Capillary Underfills for Flip Chip Packages

Copper pillar technology rapid growth is due to the ability to shrink bump pitch and decrease node size for higher density packages. One challenge for underfills in a copper pillar package is filler separation or settling resulting in a resin rich area with high CTE.

NAMICS underfills for copper pillar applications utilize proprietary filler technology to resist separation and provide superior reliability.

Current and future technology is using higher package density decreasing distance between components requiring underfills to have low resin bleed out (RBO) combined with smaller fillets.

Resin bleed occurs since the resin system will have a higher attraction to the surface.  Process like plasma cleaning will increase potential for resin bleed out.   NAMICS can dramatically reduce resin bleed out through increasing affinity of filler to resin system and special additive technology.

Growth of 2.1D, 2.5D and 3D packages requires underfills to flow under small, narrow gaps with finer pitch increasing the risk for voids due to filler entrapment in narrow gap.

For fine pitch, narrow gap applications, filler size needs to be reduced to avoid entrapment however the smaller filler size results in significant increase in viscosity.  NAMICS balances the maximum filler loading of finer particles to easily fill narrow gap packages and provide void free fill and maintain key properties for a robust solution.