JP2009225198A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To ensure isolation by preventing interference between filters, even when a surface acoustic wave (SAW) device that includes a plurality of SAW filters is reduced in size. <P>SOLUTION: The present invention relates to a SAW device, comprising a SAW element including a low-frequency side SAW filter and a high-frequency side SAW filter, which are provided on the same piezoelectric substrate, and a base substrate which has conductors on a surface thereof and in which the SAW element is FCB-packaged. All the conductors on the surface of the base substrate are disposed so as not to spread over a first counter region that is a region on the surface of the base substrate which faces a region where the low-frequency side SAW filter is formed, and a second counter region that is an region on the surface of the base substrate in counter to a region where the high-frequency side SAW filter is formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a surface acoustic wave device, and more particularly, to an electrode arrangement structure for preventing interference between filters in a surface acoustic wave device including a plurality of surface acoustic wave filters mounted by flip-chip bonding (hereinafter referred to as FCB mounting). .

  A SAW duplexer using a surface acoustic wave (hereinafter sometimes referred to as “SAW”) filter for each filter on the transmission side and the reception side is suitable for mobile communication such as a cellular phone because it is small and lightweight and suitable for high functionality. It has been widely used in equipment in recent years. A SAW filter constituting such a duplexer generally includes a plurality of interdigitated electrodes (interdigital transducer / hereinafter referred to as IDT) including a pair of comb-shaped electrodes formed on a piezoelectric substrate. A predetermined pass band (transmission frequency or reception frequency) is formed by connecting and coupling in a sound and acoustic manner.

  Of these filters, the transmission side filter is between the transmission signal terminal (transmission electrode) to which the transmission signal is input and the common terminal (common electrode) connected to the antenna, and the reception side filter is The transmission signal and the reception signal are demultiplexed by being connected between the reception signal terminal (reception electrode) from which the reception signal is output and the common terminal, respectively.

The following patent documents disclose such SAW devices (duplexers, dual filters).
JP 2006-80921 A JP 2006-180192 A JP 2005-175638 A

  By the way, the transmission side filter and the reception side filter in the duplexer are conventionally manufactured as independent chip parts, but further miniaturization of parts and reduction of manufacturing processes are required, and the same is required to realize this. In recent years, attempts have been made to form both transmitting and receiving filters on the (one) piezoelectric substrate. However, when both filters are mounted on the same piezoelectric substrate in this way and the transmission / reception filter is made into one chip, there is a problem that the filters interfere with each other and the isolation characteristics deteriorate.

  In particular, when the device is further downsized compared to the conventional case (for example, the package size (vertical and horizontal dimensions) is 2.0 mm × 1.6 mm or smaller, for example, 1.8 mm × 1.4 mm), the iris between the transmission and reception filters It is not easy to ensure. This is because the conventional device (having a package size of, for example, 2.5 mm × 2.0 mm or more) has a margin in the conductor pattern on the base substrate side on which the FCB is mounted. For example, a ground pattern is provided between the signal lines. In addition, it is possible to reinforce the ground pattern by increasing the area of the ground pattern or by connecting it to a large ground electrode on the back surface of the base substrate with a large number of vias. (For example, the package size is 2.0 mm × 1.6 mm, or even smaller, for example, 1.8 mm × 1.4 mm), the signal lines of both filters are close to each other, and a ground electrode and a large number of vias are provided between both filters. It is because it becomes impossible.

  On the other hand, the inventions described in Patent Document 1 (Japanese Patent Laid-Open No. 2006-80921) and Patent Document 2 (Japanese Patent Laid-Open No. 2006-180192) both reduce the size of the SAW device (duplexer) while maintaining good electrical characteristics. However, when considering further downsizing of the apparatus, it is desired to provide a new means for preventing interference between the two filters. Patent Document 3 (Japanese Patent Application Laid-Open No. 2005-175638) describes that a transmission-side ground pattern is separated from a common electrode and a reception-side ground pattern. No way to prevent this is shown.

  Accordingly, an object of the present invention is to prevent interference between filters in a SAW device including a plurality of SAW filters and to improve isolation characteristics.

  In order to solve the above problems and achieve the object, a SAW (surface acoustic wave) device according to the present invention includes a low-pass SAW filter and a high-pass SAW filter provided on the same piezoelectric substrate having different center frequencies. And a base substrate on which the conductor is mounted on the surface and the SAW element is mounted on the surface by FCB (flip chip bonding), the conductor on the surface of the base substrate being , Both of which are a first counter region that is a region of the base substrate surface that faces the formation region of the low-pass SAW filter and a base substrate surface region that faces the formation region of the high-pass SAW filter. It arrange | positioned so that it may not straddle two opposing area | regions.

