WO2007032580A1

WO2007032580A1 - Condenser microphone and pakaging method for the same

Info

Publication number: WO2007032580A1
Application number: PCT/KR2006/000391
Authority: WO
Inventors: Chung-Dam Song
Original assignee: Bse Co., Ltd
Priority date: 2005-09-14
Filing date: 2006-02-03
Publication date: 2007-03-22
Also published as: KR100675023B1; CN1933680B; CN101129087A; CN1933680A

Abstract

Disclosed are a silicon based condenser microphone comprising: a metal case which is a sound hole: a board which is mounted with a MEMS microphone chip and an ASIC chip having a electric pressure pump and a buffer IC and is formed with a connecting pattern for joining with the metal case; a fixing means for fixing the metal case to the board; and an adhesive for applying to the whole part where the metal case fixed to the board by the fixing means is joined with the board to bond the metal case to the board. Therefore, the metal case is tack-welded to the board by the laser to fix the case to the board and then bonds the case to the board with the adhesive, thereby decreasing an inferiority ratio and strengthening a joining force and thus enhancing a mechanical firmness and highly resisting noise from the outside.

Description

CONDENSER MICROPHONE AND PACKAGING METHOD

FOR THE SAME

Technical Field

[1] The present invention relates to a condenser microphone, and, more particularly to, a method for packaging a condenser microphone by joining a case of the microphone with a PCB, and a condenser microphone packaged by the method. Background Art

[2] Generally, a condenser microphone which has been widely used in a mobile equipment or an audio equipment consists of a voltage bias element, a pair of a diaphragm and a back plate for forming a capacitor which is changed corresponding to a sound pressure, and a JFET for buffering an output signal. This typical condenser microphone is consisted of an assembly which is integrally assembled by sequentially inserting a vibration plate, a spacer ring, an insulating ring, a back plate and a conductive ring into a case and then bending an end of the case toward a PCB side after inserting the PCB which is mounted with circuit parts.

[3] However, in a curling process for rolling and bending the end of the case on the

PCB while pressing the end of the case toward the PCB, there happen problems that the shape of the final product or an acoustic characteristic is affected by a pressure during a manufacturing process and tolerances of parts. For example, if a pressing force is not enough in the curling process, a sound pressure is entered into a gap between the case and the PCB, thereby deteriorating a sound quality. Meanwhile, if a pressing force is excessive in the curling process, the portion to be curled is torn or the parts within the case are deformed, whereby there happens a distortion phenomenon in an acoustic characteristic.

[4] To solve these problems, Korea Patent Laid open No.10-2004-0072099, which is entitled by "TRUCTURE FOR JOINING CASE OF CONDENSER MICROPHONE AND METHOD FOR THE SAME" has been disclosed in the Unexamined Patent Publication of the Korean Intellectual Property Office.

[5] The above conventional technology relates to a condenser microphone having a case 30, a vibration plate, a spacer, a back plate, an injection molded parts, a connection ring and a board 40. Referring to Fig. 9, an opened end of the case 30 is bent outwardly and a joining piece 31 is formed in a shape of a ring along the end. The board 40 is formed with a welding area 41 which is plated with a conductive metal on its part which faces the joining piece 31 of the case 30. After mounting the above elements into the case, the joining piece 31 of the case contacts the welding area 41 of the board 40. Then, two electrodes, that is, a positive electrode and a negative electrode, press the case and the board, respectively, so that the case and the board are pressed. Then, electricity is instantly applied to the electrodes so that the joining piece of the case and the metal on the welding area are melted, whereby the case and the board are joined by bonding the joining piece of the case and the welding area of the board.

[6] However, if the joining piece of the case and the welding area of the board are substantially joined by electric welding, there happen problems in that the elements within the case are deformed and stressed by heat generated upon welding and the welding operation is difficult due to the inconvenience of installation and driving of the electrodes.

[7] Meanwhile, recently, a semiconductor fabricating technology using a micro- machining technology has been introduced for an integrated micro device. According to this technology which is called MEMS (Micro Electro Mechanical System), a micro-sensor, an actuator and an electro mechanical structure can be fabricated in a D unit using a micromachining technology which applies a semiconductor fabricating process, especially, an integrated circuit technology. A MEMS chip microphone manufactured by the micromachining technology has merits that miniaturization, high- performance, multifunction and integration can be obtained through the high precise micromachining technology and safety and reliability can be enhanced.

