Process for making backing electrode electret condenser type microphones

Abstract

This invention relates to back electret capacitor microphone process method, which comprises the following steps: stretching the polyester film on the frock to form one fixation diaphragm and adjusting the film resonance frequency within designed range in the testing sound field to control the tension force place of the film; evaporating one layer nickel film with certain thickness in vacuum environment and again adjusting film tension force and then sticking it to one set of supportive rings; accomplishing flatting, baking and dividing programs to accomplish single diaphragm element process.

Description

Technical field: [0001] The invention relates to a manufacturing method of a back pole electret condenser microphone. Background technique: [0002] The pressure condenser microphone adopting the back pole electret method uses polyester film as the diaphragm, and its strength is usually 1 to 2 orders of magnitude smaller than that of the metal film, so the equivalent effect of this type of diaphragm is smooth (this force smooth determines the diaphragm f 01 ) is mainly composed of the rear cavity V 2 contribute. According to the theoretical derivation of common pressure-type condenser microphones, it is not difficult to conclude that the open-circuit sensitivity of pressure-type electret microphones in the main working frequency band is: [0003] E 0 = σd ϵ 2 · C A 2 ...

AI Technical Summary

Problems solved by technology

It is difficult to ensure the consistency of tension when the diaphragm is attached to the support ring

If the diaphragm is stretched too tightly, excessive tension will not only make the sensitivity of the microphone unable to be improved, but also cause irreversible plastic changes in the diaphragm, affecting the consistency and stability of the performance indicators of the microphone

In addition, when the tension of the diaphragm is too high, in order to make the sensitivity of the microphone reach a predetermined value, the surface charge density of the electret film must be increased, and the stability of the resident charge of the electret material will deteriorate when the charge density is too high. This also affects the stability of the microphone sensitivity

Conversely, if the tension of the diaphragm is too small, the diaphragm will easily wrinkle, and the coating quality will deteriorate when the nickel film is evaporated, and after being assembled into a microphone, the diaphragm will be attached to the back plate due to electrostatic attraction, affecting product performance

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