BACKGROUND ART Recently, as the technologies related to the communications apparatus such as telephone or cellular phone, and the sound equipment such as amplifier develop greatly, the demand for microphones that convert acoustic energy to electric energy also has been increased.

The conventional microphone for such purpose, such as a condenser microphone, is disclosed in detail in US patent No. 5,490,220,"Solid state condenser and microphone devices", US patent No. 5,870,482,"Miniature silicon condenser microphone", US patent No. 6,088,463,"Solid state silicon-based condenser microphone", Japanese patent application publication 1999-266,499,"Electret condenser microphone", Japanese patent application publication 1999-88989,"Electret condenser microphone", Korean patent application publication 2000-19963, "Condenser microphone for mobile radio communication terminal", Korean patent application publication 1999-55502,"condenser microphone", etc.

The conventional condenser microphone generally consists of a printed circuit

board ("PCB") on which a series of electrical patterns are formed, a diaphragm which is located on the PCB and vibrates by sound wave injected from outside, a dielectric plate which is located apart from the diaphragm by a predetermined gap, and a case which holds in its inside all the said elements, namely, the PCB, the diaphragm and the dielectric plate.

As shown in Korean patent [application] publication 2000-12516,"The isolation ring and fixing method for condenser microphone"for example, a dielectric plate is surrounded compactly by a base ring block including"a metal base ring and a isolation base ring", and is stably contained in a case. As the base ring block is contained, a back chamber of a certain size is defined between the PCB and the dielectric plate.

Here, because"the gap between the diaphragm and the dielectric plate"and "the back chamber between the PCB and the dielectric plate"are located in the main transmission path through which sound wave is inputted from outside, the"gap"and the"back chamber"greatly affect the overall performance of the microphone. Thus, a large amount of efforts have been made in the research on the structure of the gap and the back chamber. For example, research has frequently been carried out to precisely adjust the parallelism.

Ordinarily, a conventional microphone having the above-described structure is assembled through steps such as"a step of press fitting a dielectric plate and a base ring block into an assembly"and"a step of inserting the dielectric plate/base ring assembly between a PCB and a diaphragm, and assembling the PCB, the dielectric plate/base ring assembly and the diaphragm into a case sequentially".

However, in case of the combination of the dielectric plate and the base ring

block through a series of the press fit processes, the pressing force of a certain magnitude is inevitably applied to the joint of the dielectric plate and the base ring block, and the dielectric plate and the base ring block are inevitably deformed by the transmitted pressing force. Also, the respective joint part of the dielectric plate and the base ring block is worn and damaged by the pressing force.

In addition, because dielectric plates and base ring blocks are very small generally, even a minute processing error during the press fit process can cause serious problems of damaging these parts.

As mentioned above,"the gap formed between the diaphragm and the dielectric plate"is located in the main passage of the sound wave that flows in from outside and thus affects greatly the overall performance of the microphone.

Accordingly, if the dielectric plate and the base ring are deformed or damaged, and thus, for example, the parallelism of"the gap formed between the diaphragm and the dielectric plate"is destroyed due to the"pressure"applied during the press fit process or the"processing error", the performance and the productivity of the final microphone are resultantly degraded.

Also, as explained above, if"the dielectric plate and the base ring block"form a single assembly through a series of the press fit processes, two base rings that form the base ring block, i. e."the metal base ring and the isolation base ring,"inevitably adhere closely to each other. In this case, the unbalanced press fit between the dielectric plate and the base ring may occur and, accordingly, the dielectric plate of the final microphone assembly is not level on"the back chamber defined by the base ring block,"and is tilted to the left or the right. Consequently, the parallelism of the dielectric plate is broken and the performance and the productivity of the final

microphone are inevitably degraded.

Moreover, as described above, in case that two base rings that form the base ring block adhere closely to each other, the inner space of the back chamber defined by the base ring block may be closed. Therefore, the pressure of the inner space of the back chamber may not be in balance with the ambient air. Consequently, the frequency characteristic of the final microphone assembly is seriously deteriorated.

To complete a microphone as an independent assembled unit, as mentioned above, steps such as"a step of press fitting a dielectric plate and a base ring block into an assembly"and"a step of inserting the dielectric plate/base ring assembly between a PCB and a diaphragm, and assembling the PCB, the dielectric plate/base ring assembly and the diaphragm into a case sequentially"are individually conducted. In this case, the assembly line is inevitably divided into two lines. Accordingly, the number of required processes increases and thus the productivity is lowered seriously.

