JP4509038B2 - Elastic wave device and manufacturing method thereof - Google Patents

Description

  The present invention relates to an acoustic wave device and a manufacturing method thereof, and more particularly to an acoustic wave device including a sealing portion having a cavity above an acoustic wave element and a manufacturing method thereof.

  The acoustic wave device is, for example, various circuits that process radio signals in a frequency band of 45 MHz to 2 GHz, such as a transmission bandpass filter, a reception bandpass filter, a local oscillation filter, an antenna duplexer, an intermediate frequency filter, an FM modulator, and the like. It is used for. In recent years, these signal processing devices have been miniaturized, and electronic components such as acoustic wave devices used are also required to be miniaturized. As an acoustic wave element used for an acoustic wave element device, a surface acoustic wave (SAW) element in which a interdigital electrode (IDT) or reflector is formed using a metal film on a piezoelectric substrate, or a piezoelectric film in which a piezoelectric thin film is sandwiched between metal electrodes. Examples include a thin film resonator (FBAR) element.

  In particular, in portable electronic devices such as mobile telephone terminals, electronic parts are increasingly used as modules. Modularization is performed by surface mounting electronic components and sealing them with resin for cost reduction. Therefore, there is a demand for an acoustic wave device that can be surface-mounted and can withstand the pressure during modular resin sealing. At the same time, in order to maintain the characteristics of the acoustic wave element, it is required to provide a cavity on the upper surface of the functional part (vibration part) of the acoustic wave element. The functional part of the acoustic wave element is an IDT electrode finger in the surface acoustic wave element, and an area where the upper and lower electrodes sandwich the piezoelectric thin film in the piezoelectric thin film resonator element.

In order to satisfy such a requirement, a method of forming a structure (so-called hollow structure) provided with a sealing portion having a cavity in contact with a functional portion in an acoustic wave element has been proposed. Patent Document 1 discloses a method of forming a hollow structure by forming a dissolving resin in a region to be a cavity on an acoustic wave element, forming an upper plate on the dissolving resin, and then removing the dissolving resin. (Conventional example 1) is disclosed. In Patent Document 2, a frame structure surrounding the electrical structure element is formed, an auxiliary film is pasted on the frame structure so that the electrical structure element is hollow, and a resin layer is formed thereon. A method (conventional example 2) for forming a hollow structure by removing the frame structure other than the roof portion is disclosed. In Patent Document 3, a resin film is pasted on a piezoelectric substrate on which an acoustic wave element is formed, a resin film on an upper part of a functional part of the substrate on which a plurality of acoustic wave elements are provided is opened, and a circuit board is bonded onto the resin film. A method of forming a hollow structure (conventional example 3) is disclosed. In Patent Document 4, a photosensitive resin is formed on a substrate on which a plurality of acoustic wave elements are provided, the photosensitive resin at the upper part of the functional part of the acoustic wave element is opened, and the substrate of the wiring board assembly is mounted thereon. A method of forming a hollow structure by dividing by dicing (conventional example 4) is disclosed. Patent Document 5 discloses a method (conventional example 5) using different resins for the surrounding wall that surrounds the acoustic wave element and the lid for forming the hollow structure.
Japanese Patent No. 3291406 Special table 2003-523082 gazette Japanese Patent No. 3196693 Japanese Patent No. 3225906 JP-A-10-93383

  The elastic wave devices formed by the methods of Conventional Examples 1 to 4 cannot withstand the pressure applied during modularization, and the hollow structure is deformed. On the other hand, the method of Conventional Example 5 is intended to suppress the deformation of the hollow structure during modularization. Compared to the conventional example 5, if a connection part for electrical connection to the outside is provided on the surface side of the acoustic wave device (side on which the surface acoustic wave element is formed) due to the requirement of surface mounting, the cover body is penetrated. Thus, a connection portion is provided. The lid is made of a material having a high elastic modulus to prevent deformation. For this reason, a crack etc. generate | occur | produce in a cover body or a connection part by the thermal stress etc. of a connection part and a cover body.

  The present invention has been made in view of such problems, and has a hollow structure that does not deform due to pressure during modularization, such as cracks caused by thermal stress in the connection part and the resin sealing part around it. An object of the present invention is to provide an acoustic wave device capable of suppressing the generation and a method for manufacturing the same.

