Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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CROSS REFERENCE TO RELATED APPLICATIONS
(None)
BACKGROUND OF THE INVENTION
This invention relates to controlling the temperature coefficient
of resistivity (TCR) in resistors. More particularly, it relates to the
utilization of vanadium oxide in cermet type resistors to control TCR where-
in a distinct advantage is realized in employing a particular glass frit in
conjunction with ruthenium and iridium dioxides.
The mechanisms which control or alter the thermostability of -
~; 10 cermet resistors is not completely understood. It has been observed that
`
various semiconducting oxides exert an influence on the temperature response
of resistivity of cermet resistors so as to make them more thermally stable.
- Prior to this invention, only resistors described in the electronics industry
as thin film resistors have displayed low TCRs. In United States 2,950,995;
2,950,996 and 3,516,949 vanadium oxide is used in conjunction with noble
metal metallizing compositions in relatively small amounts to prevent agglom-
; eration of the metal particles and to improve the solderability, conduc-
` tivity and/or adhesion properties of the metallizing materials. The same
; indication of improvement in solderability for these compositions by adding
vanadium pentoxide is also indicated in United States 3,440,182.
In United States 3,553,109 vanadium pentoxide is utilized to con-
trol TCR in a resistor composition of the bismuth ruthenate type which uti-
lizes a glass frit binder consisting of 80% lead oxide, 10% silicon oxide -
and 10% boron oxide. A glass was prepared from the teachings of this partic-
ular patent and combined with a conductive phase used to fabricate the re-
sistors of this invention composed of ruthenium dioxide, vanadium pentoxide,
and aluminum trioxide as set forth in Example 11. It had a sheet resistiv-
- ity of 5.49K ohm/sq./mil. and a TCR of +170 + 10 ppm/ C when measured be-
tween +25 and -55 C and a +270 + 10 ppm/ C when measured between +25 and -
+150 C. These results clearly indicate that a low TCR cannot be obtained
with ruthenium dioxide and vanadium pentoxide which are the preferred mate-
rials of this invention when utilized with the glass described in this
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~ :1037705
particular patent. An attempt was also made to prepare a low TCR resistor
material utilizing a purchased glass containing 11% calcium oxide, 44.1%
lead oxide, 4.0% aluminum trioxide, 5.5% boron trioxide and 35.4% silicon
dioxide. This glass material was combined with a conductive material com-
posed of ruthenium dioxide in an amount of 5.34 weight percent prepared from
ruthenium resinate containing 5.26 weight percent ruthenium dioxide, iridium
dioxide in an amount of 7.2 weight percent prepared from iridium resinate
containing 6.99 weight percent iridium dioxide, 2.95 weight percent bismuth
trioxide, 4.18 weight percent vanadium pentoxide and the previously de-
scribed glass in the amount o~ 80.41 weight percent. The resistive materialprepared had a sheet resistivity of 24,000 ohms/sq./mil. and a TCR of -160 +
10 ppm/ C when measured between +25C and -55 C and a -50 + 10 ppm/ C when ~
measured between +25C and +150C which is considered poorer than when using ;
the materials of this invention.
It is an object of the present invention to provide a novel resis-
tor composition wherein the temperature coefficient of resistivity is held
within a narrow plus and minus range over a broad temperature range. It is
another object of this invention to provide a low temperature coefficient of
resistivity for a cermet material wherein a vanadium oxide is combined with
ruthenium and iridium dioxides in designated quantities. It is still anoth-
er object of this invention to provide a cermet type resistor with a low TCR
which is accomplished by employing vanadium oxides with a particular glass
frit. It is yet another object of this invention to provide a low TCR
cermet resistor which can be produced by current methods of manufacture and
can employ either oxide or metallic resinate precursor materials for both
the noble metal oxides and the vanadium oxide.
