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Патент USA US2295759

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Sept. 15, 1942.
Filed June 30, 1939
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Patented Sept._ .15, 1942
- 2,295,759
Charles L. seheer, naddon?eld. N. J., a??ig?'?or to
ne“Ilo Corporation of America, a oorpor?_tion oi
Application I??ne 30, 1939, Serial No. 282.299
5 Claims. (Cl. 175-41) i
~ This invention relates to capacitors oi the type
treated illms, may be said to lose their identity
wherein the armatures comprise metal applied in
a fineiy divided state to the mica or other dielec
' tric. and to methods oi' making such capacitors.
and form a sheet characterized by the substan
tially `perfect physical and electrical continuity
of the molecules of which it is constituted. This
desired result is achieved in accordance with the
method of the invention by subjecting a dielec
The principal object ot the invention is to pro
vide an improved capacitor, of the general type'
tric. element. upon which the opposite metallic
described. which exhibits a lower power !actor
than has heretotore been thought possible oi
practicai achievement.
Another and important object of the present
armature layers have been deposited, to a rela
tively high temperature for a period su?iclently
long to produce softening and virtual ?ow of the
invention is to provide a simple, inexpensive and
trouble-free method of accomplishing the afore
metal, so that a welding, i'using, commingling or
recrystallization of the formerly separate, or
said object, and one which iends itself readily to
the mass production oi! capacitors of the general
partly separated. molecules or globules of the
metal is e ected. as indicated by the smooth sur
iaces B in
. 2. This improved smoothness is
type described.
Other objects and advantages will be apparent
usually evidenced in the ?nished ?lm by its sur
face sheen.
While the method ot the invention will be de
accompanying drawing. wherein
scribed as applied to a metallic iilm which has
r'igure 1 is a sectional view ot part oi a capaci 20 been deposited on the mica by thermal evapora
tor and illustrates the lack oi homogeneity in the
tion. distiilation or sublimation, it will be appar
metallic iilms oi the prior art;
ent to those skilled in the art that the invention
Figure 2 is a view of the capacitor ot Fig. 1
is likewise applicable to metallic ?lms which have
been deposited by means of the Schoop spray
subsequent to being treated in accordance with
the principle oi the invention and illustrates the 25 process, or by electroplating methods, or by
cathodic disintegration, or by substantially any
homogeneity and physical continuity of the me
other'h?own method or process for creating and
tallic films;
applying' metal in a ?nely divided state.
Figure 3 shows, in sectional elevation, one ior?n
In carrying the invention into eiiect, the mica
of an apparatus for depositing metal in a ?nely
divided state upon mica or other dielectric ele 80 2 is ?rst split to the required thickness and cut
to size. The individual mica plates are then pref~
erably provided each with a punched ori?ce 4 ad
Figure 4 shows, in front elevation, a rack for
jacent one end thereof, whereby they may be
supporting a number of dielectric elements in the
. and the invention will be best understood by ref
erence to the following speci?cation and to the
Suspended on pins E, which project rearwardly
apparatus of Fig. 1;
Flgure 5 is a cross-sectional view taken on the 35 from a !rame I which is provided with apertures
?o individual to the discrete mica plates. As
shown more clearly in Figs. 4 and 5, the dimen
sions or apertures ?o are somewhat less than
those of the mica elements so that the side edges
and top edge |4 oi' each element are e?fectively
sliielded by the marginai edges IS of the frame
which surrounds each mica element. When all of
the mica elements are in place in the frame 8,
line 5-5 of Fig. 4; and
Figure 6 is a side elevational view of an ele
mental capacitor constructed in acoordance with „
the principle of the invention.
The present invention is predicated upon the
fact, revealed by microscopic examination, that
the metallic "mms" or "layers"` or "surface coat
ings” of the prior art lack perfect physical con
amasking plate ?s, which' is provided with a
to the fact that such ?lms are usually applied to 45 number of apertures zu, is clamped tightly over
the !rame as by bolts 22. The apertures 20 in
the mica or other base in the form ot spray, vapor
the masking plate ?s are preferably of the same
or solution constituted oi discrete globules, or
spaced apart molecules of metal which, as indi- ` size, but are oil'set in the vertical direction from
the apertures I? in the frame 8 whereby the mar
cated at A, Fig. l, to a substantial degree retain
' tinuity and homogeneity. This may be attributed
their physical identity and haphazard distribu
ginal side and bottom edges ?z', l4', respectively,
of the mica surface opposite the surface contain
ing the masked edges i2 and !4, are exposed.
With the mica plates mounted on írame 8 and
masked by the masking plate !8 in the manner
direct current resistance ot the metallic ?lms and
is also manifest in the' ?nished capacitor-8 by the 55 above described, the assembly is supported on a
substantial power factor which they exhibitvin
suitable bracket 24 (Fig. 3) ?xed to the base
tion when the deposition process has been com
pleted. This lack of physical continuity and
homogeneity is manifest by the relatively high
The present invention contemplates and its
practice provides, a metallic ?lm wherein the dis
' 26 oi' an evacuable enclosure 28.
in Fig. 3, the enclosure 28 comprises an inverted
vessel 30 adapted to be clamped to the base 26
crete globules of metal,_char_acteristic oi un 60 as by bolts u. suitable gaskets 34 are provided
to ensure a gas-tight seal between the base !I
and the vessel u. An outlet !I communicates
with the interier of the enclosure and is con
nected with a suitable pump, not shown, for
evaculatinz the vessel. A valve u is provided
for restoring atmospheric pressure when the mica
has been processed. Supported in spaced rela
two elemental capacitors, each of which com
prises a. sheet of mica 2 and a pair of discrete
metal films B which have been treated in accord
ance with the present invention to e?ect a com
mingling of the formerly separate, or partly
separatedmolecules or globules of metal.
