U.S. patent number 3,659,240 [Application Number 05/033,241] was granted by the patent office on 1972-04-25 for thick-film electric-pulse transformer.
This patent grant is currently assigned to Bourns, Inc.. Invention is credited to Allen J. Learned, Jason D. Provance.
United States Patent |
3,659,240 |
Learned , et al. |
April 25, 1972 |
THICK-FILM ELECTRIC-PULSE TRANSFORMER
Abstract
A toroidal pulse transformer produced by successive deposition
of thick-film deposits of conductor segments, fusible insulation,
ferrite, conductor segments completing a first transformer winding;
alumina, conductor segments, fusible insulation, ferrite, and
conductor segments completing a second transformer winding, the
ferrite films being of elongate substantially flat sheet form
joined intimately at their ends and separated between their ends by
upper conductor segments of the first winding, insulation and lower
conductor segments of the second winding; and a modified, simpler
form utilizing an integral ferrite single-layer sheet of toroidal
shape.
Inventors: |
Learned; Allen J. (Loma Linda,
CA), Provance; Jason D. (Glendora, CA) |
Assignee: |
Bourns, Inc. (Riverside,
CA)
|
Family
ID: |
21869298 |
Appl.
No.: |
05/033,241 |
Filed: |
April 30, 1970 |
Current U.S.
Class: |
336/200 |
Current CPC
Class: |
H01F
27/255 (20130101); H01F 41/0206 (20130101); H01F
41/0246 (20130101); H01F 19/08 (20130101) |
Current International
Class: |
H01F
27/255 (20060101); H01F 19/08 (20060101); H01F
41/02 (20060101); H01F 19/00 (20060101); H01f
027/30 () |
Field of
Search: |
;336/200,221,232 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kozma; Thomas J.
Claims
We claim:
1. A miniature pulse transformer consisting essentially of a solid
mass made up of an elongate non-magnetic insulation substrate and
superposed thereon and fusion-united therewith thick-film
components including,
first means including an elongate first array of thick-film
conductor segments individually disposed transversely of said
substrate and thereon,
second means including an elongate insulative thick film of glass
adherent in part to said substrate and covering intermediate
portions only of said conductor segments of said first array,
third means including a wide elongate thick film of magnetic
ferrite disposed on said film of glass over insulated intermediate
portions of said conductor segments of said first array,
fourth means including a second elongate array of transversely
disposed thick-film conductor segments intermediate portions of
which overlie said thick film of magnetic ferrite material and each
having at least one end portion fustion-united to an underlying end
portion of one of the conductor segments of said first array of
thick-film conductor segments whereby the conductor segments of
said first and second arrays thereof are electrically serially
connected to provide a first flat conductive coil encircling and
inductively linked to said thick film of magnetic ferrite, and
fifth means including third and fourth elongate arrays of
transversely disposed thick-film conductor segments and an elongate
insulative glass film and a thick film of ferrite, both interposed
between intermediate portions of the conductor segments of said
third array and those of said fourth array, end portions of said
conductor segments of said third and fourth arrays thereof being
integrally joined to form second flat elongate conductive coil
inductively linked to the thick film of ferrite of said fifth
means, and said thick film of ferrite of said fifth means joining
at its ends respective ends of said thick film of magnetic ferrite
of said third means, whereby said first and second flat elongate
conductive coils are mutually inductively related to a continuous
magnetic ferrite flux path through the integrally united elongate
ferrite components of said third and fifth means, to form
superposed primary and secondary windings of said transformer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
In respect of certain uses and procedures, this application is
related to the application of Ronald A. Ketcham and Allen J.
Learned, Ser. No. 33,423, filed on the same date as this
application and entitled "Thick Film Ferrite Information Store
Device."
BRIEF SUMMARY OF THE INVENTION
a. The prior art environment.
