Elastic wave device package and manufacturing method thereof

Abstract

The present invention provides an elastic wave device package and a manufacturing method thereof that can not only improve the frequency-temperature characteristics but also reduce the manufacturing cost and can be thinned. The elastic wave device package includes a piezoelectric substrate having an excitation electrode and a pad electrode for elastic surface waves, and a mounting substrate for mounting the piezoelectric substrate. A resin layer is provided on the mounting substrate, which surrounds the periphery of the piezoelectric substrate and is in close contact with the periphery of the piezoelectric substrate. The surface of the piezoelectric substrate located on the opposite side of the mounting substrate is formed to be the same surface as the surface of the resin layer located on the opposite side of the mounting substrate. A supporting substrate having a lower thermal expansion coefficient than the piezoelectric substrate and a larger area than the piezoelectric substrate is bonded to the surfaces of the piezoelectric substrate and the resin layer formed to be the same surface with an adhesive. In other forms, a mounting substrate having a lower thermal expansion coefficient than the piezoelectric substrate can be used, and an insulating film can be bonded to the resin layer and the piezoelectric substrate to replace the supporting substrate.

Description

Technical Field

[0001] The present invention relates to an elastic wave device package having excellent frequency-temperature characteristics and capable of achieving thinness and a manufacturing method thereof. Background Art

[0002] Generally, a surface acoustic wave device is described in, for example, Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-128809) and Figure 7 As shown, it has a package structure called CSP (Chip Scale Package). That is, this elastic wave device package includes a mounting substrate 50 for mounting on a mother substrate not shown in the figure, a bare chip 51 of the elastic wave device, and a molding resin 52. The mounting substrate 50 has a pad electrode 53 for mounting the bare chip 51. The bare chip 51 includes a bonding substrate formed by bonding a piezoelectric substrate 55 and a supporting substrate 56. On the first main surface 55a of the piezoelectric substrate 55, a comb electrode 57 as an excitation electrode, a pad electrode 58, and an electrode pattern such as a reflector and a lead wiring not shown in the figure are formed. The second main surface 55b of the piezoelectric substrate 55 is bonded to the supporting substrate 56 in a wafer state. The bare chip 51 is mounted on the mounting substrate 50 by bonding the pad electrode 53 of the mounting substrate 50 and the pad electrode 58 of the piezoelectric substrate 55 with a bump 59. The mold resin 52 is provided on the mounting substrate 50 and covers the bare chip 51, and a cavity 60 is formed between the mounting substrate 50 and the piezoelectric substrate 55. In the invention of Patent Document 1, the material of the support substrate 56 is, for example, silicon as a semiconductor for improving electrical characteristics.

[0003] like Figure 7 As shown in FIG. 1 , when manufacturing a conventional elastic wave device package, a bonding substrate of a piezoelectric substrate 55 in a wafer state and a supporting substrate 56 is prepared. Before or after the piezoelectric substrate 55 and the supporting substrate 56 are bonded, a comb electrode 57 and a pad electrode 58 are formed on the piezoelectric substrate 55. Then, the bonding substrate of the piezoelectric substrate 55 and the supporting substrate 56 is cut into individual bare chips 51.

[0004] The piezoelectric substrate 55 has always been made of LT (lithium tantalate) or LN (lithium niobate). However, because these materials expand and contract as the temperature changes according to their thermal expansion coefficients, the piezoelectric substrate 55 is deformed. Because of this deformation, the spacing of the comb electrodes 57 will change. Therefore, the frequency it filters will deviate. In order to reduce the amplitude of the change of the filtered frequency with temperature, the piezoelectric substrate 55 is bonded to a supporting substrate 56 made of a material with a smaller thermal expansion coefficient than the piezoelectric substrate 55. That is, as the supporting substrate 56, a material such as silicon, spinel, or sapphire with a smaller thermal expansion coefficient than the piezoelectric substrate 55 composed of LT or LN is used. By using such a supporting substrate 56, the deformation of the piezoelectric substrate 55 due to temperature can be suppressed. In this way, the amplitude of the change of the filtered frequency with temperature can be reduced.

[0005] As such, other prior art examples of laminating a support substrate 56 having a smaller thermal expansion coefficient than the piezoelectric substrate 55 on the piezoelectric substrate 55 include elastic wave device packages described in Patent Documents 2 to 4. The elastic wave device package described in Patent Document 2 (Japanese Patent Publication No. 2016-100744) is a piezoelectric substrate wafer bonded to a support substrate wafer made of spinel. The bonded substrate wafer bonded in this way is then bonded to a mounting substrate wafer made of spinel and then cut into individual packages.

[0006] Patent document 3 (Japanese Patent Publication No. 2002-16468) discloses the use of glass with a smaller thermal expansion coefficient than that of a piezoelectric substrate as a supporting substrate. Patent document 4 (Japanese Patent Publication No. 2009-267665) discloses a method for manufacturing a surface acoustic wave component in which a temperature compensation film (supporting substrate) with a smaller thermal expansion coefficient than that of a piezoelectric substrate is formed on a piezoelectric substrate wafer by a SOG method.

[0007] like Figure 7 The elastic wave device package shown has a structure in which a bonding substrate composed of a piezoelectric substrate 55 and a supporting substrate 56 is covered with a molding resin 52. Generally, the thermal expansion coefficient of the molding resin 52 is larger than that of the piezoelectric substrate 55. Therefore, when the molding resin 52 is bent due to heat, the piezoelectric substrate 55 is also affected by the bending, and there is a problem that the frequency characteristics of the piezoelectric substrate 55 vary with temperature changes.

