Mobile electronic device and method for waterproofing mobile electronic device

A mobile electronic device includes: a housing; an acoustic-component contained in the housing; a sound hole formed in the housing, the sound hole being configured to allow communication between an inside and an outside of the housing; a non-breathable waterproof film disposed inside the housing, the waterproof film being configured to cover the sound hole; a compressible member compressed by being pressed against the housing during assembly of the acoustic-component to the housing, the compressible member being configured to form an acoustic-component chamber together with at least the waterproof film, the acoustic-component chamber being configured to hermetically seal the acoustic-component; and an opening configured to allow communication between an inside and an outside of the acoustic-component chamber within the housing, the opening being configured to allow air in the acoustic-component chamber to escape to the outside before the opening is closed in the process of compressing the compressible member.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2013-074982, filed on Mar. 29, 2013, the entire contents of which are incorporated herein by reference.

FIELD

The embodiments discussed herein are related to a mobile electronic device and a method for waterproofing the mobile electronic device.

BACKGROUND

Mobile electronic devices that are portable outdoors, such as mobile phones, notebook computers, and tablet computers, may include acoustic components, such as a microphone and a speaker. In assembly of such an acoustic component to a housing, a compressible member made of a compressible material, such as rubber or polyurethane foam, may be placed between the housing and the acoustic component or a substrate for mounting the acoustic component, so that the acoustic component is assembled while the compressible member is being compressed. By assembling the acoustic component in this manner, it is possible to cut off an acoustic component chamber containing the acoustic component from the other space in the housing, and improve airtightness of the acoustic component chamber. This makes it possible to reduce leakage of sound from the acoustic component chamber, reduce entry of noise from the other space in the housing into the acoustic component chamber, and improve sensitivity of the acoustic component.

In a mobile electronic device including an acoustic component as described above, a device case (housing) is provided with a sound hole which allows input of sound from the outside into the acoustic component and output of sound to the outside. The sound hole is covered with a protective sheet having a waterproof and dustproof function.

A related technique has been proposed in which a sound hole in a housing is covered with a porous protective sheet, so as to ensure breathability (gas permeability) and waterproof and dustproof performance. However, for example, if the electronic device has been dropped in water many times, clogging or crystallization may occur in micropores of the porous protective sheet. For example, if the porous protective sheet is clogged with a surface-active agent or the surface-active agent is crystallized, the surface-active agent may be dissolved when the electronic device is dropped in water later on. As a result, the waterproof function of the porous protective sheet may be lost. Crystallization of seawater may also cause loss of the waterproof function of the porous protective sheet.

Related technique is disclosed in, for example, Japanese Laid-open Patent Publication Nos. 2007-37189, 2010-41671, and 2008-278064.

To ensure the waterproof function even if the electronic device has been dropped in water many times, the sound hole in the device case may be covered with a non-breathable protective sheet. However, in this instance, there is nowhere for air in the acoustic component chamber to escape.

Therefore, the resulting increase in internal pressure of the acoustic component chamber during assembly of the acoustic component to the housing may damage, for example a diaphragm (vibrating plate) of the acoustic component. The increased pressure in the acoustic component chamber may cause displacement of the diaphragm of the acoustic component, degrade sensitivity of the acoustic component, and lead to production variations.

SUMMARY

According to an aspect of the invention, A mobile electronic device includes: a housing; an acoustic-component contained in the housing; a sound hole formed in the housing, the sound hole being configured to allow communication between an inside and an outside of the housing; a non-breathable waterproof film disposed inside the housing, the waterproof film being configured to cover the sound hole; a compressible member compressed by being pressed against the housing during assembly of the acoustic-component to the housing, the compressible member being configured to form an acoustic-component chamber together with at least the waterproof film, the acoustic-component chamber being configured to hermetically seal the acoustic-component; and an opening configured to allow communication between an inside and an outside of the acoustic-component chamber within the housing, the opening being configured to allow air in the acoustic-component chamber to escape to the outside before the opening is closed in the process of compressing the compressible member.

