Sapphire structure with a concave portion including a metal substructure and method for producing the same

A sapphire structure with a metal substructure is disclosed. The sapphire structure with a metal substructure includes a sapphire structure and a metal substructure. The sapphire structure includes a flat surface and a concave portion on the flat surface. The metal substructure in the concave portion is bonded to an inner surface of the concave portion and includes a surface portion that is substantially flush with the flat surface.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2013-225829, filed on Oct. 30, 2013, entitled “Sapphire Structure with Metal Substructure and Method for Producing the Same”, the content of which is incorporated by reference herein in its entirety.

FIELD

The present invention relates to a sapphire structure with a metal substructure.

BACKGROUND

Sapphire has been widely used as a substrate for gallium nitride (GaN) crystal growth because sapphire as a single crystal of alumina has a crystal lattice whose structure is close to that of GaN. Further, various devices using the sapphire have been developed.

SUMMARY

A sapphire structure with a metal substructure and a method for producing a sapphire structure with a metal substructure are presented. The sapphire structure with a metal substructure includes a sapphire structure and a metal substructure. The sapphire structure includes a flat surface and a concave portion on the flat surface. The metal substructure is at least partially housed within the concave portion of the sapphire structure. The metal substructure housed within the concave portion of the sapphire structure is bonded to the inner surface of the concave portion. The metal substructure includes a surface portion that is substantially flush with the flat surface of the sapphire structure.

Further, a method for producing a sapphire structure with a metal substructure includes forming a concave portion on a flat surface of a sapphire structure; applying metal paste that contains metal particles and a solvent to the inside of the concave portion; forming a metal substructure in the concave portion, which is bonded to an inner surface of the concave portion, by heating the sapphire structure and the metal paste to evaporate the solvent contained in the metal paste and to bind the metal particles to each other; and making at least part of a surface of the metal substructure substantially flush with the flat surface of the sapphire structure by polishing the flat surface of the sapphire structure and a surface of the metal substructure at the same time.

DESCRIPTION

The following description is presented to enable a person of ordinary skill in the art to make and use the embodiments of the disclosure. The following detailed description is exemplary in nature and is not intended to limit the disclosure or the application and uses of the embodiments of the disclosure. Descriptions of specific devices, techniques, and applications are provided only as examples. Modifications to the examples described herein will be readily apparent to those of ordinary skill in the art, and the general principles defined herein may be applied to other examples and applications without departing from the spirit and scope of the disclosure. The present disclosure should be accorded scope consistent with the claims, and not limited to the examples described and shown herein.

Embodiments of the disclosure are described herein in the context of one practical non-limiting application, namely, an electronic apparatus such as a mobile phone. Embodiments of the disclosure, however, are not limited to such mobile phone, and the techniques described herein may be utilized in other applications. For example, embodiments may be applicable to e-readers, digital cameras, electronic game machines, digital music players, personal digital assistants (PDA), tablets, personal handy phone system (PHS), laptop computers, TV's, Global Positioning Systems (GPS's) or navigation systems, health equipment, and other communication devices. As would be apparent to one of ordinary skill in the art after reading this description, these are merely examples and the embodiments of the disclosure are not limited to operating in accordance with these examples. Other embodiments may be utilized and structural changes may be made without departing from the scope of the exemplary embodiments of the present disclosure.

FIGS. 1A and 1Bare views describing a sapphire structure10with a metal substructure (hereinafter, also simply referred to as a structure10with a metal substructure).FIG. 1Ais a schematic perspective view, andFIG. 1Bis a schematic cross-sectional view.

The structure10with a metal substructure includes a sapphire structure11, which includes a flat surface11A and a concave portion12on the flat surface11A. A metal substructure20is located within the concave portion12and is bonded to an inner surface13of the concave portion12. The metal substructure20includes a surface portion20A which is substantially flush with the flat surface11A of sapphire structure11. The sapphire structure11is a plate-like body and includes the flat surface11A as a first surface and a second surface11B on the opposite side of the flat surface11A. The sapphire structure11includes sapphire which is a single crystal of aluminum oxide (Al2O3) and contains aluminum oxide (Al2O3) in the range of 75% by mass or more. It is preferable that the sapphire structure contain aluminum oxide (Al2O3) in the range of 95% or more. In addition, the flat surface11A of the sapphire structure is substantially flush with the surface portion20A of the metal substructure20. Substantially flush means that the height difference between the flat surface11A and the surface portion20A of the metal substructure20is less than 500 μm. The height difference between the flat surface11A and the surface portion20A of the metal substructure20is preferably less than 100 μm. Further, the height difference thereof is more preferably less than 10 μm, still more preferably less than 1 μm, and still more preferably less than 0.1 μm.

The metal substructure20contains silver (Ag) as a main component. The meaning of “main component” is that the component is contained by the amount of at least 50% by mass and preferably 70% by mass.

