JP2014120966A - Piezoelectric component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric component such as a SAW (surface acoustic wave) device which has a sufficient elastic modulus and molding durability to ensure an operational space of an IDT (interdigital transducer), and which is improved in flexibility with respect to a mounting position of a terminal on a mounting board by a customer and flexibility of interactive connections for integrating devices (other components) of the same or different types into a composite device.SOLUTION: The piezoelectric component includes a piezoelectric substrate 1, an IDT 2 comprising an interdigital electrode part 2a formed on a major surface of the piezoelectric substrate and an input/output electrode wiring part 2b, a rib 7 made of a resin material disposed in a periphery of the IDT, and a cover layer 8 made of a resin material for forming an operational space of the IDT by being set on the rib 7. The resin 8a constituting the cover layer is a thermosetting photosensitive resin, which includes fine chips 8b of white mica as a filler. A plurality of rewiring layers 20 electrically connected to the input/output electrode wiring part 2b of the IDT is disposed on the cover layer; and each rewiring layer is configured to allow an external terminal to be set as desired at a position corresponding to a position of a terminal pad of a device to be mounted.

Description

  The present invention relates to a piezoelectric component such as a SAW duplexer, a surface acoustic wave device (SAW device) used in a SAW filter, and a piezoelectric thin film filter, which are used in mobile communication devices such as mobile phones.

  For example, in a SAW device that is one of piezoelectric components mounted on an electronic device such as a mobile phone, a predetermined hollow portion (operation space) around the comb electrode portion (IDT electrode portion) constituting the SAW element chip. It is necessary to secure

  Conventionally, in order to reduce the size of a SAW device, the SAW element chip is flip-chip bonded (face-down bonding) to a wiring board using gold (Au) bumps or solder bumps, and the entire SAW element chip is made of resin by resin or the like. The SAW device is sealed to form a small package device (see Patent Document 1).

  Furthermore, in order to reduce the size and height required for SAW devices mounted on this type of electronic equipment, a predetermined hollow portion (operation space) is formed around the comb electrode portion (IDT electrode portion). While maintaining this operation space, the entire mother substrate (collective piezoelectric substrate: wafer) on which a large number of comb-shaped electrodes are formed is sealed with resin, and external terminals (external connection electrodes) are formed. An ultra-miniaturized chip size package SAW device has been proposed which is divided into individual SAW devices by dicing along (see Patent Document 2).

  There is one in which the operating space of the IDT is constituted by a cover layer made of a resin material. When such a SAW device is molded with a molding resin, the cover layer may be warped or crushed at a high temperature during molding, and the operating space may be destroyed. In order to avoid this, a support layer (rib) made of a resin material is provided so as to surround the IDT, and a cover layer (which constitutes the top layer of the operation space) is disposed on the support layer (rib). What is ensured is disclosed in Patent Document 3.

  In addition, the IDT operating space is formed of ribs and cover layers made of the same resin material as described above, and the external terminals provided on the outer surface of the cover layer are electrically connected to the input / output electrodes / wirings. Patent Document 4 discloses a method in which a rewiring layer is formed on input / output electrodes / wirings, and an external terminal and a rewiring layer are connected via an electrode column penetrating a cover layer. The external terminal is formed with a conductive connection member such as a solder ball for electrical connection with the mounting substrate in a subsequent process.

  FIG. 11 is a schematic cross-sectional view schematically showing an example of a conventional SAW device in which an operation space is formed by a cover layer made of a resin material. In this SAW device 100, IDT 2 is formed on one surface (main surface) of the piezoelectric plate 1. Here, the IDT 2 is shown as comprising a comb-tooth electrode portion 2a and an input / output electrode / wiring portion 2b for inputting / outputting signals to / from the comb-tooth electrode portion 2a. The operation space 21 of the IDT 2 is formed by a cover layer 8 made of a resin material.

  In the SAW device 100 shown in FIG. 11, the rewiring layer 20 is formed so as to overlap the input / output electrode / wiring 2b. On the rewiring layer 20, a rib 7 made of a resin material is formed so as to surround the IDT 2 from the periphery, and the cover layer 8 is provided on the rib 7 by bridging. On the surface of the cover layer 8, an external terminal (mounting terminal) 26 for mounting on an applied electronic device is provided, and a conductive connection member such as a solder ball 23 is installed on the external terminal 26. The external terminal 26 is electrically connected to the rewiring layer 20 by an electrode column 22 provided through the cover layer 8 and the rib 7.

