JP2008172278A - High frequency circuit module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency circuit module effective in miniaturization while keeping an oscillating property of crystal oscillation circuit. <P>SOLUTION: An integrated circuit element 12 and passive components 14-1 to 14-5 are mounted in a front surface side of multi-layered substrate 20. A capacitor 30 to be a constituting element of the crystal oscillation circuit is installed in the multi-layered substrate 20. A cavity 22-2 is arranged in a rear surface side of the multi-layered substrate 20, and a quartz crystal oscillator 23 to be a constituting element of the crystal oscillation circuit is housed therein. An inside of the cavity 22 is sealed with a sealing cap 28, wherein this sealing cap 28 is formed by conductive material and fixed to an electrode pad formed in a mother board 100 via a solder 52. A cavity 22-1 is arranged in the rear surface side of the multi-layered substrate 20, and an EEPROM is housed inside this cavity 22-1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a high-frequency circuit module, and more particularly to a high-frequency circuit module effective for miniaturization.

  Conventionally, in order to reduce the size of wireless communication devices, high-frequency circuit modules in which the RF front end portion and baseband portion of a wireless communication circuit are modularized have been studied. Such a high-frequency circuit module is designed in accordance with a communication standard such as Bluetooth or wireless LAN, and functions as a module that gives a wireless communication function to these application devices after being incorporated in an application device such as a mobile phone or a PC.

  Here, among this type of high-frequency circuit module, one in which a high-frequency circuit and a crystal oscillation circuit that functions as a reference oscillator of the high-frequency circuit are integrated is known. The disclosed structure has already been considered.

  As an example of the crystal oscillation circuit, the one disclosed in Patent Document 3 is known.

  In Patent Document 1, as described in FIG. 1 of the same document, a cavity is provided on the front and back surfaces of a multilayer substrate, a crystal unit and an IC are disposed in the cavity on the front surface side, and passive components are disposed in the cavity on the back surface side. A structure in which is arranged is disclosed. However, in this structure, since the crystal oscillator and the IC are accommodated in the same cavity, a mounting area is required, and it is difficult to configure a module close to the chip size of the IC.

  In Patent Document 2, as shown in FIG. 1 of the same document, a crystal oscillator, a baseband IC, and a memory IC are arranged on the front surface side of a multilayer substrate, and a high frequency IC is placed in a cavity on the back surface side. Arranged structures are disclosed. However, even in this structure, since the crystal oscillator and the other IC are arranged on the same surface, a mounting area is required as in Patent Document 1.

In recent years, a single chip IC in which a high-frequency circuit block and a baseband circuit block are integrated has been studied, and in consideration of various circumstances such as a module equivalent to the chip size of the IC being considered, Patent Document 1 and Patent The structure of Document 2 has a limit on miniaturization. On the other hand, as described in Patent Document 3, the crystal oscillation circuit includes a crystal resonator, an inverting amplifier, and a feedback circuit, and the crystal resonator requires a mechanical sealing structure. Since the feedback circuit is required to be arranged with the shortest wiring, a module structure effective for miniaturization while satisfying the characteristics of the crystal oscillation circuit has been required.
Japanese Patent Laid-Open No. 10-135756 JP 2002-9225 A Japanese Patent Laid-Open No. 7-99411

  Therefore, the present invention provides a method effective for miniaturization of a high-frequency circuit module including a high-frequency circuit and a crystal oscillation circuit.

  In order to achieve the above object, the present invention provides a high-frequency circuit module in which a high-frequency circuit, a crystal oscillation circuit, and a memory circuit are configured on a multilayer substrate, and a signal processing unit of the high-frequency circuit and the signal processing unit on the surface side of the multilayer substrate. An RFIC integrated with an adjustment unit of a crystal oscillation circuit is arranged, a crystal resonator constituting a part of the crystal oscillation circuit is arranged in a first cavity provided on the back surface side of the multilayer substrate, and the multilayer A memory element constituting the memory circuit is arranged in a second cavity provided on the back side of the substrate.