Further, the metal substructure20may contain copper (Cu) or titanium (Ti). In addition, in the structure10with a metal substructure, the arithmetic average roughness (Ra) of the surface portion20A of the metal substructure20, which is substantially flush with the flat surface11A, is greater than that of the flat surface11A. In addition, the arithmetic average roughness of the flat surface11A is preferably 10 nm or less. The arithmetic average roughness of the flat surface11A is more preferably 1 nm or less. The arithmetic average roughness thereof may be a value measured by a measurement method in conformity with JIS standard B0601-2001. In the structure10with a metal substructure, since the metal substructure20is arranged in the concave portion12and bonded to the inner surface13of the concave portion12, the metal substructure20is difficult to detach from the structure10.

FIG. 2is a cross-sectional view illustrating a device configured using the structure10with a metal substructure. In the device1as illustrated inFIG. 2, a first device30and a second device40are mounted on the structure10with a metal substructure. The first device30and the second device40are electrically connected by the metal substructure20which functions as an electrical wiring. The first device30illustrated inFIG. 2is, for example, a driving circuit element including an electrode32. The second device40is, for example, a light emitting diode (LED) including an electrode42. Either the first device30or the second device40may be an exterior member. It is also possible for both first device30and second device40to be exterior members.

Since the metal substructure20includes the surface portion20A, which is substantially flush with the flat surface11A, the first device30or the second device40can be in contact with the structure10with a metal substructure with substantially no gaps between the first device30and the structure10, or between the second device40and the structure10. The first device30or the second device40is mounted on the structure10with a metal substructure as illustrated inFIG. 2.

The sapphire structure11has high thermal conductivity because of its sapphire content. Therefore, heat emitted from the first device30or the second device40can be efficiently dissipated from the sapphire structure11by bringing a portion of the first device30or the second device40into contact with the flat surface11A of the sapphire structure11, with at most only a small gap between the device30or device40and the sapphire structure11. Operational reliability of the first device30or the second device40can be improved because heat is efficiently dissipated away from the devices.

The sapphire structure11is light-transmissive. Therefore, the light emitted from the second device40, which is a light emitting diode (LED), enters the sapphire structure11on one side and can be radiated in a wide range on the opposite side of sapphire structure11, as illustrated byFIG. 2. In the device1, since the gap between the flat surface11A of the sapphire structure11and the second device40is minimal to non-existent, there is no refractive index difference between the sapphire structure11and an air layer the way there would be if there was a substantial gap present. Thus, more light can be radiated through the sapphire structure11because by extra reflection light is suppressed.

Further, sapphire has small electrical resistance, and the dark current flowing over the surface of the sapphire structure11is suppressed so as to be small. Therefore, it is less likely that either first device30or second device40mounted on the surface of the sapphire structure11will experience operation failure caused by a dark current. The first device30or the second device40may be a transmitter or a receiver for transmitting or receiving electromagnetic signals in a wireless manner. Because sapphire has very low dielectric loss, electromagnetic waves can be transmitted or received with a small loss across a wide range of frequencies when a transmitter or a receiver is mounted on the sapphire structure11. The types of devices that first device30or the second device40are not limited to the examples given above, and various devices or apparatuses can be mounted.

The structure10with a metal substructure may be used for other purposes aside from mounting devices on the structure10with a metal substructure as described above. The structure10with a metal substructure has a characteristic appearance such that the flat surface11A of the sapphire structure11, which has the property of high light transmission, is substantially flush with the surface portion20A of the metal substructure20, which has metallic glossiness. For example, when the structure10with a metal substructure is used for part of a housing which covers a device capable of transmitting and receiving a wireless signal, a transceiving device may be formed. Because sapphire has very low dielectric loss, this transceiving device has high transmitting and receiving sensitivity of the wireless signal. Furthermore, the housing in the transceiving device has high strength and is difficult to be broken. Finally, the transceiving device has a characteristic appearance, which may be considered a striking and unique design. Thus the structure10with a metal substructure can be used for different purposes.

In the structure10with a metal substructure, the arithmetic average roughness (Ra) of the surface portion20A may be greater than the arithmetic average roughness (Ra) of the flat surface11A. Accordingly, the bonding strength between the surface portion20A and either a solder layer or a metallized layer is increased by an anchor effect due to unevenness of the surface portion20A when the first device30or the second device40is bonded to the surface portion20A of the metal substructure20via the solder layer or the metallized layer. The metal substructure20is difficult to detach from the concave portion12as described above. This in turn makes it difficult to detach the first device30or the second device40, which are attached to a metal substructure20, from the sapphire structure11.

FIG. 3is a partially enlarged view ofFIG. 1B. The metal substructure20may contain silver (Ag) as a main component. In addition, the metal substructure20may also contain copper (Cu) and titanium (Ti). When the structure10is used as a wiring board or the like, silver (Ag) is preferable in terms of low electrical resistance and high conductivity. The hardness of the metal substructure20containing silver (Ag) and copper (Cu) may be higher than that of the metal substructure containing only silver (Ag). The bonding strength between the metal substructure20and the inner surface13of the concave portion12becomes relatively high when the metal substructure20contains titanium (Ti). Specifically, as illustrated inFIG. 3, a bonding layer22containing titanium (Ti) as a main component is formed in a bonding area in which the metal substructure20is bonded to the inner surface13, and the metal substructure20and the inner surface13are relatively strongly bonded to each other.

