KR20080101374A - Condenser microphone - Google Patents

Abstract

A condenser microphone minimizes the whole thickness of the condenser microphone by inserting circuit elements into a cavity formed on a predetermined region of a PCB. An MEMS(Micro Electro Mechanical System) chip converts a sound into an electrical signal. A semiconductor chip processes the electrical signal converted in the MEMS chip. A substrate includes a hole etched with a predetermined depth into which the MEMS chip(50) and the semiconductor chip are inserted. A sound hole to which the sound is inputted is formed in a case(20). The case is assembled with the substrate.

Description

Condenser microphone

1 is a perspective view of a PCB of a condenser microphone according to the present invention;

2 is a perspective view of a case of a condenser microphone according to the present invention;

3 and 4 are perspective views showing the assembly shape of the condenser microphone according to the present invention;

5 is a side sectional view of a condenser microphone according to the present invention;

6 is a sectional view of a multilayer PCB of a condenser microphone according to the present invention;

<Description of the symbols for the main parts of the drawings>

10: PCB 10a, 10b: hole

20: case 20a: sound hole

21: epoxy 30a ~ 30d for sealing: electrode pads

40: ASIC 41: coating liquid

50: MEMS Chip

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a condenser microphone, and is a technology for significantly reducing the overall thickness of a microphone by inserting a plurality of components into a cavity (Cavity) type PCB when joining a case of a condenser microphone and a PCB.

Recently, the ability to record the sound from the surroundings is common in multimedia devices commonly encountered in the surroundings, such as a camcorder, a moving picture expert crops layer 3 (MP3), and a mobile (mobile). It is provided.

In particular, one of the reasons that such a recording function can be normally performed in miniaturized and integrated multimedia devices while maintaining high performance is due to a microphone miniaturized and mounted in the multimedia device.

The microphone is typically a dynamic microphone using a magnet and a condenser microphone using a principle of a capacitor (or a capacitor, a capacitor, or a capacitor).

In the case of the dynamic microphone, an induction electromotive force is used to store a magnet capable of forming a constant magnetic field (or magnetic field) inside the microphone. And a coil connected to the diaphragm and flowing inside the magnetic field. This dynamic microphone measures the induced electromotive force generated when the coil is shaken inside the magnetic field due to vibration and converts it into an electrical signal.

However, the dynamic microphone has a mechanically strong characteristic, which is advantageous for use in a harsh environment, but has a disadvantage in that it is difficult to miniaturize because the magnet is to be housed inside the microphone, and the sensitivity is poor and the response speed is slow.

On the other hand, condenser microphones widely used in mobile communication terminals, audio, etc. among the microphones have advantages of relatively small size, excellent sensitivity and response speed. In the condenser microphone, an electric field is formed by a diaphragm and a bipolar plate, and a principle of measuring an electric field changed by vibration of the diaphragm and converting the electric field into an electrical signal is used.

To this end, the condenser microphone must be powered by either the diaphragm or the bipolar plate to form an electric field. For this reason, a method of supplying power to the bipolar plate has been used, and recently, a condenser microphone has been developed that does not require a separate power supply by an electret in which charge is accumulated.

Such condenser microphones can be further miniaturized by using electrets in which charge is almost permanently accumulated. The condenser microphone using an electret is called an electret condenser microphone (hereinafter referred to as 'ECM'), and the front type, back type, and diaphragm are used depending on the positions of the electret and the diaphragm. In the case of an electret, it is classified as a foil type.

The ECM is sequentially placed in a cylindrical or polygonal container (or case) in which one surface of a diaphragm, a dielectric plate, a spacer ring, an insulation and conductive base ring, and a printed circuit board (hereinafter referred to as a PCB) is blocked. It is manufactured in a stacked form. Then, a sound hole is formed on the closed surface of the cylinder or the container, and vibration generated by voice is transmitted through the sound hole.

In addition, when components such as a diaphragm, a dielectric plate, a spacer ring, an insulation, and a conductive base ring are accommodated in the case, the remaining portion of the case may be bent and sealed, or the end of the PCB and the case may be combined to manufacture an ECM.

At this time, a solder ball for applying SMD (Surface Mount Devices) method is attached to the part exposed to the outside of the PCB, or for connection with a mother board (main board or mother board). Terminals are formed. The ECM with solder balls or terminals is attached to the mother substrate by an attachment process such as an SMD process or a soldering process.

