JP2011171848A - Surface acoustic wave device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve isolation characteristics between elastic wave device chips. <P>SOLUTION: The surface acoustic wave device is equipped with: a substrate 10; a plurality of elastic wave device chips 20 and 22 flip-chip mounted on the substrate; and a sealing part 18 for sealing from a part of side faces of the plurality of elastic wave device chips to the substrate using metal. In at least one of the plurality of elastic wave device chips, the nearest distance L2 from at least one side face touched with the sealing part to a pattern directly contributed to excitation of elastic waves is longer than the nearest distance L1 from a side face not touched with the sealing part to pattern directly contributed to excitation of elastic waves. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an acoustic wave device, for example, an acoustic wave device in which an acoustic wave device chip is sealed using a metal.

  The acoustic wave device is used as a filter or a duplexer of a mobile communication terminal. For example, an acoustic wave device is known in which an acoustic wave device chip is mounted on a package substrate and the acoustic wave device chip is sealed with solder for miniaturization (for example, Patent Document 1).

JP 2006-203149 A

  When a plurality of acoustic wave device chips are sealed with a metal such as solder, the isolation characteristics between the acoustic wave devices provided on the acoustic wave device chip may deteriorate.

  An object of the present acoustic wave device is to improve isolation characteristics between acoustic wave device chips.

  For example, a substrate, a plurality of acoustic wave device chips flip-chip mounted on the substrate, and a sealing portion that seals from the side surface of a part of the plurality of acoustic wave device chips to the substrate using a metal, In at least one of the plurality of acoustic wave device chips, the closest distance from at least one side surface in contact with the sealing portion to a pattern that directly contributes to excitation of the elastic wave is in the sealing portion. An elastic wave device is used that is longer than the nearest distance from the side surface that does not contact to the pattern that directly contributes to the excitation of the elastic wave.

  According to this elastic wave device, the isolation characteristic between elastic wave device chips can be improved.

FIG. 1A and FIG. 1B are a plan view and a cross-sectional view of an acoustic wave device according to the first embodiment. FIG. 2 is a circuit diagram of the acoustic wave device according to the second embodiment. FIG. 3 is a plan view showing an example of an acoustic wave device chip. FIG. 4 is a plan view of the acoustic wave device according to the first embodiment. FIG. 5A to FIG. 5C are diagrams showing simulation results of Comparative Example 1 and Example 2. FIG. FIG. 6 is a diagram illustrating the worst value of isolation within the transmission band with respect to the distance L. FIG. 7 is a cross-sectional view of the acoustic wave device according to the third embodiment. FIG. 8A to FIG. 8C are diagrams illustrating simulation results of Comparative Example 1, Example 2, and Example 3. FIG. FIG. 9A to FIG. 9C are diagrams showing simulation results when the depth D is changed in Comparative Example 1 and Example 4. FIG.

  Embodiments according to the present invention will be described below with reference to the drawings.

  FIG. 1A and FIG. 1B are a plan view and a cross-sectional view of an acoustic wave device 100 according to the first embodiment. In FIG. 1A, the sealing portion on the upper surface is shown through. FIG.1 (b) is AA sectional drawing of Fig.1 (a). As shown in FIGS. 1A and 1B, the acoustic wave device chips 20 and 22 and the matching circuit chip 24 are flip-chip mounted on the insulating substrate 10. The pads of the acoustic wave device chips 20 and 22 and the matching circuit chip 24 and the wiring 14 formed on the substrate 10 are electrically connected using bumps. The sealing portion 18 is formed so as to be in contact with at least one side surface of each of the acoustic wave device chips 20 and 22 and the matching circuit chip 24. The sealing unit 18 seals the acoustic wave device chips 20 and 22 and the matching circuit chip 24 using metal (for example, solder) so that a space 17 is generated on the surface of the acoustic wave device chip. A pattern 12 is formed on the substrate 10, and the sealing portion 18 is formed on the pattern 12.