  Here, the high-frequency circuit means an RF front end unit or a baseband processing unit constituting a wireless communication circuit, and an RFIC in which a part of the high-frequency circuit is integrated is mounted on a multilayer substrate. As a circuit block integrated in the RFIC, only the RF front end unit or the baseband unit may be used. However, it is desirable to use an RFIC in which these blocks are integrated in one chip. When the RF front end portion and the baseband portion are configured by separate chips, two chips, that is, an RFIC in which the RF front end portion is integrated and a BBIC in which the baseband portion is integrated may be arranged on the surface side of the multilayer substrate.

  When a Bluetooth circuit is configured as a high-frequency circuit, the circuit configuration shown in FIG. 2 of Patent Document 2 may be used. When a wireless LAN circuit is configured, a well-known circuit is used. A circuit configuration may be used. Passive elements such as filters, inductors, and capacitors constituting the high-frequency circuit may be integrated in the RFIC, built in the multilayer substrate, or mounted as components on the surface of the multilayer substrate.

  The crystal oscillation circuit is a circuit used as a reference oscillator of a high-frequency circuit, and includes an oscillation semiconductor provided with a C-MOS inverter, a crystal resonator, and a capacitor that determines an oscillation frequency. Here, the crystal oscillation circuit generates a clock signal having a predetermined frequency by the resonance action of the crystal resonator and inputs the clock signal to the high frequency circuit. As the configuration of the crystal oscillation circuit, the one described in Patent Document 3 can be used.

  The multilayer substrate is an element that realizes part of the wiring in the high-frequency circuit, part of the wiring in the crystal oscillation circuit, or the connection between the high-frequency circuit and the crystal oscillation circuit on the substrate. Alternatively, a resin substrate may be used. In the case of a ceramic substrate, for example, a wiring pattern is formed by applying a silver or copper conductive material on a substrate formed using a low-temperature fired material, and a plurality of such substrates are stacked. Then, the multilayer substrate can be formed by baking at 900 ° to 1000 °.

  A cavity having a predetermined shape is formed on the back surface of the multilayer substrate, and a crystal resonator is accommodated in the cavity. As described above, since the cavity wall has a structure in which the crystal unit is accommodated, packaging for crystal unit sealing is not necessary, and the crystal unit can be placed on top of the RFIC. It is possible to provide a module corresponding to the chip size even when the value is large.

  Further, the memory circuit may constitute a storage area in which signal processing software and various setting data are stored, and may be configured using an EEPROM as described in FIG.

  As described above, since the cavity for housing the crystal unit and the cavity for storing the memory element are separately provided, the crystal unit can be easily sealed and the back surface region of the multilayer substrate can be effectively utilized. Therefore, it can be expected that the RFIC, which can be the largest element, can be miniaturized.

  An RFIC that integrates both the RF front end and baseband is larger than the area required for sealing the crystal unit and the area required for housing the EEPROM, so the RFIC is placed on the surface side of the multilayer board. A configuration in which a crystal resonator and a memory element are arranged on the back side of the multilayer substrate is effective.

  As described above, according to the present invention, it is possible to reduce the size of the high-frequency circuit module while satisfying the characteristics of the crystal oscillation circuit.

  Hereinafter, a high-frequency circuit module according to the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments described below, and can be modified as appropriate.

  FIG. 1 is a sectional view showing the basic structure of a high-frequency circuit module according to the present invention. As shown in the figure, in this circuit module, the integrated circuit element 12 and the passive components 14-1 to 14-5 are mounted on the surface side of the multilayer substrate 20, and the internal capacitor 30 is internally provided on the inner layer of the multilayer substrate 20. A cavity 22 is formed on the back side of the multilayer substrate 20, and a crystal piece 24 fixed with a conductive adhesive 26 is placed in the cavity. A crystal resonator 23 is constituted by the fixed crystal piece 24.