DESCRIPTION OF EMBODIMENTS

Mobile electronic devices and methods for waterproofing the same according to embodiments will now be described in detail with reference to the drawings.

Embodiments

FIG. 1is a cross-sectional view of a mobile phone1serving as a mobile electronic device according to an embodiment. The mobile phone1in the present embodiment is an example of the mobile electronic device. The mobile phone1includes a device case10that contains various components. The device case10has a front case11and a rear case12, each of which may be molded of a synthetic resin, such as polycarbonate or acrylonitrile butadiene styrene (ABS) resin. The front case11and the rear case12are coupled to each other, with a waterproof gasket13sandwiched therebetween. The device case10is an example of a housing.

The front case11has a liquid-crystal display panel14. A touch panel module14ais disposed on the back side of the liquid-crystal display panel14and functions as an operation input unit. The front case11is provided with a first speaker sound hole15and a microphone sound hole16at its end portions in the longitudinal direction. The first speaker sound hole15and the microphone sound hole16are for use in a call function. The first speaker sound hole15is located at one end of the front case11in the longitudinal direction, and the microphone sound hole16is located at the other end of the front case11in the longitudinal direction. The first speaker sound hole15and the microphone sound hole16are formed to pass through the front case11and allow communication between the inside and the outside of the device case10. The rear case12is provided with a second speaker sound hole17, which allows communication between the inside and the outside of the device case10.

A battery holder formed inside the rear case12contains a battery2. There is a removable battery cover (not illustrated) at a position corresponding to the battery holder in the rear case12. The battery2is made accessible by removing the battery cover. The battery2is a power source for driving the mobile phone1.

The device case10contains a control board3, a microphone4, a first speaker5, and a second speaker6. The microphone4is an acoustic component that converts sound into an electrical signal. In the present embodiment, the microphone4converts sound obtained through the microphone sound hole16into an electrical signal. The microphone4is mounted on, and electrically connected to, the control board3.

The control board3is disposed in the planar direction of the front case11and the rear case12. The microphone4is mounted on a surface of the control board3facing the front case11. The microphone4has a sound receiving diaphragm (vibrating plate)41for receiving sound. The diaphragm41is disposed to face the microphone sound hole16in the front case11. The microphone4detects displacement of the diaphragm41that vibrates in response to the pressure of sound that has entered the case through the microphone sound hole16. Then, the microphone4converts the received sound into an electrical signal.

In the mobile phone1according to the present embodiment, a compressible member7made of a compressible material is disposed inside the device case10. The microphone4mounted on the control board3is covered with the compressible member7. Specifically, the compressible member7has a first compression portion71and a second compression portion72. After assembly of the microphone4, the compressible member7is in a compressed state between an inner surface11aof the front case11and a mounting surface3aof the control board3on which the microphone4is mounted. Thus, since the compressible member7is flatter than it originally was, it is possible to ensure high airtightness of a microphone chamber18(described below) that contains the microphone4, and improve sensitivity of the microphone4.

The mobile phone1has a waterproof and dustproof structure for reducing entry of water and dust through the microphone sound hole16into the device case10.FIGS. 2 and 3are each an exploded perspective view schematically illustrating a waterproof structure of the microphone4. The first compression portion71of the compressible member7is substantially in the shape of a rectangular parallelepiped and is made of a compressible material, such as polyurethane foam. The first compression portion71has a through hole71athat passes therethrough in the thickness direction thereof. A waterproof film73is provided to close the through hole71a. The waterproof film73is a waterproof sheet having non-breathability and sound transmission characteristics. For example, the waterproof film73is made of polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP). As illustrated inFIG. 1, the waterproof film73is disposed at a position corresponding to the microphone sound hole16so as to cover the microphone sound hole16.

One principle surface of the first compression portion71is referred to as a “first principal surface71b”, and the other principal surface of the first compression portion71is referred to as a “second principal surface71c”. The first principal surface71bof the first compression portion71is disposed to face the inner surface11aof the front case11. As illustrated inFIG. 1, the first principal surface71bof the first compression portion71is bonded to the inner surface11aof the front case11with a double-sided tape74therebetween. This secures the first compression portion71to the front case11. Since the waterproof film73held by the first compression portion71is located to coincide with the microphone sound hole16in the front case11, it is possible to reduce entry of water and dust through the microphone sound hole16into the microphone chamber18.

