CN111836175B

CN111836175B - Micro loudspeaker

Info

Publication number: CN111836175B
Application number: CN202010588119.0A
Authority: CN
Inventors: 肖波; 令狐荣林; 孔晨亮; 章统
Original assignee: AAC Technologies Pte Ltd
Current assignee: AAC Technologies Pte Ltd
Priority date: 2020-06-24
Filing date: 2020-06-24
Publication date: 2021-09-28
Anticipated expiration: 2040-06-24
Also published as: CN111836175A; WO2021258417A1

Abstract

The invention provides a micro loudspeaker, which comprises a shell, a vibration system and a magnetic circuit system, wherein a support plate is arranged in the shell, and a first through hole is formed in the support plate; the vibration system comprises a voice coil, a first vibrating diaphragm, a second vibrating diaphragm, a hollow first connecting piece and a hollow second connecting piece, wherein the first vibrating diaphragm, the diaphragm and the second vibrating diaphragm are sequentially arranged at intervals along the short axis side direction of the voice coil; the first vibrating diaphragm and the second vibrating diaphragm are both fixedly arranged on the shell, the diaphragm is fixedly arranged on the supporting plate and covers the first through hole, and the first vibrating diaphragm is connected with the voice coil; the first vibrating diaphragm, the shell, the supporting plate and the diaphragm are arranged in an enclosing mode to form a first vibrating diaphragm front cavity, a second through hole is formed in the diaphragm, a third through hole is formed in the second vibrating diaphragm, and the first vibrating diaphragm front cavity is communicated with the outside through the hollow structure of the first connecting piece, the second through hole, the hollow structure of the second connecting piece and the third through hole in sequence. The micro loudspeaker provided by the invention can realize stronger bass performance.

Description

Micro loudspeaker

[ technical field ] A method for producing a semiconductor device

The invention relates to the field of electroacoustic conversion, in particular to a miniature loudspeaker.

[ background of the invention ]

In the existing side-sounding micro speaker, the vibration system generally only comprises one vibrating diaphragm arranged on the side surface of the micro speaker, and the arrangement mode enables the effective radiation area of the micro speaker to be limited, so that the performance of bass provided under the same amplitude is limited. That is to say, under the same bass output condition, the setting mode requires that the micro-speaker has higher amplitude, which is not only unfavorable for prolonging the service life of the micro-speaker, but also makes the volume requirement on the back cavity of the mobile phone higher.

Therefore, there is a need to provide a micro-speaker with a new structure to solve the above-mentioned technical problems.

[ summary of the invention ]

The invention aims to provide a micro-speaker, wherein an airflow enhancement system composed of a plurality of sound films is arranged in the micro-speaker, so as to solve the problem that the effective radiation area of the existing side-sounding micro-speaker is limited, so that the performance of providing bass sound under the same amplitude is limited.

The technical scheme of the invention is as follows: the micro loudspeaker comprises a shell with an accommodating space, a vibration system and a magnetic circuit system accommodated in the accommodating space, wherein the shell comprises a first side wall, a second side wall bent and extended from the edge of the first side wall and a supporting plate extended from the second side wall to the accommodating space, and a first through hole is formed in the supporting plate;

the vibration system comprises a voice coil, a first vibrating diaphragm, a second vibrating diaphragm, a hollow first connecting piece and a hollow second connecting piece, wherein the first vibrating diaphragm, the diaphragm and the second vibrating diaphragm are sequentially arranged at intervals along the short axis side direction of the voice coil; a first plane formed by the long axis side and the short axis side of the voice coil is vertical to the plane where the first diaphragm is located, the plane where the diaphragm is located and the plane where the second diaphragm is located;

the first diaphragm and the second diaphragm are fixedly fixed on the second side wall, the diaphragm is fixedly fixed on the supporting plate and covers the first through hole, and the first diaphragm is connected with the voice coil;

the first diaphragm and the second side wall, the support plate and the diaphragm are arranged in an enclosing manner to form a first diaphragm front cavity, a second through hole is formed in the diaphragm, a third through hole is formed in the second diaphragm, the first diaphragm front cavity sequentially passes through the hollow structure of the first connecting piece, and the second through hole, the hollow structure of the second connecting piece and the third through hole are communicated with the outside;

the second diaphragm, the second side wall, the support plate, the diaphragm and the outer peripheral wall of the second connecting piece are arranged in a surrounding mode to form a closed second diaphragm rear cavity;

the magnetic circuit system comprises a first magnet assembly and a second magnet assembly which are arranged at intervals along the direction vertical to the first plane, and the voice coil is arranged between the first magnet assembly and the second magnet assembly.

