates to a communication device.

  In recent years, surface acoustic wave filters that can be miniaturized and non-adjusted have come to be used in various communication devices, and are used as band-pass filters, etc., as communication devices increase in frequency and functionality. There is an increasing demand for increasing the out-of-band attenuation of the surface acoustic wave filter. For example, as a 900 MHz band cellular phone filter, it is desired to improve the out-of-band attenuation in the vicinity of the pass band, and the high-performance high-attenuation filter that also improves the out-of-band attenuation in a high frequency band of several GHz. Is desired.

  FIG. 11 is a schematic cross-sectional view of a mounting structure in a conventional surface acoustic wave (hereinafter abbreviated as SAW) apparatus. In the surface acoustic wave device shown in FIG. 11, 51 is a piezoelectric substrate, 52 is a grounding pad, 53 is an interdigital transducer (IDT) electrode (excitation electrode) formed on the piezoelectric substrate 51 for SAW elements, 54 Is a conductive pattern formed on the package 57, and 55 is a bump for connection. In the configuration shown in the figure, the ground pad 52 and the IDT electrode 53 are formed of, for example, an Al—Cu film, and the conductive pattern 54 and the ground pad 52 are electrically connected by a bump 55 made of, for example, Au. Further, the lid 56 is sealed from above the package 57 via the bonding layer 58 by seam welding or the like, and the airtightness inside the surface acoustic wave element is maintained.

The main causes of the deterioration of the out-of-band attenuation level in such a conventional surface-down surface acoustic wave device are, for example, electrodes such as the ground pad 52 of the surface acoustic wave element, the IDT electrode 53, and the conductive pattern 54 of the package 57. Electromagnetic coupling between input and output due to increase in electrical resistance, parasitic inductance and stray capacitance. In particular, a filter region having an input pad portion such as a ground pad 52 and an output pad portion together with an IDT electrode 53 is formed on one main surface of the piezoelectric substrate 51, and a conductor layer (not shown) is formed on the other main surface. In the case of a surface acoustic wave device having a structure in which a surface acoustic wave element is mounted face-down, a conductor layer is formed on the other main surface of the piezoelectric substrate 51 in a region facing the input pad portion and output pad portion of the filter region. Therefore, there is a problem that capacitive coupling occurs between the input pad portion and the output pad portion, thereby deteriorating the out-of-band attenuation.
JP-A-4-313906

  A surface acoustic wave element is an element using comb-like excitation electrodes (IDT electrodes) fabricated on a piezoelectric substrate. Usually, since a piezoelectric body exhibits pyroelectricity due to a rapid temperature change, when a device having an excitation electrode on a piezoelectric substrate is manufactured, a process with a rapid temperature change is performed due to the pyroelectricity of the piezoelectric substrate. Sparks are generated between the electrodes, and the element is destroyed. Therefore, in order to prevent electric charges from being accumulated in the piezoelectric substrate as much as possible, it is common to form a conductor layer over the entire back surface of the piezoelectric substrate. However, this backside conductor layer is effective in preventing pyroelectric breakdown during the device fabrication process, but is disadvantageous for improving out-of-band attenuation due to the configuration of the device itself for the reasons described above (for example, (See Patent Document 1).

  In addition, a surface acoustic wave element having a face-up mounting structure in which an excitation electrode, an input pad portion, and an output pad portion are formed on the surface (one main surface) of the piezoelectric substrate and a conductor layer is formed on the back surface (the other main surface). In the case of a structure in which the back side is placed on the top surface of the package and grounded, capacitive coupling between the input pad part on the front side and the output pad part through the conductor layer on the back side is not a problem, In the case of face-down mounting, since the back surface is not grounded, capacitive coupling between the input pad portion and the output pad portion through the conductor layer on the back surface becomes a problem, and the out-of-band attenuation of the filter by the surface acoustic wave element is reduced. There is a problem that it is difficult to secure enough.

  Accordingly, an object of the present invention is to provide a surface acoustic wave device that can improve the out-of-band attenuation of a filter and has excellent reliability in a surface acoustic wave device having a face-down mounting structure of surface acoustic wave elements. It is to provide a used communication device.

  The surface acoustic wave device of the present invention is a surface acoustic wave device in which a filter region including an excitation electrode, an input pad portion, and an output pad portion is formed on one main surface of a piezoelectric substrate, and a conductor layer is formed on the other main surface. Is mounted on the mounting substrate with the one main surface facing each other, and the conductor layer is formed by interspersing a large number of conductor non-forming portions.

  In the surface acoustic wave device according to the present invention, in the above configuration, the conductor non-forming portion has a ratio of the area occupied by at least one of the input pad portion and the output pad portion of the conductor layer to another region. It is characterized by being larger than.

  In the surface acoustic wave device according to the present invention, in each of the above-described configurations, the conductor non-forming portion is a direct current connection from the input pad portion of the conductor layer to the excitation electrode and from the output pad portion to the excitation electrode. In the region facing at least one of the connected parts, the ratio of the area occupied is larger than that of the other regions.

  In the surface acoustic wave device according to the present invention, in each of the above configurations, the surface roughness of the conductor non-forming portion of the other main surface of the piezoelectric substrate is larger than the surface roughness of the region where the conductor layer is formed. It is a feature.

  In the surface acoustic wave device according to the present invention, in each of the above configurations, an annular conductor is formed on the one main surface of the piezoelectric substrate so as to surround the filter region, and the annular conductor is formed on the mounting substrate. It is characterized by being joined to the base-side annular conductor.

  The surface acoustic wave device according to the present invention is characterized in that, in the above configuration, the excitation electrode is electrically connected to the annular conductor through a resistor, and the annular conductor is set to a ground potential. To do.

  In the surface acoustic wave device according to the present invention, in each of the above structures, the piezoelectric substrate has a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal having an oxygen content less than the stoichiometric composition. It is characterized by comprising crystals.

  The surface acoustic wave device according to the present invention is characterized in that, in each of the above-described configurations, the one principal surface side is made of a piezoelectric material, and the other principal surface side is made of a material having a relative dielectric constant smaller than that of the piezoelectric material. .

  A communication device of the present invention is characterized by including at least one of a reception circuit and a transmission circuit having any one of the surface acoustic wave devices of the present invention.

  A first method of manufacturing a surface acoustic wave device according to the present invention includes a step of forming a conductor layer on one main surface of a piezoelectric substrate, and patterning the conductor layer on the one main surface to output an excitation electrode, an input pad portion, and an output A step of forming a plurality of surface acoustic wave element regions having a filter region having a pad portion, a step of forming a conductor layer on the other main surface of the piezoelectric substrate, and Separating each element region to obtain a large number of surface acoustic wave elements, and then mounting the surface acoustic wave element on a mounting substrate with the one main surface facing, A step of forming a conductor layer on one principal surface of the piezoelectric substrate, a step of forming a plurality of surface acoustic wave element regions, a step of forming a conductor layer on the other principal surface of the piezoelectric substrate, and the plurality of surface acoustic waves. During the process of obtaining the element, The after the step of the mounting, is characterized in that the conductor layer formed on the other main surface are a number of conductor-free portion includes a step of partially removing such scattered.

