U.S. patent number 3,733,660 [Application Number 05/093,486] was granted by the patent office on 1973-05-22 for slot applicator method.
Invention is credited to Milton Kallianides, Gerhart P. Klein.
United States Patent |
3,733,660 |
Kallianides , et
al. |
May 22, 1973 |
SLOT APPLICATOR METHOD
Abstract
The combination of a reservoir containing a fluid and applicator
means for applying the fluid to means carrying a plurality of
pellets to be used as capacitors. The applicator means includes
upper and lower walls connected by a rear wall so as to form a slot
having a determined length and width. A channel is formed in one of
the walls so as to couple the slot to the fluid containing
reservoir allowing fluid to flow to the slot in a controlled
manner. The applicator means applies determined amounts of the
fluid to the means carrying said pellets and the pellets passing
therethrough.
Inventors: |
Kallianides; Milton (Brockton,
MA), Klein; Gerhart P. (Manchester, MA) |
Family
ID: |
22239223 |
Appl.
No.: |
05/093,486 |
Filed: |
November 27, 1970 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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701488 |
Jan 29, 1968 |
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Current U.S.
Class: |
29/25.41;
427/80 |
Current CPC
Class: |
H01G
13/00 (20130101); Y10T 29/43 (20150115) |
Current International
Class: |
H01G
13/00 (20060101); B44d 001/18 (); C23c
001/10 () |
Field of
Search: |
;117/1B,201,113,49,50,12R,213 ;29/25.41 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Leavitt; Alfred L.
Assistant Examiner: Esposito; M. F.
Parent Case Text
This is a division of application Ser. No. 701,488, filed Jan. 29,
1968, now abandoned. U.S. application Ser. No. 93,869, filed Nov.
30, 1970, now U.S. Pat. No. 3,669,062, is a continuation of U.S.
application Ser. No. 701,488, filed Jan. 29, 1968.
Claims
Having thus described our invention, we claim:
1. A method of applying a fluid to strip means carrying a pellet
for use as a capacitor anode, comprising the steps of,
depositing a moistened mass of film-forming metallic powder on
strip means of film-forming metal,
forming the moistened mass to provide a porous pellet joined to the
metal strip means,
passing the portion of the metal strip means carrying the pellet
joined thereto through slot means formed in slot applicator means,
the slot means of determined length and width, and
contacting the portion of the metal strip means and the pellet
passing through the slot with liquid retained in the slot due to
the surface tension of the liquid and the geometry of the slot.
2. The method of claim 1, wherein said slot has an upper wall,
lower wall and an end wall retaining said upper wall and said lower
wall in spaced relationship.
3. The method of claim 1, wherein the porous pellet joined to the
metal strip means is formed by sintering the metallic powder in
situ to form a porous pellet joined to the metal strip.
4. The method of claim 1, wherein the liquid contacting the pellet
and the strip is selected from the group including manganous
nitrate, a colloidal dispersion of graphite in water or silver
paint.
5. The method of claim 4, wherein the film-forming metallic powder
and the strip means of film-forming metal are selected from the
group including tantalum, zirconium, aluminum, niobium and
titanium.
6. The method of claim 5, wherein the film-forming metallic powder
and the strip means of film-forming metal are tantalum.
7. The method of claim 1, including the further steps of,
subsequent to contacting the metal strip means and pellet with the
liquid, providing a second slot means, passing the liquid contacted
metal strip means and pellet through the slot of the second slot
means and monitoring the electrical characteristics of the metal
strip means and pellet in the slot.
8. The method of claim 1 including the further step of, subsequent
to contacting the metal strip means and pellet with the liquid,
removing unjoined metallic powder and excess liquid by moving fluid
in a direction different from the direction of movement of the
metal strip means and pellet.
9. A method of making a capacitor using the anode of claim 1,
comprising contacting the metal strip means and the pellet with
dielectric means, contacting the dielectric means with electrolyte
means, and contacting the electrolyte means with cathode means.