  In the present invention, the “SAW (surface acoustic wave) filter forming region” (low-pass SAW filter forming region, high-pass SAW filter forming region) is an IDT that constitutes the SAW filter. Accordingly, it refers to a region including a reflection electrode (reflector) disposed on both sides of the IDT, a connection pad electrode for mounting the FCB, and a conductor line that connects the IDTs or the IDT and the connection pad electrode. In other words, “SAW filter formation region” refers to the constituent elements of these filters (IDT, reflector (if provided with a reflector), FCB mounting connection pad electrodes, and conductors that connect IDTs or IDTs and connection pad electrodes. It means the area connecting the outer edges of the track. The “first opposing region” is a region on the surface of the base substrate that faces the formation region of the low-frequency side SAW filter. Similarly, the “second opposing region” faces the formation region of the high-frequency side SAW filter. This is a region on the surface of the base substrate.

  In a conventional SAW device with a large package size, there is a margin in the conductor pattern on the base substrate side on which the SAW element is mounted as described above, and transmission and reception are relatively easy by a method such as providing a strong ground pattern between signal lines. It was possible to secure an eyelid between. For this reason, the present situation is that no particular attention is paid to the pattern on the base substrate side on which the SAW element is mounted, and no special measures are taken.

  On the other hand, when considering further downsizing of the device, it is difficult to provide a strong ground pattern between the signal lines as already described. In addition, when the SAW element is FCB-mounted by face down, the apparatus can be reduced in height, while the electrode pattern formation surface (filter formation surface) of the SAW element is disposed facing and close to the base substrate surface. Therefore, for example, it becomes more susceptible to the structure of the opposing base substrate compared to wire bonding mounting. Therefore, in the present invention, focusing on the side of the base substrate on which the SAW element is mounted, a structure for increasing isolation between a plurality of SAW filters included in the SAW element has been studied.

  Specifically, regarding a SAW duplexer in which a SAW element including two SAW filters (a low-pass filter and a high-pass filter) formed adjacent to each other on the same piezoelectric substrate is FCB-mounted on the surface of the base substrate, The effect of this was verified by dividing the ground electrode provided on the ground. This division is a first facing region that is a region of the base substrate surface that faces the formation region of the low-pass filter in the SAW filter, and a region that is the surface of the base substrate that faces the formation region of the high-pass filter. The ground electrode formed so as to straddle the two opposing regions (partially enter both regions) is separated (divided) so as not to straddle both opposing regions, in other words, the first opposing region The ground electrode was divided into two electrodes between the first and second opposing regions.

  In addition, this invention is not limited to the structure divided | segmented as mentioned above, ie, the structure which divides | segments the conductor conventionally arrange | positioned so that a 1st opposing area | region and a 2nd opposing area | region may be straddled, For example, the said The conductor that has been arranged so as to straddle both opposing areas may be moved so that it is arranged only in one of the opposing areas, or the conductor that has entered one of the opposing areas It is also possible to prevent the conductor from straddling both opposing regions by deleting the portion. In short, in the present invention, the conductors on the surface of the base substrate may be arranged so that none of the conductors straddles the first opposing region and the second opposing region.

The base substrate examined above has three wiring layers: a surface layer (surface layer) that is the surface of the base substrate, a back surface layer (back layer) that is the back surface of the base substrate, and a wiring layer inside the base substrate. A total of three wiring layers of a certain inner layer are provided, and each layer includes the first opposing region or the region of the substrate inner layer or the back layer corresponding to the region (identical when viewed from above) or the second opposing region or the region The ground electrode corresponding to the region (same as seen from the plane) is provided over the substrate inner layer or the region of the back layer, and the ground electrode provided in each of the back layer and the inner layer is also the surface layer. In the same manner as described above, a study was performed to divide the ground electrode into a region corresponding to the first opposing region and a region corresponding to the second opposing region. The results are as shown in Table 1 below and FIG. The SAW device has a package size (vertical and horizontal dimensions of the base substrate) of 2.5 mm × 2.0 mm (the area of the base substrate surface is 5.0 mm ² ).

  From the above examination, it is possible to obtain better isolation as the ground electrode is divided than when no division is performed (no division). In particular, it is best if the ground electrode is divided for all of the surface layer, the inner layer, and the back layer. It can be seen that the characteristics can be obtained.

On the other hand, the present inventor conducted the same examination when the apparatus was further downsized. The package size (vertical and horizontal dimensions of the base substrate) is 1.8 mm × 1.4 mm (the area of the base substrate surface is 2.52 mm ² ). The results were as shown in Table 2 below and FIG.

  From the above results, when the device is downsized, unlike the case where the device size is large, it is better to simply divide the ground electrode (divide all ground electrodes of the surface layer, inner layer, and back layer). Instead, it was found that dividing only the surface layer is effective in improving the isolation between the two filters. In particular, unlike the case where the device size is large, when the device is small, if only the back layer or all of the surface layer, inner layer, and back layer are divided, the effect of reducing electromagnetic field coupling due to the physical separation of the conductors However, the effect of increasing the electromagnetic coupling due to the increase in the ground inductance component and the weakness of the ground of the ground electrode itself becomes dominant, and the isolation characteristic is deteriorated on the contrary.