DISCLOSURE OF THE INVENTION The object of the present invention is to have a dielectric plate and base rings be assembled with other structures to form one completed microphone assembly and, accordingly, to exclude the conventional press fit process for assembling"the dielectric plate and the base ring block"from the overall assembly line of a microphone, thereby preventing"the deformation of the dielectric plate"or"the damage to the dielectric plate and the base ring"that may occur during the press fit process.

Another object of the present invention is to make it possible to maintain high performance and productivity of the final ultra-thin type condenser microphone by preventing"the deformation of the dielectric plate"and"the damage to the dielectric

plate and the base ring"that may occur during the press fit process in advance and by making"the gap formed between the diaphragm and the dielectric plate"be in parallelism.

Another object of the present invention is to induce a certain size gap to be formed between two base rings, e. g., a metal base ring and an isolation base ring, when a dielectric plate and base rings, in their independent and individual states, are combined into other structures and, accordingly, to prevent the deterioration of the parallelism of the dielectric plate caused by the close adhesion of the base rings, thereby making it possible to maintain high level of parallelism of the dielectric plate on"the back chamber defined by the base ring block"and to form a stable air flow passage between the inner space of the back chamber and the outside environment.

Another object of the present invention is to improve the frequency characteristic and the productivity of the final ultra-thin type condenser microphone by maintaining the high level of parallelism of the dielectric plate on"the back chamber defined by the base ring block"and forming a stable air flow passage between the inner space of the back chamber and the outside environment.

Another object of the present invention is to highly improve the productivity of the final ultra-thin type condenser microphone by unifying the conventional two-step assembling processes comprised of"the press fit process"and"the loading process" into the one-step assembling process of mounting each part sequentially, thereby integrating the assembly lines of an ultra-thin type microphone into one line.

The objects and characteristic of the present invention will be more apparent by describing preferred embodiments of the present invention with references to the accompanied drawings

To accomplish the above-mentioned objects, the present invention provides a method of assembling an ultra-thin type condenser microphone comprising a step of mounting a diaphragm on the bottom of a case, a step of mounting a spacer ring on said diaphragm and then mounting the second base ring on said spacer ring so that it may be in contact with the inner wall of said case, a step of mounting a dielectric plate on the inner part of said second base ring so that there may be a certain gap from said diaphragm by said spacer ring, a step of mounting the first base ring on said dielectric plate so that there may be a certain gap from said second base ring, and a step of mounting a PCB on said first base ring.

In addition to the method of assembling an ultra-thin type condenser microphone according to the present invention, an assembly of an ultra-thin type condenser microphone according to the present invention, comprising a case, a diaphragm, a dielectric plate, the first base ring, the second base ring and a PCB, will be set forth below. Differently from the conventional case, in this case, a certain size gap is formed between the first and second base rings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram illustrating the assembling process for an ultra-thin type condenser microphone assembly according to the present invention.

Fig. 2 is a combined view of an ultra-thin type condenser microphone assembly according to the present invention.

Fig. 3 is an enlarged view of the second base ring of an ultra-thin type condenser microphone assembly according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Reference will now be made in detail to the preferred embodiment of the present invention's ultra-thin type condenser microphone assembly and method for assembling the same as illustrated in the accompanying drawings.

As shown in Fig. 1, an ultra-thin type condenser microphone assembly (10) of the present invention includes a cylindrical case (1) having a series of sound wave entrances and the combination of a diaphragm assembly (11), a spacer ring (4), the second base ring (7), a dielectric plate (5), the first base ring (6) and a PCB (9), which are placed sequentially on said case (1) and loaded into the inner space of said case (1).

In this case, the diaphragm assembly (11) is composed of the combination of a polar ring (2) and a diaphragm (3).

When these elements are loaded into the inner space of said case (1), at first, a diaphragm assembly (11) is placed on the bottom of said case (1).

Then, a spacer ring (4) is placed on the circumference of said diaphragm assembly (11), and then the second base ring (7) is placed on the circumference of said spacer ring (4) so that the second base ring (7) contacts the inside wall of said case (1).

After that, in the present invention, a circular dielectric plate (5) is placed on the circumference of said spacer ring (4) within said second base ring (7). Thus, a certain size gap is maintained between said dielectric plate (5) and said diaphragm (3) by said spacer ring (4).