As illustrated inFIG. 3, the inner surface13of the concave portion12includes a bottom surface13α, a side surface13β, and a corner13γ. The bottom surface13α is substantially parallel to the flat surface11A, and the side surface13β is substantially vertical to the bottom surface13α and the flat surface11A. The corner13γ is inclined with respect to the bottom surface13α and the side surface13β. The corner13γ has an arithmetic surface roughness greater than those of the bottom surface13α and the side surface13β. The arithmetic surface roughness of the corner13γ is large enough that the unevenness of the surface of the corner13γ is relatively large when compared to the bottom surface13α and the side surface13β. Thus, the metal substructure20is rigidly bonded to the corner13γ due to the anchor effect, and the metal substructure20is difficult to detach from the concave portion12.

FIG. 4is a cross-sectional view of another embodiment of the sapphire structure with a metal substructure. In the embodiment illustrated inFIG. 4, the sapphire structure11includes a through-hole15, which has openings on the bottom surface13α of the concave portion12and the second surface11B. Further, the sapphire structure11includes a via conductor17which fills in the through-hole15. The via conductor17includes a metal.

In the embodiment illustrated inFIG. 4, a first device30including an electrode32is arranged on the flat surface11A. The first device30may be a driving circuit element. A second device40including an electrode42is arranged on the second surface11B. The second device40may be a light emitting element. The first device30and the second device40can be conducted through the via conductor17and the metal substructure20.

FIG. 5is a cross-sectional view illustrating another embodiment, in which a member with a metal pattern is attached to the sapphire structure with a metal substructure. A member50with a metal pattern, as illustrated inFIG. 5, includes a metal layer24such as a gold (Au)-plated layer on the surface portion20A of the metal substructure20. In this manner, the metal layer24made of a metal different from the metal substructure20is formed on the surface portion20A of the metal substructure20. Thus, the external appearance or the electrical characteristics of the structure10with a metal substructure can be adjusted.

FIGS. 6A to 6Eare cross-sectional views illustrating a method for producing the sapphire structure with a metal substructure. This method includes a process of forming the concave portion12(seeFIG. 6B) on the flat surface11A by performing processing on part of the flat surface11A of the sapphire structure11(seeFIG. 6A) including the flat surface11A; a process of applying metal paste19(seeFIG. 6C) which contains metal particles17and a solvent18into the concave portion12; a process of forming the metal substructure20(seeFIG. 6D) which is arranged in the concave portion12and bonded to the inner surface13of the concave portion12by heating the sapphire structure11and the metal paste19to evaporate the solvent18and bind the metal particles21to each other; and a process of making at least part of the surface portion20A substantially flush with the flat surface11A (seeFIG. 6E) by polishing the flat surface11A and the surface portion20A at the same time.

Hereinafter, respective processes will be described in detail. First, as illustrated inFIG. 6A, the sapphire structure11having the flat surface11A is prepared. The sapphire structure may be a circular sapphire substrate having a thickness of 600 μm is prepared.

Next, as illustrated inFIG. 6B, the concave portion12is formed on the flat surface11A by milling a part of the flat surface11A of the sapphire structure11using a so-called machining center device. Specifically, grinding processing is performed on a portion corresponding to the concave portion12of the sapphire structure11by rotating and moving a so-called diamond electrodeposition tool to which diamond abrasive grains are adhered. The depth of the concave portion12is set to, for example, approximately 120 μm. Sapphire has high hardness, which makes it difficult to process. Thus, the surface after milling is unlikely to be flat. Particularly, because it is difficult to ensure stable contact of the diamond electrodeposition tool on the corner13γ when compared to the bottom surface13α and the side surface13β, the arithmetic surface roughness of the corner13γ becomes greater than the arithmetic surface roughness of both the bottom surface13α and the side surface13β. After milling is complete, the temperature of the entire sapphire structure11is increased to a higher temperature, for example 1650° C. An annealing process, which maintains the temperature range of 1500° C. to 1800° C., is then performed for approximately 3 hours. The annealing process reduces the internal stress remaining on the inner surface13of the concave portion12after milling.

Next, as illustrated inFIG. 6C, the metal paste19containing metal particles17and the solvent18is applied to the concave portion12using a brush or the like. For example, the metal paste19is applied to the concave portion12such that the metal paste19forms a layer in the concave portion12with a thickness in the range of 60 μm to 120 μm. The metal particles21contain silver (Ag) as a main component, and the metal paste19further contains silicon dioxide (SiO2) together with a solvent. In addition, the metal paste19also contains copper (Cu) particles and titanium (Ti) particles. For example, the metal paste19may contain approximately 65% by mass of silver (Ag) particles, approximately 28% by mass of copper (Cu) particles, and the remaining percentage by mass composed of a mixture of titanium (Ti) particles, silicon dioxide (SiO2) particles, and the solvent18.

