For the subsequent processing of Flip Chip component into e.g. BGAs, PGAs,  and Micro-BGAs the electronic contacts (bumps) are soldered to the future component socket in a reflow process.

For Die attach during Flip Chip manufacturing, flux pastes (tacky fluxes) are used which are applied either via dispenser, spraying or through a dip chip process. 

To achieve a complete and bubble-free wetting of the material subsequently used for the underfilling process, a cleaning process is required to remove all flux residues from the narrow gaps between the Flip Chip and the socket material.