On the other hand, semiconductor processing technology using micromachining is commonly used as a technique used for integrating micro devices in recent years. This technology, called MEMS (Micro Electro Mechanical System), is an application of semiconductor processes, especially integrated circuit technology, to fabricate microscopic sensors, actuators and electromechanical structures in micrometers.

MEMS chip microphones manufactured using such micromachining technology are capable of miniaturization, high performance, multifunction, integration through ultra-precision micromachining, and have the advantage of improving stability and reliability.

However, such a conventional microphone has a structure in which the above-described components are stacked or housed on the upper part of the PCB and mounted on the main board. Accordingly, in the case of the mobile communication terminal including the main board, the thickness of the region where the condenser microphone is mounted becomes high. As a result, multimedia devices equipped with a condenser microphone having a high thickness have a limitation in slimming.

The present invention was created to solve the above problems, by inserting the circuit components in the cavity (cavity) formed in a certain area of the PCB to overlap the thickness of the components and the PCB thickness as possible, minimizing the overall thickness of the condenser microphone The purpose is to make it possible.

Condenser microphone of the present invention for achieving the above object, Memes chip for converting sound into an electrical signal; A semiconductor chip processing an electrical signal converted from the MEMS chip; And a substrate having a hole etched to a predetermined depth into which the MEMS chip and the semiconductor chip are inserted.

Hereinafter, with reference to the accompanying drawings will be described in detail an embodiment of the present invention.

1 is a perspective view of a PCB of a condenser microphone according to the present invention.

PCB 10 of the present invention is composed of a multi-layer (Printed Circuit Board) (hereinafter referred to as 'PCB'), and for amplifying and filtering the electric signals generated by the change of the electric field to deliver to the outside Circuits and terminals are formed.

Then, holes 10a and 10b are formed to insert circuit components in a predetermined region of the PCB 10. The holes 10a and 10b formed in the PCB 10 are formed through a method of etching the PCB 10 to a predetermined depth through, for example, a drill process. In addition, the holes 10a and 10b may be formed by selectively masking through a photolithography process and then etching a predetermined depth downward.

In the present invention, the formation of the holes 10a and 10b through the drill process and the photolithography process has been described in the embodiment, but the present invention is not limited thereto and may be formed through various methods.

The present invention forms holes (Cavities) (10a, 10b) having a predetermined depth in the multi-layer PCB 10, it is possible to respond strongly to electromagnetic shielding or electrostatic discharge (ESD), etc. relative to the double-sided PCB.

2 is a perspective view of a case of a condenser microphone according to the present invention.

Case 20 of the present invention is made of metal (Metal), and forms a rectangular shape covering the entire structure of the PCB (10). The case 20 allows a connection surface with the PCB 10 to be opened to mount chip components therein.

The case 20 protects the internal circuit components from external shocks. In addition, shielding the electromagnetic noise introduced from the outside to facilitate the electrical signal conversion of the sound.

In the embodiment of the present invention, the shape of the case 20 has been described as a rectangular cylinder, but the present invention is not limited thereto, and the case 20 may be formed in a cylindrical shape. In addition, the material of the case 20 may be formed of any one of brass, copper, stainless steel, and nickel alloy for noise shielding, electrical conductivity improvement, and corrosion prevention.

The case 20 has a sound hole (20a) is formed so that one side of the upper surface is open so that the voice signal can be introduced. The upper surface of the case 20 is a blockage except for the sound hole (20a) that the sound is introduced. The vibration generated by the voice is transmitted to the internal circuit through the sound hole 20a. In addition, the case 20 has a form in which the inside thereof forms an empty cavity and extends by a predetermined length.

3 and 4 are perspective views showing the assembly shape of the condenser microphone according to the present invention.

When the case 20 is aligned with the connection pattern of the PCB 10, the PCB 10 and the case 20 are integrated and assembled. In this case, the PCB 10 and the case 20 are dispensed by sealing (Epoxy) 21 for sealing (Sealing). Here, the shape of the case 20 has a size that can be fixed in contact with the side edge of the PCB 10 and the size is not limited.

The above-described PCB 10 has an anode and a cathode pattern, and at least one electrode pads 30a to 30d are attached to the lower edge region thereof to contact the anode and cathode patterns, respectively, to form electrical contact. In the present invention, the electrode pads 30a to 30d are formed in four embodiments, but the present invention is not limited thereto, and the number of electrode pads may be smaller or greater.

Electrode pads 30a to 30d for electrically connecting to an external circuit are formed on the opposite side of the PCB 10 on which the case 20 is mounted. The electrode pads 30a to 30d fix the microphone to the main board (not shown), and provide a conductive path between the microphone and the main board.

