JP2005079694A - Duplexer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a duplexer with improved frequency characteristics by miniaturization.
In a duplexer having a SAW device having a receiving filter region having an excitation electrode on a piezoelectric substrate on a package, a line pattern to be connected to an external antenna is formed on the side of the package. In addition, the duplexer is characterized in that the line pattern 6 and the reception filter region are connected.
[Selection] Figure 1

Description

  The present invention relates to a frequency band demultiplexer using a surface acoustic wave device built in a mobile radio device such as a car phone and a mobile phone, and the surface acoustic wave device is built in using a stacked package. Yes. The present invention relates to a duplexer in which a stacked package is downsized and the frequency characteristics are further improved.

  2. Description of the Related Art In recent years, as electronic components used in mobile communication devices such as mobile phones, active components made of semiconductor elements, chip capacitors, chip resistors, chip inductors, and surface acoustic wave (hereinafter also referred to as SAW) filters There are filters, duplexers, and the like using SAW devices. Active components, chip capacitors, and chip resistors have been miniaturized in response to miniaturization of mobile communication devices, but a duplexer using a SAW filter or SAW filter (hereinafter also referred to as a SAW duplexer). However, a stacked package (hereinafter referred to as a package) occupies most of the volume, and a demand for downsizing of the package is increasing.

  Here, FIG. 15 shows a block circuit diagram of a high-frequency circuit of a cellular phone. The high-frequency signal to be transmitted is removed from the unnecessary signal by the SAW filter 24, amplified by the power amplifier 25, and then radiated from the antenna 17 through the isolator 26 and the SAW duplexer 18. Further, the high frequency signal received by the antenna 17 is amplified by the low noise amplifier 19 through the SAW branching filter 18, the unnecessary signal is removed by the SAW filter 21, then re-amplified by the amplifier 22, and the low frequency by the mixer 23. Converted to a signal. In this high-frequency circuit component, the SAW duplexer 18 is particularly large in shape.

  Next, the configuration of the SAW duplexer is shown in FIG. The duplexer includes a transmission filter 8a, a reception filter 8b, and a matching circuit 9 that is an impedance matching circuit that performs matching so that a transmission signal does not leak to the reception side. The transmission filter 8a is configured as a ladder type using a SAW resonator S, as shown in FIG. 7 and the reception filter as shown in FIG. Or it is comprised with the double mode SAW filter using the longitudinal coupling of SAW (not shown). The filters 8a and 8b are formed on the piezoelectric substrate 8.

Next, a basic configuration of the SAW resonator S is shown in FIG. In the figure, 11 is a comb-like electrode (Inter Digital Transducer, hereinafter referred to as IDT electrode) formed on a piezoelectric substrate such as LiTaO ₃ by sputtering or the like, and 12 reflects SAW toward the IDT 11 side efficiently. It is a reflector to resonate. In the figure, the number of electrode fingers of the IDT 11 and the reflector 12 is shown in a simplified manner because it actually reaches several tens to several hundreds.

4 and 5 show a conventional SAW duplexer. A SAW device (element) 102 in which at least a pair of IDT electrodes and reflectors are formed on a piezoelectric substrate such as LiTaO ₃ single crystal, and a package 103 (103a, 103b, 103c, 103d) that is hermetically sealed and mounted. ). The SAW element 102 is bonded and fixed to the bottom surface of the package 103 via the gold bump 102 or the like with the electrode forming surface facing the package side, and the SAW element 102 and the electrode on the surface of the package 103 are electrically connected, and then the lid 104 is hermetically sealed.

  Here, a circuit is required for matching so that the transmission signal does not leak to the receiving side. Conventionally, this matching circuit is composed of a line pattern 106 using a strip line. The line pattern 106 must have a line width of 0.1 mm and a length of 18 mm or more in order to achieve matching. As an example, FIG. 14 shows a simulation result of the line pattern 106 and attenuation. In the case of a single layer, the line pattern 106 has a line width of 0.1 mm, a layer thickness of 0.2 mm, a film thickness of 2 μm, and a dielectric constant of 10. According to the simulation result, it is understood that a line length of 18 mm to 27 mm is necessary to obtain a good attenuation of 40 dB or more.