[0008] In addition, in the existing elastic wave device package, the Q value is improved by bonding the piezoelectric substrate 55 to the supporting substrate 56 and then thinning the piezoelectric substrate 55. Here, when bonding the piezoelectric substrate 55 to the supporting substrate 56, the bonding of the piezoelectric substrate 55 and the supporting substrate 56 is performed at the initial stage of the wafer manufacturing process. However, if the bonding of the piezoelectric substrate 55 and the supporting substrate 56 is performed by anodic bonding or resin, the wafer may be greatly bent after bonding because it needs to be heated. If such bending occurs, the manufacturing in the subsequent process may not be carried out. Therefore, the bonding of the piezoelectric substrate 55 and the supporting substrate 56 must use a room temperature bonding device that can be bonded at room temperature, and the room temperature bonding device is expensive. As a result, the cost required for the equipment used to manufacture the elastic wave device package is expensive, making the manufacturing cost very high.

[0009] In addition, in the conventional elastic wave device package manufacturing method, when the bonding substrate formed by bonding the piezoelectric substrate and the supporting substrate is mounted on the mounting substrate, the bonding substrate needs to have a certain thickness, which makes it difficult to achieve a thin elastic wave device package. Specifically, the thickness of the entire elastic wave device package is about 0.45 mm, which is the limit of thinning.

[0010] In addition, as described in Patent Document 4, when a supporting substrate of a glass material is formed on a piezoelectric substrate in a wafer state by the SOG method, the piezoelectric substrate must have a considerable degree of mechanical strength as a support for the glass. Therefore, it is difficult to reduce the thickness of the piezoelectric substrate. In addition, it is difficult to ensure the thickness of the glass layer formed by the SOG method, and it is also difficult to meet the physical surface characteristic requirements. Summary of the invention

[0011] In view of the above problems, the present invention aims to provide an elastic wave device package and a manufacturing method thereof which can improve the frequency-temperature characteristics and reduce the manufacturing cost.

[0012] A first form of an elastic wave device package of the present invention comprises a piezoelectric substrate having an excitation electrode and a pad electrode for an elastic surface wave on a first principal surface, a mounting substrate mounted in a state facing the first principal surface of the piezoelectric substrate, a resin layer surrounding the piezoelectric substrate and closely arranged on the mounting substrate with respect to the piezoelectric substrate, and a supporting substrate having a lower thermal expansion coefficient than that of the piezoelectric substrate and a larger area than that of the piezoelectric substrate, wherein a second principal surface of the piezoelectric substrate located on the opposite side of the first principal surface is formed on the same surface as a surface of the resin layer located on the opposite side of the mounting substrate, and the supporting substrate is bonded to the second principal surface of the piezoelectric substrate and the resin layer by an adhesive.

[0013] Such an elastic wave device package has a structure in which a resin layer surrounds the periphery of the piezoelectric substrate, and a supporting substrate is bonded to the piezoelectric substrate and the molding resin. In this way, this form is not a structure in which the resin layer is overlapped on the piezoelectric substrate or the supporting substrate. Therefore, the influence of the deformation of the resin layer due to temperature changes on the deformation of the piezoelectric substrate is reduced. In addition, the frequency-temperature characteristics of the elastic wave device correspond to the supporting substrate with a low thermal expansion coefficient, so the frequency-temperature characteristics can be improved. In addition, since the supporting substrate is exposed to the outside and the supporting substrate is wider than the piezoelectric substrate, the heat dissipation performance can be improved. By improving the heat dissipation performance in this way, the temperature rise of the elastic wave device package can be alleviated, thereby suppressing the frequency change caused by the temperature rise.

[0014] In addition, since the second main surface of the piezoelectric substrate and the resin layer are formed into the same surface, and the supporting substrate is bonded to the second main surface and the resin layer with an adhesive, the piezoelectric substrate and the supporting substrate can be bonded at room temperature using an adhesive, etc. Therefore, an expensive room temperature bonding device is not required, and the manufacturing cost can be reduced.

[0015] In a specific embodiment of the first aspect of the elastic wave device package of the present invention, the piezoelectric substrate has a thickness of 2 μm to 20 μm, and the support substrate has a thickness of 100 μm to 200 μm.

[0016] By setting the thickness of the piezoelectric substrate to be thinner than that of the supporting substrate, the supporting substrate can effectively suppress the expansion and contraction of the piezoelectric substrate due to temperature changes. Furthermore, since the piezoelectric substrate is thinner, the thickness of the elastic wave device package can be thinner.

[0017] The elastic wave device package of the present invention, in its second form, includes a piezoelectric substrate having an excitation electrode and a pad electrode for elastic surface waves on a first principal surface, a mounting substrate having a lower thermal expansion coefficient than that of the piezoelectric substrate and mounted in a state facing the first principal surface of the piezoelectric substrate, and a resin layer surrounding the periphery of the piezoelectric substrate and closely arranged on the mounting substrate with respect to the periphery of the piezoelectric substrate, wherein the second principal surface of the piezoelectric substrate located on the opposite side of the first principal surface is formed on the same plane as the surface of the resin layer located on the opposite side of the mounting substrate, and an insulating film with electrical insulation properties is bonded to the second principal surface of the piezoelectric substrate and the surface of the resin layer formed on the same plane as the second principal surface, and the thickness of the insulating film is thinner than the thickness of the mounting substrate.

[0018] In this way, a material with a smaller thermal expansion coefficient than the piezoelectric substrate is used as the mounting substrate, and the thickness of the insulating film is thinner than the thickness of the mounting substrate, thereby reducing the impact of the expansion and contraction of the insulating film caused by temperature changes on the piezoelectric substrate, thereby reducing the amount of expansion and contraction of the piezoelectric substrate caused by temperature changes.

[0019] In addition, since it is not necessary to bond the piezoelectric substrate and the insulating film in a wafer state, an expensive room temperature bonding device is not necessary, and the manufacturing cost can be reduced.

[0020] Furthermore, by thinning the piezoelectric substrate, the thickness of the entire conventional elastic wave device package can be further reduced.

