EP Silicone & Reworkable Underfill

Ep slicone underfill

Characteristics

• Cross-linked silicone particles dispersed in epoxy resin relieves stress from thermal and also mechanical shocks.
• Hard to crack
• It absorbs flux residue which allows for better filling underneath the device.
• Synergy between silicone and filler makes the CTE drop lower. With the same filler content(%), Ep silicone has lower CTE level than ordinary epoxy.
• Lower CTE works to relieve stress on a PCB in the process of curing.

Ep silicone sea island structure

SEM pix Ep silicone

Sunstar's original polymer technology innovated epoxy formulation for electronics industry. This sea-island structure makes the epoxy resin flexible and hard to crack. It absorbs stress from thermal and mechanical shocks. All our UF materials are based on this unique structure.

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It absorbs flux residue left on a PC
The underfill absorbs flux residue inside and thereby prevents voids from affecting the reliability of underfilled CSP.

Experiment

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

THB test after UF absorbing flux residue

Test steps

• Apply flux to IR {50µm(t)}and oven-dry at 230c for 2 min.&
• Apply underfill to the IR{200µm(t)}and cured at 150c for 30 min.
• Subject the IR to 85c85% environment, and after 1 hour, obtain an initial insulation value by applying measurement voltage of 100V. Subject the IR to the impressed voltage of 10V for 2000 hours.}
  (100V when measuring insulation resistance value.)

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Physical property

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