  The second manufacturing method of the surface acoustic wave device of the present invention includes a step of forming a conductor layer on one principal surface of the piezoelectric substrate, and patterning the conductor layer on the one principal surface to thereby form an excitation electrode and an input pad portion. Forming a plurality of surface acoustic wave element regions each having a filter region comprising an output pad portion, a step of forming a conductor layer on the other main surface of the piezoelectric substrate, and then the elasticity of the piezoelectric substrate. Mounting the surface wave element region on the mounting substrate with the one principal surface facing each other, and then separating the piezoelectric substrate and the mounting substrate for each surface acoustic wave element region. And a step of forming a conductor layer on one main surface of the piezoelectric substrate, a step of forming a plurality of surface acoustic wave element regions, a step of forming a conductor layer on the other main surface of the piezoelectric substrate, and the mounting step. During or After the step of serial implementation, is characterized in that the conductor layer formed on the other main surface are a number of conductor-free portion includes a step of partially removing such scattered.

  Furthermore, in the first and second manufacturing methods of the surface acoustic wave device according to the present invention, when the conductor layer is partially removed in each of the above configurations, the surface roughness of the other main surface of the portion to be removed is set. The surface roughness of the other main surface of the part not to be removed is larger.

  According to the surface acoustic wave device of the present invention, since the conductor layer formed on the other main surface of the piezoelectric substrate is formed by interspersing a large number of conductor non-formation portions, the input pad portion and the output of the filter The parasitic capacitance formed between the pad portions is equivalent to the amount of the area of the conductor layer formed on the other main surface being smaller than when the conductor layer is formed over the entire surface of the other main surface as in the prior art. Since it can be reduced, the deterioration of the attenuation characteristic outside the passband due to the parasitic capacitance can be suppressed according to the decrease in the area of the conductor layer on the other main surface, and the attenuation outside the passband is improved. Can be made.

  Further, according to the surface acoustic wave device of the present invention, in the above configuration, the ratio of the area occupied by the conductor non-forming portion in the region facing at least one of the input pad portion and the output pad portion of the conductor layer is other than When it is larger than the region, the parasitic capacitance formed between the input pad portion and the output pad portion in the filter region can be further reduced, so that the attenuation outside the passband can be further improved.

  Further, according to the surface acoustic wave device of the present invention, in the above configuration, the conductor non-forming portion is DC connected from the input pad portion of the conductor layer to the excitation electrode and from the output pad portion to the excitation electrode. In the region facing at least one of the connected portions, when the proportion of the area occupied is larger than that of the other regions, the parasitic capacitance formed between the input pad portion and the output pad portion of the filter region is further increased. Since it can be reduced, the attenuation outside the passband can be further improved.

  According to the surface acoustic wave device of the present invention, in each of the above configurations, when the surface roughness of the conductor non-forming portion of the other main surface of the piezoelectric substrate is larger than the surface roughness of the region where the conductor layer is formed. In addition, since the amount of deterioration outside the passband that has deteriorated due to the propagation of the bulk wave can be reduced, the out-of-band attenuation characteristic can be further greatly improved. The attenuation characteristic outside the passband deteriorates due to capacitive coupling between the input and output pads, and the acoustic wave that has become a bulk wave without being converted into a surface acoustic wave by the excitation electrode of the resonator is It also deteriorates by propagating through the inside, being reflected by the surface of the other main surface of the piezoelectric substrate and the end surface of the surface acoustic wave element, and again being coupled to the excitation electrode of the resonator formed in the filter region. Although the deterioration due to the propagation of the bulk wave is smaller than the influence due to the parasitic capacitance, it is preferable to suppress the deterioration due to the bulk wave in order to completely satisfy the strict requirement required for the attenuation characteristic outside the passband. On the other hand, the surface roughness of the other main surface of the conductor non-forming portion of the piezoelectric substrate is set to be larger than the surface roughness of the other main surface of the region where the conductor layer is formed. Since the bulk wave is scattered on the other main surface of the piezoelectric substrate having a large surface roughness, the bulk surface generated from the excitation electrode in the filter region is again excited by the excitation electrode formed in the filter region. Since the coupling with the wave can be prevented sufficiently, the attenuation characteristic outside the passband can be further improved.

  Further, according to the surface acoustic wave device of the present invention, the annular conductor is formed on one main surface of the piezoelectric substrate so as to surround the filter region, and the annular conductor is formed correspondingly on the mounting substrate. When the annular conductor is bonded to the annular conductor, the surface acoustic wave element is firmly mounted on the mounting substrate by bonding the annular conductor and the substrate-side annular conductor, and the excitation electrode, the input pad portion, and the output pad portion are hermetically sealed. As described later, when mounting a surface acoustic wave element on a mounting substrate and processing the conductor layer on the other main surface of the piezoelectric substrate later, as described later, Processing can be performed without damaging the excitation electrode formed on the surface.

  Further, according to the surface acoustic wave device of the present invention, the excitation electrode is electrically connected to the annular conductor via the resistor, and when the annular conductor is at the ground potential, the excitation electrode is DC-connected. Is connected to the ground potential, but in the frequency band in which the surface acoustic wave device is used, it can be isolated from the ground potential, so excitation without affecting the passband characteristics of the filter Charges can be prevented from accumulating on the electrode. Accordingly, pyroelectric breakdown of the surface acoustic wave device can be reliably prevented even when the conductor layer is not provided on the entire other main surface of the piezoelectric substrate.

  According to the surface acoustic wave device of the present invention, when the piezoelectric substrate is made of a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal having an oxygen content less than the stoichiometric composition. This piezoelectric substrate, like the resistor that electrically connects the excitation electrode to the annular conductor, appears to be a conductor in terms of direct current, but appears to be almost an insulator in the frequency band in which the surface acoustic wave device is used. Have. Therefore, by using this as the substrate of the surface acoustic wave device, it is possible to prevent electric charges from accumulating on the excitation electrode without affecting the passband characteristics of the filter. Therefore, the pyroelectric breakdown of the surface acoustic wave device can be more reliably prevented even if there is no conductor layer on the entire other main surface of the piezoelectric substrate. In addition, the number of processes is not increased in the manufacturing process of the surface acoustic wave device in order to prevent pyroelectric breakdown.