[0021] In a specific embodiment of the second form of the elastic wave device package of the present invention, the thickness of the piezoelectric substrate is greater than 2 μm and less than 20 μm, the thickness of the insulating film is greater than 0.3 μm and less than 20 μm, and the thickness of the mounting substrate is greater than 60 μm and less than 300 μm.

[0022] In this way, by setting the thickness of the piezoelectric substrate and the insulating film to be thinner than the thickness of the mounting substrate, the mounting substrate can be used to effectively suppress the expansion and contraction of the piezoelectric substrate caused by temperature changes. In addition, since the piezoelectric substrate is thinner, the thickness of the elastic wave device package can be thinner.

[0023] A first form of a method for manufacturing an elastic wave device package of the present invention comprises: a step of preparing a mounting substrate on which an electrode pattern is formed; a step of preparing a bare chip of an elastic surface wave component on which an excitation electrode and a pad electrode are formed on a first main surface of a piezoelectric substrate; a step of mounting the bare chip of the elastic surface wave component on the mounting substrate; a step of covering the mounting substrate on which the bare chip is mounted with a curable resin layer and curing the same; a step of grinding the resin layer to expose a second main surface of the piezoelectric substrate located on the opposite side of the first main surface, and further grinding the resin layer. The process comprises the following steps: grinding the layer and the piezoelectric substrate to make them thinner so that the ground surface of the resin layer and the second main surface are formed into the same surface; applying an adhesive on the second main surface of the piezoelectric substrate and the surface of the resin layer formed by grinding; bonding a supporting substrate whose thermal expansion coefficient is smaller than that of the piezoelectric substrate to the second main surface of the piezoelectric substrate and the resin layer with an adhesive; and separating the laminate including the mounting substrate, the bare chip, the resin layer and the supporting substrate into chip-shaped individual elastic wave device packages.

[0024] The manufacturing method of this elastic wave device package can realize a structure in which a resin layer surrounds the periphery of the piezoelectric substrate, and a supporting substrate is bonded to the piezoelectric substrate and the molding resin. Therefore, as mentioned above, the bending of the resin layer due to temperature changes will reduce the influence of the deformation of the piezoelectric substrate due to temperature. In addition, the frequency-temperature characteristics of the elastic wave device correspond to the supporting substrate with a low thermal expansion coefficient, so the frequency-temperature characteristics can be improved. In addition, since the supporting substrate is exposed to the outside and the supporting substrate is wider than the piezoelectric substrate, the heat dissipation performance can be improved. By improving the heat dissipation performance in this way, the temperature rise of the elastic wave device package can be alleviated, thereby suppressing the frequency change caused by the temperature rise.

[0025] In addition, since the second main surface of the piezoelectric substrate and the resin layer are formed into the same surface, and the supporting substrate is bonded to the second main surface and the resin layer with an adhesive, the piezoelectric substrate and the supporting substrate can be bonded at room temperature using an adhesive, etc. Therefore, an expensive room temperature bonding device is not required, and the manufacturing cost can be reduced.

[0026] In addition, since the piezoelectric substrate is mounted on the mounting substrate and is ground and thinned by the resin layer, the piezoelectric substrate can be made thinner than when the piezoelectric substrate is not mounted on the mounting substrate and thinned. By thinning the piezoelectric substrate in this way, the thermal deformation suppression effect of the support substrate with a small thermal expansion coefficient becomes more effective. Therefore, an elastic wave device package with excellent thermal deformation suppression effect can be manufactured.

[0027] Furthermore, by thinning the piezoelectric substrate, the thickness of the entire conventional elastic wave device package can be further reduced.

[0028] A second form of the method for manufacturing an elastic wave device package of the present invention includes: a step of preparing a bare chip of an elastic surface wave component on which an excitation electrode and a pad electrode are formed on a first main surface of a piezoelectric substrate; a step of preparing a mounting substrate which is thicker than the piezoelectric substrate and has a smaller thermal expansion coefficient and on which an electrode pattern is formed; a step of mounting the bare chip of the elastic surface wave component on the mounting substrate; a step of covering the mounting substrate on which the bare chip is mounted with a curable resin layer and curing the same; a step of grinding the resin layer to expose a surface of the piezoelectric substrate on the opposite side of the first main surface, and further grinding the resin layer to thin the layer so as to form a second main surface on the opposite side of the first main surface of the piezoelectric substrate; a step of bonding an insulating film thinner than the mounting substrate to the second main surface of the piezoelectric substrate formed by grinding and the surface of the resin layer; and a step of separating a laminate including the mounting substrate, the bare chip, the resin layer and the insulating film into individual chip-shaped elastic wave device packages.

[0029] The second form of this manufacturing method uses a material with a smaller thermal expansion coefficient than the piezoelectric substrate as the mounting substrate, and the thickness of the insulating film is thinner than the thickness of the mounting substrate, thereby providing an elastic wave device package that uses the mounting substrate to suppress deformation of the piezoelectric substrate caused by temperature changes.

[0030] In addition, this manufacturing method does not require the piezoelectric substrate and the insulating film to be bonded in a wafer state, so an expensive room temperature bonding device is not required, which can reduce the manufacturing cost.

[0031] In addition, since the piezoelectric substrate is mounted on the mounting substrate and is ground and thinned by the resin layer, the piezoelectric substrate can be made thinner than when the piezoelectric substrate is not mounted on the mounting substrate and thinned. By thinning the piezoelectric substrate in this way, the thermal deformation suppression effect of the support substrate with a small thermal expansion coefficient becomes more effective. Therefore, an elastic wave device package with excellent thermal deformation suppression effect can be manufactured.

[0032] Furthermore, by thinning the piezoelectric substrate, the thickness of the entire conventional elastic wave device package can be further reduced.