[8] Thus, a new packaging technology for efficiently joining a case and a board is required for a silicon based condenser microphone using the MEMS technology as well as a general condenser microphone. Disclosure of Invention

Technical Problem

[9] It is, therefore, an object of the present invention to provide a method for packaging a condenser microphone by joining a case of the microphone with a board, and a condenser microphone packaged by the method.

[10] It is another object of the invention to provide a method for packaging a condenser microphone by fixing a case of the microphone to the board to prevent the movement of the case when joining the case and the board by an adhesive and then bonding them with the adhesive, and a condenser microphone packaged by the method.

[11] It is another object to provide a silicon based condenser microphone for preventing inferiority generation and increasing a bonding strength, which has a high resistance to external noise such as electromagnetic waves, by tack- welding an end of a metal case to a board which is mounted with MEMS microphone parts and then bonding them with an adhesive, and a packaging method for the silicon based condenser microphone. Technical Solution

[12] According to one aspect of the present invention, there is provided a silicon based condenser microphone comprising: a metal case which is a sound hole: a board which is mounted with a MEMS microphone chip and an ASIC chip having a electric pressure pump and a buffer IC and is formed with a connecting pattern for joining with the metal case; a fixing means for fixing the metal case to the board; and an adhesive for applying to the whole part where the metal case fixed to the board by the fixing means is joined with the board to bond the metal case to the board.

[13] Further, according to another aspect of the present invention, there is provided a method for packaging a silicon based condenser microphone. The method comprises the steps of: inputting a board which is mounted with a MEMS chip and an ASIC chip and is formed with a connecting pattern; inputting a metal case; aligning the metal case on the connecting pattern of the board; fixing the metal case to the connecting pattern of the board by tack- welding; bonding the whole part where the metal case fixed to the board is joined with the board with an adhesive; and curing the adhesive. Brief Description of the Drawings

[14] The above and other objects and features of the invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:

[15] Fig. 1 is a sectional side view of a first embodiment of a silicon based condenser microphone according to the present invention;

[16] Fig. 2 is an exploded perspective view of a first embodiment of a silicon based condenser microphone according to the present invention;

[17] Fig. 3 is a view showing an example of a structure for a MEMS chip of a silicon based condenser microphone according to the present invention;

[18] Fig. 4 is a circuit diagram of a silicon based condenser microphone according to the present invention;

[19] Fig. 5 is a flow chart showing a packaging process of a silicon based condenser microphone according to the present invention;

[20] Fig. 6 is an exploded perspective view of a second embodiment of a silicon based condenser microphone according to the present invention;

[21] Fig. 7 is an exploded perspective view of a third embodiment of a silicon based condenser microphone according to the present invention;

[22] Fig. 8 is an exploded perspective view of a fourth embodiment of a silicon based condenser microphone according to the present invention;

[23] Fig. 9 is a sectional side view of a sixth embodiment showing that connecting terminals are formed on a part side of a PCB according to the present invention; and [24] Fig. 10 is a schematic view showing that a conventional condenser microphone is packaged. Best Mode for Carrying Out the Invention

[25] Hereinafter, preferred embodiments of the present invention will be explained in detail with reference to the appended drawings.

[26]

[27] [Embodiment 1]

[28] Fig. 1 is a sectional side view of a first embodiment according to the present invention, Fig. 2 is an exploded perspective view of a first embodiment according to the present invention, Fig. 3 is a view showing an example of a structure for a MEMS chip of a silicon based condenser microphone according to the present invention, and Fig. 4 is a circuit diagram of a silicon based condenser microphone according to the present invention.

[29] According to a first embodiment, as shown in Figs. 1 and 2, a cylindrical metal case

110 is tack- welded to a PCB 120 which is mounted with a MEMS chip 10 and an ASIC chip 20 by a laser and then the case 110 and the PCB 120 are bonded with an adhesive 140. Here, the adhesive 140 is any one selected from the group of conductive epoxy, nonconductive epoxy, silver paste, silicon, urethane, acryl and cream solder.

[30] Referring to Figs. 1 and 2, the PCB 120 is mounted with the MEMS chip 10 and the

ASIC chip 20 and is formed with a circular connecting pattern 121 on its portion which contacts the metal case 110. Meanwhile, although there is not shown in the drawing, if necessary, the PCB may be mounted with a capacitor or a resistor for shielding electromagnetic waves or ESD.

