JP2004179751A - Surface acoustic wave apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface acoustic wave apparatus at a low cost, which is compatible with communication apparatuses and attaining downsizing and low profile and having sophisticated functions wherein the IDTs are provided an one and the other principal sides of a piezoelectric substrate. <P>SOLUTION: The surface acoustic wave apparatus has the IDTs 5, 6 on one and the other principal sides of the piezoelectric substrate 4 and a resin film 9 for sealing the piezoelectric substrate 4, and the resin 9 is provided with a wire pattern 10 for electrically connecting a connection part 12 provided on an upper side of a mount board 1 to a connection part 8 of a non-mount side of the piezoelectric substrate. Since the surface acoustic wave apparatus has an increased process range to take electric joining and the resin film has excellent process performance, the surface acoustic wave apparatus with ease of high speed processing and compatible with downsizing and a low profile and with a low cost can be supplied. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface acoustic wave device having an IDT on each of one main surface and the other main surface of a piezoelectric substrate, and is used for a communication field such as a mobile phone and an electronic circuit such as a television.
[0002]
[Prior art]
In recent years, as electronic devices have been rapidly becoming smaller and thinner and signal processing speed has been increasing rapidly, there has been a vigorous effort to further downsize electronic devices. Under such circumstances, a surface acoustic wave device used in a communication field such as a mobile phone or an electronic circuit such as a television is required to have a small mounting area and a low profile in order to reduce the size of a terminal. As a method of realizing a small mounting area and a low profile, a bare chip mounting method of mounting chip components directly on a wiring board without using a package has recently been developed. Among them, a flip-chip mounting method capable of limiting a mounting area to a chip size has attracted attention.
[0003]
On the other hand, with the increase in terminals such as mobile phones, the shift to terminals capable of supporting a plurality of systems by one unit has been advanced. That is, it is required that two different circuits be condensed and mounted on a terminal such as a mobile phone having substantially the same size as the conventional one. For this reason, also in a surface acoustic wave device, a device corresponding to two or more systems is desired. Therefore, a dual type device in which two or more elements are incorporated in one package is required. When the device is configured as a dual type, various components can be shared, which is very effective in overall cost and size as compared with preparing devices for different frequencies. However, if a plurality of IDTs are provided on the same surface of the piezoelectric substrate corresponding to various frequencies, there is a problem that the surface acoustic wave device itself becomes large. Further, in order to cope with various frequencies, IDTs having different film thicknesses are required. However, forming IDTs having different film thicknesses on the same surface is difficult in a manufacturing process and leads to an increase in cost.
[0004]
Therefore, when the above-mentioned mobile phone or the like is of a dual type, one of the main surfaces of the piezoelectric substrate is used as a surface acoustic wave device capable of improving the performance by effectively utilizing the above structure in order to cope with the miniaturization. And a surface acoustic wave element having first and second IDTs formed on the other main surface, a base wiring board surrounding the surface acoustic wave element and having a connection portion electrically connected to each IDT, There has been proposed a device including a sealing cap, wherein the first and second IDTs are electrically connected to the base wiring substrate and the sealing cap via metal bumps. Further, it has been proposed that the first IDT is electrically connected to the base wiring board via metal bumps, and the second IDT is electrically connected to the base wiring board by wire connection ( For example, see Patent Document 1.)
[0005]
[Patent Document 1]
JP 2001-244784 A
[Problems to be solved by the invention]
However, the following problems exist in the surface acoustic wave device having the IDT on each of the one main surface and the other main surface of the piezoelectric substrate according to the conventional technique described above.
[0007]
In Patent Document 1, a surface acoustic wave element having an IDT on each of one main surface and the other main surface is flip-chip mounted on a base wiring substrate. After a predetermined electrical connection between the surface acoustic wave element and the base wiring board, a sealing cap is attached. The sealing cap has a structure for sealing the surface acoustic wave element with the base wiring board, and is attached to the base wiring board via an adhesive. In this structure, in order to reduce the height of the surface acoustic wave device, it is necessary to reduce the thickness of the sealing cap. However, a decrease in the thickness of the sealing cap leads to a decrease in the mechanical strength of the sealing cap, and therefore, there is a problem that the sealing cap is damaged even in the manufacturing process.
