Si-based microphone testing methodology and noise reduction

Abstract

In this paper two different packaging and testing approaches were studied for Si based microphone. Microphone performance was tested with Ceramic, Plastic and metal packages. Sensitivity testing of microphone is done when it is connected to an ASIC die. Testing was done with microphone and ASIC packaged separately and also in a single package. Substantial noise was generated when microphone and ASIC are tested separately in a PCB. Noise was detected after 150 Hz with the noise intensity reducing as it goes to higher frequencies. This was observed regardless of the packaging schemes. Different shielding methods were tried and found that copper foil shielding results in substantial noise reduction during frequency response testing and a flat response curve was observed with metal can package. Form this new testing methodology, it is demonstrated that same ASIC can be used repeatedly during microphone testing and hence some cost reduction can be expected.