  The integrated circuit element 12 is a flip-chip IC in which an RF front end portion of a high frequency circuit, a baseband portion, and a crystal oscillation circuit adjustment portion are integrated, and is formed on the surface of the multilayer substrate via a plurality of bumps. It is connected to an electrode pad (not shown) provided. The passive components 14-1 to 14-5 are passive components such as an antenna, a filter, a capacitor, and an inductor, and these passive components are connected to the surface of the multilayer substrate via external electrodes formed on the wall surfaces of the components. Are connected to electrode pads provided on the substrate.

  The multilayer substrate 20 is formed by stacking a plurality of ceramic wiring substrates, and an internal capacitor 30, a GND electrode 40, and other power supply lines and various wiring patterns are internally formed therein. Here, the internal capacitor 30 is composed of a capacitor upper electrode 32 and a capacitor lower electrode 34 disposed one above the other through a single ceramic substrate, and functions as a capacitor element in the crystal oscillation circuit. The capacitor lower electrode 34 is connected to the GND electrode 40 through a via hole, whereby the internal capacitor 30 becomes a grounding type capacitor.

  The via hole connecting the integrated circuit element 12 and the crystal resonator 23 is formed linearly from the crystal piece 24 toward the integrated circuit element 12 so as to penetrate the capacitor upper electrode 32. As a result, the crystal oscillation circuit is shortest. Consists of wiring. In this way, by forming the wiring from the crystal unit to the integrated circuit linearly, the parallel running distance with other wiring can be shortened, so the stray capacitance and circuit loss can be reduced, and the oscillation circuit The characteristics are stable.

  The sealing cap 28 seals the opening of the cavity 22 so as to fit in the same surface as the back surface of the multilayer substrate 20, and on the motherboard 100 via the solder 52 together with the external terminals 50 arranged on the outer periphery of the multilayer substrate 20. Are connected to electrode pads provided on the substrate. The sealing cap 28 is made of an AuSn alloy.

  FIG. 2 is an enlarged bottom view showing a planar structure of the crystal unit shown in FIG. As shown in the figure, the crystal piece 24 is disposed at a position overlapping the capacitor lower electrode 34 in a plan view, one end thereof is an open end, and the other end is connected to the connection pattern 25 via the conductive adhesive 26. The The connection pattern 25 is formed as an interior pattern protruding from the wall surface of the cavity 22, and a crystal piece 24 having a one-end support structure is configured by fixing the crystal piece 24 to the connection pattern 25.

  A via hole for connecting to the integrated circuit element 12 shown in FIG. 1 is connected to this connection pattern 25. In addition, the crystal piece 24 is installed at a certain distance from the wall surface of the cavity 22 and is fixed in a state where it can vibrate.

  FIG. 3 is a circuit block diagram showing a configuration of a wireless communication circuit realized by the circuit module shown in FIG. As shown in the figure, in this circuit module, an antenna ANT that transmits and receives radio waves, a bandpass filter BPF that passes a predetermined communication band, a high-frequency switch RF-SW that switches between a transmission path TX and a reception path RX, A power amplifier PA disposed on the transmission path, an RF-IC integrated with an RF front end unit, a BB-IC integrated with a baseband unit, and a crystal resonator XTAL that generates a clock signal of the BB-IC; A wireless communication circuit composed of an EEPROM functioning as a memory element is realized.

  FIG. 4 is a circuit block diagram showing a configuration of a crystal oscillation circuit realized by the circuit module shown in FIG. As shown in the figure, the crystal oscillation circuit includes an amplifier circuit composed of an inverting amplifier 60 and a resistor R, a feedback circuit composed of a variable capacitor C and fixed capacitors C1 and C2, and a feedback circuit. It is comprised with the arrange | positioned crystal oscillator XTAL.

  Here, when a supply is supplied to the crystal oscillation circuit and a signal is input to the inverting amplifier 60, a resonance signal in which the crystal resonator XTAL resonates at a predetermined frequency included in the signal is generated. This resonance signal is input again to the inverting amplifier 60 via the feedback circuit, and an oscillation signal having a predetermined frequency is generated by repeating feedback and resonance.

  The oscillation frequency of the crystal oscillation circuit is determined by the combined capacitance of the variable capacitor C and the fixed capacitors C1 and C2 constituting the feedback circuit, and the oscillation frequency can be controlled by adjusting the capacitance value of the variable capacitor. Since the configuration and operation of the crystal oscillation circuit are described in detail in Patent Document 3, they are omitted in this specification.