  From these examination results, in the SAW device according to the present invention, each of the conductors on the surface of the base substrate on which the SAW element including the low-pass SAW filter and the high-pass SAW filter is FCB-mounted is first. It arrange | positions so that it may not straddle an opposing area | region and a 2nd opposing area | region. In other words, the structure is such that there is no conductor disposed on the surface of the base substrate so as to straddle both the first facing region and the second facing region. Further, according to the structure of the present invention, it is possible to prevent or reduce the electromagnetic coupling between the two filters via the conductor (for example, the ground electrode) on the surface of the base substrate. The characteristics can be improved.

  Further, in the above-described SAW device of the present invention, the conductors on the surface of the base substrate are arranged so that none of them is located in the region between the first facing region and the second facing region on the surface of the base substrate. Anyway. If such an arrangement structure, in other words, a structure in which no conductor is provided between the two filters on the surface of the base substrate (between the first opposing region and the second opposing region), the electromagnetic waves of the two filters through the base substrate are provided. Bonding can be further reduced.

  In the present invention, the “conductor” on the base substrate is typically a ground electrode, but is not necessarily limited to this, and includes various conductors having conductivity such as a pad electrode for connection and a transmission line. . The “base substrate” in the present invention can be, for example, a ceramic substrate or a substrate made of a material mainly composed of resin (for example, a resin substrate or a composite material substrate in which an inorganic filler is mixed into a resin material). Furthermore, the SAW element mounted on the surface of the base substrate may be sealed with a resin (sealing material) applied so as to cover the SAW element and the base substrate. According to such a package structure, it is possible to reduce the size and height of the device.

As is clear from the above examination, the present invention is particularly effective when the apparatus is downsized. Specifically, for example, (1) the area of the base substrate is 3.2 mm ² or less, and (2) the horizontal dimension of the base substrate is 2.0 mm or less and the vertical dimension is 1.6 mm or less. A device that satisfies one or both of the two conditions. Or (1) The base substrate has an area of 2.52 mm ² or less, and (2) the base substrate has a horizontal dimension of 1.8 mm or less and a vertical dimension of 1.4 mm or less. The apparatus satisfies one or both of the two conditions. In these cases, the low-pass SAW filter and the high-pass SAW filter are arranged adjacent to each other on the piezoelectric substrate, and the SAW filter is arranged in the horizontal direction, parallel to the surface of the base substrate, and The direction orthogonal to the direction is the vertical direction.

  In the present invention, the number of SAW filters included in the SAW element is not limited to two, and it is apparent that the present invention can be similarly applied to three or more SAW filters. In addition, the base substrate is not limited to three layers, and may include two or less wiring layers or four or more wiring layers.

  In the SAW device of the present invention, the SAW element includes a common electrode connected to the antenna, a low-frequency signal electrode, a high-frequency signal electrode, and a ground electrode for grounding. The filter is connected between the common electrode and the low-frequency signal electrode, and the high-frequency SAW filter is connected between the common electrode and the high-frequency signal electrode, and the common electrode and the high-frequency signal electrode One or more series arm resonators connected in series on a transmission line connecting the two and two or more parallel arm resonators connected respectively to two or more transmission lines branching from the transmission line to the ground electrode. A first parallel arm resonator that is a parallel arm resonator that is connected first when viewed from the common electrode, and a second parallel arm resonator that is connected after the first parallel arm resonator when viewed from the common electrode. At least a second parallel arm resonator Including two or more parallel arm resonators including a common ground electrode, and the common ground electrode and a transmission path connecting the two or more parallel arm resonators and the common ground electrode, You may make it arrange | position to the side near the formation area of a low-frequency side surface acoustic wave filter from the transmission line which connects a common electrode and a high frequency side signal electrode.

  According to such a device structure, a common ground electrode can be interposed between the transmission line (high band side signal transmission line) connecting the common electrode and the high band side signal electrode and the low band side filter. In addition, since the ground electrode and the transmission path (branch path) to the ground electrode are shared by two or more parallel arm resonators, the size (area) of the ground electrode and the transmission path inductance to the ground electrode is increased. Since the value can be lowered, the coupling between the two filters can be further reduced in combination with the above-described electrode structure on the base substrate side.

  Conversely, even if the same configuration is adopted for the low-frequency filter, that is, between the transmission line (low-frequency signal transmission line) connecting the common electrode and the low-frequency signal electrode and the high-frequency filter. A similar effect can be obtained even if a common ground electrode is interposed.

