JP2006203652A - High frequency module and communication equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency module which can be made small and attain a high function and prevents a low frequency side attenuation characteristic of a SAW (surface acoustic waveguide) filter from deteriorating by reducing parasitic impedance in the SAW filter. <P>SOLUTION: The high frequency module comprises a power amplifier composed of a semiconductor element for power amplification and a matching circuit constituting at least a high frequency part, a filter for eliminating noise of a signal to be inputted to the power amplifier, a directional coupler and a detection circuit for detecting an output of the power amplifier and a duplexer for dividing transmission and reception signals on the surface of or inside a dielectric board obtained by laminating dielectric layers, and a terminal for external connection on the bottom of the dielectric board, wherein a semiconductor element for power amplification of the power amplifier and a filter for transmission of the duplexer are mounted on the surface side of a module board, a cavity is provided on the bottom side of the module board, and the filter for transmission of the duplexer is housed and mounted in the cavity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a small-sized, high-performance, low-cost high-frequency module integrally configured with a high-frequency power amplifying device, a high-frequency filter device, and a high-frequency demultiplexer device used in mobile communication devices such as mobile phones, and communication equipment using the same. It is about.

  In recent years, cellular phones have been widely used, and functions and services of cellular phones have been improved. In such a cellular phone, a high-frequency signal processing circuit necessary for the configuration of each transmission / reception system is mounted on a substrate.

  In a general configuration of a conventional high-frequency signal processing circuit, a transmission duplexer and a reception duplexer are provided for switching between a reception signal input from an antenna and a transmission signal fed to the antenna.

  The radio signal that has entered from the antenna is input to the reception duplexer through a matching circuit provided in the preceding stage of the reception duplexer, where the reception signal is selectively passed. The received signal is amplified by a low noise amplifier and supplied to a signal processing circuit.

  On the other hand, the transmission signal is passed through a high frequency filter that allows transmission signals in a predetermined transmission pass band to pass through, and is transmitted to the high frequency power amplifier circuit. The high frequency power amplifier circuit amplifies the power of the transmission signal and supplies it to the transmission duplexer.

  Conventionally, the transmitting and receiving duplexers, the matching circuit, the high frequency power amplifier circuit, the high frequency filter, and the like are each manufactured as individual components and discretely mounted on the upper surface of the substrate. Recently, as the transmission and reception duplexers, those using bare SAW chips that are directly flip-chip mounted using solder on the surface of a predetermined substrate have been proposed.

  7A and 7B show an example of a high-frequency module. FIG. 7A is a schematic cross-sectional view, and FIG. 7B is a pattern diagram on the back surface of a dielectric substrate. In the high-frequency module shown in FIG. 7, a power amplification semiconductor element 52 is mounted on the surface of a dielectric substrate 51 made of ceramics, and is connected to an electrode on the surface of the dielectric substrate 51 by wire bonding. Further, bare SAW chips 53 a and 53 b are flip-chip mounted directly on the surface of the dielectric substrate 51 as a duplexer for transmission and reception. Further, a filter 54 is mounted on the surface of the dielectric substrate 51, and a coupler 55, a branching circuit 56, a matching circuit 57, and the like are formed in the dielectric substrate 51 by a wiring pattern.

  Further, as shown in FIG. 7B, input / output and power line terminals 58 and other ground terminals 59 are formed on the back surface of the dielectric substrate 51.

In addition, this high-frequency module is made of ceramics as a dielectric substrate from the viewpoint of reliability such as strength, and is printed and applied to a predetermined conductive pattern using a conductive paste on a ceramic green sheet, and then laminated and fired. After the dielectric substrate is created, the power amplifying semiconductor element 52, bare SAW chips 53a and 53b, and other electronic components are mounted on the surface of the dielectric substrate 51 by soldering and assembled. (For example, refer to Patent Documents 1 and 2).
JP 2002-43977 A Japanese Patent No. 3108107

  However, the circuit including the SAW filter 101 composed of the SAW chip 53a or 53b of the duplexer is generated between the ground of the SAW filter element 101 and the ground of the package or substrate on which the SAW filter is mounted, as shown in FIG. Due to the influence of the parasitic inductance 102, there is a problem that the attenuation pole on the low frequency side becomes lower than the pass band, and the attenuation characteristic deteriorates.