Next, as illustrated inFIG. 6D, the sapphire structure11to which the metal paste19is applied is heated to a temperature of 600° C. to 900° C. The solvent18contained in the metal paste19is evaporated, and the metal particles21are bound to each other within the concave portion12. Thus, the metal substructure20is formed, and the metal substructure20is bonded to the inner surface13of the concave portion12.

Because the metal paste19includes copper (Cu), a compound of silver (Ag) and copper (Cu) is formed by firing. Thus, the hardness of the metal substructure20is higher than it would be if the metal paste19contained only silver (Ag). Further, since the metal substructure20contains titanium (Ti), the bonding layer22containing titanium (Ti) as a main component is formed in a bonding area in which the inner surface13is bonded to the metal substructure20by firing. Thus, the metal substructure20and the inner surface13are more strongly bonded to each other. Further, since the metal paste19contains silicon dioxide (SiO2), the silicon dioxide (SiO2) ingredients are diffused to the sapphire structure11by firing, and the bonding strength between the metal substructure20and the sapphire structure11is increased. After firing, the entire body is washed using an organic solvent, pure water, or the like as needed.

As illustrated byFIG. 6E, subsequently at least part of the surface20A of the metal substructure20is made substantially flush with the flat surface11A by polishing the flat surface11A and the surface portion20A of the metal substructure20. The polishing process includes a first step of polishing only the flat surface11A and a second step of polishing both the flat surface11A and the metal substructure20at the same time. In the first step, the flat surface11A is polished but the metal substructure20is not polished. In the second step, the flat surface11A and the metal substructure20are polished at the same time.

In the first step, mechanical polishing is performed using a copper plate as a polishing pad and diamond abrasive grains having a grain size of approximately 1 μm to 3 μm as abrasive grains for polishing. In the first step, only a portion of the flat surface11A which protrudes further than the surface portion20A of the metal substructure20is selectively polished so that the flat surface11A after polishing becomes substantially flush with the surface portion20A of the metal substructure20.

After the first step, chemical mechanical polishing (so-called CMP) is performed using colloidal silica abrasive grains having a grain size of approximately 20 μm to 80 μm as abrasive grains for polishing. In the chemical mechanical polishing, both the flat surface11A of the sapphire structure11and the surface portion20A of the metal substructure20are polished at the same time.

The flat surface11A of the sapphire structure11made of a single crystal of alumina is flattened with high precision by the chemical mechanical polishing. For example, the arithmetic average roughness of the flat surface11A of the sapphire structure11can be made to be10nm or less by the chemical mechanical polishing and, it is possible for the arithmetic average roughness of the flat surface11A can be made to be 1 nm or less.

The metal substructure20is a layer obtained by metal particles17in the metal paste19described above being bound to each other, and as polishing advances, the metal particles21are partially peeled off by the chemical mechanical polishing. Therefore, even after the chemical mechanical polishing there is unevenness present in the surface portion20A of the metal substructure20due to the shape of the metal particles21, and the arithmetic average roughness (Ra) of the surface portion20A, which is substantially flush with the flat surface11A, is greater than the arithmetic average roughness (Ra) of the flat surface11A.

The structure10with a metal substructure may be produced by performing the above-described processes. In addition, the above-described processes may be used to form the through-hole15and the via conductor17. First the through-hole15is formed. Then the through-hole15is filled with the metal paste19using the same methods described above to apply the metal paste19to the concave portion12in order to form the via conductor17. The production method of the present invention is not particularly limited in regard to other conditions or the like.

FIGS. 7 to 10are views illustrating the external appearance of the electronic apparatus configured using an embodiment of the sapphire structure with a metal substructure described above, andFIG. 7is a perspective view,FIG. 8is a front view,FIG. 9is a rear view, andFIG. 10is an exploded perspective view. An electronic apparatus101as illustrated byFIGS. 7 through 10is a mobile phone such as a smart phone, and the electronic apparatus10can communicate with another communication device via a base station, a server, and the like. The shape of the electronic apparatus101is a rectangular plate-like shape in a plan view or top view. An exterior body300of the electronic apparatus101is configured of a first surface panel102, a housing103, and a rear surface side panel104.

The first surface panel102contains a transparent hard material. The first surface panel102contains sapphire as a main component. Sapphire has the characteristics of being difficult to damage or break, having high transparency, and having high thermal conductivity when compared to strengthened glass or the like.

As illustrated byFIG. 7, the first surface panel102includes a display area102aand a peripheral edge area102b. Various pieces of information such as characters, symbols, figures, and moving images displayed by a display device112described below are visually recognized by a user through the display area102ain the first surface panel102.

