GB2086368A - Improved Crossover Dielectric Inks - Google Patents
Improved Crossover Dielectric Inks Download PDFInfo
- Publication number
- GB2086368A GB2086368A GB8131326A GB8131326A GB2086368A GB 2086368 A GB2086368 A GB 2086368A GB 8131326 A GB8131326 A GB 8131326A GB 8131326 A GB8131326 A GB 8131326A GB 2086368 A GB2086368 A GB 2086368A
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- GB
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- Prior art keywords
- percent
- weight
- circuit board
- borosilicate glass
- accordance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/01—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate comprising only passive thin-film or thick-film elements formed on a common insulating substrate
- H01L27/013—Thick-film circuits
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
- C03C8/24—Fusion seal compositions being frit compositions having non-frit additions, i.e. for use as seals between dissimilar materials, e.g. glass and metal; Glass solders
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/46—Manufacturing multilayer circuits
- H05K3/4685—Manufacturing of cross-over conductors
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Power Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Life Sciences & Earth Sciences (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Manufacturing & Machinery (AREA)
- Computer Hardware Design (AREA)
- Glass Compositions (AREA)
Abstract
Novel thick-film crossover dielectric inks useful in constructing multilayer circuits on suitable substrates comprise 30-70% by wt. barium magnesium borosilicate glass powder, 10-30% by wt. of a pinhole reducing component consisting of silicon dioxide and/or an alkaline earth aluminium borosilicate glass having a softening point above 700 DEG C and a suitable organic vehicle.
Description
SPECIFICATION improved Crossover Dielectric Inks
This invention pertains to thick film crossover dielectric inks and their use in constructing multilayer electrical circuit structures on porcelain-coated metal substrates.
The use of specialized ink formulations to form thick films having various functions on suitable substrates in the construction of multilayer integrated circuit structures is well known in the art. Such technology is of increasing interest in the fabrication of very dense multilayer circuit patterns on various substrates for a wide variety of applications in the electronics industry.
Significantly improved substrates for the fabrication of such circuits are disclosed and claimed in
Hang et al., U.S. Patent No. 4,256,796, issued March 17, 1981,the disclosure of which is incorporated herein by reference. The Hang et al. substrates are metal coated with an improved porcelain composition comprised of a mixture, based on its oxide content, of magnesium oxide (MgO) or mixtures of magnesium oxide and certain other oxides, barium oxide (BaO), boron trioxide (B2O3) and silicon dioxide (SiO2). The preferred metal is steel, particularly low carbon steel, which may be coated with various other metals such as, for example, copper. The porcelain compositions are applied to the metal core and fired to provide a partially devitrified porcelain coating on the metal core.The coating has a very low viscosity at its initial fusion point and then almost instantaneously obtains a high viscosity due to devitrification. The fired coatings which are preferred for hybrid circuit applications have a deformation temperature of at least 7000C and a high coefficient of thermal expansion of at least about 11 Ox1 10x10-7/OC.
While the porcelain-coated metal substrates of Hang et al. represent a significant improvement over previously known substrate materials, they are disadvantageous only in being incompatible or poorly compatible with commercially available thick film inks. In accordance with this invention, improved crossover dielectric inks are provided which are compatible with the Hang et al. porcelain metal substrates.
The improved crossover dielectric inks provided in accordance with this invention are based on the system BaO-MgO-B203-SiO2. In addition to the barium magnesium borosilicate devitrifying glass powder, the novel inks of this invention contain a pinhole-reducing component comprising silicon dioxide powder, an alkaline earth aluminum borosilicate glass having a high softening point or mixtures thereof, and a suitable organic vehicle.
In accordance with this invention, there are provided improved crossover dielectric inks useful in the production of complex, multilayer thick film integrated circuits on porcelain-coated metal substrate boards. Crossover dielectric films provide insulation between intersecting layers of conductors in a multilayered circuit array. Conventional thick-film dielectric inks generally consist of a mixture of dielectric oxide powder and a low softening point glass frit with a suitable screening medium.