Forming a long line pattern in a single layer of the package increases the size of the package. In order to reduce the size of the package, the line length can be increased by folding the line pattern in a meander shape, but this also has a limit in printing accuracy. Therefore, generally, a line pattern is formed across a plurality of layers of a package, and a method of connecting via vias 108 and via receiving electrodes 108 is generally performed (see Patent Document 1).
Japanese Patent Application No. 2000-137191

  However, in the conventional SAW duplexer, via receiving electrodes are formed in each layer of the package to eliminate poor connection of vias. This via receiving electrode needs to be larger than the diameter of the via in order to provide a margin for stacking deviation, and there is a problem that the area where the line pattern can be formed becomes very narrow. In addition, the SAW duplexer has conventionally been mainly used in the size of 5 mm square, but it is desired to reduce the size to 3 mm square or less, for example. In this case, the area where the line pattern can be formed is further reduced. The longest line pattern that can be formed in a 3 mm square package is about 15 mm, and sufficient alignment cannot be obtained. The SAW branching filter is very problematic in terms of characteristics.

  Accordingly, the present invention has been completed in view of the above circumstances, and an object of the present invention is to provide a duplexer having good characteristics and a reduced size.

  The duplexer according to the present invention includes: 1) a duplexer having a surface acoustic wave device provided with a receiving filter region having an excitation electrode on a piezoelectric substrate on a substrate, and an external antenna on a side surface of the substrate. An impedance matching line to be connected to the filter is formed, and the impedance matching line and the reception filter region are connected.

  2) In the above 1), the base body is formed by laminating a plurality of layers in which the impedance matching line is formed from a side surface to an upper surface or a lower surface, and the impedance matching line is formed in the plan view of the base body. The impedance matching lines are formed so as not to overlap each other.

  3) In the above 1), the base is formed by laminating a plurality of layers on which the impedance matching lines are formed, and the impedance matching lines are arranged between the impedance matching lines in a plan view of the base. It is drawn around so as to include an orthogonal part.

  In particular, 4) the impedance matching line has a meander shape, and the line pattern of each layer is substantially orthogonal.

  According to the duplexer of the present invention, since it is not necessary to form vias and via receiving electrodes, the area where a line pattern can be formed can be increased, and sufficient impedance matching can be achieved. Further, the impedance matching lines are formed so as not to cross each other. Alternatively, since the impedance matching lines are formed so as to include a portion where they intersect at right angles, the impedance matching lines are prevented from interfering with each other as much as possible. As a result, it is possible to provide a duplexer with good characteristics and reduced size.

The surface acoustic wave (hereinafter referred to as SAW) device of the present invention will be described below. FIG. 1 shows a duplexer according to the present invention. The duplexer of the present invention includes a SAW device 2, a package 3 that is a base on which the SAW device 2 is mounted, and a member 4 that is hermetically sealed. The SAW device 2 is configured by forming an IDT electrode, a reflector, an input / output electrode, a ground electrode, and the like as excitation electrodes on a piezoelectric substrate such as a LiTaO ₃ single crystal or a LiNbO ₃ single crystal. The package 3 is made of a resin such as alumina, low-temperature fired ceramic, or BT resin, and has a laminated structure of a plurality of layers 3a, 3b, 3c, and 3d. The high-frequency signal input / output electrode and the ground electrode are formed by a thick film printing method. A line pattern 6 for matching so that a transmission signal does not leak to the receiving side is formed in a plurality of layers of the package 3. The member 4 to be hermetically sealed is hermetically sealed by welding or soldering a lid made of metal. Reference numeral 5 denotes a bump made of Au (gold) or the like.

