  Advancements in miniaturisation and new capabilities of implantable devices
impose a need for the development of compact, hermetic, and CMOS-compatible
micro packaging methods. Gold-tin-based eutectic bonding presents the potential
for achieving low-footprint seals with low permeability to moisture at process
temperatures below 350\degree C. In this paper, a method for the deposition of
gold-tin eutectic alloy frames via sequential electroplating from commercially
available solutions, with no special fabrication process, is described in
detail. Bond quality was characterised through shear force measurements,
scanning electron microscopy, visual inspection, and immersion tests.
Characterisation of seals geometry, solder thickness, and bonding process
parameters were evaluated, along with toxicity assessment of bonding layers to
the human fibroblast cells. With a successful bond yield of over 70\% and no
cytotoxic effect, AuSn eutectic bonding appears as a suitable method for the
protection of integrated circuitry in implantable applications.

Materials Science;Medical Physics