Each of the electrode pads 30a to 30d may be electrically connected to the chip component surface through a through hole (not shown) passing through the PCB 10. Each of the electrode pads 30a to 30d may be attached to one surface of the PCB 10 by a laser welding, resistance welding, high temperature adhesive, soldering, or the like.

Here, the contact area between the PCB 10 and the case 20 may be integrated through the method of laser welding, using an adhesive, for robustness. The adhesive described above may be made of any one of conductive epoxy, non-conductive epoxy, silver paste, silicone, urethane, acrylic, cream solder. In addition, the through hole may be formed on one side of the PCB 10, and the PCB 10 and the case 20 may be integrated by various methods, such as a method of manufacturing the case 20 in a concave-convex shape and combining the same.

In the present invention, after aligning the case 20 to the connection pattern of the PCB 10, the case 20 and the PCB 10 is first welded by using a laser processing machine (not shown), and then fixed around the entire surface of the joint. Sealing with epoxy for sealing completes the package of the microphone.

Fig. 5 is a side sectional view of the condenser microphone according to the present invention seen from the direction of A-A '.

In the holes 10a and 10b of the PCB 10, circuit components electrically connected to the electrode pads 30a to 30d are inserted and seated.

The PCB 10 processes the amplified, filtered, and the like electrical signals converted by the circuit components and supplies them to the main board through the electrode pads 30a to 30d.

Here, the holes 10a and 10b are formed at both corners or the center of the PCB 10 and may be formed anywhere according to the positions of the electrode pads 30a to 30d electrically connected thereto.

In the present invention, although the shape of the holes 10a and 10b has been described as the embodiment, the insertion is formed similarly to the external shape of the circuit components in consideration of the insertion direction and the shape of the circuit components. It is desirable to facilitate.

That is, the shapes of the holes 10a and 10b may be formed differently according to the shapes of the circuit components. For example, when the circuit components are manufactured in a cylindrical shape, the shapes of the holes 10a and 10b are also cylindrical, and when the circuit components are manufactured in a cube, the shapes of the holes 10a and 10b are formed into hexahedrons. It is preferable to be.

Examples of the above-described circuit components include an application spec integrated circuit (ASIC) chip 40 and a MEMS chip with a voltage pump and a buffer IC. 50 and the like. The ASIC chip 40 is inserted into the hole 10a formed in the PCB 10, and the MEMS chip 50 is inserted into the hole 10b formed in the PCB 10.

In the present invention, the ASIC chip 40 has been described as an embodiment of the circuit component. However, the present invention is not limited thereto, and the circuit component corresponds to an electronic circuit portion formed by a semiconductor process, and may be formed of, for example, a conventional FET or IC.

Here, the MEMS chip 50 converts the voice signal supplied through the sound hole 20a formed in the case 20 into an electric signal by applying a change in capacitance. That is, the MEMS chip 50 detects the capacitance changing according to the vibration of the vibration membrane generated by the incoming sound wave and converts it into an electrical signal. The MEMS chip 50 has a structure in which a back plate is formed on a silicon wafer by using MEMS technology, and a vibrating membrane is formed between spacers.

The ASIC chip 40 is connected to the MEMS chip 50 to process an electrical signal. The ASIC chip 40 includes a voltage pump for providing a voltage to be applied to the MEMS chip 50 so that the MEMS chip 50 operates as a condenser microphone, and a buffer IC for amplifying an electrical signal of the MEMS chip 50. ) Is built.

The buffer IC is configured to amplify or match an electric sound signal detected through the MEMS chip 50 and to provide the same to the outside through a connection terminal. Here, the voltage pump may be a DC-DC converter, and the buffer IC may be an analog amplifier or an analog-to-digital converter (ADC).

In addition, the coating liquid 41 is applied and cured through an encapsulation process around the upper front surface and the bonding surface of the ASIC 40 to protect the circuit elements of the ASIC 40 from external harmful substances. . Here, the coating liquid 41 may be made of an epoxy solution. In the embodiment of the present invention, the coating liquid 41 is described as an epoxy solution, but the present invention is not limited thereto, and may be formed of any material suitable for the characteristics of each product.

6 is a cross-sectional view of a multilayer PCB of a condenser microphone according to the present invention.

