A study on damage progression in MEMS based Silicon oscillators subjected to high-g harsh environments

Abstract

Traditional Quartz based oscillators still outnumber their MEMS counterparts in the industry therefore no extensive prior studies exist which provide harsh environment reliability data for Silicon oscillators. MEMS based oscillators serve as clocks which control the timing in electronics, a better clock signal ensures higher performance, more consistent behavior and reliable operation. Harsh environment applications such as under the hood automotive, military, space navigation all make use of MEMS oscillators. None of the previous studies look into the impact of sequential harsh environment operating conditions. Survivability of MEMS oscillators at high relative humidity and high G environments is unknown. The effects of these pre-conditions along with the drop test conditions have been studied and analyzed. Anomalies in the oscillator behavior due to the presence of harsh environments lead to mismatch in the electronic timing of the circuit resulting in a bad consumer product, thus the importance of reliability data. In this paper a test vehicle with a MEMS oscillator, SiT 8103, has been tested under: high relative temperature humidity exposure and then followed by subjection to high-g shock loading environments. The test boards have been subjected to mechanical shocks using the method 2002.5, condition G, under the standard MIL-STD-883H test. The effect of temperature, humidity and shock on the oscillator has been studied. The survivability of SiT 8103 has been demonstrated as a function of change in the output frequency, rise/fall time(s) and duty cycle. Later the deterioration in oscillator output parameters has been characterized using the techniques of Fast Fourier Transform and Principal Component Analysis. The results obtained show that exposure to sequential high relative temperature-humidity and high-g shock affects the working of Silicon MEMS oscillators more than just the high-g shock environment. Rise and fall times, Output frequency and Duty cycle show more deterioration and drift in the 85°C/85%RH cases on comparison with their pristine counterparts. The energy spectrum data obtained after conducting the FFT analysis demonstrate that 85°C/85%RH samples have lower peak amplitudes/signal energy than the pristine samples especially during the first 50 drops.