The present invention is an elastic wave device provided on a substrate, a first sealing portion provided in the elastic wave element on on the substrate so as to cover the side surfaces and the upper surface of said cavity has a cavity, the A second sealing portion provided on the first sealing portion and on the substrate surrounding the first sealing portion; and the acoustic wave element is electrically connected to the outside through the second sealing portion. to comprise a terminal portion, wherein the 280 ° C. modulus of from 240 ° C. of the second sealing portion rather low than 280 ° C. of the elastic modulus from 240 ° C. of the first sealing portion, the first sealing portion The elastic wave device is characterized in that the elastic modulus at 150 ° C. to 200 ° C. is 1.8 GPa or more, and the first sealing portion and the second sealing portion are organic materials . According to the present invention, it has a hollow structure that is not deformed by the pressure at the time of modularization, and it is possible to suppress the occurrence of cracks and the like due to thermal stress in the connection part and the resin sealing part around it.

The said structure WHEREIN: The said 1st sealing part can be set as the structure containing an epoxy resin or a polyimide resin.

In the above structure, the first sealing portion, the side surface and form a step, can be the width of the substrate side of the stage is configured not larger than the width of the opposite side of the step and the substrate side. According to this structure, it can suppress that a bubble remains between a 2nd sealing part and a 1st sealing part.

The said structure WHEREIN: The said 1st sealing part has a width | variety on the said substrate side larger than the width | variety on the opposite side to the said substrate side, and the angle which the side surface of the said 1st sealing part and the surface of the said board | substrate make is 90 degrees or less. It can be configured. According to this structure, it can suppress that a bubble remains between a 2nd sealing part and a 1st sealing part.

The present invention includes a step of forming a surface acoustic wave element on a substrate, and a step of forming a first sealing portion on the substrate so as to cover a side surface and an upper surface of the cavity having a cavity on the acoustic wave element. And on the first sealing portion and on the substrate surrounding the first sealing portion, a second sealing whose elastic modulus from 240 ° C. to 280 ° C. is lower than that of the first sealing portion from 240 ° C. to 280 ° C. forming a part, the second through the sealing portion, wherein possess a step of forming a terminal portion for connecting the acoustic wave device external to electrically and, 0.99 ° C. of the first sealing portion The elastic modulus at 200 ° C. is 1.8 GPa or more, and the first sealing portion and the second sealing portion are organic materials . According to the present invention, it has a hollow structure that is not deformed by the pressure at the time of modularization, and it is possible to suppress the occurrence of cracks and the like due to thermal stress in the connection part and the surrounding sealing part.

  In the above configuration, the step of forming the first sealing portion includes the step of forming a first resin film having an opening in the region to be the cavity on the substrate, the step of forming the first resin film on the first resin film, Forming the second resin film so that the opening remains as the cavity, removing a predetermined region of the second resin film, and forming the first sealing by the first resin film and the second resin film. Forming the second sealing portion, the step of forming the second sealing portion includes the step of forming a third resin film on the first sealing portion, and the second sealing from the third resin film. And a step of forming a stop portion. According to this structure, the 2nd sealing part which covers the 1st sealing part which has a cavity can be formed.

In the above configuration, the step of forming the first sealing portion includes a step of performing a heat treatment at a first temperature in order to cure the first resin film and the second resin film, forming includes the step of heat treatment at a second temperature for curing the third resin layer, wherein the first temperature is rather high than the second temperature, the first temperature, the first seal It can be set as the structure which is the temperature from which the elasticity modulus in 150 to 200 degreeC of a stop part becomes 1.8 GPa or more . According to this configuration, since the first temperature is higher than the second temperature, the elastic modulus of the first sealing portion can be made higher than that of the second sealing portion.

  According to the present invention, it has a hollow structure that is not deformed by the pressure at the time of modularization, and it is possible to suppress the occurrence of cracks and the like due to thermal stress in the connection part and the resin sealing part around it. An acoustic wave device and a manufacturing method thereof can be provided.