JP 2004-147220 A JP 2006-246112 A WO2006 / 134928 JP 2010-10812 A

  In the conventional SAW device, as described with reference to FIG. 11, the rewiring layer 20 is formed outside the IDT 2 due to its structure. Thereby, since the position of the external terminal 26 is also limited to the vicinity of the outer periphery of the device, the degree of freedom is small in the terminal position with respect to the connection pad or the like formed on the mounting board of the application device of the customer manufacturer or the application device of the customer manufacturer. In addition, the formation of the conductive connection member such as the solder ball 23 on the external terminal 26 is performed directly on the external terminal 26 at a limited position on the upper surface of the cover layer after the cover layer 8 forming the operation space is installed. Therefore, heat such as molten solder during the reflow process may cause the cover layer 8 to bend and cause distortion in the operation space.

  The object of the present invention is to provide a sufficient elastic modulus and mold resistance for securing the IDT operating space in view of the above prior art, the degree of freedom with respect to the mounting terminal position on the mounting board of the customer, An object of the present invention is to provide a piezoelectric component such as a SAW device in which the degree of freedom of interconnection is improved when different devices (other components) are integrated into a composite device.

In order to achieve the above object, the present invention provides a piezoelectric substrate, comb-shaped electrode portions and input / output electrodes / wiring portions formed on the main surface of the piezoelectric substrate, a rib of resin material provided around the IDT, A piezoelectric component comprising a cover layer of a resin material that is installed on the rib to form an operation space of the IDT,
The resin constituting the cover layer is a thermosetting photosensitive resin, and the thermosetting photosensitive resin contains fine pieces of white mica as a filler.
A plurality of rewiring layers electrically connected to the input / output electrodes / wirings of the IDT are provided on the cover layer,
In each of the rewiring layers, an external terminal can be arbitrarily installed at a position corresponding to the position of the terminal pad of the mounting device at an arbitrary position on the rewiring layer.

  In this invention, the thermosetting photosensitive resin which comprises the said cover layer is a thermosetting photosensitive resin material which uses the polyimide resin with low gas generating property suitably, It contained in this thermosetting photosensitive resin material The content of the fine pieces of the white mica is 40% by weight to 60% by weight.

In addition, the edge of the cover layer is in a position retreated from the edge of the piezoelectric substrate, and the IDT input / output electrodes / wirings and electrical surfaces are exposed on the upper surface exposed by the retreat of the edge of the cover layer of the piezoelectric substrate. Having a metal electrode layer connected to the rewiring layer connected
The rewiring layer extends on the cover layer and is electrically connected.

A metal electrode layer extending on the outer periphery of the main surface of the piezoelectric substrate on the input / output electrodes / wirings of the IDT,
The redistribution layer may be configured to be electrically connected to the metal electrode layer by an electrode column penetrating the rib and the cover layer.

  Since there is no structure that restricts electrode formation on the upper surface of the cover layer, the rewiring layer can be provided in any shape and size. For this reason, electrical connection members such as solder balls and solder bumps for mounting can be arbitrarily arranged according to the position of the terminal pads on the mounting board of customer electronic equipment, etc., and the mounting terminal design at the customer site Contributes to improved margins.

  Further, the cover layer forming the IDT operating space is contained in the thermosetting photosensitive resin in the range of 40 wt% to 60 wt% of translucent white mica fine pieces. Efficient curing treatment of the resin can be realized, the elastic modulus can be remarkably improved, and the IDT operating space can suppress damage due to heating and pressurization in the molding process of the component.