A touch panel113described below is attached to an inner surface171of the first surface panel102. The user can issue various instructions with respect to the electronic apparatus101by operating the display area102aof the first surface panel102using a finger or the like. Further, as illustrated inFIG. 8, a piezoelectric vibrating element114and a microphone115are attached to the inner surface171of the first surface panel102.

The housing103constitutes part of the side surface portion of the electronic apparatus101. The housing103contains sapphire as a main component similarly to the first surface panel102.

As illustrated byFIG. 11A, the rear surface panel104is a sapphire structure with a metal substructure as described above. The rear surface panel104includes a first surface172, a sapphire structure140in which a concave portion141is on the first surface172, and a metal substructure142arranged in the concave portion141and bonded to an inner surface143of the concave portion141.

As illustrated byFIG. 11B, the metal substructure142includes a surface portion142A which is substantially flush with the flat surface. The rear surface side panel104is plate-like and has a rectangular shape in a plan view or top view. The rear surface panel104constitutes the rear surface portion of the electronic apparatus101. As shown byFIG. 11A, the rear surface panel104includes a first surface172constituting the rear surface of the electronic apparatus101and a second surface173positioned on the opposite side to the first surface172. In the present embodiment, the metal substructure142contains antenna105(or alternatively, antennas105aand105b) and the terminal106for charging.

FIG. 10is an exploded perspective view of the electronic apparatus101. The first surface panel102and the housing103are bonded to each other.

In addition, in the same manner as bonding of the first surface panel102and the housing103, the housing103and the rear surface panel104are bonded to each other.

The exterior body300includes three members which are the first surface panel102, the housing103, and the rear surface side panel104. The exterior body300may include one, two, four or more members.

The touch panel113, the piezoelectric vibrating element114, and the microphone115are attached to the inner surface171of the first surface panel102using a double-sided tape or the like. The display device112is arranged so as to face the first surface panel102and the touch panel113(more specifically, the first surface panel102to which the touch panel113is attached).

A printed board117and a battery116are arranged on the rear surface of the display device112. Various components such as a CPU201and a DSP202are installed on a printed board117. The printed board117is electrically connected to other components included in the electronic apparatus101by a cable. In addition, the rear surface panel104is arranged so as to face the printed board117and the battery116. The battery116is connected with a terminal106for charging by a conductor embedded in the rear surface side panel104.

In this manner, the exterior body300accommodates electronic devices such as the CPU201and the DSP202. The devices in the exterior body300generate heat during operation in some cases. However, sapphire contained in the exterior body300has high heat dissipation when compared to an exterior body that is at least partially made of resin. For this reason, heat emitted from the device during the operation of the device can be efficiently dissipated to the outside of the electronic apparatus101through the exterior body300. As a result, in the electronic apparatus101, it is possible to suppress any rise in temperature of the devices contained in the exterior body300and also suppress the rise in temperature in the exterior body300. Accordingly, the likelihood that the electronic apparatus101will experience an operation failure due to high temperature can be reduced.FIG. 11Ais a perspective view when the rear surface panel104is seen from the inside of the housing103, andFIG. 11Bis a cross-sectional view taken along a plane containing a B-B line.

As illustrated byFIG. 9, the metal substructure142, which includes a surface that is flush with the first surface172, is arranged on the rear surface of the electronic apparatus101. The metal substructure142contains antenna105(or alternatively, antennas105aand105b) and the terminal106for charging. An imaging unit107is arranged on the second surface173of the rear surface side panel104. The imaging unit107includes a lens107afacing the second surface173. Because sapphire has the property of high light transmission and because the rear surface panel104is a sapphire structure, the imaging unit107in the exterior body300is capable of performing photography. A communication circuit component118is arranged on the second surface173.

As illustrated inFIGS. 11A and 11B, the rear surface side panel104includes a through-hole175including openings on a bottom surface141α of the concave portion141and the second surface173. Further, the rear surface panel104includes a via conductor217which fills in the through-hole175and includes a metal. In the embodiment illustrated inFIGS. 11A and 11B, the antenna105ais exposed to the surface of the electronic apparatus101, and the metal substructure142constituting the antenna105ais electrically connected to a communication circuit component118or the like arranged on the second surface173side through the via conductor217. The terminal106is exposed to the surface of the electronic apparatus101, and the metal substructure142constituting the terminal106is electrically connected to a power terminal or the like (not illustrated) arranged on the second surface173side through the via conductor217.

In the electronic apparatus101, since the rear surface panel104contains sapphire as a main component, the rear surface panel104has high thermal conductivity. Thus, heat emitted by various devices or electronic circuits arranged in the exterior body300can be efficiently dissipated from the inside of the exterior body300. Since sapphire has low electrical resistance, current leakage from the antenna105or the terminal106arranged in the rear surface side panel104is small. Thus, electronic apparatus101is less likely to malfunction. The rear surface panel104includes the first surface172and has a light transmission property. The metal substructure142has a metallic glossiness. The first surface172is substantially flush with the surface of the metal substructure so that the appearance of the electronic apparatus101is unique and different from that of a conventional apparatus.

