Title :
Fill pattern and particle distribution of underfill material
Author :
Huang, Yue ; Bigio, David ; Pecht, Michael G.
Author_Institution :
CALCE Electron. Products & Syst. Center, Univ. of Maryland, College Park, MD, USA
Abstract :
Underfills can dramatically improve flip chip reliability. However, the fillers used in some underfills can be dispersed unevenly, causing less than optimal reliability. In this study, underfill dispensing was conducted using various fill patterns. Experimental results show that particle settling occurs during the curing process, rather than during dispensing, and is affected by the difference between filler and matrix densities and underfill viscosity. Particle migration is a secondary mechanism, which causes uneven filler distribution. A vertically oriented transfer molding machine could help to mitigate settling.
Keywords :
curing; flip-chip devices; integrated circuit reliability; soldering; transfer moulding; coefficient of thermal expansion; curing process; fill pattern; fill patterns; filler densities; flip chip reliability; matrix densities; optimal reliability; particle distribution; particle migration; particle settling; printed circuit board; transfer molding machine; underfill dispensing; underfill material; underfill viscosity; uneven filler distribution; Conducting materials; Curing; Filling; Flip chip; Materials reliability; Packaging; Solids; Thermal expansion; Thermal stresses; Viscosity; CTE; Coefficient of thermal expansion; PCB; curing process; flip chip; particle migration; printed circuit board; underfill dispensing;
Journal_Title :
Components and Packaging Technologies, IEEE Transactions on
DOI :
10.1109/TCAPT.2004.831776