It is explanatory drawing of the SAW device which is Example 1 of the piezoelectric component of this invention. It is the top view which looked at Fig.1 (a) from the arrow A direction. It is a figure explaining the appropriate quantity of the quantity (weight percent: wt%) of the filler (micro mica piece) mixed in the polyimide resin as resin which comprises a cover layer. It is a schematic cross section explaining the SAW device which is Example 2 of the piezoelectric component of the present invention. It is the top view which looked at FIG. 4 from the arrow A direction. It is explanatory drawing of the example of arrangement | positioning of the conductive connection member for mounting the SAW device which concerns on this invention to a mounting substrate, or a composite with another device. It is explanatory drawing of the example of arrangement | positioning of the conductive connection member for mounting the SAW device which concerns on this invention to a mounting substrate, or the conductive connection member for integration with another device. It is explanatory drawing of the example of arrangement | positioning of the conductive connection member for mounting the SAW device which concerns on this invention to a mounting substrate, or the conductive connection member for integration with another device. FIG. 3 is a schematic diagram for explaining an example in which a SAW device according to the present invention is integrated with another device to form a composite part. It is a schematic diagram explaining an example which mounts the SAW device which concerns on this invention on the circuit board of an applicable apparatus with another device. It is a schematic cross-sectional view showing a simplified example of a conventional SAW device in which an operation space is formed by a cover layer made of a resin material.

  Hereinafter, embodiments of a piezoelectric component and a manufacturing method thereof according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view of a SAW device that is a first embodiment of a piezoelectric component according to the present invention. FIG. 1 (a) is a schematic cross-sectional view, and FIG. 1 (b) is an enlarged view of the cover of FIG. It is sectional drawing. FIG. 2 is a plan view of FIG. 1A viewed from the direction of arrow A. FIG. The main part of the SAW device 100 is formed by forming the IDT electrode 2 on one surface (main surface) of the piezoelectric substrate 1 as shown in FIG. The IDT electrode 2 includes a comb electrode part 2a and an input / output electrode / wiring part 2b for inputting / outputting signals to / from the comb electrode part 2a and for electrical connection to the outside of the component. The IDT structure in FIG. 1 has only one IDT for the sake of simplicity of explanation, but a configuration in which two or more IDTs are formed in a composite manner is also included in this embodiment. The same applies to other embodiments described later. The piezoelectric substrate 1 is made of lithium tantalate (LiTaO ₃ ), but in addition to this, lithium niobate (LiNbO ₃ ), crystal, or the like is also used.

  The IDT electrode 2 is formed by depositing an aluminum (Al) thin film on the main surface of the piezoelectric substrate 1 and patterning the thin film by a photolithography technique (hereinafter simply referred to as photolithography). A metal electrode layer 6 made of aluminum is formed from the input / output electrode / wiring portion 2 b of the IDT electrode 2 to the outer edge of the piezoelectric plate 1. On the input / output electrode / wiring part 2b and on the metal electrode layer 6, ribs 7 are provided around the comb electrode part 2a of the IDT 2. The rib 7 is made of resin, and supports the cover layer 8 to secure the operation space 21 of the comb electrode portion 2a of the IDT 2.

  The material of the IDT electrode 2 is not limited to the above-mentioned aluminum, but is a metal mainly containing any one of Cu, Au, Cr, Ru, Ni, Mg, Ti, W, V, Mo, Ag, In, and Sn. A single layer film or a multilayer film of a material, a compound of these materials and oxygen, nitrogen, silicon, or an alloy of these metals or an intermetallic compound can be used.

  In the cover layer 8 of this example, as shown in FIG. 1B, a white mica fine piece 8b was mixed as a filler into a thermosetting polyimide to which a photosensitizer, a curing auxiliary agent and the like were added. It is a film-shaped member. The white mica fine pieces 8b are translucent, and have an effect that exposure light (ultraviolet light or the like) sufficiently reaches the thickness direction of the film in the photolithography process in the patterning after film attachment at the wafer stage. In the following, white mica fine pieces are also referred to as mica filler or simply filler). Since this filler transmits the inside of the resin film without blocking exposure light such as ultraviolet rays, a precise tenting process can be performed. The resin used for the cover layer 8 is not limited to the above-described polyimide, and may be any resin that is thermosetting and generates little gas.

  The physical shape of the mica filler is a scaly flake. The mechanical strength of the cover layer can be improved by the plurality of fillers overlapping each other in the thickness direction of the film and sequentially overlapping in the plane direction. In addition, the filler mixed in the photosensitive thermosetting resin is not limited to white mica pieces, as long as it has the same translucency and can give mechanical strength to the photosensitive thermosetting resin. You can use it.