  A feature of the present invention is that a line pattern (impedance matching line) 6 for matching formed in a plurality of layers 3 c and 3 d of the package 3 is joined through a groove portion 7 formed on the side surface of the package 3. In the configuration. That is, in the duplexer having the SAW device 2 having the receiving filter region having the excitation electrode on the piezoelectric substrate on the package 3, the line pattern 6 to be connected to the external antenna is formed on the side surface of the package 3. The line pattern 6 is connected to the reception filter region. In particular, the package 3 is formed by laminating a plurality of layers in which the line pattern 6 is formed from the side surface to the upper surface or the lower surface, and the line pattern 6 is formed in a state where the line patterns 6 do not overlap with each other in a plan view of the package 3. It is characterized by being. Alternatively, the package 3 is formed by laminating a plurality of layers in which the line pattern 6 is formed, and the line pattern 6 is formed so as to include a portion where the line patterns 6 are orthogonal to each other in a plan view of the package 3. And As a result, it is not necessary to form vias and via receiving electrodes in each layer of the package, so that the area where the line pattern can be formed can be increased, and electromagnetic interference between the line patterns can be prevented as much as possible to achieve sufficient matching. it can.

  2 and 3 are plan views of the duplexer of the present invention as viewed from the top for each layer. FIG. 2 shows a state in which the line pattern 6 is formed in a state in which the line patterns 6 do not overlap with each other in the plan view of the package 3. FIG. 3 shows the line pattern 6 in the plan view of the package 3. It shows a state in which the six are formed so as to include a crossing point. Line patterns for impedance matching are formed on the layers 3c and 3d. Thus, since the via and via receiving electrode are not formed, it can be seen that the area where the line pattern can be formed can be significantly increased compared to the conventional case. The longest line pattern that can be formed in a 3 mm square package is about 25 mm, and sufficient alignment can be obtained. Further, the present invention is characterized in that line patterns formed in a plurality of layers are arranged so that overlapping positions are different in order to prevent an effective line length from being shortened due to capacitive coupling between lines. Further, the present invention is characterized in that the line patterns formed in a plurality of layers are arranged so that the directions thereof are orthogonal to each other. In this case, the overlapping position of the line patterns formed in the plurality of layers is minimized, and good characteristics can be obtained.

  The thickness of each layer of the package 3 of the present invention is preferably 75 to 800 μm. This is because if the thickness is less than 75 μm, the strength is reduced and it is difficult to produce the green sheet, and if the thickness exceeds 800 μm, it is difficult to produce the green sheet by extrusion molding. More preferably, it is in the range of 100 to 500 μm.

  In the SAW resonator for a duplexer according to the present invention, the IDT electrode is Al or Al-Cu-based, Al-Ti-based, Al-Mg-based, Al-Mg-Cu-based Al alloy, or AlCu / Cu / AlCu, It is good to consist of laminated films, such as Ti / AlCu and Ti / AlCu / Ti. The IDT electrode is formed by a thin film forming method such as an evaporation method, a sputtering method, or a CVD method.

  The number of electrode fingers of the IDT electrode is about 50 to 250, the line width of the electrode fingers is about 0.1 to 10.0 μm, the distance between the electrode fingers is about 0.1 to 10.0 μm, and the opening width (intersection width) of the electrode fingers is 10 to It is preferable that the thickness of the IDT electrode is about 200 μm and the thickness of the IDT electrode is about 0.2 to 0.5 μm in order to obtain desired characteristics as a SAW resonator or SAW filter.

As the piezoelectric substrate, 36 ° ± 10 ° Y cut-X propagation LiTaO ₃ single crystal, 64 ° ± 10 ° Y cut-X propagation LiNbO ₃ single crystal, 45 ° ± 10 ° X cut-Z propagation LiB ₄ An O ₇ single crystal or the like is preferable because it has a large electromechanical coupling coefficient and a small group delay time temperature coefficient, and a 36 ° ± 10 ° Y cut-X propagation LiTaO ₃ single crystal having a large electromechanical coupling coefficient is particularly preferable. Further, the cut angle in the crystal Y-axis direction may be in the range of 36 ° ± 10 °, and in that case, sufficient piezoelectric characteristics can be obtained. The thickness of the piezoelectric substrate is preferably about 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost increases.

  Further, in the above example, the receiving SAW element and the transmitting SAW element are formed on the main surface of one piezoelectric substrate, but each is formed on a separate piezoelectric substrate and individually mounted on a package. There is no problem.

