Manufacturing Optimization for Improved Reliability in TCXO Oscillator Designs

The reliability of temperature controlled crystal oscillator designs can be improved through process optimization and controlling key process variables. Industry demands for a highly reliable TCXO combines the need for the frequency accuracy of complex oscillator designs with long-term reliability. A project intended to improve the long-term reliability focused on key process steps of oscillator thick film substrate assembly including design layout, solder application, solder reflow, and component circuit tuning. The project starting point was an oscillator design statistically capable of meeting the customer´s requirements. Design layouts were evaluated to minimize unbalanced or abnormal component stresses. The solder application and solder reflow process points were closely evaluated through a design of experiments to provide the most robust construction. Component circuit tuning is a common practice in TCXO and OCXO products. Because of the manual nature of component selecting it is difficult to maintain quality control. Focused reliability testing, along with accelerated life testing verified or identified product and process improvements. Optimization was measured through a quantifiable increase of performance during qualification tests, accelerated life test, test to failure, and ultimately field performance. Selecting the correct test method to measure meaningful reliability improvement was a key element in the project. Test to failure and accelerated life tests identified reliability optimization opportunities on parts that successfully passed all required qualification tests