[31] Since the PCB 120 is broader than the metal case 110, connecting pads or connecting terminals for connecting with an external device can be freely disposed on the broad PCB. The connecting pattern 121 is formed by forming a copper clad through a general PCB manufacturing process and then plating the copper clad with Ni or Au. Here, the board 120 may be a PCB, a ceramic board, a FPCB or a metal PCB.

[32] The metal case 110 has a cylindrical shape having an opening which faces the PCB

120 to receive the chip parts therein, wherein an upper surface thereof is formed with a sound hole 112 for collecting sound. The metal case 110 is made of any one selected from the group of brass, copper, stainless steel, aluminum, nickel alloy and the like. Further, the metal case 110 is plated with Au or Ag. The metal case 110 may have various shapes such as a circle, a square and the like.

[33] The metal case 110 is aligned on the connecting pattern 121 of the PCB 120 and then the tack- welding point of a connecting portion therebetween is partially tack- welded by a laser (not shown) to temporarily fix the case 110 to the board 120. Then, the adhesive 140 is evenly applied on the whole connecting portion between the case and the board, whereby microphone packaging is finished. Here, the 'tack-welding' does not mean welding for a whole connecting portion between the case 110 and the PCB 120, but means spot welding for one or more connecting points (that is, tack- welding points, preferably, two to four points) therebetween so that the case 110 is fixed to the PCB 120. As such, a joining point which is formed between the case 110 and the PCB 120 by the tack- welding is called a tack- welding point 130. The case 110 is fixed to the PCB 120 through the tack-welding point 130. Thus, since the case 110 is not moved when the case 110 is adhered to the PCB 120 by the adhesive 140 or upon a curing process, joining of the case 110 and the PCB 120 can be performed in a correct position. Here, the connecting pattern 121 is connected with a ground terminal 125, wherein, if the metal case 110 is adhered to the connecting pattern 121, there is a merit that it is easy to eliminate noise by interrupting noise from the outside.

[34] According to the microphone assembly packaged as described above, the metal case

110, as shown in Fig. 1, is fixed to the connecting pattern 121 of the PCB 120 by tack- welding of the laser, wherein a space 150 between the metal case 110 and the PCB 120 is served as a sound chamber.

[35] Further, the PCB 120 is formed with connecting terminals 123 and 125 for connecting with the external device on a bottom surface thereof, wherein the number of the connecting terminals 123 and 125 may be two to eight. Each of the connecting terminals 123 and 125 is electrically connected through a through-hole 124 to a chip part surface of the PCB. Specially, in the embodiment of the present invention, if extending the connecting terminals 123 and 125 to a circumference of the PCB 120, an electric soldering iron is approached to an exposed surface of the terminals, whereby a rework operation can be easily performed.

[36] The MEMS chip 10, as shown in Fig. 3, has a structure that a back plate 13 is formed on a silicon wafer 14 by using a MEMS technology and then a vibration membrane 11 is formed to face the back plate 13 with a spacer 12 interposed between the vibration membrane 11 and the back plate 13. Since this fabricating technology of the MEMS chip 10 has been known, the further explanation will be omitted.

[37] The ASIC chip 20 which is connected with the MEMS chip 10 to process electrical signals, as shown in Fig. 4, consists of an electric pressure pump 22 for supplying an electric pressure to allow the MEMS chip 10 to be operated as a condenser microphone, and a buffer IC 24 for amplifying an electric sound signal sensed through the MEMS chip 10 or performing impendence matching of the sensed electric sound signal, thereby supplying the processed signal through the connecting terminal to the outside. Here, the electric pressure pump 22 may be a DC-DC converter, and the buffer IC 24 may use an analogue amplifier or an ADC. Referring to Fig. 4, a condenser symbol "CO" indicates an electrical equilibrium circuit for the MEMS chip 10. Here, the MEMS microphone package 100 is connected through three connecting terminals (Vdd, GND, Output) to the external device.

[38] According to the embodiment of the present invention, the tack-welding for fixing the case 110 to the PCB 120 is performed by laser welding. However, the tack- welding may be performed by another method, for example, soldering or punching. Further, the adhesive 140 may use any of conductive or nonconductive epoxy series, silver paste, silicon, urethane, acryl, cream solder and the like.

[39]

[40] [Packaging method]

[41] Fig. 5 is a flow chart showing a packaging process of a silicon based condenser microphone according to the present invention.