  Specifically, in the SAW device of the present invention, the SAW element includes a common electrode connected to the antenna, a low-frequency signal electrode, a high-frequency signal electrode, and a ground electrode for grounding. The band-side SAW filter is connected between the common electrode and the high-frequency side signal electrode, and the low-frequency side SAW filter is connected between the common electrode and the low-frequency side signal electrode. One or more series arm resonators connected in series on the transmission line connecting the side signal electrode, and two or more parallel arm resonators connected respectively to two or more transmission lines branching from the transmission line to the ground electrode Of these parallel arm resonators, the first parallel arm resonator which is the first connected parallel arm resonator as viewed from the common electrode, and the first parallel arm resonator as viewed from the common electrode. Less the second parallel arm resonator which is the parallel arm resonator Two or more parallel arm resonators including a common ground electrode, and a transmission path for connecting the common ground electrode and the two or more parallel arm resonators and the common ground electrode, You may arrange | position to the side near the formation area of the high band side SAW filter from the transmission line which connects a common electrode and a low band side signal electrode.

  According to the present invention, even when a SAW device including a plurality of SAW filters is downsized, interference between filters can be prevented and isolation characteristics can be improved.

  Other objects, features, and advantages of the present invention will become apparent from the following description of embodiments of the present invention described with reference to the drawings. In the following description of the embodiment, in order to facilitate understanding, a SAW duplexer according to a comparative example, which is a premise of the present invention, will be described first, and the SAW duplexer according to the embodiment will be described in comparison with this. Moreover, the same code | symbol is attached | subjected about the same or an equivalent part in each figure, and the duplicate description is abbreviate | omitted.

[First Embodiment]
3 to 4 schematically show the SAW duplexer according to the first comparative example. FIG. 3 shows the surface of the base substrate, and FIG. 4 shows the SAW element (hereinafter referred to as a chip) on the base substrate. Each state is shown. Note that conductor patterns such as IDTs and connection pads constituting the filter are formed on the lower surface of the chip in the mounted state, but FIG. 4 shows the chip lower surface (conductor pattern) seen through from the upper surface side of the chip. Yes.

  As shown in FIGS. 3 and 4, this SAW duplexer has a base substrate 101 on which a SAW element 121 is mounted having an electrode structure similar to the conventional one, and a bare chip-shaped SAW element 121 is faced on the surface of the base substrate 101. FCB mounted by down. The SAW element 121 has a low-frequency side SAW filter 21 and a high-frequency side SAW filter 31 formed side by side on the front surface (lower surface) of the piezoelectric substrate. The low-frequency side SAW filter 21 is a transmission-side filter and a high-frequency side SAW. The filter 31 is a reception side filter.

  In the following description, the arrangement direction of the low-frequency and high-frequency filters 21 and 31 (the horizontal direction / x-axis direction in FIGS. 3 and 4) is the horizontal direction, parallel to the base substrate surface, and the horizontal direction. A direction perpendicular to the vertical direction (vertical direction in FIG. 3 and FIG. 4 / y-axis direction) is referred to as a vertical direction (the same applies to the following description including FIG. 5, FIG. 6, FIG. 10 and FIG. 12). In FIG. 4, the transmission-side filter 21 formation region is surrounded by a two-dot chain line and denoted by reference numeral 102, and the reception-side filter 31 formation region is similarly surrounded by a two-dot chain line and denoted by reference numeral 103. Further, in FIG. 3, the first facing region facing the forming region 102 of the transmission filter 21 is similarly surrounded by a two-dot chain line and indicated by the same reference numeral 102, and facing the forming region 103 of the receiving filter 31. The second facing region is similarly surrounded by a two-dot chain line and indicated by the same reference numeral 103.

  The transmission-side filter 21 includes three series arm resonators 22, 23, 24 connected in series on a transmission line between the common electrode C1 connected to the antenna and the transmission electrode T to which a transmission signal is input. A five-stage ladder-type SAW filter having three parallel arm resonators 25, 26, and 27 connected to a branch line that branches from the transmission line to the ground electrode G1. On the other hand, the reception-side filter 31 includes two series arm resonators 32 and 33 connected in series on a transmission line between the common electrode C2 connected to the antenna and the reception electrode R from which a reception signal is output. , A four-stage ladder-type SAW filter having three parallel arm resonators 35, 36, and 37 connected to a branch line that branches from the transmission line to the ground electrodes G and G4. In addition, each of the series arm resonators 22 to 24 and 32 to 33 and each of the parallel arm resonators 25 to 27 and 35 to 37 in both the filters 21 and 31 includes a pair of comb-shaped electrodes and includes reflectors on both sides thereof. It consists of IDT. Note that a preferred configuration example of the SAW element 121 will be described later as a second embodiment.

  The base substrate 101 is a ceramic substrate having three wiring layers, a surface layer, an inner layer, and a back layer. As shown in FIG. 3, the surface (surface layer) has a transmission pad 111 for a transmission signal and a reception signal for a reception signal. A plurality of conductors including a receiving pad 115, common pads 113 and 114 for antenna connection, ground pads 112 and 116 for grounding, and a ground electrode 117 are provided. On the transmission pad 111, the reception pad 115, the common pads 113 and 114, and the ground pads 112 and 116, the transmission electrode T, the reception electrode R, the common electrodes C1 and C2, and the ground electrodes G1 and G4 of the SAW element 121 are respectively metal bumps. Connected via B.

