JP2010166307A - Microphone package and mounting structure of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce acoustic resistance against a pressure variation propagating toward a microphone chip while reducing an influence of an electromagnetic wave on the microphone chip. <P>SOLUTION: This microphone package 1 includes a housing 3 having a hollow cavity S1 and the microphone chip 5 including a diaphragm 33B for detecting a pressure variation and mounted to the upper surface 9a in the cavity S1 within a board 9 constituting the housing 3. On the board 9, an acoustic hole 21 penetrating its thickness direction is formed. The microphone chip 5 is mounted to the upper surface 9a of the board 9 to close an opening on the cavity S1 side of the acoustic hole 21 by making a diaphragm 33B face the acoustic hole 21. On the lower surface 9b of the board 9, a recess 23 recessed in the thickness direction from the lower surface 9b and continuously extending from an edge of the acoustic hole 21 in the surface direction of the board 9, and an annular conductive pad 25 surrounding circumferences of the acoustic hole 21 and the recess 23 are formed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a microphone package and a mounting structure thereof.

A conventional microphone package includes, for example, a microphone chip having a diaphragm, a circuit board on which the microphone chip is mounted, and a lid that forms a hollow cavity including the microphone chip together with the circuit board as disclosed in Patent Document 1. There is something. In this type of microphone package, a through hole (acoustic hole) is formed in the circuit board in the thickness direction, and a microphone chip is mounted on the upper surface of the circuit board so that the diaphragm faces the through hole. There is one in which the opening on the cavity side of the through hole is blocked.
In this microphone package, pressure fluctuations such as sound propagated from the outside to the microphone chip through the through hole are detected by vibration of the diaphragm. Note that the cavity defined by the circuit board and the lid is sealed from the outside and functions as a back air chamber for vibrating the diaphragm.

  The microphone package has, for example, a circuit board in which a through hole is opened and a lower surface of the circuit board facing the mounting surface of the mounting board, and a connection terminal formed on the lower surface of the circuit board and a land formed on the mounting surface of the mounting board. Are mounted on a mounting board by joining them together with solder. In this case, the mounting substrate is formed with a communication hole for allowing the through hole to communicate outwardly in the thickness direction of the mounting substrate. Therefore, in a state where the microphone package is mounted on the mounting board, the microphone package reaches the diaphragm of the microphone chip by sequentially propagating through the communication hole of the mounting board and the through hole of the circuit board.

US Patent Application Publication No. 2005/0018864

However, in the conventional microphone package, when the communication hole and the through hole overlap in the thickness direction of the circuit board and the mounting board, electromagnetic waves such as sunlight easily reach the diaphragm of the microphone chip. As a result, the microphone chip There is a problem that adversely affects the characteristics of
Conventionally, in order to prevent such invasion of sunlight and the like, it has been considered to provide an environmental filter (environmental barrier) such as a nonwoven fabric in the through hole. It is troublesome to make it complicated.

  In addition, since a gap is generated between the lower surface of the circuit board and the mounting surface of the mounting board by the solder that joins the connection terminals and the lands, the communication hole and the through hole are shifted from each other in the surface direction of the circuit board or the mounting board. It is also possible to prevent the invasion of sunlight and the like. However, in this configuration, since the gap due to the solder is small, the acoustic resistance against the pressure fluctuation such as sound becomes high, that is, the pressure fluctuation such as the sound is greatly attenuated before reaching the diaphragm. is there.

  The present invention has been made in view of the above-described circumstances, and provides a microphone package and a mounting structure thereof capable of reducing acoustic resistance while reducing the influence of electromagnetic waves on a microphone chip without providing a separate member. With the goal.

In order to solve the above problems, the present invention proposes the following means.
A microphone package of the present invention includes a housing having a hollow cavity portion, and a microphone chip having a diaphragm for detecting pressure fluctuation and mounted on an upper surface of the cavity portion among substrates constituting the housing, Is formed with an acoustic hole penetrating in the thickness direction, and the microphone chip is formed on the upper surface of the substrate so that the diaphragm faces the acoustic hole and closes the opening on the cavity portion side of the acoustic hole. Mounted on the lower surface of the substrate, is recessed in the thickness direction from the lower surface and extends from the periphery of the acoustic hole in the surface direction of the substrate, and the periphery of the acoustic hole and the recessed portion An annular conductive pad is formed to surround the substrate.