[0008]
Also, the surface acoustic wave element has IDTs formed on one main surface and the other main surface, and may be arbitrarily selected and used. In consideration of this, it is necessary to connect each input / output unit to an electric circuit independently. For this electrical connection, the base wiring board and the sealing cap are provided with corresponding connection portions and wiring patterns at positions facing the connection portions provided on the surface acoustic wave element. However, it is clear that the sealing cap requires a complicated process to form these wiring patterns and the like due to its structure, and has a high cost.
[0009]
Further, the IDTs provided on each of the one main surface and the other main surface of the surface acoustic wave element may be electrically connected to each other in order to bring out the functions of the IDT.
In that case, for example, it is performed via a through hole formed in the surface acoustic wave element.
[0010]
In general, a piezoelectric substrate used as a surface acoustic wave element has poor workability due to its material properties and is easily broken, so that it is difficult to form a hole or the like. It is considered that it is not practical to electrically connect the IDTs provided on the one main surface and the other main surface via through holes formed in the surface acoustic wave element. Further, an electrical connection may be formed by forming a wiring pattern inside the sealing cap. However, fine wiring is difficult due to the structure of the sealing cap as described above.
[0011]
On the other hand, in the base wiring board, it is necessary to take into account cracks, chips, and the like at the edge of the base wiring board due to the impact when the sealing cap is bonded. For this reason, the size of the base wiring board tends to increase. Further, when an electrical connection is made between the piezoelectric substrate and the base wiring substrate by a wire, it is necessary to form the space in the sealing cap, and thus there is a limit to the reduction in size and height.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention provides a mounting substrate having a connection portion on an upper surface, a piezoelectric substrate having at least one IDT and a connection portion on one main surface and the other main surface, and a mounting substrate on one main surface. The surface acoustic wave device includes a piezoelectric substrate mounted on the substrate, and a resin film covering a connection portion between the piezoelectric substrate and the mounting substrate.
[0013]
The resin film is a surface acoustic wave device that seals the piezoelectric substrate and has a wiring pattern that electrically connects a connection portion provided on the upper surface of the mounting substrate and a connection portion provided on the other main surface of the piezoelectric substrate. is there.
[0014]
Further, the resin film is a surface acoustic wave device that is a polyimide or a liquid crystal polymer.
[0015]
According to the surface acoustic wave device using the resin film of the present invention as described above, the formation process for electrically connecting the IDTs formed on the one main surface and the other main surface is easy. In addition, it is possible to form a surface acoustic wave device corresponding to reduction in height and size. Further, by forming the wiring pattern on the resin film, high-precision wiring becomes possible and the formation can be performed at low cost. In addition, since the resin film has good workability, high-speed processing is also facilitated.
[0016]
A low-cost surface acoustic wave device corresponding to miniaturization and height reduction by sealing a piezoelectric substrate and using a resin film having a wiring function on a piezoelectric substrate provided with an IDT on one main surface and the other main surface. Can be supplied.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0018]
FIG. 1 is a schematic sectional view of one embodiment of the surface acoustic wave device according to the present invention.
[0019]
In FIG. 1, the surface acoustic wave device 20 has a mounting substrate 1, a piezoelectric substrate 4, and a resin film 9.
[0020]
The connection portion 2 on which the piezoelectric substrate 4 is mounted and the connection portion 12 separately from the connection portion 2 are formed on the mounting substrate 1. The piezoelectric substrate 4 has IDTs 5 and 6 on one main surface and the other main surface, respectively. On the other hand, on the main surface, a connection portion 7 having a bump 11 formed on the upper surface is formed for mounting on the mounting substrate 1 and forming an electrical connection with the connection portion 2. A connection portion 8 is formed on the other main surface. On the resin film 9, a wiring pattern 10 for electrically connecting the connection portion 12 of the mounting substrate 1 and the connection portion 8 on the other main surface of the piezoelectric substrate 4 is formed. Further, at one end and the other end of the wiring pattern 10, solder bumps 3 that are respectively connected to the connection portions 8 of the piezoelectric substrate 4 and the connection portions 12 of the mounting substrate 1 are formed.