  In the surface acoustic wave device of the present invention described above, the conductor layer on the other principal surface of the piezoelectric substrate is formed by interspersing a large number of conductor non-forming portions. With such a configuration, the parasitic capacitance generated between the input pad portion and the output pad portion in the filter region has been reduced (this corresponds to reducing the area of the electrode forming the parasitic capacitance). ) When the piezoelectric substrate is made of a piezoelectric material on one main surface side and a material having a relative dielectric constant smaller than that of the piezoelectric material, the effective dielectric constant between the input pad portion and the output pad portion of the filter. This can also reduce the parasitic capacitance (this corresponds to reducing the dielectric constant between the electrodes forming the parasitic capacitance), so that the attenuation outside the passband can be further improved. It can be. In particular, when this piezoelectric material is a lithium tantalate single crystal, a lithium niobate single crystal or a lithium tetraborate single crystal whose oxygen content is less than the stoichiometric composition, the effect of preventing pyroelectric breakdown well And the effect of reducing the effective dielectric constant can be obtained.

  According to the communication device of the present invention, by using the surface acoustic wave device of the present invention as described above for at least one of the reception circuit and the transmission circuit of the communication device, severe out-of-band attenuation conventionally required. As a surface acoustic wave device having a good out-of-pass attenuation characteristic, it is small in size, so that it can take a larger mounting area for other components, Since the range of selection widens, a highly functional communication device can be realized.

  In order to produce the surface acoustic wave device of the present invention as described above, the following method for producing the surface acoustic wave device of the present invention is suitable.

  According to the first method of manufacturing a surface acoustic wave device of the present invention, a step of forming a conductor layer on one main surface of the piezoelectric substrate, a step of forming a large number of surface acoustic wave element regions, and the other main surface of the piezoelectric substrate In the case where the conductor layer on the other main surface is partially removed so that a large number of conductor non-forming portions are scattered between the step of forming the conductor layer and the step of obtaining a large number of surface acoustic wave elements, Since the piezoelectric substrate on which a large number of surface acoustic wave elements are integrally formed can be collectively processed with respect to the conductor layer on the other main surface, the efficiency is improved. In addition, after the step of mounting the surface acoustic wave element with the one main surface facing the mounting substrate, the conductor layer on the other main surface of the piezoelectric substrate is partially separated so that a large number of conductor non-forming portions are scattered. In the case of removal, it is possible to reliably prevent pyroelectric breakdown of the surface acoustic wave element that may occur due to the temperature history applied in the mounting process.

  According to the second method of manufacturing a surface acoustic wave device of the present invention, the step of forming a conductor layer on one main surface of the piezoelectric substrate, the step of forming a large number of surface acoustic wave element regions, and the other main surface of the piezoelectric substrate When the conductor layer on the other main surface of the piezoelectric substrate is partially removed so that many conductor non-forming portions are scattered between the step of forming the conductor layer and the step of obtaining a large number of surface acoustic wave elements. In this case, the removal process for the conductor layer on the other main surface can be collectively performed on the piezoelectric substrate on which a large number of surface acoustic wave elements are integrally formed, so that the efficiency in the removal process is improved. In the case where the conductor layer on the other main surface of the piezoelectric substrate is partially removed after the step of mounting the surface acoustic wave element region of the piezoelectric substrate with the main surface facing the mounting substrate, It is possible to reliably prevent pyroelectric breakdown of the surface acoustic wave element that may occur due to the history. Furthermore, since the removal process can be performed on the conductor layer on the other main surface in a state where the piezoelectric substrate on which a large number of surface acoustic wave element regions are fabricated is mounted on the mounting base, the efficiency in the removal process is improved. Of course, the removal process for the conductor layer on the other main surface may be performed after the step of separating the piezoelectric substrate and the mounting substrate for each surface acoustic wave element region. In this separation step, either the piezoelectric substrate or the mounting substrate may be separated first, or the piezoelectric substrate and the mounting substrate may be separated simultaneously.

  By the way, the deterioration of the attenuation outside the passband due to the propagation of the bulk wave can be suppressed by using a piezoelectric substrate whose surface has been greatly roughened. However, while the excitation electrode that propagates the surface acoustic wave is formed, Since the surface needs to be a mirror surface, there is a problem in that the piezoelectric substrate with only the other main surface largely rough is warped greatly due to temperature change and is easily damaged during the manufacturing process of the surface acoustic wave element. On the other hand, the thickness of piezoelectric substrates for surface acoustic wave elements has been gradually reduced due to the recent demand for smaller and lower height electronic components. However, the probability of breakage increases as the thickness of piezoelectric substrates decreases. End up.

  On the other hand, according to the method for manufacturing a surface acoustic wave device of the present invention, when the conductor layer on the other main surface of the piezoelectric substrate is partially removed so that a large number of conductor non-forming portions are scattered, the conductor layer If the surface roughness of the other main surface of the region where the layer is removed is made larger than the surface roughness of the other main surface of the region where the conductor layer is formed, the piezoelectric substrate whose thickness is being reduced is also damaged. Without increasing the risk, it is possible to efficiently suppress the deterioration of the attenuation characteristic outside the passband due to the propagation of the bulk wave. In addition, this is efficient because it can be performed simultaneously with countermeasures against deterioration of the attenuation characteristic outside the passband due to parasitic capacitance.

  As described above, according to the present invention, even when the mounting (flip chip mounting) is performed with the excitation electrode forming surface of the piezoelectric substrate facing the main surface of the mounting substrate, the input pad portion and the output pad portion of the filter Is not capacitively coupled through the conductor layer on the other main surface, so that the attenuation outside the passband is not deteriorated even though the surface acoustic wave device is small. In addition, pyroelectric breakdown of the surface acoustic wave element can be prevented even if there is no conductor layer on the entire other main surface of the piezoelectric substrate in the manufacturing process. Also, due to recent demands for miniaturization and low profile of parts, surface acoustic wave devices are also required to reduce the thickness of the piezoelectric substrate, but the electrodes on one main surface and the other main surface of the piezoelectric substrate are required. The capacitance between the conductive layer on the surface increases, and therefore the deterioration of the attenuation outside the passband caused by the coupling of the parasitic capacitance between the input and output pad portions of the filter becomes more serious. By partially removing the conductor layer on the other main surface so that a large number of conductor non-forming portions are scattered, it is possible to obtain a surface acoustic wave device that is thin and has good out-of-band attenuation characteristics .

  Since the surface acoustic wave device of the present invention has a good out-of-pass band attenuation characteristic and is small in size, the receiving circuit having the surface acoustic wave device of the present invention and the surface acoustic wave device of the present invention According to the communication device of the present invention including at least one of the transmission circuits having high performance by realizing a large mounting area of other components while utilizing the good filter characteristics of the surface acoustic wave device of the present invention. A communication device that can be manufactured is manufactured.

  Hereinafter, an example of an embodiment of a surface acoustic wave device and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. In the drawings described below, the same portions are denoted by the same reference numerals. Further, the size of each electrode, the distance between the electrodes, the number of electrode fingers, the interval, and the like are schematically illustrated for explanation, and are not limited to these.