It is generally recognized that films formed from crossover dielectric inks should possess: a thermal coefficient of expansion reasonably close to that of the substrate being utilized; good mechanical strength and reheat stability; little porosity in general and no open porosity to prevent shorts between the top and bottom conductors; chemical compatibility with the conductor pads; low dielectric constant; high insulation resistance; and good voltage breakdown characteristics. Dielectric inks according to this invention can satisfy all of these criteria and, in addition, possess excellent compatibility with the aforementioned Hang et al. porcelain-coated metal circuit boards.The crossover dielectric inks of this invention are likewise compatible with various types of thick-film inks formulated for the Hang et al. porcelain-coated metal substrates, thus providing a significant advance in multilayer integrated circuit systems.
The crossover dielectric inks of this invention are unique in that they may be fired in either air or inert environments, e.g. nitrogen. Since most conventional inks are fireable in only one of these environments, the capacity of the inks of this invention to be fired in either atmosphere is particularly advantageous in the production of highly complex multilayer integrated circuits.
The subject dielectric inks are based on the system BaO-MgO-B2O3-SiO2 and are specially formulated so that, during initial firing, a liquid/liquid phase separation occurs. One of the phases begins to precipitate from the glass as microcrystals. These microcrystals build slowly into polycrystalline bodies which are exceptionally stable during reheating. The resulting films are therefore partially devitrified with the polycrystalline mass comprising from about 60 to about 75 percent by volume of the film. The partial devitrification of the inks of this invention during firing, in a sense, forms an in situ ceramic. The inks of this invention are formulated to achieve this effect and to minimize pinholes in the thick-films prepared therefrom.
The glass frit component of the inks of this invention may on a weight basis consist of
a) from about 17 to about 49 percent of barium oxide;
b) from about 16 to about 43 percent of magnesium oxide;
c) from about 13 to about 33 percent of boron trioxide; and
d) from about 8 to about 22 percent of silicon dioxide.
The barium oxide may be replaced in part by including up to 12 percent by weight, based on the total frit, of lanthanum oxide (La203). The partial replacement of BaO with La2O3 modifies the crystal structure somewhat for particular applications. The glass composition may additionally contain small amounts of a mixture of phosphorous pentoxide (P205) and zirconium oxide (ZrO2) which acts to further retard the rate of crystaliization. Such mixture, when present, comprises up to about 6 percent by weight, preferably from about 3 to about 4 percent by weight, of the glass frit. The mixture contains P205 and ZrO2 in a weight ratio of between about 1:2 and 1:7, preferably between about 1:3 and 1:4.
The glass frit comprises from about 30 to about 70 percent by weight of the total ink composition.
The pinhole reducing component of the novel crossover dielectric inks of this invention consists
of silicon dioxide, an alkaline earth aluminum borosilicate glass having a high softening point or
mixtures thereof, with mixtures being preferred. The presence of this component in the subject inks
helps slow the rate of crystallization and, more importantly, provides a physical aid to entrapped gas
bubbles which result from decomposition or volatilization of the organic vehicle during firing so that
they may reach the surface of the ink and escape into the environment. By aiding the gas to escape more
rapidly and exerting a retarding effect on crystallization, this component virtually eliminates through pinholes
and significantly reduces pinhole density in films in excess of 1 mil thick, formed from the inks of this
invention.
The terminology "high softening point" with regard to the glass utilized as a pinhole reducing
component in the context of this invention means an alkaline earth aluminum borosilicate glass having
a softening point in excess of 7000C. A preferred glass is based on the system BaO-CaO-B203- Al203SiO2 with a particularly referred glass having, on a weight basis, 45 to 55 percent of BaO, 6 to
15 percent of CaO, 10 to 20 percent of B203, 6 to 13 percent of AT203 and 5 to 1 5 percent of SiO2.
As stated above, it is preferred to utilize mixtures of the alkaline earth aluminum borosilicate glass and
silicon dioxide as the pinhole reducing component. While these two may be mixed in any proportions,
approximately equal parts by weight are preferred. The pinhole reducing component comprises from
about 10 to about 30 percent, preferably from 1 5 to about 25 percent, by weight of the total ink
composition.
The ink formulations of this invention may also contain a minor amount of a conventional
colorant oxide such as the oxides of chromium, cobalt, nickel and the like. The inks of this invention
may contain up to about 5, preferably from about 0.1 to about 1.0, weight percent of a colorant oxide.
