J. Kloeser et al., RELIABILITY INVESTIGATIONS OF FLUXLESS FLIP-CHIP INTERCONNECTIONS ON GREEN TAPE CERAMIC SUBSTRATES, IEEE transactions on components, packaging, and manufacturing technology. Part A, 19(1), 1996, pp. 24-33
The use of flip chip bonding technology has a growing importance in th
e construction of novel hybrid microelectronic devices and is of incre
asing interest for the application in consumer oriented products. Flux
less processes, especially, are demanded for the compatibility with un
derfill materials and for an improved reliability performance. This pa
per describes the development of a fluxless flip chip mounting process
by use of Au/Sn solder bumps on different thick film metallizations o
f green tape ceramic substrates. The results of the investigations sho
w that fluxless flip chip bonding is possible directly on Au as well a
s Ag and Pd/Ag thick film pattern and via metallizations. The hip chip
assembly process is performed by single chip bonding and requires sub
strates with narrow planarity tolerances.For the different substrate m
etallizations, the range of optimal bonding parameters are determined.
Best mechanical and electrical results are achieved with Au/Sn bumps
on Pd/Ag thick film metallizations. For this system, the investigation
s are performed to show the influence of the chip size and bump height
on reliability. The fatigue life of solder joints, which is limited b
y the thermal expansion mismatch between chip and substrate, could be
significantly increased by an adequate encapsulation process. The reli
ability results of the fluxless flip chip joints after thermal cycling
, temperature storage, temperature-humidity, and pressure cooker tests
are presented.