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Termination system protects MLCCs

Posted: 14 Mar 2005 ?? ?Print Version ?Bookmark and Share

Keywords:avx? soft termination system? flexiterm? multilayer ceramic chip capacitor? mlcc?

In response to demand from the automotive industry for more robust components, AVX Corp. has developed a soft termination system, called FlexiTerm, for its line of multilayer ceramic chip capacitors (MLCCs) that allows nearly three times the amount of board flexure when compared to standard termination systems. This means that capacitors won't crack even under severe environmental stress.

The company said fractures in MLCC components most often occur as a direct consequence of flexing the PC-board where the component is attached, putting excessive mechanical stress on the component. In a worst case scenario, a low resistance fracture failure can lead to extremely high temperatures when the component is connected to a power line and due to the current supply could result in damage to the circuit board.

Product manager Mark Obuszewski said the company has seen a lot of failure analysis point to board flexure as the cause of component reliability problems. As a result, the company developed the soft termination system as a way to improve the MLCCs quality and reduce circuit board flex failures. Although this problem is more prevalent among larger package sizes, typically above 1206, AVX offers the FlexiTerm system with cases sizes as small as 0603 because it improves overall component reliability.

FlexiTerm was developed as an additional flexible termination layer for MLCCs to ensure that electrical integrity is maintained when external forces are applied, particularly in auto apps where the components are sometimes subjected to severe flexing and vibration, which can damage the components. However, the additional termination layer squeezed between the copper and nickel layers of the standard MLCC termination, doesn't add to the thickness of the component.

AVX offers the new high conductivity termination material with the most commonly used x7r ceramic capacitor to prevent failures in the system due to cracking. The company also has plans to offer the FlexiTerm with other MLCC dielectrics including NPO/COG.

Available in a wide capacitance value range, MLCCs with FlexiTerm are available in 0603 to 1812 case sizes, with voltages ranging from 6.3V to 100V. The company offers a guaranteed minimum flexure of 5mm, without internal cracks, versus the industry standard of 2mm. In addition, FlexiTerm can achieve 3,000 temperature cycles as compared to the industry standard of 1,000 cycles. The company also notes that under temperature cycling there is no change in equivalent series resistance (ESR) up to 3,000 cycles.

FlexiTerm's flexible termination is constructed of a conductive polymer used in conjunction with base metal electrode (BME) technology. The conductive polymer coats a copper termination that is then plated with nickel and tin.

In addition, the new termination system improves the mechanical strength of the MLCC by reducing the transfer of mechanical stress exerted on the component body. The ruggedness makes it a suitable for applications such as depanelization in high flexure stress circuit boards, variable temperature applications, power supplies and automotive applications.

- Gina Roos

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