[0033] The beneficial effects of the present invention are as follows: according to the present invention, not only the frequency-temperature characteristics can be improved, but also an elastic wave device package with reduced manufacturing cost and thinness and a manufacturing method thereof can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which:

[0035] Figure 1 A cross-sectional view showing a first embodiment of an elastic wave device package according to the present invention;

[0036] Figure 2 (a)-(c) Display Figure 1 A diagram showing a first stage of an example of a manufacturing process of an elastic wave device package;

[0037] Figure 3 (a)-(b) Display Figure 1 A diagram showing a second stage of an example of a manufacturing process of an elastic wave device package;

[0038] Figure 4 (a)-(b) Display Figure 1 A diagram showing a third stage of an example of a manufacturing process of an elastic wave device package;

[0039] Figure 5 A cross-sectional view showing a second embodiment of an elastic wave device package according to the present invention;

[0040] Figure 6(a)-(b) are diagrams showing a part of the manufacturing process of an example of an elastic wave device package according to the second embodiment; and

[0041] Figure 7 A cross-sectional view showing an example of a conventional elastic wave device package. DETAILED DESCRIPTION

[0042] <First embodiment>

[0043] according to Figure 1 A first embodiment of an elastic wave device package of the present invention is described. The elastic wave device package 1 includes a mounting substrate 2, a piezoelectric substrate 3, a resin layer 4, an adhesive 5, and a support substrate 6. The mounting substrate 2 is used to mount the elastic wave device on a mother substrate (not shown). The mounting substrate 2 can be made of an insulating material such as ceramic, glass, or resin.

[0044] The mounting substrate 2 has a pad electrode 8 for mounting an elastic wave device formed on its upper surface facing upward in the figure. In addition, the mounting substrate 2 has a pad electrode 9 for mounting on a mother substrate formed on its lower surface facing downward in the figure. The pad electrode 8 on the upper surface of the mounting substrate 2 and the pad electrode 9 on the lower surface are connected to each other by a conductor 11 provided on the side or inside the mounting substrate 2. If a build-up substrate is used as the mounting substrate 2, a conductor layer 12 or the like may be formed inside the build-up substrate as a component or wiring. If the mounting substrate 2 has a component built in, the pad electrode 8 and the pad electrode 9 may be connected via the built-in component.

[0045] The material of the piezoelectric substrate 3 is LT (lithium tantalate) or LN (lithium niobate). The first main surface 3a of the piezoelectric substrate 3 is formed with an electrode pattern of a comb-shaped electrode 14 (i.e., an excitation electrode), a pad electrode 15, and a reflector and wiring (not shown). The comb-shaped electrode 14, the pad electrode 15, the reflector and the wiring can be made of, for example, gold, copper or aluminum, or alloys of these metals, or other metals.

[0046] The resin layer 4 surrounds the piezoelectric substrate 3 and is closely arranged on the mounting substrate 2 along the periphery of the piezoelectric substrate 3. The resin layer 4 can be made of a light-curing or thermosetting hardening resin such as a polyimide resin or an epoxy resin. The upper surface 4a of the resin layer 4 in the figure is formed into the same surface as the second main surface 3b of the piezoelectric substrate 3 by grinding. The second main surface 3b of the piezoelectric substrate 3 is the surface on the opposite side of the first main surface 3a of the mounting substrate 2.

[0047] The second main surface 3b of the piezoelectric substrate 3 and the surface 4a of the resin layer 4 formed on the same plane as the second main surface 3b are bonded to the support substrate 6 by the adhesive 5. That is, the support substrate 6 covers not only the piezoelectric substrate 3 but also the resin layer 4. Therefore, the area of ​​the support substrate 6 is larger than that of the piezoelectric substrate 3. The adhesive 5 that bonds the support substrate 6 to the piezoelectric substrate 3 or the resin layer 4 may be made of a material that needs to be heated during bonding, or a material that can bond the support substrate 6 to the piezoelectric substrate 3 and the resin layer 4 at room temperature.

[0048] The piezoelectric substrate 3 is mounted in such a manner that its pad electrode 15 is bonded to the pad electrode 8 of the mounting substrate 2 via the bump 17. In this mounted state, a cavity 18 surrounded by the resin layer 4 is formed between the piezoelectric substrate 3 and the mounting substrate 2. In the elastic wave device package 1 thus constructed, the adhesive 5 prevents the formation of a gap between the resin layer 4 and the side surface of the piezoelectric substrate 3, thereby playing a role in maintaining moisture resistance.

[0049] The support substrate 6 has the function of suppressing the deformation of the piezoelectric substrate 3 due to temperature changes. Therefore, the support substrate 6 uses a material with a lower thermal expansion coefficient than the piezoelectric substrate 3, such as silicon, spinel, or sapphire. The thermal expansion coefficients of LT and LN used in the piezoelectric substrate 3 in the propagation direction of the elastic surface wave are 16.1ppm / ℃ and 15.4ppm / ℃ respectively. In addition, the thermal expansion coefficients of silicon, spinel, and sapphire used as the support substrate 6 are 3.4ppm / ℃, 7.3ppm / ℃, and 7.7ppm / ℃ respectively.

[0050] In addition, in addition to the thermal expansion coefficient, the conditions for suppressing the expansion and contraction of the piezoelectric substrate 3 with temperature changes by the support substrate 6 include high rigidity, that is, the higher the Young's modulus, the better. LT and LN used as the piezoelectric substrate 3 have Young's moduli of 230 GPa and 203 GPa respectively. The Young's moduli of silicon, spinel and sapphire used as the support substrate 6 are 120 GPa, 280 GPa and 470 GPa respectively. In addition, the sheet molding resin used for the resin layer 4 is, for example, a molding resin using an epoxy resin manufactured by NAGASE Industries (NAGASE & CO., LTD.), one example of which is a product with a thermal expansion coefficient of 33 ppm / °C and a Young's modulus of 9 GPa. Another example is an epoxy resin molding resin manufactured by Taiyo Ink MFG.CO., LTD., one example of which is a product having a thermal expansion coefficient of 15 to 20 ppm / °C and a Young's modulus of 8.7 GPa.

