Reliability of bondcontacts in chip-in-board assemblies

摘要

The degradation of bondcontacts in Chip-on-Board assemblies under thermal and corrosive stresses was investigated. Interconnections between the silicon die and the printed circuit board and between different lines of the printed circuit board were manufactured using the well known ultrasonic bonding process and AlSil microwires. Different Ni-, NiAu, Pd and PdAu-metallization systems on the printed circuit board were realized. During stressing the contact resistance was measured periodically. For this purpose a special high resolution measuring system equipped with a PC-based switching unit was build up. The results were analysed using statistical methods. After stressing microanalytical techniques were used for the determination of the relevant degradation mechanisms. It was found, that the corresponding board-contacts are stable, if all technological conditions are correct. The formation of intermetallics is shown by Scanning Electron Microscopy. Intermetallics do not contribute to a significant enhancement of the contact resistance. There are good results for Al-Ni and Al-Pd contacts too. Some conclusions could be drawn regarding optimal material combinations and technological conditions for high reliability contact systems.