In certain technical fields, for example the digital information
processing or "computer" hardware field, fast-acting transformers
for supplying rapidly recurring energetic electric current pulses
are required. In those instances where energy content of the pulses
is of primary importance, squareness of the wave form or pulse
configuration is of important significance, since the energy
contained in the pulse is proportional to the time-integral of the
current and hence to the area of the graphical equivalent of the
pulse. Thus it is desirable that the pulses produced by the
transformer and output from the secondary have steep fronts and
rapid decay. In the prior art, transformers have been produced by
winding insulated conductors on ferrite cores of toroid form. Such
winding is tedious and expensive, and especially so when the
transformers are of small size such as one-fourth inch maximum
dimension. Accordingly, it has been proposed, as in the patent to
Craig, U.S. Pat. No. 2,937,351, for example, to electro-deposit
magnetic cores upon an insulative backing or support, and to
produce windings by selective application of conductive paint on
both sides of the support and through apertures formed in the
support, the paint being reduced to metal. As an alternative,
rivets are disposed in the apertures and the paint is applied as
lines connecting rivets. By utilizing the procedure outlined in the
Craig patent, a large number of transformers could be
simultaneously produced upon a single large support, the support
later being cut or otherwise divided into individual units. In
another prior art effort to avoid having to wind conductors upon a
toroidal core, in the production of inductors it has been proposed
to deposit in successive layers thin-film segments of conductors,
dielectric or insulation, magnetic material, insulation, conductor
segments, and insulation, the sequence being repeated as many times
as may be desired to provide the required value of inductance.
However the procedure is quite expensive since it involves several
successive deposition steps each of which must be performed in a
high vacuum and between which a change of mask means and vapor
source must be effected. Thus, despite the time advantage gained by
making a large number of inductors as a group rather than one by
one, the cost is quite high. Exemplary of this facet of the art is
the patent to Constantakes, U.S. Pat. No, 3,210,707.
Also the prior art shows, as exemplified in the patent to Roy, et
al., U.S. Pat. No. 3,372,358, the manufacture of a transformer by
thick-film deposition techniques, using a slot in a magnetic
substrate as a means for effecting conductive turns encircling a
sheet of magnetic material presenting a closed path for magnetic
flux. That procedure precludes the formation of more than one
transformer on an individual substrate, and further requires a
sheet or chip of magnetic material having an elongate slot therein,
both of which are responsible for making the produced device
expensive and time-consuming in manufacture and use.
b. The present invention.
The present invention permits concurrent manufacture of an
indefinitely large number of pulse transformers upon a single
substrate and without prior creation of slotted or apertured
magnetic core means, and further permits production of such
transformers upon the same base or substrate as supports the
bistable magnetic binary information store devices such as are
fully disclosed in the previously identified application of Ronald
A. Ketcham and Allen J. Learned. Further, the invention permits
production of the transformers, at least in part, concurrently with
production of adjacently disposed binary information store units
and adjunct conductor means, on the same base or substrate. In a
presently preferred exemplary form, a transformer is produced by
producing on a substrate, by thick-film techniques, in successive
order, the following items: (a) a first elongate array or set of
transversely extending conductor segments comprised in a first
winding; (b) a film of insulation such as glass or SiO.sub.2 or a
mixture of glass and ceramic material, which covers intermediate
portions of the conductor segments of the first array; (c) an
elongate first film of ferrite magnetic material extending beyond
the ends of the array of conductor segments; (d) a second set or
array of transversely extending conductor segments comprised in and
completing the first winding; (e) a glass or glass-ceramic
composite, such as a film of alumina in a glass binder, covering
all of the previously deposited films except end portions of the
ferrite film and endmost points of certain conductor segments that
are to remain exposed as terminals; (f) a first elongate array of
transversely oriented conductor segments comprised in a second
winding; (g) an elongate film of glass or like insulation similar
to that in (b) above which leaves exposed the ends of the segments
defined in (f) above and the exposed ends of the first film of
ferrite; (h) a second elongate film of ferrite which at its ends
blends with the corresponding exposed ends of the first film of
ferrite; and (i) a second elongate array of transversely oriented
conductor segments comprised in a second winding. The arrangement
is such that the first and second arrays of conductor segments
comprised in the first winding are serially connected to form in
effect a flat elongate coil the convolutions of which encircle and
inductively link the first deposit or film of ferrite, and further
is such that the conductor segments comprised in the second winding
similarly form a similar coil encircling and inductively linking
the second film of ferrite, and such that because of the fusion or
intimate joining of respective end portions of the elongate ferrite
films, the latter form an effective magnetic ring or closed
magnetic flux circuit that is inductively linked with both of the
first and second windings, whereby a transformer of substantially
two-dimensional form or character is provided. In a second physical
embodiment, by similar steps, two sets of arrays of conductor
segments, with appropriate insulative films, combine with a single
film of ferrite material of flat toroidal configuration, to
similarly provide a transformer. As a matter of convenience and
brevity of description as well as in the interest of reduction of
drawings, the latter, or second, embodiment of the invention is
first illustrated in the drawings and first described in detail
hereinafter.