[0051] Figure 1The elastic wave device package 1 shown is a structure in which a resin layer 4 is provided around a piezoelectric substrate 3, rather than a structure in which the resin layer 4 is overlapped on the piezoelectric substrate 3 or the supporting substrate 6. Therefore, the deformation of the resin layer 4 in the propagation direction due to temperature changes exerts a smaller force on the piezoelectric substrate 3. Therefore, the deformation of the piezoelectric substrate 3 due to the deformation of the resin layer 4 due to temperature changes can be suppressed. In addition, the frequency-temperature characteristics of the elastic wave device correspond to the supporting substrate 6 having a low thermal expansion coefficient, so the frequency-temperature characteristics can be improved. In addition, the supporting substrate 6 is exposed to the outside and is wider than the piezoelectric substrate 3, so the heat dissipation can be improved. By improving the heat dissipation in this way, the temperature rise of the elastic wave device package 1 can be slowed down, and the frequency change caused by the temperature rise can be further suppressed.

[0052] In addition, the second main surface 3b of the piezoelectric substrate 3 and the surface 4a of the resin layer 4 are formed as the same surface, and the support substrate 6 is bonded to the second main surface 3b and the surface 4a with an adhesive 5. Therefore, the piezoelectric substrate 3 and the support substrate 6 can be bonded at room temperature without heating using an adhesive or the like. Therefore, it is not necessary to use an expensive room temperature bonding device, and the manufacturing cost can be reduced.

[0053] Furthermore, since the piezoelectric substrate 3 is ground and thinned while being fixed to the mounting substrate 2 and the resin layer 4, a thinner piezoelectric substrate 3 can be obtained compared to a manufacturing method in which the piezoelectric substrate 3 is thinned without being fixed to the resin layer 4 and then fixed to the resin layer 4. Therefore, an elastic wave device package having a thinner piezoelectric substrate can be obtained.

[0054] In addition, by thinning the piezoelectric substrate 3, the volume thereof is reduced, so that the force of the piezoelectric substrate 3 with a large thermal expansion coefficient expanding due to heat is also reduced, and therefore the force applied by the piezoelectric substrate 3 to the supporting substrate 6 is also reduced. Therefore, the supporting substrate 6 with a small thermal expansion coefficient has a higher thermal deformation suppression effect. Therefore, an elastic wave device package with excellent thermal deformation suppression effect can be manufactured.

[0055] In addition, by thinning the piezoelectric substrate 3, the thickness of the entire conventional elastic wave device package 1 can be reduced. Specifically, the thickness of the piezoelectric substrate 3 can be set to be greater than 2 μm and less than 20 μm. Here, the thickness of the support substrate 6 is set to be greater than 100 μm and less than 200 μm, and the thickness of the mounting substrate 2 is also set to be greater than 100 μm and less than 300 μm, so that an elastic wave device package with a thickness of less than 400 μm can be realized, which is a goal that is difficult to achieve with conventional elastic wave device packages.

[0056] Thus, by setting the thickness of the piezoelectric substrate 3 to be thinner than the thickness of the supporting substrate 6, the supporting substrate 6 can effectively suppress the expansion and contraction of the piezoelectric substrate 3 due to temperature changes. Furthermore, since the piezoelectric substrate 3 is thinner, the thickness of the elastic wave device package can also be thinner.

[0057] according to Figure 2 (a)-2)(c), Figure 3 (a)-3(b) and Figure 4 (a) to (b) illustrate an example of a manufacturing process of the elastic wave device package 1 according to the first embodiment. Figure 2 (a) The bare chip 20 shown has electrode patterns such as comb electrodes 14, pad electrodes 15 and reflectors not shown in the figure formed on the first main surface 3a of the piezoelectric substrate 3. This bare chip 20 is manufactured in the same way as in the past. In addition, the piezoelectric substrate 3 uses LT or LN. The comb electrodes 14, pad electrodes 15 and reflectors not shown in the figure are formed on the first main surface 3a of the piezoelectric substrate 3 in a wafer state by photolithography technology. These comb electrodes 14 and pad electrodes 15 can be made of, for example, gold, copper or aluminum, or alloys of these metals. The thickness of the piezoelectric substrate 3 in the wafer state can be about 100μm or more and 300μm or less. The piezoelectric substrate 3 in the wafer state on which the comb electrodes 14 and pad electrodes 15 are formed is divided into chips by knife cutting or laser cutting to form individual bare chips 20.

[0058] On the other hand, in the process other than the manufacturing process of the bare chip 20, Figure 2As shown in (b), an undivided mounting substrate 2A made of insulating materials such as ceramic, glass, and resin is prepared according to the method used in the past. The undivided mounting substrate 2A has electrode patterns formed vertically and horizontally for use with several elastic surface wave components. When the mounting substrate 2A is provided with a conductor layer 12 for forming wiring or components inside, a mounting substrate 2A formed by overlapping and bonding a mounting substrate forming a conductor layer 12 and one or more other mounting substrates can be used. Then, on such a mounting substrate 2A, a hole for setting a conductor 11 on the mounting substrate 2A is formed by laser or the like. Then, a seed layer made of, for example, copper is formed on the inner and outer surfaces of this hole and the mounting substrate. On this seed layer, a metal serving as the conductor 11 is formed by electrolysis. Thereafter, unnecessary metal is removed from outside the interior of this mounting substrate 2A. In addition to using such an electrolytic method, the hole formed by a laser or the like can also be filled with a bump and solidified. After the conductor 11 is provided on the mounting substrate 2A, the pad electrodes 8 and 9 are formed on the inner and outer surfaces of the mounting substrate 2A where the conductor 11 is exposed. When forming the pad electrodes 8 and 9, a protective layer is applied to the area around the end of the conductor 11 in the mounting substrate 2A. Next, a metal layer such as copper or gold that will become the pad electrodes 8 and 9 is formed and covered on the end of the conductor 11 not covered with the protective layer and its surroundings by evaporation or sputtering. Thereafter, the protective layer and the conductor formed on the protective layer are removed.