  First, an experiment conducted by the inventor in order to clarify the problems of the conventional examples 1 to 5 will be described. FIG. 1A to FIG. 1C are diagrams showing an acoustic wave device according to Comparative Example 1 used in the experiment. 1A is a plan view, FIG. 1B is a cross-sectional view taken along the line AA in FIG. 1A, and FIG. 1C is a cross-sectional view taken along the line BB in FIG. 1A shows the acoustic wave element 12, the wiring 16, and the cavity 18 through the sealing portion 20a, and the acoustic wave element 12 and the wiring 16 are indicated by a solid line, and the cavity 18 is indicated by a broken line. Referring to FIGS. 1A and 1B, an acoustic wave element 12 made of a metal film, such as an IDT and a reflector, is provided on the surface of the piezoelectric substrate 10, and an acoustic wave is further formed on the piezoelectric substrate 10. A sealing part 20 a having a cavity 18 is provided on the functional part of the element 12.

  With reference to FIGS. 1A and 1C, a wiring 16 is formed on the piezoelectric substrate 10, and a sealing portion 20 a is provided on the wiring 16. A plug metal 30 penetrating through the sealing portion 20 a is provided, and the acoustic wave element 12 and the plug metal 30 are connected by the wiring 16 and the electrode pad 17 on the wiring 16. Solder balls 32 are provided on the plug metal 30. Thereby, the plug metal 30 and the solder ball 32 function as a terminal portion that electrically connects the acoustic wave element 12 to the outside when the acoustic wave device is surface-mounted. As described above, the acoustic wave element 12 is sealed by the sealing portion 20 a having a hollow structure, and is connected to the solder ball 32 via the wiring 16 and the plug metal 30. In the acoustic wave device according to Comparative Example 1, the height of the sealing portion 20a is about 90 μm, the height of the cavity 18 is about 30 μm, and the width of the cavity 18 is about 500 μm.

  With reference to FIG. 2A to FIG. 2F, a process of forming the sealing portion 20a of the acoustic wave device according to the comparative example 1 will be described. 2 (a) to 2 (c) are cross-sectional views corresponding to the AA cross section of FIG. 1 (a), and FIGS. 2 (d) to 2 (f) are B- It is sectional drawing equivalent to B cross section. 2A and 2D, a first resin film 19 having photosensitivity and containing a novolac type epoxy resin is formed on the piezoelectric substrate 10 on which the acoustic wave element 12 and the wiring 16 are formed. Application is performed using a spin coat method so as to have a film thickness of about 30 μm. Then dry. By exposing and developing, the first resin film 19 on the acoustic wave element 12, the cutting region 64, and the electrode pad 17 is removed. As a result, an opening 60 is formed in the first resin film 19 on the acoustic wave element 12, an opening 62 is formed on the electrode pad 17, and an opening is formed on the cutting region 64. Further, the first resin film 19 is cured by heating in a nitrogen atmosphere at about 200 ° C. for about 1 hour.

  2B and 2E, a film-like photosensitive novolac epoxy having a thickness of about 60 μm so as to hold the openings 60, 62 and the like on the first resin film 19. A second resin film 21 containing a resin is attached using a laminating method. As a result, the opening 60 becomes the cavity 18 and the opening 62 becomes the cavity 66. With reference to FIG. 2C and FIG. 2F, an opening is formed in the second resin film 21 on the cavity 66 and on the cavity on the cutting region 64 formed in the first resin film 19 by exposure and development. Is provided. As a result, the sealing portion 20 a having the cavity 18 on the acoustic wave element 12 and the opening 68 in which the plug metal 30 is to be formed on the electrode pad 17 is formed.

  Since the acoustic wave device according to Comparative Example 1 is protected by the sealing portion 20a having the cavity 18 on the functional portion of the acoustic wave element 12, the function of the acoustic wave element 12 is obtained when resin-sealed for modularization. The part is protected by a hollow structure. The plug metal 30 is provided in the sealing portion 20a, and the plug metal 30 connects the solder ball 32 formed on the sealing portion 20a and the acoustic wave element 12. Since the plug metal 30 is formed by filling the opening 68 surrounded by the sealing portion 20a with metal, the plug metal 30 can be easily formed. Since the solder ball 32 is provided on the sealing portion 20a, the solder ball 32 can be made higher than the upper surface of the sealing portion 20a, and surface mounting can be performed.