  In order to reduce the size and height, it is desirable to reduce the thickness of the dielectric substrate 23 constituting the module. However, in order to increase the functionality of the high-frequency module, there are various types of components inside the dielectric substrate 23. However, there is a limit to reducing the thickness because it is necessary to incorporate such functions. As a result, there has been a problem that the attenuation amount on the low band side of the SAW filter on the reception side of the duplexer is deteriorated, and further, transmission power leaking from transmission to reception, that is, isolation is deteriorated.

  Therefore, the present invention eliminates the problems in the prior art described above, further reduces the size and functions, and reduces the parasitic inductance and prevents the low frequency side attenuation characteristics of the SAW filter from deteriorating. The purpose is to provide.

  A high-frequency module according to the present invention includes a power amplifier composed of a power amplifying semiconductor element and a matching circuit at least on a surface of a dielectric substrate formed by laminating dielectric layers, and a matching circuit. A filter that removes noise from the input signal, a directional coupler and detector circuit for detecting the output of the power amplifier, a duplexer that separates signals to be transmitted and received, and a terminal for external connection on the bottom surface of the dielectric substrate. A power amplification semiconductor element of the power amplifier and a transmission filter of the duplexer are mounted on the surface side of the module substrate, and a cavity is provided on the bottom surface side of the module substrate. The transmission filter of the duplexer is housed and mounted therein.

  Further, it is desirable that both the transmission filter and the reception filter constituting the duplexer are SAW filters. In this case, the SAW filter is flip-chip mounted via bumps, and further mounted by the bumps. The portion is sealed with solder arranged in a ring shape.

  Furthermore, a ground electrode is provided at the bottom in the cavity on the bottom surface side, and the ground electrode is connected to a ground terminal formed on the bottom surface side of the dielectric substrate.

  According to the present invention, a cavity is provided on the bottom surface side of the module substrate, and the transmission filter of the duplexer is accommodated and mounted in the cavity, thereby connecting to the ground terminal formed on the bottom surface side of the module substrate. As a result of shortening the length, it is possible to reduce the parasitic inductance generated between the ground of the element in the filter for reception and the ground terminal of the module board, thereby reducing the deterioration of the low-frequency attenuation characteristics of the filter. I can do it. Further, since the transmission filter and the reception filter are divided, it is possible to improve the isolation characteristic in which power leaks from transmission to reception. Furthermore, since the SAW filter is disposed on the top and bottom surfaces of the dielectric substrate, the area ratio occupied by the duplexer can be reduced, and as a result, the high-frequency module can be downsized.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram of a CDMA dual-band high-frequency signal processing circuit used for mobile communication devices such as mobile phone devices.

  In this CDMA dual band system, a GPS reception band of 1.5 GHz is used in order to use two transmission / reception systems having a frequency band of the cellular system 800 MHz band and the PCS system 1.9 GHz band and a positioning function by GPS (Global Positioning System). It consists of one receiving system with a band.

  In FIG. 1, 1 is an antenna, 2 is a duplexer including LPF and HPF for dividing a frequency band, 3a is a SAW duplexer that separates a transmission system in the 1.9 GHz band, and 3b is a SAW duplexer that separates the reception system. 4a is a SAW duplexer that separates the transmission system of the 800 MHz band, and 4b is a SAW duplexer that separates the reception system. Reference numeral 12 denotes a SAW filter for passing a GPS signal taken from the duplexer 2. Reference numerals 3c and 4c denote matching circuits that rotate the phase of the received signal.

  In the transmission system, the cellular transmission signal output from the transmission signal processing circuit RFIC 17 is subjected to noise reduction by the BPF 9 having a SAW filter and transmitted to the high frequency power amplifier circuit 7. The PCS transmission signal output from the transmission signal processing circuit RFIC 17 is subjected to noise reduction by the BPF 10 having a SAW filter and transmitted to the high-frequency power amplifier circuit 8.

  The high frequency power amplifier circuits 7 and 8 are driven at frequencies of 800 MHz band and 1.9 GHz band, respectively, and amplify transmission power. The amplified transmission signal passes through the directional couplers 5 and 6 and is input to the SAW duplexers 4a and 3a.

  The directional couplers 5 and 6 have a function of monitoring the level of the output signal from the high frequency power amplifier circuits 7 and 8 and performing auto power control of the high frequency power amplifier circuit based on the monitor signal. , And input to the detection circuit 11.

  On the other hand, the reception system includes low noise amplifiers LNAs 14 and 13 for amplifying the reception signals separated by the SAW duplexers 4b and 3b, and high frequency filters 16 and 15 for removing noise from the reception signals. The received signals that have passed through the high frequency filters 16 and 15 are transmitted to the received signal processing circuit RFIC 18 and processed. The GPS signal separated by the GPS SAW filter 12 is subjected to signal processing by the reception signal processing circuit RFIC18.

