Pre-applied thermoplastic reinforcement for electronic components

摘要

Pre-formed underfill compositions utilized in the application of surface mount components, most commonly chip scale packages (CSP's), in electronic devices. The pre-formed underfill of the invention is applied directly to the top of the CSP before the reflow process and softens during reflow to flow across the circuit/board gap. One underfill composition utilized for this method comprises a thermoplastic film system that provides a coating on the component that is smooth and non-tacky. The film may be applied selectively to parts of the CSP such that it overhangs the top of the component and upon reflow flows over the edge of the CSP to form a connection with the substrate. In an alternative embodiment, the underfill coats all or portions of multiple surface mount components. A second pre-applied underfill composition or solder paste may be applied as an adhesive to provide sufficient tack in order to hold the electronic assembly together during the assembly process and to serve as a flux to facilitate solder wetting.