An experiment was conducted to determine whether such an acoustic wave device can withstand modular resin sealing. First, referring to FIG. 3A, the acoustic wave device having the sealing portion 20 a on the piezoelectric substrate 10 was attached to the printed board 70. Usually, when modularizing, the sealing portion 20a is attached to the printed board 70. In this experiment, the piezoelectric substrate 10 is attached to the printed board 70 in order to make it easy to confirm the deformation of the hollow structure. With reference to FIG. 3B, the printed board 70 to which the acoustic wave device was attached was attached in the transfer mold 72. A thermosetting epoxy resin 80 containing a filler heated to 175 ° C. was sealed in a sealing resin injection mold 74. A pressure of 70 kg / cm ² was applied to the thermosetting epoxy resin 80 using a plunger 76 and pushed into the transfer mold die 72. At the time of modular resin sealing, the temperature of the resin 80 is generally 150 ° C. to 200 ° C., and the pressure of the resin 80 to be sealed is generally 30 to 100 Kg / cm ² . In this experiment, the value at the center of these values is used. In this way, the pressure applied during modularization was applied to the acoustic wave device.

  FIG. 4 is a schematic diagram of a cross-sectional SEM photograph of the acoustic wave device after the experiment. In the sealing portion 20a provided on the piezoelectric substrate 10 by the epoxy resin 80 containing the filler 82, the cavity 18 is crushed and the sealing portion 20a is deformed. This is probably because the sealing portion 20 a has the cavity 18, and the sealing portion 20 a cannot withstand the pressure of the epoxy resin 80 and is plastically deformed. The elastic modulus of the first resin film 19 and the second resin film 21 used in the elastic wave device according to Comparative Example 1 is 2.4 MPa at room temperature, and 900 MPa at 150 to 200 ° C., which is a temperature applied when modularizing. It will drop to. Thus, with a general resin, the elastic modulus decreases when the temperature becomes high. For this reason, at the time of modular resin sealing, it was thought that the sealing part 20a might be plastically deformed by the temperature and pressure.

  Therefore, the deformation state of the hollow structure of the acoustic wave device according to Comparative Example 1 was investigated. With reference to Fig.5 (a), the indenter of the dynamic micro hardness tester (made by Shimadzu Corporation) was pushed into the ceiling part of the elastic wave device which concerns on the comparative example 1. FIG. The amount of dent in the ceiling at this time was D. As described above, when the dent amount D of the ceiling portion was changed, the deformation was not restored when the dent amount D of the ceiling portion exceeded 10 μm, and it was found to be completely plastically deformed when it exceeded 12 μm.

  Furthermore, when using a model having the same dimensions as the sealing part 20a of Comparative Example 1 and applying a pressure of 70 kg / cm 2 to the ceiling part of the sealing part 20a, the amount of ceiling dent D relative to the elastic modulus of the sealing part 20a Was calculated. FIG. 5B shows the result. In the calculation, simulation software ANSYS (trade name) using a finite element was used, and the sealing portion 20a was assumed to be a complete elastic body. When the temperature of the resin is 900 MPa, which is an elastic modulus of 150 ° C. to 200 ° C., the amount of recess in the ceiling is 22 μm (point A in FIG. 5B). Thus, when the elastic modulus of the resin is 900 MPa, the amount of recess in the ceiling part greatly exceeds 12 μm, which is the elastic limit of the ceiling part. Considering the above, when the transfer mold is formed, the elastic modulus of the ceiling portion of the sealing portion 20a is reduced due to overheating, and the depression amount of the ceiling portion exceeds the elastic limit due to pressure, and as shown in FIG. 4, the sealing portion 20a Is thought to have led to plastic deformation. In order that the ceiling part of the sealing part 20a does not exceed the elastic limit, the elastic modulus from 150 ° C. to 200 ° C. of the ceiling part of the sealing part 20a is preferably 1.8 GPa or more from FIG.

  However, when the elastic modulus of the sealing portion 20a of Comparative Example 1 is increased, or when the elastic modulus of the lid is increased as in Conventional Example 5, the following problems occur. A solder ball 32 as a connecting portion is used to electrically connect to a printed circuit board, and solder reflow is performed. The solder reflow is performed at 240 ° C. to 280 ° C. in the case of commonly used lead-free solder (SnAgCu). At this time, thermal stress is applied to the sealing portion 20a, the plug metal 30, and the solder ball 32. If the elastic modulus of the sealing part 20a is high, cracks will occur in the solder balls 32 and the plug metal 30. Thus, there exists a subject that reflow resistance is bad. An embodiment for solving the above problem will be described below.