Preferably, the first connecting piece includes a hollow supporting column, a first fixing portion bent and extended from an edge of the supporting column, and two second fixing portions relatively spaced apart from an end of the supporting column far away from the first fixing portion, and the second fixing portions include a supporting arm extended from the edge of the supporting column and a supporting table bent and extended from the end of the supporting arm far away from the supporting column; the first fixing portion is sandwiched between the support column and the inner peripheral side of the diaphragm, and the support table is sandwiched between the support arm and the inner peripheral side of the first diaphragm.

Preferably, the outer circumferential side cover of the diaphragm is provided in the first through hole, and the inner circumferential side of the diaphragm is interposed between the first connecting member and the second connecting member; the second through hole is arranged on the inner peripheral side of the diaphragm, and the diaphragm further comprises a first ring folding portion protruding towards the second diaphragm direction.

Preferably, the casing further includes a first joint ring bent and extended from an edge of the supporting plate, and a third fixing portion bent and extended from an end of the first joint ring, the end being away from the supporting plate, the first joint ring being fixed to the second sidewall, and the third fixing portion being sandwiched between the second diaphragm and the second sidewall.

Preferably, the housing further includes a second joint ring fixedly disposed on the second sidewall for holding the first diaphragm.

Preferably, the vibration system further comprises a framework component combined on one side of the first diaphragm and used for connecting the voice coil and the first diaphragm, the framework component comprises two frameworks which are arranged along the opposite direction of the long axis side of the voice coil at intervals, the frameworks comprise a first joint part and a second joint part which are arranged along the direction of the long axis side of the voice coil at intervals and used for clamping the short axis side of the voice coil and a first main body part connected with the first joint part and the second joint part, and the first main body part is connected with the first diaphragm.

Preferably, the first diaphragm includes a first sound film and a first dome sandwiched between the first sound film and the first connecting member; the first ball is attached to the inner peripheral side of the first sound film, and the first sound film comprises a second flange part protruding towards the second vibrating diaphragm.

Preferably, the second diaphragm comprises a second sound film and a second dome attached to the inner peripheral side of the second sound film and far away from the second side wall; the second sound film comprises a third folded ring part protruding away from the second side wall.

Preferably, the vibration system further includes a flexible circuit board assembly fixedly disposed on the first side wall, the flexible circuit board assembly includes two flexible circuit boards disposed along the long axis side direction of the voice coil at opposite intervals, and the flexible circuit boards are electrically connected to the voice coil.

Preferably, the magnetic circuit system further includes a first clamping plate and a second clamping plate disposed at intervals along the short axis direction of the voice coil, the first magnet assembly and the second magnet assembly are disposed between the first clamping plate and the second clamping plate, the first clamping plate is fixedly disposed on the first sidewall, and the second joint ring is disposed between the second clamping plate and the first diaphragm.

Preferably, the first side wall is provided with a first assembling port and second assembling ports symmetrically arranged on two sides of the first assembling port, the first clamping plate is embedded in the first assembling port, and partial structures of the flexible circuit board are respectively embedded in the corresponding second assembling ports.

The invention has the beneficial effects that: the micro loudspeaker comprises a shell, a vibration system and a magnetic circuit system, wherein a support plate is arranged in the shell, and a first through hole is formed in the support plate; the vibration system comprises a voice coil, a first vibrating diaphragm, a second vibrating diaphragm, a hollow first connecting piece and a hollow second connecting piece, wherein the first vibrating diaphragm, the diaphragm and the second vibrating diaphragm are sequentially arranged at intervals along the short axis side direction of the voice coil; the first vibrating diaphragm and the second vibrating diaphragm are fixedly fixed on the shell, the diaphragm is fixedly fixed on the supporting plate and covers the first through hole, and the first vibrating diaphragm is connected with the voice coil; the first vibrating diaphragm and the shell, the supporting plate and the diaphragm are arranged in a surrounding mode to form a first vibrating diaphragm front cavity, a second through hole is formed in the diaphragm, a third through hole is formed in the second vibrating diaphragm, and the first vibrating diaphragm front cavity is communicated with the outside through the hollow structure of the first connecting piece, the second through hole, the hollow structure of the second connecting piece and the third through hole in sequence. By the mode, more air can be pushed to sound under the same amplitude, the effective radiation area of the micro loudspeaker is increased, and stronger bass performance is realized; meanwhile, under the condition of same bass output, the requirement on the amplitude of the micro loudspeaker is reduced, the service life of the micro loudspeaker is prolonged, and the requirement on the volume of a rear cavity of the mobile phone is reduced.