  As the sealing method, sealing with resin may be performed as shown in FIG. Further, as shown in FIG. 13, there is no problem even if mounting is performed by the wire bonding method.

  In addition, this invention is not limited to said embodiment, A various change does not interfere in the range which does not deviate from the summary of this invention.

  Examples that further embody the present invention will be described below.

  The duplexer 1 of FIG. 1 is configured as follows. In this embodiment, a case where a ceramic package is used will be described. First, the package 3 will be described. A large number of ceramic substrates were taken, and electrode patterns were printed and fired on the parent substrate, and then cut individually to form input / output electrodes and ground electrodes of the package by a printing method.

Next, the SAW element 2 will be described. On a 38.7 ° Y-cut LiTaO ₃ single crystal piezoelectric substrate, a two-layer structure of Ti (thickness 90 nm) / Al (99 wt%)-Cu (1 wt%) as shown in FIG. 99 wt%)-Cu (1 wt%)-Mg (1 wt%) was formed as a fine electrode pattern having a single layer structure. The transmitting SAW filter was a 2.5-stage T-type ladder, and the receiving SAW filter was a 2.5-stage π-type ladder. The electrode period of the transmitting SAW filter at this time was about 2.2 to 2.3 μm. The electrode period of the receiving SAW filter was 2.0 to 2.2 μm. For pattern production, photolithography was performed using a sputtering apparatus, a reduction projection exposure machine (stepper), and an RIE (Reactive Ion Etching) apparatus.

  First, the substrate material was scrubbed to remove impurities. Next, an electrode was formed. A sputtering apparatus was used for film formation of the electrode, and the electrode film thickness at this time was about 0.35 μm.

  Next, a photoresist is spin-coated to a thickness of about 0.5 μm, patterned into a desired shape by a reduction projection exposure apparatus (stepper), and an unnecessary portion of the photoresist is dissolved with an alkaline developer by a developing device. After the pattern was exposed, the electrode film was etched by the RIE apparatus, and the patterning was finished, and the electrode pattern of the surface acoustic wave resonator constituting the ladder type surface acoustic wave filter was obtained.

Thereafter, a protective film was formed on a predetermined region of the electrode. That is, SiO ₂ was formed to a thickness of about 0.02 μm on the electrode pattern and the piezoelectric substrate by a CVD (Chemical Vapor Deposition) apparatus. Thereafter, the photoresist was patterned by photolithography, and the flip-chip window opening was etched by an RIE apparatus or the like. Thereafter, an electrode mainly composed of Al was formed using a sputtering apparatus. The electrode film thickness at this time was about 1.0 μm. Thereafter, the photoresist and unnecessary portions of Al were simultaneously removed by a lift-off method to complete a pad for forming a flip chip bump.

  Next, a flip-chip bump made of Au was formed on the pad using a bump bonding apparatus. The bump has a diameter of about 80 μm and a height of about 30 μm.

Next, the substrate was diced along dicing lines and divided into chips. Thereafter, each chip was bonded to the inside of the package with the flip chip mounting apparatus with the electrode forming surface on the bottom surface. Thereafter, baking was performed in a nitrogen atmosphere, and a metal lid was welded to complete the duplexer. A package having a laminated structure of 3.0 mm × 3.0 mm square was used.

  As a comparative sample, a conventional package as shown in FIGS. 4 and 5 was also manufactured in the same process as described above.

  Next, the characteristic measurement of the demultiplexing period in this example was performed. A signal of 0 dBm was input, and measurement was performed under conditions of a frequency of 760 MHz to 960 MHz and 80 measurement points. The number of samples is 10, and the measuring instrument is a multiport network analyzer E5071B manufactured by Agilent Technologies.

  A frequency characteristic graph near the passband is shown in FIG. Here, FIG. 10 is a graph showing the frequency dependence of the insertion loss representing the transmission characteristics of the duplexer.