<Example 1 of embodiment>
FIG. 6 is a top view showing one main surface of the surface acoustic wave element in Example 1 of the embodiment of the surface acoustic wave device of the present invention. A top view of the other main surface of the surface acoustic wave element in Example 1 is shown in FIG.

  As shown in FIG. 6, a filter region 9 is formed on the piezoelectric substrate 2 of the surface acoustic wave element 1. In the filter region 9, a plurality of excitation electrodes 3 constituting a resonator, a connection electrode 4 connecting them, and an excitation electrode 3 for connecting the surface acoustic wave element 1 and a mounting substrate (not shown) are connected. An electrically connected input pad portion 5 and an output pad portion 6 are formed.

  The annular conductor 7 is connected to the substrate-side annular conductor of the mounting substrate using solder or the like, functions as a ground electrode of the surface acoustic wave filter, and seals the space between the piezoelectric substrate 2 and the mounting substrate. Have a role. Reference numeral 8 denotes a ground electrode pad.

  Further, as shown in FIG. 1, a conductor layer 10 is formed on the other main surface of the piezoelectric substrate 2. Here, as shown in the pattern of FIG. 1, the conductor layer 10 is formed such that a large number of conductor non-formation regions are scattered, and in this example, the conductor layer 10 has a lattice shape. By making the conductor layer 10 into such a shape, for example, the area of the conductor layer can be reduced as compared with the case where the conductor layer 10 is formed over the entire surface of the other main surface as in the prior art. And parasitic capacitance generated between the output pad portion 6 of the filter region 9 and the conductor layer 10 can be reduced. Therefore, the attenuation amount outside the passband can be greatly improved. In FIG. 1, 9 a indicates a region facing the filter region 9.

  In this example, many conductor non-formation regions are dotted in both the region 5 a facing the input pad portion 5 and the region 6 a facing the output pad portion 6 of the filter region 9 on the other main surface of the piezoelectric substrate 2. However, if a large number of conductor non-formation regions are interspersed in at least one of these regions 5a and 6a, a certain degree of effect of improving the attenuation outside the passband can be obtained. . Further, since the pattern of the conductor layer 10 is continuously formed over a wide area of the other main surface of the piezoelectric substrate 1, it is possible to prevent charges from being accumulated in a partial area of the other main surface. Therefore, the occurrence of pyroelectric breakdown can be reliably prevented.

  As an example of the conductor layer 10, FIG. 1 shows a simple lattice pattern in which conductor non-forming portions are arranged vertically and horizontally as a rectangular shape. However, for example, as shown in FIG. It is also possible to form a pattern in which the conductor non-formed portions are arranged in a circular shape in the vertical and horizontal directions, and the effect is the same in this case. Further, the lattice pattern as shown in FIG. 1 may be formed to be inclined with an angle of 45 degrees, for example.

  In this example, the annular conductor 7 is used as the ground electrode of the surface acoustic wave filter, but the ground conductor of the surface acoustic wave filter may be directly connected to the ground electrode of the mounting substrate without using the annular conductor 7 as the ground electrode. I do not care.

<Example 2 of embodiment>
FIG. 2 is a top view showing the other main surface of the surface acoustic wave element in Example 2 of the embodiment of the surface acoustic wave device of the invention. In this example, the configuration on the one main surface side of the piezoelectric substrate 2 is the same as in Example 1, but the pattern of the conductor layer 10 on the other main surface is different. In Example 2, as shown in FIG. 2, the pattern of the conductor layer 10 is formed on the region opposite to the input pad portion 5 in the filter region on one main surface of the piezoelectric substrate 2, the periphery thereof, and the output pad portion 6 in the filter region. Except for the opposing region and its periphery, small rectangular conductor non-formation portions are arranged vertically and horizontally to form a lattice pattern.

  Further, in the region facing the input pad portion 5 in the filter region 9 and the region facing the output pad portion 6 in the filter region 9, the area of the rectangular conductor non-formation portion is increased, and the ratio of the occupied area to other regions is changed. It is larger than the area. By doing so, the capacitive coupling through the parasitic capacitance generated between the input pad portion 5 and the output pad portion 6 in the filter region and the conductor layer 10 is the occupation ratio of the conductor non-forming portion. Therefore, the attenuation amount outside the passband can be further greatly improved.

  In Example 2, the ratio of the area occupied by the conductor non-forming portion in both the region facing the input pad portion 5 in the filter region 9 and the region facing the output pad portion 6 in the filter region 9 is larger than that in the other regions. Although it is assumed to be large, the proportion of the area occupied by the conductor non-forming portion may be increased in one of the regions, and in that case also, the parasitic between the input pad portion 5 in the filter region and the output pad portion 6 in the filter region Since capacitive coupling through the capacitance can be prevented, the attenuation outside the passband can be greatly improved.

  Also, in this example, the area of the rectangular conductor non-forming portion is increased in the region facing the input pad portion 5 of the filter region 9 and the region facing the output pad portion 6 of the filter region 9, Although the ratio is larger than the other areas, the area of the rectangular conductor non-formation part is the same as the other areas, and the ratio of the occupied area is made larger than the other areas by arranging them closely. Also good.

<Example 3 of embodiment>
FIG. 3 is a top view showing the other main surface of the surface acoustic wave element in Example 3 of the embodiment of the surface acoustic wave device of the invention. In this example, the configuration on one main surface side of the piezoelectric substrate 2 is the same as that in Example 2, but the pattern of the conductor layer 10 on the other main surface is different. In Example 2, as shown in FIG. 2, the pattern of the conductor layer 10 is a region facing the input pad portion 5 of the filter region 9 on one main surface of the piezoelectric substrate 2, its periphery, and the output pad portion 6 of the filter region 9. In this example 3, a pattern in which the area occupied by the conductor non-forming portion is large in the region opposite to the region is used. However, in this example 3, the input pad portion 5 of the filter region 9 on the one main surface of the piezoelectric substrate 2 is connected to the resonator. In the region 5b facing the portion connected to the excitation electrode 3 in a direct current and the region 6b facing the portion connected in a direct current from the output pad portion 6 of the filter region 9 to the excitation electrode 3 of the resonator, a square is formed. By enlarging and densely arranging the shape of the conductor non-forming portion, the conductor layer 10 in which the proportion of the conductor non-forming portion is larger than that of the other regions is formed. By doing so, the capacitive coupling through the parasitic capacitance between the input pad portion 5 of the filter region 9a and the output pad portion 6 of the filter region 9a can be more reliably suppressed, so that the attenuation outside the passband is achieved. The amount can be greatly improved.