The preceding brief summary of the invention makes it evident that
it is a principal object of the invention to provide improvements
in very small pulse transformers and methods of making the
same.
Another object of the invention is to provide a means and method
for concurrent production of a large number of very small pulse
transformers, either together with magnetic information store units
or separate from the latter.
Other objects and advantages of the invention are hereinafter set
out or made evident in the appended claims and the following
detailed description of the illustrated forms of devices embodying
the invention.
DESCRIPTION OF THE DRAWINGS
A subsidiary and simpler form of device embodying the invention,
and a more complex and preferred form os such device, are somewhat
diagrammatically depicted in the accompanying drawings, in
which:
FIG. 1 is a plan view of a fragment of an insulative base or
substrate that is readily divisible into chips on each of which is
a very small pulse transformer of simple form utilizing a flat-ring
film-type ferrite magnetic core and thick-film windings, the scale
being one of gross enlargement;
FIGS. 2, 3, 4 and 5 are diagrammatic plan views of a portion of the
fragment of substrate depicted in FIG. 1, showing successive steps
or stages of formation of a complete very small pulse transformer
such as are shown to a different dimensional scale in FIG. 1;
FIG. 6 is a diagrammatic plan view of the more complex form of very
small pulse transformer of preferred construction according to the
invention, to grossly enlarged scale in the interest of clarity of
illustration;
FIG. 7 is a fragmentary diagrammatic plan view, similar to FIG. 6
but with portions of films broken away to illustrate details of the
transformer depicted in FIG. 6, the scale or enlargement being
somewhat greater; and
FIG. 8 is DESCRIPTION exploded sectional view, to the same plan
scale as used in FIG. 7, of portions of the transformer of FIG. 1,
the thickness dimension of components being grossly exaggerated in
the interest of clarity of illustration.
DETAILED DESCRIPTION OF THE INVENTION AS ILLUSTRATED IN THE
DRAWINGS
In the simplest construction, as illustrated in FIGS. 1 to 5,
inclusive, a thin sheet-like substrate 20 of high-temperature
insulation such as alumina ceramic is used as a base on which a
large number of the transformers are concurrently produced. As is
indicated in FIG. 1, the substrate may be provided with an array of
weakened zones in the form of lines 22 along which the substrate is
made thinner or weaker, as by scribing or other operation performed
while the substrate is in the greenware form, whereby the substrate
may be easily subdivided to separate individual transformer units,
or groups thereof, as may be necessary or convenient.
For convenience in describing the steps of forming the
transformers, enlarged views of a fragment, 20', of the substrate
20 is depicted in FIGS. 2-5, it being understood that all of the
transformers on the remainder of the substrate are produced at the
same time by the same procedural steps as presently explained in
connection with fragment 20'.
The first step, following cleaning and inspection of the substrate,
is deposition of first and second arrays, 24 and 26 (FIG. 2), of
line segments of conductive ink by a conventional silk-screening
procedure using an appropriately formed screen. Since a high
temperature is attained during a subsequent step in which a ferrite
layer is produced, the ink used for the arrays of line segments
should be one capable of withstanding the latter operation. A noble
metal ink, such as platinum ink, gold ink, or a combination or
mixture thereof, is preferable, but an ink composed essentially of
about 80 percent noble metal and 20 percent lead-borosilicate glass
in an organic screening vehicle may be used. The line segments are
arranged on a preferably annular area as indicated, with first and
second substantially radial terminating segments 24a and 26a, and
with the remainder of the segments somewhat inclined to a truly
radial direction. The other segments of array 24 comprise, for
example, segments 24b-24f as indicated in FIG. 2; and it will be
noted that the second array, 26, may comprise, for example, those
denominated 26b, 26c, 26d, 26e and 26f, or may comprise fewer or
more segments. After deposition of the tow arrays of line segments
of conductive ink, the entire device is fired to reduce the ink to
line segments of conductive metal by removal of organic screening
vehicle and softening of glass to firmly bond the metal to the
substrate.
