ROCK SOLID AND UNDER 10 m Ω - NEW HEAT AND MOISTURE-STABLE, LOW-ESR TANTALUM CHIP CAPACITORS

摘要

A tantalum chip capacitor having equivalent series resistance (ESR) less than 18 m Ω was described last year at the 19th Capacitor and Resistor Technology Symposium. The technological forces that drove the development of this device were detailed in that paper and a prediction was made that ESR requirements would fall by half every 1 to 1.5 years if the trends of the last 5 years were to continue. Also it was predicted that the ESR of individual capacitors would have to fall at least this quickly if a manufacturer wished to remain competitive The demand for capacitors having ever-lower ESR continues unabated. In this paper is described the next step in the evolution of ultra-low ESR surface-mount tantalum chip capacitors - devices boasting ESR lower than 10 m Ω. Not only must ESR be ever-lower with each new generation of low-ESR capacitors, but also it is becoming ever more crucial that the ESR of these capacitors be stable during the solder-reflow mounting process and over their operational life. Environmental threats include exposure to reflow temperatures between 200C and 250C, moisture, thermal shock, and long-term exposure to temperatures well above 100C. The latest-generation, low-ESR tantalum chip capacitors described here take advantage of an optimal combination of materials and methods to produce devices that not only have exceptionally low ESR, but also have ESR stability that is nothing short of phenomenal in the face of severe environmental stress. The general principles and strategies used to develop these new capacitors are described and data are presented to document the stability of the resulting devices when they are exposed to multiple IR reflows, moisture, thermal shock, and long-term lifetest at elevated temperatures.