  The microphone package mounting structure of the present invention includes the microphone package and a mounting substrate having a mounting surface for mounting the microphone package, and the mounting substrate penetrates in the thickness direction and has an acoustic hole outward. A communication hole for communicating with the mounting surface, and an annular bonding land arranged on the mounting surface and corresponding to the shape of the conductive pad, and the lower surface of the substrate faces the mounting surface and the conductive pad In the state where the bonding lands are bonded to each other by solder, the opening on the mounting surface side of the communication hole faces the formation region of the recess.

In this state where the microphone package is mounted on the mounting substrate, the opening on the lower surface side of the acoustic hole and the opening on the mounting surface side of the communication hole are arranged so as to be shifted from each other in the surface direction of the substrate or the mounting substrate. Does not overlap in the thickness direction of the mounting board. As a result, the opening on the lower surface side of the acoustic hole is covered with the mounting substrate, and it is possible to prevent electromagnetic waves having high straightness such as sunlight from reaching the diaphragm.
In this mounted state, a gap is generated between the lower surface of the substrate and the mounting surface of the mounting substrate by the solder that joins the conductive pad and the bonding land. Therefore, pressure fluctuations such as sound reach the microphone chip by propagating from the outside into the acoustic hole through the communication hole and the gap between the circuit board and the mounting board.

Here, in the gap between the circuit board and the mounting board, the area where the acoustic hole and the communication hole are opened (one gap area) is different from the other gap area by the solder that joins the annular conductive pad and the bonding land. Since it is divided, it can prevent that the pressure fluctuation from the outside leaks out to another gap area.
Since the one gap region is widened by the recess, the acoustic resistance of the one gap region is reduced with respect to the pressure fluctuation propagating through the one gap region from the acoustic hole to the communication hole, and the pressure fluctuation is reduced. Can be prevented from being attenuated before reaching the diaphragm.

In the microphone package, the recess may be constituted by a plurality of slit-shaped recesses extending in one direction along the lower surface of the substrate in parallel with each other.
In this case, since one gap region in which pressure fluctuations propagate is divided and formed mainly by a plurality of slit-shaped recesses, dust entering the communication hole from the outside is acoustically transmitted through the gap. Reaching the hole can be prevented. That is, the diaphragm can be protected from dust.

  According to the present invention, even if the microphone chip is provided so that the diaphragm faces the acoustic hole formed in the housing, the acoustic resistance against the pressure fluctuation from the outside toward the diaphragm is reduced while reducing the influence of the electromagnetic wave on the microphone chip. Can be reduced.

It is side sectional drawing which shows the microphone package which concerns on one Embodiment of this invention. It is the top view which shows the state which looked at the circuit board which comprises the microphone package of FIG. 1 from the lower surface side. It is a sectional side view which shows the state which mounted the microphone package of FIG. 1 on the mounting board | substrate. It is a sectional side view which shows the microphone package which concerns on other embodiment of this invention. It is the top view which shows the state which looked at the circuit board which comprises the microphone package of FIG. 4 from the lower surface side.

Hereinafter, a microphone package according to an embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 and 2, a microphone package 1 according to this embodiment includes a housing 3 having a hollow cavity S1, and a microphone chip 5 and an LSI chip 7 disposed in the cavity S1. .
The housing 3 is formed in a substantially plate shape, and a circuit board (substrate) 9 on which the microphone chip 5 and the LSI chip 7 are mounted on the upper surface 9a, and a substantially annular side wall member standing on the periphery of the upper surface 9a of the circuit board 9 11 and a plate-like top plate member 13 fixed to the annular front end surface of the side wall member 11. The top plate member 13 closes the opening of the recess defined by the circuit board 9 and the side wall member 11, thereby forming a cavity S <b> 1.

