WO2009051317A1

WO2009051317A1 - Mems microphone package

Info

Publication number: WO2009051317A1
Application number: PCT/KR2008/001862
Authority: WO
Inventors: Chung-Dam Song
Original assignee: Bse Co., Ltd.
Priority date: 2007-10-18
Filing date: 2008-04-03
Publication date: 2009-04-23
Also published as: MY150111A; TWM345339U; JP2009100471A; JP4777406B2; KR100925558B1; CN201195694Y; KR20090039375A; SG152176A1; EP2051539A1

Abstract

Provided is a micro electro mechanical system (MEMS) microphone package. In the MEMS microphone package, a PCB on which a MEMS microphone chip is mounted is inserted into a metal case. The metal case is directly attached to a main board using an assembling process in which an end portion of the metal case is bent and clamped to shield the MEMS microphone chip from a nose, thereby significantly improving an acoustic quality and reducing manufacturing costs. The end portion of the metal case having a square shape is chamfered such that a curling process is performed in the microphone having a square shape. A support member is disposed to provide a space between the PCB on which the MEMS microphone chip is mounted and the metal case. Such a MEMS microphone package includes: a metal case in which edges of an opened end portion are chamfered to easily perform a curling process in a square box shape in which one surface is opened to insert components through the opened surface; a PCB on which a MEMS microphone chip and an application specific integrated circuit (ASIC) chip are mounted, the PCB being inserted into the metal case; and a support member supporting the PCB to provide a space between the metal case and the PCB.

Description

Description MEMS MICROPHONE PACKAGE

Technical Field

[1] The present invention relates to a micro electro mechanical system (MEMS) microphone package, and more particularly, to a MEMS microphone package that can directly attaches a metal case to a main board using an assembling process in which an end portion of the metal case is bent and clamped to shield a MEMS microphone chip from a nose, thereby significantly improving an acoustic quality and reducing manufacturing costs. Background Art

[2] Typical condenser microphones include a diaphragm in which a flexible membrane is attached to one side electrode thereof and vibrated by an acoustic pressure and a back plate facing the diaphragm with a predetermined distance therebetween by a spacer. The diaphragm and the back plate constitute parallel electrode plates of the condenser. A DC voltage is applied to the both electrode plates, or an electret is formed on one of the electrode plates to generate a charge therebetween. Such a typical condenser microphone is assembled using a curling method in which the diaphragm, the spacer, a first base, the back plate, a second base, and a printed circuit board (PCB) on which an electronic circuit is mounted are successively stacked inside a cylindrical case, and an end portion of the case is bent toward the PCB and clamped.

[3] In the completely assembled condenser microphone, a capacitance of the condenser is changed when a distance between the diaphragm and the back plate is changed due to the external acoustic pressure. As a result, the electronic circuit processes the change of the capacitance to provide an electrical signal according to the change of the acoustic pressure.

[4] A condenser microphone used in communication products denotes an electret condenser microphone in which the electret is formed on the back plate using a polymeric membrane. The electret condenser microphone is manufactured at low cost, but it is difficult to miniaturize the electret condenser microphone. Thus, for miniaturi zing the microphone, a semiconductor manufacturing technique and a micromachining technique are applied to a silicon wafer to realize a capacitance structure with a die shape. This chip is called a silicon condenser microphone chip or a MEMS microphone chip. The MEMS microphone chip must be packaged to shield the chip from an external interference.

[5] A technique for packaging the MEMS microphone chip is disclosed in U.S patent

No. 6,781,231, "Microelectomechanical System Package with Environmental and In- terference Shield", which issued on August 24, 2004. As illustrated in FIG. 1, such a MEMS microphone package technique uses a method in which a case 34 including a conductive layer or formed of a conductive material is attached to a printed circuit board (PCB) 32 using a conductive adhesive 36 to manufacture a housing. Referring to FIG. 1, a MEMS microphone chip 10 and an application specific integrated circuit (ASIC) chip 20 are mounted on the PCB 32, and a case 34 having an acoustic hole 34a is attached to the PCB 32 using the adhesive 36 to shield the MEMS microphone chip 10 disposed therein.

[6] In a process for manufacturing a MEMS microphone package by packaging a conventional MEMS microphone chip, when a case is attached to a PCB using an adhesive or welded to the PCB, an external noise is introduced into the PCB that is a dielectric between the case and a main board to reduce a shield effect shielding the PCB from the external noise in case where the microphone package is mounted on the main board. Furthermore, in case of a most popular built-in antenna portable terminal, since a position of the antenna is very close to a position of a microphone due to their configuration, a radio frequency (RF) noise of the antenna is easily introduced into the microphone. In this case, it is more important to shield the microphone from the RF noise. However, it is difficult to satisfy these demands using the conventional MEMS microphone package.

