CONDENSER MICROPHONE

Abstract

The present invention is directed to a condenser microphone with a microphone housing cap with a sound inlet opening, a microphone housing with a cross-sectional opening facing the microphone housing cap, and a diaphragm resting along the cross-sectional opening on the front side of the microphone housing surrounding the cross-sectional opening, and a counter-electrode which faces this diaphragm and which is arranged at a short distance from the diaphragm. The invention is further directed to a corresponding method for producing a condenser microphone of this kind. The invention provides an improved condenser microphone and an improved method for producing such a condenser microphone so that the disadvantages of the prior art are overcome while reducing manufacturing-related resources and, therefore, costs at the same time in that the diaphragm of the condenser microphone is glued to the microphone housing in an angle area between the underside of the diaphragm and the outer side of the microphone housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a cross section through a first embodiment form of a condenser microphone according to the invention;

FIG. 2 shows a section from the cross section through the first embodiment form of a condenser microphone according to the invention;

FIG. 3 shows a section from the cross section of another embodiment form of a condenser microphone according to the invention; and

FIG. 4 is a schematic view of a closure mechanism for the microphone housing cap and/or closing cap and microphone housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment form of a condenser microphone according to the invention is shown in FIG. 1. The condenser microphone comprises a microphone housing 10, a microphone housing cap 12 and a closing cap 14. The microphone housing 10 is constructed as a tube which is open at both ends and contains practically the entire transducer.

The microphone housing cap 12 and the closing cap 14 are each constructed as a kind of sleeve and essentially serve as a protective and decorative covering for the microphone housing 10. Both the microphone housing cap 12 and the closing cap 14 have an inner diameter that is greater than the outer diameter of the microphone housing 10 so that the microphone housing cap 12 and closing cap 14 can both be placed over the cross-sectional opening of the microphone housing 10.

The microphone housing cap 12 has sound inlet openings 16. An acoustically permeable protective gauze 18 is arranged inside the microphone housing cap 12 behind the sound inlet openings 16. The inner diameter of the microphone housing cap 12 has a step so that the inner diameter near the sound inlet openings 16 is smaller than the inner diameter remote of the sound inlet openings 16. Only the inner diameter remote of the sound inlet openings 16 is greater than the outer diameter of the microphone housing 10 so that the microphone housing cap 12 rests by the step on a diaphragm 24 arranged on the microphone housing 10.

The closing cap 14 has a bottom opening 20. The diaphragm 24 which has an electrically conductive coating on both sides lies on the front side 25 of the microphone housing 10 which surrounds the cross-sectional opening facing the microphone housing cap 12. The coating of the diaphragm 24 contacts the microphone housing 10. On the outer side 27 of the microphone housing 10, the front side 25 has a bevel 26 forming the outer side 27 (shown in FIG. 2). In this embodiment form, the bevel 26 has, e.g., an angle of 45° from the front side 25. An adhesive 28 which glues the underside of the diaphragm 24 to the outer side 27 of the microphone housing 10 is arranged in the bevel 26.

To fasten the diaphragm 24 to the microphone housing 10 in this way, the pretensioned diaphragm 24 is first placed on the front side 25 of the microphone housing 10 surrounding the cross-sectional opening and facing the microphone housing cap 12. Adhesive 28 is then applied to only one point between the underside of the diaphragm 24 and the outer side 27 of the microphone housing 10 and then distributes itself in the bevel 26 on the circumference. The projecting edge of the diaphragm 24 is trimmed and the remaining projecting portion, if any, is bent slightly by placing the microphone housing cap 12 on it, resulting in a contact between the coating of the diaphragm 24, e.g., a gold coating, and the inner side of the microphone housing cap 12.

An insulating part 30 which is made of plastic, for example, is arranged in the microphone housing 10. In this first embodiment form, the insulating part 30 has a bevel 32 at its side remote of the diaphragm 24 and adhesive 28 is arranged in the bevel 32 so that the insulating part 30 is glued to the inner side of the microphone housing 10.

A counter-electrode 34 is arranged on the side of the insulating part 30 facing the diaphragm 24 and is glued to the insulating part 30 by means of adhesive 28 which is arranged in a groove 36 arranged on the insulating part 30. An electret layer 38 is arranged at a short distance from the diaphragm on the side of the counter-electrode 24 facing the diaphragm 24.

For example, when producing the condenser microphone, the counter-electrode 34 (with electret layer 38) is first arranged in the microphone housing 10 so as to produce an air gap—defined as the distance between the front side of the microphone housing and the surface of the counter-electrode—of the desired value, usually on the order of 20 to 30 μm. The diaphragm 24 is then laid on the front side 25 of the microphone housing 10. Subsequently, the diaphragm is glued to the microphone housing as was described above.

A printed circuit board 40 is arranged at the cross-sectional opening of the microphone housing 10 facing the closing cap 14 in such a way that it contacts the second front side 41 of the microphone housing 10 in an insulated manner. The printed circuit board 40 is provided with an outer copper ring 50 and an inner copper surface 22 on its side facing the closing cap 14. The printed circuit board 40 contacts the closing cap 14 by the outer copper ring 50. The printed circuit board likewise has an annular copper coating 46 on the side facing the microphone housing 10.

A connecting member 42 which can be constructed, e.g., as a contact spring extends on the printed circuit board 40 within the microphone housing 10 from the counter-electrode 34 to the annular copper coating 46. A circuit arrangement 44, e.g., an integrated circuit, is arranged on the part of the connecting member 42 near the printed circuit board 40.