[42] A method for packaging a silicon based condenser microphone according to the present invention, as shown in Fig. 5, includes the steps of inputting the board (Sl), mounting the MEMS part 10 and the ASIC chip 20 on the board 120 (S2), inputting the metal case (S3), aligning the case 110 on the connecting pattern 121 of the board 120 (S4), fixing the end of the case 110 to the connecting pattern 121 of the board by the tack- welding (S5), applying the adhesive 140 to the whole part where the case 110 meets the board 120 to bond the case 110 and the board 120 after fixing the case 110 to the board 120 (S6), and curing the adhesive 140 (S7).

[43] Here, the board 120 may be a PCB, a ceramic board, a FPCB or a metal PCB. The board 120 is formed with the connecting pattern 121 for connecting with the metal case 110.

[44] The metal case 110 is made of any one selected from the group of brass, copper, stainless steel, aluminum, nickel alloy and the like. Further, the metal case 110 may be plated with Au or Ag. The metal case 110 may have various shapes such as a circle, a square and the like.

[45] Further, in the step S5 of fixing the metal case 110 to the board 120, the tack- welding may be performed by laser welding or soldering. Further, the fixing operation may be performed by punching and the like. The adhesive 140 may use conductive or nonconductive epoxy series. After bonding the case 110 and the board 120 with the adhesive, the adhesive is cured by any of natural curing, ultraviolet curing, heat curing and the like to finish the manufacturing of the microphone.

[46]

[47] According to the packaging method of the present invention, the metal case 110 is tack- welded to the board 120 by the laser to fix the case 110 to the board 120 and then the case 110 is adhered to the board 120 with the adhesive 140 and finally the adhesive 140 is cured, whereby a joining force (that is, an electrical connecting force and a sealing performance) is strengthened. As a result, a sound quality is enhanced, and the microphone has a high-resistance to noise from the outside. Specially, the inferiority generation ratio is decreased and a process expense is saved, thereby sharply cutting a total manufacturing cost.

[48]

[49] [Embodiment 2]

[50] Fig. 6 is an exploded perspective view of a second embodiment according to the present invention, wherein a rectangular parallelepiped shaped metal case 210 is tack- welded to a PCB 220 by a laser to fix the case to the PCB and then the case is adhered to the PCB with an adhesive and finally the adhesive is cured.

[51] Referring to Fig. 6, the PCB 220 is mounted with the MEMS chip 10 and the ASIC chip 20 and is formed with a rectangular connecting pattern 221 on its portion which contacts the metal case 210. The connecting pattern 221 is made of a copper clad film through a general PCB pattern forming technology.

[52] The metal case 210 has a rectangular parallelepiped shape having an opening which faces the PCB 220, wherein an upper surface thereof is formed with a sound hole 212 for collecting sound.

[53] The metal case 210 is aligned on the connecting pattern 221 of the PCB 220 and then a tack- welding point 130, as shown in Fig. 6, is formed by welding one connecting point of each portion of the connecting pattern 221 using a laser (not shown). Then, the adhesive 140 is evenly applied on the whole connecting part between the case and the board and then is cured to finish microphone packaging. Here, the connecting pattern 221 is connected with a ground terminal, wherein, if the metal case 210 is welded to the connecting pattern 221, there is a merit that it is easy to eliminate noise itself by interrupting noise collected from the outside.

[54] Since a microphone assembly which is packaged as described above has the same structure as the assembly shown in Fig. 1, the further explanation will be omitted to avoid a repetition.

[55]

[56] [Embodiment 3]

[57] Fig. 7 is an exploded perspective view of a third embodiment according to the present invention, wherein a cylindrical metal case 110 which is formed with a skirt 116 projected in a shape of "D" from an end of the case is tack- welded to a PCB 120 by a laser to fix the case to the PCB and then the case is bonded to the PCB with an adhesive and finally the adhesive is cured.

[58] Referring to Fig. 7, the PCB 120 is mounted with the MEMS chip 10 and the ASIC chip 20 and is formed with a circular connecting pattern 121 on its portion which contacts the metal case 110' Since the PCB 120 is broader than the metal case, connecting pads or connecting terminals for connecting with an external device can be freely disposed on the broad PCB. Preferably, the connecting pattern 121 is formed by forming a copper clad through a general PCB manufacturing process and then plating the copper clad with Ni or Au. Further, preferably, the width of the connecting pattern 121 according to the third embodiment is wider than that of the connecting pattern of the first embodiment to correspond to the skirt 116 of the metal case.