This invention relates to a cermet resistor composition having a
low temperature coefficient of resistivity and adapted to be fused to a
substrate composed of high temperature, electrically nonconductive material
comprising: a conductive phase composed of vanadium oxide in the range from
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about 1.00 to about 10.00 weight percent and ruthenium dioxide in the range
of from about 1.00 to about 30.00 weight percent, and an interdispersed
glass phase in the range of about 50.00 to about 98.00 weight percent, said
glass phase composed of lead oxide in the range of about 35.00 to about
45.00 weight percent, boron trioxide in the range of about 15.00 to about
25.00 weight percent and silicon dioxide present in the range of about 30.00
to about 40.00 weight percent.
This invention further relates to a starting material composition
for manufacturing the cermet resistor composition of this invention, com-
prising ruthenium resinate present in the range of about 20.00 to about85.00 weight percent, iridium resinate present in the range of about 5.00
to about 45. oo weight percent, vanadium oxide present in the range of about
0.50 to 2. 50 weight percent and glass frit present in the range of about
5.00 to 40.00 weight percent, said glass frit comprising lead oxide present
in the range of about 35.00 to 45.oo weight percent, boron trioxide present
in the range of about 15.00 to about 25.00 weight percent and silicon oxide
present in the range of about 30.00 to about 40.00 weight percent.
The shortcomings of the prior art are overcome by the present
resistor composition wherein a conductive phase composed of ruthenium diox-
ide and, preferably, in addition iridium dioxide, is combined with a vanad-
ium oxide in designated quantities and with a glass phase composed of a
glass frit of a particular composition. These materials are fired together
to result in the unique resistor composition having unexpected low TCRs
over a broad temperature range. Alternatively, bismuth trioxide can be uti-
lized in the resistive material composition. The ruthenium, iridium and
vanadium oxides can be supplied in their oxide form or in the form of res-
inate precursor materials combined with the particular glass frit.
BRIEF DESCRIPTION OF DRAWING
A better understanding of the advantages of the present resistor
material will be afforded by reference to the drawing wherein:
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Figure I is a graph illustrating the low and narrow range of TCR
in ppm/ C for the resistor compositions of this invention plotted over a - -
temperature range of -55 C to +150 C wherein the conductive phase i5 pre-
pared from the resinate of the metals and the data plotted for the material
prepared in accordance with Examples 2, 3 and 5.
- Figure II is a graph similar to that of Figure I and illustrating
these same critical characteristics but for the resistor material prepared
from oxides as described in Examples 11, 14 and 15 with the data plotted for
these particular materials.
DESCRIPTION OF THE RESINATE EMBODIMENT
The cermet resistor composition of this invention can be prepared
either by utilizing the ruthenium and iridium dioxides in a resinate form
for ultimate conversion to the dioxide or can be prepared by utilizing the
ruthenium and/or iridium dioxides themselves as starting materials. A de-
scription of the cermet resistor composition as prepared from the resinates
of ruthenium and iridium will first be given. The particular resinates of
ruthenium and iridium employed in the Examples of Table III and in Examples
20, 21 and 22 are designated A-1124 and A-1123, respectively, by the sup-
`; plier, Engelhard Industries, Inc., Hanovia Liquid Gold Division of East
Newark, New Jersey. They are resinate solutions containing 4.0% rutheniumor 5.26% ruthenium dioxide and 6.o% iridium or 6.99% iridium dioxide, re-
spectively. The range of starting materials for the resinate-prepared com-
positions and for the glass are described in the following Tables I and II.
TABLE I
,
Composition Range of Resistive Material
(Conductive Phase)
.
Constituents % By Weight % By Weight -
_ (Oxide)
Ruthenium Resinate 20.00 to 85.00 1.00 to 30.00
Iridium Resinate 5.00 to 45.00 1.00 to 15.00
: Bismuth Trioxide 0.00 to 2.25 0.00 to 10.00
Vanadium Pentoxide 0.50 to 2.50 1.00 to 10.00
Glass 5.0 to 40.00 50.00 to 98.00
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ABLE II
_
Composition Range of Glass Matrix
(Glass Phase)
Constituent% ~y Weight% By Weight Preferred
:'
PbO 35.0 to 45.038.0 to 45.0
B203 15.0 to 25.017.0 to 21.0
SiO2 30.0 to 40.033.0 to 37-
CaO O to 2.0 1.0 to 2.0
A123 O to 2.0 1.0 to 2.0
In the following Examples 1-10, -20, -21 and -22, deriving the
oxides from resinate precursors, the following procedures which are standard
in this art are employed in all instances:
RESINATE METHOD
1. Weigh constituents in desired proportions.
2. Burn off organic portions of resinate solution at 300 C to 480 C in the
presence of the glass frit of median particle size of less than 20
microns.