The transmission pad T is on one end of one edge of the base substrate surface (one vertical edge), and the reception pad R is one edge on the base substrate (one vertical edge). ) On the other end. The common pad 113 on the transmission side is at the center of the other edge of the base substrate surface (the other end edge in the vertical direction), and the common pad 114 on the reception side is the other edge of the base substrate surface (the other in the vertical direction). Are arranged at the other end of each other. Further, a ground pad 116 is provided between the transmission pad 111 and the reception pad 115, and a ground electrode 117 is formed at the center of the base substrate 101 surrounded by the ground pad 116, the reception pad 115 and the common pads 113 and 114. It is. The size of the base substrate 101 is such that the horizontal dimension x ₁ is 1.8 mm, the vertical dimension y ₁ is 1.4 mm, and the area is 2.52 mm ² (first embodiment shown in FIGS. 5 and 6). The form is the same).

  On the back surface (back layer) of the base substrate 101, external connection terminals for mounting the SAW duplexer, that is, the antenna common terminal 1 (see FIGS. 11 and 13), the transmission terminal 2, the reception terminal 3, and the ground are provided. A common pad 113, 114 on the base substrate is connected to the antenna common terminal 1, the transmission pad 111 is connected to the transmission terminal 2, the reception pad 115 is connected to the reception terminal 3, and the ground pads 112, 116 are provided. The ground electrode 117 is electrically connected to the ground terminal via a via V, respectively. A ground electrode (so-called solid electrode) is formed on substantially the entire back surface of the base substrate excluding these external connection terminals.

  5 to 6 schematically show the SAW duplexer according to the first embodiment of the present invention. FIG. 5 shows the surface of the base substrate 101 as in FIG. 3, and FIG. 4 shows a state where the chip 121 is mounted on the base substrate 101 as in FIG. The SAW duplexer of this embodiment differs from the comparative example only in the shape and arrangement of conductors (pads and ground electrodes) on the surface of the base substrate 101.

  Specifically, in the duplexer according to the comparative example shown in FIG. 3, the ground pad 116 provided between the transmission pad 111 and the reception pad 115 and the ground electrode 117 disposed in the center portion of the base substrate 101 are provided. In the duplexer according to this embodiment, the ground pad 116 and the second opposing region 102 and the second opposing region 103 are formed so as to straddle the first opposing region 102 and the second opposing region 103, as shown in FIG. The two parts 116a and 116b are separated from the opposing region 103, and the portion of the ground electrode 117 at the center of the base substrate that is disposed in the first opposing region 102 and the region 104 between the opposing regions is deleted. Thus, the ground electrode 117 a having a shape that fits almost entirely within the second facing region 103 was obtained. Thereby, the structure which does not have the conductor which straddles the 1st opposing area | region 102 and the 2nd opposing area | region 103 on the surface of the base substrate 101, in other words, all the conductors on the surface of the base substrate 101 are 1st opposing area | regions. The structure which does not straddle 102 and the 2nd opposing area | region 103 is implement | achieved.

  The ground electrode 117 at the center of the base substrate is electrically connected to the ground electrode on the back surface of the base substrate through two vias V. However, more vias (for example, three or more) are provided. By connecting to the ground electrode on the back surface of the base substrate, the ground electrode 117a on the surface of the base substrate can be strengthened.

  Further, as in this embodiment, a region between the first facing region 102 and the second facing region 103 on the surface of the base substrate (a region on the base substrate 101 sandwiched between the first facing region 102 and the second facing region 103) (Hereinafter referred to as the boundary region), it is preferable to prevent the presence of the conductor in 104 from the viewpoint of preventing interference between the filters 21 and 31. In the example shown in FIGS. 5 to 6, a part of the divided ground pad part 116 a and a part of the common pad 113 of the transmission-side filter 21 slightly enter the boundary region 104. Substantially the entire conductor is accommodated in the first facing region 102 and hardly affects the characteristics. However, it is also possible to completely eliminate the intrusion portion into the boundary region 104 by moving the ground pad portion 116a and the common pad 113, for example, or changing the shape and size. A structure in which no conductor is present may be used.

  7 to 9 show the isolation characteristics (frequency-attenuation characteristics) of the duplexer according to the present embodiment in comparison with the duplexer according to the comparative example (the solid line is the present embodiment, and the broken line is the comparative example). . As an example of a standard required for a duplexer, there is one that requires an attenuation of −50 dB in a transmission frequency band of 1.75 GHz to 1.785 GHz, and the standard is shown in the diagrams of FIGS. 8 and 9. . As is apparent from these diagrams, according to this embodiment, the isolation characteristics between the filters can be improved and the above-mentioned standard can be sufficiently satisfied.

