Transformation Of Thermal Ink-Jet Product Reliability Strategy

Over the course of the last 25 years, Hewlett-Packard has dramatically improved the performance, speed, and print quality of its Thermal Inkjet (TIJ) products. Reliability test and integration has evolved alongside the technology. Early reliability drivers focused on characterizing the TIJ technology by conducting high sample size tests at the system level. As HP's product lines diversified and the technology became more complex, reliability drivers turned to increasing quality. With abundant resources fueled by high growth, reliability teams could run large experiments at all levels of the system and conduct elaborate multi-stress experiments to investigate failure mechanisms. More recently, cost considerations have forced a shift in the reliability approach at Hewlett-Packard. Under the new Reliability Strategy TIJ programs are now developed around three core reliability concepts; Analyze, Discover and Characterize. The reliability and integration challenges of a development program are anticipated and then designed out at a fundamental level. Overstress testing is used to build confidence in design iterations and failure mechanisms are explored to the lowest possible level. System reliability is calculated by a roll-up of failure mode and sub-system experimental data with system test run only as a validation of the model. Use of the Reliability Strategy methodology is illustrated with two case studies. Using the new Reliability Strategy Hewlett-Packard's Inkjet Division has achieved a significant reduction in both testing cost and development iteration time while maintaining a high level of product reliability.