3. Calcine inorganic residue for 30 to gO minutes at 400 to 600 C in air.
4. Reduce the particle size of the residue to less than 20 microns, pref-
erably to a median particle size of 5 ~ 2 microns by such means as ball
milling with alumina grinding media.
5. Mix the resulting powder with a suitable vehicle to a paste of desired
consistency. The vehicle may consist of any number of high boiling
point organic liquids such as 1-ethyl-2-hexanol which, in combination
with the resistive powder, have a viscosity suitable for screen print-
ing, dipping, or painting onto a substrate.
6. Screen print onto a ceramic insulating substrate by methods common to
the thick film electronic art. An example of applicable substrate
material is CRL 95 alumina. (Centralab Division of Globe-Union Inc.)
7. Fire at 850 C to 950 C in belt kiln using a 0.5 to 3 hour firing cycle.
Table III illustrates the compositions and test results for the
novel resistor material prepared in accordance with this invention and em-
ploying ruthenium and iridium resinates as starting materials.
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As is seen in Table III, and particularly Example 10, the best results are
obtained utilizing the resinate starting materials at lower resistive val-
ues.
DESCRIPTION OF THE OXIDE EMBODIMENT
Examples 11-18 in Table V illustrate the utilization of ruthenium
oxide as the starting material combined with a glass frit generally de-
scribed in Table II. For a series of resistive materials, using oxides as
starting materials, the compositions described in the following Table IV are
suitable:
- Table IV
Composition Ran~e of Resistive Material
Conductive Phase)
_ . _ . ............................ .
Constituent% By Weight% By Weight Preferred
Ru02 1.00 to 30.002.00 to 25.00
IrO2 1.00 to 15.003.00 to 14.00
2 3 0.00 to 10.000.00 to 5.00
, V205 1.00 to 10.001.00 to 8.oo
A1203*0.00 to 10.000.00 to 7.00 -~
Glass50.00 to 98.0063.00 to 95.00
., . _ ....
. . *
, 10 Same composition as in Table II
It should be recognized that the amounts of the designated compositions
, after they are fired onto the substrate will be as indicated in this Table
; and in the column entitled "% By Weig'ht (Oxide)" in Table I. Consequently,
the preferred amounts of the materials indicated in Tables I and IV are the
same.
The method for preparing each of the cermet resistor compositions
of Examples 11-18 is standard in the art and is as follows:
OXIDE METHOD
1. Weigh constituents in desired proportions.
2. Mix constituents together in a ball mill with acetone to form a slurry
and ball mill with a grinding medium alumina for 0.1 to 8.o hours.
3. Dry mixture at 70 C.
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4. Mix with a vehicle such as 1-ethyl-2-hexanol to form a paint.
5. Mill the resulting paint in a three roll mill for 0.1 to 2 hours to
assure dispersion and adJust consistency for screen printing by adding
solvent.
6. Screen onto a ceramic insulating subs-trate.
7. Fire at 850 C to 950 C in a belt type kiln in a 0.5 to 3 hour firing
cycle.
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Table V illustrates that low TCRs over the entire temperature range are
obtained with the oxide of ruthenium in conjunction with vanadium pentoxide.
As indicated in Examples 1-18 in Tables III and V, the TCRs of
the designated novel compositions have very low values over a broad temper-
ature range. The low temperature coefficient of resistivity, thick film
resistor materials of this invention may also be prepared from precursors
of the conductive phase other than resinates. For example, ruthenium hy-
drate may be utilized as a starting material. This is illustrated in the
following example:
Fxample 19
Ingredients~ By Weight
Ruthenium Hydrate 5.78
(55% RUO2)
V25 1.73
Glass FB-199N
(As indicated in
Tables III and V) 92.49
This material is processed in the same method as indicated for the
oxide starting materials under the heading "Oxide Method."
