Author: Dan Lilie
Abstract: Underfilled components are used in consumer electronic products (mobile devices, portable computers etc.), in the automotive industry (sensor modules, engine control units etc.) or whenever flip chips are incorporated in products with maximum miniaturization. An underfilled chip contributes to an improved overall product quality, offering higher reliability and better lifetime. The underfill material provides protection against humidity, thermal stress and all kinds of mechanical impact. Underfill represents a very special challenge for the rework process, because in addition to thermal energy, mechanical energy must be applied in order to separate the chip from the substrate again. Up till now there is no typical “reworkable underfill”, so rework success depends mainly on the materials used, surface properties as well as component and substrate quality. The equipment and tooling used also have a major impact on the general success. Reworking components with rework-able underfill is applicable if the components or substrates are expensive, hard to obtain or if complete products need to be saved.