George A. Riley, PhD For years, ultrasonic vapor jet deposition
has been an elegant solution in search of a problem. Now, with
our growing 21st-century needs for die and wafer stacking, post-
processing, lead-free solder deposition, smaller feature sizes,
higher power densities, increased electrical and thermal
conductivity, and smaller, higher quality bumps ― its time has
come. Vapor jet deposition produces uniform, low-stress layers
of metals, alloys, lead-free solders, and other materials,
deposited in carefully controlled patterns onto a wide variety
of surfaces at high throughput, low temperature, and low cost.
The system has produced solder bumps, including gold-tin,
indium-tin, pure indium, and other lead-free alloys, with
feature sizes below ten microns, including four micron bumps on
eight micron pitch. Beyond solder bumping, eutectic gold-tin
solder pre-forms, a packaging mainstay for many years, can’t
cope with today’s tiny dimensions. Vapor-deposited gold-tin can
pattern an entire wafer or substrat