Results:
Sheet ReOistivity: 20,000 ohms/sq./mil.
TCR ppm/ C: O
-550C to 25 C -12
25 C to 150C +47
As indicated in this Example 19, when the ruthenium oxide is added
in the form of the hydrate the TCR is not as low as when the starting mate-
rial is the oxide or the resinate.
- The following Example 20 illustrates the utilization of vanadium
pentoxide predissolved in the glass designated FB-199N to the extent of
6.48% by weight.
-- 10 --
'; ' :,
Example 20
Ingredients% By Weight Oxide -
Ruthenium Resinate 10.37
(5.26% Ru02)
Iridium Resinate13-78
(6.99% IrO2)
Bi23 2.99
Glass
FB-199~/V O
(FB-199N:2 5as indicated
in Tables III and V) 72.85
These materials are processed by the method indicated above under
the heading "Resinate Method."
Results:
Sheet Resistivity: approximately 500 ohms/sq./mil.
TCR ppm/ C:
-550C to 25 C -29 + 3
25 C to 150C -27 + 3
In all of the previous Examples, the vanadium oxide has been in-
troduced pre~erably as vanadium pentoxide. It should be understood that
other oxides o~ vanadium such as vanadium trioxide can likewise be employed.
Additionally, the vanadium oxide can be introduced through a vanadium
resinate precursor material. Examples 21 and 22 ~ollowing illustrate these.
Example 21
Ing~edients % By Weight Oxide
Ruthenium Resinate 10.48
(5.26% Ru02)
Iridium Resinate13.93
(6.99% IrO2)
V23 4.81l
Bi23 3.02
Glass
FB-199N
(As indicated in
Tables III and V)67.72
These materials are processed by the method indicated above under
the heading "Resinate Method."
-- 11 --
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1037705
Results:
Sheet Resistivity: approximately 330 ohms/sq./mil.
TCR ppm/ C: O
-550C to 250C +13 + 3
25 C to 150 C +19 + 3
The following Example 22 indicates utili~ation of vanadium oxide ;~
introduced as vanadium resinate.
Example 22
Ingr dients% By Weight Oxide
Ruthenium Resinate 9.98
Iridium Resinate 13.27
(6.99% IrO2)
Vanadium Resinate 9.48
, (13-92% V25) -
3i23 2.88
Glass
FB-199N
(As indicated in
Tables III and V) 64.39 -
The above materials are processed by the method indicated above
- under the heading "Resinate Method."
Results:
Sheet ReOsistivity: 280 ohms/sq./mil.
TCR ppm/ C: O O
-55 C to 25 C +26 + 3
25C to 150C +21 + 3
As indicated above, the important conditions for achieving the low
temperature coefficient of resistivity are the utilization of vanadium oxide
with ruthenium dioxide, which preferably can also include iridium dioxide,
in the designated amount with a particular glass composition. The vanadium
oxide as well as the ruthenium and iridium dioxides can be utilized as
oxides or derived from resinate precursors. While vanadium pentoxide is the
preferred oxide of vanadium, other oxides such as vanadium trioxide or those
oxides resulting from the pyrolysis of vanadium resinate can likewise be
employed to advantage.
It will thus be seen that through the present invention, there is
now provided a cermet resistor composition having a low temperature coeffi-
- - 12 -
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cient of resistivity which can be effected at the extremes and generally
less than 20 ppm/ C, maintained over a broad temperature range. The
- vanadium oxide can be utilized in various stages of oxidation and in the
form of the resinate as can the ruthenium and the iridium dioxides. The
materials are easily processed into resistive paints. ~o additional capital
investment need be incurred to substitute the cermet resistor compositions
of this invention for more conventional compositions, and they can be easily
fabricated into thick film resistors without additional skills being re-
quired by the fabricator.
10The foregoing invention can now be practiced by those skilled in
the art. Such skilled persons will know that the invention is not neces-
sarily restricted to the particular embodiments herein. The scope of the
invention is to be defined by the terms of the following claims as given
meaning by the preceding description.
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