Description
Solid electrolyte capacitors may be manufactured using any one of
several different techniques. For example, a determined amount of a
film-forming metal powder selected from the group consisting of
tantalum, zirconium, aluminum, niobium, and titanium may be pressed
to a desired density and then sintered so as to provide a sintered
porous anode slug or pellet. In addition, the anode slug may be
prepared using a mixture of metal powder and a binder such as
stearic acid or the like. During sintering of the compact, the
stearic acid is evaporated without leaving traces of impurities on
or in the compact. The binder is used to hold the compressed
particles together until the sintering process has been initiated.
Sintering cements the individual metal powder particles together so
as to form a slug having a myriad of intercommunicating voids. An
oxide film formed on the film-forming material using any of the
known electro-formation methods. The oxide film has asymmetrical
conductive characteristics and serves as the dielectric for the
capacitor. In the case of a tantalum slug, the oxide film is
tantalum pentoxide. The oxide coated slugs are dipped into a bath
of manganese nitrate. The manganese nitrate coated slugs are passed
through ovens in which the manganese nitrate is pyrolytically
converted to a semiconductive layer of manganese oxide. The
manganese dioxide layer is the solid electrolyte of the capacitor.
The step of forming the manganese dioxide layer and/or the oxide
film layer on the slug may be repeated as many times as is
necessary to achieve the desired electrical characteristics. The
slugs are dipped into a suitable contact material such as a
colloidal dispersion of graphite in water or the like and suitably
cured in an oven. This is done to deposit a graphite contact layer
on the end of the slug remote from the anode riser. Silver "paint"
is applied over the graphite layer and cured. Thereafter, the slugs
are dipped in solder. The slug is placed in a suitable container or
housing generally having an open end and a closed end. The end of
the slug coated with solder is suitably attached to the casing. The
open end of the container is closed with a suitable end seal.
It was found that solid electrolyte capacitors can be fabricated
using a continuous processing method. The process may be initiated
by depositing a wet mass of film-forming metallic powder on a
substantially continuous foil strip fabricated from the same
film-forming metal and sintering the moistened mass of metallic
powder in situ to form a porous pellet connected to the foil strip.
The use of a moistened mass of film-forming metal powder has
several advantages among which are that the powder is moistened so
that it flows dropwise from a suitable dispenser means thereby
facilitating dispensation of the moistened mass in determined
amounts. Another advantage is that the moistened mass has a
significantly reduced volume when compared to the volume of the dry
powder before moistening thereby providing a green compact having
the required density without the necessity of compacting the
powder. When the foil strip and the pellet, comprising the anode,
are anodized in accordance with generally accepted practices, a
dielectric film is formed thereon. A semiconductive layer is formed
on the anode using generally accepted procedures. A suitable
electrically conductive coating is deposited over the
semiconductive layer to form the cathode of the capacitor. The
capacitor has leads attached thereto and is suitably
encapsulated.
The continuous fabrication process, referred to hereinafter as the
"powder on foil" technique, was conceived and developed to
eliminate handling problems experienced during the fabrication of
small, solid electrolyte capacitors. The "powder on foil" technique
of manufacturing small, solid capacitors significantly reduced the
handling required of the individual capacitors when compared to the
handling required during the fabrication of solid electrolyte
capacitors using individual sintered anode slugs. Also, it was
found that elimination of the pressing operation and the binder
significantly improved the quality of the solid electrolyte
capacitor.
Previously, "powder on foil" capacitors were fabricated by
dispensing a predetermined amount of a moistened mass including a
film-forming metallic powder in the form of a droplet or droplets
on a selected area on a film-forming metal foil. The metal foil may
be provided with depressions or indentations for locating and
retaining the slurry at a predetermined area on the foil. The
moistened mass of film-forming metallic powder and the metal foil
must be the same film-forming metal. The foil carrying the
moistened mass is processed in a substantially continuous fashion
until the individual capacitors are separated from one another as
the last step of the process. It is seen that the outlined
procedure reduces the amount of handling required during
fabrication of capacitors, substantially eliminates contamination
which may occur during handling and minimizes the possibility of
structural damage occurring during fabrication by eliminating the
steps of pressing and adding binders to the powder prior to
sintering. After the pellet is formed on the foil strip, the
cathode formation is accomplished by using the generally accepted
method steps for fabricating solid electrolyte capacitors.
