  A reliable and cost-effective interconnect technology is required for the
development of hybrid pixel detectors. The interconnect technology needs to be
adapted for the pitch and die sizes of the respective applications. For
small-scale applications and during the ASIC and sensor development phase,
interconnect technologies must also be suitable for the assembly of single-dies
typically available from Multi-Project-Wafer submissions. Within the CERN EP
R&D program and the AIDAinnova collaboration, innovative and scalable
hybridization concepts are under development for pixel-detector applications in
future colliders. This contribution presents recent results of a newly
developed in-house single-die interconnection process based on Anisotropic
Conductive Adhesives (ACA). The ACA interconnect technology replaces solder
bumps with conductive micro-particles embedded in an epoxy layer applied as
either film or paste. The electro-mechanical connection between the sensor and
ASIC is achieved via thermocompression of the ACA using a flip-chip device
bonder. A specific pixel-pad topology is required to enable the connection via
micro-particles and create cavities into which excess epoxy can flow. This
pixel-pad topology is achieved with an in-house Electroless Nickel Immersion
Gold process that is also under development within the project. The ENIG and
ACA processes are qualified with a variety of different ASICs, sensors, and
dedicated test structures, with pad diameters ranging from 12 {\mu}m to 140
{\mu}m and pitches between 20 {\mu}m and 1.3 mm. The produced assemblies are
characterized electrically, with radioactive-source exposures, and in tests
with high-momentum particle beams. A focus is placed on recent optimization of
the plating and interconnect processes, resulting in an improved plating
uniformity and interconnect yield.