The circuit board 9 is constituted by a so-called multilayer wiring board in which an electrical wiring part (not shown) is provided, and the wiring part exposed on the upper surface 9a is directly or via a wire (not shown). The LSI chip 7 is electrically connected. The circuit board 9 has an acoustic hole 21 penetrating in the thickness direction, and is open to the upper surface 9 a and the lower surface 9 b of the circuit board 9.
Further, the circuit board 9 is formed with a recess 23 that extends in the thickness direction from the lower surface 9b and extends from the peripheral edge of the acoustic hole 21 that opens to the lower surface 9b to the surface direction of the circuit board 9. In the present embodiment, the recess 23 is constituted by a plurality of slit-shaped recesses 24 extending in one direction along the lower surface 9b of the circuit board 9 in parallel with each other.
Further, a plurality of external connection pads 25 to 28 for electrically connecting the microphone chip 5 to the outside are formed on the lower surface 9 b of the circuit board 9. One of these external connection pads 25 to 28 constitutes a ground connection pad (conductive pad) 25 for grounding, and is formed in an annular shape having a rectangular shape in plan view surrounding the acoustic hole 21 and the recess 23 collectively. Yes.

The microphone chip 5 is provided so as to cover the annular support portion 31 formed with an inner hole 31a penetrating in the thickness direction and the inner hole 31a of the support portion 31, and detects pressure fluctuations such as sound by vibration. And a sound detection unit 33. The acoustic detection unit 33 is a substantially plate-shaped fixed electrode 33A provided so as to cover the inner hole 31a of the support unit 31, and is disposed opposite to the fixed electrode 33A and the support unit 31 in the thickness direction with a predetermined interval. And a diaphragm 33B that vibrates in accordance with fluctuations. That is, the microphone chip 5 constitutes a so-called sound pressure sensor chip that converts the vibration of the diaphragm 33B into an electric signal.
The microphone chip 5 is formed of a circuit board 9 with a die bond material (not shown) so that the diaphragm 33B faces the acoustic hole 21 through the inner hole 31a and closes the opening on the upper surface 9a side of the acoustic hole 21. Is fixed to the upper surface 9a. In this fixed state, the cavity S1 of the housing 3 is sealed from the outside and functions as a back air chamber for vibrating the diaphragm 33B.

The LSI chip 7 includes, for example, an amplifier circuit for amplifying an electric signal from the microphone chip 5, an A / D converter for processing the electric signal as a digital signal, a DSP (digital signal processor), and the like. Has been.
Similar to the microphone chip 5, the LSI chip 7 is fixed to the upper surface 9 a of the circuit board 9 by a die bond material (not shown). Further, the LSI chip 7 is electrically connected to the microphone chip 5 by a wire (not shown) or a wiring part (not shown) provided inside the circuit board 9. Therefore, the microphone chip 5 is electrically connected to the circuit board 9 via the LSI chip 7.

Next, a mounting structure of the microphone package 1 having the above configuration will be described.
As shown in FIG. 3, the mounting substrate 41 on which the microphone package 1 is mounted is formed with a communication hole 43 that penetrates in the thickness direction and communicates the acoustic hole 21 outward. In addition, a plurality of bonding lands 45 to 48 that individually bond the plurality of external connection pads 25 to 28 of the microphone package 1 with the solder 51 are formed on the mounting surface 41 a of the mounting substrate 41.
The planar view shape and relative arrangement of the plurality of bonding lands 45 to 48 correspond to the planar view shape and arrangement of the plurality of external connection pads 25 to 28 shown in FIG. For example, similarly to the ground connection pad 25, the ground connection land 45 that joins the ground connection pad 25 is formed in an annular shape having a rectangular shape in plan view. The ground junction land 45 is formed so as to surround the communication hole 43.