[59] The metal case 110' has a cylinder shape having an opening which faces the PCB

120, wherein an upper surface thereof is formed with a sound hole 112 for collecting sound. The case body 114 is formed with the skirt 116 projected outwardly on the end thereof.

[60] The skirt 116 of the metal case 110' is aligned on the connecting pattern 121 of the

PCB 120 and then the case 110' is tack- welded to the board 120 using a laser (not shown) to fix the case to the board. Then, the case 110 is adhered to the board 120 with the adhesive 140 to finish microphone packaging.

[61]

[62] [Embodiment 4]

[63] Fig. 8 is an exploded perspective view of a fourth embodiment according to the present invention, wherein a rectangular parallelepiped shaped metal case 210' which is formed with a skirt 216 projected in a shape of "D" from an end of the case is tack- welded to a PCB 220 by a laser to fix the case to the PCB and then the case is bonded to the PCB with an adhesive 140 and finally the adhesive is cured.

[64] Referring to Fig. 8, the PCB 220 is mounted with the MEMS chip 10 and the ASIC chip 20 and is formed with a rectangular connecting pattern 221 on its portion which contacts the metal case 210' Since the PCB 220 is broader than the metal case 210' connecting pads or connecting terminals for connecting with an external device can be freely disposed on the broad PCB. Preferably, the connecting pattern 221 is formed by forming a copper clad through a PCB manufacturing process and then plating the copper clad with Ni or Au. Preferably, the width of the connecting pattern 221 according to the fourth embodiment is wider than that of the connecting pattern of the second embodiment to correspond to the skirt 216 of a body 214 of the metal case 210'.

[65] The metal case 210' has a rectangular parallelepiped shape having an opening which faces the PCB 220, wherein an upper surface thereof is formed with a sound hole 212 for collecting sound. A case body 214 is formed with the skirt 216 projected outwardly on the end thereof.

[66] The skirt 216 of the metal case 210' is aligned on the connecting pattern 221 of the

PCB 220 and then the case 210 is tack- welded to the board 220 using a laser (not shown) to fix the case to the board. Then, the case 210' is adhered to the board 220 with the adhesive 140 to finish microphone packaging. [67]

[68] [Embodiment 5]

[69] Fig. 9 is a sectional side view of a fifth embodiment of a silicon based condenser microphone according to the present invention.

[70] According to the silicon based condenser microphone of the fifth embodiment of the present invention, a cylindrical metal case 110 is fixed to a board 120 which is broader than the case by tack- welding and then the case is bonded to the board with an adhesive. The board is formed with connecting terminals 122 which are connected with connecting pads 320 of a main PCB 310 of a product having the microphone on a part side 120a thereof. In the sixth embodiment of the present invention, four connecting terminals are provided, but the number is merely an example. That is, two to eight connecting terminals may be provided. The reference number 130 indicates a tack- welding point. Further, if extending the connecting terminals 122 to a circumference of the board or the reverse side of the part side, heat transfer of an electric iron is improved, whereby a rework operation can be more convenient.

[71] The main PCB 310 of the product where the silicon based condenser microphone according to the sixth embodiment is mounted is formed with a circular inserting hole 310a for mounting the case 110 of the silicon based condenser microphone and the connecting pads 320 corresponding to the connecting terminals 122 which are formed on the board 120 of the microphone.

[72] As such, according to a structure of Fig. 9 showing that the silicon based condenser microphone is mounted on the main PCB 310, the metal case 110 projected from the central portion of the part side 120a of the board is inserted the inserting hole 310a of the main PCB 310, and the connecting pads 320 of the main PCB and the connecting terminals 122 of the microphone are connected by a solder 330.

[73] Thus, according to a mounting method of the present invention, since the case 110 projected from the board of the microphone is inserted into the inserting hole 310a of the main PCB 310, a total height t of an assembly according to the present invention is lower than that of an assembly assembled when the conventional microphone having the board which is formed with the connecting terminals on the reverse side of the part side thereof, thereby efficiently saving a space for mounting a part of the product.

[74] Referring again to Fig. 9, the board 120 is mounted with the MEMS chip 10 and the

ASIC chip 20 within the metal case of the silicon based condenser microphone and is formed with a circular connecting pattern 121 on its portion which contacts the metal case 110.