  In Example 3, the region 5b facing the portion DC-connected from the input pad portion 5 to the excitation electrode 3 in the filter region 9 and the output pad portion 6 to the excitation electrode 3 in the filter region 9 are DC-directed. The proportion of the area occupied by the conductor non-forming portion in both the regions 6b facing the connected portion is assumed to be larger than that of the other regions, but which of the areas occupied by the non-conductor forming portion is larger? In this case, the capacitive coupling between the input pad portion 5 of the filter region 9 and the output pad portion 6 of the filter region 9 through the parasitic capacitance can be prevented. The amount of attenuation can be greatly improved.

  Further, as in Example 3, the region facing the portion of the conductor layer 10 facing the DC connection from the input pad portion 5 on one main surface of the piezoelectric substrate 2 to the excitation electrode 3 and the output pad portion of the filter region 9 When the ratio of the area is increased in a region facing at least one of the regions facing the DC-connected portion from 6 to the excitation electrode 3 and many conductor non-formed portions are scattered, other conductors By increasing the surface roughness of the non-formed portion, in particular, the non-formed portion of the conductor, more than the surface roughness of the region where the conductor layer 10 is formed, the surface roughness is increased in a wider area, thereby Propagation can be suppressed more reliably, and the amount of attenuation outside the passband can be effectively reduced due to the propagation of bulk waves. In It will be advantageous to improve.

  It should be noted that the surface roughness of the conductor non-forming portions scattered in a large number in the conductor layer 10 in this way is made larger than the surface roughness of the region where the conductor layer 10 is formed, resulting in deterioration due to bulk wave propagation. The effect of improving the amount of attenuation outside the passband is the same in Example 1 and Example 2.

<Example 4 of embodiment>
In this example, the configuration on the one main surface side of the piezoelectric substrate 2 is the same as the example shown in FIG. 6, and the capacitive coupling between the filter region 9, the input pad portion 5, and the output pad portion 6 of the filter region 9 is further ensured. In order to suppress the noise, the filter layer 9 is provided with a large number of rectangular conductor non-forming portions on the conductor layer 10 in the region facing the input pad portion 5, thereby forming the filter region 9 on the other main surface of the piezoelectric substrate 2. Compared with the region facing the output pad portion 6, the proportion of the area occupied by the conductor non-formed portions scattered in the conductor layer 10 was made larger than that of the other regions. The pattern of the conductor layer 10 is shown in a top view similar to FIGS.

  In the example 4 shown in FIG. 4, the ratio of the area occupied by the conductor non-forming portion in the region facing the input pad portion 5 in the filter region 9 is larger than that in the other region, in this case, the output pad portion 6 in the filter region 9. is doing. On the other hand, the proportion of the area occupied by the conductor non-forming portion in the region facing the output pad portion 6 of the filter region 9 may be larger than that of the input pad portion 5 of the filter region 9. The proportion of the area occupied by the conductor non-forming portion in both the portion 5 and the region facing the output pad portion 6 of the filter region 9 may be made larger than that in the other regions. In any case, capacitive coupling between the input pad portion 5 of the filter region 9 and the output pad portion 6 of the filter region 9 through the parasitic capacitance can be prevented, so that the attenuation outside the passband is greatly increased. Can be improved.

  Also in the case of Example 4, the surface roughness of the conductor non-forming portion is made larger than the surface roughness of the region where the conductor layer 10 is formed, thereby increasing the surface roughness over a wider area. Therefore, it is possible to more reliably suppress bulk wave propagation, and it is possible to effectively reduce the deterioration due to bulk wave propagation out of the deterioration of the attenuation outside the pass band. It would be advantageous to further improve the amount.

<Example 5 of embodiment>
FIG. 7 is a top view showing one main surface of the surface acoustic wave element in Example 4 of the embodiment of the surface acoustic wave device of the invention. In this example, the configuration on the other main surface side of the piezoelectric substrate 2 is the same as the example shown in FIG. 4 so that all the excitation electrodes 3 are in direct current conduction with the annular conductor 7 on the one main surface side of the piezoelectric substrate 2. The excitation electrode 3 forming the resonator and the annular conductor 7 were connected via a resistor 11. Further, the annular electrode 7 is connected to the substrate-side annular conductor of the mounting substrate so as to have a ground potential. As described above, the excitation electrode 3 is electrically connected to the annular conductor 7 via the resistor 11, and the annular conductor 7 is set to the ground potential. Therefore, it is possible to effectively prevent the pyroelectric breakdown of the surface acoustic wave element 1.

  The resistor 11 is selected to have a sufficiently high resistance in the frequency band in which the filter is used and a resistance value that looks almost like an insulator. As the material of the resistor 11, a high resistance semiconductor such as silicon or titanium oxide is preferably used. These materials can control the resistance value to an appropriate value by adding a trace amount of an element such as boron or adjusting the composition ratio.

<Example 6 of embodiment>
In this example, as a configuration for preventing pyroelectric breakdown more simply, the piezoelectric substrate 2 includes a lithium tantalate single crystal, a lithium niobate single crystal, or a lithium tetraborate single crystal having an oxygen content lower than the stoichiometric composition. Crystals were used. Similar to the resistor 11 described above, these materials have the property that even though they look like conductors in terms of direct current, they have a sufficiently high resistance in the frequency band in which the filter is used and look almost like insulators. Therefore, by using these materials for the piezoelectric substrate 2, it is possible to prevent electric charges from accumulating on the excitation electrode 3 without affecting the bandpass characteristics of the filter, so that the entire surface of the other main surface of the piezoelectric substrate 2 can be prevented. Even without the conductor layer 10, pyroelectric breakdown of the surface acoustic wave element 1 can be satisfactorily prevented. Moreover, it is advantageous in that the number of steps is not increased in the manufacturing process of the surface acoustic wave device in order to prevent pyroelectric breakdown.

<Example 7 of embodiment>
In this example, the effective dielectric constant between each electrode (excitation electrode 3, connection electrode 4, input pad portion 5, output pad portion 6) on one main surface of the piezoelectric substrate 2 and the conductor layer 10 on the other main surface is reduced. By doing so, the parasitic capacitance was reduced. Specifically, the piezoelectric substrate 2 is made of a piezoelectric material such as a lithium tantalate single crystal or a lithium niobate single crystal on one main surface side, and a material having a lower relative dielectric constant on the other main surface side than the piezoelectric material on the one main surface. It can be realized while ensuring the necessary piezoelectric characteristics.

  As this piezoelectric material, various piezoelectric materials used for surface acoustic wave elements may be used. In particular, lithium tantalate single crystal or lithium niobate single crystal whose oxygen content is less than the stoichiometric composition. Alternatively, when lithium tetraborate single crystal is used, it is possible to obtain both the effect of preventing pyroelectric breakdown well and the effect of reducing the effective dielectric constant. Further, quartz, silicon, silicon carbide, glass or the like can be used as the dielectric material having a small relative dielectric constant. The piezoelectric substrate 2 made of such two kinds of materials can be obtained by laminating a substrate made of these piezoelectric materials and a substrate made of a dielectric material.