The insulating substrate 10 is, for example, a resin or a ceramic substrate, and includes a plurality of layers and wiring between the layers. The acoustic wave device chip is a piezoelectric substrate such as LiNbO ₃ or LiTaO ₃ , and a surface acoustic wave element is formed thereon. The matching circuit chip 24 is an integrated passive element in which passive elements such as inductors and capacitors are formed on, for example, a Si substrate or a glass substrate. For example, Au or solder can be used for the bump 16. Solder such as AgSn can be used for the sealing portion 18. By using solder for the sealing portion 18, the sealing portion 18 can be easily formed as described in Patent Document 1. The upper surfaces of the acoustic wave device chips 20 and 22 and the matching circuit chip 24 may be covered with a metal plate or an insulating plate instead of solder. The wiring 14 and the pattern 12 are metal, and for example, Cu, Al, Au, W, Ni, or the like can be used.

  In this structure, since the space 17 is provided on the surface of the acoustic wave device chips 20 and 22, the functional region of the acoustic wave device (for example, the comb-shaped electrode of the acoustic wave surface element) faces the space and functions. It can suppress that the vibration of a field is controlled. Further, since the sealing portion 18 seals the acoustic wave device chips 20 and 22 and the matching circuit chip 24 using metal, the acoustic wave device chips 20 and 22 and the matching circuit chip 24 are shielded. Further, the airtightness is higher than that of sealing using a resin or the like.

  FIG. 2 is a circuit diagram of the acoustic wave device 100 according to the first embodiment. The acoustic wave device 100 is a duplexer including a transmission filter 30, a reception filter 32, and a matching circuit 34. The transmission filter 30 is connected between the antenna terminal Ant and the transmission terminal Tx. The reception filter 32 is connected between the antenna terminal Ant and the reception terminals Rx1 and Rx2. A matching circuit 34 is connected between the antenna terminal Ant and the reception filter 32. The transmission filter 30 passes a transmission signal in the transmission band input from the transmission terminal Tx, and attenuates a signal having a frequency other than the transmission band (for example, a signal in the reception band). The matching circuit 34 is impedance matched so as not to pass the transmission signal but to pass the reception signal. The matching circuit 34 has a function as a balun that converts an unbalanced signal from the antenna terminal Ant into a balanced signal. The reception filter 32 passes the reception signal in the reception band input from the matching circuit 34 to the reception terminals Rx1 and Rx2, and attenuates signals of frequencies other than the reception band (for example, signals in the transmission band).

  With the circuit configuration as shown in FIG. 2, a signal input from the transmission terminal Tx is output from the antenna terminal Ant. On the other hand, the reception signal input from the antenna terminal Ant is output as a balanced signal from the reception terminals Rx1 and Rx2. In the first embodiment, the transmission filter 30, the reception filter 32, and the matching circuit 34 are formed on the acoustic wave device chips 20 and 22 and the matching circuit chip 24, respectively.

  FIG. 3 is a plan view showing an example of an acoustic wave device chip. It is the figure which looked at the elastic wave device chip 20 from the board | substrate 10 side of FIG.1 (b). A metal pattern such as Al is formed on the surface of the piezoelectric substrate. Examples of the metal pattern include IDT (Interdigital Transducer), reflector R0, pad 37, and wiring 39. A resonator is formed from the IDT and the reflector R0 provided on both sides of the IDT. The pads 37 are provided with bumps 16 for flip chip mounting. The wiring 39 electrically connects the resonators or resonators and bumps. Series resonators S1 to S3 are connected in series between the input / output pad In / Out1 and the input / output pad In / Out2. Parallel resonators P1 and P2 are connected in parallel between the wiring between the series resonators S1 and S2 and the ground pad Gnd. A parallel resonator P3 is connected between the input / output pad In / Out2 and the ground pad Gnd. Thus, the acoustic wave device chip 20 is formed with a ladder type filter.

