High Sensitive Diaphragm Essay

Design of High Sensitive Diaphragm for MEMS Condenser Microphones

Amit Kumar Patra
Instrumentation and Control Dept.
SRM University
Chennai, India [e-mail] Dr. E. Paul Braineard
Instrumentation and Control Dept.
SRM University
Chennai, India [e-mail] Abstract¬¬¬¬¬ – Generally a condenser microphone consist of two foremost segment. One is membrane or diaphragm and other one is backplate. In condenser microphone diaphragm is the essential segment. When acoustic pressure acting on the membrane surface, it helps membrane to deflect. At that time the distance between the membrane and the backplate become reduced and it changes the capacitance. The deflection of the membrane due to acoustic pressure negatively affects the sensitivity of the microphone.

Deflection analysis of perforated membrane

Calculation of mechanical parameters for a perforated membrane is very difficult. The stress concentration will be maximum around the hole of deflected membrane. By inserting a boundary condition of a free edge on the edges of each hole, the stress distribution can be calculated correctly.

To avoid the complexity it is assumed that the holes created on perforated membrane is in square structure, which is shown in Fig. 3. Fig. 3. Perforated membrane with square hole

From the description of the stress-strain relation in a orthotropic plate, the bending moments are given by []:

〖 M〗_x=-h^3/12 [C_11 (∂^2 w)/(∂x^2 )+C_12 (∂^2 w)/(∂y^2 )] (3)
〖 M〗_y=-h^3/12 [C_21 (∂^2 w)/(∂x^2 )+C_22 (∂^2 w)/(∂y^2 )] (4)
〖 M〗_xy=h^3/6 C_44 (∂^2 w)/∂x∂y