Tantalum Capacitor Technology Options for High Temperature and Harsh Environment Applications

Abstract

Abstract As new temperature critical applications continue to emerge, the need for components capable of enduring temperatures up to and exceeding 200°C is increasing. Advanced down-hole electronics, underhood automotive and aerospace systems rely on components delivering optimal performance while subject to extreme environmental conditions. This paper will discuss the design advances in tantalum technology that have given rise to innovative devices that provide the enabling technology for a new generation of applications. Traditionally, hermetically sealed “wet” axial tantalum capacitors (utilizing a non-solid electrolyte that promotes self-healing and long lifetime), have been used for both high bulk capacitance (to 5,600uF) and high voltage applications (to 125VDC). In recent years, this technology has been developed to meet the 200°C operational requirements of harsher environment industrial applications. For lower operating voltages (6v – 25v), SMD packages are preferred, and for several years, 200°C rated high temperature solid tantalum chip devices have been the preferred technology over “wet” tantalum for capacitances to 220uF, being smaller size, lower cost and having the combination of lower ESR and higher frequency response. More recently, hermetic SMD packaging has been developed for SMD solid tantalum capacitors. The hermetic seal enables the internal element to be operated in an inert gas environment, while offering superior resistance to moisture ingress. These two factors enable operation to 230°C, with higher capacitance (up to 330uF) and voltage (up to 63vDC) ranges. Both molded and hermetic high temperature SMD solid tantalum capacitors have been developed to be compatible with high temperature pcb or hybrid circuit assembly processes, with a range of termination finishes compatible with HMP solder, epoxy or wire bonding. Their design also harsh mechanical environment shock & vibration. This paper will discuss the evolution in materials, design and testing for each of these technologies, along with the considerations taken into account to give maximum compatibility with emerging requirements in high temperature and harsh environment applications, with emphasis on down-hole oil exploration, aerospace and military systems and underhood automotive electronics.