Define TCR and stiffness and its significance with respect to MEMS.

1. TCR :- TCR stands for the Temperature Coefficient of Resistance. TCR is one of the main used parameter to characterize a resistor. The TCR define the changes in resistance as a function of the ambient temperature. The common way to express the TCR is in ppm/°C.

   The temperature coefficient of the resistance is calculated as follows :-

   $$TCR = \frac {R_2 - R_1} {R_1 [T_2 - T_1]} * 10^{-6}$$

   where,

   $R_1$ = Resistance at room temperature (Ω)

   $R_2$ = Resistance at operating temperature (Ω)

   $T_1$ = Room temperature (°C )

   $T_2$ = Operating temperature (°C )

   For pure metals, it is positive means the resistance increases with temperature whereas for non-metals this coefficient is negative means the resistance decreases with increasing temperature.

1. Stiffness :-

• Stiffness is a fundamental qualifier of elastically deformable mechanical micro component and micro mechanisms whose static modal, or dynamic response need to be evaluated.

• MEMS mainly move by elastic deformation of their flexible components.

• One way of characterizing the static response of elastic members is by defining, their relevant stiffnesses.