The solid components of the subject ink formulations may in practice have an average particle
size of between about 1 and 5 ym. They are thoroughly mixed, preferably in a ball mill or other suitable
grinding apparatus with an aliphatic alcohol, preferably isopropanol, for from 8~48 hours. The alcohol
is then evaporated and the solids combined with from about 20 to about 50 percent, preferably from
about 30 to about 40 percent, by weight, of a suitable organic vehicle to make the ink. The organic
vehicles are selected to give screen printing characteristics to the inks and to burn off cleanly during
firing in nitrogen or air, i.e. without leaving a carbonaceous residue.
The organic vehicles are binders such as, for example, cellulose derivatives, particularly ethyl
cellulose, synthetic resins such as polyacrylates or methacrylates, polyesters, polyolefins and the like.
In general, conventional vehicles utilized in inks of the type described herein may be used in the subject
inks. Preferred commercially available vehicles include, for example, pure liquid polybutenes available
as Amoco H-25, Amoco H-50 and Amoco L-100 from Amoco Chemicals Corporation, poly n
butylmethacrylate available from E. I. duPont de Nemours and Co., and the like.
The above resins may be utilized individually or in any combination of two or more. A suitable
viscosity modifier can be added to the resin material if desired. These modifiers can be solvents such as
those conventionally used in similar ink compositions, e.g. pine oil, terpineol, butyl carbitol acetate, an
ester alcohol available from Texas Eastman Company under the trademark Texanol and the like or solid
materials such as, for example, a castor oil derivative available from NL Industries under the trademark
Thixatrol. Regardless of the vehicle utilized, it is important that dispersion and homogeneity of the
solids in the vehicle be maximized For this reason, mixing is usually carried out in conventional
apparatus which disperses the mixture and subjects it to a shearing force at the same time. Generally,
the higher the shearing forces, the better the resulting dispersion.
The crossover dielectric inks of this invention are applied to the substrate board, preferably the
porcelain-coated metal boards of Hang et al., by conventional means, i.e. screen printing, brushing,
spraying and the like with screen printing being preferred. Generally, as is conventional in the art, two
individually dried and fired layers of dielectric are utilized to minimize the potential for through
pinholes. The coating of ink is then dried in air at 1000--1250C for about 15 minutes. The resulting film may be fired in air or nitrogen at temperatures from 8500 to 9500C for from 4 to 10 minutes. The
dielectric films thus obtained have good mechanical strength and good reheat stability. When utilized
in multilayer circuits, they have demonstrated excellent isolation between layers of copper conductors.
In addition to the porcelain-coated metal boards of Hang et al, the crossover dielectric inks of this
invention are compatible with and can be utilized with conventional circuit boards, e.g. alumina circuit
boards.
The following Example further illustrates this invention, it being understood that the invention is in
no way intended to be limited to the details described therein. In the Example all parts and percentages
are on a weight basis and all temperatures are in degrees Celsius, unless otherwise stated.
Example
Crossover dielectric inks were prepared from the following formulations:
Composition (percent)
Devitrifying High Softening
Ink Glass Powder Silicon Point Glass Organic
No. I ii Dioxide Colorant Powder Vehicle 1 57.14 - - ~- 42.86 2 47.62 - 19.05 - - 33.33
3 51.95 - 20.78 - - 27.27
4 53.34 - - - 13.33 33.33
5 - 42.12 16.84 - 2.11 38.93
6 - 42.74 17.09 0.43 6.41 33.33
The vehicle for Ink No. 1 was a mixture of 28.57 and 14.29 percent, respectively, of the liquid polybutenes Amoco H-25 and L-100 available from Amoco Chemical Co.In Ink No. 2, a mixture of
10.00 percent Amoco H-50, 1 6.67 percent Amoco L-100 and 6.66 percent of the ester alcohol
Texanol available from Texas Eastman Company was the vehicle. In the remaining ink formulations, the vehicle was a 13 percent solution of Elvacite 2044 in pine oil. Elvacite 2044 is a poly(nbutylmethacrylate) resin available from E. I. duPont de Numours and Co. The colorant for Ink No. 6 was chromium oxide.
In the above inks, the devitrifying glass powders had the following formulations:
Formula (Percent)
Ingredient I II MgO 27.83 41.05
BaO 37.16 18.22 B203 20.45 23.63
SiO2 14.56 13.25 Zero, - 2.89 P206 - 0.96
The high softening point glass had the following composition by weight percent: BaO (49.28),
CaO (12.01), B203 (14.92), Al2O3 (10.92), and SiO2 (12.87).