[Second Embodiment]
12 to 13 show a SAW duplexer (SAW element) according to the second embodiment of the present invention, and FIGS. 10 to 11 show a second comparative example which is a premise of the second embodiment. The SAW duplexer (SAW element) according to FIG. This embodiment improves the isolation characteristics between the transmission / reception filters 21 and 31 as in the first embodiment, but is particularly characterized by the electrode pattern on the SAW element side. 10 and 12, the lower surface of the SAW element is seen through from the upper surface of the chip, as in FIGS.

  As shown in FIGS. 10 to 11, first, the SAW duplexer according to the second comparative example has a low frequency band on the surface (lower surface) of one piezoelectric substrate, similarly to the duplexer according to the first comparative example and the first embodiment. The SAW element 121a is formed by arranging a side (transmission side) SAW filter 21 and a high frequency side (reception side) SAW filter 31 side by side.

  The transmission-side filter 21 has three series arm resonators 22, 23, 24 connected in series on the transmission line between the transmission electrode T and the common electrode C1, and branches from the transmission line to the ground electrode G1. This is a five-stage ladder-type SAW filter having three parallel arm resonators 25, 26, and 27 connected on a branch line. On the other hand, the reception-side filter 31 includes two series arm resonators 32 and 33 connected in series on a transmission line (hereinafter referred to as a reception signal line) between the common electrode C2 and the reception electrode R, and A four-stage ladder-type SAW filter having three parallel arm resonators 35, 36, and 37 connected to a branch line (hereinafter referred to as a ground line) that branches from the transmission line to the ground electrodes G2, G3, and G4. It is. Each of the series arm resonators 22 to 24 and 32 to 33 and each of the parallel arm resonators 25 to 27 and 35 to 37 is composed of an IDT in which a pair of comb electrodes are combined and reflectors are provided on both sides thereof.

  Further, as shown in FIGS. 10 and 11, in the reception side (low frequency side) filter 31, a ground line (branch line) is individually provided for each of the parallel arm resonators 35, 36, and 37, and each parallel arm resonator 35 is provided. , 36, 37 and individual ground electrodes G2, G3, G4 corresponding to the respective ground lines are provided.

  On the other hand, the SAW duplexer according to the present embodiment has the same transmission side filter 21 composed of a five-stage ladder type SAW filter and the reception side filter 31 composed of a four-stage ladder type SAW filter as in the second comparative example. The SAW element 121b formed side by side on the piezoelectric substrate is provided with a parallel arm resonator for the reception side (high frequency side) filter 31 as shown in FIGS. 35 to 37, the first parallel arm resonator 35 that is the first connected parallel arm resonator as viewed from the common electrode C2 and the first parallel arm resonator 35 that is connected from the common electrode C2 are connected next to the first parallel arm resonator 35. A second parallel arm resonator 36, which is a parallel arm resonator, is connected to a common ground electrode G22. At the same time, the common ground electrode G22 and a transmission line (hereinafter referred to as a common branch line) 106 that connects the first parallel arm resonator 35 and the second parallel arm resonator 36 to the common ground electrode G22 are provided. These are arranged closer to the center than the reception signal line 107 (on the side closer to the transmission side (low frequency side) filter 21).

  With such an arrangement structure, the common branch line 106 can be formed wider and thicker as shown in FIGS. 12 and 13, and the inductance value of the transmission line 106 is lowered to reduce the transmission / reception between the filters 21 and 31. Interference can be reduced. If another way of understanding (representing) such a configuration according to the present embodiment, the common ground electrode G22 and the common branch line 106 are arranged at the center (center line 105) of the formation region 103 of the high-pass filter 31. It is also possible to define that the filter is disposed closer to the formation region 102 of the lower-pass filter 21. With this configuration, the signal line 107 of the high-pass filter 31 is placed outside the center (center line 105) of the formation region 103 of the high-pass filter 31 (on the side far from the formation region 102 of the low-pass filter 21). The common ground electrode G22 and the common branch line 106 are disposed between the high-frequency signal line 107 and the low-frequency filter 21 to suppress interference between the filters 21 and 31. Is possible.

  14 to 15 show the isolation characteristics (frequency-attenuation characteristics) of the duplexer according to the present embodiment in comparison with the duplexer according to the second comparative example (the solid line is the present embodiment and the broken line is the comparison). Example). 8 and 9, an example of the standard (1.75 GHz to 1.785 GHz and attenuation of -50 dB) is shown in the diagram. As is apparent from these diagrams, according to this embodiment, it is possible to prevent interference between filters and improve isolation characteristics. Therefore, by combining the structure of the base substrate described in the first embodiment with the SAW element structure described in the second embodiment, the SAW is small and has excellent isolation characteristics with very little interference between filters. A duplexer can be realized.

