A STUDY OF THE EFFECTS OF PACKAGING INDUCED STRESS ON THE RELIABILITY OF THE SANDIA MEMS MICROENGINE

摘要

MEMS packaging is application specific, and device perfbrmance can be greatly affected by the packaging parmeters. MEMS packaging impacts areas like system on a chip (SOC) and system on a package (SOP). The Sandia MEMS microengine was used as the test subject to evaluate the effects of packaging-induced stress, a parameter that is largely unmeasured in MEMS packaging. Three die attach materials, a cynate ester and two solder preforms, were selected for study based on their material properties to yield low, medium, and high packaging stresses. Stress on the top surface of the chip was determined using x-ray diffraction, on-chip strain sensors, analtical equations, and finite element predictions. Five devices were tested using each of the three die attachment materials. The devices were operated at 500 Hz until failure, and the number of cycles to failure was recorded. The maximum number of cycles ranged between 1 and 4 million cycles for the three cases. The range of cycles to failure for the tested devices was 4 thousand to 4 million cycles. The time to failure plots for the three cases cross each other and have similar values indicating that the reliability does not depend on stress. The data suggest that any of these and similar die attachment materials could be used with this type of devices without affecting reliability.