Underfill is a process in which an epoxy resin, typically used as the material, is applied beneath the bottom of a Ball Grid Array (BGA) component. After application, the epoxy resin is heated to solidify. This process serves to significantly improve the mechanical strength of the solder joints, resulting in enhanced resistance to vibrations and a reduction in the occurrence of virtual soldering between the main control and particles. As a result, the product’s lifespan is extended, and its overall reliability is increased, making it better equipped to endure harsh conditions such as high thermal or vibratory stress, gravitational acceleration, and fatigue cycle applications.

In summary, Underfill is a technique used to reinforce solder joints in BGAs, increase the product’s durability, and enhance its resilience to various mechanical and environmental stresses, ultimately contributing to improved reliability and a longer operational lifespan.