  The surface acoustic wave device of the present invention can be applied to a communication device. That is, the surface acoustic wave device of the present invention is used as a band-pass filter included in these circuits in a communication device including at least one of a receiving circuit and a transmitting circuit. For example, the transmission signal output from the transmission circuit is put on the carrier frequency by the mixer, the unnecessary signal is attenuated by the band pass filter, and then the transmission signal is amplified by the power amplifier and transmitted from the antenna through the duplexer. A communication device equipped with a transmission circuit that can perform reception, receives the received signal with an antenna, passes through a duplexer, amplifies the received signal with a low noise amplifier, attenuates unnecessary signals with a band-pass filter, and then uses a carrier frequency with a mixer Can be applied to a communication device including a receiving circuit that separates a signal from the signal and transmits the signal to a receiving circuit that extracts the signal. The surface acoustic wave device of the present invention is employed in at least one of the receiving circuit and the transmitting circuit. Thus, an excellent communication device of the present invention with improved transmission characteristics can be provided.

  Next, an example of an embodiment of a method for manufacturing a surface acoustic wave device according to the present invention will be described according to steps.

<Example 8 of embodiment>
FIG. 8A to FIG. 8J show an example of an embodiment of the first manufacturing method of the surface acoustic wave device of the present invention in cross-sectional views for each process.

  First, as shown in FIG. 8A, (1) a conductor layer is formed on one main surface of the piezoelectric substrate, and as shown in FIG. 8B, (2) a conductor layer on one main surface of the piezoelectric substrate. Are formed to form a plurality of surface acoustic wave element regions each having a filter region having an excitation electrode, an input pad portion, and an output pad portion, as shown in FIG. A conductor layer is formed on the other main surface. The steps so far may be performed in the order of (1), (3), (2) or (3), (1), (2) other than the above order.

  Here, as the piezoelectric substrate, a lithium tantalate single crystal, a lithium niobate single crystal, a lithium tetraborate single crystal, or the like can be used.

  On the other hand, the conductor layer on the main surface is made of aluminum, aluminum alloy, copper, copper alloy, gold, gold alloy, tantalum, tantalum alloy, or a laminated film of these materials, and these materials and titanium, chromium, etc. A laminated film with a layer made of the above material can be used. As a method for forming the conductor layer, a sputtering method or an electron beam evaporation method can be used.

  As a method for patterning the conductor layer, there is a method in which photolithography is performed after forming the conductor layer, and then RIE (Reactive Ion Etching) or wet etching is performed. Alternatively, a resist is formed on one main surface of the piezoelectric substrate before the conductor layer is formed and photolithography is performed to open a desired pattern, and then a conductor layer is formed, and then the resist is formed on an unnecessary portion. A lift-off process for removing the entire conductor layer may be performed.

  Moreover, aluminum etc. can be used as a material of the conductor layer of the other main surface of the piezoelectric substrate. As the film formation method, a sputtering method or an electron beam evaporation method can be used.

  Next, as shown in FIG. 8D, a protective film for protecting the excitation electrode is formed. Silicon, silica or the like can be used as the material for the protective film. As a film forming method, a sputtering method, a CVD (Chemical Vapor Deposition) method, an electron beam evaporation method, or the like can be used. In this protective film forming process, a temperature of about 50 to 300 ° C. may be necessary to obtain good film quality and adhesion. In such a case, the conductor layer on the other main surface is subjected to pyroelectric breakdown. Works effectively in prevention.

  Next, as shown in FIG. 8E, (4) a new conductor layer is laminated on the input pad portion and the output pad portion to form the input pad and the output pad. This new conductor layer has a structure for electrically and / or structurally connecting the surface acoustic wave element and the mounting substrate with high reliability. For example, if solder is used for connection, the solder is wet. In the case of using gold bumps for connection, it has a function of adjusting the hardness of the pad so that gold can be bonded using ultrasonic waves or the like. As a material and structure of such a new conductor layer, a laminated film of chromium / nickel / gold or chromium / silver / gold, or a thick film of gold or aluminum can be used. As a film forming method, a sputtering method or an electron beam evaporation method can be used. In addition, in order to obtain good film quality and adhesion even in this new conductor layer film forming step, a temperature of about 50 to 300 ° C. may be necessary, but even in such a case, the conductor layer on the other main surface is It functions effectively to prevent pyroelectric breakdown.

  The pattern of the excitation electrode, the input pad portion, and the output pad portion on one main surface of the piezoelectric substrate manufactured through the steps up to here is the same as that shown in FIG. However, the protective film is not shown in FIG.

  Next, when the fabrication is performed by the so-called multi-cavity method in which a large number of surface acoustic wave element regions are formed on one piezoelectric substrate so far, as shown in FIG. The piezoelectric substrate is separated for each surface acoustic wave element region to obtain a large number of surface acoustic wave elements. As a separation method, for example, a dicing method using a dicing blade, a laser cutting method by laser processing, or the like can be used.

  Next, as shown in FIG. 8H, (6) the surface acoustic wave element is mounted on the mounting substrate with one main surface facing it. Here, as shown in FIG. 8F, between the steps (1) to (3) and the step (5) of obtaining a large number of surface acoustic wave elements, or the step (6) of mounting. Thereafter, the conductor layer on the other main surface of the piezoelectric substrate is partially removed so as to have a lattice shape, for example, and a large number of conductor non-forming portions are provided in a scattered manner.

  As a method of partially removing the conductor layer in this way, before the step (5), after protecting one main surface of the piezoelectric substrate with a resist or the like, a resist is formed on the other main surface of the piezoelectric substrate. After performing photolithography and opening a necessary portion of the resist, the conductive layer in the opening may be removed by a method such as wet etching, RIE (Reactive Ion Etching), or sandblasting. At this time, if a method of etching and removing the conductor layer mainly by a chemical action is used, the conductor layer on the other main surface can be removed with certainty without damaging the piezoelectric substrate. Also, if a method of grinding and removing the conductor layer mainly by physical action is used, the conductor layer can be removed and at the same time the other main surface of the piezoelectric substrate in that portion can be made rougher than the original state. , Propagating through the inside of the piezoelectric substrate from one filter region, reflected by the other main surface of the piezoelectric substrate, and coupled to the excitation electrode formed in the other filter region, and deteriorated the attenuation characteristic outside the passband Bulk waves can be scattered at this portion of the other principal surface of the piezoelectric substrate, and the out-of-passband attenuation characteristics can be further improved.

  Thereafter, the resist on one main surface side and the resist on the other main surface side of the piezoelectric substrate are removed.

  In these steps, since each process can be performed on the piezoelectric substrate on which a plurality of surface acoustic wave elements are formed, the plurality of surface acoustic wave elements can be processed in a batch, which is efficient.