The electronic apparatus101has high transmitting and receiving sensitivity of the wireless signal because of the antenna105, is less likely to have malfunctions caused by the dark current, is difficult to be broken because of high strength of the exterior body300, and has a unique appearance that lends itself to design.

FIGS. 12A and 12Billustrate another embodiment in which the sapphire structure with a metal substructure described above is used for the electronic apparatus.FIGS. 12A and 12Bare schematic views describing a mounting body600.FIG. 12Ais a plan view or top view andFIG. 12Bis a cross-sectional view. The mounting body600includes a mount board620including a first surface620A and a concave portion622on the first surface620A. A metal substructure630is arranged in the concave portion622and is bonded to the inner surface of the concave portion622. The metal substructure630includes a surface which is substantially flush with the first surface620A.

The metal substructure630contains silver (Ag) as a main component. In addition, the metal substructure20contains copper (Cu) and titanium (Ti). Further, the mount board620includes a through-hole625and a via conductor627. The through-hole625has openings on the bottom surface of the concave portion622and on a second surface620B. The via conductor627fills in the through-hole625and includes a metal.

In the mounting body600, a wireless communication unit510and the control unit500are arranged on the mount board620. The control unit500includes the CPU500a, the storage unit500b, and the like. In the control unit500, the CPU500aand the storage unit500bare mounted on the second surface620B. In addition, the wireless communication unit510on the first surface620A includes an antenna510aand a wireless information processing unit510b. The antenna510includes the metal substructure630, and the wireless information processing unit510bis mounted on the mount board620. The wireless information processing unit510b, the CPU500a, and the storage unit500bare devices including semiconductor elements. In the mounting body600, the metal substructure630constitutes the antenna510b. The CPU500a, the storage unit500b, and the wireless information processing unit510bare connected to one another using the metal substructure630or the via conductor627as electrical wiring.

The mount board620has high thermal conductivity because the mount board620is made of sapphire. Thus when heat is emitted from the wireless communication unit510or the control unit500, this heat can be efficiently dissipated through the mount board620. Since sapphire has low electrical resistance, a dark current flowing over the surface of the mount board620is suppressed and so therefore is small. Thus, the CPU500a, the storage unit500b, and the wireless information processing unit510bis less likely to malfunction due to heat emissions or dark currents.

The wireless information processing unit510b, the CPU500a, and the storage unit500bare not limited to device components including semiconductor elements. They may be integrally formed on the mount board620by performing processing on a compound semiconductor layer which is formed on the mount board620made of sapphire. The mounting body600illustrated inFIG. 12Amay be arranged in the inside of the exterior body300of the electronic apparatus101, for example.

<Electrical Configuration of Electronic Apparatus>

FIG. 13is a block diagram illustrating the electrical configuration of the electronic apparatus101. As illustrated inFIG. 13, the electronic apparatus101includes a control unit110, a wireless communication unit111, a display device112, a touch panel113, a piezoelectric vibrating element114, a microphone115, an imaging unit107, and a battery116. These constituent elements in the electronic apparatus101are accommodated in the exterior body300of the electronic apparatus101.

The control unit110includes a Central Processing Unit (CPU)201, a Digital Signal Processor (DSP)202, a storage unit203, and the like. The control unit110manages the overall operation of the electronic apparatus101by controlling other constituent elements of the electronic apparatus101. The storage unit203may include a Read Only Memory (ROM), a Random Access Memory (RAM), and the like. Main programs, a plurality of application programs, and the like are stored in the storage unit203and are control programs for controlling the electronic apparatus101. Specifically, the control programs control respective constituent elements such as the wireless communication unit11and the display device12included in the electronic apparatus101. Various functions of the control unit110can be realized by the CPU201and the DSP202executing various programs in the storage unit203.

The wireless communication unit111includes antennas105(antennas105aand105b). The wireless communication unit111receives or transmits a communication signal from/to a mobile phone other than the electronic apparatus101or a communication device such as a web server connected to the Internet using an antenna105via a base station or the like.

In the present embodiment, the antenna105is included in the rear surface panel104. However, the antenna105may be arranged in the exterior body300. Since the sapphire has a low dielectric loss in a high frequency area, transparency of the high frequency wireless signal in the exterior body300is improved when the exterior body300(including first surface panel102, the housing103, and the rear surface side panel104) of the electronic apparatus101is a sapphire member. Therefore, when the antenna105receiving a high frequency wireless signal is arranged in the exterior body300, the degree of freedom of the arrangement location of the antenna105in the exterior body300is improved.

The display device112is, for example, a liquid crystal display or an organic EL display. As described above, various pieces of information displayed by the display device112are visually recognized from the outside of the electronic apparatus101through the display area102a.

The touch panel113is, for example, a projection type electrostatic capacitance touch panel. The touch panel113is attached to the inner surface171of the first surface panel102. The touch panel113includes two sheet-like electrode sensors which are arranged so as to face each other. When the user touches the display area102ausing an operator such as a finger or the like, the electrostatic capacitance of the portion facing the operator in the touch panel113is changed. Further, the touch panel113outputs an electrical signal according to the change of the electrostatic capacitance to the control unit110. In this manner, the touch panel113can detect contact with respect to the display area102aof the operator.