  FIG. 6A is a plan view of the acoustic wave device according to the first embodiment. The acoustic wave element 12, the wiring 16, and the cavity 18 are illustrated through the first sealing part 20 and the second sealing part 40. The acoustic wave element 12 and the wiring 16 are solid lines, and the cavity 18 and the first sealing part 20 are It is indicated by a broken line. FIGS. 6B and 6C are cross-sectional views taken along lines AA and BB in FIG. 6A, respectively. With reference to FIG. 6A to FIG. 6C, a first sealing portion 20 and a second sealing portion 40 are formed instead of the sealing portion 20 a of Comparative Example 1. A first sealing portion 20 is formed around the cavity 18 on the piezoelectric substrate 10. That is, the first sealing portion 20 is provided on the piezoelectric substrate 10 so as to cover the side surface and the upper surface of the cavity 18. The first sealing portion 20 has a stepped shape that decreases as it goes upward (opposite to the piezoelectric substrate 10). A second sealing portion 40 is provided so as to cover the first sealing portion 20 on the piezoelectric substrate 10. The plug metal 30 penetrates through the second sealing portion 40, and solder balls 32 are formed in the plug metal 30. Other configurations are the same as those of Comparative Example 1, and the same members are denoted by the same reference numerals and description thereof is omitted.

  Next, a method for manufacturing the acoustic wave device according to the first embodiment will be described with reference to FIGS. 7A to 10F. 7 (a) through 7 (c), 8 (a) through 8 (c), 9 (a) through 9 (c), and 10 (a) through 10 (c) are shown in FIG. It is the figure which showed the manufacturing process of the cross section corresponded to the AA cross section of (a). 7 (d) to 7 (f), 8 (d) to 8 (f), 9 (d) to 9 (f), and 10 (d) to 10 (f). It is the figure which showed the manufacturing process of the cross section corresponded to the BB cross section of Fig.6 (a). FIGS. 7A to 10F show a manufacturing process performed using the piezoelectric substrate 10 in a wafer state, and a plurality of regions to be acoustic wave devices exist on the wafer. A region to be a plurality of acoustic wave devices is illustrated and described. In FIG. 10C and FIG. 10F, the cut region 64 is separated by dicing to be separated into a plurality of acoustic wave devices.

  7A and 7D, a metal film is formed using Al on the piezoelectric substrate 10 (LiTaO 3, LiNbO 3, etc.), and the acoustic wave element 12 and the wiring 16 are formed. An electrode pad 17 is formed in a region on the wiring 16 where the plug metal 30 is to be formed. Referring to FIGS. 7B and 7E, a first novolak epoxy resin having negative photosensitivity that prevents the irradiated portion from being developed on the piezoelectric substrate 10, the acoustic wave element 12, and the wiring 16 is provided. A resin film 19 is applied to about 30 μm and post-baked. With reference to FIG. 7C and FIG. 7F, ultraviolet rays (UV light) using a mask are used to form a region 18 and a peripheral region in which the cavity 18 on the functional portion of the acoustic wave element 12 of the first resin film 19 is to be formed. Irradiate other areas.

  Referring to FIGS. 8A and 8D, the first resin film 19 is developed to remove the first resin film 19 in the region not irradiated with ultraviolet rays (UV light). Thereby, an opening 60 to be a cavity is formed in the first resin film 19, and the first resin film 19 remains around the opening 60. The first resin film 19 is cured by heat treatment at 300 ° C. for 1 hour in a nitrogen atmosphere. Usually, when curing an epoxy resin, heat treatment is performed at about 200 ° C. In the first embodiment, the first resin film 19 is further cured by heat treatment at 300 ° C., and the elastic modulus is increased. Thereby, the elasticity modulus of 150 to 200 ° C. of the first resin film 19 can be set to 1.8 GPa or more. 8 (b) and 8 (e), the second resin film 21 that is a film-like negative photosensitive resin applied to the protective film 52 is pressed using a pressing roll 50 such as a laminator. Press and paste onto the film 19. With reference to FIG. 8C and FIG. 8F, the region other than the peripheral region is irradiated with ultraviolet rays.