  The closest distance L2 from the side surface in contact with the sealing portion 18 to the metal pattern in the acoustic wave device chip 20 is longer than the closest distance L1 from the side surface not in contact with the sealing portion 18 to the metal pattern. The distance L1 is, for example, a cutting margin for separating the acoustic wave device chip, and is, for example, about 20 μm.

  The deterioration of the isolation characteristics between the transmission filter 30 and the reception filter 32 formed on the acoustic wave device chips 20 and 22 sealed by the sealing portion 18 does not occur if the sealing portion 18 is completely grounded. . In FIG. 1B, the sealing portion 18 is grounded (or connected to a constant potential) by via wiring provided on the substrate 10. In order to reduce the size of the acoustic wave device, the sealing portion 18 is thinned, the via wiring for grounding the sealing portion 18 is small, and the number of via wirings is reduced. For this reason, the grounding of the sealing part 18 becomes insufficient. As a result of analysis by the inventors, for example, when the grounding of the sealing part 18 is insufficient, the transmission filter 30 and the receiving filter 32 are electrically coupled via the sealing part 18, and the isolation characteristics may deteriorate. all right.

  According to Example 1, in at least one of the acoustic wave device chips 20 and 22, the shortest distance L2 from at least one side surface in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the acoustic wave is It is longer than the shortest distance L1 from the side surface not in contact with the stop portion 18 to the pattern directly contributing to the excitation of the elastic wave. Thereby, the isolation characteristic between the filters formed in the acoustic wave device chips 20 and 22 can be improved. The pattern that directly contributes to the excitation of the acoustic wave is, for example, a resonator such as an IDT or a reflector R0, a wiring 39 that connects the resonators, an input pad In or an output pad Out that is connected to the wiring, and the like. For example, a pattern such as a short bar or chip identification number that is electrically connected to an adjacent chip or the like is a pattern that directly contributes to the excitation of the acoustic wave in order to suppress the destruction of the acoustic wave element due to the piezoelectric effect during manufacturing. Is not included.

  Further, in at least one of the acoustic wave device chips 20 and 22, the shortest distance L2 from all the side surfaces in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the elastic wave does not contact the sealing portion 18. It is preferable that the distance is longer than the shortest distance L1 from all sides to the pattern that directly contributes to the excitation of the elastic wave. Thereby, the isolation characteristic can be further suppressed.

  In at least one of the acoustic wave device chips 20 and 22, the distance L2 may be longer than the distance L1, but in both the acoustic wave device chips 20 and 22, it is more preferable that the distance L2 is longer than the distance L1. That is, it is preferable that the distance L2 is longer than the distance L1 in all of the plurality of acoustic wave device chips. Thereby, the isolation characteristic can be further improved.

  In the first embodiment, the acoustic wave device chip 20 in which the transmission filter 30 is formed and the acoustic wave device chip 22 in which the reception filter 32 is formed are described as examples. However, the number of acoustic wave device chips may be three or more. Also in the case of 3 or more, the isolation characteristic between acoustic wave elements, such as a filter formed in each acoustic wave device chip, can be improved by making distance L2 longer than distance L1.

  When a plurality of acoustic wave device chips are provided with filters having different pass bands, the idling characteristics often become a problem. Therefore, in this case, it is preferable that the distance L2 is longer than the distance L1.

  Further, as in the first embodiment, the isolation characteristics between the transmission filter 30 and the reception filter 32 of the duplexer are particularly problematic. Therefore, in the diplexer, it is preferable that the distance L2 is longer than the distance L1. In the duplexer of the first embodiment, the reception filter 32 is a balanced input / output type as shown in FIG. 2, but may be an unbalanced input / output type. Further, the matching circuit 34 may not be provided.