  In addition, when the conductor layer on the other main surface of the piezoelectric substrate is partially removed after the step (6) to provide a large number of conductor non-forming portions, the one main surface of the piezoelectric substrate is already provided. Since it is arranged facing the mounting substrate, the step of protecting the one main surface can be omitted. In particular, when sealing is performed using an annular conductor, the surface acoustic wave element is firmly fixed to the mounting substrate, and the filter region is shielded from the outside air. By using a method such as etching, RIE (Reactive Ion Etching), sand blasting or the like, the conductor layer of the other main surface to be processed can be efficiently removed. Further, the conductor layer on the other main surface may be removed by grinding and polishing using a router or sandpaper.

  In this example, as shown in FIG. 8 (i), (7) the surface acoustic wave element mounted on the mounting substrate is resin-molded using a sealing resin, and then shown in FIG. 8 (j). (8) The mounting substrate is divided for each surface acoustic wave element together with the mold resin by dicing or the like to obtain the surface acoustic wave device of the present invention.

  In this example, a predetermined region of the conductor layer formed on the other main surface of the piezoelectric substrate, for example, a region facing at least one of the input pad portion of the filter region and the output pad portion of the filter region is partially removed in a lattice shape. In this case, the conductor layer is formed by interspersing a large number of conductor non-forming portions. However, the partial removal of the conductor layer further includes a portion of the conductor layer that is connected in a direct current from the input pad portion to the excitation electrode and the filter. You may further remove the area | region which opposes at least one of the part currently connected by direct current from the output pad part of an area | region to an excitation electrode. Furthermore, the conductor layer on the other main surface is further removed, for example, by partially removing a region facing at least one of the input pad portion of the filter region and the output pad portion of the filter region in a lattice shape, so that a large number of conductor non-forming portions are formed. May be scattered.

<Example 9 of embodiment>
In Example 8 of the embodiment, after passing through the step of obtaining a large number of surface acoustic wave elements by separating the piezoelectric substrate on which the large number of surface acoustic wave elements are formed in the step (5) for each surface acoustic wave element region. In this example, as shown in FIG. 9A to FIG. 9J with cross-sectional views similar to FIG. 8A to FIG. In the step shown in FIG. 9 (g), mounting is performed with one main surface of the piezoelectric substrate on which a number of surface acoustic wave element regions are formed on the mounting substrate facing each other before separation for each surface acoustic wave element region. (This step is referred to as (7).) Then, as shown in FIG. 9 (h), the piezoelectric substrate integrated with the mounting substrate is divided into surface acoustic wave element regions by so-called half dicing, As shown in FIG. 9 (i), the surface acoustic wave element mounted on the mounting substrate is resin-molded using a sealing resin. And de, then separating the base for mounting with the molding resin for each surface acoustic wave element (for this step (8).) And may be. In the case of this Example 8, the other main piezoelectric substrate is interposed between the steps (1) to (3) and the step (7) or after the step (7) as shown in FIG. The conductor layer is partially removed in a predetermined region of the conductor layer formed on the surface, for example, in a region facing at least one of the input pad portion of the filter region and the output pad portion of the filter region. A forming part is provided. This removal method is the same as described above.

First, Ti / Al-1 mass% Cu / Ti / Al-1 is formed on one main surface of a piezoelectric substrate 2 (substrate thickness is 250 μm) made of a 38.7 ° Y-cut X-propagating lithium tantalate single crystal substrate from the substrate side by sputtering. Four conductor layers made of mass% Cu were formed. The film thicknesses are 6 nm / 209 nm / 6 nm / 209 nm, respectively. Next, this conductor layer is patterned by photolithography and RIE to form filter regions each including the excitation electrode 3, the input pad portion 5, and the output pad portion 6, and a plurality of surface acoustic wave element regions are formed. did. A mixed gas of BCl ₃ and Cl ₂ was used as an etching gas at this time. The line width of the comb-like electrode forming the excitation electrode 3 and the distance between adjacent comb-like electrodes are both about 1 μm.

  Next, a conductor layer 10 made of pure Al was formed on the other main surface of the piezoelectric substrate 2 by sputtering. The conductor layer 10 has a thickness of 200 nm.

  Next, a new conductor layer made of Cr / Ni / Au was laminated on the input pad portion 5 and the output pad portion 6 to form an input pad and an output pad. The thicknesses of the new conductor layers are 6 nm / 1000 nm / 100 nm, respectively.

  Next, one main surface of the piezoelectric substrate 2 is protected with a photoresist, and then the other main surface is coated with a photoresist and subjected to photolithography, and then subjected to piezoelectric etching by wet etching using a mixed acid of nitric acid, phosphoric acid, and acetic acid. The conductor layer 10 on the other main surface of the substrate 2 was patterned as shown in FIG.

  Next, after removing the photoresist, the piezoelectric substrate 2 was separated by dicing for each surface acoustic wave element region to obtain a large number of surface acoustic wave elements 1.

  Next, the surface acoustic wave element 1 was mounted on a mounting base made of a LTCC (Low Temperature Co-fired Ceramics) substrate with one main surface facing each other. Here, the LTCC substrate has a base-side annular conductor corresponding to the annular conductor 7 formed on one main surface of the piezoelectric substrate 2 and pad electrodes connected to the input / output pads of the surface acoustic wave element 1. Solder was printed on the base-side annular conductor and the pad electrode. When the surface acoustic wave element 1 is mounted thereon, the surface acoustic wave element 1 is disposed so as to coincide with these solder patterns, temporarily fixed by applying ultrasonic waves, and then heated to melt the solder. By doing so, the annular conductor 7 and the base-side annular conductor were connected, and the input / output pad and the pad electrode were connected. As a result, the filter region 9 of the surface acoustic wave element 1 is completely hermetically sealed by the base-side annular conductor of the LTCC substrate and the annular conductor 7 connected thereto. The mounting process of the surface acoustic wave element 1 was performed in a nitrogen atmosphere.

  Next, a resin mold is performed, the other main surface (back surface) of the surface acoustic wave element 1 is protected with a mold resin, and finally the mounting substrate is diced between the surface acoustic wave elements, whereby the elastic surface of the present invention is obtained. A wave device was obtained.

  As a comparative example, a surface acoustic wave in which a filter region including an excitation electrode, an input pad portion, and an output pad portion is formed on one main surface of a piezoelectric substrate as in the prior art, and a conductor layer is formed on the entire other main surface. A surface acoustic wave device was fabricated in which the element was mounted on the mounting substrate with one main surface facing. The top view of this comparative example is the same as FIG.

