Ep Silicone Underfill

Application: Flip Chip

A sea island structure, Sunstar’s original polymer technology innovated epoxy formulation for electronics industry. Sea-island structure makes the epoxy resin flexible and hard to crack. It absorbs stress from thermal and mechanical shocks.

Absorbs flux residue left on a PC:

The underfill absorbs flux residue inside and therefore prevents voids from affecting the reliability of underfilled CSP.

Apply flux on to FR-4 => heat 3 min. at 220 degrees => apply UF from above and cures at 150 degrees 30 minutes => cross-section examination

Reparable Underfill

Application: BGA


  • Low temp. snap cure 500μm layer of the material takes only 1 second to gel at over 70 degrees.
  • Excellent reworkability allows for the easy wiping of the resin residue left on PCB.
  • Excellent electrical insulation
  • Excellent storage stability at 5~10C
  • Excellent endurance for mechanical stress(bending stress)
  • Elastic urethane protects solder interconnects from drop shocks.


Urethane based underfill, 991 series, eliminates the stressful process of taking the underfilled CSP off and cleaning the material residue off of the PCB. The underfill chemically dissolves after a heat treatment and allows for an easy wiping of little residue left on the PCB, which makes it possible for engineers to analyze a defect device and also to save expensive PCBs.