[0021]
The piezoelectric substrate 4 is mounted on the mounting substrate 1 with one main surface facing down. The resin film 9 covers the connection part 12 on the piezoelectric substrate 4 and the mounting substrate 1, and at this time, connects one end of the wiring pattern 10 to the connection part 8 and connects the other end of the wiring pattern 10 to the connection part 12. Thereby, the connection part 8 and the connection part 12 are connected.
[0022]
A space exists between the IDT 5 of the piezoelectric substrate 4 and the mounting substrate 1 by at least the thickness of the bump 11. Also, a space exists between the IDT 6 of the piezoelectric substrate 4 and the resin film 9 by at least the thickness of the bump 3.
[0023]
In addition, the connection part 2 formed on the upper surface of the mounting substrate 1 may be electrically connected to the connection part 12 formed on the upper surface of the mounting substrate 1 in order to bring out a desired function. The IDTs 5 and 6 formed on the one main surface and the other main surface are formed with electrodes having a pattern shape and a film thickness corresponding to a required function.
[0024]
As described above, by providing the resin film 9 having the function of sealing the piezoelectric substrate 4 and electrically connecting the piezoelectric substrate 4 and the mounting substrate 1, the volume of the surface acoustic wave device by the sealing and the electrical connection is provided. The increase can be minimized. Further, since the thickness of the resin film 9 can be set to about 0.05 mm, it is possible to provide a surface acoustic wave device corresponding to a reduction in height. Moreover, the wiring pattern 10 formed on the resin film 9 can easily form a high-precision wiring pattern. Further, it is possible to provide a surface acoustic wave device which can cope with a fine wiring pattern and which can be downsized. Furthermore, since the resin film 9 has flexibility, sealing and electrical connection corresponding to the shape of the piezoelectric substrate 4 are possible. Further, since it has excellent workability, it can be formed at low cost.
[0025]
FIGS. 2 to 4 show details of a manufacturing method for the above-described contents. Schematic processes in forming a piezoelectric substrate, mounting on a mounting substrate, forming a temporary adhesive substrate having a resin film, bonding a resin film to forming a surface acoustic wave device. This will be described using a flow.
[0026]
First, FIG. 2 illustrates a schematic process flow from formation of a piezoelectric substrate to mounting on a mounting substrate.
[0027]
As shown in FIG. 2A, an IDT 5 and a connection portion 7 are formed on one main surface of a piezoelectric substrate 4 made of LiTaO ₃ having one main surface and the other main surface polished by photolithography. I do.
[0028]
In the photolithography technique, first, a resist having a predetermined thickness is applied using a spin coater or the like. Next, the resist is exposed through a photolithographic mask on which a predetermined pattern is formed. Next, by performing development processing, a lift-off resist pattern in which a portion where a metal film is to be formed is opened is formed. At this time, it is desirable that the resist pattern is formed in an inverse tapered shape in consideration of lift-off. Further, in consideration of forming a pattern such as an IDT on the other main surface, an alignment mark for positioning may be provided.
[0029]
Next, a 300 nm-thick metal film mainly composed of Al is formed as an electrode material by a vacuum evaporation method, and then immersed in a stripping solution and rocked, whereby the lift-off resist film is stripped (lift-off), and the IDT 5 and the connection are removed. The part 7 is formed.
[0030]
Next, as shown in FIG. 2B, the IDT 6 and the connection portion 8 are formed on the other main surface of the piezoelectric substrate 4 by using a photolithography technique.
[0031]
The description of the photolithography technique is omitted because it is the same as that described above. At this time, a desired positional accuracy can be obtained by performing alignment using the previously formed alignment marks. Next, after forming a metal film having a thickness of 120 nm as a main component of Al by vacuum evaporation, the resist for lift-off is stripped by immersing in a stripping solution and oscillating to form an IDT 6 and a connection portion 8. .
