Vibration Analysis Of Test Chips With Integrated Piezoresistive Stress Sensors

Abstract

Vibration analysis of the WB200 test chip containing an array of optimized piezoresistive stress sensor rosettes has been performed. The test chip was attached to the printed circuit board with an underfill encapsulant used as an adhesive. Different underfill dispense patterns were studied and the best suited pattern was selected for die attachment. Cross-sections of the chip-on-board assembly were made and observed to record the thickness values. Values of junction capacitances in the test chip were measured, calculated and used in SPICE simulations to obtain the electrical cut-off frequency of the stress sensors. A shaker system was then used to vibrate the chip-on-board assembly over a range of frequencies to study the response curves of the stress sensors. Static bending experiments of the assembly were performed, and the results were compared with the finite element analysis predictions obtained from ANSYS.