The multilayer PCB 10 of the present invention includes a plurality of conductive layers 12, 14 and 16 and a plurality of nonconductive layers 11, 13, 15 and 17. Here, the conductive layers 12, 14, and 16 may be formed of a copper foil layer including circuit configurations. In addition, the non-conductive layers 11 and 17 may be made of a PSR (Photo Solder Resist) layer for protecting circuit components. In addition, the non-conductive layers 13 and 15 may be made of a FR-4 (Flame Retardant composition 4) layer as an adhesive layer.

The multilayer PCB 10 is formed by alternately stacking a plurality of nonconductive layers 11, 13, 15, and 17 and a plurality of conductive layers 12, 14, and 16.

That is, the non-conductive layer 11 codes an insulating material such as a PSR layer to form a film. The copper foil layer serving as the conductive layer 12 is formed on the non-conductive layer 11 through a general PCB manufacturing process. Thereafter, the non-conductive layer 13 is formed on the conductive layer 12. Here, it is preferable that the non-conductive layer 13 consists of a FR-4 (Flame Retardant composition 4) layer which is an epoxy resin.

Subsequently, the copper foil layer, which is the conductive layer 14, the FR-4 layer, which is the non-conductive layer 15, the conductive layer 16, and the non-conductive layer 17 are sequentially stacked on the non-conductive layer 13 to form the multilayer PCB 10. Will form.

The ASIC 40 and the MEMS chip 50 may be inserted into the holes 10a and 10b of the PCB 10 having such a structure.

That is, in the present invention, forming the holes 10a and 10b of the multilayer PCB 10 by etching the PSR layer as the non-conductive layer 17 and the FR-4 layer as the copper foil layer 16 and the non-conductive layer 15. desirable. For example, when the thickness t of the PCB 10 is 0.3 mm, the depths of the holes 10a and 10b are preferably etched to 0.2 mm. When the thickness of the PCB 10 is 0.5 mm, the depths of the holes 10a and 10b may be etched up to 0.4 mm.

In addition, the present invention has been described in the embodiment that the etching to the depth to expose the copper foil layer 14, the depth in which the holes (10a, 10b) are etched is not limited to this, but the depth is different depending on the specification of the PCB Can be formed.

As described above, the present invention provides the following effects.

First, the present invention inserts circuit components into a cavity formed in a predetermined area of the PCB so that the thickness of the components and the thickness of the PCB overlap as much as possible, thereby minimizing the overall thickness of the condenser microphone.

Second, it provides an effect that can realize the slimmer of the mobile communication terminal including the condenser microphone described above.

In addition, a preferred embodiment of the present invention is for the purpose of illustration, those skilled in the art will be able to various modifications, changes, substitutions and additions through the spirit and scope of the appended claims, such modifications and changes are the following claims It should be seen as belonging to a range.

Claims (15)

MEMS chip for converting sound into an electrical signal; A semiconductor chip processing an electrical signal converted from the MEMS chip; And And a substrate having a hole etched to a predetermined depth into which the MEMS chip and the semiconductor chip are inserted. The condenser microphone of claim 1, further comprising a case in which a sound hole into which the sound is introduced is formed and assembled with the substrate. 3. The condenser microphone according to claim 2, wherein the case has a tubular structure covering the entire structure of the substrate. The condenser microphone according to claim 2, wherein the substrate and the case are packaged by a sealing epoxy. 5. The condenser microphone of claim 4, wherein the case has the same shape as the substrate and is fixed in contact with a side edge of the substrate. 2. The condenser microphone of claim 1, further comprising at least one electrode pad attached to and electrically connected to a lower surface of the substrate. The condenser microphone of claim 1, wherein the hole has the same shape as the MEMS chip and the semiconductor chip. The condenser microphone of claim 1, wherein the semiconductor chip is a special purpose semiconductor (ASIC) chip. The condenser microphone according to claim 1, wherein a coating liquid is applied to the semiconductor chip. The condenser microphone of claim 1, wherein the substrate is a multilayer PCB substrate. The condenser microphone according to claim 1 or 10, wherein the substrate is formed by alternately stacking a plurality of conductive layers and a plurality of nonconductive layers. The condenser microphone according to claim 11, wherein the plurality of conductive layers comprises a copper foil layer. The condenser microphone of claim 11, wherein the plurality of non-conductive layers include a photo solder resist (PSR) layer and a flame retardant composition 4 (FR-4) layer. The condenser microphone of claim 13, wherein the hole is formed in an area in which at least one conductive layer, one PSR layer, and one FR-4 layer are etched. 12. The condenser microphone of claim 11, wherein the hole is formed in an area where at least one conductive layer and at least two nonconductive layers are etched.

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