The second compression portion72of the compressible member7is made of a compressible material, such as rubber. The second compression portion72has a first pad72athat faces the second principal surface71cof the first compression portion71, a second pad72bthat faces the mounting surface3aof the control board3having the microphone4mounted thereon, and a peripheral wall72cthat connects the first pad72ato the second pad72b. The first pad72aof the second compression portion72is substantially rectangular in outer shape and has substantially the same size as that of the second principal surface71cof the first compression portion71. The first pad72aof the second compression portion72and the second principal surface71cof the first compression portion71are pressed against each other. The first pad72aof the second compression portion72is provided with a through hole72dthat passes through the first pad72ain the thickness direction. The through hole72dallows sound that has entered the device case10through the microphone sound hole16to pass through.

As illustrated inFIG. 2, the second pad72bof the second compression portion72has a flat annular shape. The peripheral wall72cof the second compression portion72extends substantially vertically from both the first pad72aand the second pad72b. The first pad72aand the second pad72bare connected to each other by the peripheral wall72c. The second pad72bof the second compression portion72is attached with a double-sided tape75to the mounting surface3aof the control board3while being pressed against the mounting surface3a.

In the mobile phone1, the microphone chamber18that hermetically contains the microphone4is formed (defined) by the compressible member7(having the first compression portion71and the second compression portion72), the waterproof film73, and the mounting surface3aof the control board3. This allows the microphone chamber18to be cut off from the other space in the device case10. The microphone chamber18is an example of an acoustic component chamber. The front case11and the control board3are fastened together with fastening members, such as fixing screws (not illustrated). Fastening the control board3to the front case11secures the microphone4to the front case11. In the process of tightening the fixing screws, a compressive force acts on the compressible member7(having the first compression portion71and the second compression portion72), so that the compressible member7is compressed by a predetermined amount in the thickness direction.

The control board3is provided with an air escape hole3bnear the microphone4. The air escape hole3bis a through hole that passes through the control board3in the thickness direction. The air escape hole3bin the control board3is located in a region inside the microphone chamber18. As illustrated inFIG. 1, after assembly of the microphone4, the air escape hole3bin the control board3is closed by a cover member3c. For example, the cover member3cmay be an adhesive or an adhesive tape attached to a back surface3dof the control board3opposite the mounting surface3aso as to close the air escape hole3b.

Sound that has entered the microphone chamber18from the outside through the microphone sound hole16is obtained by the microphone4and converted into an electrical signal. In the mobile phone1of the present embodiment, after assembly of the microphone4, the compressible member7is in a compressed state and high airtightness of the microphone chamber18may be ensured. It is thus possible to improve sensitivity of the microphone4.

Next, the first speaker5and the second speaker6in the mobile phone1will be described. The first speaker5and the second speaker6are each an acoustic component that converts an electrical signal into sound, and are electrically connected via a wiring cable (not illustrated) to the control board3. In the present embodiment, the first speaker5functions as a speaker that outputs voice for reception in the mobile phone1. Sound output from the first speaker5is emitted through the first speaker sound hole15to the outside. The second speaker6functions as a speaker that outputs bell sound or voice for a so-called hands-free call of the mobile phone1. Sound output from the second speaker6is emitted through the second speaker sound hole17to the outside.

The first speaker5and the second speaker6have the same structure, and each include a magnet81, a coil82, and a diaphragm (vibrating plate)83. The coil82is placed around the magnet81and secured to the diaphragm83having a thin-plate shape. The diaphragm83vibrates when current including a sound signal is applied through the control board3to the coil82. This changes air pressure and produces sound. The sound output from the first speaker5is emitted through the first speaker sound hole15to the outside. Similarly, sound output from the second speaker6is emitted through the second speaker sound hole17to the outside. The first speaker5and the second speaker6are each protected by being covered with a speaker cover84. The speaker cover84is substantially in the shape of a rectangular parallelepiped in the present embodiment, but may be of other shapes.