[0032]
Note that LiNbO ₃ , quartz and LiB ₄ O ₇ may be used for the piezoelectric substrate 4 depending on desired characteristics. Further, the metal film is not limited to Al, and a metal film of Au, Ta, W, or the like may be used. Further, the metal film formed as the IDT has an optimum film thickness set for each surface according to the required characteristics.
[0033]
Next, as shown in FIG. 2C, an Au bump 11 is formed on the upper surface of the connection portion 7 formed on one main surface. The Au bump 11 forms, for example, a head at the tip of a metal wire of Au derived from the tip of the capillary, presses against the connection part, crushes the head at the tip, and press-bonds it. It is formed by cutting a wire from the web or by a shredding method.
[0034]
Next, as shown in FIG. 2D, a piezoelectric substrate 40 singulated into a desired size that generates a desired function is formed from the piezoelectric substrate 4 using a dicing cut saw. The cutting method is not limited to the dicing cut saw, and is not particularly limited as long as desired accuracy and quality can be obtained.
[0035]
Next, as shown in FIG. 2E, the singulated piezoelectric substrate 40 is mounted on the mounting substrate 1 having the connection portions 2 and 12 formed on the upper surface, and the singulated piezoelectric substrate 40 is mounted on the mounting substrate. 1 is formed. Here, the connection part 7 of the piezoelectric substrate 40 is joined to the connection part 2 of the mounting substrate 1 via the bump 11. For the joining, it is preferable to use an ultrasonic heat combined type.
[0036]
Next, FIG. 3 shows a schematic process flow in forming a resin film.
[0037]
First, as shown in FIG. 3A, a resin film 9 is adhered to a temporary adhesive substrate 13 made of a glass substrate to which wax has been applied by applying pressure while heating. As the resin film 9, a film having high heat resistance and a flexible state, such as a polyimide film or a liquid crystal polymer film, may be used. Next, a wiring pattern material Cu is formed on the upper surface of the resin film 9 by using a vacuum evaporation method.
[0038]
Next, as shown in FIG. 3B, a wiring pattern 10 is formed by using a photolithography technique.
[0039]
In the photolithography technique, a resist having a predetermined thickness is applied to the upper surface of Cu formed as a wiring pattern material. Next, the resist is exposed through a photolithographic mask on which a predetermined pattern is formed so that an unnecessary portion is opened. Next, a resist pattern is formed by performing development processing. Thereafter, unnecessary wiring material is removed by dipping or rocking in an etching solution. After that, the wiring pattern 10 is formed by removing the resist. As described above, since the formation of the wiring pattern 10 on the resin film 9 is performed on the temporary adhesive substrate 13, high-precision wiring becomes possible, and the pattern can be formed at low cost.
[0040]
The wiring material is not limited to Cu, but may be any material having a sufficiently high conductivity such as Al and Au. Also, the method for forming the wiring pattern 10 is not limited to the above-described wet etching method, and may be formed using a dry etching method, a lift-off method, a plating method, and a screen printing method.
[0041]
Next, as shown in FIG. 3C, Sn / Au / Ni films and solder are formed as bumps 3 on the upper surfaces at both ends of the wiring pattern 10 by electrolytic plating or the like. The method for forming the solder of the bumps 3 is not particularly limited to a forming method such as a printing method, an electron beam vacuum evaporation method and a sputtering method, or a sheet solder punching method.
[0042]
Next, as shown in FIG. 3D, the resin film 9 is cut into a predetermined chip size. In FIG. 3D, a portion cut by a laser beam is indicated by an a portion. In this way, a temporary adhesive substrate 60 having the cut resin film 9 is formed. The laser beam cutting method for the resin film 9 shows very good workability with low cost, high throughput and high accuracy. It is preferable to use a laser beam having a wavelength of 532 nm or less, which has good absorbability to the resin film 9 and little thermal influence.