The solid ingredients were mixed in a ball mill, with sufficient isopropyl alcohol to thoroughly wet them, for a period of 12 hours. The alcohol was evaporated and the solids were combined with the organic vehicle. All ingredients were first hand mixed, then mixed on a 3 roll mill to obtain a smooth paste suitable for screen printing. Additional vehicle was added to replace loss during mixing and assure proper rheology.
Copper conductor inks were printed and fired onto a porcelain steel substrate of the type disclosed by Hang et al. The copper inks were air dried at 1250 for about 15 minutes, then fired in nitrogen at about 8500. Samples of each of the above inks were printed over the copper electrodes through a 200 mesh stainless steel screen, 1 mil emulsion thickness. The crossover dielectric inks were dried in air at 1250 for 15 minutes and fired in nitrogen in an Inconel Muffle, 5 zone, BTU Transheat belt furnace with a belt width of 6 inches at a peak temperature of 9000. Time at peak temperature was about 4-8 minutes. Total cycle time was about 30 4-5 minutes. A second dielectric layer was printed and fired over the first. Finally, a top copper electrode was printed, dried and fired. The fired parts were tested for electrical shorts between the top and bottom copper electrodes, dielectric constant, dielectric loss, insulation resistance and breakdown voltage of the dielectric films.
Ink No. 1 was unacceptable because of pinholes which produced shorts between the copper electrodes. Ink No. 4 had some blistering in the films. inks 2 and 3 had significantly decreased pinholes in comparison to Ink No. 1. inks 5 and 6 demonstrated excellent results in all tests.
Claims (20)
1. A crossover dielectric ink suitable for forming an intermediary film between two or more conductor films on a substrate comprising:
a) from about 30 to about 70 percent by weight of a partially devitrifying barium magnesium
borosilicate glass;
b) from about 10 to about 30 percent by weight of a pinhole reducing component selected from
the group consisting of silicon dioxide, an alkaline earth aluminum borosilicate glass having a
softening point above about 7000C, and mixtures thereof; and
c) from about 20 to about 50 percent by weight of a suitable organic vehicle.
2. A crossover dielectric ink in accordance with Claim 1, wherein said partially devitrifying glass consists essentially of:
a) from about 17 to about 49 percent by weight of barium oxide;
b) from about 16 to about 43 percent by weight of magnesium oxide;
c) from about 13 to about 33 percent by weight of boron trioxide;
d) from about 8 to about 22 percent by weight of silicon dioxide;
e) from 0 to about 12 percent by weight of lanthanum trioxide; and
f) from 0 to about 6 percent by weight of a mixture of phosphorus pentoxide and zirconium oxide
in a weight ratio of from about 1:2 to about 1:7.
3. A crossover dielectric ink in accordance with Claim 2, wherein said glass contains from about 3 to about 4 percent by weight of said mixture of phosphorus pentoxide and zirconium oxide.
4. A crossover dielectric ink in accordance with Claim 1, including said alkaline earth aluminum borosilicate glass as a barium calcium aluminum borosilicate glass.
5. A crossover dielectric ink in accordance with Claim 4, wherein said barium calcium aluminum borosilicate glass consists essentially of:
a) from about 45 to about 55 percent by weight of barium oxide;
b) from about 6 to about 1 5 percent by weight of calcium oxide;
c) from about 10 to about 20 percent by weight of boron trioxide;
d) from about 6 to about 13 percent by weight of aluminum oxide; and
e) from about 5 to about 1 5 percent by weight of silicon dioxide.
6. A crossover dielectric ink in accordance with any preceding Claim, wherein said pinhole reducing component is a mixture of silicon dioxide and said alkaline earth aluminum borosilicate glass.
7. A crossover dielectric ink in accordance with any preceding claim wherein said ink contains up to about 5 percent by weight of a colorant oxide selected from the group consisting of chromium oxide, cobalt oxide and nickel oxide.
8. A process of forming a multilayer electrical circuit on a circuit board comprising:
a) applying and firing on said board a conductor ink thereby forming a first conductor film;
b) applying and firing on the portion of said conductor film which will intersect a second
conductor film in said circuit, an ink according to any preceding Claim thereby forming a
crossover dielectric film on said portion of said first conductor film; and
c) applying and firing a conductor ink on said board thereby forming a second conductor film
having said crossover dielectric film interposed between said first and second conductor
films.
