Solar integration takes a page from the semi wafer CSP playbook
Solar integration takes a
page from the semi wafer
CSP playbook
by Steve T. Cho, Ph.D. and Steve Anderson, Surfect Technologies, Tempe, AZ, USA
introduction
Both the integrated circuit and
The current petroleum crisis induced by
solar industries face the same
growing demand and limited supply has
challenge: the need to improve
put industrial focus on alternative energy
performance in the face of a man-
sources. To date, only nuclear and hydro-
electricity have been widely adopted as
date to reduce cost. Both busi-
options to fossil fuels. As emerging nations
nesses are finding that the cost-
such as China and India evolve into more
!
performance ratio of achieving
energy-based societies, the demand for low
improvement through the semicon-
cost power will only continue to grow. Solar
Figure 1. Output of solar energy compared to other
ductor (or front) end is continuing
sources
1
.
energy is an extremely attractive option due
to climb. The semi industry has to 1) lack of a waste product, 2) large power
recognized the benefits of chip
source (Figure 1) and 3) inexhaustible supply.
scale packaging but struggles with
The main drawback to the adoption of solar
controlling expense. The solar in-
energy is cost. A typical power system costs
dustry is learning from semi and
$0.08-0.15/kWh while solar costs $0.25-
is starting to implement lower cost
0.35/kWh. Subsidies currently absorb the
excess expense, but many nations are on
materials and processes (such as
track to drop their subsidies in the near
multi-metal stacks) while improv-
future; hence cost is driving the solar indus-
ing performance and reliability in
!
try. Some of the key factors for solar prices
the back end. However, the solar
Figure 2. Basic solar generation system and system
include location (some areas have more
industry can delve deeper into
componenents.
sunlight than others) and system and instal-
the semi playbook and find that lation expense. The cost of solar energy is
the flexibility in form factor that
about $8/Wp, and a price of about $3/Wp
chip scale packaging presents, as
will make solar cost competitive with other
well as the integration of multiple
energy sources (i.e., reach grid parity).
functions (e.g., power manage-
Figure 2 shows the breakdown of a basic
ment), can accelerate the solar
solar generation system. About 50-60% of
the cost of a solar panel is in the energy
drive towards power grid parity.
absorbing materials and packaging (solar cell
This paper reviews how the solar
and the module), but the remaining cost is
industry is integrating semicon-
in elements such as labor and power system
Figure 3. Itemized solar costs.
ductor packaging technology into
conversion (inverters, rectifiers, batteries, !
its cells and modules and how etc) (Figure 3). If the price of solar cells were
controlling the costs of processes, to drop 50% today, the total impact on the
not applicable. Table 1 outlines some of the
materials and tools will be a key
system cost would only be 17-25%.
main differences between semi processing
enabler for the growth of solar.
In order to drive down the price of solar
and solar. Whereas semi works at high
to reach grid parity, a system approach for
frequencies and high pin counts, a solar cell
silicon cells will be required. How compo-
has two outputs and typically runs at DC
nents are integrated and how interconnect is
before rectification. A common solar cell
Keywords: CSP, Solar, Plating, performed will be critical. Therefore, packag-
produces only a few watts; in order to meet
Module, Interconnect
ing will end up playing an important role in
the requirement of hundreds of MW for
solar development.
solar generators, a substantial number of
The integrated circuit industry can teach
cells are required. A good size bumping line
This paper was originally published in the
the solar industry many lessons, but at the
will bump about 50,000 wafers per month;
proceedings of the SMTA International
same time, many of the technologies are
a single solar line runs at 1500-2000 wafers
Conference, Orlando, Florida, August 2008.
per hour (an order or magnitude more
6 – Global Solar Technology – March/April 2009 www.globalsolartechnology.com
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