In the microphone package 1, the plurality of external connection pads 25 to 28 are individually attached to the plurality of bonding lands 45 to 48 by the solder 51 with the lower surface 9 b of the circuit board 9 facing the mounting surface 41 a of the mounting substrate 41. It is mounted on the mounting substrate 41 by bonding.
In this state, the entire opening on the mounting surface 41a side of the communication hole 43 faces the formation region of the recessed portion 23 in the lower surface 9b of the circuit board 9 (see FIG. 2). That is, the opening on the lower surface 9 b side of the acoustic hole 21 and the opening on the mounting surface 41 a side of the communication hole 43 are arranged so as to be shifted from each other in the surface direction of the circuit board 9 or the mounting substrate 41. Does not overlap in the thickness direction. As a result, the opening on the lower surface 9b side of the acoustic hole 21 is covered with the mounting substrate 41, and electromagnetic waves having high straightness such as sunlight can be prevented from reaching the diaphragm 33B.

Further, in this state, a gap is generated between the lower surface 9 b of the circuit board 9 and the mounting surface 41 a of the mounting board 41 by the solder 51 that joins the ground connection pad 25 and the ground bonding land 45. Therefore, pressure fluctuations such as sound propagate from the outside to the acoustic hole 21 through the communication hole 43 and the gap between the circuit board 9 and the mounting board 41, thereby reaching the diaphragm 33 </ b> B of the microphone chip 5.
Here, a region G1 in which the acoustic hole 21 and the communication hole 43 are opened in the gap between the circuit board 9 and the mounting substrate 41 (hereinafter referred to as one gap region G1) is the ground connection pad 25 and the ground junction land 45. Is separated from the other gap region by the solder 51 that joins to each other, it is possible to prevent the pressure fluctuation from the outside from leaking into the other gap region.
Since one gap region G1 is widened by the recess 23, the acoustic resistance of the one gap region G1 with respect to pressure fluctuations propagating through the one gap region G1 from the acoustic hole 21 toward the communication hole 43 is reduced. The pressure fluctuation can be suppressed from being attenuated before reaching the diaphragm 33B.

As described above, according to the microphone package 1 and its mounting structure, even if the microphone chip 5 is provided so that the diaphragm 33 </ b> B faces the acoustic hole 21 formed in the housing 3, the influence of electromagnetic waves on the microphone chip 5. The acoustic resistance against pressure fluctuations from the outside toward the diaphragm 33B can also be reduced.
In addition, since the recess 23 is constituted by the plurality of slit-shaped recesses 24, the one gap region G1 through which the pressure fluctuation propagates is mainly divided and formed by the plurality of slit-shaped recesses 24. Become. For this reason, it is difficult for dust that has entered the communication hole 43 from the outside to pass through the one gap region G1 and reach the acoustic hole 21 via the one gap region G1. That is, the diaphragm 33B can be protected from dust.

In addition, in the said embodiment, although the hollow part 23 was comprised by the some slit-shaped recessed part 24, it is depressed from the lower surface 9b of the circuit board 9 at least and the surface direction of the circuit board 9 from the periphery of the acoustic hole 21 What is necessary is just to extend in a row. Therefore, the hollow part 23 may be comprised only by the one recessed part formed wider than the slit-shaped recessed part 24, for example.
The recess 23 is not limited to extending in one direction from the periphery of the acoustic hole 21 along the lower surface 9b. For example, as shown in FIGS. It may be formed to extend. In the illustrated example, the ground connection pad 25 is formed in an annular shape in plan view following the outer edge shape of the recess 23.

In the configuration shown in FIGS. 4 and 5, for example, a through hole that penetrates the top plate member 13 in the thickness direction and functions as an acoustic hole may be formed. In this case, since the cavity S1 communicates outward through the through hole of the top plate member 13, pressure fluctuations such as sound are transmitted to the cavity S1 through the through hole of the top plate member 13. The fluctuation is detected by reaching the diaphragm 33B.
The microphone package having this configuration may be mounted on the mounting substrate 41 in which the communication hole 43 is not formed in the same manner as in the above embodiment. In this mounted state, the inner hole 31a of the microphone chip 5, the acoustic hole 21 and the recess 23 of the circuit board 9, the mounting surface 41a of the mounting board 41, and the ground connection pad 25 of the circuit board 9 are bonded to the mounting board 41. The space defined by the solder 51 to be sealed is sealed to the outside and functions as a back air chamber for vibrating the diaphragm 33B. In this configuration, the volume of the space can be increased by forming the recess 23. Thereby, it can prevent that the vibration of the diaphragm 33B based on pressure fluctuations, such as sound, is inhibited by the pressure rise in a space part. That is, it is possible to prevent the S / N ratio of the microphone chip 5 that detects pressure fluctuations such as sound from becoming small.