[0059] On the mounting substrate 2A provided with the pad electrodes 8, 9 and the conductor 11, as shown in FIG. Figure 2 As shown in (c), bare chip 20 of the acoustic wave device is mounted by flip-chip method. That is, pad electrodes 15 of bare chip 20 are bonded to pad electrodes 8 of mounting substrate 2A via bumps 17 .

[0060] Then as Figure 3 As shown in (a), a hardening resin layer 4A is covered on the mounting substrate 2A on which the bare chip 20 is mounted. The resin layer 4A can be provided by bonding a thermosetting resin or light-curing resin film, or by coating a thermosetting resin or light-curing resin, instead of bonding the film layer. The resin layer 4 is then heated or irradiated with light to harden the resin.

[0061] Next, the resin layer 4A and the piezoelectric substrate 3 are polished until Figure 3 The degree indicated by the dot-dash line 23 in (a) is such that the surface of the piezoelectric substrate 3 located on the opposite side of the first principal surface 3a, that is, the second principal surface 3b is exposed, and the resin layer 4A and the piezoelectric substrate 3 are further polished to be thinner. By such polishing, Figure 3 As shown in (b), the polished surface 4a of the resin layer 4 is formed flush with the second main surface 3b.

[0062] The grinding of the resin layer 4A and the piezoelectric substrate 3 can be performed by a conventionally used surface grinding device. This surface grinding device uses the mounting substrate 2A having the resin layer 4A as a workpiece, and is provided with a first table for fixing the workpiece, and a second table for fixing a grindstone. When grinding, at least one of the two tables is operated to push the grindstone toward the resin layer 4A on the mounting substrate 2A. Then, while the two tables are rotated together in different tracks, the two tables are gradually brought closer to each other, and abrasive grains are supplied between the resin layer 4A and the grindstone to grind the resin layer 4A on the entire surface of the mounting substrate 2A, and further grind the piezoelectric substrate 3. The grinding method is, for example, that the table on which the mounting substrate 2A is mounted rotates with the center of the mounting substrate 2A as the rotation center, and a grindstone with a smaller radius than the mounting substrate 2A is used on the grindstone, and the grindstone is driven and rotated reciprocally in the radial direction of the mounting substrate 2A, for example. By such operation, the resin layer 4 of the mounting substrate 2A and the piezoelectric substrate 3 are completely polished. By such polishing, the thickness of the piezoelectric substrate 3 is polished to about 2 μm to 20 μm.

[0063] After the resin layer 4 and the piezoelectric substrate 3 are polished in this manner, Figure 4 As shown in (a), the adhesive 5 is applied to the second main surface 3b of the piezoelectric substrate 3 and the surface 4a of the resin layer 4 flush with the second main surface 3b. The thickness of the adhesive 5 is preferably 0.3 μm to 0.5 μm.

[0064] Then as Figure 4 As shown in (b), a support substrate 6A which is thicker than the piezoelectric substrate 3 and is not divided is bonded to the resin layer 4 and the piezoelectric substrate 3 by an adhesive 5. The support substrate 6A is made of silicon, sapphire or spinel. Figure 4 As shown in (b), the package is divided into individual chips along the line 24 by cutting with a knife or laser, thereby forming an elastic wave device package 1.

[0065] In the manufacturing method of this elastic wave device package, a structure can be realized in which a resin layer 4 is provided to surround the piezoelectric substrate 3, and a supporting substrate 6 is bonded to the piezoelectric substrate 3 and the resin layer 4. In addition, the piezoelectric substrate 3 is not completely covered by the resin layer 4, so that the piezoelectric substrate 3 can be prevented from being deformed due to the temperature change of the resin layer 4. In addition, the frequency-temperature characteristic of the elastic wave device corresponds to the supporting substrate 6 which is thicker than the piezoelectric substrate 3 and has a lower thermal expansion coefficient, so the frequency-temperature characteristic can be improved. In addition, a structure is achieved in which the supporting substrate 6 is exposed to the outside and is wider than the piezoelectric substrate 3, so that the heat dissipation can be improved. By improving the heat dissipation, the temperature rise of the elastic wave device package 1 can be alleviated, and the frequency change caused by the temperature rise can be suppressed.

[0066] In addition, the manufacturing method of the elastic wave device package includes the steps of forming the second main surface 3b of the piezoelectric substrate 3 and the surface 4a of the resin layer 4 to be the same surface, and bonding the supporting substrate 6 to the second main surface 3b and the surface 4a with the adhesive 5. Therefore, the piezoelectric substrate 3 and the supporting substrate 6 can be bonded at room temperature using, for example, an adhesive that does not require heating. Therefore, it is not necessary to use an expensive room temperature bonding device as in the prior art to bond the piezoelectric substrate and the supporting substrate in a wafer state at room temperature, and the manufacturing cost can be reduced.

[0067] In addition, the manufacturing method of the elastic wave device package includes a step of grinding and thinning the piezoelectric substrate 3 in a state where the piezoelectric substrate 3 is fixed to the mounting substrate 2 and the resin layer 4. Therefore, a thinner piezoelectric substrate 3 can be obtained compared with a method in which the piezoelectric substrate 3 is thinned in a state where it is not fixed to the resin layer 4 and then fixed to the resin layer 4. Therefore, an elastic wave device package having a thinner piezoelectric substrate can be obtained. In addition, due to the thinning of the piezoelectric substrate 3, the influence of the expansion force of the piezoelectric substrate 3 having a large thermal expansion coefficient is reduced, so the thermal deformation suppression effect of the support substrate 6 having a small thermal expansion coefficient can be improved.