The front case11has a first rib11bthat surrounds the first speaker sound hole15. The first rib11bprotrudes from the inner surface11aof the front case11toward the inside of the device case10. The speaker cover84for the first speaker5is fitted in the first rib11b. Similarly, the rear case12has a second rib12bthat surrounds the second speaker sound hole17. The second rib12bprotrudes from an inner surface12aof the rear case12toward the inside of the device case10. The speaker cover84for the second speaker6is fitted in the second rib12b. Hereinafter, a portion of the speaker cover84that covers the front side of the diaphragm83will be referred to as a front cover portion84a. Although the speaker cover84in the present embodiment is made of stainless steel, other materials may be used to form the speaker cover84. The speaker cover84is provided with a rear sound hole85on the back side thereof. The rear sound hole85is for improved acoustic characteristics of the speaker. Sound having a phase opposite that of sound emitted from the first speaker sound hole15is emitted through the rear sound hole85into the device case10.

The mobile phone1has a waterproof and dustproof structure for reducing the entry of water and dust through the first speaker sound hole15and the second speaker sound hole17into the device case10. As illustrated inFIG. 1, the first speaker5is provided with a waterproof film20and a compressible member21disposed in this order between the inner surface11aand the first rib11bof the front case11. Similarly, the second speaker6is provided with the waterproof film20and the compressible member21disposed in this order between the inner surface12aand the second rib12bof the rear case12. The waterproof films20are each a waterproof sheet having non-breathability and sound transmission characteristics and disposed to cover the first speaker sound hole15or the second speaker sound hole17. Like the waterproof film73described above, the waterproof film20may be made, for example, of polyethylene terephthalate (PET), polyethylene (PE), or polypropylene (PP).

Double-sided tapes20aand20bare attached to both sides (front and back sides) of the edge of the waterproof film20. The inner surface11aof the front case11(or the inner surface12aof the rear case12) is bonded with the double-sided tape20ato the waterproof film20, which is bonded with the double-sided tape20bto the compressible member21.

Like the compressible member7described above, the compressible member21is made of a compressible material, such as polyurethane foam or rubber. As illustrated inFIG. 1, after assembly of the first speaker5and the second speaker6to the device case10, the compressible member21is in a more compressed state (flatter) than it originally was in the thickness direction. Since the compressible member21is thus in a compressed state after assembly of the first speaker5and the second speaker6, it is possible to ensure high airtightness of a speaker chamber19, and improve sensitivity of the first speaker5and the second speaker6. Like the second pad72bof the second compression portion72described above, the compressible member21is annular in plan view. In the mobile phone1, the speaker chamber19that hermetically contains each of the first speaker5and the second speaker6is formed by the compressible member21, the waterproof film20, and the speaker cover84. The speaker chamber19is cut off from the other space in the device case10. The speaker chamber19is an example of the acoustic component chamber.

A process of assembling acoustic components, such as the microphone4, the first speaker5, and the second speaker6, to the device case10will now be described in detail. First, a process of assembling the microphone4will be described. In assembling the microphone4, as illustrated inFIGS. 2 and 3, the first compression portion71of the compressible member7is attached to the inner surface11aof the front case11with the double-sided tape74(seeFIG. 1) therebetween. That is, the first principal surface71bof the first compression portion71is attached with the double-sided tape74to the inner surface11aof the front case11. Additionally, the second compression portion72of the compressible member7is attached with the double-sided tape75to the control board3having the microphone4mounted thereon. Then, the control board3(microphone4) is secured to the front case11by tightening the fixing screws (not illustrated) for fastening the control board3(microphone4) to the front case11.

In tightening the fixing screws for fastening the control board3(microphone4) to the front case11, a compressive force acts on the compressible member7(having the first compression portion71and the second compression portion72), so that the compressible member7is compressed in the thickness direction. Thus, by compressing the compressible member7during assembly of the microphone4, it is possible to enhance hermeticity of the microphone chamber18and improve sensitivity of the microphone4.