  FIG. 10 is a diagram illustrating the frequency characteristics of the examples and comparative examples of the present invention thus manufactured. In the diagram of FIG. 10, the horizontal axis represents frequency (unit: MHz), the vertical axis represents attenuation (unit: dB), and the characteristic curve indicated by a broken line is a conductor layer formed on the entire other main surface of the LT substrate. The result of the comparative example is shown, and the solid characteristic curve shows the result of the example in which the conductor layer on the other main surface of the LT substrate is formed by interspersing a large number of conductor non-formation regions. As can be seen from the results shown in FIG. 10, the surface acoustic wave device of the present invention of this example has a much better out-of-passband attenuation than that of the comparative example. In particular, the amount of attenuation outside the pass band in the vicinity of the pass band is greatly improved as compared with the comparative example.

  In addition, when the conductor layer 10 was patterned as shown in FIGS. 2 to 5 in the embodiment and the frequency characteristics were evaluated in the same manner, the attenuation outside the passband in the vicinity of the passband was greatly increased. It was confirmed that it was improved.

  In addition, this invention is not limited to the example of the above embodiment, A various change may be added in the range which does not deviate from the summary of this invention. For example, two or more filter regions may be provided on the same piezoelectric substrate. In that case, the area occupied by the whole can be reduced compared with the case where a plurality of surface acoustic wave elements are separately manufactured.

  6 and the like show the case where a ladder type filter is used, the present invention does not limit the structure of the filter, and a DMS type or an IDT type filter may be used. Further, the arrangement of the input / output terminals is not limited to that shown in FIG. 6 and the like, and may be located on the diagonal of the piezoelectric substrate.

  Further, the material of the excitation electrode is not limited to the materials mentioned in the embodiments, and a single layer of Al, Au, Ta, W, Mo, Ti, Cu or an alloy thereof may be used, or between these and the piezoelectric substrate. Alternatively, a structure in which an adhesion layer is inserted may be used.

  Furthermore, in the above example, a conductor layer is once formed on the other main surface of the piezoelectric substrate, and then the conductor layer in a desired region is partially removed to form a plurality of non-conductor-formed portions. As described above, a region of a conductor non-formation portion where a conductor layer is not formed may be set in advance, and a desired conductor non-formation portion may be arranged so as to form a conductor layer outside the region. Absent.

It is a top view which shows the other main surface (pattern of a conductor layer) of the piezoelectric substrate of the surface acoustic wave element in Example 1 of Embodiment of the surface acoustic wave apparatus of this invention. It is a top view which shows the other main surface (pattern of a conductor layer) of the piezoelectric substrate of the surface acoustic wave element in Example 2 of Embodiment of the surface acoustic wave apparatus of this invention. It is a top view which shows the other main surface (pattern of a conductor layer) of the piezoelectric substrate of the surface acoustic wave element in Example 3 of the surface acoustic wave apparatus of this invention. It is a top view which shows the other main surface (pattern of a conductor layer) of the piezoelectric substrate of the surface acoustic wave element in Example 4 of Embodiment of the surface acoustic wave apparatus of this invention. It is a top view which shows the other main surface (pattern of a conductor layer) of the piezoelectric substrate of the surface acoustic wave element in other examples of Example 1 of the surface acoustic wave device according to the present invention. It is a top view which shows one main surface of the piezoelectric substrate of the surface acoustic wave element showing an example of the surface acoustic wave apparatus of this invention. It is a top view which shows one main surface of the piezoelectric substrate of the surface acoustic wave element showing an example of the surface acoustic wave apparatus of this invention. (A)-(j) is sectional drawing for every process which shows an example of embodiment of the 1st manufacturing method of the surface acoustic wave apparatus of this invention, respectively. (A)-(j) is sectional drawing for every process which shows an example of embodiment of the 2nd manufacturing method of the surface acoustic wave apparatus of this invention, respectively. It is a diagram which shows the bandpass characteristic of the surface acoustic wave apparatus produced in the Example of this invention. It is sectional drawing which shows the mounting structure of the conventional surface acoustic wave apparatus typically.

Explanation of symbols

1: Surface acoustic wave element 2: Piezoelectric substrate 3: Excitation electrode 4: Connection electrode 5: Input pad portion 6: Output pad portion 7: Ring conductor 8: Ground electrode pad 9: Filter region
10: Conductor layer
11: Resistor 5a: Region facing the input pad portion 5b: Region facing the DC connection portion from the input pad portion to the excitation electrode 6a: Region facing the output pad portion 6b: From the output pad portion Region facing the portion connected to the excitation electrode in a direct current manner 9a: Region facing the filter region

Claims (9)

A surface acoustic wave device in which a filter region having an excitation electrode, an input pad portion, and an output pad portion is formed on one main surface of a piezoelectric substrate and a conductor layer is formed on the other main surface is formed on the mounting substrate. The conductor layers are mounted facing each other, and the conductor layer is formed by interspersing a large number of conductor non-forming portions, and the conductor non-forming portions are the input pad portion and the output pad portion of the conductor layer. A surface acoustic wave device characterized in that a ratio of the area occupied in a region opposite to is larger than that in other regions . A surface acoustic wave device in which a filter region having an excitation electrode, an input pad portion, and an output pad portion is formed on one main surface of a piezoelectric substrate and a conductor layer is formed on the other main surface is formed on the mounting substrate. The conductor layers are mounted facing each other, and the conductor layer is formed by interspersing a large number of conductor non-formation portions, and the conductor non-formation portions are formed from the input pad portion of the conductor layer to the excitation electrode. in a region facing the portion and the output pad unit are galvanically connected to a portion which is galvanically connected to the excitation electrode, you ratio of the area occupied its being larger than the other regions surface acoustic wave devices. The surface acoustic wave device according to claim 1 or 2, wherein the filter formed in the filter region is a ladder type filter . The surface roughness of the other main surface of the conductor non-forming portion of the piezoelectric substrate is larger than the surface roughness of the other main surface of the region where the conductor layer is formed. 4. The surface acoustic wave device according to any one of 3 above. An annular conductor is formed on the one main surface of the piezoelectric substrate so as to surround the filter region, and the annular conductor is joined to a substrate-side annular conductor formed on the mounting substrate. The surface acoustic wave device according to any one of claims 1 to 4, wherein the surface acoustic wave device is characterized. 6. The surface acoustic wave device according to claim 5, wherein the excitation electrode is electrically connected to the annular conductor via a resistor, and the annular conductor is at a ground potential. The piezoelectric substrate, surface acoustic wave device according to any one of claims 1 to 6, characterized in that it consists of tantalum single crystal of lithium or lithium niobate single crystal or lithium tetraborate single crystal. 8. The piezoelectric substrate according to claim 1, wherein the one principal surface side is made of a piezoelectric material, and the other principal surface side is made of a material having a relative dielectric constant smaller than that of the piezoelectric material. Surface acoustic wave device. A communication apparatus comprising at least one of a reception circuit and a transmission circuit, comprising the surface acoustic wave device according to claim 1.

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