The structure of the duplexer is not limited, but preferably 36 ° Y cut-X propagation LiTaO ₃ crystal, 64 ° Y cut-X propagation LiNbO ₃ crystal, 45 ° X cut-Z propagation LiB ₄ O ₇ crystal, etc. A comb-shaped IDT (Inter Digital Transducer) electrode is formed on a substrate made of

  The configuration of the high-frequency power amplifier circuit is not limited, but preferably has a function of amplifying a high-frequency signal, and a GaAsHBT (gallium arsenide heterojunction bipolar transistor) structure or a P-HEMT structure in order to reduce the size and increase the efficiency. The semiconductor device includes a GaAs transistor, a silicon or germanium transistor.

  In a mobile communication device including a high-frequency signal processing circuit having the above-described configuration, there is a great demand for miniaturization and weight reduction of each part. In consideration of these requirements, the high-frequency signal processing circuit achieves desired characteristics. It is modularized in units that can be done.

  That is, as indicated by a thick dotted line 22 in FIG. 1, a demultiplexing system including the demultiplexer 2, SAW duplexers 3a, 3b, 4a, 4b, high-frequency power amplifier circuits 7, 8, directional couplers 5, 6 and the like. The circuit and the transmission system circuit form one high-frequency module 22 formed on one substrate.

  A mounting method is also possible in which the high-frequency module 22 is divided into a high-frequency module in the 800 MHz band and two high-frequency modules in the 1.9 GHz band. Further, a module including the low noise amplifiers LNA 13 and 14 and the reception high frequency filters 15 and 16 may be additionally formed.

  Hereinafter, description will be given based on one high-frequency module 22 including two frequency bands of 800 MHz band and 1.9 GHz band.

  FIG. 2 shows a schematic plan view of the high-frequency module 22, and FIG. 3 shows a schematic cross-sectional view thereof. The high-frequency module 22 has a multilayer substrate 23 on which nine dielectric layers having the same size and shape are stacked.

  On the surface layer of the multilayer substrate 23, in addition to various patterns and various chip components, BPF 9, 10, GPS SAW filter 12, detection circuit 11, bare SAW chips 3a, 4a, 3b, 4b as SAW duplexers, and high frequency Power amplifying semiconductor elements 24 and 25 constituting part of the power amplifying circuits 7 and 8 are mounted, and these are mounted and mounted on a conductor pattern on a dielectric layer with solder or the like.

  The power amplification semiconductor elements 24 and 25 are connected to the conductor pattern on the multilayer substrate 23 by wire bonding. Around the power amplifying semiconductor elements 24 and 25, power amplifying matching circuits 26 and 27 that are also part of the high-frequency power amplifying circuits 7 and 8 are formed by chip parts or conductor patterns.

  The power amplification semiconductor elements 24 and 25, the power amplification matching circuits 26 and 27, and the like may be mounted on the back surface of the multilayer substrate.

  Matching circuits 3c and 4c and directional couplers 5 and 6 are housed inside the multilayer substrate 23, and a DC-cut coupling capacitor 28 is provided between the power amplification semiconductor elements 24 and 25 and the BPFs 9 and 10. , BPFs 9 and 10 and a capacitor 29 are provided between the ground.

  In terms of structure, conductor patterns such as distributed constant lines, coupled lines, distributed capacitors, resistors, and the like that constitute these internal elements are respectively formed in the dielectric layers. For example, the coupling lines constituting the directional couplers 5 and 6 are respectively formed on two overlapping dielectric layers. In each dielectric layer, via hole conductors necessary for vertically connecting circuits are formed in a vertical direction across a plurality of layers. In particular, a thermal via 50 that vertically penetrates the dielectric layer is provided to release heat generated in the power amplification semiconductor elements 24 and 25.

  On the other hand, a mounting structure of a bare SAW chip mounted on the surface of the dielectric substrate 23 will be described. FIG. 4A is a pattern diagram of the surface pattern on the mounting surface side of the bare SAW chip and the mounting portion on the high frequency module side, and FIG. 4B is a schematic cross-sectional view when the bare SAW chip is flip-chip mounted.

