Chip Scale Review January • February • 2017[ChipScaleReview.com]
the resulting gold thickness on the front and
backside of the part from each plating bath.
The alkaline pH bath has a large discrepancy
between the gold thickness on the front versus
the backside of the parts. The frontside is three
times thicker than the backside. Whereas, the
part plated with the acid sulfite gold chemistry
has the same thickness on the front and back
of the part even though the backside was not
facing an anode or controlled by a separate
The versatility and unique features of a
newly formulated acid sulfite gold plating
bath have been discussed. A proprietary
stabilizer enables this bath to operate at an
acidic pH, whereas, the competitive sulfite
gold baths operate at an alkaline pH. The
acidic pH plating bath is more compatible with
photoresist than the alkaline pH baths. Gold
deposited from this plating bath is smooth with
low roughness even though the bath does not
contain any heavy metal grain refiners. This
bath is non-toxic and does not require any
complicated waste treatment because the bath
is free of harmful components such as cyanide,
thallium, and arsenic. The unique chemistry of
this bath enables excellent step coverage and
bath efficiency over two metal turnovers. In
addition, the stress of the gold deposit is very
low at 5-10MPa compressive. This acid sulfite
gold plating bath can be used for a wide range
As discussed, pattern plating ranging from 5
to 30+ microns of gold has been demonstrated.
In addition, the excellent throwing power of
this bath has been demonstrated by uniform
gold plating across the backside and in vias.
Also, this bath has been successfully operated
on four production plating tools, numerous
research tools, and various wet benches
demonstrating the versatility of this chemistry.
This plating bath is commercially available as
Elevate® Gold 7990. Future research on this
plating bath will include additional studies to
understand the performance of this chemistry
The authors wish to thank the research
team at Technic including Scott Bateson
and Tom Tyson for their work on this
project and Bob Foreman, General
Manager, 1 Zone, LLC, for his valuable
contributions to this paper.
1. P. A. Kohl, “Deposition of Gold”
in Modern Electroplating, 5th ed.;
Hoboken, Ontario, Canada: John
Wiley & Sons, 2010, 115-130.
2. T. A. Green. “Gold electrodeposition
for microelectronic, optoelectronic
and microsystem applications,” Gold
Bulletin, vol. 40, pp. 105-114, 2007.
3. S. Dimitrijevic et al., “Non-cyanide
electrolytes for gold plating – a
review,” Int. J. Electrochem. Sci., vol.
8, pp. 6620-6646, 2013.
4. R. J. Morrissey, “A versatile non-
cyanide gold plating system,” Plat.
Surf. Fin., vol. 80, p.75, 1993.
Therese Souza received her BS in
Chemistry from Providence College and is a
Senior Research Chemist at Technic Inc.
Contact author: Lynne Michaelson
received her BS in Materials Science &
Engineering from the U. of Michigan, and
her PhD in Materials Science & Engineering
from Massachusetts Institute of Technology.
She is a Senior Materials Scientist at Technic
R&D Altanova 3601 So. Clinton Ave. South Plainfield, NJ 07080rdaltanova.com
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High Aspect Ratio Load
Board Drilling & Plating
• 0.4mm pitch
• 4.75mm thick
• 37:1 Aspect Ratio
• 1 mil plating
4/8/14 1:00 PM