Following concurrent formation of arrays 24 and 26 of line segments
for all of the plurality of transformers or units on substrate 20,
annular films 28 (FIG. 3) of fused insulation such as high melting
temperature glass, glass ceramic or ceramic are formed by screening
or printing onto the substrate and over intermediate portions of
the line segments a slurry or ink comprising volatile carrier and
finely divided particles of the fusible insulation. Following
deposition and drying, the particles in the annular films are fused
by firing in a kiln.
The nest step of the procedure is application of an annular film 30
(FIG. 4) of magnetic material in a fugitive binder, the film 30
being confined to an area within the boundaries of insulation film
28. Film 30 may, for example, be of type TTI-390 Mg Mn ferrite,
marketed by Trans-Tech, Inc., Gaithersburg, Maryland; the ferrite
being subdivided to below 325 mesh size. The ink may be, for
example, 80 percent solids and 20 percent vehicle, the latter being
any ordinary liquid alcohol with or without a thickening agent such
as ethyl cellulose.
Following deposition and drying of the annuli of magnetic ink, the
substrate and applied films are fired to consolidate the magnetic
particles into an adherent and coherent unit which provides an
annular magnetic-flux path of low coercivity. As is indicated in
FIG. 4, the film 30 when fired is firmly affixed to the underlying
film 28 of insulation.
A second annular film 32 (FIG. 5) of insulation, like or similar to
film 28 in composition, mode of application, and firing, is then
preferably formed, over and covering the magnetic film 30. The
areal extent of film 32 is preferably coextensive with film 28, but
is such as to cover the ferrite film and leave exposed the inner
and outer ends of the previously formed conductor segments. In
those instances in which the magnetic film is a good insulator, the
second insulation film may be omitted. Following deposition of the
second layer of insulation, or the ferrite film if the insulation
is omitted, a second group or series of arrays of conductor
segments is produced, similar in all respects to the first produced
arrays except as to areal disposition. As is indicated in FIG. 5,
the uppermost conductor-segment arrays on the fragment 20' of the
substrate include termination segments 24n and 26n, and segments
24g, 24h, 24i, 24k and 24m of a first upper array and segments 26g,
26h, 26i, 26k and 26m of a second upper array. As is made evident
in FIG. 5, the segments of the first upper array form conductive
junctures with respective exposed ends of the conductor segments of
the first lower array which includes segments 24a, etc.; and those
of the second upper array form junctures with ends of the
conductors 26a, etc. of the second lower array. Thus the conductor
segments of prefix 24 are serially joined to form, in effect, a
flat coil encircling the magnetic annulus 30; and similarly the
lower and upper conductor segments of the second arrays are
serially joined to form, in effect, a flat coil encircling the same
magnetic annulus or core. Thus, for example, the ends of the
conductor segments 24a and 24n may be taken as terminals of a
transformer primary winding, and the ends of the conductor segments
26a and 26n may be considered to be terminals of the transformer
secondary winding, or vice versa. Thus the group of transformers
depicted in FIG. 1, together with many more concurrently produced
therewith on the substrate 20, are provided. As will be evident to
those skilled in thick-film electronics circuits and apparatus
arts, the dimensions and shapes of the magnetic and conductive
portions of the transformers may be considerably varied, as may be
the ratio of the flat convolutions or turns of the primary to those
of the secondary coils or windings. Since the conductors are not
wound but are produced in situ, the term "windings" is herein used
in the electrical sense.