[75] Here, the board 120 may be selected among a PCB, a ceramic board, a FPCB, a metal PCB and the like. The metal case is formed with a sound hole for collecting a sound. The metal case is made of any one selected from the group of brass, copper, stainless steel, aluminum, nickel alloy and the like. Further, the metal case may be plated with Au or Ag.

[76] Further, as shown in Fig. 9, if extending the connecting terminal 122 through the circumferential part to the reverse side of the part side, a heat transfer of an electric iron is improved, whereby a rework operation can be more easily performed. Meanwhile, although there is not shown in the drawing, the connecting terminal 122 may be extended up to the circumferential part of the board.

[77]

[78] In the above embodiments according to the present invention, the silicon based condenser microphone is provided as an example. However, the present invention may be also applied to a typical condenser microphone having a structure which is integrally assembled by sequentially inserting a vibration plate, a spacer ring, an insulating ring, a back plate and a conductive ring into a case and then joining the case with a PCB which is mounted with circuit parts. Industrial Applicability

[79] From the foregoing, the metal case is tack- welded to the board by the laser to fix the case to the board and then bonds the case to the board with the adhesive, thereby decreasing an inferiority ratio and strengthening a joining force and thus enhancing a mechanical firmness and highly resisting noise from the outside. As a result, the process expense is saved, thereby sharply cutting a total manufacturing cost.

[80] Further, the conventional curling process for joining a metal case with a PCB is removed and the metal case is joined to the PCB which is mounted with condenser microphone parts with the adhesive, thereby enhancing an electrical conductivity between the case and the PCB and also enhancing a sound characteristic by sealing the case so that a sound pressure from the outside does not enter the case.

[81] Further, since the shape of the PCB is not limited by the size of the case, the PCB which is used in the microphone is freely designed, thereby forming various shapes of terminals. Further, since an assembling work can be performed without a physical force applied in the curling process, a more thin PCB can be adapted. As a result, the height of a product can be lowered, whereby a more thin microphone can be manufactured.

[82]

Claims

[I] A silicon based condenser microphone comprising: a metal case which is a sound hole: a board which is mounted with a MEMS microphone chip and an ASIC chip having a electric pressure pump and a buffer IC and is formed with a connecting pattern for joining with the metal case; a fixing means for fixing the metal case to the board; and an adhesive for applying to the whole part where the metal case fixed to the board by the fixing means is joined with the board to bond the metal case to the board. [2] The silicon based condenser microphone according to claim 1, wherein the fixing means is a tack- welding point formed by laser welding or soldering. [3] The silicon based condenser microphone according to claim 1, wherein the adhesive is any one selected from the group of conductive epoxy, nonconductive epoxy, silver paste, silicon, urethane, acryl and cream solder. [4] The silicon based condenser microphone according to claim 1, wherein the metal case has any one of a cylindrical shape and a rectangular parallelepiped shape. [5] The silicon based condenser microphone according to claim 4, wherein an end of the metal case has a shape of a straight line. [6] The silicon based condenser microphone according to claim 4, wherein an end of the metal case has a skirt shape which is formed by bending the end outwardly. [7] The silicon based condenser microphone according to claim 1, wherein the board is any one selected from the group of a PCB, a ceramic board, a FPCB and a metal PCB. [8] The silicon based condenser microphone according to claim 1, wherein the metal case is made of any one selected from the group of brass, aluminum and nickel alloy. [9] The silicon based condenser microphone according to claim 1, wherein the board is formed with connecting terminals for connecting with an external circuit on the riverside of the side which is mounted with the metal case. [10] The silicon based condenser microphone according to claim 1, wherein the board is formed with connecting terminals for connecting with an external circuit on the side which is mounted with the metal case.

[I I] A method for packaging a silicon based condenser microphone, the method comprising the steps of: inputting a board which is mounted with a MEMS chip and an ASIC chip and is formed with a connecting pattern; inputting a metal case; aligning the metal case on the connecting pattern of the board; fixing the metal case to the connecting pattern of the board by tack-welding; bonding the whole part where the metal case fixed to the board is joined with the board with an adhesive; and curing the adhesive. [12] The method according to claim 11, wherein the metal case has any one of a cylindrical shape and a rectangular parallelepiped shape. [13] The method according to claim 11, wherein the tack- welding operation is performed by any one of laser welding and soldering. [14] The method according to claim 11, wherein the adhesive is any one selected from the group of conductive epoxy, nonconductive epoxy, silver paste, silicon, urethane, acryl and cream solder.