[ description of the drawings ]

FIG. 1 is a schematic diagram of an overall structure of a micro-speaker according to an embodiment of the present invention;

FIG. 2 is an exploded view of a micro-speaker according to an embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view taken along the line A-A in FIG. 1;

FIG. 4 is a schematic cross-sectional view taken along line B-B of FIG. 1;

FIG. 5 is a schematic cross-sectional view taken along the line C-C in FIG. 1;

FIG. 6 is a schematic diagram of a portion of a micro-speaker according to an embodiment of the present invention;

FIG. 7 is a schematic diagram of a second partial structure of a micro-speaker according to an embodiment of the present invention;

reference numerals: a micro-speaker 100; a housing 1; a housing space 10; a first side wall 11; the first fitting opening 111; a second fitting opening 112; a second side wall 12; a support plate 13; a first through hole 131; a second mating ring 14; a first mating ring 15; a third fixing portion 16; a vibration system 2; a voice coil 21; a first diaphragm 22; a first diaphragm 221; a first dome 222; a diaphragm 23; a second through hole 231; a second diaphragm 24; a third through hole 241; a second diaphragm 242; a second dome 243; a first connecting member 25; a support column 251; a first fixed portion 252; a second fixing portion 253; a support arm 2531; a support platform 2532; a second connecting member 26; a skeleton assembly 27; a skeleton 271; the first engaging portion 271 a; the second engaging portion 271 b; a first body portion 271 c; the third engaging portion 271 d; a flexible circuit board assembly 28; a flexible circuit board 281; the second body portion 281 a; an elastic connecting portion 281 b; a holding portion 281 c; a magnetic circuit system 3; a first magnet assembly 31; a first magnetic steel 311; pole piece & second magnet 312; a second magnet assembly 32; a first clamping plate 33; a second clamping plate 34.

[ detailed description ] embodiments

The invention is further described with reference to the following figures and embodiments.

Referring to fig. 1 to 7, an embodiment of the invention provides a micro-speaker 100, which includes a housing 1 having an accommodating space 10, a vibration system 2, and a magnetic circuit system 3 accommodated in the accommodating space 10 for driving the vibration system 2 to vibrate. The housing 1 includes a first sidewall 11 and a second sidewall 12 extending from the first sidewall 11. The first side wall 11 and the second side wall 12 enclose the accommodating space 10. The housing 1 further includes a support plate 13 extending from the second sidewall 12 into the accommodating space 10, and the support plate 13 is provided with a first through hole 131.

Specifically, the vibration system 2 includes a voice coil 21, a first diaphragm 22, a diaphragm 23, a second diaphragm 24, a first connecting member 25 interposed between the first diaphragm 22 and the diaphragm 23, and a second connecting member 26 interposed between the diaphragm 23 and the second diaphragm 24, which are sequentially arranged along a short axis side direction of the voice coil 21 at intervals. A first plane (XY plane shown in fig. 4) formed by the long axis side and the short axis side of the voice coil 21 is perpendicular to the plane of the first diaphragm 22, the plane of the diaphragm 23, and the plane of the second diaphragm 24. The magnetic circuit system 3 includes a first magnet assembly 31 and a second magnet assembly 32 spaced apart in a direction perpendicular to the first plane, and the voice coil 21 is disposed between the first magnet assembly 31 and the second magnet assembly 32.

According to the invention, the voice coil 21 and the magnetic circuit system 3 are arranged according to the above manner, so that the ultra-large low-frequency amplitude Xmax of the micro-speaker 100 is larger than 1.0mm, the driving force (Bli) of the speaker product is improved, and the ultra-strong bass performance is realized under the condition of lower power consumption.