[7] In addition, since the MEMS microphone packaging process in which the case is attached to the PCB using the adhesive or welded to the PCB is different from an inexpensive curling process in which a metal case is bent to fix components to the metal case, thereby assembling the microphone. Thus, new machineries for adhesion or welding are required to generate construction costs for a new assembly line. Disclosure of Invention Technical Problem

[8] An object of the present invention is to provide a MEMS microphone package that can directly attaches a metal case of the MEMS microphone package to a main board when the metal case is mounted on the main board using a curling process in which an end portion of the metal case is bent and clamped in a condenser microphone assembly process to improve a noise shielding characteristic and manufacture the MEMS microphone package at low costs without requiring new machineries. Technical Solution

[9] A typical condenser microphone has a circular shape. On the other hand, a MEMS microphone package has square shape. Thus, in the MEMS microphone package, orientation is easily recognized in a process in which a main substrate is mounted using a surface mount technology (SMT). In case of the circular microphone, components are inserted into a case, and then a curling process in which an end portion of the case is bent and clamped is easily performed. However, it is difficult to bend edge portions in case of the square microphone. Thus, in a conventional MEMS microphone package, the case is attached to the PCB using an adhesive or welded to the PCB.

[10] In the MEMS microphone package, an end portion of the metal case having a square shape is chamfered such that a curling process is performed in the microphone having a square shape. A support member is disposed to provide a space between the PCB on which the MEMS microphone chip is mounted and the metal case.

[11] To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a MEMS microphone package includes: a metal case in which edges of an opened end portion are chamfered to easily perform a curling process in a square box shape in which one surface is opened to insert components through the opened surface; a PCB on which a MEMS microphone chip and an application specific integrated circuit (ASIC) chip are mounted, the PCB being inserted into the metal case; and a support member supporting the PCB to provide a space between the metal case and the PCB.

[12] The metal case may have the square box shape having the one opened surface, four edges of the opened surface of the metal case may be chamfered to prevent the end portion of each surface and an end portion of the metal case adjacent to the end portion from overlapping each other during curling, and an acoustic hole may be formed in a bottom surface of the metal case.

[13] The PCB may have one surface on which the MEMS microphone chip and the ASIC chip are mounted and the other surface on which a conductive pattern to be connected to the metal case is disposed on a circumference portion thereof, and connection terminals such as a power source terminal Vdd, an output terminal OUTPUT, and a ground terminal GND may be disposed on a central portion of the PCB.

[14] The MEMS microphone package may further include a metal mesh for preventing a foreign substance and an electromagnetic wave from being introduced through the acoustic hole of the metal case.

Advantageous Effects

[15] As described above, in the MEMS microphone package manufactured in the curling method in which the end portion of the metal case is bent and clamped, the bent end portion of the case can be directly connected to the main board in case where the microphone package is mounted on the main board to form a kind of Faraday cup structure and shield the MEMS microphone from the external noise, thereby significantly improving the acoustic quality.

[16] In case where the MEMS microphone package is used for communication ap- plication, the noise shielding performance can be improved to prevent the RF noise of the antenna from being introduced into the antenna even if the antenna is adjacent to a microphone, thereby maintaining the good acoustic quality property.

[17] The packing process of the MEMS microphone chip can be performed at low costs without requiring additional machineries. In addition, the curling process can be easily performed because the end portion of the case does not overlap with the end portion of the adjacent surface during curling. Also, it can be prevented that the form of the case from being deformed during curling due to the support member. Brief Description of the Drawings

[18] FIG. 1 is a side cross-sectional view of a conventional MEMS microphone package.

[19] FIG. 2 is a perspective view of a MEMS microphone package in which a portion thereof is cut according to an embodiment of the present invention.

[20] FIG. 3 is a side cross-sectional view of the MEMS microphone package according to an embodiment of the present invention.

[21] FIG. 4 is a bottom view of the MEMS microphone package according to an embodiment of the present invention.

[22] FIG. 5 is a perspective view of a case used in the MEMS microphone package according to an embodiment of the present invention.

[23] FIG. 6 is a perspective view of a support member used in the MEMS microphone package according to an embodiment of the present invention.

[24] FIG. 7 is a perspective view of a MEMS microphone package in which a portion thereof is cut according to another embodiment of the present invention.

[25] FIG. 8 is a side cross-sectional view of the MEMS microphone package according to another embodiment of the present invention. Mode for the Invention

[26] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The following embodiments are used only for explain a specific exemplary embodiment while not limiting the present invention.

