Low Expansivity Organic Substrate for Flip-Chip Bonding

Organic substrate materials with thermal expansion coefficients (TEC) approaching that of silicon have been fabricated with laminate composites using DuPont's Kevlar® fiber. When combined with controlled-collapse solder chip joining technology, chip-to-substrate interconnections are essentially free of fatigue failure caused by thermal cycling. This failure mode limits the ultimate silicon chip size on products joined by flip-chip bonding to alumina substrates. By using conventional printed circuit board fabrication techniques, extensions of these organic structures to multilevel applications have been shown feasible.