LIGA fabricated 19-element threshold accelerometer array

This paper reports the design, fabrication, packaging, and testing of a relay-type threshold accelerometer array. The array includes 15 different sense elements ranging from 10 to 150 g in 10 g increments, and triply redundant 20 and 100 g sense elements for a total of 19 elements. The devices were fabricated using a modified sacrificial LIGA technique that creates a 100–300 μm thick nickel structure with gold plated contacts. The threshold accelerometer array was evaluated by measuring its response to an applied acceleration (using a centrifuge) and by using two built-in testing methods: a pull-in voltage test, and a transit time test. Unlike the pull-in voltage test, the transit time test is sensitive to variations in the proof mass and spring constant. The average results from the centrifuge test, pull-in voltage test, and transit time test are all within approximately 20% of the expected values that are analytically calculated. In addition to the relay-type threshold sensing, the devices permit non-discretized readout of the acceleration using an alternative sense mode, in which the capacitance between the test electrode and proof mass was measured. This measurement shows a sensitivity of 670 aF/g for a 50 g threshold accelerometer, which is also within 20% of theoretical estimates. [Copyright &y& Elsevier]