  Referring to FIGS. 9A and 9D, the protective film 52 is peeled off and developed to remove the second resin film 21 in the region not irradiated with ultraviolet rays. The second resin film 21 is cured by heat treatment at 300 ° C. for 1 hour in a nitrogen atmosphere. As a result, the first sealing portion 20 having the cavity 18 is formed on the acoustic wave element 12 on the piezoelectric substrate 10 from the first resin film 19 and the second resin film 21. Since the first sealing portion 20 is heat treated at, for example, 300 ° C., the elastic modulus from 150 ° C. to 200 ° C. can be set to 1.8 GPa or more. Referring to FIGS. 9B and 9E, a third resin film 41, which is a novolak type epoxy resin having negative photosensitivity, is formed so as to cover the first sealing portion 20. The third resin film 41 is, for example, in the form of a film, and is formed using vacuum lamination or a vacuum press method. By using these methods, it is possible to prevent bubbles from entering between the first sealing portion 20 and the third resin film 41. 9C and 9F, the region on the electrode pad 17 and the region other than the cutting region 64 are irradiated with ultraviolet rays.

  With reference to FIG. 10A and FIG. 10D, the third resin film 41 in the region on the electrode pad 17 that is not irradiated with ultraviolet rays and the cutting region 64 is removed by development. The third resin film 41 is cured by heat treatment at 200 ° C. for 1 hour in a nitrogen atmosphere. Thereby, the second sealing portion 40 is formed on the first sealing portion 20 and on the surface of the piezoelectric substrate 10 surrounding the first sealing portion 20 by the third resin film 41. Since the heat treatment temperature is lower than that in the case of the first sealing portion 20 described in FIGS. 8A and 8D and FIGS. 9A and 9D, the elasticity of the second sealing portion 40 The rate is lower than that of the first sealing part 20. The second sealing portion 40 has an opening 68 on the electrode pad 17. Further, the second sealing portion 40 is not formed in the cutting region 64. Referring to FIGS. 10B and 10E, Ni, Cu, Au, or the like is electrolessly plated in opening 68 to form conductive plug metal 30. The plug metal 30 may be formed by a method of filling a conductive material such as silver paste into the opening 42 by printing. With reference to FIG. 10C and FIG. 10F, solder balls 32 connected to the plug metal 30 are formed on the plug metal 30. Thus, the plug metal 30 (connection portion) and the solder ball 32 that are electrically connected to the acoustic wave element 12 are formed. Thereafter, the piezoelectric substrate 10 in the cutting region 64 is cut by dicing. Thus, the acoustic wave device according to Example 1 is completed.

  In the acoustic wave device according to the first embodiment, the first sealing portion 20 is provided so as to cover the side surface and the upper surface of the cavity 18 on the acoustic wave element 12, and around the plug metal 30 and the solder ball 32 that are terminal portions. A second sealing portion 40 is provided. The elastic modulus of the second sealing part 40 is lower than the elastic modulus of the first sealing part 20. By increasing the elastic modulus of the first sealing portion 20, it is possible to prevent the cavity 18 from being crushed when the elastic wave device is modularized. Further, since the elastic modulus of the second sealing portion 40 around the plug metal 30 and the solder ball 32 is low, the heat of the second sealing portion 40, the plug metal 30 and the solder ball 32 during the solder reflow or temperature cycle test. It is possible to suppress the occurrence of cracks in the solder balls 32 and the second sealing portion 40 due to the stress.

  As described in FIG. 5A and FIG. 5B, the elastic modulus of the first sealing portion 20 from 150 ° C. to 200 ° C. is preferably 1.8 GPa or more. Thereby, when the elastic wave device is modularized, the collapse of the cavity 18 can be suppressed.

  The elastic modulus of 240 ° C. to 280 ° C. of the second sealing part 40 is preferably lower than the elastic modulus of 240 ° C. to 280 ° C. of the first sealing part 20. The reflow resistance can be improved because the elastic modulus of the second sealing portion 40 is lower than that of the first sealing portion 20 at 240 ° C. to 280 ° C., which is the temperature at which solder reflow is performed.

  It is preferable that the 1st sealing part 20 and the 2nd sealing part 40 are organic materials. In particular, the first sealing portion 20 preferably includes an epoxy resin or a polyimide resin. When the first sealing portion 20 includes a polyimide resin, the heat treatment described with reference to FIGS. 8A and 8D and FIGS. 9A and 9D is performed at a temperature higher than 300 ° C. preferable. This is because the polyimide resin has high heat resistance and is required to be cured at a higher temperature in order to form a sealing portion having a high elastic modulus.

