Advances in solder ball placement for surface-mountable packages
Figure 19. Automated wafer-level ball-place line for
300 mm wafers.
cost, interchangeable top plate or wafer
shim. The base plate has vacuum channels
and lift pins for any wafer diameter, and
the top plate matches the wafer’s diameter Figure 20. 3D packaging & TSV (source: Yole & ITRS).
and thickness to provide a full width, flat
surface for perfect screen printing or ball
3D packaging, board level integration San Jose, Sept 2007.
placement.
and through silicon vias have received [4] F Carson, STATS ChipPAC Inc.,
Another tool to aid the accurate
much press in the last few months, and “Package-on-Package Variations
placement of hundreds of thousands of
these components will quickly become On the Horizon” Semiconductor
solder balls onto a single wafer is the
mainstream, presenting further challenges International, 5/1/2008
use of precision electro-formed nickel
for ball placement. The system in package
or chemically etched stainless steel ball
format combining these technologies
place stencils. Using advanced clean-room
will take the place of many ‘single-die’
lithography, these stencils can be fabricated
packages. Figure 20 illustrates this trend
to extremely fine tolerances, whilst still
with the SiP featuring heavily over the
remaining extremely cost effective.
next few years.
Whilst manual wafer loading is an
option for low to medium volumes, for
Conclusions
optimum throughput the use of automated
The growth in area array packages has
robotic wafer handling is essential.
already been, and will continue to be,
This technology enables the ball place
exponential. This will have the knock-
equipment to process several cassettes of
on effect that the demand for faster,
wafers at maximum throughput with no
cheaper, more accurate and more flexible
operator intervention. Figure 18 shows a
ball placement equipment will increase
robot end-effector loading a wafer onto a
proportionally.
universal wafer pallet.
The increasing diversity of
Figure 19 shows an automated wafer
semiconductor packages presents significant
level ball place line for 300 mm wafers,
challenges to anyone developing ball
with the robot wafer handler feeding the
placement equipment. The sheer volumes
flux printer, the ball place machine, and
involved have already promoted, and will
the reflow oven. Such a line can process
continue to promote, innovative technical
over 250,000 wafers a year, potentially
solutions to these challenges.
placing over 50 billion solder balls.
References
The future
[1] The International Technology
There is no reason to expect the
Roadmap for Semiconductors. 2007
miniaturisation of portable electronic
Edition. Assembly & Packaging.
devices will end any time soon, and so
[2] R. Chilukuri, Amkor Technology,
the ball placement equipment makers
D. Hays, Amkor Technology.
must continue to be ahead of the market’s
“Wafer Level Packaging: Yesterday,
requirements in order to provide fully
Today and Tomorrow” Future Fab
functional solutions when they are needed.
International, Volume 21.
There will also be further blurring of the
[3] T. Falcon, DEK Printing Machines.
lines between semiconductor packaging and
“0.2mm Ball Placement for 0.3mm
surface mount technology, with techniques
Pitch Wafer Level CSPs”. Originally
from both industries being used on the
distributed at the International
same components.
Wafer Level Packaging Conference,
20 – Global SMT & Packaging - August 2008 www.globalsmt.net
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