Comparative tests of evaporated-metal ?lms
before and after the described heat treatment
tion above the base 2', as on rods 40 which ex
showed a reduction of the order of substantially
tend between and along the frames C-il which
support the mica, are a plurality of tungsten or 10 ?fty percent in direct current resistance. Tests
of complete capacitors showed a reduction in
other refractory metal ?laments u which are
each bent in a convenient form suitable for hold
ing a piece u of the metal to be evaporated and
deposited upon the exposed areas of the opposite
surfaces of the mica.
The number and spacing of the illaments 42
containing the metal to be evaporated is pref
erably such that all of the mica plates are thor
oughly and substantially equally bathed in metal
power factor of the order of seventy-?ve percent.
By way of example, a number of untreated (but
its evaporation and deposited upon the mica.
temperature of the order of from substantially
substantial freedom from occluded gases and for
eign solids is achieved at the lowest pressure
275° C. to substantially 325° C. for a period su?l
ciently long to cause softening and virtual ?ow
otherwise similar capacitors) exhibited a power
factor of the order of .0006-.0008 at 1000 kilo
cycles. whereas those treated in accordance with
the present invention exhibited a power factor
of .0001 to .0003.
The foregoing description of the presently pre-~
vapor. The ?laments 42 are preferably con 20 ferred apparatus and means for achieving the
obiects of the invention should be interpreted as
nected to a common source of heating current,
illustrative and not in a limiting sense except as
not shown, so that when the enclosure 20 has
required by the prior art and by the spirit of the
become evacuated, evaporation of all of the metal
appended claims.
elements 44 occurs, thereby effecting the coating
What is claimed is:
of both sides of each mica plate simultaneously. 25
1. Method of decreasing the dielectric iosses
The absolute pressure maintained in the en
oi a capacitor comprised of a pair of conductive
closure 28 during evaporation of the metal
?lm-like armatures constituted of metal in a
should, for optimum results, preferably be no
?nely divided state and adhering to the opposite
higher and preferably less than 0.0001 mm. of
mercury (one-tenth of a micron). However, the 30 surfaces of an interposed dielectrlc layer, said
method comprising subiecting said capacitor to a
use of vacuum pressure considerably higher than
temperature sufnciently high and for a period suf
one-tenth of a micron may be employedas it has
?ciently long to cause softening and virtual ?ow
been discovered that by varying the degree of
of the metal.
vacuum up to, say, two microns. the ultimate
2. Method of decreasing the dielectric iosses
capacitance of the elements may be varied over 85
oi a capacitor comprised of a pair of conductive
a substantial range. The general rule is the
?lm-like armatures constituted of metal in a
higher the vacuum, the higher the ultimate ca
?nely divided state and adhering to the opposite
pacitance. This phenomenon obtains by reason
surfaces of an interposed dielectric layer, said
of the relative quantity of gas and other foreign
substances which are occluded in the metal during 40 method comprising subjecting said capacitor to a
of the metal.
3. Method of decreasing the dielectric losses of
The deposition of the metal having been com 45
a capacitor comprised of a pair of conductive
pleted the vacuum is broken by opening the valve
film-like armatures constituted of metal in a
u, the frames 8 are taken from the brackets 24,
ilnely divided state and adhering to the opposite
the masks !8 are lifted and the now coated mica
surfaces of an interposed dielectric layer, said
plates 2 are removed. subsequently and in ac
cordance with the invention, these metallized di 50 method comprising subjecting said capacitor to a
temperature of the order of from substantially
electric plates are subiected to a temperature suf
275" C. to substantialiy 325° C. for a period of
the order of from substantially flfteen to thirty
lent results have been achieved simply by placing 55 4. Method of manufacturing a capacitor which
comprises depositing a ?lm constituted of metal
a batch of several hundred of these plates 2
?clent to cause a welding, fusing, commingling
or recrystallization of the moleculesor globules
of which the metal ?lms are constituted. Excel
in a tray in an ordinary oven (not shown) and
in a ñnely divided _state upon the opposite sur
subjecting them to temperatures of the order
faces of a dielectric element, and subsequently
subjecting said deposited ?lm to a temperature
of 275-325° C. for a period of from, say, ?fteen
to thirty minutes. The temperature and dura 60 su?lciently high and for a period su?lciently long
to cause softening and virtual ?ow of said metal.
tion of this heat treatment are not especially
critical but may vary somewhat as determined
by the nature of the metal and thickness of the
5. Method of manufacturing a capacitor which
comprises mounting a dielectric element and a
piece of metal in a vacuum, then subjecting said
applied ?lms. Twenty minutes at apprcximately
300° C. is usually su?icient where the ?lm is silver 65 metal to a temperature sumcient to cause thermal
evaporation of the metal whereby to cause it to
and of a thiclmess of the order of a few one
be deposited in the form of a ?lm upon the op
millionths of an inch. The heating may be done
posite surfaces of said dielectric element, and
in vacuo, if desired, or partly in vacuo and partly
subsequently subiecting said coated element to a
at atmospheric pressure; however, as above indi
cated, excellent results have been achieved on a 70 temperature sumciently high and for. a period
sumciently long to cause virtual flow of the metal
commercial scale in an ordinary oven Operating
at substantially atmospheric pressure.
Flg. 6 shows a capacitor comprising a stacir of
constituting said ?lm.
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