Packaging and assembly
In flip-chip mounting, what is the main purpose of filling the gap between chip and substrate with underfill resin?
- ATo keep stress from thermal expansion mismatch between chip and substrate from concentrating on the bumps, improving connection reliability
- BTo make the chip emit light
- CTo block heat dissipation from the chip
Show answer and explanation
Answer: A. To keep stress from thermal expansion mismatch between chip and substrate from concentrating on the bumps, improving connection reliability
Silicon chips and organic substrates have very different coefficients of thermal expansion, so temperature changes put large strain on the bumps, which may crack from fatigue. Filling the gap with underfill resin distributes the stress and greatly extends connection life.