This paper presents a novel method to determine 3D stress in microsystem packaging. The stress components sigmaxx, sigmayy, sigmazz, and sigmaxy are found in an epoxy package using a piezocoefficient mapping device as stress sensor. We spin the current 360deg in a circular n-type (001) Si piezoresistor by contacts located near the perimeter of the resistor and do high impedance voltage measurements on contacts located near the centre of the resistor. By measuring the potential drops in these contacts we can determine the stress in the chip. The epoxy is potted in a polystyrene tube using the same concept as in  used for chip packaging for fisheries research. We investigate the EpoTek 305 epoxy and find stress values of sigmaxx ap -23 MPa, sigmayy ap -1 MPa, sigmaxy = 0.3 MPa, and sigmazz = 40 MPa. The presented method can be used for 3D stress measurements of various packaging concepts.
|Title of host publication||20th IEEE International Micro Electro Mechanical Systems (MEMS) Conference|
|Publication status||Published - 2007|
|Event||2007 IEEE 20th International Conference on Micro Electro Mechanical Systems - Kobe, Japan|
Duration: 21 Jan 2007 → 25 Jan 2007
Conference number: 20
|Conference||2007 IEEE 20th International Conference on Micro Electro Mechanical Systems|
|Period||21/01/2007 → 25/01/2007|