  The first sealing portion 20 is preferably formed in a stepped shape having a large width on the piezoelectric substrate 10 side. Alternatively, as shown in FIG. 11, the angle θ formed by the side surface of the first sealing portion 20b and the surface of the piezoelectric substrate is preferably 90 ° or less. 9B and 9E, when the third resin film 41 is formed, if the angle θ formed between the side surface of the first sealing portion 20b and the surface of the piezoelectric substrate is larger than 90 °, Bubbles remain between the first sealing portion 20 and the third resin film 41. Therefore, by making the shape of the first sealing portion 20 stepped or by setting the angle θ to 90 ° or less, bubbles remain between the first sealing portion 20 and the third resin film 41. Can be suppressed.

  In the method of manufacturing the acoustic wave device according to the first embodiment, the step of forming the first sealing portion 20 includes the opening 60 in the region to be the cavity 18 as shown in FIGS. 8A and 8D. A first resin film 19 having the following is formed on the piezoelectric substrate 10. As shown in FIGS. 8B and 8E, the second resin film 21 is formed on the first resin film 19 so that the opening 60 remains as the cavity 18. As shown in FIGS. 9A and 9D, a predetermined region of the second resin film 21 is removed, and the first sealing portion 20 is formed by the first resin film 19 and the second resin film 21. Further, in the step of forming the second sealing portion 40, the third resin film 41 is formed on the first sealing portion 20 as shown in FIGS. 9B and 9E. Then, the second sealing portion 40 is formed from the third resin film 41. Thus, the 1st sealing part 20 and the 2nd sealing part 40 can be formed.

  Furthermore, when the first sealing portion 20 is formed, as described with reference to FIGS. 8A and 8D and FIGS. 9A and 9D, the first resin film 19 and the first sealing portion 20 are formed. 2 Heat treatment is performed at 300 ° C. (first temperature) in order to cure the resin film 21. On the other hand, when forming the 2nd sealing part 40, in order to harden the 3rd resin film 41, it heat-processes at 200 degreeC (2nd temperature). Thus, when the first temperature is higher than the second temperature, the elastic modulus of the first sealing portion 20 can be made higher than that of the second sealing portion 40.

  In the first embodiment, the acoustic wave element is an example of a surface acoustic wave (SAW) element formed on the piezoelectric substrate 10. The acoustic wave element may be a surface acoustic wave element formed on a piezoelectric film formed on a substrate such as a silicon substrate. A piezoelectric thin film resonator (FBAR) element can also be used as the acoustic wave element. When the FBAR element is used, the substrate is not a piezoelectric substrate, but a silicon substrate, a glass substrate, a sapphire substrate, or the like is used, and the FBAR is formed using a piezoelectric film on the substrate.

  In the first embodiment, two acoustic wave elements 12 and two cavities 18 are formed, but the number is not limited thereto. Although the example of the epoxy resin or the polyimide resin was shown as the 1st sealing part 20 and the 2nd sealing part 40, it is not restricted to these, What is necessary is just a resin which protects the acoustic wave element 12. FIG. Moreover, in order to improve the elasticity modulus of the 1st sealing part 20, the heat processing temperature for resin hardening is made high. Even if it is other than this method, you may make the elasticity modulus of the 1st sealing part 20 larger than the elasticity modulus of the 2nd sealing part 40, for example using resin from which the elasticity modulus of resin differs. Further, a filler may be added to the first sealing portion 20 to increase the elastic modulus. In the first embodiment, the example of the plug metal 30 and the solder ball 32 has been described as the connection portion. However, the connection portion may be any one that is electrically connected to the outside for surface mounting. For example, Au, It may be a bump using a metal such as Cu.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. It can be changed.