Generally, the foil strip and the associated pellets are dipped in
an appropriate solution such as manganous nitrate, a dispersion of
graphite in water, silver paint and the like during processing.
It was found that the depth of immersion of the pellet in the
appropriate solution should be accurately controlled in order to
limit undesirable build-up of excess material on the pellet.
Generally, dipping of the pellet in the appropriate solution was
accomplished by rotating the foil strip and the attached pellets
about 90.degree. and immersing the foil strip and pellets by
dipping in containers or vats. The depth of immersion is determined
by the position of the foil strip and the level of the solution. It
was found that both of these factors were difficult to control
within the accuracy required to achieve a quality capacitor.
In addition, it was found that when the foil strip and the pellets
were dipped into the appropriate solution, the solution had to be
discarded after a determined amount of use or passage of time due
to the nature of the dipping process and the nature of the
properties of the reagents in the solutions. For example, the
manganous nitrate solution is diluted as water soaked anodes are
immersed therein and on standing for a length of time, the solution
may become contaminated. In order to prevent contamination of the
pellet with impurities or the like, the solution should be
discarded after a determined amount of use and replaced by a
"fresh" solution. In the case of the colloidal dispersion of
graphite in an aqueous solution, deterioration thereof during
standing results in the loss of a large portion of ammonia from the
aqueous solution. Dilution of the colloidal dispersion of graphite
in an aqueous solution may occur due to water carried by the
pellets from previous process stations mixing with the aqueous
solution. Silver "paint" is particularly sensitive to standing for
periods of time in contact with air. It was found that the silver
"paint" dries quickly and tends to form a skin on the surface
thereof which makes dipping of the pellets therein more difficult
and leads to a considerable waste of the relatively expensive
silver "paint".
The present invention has eliminated the above-mentioned problems
by using slot applicator means which permits immersion of the foil
strip and the attached pellet or pellets in the appropriate
solution while being displaced with their major axis in the
horizontal plane. It was also found that the depth of immersion of
the foil strip and the attached pellets can be easily reproduced
and conveniently controlled within close tolerances. A major
advantage of the slot applicator means over the standard technique
of dipping capacitor anodes in solution containing vats is that
waste by contamination and the like of the solution is minimized
since the major portion of the solution is retained in an enclosed
reservoir removed from the applicator means. The solution to be
supplied to the applicator means is retained under substantially
clean and uncontaminated conditions. In addition, since the
solution is drawn from a reservoir where the environment is closely
controlled, variations of the electrical properties of the pellet
due to changes in the composition of the solutions in which the
pellet is immersed are substantially eliminated. The variations in
the solutions due to large surface area contact with ambient air
when retained in dipping vats having large openings to allow for
dipping the anodes therein is substantially eliminated due to the
relatively small surface area contact of the solution with ambient
air when dispensed using the slot applicator means of the present
invention. Cleaning or washing of the pellet to remove loose
particles or solution excess therefrom is most effective when the
washing fluid and foil strip retaining the pellet are displaced in
opposite directions. In addition, the amount of washing fluid
necessary to obtain a desired cleaning result is less if the fluid
flows in a direction opposite to the displacement of the pellet.
The slot applicator means permits the flow of the fluid in a
direction opposite to the movement of the foil strip and
pellet.
With slight modifications, the slot applicator or slotted means may
be used as an in-line monitoring device. The monitoring device
permits the measurement of the electrical parameters of the
capacitor. The slotted means contains a suitable electrode which is
the cathode of a measuring cell. Electrical characteristics of the
pellet such as capacitance, equivalent series resistance and
leakage current can be determined for individual pellets at any one
of several selected points in the process without interrupting the
movement of the foil strip during fabrication of the capacitors. It
is seen that substantially continuous in-line monitoring of the
electrical properties of a capacitor is a reality. The contact slot
has to remain in contact with an individual pellet until the
measurement of capacitance, DF, or DCL has been completed. With a
continuously moving strip this can be realized by either reducing
the length of the slot so that there is a sufficient time interval
without electrolyte bridging between adjacent pellets, or by moving
the measuring slot synchronously with the tape for a distance
equivalent to the time needed to complete the measurement.
