Issue link: https://iconnect007.uberflip.com/i/1544707
40 SMT007 MAGAZINE I MAY 2026 U nderfill is a polymeric material used to fill the gap between a printed circuit board and the underside of surface-mount area-array pack- ages such as BGA, QFP, and QFN devices, thereby surrounding and protecting the solder interconnec- tions. This material increases the component's reli- ability when subjected to mechanical impacts and shocks by distributing forces. Conventional rework methods for underfilled SMT components that use heat can result in physical damage to the PCB, including laminate damage, mask destruction, and lifted or missing pads, thereby reducing manufacturing yields and product reliability. In most cases, these defects are irreparable and can result in the scrapping of a very expensive multilayer PCB. Available Underfill Rework Methods The downside of using underfill is that it makes the rework process extremely difficult. While some underfills are categorized as "reworkable," this does not mean that the underfill removal process is without challenges. There are several problems that arise when removing an underfilled surface BY N AS H B E L L , B EST, I N C. PRECISION MILLING OF Underfilled SMT Components K N O C K I N G D OW N T H E B O N E P I L E