When said diaphragm assembly (11), said spacer ring (4), said second base ring (7) and said dielectric plate (5) are all loaded into the inside of said case (1) through the above-mentioned processes, the first base ring (6) is placed on the circumference of said dielectric plate (5) within said second base ring (7). Here, as

shown in Fig. 1, because the diameter of said second base ring (7) is greater than that of said first base ring (6), if said first base ring (6) is placed on the circumference of said dielectric plate and is located inside of said second base ring (7), the gap of a certain size naturally results.

Thereafter, a PCB (9) is placed on the circumference of said first base ring (6).

Then, the rim of said case (1) is bended toward said PCB (9) to seal the inner space of said case (1). Resultantly, the present invention's ultra-thin type condenser microphone assembly is completed.

As explained above, in present invention, individual elements of an ultra-thin condenser microphone, namely, said diaphragm assembly (11), said spacer ring (4), said second base ring (7), said dielectric plate (5), said first base ring (6) and said PCB (9), are sequentially assembled in their independent states, forming a finished ultra-thin type condenser microphone assembly (10). This assembling method has not been adopted in the prior art.

In the conventional microphone, the process of assembling an ultra-thin type condenser microphone is composed of two steps, the first step being"the step of press fitting a dielectric plate and a base ring block to assemble one assembly"and the second step being"the step of inserting the assembled dielectric plate/base ring block assembly between a PCB and a diaphragm and assembling the PCB, the dielectric plate/base ring block assembly, the diaphragm into a case sequentially." In such conventional method, due to a series of the press fitting processes for assembling"the dielectric plate and base ring block","the dielectric plate"and"the joint of the base ring that is combined with the dielectric plate"are deformed or damaged. Thus, the parallelism of the diaphragm and the dielectric plate may not be

strictly guaranteed and accordingly serious problems such as the uneven parallelism in the gap between the diaphragm and the dielectric plate is caused. Also, as the overall process flow is divided into"the press fit process"and"the loading process", the productivity and quality of the finished ultra-thin type condenser microphone is seriously deteriorated.

In contrast, according to the present invention, because the assembling process of an ultra-thin type condenser microphone is unified as"one process of mounting the individual independent components, a diaphragm assembly (11), a spacer ring (4), the second base ring (7), a dielectric plate (5), the first base ring (6) and a PCB (9)", the dielectric plate (5) is not subject to any deformation or damage caused by the press fitting process. As a result, the finished ultra-thin type condenser microphone (10) may have the gap of high parallelism above a certain level and accordingly the productivity and quality of said ultra-thin type condenser microphone are effectively enhanced.

As shown in Fig. 2, according to the present invention, the ultra-thin type condenser microphone (10) assembled via above-mentioned process has the structure wherein a diaphragm assembly (11), a spacer ring (4), the second base ring (7), a dielectric plate (5), the first base ring (6) and a PCB (9), etc., are placed sequentially within a cylindrical metal case (1) which has a number of sound wave entrances.

In this case, the gap Gl of a certain size is formed between said diaphragm (3) and said dielectric plate (5) by said spacer ring (4), and said gap Gl is located in the main transmission passage of sound wave flowing in through said sound wave entrances (la), thereby having a great influence on the overall performance of the ultra- thin type condenser microphone. Of course, contrary to a conventional condenser

microphone, because this gap Gl is not affected by the press fit process, the condenser microphone according to present invention keeps far better parallelism than a conventional condenser microphone. Here, said diaphragm (3) and said dielectric plate (5) are located apart from each other by the gap G1, forming the condenser structure.

Here, said case (1) is made of aluminum (Al), for example, and the polar ring (2) is made of the brass plate plated with nickel (Ni), for example, and the spacer ring (4) is made of PET (Polyetyleneterephtalate) film having about 35im-45gm thickness, for example.

Also, as shown in Fig. 2, the diaphragm (3) has the structure wherein a gold (Au) or nickel (Ni) coating layer (3b) is placed on the PET film (3a) of about 2.5pm~3. 5pm thickness. Said dielectric plate (5) located apart from said diaphragm (3) by said gap Gl has the structure wherein an FEP (fluorinated ethylene propylene) film layer (5 a) and a gold (Au) or nickel (Ni) coating layer (5b) are placed on the surface of the brass plate (5c), and where another gold (Au) or nickel (Ni) coating layer (5d) is placed on the other side of the brass plate (5c).

The first base ring (6) supports the dielectric plate (5) and is electrically connected with the PCB (9). The second base ring (7) surrounds the first base ring (6) and contacts the inner wall of the case (1). Here, the first base ring (6) is made of brass plated with gold, for example, and the second base ring (7) is made of glass- containing plastic material, for example.