FIG. 1A is a plan view of an acoustic wave device according to Comparative Example 1. FIG. FIG.1 (b) is AA sectional drawing of Fig.1 (a). FIG.1 (c) is BB sectional drawing of Fig.1 (a). FIG. 2A to FIG. 2F are cross-sectional views illustrating manufacturing steps of the acoustic wave device according to Comparative Example 1. FIGS. 3A and 3B are schematic views for explaining an experiment assuming modularization of the acoustic wave device according to Comparative Example 1. FIG. FIG. 4 is a schematic diagram of a cross-sectional SEM photograph after the experiment assuming the modularization of Comparative Example 1. FIG. 5A is a view showing a recess in the ceiling portion of the resin portion of Comparative Example 1. FIG. FIG. 5B is a diagram illustrating a result of simulating the amount of depression in the ceiling with respect to the elastic modulus of the ceiling of the resin portion. FIG. 6A is a plan view of the acoustic wave device according to the first embodiment. FIG. 6B is a cross-sectional view taken along the line AA in FIG. FIG.6 (c) is BB sectional drawing of Fig.6 (a). FIG. 7A to FIG. 7F are cross-sectional views (part 1) illustrating the manufacturing process of the acoustic wave device according to the first embodiment. FIG. 8A to FIG. 8F are cross-sectional views (part 2) illustrating the manufacturing process of the acoustic wave device according to the first embodiment. FIG. 9A to FIG. 9F are cross-sectional views (part 3) illustrating the manufacturing process of the acoustic wave device according to the first embodiment. FIG. 10A to FIG. 10F are cross-sectional views (part 4) illustrating the manufacturing process of the acoustic wave device according to the first embodiment. FIG. 11 is a plan view of an acoustic wave filter according to a modification of the first embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Piezoelectric substrate 12 Elastic wave element 16 Wiring 17 Electrode pad 18 Cavity 19 1st resin film 20a Sealing part 20, 20b 1st sealing part 21 2nd resin film 30 Plug metal 32 Solder ball 40 2nd sealing part 41 1st 3 Resin film 60 Opening to be hollow

Claims (7)

An acoustic wave device provided on a substrate;
A first sealing portion provided on the substrate so as to have a cavity on the acoustic wave element and cover a side surface and an upper surface of the cavity;
A second sealing portion provided on the first sealing portion and on the substrate surrounding the first sealing portion;
A terminal portion that penetrates the second sealing portion and electrically connects the acoustic wave element to the outside;
Comprising
The 280 ° C. modulus of from 240 ° C. of the second sealing portion rather low than 280 ° C. of the elastic modulus from 240 ° C. of the first sealing portion,
The elastic modulus at 150 ° C. to 200 ° C. of the first sealing portion is 1.8 GPa or more,
The first sealing portion and the second sealing portion are made of an organic material . The acoustic wave device as claimed in claim 1, wherein the first sealing portion, characterized in that it comprises an epoxy resin or polyimide resin. Said first sealing portion, side surface forms a step, the substrate side of the stage acoustic wave device width the substrate side opposite the stage width than the size not according to claim 1 or 2 in. The first sealing portion has a width on the substrate side larger than a width on the opposite side of the substrate side, and an angle formed between a side surface of the first sealing portion and the surface of the substrate is 90 ° or less. The elastic wave device according to claim 1 or 2 . Forming a surface acoustic wave element on a substrate;
Forming a first sealing portion on the substrate so as to have a cavity on the acoustic wave element and cover a side surface and an upper surface of the cavity;
On the first sealing portion and on the substrate surrounding the first sealing portion, a second sealing portion having an elastic modulus of 240 ° C. to 280 ° C. lower than that of the first sealing portion of 240 ° C. to 280 ° C. Forming, and
Penetrating the second sealing portion, have a, forming a terminal portion for electrically connecting the acoustic wave device to the outside,
The elastic modulus at 150 ° C. to 200 ° C. of the first sealing portion is 1.8 GPa or more,
The method for manufacturing an acoustic wave device, wherein the first sealing portion and the second sealing portion are made of an organic material . The step of forming the first sealing portion includes a step of forming a first resin film having an opening in the region to be the cavity on the substrate, and the opening on the first resin film. Forming a second resin film so as to remain as a cavity, removing a predetermined region of the second resin film, and forming the first sealing portion from the first resin film and the second resin film; Including a process,
The step of forming the second sealing portion includes a step of forming a third resin film on the first sealing portion, and a step of forming the second sealing portion from the third resin film. The method of manufacturing an acoustic wave device according to claim 5 . The step of forming the first sealing portion includes a step of performing a heat treatment at a first temperature in order to cure the first resin film and the second resin film,
The step of forming the second sealing portion includes a step of heat-treating at a second temperature in order to cure the third resin film,
The first temperature is rather high than the second temperature,
The method of manufacturing an acoustic wave device according to claim 6 , wherein the first temperature is a temperature at which an elastic modulus at 150 ° C. to 200 ° C. of the first sealing portion is 1.8 GPa or more .

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