[0068] Furthermore, by thinning piezoelectric substrate 3 , the thickness of the entire conventional elastic wave device package 1 can be further reduced.

[0069] <Second embodiment>

[0070] according to Figure 5 A second embodiment of the elastic wave device package of the present invention is described. The elastic wave device package 1X of the second embodiment includes a mounting substrate 2, a piezoelectric substrate 3, a resin layer 4, and an insulating film 25. The elastic wave device package 1X of the second embodiment is different from the first embodiment in that the adhesive 5 is not required, and the resin layer 4 and the piezoelectric substrate 3 can be bonded by the components of the insulating film 25 itself. The piezoelectric substrate 3 uses LT or LN as in the first embodiment. The resin layer 4 also uses a curable resin that can be cured by heat or light as in the first embodiment.

[0071] The mounting substrate 2 uses a ceramic substrate or an organic substrate having a lower thermal expansion coefficient than the piezoelectric substrate 3. In addition, in order to reduce the influence of the insulating film 25 on the piezoelectric substrate 3 due to temperature changes, the thickness of the insulating film 25 is set to be thinner than the thickness of the mounting substrate 2. Specifically, the thickness of the piezoelectric substrate 3 is greater than 2 μm and less than 20 μm, the thickness of the insulating film 25 is greater than 0.3 μm and less than 20 μm, and the thickness of the mounting substrate 2 is greater than 60 μm and less than 300 μm. In this way, the mounting substrate 2 can suppress the expansion and contraction of the piezoelectric substrate 3 due to temperature changes.

[0072] A specific example of the mounting substrate 2 is HTCC (High Temperature Co-Fired Ceramic) made of alumina, one example of which is A440 produced by KYOCERA Corporation, and its thermal expansion coefficient is 7.1. Other examples of the mounting substrate 2 that can be used are BT resin copper laminates of CCL-HL832NS produced by Mitsubishi Chemical Corporation, and its thermal expansion coefficient is 10.0. In addition, CCL-HL832NSF-LCA produced by the same company can also be used, and its thermal expansion coefficient is 3.0. In addition, as another example, a resin inner layer circuit substrate of "MCL-E705G" produced by Hitachi Chemical Co., Ltd. can also be used, and its thermal expansion coefficient is 6.0. In addition, "MCL-E-770G" produced by the same company can also be used, and its thermal expansion coefficient is 5.0.

[0073] In the second embodiment, the surface 4a of the resin layer 4 is also polished to be flush with the second principal surface 3b of the piezoelectric substrate 3. The insulating film 25 is bonded to the surface 4a of the resin layer 4 and the second principal surface 3b of the piezoelectric substrate 3 in an undivided state.

[0074] The insulating film 25 is preferably made of a material having a smaller thermal expansion coefficient than the piezoelectric substrate 3. However, in this embodiment, the expansion and contraction of the piezoelectric substrate 3 due to temperature changes is suppressed by the mounting substrate 2. Therefore, the insulating film 25 may also be made of a material having a larger thermal expansion coefficient than the piezoelectric substrate 3.

[0075] The insulating film 25 is preferably made of a material that can be bonded at room temperature or at a relatively low temperature. For example, as long as it can be bonded to the resin layer 4 and the piezoelectric substrate 3 at a temperature below 150°C, the piezoelectric substrate 3 and the like can be prevented from bending after heating. The insulating film 25 can be made of, for example, a cloth made of glass fiber or polyamide fiber impregnated with polyimide resin or epoxy resin to form an adhesive sheet that is in a semi-hardened state and easy to bond. For example, by hardening one or more overlapping adhesive sheets with a single thickness of 30 to 40 μm, an insulating film 25 with a thermal expansion coefficient of about 8 to 13 ppm / °C in the longitudinal direction of the fiber can be obtained.

[0076] When manufacturing the elastic wave device package of this embodiment, Figure 2 (a)-2(b) and Figure 3 The same process as in the first embodiment can be used until the step (a) to step (b). That is, the resin layer 4A is polished to expose the piezoelectric substrate 3, and the polishing is continued. Figure 6 As shown in (a), the second main surface 3b of the piezoelectric substrate 3 is formed.

[0077] Afterwards, if Figure 6 As shown in (b), an undivided insulating film 25A is bonded to the second main surface 3b of the piezoelectric substrate 3 which is flush with the surface 4a of the resin layer 4. When the insulating film 25A uses the above-mentioned adhesive sheet, it is pressed while being heated to about 180°C to bond to the resin layer 4 and the piezoelectric substrate 3. Then, as shown in Figure 6 As shown in (b), the wafer is divided along the line 24 by knife cutting or laser cutting to form individual chips, and an elastic wave device package is produced.

[0078] In this embodiment, the expansion and contraction of the piezoelectric substrate 3 due to temperature changes is suppressed by the mounting substrate 2. In addition, the piezoelectric substrate 3 and the insulating film 25 do not need to be bonded in a wafer state. Therefore, an expensive room temperature bonding device is not required, and the manufacturing cost can be reduced.

[0079] In addition, since the piezoelectric substrate 3 is mounted on the mounting substrate 2 and polished with the resin layer 4 fixed, a thinner piezoelectric substrate 3 can be obtained. Therefore, compared with the manufacturing method of thinning the piezoelectric substrates separately and then mounting them, a thinner piezoelectric substrate can be obtained. By thinning the piezoelectric substrate 3 in this way and making the insulating film 25 thinner than the mounting substrate 2, the influence of the thermal expansion of the piezoelectric substrate 3 and the insulating film 25 on the mounting substrate 2 can be reduced, thereby further improving the thermal deformation suppression effect of the mounting substrate 2 with a smaller thermal expansion coefficient.