The PCB (9) which is electrically in contact with the first base ring (6), while equipped with an FET (field effect transistor) (8), a capacitor and so on, also includes the back chamber (9a) defined by the arrangement of the first base ring (6) on said PCB

(9) itself. The back chamber (9a) located in the main passage of sound waves flowing in through sound wave entrances (la) of the case (I) has a great effect on the overall performance of the ultra-thin type microphone (10).

As mentioned above, instead of conducting a series of conventional complicated press fit processes, the ultra-thin type condenser microphone according to present invention is assembled simply through sequential carrying out of the following processes,"the process of mounting the second base ring (7) on the circumference of the spacer ring (4)","the process of mounting the dielectric plate (5) on the circumference of the spacer ring (4) inside of the second base ring (7)","the process of mounting the first base ring (6) having a smaller diameter than the second base ring (7) on the circumference of the dielectric plate (5) inside of the second base ring (7)." Therefore, upon the completion of the assembling processes, as shown in Fig. 2, the gap G2 is formed between the first base ring (6) and the second base ring (7).

As in this case, if the gap G2 is formed without the press fit processes of respective base rings (6,7), the diaphragm (3), the dielectric plate (5), etc. that are supported by the base rings (6,7) are not affected by the press fit processes.

Therefore, the parallelism above a certain level is guaranteed. In this case, as shown in Fig. 2, the dielectric plate (5) forming a final microphone assembly (10) can maintain a leveled condition on the back chamber (9a). Consequently, the ultra-thin type condenser microphone (10) according to the present invention may achieve highly improved frequency characteristic and productivity.

Also, when the gap G2 is formed as described above, the air inside of the back chamber (9a) may flow outward quickly through the air flow paths indicated in Fig. 2.

Accordingly, the air inside of the back chamber (9a) and ambient air may be in a stable

parallelism. Consequently, the finished ultra-thin type condenser microphone (10) according to the present invention may have a good frequency characteristic above a certain level.

As shown in Fig. 3, a number of (for example, three) air discharging slots (7a) are provided on the rim of the second base ring (7) that is close toward the side of the case (1). Because said air discharging slots (7a), together with said gap G2, form additional air discharging paths that extend from"the inside of back chamber (9a)"to the gap to the air discharging slots (7a) and to the sound wave entrances (la)", when these air discharging slots are provided, the air of back chamber (9a) can be discharged easily to the outside.

In the ultra-thin type condenser microphone assembly (10) according to present invention, if certain sound wave, for example, the user's voice, enters through the sound wave entrances (la) of the case (1), the diaphragm (3) is vibrated at certain rate by this sound wave.

If the diaphragm (3) vibrates as described above, the gap Gl between the diaphragm (3) and the dielectric plate (5) changes at a certain rate due to the vibration.

Further, according to the change of the gap G1, the capacitance between the diaphragm (3) and the dielectric plate (5) also changes. Consequently, the electric potential of the dielectric plate (5) varies promptly corresponding to the sound wave.

Thereafter, when the variable value of electric potential of above-mentioned dielectric plate (5) is transferred to the FET (8) of the PCB (9) via the first base ring (6), this FET (8) amplifies the current value according to the variable value of electric potential and outputs it to the outside. Resultantly, the ultra-thin type condenser microphone assembly (10) according to present invention completes its inherent work

of converting the sound wave inputted through the sound wave entrances to the electric signal and amplifying it.

INDUSTRIAL APPLICABILITY As explained in detail in the foregoing, the assembling process of the ultra-thin type condenser microphone according to the present invention is unified into the one process of mounting the diaphragm assembly, the spacer ring, the second base ring, the dielectric plate, the first base ring and the PCB as independent individual bodies.

According to the present invention, the dielectric plate and the base ring will not be subject to any deformation or damage caused by the press fit process. Thus, the diaphragm, the dielectric plate and so on are guaranteed to maintain the strict parallelism. Consequently, the ultra-thin type condenser microphone assembly according to the present invention may achieve accordingly improved productivity and quality above a certain level.

Also, in the present invention, the dielectric plate and the base rings are assembled with other structures naturally in their independent individual states to form a final ultra-thin type condenser microphone assembly according to the present invention without"the press fit process for assembly." According to such embodiment of the present invention, a series of gaps that can discharge the air in the back chamber can be formed naturally in between the first base ring and the second base ring. Thus, the air pressure in the back chamber and the ambient air can remain in the parallelism. Consequently, the ultra-thin type condenser microphone assembly according to the present invention can maintain its high quality above a certain level.