Further, the first diaphragm 22 is accommodated in the accommodating space 10 and connected to the voice coil 21, the first diaphragm 22 is fixed on the second sidewall 12, and the second diaphragm 24 is fixed on the end of the second sidewall 12 away from the first sidewall 11. The diaphragm 23 is fixed on the support plate 13 and covers the first through hole 131. The first diaphragm 22, the second sidewall 12, the supporting plate 13 and the diaphragm 23 are enclosed to form a first diaphragm front cavity. The second diaphragm 24 and the second side wall 12, the support plate 13, the diaphragm 23 and the outer peripheral wall of the second connecting member 26 are surrounded to form a closed second diaphragm rear cavity. The diaphragm 23 is provided with a second through hole 231, the second diaphragm 24 is provided with a third through hole 241, the first diaphragm front cavity sequentially passes through the hollow structure of the first connecting piece 25, and the second through hole 231, the hollow structure of the second connecting piece 26 and the third through hole 241 are communicated with the outside.

In the invention, the accommodating space 10 of the housing 1 is internally provided with the first diaphragm front cavity which is formed by enclosing the first diaphragm 22, the diaphragm 23, the second side wall 12 and the supporting plate 13 and is communicated with the outside, so that more air can be pushed to sound under the same amplitude, the effective radiation area of the micro-speaker 100 is increased, and stronger bass performance is realized; meanwhile, under the condition of the same bass output, the requirement on the amplitude of the micro-speaker 100 is reduced, which is beneficial to prolonging the service life of the micro-speaker 100 and reducing the requirement on the volume of the rear cavity of the mobile phone. It should be noted that, in other embodiments of the present invention, the first diaphragm front cavity may be communicated with the outside in other manners, for example, a through hole communicated with the outside is provided at a corresponding position of the second sidewall 12, and it is understood that the above all belong to the protection scope of the present invention.

Optionally, the first connecting element 25 includes a hollow supporting column 251, a first fixing portion 252 bent and extended from an edge of the supporting column 251, and two second fixing portions 253 relatively spaced apart from each other at an end of the supporting column 251 far from the first fixing portion 252. The second fixing portion 253 includes a support arm 2531 extending from an edge of the support column 251 and a support platform 2532 extending from an end of the support arm 2531 away from the support column 251. The first fixing portion 252 is interposed between the supporting column 251 and the inner peripheral side of the diaphragm 23, and the supporting stage 2532 is interposed between the supporting arm 2531 and the inner peripheral side of the first diaphragm 22.

Alternatively, the outer peripheral side of the diaphragm 23 covers the first through hole 131, the inner peripheral side of the diaphragm 23 is interposed between the first connector 25 and the second connector 26, and the second through hole 231 is provided on the inner peripheral side of the diaphragm 23. The diaphragm 23 further includes a first collar portion a protruding toward the second diaphragm 24, so as to increase the volume of the front cavity of the first diaphragm, thereby increasing the effective radiation area of the micro-speaker 100.

Optionally, in this embodiment, the housing 1 further includes a first engaging ring 15 extending from the edge of the supporting plate 13, and a third fixing portion 16 extending from the end of the first engaging ring 15 away from the supporting plate 13. The first joint ring 15 is fixedly disposed on the second sidewall 12, and the third fixing portion 16 is interposed between the second diaphragm 24 and the second sidewall 12. The second diaphragm 24 is surrounded with the outer peripheral walls of the first joint ring 15, the support plate 13, the diaphragm 23, and the second connector 26 to form the second diaphragm back cavity.

Optionally, in this embodiment, the housing 1 further includes a second joint ring 14 fixedly disposed on the second sidewall 12 for holding the first diaphragm 22. The magnetic circuit system 3 further includes a first clamping plate 33 and a second clamping plate 34 which are spaced apart in a short axial direction (Y direction as shown in fig. 3 to 5) of the voice coil 21, and the first magnet assembly 31 and the second magnet assembly 32 are disposed between the first clamping plate 33 and the second clamping plate 34. The first clamping plate 33 is fixed on the first sidewall 11, and the second joint ring 14 is clamped between the second clamping plate 34 and the first diaphragm 22. By arranging the first magnet assembly 31 and the second magnet assembly 32 between the upper clamping plate 33 and the lower clamping plate 34 to fix the two

magnet assemblies

31 and 32, the structure of a magnetic circuit system can be effectively protected when a product falls, and the falling resistance of the product is improved.