Compressing the compressible member7during assembly of the microphone4reduces the capacity of the microphone chamber18. The waterproof film73that covers the microphone sound hole16does not allow air to pass therethrough. This means that if there is nowhere for air (pressure) in the microphone chamber18to escape during assembly of the microphone4, the resulting increase in internal pressure of the microphone chamber18may damage the diaphragm41of the microphone4. The increase in internal pressure of the microphone chamber18may cause continuous displacement of the diaphragm41and this may lead to production variations.

To reduce such problems, in the mobile phone1of the present embodiment, the air escape hole3bin the control board3allows communication between the inside and the outside of the microphone chamber18within the device case10. The air escape hole3bis kept open until it is closed in the process of compressing the compressible member7during assembly of the microphone4, and allows communication between the inside and the outside of the microphone chamber18within the device case10. Therefore, as illustrated inFIG. 4, when the compressible member7is compressed during assembly of the microphone4, air inside the microphone chamber18may escape through the air escape hole3bto the outside of the microphone chamber18within the device case10. It is thus possible to reduce an increase in pressure inside the microphone chamber18, and reduce damage to the diaphragm41of the microphone4. Since it is possible to reduce application of continuous displacement to the diaphragm41during assembly of the microphone4, production variations may be made less likely to occur.

The air escape hole3bin the control board3is closed in the process of compressing the compressible member7during assembly of the microphone4. When there is a predetermined amount by which the compressible member7is to be compressed during assembly of the microphone4, the term “process of compressing” includes not only the state in which the amount of compression of the compressible member7has not yet reached the predetermined amount, but also the state in which the amount of compression of the compressible member7has reached the predetermined amount. For example, the configuration may be made such that the compressible member7is compressed by a predetermined amount at the point when the fixing screws for securing the microphone4to the front case11are fully tightened, and that the air escape hole3bis closed after the amount of compression of the compressible member7reaches the predetermined amount. Alternatively, the air escape hole3bmay be closed before the amount of compression of the compressible member7reaches the predetermined amount. In the present embodiment, as illustrated inFIG. 5, after the compressible member7is compressed until the amount of compression of the compressible member7reaches a predetermined amount, the air escape hole3bis closed by the cover member3c, such as an adhesive seal. The cover member3cmay be attached to the back surface3dof the control board3so as to close the air escape hole3b.

In the present embodiment, in assembling the microphone4to the device case10, before the air escape hole3bis closed in the process of compressing the compressible member7, the compressible member7is compressed while air in the microphone chamber18is being allowed to escape through the air escape hole3bto the outside. Thus, even when a non-breathable sheet is used as the waterproof film73, an excessive increase in pressure in the microphone chamber18during assembly of the microphone4may be reduced. Therefore, it is possible to reduce the occurrence of damage to a component of the microphone4, such as the diaphragm41, during assembly of the microphone4, and to reduce production variations. Note that the term “outside” mentioned above refers to a region which is inside the device case10and outside the microphone chamber18.

As described above, the waterproof film73having non-breathability may be used (that is, damage to components and production variations may be reduced even when such a waterproof film is used) in the present embodiment. Therefore, even if the mobile phone1has been dropped in water many times, a degradation of the waterproof function may be reduced. That is, without using a porous waterproof film, it is possible, during assembly, to allow air in the microphone chamber18to escape to the outside. Therefore, even if the mobile phone1has been dropped in water many times, it is possible not to cause clogging and crystallization in the waterproof film, and degradation of the waterproof function may be reduced.

In the present embodiment, the air escape hole3bis closed by the cover member3cin the process of compressing the compressible member7. Therefore, the mobile phone1may be made available to the user with the air escape hole3bclosed. Since the hermeticity or airtightness of the microphone chamber18may be kept at a high level when the mobile phone1is made available to the user, a high sensitivity of the microphone4may be ensured. In the present embodiment, the air escape hole3bis an example of an opening that allows communication between the inside and the outside of the acoustic chamber space.

