Underfill formula reduces stress and controls warpage for next-generation flip chip devices
Because the substrate and flip chip die have different coefficient of thermal expansion (CTE) characteristics, thermal processing (secondary reflow) can lead to either upward (“smiling”) or downward (“crying”) package warpage which may ultimately result in poor reliability. Loctite Eccobond UF 8840 offers compatibility with a wide variety of flux systems, has minimum resin bleed out, delivers maximum process adaptability through compatibility with both traditional needle dispensing and non-contact dispensing and has a wide dispense process window for manufacturing flexibility. The formula flows consistently with no voids on flip chip die up to 15x15mm. Testing in an applications laboratory environment shows reduced warpage – less than 80 µm on a 20x20mm flip chip die with a thickness of 730 µ m – and compatibility with a variety of die passivations.
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