A spacer element for preserving the distance between the printed circuit board and the counter-electrode is not required in this embodiment form because the housing itself takes over the function of the spacer element. Alternatively, separate spacer elements can be used.

In an alternative embodiment form, the front side 25 of the microphone housing has no bevel. Rather, as can be seen from FIG. 3, the adhesive 28 is arranged in the angle area between the underside of the diaphragm 24 and the outer side 27 of the microphone housing 10. The projecting edge of the diaphragm 24 is again trimmed and the remaining portion having a width of, e.g., 200 μm is bent slightly by placing the microphone housing cap 12 on it, resulting in a contact between the diaphragm 24 and the microphone housing cap 12. Consequently, the gap between the microphone housing 10 and the microphone housing cap 12 is not as large in this embodiment form.

Alternatively, it is also possible that the microphone housing cap has a uniform inner diameter, that is, it does not rest on the diaphragm arranged on the microphone housing and, for example, the microphone housing has a step as spacer on which the fitted microphone housing cap rests.

In another alternative construction, it is can be provided that the insulating part carrying the counter-electrode is not connected over its full circumferential area to the microphone housing so that at least one gap serving as air outlet is formed between the edge of the insulating part and the inner wall of the microphone housing.

FIG. 4 shows a possible connection of the microphone housing cap 12 and/or closing cap 14 to the microphone housing 10. The microphone housing 10 has webs 48 on its outer circumference which are formed in this instance as strips with a triangular cross section. These webs 48 can have a width of 20 to 30 μm and a depth of up to 50 μm, for example. When the microphone housing cap 12 and/or closing cap 14 are placed on the microphone housing 10, a slight pressure is applied to the strips and the microphone housing cap 12 and/or closing cap 14 can only be detached from the microphone housing 10 with great difficulty.

Accordingly, the invention proposes that the diaphragm is glued by its underside to the outer side of the microphone housing in an angle area. Therefore, the use of the customary diaphragm ring which reduces the effective usable surface of the diaphragm is obviated. It is likewise unnecessary to fold and clamp the diaphragm surface. Further, the evenness of the diaphragm surface is further improved over the prior art and the loss of diaphragm surface capable of oscillation can be further reduced. Miniature condenser microphones of higher quality can be built by means of the invention in less time and with less material. Beyond this, the invention has the advantage that the cost of rejects can be reduced because the individual assemblies can be tested before final assembly.

While the foregoing description and drawings represent the present invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the true spirit and scope of the present invention.

Claims

1. A condenser microphone comprising: a microphone housing cap with a sound inlet opening;a microphone housing with a cross-sectional opening facing the microphone housing cap;a diaphragm resting along the cross-sectional opening on the front side of the microphone housing surrounding the cross-sectional opening;a counter-electrode which faces said diaphragm and which is arranged at a short distance from the diaphragm; andsaid diaphragm being glued to the microphone housing in an angle area between the underside of the diaphragm and the outer side of the microphone housing.

2. The condenser microphone according to claim 1, wherein the diaphragm is glued to the microphone housing only in the angle area between the underside of the diaphragm and the outer side of the microphone housing.

3. The condenser microphone according to claim 1, wherein the microphone housing has a bevel at the outer side of the microphone housing in the front and the diaphragm is glued to the microphone housing in the angle area between the underside of the diaphragm and the outer side of the microphone housing formed by the bevel.

4. The condenser microphone according to claim 3, wherein the angle between the outer side formed by the bevel and the front side of the microphone housing is between 15° and 45°.

5. The condenser microphone according to claim 1, wherein the radial width of the glued portion is in the range of 30 μm to 100 μm.

6. The condenser microphone according to claim 1, wherein no adhesive is arranged between the front side of the microphone housing and the diaphragm or an electrically conductive coating arranged at least partially on the diaphragm.

7. The condenser microphone according to claim 1, wherein the underside of the diaphragm is glued to the outer side of the microphone housing by means of a highly liquid adhesive.

8. The condenser microphone according to claim 1, wherein the inner diameter of the microphone housing cap is greater than the outer diameter of the microphone housing, and the microphone housing cap is arranged over the microphone housing.

9. The condenser microphone according to claim 8, wherein the microphone housing has concentrically arranged webs, particularly strips, on its outer circumference.

10. The condenser microphone according to claim 1, wherein a printed circuit board with a circuit arrangement for signal processing is arranged at the microphone housing and is arranged at a distance from the counter-electrode and electrically connected to the counter-electrode by electric connecting means, the distance of the printed circuit board from the counter-electrode being defined by the microphone housing itself.

11. The condenser microphone according to claim 1, wherein the counter-electrode is carried by an insulating part which is not connected to the microphone housing over its full circumferential area, so that at least one gap serving as an air outlet is formed between the edge of the insulating part and the inner wall of the microphone housing.

12. A method for producing a condenser microphone with a microphone housing cap with a sound inlet opening, a microphone housing with a cross-sectional opening, and a diaphragm resting along the cross-sectional opening on the front side of the microphone housing surrounding the cross-sectional opening, and a counter-electrode which faces this diaphragm and which is arranged at a short distance from the diaphragm, comprising the step of gluing the diaphragm to the microphone housing in an angle area between the underside of the diaphragm and the outer side of the microphone housing.

13. The method according to claim 12, further comprising the steps of applying adhesive only at one point in the angle area between the underside of the diaphragm and the outer side of the microphone housing for gluing the diaphragm to the microphone housing, and allowing the adhesive to subsequently distribute itself in the angle area.