  Example 2 is an example showing a result of simulation. FIG. 4 is a plan view of the acoustic wave device according to the first embodiment. The shortest distance L2 of the region 40 from the two side surfaces in contact with the sealing portion 18 of the acoustic wave device chip 22 to the pattern that directly contributes to the excitation of the elastic wave is the distance from the other side surface to the pattern that directly contributes to the excitation of the elastic wave. The distance was longer than the shortest distance L1 (20 μm corresponding to the dicing margin). In the acoustic wave device chip 20, the shortest distance from all the side surfaces to the pattern that directly contributes to the excitation of the elastic wave is set to 20 μm corresponding to the dicing margin. In Comparative Example 1, the shortest distance from all the side surfaces of the elastic wave device chip 22 to the pattern that directly contributes to the excitation of the elastic wave was set to 20 μm corresponding to the dicing margin.

The conditions used for the simulation are as follows. The circuit is a duplexer as shown in FIG. The piezoelectric substrate used as the acoustic wave device chips 20 and 22 is LiNbO ₃ and has a thickness of 250 μm. The transmission filter 30 is a surface acoustic wave ladder type filter having four stages of combination of a series resonator and a parallel resonator, and has a passband of 1710 to 1785 MHz. The reception filter 32 is a surface acoustic wave ladder type filter having seven stages, and the passband is 1805 to 1880 MHz. The substrate 10 is an alumina ceramic. The bump has a diameter of about 90 μm and a height of 15 μm. The sealing part 18 is SnAg solder and has a width of about 130 μm. The sealing portion 18 is grounded via, for example, the pattern 12 and via wiring formed on the substrate 10.

  FIG. 5A to FIG. 5C are diagrams showing simulation results of Comparative Example 1 and Example 2. FIG. In the simulations from FIG. 5A to FIG. 5C, the distance L2 is set to 100 μm. FIG. 5A is a diagram illustrating isolation from the transmission terminal Tx to the reception terminal Rx with respect to the frequency. In Example 2 (solid line), the isolation characteristics are improved compared to Comparative Example 1 (dotted line). FIG. 5B is an enlarged view of the vicinity of the transmission band in FIG. 5A (the square portion in FIG. 5A). In the second embodiment, the isolation characteristic of the transmission band is improved by about 2 dB compared to the first comparative example. FIG. 5C is a diagram showing pass characteristics with respect to frequency. Tx indicates the pass characteristic of the transmission filter 30, and Rx indicates the pass characteristic of the reception filter. In the transmission filter 30, although the insertion loss of Example 2 is slightly larger than that of Comparative Example 1, the pass characteristics of Example 2 and Comparative Example 1 are substantially the same. As described above, according to the second embodiment, it is possible to improve the isolation characteristics without significant deterioration of the pass characteristics.

  FIG. 6 is a diagram illustrating the worst value of isolation within the transmission band with respect to the distance L2. As a result of the simulation, the solid circle in FIG. 6 is an approximate line. As shown in FIG. 6, the isolation deteriorates when L2 is smaller than 50 μm, but the isolation is hardly deteriorated when L2 is 50 μm or more. Therefore, in at least one of the plurality of acoustic wave device chips 20 and 22, the nearest distance L2 from at least one side surface in contact with the sealing portion 18 to the pattern directly contributing to the excitation of the acoustic wave is 50 μm or more. It is preferable.

  Further, in at least one of the plurality of acoustic wave device chips 20 and 22, the closest distance L2 from all the side surfaces in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the acoustic wave is 50 μm or more. Is preferred. Thereby, isolation can be improved more.

  Further, in all of the plurality of acoustic wave device chips 20 and 22, the nearest distance L2 from all the side surfaces in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the acoustic wave is preferably 50 μm or more. Thereby, isolation can be improved more.

  The distance L2 is preferably 60 μm or more and more preferably 80 μm or more in consideration of a manufacturing margin or the like. Further, it may be 100 μm or more.

  Example 3 is an example in which the surface of the acoustic wave device chip is cut from the surface where the acoustic wave is excited. FIG. 7 is a cross-sectional view of the acoustic wave device according to the third embodiment. As shown in FIG. 7, the elastic wave device chip 20 from the sealing portion 18 to the pattern that directly contributes to the excitation of the elastic wave is cut from the surface on which the elastic wave is excited as compared to FIG. It has been. In other words, the acoustic wave device chip 20 is thinner by the cut depth D in the region from the sealing portion 18 to the pattern that directly contributes to the excitation of the acoustic wave, compared to the region in which the acoustic wave element is formed.