When the amount of filler mixed is small, the mechanical strength, in particular, the effect of suppressing deflection is lowered, making it difficult to maintain voids. When the amount of mixed filler is excessive, brittleness increases and cracking easily occurs. For example, the piezoelectric plate is made of quartz or LiTaO ₃ . For example, when a LiTaO ₃ piezoelectric plate is used, the thermal expansion coefficient of the cover layer is approximated to the thermal expansion coefficient to avoid peeling of the cover layer and void destruction due to thermal strain. For this purpose, a breakdown voltage of 10 GPa or more is required.

  FIG. 3 is a diagram for explaining an appropriate amount of filler (micro mica pieces) mixed in polyimide resin as a resin constituting the cover layer (weight percent: wt%), and the horizontal axis shows the amount of micro mica pieces mixed (Wt%) is indicated by taking the strength (GPa) of the cover layer on the vertical axis. When this type of device is resin-molded, a high pressure is applied. For example, in the transfer mold, it is about 5 to 15 GPa. For this reason, the strength of the cover layer is required not to be lower than 10 GPa.

  Further, as described above, when the mixing amount becomes excessive, brittleness increases and impact resistance decreases. The inventor of the present application found a relationship as shown in FIG. 3 through an experiment. Based on this relationship, the distance between ribs (between both ends supported by ribs 7) was calculated from the relationship between the experimentally obtained mixing amount (weight percent: wt%), the resin mixed with this filler, and the pressure resistance. When the distance) is 5 to 10 μm and the thickness of the cover layer 8 is 25 to 35 μm, the amount of white mica pieces mixed is 40 to 60 wt%, preferably 45 to 55 wt%.

  The SAW device 100 is resin-molded after being separated from the wafer. Here, illustration of the mold resin is omitted (the same applies to the following description). As shown in FIG. 2, the planar outline is substantially rectangular, and the edge of the cover layer 8 forming the operation space 21 is in a position retracted inward of the device from the edge of the piezoelectric substrate 1, A metal electrode layer 6 electrically connected to the input / output electrode / wiring 2b of the IDT 2 is provided on the upper surface of the piezoelectric substrate exposed by retreating the edge of the cover layer. A rewiring layer 20 (four in this embodiment, 20a, 20b, 20c, and 20d) is provided from the surface of the piezoelectric plate 1 (the upper surface of the device, specifically, on the metal electrode layer) to the upper surface of the cover layer 8. Yes. Since there is no other electrode on the upper surface of the device and it is a relatively flat surface, the rewiring layer 20 is formed on this surface with a sufficient width and an arbitrary shape. Therefore, as will be described later, when this device is mounted on another substrate or when it is combined with another device as a composite device, a solder ball or solder formed on the rewiring layer 20 for mounting or integration A large degree of freedom is secured in the formation position of the conductive connection member such as the bump.

  The metal electrode layer 6 and the rewiring layer 20 are formed of a thin film such as Al, Pt, Au, Cu, W, Mo, and Ti. The film thickness is about 0.1 to 0.5 μm.

  FIG. 4 is a schematic cross-sectional view illustrating a SAW device that is Embodiment 2 of the piezoelectric component of the present invention. FIG. 5 is a plan view of FIG. 4 as viewed from the direction of arrow A, and the planar contour viewed from the upper surface of the device is substantially rectangular as in the first embodiment, but there is no step due to the cover layer 8. Hereinafter, a configuration different from the SAW device according to the first embodiment will be mainly described. Also in this embodiment, illustration of the mold resin is omitted.

  In the SAW device 200 of the second embodiment, the rib 7 is provided around the comb electrode portion 2a of the IDT 2 on the input / output electrode / wiring portion 2b and on the metal electrode layer 6 as in the first embodiment. Yes. On the rib 7, a cover layer 8 is formed by tenting over the entire outer periphery of the main surface of the piezoelectric plate 1. An electrode column 22 is formed through the metal electrode layer 6 and the cover layer 8. The electrode column 22 is connected to the metal electrode layer 6 and extends to information, and the upper end surface is exposed on the upper surface of the cover layer 8. The rewiring layer 20 is formed on the cover layer 8 and in the shape and arrangement as shown in FIG. 5 by patterning by vapor deposition of aluminum film and photolithography.

