LASER REWORK PROCESS FOR BGA A NEW METHOD FOR PCBA REWORK INSTEAD OF HOT AIR/ INFRARED HEATING

摘要

The laser rework machine replaces the hot air nozzle with semiconductor fiber laser, spot size Ф1~3mm; programmable for the heat area. Using conventional hot air or infrared heating, this methods reworks the component, however the adjacent component also gets heated which can lead to partial reflow and subsequent reliability issues. Currently high density interconnect PCB designs are more and more densely packed, when one BGA is reworked, another adjacent BGA also becomes partially reflowed. When the adjacent BGA has under fill or edge bonding glue, the failure rate with conventional rework methods, is over 80% when the BGAs body to body clearance is less than 0.5 mm. Laser rework only heats the component which needs to be replaced by NC programming control, and doesn't impact the adjacent component. Reworked component with an adjacent component (body to body clearance is 0.4 mm), temperature delta can be controlled to 35+ degree C; this means the reworked component solder ball temperature is 245 degree C, but the adjacent BGA solder ball is less than 210 degree C, resulting in no reflow. The laser rework process benefits: 1. Programmable heat area, by controlling the laser scan area, 2. Minimum laser spot size 0 1 mm. 3. No damage to component body 4. Temperature range of opposite side of PCB -50 °C (Depends on the PCB design) 5. No impact adjacent BGA (temperature gap over 35 °C, BGA body to body clearance is 0.5 mm).