For example, when the acoustic wave device chips 20 and 22 are piezoelectric substrates, the dielectric constant is large. For example, for LiNbO ₃ and LiTaO ₃ , the dielectric constant is about 40. For this reason, the coupling of the transmission filter 30 and the reception filter 32 is strongly influenced by the piezoelectric substrate. Therefore, the isolation characteristic can be improved by removing a part of the piezoelectric substrate between the sealing portion 18 and the pattern that directly contributes to the excitation of the elastic wave.

  FIG. 8A to FIG. 8C are diagrams illustrating simulation results of Comparative Example 1, Example 2, and Example 3. FIG. In Example 3, the distance L2 is set to 100 μm in the region 40 of FIG. FIG. 8A is a diagram illustrating isolation from the transmission terminal Tx to the reception terminal Rx with respect to the frequency. In the third embodiment (broken line), the isolation characteristics are further improved in the transmission band than in the second embodiment (solid line). FIG. 8B is an enlarged view of the vicinity of the transmission band in FIG. 8A (the square portion in FIG. 8A). In Example 3, the isolation characteristics are slightly improved from those in Example 2. FIG. 8C is a diagram showing pass characteristics with respect to frequency. Tx indicates the pass characteristic of the transmission filter 30, and Rx indicates the pass characteristic of the reception filter. In the transmission filter 30 and the reception filter 32, the insertion loss in the third embodiment is slightly smaller than that in the second embodiment. As described above, according to the third embodiment, the pass characteristic is good and the isolation characteristic can be improved.

  The fourth embodiment is an example in which the elastic wave device chip 20 is cut in addition to the elastic wave device chip 22. In Example 4, in addition to the region 40 of the acoustic wave device chip 22 in FIG. 4, the region 42 of the acoustic wave device chip 20 is closest to the pattern directly contributing to the excitation of the acoustic wave from the side surface in contact with the sealing portion 18. The distance L2 was set to 100 μm, and a depth D cut was made.

  FIG. 9A to FIG. 9C are diagrams showing simulation results when the depth D is changed in Comparative Example 1 and Example 4. FIG. In Example 3, the depth D is 100 μm (solid line), 150 μm (dashed line), and 200 μm (dashed line). FIG. 9A is a diagram illustrating isolation from the transmission terminal Tx to the reception terminal Rx with respect to the frequency. FIG. 9B is an enlarged view of the vicinity of the transmission band in FIG. 9A (the square portion in FIG. 9A). As shown in FIGS. 9A and 9B, the isolation characteristic is improved as the depth D increases. FIG. 9C is a diagram showing pass characteristics with respect to frequency. Tx indicates the pass characteristic of the transmission filter 30, and Rx indicates the pass characteristic of the reception filter. In the transmission filter 30 and the reception filter 32, the insertion loss of the fourth embodiment is smaller than that of the first comparative example. 8C, the insertion loss of the transmission filter 30 is smaller in the fourth embodiment than in the third embodiment. As described above, the fourth embodiment in which both the transmission filter 30 and the reception filter 32 are cut has less insertion loss and better pass characteristics. This is presumably because there is little signal leakage from the transmission terminal Tx to the reception terminal Rx. As described above, when the depth D is increased, the isolation characteristics can be improved. Furthermore, in both the acoustic wave device chips 20 and 22, it is preferable to make the distance L2 longer than the distance L1 and make a cut. Further, the depth D of the cut is preferably 100 μm or more.

  According to Example 3 and Example 4, the elastic wave device chip 20 or 22 from at least one side surface in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the elastic wave is from the surface on which the elastic wave is excited. It is shaved. Thereby, the isolation characteristic can be improved.