  The microphone chip 5 is mounted on the circuit board 9 such that the diaphragm 33B faces the acoustic hole 21 via the inner hole 31a of the support portion 31. At least the diaphragm 33B faces the acoustic hole 21. What is necessary is just to distribute | arrange so that the opening by the side of the upper surface 9a of the acoustic hole 21 may be plugged up. Therefore, the microphone chip 5 may be mounted on the upper surface 9a upside down from the state of the illustrated example, that is, mounted so that the inner hole 31a of the support portion 31 opens into the cavity S1. .

  Further, an annular conductive pad 25 formed on the lower surface 9 b of the circuit board 9 and surrounding the acoustic hole 21 and the recess 23 is a ground connection pad 25 for grounding the microphone chip 5 and the LSI chip 7. However, as long as it can be bonded to the annular bonding land 45 formed on the mounting substrate 41 via the solder 51, it is not particularly necessary to be electrically connected to the microphone chip 5 or the LSI chip 7.

Moreover, although the housing 3 was comprised by three, the circuit board 9, the top-plate member 13, and the side wall member 11, it does not restrict to this. For example, the side wall member 11 of the above embodiment may be formed integrally with the circuit board 9 of the above embodiment so as to form a multilayer wiring board together with the circuit board 9, or the upper surface of the circuit board 9 together with the top plate member 13. It may be formed integrally with the top plate member 13 so as to form a lid member covering 9a.
Furthermore, in the above-described embodiment, the microphone package 1 on which the LSI chip 7 is mounted has been described. However, the present invention is not limited to this and can be applied to at least a microphone package on which the microphone chip 5 is mounted.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

DESCRIPTION OF SYMBOLS 1 ... Microphone package, 3 ... Housing, 5 ... Microphone chip, 9 ... Circuit board (board | substrate), 9a ... Upper surface, 9b ... Lower surface, 21 ... Acoustic hole, 23 ... Recessed part, 24 ... Slit-shaped recessed part, 25 ... Ground connection Pad (conductive pad), 33B ... Diaphragm, 41 ... Mounting substrate, 41a ... Mounting surface, 43 ... Communication hole, 45 ... Junction land, 51 ... Solder, S1 ... Cavity

Claims (3)

A housing having a hollow cavity, and a microphone chip having a diaphragm for detecting pressure fluctuation and mounted on an upper surface of the cavity among the substrates constituting the housing;
In the substrate, an acoustic hole penetrating in the thickness direction is formed,
The microphone chip is mounted on the upper surface of the substrate so that the diaphragm faces the acoustic hole and closes the opening on the cavity side of the acoustic hole,
The lower surface of the substrate is recessed in the thickness direction from the lower surface and extends from the peripheral edge of the acoustic hole in the surface direction of the substrate, and an annular shape surrounding the acoustic hole and the recessed portion A microphone package in which a conductive pad is formed.   2. The microphone package according to claim 1, wherein the recess is configured by a plurality of slit-like recesses extending in one direction along the lower surface of the substrate in parallel with each other. A microphone package according to claim 1 or 2, and a mounting substrate having a mounting surface for mounting the microphone package,
The mounting board includes a communication hole that penetrates in the thickness direction to communicate the acoustic hole outward, and an annular bonding land that is disposed on the mounting surface and corresponds to the shape of the conductive pad. Formed,
In the state where the lower surface of the substrate is opposed to the mounting surface and the conductive pad and the bonding land are bonded by solder, the opening on the mounting surface side of the communication hole is opposed to the formation region of the recess. A mounting structure of a microphone package, which is characterized by

Images