Therefore, it is an object of the present invention to provide
method which overcomes the above-mentioned problems.
Another object of the present invention is to provide a method for
applying an appropriate solution to a plurality of pellets passing
therethrough with substantially no waste and/or contamination of
the solution.
Yet another object of the present invention is to provide a method
for applying a controlled amount of an appropriate solution to a
continuous succession of pellets carried on a continuous foil strip
passing therethrough.
A further object of the present invention is to provide a method
for applying an appropriate solution to a plurality of pellets
carried by a foil strip, said means being an integral part of a
continuous process for fabricating an infinite strip of anodes for
solid electrolytic capacitors.
Yet another object of the present invention is to provide method
which accurately applies a predetermined amount of an appropriate
solution to pellets carried by a film-forming metal strip, said
pellet, metal strip and solution operating so as to form a portion
of an electrolytic capacitor.
Another object of the present invention is to provide a method
having apparatus comprising an applicator means including slotted
head means wherein the head means includes a slot which is capable
of accommodating pellet thicknesses of about 0.1 inches.
Yet another object of the present invention is to provide a method
having apparatus comprising a slotted applicator means having a
slotted head in which the slot retains an appropriate fluid due to
the geometry of the slot and the surface tension of the fluid.
Still another object of the present invention is to provide a
method having apparatus comprising a slotted applicator means
wherein fluid is gravity fed to the slot from a reservoir means
located above the applicator means and coupled to the applicator
means by a suitable conduit means.
Yet another object of the present invention is to provide a method
for in-line monitoring of the electrical characteristics of
capacitors as the capacitors pass through the slot of the slotted
means.
A further object of the present invention is to provide method for
applying a determined amount of an appropriate solution to a pellet
as the pellet passes through the slotted applicator and further
including means for removing excess amounts of the solution from
the pellet as the pellet leaves the slotted applicator means.
Yet still another object of the present invention is to provide
method for applying a determined amount of an appropriate solution
to a pellet as the pellet passes through the slotted applicator
without wasting and/or contaminating the solution that is
efficient, effective and accurate in application of the solution to
the pellet.
The present invention, in another of its aspects, relates to the
novel features of the instrumentalities of the invention described
herein for teaching the principal object of the invention and to
the novel principles employed in the instrumentalities whether or
not these features and principles may be used in the said object
and/or in the said field.
With the aforementioned objects enumerated, other objects will be
apparent to those persons possessing ordinary skill in the art.
Other objects will appear in the following description, appended
claims and appended drawing. The invention resides in the novel
construction, combination, arrangement, and cooperation of elements
as hereinafter described and more particularly as defined in the
appended claims. The appended drawings illustrate an embodiment of
the present invention constructed to function in the most
advantageous modes devised for the practical application of the
basic principles involved in the hereinafter described
invention.
In the drawings:
FIG. 1 is an enlarged top view of the slotted applicator means
illustrating cut-out cups formed in a substantially continuous foil
strip means carrying a pellet consisting essentially of
film-forming metal powder passing through a slot of the applicator
means.
FIG. 2 is an enlarged cross sectional view of the slotted
applicator means and the foil strip means carrying pellets taken
across the lines 2--2 of FIG. 1.
FIG. 3 is an enlarged top view of applicator means adjustable with
respect to the foil strip means and the pellets allowing accurate
adjustment of the depth of immersion of the pellets in the solution
retained in the slot of the applicator.
FIG. 4 is an enlarged cross sectional view of the slotted
applicator means and the foil strip means carrying pellets taken
across the lines 4--4 of FIG. 3.
FIG. 5 is an enlarged partial side view of the slot of the slotted
applicator means taken across lines 5--5 of FIG. 3 illustrating the
spaced, parallel relationship of the top and bottom walls of the
applicator means.