  As shown in FIG. 4A, the bare SAW chip has a pair of input / output terminals 31a and 31b, a comb-like resonator electrode 32, and these on the surface of a piezoelectric substrate 30 such as a lithium tantalate single crystal. In order to seal, the grounding terminal 33 is formed in a ring shape. On the other hand, on the dielectric substrate 23 side, a pair of input / output electrodes 34a and 34b and a grounding electrode 35 are formed in a ring shape at positions facing the above terminals, and the terminals and electrodes are bonded by solder 36. And flip chip mounting. With this configuration, the region surrounded by the grounding terminal 33 and the grounding electrode 35 forms an airtight space 37, and the comb-like resonator electrode 32 as an excitation electrode is sealed in the airtight space 37. Is done.

  Next, FIG. 5 shows a conductor pattern diagram on the back surface of the high-frequency module. On the back surface of the dielectric substrate 23, an input / output terminal of a module for connecting to an external circuit, a power supply terminal 38, and a ground terminal 39 are provided.

  According to the present invention, it is important that the SAW filters 4 a and 4 b on the transmission side of the duplexer are mounted and mounted on the front surface side, and the SAW filters 4 b and 5 b on the receiving side are mounted and mounted on the bottom surface of the dielectric substrate 23.

  That is, the SAW filters 4 a and 5 a on the transmission side of the duplexer are flip-chip mounted on a conductor pattern formed on the surface of the dielectric substrate 23, and the ground of the SAW filters 4 a and 5 a is dielectrically passed through the via-hole conductor 41. The back surface of the body substrate 23 is connected to the ground terminal 39.

  On the other hand, it is important that the SAW filters 4b and 5b on the transmission side of the duplexer are housed in the formed cavity 43 and directly mounted on the mounting pattern formed on the bottom surface of the cavity 43 by flip chip mounting.

  Similarly to FIG. 4A, a pair of input / output electrodes 34a and 34b and a grounding electrode 35 are formed in a ring shape on the bottom surface of the cavity 43, and the SAW filters 4b and 5b on the receiving side are formed. It is flip-chip mounted with solder. The grounding electrode 35 is connected to a ground terminal 39 formed on the back surface of the dielectric substrate 20 by a via-hole conductor 42 formed around the cavity 60.

  According to the present invention, the reception SAW filter is provided with a cavity on the back surface of the dielectric substrate 23 in the high-frequency module, and is housed and mounted therein. As a result, the reception SAW filter is connected to the ground terminal of the module substrate in the shortest time. The parasitic inductance generated between the ground of the filter element and the ground terminal can be reduced.

  In particular, according to the present invention, when the depth of the cavity 43 is 50% or less of the entire thickness of the dielectric substrate 23, the parasitic inductance can be reduced more effectively.

  In addition, since the inductance can be reduced as the diameter of the via-hole conductor connecting the ground of the SAW filter for reception and the ground terminal increases, the diameter of the via-hole conductor 42 is particularly 50 μm or more, particularly 100 μm or more. Is preferred.

  In addition, it is desirable to improve the reliability by filling the SAW filter with a resin or the like in the cavity 43 on the bottom surface of the dielectric substrate.

  The high-frequency module in the present invention is composed of a ceramic dielectric substrate 23, a conductor pattern disposed on the surface and inside thereof, and a via conductor, and is formed on the surface of a sheet molded body made of ceramics. After printing and applying a conductive paste, as a vertical conductor, after forming a through hole in the sheet-like molded body and filling the conductor paste to form a via conductor, the sheet-like molded body is laminated, It is produced by firing a conductor paste, and has a multilayer wiring structure in which ceramic dielectric layers and conductor patterns are alternately arranged.

  The dielectric substrate in the high frequency module of the present invention is preferably composed of at least one selected from the group of low-temperature fired ceramics such as alumina ceramics, mullite ceramics, and glass ceramics. In particular, a low-resistance conductor such as Cu or Ag can be used as a conductor for forming a conductor pattern or a via conductor, and from the convenience that it can be formed by co-firing with these low-resistance conductors, at 1000 ° C. or less. Low temperature fired ceramics such as fireable glass ceramics are most desirable.

  The characteristics of the ground inductor are shown in FIGS. First, the solid line 1) of (a) shows the attenuation characteristic when there is no ground inductance with respect to the transmission filter. On the other hand, when the reception filter is mounted on the surface of the dielectric substrate 23 and connected to the ground terminal on the bottom surface of the dielectric substrate 23 via the via-hole conductor 41 from the surface of the dielectric substrate 23 to the bottom surface, the dielectric substrate 23 Therefore, for example, in a ceramic dielectric substrate having a thickness of 0.6 mm, the inductance of a via-hole conductor having a diameter of 0.1 mm is equivalent to 0.6 nH. When such an inductance is generated, the attenuation characteristic can be improved by about 5 dB on the high frequency side as shown by the dotted line 2).