A process of assembling the first speaker5and the second speaker6and a method for waterproofing them will now be described. The process of assembling and the method for waterproofing are common to both the first speaker5and the second speaker6, and thus will be described only for the first speaker5. In assembling the first speaker5to the device case10, as illustrated inFIG. 6, the waterproof film20is attached with the double-sided tape20ato the inner surface11aof the front case11so as to cover the first speaker sound hole15. Then, the first speaker5and the compressible member21attached to the front cover portion84aof the speaker cover84are fitted into the first rib11bon the inner surface11aof the front case11.

FIGS. 7 and 8each illustrate a detailed structure of the compressible member21. A surface of the compressible member21facing the front cover portion84aof the speaker cover84will be referred to as a “bottom surface21a”.FIG. 7illustrates the bottom surface21aof the compressible member21.FIG. 8illustrates the compressible member21as viewed from the direction of arrow VIII inFIG. 7. As illustrated inFIGS. 7 and 8, the bottom surface21aof the compressible member21is provided with a communication groove21b, which allows communication between the inside and the outside of the speaker chamber19within the device case10. The communication groove21bof the compressible member21is compressed in the process of compressing the compressible member21. This closes the communication groove21band blocks the communication between the inside and the outside of the speaker chamber19through the communication groove21b.

For example, an end of the first rib11bmay be provided with a locking hook (not illustrated) which is designed to be locked to the back side of the speaker cover84when the amount of compression of the compressible member21reaches a predetermined amount. The communication groove21bin the compressible member21may be configured to be compressed and closed slightly before the amount of compression of the compressible member21reaches the predetermined amount. The timing of closing the communication groove21bin the process of compressing the compressible member21is not limited to that described above, and may be changed as appropriate.

In the present embodiment, in assembling the first speaker5to the device case10, air in the speaker chamber19may be allowed to escape to the outside before the communication groove21bis closed by being compressed in the process of compressing the compressible member21. Note that the term “outside” refers to a region which is inside the device case10and outside the speaker chamber19.FIG. 9illustrates a state before the communication groove21bis closed in the process of compressing the compressible member21. By compressing the compressible member21while allowing air in the speaker chamber19to escape to the outside, it is possible to reduce an excessive increase in pressure in the speaker chamber19during assembly of the first speaker5. Therefore, it is possible to reduce damage to the diaphragm83of the first speaker5. Since it is possible to reduce application of continuous displacement to the diaphragm83during assembly of the first speaker5, production variations may be made less likely to occur. Since a non-breathable sheet may be used as the waterproof film20, even if the mobile phone1has been dropped in water many times, it is possible to reduce degradation of the waterproof function of the first speaker5.

In the present embodiment, an adjustment is made such that the communication groove21bis compressed in the process of compressing the compressible member21. Therefore, the mobile phone1may be made available to the user with the communication groove21bclosed. Since the hermeticity or airtightness of the speaker chamber19may be kept at a high level when the mobile phone1is made available to the user, a high sensitivity of the first speaker5may be ensured. The timing of closing the communication groove21bin the process of compressing the compressible member21may be adjusted, for example, by adjusting the ratio of the depth of the communication groove21bto the thickness of the compressible member21. Alternatively, the timing of closing the communication groove21bmay be adjusted by making the hardness of a region (hereinafter referred to as a “communication-groove region”) of the compressible member21adjacent to the bottom surface21ahaving the communication groove21bin the thickness direction different from the hardness of the other region (hereinafter referred to as a “non-communication-groove region”) of the compressible member21. For example, in the compressible member21, the hardness of the communication-groove region may be made greater than that of the non-communication-groove region. Thus, at an early stage of assembly of the first speaker5, the non-communication-groove region in the compressible member21may be compressed first (selectively). After the non-communication-groove region is compressed, the communication-groove region in the compressible member21is compressed, so that the communication groove21bmay be closed at a final stage of assembly of the first speaker5.