[27] FIG. 2 is a perspective view of a MEMS microphone package in which a portion thereof is cut according to an embodiment of the present invention, FIG. 3 is a side cross-sectional view of the MEMS microphone package according to an embodiment of the present invention, and FIG. 4 is a bottom view of the MEMS microphone package according to an embodiment of the present invention.

[28] Referring to FIGS. 2 to 4, a condenser microphone having a square shape according to the present invention includes a metal case 102 in which edges 102b of an opened end portion 102c are chamfered to easily perform a curling process in the case 102 having a square box shape in which one surface thereof is opened to insert components through the opened surface, a PCB 106 on which a MEMS microphone chip 10 and an ASIC chip 20 are mounted, the PCB being inserted into the case 102, and a support member 104 supporting the PCB 106 to provide a space between the case 102 and the PCB.

[29] Referring to FIG. 5, the metal case 102 used in the microphone package of the present invention has a square box shape having an opened surface. Four edges of the opened surface are chamfered to prevent the end portion 102c of each surface and the end portion 102c of the case 102 adjacent to the end portion 102c from overlapping each other during curling. An acoustic hole 102a is formed in a bottom surface of the case 102. The acoustic hole 102a may be formed in the PCB 106, but the case 102, according to an acoustic inflow structure.

[30] Referring to FIG. 6, the support member 104 used in the microphone package of the present invention has a square ring shape and is disposed between the bottom surface of the case 102 and the PCB 106. The support member 104 supports the PCB 106 when the end portion 102c of the case 102 is curled and provides an inner space. The microphone package 100 according to the present invention can easily perform a curling process because the end portion 102c of the case 102 does not overlap with the end portion 102c of the adjacent surface during curling, as well as prevent a form of the case 102 from being deformed during curling due to the support member 104.

[31] The PCB 106 used in the microphone package 100 of the present invention has one surface on which the MEMS microphone chip 10 and the ASIC chip 20 are mounted and the other surface on which a conductive pattern to be connected to the case 102 is disposed on a circumference portion thereof, and connection terminals such as a power source terminal Vdd, an output terminal OUTPUT, and a ground terminal GND are disposed on a central portion thereof. Although four connection terminals 108 are provided in the embodiment of the present invention as an example, the present invention is not limited thereto. For example, two or more plurality of connection terminals may be provided according to application. The MEMS microphone chip 10 has a structure in which a back plate is disposed on a silicon wafer using a MEMS technique to dispose a diaphragm between spacers. The ASIC chip 20 includes a voltage pump and a buffer amplifier. The voltage pump is connected to the MEMS microphone chip 10 to process an electrical signal and provides a bias voltage such that the MEMS microphone chip 10 operates as the condenser microphone. The buffer amplifier amplifies or impedance-matches an electrical acoustic signal detected through the MEMS microphone chip 10 to provide the amplified or impedance- matched acoustic signal to the outside through a connection terminal 108. The connection terminal 108 protrudes, and thus is easily surface-mounted on a main substrate 200.

[32] In the MEMS microphone package 100 according to the present invention, the support member 104 having the square ring shape is inserted into the metal case 102 having the square box shape and one opened surface. The PCB 106 on which the MEMS microphone chip 10 and the ASIC chip 20 are mounted is disposed on the support member 104. The curling process in which the end portion 102c of the case 102 is bent toward the PCB 106 to closely attach the bent portion to the conductive pattern is performed to complete the assembly of the MEMS microphone package 100.

[33] Referring to FIGS. 2 to 4, in the MEMS microphone package 100 completely assembled in above-described method, the support member 104 is inserted into the case 102. The support member 104 supports the PCB 106 on which circuit components are mounted to provide an inner space. The end portion 102c of the case 102 is closely attached to the PCB 106 using the curling process.

[34] Referring to FIG. 3, the MEMS microphone package 100 according to the present invention is mounted on the main substrate 200 using a surface mount technology (SMT) or a soldering method and connected to pads 204 of the main substrate 200 corresponding to the connection terminals 108 of the PCB 106. The bent end portion of the case is connected to a ground pattern 202 of the main substrate 200 to electrically shield the whole microphone, thereby forming a kind of Faraday cup. As a result, it prevents the noise from being introduced into the microphone. Therefore, in case where the microphone package 100 according to the present invention is used in a portable terminal, it can be prevented that a RF noise of an antenna is introduced into the antenna even if the antenna is adjacent to a microphone to maintain a good acoustic quality property.

