Ohmic contacts adhesives

Adhesives used for screen or stencil printing in surface-mount applications are generally electrically insulative types whose functions are mechanical attachment and thermal dissipation. However, electrically conductive, silver-filled epoxies have been used for many years as ohmic contact adhesives to interconnect bare-chip devices in hybrid microcircuits and are used as solder replacements for surface mounting of components on printed-circuit boards. Regardless of their... 

The WFg H2 System. The reaction WFg + 3H2 W + 6HF is possible from 300 to 800 °C and is also used in thin-film production. There are several disadvantages in comparison to the other reduction methods. The HF formed during the reaction may cause defects, like encroachment or wormholes. The layers show poor adhesion on native Si02, which is always present on Si. Therefore, tungsten is not directly deposited on Si but on a bilayer. One layer provides an ohmic contact with Si, and the other acts as an adhesion promotor for W. 

A second key function for adhesives is to form ohmic contacts or electrical connections between active and passive devices, connectors, leadffames, I/O leads, or other electronic parts to form a circuit. Other applications for electrically conductive adhesives include electrostatic dissipation and electrical grounding connections. 

A reliability concern with semiconductor devices, such as chip transistors in which one of the connections is made through the backside metallization by attaching with either eutectic alloy or conductive epoxy, is the loss of backside ohmic contact. Loss of ohmic contact may be due either to mechanical/physical or chemical mechanisms. Mechanical failures occur from partial or complete delamination of the adhesive interface. The smooth surface of the die metallization contributes to the problem whereas roughening the surface improves results. Loss of contact is evident from increases in resistance during initial electrical testing, but may better be detected... 

The depositing film material may diffuse and react with the substrate to form an interfacial region . The material in the interfacial region has been called the interphase material and its properties are important to the adhesion, electrical, and electronic properties of film-substrate systems. In particular, the development of ohmic contacts to semiconductor materials is very dependent on the interface formation process, The type and extent of the interfacial region can change as the deposition process proceeds or may be modified by post-deposition treatments. Interfacial regions are categorized as ... 

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