[Third Embodiment]
16 to 17 show a SAW duplexer (SAW element) according to a third embodiment of the present invention. Similar to the second embodiment, this embodiment is characterized by the electrode pattern on the SAW element side, and improves the isolation characteristics between the transmission and reception filters 21 and 31. 16 and 17 show the bottom surface of the SAW element seen through from the top surface of the chip as in FIG.

  As shown in FIGS. 16 to 17, the SAW duplexer according to the present embodiment is similar to the SAW duplexer of the second embodiment in that it includes a transmission filter 21 including a five-stage ladder type SAW filter and a four-stage ladder type. The SAW element 121c is formed by arranging the reception filter 31 made of a SAW filter side by side on the same piezoelectric substrate, and the SAW element 121c is provided on the transmission side (low-power) as shown in FIGS. For the filter 21, all the parallel arm resonators 25 to 27 (first parallel arm resonator 27 that is the first connected parallel arm resonator as viewed from the common electrode C 1, and the first electrode viewed from the common electrode C 1, The second parallel arm resonator 26, which is a parallel arm resonator connected next to the one parallel arm resonator 27, and the parallel arm connected next to the second parallel arm resonator 26 as viewed from the common electrode C1. Is connected to the third parallel arm resonator 25) is a child to the common ground electrode G1. At the same time, the common ground electrode G1 and the transmission line (common branch line) 132 connecting the parallel arm resonators 25 to 27 to the common ground electrode G1 are closer to the center than the transmission signal line 133 (reception side). (High frequency side) Close to the filter 31).

  If comprised in this way, like the said 2nd embodiment, it is low outside the center (centerline 131) of the formation area 102 of the low-pass filter 21 (the side far from the formation area 103 of the high-pass filter 31). The signal line 133 of the band-side filter 21 can be arranged, and the common ground electrode G1 and the common branch line 132 are arranged between the low-band side signal line 133 and the high-band filter 31 so that both filters 21 , 31 can be suppressed.

  It will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims. For example, in the above embodiment, the low-pass filter is a transmission filter and the high-pass filter is a reception filter. Conversely, the low-pass filter is a reception filter and the high-pass filter is a transmission filter. It can also be a filter. In addition, the low-pass and high-pass filters are both ladder-type SAW filters in the embodiment, but one or both of these filters have a structure other than the ladder-type (for example, an acoustic coupling type or other structure). It is good also as a filter which has. Further, the frequency bands shown in the above embodiment are shown as an example, and it is apparent that the same effect can be obtained by configuring a SAW device using other frequency bands based on the present invention.

It is a diagram which shows the result of having examined the influence (isolation characteristic) at the time of dividing | segmenting the ground electrode with which a base board is provided about the SAW duplexer with a large package size. It is a diagram which shows the result of having examined the influence (isolation characteristic) at the time of dividing | segmenting the ground electrode with which a base board is provided about the SAW duplexer with a small package size. It is a top view which shows typically the SAW duplexer (surface of a base substrate) which concerns on a 1st comparative example. It is a top view which shows typically the SAW duplexer which concerns on a said 1st comparative example in the state which permeate | transmitted the SAW element mounted on the base substrate. It is a top view which shows typically the surface of the base substrate in the SAW duplexer which concerns on 1st embodiment of this invention. It is a top view which shows typically the SAW duplexer which concerns on said 1st embodiment in the state which permeate | transmitted the SAW element mounted on the base substrate. It is a diagram which shows the isolation characteristic (broadband) in the SAW duplexer of said 1st embodiment. It is a diagram which shows the isolation characteristic (pass band) in the SAW duplexer of said 1st embodiment. FIG. 7 is an enlarged diagram showing a part (transmission frequency band) of the diagram of FIG. 6. It is a top view which shows typically the conductor pattern of the SAW element which concerns on a 2nd comparative example. It is a circuit diagram which shows the SAW element which concerns on said 2nd comparative example. It is a top view which shows typically the conductor pattern of the SAW element which concerns on 2nd embodiment of this invention. It is a circuit diagram which shows the SAW element which concerns on said 2nd embodiment. It is a diagram which shows the isolation characteristic by said 2nd embodiment compared with a 2nd comparative example. It is a diagram which expands and shows a part (transmission frequency band) of the diagram of the said FIG. It is a circuit diagram which shows the SAW element which concerns on the said 3rd embodiment. It is a top view which shows typically the conductor pattern of the SAW element which concerns on 3rd embodiment of this invention.