Optionally, in this embodiment, the vibration system 2 further includes a bobbin assembly 27 coupled to one side of the first diaphragm 22 for connecting the voice coil 21 and the first diaphragm 22, where the bobbin assembly 27 includes two bobbins 271 disposed at intervals along a long-axis side direction (such as an X direction shown in fig. 4) of the voice coil 21, the bobbin 271 includes a first joint portion 271a and a second joint portion 271b disposed at intervals along the long-axis side direction of the voice coil 21 for clamping a short-axis side of the voice coil 21, and a first main body portion 271c connecting the first joint portion 271a and the second joint portion 271b, and the first main body portion 271c is connected to the first diaphragm 22. The first joint 271a and the second joint 271b clamp the short shaft side of the voice coil 21 together, and the voice coil 21 is suspended between the first magnet assembly 31 and the second magnet assembly 32, so that the voice coil 21 is prevented from shaking during reciprocating motion, and the motion stability of the vibration system 2 is improved.

Further, the first engaging portion 271a is connected to the outer periphery of the voice coil 21, and the second engaging portion 271b is connected to the inner periphery of the voice coil 21, as shown in fig. 4, so that the voice coil 21 can be prevented from shaking during the reciprocating movement. The length of the second engaging portion 271b is designed according to the length of the short side of the inner circumference of the voice coil 21. The length of the first engaging portion 271a is not limited to that shown in this embodiment, one end of the first engaging portion 271a is connected to the outer periphery of the voice coil 21, and the other end of the first engaging portion 271a extends to the first diaphragm 22.

Optionally, the first body 271c is attached to the voice coil 21 to provide more support points for the voice coil 21, so as to further improve the motion stability of the voice coil 21.

Optionally, in this embodiment, the framework 271 further includes a third engaging portion 271d bent and extended from an edge of the first main body portion 271c, and the third engaging portion 271d is fixedly disposed on a side of an inner edge of the first diaphragm 22, which is close to the first sidewall 11.

Optionally, the first diaphragm 22 may be a complete diaphragm, or a diaphragm and a dome. In this embodiment, the first diaphragm 22 includes a first sound film 221, and a first dome 222 interposed between the first sound film 221 and the first connecting member 25. The first dome 222 is attached to the inner peripheral side of the first diaphragm 221, the outer peripheral side of the first diaphragm 221 is fixed to the second joint ring 14, and the first diaphragm 221 further includes a second flange portion b protruding toward the second diaphragm 24.

Optionally, the second diaphragm 24 may be a complete diaphragm, or a diaphragm and a dome. In this embodiment, the second diaphragm 24 includes a second sound film 242, a second dome 243 attached to the inner peripheral side of the second sound film 242 and far from the second sidewall 12, and the second sound film 242 further includes a third folded ring portion c protruding in the direction far from the second sidewall 12.

Specifically, the vibration system 2 further includes a flexible circuit board assembly 28 fixedly disposed on the first sidewall 11, the flexible circuit board assembly 28 includes two flexible circuit boards 281 disposed at opposite intervals along the long axis side direction of the voice coil 21, and both of the two flexible circuit boards 281 are electrically connected to the voice coil 21.

Optionally, in this embodiment, the flexible circuit board 281 includes a second main body portion 281a connected to the voice coil 21, an elastic connection portion 281b connected to one end of the second main body portion 281a, and a holding portion 281c connected to the elastic connection portion 281 b. The holding portion 281c is fixed on the first sidewall 11, and the other end of the second main body portion 281a is connected to the end of the frame 271 on the same side close to the first sidewall 11. More specifically, the other end of the second main body portion 281a is connected to the end of the first main body portion 271c on the same side, which is close to the first sidewall 11.

Optionally, in this embodiment, as shown in fig. 7, a first assembling hole 111 and second assembling holes 112 symmetrically disposed on two sides of the first assembling hole 111 are formed in the first sidewall 11, the first clamping plate 33 is embedded in the first assembling hole 111, and the holding portions 281c are respectively embedded in the corresponding second assembling holes 112.

Optionally, in this embodiment, the first magnet assembly 31 is composed of five elements with magnetic conductive function. The five elements with the magnetic conduction function comprise three first magnetic steels 311 arranged at intervals along the short axis side direction of the voice coil 21 and pole cores 312 respectively arranged between the adjacent first magnetic steels 311, or second magnetic steels 312 respectively arranged between the adjacent first magnetic steels 311. It should be noted that in some other embodiments, the first magnet assembly 31 is composed of three elements having magnetic conductive function, and in other embodiments, the first magnet assembly 31 is composed of only one element having magnetic conductive function. It is understood that the above all belong to the protection scope of the present invention.

