Patent Publication Number: US-2023156405-A1

Title: Microspeaker having a flexible printed circuit board as a diaphragm

Description:
TECHNICAL FIELD 
     The present disclosure relates to a microspeaker using a flexible printed circuit board (FPCB) as a diaphragm. 
     BACKGROUND 
     With the development of true wireless stereo (TWS) technology for the convenience of users, a more compact structure has been required for earphones. In addition, as audio equipment has been spread, the level of sound quality desired by users has increased, and accordingly, higher performance and high-quality sound characteristics are required for audio equipment. 
     In general, microspeakers employing a dynamic structure adopt a voice coil that generates mutual electromagnetic force with a magnetic circuit to convert an electrical signal into a physical motion and include a diaphragm to which a voice coil is attached to convert the physical motion into sound. A vibration plate is provided. However, since a relatively heavy voice coil is attached to a thin and light diaphragm, a weight of a vibration system increases and a response speed decreases, which deteriorates the performance during high-pitched sound reproduction. 
     Therefore, it is required to develop a microspeaker capable of reducing the weight of the vibration system and improving the performance of sound reproduction. 
     SUMMARY 
     An aspect of the present disclosure is to provide a microspeaker in which a diaphragm and a voice coil are replaced with a flexible printed circuit board (FPCB). 
     In an aspect of the present disclosure, a microspeaker using a flexible printed circuit board (FPCB) as a diaphragm includes a magnetic circuit having a yoke and a magnet and an FPCB diaphragm installed on the magnetic circuit and having a conductive coil pattern formed on a non-conductive film, wherein when an electric signal is applied to the conductive coil pattern of the FPCB diaphragm, the FPCB diaphragm vibrates by mutual electromagnetic force with a magnetic circuit to generate sound. 
     In another example of the present disclosure, the microspeaker may further includes: a damper installed between FPCB diaphragm and the magnetic circuit. 
     In another example of the present disclosure, the conductive coil pattern may be formed on both upper and lower surfaces of the non-conductive film. 
     In another example of the present disclosure, the non-conductive film may be formed of a polymer compound such as polyamide, a PET film, an elastomer, and silicone rubber. 
     In another example of the present disclosure, the conductive coil pattern may be formed of a highly conductive material such as Cu, Al, Au, or Ag. 
     Unlike the dynamic speaker structure of the related art, the microspeaker provided in the present disclosure uses an FPCB as a diaphragm, thereby improving high-pitched sound reproduction performance and having a reduced size. 
     In addition, in the microspeaker provided in the present disclosure, since the FPCB vibrates directly to generate sound, sound distortion may be reduced and clear sound may be reproduced, compared to the existing structure in which a voice coil is attached to a diaphragm to transmit vibration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a microspeaker using a flexible printed circuit board (FPCB) as a diaphragm according to a first embodiment of the present disclosure. 
         FIG.  2    is a cross-sectional view taken along line A-A of  FIG.  1   . 
         FIG.  3    is a cross-sectional view of a microspeaker using an FPCB as a diaphragm according to a second embodiment of the present disclosure. 
         FIG.  4    is a cross-sectional view of a microspeaker using an FPCB as a diaphragm according to a third embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, the present disclosure will be described in more detail with reference to the accompanying drawings. 
       FIG.  1    is a perspective view of a microspeaker using an FPCB as a diaphragm according to a first embodiment of the present disclosure, and  FIG.  2    is a cross-sectional view taken along line A-A of  FIG.  1   . 
     A microspeaker using an FPCB as a diaphragm according to the first embodiment of the present disclosure is formed to have a rectangular shape as a whole, and accordingly, a yoke  210  or an FPCB diaphragm  300  is also formed to have a rectangular shape. 
     Two or more rod-shaped magnets  210  and  220  are disposed parallel to a longer side of the yoke  210  at a distance from each other on the rectangular yoke  210 . In the first embodiment of the present disclosure, a side magnet  220  disposed along the edge of the longer side of the yoke  210  and a center magnet  230  disposed in the center between the side magnet  220  are included. A frame  100  is disposed on a shorter side of the yoke  210  to support the FPCB diaphragm  300 . 
     In the FPCB diaphragm  300 , a conductive coil pattern  320  formed of a highly conductive material, such as Cu, Al, Au, or Ag is formed on a non-conductive film  310  formed of a polymer compound, such as polyamide, PET film, elastomer, or silicone rubber, and a terminal  330  for transmitting an electrical signal to the conductive coil pattern  320  is provided. 
     The conductive coil pattern  320  is preferably disposed in a gap between the magnets  210  and  220  as shown in  FIGS.  1  and  2   . When the conductive coil pattern  320  is concentrated in the gap portion between the magnets  210  and  220 , a magnetic field may be concentrated and induced in the gap between the magnets  210  and  220  on the FPCB diaphragm  300 , and accordingly, an amplitude of the FPCB diaphragm  300  may increase, thereby improving the performance of the microspeaker using the FPCB as a diaphragm. 
       FIG.  3    is a cross-sectional view of a microspeaker using an FPCB as a diaphragm according to a second embodiment of the present disclosure. 
     The microspeaker using an FPCB as a diaphragm according to the second embodiment of the present disclosure has all the same components as those of the first embodiment, except that a damper  400  is installed on the frame  100  and the side magnet  220  to support the diaphragm  300 . 
     Since the damper  400  is installed, a distance between the diaphragm  300  and the magnets  210  and  220  may be constantly maintained. 
       FIG.  4    is a cross-sectional view of a microspeaker using an FPCB as a diaphragm according to a third embodiment of the present disclosure. The microspeaker using an FPCB as a diaphragm according to the third embodiment of the present disclosure is different from the first embodiment in that a conductive coil pattern  320   a  is formed on both upper and lower surfaces of a diaphragm  300   a.    
     An upper conductive coil pattern  322   a  formed on an upper surface of a non-conductive film  310   a  and a lower conductive coil pattern  324   a  formed on a lower surface of the non-conductive film  310   a  need to match in the direction of an induced magnetic force to improve vibration performance by the mutual electromagnetic force with the magnets  220  and  230 , and therefore, winding directions thereof match each other. 
     Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this invention be limited only by the claims and the equivalents thereof.