Explanation of symbols

1 antenna common terminal 2 transmission terminal 3 reception terminal 21 low band side SAW filter (transmission side filter)
22, 23, 24, 32, 33 Series arm resonator 25, 26, 27, 35, 36, 37 Parallel arm resonator 31 High band side SAW filter (reception side filter)
101 Base substrate 102 Low band side (transmission side) filter formation area (first counter area)
103 High band side (receiving side) filter formation area (second facing area)
104 Boundary area 105 Center line 106,132 High-frequency side (reception side) filter formation area 106,132 Common branch line 111 Transmission pad 112,116 Ground pad 113,114 Common pad 115 Reception pad 117 Ground electrode 121 SAW element 131 Low-frequency side ( Transmission side) Center line of filter formation region B Metal bump C1, C2 Common electrode G, G1, G2, G3, G4 Ground electrode G22 Common ground electrode R Reception electrode T Transmission electrode V Via hole

Claims (9)

A surface acoustic wave element including a low-frequency side surface acoustic wave filter and a high-frequency side surface acoustic wave filter that have different center frequencies and are provided on the same piezoelectric substrate;
A base substrate having a conductor on the surface and the surface acoustic wave element mounted on the surface by flip chip bonding;
A surface acoustic wave device comprising:
A conductor on the surface of the base substrate, a first facing region, each of which is a region of the base substrate surface facing the region where the low-frequency surface acoustic wave filter is formed, and the high-frequency surface acoustic wave filter A surface acoustic wave device, characterized in that the surface acoustic wave device is arranged so as not to straddle a second facing region that is a region on the surface of the base substrate facing the forming region. The elastic surface according to claim 1, wherein the conductors on the surface of the base substrate are arranged so that none of them is located in a region between the first opposing region and the second opposing region on the surface of the base substrate. Wave equipment. The low-frequency surface acoustic wave filter and the high-frequency surface acoustic wave filter are arranged next to each other on the piezoelectric substrate,
The surface acoustic wave device according to claim 1, wherein an area of the base substrate is 3.2 mm ² or less. The low-frequency surface acoustic wave filter and the high-frequency surface acoustic wave filter are arranged next to each other on the piezoelectric substrate,
When the arrangement direction of these surface acoustic wave filters is the horizontal direction, and the direction parallel to the surface of the base substrate and perpendicular to the horizontal direction is the vertical direction, the base substrate has a horizontal dimension of 2.0 mm or less. The surface acoustic wave device according to any one of claims 1 to 3, wherein the vertical dimension is 1.6 mm or less. The surface acoustic wave device according to any one of claims 1 to 4, wherein the base substrate is a ceramic substrate. The surface acoustic wave device according to any one of claims 1 to 4, wherein the base substrate is a substrate made of a resin-based material. The surface acoustic wave device according to any one of claims 1 to 6, wherein the surface acoustic wave element mounted on the surface of the base substrate is sealed with a resin applied so as to cover the surface acoustic wave element and the base substrate. . The surface acoustic wave element is
A common electrode connected to the antenna;
A low-frequency signal electrode;
A high-frequency signal electrode;
A ground electrode for grounding;
With
The low-frequency surface acoustic wave filter is connected between the common electrode and the low-frequency signal electrode,
The high-frequency surface acoustic wave filter is
Connected between the common electrode and the high-frequency signal electrode,
One or more series arm resonators connected in series on a transmission line connecting the common electrode and the high-frequency signal electrode, and two or more transmission lines branched from the transmission line to the ground electrode, respectively. Two or more parallel arm resonators,
Of these parallel arm resonators, the first parallel arm resonator that is the first connected parallel arm resonator as viewed from the common electrode and the first parallel arm resonator as viewed from the common electrode are connected next to the first parallel arm resonator. Two or more parallel arm resonators including at least a second parallel arm resonator which is a parallel arm resonator connected to a common ground electrode, and the common ground electrode and the two or more parallel arm resonances A transmission path that connects a child and the common ground electrode is disposed closer to a region where the low-frequency surface acoustic wave filter is formed than a transmission path that connects the common electrode and the high-frequency signal electrode. Item 8. The surface acoustic wave device according to any one of Items 1 to 7. The surface acoustic wave element is
A common electrode connected to the antenna;
A low-frequency signal electrode;
A high-frequency signal electrode;
A ground electrode for grounding;
With
The high-frequency surface acoustic wave filter is connected between the common electrode and the high-frequency signal electrode,
The low-frequency surface acoustic wave filter is
Connected between the common electrode and the low-frequency signal electrode,
One or more series arm resonators connected in series on a transmission line connecting the common electrode and the low-frequency side signal electrode, and two or more transmission lines branched from the transmission line to the ground electrode, respectively. Two or more parallel arm resonators,
Of these parallel arm resonators, the first parallel arm resonator that is the first connected parallel arm resonator as viewed from the common electrode and the first parallel arm resonator as viewed from the common electrode are connected next to the first parallel arm resonator. Two or more parallel arm resonators including at least a second parallel arm resonator which is a parallel arm resonator connected to a common ground electrode, and the common ground electrode and the two or more parallel arm resonances A transmission path that connects a child and the common ground electrode is disposed closer to a region where the high-frequency surface acoustic wave filter is formed than a transmission path that connects the common electrode and the low-frequency signal electrode. Item 8. The surface acoustic wave device according to any one of Items 1 to 7.

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