The piezoelectric vibrating element114and the microphone115are attached to the inner surface171of the first surface panel102. The piezoelectric vibrating element114is vibrated by a driving voltage applied from the control unit110. The control unit110generates a driving voltage based on a sound signal and applies the driving voltage to the piezoelectric vibrating element114. The first surface panel102is vibrated based on the sound signal by the piezoelectric vibrating element114being vibrated based on the sound signal by the control unit110. As a result, a reception sound is transmitted to the user from the first surface panel102. The volume of the reception sound is set to a degree such that the user can appropriately hear the sound when the first surface panel102is set close against an ear of the user. Details of the piezoelectric vibrating element114and the reception sound transmitted to the user from the first surface panel102will be described below in detail.

Further, a case in which the reception sound is transmitted to the user from the first surface panel102by the piezoelectric vibrating element114will be described below, but a dynamic speaker that converts the electric sound signal from the control unit110into a sound and then outputs the sound may be adopted instead of the piezoelectric vibrating element114. In the case of adopting the dynamic speaker, receiver holes are provided in the exterior body300. The sound output from the dynamic speaker is output to the outside from the receiver holes provided on the exterior body300. Since sapphire is hard as described above, a process of providing a through-hole such as a receiver hole in the exterior body300made of sapphire is difficult to perform. Therefore, the number of processes on the exterior body300for providing the receiver hole is reduced by adopting the piezoelectric vibrating element114in which the receiver hole is not necessary to the electronic apparatus101. As a result, the electronic apparatus101can be easily produced. Further, the exterior body300becomes weak by receiver hole being provided. However, in a case where the piezoelectric vibrating element114is adopted, since the receiver hole is not necessary in the exterior body300, the strength of the exterior body300can be maintained.

The microphone115converts vibration of the first surface panel102into the electrical signal and outputs the converted signal to the control unit110. The vibration of the first surface panel102generates by the voice or the like of the user during communication on the phone or the like.

Further, the microphone115may not convert the vibration of the first surface panel102into the electrical signal. The microphone115may convert air vibration such as the voice or the like of the user directly into an electrical signal and output the converted signal in the control unit110. In this case, a microphone hole is provided in the exterior body300. The voice or the like of the user is incorporated in the inside of the electronic apparatus101from the microphone hole and input to the microphone115.

The imaging unit107images a still image and a moving image. The battery116outputs power of the electronic apparatus101. The power output from the battery116is supplied to each of the electronic components included in the control unit110, the wireless communication unit111, and the like included in the electronic apparatus101.

FIGS. 14A,14B14C and14D are respectively a top view and side views illustrating a structure of the piezoelectric vibrating element114. As illustrated inFIGS. 14A and 14B, the piezoelectric vibrating element114has a long shape in one direction. Specifically, the piezoelectric vibrating element114has a long and narrow rectangular plate shape in a plan view. The piezoelectric vibrating element114has, for example, a bimorph structure and includes a first piezoelectric ceramic plate114aand a second piezoelectric ceramic plate114bwhich are attached to each other through a shim material114c.

In the piezoelectric vibrating element114, when a positive voltage is applied to the first piezoelectric ceramic plate114aand a negative voltage is applied to the second piezoelectric ceramic plate114b, the first piezoelectric ceramic plate114aextends along the longitudinal direction and the second piezoelectric ceramic plate114bcontracts along the longitudinal direction. Accordingly, as illustrated inFIG. 14C, the piezoelectric vibrating element114is bent into a convex shape with the first piezoelectric ceramic plate114abeing outside.

In contrast, in the piezoelectric vibrating element114, when a negative voltage is applied to the first piezoelectric ceramic plate114aand a positive voltage is applied to the second piezoelectric ceramic plate114b, the first piezoelectric ceramic plate114acontracts along the longitudinal direction and the second piezoelectric ceramic plate114bextends along the longitudinal direction. Accordingly, as illustrated inFIG. 14D, the piezoelectric vibrating element114is bent into a convex shape with the second piezoelectric ceramic plate114bbeing outside.

The piezoelectric vibrating element114vibrates while being bent by alternatively taking the state ofFIG. 14Cand the state ofFIG. 14D. The control unit110allows the piezoelectric vibrating element114to vibrate while being bent by applying an AC voltage in which the positive voltage and the negative voltage alternatively appear at an area between the first piezoelectric ceramic plate114aand the second piezoelectric ceramic plate114b.

FIGS. 14A to 14Dillustrates one structure made of the first piezoelectric ceramic plate114aand the second piezoelectric ceramic plate114bwhich are bonded to each other by interposing the shim material114ctherebetween in the piezoelectric vibrating element114. However, a plurality of the structures may be laminated to each other.

