Alcon: - Once upon a time we (USN) did some experimentation with Tce differentials. We found that as long as the Tce differential was < 5 ppm/C degree and the component was no larger that 0.5 inch we had long product life. Experiments were conducted with LCCCC in the early 80's time frame. - In addition, the Air Force funded some pretty comprehensive (MANTEC) studies that assessed the effect of Tce differential across five different substrates with various types of components. Contact the MANTEC office at WPAFB (if it still exists) for additional info on getting copies of MANTEC under FOI. - Hope the above helps. Regards, Jim Moffitt, Technical Director, Electronics Training Advantage, Indianapolis, IN