FIG. 6 is an enlarged partial side view of the slot of the slotted
applicator means illustrating the top and bottom walls at an angle
with respect to one another so as to facilitate removal of excess
solution from the pellet as the pellet exits the applicator
means.
FIG. 7 is an enlarged partial cross sectional view of an apertured
applicator means for washing the foil strip and attached
pellets.
FIG. 8 is an enlarged partial cross sectional view of a slotted
means including an electrode for measuring selected electrical
characteristics of the foil strip and attached pellets passing
therethrough.
FIG. 9 is an enlarged side view of the slotted means taken across
the lines 9--9 of FIG. 8.
FIG. 10 is an enlarged partial cross sectional view of slotted
means including an electrode for measuring selected electrical
characteristics of the foil strip and attached pellets passing
therethrough.
Generally speaking, the means and methods of the present invention
relate to an applicator means in combination with a reservoir
containing fluid. The applicator means includes a slot through
which a foil strip and pellets pass in substantially continuous
fashion. The slot of the applicator means applies determined
amounts of the fluid from the reservoir to the foil strip and
pellets passing therethrough.
Referring now to the figures of the drawing and more particularly
to FIG. 1, the slotted applicator means is generally indicated by
the reference number 10. The applicator means has a substantially
C-shaped cross section and is fabricated from any suitable material
such as stainless steel, teflon, plexiglas or the like. The
applicator means includes a slot 11, upper wall 12, lower wall 13
in substantially spaced parallel relationship with the upper wall
12, end wall 14 which couples upper wall 12 to lower wall 13 and a
channel 15 formed in end wall 14. The channel connects the slot 11
with a reservoir (not shown) containing an appropriate solution
through a conduit means (not shown). The solution is illustrated in
FIG. 1 as 21.
A substantially continuous foil strip 16 fabricated from a suitable
film-forming metal selected from the group consisting of tantalum,
zirconium, aluminum, niobium and tantalum has attached thereto a
pellet 17 which generally has a hemiellipsoidal shape. The foil
strip includes a plurality of substantially equally spaced cut-out
cups 18. Each of the cups includes a depression or indentation (not
shown) for predeterminately locating the pellet on the foil strip.
The foil strip is displaced in the direction of arrow 19 by any
suitable means such as a conveyor means or the like (not shown).
The foil strip may have a thickness of about 0.002 inch and the
cups may have a diameter of about 0.2 inch. The cup may or may not
have an indentation of about 0.02 inch. The pellets of film-forming
metal typically have a thickness of about 0.02 to 0.1 inch. Typical
dimensions of the pellet are a width of about 0.2 inch and
thickness of about 0.05 inch which provides a capacitor having a
capacitance value of about 50 microfarad-volt. It is to be
understood that the thickness of the droplet is proportional to the
capacitance of the device, therefore the limits given as to the
thickness of the droplets aremmerely illustrative of how thin the
anodes are and are not intended to be limiting with regard to the
inventive aspects of the present invention. The anodes may be made
thicker or thinner if desired.
As the foil strip advances in the direction of arrow 19, a cut-out
cup 18 and its attached pellet are introduced to the slot 11 of the
applicator means 10 as shown in FIGS. 1 and 2. An appropriate
solution 21 such as manganous nitrate, a colloidal dispersion of
graphite in water, silver paint or the like is applied to the cup
and the pellet by the applicator means. The retention of the
solution in the slot 11 is due to the surface tension of the fluid
and the geometry of the slot. The width and height of the cut-out
cup and the attached pellet are compatible with the slot 11 of the
applicator means. The length of the slot of the applicator means is
proportional to the elapsed time required for optimum soaking of
the individual units. The application time depends, therefore, on
the length of the applicator means and the foil strip speed.