Optionally, in this embodiment, the structure of the second magnet assembly 32 is the same as that of the second magnet assembly 31.

While the foregoing is directed to embodiments of the present invention, it will be understood by those skilled in the art that various changes may be made without departing from the spirit and scope of the invention.

Claims

1. A micro-speaker is characterized by comprising a shell with an accommodating space, a vibration system and a magnetic circuit system accommodated in the accommodating space, wherein the shell comprises a first side wall, a second side wall bent and extended from the edge of the first side wall and a support plate extended from the second side wall to the accommodating space, and a first through hole is formed in the support plate;

2. The micro-speaker as claimed in claim 1, wherein the first connector comprises a hollow support pillar, a first fixing portion extending from an edge of the support pillar in a bending manner, and two second fixing portions disposed at opposite intervals at an end of the support pillar away from the first fixing portion, the second fixing portions comprising a support arm extending from the edge of the support pillar and a support base extending from the support arm in a bending manner at an end of the support pillar away from the support pillar; the first fixing portion is sandwiched between the support column and the inner peripheral side of the diaphragm, and the support table is sandwiched between the support arm and the inner peripheral side of the first diaphragm.

3. The micro-speaker as claimed in claim 1, wherein the outer peripheral side cover of the diaphragm is disposed at the first through hole, the inner peripheral side of the diaphragm is sandwiched between the first connecting member and the second connecting member, the second through hole is disposed at the inner peripheral side of the diaphragm, and the diaphragm further includes a first loop portion protruding toward the second diaphragm.

4. The micro-speaker of claim 1, wherein the housing further comprises a first engagement ring extending from an edge of the supporting plate and a third fixing portion extending from the first engagement ring away from the end of the supporting plate; the first joint ring is fixedly arranged on the second side wall, and the third fixing part is clamped between the second diaphragm and the second side wall.

5. The microspeaker of claim 1 wherein the housing further comprises a second adapter ring fixedly disposed on the second sidewall for holding the first diaphragm.

6. The micro-speaker of claim 1, wherein the vibration system further comprises a bobbin assembly coupled to one side of the first diaphragm for connecting the voice coil to the first diaphragm, the bobbin assembly comprising two bobbins oppositely spaced apart along a long axis side of the voice coil, the bobbin comprising a first joint portion and a second joint portion spaced apart along the long axis side of the voice coil for clamping a short axis side of the voice coil, and a first main body portion connecting the first joint portion and the second joint portion, the first main body portion being connected to the first diaphragm.

7. The micro-speaker of claim 1, wherein the first diaphragm includes a first diaphragm and a first dome interposed between the first diaphragm and the first connecting member, the first dome is attached to an inner peripheral side of the first diaphragm, and the first diaphragm includes a second flange portion protruding toward the second diaphragm.

8. The micro-speaker of claim 1, wherein the second diaphragm comprises a second diaphragm and a second dome attached to an inner peripheral side of the second diaphragm, the second dome being away from the second sidewall; the second sound film comprises a third folded ring part protruding away from the second side wall.

9. The micro-speaker of claim 5, wherein the vibration system further comprises a flexible circuit board assembly fixedly disposed on the first sidewall, the flexible circuit board assembly comprising two flexible circuit boards disposed at opposite intervals along the long axis of the voice coil, the flexible circuit boards being electrically connected to the voice coil.

10. The micro-speaker of claim 9, wherein the magnetic circuit further comprises a first clamping plate and a second clamping plate spaced apart along a short axis of the voice coil, the first magnet assembly and the second magnet assembly being disposed between the first clamping plate and the second clamping plate, the first clamping plate being fixedly disposed on the first sidewall, and the second engaging ring being interposed between the second clamping plate and the first diaphragm.

11. The micro-speaker as claimed in claim 10, wherein the first sidewall has a first assembling hole and second assembling holes symmetrically formed at two sides of the first assembling hole, the first clamping plate is embedded in the first assembling hole, and the flexible printed circuit board has partial structures respectively embedded in the corresponding second assembling holes.