Author: Theodore J. Krellner Company: Keystone Thermometrics Date Published: 8/23/1998
Surface Mount International
Abstract: This article focuses on the construction and application of SMT power negative temperature coefficient (NTC) and positive temperature coefficient (PTC) thermistors and the problems overcome in the conversion to SMT. The application specific requirements of power thermistors have made the conversion to Sh4T difficult. Thus the performance of the device is dependent upon the part size along with carefully controlled thermal impedances from the thermistor to the ambient. The scope of the article will be on ceramic NTC and PTC power thermistors. Special emphasis will be on the end applications of current limiting for the NTC thermistors and over-current protection for PTC thermistors. A comparison to other type of non-power SMT thermistors will be made to enhance the understanding of the reader of the SMT technologies used in the ceramic based thermistor industry. The manufacturing method employed in construction will be presented. Also included will be current limitations and a comparison to leaded devices.