[0043]
Next, FIG. 4 shows a schematic process flow in resin film adhesion to formation of a surface acoustic wave device.
[0044]
As shown in FIG. 4A, a temporary adhesive substrate 60 provided with a resin film 9 is mounted on a substrate 50 on which the piezoelectric substrate 40 is mounted on the mounting substrate 1. At this time, one end of the wiring pattern 10 is connected to the connection portion 8 via the bump 3 provided on the upper surface of the wiring pattern 10.
[0045]
Next, as shown in FIG. 4B, the temporary adhesive substrate 13 is separated from the resin film 9. Since the interface between the temporary adhesive substrate 13 and the resin film 9 is previously coated with wax, it can be easily peeled off.
[0046]
Next, as shown in FIG. 4C, the peripheral portion of the resin film 9 is bent toward the mounting substrate 1, thereby connecting the wiring whose one end is joined to the connecting portion 8 provided on the other main surface of the piezoelectric substrate 4. The other end of the pattern 10 is connected to the connection section 12 provided on the mounting substrate 1 via the bump 3. At the same time, the piezoelectric substrate 4 is sealed by thermocompression bonding of the peripheral portion of the resin film 9 with the upper surface of the mounting substrate 1.
[0047]
The mounting substrate 1 on which the thus formed piezoelectric substrate 4 is mounted and sealed is divided into individual pieces by a dicing cut-saw or the like, and the dual-band surface acoustic wave device 20 shown in FIG. 1 is formed. The cutting method is not limited to dicing cutsaw. There is no particular limitation as long as desired accuracy and quality can be obtained.
[0048]
Regarding the sealing, as in the case of the surface acoustic wave device 30 shown in FIG. It is also possible to improve the sealing property.
[0049]
【The invention's effect】
According to the surface acoustic wave device using the resin film of the present invention as described above, it is easy to form the IDT formed on each of the one main surface and the other main surface for electrical connection. Become. In addition, the height and the size can be reduced. Further, high-speed processing for singulation is also facilitated. In addition, by forming a wiring pattern on a resin film, high-precision wiring becomes possible.
[0050]
A low-cost surface acoustic wave device corresponding to miniaturization and height reduction by sealing a piezoelectric substrate and using a resin film having a wiring function on a piezoelectric substrate provided with an IDT on one main surface and the other main surface. Can be supplied.
[Brief description of the drawings]
FIG. 1 is a sectional view of one embodiment of a surface acoustic wave device according to the present invention.
FIG. 2 is a schematic process flow of a surface acoustic wave device in the formation of a piezoelectric substrate to mounting on a mounting substrate according to the present invention.
FIG. 3 is a schematic process flow of a surface acoustic wave device for forming a resin film of the present invention.
FIG. 4 is a schematic process flow in bonding a resin film to a surface acoustic wave device according to the present invention.
FIG. 5 is a sectional view of an embodiment of the surface acoustic wave device according to the present invention using another sealing method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Mounting board 2, 7, 8, 12 ... Connection part 3 ... Bump 4, 40 ... Piezoelectric board 5, 6 ... IDT
9 Resin film 10 Wiring pattern 13 Temporary adhesive substrate 14 Sealing resin 20 and 30 Surface acoustic wave device 50 Piezoelectric substrate 60 in a mounted state Temporary adhesive substrate provided with resin film

Claims (3)

A mounting substrate having a connection portion on the top surface, at least one IDT and a connection portion provided on each of one main surface and the other main surface, and a piezoelectric substrate mounted on the mounting substrate on one main surface; and A surface acoustic wave device comprising a resin film that covers a connection portion of the mounting board,
The surface acoustic wave device, wherein the resin film includes a wiring pattern for electrically connecting a connection portion of the mounting substrate and a connection portion of the other main surface of the piezoelectric substrate. The surface acoustic wave device according to claim 1, wherein the resin film seals the piezoelectric substrate. The surface acoustic wave device according to claim 1, wherein the resin film is a polyimide film or a liquid crystal polymer film.

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