  In the crystal oscillation circuit according to the present invention, the region indicated by symbol A in FIG. The regions, that is, the fixed capacitors C1 and C2 are formed in the multilayer substrate 20 of FIG. 1, and the region indicated by the symbol C, that is, the crystal resonator XTAL is formed in the cavity 22 of FIG.

  FIG. 5 is a sectional view showing a position example of the high-frequency circuit module according to the present invention. The circuit module shown in the figure has a structure in which an EEPROM is mounted on the back surface of the multilayer substrate 20 in addition to the integrated circuit element 12 and the crystal resonator 23 shown in FIG.

  In this circuit module, the antenna ANT and the integrated circuit element 12 are mounted on the surface side of the multilayer substrate 20. In FIG. 1, passive elements such as filters and inductors mounted as components and the inversion of the crystal oscillation circuit shown in FIG. The amplifier 60, the variable capacitor C, and the resistor R are integrated in the integrated circuit element 12.

  In the multilayer substrate 20, fixed capacitors C1 and C2 of the crystal oscillation circuit shown in FIG. 4 are formed in contact with independent via holes, respectively, and a grounding type capacitor is configured using the internal ground electrode GND. Each via hole connected to the fixed capacitors C1 and C2 functions as a connection line between the integrated circuit element 12 and the crystal resonator XTAL.

  An internal power supply electrode PWR is disposed below the internal ground electrode GND, and the power supply line and the GND line are provided in parallel. Of the interior ground electrode GND and the interior power supply electrode PWR, a slit having a predetermined shape is provided in a portion where each via hole for connecting the integrated circuit element 12 and the crystal resonator XTAL is formed. Is prevented.

  A first cavity 22-1 for accommodating an EEPROM and a second cavity 22-2 for accommodating a crystal resonator XTAL are formed on the back side of the multilayer substrate 20, and the crystal resonator XTAL is formed in the second cavity. A sealing cap 28 is provided for sealing. The crystal resonator XTAL is configured using a crystal piece 24 in the same manner as the structure shown in FIG.

  According to the present invention, it is possible to reduce the size of a high-frequency circuit module including a crystal oscillation circuit. Therefore, application to mobile communication devices such as mobile phones and mobile devices that are required to be further downsized is expected. .

It is sectional drawing which shows the basic structure of the high frequency circuit module which concerns on this invention. FIG. 2 is an enlarged bottom view showing a planar structure of the crystal unit shown in FIG. 1. FIG. 2 is a circuit block diagram illustrating a configuration of a wireless communication circuit realized by the circuit module illustrated in FIG. 1. FIG. 2 is a circuit block diagram showing a configuration of a crystal oscillation circuit realized by the circuit module shown in FIG. 1. It is sectional drawing which shows one Example of the high frequency circuit module which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 12 ... Integrated circuit element, 14 ... Passive component, 20 ... Multilayer substrate, 22 ... Cavity, 23 ... Quartz crystal, 24 ... Crystal piece, 25 ... Connection pattern, 26 ... Conductive adhesive, 28 ... Sealing cap, 30 ... Internal capacitor 32 ... Capacitor upper electrode 34 ... Capacitor lower electrode 40 ... GND electrode 50 ... External terminal 52 ... Solder 60 ... Inverting amplifier 100 ... Motherboard

Claims (1)

In a high-frequency circuit module in which a high-frequency circuit, a crystal oscillation circuit, and a memory circuit are configured on a multilayer substrate,
An RFIC in which the signal processing unit of the high-frequency circuit and the adjustment unit of the crystal oscillation circuit are integrated on the surface side of the multilayer substrate is disposed,
A crystal resonator constituting a part of the crystal oscillation circuit is disposed in a first cavity provided on the back side of the multilayer substrate,
A high-frequency circuit module, wherein a memory element constituting the memory circuit is arranged in a second cavity provided on a back surface side of the multilayer substrate.

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