[0080] Furthermore, by thinning the piezoelectric substrate, the thickness of the entire conventional elastic wave device package can be further reduced.

[0081] In this embodiment, the deformation of the piezoelectric substrate 3 due to temperature is suppressed by the mounting substrate 2. Preferably, as described above, by using an adhesive sheet having a lower thermal expansion coefficient than the piezoelectric substrate 3, the amount of deformation of the piezoelectric substrate 3 due to temperature can be made smaller.

[0082] The above are merely embodiments of the present invention and should not be used to limit the scope of the present invention. That is, any simple equivalent changes and modifications made according to the claims and description of the present invention still fall within the scope of the present invention.

Claims

1. An elastic wave device package, comprising a piezoelectric substrate having an excitation electrode for an elastic surface wave and a pad electrode on a first main surface, a mounting substrate mounted in a state facing the first main surface of the piezoelectric substrate, a resin layer surrounding the periphery of the piezoelectric substrate and provided on the mounting substrate in close contact with the periphery of the piezoelectric substrate, and a supporting substrate having a lower thermal expansion coefficient than the piezoelectric substrate and a larger area than the piezoelectric substrate, characterized in that: The second main surface of the piezoelectric substrate located on the opposite side of the first main surface is formed on the same surface as the surface of the resin layer located on the opposite side of the mounting substrate, and the support substrate is bonded to the second main surface of the piezoelectric substrate and the resin layer by an adhesive.

2. The elastic wave device package according to claim 1, characterized in that: The piezoelectric substrate has a thickness of not less than 2 μm and not more than 20 μm, and the support substrate has a thickness of not less than 100 μm and not more than 200 μm.

3. The elastic wave device package according to claim 1, characterized in that: The adhesive has a thickness of 0.3 μm to 0.5 μm.

4. The elastic wave device package according to claim 1, characterized in that: The mounting substrate has a thickness of 100 μm or more and 300 μm or less.

5. An elastic wave device package, comprising a piezoelectric substrate having an excitation electrode for an elastic surface wave and a pad electrode on a first main surface, a mounting substrate having a lower thermal expansion coefficient than the piezoelectric substrate and mounted in a state facing the first main surface of the piezoelectric substrate, and a resin layer surrounding the periphery of the piezoelectric substrate and provided on the mounting substrate in close contact with the periphery of the piezoelectric substrate, characterized in that: The second main surface of the piezoelectric substrate located on the opposite side of the first main surface is formed into the same plane as the surface of the resin layer located on the opposite side of the mounting substrate, and an insulating film with electrical insulation properties is bonded to the second main surface of the piezoelectric substrate and the surface of the resin layer formed into the same plane as the second main surface, and the thickness of the insulating film is thinner than the thickness of the mounting substrate.

6. The elastic wave device package according to claim 5, characterized in that: The insulating film is made of cloth made of glass fiber or polyamide fiber impregnated with polyimide resin or epoxy resin to form an adhesive sheet in a semi-hardened state for easy bonding.

7. The elastic wave device package according to claim 5, characterized in that: The insulating film is made of a material having a smaller thermal expansion coefficient than that of the piezoelectric substrate.

8. The elastic wave device package according to claim 5, characterized in that: The piezoelectric substrate has a thickness of 2 μm to 20 μm, the insulating film has a thickness of 0.3 μm to 20 μm, and the mounting substrate has a thickness of 60 μm to 300 μm.

9. A method for manufacturing an elastic wave device package, comprising: a step of preparing a mounting substrate on which an electrode pattern is formed; a step of preparing a bare chip of an elastic surface wave component on which an excitation electrode and a pad electrode are formed on a first main surface of a piezoelectric substrate; a step of mounting the bare chip of the elastic surface wave component on the mounting substrate; a step of covering the mounting substrate on which the bare chip is mounted with a curable resin layer and curing the same; a step of grinding the resin layer to expose a second main surface of the piezoelectric substrate located on the opposite side of the first main surface, and further grinding the resin layer and The piezoelectric substrate is ground to be thinned so that the ground surface of the resin layer and the second main surface are formed into the same surface; an adhesive is applied on the second main surface of the piezoelectric substrate and the surface of the resin layer formed by grinding; a support substrate whose thermal expansion coefficient is smaller than that of the piezoelectric substrate is bonded to the second main surface of the piezoelectric substrate and the resin layer with an adhesive; and a laminate including the mounting substrate, the bare chip, the resin layer and the support substrate is separated into chip-shaped individual elastic wave device packages.

10. A method for manufacturing an elastic wave device package, comprising: a step of preparing a bare chip of an elastic surface wave component on a first main surface of a piezoelectric substrate, on which an excitation electrode and a pad electrode are formed; a step of preparing a mounting substrate which is thicker than the piezoelectric substrate and has a lower thermal expansion coefficient than the piezoelectric substrate and on which an electrode pattern is formed; a step of mounting the bare chip of the elastic surface wave component on the mounting substrate; a step of covering the mounting substrate on which the bare chip is mounted with a curable resin layer and curing the same; a step of grinding the resin layer to expose a surface of the piezoelectric substrate on the opposite side of the first main surface, and further grinding the resin layer to thin the layer to form a second main surface on the opposite side of the first main surface of the piezoelectric substrate; a step of bonding an insulating film thinner than the mounting substrate to the second main surface of the piezoelectric substrate formed by grinding and the surface of the resin layer; and a step of separating a laminate including the mounting substrate, the bare chip, the resin layer and the insulating film into individual chip-shaped elastic wave device packages.

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