Characterization and Reliability Testing on an LTCC Transformer Operable to 250 °C

Environments prone to vibration and shocks can cause premature failure in small wire-wound transformers due to cracked cores and broken wires. These problems are only exacerbated by temperatures exceeding 200 °C where the heat causes organic compounds to age rapidly. As more electronics are used in harsh, high temperature environments, high reliability, compact transformers for use in power, filtering, and isolation applications are needed. To address this need monolithic low-temperature co-fired ceramic transformers were developed. In this work transformers were made from a low-temperature, co-fire compatible, ferrite with a Curie temperature of 350 °C. The transformers were first subjected to a 2,000 hour life test at 250 °C in which the transformer was used to charge a load capacitor once every two seconds. The inductance, resistance, core loss, and saturation flux density of the transformers were measured at various temperatures. Additional testing focused on the effect of temperature on the device's frequency profile and performance changes under thermal cycling.