The appropriate solution is fed into the slot 11 through one or
more channels in the applicator. FIG. 1 shows a single channel 15
through which the fluid from the reservoir flows to the slot of the
applicator means. The channel or channels are formed in the rear
wall of the slotted applicator means equally spaced from one
another and the extremities of applicator means in order to provide
substantially uniform feeding of the solution to all areas of the
slot of the applicator means. For relatively short applicator
means, as shown in FIGS. 1 and 3, which are on the order of a few
inches in length, one channel is thought to be adequate. In
applicator means having extended lengths, one channel for every 3-5
inches of length is thought to be desirable.
The applicator means should be provided with a suitable guide means
20 for maintaining the foil strip properly positioned with respect
to the slot 11. In order to prevent bridging of the gap between
slot and guide means 20, it may be necessary to place guides at the
ends of the slot only.
The appropriate solution is gravity fed to the slot 11 from a
reservoir (not shown) positioned above the slot and connected to it
through a suitable conduit (not shown) such as capillary tubing.
The flow rate of the solution may be adjusted by altering the
height of the reservoir above the slot 11 or by changing the length
or diameter of the capillary tubing. It is thought that accurate
and reproducible feed rates can be obtained through the use of
suitable metering pumps (not shown).
FIGS. 3 and 4 illustrate an adjustable applicator means 10' in
which a slotted head 30 carried by guide means 31 of the applicator
means may be adjusted with respect to the foil strip thereby
allowing accurate adjustment of the depth of immersion of the
cut-out cup and the attached pellet in the appropriate solution.
The slot illustrated in FIG. 3 is of such length so as to
accommodate the entire area of a single capacitor. The so-called
"short" applicator means are more suitable for the application of
viscous solutions such as silver paint to the strip and pellet than
the "long" applicator means although the "short" applicator means
may be used to apply other solutions thereto. The upper and lower
walls of the applicator means may be in substantially spaced
parallel relationship as shown in FIG. 5 or the walls may be
tapered as shown in FIG. 6 at 12' and 13' in such a way that the
excess solution, if any, applied to the pellet is removed as the
capacitor foil strip and attached pellet exit the slot.
It is thought that slurries such as silver paint and the colloidal
dispersion of graphite should be agitated while confined within the
reservoir in order to keep the particles appropriately dispersed in
the liquid.
Slot applicator means may be used for washing and rinsing of the
foil strip and the attached pellet. However, the length of the slot
required may make it more desirable to move the foil strip and
attached pellet through aperture 70 which is substantially
completely enclosed as illustrated in FIG. 7. Channel 15 is used to
feed water into aperture of the applicator means. Another
embodiment which increases the washing efficiency of the applicator
means is realized by displacing the foil strip and pellet through a
series of "short" slots.
FIGS. 8 and 9 show a slotted means 90 fabricated from any suitable
material such as Teflon or the like including a sensing slot 93 and
an electrode 91 fabricated from platinum wire for measuring
selected ones of the electrical properties of capacitors passing
through the slot and in close proximity to the electrode. The
electrode is coupled to any suitable measuring device (not shown).
The slot of the means 90 is of such length that no bridging of the
electrolyte occurs between adjacent capacitor units. The electrode
91 includes an insulative spacer 92 which spaces the electrode from
the side wall of T-shaped channel 15. Channel 15' is used to
provide a suitable electrolyte solution to the slot 93. The
electrolyte is used during the testing of the capacitors.
FIG. 10 shows another embodiment of the slotted means at 95. The
slotted means includes a sensing slot 96. An electrode 97 is
retained by the applicator means in such a way that it contacts the
electrolyte in the slot fed thereto by supply channel 15. The
electrode 92 includes a relatively large sensing area and is
fabricated from a platinized platinum material. The slotted means
95 is used for measuring the capacitance of the pellets and foil
passing therethrough. The electrode is positioned in the slot
itself and is separated from the capacitor unit by a suitable
porous separator 94. When the slotted means is used to make
electrical measurements, the foil strip is the anode, the electrode
in the slotted means the cathode.
While this invention is illustrated and described in embodiments,
it will be understood that modifications and variations may be
effected without departing from the scope of the novel concepts of
this invention and as set forth in the appended claims.
* * * * *