Although the bottom surface21aof the compressible member21is provided with the communication groove21bin the present embodiment, the configuration is not limited to this. For example, the compressible member21may be provided with a through hole in the middle in the thickness direction thereof, the through hole extending in the planar direction the compressible member21. Until the middle of the process of assembling the first speaker5, the communication through the through hole between the inside and the outside of the speaker chamber19within the device case10may be maintained so that the compressible member21is compressed while air in the speaker chamber19is being allowed to escape to the outside. Then, the through hole may be closed by being compressed in the process of compressing the compressible member21. In the present embodiment, the communication groove21bis an example of the opening that allows communication between the inside and the outside of the acoustic chamber space. The bottom surface21aof the compressible member21having the communication groove21bis an example of a pressed surface.

The waterproof structure and the waterproofing method for the second speaker6are the same as those for the first speaker5. Therefore, the description of the functional effects for the first speaker5may be used to describe the second speaker6. The waterproof structure of the microphone4described above may be applied to the waterproof structure of the first speaker5or the second speaker6.

Modifications

A modification of the mobile phone1according to the present embodiment will now be described.FIGS. 10 and 11are each an exploded perspective view schematically illustrating a waterproof structure of the microphone4according to the modification.FIGS. 10 and 11correspond toFIGS. 2 and 3in the embodiment described above. In the present modification, the second compression portion72is provided with a communication groove72ein a bottom surface of the second pad72b. The communication groove72eis formed in the bottom surface of the second pad72bso as to allow communication between the inner and outer peripheries of the second pad72bhaving an annular shape. Here, the bottom surface of the second pad72brefers to a pressed surface pressed against the mounting surface3aof the control board3during assembly of the microphone4. In the present modification, the control board3is not provided with the air escape hole3b.

In the mobile phone1of the present modification, in assembling the microphone4to the device case10, the communication groove72eof the second compression portion72allows communication between the inside and the outside of the microphone chamber18within the device case10until the middle of the process of compressing the compressible member7. An adjustment is made such that the communication groove72eof the second compression portion72is compressed in the middle of the process of compressing the compressible member7. For example, in assembling the microphone4, the communication groove72emay be compressed and closed slightly before the fixing screws for securing the microphone4to the front case11are tightened by a predetermined amount. Thus, as in the embodiments described above, the compressible member7may be compressed while air in the microphone chamber18is being allowed to escape to the outside. It is thus possible to reduce an excessive increase in pressure in the microphone chamber18during assembly of the microphone4. Therefore, it is possible to reduce damage to the diaphragm41in the microphone4, and reduce production variations of the microphone4.

The timing of closing the communication groove72ein the process of compressing the compressible member7is not limited to that described above, and may be changed as appropriate. The timing of closing the communication groove72emay be adjusted by the same technique as in the case of the communication groove21bof the compressible member21. For example, the timing of closing the communication groove72eduring assembly of the microphone4may be adjusted by adjusting the ratio of the depth of the communication groove72eto the thickness of the second compression portion72. Alternatively, the timing of closing the communication groove72emay be adjusted by making the hardness of a region (hereinafter referred to as a “communication-groove region”) of the second compression portion72adjacent to the bottom surface having the communication groove72ein the thickness direction different from the hardness of the other region (hereinafter referred to as a “non-communication-groove region”) of the second compression portion72. For example, in the second compression portion72, the hardness of the communication-groove region may be made greater than that of the non-communication-groove region. Thus, at an early stage of assembly of the microphone4, the non-communication-groove region in the second compression portion72may be compressed first (selectively). After the non-communication-groove region is compressed, the communication-groove region in the second compression portion72is compressed, so that the communication groove72emay be closed at a final stage of assembly of the microphone4.

As described above, in the present modification, an adjustment is made such that the communication groove72eis compressed in the process of compressing the compressible member7. Therefore, the mobile phone1may be made available to the user with the communication groove72eclosed. Since the hermeticity or airtightness of the microphone chamber18may be kept at a high level when the mobile phone1is made available to the user, a high sensitivity of the microphone4may be ensured.

Various changes may be made to the embodiments described above without departing from the scope of the present disclosure. The embodiments and modifications described above may be combined together where possible. In the embodiments described above, the waterproof structure and the waterproofing method of the present disclosure are applied to a mobile phone which is an example of the mobile electronic device. The waterproof structure and the waterproofing method of the present disclosure are applicable to various mobile terminals, such as notebook computers and tablet computers.