The impact of seal selection on PV productivitiy and cost
The impact of seal selection on
PV productivitiy and cost
Test results from DuPont
demonstrates that performance variation
Perofrmance Elastomers (DPE)
“Understanding
can exist within the same elastomer
category.
for various sealing materials
elastomer performance In addition to “wet” applications,
used in demanding cell
helps reduce unplanned
Vigliotti also discussed test results in
manufacturing processes indicate
high-temperature applications like doping
maintenance as a result in crystalline silicon and diffusion in
that selecting the appropriate
sealing materials can help
of incompatible sealing
Cu (In, Ga) Se2 (CIGS). Exposure to
high temperatures can cause seals to
improve seal performance and
materials.” become hard and brittle, thereby losing
their sealing functionality. Additionally,
lower cost of ownership in both
elastomeric seals can degrade under
bulk crystalline silicon and thin
environment does not guarantee that it will
high temperatures causing outgassing to
film photovoltaic processes that work in all environments.”
occur, thereby contaminating the process
environment. Hydrofluoric acid (HF) is
use aggressive “wet” chemistries,
In his presentation, Vigliotti reviewed
elastomer properties and the results of
one of the gases evolved when FFKM and
high temperatures or reactive
elastomer testing in various processes used
FKM begin to degrade. It can be harmful
plasma/gas. The test results in photovoltaic manufacturing. In “wet”
to process equipment, especially to quartz
were presented at InterSolar/
processes where aggressive acids and bases
and stainless steel components. The
outgassing performance of FFKM, FKM
SMET on May 27, 2009, in
such as HF, HCl, HNO3, KOH and NaOH
are used for etching and cleaning, Vigliotti
and silicone (VMQ) are compared in Figure
Munich, Germany by Michele
discussed how perfluoroelastomer parts
1.
Vigliotti, in a presentation
(FFKM) tend to show better resistance to
In chemical vapor deposition and
plasma etch processes, the plasmas
titled “Perfluoroelastomer
chemical attack, suggesting longer seal life.
Seals also can leach contaminants into the
used can be extremely aggressive and
and Fluoroelastomer Seals for
process system and ultimately contaminate
can cause seals to fail rapidly, thereby
Photovoltaic Cell Manufacturing
the finished product. Since ultrapure
leading to problems during pump-down
or causing toxic gasses to be released
Processes.”
deionized (UPDI) water is used in many
into the atmosphere. In order to better
According to Vigliotti, “Elastomer
rinsing steps, maintaining purity is critical
predict seal life, a more thorough
performance can vary dramatically,
for success. Test results in UPDI water
understanding of plasma attack mode
especially if more aggressive processing
illustrate how FFKMs have considerably
and chemistry is discussed. Test results
variants and technologies are used to
less metallic and total organic carbon
highlighted the weight-loss properties
help increase output and cell efficiency.
(TOC) extractables than fluoroelastomer
of various fluorinated elastomers and
Finding an elastomer that works in one
(FKM) parts. The comparison also
silicone as result of exposure to both
fluorine and oxygen containing plasma.
Test results also indicated that “cleaner”
elastomer formulations can help reduce
particle generation, thus improving
photovoltaic cell manufacturing processes.
As photovoltaic manufacturers improve
productivity by using increasingly aggressive
chemical, plasma and temperature
environments, increased strain is placed on
manufacturing systems.
“Seal selection is a science,” Vigliotti
said. “When manufacturers use the science
for their benefit, productivity can improve
beyond the added cost of purchasing a
high-performance seal.”
Figure 1. Outgassing Comparison: FFKM Versus FKM And VMQ.
10 – Global Solar Technology – July/August 2009
www.globalsolartechnology.com
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