9. A process in accordance with Claim 8 wherein said circuit board is a porcelain-coated metal circuit board.
1 0. A circuit board having on a portion of the surface thereof a conductor film, said conductor film having on a predetermined portion a coating of a crossover dielectric ink comprising:
a) from about 30 to about 70 percent by weight of a partially devitrifying barium magnesium
borosilicate glass;
b) from about 10 to about 30 percent by weight of a pinhole reducing component selected from
the group consisting of silicon dioxide, an alkaline earth aluminum borosilicate glass having a
softening point above about 7000C, and mixtures thereof; and
c) from about 20 to about 50 percent by weight of a suitable organic vehicle.
11. A circuit board in accordance with Claim 10, wherein said board is porcelain-coated metal.
12. A circuit board in accordance with Claim 1 wherein said metal is steel.
13. An electronic assembly comprising a circuit board having a multilayer circuit thereon, said circuit containing two or more layers of conductor film, each pair of layers of conductor film having interposed between them at their intersecting portion a layer of crossover dielectric film formed by applying and firing a crossover dielectric ink comprising:
a) from about 30 to about 70 percent by weight of a partially devitrifying barium magnesium
borosilicate glass;
b) from about 10 to about 30 percent by weight of a pinhole reducing component selected from
the group consisting of silicon dioxide, an alkaline earth aluminum borosilicate glass having a
softening point above about 7000C, and mixtures thereof; and
c) from about 20 to about 50 percent by weight of a suitable organic vehicle.
14. An assembly in accordance with Claim 13, wherein said circuit board is a porcelain-coated metal circuit board.
15. An assembly in accordance with Claim 14, wherein said metal is steel.
16. A circuit board, or electronic assembly comprising such board, as claimed in any of claims 10~15 wherein said partially devitrifying glass is as recited in claim 2 or 3.
1 7. A circuit board, or electronic assembly comprising such board, as claimed in any of claims 10~16 including said alkaline earth aluminum borosilicate glass as recited in claim 4, 5 or 6.
18. A crossover dielectric ink substantially as hereinbefore described.
19. A circuit board substantially as hereinbefore described.
20. An electronic assembly substantially as hereinbefore described.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8131326A GB2086368B (en) | 1980-10-17 | 1981-10-16 | Improved crossover dielectric inks |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8033567 | 1980-10-17 | ||
US06/280,916 US4369254A (en) | 1980-10-17 | 1981-07-06 | Crossover dielectric inks |
GB8131326A GB2086368B (en) | 1980-10-17 | 1981-10-16 | Improved crossover dielectric inks |
Publications (2)
Publication Number | Publication Date |
---|---|
GB2086368A true GB2086368A (en) | 1982-05-12 |
GB2086368B GB2086368B (en) | 1984-06-06 |
Family
ID=27261037
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB8131326A Expired GB2086368B (en) | 1980-10-17 | 1981-10-16 | Improved crossover dielectric inks |
Country Status (1)
Country | Link |
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GB (1) | GB2086368B (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1989002135A1 (en) * | 1987-09-04 | 1989-03-09 | Calcomp Inc. | Digitizing tablet |
WO2008027352A1 (en) * | 2006-08-30 | 2008-03-06 | Corning Incorporated | Ink for printing data carrying mark on honeycomb structures |
-
1981
- 1981-10-16 GB GB8131326A patent/GB2086368B/en not_active Expired
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1989002135A1 (en) * | 1987-09-04 | 1989-03-09 | Calcomp Inc. | Digitizing tablet |
US4859813A (en) * | 1987-09-04 | 1989-08-22 | Calcomp Inc. | Digitizer tablet having electrical interconnect components on the writing substrate |
WO2008027352A1 (en) * | 2006-08-30 | 2008-03-06 | Corning Incorporated | Ink for printing data carrying mark on honeycomb structures |
US7695556B2 (en) | 2006-08-30 | 2010-04-13 | Corning Incorporated | Ink for printing data carrying mark on honeycomb structures |
Also Published As
Publication number | Publication date |
---|---|
GB2086368B (en) | 1984-06-06 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19981016 |