  Furthermore, it is preferable that the elastic wave device chip 20 or 22 from all the side surfaces in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the elastic wave is scraped from the surface on which the elastic wave is excited. Thereby, the isolation characteristic can be further improved.

  In order to improve the isolation characteristic, it is preferable that the elastic wave device chip 20 or 22 is cut in all the regions 40 or 42. Further, for example, a groove is continuously provided between the sealing portion 18 and the pattern that directly contributes to the excitation of the elastic wave (that is, the elastic wave element cannot reach the sealing portion unless it passes through the groove). It is preferable that a groove is provided. Furthermore, the elastic wave device chip 20 or 22 in a partial region of the region 40 or 42 may be removed.

  Furthermore, in all of the plurality of elastic wave device chips, the elastic wave device chips 20 or 22 from all the side surfaces in contact with the sealing portion 18 to the pattern that directly contributes to the excitation of the elastic wave are from the surface on which the elastic wave is excited. It is preferable that it is shaved.

  As described above, in the first to fourth embodiments, the acoustic wave surface device is described as an example of the acoustic wave device. However, the acoustic wave device may be a piezoelectric thin film resonator such as an FBAR (Film Bulk Acoustic Wave Resonator). From the viewpoint of suppressing the coupling with the acoustic wave element through the sealing portion 18, when the acoustic wave device chip is a piezoelectric substrate, the effect of making the distance L2 longer than the distance L1 and the acoustic wave device chip are cut. Great effect. Moreover, in order to use for a mobile phone terminal etc., the pass band of a filter can be made into arbitrary bands, for example of 1 GHz-3 GHz.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

DESCRIPTION OF SYMBOLS 10 Board | substrate 16 Bump 17 Space 18 Sealing part 20, 22 Elastic wave device chip 30 Transmission filter 32 Reception filter

Claims (8)

A substrate,
A plurality of acoustic wave device chips flip-chip mounted on the substrate;
A sealing part that seals from the side surface of a part of the plurality of acoustic wave device chips to the substrate using a metal,
In at least one of the plurality of acoustic wave device chips, the closest distance from the at least one side surface in contact with the sealing portion to the pattern that directly contributes to the excitation of the elastic wave is from the side surface not in contact with the sealing portion. An elastic wave device characterized by being longer than the nearest distance to the pattern that directly contributes to the excitation of the elastic wave.   In at least one of the plurality of acoustic wave device chips, all the side surfaces where the closest distance from all the side surfaces in contact with the sealing part to the pattern directly contributing to the excitation of the elastic wave is not in contact with the sealing part 2. The acoustic wave device according to claim 1, wherein the acoustic wave device is longer than a nearest distance from a pattern directly contributing to excitation of the acoustic wave.   In at least one of the plurality of acoustic wave device chips, a closest distance from at least one side surface in contact with the sealing portion to a pattern that directly contributes to excitation of the acoustic wave is 50 μm or more. The acoustic wave device according to claim 1.   In at least one of the plurality of acoustic wave device chips, a closest distance from all side surfaces in contact with the sealing portion to a pattern that directly contributes to excitation of the acoustic wave is 50 μm or more. Item 10. The acoustic wave device according to Item 1.   2. The elastic wave device chip from at least one side surface in contact with the sealing portion to a pattern that directly contributes to excitation of the elastic wave is cut from a surface on which the elastic wave is excited. Or the elastic wave device of 3.   3. The device according to claim 2, wherein the elastic wave device chip from all side surfaces in contact with the sealing portion to a pattern that directly contributes to the excitation of the elastic wave is cut from a surface on which the elastic wave is excited. 4. The acoustic wave device according to 4.   The acoustic wave device according to claim 1, wherein each of the plurality of acoustic wave device chips is provided with a filter having a different pass band.   The plurality of acoustic wave device chips include an acoustic wave device chip provided with a transmission filter connected between an antenna terminal and a transmission terminal, an elastic wave filter chip provided with the antenna terminal and the reception filter, The acoustic wave device according to claim 1, comprising:

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