  On the other hand, in the receiving filter shown in (b), the characteristic when there is no ground inductance is shown by a solid line 1). Similarly to the above, the attenuation characteristic when the reception filter is mounted on the surface side of the dielectric substrate is indicated by a dotted line 2). As is clear from comparison between the solid line 1) and the dotted line 2), the attenuation of the transmission band deteriorates by 5 to 10 dB on the low frequency side.

  Therefore, based on the present invention as shown in FIGS. 3 and 5, the reception filter is divided from the transmission filter, and a cavity having a depth of 0.3 mm is formed on the back surface of the ceramic dielectric substrate of the module, and a SAW chip having a thickness of 250 μm is formed therein. The reception filter made of was flip-chip mounted, filled with resin in the cavity, and sealed. As a result, the ground inductance of the reception filter was connected from the ground of the SAW chip to the ground terminal 39 on the back surface of the dielectric substrate 23 via the via-hole conductor 42. According to such a structure, the ground inductance is reduced from 0.6 nH to 0.3 nH, and as shown by the one-dot chain line 3) in FIG. 6B, the low frequency side is improved by about 5 dB, and a good attenuation characteristic is obtained.

A typical block diagram of a CDMA dual-band high-frequency signal processing circuit is shown. The schematic plan view of the high frequency module which comprises the circuit of FIG. 1 is shown. The schematic sectional drawing of the high frequency module of FIG. 2 is shown. (A) is a pattern diagram of the surface pattern on the mounting surface side of the bare SAW chip and the mounting portion on the high frequency module side, and (b) is a schematic cross-sectional view when the bare SAW chip is flip-chip mounted. The conductor pattern figure of the back surface of the high frequency module of this invention is shown. It is the figure which showed the characteristic by the ground inductance of a SAW filter. It is a schematic sectional drawing which shows an example of the conventional high frequency module. It is an equivalent circuit diagram of a SAW filter having a ground inductor.

Explanation of symbols

1 .... Antenna 2 ... Demultiplexer 3, 4 ... Duplexer 5, 6 ... Directional coupler (coupler)
7, 8... Power amplifier 9, 10... Transmission SAW filter 11... Detection circuit 12... Reception GPS SAW filter 13, 14.
15, 16 ... SAW filter for reception 17 ... RFIC for transmission
18 ... RFIC for reception
19 ... Baseband IC
20 ... TCXO
21 ... VCO
22... High frequency module 23... Dielectric substrate 24 and 25... Power amplification semiconductor element 26 and 27. SAW input / output electrode 32 SAW filter electrode 33 SAW hermetic sealing electrode 34 Input / output electrode bump 35 Hermetic sealing electrode bump 40... Epoxy resin 41... Via 42 between surface layer and bottom surface... Via hole conductor 43.・ Coupler (built-in parts)
56 ······ Demultiplexer circuit (built-in parts)
57 .... Matching circuit (built-in parts)
58 ... I / O terminal 59 ... Ground terminal

Claims (5)

A power amplifier composed of a power amplifying semiconductor element constituting at least a high frequency portion and a matching circuit on the surface or inside of a dielectric substrate formed by laminating dielectric layers, and noise of signals entering the power amplifier are removed. A high-frequency module comprising a filter, a directional coupler and detector circuit for detecting the output of the power amplifier, a duplexer for separating transmission and reception signals, and an external connection terminal on the bottom surface of the dielectric substrate. And
The power amplification semiconductor element of the power amplifier and the transmission filter of the duplexer are mounted on the surface side of the module substrate, a cavity is provided on the bottom surface side of the module substrate, and the transmission filter of the duplexer is provided in the cavity. A high-frequency module characterized by being housed and mounted. The high-frequency module according to claim 1, wherein each of the transmission filter and the reception filter constituting the duplexer is a SAW filter. The high-frequency module according to claim 2, wherein the SAW filter is flip-chip mounted via a bump. A ground electrode is provided at the bottom of the bottom cavity, and the ground electrode is connected to a ground terminal formed on the bottom surface of the dielectric substrate through a via-hole conductor provided in the dielectric substrate. The high-frequency module according to claim 1, wherein A communication device comprising the high-frequency module according to claim 1.

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