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The
parylenes
resist
attack
and are
insoluble
in all
organic
solvents
up to
150ºC.
Parylene
C can be
dissolved
in
chloro-naphthalene
at 175ºC
and
parylene
N is
soluble
at the
solvent
boiling
point of
265ºC.
Both
polymers
are
resistant
to
permeation
by most
solvents
with the
exception
of
aromatic
hydrocarbons.
They are
also
unaffected
by
stress-cracking
agents
such as
"Hostepal,"
"Igepal"
and
lemon
oil.
The
effect
of a
wide
variety
of
organic
solvents
on
parylenes
N, C and
D was
investigated.
Six
classes
of
organic
solvents
were
examined:
alcohol
(isopropyl),
ketones
(acetone
and
2,4-pentanedione),
aliphatic
hydrocarbon
(iso-octane),
aromatic
hydrocarbon
(xylene),
chlorinated
olefin
(trichloroethylene),
chlorinated
aromatic
(chlorobenzene
and
o-dichlorobenzine),
heterocyclic
base
(pyridene),
and
fluorinated
solvent
(trichlorotrifluoroethane).
These
solvents
had a
minor
swelling
effect
on the
parylenes
with a
3%
maximum
increase
in film
thickness.
The
swelling
was
found to
be
completely
reversible
after
the
solvents
were
removed
by
vacuum
drying.
Some
inorganic
reagents
were
also
examined.
These
included:
deionized
water;
10%
solutions
of
sodium
hydroxide
and
ammonium
hydroxide;
non-oxidizing
acids,
hydrochloric
and
sulfuric,
in
concentrated
and 10%
solutions;
and
oxidizing
acids,
nitric
and
chromic,
concentrated
and 10%
solutions.
The
diluted
inorganic
reagents
had
little
effect
on the
parylenes.
The
acids at
10%
concentrations
had
virtually
no
effect
at room
temperature
and,
except
for
chromic,
no
effect
at 75ºC.
Concentrated
acids at
room
temperature
(23ºC)
had
little
effect.
Under
severe
conditions,
75ºC for
30
minutes,
all
acids
had a
measurable
effect
ranging
from
0.7%
swelling
with
hydrochloric
to 8.2%
with
chromic.
Additionally,
nitric
acid
under
these
same
severe
conditions
caused
severe
degradation.
Both
concentrated
nitric
and
sulfuric
acids
caused
some
discoloration.
Earlier
experience
had
indicated
that
parylenes
N, C and
D were
insoluble
in all
common
solvents.
Parylene
C, it
was
found,
could be
dissolved
in high
boiling
liquids
such as
X-chloronaphthelene
or
benzoyl
benzoate
at
temperatures
above
150ºC.
However,
these
solvents
are
seldom
encountered
in the
electronic
industry.
Of
greater
importance
are
those
solvents
and
reagents
used in
processing,
especially
in
cleaning
of
components
and
assemblies.
This
study
was
undertaken
to
quantitatively
measure
the
effect
of the
more
common
solvents
and
reagents
on the
parylenes.
Included
also
were
certain
hydrocarbons
serving
as
models
for
fuels.
The
organic
liquids
chosen
for this
study
were
selected
as being
representative
of
typical
solvent
classes.
The
protection
provided
to the
coated
substrates
by the
parylenes
was also
observed.
It was
also
known
that the
parylenes
were
inert to
inorganic
reagents
(except
for
oxidizing
agents).
This
conclusion
was
confirmed
by the
work
reported
here and
quantitative
results
given.
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