<Regarding Generation of Reception Sound Due to>Vibration of Piezoelectric Vibrating Element

In the present embodiment, an air conduction sound and a conduction sound are transmitted to the user from the first surface panel102via the vibration of the piezoelectric vibrating element114. That is, the vibration of the piezoelectric vibrating element114is transmitted to the first surface panel102so that the air conduction sound and the conduction sound are transmitted to the user from the first surface panel102.

Here, the term “air conduction sound” means a sound recognized in a human brain by the vibration of an eardrum due to a sound wave (or air vibration) which enters an external auditory meatus hole (a so-called also known as an “ear hole”). On the other hand, the term “conduction sound” is a sound recognized in a human brain by the vibration of the eardrum due to the vibration of an auricle transmitted to the eardrum. Hereinafter, the air conduction sound and the conduction sound will be described in detail.

FIG. 15is a view for describing the air conduction sound and the conduction sound.FIG. 15illustrates a structure of an ear of the user of the electronic apparatus101. InFIG. 15, a wavy line800indicates a conduction path of a sound signal (sound information) of the air conduction sound. A solid line810indicates the conduction path of the sound signal of the conduction sound.

When the piezoelectric vibrating element114mounted to the first surface panel102vibrates based on the electric sound signal indicating the reception sound, the first surface panel102vibrates and a sound wave is outputted from the first surface panel102. When the user moves the first surface panel102of the electronic apparatus101close to an auricle700of the user by holding the electronic apparatus101in a hand or the first surface panel102of the electronic apparatus101is put to the auricle700of the user, the sound wave output from the first surface panel102enters an external auditory meatus hole710. The sound wave from the first surface panel102enters in the external auditory meatus hole710and the eardrum720vibrates. The vibration of the eardrum720is transmitted to an auditory ossicle730and the auditory ossicle730vibrates. In addition, the vibration of the auditory ossicle730is transmitted to a cochlea740and is converted into an electrical signal in the cochlea740. The electrical signal is transmitted to the brain by passing through an acoustic nerve750and the reception sound is recognized in the brain. In this manner, the air conduction sound is transmitted from the first surface panel102to the user.

When the user puts the first surface panel102of the electronic apparatus101to the auricle700of the user by holding the electronic apparatus101in a hand, the auricle700is vibrated by the first surface panel102which is vibrated by the piezoelectric vibrating element114. The vibration of the auricle700is transmitted to the eardrum720, and thus the eardrum720vibrates. The vibration of the eardrum720is transmitted to the auditory ossicle730, and thus the auditory ossicle730vibrates. The vibration of the auditory ossicle730is transmitted to the cochlea740and is converted into an electrical signal in the cochlea740. The electrical signal is transmitted to the brain by passing through the acoustic nerve750and the reception sound is recognized in the brain. In this manner, the conduction sound is transmitted from the first surface panel102to the user.FIG. 153illustrates an auricular cartilage700ain the inside of the auricle700.

In addition, the conduction sound herein is different from a bone conduction sound (also referred to as a “bone conduction sound”). The bone conduction sound is a sound recognized in a human brain by the vibration of the skull and direct stimulation of the inner ear such as the cochlea caused by the vibration of the skull. InFIG. 15, in a case of vibrating the jawbone900, the transmission path of the sound signal while the bone conduction sound is recognized in the brain is indicated with a plurality of arcs820.

In this manner, in the electronic apparatus101according to the present embodiment, the air conduction sound and the conduction sound can be transmitted from the first surface panel102to the user of the electronic apparatus101due to the vibration of the first surface panel102through the vibration of the piezoelectric vibrating element114. Since the user can hear a sound when the user puts the first surface panel102to the auricle700of the user, the communication using a telephone can be performed without concerning the position of the electronic apparatus101put against an ear so much. In addition, the user can hear the conduction sound due to the vibration of the auricle, the electronic apparatus101makes it easy for the user to hear the sound even when there is a large amount of the ambient noise. Accordingly, the user can appropriately perform communication using a telephone even when there is a large amount of the ambient noise.

In addition, even in a state in which earplugs or earphones are fixed to the ears of the user, the reception sound from the electronic apparatus101can be recognized by putting the first surface panel102to the auricle700. Further, even in the state in which headphones are fixed to the ears of the user, the reception sound from the electronic apparatus101can be recognized by putting the first surface panel102to the headphones.

In the above-described embodiment, a case of a mobile phone case to which the present invention is applied is described as an embodiment. However, the present invention can be applied to an electronic apparatus other than the mobile phone. For example, embodiments may be applicable to tablets, e-Readers, digital cameras, electronic game machines, digital music players, personal digital assistants (PDAs), personal handy phone system (PHS), laptop computers, portable TV's, Global Positioning Systems (GPS's) or navigation systems, machining tools, pedometers, health equipment such as weight scales, display monitors, smartwatches, wearables, and the like. In addition, the present invention is not limited to the above-described embodiments, and various modifications and changes may be made in the range not departing from the scope of the present invention.