[35] Referring to FIG. 3, in the microphone package 100 mounted on the main substrate

200, when a power is supplied from the main substrate 200 through the power source terminal and the ground terminal, an appropriate bias voltage generated by the voltage pump of the ASIC chip 20 is applied to the MEMS microphone chip 10 to generate a charge between the diaphragm of the MEMS microphone chip 10 and the back plate.

[36] When an external acoustic pressure is introduced into the microphone 10 through the acoustic hole 102a of the case, the diaphragm of the MEMS microphone chip 10 is vibrated, and at the same time, a capacitance between the diaphragm and the back plate is changed. The change of the capacitance is amplified into an electrical signal in the buffer amplifier and outputted to the main substrate 200 through the output terminal.

[37] FIG. 7 is a perspective view of a MEMS microphone package in which a portion thereof is cut according to another embodiment of the present invention, and FIG. 8 is a side cross-sectional view of the MEMS microphone package according to another embodiment of the present invention. [38] Referring to FIGS. 7 and 8, a MEMS microphone package according to another embodiment of the present invention includes a metal case 102 in which edges 102b of an opened end portion 102c are chamfered to easily perform a curling process in the case 102 having a square box shape in which one surface thereof is opened to insert components through the opened surface, a metal mesh 110 preventing a foreign substance from being introduced into the microphone through an acoustic hole 102a, a support member 104 supporting a PCB 106 to provide a space between the case 102 and the PCB, and a PCB on which a MEMS microphone chip 10 and an ASIC chip 20 are mounted, the PCB being inserted into the case 102.

[39] The MEMS microphone package according to another embodiment of the present invention prevents the foreign substance form being introduced into the microphone through the acoustic hole 102a in the structure as illustrated in FIG. 2 and adds the metal mesh 110 for shielding the MEMS microphone from an external noise to further improve a shielding performance, thereby further improving a characteristic in which it is prevented that an RF noise as well as the foreign substance are introduced into the microphone through the acoustic hole 102a.

[40] Since the microphone package according to another embodiment has the same construction as that according to the preceding embodiment, their description will be omitted.

[41] As described above, in the MEMS microphone package manufactured in the curling method in which the end portion of the metal case is bent and clamped, the bent end portion of the case can be directly connected to the main board in case where the microphone package is mounted on the main board to form a kind of Faraday cup structure and shield the MEMS microphone from the external noise, thereby significantly improving the acoustic quality.

[42] In case where the MEMS microphone package is used for communication application, the noise shielding performance can be improved to prevent the RF noise of the antenna from being introduced into the antenna even if the antenna is adjacent to a microphone, thereby maintaining the good acoustic quality property.

[43] The packing process of the MEMS microphone chip can be performed at low costs without requiring additional machineries. In addition, the curling process can be easily performed because the end portion of the case does not overlap with the end portion of the adjacent surface during curling. Also, it can be prevented that the form of the case from being deformed during curling due to the support member.

[44] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

[1] A MEMS microphone package comprising: a metal case in which edges of an opened end portion are chamfered to easily perform a curling process in a square box shape in which one surface is opened to insert components through the opened surface; a PCB on which a micro electro mechanical system (MEMS) microphone chip and an application specific integrated circuit (ASIC) chip are mounted, the PCB being inserted into the metal case; and a support member supporting the PCB to provide a space between the metal case and the PCB.

[2] The MEMS microphone package of claim 1, wherein the metal case has the square box shape having the one opened surface, four edges of the opened surface of the metal case are chamfered to prevent the end portion of each surface and an end portion of the metal case adjacent to the end portion from overlapping each other during curling, and an acoustic hole is formed in a bottom surface of the metal case.

[3] The MEMS microphone package of claim 2, further comprising a metal mesh for preventing a foreign substance and an electromagnetic wave from being introduced through the acoustic hole of the metal case.

[4] The MEMS microphone package of claim 1, wherein the PCB has one surface on which the MEMS microphone chip and the ASIC chip are mounted and the other surface on which a conductive pattern to be connected to the metal case is disposed on a circumference portion thereof, and connection terminals such as a power source terminal Vdd, an output terminal OUTPUT, and a ground terminal GND are disposed on a central portion of the PCB.

[5] The MEMS microphone package of claim 4, wherein the MEMS microphone chip has a structure in which a back plate is disposed on a silicon wafer using a MEMS technique to dispose a diaphragm between spacers, and the ASIC chip includes a voltage pump providing a bias voltage such that the MEMS microphone chip operates as a condenser microphone and a buffer amplifier amplifying or impedance-matching an electrical acoustic signal detected through the MEMS microphone chip to provide the amplified or impedance-matched acoustic signal to the outside through the connection terminal.