  The electrode column 22 of this embodiment is formed by Cu electroplating. Electroless plating of Ni and Au is performed on the end face of the electrode column, but the illustration is omitted. By applying the electroless plating of Ni and Au, the oxidation prevention of the Cu electrode column 22 and the solderability during mounting are improved. Instead of electroless plating of Ni and Au, electroless plating of only Ni, Ni, Pd, and Au can be performed.

  Since the SAW device 200 according to the second embodiment is also a relatively flat surface without any other electrodes on the upper surface of the device, the rewiring layer 20 is formed in a sufficiently wide and arbitrary shape on this surface. Is done. Therefore, as will be described later, when this device is mounted on another substrate or integrated as a composite device on another device, a solder ball or solder bump formed on the rewiring layer 20 for mounting or integration. A great degree of freedom is secured in the formation position of the conductive connection member.

  FIG. 6 is an explanatory view of an arrangement example of the conductive connection member for mounting the SAW device according to the present invention on the mounting substrate, or the conductive connection member for compounding with other devices. Here, an example in which the solder ball 23 is used as the conductive connection member for mounting the SAW device 100 according to the first embodiment described in FIG. 1 on the mounting board will be described. Since the rewiring layer 20 is arranged so as to spread on the surface of the cover layer 8, the solder ball 23 can be provided at a position corresponding to the wiring board or device terminal electrode or connection pad of the mounting partner. FIG. 6 shows a state in which four solder balls 23a, 23b, 23c, and 23d are provided without being aligned on the upper surface of the device, corresponding to the positions of the terminal pads of the mounting board. It goes without saying that the four solder balls 23a, 23b, 23c, and 23d may be arranged in two orthogonal directions depending on the arrangement of terminal pads such as a mounting board.

  FIG. 7 is an explanatory view of an arrangement example of the conductive connection member for mounting the SAW device according to the present invention on the mounting substrate, or the conductive connection member for integration with other devices. Here, an example in which a solder ball is used as a conductive connection member for mounting the SAW device 200 according to the second embodiment described with reference to FIG. 4 on a mounting board will be described. Similar to the first embodiment, since the rewiring layer 20 is arranged so as to spread on the surface of the cover layer 8, the solder balls 23 are provided at positions corresponding to the terminal electrodes and connection pads of the wiring board to be mounted or the device. be able to. FIG. 7 shows a state in which four solder balls 23a, 23b, 23c, and 23d are provided without being aligned in correspondence with the positions of the terminal pads of the mounting board. It goes without saying that the four solder balls 23a, 23b, 23c, and 23d may be arranged in two orthogonal directions depending on the arrangement of terminal pads such as a mounting board.

  FIG. 8 is an explanatory diagram of an arrangement example of the conductive connection member for mounting the SAW device according to the present invention on the mounting substrate, or the conductive connection member for integration with other devices. Here, an example in which a solder ball is used as a conductive connection member for mounting the SAW device 100 according to the first embodiment described in FIG. 1 on a mounting board will be described. This mounting example explains that even a SAW device according to the present invention can be mounted in the same manner as a conventional device. The case where the solder balls 23 (23a, 23b, 23c, 23d) are provided at the four fixed corners of the upper surface of the device at the same fixed positions as in the conventional device is shown.

  FIG. 9 is a schematic diagram illustrating an example in which the SAW device according to the present invention is integrated with other devices to form a composite part. Here, an example in which the SAW device 100 according to the first embodiment described with reference to FIG. The other parts 300 are piezoelectric parts or discrete parts other than piezoelectric parts that can be combined. A terminal pad 302 that does not consider the arrangement of the external terminals of the SAW device 100 is provided on one surface of the other component (the upper surface in the figure). In addition, a mounting terminal 303 connected to a mounting terminal (pad) of a mounting board (not shown) is provided on the other surface (the lower surface in the figure) of the other component 300.