In FIGS. 6, 7 and 8, there is diagrammatically illustrated a more
complex but more compact form of pulse transformer according to the
invention and produced either singly or concurrently in multiple as
in the preceding example. In the interest of brevity and
conciseness, a single unit is illustrated and described. The single
transformer is produced by successive depositions of materials by
thick-film techniques, firing, etc., similar to the previously
described steps but with a notable exception as will be explained.
The transformer is produced on a substrate 40 by successively
depositing and firing: (a) a first array of conductor segments,
such as those indicated at 42 (FIGS. 7 and 8), comprised in a lower
winding; (b) a rectangular insulative film 44 of, for example,
glass, so shaped as to cover only the intermediate but major
portions of the conductor segments 42; (c) a rectangular film of
ferrite 46, of composition like or similar to that previously
noted, the film extending beyond the ends of the array of conductor
segments 42 previously formed; (d) a second array of conductor
segments, such as 48, that are formed and disposed transversely of
the sheet or film of ferrite and end portions of which extend
beyond the side boundaries of the glass 44 and ferrite 46 and fuse
with respective ends of adjacent companion conductor segments 42,
whereby to form, in effect, a flat coil encircling and
electromagnetically linked with the ferrite film or sheet 46; (e) a
sheet or film of glass, glass-ceramic, ceramic or other
high-temperature insulation 50. As examples, this insulation may be
a screenable glass ink made from Corning Glass Works borosilicate
(No. 7740) glass, or any low-alkali composition, containing about
30 percent by weight of finely divided particles of silica,
alumina, zirconia or other relatively inert ceramic material, or a
commercial glass-ceramic coating such as "Ceramic Dielectric
Coating No. 4610" marketed by Electro Science Laboratories, 1133
Arch Street, Philadelphia, Pennsylvania a 19107, the film
preferably being applied as first and second coats and fired either
after or concurrently with the next lower array of conductor
segments of a second winding, the film covering all the previously
formed components except terminal portions 42a and 42b (FIGS. 6 and
7) of the lower winding and the ends of the ferrite film; (f) a
lower array of conductor segments, such as 52, comprised in a
second flat coil or winding, the entire extent of the array
excepting a terminal portion 52a being formed on the insulative
film 50 of alumina or the like; (g) a film of fused glass or silica
insulation 54, which is formed to cover only intermediate portions
of the array of conductor segments 52 leaving end portions thereof
exposed, as in the deposition of the segments 42 and insulation
film 44; (h) formation of a second or upper magnetic film or layer
56 of ferrite, the end portions of which overlie and intimately
blend with or bond to respective end portions of the lower ferrite
film 46; and (i) an upper or second array of conductor segments 58,
comprised in the upper coil or winding, end portions of which
extend beyond the side boundaries of the glass film 54 and the
ferrite film 56 and overlie and fuse intimately with respective end
portions of conductor segments 52 to thereby provide a second flat
coil encircling and inductively linked to the upper sheet of
ferrite. The extended end portions of the endmost conductor
segments of the arrays of segments 52 and 58 form terminals 52a and
58a for the upper coil.
As will be evident, the two ferrite layers or films form a flat
wide closed magnetic flux path which is inductively linked with
both of the windings or flat coils. Also, either of the upper and
lower coils may be used as the primary and the other as the
secondary. While the several components are shown separated and
greatly exaggerated in dimension in FIG. 8, it will be evident that
since each film is of thickness measurable in mils, the actual
thickness of the transformer is very little more than that of
substrate 40. As will also be evident, a large number of
transformers of the construction illustrated in FIGS. 6, 7 and 8
may be simultaneously produced on a large substrate similar to that
depicted in FIG. 1. For protection of the transformer units from
chemical and/or mechanical injury, the units are potted, subsequent
to attachment of terminal leads, using conventional techniques and
materials.
The conductive inks may in general be fired at temperatures of the
order of 850.degree. C., and the glass and ferrite films at
temperatures of the order of 900.degree. C.; however, variations
may be made in accord with good thick-film techniques practice and
depending upon the metals and glasses, etc. used.
The preceding descriptions of a simple and of a more complex
transformer device according to the invention make it evident that
the noted objectives have been fully attained. Accordingly,
* * * * *