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Technical Paper

Wafer Applied Underfill – Delivering Flip Chip to the Mainstream

Flip Chip packaging has found limited use for a technology that was introduced decades ago. Its application widened with the use of underfill, a necessary constituent to minimizing CTE mismatch between the component and substrate. Its reliability has been established on laminate substrates for automotive applications, an important development in light of the continuous increase in vehicle electronic content and function. Unfortunately, the assembly process incorporating underfill is cumbersome and batch-like. Also, the adhesive strength of the underfill depends critically on the cleanliness of the die after reflow, necessitating costly cleaning equipment and complex process monitoring protocols. Hence, the process of manufacturing is not SMT-friendly. A new technology, Wafer Applied Underfill (WAU), addresses the shortcomings of the traditional underfill process.
Technical Paper

Container Deformation Procedure for Ceramic Monolith Catalytic Converters

A typical automotive catalytic converter is constructed with a ceramic substrate and a steel shell. Due to a mismatch in coefficients of thermal expansion, the steel shell will expand away from the ceramic substrate at high temperatures. The gap between the substrate and shell is usually filled with a fiber composite material referred to as “mat.” Mat materials are compressed during assembly and must maintain an adequate pressure around the substrate under extreme temperature conditions. The container deformation measurement procedure is used to determine catalytic converter shell expansion during and after a period of hot catalytic converter operation. This procedure is useful in determining the potential physical durability of a catalytic converter system, and involves measuring converter shell expansion as a function of inlet temperature. A post-test dimensional measurement is used to determine permanent container deformation.