  When the SAW device 100 is combined with such another component 300, the solder ball 23 or bump (solder bump or the like) is disposed on the rewiring layer 20 of the SAW device 100 at a position facing the terminal pad 302 of the other component 300. ) 25 is placed and positioned, and both are temporarily fixed. By performing the reflow process in this state response, the two are joined together and become a composite part. Thus, the SAW device 100 according to the present invention can be connected at an arbitrary position according to the arrangement of the terminal pads 302 of the other components 300 to be combined.

  FIG. 10 is a schematic diagram for explaining an example in which the SAW device according to the present invention is mounted together with other devices on a circuit board of an applied device. Here, an example will be described in which the SAW device 100 according to the present invention described with reference to FIG. 1 and the SAW device 200 according to the present invention described with reference to FIG. 4 are mounted on a circuit board 301 of an applied device. A plurality of terminal pads 302 are formed along with a wiring pattern on one surface of the circuit board 301 (upper surface in the figure). In addition to this, other components (not shown) are also mounted on the circuit board 301.

  The terminal pads 302 provided on the circuit board 301 do not consider the arrangement of the external terminals of the SAW devices 100 and 200 according to the present invention. With respect to such a circuit board 301, the SAW devices 100 and 200 are soldered between the rewiring layer 20 and the terminal pads 302 provided on the circuit board 301 at appropriate positions facing the positions of the terminal pads 302. Balls 23 or solder bumps 25 are arranged and connected. As a result, the degree of freedom in circuit design on the customer side that manufactures the applicable device is expanded, and efficient circuit design becomes possible.

  The present invention relates to SAW devices, piezoelectric thin film filters, FBAR (Film Bulk Acoustic Resonator), MEMS (Micro Electro Mechanical Systems), and other piezoelectric elements and components that require extremely high impact resistance and high reliability, and Widely available for their manufacture. Further, the present invention can be applied to a so-called filter bank, a plurality of filter modules, etc., or can be applied to one in which a plurality of piezoelectric elements having different operation characteristics are mounted on one component.

1 .. Piezoelectric plate (LiTaO ₃ ), 2.. IDT, 2 a .. Comb electrode part, 2 b .. I / O electrode and wiring part, 6 .. Metal electrode layer, 7 .. Rib, 8. (Ceiling layer), 8a..resin, 8b..filler (micro mica piece), 20..redistribution layer, 21..void (operating space, hollow structure, cavity), 22 .... electrode column, 23. Solder balls 25 Solder bumps 100, 200 Piezoelectric parts (SAW devices) 300 Other parts 301 Circuit boards 302 Pads

Claims (4)

A piezoelectric substrate, an IDT formed of comb-shaped electrode portions and input / output electrodes / wiring portions formed on the main surface of the piezoelectric substrate, a rib of resin material provided around the IDT, and the rib placed on the rib A piezoelectric component including a cover layer of a resin material that forms an operation space of the IDT,
The cover layer contains a filler made of fine pieces of white mica in a thermosetting photosensitive resin,
A plurality of rewiring layers electrically connected to the input / output electrodes / wirings of the IDT are provided on the cover layer,
Each of the rewiring layers can be provided with an external terminal at an arbitrary position on the rewiring layer. In claim 1,
The thermosetting photosensitive resin constituting the cover layer is obtained by adding a photosensitive agent, a curing agent, or the like to a resin material suitable for polyimide resin, and the content of fine pieces of the white mica is 40% by weight or more. A piezoelectric component characterized by being 60% by weight. In claim 1 or 2,
The edge of the cover layer is located at a position retreated from the edge of the piezoelectric substrate, and is electrically connected to the input / output electrodes / wirings of the IDT on the upper surface exposed by the retreat of the edge of the cover layer of the piezoelectric substrate. Having a metal electrode layer connected to the connected rewiring layer;
The piezoelectric component, wherein the rewiring layer extends on the cover layer and is electrically connected. In claim 1,
A metal electrode layer extending on the outer periphery of the main surface of the piezoelectric substrate on the input / output electrodes / wirings of the IDT,
The piezoelectric component, wherein the rewiring layer is electrically connected to the metal electrode layer through an electrode column penetrating the rib and the cover layer.

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