  The filter characteristics of the product of the present invention were very good. As shown by the solid line in FIG. 10, the characteristic 14 of the reception filter is an insertion loss of about 2.9 dB or less in the reception band of 869 MHz to 894 MHz, and an attenuation of 43 dB or more in the transmission band of 824 MHz to 869 MHz. The transmission filter characteristic 13 was an insertion loss of about 3.0 dB or less in the transmission band of 824 MHz to 869 MHz, and an attenuation of 55 dB or more in the reception band of 869 MHz to 894 MHz.

  On the other hand, as shown by the solid line in FIG. 11, the branching filter having a conventional structure manufactured as a comparative sample has a receiving filter characteristic 16 of an insertion loss of about 869 MHz to 894 MHz within a reception band of about 3.2 dB or less. The attenuation of 824 MHz to 869 MHz in the transmission band was 33 dB or more. The transmission filter characteristic 15 was an insertion loss of about 3.4 dB or less in the transmission band of 824 MHz to 869 MHz, and an attenuation of 53 dB or more in the reception band of 869 MHz to 894 MHz.

  As for the receiving filter, insertion loss was improved by 0.3 dB and attenuation was improved by 10 dB. As for the transmission filter, insertion loss was improved by 0.4 dB and attenuation was improved by 2 dB.

  As described above, the duplexer of the present invention includes a surface acoustic wave device in which two or more excitation electrodes composed of at least one pair of comb-like electrode fingers are arranged on a main surface of a piezoelectric substrate in one package. The matching line pattern of the surface acoustic wave element is formed in a plurality of layers of the package, and the matching line pattern of each layer is connected through a groove formed on the side surface of the package. And Further, the matching line patterns of each layer are arranged so as not to overlap. In addition, the matching line pattern of each layer has a meander shape, and may include a portion where the line pattern of each layer is substantially orthogonal. As a result, there is no need to form vias and via receiving electrodes, so the area where the line pattern can be formed can be increased and sufficient impedance matching can be achieved. As a result, it was possible to provide a SAW duplexer with good characteristics and reduced size.

It is sectional drawing of the duplexer of this invention. It is a top view which shows an example for every layer of the splitter of this invention. It is a top view which shows the other example for every layer of the splitter of this invention. It is sectional drawing of the duplexer of this invention. It is a top view which shows the other example for every layer of the splitter of this invention. It is a block diagram which shows the structure of the splitter of this invention. It is a block diagram which shows the structure of the transmission filter of the branching filter of this invention. It is a block diagram which shows the structure of the filter for reception which comprises the splitter of this invention. It is a top view of the basic composition of the SAW resonator used for the duplexer of the present invention. It is a graph which shows the relationship between the frequency of the splitter of this invention, and insertion loss. It is a graph which shows the relationship between the frequency of the conventional branching filter, and insertion loss. It is sectional drawing at the time of resin-sealing the splitter of this invention. It is sectional drawing at the time of carrying out the wire bonding mounting of the splitter of this invention. It is a graph of the simulation result which shows the relationship between the line pattern length of a duplexer package, and the attenuation amount of a duplexer. It is a block diagram of the high frequency circuit of a mobile phone.

Explanation of symbols

1: duplexer 2: SAW device 3: package (base)
3a to 3d: Package layer 4: Lid 5: Au bump 6: Impedance matching line pattern (line pattern)
7: Groove

Claims (3)

A duplexer having a surface acoustic wave device having a receiving filter region having an excitation electrode on a piezoelectric substrate, the impedance matching line connected to an external antenna being formed on a side surface of the substrate. A duplexer characterized in that the impedance matching line and the reception filter region are connected. The base is formed by laminating a plurality of layers in which the impedance matching line is formed from a side surface to an upper surface or a lower surface, and the impedance matching line is in a state where the impedance matching lines do not overlap with each other in a plan view of the base. The duplexer according to claim 1, wherein the duplexer is formed as follows. The base is formed by laminating a plurality of layers on which the impedance matching lines are formed, and the impedance matching lines are formed to include portions where the impedance matching lines are orthogonal to each other in a plan view of the base. The duplexer according to claim 1, wherein the duplexer is provided.

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